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Physical properties of the R3Pt23Si11 compounds with volatile rare earth: Sm, Eu, Tm and Yb
NASA Astrophysics Data System (ADS)
Opagiste, C.; Barbier, C.; Haettel, R.; Galķra, R. M.
The new R3Pt23Si11 series, where R is a rare earth, has been completed with the synthesis of three new compounds with volatile rare earth: R=Eu, Sm, and Tm. The studies of their physical properties have been performed along with those of the Yb3Pt23Si11 compound. The X-ray powder diffraction patterns confirm that they all crystallize in the same face-centered cubic structure, space group Fm 3 bar m, as the rest of the series. The refinements of the diffraction patterns show an anomalously high lattice parameter in Eu3Pt23Si11 and Yb3Pt23Si11, indicating a divalent valence state for Eu and Yb. This 2+ valence state for Eu and Yb ions is confirmed by the magnetic measurements. A ferromagnetic order is observed at TC=5.54▒0.07 K and 10.12▒0.07 K in Eu3Pt23Si11 and Sm3Pt23Si11 respectively. In Tm3Pt23Si11 no magnetic order is found down to 0.36 K while Yb3Pt23Si11 reveals a diamagnetic behavior. At low temperatures the spontaneous moment, Ms, in Eu3Pt23Si11 is in agreement with a L=0, S=7/2 state for the Eu2+ ion. On the contrary in Sm3Pt23Si11, Ms is far below the 0.714?B expected for the saturated moment of the Sm3+ in the J=7/2 ground state multiplet.
Facile synthesis and luminescence properties of Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+), Yb(3+)/Er(3+), Yb(3+)/Tm(3+), Yb(3+)/Ho(3+)) microspheres.
Xu, Zhenhe; Zhao, Qian; Ren, Baoyi; You, Lixin; Sun, Yaguang
Multicolor and monodisperse Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+), Yb(3+)/Er(3+), Yb(3+)/Ho(3+)) microspheres were prepared through a facile urea-assisted homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), Fourier transformed infrared (FT-IR), thermogravimetric analysis (TGA), photoluminescence (PL) and cathodoluminescence (CL) spectra were employed to characterize the samples. The XRD results reveal that the as-prepared spheres can be well indexed to cubic Y2O3 phase with high purity. The SEM and TEM images show the obtained Y2O3:Ln(3+) samples consist of regular nanospheres with the mean diameter of 350 nm. And the possible formation mechanism is also proposed. Upon ultraviolet and low-voltage electron beams excitation, Y2O3:Ln(3+) (Ln(3+) = Eu(3+), Tb(3+), Dy(3+), Sm(3+), Er(3+), Ho(3+), Tm(3+)) samples exhibit respective bright red (Eu(3+), (5)D0 --> (7)F2), green (Tb(3+), (5)D4 --> (7)F5), blue (Dy(3+), (4)F9/2 --> (6)H13/2), yellow (Sm(3+), (4)G5/2 --> (6)H7/2), green (Er(3+), (4)S3/2 --> (4)I15/2), green (Ho(3+), (5)S2 --> (5)I8), blue (Tm(3+), (1)D2 --> (3)F4) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Y2O3:Ln(3+) (Ln(3+) = Yb(3+)/Er(3+), Yb(3+)/Tm(3+) and Yb(3+)/Ho(3+)) exhibit characteristic up-conversion (UC) emissions of green (Er(3+), (2)H11/2, (4)S3/2, (2)H11/2 --> (4)I5/2), blue (Tm(3+), (1)G4 --> (3)H6) and green (Ho(3+), (5)F4, (5)S2 --> (5)I8), respectively. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the field of light display systems, lasers, and optoelectronic devices. PMID:25936002
Raman spectra of 2Ln/sub 2/O/sub 3/ /times/ 9TiO/sub 2/ compounds (Ln = Ce, La, Nd, Pr, Sm, Eu, Gd, Tm, Yb, Tb)
Mel'nik, N.N.; Tsapenko, L.M.
This work uses Raman and x-ray phase analysis methods to investigate compounds of the type 2Ln/sub 2/O/sub 3/ /times/ 9TiO/sub 2/ (where Ln = Ce, La, Nd, Pr, Sm, Eu, Gd, Tm, and Yb). The compounds were synthesized by melting in an optical beam on a water-cooled substrate (quench rate approx. 10/sup 2/ deg/sec) and by rapid quenching of a melt cupel by slamming with water-cooled blocks quench rate approx. 10/sup 5/ - 10/sup 6/ deg/sec. The x-ray diffraction study was done on a DRON-2 diffractometer. The Raman light spectra were recorded with a DFS-24 double monochromator employing argon laser excitation.
Syntheses, structure and rare earth metal photoluminescence of new and known isostructural A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) compounds
Mohitkar, Shrikant A.; Kalpana, G. [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036 (India); Vidyasagar, K., E-mail: firstname.lastname@example.com [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036 (India)
Nine new A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds have been synthesized by solid-state reactions. They are isostructural with six reported analogues of yttrium and other lanthanides and the monoclinic unit cell parameters of all fifteen of them vary linearly with the size of A{sup 3+} ion. Single crystal X-ray structures of eight A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds have been determined. Neat A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit characteristic rare earth metal photoluminescence. -- Graphical abstract: Among the fifteen isostructural A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=rare earth metal) molybdoantimonites, eight (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds exhibit neat characteristic lanthanide photoluminescence in the 200-800 nm range at room temperature. Display Omitted Research highlights: {yields} Syntheses of nine new A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Tb, Ho, Er, Tm, Yb, Lu) compounds. {yields} X-ray structures of eight A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Ce, Pr, Eu, Gd, Tb, Ho, Er, Tm) compounds. {yields} Photoluminescence of neat A{sub 2}Mo{sub 4}Sb{sub 2}O{sub 18} (A=Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm) compounds.
Upconversion processes in Yb-sensitized Tm:ZBLAN
Carrig, T.J. [Coherent Technologies, Inc., Lafayette, CO (United States); Cockroft, N.J. [Los Alamos National Lab., NM (United States)
A spectroscopic study of 22 rare-earth-ion doped ZBLAN (fluorozirconate) glass was done to study feasibility of sensitizing Tm:ZBLAN with Yb to facilitate development of an efficient, conveniently pumped blue upconversion fiber laser. it was found that, under single-color pumping, 480 nm emission from Tm{sup 3+} was strongest when Yb,Tm:ZBLAN is excited at 975 nm; the strongest blue blue emission was obtained from a glass sample with 2.0 wt% Yb + 0.3 wt% Tm. Also, for weak 975 nm pump intensities, strength of blue upconversion emission can be greatly enhanced by simultaneously pumping at 785 nm. This increased upconversion efficiency is due to reduced number of energy transfer steps needed to populate the Tm{sup 3+} {sup 1}G{sub 4} energy level. Measurements of fluorescence lifetimes vs dopant concentration were also made for Yb{sup 3+}, Tm{sup 3+}, and Pr{sup 3+} transitions in ZBLAN in order to better characterize concentration quenching effects. Energy transfer between Tm{sup 3+} and Pr{sup 3+} in ZBLAN is also described.
Cooperative downconversion in Yb3+/-RE3+ (RE=Tm or Pr) codoped lanthanum borogermanate glasses.
Liu, Xiaofeng; Qiao, Yanbo; Dong, Guoping; Ye, Song; Zhu, Bin; Lakshminarayana, Gandham; Chen, Danping; Qiu, Jianrong
We report on cooperative downconversion in Yb(3+)-RE(3+) (RE=Tm or Pr) codoped lanthanum borogermanate glasses (LBG), which are capable of splitting a visible photon absorbed by Tm(3+) or Pr(3+) ions into two near-infrared photons. The results indicate that Pr(3+)-Yb(3+) is a more efficient ion couple than Tm(3+)-Yb(3+) in terms of cooperative downconversion. We have obtained a highest quantum yield of 165% and 138% for Pr(3+)-Yb(3+) and Tm(3+)-Yb(3+) codoped LBG glasses under 468 nm excitation, respectively. However, ultraviolet light excitation to the charge transfer band of Yb(3+) does not result in quantum splitting as rapid relaxation from the charge transfer band to 4f(13) levels of Yb(3+) dominates. PMID:19037451
Fluorescence mechanisms of Tm3+- and Yb3+/Tm3+ doped AlF3-based fluoride glass
NASA Astrophysics Data System (ADS)
Zhang, Long; Zhang, Jun-jie; Hu, He-fang; Lin, Feng-ying
A complete set of spectroscopic parameters, including Judd-Ofelt parameters, radiative transition probabilities, radiative lifetime, branching ratios and integrated absorption cross section, have been calculated for Tm3+- doped fluoroaluminate (AYF) glass, based on the measured absorption spectra. The mechanism of Tm3+?Tm3+ and Yb3+??Tm3+ energy transfers and fluorescence properties have been investigated in both Tm3+ single-doped and Yb3+/Tm3+ double-doped AYF glasses. The cross-relaxation process, 3F4+3H6?23H4, is proved, which makes the optimum Tm3+ concentration of 1.77Ąm fluorescence (3H4? 3H6) much higher than 1.45Ąm fluorescence (3F4? 3H4) in Tm3+:AYF glasses. In Yb3+/Tm3+:AYF glasses, a stronger concentration quenching is found for the 476nm emission than that for the 797nm emission and is discussed under the 970nm-excitation.
Optical properties and laser performance of some Yb 3+, Er 3+ and Tm 3+-doped silicates
NASA Astrophysics Data System (ADS)
Souriau, J. C.; Romero, R.; Borel, C.; Wyon, Ch.; Li, C.; Moncorgķ, R.
This paper reports the main spectroscopic characterizations and laser experiments carried out on two new crystal hosts: the yttrium orthosilicate Y 2SiO 5 and the silicate oxyapatite SrY 4(SiO 4) 3O (hereafter noted SYS), doped with ytterbium and erbium for a 1.55 ?m laser emission and with thulium for a 2 ?m emission. Four new lasers have been demonstrated at 1.554 ?m, 1.576 ?m, 1.99 ?m and 2.05 ?m for respectively Yb, Er:SYS; Yb,Er:Y 2SiO 5; Tm:SYS and Tm:Y 2SiO 5. If for Yb,Er-codoped materials laser performances are still poor compared with the Yb,Er phosphate glass, the Tm-doped materials exhibit laser performances similar to the Tm: YAG and look very promising.
Infrared luminescence of Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate glasses
Zhang Qiang; Zhang Guang [Key Laboratory of Material Science and Technology for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Chen Guorong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Qiu Jianrong [State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Chen Danping [Key Laboratory of Material Science and Technology for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)
Tm{sup 3+} doped and Tm{sup 3+}/Yb{sup 3+} codoped lanthanum aluminum germanate (LAG) glasses are prepared by melt-quenching method and characterized optically. Based on the measurement of absorption spectrum, Judd-Ofelt intensity parameters ({Omega}{sub 2},{Omega}{sub 4},{Omega}{sub 6}) are calculated. The radiation emission rates, branching ratios, and lifetimes of Tm{sup 3+} are calculated to evaluate the spectroscopic properties of Tm{sup 3+} in LAG glass. The infrared emission properties of the samples are investigated and the results show that the 1.8 {mu}m emission can be greatly enhanced by adding proper amount of Yb{sup 3+} under the excitation of 980 nm. The energy transfer processes of Yb{sup 3+}-Yb{sup 3+} and Yb{sup 3+}-Tm{sup 3+} are analyzed, and the results show that Yb{sup 3+} ions can transfer their energy to Tm{sup 3+} ions with high efficiency and large energy transfer coefficient.
Yb3+ sensitized Tm3+ upconversion in tellurite lead oxide glass.
Mohanty, Deepak Kumar; Rai, Vineet Kumar; Dwivedi, Y
Triply ionized thulium/thulium--ytterbium doped/codoped TeO2-Pb3O4 (TPO) glasses have been fabricated by classical quenching method. The upconversion emission spectra in the Tm3+/Tm3+-Yb3+ doped/codoped glasses upon excitation with a diode laser lasing at ?980 nm has been studied. Effect of the addition of the Yb3+ on the upconversion emission intensity in the visible and near infrared regions of the Tm3+ doped in TPO glass has been studied and the processes involved explored. PMID:22265952
Complexation of trivalent rare earth elements (Ce, Eu, Gd, Tb, Yb) by carbonate ions
Jong Hyeon Lee; R. H. Byrne
Carbonate stability constants for five rare earth elements (Ce[sup 3+], Eu[sup 3+], Gd[sup 3+], Tb[sup 3+], and Yb[sup 3+]) have been determined at t = 25[degrees]C and 0.70 [plus minus] 0.02 M ionic strength through solvent exchange techniques. Estimated stability constants for Ce, Eu, and Yb are in close agreement with previous work. Analyses using Gd and Tb provide the
Solvothermal route to colloidal upconverting NaYF4: Yb3+/Er3+ and Yb3+/Tm3+ nanocrystals.
Chen, Shi; Wang, Shiwei; Zhang, Jian; An, Liqiong
Monodispersed nanocrystals of NaYF4: Yb3+, Er3+/Tm3+ that exhibited a high luminescence intensity were chemically synthesized by a non-aqueous solvothermal approach. These nanocrystals were easily dispersed in non-polar solvent and subsequently formed a transparent colloidal solution. Under 980 nm NIR excitation, green and blue emissions were observed from colloidal solutions of the NaYF4: Yb3+, Er3+/Tm3+, respectively. The effects of different solvents used and solvent concentration on the shape, size and size distribution of the nanocrystals have been investigated. It has been revealed that the doping ions diffused into NaYF4 lattice, and they formed a solid solution. The fluorescence photos, spectra, luminescence mechanism, and the formation mechanism of the nanocrystals have also been demonstrated. Emission spectrums of the nanocrystals prepared by this method show much more complicated emission peaks than by other methods. PMID:19435063
Excitation power controlled luminescence switching in Yb3+Tm3+ co-doped hexagonal NaYF4 nanorods
Y. Y. Zhang; L. W. Yang; H. L. Han; J. X. Zhong
Intense infrared-to-visible up-conversion (UC) emissions were obtained in hexagonal Yb3+-Tm3+ co-doped NaYF4 nanorods under excitation at 980 nm. Especially, luminescent switching between different UC emission wavelengths at 800, 480 and 450 nm were observed by adjusting excitation powers. Based on power-dependent spectral analyses, it was found that the cooperative energy transfer between Yb3+-Yb3+ pairs and Tm3+ ions play a key
A new series of lanthanoid containing Keggin-type germanotungstates with acetate chelators: [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} {l_brace}Ln=Eu{sup III}, Gd{sup III}, Tb{sup III}, Dy{sup III}, Ho{sup III}, Er{sup III}, Tm{sup III}, and Yb{sup III{r_brace}}
Hussain, Firasat; Sandriesser, Stefan [Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland); Speldrich, Manfred [Institute of Inorganic Chemistry, RWTH Aachen University, D-52074 Aachen (Germany); Patzke, Greta R., E-mail: email@example.com [Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)
A series of head-on complexes of lanthanoid containing germanotungstates was isolated from a one pot reaction in an acetate buffer at pH 4.5. This convenient approach brought forward the [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} (Ln=Eu{sup III}, Gd{sup III}, Tb{sup III}, Dy{sup III}, Ho{sup III}, Er{sup III}, Tm{sup III}, and Yb{sup III}) family with acetate chelators in the rarely observed {mu}{sub 2}: {eta}{sup 2}-{eta}{sup 1} mode. All compounds were structurally characterized using various solid state analytics, such as single crystal X-ray diffraction, FT-IR spectroscopy, and thermogravimetric analysis. The isostructural polyanions crystallize in the monoclinic system (S.G. P2{sub 1}/c). Temperature-dependent magnetic susceptibility measurements were performed on the Gd{sup III}-complex which exhibits near perfect Curie-type behavior. -- Graphical abstract: A new series of acetate-chelated lanthanoid containing germanotungstates [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} (Ln=Eu to Yb) is available from a convenient one-pot reaction. The influence of the lanthanide contraction on the structural properties is discussed and the magnetic properties of the Gd-representative are investigated in detail. Display Omitted Research Highlights: {yields}Lanthanoid containing germanotungstates with acetate chelators in {mu}{sub 2} : {eta}{sup 2}-{eta}{sup 1} mode. {yields}Lanthanoid contraction in [{l_brace}Ln(CH{sub 3}COO)GeW{sub 11}O{sub 39}(H{sub 2}O){r_brace}{sub 2}]{sup 12-} (Ln=Eu{sup III}-Yb{sup III}). {yields}Facile one-pot synthesis of the lanthanoid containing germanotungstate series.
Buffer-gas loaded MOTs for Ho, Yb,Tm, and Er
NASA Astrophysics Data System (ADS)
Chae, Eunmi; Drayna, Garrett; Hemmerling, Boerge; Hutzler, Nick; Ravi, Aakash; Collopy, Alejandra; Hummon, Matthew; Stuhl, Benjamin; Yeo, Mark; Ye, Jun; Doyle, John
We report on direct loading of lanthanide atoms into MOTs from a two-stage slow buffer-gas beam source, which has a peak forward velocity of ~ 30 - 60 m/s, considerably lower than other beam implementations. The low velocity combined with species generality makes this source useful for loading magneto-optical traps (MOTs), especially for species that are not well suited to the traditional approach of oven plus Zeeman slower. We report loading MOTs with Yb, Tm, Er, and Ho, without any additional slowing stages. Application of a single frequency slowing laser to the buffer-gas beam of Yb results in an unprecedentedly high loading rate of 2 . 0 (1 . 0) ū1010 Yb atoms/s and 1 . 3 (0 . 7) ū108 Yb atoms in the MOT. We plan to use this versatile source to load a MOT with CaF, following the same general approach to that used with YO and SrF.
Thermoelectric properties of Yb(x)Eu(1-x)Cd2Sb2.
Zhang, H; Fang, L; Tang, M-B; Man, Z Y; Chen, H H; Yang, X X; Baitinger, M; Grin, Y; Zhao, J-T
The thermoelectric performance of EuCd(2)Sb(2) and YbCd(2)Sb(2) was improved by mixed cation occupation. The composition, structure, and thermoelectric properties of Yb(x)Eu(1-x)Cd(2)Sb(2) (x=0, 0.5, 0.75, and 1) have been investigated. Polycrystalline samples are prepared by direct reaction of the elements. Thermoelectric properties were investigated after densification of the materials by spark plasma sintering. Yb(x)Eu(1-x)Cd(2)Sb(2) crystallizes in the P3m1 space group. The lattice parameters increase with the europium content. These materials show low electrical resistivity, high Seebeck coefficient, and low thermal conductivity together with high carrier concentration and high carrier mobility. ZT values of 0.88 and 0.97 are obtained for Yb(0.5)Eu(0.5)Cd(2)Sb(2) and Yb(0.75)Eu(0.25)Cd(2)Sb(2) at 650 K, respectively. PMID:21090867
Magnetic and Electrical Properties, 151Eu M÷ssbauer Spectroscopy, and Chemical Bonding of REAgMg ( RE=La, Ce, Eu, Yb) and EuAuMg
NASA Astrophysics Data System (ADS)
Johrendt, Dirk; Kotzyba, Gunter; Trill, Henning; Mosel, Bernd D.; Eckert, Hellmut; Fickenscher, Thomas; P÷ttgen, Rainer
Single-phase samples of REAgMg (RE=La, Ce, Eu, Yb) and EuAuMg were prepared by reacting the elements in sealed tantalum tubes in a high-frequency furnace. LaAgMg and CeAgMg adopt the hexagonal ZrNiAl-type structure, while EuAgMg, YbAgMg, and EuAuMg crystallize with the orthorhombic TiNiSi type. Chemical bonding was exemplarily investigatedfor EuAgMg and EuAuMg on the basis of TB-LMTO-ASAcalculations. Magnetic susceptibility measurements indicatePauli paramagnetism for LaAgMg and YbAgMg with room-temperature susceptibilities of 2.4(1)ū10-9 and 1.5(1)ū10-9 m3/mol, respectively. CeAgMg remains paramagnetic down to 2 K. The experimental magnetic moment of 2.52(2) ?B/Ce above 50 K is compatible with trivalent cerium. EuAgMg and EuAuMg are paramagnetic above 50 K with experimentalmagnetic moments of 7.99(5) ?B/Eu for the silver and 7.80(5) ?B/Eu for the gold compound, indicating divalent europium. Ferromagnetic ordering is detected at TC=22.0(3) K (EuAgMg) and TC=36.5(5) K (EuAuMg). At 4.2 K and 5 T the saturation magnetizations are 7.1(1) and 7.3(1) ?B/Eu for EuAgMg and EuAuMg, respectively. According to the very small hysteresis, EuAgMg and EuAuMg may be classified as soft ferromagnets. All compounds are metallic conductors. For EuAgMg and EuAuMg freezing of spin-disorder scattering is observed below TC. At 78 K 151Eu M÷ssbauer spectra show isomer shifts of -9.00(4) and -8.72(8) mm/s for EuAgMg and EuAuMg, respectively. Full magnetic hyperfine field splitting is detected at 4.2 K with hyperfine fields of 17.4(1) and 18.3(2) T at the europium nuclei of EuAgMg and EuAuMg.
Visible-to-infrared quantum cutting by phonon-assisted energy transfer in YPO(4):Tm(3+), Yb(3+) phosphors.
Zheng, Wei; Zhu, Haomiao; Li, Renfu; Tu, Datao; Liu, Yongsheng; Luo, Wenqin; Chen, Xueyuan
Quantum cutting (QC) of one visible photon into two infrared ones has been reported for the lanthanide ion couple (Tm(3+), Yb(3+)) in a variety of host lattices. The mechanism responsible for QC was assumed to be a cooperative energy transfer (ET) process from Tm(3+) to two Yb(3+) ions, however, no solid evidence was presented. Herein we report visible-to-infrared QC for (Tm(3+), Yb(3+)) in YPO(4) phosphors. The ET process from the excited (1)G(4) level of Tm(3+) to Yb(3+) was investigated in detail by means of optical spectroscopy. By monitoring the steady-state photoluminescence (PL) and PL decay of the intermediate (3)F(4) level of Tm(3+) as a function of the Yb(3+) concentration, we demonstrated the QC of one incident blue photon into one near-infrared emitting photon at 1004 nm from Yb(3+) and simultaneously into one mid-infrared emitting photon at 1791 nm from Tm(3+), rather than two emitting photons from Yb(3+). It was revealed that such visible-to-infrared QC was induced by phonon-assisted ET instead of cooperative ET as previously reported. This kind of QC phosphors may have potential as solar spectral converters to enhance the external quantum efficiency in multi-junction solar cells based on narrow band-gap semiconductors such as Ge, PbS or In(1-x)Ga(x)N. PMID:22441530
Upconversion emission in antimony-germanate double-clad optical fiber co-doped with Yb3+/Tm3+ ions
NASA Astrophysics Data System (ADS)
Kochanowicz, M.; Dorosz, D.; Zmojda, J.; Miluski, P.; Dorosz, J.; Pisarska, J.; Pisarski, W. A.
In the paper upconversion luminescence properties in Yb3+/Tm3+ co-doped antimony-germanate glass and double-clad optical fiber were studied. The concentration of lanthanides, which has shown the highest upconversion emission intensity at 478 nm (1G4 ? 3H6) and 650 nm (1G4 ? 3F4), is 1Yb2O3/0.1Tm2O3 (mol%) as a result of exciting with a laser diode (976 nm). The lifetime of 2F5/2 (Yb3+) level decreases from 781 ?s to 71 ?s in the presence of Tm3+ 0.1-0.75 mol% respectively. Luminescence decay curve of glass co-doped with 1Yb2O3/0.75Tm2O3 suggests donor-donor fast migration followed by Tm3+ ? Yb3+ energy transfer. Glass characterized by highest intensity of upconversion luminescence (1Yb2O3/0.1Tm2O3 mol%) was used as core of double-clad optical fiber made by modified rod-in-tube method. Mechanisms influencing differences in upconversion amplified spontaneous emission of the fabricated optical fiber and bulk glass were discussed. Reabsorption of the amplified spontaneous emission signal along the fibre resulting from Tm3+:3H6 ? 1G4, transition was observed.
Structural waveguide co-doped with Yb3+/Tm3+ for measurement of chlorophyll concentration
NASA Astrophysics Data System (ADS)
Czajkowski, Karol; Kochanowicz, Marcin; Zmojda, Jacek; Szczykowska, Joanna; Dorosz, Dominik
In the article a system for measuring the concentration of chlorophyll in methanol solution have been developed. Microstructural waveguide co- doped with Yb3+/Tm3+ ions was used as a sensing element. The waveguide consisted of thirty-seven glass capillaries arranged hexagonally was fabricated using the stacking and drawing method. Due to the excitation of the active core by laser diode (?=980nm), an effective energy transfer between Yb3+ and Tm3+ ions occurs. As a result, two luminescence bands at 480 nm (1G4-->3H6) and 650 nm (1G4-->3F4) were obtained. Concentration of chlorophyll methanol solution in the range from 2.75 to 13.66 [mh/dms] was measured. Linear dependence of the decrease of luminescence intensity of thulium ions on its concentration was obtained. The sensitivity of the developed system was 0.005 [1/(mg/dm3)].
An Overview of 166Er, 169Tm and 170Yb M÷ssbauer Spectroscopy
NASA Astrophysics Data System (ADS)
Cadogan, J. M.; Ryan, D. H.
The hyperfine splittings of the nuclear energy levels in rare-earth (R) isotopes are sensitive measures of the complex interplay between magnetic exchange and electrostatic crystal-field interactions operating at the atomic level. M÷ssbauer spectroscopy has been used to great effect in the on-going investigation of these fundamental interactions in R compounds and in this paper we present an overview of 166Er, 169Tm and 170Yb M÷ssbauer spectroscopy. In particular, we derive expressions for the nuclear energy level splittings incorporating both magnetic and electric quadrupole interactions, using second-order perturbation theory. Such expressions provide a useful means of fitting experimental spectra and also yield criteria for determining whether or not a proposed set of energy level values is physical or not. We also present a number of useful rules of thumb for the analysis of 166Er, 169Tm and 170Yb M÷ssbauer spectra and, as such, this paper is in effect a Resource Letter.
Composition tuning the upconversion emission in NaYF4:Yb\\/Tm hexaplate nanocrystals
Hua Zhang; Yujing Li; Yungchen Lin; Yu Huang; Xiangfeng Duan
Single crystal hexagonal NaYF4:Yb\\/Tm nanocrystals have been synthesized with uniform size, morphology and controlled chemical composition. Spectroscopic studies show that these nanocrystals exhibit strong energy upconversion emission when excited with a 980 nm diode laser, with two primary emission peaks centered around 452 nm and 476 nm. Importantly, the overall and relative emission intensity at these wavelengths can be readily
Multicolor upconversion emission and energy transfer mechanism in Er3+/Tm3+/Yb3+ codoped tellurite glasses
NASA Astrophysics Data System (ADS)
Peng, Shengxi; Yang, Fengjing; Wu, Libo; Qi, Yawei; Zheng, Shichao; Yin, Dandan; Wang, Xunsi; Zhou, Yaxun
A novel Er3+, Tm3+ and Yb3+ codoped tellurite glasses with composition of TeO2-Bi2O3-ZnO-Na2O was prepared by conventional melt-quenching technique to realize the multicolor upconversion (UC) emissions. The absorption spectrum, UC emission spectrum, Raman spectrum, X-ray diffraction (XRD) and differential scanning calorimeter (DSC) curves were measured to characterize the prepared glass samples. Under the excitation of 980 nm laser diode (LD), bright multicolor luminescence composed of red, green and/or blue UC emissions corresponding to the transitions 4F9/2?4I15/2, 2H11/2(4S3/2)?4I15/2 of Er3+ and 1G4?3H6 of Tm3+ were observed in the Er3+/Yb3+, Tm3+/Yb3+ and Er3+/Tm3+/Yb3+ codoped glass samples, which were mainly attributed to the successive energy transfers from Yb3+ to Er3+ and Tm3+, respectively. The energy transfer mechanisms from the Yb3+:2F5/2 level to Er3+:4I11/2 and Tm3+:3H5 levels were further investigated by quantitatively calculating the energy transfer micro-parameters and phonon contribution ratios. Meanwhile, the difference (?T=Tx-Tg) between the glass crystallization onset temperature (Tx) and the transition temperature (Tg) which increase slightly with rare-earth (RE) doped concentration, was larger than 140 ░C for all glass samples. Furthermore, the amorphous nature of glass structure was demonstrated by the measured XRD curves. The excellent thermal stability and multicolor luminescent characteristic indicate that the present investigated Er3+/Tm3+/Yb3+ codoped tellurite glasses could be used in the fields of solid state multicolor displays and other luminescent devices.
Optical parameters and upconversion fluorescence in Tm3+/Yb3+-doped alkali-barium-bismuth-tellurite glasses.
Lin, Hai; Liu, Ke; Lin, Lin; Hou, Yanyan; Yang, Dianlai; Ma, Tiecheng; Pun, Edwin Yun Bun; An, Qingda; Yu, Jiayou; Tanabe, Setsuhisa
Tm(3+)/Yb(3+)-doped alkali-barium-bismuth-tellurite (LKBBT) glasses have been fabricated and characterized. Density, refractive index, optical absorption, absorption and emission cross-sections of Yb(3+), Judd-Ofelt parameters and spontaneous transition probabilities of Tm(3+) have been measured and calculated, respectively. Intense blue three-photon upconversion fluorescence and near-infrared two-photon upconversion fluorescence were investigated under the excitation of a 980 nm diode laser at room temperature. Wide infrared transmission window, high refractive index and strong blue three-photon upconversion emission of Tm(3+) indicate that Tm(3+)/Yb(3+) co-doped LKBBT glasses are promising upconversion optical and laser materials. PMID:16527521
Activation cross sections of the 169Tm(d,2n) reaction for production of the therapeutic radionuclide 169Yb.
Tßrkßnyi, F; Hermanne, A; Takßcs, S; Ditr¾i, F; Spahn, I; Kovalev, S F; Ignatyuk, A V; Qaim, S M
Activation cross sections of deuteron induced nuclear reactions on (169)Tm were measured up to 20 MeV by using the stacked-foil technique. Special emphasis was on production of the internal radiotherapy related radionuclide (169)Yb. No earlier experimental cross-section data on deuteron induced reactions on (169)Tm were found in the literature. The experimental data were compared with the results of the nuclear model codes ALICE-IPPE and EMPIRE-II. The integral yield of the (169)Tm(d,2n)(169)Yb reaction was deduced over the optimum energy range Ed = 20-->9 MeV. At 3.8 MBq/microA.h the yield is lower than that available from the commonly used (168)Yb(n,gamma) (169)Yb reactor method but on the other hand, it is higher than the yields from the earlier investigated (169)Tm(p,n)(169)Yb and (nat)Er(alpha,x) (169)Yb reactions. PMID:17353128
Synthesis, phase structure and up-conversion luminescence of NaYF4:Yb3+, Er3+/Tm3+ nanorods.
Liu, Yunxia; Liu, Baocang; Xu, Guangran; Wang, Qin; Hu, Wenting; Liu, Yang; Jia, Wenjing; Liu, Yongxin; Zhang, Jun
Upconversion luminescent NaYF4:Yb3+, Er3+/Tm3+ nanocrystals were successfully synthesized via a facile and one-pot solvothermal method using oleic acid/oleylamine (OA/OM) as surfactants. The effects of synthetic parameters including rare earth ion doping concentrations and temperatures on the crystal phase structure, size and shape of NaYF4:Yb3+, Er3+/Tm3+ nanocrystals were systematically investigated. By modulating the synthetic parameters, the shape of NaYF4:Yb3+, Er3+/Tm3+ nanocrystals were controlled in forms of nanorods and nanowires. The reaction temperature has large effects on the phase structure of NaYF4:Yb3+, Er+/Tm3+ nanorods, exhibiting a phase transformation from cubic phase (alpha-) in low temperatures to hexagonal phase (beta-) in high temperatures. Moreover, the upconversion luminescence of NaYF4:Yb3+, Er3+/Tm3+ nanocrystals was found to be dependent on the rare earth ion doping concentrations and temperatures. PMID:24734619
Visible to near-infrared downconversion in Tm3+/Yb3+ co-doped chalcohalide glasses for solar spectra converter
NASA Astrophysics Data System (ADS)
Huang, Fei; Chen, Liyan; Han, Ying; Tang, Junzhou; Nie, Qiuhua; Zhang, Peiqing; Xu, Yinsheng
Near-infrared downconversion which can be used to improve the utilization of solar spectral has drawn much attention. In this work, chalcohalide glasses with compositions of 50GeS2-25Ga2S3-25CsCl (in mol.%): 0.1 wt.% Tm2 S3 - x wt.% Yb2S3 (x = 0, 0.1, 0.2, 0.3) were synthesized by vacuumed melt-quenching method. Absorption spectra, emission spectra, excitation spectra, and decay measurements were performed to prove the occurrence of cooperative energy transfer from the 1G4 level of Tm3+ ions to two Yb3+ ions. Quantum efficiency depends on Yb3+ concentration is calculated, and the highest is 114.1%. The photon energy of Yb3+ emission around 1 ?m well matched with the operation band gap of the crystalline Si, so the glasses could potentially be applied in Si-based solar cell.
Thermoelectric properties of Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2}
Zhang, H. [Key Laboratory of Transparent Opto-Functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 200050 Shanghai (China); Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Str. 40, 01187 Dresden (Germany); Fang, L. [State Key Laboratory Breeding Base of Nonferrous Metals and Specific Materials Processing, Guilin University of Technology, Guilin 541004 (China); Tang, M.-B.; Man, Z. Y.; Chen, H. H.; Yang, X. X.; Zhao, J.-T. [Key Laboratory of Transparent Opto-Functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 200050 Shanghai (China); Baitinger, M.; Grin, Y. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, Noethnitzer Str. 40, 01187 Dresden (Germany)
The thermoelectric performance of EuCd{sub 2}Sb{sub 2} and YbCd{sub 2}Sb{sub 2} was improved by mixed cation occupation. The composition, structure, and thermoelectric properties of Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2} (x=0, 0.5, 0.75, and 1) have been investigated. Polycrystalline samples are prepared by direct reaction of the elements. Thermoelectric properties were investigated after densification of the materials by spark plasma sintering. Yb{sub x}Eu{sub 1-x}Cd{sub 2}Sb{sub 2} crystallizes in the P3m1 space group. The lattice parameters increase with the europium content. These materials show low electrical resistivity, high Seebeck coefficient, and low thermal conductivity together with high carrier concentration and high carrier mobility. ZT values of 0.88 and 0.97 are obtained for Yb{sub 0.5}Eu{sub 0.5}Cd{sub 2}Sb{sub 2} and Yb{sub 0.75}Eu{sub 0.25}Cd{sub 2}Sb{sub 2} at 650 K, respectively.
Quenching of the upconversion luminescence of NaYF4:Yb(3+),Er(3+) and NaYF4:Yb(3+),Tm(3+) nanophosphors by water: the role of the sensitizer Yb(3+) in non-radiative relaxation.
Arppe, Riikka; Hyppõnen, Iko; Perõlõ, Niina; Peltomaa, Riikka; Kaiser, Martin; W³rth, Christian; Christ, Simon; Resch-Genger, Ute; Schõferling, Michael; Soukka, Tero
We have studied the mechanisms of water-based quenching of the upconversion photoluminescence of upconverting nanophosphors (UCNPs) via luminescence decay measurements for a better understanding of the non-radiative deactivation pathways responsible for the relatively low upconversion luminescence efficiency in aqueous solutions. This included both upconversion luminescence measurements and the direct excitation of emissive energy states of Er(3+) and Yb(3+) dopants in NaYF4:Yb(3+),Er(3+) UCNPs by measuring the decays at 550 and 655 nm upon 380 nm excitation and at 980 nm upon 930 nm excitation, respectively. The luminescence intensities and decays were measured from both bare and silanized NaYF4:Yb(3+),Er(3+) and NaYF4:Yb(3+),Tm(3+) UCNPs in H2O and D2O. The measurements revealed up to 99.9% quenching of the upconversion photoluminescence intensity of both Er(3+) and Tm(3+) doped bare nanophosphors by water. Instead of the multiphonon relaxation of excited energy levels of the activators, the main mechanism of quenching was found to be the multiphonon deactivation of the Yb(3+) sensitizer ion caused by OH-vibrations on the surface of the nanophosphor. Due to the nonlinear nature of upconversion, the quenching of Yb(3+) has a higher order effect on the upconversion emission intensity with the efficient Yb-Yb energy migration in the ?35 nm nanocrystals making the whole nanophosphor volume susceptible to surface quenching effects. The study underlines the need of efficient surface passivation for the use of UCNPs as labels in bioanalytical applications performed in aqueous solutions. PMID:26104183
Properties of single crystalline AZn2Sb2 (A=Ca,Eu,Yb)
May, Andrew F [ORNL; McGuire, Michael A [ORNL; Ma, Jie [ORNL; Delaire, Olivier A [ORNL; Huq, Ashfia [ORNL; Custelcean, Radu [ORNL
Single crystals of CaZn{sub 2}Sb{sub 2}, EuZn{sub 2}Sb{sub 2}, and YbZn{sub 2}Sb{sub 2} were grown from melts of nominal composition AZn{sub 5}Sb{sub 5} (A = Ca,Eu,Yb) with the excess melt being removed at 1073 K. The electrical transport properties are consistent with those previously reported for polycrystalline samples. This confirms that the p-type carrier concentrations ranging from 2 x 10{sup 19} cm{sup -3} to -1 x 10{sup 20} cm{sup -3} are intrinsic to these materials. Also consistent with transport in polycrystalline materials, the carrier mobility is found to be lowest in CaZn{sub 2}Sb{sub 2}, suggesting the trends in mobility and thermoelectric efficiency within these compounds are inherent to the material systems and not due to inhomogeneity or impurities in polycrystalline samples. These results suggest CaZn{sub 2}Sb{sub 2} has the strongest coupling between the doping/defects and the electronic framework. Magnetization measurements reveal an antiferromagnetic transition near 13 K in EuZn{sub 2}Sb{sub 2}, and the observed magnetic anisotropy indicates the spins align parallel and anti-parallel to c in the trigonal lattice. Powder neutron diffraction on polycrystalline samples of CaZn{sub 2}Sb{sub 2} and YbZn{sub 2}Sb{sub 2} reveals smooth lattice expansion to 1000 K, with c expanding faster than a. The Debye temperatures calculated from specific heat capacity data and the isotropic displacement parameters are found to correlate with the carrier mobility, with the CaZn{sub 2}Sb{sub 2} displaying the largest Debye temperature and smallest mobility.
Thermal decomposition assisted synthesis and upconversion property of Fe3O4@YPO4:Tm/Yb hybrid nano-composite phosphor
NASA Astrophysics Data System (ADS)
Tiwari, S. P.; Kumar, K.; Rai, V. K.
Hybrid nano-composite phosphor has been successfully synthesized through thermal decomposition method. The dual phase of samples assigned by XRD analysis shows the formation of nano-composite with crystallite size 20 nm and 12 nm for YPO4: Tm/Yb and Fe3O4@YPO4:Tm/Yb respectively. The FESEM images show the spherical shape and non agglomerated formation of nanoparticles. Three bands in upconversion emission mode were found in intense blue at 472 nm, red at 662 nm and NIR at 798 nm regions corresponding to1G4 ? 3H6, 1G4 ? 3F4 and 3H4 ? 3H6 transition states respectively. The lifetime for1G4 ? 3H6 level is found 1150 microsecond and 1400 microsecond for YPO4: Tm/Yb and Fe3O4@YPO4:Tm/Yb samples respectively.
Colloidal synthesis and blue based multicolor upconversion emissions of size and composition controlled monodisperse hexagonal NaYF4 : Yb,Tm nanocrystals
Anxiang Yin; Yawen Zhang; Lingdong Sun; Chunhua Yan
Monodisperse beta-NaYF4 : Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800
Sensitized deep-ultraviolet up-conversion emissions of Gd3+ via Tm3+ and Yb3+ in hexagonal NaYF4 nanorods
Y. Y. Zhang; L. W. Yang; C. F. Xu; J. X. Zhong; C. Q. Sun
Deep-ultraviolet (UV) up-conversion (UC) emissions in the region of 270ś330 nm of Gd3+ under the excitation of a 980 nm laser diode in hexagonal Yb3+-Tm3+-Gd3+ triply doped NaYF4 nanorods synthesized using a hydrothermal method are reported. Spectral analyses indicate that the UV UC emissions originate from highly efficient energy transfer from Yb3+ to Tm3+, then to Gd3+ions, and the intensity
Tm3+/Er3+/Yb3+ tri-doped TeO2-PbF2-AlF3 glass for white-light-emitting diode
NASA Astrophysics Data System (ADS)
Ming, Chengguo; Song, Feng; Ren, Xiaobin; An, Liqun; Qin, Yueting
By the high temperature melting method, Er3+/Yb3+, Tm3+/Yb3+, and Tm3+/Er3+/Yb3+ co-doped oxyfluoride telluride glasses with the compositions of (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.2Er2O3), (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.5Tm2O3), and (50TeO2-30PbF2-20AlF3)+(5Yb2O3-0.2Er2O3-0.5Tm2O3) (mol%) were prepared. The emission spectra of the samples were measured under 975 nm excitation. The emission color of Tm3+/Er3+/Yb3+ tri-doped glass is white to the naked eye. The International Commission on Illumination (CIE) coordinates (0.353,0.308) of the sample are close to the equal energy white-light illumination standard (x=0.333,y=0.333) and the color temperature is 4381 K. Our research will be helpful in developing luminescent materials for white light-emitting-diodes (LEDs).
Multicolour upconversion emission from Ho3+-Tm3+-Yb3+ codoped CaMoO4 phosphor
NASA Astrophysics Data System (ADS)
Dey, Riya; Rai, Vineet Kumar
The Ho3+-Tm3+-Yb3+ codoped CaMoO4 phosphor powder has been synthesized by chemical coprecipitation technique. For the structural investigation the X-ray diffraction analysis has been done. Multicolour upconversion (UC) emission in the visible region from the prepared material has been observed under the 980 nm near infrared (NIR) excitation. The UC emission bands ś 474 nm (blue), ś 541 nm (green) and ś 661 nm (red) region have been assigned as 1G4?3H6 (Tm3+), 5F45S2?5I8 (Ho3+) and 5F5?5I8 (Ho3+) transitions respectively.
Upconversion spectroscopy and properties of NaYF 4 doped with Er 3 + , Tm 3 + and\\/or Yb 3 +
J. F. Suyver; J. Grimm; M. K. van Veen; D. Biner; K. W. Krõmer; H. U. G³del
A spectroscopic investigation of NaYF4 powders doped with several different concentrations of Er3+, Tm3+ and\\/or Yb3+ is described. Rare earth-doped NaYF4 is known to be a very efficient near-infrared to visible upconverter. The overview emission spectra for all samples are presented and from these the upconversion efficiency is calculated. Raman spectroscopy of undoped NaYF4 is presented here for the first
Synthesis of monodisperse hexagonal NaYF4:Yb, Ln (Ln = Er, Ho and Tm) upconversion nanocrystals in TOPO
Jingning Shan; Xiao Qin; Nan Yao; Yiguang Ju
NaYF4 doped with Yb, Ln (Ln = Er, Ho and Tm) upconversion nanocrystals (UP-NCs) were synthesized in trioctylphosphine oxide (TOPO) solvent via a thermolysis method. It was found that the energy barrier of the phase transition from cubic (alpha) to hexagonal (beta) was significantly reduced in TOPO, and the beta-phase NCs were obtained in a broad temperature window from 330
Color tunability with temperature and pump intensity in Yb3+/Tm3+ codoped aluminosilicate glass under anti-Stokes excitation.
Silva, W F; Eliel, G S N; dos Santos, P V; de Araujo, M T; Vermelho, M V D; Udo, P T; Astrath, N G C; Baesso, M L; Jacinto, C
Pump and thermally induced color tunabilities were demonstrated in Yb(3+)/Tm(3+) codoped low silica calcium aluminosilicate (LSCAS) glass under anti-Stokes excitation at 1.064 microm. The effects of pump intensity and sample's temperature on the upconversion emissions and mainly on the color tunabilities (from 800 to 480 nm) were investigated. The results revealed a 20- and a threefold reductions at 800/480 nm ratio as, respectively, the pump intensity and sample's temperature were increased from 27 to 700 kW/cm(2) and from 296 to 577 K. These behaviors with pump intensity and temperature (a strong increase of the 480 nm emission in comparison with the 800 nm one) were attributed to the several efficient processes occurring in the LSCAS system (Yb(3+)-->Tm(3+) energy-transfer processes, easy saturations of the Yb(3+) and Tm(3+) excited states, and radiative emissions). Besides these assigns, the temperature dependence is mainly assigned to the temperature-dependent effective absorption cross section of the ytterbium sensitizer through the so-called multiphonon-assisted anti-Stokes excitation process. Theoretical analyses and fits of the experimental data provided quantitative information. PMID:20649337
Intense white light emission in Tm3+/Er3+/Yb3+ co-doped Y2O3-ZnO nano-composite
NASA Astrophysics Data System (ADS)
Yadav, R. S.; Verma, R. K.; Rai, S. B.
The Tm3+/Er3+/Yb3+ co-doped Y2O3-ZnO nano-composite is synthesized using the solution combustion technique. The structural morphology is monitored using x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The Yb3+/Tm3+ co-doped nano-phosphor emits intense blue as well as weak red emissions, while Yb3+/Er3+ co-doped nano-phosphor emits strong green along with red emissions on excitation with 976 nm laser. Joining these together (i.e. Tm3+/Er3+/Yb3+ co-doped phosphor) give very strong white light, which is further verified by CIE coordinates (0.32, 0.36). The addition of ZnO with Y2O3 phosphor gives further enhancement in the intensity of white light. The possible reason for this enhancement is the removal of optical quenching sites.
Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass.
Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua
Eu(2+)-Yb(3+) co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu(2+) indicated the partition of Eu(2+) into FAP nanocrystals in glass ceramic. NIR emission due to the transition (2)F5/2?(2)F7/2 of Yb(3+) ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu(2+) to Yb(3+), which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu(2+)-Yb(3+) co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells. PMID:23816484
Preferential suppression of high-energy upconverted emissions of Tm3+ by Dy3+ ions in Tm3+/Dy3+/Yb3+-doped LiYF4 colloidal nanocrystals.
Mahalingam, Venkataramanan; Naccache, Rafik; Vetrone, Fiorenzo; Capobianco, John A
The intensity of high energy UV and blue upconverted emissions of Tm(3+) ions in Tm(3+)/Yb(3+) co-doped LiYF(4) colloidal nanocrystals was selectively reduced compared to the NIR emission at 802 nm. This was achieved by doping a small amount of Dy(3+) ions into the host matrix. PMID:21308114
Structural, electronic, mechanical and magnetic properties of rare earth nitrides REN (RE= Pm, Eu and Yb)
NASA Astrophysics Data System (ADS)
Murugan, A.; Rajeswarapalanichamy, R.; Santhosh, M.; Iyakutti, K.
The structural, electronic and mechanical properties of rare earth nitrides REN (RE=Pm, Eu and Yb) are investigated in NaCl and CsCl, and zinc blende structures using first principles calculations based on density functional theory. The calculated lattice parameters are in good agreement with the available results. Among the considered structures, these nitrides are most stable in NaCl structure. A pressure induced structural phase transition from NaCl to CsCl phase is observed in all these nitrides. The electronic structure reveals that these rare earth nitrides are half metallic at normal pressure. These nitrides are found to be covalent and ionic in the stable phase. The computed elastic constants indicate that these nitrides are mechanically stable and elastically anisotropic. Our results confirm that these nitrides are ferromagnetic in nature. A ferromagnetic to non-magnetic phase transition is observed at the pressures of 21.5 GPa and 46.1 GPa in PmN and YbN respectively.
MOLTEN SALT SYNTHESIS OF YF3:Yb3+/Ln3+(Ln = Er3+, Tm3+) MICROSHEETS WITH MULTICOLOR UPCONVERSION LUMINESCENCE
NASA Astrophysics Data System (ADS)
Ding, Mingye; Lu, Chunhua; Cao, Linhai; Ni, Yaru; Xu, Zhongzi
In this paper, highly crystalline YF3:Yb3+/Ln3+(Ln = Er3+, Tm3+) microsheets were successfully synthesized by a surfactant-free molten salt method for the first time. The results indicated that the as-obtained samples belonged to orthorhombic system and exhibited microsheets morphology with side lengths of 30 to 80 ?m and wall thickness from 1 to 1.5 ?m. By changing the dopant's species (Ln3+), multicolor (yellow and blue) upconversion emission can be observed in YF3:Yb3+/Ln3+ microsheets under 980 nm laser diode (LD) excitation. The upconversion mechanisms in co-doping YF3 samples were analyzed in detail based on the emission spectra. Importantly, this approach not only proposes a new alternative in synthesizing such materials, but also opens the possibility to meet the increasing commercial demand.
Upconversion luminescent property and EPR study of NaGdF4:Yb3+/Tm3+ synthesized by the hydrothermal method
NASA Astrophysics Data System (ADS)
Liu, Jing; Zhang, Jing-Ying; Liu, Kai; Gao, Hong-Jian; Yu, Xiao-Long; Cao, Yang; Liu, Zhong-Xin
Water soluble upconversion (UC) luminescence hexagonal-phase NaGdF4: Yb3+/Tm3+ nanoparticles have been successfully synthesized by the hydrothermal method. XRD, SEM, UC photoluminescence spectra and electron paramagnetic resonance (EPR) spectrum were used to characterize the nanoparticles. The intensity of UC emission region could be controlled through different sodium source and the fluorine source, 6PJ?8S7/2 emission of Gd3+ is also observed at 310 nm. A broad spectrum with a dominant resonance at g of about 2 was observed by the EPR spectrum of the NaGdF4:Yb3+/Tm3+ nanoparticles. The transparent NaGdF4:Yb3+/Tm3+ solution presented naked eye-visible violet-blue light under the 980 nm LD excitation. The current work paves the way for their potential application in infrared tomography and magnetic resonance imaging (MRI).
Intense NIR emissions at 0.8 ?m, 1.47 ?m, and 1.53 ?m from colloidal LiYbF4:Ln(3+) (Ln = Tm(3+) and Er(3+)) nanocrystals.
Sarkar, Shyam; Adusumalli, Venkata N K B; Mahalingam, Venkataramanan; Capobianco, John A
We report on the synthesis of diamond shaped Ln(3+)-doped LiYbF4 (Ln = Tm and Er) nanocrystals with flat edges via the thermal decomposition method. Strong near-infrared emissions at 0.8 ?m, 1.47 ?m and 1.53 ?m are observed from colloidal dispersions of Tm(3+)-doped and Er(3+)-doped LiYbF4 nanocrystals, respectively, under 0.98 ?m diode laser excitation. The NIR emission intensities for Tm(3+)-doped and Er(3+)-doped LiYbF4 nanocrystals are comparable with those of the sodium counterpart NaYbF4, suggesting that LiYbF4 is also an excellent host matrix for lanthanide ions to obtain strong NIR emissions in colloidal solutions of LiYbF4 (Tm(3+) or Er(3+)) nanocrystals. PMID:26096921
Simultaneous size and luminescence control of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) microcrystals via Li+ doping
NASA Astrophysics Data System (ADS)
Lin, Hao; Xu, Dekang; Teng, Dongdong; Yang, Shenghong; Zhang, Yueli
Enhancement of upconversion (UC) luminescence is imperative for the applications of UC microcrystals (MCs). In this work, NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping were successfully prepared by a simple hydrothermal process with the assistance of citric acid. The UC luminescence intensities of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) are significantly enhanced via Li+ doping at different concentrations. Compared to Li+-absent sample, UC luminescence intensities of blue emission (477 nm) and red emission (649 nm) in NaYF4:Yb3+/Tm3+ MCs via 15 mol% Li+ doping are improved by 10 and 9 times, respectively; UC luminescence intensities of green emission (538 nm) and red emission (644 nm) in NaYF4:Yb3+/Ho3+ MCs via 15 mol% Li+ doping are improved by 12 and 3 times, respectively. The mechanism of the enhancement via Li+ doping is discussed in details, which may be attributed to the fact that Li+ doping can cause the distortion of the local symmetry around RE ions. Our results indicate that the enhanced UC luminescence of NaYF4:Yb3+/RE3+ (RE = Tm, Ho) MCs via Li+ doping may have potential applications in optoelectronic devices such as solar cells and plasma display panel.
Hydrothermal synthesis of Yb3+, Tm3+ co-doped Gd6MoO12 and its upconversion properties
NASA Astrophysics Data System (ADS)
Di, Qiu-Mei; Sun, Yu-Mei; Xu, Qi-Guang; Han, Liu; Xue, Bing; Sun, Jia-Yue
Yb3+, Tm3+ co-doped Gd6MoO12 phosphors with different morphologies are prepared by the hydrothermal method. The dendrites present different morphologies (including hexagonal prisms, spindles, and spheres) after changing the pH value and edetate disodium (EDTA) usage. It is found that each of the two factors plays a crucial role in forming different morphologies. The up-conversion (UC) luminescence is studied. Under 980-nm semiconductor laser excitation, relatively strong blue emission and weak red emission are observed. Finally, the effect of pumping power on the UC luminescence properties and the level diagram mechanism of Gd6MoO12:Yb3+/Tm3+ phosphor are also discussed. Project supported by the National Natural Science Foundation of China (Grant No.Ā20976002), the Beijing Natural Science Foundation, China (Grant No.Ā2122012), the Key Projects for Science and Technology of Beijing Education Commission, China (Grant No.ĀKZ201310011013), and the Education and Research Fund of Guangdong Province, China (Grant No.Ā2011B090400100).
Intense ultraviolet and blue upconversion emissions in Yb 3+-Tm 3+ codoped stoichiometric Y 7O 6F 9 powder
NASA Astrophysics Data System (ADS)
Ma, Mo; Xu, Changfu; Yang, Liwen; Ren, Guozhong; Lin, Jianguo; Yang, Qibin
Stoichiometric Y 7O 6F 9 powder codoped with Yb 3+-Tm 3+ was synthesized via co-precipitation and subsequent calcining route. The results of X-ray diffraction and transmission electron microscopy reveal that when the calcining temperature is beyond 800 ░C, orthorhombic YF 3 nanoparticles can be completely oxidized into orthorhombic Y 7O 6F 9 powder. Under the excitation of a 980 nm laser, Y 7O 6F 9 powder exhibits multicolor UC emission in regions spanning the UV to the NIR. In addition, the upconversion emission intensities of YF 3, Y 7O 6F 9 and Y 2O 3 powders were compared under the same dopant condition (Yb/Tm=5/0.5 mol%). The low phonon energy revealed by Raman spectra helped to understand the high efficient upconversion emission of Y 7O 6F 9 and the main phonon vibration of Y 7O 6F 9 lies at 472 cm -1, which is far lower that of Y 2O 3 (at 708 cm -1). Our results indicate that orthorhombic rare earth ions doped Y 7O 6F 9 is an efficient matrix for UV and blue UC emission, and has potential applications in color displays, anti-counterfeiting and multicolor fluorescent labels.
Hall and transverse even effects in the vicinity of a quantum critical point in Tm{sub 1-x}Yb{sub x}B{sub 12}
Sluchanko, N. E., E-mail: email@example.com; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Anisimov, M. A. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Levchenko, A. V.; Filipov, V. B.; Shitsevalova, N. Yu. [National Academy of Sciences of Ukraine, Frantsevich Institute for Problems of Materials Science (Ukraine)
The angular, temperature, and magnetic field dependences of the resistance recorded in the Hall effect geometry are studied for the rare-earth dodecaboride Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions where the metal-insulator and antiferromagnetic-paramagnetic phase transitions are observed in the vicinity of the quantum critical point x{sub c} Almost-Equal-To 0.3. The measurements performed on high-quality single crystals in the temperature range 1.9-300 K for the first time have revealed the appearance of the second harmonic contribution, a transverse even effect in these fcc compounds near the quantum critical point. This contribution a is found to increase drastically both under the Tm-to-ytterbium substitution in the range x > x{sub c} and with an increase in the external magnetic field. Moreover, as the Yb concentration x increases, a negative peak of a significant amplitude appears on the temperature dependences of the Hall coefficient R{sub H}(T) for the Tm{sup 1-x}Yb{sub x}B{sub 12} compounds, in contrast to the invariable behavior R{sub H}(T) Almost-Equal-To const found for TmB{sub 12}. The complicated activation-type behavior of the Hall coefficient is observed at intermediate temperatures for x {>=} 0.5 with activation energies E{sub g}/k{sub B} Almost-Equal-To 200 K and E{sub a}/k{sub B} 55-75 K, and the sign inversion of R{sub H}(T) is detected at liquid-helium temperatures in the coherent regime. Renormalization effects in the electron density of states induced by variation of the Yb concentration are analyzed. The anomalies of the charge transport in Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions in various regimes (charge gap formation, intra-gap many-body resonance, and coherent regime) are discussed in detail and the results are interpreted in terms of the electron phase separation effects in combination with the formation of nanosize clusters of rare earth ions in the cage-glass state of the studied dodecaborides. The data obtained allow concluding that the emergence of Yb-Yb dimers in the Tm{sub 1-x}Yb{sub x}B{sub 12} cage-glass matrix is the origin of the metal-insulator transition observed in the achetypal strongly correlated electron system of YbB{sub 12}.
The action mechanism of TiO2:NaYF4:Yb3+,Tm3+ cathode buffer layer in highly efficient inverted organic solar cells
NASA Astrophysics Data System (ADS)
Liu, Chunyu; Chen, Huan; Zhao, Dan; Shen, Liang; He, Yeyuan; Guo, Wenbin; Chen, Weiyou
We report the fabrication and characteristics of organic solar cells with 6.86% power conversion efficiency (PCE) by doping NaYF4:Yb3+,Tm3+ into TiO2 cathode buffer layer. The dependence of devices performance on doping concentration of NaYF4:Yb3+,Tm3+ is investigated. Results indicate that short-circuit current density (Jsc) has an apparent improvement, leading to an enhancement of 22.7% in PCE for the optimized doping concentration of 0.05 mmol ml-1 compared to the control devices. NaYF4:Yb3+,Tm3+ nanoparticles (NPs) can play threefold roles, one is that the incident light in visible region can be scattered by NaYF4 NPs, the second is that solar irradiation in infrared region can be better utilized by Up-conversion effect of Yb3+ and Tm3+ ions, the third is that electron transport property in TiO2 thin film can be greatly improved.
Measurements of activation cross sections for 175Lu(n, ?) 172Tm, 176Lu(n, ?) 173Tm and 175Lu(n, p) 175m+gYb reactions induced by neutrons around 14 MeV
Junhua Luo; Fei Tuo; Xiangzhong Kong
The cross sections for the 175Lu(n,?)172Tm, 176Lu(n,?)173Tm and 175Lu(n,p)175m+gYb reactions have been measured in the neutron energy range of 13.5¢14.8MeV using the activation technique. The first data for 175Lu(n,?)172Tm reaction cross sections are presented. In our experiment, the fast neutrons were produced via the 3H(d,n)4He reaction on K-400 Neutron Generator at Chinese Academy of Engineering Physics (CAEP). Induced gamma activities
Frequency upconversion luminescence from Yb{sup +3}-Tm{sup +3} codoped PbO-GeO{sub 2} glasses containing silver nanoparticles
Assumpcao, Thiago A. A.; Silva, Davinson M. da [Departamento de Engenharia de Sistemas Eletronicos, Escola Politecnica da USP, 05508-900 Sao Paulo, SP (Brazil); Kassab, Luciana R. P. [Laboratorio de Vidros e Datacao, Faculdade de Tecnologia de Sao Paulo (FATEC-SP), CEETEPS/UNESP, 01124-060 Sao Paulo, SP (Brazil); Araujo, Cid B. de [Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)
Infrared-to-visible and infrared-to-infrared frequency upconversion processes in Yb{sup 3+}-Tm{sup 3+} doped PbO-GeO{sub 2} glasses containing silver nanoparticles (NPs) were investigated. The experiments were performed by exciting the samples with a diode laser operating at 980 nm (in resonance with the Yb{sup 3+} transition {sup 2}F{sub 7/2}->{sup 2}F{sub 5/2}) and observing the photoluminescence (PL) in the visible and infrared regions due to energy transfer from Yb{sup 3+} to Tm{sup 3+} ions followed by excited state absorption in the Tm{sup 3+} ions. The intensified local field in the vicinity of the metallic NPs contributes for enhancement in the PL intensity at 480 nm (Tm{sup 3+}:{sup 1}G{sub 4}->{sup 3}H{sub 6}) and at 800 nm (Tm{sup 3+}:{sup 3}H{sub 4}->{sup 3}H{sub 6}).
Intermetallics as zintl phases: Yb2Ga4Ge6 and RE3Ga4Ge6 (RE=Yb, Eu): structural response of a [Ga4Ge6]4- framework to reduction by two electrons.
Zhuravleva, Marina A; Salvador, James; Bilc, Daniel; Mahanti, Subhendra D; Ireland, John; Kannewurf, Carl R; Kanatzidis, Mercouri G
Two new intermetallic compounds, Yb(2)Ga(4)Ge(6) and Yb(3)Ga(4)Ge(6), were obtained from reactions in molten Ga. A third compound, Eu(3)Ga(4)Ge(6), was produced by direct combination of the elements. The crystal structures of these compounds were studied by single-crystal X-ray diffraction. Yb(2)Ga(4)Ge(6) crystallizes in an orthorhombic cell with a=4.1698(7), b=23.254(4), c=10.7299(18) A in the polar space group Cmc2(1). The structure of RE(3)Ga(4)Ge(6) is monoclinic, space group C2/m, with cell parameters a=23.941(6), b=4.1928(11), c=10.918(3) A, beta=91.426(4) degrees for RE=Yb, and a=24.136(2), b=4.3118(4), c=11.017(1) A, beta=91.683(2) degrees for RE=Eu. The refinement [I>2 sigma(I)] converged to the final residuals R(1)/wR(2)=0.0229/0.0589, 0.0411/0.1114, and 0.0342/0.0786 for Yb(2)Ga(4)Ge(6), Yb(3)Ga(4)Ge(6), and Eu(3)Ga(4)Ge(6), respectively. The structures of these two families of compounds can be described by a Zintl concept of bonding, in which the three-dimensional [Ga(4)Ge(6)](n-) framework serves as a host and electron sink for the electropositive RE atoms. The structural relation of RE(3)Ga(4)Ge(6) to of Yb(2)Ga(4)Ge(6) lies in a monoclinic distortion of the orthorhombic cell of Yb(2)Ga(4)Ge(6) and reduction of the [Ga(4)Ge(6)] network by two electrons per formula unit. The results of theoretical calculations of the electronic structure, electrical transport data, and thermochemical and magnetic measurements are also reported. PMID:15224328
Au nanorod decoration on NaYF?:Yb/Tm nanoparticles for enhanced emission and wavelength-dependent biomolecular sensing.
Kannan, Palanisamy; Abdul Rahim, Ferhan; Chen, Rui; Teng, Xue; Huang, Ling; Sun, Handong; Kim, Dong-Hwan
We introduce gold nanorods (GNRs) decoration on NaYF4:Yb/Tm upconversion nanocrystals (UCNCs) by functionalizing the UCNCs with polyamidoamine generation 1 (PAMAM G1) dendrimer, followed by a single-step seed-mediated growth of long-range GNRs to enhance "biological window" upconversion emission. The up-conversion emission of GNR-decorated UCNCs can be enhanced beyond the level typically obtainable using shell-like structures up to 27-fold enhancement. Also, the enhancement can be tuned at different wavelength regions by varying the GNR aspect ratio. The GNR-decorated UCNC is further modified with 2-thiouracil for nonenzymatic detection of uric acid, revealing a detection limit as 1 pM. PMID:23591121
White light generation by frequency upconversion in Tm3+/Ho3+/Yb3+-codoped fluorolead germanate glass
NASA Astrophysics Data System (ADS)
Gouveia-Neto, A. S.; Bueno, L. A.; do Nascimento, R. F.; da Silva, E. A.; da Costa, E. B.; do Nascimento, V. B.
White light was produced exploiting an additive synthesis of red, green, and blue fluorescence through frequency upconversion in fluorolead-germanate glass codoped with Ho3+, Tm3+, and Yb3+. The 475, 540, and 650nm signals were, respectively, assigned to thulium (G41-H63) and holmium (S25;F45)?I85 and F55?I85, excited via energy tranfer from ytterbium. The dopant concentrations were adjusted, yielding the emission of a wide color gamut in the visible spectrum and the production of white light using excitation at 975nm. The spectral positions and purity (blue, 97%; green, 100%; red, 95%) of the three colors produced CIE-X =0.3438 and CIE-Y =0.3639 coordinates.
Investigation on upconversion luminescence properties of Gd2O3: Ho3+/Yb3+/Tm3+ nanotubes
NASA Astrophysics Data System (ADS)
Ye, Fei; Fang, Yu; Liu, Xiao-bo; Xu, Fang; Song, Ying-lin
Lanthanide doped oxides nano materials have novel optical, physical and structural properties. Cubic Ho3+-Yb3+-Tm3+ co-doped Gd2O3 nanotubes are synthetize by a simple wet-chemical route at low temperature and ambient pressure followed by subsequent annealing heat treatment in muffle furnace. Nanotubes are formed by adjusting the pH value of reacting solution. The introduction of Yb3+ leads to strong visible upconversion luminescence and change the intensity ratio of the green, blue and red luminescence. In trichromatic laser display, research of how to enhance blue light is in the bottleneck period. In the experiment, the blue emission has been successfully improved. In certain doping ratio, distinct enhancement of blue emission and obvious degradation of green light have been observed, which is discussed in detail. X-Ray powder diffraction (XRD), scanning electron microscope (SEM) and upconversion (UC) emission spectra are used to characterize the sample. Strong and adjusted upconversion luminescence determine that the nano material is a potential candidate for applications of biological probe, color displays, lighting and photonics.
Synthesis, structure, magnetism, and optical properties of theordered mixed-lanthanide sulfides gamma-LnLn'S3 (Ln=La, Ce; Ln'=Er, Tm,Yb)
Jin, G.B.; Choi, E.S.; Guertin, R.P.; Brooks, J.S.; Bray, T.H.; Booth, C.H.; Albrecht-Schmitt, T.E.
{gamma}-LnLn{prime}S{sub 3} (Ln = La, Ce; Ln{prime} = Er, Tm, Yb) have been prepared as dark red to black single crystals by the reaction of the respective lanthanides with sulfur in a Sb{sub 2}S{sub 3} flux at 1000 C. This isotypic series of compounds adopts a layered structure that consists of the smaller lanthanides (Er, Tm, and Yb) bound by sulfide in six- and seven-coordinate environments that are connected together by the larger lanthanides (La and Ce) in eight- and nine-coordinate environments. The layers can be broken down into three distinct one-dimensional substructures containing three crystallographically unique Ln{prime} centers. The first of these is constructed from one-dimensional chains of edge-sharing [Ln{prime}S{sub 7}] monocapped trigonal prisms that are joined to equivalent chains via edge-sharing to yield ribbons. There are parallel chains of [Ln{prime}S{sub 6}] distorted octahedra that are linked to the first ribbons through corner-sharing. These latter units also share corners with a one-dimensional ribbon composed of parallel chains of [Ln{prime}S{sub 6}] polyhedra that edge-share both in the direction of chain propagation and with adjacent identical chains. Magnetic susceptibility measurements show Curie-Weiss behavior from 2 to 300 K with antiferromagnetic coupling, and no evidence for magnetic ordering. The {theta}{sub p} values range from -0.4 to -37.5 K, and spin-frustration may be indicated for the Yb-containing compounds. All compounds show magnetic moments substantially reduced from those calculated for the free ions. The optical band gaps for {gamma}-LaLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.6 eV, whereas {gamma}-CeLn{prime}S{sub 3} (Ln{prime} = Er, Tm, Yb) are approximately 1.3 eV.
Eu/sup 2 +/, Yb/sup 2 +/, and Es/sup 2 +/ coordination with sodium tetraphenylborate in water-ethanol solutions
Mikheev, N.B.; Kulyukhin, S.A.; Rumer, I.A.; Kamenskaya, A.N.
Measurements have been made on the coordination of divalent lanthanoid s and actinoids with sodium tetraphenylborate (NaTPB) in water-ethanol solutions. Ln/sup 2 +/ and An/sup 2 +/ form cationic and neutral complexes. The coordination constants ..beta../sub 1/ and ..beta../sub 2/ have been determine: 6.5 and 25.7 for Yb/sup 2 +/, 1.7 and 52.7 for Eu/sup 2 +/, and 6.2 and 106.4 for Es/sup 2 +/. The trend indicates that the hydrated Es/sup 2 +/ is smaller than Yb/sup 2 +/ and Eu/sup 2 +/.
Near-infrared to visible upconversion in Tm3+ and Yb3+ codoped Lu2O3 nanocrystals synthesized by hydrothermal method.
Li, Li; Zhang, Xingli; Wei, Xiantao; Wang, Guangchuan; Guo, Changxin
Lutetium oxide nanocrystals codoped with Tm3+ and Yb3+ have been successfully synthesized via adjusting the pH values of the precursor solution in a hydrothermal method followed by a subsequent calcination process. The samples were systematically characterized by X-ray diffraction, field-emission scanning microscopy, Fourier transform infrared transmittance spectroscopy, and upconversion luminescent spectra. The experimental results show that the pH values of the precursor solution have great effects on the structural, morphological, and upconversion luminescent properties of Lu2O3:2%Yb3+, 0.2%Tm3+ nanocrystals. The as-formed lutetium oxide precursors could transform to cubic Lu2O3 with the same morphology and a slight shrinkage in size after a calcination process. The upconversion emission intensity of Lu2O3:2%Yb3+, 0.2%Tm3+ nanocrystals obtained from the precursor solution with pH = 9 is the strongest. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing the number of OH- groups and the enlarged nanocrystals size. Strong blue and weak red emissions from the prepared nanocrystals were observed under 980 nm laser excitation, which were attributed to the 1G4 --> 3H6 and 1G4 --> 3F4 transitions of Tm3+ ion, respectively. PMID:24738389
Spectroscopic properties and mechanism of Tm3+/Er3+/Yb3+co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals
NASA Astrophysics Data System (ADS)
Hu, Yue-Bo; Qiu, Jian-Bei; Zhou, Da-Cheng; Song, Zhi-Guo; Yang, Zheng-Wen; Wang, Rong-Fei; Jiao, Qing; Zhou, Da-Li
Transparent Tm3+/Er3+/Yb3+ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode (LD), compared with the glass before heat treatment, the Tm3+/Er3+/Yb3+co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark-split peaks; X-ray diffraction (XRD) and transmission electron microscope (TEM) results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm3+, Er3+ and (or) Yb3+ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm3+, Er3+ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.
Multifunctional SiO2@Gd2O3:Yb/Tm hollow capsules: controllable synthesis and drug release properties.
Yang, Guixin; Lv, Ruichan; Gai, Shili; Dai, Yunlu; He, Fei; Yang, Piaoping
A series of hollow and luminescent capsules have been fabricated by covering luminescent Gd2O3:Yb/Tm nanoparticles on the surface of uniform hollow mesoporous silica capsules (HMSCs), which were obtained from an etching process using Fe3O4 as hard templates. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), up-conversion (UC) fluorescence spectra, and N2 adsorption-desorption were used to characterize these samples. It is found that the as-prepared products have mesoporous pores, large specific surface, and high dispersity. In particular, the size, shape, surface area, and interior space of the composites can be finely tuned by adjusting the size and morphology of the magnetic cores. Under 980 nm near-infrared (NIR) laser irradiation, the composites show characteristic blue UC emissions of Tm(3+) even after carrying doxorubicin hydrochloride (DOX). The drug-release test reveals that the capsules showed an apparent sustained release character and released in a pH-sensitive manner. Interestingly, the UC luminescence intensity of the drug-carrying system increases with the released DOX, realizing the possibility to track or monitor the released drug by the change of UC fluorescence simultaneously, which should be highly promising in anticancer drug delivery and targeted cancer therapy. PMID:25285784
Colour emission tunability in Ho3+-Tm3+-Yb3+ co-doped Y2O3 upconverted phosphor
NASA Astrophysics Data System (ADS)
Pandey, Anurag; Rai, Vineet Kumar
The frequency upconversion (UC) emission throughout the visible region from the Y2O3:Ho3+-Tm3+-Yb3+ co-doped phosphors synthesized by using low temperature combustion process upon excitation with a diode laser operating at 980 nm have been presented. The colour emission tunability in co-doped phosphor has been observed on increasing the pump power and seen by the naked eyes. The tunability in colour emission has also been visualized by CIE chromaticity diagram. The variation in UC emission intensity of the 1G4 ? 3H6 (Tm3+) and 5F3 ? 5I8 (Ho3+) transitions lying in the blue region has been monitored with increase in the pump power and marked that their ratio can be used to determine the temperature. The developed phosphor has been used to record fingerprints. The observed most intense visible colour emission from the developed material may be used for photodynamic therapy and as an alternative of traditional fluorescent biolabels.
Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method
Gavrilovi?, Tamara V.; Jovanovi?, Dragana J.; Lojpur, Vesna; Drami?anin, Miroslav D.
Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4?nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980?nm) into visible green light. The ratio of green emissions from 2H11/2 ? 2I15/2 and 4S3/2 ? 4I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K?1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers. PMID:24572638
Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K 3 RESi 2O 7 ( RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)
Ioana Vidican; Mark D. Smith; Hans-Conrad zur Loye
Single crystals of K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K3RESi2O7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal
Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)
Ioana Vidican; Mark D. Smith; Hans-Conrad Zur Loye
Single crystals of K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K3RESi2O7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal
Highly efficient Yb3+/Tm3+ co-doped NaYF4 nanotubes: Synthesis and intense ultraviolet to infrared up-conversion luminescence
NASA Astrophysics Data System (ADS)
Zhang, Y. Y.; Wang, Y.; Deng, J. Q.; Wang, J.; Ni, S. C.
Nanocrystals of up-conversion (UC) phosphor Yb3+/Tm3+ co-doped NaYF4 are prepared by a facile hydrothermal method using oleic acid as a stabilizing agent. The as-prepared nanocrystals are of hexagonal phase, and have tube-like morphology and strong ultraviolet (UV) and blue UC fluorescence intensity, which have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectroscopy. The effect of Yb3+ concentration on the UC emission properties is also analyzed. Our results reveal that the intensity of emission peaks can be controlled by varying the Yb3+ concentration and these NaYF4 nanotubes are highly efficient host material. The as-prepared NaYF4 nanotubes show potential applications in UV compact solid state lasers and multi-channel fluorescent label.
Sensitized deep-ultraviolet up-conversion emissions of Gd3+ via Tm3+ and Yb3+ in hexagonal NaYF4 nanorods
NASA Astrophysics Data System (ADS)
Zhang, Y. Y.; Yang, L. W.; Xu, C. F.; Zhong, J. X.; Sun, C. Q.
Deep-ultraviolet (UV) up-conversion (UC) emissions in the region of 270ś330 nm of Gd3+ under the excitation of a 980 nm laser diode in hexagonal Yb3+-Tm3+-Gd3+ triply doped NaYF4 nanorods synthesized using a hydrothermal method are reported. Spectral analyses indicate that the UV UC emissions originate from highly efficient energy transfer from Yb3+ to Tm3+, then to Gd3+ions, and the intensity of the emission as well as the ratios of the emission peaks are strongly dependent on the doping concentrations and pump power. The materials are envisioned to have potential applications in anti-counterfeiting, optical and magnetic dual modal nanoprobes for biomedicine, solution-based scintillator materials and UV compact solid-state lasers.
High-efficient near-infrared quantum cutting based on broadband absorption in Eu2+-Yb3+ co-doped glass for photovoltaic applications
NASA Astrophysics Data System (ADS)
Liu, Zijun; Dai, Nengli; Yang, Luyun; Li, Jinyan
We report that Eu2+-Yb3+ system with high luminescent quantum efficiency and broadband excitation could be playing a significant role in solar cells. This borosilicate glass used as conversion layer can efficiently minimize the energy loss of thermalization. The cooperative energy transfer between Eu2+ and Yb3+ realized the emission of greenish and near-infrared light simultaneously with the blue light of xenon lamp excitation. The emission peaks located at 980 nm and 1,030 nm are the characteristic emission of Yb3+ with the energy matches well with the bandgap of silicon solar cells. The luminescent quantum efficiency is up to 163.5 % with the radiation rate being considered. Given the broad excitation band, high quantum efficiency and excellent mechanical, thermal and chemical stability, this system can be useful as down-conversion layer for solar cells.
> Upconversion Nanophosphors (UCNPs) areYb, Ln (Er, Tm, and Ho) doped into hosts of NaYF4, LaF3, Y2O3,
Petta, Jason
> Upconversion Nanophosphors (UCNPs) areYb, Ln (Er, Tm, and Ho) doped into hosts of NaYF4, LaF3, Y2 by multi excitation. > Prof. Ju'sgroup hasdeveloped NaYF4 based UCNPs. Optimizing BlueEmission Up of 20% Yband 2% Er isdoped into the NaYF4 structure. (authorized) (e.g.2) For blue emissions, an ion
Effect of Li{sup +} ions on enhancement of near-infrared upconversion emission in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals
Li Dongyu [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Department of Physics, Zhanjiang Normal College, Zhanjiang 524048 (China); Wang Yuxiao; Zhang Xueru; Dong Hongxing; Shi Guang [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Liu Lu [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); School of Science, Harbin Engineering University, Harbin 150001 (China); Song Yinglin [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); School of Physical Science and Technology, Suzhou University, Suzhou 215006 (China)
Near-infrared (NIR) to NIR upconversion emission is investigated in Tm{sup 3+}/Yb{sup 3+}/Li{sup +} triply doped Y{sub 2}O{sub 3} nanocrystals. Li{sup +} ions doped in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals can greatly enhance the NIR upconversion emission intensity of Tm{sup 3+} ions. The abnormal shift of the (222) diffraction peak position determined from x-ray diffraction measurements is discussed, by introducing Li{sup +} ions in the Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals. The cause of the enhancement is the modification of the local symmetry induced by the Li{sup +} ions, which increases the intra-4f transitions of Tm{sup 3+} ion. Li{sup +} ions doped in Y{sub 2}O{sub 3}:Tm{sup 3+}/Yb{sup 3+} nanocrystals also can reduce the OH groups, dissociate the Yb{sup 3+} and Tm{sup 3+} ion clusters, and create the oxygen vacancies, which are the other reasons for enhancing the upconversion emission intensities. This material may be promising for in vitro and in vivo bioimaging probes.
White upconversion emission in Y{sub 2}O{sub 3}:Er{sup 3+}¢Tm{sup 3+}¢Yb{sup 3+}phosphor
Rai, Vineet Kumar, E-mail: email@example.com [Laser and Spectroscopy Laboratory, Department of Applied Physics, Indian School of Mines, Dhanbad 826004, Jharkhand (India); Dey, Riya; Kumar, Kaushal [Laser and Spectroscopy Laboratory, Department of Applied Physics, Indian School of Mines, Dhanbad 826004, Jharkhand (India)
Graphical abstract: Schematic energy level diagram of Er{sup 3+}¢Yb{sup 3+}¢Tm{sup 3+} system upon excitation at 980 nm. Highlights: ? Prepared the Er{sup 3+}¢Tm{sup 3+}¢Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor. ? Excitation of the sample by 980 nm diode laser is studied. ? Explored the possibility of getting white light emission from the synthesized phosphor. ? Colour tunability of the prepared phosphor is studied. ? Temperature sensing behaviour is investigated using FIR studied. - Abstract: Er{sup 3+}¢Tm{sup 3+}¢Yb{sup 3+} codoped Y{sub 2}O{sub 3} phosphor has been synthesized by optimized combustion synthesis process and its white light upconversion emission property is investigated using cheap 980 nm diode laser excitation. Efficient red, green and blue light emission bands, necessary for attaining white light emission, are observed in the codoped sample. The concentration of each rare earth ion is adjusted to get the required emission. In this phosphor, interestingly, emission colour coordinates are found to almost independent on the excitation power density. The temperature sensing behaviour of the prepared samples has also been studied using fluorescence intensity ratio (FIR) technique.
Specific features of magnetoresistance during the antiferromagnet-paramagnet transition in Tm{sub 1-x}Yb{sub x}B{sub 12}
Sluchanko, N. E., E-mail: firstname.lastname@example.com; Azarevich, A. N.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Levchenko, A. V.; Filippov, V. B.; Shitsevalova, N. Yu. [National Academy of Sciences of Ukraine, Institute of Problems of Materials Science (Ukraine)
The transverse magnetoresistance {Delta}{rho}/{rho}(H, T) of Tm{sub 1-x}Yb{sub x}B{sub 12} single crystals is studied in the ytterbium concentration range corresponding to the antiferromagnet-paramagnet transition in a magnetic field up to 80 kOe at low temperatures. A magnetic H-T phase diagram is constructed for the antiferromagnetic state of substitutional Tm{sub 1-x}Yb{sub x}B{sub 12} solid solutions with x {<=} 0.1. The contributions to the magnetoresistance in the antiferromagnetic and paramagnetic phases of the dodecaborides under study are separated. Along with negative quadratic magnetoresistance -{Delta}{rho}/{rho} {proportional_to} H{sub 2}, the magnetically ordered phase of these compounds is found to have component {Delta}{rho}/{rho} {proportional_to} H that linearly changes in a magnetic field. The negative contribution to the magnetoresistance of Tm{sub 1-x}Yb{sub x}B{sub 12} is analyzed in terms of the Yosida model for a local magnetic susceptibility.
White emission from Tm3+/Tb3+/Eu3+ co-doped fluoride zirconate under ultraviolet excitation
NASA Astrophysics Data System (ADS)
Sun, Jian; Zhang, Xiao-Song; Yuan, Lin-Lin; Feng, Zhi-Jun; Ling, Zhi; Li, Lan
We synthesize Tm3+/Tb3+/Eu3+ triply-doped ZrF4ŚBaF2ŚLaF3ŚAlF3ŚNaF (ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL'Eclairage (CIE) coordinates of (0.33, 0.33) is achieved at the Eu3+ concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+ ? Eu3+ are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+ ? Eu3+ energy transfer is described with the aid of an energy level diagram.
NIR to blue light upconversion in Tm3+/Yb3+ codoped BaTiO3 tellurite glass
NASA Astrophysics Data System (ADS)
Kumari, Astha; Rai, Vineet Kumar
Upconversion is an interesting optical property, generally shown by rare-earth doped materials. This unusual optical behavior shown by these rare-earths doped materials are due to their peculiar atomic configuration and electronic transitions. Here, the Tm3+-Yb3+ codoped BaTiO3 glass with TeO2 as former has been prepared by conventional melt and quench technique and the upconversion property has been investigated with the help of near infrared (NIR) to Visible UC study. The generation of the visible UC bands around ś 476 nm, ś 653 nm, ś 702 nm and one NIR UC band at ś795 nm are assigned due to the 1G4? 3H6, 1G4? 3F4, 3F2? 3H6 and 3H4? 3H6 transitions respectively. The generations of these upconversion bands have been discussed in detail with the help of energy level diagram. The colour coordinates corresponding to the prepared material have been shown with the help of CIE chromaticity diagram. These glasses can be very appropriately used in the fabrication of solid state laser and as NIR to blue light upconverter.
Plasmonic enhanced emissions from cubic NaYF4:Yb: Er/Tm nanophosphors
Sudheendra, L.; Ortalan, Volkan; Dey, Sanchita; Browning, Nigel D.; Kennedy, I.M.
A metal shell was used in this study to provide significant enhancement of the up-converted emission from cubic NaYF4 nanoparticles, creating a valuable composite material for labeling in biology and other applications ¢ use of the cubic form of the material obviates the need to undertake a high temperature transformation to the naturally more efficient hexagonal phase. The NaYF4 matrix contained ytterbium sensitizer and an Erbium (Er) or Thulium (Tm) activator. The particle sizes of the as-synthesized nanoparticles were in the range of 20¢40 nm with a gold shell thickness of 4¢8 nm. The gold shell was macroscopically amorphous. The synthesis method was based on a citrate chelation. In this approach, we exploited the ability of the citrate ion to act as a reductant and stabilizer. Confining the citrate ion reductant on the nanophosphor surface rather than in the solution was critical to the gold shell formation. The plasmonic shell enhanced the up-conversion emission of Tm from visible and near-infrared regions by up to a factor of 8, in addition to imparting a visible color arising from the plasmon absorption of the gold shell. The up-conversion enhancement observed with Tm and Er were different for similar gold coverages, with local crystal field changes as a possible route to enhance up-conversion emission from high symmetry structural hosts. These novel up-converting nanophosphor particles combine the phosphor and features of a gold shell, providing a unique platform for many biological imaging and labeling applications. PMID:21709812
Structure and Properties of Single Crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2
May, Andrew F [ORNL; McGuire, Michael A [ORNL; Singh, David J [ORNL; Custelcean, Radu [ORNL; Jellison Jr, Gerald Earle [ORNL
Single crystals of CaMg{sub 2}Bi{sub 2}, EuMg{sub 2}Bi{sub 2}, and YbMg{sub 2}Bi{sub 2} were obtained from a Mg-Bi flux cooled to 650 C. These materials crystallize in the CaAl{sub 2}Si{sub 2} structure-type (P3{bar m}1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg{sub 2}Bi{sub 2} displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg{sub 2}Bi{sub 2} reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) x 10{sup 19} cm{sup -3} for CaMg{sub 2}Bi{sub 2}, 1.7(1) x 10{sup 19} cm{sup -3} for EuMg{sub 2}Bi{sub 2}, and 4.6(7) x 10{sup 19} cm{sup -3} for YbMg{sub 2}Bi{sub 2}, which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios {rho}(300 K)/{rho}(10 K) {le} 1.6 in all cases, indicating significant defect scattering.
Synthesis and luminescence properties of LaVO4:RE3+ (RE = Sm, Eu, Tb, Tm) phosphors.
Cho, Shinho
Rare earth (RE)-doped lanthanide vanadate phosphors for multicolor display applications were synthesized with different activator ions by using a solid-state reaction method. The effects of activator ions on the structural, morphological, and optical properties of lanthanide vanadate phosphors were investigated. X-ray diffaction data exhibited that the main peak of the phosphors occurs at a (120) plane. Maximum grain size and hexagonal morphology are observed by incorporating Eu3+ activator ions into a host lattice. The emission spectra of RE ions-doped LaVO4 phosphors under excitation at 324 nm consist of multicolor emissions: the main red emission for Eu3+, Orange for Tm3+, green for Tb3+, and blue for Tm3+ activator ions. These results suggest that the multicolor emissions can be realized by controlling activator ions incorporated into host crystals. PMID:24245289
Effect of C6+ Ion Irradiation on structural and electrical properties of Yb and Eu doped Bi1.5 Zn0.92 Nb1.5 O6.92 pyrochlores
NASA Astrophysics Data System (ADS)
Yumak, Mehmet; Mergen, Ayhan; Qureshi, Anjum; Singh, N. L.
Pyrochlore general formula of A2B2X7 where A and B are cations and X is an anion Pyrochlore compounds exhibit semiconductor, metallic or ionic conduction properties, depending on the doping, compositions/ substituting variety of cations and oxygen partial pressure. Ion beam irradiation can induce the structural disordering by mixing the cation and anion sublattices, therefore we aim to inevestigate effects of irradiation in pyrochlore compounds. In this study, Eu and Yb-doped Bi1.5Zn0.92Nb1.5O6.92 (Eu-BZN, Yb-BZN) Doping effect and single phase formation of Eu-BZN, Yb-BZN was characterized by X-ray diffraction technique (XRD). Radiation-induced effect of 85 MeV C6+ ions on Eu-BZN, Yb-BZN was studied by XRD, scanning electron microscopy (SEM) and temperature dependent dielectric measurements at different fluences. XRD results revealed that the ion beam-induced structural amorphization processes in Eu-BZN and Yb-BZN structures. Our results suggested that the ion beam irradiation induced the significant change in the temprature depndent dielectric properties of Eu-BZN and Yb-BZN pyrochlores due to the increased oxygen vacancies as a result of cation and anion disordering. Department of Metallurgical and Materials Eng., Marmara University, Istanbul-81040, Turkey.
Multiple thermoluminescence glow peaks and afterglow suppression in CsI:Tl co-doped with Eu2+ or Yb2+
NASA Astrophysics Data System (ADS)
Bartram, R. H.; Kappers, L. A.; Hamilton, D. S.; Brecher, C.; Ovechkina, E. E.; Miller, S. R.; Nagarkar, V. V.
CsI:Tl is a widely utilized scintillator material with many desirable properties but its applicability is limited by persistent afterglow. However, effective afterglow suppression has been achieved by co-doping with divalent lanthanides. The present report is concerned with observation of multiple thermoluminescence glow peaks in CsI:Tl,Eu and CsI:Tl,Yb, attributed to varying distributions of charge-compensating cation vacancies relative to divalent lanthanide co-dopants, and the subsequent modification of these distributions by repeated observations. It is observed that Yb2+ provides a slightly shallower electron trap than Eu2+, and that it can occupy a face-centered position by virtue of its relatively small ionic radius; the latter observation is confirmed by electrostatic calculations. It is also found that repeated observation of thermoluminescence in these materials has a modest adverse effect on afterglow suppression.
TUDE DES LECTRONS DE CONVERSION ET DES LECTRONS AUGER K ET L DE LA DSINTGRATION 170Tm 2014 170Yb
Paris-Sud XI, Universitķ de
sources de thulium ķpaisses (1 mg/cm2). Graham, Wolfson et Bell [1] ont utilisķ, pour cette mĻme ķtude, l rķaction de for- mation du 170Tm est 169Tm(n, y)170Tm. De l'oxyde de thulium Tm203 spectroscopiquement pur. Pour cela, l'oxyde de thulium est transformķ en chlorure par addition Article published online by EDP
Investigation on up-conversion luminescence properties of novel transparent Ho3+-Tm3+-Yb3+ co-doped oxyfluoride glass ceramics
NASA Astrophysics Data System (ADS)
Liu, Xiao-bo; Han, Wan-lei; Xu, Fang; Song, Ying-lin
In the present letter, the transparent oxyfluoride glass ceramics containing Ho3+-Tm3+-Yb3+:NaYF4 were successfully prepared by melt-quenching at 1400░C and subsequent heating at 650-680░C for 1~2 hours . X-ray diffraction (XRD) with Cu K? radiation (?=0.154nm) investigation revealed that NaYF4 nano-crystals in the glass ceramics was fabricated. Their sizes were determined by Sherrer's equation. The emission spectra red green and blue up-conversion (UC) under 980nm laser diode (LD) pumping and absorption spectra were measured. Luminescence measurements confirmed the partition of RE ions in nano-crystals NaYF4. The blue red and green UC radiations correspond to the transitions 1G4-3H6, 1G4-3H4 of Tm3+, 5F4, 5S2-5I8, 5F5-5I8, of Ho3+ ions, respectively. This is similar to that in Tm3+-Yb3+ and/or Ho3+-Yb3+ co-doped glass ceramics. To obtain upconversion fluorescence mechanisms, upconversion fluorescence intensity versus LD pump power were analyzed in view of energy levels of rare earth. Up-conversion mechanisms were discussed and the ratio between red, green and blue UC emission bands was found to be varied as a function of temperature of heat treatment and pump power. This result could be mainly attributed to the cross-relaxation between Ho3+ ions. The excellent optical properties and its convenient, low-cost synthesis of the present glass ceramic imply that it is an excellent substitution material for the unobtainable bulk NaYF4 crystal and may have potentially applications in tunable visible laser or many other fields.
Optical properties of trigonal single crystals (Yb,Tm)Al{sub 3}(BO{sub 3}){sub 4} grown from fluxes based on the bismuth and lithium molybdates
Temerov, V. L., E-mail: email@example.com; Sokolov, A. E.; Sukhachev, A. L.; Bovina, A. F.; Edel'man, I. S.; Malakhovskii, A. V. [Russian Academy of Sciences, Akademgorodok, Kirensky Institute of Physics, Siberian Branch (Russian Federation)
The conditions for synthesis of Yb{sub x}Tm{sub 1-x}Al{sub 3}(BO{sub 3}){sub 4} (x = 0, 0.1, 0.2, 1.0) single crystals from fluxes based on bismuth trimolybdate Bi{sub 2}Mo{sub 3}O{sub 12} and lithium molybdate Li{sub 2}MoO{sub 4} are investigated. It is proposed to grow them by the group method on seeds. The polarized optical absorption spectra are measured for two mutually orthogonal linear polarizations at temperatures of 100 and 300 K.
Photoluminescence of Eu3+-, Tb3+-, Dy3+- and Tm3+-doped transparent GeO2 TiO2 K2O glass ceramics
G. Lakshminarayana; Jianrong Qiu; M. G. Brik; I. V. Kityk
In this paper, we present the photoluminescence properties of Eu3+-, Tb3+-, Dy3+- and Tm3+-doped potassium-titanium-germanate glasses and glass ceramics. Following the x-ray diffraction measurement, the glass structure was established. Compared to Eu3+-, Tb3+-, Dy3+- and Tm3+-doped glasses, their respective glass ceramics show stronger emissions due to the presence of the K2TiGe3O9 crystalline phase. For Eu3+-doped glass and glass ceramics, five
Intense upconversion luminescence and effect of local environment for Tm3+/Yb3+ co-doped novel TeO2-BiCl3 glass system.
Wang, Guonian; Dai, Shixun; Zhang, Junjie; Wen, Lei; Yang, Jianhu; Jiang, Zhonghong
We present the results of a study that uses theoretical and experimental methods to investigate the characteristics of the upconversion luminescence of Tm3+/Yb3+ codoped TeO2-BiCl3 glass system as a function of the BiCl3 fraction. These glasses are potentially important in the design of upconversion fiber lasers. Effect of local environment around Tm3+ on upconversion fluorescence intensity was analyzed by theoretical calculations. The structure and spectroscopic properties were investigated in the experiments by measuring the Raman spectra, IR transmission spectra, and absorption and fluorescence intensities at room temperature. The results indicate that blue luminescence quantum efficiency increases with increasing BiCl3 content from 10 to 60 mol%, which were interpreted by the increase of asymmetry of glass structure, decrease of phonon energy and removing of OH- groups. PMID:16378753
Hydrothermal derived LaOF:Ln3+ (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) nanocrystals with multicolor-tunable emission properties.
Shang, Mengmeng; Geng, Dongling; Kang, Xiaojiao; Yang, Dongmei; Zhang, Yang; Lin, Jun
A series of LaOF:Ln(3+) (Ln = Eu, Tb, Sm, Dy, Tm, and/or Ho) nanocrystals with good dispersion have been successfully prepared by the hydrothermal method followed a heat-treatment process. Under ultraviolet radiation and low-voltage electron beam excitation, the LaOF:Ln(3+) nanocrystals show the characteristic f-f emissions of Ln(3+) (Ln = Eu, Tb, Sm, Dy, Tm, or Ho) and give red, blue-green, orange, yellow, blue, and green emission, respectively. Moreover, there exists simultaneous luminescence of Tb(3+), Eu(3+), Sm(3+), Dy(3+), Tm(3+), or Ho(3+) individually when codoping them in the single-phase LaOF host (for example, LaOF:Tb(3+), Eu(3+)/Sm(3+); LaOF:Tm(3+), Dy(3+)/Ho(3+); LaOF:Tm(3+), Ho(3+), Eu(3+) systems), which is beneficial to tune the emission colors. Under low-voltage electron beam excitation, a variety of colors can be efficiently adjusted by varying the doping ions and the doping concentration, making these materials have potential applications in field-emission display devices. More importantly, the energy transfer from Tm(3+) to Ho(3+) in the LaOF:Tm(3+), Ho(3+) samples under UV excitation was first investigated and has been demonstrated to be a resonant type via a quadrupole-quadrupole mechanism. The critical distance (R(Tm-Ho)) is calculated to be 28.4 ┼. In addition, the LaOF:Tb(3+) and LaOF:Tm(3+) phosphors exhibit green and blue luminescence with better chromaticity coordinates, color purity, and higher intensity compared with the commercial green phosphor ZnO:Zn and blue phosphor Y(2)SiO(5):Ce(3+) to some extent under low-voltage electron beam excitation. PMID:23020114
First-principles investigations on vibrational, thermodynamic, mechanical properties and thermal conductivity of L12 Al3X (XĀ=ĀSc, Er, Tm, Yb) intermetallics
NASA Astrophysics Data System (ADS)
Zhang, Xudong; Jiang, Wei
The lattice dynamics, thermodynamic, mechanical properties and thermal conductivity of L12 Al3X (X = Sc, Er, Tm, Yb) intermetallics have been investigated from first-principles calculations by means of using the VASP code. Our results agree well with the previous experiments and calculations. The phonon dispersion curves and the density of phonon states have been calculated by means of using the PHONONPY code and compared with the experimental results. The four compounds stay dynamically stable in the L12 structure. We also calculated the thermodynamics properties and give the relationships between thermal parameters and temperature. The elastic constants of the considered compounds are satisfied with mechanical stability criteria. The related mechanical parameters predict that Al3Sc has higher hardness than the other three compounds, and four compounds all posses a brittle nature. The mechanical anisotropy is predicted by anisotropic constants AU and AZ. The results show that the four compounds are all elastically isotropic. We also calculated the thermal conductivity by means of the ClarkeÆs model and CahillÆs model and found that the thermal conductivity of the four intermetallics follows the order: Al3Sc > Al3Er > Al3Tm > Al3Yb.
Enhanced near-infrared response of CdS/CdTe solar cell using Tm3+ and Yb3+ co-doped upconverting glass phosphors
NASA Astrophysics Data System (ADS)
Pan, Z.; Whyte, D.; Morgan, S. H.; Li, J.; Alaswad, A.; Beach, J. D.; Ohno, T. R.; Wolden, C. A.
Tm3+ and Yb3+ co-doped upconverting (UC) glass phosphors were used to converting near-infrared to visible light and input to a CdS/CdTe solar cell, therefore to enhance solar cell's response in the near-infrared of the sub-bandgap region. Current-voltage measurements were performed on the solar cell with a UC glass phosphor. A short-circuit photocurrent enhancement of 31 ?A was obtained using a Tm3+and Yb3+ co-doped glass UC phosphor, illuminated by a 980 nm diode laser at 100 mW. This photocurrent response corresponds to external quantum efficiency (EQE) of 0.04 % at 980 nm. For full collection of the UC light in 4? solid angle, the EQE value is expected to reach 1.6 %. The photo-current observed was proportional to the effective UC light intensity from glass UC phosphor. A non-linear relation between the output photo-current and the incident power of the infrared light was observed, similar to the relation between UC intensity and the incident power. UC efficiency of the glass phosphor was calculated using EQE values at both UC wavelengths and at 980 nm.
Enhanced photocatalytic activities of the heterostructured upconversion photocatalysts with cotton mediated on TiO2/ZnWO4:Yb(3+),Tm(3.).
Feng, Kaili; Huang, Shouqiang; Lou, Ziyang; Zhu, Nanwen; Yuan, Haiping
To improve the photocatalytic efficiency and make full use of solar energy, ZnWO4:Yb(3+),Tm(3+) (ZYT) was introduced as the upconversion luminescence agent on TiO2 with a cotton template, and novel upconversion photocatalysts of TiO2/ZnWO4:Yb(3+),Tm(3+) (TZYT-C) were synthesized and optimized with 5%-30% of ZYT. The heterostructure between ZYT and TiO2 was formed in the TZYT-C composites with the presence of tube-like morphologies due to the addition of the cotton template. UV (364 nm) and blue (484 nm) light was emitted from ZYT upon 980 nm NIR irradiation. The BET specific surface areas of all the TZYT-C composites increased from 37 m(2) g(-1) (TiO2-C) to the maximum value of 75 m(2) g(-1) on 5%TZYT-C. The photocatalytic activities of the TZYT-C composites were tested using the degradation process of methyl orange (MO). 5%TZYT-C showed the highest degradation efficiency, with a value of 55.6% under sun-like irradiation for 210 min. The same performance was observed on 5%TZYT-C under NIR (? ? 780 nm) irradiation, with a maximum removal rate of 9.02%, since 5%TZYT-C showed the most efficient electron-hole (e(-)/h(+)) pair separation, compared to ZYT and other TZYT-C composites. PMID:26150279
Vacuum ultraviolet and near-infrared excited luminescence properties of Ca{sub 3}(PO{sub 4}){sub 2}:RE{sup 3+}, Na{sup +} (RE=Tb, Yb, Er, Tm, and Ho)
Zhang Jia [Department of Material Science, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Wang Yuhua, E-mail: email@example.com [Department of Material Science, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Guo Linna; Zhang Feng; Wen Yan; Liu Bitao [Department of Material Science, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Huang Yan [Laboratory of Beijing Synchrotron Radiation, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)
Tb{sup 3+}, Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2} were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb{sup 3+}-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb{sup 3+} content is comparable with that of the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb{sup 3+}, Tm{sup 3+}, Er{sup 3+}, and Ho{sup 3+} doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb{sup 3+}-Ho{sup 3+}, Yb{sup 3+}-Er{sup 3+}, and Yb{sup 3+}-Tm{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} in Ca{sub 3}(PO{sub 4}){sub 2}, in which the cross-relaxation process between Er{sup 3+} and Tm{sup 3+}, producing the {sup 1}D{sub 2}-{sup 3}F{sub 4} transition of Tm{sup 3+}, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams. - Graphical abstract: The CPO:0.25Tb{sup 3+}, 0.25Na{sup +} exhibits a comparable brightness to the commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+} upon 147 nm excitation. Good white light color is achieved in CPO:Yb{sup 3+}-Tm{sup 3+}-Er{sup 3+}-Ho{sup 3+} under 980 nm excitation. Highlights: > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+},Na{sup +} exhibits a comparable brightness with commercial Zn{sub 2}SiO{sub 4}:Mn{sup 2+}. > Red, green and blue colors are achieved in Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} doped Ca{sub 3}(PO{sub 4}){sub 2}. > Good white emission is obtained in Yb{sup 3+}-Ho{sup 3+}-Er{sup 3+}-Tm{sup 3+} quadri-doped Ca{sub 3}(PO{sub 4}){sub 2}. > Ca{sub 3}(PO{sub 4}){sub 2}:Tb{sup 3+}, Yb{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+} could be potential phosphors.
Size-Tunable and Monodisperse Tm3+/Gd3+-Doped Hexagonal NaYbF4 Nanoparticles with Engineered Efficient Near Infrared-to-Near Infrared Upconversion for In Vivo Imaging
Hexagonal NaYbF4:Tm3+ upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm3+ nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd3+) can convert NaYbF4:Tm3+ 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm3+ 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibit a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ?2 nm on the ?22 nm core of hexagonal NaYbF4:Gd3+ 30%/Tm3+ 0.5% nanoparticles resulted in a dramatic 350 fold NIR upconversion efficiency enhancement, because of effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline. PMID:25027118
Effects of water on Eu/sup 2 +/, Yb/sup 2 +/, and Es/sup 2 +/ cocrystallization in the Sr(Sm)SO/sub 4/-ethanol system
Mikheev, N.B.; Kamenskaya, A.N.; Kulyukhin, S.A.
Measurements have been made on the effects of water on the cocrystallization of divalent europium, ytterbium, and einsteinium in the Sr(Sm)SO/sub 4/-ethanol system. Water levels from 3 to 6 M affect the Eu/sup 2 +/ and Yb/sup 2 +/ cocrystallization coefficients, while above 6 M, they do not alter. With divalent einsteinium, there are changes in the coefficient up to (H/sub 2/O) = 10 M. The effects of the water concentration on the solubility have been examined for the sulfates of these three elements.
Color-tunable upconversion luminescence of Yb3+, Er3+, and Tm3+ tri-doped ferroelectric BaTiO3 materials
NASA Astrophysics Data System (ADS)
Zhang, Yang; Hao, Jianhua
Tunable upconversion (UC) multicolor luminescence is observed from Yb3+, Er3+, and Tm3+ tri-doped ferroelectric BaTiO3 (BTO) materials. By control of dopant concentrations, the lanthanide-doped BTO powders are capable of generating various UC spectra and color tunability. A white-light emission is achieved through an optimal design. Strong UC luminescence is also observed in the lanthanide-doped BTO thin-films grown on Pt/TiO2/SiO2/Si substrate, which can retain well-defined hysteresis loops with a remnant polarization (2Pr) of 17.8 ?C/cm2. These findings open the possibility of lanthanide-doped BTO as multifunctional materials, in which both luminescent and ferroelectric properties co-exist.
[Effect of bivalent alkaline earth fluorides introduction on thermal stability and spectroscopic properties of Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses].
Hu, Yue-bo; Zhang, Xin-na; Zhou, Da-li; Jiao, Qing; Wang, Rong-fei; Huang, Jin-feng; Long, Xiao-bo; Qiu, Jian-bei
Transparent Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses alone containing MgF2, CaF2, SrF2 or BaF2 and nano-glass-ceramics only containing BaF2 were prepared. The thermal stabilities and the up-conversion emission properties of the samples were investigated. Analyses of absorbance spectra reveal that the UV cutoff band moves slightly to shortwave band with the doping bivalent cation mass increasing. The results show that the emission color can be adjusted by changing the alkaline earth cation species in the glass matrixes, especially as Mg2+ is concerned, and the emission intensity can increase notably by heating the glass containing alkaline-earth fluoride into glass ceramic containing alkaline-earth fluoride nanocrystals or increasing the content of bivalent alkaline earth fluorides. PMID:22497127
Colour tuneability in sol-gel nano-glass-ceramics comprising Yb(3+)-Er(3+)-Tm3+ Co-doped NaYF4 nanocrystals.
Mķndez-Ramos, J; Yanes, A C; Santana-Alonso, A; Del-Castillo, J; RodrĒguez, V D
White light can be obtained by up-conversion processes in a cheap and efficient way, being of great interest for lighting, displays, and photonic integrated devices. Here we report a generation of white light under 980 nm laser infrared excitation in Y(b3+)-Er(3+)-Tm3+ triply doped sol-gel derived nano-glass-ceramics containing NaYF4 nanocrystals where co-dopants ions are partitioned. Efficient simultaneous blue, green, and red up-conversion emissions give rise to a balanced white overall emission and corresponding up-conversion mechanisms have been analyzed. Changes in pump power intensity or heat treatment temperature widely vary the ratio of emission bands, resulting in a colour tuneability which has been analyzed and quantified in terms of CIE standard chromaticity diagram. PMID:20352788
Structural and Magnetothermal Properties of Compounds: Yb5SixGe4-x,Sm5SixGe4-x, EuO, and Eu3O4
Kyunghan Ahn
The family of R{sub 5}Si{sub x}Ge{sub 4-x} alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R{sub 5}Si{sub x}Ge{sub 4-x} systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R{sub 5}Si{sub x}Ge{sub 4-x} systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb{sub 5}Si{sub x}Ge{sub 4-x} and Sm{sub 5}Si{sub x}Ge{sub 4-x} pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys with 0 {le} x {le} 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R{sub 5}Si{sub x}Ge{sub 4-x} systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd{sub 5}Si{sub 4}-type structure. The magnetic properties of Yb{sub 5}Si{sub x}Ge{sub 4-x} materials are nearly composition-independent, reflecting the persistence of the same crystal structure over the whole range of x from 0 to 4. Both the crystallographic and magnetic property data indicate that Yb{sub 5}Si{sub x}Ge{sub 4-x} alloys are mixed valence systems, in which the majority (60%) of Yb atoms is divalent, while the minority (40%) is trivalent. This finding is supported by recent Moessbauer spectroscopy data.
Real-time, non-invasive monitoring of hydrogel degradation using LiYF4:Yb(3+)/Tm(3+) NIR-to-NIR upconverting nanoparticles.
Jalani, Ghulam; Naccache, Rafik; Rosenzweig, Derek H; Lerouge, Sophie; Haglund, Lisbet; Vetrone, Fiorenzo; Cerruti, Marta
To design a biodegradable hydrogel as cell support, one should know its in vivo degradation rate. A technique commonly used to track gel degradation is fluorescence spectroscopy. However, the fluorescence from conventional fluorophores quickly decays, and the fluorophores are often moderately cytotoxic. Most importantly, they require ultraviolet or visible (UV-Vis) light as the excitation source, which cannot penetrate deeply through biological tissues. Lanthanide-doped upconverting nanoparticles (UCNPs) are exciting alternatives to conventional fluorophores because they can convert near-infrared (NIR) to UV-Vis-NIR light via a sequential multiphoton absorption process referred to as upconversion. NIR light can penetrate up to few cm inside tissues, thus making these UCNPs much better probes than conventional fluorophores for in vivo monitoring. Also, UCNPs have narrow emission bands, high photoluminescence (PL) signal-to-noise ratio, low cytotoxicity and good physical and chemical stability. Here, we show a nanocomposite system consisting of a biodegradable, in situ thermogelling injectable hydrogel made of chitosan and hyaluronic acid encapsulating silica-coated LiYF4:Yb(3+)/Tm(3+) UCNPs. We use these UCNPs as photoluminescent tags to monitor the gel degradation inside live, cultured intervertebral discs (IVDs) over a period of 3 weeks. PL spectroscopy and NIR imaging show that NIR-to-NIR upconversion of LiYF4:Yb(3+)/Tm(3+)@SiO2 UCNPs allows for tracking of the gel degradation in living tissues. Both in vitro and ex vivo release of UCNPs follow a similar trend during the first 5 days; after this time, ex vivo release becomes faster than in vitro, indicating a faster gel degradation ex vivo. Also, the amount of released UCNPs in vitro increases continuously up to 3 weeks, while it plateaus after 15 days inside the IVDs showing a homogenous distribution of UCNPs throughout the IVD tissue. This non-invasive optical method for real time, live tissue imaging holds great potential for tissue analysis, biomapping and bioimaging applications. PMID:26067274
Spectral conversion for solar cell efficiency enhancement using YVO4:Bi3+,Ln3+ (Ln = Dy, Er, Ho, Eu, Sm, and Yb) phosphors
NASA Astrophysics Data System (ADS)
Huang, X. Y.; Wang, J. X.; Yu, D. C.; Ye, S.; Zhang, Q. Y.; Sun, X. W.
Bi3+-Ln3+ (Ln = Dy, Er, Ho, Eu, and Sm) co-doped YVO4 phosphors are proposed as UV-absorbing luminescent converter candidate to enhance the power conversion efficiency and photochemical stability of dye-sensitized solar cells (DSSCs). The phosphors can efficiently convert UV photons in a broad range from 250 to 400 nm into visible emissions, which can be absorbed by DSSCs. Efficient broadband down-conversion UV light into near-infrared emission around 1000 nm was achieved in the YVO4:Bi3+,Yb3+ phosphors. The energy transfer from V5+-Bi3+ charge-transfer state to Yb3+ was shown to be a cooperative down-conversion type by the luminescence spectra, energy transfer efficiency, and luminescence decay curves. The YVO4:Bi3+,Yb3+ phosphors are promising for boosting the efficiency of crystalline silicon solar cells by down-converting the UV part of the solar spectrum to near-infrared photons with a twofold increase in the photon number. This research may open up promising new perspectives for designing novel luminescent materials for photovoltaic cells with high efficiency.
Vibrational structure in optical spectra of the Ca 4GdO(BO 3) 3 (GdCOB) single crystal doped with Re 3+ (Eu, Tb, Yb)
NASA Astrophysics Data System (ADS)
Dominiak-Dzik, G.; Ryba-Romanowski, W.; Go??b, S.; Baba, M.; Paj?czkowska, A.
The optical spectra of compounds containing trivalent rare earth (Re 3+) ions often show vibronic features. The intensity of vibronic transitions is determined by the strength of the electron-phonon (ion-lattice) coupling and depends strongly on the rare earth and the host lattice. In this paper we report on electron-phonon coupling in the GdCOB system doped with Eu 3+, Tb 3+ and Yb 3+ ions. According to general theory intense vibronic lines are to be expected for electronic transitions with ? J=0, ▒2 and these transitions were mainly considered in this paper for both Eu 3+ and Tb 3+ ions. In the case of Yb 3+ ions, a strong vibronic sideband belongs to the 2F 7/2? 2F 5/2 transition with ? J=1 although it seems to be in contradiction to the general selection rule. The vibronic features observed in absorption, excitation and emission spectra were analysed on the basis of the host lattice modes obtained from Raman and the far infrared spectra of the matrix.
Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO4)2 phosphate
NASA Astrophysics Data System (ADS)
Zhang, Z. J.; Yuan, J. L.; Duan, C. J.; Xiong, D. B.; Chen, H. H.; Zhao, J. T.; Zhang, G. B.; Shi, C. S.
Hexagonal KCaGd(PO4)2:RE3+ (RE =Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet-ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce3+-doped samples, the bands at 207, 256, 275, and 320nm are assigned to the 4f-5d transitions of Ce3+ in KCaGd(PO4)2. For Tb3+-doped sample, the bands at 203 and 222nm are related to the 4f-5d spin-allowed transitions. For Eu3+-doped sample, the O2--Eu3+ charge-transfer band (CTB) at 229nm is observed, and the fine emission spectrum of Eu3+ indicates that Eu3+ ions prefer to occupy Gd3+ or Ca2+ sites in the host lattice. For Tm3+- and Sm3+-doped samples, the O2--Tm3+ and O2--Sm3+ CTBs are observed to be at 176 and 186nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb3+-doped KCaGd(PO4)2 is a potential candidate for 172nm excited green plasma display phosphors.
Efficient energy upconversion emission in Tm3+/Yb3+-codoped TeO2-based optical glasses excited at 1.064 ?m
NASA Astrophysics Data System (ADS)
dos Santos, P. V.; Vermelho, M. V. D.; Gouveia, E. A.; de Ara·jo, M. T.; Gouveia-Neto, A. S.; Cassanjes, F. C.; Ribeiro, S. J. L.; Messaddeq, Y.
Efficient energy upconversion of cw radiation at 1.064 ?m into blue, red, and near infrared emission in Tm3+-doped Yb3+-sensitized 60TeO2-10GeO2-10K2O-10Li2O-10Nb2O5 glasses is reported. Intense blue upconversion luminescence at 485 nm corresponding to the Tm3+ 1G4?3H6 transition with a measured absolute power of 0.1 ?W for 800 mW excitation power at room temperature is observed. The experimental results also revealed a sevenfold enhancement in the upconversion efficiency when the sample was heated from room temperature to 235 ░C yielding 0.7 ?W of blue absolute fluorescence power for 800 mW pump power. High brightness emission around 800 nm (3F4?3H6) in addition to a less intense 655 nm (1G4?3H4 and 3F2,3?3H6) fluorescence is also recorded. The energy upconversion excitation mechanism for thulium emitting levels is assigned to multiphonon-assisted anti-Stokes excitation of the ytterbium-sensitizer followed by multiphonon-assisted sequential energy-transfer processes.
Cross-section measurement of the 169 Tm p,n reaction for the production of the therapeutic radionuclide 169 Yb and comparison with its reactor-based generation.
Spahn, I; Takßcs, S; Shubin, Yu N; Tßrkßnyi, F; Coenen, H H; Qaim, S M
The radionuclide (169)Yb (T(1/2)=32.0 d) is potentially important for internal radiotherapy. It is generally produced using a nuclear reactor. In this work the possibility of its production at a cyclotron was investigated. A detailed determination of the excitation function of the (169)Tm(p,n)(169)Yb reaction was done over the proton energy range up to 45 MeV using the stacked-foil technique and high-resolution gamma-ray spectrometry. The integral yield of (169)Yb was calculated. Over the optimum energy range E(P)=16-->7 MeV the yield amounts to 1.5 MBq/micro Ah and is thus rather low. A comparison of this production route with the established (168)Yb(n,gamma)(169)Yb reaction at a nuclear reactor is given. The (169)Yb yield via the reactor route is by several orders of magnitude higher than by the cyclotron method. The latter procedure, however, leads to "no-carrier-added" product. PMID:15919210
In situ neutron powder diffraction of the formation of SrGa2D2, and hydrogenation behavior of YbGa2 and EuGa2.
Wenderoth, Patrick; Kohlmann, Holger
The hydrogenation behavior of the Zintl phases MGa2 (M = Sr, Eu, Yb) was investigated. Upon being heated under 50 bar of hydrogen gas pressure, SrGa2 starts forming the polyanionic hydride SrGa2H2 at 125 ░C as observed by in situ differential scanning calorimetry (DSC) and ex situ X-ray powder diffraction. The deuteration of SrGa2 was studied by in situ neutron powder diffraction at temperatures up to 300 ░C in the pressure range of 50 ? p(D2) ? 61 bar with a time resolution of two minutes. Neither incorporation of deuterium into the interstitials of the crystal structure of SrGa2 nor any other intermediate of the reaction was observed. No significant variation in positional or occupational parameters as refined by the Rietveld method was observed for the deuteride SrGa2D2 under various temperature and pressure conditions (e.g., at T = 299 ░C, p(D2) = 60 bar, space group P3m1, a = 4.4098(2) ┼, c = 4.7429(3) ┼, Sr in 1a, 0 0 0; Ga in 2d, 1/3 2/3 0.474(1); D in 2d, 1/3 2/3 0.120(2)). In situ DSC complemented by ex situ X-ray powder diffraction revealed that EuGa2 and YbGa2 do not form polyanionic hydrides in the investigated temperature-pressure ranges (20 ░C ? T ? 220 ░C, 5 bar ? p ? 54 bar). Instead binary hydrides and gallium-rich intermetallics are formed. The first refined crystal structural data are presented for YbGa6 in the tetragonal PuGa6-type structure (space group P4/nbm (No. 125), a = 6.0890(3) ┼, c = 7.6562(4) ┼, Yb in 2c, 3/4 1/4 0; Ga1 in 8m, 0.4750(4) 0.5250(4) 0.3377(4); Ga2 in 4g, 1/4 1/4 0.1691(5)). PMID:24003866
Upconversion luminescence properties of Yb3+ and Tm3+ codoped amorphous fluoride ZrF4-BaF2-LaF3-AlF3-NaF thin film prepared by pulsed laser deposition.
He, Chunfeng; Qin, Guanshi; Zhao, Dan; Chuai, Xiaohong; Wang, Lili; Zheng, Kezhi; Qin, Weiping
The Yb3+ and Tm3+ co-doped 55.98ZrF4-28BaF2-2.5LaF3-4AlF3-7NaF-2.5YbF3-0.02TmF3 amorphous fluoride film was prepared by pulsed laser deposition. The spectroscopic properties and energy transfer analysis of this film were studies in detail. Ultraviolet and visible upconversion emissions were observed under the infrared excitation at 980 nm. In comparison with that of its target, the upconversion emissions of the film in the visible and ultraviolet range were greatly enhanced. The possible energy transfer mechanism of the emissions was given to understand the upconversion process. This kind of thin films has potential applications for the integrated optical waveguide amplifier and ultraviolet laser. PMID:24734646
Tunnel-diode Resonator Spectroscopy of Quantum Levels in Cr12 Ln 4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) Magnetic Molecules
NASA Astrophysics Data System (ADS)
Yeninas, Steven; Luban, Marshall; Prozorov, Ruslan; Coniglio, William A.; Agosta, Charles C.; Engelhardt, Larry; Timco, Grigore A.; Winnpenny, Richard E. P.
The differential magnetic susceptibility for a series of Cr 12 Ln 4 (Ln=Y,Eu,Gd,Tb,Dy,Ho,Yb) magnetic molecules was measured in static (up to 16 T) and pulsed (up to 45 T) magnetic fields using a rf tunnel-diode resonator (TDR). At low temperatures, the behavior of these finite spin systems is governed by discrete energy spectra of the individual molecules. In magnetic field, low-energy quantum levels Zeeman-split, crossing at field values where magnetization exhibits a step corresponding to switching between different spin states. In high fields, we detect multiple level crossings which allow for a detailed mapping of the energy diagram. We then perform quantum Monte Carlo (QMC) using a Heisenberg Hamiltonian with three adjustable exchange constants whose values are chosen so as to optimize agreement with the experimental energy spectrum. The variations in results for the studied molecules are correlated to the magnetic properties of the lanthanide ions.
Rare-Earths Centers (Sm{sup 3+}, Eu{sup 3+}, Yb{sup 3+}) in MeF{sub 2}(Me = Ca, Sr, Ba, Cd) Crystals
Nikiforov, A. E.; Chernyshev, V. A.; Volodin, V. P. [Ural State University, 620083-Ekaterinburg, Lenin av. 51 (Russian Federation); Avram, N. M. [West University of Timisoara, Dept. of Physics, 300223-Timisoara, Bd. V. Parvan No. 4 (Romania); Academy of Romanian Scientists, Independentei 54, 050094-Bucharest (Romania); Avram, C. N.; Vaida, M. [West University of Timisoara, Dept. of Physics, 300223-Timisoara, Bd. V. Parvan No. 4 (Romania)
Rare-earth elements RE{sup 3+}(RE = Sm, Eu, Yb) form impurity centers in fluorite-like crystals MeF{sub 2}(Me = Ca, Sr, Ba, Cd). The crystal structure of cubic, trigonal and tetragonal centers in MeF{sub 2} has been investigated in the framework of shell model and pair potential approximation. The crystal field parameters were calculated with the exchange charges model, using the optimized geometry of the doped host matrix. With these parameters we have been calculated the optical spectra and spin-Hamiltonian (g-factors) of RE{sup 3+} in MeF{sub 2}, for some combination of R{sup 3+} and MeF{sup 2}. The obtained results were discussed and comparison with experimental data was made. A good agreement confirms the method and model of calculations.
New high pressure rare earth tantalates RExTa2O5+1.5x (RE=La, Eu, Yb)
NASA Astrophysics Data System (ADS)
Zibrov, Igor P.; Filonenko, Vladimir P.; Zakharov, Nikolai D.; Werner, Peter; Drobot, Dmitrii V.; Nikishina, Elena E.; Lebedeva, Elena N.
Rare earth tantalates La0.075Ta2O5.113, Eu0.089Ta2O5.134 and Yb0.051Ta2O5.077 have been prepared by solid state reaction at P=7.0 GPa and T=1050-1100 ░C and studied by X-ray diffraction, thermal analysis and electron microscopy. Low hydrated amorphous tantalum, lanthanum, europium and ytterbium hydroxides were used as starting materials. Aqueous as well as anhydrous compounds were obtained. Title tantalates are crystallized in the structure type of F-Ta2O5 [Zibrov et al. Russ. J. Inorg. Chem. 48 (2003) 464-471] [5]. The structure was refined by the Rietveld method from X-ray powder diffractometer data: La0.075Ta2O5.113, a=10.5099(2), b=7.2679(1), c=6.9765(1) ┼, V=532.90(1) ┼3, Z=6, space group Ibam; Eu0.089Ta2O5.134, a=10.4182(3), b=7.2685(1), c=6.9832(1) ┼, V=528.80(2) ┼3, Z=6, space group Ibam; Yb0.051Ta2O5.077, a=10.4557(2), b=7.3853(1), c=6.8923(1) ┼, V=532.21(1) ┼3, Z=6, space group Ibam. RE atoms do not replace the tantalum in its positions but the only water in the channels of the structure. Highly charged cations RE+3 compress the unit cell so that its volume becomes less than that of F-Ta2O5. Significant decrease of the unit cell volume after water removal from the structure is possible due to the puckering of pentagonal bipyramid layers and change of the corrugation angle in the layer.
VUV spectroscopic properties of rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) type phosphate
Zhi-Jun Zhang; Hao-Hong Chen; Xin-Xin Yang; Jing-Tai Zhao; Guo-Bin Zhang; Chao-Shu Shi
The excitation spectra of pure and rare-earth (RE3+ = Eu, Tb, Tm)-doped AZr2(PO4)3 (A+ = Li, Na, K) in the vacuum ultraviolet (VUV) regions are investigated. The results indicate that these samples show strong absorption in the VUV range. The band ranging from 130 to 160 nm is due to the absorption band of host lattice or PO4 groups; the
Structural and thermoelectric properties of BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu)
Wong-Ng, W.; Yan, Y.; Liu, G. [Ceramics Division, NIST, Gaithersburg, Maryland 20899 (United States); Xie, W.; Tritt, T. [Department of Physics, Clemson University, Greensville, South Carolina 29634 (United States); Kaduk, J. [Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Thomas, E. [Air Force Research Laboratory, Wright Pattersen, Ohio 45433 (United States)
The structure and thermoelectric properties of a series of barium lanthanide cobaltites, BaRCo{sub 4}O{sub 7} (R = Dy, Ho, Er, Tm, Yb, and Lu), which were prepared using the spark plasma synthesis technique, have been investigated. The space group of these compounds was re-determined and confirmed to be P31c instead of the reported P6{sub 3}mc. The lattice parameters a and c range from 6.26279(2) Angst to 6.31181(6) Angst , and from 10.22468(6) Angst to 10.24446(15) Angst for R = Lu to Dy, respectively. The crystal structure of BaRCo{sub 4}O{sub 7} is built up from Kagome sheets of CoO{sub 4} tetrahedra, linked by triangular layers of CoO{sub 4} tetrahedra. The values of figure of merit (ZT) of the BaRCo{sub 4}O{sub 7} samples were determined to be around 0.02 at 800 K. X-ray diffraction patterns of these samples have been determined and submitted to the Powder Diffraction File.
White up-conversion luminescence power and efficiency in Yb(3+)-, Er(3+)- and Tm(3+)-doped BaIn6Y2O13.
Zhang, Jiao; Yang, Yanmin; Mi, Chao; Liu, Yanzhou; Yu, Fang; Li, Xiaohong; Mai, Yaohua
A series of BaIn6Y2O13:Yb(3+), Er(3+), Tm(3+) phosphors with different dopant concentrations have been successfully synthesized by a sol-gel method. In order to obtain efficient white light emitting samples, tri-doped and biphasic samples were prepared. Afterwards, we carried out a systematic study on the up-conversion luminescence (UCL) properties of the samples as functions of doping concentrations and excitation densities. The up-conversion (UC) white light emission powers and efficiencies of samples with different dopant concentrations at different excitation power densities were obtained. The highest white UCL efficiency of up to 0.38% was achieved at excitation densities down to 17.5 W cm(-2) in the biphasic samples. More importantly, we demonstrated that the UC materials with higher efficiency do not necessarily have stronger emission power, and the emission power is the most important parameter. A maximum emission power of up to 1.23 mW was obtained. Furthermore, the impact of temperature on the white UCL was studied, and transparent polymer composites that can emit white light were synthesized by doping BaIn6Y2O13 samples into polymethylmethacrylate (PMMA). PMID:25409772
Crystal structures of the R 3.33CuPb 1.5Se 7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds
L. D. Gulay; I. D. Olekseyuk
The crystal structures of the R3.33CuPb1.5Se7 (R=Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds (space group Cm, Pearson symbol mC25.67) were determined by means of X-ray powder diffraction: a=1.3624(3)nm, b=0.41144(8)nm, c=1.2645(3)nm, ?=104.68(1)░ (for Tb3.33CuPb1.5Se7); a=1.3557(5)nm, b=0.4091(1)nm, c=1.2574(4)nm, ?=104.59(2)░ (for Dy3.33CuPb1.5Se7); a=1.35314(8)nm, b=0.40819(2)nm, c=1.25609(7)nm, ?=104.577(3)░, RI=0.0797 (for Ho3.33CuPb1.5Se7); a=1.35018(7)nm, b=0.40693(2)nm, c=1.25433(6)nm, ?=104.492(2)░, RI=0.0845 (for Er3.33CuPb1.5Se7); a=1.34584(7)nm, b=0.40560(2)nm, c=1.25083(6)nm, ?=104.342(3)░, RI=0.0866
Infrared-active optical phonons and magnetic excitations in the hexagonal manganites RMnO3 (R =Ho, Er, Tm, Yb, and Lu)
NASA Astrophysics Data System (ADS)
Basistyy, R.; Stanislavchuk, T. N.; Sirenko, A. A.; Litvinchuk, A. P.; Kotelyanskii, M.; Carr, G. L.; Lee, N.; Wang, X.; Cheong, S.-W.
Optical properties of hexagonal multiferroic oxides RMnO3, where R=Ho, Er, Tm, Yb, and Lu, have been studied in the far-infrared spectral range between 100 and 2000 cm-1 and temperatures between 1.5 and 300 K by means of several experimental techniques: Mueller matrix spectroscopic ellipsometry, rotating analyzer ellipsometry, and optical transmission spectroscopy. Spectra of the optical phonons are described in terms of the temperature dependencies of their frequency, damping, and oscillator strength. For all studies, oxide materials' clear signatures of the spin-phonon interaction have been found below the temperature of the antiferromagnetic phase transition TN due to magnetic ordering of Mn3+ spins. A decrease of the ionic radius for R3+ ions between Ho3+ and Lu3+ in the corresponding RMnO3 compounds resulted in systematic variation of the frequency for several optical phonons. A magnetic excitation at ś190 cm-1 was observed at low temperatures below TN and interpreted as resulting from two-magnon absorption.
Thermoelectric transport properties of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2
May, Andrew F [ORNL; McGuire, Michael A [ORNL; Ma, Jie [ORNL; Delaire, Olivier A [ORNL; Huq, Ashfia [ORNL; Singh, David J [ORNL; Cai, Wei [ORNL; Wang, Hsin [ORNL
The thermoelectric transport properties of CaMg{sub 2}Bi{sub 2}, EuMg{sub 2}Bi{sub 2}, and YbMg{sub 2}Bi{sub 2} were characterized between 2 and 650 K. As synthesized, the polycrystalline samples are found to have lower p-type carrier concentrations than single-crystalline samples of the same empirical formula. These low carrier concentration samples possess the highest mobilities yet reported for materials with the CaAl{sub 2}Si{sub 2} structure type, with a mobility of {approx}740 cm{sup 2}/V/s observed in EuMg{sub 2}Bi{sub 2} at 50 K. Despite decreases in the Seebeck coefficient ({alpha}) and electrical resistivity ({rho}) with increasing temperature, the power factor ({alpha}{sup 2}{rho}) increases for all temperatures examined. This behavior suggests a strong asymmetry in the conduction of electrons and holes. The highest figure of merit (zT) is observed in YbMg{sub 2}Bi{sub 2}, with zT approaching 0.4 at 600 K for two samples with carrier densities of approximately 2 x 10{sup 18} cm{sup -3} and 8 x 10{sup 18} cm{sup -3} at room temperature. Refinements of neutron powder diffraction data yield similar behavior for the structures of CaMg{sub 2}Bi{sub 2} and YbMg{sub 2}Bi{sub 2}, with smooth lattice expansion and relative expansion in c being {approx}35% larger than relative expansion in a at 973 K. First-principles calculations reveal an increasing band gap as Bi is replaced by Sb and then As, and subsequent Boltzmann transport calculations predict an increase in {alpha} for a given n associated with an increased effective mass as the gap opens. The magnitude and temperature dependence of {alpha} suggests higher zT is likely to be achieved at larger carrier concentrations, roughly an order of magnitude higher than those in the current polycrystalline samples, which is also expected from the detailed calculations.
Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO{sub 4}){sub 2} phosphate
Zhang, Z. J.; Yuan, J. L.; Duan, C. J.; Xiong, D. B.; Chen, H. H.; Zhao, J. T.; Zhang, G. B.; Shi, C. S. [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China) and Graduate School of Chinese Academy of Science, Beijing 100039 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Heifei 230026 (China)
Hexagonal KCaGd(PO{sub 4}){sub 2}:RE{sup 3+} (RE=Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet-ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165 nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce{sup 3+}-doped samples, the bands at 207, 256, 275, and 320 nm are assigned to the 4f-5d transitions of Ce{sup 3+} in KCaGd(PO{sub 4}){sub 2}. For Tb{sup 3+}-doped sample, the bands at 203 and 222 nm are related to the 4f-5d spin-allowed transitions. For Eu{sup 3+}-doped sample, the O{sup 2-}-Eu{sup 3+} charge-transfer band (CTB) at 229 nm is observed, and the fine emission spectrum of Eu{sup 3+} indicates that Eu{sup 3+} ions prefer to occupy Gd{sup 3+} or Ca{sup 2+} sites in the host lattice. For Tm{sup 3+}- and Sm{sup 3+}-doped samples, the O{sup 2-}-Tm{sup 3+} and O{sup 2-}-Sm{sup 3+} CTBs are observed to be at 176 and 186 nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb{sup 3+}-doped KCaGd(PO{sub 4}){sub 2} is a potential candidate for 172 nm excited green plasma display phosphors.
Syntheses, Thermal Stability, and Structure Determination of the Novel Isostructural RBa3B9O18 (R ) Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er,
Wang, Wei Hua
interest as universal hosts of the luminescent materials for tricolor lamps. Consequently, the structure ) Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) X. Z. Li, C. Wang, X. L. Chen,*, H. Li, L. S. Jia, L an analogue structure of -BaB2O4. A series of isostructural borate compounds RBa3B9O18 (R ) Y, Pr, Nd, Sm, Eu
Single-component and warm-white-emitting phosphor NaGd(WO4)2:Tm3+, Dy3+, Eu3+: synthesis, luminescence, energy transfer, and tunable color.
Liu, Yan; Liu, Guixia; Wang, Jinxian; Dong, Xiangting; Yu, Wensheng
Tm(3+), Dy(3+), and Eu(3+) codoped NaGd(WO4)2 phosphors were prepared by a facile hydrothermal process; they were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectrometer (EDS), photoluminescence spectra, and fluorescence lifetime. The results show that the novel octahedral microcrystals with a mean side length of 2 ?m are obtained. Under the excitation of ultraviolet, individual RE(3+) ion (Tm(3+), Dy(3+), and Eu(3+)) activated NaGd(WO4)2 phosphors exhibit excellent emission properties in their respective regions. Moreover, when codoping Dy(3+) and Eu(3+)/Tm(3+) in the single component, the energy migration from Dy(3+) to Eu(3+) has been demonstrated to be a resonant type via a dipole-quadrupole mechanism as well as that from Tm(3+) to Dy(3+) ions, of which the critical distance (R(Dy-Eu)) is calculated to be 11.08 ┼. More significantly, in the Tm(3+), Dy(3+), and Eu(3+) tridoped NaGd(WO4)2 phosphors, the energy migration of Tm(3+)-Dy(3+)-Eu(3+), utilized for sensitizing Eu(3+) ions besides compensating the red component at low Eu(3+) doping concentration, has been discussed first. In addition, under 365 nm near-ultraviolet radiation (nUV), the color-tunable emissions in octahedral NaGd(WO4)2 microcrystals are realized by giving abundant blue, green, white, yellow, and red emissions, especially warm white emission, and could be favorable candidates in full-color phosphors for nUV-LEDs. PMID:25303406
Up-conversion emission tuning in triply-doped Yb3+/Tm3+/Er3+ novel fluoro-phosphate glass and glass-ceramics
NASA Astrophysics Data System (ADS)
Ledemi, Yannick; Trudel, Andrķe.-Anne; Rivera, Victor A. G.; Messaddeq, Younes
New Yb3+, Er3+ and Tm3+ triply doped fluoro-phosphate glasses belonging to the system NaPO3-YF3-BaF2-CaF2 have been prepared by the classical melt-casting technique. Glasses containing up to 10 wt.% of rare-earth ions fluorides have been obtained and characterized by using differential scanning calorimetry (DSC), UV-visible-near-infrared spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and optically homogeneous glass-ceramics have been reproducibly obtained by appropriate heat treatment in view to manage the red, green and blue emissions upon 975 nm laser excitation. According to the applied thermal heat-treatment, a large enhancement of intensity of the up-conversion emission - from 10 to 160 times higher - has been achieved in the glassceramics compared to that of glasses, suggesting incorporation of the rare-earth ions into the crystalline phase. Furthermore, a large range of color rendering has been observed in these materials by controlling the laser excitation power and material crystallization rate. Time-resolved luminescence experiments as well as X-ray diffractometry and scanning electron microscopy techniques have been employed in order to understand and correlate the multicolor emission changes to the crystallization behavior of this material. A progressive phase transformation of the fluorite-type CaF2-based nanocrystals initially generated was observed along with increasing heat-treatment time, thus modifying the rare earth ions spectroscopic features.
Hydrothermal synthesis and luminescence properties of hierarchical SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) micro/nanocomposite architectures
Peng, Jing; Hou, Suying; Liu, Xianchun [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China); Feng, Jing [State Key Laboratory of Rare Earth Resource Utilizations, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)] [State Key Laboratory of Rare Earth Resource Utilizations, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Yu, Xiaodan [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China); Xing, Yan, E-mail: firstname.lastname@example.com [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China); Su, Zhongmin [College of Chemistry, Northeast Normal University, Changchun 130024 (China)] [College of Chemistry, Northeast Normal University, Changchun 130024 (China)
Graphical abstract: Uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microsphere assembled by numerous nanoplates have been successfully synthesized via a facile hydrothermal process in the presence of chelating reagent. Highlights: Black-Right-Pointing-Pointer Uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microsphere were obtained by a simple hydrothermal method. Black-Right-Pointing-Pointer The reaction time, chelating reagent and F source play important roles for the formation of hierarchical microspheres. Black-Right-Pointing-Pointer The luminescence properties of lanthanide ion-doped SrF{sub 2} hierarchical microstructures were discussed. -- Abstract: Highly uniform SrF{sub 2} and SrF{sub 2}:Ln{sup 3+} (Ln = Er, Nd, Yb, Eu, Tb) hierarchical microspheres assembled by 2D nanoplates have been successfully synthesized by a facile and friendly hydrothermal route. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra were used to characterize the samples. The experimental results indicate that reaction time and chelating reagent play a key role in forming the hierarchical microspheres. The formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. The near-infrared luminescence of lanthanide ions (Er, Nd, and Yb) doped SrF{sub 2} microspheres were discussed in detail. In addition, the as-obtained SrF{sub 2}:Eu{sup 3+} sample exhibits orange-red emission centered at 590 nm under excitation at 393 nm, while the SrF{sub 2}:Tb{sup 3+} exhibits a strong green emission at 540 nm. The as-synthesized SrF{sub 2}:Ln{sup 3+} luminescent microspheres might find some potential applications in areas of photoluminescence, telecommunication and laser emission.
Structure, enhancement and white luminescence of multifunctional Lu6O5F8:20%Yb3+,1%Er3+(Tm3+) nanoparticles via further doping with Li+ under different excitation sources
NASA Astrophysics Data System (ADS)
Guo, Linna; Wang, Yuhua; Wang, Yanzhao; Zhang, Jia; Dong, Pengyu; Zeng, Wei
A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices.A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 <= x <= 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33577h
New high pressure rare earth tantalates RE{sub x}Ta{sub 2}O{sub 5+1.5x} (RE=La, Eu, Yb)
Zibrov, Igor P., E-mail: email@example.com [Institute for High Pressure Physics, Russian Academy of Sciences, Kaluzhskoe Highway 14, Troitsk, Moscow 142190 (Russian Federation); Filonenko, Vladimir P., E-mail: firstname.lastname@example.com [Institute for High Pressure Physics, Russian Academy of Sciences, Kaluzhskoe Highway 14, Troitsk, Moscow 142190 (Russian Federation); Zakharov, Nikolai D., E-mail: email@example.com [Max Planck Institute for Microstructure Physics, Weinberg 2, D-06120 Halle/Saale (Germany); Werner, Peter, E-mail: email@example.com [Max Planck Institute for Microstructure Physics, Weinberg 2, D-06120 Halle/Saale (Germany); Drobot, Dmitrii V., E-mail: email@example.com [Lomonosov Moscow University of Fine Chemical Technology, Prospect Vernadskogo 86, Moscow 119571 (Russian Federation); Nikishina, Elena E.; Lebedeva, Elena N., E-mail: firstname.lastname@example.com [Lomonosov Moscow University of Fine Chemical Technology, Prospect Vernadskogo 86, Moscow 119571 (Russian Federation)
Rare earth tantalates La{sub 0.075}Ta{sub 2}O{sub 5.113}, Eu{sub 0.089}Ta{sub 2}O{sub 5.134} and Yb{sub 0.051}Ta{sub 2}O{sub 5.077} have been prepared by solid state reaction at P=7.0 GPa and T=1050¢1100 ░C and studied by X-ray diffraction, thermal analysis and electron microscopy. Low hydrated amorphous tantalum, lanthanum, europium and ytterbium hydroxides were used as starting materials. Aqueous as well as anhydrous compounds were obtained. Title tantalates are crystallized in the structure type of F¢Ta{sub 2}O{sub 5} [Zibrov et al. Russ. J. Inorg. Chem. 48 (2003) 464¢471] [5]. The structure was refined by the Rietveld method from X-ray powder diffractometer data: La{sub 0.075}Ta{sub 2}O{sub 5.113}, a=10.5099(2), b=7.2679(1), c=6.9765(1) ┼, V=532.90(1) ┼{sup 3}, Z=6, space group Ibam; Eu{sub 0.089}Ta{sub 2}O{sub 5.134}, a=10.4182(3), b=7.2685(1), c=6.9832(1) ┼, V=528.80(2) ┼{sup 3}, Z=6, space group Ibam; Yb{sub 0.051}Ta{sub 2}O{sub 5.077}, a=10.4557(2), b=7.3853(1), c=6.8923(1) ┼, V=532.21(1) ┼{sup 3}, Z=6, space group Ibam. RE atoms do not replace the tantalum in its positions but the only water in the channels of the structure. Highly charged cations RE{sup +3} compress the unit cell so that its volume becomes less than that of F¢Ta{sub 2}O{sub 5}. Significant decrease of the unit cell volume after water removal from the structure is possible due to the puckering of pentagonal bipyramid layers and change of the corrugation angle in the layer. - Graphical abstract: The structure of RE{sub x}Ta{sub 2}O{sub 5+1.5x} and its HRTEM image (ōAö arrows show empty channel, ōBö arrows show filled channel). - Highlights: Ģ We synthesized new tantalates of RE under high pressure high temperature conditions. Ģ RE atoms replace water molecules in the channels of the structure. Ģ Aqueous as well as anhydrous tantalates were obtained. Ģ Highly charged cations RE{sup +3} compress the unit cell decreasing RE¢O distances.
Turn-on detection of a cancer marker based on near-infrared luminescence energy transfer from NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles to gold nanorods.
Chen, Hongqi; Guan, Yingying; Wang, Shaozhen; Ji, Yuan; Gong, Mengqi; Wang, Lun
A homogeneous immunoassay for the sensitive and selective determination of trace amounts of ?-fetoprotein (AFP, a cancer marker) by detection in the near-infrared (NIR) region based on luminescence energy transfer (LET) from NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles to gold nanorods (GNRs) is presented. The carboxyl-functionalized NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles (UCNPs) were excited by a 980 nm continuous wavelength laser, and its emission peak appeared at a near-infrared wavelength (?804 nm). The carboxyl-functionalized upconverting nanoparticles were conjugated with the anti-AFP (Ab1) and acted as donor. GNRs with a high absorption band around 790 nm, which was overlapped the UCNPs emission, were synthesized and acted as the acceptor. The donor (negatively charged) interacted with the acceptor (positively charged) via electrostatic interactions to bring them into close proximity. LET could occur, producing a quenching phenomenon. When the AFP antigens were added into the system, the binding affinity between AFP and Ab1 was stronger than the electrostatic interactions, which released the energy acceptors from the energy donors, interrupting luminescence energy transfer, and therefore, the luminescence was recovered. On the basis of the restored luminescence, a turn-on optical immunosening system was developed. Under the optimal conditions, the linear range of detection was from 0.18 to 11.44 ng/mL for AFP (R = 0.99), with a detection limit as low as 0.16 ng/mL. The proposed method has also been used to monitor AFP in human serum samples. Therefore, further study based on the NaYF4:Yb,Tm/NaGdF4 core-shell nanoparticles-GNRs construction may open the way for a new class of NIR-LET biosensors with wide applications. PMID:25296290
Spatial distribution of defects and the kinetics of nonequilibrium charge carriers in GaN wurtzite crystals doped with Sm, Eu, Er, Tm, and supplementary Zn impurities
Mezdrogina, M. M., E-mail: firstname.lastname@example.com; Krivolapchuk, V. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Kozhanova, Yu. V. [St. Petersburg State Polytechnical University (Russian Federation)
By analyzing time-resolved and steady-state photoluminescence spectra, it is established that the spatial distribution of rare-earth ion dopants in wurtzite GaN crystals doped with Sm, Eu, Er, or Tm is governed by the type and concentration of defects in the initial semiconductor matrix as well as by the type of the impurity (its capacity for segregation). Doping with multicharged rare-earth impurities and additionally introduced Zn impurity leads to an intensification of emission. The effect of intensification of emission in the case of n-and p-GaN crystals is considered with the use of the model of isoelectronic traps.
Photoluminescence properties of rare earths (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+}) activated NaInW{sub 2}O{sub 8} wolframite host lattice
Asiri Naidu, S.; Boudin, S. [Laboratoire de Cristallographie et Sciences des Materiaux, ENSICAEN, Universite de Caen, CNRS, 6 Bd Marechal Juin, F-14050 Caen (France); Varadaraju, U.V. [Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India); Raveau, B., E-mail: firstname.lastname@example.com [Laboratoire de Cristallographie et Sciences des Materiaux, ENSICAEN, Universite de Caen, CNRS, 6 Bd Marechal Juin, F-14050 Caen (France)
The photoluminescence (PL) studies on NaIn{sub 1-x}RE{sub x}W{sub 2}O{sub 8}, with RE=Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+} phases have shown that the relative contribution of the host lattice and of the intra-f-f emission of the activators to the PL varies with the nature of the rare earth cation. In the case of Dy{sup 3+} and Tm{sup 3+} activators, with yellow and blue emission, respectively, the energy transfer from host to the activator plays a major role. In contrast for Eu{sup 3+}, with intense red emission, the host absorption is less pronounced and the intra-f-f transitions of the Eu{sup 3+} ions play a major role, whereas for Tb{sup 3+} intra-f-f transitions are only observed, giving rise to green emission. - Graphical abstract: NaInW{sub 2}O{sub 8} double tungstate doped with Eu{sup 3+}, Dy{sup 3+}, Tb{sup 3+}and Tm{sup 3+} shows characteristic emission of intense red for Eu{sup 3+}, yellow for Dy{sup 3+}, green for Tb{sup 3+} and blue for Tm{sup 3+}. Highlights: Black-Right-Pointing-Pointer Characteristic emissions of rare earths (Eu{sup 3+}, Tb{sup 3+}, Dy{sup 3+} and Tm{sup 3+}) are observed NaInW{sub 2}O{sub 8} wolframite. Black-Right-Pointing-Pointer Energy transfer from host to the activators (Eu{sup 3+} Dy{sup 3+} Tm{sup 3+} is observed. Black-Right-Pointing-Pointer PL properties of rare earth ions depend on minor structural variations in the host lattice.
Lattice dynamics of rare-earth titanates with the structure of pyrochlore R 2Ti2O7 ( R = Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu): Ab initio calculation
NASA Astrophysics Data System (ADS)
Chernyshev, V. A.; Petrov, V. P.; Nikiforov, A. E.
The ab initio calculation has been performed for the crystal structure and the phonon spectrum of titanates with the structure of pyrochlore R 2Ti2O7 ( R = Gd-Lu). The frequencies and types of fundamental vibrations have been found. For R = Tb, Tm, and Yb, this calculation has been carried out for the first time; furthermore, there is no available information on experimental studies of the phonon spectrum for Tm and Yb. The influence of hydrostatic pressure to 35 GPa on the structure, dynamics, and elastic properties of the Gd2Ti2O7 lattice has been investigated. The dependence of the phonon frequencies on the pressure has been obtained. The calculations have predicted that the relative change in the pyrochlore structure volume during compression at pressures to 35 GPa is well described by the third-order Birch-Murnaghan equation of states. The results of the calculations agree with the available experimental data. It has been shown that the structural, dynamic, and elastic properties of the R 2Ti2O7 crystal lattice can be adequately described in the case where the inner shells of the RE ion up to 4 f are replaced by the pseudopotential.
Highly uniform and monodisperse GdOF:Ln3+ (Ln = Eu, Tb, Tm, Dy, Ho, Sm) microspheres: hydrothermal synthesis and tunable-luminescence properties.
Zhang, Yang; Kang, Xiaojiao; Geng, Dongling; Shang, Mengmeng; Wu, Yuan; Li, Xuejiao; Lian, Hongzhou; Cheng, Ziyong; Lin, Jun
GdOF:Ln(3+) (Ln = Eu, Tb, Tm, Dy, Ho and Sm) microspheres (1.5 ?m) with high uniformity and monodispersity have been synthesized via a facile hydrothermal method followed by heat treatment (600 ░C). X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the resulting samples. A series of controlled experiments indicate that sodium citrate (Cit(3-)) as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the dosage of Cit(3-) and pH values in the initial solution. The possible formation mechanism for these microspheres has been presented. Under UV light and low-voltage electron beam excitation, GdOF:Ln(3+) microspheres show the characteristic f-f transitions of Ln(3+) (Eu, Tb/Ho, Tm, Dy and Sm) ions and give bright red, green, blue, yellow and yellowish-orange emission, respectively. In addition, multicolored luminescence containing white emission have been successfully confected for co-doped GdOF:Ln(3+) phosphors by changing the doped Ln(3+) ions and adjusting their doping concentrations due to the simultaneous luminescence of Ln(3+) in the GdOF host, making these materials have potential applications in field-emission display devices. PMID:23942823
EPR study of the ground state of Mn2+ impurity ions in alumoborates MAl3(BO3)4 (MĀ=ĀY, Eu, Tm)
NASA Astrophysics Data System (ADS)
Prokhorov, ? ?; Prokhorov, A. D.; Chernush, L. F.; Dyakonov, V. P.; Szymczak, H.; Dejneka, A.
New data about the ground state of the Mn2+ impurity ions in a series of single crystals of alumbrados MAl3(BO3)4, where M = Y,Eu,Tm were obtained. The electron paramagnetic resonance (EPR) spectra of the Mn2+ spectra were studied, the parameters of the spin Hamiltonian describing the angular dependence of the spectrum were defined. It was shown that Mn2+ ions substitute trivalent ions of rare earth metals without changing the symmetry of the substitution site. The charge compensation process was found to be a nonlocal one. The cooling of the crystals leads to the increase of the splitting of the ground state, which is associated with the anisotropy of the thermal expansion coefficient. It was shown that an application of the superposition model to explain the distortions induced by an impurity Mn2+ ion has some limitations. The EPR linewidth of the Mn2+ ion in the TmAl3(BO3)4 crystal increases with increasing temperature as a result of the dipole¢dipole and exchange interactions with the excited states of the host lattice Tm3+ ion.
Crystal structures of RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) studied by single crystal X-ray diffraction
Gribanov, Alexander [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Chemistry Department of the Moscow State University, Leninskie Gory, GSP-1, 119991 Moscow (Russian Federation); Grytsiv, Andriy [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Rogl, Peter, E-mail: email@example.com [Institute of Physical Chemistry, University of Vienna, Waehringerstrasse 42, A-1090 Wien (Austria); Seropegin, Yurii [Chemistry Department of the Moscow State University, Leninskie Gory, GSP-1, 119991 Moscow (Russian Federation); Giester, Gerald [Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14, A-1090 Wien (Austria)
The crystal structures of ternary compounds RPt{sub 3-x}Si{sub 1-y}(R=Y, Tb, Dy, Ho, Er, Tm, Yb) have been elucidated from X-ray single crystal CCD data. All compounds are isotypic and crystallize in the tetragonal space group P4/mbm. The general formula RPt{sub 3-x}Si{sub 1-y} arises from defects: x{approx}0.20, y{approx}0.14. The crystal structure of RPt{sub 3-x}Si{sub 1-y} can be considered as a packing of four types of building blocks which derive from the CePt{sub 3}B-type unit cell by various degrees of distortion and Pt, Si-defects. - Graphical Abstract: Electron density in RPt{sub 3-x}Si{sub 1-y} at 0, 1/2 , 0.
High-throughput and microwave investigation of rare earth phosphonatoethanesulfonates-Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) (Ln=Ho, Er, Tm, Yb, Lu, Y)
Sonnauer, Andreas [Institute of Inorganic Chemistry, Christian-Albrechts-University, Otto-Hahn-Platz 6/7, D 24118 Kiel (Germany); Stock, Norbert [Institute of Inorganic Chemistry, Christian-Albrechts-University, Otto-Hahn-Platz 6/7, D 24118 Kiel (Germany)], E-mail: email@example.com
Following the strategy of using bifunctional phosphonic acids for the synthesis of new metal phosphonates, the flexible ligand 2-phosphonoethanesulfonic acid, H{sub 2}O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}H (H{sub 3}L), was used in a high-throughput (HT) and microwave investigation of rare earth phosphonatoethanesulfonates. The HT-investigation led to six isotypic compounds Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) with Ln=Ho (1), Er (2), Tm (3), Yb (4), Lu (5) and Y (6). The syntheses were scaled-up in glass reactor tubes in order to obtain larger amounts for a detailed characterization. Based on these results all compounds could be also synthesized by microwave-assisted heating and the influence of reaction time and stirring rate during the synthesis was established. For compound 2 the crystal structure was determined by single-crystal X-ray diffraction. The compounds contain isolated slightly distorted LnO{sub 6} octahedra that are connected by the phosphonate and sulfonate groups into a three-dimensional framework. Thermogravimetric investigations demonstrate the high thermal stability of the compounds up to 460 deg. C. - Graphical abstract: A high-throughput and microwave investigation of the System LnX{sub 3}/H{sub 2}O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}/NaOH/H{sub 2}O led to six new compounds Ln(O{sub 3}P-C{sub 2}H{sub 4}-SO{sub 3}) with Ln=Ho, Er, Tm, Yb, Lu, Y.
Enhancing upconversion emissions of NaTm0.02YbxY0.98xF4 nanocrystals through increasing Yb3
Cao, Wenwu
March 2011 Available online 12 April 2011 Keywords: Upconversion Enhancement NaYF4 a b s t r a c and Tm3■ ions [8Ł12]. Among inorganic nanocrystals, NaYF4 has been known to be the most efficient UC host experimen- tal investigations demonstrated that 2 mol% Tm3■ in NaYF4 nano- crystals is the optimal doping
Ag{sub 2}O dependent up-conversion luminescence properties in Tm{sup 3+}/Er{sup 3+}/Yb{sup 3+} co-doped oxyfluorogermanate glasses
Hu, Yuebo [Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Qiu, Jianbei, E-mail: email@example.com; Song, Zhiguo; Zhou, Dacheng [Key Laboratory of Advanced Materials in Rare and Precious and Non-ferrous Metals, Ministry of Education, Key Laboratory of Advanced Materials of Yunnan Province, Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)
Up-conversion (UC) luminescence properties of Ag/Tm{sup 3+}/Er{sup 3+}/Yb{sup 3+} co-doped oxyfluorogermanate glasses have been studied to assess the effective role of silver nanoparticles as a sensitizer for Tm{sup 3+} and Er{sup 3+} ions. The X-ray diffraction patterns obtained in this work do not reveal any crystalline phase in the glass. However, the absorption spectra reveal that surface plasmons resonance band of Ag undergoes a distinct split with two maxima and a very broad absorption peak with a background that extends toward the near infrared (NIR) with the increasing of Ag{sub 2}O added concentration. Transmission electron microscope images confirm that silver nanoparticles have been precipitated from matrix glasses and show their distribution, size, and shapes. In addition, changes in UC luminescence intensity of four emission bands 476, 524, 546, and 658?nm corresponding to {sup 1}G{sub 4} ? {sup 3}H{sub 6} (Tm{sup 3+}), ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) ? {sup 4}I{sub 15/2} (Er{sup 3+}), and {sup 4}F{sub 9/2} ? {sup 4}I{sub 15/2} (Er{sup 3+}) transitions, respectively, as a function of silver addition to the base composition have been measured under 980?nm excitation. It is confirmed that Ag{sub 2}O added concentration plays an important role in increasing the UC luminescence intensity; however, further increase in Ag{sub 2}O added concentration reduces the intensity.
Structure determination of KScS2, RbScS2 and KLnS2 (Ln = Nd, Sm, Tb, Dy, Ho, Er, Tm and Yb) and crystal-chemical discussion.
Havlßk, LubomĒr; Fßbry, Jan; Henriques, Margarida; DuÜek, Michal
The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the ?-NaFeO2 structure type in agreement with the ratio of the ionic radii r(3+)/r(+). KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S-S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S(2-)) and the bond-valence sums. PMID:26146403
Synthesis, Characterization, and Application in HeLa Cells of an NIR Light Responsive Doxorubicin Delivery System Based on NaYF4:Yb,Tm@SiO2-PEG Nanoparticles.
Alonso-Cristobal, Paulino; Oton-Fernandez, Olalla; Mendez-Gonzalez, Diego; DĒaz, J Fernando; Lopez-Cabarcos, Enrique; Barasoain, Isabel; Rubio-Retama, Jorge
Herein, we present a phototriggered drug delivery system based on light responsive nanoparticles, which is able to release doxorubicin upon NIR light illumination. The proposed system is based on upconversion fluorescence nanoparticles of ?-NaYF4:Yb,Tm@SiO2-PEG with a mean diameter of 52 ▒ 2.5 nm that absorb the NIR light and emit UV light. The UV radiation causes the degradation of photodegradable ortho-nitrobenzyl alcohol derivates, which are attached on one side to the surface of the nanoparticles and on the other to doxorubicin. This degradation triggers the doxorubicin release. This drug delivery system has been tested "in vitro" with HeLa cells. The results of this study demonstrated that this system caused negligible cytotoxicity when they were not illuminated with NIR light. In contrast, under NIR light illumination, the HeLa cell viability was conspicuously reduced. These results demonstrated the suitability of the proposed system to control the release of doxorubicin via an external NIR light stimulus. PMID:26094748
Enhanced dual contrast agent, Co(2+)-doped NaYF4:Yb(3+),Tm(3+) nanorods, for near infrared-to-near infrared upconversion luminescence and magnetic resonance imaging.
Xia, Ao; Zhang, Xiaofeng; Zhang, Jun; Deng, Yunyun; Chen, Qiang; Wu, Shishan; Huang, Xiaohua; Shen, Jian
Dual-modality imaging with magnetic resonance (MR) and upconversion luminescence (UCL) is a promising technique for molecular imaging in biomedical research. Multifunctional lanthanide-based nanoparticles have been widely investigated as agents for contrast enhanced MR and fluorescence imaging. However, the use of rare earth fluoride nanoparticles for dual-modality imaging of T2-weighted MR and UCL is rarely reported. We find that NaYF4:Yb(3+),Tm(3+),Co(2+) (MUC) nanorods can be applied as a high-performance dual contrast agent for both T2-weighted MR and UCL dual-modality imaging. After modification with 6-O-carboxymethyl chitosan (OCC), MUC nanorods can be endocytosed by cells without showing signs of cytotoxicity. High-quality UCL images of living cells incubated with MUC-OCC nanorods were acquired on a near-infrared (NIR) confocal microscopy under the excitation at 980Ānm. Moreover, MUC-OCC nanorods display high transverse (r2) relaxivities inĀvitro. The application of low-dose MUC-OCC nanorods for NIR-to-NIR UCL and MR dual-modality inĀvivo imaging was also carried out successfully. In addition, the toxicity of MUC-OCC nanorods was evaluated by MTT assay, serological tests and histological analysis of visceral organs. PMID:25108318
Enhanced ultraviolet upconversion luminescence of Tm and Yb codoped ZrF4-BaF2-LaF3-AlF3-NaF glass.
He, Chunfeng; Zhao, Dan; Qin, Guanshi; Zheng, Kezhi; Qin, Weiping
Ultraviolet (UV) upconversion (UC) luminescence properties of Tm3+ ions sensitized by Yb3+ ions in ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass were studied in detail. Under the excitation from a 980 nm continuous wave (CW) diode laser, red, blue, and even UV emissions were observed in the fluorozirconate glass. Several fluorescence bands appeared in the UC emission spectrum from 292.8 nm to 805.8 nm. The UC emission peaks at 291 nm, 347 nm, 363 nm, 454 nm, 475 nm, 647 nm, 687 nm, and 804 nm correspond to the transitions of 1I6 --> 3H6, 1I6 --> 3F4, 1D2 --> 3H6, 1D2 --> 3F4, 1G4 --> 3H6, 1G4 --> 3F4, 3F3 --> 3H6, and 3H4 --> 3H6, respectively. Experimental results of intensity dependence of the up-converted fluorescence on the pump power indicate a five-photon excitation scheme of 1I6 energy level. PMID:22413235
Direct synthesis of hexagonal NaGdF? nanocrystals from a single-source precursor: upconverting NaGdF? :Yb│? ,Tm│? and its composites with TiO? for near-IR-driven photocatalysis.
Chen, Ying; Mishra, Shashank; Ledoux, Gilles; Jeanneau, Erwann; Daniel, Marlene; Zhang, Jinlong; Daniele, Stķphane
A novel single-source precursor NaGd(TFA)4 (diglyme) (TFA=trifluoroacetate) was synthesized, characterized thoroughly, and used to obtain the hexagonal phase of NaGdF4 nanoparticles as an efficient matrix for lanthanide-doped upconverting nanocrystals (NCs) that convert near-infrared radiation into shorter-wavelength UV/visible light. These NCs were then used to prepare well-characterized TiO2@NaGdF4:Yb(3+),Tm(3+) nanocomposites to extend the absorption range of the TiO2 photocatalyst from the UV to the IR region. While the visible/near IR part of the photoluminescent spectra remains almost unaffected by the presence of TiO2, the UV part is strongly quenched due to the absorption of TiO2 above its gap at approximately 380?nm by energy transfer or FRET. Preliminary results on the photocatalytic activity of the above obtained nanocomposites are presented. PMID:24910325
Electronic states of R F e2O4(R =Lu ,Yb ,Tm ,Y ) mixed-valence compounds determined by soft x-ray absorption spectroscopy and x-ray magnetic circular dichroism
NASA Astrophysics Data System (ADS)
Lafuerza, Sara; GarcĒa, JoaquĒn; SubĒas, Gloria; Blasco, Javier; Herrero-MartĒn, Javier; Pascarelli, Sakura
We here report an investigation of the electronic states in the R F e2O4(R =Lu ,Yb ,Tm ,Y ) mixed-valence ferrites by means of soft x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements together with ab initio theoretical calculations. The presence of Fe+2 and Fe+3 pure ionic species is discarded in the XAS spectra at the O K edge in both experimental data and simulations based on the multiple scattering theory. Similarly, no trace of F e+2/F e+3 contributions is detected in the XMCD spectra at the Fe K edge. On the other hand, the XAS and XMCD spectra at the Fe L2 ,3 edges can be well described in terms of F e+2/F e+3 contributions, and are also supported by multiplet calculations. This finding can be interpreted as the existence of a mixture of 3 d5/3 d6 configurations at the Fe atoms. Alternative ferrimagnetic spin orderings based on a trimodal Fe valence distribution are also proposed and discussed. Finally, a possible explanation for the strong dependence of the Fe L2 ,3 edges XMCD signal magnitude on both the sample surface preparation and detection method is presented.
(?-NaYbF4:Tm3+)/CaF2 Core/Shell Nanoparticles with Efficient Near-Infrared to Near-Infrared Upconversion for High-Contrast Deep Tissue Bioimaging
Chen, Guanying; Shen, Jie; Ohulchanskyy, Tymish Y.; Patel, Nayan J.; Kutikov, Artem; Li, Zhipeng; Song, Jie; Pandey, Ravindra K.; ┼gren, Hans; Prasad, Paras N.; Han, Gang
We describe the development of novel and biocompatible core/shell (?-NaYbF4:Tm3+)/CaF2 nanoparticles which exhibit highly efficient NIRin-NIRout upconversion (UC) for high contrast and deep bioimaging. When excited at ~980 nm, these nanoparticles emit photoluminescence (PL) peaked at ~800 nm. The quantum yield of this UC PL under low power density excitation (~0.3 W/cm2) is 0.6▒0.1%. This high UC PL efficiency is realized by suppressing surface quenching effects via hetero-epitaxial growth of a biocompatible CaF2 shell which results in a 35-fold increase in the intensity of UC PL from the core. Small animal whole-body UC PL imaging with exceptional contrast (signal-to-background ratio of 310) is shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles (700 pmol/kg). High-contrast UC PL imaging of deep tissues is also demonstrated, using a nanoparticle-loaded synthetic fibrous mesh wrapped around rat femoral bone, and a cuvette with nanoparticle aqueous dispersion - covered with a 3.2-cm thick animal tissue (pork). PMID:22928629
The high-pressure synthesis and characterization of some praseodymium-substituted rare-earth-based R{sub 2}Ba{sub 4}Cu{sub 7}O{sub 14-{delta}} (R = Nd, Eu, Tm)
Teng-Ming Chen; Kao, F.S. [National Chiao-Tung Univ., Taiwan (China)
The formation of phases in the (R{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} (Pr-doped R247; R = Nd, Eu, Tm) system with x = 0-1.0 was investigated. Samples of the title series were synthesized at 980-990{degree}C at 25 bar O{sub 2}, followed by annealing at 300{degree}C under 130 bar O{sub 2} for 30 hr. Oxygen content of the samples has been determined by iodometric titration. Single-phased samples has been determined by iodometric titration. Single-phased samples were obtained with x smaller than or equal to 0.3, 0.4, and 0.4 for R = Nd, Eu, and Tm, respectively, as indicated by X-ray diffraction measurements. With increasing amount of Pr substituting for R, the cell dimensions of the Pr-doped R247 phases were found to expand steadily, whereas the corresponding structural orthorhombicity was observed to decrease systematically. Superconducting transition temperatures (T{sub c}`s) of the title phases were found to be significantly suppressed upon Pr doping, as indicated by field-cooled temperature-dependent magnetization studies. The effect of Pr substitution on T{sub c}`s of R247 (R = Y, Eu, Er, Tm, Nd, Dy) phases was investigated and compared as a function of R{sup 3+} radii, but no size dependence effect was observed. In addition, field-dependent magnetization studies for a series of (Eu{sub 1-x}Pr{sub x}){sub 2}Ba{sub 4}Cu{sub 7}O{sub 14+{delta}} samples with x = 0, 0.2, and 0.4, respectively, are also reported.
Ce{sub 2}AgYb{sub 5/3}Se{sub 6}, La{sub 2}CuErTe{sub 5}, and Ce{sub 2}CuTmTe{sub 5}: Three new quaternary interlanthanide chalcogenides
Babo, Jean-Marie [Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Albrecht-Schmitt, Thomas E., E-mail: email@example.com [Department of Chemistry and Biochemistry, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, IN 46556 (United States)
Three new ordered quaternary interlanthanide chalcogenides, Ce{sub 2}AgYb{sub 5/3}Se{sub 6}, La{sub 2}CuErTe{sub 5}, and Ce{sub 2}CuTmTe{sub 5}, have been prepared by direct reaction of the elements in molten NaBr at 900 Degree-Sign C. Each compound forms a new structure-type. The Ce{sub 2}AgYb{sub 5/3}Se{sub 6} structure consists of {infinity}{sup 2}{l_brace} [AgYb{sub 5/6}Se{sub 6}]{sup 6-}{r_brace} layers intercalated by Ce{sup 3+} cations. These layers are composed of {infinity}{sup 1}{l_brace} [Yb{sub 5/3}Se{sub 6}]{sup 7-}{r_brace} quadruplet ribbons of [YbSe{sub 6}]{sup 9-} octahedra and infinite {infinity}{sup 1}{l_brace} [AgSe{sub 6}]{sup 11-}{r_brace} double chains of [AgSe{sub 5}]{sup 9-}. The La{sub 2}CuErTe{sub 5} structure is made of one-dimensional {infinity}{sup 1}{l_brace} [CuErTe{sub 5}]{sup 6-}{r_brace} ribbons separated by La{sup 3+} cations. These ribbons are formed by cis-edge sharing {infinity}{sup 1}{l_brace} [CuTe{sub 2}]{sup 3-}{r_brace} tetrahedral chains and trans-edge sharing {infinity}{sup 1}{l_brace} [ErTe{sub 4}]{sup 5-}{r_brace} chains. While La{sub 2}CuErTe{sub 5} crystallizes in the orthorhombic space group Pnma, Ce{sub 2}CuTmTe{sub 5} crystallizes in the monoclinic space group C2/m. The latter crystal structure is assembled from {infinity}{sup 2}{l_brace} [CuTmTe{sub 5}]{sup 6-}{r_brace} layers intercalated by Ce{sup 3+} cations. These layers consist of single {infinity}{sup 1}{l_brace} [TmTe{sub 4}]{sup 5-}{r_brace} chains connected to each other through dimers or pseudo-double chains. - Graphical abstract: [CuTe{sub 4}]{sup 7-} tetrahedra sharing cis-edges to yield chains in the La{sub 2}CuErTe{sub 5}. Highlights: Black-Right-Pointing-Pointer New ordered interlanthanide tellurides. Black-Right-Pointing-Pointer New quaternary chalcogenides. Black-Right-Pointing-Pointer Low-dimensional lanthanide chalcogenide substructures. Black-Right-Pointing-Pointer Flux synthesis of new chalcogenides.
A NEW VISION OF PHOTODARKENING IN Yb3+ -DOPED FIBERS
Paris-Sud XI, Universitķ de
operation, which strongly lowers the laser efficiency. We show how thulium impurities, present at the parts here that the presence of thulium ions, even at very low concentration levels, can lead to UV light to as the Yb sample. The second one is co-doped with 0.03 wt.% thulium (Yb-Tm sample). Despite the Optical
Rapid, large-scale, morphology-controllable synthesis of YOF:Ln3+ (Ln = Tb, Eu, Tm, Dy, Ho, Sm) nano-/microstructures with multicolor-tunable emission properties.
Zhang, Yang; Geng, Dongling; Kang, Xiaojiao; Shang, Mengmeng; Wu, Yuan; Li, Xuejiao; Lian, Hongzhou; Cheng, Ziyong; Lin, Jun
YOF:Ln(3+) (Ln = Tb, Eu, Tm, Dy, Ho, Sm) nano-/microstructures with a variety of novel and well-defined morphologies, including nanospheres, nanorod bundles, and microspindles, have been prepared through a convenient modified urea-based homogeneous precipitation (UBHP) technique followed by a heat treatment. The sizes and morphologies of the YOF products could be easily modulated by changing the pH values and fluoride sources. XRD, TG-DTA, FT-IR, SEM, and TEM, as well as photoluminescence (PL) and cathodoluminescence (CL) spectra, were used to characterize the prepared samples. The YOF:Ln(3+) nanospheres show the characteristic f-f transitions of Ln(3+) (Ln = Tb, Eu, Tm, Dy, Ho, Sm) ions and give bright green, red, blue, yellow, blue-green, and yellow-orange emission, respectively, under UV light and low-voltage electron beam excitation. Furthermore, YOF:0.03Tb(3+) phosphors exhibit green luminescence with superior properties in comparison with the commercial phosphor ZnO:Zn to a degree, which is advantageous for improving display quality. Because of the simultaneous luminescence of Ln(3+) in the YOF host, the luminescence colors of YOF:Ln(3+) phosphors can be precisely adjusted by changing the doped Ln(3+) ions and corresponding concentrations, which makes these materials hold great promise for applications in field-emission displays. PMID:24195545
Two new ternary lanthanide antimony chalcogenides: Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.68} containing chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anions
Babo, Jean-Marie [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States); Albrecht-Schmitt, Thomas E., E-mail: firstname.lastname@example.com [Department of Civil Engineering and Geological Sciences and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)
Dark red and dark brown crystals of Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 8}Sb{sub 4}Se{sub 11.68}, respectively, were obtained from the reaction of the elements in Sb{sub 2}Q{sub 3} (Q=S, Se) fluxes. Both non-stoichiometric compounds are orthorhombic and crystallize in the same space group Pnnm, with two formula units per unit cell (a=12.446(2), b=5.341(1), c=12.058(2) for sulfide and a=13.126(2), b=5.623(1), c=12.499(2) for the selenide). Their crystal structures are dominated by lanthanide-chalcogenide polyhedra (CN=7 and 8), which share corners, edges, triangular- and square-faces to form a three-dimensional framework embedding antinomy cations. The latter are coordinated by three sulfide anions with 5(1+2+2) secondary contacts forming basically infinite chains running along [0 1 0]. The chalcogens in both compounds form chalcogenide Q{sup 2-} and dichalcogenide (Q{sub 2}){sup 2-} anionic units. The optical analysis made on those compounds shows that both are semiconductors with band gap of 1.71 and 1.22 eV for Yb{sub 4}Sb{sub 2}S{sub 11.25} and Tm{sub 4}Sb{sub 2}Se{sub 11.75,} respectively. - Graphical Abstract: The crystal structure of Yb{sub 4}Sb{sub 2}S{sub 11} viewed along the [0 1 0]. Highlights: Black-Right-Pointing-Pointer Lanthanide chalcogenides. Black-Right-Pointing-Pointer Semiconductors. Black-Right-Pointing-Pointer Tunnel structures. Black-Right-Pointing-Pointer Lone-pair effects.
Re-dispersion and film formation of GdVO4?:? Ln3+ (Ln3+ = Dy3+, Eu3+, Sm3+, Tm3+) nanoparticles: particle size and luminescence studies.
Shanta Singh, N; Ningthoujam, R S; Phaomei, Ganngam; Singh, S Dorendrajit; Vinu, A; Vatsa, R K
GdVO(4)?:?Ln(3+) (Ln(3+) = Dy(3+), Eu(3+), Sm(3+), Tm(3+)) nanoparticles are prepared by a simple chemical route at 140 ░C. The crystallite size can be tuned by varying the pH of the reaction medium. Interestingly, the crystallite size is found to increase significantly when pH increases from 6 to 12. This is related to slower nucleation of the GdVO(4) formation with increase of VO(4)(3-) present in solution. The luminescence study shows an efficient energy transfer from vanadate absorption of GdVO(4) to Ln(3+) and thereby enhanced emissions are obtained. A possible reaction mechanism at different pH values is suggested in this study. As-prepared samples are well dispersed in ethanol, methanol and water, and can be incorporated into polymer films. Luminescence and its decay lifetime studies confirm the decrease in non-radiative transition probability with the increase of heat treatment temperature. Re-dispersed particles will be useful in potential applications of life science and the film will be useful in display devices. PMID:22334276
An investigation of the thermal sensitivity and stability of the -NaYF4:Yb,Er upconversion nanophosphors
Ju, Yiguang
An investigation of the thermal sensitivity and stability of the -NaYF4:Yb,Er upconversion of the hexagonal -phase NaYF4:Yb,Er nanophosphors as a function of temperature 300Ł450 K was examined under 978 nm The lanthanide ions Ln3+ Ln=Yb, Er, Tm, and Ho doped into either fluorides, e.g., NaYF4 and LaF3, or oxides, e
Synthesis, structure, and thermally stable luminescence of Eu(2+)-doped Ba2Ln(BO3)2Cl (Ln = Y, Gd and Lu) host compounds.
Xia, Zhiguo; Wang, Xiaoming; Wang, Yingxia; Liao, Libing; Jing, Xiping
A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba(2)Ln(BO(3))(2)Cl:Eu(2+) (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln(3+) sites in Ba(2)Ln(BO(3))(2)Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba(2)Ln(BO(3))(2)Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P2(1)/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping. Ba(2)Ln(BO(3))(2)Cl:Eu(2+) phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba(2)Y(BO(3))(2)Cl:Eu(2+), Ba(2)Gd(BO(3))(2)Cl:Eu(2+), and Ba(2)Lu(BO(3))(2)Cl:Eu(2+), respectively. Furthermore, they possess a high thermal quenching temperature. With the increase of temperature, the emission bands show blue shifts with broadening bandwidths and slightly decreasing emission intensities. It is expected that this series of chloroborate phosphors can be used in white-light UV-LEDs as a good wavelength-conversion phosphor. PMID:21919480
Triaxial strongly deformed bands in {sup 160,161}Tm
Teal, C.; Lagergren, K.; Aguilar, A.; Riley, M. A. [Department of Physics, Florida State University, Tallahassee, Florida 32306 (United States); Hartley, D. J. [Department of Physics, U.S. Naval Academy, Annapolis, Maryland 21402 (United States); Simpson, J.; Joss, D. T. [STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Carpenter, M. P.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; Zhu, S. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Garg, U. [Physics Department, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Kondev, F. G. [Nuclear Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Wang, X. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Physics Department, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Ragnarsson, I. [Division of Mathematical Physics, LTH, Lund University, P.O. Box 118, S-22100 Lund (Sweden)
High-spin states in {sup 160,161}Tm were populated using the {sup 128}Te({sup 37}Cl, 5n and 4n) reactions at a beam energy of 170 MeV. Emitted {gamma} rays were detected in the Gammasphere spectrometer. Two rotational bands with high moments of inertia were discovered, one assigned to {sup 160}Tm, while the other tentatively assigned to {sup 161}Tm. These sequences display features similar to bands observed in neighboring Er, Tm, Yb, and Lu nuclei which have been discussed in terms of triaxial strongly deformed structures. Cranked Nilsson Strutinsky calculations have been performed that predict well-deformed triaxial shapes at high spin in {sup 160,161}Tm.
Amphiphilic silane modified NaYF4:Yb,Er loaded with Eu(TTA)3(TPPO)2 nanoparticles and their multi-functions: dual mode temperature sensing and cell imaging
NASA Astrophysics Data System (ADS)
Chen, Boting; Dong, Biao; Wang, Jing; Zhang, Shuang; Xu, Lin; Yu, Wei; Song, Hongwei
Rare-earth upconversion nanophosphors (UCNPs) have become one of the most promising luminescent materials for bio-applications, but their use still meets some limitations by difficulties in obtaining biocompatible UCNPs. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into hydrophilic ones by amphiphilic silane modification with ultrathin thickness at room temperature (RT). In this strategy, the coating layers can also afford the place for loading with Eu(TTA)3(TPPO)2 complex which displays down conversion luminescence (DCL). Due to the UC and DC properties, we achieved the dual mode physiological range temperature sensing and dual mode cell imaging. Such novel nanomaterials offer a new surface modification strategy for the NPs that are formed in the oil phase for bio-applications.Rare-earth upconversion nanophosphors (UCNPs) have become one of the most promising luminescent materials for bio-applications, but their use still meets some limitations by difficulties in obtaining biocompatible UCNPs. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into hydrophilic ones by amphiphilic silane modification with ultrathin thickness at room temperature (RT). In this strategy, the coating layers can also afford the place for loading with Eu(TTA)3(TPPO)2 complex which displays down conversion luminescence (DCL). Due to the UC and DC properties, we achieved the dual mode physiological range temperature sensing and dual mode cell imaging. Such novel nanomaterials offer a new surface modification strategy for the NPs that are formed in the oil phase for bio-applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02670a
NSDL National Science Digital Library
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Uniform and well-dispersed YbVO4 hierarchical nanoarchitectures: synthesis and luminescence properties.
Xu, Zhenhe; Zhao, Qian; Liu, Tao; Wang, Liming; Bian, Shasha
The YbVO4 micro-doughnuts were successfully fabricated by a facile hydrothermal method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) were used to characterize the resulting samples. The diameter and thickness of YbVO4 micro-doughnuts are around 750 nm and 480 nm, respectively. It is found that trisodium citrate (Na3Cit) is essential for obtaining YbVO4 microdoughnuts. Moreover, the crystal growth process was thoroughly discussed through a series of time-dependent experiments and a possible formation mechanism was proposed. Furthermore, the up-conversion (UC) luminescent properties as well as the emission mechanisms of YbVO4:Ln3+ (Ln3+ = Er3+, Tm3+ and Ho3+) microcrystals were systematically investigated. PMID:23646736
Optical study of archetypical valence-fluctuating Eu systems.
Guritanu, V; Seiro, S; Sichelschmidt, J; Caroca-Canales, N; Iizuka, T; Kimura, S; Geibel, C; Steglich, F
We have investigated the optical conductivity of the prominent valence-fluctuating compounds EuIr(2)Si(2) and EuNi(2)P(2) in the infrared energy range to get new insights into the electronic properties of valence-fluctuating systems. For both compounds, we observe upon cooling the formation of a renormalized Drude response, a partial suppression of the optical conductivity below 100 meV, and the appearance of a midinfrared peak at 0.15 eV for EuIr(2)Si(2) and 0.13 eV for EuNi(2)P(2). Most remarkably, our results show a strong similarity with the optical spectra reported for many Ce- or Yb-based heavy-fermion metals and intermediate valence systems, although the phase diagrams and the temperature dependence of the valence differ strongly between Eu systems and Ce- or Yb-based systems. This suggests that the hybridization between 4f and conduction electrons, which is responsible for the properties of Ce and Yb systems, plays an important role in valence-fluctuating Eu systems. PMID:23368375
Ultraviolet upconversion luminescence of Gd{sup 3+} and Eu{sup 3+} in nano-structured glass ceramics
Lin, Hang; Chen, Daqin; Yu, Yunlong; Yang, Anping; Zhang, Rui [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)] [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wang, Yuansheng, E-mail: firstname.lastname@example.com [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)] [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)
Highlights: Black-Right-Pointing-Pointer Ultraviolet upconversion emissions of Eu{sup 3+} and Gd{sup 3+} are rarely studied. Black-Right-Pointing-Pointer Nanostructured glass ceramic is developed as a host for ultraviolet upconversion. Black-Right-Pointing-Pointer Ultraviolet upconversion signal are found greatly enhanced after crystallization. Black-Right-Pointing-Pointer It is promising for fabricating novel ultraviolet upconversion lasers. -- Abstract: Ultraviolet multiphoton upconversion emissions of Eu{sup 3+} ({sup 5}H{sub 3-7}, {sup 5}G{sub 2-6}, {sup 5}L{sub 6} {yields} {sup 7}F{sub 0}) and Gd{sup 3+} ({sup 6}I{sub J}, {sup 6}P{sub J} {yields} {sup 8}S{sub 7/2}) are studied in the Eu{sup 3+} (or Gd{sup 3+}) doped SiO{sub 2}-Al{sub 2}O{sub 3}-NaF-YF{sub 3} precursor glasses and glass ceramics containing {beta}-YF{sub 3} nanocrystals, under continuous-wavelength 976 nm laser pumping. It is experimentally demonstrated that energy transfer from Yb{sup 3+} to Tm{sup 3+}, then further to Eu{sup 3+} or Gd{sup 3+} is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of {beta}-YF{sub 3} nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers.
Pressure dependence of the emission in CaF2?:?Yb(2.).
Mahlik, S; Lazarowska, A; Grinberg, M; Wells, J-P R; Reid, M F
We present a detailed spectroscopic investigation of CaF2 doped with Yb(2+) performed at high hydrostatic pressure which is applied in a diamond anvil cell. At ambient pressure and at temperatures lower than 175?K, the luminescence consists of a single broad band peaked at 18?500?cm(-1), attributed to the recombination of impurity-trapped excitons. Increasing pressure causes the luminescence to be observable at higher temperature. At a pressure of 72?kbar luminescence can be observed up to 275?K. The emission lineshape does not strongly depend on pressure below 85?kbar. However, at 85?kbar it is blue shifted to 21?630?cm(-1). This is attributed to the known phase transition of the CaF2 crystal from cubic to the orthorhombic phase. The absolute energy of the ground and 4f(13)5d states of Yb(2+) as well as the energy of the impurity-trapped exciton with respect to valence and conduction bands have been estimated. The results, are discussed in comparison with the pressure dependences observed for the luminescence of BaF2?:?Eu(2+) and CaF2?:?Eu(2+). The difference between the spectral properties of Eu(2+) and Yb(2+) is attributable to the fact that the ground and 4f(6)5d states of Eu(2+) are placed deeper in the CaF2 bandgap than the ground and excited 4f(13)5d states of Yb(2+), whereas the energies of the impurity-trapped exciton states for Yb(2+) and Eu(2+) with respect to the conduction band are approximately the same. PMID:26171576
Stephens, F.S.; Deleplanque, M.A.; Lee, I.Y.; Ward, D.; Fallon, P.; Cromaz, M.; Macchiavelli, A.O.; Clark, R.M.; Diamond, R.M.; Gorgen, A.
In a mixture of three Yb nuclei, we find the rotational damping widths vary from 180 keV at 1.1 MeV {gamma}-ray energy to 290 keV at 1.5 MeV, and the average compound damping widths (or spreading widths) vary from 40 keV at 1.1 MeV {gamma}-ray energy to 60 keV at 1.3 MeV. The simulations also suggest extensive motional narrowing.
Syntheses and structures of novel complex Yb(II) fluorides: YbBeF 4, YbAlF 5 and LiYbAlF 6
NASA Astrophysics Data System (ADS)
K÷hler, J.
Light green powder samples and single crystals of YbBeF 4, YbAlF 5, and LiYbAlF 6 have been prepared by heating appropriate mixtures of YbF 2 and BeF 2, YbF 2 and AlF 3, or YbF 2, LiF, and AlF 3 at 750 ░C under argon in a closed silica ampoule. YbBeF 4 crystallises monoclinic with a = 667.4(2), b = 691.1(2), c = 640.2(2) pm, ? = 103.87(2)░, YbAlF 5 crystallises tetragonal with a = 1380.3(3), c = 701.3(3) pm, and LiYbAlF 6 crystallises trigonal with a = 504.2(2) and c = 986.8(1) pm. YbBeF 4 is the first fluoroberyllate, which adopts the monazite type structure, YbAlF 5 is isotypic with BaTiF 5 and LiYbAlF 6 crystallises in the LiCaAlF 6 type structure. In all three fluorides the Yb atoms are in the oxidation state +2 and the Yb-F distances range from 232 to 280 pm. Measurements of the magnetic susceptibilities have shown that YbBeF 4, YbAlF 5 and LiYbAlF 6 are diamagnetic. The structures of YbBeF 4, YbAlF 5 and LiYbAlF 6 are discussed in comparison to the corresponding fluoroberyllates and -fluoroaluminates with Sr and Ca.
CLEO 2007: CFJ -Yb Lasers Low-threshold On-chip Yb3+ Silica Laser
CLEO 2007: CFJ - Yb Lasers Low-threshold On-chip Yb3+ Silica Laser Eric Ostby, Lan Yang*, and Kerry University #12;CLEO 2007: CFJ - Yb Lasers Low-Threshold Yb3+ Lasers Ę Fabry-Perot type Pth Finesse Ę Microchip lasers - 71 mW 50 Ę Fiber lasers - 230 ĄW 500 Ę Ring type Ę Microtoroid - ? 10,000 Ę High Quality
Thermal expansion of a Au-Al-Yb intermediate valence quasicrystal
NASA Astrophysics Data System (ADS)
Watanuki, T.; Kashimoto, S.; Ishimasa, T.; Machida, A.; Yamamoto, S.; Tanaka, Y.; Mizumaki, M.; Kawamura, N.; Watanabe, S.
The thermal expansion of a Au-Al-Yb intermediate-valence quasicrystal has been studied. X-ray diffraction measurements showed zero thermal expansion below 50 K. By comparison with an isostructural Au-Al-Tm quasicrystal, the contribution of the Yb valence variation was extracted, and it was shown that its negative thermal expansion component compensated for the positive thermal expansion of the original lattice. On cooling, the Yb contribution grew steeply below approximately 155 K down to the lowest experimental temperature of 5 K, due to enlargement of the Yb atomic radius, which was caused by the valence shift toward the divalent state. Additionally, a larger Yb contribution to the thermal expansion was demonstrated in a crystalline approximant to this quasicrystal. The magnitude of this contribution was approximately 1.4 times larger than in the case of the quasicrystal itself, resulting in a slight negative thermal expansion below 50 K. A heterogeneous valence model for the quasicrystal that we proposed previously accounts for this magnitude difference.
Flux growth and spectral properties of Yb:YAB single crystal with high Yb 3+ concentration
Jinsheng Liao; Yanfu Lin; Yujin Chen; Zundu Luo; Yidong Huang
Ytterbium-doped yttrium aluminium borate (Yb:YAB) crystals with high Yb3+ concentration have been obtained by the top-seeded solution growth techniques. The polarized absorption spectra, fluorescence spectra and lifetime of 65.5at% Yb3+-doped YAB crystal were measured at room temperature. The spectroscopic parameters of the crystal were compared with those of low Yb3+-doped YAB crystal. The results demonstrated that the Yb:YAB crystals with
Pressure-Driven Topological Phase Transition in the Yb Chalcogenides YbO and YbS
NASA Astrophysics Data System (ADS)
Li, Zhi; Zhang, Jiu-Xing
By first-principles calculation based on the density functional theory (DFT) with the modified Becke-Johnson local density approximation plus Hubbard U (MBJLDA+U), we studied the band structures of the Yb chalcogenides YbO and YbS under ambient and high pressures. It was revealed that both YbO and YbS have a trivial band topology under ambient pressure, and a nontrivial band topology under high pressure. The topological phase transition is reduced by the pressure-driven single-band inversion between 5d- and 4f-orbitals at the time-reversal invariant momentum (TRIM) point X. A bulk Dirac cone coexisting with a pair of metallic surface states on the [001] surface determined by tight binding model calculation with a slab geometry also demonstrates the nontrivial band topology of YbO and YbS under high pressure.
Lifetime measurement in ^170Yb
NASA Astrophysics Data System (ADS)
Wang, Z.; Kr³cken, R.; Beausang, C. W.; Casten, R. F.; Cooper, J. R.; Cederkõll, J.; Caprio, M.; Novak, J. R.; Zamfir, N. V.; Barton, C.
The nature of the low lying K^?=0^+ excitations in deformed nuclei have recently been subject of intense discussion. In this context we present results from a Coulomb excitation experiment on ^170Yb using a 70MeV ^16O beam on a gold backed, 1.5 mg/cm^2 thick ^170Yb target. The beam was delivered by the ESTU tandem accelerator of WNSL at Yale University. Gamma rays were detected by the YRAST Ball array in coincidence with back-scattered ^16O particles, which were detected in an array of 8 solar cells. Lineshapes were observed for several transitions from collective states in ^170Yb and the lifetimes for those states were extracted using a standard DSAM analysis. The results will be presented together with a short introduction to the solar cell array at Yale (SCARY) that was used to make angular selection of the excited ^170Yb nuclei. This work is supported by the US-DOE under grant numbers DE-FG02-91ER-40609 and DE-FG02-88ER-40417.
Structural and physical properties of the new intermetallic compound Yb{sub 3}Pd{sub 2}Sn{sub 2}
Solokha, P. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Curlik, I. [Institute of Experimental Physics, Watsonova 47, SK 043 53 Kosice (Slovakia); Giovannini, M., E-mail: firstname.lastname@example.com [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Lee-Hone, N.R. [Physics Department and Centre for the Physics of Materials, McGill University, Montreal, Canada H3A 2T8 (Canada); Reiffers, M. [Institute of Experimental Physics, Watsonova 47, SK 043 53 Kosice (Slovakia); Faculty of Sciences, University of Presov, 17. Novembra 1, SK 080 78 Presov (Slovakia); Ryan, D.H. [Physics Department and Centre for the Physics of Materials, McGill University, Montreal, H3A 2T8 (Canada); Saccone, A. [Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy)
The crystal structure of the ternary intermetallic compound Yb{sub 3}Pd{sub 2}Sn{sub 2} has been determined ab initio from powder X-ray diffraction data. The compound crystallizes as a new structure type in the orthorhombic space group Pbcm and lattice constants a=0.58262(3), b=1.68393(8), c=1.38735(7) nm. Yb{sub 3}Pd{sub 2}Sn{sub 2} is composed of a complex {sub {infinity}}[Pd{sub 2}Sn{sub 2}]{sup {delta}-} polyanionic network in which the Yb ions are embedded. A comparison between this structure and those of Eu{sub 3}Pd{sub 2}Sn{sub 2} and Ca{sub 3}Pd{sub 2}Sn{sub 2}, other novel polar intermetallic compounds, was made. DC susceptibility and {sup 170}Yb Moessbauer spectroscopic measurements indicate a close-to divalent Yb behavior. Moreover, a hybridization between 4f and conduction electrons is suggested by electronic structure calculations and heat capacity measurements. - Graphical Abstract: Polyanionic networks for Yb{sub 3}Pd{sub 2}Sn{sub 2} and Eu{sub 3}Pd{sub 2}Sn{sub 2}. Highlights: > We determined ab initio the crystal structure of the novel ternary Yb{sub 3}Pd{sub 2}Sn{sub 2} stannide. > This structure has been compared with those of other polar 3:2:2 stannides discovered in this work. > Measurements of physical properties on Yb{sub 3}Pd{sub 2}Sn{sub 2} point to a close-to-divalent Yb ion. > Electron structure calculation and heat capacity indicate some hybridization between 4f and conduction electrons.
Atmospheric Science Data Center
... MOP03TM MOPITT CO gridded monthly means (Thermal Infrared Radiances) News:Ā MOPITT Science Team ... CO (on a latitude/longitude/pressure grid) derived from Thermal Infrared Radiances, version 6, Hampton, VA, USA:NASA Atmospheric ...
1 W single-frequency Tm-doped ZBLAN fiber MOPA around 810 nm.
Kohno, Kenta; Takeuchi, Yu-ichi; Kitamura, Toshiyuki; Nakagawa, Ken'ichi; Ueda, Ken-ichi; Musha, Mitsuru
We demonstrate a tunable narrow-linewidth fiber MOPA system around 810 nm for the light source of the Sr optical lattice clock. The coherent cw light source with a wavelength of 813.42 nm was generated by a combination of a narrow linewidth external-cavity laser diode and a Tm-doped ZBLAN fiber amplifier, which was upconversion-pumped by an Yb-doped fiber laser at 1064 nm. The maximum output power of 1.1 W was obtained with the launched power of 17 W, which is the highest power obtained from a Tm-doped fiber amplifier ever reported. PMID:24686708
Optical refrigeration of Yb3+:YAG nanocrystals
NASA Astrophysics Data System (ADS)
Nemova, Galina; Kashyap, Raman
We have theoretically investigated the laser cooling process in Yb3+:YAG nanocrystals. We have developed an approach, which permits not only estimate the cooling process in Yb3+:YAG nanocrystals but compare this process with the laser cooling of the Yb3+:YAG bulk samples. The temperature dependences of all parameters of the system are taken into account. The cooperative effects such as re-absorption, the energy migration and cooperative luminescence have been considered.
[Study on ultraviolet upconversion emissions of Gd3+ induced by Tm3+ under 980 nm excitation].
Cao, Chun-Yan; Yu, Xiao-Guang; Qin, Wei-Ping; Zhang, Ji-Sen
Series of Tm3+/Yb3+ co-doped GdF3 powders were synthesized through an easy and mild hydrothermal method. The phase and purity of powders were characterized by powder X-ray diffraction (XRD) (Rigaku RU-200b). The morphologies of the samples were characterized by field emission scanning electron microscopy (FE SEM) (Hitachi S-4800). The ultraviolet (UV) up-conversion (UC)emission spectra were recorded by a fluorescence spectrophotometer (Hitachi F-4500) with a 980 nm semiconductor continuous wave laser diode as the excitation source. And the luminescent dynamics was measured by excitation with 980 nm using an optical parameter oscillator (OPO) laser pumped by a pulsed Nd : YAG laser with a pulse duration of 10 ns, repetition frequency of 10 Hz, and the signal was recorded by using a monochromator and an oscillograph. Under 980 nm excitation, Gd3+, acting as a kind of host ion in the studied system, and its UV UC emissions were observed and studied. The luminescent dynamics of the characteristic emission of Gd3+ (311.6 nm, 6P7/2 --> 8S7/2) was explored and studied. The luminescent dynamics analysis results indicated that, on UV UC emissions of Gd3+, Yb3+ ions served as primary sensitizer ions successively transferring energy to Tm3+ to populate the 3P2 level. Then, Tm3+ ions served as secondary sensitizer ions transferring energy to populate the multiple 6 I(J) states of Gd3+ 3P2 --> 3H6 (Tm3+): 8S7/2 --> 6 I(J) (Gd3+). Further, 6D(J) levels were populated through other energy transfer processes between Gd3+ and Yb3+ or Tm3+. Finally, UV UC emissions from the excited 6D9/2, 6 I(J), 6P5/2, and 6P7/2 states to the ground state 8S7/2 were observed. Meanwhile, Tm3+ acted as activator in its own UC emissions, and the article did not put emphasis on those except the 3P2 and 1 I6 levels to the ground state 3 H6 transitions. Especially, the dependences of UV UC emissions of Gd3+ on the Yb3+ concentrations, the Tm3+ concentrations, the annealing temperatures, and the excitation power densities of the 980 nm semiconductor continuous wave laser diode were studied, too. PMID:20496672
Magnetic and transport properties of Yb1 - xTmxS
NASA Astrophysics Data System (ADS)
Suryanarayanan, R.; Bach, H.; Westerholt, K.; Gorochov, O.
With a view to studying the behavior of diluted Tm in a nonmagnetic matrix, we have prepared single crystals of Yb1-xTmxS (0?x?0.25). The lattice constant a0 decreases abruptly as x approaches 0.14, which is interpreted as a valence transition of Tm towards 3+. For 50
Thermoelectric properties of the Zintl phases Yb5M2Sb6 (M = Al, Ga, In).
Aydemir, Umut; Zevalkink, Alex; Ormeci, Alim; Wang, Heng; Ohno, Saneyuki; Bux, Sabah; Snyder, G Jeffrey
Zintl compounds with chemical formula Yb5M2Sb6 (M = Al, Ga, and In) form one of two known A5M2Pn6 structure types characterized by double chains of corner-linked MPn4 tetrahedra bridged by Pn2 dumbbells. High temperature electronic and thermal transport measurements were used to characterize the thermoelectric properties of Yb5M2Sb6 compounds. All samples were found to exhibit similar high p-type carrier concentrations, low resistivity and low Seebeck coefficients in agreement with the band structure calculations. These results, combined with previous studies, suggest that Yb5M2Sb6 compounds are semimetals (i.e., they lack an energy gap between the valence and conduction bands), in contrast to the semiconducting alkaline earth (Ca, Sr, Ba) and Eu based A5M2Sb6 compounds. Yb5M2Sb6 compounds have very low lattice thermal conductivity, comparable to other closely related A5M2Sb6 and A3MSb3 phases. However, due to the semimetallic behaviour, the figure of merit of investigated samples remains low (zT < 0.15). PMID:25670617
Efficient laser action of Yb:LSO and Yb:YSO oxyorthosilicates crystals under high-power diode-pumping
M. Jacquemet; C. Jacquemet; N. Janel; F. Druon; F. Balembois; P. Georges; J. Petit; B. Viana; D. Vivien; B. Ferrand
We report here on the efficient laser action of a new Yb-doped crystal Yb 3+:Lu 2SiO 5 (Yb:LSO) under high power diode-pumping (15ĀW). Its performances were compared to another Yb-doped crystal belonging to the oxyorthosilicate family: the Yb:YSO. For both crystals, more than 7ĀW of laser radiation around 1Ā?m was obtained under 14.4ĀW of incident pump power at 978Ānm, leading
170 Yb Mossbauer study of the YbCd 5:7 binary quasi-crystal and related phases
Ryan, Dominic
-crystalline YbCd 5:7 alloy. Comparison with other phases in the Yb{Cd phase diagram shows that the local]. This phase was #12;rst prepared nearly 30 years ago during an investigation of the Yb{Cd binary phase diagram170 Yb Mossbauer study of the YbCd 5:7 binary quasi-crystal and related phases D H Ryan, Saleema N
Structural, morphological and spectroscopic properties of Eu{sup 3+}-doped rare earth fluorides synthesized by the hydrothermalmethod
Grzyb, Tomasz, E-mail: email@example.com [Department of Rare Earths, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, Pozna? 60-780 (Poland); Runowski, Marcin [Department of Rare Earths, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, Pozna? 60-780 (Poland); Szczeszak, Agata [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, Pozna? 60-179 (Poland); Lis, Stefan [Department of Rare Earths, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, Pozna? 60-780 (Poland)
Rare earth fluorides (REF{sub 3}, RE=Y, La, Gd or Yb) doped with 5% of Eu{sup 3+} ions were synthesized via the hydrothermal method and their physicochemical properties were compared. The synthesis was carried out in an aqueous medium at elevated pressure and temperature. The reaction was performed in situ, with use of NaBF{sub 4} as a source of fluoride ions. Structural and morphological properties of obtained nanophosphors were characterized with the use of powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. Synthesized products were nanocrystalline with hexagonal or orthorhombic crystal structures. They showed different morphology, from nanoplates to nanorings, depending on the used REF{sub 3} fluoride as the host for the Eu{sup 3+} ions. The elemental composition was confirmed by the energy-dispersive X-ray spectroscopy (EDX) results. Spectroscopic properties were investigated by measuring the excitation and emission spectra. Also luminescence lifetimes were determined. The synthesized materials showed bright red luminescence, due to the presence of Eu{sup 3+} ions in their structure. - Graphical abstract: Luminescence spectra of the REF{sub 3}:Eu{sup 3+} (RE=Y, La, Gd and Yb) fluorides and their TEM images as background. Highlights: ? Nanocrystalline fluorides were synthesized using modified hydrothermal method. ? Structural and morphological properties of in situ prepared nanomaterials were studied. ? Luminescence properties of REF{sub 3}:Eu{sup 3+} (RE=Y, La, Gd, Yb) were compared and investigated.
Lattice dynamics of fluoride scheelites: I. Raman and infrared study of ? and ? (? and Yb)
NASA Astrophysics Data System (ADS)
Sala³n, S.; Fornoni, M. T.; Bulou, A.; Rousseau, M.; Simon, P.; Gesland, J. Y.
IR and Raman active modes have been measured in several fluoride scheelites, namely the laser matrix 0953-8984/9/32/016/img12 (studied as a reference) and four 0953-8984/9/32/016/img13 compounds (Ln = Ho, Er, Tm and Yb). The observed phonons have been assigned in accordance with the various irreducible representations of the point group of the crystal. In 0953-8984/9/32/016/img12 three modes never observed before have been measured. The polarized experimental IR reflection spectra have been analysed through a `four-parameters' model to give the mode frequencies and dampings. For the whole set of the compounds, the frequency dependence of the dielectric function, optical indices and absorption coefficient have been deduced from the IR study. The electronic Raman effect has been shown in the low-temperature Raman spectra for Ln= Tm, Ho and Yb. The corresponding measured wavenumbers are compared with the calculated energies between crystal-field levels of L SJ states, each being associated to an irreducible representation of the ion-site group 0953-8984/9/32/016/img15.
Magnetic coupling between nonmagnetic ions: Eu3+ in EuN and EuP
Pickett, Warren
configuration, we estimate semi- metallic band overlaps Eu 5d with pnictide 2p or 3p of 0.1 eV EuN and 1.0 eV Eu. The canonical example is Eu3+ f 6 : S=3, L=3, J =0. Whereas Eu3+ is nonmagnetic experimentally unrespon- sive
Laser action in yb 3+:YCOB (Yb 3+:YCa 4O(BO 3) 3)
NASA Astrophysics Data System (ADS)
Hammons, D. A.; Eichenholz, J. M.; Ye, Q.; Chai, B. H. T.; Shah, L.; Peale, R. E.; Richardson, M.; Qiu, H.
Infrared laser action in Yb 3+:YCOB (Yb 3+:YCa 4O(BO 3) 3) is reported for the first time. Maximum output powers of ś300 mW with a slope efficiency of 35.8% have been obtained. The observation of self-frequency doubling in this material is also reported.
NSDL National Science Digital Library
Facing the Future(TM) provides educational materials and professional development opportunities for educators that address environmental issues such as population growth, poverty and equity, consumption trends, peace and conflict, health, climate change, and sustainability. These materials include textbooks for students, service learning and action projects, and curriculum units with activities and lesson plans that meet educational standards. The organization's web site provides information on downloading and/or purchasing these materials, information on a featured curriculum unit, news and event announcements, and information on professional development opportunities for in-service and pre-service educators.
The formation of Yb silicates and its luminescence in Yb heavily doped silicon oxides after high temperature annealing
NASA Astrophysics Data System (ADS)
Heng, C. L.; Li, J. T.; Su, W. Y.; Han, Z.; Yin, P. G.; Finstad, T. G.
We report on the formation of ytterbium (Yb) silicates and its photoluminescence (PL) properties for heavily Yb doped Si oxide films after various annealings. X-ray diffraction patterns and transmission electron microscopy indicate that different Yb silicates have formed in the oxides upon 1100 and 1200 ░C annealing. The Yb PL intensities after the high temperature annealings are much stronger than those after lower temperatures, which indicates that the Yb silicates have higher emission efficiency than the Yb configurations found for lower temperature annealing. The PL intensities of the films can be altered considerably by secondary oxidizing or annealing in forming gas (N2 + 7% H2) ambience.
Lattice dynamics in the thermoelectric Zintl compound Yb[subscript 14]MnSb[subscript 11
M÷chel, A.; Sergueev, I.; Wille, H.-C.; Juranyi, F.; Schober, H.; Schweika, W.; Brown, S.R.; Kauzlarich, S.M.; Hermann, R.P. (DESY); (UCD); (Julich); (ILL); (ESRF); (ETH Zurich)
The density of phonon states in the thermoelectric material Yb{sub 14}MnSb{sub 11} has been studied first by inelastic neutron scattering and second in an element-specific way by nuclear inelastic x-ray scattering. The low sound velocity of 1880(50) m/s as obtained from the density of phonon states can be identified as an important reason for the low heat transport in this system. The high melting temperature of Yb{sub 14}MnSb{sub 11} contrasts with the low energy of all phonons (<25 meV) and relates to an unusual lack of softening of phonon modes with temperature, when comparing the phonon density of states observed at ambient temperatures and at 1200 K. We have also measured the density of phonon states of the related Eu{sub 14}MnSb{sub 11} compound and of the thermoelectric Zintl phase Zn{sub 4}Sb{sub 3} in order to compare with related thermodynamic properties of Yb{sub 14}MnSb{sub 11} and to elucidate the different mechanisms of the heat conductivity reduction in Zintl phases.
ERIC Educational Resources Information Center
McLeod, John
Reports on research which indicates that much of the meaning of transcendental meditation (TM) is constructed from preexisting understandings and expectations. Various influences for the impact of TM are suggested including the language, rules, and world view of the social environment. (RC)
Anomalies in the Young modulus at structural phase transitions in rare-earth cobaltites RBaCo{sub 4}O{sub 7} (R = Y, Tm-Lu)
Kazei, Z. A., E-mail: firstname.lastname@example.com; Snegirev, V. V.; Andreenko, A. S. [Moscow State University (Russian Federation); Kozeeva, L. P. [Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry, Siberian Branch (Russian Federation)
The elastic properties of rare-earth cobaltites RBaCo{sub 4}O{sub 7} (R = Y, Tm-Lu) have been experimentally studied in the temperature range of 80-300 K. The strong softening of the Young modulus {Delta}E(T)/E{sub 0} Almost-Equal-To -(0.1-0.2) of cobaltites with Lu and Yb ions has been revealed, which is due to the instability of the crystal structure upon cooling and is accompanied by an inverse jump at the second-order structural phase transition. The softening of the Young modulus and the jump at the phase transition decrease by an order of magnitude and the transition temperature T{sub s} and hysteresis {Delta}T{sub s} increase from a compound with Lu to that with Tm. A large softening of the Young modulus at the structural transition in Lu- and Yb cobaltites indicates that the corresponding elastic constant goes to zero, whereas this constant in Tm cobaltite is not a 'soft' mode of the phase transition. It has been found that the structural phase transition in Lu- and Yb cobaltites is accompanied by a large absorption maximum at the phase transition point and an additional maximum in the low-temperature phase and absorption anomalies in Tm cobaltite is an order of magnitude smaller.
Hudson, Corey M; Williams, Kelly P
The transfer-messenger RNA (tmRNA) and its partner protein SmpB act together in resolving problems arising when translating bacterial ribosomes reach the end of mRNA with no stop codon. Their genes have been found in nearly all bacterial genomes and in some organelles. The tmRNA Website serves tmRNA sequences, alignments and feature annotations, and has recently moved to http://bioinformatics.sandia.gov/tmrna/. New features include software used to find the sequences, an update raising the number of unique tmRNA sequences from 492 to 1716, and a database of SmpB sequences which are served along with the tmRNA sequence from the same organism. PMID:25378311
Local moment behaviors of the valence fluctuating systems ?-YbAlB4 and ?-YbAlB4
Y Matsumoto; K Kuga; N Horie; S Nakatsuji
?-YbAlB4 is the first example of an Yb-based heavy Fermion superconductor with Tc = 80 mK and exhibits pronounced non-Fermi-liquid behavior above Tc. On the other hand, recent hard x-ray photoemission spectroscopy measurements have revealed strong intermediate valence of both ?-YbAlB4 and its locally isostructural polymorph ?-YbAlB4 . Here we present the results of the specific heat and magnetization measurements
Temperature Dependence and Optimization of 970-nm Diode-Pumped Yb:YAG and Yb:LuAG Lasers
Tadashi Kasamatsu; Hitoshi Sekita; Yasuhiko Kuwano
We have investigated the temperature dependence of output performances for 970-nm diode-pumped Yb:YAG (Yb 3 :Y 3 Al 5 O 12 ) and Yb:LuAG (Yb 3 :Lu 3 Al 5 O 12 ) lasers over the wide temperature range from 80 to 310 K. Temperature-optimized operation was experimentally demonstrated at around 160 K and was theoretically confirmed by taking into
Near infrared activation of an anticancer Pt(IV) complex by Tm-doped upconversion nanoparticles.
Ruggiero, Emmanuel; Hernßndez-Gil, Javier; Mareque-Rivas, Juan C; Salassa, Luca
The Pt(IV) complex cis,cis,trans-[Pt(NH3)2(Cl)2(O2CCH2CH2CO2H)2] is photoactivated by near infrared light (980 nm) using NaYF4:Yb(3+)/Tm(3+)@NaYF4 core-shell upconversion nanoparticles. Coupling of this cisplatin precursor with the biocompatible PEGylated phospholipid DSPE-PEG(2000)-NH2 affords a valuable approach to decorate the surface of the nanoparticles, providing novel photoactivatable nanomaterials capable of releasing Pt(II) species upon NIR light excitation. PMID:25536114
An Yb-Raman cascaded fiber laser with temporal stability
NASA Astrophysics Data System (ADS)
Wenliang, Wang; Jinyong, Leng; Yang, Gao; Shaofeng, Guo; Zongfu, Jiang
We report a new structure of fiber laser, which has the advantages of temporal stability and wavelength agility. An Yb-Raman cascaded fiber oscillator generating 168 mW 1137 nm stable CW signal with 18.2% slope efficiency is demonstrated. In this fiber oscillator, the gain from both Yb ion and SRS effect is utilized. By comparison, the characteristics of the 1137 nm Yb-doped fiber laser are studied. The results show that the serious self-pulsation effect in the Yb-doped fiber laser is suppressed in the Yb-Raman cascaded fiber oscillator.
Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O7
Songrui Zhao. J. M. Mackie; D. E. MacLaughlin; O. O. Bernal; J. J. Ishikawa; Y. Ohta; S. Nakatsuji
Muon spin rotation and relaxation experiments in the pyrochlore iridate Eu2Ir2O7 yield a well-defined muon spin precession frequency below the metal-insulator\\/antiferromagnetic transition temperature TM = 120 K, indicative of long-range commensurate magnetic order and thus ruling out quantum spin liquid and spin-glass-like ground states. The dynamic muon spin relaxation rate is temperature-independent between 2 K and ~TM and yields an
Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O7
Songrui Zhao; J. M. Mackie; D. E. Maclaughlin; O. O. Bernal; J. J. Ishikawa; Y. Ohta; S. Nakatsuji
Muon spin rotation and relaxation experiments in the pyrochlore iridate Eu2Ir2O7 yield a well-defined muon spin precession frequency below the metal-insulator\\/antiferromagnetic transition temperature TM=120 K, indicative of long-range commensurate magnetic order and thus ruling out quantum spin liquid and spin-glass-like ground states. The dynamic muon spin relaxation rate is temperature-independent between 2 K and ~TM and yields an anomalously long
Ab initio calculations on RE-TM-O3 perovskites: A comparative study of cation effect
NASA Astrophysics Data System (ADS)
Mekam, D.; Kacimi, S.; Djermouni, M.; Azzouz, M.; Zaoui, A.
The electronic and magnetic structures of orthorhombic perovskites RE-TM-O3 (RE = Eu, Gd, Tb and RE = Mn, Fe, Co) are studied using ab initio density functional theory in the local density approximation (LDA) with the on-site Hubbard Ueff parameter (LDA + U). To show rare earth (RE) and transition metal (TM) cations effect, we have analyzed the structural parameters, charge and spin densities and partial densities of states. We have also shown how the results can be made relatively sensitive to the choice of cation and to ion size. Valence electronic structures obtained from subsequent LDA + U calculations are compared and discussed.
Syntheses, structures, and magnetic properties of diphenoxo-bridged M(II)Ln(III) complexes derived from N,N'-ethylenebis(3-ethoxysalicylaldiimine) (M = Cu or Ni; Ln = Ce-Yb): observation of surprisingly strong exchange interactions.
Koner, Rajesh; Lin, Hsin-Huang; Wei, Ho-Hsiang; Mohanta, Sasankasekhar
A series of heterodinuclear Cu(II)Ln(III) and Ni(II)Ln(III) complexes, [M(II)L(1)Ln(III)(NO(3))(3)] (M = Cu or Ni; Ln = Ce-Yb), with the hexadentate Schiff base compartmental ligand N,N'-ethylenebis(3-ethoxysalicylaldiimine) (H(2)L(1)) have been synthesized and characterized. The X-ray crystal structure determinations of 13 of these compounds reveal that they are all isostructural. All of these complexes crystallize with the same orthorhombic P2(1)2(1)2(1) space group with closely similar unit cell parameters. Typically, the structure consists of a diphenoxo-bridged 3d-4f dinuclear core, self-assembled to two dimensions due to the intermolecular nitrate...copper(II) or nitrate...nickel(II) semicoordination and weak C-H...O hydrogen bonds. Despite that, the metal centers of the neighboring units are well separated (the ranges of the shortest intermolecular contacts (A) are (M...M) 7.46-7.60, (Ln...Ln) 8.56-8.69, and (M...Ln) 6.12-6.20). Variable-temperature (5-300 K) magnetic susceptibility measurements of all the complexes have been made. The nature of exchange interactions in the Cu(II)Ln(III) systems has been inferred from the Deltachi(M)T versus T plots, where Deltachi(M)T is the difference between the values of chi(M)T for a Cu(II)Ln(III) system and its corresponding Ni(II)Ln(III) analogue. Ferromagnetic interactions seem to be exhibited by the Cu(II)Gd(III), Cu(II)Tb(III), Cu(II)Dy(III), Cu(II)Ho(III), Cu(II)Tm(III), and Cu(II)Yb(III) complexes, while, for the Cu(II)Er(III) complex, no definite conclusion could be reached. On the other hand, among the lower members of the series, the complexes of Ce(III), Nd(III), and Sm(III) exhibit antiferromagnetic interactions, while the Cu(II)Pr(III) and Cu(II)Eu(III) analogues behave as spin-uncorrelated systems. The observations made here vindicate the proposition of Kahn (Inorg. Chem. 1997, 36, 930). The Deltachi(M)T versus T plots also suggest that, for most of the Cu(II)Ln(III) complexes, the exchange interactions are fairly strong, which probably could be related to the small dihedral angle (ca. 4 degrees) between the CuO(2) and LnO(2) planes. PMID:15877435
Rodriguez, Carlos
LiquichekTM Diabetes Control Bio-Rad Laboratories D I A B E T E S / H E M O G L O B I N C O N T R O L S #12;LiquichekTM Diabetes Control Hemoglobin A1C Hemoglobin, Total A liquid human whole blood based product designed to monitor the performance of hemoglobin tests associated with diabetes
Highly efficient Er/Yb-codoped fiber amplifier with an Yb-band fiber Bragg grating.
Han, Qun; Yao, Yunzhi; Chen, Yaofei; Liu, Fangchao; Liu, Tiegen; Xiao, Hai
In this Letter, a high-power Er/Yb-codoped fiber amplifier (EYDFA) with a high-reflection Yb-band fiber Bragg grating (FBG) at the pump end is experimentally investigated. The FBG was inscribed on a piece of double-clad fiber with a center wavelength of 1032Ānm. Due to the selective reflection of the backward Yb-band amplified spontaneous emission (Yb ASE) by the FBG, a co-pump-propagating Yb-band auxiliary signal was generated. Because of the stimulated amplification and reabsorption of the auxiliary signal, the Yb ASE was dramatically suppressed and the pump conversion efficiency (PCE) of the EYDFA was notably improved. An output power of 6.48ĀW was achieved at a pump power of 16.5ĀW, which is equivalent to a PCE of ?39%. The slope efficiency relative to applied pump power was ?40%. The maximum output power was improved ?20% because of the introduction of the FBG. PMID:26030576
Rare earth-copper-magnesium compounds RECu{sub 9}Mg{sub 2} (RE=Y, La-Nd, Sm-Ho, Yb) with ordered CeNi{sub 3}-type structure
Solokha, P. [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryl and Mefodiy str. 6, 79005 Lviv (Ukraine)]. E-mail: email@example.com; Pavlyuk, V. [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryl and Mefodiy str. 6, 79005 Lviv (Ukraine); Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Saccone, A. [Dipartimento di Chimica e Chimica Industriale, Sezione di Chimica Inorganica e Metallurgia, Universita di Genova, Via Dodecaneso 31, I-16146 Genova (Italy); De Negri, S. [Dipartimento di Chimica e Chimica Industriale, Sezione di Chimica Inorganica e Metallurgia, Universita di Genova, Via Dodecaneso 31, I-16146 Genova (Italy); Prochwicz, W. [Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Marciniak, B. [Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland); Rozycka-Sokolowska, E. [Jan Dlugosz University of Czestochowa, Institute of Chemistry and Environmental Protection, al. Armii Krajowej 13/15, 42200, Czestochowa (Poland)
A series of ternary compounds RECu{sub 9}Mg{sub 2} (RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb) have been synthesized via induction melting of elemental metal ingots followed by annealing at 400 deg. C for 4 weeks. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS) was used for examining microstructure and phase composition. These phases crystallize with an ordered version of the binary hexagonal structure type first reported for CeNi{sub 3}. The crystal structure was solved for TbCu{sub 9}Mg{sub 2} from single crystal X-ray counter data (TbCu{sub 9}Mg{sub 2}-structure type, P6{sub 3} /mmc-space group, hP24-Pearson symbol, a=0.49886 (7) nm, c=1.61646 (3) nm, R {sub F}=0.0474 for 190 unique reflections). The Rietveld refinement of the X-ray powder diffraction patterns of RECu{sub 9}Mg{sub 2} confirmed the same crystal structure for the reported rare earth metals. The unit cell volumes for RECu{sub 9}Mg{sub 2} smoothly follow the lanthanide contraction. The existence of a RECu{sub 9}Mg{sub 2} phase was excluded for RE=Er Tm under the investigated experimental conditions. - Graphical abstract: The perspective view of the arrangement of the icosahedrons and anti-cubooctahedrons in the structure of TbCu{sub 9}Mg{sub 2}.
Effects of Second Phase Yb5Sb3 on the Thermoelectric Properties of YbAl3
NASA Astrophysics Data System (ADS)
Li, J. Q.; Liu, X. Y.; Li, Y.; Deng, J. F.; Ye, R. F.; Song, S. H.; Liu, F. S.; Ao, W. Q.
The compound YbAl3 exhibits a very high power factor but also rather a large thermal conductivity, leading to a low figure of merit. The second phase Yb5Sb3 was introduced in the YbAl3 matrix to reduce its thermal conductivity. The composites (YbAl3)1- x (Yb5Sb3) x with x = 0, 0.01, 0.05, 0.10, and 0.20 were synthesized by high frequency induction melting, annealing treatment, and spark plasma sintering. The thermoelectric properties of the composites were evaluated. The composites are of n-type conduction. The pure YbAl3 obtained in this work shows a high power factor of 11,500 ?W m-1 K-2 but also a high thermal conductivity of 19.6 W m-1 K-1. However, the existence of Yb5Sb3 compound in the YbAl3 matrix enhances the electrical resistivity and the absolute Seebeck coefficient of the composite, but significantly reduces its thermal conductivity in the temperature range considered, thereby enhancing the figure of merit. The highest ZT value of 0.23 may be obtained in the sample (YbAl3)0.95(Yb5Sb3)0.05 at room temperature, which is apparently higher than that of pure YbAl3.
Resonantly pumped amplification in a Tm-doped large mode-area photonic crystal fiber
NASA Astrophysics Data System (ADS)
Sincore, Alex; Shah, Lawrence; Wysmolek, Mateusz; Ryan, Robert; Abdulfattah, Ali; Richardson, Martin
Ultra-large mode area thulium-doped photonic crystal fibers (Tm:PCF) have enabled the highest peak powers in 2 micron fiber laser systems to date. However, Tm:PCFs are limited by slope efficiencies of <50% when pumped with 790 nm laser diodes. A well-known alternative is pumping at 1550 nm with erbium/ytterbium-doped fiber (Er/Yb:fiber) lasers for efficiencies approaching ~70%. However, these 1550 nm pump lasers are also relatively inefficient themselves. A recently demonstrated and more attractive approach to enable slope efficiencies over 90% in thuliumdoped step-index fibers is resonant pumping (or in-band pumping). This utilizes a high power thulium fiber laser operating at a shorter wavelength as the pump. In this manuscript, we describe an initial demonstration of resonant pumping in Tm:PCF. While the extracted power was still in the exponential regime due to pump power limitations, slope efficiencies in excess of ~64 have been observed, and there is still room for improvement. These initial results show promise for applying resonant pumping in Tm:PCF to improve efficiencies and facilitate high power scaling in ultralarge mode area systems.
Study of encapsulated {sup 170}Tm sources for their potential use in brachytherapy
Ballester, Facundo; Granero, Domingo; Perez-Calatayud, Jose; Venselaar, Jack L. M.; Rivard, Mark J. [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, E-46100 Burjassot (Spain) and IFIC, CSIC, University of Valencia, E-46100 Burjassot (Spain); Department of Radiation Oncology, ERESA, Hospital General Universitario, E-46014 Valencia (Spain); Department of Radiation Oncology, La Fe University Hospital, E-46009 Valencia (Spain); Department of Medical Physics, Instituut Verbeeten, Tilburg 5000LA (Netherlands); Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States)
Purpose: High dose-rate (HDR) brachytherapy is currently performed with {sup 192}Ir sources, and {sup 60}Co has returned recently into clinical use as a source for this kind of cancer treatment. Both radionuclides have mean photon energies high enough to require specific shielded treatment rooms. In recent years, {sup 169}Yb has been explored as an alternative for HDR-brachytherapy implants. Although it has mean photon energy lower than {sup 192}Ir, it still requires extensive shielding to deliver treatment. An alternative radionuclide for brachytherapy is {sup 170}Tm (Z=69) because it has three physical properties adequate for clinical practice: (a) 128.6 day half-life, (b) high specific activity, and (c) mean photon energy of 66.39 keV. The main drawback of this radionuclide is the low photon yield (six photons per 100 electrons emitted). The purpose of this work is to study the dosimetric characteristics of this radionuclide for potential use in HDR-brachytherapy. Methods: The authors have assumed a theoretical {sup 170}Tm cylindrical source encapsulated with stainless steel and typical dimensions taken from the currently available HDR {sup 192}Ir brachytherapy sources. The dose-rate distribution was calculated for this source using the GEANT4 Monte Carlo (MC) code considering both photon and electron {sup 170}Tm spectra. The AAPM TG-43 U1 brachytherapy dosimetry parameters were derived. To study general properties of {sup 170}Tm encapsulated sources, spherical sources encapsulated with stainless steel and platinum were also studied. Moreover, the influence of small variations in the active core and capsule dimensions on the dosimetric characteristics was assessed. Treatment times required for a {sup 170}Tm source were compared to those for {sup 192}Ir and {sup 169}Yb for the same contained activity. Results: Due to the energetic beta spectrum and the large electron yield, the bremsstrahlung contribution to the dose was of the same order of magnitude as from the emitted gammas and characteristic x rays. Moreover, the electron spectrum contribution to the dose was significant up to 4 mm from the source center compared to the photon contribution. The dose-rate constant {Lambda} of the cylindrical source was 1.23 cGy h{sup -1} U{sup -1}. The behavior of the radial dose function showed promise for applications in brachytherapy. Due to the electron spectrum, the anisotropy was large for r<6 mm. Variations in manufacturing tolerances did not significantly influence the final dosimetry data when expressed in cGy h{sup -1} U{sup -1}. For typical capsule dimensions, maximum reference dose rates of about 0.2, 10, and 2 Gy min{sup -1} would then be obtained for {sup 170}Tm, {sup 192}Ir, and {sup 169}Yb, respectively, resulting in treatment times greater than those for HDR {sup 192}Ir brachytherapy. Conclusions: The dosimetric characteristics of source designs exploiting the low photon energy of {sup 170}Tm were studied for potential application in HDR-brachytherapy. Dose-rate distributions were obtained for cylindrical and simplified spherical {sup 170}Tm source designs (stainless steel and platinum capsule materials) using MC calculations. Despite the high activity of {sup 170}Tm, calculated treatment times were much longer than for {sup 192}Ir.
Blue up-conversion emission in Yb and Tm-codoped potassium yttrium tungstate
A. N. Kuzmin; A. V. Kachynski; P. N. Prasad; A. A. Demidovich; L. E. Batay; A. Bednarkiewicz; W. Strek; A. N. Titov
The spectroscopic characteristics of potassium yttrium tungstate crystal (KYW), codoped with ytterbium and thulium ions, have been investigated from the point of view of up-conversion blue lasing from 1G4 multiplet. An overall 3H6 multiplet splitting of ~530 cm-1 for the trivalent thulium ion in the KYW host was obtained. A decay time of ~112 mus for the 1G4-->3H6 blue luminescence
Semiconducting properties of Tm doped Yb-ZnO films by spray pyrolysis
NASA Astrophysics Data System (ADS)
Chaki, Imane; Belayachi, Azzam; El Bahraoui, Toufik; Regragui, Mohamed; Abd-Lefdil, Mohamed
In this work, we have investigated the structural, optical and electrical properties of rare earth co-doped zinc oxide thin films prepared by spray pyrolysis technique. X-ray diffraction has shown that the films are polycrystalline and textured with the c-axis of the wurtzite structure along the growth direction. Scanning electronic microscopy and transmission electronic microscopy were used to study the films composition and morphology. Photoluminescence measurements showed that all the films have a strong emission band at around 380 nm. Layers with electrical resistivity values as low as 5.7 ū 10-2 ? cm were obtained.
Power scaling of cryogenic Yb:LiYF(4) lasers.
Zapata, Luis E; Ripin, Daniel J; Fan, Tso Yee
We demonstrate a cryogenically cooled Yb:LiYF(4) (Yb:YLF) laser with 224W linearly polarized output power (pump-power limited) and a slope efficiency of 68%. The beam quality is characterized by an M(2) approximately 1.1 at 60W output and M(2) approximately 2.6 at 180W output. This level of average laser power is approximately 2 orders of magnitude higher than demonstrated previously in cryogenic Yb:YLF. Yb:YLF is attractive for femtosecond pulse generation because of its wide gain bandwidth, and this demonstration shows the potential for high-average-power subpicosecond pulse lasers. PMID:20517440
Cryogenic Yb:YAG thin-disk laser
NASA Astrophysics Data System (ADS)
Vretenar, N.; Carson, T.; Lucas, T.; Newell, T.; Latham, W. P.; Peterson, P.; Bostanci, H.; Lindauer, J. J.; Saarloos, B. A.; Rini, D. P.
At cryogenic temperatures, Yb:YAG behaves as a 4-level laser. Its absorption and emission cross-sections increase, and its thermal conductivity improves. Yb:YAG thin disk laser performance at room and cryogenic (80░K) temperatures will be presented. The Yb:YAG gain media is cooled using either a pressurized R134A refrigerant system or by a two-phase liquid nitrogen spray boiler. Interchangeable mounting caps allow the same Yb:YAG media to be switched between the two systems. This allows direct comparison of lasing, amplified spontaneous emission, and temperature performance between 20░C and -200░C.
From Biology to DiscoveryTM LipodinProTM
Lebendiker, Mario
an alternative to nucleic acids transfection and a powerful strategy for functional studies or therapeutic with a single sample. Principal LipodinPro TM advantages: Ę No need for DNA cloning or nucleic acid approaches. Several technologies based on the use of peptide transduction domain (PTD) were developed
170 Yb Mossbauer study of magnetic ordering in Yb 2 D.H. Ryan, Saleema N.M. and R. Gagnon
Ryan, Dominic
170 Yb Mossbauer study of magnetic ordering in Yb 2 Cu 2 O 5 D.H. Ryan, Saleema N.M. and R. Gagnon, The University of New South Wales, Sydney, NSW 2052, Australia August 15, 2001 Abstract. 170 Yb Mossbauer shows is needed. We present here a 170 Yb Mossbauer study of Yb 2 Cu 2 O 5 at temperatures from 2 K to 18 K. 2
From stable divalent to valence-fluctuating behaviour in Eu(Rh(1-x)Ir(x))2Si2 single crystals.
Seiro, Silvia; Geibel, Christoph
We have succeeded in growing high-quality single crystals of the valence-fluctuating system EuIr(2)Si(2), the divalent Eu system EuRh(2)Si(2) and the substitutional alloy Eu(Rh(1-x)Ir(x))(2)Si(2) across the range 0 < x < 1, which we characterized by means of x-ray diffraction, energy-dispersive x-ray spectroscopy, specific heat, magnetization and resistivity measurements. On increasing x, the divalent Eu ground state subsists up to x = 0.25 with a slight increase in Nķel temperature, while for 0.3?x < 0.7 a sharp hysteretic change in susceptibility and resistivity marks the first-order valence transition. For x?0.7 the broad feature observed in the physical properties is characteristic of the continuous valence evolution beyond the critical end point of the valence transition line, and the resistivity is reminiscent of Kondo-like behaviour while the Sommerfeld coefficient indicates a mass renormalization of at least a factor of 8. The resulting phase diagram is similar to those reported for polycrystalline Eu(Pd(1-x)Au(x))(2)Si(2) and EuNi(2)(Si(1-x)Ge(x))(2), confirming its generic character for Eu systems, and markedly different to those of homologue Ce and Yb systems, which present a continuous suppression of the antiferromagnetism accompanied by a very smooth evolution of the valence. We discuss these differences and suggest them to be related to the large polarization energy of the Eu half-filled 4f shell. We further argue that the changes in the rare earth valence between RRh(2)Si(2) and RIr(2)Si(2) (R = Ce, Eu, Yb) are governed by a purely electronic effect and not by a volume effect. PMID:21878716
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Constitutive and functional expression of YB-1 in microglial cells.
Keilhoff, G; Titze, M; Esser, T; Langnaese, K; Ebmeyer, U
Y-box-binding protein (YB-1) is a member of the cold-shock protein family and participates in a wide variety of DNA/RNA-dependent cellular processes including DNA repair, transcription, mRNA splicing, packaging, and translation. At the cellular level, YB-1 is involved in cell proliferation and differentiation, stress responses, and malignant cell transformation. A general role for YB-1 during inflammation has also been well described; however, there are minimal data concerning YB-1 expression in microglia, which are the immune cells of the brain. Therefore, we studied the expression of YB-1 in a clinically relevant global ischemia model for neurological injury following cardiac arrest. This model is characterized by massive neurodegeneration of the hippocampal CA1 region and the subsequent long-lasting activation of microglia. In addition, we studied YB-1 expression in BV-2 cells, which are an accepted microglia culture model. BV-2 cells were stressed by oxygen/glucose deprivation (OGD), OGD-relevant mediators, lipopolysaccharide (LPS), and phagocytosis-inducing cell debris and nanoparticles. Using quantitative polymerase chain reaction (PCR), we show constitutive expression of YB-1 transcripts in unstressed BV-2 cells. The functional upregulation of the YB-1 protein was demonstrated in microglia in vivo and in BV-2 cells in vitro. All stressors except for LPS were potent enhancers of the level of YB-1 protein, which appears to be regulated primarily by proteasomal degradation and, to a lesser extent, by the activation (phosphorylation) of the translation initiation factor eIF4E. The proteasome of BV-2 cells is impaired by OGD, which results in decreased protein degradation and therefore increased levels of YB-1 protein. LPS induces proteasome activity, which enables the level of YB-1 protein to remain at control levels despite enhanced protein ubiquitination. The proteasome inhibitor MG-132 was able to increase YB-1 protein levels in control and LPS-treated cultures. YB-1 upregulation was not accompanied by its translocation from the cytoplasm to the nucleus. YB-1 induction appeared to be related to microglial proliferation because it was partially co-regulated with Ki67. In addition, YB-1 protein levels correlated with microglia phagocytic activity because its upregulation could also be induced by inert NPs. PMID:26102006
Eu{sub 3}F{sub 4}S{sub 2}: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF{sub 2}.(EuFS){sub 2}
Grossholz, Hagen; Hartenbach, Ingo [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany); Kotzyba, Gunter [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Poettgen, Rainer, E-mail: email@example.com [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Trill, Henning; Mosel, Bernd D. [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Schleid, Thomas, E-mail: email@example.com [Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)
Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS (M=Y, La, Ce-Lu), in some cases we were able to obtain mixed-valent compounds such as Yb{sub 3}F{sub 4}S{sub 2} instead. With Eu{sub 3}F{sub 4}S{sub 2} another isotypic representative has now been synthesized. Eu{sub 3}F{sub 4}S{sub 2} (tetragonal, I4/mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 deg. C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF{sub 2}-type EuF{sub 2} is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu{sup 2+}) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu{sup 3+}) exhibits a monocapped square antiprismatic coordination sphere with four F{sup -} and five S{sup 2-} anions. Although the structural ordering of the different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu{sub 3}F{sub 4}S{sub 2} show Curie-Weiss behavior with an experimental magnetic moment of 8.19(5) mu{sub B} per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu{sup II})(Eu{sup III}){sub 2}F{sub 4}S{sub 2} only one third of the europium centers in Eu{sub 3}F{sub 4}S{sub 2} carry permanent magnetic moments. {sup 151}Eu-Moessbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of -12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu{sup 2+} and Eu{sup 3+}, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu{sup 2+}/Eu{sup 3+} fraction can be detected. - Graphical abstract: Crystal structure and {sup 151}Eu-Moessbauer spectra of mixed-valent Eu{sub 3}F{sub 4}S{sub 2}.
Efficient diode-pumped Yb3+ :Y2SiO5 and
Paris-Sud XI, Universit├® de
(YSO) and Lu2SiO5 (LSO), that are longitudinally diode pumped. Yb:YSO supplied pulses as short as 122 durations of 198 fs at 1044 nm and 260 fs at 1059 nm for Yb:YSO and Yb:LSO, respectively, were provided Yb:LSO with interesting potential to be short-pulsed high- power lasers, partly based
Valence fluctuation of Yb in the superconducting ytterbium-rhodium stannides
P. Bordet; J. L. Hodeau; P. Wolfers; G. Krill; F. Weiss; M. Marezio
Yb LIII X-ray absorption edge measurements yielded 2.20+ and 2.50+ for the Yb valence in the Yb-Rh-Sn compounds with phase I and II', respectively. The former is superconducting (Tc ~ 8 K), and contains only one crystallographic site for Yb, which suggests that this atom is in a valence fluctuation state.
Water Research 39 (2005) 239247 Biosorption of La, Eu and Yb using Sargassum biomass
Volesky, Bohumil
), copper/lead (Math- eickal and Yu, 1999) and uranium (Yang and Volesky, 1999a). Sargassum contains high and alloys (9%), rare-earth phosphors for lighting, televisions, computer monitors, radar, and X
Anisotropic heavy-Fermi-liquid formation in valence-fluctuating alpha-YbAlB4
Yosuke Matsumoto; Kentaro Kuga; Takahiro Tomita; Yoshitomo Karaki; Satoru Nakatsuji
alpha-YbAlB4 is the locally isostructural polymorph of beta-YbAlB4, the first example of a Yb-based heavy fermion superconductor that exhibits pronounced non-Fermi-liquid behavior above Tc. Interestingly, both alpha-YbAlB4 and beta-YbAlB4 have strongly intermediate valence. Our single-crystal study of the specific heat, magnetization, and resistivity has confirmed the Fermi-liquid ground state of alpha-YbAlB4 in contrast to the quantum criticality observed in beta-YbAlB4.
Laser spectroscopy and cooling of Yb+ ions on a deep-UV transition
Hendrik M. Meyer; Matthias Steiner; Lothar Ratschbacher; Christoph Zipkes; Michael K÷hl
We perform laser spectroscopy of Yb+ ions on the 4f14 6s 2S_{1/2} - 4f13 5d 6s 3D[3/2]_{1/2} transition at 297 nm. The frequency measurements for 170Yb+, 172Yb+, 174Yb+, and 176Yb+ reveal the specific mass shift as well as the field shifts. In addition, we demonstrate laser cooling of Yb+ ions using this transition and show that light at 297 nm can be used as the second step in the photoionization of neutral Yb atoms.
Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)
Myers, Kenneth D.
This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds containing magnetic rare earths, antiferromagnetically ordered at low temperatures. The ordering temperatures of these compounds are approximately proportional to the de Gennes factor, which suggests that the RKKY interaction is the dominant exchange interaction between local moments. Although metamagnetic transitions were observed in many members of the series, the series of sharp step-like transitions in DyAgSb{sub 2} are impressive. In this compound, up to 11 different magnetic states are stable depending on the magnitude and direction of the applied field. The saturated magnetization of these states and the critical fields needed to induce a phase transition vary with the direction of the applied field. Through detailed study of the angular dependence of the magnetization and critical fields, the net distribution of magnetic moments was determined for most, of the metamagnetic states. In DyAgSb{sub 2}, the crystal electric field (CEF) splitting of the Hund's rule ground state creates a strong anisotropy where the local Dy{sup 3+} magnetic moments are constrained to one of the equivalent {l_angle}110{r_angle} directions within the basal plane. The four position clock model was introduced to account for this rich metamagnetic system. Within this model, the magnetic moments are constrained to one of four equivalent orientations within the basal plane and interactions are calculated for up third nearest neighbors. The theoretical phase diagram, generated from the coupling constants is in excellent agreement with the experimental phase diagram. Further investigation of this compound using magnetic X-ray or neutron diffraction would be extremely useful to verify the net distributions of moments and determine the wave vectors of each of the ordered states.
Energy transfer mechanisms in Yb3+ doped YVO4 near-infrared downconversion phosphor
Xiantao Wei; Shan Huang; Yonghu Chen; Changxin Guo; Min Yin; Wu Xu
Upon ultraviolet (UV) light excitation, an intense near-infrared (NIR) emission of Yb3+ (2F5\\/2-->2F7\\/2) around 980 nm is observed in YVO4:Yb3+ phosphors. Owing to host absorption of YVO4, a broad excitation band ranging from 250 to 350 nm is recorded when the Yb3+ emission was monitored, which suggests an efficient energy transfer from host to Yb3+ ions. The Yb3+ concentration dependence
Comparative study on enhancement of self-Q-switched Cr,Yb:YAG lasers by bonding Yb:YAG ceramic and crystal
NASA Astrophysics Data System (ADS)
Dong, J.; Ma, J.; Cheng, Y.; Ren, Y. Y.; Ueda, K.; Kaminskii, A. A.
Enhancement of laser-diode pumped self-Q-switched Cr, Ca, and Yb3+ ions co-doped YAG (Cr,Yb:YAG) lasers by bonding Yb:YAG ceramic to increase pump power absorption efficiency have been demonstrated for the first time to our best knowledge. Efficient Cr,Yb:YAG self-Q-switched laser performance has been achieved by bonding Yb:YAG ceramic. The effect of transmission of output coupler (TOC) on the laser performance has been investigated and found that the best laser performance was achieved with TOC = 20% for Yb:YAG ceramic. Slope efficiency of 20% was achieved with TOC = 20% for Cr,Yb:YAG self-Q-switched laser by bonding Yb:YAG ceramic. Maximum average output power of 683 mW was measured at absorbed pump power of 4.5 W; the corresponding optical-to-optical efficiency is 15.2%. The output laser pulse characteristics were compared for Cr,Yb:YAG self-Q-switched lasers by bonding Yb:YAG ceramic and crystal under different transmission of output coupler. For the same TOC, the laser performance of Cr,Yb:YAG self-Q-switched lasers by bonding Yb:YAG ceramic is better than that by bonding Yb:YAG crystal.
Magnetic Order in single-crystalline YbPtSi
NASA Astrophysics Data System (ADS)
Yiu, Yuen; Janssen, Yuri; Khalifah, Peter; Aronson, Meigan; Kim, Moosung; Bennett, Marcus
We report the first measurements on YbPtSi, which we synthesized as single crystals by means of flux growth from Indium. Single crystal x-ray diffraction measurements find that the YbPtSi crystal structure is the orthorhombic Co2Si-type, with one crystallographic site for Yb. Magnetic susceptibility measurements find Curie-Weiss behavior above 100 K with a moment of 4.35 ?B, close to the 4.54 ?B expected for trivalent Yb. Measurements of the heat capacity find a mean field-like magnetic ordering transition at T=4.65K. DC-susceptibility measurements show substantial single ion anisotropy, but also exhibit a peak at 4.65 K, indicating possible antiferromagnetic ordering. The electrical resistivity is metallic, and the magnetic ordering is accompanied by a change in slope. The magnetic entropy amounts to only about 65 % of Rln2 expected from an ordering Yb ground state doublet at the ordering temperature, suggesting a possible role for the Kondo effect. Our measurements indicate that YbPtSi is an unusual example of an Yb-based Kondo lattice system, ordering at an unusually high temperature.
Magnetic and transport properties of the narrow-gap semiconductor Yb5Si4
NASA Astrophysics Data System (ADS)
Kosaka, Masashi; Ottomo, Shingo; Machida, Ayumi; Kirigane, Tomoyuki; Numakura, Ryosuke; Katano, Susumu; Michimura, Shinji
We report the synthesis and basic properties of the binary compound Yb5Si4. In this compound, Yb ions occupy three different crystallographic sites, the multiplicity of which is represented by Yb1 : Yb2 : Yb3 = 1:2:2. The estimated effective magnetic moment and magnetic entropy can be explained by the proportion of Yb valence states, Yb3+ : Yb2+ = 2:3. This result suggests the possibility that Yb3+ ions occupy either Yb2 or Yb3 site. Yb5Si4 undergoes an antiferromagnetic transition at TN = 1.7 K. The extended high temperature tail in the temperature dependence of the specific heat just above TN has been observed. Yb5Si4 also exhibits the broad maximum peak around 2.3 K in the magnetic susceptibility, corresponding to the specific heat anomaly. We propose that these anomalies are possible to originate from magnetic fluctuations caused by low-dimensional Yb3+ networks. Electrical resistivity measurements on Yb5Si4 reveal semiconducting behavior at all temperatures. The small energy gap ? = 430 K has been obtained at room temperature estimated by the thermal activation model. The energy gap gradually decreases with decreasing temperature, and reaches about 3 K at low temperatures.
Monodisperse and core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} (Ln=Eu, Tb, Dy, Sm, Er, Ho, and Tm) spherical particles: A facile synthesis and luminescent properties
Xu, Zhenhe, E-mail: email@example.com [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)] [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China); Feng, Bin [China National Aviation Fuel Group Corporation, Planning and Development Department, Beijing 100088 (China)] [China National Aviation Fuel Group Corporation, Planning and Development Department, Beijing 100088 (China); Bian, Shasha; Liu, Tao; Wang, Mingli; Gao, Yu; Sun, Di; Gao, Xin [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)] [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China); Sun, Yaguang, E-mail: firstname.lastname@example.com [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)] [College of Applied Chemistry, Shenyang University of Chemical Technology, Shenyang 100142 (China)
The core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles were realized by coating the Lu{sub 2}O{sub 3}:Ln{sup 3+} phosphors onto the surface of non-aggregated, monodisperse and spherical SiO{sub 2} particles by the Pechini sol-gel method. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photolumiminescence (PL), and low-voltage cathodoluminescence (CL). The results indicate that the 800 Degree-Sign C annealed sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores, in spherical shape with a narrow size distribution. The as-obtained particles show strong light emission with different colors corresponding to different Ln{sup 3+} ions under ultraviolet-visible light excitation and low-voltage electron beams excitation, which have potential applications in fluorescent lamps and field emission displays. - Graphical Abstract: Representative SEM and TEM images of the core-shell structured SiO{sub 2}-Lu{sub 2}O{sub 3}:Eu{sup 3+} particles; CIE chromaticity diagram showing the emission colors for SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+}; Multicolor emissions of SiO{sub 2}-Lu{sub 2}O{sub 3}:Ln{sup 3+} particles. Highlights: Black-Right-Pointing-Pointer The core-shell particles were realized by coating the phosphors onto the surface of SiO{sub 2} particles. Black-Right-Pointing-Pointer The sample consists of crystalline Lu{sub 2}O{sub 3} shells and amorphous SiO{sub 2} cores. Black-Right-Pointing-Pointer The particles show different light emission colors corresponding to Ln{sup 3+} ions. Black-Right-Pointing-Pointer They have potential applications in fluorescent lamps and field emission displays.
Spectroscopic properties of Eu3+, Dy3+ and Tb3+ ions in lead silicate glasses obtained by the conventional high-temperature melt-quenching technique
NASA Astrophysics Data System (ADS)
?ur, L.; Janek, J.; So?tys, M.; Pisarska, J.; Pisarski, W. A.
The luminescence properties of selected rare-earth ions in lead silicate glasses have been studied. Europium, dysprosium and terbium ions were chosen as active dopants. Based on excitation and emission measurements as well as luminescence decay analysis, some spectroscopic parameters for these lanthanide ions were determined. In particular, the intensity ratios R/O (Eu3+), Y/B (Dy3+) and G/B (Tb3+) were calculated. Luminescence lifetimes for the 5D0 state of Eu3+ ions, the 4F9/2 state of Dy3+ ions and the 5D4 state of Tb3+ ions were also determined.
YbN: An intrinsic semiconductor with antiferromagnetic exchange
NASA Astrophysics Data System (ADS)
Warring, H.; Ruck, B. J.; McNulty, J. F.; Anton, E.-M.; Granville, S.; Koo, A.; Cowie, B.; Trodahl, H. J.
We present a study of the structural, conducting, magnetic, and optical properties of YbN thin films. Magnetic measurements reveal an antiferromagnetic Curie-Weiss temperature dependence. We find the temperature-dependent resistivity and carrier concentration to be indicative of YbN being semiconducting in nature. Along with this we observe an absorption onset at 1.5 eV, found from optical transmission and reflection measurements. This apparent combination of antiferromagnetism and semiconductivity present in YbN makes it unique among the rare earth nitrides, a series dominated by ferromagnetic semiconductors.
Fabrication and laser properties of transparent Yb:YAG ceramics
NASA Astrophysics Data System (ADS)
Luo, Dewei; Zhang, Jian; Xu, Changwen; Qin, Xianpeng; Tang, Dingyuan; Ma, Jan
High optical quality transparent Yb:YAG laser ceramics have been successfully fabricated by a vacuum reactive sintering method. Commercial Al2O3 powder and co-precipitated Y2O3 and Yb2O3 powders were used as the raw materials. In-line transmittances at 1300 nm and 400 nm were measured to be 83.6% and 81.8% respectively for a 3 mm thick mirror polished Yb:YAG ceramics sample. Continuous wave (CW) lasing at the wavelength of 1030 nm was achieved when pumped by a 940 nm fiber coupled laser diode. A slope efficiency as high as 62.7% was obtained.
Fabrication and laser properties of transparent Yb:YAG ceramics
Dewei Luo; Jian Zhang; Changwen Xu; Xianpeng Qin; Dingyuan Tang; Jan Ma
High optical quality transparent Yb:YAG laser ceramics have been successfully fabricated by a vacuum reactive sintering method. Commercial Al2O3 powder and co-precipitated Y2O3 and Yb2O3 powders were used as the raw materials. In-line transmittances at 1300nm and 400nm were measured to be 83.6% and 81.8% respectively for a 3mm thick mirror polished Yb:YAG ceramics sample. Continuous wave (CW) lasing at
Fabrication and properties of highly transparent Tm 3Al 5O 12 (TmAG) ceramics
Wen-Xin Zhang; Jiang Li; Wen-Bin Liu; Yu-Bai Pan; Jing-Kun Guo
Highly transparent Tm3Al5O12 (TmAG) ceramics were fabricated by solid-state reaction and vacuum sintering. Densification, microstructure evolution, mechanical, thermal, and optical properties of the TmAG ceramics were investigated. Fully dense TmAG ceramic with average grain size of ?15?m was obtained by sintering at 1780░C for 20h. The in-line transmittance was 80.5% at 2000nm. The absorption coefficients at 682nm and 785nm were
Laser tunability in Yb 3+:YCa 4O(BO 3) 3 {Yb:YCOB}
NASA Astrophysics Data System (ADS)
Shah, L.; Ye, Q.; Eichenholz, J. M.; Hammons, D. A.; Richardson, M.; Chai, B. H. T.; Peale, R. E.
Tunable laser operation in Yb:YCOB from 1018 to 1087 nm pumped by 1.4 W from a Ti:Sapphire laser tuned to 900 nm is demonstrated. The combination of the ability to grow large crystals with high optical quality, broad infrared emission, diode pumpable absorption bands, and a significant non-linear coefficient makes this material very promising for use in tunable and ultrafast laser systems.
Local moment behaviors of the valence fluctuating systems beta-YbAlB4 and alpha-YbAlB4
Y. Matsumoto; K. Kuga; N. Horie; S. Nakatsuji
beta-YbAlB4 is the first example of an Yb-based heavy Fermion superconductor with Tc = 80 mK and exhibits pronounced non-Fermi-liquid behavior above Tc. On the other hand, recent hard x-ray photoemission spectroscopy measurements have revealed strong intermediate valence of both beta-YbAlB4 and its locally isostructural polymorph alpha-YbAlB4 . Here we present the results of the specific heat and magnetization measurements
The optical properties of Yb3+ ions in LiTaO3:Nd,Yb crystals
NASA Astrophysics Data System (ADS)
Sok¾lska, I.; Ryba-Romanowski, W.; Go?ab, S.; Lukasiewicz, T.
The optical properties of Yb3+ ions excited by energy transfer from Nd3+ ions in LiTaO3:Nd, Yb crystals are presented. The emission band of Yb3+ ions is broad, due to the strong phonon-coupling and to the relative large Stark-splitting of the ground 2F7/2 multiplet. The emission cross-section was evaluated by the reciprocity method, and a value of 0.53᎒-20 cm2 was obtained. The gain coefficients derived for the inversion parameters in the range 0.05 to 0.5 indicate positive gain in the 985-1070 nm range.
Pressure-induced valence change of YbNiGe3 investigated by resonant x-ray emission spectroscopy at the Yb L3 edge
NASA Astrophysics Data System (ADS)
Sato, Hitoshi; Yamaoka, Hitoshi; Utsumi, Yuki; Nagata, Heisuke; Avila, Marcos A.; Ribeiro, Raquel A.; Umeo, Kazunori; Takabatake, Toshiro; Zekko, Yumiko; Mizuki, Jun'ichiro; Lin, Jung-Fu; Hiraoka, Nozomu; Ishii, Hirofumi; Tsuei, Ku-Ding; Namatame, Hirofumi; Taniguchi, Masaki
Pressure dependence of the Yb valence in YbNiGe3 has been investigated up to 15.6 GPa at 300 K and up to 7.7 GPa at 17 K by means of x-ray absorption spectroscopy in L?1 partial fluorescence yield mode and resonant x-ray emission spectroscopy around the Yb L3 absorption edge. The Yb valence in YbNiGe3 at ambient pressure strongly fluctuates with the mean valence of v =2.52▒0.01 at 300 K. The Yb valence rapidly changes toward a trivalent state with pressure up to ś5 GPa, slowly increases up to ś10 GPa, and then reaches a saturated value of v ś2.87 at 15.6 GPa. The Yb valence at 17 K slightly decreases compared to that at 300 K; v ś2.45 at ambient pressure and ś2.72 at 7.7 GPa. We found that the pressure-induced change in the intensity of a quadrupole component in the x-ray absorption spectra shows the same trend as the Yb valence in YbNiGe3. In contrast to YbNiGe3, the Yb valence in YbNiSi3 is nearly 3 at ambient pressure with almost no temperature dependence.
Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals
NASA Astrophysics Data System (ADS)
Wang, Xinshun; Liu, Yang; Zhao, Panjuan; Guo, Zhongyi; Li, Yan; Qu, Shiliang
The broad band upconversion luminescence in Yb3+:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d ? 4f transitions of Yb2+ ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb2+-F+) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb3+ to Yb2+ and (Yb2+-F+) centers have been induced by infrared femtosecond laser irradiation in Yb3+:YAG crystal.
High power Yb-Raman combined nonlinear fiber amplifier.
Zhang, Hanwei; Xiao, Hu; Zhou, Pu; Wang, Xiaolin; Xu, Xiaojun
We demonstrated a high power Yb-Raman combined nonlinear fiber amplifier. The seed is a 30 W dual-wavelength Yb-doped fiber laser formed by 1070 nm and 1120 nm lasers. The gain medium in the amplifier stage is a 45-meters-long Yb-doped fiber, which power scaled the 1070 nm laser and Raman amplified the 1120 nm laser simultaneously. A record 1120 nm power of 732 W is obtained with pump power of 890 W. Numerical study taking into account of both Yb and Raman gain has been conducted to analyze the output characters and power evolution in the amplifier under different conditions. The numerical results are in good agreement with the experiment. This amplifier is also suitable to amplify laser in the wavelength range of 1100-1150 nm. PMID:24921728
Fight against terror in the EU: does EU citizenship matter?
T. P. Marguery
This paper challenges the assumption that the Union actually offers its citizens an AFSJ.\\u000aIn fact, European criminal justice is actually offered ¢ and should be offered ¢ to all\\u000aindividuals whether EU citizens or not. The fight against crime as organised in the AFSJ\\u000aactually affects all individuals and EU citizenship-related rights have a little impact therein.\\u000aFirst, this
Optical spectra of Yb 3+ and Yb 3+-Nd 3+ interaction in Cs 2NaNd 0,4Yb 0,6Cl 6
NASA Astrophysics Data System (ADS)
Ryba-Romanowski, W.; Golab, S.
Interaction between octahedrally coordinated Nd 3+ and Yd 3+ in Cs 2NaNd 0,4Yb 0,6Cl 6 reduces the Nd 3+ luminescence lifetime by roughly two orders of magnitude with respect to that found in Cs 2NaNdCl 6- Ę - Analysis of low temperature absorption and emission spectra reveals that the nonradiative Nd 3+-Yb 3+ energy transfer has to be assisted by lattice phonon emission, nevertheless the rate of the transfer is high in the 4-300 K temperature region and attains 5.8ū10 5s -1 at room temperature. A phase transition of Cs 2NaNd 0,4Yb 0,6Cl 6 between 12 and 13 K is evidenced by abrupt change of both the spectra and lifetimes of Yb 3+. Reduction of Yb 3+ lifetime from 5.3 ms to 150 ?s is at the transition from low symmetry phase to high symmetry phase is supposed to be associated with a three ion interaction which occurs in ordered lattice and disappears in low temperature disordered structure.
Luminescence of re 2+ (re = Sm, Yb) in barium octoborate
Qinghua Zeng; Zhiwu Pei; Shubing Wang; Qiang Su; Shaozhe Lu
The reduction process from trivalent to divalent state for Sm3+ and Yb3+ ions in barium borates (BaB8O13) prepared in air was observed. The luminescence properties of these divalent rare-earth ions were studied. Yb2+ shows an f-d broad emission band, due to the 4f14 ? 4f135d transition, while the Sm2+ ion shows an f ? f transition. From the spectra of
Application of Yb:YAG short pulse laser system
Erbert, Gaylen V.; Biswal, Subrat; Bartolick, Joseph M.; Stuart, Brent C.; Crane, John K.; Telford, Steve; Perry, Michael D.
A diode pumped, high power (at least 20W), short pulse (up to 2 ps), chirped pulse amplified laser using Yb:YAG as the gain material is employed for material processing. Yb:YAG is used as the gain medium for both a regenerative amplifier and a high power 4-pass amplifier. A single common reflective grating optical device is used to both stretch pulses for amplification purposes and to recompress amplified pulses before being directed to a workpiece.
Digital MicrofilmTM Quick Start Guide
Olsen, Stephen L.
Optical and scintillation properties of transparent ceramic Yb:Lu2O3 with different Yb concentrations
NASA Astrophysics Data System (ADS)
Yanagida, Takayuki; Fujimoto, Yutaka; Yagi, Hideki; Yanagitani, Takagimi
Yb 0.1-100% doped Lu2O3 transparent ceramic scintillators were prepared by Konoshima Chemical. They had 60-80% transparency at wavelength longer than 240 nm and absorption bands around 970 nm due to 4f-4f transition of Yb3+ were observed. In photoluminescence and X-ray induced radioluminescence, Yb3+ charge transfer luminescence appeared at 330 and 490 nm. Photoluminescence and scintillation decay times of the charge transfer luminescence resulted 0.5-1.5 ns. 137Cs excited pulse height spectrum was evaluated to determine the light yield of the fast component and Yb 0.3% doped sample exhibited the highest light yield of ś500 ph/MeV.
Beta-Decay Study of ^{150}Er, ^{152}Yb, and ^{156}Yb: Candidates for a Monoenergetic Neutrino Beam Facility
Estevez Aguado, M. E. [CSIC-Universidad de Valencia; Algora, A. [CSIC-Universidad de Valencia; Rubio, B. [CSIC-Universidad de Valencia; Bernabeu, J. [CSIC-Universidad de Valencia; Nacher, E. [CSIC-Universidad de Valencia; Tain, J. L. [CSIC-Universidad de Valencia; Gadea, A. [CSIC-Universidad de Valencia; Agramunt, J. [CSIC-Universidad de Valencia; Burkard, K. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Hueller, W. [GSI-Hemholtzzentrum fur Schwerionenforschung, Darmstadt, Germany; Doring, J. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Kirchner, R. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Mukha, I. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Plettner, C. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Roeckl, E. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Grawe, H. [GSI-Hemholtzzentrum fur Schwerionenforschung, Darmstadt, Germany; Collatz, R. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Hellstrom, M. [Gesellschaft fur Schwerionenforschung (GSI), Germany; Cano-Ott, D. [CIEMAT, Madrid; Karny, M. [University of Warsaw; Janas, Z. [University of Warsaw; Gierlik, M. [University of Warsaw; Plochocki, A. [University of Warsaw; Rykaczewski, Krzysztof Piotr [ORNL; Batist, L. [Petersburg Nuclear Physics Institute, Gatchina, Russia; Moroz, F. [Petersburg Nuclear Physics Institute, Gatchina, Russia; Wittman, V. [Petersburg Nuclear Physics Institute, Gatchina, Russia; Blazhev, A. [University of Cologne; Valiente, J. J. [INFN, Laboratori Nazionali di Legnaro, Italy; Espinoza, C. [CFPT-IST, Lisbon
The beta decays of ^{150}Er, ^{152}Yb, and ^{156}Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied, the EC decay proceeds mainly to a single state in the daughter nucleus.
Yb(Cu,T) 5 and Yb(Cu,T) 4.5 solid solutions (T = Ag, Au, Pd)
M. Giovannini; R. Pasero; S. De Negri; A. Saccone
The binary Yb¢Cu phase diagram was re-investigated in the Cu-rich part. Starting from this region, solid solutions formed by substitution of Cu by Ag, Au, and Pd have been investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). A competition in compound formation between Yb(Cu,T)5 (T=Ag, Au, Pd), cubic AuBe5-type and its monoclinic superstructure
Unusual weak magnetic exchange in two different structure types: YbPt2Sn and YbPt2In.
Gruner, T; Jang, D; Steppke, A; Brando, M; Ritter, F; Krellner, C; Geibel, C
We present the structural, magnetic, thermodynamic and transport properties of the two new compounds YbPt(2)Sn and YbPt(2)In. X-ray powder diffraction shows that they crystallize in different structure types, the hexagonal ZrPt(2)Al and the cubic Heusler type, respectively. Despite quite different lattice types, both compounds present very similar magnetic properties: a stable trivalent Yb(3+), no evidence for a sizeable Kondo interaction and very weak exchange interactions with a strength below 1 K as deduced from specific heat C(T). Broad anomalies in C(T) suggest short range magnetic ordering at about 250 mK and 180 mK for YbPt(2)Sn and YbPt(2)In, respectively. The weak exchange and the low ordering temperature result in a large magnetocaloric effect as deduced from the magnetic field dependence of C(T), making these compounds interesting candidates for magnetic cooling. In addition we found in YbPt(2)In evidences for a charge density wave transition at about 290 K. The occurrence of such transitions within several RET2X compound series (RE = rare earth, T = noble metal, X = In, Sn) is analyzed. PMID:25322667
The new binary intermetallic YbGe{sub 2.83}
Peter Sebastian, C. [Department of Chemistry, Northwestern University, 2145 N. Sheridan Road, Evanston, IL 60208-3113 (United States); Kanatzidis, Mercouri G., E-mail: email@example.com [Department of Chemistry, Northwestern University, 2145 N. Sheridan Road, Evanston, IL 60208-3113 (United States)
The new compound YbGe{sub 2.83} was obtained from the reaction of Yb and Ge in liquid indium. The crystal structure of YbGe{sub 2.83} adopts the trigonal, P3m1 space group with a=b=8.3657(12) A and c=7.0469(14) A. The structure of YbGe{sub 2.83} is a variant of the CaAl{sub 2}Si{sub 2} structure type with ordered vacancies. Germanium atoms form double layers of puckered hexagons creating slabs that sandwich the Yb atoms. YbGe{sub 2.83} can be classified as a Zintl compound with the formula Yb{sup (2+x)+}(Ge{sub 2.83}){sup (2+x)-}. The deficiencies at the Ge sites cause a mixed/intermediate valent state of ytterbium (Yb{sup 2.35+}). Valence bond sum calculations suggest an average valence of Yb ions in YbGe{sub 2.83} of 2.51 consistent with an intermediate valence compound. - Graphical abstract: The new binary compound YbGe{sub 2.83} is a variant of the CaAl{sub 2}Si{sub 2} structure type with ordered vacancies. Zintl formalism and valence bond sum calculations suggest intermediate valence of Yb ions in YbGe{sub 2.83}.
HSP60 interacts with YB-1 and affects its polysome association and subcellular localization
Ohashi, Sachiyo; Atsumi, Megumi [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)] [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan); Kobayashi, Shunsuke, E-mail: email@example.com [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)] [Research Unit of Biochemistry, College of Pharmacy, Nihon University, Narashinodai, Funabashi, Chiba 274-8555 (Japan)
YB-1 is a DNA/RNA-binding protein which, in the cytoplasm, associates with polysomes and regulates translation. However, YB-1 has a novel nuclear localization signal, and its nuclear accumulation is correlated with cancer induction. Here we designated the amino-acid sequence as YB-NLS and demonstrated that YB-NLS is necessary for the nuclear translocation of overexpressed YB-1 in NG108-15 cells. In addition, we found that a heat shock protein, HSP60, binds to YB-NLS in the cytoplasm. Interestingly, when HSP60 expression was repressed, an increase of polysome-associated YB-1 was observed in heavy-sedimenting fractions on a sucrose gradient. Overexpression of HSP60 resulted in a decrease of YB-1 in the heavy-sedimenting fractions and suppression of YB-NLS activity. Furthermore, the NLS-deleted YB-1 was apparently associated with the heavy-sedimenting polysomes. These results suggest that HSP60 interacts with YB-1 at the YB-NLS region and acts as a regulator of polysome association and the subcellular distribution of YB-1.
Laser action in Yb3+: Ycob (Yb3+:YCa4O(BO3)3)
NASA Astrophysics Data System (ADS)
Hammons, Dennis A.; Eichenholz, Jason M.; Shah, Lawrence; Ye, Q.; Peale, Robert E.; Chai, Bruce H. T.; Richardson, Martin C.; Chin, Aland K.
Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class of laser materials that can be used as both a laser host and a nonlinear frequency converter. Laser action and self-frequency doubling (SFD) has been observed with both 10% and 20% Yb3+-doped YCOB crystals. Laser operation was obtained in a hemispherical linear cavity, end-pumped with a tunable cw Ti:Sapphire or a 980 nm laser diode pump source. Under Ti:Sapphire pumping at 900 nm, an output power of 230 mW and a slope efficiency of 29% was obtained using the 10% doped sample. Laser action was seen at 1050 nm. Laser operation of the 20% sample had a maximum output power of approximately 300 mW with a slope efficiency of 35.8% at 1088 nm. Laser action was not obtained at the peak of the fluorescence emission (approximately 1030 nm) in this crystal as a consequence of self-absorption on the short- wavelength side of the emission band. Diode-pumped operation at the narrow absorption peak of 977 nm was achieved and early results show an improved slope efficiency of 34% in comparison to the 10% doped crystal under Ti:Sapphire pumping. We have also observed self-frequency doubling in Yb3+:YCOB. The 20% Yb3+:YCOB crystal used for this test was cut with a phase-matching angle of 36.22 degree(s). The self-frequency doubling efficiency was low due to the absence of any frequency selective elements in the cavity to narrow the linewidth of the fundamental emission. The SFD emission occurred at 543 nm.
High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}
Haberer, Almut [Institut fuer Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universitaet Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria); Huppertz, Hubert, E-mail: firstname.lastname@example.com [Institut fuer Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universitaet Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria)
Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO{sub 3}-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}. Monoclinic Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} crystallizes in space group C2/c with the lattice parameters a=2028.2(4) pm, b=602.5(2) pm, c=820.4(2) pm, and beta=100.63(3){sup o} (Z=4). Three different ytterbium cations can be identified in the crystal structure, each coordinated by nine fluoride and oxygen anions. None of the five crystallographically independent fluoride ions is coordinated by boron atoms, solely by trigonally-planar arranged ytterbium cations. In close proximity to the above mentioned compounds RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}, Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} can be described via alternating layers with the formal compositions 'YbBO{sub 3}' and 'YbF{sub 3}' in the bc-plane. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}, built up from isolated BO{sub 3}-groups. The compound shows structural relations to the known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}.
Magnetic transition, long-range order, and moment fluctuations in the pyrochlore iridate Eu2Ir2O7
NASA Astrophysics Data System (ADS)
Zhao, Songrui; Mackie, J. M.; Maclaughlin, D. E.; Bernal, O. O.; Ishikawa, J. J.; Ohta, Y.; Nakatsuji, S.
Muon spin rotation and relaxation experiments in the pyrochlore iridate Eu2Ir2O7 yield a well-defined muon spin precession frequency below the metal-insulator/antiferromagnetic transition temperature TM=120 K, indicative of long-range commensurate magnetic order and thus ruling out quantum spin liquid and spin-glass-like ground states. The dynamic muon spin relaxation rate is temperature-independent between 2 K and ~TM and yields an anomalously long Ir4+ spin correlation time, suggesting a singular density of low-lying spin excitations. Similar behavior is found in other pyrochlores and geometrically frustrated systems, but also in the unfrustrated iridates BaIrO3 and Sr2Ir2O4. Eu2Ir2O7 may be only weakly frustrated; if so, the singularity might be associated with the small-gap insulating state rather than frustration.
Photoemission Studies of Kondo Lattice Compounds YbNi3(Ga1-xAlx)9
NASA Astrophysics Data System (ADS)
Utsumi, Yuki; Sato, Hitoshi; Nagata, Heisuke; Kodama, Junichi; Ohara, Shigeo; Yamashita, Tetsuro; Mimura, Kojiro; Motonami, Satoru; Arita, Masashi; Ueda, Shigenori; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki
We have investigated the electronic structure of YbNi3 (Ga1-xAlx)9 (x = 0, 0.05, 0.10, 0.15) by means of hard x-ray (h? ś 6 keV) and low energy (h? ś 7 eV) photoemission spectroscopies (HAXPES and LEPES). Both Yb2+ and Yb3+ components are observed in the Yb 3d HAXPES spectra, which is an evidence of the valence fluctuation in YbNi3(Ga1-xAlx)9. A substitution of an Al ion for a Ga ion in YbNi3Ga9 changes the Yb ion into a trivalent state. The LEPES spectra of YbNi3Ga9 clearly exhibit the Kondo peak near the Fermi level (EF) and the Kondo temperature is estimated to be TK ś 550 K. With the Al substitution, the Kondo peak is shifted toward EF, indicating the decrease of TK
Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent
Moore, Evan G.; Seitz, Michael; Raymond, Kenneth N.
It has been more than a decade since the first reports of [Gd(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] as a potential new class of magnetic resonance imaging contrast agent (MRI-CA). The defining feature of these 1-methyl-3-hydroxypyridin-2-one (Me-3,2-HOPO) based compounds has been the use of a hexadentate ligand design, and hence an increase in the number of metal bound water molecules, without sacrificing complex stability compared to the typically octadentate contrast agents used commercially. Since that time, significant advances in the properties of these chelates have been steadily reported, including improvements in relaxivity, incorporation into macromolecular architectures and, recently, the first direct verification of solution structure using the discovery of Eu(III) centered luminescence with the isomeric 1-hydroxypyridin-2-one (1,2-HOPO) chelate as a sensitizing chromophore. Nonetheless, it has remained frustrating that direct measurements of the inner sphere hydration state, q, using luminescence techniques with the parent Me-3,2-HOPO compounds have remained elusive, even when direct laser excitation of weakly absorbing f-f transitions were employed (eg. for Eu(III) complexes). This failing can likely be traced to the presence of a low lying LMCT state which efficiently quenches metal based emission. Instead, estimates of the q and hence solution structure have relied on the fitting of relaxivity data to the Solomon-Bloembergen-Morgan equations or, where sufficiently soluble in aqueous solution, studies on the temperature dependence of the paramagnetic contribution to the water {sup 17}O NMR transverse relaxation rate. Recently, Beeby et al reported on a qualitative equation to determine inner sphere hydration based on the change in lifetimes for Yb(III) in going from H{sub 2}O to D{sub 2}O solution, and we reasoned that the lower energy accepting state of Yb(III) may lie below the LMCT state which quenches Eu(III) emission, and hence may facilitate sensitized emission from Yb(III). This hypothesis was borne out experimentally, and herein we describe for the first time sensitized luminescence in the Near Infra-Red (NIR) region from a [Yb(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] complex, and hence the direct measurement of q for the archetypical member of this family of compounds.
Morphology and microstructure investigations of YB66 nano-particles prepared by plasma chemical process
J. Y. Huang; T. Ishigaki; T. Tanaka; S. Horiuchi
Nanocrystalline particles of YB66 were prepared by plasma chemical process, using starting powders of YB4 and B, and the morphology was examined by high-resolution transmission electron microscopy (HRTEM). The average grain size of the YB66 particles is less than 100 nm. All the YB66 nano-particles are cubic in shape, suggesting that they have been formed through a direct coagulation from
Determination of the 151Eu(n,?)152Eu and 153Eu(n,?)154Eu Reaction Cross Sections at Thermal Neutron Energy
NASA Astrophysics Data System (ADS)
Basunia, M. S.; Firestone, R. B.; Rķvay, Zs.; Choi, H. D.; Belgya, T.; Escher, J. E.; Hurst, A. M.; Krti?ka, M.; Szentmikl¾si, L.; Sleaford, B.; Summers, N. C.
We have measured partial ?-ray cross sections following neutron capture in enriched 151Eu and 153Eu targets at the cold-neutron-beam facility of the Budapest Research Reactor. The cross sections were standardized using a stoichiometric natEuCl3 target with the well-known 1951-keV ?-ray cross section from the 35Cl(n,?)36Cl reaction at the cold-neutron-beam facility of the Garching Research Reactor. The ?-ray cross sections were corrected for effective g-factors. These data were combined with the structural information of 152Eu and 154Eu given in the Evaluated Nuclear Structure Data File to produce capture ?-ray level schemes. The total radiative capture cross sections of the 151Eu(n,?)152Eu and 153Eu(n,?)154Eu reactions were determined by summing the experimental transition intensities from known levels with simulated intensities of transitions from higher excitations to the ground- or metastable-state. The individual 151Eu(n,?)152Eu and 151Eu(n,?)152gEu reaction cross sections disagree with values in the literature. However, the total cross section of the 151Eu(n,?)152Eu reaction does agree with those values. Also, our deduced cross section for the 153Eu(n,?)154Eu reaction closely follows the data in the literature. These results are supported by an earlier standardization experiment done at the Budapest Research Reactor using a target of Eu2O3 solution in H2SO4.
Yb3+/Ho3+-codoped antimony-silicate optical fiber
NASA Astrophysics Data System (ADS)
?mojda, Jacek; Dorosz, Dominik; Kochanowicz, Marcin; Miluski, Piotr; Dorosz, Jan
The emission properties of Yb3+/Ho3+-codoped antimony-silicate optical fiber has been investigated. Luminescence at 2.1 ?m corresponding to 5I7--> 5I8 transition in holmium was obtained by energy transfer between Yb3+ and Ho3+ ions. According to the Dexter-Miyakawa model, the parameters of energy migration CDD of the 2F5/2 (Yb3+) <--> 2F5/2 (Yb3+) transition and direct energy transfer CDA of the 2F5/2 (Yb3+) --> 5I6 (Ho3+) transition was calculated. The optimization of the activator content and the concentration ratio were conducted with the purpose of maximizing the efficiency of energy transfer. It made possible to select best-suited glass which was used to manufacture double-clad optical fiber. Strong and narrow bands of spontaneous emission which formed as a result of energy transfer between ytterbium and holmium ions were observed in the fiber under exciting with radiation at 978 nm wavelength.
Femtosecond pulses at 50-W average power from an Yb:YAG planar waveguide amplifier seeded
efficient femtosecond Yb:KYW laser pumped by single narrow-stripe laser diode," Electron. Lett. 39, 1108, "Mode-locked Yb:KGW laser longitudinally pumped by polarization-coupled diode bars," Opt. Lett. 31 threshold diode-pumped Kerr-lens mode-locked Yb:KYW laser," Opt. Express 12(17), 3928Ł3933 (2004). 9. A. A
Thermal conductivity of TmSeTe
NASA Astrophysics Data System (ADS)
Bucher, Benno; Malar, Jan; Wachter, Peter
The rare earth compound TmSeTe is a mixed valent semiconductor at ambient pressure. On increasing pressure the substance reveals a phase transition into an excitonic insulator phase(B. Bucher et al., PRL 66, (1991) 2717). The transition into the coherent excitonic groundstate might be interpreted as a Bose condensation. Different methodes have been applied on TmSeTe in order to search for features which are typical for a Bose condensate. The thermal conductivity of TmSeTe has been measured for pressures up to 20 kbar and temperatures down to 2 K. The thermal conductivity is enhanced within the excitonic phase. Furthermore the elastic properties of TmSeTe revealed an extremely small compressibility which must be attributed to the formation of the coherent ground state.
ProteoStatTM Protein Aggregation Assay
Lebendiker, Mario
ProteoStatTM Protein Aggregation Assay Biochemical assays for monitoring protein aggregates often:EffectivelineardynamicrangeforantibodyaggregatedetectionusingtheEnzo LifeSciencesProteoStatTMdetectionreagentcomparedwithThioflavinT:Rabbitanti-goat IgG(4.26mg- wellmicroplate.Aggregationwasmonitoredforseveralweeksatroomtemperature.TheEnzo
Preparation and characterization of Yb-doped YAG ceramics
NASA Astrophysics Data System (ADS)
HostaÜa, Jan; Esposito, Laura; Alderighi, Daniele; Pirri, Angela
This work presents the results of the preparation of polycrystalline Yb:YAG ceramics for laser sources with dopant concentration from 0 up to 20 at.% via solid state reactive sintering. Samples were prepared via cold isostatic pressing of spray dried mixture of pure oxide powders with TEOS as a sintering aid. Sintering was conducted under high vacuum and clean atmosphere. Various sintering cycles were tested, so that optimum conditions could be selected in dependence on Yb concentration. Samples with optical transmittance higher than 80% were prepared and their laser performance was examined. Slope efficiency as high as 73% and a maximum output power of 6 W were obtained for the sample doped with 10% Yb. Final microstructure of prepared samples was analyzed via optical microscopy, scanning and transmission electron microscopy, and EDS.
Short-wavelength Yb:fiber laser analysis
NASA Astrophysics Data System (ADS)
Yi, J. Y.; Chang, S. F.; Hsu, C. N.
Yb:fiber lasers have shown excellent performance in the 980¢1100 nm wavelength range. To extend the range below 980 nm, it becomes difficult to reach the transparent condition due to the smaller ratio between emission and absorption cross sections. As a result, a high demand of population inversion is needed, and the selection of pump wavelength as well as other intra-cavity parameters are crucial for lasing in the 920¢960 nm wavelength range. To find a feasible solution, the pump wavelength, fiber length, and laser cavity transmittance were systematically studied. Based on the experimental result of a 960 nm Yb:fiber laser, the re-absorption loss and temperature dependent gain can be reliably modeled. The result shows promise in the development of a Yb:fiber laser at a wavelength as short as 920 nm.
Yb:YAG Lasers for Space Based Remote Sensing
NASA Technical Reports Server (NTRS)
Ewing, J.J.; Fan, T. Y.
Diode pumped solid state lasers will play a prominent role in future remote sensing missions because of their intrinsic high efficiency and low mass. Applications including altimetry, cloud and aerosol measurement, wind velocity measurement by both coherent and incoherent methods, and species measurements, with appropriate frequency converters, all will benefit from a diode pumped primary laser. To date the "gold standard" diode pumped Nd laser has been the laser of choice for most of these concepts. This paper discusses an alternate 1 micron laser, the YB:YAG laser, and its potential relevance for lidar applications. Conceptual design analysis and, to the extent possible at the time of the conference, preliminary experimental data on the performance of a bread board YB:YAG oscillator will be presented. The paper centers on application of YB:YAG for altimetry, but extension to other applications will be discussed.
980 nm narrow linewidth Yb-doped phosphate fiber laser
NASA Astrophysics Data System (ADS)
Li, Pingxue; Yao, Yifei; Hu, Haowei; Chi, Junjie; Yang, Chun; Zhao, Ziqiang; Zhang, Guangju
A narrow-linewidth ytterbium (Yb)-doped phosphate fiber laser based on fiber Bragg grating (FBG) operating around 980 nm is reported. Two different kinds of cavity are applied to obtain the 980 nm narrow-linewidth output. One kind of the cavity consists of a 0.35 nm broadband lindwidth high-reflection FBG and the Yb-doped phosphate fiber end with 0░ angle, which generates a maximum output power of 25 mW. The other kind of resonator is composed of a single mode Yb-doped phosphate fiber and a pair of FBGs. Over 10.7 mW stable continuous wave are obtained with two longitudinal modes at 980 nm. We have given a detailed analysis and discussion for the results.
Heavy quasiparticles formed in the ferromagnetic Yb layers in the Kondo helical magnet YbNi3Al9 as revealed by specific-heat measurements
NASA Astrophysics Data System (ADS)
Miyazaki, Ryoichi; Aoki, Yuji; Higashinaka, Ryuji; Sato, Hideyuki; Yamashita, Testuro; Ohara, Shigeo
We report specific-heat and magnetocaloric-effect studies on single-crystalline Kondo helical magnet YbNi3Al9. Molecular field analysis of a Schottky peak due to the Zeeman splitting of the Yb-ion doublet crystalline-field ground state demonstrates that the interlayer antiferromagnetic exchange interactions are 2 orders of magnitude smaller than that of the intralayer ferromagnetic coupling among Yb ions, reflecting realization of magnetically well separated Yb layers. The Sommerfeld coefficient ?, which is 110 mJ/K2mol in zero field, decreases smoothly with increasing field without any noticeable anomalies at the helical magnetic phase boundary. This fact confirms that heavy quasiparticles are formed on a part of the Fermi surface away from ōhot sheetsö that have nesting instabilities responsible for the helical magnetic structure. These results indicate that YbNi3Al9 is a novel system where heavy quasiparticles are confined within the two-dimensional Yb layers.
Multiferroic Properties of Hexagonal YbMnO Thin Films
T. C. Han; J. G. Lin
The hexagonal (HX) YbMnO3 thin films were synthesized on the substrates of (111)Y2O3:ZrO2 and (111)Pt\\/(0001)Al2O3 by pulsed laser deposition (PLD), and their structural, magnetic, and electrical properties are measured. The temperature-dependent magnetization clearly displays an antiferromagnetic ordering near 80 K with field perpendicular to the film surface. In the curve of polarization-voltage, the HX-YbMnO3 thin films show distinct ferroelectricity with
Cdigo Candidato Inscrio TM1 ANICETO JOZIEL RABELO GOMES ANDRADE 790
1298 TM1 JEHAN CARLOS SARAIVA DE SOUSA 926 TM1 JORGE ANTONIO FURTADO LIMA 4 TM1 JOS╔ PINHEIRO DE MOURA1 / 14 C¾digo Candidato InscrińŃo TM1 ANICETO JOZIEL RABELO GOMES ANDRADE 790 TM1 ANTONIO CARLOS WILLIAM C╔SAR LIVRAMENTO SILVA 1059 TM2 ANTONIO FEITOSA CASTELO BRANCO 550 TM2 DENIVALDO REIS PINHEIRO
SPECTRE D'ABSORPTION DE Yb I (1) Par PIERRE CAMUS (2) et FRANK S. TOMKINS,
Paris-Sud XI, Universitķ de
fondamental 6s 2S1/2 de Yb II. Le potentiel d'ionisation de Yb I est donc de : 6,2537 ▒ 0,0002 volts, la and the 1P1 and 3P1 levels of the excited configuration 6s np of Yb I. Examination of the Rydberg series 6s2 is the ground state 6s 2S1/2 of Yb II. The ionization potential of Yb I is thus 6.2537 ▒ 0.0002 volts
Improvements in the production of Yb:YAG transparent ceramic materials: Spray drying optimisation
Marina Serantoni; Andreana Piancastelli; Anna Luisa Costa; Laura Esposito
Spray drying parameters have been optimized for the preparation of granulated stoichiometric mixture of oxides. These oxides are used in the production of Yb:YAG laser grade ceramic materials by reactive sintering. The selected compositions were Yb0.294Y2.706Al5O12 and Yb0.03Y2.97Al5O12, i.e. YAG doped with 9.8 and 1.0at% of Yb with respect to the overall Y+Yb amount. The influence of solid content, drying
Magnetic properties of YbTGe (T=Rh, Cu, Ag)
K. Katoh; Y. Mano; K. Nakano; G. Terui; Y. Niide; A. Ochiai
The magnetic properties of ternary equiatomic YbTGe (T=Rh, Cu, Ag) compounds have been investigated. YbRhGe is a new antiferromagnet with TN=7K which crystallizes in the orthorhombic TiNiSi-type structure. In YbCuGe, with the hexagonal LiGaGe-type structure, ferromagnetic ordering with a magnetic moment of 0.7?B\\/Yb occurs below 8K. On the other hand, in YbAgGe with the hexagonal ZrNiAl-type structure, the magnetic susceptibilities
Studies on the development of (169)Yb-brachytherapy seeds: New generation brachytherapy sources for the management of cancer.
Saxena, Sanjay Kumar; Kumar, Yogendra; Jagadeesan, K C; Nuwad, Jitendra; Bamankar, Y R; Dash, Ashutosh
This paper describes development of (169)Yb-seeds by encapsulating 0.6-0.65mm (?) sized (169)Yb2O3 microspheres in titanium capsules. Microspheres synthesized by a sol-gel route were characterized by XRD, SEM/EDS and ICP-AES. Optimization of neutron irradiation was accomplished and (169)Yb-seeds up to 74MBq of (169)Yb could be produced from natural Yb2O3 microspheres, which have the potential for use in prostate brachytherapy. A protocol to prepare (169)Yb-brachytherapy sources (2.96-3.7TBq of (169)Yb) with the use of enriched targets was also formulated. PMID:25846454
The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub2}.
Peter, S. C.; Malliakas, C. D.; Nakotte, H.; Kothapilli, K.; Rayaprol, S.; Schultz, A. J.; Kanatzidis, M. G. (Materials Science Division); ( XSD); (Northwestern Univ.); (Jawaharlal Nehru Centre for Adv. Sci. Res.); (New Mexico State Univ.); (Los Alamos Nat. Lab.); (UGC-DAE Consortium for Sci. Res.)
Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a = 12.2261(20) {angstrom}, b = 10.7447(20) {angstrom}, c = 8.4754(17) {angstrom} and {beta} = 110.288(30){sup o} (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge)n. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a = b = 5.9874(6) {angstrom} and c = 15.1178(19) {angstrom}. The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{alpha}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures.
Thermoelectric properties of Yb-filled CoSb3 skutterudites
NASA Astrophysics Data System (ADS)
Park, Kwan-Ho; Seo, Won-Seon; Shin, Dong-Kil; Kim, Il-Ho
Yb-filled skutterudites Yb z Co4Sb12 (z = 0, 0.1, 0.2, 0.3, 0.4) were prepared by encapsulated melting and hot pressing. The filling effects of Yb on the transport and the thermoelectric properties of the skutterudites were examined. In the case of z ? 0.3, a secondary phase (YbSb2) was formed, indicating that the filling fraction limit of Yb was z = 0.2 - 0.3. The intrinsic CoSb3 had a high positive Seebeck coefficient, but Yb-filled CoSb3 exhibited a negative Seebeck coefficient. In the case of z ? 0.1, the maximum absolute value of the Seebeck coefficient was | -231| ?VK-1, and in the case of z ? 0.2, the absolute value of the Seebeck coefficient increased with increasing temperature. The electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling content due to the increased carrier concentration. The thermal conductivity was reduced significantly by Yb filling, mainly due to a decrease in the lattice thermal conductivity. Also, the lattice thermal conductivity decreased with increasing Yb filling content, indicating that the phonon scattering was caused by the rattling of Yb fillers in the voids of the skutterudite structure. Yb0.2Co4Sb12 showed the highest figure of merit of 1.0 at 823 K.
Concurrent Validity of LibQUAL+[TM] Scores: What Do LibQUAL+[TM] Scores Measure?
ERIC Educational Resources Information Center
Thompson, Bruce; Cook, Colleen; Kyrillidou, Martha
The present study investigated the validity of LibQUAL+[TM] scores, and specifically how total and subscale LibQUAL+[TM] scores are associated with self-reported, library-related satisfaction and outcomes scores. Participants included 88,664 students and faculty who completed the American English (n[AE] = 69,494) or the British English (n[BE] =ģ
Innate immunity: Bacterial cell-wall muramyl peptide targets the conserved transcription factor YB-1.
Laman, A G; Lathe, R; Savinov, G V; Shepelyakovskaya, A O; Boziev, Kh M; Baidakova, L K; Chulin, A N; Brovko, F A; Svirshchevskaya, E V; Kotelevtsev, Y; Eliseeva, I A; Guryanov, S G; Lyabin, D N; Ovchinnikov, L P; Ivanov, V T
The bacterial cell wall muramyl dipeptides MDP and glucosaminyl-MDP (GMDP) are powerful immunostimulators but their binding target remains controversial. We previously reported expression cloning of GMDP-binding polypeptides and identification of Y-box protein 1 (YB-1) as their sole target. Here we show specific binding of GMDP to recombinant YB-1 protein and subcellular colocalization of YB-1 and GMDP. GMDP binding to YB-1 upregulated gene expression levels of NF-?B2, a mediator of innate immunity. Furthermore, YB-1 knockdown abolished GMDP-induced Nfkb2 expression. GMDP/YB-1 stimulation led to NF-?B2 cleavage, transport of activated NF-?B2 p52 to the nucleus, and upregulation of NF-?B2-dependent chemokine Cxcr4 gene expression. Therefore, our findings identify YB-1 as new target for muramyl peptide signaling. PMID:26026270
Growth and optical properties of Yb x Gd 1? x Al 3(BO 3) 4 single crystals with different Yb 3+ concentration
Jinsheng Liao; Yanfu Lin; Yujin Chen; Zundu Luo; Yidong Huang
Top seeded solution growth of ytterbium-doped gadolinium aluminium borate (Yb3+:GAB) crystals with different Yb3+ concentration (x=0.125, 0.33, 0.509, and 0.74) is reported. The polarized absorption spectra, emission spectra, and fluorescence lifetime of 50.9at.% Yb3+-doped GAB crystal were measured at room temperature. The X-ray powder diffraction proved that the structure of the 50.9at.% Yb3+:GAB crystal is the same as the pure
Low-energy magnetic response and Yb valence in the Kondo insulator YbB{sub 12}
Alekseev, P. A.; Nefeodova, E. V.; Staub, U.; Mignot, J.-M.; Lazukov, V. N.; Sadikov, I. P.; Soderholm, L.; Wassermann, S. R.; Paderno, Yu. B.; Shitsevalova, N. Yu. (and others)
X-ray absorption and high-resolution inelastic neutron-scattering experiments on the Kondo insulator YbB{sub 12} are reported. The ytterbium L{sub 3}-edge spectrum consists of a single white line with no observable temperature dependence between 10 and 295 K, indicating that the Yb valence is closer to 3+ than was concluded from previous high-resolution photoemission and XPS results. The neutron measurements confirm the existence of a gap in the magnetic excitation spectrum for T=5K, and show that its gradual suppression as temperature increases is due to the appearance of an extra quasielastic component in the magnetic dynamical response.
The optical properties of Yb3+ ions in LiTaO3:Nd,Yb crystals
I. Sok¾lska; W. Ryba-Romanowski; S. Golab; T. Lukasiewicz
3+ĀĀ ions excited by energy transfer from Nd3+ ions in LiTaO3:Nd,?Yb crystals are presented. The emission band of Yb3+ ions is broad, due to the strong phonon-coupling and to the relative large Stark-splitting of the ground 2F7\\/2 multiplet. The emission cross-section was evaluated by the reciprocity method, and aĀvalue of 0.53ū10-20Ācm2 was obtained. The gain coefficients derived for the inversion
Measurement of high photodarkening resistance in heavily Yb31
Byer, Robert L.
power from Yb3■ -doped fibre lasers and amplifiers has been scaled to well above the kilowatt level. One durability. Alkali, Fe and Cu ions were also elimi- nated to further enhance the glass properties. Fibre C et al. [1]. It uses a visible laser to probe the transmission of the core-pumped active fibre under
Multimodal microscopy with sub-30 fs Yb fiber laser oscillator
Nie, Bai; Saytashev, Ilyas; Chong, Andy; Liu, Hui; Arkhipov, Sergey N.; Wise, Frank W.; Dantus, Marcos
Nonlinear optical microscopy with sub-30 fs pulses from an Yb-fiber laser, approximately three times shorter than typical fiber laser pulses, leads to an order of magnitude brighter third harmonic generation imaging. Multiphoton fluorescence, second and third harmonic generation modalities are compared on stained microspheres and unstained biological tissues. PMID:22808444
Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates
Eu2O3/Si multilayer nanostructured films are deposited on Si substrates by magnetron sputtering. Transmission electron microscopy and X-ray diffraction measurements demonstrate that multicrystalline Eu silicate is homogeneously distributed in the film after high-temperature treatment in N2. The Eu2+ silicate is formed by the reaction of Eu2O3 and Si layers, showing an intense and broad room-temperature photoluminescence peak centered at 610 nm. It is found that the Si layer thickness in nanostructures has great influence on Eu ion optical behavior by forming different Eu silicate crystalline phases. These findings open a promising way to prepare efficient Eu2+ materials for photonic application. PMID:23618344
Nanocrystallization in Yb3+-doped oxyfluoride glasses for laser cooling
NASA Astrophysics Data System (ADS)
Kummara, Venkata Krishaniah; Ledemi, Yannick; Soares de Lima Filho, Elton; Messaddeq, Younes; Kashyap, Raman
Glass-ceramics are composite materials consisting of crystals which are controllably grown within a glass matrix usually by applying an appropriate heat treatment. They possess outstanding optical properties with applications in solid state lasers, optical amplifiers, and now, laser induced cooling. For laser cooling, the material should exhibit specific properties like low phonon energy environment around the lanthanide ions, low background losses, high transparency and high photoluminescence quantum yield. In the present study, oxyfluoride glasses and ultra-transparent nano glassceramics doped with different concentrations (2, 5, 8, 12, 16 and 20 mol %) of Yb 3+ ions have been prepared by conventional melt-quenching and subsequent thermal treatments at different temperatures, respectively. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements have been performed to characterize the thermal properties of the glass and the structural changes in the glass-ceramics, respectively. The XRD patterns confirm the growth of ?-PbF2 nanocrystals as well as progressive incorporation of Yb 3+ ions. This enhances the Yb 3+ ion emission intensity which depends on the doping concentration and ceramization temperatures. The size (20 nm) of the nanocrystallites was estimated from the Sherrer's formula and found to increase with increasing ceramization temperature, small enough to avoid scattering losses and ensure an excellent transparency of the glass-ceramics comparable with that of the parent glass. An enhancement of the luminescence properties of Yb 3+ ions surrounded by a crystalline low phonon environment is observed. Finally, the utilization of these heavily Yb 3+-doped ultra-transparent materials for laser cooling and solid state laser applications is discussed.
Post-adsorption process of Yb phosphate nano-particle formation by Saccharomyces cerevisiae
NASA Astrophysics Data System (ADS)
Jiang, MingYu; Ohnuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Kamiishi, Eigo; Utsunomiya, Satoshi
In this study, we have investigated the post-adsorption process of ytterbium (Yb) phosphate nano-particle formation by Saccharomyces cerevisiae (yeast). The yeast grown in P-rich medium were exposed to 1.44 ū 10-4 mol/L Yb(III) solution for 2-120 h, and 2 months at 25 ▒ 1 ░C at an initial pH of 3, 4, or 5, respectively. Ytterbium concentrations in solutions decreased as a function of exposure time. Field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FESEM), transmission electron microscopy (TEM), and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses revealed that nano-sized blocky Yb phosphate with an amorphous phase formed on the yeast cells surfaces in the solutions with Yb. These nano-sized precipitates that formed on the cell surfaces remained stable even after 2 months of exposure at 25 ▒ 1 ░C around neutral pHs. The EXAFS data revealed that the chemical state of the accumulated Yb on the cell surfaces changed from the adsorption on both phosphate and carboxyl sites at 30 min to Yb phosphate precipitates at 5 days, indicating the Yb-phosphate precipitation as a major post-adsorption process. In addition, the precipitation of Yb phosphate occurred on cell surfaces during 7 days of exposure in Yb-free solution after 2 h of exposure (short-term Yb adsorption) in Yb solution. These results suggest that the released P from the inside of yeast cells reacted with adsorbed Yb on cell surfaces, resulting in the formation of Yb precipitates, even though no P was added to the exposure solution. In an abiotic system, the EXAFS data showed that the speciation of sorbed Yb on the reference materials, carboxymethyl cellulose and Ln resin, did not change even when the Yb was exposed to P solution, without forming Yb phosphate precipitates. This result strongly suggests that the cell surface of the yeast plays an important role in the Yb-phosphate precipitation process, not only as a carrier of the functional groups but also as a substrate inducing the nucleation of phosphate nanoparticles. Stable nano-sized Yb phosphate precipitates formed on yeast cell surfaces in the present study, which implies that this post-adsorption nano-particle formation process caused by microbial cells should be one of the important processes governing the long-term migration of heavy rare earth elements and presumably trivalent actinides in geological repository.
Ultrasensitive polarized up-conversion of Tm(3+)-Yb3+ doped ?-NaYF4 single nanorod.
Zhou, Jiajia; Chen, Gengxu; Wu, E; Bi, Gang; Wu, Botao; Teng, Yu; Zhou, Shifeng; Qiu, Jianrong
Up-conversion luminescence in rare earth ions (REs) doped nanoparticles has attracted considerable research attention for the promising applications in solid-state lasers, three-dimensional displays, solar cells, biological imaging, and so forth. However, there have been no reports on REs doped nanoparticles to investigate their polarized energy transfer up-conversion, especially for single particle. Herein, the polarized energy transfer up-conversion from REs doped fluoride nanorods is demonstrated in a single particle spectroscopy mode for the first time. Unique luminescent phenomena, for example, sharp energy level split and singlet-to-triplet transitions at room temperature, multiple discrete luminescence intensity periodic variation with polarization direction, are observed upon excitation with 980 nm linearly polarized laser. Furthermore, nanorods with the controllable aspect ratio and symmetry are fabricated for analysis of the mechanism of polarization anisotropy. The comparative experiments suggest that intraions transition properties and crystal local symmetry dominate the polarization anisotropy, which is also confirmed by density functional theory calculations. Taking advantage of the REs based up-conversion, potential application in polarized microscopic multi-information transportation is suggested for the polarization anisotropy from REs doped fluoride single nanorod or nanorod array. PMID:23611309
Interactions of CT DNA with hexagonal NaYF4 co-doped with Yb(3+)/Tm(3+) upconversion particles.
Yuan, Xiuxue; Gu, Wenchao; Xiao, Mengsi; Xie, Wenli; Wei, Shaohua; Zhou, Lin; Zhou, Jiahong; Shen, Jian
The interaction of UCPs with CT DNA are studied in detail by zeta potential, Energy dispersive spectrometer (EDS) spectroscopy, Thermogravimetric (TGA) analysis, DNA melting determination and various spectroscopic techniques including Ultraviolet-Visible (UV-Vis) absorption, fluorescence, circular dichroism (CD), Fourier transform infrared (FTIR) and Raman spectroscopy. The results indicate that CT DNA can assemble on the surface of UCPs mainly by relative stronger hydrophobic force and electrostatic binding, and the predominant interaction site is the deoxyribosyl phosphate backbone of CT DNA. Moreover, after interacting with UCPs, the double helix structure of DNA is undamaged. PMID:25305602
Interactions of CT DNA with hexagonal NaYF4 co-doped with Yb3+/Tm3+ upconversion particles
NASA Astrophysics Data System (ADS)
Yuan, Xiuxue; Gu, Wenchao; Xiao, Mengsi; Xie, Wenli; Wei, Shaohua; Zhou, Lin; Zhou, Jiahong; Shen, Jian
The interaction of UCPs with CT DNA are studied in detail by zeta potential, Energy dispersive spectrometer (EDS) spectroscopy, Thermogravimetric (TGA) analysis, DNA melting determination and various spectroscopic techniques including Ultraviolet-Visible (UV-Vis) absorption, fluorescence, circular dichroism (CD), Fourier transform infrared (FTIR) and Raman spectroscopy. The results indicate that CT DNA can assemble on the surface of UCPs mainly by relative stronger hydrophobic force and electrostatic binding, and the predominant interaction site is the deoxyribosyl phosphate backbone of CT DNA. Moreover, after interacting with UCPs, the double helix structure of DNA is undamaged.
Preparation and Thermoelectric Properties of YbAl3 Thermoelectric Materials with Excessive Al
NASA Astrophysics Data System (ADS)
He, Dan-qi; Zhao, Wen-Yu; Mu, Xin; Zhou, Hong-yu; Zhang, Qing-jie
A method to prepare YbAl3 sample with an accurate stoichiometric ratio has been developed by a melting, quenching, annealing and spark plasma sintering (SPS) method. A series of YbAl3 thermoelectric materials with nominal compositions YbAl3+ x ( x = 0-0.3, ? x = 0.1) have been prepared using the method. We have explored the effects of the excessive Al on phase compositions, microstructure and transport properties. The quenched samples are composed of YbAl3, YbAl2, Yb, and Al. All the annealed samples are composed of main phase YbAl3 and a trace of Al; some annealed samples with x = 0 and x = 0.1 still contain a trace of YbAl2. The SPSed samples with x ? 0.1 are composed of single-phase YbAl3, though a trace of YbAl2 still occured in the SPSed sample with x = 0. The electrical conductivity, Seebeck coefficient, power factor, thermal conductivity and ZT values are first increased with increasing x in the range of 0-0.2 and then decreased when x > 0.2. These thermoelectric properties evolutions originate from the change of densities and chemical composition induced by the excessive Al. The highest ZT value reaches 0.28 at 300 K for the SPSed sample with x = 0.2.
Reactivation of methionine synthase from Thermotoga maritima (TM0268) requires the downstream gene product TM0269
Huang, Sha; Romanchuk, Gail; Pattridge, Katherine; Lesley, Scott A.; Wilson, Ian A.; Matthews, Rowena G.; Ludwig, Martha
The crystal structure of the Thermotoga maritima gene product TM0269, determined as part of genome-wide structural coverage of T. maritima by the Joint Center for Structural Genomics, revealed structural homology with the fourth module of the cobalamin-dependent methionine synthase (MetH) from Escherichia coli, despite the lack of significant sequence homology. The gene specifying TM0269 lies in close proximity to another gene, TM0268, which shows sequence homology with the first three modules of E. coli MetH. The fourth module of E. coli MetH is required for reductive remethylation of the cob(II)alamin form of the cofactor and binds the methyl donor for this reactivation, S-adenosylmethionine (AdoMet). Measurements of the rates of methionine formation in the presence and absence of TM0269 and AdoMet demonstrate that both TM0269 and AdoMet are required for reactivation of the inactive cob(II)alamin form of TM0268. These activity measurements confirm the structure-based assignment of the function of the TM0269 gene product. In the presence of TM0269, AdoMet, and reductants, the measured activity of T. maritima MetH is maximal near 80░C, where the specific activity of the purified protein is ?15% of that of E. coli methionine synthase (MetH) at 37░C. Comparisons of the structures and sequences of TM0269 and the reactivation domain of E. coli MetH suggest that AdoMet may be bound somewhat differently by the homologous proteins. However, the conformation of a hairpin that is critical for cobalamin binding in E. coli MetH, which constitutes an essential structural element, is retained in the T. maritima reactivation protein despite striking divergence of the sequences. PMID:17656578
Reactivation of methionine synthase from Thermotoga maritima (TM0268) requires the downstream gene product TM0269.
Huang, Sha; Romanchuk, Gail; Pattridge, Katherine; Lesley, Scott A; Wilson, Ian A; Matthews, Rowena G; Ludwig, Martha
The crystal structure of the Thermotoga maritima gene product TM0269, determined as part of genome-wide structural coverage of T. maritima by the Joint Center for Structural Genomics, revealed structural homology with the fourth module of the cobalamin-dependent methionine synthase (MetH) from Escherichia coli, despite the lack of significant sequence homology. The gene specifying TM0269 lies in close proximity to another gene, TM0268, which shows sequence homology with the first three modules of E. coli MetH. The fourth module of E. coli MetH is required for reductive remethylation of the cob(II)alamin form of the cofactor and binds the methyl donor for this reactivation, S-adenosylmethionine (AdoMet). Measurements of the rates of methionine formation in the presence and absence of TM0269 and AdoMet demonstrate that both TM0269 and AdoMet are required for reactivation of the inactive cob(II)alamin form of TM0268. These activity measurements confirm the structure-based assignment of the function of the TM0269 gene product. In the presence of TM0269, AdoMet, and reductants, the measured activity of T. maritima MetH is maximal near 80 degrees C, where the specific activity of the purified protein is approximately 15% of that of E. coli methionine synthase (MetH) at 37 degrees C. Comparisons of the structures and sequences of TM0269 and the reactivation domain of E. coli MetH suggest that AdoMet may be bound somewhat differently by the homologous proteins. However, the conformation of a hairpin that is critical for cobalamin binding in E. coli MetH, which constitutes an essential structural element, is retained in the T. maritima reactivation protein despite striking divergence of the sequences. PMID:17656578
The TM/TC processor study report
NASA Astrophysics Data System (ADS)
Requirements of a TM/TC Front End Equipment (FEE) for ESA spacecraft, particularly communications spacecraft using conventional and packet command and telemetry systems are specified. Parts necessary to form a comprehensive test system for checking operational spacecraft systems in conjunction with the master test processor and the checkout equipment are described. The use of TM/TC FEE at subsystem integration level, spacecraft system test level and as front end to a ground station operational control center is discussed. A self contained test system, including its digital handling capabilities, microwave measurements, the software, and self checking possibilities were examined.
Landsat TM and ETM+ Thermal Band Calibration
NASA Technical Reports Server (NTRS)
Barsi, Julia A.; Hook, Simon J.; Palluconi, Frank D.; Schott, John R.; Raqueno, Nina G.
Landsat-5 Thematic Mapper (TM) has been imaging the Earth since March 1984 and Landsat-7 Enhanced Thematic Mapper Plus (ETM+) was added to the series of Landsat instruments in April 1999. The stability and calibration of the ETM+ has been monitored extensively since launch. Though not monitored for many years, TM now has a similar system in place to monitor stability and calibration. University teams have been evaluating the on-board calibration of the instruments through ground-based measurements since 1999. This paper considers the calibration efforts for the thermal band, Band 6, of both the Landsat-5 and Landsat-7 instruments.
Efficient sensitization of Yb3+ emission by Nd3+ in Y2O3 transparent ceramics and the prospect for high-energy Yb lasers.
Lupei, Voicu; Lupei, Aurelia; Gheorghe, Cristina; Hau, Stefania; Ikesue, Akio
Very efficient energy transfer from Nd3+ to Yb3+ in transparent Y2O3 ceramics in the temperature range 10-300 K is demonstrated. It is inferred that this shows potential for the construction of high-energy Yb3+ lasers under diode or flash-lamp excitation of Nd3+. PMID:19823528
Hively, Lee M.
ORNL/TM-13283 PROSPECTS FOR CHAOS CONTROL OF MACHINE TOOL CHATTER L. M. Hively V. A. Protopopescu N. #12;ORNL/TM-13283 PROSPECTS FOR CHAOS CONTROL OF MACHINE TOOL CHATTER L. M. Hively V. A. Protopopescu
CCRS proposal for evaluating LANDSAT-4 MSS and TM data
NASA Technical Reports Server (NTRS)
Strome, W. M.; Cihlar, J.; Goodenough, D. G.; Guertin, F. E. (principal investigators); Guindon, B.; Murphy, J.; Butlin, J. M.; Duff, P.; Fitzgerald, A.; Grieve, G.
The measurement of registration errors in LANDSAT MSS data is discussed as well as the development of a revised algorithm for the radiometric calibration of TM data and the production of a geocoded TM image.
Yb{sub 3}AuGe{sub 2}In{sub 3} : an ordered variant of the YbAuIn structure exhibiting mixed-valent Yb behavior.
Chondroudi, M.; Peter, S. C.; Malliakas, C. D.; Balasubramanian, M.; Li, Q.; Kanatzidis, M. G. (Advanced Photon Source); ( MSD); (Michigan State Univ.); (Northwestern Univ.)
Yb{sub 3}AuGe{sub 2}In{sub 3} was obtained as large single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data show that Yb{sub 3}AuGe{sub 2}In{sub 3} is an ordered variant of YbAuIn with lattice constants, a = b = 7.3153(8) {angstrom} and c = 4.4210(5) {angstrom}, and space group P{sub 6}2m. The parent compound YbAuIn was also studied for comparison. YbAuIn crystallizes in the ZrNiAl structure type, hexagonal, P{sub 6}2m space group with lattice parameters a = b = 7.7127(11) {angstrom} and c = 4.0294(8) {angstrom}. In Yb{sub 3}AuGe{sub 2}In{sub 3}, Ge substitutes for one of the two Au positions in the ternary compound Yb{sub 3}Au{sub 3}In{sub 3}. The structure can be described as alternating [Ge{sub 2}In{sub 3}] and [Yb{sub 3}Au] slabs that stack along the c-axis. The magnetic susceptibility data follow a modified Curie-Weiss law. The effective magnetic moment {mu}{sub eff} of 0.52 {micro}B/Yb atom was deduced from the Curie constant and Curie-Weiss constant of {Theta}{sub p} = -1.5 K indicating antiferromagnetic interactions in Yb{sub 3}AuGe{sub 2}In{sub 3}. X-ray absorption near edge spectroscopy (XANES) measurements indicate intermediate valency for Yb in both compounds. The metallic nature of both compounds was confirmed by the resistivity measurements. Specific heat data for Yb{sub 3}AuGe{sub 2}In{sub 3} and YbAuIn give an electronic {gamma} term of 31 and 84 mJ/mol {center_dot} K{sup 2}, respectively, suggesting that the ternary analog is a 'light' heavy fermion compound.
The tmRNA Website: invasion by an intron
Kelly P. Williams
tmRNA (also known as 10Sa RNA or SsrA) plays a central role in an unusual mode of translation, whereby a stalled ribosome switches from a prob- lematic mRNA to a short reading frame within tmRNA during translation of a single polypeptide chain. Research on the mechanism, structure and biology of tmRNA is served by the tmRNA Website, a collection of
Enhanced thermoelectric power factor in Yb1-xScxAl2 alloys using chemical pressure tuning of the Yb valence
NASA Astrophysics Data System (ADS)
Lehr, Gloria J.; Morelli, Donald T.; Jin, Hyungyu; Heremans, Joseph P.
We have investigated the influence of Sc substitution on the transport and magnetic properties of YbAl2, a well-known intermediate valence compound. Sc substitution provides a chemical pressure that decreases the lattice constant and thereby alters the Yb valence as a function of composition and temperature. We observe a strong correlation between the Seebeck coefficient and the ratio of trivalent to divalent Yb in these compounds, as determined from magnetic susceptibility measurements. This correlation indicates that the largest absolute value of the Seebeck coefficient is achieved when the average Yb valence is near 2.5 (the ratio of divalent to trivalent Yb is 1:1). It is shown that Sc concentration can be used as a means to tune both the magnitude of the maximum of the Seebeck coefficient and the temperature at which this absolute maximum occurs, improving the prospects of the use of these materials in cryogenic Peltier coolers.
The polygallides: Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2}
Peter, Sebastian C. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064 (India); Malliakas, Christos D. [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Nakotte, Heinze; Kothapilli, Karunakar [Physics Department, New Mexico State University, Las Cruces, NM 88003 (United States); Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC, R-5 Shed, Trombay, Mumbai 400085 (India); Schultz, Arthur J. [X-Ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Kanatzidis, Mercouri G., E-mail: firstname.lastname@example.com [Department of Chemistry, Northwestern University, 2145N. Sheridan Road, Evanston, IL 60208 (United States); Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)
Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} were obtained from reactions of Yb and Ge in excess liquid gallium. The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was refined using X-ray and neutron diffraction data on selected single crystals. Yb{sub 3}Ga{sub 7}Ge{sub 3} crystallizes in the monoclinic space group C2/c with lattice constants a=12.2261(20) Angstrom-Sign , b=10.7447(20) Angstrom-Sign , c=8.4754(17) Angstrom-Sign and {beta}=110.288(30) Degree-Sign (neutron diffraction data). The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} is an intergrowth of planar layers of YbGa{sub x}Ge{sub y} and puckered layers of (Ge){sub n}. YbGa{sub 4}Ge{sub 2} crystallizes in a modified PuGa{sub 6} structure type in the tetragonal polar space group I4cm with lattice constants a=b=5.9874(6) Angstrom-Sign and c=15.1178(19) Angstrom-Sign . The structure of YbGa{sub 4}Ge{sub 2} is an intergrowth of puckered Ga layers and puckered Ga{sub x}Ge{sub y} layers with Yb atoms residing within the channels formed by the connection of the two layers. Physical properties, resistivity ({rho}), magnetic susceptibility ({chi}) and specific heat (C) were measured for Yb{sub 3}Ga{sub 7}Ge{sub 3}. No magnetic ordering was observed. It was found that at low temperatures, {rho} varied as T{sup 2} and C{proportional_to}T, indicating Fermi-liquid regime in Yb{sub 3}Ga{sub 7}Ge{sub 3} at low temperatures. - Graphical abstract: The compounds Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are obtained from reactions of Yb and Ge in excess liquid gallium. Highlights: Black-Right-Pointing-Pointer Yb{sub 3}Ga{sub 7}Ge{sub 3} and YbGa{sub 4}Ge{sub 2} are two new polygallides. Black-Right-Pointing-Pointer The crystal structure of Yb{sub 3}Ga{sub 7}Ge{sub 3} was established using neutron diffraction data. Black-Right-Pointing-Pointer YbGa{sub 4}Ge{sub 2} is one of the rare polar intermetallic compounds. Black-Right-Pointing-Pointer The physical properties of Yb{sub 3}Ga{sub 7}Ge{sub 3} point to a Fermi-liquid regime at low temperature.
ORNL/TM-2000/91 ENERGY DIVISION SUPPORTING INFRASTRUCTURE AND ACCEPTABILITY ISSUES ASSOCIATED contract DE-AC05-00OR22725 #12;Infrastructure, Acceptability, and Lifecycle Issues: 3XVs ORNL/TM-2000/91 ii #12;Infrastructure, Acceptability, and Lifecycle Issues: 3XVs ORNL/TM-2000/91 iii Table of Contents
Department of Bioengineering Spring 2011 Adaptive WiiTM
Demirel, Melik C.
PENNSTATE Department of Bioengineering Spring 2011 Adaptive WiiTM Remote for C-6 Quadriplegic Overview Mr. Bob Yorty is a C-6 quadriplegic that strives to play to the WiiTM video game system. The Wii quadriplegics to play the WiiTM The product is rehabilitative and still allows the user to enjoy using the Wii
Pioneers--The "Engineering byDesign[TM]" Network
ERIC Educational Resources Information Center
Burke, Barry N.
This article discusses the standards-based instruction model, Engineering byDesign[TM] (EbD), and a network of teachers called the Engineering byDesign[TM] Network. Engineering byDesign[TM] is the only standards-based national model for Grades K-12 that delivers technological literacy which was developed by the International Technology Educationģ
Nernst effect of the intermediate valence compound YbAl3: revisiting the thermoelectric properties.
Wei, Beipei; Zhang, Jiahao; Sun, Peijie; Wang, Wenquan; Wang, Nanlin; Steglich, Frank
The Nernst effect and thermopower of the prototypical Yb-based intermediate valence compound YbAl(3) were investigated. Different to the thermopower whose absolute values are enhanced with increasing temperature and assume a broad maximum at 175 K, the Nernst coefficient of YbAl(3) is enhanced only below T ? 75 K. While the two quantities in the heavy-fermion compound CeCu(2)Si(2) were recently found to be related by the anomalous Hall mobility due to the local asymmetric Kondo scattering, this theorem fails when being applied to YbAl(3). Rather, the thermopower of YbAl(3) is well described by a simple narrow-band model. We discuss the reason for this in terms of the intermediate valence nature of YbAl(3) that is conceptually different from the local Kondo physics. PMID:25706931
Berns, Hans-Gerd
UT Plus OncoreTM GPS Receiver There's only one name for quality and performance in GPS technology and Systems Integrator marketplace. The UT Plus Oncore is one of the newest members of the successful Oncore family, developed specifically for timing applications. The UT Plus Oncore adds more features at a lower
Water Quality Retrieval from Landsat TM Imagery
Arun Kulkarni
In this paper, the utility of Landsat TM imagery for water quality studies in East Texas is investigated. Remote sensing has an important and effective role in water quality management. Remote sensing satellites measure the amount of solar radiation reflected by surface water and the reflectance of water depend upon the concentration and character of water quality parameters. Three water
Doors to Discovery [TM]. WWC Intervention Report
ERIC Educational Resources Information Center
What Works Clearinghouse, 2009
Doors to Discovery[TM], an early childhood curriculum, focuses on the development of children's vocabulary and expressive and receptive language through a learning process called "shared literacy," where adults and children work together to develop literacy-related skills. Literacy activities, organized into thematic units, encourage children'sģ
Defying Gravity Using Jenga[TM] Blocks
ERIC Educational Resources Information Center
Tan, Yin-Soo; Yap, Kueh-Chin
This paper describes how Jenga[TM] blocks can be used to demonstrate the physics of an overhanging tower that appears to defy gravity. We also propose ideas for how this demonstration can be adapted for the A-level physics curriculum. (Contains 8 figures and 1 table.)
Oak Ridge National Laboratory
Division THE STIRLING ENGINE WITH ONE ADIABATIC CYLINDER C. D. West Date Published: March 1982 DISCLAIMER #12;#12;THE STIRLING ENGINE WITH ONE ADIABATIC CYLINDER C. D. West This report shows that integration:>':. '*>3 1 /? ORNL/TM-8022 ^S] ~/ 3)/:: 60g7b6( Contract No. W-7405-eng-26 Engineering Technology
Technology Transfer Automated Retrieval System (TEKTRAN)
Fantesk**TM is a stable dispersion of a jet-cooked starch slurry-oil mixture. The jet cooked material can be air- or drum-dried. Jet cooking and shear of the mixture liquefies the starch and lowers its MW. Various oils and fats and different starches can be used to produce Fantesk. Fantesk is a ...
Apollo 324TM System PrepX SPIA« RNA-Seq Library Protocol #12;® Copyright 2012, IntegenX Inc. All no responsibility for any errors that may appear in this document. RESEARCH USE ONLY The Apollo 324 System and conditions of sale. TRADEMARKS Apollo 324, BeadX and PrepX are trademarks of IntegenX Inc. Agencourt, AMPure
Rathbun, Julie A.
1\\TM-1074 I ASE GRENADE TRANSMITTER FREQUENCY DRIFT 01' zo DAiE 19 Nov 197 1 This ATM provides a projection of the maximum frequency of the Flight 5 and Spare ASE grenade transmitters up to 6 years from transmitter acceptance testing. This projection is based on recent KSC test results and provides assurance
Tm:fiber lasers for remote sensing
Norman P. Barnes; Brian M. Walsh; Donald J. Reichle; Russell J. DeYoung
Tm:fiber lasers are an attractive choice for remote sensing of water under arid conditions, such as found on Mars. Renewed interest in Martian exploration and discovery of huge deposits of water at the Martian south pole fuel interest in a water vapor lidar. The potential for high efficiency and the robust and compact nature of fiber lasers are very attractive
Crystallization of BaF2-ZnF2-YbF3-ThF4 glass
NASA Technical Reports Server (NTRS)
Garcia, Roberto; Doremus, Robert H.; Ko, Sen-Hou; Margraf, Tracey; Bansal, Narottam P.
The phases and the rates of crystallization in a Ba-Zn-Yb-Th fluoride glass were studied using differential scanning calorimetry, XRD, and observational and chemical SEM analyses. The crystallizing phases that were identified included a BaYbTh fluoride, ZnF2, and YbF3. The BaYbTh fluoride crystallized first at about 450 C, and ZnF2, which was excluded from this phase, crystallized at its surfaces. At higher temperatures, the BaYbTh fluoride phase decomposed partially to BaThF6 and YbF3 phases.
LaVo4: Eu Phosphor Films with Enhanced Eu Solubility
Hwang, Harold
Eu doped rare-earth orthovanadates are known to be good red phosphor materials. In particular, LaVO{sub 4}:Eu is a promising candidate due to the low Eu-site point symmetry, and thus high dipole transition probability within Judd-Ofelt theory. However, the low solubility limit (< 3 mol %) of Eu in LaVO{sub 4} prevents its efficient use as a phosphor. We present optical evidence of enhanced Eu solubility as high as 10 mol % in LaVO{sub 4}:Eu thin films grown by pulsed laser deposition and postannealing. The photoluminescent intensity exceeded that of YVO{sub 4}:Eu thin films when excited below the host bandgap, indicating stronger direct emission of Eu in LaVO{sub 4}.
High-resolution study of 0{sup +} states in {sup 170}Yb
Bettermann, L. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstrasse 77, D-50937 Koeln (Germany); Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124 (United States); Heinze, S.; Jolie, J.; Muecher, D.; Moeller, O.; Scholl, C. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicherstrasse 77, D-50937 Koeln (Germany); Casten, R. F. [Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124 (United States); Meyer, D. [Rhodes College, 2000 N. Parkway, Memphis, Tennessee 38112-1690 (United States); Graw, G.; Hertenberger, R.; Wirth, H.-F. [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany); Bucurescu, D. [Horia Hulubei Institute for Physics and Nuclear Engineering, RO-76900 Bucharest (Romania)
Recently, 0{sup +} excitations, especially in the rare-earth region, were studied extensively. We extend this work by studying the excited 0{sup +} states in {sup 170}Yb using the {sup 172}Yb(p,t){sup 170}Yb reaction. Eighteen excited 0{sup +} states, 14 of which are new, are observed up to an energy of 3.5 MeV. The results are analyzed using the sd and spdf interacting boson models.
Bistable chromatic switching in Yb3+ -doped NdPO4 crystals
A. R¾denas; D. Jaque; J. GarcĒa Solķ; A. Speghini; M. Bettinelli; E. Cavalli
Pump-induced chromatic switching is reported for an 808nm pumped Yb3+ -doped NdPO4 crystal. This effect is based on the interplay between the Nd3+Yb3+ energy transfer processes and on the large pump-induced thermal loading characteristic of this neodymium compound. For temperatures below 300K , a noticeable hysteresis is observed in the relative Nd3+ and Yb3+ contributions to the emission spectra; this
Growth and spectral properties of Yb 3+:GdAl 3(BO 3) 4 single crystal
Jinsheng Liao; Yanfu Lin; Yujin Chen; Zundu Luo; Yidong Huang
Ytterbium-doped gadolinium aluminum borate (Yb3+:GAB) crystal with size up to 25mmū15mmū15mm has been grown by the top seeded solution growth method. The X-ray powder diffraction proved that the structure of the Yb3+:GAB crystal has the same space group R32 as pure GAB crystal. The polarized absorption spectra, emission spectra, and fluorescence lifetime of the Yb3+:GAB crystal were measured at room
Investigation of loss processes of Tm and Tm,Ho in YAG
NASA Technical Reports Server (NTRS)
Armagan, G.; Buoncristiani, A. M.; Bair, C. H.; Inge, A. T.; Hess, R. V.
The loss of excitation from various manifolds of Tm and Tm,Ho in YAG as a function of temperature and concentration is studied. Two probable loss mechanisms - a Tm up-conversion and a Ho up-conversion - are identified. A 785-nm CW diode laser with 400-nW peak power was focused to a small spot on the sample. The emission from the sample observed at 90 deg was monitored through a monochromator with slits open to 3 mm. Intensity of emission was measured by varying the power of the excitation source using a set of neutral density filters. Power is reported as the percentage of the peak power, and the intensity curves were normalized below 20 percent of transmission. The fact that there is emission above the pump energy indicates an up-conversion from excited manifolds. Nonlinear changes in the intensity of the emission from the Tm 3F4 manifold with the pump power reveals a loss of excitation from this manifold. The linear dependence of the 5I7 manifold emission with pump power at low Tm and high Ho concentrations and the gain of energy in the 5I6 manifold of Ho indicate that the 5I7 manifold loss is due to the coupling of Tm and Ho ions.
Reliability and Validity of the Zephyr[TM] BioHarness[TM] to Measure Respiratory Responses to Exercise
ERIC Educational Resources Information Center
Hailstone, Jono; Kilding, Andrew E.
The Zephyr[TM] BioHarness[TM] (Zephyr Technology, Auckland, New Zealand) is a wireless physiological monitoring system that has the ability to measure respiratory rate unobtrusively. However, the ability of the BioHarness[TM] to accurately and reproducibly determine respiratory rate across a range of intensities is currently unknown. The aim ofģ
Contribution of Eu 4f states to the magnetic anisotropy of EuO
Arenholz, E.; Schmehl, A.; Schlom, D.G.; van der Laan, G.
Anisotropic x-ray magnetic linear dichroism (AXMLD) provides a novel element-, site-, shell-, and symmetry-selective techniques to study the magnetic anisotropy induced by a crystalline electric field. The weak Eu2+ M4,5 AXMLD observed in EuO(001) indicates that the Eu 4f states are not rotationally invariant and hence contribute weakly to the magnetic anisotropy of EuO. The results are contrasted with those obtained for 3d transition metal oxides.
Narrow linewidth Yb-doped fiber laser at 1120 nm.
Xiaojuan, Liu; Shenggui, Fu; Liping, Guo; Kezhen, Han
A 974 nm laser diode pumped 1120 nm ytterbium (Yb)-doped fiber laser with all fiber components has been experimentally demonstrated. The resonator is composed of a normal single-mode Yb-doped fiber 1 m long and a pair of fiber Bragg gratings. Up to 21.6 mW of continuous-wave output power is generated when the launched pump power is 161 mW with an optical-to-optical conversion efficiency of 13.4%. The central wavelength is 1120.89 nm with a linewidth as narrow as 0.02 nm. Additionally, a similar fiber laser with a 2 m long gain medium displays a broadened linewidth. The results of the two fiber lasers are compared and discussed in the paper. PMID:23518724
Compact nanosecond pulsed single stage Yb-doped fiber amplifier
NASA Astrophysics Data System (ADS)
Balliu, E.; Engholm, M.; Hellstr÷m, J.; Elgcrona, G.; Karlsson, H.
In this work we present a compact, nanosecond pulsed, single frequency, single stage Yb-doped fiber amplifier by using an overall fiber core diameter of 20 ?m. The key component is a custom made, compact, ultra-low noise, single frequency ring-cavity solid state laser (SSL) at 1064 nm used as a master oscillator. The SSL can be designed to provide nanosecond pulses with pulse energies in the sub-mJ range. Our ultimate goal is to develop a compact linearly polarized, single frequency, nanosecond pulsed laser source in an all-fiber format. Short (less than 1m), highly Yb-doped fibers have been used in order to suppress non-linear effects.
Factors governing Yb magnetism in Yb{sub 0.95}PtIn{sub 2} and other MgCuAl{sub 2}-type structures
Malingowski, Andrew C. [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States)] [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Kim, Moosung [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Liu, Jue [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States)] [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Wu, Liusuo [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States)] [Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Aronson, Meigan C. [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States) [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Department of Physics and Astronomy, State University of New York - Stony Brook, Stony Brook, NY 11794-3800 (United States); Khalifah, Peter G., E-mail: firstname.lastname@example.com [Department of Chemistry, State University of New York - Stony Brook, Stony Brook, NY 11794-3400 (United States); Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)
The ternary compound 'YbPtIn{sub 2}' has been synthesized and its crystal structure determined using single crystal X-ray diffraction techniques. The compound crystallizes in the MgCuAl{sub 2} structure, a ternary structure type often formed when rare earth metals, Group 10 transition metals, and indium are present in a 1:1:2 ratio. The unit cell is C-centered orthorhombic, space group Cmcm (no. 63) with lattice parameters of a=4.3410(1) A, b=10.3230(2) A, and c=7.8510(2) A. Evidence is found for a substantial non-stoichiometry on the Yb site, in contrast to the Pt and In sites which behave as expected, and it is believed that the stoichiometry of this compound is more properly described as Yb{sub 0.95}PtIn{sub 2}. Magnetic and resistivity measurements reveal that 'YbPtIn{sub 2}' is a weakly interacting, non-magnetic metal exclusively containing Yb{sup 2+}, and with a resistivity ({rho}) varying from 34 {mu}{Omega} cm at room temperature to a residual resistivity {rho}{sub 0} of 23 {mu}{Omega} cm at 1.8 K. Density functional theory calculations suggest that the observed diamagnetic Yb behavior is expected for this compound, but that certain substitutions on the Pt or In site could help stabilize magnetic Yb{sup 3+} and potentially induce heavy fermion behavior. - Graphical abstract: The crystal structure, magnetic behavior, and temperature-dependent resistivity of the new ternary compound Yb{sub 0.95}PtIn{sub 2.} Highlights: Black-Right-Pointing-Pointer Flux growth method used to produce Yb{sub 0.95}PtIn{sub 2} single crystals. Black-Right-Pointing-Pointer Found rare example of non-stoichiometry in a MgCuAl{sub 2}-type structure. Black-Right-Pointing-Pointer The resistivity and diamagnetic response of Yb{sub 0.95}PtIn{sub 2} were modeled. Black-Right-Pointing-Pointer DFT correctly predicts presence of Yb{sup 2+} in Yb{sub 0.95}PtIn{sub 2}. Black-Right-Pointing-Pointer COHP results suggest other MgCuAl{sub 2}-type indides that may contain paramagnetic Yb{sup 3+}.
Electronic structure of Kondo lattice compounds YbNi3X9 (X = Al, Ga) studied by hard x-ray spectroscopy
NASA Astrophysics Data System (ADS)
Utsumi, Yuki; Sato, Hitoshi; Ohara, Shigeo; Yamashita, Tetsuro; Mimura, Kojiro; Motonami, Satoru; Shimada, Kenya; Ueda, Shigenori; Kobayashi, Keisuke; Yamaoka, Hitoshi; Tsujii, Naohito; Hiraoka, Nozomu; Namatame, Hirofumi; Taniguchi, Masaki
We have performed hard x-ray photoemission spectroscopy (HAXPES) for Yb-based Kondo lattice compounds; an antiferromagnetic heavy-fermion system YbNi3Al9 and a valence fluctuation system YbNi3Ga9. The Yb 3d5/2 spectra of YbNi3Ga9 showed both Yb2+ and Yb3+-derived structures indicating strong valence fluctuation, and the intensity of Yb2+ (Yb3+) structures gradually increased (decreased) on cooling. The Yb 3d5/2 spectra of YbNi3Al9 mostly consisted of Yb3+-derived structures and showed little temperature dependence. The Yb valences of YbNi3Ga9 and YbNi3Al9 at 22 K were evaluated to be 2.43 and 2.97, respectively. Based on the results of the Ni 2p and valence-band HAXPES spectra together with soft x-ray valence-band spectra, we described that the difference of physical properties of YbNi3X9 (X= Al, Ga) is derived from the differences of the 4f-hole level relative to the Fermi level (EF) and Ni 3d density of states at EF. The HAXPES results on the Yb valences were consistent with those obtained by x-ray absorption spectroscopy using the partial fluorescence yield mode and resonant x-ray emission spectroscopy at the Yb L3 edge.
Single crystal growth and physical properties of YbPd2Si2
NASA Astrophysics Data System (ADS)
Matsumoto, Y.; Hanya, K.; Haga, Y.; Fisk, Z.; Ohara, S.
We report the heat capacity and magnetic properties of single crystals of YbPd2Si2 grown from Sn flux. YbPd2Si2 is a non magnetic heavy fermion compound with electronic specific heat coefficient ? = 95 mJ/mol K2 and Pauli paramagnetic susceptibility ?0 = 0.0115 emu/mol. The density of states of single crystal YbPd2Si2 is approximately half that of polycrystalline YbPd2Si2 while the strength of the Kondo effect in the single crystal is approximately twice that of poly crystal.
Experimental studies of the phase transition in YbIn1-xAgxCu4
A. L. Cornelius; J. M. Lawrence; J. L. Sarrao; Z. Fisk; M. F. Hundley; G. H. Kwei; J. D. Thompson; C. H. Booth; F. Bridges
We report measurements of the low-temperature specific-heat coefficient gamma=Cp(T)\\/T, cell volume V(T), Hall coefficient RH(T), and valence z=2+nf [where the Yb hole occupation nf(T) was determined from Yb-L3 x-ray absorption] of single crystals of YbIn1-xAgxCu4. Alloying YbInCu4 with Ag increases the temperature Ts(x) of the first-order isomorphic phase transition and causes it to terminate at a critical point at xc=0.195
Experimental studies of the phase transition in YbIn{sub 1-x}AgŌCuŌ
A. L. Cornelius; J. M. Lawrence; J. L. Sarrao; Z. Fisk; M. F. Hundley; G. H. Kwei; J. D. Thompson; C. H. Booth; F. Bridges
We report measurements of the low-temperature specific-heat coefficient ╬│=C{sub p}(T)\\/T, cell volume V(T), Hall coefficient R{sub H}(T), and valence z=2+n{sub f} [where the Yb hole occupation n{sub f}(T) was determined from Yb-LŌ x-ray absorption] of single crystals of YbIn{sub 1-x}AgŌCuŌ. Alloying YbInCuŌ with Ag increases the temperature T{sub s}(x) of the first-order isomorphic phase transition and causes it to terminate
Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals.
Di Lieto, Alberto; Sottile, Alberto; Volpi, Azzurra; Zhang, Zhonghan; Seletskiy, Denis V; Tonelli, Mauro
We investigated the effect of rare earth impurities on the cooling efficiency of Yb│?:LiYF? (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance. PMID:25402099
Thermoelectric and Transport Properties of Yb z Fe4- x Ni x Sb12 Skutterudites
NASA Astrophysics Data System (ADS)
Lee, Woo-Man; Shin, Dong-Kil; Kim, Il-Ho
p-Type Yb z Fe4- x Ni x Sb12 (0.8 ? z ?1.0, and 0.25 ? x ?0.5) skutterudites were prepared, and the effects of Yb filling and Ni substitution on the thermoelectric properties were examined. X-ray diffraction patterns revealed that Yb z Fe4- x Ni x Sb12 skutterudites were synthesized, but small amounts of secondary phases (FeSb2 and Sb) were produced, except for the YbFe3.5Ni0.5Sb12 specimen. This meant that the charge compensation with Ni and the amount of Yb filling should be sufficient to stabilize the skutterudite structure. All specimens had positive Hall coefficients and Seebeck coefficients, and the carrier concentration ranged from 9.80 ū 1020 cm-3 to 3.37 ū 1021 cm-3. The electrical conductivity decreased and the Seebeck coefficient increased with increasing Yb and Ni contents due to the decreased carrier concentration. The thermal conductivity decreased with increasing Yb and Ni contents, and YbFe3.5Ni0.5Sb12 showed the lowest thermal conductivity. The maximum dimensionless figure of merit achieved was of 0.62 at 723 K for YbFe3.5Ni0.5Sb12, based on the high power factor (2.6 mWm-1 K-2) and the low thermal conductivity (2.9 Wm-1 K-1).
A metastable icosahedral quasicrystal in the Zn--Mg--Yb alloy system
T. Mitani; T. Ishimasa
The formation conditions for a Zn¢Mg¢Yb icosahedral quasicrystal, which is primitive (P) type and has a six-dimensional lattice parameter a6D?=?7.371?┼, have been studied. This quasicrystal is formed only by quenching from a temperature higher than 650░C in the narrow composition region between approximately Zn76Mg9Yb15 and Zn71Mg17Yb12. On annealing, this quasicrystal transforms to the Zn17Yb3-type cubic phase and the hexagonal Z
Flux growth of Yb(6.6)Ir(6)Sn(16) having mixed-valent ytterbium.
Peter, Sebastian C; Subbarao, Udumula; Rayaprol, Sudhindra; Martin, Joshua B; Balasubramanian, Mahalingam; Malliakas, Christos D; Kanatzidis, Mercouri G
The compound Yb6.6Ir6Sn16 was obtained as single crystals in high yield from the reaction of Yb with Ir and Sn run in excess indium. Single-crystal X-ray diffraction analysis shows that Yb6.6Ir6Sn16 crystallizes in the tetragonal space group P42/nmc with a = b = 9.7105(7) ┼ and c = 13.7183(11) ┼. The crystal structure is composed of a [Ir6Sn16] polyanionic network with cages in which the Yb atoms are embedded. The Yb sublattice features extensive vacancies on one crystallographic site. Magnetic susceptibility measurements on single crystals indicate Curie-Weiss law behavior <100 K with no magnetic ordering down to 2 K. The magnetic moment within the linear region (<100 K) is 3.21 ?B/Yb, which is ?70% of the expected value for a free Yb(3+) ion suggesting the presence of mixed-valent ytterbium atoms. X-ray absorption near edge spectroscopy confirms that Yb6.6Ir6Sn16 exhibits mixed valence. Resistivity and heat capacity measurements for Yb6.6Ir6Sn16 indicate non-Fermi liquid metallic behavior. PMID:24921221
Citron, Robert; Kropf, A.J.
Optical fibers doped with Ytterbium-3+ have become increasingly common in fiber lasers and amplifiers. Yb-doped fibers provide the capability to produce high power and short pulses at specific wavelengths, resulting in highly effective gain media. However, little is known about the local structure, distribution, and chemical coordination of Yb3+ in the fibers. This information is necessary to improve the manufacturing process and optical qualities of the fibers. Five fibers doped with Yb3+ were studied using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy and X-ray Absorption Near Edge Spectroscopy (XANES), in addition to Yb3+ mapping. The Yb3+ distribution in each fiber core was mapped with 2D and 1D intensity scans, which measured X-ray fluorescence over the scan areas. Two of the five fibers examined showed highly irregular Yb3+ distributions in the core center. In four of the five fibers Yb3+ was detected outside of the given fiber core dimensions, suggesting possible Yb3+ diffusion from the core, manufacturing error, or both. X-ray absorption spectroscopy (XAS) analysis has so far proven inconclusive, but did show that the fibers had differing EXAFS spectra. The Yb3+ distribution mapping proved highly useful, but additional modeling and examination of fiber preforms must be conducted to improve XAS analysis, which has been shown to have great potential for the study of similar optical fi bers.
The Cold Shock Domain of YB-1 Segregates RNA from DNA by Non-Bonded Interactions
Kljashtorny, Vladislav; Nikonov, Stanislav; Ovchinnikov, Lev; Lyabin, Dmitry; Vodovar, Nicolas; Curmi, Patrick; Manivet, Philippe
The human YB-1 protein plays multiple cellular roles, of which many are dictated by its binding to RNA and DNA through its Cold Shock Domain (CSD). Using molecular dynamics simulation approaches validated by experimental assays, the YB1 CSD was found to interact with nucleic acids in a sequence-dependent manner and with a higher affinity for RNA than DNA. The binding properties of the YB1 CSD were close to those observed for the related bacterial Cold Shock Proteins (CSP), albeit some differences in sequence specificity. The results provide insights in the molecular mechanisms whereby YB-1 interacts with nucleic acids. PMID:26147853
Yb-based heavy fermion compounds and field tuned quantum chemistry
Mun, Eundeok
The motivation of this dissertation was to advance the study of Yb-based heavy fermion (HF) compounds especially ones related to quantum phase transitions. One of the topics of this work was the investigation of the interaction between the Kondo and crystalline electric field (CEF) energy scales in Yb-based HF systems by means of thermoelectric power (TEP) measurements. In these systems, the Kondo interaction and CEF excitations generally give rise to large anomalies such as maxima in {rho}(T) and as minima in S(T). The TEP data were use to determine the evolution of Kondo and CEF energy scales upon varying transition metals for YbT{sub 2}Zn{sub 20} (T = Fe, Ru, Os, Ir, Rh, and Co) compounds and applying magnetic fields for YbAgGe and YbPtBi. For YbT{sub 2}Zn{sub 20} and YbPtBi, the Kondo and CEF energy scales could not be well separated in S(T), presumably because of small CEF level splittings. A similar effect was observed for the magnetic contribution to the resistivity. For YbAgGe, S(T) has been successfully applied to determine the Kondo and CEF energy scales due to the clear separation between the ground state and thermally excited CEF states. The Kondo temperature, T{sub K}, inferred from the local maximum in S(T), remains finite as magnetic field increases up to 140 kOe. In this dissertation we have examined the heavy quasi-particle behavior, found near the field tuned AFM quantum critical point (QCP), with YbAgGe and YbPtBi. Although the observed nFL behaviors in the vicinity of the QCP are different between YbAgGe and YbPtBi, the constructed H-T phase diagram including the two crossovers are similar. For both YbAgGe and YbPtBi, the details of the quantum criticality turn out to be complicated. We expect that YbPtBi will provide an additional example of field tuned quantum criticality, but clearly there are further experimental investigations left and more ideas needed to understand the basic physics of field-induced quantum criticality in Yb-based systems.
Internet: http://ue.eu.int E-mail: email@example.com
Internet: http://ue.eu.int E-mail: email@example.com For further information call 32 2 references are given in the text are available on the Council's Internet site http://ue.eu.int. Acts adopted; these statements are available on the above mentioned Council Internet site or may be obtained from the Press
Introduction: Explaining the EU Political System The EU: a political system but not a state
Franz, Sven Oliver
others oppose them? How important are political parties and elections in shaping political choices? Why1 Chapter 1 Introduction: Explaining the EU Political System The EU: a political system but not a state How the EU political system works Actors, institutions and outcomes: the basics of modern
The hyperfine interaction in 171YbF
NASA Astrophysics Data System (ADS)
Mawhorter, Richard; Glassman, Zachary; Grabow, Jens-Uwe; Le, Anh; Steimle, Timothy
Motivated by recent further improvements in determining the upper limit for the CP-violating electric dipole moment of the electron (eEDM), the pure rotational spectrum of the open shell molecule ytterbium fluoride, 171YbF, in the X2?+ (v = 0) state has been recorded using Fourier transform microwave (FTMW) spectroscopy and pump/probe microwave optical double resonance (PPMODR) spectroscopy. The pure rotational spectra and precisely measured splittings in the (0,0) A2?1 / 2 <-- X2?+ band were analyzed to produce an improved set of fine and magnetic hyperfine parameters for the X2?+ (v = 0) state of 171YbF. These will be used in conjunction with new FTMW data for 170 , 172 , 174 , 176YbF in a multi-isotope Dunham Uij fit to provide stable predictions for the rotational spectrum of 173YbF. Observing the nuclear electric quadrupole hyperfine structure of this isotopologue will help characterize the critical electric field at the heavy atom nucleus. This provides an important benchmark for the molecular wavefunctions used to calculate the effective internal field strength in this and other species, which in turn go into determining the eEDM upper limit. Similar work with the isotopologues of PbF, where nearby states of opposite parity have already been found, will also benefit proposed anapole moment and variation of fundamental constants studies. TS & AL acknowledge support from NSF CHE-1265885, JUG from DFG & Land Niedersachsen, RM from DAAD & Pomona College, and ZG from the Sherman Fairchild Foundation.
Spectroscopy of Nd3+ and Yb3+ codoped fluoroindogallate glasses
NASA Astrophysics Data System (ADS)
de Sousa, D. F.; Batalioto, F.; Bell, M. J. V.; Oliveira, S. L.; Nunes, L. A. O.
The Nd-Nd and Nd-Yb energy transfer processes are studied in lead fluoroindogallate glasses with the following molar composition: 30PbF2-20GaF3-15InF3-15ZnF2-(20-X)CaF2-XNdF3 (with X=0.1, 0.5, 1, 2, 4, and 5), 30PbF2-20GaF3-15InF3-15ZnF2-(20-X)CaF2-XYbF3 (with X=0.1, 0.5, 1, 2, 3, and 5), and 30PbF2-20GaF3-15InF3-15ZnF2-(19-X)CaF2-XYbF3-1NdF3 (with X=0.1, 0.5, 1, 2, 3, and 5.5). The Dexter, Yokota-Tanimoto, and Holstein formalisms were used to treat the experimental data. The following microparameters of energy transfer were obtained: CDD(Nd-Nd)?7ū10-40, CDA(Nd-Nd)=2.5ū10-40, and CDA(Nd-Yb)?3ū10-40 cm6/s. It was also shown that the energy migration between Nd ions depends on the third power of temperature (T3) up to a saturation value of about 80 K. This behavior was attributed to the site to site energy migration. The Yb doped samples presented no nonradiative losses for the Yb3+ emission at 969 nm.
Crystal-Field Splitting in Yb3+ Chelates
W. G. Perkins; G. A. Crosby
Optical absorption and emission spectra of trivalent ytterbium in various chelates are reported. The experimental energy levels of Yb3+ are compared with predictions of electrostatic crystal-field theory and of a contact model of ligand-field theory. Good agreement is found between theory and experiment for the electrostatic crystal-field calculation. Poorer agreement is obtained using the ligand-field contact model calculation. The crystal-field
Heat generation in Nd:YAG and Yb:YAG
T. Y. Fan
The fractional thermal loading, the ratio of heat generated to absorbed energy, at a 6.5 at.% doped Yb:YAG crystal diode pumped at 0.943 ?m has been measured to be <0.11 under conditions of no laser extraction. This quantity ranged from 0.37-0.43 in 1.04 at.% doped Nd:YAG pumped at 0.808 ?m. Under conditions of laser extraction, the fractional thermal loading in
Photoemission study of valence fluctuation in YbCu2
A. Fujimori; T. Shimizu; H. Yasuoka
Mixed-valence YbCu2 has been studied by x-ray and ultraviolet photoemission spectroscopy (XPS and UPS). UPS results reveal a bulk divalent (4f14-->4f13) peak ~0.3 eV below the Fermi level, and a valence of 2.2 is deduced from XPS. These values are compared with the ground-state magnetic susceptibility, the specific heat, and the magnetic relaxation rate of 4f electrons by using the
Efficient lasing in Yb:(YLa)2O3 ceramics
NASA Astrophysics Data System (ADS)
Snetkov, I. L.; Mukhin, I. B.; Balabanov, S. S.; Permin, D. A.; Palashov, O. V.
A high-optical-quality sample of Yb0.1Y1.7La0.2O3 ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate ¢ nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%.
8-W highly efficient Yb-doped fiber laser
Volker Reichel; S. Unger; Volker Hagemann; Hans-Rainer Mueller; M. Auerbach
In this paper a very compact device of a very efficient high- power fiber-laser based on a specially designed Ytterbium (Yb)-doped double-clad D-Shape silica fiber with an output power of more than 8 watts will be described. The development, preparation and characterization of rare-earth doped double- clad optical fibers based on silica for the application in high-power fiber-lasers were done
Frequency tuning and doubling in Yb-doped fiber lasers
V. A. Akulov; D. M. Afanasiev; S. A. Babin; D. V. Churkin; S. I. Kablukov; M. A. Rybakov; A. A. Vlasov
A compact Yb-doped fiber laser (YDFL) based on a tunable fiber Bragg grating (FBG) with ?6 W output power and ?45 nm tuning\\u000a around 1080 nm has been developed. The laser output power and its spectral width (?0.15 nm) do not change significantly at\\u000a the tuning, while the FBG reflection coefficient increases with an increase in FBG compression. It has
30-W Yb3+-pulsed fiber laser with wavelength tuning
NASA Astrophysics Data System (ADS)
Davydov, B. L.; Krylov, A. A.
We have investigated various pulsed operation regimes of a diode-pumped Yb3+-doped fiber laser with both an acoustooptic filter and a shutter inside the resonator. To imbed the polarization-sensitive acoustooptic-tunable spectral filter into the polarization-nonmaintaining resonator, based on an ōisotropicö single-mode fiber without ōpolarizationÆ losses, we have used a CaCO3 single-crystal nondispersive thermostable polarization splitter. Stable smooth bell-shaped laser pulses were obtained in the Q-switch generation regime across the entire wavelength tuning band. Their duration depended on the resonator travel time and their repetition rate was determined exclusively by the outer high-frequency generator controlling the acoustooptic shutter. A pulsed laser radiation tuning bandwidth of more than 20-nm at a repetition rate band of 10-100 kHz was observed in the amplification band of the Yb3+-doped fiber. A stable average power of 30 W of the pulsed 70-ns 100-kHz laser radiation in a near Gaussian beam was reached by means of the two-stage amplifier based on Yb3+-doped fibers with an enlarged mode field diameter (14 ?m). The amplifier was pumped by ? = 975 nm CW multimode laser diodes with a maximum average power of 42 W.
Dual-gain SESAM modelocked thin disk laser based on Yb:Lu?O? and Yb:Sc?O?.
Schriber, Cinia; Emaury, Florian; Diebold, Andreas; Link, Sandro; Golling, Matthias; Beil, Kolja; Krõnkel, Christian; Saraceno, Clara J; S³dmeyer, Thomas; Keller, Ursula
We present for the first time a SESAM-modelocked thin-disk laser (TDL) that incorporates two gain materials with different emission spectra in a single TDL resonator. The two gain media used in this experiment are the sesquioxide materials Yb:Lu2O3 and Yb:Sc2O3, which have their spectral emission peak displaced by ?7 nm. We can benefit from a combined gain bandwidth that is wider than the one provided by a single gain material alone and still conserve the excellent thermal properties of each disk. In these first proof-of-principle experiments we demonstrate pulse durations shorter than previously achieved with the single gain material Yb:Lu2O3. The oscillator generates pulses as short as 103 fs at a repetition rate of 41.7 MHz and a center wavelength of around 1038 nm, with an average output power of 1.4 W. A different cavity layout provides pulses with a duration of 124 fs at an output power of 8.6 W. This dual-gain approach should allow for further power scaling of TDLs and these first results prove this method to be a promising new way to combine the record output-power performance of modelocked TDLs with short pulse durations in the sub-100 fs regime. PMID:25320984
Some comments on 151Eu M÷ssbauer spectroscopy
NASA Astrophysics Data System (ADS)
Bibicu, Ion
The possibility to do surface measurements on sample containing151Eu by detection of Auger electrons delivered in the decay process of the M÷ssbauer nucleus is briefly presented herein. The test measurements have been carried out on Eu2O3 powder sample. A higher resonance effect and a lower line width have been obtained in backscattering geometry compared with transmission geometry.
EU anti-fraud enforcement: overcoming obstacles
Simone White
Purpose ¢ The purpose of this paper is to analyse the extent to which the (changing) European Union (EU) constitutional context impacts on the investigation of fraud affecting the EU budget, with a focus on fraud affecting expenditure. Design\\/methodology\\/approach ¢ The paper is based on legal issues perceived by a European law specialist working within OLAF. The legal framework and
Greening EU Studies: An Academic Manifesto
Alex Warleigh-Lack
This article responds to Ian Manners' challenge to scholars of EU studies to engage with a broader range of theoretical perspectives and projects than is conventional. Specifically, it investigates the benefits of such an epistemological shift as that called for by Manners, critiquing the condition of the mainstream in EU studiesŚwhich is still somewhat unreflexively defined by dominant norms of
EU MARKET SURVEY 2004 Timber and timber
EU MARKET SURVEY 2004 Timber and timber products #12;EU MARKET SURVEY 2004 TIMBER AND TIMBER DISCLAIMER Although the content of its market information tools has been compiled with the greatest care of the information. In the case of the market publications, neither CBI nor the authors of the publications accept
Laser excited long lasting luminescence in CaAl?O?: Eu│?/Eu▓?+Nd│? phosphor.
Kumar, K; Singh, A K; Rai, S B
The europium and neodymium oxides doped nano-structured calcium aluminate phosphor samples have prepared through combustion technique and their luminescence properties are studied using laser excitations. Samples prepared in open atmosphere showed the presence of both Eu(3+) and Eu(2+) states and their ratio changes with calcination temperature. Single Eu(3+)/Eu(2+) ions doped sample has found to give broad emission at 450 nm without the persistence glow while the Eu(3+)+Nd(3+) ions codoped sample has shown persistence glow at 450 nm (Eu(2+)) on 355 nm laser excitation. Wavelength selective excitations show that 266 nm excitation gives the intense emissions from both Eu(3+) and Eu(2+) states with no afterglow but 355 nm excitation gives negligible emission from Eu(3+) ions and a strong afterglow at 450 nm wavelength. The mechanism of wavelength dependent phosphorescence has been discussed. Studies on Stark splittings and their relative intensities in emission spectra of Eu(3+) ions have shown that Eu(3+) ion can be used as excellent probe of crystal structure. PMID:23220659
Optical properties of strongly coupled Yb2+ and CN ions in alkali halide crystals: Electronic absorption and emission
C. P. An; Volkmar Dierolf; Fritz Luty
We have studied absorption and emission spectra of the 4f144f135d electronic transitions of Yb2+:(CN-)n defect complexes in NaCl, KCl, RbCl, and KBr host crystals under concentration variation of both dopants Yb2+ and CN-. Due to strong coupling between Yb2+ and (CN-)n, the Yb2+ electronic transitions shift drastically towards lower energies (from near uv to near ir) as the n value
Radiative-trapping and fluorescence-concentration quenching effects of Yb:YAl3(BO3)4 crystals
Jinsheng Liao; Yanfu Lin; Yujin Chen; Zundu Luo; En Ma; Xinghong Gong; Qiguang Tan; Yidong Huang
The effects of radiative-trapping and fluorescence-concentration quenching on the emission spectra and fluorescence lifetimes of Yb3+-doped YAl3(BO3)4 crystals with a series of Yb3+ concentrations were studied. The shift of barycenters in emission spectra, Deltalambda, was proposed as an appraisement of the radiative-trapping effect on the spectra, and an empirical relation between Deltalambda and Yb3+ concentration in the Yb:YAl3(BO3)4 crystals was
Evaluating LANDSAT-4 MSS and TM data
NASA Technical Reports Server (NTRS)
Strome, W. M.; Cihlar, J.; Goodenough, D. G.; Guertin, F. E. (principal investigator); Murphy, J. M.; Grieve, G.; Simard, R.; Horler, D.; Ahern, F. J.
Interband line pixel misregistrations were determined for the four MSS bands of the Mistassini, Ontario scene and multitemporal registration of LANDSAT-4 products were tested for two different geocoded scenes. Line and pixel misregistrations are tabulated as determined by the manual ground control points and the digital band to band correlation techniques. A method was developed for determining the spectral information content of TM images for forestry applications.
Long-period fiber grating as wavelength selective element in double-clad Yb-doped fiber-ring lasers
Paris-Sud XI, Universitķ de
Long-period fiber grating as wavelength selective element in double-clad Yb-doped fiber-ring lasers wavelength of the Yb-doped fiber-ring lasers using long- period fiber gratings (LPFGs) is suggested be extended to both shorter and longer wavelengths with proper design of the LPFG and length of the Yb
Femtosecond Yb:KGd(WO4)2 laser oscillator pumped by a high power fiber-coupled diode
Major, Arkady
, and W. Sibbett, "Highly efficient femtosecond Yb:KYW laser pumped by single narrow-stripe laser diodeFemtosecond Yb:KGd(WO4)2 laser oscillator pumped by a high power fiber-coupled diode laser firstname.lastname@example.com Abstract: The development and characterization of a diode-pumped ultrashort pulse Yb:KGd(WO4)2 laser
Long-Range Magnetic Ordering in Pyrochlore Iridate Eu2Ir2O7
NASA Astrophysics Data System (ADS)
Zhao, S.; Mackie, J. M.; Maclaughlin, D. E.; Bernal, O. O.; Ohta, Y.; Nakatsuji, S.
In the pyrochlore iridate Eu2Ir2O7 [1,,] Eu^3+ is nonmagnetic (L = S, J = 0) and S(Ir^4+) = 1/2 [1], so that it is a rare example of a frustrated S=1/2 pyrochlore. Spin-glass-like behavior at the metal-insulator transition (MIT) and no magnetic ordering down to 0.3 K have been reported for this compound [2,,]. We discuss ?SR measurements on Eu2Ir2O7 polycrystalline samples that yield strong evidence for long-range magnetic ordering. We observe well-defined muon spin precession frequencies below TM 120 K, consistent with the MIT temperature [2] but indicating long-range ordering instead of a spin-glass like transition. Significant dynamic muon spin relaxation persists to low temperatures, as is often the case in frustrated antiferromagnets. Work supported by NSF (U.S.), Grants 0801407 (UCR) and 0604105 (CSULA), and MEXT (Japan), Grants-in-Aid Nos. 17071003 and 19052003. [1] B. J. Kim et al., Phys. Rev.Lett. 101, 076402 (2008). [2] N. Taira et al., J. Phys.: Condens. Matter 13, 5527 (2001). [3] C. L. Chien and A. W. Sleight, Phys. Rev. B 18, 2031 (1978).
Tuning the Kondo effect in YbFe1-xCoxZn20
NASA Astrophysics Data System (ADS)
Kong, Tai; Taufour, Valentin; Bud'Ko, Sergey; Canfield, Paul
YbCo2Zn20 is a heavy fermion compound with a Sommerfeld coefficient, ? value, of about 8000 mJ/mol-K2 with an estimated single ion Kondo temperature, TK, of about 1.5 K. One the other hand, YbFe2Zn20 is less heavy with ? ~ 500 mJ/mol-K2 and TK ~ 30 K. From a generalized Kadowaki-Woods picture, degeneracies that relate to their Kondo phenomena are large while different: 8 for YbFe2Zn20 and 4 for YbCo2Zn20. In order to understand the effects of Fe-Co substitution on the Kondo effect, a family of YbFe1-xCoxZn20 were studied. We performed zero-field resistivity and specific heat measurements on single crystals of YbFe1-xCoxZn20 that were synthesized using a high-temperature solution growth technique. The Kondo characteristic temperatures do not change monotonically in between pure YbFe2Zn20andYbCo2Zn20. Data and a summarize phase diagram of characteristic temperatures as a function of Co doping will be presented and discussed. This work is supported by the US DOE, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.
A gigahertz multimode-diode-pumped Yb:KGW enables a strong frequency comb offset beat
Keller, Ursula
A gigahertz multimode-diode-pumped Yb:KGW enables a strong frequency comb offset beat signal SESAM modelocked Yb:KGW laser is pumped with a commercial multimode diode laser and enables a strong oscillators: a success story for the last 20 years with no end in sight," Appl. Phys. B 100(1), 15Ł28 (2010
Modeling of quasi-three-level lasers and operation of cw Yb:YAG lasers
Byer, Robert L.
Modeling of quasi-three-level lasers and operation of cw Yb:YAG lasers Takunori Taira, William M. Tulloch, and Robert L. Byer We present modeling studies of quasi-three-level laser oscillators, the validity of which was revealed by Ti:Al2O3-pumped Yb:YAG laser experiments, and these results are shown
Yb:fiber-laser-pumped high-energy picosecond optical parametric oscillator
-frequency of 15.3 MHz (9.8 m length) achieved using intracavity relay-imaging optics. The signal pulses hadYb:fiber-laser-pumped high-energy picosecond optical parametric oscillator T. P. Lamour,1,* L-pumped by a femtosecond Yb:fiber laser. The oscillator operated at a signal wavelength of 1530 nm with a repetition
Feasibility study for production of 175Yb: a promising therapeutic radionuclide.
Chakraborty, Sudipta; Unni, P R; Venkatesh, Meera; Pillai, M R A
Owing to its favourable decay characteristics 175Yb (T1/2 = 4.2 d, E beta(max) = 480 keV) can be regarded as a potential radionuclide for therapeutic applications. Production of 175Yb using (174Yb(n, gamma)175Yb) reaction by thermal neutron bombardment on natural ytterbium target is described. The activity of 175Yb produced as well as its radionuclidic purity under different irradiation conditions were determined by gamma-ray spectrometry using an HPGe 4 K MCA system and compared with theoretically calculated values. The radiochemical purity after chemical processing was determined by paper chromatography as well as paper electrophoresis techniques. It is found that 31 Ci/g (1145 GBq/g) of 175Yb can be produced with > 95% radionuclidic purity (with approximately 3% of 169Yb and approximately 2% of 177Lu) by irradiating natural Yb2O3 target at a thermal neutron flux of 3 x 10(13) n/cm2/s for a period of 5 d. PMID:12201133
Broadband Yb:CaF2 regenerative amplifier for millijoule range ultrashort pulse amplification
Paris-Sud XI, Universitķ de
Broadband Yb:CaF2 regenerative amplifier for millijoule range ultrashort pulse amplification, 14050 Caen, France ABSTRACT We report on a diode-pumped regenerative amplifier based on Yb:CaF2 material lasers. Keywords: Regenerative amplifier, Ytterbium doped material, Ultrafast laser 1. INTRODUCTION More
Short pulse and high repetition rate diode-pumped Yb:CaF2 regenerative amplifier
Boyer, Edmond
Short pulse and high repetition rate diode-pumped Yb:CaF2 regenerative amplifier S. Ricaud1,4 , email@example.com Abstract: We present a diode-pumped regenerative amplifier based on an Yb:CaF2 crystal optimized to produce obtained. Nevertheless, for energies above the mJ range, regenerative amplifiers are required
Spectrum-, pulsewidth-, and wavelength-switchable all-fiber mode-locked Yb laser with
Turitsyn, Sergei K.
Spectrum-, pulsewidth-, and wavelength- switchable all-fiber mode-locked Yb laser with fiber based 1 Division of Laser Physics and Innovative Technologies, Novosibirsk State University, Novosibirk and wavelength of the output from an all-fiber Yb laser mode-locked by carbon nanotubes. It is shown
Calibration of the EU Oxybarometer for Nakhlites
NASA Technical Reports Server (NTRS)
Makishima, J.; McKay, G.; Le, L.; Miyamoto; Mikouchi, T.
Martian meteorites have various characteristics, which are direct clues to understanding the petrogenesis of Mars rocks. The variation in oxidation state among the Martian meteorites must have important implications for redox conditions of the Martian crust/mantle and overall differentiation on Mars. Wadhwa [1] and Herd et al. [2] reported that Martian basalts were formed under a range of oxidation states, suggesting complex petrogenesis processes. The nakhlites, which have rather different characteristics from basaltic shergottites, may give us additional clues to Martian petrogenesis. The oxidation states of meteorites are usually described by the oxygen fugacity (fO2) under which the meteorites crystallized. One of the methods to estimate the oxygen fugacity is the depth of Eu anomaly. Eu(2+)/Eu(3+) is determined by the oxygen fugacity and partitioning is different for Eu(2+) and Eu(3+). Therefore, the depth of Eu anomaly in a mineral is a function of the oxygen fugacity and the Eu2+/Eu3+ in the melt from which the mineral crystallized. This method has some advantages over another major method, the two-oxide oxybarometer [3], which can more easily be affected by subsolidus processes. The Eu oxybarometer can analyze the cores of the earliest formed crystals in Martian meteorites, which means it can give us a better indication of the oxygen fugacity of the parent melt. The calibration of the Eu oxybarometer has been done with the basaltic shergottites before [4]. However, it has never been applied to nakhlites (Oe et al. [5] measured the depth of Eu anomaly in the synthetic pyroxene only at QFM). Partition coefficients are strongly affected by phase compositions, especially pyroxene Ca content and melt Al content [e.g., 5,6]. The composition of nakhlite pyroxene is rather different from basaltic shergottite pyroxene. Thus, there may be problems in applying the Eu oxybarometer calibration for the basaltic shergottites [7] to nakhlites. Thus, we report in this abstract preliminary results of our experimental calibration of the depth of Eu anomaly in pyroxene vs. oxygen fugacity for nakhlites.
Structural and magnetic properties of TM-SiO2 (TM = Fe, Co, Ni) films
NASA Astrophysics Data System (ADS)
Socolovsky, L. M.; Denardin, J. C.; Brandl, A. L.; Knobel, M.; Zhang, X. X.
TMx-(SiO2)1-x (TM=Fe, Co, Ni) thin films were prepared in a wide concentration range (0.35 ?x?1). Structure was studied with transmission electron microscopy (TEM), X-ray diffraction (XRD) and small angle X-ray scattering (SAXS). Magnetic and magnetotransport properties were investigated by means of magnetization and Hall effect measurements. TEM images display nanometric spherical structures embedded in a SiO2 amorphous matrix, with typical sizes increasing from 3 to 5nm when TM volume concentration x is increased. SAXS measurements indicate a complex structure formed by nanosized objects. XRD measurements show that the structure is composed by amorphous SiO2 and TM crystallites. Slightly above the percolation threshold all samples display giant Hall effect. The observed magnetic properties are dependent on x, and display an evolution resulting from the progressive increase of the mean particle size.
Yb band parasitic lasing suppression in Er/Yb-co-doped pulsed fiber amplifier based on all-solid photonic bandgap fiber
NASA Astrophysics Data System (ADS)
Ouyang, Deqin; Guo, Chunyu; Ruan, Shuangchen; Yan, Peiguang; Wei, Huifeng; Luo, Jie
A novel kind of all-solid photonic bandgap fiber (AS-PBGF) has been used in the master oscillator power amplifier structured Er/Yb-co-doped pulsed fiber amplifier to suppress the Yb band parasitic lasing for the power scaling and safety operation. To the best of our knowledge, this is the first time to report the use of AS-PBGF to suppress the Yb band parasitic lasing. The experimental results show that the Yb band parasitic lasing has been suppressed efficiently and the amplifier power has been raised dramatically with the utilization of AS-PBGF. An output power of 2.66 W was finally obtained without any unwanted parasitic lasing.
Output characteristics of high power cryogenic Yb:YAG TRAM laser oscillator.
Furuse, Hiroaki; Kawanaka, Junji; Miyanaga, Noriaki; Chosrowjan, Haik; Fujita, Masayuki; Takeshita, Kenji; Izawa, Yasukazu
We analyzed the output power characteristics of a cryogenically cooled Yb:YAG total-reflection active-mirror (TRAM) laser oscillator including the temperature dependence of the emission cross section and the reabsorption loss of the Yb:YAG TRAM. A CW multi-transverse mode oscillation of a 9.8 at.% doped 0.6 mm thick Yb:YAG ceramic TRAM was investigated for various pump spot sizes and compared with theoretical results. The Yb:YAG temperatures were inferred from the ratio between fluorescence intensities at 1022 nm and 1027 nm which varied significantly with temperature below 200 K. Output power calculations using evaluated temperatures were in good agreement with the experimental data measured between 77 and 200 K, and the output power suppression due to the temperature rise observed above ~140 K. To the best of our knowledge, this is the first evaluation of output power for a cryogenically cooled Yb:YAG TRAM laser. PMID:23037293
Noncoding RNAs that associate with YB-1 alter proliferation in prostate cancer cells.
Liu, Teresa T; Arango-Argoty, Gustavo; Li, Zhihua; Lin, Yuefeng; Kim, Sang Woo; Dueck, Anne; Ozsolak, Fatih; Monaghan, A Paula; Meister, Gunter; DeFranco, Donald B; John, Bino
The highly conserved, multifunctional YB-1 is a powerful breast cancer prognostic indicator. We report on a pervasive role for YB-1 in which it associates with thousands of nonpolyadenylated short RNAs (shyRNAs) that are further processed into small RNAs (smyRNAs). Many of these RNAs have previously been identified as functional noncoding RNAs (http://www.johnlab.org/YB1). We identified a novel, abundant, 3'-modified short RNA antisense to Dicer1 (Shad1) that colocalizes with YB-1 to P-bodies and stress granules. The expression of Shad1 was shown to correlate with that of YB-1 and whose inhibition leads to an increase in cell proliferation. Additionally, Shad1 influences the expression of additional prognostic markers of cancer progression such as DLX2 and IGFBP2. We propose that the examination of these noncoding RNAs could lead to better understanding of prostate cancer progression. PMID:25904138
Translational Activation of HIF1? by YB-1 Promotes Sarcoma Metastasis.
El-Naggar, Amal M; Veinotte, Chansey J; Cheng, Hongwei; Grunewald, Thomas G P; Negri, Gian Luca; Somasekharan, Syam Prakash; Corkery, Dale P; Tirode, Franck; Mathers, Joan; Khan, Debjit; Kyle, Alastair H; Baker, Jennifer H; LePard, Nancy E; McKinney, Steven; Hajee, Shamil; Bosiljcic, Momir; Leprivier, Gabriel; Tognon, Cristina E; Minchinton, Andrew I; Bennewith, Kevin L; Delattre, Olivier; Wang, Yuzhuo; Dellaire, Graham; Berman, Jason N; Sorensen, Poul H
Metastatic dissemination is the leading cause of death in cancer patients, which is particularly evident for high-risk sarcomas such as Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma. Previous research identified a crucial role for YB-1 in the epithelial-to-mesenchymal transition (EMT) and metastasis of epithelial malignancies. Based on clinical data and two distinct animal models, we now report that YB-1 is also a major metastatic driver in high-risk sarcomas. Our data establish YB-1 as a critical regulator of hypoxia-inducible factor 1? (HIF1?) expression in sarcoma cells. YB-1 enhances HIF1? protein expression by directly binding to and activating translation of HIF1A messages. This leads to HIF1?-mediated sarcoma cell invasion and enhanced metastatic capacity inĀvivo, highlighting a translationally regulated YB-1-HIF1? axis in sarcoma metastasis. PMID:25965573
Low-temperature properties of Ca-doped YbMnO3 multiferroic single crystals
NASA Astrophysics Data System (ADS)
Abramov, N.; Chichkov, V.; Lofland, S. E.; Mukovskii, Y. M.
The specific heat cp and magnetization of single crystal hexagonal manganites of the type Yb1-xCaxMnO3 (x = 0, 0.05, and 0.10) were measured in a wide temperature range as a function of magnetic field. Antiferromagnetic ordering of the Mn sublattice occurs at TN = 83 K. Ca doping has surprisingly minimal effect on the magnetic properties. At low temperature (ś3.5 K), all compounds show ferromagnetic (FM) ordering in the basal plane attributed to Yb in site 2a. For low fields applied along the c direction, Yb spin reorientation occurs and FM ordering disappears. cp shows a broad maximum centered at the temperature ś6 K that is consistent with a Schottky anomaly related to the Zeeman splitting of the Yb moments due to Mn molecular field. In the field of 30 kOe, the re-entrant FM transition takes place with Yb ions in sites 2a and 4b.
Reflection symmetry instability at high spins in 162,164Yb
R. G. Nazmitdinov; J. Kvasil; A. Tsvetkov
A shape evolution of 162,164Yb in yrast states is traced using the self-consistent Skyrme Hartree-Fock calculations. We found that nonaxial octupole deformations (in particular, Y_{31} term) become favorable at large rotational frequencies (> 0.4 MeV) in 162Yb, while in 164Yb a nonaxial quadrupole shape is dominant at fast rotation. The cranked Nilsson model and random phase approximation are used to understand the dynamics of octupole correlations in both nuclei. We demonstrate that the disappearance of one of the octupole vibrational modes in the rotating frame gives rise to the nonaxial octupole deformations in 162Yb, while the octupole modes are nonzero in 164Yb.
Strong correlation between oxygen vacancy and ferromagnetism in Yb-doped ZnO thin films
NASA Astrophysics Data System (ADS)
Li, Fei; Liu, Xue-Chao; Zhou, Ren-Wei; Chen, Hong-Ming; Zhuo, Shi-Yi; Shi, Er-Wei
Zn1-xYbxO (0 ? x ? 0.02) thin films have been prepared by inductively coupled plasma enhanced physical vapor deposition method. All the Yb-doped ZnO thin films show room-temperature ferromagnetism. The correlation between oxygen vacancy and magnetism in Yb-doped ZnO thin films is studied. It is found that Yb irons initially substitute for Zn sites when x ? 0.01 and then enter the interstitial sites of ZnO with increasing Yb concentration of x > 0.01. The ferromagnetism is induced by the coexistence of oxygen vacancy and Yb point defects. A strong correlation between oxygen vacancy and saturation magnetization is observed.
Photoluminescence properties and energy levels of RE (RE?=?Pr, Sm, Er, Tm) in layered-CaZnOS oxysulfide
Zhang, Zhi-Jun, E-mail: firstname.lastname@example.com [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai 200050 (China); Feng, Ang; Chen, Xiang-Yang [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Zhao, Jing-Tai, E-mail: email@example.com [Key Laboratory of Transparent Opto-Functional Inorganic Materials of Chinese Academy of Sciences, Shanghai Institute of Ceramics, Shanghai 200050 (China); School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)
RE{sup 3+} (RE?=?Pr, Sm, Er, Tm)-activated CaZnOS samples were prepared by a solid-state reaction method at high temperature, and their photoluminescence properties were investigated. Doping with RE{sup 3+} (RE?=?Pr, Sm, Er, Tm) into layered-CaZnOS resulted in typical RE{sup 3+} (RE?=?Pr, Sm, Er, Tm) f-f line absorptions and emissions, as well as the charge transfer band of Sm{sup 3+} at about 3.3?eV. The energy level scheme containing the position of the 4f and 5d levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of CaZnOS has been constructed based on the new data presented in this work, together with the data from literature on Ce{sup 3+} and Eu{sup 2+} doping in CaZnOS. The detailed energy level scheme provides a platform for interpreting the optical spectra and could be used to comment on the valence stability of the lanthanide ions in CaZnOS.
Independence(TM) iBOT(TM) 3000 Mobility System: a stair-climbing wheelchair.
Independence (TM) iBOT(TM) 3000 is a wheelchair that may be used to climb stairs, elevate the user to standing adult eye level and cross uneven terrain. Limited evidence indicates that the device may offer more mobility and freedom to users than conventional wheelchairs. The iBOT may be difficult to manoeuvre indoors due to the seat height, but it operates well outdoors. The use of this technology is limited by the high cost of ownership and uncertain incremental benefit for users. While the device is not yet licensed for use in Canada, it is approved by the Food and Drug Administration for use in the US. PMID:15164734
{beta}-decay study of {sup 150}Er, {sup 152}Yb, and {sup 156}Yb: Candidates for a monoenergetic neutrino beam facility
Estevez Aguado, M. E.; Algora, A.; Rubio, B.; Bernabeu, J.; Nacher, E.; Tain, J. L.; Gadea, A.; Agramunt, J.; Burkard, K.; Hueller, W.; Doering, J.; Kirchner, R.; Mukha, I.; Plettner, C.; Roeckl, E.; Grawe, H.; Collatz, R.; Hellstroem, M.; Cano-Ott, D.; Karny, M. [IFIC, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); GSI, D-64291 Darmstadt (Germany); CIEMAT, E-28000, Madrid (Spain); Institute of Experimental Physics, University of Warsaw, PL-00-681 Warsaw (Poland); ORNL, Oak Ridge, Tennessee 37831 (United States); PNPI, 188300 Gatchina (Russian Federation); IKP, University of Cologne, D-50937 Cologne (Germany); INFN LNL, I-35020 Legnaro (Padova) (Italy); CFPT-IST, 1049-001 Lisbon (Portugal)
The {beta} decays of {sup 150}Er, {sup 152}Yb, and {sup 156}Yb nuclei are investigated using the total absorption spectroscopy technique. These nuclei can be considered possible candidates for forming the beam of a monoenergetic neutrino beam facility based on the electron capture (EC) decay of radioactive nuclei. Our measurements confirm that for the cases studied the EC decay proceeds mainly to a single state in the daughter nucleus.
An Acidic Protein, YBAP1, Mediates the Release of YB1 from mRNA and Relieves the Translational Repression Activity of YB1
Ken Matsumoto; Kimio J. Tanaka; Masafumi Tsujimoto
Eukaryotic Y-box proteins are nucleic acid-binding proteins implicated in a wide range of gene regulatory mechanisms. They contain the cold shock domain, which is a nucleic acid-binding structure also found in bacterial cold shock proteins. The Y-box protein YB-1 is known to be a core component of messenger ribonucleoprotein particles (mRNPs) in the cytoplasm. Here we disrupted the YB-1 gene
Orthorhombic KSc2F7:Yb/Er nanorods: controlled synthesis and strong red upconversion emission
NASA Astrophysics Data System (ADS)
Ding, Yujie; Teng, Xue; Zhu, Hao; Wang, Lili; Pei, Wenbo; Zhu, Jun-Jie; Huang, Ling; Huang, Wei
For the first time, we have synthesized orthorhombic phase KSc2F7:20%Yb/2%Er (KSc2F7:Yb/Er) nanorods and further studied the crystal structure and morphology evolution, as well as their upconversion (UC) properties under varying F- contents and reaction temperatures. Different from ?-NaYF4:20%Yb/2%Er (NaYF4:Yb/Er) nanorods that usually give strong green UC luminescence, strong red UC emission was observed in KSc2F7:Yb/Er nanorods under 980 nm laser excitation. Their UC mechanisms are further analyzed and compared. This study provides a novel type of rare earth nanorods with strong red UC emissions which have great potential in high resolution 3-dimensional bioimaging, color displays, solid-state lasers, and photocatalysis.For the first time, we have synthesized orthorhombic phase KSc2F7:20%Yb/2%Er (KSc2F7:Yb/Er) nanorods and further studied the crystal structure and morphology evolution, as well as their upconversion (UC) properties under varying F- contents and reaction temperatures. Different from ?-NaYF4:20%Yb/2%Er (NaYF4:Yb/Er) nanorods that usually give strong green UC luminescence, strong red UC emission was observed in KSc2F7:Yb/Er nanorods under 980 nm laser excitation. Their UC mechanisms are further analyzed and compared. This study provides a novel type of rare earth nanorods with strong red UC emissions which have great potential in high resolution 3-dimensional bioimaging, color displays, solid-state lasers, and photocatalysis. Electronic supplementary information (ESI) available: See DOI: 10.1039/c3nr01840g
Synthesis, crystal structure and physical properties of Yb11Bi10 -xSnx
NASA Astrophysics Data System (ADS)
Liang, Ying; Cardoso-Gil, Raul; Schnelle, Walter; Zhao, Jing-Tai; Grin, Yuri
The intermetallic phase Yb11Bi10 -xSnx (x = 0 and 4.8) crystallizing in the Ho11Ge10 structure type was synthesized and characterized. The crystal structure was established by single-crystal X-ray diffraction data in the tetragonal space group I4/mmm (no.139), Pearson code tI84, Z = 4, a = 12.2043(4) ┼, c = 17.7227(9) ┼, and V = 2639.7(2) ┼3, Rgt(F) = 0.040, 763 observed reflections for Yb11Bi10, and a = 12.0183(5) ┼, c = 17.413(1) ┼, and V = 2515.1(2) ┼3, Rgt(F) = 0.027, 762 observed reflections for Yb11Bi5.2Sn4.8. The crystal structure of Yb11Bi10 contains three discrete anionic moieties: isolated Bi3- anions, Bi24- dimers and Bi44- squares. In Yb11Bi5.2Sn4.8, the square units are formed solely by Sn, and the structure shows a mixed Bi/Sn occupancy at the 8i and 16m Wyckoff sites. Magnetization measurements show that the title phase contains ytterbium exclusively in the 4f14 configuration up to 400 K. The Yb-LIII X-ray absorption spectrum attests also the presence of Yb with a 4f14 (Yb2+) configuration for Yb11Bi10, while the average valence of ytterbium was found to be 2.09 for Yb11Bi5.2Sn4.8.
In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications
NASA Technical Reports Server (NTRS)
Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.
The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.
Optical Properties of Tm(3+) Ions in Alkali Germanate Glass
NASA Technical Reports Server (NTRS)
Walsh, Brian M.; Barnes, Norman P.; Reichle, Donald J.; Jiang, Shibin
Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.
Intestinal TM7 bacterial phylogenies in active inflammatory bowel disease
Tanja Kuehbacher; Ateequr Rehman; Patricia Lepage; Stephan Hellmig; Ulrich R. Folsch; Stefan Schreiber; Stephan J. Ott
TM7 is a recently described subgroup of Gram-positive uncultivable bacteria originally found in natural environmental habitats. An association of the TM7 bacterial division with the inflammatory pathogenesis of periodontitis has been previously shown. This study investigated TM7 phylogenies in patients with inflammatory bowel diseases (IBDs). The mucosal microbiota of patients with active Crohn's disease (CD; n542) and ulcerative colitis (UC;
Optical Lattice Induced Light Shifts in an Yb Atomic Clock
Z. W. Barber; J. E. Stalnaker; N. D. Lemke; N. Poli; C. W. Oates; T. M. Fortier; S. A. Diddams; L. Hollberg; C. W. Hoyt; A. V. Taichenachev; V. I. Yudin
We present an experimental study of the lattice-induced light shifts on the S01-->P03 optical clock transition (nuclock≈518THz) in neutral ytterbium. The ``magic'' frequency numagic for the Yb174 isotope was determined to be 394799475(35)MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6pP03-->6s8pP03, 6s8pP23, and 6s5fF23 two-photon
Front-end system for Yb : YAG cryogenic disk laser
NASA Astrophysics Data System (ADS)
Perevezentsev, E. A.; Mukhin, I. B.; Kuznetsov, I. I.; Vadimova, O. L.; Palashov, O. V.
A new front-end system for a cryogenic Yb : YAG laser is designed. The system consists of a femtosecond source, a stretcher and a regenerative amplifier with an output energy of 25 ?J at a pulse repetition rate of 49 kHz, a pulse duration of ~2 ns and a bandwidth of ~1.5 nm. After increasing the pump power of the regenerative amplifier, it is expected to achieve a pulse energy of ~1 mJ at the input to cryogenic amplification stages, which will allow one to obtain laser pulses with a duration of several picoseconds at the output of the cryogenic laser after compression.
Output spectrum of Yb-doped fiber lasers.
Kablukov, S I; Zlobina, E A; Podivilov, E V; Babin, S A
An analytical model for self phase modulation in Yb-doped fiber laser (YDFL) describing output spectrum and its broadening with increasing power has been developed. Spectral measurements in continuous wave (CW) cladding-pumped YDFL have proved the validity of the model demonstrating hyperbolic secant shape of the spectrum and linear increase of the line width with power in 1-12 W range. At lower powers, spatial hole burning and line self-sweeping effects become important and define the lower limit for the line width. PMID:22743437
Reduced Probabilities of E2-Transitions in {sup 174}Yb
Okhunov, A. A. [Quantum Science Center Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Institute for Nuclear Physics, Academy Science of Uzbekistan, 100214 Tashkent (Uzbekistan); Kassim, Hasan Abu [Quantum Science Center Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia)
This paper describes the ground (gr) and exited states of even-even deformed nuclei with a phenomenological model, which takes into account the mixing of gr states, 0{sub n}{sup +}({beta}{sub n})-, 2{sub n}{sup +}({gamma}{sub n})- and {Kappa}{sup {pi}} 1{sub n}{sup +}- rotational bands. The calculation has been done for the isotope Yb. The energy spectra are found to be consistent with the energies from experimental data. The reduced probabilities of the electric quadrupole E2-transitions from {beta}{sub n} and {gamma}{sub n} band states are calculated and agree quite well with the experimental values.
EU Policy in the South Caucasus A view from Azerbaijan
Elkhan Nuriyev
Since the accession of Romania and Bulgaria to the EU in January 2007, the South Caucasus has become a region of direct concern to the EU's strategy in its wider neighbourhood. This study examines the trends affecting EU policies in the South Caucasus, with a specific focus on EU-Azerbaijan relations. It argues that in the three main areas in which
Functionality in EU Foreign Policy: Towards a New Research Agenda?
Christopher J. Bickerton
The study of European Union (EU) foreign policy has hitherto been dominated by the question of effectiveness, i.e. does it work? This takes the external impact of the EUÆs foreign policy as its analytical starting point. In addition to asking whether EU foreign policy works, we should also inquire into its functions. The article identifies three functions served by EU
High magnetic field study of the Tm2Fe17 and Tm2Fe17D3.2 compounds
NASA Astrophysics Data System (ADS)
Isnard, O.; Andreev, A. V.; Kuz'min, M. D.; Skourski, Y.; Gorbunov, D. I.; Wosnitza, J.; Kudrevatykh, N. V.; Iwasa, A.; Kondo, A.; Matsuo, A.; Kindo, K.
A magnetization study of a Tm2Fe17 single crystal and aligned powder of the deuteride Tm2Fe17D3.2 has been carried out in steady (14 T) and pulsed (60 T and, in one case, up to 74 T) magnetic fields at temperatures between 1.5 and 300 K. Tm2Fe17 is a ferrimagnet with TC = 295 K and a spontaneous moment of 22 ?B/f.u. at T = 4.2 K. Of particular interest are low-temperature magnetization curves along the sixfold crystal axis c, which is an easy direction in Tm2Fe17 and a hard direction in the deuteride. In either case the magnetization increases with magnetic field undulatorily in broad steps whose height is a multiple of the atomic moment of Tm, ?Tm = 7 ?B. In Tm2Fe17, the positions of the steps yield information on the Fe-Tm molecular field, 48 T on the Tm 2d site and 60 T on the Tm 2b site, whereas the crystal field parameter A66 is found from the widths of the steps: A66(b) = -35 Ka0-6 and A66(d) = -26 Ka0-6 (here a0 is the Bohr radius). It also proves possible to estimate the other sixth-order crystal field parameter: A60 ś -4 Ka0-6 (on average for both sites). Less information can be extracted from the powder data for the deuteride. Thus, the mean molecular field on Tm in Tm2Fe17D3.2 is found to be 49 T or 9% less than in the parent binary compound.
Elevated serum dehydroepiandrosterone sulfate levels in practitioners of the Transcendental Meditation (TM) and TM-Sidhi programs
Jay L. Glaser; Joel L. Brind; Joseph H. Vogelman; Michael J. Eisner; Michael C. Dillbeck; R. Keith Wallace; Deepak Chopra; Norman Orentreich
Serum dehydroepiandosterone sulfate (DHEA-S) levels were measured in 270 men and 153 women who were experienced practitioners of the Transcendental Meditation (TM) and TM-Sidhi programs, mental techniques practiced twice daily, sitting quietly with the eyes closed. These were compared according to sex and 5-year age grouping to 799 male and 453 female nonmeditators. The mean DHEA-S levels in the TM
Reduction of Yb(III) to Yb(II) by two-color two-photon excitation.
Nakashima, Nobuaki; Yamanaka, Ken-ichi; Yatsuhashi, Tomoyuki
Ytterbium 3+ ions in alcohol were found to be reduced to the corresponding 2+ ions upon laser irradiation with a stepwise two-color two-photon excitation. The infrared (975-nm) pulse with a duration of 4 ns pumps the ground state to the 4f excited state with the transition of (2)F(5/2) ? (2)F(7/2), and the second photon (355-nm) generates the charge transfer (CT) state of Cl 3p to Yb 4f; the reduction then occurs. Laser energy and excitation wavelength dependencies well-explain the above mechanism. The product Yb(2+) was detected by its absorption spectrum peak at 367 nm. The absorption spectrum of the intermediate in the two-photon chemistry was measured from the 4f excited state ((2)F(5/2)) to the CT state by nanosecond laser photolysis. The intermediate spectrum appears in the wavelengths shorter than 400 nm with the molar extinction coefficient on the order of (10(2) M(-1) cm(-1)) at 340 nm and can be explained in terms of the CT absorption shifted by IR photon energy. A UV nanosecond laser pulse (266 nm from a YAG laser with a duration of 6 ns) can generate the reactive CT state by one-photon absorption and leads to Yb(2+) formation. The reaction yields for single-photon UV excitation and the second photon in the two-photon excitation are on the order of 0.1, suggesting that the reactive states are a common CT state. PMID:23968280
Choosing the right parameters to optimize the laser pulse from a ring cavity with an Yb3+:LSO crystal
NASA Astrophysics Data System (ADS)
Liu, Yonghao
In LSO host crystal, Yb3+ occupies two different Lu3+ sites and the character makes the spectra of Yb3+:LSO complicated compared with those of Yb3+:YAG. Due to the difference, the model for Yb3+:YAG can not be used directly for Yb3+:LSO. In this letter, on the basis of the spectral information and the energy level diagram, a theoretical model is developed to treat the laser pulse generated from an active CW injected ring cavity with an Yb3+:LSO crystal. Starting from the rate equation, the equation describing the laser pulse is obtained. As a computable model, it also takes into account the pump absorption saturation and the laser reabsorption. For a typical Yb3+ concentration and crystal length, the experimental parameters are chosen by the calculation.
Light storage protocols in Tm:YAG
T. ChaneliĶre; R. Lauro; J. Ruggiero; J. -L. Le Gouļt
We present two quantum memory protocols for solids: A stopped light approach based on spectral hole burning and the storage in an atomic frequency comb. These procedures are well adapted to the rare-earth ion doped crystals. We carefully clarify the critical steps of both. On one side, we show that the slowing-down due to hole-burning is sufficient to produce a complete mapping of field into the atomic system. On the other side, we explain the storage and retrieval mechanism of the Atomic Frequency Comb protocol. This two important stages are implemented experimentally in Tm$^{3+}$- doped yttrium-aluminum-garnet crystal.
CaS: Cu, Eu ELECTROLUMINESCENT PHOSPHORS
A. Wachtel
Introduction of Cu into CaS: Eu does not interfere with the red Eu\\/sup ; 2+\\/ emission. Excitation of the blue CaS: Cu emission is more effective by 3650A ; than by 2537A. Firing with excess Cu gives rise to deposits of free CuŌS ; which may cause an efficient system of contact electroluminescence. The ; electroluminescent properties depend on the
Optical Lattice Induced Light Shifts in an Yb Atomic Clock
Barber, Z. W.; Stalnaker, J. E.; Lemke, N. D.; Poli, N.; Oates, C. W.; Fortier, T. M.; Diddams, S. A.; Hollberg, L.; Hoyt, C. W.; Taichenachev, A. V.; Yudin, V. I. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States); Institute of Laser Physics SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation)
We present an experimental study of the lattice-induced light shifts on the {sup 1}S{sub 0}{yields}{sup 3}P{sub 0} optical clock transition ({nu}{sub clock}{approx_equal}518 THz) in neutral ytterbium. The 'magic' frequency {nu}{sub magic} for the {sup 174}Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p{sup 3}P{sub 0}{yields}6s8p{sup 3}P{sub 0}, 6s8p{sup 3}P{sub 2}, and 6s5f{sup 3}F{sub 2} two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 {mu}K deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10{sup -17}.
Precision Quantum Control with Trapped 171Yb+ Ions
NASA Astrophysics Data System (ADS)
Soare, Alexander; Hayes, David; McLoughlin, James; Zhen, Xinglong; Lee, Michael; Jarrat, M. C.; Ball, Harrison; Green, Todd; Biercuk, Michael; Quantum Control Laboratory Team
We present our recent work in developing and characterizing novel methods for quantum error suppression using trapped 171Yb+ ions as a model experimental platform. A flexible, robust microwave system allows us to access the 12.6 GHz, hyperfine qubit manifold in trapped 171Yb+. The ultra low phase noise characteristics of our source allow the realization of free-evolution coherence times in excess of three seconds, and operational fidelities F>99.99%, characterized by randomized benchmarking. Starting from this baseline, we leverage high-bandwidth vector modulation capabilities to experimentally validate our recent theoretical work developing Walsh-modulated control operations for error-resilient single-qubit control in the presence of synthesized noise. This theory is based on a generalized filter-transfer-function formalism useful for predicting the fidelity of arbitrary operations in the presence of general Gaussian noise. We provide the first experimental validation of this formalism, showing good agreement between experimental measurements and theoretical predictions with no free parameters. These demonstrations support the notion of physical-layer error evasion as an efficient means to realize high-fidelity quantum control across a wide range of quantum technologies.
An Yb optical lattice clock: Current status at KRISS
NASA Astrophysics Data System (ADS)
Yu, Dai-Hyuk; Park, Chang Yong; Lee, Won-Kyu; Lee, Sangkyung; Park, Sang Eon; Mun, Jongchul; Lee, Sang-Bum; Kwon, Taeg Yong
The current status of an Yb optical lattice clock at the Korea Research Institute of Standards and Science (KRISS) is reported. The systematic uncertainty of the Yb clock in the first accuracy evaluation was 1.5 ū 10-14 [Park et al., Metrologia 50, 119 (2013)]. The uncertainty was dominated by the large uncertainties in the lattice ac Stark shift and the collisional shift, which were mainly limited by the large linewidth and jitter of the clock laser. Recently, a highly stable clock laser at 578 nm was developed with a short-term linewidth of 3.5 Hz and a frequency jitter of about 25 Hz at 1 s and 10 s measurement times, respectively. The long-term frequency drift showed only a linear dependence on time, confirming that the temperature of the super-cavity was maintained a zero coefficient of thermal expansion. The frequency of the lattice laser at 759 nm was phase locked to the optical frequency comb and could be stabilized at the "absolute" frequency of the "magic wavelength", to within a 1-MHz uncertainty. This improvement greatly reduced the fractional uncertainty due to the lattice ac Stark shift down to 2 ū 10-16. The systematic uncertainty of the clock is currently 5.3 ū 10-15 and is dominated by the collisional frequency shift.
Microwave sintering of Yb:YAG transparent laser ceramics
NASA Astrophysics Data System (ADS)
Esposito, Laura; Piancastelli, Andreana; Bykov, Yury; Egorov, Sergei; Eremeev, Anatolii
Reactive sintering of YAG based ceramics is generally performed under high vacuum in graphite-free furnaces in order to guarantee the elimination of pores and absence of any contamination. An alternative densification technique is the field assisted process such as spark plasma sintering and microwave sintering. Both of these methods are characterized by very fast heating rates, low sintering temperatures and short sintering times. The microwave sintering process is different from electric resistance heating since heat is generated in the bulk of the powder compact through electromagnetic radiation absorption and creates within its body uniform temperature distribution. Microwave sintering of laser ceramics is advantageously distinguished by the absence of any elements having high temperature such as electric heaters or dies which materials can contaminate the sintered parts. In addition, the inverse temperature distribution that exists within the body under volumetric microwave heating is favorable for elimination of porosity. Microwave sintering of Yb:YAG samples were tested and the obtained results are presented. The samples were sintered on a gyrotron-based system operating at a frequency of 24 GHz with microwave power up to 6 kW. Reactive sintering of YAG doped with 1.0, 5.0, and 9.8 at.% Yb2O3 was performed in different temperature-time regimes. The microstructure and the optical transmittance of the obtained samples were compared to those of samples obtained by conventional high vacuum sintering.
Induced Magnetic Order in Yb2Ti2O7
NASA Astrophysics Data System (ADS)
Adams, Carl; Ross, K. A.; Ruff, J. P.; Gaulin, B. D.; Dabkowska, H.; Qiu, Y.; Copley, J. R. D.; Gardner, J. S.
Yb2Ti2O7 is part of family of pyrochlore materials with a magnetic rare-earth and a non-magnetic transition metal. In similar compounds containing holmium, erbium, or terbium the geometric frustration results in several exotic ground states including spin-ice, spin-liquid, field-induced ordering, and low-dimensional behavior. The ytterbium-based compound has a strong anomaly in the specific heat at 240 mK [Hodges et al., J Phys Cond Mat 13, 9301 (2001)] but without accompanying long range order. We have made measurements of the elastic and inelastic neutron scattering on a large single crystal of Yb2Ti2O7 over a broad range of the (hhl) scattering plane using the DCS spectrometer at the NIST Center for Neutron Research. Our studies have confirmed the presence of diffuse ``rods'' of scattering along the (111) directions that persist below 100 mK. However, when the sample is field-cooled in fields as low as 0.5 T the rods of scattering are replaced by well-defined magnetic excitations. We will present the results of our studies at a variety of temperatures and fields.
p-wave optical Feshbach resonances in {sup 171}Yb
Goyal, Krittika; Deutsch, Ivan [Center for Quantum Information and Control, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Reichenbach, Iris [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany)
We study the use of an optical Feshbach resonance to modify the p-wave interaction between ultracold polarized {sup 171}Yb spin-1/2 fermions. A laser exciting two colliding atoms to the {sup 1}S{sub 0}+{sup 3}P{sub 1} channel can be detuned near a purely-long-range excited molecular bound state. Such an exotic molecule has an inner turning point far from the chemical binding region, and thus, three-body recombination in the Feshbach resonance will be highly suppressed in contrast to that typically seen in a ground-state p-wave magnetic Feshbach resonance. We calculate the excited molecular bound-state spectrum using a multichannel integration of the Schroedinger equation, including an external perturbation by a magnetic field. From the multichannel wave functions, we calculate the Feshbach resonance properties, including the modification of the elastic p-wave scattering volume and inelastic spontaneous scattering rate. The use of magnetic fields and selection rules for polarized light yields a highly controllable system. We apply this control to propose a toy model for three-color superfluidity in an optical lattice for spin-polarized {sup 171}Yb, where the three colors correspond to the three spatial orbitals of the first excited p band. We calculate the conditions under which tunneling and on-site interactions are comparable, at which point quantum critical behavior is possible.
Microstructure and luminescence of Yb{sup 3+}-doped fluorosilicate glass ceramics
Qiao, Xvsheng, E-mail: firstname.lastname@example.com [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)] [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Fan, Xianping; Pan, Yu [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)] [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Lotnyk, Andriy; Kienle, Lorenz [Synthesis and Real Structure, Institute for Material Science, Faculty of Engineering, Christian Albrechts University Kiel, Kaiserstr. 2, 24143 Kiel (Germany)] [Synthesis and Real Structure, Institute for Material Science, Faculty of Engineering, Christian Albrechts University Kiel, Kaiserstr. 2, 24143 Kiel (Germany)
Highlights: Black-Right-Pointing-Pointer Fine nano-SrF{sub 2} lattices were observed in the fluorosilicate glass ceramics. Black-Right-Pointing-Pointer EDXS analysis showed Yb{sup 3+} was enriched into the SrF{sub 2} nanocrystals. Black-Right-Pointing-Pointer That deduced intense cooperative luminescence of the glass ceramics. Black-Right-Pointing-Pointer NIR emissions appeared large bandwidths and long lifetimes simultaneously. Black-Right-Pointing-Pointer Yb{sup 3+} can be an efficient upconversion sensitizer or NIR activator in this host. -- Abstract: Yb{sup 3+}-doped transparent glass ceramics containing cubic SrF{sub 2} nanocrystals were prepared by heat treating the precursor fluorosilicate glass. The precipitated crystals increase in size and the crystallinity decreases with increasing Yb{sup 3+} doping level. With high-resolution transmission electron microscopy and electron diffraction, the nano-sized nature of SrF{sub 2} was clearly observed. Owing to a significant change in the crystal-field effects with Yb{sup 3+} enriching in the SrF{sub 2} phase, the glass ceramics present near infrared emission with large bandwidths and long lifetimes, simultaneously. This indicates the glass ceramics have potential application in the efficient IR lasers pumping by InGaAs diodes. The glass ceramics can also emit blue upconversion luminescence, deriving from Yb{sup 3+} pairs' cooperative luminescence. It suggested that Yb{sup 3+} can be an efficient upconversion sensitizer for other rare earth ions.
Intermediate Valence Tuning and Seebeck Coefficient Optimization in Yb-based Low-Temperature Thermoelectric Materials
NASA Astrophysics Data System (ADS)
Lehr, Gloria; Morelli, Donald; Jin, Hyungyu; Heremans, Joseph
Several Yb-based intermediate valence compounds have unique thermoelectric properties at low temperatures. These materials are interesting to study for niche applications such as cryogenic Peltier cooling of infrared sensors on satellites. Elements of different sizes, which form isostructural compounds, are used to form solid solutions creating a chemical pressure (smaller atoms - Sc) or relaxation (larger atoms - La) to alter the volume of the unit cell and thereby manipulate the average Yb valence. Magnetic susceptibility measurements show a strong correlation between the Seebeck coefficient and the ratio of trivalent to divalent Yb in these compounds. Two different Yb-based solid solution systems, Yb1-xScxAl2 and Yb1-xLaxCu2Si2, demonstrate that the concentration of Yb can be used to tune both the magnitude of the Seebeck coefficient as well as the temperature at which its absolute maximum occurs. This work is supported by Michigan State University and AFOSR-MURI ``Cryogenic Peltier Cooling'' Contract #FA9550-10-1-0533.
Diode pumped Yb-lasers Q-switched by V:YAG saturable absorber
NASA Astrophysics Data System (ADS)
Ŗulc, Jan; Kaskow, Mateusz; JelĒnkovß, Helena; Jabczynski, Jan K.
V:YAG saturable absorber, developed mainly for 1.3 ?m lasers Q-switching, was used as a passive Q-switch for the 1.03 ?m Yb-doped YAG (10% Yb/Y, 3mm long) and LuAG (15% Yb/Lu, 1mm long) lasers. Longitudinally diode pumped gain medium together with the V:YAG crystal were placed inside the 22mm long hemispherical laser cavity. For Yb-doped crystal excitation fibre-coupled (fibre core diameter 100 ?m) laser diode (max power amplitude 20W, emission wavelength 968 nm) was used. The laser diode was operating in a pulsed regime (repetition rate 10 Hz, pumping pulse width 2 ms) to reduce parasitic thermal effects inside the gain medium. Stable Q-switching was obtained for laser output coupler reflectivity 70% and V:YAG initial transmission 70% at Yb laser emission wavelength. For the both tested active media the parameters of the generated giant pulses were similar. Pulses with duration of 2.5 ns (FWHM), energy about 0.3 mJ, and peak power up to 120kW were generated. The maximal Q-switched pulses repetition rate inside the single pumping pulse was 6.6 kHz in case of Yb:YAG and 8.6 kHz in case of Yb:LuAG. The beam transversal profile was close to the fundamental Gaussian mode. The output was partially polarized.
Magnetic properties of YbTGe (T=Rh, Cu, Ag)
NASA Astrophysics Data System (ADS)
Katoh, K.; Mano, Y.; Nakano, K.; Terui, G.; Niide, Y.; Ochiai, A.
The magnetic properties of ternary equiatomic YbTGe (T=Rh, Cu, Ag) compounds have been investigated. YbRhGe is a new antiferromagnet with TN=7 K which crystallizes in the orthorhombic TiNiSi-type structure. In YbCuGe, with the hexagonal LiGaGe-type structure, ferromagnetic ordering with a magnetic moment of 0.7 ?B/Yb occurs below 8 K. On the other hand, in YbAgGe with the hexagonal ZrNiAl-type structure, the magnetic susceptibilities along the a- and c-axis follow the Curie-Weiss law with trivalent Yb at high temperatures. No feature of some kind of phase transition is found above 1.2 K. The electrical resistivity along the a- and c-axis shows metallic behavior. The ratio of the specific heat to temperature increases remarkably below 10 K and shows a large value of 570 mJ/molK 2 at 1.6 K which indicates a heavy-fermion nature of YbAgGe.
EU fta Negotiations with sadc and Mercosur: integration into the world economy or market access for EU firms?
Alfredo C Robles Jr
The EU claims that its free trade agreements with regional organisations of developing countries can promote the respective regions' integration into the world economy. Taking as case studies EU negotiations with the Southern African Development Community and Mercosur, the paper argues that the EU and its partners have different conceptions of integration into the world economy. For the EU the
Complete recovery of Eu from BaMgAl10O17:Eu2+ alkaline fusion and its mechanism
Volinsky, Alex A.
Complete recovery of Eu from BaMgAl10O17:Eu2+ by alkaline fusion and its mechanism Shengen Zhang and efficient process for recycling waste phosphors has been developed. The alkaline fusion process is used for recycling Eu from BaMgAl10O17:Eu2+ (BMA) completely. The comprehensive BMA disintegration via alkaline
77 FR 40364 - Announcement of Requirements and Registration for Million Hearts TM
Federal Register 2010, 2011, 2012, 2013, 2014
...of Requirements and Registration for Million Hearts TM Caregiver Video Challenge AGENCY: Centers...Human Services, in partnership with Million Hearts TM announces the launch of The Million Hearts TM Caregiver Video Challenge. We invite...
First direct high-precision energy determination for the 8.4 and 20.7 keV nuclear transitions in 169Tm
NASA Astrophysics Data System (ADS)
Inoyatov, A. Kh.; KovalĒk, A.; Filosofov, D. V.; RyÜav², M.; Perevoshchikov, L. L.; Gurov, Yu. B.
Energies of 8410.1 ▒ 0.4, 20743.9 ▒ 0.3, and 63121.6 ▒ 1.2 eV were determined for the 8.4 keV M1 + E2, 20.7 keV M1 + E2, and 63.1 keV E1 nuclear transitions in 169Tm (generated in the EC decay of 169Yb, respectively, by means of the internal conversion electron spectroscopy. The 169Yb sources used were prepared by vacuum evaporation deposition on polycrystalline carbon and platinum foils as well as by ion implantation at 30keV into a polycrystalline aluminum foil. The relevant conversion electron spectra were measured by a high-resolution combined electrostatic electron spectrometer at 7 eV instrumental resoluition. Values of 0.0326(14) and 0.0259(17) were derived from our experimental data for the E2 admixture parameter |? ( E2/ M1)| for the 8.4 and 20.7 keV transitions, respectively. A possible effect of nuclear structure on multipolarity of the 20.7 keV transition was also investigated.
Eu(2+) luminescence in strontium aluminates.
Dutczak, D; J³stel, T; Ronda, C; Meijerink, A
The luminescence properties of Eu(2+) doped strontium aluminates are reported and reviewed for a variety of aluminates, viz. SrAl12O19, SrAl4O7, Sr4Al14O25, SrAl2O4 and Sr3Al2O6. The aim of the research is to investigate the role of local coordination and covalency of the aluminate host lattice, related to the Sr/Al ratio, on the optical properties of the Eu(2+) ion. The UV and VUV excited luminescence spectra as well as luminescence decay curves were recorded to characterize the luminescence properties of the investigated aluminates. The emission of Eu(2+) ions varies over a wide spectral range, from ultraviolet (UV) to red, for the series of aluminates. The variation in emission color can be related to the crystal-field splitting of the 5d levels and the covalent interaction with the surrounding oxygen anions. In the least covalent material, viz. SrAl12O19:Eu(2+), narrow line emission due to the (6)P7/2-(8)S7/2 transition occurs at 4 K, indicating that the 4f(6)5d excited state is situated above the (6)P7/2(4f(7)) excited state around 360 nm. The most alkaline material, viz. Sr3Al2O6:Eu(2+) is the most covalent host and exhibits several d-f emission bands in the yellow to red spectral range due to the Eu(2+) ions located on different crystallographic Sr(2+) sites. The Eu(2+) emission spectra in the other aluminates confirm the trend that with increasing Sr/Al ratio the Eu(2+) emission shifts to longer wavelengths. Interesting differences are observed for the Eu(2+) from different crystallographic sites which cannot always be related with apparent differences in the first oxygen coordination sphere. The discussion gives insight into how in a similar class of materials, strontium aluminates, the emission color of Eu(2+) can be tuned over a wide spectral region. PMID:25993133
Yb:FAP and related materials, laser gain medium comprising same, and laser systems using same
Krupke, W.F.; Payne, S.A.; Chase, L.L.; Smith, L.K.
An ytterbium doped laser material remarkably superior to all others, including Yb:YAG, comprises ytterbium doped apatite (Yb:Ca{sub 5}(PO{sub 4}){sub 3}F) or Yb:FAP, or ytterbium doped crystals structurally related to FAP. The new laser material is used in laser systems pumped by diode pump sources having an output near 0.905 microns or 0.98 microns, such as InGaAs and AlInGaAs, or other narrowband pump sources near 0.905 microns or 0.98 microns. The laser systems are operated in either the conventional or ground state depletion mode.
Yb:FAP and related materials, laser gain medium comprising same, and laser systems using same
Krupke, William F. (Pleasanton, CA); Payne, Stephen A. (Castro Valley, CA); Chase, Lloyd L. (Livermore, CA); Smith, Larry K. (Salida, CA)
An ytterbium doped laser material remarkably superior to all others, including Yb:YAG, comprises Ytterbium doped apatite (Yb:Ca.sub.5 (PO.sub.4).sub.3 F) or Yb:FAP, or ytterbium doped crystals that are structurally related to FAP. The new laser material is used in laser systems pumped by diode pump sources having an output near 0.905 microns or 0.98 microns, such as InGaAs and AlInGaAs, or other narrowband pump sources near 0.905 microns or 0.98 microns. The laser systems are operated in either the conventional or ground state depletion mode.
Bistable chromatic switching in Yb3+ -doped NdPO4 crystals
NASA Astrophysics Data System (ADS)
R¾denas, A.; Jaque, D.; Solķ, J. GarcĒa; Speghini, A.; Bettinelli, M.; Cavalli, E.
Pump-induced chromatic switching is reported for an 808nm pumped Yb3+ -doped NdPO4 crystal. This effect is based on the interplay between the Nd3+?Yb3+ energy transfer processes and on the large pump-induced thermal loading characteristic of this neodymium compound. For temperatures below 300K , a noticeable hysteresis is observed in the relative Nd3+ and Yb3+ contributions to the emission spectra; this leads to a bistable chromatic switching. This optical bistability is related to a nonlinear pump-induced heating rate that produces abrupt changes in the local temperature.
Social Stories[TM] for Children with Disabilities
ERIC Educational Resources Information Center
Reynhout, Georgina; Carter, Mark
A review of the empirical research literature on Social Stories[TM] is presented, including a descriptive review and single-subject meta-analysis of appropriate studies. Examination of data suggests the effects of Social Stories[TM] are highly variable. Interpretations of extant studies are frequently confounded by inadequate participantģ
ISI TechnicalManual ISI/TM-88-197
Robins, Gabriel
ISI TechnicalManual ISI/TM-88-197 February1988 University ofSouthern California Gabriel Robins %% ... ... .. The ISI Grapher Manual INFORMATION SCIENCES 213/822-1511 INSTITUTEJ f-"-676 292-t5466Admiralty Way. MONITORING ORGANIZATION REPORT NUMBER(S) ISI/TM-88-197 6a. NAME OF PERFORMING ORGANIZATION USC
Full Immersive Virtual Environment Cave[TM] in Chemistry Education
ERIC Educational Resources Information Center
Limniou, M.; Roberts, D.; Papadopoulos, N.
By comparing two-dimensional (2D) chemical animations designed for computer's desktop with three-dimensional (3D) chemical animations designed for the full immersive virtual reality environment CAVE[TM] we studied how virtual reality environments could raise student's interest and motivation for learning. By using the 3ds max[TM], we can visualizeģ
of this Contract. TM02 - APPLICABLE LAW The rights and obligations of the parties hereto shall be governed by this Agreement and construed in accordance with federal law of government contracts. TM03 - ASSIGNMENT Contractor personally violate any requirements of this contract may be denied access to any Government site
Relative radiometric calibration of LANDSAT TM reflective bands
NASA Technical Reports Server (NTRS)
Barker, J. L.
A common scientific methodology and terminology is outlined for characterizing the radiometry of both TM sensors. The magnitude of the most significant sources of radiometric variability are discussed and methods are recommended for achieving the exceptional potential inherent in the radiometric precision and accuracy of the TM sensors.
ORNL/TM-1999/216 Characterizing Land Cover, LAI,
ORNL/TM-1999/216 BigFoot Characterizing Land Cover, LAI, and NPP at the Landscape Scale for EOS/MODIS Validation Field Manual Version 2.1 #12;ORNL/TM-1999/216 Environmental Sciences Division BIGFOOT FIELD MANUAL
SpellRead[TM]. What Works Clearinghouse Intervention Report
ERIC Educational Resources Information Center
What Works Clearinghouse, 2013
"SpellRead"[TM], formerly known as "SpellRead Phonological Auditory Training"[R], is a small-group literacy program for struggling readers in grades 2-12. "SpellRead"[TM] integrates the auditory and visual aspects of the reading process and emphasizes specific skill mastery through systematic and explicit instruction. Students are taught toģ
Whole Systems Modelling with iThinkTM and STELLATM
Oakley, Jeremy
Whole Systems Modelling with iThinkTM and STELLATM Subject Introduction to Systems Thinking and System Dynamics Modelling and Simulation using the iThinkTM or STELLATM software Suitable for The full responsibilities. Learn the basic of systems thinking and building simple models to demonstrate and communicate
Whole Systems Modelling with iThinkTM and STELLATM
Oakley, Jeremy
Whole Systems Modelling with iThinkTM and STELLATM Subject Introduction to Systems Thinking and System Dynamics Modelling and Simulation using the iThinkTM or STELLATM software Suitable for The full change management responsibilities. Learn the basic of systems thinking and building simple models
ORNL/TM-2001/277 Demonstration Project 111
ORNL/TM-2001/277 Demonstration Project 111 ITS/CVO Technology Truck Final Project Report December 2001 Prepared by G. J. Capps, ORNL Project Manager K. P. Gambrell, Technical Associate K. L. Johnson Government or any agency thereof. #12;ORNL/TM-2001/277 DEMONSTRATION PROJECT 111 ITS/CVO TECHNOLOGY TRUCK
ORNL/TM-2012/143 Light Commercial Building Flexible
Oak Ridge National Laboratory
ORNL/TM-2012/143 Light Commercial Building Flexible Research Platforms April 2012 Prepared Government or any agency thereof. #12;ORNL/TM-2012/143 Energy and Transportation Science Division LIGHT....................................................................... 2 1.4 RELATIONSHIP OF FRPS TO ORNL'S CENTERS OF EXCELLENCE FOR BTP ............. 3 2. RESEARCH
Oak Ridge National Laboratory
ORNL/TM-2004/91 MEASUREMENT PRACTICES FOR RELIABILITY AND POWER QUALITY A TOOLKIT OF RELIABILITY MEASUREMENT PRACTICES June 2004 #12;#12;ORNL/TM-2004/91 MEASUREMENT PRACTICES FOR RELIABILITY AND POWER QUALITY A TOOLKIT OF RELIABILITY MEASUREMENT PRACTICES John D. Kueck and Brendan J. Kirby Oak Ridge
The ground state of dilute Tm systems is degenerate
M. Bali±a; A. A. Aligia
The ground state of the appropriate generalization of the impurity Anderson model for valence fluctuations between two realistic Tm+2 and Tm+3 configurations is obtained, in the narrowband limit, using the Lanczos' method. This limit describes the strong-coupling fixed point of renormalization group treatments for intermediate valence and Kondo impurities. The resulting ground state is highly degenerate and contains states of
ORNL/TM-2001-266 Environmental Evaluation of New
ORNL/TM-2001-266 Environmental Evaluation of New Generation Vehicles and Vehicle Components/TM-2001-266 Engineering Science and Technology Division ENVIRONMENTAL EVALUATION OF NEW GENERATION VEHICLES AND VEHICLE COMPONENTS December 2001 Susan M. Schexnayder1 Sujit Das2 Rajive Dhingra1 Jonathan G
Unified formalism for TE and TM beam propagators
Leon Poladian; Francois J. Ladouceur
The unification of transverse electric (TE) and transverse magnetic (TM) beam propagation algorithms is made possible through a transformation which converts the wave equation for TM fields in planar waveguides into a form identical to the corresponding TE wave equation. The transformation can be applied to any smoothly varying waveguide. This transformation can be made independently of any paraxial or
Accelerated Math[TM]. What Works Clearinghouse Intervention Report
ERIC Educational Resources Information Center
What Works Clearinghouse, 2011
"Accelerated Math"[TM], published by Renaissance Learning, is a software tool used to customize assignments and monitor progress in math for students in grades 1-12. The "Accelerated Math"[TM] software creates individualized assignments aligned with state standards and national guidelines, scores student work, and generates reports on studentģ
Superconducting Wires Enabled by Nanodots wins Nano50TM Award
. Ę Awarded the Nano 50TM Award from Nanotech Briefs« Magazine for technology. Developers: Ę A. Goyal S. KangSuperconducting Wires Enabled by Nanodots wins Nano50TM Award HTS Wires Enabled via 3D Self . Ę The technology meets performance requirements for most large-scale applications of HTS, including underground
Inside Linden Lab: Second Life [TM] for Educators
ERIC Educational Resources Information Center
Atkinson, Tom
A new culture called Second Life [TM] has emerged that promises innovative strategies for everything from social interactions to business. Some educators believe it may hold new and unique opportunities for teaching and learning. Second Life [TM] (SL) is the creation of Linden Labs, a San Francisco-based corporation defined by its creators as "anģ
Interfacial effects in Fe/4d TM multilayers (abstract)
Tomaz, M.A.; Antel, W.J., Jr.; Harp, G.R. [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States)] [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); OBrien, W.L. [Synchrotron Radiation Center, University of Wisconsin, Stoughton, Wisconsin 53589 (United States)] [Synchrotron Radiation Center, University of Wisconsin, Stoughton, Wisconsin 53589 (United States)
We have studied Fe/TM multilayers (TM=Mo, Nb, Ru, Rh, Pd) using x-ray magnetic circular dischroism, magneto-optical Kerr effect, and x-ray diffraction. A diverse set of magnetic behaviors emerges from the analysis. We focus on the behavior which can be attributed to the existence of a physical interface between different chemical species. In particular, we have measured an enhanced Fe moment in some cases (TM=Ru, Mo, Rh, Pd) yet not in others (TM=Nb). These results will be discussed, including the relative orbital and spin moments and the effects of alloying at the interface. The measured induced moments in the TM layer will be presented as well where applicable. {copyright} {ital 1997 American Institute of Physics.}
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Facebook and its EU users Applicability of the EU data protection law
Boyer, Edmond
Facebook and its EU users Ł Applicability of the EU data protection law to US based SNS* Aleksandra (SNS). The analysis will be conducted on the example of Facebook, which is one of the most popular SNS. The goal of the paper is to examine whether European users of Facebook can rely on their national data
Magnetic susceptibility and EPR of europium compounds: EuGa2S4, EuGa2Se4 and EuAl2S4
R. Rimet; R. Buder; C. Schlenker; J. V. Zanchetta
The magnetic susceptibility of EuGa2S4, EuGa2Se4 and EuAl2S4, measured between 4.2 and 300 K, is found to obey Curie-Weiss laws. EPR spectra show a single broad line at g = 2.00, characteristic of Eu2+; the linewidth (in the range 900-1500 G at 200 K) is found to increase steeply below ∽ 50 K.
High-resolution laser spectroscopy of YbBr. Part I: the B2? +? X2? + system
NASA Astrophysics Data System (ADS)
Dickinson, Cameron S.; Coxon, John A.
The highly congested spectra of the 0-0, 1-0, 0-1, and 1-1 bands of the B2? +? X2? + system of YbBr have been analyzed for the 174Yb 79Br, 174Yb 81Br, 172Yb 79Br, and 172Yb 81Br isotopomers. A multi-isotopomer, multi-band fit of all data was employed in the determination of an isotopically consistent set of equilibrium parameters. From the fitted Be values, estimates of the equilibrium bond lengths for the B and X states of YbBr were calculated as 2.58275(1) and 2.645386(4) ┼, respectively. Differences in the electronic term values between the 172YbBr and 174YbBr isotopomers have been interpreted in terms of the Field Shift Effect. This effect, well known in atomic spectroscopy, is the result of a small difference in the nuclear charge distribution between the 172Yb and 174Yb nuclei, and has been observed for very few molecules.
YB-1 expression promotes epithelial-to-mesenchymal transition in prostate cancer that is inhibited by a small molecule fisetin
Khan, Mohammad Imran; Adhami, Vaqar Mustafa; Lall, Rahul Kumar; Sechi, Mario; Joshi, Dinesh C.; Haidar, Omar M.; Syed, Deeba Nadeem; Siddiqui, Imtiaz Ahmad; Chiu, Shing-Yan; Mukhtar, Hasan
Epithelial-to-mesenchymal transition (EMT) plays an important role in prostate cancer (PCa) metastasis. The transcription/translation regulatory Y-box binding protein-1 (YB-1) is known to be associated with cancer metastasis. We observed that YB-1 expression increased with tumor grade and showed an inverse relationship with E-cadherin in a human PCa tissue array. Forced YB-1 expression induced a mesenchymal morphology that was associated with down regulation of epithelial markers. Silencing of YB-1 reversed mesenchymal features and decreased cell proliferation, migration and invasion in PCa cells. YB-1 is activated directly via Akt mediated phosphorylation at Ser102 within the cold shock domain (CSD). We next identified fisetin as an inhibitor of YB-1 activation. Computational docking and molecular dynamics suggested that fisetin binds on the residues from ?1 - ?4 strands of CSD, hindering Akt's interaction with YB-1. Calculated free binding energy ranged from ?11.9845 to ?9.6273 kcal/mol. Plasmon Surface Resonance studies showed that fisetin binds to YB-1 with an affinity of approximately 35 ?M, with both slow association and dissociation. Fisetin also inhibited EGF induced YB-1 phosphorylation and markers of EMT both in vitro and in vivo. Collectively our data suggest that YB-1 induces EMT in PCa and identify fisetin as an inhibitor of its activation. PMID:24770864
The Yb protein defines a novel organelle and regulates male germline stem cell self-renewal in Drosophila melanogaster
Szakmary, Akos; Reedy, Mary; Qi, Hongying
Yb regulates the proliferation of both germline and somatic stem cells in the Drosophila melanogaster ovary by activating piwi and hh expression in niche cells. In this study, we show that Yb protein is localized as discrete cytoplasmic spots exclusively in the somatic cells of the ovary and testis. These spots, which are different from all known cytoplasmic structures in D. melanogaster, are evenly electron-dense spheres 1.5 Ąm in diameter (herein termed the Yb body). The Yb body is frequently associated with mitochondria and a less electron-dense sphere of similar size that appears to be RNA rich. There are one to two Yb bodies/cell, often located close to germline cells. The N-terminal region of Yb is required for hh expression in niche cells, whereas the C-terminal region is required for localization to Yb bodies. The entire Yb protein is necessary for piwi expression in niche cells. A double mutant of Yb and a novel locus show male germline loss, revealing a function for Yb in male germline stem cell maintenance. PMID:19433453
Performance of a minimally invasive uncalibrated cardiac output monitoring system (FlotracTM\\/VigileoTM) in haemodynamically unstable patients
F. D. Compton; B. Zukunft; C. Hoffmann; W. Zidek; J.-H. Schaefer
Background. Early haemodynamic assessment is of particular importance in the evaluation of haemodynamically compromised patients, but is often precluded by the invasiveness and com- plexity of the established cardiac output (CO) monitoring techniques. The FloTrac TM \\/Vigileo TM system allows minimally invasive CO determination based on the arterial pressure waveform derived from any standard arterial catheter, and the algorithm underlying
High-spin states in {sup 156}Yb and structure evolutions at large angular momenta in even-A Yb isotopes
Li, Z. Y.; Hua, H.; Wang, S. Y.; Meng, J.; Li, Z. H.; Li, X. Q.; Xu, F. R.; Liu, H. L.; Zhang, S. Q.; Ye, Y. L.; Jiang, D. X.; Zheng, T.; Ma, L. Y.; Lu, F.; Fan, F. Y.; Han, L. Y.; Wang, H.; Xiao, J.; Chen, D.; Fang, X. [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100080 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000 (China); China Institute of Atomic Energy, Beijing 102413 (China)] (and others)
High-spin states of {sup 156}Yb have been studied via the {sup 144}Sm({sup 16}O,4n){sup 156}Yb fusion-evaporation reaction at beam energy 102 MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. In the present work, the negative-parity sequence above the 25{sup -} state was found to be irregular and fragment into many parallel branches. This pattern may related to the excitation from the nucleon in the Z=64,N=82 core. The characteristics of alignment plot and E-GOS curve for the positive-parity yrast sequence in {sup 156}Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. Based on a systematic summary of the available experimental alignments for the even-A {sup 156,158,160,162,164}Yb isotopes, the structural evolutions induced by the increase in angular momentum, as well as by the change in neutron numbers, in these even-A Yb isotopes have been discussed in comparison with the cranked Woods-Saxon-Strutinsky calculations by means of total-Routhian-surface (TRS) methods.
Structural and magnetic study of Yb3+ in the perovskites Sr2YbMO6 (M=Nb, Ta, Sb)
NASA Astrophysics Data System (ADS)
Coomer, Fiona C.; Campbell, John; Giordano, Nico; Collins, Oonagh M.; Cussen, Edmund J.
The compounds Sr2YbNbO6, Sr2YbTaO6 and Sr2YbSbO6 have been prepared using solid state methods by heating pelleted reagents in air at temperatures up to 1400 ░C. Rietveld refinement against room temperature neutron powder diffraction data show that all three compounds crystallise with a cation-ordered variant of the perovskite structure in the P21/n space group. Complete cation ordering occurs between M5+ and Yb3+ over two octahedrally-coordinated sites in the structure and all compounds are stoichiometric in oxygen. The Sb-O bond lengths are similar to related perovskite compounds but differ slightly from those indicated by bond valence sums. Magnetic susceptibility data resemble Curie-Weiss paramagnetic behaviour, but can be better understood as arising from the effect of the octahedral crystal field on the 2F5/2 ground state of Yb3+ leading to a temperature dependent magnetic moment on this ion below 100 K.
New universality class of quantum criticality in Ce- and Yb-based heavy fermions.
Watanabe, Shinji; Miyake, Kazumasa
A new universality class of quantum criticality emerging in itinerant electron systems with strong local electron correlations is discussed. The quantum criticality of a Ce- or Yb-valence transition gives us a unified explanation for unconventional criticality commonly observed in heavy fermion metals such as YbRh(2)Si(2), ?-YbAlB(4), YbCu(5-x)Al(x), and CeIrIn(5). The key origin is due to the locality of the critical valence fluctuation mode emerging near the quantum critical end point of the first-order valence transition, which is caused by strong electron correlations for f electrons. The wider relevance of this new criticality and important future measurements to uncover its origin are also discussed. PMID:22771583
Cell Fate Factor DACH1 Represses YB-1-mediated Oncogenic Transcription and Translation
Wu, Kongming; Chen, Ke; Wang, Chenguang; Jiao, Xuanmao; Wang, Liping; Zhou, Jie; Wang, Jing; Li, Zhiping; Addya, Sankar; Sorensen, Poul H.; Lisanti, Michael P.; Quong, Andrew; Ertel, Adam; Pestell, Richard G.
The epithelial-mesenchymal transition (EMT) enhances cellular invasiveness and confers tumor cells with cancer stem cell like characteristics, through transcriptional and translational mechanisms. The mechanisms maintaining transcriptional and translational repression of EMT and cellular invasion are poorly understood. Herein, the cell fate-determination factor Dachshund (DACH1), suppressed EMT via repression of cytoplasmic translational induction of Snail by inactivating the Y box-binding protein (YB-1). In the nucleus, DACH1 antagonized YB-1-mediated oncogenic transcriptional modules governing cell invasion. DACH1 blocked YB-1-induced mammary tumor growth and EMT in mice. In basal-like breast cancer (BLBC) the reduced expression of DACH1 and increased YB-1, correlated with poor metastasis free survival. The loss of DACH1 suppression of both cytoplasmic translational and nuclear transcriptional events governing EMT and tumor invasion may contribute to poor prognosis in basal-like forms of breast cancer, a relatively aggressive disease subtype. PMID:24335958
Centrosome maturation requires YB-1 to regulate dynamic instability of microtubules for nucleus reassembly
Kawaguchi, Atsushi; Asaka, Masamitsu N.; Matsumoto, Ken; Nagata, Kyosuke
Microtubule formation from the centrosome increases dramatically at the onset of mitosis. This process is termed centrosome maturation. However, regulatory mechanisms of microtubule assembly from the centrosome in response to the centrosome maturation are largely unknown. Here we found that YB-1, a cellular cancer susceptibility protein, is required for the centrosome maturation. Phosphorylated YB-1 accumulated in the centrosome at mitotic phase. By YB-1 knockdown, microtubules were found detached from the centrosome at telophase and an abnormal nuclear shape called nuclear lobulation was found due to defective reassembly of nuclear envelope by mis-localization of non-centrosomal microtubules. In conclusion, we propose that YB-1 is important for the assembly of centrosomal microtubule array for temporal and spatial regulation of microtubules. PMID:25740062
Kondo effect in a novel 5d quasi-skutterudite Yb3Os4Ge13
NASA Astrophysics Data System (ADS)
Shi, Youguo; Yang, Chongli; Wang, Xia; Zhang, Xu; Wu, Desheng; Yang, Yifeng; Luo, Jianlin
We report the crystal growth of a new compound, Yb3Os4Ge13, by using a Bi-flux method. It crystalizes in the quasi-skutterudite-type caged structure with a cubic space group of Pm-3n (No. 223). Magnetic measurements reveal almost fully localized Yb f-moments above 120 K. The resistivity exhibits a crossover from metallic to insulating behavior with a logarithmic increase below ~ 40 K. The specific heat coefficient shows a rapid upturn below ~ 5 K and exceeds 2 J mol-1 K-2 at 2 K. Our experimental analysis and electronic band structure calculations demonstrate that Yb3Os4Ge13 exhibits the Kondo effect due to strong hybridization of the localized Yb f-moments with the p-electrons of the surrounding Ge-cages.
Generation of 150-fs pulses from a diode-pumped Yb:KYW nonlinear regenerative amplifier.
Pouysegur, Julien; Delaigue, Martin; H÷nninger, Clemens; Georges, Patrick; Druon, Frķdķric; Mottay, Eric
Generation of sub-150-fs-level pulses has been obtained from an Yb-doped crystal-based regenerative amplifier by applying an innovative amplification scheme. This scheme is based on optimization of the linear and non-linear phase during the amplification process inside the regenerative amplifier cavity. This technique with Yb:KYW allows to achieve pulse durations from diode-pumped Yb-doped regenerative amplifiers that were up to now only accessible with more complex Ti:sapphire amplifiers. With this Yb-doped tungstate crystal used in regenerative amplifiers, 145 fs pulses centered at 1026 nm with a spectral bandwidth of 14 nm at 50 kHz for an average power of 1.6 W have been generated. PMID:24787830
Preparation and Spectroscopic Properties of Yb:YAG Glass-Ceramics
NASA Astrophysics Data System (ADS)
Lai, Fei; Zhang, Yue-Pin; Xia, Hai-Ping; Zhang, Xin-Ming; Wang, Jin-Hao
Yb3+-doped 32CaO-12Y2O3-24Al2O3-31SiO2-1Yb2O3 glasses were prepared by melting method, and then annealed at 950░C, 1050░C and 1100░C, respectively. We analyzed the crystallographic structures of the glasses annealed at different temperatures by XRD, and observed the glass annealed at 1050░C by TEM. The spectroscopic properties of glass before and after annealing were also investigated. Results show that the glasses annealed at 1050░C are YAG glass-ceramics with no impurity crystalline phase. Variances in the spectroscopic properties before and after heat treatment indicate that Yb3+ ions were preferentially partitioned into the YAG crystal phase, and the transparent Yb:YAG glass-ceramics were obtained.
Anisotropic intermediate valence in Yb2M3Ga9 (M = Rh, Ir)
Christianson, A.D.; Lawrence, J.M.; Lobos, A.M.; Aligia, A.A.; Bauer, E.D.; Moreno, N.O.; Booth, C.H.; Goremychkin, E.A.; Sarrao, J.L.; Thompson, J.D.; Batista, C.D.; Trouw, F.R.; Hehlen, M.P.
The intermediate valence compounds Yb{sub 2}M{sub 3}Ga{sub 9} (M = Rh, Ir) exhibit an anisotropic magnetic susceptibility. We report measurements of the temperature dependence of the 4f occupation number, n{sub f}(T), for Yb{sub 2}M{sub 3}Ga{sub 9} as well as the magnetic inelastic neutron scattering spectrum S{sub mag}({Delta}E) at 12 and 300 K for Yb{sub 2}Rh{sub 3}Ga{sub 9}. Both n{sub f}(T) and S{sub mag}({Delta}E) were calculated for the Anderson impurity model with crystal field terms within an approach based on the non-crossing approximation. These results corroborate the importance of crystal field effects in these materials; they also suggest that Anderson lattice effects are important to the physics of Yb{sub 2}M{sub 3}Ga{sub 9}.
Water quality mapping using Landsat TM imagery
NASA Astrophysics Data System (ADS)
Lim, H. S.; MatJafri, M. Z.; Abdullah, K.; Alias, A. N.; Wong, C. J.; Mustapha-Rosli, M. R.; Mohd Saleh, N.
Environmental monitoring through the method of traditional ship sampling is time consuming and requires a high survey cost. The objective of this study is to evaluate the feasibility of Landsat TM imagery for total suspended solids (TSS) mapping using a newly developed algorithm over Penang Island. The study area is the seawater region around Penang Island, Malaysia. Water samples were collected during a 3-hour period simultaneously with the satellite image acquisition and later analyzed in the laboratory above the study area. The samples locations were determined using a handheld GPS. The satellite image was geometrically corrected using the second order polynomial transformation. The satellite image also was atmospheric corrected by using ATCOR2 image processing software. The digital numbers for each band corresponding to the sea-truth locations were extracted and then converted into reflectance values for calibration of the water quality algorithm. The proposed algorithm is based on the reflectance model that is a function of the inherent optical properties of water, which can be related to its constituent's concentrations. The generated algorithm was developed for three visible wavelenghts, red, green and blue for this study. Results indicate that the proposed developed algorithm was superior based on the correlation coefficient (R) and root-mean-square deviation (RMS) values. Finally the proposed algorithm was used for TSS mapping at Penang Island, Malaysia. The generated TSS map was colour-coded for visual interpretation and image smoothing was performed on the map to remove random noise. This preliminary study has produced a promising result. This study indicates that the empirical algorithm is suitable for TSS mapping around Penang Island by using satellite Landsat TM data.
Doppler-free Yb spectroscopy with the fluorescence spot technique
Nizamani, Altaf H.; McLoughlin, James J.; Hensinger, Winfried K. [Department of Physics and Astronomy, University of Sussex, Falmer, Brighton, East-Sussex, BN1 9QH (United Kingdom)
We demonstrate a simple technique to measure the resonant frequency of the 398.9-nm {sup 1}S{sub 0}{leftrightarrow}{sup 1}P{sub 1} transition for the different Yb isotopes. The technique, which works by observing and aligning fluorescence spots, has enabled us to measure transition frequencies and isotope shifts with an accuracy of 60 MHz. We provide wavelength measurements for the transition that differ from previously published work. Our technique also allows for the determination of Doppler-shifted transition frequencies for photoionization experiments when the atomic beam and the laser beam are not perpendicular and furthermore allows us to determine the average velocity of the atoms along the direction of the atomic beam.
Do YB2/0 cells produce alien sugars?
Quagliaroli, D
Olovnikova et al. ("Impact on N-glycosylation profile of monoclonal anti-D antibodies as a way to control their immunoregulatory and cytotoxic properties" (2012) Biochemistry (Moscow), 77, 925-933) mentioned the presence of "alien sugars" on monoclonal antibodies (mAbs) produced by YB2/0 cell line. We summarize in this paper our previous findings on the glycosylation profile of two anti-D mAbs produced in this cell line (LFB-R297 and LFB-R593, so-called Roledumab). Our results show the absence of any immunogenic glycotopes, and furthermore neither immunogenicity nor other serious adverse reactions were observed during clinical trials. PMID:24460972
Laser-induced luminescence of rare-earth elements in natural fluor-apatites
R. Reisfeld; M. Gaft; G. Boulon; C. Panczer; C. K. J°rgensen
The luminescence spectra of naturally occurring fluor-apatites containing traces of rare-earth elements have been compared with synthetic fluor-apatites to which single rare-earth elements have been intentionally added. Comparison of the laser-induced spectra obtained after different time delays allows identification of the following luminescence centers: Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, Tm3+, Yb3+ and possibly Yb2+. The technique described
The phase diagram of the Eu¢Sn system
A Palenzona; P Manfrinetti; M. L Fornasini
The phase diagram of the Eu¢Sn system has been investigated in the whole composition range using differential thermal analysis, metallographic analysis, X-ray diffraction and electron microscopy. Five intermediate phases have been found. Two of them have been confirmed: EuSn3 (AuCu3-type) and EuSn (CrB-type); while Eu3Sn5 (Pu3Pd5-type), Eu5Sn3 (W5Si3-type) and Eu2Sn (Co2Si-type) have been prepared and characterized for the first time.
The effect of temperature on absorption in end-pumped Yb:YAG thin disk lasers
Seyfollah Toroghi; Ahmad Khayat Jafari; Ala Hashemi Golpayegani
In this paper, the dependence of the absorbed power on the temperature in an end-pumped CW quasi-three-level Yb:YAG thin disk laser is calculated. Here, we have used the temperature-dependent form of the Boltzmann occupation factors, absorption cross-section and thermal conductivity of the Yb:YAG crystal. A Monte Carlo ray tracing code and a 2D finite element analysis (FEA) with the ANSYS
Thermal expansion and specific heat of intermediate valent YbCuAl
R. Pott; R. Schefzyk; D. Wohlleben; A. Junod
The specific heat, thermal expansion and resistivity was measured for the intermediate valence compound YbCuAl and its reference compound LuCuAl between 1.5 and 400 K. All quantities show strong anomalies. The entropy of the specific heat anomaly is found to be nearRĘln9, the value expected for the entropy of a high temperature mixture of Yb-ions in the ratio dictated by
Icosahedral quasicrystal and 1\\/1 cubic approximant in Au-Al-Yb alloys
Tsutomu Ishimasa; Yukinori Tanaka; Shiro Kashimoto
A P-type icosahedral quasicrystal is formed in Au-Al-Yb alloy of which 6-dimensional lattice parameter a6D = 7.448 {\\\\AA}. The composition of the quasicrystal was analyzed to be Au51Al34Yb15. This quasicrystal is formed in as-cast alloys, and is regarded as metastable because of decomposition into other crystalline phases by annealing at 700 \\\\degree C. Among Tsai-type quasicrystals, this quasicrystal is situated
High-energy, diode-pumped, nanosecond Yb:YAG MOPA system
of 15 W at a repetition rate of 10 Hz has been measured. We also present a relay imaging semi-pumped nanosecond multi-pass laser amplification to the joule level using an Yb:YAG slab crystal has been achieved. The seed pulses with a pulse duration of 6.4 ns were generated in a Q-switched Yb:YAG laser
Downconversion for solar cells in NaYF4:Er,Yb
L. Aarts; B. M. van der Ende; A. Meijerink
Downconversion is a promising avenue to boost the efficiency of solar cells by absorbing one higher energy visible photon and emitting two lower energy near-infrared (NIR) photons. Here the efficiency of downconversion for the (Er3+,Yb3+) couple is investigated in NaYF4, a well-known host lattice for efficient upconversion with (Er3+,Yb3+). Analysis of the excitation and emission spectra for NaYF4 doped with
Controlled synthesis and morphology dependent upconversion luminescence of NaYF4:Yb, Er nanocrystals
Yajuan Sun; Yue Chen; Lijin Tian; Yi Yu; Xianggui Kong; Junwei Zhao; Hong Zhang
Size and morphology controlled NaYF4:Yb, Er nanocrystals were synthesized via the hydrothermal method. Polydentate ligands, such as EDTA and citrate, were used in the synthesis of cubic and hexagonal Yb3+, Er3+ codoped NaYF4 nanocrystals as a means of controlling the size and morphology of the nanocrystals. Subsequently, the particle size was found to be dependent on the nucleation rate, which,
NaYF4: Yb,Er-an efficient upconversion phosphor
N. Menyuk; K. Dwight; J. W. Pierce
Studies of the infrared-pumped visible luminescence of NaYF4 : Yb, Er show it to have at least twice the visible output of YF3 : Yb, Er when pumped with a narrow-band excitation source at the optimum frequency. It is also free from saturation effects until very intense excitation levels are reached. The mechanism for red upconversion appears to change with
Strong green upconversion emission in ZrO2:Yb3+Ho3+ nanocrystals
E. de La Rosa; P. Salas; H. Desirena; C. Angeles; R. A. RodrĒguez
Structural and upconversion emission properties of ZrO2:Yb3+-Ho3+ nanocrystals were analyzed as function of Yb3+ concentration. Structural characterization shows a crystallite size up to 80 nm and tetragonal and cubic phase as the main crystalline structures. Strong green (540 nm) and weak red (670 nm) and near infrared (760 nm) emission bands were observed with 968 nm excitation. The upconversion is
"Half-sandwich" Yb(III) single-ion magnets with metallacrowns.
Li, Quan-Wen; Liu, Jun-Liang; Jia, Jian-Hua; Chen, Yan-Cong; Liu, Jiang; Wang, Long-Fei; Tong, Ming-Liang
The first "half-sandwich" Yb(III) single-ion magnets (SIMs) based on [12-MCZn(ii)-4] are reported, in which the central ytterbium ion is coordinated by YbO8 geometry in D4d symmetry. The anisotropic barrier is extracted from the analysis of static, dynamic magnetism and emission spectrum offering an insight into the magneto-optical correlation. PMID:26022279
Fabrication of transparent Yb,Cr:YAG ceramics by a solid-state reaction method
Yusong Wu; Jiang Li; Fagui Qiu; Yubai Pan; Qian Liu; Jingkun Guo
Transparent ytterbium and chromium codoped yttrium aluminum garnet (Yb,Cr:YAG) ceramics, containing Ca as charge counter element and TEOS as sintering aid, were fabricated by a solid-state reaction method using high-purity Y2O3, Al2O3, Cr2O3 and Yb2O3 powders as raw materials. The mixed powder compacts were sintered at 1770░C for 10h under vacuum and annealed at 1450░C for 20h in air. The
Optical properties of Er,Yb co-doped YAG transparent ceramics
Jun Zhou; Wenxin Zhang; Tongde Huang; Liang Wang; Jiang Li; Wenbin Liu; Benxue Jiang; Yubai Pan; Jingkun Guo
The transparent polycrystalline erbium and ytterbium co-doped yttrium aluminum garnet (Er,Yb:YAG) ceramics with various Yb contents from 5% to 25% were prepared by the solid-state reaction and the vacuum-sintering technique. The in-line transmittances of the mirror-polished ceramics exceed 80% from the visible band to the infrared band. The samples are very compact with few pores. The average grain size of
Sintering of Yb 3+:Y 2O 3 transparent ceramics in hydrogen atmosphere
Jian Zhang; Liqiong An; Min Liu; Shunzo Shimai; Shiwei Wang
Highly transparent Yb3+:Y2O3 ceramics with doping concentration up to 40.0 at.% had been fabricated successfully via hydrogen atmosphere sintering, where the raw powders were synthesized by co-precipitation method. The sintering temperature is about 600░C lower than its melting temperature. SEM investigation revealed the average grain size of Yb3+:Y2O3 ceramics sintered at 1850░C for 9h was about 7?m. The highest transmittance
Temperature dependence of the crystal structure and charge ordering in Yb4 As3
U. Staub; M. Shi; C. Schulze-Briese; B. D. Patterson; F. Fauth; E. Dooryhee; L. Soderholm; J. O. Cross; D. Mannix; A. Ochiai
Resonant and nonresonant x-ray scattering, combined with x-ray absorption data, are presented on Yb4As3 . The nonresonant data allow a detailed determination of the low-temperature crystal structure and its evolution as a function of temperature. Bond-valence-sum calculations are performed and compared with theoretical predictions. Using the structural knowledge, the energy dependence, near the Yb L3 edge, of particular x-ray reflections
Alternative Splicing of Transcripts from crtI and crtYB Genes of Xanthophyllomyces dendrorhous
P. Lodato; J. Alcaino; S. Barahona; P. Retamales; V. Cifuentes
Xanthophyllomyces dendrorhous is one of the relevant sources of the carotenoid astaxanthin. In this paper, we describe for the first time cloning of unexpected cDNAs obtained from the crtI and crtYB genes of X. dendrorhous strain UCD 67-385. The cDNA of the crtI gene conserves 80 bp of the first intron, while the cDNA of the crtYB gene conserves 55
Search for a ferromagnetic quantum criticality in YbIn11-xRhxCu4
Y. Tokiwa; F. Ronning; V. Fritsch; R. Movshovich; J. D. Thompson; J. L. Sarrao
The geometrically frustrated system YbIn1-xRhxCu4 is investigated in order to search for a quantum criticality associated with ferromagnetic correlations. The undoped YbInCu4 undergoes a first-order isostructural valance transition at 42K. The valance transition is suppressed with Rh substitution of xś0.3 and ferromagnetic correlations grow with increasing Rh content as can be seen from the increasing Weiss temperature in magnetic susceptibility.
Effects of Eu concentration control on crystal growth and scintillation properties for Eu:LiSrAlF6 crystals
NASA Astrophysics Data System (ADS)
Suzuki, S.; Yokota, Y.; Yamaji, A.; Kurosawa, S.; Kamada, K.; Yoshikawa, A.
Eu doped LiSrAlF6 (Eu:LiSAF) crystals with various Eu concentrations were grown by a micro-pulling-down (?-PD) method and the effects of Eu concentration control on crystal growth and scintillation properties for Eu:LiSAF crystals were investigated as a neutron scintillator. As-grown Eu0.3%:LiSAF crystal had no visible inclusion while milky parts were observed in the crystals with higher Eu contents. The secondary phases with the chemical composition of EuF2 or EuF3 in the Eu:LiSAF matrix were observed for the crystals with high Eu contents while the secondary phase couldnÆt be observed in the powder XRD patterns. In the radioluminescence spectra of Eu:LiSAF crystals under ?-ray irradiation, emission peaks around 375 nm originated from 5d-4f transition of Eu2+ ion were observed. The light yields systematically increased with an increase of actual Eu contents in the crystals and the decay times were 1490-1620 ns.
Synthesis, Structure, and Transport Properties of YbSb2Te4 and YbSb4Te7 for Thermoelectric Applications
NASA Technical Reports Server (NTRS)
Guloy, Amado S.
Very little work has been done in the Yb-Sb-Te system of compounds. Exploratory synthesis of various compounds in the system has been performed in the search for new thermoelectric materials. The compounds in the system were examined due to the fact that the system is known to act as a concentrated Kondo system, a heavy fermion. Heavy fermions are known to possess high densities of state which are useful in thermoelectric applications. TWO compounds in the system, YbSb2Te4 and YbSb4Te7, have been successfully synthesized in bulk by two methods: low temperature mechanical alloying and high temperature direct synthesis. The Hall mobility, Seebeck coefficient, electrical resistivity, and thermal conductivity were measured on both the unannealed and annealed compounds up to 550 C to determine the dimensionless thermoelectric figure of merit, ZT. The results indicate that both compounds make promising candidates for use in thermoelectric devices.
Zeeman relaxation of magnetically trapped Eu atoms
Suleimanov, Yury V. [Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom)
We perform rigorous quantum mechanical calculations for collisions between magnetically trapped Eu atoms to elucidate the results of recent experimental studies. We show that the relaxation from the maximally stretched m{sub s}=7/2 level is entirely determined by the magnetic dipole-dipole interaction and analyze the role of the electronic spin-exchange interaction in transitions from the lower-energy Zeeman levels. The relaxation of the m{sub s}=5/2 state is shown to be very sensitive to the spin-exchange parameter that determines the splitting between the lowest electronic states of the Eu dimer. We suggest that cold collision experiments with trapped atoms can be used as a tool for obtaining accurate information on the electronic spin anisotropy in complex molecules such as Eu{sub 2}.
A dosimetric comparison of 169Yb versus 192Ir for HDR prostate brachytherapy.
Lymperopoulou, G; Papagiannis, P; Sakelliou, L; Milickovic, N; Giannouli, S; Baltas, D
For the purpose of evaluating the use of 169Yb for prostate High Dose Rate brachytherapy (HDR), a hypothetical 169Yb source is assumed with the exact same design of the new microSelectron source replacing the 192Ir active core by pure 169Yb metal. Monte Carlo simulation is employed for the full dosimetric characterization of both sources and results are compared following the AAPM TG-43 dosimetric formalism. Monte Carlo calculated dosimetry results are incorporated in a commercially available treatment planning system (SWIFT), which features an inverse treatment planning option based on a multiobjective dose optimization engine. The quality of prostate HDR brachytherapy using the real 192Ir and hypothetical 169Yb source is compared in a comprehensive analysis of different prostate implants in terms of the multiobjective dose optimization solutions as well as treatment quality indices such as Dose Volume Histograms (DVH) and the Conformal Index (COIN). Given that scattering overcompensates for absorption in intermediate photon energies and distances in the range of interest to prostate HDR brachytherapy, 169Yb proves at least equivalent to 192Ir irrespective of prostate volume. This has to be evaluated in view of the shielding requirements for the 169Yb energies that are minimal relative to that for 192Ir. PMID:16475783
Electronic band structure and Kondo coupling in YbRh2Si2
Wigger, G.A.
The electronic band structure of YbRh2Si2 is calculated in a relativistic framework including correlation corrections and magnetization of the Yb ion and compared to detailed angle-resolved photoemission spectra. The photoemission spectra for LuRh2Si2 are used as reference to identify electronic bands with no f symmetry. The calculated band structure manifests a 4f13 spin-polarized configuration leaving the unoccupied state at 1.4eV above the Fermi energy. At the band theory level, the 4f bands are located far below the Fermi level and the anisotropic Coulomb interaction within the 4f shell spreads the multilevel into broader 4f complexes below -2.5eV . The photoemission spectra obtained on YbRh2Si2 show a clear f -multilevel splitting into j=7/2 and 5/2 excitations. The interaction of the 4f7/2 levels close to the Fermi energy with two conduction bands shows visible hybridization gaps of 45 and 80meV, respectively. We discuss the origin of these excitations and provide an analysis according to Anderson's single-impurity model with parameters suggested by the band-structure calculation and the photoemission spectra. Both experiment and theory indicate nearly identical Fermi surfaces for LuRh2Si2 and YbRh2Si2 . The valency of Yb in YbRh2Si2 is estimated to be close to +3.
Optimization of signal gain and core composition for low photodegradation in Yb-doped fiber amplifiers
NASA Astrophysics Data System (ADS)
Laperle, Pierre; Desbiens, Louis; Zheng, Huimin; Le Foulgoc, Karine; Drolet, Mathieu; Deladurantaye, Pascal; Proulx, Antoine; Taillon, Yves
Photodarkening and photobleaching processes affect the level of photodegradation of Yb-doped fibers. Characterization and modeling of each process is crucial to understand how to optimize the operating conditions of fiber amplifiers and lasers to obtain acceptable output power degradation. We show that photobleaching is a key factor in the modeling and simulation of a 10-ns pulsed Yb-doped LMA fiber amplifier. Each parameter of the model was separately determined from induced excess loss measurements under selective pump and wavelength excitations. The model was used to simulate accurately the measured fiber amplifier degradation. Optimized fiber length and gain were calculated to improve the output power stability over time and increase the fiber lifetime. Furthermore, eight fibers have been fabricated with various Yb, Al, and P content using the MCVD process to optimize the core composition. The level of photodarkening in each fiber was evaluated by measuring separately rate coefficient and excess loss. It was found that all fibers followed a similar inversion-dependent rate while the maximum excess loss was dependent on the ratios [Al]/[Yb] and [P]/[Yb]. The proposed model allows for rapid evaluation and optimization of fiber parameters and operation conditions to assist Yb-doped laser system design in achieving the desired performance with low photodegradation.
Structural and spectroscopic properties of Yb│?-doped MgAl?O? nanocrystalline spinel.
Wiglusz, Rafal J; Boulon, Georges; Guyot, Yannick; Guzik, Malgorzata; Hreniak, Dariusz; Strek, Wieslaw
Magnesium spinel (MgAl2O4) powders doped with Yb(3+) ions have been synthesized by a sol-gel method and heat-treated in the range of 700-1000 ░C for 3 h. XRD patterns indicated that the powders have a cubic structure with high crystallite dispersion. Nanoparticles in the range of 10-30 nm are obtained as a function of the dopant concentration and sintering temperature. The main Yb(3+) zero-phonon line is located at 976 nm. The spectroscopic properties of the Yb(3+) ions are characterized by broad absorption spectroscopy and emission spectroscopy. Even at low temperature, the spectra reveal a strong distorted spinel lattice due to the high inversion rate between Mg(2+) tetrahedral sites and Al(3+) octahedral sites. The substitution of Mg(2+) ions by Yb(3+) ions favors the creation of Yb(3+) ion pairs which are observed in the cooperative luminescence spectra at around 500 nm. The luminescence decays are influenced by both the Yb(3+) content, the energy transfer between ions and by the presence of pairs and aggregates. Detailed analysis of the observed structural and spectroscopic measurements has been described in this manuscript. PMID:24699861
Lanthanide near infrared imaging in living cells with Yb3+ nano metal organic frameworks
Foucault-Collet, Alexandra; Gogick, Kristy A.; White, Kiley A.; Villette, Sandrine; Pallier, AgnĶs; Collet, Guillaume; Kieda, Claudine; Li, Tao; Geib, Steven J.; Rosi, Nathaniel L.; Petoud, Stķphane
We have created unique near-infrared (NIR)¢emitting nanoscale metal-organic frameworks (nano-MOFs) incorporating a high density of Yb3+ lanthanide cations and sensitizers derived from phenylene. We establish here that these nano-MOFs can be incorporated into living cells for NIR imaging. Specifically, we introduce bulk and nano-Yb-phenylenevinylenedicarboxylate-3 (nano-Yb-PVDC-3), a unique MOF based on a PVDC sensitizer-ligand and Yb3+ NIR-emitting lanthanide cations. This material has been structurally characterized, its stability in various media has been assessed, and its luminescent properties have been studied. We demonstrate that it is stable in certain specific biological media, does not photobleach, and has an IC50 of 100 ?g/mL, which is sufficient to allow live cell imaging. Confocal microscopy and inductively coupled plasma measurements reveal that nano-Yb-PVDC-3 can be internalized by cells with a cytoplasmic localization. Despite its relatively low quantum yield, nano-Yb-PVDC-3 emits a sufficient number of photons per unit volume to serve as a NIR-emitting reporter for imaging living HeLa and NIH 3T3 cells. NIR microscopy allows for highly efficient discrimination between the nano-MOF emission signal and the cellular autofluorescence arising from biological material. This work represents a demonstration of the possibility of using NIR lanthanide emission for biological imaging applications in living cells with single-photon excitation. PMID:24108356
Discovery of the 151Eu ? decay
NASA Astrophysics Data System (ADS)
Casali, N.; Nagorny, S. S.; Orio, F.; Pattavina, L.; Beeman, J. W.; Bellini, F.; Cardani, L.; Dafinei, I.; Di Domizio, S.; Di Vacri, M. L.; Gironi, L.; Kosmyna, M. B.; Nazarenko, B. P.; Nisi, S.; Pessina, G.; Piperno, G.; Pirro, S.; Rusconi, C.; Shekhovtsov, A. N.; Tomei, C.; Vignati, M.
We report on the first compelling observation of ? decay of 151Eu to the ground state of 147Pm. The measurement was performed using a 6.15 g Li6Eu(BO3)3 crystal operated as a scintillating bolometer. The Q-value and half-life measured are: Q = 1948.9▒6.9(stat.) ▒ 5.1(syst.) keV, and T1/2 = (4.62 ▒ 0.95(stat.) ▒ 0.68(syst.)) ū 1018 y. The half-life prediction of nuclear theory using the Coulomb and proximity potential model are in good agreement with this experimental result.
College of Europe: EU Diplomacy Papers
NSDL National Science Digital Library
Persons interested in the affairs of Europe will find the College of Europe's Diplomacy Papers site to be most helpful. These working papers are part of a series "dedicated to the interdisciplinary study of the European Union's external relations and external aspects of EU internal policies." Currently, the site contains about two dozen papers that date back to 2006. The papers are authored by a range of experts, including individuals from the University of Dresden, the University of Heidelberg, and the Universite Libre de Bruxelles. Some of the recent papers include "A Misleading Promise? Rethinking European Support for Biofuels" and "The EU and Iran's Nuclear Programme: Testing the Limits of Coercive Diplomacy".
The EU's Dark Hour: Special Report
NSDL National Science Digital Library
Released on March 15, 1999, a 140-page report by independent experts looked into charges of widespread fraud, nepotism, and corruption in the European Commission, the executive body of the EU, and found numerous cases where "commissioners or the Commission as a whole bear responsibility for instances of fraud, irregularities or mismanagement." In response, the President of the Commission, who is also the chief executive of the EU, and nineteen other senior officials abruptly resigned on March 16. This would be roughly equivalent to the entire US Cabinet resigning. Users interested in further analysis of the crisis and the latest developments will want to visit the BBC Special Report site.
The European Union (EU) Agenda 2000
NSDL National Science Digital Library
The European Commission released its opinions on the ten applications for EU membership from Central and Eastern Europe in July 1997. They were released with documents outlining the "Agenda 2000" program, which "comprises the Commission's proposals for agricultural, structural and horizontal policies, a reinforced preaccession strategy, and the financial framework beyond 1999." At the EU's US homepage, users can view Commission Opinions on Applicants for Enlargement of the Union and an Executive Summary of the Applicant Opinions. The two volume Agenda 2000 program (459k combined) as well as press notes on both issues are also available.
Laser-diode-pumped Yb:YAG laser as a new pump source and its application to an Er3+, Yb3+-codoped high-output-power fiber amplifier
T. Kasamatsu; T. Sumiyoshi; H. Sekita
. ĀĀWe propose a laser-diode-pumped Yb:YAG laser as a novel practical fiber amplifier pump source, and describe its first successful\\u000a application of high-output-power operation (850ĀmW=+29.3ĀdB?m) of an Er3+,Yb3+-codoped fiber amplifier at 1.55Ā?m. We have developed both bulk and microchip Yb:YAG lasers and obtained 3.3ĀW and 2.7ĀW,\\u000a respectively, in the cw mode at room temperature. Laser-diode-pumped Yb:YAG lasers are shown to
Quasi four-level Tm:LuAG laser
NASA Technical Reports Server (NTRS)
Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Hutcheson, Ralph L. (Inventor); Rodriguez, Waldo J. (Inventor)
A quasi four-level solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG-based host material doped to a final concentration between about 2% and about 7% thulium (Tm) ions. For the more heavily doped final concentrations, the LuAG-based host material is a LuAG seed crystal doped with a small concentration of Tm ions. Laser diode arrays are disposed transversely to the laser crystal for energizing the Tm ions.
Stimulated Raman adiabatic passage in Tm{sup 3+}:YAG
Alexander, A. L.; Lauro, R.; Louchet, A.; Chaneliere, T.; Le Goueet, J. L. [Laboratoire Aime Cotton, CNRS-UPR 3321, University Paris-Sud, Bat. 505, 91405 Orsay Cedex (France)
We report on the experimental demonstration of stimulated Raman adiabatic passage in a Tm{sup 3+}:YAG crystal. Tm{sup 3+}:YAG is a promising material for use in quantum information processing applications, but as yet there are few experimental investigations of coherent Raman processes in this material. We investigate the effect of inhomogeneous broadening and Rabi frequency on the transfer efficiency and the width of the two-photon spectrum. Simulations of the complete Tm{sup 3+}:YAG system are presented along with the corresponding experimental results.
Tm:germanate Fiber Laser: Tuning And Q-switching
NASA Technical Reports Server (NTRS)
Barnes, Norman P.; Walsh, Brian M.; Reichle, Donald J.; DeYoung, R. J.; Jiang, Shibin
A Tm:germanate fiber laser produced >0.25 mJ/pulse in a 45 ns pulse. It is capable of producing multiple Q-switched pulses from a single p ump pulse. With the addition of a diffraction grating, Tm:germanate f iber lasers produced a wide, but length dependent, tuning range. By s electing the fiber length, the tuning range extends from 1.88 to 2.04 ?m. These traits make Tm:germanate lasers suitable for remote sensin g of water vapor.
Photoexcitation of Yb-doped aluminosilicate fibers at 250 nm: evidence for excitation transfer from oxygen deficiency centers to Yb{sup 3+}
Carlson, C. G. [Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Present address: Laser and Optics Research Center, USAF Academy, Colorado Springs, Colorado 80840 (United States); Keister, K. E.; Dragic, P. D.; Eden, J. G. [Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Croteau, A. [INO, 2740 Einstein Street, Quebec City, Quebec G1P 4S4 (Canada)
Emission spectra in the {approx}240-1100 nm wavelength region as well as the temporally resolved decay of Yb{sup 3+} and point defect spontaneous emission have been recorded when aluminosilicate optical fibers doped with Yb are irradiated with {approx}160 fs laser pulses having a central wavelength of {approx}250 nm (({Dirac_h}/2{pi}){omega}=5 eV). Photoexcitation of the fibers in this region of the deep ultraviolet (UV) provides access simultaneously to the Type II Si oxygen deficiency center (ODC), the non-bridging oxygen hole center (NBOHC: an oxygen-excess defect), and the Ge ODC. Emission from all of these defects in the ultraviolet and/or visible is observed, as is intense fluorescence at 976 nm from Yb{sup 3+}. Absorption measurements conducted in the {approx}230-265 nm region with a sequence of UV light-emitting diodes reveal a continuum peaking at {approx}248 nm and having a spectral width of {approx}18 nm (FWHM), confirming that the 250 nm laser pump is photoexciting predominantly the ODC. The temporal histories of the optically active defect and rare earth ion emission waveforms, in combination with time-integrated spectra, suggest that the Si ODC(II) triplet state directly excites Yb{sup 3+} as well as at least one other intrinsic defect in the silica network. Prolonged exposure of the Yb-doped fibers to 250 nm radiation yields increased Yb{sup 3+}, NBOHC, and Si ODC(II) singlet emission which is accompanied by a decline in Si ODC(II) triplet fluorescence, thus reinforcing the conclusion--drawn on the basis of luminescence decay constants--that the triplet state of Si ODC(II) is the immediate precursor to the NBOHC and is partially responsible for Yb ion emission at 976 nm. This conclusion is consistent with the observation that exposure of fiber to 5 eV radiation slightly suppresses ODC absorption in the {approx}240-255 nm region while simultaneously introducing an absorption continuum extending from 260 nm to below 235 nm (({Dirac_h}/2{pi}){omega}{approx_equal}5.28 eV). These results suggest that ODC{yields}E{sup '} center conversion assumes a role in excitation transfer to Yb{sup 3+}.
Luminescence and decay kinetics of Yb 2+ in LiCaAlF 6 single crystal host
NASA Astrophysics Data System (ADS)
Nikl, M.; Bensalah, A.; Mihokova, E.; Hybler, J.; Sato, H.; Fukuda, T.; Boulon, G.
Single crystals of Yb-doped LiCaAlF 6 were grown by the Czochralski technique under CF 4 atmosphere. Photoluminescence and decay kinetics of Yb 2+ center in the LiCalF 6 single crystal host is described in 4-300 K. Phenomenological two excited-state-level model is introduced to obtain quantitative characteristics of the excited state dynamics of Yb 2+ emission center.
Near-IR Photoresponse in New Up-Converting CdSe/NaYF4:Yb,Er Nanoheterostructures
Near-IR Photoresponse in New Up-Converting CdSe/NaYF4:Yb,Er Nanoheterostructures Chenglin Yan nanoheterostructures consisting of lanthanide (Ln)-doped NaYF4 nanocrystals dendritically decorated with CdSe quantum-converting nanocrystals is NaYF4: Yb,Er, in which Yb dopant ions absorb NIR photons and the Er ions emit the up
NaYF4:Yb,Er-MoS2: from synthesis and surface ligand stripping to negative infrared photoresponse.
Niu, Wenbin; Chen, Hu; Chen, Rui; Huang, Jingfeng; Sun, Handong; Tok, Alfred Iing Yoong
The synthesis, surface ligand stripping, and infrared optoelectronic device application of NaYF4:Yb,Er-MoS2 nanocomposites are reported. NaYF4:Yb,Er-MoS2 film shows an unusual negative infrared photoresponse after SOCl2/DMF treatment, which exhibits more than two times the photoresponsivity of pure NaYF4:Yb,Er, showing great potential for the development of novel infrared optoelectronic devices. PMID:25941681
Journal of Crystal Growth 304 (2007) 114117 Single crystal growth of YbRh2Si2 using Zn flux
Broholm, Collin Leslie
Journal of Crystal Growth 304 (2007) 114Ł117 Single crystal growth of YbRh2Si2 using Zn flux-temperature solution technique, using Zn flux and followed by a decanting process. As opposed from the crystals growth: A1. Growth from high-temperature solutions; A1. Single crystal; B2. YbRh2Si2 1. Introduction YbRh2Si
Combining EU Terminology with Communication and Ontology Research Rodolfo Maslias
Boyer, Edmond
Combining EU Terminology with Communication and Ontology Research Rodolfo Maslias Terminology Coordination Unit, European Parliament, Luxembourg Abstract The Terminology Coordination Unit of the European up EU terminology to the science and industry aspects of the field. This presentation will focus
Emission behaviors of Yb2O3 nanoparticles pumped by 980 nm laser at different power densities
NASA Astrophysics Data System (ADS)
Zheng, Youjin; L³, Qiang; Wang, Jialiang; Zhang, Guohai; Gao, Yang; Liu, Zhanbo
Yb2O3 nanoparticles synthesized via Pechini type sol-gel method were characterized by TEM, SAED, EDS, XRD, SEM and Raman spectrometer. Their emission properties were recorded by a fluorescence spectrophotometer with a 980 nm laser as the excitation source. These spectral results indicate that there are two optical bistable emissions at low/high laser power densities, i.e. Yb3+-Yb3+ dimer cooperative upconversion luminescence and thermal emission. Thus, Yb2O3 nanoparticles might be regarded as a candidate for intrinsic optical bistability.
Construction of four low-dimensional NIR-luminescence-tunable Yb(III) complexes.
Zheng, Zhi-Peng; Zhang, Xiu-Xia; Li, Teng; Yang, Jian; Wei, Lei-Ming; Zhang, Li-Guo; Lin, Xiao-Ming; Cai, Yue-Peng
Four low-dimensional ytterbium(iii)-organic compounds through hydrothermal reactions of quinoline-2,3-dicarboxylic acid (2,3-H2qldc) and oxalic acid (H2ox) with Yb2O3, namely, [Yb(2,3-qldc)(ox)1/2(H2O)3Ę(H2O)4]n (1), [Yb(2,3-qldc)(ox)1/2(H2O)2Ę(H2O)2]n (2), [Yb(2,3-Hqldc)(ox)(H2O)2Ę(H2O)]n (3) and [Yb(2,3-Hqldc)(ox)(H2O)Ę(H2O)2]n (4), were first synthesized and characterized by elemental analysis (EA), infrared spectroscopy (IR), thermogravimetric analysis (TG), and single-crystal X-ray diffraction. When the reactant ratio of 2,3-H2qldc?:?H2ox?:?Yb2O3 is 2?:?1?:?1, 1-D chain-like complex 1 with three coordinated water molecules around the Yb(iii) ion was obtained in mixed solvents of H2O and CH3OH (v?:?v = 10?:?1) at 70 ░C, and with the increase of temperature to 100 ░C, the same reactants gave 2-D 6(3) topological layer-like complex 2 with two coordinated water molecules in the coordination sphere of the Yb(iii) ion. However, when the reactant ratio was changed to 1?:?1?:?1, two 2-D 6(3) topological layer-like complexes 3 (70 ░C) and 4 (100 ░C) were obtained at different temperatures, in which the coordination water molecules in 3 and 4 are two and one, respectively. Obviously, these results reveal that the reaction temperature and reactant ratios play critical roles in the structural direction of these low-dimensional compounds. Interestingly, with the gradual loss of coordination water molecules to the Yb(iii) ion, the near infrared (NIR) emission of four Yb(iii)-based compounds 1-4 can be gradually strengthened with increasing order of 1 < 3 < 2 < 4, indicating that these ytterbium(iii) complexes have tunable near infrared luminescence. PMID:25116388
Thermodynamic and transport properties of single crystalline RCo2Ge2 (R=Y, La¢Nd, Sm¢Tm)
Kong, Tai [Ames Laboratory; Cunningham, Charles E. [Grinnell College; Taufour, Valentin [Iowa State University; Budko, Sergey L. [Ames Laboratory; Buffon, Malinda L.C. [Ames Laboratory; Lin, Xiao [Ames Laboratory; Emmons, Heather [Grinnell College; Canfield, Paul C. [Ames Laboratory
Single crystals of RCo2Ge2 (R=Y, La¢Nd, Sm¢Tm) were grown using a self-flux method and were characterized by room-temperature powder X-ray diffraction; anisotropic, temperature and field dependent magnetization; temperature and field dependent, in-plane resistivity; and specific heat measurements. In this series, the majority of the moment-bearing members order antiferromagnetically; YCo2Ge2 and LaCo2Ge2 are non-moment-bearing. Ce is trivalent in CeCo2Ge2 at high temperatures, and exhibits an enhanced electronic specific heat coefficient due to the Kondo effect at low temperatures. In addition, CeCo2Ge2 shows two low-temperature anomalies in temperature-dependent magnetization and specific heat measurements. Three members (R=Tb¢Ho) have multiple phase transitions above 1.8 K. Eu appears to be divalent with total angular momentum L =0. Both EuCo2Ge2 and GdCo2Ge2 manifest essentially isotropic paramagnetic properties consistent with J =S =7/2. Clear magnetic anisotropy for rare-earth members with finite L was observed, with ErCo2Ge2 and TmCo2Ge2 manifesting planar anisotropy and the rest members manifesting axial anisotropy. The experimentally estimated crystal electric field (CEF) parameters B 20 were calculated from the anisotropic paramagnetic ? ab and ? c values and follow a trend that agrees well with theoretical predictions. The ordering temperatures, TNTN, as well as the polycrystalline averaged paramagnetic Curie¢Weiss temperature, ?avg, for the heavy rare-earth members deviate from the de Gennes scaling, as the magnitude of both is the highest for Tb, which is sometimes seen for extremely axial systems. Except for SmCo2Ge2, metamagnetic transitions were observed at 1.8 K for all members that ordered antiferromagnetically.
Revenue Recognition and EU Endorsement of IFRS
Christopher W. Nobes
This paper comments on a previous paper in this journal concerning EU endorsement of IFRS. It is suggested here that the previous authors should consider whether there can be more than one true and fair view even in one country and especially across European countries. It is further suggested that the previous analysis of five accounting standards does not support
Transgenic crops, EU precaution, and developing countries
Kym Anderson; Lee Ann Jackson
Agricultural biotechnologies have the potential to offer higher incomes for farmers in developing countries and lower-priced and better-quality food, feed and fibre. That potential is being heavily compromised, however, because of strict regulatory systems in the European Union and elsewhere governing transgenically modified (GM) crops. This paper examines why the EU has taken the extreme opposite policy position on GM
EU Verbraucherrechte Apple One-Year Limited
Fiebig, Peter
EU Verbraucherrechte Apple One-Year Limited Warranty AppleCare Protection Plan CC Service Pack, Kabel. Zusõtzlich bei allen Macs: 1x Time Capsule oder 1x Airport Gerõt sowie 1x Apple Display Macs u sowie 1x Apple Display Material- u. Herstellungsfehler. Keine Leistung f³r Verschlei▀teile wie Akku
ORNL/TM-2001/116 TRUCK ROLL STABILITY DATA COLLECTION AND ANALYSIS S. S. Stevens, Principal ............................................................................................................8 2.2.1 Data Collection and Transmission.1 System Hardware
High-spin states in odd-odd 168Tm
Cardona, M. A.; Hojman, D.; Davidson, J.; Davidson, M.; Kreiner, A. J. [Departamento de Fisica, CNEA, Buenos Aires (Argentina); CONICET, Buenos Aires (Argentina); Bazzacco, D.; Lenzi, S. M.; Rossi Alvarez, C. [Dipartimento di Fisica, Sezione di Padova, Padova (Italy); INFN, Sezione di Padova, Padova (Italy); Blasi, N. [Dipartimento di Fisica, Sezione di Milano, Milan (Italy); INFN, Sezione di Milano, Milan (Italy); Debray, M. E.; Levinton, G.; Marti, G. [Departamento de Fisica, CNEA, Buenos Aires (Argentina); De Poli, M.; Napoli, D. R. [INFN, Laboratori Nazionali di Legnaro, Legnaro (Italy); Lo Bianco, G. [Dipartimento di Matematica e Fisica, Universita di Camerino, Camerino (Italy)
High-spin states in 168Tm were investigated by means of {gamma}-ray spectroscopy techniques using the GASP multidetector array. Rotational bands have been established and identified in terms of their configurations.
Resonant tandem pumping of Tm-doped fiber lasers
NASA Astrophysics Data System (ADS)
Creeden, Daniel; Johnson, Benjamin R.; Rines, Glen A.; Setzler, Scott D.
We have demonstrated efficient lasing of a Tm-doped fiber when pumped with another Tm-doped fiber. In these experiments, we use a 1908 nm Tm-doped fiber laser as a pump source for another Tm-doped fiber laser, operating at a slightly longer wavelength (~2000 nm). Pumping in the 1900 nm region allows for very high optical efficiencies, low heat generation, and significant power scaling potential due to the use of fiber laser pumping. The trade-off is that the ground-state pump absorption at 1908 nm is ~37 times lower than at 795nm. However, the absorption cross-section is still sufficiently high enough to achieve effective pump absorption without exceedingly long fiber lengths. This may also be advantageous for distributing the thermal load in higher power applications.
bdbiosciences.com 1 BD FalconTM
Wu, Mingming
., et al., Endothelial cell growth on oxygen-containing films deposited by radio- frequency plasmas,TM the first name in cell culture As the first company to produce sterile, disposable labware more than 50
75 FR 61479 - Western Passage OCGenTM
Federal Register 2010, 2011, 2012, 2013, 2014
...waters owned by others without the owners' express permission. The proposed project would consist of: (1) 2 OCGen\\TM\\ hydrokinetic tidal devices each consisting of four 150-kilowatt turbine generator units for a combined capacity of 1,200...
The Republican People's Party and Turkey's EU Membership
ųd³l Celep
As the founder of the Turkish secular state, the Republican People's Party (CHP) has defended the Westernisation of Turkish society, supported Turkey's acceptance to the EU as a full member, and played crucial roles in Turkey¢EU relations. Nevertheless, the CHP's language towards the EU started to sound critical during the 2000s. This study argues that the CHP's seeming scepticism towards
Japan, EU reach basic agreement over ITER The Yomiuri Shimbun
Japan, EU reach basic agreement over ITER The Yomiuri Shimbun The government and the European Union to the unsuccessful candidate country. Japan and France, the EU's candidate, have been bidding to host the facility bidder's country. The ITER project participants--Japan, China, the EU, Russia, South Korea and the United
EC4: Clinical laboratory globalisation; the EU directives
The directives of the European Union form the legis- lation of the European Union. The directives have power of law for the 27 member countries of the EU, however, because of the scale of the EU market, there is a strong influence far beyond the EU borders. Three directives that have large impact on laboratory medicine and the profession of
A study of phamaceutical policies in the EU
This paper identifies and explores some of the major current policy developments in the EU pharmaceutical environment. The policies considered are: the new pan?EU drug licensing system; changes to the rules of the system over time; the BSE crisis as it affects Pharmaceuticals; member states' pricing and reimbursement policies and the EU Directive; companies calling government policy into account; governments
Implementing IFRS from the perspective of EU publicly traded companies
Eva K. Jermakowicz; Sylwia Gornik-Tomaszewski
This study examines implementation of International Financial Reporting Standards (IFRS) by European Union (EU) companies. All listed EU companies are required to prepare their consolidated financial statements in accordance with IFRS for years beginning on or after January 1, 2005 (Regulation (EC) 1606\\/2002). The paper provides insight into the IFRS adoption process based on a questionnaire sent to EU-listed companies
The EU Biocidal Products Directive and the consequences for Dinsinfectants
M. L. M. Claassens
The title of my presentation suggests or at least anticipates that the EU legislative process, to provide a harmonised regulatory platform for biocides in the EU, has been finalised when this symposium takes place.When adapted and subsequently implemented in the EU member states (estimation Q3 1999), this directive will have a major impact on the market of disinfectants for both
Eu3+ reduction and efficient light emission in Eu2O3 films deposited on Si substrates.
Bellocchi, Gabriele; Franz", Giorgia; Iacona, Fabio; Boninelli, Simona; Miritello, Maria; Cesca, Tiziana; Priolo, Francesco
A stable Eu3+ ? Eu2+ reduction is accomplished by thermal annealing in N2 ambient of Eu2O3 films deposited by magnetron sputtering on Si substrates. Transmission electron microscopy and x-ray diffraction measurements demonstrate the occurrence of a complex reactivity at the Eu2O3/Si interface, leading to the formation of Eu2+ silicates, characterized by a very strong (the measured external quantum efficiency is about 10%) and broad room temperature photoluminescence (PL) peak centered at 590 nm. This signal is much more efficient than the Eu3+ emission, mainly consisting of a sharp PL peak at 622 nm, observed in O2-annealed films, where the presence of a SiO2 layer at the Eu2O3/Si interface prevents Eu2+ formation. PMID:22418355
Flashlamp-pumped Ho:Tm:Cr:LuAG laser
NASA Technical Reports Server (NTRS)
Jani, Mahendra G. (Inventor); Barnes, Norman P. (Inventor); Murray, Keith E. (Inventor); Kokta, Milan R. (Inventor)
A room temperature solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG host material doped with a concentration of about 0.35% Ho ions, about 5.57% Tm ions and at least about 1.01% Cr ions. A broadband energizing source such as a flashlamp is disposed transversely to the laser crystal to energize the Ho ions, Tm ions and Cr ions.
Spectroscopic and lasing properties of Ho:Tm:LuAG
NASA Technical Reports Server (NTRS)
Barnes, Norman P.; Filer, Elizabeth D.; Naranjo, Felipe L.; Rodriguez, Waldo J.; Kokta, Milan R.
Ho:Tm:LuAG has been grown, examined spectroscopically, and lased at 2.1 microns. Ho:Tm:LuAG was selected for this experimental investigation when quantum-mechanical modeling predicted that it would be a good laser material for Ho laser operation on one of the 5I7 to 5I8 transitions. Lasing was achieved at 2.100 microns, one of the three wavelengths predicted to be most probable for laser action.
Quiet Spike (TM) Build-Up Ground Vibration Testing Approach
NASA Technical Reports Server (NTRS)
Spivey, Natalie D.; Herrera, Claudia; Truax, Roger; Pak, Chan-gi; Freund, Donald
Flight tests of Gulfstream Aerospace Corporation s Quiet Spike(TM) hardware were recently completed on the NASA Dryden Flight Research Center F-15B airplane. NASA Dryden uses a modified F-15B airplane as a testbed aircraft to cost-effectively fly flight research experiments that are typically mounted underneath the F-15B airplane, along the fuselage centerline. For the Quiet Spike(TM) experiment, however, instead of a centerline mounting, a relatively long forward-pointing boom was attached to the radar bulkhead of the F-15B airplane. The Quiet Spike(TM) experiment is a stepping-stone to airframe structural morphing technologies designed to mitigate the sonic-boom strength of business jets over land. The Quiet Spike(TM) boom is a concept in which an aircraft's noseboom would be extended prior to supersonic acceleration. This morphing effectively lengthens the aircraft, thus reducing the peak sonic-boom amplitude, but is also expected to partition the otherwise strong bow shock into a series of reduced-strength, noncoalescing shocklets. Prior to flying the Quiet Spike(TM) experiment on the F-15B airplane several ground vibration tests were required to understand the Quiet Spike(TM) modal characteristics and coupling effects with the F-15B airplane. However, due to the flight hardware availability and compressed schedule requirements, a "traditional" ground vibration test of the mated F-15B Quiet Spike(TM) ready-for-flight configuration did not leave sufficient time available for the finite element model update and flutter analyses before flight testing. Therefore, a "nontraditional" ground vibration testing approach was taken. This paper provides an overview of each phase of the "nontraditional" ground vibration testing completed for the Quiet Spike(TM) project which includes the test setup details, instrumentation layout, and modal results obtained in support of the structural dynamic modeling and flutter analyses.
Scientific data mining with StripMinerTM
Mark J. Embrechts; Fabio Arciniegas; Muhsin Ozdemir; Michinari Momma
The paper introduces scientific data mining, the standard data-mining problem, and the strip-mining problem. StripMinerTM , a shell program for feature reduction and predictive modeling, integrates the executions of several different machine-learning models (partial least squares regression, genetic algorithms, support vector machines, neural networks, and local learning). This paper introduces the StripMinerTM code, its functionality, and its options
Comparative 3-D Modeling of tmRNA
Jody Burks; Christian Zwieb; Florian M³ller; Iwona Wower; Jacek Wower
BACKGROUND: Trans-translation releases stalled ribosomes from truncated mRNAs and tags defective proteins for proteolytic degradation using transfer-messenger RNA (tmRNA). This small stable RNA represents a hybrid of tRNA- and mRNA-like domains connected by a variable number of pseudoknots. Comparative sequence analysis of tmRNAs found in bacteria, plastids, and mitochondria provides considerable insights into their secondary structures. Progress toward understanding the
Enhanced high-temperature thermoelectric performance of Yb(14-x)Ca(x)MnSb11.
Uvarov, Catherine A; Ortega-Alvarez, Francisco; Kauzlarich, Susan M
The high temperature p-type thermoelectric material Yb(14)MnSb(11) has been of increasing research interest since its high temperature thermoelectric properties were first measured in 2006. Subsequent substitutions of Zn, Al, and La into the structure have shown that this material can be further optimized by altering the carrier concentration or by reduction of spin-disorder scattering. Here the properties of the Yb(14-x)Ca(x)MnSb(11) solid solution series where isovalent Ca(2+) is substituted for Yb(2+) will be presented. Crystals of the Yb(14-x)Ca(x)MnSb(11) solid solution series were made by Sn-flux (x = 2, 4, 6, 8) with the following ratio of elements: (14-x)Yb: xCa: 6 Mn: 11Sb: 86Sn, and their structures determined by single crystal X-ray diffraction. The density of the material significantly decreases by over 2 g/cm(3) as more Ca is added (from x = 1 to 8), because of the lighter mass of Ca. The resulting lower density is beneficial from a device manufacturing perspective where there is often a trade-off with the specific power per kilogram. The compounds crystallize in the Ca(14)AlSb(11) structure type. The Ca substitution contributes to systematic lengthening the Mn-Sb bond while shortening the Sb-Sb bond in the 3 atom linear unit with increasing amounts of Ca. Temperature dependent thermoelectric properties, Seebeck, electrical resistivity, and thermal conductivity were measured from room temperature to 1273 K. Substitution of Yb with Ca improves the Seebeck coefficient while decreasing the thermal conductivity, along with decreasing the carrier concentration in this p-type material resulting in an enhanced thermoelectric figure of merit, zT, compared to Yb(14)MnSb(11). PMID:22755507