D-Scholarship@Pitt: No conditions. Results ordered -Date Deposited. 2020-05-29T02:03:20Z EPrints http://d-scholarship.pitt.edu/images/sitelogo.png http://d-scholarship.pitt.edu/ 2016-11-29T21:07:08Z 2019-02-02T15:55:41Z http://d-scholarship.pitt.edu/id/eprint/29842 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/29842 2016-11-29T21:07:08Z An integer optimization algorithm for robust identification of non-linear gene regulatory networks

Background: Reverse engineering gene networks and identifying regulatory interactions are integral to understanding cellular decision making processes. Advancement in high throughput experimental techniques has initiated innovative data driven analysis of gene regulatory networks. However, inherent noise associated with biological systems requires numerous experimental replicates for reliable conclusions. Furthermore, evidence of robust algorithms directly exploiting basic biological traits are few. Such algorithms are expected to be efficient in their performance and robust in their prediction.Results: We have developed a network identification algorithm to accurately infer both the topology and strength of regulatory interactions from time series gene expression data in the presence of significant experimental noise and non-linear behavior. In this novel formulism, we have addressed data variability in biological systems by integrating network identification with the bootstrap resampling technique, hence predicting robust interactions from limited experimental replicates subjected to noise. Furthermore, we have incorporated non-linearity in gene dynamics using the S-system formulation. The basic network identification formulation exploits the trait of sparsity of biological interactions. Towards that, the identification algorithm is formulated as an integer-programming problem by introducing binary variables for each network component. The objective function is targeted to minimize the network connections subjected to the constraint of maximal agreement between the experimental and predicted gene dynamics. The developed algorithm is validated using both in silico and experimental data-sets. These studies show that the algorithm can accurately predict the topology and connection strength of the in silico networks, as quantified by high precision and recall, and small discrepancy between the actual and predicted kinetic parameters. Furthermore, in both the in silico and experimental case studies, the predicted gene expression profiles are in very close agreement with the dynamics of the input data.Conclusions: Our integer programming algorithm effectively utilizes bootstrapping to identify robust gene regulatory networks from noisy, non-linear time-series gene expression data. With significant noise and non-linearities being inherent to biological systems, the present formulism, with the incorporation of network sparsity, is extremely relevant to gene regulatory networks, and while the formulation has been validated against in silico and E. Coli data, it can be applied to any biological system. © 2012 Chemmangattuvalappil et al.; licensee BioMed Central Ltd.

N Chemmangattuvalappil K Task I Banerjee IPB1
2016-10-11T18:26:27Z 2018-10-30T13:55:36Z http://d-scholarship.pitt.edu/id/eprint/29830 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/29830 2016-10-11T18:26:27Z Bench to bedside review: Extracorporeal carbon dioxide removal, past present and future

Acute respiratory distress syndrome (ARDS) has a substantial mortality rate and annually affects more than 140,000 people in the USA alone. Standard management includes lung protective ventilation but this impairs carbon dioxide clearance and may lead to right heart dysfunction or increased intracranial pressure. Extracorporeal carbon dioxide removal has the potential to optimize lung protective ventilation by uncoupling oxygenation and carbon dioxide clearance. The aim of this article is to review the carbon dioxide removal strategies that are likely to be widely available in the near future. Relevant published literature was identified using PubMed and Medline searches. Queries were performed by using the search terms ECCOR, AVCO2R, VVCO2R, respiratory dialysis, and by combining carbon dioxide removal and ARDS. The only search limitation imposed was English language. Additional articles were identified from reference lists in the studies that were reviewed. Several novel strategies to achieve carbon dioxide removal were identified, some of which are already commercially available whereas others are in advanced stages of development. © 2012 BioMed Central Ltd.

ME Cove G MacLaren WJ Federspiel WFEDERSP JA Kellum KELLUM
2014-03-04T19:41:44Z 2019-02-03T07:55:03Z http://d-scholarship.pitt.edu/id/eprint/20666 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/20666 2014-03-04T19:41:44Z Analysis of alternative signaling pathways of endoderm induction of human embryonic stem cells identifies context specific differences


S Mathew M Jaramillo X Zhang LA Zhang A Soto-Gutiérrez I Banerjee IPB1
2012-09-26T15:21:08Z 2016-11-15T14:00:07Z http://d-scholarship.pitt.edu/id/eprint/12885 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/12885 2012-09-26T15:21:08Z Modeling, Scaleup and Optimization of Slurry Bubble Column Reactors for Fischer-Tropsch Synthesis

The hydrodynamic and mass transfer parameters of gaseous mixtures of N2 and He, used as surrogate components for CO and H2 respectively, were measured in three Fischer-Tropsch (F-T) liquids in the presence and absence of solid particles (Al2O3, FeOx). The data were obtained in a pilot-scale (0.29 m ID and 3 m high) slurry bubble column reactor (SBCR) within wide ranges of operating conditions covering those of F-T synthesis. The manometric method, the Transient Physical Gas Absorption technique and the Dynamic Gas Disengagement technique were employed to obtain the gas holdup, the volumetric liquid-side mass transfer coefficient and the gas bubbles Sauter mean diameter, respectively. Statistical experimental design was used to investigate the effect of these operating conditions on those parameters. The gas-liquid interfacial area appeared to control the mass transfer behavior of the SBCR operating in the churn-turbulent flow regime.
A user-friendly simulator based on a comprehensive computer model for F-T SBCRs, taking into account the hydrodynamics, kinetics, heat transfer, and mass transfer was developed. Novel hydrodynamic and mass transfer correlations, covering wide ranges of reactor geometry, gas distributor types, and operating conditions were established using our experimental data and those available in the literature; and a new relationship between the axial dispersion of large gas bubbles and their average diameter were developed and included in the reactor model. All reactor partial differential equations, equation parameters along with the pertinent boundary conditions were simultaneously solved numerically using the finite elements method. Different kinetic rate expressions available in the literature for iron and cobalt-based catalysts were included in the simulator which was used to predict the effects of the operating conditions, such as catalyst concentration, pressure, temperature, H2/CO ratio, and superficial gas velocity on the performance of a F-T SBCR. The predictions showed that the performance of the reactor was strongly dependent on the catalyst type and the kinetic rate expression used. The simulator was also used to optimize the reactor geometry and operating conditions in order to produce 10,000 barrels per day of synthetic hydrocarbons.

Laurent Sehabiague
2012-09-26T15:12:34Z 2017-09-26T05:15:07Z http://d-scholarship.pitt.edu/id/eprint/12205 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/12205 2012-09-26T15:12:34Z On Hydrocracking of Vacuum Residues in Slurry Reactors

The equilibrium solubility (C*) and liquid-side mass transfer coefficient (kLa) were measured for H2 in four liquids, two vacuum residues (A and B); and two mixtures (vacuum residue B + liquid paraffins and vacuum residue B + liquid paraffins + molten wax). The data were measured in the presence and absence of solid particles (activated carbon) in one-liter agitated autoclave operating in a gas-inducing mode. The effect of operating variables, including pressure (27.5–55bar), temperature (423–623K), mixing speed (20–33Hz), and activated carbon concentration (0-40wt %) on kLa and C* values were statistically investigated using the Central Composite Statistical Design technique. The kLa values were obtained using the Transient Physical Gas Absorption technique and the C* values were calculated at the thermodynamic equilibrium.
The experimental data showed that C* values of hydrogen in the four liquids increase linearly with pressure at constant temperature following Henry’s law. The C* values also increased with temperature at constant pressure and the temperature effect was modeled using an Arrhenius-type equation.
The kLa values of H2 in the four liquids strongly increased with temperature and mixing speed, and slightly increased with H2 partial pressure. The kLa values, however, decreased with increasing solid concentrations in the vacuum residues A and B. Statistical correlations and empirical correlations, using dimensionless numbers, were developed to predict kLa values of H2 in the liquids used in the presence and absence of solid particles in the gas-inducing slurry agitated reactor.
The kinetic rate constants proposed by Sanchez at al.[1] for hydrocracking of vacuum residue at 380, 400 and 420oC were used in a simple kinetic model using a series of CSTRs to calculate the residue conversion and the VGO, distillate, naphtha and gaseous products concentrations and molar flow rates. For a series arrangements of 4-CSTRs(3-m inside diameter and 3-m height), operating at 400oC with an LHSV of 0.33h-1 corresponding to an inlet liquid superficial velocity of 0.99m s-1, the residue conversion reached 91.8%. However, for the same arrangement at 400oC with an LHSV of 1.5h-1 corresponding to an inlet liquid superficial velocity of 4.5m s-1, the residue conversion was only 50.36%.

Mariela Sanoja
2012-09-26T15:09:42Z 2016-12-19T14:38:31Z http://d-scholarship.pitt.edu/id/eprint/12733 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/12733 2012-09-26T15:09:42Z Albumin in Artificial Liver Support Systems

While liver transplantation is the only accepted therapy for liver failure, bound solute dialysis (BSD) may provide an alternative. Current BSD methods, MARS and SPAD, are unfortunately poorly characterized. The studies presented here address basic questions involved in making BSD effective. First, Biacore surface plasmon resonance (SPR) was used to measure binding and reaction rate constants of albumin-solute pairs relevant to designing and testing BSD systems. Much is known about albumin equilibrium binding properties, but little is known regarding albumin-solute binding kinetics. Additionally, testing and clinical application of BSD systems are often done at different temperatures (i.e. room temperature (22°C) and body temperature (37°C)), and changes in reaction rates and binding constants with temperature need to be considered. Human and bovine serum albumin were immobilized on Biacore sensor chip surfaces, and reacting solutes (bilirubin, FK506, cyclosporine A, cholate, deoxycholate, and glycocholate) flowed across the surfaces. The SPR response was tracked during the association and dissociation of the albumin-solute complex. Reactions were performed at 22°C and 37°C. Equilibrium constants consistent with previously reported values and reaction rates were determined for all reactions tested except cyclosporine A. Second, I developed a mathematical model describing the removal of albumin bound solutes using BSD that incorporates albumin-solute reaction kinetics. Previous BSD models focused on the amount of binder in the dialysate, ultrafiltration, and the use of solid adsorbents. The new model relaxes the assumption of reaction equilibrium built into previous BSD models. For a given equilibrium binding constant and set of mass transport parameters, the model was solved for several reaction rates. In all cases tested, the equilibrium BSD model overestimated removal compared to the kinetic model, but the kinetic model displayed greater numerical instability. A third project explored methods to direct visualize protein deposition in and on commercial dialysis membranes during use. A novel slide dialyzer design incorporating commercial renal dialyzer membranes was developed and tested.

Richard H. Miller
2012-09-26T15:04:24Z 2016-11-15T14:00:56Z http://d-scholarship.pitt.edu/id/eprint/13172 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/13172 2012-09-26T15:04:24Z MODELING OF CONSOLIDATION AND FLOW OF GRANULAR MATERIAL UNDER VARYING CONDITIONS

Granular materials are ubiquitous. They are widely used in many natural and man-made processes such as formation of lunar regolith, dunes and beach sand, as well as processes in pharmaceutical, chemical, and construction industries. Despite their clear industrial relevance, a fundamental understanding of most of the phenomena that involve granular materials in the chemical industry is lacking. Recently, it has been found that cyclic variation of the temperature of a granular bed can cause static particle beds to consolidate (increase their packing fraction) over time due to thermo-mechanical coupling. We employ experimental techniques and numerical simulations, using the thermal particle dynamics method (TPD), to study this phenomenon. In order to simulate many natural phenomena such as lunar regolith formation, one needs to determine a simulation depth of the bed which will yield realistic results yet be manageable computationally. Here we use penetration theory to estimate the required simulation bed height. Lateral periodic boundary conditions are used in our simulations to show that consolidation still occurs during vertical heating even in the absence of confining side walls.

Granular flows in which shearing plays a key role are prevalent in natural and industrial applications and understanding their behavior and flow characteristics is of considerable importance. Nevertheless, difficulties in making accurate experimental measurements, complexities involved in doing bulk characterization, and the non-linear nature of interparticle interactions have made development and testing of theoretical models extremely challenging. For this reason, the discrete element method (DEM) is often used as the gold standard for comparison to continuum-level theories of granular material flows. Due to the fact that this modeling approach is derived from first-principle constructs -- like contact mechanics -- its use in lieu of experimentation is reasonably wide-spread and is becoming a staple even in industrial practice. In this work, we explore various aspects of quantitative validation of DEM simulations using detailed measurements of simple, well-characterized flows that allow us to examine the effect of rough surfaces, rotational rates, collisional and frictional force models on granular flow using different devices. Experimentally, we use digital particle tracking velocimetry (DPTV) to obtain velocity, solids fractions, and granular temperature profiles. Computationally, we compare the results obtained using different contact mechanics force laws to those from experimental measurements and perform sensitivity analyses on device and particle geometry as well as material properties employed. In general, the frictional force models range from pragmatic linear techniques to rigorously more complex (nonlinear) contact mechanics inspired routines. Here, we examine both force models to compare with the experimental measurements. In addition, we examine the robustness of these observations to both particle materials properties as well as systemic variables (such as total system solids fraction).

Adel F. Alenzi
2012-09-26T13:55:34Z 2016-11-15T13:59:07Z http://d-scholarship.pitt.edu/id/eprint/12528 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/12528 2012-09-26T13:55:34Z Microfluidic Drop Formation with Polymer Plastics

The aim of this study is to develop a microfluidic platform for making particles from molten polymers. This thesis describes the process of formation of droplets and bubbles in microfluidic flow-focusing geometries. High viscosity and low interfacial tension of molten polymers makes it difficult to break a continuous fluid stream into drops. Furthermore, the eventual requirements that the polymers can only flow when heated far above room temperature require a new approach to fluid handling.
This thesis describes the development of a platform for molten polymer microfluidics based on a pressure-driven flow of polymer into micro-channels etched out of metal foils. This platform is developed for room temperature operation to test whether undiluted polymer melts can be emulsified in a controlled fashion in a microfluidic device. We report the results of a comparative study of microfluidic emulsification (i.e. drop or bubble formation) with different viscosities polymer liquids. At room temperature, depending on the properties of the polymer fluids and the flow rate, emulsification occurred in the dripping and jetting regions. We developed a simple circuit model to describe the observed dependence of the size of bubbles on the supplied pressure. The bubble shape, size, velocity, frequency were well investigated under various experimental conditions.
This study demonstrates the possibility of polymer drop formation in the room temperature device that can be used to further research using polymers need high temperature to be melted.

Shu-Che Peng
2012-09-26T13:50:11Z 2016-11-15T14:00:50Z http://d-scholarship.pitt.edu/id/eprint/13139 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/13139 2012-09-26T13:50:11Z Surface Wrinkling Based Method of Measuring Thin Film’s Mechanical Properties

The main goal of this project is to develop a wrinkle-based method to measure mechanical properties of thin interfacial polymeric films. Instead of working on a mechanically equilibrium system, this study is focusing on the case where mechanical equilibrium is hard to reach due to the very high viscosity of the bulk phases.
This thesis describes an air/viscous polymer system with a few-micron scale thick polymer film placed at the interface. We have developed a method to generate dynamic wrinkle patterns on the film via compressing the high viscous substrate. Two experiment parameters are controlled: the substrate thickness H and the compressing strain rateε ̇. This thesis developed an accurate method to measure H while avoiding the interference from the edge effect of the fluid. The compressing strain rate is calculated upon a Matlab program.
We report the value of wrinkle number under different compressing strain rate and different substrate thickness. Critical strains under different compression strain rate and substrate thickness has been obtained via analyzing the strain for the onset wrinkle.
We normalize the wrinkle number as well as the compressing strain rate in order to compare them with previous works. With dimensional analysis, a power law relation has been demonstrated between normalized wrinkle number and normalized strain rate.

Jiani Niu
2012-09-26T13:40:01Z 2017-09-26T05:15:05Z http://d-scholarship.pitt.edu/id/eprint/13015 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/13015 2012-09-26T13:40:01Z CONTINUOUS SEPARATION OF WATER-OIL MIXTURE USING SURFACE MODIFIED MEMBRANES

In this study, the surfaces of membranes are modified with custom-designed polymers for separation of water-oil mixture. By tuning the chemical structure of the polymers, the water and oil repellencies of the membrane can be tailored. In particular, two types of membranes have been made and used to construct a continuous water-oil separator: one allows oil to pass but stops water, and the other allows water to pass but stops oil. The continuous water-oil separator splits one stream of water-oil mixture into two streams: a water stream that has less than 0.075 wt% of oil, and an oil stream that has less than 0.01 wt% of water.
Because of the surface texture of the membranes, the modified membranes possess extreme repellencies to either water or oil while can be completely wetted by the other liquid. The two types of membranes used in the water-oil separator are (i) superhydrophilic but superoleophobic (denote as HBO) and (ii) superoleophilic but superhydrphobic (denote as OBH). The super hydro/oleo-philicity and hydro/oleo-phobicity are characterized and explained by Wenzel and Cassie-Baxter models. In addition, the robustness of the hydro/oleo-philic and hydro/oleo-phobic states is analyzed, and critical parameters that affect the robustness of these states are determined.
The performance of the membranes during the separation of water-oil mixture is characterized by measuring (i) the relationship between pressure and volume flux, (ii) break-down pressure, (iii) break-down time, and (iv) the oil (water) percentage in the water (oil) stream after separation. These parameters provide guidance to the design and operation of the continuous water-oil separator.

Tianhan Jiang TIJ5
2012-09-24T20:21:54Z 2019-02-05T17:55:04Z http://d-scholarship.pitt.edu/id/eprint/14176 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/14176 2012-09-24T20:21:54Z Analysis of regulatory network involved in mechanical induction of embryonic stem cell differentiation

Embryonic stem cells are conventionally differentiated by modulating specific growth factors in the cell culture media. Recently the effect of cellular mechanical microenvironment in inducing phenotype specific differentiation has attracted considerable attention. We have shown the possibility of inducing endoderm differentiation by culturing the stem cells on fibrin substrates of specific stiffness [1]. Here, we analyze the regulatory network involved in such mechanically induced endoderm differentiation under two different experimental configurations of 2-dimensional and 3-dimensional culture, respectively. Mouse embryonic stem cells are differentiated on an array of substrates of varying mechanical properties and analyzed for relevant endoderm markers. The experimental data set is further analyzed for identification of co-regulated transcription factors across different substrate conditions using the technique of bi-clustering. Overlapped bi-clusters are identified following an optimization formulation, which is solved using an evolutionary algorithm. While typically such analysis is performed at the mean value of expression data across experimental repeats, the variability of stem cell systems reduces the confidence on such analysis of mean data. Bootstrapping technique is thus integrated with the bi-clustering algorithm to determine sets of robust bi-clusters, which is found to differ significantly from corresponding bi-clusters at the mean data value. Analysis of robust bi-clusters reveals an overall similar network interaction as has been reported for chemically induced endoderm or endodermal organs but with differences in patterning between 2-dimensional and 3-dimensional culture. Such analysis sheds light on the pathway of stem cell differentiation indicating the prospect of the two culture configurations for further maturation. © 2012 Zhang et al.

X Zhang M Jaramillo S Singh P Kumta PKUMTA I Banerjee IPB1
2012-09-13T19:16:28Z 2019-02-02T15:55:41Z http://d-scholarship.pitt.edu/id/eprint/14152 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/14152 2012-09-13T19:16:28Z Population based model of human embryonic stem cell (hESC) differentiation during endoderm induction

The mechanisms by which human embryonic stem cells (hESC) differentiate to endodermal lineage have not been extensively studied. Mathematical models can aid in the identification of mechanistic information. In this work we use a population-based modeling approach to understand the mechanism of endoderm induction in hESC, performed experimentally with exposure to Activin A and Activin A supplemented with growth factors (basic fibroblast growth factor (FGF2) and bone morphogenetic protein 4 (BMP4)). The differentiating cell population is analyzed daily for cellular growth, cell death, and expression of the endoderm proteins Sox17 and CXCR4. The stochastic model starts with a population of undifferentiated cells, wherefrom it evolves in time by assigning each cell a propensity to proliferate, die and differentiate using certain user defined rules. Twelve alternate mechanisms which might describe the observed dynamics were simulated, and an ensemble parameter estimation was performed on each mechanism. A comparison of the quality of agreement of experimental data with simulations for several competing mechanisms led to the identification of one which adequately describes the observed dynamics under both induction conditions. The results indicate that hESC commitment to endoderm occurs through an intermediate mesendoderm germ layer which further differentiates into mesoderm and endoderm, and that during induction proliferation of the endoderm germ layer is promoted. Furthermore, our model suggests that CXCR4 is expressed in mesendoderm and endoderm, but is not expressed in mesoderm. Comparison between the two induction conditions indicates that supplementing FGF2 and BMP4 to Activin A enhances the kinetics of differentiation than Activin A alone. This mechanistic information can aid in the derivation of functional, mature cells from their progenitors. While applied to initial endoderm commitment of hESC, the model is general enough to be applicable either to a system of adult stem cells or later stages of ESC differentiation. © 2012 Task et al.

K Task M Jaramillo I Banerjee IPB1
2012-09-13T18:23:39Z 2019-01-26T10:55:07Z http://d-scholarship.pitt.edu/id/eprint/14150 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/14150 2012-09-13T18:23:39Z Ensemble models of neutrophil trafficking in severe sepsis

A hallmark of severe sepsis is systemic inflammation which activates leukocytes and can result in their misdirection. This leads to both impaired migration to the locus of infection and increased infiltration into healthy tissues. In order to better understand the pathophysiologic mechanisms involved, we developed a coarse-grained phenomenological model of the acute inflammatory response in CLP (cecal ligation and puncture)-induced sepsis in rats. This model incorporates distinct neutrophil kinetic responses to the inflammatory stimulus and the dynamic interactions between components of a compartmentalized inflammatory response. Ensembles of model parameter sets consistent with experimental observations were statistically generated using a Markov-Chain Monte Carlo sampling. Prediction uncertainty in the model states was quantified over the resulting ensemble parameter sets. Forward simulation of the parameter ensembles successfully captured experimental features and predicted that systemically activated circulating neutrophils display impaired migration to the tissue and neutrophil sequestration in the lung, consequently contributing to tissue damage and mortality. Principal component and multiple regression analyses of the parameter ensembles estimated from survivor and non-survivor cohorts provide insight into pathologic mechanisms dictating outcome in sepsis. Furthermore, the model was extended to incorporate hypothetical mechanisms by which immune modulation using extracorporeal blood purification results in improved outcome in septic rats. Simulations identified a sub-population (about 18% of the treated population) that benefited from blood purification. Survivors displayed enhanced neutrophil migration to tissue and reduced sequestration of lung neutrophils, contributing to improved outcome. The model ensemble presented herein provides a platform for generating and testing hypotheses in silico, as well as motivating further experimental studies to advance understanding of the complex biological response to severe infection, a problem of growing magnitude in humans. © 2012 Song et al.

SOK Song J Hogg ZY Peng R Parker RPARKER JA Kellum KELLUM G Clermont CLER
2012-06-04T18:49:28Z 2017-06-04T05:15:06Z http://d-scholarship.pitt.edu/id/eprint/10910 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/10910 2012-06-04T18:49:28Z Nanostructured Noble Metal Catalysts for Water-Gas Shift Reaction

The water-gas shift (WGS) reaction (CO + H2O = CO2 + H2) has attracted great research attention because of its applications in adjusting H2/CO ratio for the Fischer-Tropsch process, providing hydrogen-rich streams for fuel cells and processing exhaust gases from automobiles. However, the current WGS process suffers from certain drawbacks of traditional catalysts, such as the toxicity of Fe-Cr-based catalysts and the instability/low space velocity of Cu-based catalysts. In the search for alternative catalysts to overcome these drawbacks, novel metal-based catalysts have been the focal point of most recent studies. The structures and properties of CeO2, on which the rate determining step proceeds (i.e. water dissociation), are believed to fundamentally impact the performance of this catalyst.
In this project, the objective is to develop a rational design of novel metal-based WGS catalyst which combines high activity with stability against sintering and poisoning. In order to achieve this objective, we have prepared pure and mixed lanthanum-cerium oxide supports, and investigated the effects of these compositions and morphologies to the material’s reducibility and catalytic activity. For the composition, it was found that a proper amount of La doping can improve the WGS activity by tailoring the Ce4+/Ce3+ ratio. When we change the morphology, the CeO2 nanorods were observed to be a better support for Au than the CeO2 nanoparticles. The outstanding performance of the CeO2 nanorods were attributed to its predominantly exposed crystal plane {110}, which is more active to be reduced and to form oxygen vacancies than the {111} exposed by CeO2 nanoparticles.
After obtaining the high activity WGS catalysts, we have improved our catalysts against particle sintering and S-poisoning. Surface decoration technique has been applied to prepare layered La2O3/M/CeO2 (M = Au, Pt) with sulfur resistance and regeneration ability during cyclic sour WGS. On one hand, La2O3 has been demonstrated as a protective overlayer against H2S in syngas feedstocks in addition to its stabilizing effect to prevent Au nanoparticles sintering. On the other hand, reducible CeO2 supports enable complete regeneration of sulfur-poisoned Pt catalysts due to the strong metal support interaction (SMSI).

Shuang Liang SHL50
2012-02-02T16:01:24Z 2016-11-15T13:55:20Z http://d-scholarship.pitt.edu/id/eprint/10573 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/10573 2012-02-02T16:01:24Z RAPID DNA-BASED POINT-OF-CARE DIAGNOSTICS

DNA-based biosensors for detection of genetic mutations and infectious diseases have attracted a lot of attention recently owing to the large amount of genetic information available and the high specificity of these sensors due to the uniqueness of DNA sequences.
In the first part of my work, the viscoelastic properties of single-strand DNA are made use of to rapidly screen for disease causing mutations. Single strand DNA (ssDNA) films have viscoelastic properties which are dependent on their 3-D conformation in solution which in turn is dependent on their base sequence. The mutation of the p53 gene which is responsible for almost half of all cancers was chosen as our case study. The appreciable differences in the viscoelastic properties between the p53 wild type ssDNA film and the p53 mutant R type ssDNA film were evaluated using a quartz crystal resonator showing that this method holds much promise to be used as a rapid DNA mutation screening technique.
In the second part of my work, we have made use of novel isothermal DNA amplification techniques to specifically amplify the target DNA which is then detected on lateral flow strips in a low cost manner. Escherichia coli and Klebsiella pneumoniae are responsible for a large number of infections including Urinary Tract Infection (UTI) and life threatening conditions such as neonatal meningitis and neonatal sepsis. A rapid and sensitive detection scheme has been developed for these bacteria by amplification of the DNA with Loop mediated isothermal amplification technique (LAMP) and its subsequent detection on lateral flow strips. Patient urine samples were screened for the presence of these two organisms and the LAMP-lateral flow detection scheme is comparable to the bacterial culture methods which is the current gold standard. Furthermore, multiplexing the amplification and detection has been demonstrated successfully which shows great potential to be employed as a reliable point-of-care diagnostic tool in the clinical setting.

2012-02-02T15:55:03Z 2017-02-02T06:15:04Z http://d-scholarship.pitt.edu/id/eprint/10477 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/10477 2012-02-02T15:55:03Z SYNTHESIS AND EVALUATION OF METAL-SILICA CORE-SHELL NANOMATERIALS FOR CATALYSIS

Nanocatalysts have drawn considerable interest because of their high selectivity and reactivity compared with conventional catalysts. However, the catalyst deactivation due to the sintering under moderate/high temperature operation and coke formation in hydrocarbon participating systems poses a challenge for their usage. Our work focuses on solving the above issues by designing and developing a series of metal core silica shell materials. The fundamental understanding of core shell materials is facilitated by systematic investigation via synthesis, characterization (XRD, TEM, BET, EDX) and catalytic tests (CO oxidation, ethylene hydrogenation, CO methanation and catalytic partial oxidation of methane).
The synthesis and post-treatment methods for this newly developed core shell material are optimized and standardized. We demonstrate fine control over the key structural elements of nickel core silica shell material. Two different nickel core silica shell structures are obtained with the distinction of a pronounced cavity in the core. The synthesis route is not limited to nickel particles, but also applied for a range of other metals (e.g. Cu, Co, Pd). The pore size of silica shell is around ~1nm independent of the shell thickness and structure difference. The thermal stability of nickel particles as a function of particle size as well as silica support is thoroughly studied. The nickel particles in core shell materials are stabilized under 5nm up to 1000C with the comparison of strong sintering of unprotected nickel particles beyond 10nm as low as 500C. The stable core shell material not only shows its advantage for stable operation under high temperature reactive condition (>800C), but also possesses the highly coking resistant property in fuel participating reactions. Even though the presence of silica shell is beneficial for improving stability of nickel particles, it brings up significant mass transfer limitation when shell thickness is beyond 10nm.
We not only demonstrate the capability to synthesize the well controlled nanocatalysts with high temperature stability and minimal mass transfer limitation, but also understand the structure correlated reactivity in several reaction systems. Additionally, we highlight the correlation between sintering, mass transfer and coking properties of the catalysts.

Lu Whaley
2012-02-02T15:45:56Z 2016-11-15T13:55:13Z http://d-scholarship.pitt.edu/id/eprint/10519 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/10519 2012-02-02T15:45:56Z INVESTIGATION OF HOMOGENEOUS-HETEROGENEOUS COUPLING EFFECTS IN THE HIGH TEMPERATURE CATALYTIC OXIDATION REACTIONS OF LIGHT ALKANES IN A NOVEL MICROCHEMICAL REACTOR SYSTEM

Understanding the coupling effects between homogeneous and heterogeneous (HH) chemistry is crucial in the field of high-temperature catalysis. An important example in this area is the catalytic oxidation of light hydrocarbons. Microreactor technology, with its precise control of fluid and temperature fields, improved reactant mixing, and large surface-to-volume ratio, is ideally suited for the study of such reaction systems. Most significantly, the pathways of homogeneous-heterogeneous coupling can be better understood as critical reactor dimensions are reduced into micrometer range, where diffusive flux starts to play an equally important role as convective transport.
Here, we are reporting a novel modular microreactor system based on the use of silicon-based thin-film catalysts, which allows stable operation during thermal cycling up to 800 oC. Precise control and adjustment of the critical dimension, i.e. the height of reaction chamber, offers the ability to steer the relative importance of gas- and catalytic-phase chemistries due to transport of reactants between the gas phase and the catalytic walls. Additionally, a moveable thermocouple and quartz-glass capillary (connected to a mass spectrometer) allow the in-situ measurement of temperature and composition profiles in the reaction chamber. By combining these two capabilities, the system thus provides an efficient and sensitive way to investigate the interplay between gas phase and catalytic chemistries, and to evaluate the catalytic performance of thin-film catalysts. The reactor system was tested using oxidative coupling of methane (OCM) as model reaction. OCM has been studied intensively for many decades and offers a potentially highly efficient path for direct upgrading of methane to higher-value C2 products. The reaction is also well known to include catalytic steps in the generation of methyl radicals (as well as in undesired methane combustion) and homogeneous reaction steps in which methyl radicals are coupled to form the desired C2 products (C2H6 and C2H4). It thus forms an ideal test system for the above described microreactor system.
A La-based thin-film catalyst was deposited onto a silicon chip via dip-coating, characterized, and inserted into the microreactor. The effect of major reactor operating parameters, such as temperature, flow rate, C:O feed ratio, and, most importantly, the surface-to-volume ratio were tested in detailed experimental studies using both reactor outlet and spatially-resolved concentration profiles. The results show a strong decrease of C2 production rates with decreasing microreactor channel height (680 µm to 460 and 330 µm), in agreement with the established OCM reaction mechanism. A 2D FEM-based numeric model was also carried out to provide supports and further insights into OCM system. While the Pt- and Rh-catalyzed oxidative dehydrogenation of ethane (ODH) is currently under investigation as the second model reaction, it is promising that this methodology can be transferred to study several other systems, e.g. hydrogen oxidation and catalytic partial oxidation of methane (CPOM) and propane (CPOP).

Sen Liu SEL44
2012-02-02T15:39:53Z 2016-11-15T13:55:09Z http://d-scholarship.pitt.edu/id/eprint/10482 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/10482 2012-02-02T15:39:53Z Carbon Dioxide Capture from Fuel Gas Streams under Elevated Pressures and Temperatures Using Novel Physical Solvents


Yannick J. Heintz
2012-02-02T15:36:28Z 2016-11-15T13:55:22Z http://d-scholarship.pitt.edu/id/eprint/10610 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/10610 2012-02-02T15:36:28Z CONTROLLING MIXING AND SEGREGATION IN TIME PERIODIC GRANULAR FLOWS

Segregation is a major problem for many solids processing industries. Differences in particle
size or density can lead to flow-induced segregation. In the present work, we employ
the discrete element method (DEM) – one type of particle dynamics (PD) technique – to
investigate the mixing and segregation of granular material in some prototypical solid handling
devices, such as a rotating drum and chute. In DEM, one calculates the trajectories of
individual particles based on Newton’s laws of motion by employing suitable contact force
models and a collision detection algorithm. Recently, it has been suggested that segregation
in particle mixers can be thwarted if the particle flow is inverted at a rate above a critical
forcing frequency. Further, it has been hypothesized that, for a rotating drum, the effectiveness
of this technique can be linked to the probability distribution of the number of times
a particle passes through the flowing layer per rotation of the drum. In the first portion of
this work, various configurations of solid mixers are numerically and experimentally studied
to investigate the conditions for improved mixing in light of these hypotheses.

Besides rotating drums, many studies of granular flow have focused on gravity driven
chute flows owing to its practical importance in granular transportation and to the fact
that the relative simplicity of this type of flow allows for development and testing of new
theories. In this part of the work, we observe the deposition behavior of both mono-sized
and polydisperse dry granular materials in an inclined chute flow. The effects of different
parameters such as chute angle, particle size, falling height and charge amount on the mass fraction distribution of granular materials after deposition are investigated. The simulation
results obtained using DEM are compared with the experimental findings and a high degree
of agreement is observed. Tuning of the underlying contact force parameters allows the
achievement of realistic results and is used as a means of validating the model against
available experimental data. The tuned model is then used to find the critical chute length
for segregation based on the hypothesis that segregation can be thwarted if the particle
flow is inverted at a rate above a critical forcing frequency. The critical frequency, fcrit,
is inversely proportional to the characteristic time of segregation, ts. Mixing is observed
instead of segregation when the chute length L < Uavg*ts, where Uavg denotes the average
stream-wise flow velocity of the particles.

While segregation is often an undesired effect, sometimes separating the components
of a particle mixture is the ultimate goal. Rate-based separation processes hold promise
as both more environmentally benign as well as less energy intensive when compared to
conventional particle separations technologies such as vibrating screens or flotation methods.
This approach is based on differences in the kinetic properties of the components of a mixture,
such as the velocity of migration or diffusivity. In this portion of the work, two examples of
novel rate-based separation devices are demonstrated. The first example involves the study of
the dynamics of gravity-driven particles through an array of obstacles. Both discrete element
(DEM) simulations and experiments are used to augment the understanding of this device.
Dissipative collisions (both between the particles themselves and with the obstacles) give rise
to a diffusive motion of particles perpendicular to the flow direction and the differences in
diffusion lengths are exploited to separate the particles. The second example employs DEM
to analyze a ratchet mechanism where a current of particles can be produced in a direction
perpendicular to the energy input. In this setup, a vibrating saw-toothed base is employed
to induce different mobility for different types of particles. The effect of operating conditions
and design parameters on the separation efficiency are discussed.

2012-02-02T13:42:42Z 2016-12-19T14:34:54Z http://d-scholarship.pitt.edu/id/eprint/6235 This item is in the repository with the URL: http://d-scholarship.pitt.edu/id/eprint/6235 2012-02-02T13:42:42Z THERAPEUTIC DEVELOPMENT FOR CYSTIC FIBROSIS

This thesis considers the aspects of therapeutics development for Cystic Fibrosis (CF). The studies are directed at the development of a new therapeutic outcome measurement for evaluating the performance of CF medications. This imaging-based outcome measures the absorption of a small-molecular radiopharmaceutical, Diethylene triamine pentaacetic acid (DTPA) from the airways as a surrogate measure of liquid absorption. Airway liquid hyper-absorption is a key aspect of CF lung disease that would be expected to correct rapidly after administration of a successful therapy. In vivo pilot studies of this technique have been previously performed at our center [1]. Here we report the results of in vitro studies performed to better define the mechanism underpinning our method and define its utility and limitations.

Kristina Thomas KMT12