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Electrical resistivity and conductivity
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows electric current. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm-meter (Ω⋅m).[1][2][3] For example, if a 1 m3 solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity of the material is 1 Ω⋅m.
Resistivity | |
Common symbols | ρ |
SI unit | ohm meter (Ω⋅m) |
In SI base units | kg⋅m3⋅s−3⋅A−2 |
Derivations from other quantities | |
Dimension |
Conductivity | |
Common symbols | σ, κ, γ |
SI unit | siemens per metre (S/m) |
In SI base units | kg−1⋅m−3⋅s3⋅A2 |
Derivations from other quantities | |
Dimension |
Electrical conductivity or specific conductance is the reciprocal of electrical resistivity. It represents a material's ability to conduct electric current. It is commonly signified by the Greek letter σ (sigma), but κ (kappa) (especially in electrical engineering) and γ (gamma) are sometimes used. The SI unit of electrical conductivity is siemens per metre (S/m). Resistivity and conductivity are intensive properties of materials, giving the opposition of a standard cube of material to current. Electrical resistance and conductance are corresponding extensive properties that give the opposition of a specific object to electric current.
Ideal case
In an ideal case, cross-section and physical composition of the examined material are uniform across the sample, and the electric field and current density are both parallel and constant everywhere. Many resistors and conductors do in fact have a uniform cross section with a uniform flow of electric current, and are made of a single material, so that this is a good model. (See the adjacent diagram.) When this is the case, the electrical resistivity ρ (Greek: rho) can be calculated by:
- is the electrical resistance of a uniform specimen of the material
- is the length of the specimen
- is the cross-sectional area of the specimen
The resistivity can be expressed using the SI unit ohm metre (Ω⋅m) — i.e. ohms multiplied by square metres (for the cross-sectional area) then divided by metres (for the length).
Both resistance and resistivity describe how difficult it is to make electrical current flow through a material, but unlike resistance, resistivity is an intrinsic property. This means that all pure copper wires (which have not been subjected to distortion of their crystalline structure etc.), irrespective of their shape and size, have the same resistivity, but a long, thin copper wire has a much larger resistance than a thick, short copper wire. Every material has its own characteristic resistivity. For example, rubber has a far larger resistivity than copper.
In a hydraulic analogy, passing current through a high-resistivity material is like pushing water through a pipe full of sand - while passing current through a low-resistivity material is like pushing water through an empty pipe. If the pipes are the same size and shape, the pipe full of sand has higher resistance to flow. Resistance, however, is not solely determined by the presence or absence of sand. It also depends on the length and width of the pipe: short or wide pipes have lower resistance than narrow or long pipes.
The above equation can be transposed to get Pouillet's law (named after Claude Pouillet):
The resistance of a given element is proportional to the length, but inversely proportional to the cross-sectional area. For example, if A = 1 m2, = 1 m (forming a cube with perfectly conductive contacts on opposite faces), then the resistance of this element in ohms is numerically equal to the resistivity of the material it is made of in Ω⋅m.
Conductivity, σ, is the inverse of resistivity:
Conductivity has SI units of siemens per metre (S/m).
General scalar quantities
For less ideal cases, such as more complicated geometry, or when the current and electric field vary in different parts of the material, it is necessary to use a more general expression in which the resistivity at a particular point is defined as the ratio of the electric field to the density of the current it creates at that point:
- is the resistivity of the conductor material,
- is the magnitude of the electric field,
- is the magnitude of the current density,
in which and are inside the conductor.
Conductivity is the inverse (reciprocal) of resistivity. Here, it is given by:
For example, rubber is a material with large ρ and small σ — because even a very large electric field in rubber makes almost no current flow through it. On the other hand, copper is a material with small ρ and large σ — because even a small electric field pulls a lot of current through it.
As shown below, this expression simplifies to a single number when the electric field and current density are constant in the material.
Derivation from general definition of resistivity There are three equations to be combined here. The first is the resistivity for parallel current and electric field: If the electric field is constant, the electric field is given by the total voltage V across the conductor divided by length ℓ of the conductor:
If the current density is constant, it is equal to the total current divided by the cross sectional area:
Plugging in the values of E and J into the first expression, we obtain:
Finally, we apply Ohm's law, V/I = R:
Tensor resistivity
When the resistivity of a material has a directional component, the most general definition of resistivity must be used. It starts from the tensor-vector form of Ohm's law, which relates the electric field inside a material to the electric current flow. This equation is completely general, meaning it is valid in all cases, including those mentioned above. However, this definition is the most complicated, so it is only directly used in anisotropic cases, where the more simple definitions cannot be applied. If the material is not anisotropic, it is safe to ignore the tensor-vector definition, and use a simpler expression instead.
Here, anisotropic means that the material has different properties in different directions. For example, a crystal of graphite consists microscopically of a stack of sheets, and current flows very easily through each sheet, but much less easily from one sheet to the adjacent one.[4] In such cases, the current does not flow in exactly the same direction as the electric field. Thus, the appropriate equations are generalized to the three-dimensional tensor form:[5][6]
where the conductivity σ and resistivity ρ are rank-2 tensors, and electric field E and current density J are vectors. These tensors can be represented by 3×3 matrices, the vectors with 3×1 matrices, with matrix multiplication used on the right side of these equations. In matrix form, the resistivity relation is given by:
- is the electric field vector, with components (Ex, Ey, Ez);
- is the resistivity tensor, in general a three by three matrix;
- is the electric current density vector, with components (Jx, Jy, Jz).
Equivalently, resistivity can be given in the more compact Einstein notation:
In either case, the resulting expression for each electric field component is:
Since the choice of the coordinate system is free, the usual convention is to simplify the expression by choosing an x-axis parallel to the current direction, so Jy = Jz = 0. This leaves:
Conductivity is defined similarly:[7]
both resulting in:
Looking at the two expressions, and are the matrix inverse of each other. However, in the most general case, the individual matrix elements are not necessarily reciprocals of one another; for example, σxx may not be equal to 1/ρxx. This can be seen in the Hall effect, where is nonzero. In the Hall effect, due to rotational invariance about the z-axis, and , so the relation between resistivity and conductivity simplifies to:[8]
If the electric field is parallel to the applied current, and are zero. When they are zero, one number, , is enough to describe the electrical resistivity. It is then written as simply , and this reduces to the simpler expression.
Conductivity and current carriers
Relation between current density and electric current velocity
Electric current is the ordered movement of electric charges.[2]
Causes of conductivity
Band theory simplified
According to elementary quantum mechanics, an electron in an atom or crystal can only have certain precise energy levels; energies between these levels are impossible. When a large number of such allowed levels have close-spaced energy values – i.e. have energies that differ only minutely – those close energy levels in combination are called an "energy band". There can be many such energy bands in a material, depending on the atomic number of the constituent atoms[lower-alpha 1] and their distribution within the crystal.[lower-alpha 2]
The material's electrons seek to minimize the total energy in the material by settling into low energy states; however, the Pauli exclusion principle means that only one can exist in each such state. So the electrons "fill up" the band structure starting from the bottom. The characteristic energy level up to which the electrons have filled is called the Fermi level. The position of the Fermi level with respect to the band structure is very important for electrical conduction: Only electrons in energy levels near or above the Fermi level are free to move within the broader material structure, since the electrons can easily jump among the partially occupied states in that region. In contrast, the low energy states are completely filled with a fixed limit on the number of electrons at all times, and the high energy states are empty of electrons at all times.
Electric current consists of a flow of electrons. In metals there are many electron energy levels near the Fermi level, so there are many electrons available to move. This is what causes the high electronic conductivity of metals.
An important part of band theory is that there may be forbidden bands of energy: energy intervals that contain no energy levels. In insulators and semiconductors, the number of electrons is just the right amount to fill a certain integer number of low energy bands, exactly to the boundary. In this case, the Fermi level falls within a band gap. Since there are no available states near the Fermi level, and the electrons are not freely movable, the electronic conductivity is very low.
In metals
A metal consists of a lattice of atoms, each with an outer shell of electrons that freely dissociate from their parent atoms and travel through the lattice. This is also known as a positive ionic lattice.[9] This 'sea' of dissociable electrons allows the metal to conduct electric current. When an electrical potential difference (a voltage) is applied across the metal, the resulting electric field causes electrons to drift towards the positive terminal. The actual drift velocity of electrons is typically small, on the order of magnitude of meters per hour. However, due to the sheer number of moving electrons, even a slow drift velocity results in a large current density.[10] The mechanism is similar to transfer of momentum of balls in a Newton's cradle[11] but the rapid propagation of an electric energy along a wire is not due to the mechanical forces, but the propagation of an energy-carrying electromagnetic field guided by the wire.
Most metals have electrical resistance. In simpler models (non quantum mechanical models) this can be explained by replacing electrons and the crystal lattice by a wave-like structure. When the electron wave travels through the lattice, the waves interfere, which causes resistance. The more regular the lattice is, the less disturbance happens and thus the less resistance. The amount of resistance is thus mainly caused by two factors. First, it is caused by the temperature and thus amount of vibration of the crystal lattice. Higher temperatures cause bigger vibrations, which act as irregularities in the lattice. Second, the purity of the metal is relevant as a mixture of different ions is also an irregularity.[12][13] The small decrease in conductivity on melting of pure metals is due to the loss of long range crystalline order. The short range order remains and strong correlation between positions of ions results in coherence between waves diffracted by adjacent ions.[14]
In semiconductors and insulators
In metals, the Fermi level lies in the conduction band (see Band Theory, above) giving rise to free conduction electrons. However, in semiconductors the position of the Fermi level is within the band gap, about halfway between the conduction band minimum (the bottom of the first band of unfilled electron energy levels) and the valence band maximum (the top of the band below the conduction band, of filled electron energy levels). That applies for intrinsic (undoped) semiconductors. This means that at absolute zero temperature, there would be no free conduction electrons, and the resistance is infinite. However, the resistance decreases as the charge carrier density (i.e., without introducing further complications, the density of electrons) in the conduction band increases. In extrinsic (doped) semiconductors, dopant atoms increase the majority charge carrier concentration by donating electrons to the conduction band or producing holes in the valence band. (A "hole" is a position where an electron is missing; such holes can behave in a similar way to electrons.) For both types of donor or acceptor atoms, increasing dopant density reduces resistance. Hence, highly doped semiconductors behave metallically. At very high temperatures, the contribution of thermally generated carriers dominates over the contribution from dopant atoms, and the resistance decreases exponentially with temperature.
In ionic liquids/electrolytes
In electrolytes, electrical conduction happens not by band electrons or holes, but by full atomic species (ions) traveling, each carrying an electrical charge. The resistivity of ionic solutions (electrolytes) varies tremendously with concentration – while distilled water is almost an insulator, salt water is a reasonable electrical conductor. Conduction in ionic liquids is also controlled by the movement of ions, but here we are talking about molten salts rather than solvated ions. In biological membranes, currents are carried by ionic salts. Small holes in cell membranes, called ion channels, are selective to specific ions and determine the membrane resistance.
The concentration of ions in a liquid (e.g., in an aqueous solution) depends on the degree of dissociation of the dissolved substance, characterized by a dissociation coefficient , which is the ratio of the concentration of ions to the concentration of molecules of the dissolved substance :
The specific electrical conductivity () of a solution is equal to:
where : module of the ion charge, and : mobility of positively and negatively charged ions, : concentration of molecules of the dissolved substance, : the coefficient of dissociation.
The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In normal (that is, non-superconducting) conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. In a normal conductor, the current is driven by a voltage gradient, whereas in a superconductor, there is no voltage gradient and the current is instead related to the phase gradient of the superconducting order parameter.[15] A consequence of this is that an electric current flowing in a loop of superconducting wire can persist indefinitely with no power source.[16]
In a class of superconductors known as type II superconductors, including all known high-temperature superconductors, an extremely low but nonzero resistivity appears at temperatures not too far below the nominal superconducting transition when an electric current is applied in conjunction with a strong magnetic field, which may be caused by the electric current. This is due to the motion of magnetic vortices in the electronic superfluid, which dissipates some of the energy carried by the current. The resistance due to this effect is tiny compared with that of non-superconducting materials, but must be taken into account in sensitive experiments. However, as the temperature decreases far enough below the nominal superconducting transition, these vortices can become frozen so that the resistance of the material becomes truly zero.
Plasmas are very good conductors and electric potentials play an important role.
The potential as it exists on average in the space between charged particles, independent of the question of how it can be measured, is called the plasma potential, or space potential. If an electrode is inserted into a plasma, its potential generally lies considerably below the plasma potential, due to what is termed a Debye sheath. The good electrical conductivity of plasmas makes their electric fields very small. This results in the important concept of quasineutrality, which says the density of negative charges is approximately equal to the density of positive charges over large volumes of the plasma (ne = ⟨Z⟩>ni), but on the scale of the Debye length there can be charge imbalance. In the special case that double layers are formed, the charge separation can extend some tens of Debye lengths.
The magnitude of the potentials and electric fields must be determined by means other than simply finding the net charge density. A common example is to assume that the electrons satisfy the Boltzmann relation:
Differentiating this relation provides a means to calculate the electric field from the density:
(∇ is the vector gradient operator; see nabla symbol and gradient for more information.)
It is possible to produce a plasma that is not quasineutral. An electron beam, for example, has only negative charges. The density of a non-neutral plasma must generally be very low, or it must be very small. Otherwise, the repulsive electrostatic force dissipates it.
In astrophysical plasmas, Debye screening prevents electric fields from directly affecting the plasma over large distances, i.e., greater than the Debye length. However, the existence of charged particles causes the plasma to generate, and be affected by, magnetic fields. This can and does cause extremely complex behavior, such as the generation of plasma double layers, an object that separates charge over a few tens of Debye lengths. The dynamics of plasmas interacting with external and self-generated magnetic fields are studied in the academic discipline of magnetohydrodynamics.
Plasma is often called the fourth state of matter after solid, liquids and gases.[18][19] It is distinct from these and other lower-energy states of matter. Although it is closely related to the gas phase in that it also has no definite form or volume, it differs in a number of ways, including the following:
Property | Gas | Plasma |
Electrical conductivity | Very low: air is an excellent insulator until it breaks down into plasma at electric field strengths above 30 kilovolts per centimeter.[20] | Usually very high: for many purposes, the conductivity of a plasma may be treated as infinite. |
Independently acting species | One: all gas particles behave in a similar way, influenced by gravity and by collisions with one another. | Two or three: electrons, ions, protons and neutrons can be distinguished by the sign and value of their charge so that they behave independently in many circumstances, with different bulk velocities and temperatures, allowing phenomena such as new types of waves and instabilities. |
Velocity distribution | Maxwellian: collisions usually lead to a Maxwellian velocity distribution of all gas particles, with very few relatively fast particles. | Often non-Maxwellian: collisional interactions are often weak in hot plasmas and external forcing can drive the plasma far from local equilibrium and lead to a significant population of unusually fast particles. |
Interactions | Binary: two-particle collisions are the rule, three-body collisions extremely rare. | Collective: waves, or organized motion of plasma, are very important because the particles can interact at long ranges through the electric and magnetic forces. |
Resistivity and conductivity of various materials
- A conductor such as a metal has high conductivity and a low resistivity.
- An insulator like glass has low conductivity and a high resistivity.
- The conductivity of a semiconductor is generally intermediate, but varies widely under different conditions, such as exposure of the material to electric fields or specific frequencies of light, and, most important, with temperature and composition of the semiconductor material.
The degree of semiconductors doping makes a large difference in conductivity. To a point, more doping leads to higher conductivity. The conductivity of a water/aqueous solution is highly dependent on its concentration of dissolved salts, and other chemical species that ionize in the solution. Electrical conductivity of water samples is used as an indicator of how salt-free, ion-free, or impurity-free the sample is; the purer the water, the lower the conductivity (the higher the resistivity). Conductivity measurements in water are often reported as specific conductance, relative to the conductivity of pure water at 25 °C. An EC meter is normally used to measure conductivity in a solution. A rough summary is as follows:
Material | Resistivity, ρ (Ω·m) |
Superconductors | 0 |
Metals | 10−8 |
Semiconductors | Variable |
Electrolytes | Variable |
Insulators | 1016 |
Superinsulators | ∞ |
This table shows the resistivity (ρ), conductivity and temperature coefficient of various materials at 20 °C (68 °F; 293 K).
Material | Resistivity, ρ, at 20 °C (Ω·m) |
Conductivity, σ, at 20 °C (S/m) |
Temperature coefficient[lower-alpha 3] (K−1) |
Reference |
Silver[lower-alpha 4] | 1.59×10−8 | 6.30×107 | 3.80×10−3 | [21][22] |
Copper[lower-alpha 5] | 1.68×10−8 | 5.96×107 | 4.04×10−3 | [23][24] |
Annealed copper[lower-alpha 6] | 1.72×10−8 | 5.80×107 | 3.93×10−3 | [25] |
Gold[lower-alpha 7] | 2.44×10−8 | 4.11×107 | 3.40×10−3 | [21] |
Aluminium[lower-alpha 8] | 2.65×10−8 | 3.77×107 | 3.90×10−3 | [21] |
Brass (5% Zn) | 3.00×10−8 | 3.34×107 | [26] | |
Calcium | 3.36×10−8 | 2.98×107 | 4.10×10−3 | |
Rhodium | 4.33×10−8 | 2.31×107 | ||
Tungsten | 5.60×10−8 | 1.79×107 | 4.50×10−3 | [21] |
Zinc | 5.90×10−8 | 1.69×107 | 3.70×10−3 | [27] |
Brass (30% Zn) | 5.99×10−8 | 1.67×107 | [28] | |
Cobalt[lower-alpha 9] | 6.24×10−8 | 1.60×107 | 7.00×10−3[30] | |
Nickel | 6.99×10−8 | 1.43×107 | 6.00×10−3 | |
Ruthenium[lower-alpha 9] | 7.10×10−8 | 1.41×107 | ||
Lithium | 9.28×10−8 | 1.08×107 | 6.00×10−3 | |
Iron | 9.70×10−8 | 1.03×107 | 5.00×10−3 | [21] |
Platinum | 10.6×10−8 | 9.43×106 | 3.92×10−3 | [21] |
Tin | 10.9×10−8 | 9.17×106 | 4.50×10−3 | |
Phosphor Bronze (0.2% P / 5% Sn) | 11.2×10−8 | 8.94×106 | [31] | |
Gallium | 14.0×10−8 | 7.10×106 | 4.00×10−3 | |
Niobium | 14.0×10−8 | 7.00×106 | [32] | |
Carbon steel (1010) | 14.3×10−8 | 6.99×106 | [33] | |
Lead | 22.0×10−8 | 4.55×106 | 3.90×10−3 | [21] |
Galinstan | 28.9×10−8 | 3.46×106 | [34] | |
Titanium | 42.0×10−8 | 2.38×106 | 3.80×10−3 | |
Grain oriented electrical steel | 46.0×10−8 | 2.17×106 | [35] | |
Manganin | 48.2×10−8 | 2.07×106 | 0.002×10−3 | [36] |
Constantan | 49.0×10−8 | 2.04×106 | 0.008×10−3 | [37] |
Stainless steel[lower-alpha 10] | 69.0×10−8 | 1.45×106 | 0.94×10−3 | [38] |
Mercury | 98.0×10−8 | 1.02×106 | 0.90×10−3 | [36] |
Manganese | 144×10−8 | 6.94×105 | ||
Nichrome[lower-alpha 11] | 110×10−8 | 6.70×105 | 0.40×10−3 | [21] |
Carbon (graphite) parallel to basal plane[lower-alpha 12] |
250×10−8 to 500×10−8 | 2×105 to 3×105 | [4] | |
Carbon (amorphous) | 0.5×10−3 to 0.8×10−3 | 1.25×103 to 2.00×103 | −0.50×10−3 | [21][39] |
Carbon (graphite) perpendicular to basal plane |
3.0×10−3 | 3.3×102 | [4] | |
GaAs | 10−3 to 108 | 10−8 to 103 | [40] | |
Germanium[lower-alpha 13] | 4.6×10−1 | 2.17 | −48.0×10−3 | [21][22] |
Sea water[lower-alpha 14] | 2.1×10−1 | 4.8 | [41] | |
Swimming pool water[lower-alpha 15] | 3.3×10−1 to 4.0×10−1 | 0.25 to 0.30 | [42] | |
Drinking water[lower-alpha 16] | 2×101 to 2×103 | 5×10−4 to 5×10−2 | ||
Silicon[lower-alpha 13] | 2.3×103 | 4.35×10−4 | −75.0×10−3 | [43][21] |
Wood (damp) | 103 to 104 | 10−4 to 10−3 | [44] | |
Deionized water[lower-alpha 17] | 1.8×105 | 4.2×10−5 | [45] | |
Ultrapure water | 1.82×109 | 5.49×10−10 | [46][47] | |
Glass | 1011 to 1015 | 10−15 to 10−11 | [21][22] | |
Carbon (diamond) | 1012 | ~10−13 | [48] | |
Hard rubber | 1013 | 10−14 | [21] | |
Air | 109 to 1015 | ~10−15 to 10−9 | [49][50] | |
Wood (oven dry) | 1014 to 1016 | 10−16 to 10−14 | [44] | |
Sulfur | 1015 | 10−16 | [21] | |
Fused quartz | 7.5×1017 | 1.3×10−18 | [21] | |
PTFE (teflon) | 1023 to 1025 | 10−25 to 10−23 |
The effective temperature coefficient varies with temperature and purity level of the material. The 20 °C value is only an approximation when used at other temperatures. For example, the coefficient becomes lower at higher temperatures for copper, and the value 0.00427 is commonly specified at 0 °C.[51]
The extremely low resistivity (high conductivity) of silver is characteristic of metals. George Gamow tidily summed up the nature of the metals' dealings with electrons in his popular science book One, Two, Three...Infinity (1947):
The metallic substances differ from all other materials by the fact that the outer shells of their atoms are bound rather loosely, and often let one of their electrons go free. Thus the interior of a metal is filled up with a large number of unattached electrons that travel aimlessly around like a crowd of displaced persons. When a metal wire is subjected to electric force applied on its opposite ends, these free electrons rush in the direction of the force, thus forming what we call an electric current.
More technically, the free electron model gives a basic description of electron flow in metals.
Wood is widely regarded as an extremely good insulator, but its resistivity is sensitively dependent on moisture content, with damp wood being a factor of at least 1010 worse insulator than oven-dry.[44] In any case, a sufficiently high voltage – such as that in lightning strikes or some high-tension power lines – can lead to insulation breakdown and electrocution risk even with apparently dry wood.
Temperature dependence
Linear approximation
The electrical resistivity of most materials changes with temperature. If the temperature T does not vary too much, a linear approximation is typically used:
where is called the temperature coefficient of resistivity, is a fixed reference temperature (usually room temperature), and is the resistivity at temperature . The parameter is an empirical parameter fitted from measurement data, equal to 1/. Because the linear approximation is only an approximation, is different for different reference temperatures. For this reason it is usual to specify the temperature that was measured at with a suffix, such as , and the relationship only holds in a range of temperatures around the reference.[52] When the temperature varies over a large temperature range, the linear approximation is inadequate and a more detailed analysis and understanding should be used.
In general, electrical resistivity of metals increases with temperature. Electron–phonon interactions can play a key role. At high temperatures, the resistance of a metal increases linearly with temperature. As the temperature of a metal is reduced, the temperature dependence of resistivity follows a power law function of temperature. Mathematically the temperature dependence of the resistivity ρ of a metal can be approximated through the Bloch–Grüneisen formula:[53]
where is the residual resistivity due to defect scattering, A is a constant that depends on the velocity of electrons at the Fermi surface, the Debye radius and the number density of electrons in the metal. is the Debye temperature as obtained from resistivity measurements and matches very closely with the values of Debye temperature obtained from specific heat measurements. n is an integer that depends upon the nature of interaction:
- n = 5 implies that the resistance is due to scattering of electrons by phonons (as it is for simple metals)
- n = 3 implies that the resistance is due to s-d electron scattering (as is the case for transition metals)
- n = 2 implies that the resistance is due to electron–electron interaction.
The Bloch–Grüneisen formula is an approximation obtained assuming that the studied metal has spherical Fermi surface inscribed within the first Brillouin zone and a Debye phonon spectrum.[54]
If more than one source of scattering is simultaneously present, Matthiessen's rule (first formulated by Augustus Matthiessen in the 1860s)[55][56] states that the total resistance can be approximated by adding up several different terms, each with the appropriate value of n.
As the temperature of the metal is sufficiently reduced (so as to 'freeze' all the phonons), the resistivity usually reaches a constant value, known as the residual resistivity. This value depends not only on the type of metal, but on its purity and thermal history. The value of the residual resistivity of a metal is decided by its impurity concentration. Some materials lose all electrical resistivity at sufficiently low temperatures, due to an effect known as superconductivity.
An investigation of the low-temperature resistivity of metals was the motivation to Heike Kamerlingh Onnes's experiments that led in 1911 to discovery of superconductivity. For details see History of superconductivity.
Wiedemann–Franz law
The Wiedemann–Franz law states that the coefficient of electrical conductivity of metals at normal temperatures is inversely proportional to the temperature:[57]
For metals at high temperatures, the Wiedemann–Franz law holds:
where is the thermal conductivity of the metal, is the Boltzmann constant, is the electron charge, is temperature, and is the electrical conductivity coefficient.
In general, intrinsic semiconductor resistivity decreases with increasing temperature. The electrons are bumped to the conduction energy band by thermal energy, where they flow freely, and in doing so leave behind holes in the valence band, which also flow freely. The electric resistance of a typical intrinsic (non doped) semiconductor decreases exponentially with temperature:
An even better approximation of the temperature dependence of the resistivity of a semiconductor is given by the Steinhart–Hart equation:
where A, B and C are the so-called Steinhart–Hart coefficients.
This equation is used to calibrate thermistors.
Extrinsic (doped) semiconductors have a far more complicated temperature profile. As temperature increases starting from absolute zero they first decrease steeply in resistance as the carriers leave the donors or acceptors. After most of the donors or acceptors have lost their carriers, the resistance starts to increase again slightly due to the reducing mobility of carriers (much as in a metal). At higher temperatures, they behave like intrinsic semiconductors as the carriers from the donors/acceptors become insignificant compared to the thermally generated carriers.[58]
In non-crystalline semiconductors, conduction can occur by charges quantum tunnelling from one localised site to another. This is known as variable range hopping and has the characteristic form of
where n = 2, 3, 4, depending on the dimensionality of the system.
Complex resistivity and conductivity
When analyzing the response of materials to alternating electric fields (dielectric spectroscopy),[59] in applications such as electrical impedance tomography,[60] it is convenient to replace resistivity with a complex quantity called impedivity (in analogy to electrical impedance). Impedivity is the sum of a real component, the resistivity, and an imaginary component, the reactivity (in analogy to reactance). The magnitude of impedivity is the square root of sum of squares of magnitudes of resistivity and reactivity.
Conversely, in such cases the conductivity must be expressed as a complex number (or even as a matrix of complex numbers, in the case of anisotropic materials) called the admittivity. Admittivity is the sum of a real component called the conductivity and an imaginary component called the susceptivity.
An alternative description of the response to alternating currents uses a real (but frequency-dependent) conductivity, along with a real permittivity. The larger the conductivity is, the more quickly the alternating-current signal is absorbed by the material (i.e., the more opaque the material is). For details, see Mathematical descriptions of opacity.
Resistance versus resistivity in complicated geometries
Even if the material's resistivity is known, calculating the resistance of something made from it may, in some cases, be much more complicated than the formula above. One example is spreading resistance profiling, where the material is inhomogeneous (different resistivity in different places), and the exact paths of current flow are not obvious.
In cases like this, the formulas
must be replaced with
where E and J are now vector fields. This equation, along with the continuity equation for J and the Poisson's equation for E, form a set of partial differential equations. In special cases, an exact or approximate solution to these equations can be worked out by hand, but for very accurate answers in complex cases, computer methods like finite element analysis may be required.
Resistivity-density product
In some applications where the weight of an item is very important, the product of resistivity and density is more important than absolute low resistivity – it is often possible to make the conductor thicker to make up for a higher resistivity; and then a low-resistivity-density-product material (or equivalently a high conductivity-to-density ratio) is desirable. For example, for long-distance overhead power lines, aluminium is frequently used rather than copper (Cu) because it is lighter for the same conductance.
Silver, although it is the least resistive metal known, has a high density and performs similarly to copper by this measure, but is much more expensive. Calcium and the alkali metals have the best resistivity-density products, but are rarely used for conductors due to their high reactivity with water and oxygen (and lack of physical strength). Aluminium is far more stable. Toxicity excludes the choice of beryllium.[61] (Pure beryllium is also brittle.) Thus, aluminium is usually the metal of choice when the weight or cost of a conductor is the driving consideration.
Material | Resistivity (nΩ·m) |
Density (g/cm3) |
Resistivity × density | Resistivity relative to Cu, ie cross-sectional area required to give same conductance | Approx. price, at 9 December 2018 | ||
(g·mΩ/m2) | Relative to Cu |
(USD per kg) |
Relative to Cu | ||||
Sodium | 47.7 | 0.97 | 46 | 31% | 2.843 | ||
Lithium | 92.8 | 0.53 | 49 | 33% | 5.531 | ||
Calcium | 33.6 | 1.55 | 52 | 35% | 2.002 | ||
Potassium | 72.0 | 0.89 | 64 | 43% | 4.291 | ||
Beryllium | 35.6 | 1.85 | 66 | 44% | 2.122 | ||
Aluminium | 26.50 | 2.70 | 72 | 48% | 1.579 | 2.0 | 0.16 |
Magnesium | 43.90 | 1.74 | 76 | 51% | 2.616 | ||
Copper | 16.78 | 8.96 | 150 | 100% | 1 | 6.0 | 1 |
Silver | 15.87 | 10.49 | 166 | 111% | 0.946 | 456 | 84 |
Gold | 22.14 | 19.30 | 427 | 285% | 1.319 | 39,000 | 19,000 |
Iron | 96.1 | 7.874 | 757 | 505% | 5.727 |
See also
- Charge transport mechanisms
- Chemiresistor
- Classification of materials based on permittivity
- Conductivity near the percolation threshold
- Contact resistance
- Electrical resistivities of the elements (data page)
- Electrical resistivity tomography
- Sheet resistance
- SI electromagnetism units
- Skin effect
- Spitzer resistivity
- Dielectric strength
- The atomic number is the count of electrons in an atom that is electrically neutral – has no net electric charge.
- Other relevant factors that are specifically not considered are the size of the whole crystal and external factors of the surrounding environment that modify the energy bands, such as imposed electric or magnetic fields.
- The numbers in this column increase or decrease the significand portion of the resistivity. For example, at 30 °C (303 K), the resistivity of silver is 1.65×10−8. This is calculated as Δρ = α ΔT ρ0 where ρ0 is the resistivity at 20 °C (in this case) and α is the temperature coefficient.
- The conductivity of metallic silver is not significantly better than metallic copper for most practical purposes – the difference between the two can be easily compensated for by thickening the copper wire by only 3%. However silver is preferred for exposed electrical contact points because corroded silver is a tolerable conductor, but corroded copper is a fairly good insulator, like most corroded metals.
- Copper is widely used in electrical equipment, building wiring, and telecommunication cables.
- Referred to as 100% IACS or International Annealed Copper Standard. The unit for expressing the conductivity of nonmagnetic materials by testing using the eddy current method. Generally used for temper and alloy verification of aluminium.
- Despite being less conductive than copper, gold is commonly used in electrical contacts because it does not easily corrode.
- Commonly used for overhead power line with steel reinforced (ACSR)
- Cobalt and ruthenium are considered to replace copper in integrated circuits fabricated in advanced nodes[29]
- 18% chromium and 8% nickel austenitic stainless steel
- Nickel-iron-chromium alloy commonly used in heating elements.
- Graphite is strongly anisotropic.
- The resistivity of semiconductors depends strongly on the presence of impurities in the material.
- Corresponds to an average salinity of 35 g/kg at 20 °C.
- The pH should be around 8.4 and the conductivity in the range of 2.5–3 mS/cm. The lower value is appropriate for freshly prepared water. The conductivity is used for the determination of TDS (total dissolved particles).
- This value range is typical of high quality drinking water and not an indicator of water quality
- Conductivity is lowest with monatomic gases present; changes to 12×10−5 upon complete de-gassing, or to 7.5×10−5 upon equilibration to the atmosphere due to dissolved CO2
- Lowrie, William (2007). Fundamentals of Geophysics. Cambridge University Press. pp. 254–55. ISBN 978-05-2185-902-8. Retrieved March 24, 2019.
- Kumar, Narinder (2003). Comprehensive Physics for Class XII. New Delhi: Laxmi Publications. pp. 280–84. ISBN 978-81-7008-592-8. Retrieved March 24, 2019.
- Bogatin, Eric (2004). Signal Integrity: Simplified. Prentice Hall Professional. p. 114. ISBN 978-0-13-066946-9. Retrieved March 24, 2019.
- Hugh O. Pierson, Handbook of carbon, graphite, diamond, and fullerenes: properties, processing, and applications, p. 61, William Andrew, 1993 ISBN 0-8155-1339-9.
- J.R. Tyldesley (1975) An introduction to Tensor Analysis: For Engineers and Applied Scientists, Longman, ISBN 0-582-44355-5
- G. Woan (2010) The Cambridge Handbook of Physics Formulas, Cambridge University Press, ISBN 978-0-521-57507-2
- Josef Pek, Tomas Verner (3 Apr 2007). "Finite‐difference modelling of magnetotelluric fields in two‐dimensional anisotropic media". Geophysical Journal International. 128 (3): 505–521. doi:10.1111/j.1365-246X.1997.tb05314.x.
- David Tong (Jan 2016). "The Quantum Hall Effect: TIFR Infosys Lectures" (PDF). Retrieved 14 Sep 2018.
- Bonding (sl). ibchem.com
- "Current versus Drift Speed". The physics classroom. Retrieved 20 August 2014.
- Lowe, Doug (2012). Electronics All-in-One For Dummies. John Wiley & Sons. ISBN 978-0-470-14704-7.
- Keith Welch. "Questions & Answers – How do you explain electrical resistance?". Thomas Jefferson National Accelerator Facility. Retrieved 28 April 2017.
- "Electromigration : What is electromigration?". Middle East Technical University. Retrieved 31 July 2017.
When electrons are conducted through a metal, they interact with imperfections in the lattice and scatter. […] Thermal energy produces scattering by causing atoms to vibrate. This is the source of resistance of metals.
- Faber, T.E. (1972). Introduction to the Theory of Liquid Metals. Cambridge University Press. ISBN 9780521154499.
- "The Feynman Lectures in Physics, Vol. III, Chapter 21: The Schrödinger Equation in a Classical Context: A Seminar on Superconductivity". Retrieved 26 December 2021.
- John C. Gallop (1990). SQUIDS, the Josephson Effects and Superconducting Electronics. CRC Press. pp. 3, 20. ISBN 978-0-7503-0051-3.
- See Flashes in the Sky: Earth's Gamma-Ray Bursts Triggered by Lightning
- Yaffa Eliezer, Shalom Eliezer, The Fourth State of Matter: An Introduction to the Physics of Plasma, Publisher: Adam Hilger, 1989, ISBN 978-0-85274-164-1, 226 pages, page 5
- Bittencourt, J.A. (2004). Fundamentals of Plasma Physics. Springer. p. 1. ISBN 9780387209753.
- Hong, Alice (2000). "Dielectric Strength of Air". The Physics Factbook.
- Raymond A. Serway (1998). Principles of Physics (2nd ed.). Fort Worth, Texas; London: Saunders College Pub. p. 602. ISBN 978-0-03-020457-9.
- David Griffiths (1999) [1981]. "7 Electrodynamics". In Alison Reeves (ed.). Introduction to Electrodynamics (3rd ed.). Upper Saddle River, New Jersey: Prentice Hall. p. 286. ISBN 978-0-13-805326-0. OCLC 40251748.
- Matula, R.A. (1979). "Electrical resistivity of copper, gold, palladium, and silver". Journal of Physical and Chemical Reference Data. 8 (4): 1147. Bibcode:1979JPCRD...8.1147M. doi:10.1063/1.555614. S2CID 95005999.
- Douglas Giancoli (2009) [1984]. "25 Electric Currents and Resistance". In Jocelyn Phillips (ed.). Physics for Scientists and Engineers with Modern Physics (4th ed.). Upper Saddle River, New Jersey: Prentice Hall. p. 658. ISBN 978-0-13-149508-1.
- "Copper wire tables". United States National Bureau of Standards. Retrieved 3 February 2014 – via Internet Archive - archive.org (archived 2001-03-10).
- . (Calculated as "56% conductivity of pure copper" (5.96E-7)). Retrieved on 2023-1-12.
- Physical constants. (PDF format; see page 2, table in the right lower corner). Retrieved on 2011-12-17.
- . (Calculated as "28% conductivity of pure copper" (5.96E-7)). Retrieved on 2023-1-12.
- IITC – Imec Presents Copper, Cobalt and Ruthenium Interconnect Results
- "Temperature Coefficient of Resistance | Electronics Notes".
- . (Calculated as "15% conductivity of pure copper" (5.96E-7)). Retrieved on 2023-1-12.
- Material properties of niobium.
- AISI 1010 Steel, cold drawn. Matweb
- Karcher, Ch.; Kocourek, V. (December 2007). "Free-surface instabilities during electromagnetic shaping of liquid metals". Proceedings in Applied Mathematics and Mechanics. 7 (1): 4140009–4140010. doi:10.1002/pamm.200700645. ISSN 1617-7061.
- "JFE steel" (PDF). Retrieved 2012-10-20.
- Douglas C. Giancoli (1995). Physics: Principles with Applications (4th ed.). London: Prentice Hall. ISBN 978-0-13-102153-2.
(see also Table of Resistivity. hyperphysics.phy-astr.gsu.edu) - John O'Malley (1992) Schaum's outline of theory and problems of basic circuit analysis, p. 19, McGraw-Hill Professional, ISBN 0-07-047824-4
- Glenn Elert (ed.), "Resistivity of steel", The Physics Factbook, retrieved and archived 16 June 2011.
- Y. Pauleau, Péter B. Barna, P. B. Barna (1997) Protective coatings and thin films: synthesis, characterization, and applications, p. 215, Springer, ISBN 0-7923-4380-8.
- Milton Ohring (1995). Engineering materials science, Volume 1 (3rd ed.). Academic Press. p. 561. ISBN 978-0125249959.
- Physical properties of sea water Archived 2018-01-18 at the Wayback Machine. Kayelaby.npl.co.uk. Retrieved on 2011-12-17.
- . chemistry.stackexchange.com
- Eranna, Golla (2014). Crystal Growth and Evaluation of Silicon for VLSI and ULSI. CRC Press. p. 7. ISBN 978-1-4822-3281-3.
- Transmission Lines data. Transmission-line.net. Retrieved on 2014-02-03.
- R. M. Pashley; M. Rzechowicz; L. R. Pashley; M. J. Francis (2005). "De-Gassed Water is a Better Cleaning Agent". The Journal of Physical Chemistry B. 109 (3): 1231–8. doi:10.1021/jp045975a. PMID 16851085.
- ASTM D1125 Standard Test Methods for Electrical Conductivity and Resistivity of Water
- ASTM D5391 Standard Test Method for Electrical Conductivity and Resistivity of a Flowing High Purity Water Sample
- Lawrence S. Pan, Don R. Kania, Diamond: electronic properties and applications, p. 140, Springer, 1994 ISBN 0-7923-9524-7.
- S. D. Pawar; P. Murugavel; D. M. Lal (2009). "Effect of relative humidity and sea level pressure on electrical conductivity of air over Indian Ocean". Journal of Geophysical Research. 114 (D2): D02205. Bibcode:2009JGRD..114.2205P. doi:10.1029/2007JD009716.
- E. Seran; M. Godefroy; E. Pili (2016). "What we can learn from measurements of air electric conductivity in 222Rn ‐ rich atmosphere". Earth and Space Science. 4 (2): 91–106. Bibcode:2017E&SS....4...91S. doi:10.1002/2016EA000241.
- Copper Wire Tables Archived 2010-08-21 at the Wayback Machine. US Dep. of Commerce. National Bureau of Standards Handbook. February 21, 1966
- Ward, Malcolm R. (1971). Electrical engineering science. McGraw-Hill technical education. Maidenhead, UK: McGraw-Hill. pp. 36–40. ISBN 9780070942554.
- Grüneisen, E. (1933). "Die Abhängigkeit des elektrischen Widerstandes reiner Metalle von der Temperatur". Annalen der Physik. 408 (5): 530–540. Bibcode:1933AnP...408..530G. doi:10.1002/andp.19334080504. ISSN 1521-3889.
- Quantum theory of real materials. James R. Chelikowsky, Steven G. Louie. Boston: Kluwer Academic Publishers. 1996. pp. 219–250. ISBN 0-7923-9666-9. OCLC 33335083.
{{cite book}}
: CS1 maint: others (link) - A. Matthiessen, Rep. Brit. Ass. 32, 144 (1862)
- A. Matthiessen, Progg. Anallen, 122, 47 (1864)
- Jones, William; March, Norman H. (1985). Theoretical Solid State Physics. Dover Publications.
- J. Seymour (1972) Physical Electronics, chapter 2, Pitman
- Stephenson, C.; Hubler, A. (2015). "Stability and conductivity of self-assembled wires in a transverse electric field". Sci. Rep. 5: 15044. Bibcode:2015NatSR...515044S. doi:10.1038/srep15044. PMC 4604515. PMID 26463476.
- Otto H. Schmitt, University of Minnesota Mutual Impedivity Spectrometry and the Feasibility of its Incorporation into Tissue-Diagnostic Anatomical Reconstruction and Multivariate Time-Coherent Physiological Measurements. otto-schmitt.org. Retrieved on 2011-12-17.
- "Berryllium (Be) - Chemical properties, Health and Environmental effects".
Further reading
- Paul Tipler (2004). Physics for Scientists and Engineers: Electricity, Magnetism, Light, and Elementary Modern Physics (5th ed.). W. H. Freeman. ISBN 978-0-7167-0810-0.
- Measuring Electrical Resistivity and Conductivity
External links
- "Electrical Conductivity". Sixty Symbols. Brady Haran for the University of Nottingham. 2010.
- Comparison of the electrical conductivity of various elements in WolframAlpha
- Partial and total conductivity. "Electrical conductivity" (PDF).


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Tim McGraw Recalls the Moment When His Drinking Hit Rock Bottom: 'I Was Scared'
Tim McGraw makes no secret of the fact that he has struggled with alcohol in the past. Now the country superstar is opening up to Esquire about an incident that scared him and forced him to admit his problem to his wife, Faith Hill, whose support "changed my life."
McGraw has said that he began drinking in his teenage years, and by the time he had established himself as a leading star in country music, his habit had progressed to where he felt it was a problem. In an article titled 'What I've Learned,' he shares how deep he sank into problem drinking before he turned things around.
"I remember a moment when I was getting out of bed and going to the liquor cabinet and taking a big shot at 8:00 in the morning and thinking, 'I have to wake the kids up,'" McGraw relates.
"I went straight to my wife and said, 'This is where I'm at.' I was scared," he admits. "She just grabbed me and hugged me and changed my life."
McGraw told Men's Health in 2014 that he'd known he had to quit drinking for his wife and daughters. Hill had reached a breaking point.
"When your wife tells you it's gone too far, that's a big wake-up call," McGraw recalled. "That, and realizing you're gonna lose everything you have. Not monetarily, not career-wise, but family-wise."
"It got to the point where my kids were getting older, and it was way past the point that they noticed it," he said. "And I noticed that they noticed. That's enough to straighten you out ... I drank too much. I partied too much. And did other things too much. Chemically. No needles or that kind of stuff, but ... use your imagination."
McGraw said Keith Whitley's death in 1989 from alcohol poisoning was one thing that made him start looking at his own drinking habits differently.
"Keith Whitley taught me how demons can overtake you if you let 'em," he observed. "And I was headed down that path. You feel like you're supposed to be 'on' all the time. Then you drink and get onstage, and all of a sudden you feel confident and powerful."
"It becomes a habit," McGraw continued, admitting that up until 2007 when he got sober, "there were not a lot of shows that I didn't have something in my system."
McGraw and Hill are set to star in the upcoming Yellowstone prequel, 1883, in which they'll play the great-grandparents of John Dutton, Kevin Costner's Yellowstone character, who owns the largest contiguous cattle ranch in the United States. The story will follow their family's journey west from Texas to Montana, where they eventually establish the ranch that sets the stage for the runaway hit show on the Paramount Network.
1883 is set to premiere on Dec. 19. The show will air on Paramount's streaming service, Paramount+. Subscribe to the streaming service to make sure you don't miss out.
PICTURES: Sweet Tim McGraw + Faith Hill Moments


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BASF pulls out of European GM market
The German chemical and biotechnology company said it would relocate the headquarters of its BASF Plant Science group from Limburgerhof in Germany, to Raleigh in the USA. The company added that it will be concentrating its plant biotechnology activities on its main markets in North and South America in the future.
The company added that its development and commercialisation of all GM products targeted solely at cultivation in the European market will be halted – these include four varieties of potato and one of wheat.
"We are convinced that plant biotechnology is a key technology for the 21st century. However, there is still a lack of acceptance for this technology in many parts of Europe – from the majority of consumers, farmers and politicians," said Dr. Stefan Marcinowski, a member of the BASF board of executive directors, responsible for plant biotechnology.
"It does not make business sense to continue investing in products exclusively for cultivation in this market," he said. "We will therefore concentrate on the attractive markets for plant biotechnology in North and South America and the growth markets in Asia."
Acceptance for innovation?
BASF cited a lack of consumer and industry acceptance as the main reason for its decision to halt European operations in GM products. It added that the decision to relocate to the USA was taken because there is "less resistance" to the technology.
The announcement was celebrated by environmental campaign groups Greenpeace and Friends of the Earth: "This is another nail in the coffin for genetically modified foods in Europe," said Adrian Bebb of Friends of the Earth.
Whilst Greenpeace EU agriculture policy director Marco Contiero said the announcement shows that "BASF admits Europeans don't want GM crops."
"Europeans are not alone in rejecting GM food," he added. "BASF's retreat to the Americas follows a string of defeats for the industry over the last two years in China, India, the Philippines, Thailand and elsewhere. Over 90% of GM food crops are grown in just four countries in the Americas."
However, the move by BASF has also been also been seen a major blow for science and innovation in the European market. Professor Denis Murphy of the University of Glamorgan, UK, warned that Europe "is now in danger of becoming a scientific backwater and will be unable to assist developing countries the address food insecurity."
"There is now a danger that we will lose, not only companies like BASF, but also academic researchers and students – as well as any influence that we have had previously in developing countries where we used to be major providers of assistance and expertise," argued Murphy – an expert in biotechnology.
BASF said it will adjust the portfolio and site footprint of its plant science to reflect the move. The chemical giant said the move to new headquarters for activities in the area of plant biotechnology at Raleigh in North Carolina will see the current HQ site in Limburgerhof, Germany retain 11 positions in some functions, such as regulatory experts for Europe.
The division employees 157 people in Limburgerhof, plus another 63 at facilities elsewhere in Europe. BASF said it would relocate 123 of those jobs to the North Carolina facility. The company plans to close its sites in Gatersleben, Germany, and in Svalöv, Sweden.
The announcement will mean a reduction of 140 jobs in BASF's European operations. The company said it aims to offer the affected employees other positions within the BASF wherever possible.
"Our employees have done excellent work over the past years. We regret that we are losing these high-quality jobs in Germany and Sweden," said Marcinowski.
What do you think of BASF's decision to pull out ofthe European GM market? Does the move add further stagnation to innovation in the EU? Get in touch with us by emailing: nathan.gray<at>wrbm.com or tweeting @nathanrgray


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Archive for November, 2006
ArmA : and BIStudio invent the modern FPS game
I spent the last two days on the second game of Bohemia Interactive Studio (BIStudio in short) called "Armed Assault" Wich is some kind of sequel to Operation Flashpoint.
Flashpoint was a great war simulation game, the point where it sucked was the graphic engine, a bit old, wich was forgiven considering the game was designed to be played on large scale islands with 2000 meters of view distance (not quite what we have in SL :p)
ArmA is some sort of "Flashpoint2.0" the engine clearly smell about Flashpoint but is much better with some nice HDR effects, high detail characters and landscapes (the viewdistance can be cranked to a spiffy 10 kilometers range) and dynamic shadows, the sort of coldness that flashpoint had is gone now, the surfaces feel detailed and shine under the sun in warm tones, the foliages are rich and project shadows in the grassy hills… splendid.
ArmA is set in a present setting and all the 1982 equipment have been replaced by more modern ones, the vehicle array got a lifting, and the less interesting ones got removed.
They added a pretty nice little training, (wich feel a lot like the one you get forced down in america's army) where you learn the basic US weaponry (unfortunately no training for the OPFOR weaponry) , weapons like the grenade launcher M203 will definitely require some training…
The Singleplayer campain is pretty amusing, architectured around a system of main missions with 2 or more secondary missions of sabotage or marksmanship wich sometimes bring you an advantage in the main mission if you success them.
Instead of the 4 old islands of Operation Flashpoint, ArmA has one massive island of 400km2 (it is bigger than all the flashpoint islands joined) and one "desert" island wich has some grass, terrain reliefs and one small village. The main island is divided in 2 parts, north wich is in an european style and will remind you a lot from Flashpoint, and the south wich is of a mediterranean style. All dotted of many interesting spots, cities, forests and buildings.
It looks like BIStudio kept their promises and raised again the bar for the best Military simulation.
virtual vs real, and why any regulation over internet is deemed to fail.
When we go surf on the net we have a link established between virtuality and reality, a real human use several interfaces to access a virtual space.
When a hacker is breaking into a system, he is doing so at light speed, trough optic fibers, remotely, sometimes tousand kilometers from the physical computer he attack. If the law of the real world want to counter attack him, it cannot be done at the same speed, and distance abstraction, since the virtual world cannot influence a human directly. So we have to run a hunt in the physical world. Problem, the physical world is nowhere near as fast and flexible. A hacker could literally hop from place to place without ever being caught.
price update
the KDC ponygirl set goes down from 900L$ to 400L$
Retracting bridge
Since i do not plan to limit the dead realm sky city just to the KDC shop i started building a metal bridge that expand to reach a second rock formation.
Though i don't know yet what will be on the second island…
Note: Since the light in dead realm is set super dark and there is no glowing crystals around the bridge, i changed the color contrast in photoshop so "something" can be seen.
ethernia wiki
total mess of random informations i write/collect and that you can contribute too, if you seek something to read, it's here
—> http://wiki.ethernia.net


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Backyard Wedding Bliss – Catchlight Photography
By dcarpenito at July 25, 2014 | 7:52 pm | 0 Comment
// A backyard is a perfect spot for a rustic wedding reception. Depending on your space, a backyard wedding can range from small and intimate to a grand affair. Planning a wedding reception at home can be more work, and may even be more expensive than you thought. But, there's nothing like celebrating your special day in your very own backyard. Cassie & Jon had


text:
Better sound is just the beginning. We're passionate engineers, developers, researchers, retailers, marketers … and dreamers. One goal unites us—to create products and experiences our customers simply can't get anywhere else. If you want to hear more, we invite you to explore.
We have a simple mission: think of better solutions, create better products, help people enjoy the things they love. Everything we do supports this mission and points us forwards. It started when Dr Bose founded the company in 1964 and continues today with innovative, passionate employees around the globe.
And while it's true that we're a company built on scientific research, our vision is guided by human interests—how better sound affects us or what it means to find joy in products that work exactly how you want them to or why solid customer service isn't a nice-to-have, but a promise we keep.
But maybe the most important principle we live by is that innovation is not a destination, but a journey requiring new ideas from new players. So we invite creators, inventors, dreamers and talented people from all walks of life to bring their big ideas, passion and enthusiasm to a career at Bose. See how you can be part of our innovation.
1929: Birth of Amar Gopal Bose
Born in Philadelphia, PA, to a Bengali father (Noni Gopal Bose) and a US-born mother of English and German ancestry (Charlotte).
1930s: Developing a keen ear
For many years, young Amar Bose studies violin (reluctantly, like many children), developing a keen ear and a lifelong appreciation for classical music.
1940s: From first startup to city's largest radio repair store
Though just a teenager, Amar Bose repairs broken radios in his parents' basement to support his family when his father's import business collapses during World War II.
1947: A father's dream—accepted at MIT
Amar Bose fulfils his father's dream for his son to attend the most prestigious technical university, as well as his own desire to pursue learning how to design electronics, rather than merely to repair them.
1948: Temporarily outclassed at MIT
Amar Bose finds himself much less prepared for MIT than his peers. In order to focus on his studies, he limits his free time (including listening to music) to only a few hours per week. By year's end, he earns a full scholarship and will go on to earn a BS and MS in electrical engineering.
1953: Joins MIT's legendary Research Laboratory of Electronics [RLE]
Amar Bose works on statistical communication theory at the RLE with three professors who become his lifelong mentors: Jerome Wiesner, Yuk Wing Lee and Norbert Wiener.
1956: Amar becomes Dr Bose
Amar Bose earns his doctorate in electrical engineering with a ground-breaking mathematical thesis, "A theory of nonlinear systems", based on material originally sketched by world-renowned mathematician Dr Norbert Wiener.
1956: The passion for better sound begins
Dr Bose celebrates earning his PhD by buying himself a new hi-fi. Though he chooses the system based on his analysis of specifications, the sound quality of the winning design disappoints him. His curiosity about the discrepancy compels him to study and research acoustics at MIT in his spare time.
1957: Reluctant teacher
Dr Bose is recruited to join the faculty at MIT to teach "Introduction to Network Theory." Despite his preference for research, he resolves to become the best teacher he can. In the process, he revolutionises what becomes the school's largest undergraduate course.
1964: Founding of Bose Corporation
Rather than look for an established company to license his loudspeaker patents, Dr Bose launches his own company. By day, he and his two employees develop power-regulating systems for the military and other government agencies. By night, they explore acoustics and speaker design.
1966: First consumer product: 2201 speaker
The company introduces its first loudspeaker. Though the product technologically leapfrogs conventional speakers, its high price, plus the company's naiveté in matters of marketing and sales, makes it largely unattractive to consumers. As a result, sales are dismal. Lesson learned: products need to be practical as well as innovative.
1968: Revolutionary 901 speaker changes the way people listen to music
Based on extensive research in the fields of speaker design and psychoacoustics, the ground-breaking speaker system wins immediate acclaim for its extraordinary ability to more closely approximate the essence and emotional impact of a live concert. A new focus on explanation and demonstration at retail helps to propel the 901 speaker to becoming a major commercial success.
1972: Beginning of global expansion
Through a relationship with an audio retailer in Bad Homburg, Germany, Bose products are sold outside the U.S. for the first time.
1972: Realising a dream
Early in the company's history, Dr Bose had expressed a desire to one day move his company's headquarters from its offices in Natick to The Mountain, a prominent location in Framingham, MA. Though it required a major financial investment for a company of its size at the time, his persistence in pursuing this goal is finally rewarded.
1972: Birth of Professional Products Division
After noting that professional musicians were using Bose 901 speakers as PA speakers and onstage monitors, the company develops the Bose 800, which maximises sound quality through use of an equaliser and eight 11.43 cm drivers. A new division is born that will make a number of major technological advancements in the coming years.
1975: World's top-selling loudspeaker introduced
Bose® makes lifelike sound available in bookshelf-size speakers. Thanks to its quality and affordability, the Bose 301 Direct/Reflecting speaker becomes the world's best-selling speakers for many years to come.
1978: Quest for noise cancelling technology begins
On a transatlantic flight aboard Swiss Air, Dr Bose is disappointed by how the sound produced by the then-new electronic headphones he's been given is marred by aeroplane noise. He conceives the mathematics for noise cancelling headphones before the flight touches down hours later.
1982: First premium sound system debuts in a Cadillac Seville
Bose launches an entirely new sound category, becoming the first company to offer factory-installed sound systems custom-engineered to the acoustics of a specific vehicle model.
1984: Ground-breaking high-fidelity room-filling sound from a compact tabletop system
A decade of Bose® research results in patented acoustic waveguide technology that packs the performance of a large, multi-component system into a compact, all-in-one system. The Acoustic Wave music system is introduced and immediately receives high praise.
1986: Prototype noise cancelling headphones make historic flight
Though Bose active noise-reducing headsets are still in development, the company makes two prototypes available to preserve the hearing of pilots Dick Rutan and Jeana Yeager on their record-breaking, non-stop, around-the-world voyager flight.
1987: Acoustimass 5 redefines home stereo
Using newly patented Bose technologies, tiny cube speakers are able to deliver concert-like sound, while the bass module, which provides the deep low frequencies, can be hidden out of sight. Within a few years, Acoustimass systems become a new standard in home hi-fi and go on to dominate the emerging home cinema market.
1987: Inventors of the year
Dr Bose and Dr William R. Short win the Intellectual Property Owners Education Foundation's Inventor of the Year Award for the waveguide loudspeaker system.
1988: First-ever official Olympics sound system supplier
Bose becomes the first company contracted to provide sound systems for every event at the winter Olympics in Calgary, Canada.
1989: First commercial Acoustic Noise Cancelling headset
Bose revolutionises flying for pilots by introducing a headset that provides effective noise reduction and communication, as well as comfort.
1990: A new standard in home audio
Bose Lifestyle systems take home audio to a new level of performance and simplicity, eliminating the need for the massive speakers and racks of components.
1991: Investigating cold fusion
Assembling a team of physicists, chemists and materials scientists, Bose conducts several years of experiments in an attempt to prove or disprove cold fusion. The research exposes a flaw in the original research and precisely accounts for the erroneously reported excess energy effect in cold fusion theory.
1993: Bose Wave redefines radio
Bose patented acoustic waveguide speaker technology is reintroduced in a small tabletop music system. It redefines the concept of a radio by delivering rich, deep sound not previously heard from such a small unit. Though at $349, it costs nearly ten times the price of an ordinary clock radio, the Wave radio goes on to become a product beloved by owners, and a huge commercial success.
1993: First Bose store
Bose opens its first retail store in Kittery, Maine.
1994: A breakthrough in sound predictions
Bose® announces a new technology and tool that allows acoustical engineers and their clients to hear the sound a listener will experience in any particular seat in a venue—before the building is built or any sound equipment is installed. Over the years to come, the Auditioner audio demonstrator is used on thousands of projects throughout the world, including sound systems at the Sistine Chapel, St. Peter's Cathedral in Rome, the Grand Mosque in Mecca, and at Olympic and World Cup venues.
1997: First automotive usage of Bose Nd woofer
This ground-breaking Bose technology, which delivers powerful sound while taking up less space than an ordinary woofer, debuts in the Chevrolet Corvette.
1998: Aviation headsets get smaller, lighter, better
The new Headset X with innovative Triport technology improves pilot comfort while providing a level of noise reduction that's comparable to the larger, heavier Bose models that had first established the active noise reduction category. The Headset X will go on to dominate the category, with Bose being voted as the no. 1 headset manufacturer for nine consecutive years in the Professional Pilot magazine survey.
1998: First international Bose store
First international store opens in New Delhi. In time, Bose will operate hundreds of its own stores on four continents.
1998: AudioPilot technology takes in-vehicle listening to new level
This revolutionary noise compensation circuit technology, which monitors and adjusts the music signal in response to vehicle speed and external noise, is introduced in the Cadillac Seville STS.
2000: Pioneering Bose® technology changes the way people fly
Building on the success of Bose Acoustic Noise Cancelling headset technology, the QuietComfort headphones forever change air travel for passengers by drastically reducing noise and providing better in-flight entertainment sound quality than ever before.
2001: A beloved and renowned MIT professor retires
In addition to being CEO of the company he founded, Dr Bose was a professor at MIT for 45 years. Awarded many times by students and faculty for his teaching, Dr Bose's classes were renowned as some of the most challenging—and most popular at the institute.
2003: An entirely new way to amplify live music
By replacing conventional PA, floor monitors and backline amps, the Bose L1 system creates a breakthrough in live music amplification. It relies on the unusual properties of a special loudspeaker, 2.1 metres tall and only 12.7 cm wide, which is placed behind each individual musician.
2004: New Bose division: ElectroForce linear motion systems
Bose applies its linear-motion actuator technology to a new area and begins a new business through the Bose ElectroForce Systems Group, a leading supplier of materials testing and durability simulation instruments to research institutions, universities, medical device companies and engineering companies worldwide.
2004: Secret, multi-decade, non-audio research project unveiled
Bose shares the results of a secret project with the press and the automotive industry—a revolutionary automotive suspension technology that uses electromagnetic actuators instead of springs or hydraulics, for a ride that's smoother than a luxury car and offers better handling than a sports car.
2004: Sound for iPod
The SoundDock digital music system quickly becomes the sound standard for iPod-compatible speaker systems, allowing iPod owners to listen unrestrained by earbuds, and share their music with others.
2008: Hall of Fame induction
Dr Bose is inducted into the National Inventors Hall of Fame in Akron, Ohio, for achievements in audio technology that "have significantly influenced the quality of how we live".
2008: International Design Team of the Year
Bose receives the prestigious Red Dot International Design Team of the Year award for continuous innovation and achievement in design.
2009: New standard in noise cancelling headphones
Already the market leader in noise cancelling headphones, Bose introduces the QuietComfort 15 headphones, a major advancement in noise cancelling technology. The product quickly becomes the gold standard for frequent flyers and becomes a major commercial success.
2009: First Energy Efficient Series sound system
The Chevrolet Volt becomes the first car to offer this technology, which delivers high-quality acoustic performance while using 50% less energy than conventional systems.
2010: New technology protects long-haul drivers from punishing road vibration
Utilising Bose seat suspension technology, the Bose Ride system replaces conventional air-suspension truck seats to provide over-the-road drivers with an unprecedented level of protection from harmful road-induced vibration.
2010: Better in-flight experience for pilots: A20® Aviation Headset
Bose® introduces its most advanced aviation headset ever, featuring greater noise reduction, improved comfort and Bluetooth® connectivity for GPS and cell phones.
2010: Home cinema experience is simplified and improved
Bose introduces the VideoWave entertainment system, a high-definition television delivering home cinema sound from a 16-speaker audio system built entirely behind the screen, and combines it with a totally new kind of remote control that drastically reduces complexity.
2010: Controlling vehicle noise through Active Sound Management (ASM) technology
Leveraging over 30 years of Bose research into acoustics and noise cancellation, this new technology debuts in the Cadillac Escalade and Infiniti M. It enables car makers to more effectively control vehicle cabin noise without compromising the vehicle's desirable sound characteristics.
2011: A new standard in mobile sound
The SoundLink wireless mobile speaker wirelessly connects to a smartphone or other Bluetooth® enabled device, so that music can be shared out loud almost anywhere. It delivers an unprecedented combination of performance, mobility and durability.
2011: Dr Bose's gift to MIT
Dr Bose donates a majority of Bose Corporation's non-voting shares to MIT. The dividends on those shares are used to sustain and advance MIT's education and research mission. The company will remain private and independent and continue to operate according to its values and guiding principles.
2013: Dr Amar Gopal Bose dies at age 83
"Dr Bose founded Bose Corporation almost 50 years ago with a set of guiding principles centred on research and innovation. That focus has never changed, and never will". Bob Maresca, president and newly appointed CEO, Bose Corporation.
2013: Another breakthrough in noise cancelling headphones
The QuietComfort 20 headphones are the first in-ear noise cancelling headphones from Bose that deliver a stunning breakthrough in noise reduction, audio performance and comfort, and offer two ways to listen—one to shut out the world, and one to keep you connected. The company has been granted more patents for this product than for any other in its history.
2013: SoundLink Mini takes off
The ultra-compact SoundLink® Mini Bluetooth® speaker fits in the palm of your hand, connects wirelessly to a smart device or tablet, and delivers a new level of performance for personal, out-loud listening. It becomes the fastest-selling product in Bose® history.
2013: Revolutionising Wi-Fi® music listening at home
SoundTouch Wi-Fi music systems brings lifelike sound to every room in the home. Users can now stream music wirelessly from the Internet, music libraries and other music services, at the simple touch of a button.
2013: Premium sound: now in 15 global auto brands
Thirty years after Bose partnered with General Motors to pioneer the premium automotive sound industry, Bose systems are featured in over 100 vehicle models, from more than 15 manufacturers.
2014: Voted one of the "5 Most Innovative Brands" for the 7th consecutive year
Bose wins its seventh Plus X Award since 2007. The award is the world's largest competition for technology, sports and lifestyle brands.
2014: Official Headphones and Headset of the NFL
Bose brings noise cancelling technology to the NFL, improving coaches' on-field communication and enhancing the in-game experience for fans in the stadium and at home.
2014: The most respected name in sound
Bose® is known globally as the most respected name in sound. From two employees in a small office in Natick, MA to a business that spans continents and categories.
Today, the company remains private and independent, as committed to its founding principles and customers as it was in 1964. And today, Bose celebrates, honours and humbly thanks the millions of people around the world who have chosen Bose for the last five decades.
2015: The Panaray system moves passengers and critics alike
No matter what music you listen to in the Cadillac CT6, what you're really hearing is Bose's greatest hits. To create a truly premium experience worthy of Cadillac's flagship vehicle, we adapted some of our best-performing innovations from all corners of the company. We used our headphones' noise cancelling technology to help silence the noise of the road. To create sound where there were no speakers, we leveraged the array speaker breakthroughs first pioneered for home cinema products. We even featured anti-reverberation technologies from our own automotive research. The system is so finely tuned, it took our engineers three years to perfect it.
2016: Blurring the line between industry-defining performance and modern art
Constantly learning from our past achievements, we've developed a reputation for creating more powerful—yet somehow smaller—versions of our products with each new generation. But with the Lifestyle 650 home entertainment system, it's not just the sound that turns heads. The glass top of the Acoustimass bass unit was custom crafted by the same company that's famous for making windshields for Italian super cars. The satellite speakers are fashioned from a single piece of extruded aluminium with 4000 precision-drilled holes.
When presenting the prestigious Red Dot 'Best of the Best' Design Award in 2017, the jury said, "All elements of this system have been perfectly matched in terms of form and function. The compact and reduced design allows users to concentrate fully on the delivered sound quality."
2017: Our software engineers begin working by a new code
When we released our first wireless headphones with active noise cancelling technology, they quickly became our bestselling product of all time. Just a year later, we introduced the QC35 Series II, which gave our listeners instant access to the Google Assistant. But to embed voice control into the QC35 II, we first needed to embed a team at Google. Working "bench to bench" with their coders, we did more than create the world's first headphones with a dedicated Google Assistant button—we launched a whole new process for collaborative design.
2017: Improving conversations by hearing our customers
In 1997, a letter arrived on the desk of Dr Bose. Inside was a handwritten note from a customer asking if it would be possible for the company to develop a headphone that could help people hear their conversations as clearly as their music.
Meanwhile, across our campus, some of our R&D engineers had already wondered the same thing — and had begun work on their prototype. Simple as our customer's question was, the answer was incredibly complex. Before Hearphones were ready to share with the world, it would take multiple teams and nearly 20 years of intermittent experimentation to develop and adopt the various new technologies we needed, including in-ear noise cancelling and user-adjustable tuning. But based on the letters we've received since launching Hearphones, it was worth the wait.
The future
We can't wait. Because we're just getting started.
Our Pro division develops custom-built audio solutions for large-scale projects. They work closely with the facility to create a sound experience that lives up to the Bose® reputation. You'll also find specialised Bose® noise reduction products quietly serving worldwide military forces that face elevated levels of noise daily in the line of duty.


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The Toronto Star: Anger as cars clog new Simcoe St. bike lane
Published On Thu Mar 11 2010
There's a fresh new bike lane on Simcoe St. Just six months old, it was meant to calm the nerves of cyclists travelling the busy stretch under the GO lines and the Gardiner.
Instead, it's a parking lot.
As convention season heats up in Toronto, every major taxi company has cars sitting in the Simcoe St. bike lane, waiting to pick up fares from the Metro Toronto Convention Centre.
On Wednesday, a uniformed police officer ushered taxis into the centre's parking lot. He didn't chastise them for clogging the bike lane, or for idling, which carries a fine of up to $5,000. When the Star asked him to clear the bike lane, he said he'd "call someone."
Minutes ticked by. A cyclist stopped to make the same request. "I'm pissed off and frustrated," said the cyclist, Daniel Hall. On his way south to the ferry docks, Hall was attempting to use the lane for the first time. Instead, he found cars backed up all the way from Bremner Blvd. to Front St.
The officer finally said he'd notified parking enforcement. While waiting for them to show up, the Star chatted with a few drivers. When told it was illegal to stand in a bike lane, some said, "No it's not," and others, "It's only for today."
Beck and Royal taxi dispatchers said they'd get their cars to leave the lane, but no one did.
Twenty minutes after the officer called for parking enforcement, no one had shown up. So, the Star called and was told a car would be sent out.
Thirty-five minutes later, the lane was still full of idling cars.


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Cloud Cover is your eye on the Microsoft Cloud. In each episode, Wade and Steve cover Windows Azure, digging into features, discussing the latest news and announcements, and sharing tips and tricks. Here's what Wade and Steve covered last month:
Episode 63: Securely Sharing Files with Windows Azure
In this episode, Wade shows a new sample application called BlobShare. The BlobShare Sample is a simple file sharing application that demonstrates the storage services of the Windows Azure Platform together with the authentication and authorization capabilities of Access Control Service (ACS). (Posted 10/28/11)
Episode 62: Marketplace with Christian Liensberger
In this episode, Christian Liensberger, program manager for the Windows Azure Marketplace, joins Steve and Wade to talk about data and apps in the Marketplace. News covered includes improved in-place updates and the expanded global availability of Windows Azure Marketplace. (Posted 10/21/11)
Episode 61: Updates to SQL Azure Database with Roger Doherty
In this episode, SQL Server and SQL Azure Technical Evangelist Roger Doherty joins Steve and Wade to discuss recent updates to SQL Azure database. Also covered is a recap of the Big Data roadmap and Hadoop announcement made at PASS Summit 2011. (Posted 10/14/11)
Follow and interact with the show @CloudCoverShow.


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Manipulation is generally a bad skill to use to get what you want, but sometimes it's justifiable when you have a noble cause. Perhaps you're trying to get someone to live a healthier lifestyle or enjoy an activity with you. When other tactics fail you and it's time to resort to a little manipulative behavior, here are some tricks you can use to get what you want without being completely abandoning your ethics.
Title image remixed from originals by Lorelyn Medina (Shutterstock).
Nobody enjoys being tricked, so you don't want to use anything you learn in this post for evil purposes. Most of what we're going to discuss is simply a matter of creating a scenario where it's more likely that whoever you're trying to manipulate will be happier and enjoy themselves more. This isn't about simply getting what you want, but creating a positive experience for the manipulator and the manipulatee. Rather than dive into many possible situations, we're just going to use one scenario as an example: getting a friend (or whomever) to join you on an activity and have a good time. That said, these same tricks can be repurposed for other situations as well. We just want to keep it simple. All you need to follow are two steps.
Step One: Convince Your Friend to Do the Thing They Don't Want to Do
It's nice when you have someone with whom you can share an activity. The problem is, you may love interpretive sculpting but will have a hard time selling your friends on the joy it can provide. Fortunately, most people can come around under the right circumstances. You probably thought you'd absolutely hate the butt pinching festival last Spring but, as things turned out, you're going back for the fifth time with hopes of taking home a blue ribbon. In all seriousness, what we end up liking is often a matter of circumstance. If you want your friend to partake in something you enjoy, they'll be more likely to join in under the right conditions.
First things first, you have to get your friend to go with you. Rather than trying to convince them that they'll want to join you, as that will cause them to naturally come up with counterarguments, ask them to join you as a favor. As Ben Franklin discovered and David McRaney, of the blog You Are Not So Smart, highlighted, doing something nice for another person can get you to like them more (rather than the other way around):
[Ben] Franklin set out to turn [a] hater into a fan, but he wanted to do it without "paying any servile respect to him." Franklin's reputation as a book collector and library founder gave him a reputation as a man of discerning literary tastes, so Franklin sent a letter to the hater asking if he could borrow a selection from the his library, one which was a "very scarce and curious book." The rival, flattered, sent it right away. Franklin sent it back a week later with a thank you note. Mission accomplished.
This works because although we think that we do nice things for people because we like them, our brains tend to process things the other way around. The reality is that we tend to like someone because we did something nice for them. If your friend sees this activity as a favor, they'll feel better about you than they will if you're trying to drag them along.
Step Two: Make Your Friend Have Fun
How can you ensure your friend will enjoy the activity? You can't, but you can increase the odds. Let's take a look at a few ways you can do just that.
Handle Challenges Together
First, it can help if there's anything remotely challenging about that activity. If there is, do it with them and it can become a bonding experience. Even if they didn't enjoy the activity, they'll look back on it fondly, later, because it brought you both closer together.
Choose a Familiar and Comfortable Environment
It can help if the activity will surround the person with familiar things and the kinds of people they like. While we like to believe we're open to new possibilities and respect the differences in others, we really don't. If you want to get someone to like something different, it helps if you can make them feel comfortable in as many other ways as possible.
Photo by genvessel.
Boost Your Friend's Mood
Finally, get them in a good mood beforehand. This may seem difficult, especially if the person in question is an awful and negative person that you've somehow managed to love, but it's easier than you think. As noted in our brain hacking guide, there are a few simple ways to prime a person's brain to have the right attitude for a given situation. While there are little things you can do like reciting a list of positive words, that's kind of a weird thing to do in the company of others. Instead, you can use your enthusiasm to put them in a better mindset. Making them laugh is one of the best options, but if you're not naturally funny and afraid to break out the tickler, frequent smiling can do the trick. Next time you see someone smile, notice how you're probably smiling in return. It's hard not to mirror happy expressions because it often happens without our full awareness. Little things like smiling and humor can go a long way, even when they're completely unrelated to the given activity.
Reward Your Friend's Competency with Compliments
And don't forget the compliments. If the given activity requires your tag-a-long activity buddy to do or create anything, let them know you think they're doing a great job once they've finished. People tend to like things more when their efforts are rewarded in ways that highlight their competence. You don't want to outright lie, but something like "wow, you're picking this up quicker than I expected" can make a big difference in your friend's perception of the activity.
If you've got any other tips for getting your friends to do what you want while maintaining a positive experience for both of you, let us know in the comments!


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How food companies are innovating to beat the financial crisis
Speaking at last month's SIAL show in Paris, de Reynal said that food manufacturers and ingredient firms were less innovative in the first years of the financial crisis, but they are now looking to use innovative new products and ideas to deal with a less secure economy and to appeal to frugal consumers.
"This year has been a better year for innovation," she said. "But 59% of French consumers are still buying cheaper products. Price is still the biggest driver for purchases."
The ways in which companies are innovating have changed. In 2007, product launches touting healthy ingredients were up 16.3% in France compared to the previous year. In 2011, they were down 2%.
Meanwhile, ingredient companies have come forward with ingredients to help manufacturers switch out costly commodities, such as egg, milk and natural flavourings like vanilla.
De Reynal said that in 2008, about 58% of French food manufacturers had modified proportions of ingredients in an effort to cut costs, while 46% had tried to use less expensive ingredients.
However, despite a general desire among consumers to save money, shoppers are also willing to pay more if they perceive a real benefit, with digestive health claims leading the way.
"Health claims bring many opportunities for the food industry and are getting a lot of attention as a way to have a real conversation about health," she said.
Citing Ethycity survey data, de Reynal said that 88% of French consumers see the financial crisis as a chance to revise their way of life and consumption, and 79% say they are ready to increase the sustainability of their purchases.
This has meant that recycled and recyclable packaging and 'back to basics' products have come to the fore over the past couple of years, along with traditional and local foods, and those that trumpet the origins of ingredients and recipes.


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Cuneiform clay tablet translated for the first time
A cuneiform clay tablet that has puzzled scholars for over 150 years has been translated for the first time. The tablet is now known to be a contemporary Sumerian observation of an asteroid impact at Köfels, Austria and is published in a new book, 'A Sumerian Observation of the Köfels' Impact Event.'
The giant landslide centred at Köfels in Austria is 500m thick and five kilometres in diameter and has long been a mystery since geologists first looked at it in the 19th century. The conclusion drawn by research in the middle 20th century was that it must be due to a very large meteor impact because of the evidence of crushing pressures and explosions. But this view lost favour as a much better understanding of impact sites developed in the late 20th century.
In the case of Köfels there is no crater, so to modern eyes it does not look as an impact site should look. However, the evidence that puzzled the earlier researchers remains unexplained by the view that it is just another landslide.
This new research by Alan Bond, Managing Director of Reaction Engines Ltd and Mark Hempsell, Senior Lecturer in Astronautics at Bristol University, brings the impact theory back into play. It centres on another 19th century mystery, a Cuneiform tablet in the British Museum collection No K8538 (known as "the Planisphere").
It was found by Henry Layard in the remains of the library in the Royal Place at Nineveh, and was made by an Assyrian scribe around 700 BC. It is an astronomical work as it has drawings of constellations on it and the text has known constellation names. It has attracted a lot of attention but in over a hundred years nobody has come up with a convincing explanation as to what it is.
With modern computer programmes that can simulate trajectories and reconstruct the night sky thousands of years ago the researchers have established what the Planisphere tablet refers to. It is a copy of the night notebook of a Sumerian astronomer as he records the events in the sky before dawn on the 29 June 3123 BC (Julian calendar). Half the tablet records planet positions and cloud cover, the same as any other night, but the other half of the tablet records an object large enough for its shape to be noted even though it is still in space. The astronomers made an accurate note of its trajectory relative to the stars, which to an error better than one degree is consistent with an impact at Köfels.
The observation suggests the asteroid is over a kilometre in diameter and the original orbit about the Sun was an Aten type, a class of asteroid that orbit close to the earth, that is resonant with the Earth's orbit. This trajectory explains why there is no crater at Köfels. The in coming angle was very low (six degrees) and means the asteroid clipped a mountain called Gamskogel above the town of Längenfeld, 11 kilometres from Köfels, and this caused the asteroid to explode before it reached its final impact point. As it travelled down the valley it became a fireball, around five kilometres in diameter (the size of the landslide). When it hit Köfels it created enormous pressures that pulverised the rock and caused the landslide but because it was no longer a solid object it did not create a classic impact crater.
Mark Hempsell, discussing the Köfels event, said: "Another conclusion can be made from the trajectory. The back plume from the explosion (the mushroom cloud) would be bent over the Mediterranean Sea re-entering the atmosphere over the Levant, Sinai, and Northern Egypt.
"The ground heating though very short would be enough to ignite any flammable material - including human hair and clothes. It is probable more people died under the plume than in the Alps due to the impact blast."
Source: University of Bristol


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- LifestyleGenuine hospitality. While Generator works on a wide variety of building projects, what binds our work together is not architecture. It is the art of hospitality – of being genuine about who we are and what we can accomplish for those we serve. From nationally recognized sports arenas to a little grocery store for a food desert in Kansas City, Kansas, the concepts are the same: Do people feel welcome, and is the space livable? Our award-winning work stems from these ideas. At the end of the day, it's about helping clients create environments responsive to their programmatic and budget requirements, and creating lifestyle-oriented designs that are uniquely authentic to their place and time.
- NonprofitDesign for good. Generator believes in contributing to the greater community we live, work and play in. Our skill set and perspective grows exponentially with exposure to new people and new ideas, and a large part of that exposure comes from giving back to local community organizations. We continue to support various local charitable organizations with our time and resources. Our personal and professional commitment is long standing. We strive to provide solutions that allow user experiences to evolve through human interaction with the environment; a goal that is critical for many not-for-profit clients and the people they serve.
- ResidentialCrafted experiences. In our residential design work, we often get asked to create an experience that is similar to a particular hotel or place that our clients have brought back from their travels around the world. Our approach in residential design has therefore evolved to allow authentic experiences to naturally arise through our clients' personal interaction with their homes. In doing this, the design takes care of itself; leaving no doubt as to why a space is designed a certain way. Every client we have is different, and we believe in celebrating our clients' unique wants and needs through tailored design solutions, whether ground-up new construction or custom renovations. Our clients love the experiences we craft with them.
- VenueUser focused design always wins. Founders Tom Proebstle and Mike Kress have shaped the landscape of sports architecture over the last two decades. While at previous firms Ellerbe Becket and Crawford Architects, they shaped landmark projects such as Conseco Fieldhouse, Lambeau Field, UNI's McLeod Center, Fenway Park, and Qwest Field. Since founding Generator studio, Tom and Mike's legacy in the world of sports architecture continues to grow, with clients including the Kansas City Current, Seattle Kraken, Seattle Sounders FC, Brooklyn Nets, New York Liberty, St. Louis Blues, Minnesota Vikings, Tampa Bay Lightning, and Minnesota Wild. What distinguishes Generator's work is a passion for sports business, first understanding an organization's unique challenges, market, brand essence, and revenue goals. What results is differentiated design, with branding rooted in the very architecture itself and revenue opportunities steeped in immersive fan experiences.
- WorkplaceWork spaces that feel like home. We solve problems for our workplace clients through an immersive approach to design. Our process often includes a deep dive into our client's business model, helping them plan growth strategies, ensure corporate objectives are represented in design, advise on trends, and review branding and marketing strategies among other advisory roles. It speaks to the level of trust we're known for establishing, and we believe necessary to create meaningful and authentic architectural environments for employees. Thoughtful work environments built on corporate strategy helps with employee retention, improves corporate identity, improves efficiency, and opens up new opportunities for return on investment.
Our approach.
Through a wealth of experience and a collaborative approach focused on helping our clients achieve their business goals, we have built a sterling industry reputation and growth fueled by repeat business and both local and national referrals. But make no mistake – at Generator, there is no formula for success. We approach each project and client with fresh eyes focused on creating developments that are inherently economically and environmentally sustainable.