Positive and negative temperature coefficients of resistance

1975 ◽  
Vol 43 (12) ◽  
pp. 1100-1101 ◽  
Author(s):  
A. G. Klein
Keyword(s):  
Negative Temperature ◽  
Temperature Coefficients

scholarly journals THE EFFECT OF TEMPERATURE AND OF LYSIN CONCENTRATION ON THE ACCELERATION OF HEMOLYSIS

1941 ◽  
Vol 25 (2) ◽  
pp. 247-261
Author(s):  
Eric Ponder
Keyword(s):  
Cell Surface ◽  
Quantitative Description ◽  
Negative Temperature ◽  
Effect Of Temperature ◽  
Membrane Component ◽  
Temperature Coefficients ◽  
Rate Of Escape ◽  
Point To Point ◽  
Special Case ◽  
Do So

The acceleration of saponin hemolysis by benzene, indol, and nonyl alcohol has been investigated as a function of temperature, and it has been found that these accelerators have negative temperature coefficients. This points to their being concentrated at the cell surface, and to the surface being the seat of their accelerating action. It is shown that the accelerating power of indol (used as a typical accelerator) is constant so long as the lysin in the system is capable of producing lysis per se, but that the acceleration falls off when only sublytic concentrations are present. The relations are expressed in a series of equations, and explained in terms of the reactions among the accelerator, the lysin, and the membrane component, which breaks down in spots, rather than uniformly, when lysis occurs. The argument involves a consideration of the idea that a monolayer of lysin at the cell surface is necessary for hemolysis, of Abramson's hypothesis of "key spots" on the surface, of the rate of escape of hemoglobin from the hemolyzing cell, and of the results of electrophoretic and impedance measurements. The existing theory of the kinetics is extended by introducing the idea of a variation in resistance from point to point in the cell membrane; in this form it describes the situation so far as is at present known, and shows that the results of the various methods of investigation are consistent with each other. The only idea discussed which seems to have little foundation is that lysis is determined by the formation of a monolayer of lysin at the cell surface; when this occurs, it must do so only as a special case. Finally, a semi-quantitative description of the frequency distribution of the resistances in the membrane is derived from existing data. The variation in resistance which it is necessary to assume is quite small, as might be expected in the case of a membrane with a regular ultra-structure.

scholarly journals On the direct determination of the electrostatic moments of molecules

1929 ◽  
Vol 124 (795) ◽  
pp. 689-698 ◽  
Keyword(s):  
Dielectric Constant ◽  
Direct Determination ◽  
Negative Temperature ◽  
Dielectric Constants ◽  
Temperature Coefficients ◽  
Different Temperatures

According to Faraday's ideas, the specific inductive capacity of a substance is due to the polarisation of the molecules as wholes. This is the basis of the old Clausius-Mosotti theory of dielectrics, on which it is shown first that the polarisation P is proportional to the polarising field, i. e. , P = k E, k being the dielectric constant, and second that δ being the density of the dielectric, k - 2/ k + 2 ·1/δ = constant. Now it is known that some substances have large negative temperature coefficients for their dielectric constants which cannot thus be accounted for. To provide for this Debye proposed the theory that the molecules were permanently polarised and that they were systematically orientated in the field. This leads to the equation k - 2/ k + 2 = a T -1 + b T -2 , to represent the change of specific inductive capacity with temperature. This theory has been developed by Gans and others, and a number of measurements have been made by Smyth and others, who have found the molecular moments of many substances by measuring the dielectric constants at different temperatures.

The Master Equation for the Dissociation of a Dilute Diatomic Gas. X. How Rotation Causes Low Arrhenius Temperature Coefficients

1973 ◽  
Vol 51 (18) ◽  
pp. 3152-3155 ◽  
Author(s):  
Huw O. Pritchard
Keyword(s):  
Low Temperature ◽  
Temperature Coefficient ◽  
Rate Constants ◽  
Recombination Rate ◽  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Equilibrium Form ◽  
Temperature Coefficients ◽  
Recombination Rate Constant ◽  
Arrhenius Temperature

It is shown that previously calculated nonequilibrium rate constants for the dissociation of H2 and D2 appear to approach a rotationally averaged equilibrium expression at low temperature. This equilibrium form of the rate expression itself has an Arrhenius temperature coefficient for dissociation which is significantly less than the dissociation energy, and the corresponding recombination rate constant has a negative temperature coefficient. The reasons for this are explained.

Negative Temperature Coefficients for Ion-Molecule Reactions

1962 ◽  
Vol 84 (18) ◽  
pp. 3592-3593 ◽  
Author(s):  
N. A. I. M. Boelrijk ◽  
T. P. J. H. Babeliowsky
Keyword(s):  
Negative Temperature ◽  
Temperature Coefficients ◽  
Ion Molecule Reactions

Electronic properties of the actinide metals at low temperatures

1963 ◽  
Vol 276 (1367) ◽  
pp. 553-570 ◽  
Keyword(s):  
Electrical Resistivity ◽  
Low Temperatures ◽  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Al Alloys ◽  
Positive Temperature ◽  
Positive Coefficient ◽  
Disorder Effects ◽  
Temperature Coefficients ◽  
Spin Disorder

The electrical resistivity and thermoelectric power of thorium, uranium, neptunium and plutonium have been measured down to liquid-helium and liquid-hydrogen temperatures. The resistivities are relatively high, especially those of neptunium and plutonium, while all the thermoelectric powers show complicated temperature relations. The temperature dependence of the resistance of a-plutonium is abnormal, being characterized by a small negative temperature coefficient above 105 °K and a large positive coefficient below this temperature. Some plutonium rich d-Pu + Al alloys also show similar behaviour. An explanation in terms of spin-disorder effects seems most reasonable, and it is suggested that both a- and d-plutonium may be antiferromagnetic. The resistance—temperature curves of uranium and neptunium also are unusual in that the positive temperature coefficients decrease monotonically with rising temperature. Possible reasons for this have been discussed.

Tetraguanidium Hexabromocadmate, [C(NH2)3]4[CdBr6]. Crystal Structure and Bromine Nuclear Quadrupole Resonance

1994 ◽  
Vol 49 (1-2) ◽  
pp. 223-231 ◽  
Author(s):  
V.G. Krishnan ◽  
Shi-qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Room Temperature ◽  
Negative Temperature ◽  
Temperature Coefficients ◽  
Moment Ratio ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole Moment ◽  
Nuclear Quadrupole

AbstractThe 79, 81Br NQR spectra of tetraguanidinium hexabromocadmate, [C(NH2)3]4[CdBr6] have been studied as a function of temperature from 77 K to 390 K and the crystal structure of the compound was determined at room temperature. The title compound crystallizes monoclinic, P21/c, with four formula units in the unit cell, a = 839.2(3) pm, b = 1895.8(6) pm, c= 1527.4(5) pm, β= 108.14(1)°. The anion [CdBr6]4⊖ is an isolated octahedron, with bond lengths 275≤d(Cd-Br)/pm ≤ 281, and bond angles 88 ≤(Br-Cd-Br)/° ≤95, slightly distorted by hydrogen bonds N -H ··· Br. The 81Br NQR sextet, in dependence from temperature, shows positive and negative temperature coefficients. At 77 K the 81Br NQR frequencies have been found between 42.42 MHz and 31.99 MHz; the 79Br NQR at the frequencies expected from the nuclear quadrupole moment ratio Q(79Br)/Q(81Br). Relations between the 81Br NQR spectrum, the crystal structure, and the hydrogen bonds are discussed.

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