Temperature Dependence Of Fraction Research Articles

Vibrational Anisotropy and Gol'Danskii–Karyagin Effect in Trimethyltin Cyanide

Mössbauer effect measurements have been carried out on (CH3)3SnCN in the temperature range 9°K < T < 204°K. From the asymmetry of the intensity of the two components of the quadrupole split spectrum it is possible to calculate the anisotropy in the mean-square amplitude of vibration of the metal atom parallel and perpendicular to the molecular symmetry axis. Extrapolation of the low-temperature data to 300°K gives a value of this anisotropy which is in good agreement with the value derived from x-ray diffraction data. The latter can be used to normalize the temperature-dependent recoil-free fraction data which in turn permit an estimate to be made of the anharmonicity of the heavy atom vibration in the low-and high-temperature limits. The present data on (CH3)3SnCN are in agreement with an oblate electrostatic field (Vzz>0) around the metal atom and show that the vibrational amplitudes involving this atom approach an isotropic behavior in the low-temperature limit.

On the possibility of measuring thermal fields using the mössbauer effect-application to turbine blading

The use of the Mössbauer effect to measure thermal gradients inside solid samples is proposed and described. The gamma rays produced in a Mössbauer source are absorbed by active nuclei seeded in the sample under observation. It is then possible, by analysing the data relative to the absorption intensity, to obtain the values of both the strongly temperature-dependent recoil-less fraction and secondorder Doppler shift. The knowledge of the mean temperature value along the penetration direction can be reached with fair accuracy and then by repeating the measurement, the thermal gradients inside the sample. Moreover, the application of this method to the study of thermal fields in turbine blading is proposed, and some rough estimates of the source intensity, resolving power and time intervals needed are given.

Fractionation of carbon isotopes and its temperature dependence in the system CO 2-Gas-CO 2 in solution and HCO 3-CO 2 in solution

Isotope fractionation between the carbon isotopes in certain molecules has been measured at different temperatures. The difference in isotope ratios of CO 2 in the gas phase and CO 2 dissolved in water amounts to (−0.56 ± 0.09)‰. For the system HCO 3-CO 2 in solution a temperature-dependent fractionation Δ 1 of Δ 1 = (10.2 − 0.064 · T)‰ ( T = °C) has been found.

Effects of temperature on membrane potentials of lobster giant axon

In the range 2–20 C, the resting potential of the lobster axon shows a greater increase with increase of temperature than can be explained by the Nernst relationship. Action potential also shows an initial increase with temperature, peaks at about 16 C, then decreases. Maximum rates of rise and fall of the action potential increase with temperature increase; duration of the propagated action potential decreases. Afterpotentials in this preparation are in the form of a delayed repolarization; as temperature is increased, the magnitude of the afterpotentials increases, as does the rate of repolarization. These results have been compared with results already available for the squid axon. Differences between the two preparations occur in the relationship of the resting potential, action potential magnitude, and afterpotentials to temperature. It is suggested that these differences may be explained by the presence of a temperature-dependent fraction of the resting potential in the lobster axon which is not present, or is inactive, in the squid axon.