Influence of the boundary conditions on the thermostimulated depolarization current

Thermally stimulated depolarization currents (TSD) are analyzed as a function of conditions on the contacts (within the framework of blocking and unblocking the electrodes). It is shown that in the case of the blocking electrodes the TSD can be due to resorption of the volume charge, neutralization of the volume charge because of equilibrium conduction, and repolarization in the internal field. In the case of the unblocking electrodes, the TSD depends substantially on the electrical neutrality of the object. The influence of the diffusion component of the conduction current on the TSD current is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 7–13, December, 1979.     

Determination of the relaxation function in a quartz single crystal

A method is presented for determining the relaxation function from experimental frequency-temperature dependences of the dielectric constant on the basis of a general dispersion relation. Three relaxation processes have been detected in a quartz single crystal with the aid of this method. The relaxation times of these processes and their contribution to the relaxation function at elevated temperatures have been determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 76–81, October, 1986.We thank S. V. Kolodieva and her co-workers for supplying the samples of single-crystal quartz, the arrangement for measuring the dielectric parameters, and for discussion of the results of our work.     

Thermally stimulated relaxation currents due to forces of nonelectrostatic origin

It is shown that unusual thermally stimulated relaxation currents can arise in the external circuit on homogeneous heating of an insulator with a polar direction that is in a thermodynamically nonequilibrium state. These currents differ from thermally stimulated depolarization currents in being observed in a specimen that is unpolarized or has been depolarized. The temperature dependence of these relaxation currents is obtained for a particular model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 32–35, July, 1982.     

Automorphism Groups of Countably Categorical Linear Orders are Extremely Amenable

We show that the automorphism groups of countably categorical linear orders are extremely amenable. Using methods of Kechris, Pestov, and Todorcevic, we use this fact to derive a structural Ramsey theorem for certain families of finite ordered structures with finitely many partial equivalence relations with convex classes.