Inverse regime of ionic modification of surface anchoring in nematic droplets

JETP Letters - It was found that the effect of the ionic modification of anchoring in liquid-crystal droplets can be implemented in the inverse regime. Droplets of 4-n-pentyl-4′-cyanobiphenyl...     

High-voltage electroconduction in molten chlorides of alkaline-earth metals

Effects of high-voltage pulses on electroconduction of molten chlorides of alkaline-earth metals and their mixtures with potassium chloride are studied experimentally. It is established that the electroconductivity of the melts subjected to the pulses increases proportionally to the voltage amplitude and the number of activating pulses in a pulse series. Oscillatory relaxation of nonequilibrium melts is discovered.     

Anomalous birefringence of light in free-standing samples of porous silicon

The birefringence of light in freely suspended samples of porous silicon is observed and investigated. The effect is interpreted as “shape birefringence,” i.e., the effect caused by the structure of a material consisting of anisotropic formations with sizes less than the wavelength of the light and with a predominant orientation. It is checked experimentally that the samples do not possess optical activity or optical anisotropy in the plane of the porous-silicon film. It is determined that the effect is observed for polarization of incident light that rules out the possibility of observing birefringence in a uniform optical medium, and it is not observed in the conventional experimental geometry. Qualitative explanations are given for the anomalous character of the observed defect.     

Interference-sensitive photodetector-correlometer of optical signals

The use of an interference-sensitive photodetector for recording a correlation function of counterpropagating light beams and for recording an autocorrelation function (interferogram) of a light beam is considered. A scheme of the correlometer of optical signals without mechanical scanning is presented. Fields of application of new correlometers are suggested.     

Stereochemistry of cyclic compounds Communication 62. Stereochemistry of the oxidation of 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride

Summary The stereochemistry of the oxidation of 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride with peroxyacetic acid was studied, and by a series of transformations it was proved that the epoxide then formed has the ßconfiguration. The observed stereospecificity of the oxidation is explained on the basis of views on a predominant boat conformation for 4-cyclohexane-1,2-dicarboxylic anhydrides.This article is published in accordance with a resolution of the Conference of Chief Editors of the Journals of the Academy of Sciences of the USSR, July 12, 1962, as a dissertation paper by A. L. Shabanov.     

Distribution function of relaxation times for a 4-<Emphasis Type="Italic">n</Emphasis>-pentyl-4′-cyanobiphenyl liquid crystal

The distribution function of relaxation times is reconstructed from the dielectric loss spectrum measured over a wide range of frequencies for a 4-n-pentyl-4′-cyanobiphenyl (5CB) liquid crystal. It is demonstrated that the distribution function for the isotropic and nematic phases is asymmetric in shape. Comparison shows that the reconstructed distribution function is in qualitative agreement with similar functions that are analytically derived from the Cole-Davidson and Havriliak-Negami empirical equations. The specific features observed in the behavior of the distribution function with a variation in the angle between the direction of polarization of a microwave electric field and the director of the liquid-crystal molecules are analyzed. A complex dependence of the permittivity for the liquid crystal in the range of ultrahigh frequencies is explained in terms of additional relaxation mechanisms associated with different motions of molecular fragments of alkyl chains.