Thermal expansion of crystal lattices of germanium with different isotopic compositions

The linear thermal expansion coefficient of crystal lattices of germanium with different isotopic compositions is analyzed. Fiz. Tverd. Tela (St. Petersburg) 40, 1829–1831 (October 1998)     

Entropy of crystallization of materials from a “molten” sublattice of superionic conductors

It is shown that the entropy of crystallization of materials (such as Cu, Ag, Au, and Li) in a “molten” sublattice of superionic conductors→crystal system may substantially exceed the entropy of crystallization of the same materials from a melt. The observed behavior explains the known tendency of various superionic conductors to form filamentary crystals (whiskers) in the solid phase, together with the completely different structure of these whiskers. Fiz. Tverd. Tela (St. Petersburg) 40, 227–228 (February 1998)     

Distinctive features of time-resolved photoluminescence of porous silicon coated with a layer of diamondlike carbon

Time-resolved photoluminescence from porous silicon coated with a diamondlike carbon film is investigated. The intensity of the photoluminescence from the carbon film is obserd to increase after deposition, and there is an accompanying change in the intensity and a shortwavelength shift of the photoluminescence band of porous silicon that depends on the porosity of its original layers. These changes are explained by the formation of carbon nanoclusters on the surface of the silicon filaments. Zh. Tekh. Fiz. 68, 83–87 (April 1998)     

A spectropolarimetric study of theH α radiation from ellerman bombs

Polarization data are given for three whiskers recorded with the large solar vacuum telescope at the Baikal Observatory, Institute of Solar-Terrestrial Physics, Russian Academy of Sciences. The observed degree of polarization varies from 2 to 13%. The direction of the polarization plane for the mediumintensity whisker was tangential, while that for the weakest one was radial. The brightest whisker had the polarization plane direction close to radial at the center of the line but tangential at the flanks. It is assumed that the polarization is due to impact excitation of a hydrogen-atom ensemble in the solar chromosphere by an electron beam, and estimates are made of the beam energy. St. Petersburg Fine Mechanics and Optics Institute, St. Petersburg. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 85–89, December 1998.     

The temperature jump and slow evaporation in molecular gases

We set up model transport equations that describe the behavior of molecular (diatomic and polyatomic) gases with a molecule collision rate proportional to the molecular velocity. In deriving these equations we allow for the internal (rotational) degrees of freedom, while the vibrational degrees of freedom are assumed “frozen.” We also set up an exact equation for the problem of the temperature jump with allowance for slow evaporation from the liquid surface into the saturated vapor atmosphere. Finally, we derive explicit formulas for calculating the coefficients of the temperature jump and gas-density jump above a flat surface and do the necessary numerical calculations. Zh. éksp. Teor. Fiz. 114, 956–971 (September 1998)     

Towards an universal classification of scale invariant processes

We consider fields which take random values over several decades. Starting from physical examples, we postulate that scale is not an absolute quantity. We then establish the equivalence between two existing approaches based on scale symmetry arguments as general as possible. This yields a classification of log-infinitely divisible laws, possibly universal. The physical significance of the parameters entering in the classification is discussed. Received: 7 November 1997 / Received in final form: 26 March 1998 / Accepted: 30 March 1998     

Influence of the surface on the elastic properties of liquid crystals

A statistical approach including direct correlation functions is applied to study the influence of the surface confining the nematic liquid phase on the Franck elastic coefficients. Specific calculations are made for a model system composed of ellipsoidal molecules interacting by means of the Gay-Berne potential near the interacting surface. Fiz. Tverd. Tela (St. Petersburg) 40, 1356–1359 (July 1998)     

Anomalous light diffusion in ferroelectrics having a diffuse phase transition

It has been shown by using the statistical approach that the angular dependence of intensity I(θ) in multiple small-angle light scattering can be described by Lévy’s universal distribution functions. The fundamental property of the stability of these distributions permits one to extract information on the characteristics of fractal media as complete as it is possible in the simple single-scattering case. In particular, an analysis of the polarization characteristics of I(θ) in disordered PST reveals that the surface fractals observed in these crystals are of the heterophase rather than domain origin. Fiz. Tverd. Tela (St. Petersburg) 40, 1537–1541 (August 1998)     

Experiments on two-step heating of a dense plasma in the GOL-3 facility

This paper presents the results of experiments on two-stage heating of a dense plasma by a relativistic electron beam in the GOL-3 facility. A dense plasma with a length of about a meter and a hydrogen density up to 10¹⁷ cm⁻³ was created in the main plasma, whose density was 10¹⁵ cm⁻³. In the process of interacting with the plasma, the electron beam (1 MeV, 40 kA, 4 μs) imparts its energy to the electrons of the main plasma through collective effects. The heated electrons, as they disperse along the magnetic field lines, in turn reach the region of dense plasma and impart their energy to it by pairwise collisions. Estimates based on experimental data are given for the parameters of the flux of hot plasma electrons, the energy released in the dense plasma, and the energy balance of the beam-plasma system. The paper discusses the dynamics of the plasma, which is inhomogeneous in density and temperature, including the appearance of pressure waves. Zh. éksp. Teor. Fiz. 113, 897–917 (March 1998)     

Continuum many universal Horn classes of graphs of bounded chromatic number

Received February 28, 1997; accepted in final form July 19, 1998.