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)     

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.     

Influence of dissipation on one- and two-dimensional quantum tunneling

The influence of low-frequency oscillations of the medium on the particle tunneling probability is investigated in a system with a selected tunneling coordinate, when the two-well tunnel potential takes the form of two parabolas of the same frequency. With parallel or antiparallel tunneling of two interacting particles, taking the interaction with the medium into account has no qualitative effect on the process. Quantitatively, however, the medium always influences the parallel motion of the tunneling particles and does not influence the action along the basic trajectory (R₁=−R₂) with antiparallel motion of the tunneling particles. Penzensk State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 103–107, July, 1998.     

Electrical characterization of the SiO2---Si system

The classical capacitance-voltage measurement methods and the conductance technique which are frequently used to analyze the SiO₂---Si system, are briefly introduced and critically evaluated. These measurement techniques are based on macroscopic device structures, average structure parameters are determined. Transient and random telegraph signal measurements, and charge pumping are now available as new methods to study the SiO₂---Si interface in sub-μm device structures. These techniques permit to analyze single, individual traps in the interface. Traps in small devices are isolated. The capture rates are thermally activated by the Coulomb energy.     

On a problem of Zygmund

It is proved that there exists an integrable function on [0, 1]² whose integral is nondifferentiable in each direction belonging to a set everywhere dense in [0, 2π] but is strongly differentiable. Translated fromMatematicheskie Zametki, Vol. 64, No. 5, pp. 749–762, November, 1998.     

Calculation of the noise factor of a traveling-wave gyrotron

The problem of calculating the noise factor of a traveling-wave gyrotron is solved for a model of a thin annular multistart-helical electron flux taking into account the effect of the quasistatic space-charge field. Plots of the gain and the noise factor of the traveling-wave gyrotron versus the electrical parameters of the amplifier are obtained. Zh. Tekh. Fiz. 68, 130–132 (February 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)     

Orientational ordering of liquid crystals containing a difluoro-substituted phenyl ring

The orientational ordering of several liquid crystals containing a difluorosubstituted phenyl ring has been studied through the use of C-13 NMR. The fluorinated phenyl ring of these liquid crystals have C_s symmetry, so three order parameters are required to completely describe the ordering of this ring. All three of these order parameters have been calculated from carbon-fluorine dipolar coupling constants obtained from the carbon-fluorine splittings in the C-13 NMR spectra. Because of the complexity of the fluorine-coupled spectra, variable angle spinning (VAS) was used to resolve the carbon-fluorine splittings. In order to study the orientational ordering over wide ranges of temperature, we have developed an empirical correlation between the order parameter and the value of a carbon-fluorine dipolar coupling constant. This enabled us to study the change in the order parameter with temperature. The results of applying this method to several structurally similar liquid crystals containing the same type of difluorinated phenyl ring are presented. A comparison is made to a similar mono-fluorinated liquid crystal.