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.     

Electron screening in backward elastic scattering

Abstact: The elastic scattering cross sections, σ (E,θ), for the systems He+Ta and He+W have been measured at θ_lab=165° and E _lab=76.1 keV to 3.988 MeV using targets with a thickness of a few atomic layers. The results are smaller than the results given by the Rutherford scattering law, σ_R(E,θ), due to the effects of electron screening and can be described by σ(E,θ)/σ_R(E,θ)=(1+U_e/E)⁻¹, where U _e is an atomic screening potential energy. The deduced average value, U _e=28 ± 3 keV, is consistent with the Moliére- and Lenz-Jensen-models as well as electron binding energies. Received: 25 May 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)     

Two Theorems of Hardy-Bennett-Type

The factorization of inequalities, introduced by G. Bennett, is a new and very effective method providing the best possible version of several classical and latest inequalities. Here two theorems of G. Bennett are extended into factorized forms up to the exact values of the constants. In the proofs we construct appropriate sequence spaces and utilize one of our recent theorems.     

H andH NMR Relaxation in Hydrogen-Bonded Solids Due to a Complex Motion: Classical Jumps over a Barrier and Incoherent Tunneling

Equations for the temperature dependence of proton and deuteron spin–lattice relaxation rates and second moments due to a complex motion consisting of classical jumps over a potential barrier and quantum mechanical tunneling through the barrier have been derived. Asymmetric double and triple potential wells are considered. These equations have been employed to analyze proton spin–lattice relaxation data for solid naphthazarin in the laboratory and rotating frames as a function of temperature. It is shown that tunneling plays an important role in the proton transfer dynamics of this compound.     

Underdoped manganites: Canted antiferromagnetic ordering or two-phase ferro-antiferromagnetic state?

We calculate the energy of charge-carrier-induced canted ordering in conducting layered antiferromagnetic systems with double exchange. The quantum approach to the d-spins is used. In the jellium model the energy of the canted state is lower than the energies of both collinear ferro-and antiferromagnetic states over a certain range of charge carrier densities, beginning with arbitrarily small densities. Nevertheless, the canted state cannot be realized, because it is unstable against charge-carrier density fluctuations. The two-phase ferro-antiferromagnetic state can play the role of an alternative to canting. The case of an intermediate electronic-impurity phase separation is investigated. Zh. éksp. Teor. Fiz. 114, 2225–2237 (December 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

A shape model for the twisting power of chiral solutes in nematics

The twisting power of chiral probes in nematics is interpreted in terms of a shape model, in which the surface elements of the solute molecules tend to align with the local director. The theoretical treatment is based on a previous approach, suitable for relating order parameters in nematics to molecular shape, and leads to the definition of a molecular pseudo-tensor whose orientational average determines the pitch and handedness of the helical macrostructures. Results of numerical calculations performed for distorted biphenyl and binaphthyl molecules are in agreement with the experimental results.