Logarithmic conformal field theory and boundary effects in the dimer model

We study the finite-size corrections of the dimer model on a square lattice with two different boundary conditions: free and periodic. We find that the finite-size corrections depend in a crucial way on the parity of ; we also show that such unusual finite-size behavior can be fully explained in the framework of the logarithmic conformal field theory.     

Determination of the parameters characterizing the superexchange interaction in complex ferrite-spinels

A calculation procedure is proposed here for determining the values of exchange parameters, applicable to spinels which contain three kinds of ions in tetrahedral positions and which have an arbitrary distribution of cations. The values of exchange integrals obtained here for ferrites of the manganese-zinc system provide a useful basis for a quantitative interpretation of the spread of Curie-temperature readings in experiments which involve ferrites with the same composition.     

Onset of detonation in polydispersed fuel–air mixtures

Investigations of detonation onset in pulverized fuel–air mixtures were carried out. Combustion and detonation processes in sprays differ greatly from that in homogeneous mixtures, because not only chemical reactions, but physical processes of combustible mixture formation take place within the combustion zone (droplets atomization and evaporation). The polydispersed character of mixture and non-uniformity of droplet spatial distribution strongly affects spray combustion and detonation onset. The present paper contains the results of theoretical and experimental investigations of detonation onset peculiarities in polydispersed non-uniform hydrocarbon–air mixtures.     

Grüneisen parameter and propagation velocities of acoustic waves in vitreous solids

A linear correlation has been found between the Grüneisen parameter and the ratio of the propagation velocities of longitudinal and transverse acoustic waves in vitreous solids. The relation between these quantities has been interpreted in terms of the Pineda model.     

Nonlinear optical parameters of colloidal silver at various stages of aggregation

The Z-scan method is used to study the variation in the nonlinear susceptibility χ⁽³⁾ (−gw; ω, ω, −ω) and nonlinear refractive index of colloidal silver with the degree of aggregation under the action of picosecond and nanosecond radiation (λ=1064 nm). The values of χ⁽³⁾ for aggregated silver that are defined by Kerr nonlinearity and thermal self-focusing are found to be −1.5×10⁻¹⁴ and −4.4×10⁻¹¹ esu, respectively. The time evolution of the picosecond pulses passing through the colloid is investigated.     

Investigation of Nd2CuO4 crystal structure at high pressure by neutron diffraction

Abstract

The crystal structure of Nd₂CuO₄ has been studied by neutron diffraction at pressure up to 5 Gpa. The volume compressibility value was determined as 5·6·10^?3/Gpa. The decrease of positional parameter of neodymium at high pressure has been observed. This structural change is explained by pressure induced neodymium ions charge increase.     

Electrical and optical absorption studies of Cu7GeS5I fast-ion conductor

Electrical conductivity and fundamental absorption spectra of monocrystalline Cu₇GeS₅I were measured in the temperature ranges 95-370 and 77-373 K, respectively. A rather high electrical conductivity (σ_t=6.98×10⁻³Ω⁻¹ cm⁻¹ at 300 K) and low activation energy (ΔE_a=0.183 eV) was found. The influence of different types of disordering on the Urbach absorption edge and electron-phonon interaction parameters were calculated, discussed and compared with the same parameters in Cu₇GeS₅I, Cu₆PX₅I (X=S,Se) and Ag₇GeX₅I (X=S,Se) compounds. We have concluded that the P→Ge and Cu→Ag cation substitution results in an increase of the electrical conductivity and a decrease of the activation energy. Besides, P→Ge substitution, results in complete smearing and disappearance of the exciton absorption bands and in blue shift of the Urbach absorption edge, an increase of the edge energy width and an electron-phonon-interaction enhancement.     

Investigations of fission characteristics and correlation effects

We review the experimental results on the P-even and P-odd angular correlations of fission fragments in the fission of the ²³⁵U and ²³⁹Pu nuclei induced by unpolarized and polarized resonance neutrons, and on the TRI and ROT effects in the ternary and binary fission of actinides induced by polarized thermal neutrons. Also reported are the measured yields of prompt and delayed neutrons per fission event. The experimental data are analyzed within a novel theoretical framework developed by the JINR—RNC KI Collaboration, whereby the reduction of the multidimensional phase space of fission fragments to the JπK-channel space is consistently validated and the role of resonance interference in the observed correlation effects is revealed.     

Model of diffusion-drift charge carrier transport in layers with a fractal structure

A new theoretical (semiempirical) model of diffusion-drift charge carrier transport in layers with a fractal structure based on a partial differential equation with a fractional time derivative has been proposed. It has been shown by numerical calculations that a decrease in the order of the fractional derivative in the presence of the external electric field leads to broadening and asymmetry of the spatial distributions of charge carriers, which physically corresponds to intensification of scattering processes.