Structure and Magnetoresistance of Co–Gd and Al–Co–Gd Alloy Films

Technical Physics - Structural data and dependences of the film resistance on magnetic field strength R(H) are presented for Co–Gd and Al–Co–Gd alloy films obtained by vacuum...     

Thermal ignition of a heterogeneous system in a stirring semibatch reactor

The thermal ignition of a heterogeneous two-phase system of two immiscible liquids in a stirring semibatch reactor was modeled. The model took into account the dispersion of one phase in the other, the mass transfer of a reagent from the disperse phase into the dispersion medium, and the bimolecular exothermal reaction that occurred in the latter. The kinetic dependences of reagent concentrations, the dynamics of reactor heating, and the critical conditions of thermal ignition were studied. It was found that the initial temperature of the reactor had a considerable effect on its dynamic behavior.     

Phase transitions in a different-scale atomic structure during annealing of magnesium-zinc ferrites

Mg_0.54Zn_0.46Fe₂O₄ ferrites are studied by X-ray diffraction, and different-scale structural groups with short-range, mesoscopic, and long-range atomic orders are revealed in them. These groups are shown to undergo interrelated order-disorder-order phase transitions during high-temperature annealing at 1280°C for 0.5–8.0 h, which are accompanied by maximum changes in the structural parameters.

     

Steady States of a Plug Flow Reactor Operating on a Heterogeneous Liquid−Liquid System

A plug flow reactor operating on a heterogeneous liquid?liquid system in which an exothermic bimolecular reaction takes place is modeled. The effect of the main governing parameters (Peclet and Damkheler numbers and a dimensionless parameter P characterizing mass transfer between the liquid phases) on the thermal modes of the reactor is examined. Depending on the values of these parameters, one or three steady states can be realized in the reactor. It is established that, with increasing parameter P, the region of multiplicity of steady states expands and shift toward lower values of the Damkohler number. The phenomenon of hysteresis is observed in the region of multiplicity of steady states.     

Studying the structural features of oxide nanoclusters of cerium and titanium in a silicate glass by means of the small-angle neutron scattering

The features of the formation of Ce-Ti-O complex oxide nanoclusters in a silicate glass are studied by means of the small-angle neutron scattering technique. It is found that bounded regions of density fluctuation of the glass material are formed in the initial glass matrix without the addition of titanium and cerium oxides. These regions could serve as nucleation centers for oxide clusters of cerium and titanium upon their introduction into the matrix. The calculated average size of these inhomogeneities does not exceed 30 ± 1 nm, and their surface volume equals 0.72 ± 3 nm³. A structural mechanism for Ce-Ti-O oxide formation in a silicate glass, in which the nanoclusters are formed within a bounded region of glass material inhomogeneities at low concentrations of the initial cerium oxide (CeO₂), is proposed. At high cerium oxide concentrations, oxide nanocluster growth occurs predominantly on the surface of these inhomogeneities. This leads to a sharp change in the nanocluster sizes and their fractal dimension.     

Anomalous diamagnetic transitions in Ba2Cu3O4Cl2 and Sr2Cu3O4Cl2 antiferromagnets

The magnetic properties of Ba₂Cu₃O₄Cl₂ and Sr₂Cu₃O₄Cl₂ oxychlorides have been studied. A spontaneous manifestation of diamagnetism has been found at quasi-zero and low fields. The temperature of these transitions coincides with the temperature of the antiferromagnetic ordering in Ba₂Cu₃O₄Cl₂ (T _NI ≈ 337 K) and Sr₂Cu₃O₄Cl₂ (T _NI ≈ 386 K). The recorded diamagnetic signal is ?10^?4 emu. It is comparable with the percentage of the superconducting phase in the sample. It is supposed that the arising superconductivity is due to the formation of the superconducting clusters with the direct overlap of the copper d orbitals owing to the frustration processes.     

Moments of Markov Random Evolutions

We find moments of a process of Markov random evolutions in a finite-dimensional space.     

The Coherent Production of the (K +π0) System by K + Beam on Copper Nuclei at the OKA Setup

Journal of Experimental and Theoretical Physics - On the statistics of ~1.7 × 108 interactions of positively charged kaons on copper nuclei, coherent events of the K+π0 system production...     

On Some Spectral Properties of the Energy Operator for an Infinite System in a Magnetic Field

For systems in a magnetic field, we investigate the form sum of an infinite-dimensional energy operator perturbed by a potential. We also investigate changes in the spectrum of the energy operator in the case of its perturbation by a potential.