Quasi-particles method in solid solution theory

In this paper the method of cluster components is treated for calculations of cation exchange. It gives the dependence of the properties on the equilibrium constant. The interdependence of the method of cluster components with the quasi-chemical approximation is discussed. Possible applications of this technique are illustrated for spinel solid solutions.     

On a negative thermal expansion in heavy fermion systems

We explain negative thermal expansion observed in some heavy fermion systems at low temperatures within a two-component Fermi-liquid picture: α may become negative if Fermi-level falls on a region of steep increase in the density-of-states. The results obtained account for the correlation between the sign of thermal expansion and that of thermopower, and give certain information about the band structure of these systems.     

Immobilization of luminescent nanosilicon in a microfine polytetrafluoroethylene matrix by means of supercritical carbon dioxide

With the use of supercritical carbon dioxide (SC-CO₂), the matrix immobilization of photoluminescent silicon nanocrystals (nc-Si) in polytetrafluoroethylene microparticles (mp-PTFE) is performed, which leads to the formation of mp-PTFE/nc-Si photoluminescent nanocomposite containing ∼10³–10⁴ nc-Si particles per mp-PTFE particle (1–2 μm in size). This approach is based on the effect of polymer swelling in SC-CO₂, efficient SC-CO₂-assisted transport of nanoparticles into the internal free volume of the polymer, and contraction of the nanocomposite after the release of CO₂, an effect that prevents the subsequent agglutination of nanoparticles. Particles of nc-Si photoluminescent in the visible spectrum were synthesized from silicon suboxide powder (SiO _x , x ≈ 1) heated at various temperatures within 25–950°C and then etched in concentrated hydrofluoric acid. The hydrosilylation procedure was used to graft 1-octadecene molecules to the surface of nc-Si particles. As a result, the photoluminescence intensity of nc-Si increased substantially. According to TEM images and small angle X-ray scattering data, the maximum size of nc-Si particles did not exceed 5 nm and 7 nm, respectively, and the core of these nanoparticles consisted of crystalline silicon. The structure and spectral properties of the initial nc-Si particles and synthesized mp-PTFE/nc-Si photoluminescent nanocomposite microparticles were studied.     

Investigation of Eco-Friendly Gas Mixture for Gas Discharge Particle Detectors

Physics of Atomic Nuclei - The first results of studying the Ar/CO2/HFO1234ze eco-friendly gas mixture for gas discharge detectors are presented. The work is performed using a prototype multiwire...     

Electrochemical dissolution of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> in acidic solutions

The cyclic voltammetry method was used to study the regularities of the electrochemical behavior of cobalt cobaltite in an acidic medium. It is shown that cathodic reduction of Co₃O₄ in the studied range of potentials of +1.0 to −0.8 V is a multistage process occurring according to the scheme:      

Effect of mechanical activation on the phase composition,structure, and polymorphism of YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O6 + δ oxide

The mechanical activation of YBa₂Cu₃O_6+δ powders is studied comprehensively using thermal analysis, scanning electron microscopy, high-temperature x-ray diffraction, and x-ray photoelectron spectroscopy. It is shown that the size of the coherent scattering regions is substantially reduced by intensive grinding (from 83 to 17 nm) and the material transforms to a nanostructured state. An increase in the reactivity of the material is found, which shows up as an enhanced accumulation of intercalated water in its structure. At the same time, no significant increase in the volume of impurity phases in the powder or in the influence of impurities on the crystal lattice parameters was observed. High-temperature x-ray studies of the lattice parameters of the YBa₂Cu₃O_6+δ phase reveal a jump (at temperatures of 430–630°C) and a decrease (above 630°C) in the parameter c when the powder is mechanically activated. A significant reduction in the temperature of the transition from the orthorhombic to the tetragonal structural modification is observed. These effects are explained by a change in the charge states of oxygen ions belonging to the base plane of the YBa₂Cu₃O_6+δ oxide during mechanical activation.     

Wide-band magnetoelectric characterization of a ferrite-piezoelectric multilayer using a pulsed magnetic field

The use of a pulsed magnetic field for studies on frequency characteristics of the magnetoelectric (ME) effect in multilayer composite structures is described. The method is based on the excitation of a ferrite-lead zirconate titanate multilayer with short magnetic field pulses, followed by the measurement and Fourier analysis of the ME response signal. It is shown that the ME voltage coefficient α_E generally decreases as the frequency increases from 1 kHz to 1 MHz except (i) at some discrete frequencies where the coefficient increases by an order of magnitude due to electromechanical resonance in the structure and (ii) a local maximum at 2-4 kHz in α_E vs. frequency due to relaxation processes caused by the conductivity of individual layers.     

X-ray structural study of 1-oxo-4-isopropyl-and 1-thio-4-propyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octanes

Institute of Physiologically Active Substances, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 3, pp. 108–113, May–June, 1989.     

On the configurational splitting of strangeness analog state

Signatures and behaviour of s^–1s configurations are qualitatively discussed. Suppression of baryon-decay channels and an enhancement of cluster-decay channels are the relevant signals. The hypernuclear-quanta from constitute a novel example of the decay of s^–1 s^–1s configuration.Dedicated to the memory of M. Gmitro.We dedicate this article to our colleague and friend Dr. Marian Gmitro, whose premature death brought a profound grief upon our community. During years, his activities and knowledge in meson-nuclear physics have been very helpful in further development of hypernuclear physics. Also, his role in an efficient topical collaboration between Soviet and Czechoslovak physicists is to be greatly acknowledged.