Skin effect in a thin cylindrical metallic wire

The problem of distribution of the electric field and electric current in a thin cylindrical metallic wire in the presence of the skin effect taking into account specular-diffuse reflection of electrons from the inner surface of the wire has been solved for the first time. The limiting cases have been considered. The obtained results have been discussed.     

Synthesis and crystal structure of the gallium-containing montebrasite analogue LiGa(OH)PO4

Gallium lithium hydroxyphosphate LiGa(OH)PO₄ was prepared under mild hydrothermal conditions (T = 160°C, τ = 48 h) and characterized (IR spectroscopy, chemical and thermal analysis). LiGa(OH)PO₄ was found to be structurally similar to the ambligonite family phases. The crystal structure was refined by the Rietveld method (space group $P\bar 1$ , Z = 2): a = 5.0853(1) Å, b = 5.2973(1) Å, c = 7.3006(1) Å, α = 67.830(1)°, β = 67.839(1)°, γ = 82.027(1)°, R _p = 0.0519, R _wp = 0.0765. A zero SHG signal confirmed a centrosymmetric structure of the compound. The structure is represented by a mixed {Ga(OH)[PO₄]} _3∞ ^? framework composed of the PO₄ tetrahedra and GaO₄(OH)₂ octahedra. The framework contains hexagonal channels running in the [100] and [010] directions. The basic element of the framework is a linear chain of GaO₄(OH)₂ octahedra sharing trans OH vertices. The Li⁺ ions reside in the framework voids.     

Synthesis and transformations of metallacycles

The Cp₂ZrCl₂-catalyzed reaction of arylolefins (styrene,o- andp-methylstyrenes,trans-stilbene, 1,4-diphenyl-1,3-butadiene) with AlEt₃ resulting in mono- and disubstituted alumacyclopentanes and substituted alumacyclopropanes was studied. The yield and ratio of cyclic organoaluminum compounds depend on the structure of the initial arylolefins and conditions of cycloalumination.     

Mössbauer Study of Ferrite-garnets as Matrixes for Disposal of Highly Radioactive Waste Products

Mössbauer study of synthesized ferrite-garnet samples containing Zr, Th, Ce and Gd of the following composition: 1C – Ca_{2, 5} Ce_{0, 5} Zr₂ Fe₃ O₁₂, 2C – Ca_{1, 5} GdCe_{0, 5} ZrFeFe₃ O₁₂, 1T – Ca_{2, 5} Th_{0, 5}Zr₂ Fe₃ O₁₂ and 2T – Ca_{1, 5} GdTh_{0, 5} ZrFeFe₃ O₁₂ are carried out. As a result of ⁵⁷Fe Mössbauer study it is found that iron atoms in all investigated samples of garnets are in a trivalent state. The analysis of experimental Mössbauer spectra definitely specifies a various structural state of iron atoms in two investigated groups of samples: 1T, 1C and 2T, 2C. X-ray study have shown that 1T and 1C garnet samples crystallize in tetragonal space group I4₁/acd, but 2T and 2C samples crystallize in cubic space group Ia3d.     

The effect of superstructural ordering on the properties of high-temperature oxide superconductor systems

The effect of superstructural ordering in the oxygen sublattice (in addition to the influence of the antiferromagnetic interaction of copper ions) on the electron and phonon characteristics of oxide high-temperature superconductor (HTSC) systems has been studied. Taking into account this ordering effect, it is possible to explain a wide range of experimental data, including doping-induced changes in shape of the Fermi surface, features of the phonon spectra, the existence of stripes, the presence of a pseudogap and its coexistence with the superconducting gap, and some peculiarities in the phase diagrams of HTSCs.     

Kinetics and thermodynamics of reversible disproportionation–comproportionation in redox triad oxoammonium cations – nitroxyl radicals – hydroxylamines

Kinetics and equilibrium of the acid‐catalyzed disproportionation of cyclic nitroxyl radicals R₂NO^? to oxoammonium cations R₂NO⁺ and hydroxylamines R₂NOH is defined by redox and acid–base properties of these compounds. In a recent work (J. Phys. Org. Chem. 2014, 27, 114‐120), we showed that the kinetic stability of R₂NO^? in acidic media depends on the basicity of the nitroxyl group. Here, we examined the kinetics of the reverse comproportionation reaction of R₂NO⁺ and R₂NOH to R₂NO^? and found that increasing in –I‐effects of substituents greatly reduces the overall equilibrium constant of the reaction K₄. This occurs because of both the increase of acidity constants of hydroxyammonium cations K_3H+ and the difference between the reduction potentials of oxoammonium cations E_R2NO+/R2NO? and nitroxyl radicals E_R2NO?/R2NOH. pH dependences of reduction potentials of nitroxyl radicals to hydroxylamines E_1/3Σ and bond dissociation energies D(O–H) for hydroxylamines R₂NOH in water were determined. For a wide variety of piperidine‐ and pyrrolidine‐1‐oxyls values of pK_3H+ and E_R2NO+/R2NO? correlate with each other, as well as with the equilibrium constants K₄ and the inductive substituent constants σ_I. The correlations obtained allow prediction of the acid–base and redox characteristics of redox triads R₂NO^?–R₂NO⁺–R₂NOH. Copyright © 2014 John Wiley & Sons, Ltd.     

Phase formation in the Ag3PO4-ScPO4 quasi-binary system

The phase formation in the subsolidus region of the Ag₃PO₄-ScPO₄ quasi-binary system was studied by X-ray powder diffraction and differential thermal analyses throughout the range of concentration ratios of the initial components at an interval of 10 mol % within the temperature range 20–1000°C in air at atmospheric pressure. A T-x section was constructed. The formation of the binary phosphate Ag₃Sc₂(PO₄)₃ melting incongruently at 1300 ± 5°C was detected. The composition of an eutectic (with the melting point 900 ± 5°C) is between those of the compounds Ag₃PO₄ and Ag₃Sc₂(PO₄)₃.     

Reason for line broadening in emission Mössbauer spectra

Summary Resonant lines observed in source experiments are usually significantly broader thanthosein the corresponding absorber experiments. In order to explain this phenomenon, the model of a trapped electron has been proposed. Auger electrons emitted, for instance, after electron capture by ⁵⁷Со or after the converted isomeric transition of^119mSn, as well as secondary electrons, may be trapped in the vicinity of the nucleogenic ion. An asymmetric distribution of quadrupole splittings in the resulting emission M?ssbauer spectra is thus a consequence of electron capture by lattice traps located at different distances from the daughter ion. Estimates of quadrupole splitting values, which may be causedby trapped electrons located at different distances from the nucleogenic atom, support the above mentioned model.     

Thermal Induced Processes in Laminar System of Stainless Steel – Beryllium

The paper reports on investigation of the laminar system ‘stainless steel 12Cr18Ni10Ti – Be’ at thermal treatment. There have been determined sequences of phase transformations along with relative amount of iron-containing phases in the samples subjected to thermal beryllization. It has been revealed that thermal beryllization of stainless steel thin foils results in γ→α transformation and formation of the beryllides NiBe and FeBe₂. It has also been revealed that direct γ→α- and reverse α→γ-transformations are accompanied by, correspondingly, formation and decomposition of the beryllide NiBe. It is shown that distribution of the formed phases within sample bulk is defined by local concentration of beryllium. Based on obtained experimental data there is proposed a physical model of phase transformations in stainless steel at thermal beryllization.