Peak effect studies in single crystals CeRu2 and 2H-NbS2

We have studied the peak effect (PE) phenomenon in single crystals of weakly pinned superconductors CeRu₂ and 2H-NbS₂. 2H-NbS₂ is iso-structural and iso-electronic to 2H-NbSe₂, whose similarity with CeRu₂ as regards the PE representing the order-to-disorder transformation of the flux line lattice was claimed some time ago. We report on the step change in equilibrium magnetization across the peak effect in CeRu₂. We also present the vortex phase diagram of 2H-NbS₂ obtained from the magnetization data, and compare the PE phenomenon in 2H-NbS₂ and 2H-NbSe₂.     

Complex-forming and selectivity properties of substituted tetraphenylethylenediphosphine dioxides with respect to alkali metal cations

The complex-forming reactivity of mono- and disubstituted ethylenediphosphine dioxides of the general formula Ph₂P(O)CH₂C(R¹R²)P(O)Ph₂, and of a tetraphosphorylated monopodand, ortho-bis[4,5-bis(diphenylphosphinyl)-pentoxy]benzene, relative to alkali metal cations have been determined conductometrically in THF-CHCl₃ medium (4:1). Introduction of alkyl substituants in the ethylene bridge of tetraphenylethylenediphosphine dioxide increases its Li/Na selectivity; maximum Li/Na selectivity equal to 40 is observed for the dimethyl-substituted tetraphenylethylenediphosphine dioxide derivative. Among the ligands examined herein the hexadentate tetraphosphoryl-containing monopodand ortho-bis[4,5-bis(diphenylphosphinyl)pentoxy]benzene was found to be the most effective complex-forming agent with respect to lithium (log=6.0), with a high Li/Na selectivity value equal to 40. The syntheses of 1,1-dimethyltetraphenylethylenediphosphine dioxide and of ortho-bis[4,5-bis(diphenylphosphinyl)pentoxy]benzene are described.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 873–877, April, 1990.The authors wish to thank Z. N. Vostroknutovii for carrying out the stability constant measurements in anhydrous acetonitrile.     

Measuring deuteron beam parameters with solid-state track detectors in experiments with the QUINTA target assembly

The results of measurements of the beam parameters on the target upon irradiation of the QUINTA subcritical uranium assembly with deuterons with energies of 1, 4, and 8 GeV are presented. Data on the position of the incident particle beam relative to the assembly axis and on the actual geometric parameters of the beam make it possible to analyze information on the spatial distributions of reaction rates within the target assembly correctly, comparing such distributions obtained at different irradiation sessions and modeling the experiments with the use of MCNPX, GEANT4, FLUKA, and other similar software tools.     

Study of the formation mechanisms of forced expiratory wheezes in a healthy person when breathing gas mixtures of different density

The aim of the study is to specify the localization and formation mechanisms of forced expiratory wheezes (FEWs) in the bronchial tree. Statistical modeling of FEW spectral parameters has been performed, which were recorded above the lower sections of the lungs to the right and left, as well as over the trachea, from a sampling of 25 volunteers who breathed gases of different density. It was established that the highest amplitude FEWs formed closer to the trachea, and the lowest, in more distally located levels of the bronchial tree. The lower the density of the gas, the closer to the trachea the formation of mid-frequency FEWs occurs. For earlier high-frequency FEWs, an indirect dependence of their peak frequency on the Reynolds number was revealed. Turbulent-flow-induced forced oscillations and, in particular, vortex shedding are the probable formation mechanism for some of the FEWs.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

Theoretical study of the spectra of the oxygen isoelectron series

By applying perturbation theory to the reciprocal of the nuclear charge (1/Z), the spectra of a series of oxygen-like ions (having configurations of the 1s²2s²2pⁿ, 1s²2s2pⁿ⁺¹, 1s²2pⁿ⁺², n =4 type) are calculated. The results of the calculation are compared with existing experimental data. The difference between the theoretical and experimental energies of the terms is 0.1–1%.     

Decay of metastable autoionization state in a highly charged lithium-type ion

Relativistic wave functions have been used to calculate the probabilities for (1s2s2p)⁴P_5/2-(1s²Kf)²F₅/₂ autoionization and (ls2s2p)⁴P₅/₂-(1s²2s)² S_1/2 magnetic quadrupole transition, together with the lifetimes of the (1s2s2p)⁴P_5/2 states, for lithium-type ions with Z from 10 to 60; the results are compared with measurements and with calculations from literature sources.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 13–18, December, 1977.I am indebted to A. D. Gurchumeliya and L. N. Ivanov for valuable discussions.