First principle study of the magnetism of Sr2CoMoO6-δ (δ = 0, 1/2) double perovskites

We investigate the electronic structure of bulk Sr₂CoMoO_6-δ double perovskites using the ab initio Full Potential Linearized Augmented Plane Wave method in order to study their magnetic properties within the GGA and GGA+U methods. We discuss the relative stability of ferromagnetic (FM) and antiferromagnetic (AFM) orders (i) without and with taking into account the observed tilting of the oxygen octahedra and (ii) by introducing oxygen vacancies. We show that a very good agreement with experimental results — AFM order for δ= 0 and FM order for δ= 1/2 — is obtained only when the tilting of the oxygen tetrahedra is taking into account and when the GGA+U method is used.     

Interface design in nanosystems of Advanced Superionic Conductors

First attempt of practical realization of new interface engineering approach “from advanced materials to advanced devices” for nanosystems of Advanced Superionic Conductors (ASICs), based on AgI (CuI) compounds is presented. Crystallochemical method of symmetry perfect ASIC//electrode interface searching is developed. Some new theoretical results of ASIC//indifferent electrode conjugated commensurate heteropairs with coherent interfaces and preliminary experimental results of the creation of thin-film supercapacitor — prototype based on the lattice matched heterojunction — are given. Future perspectives of the ASIC//electrode interface design suited for micro(nano)electronics and microsystem technology (MST) are discussed. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14–18, 2004.     

Neutron-, ion-, and electron-energy spectra in a 1 kJ plasma focus

The neutron energy spectrum (4 Torr deuterium) was determined from 30 m flight histograms.—An average energy of approximately 100±20 keV of the neutron producing deuterons within an assumed cone angle of approximately 40 degrees along thez-axis was calculated by means of the target beam model.—Shadow bar techniques reveal that only 10% of the neutrons are produced in the ≈1 cm long focus.—Experimental time of flight analysis confirms that the ion spectrum extends from less than 70 to greater than 400 keV. The electron spectrum in 8 Torr hydrogen follows a ≈3 keV Boltzmann distribution, but demonstrates the presence of nonthermal >100 keV electrons.     

Sounding of an artificially perturbed ionosphere by means of an ionosonde/position finder with chirp modulation of the signal

We describe the operation of an ionosonde/position finder with chirp modulation of the signal. The first results of measuring the characteristics of short-wave radio signals scattered by artificial small-scale inhomogeneities, which were obtained by means of an ionosonde/position finder on the IZMIRAN—“SURA”—Rostov-on-Don path are presented. It was found that under certain ionospheric conditions, the angular and frequency selection of the scattered signals take place, in which case the signals are observed simultaneously in several frequency intervals (mainly, in three, namely, 6–9.5 MHz, 10–12 MHz, and 15–18 MHz) with different angles of incidence of radio waves in the vertical plane. In this case, the incidence angles were 20◦–35◦, 18◦–32◦, and 10◦–20◦ from the horizon for the first, second, and third frequency interval, respectively. Ionograms of oblique sounding were modeled allowing for the scattering of radio waves by artificial small-scale inhomogeneities. It is shown that at frequencies from 10 to 12 MHz, aspect conditions are fulfilled for the signals ducting along the high-angle beam (Pedersen mode). At frequencies 15–18 MHz (higher than the maximum observable frequency of the forward signal on the path IZMIRAN—Rostov-on-Don), aspect scattering conditions are fulfilled for the signals incident on a scattering area in the ascending part of the trajectory. At low frequencies 6–9.5 MHz (below the maximum observed frequency of the forward signal on the IZMIRAN—Rostov-on-Don path), the observable additional signals are caused by the scattering of radio waves by artificial inhomogeneities with subsequent relfection of the scattered signal from the Earth on the “SURA”—Rostov-on-Don path. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 4, pp. 267–278, April 2009.     

Electron impact excitation of hydrogen and helium in Coulomb-projected Born methods

Coulomb-projected Born methods for the theoretical study of electron impact excitation of hydrogen and helium are reviewed. The results obtained by using different forms of Coulomb-projected Born methods are compared with other theoretical and experimental results and analyzed. The inadequacy of the variable charge Coulomb-projected Born approximation (VCCPB)—the most recent form of the Coulomb-projected Born methods—in giving good results in processes where exchange is dominant is discussed in detail. The ‘modified’ VCCPB approximation obtained by modifying the VCCPB method to remove its shortcomings is also discussed and its application to electron impact excitation of 2³ s state of helium is studied.     

Fluorometric determination of association constants of three estrogens with cyclodextrins

It was found that the fluorescence intensity in solutions of three estrogens—estradiol, ethinyloestradiol, and estriol—increased upon the addition of Β- or γ-cyclodextrin, the effect being greater with the first ligand. These changes in fluorescence intensity were used for the determination of association constants of the compounds with the two cyclodextrins. An iterative procedure was used to calculate the concentrations of free (uncomplexed) ligand, which are needed for the calculation of the association constants. These values were compared with the constants previously determined by HPLC. The fluorometric association constants with Β-cyclodextrin were ower than the corresponding HPLC values, whereas for the complexes with γ-cyclodextrin the results of both methods coincide.     

Studies of phase transitions and quantum chaos relationships in extended Casten triangle of IBM-1

A precise solution of the classical energy functional E(N, η, χ; β) minimum problem with respect to deformation parameter β is obtained for the simplified Casten version of the standard interacting boson model (IBM-1) Hamiltonian. The first-order phase transition lines as well as the critical points of X(5), -X(5), and E(5) symmetries are considered. The dynamical criteria of quantum chaos—the basis state fragmentation width and the wave function entropy—are studied for the (η, χ) parameter space of the extended Casten triangle, and the possible relationships between these criteria and phase transition lines are discussed. The text was submitted by the authors in English.     

μ+ shift study inCdMgx (x=1%, 2%, 2.5%)shift study inCdMgx (x=1%, 2%, 2.5%)

In continuation of our earlier studies of the anomalous temperature dependence of the μ⁺ Knight shift K_μ in Cd,CdHg (1.2 at %) andCdMg (3.38 at %) — interpreted as due to Van Hove-type singularities in the local density of electron states /1/ — we have studied the temperature dependence of the μ⁺ Knight shift in polycrystallineCdMg (1.04 at %, 2.05 at %) and in a single crystal ofCdMg (2.5 at %). In contrast to pure Cd no anisotropies in K_μ could be detected. The temperature dependence of K_μ in aCdMg (2.05 at %) sample and in the monocrystallineCdMg (2.5 at %) sample essentially reproduces the one previously observed in polycrystallineCdMg (3.38 at %), showing a steplike discontinuity and a logarithmic singularity. A complete different behaviour is observed inCdMg (1.04 at %), where no logarithmic singularity seems to show up and where a steplike discontinuity of opposite sign at around 90 K is clearly seen. If these singularities are still to be interpreted in terms of Van Hove singularities, the question arises why there is such a nonlinear dependence on the Mg concentration.     

UV degradability of polysilanes for nanoresists examined by electron spectroscopies and photoluminescence

The aim of this study was to elucidate the degradation mechanisms in polysilanes, especially one-dimensional polysilylenes, with respect to the search for suitable resists for silicon industrial nanotechnologies. To this end we used the combined methods of photoelectron spectroscopies — PES (UPS and XPS) and photoluminescence — PL. Films of aryl-methyl-substituted polysilane chain, poly[methyl(phenyl)silylene] (PMPSi), prepared by casting from benzene solution, were analysed by X-ray and UV-induced photoelectron spectroscopy. Photoelectron spectra were recorded from the pristine PMPSi surface and after the UV photodegradation. Pronounced changes were found in the HeI induced photoelectron spectra indicating redistribution of filled Si 3s-like and Si 3p-like states. The photodegradation by UV radiation for two different degradation wavelengths λ = 266 and 355 nm was examined also by PL. We concentrated on the PL study in the region of the σ*-σ excitonic deexcitation after major degradations, studying the disorder and dangling bonds (DB) created by the degradation process. The results of both complementary methods are interpreted in accordance with our recent paper [1], with the degradation process explained by two competing phenomena, i.e. the energy dependent exciton transport by diffusion process and Si-Si bond scission. Presented at the X-th Symposium on Suface Physics, Prague, Czech Republic, July 11–15, 2005.     

Transport coefficients of quasicrystals

The transport coefficients for the nine point groups —which represent the symmetry groups of the quasicrystals in two and three dimensions—have been evaluated and tabulated in this work, employing group-theoretical methods.     

Thermooxidative degradation of blends based on poly(3-Hydroxybutyrate). Specifics of the process

The relationship between the structure and the kinetics of the thermal oxidation of the poly(3-hydroxybutyrate) — ethylene propylene rubber and polyethylene — poly(3-hydroxybutyrate) systems is studied. For the first system containing 30–50 wt % poly(3-hydroxybutyrate), phase inversion is observed, which affects its reactivity. For the compositions with polyethylene, two stages of oxidation manifest themselves: before and after poly(3-hydroxybutyrate) degradation.     

New problems in general relativity

The problem of strong gravitational fields in classical (h = 0) general relativity is discussed. Strong fields require complex space—time topology; they require investigation by the methods of Riemann geometry as a whole over the complete atlas of mappings. Static solutions may not exist; dynamic oscillatory configurations of matter arise. A crucial spherically symmetric self-similar solution is described. The physical consequences are enumerated: there is no gravitational grave for matter and energy — there are no black holes; energy can emerge during and after gravitational collapse. The theoretical conclusions are confirmed by observations. A physical singularity of the infinite-density type arises in solutions with high symmetry. The crucial solution in flat space is continuable at spatial infinity through the singularity with conservation of the arrow of time; continuation through the singularity — the Big Bang — also occurs for cosmological models. Scientific Research Institute of Nuclear Physics, M. V. Lomonsov State University, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 3–12, March, 1998.     

Finite systems,fractional Fourier transforms and their finite phase spaces

Various harmonic oscillator models define — in a sense to be explained here — fractional Fourier transforms (up to a phase). The fractionalization of the Fourier integral transform is well understood; the finite case is less. There are several discrete and finite oscillator models that contract to the continuous, integral model. The Ankara model can be thought as a ring of point masses joined by springs to their equilibrium positions and to each other; the Cuernavaca model uses the su(2) algebra with a distinct physical interpretation. Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005.     

Parameters of the discharge plasmas of surface-plasma sources of negative hydrogen ions

The main parameters of the plasma of high-current hydrogen-cesium glow discharges of surface-plasma (planotron and Penning) sources of negative hydrogen ions are determined using contact-free spectroscopic methods and compared for identical discharge current densities. The elemental and charge composition of the plasma is established. The temperature of the hydrogen atoms and the energy of the visible-range radiation of the plasma discharge are measured and estimates of the electron density in the plasma are made. The dynamics of the change in the parameters of the discharge plasma of a Penning source — the densities of hydrogen atoms, cesium atoms and ions, and molybdenum atoms — is tracked during a discharge pulse with spatial resolution along two coordinates. It is observed that cesium atoms and ions and molybdenum atoms are pent up near the cathode surface. Zh. Tekh. Fiz. 68, 32–38 (October 1998)     

Interdiffusion of layers in PbSe-PbS epitaxial superlattices

X-ray diffraction methods are used to investigate the diffusional mixing of layers in PbSe-PbS superlattices. The interdiffusion coefficients of the layers are determined from the change in the intensity of satellite reflections. Two stages of diffusion are observed — fast (at the initial stages of anneals) and slow. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 9, 685–687 (10 November 1998)     

Investigation of the electronic structure of the SbSeBr cluster

The energy levels of valence bands (VB) in SbSeBr crystals were calculated for investigation of the photoelectron emission spectra of A⁵B⁶C⁷ — type crystals. The molecular model of this crystal was used for calculation of VB by the Density Functional Theory (DFT) and Unrestricted Hartree — Fock (UHF) methods. The molecular cluster consisting of 20 molecules of SbSeBr was used for calculations of averaged total density of states including atom vibrations. The spectra of averaged total density of states from VB in the SbSeBr cluster were compared with experimental photoelectron emission spectra from VB of A⁵B⁶C⁷ — type crystals. The results of comparison clarify that the atomic vibrations are one of possible reasons for the smoother appearance of the experimental X-ray photoelectron spectrum (XPS).      

Evolution of vacancy defects in the surface layers of a metal irradiated with a pulsed electron beam

The distribution of vacancy defects in the surface layers of α-Fe after irradiation with a high-current pulsed electron beam is studied experimentally by unique nuclear-physical methods — low-energy positron annihilation, Rutherford backscattering (RBS), and proton-induced x-ray emission (PIXE). Regions with low local density, which are sources of crater formation on the surface of the irradiated sample, are observed by scanning a proton microbeam. Positron lifetime measurements reveal that as the electron beam power increases, nonequilibrium vacancies tend to be captured by carbon impurity atoms. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 618–622 (25 April 1997)     

Structures of some surfactant—polyelectrolyte complexes

Structures of complexes formed in aqueous solutions by some anionic polyelectrolytes (double and single stranded (ds and ss) DNA, poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS)) with a cationic surfactant system consisting of cetyltrimethylammonium bromide (CTAB) and sodium 3-hydroxy-2-naphthoate (SHN) have been determined using small angle X-ray diffraction. All complexes are found to have a two-dimensional (2-D) hexagonal structure at low SHN concentrations. Analysis of the diffraction data shows that the ds DNA—CTAB complex has an intercalated structure, with each DNA strand surrounded by three cylindrical micelles. On increasing SHN concentration, DNA—CTAB—SHN complexes exhibit a hexagonal-to-lamellar transition, whereas PVS complexes show a hexagonal → centered rectangular → lamellar transition. PSS complexes show yet another sequence of structures. These results indicate the significant influence of the chemical nature of the polyelectrolyte on the structure of the complexes.     

Investigating the composition of periodic nano-size column structures of anodic titanium oxide by the method of IR spectroscopy

Periodic column structures of anodic tantalum oxide (ATO), formed by anodizing in different regimes a Ta—Al two-layer thin-film composition in an oxalic-acid solution as well as the films of dense anodic oxide and thermal tantalum oxide, are investigated by the methods of scanning electron microscopy and reflection IR spectroscopy. It is established that the ATO nano-size columns are composed of at least three known oxide phases from a Ta—O system: TaO, TaO₂ and Ta₂O₅. The structure of tantalum oxide compounds is amorphous with the near order (inclusions) of TaO₂ rutile, rhombic Ta₂O₅, and α- and β-modifications of tantalum pentoxide. The dense-ATO films are distinguished by a more disordered structure of the oxygen compounds of tantalum and an increased content of amorphous tantalum pentoxide. The thermal-ATO films have the most ordered structure of all the oxide phases that enter in their composition and increased relative contents of α- and β-Ta₂O₃. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 850–856, November–December, 1998.     

Polarization effects in Drell-Yan processes

Effects of polarization of hadrons and constituent quarks in Drell-Yan processes are considered; they are one of the most efficient tools for investigation of the quark structure of hadrons. Special attention is paid to such important parton distribution functions as the transversity and T-odd Sivers and Boer—Mulders functions whose study is necessary for understanding the effects connected with the nonzero transverse component of the quark momentum. An original method for direct extraction of transversity and Boer—Mulders function in the proton from the data on Drell—Yan processes, in which a maximum of one hadron in the initial state is transversely polarized, is presented. This method possesses a number of important advantages. The method is applied both to Drell—Yan processes with a valence antiquark (antiproton-proton and pion-proton collisions) and with a sea antiquark (proton-proton, proton-deuteron, and deuteron-deuteron collisions). Theoretical estimates of asymmetries and cross sections for setups at RHIC (BNL, US), NICA (JINR, Russia), COMPASS (CERN, Switzerland), PAX (GSI, Germany), and J-PARC (Japan) are presented for evaluation of the measurability of transversity and T-odd distributions. These theoretical estimates are accompanied by calculations of statistical uncertainties for measured asymmetries using the new Monte Carlo generator of Drell—Yan events. The duality of Drell—Yan processes and those of production of J/Φ resonance is studied, and it may allow one to considerably reduce statistical uncertainties of parton distributions. Kinematical conditions, for which this duality can be observed, are evaluated.