Spherical Model in a Random Field

We investigate the properties of the Gibbs states and thermodynamic observables of the spherical model in a random field. We show that on the low-temperature critical line the magnetization of the model is not a self-averaging observable, but it self-averages conditionally. We also show that an arbitrarily weak homogeneous boundary field dominates over fluctuations of the random field once the model transits into a ferromagnetic phase. As a result, a homogeneous boundary field restores the conventional self-averaging of thermodynamic observables, like the magnetization and the susceptibility. We also investigate the effective field created at the sites of the lattice by the random field, and show that at the critical temperature of the spherical model the effective field undergoes a transition into a phase with long-range correlations $\sim r^{4-d}$.Comment: 29 page

Structural effects in UO2 thin films irradiated with fission-energy Xe ions

Uranium dioxide thin films have been successfully grown on LSAT (Al10La3O51Sr14Ta7) substrates by reactive magnetron sputtering. Irradiation by 92 MeV 129Xe23+ ions to simulate fission damage that occurs within nuclear fuels caused microstructural and crystallographic changes. Initially flat and continuous thin films were produced by magnetron sputtering with a root mean square roughness of 0.35 nm determined by AFM. After irradiation, this roughness increased to 60–70 nm, with the films developing discrete microstructural features: small grains (∼3 μm), along with larger circular (up to 40 μm) and linear formations with non-uniform composition according to the SEM, AFM and EDX results. The irradiation caused significant restructuring of the UO2 films that was manifested in significant film-substrate mixing, observed through EDX analysis. Diffusion of Al from the substrate into the film in unirradiated samples was also observed

Spectroscopic study of impurities and associated defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) meteorites

The results of spectroscopic and structural studies of phase composition and of defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) chondrites indicate that nitrogen atomic environment in meteoritic nanodiamonds (MND) is similar to that observed in synthetic counterparts produced by detonation and by the Chemical Vapour Deposition (CVD)-process. Most of the nitrogen in MND appears to be confined to lattice imperfections, such as crystallite/twin boundaries and other extended defects, while the concentration of nitrogen in the MND lattice is low. It is suggested that the N-rich sub-population of MND grains may have been formed with high growth rates in environments rich in accessible N (i.e., N in atomic form or as weakly bonded compounds). For the first time the silicon-vacancy complex (the "silicon" defect) is observed in MND by photoluminescence spectroscopy.Comment: 33 pages, 5 figures, submitted to Geochimica et Cosmochimica Act

Interplay of structural and electronic phase separation in single crystalline La(2)CuO(4.05) studied by neutron and Raman scattering

We report a neutron and Raman scattering study of a single-crystal of La(2)CuO(4.05) prepared by high temperature electrochemical oxidation. Elastic neutron scattering measurements show the presence of two phases, corresponding to the two edges of the first miscibility gap, all the way up to 300 K. An additional oxygen redistribution, driven by electronic energies, is identified at 250 K in Raman scattering (RS) experiments by the simultaneous onset of two-phonon and two-magnon scattering, which are fingerprints of the insulating phase. Elastic neutron scattering measurements show directly an antiferromagnetic ordering below a N\'eel temperature of T_N =210K. The opening of the superconducting gap manifests itself as a redistribution of electronic Raman scattering below the superconducting transition temperature, T_c = 24K. A pronounced temperature-dependent suppression of the intensity of the (100) magnetic Bragg peak has been detected below T_c. We ascribe this phenomenon to a change of relative volume fraction of superconducting and antiferromagnetic phases with decreasing temperature caused by a form of a superconducting proximity effect.Comment: 9 pages, including 9 eps figures, submitted to PR

Опыт сотрудничества России и Вьетнама в сфере образования во второй половине XX - начале XXI вв

The main aspects of cooperation between Russia and Vietnam in the field of education are considered. The relevance of the topic is due to the fact that in conditions of scientific and technological progress and the emergence of new technologies, education becomes strategically important. The purpose of the article is to investigate the most important aspects of the development of cooperation between Russia and Vietnam in the field of education; to study the basic tendencies in the given sphere; determine the prospects for the development of this area of study. The authors conclude that Russia and Vietnam pursue a joint policy of attracting Russian and Vietnamese students to higher educational institutions, create favorable conditions for students to stay both within the countries themselves and within the universities.Рассмотрены основные аспекты сотрудничества России и Вьетнама в области образования. Актуальность темы обусловлена тем, что в условиях научно-технического прогресса и появления новых технологий, образование приобретает стратегически важное значение. Цель статьи - исследовать важнейшие аспекты развития сотрудничества России и Вьетнама в области образования; изучить основные тенденции в данной сфере; определить перспективы развития данной области изучения. Авторы приходят к выводу, что Россия и Вьетнам проводят совместную политику привлечения российских и вьетнамских студентов в высшие учебные заведения, создают благоприятные условия пребывания студентов как внутри самих стран, так и в рамках вузов

Опыт сотрудничества России и Вьетнама в сфере образования во второй половине XX - начале XXI вв

The main aspects of cooperation between Russia and Vietnam in the field of education are considered. The relevance of the topic is due to the fact that in conditions of scientific and technological progress and the emergence of new technologies, education becomes strategically important. The purpose of the article is to investigate the most important aspects of the development of cooperation between Russia and Vietnam in the field of education; to study the basic tendencies in the given sphere; determine the prospects for the development of this area of study. The authors conclude that Russia and Vietnam pursue a joint policy of attracting Russian and Vietnamese students to higher educational institutions, create favorable conditions for students to stay both within the countries themselves and within the universities.Рассмотрены основные аспекты сотрудничества России и Вьетнама в области образования. Актуальность темы обусловлена тем, что в условиях научно-технического прогресса и появления новых технологий, образование приобретает стратегически важное значение. Цель статьи - исследовать важнейшие аспекты развития сотрудничества России и Вьетнама в области образования; изучить основные тенденции в данной сфере; определить перспективы развития данной области изучения. Авторы приходят к выводу, что Россия и Вьетнам проводят совместную политику привлечения российских и вьетнамских студентов в высшие учебные заведения, создают благоприятные условия пребывания студентов как внутри самих стран, так и в рамках вузов

Isotopic heterogeneity in synthetic and natural silicon carbide

The distribution of both carbon and silicon isotopes in synthetic sublimation growth SiC wafers and in natural SiC grains was studied using secondary ion mass-spectrometry (SIMS). Significant variations in both isotopic ratios were observed which were broadly correlated with the crystalline perfection as documented by Raman microspectroscopy. Domains consisting of 15R (or with its admixture) are, on average, enriched in 12C isotope relative to 6H domains, and they also show larger scatter in their observed silicon isotope ratios. We ascribe such heterogeneity to fluctuations of Si/C ratio in the growth medium and it is possible to model the spatial extent of such fluctuations. For the natural SiC grains the isotopic data suggest that they grew under relatively stable conditions, although some of them show significant isotopic zoning.Original publication: A.A. Shiryaev, M. Wiedenbeck, V. Reutsky, V.B. Polyakov, N.N. Mel’nik, A.A. Lebedev and R. Yakimova, Isotopic heterogeneity in synthetic and natural silicon carbide, 2008, Journal of Physics and Chemistry of Solids, (69), 10, 2492-2498.http://dx.doi.org/10.1016/j.jpcs.2008.05.005. Copyright: Elsevier B.V., http://www.elsevier.com