Electronic structure and magnetic properties of the spin-1/2 Heisenberg system CuSe2O5

A microscopic magnetic model for the spin-1/2 Heisenberg chain compound CuSe2O5 is developed based on the results of a joint experimental and theoretical study. Magnetic susceptibility and specific heat data give evidence for quasi-1D magnetism with leading antiferromagnetic (AFM) couplings and an AFM ordering temperature of 17 K. For microscopic insight, full-potential DFT calculations within the local density approximation (LDA) were performed. Using the resulting band structure, a consistent set of transfer integrals for an effective one-band tight-binding model was obtained. Electronic correlations were treated on a mean-field level starting from LDA (LSDA+U method) and on a model level (Hubbard model). In excellent agreement of experiment and theory, we find that only two couplings in CuSe2O5 are relevant: the nearest-neighbour intra-chain interaction of 165 K and a non-frustrated inter-chain coupling of 20 K. From a comparison with structurally related systems (Sr2Cu(PO4)2, Bi2CuO4), general implications for a magnetic ordering in presence of inter-chain frustration are made.Comment: 20 pages, 8 figures, 3 table

Biological resources of the Hyssopus l on the south of European Russia and prospects of its introduction

The south of European Russia (geographically - the southern part of the Central Russian Upland) has large biological and plant genetic resources. There is a concept considering the region as the second anthropogenic microgen center of formation of economically valuable plants. In the south of the Central Russian Upland, the genus Hyssopus L. is represented by two species: Hyssopus cretaceus Dubjan. and Hyssopus officinalis L. Accomplished the study of biological resources of species of the genus Hyssopus L. in vivo and in vitr

The crystal structure of fedotovite, K2Cu30(SO4) 3

Abstract The crystal structure of fcdotovite, K1CU30(S04h has been determined, space group C2/e, a 19.037(6), h 9.479(2), e 14.231(5) A,~1 11.04(3t, Z = 8, Dx = 3.09 g/cm3. The main units of the fedotovite structure are formed around two additional oxygen atoms and consist of edge-sharing [OCU4J tetrahedra and four [S04J tetrahedra attached to them. The units are further connected by two [S04J tetrahedra, building distinct layers parallel to the yz plane. These layers are interconnected by potassium atoms. In the fedotovite structure, the three kinds of copper atoms are fivefold (4 + 1) coordinated to oxygen atoms with a strong Jahn-Teller effect. The coordination polyhedra of Cui and Cu2 atoms are distorted and flattened orthorhombic pyramids with Cu-O distances varying from 1.912 to 2.333 A,. the sixth neighbour of the both atoms is the copper atom lying at 2.975 and 2.981 Afor Cu2 and Cui respectively. The coordination environment of the Cu3 atom is a distorted elongated orthorhombic pyramid with four Cu-O distances from 1.943 to 1.961 A, a fifth at 2.558 A, and further sixth and seventh neighbours (oxygen and copper atoms) at 2.809 and 2.806 A, respectively

Self - Consistent Description of e+e-gamma Plasma Created from the Vacuum in a Strong Electric Laser Field

In the present work a closed system of kinetic equations is obtained for the description of the vacuum creation of an electron - positron plasma and secondary photons due to a strong laser field. An estimate for the photon energy distribution is obtained. In the Markovian approximation the photon distribution has a 1/k spectrum (flicker noise).Comment: 6 pages, contribution to Proceedings of the International Bogolyubov Conference, Dubna (Russia), August 21-27, 200

AUTOIMMUNE ORIGIN OF SARCOIDOSIS: DETERMINATION OF SPECIFIC IMMUNE COMPLEXES IN PATIENTS WITH RESPIRATORY SARCOIDOSIS

The etiology of sarcoidosis is not completely understood. A hypothesis exists about the relationship between sarcoidosis and a complex of pathological autoimmune reactions that occur under the influence of triggering factors. In this study, specific immune complexes in the blood plasma of patients have been determined, which can indirectly reveal the causes of the disease.The study included 33 patients with lung sarcoidosis (I group), compared to 24 healthy donors who served as a control group (II group). The patients underwent standard examination. Their blood plasma was investigated by the dynamic light scattering method with addition of tuberculosis antigens (ESAT-6/SFP-10) and “lung healthy tissue extract”. Statistical analysis was performed using the Statistica 7.0 program. Test results were considered significant at p < 0.05.Аccording to the data obtained, addition of ESAT-6/SFP-10 to patient’s blood plasma almost did not lead to the formation of immune complexes in most samples. Meanwhile, development of such complexes after addition of “lung tissue extract” was revealed in all the patients. The immune complexes were not detected in any donor from control group after stimulation with both kinds of antigens (p < 0.01).The data on distinct formation of immune complexes with the addition of “lung healthy tissue extract” in patients with lung sarcoidosis may be considered an indirect evidence for occurrence of autoimmune reaction under the influence of some pathogenic factors. Absence of de novo immune complex formation after addition of tuberculosis antigens (ESAT-6/SFP-10) makes it unlikely any direct effects of tuberculosis bacteria upon development of sarcoidosis

W- rich mixed oxide solid solutions under pressure

We report high-pressure synchrotron X-ray powder diffraction data for the W-rich cubic ZrW[2-x]Mo[x]O[8] (x=0.4) up to 10 GPa with open decompression. This study shows that cubic- ZrW[1.6]Mo[0.4]O[8] transforms to orthorhombic phase at the 5.04 GPa. Pressure-induced reversable amorphization of material was observed at 8.13 GPa. The obtained data suggest that W-rich cubic ZrW[2-x]Mo[x]O[8] (x=0.4) solid solutions are more attractive for creating products working under extreme conditions and mechanic stress