Exchange interaction and its tuning in magnetic binary chalcogenides

Using a first-principles Green's function approach we study magnetic properties of the magnetic binary chalcogenides Bi2Te3, Bi2Se3, and Sb2Te3. The magnetic coupling between transition-metal impurities is long-range, extends beyond a quintuple layer, and decreases with increasing number of d electrons per 3d atom. We find two main mechanisms for the magnetic interaction in these materials: the indirect exchange interaction mediated by free carriers and the indirect interaction between magnetic moments via chalcogen atoms. The calculated Curie temperatures of these systems are in good agreement with available experimental data. Our results provide deep insight into magnetic interactions in magnetic binary chalcogenides and open a way to design new materials for promising applications

Silicon surface with giant spin-splitting

We demonstrate the induction of a giant Rashba-type spin-splitting on a semiconducting substrate by means of a Bi trimer adlayer on a Si(111) wafer. The in-plane inversion symmetry is broken so that the in-plane potential gradient induces a giant spin-splitting with a Rashba energy of about 140 meV, which is more than an order of magnitude larger than what has previously been reported for any semiconductor heterostructure. The separation of the electronic states is larger than their lifetime broadening, which has been directly observed with angular resolved photoemission spectroscopy. The experimental results are confirmed by relativistic first-principles calculations. We envision important implications for basic phenomena as well as for the semiconductor based technology

Temperature dependent magnetic anisotropy in metallic magnets from an ab-initio electronic structure theory: L1_0-ordered FePt

On the basis of a first-principles, relativistic electronic structure theory of finite temperature metallic magnetism, we investigate the variation of magnetic anisotropy, K, with magnetisation, M, in metallic ferromagnets. We apply the theory to the high magnetic anisotropy material, L1_0-ordered FePt, and find its uniaxial K consistent with a magnetic easy axis perpendicular to the Fe/Pt layering for all M and to be proportional to M^2 for a broad range of values of M. For small M, near the Curie temperature, the calculations pick out the easy axis for the onset of magnetic order. Our results are in good agreement with recent experimental measurements on this important magnetic material.Comment: 4 pages, 2 figure

Tight-binding study of high-pressure phase transitions in titanium: alpha to omega and beyond

We use a tight-binding total energy method, with parameters determined from a fit to first-principles calculations, to examine the newly discovered gamma phase of titanium. Our parameters were adjusted to accurately describe the alpha Ti-omega Ti phase transition, which is misplaced by density functional calculations. We find a transition from omega Ti to gamma Ti at 102 GPa, in good agreement with the experimental value of 116 GPa. Our results suggest that current density functional calculations will not reproduce the omega Ti-gamma Ti phase transition, but will instead predict a transition from omega Ti to the bcc beta Ti phase.Comment: 3 encapsulated Postscript figures, submitted to Phyical Review Letter

IMMUNE PREDICTORS OF FIBROGENESIS AND THEIR APPLICATION FOR NON-INVASIVE DIAGNOSTICS OF LIVER FIBROSIS IN PATIENTS WITH CHRONIC VIRAL HEPATITIS

The study was devoted to development of non-invasive methods for diagnosis of liver fibrosis in patients with chronic viral hepatitis (CVH). The stepwise logistic multivariate regression analysis of biochemical (PTI, glucose, albumin, AST, LDH) and immunological parameters (the functional activity of neutrophils and monocytes, the relative content of CD8+ T- and CD19+B-cells) was used for the establishment of diagnostic model. Based on the multiple regression analysis we derived a 2 novel Integral Indexes of Liver Fibrosis (IILF-biochem and IILF-immun, respectively). It is shown that IILF-biochem allows, without resorting to liver biopsy to predict the appropriate stage of fibrosis in CHV patients with diagnostic accuracy of 86—87 %, and in combination with IILF — at 97.7 %

Effect of soluble factors of macrophages polarized by efferocytosis on neuronal density in the frontal cortex and hippocampus of mice in a model of stress-induced depression

Recently, there has been a steady increase in depressive disorders, which occupy an important place in the structure of the causes of disability. In the pathogenesis of depression, an important role is played by neuroinflammation, which is associated with impaired adult neurogenesis. Notably, neuroinflammation is partially reversible, and the leading role in the initiation and regulation of neuroregeneration is given to macrophages. Opposite states of macrophage activation are classically activated M1 and alternatively activated M2 macrophages, characterized, respectively, by pro- and anti-inflammatory activity. A balance shift towards M2 macrophages has been considered as a new therapeutic strategy of psycho-neurological disorders. One of the inducers of the M2 phenotype is the efferocytosis. We have previously developed an original protocol for the generation of human macrophages under conditions of deficiency of growth / serum factors, in which M2 phenotype is formed through efferocytosis. Macrophages (M2(LS), LS – Low Serum) obtained according to this protocol express M2-associated markers, and are characterized by high production of growth and pro- angiogenic factors (IGF-1, VEGF, BDNF, EGF, FGF-basic, etc.), which can suppress inflammation and stimulate neuroregeneration / neuroplasticity. In the model of stress-induced depression, the antidepressant effect of soluble factors of M2(LS) macrophages was shown, accompanied by a decrease in the level of pro- inflammatory cytokines in certain brain structures. However, the effect of M2(LS) factors on neurogenesis remained unexplored. In the present work, which is a continuation of the aforementioned study, we analyzed the effect of intranasal administration of M2(LS) soluble factors on neuronal density in different brain areas – the frontal cortex and hippocampus – of depression-like mice. The results obtained showed that neuronal density in the frontal cortex, CA1 and CA3 zones of the hippocampus, was significantly higher in mice with intranasal administration of M2(LS) conditioned medium than in depression-like mice, and reached the level of neuronal density in intact animals. These results may indicate the neuroregenerative activity of M2(LS) macrophages in the model of stress-induced depression, which is mediated through soluble factors and manifests itself in an increase in the density of neurons in the brain

CYTOTOXIC ACTIVITY OF DENDRITIC CELLS AGAINST ACTIVATED CD4+ AND CD8+T-LYMPHOCYTES IN THE CULTURE IN VITRO

The aim of the present study was a comparative assessment of the cytotoxic activity of IFNα-induced dendritic cells (IFN-DCs) and IL-4-induced DCs (IL4-DCs) against allo-MLC- activated CD4+ and CD8+T-lymphocytes. It was shown the level of AnnexinV+/PI- cells corresponding to early apoptosis among CD4+T-lymphocytes was lower in cultures with IFN-DCs compared with IL4-DCs. At the same time the relative number of AnnexinV+/ PI+ cells (late phase of apoptosis/necrosis) among CD4+T-lymphocytes activated by allogenic IFN-DCs and IL4-DCs increased in an equal degree. It was demonstrated that IFN-DCs possesed similar ability to induce apoptosis of CD3+CD8+T-lymphocytes

INTERLEUKIN-10 REGULATES PD-1-B7-H1-MEDIATED CYTOTOXIC ACTIVITY OF DENDRITIC CELLS

In this investigation the phenotypic and functional properties of healthy donor and patient with pulmonary tuberculosis (PT) dendritic cells (DCs) were characterized. We also studied the influence of IL-10 on the phenotype and apoptosis-inducing activity of healthy donor DCs. 60 patients with pulmonary tuberculosis with different proliferative response to antigens of M. tuberculosis (purified protein derivative, PPD) and 40 healthy donors were enrolled in this study. It was revealed that DCs, generated in vitro from PT patient's blood monocytes with GM-CSF+IFN-α, were characterized by increased B7-H1 expression, up-production of IL-10 and reducing of allostimulatory activity in mixed lymphocyte culture (MLC). The endogenous IL-10 production by DCs was correlated with expression of B7-H1 in the general group of persons. It was revealed that addition of IL-10 to semi-mature DCs of healthy donor results in increasing of B7-H1 expression, diminishing of allostimulatory activity and enlargement of pro-apoptogenic activity of DCs

VASCULAR ENDOTHELIAL GROWTH FACTOR RECEPTOR-1 SIGNALING AS A NOVEL MECHANISM OF T CELL SUPPRESSION IN TUMOR NEOANGIOGENESIS

The immunomodulatory activity of vascular endothelial growth factors (VEGFs) reveals a new role of neoangiogenesis in tumor development. Most of VEGF effects on T cells are mediated through the VEGF-R2 receptors. Placental growth factor (PlGF) belongs to the VEGFs family and is a selective ligand for VEGF-R1. In order to study the role of VEGF-R1-signaling in the regulation of T-cell functions, the effect of PlGF on the proliferation of donor T cell has been investigated. PlGF has been shown to inhibit the proliferation of T-lymphocytes in cultures of anti-CD3-stimulated mononuclear cells in a wide dose range, suppressing the proliferative response of both CD4 + and CD8 + T cells. The suppressive effect of PlGF was mediated through the direct interaction with VEGFR-1 on T-cells that was evidenced by the expression of VEGFR-1 by T-lymphocytes (especially after their activation) and by blocking the suppressive effect of PlGF with neutralizing anti-VEGFR-1 antibodies. Given the increased levels of PlGF in many tumors, this factor may play an important role in immunomodulation during tumor growth, mediating its effect through the VEGFR-1 signaling pathway