21 research outputs found
Global Phase Diagram of nu = 2 Quantum Hall Bilayers in Tilted Magnetic Field
We consider a bilayer quantum Hall system at total filling fraction nu=2 in
tilted magnetic field allowing for charge imbalance as well as tunneling
between the two layers. Using an "unrestricted Hartree Fock," previously
discussed by Burkov and MacDonald (Phys Rev B 66 115323 2002), we examine the
zero temperature global phase diagrams that would be accessed experimentally by
changing the in-plane field and the bias voltage between the layers while
keeping the tunneling between the two layers fixed. In accordance with previous
work, we find symmetric and ferromagnetic phases as well as a first order
transition between two canted phases with spontaneously broken U(1) symmetry.
We find that these two canted phases are topologically connected in the phase
diagram and, reminiscent of a first order liquid-gas transition, the first
order transition line between these two phases ends in a quantum critical
point. We develop a physical picture of these two phases and describe in detail
the physics of the transition
Quantum Hall Smectics, Sliding Symmetry and the Renormalization Group
In this paper we discuss the implication of the existence of a sliding
symmetry, equivalent to the absence of a shear modulus, on the low-energy
theory of the quantum hall smectic (QHS) state. We show, through
renormalization group calculations, that such a symmetry causes the naive
continuum approximation in the direction perpendicular to the stripes to break
down through infrared divergent contributions originating from naively
irrelevant operators. In particular, we show that the correct fixed point has
the form of an array of sliding Luttinger liquids which is free from
superficially "irrelevant operators". Similar considerations apply to all
theories with sliding symmetries.Comment: 7 pages, 3 figure
TUMOR NECROSIS FACTOR-α MEMBRANE-BOUND AND SOLUBLE RECEPTORS IN NORM AND IN RHEUMATOID ARTHRITIS
TNFα — a multifunctional pleiotropic cytokine, considered to have a special significance in the immunopathogenesis of rheumatoid arthritis. Herewith the effectiveness of immunomodulatory cytokine and its role in the development of pathological states of the organism may depend largely on the content of soluble receptors and expression of membrane-bound receptors. The study shows several significant differences not only in the percentage of cells with. TNFα receptors, but also in the absolute number of receptors expressed on cells from different subsets of immunocompetent cells in health and in rheumatoid arthritis, establishes correlation relationships of these parameters with serum contents of the cytokine and its soluble receptors. The mechanisms and the role of changes in the expression of TNFα receptors in different subsets of leukocytes in immunopathological state and in compare with healthy donors are discussed
Strongly Asymmetric Tricriticality of Quenched Random-Field Systems
In view of the recently seen dramatic effect of quenched random bonds on
tricritical systems, we have conducted a renormalization-group study on the
effect of quenched random fields on the tricritical phase diagram of the spin-1
Ising model in . We find that random fields convert first-order phase
transitions into second-order, in fact more effectively than random bonds. The
coexistence region is extremely flat, attesting to an unusually small
tricritical exponent ; moreover, an extreme asymmetry of the phase
diagram is very striking. To accomodate this asymmetry, the second-order
boundary exhibits reentrance.Comment: revtex, 4 pages, 2 figs, submitted to PR
TNF, SOLUBLE RECEPTORS AND AUTOANTIBODIES TO TNF OF PATIENTS WITH RHEUMATOID ARTHRITIS AND HEALTHY DONORS
The content of autoantibodies to TNF in the sera of patients with rheumatoid arthritis (RA) in conjunction with the definition of soluble receptors and TNF was investigated. A significant increase in the content of TNF and I and II types soluble receptors to TNF in sera of RA patients in the acute stage and of responding to therapy RA patients compared with relatively healthy donors was demonstrated. In determining autoantibodies subclasses a significant increase in the relative content of subclasses IgG2, IgG3 and IgG4 autoantibodies in sera of RA patients in the acute stage compared with relatively healthy donors, as well as a significant increase in the relative content of subclasses IgG2 and IgG4 autoantibodies in RA patients in the acute stage compared with RA patients, responding to therapy were shown. Thus we have shown the presence of antibodies, soluble receptors to TNF and cytokine in the serum of relatively healthy donors and RA patients, herewith taking into account significant changes in the relative content of the subclasses of autoantibodies and in the content of TNF and soluble receptors we can talk about the functional role of the autoantibodies and soluble receptors to TNF in the pathology
Association of Single Nucleotide Polymorphisms in the IL-18 Gene with Production of IL-18 Protein by Mononuclear Cells from Healthy Donors
IL-18 has proinflammatory effects and participates in both innate and adaptive cellular and humoral immunity. A number of SNPs that influence IL-18 production are found in the gene promoter region. We investigated the association of SNPs in the IL-18 promoter at −607 and −137 with the level of IL-18 protein production by PBMC from healthy donors from Southwestern Siberia. The genetic distribution of these SNPs in the promoter site was established by PCR. IL-18 protein production was determined by ELISA. Our results showed that PBMC from donors carrying allele 137C have lower levels of both spontaneous and LPS-stimulated IL-18 production. In contrast, PBMC from donors carrying allele 607A showed significant increases in spontaneous and stimulated IL-18 production compared to wild type. Our study suggests that the SNPs −607 and −137 in the promoter region of the IL-18 gene influence the level of IL-18 protein production by PBMC from healthy donors in Southwestern Siberia
Effects of Pore Walls and Randomness on Phase Transitions in Porous Media
We study spin models within the mean field approximation to elucidate the
topology of the phase diagrams of systems modeling the liquid-vapor transition
and the separation of He--He mixtures in periodic porous media. These
topologies are found to be identical to those of the corresponding random field
and random anisotropy spin systems with a bimodal distribution of the
randomness. Our results suggest that the presence of walls (periodic or
otherwise) are a key factor determining the nature of the phase diagram in
porous media.Comment: REVTeX, 11 eps figures, to appear in Phys. Rev.
Effect of different types of immunosuppressive therapy on the parameters of TNF receptor expression in patients with rheumatoid arthritis
Background. The balance of TNF receptor expression on immune cells is a key factor determining cytokine-induced activation of proapoptotic or proliferative signaling pathways. As a result, the changes in cytokine level and in expression of its receptors may be one of the mechanisms that regulate the level of systemic and local inflammation in rheumatoid arthritis (RA) and determine the degree of therapy effectiveness. The aim. To study the effect of rheumatoid arthritis therapy on the change in the patterns of TNF receptors expression in terms of co-expression and the number of receptors on the main subpopulations of immunocompetent cells.Materials and methods. A comparative analysis of the profiles of TNF receptors type 1 and 2 (TNFR1/2) co-expression was carried out in patients with RA (n = 16) before and after having inpatient effective therapy and in comparison with a group of healthy individuals (n = 21). We compared the number of receptors and the proportion of cells expressing the corresponding receptor using flow cytometry and studied the subpopulations of regulatory T cells, T cells, B cells, and monocytes. Results. In patients with RA, there is a significant redistribution of TNFR1 and TNFR2 expression on immunocompetent cells, while the intensity of changes is associated not only with disease severity indicators, but also with the therapy received. The key adaptive mechanism of the TNF system in long-term treatment refractory course of RA is a change in the proportion of double-positive TNFR1+TNFR2+ cells, while the effectiveness of therapy and clinical indicators of the disease severity are associated with individual variability in the parameters of type 2 receptors expression. Conclusions. The data obtained confirm the existence of a relationship between an imbalance in the expression of type 1 and type 2 TNF receptors on immunocompetent cells and the effectiveness of response to therapy. The identified patterns of typical changes in TNFR1/2 co-expression in RA can be used as potential therapeutic targets and predictive factors for the effectiveness of therapy
Mean-field Phase Diagram of Two-Dimensional Electrons with Disorder in a Weak Magnetic Field
We study two-dimensional interacting electrons in a weak perpendicular
magnetic field with the filling factor and in the presence of a
quenched disorder. In the framework of the Hartree-Fock approximation, we
obtain the mean-field phase diagram for the partially filled highest Landau
level. We find that the CDW state can exist if the Landau level broadening
does not exceed the critical value .
Our analysis of weak crystallization corrections to the mean-field results
shows that these corrections are of the order of and
therefore can be neglected
Interacting Electrons on a Fluctuating String
We consider the problem of interacting electrons constrained to move on a
fluctuating one-dimensional string. An effective low-energy theory for the
electrons is derived by integrating out the string degrees of freedom to lowest
order in the inverse of the string tension and mass density, which are assumed
to be large. We obtain expressions for the tunneling density of states, the
spectral function and the optical conductivity of the system. Possible
connections with the phenomenology of the cuprate high temperature
superconductors are discussed.Comment: 14 pages, 1 figur