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

Global phase diagram of = 2 quantum Hall bilayers in tilted magnetic fields

We consider a bilayer quantum Hall system at total filling fraction n=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.Physic

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 $d=3$. 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 $\beta_u$; 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

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

Collective modes of = 2 quantum Hall bilayers in tilted magnetic fields

We use the time-dependent Hartree Fock approximation to study the collective-mode spectra of n=2 quantum Hall bilayers in tilted magnetic fields, allowing for charge imbalance as well as tunneling between the two layers. In a previous companion paper to this work, we studied the zero-temperature global phase diagram of this system, which was found to include symmetric and ferromagnetic phases as well as a first-order transition between two canted phases with spontaneously broken U(1) symmetry. We further found that this first-order transition line ends in a quantum critical point within the canted region. In the current work, we study the excitation spectra of all of these phases and pay particular attention to the behavior of the collective modes near the phase transitions. We find, most interestingly, that the first-order transition between the two canted phases is signaled by a near softening of a magnetoroton minimum. Many of the collective-mode features explored here should be accessible experimentally in light-scattering experiments.Physic

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$^3$--He$^4$ 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.

EXPRESSION DENSITY OF RECEPTORS FOR IMMUNOREGULATORY MEDIATORS AS A MODULATORY COMPONENT OF BIOLOGICAL EFFECTS OF MEDIATORS UPON CELLS (PART 2)

The present review article summarizes the latest world scientific data on the role of receptors for immune mediators in regulating biological effects on the cells. For the main classes of immune regulators (interleukins, interferons, growth factors and tumor necrosis factors), the variants are presented for participation of receptors as components of cytokine/cell interaction, as proven by in vitro and in vivo studies. Ability of the receptors expression to modify characteristics and type of these interactions is shown. The data on participation of receptors for regulatory molecules in development of immune-mediated diseases of various genesis have been analyzed. It was demonstrated that the changes in the receptor expression are of great importance when evaluating functional response of the cells to the mediators and in development of pathological conditions. Current studies confirmed the data suggesting effects of receptor density upon the processes of proliferation and apoptosis, as well as metabolic processes that trigger development of autoimmune, oncological and dystrophic diseases. For all the considered classes of regulatory molecules, the change in the density of receptor expression is one of the key aspects in regulating functional activity of the cells. Thus, studying expression levels of receptors on the cell membrane is important in understanding pathogenesis, whereas changing expression level may be considered as a therapeutic target in the treatment of various diseases