160 research outputs found
Two-Phase Region of the Vortex-Solid Melting Transition: 3D XY Theory
In clean enough samples of the high- oxide materials, the phase
transition into the superconducting state occurs along a first order line in
the - plane. This means that a two-phase region occurs in the B-
plane, in which the liquid and solid vortex phases coexist. We discuss the
thermodynamics of this two-phase region, developing formulae relating
experimental quantities of interest. We then apply the 3D XY scaling theory to
the problem, obtaining detailed predictions for the boundaries of the
coexistence region. By using published data, we are able to predict the width
of the two-phase region, and determine the physical parameters involved in the
3D XY description.Comment: 5 pages LaTeX, 1 .eps figure, uses epsf.st
Repression of DNA-binding dependent glucocorticoid receptor-mediated gene expression
The glucocorticoid receptor (GR) affects the transcription of genes involved in diverse processes, including energy metabolism and the immune response, through DNA-binding dependent and independent mechanisms. The DNA-binding dependent mechanism occurs by direct binding of GR to glucocorticoid response elements (GREs) at regulatory regions of target genes. The DNA-binding independent mechanism involves binding of GR to transcription factors and coactivators that, in turn, contact DNA. A small molecule that competes with GR for binding to GREs could be expected to affect the DNA-dependent pathway selectively by interfering with the protein-DNA interface. We show that a DNA-binding polyamide that targets the consensus GRE sequence binds the glucocorticoid-induced zipper (GILZ) GRE, inhibits expression of GILZ and several other known GR target genes, and reduces GR occupancy at the GILZ promoter. Genome-wide expression analysis of the effects of this polyamide on a set of glucocorticoid-induced and -repressed genes could help to elucidate the mechanism of GR regulation for these genes
Critical velocity and event horizon in pair-correlated systems with "relativistic" fermionic quasiparticles
The condition for the appearance of event horizon is considered in such
pair-correlated systems (superfluids and superconductors) where the fermionic
quasiparticles obey the "relativistic" equations. In these systems, the Landau
critical velocity of superflow corresponds to the speed of light. In
conventional systems, such as s-wave superconductors, the superflow remains
stable even above the Landau treshold. We showed that in the "relativistic"
systems however the quantum vacuum becomes unstable and the superflow collapses
after the "speed of light" is reached, so that horizon cannot appear. Thus an
equilibrium dissipationless superfluid flow state and the horizon are
incompatible due to quantum effects. This negative result is consistent with
the quantum Hawking radiation from the horizon, which would lead to the
dissipation of the flow.Comment: RevTex file, 4 pages, 1 Figur
Quantitative microarray profiling of DNA-binding molecules
A high-throughput Cognate Site Identity (CSI) microarray platform interrogating all 524 800 10-base pair variable sites is correlated to quantitative DNase I footprinting data of DNA binding pyrrole-imidazole polyamides. An eight-ring hairpin polyamide programmed to target the 5 bp sequence 5'-TACGT-3' within the hypoxia response element (HRE) yielded a CSI microarray-derived sequence motif of 5'-WWACGT-3' (W = A,T). A linear beta-linked polyamide programmed to target a (GAA)_3 repeat yielded a CSI microarray-derived sequence motif of 5'-AARAARWWG-3' (R = G,A). Quantitative DNase I footprinting of selected sequences from each microarray experiment enabled quantitative prediction of K_a values across the microarray intensity spectrum
Expanding the Repertoire of Natural Product-Inspired Ring Pairs for Molecular Recognition of DNA
A furan amino acid, inspired by the recently discovered proximicin natural products, was incorporated into the scaffold of a DNA-binding hairpin polyamide. While unpaired oligomers of 2,4-disubstituted furan amino acids show poor DNA-binding activity, furan (Fn) carboxamides paired with N-methylpyrrole (Py) and N-methylimidazole (Im) rings demonstrate excellent stabilization of duplex DNA as well as discrimination of noncognate sequences, consistent with function as a Py mimic according to the Py/Im polyamide pairing rules
Generalized Statistics and High Tc Superconductivity
Introducing the generalized, non-extensive statistics proposed by
Tsallis[1988], into the standard s-wave pairing BCS theory of superconductivity
in 2D yields a reasonable description of many of the main properties of high
temperature superconductors, provided some allowance is made for non-phonon
mediated interactions.Comment: 14 pages, 5 figure
Effects of Magnetic Order on the Upper Critical Field of UPt
I present a Ginzburg-Landau theory for hexagonal oscillations of the upper
critical field of UPt near . The model is based on a
representation for the superconducting order parameter,
, coupled to an in-plane AFM order parameter,
. Hexagonal anisotropy of arises from the weak in-plane
anisotropy energy of the AFM state and the coupling of the superconducting
order parameter to the staggered field. The model explains the important
features of the observed hexagonal anisotropy [N. Keller, {\it et al.}, Phys.
Rev. Lett. {\bf 73}, 2364 (1994).] including: (i) the small magnitude, (ii)
persistence of the oscillations for , and (iii) the change in
sign of the oscillations for and (the temperature at the
tetracritical point). I also show that there is a low-field crossover
(observable only very near ) below which the oscillations should vanish.Comment: 9 pages in a RevTex (3.0) file plus 2 postscript figures (uuencoded).
Submitted to Physical Review B (December 20, 1994)
Singularity of the Vortex Density of States in d-wave Superconductors
In d-wave superconductors, the electronic density of states (DOS) induced by
a vortex exhibits 1/|E| divergency at low energies. It is the result of gap
nodes in the excitations spectrum outside the vortex core. The heat capacity in
two regimes, (T/T_c)^2 >> B/B_{c2} and (T/T_c)^2 << B/B_{c2}, is discussed.Comment: LaTeX file, 8 pages, no figures, submitted to JETP Letter
Toroidal Magnetic Fields in Type II Superconducting Neutron Stars
We determine constraints on the form of axisymmetric toroidal magnetic fields
dictated by hydrostatic balance in a type II superconducting neutron star with
a barotropic equation of state. Using Lagrangian perturbation theory, we find
the quadrupolar distortions due to such fields for various models of neutron
stars with type II superconducting and normal regions. We find that the star
becomes prolate and can be sufficiently distorted to display precession with a
period of the order of years. We also study the stability of such fields using
an energy principle, which allows us to extend the stability criteria
established by R. J. Tayler for normal conductors to more general media with
magnetic free energy that depends on density and magnetic induction, such as
type II superconductors. We also derive the growth rate and instability
conditions for a specific instability of type II superconductors, first
discussed by P. Muzikar, C. J. Pethick and P. H. Roberts, using a local
analysis based on perturbations around a uniform background.Comment: 32 pages, 6 figures; derivations shortened, comments and references
added; accepted for publication in MNRA
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