8,484 research outputs found
The Influence of Quantum Critical Fluctuations of Circulating Current Order Parameters on the Normal State Properties of Cuprates
We study a model of the quantum critical point of cuprates associated with
the "circulating current" order parameter proposed by Varma. An effective
action of the order parameter in the quantum disordered phase is derived using
functional integral method, and the physical properties of the normal state are
studied based on the action. The results derived within the ladder
approximation indicate that the system is like Fermi liquid near the quantum
critical point and in disordered regime up to minor corrections. This implies
that the suggested marginal Fermi liquid behavior induced by the circulating
current fluctuations will come in from beyond the ladder diagrams.Comment: 7pages, 1 figure included in RevTex file. To appear in Phys. Rev.
A second-order closure analysis of turbulent diffusion flames
A complete second-order closure computer program for the investigation of compressible, turbulent, reacting shear layers was developed. The equations for the means and the second order correlations were derived from the time-averaged Navier-Stokes equations and contain third order and higher order correlations, which have to be modeled in terms of the lower-order correlations to close the system of equations. In addition to fluid mechanical turbulence models and parameters used in previous studies of a variety of incompressible and compressible shear flows, a number of additional scalar correlations were modeled for chemically reacting flows, and a typical eddy model developed for the joint probability density function for all the scalars. The program which is capable of handling multi-species, multistep chemical reactions, was used to calculate nonreacting and reacting flows in a hydrogen-air diffusion flame
Developmental Lead and/or Prenatal Stress Exposures Followed by Different Types of Behavioral Experience Result in the Divergence of Brain Epigenetic Profiles in a Sex, Brain Region, and Time-Dependent Manner: Implications for Neurotoxicology.
Over a lifetime, early developmental exposures to neurocognitive risk factors, such as lead (Pb) exposures and prenatal stress (PS), will be followed by multiple varied behavioral experiences. Pb, PS and behavioral experience can each influence brain epigenetic profiles. Our recent studies show a greater level of complexity, however, as all three factors interact within each sex to generate differential adult variation in global post-translational histone modifications (PTHMs), which may result in fundamentally different consequences for life-long learning and behavioral function. We have reported that PTHM profiles differ by sex, brain region and time point of measurement following developmental exposures to Pb±PS, resulting in different profiles for each unique combination of these parameters. Imposing differing behavioral experience following developmental Pb±PS results in additional divergence of PTHM profiles, again in a sex, brain region and time-dependent manner, further increasing complexity. Such findings underscore the need to link highly localized and variable epigenetic changes along single genes to the highly-integrated brain functional connectome that is ultimately responsible for governing behavioral function. Here we advance the idea that increased understanding may be achieved through iterative reductionist and holistic approaches. Implications for experimental design of animal studies of developmental exposures to neurotoxicants include the necessity of a \u27no behavioral experience\u27 group, given that epigenetic changes in response to behavioral testing can confound effects of the neurotoxicant itself. They also suggest the potential utility of the inclusion of salient behavioral experiences as a potential effect modifier in epidemiological studies
Phase Transitions in the Symmetric Kondo Lattice Model in Two and Three Dimensions
We present an application of high-order series expansion in the coupling
constants for the ground state properties of correlated lattice fermion
systems. Expansions have been generated up to order for and
for for certain properties of the symmetric Kondo lattice
model. Analyzing the susceptibility series, we find evidence for a continuous
phase transition from the ``spin liquid'' phase characteristic of a ``Kondo
Insulator'' to an antiferromagnetically ordered phase in dimensions as
the antiferromagnetic Kondo coupling is decreased. The critical point is
estimated to be at for square lattice and
for simple-cubic lattice.Comment: 12 pages, Revtex, replace previous corrupted fil
Hall effect in the marginal Fermi liquid regime of high-Tc superconductors
The detailed derivation of a theory for transport in quasi-two-dimensional
metals, with small-angle elastic scattering and angle-independent inelastic
scattering is presented. The transport equation is solved for a model Fermi
surface representing a typical cuprate superconductor. Using the small-angle
elastic and the inelastic scattering rates deduced from angle-resolved
photoemission experiments, good quantitative agreement with the observed
anomalous temperature dependence of the Hall angle in optimally doped cuprates
is obtained, while the resistivity remains linear in temperature. The theory is
also extended to the frequency-dependent complex Hall angle
Prevention of opportunistic infections in HIV infection by pentoxiphylline
Background & objectives: Levels of tumour necrosis factor (TNF) are increased in patients with HIV infection leading to increased apoptosis and reduced CD4 cell life. Pentoxiphylline is a TNF inhibitor with properties that might make it useful for the treatment of HIV infection. These include improved cell mediated immunity and inhibition of viral replication. We carried out this study to determine the therapeutic utility of pentoxiphylline in improving constitutional manifestations, preventing opportunistic infections and sustaining CD4 counts among asymptomatic HIV infected individuals (i.e., those with no opportunistic infection)
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