Dimension 2 condensates and Polyakov Chiral Quark Models

We address a possible relation between the expectation value of the Polyakov loop in pure gluodynamics and full QCD based on Polyakov Chiral Quark Models where constituent quarks and the Polyakov loop are coupled in a minimal way. To this end we use a center symmetry breaking Gaussian model for the Polyakov loop distribution which accurately reproduces gluodynamics data above the phase transition in terms of dimension 2 gluon condensate. The role played by the quantum and local nature of the Polyakov loop is emphasized.Comment: 3 pages, 1 figure. Talk given at the IVth International Conference on Quarks an Nuclear Physics, Madrid, June 5th-10th 200

QCD at non-zero chemical potential and temperature from the lattice

A study of QCD at non-zero chemical potential, mu, and temperature, T, is performed using the lattice technique. The transition temperature (between the confined and deconfined phases) is determined as a function of mu and is found to be in agreement with other work. In addition the variation of the pressure and energy density with mu is obtained for small positive mu. These results are of particular relevance for heavy-ion collision experiments.Comment: Invited paper presented at the Joint Workshop on Physics at the Japanese Hadron Facility, March 2002, Adelaide. 10 pages, uses ws-procs9x6.cls style file (provided

Competition and coexistence of multiple mutually pumped oscillations in the visible and infra-red

A photorefractive oscillator. mutually pumped by three wavelengths is presented in various configurations and competition effects demonstrated. The theoretical model used to simulate the behaviour of the oscillation beams is in good agreement with experimental data

The Energetics of Molecular Adaptation in Transcriptional Regulation

Mutation is a critical mechanism by which evolution explores the functional landscape of proteins. Despite our ability to experimentally inflict mutations at will, it remains difficult to link sequence-level perturbations to systems-level responses. Here, we present a framework centered on measuring changes in the free energy of the system to link individual mutations in an allosteric transcriptional repressor to the parameters which govern its response. We find the energetic effects of the mutations can be categorized into several classes which have characteristic curves as a function of the inducer concentration. We experimentally test these diagnostic predictions using the well-characterized LacI repressor of Escherichia coli, probing several mutations in the DNA binding and inducer binding domains. We find that the change in gene expression due to a point mutation can be captured by modifying only a subset of the model parameters that describe the respective domain of the wild-type protein. These parameters appear to be insulated, with mutations in the DNA binding domain altering only the DNA affinity and those in the inducer binding domain altering only the allosteric parameters. Changing these subsets of parameters tunes the free energy of the system in a way that is concordant with theoretical expectations. Finally, we show that the induction profiles and resulting free energies associated with pairwise double mutants can be predicted with quantitative accuracy given knowledge of the single mutants, providing an avenue for identifying and quantifying epistatic interactions.Comment: 11 pages, 6 figures, supplemental info. available via http://rpgroup.caltech.edu/mwc_mutant

Quarkonia and Heavy-Quark Relaxation Times in the Quark-Gluon Plasma

A thermodynamic T-matrix approach for elastic 2-body interactions is employed to calculate spectral functions of open and hidden heavy-quark systems in the Quark-Gluon Plasma. This enables the evaluation of quarkonium bound-state properties and heavy-quark diffusion on a common basis and thus to obtain mutual constraints. The two-body interaction kernel is approximated within a potential picture for spacelike momentum transfers. An effective field-theoretical model combining color-Coulomb and confining terms is implemented with relativistic corrections and for different color channels. Four pertinent model parameters, characterizing the coupling strengths and screening, are adjusted to reproduce the color-average heavy-quark free energy as computed in thermal lattice QCD. The approach is tested against vacuum spectroscopy in the open (D, B) and hidden (Psi and Upsilon) flavor sectors, as well as in the high-energy limit of elastic perturbative QCD scattering. Theoretical uncertainties in the static reduction scheme of the 4-dimensional Bethe-Salpeter equation are elucidated. The quarkonium spectral functions are used to calculate Euclidean correlators which are discussed in light of lattice QCD results, while heavy-quark relaxation rates and diffusion coefficients are extracted utilizing a Fokker-Planck equation.Comment: 33 pages, 28 figure

Relationships between circadian rhythms, timing of eating behaviors, and the human gastrointestinal microbiota

In the obesity-prone environment in which we live, no avenue for potentially health-promoting intervention should be ignored. One such avenue that has gained recent attention is the modulation of the gastrointestinal microbiota. Microbiota interventions have come into the spotlight because of the proposed relationships between the microbial community’s composition, function, and human health. One of the most common strategies for modulating the microbial community for potential health benefit is by dietary modifications, although antibiotics, microbial transplant, probiotics, and even exercise can also impact the gastrointestinal microbiome. With the emergence of evidence that timing of eating can impact health, it follows that the connection of eating behaviors to the gastrointestinal microbiota should be explored further. The objective of this research was to assess the links between circadian rhythms, timing of eating, and the human gastrointestinal microbiota. To accomplish this goal, a thorough review of the current literature was first conducted. Second, a cross-section of healthy, adult subjects was examined to determine the relative abundances of bacterial genera and concentrations of bacterial metabolites in fecal samples collected throughout the day. These variables were additionally assessed in relation to the subjects’ eating habits, including eating frequency, consumption of energy earlier in the day, and overnight fast duration. This study found strong evidence in the existing literature for the impact of circadian rhythms and eating behaviors on the gastrointestinal microbiota and health. Additionally, this work presents the results of a large, cross-sectional clinical study which found an association between time of day, microbiota composition and function, and eating behaviors. The results presented herein propose that this connection not only exists, but also could hold relevance for human health, with application to health-promoting interventions

Critical Behavior of J/psi across the Phase Transition from QCD sum rules

We study behavior of J/psi in hot gluonic matter using QCD sum rules. Taking into account temperature dependences of the gluon condensates extracted from lattice thermodynamics for the pure SU(3) system, we find that the mass and width of J/psi exhibit rapid change across the critical temperature.Comment: 5 pages, 3 figures. Poster contribution for Quark Matter 2008. To be published in the proceeding

Magnetoelectricity at room temperature in Bi0.9-xTbxLa0.1FeO3 system

Magnetoelectric compounds with the general formula, Bi0.9-xRxLa0.1FeO3 (R =Gd, Tb, Dy, etc.), have been synthesized. These show the coexistence of ferroelectricity and magnetism, possess high dielectric constant and exhibit magnetoelectric coupling at room temperature. Such materials may be of great significance in basic as well as applied research.Comment: 11 pages of text and figure

Tactile experience induces c-fos expression in rat barrel cortex

Understanding gene expression that is responsive to sensory stimulation is central to elucidate molecular mechanisms underlying neuronal plasticity. In this study we demonstrate two new methods of stimulating whiskers that provide major sensory input to rat neocortex. In the first paradigm, animals were placed on the top of a cylinder and their vibrissae were brushed by hand, In the second paradigm, animals were placed for a brief period or time into a new, wired cage resulting in vibrissae stimulation when they explored the new environment. Both approaches induced c-Fos expression in barrel cortex corresponding to the stimulated vibrissae, especially in layer IV. Layers II/III and V/VI also showed c-Fos induction, but there were no detectable changes in layer VIb. The majority of c-Fos-expressing cells are probably not inhibitory neurons, because they do not show parvalbumin staining. Both paradigms, in contrast to the previous methods, are simple to use and do not require anesthesia, restraint of animals, or elaborate experimental setups