Correlations and fluctuations of a confined electron gas

The grand potential $\Omega$ and the response $R = - \partial \Omega /\partial x$ of a phase-coherent confined noninteracting electron gas depend sensitively on chemical potential $\mu$ or external parameter $x$. We compute their autocorrelation as a function of $\mu$, $x$ and temperature. The result is related to the short-time dynamics of the corresponding classical system, implying in general the absence of a universal regime. Chaotic, diffusive and integrable motions are investigated, and illustrated numerically. The autocorrelation of the persistent current of a disordered mesoscopic ring is also computed.Comment: 12 pages, 1 figure, to appear in Phys. Rev.

Dynamic Correlation in Wave Propagation in Random Media

We report time-resolved measurements of the statistics of pulsed transmission through quasi-one-dimensional dielectric media with static disorder. The normalized intensity correlation function with displacement and polarization rotation for an incident pulse of linewidth $\sigma$ at delay time t is a function only of the field correlation function, which is identical to that found for steady-state excitation, and of $\kappa_{\sigma}(t)$, the residual degree of intensity correlation at points at which the field correlation function vanishes. The dynamic probability distribution of normalized intensity depends only upon $\kappa_{\sigma}(t)$. Steady-state statistics are recovered in the limit $\sigma$->0, in which $\kappa_{\sigma=0}$ is the steady-state degree of correlation.Comment: 4 RevTex pages, 4 figure

Molecules empowering animals to sense and respond to temperature in changing environments

Adapting behavior to thermal cues is essential for animal growth and survival. Indeed, each and every biological and biochemical process is profoundly affected by temperature and its extremes can cause irreversible damage. Hence, animals have developed thermotransduction mechanisms to detect and encode thermal information in the nervous system and acclimation mechanisms to finely tune their response over different timescales. While temperature-gated TRP channels are the best described class of temperature sensors, recent studies highlight many new candidates, including ionotropic and metabotropic receptors. Here, we review recent findings in vertebrate and invertebrate models, which highlight and substantiate the role of new candidate molecular thermometers and reveal intracellular signaling mechanisms implicated in thermal acclimation at the behavioral and cellular levels

The stationary phase point method for transitional scattering: diffractive radio scintillation for pulsar

The stationary phase point (SPP) method in one-dimensional case is introduced to treat the diffractive scintillation. From weak scattering, where the SPP number N=1, to strong scattering (N$\gg$1), via transitional scattering regime (N$\sim$2,3), we find that the modulation index of intensity experiences the monotonically increasing from 0 to 1 with the scattering strength, characterized by the ratio of Fresnel scale \rf to diffractive scale \rdiff.Comment: Hanas Meeting paper, appear in ChJAA, 2006, 6, Su

Hunting Galaxies to (and for) Extinction

In studies of star-forming regions, near-infrared excess (NIRX) sources--objects with intrinsic colors redder than normal stars--constitute both signal (young stars) and noise (e.g. background galaxies). We hunt down (identify) galaxies using near-infrared observations in the Perseus star-forming region by combining structural information, colors, and number density estimates. Galaxies at moderate redshifts (z = 0.1 - 0.5) have colors similar to young stellar objects (YSOs) at both near- and mid-infrared (e.g. Spitzer) wavelengths, which limits our ability to identify YSOs from colors alone. Structural information from high-quality near-infrared observations allows us to better separate YSOs from galaxies, rejecting 2/5 of the YSO candidates identified from Spitzer observations of our regions and potentially extending the YSO luminosity function below K of 15 magnitudes where galaxy contamination dominates. Once they are identified we use galaxies as valuable extra signal for making extinction maps of molecular clouds. Our new iterative procedure: the Galaxies Near Infrared Color Excess method Revisited (GNICER), uses the mean colors of galaxies as a function of magnitude to include them in extinction maps in an unbiased way. GNICER increases the number of background sources used to probe the structure of a cloud, decreasing the noise and increasing the resolution of extinction maps made far from the galactic plane.Comment: 16 pages and 16 figures. Accepted for publication in ApJ. Full resolution version at http://www.cfa.harvard.edu/COMPLETE/papers/Foster_HuntingGalaxies.pd

Wall turbulence control

A variety of wall turbulence control devices which were experimentally investigated are discussed; these include devices for burst control, alteration of outer flow structures, large eddy substitution, increased heat transfer efficiency, and reduction of wall pressure fluctuations. Control of pre-burst flow was demonstrated with a single, traveling surface depression which is phase-locked to elements of the burst production process. Another approach to wall turbulence control is to interfere with the outer layer coherent structures. A device in the outer part of a boundary layer was shown to suppress turbulence and reduce drag by opposing both the mean and unsteady vorticity in the boundary layer. Large eddy substitution is a method in which streamline curvature is introduced into the boundary layer in the form of streamwise vortices. Riblets, which were already shown to reduce turbulent drag, were also shown to exhibit superior heat transfer characteristics. Heat transfer efficiency as measured by the Reynolds Analogy Factor was shown to be as much as 36 percent greater than a smooth flat plate in a turbulent boundary layer. Large Eddy Break-Up (LEBU) which are also known to reduce turbulent drag were shown to reduce turbulent wall pressure fluctuation