Density Fluctuations in the Quark-Gluon Plasma

Using the kinetic theory we discuss how the particle and energy densities of the quark-gluon plasma fluctuate in a space-time cell. The fluctuations in the equilibrium plasma and in that one from the early stage of ultrarelativistic heavy-ion collisions are estimated. Within the physically interesting values of the parameters involved the fluctuations appear sizeable in both cases.Comment: 8 pages, no macro

Atmospheric pressure glow discharge for CO2 conversion : model-based exploration of the optimum reactor configuration

We investigate the performance of an atmospheric pressure glow discharge (APGD) reactor for CO2 conversion in three different configurations, through experiments and simulations. The first (basic) configuration utilizes the well-known pin-to-plate design, which offers a limited conversion. The second configuration improves the reactor performance by employing a vortex-flow generator. The third, "confined" configuration is a complete redesign of the reactor, which encloses the discharge in a limited volume, significantly surpassing the conversion rate of the other two designs. The plasma properties are investigated using an advanced plasma model

Turbo-FLASH based arterial spin labeled perfusion MRI at 7 T.

Motivations of arterial spin labeling (ASL) at ultrahigh magnetic fields include prolonged blood T1 and greater signal-to-noise ratio (SNR). However, increased B0 and B1 inhomogeneities and increased specific absorption ratio (SAR) challenge practical ASL implementations. In this study, Turbo-FLASH (Fast Low Angle Shot) based pulsed and pseudo-continuous ASL sequences were performed at 7T, by taking advantage of the relatively low SAR and short TE of Turbo-FLASH that minimizes susceptibility artifacts. Consistent with theoretical predictions, the experimental data showed that Turbo-FLASH based ASL yielded approximately 4 times SNR gain at 7T compared to 3T. High quality perfusion images were obtained with an in-plane spatial resolution of 0.85×1.7 mm(2). A further functional MRI study of motor cortex activation precisely located the primary motor cortex to the precentral gyrus, with the same high spatial resolution. Finally, functional connectivity between left and right motor cortices as well as supplemental motor area were demonstrated using resting state perfusion images. Turbo-FLASH based ASL is a promising approach for perfusion imaging at 7T, which could provide novel approaches to high spatiotemporal resolution fMRI and to investigate the functional connectivity of brain networks at ultrahigh field

Quasiquarks in two stream system

We study the collective quark excitations in an extremely anisotropic system of two interpenetrating streams of the quark-gluon plasma. In contrast to the gluon modes, all quark ones appear to be stable in such a system. Even more, the quark modes in the two-stream system are very similar to those in the isotropic plasma.Comment: 4 pages, 2 figures, minor corrections, to appear in Phys. Rev.

Chromodynamic Weibel instabilities in relativistic nuclear collisions

Employing a previously derived formulation, and extending the treatment from purely transverse modes to wave vectors having a longitudinal component, we discuss the prospects for the occurrence of Weibel-type color-current filamentation in high-energy nuclear collisions. Numerical solutions of the dispersion equation for a number of scenarios relevant to RHIC and LHC suggest that modes with (predominantly transverse) wave numbers of several hundred MeV may become moderately agitated during the early collision stage. The emergence of filamentation helps to speed up the equilibration of the parton plasma and it may lead to non-statistical azimuthal patterns in the hadron final state.Comment: 11 pages, RevTex, 13 (e)ps files (revised for PRC

Influence of convection and biomass burning outflow on tropospheric chemistry over the tropical Pacific

Observations over the tropics from the Pacific Exploratory Mission-Tropics A Experiment are analyzed using a one-dimensional model with an explicit formulation for convective transport. Adopting tropical convective mass fluxes from a general circulation model (GCM) yields a large discrepancy between observed and simulated CH3I concentrations. Observations of CH3I imply the convective mass outflux to be more evenly distributed with altitude over the tropical ocean than suggested by the GCM. We find that using a uniform convective turnover lifetime of 20 days in the upper and middle troposphere enables the model to reproduce CH3I observations. The model reproduces observed concentrations of H2O2 and CH3OOH. Convective transport of CH3OOH from the lower troposphere is estimated to account for 40-80% of CH3OOH concentrations in the upper troposphere. Photolysis of CH3OOH transported by convection more than doubles the primary HOx source and increases OH concentrations and O3 production by 10-50% and 0.4 ppbv d-1, respectively, above 11 km. Its effect on the OH concentration and O3 production integrated over the tropospheric column is, however, small. The effects of pollutant import from biomass burning regions are much more dominant. Using C2H2 as a tracer, we estimate that biomass burning outflow enhances O3 concentrations, O3 production, and concentrations of NOx and OH by 60%, 45%, 75%, and 7%, respectively. The model overestimates HNO3 concentrations by about a factor of 2 above 4 km for the upper one-third quantile of C2H2 data while it generally reproduces HNO3 concentrations for the lower and middle one-third quantiles of C2H2 data. Copyright 2000 by the American Geophysical Union

Magnetosphere-Ionosphere Coupling Through E-region Turbulence: Anomalous Conductivities and Frictional Heating

Global magnetospheric MHD codes using ionospheric conductances based on laminar models systematically overestimate the cross-polar cap potential during storm time by up to a factor of two. At these times, strong DC electric fields penetrate to the E region and drive plasma instabilities that create turbulence. This plasma density turbulence induces non-linear currents, while associated electrostatic field fluctuations result in strong anomalous electron heating. These two effects will increase the global ionospheric conductance. Based on the theory of non-linear currents developed in the companion paper, this paper derives the correction factors describing turbulent conductivities and calculates turbulent frictional heating rates. Estimates show that during strong geomagnetic storms the inclusion of anomalous conductivity can double the total Pedersen conductance. This may help explain the overestimation of the cross-polar cap potentials by existing MHD codes. The turbulent conductivities and frictional heating presented in this paper should be included in global magnetospheric codes developed for predictive modeling of space weather.Comment: 13 pages, 5 figures, 2nd of two companion paper

Performance of entrepreneurial Chinese immigrants in network marketing organisations

Immigrant entrepreneurship has started attracting much empirical research in the literature. There is an increasing trend in Australia where a large number of Chinese immigrants have joined network marketing organisations (NMOs). However, only a small number of empirical studies on NMOs have been conducted and most of these do not examine the factors contributing to explaining the performance of Chinese immigrants in NMOs. The objective of this paper is to develop an integrative model to examine the factors contributing to the action of Chinese immigrants who engage in network marketing business