Hydrodynamic Model for Conductivity in Graphene

Based on the recently developed picture of an electronic ideal relativistic fluid at the Dirac point, we present an analytical model for the conductivity in graphene that is able to describe the linear dependence on the carrier density and the existence of a minimum conductivity. The model treats impurities as submerged rigid obstacles, forming a disordered medium through which graphene electrons flow, in close analogy with classical fluid dynamics. To describe the minimum conductivity, we take into account the additional carrier density induced by the impurities in the sample. The model, which predicts the conductivity as a function of the impurity fraction of the sample, is supported by extensive simulations for different values of ${\cal E}$, the dimensionless strength of the electric field, and provides excellent agreement with experimental data.Comment: 19 pages, 4 figure

Internal avalanches in models of granular media

We study the phenomenon of internal avalanching within the context of recently introduced lattice models of granular media. The avalanche is produced by pulling out a grain at the base of the packing and studying how many grains have to rearrange before the packing is once more stable. We find that the avalanches are long-ranged, decaying as a power-law. We study the distriution of avalanches as a function of the density of the packing and find that the avalanche distribution is a very sensitive structural probe of the system.Comment: 12 pages including 9 eps figures, LaTeX. To appear in Fractal

Cooling Effect of the Richtmyer-Meshkov Instability

We provide numerical evidence that the Richtmyer-Meshkov (RM) instability contributes to the cooling of a relativistic fluid. Due to the presence of jet particles traveling throughout the medium, shock waves are generated in the form of Mach cones. The interaction of multiple shock waves can trigger the RM instability, and we have found that this process leads to a down-cooling of the relativistic fluid. To confirm the cooling effect of the instability, shock tube Richtmyer-Meshkov instability simulations are performed. Additionally, in order to provide an experimental observable of the RM instability resulting from the Mach cone interaction, we measure the two particle correlation function and highlight the effects of the interaction. The simulations have been performed with an improved version of the relativistic lattice Boltzmann model, including general equations of state and external forces.Comment: 10 pages, 6 figure

Health-related quality of life in the WA HIV Cohort: 2008

Quality of life (QOL) is an important outcome of HIV treatment and a priority in the management of HIV. A new Patient-Reported Outcomes (PRO) questionnaire to measure the QOL in people living with HIV/AIDS (PLWHA) from different cultures and language groups has been developed. The instrument, PROQOL-HIV, has undergone psychometric validation in 791 individuals from 8 countries including 99 people from the WA HIV Cohort Study