Concentration Gradient, Diffusion, and Flow Through Open Porous Medium Near Percolation Threshold via Computer Simulations

The interacting lattice gas model is used to simulate fluid flow through an open percolating porous medium with the fluid entering at the source-end and leaving from the opposite end. The shape of the steady-state concentration profile and therefore the gradient field depends on the is found to scale with the porosity according to porosity p. The root mean square (rms) displacements of fluid and its constituents (tracers) show a drift power-law behavior, in the asymptotic regime. The flux current density is found to scale with the porosity according to an exponent near 1.7.Comment: 8 figure

Density and conformation with relaxed substrate, bulk, and interface electrophoretic deposition of polymer chains

Characteristics of relaxed density profile and conformation of polymer chains are studied by a Monte Carlo simulation on a discrete lattice in three dimensions using different segmental (kink-jump $K$, crank-shaft $C$, reptation $R$) dynamics. Three distinct density regimes, substrate, bulk, and interface, are identified. With the $KC$ segmental dynamics we find that the substrate coverage grows with a power-law, $d_s \propto t^{\gamma}$ with a field dependent nonuniversal exponent $\gamma = 0.23 + 0.7 E$. The bulk volume fraction $d_b$ and the substrate polymer density ($d_s$) increases exponentially with the field ($d_b \propto E^{0.4}$, $d_s \propto E^{0.2}$) in the low field regime. The interface polymer density $d_f$ increases with the molecular weight. With the $KCR$ segmental dynamics, bulk and substrate density decreases linearly with the temperature at high temperatures. The bulk volume fraction is found to decay with the molecular weight, $d_b \propto L_c^{-0.11}$. The radius of gyration remains Gaussian in all density regions.Comment: Changed double to single spacin

Power-law persistence and trends in the atmosphere: A detailed study of long temperature records

We use several variants of the detrended fluctuation analysis to study the appearance of long-term persistence in temperature records, obtained at 95 stations all over the globe. Our results basically confirm earlier studies. We find that the persistence, characterized by the correlation C(s) of temperature variations separated by s days, decays for large s as a power law, C(s) ~ s^(-gamma). For continental stations, including stations along the coastlines, we find that gamma is always close to 0.7. For stations on islands, we find that gamma ranges between 0.3 and 0.7, with a maximum at gamma = 0.4. This is consistent with earlier studies of the persistence in sea surface temperature records where gamma is close to 0.4. In all cases, the exponent gamma does not depend on the distance of the stations to the continental coastlines. By varying the degree of detrending in the fluctuation analysis we obtain also information about trends in the temperature records.Comment: 5 pages, 4 including eps figure

Dynamics and Conformation of Polymer Chains in a Porous Medium

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics534 SUPPL. B3717-3731PLEE

The upstream magnetic field of collisionless GRB shocks: constraint by Fermi-LAT observations

Long-lived >100 MeV emission has been a common feature of most Fermi-LAT detected gamma-ray bursts (GRBs), e.g., detected up to ~10^3s in long GRBs 080916C and 090902B and ~10^2s in short GRB 090510. This emission is consistent with being produced by synchrotron emission of electrons accelerated to high energy by the relativistic collisionless shock propagating into the weakly magnetized medium. Here we show that this high-energy afterglow emission constrains the preshock magnetic field to satisfy 1(n/1cc)^{9/8} mG<B<10^2(n/1cc)^{3/8}mG, where n is the preshock density, more stringent than the previous constraint by X-ray afterglow observations on day scale. This suggests that the preshock magnetic field is strongly amplified, most likely by the streaming of high energy shock accelerated particles.Comment: 9 pages, JCAP accepte

HEPATOPROTECTIVE ACTIVITY OF BERBERISARISTATA ROOT EXTRACT AGAINST CHEMICAL INDUCED ACUTE HEPATOTOXICITY IN RATS

Objective: To study the effects of root extract of Berberis aristata in rat model of acute hepatotoxicity induced by carbon tetrachloride (CCl4). CCL4 is commonly used hepatotoxin in the experimental studies of liver diseases. Liver damage induced by CCL4 involves biotransformation of free radicals derivatives, increased lipid peroxidation and excessive cell death. Berberis aristata root extract, berberine chloride†is known to possess multiple pharmacological activities including anti-microbial, antiviral, anti-inflammatory, cholesterol lowering, anti cancer and anti-oxidant effects. The present study was conducted to evaluate the hepatoprotective activity of berberine in chemical induced hepatotoxicity in rats. Material &amp; Methods: The experimental protocol was approved be the IAEC. Adult wistar rats aged 7-9 weeks were injected intraperitoneally with 50 percent CCl4 as 1:1 mixture in liquid paraffin. Berberine was administered i/p before or after CCl4 treatment in various groups. Twenty-four hours after CCl4 injection, serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase(ALP) activities, total serum bilirubin levels and liver weight were measured. Histological changes of liver were examined with microscopy. Results: Serum ALT, AST, ALP activities significantly decreased in a dose-dependent manner in both pre-treatment and post-treatment groups with berberine. Histological examination showed lowered liver damage in berberine-treated groups. Conclusion: The present study demonstrates that berberine possesses hepatoprotective effects against CCl4-induced hepatotoxicity and that the effects are both preventive and curative. Berberine should have potential for developing a new drug to treat liver toxicity. Key words: CCl4, Berberine, hepatoprotective activity, antioxidantÂ