Supernova Simulations with Boltzmann Neutrino Transport: A Comparison of Methods

Accurate neutrino transport has been built into spherically symmetric simulations of stellar core collapse and postbounce evolution. The results of such simulations agree that spherically symmetric models with standard microphysical input fail to explode by the delayed, neutrino-driven mechanism. Independent groups implemented fundamentally different numerical methods to tackle the Boltzmann neutrino transport equation. Here we present a direct and detailed comparison of such neutrino radiation-hydrodynamical simulations for two codes, Agile-Boltztran of the Oak Ridge-Basel group and Vertex of the Garching group. The former solves the Boltzmann equation directly by an implicit, general relativistic discrete angle method on the adaptive grid of a conservative implicit hydrodynamics code with second-order TVD advection. In contrast, the latter couples a variable Eddington factor technique with an explicit, moving-grid, conservative high-order Riemann solver with important relativistic effects treated by an effective gravitational potential. The presented study is meant to test both neutrino radiation-hydrodynamics implementations and to provide a data basis for comparisons and verifications of supernova codes to be developed in the future. Results are discussed for simulations of the core collapse and post-bounce evolution of a 13 solar mass star with Newtonian gravity and a 15 solar mass star with relativistic gravity.Comment: 23 pages, 13 figures, revised version, to appear in Ap

The effect of short – term exercise on nitric oxide (NO) serum concentrations in overweight and obese women

Objective: The aims of the present study was to examine the effect of overweight and obesity on serum concentrations of nitric oxide metabolites and evaluate the differences of exercise induced NO production in obese and lean women. Materials and Methods: The study groups consisted of 154 women including 102 obese and 24 overweight patients and 28 lean controls. Serum concentrations of nitric oxide metabolites were measured before and after exercise with the use of ELISA kits. The serum concentrations of lactate before and after exercise were measured with the use of strip test (ACCUSPORT analyzer). Serum concentration of insulin was measured with the use of RIA. Plasma glucose, cholesterol, HDL cholesterol and triglicerydes were determined by enzymatic procedure. Impedance analysis (Bodystat) was used to determine body composition. Results: Serum concentration of NO in overweight group and obese group was significantly higher when compared to controls, p<0.05 and p<0.01, respectively. There was no difference in levels of NO between overweight and obese groups .During exercise NO concentrations increased significantly in all groups and the post- exercise levels did not differ statistically in overweight and obese groups from that in controls. The value of NO was the lowest in obese group but there were no significant differences between obese, overweight and control groups. Conclusions: Obesity may attenuate the exercise - induced endothelial NO release

The effect of weight loss on serum concentrations of nitric oxide induced by short - term exercise in obese women

Objective: The aim of present study was to examine the effect of weight loss comprising regular moderate physical activity on resting serum concentrations of nitric oxide metabolites and exercise induced NO release. Materials and Methods: The study was carried out in 43 obese women without additional diseases (age 41.8±11.9y, body weight 94.5±15.1kg, BMI 36.5±4.6kg/m2). All obese patients participated in a 3-month weight reduction programme that consisted of 1) a group instruction in behavioural and dietary methods of weight control every two weeks; 2) 1000-1400kcal/day balanced diet, and 3) moderate physical exercises (30 minutes, 3 times a week). Before and after treatment body mass and height were measured, body mass index (BMI) was calculated. Body composition was determined by impedance analysis using a Bodystat analyser. The serum concentration of nitric oxide metabolites before and after exercise was measured using spectrophotometry method by Griess. The serum concentrations of lactate before and after exercise were measured with the use of strip test (ACCUSPORT analyzer). Serum concentration of insulin was measured with the use of RIA. Plasma glucose, cholesterol, HDL cholesterol and triglicerydes were determined by enzymatic procedure. Results: The mean weight loss during treatment was 8.3±4.3 kg. We did not observe differences between resting serum concentrations of NO and lactate before and after weight loss. During exercise serum NO concentrations increased significantly both before and after weight loss treatment. After the weight reduction treatment, the time of exercise test increased significantly P<0.005, but there were no significant differences between the value of NO before and after weight loss. Conclusion: 3 – month regular physical activity and weight loss did not influence exercise-induced nitric oxide production

On the apparent horizon in fluid-gravity duality

This article develops a computational framework for determining the location of boundary-covariant apparent horizons in the geometry of conformal fluid-gravity duality in arbitrary dimensions. In particular, it is shown up to second order and conjectured to hold to all orders in the gradient expansion that there is a unique apparent horizon which is covariantly expressible in terms of fluid velocity, temperature and boundary metric. This leads to the first explicit example of an entropy current defined by an apparent horizon and opens the possibility that in the near-equilibrium regime there is preferred foliation of apparent horizons for black holes in asymptotically-AdS spacetimes