Thermophysical properties of warm dense hydrogen

We study the thermophysical properties of warm dense hydrogen using quantum molecular dynamics simulations. New results are presented for the pair distribution functions, the equation of state, the Hugoniot curve, and the reflectivity. We compare with available experimental data and predictions of the chemical picture. Especially, we discuss the nonmetal-to-metal transition which occurs at about 40 GPa in the dense fluid

Hemorrhagic Metritis with Resulting Anemia

On Feb. 20, 1950, a 12 year old Boston bitch was admitted to Stange Memorial Clinic with a history of having hemorrhaged from the uterus over a period of three weeks. Upon admittance the dog showed extreme depression and a very pronounced anemia of the mucus membranes. A diagnosis of hemorrhagic metritis was made

Recent applications of the transonic wing analysis computer code, TWING

An evaluation of the transonic-wing-analysis computer code TWING is given. TWING utilizes a fully implicit approximate factorization iteration scheme to solve the full potential equation in conservative form. A numerical elliptic-solver grid-generation scheme is used to generate the required finite-difference mesh. Several wing configurations were analyzed, and the limits of applicability of this code was evaluated. Comparisons of computed results were made with available experimental data. Results indicate that the code is robust, accurate (when significant viscous effects are not present), and efficient. TWING generally produces solutions an order of magnitude faster than other conservative full potential codes using successive-line overrelaxation. The present method is applicable to a wide range of isolated wing configurations including high-aspect-ratio transport wings and low-aspect-ratio, high-sweep, fighter configurations

An exact Riemann solver based solution for regular shock refraction

We study the classical problem of planar shock refraction at an oblique density discontinuity, separating two gases at rest. When the shock impinges on the density discontinuity, it refracts and in the hydrodynamical case 3 signals arise. Regular refraction means that these signals meet at a single point, called the triple point. After reflection from the top wall, the contact discontinuity becomes unstable due to local Kelvin-Helmholtz instability, causing the contact surface to roll up and develop the Richtmyer-Meshkov instability. We present an exact Riemann solver based solution strategy to describe the initial self similar refraction phase, by which we can quantify the vorticity deposited on the contact interface. We investigate the effect of a perpendicular magnetic field and quantify how addition of a perpendicular magnetic field increases the deposition of vorticity on the contact interface slightly under constant Atwood number. We predict wave pattern transitions, in agreement with experiments, von Neumann shock refraction theory, and numerical simulations performed with the grid-adaptive code AMRVAC. These simulations also describe the later phase of the Richtmyer-Meshkov instability.Comment: 21 pages, 17 figures in 41 ps-files, accepted by J. Fluid Mec

Black Holes and Wormholes in 2+1 Dimensions

A large variety of spacetimes---including the BTZ black holes---can be obtained by identifying points in 2+1 dimensional anti-de Sitter space by means of a discrete group of isometries. We consider all such spacetimes that can be obtained under a restriction to time symmetric initial data and one asymptotic region only. The resulting spacetimes are non-eternal black holes with collapsing wormhole topologies. Our approach is geometrical, and we discuss in detail: The allowed topologies, the shape of the event horizons, topological censorship and trapped curves.Comment: 23 pages, LaTeX, 11 figure

A Bose-Einstein Approach to the Random Partitioning of an Integer

Consider N equally-spaced points on a circle of circumference N. Choose at random n points out of $N$ on this circle and append clockwise an arc of integral length k to each such point. The resulting random set is made of a random number of connected components. Questions such as the evaluation of the probability of random covering and parking configurations, number and length of the gaps are addressed. They are the discrete versions of similar problems raised in the continuum. For each value of k, asymptotic results are presented when n,N both go to infinity according to two different regimes. This model may equivalently be viewed as a random partitioning problem of N items into n recipients. A grand-canonical balls in boxes approach is also supplied, giving some insight into the multiplicities of the box filling amounts or spacings. The latter model is a k-nearest neighbor random graph with N vertices and kn edges. We shall also briefly consider the covering problem in the context of a random graph model with N vertices and n (out-degree 1) edges whose endpoints are no more bound to be neighbors

Numerical Bifurcation Analysis of Conformal Formulations of the Einstein Constraints

The Einstein constraint equations have been the subject of study for more than fifty years. The introduction of the conformal method in the 1970's as a parameterization of initial data for the Einstein equations led to increased interest in the development of a complete solution theory for the constraints, with the theory for constant mean curvature (CMC) spatial slices and closed manifolds completely developed by 1995. The first general non-CMC existence result was establish by Holst et al. in 2008, with extensions to rough data by Holst et al. in 2009, and to vacuum spacetimes by Maxwell in 2009. The non-CMC theory remains mostly open; moreover, recent work of Maxwell on specific symmetry models sheds light on fundamental non-uniqueness problems with the conformal method as a parameterization in non-CMC settings. In parallel with these mathematical developments, computational physicists have uncovered surprising behavior in numerical solutions to the extended conformal thin sandwich formulation of the Einstein constraints. In particular, numerical evidence suggests the existence of multiple solutions with a quadratic fold, and a recent analysis of a simplified model supports this conclusion. In this article, we examine this apparent bifurcation phenomena in a methodical way, using modern techniques in bifurcation theory and in numerical homotopy methods. We first review the evidence for the presence of bifurcation in the Hamiltonian constraint in the time-symmetric case. We give a brief introduction to the mathematical framework for analyzing bifurcation phenomena, and then develop the main ideas behind the construction of numerical homotopy, or path-following, methods in the analysis of bifurcation phenomena. We then apply the continuation software package AUTO to this problem, and verify the presence of the fold with homotopy-based numerical methods.Comment: 13 pages, 4 figures. Final revision for publication, added material on physical implication

Investigation on the influence of nematophagous fungi as feed additive on nematode infection risk of sheep and goats on pasture

Gastrointestinal nematodes in small ruminants cause high economic losses. Thus on most farms anthelmintic treatment is required. In response to increasing problems with anthelmintic resistance, biological control, for example the use of nematophagous fungi, has received significant attention. The aim of this study was to investigate the effect of Duddingtonia flagrans orally applied to small ruminants on natural infection with gastrointestinal nematodes in a field study in Northern Germany. 20 goats and 20 sheep were fed daily for 3 months with 5x105 spores of D. flagrans per kg bodyweight. Differences in body weight, faecal egg count and larval development in faeces and on pasture in comparison with same-sized control groups were analysed. After 3 months the control goats showed significantly higher mean faecal egg count than the fungus-fed group. No significant difference was found between the two sheep groups. The maximum in larval reduction in faeces was 81.3 % in the sheep groups and 67.9 % in the goat groups (not significant). At the end of the study the body weight gain in the fungus-treated groups was 1.7 kg higher in goats and 0.7 kg higher in sheep than in the control groups (not significant). Regarding the first-year-grazing goats only, the bodyweights revealed significant differences (p<0.05). No statistically significant differences were observed in pasture larval counts. In the study presented here, no clear effect of fungus could be observed. A modified feeding regimen, perhaps with permanent release boluses or feed blocks, may improve the efficacy. Furthermore, it seems that climatic conditions during the study period could have influenced the results and displayed how sensitive the fungus application may be on such parameters