Fluctuating parts of nuclear ground state correlation energies

Background: Heavy atomic nuclei are often described using the Hartree-Fock-Bogoliubov (HFB) method. In principle, this approach takes into account Pauli effects and pairing correlations while other correlation effects are mimicked through the use of effective density-dependent interactions. Purpose: Investigate the influence of higher order correlation effects on nuclear binding energies using Skyrme's effective interaction. Methods: A cut-off in relative momenta is introduced in order to remove ultraviolet divergences caused by the zero-range character of the interaction. Corrections to binding energies are then calculated using the quasiparticle-random-phase approximation (QRPA) and second order many-body perturbation theory (MBPT2). Result: Contributions to the correlation energies are evaluated for several isotopic chains and an attempt is made to disentangle which parts give rise to fluctuations that may be difficult to incorporate on the HFB level. The dependence of the results on the cut-off is also investigated. Conclusions: The improved interaction allows explicit summations of perturbation series which is useful for the description of some nuclear observables. However, refits of the interaction parameters are needed to obtain more quantitative results

Initiation of hepatitis C virus infection is dependent on cholesterol and cooperativity between CD81 and scavenger receptor B type I.

In the past several years, a number of cellular proteins have been identified as candidate entry receptors for hepatitis C virus (HCV) by using surrogate models of HCV infection. Among these, the tetraspanin CD81 and scavenger receptor B type I (SR-BI), both of which localize to specialized plasma membrane domains enriched in cholesterol, have been suggested to be key players in HCV entry. In the current study, we used a recently developed in vitro HCV infection system to demonstrate that both CD81 and SR-BI are required for authentic HCV infection in vitro, that they function cooperatively to initiate HCV infection, and that CD81-mediated HCV entry is, in part, dependent on membrane cholesterol

Generating Generalized Distributions from Dynamical Simulation

We present a general molecular-dynamics simulation scheme, based on the Nose' thermostat, for sampling according to arbitrary phase space distributions. We formulate numerical methods based on both Nose'-Hoover and Nose'-Poincare' thermostats for two specific classes of distributions; namely, those that are functions of the system Hamiltonian and those for which position and momentum are statistically independent. As an example, we propose a generalized variable temperature distribution that designed to accelerate sampling in molecular systems.Comment: 10 pages, 3 figure

The String Deviation Equation

The relative motion of many particles can be described by the geodesic deviation equation. This can be derived from the second covariant variation of the point particle's action. It is shown that the second covariant variation of the string action leads to a string deviation equation.Comment: 18 pages, some small changes, no tables or diagrams, LaTex2

Raman signatures of classical and quantum phases in coupled dots: A theoretical prediction

We study electron molecules in realistic vertically coupled quantum dots in a strong magnetic field. Computing the energy spectrum, pair correlation functions, and dynamical form factor as a function of inter-dot coupling via diagonalization of the many-body Hamiltonian, we identify structural transitions between different phases, some of which do not have a classical counterpart. The calculated Raman cross section shows how such phases can be experimentally singled out.Comment: 9 pages, 2 postscript figures, 1 colour postscript figure, Latex 2e, Europhysics Letters style and epsfig macros. Submitted to Europhysics Letter

A Log-Quadratic Relation Between the Nuclear Black-Hole Masses and Velocity Dispersions of Galaxies

We demonstrate that a log-linear relation does not provide an adequate description of the correlation between the masses of Super-Massive Black-Holes (SMBH, M_bh) and the velocity dispersions of their host spheroid (sigma). An unknown relation between log(M_bh) and log(sigma) may be expanded to second order to obtain a log-quadratic relation of the form log(M_bh)=alpha+beta log(sigma/200) + beta_2[log(sigma/200)]^2. We perform a Bayesian analysis using the Nuker sample, and solve for beta, beta_2 and alpha, in addition to the intrinsic scatter (delta). We find unbiased parameter estimates of beta=4.2+/-0.37, beta_2=1.6+/-1.3 and delta=0.275+/-0.05. At the 80% level the M_bh-sigma relation does not follow a uniform power-law. Indeed, over the velocity range 70km/s<sigma<380km/s the logarithmic slope of the best fit relation varies between 2.7 and 5.1, which should be compared with a power-law estimate of 4.02+/-0.33. Assuming no systematic offset, single epoch virial SMBH masses estimated for AGN follow the same log-quadratic M_bh-sigma relation as the Nuker sample, but extend it downward in mass by an order of magnitude. The log-quadratic term in the M_bh-sigma relation has a significant effect on estimates of the local SMBH mass function at M_bh>10^9 solar masses, leading to densities of SMBHs with M_bh>10^10 solar masses that are several orders of magnitude larger than inferred from a log-linear relation. We also estimate unbiased parameters for the SMBH-bulge mass relation. With a parameterisation log(M_bh)=alpha_b + beta_b log(M_b/10^{11}) + beta_2b[log(M_b/10^{11})]^2, we find beta_b=1.15+/-0.18 and beta_2b=0.12+/-0.14. We determined an intrinsic scatter delta_b=0.41+/-0.07 which is ~50% larger than the scatter in the M_bh-sigma relation.Comment: 21 pages, 14 figures. Replaced to correct errors in published versio

Preliminary evaluation of grain yield components in hexaploid tritordeum

Chromosome duplication of Hordeum chilense and Triticum turgidum conv. durum hybrids created a new cereal with favorable characteristics for planting: the hexaploid tritordeum (X Tritordeum Ascherson et Graebner). A field experiment with three replications was carried out in Cordoba, Spain, to obtain more information on the potential yield of tritordeum for grain yield and its components. The performance of two advanced tritordeums was compared with the yield of two commercial wheat varieties, two durum wheats and four triticales. Results showed that tritordeum has a great potential for the development of highly productive varieties, especially because it is a new and rarely bred specie

Vergleich der muttergebundenen und der künstlichen Aufzucht in Bezug auf Gesundheit, Gewichtsentwicklung und chronischen Stress bei Milchviehkälbern

In artificial rearing, calves are separated from their dam usually within 24h after birth and any further social contacts to the mother are prevented. Although this is common in practice we expect severe consequences on the health state, weight gain and stress response of the young calf. Two groups of calves suckled by their mother (unrestricted contact, n=14; contact twice daily for 15 minutes each before milking, n=15) were compared to two control groups that were both fed via automatic milk feeder (maximal six times daily, n=14; twice daily, n=14). The calves of the four treatment groups were kept in the same barn and cows were milked twice daily. All calves were weaned at 13 weeks of age. The calves were weighed weekly until 3 weeks after weaning. The health state of each animal was assessed daily and all veterinary treatments were recorded until weaning. Stress response to a long-term stressor (absence of the mother) was assessed by stimulation of the HPA axis by ACTH administration (at 11 weeks of age). For statistical analyses, linear mixed-effects models were used. The health state of both suckled groups was poorer (p=0.046, caused by diarrhoea), but the number of animals that had to be treated by a veterinarian did not differ. During the milk feeding period, weight gain was better in suckled calves (p<0.001). After weaning, the weight gain of all treatment groups was diminished, especially in suckled calves (p<0.001). Cortisol response to ACTH administration was reduced in calves fed via an automatic milk feeder (p<0.001). The higher weight gain in suckled calves before weaning can be explained by the large milk amounts the calves received. These results suggest that suckled calves show fewer signs of chronic stress. We conclude that rearing without contact with the mother causes chronic stress in young calves in terms of desensitization of the HPA axis