Bottom quark electroproduction in variable flavor number schemes

Two variable flavor number schemes are used to describe bottom quark production in deep inelastic electron-proton scattering. In these schemes the coefficient functions are derived from mass factorization of the heavy quark coefficient functions presented in a fixed flavor number scheme. Also one has to construct a parton density set with five light flavors (u,d,s,c,b) out of a set which only contains four light flavors (u,d,s,c). In order $\alpha_s^2$ the two sets are discontinuous at $\mu=m_b$ which follows from mass factorization of the heavy quark coefficient functions when it is carried out in the ${\bar {\rm MS}}$-scheme. Both variable flavor number schemes give almost identical predictions for the bottom structure functions $F_{2,b}$ and $F_{L,b}$. Also they both agree well with the corresponding results based on fixed order four-flavor perturbation theory over a wide range in $x$ and $Q^2$.Comment: Latex with seventeen PostScript figure

An extremely low gas-to-dust ratio in the dust-lane lenticular galaxy NGC 5485

Date of Acceptance: 21/07/2014Peer reviewe

High Pressure Study on MgB2

The hydrostatic pressure effect on the newly discovered superconductor MgB2 has been determined. The transition temperature Tc was found to decrease linearly at a large rate of -1.6 K/GPa, in good quantitative agreement with the ensuing calculated value of -1.4 K/GPa within the BCS framework by Loa and Syassen, using the full-potential linearlized augmented plane-wave method. The relative pressure coefficient, dlnTc/dp, for MgB2 also falls between the known values for conventional sp- and d-superconductors. The observation, therefore, suggests that electron-phonon interaction plays a significant role in the superconductivity of the compound.Comment: 8 pages, 3 figures; submitted to Physical Review B (February 14, 2001; revised March 21, 2001); minor modifications, including a discussion of the preprint by Vogt et a

Comparison between variable flavor number schemes for charm quark electroproduction

Where appropriate, the abbreviation 'VFNS' is replaced by 'CSN' to indicate the scheme using massive heavy quark coefficient functions proposed in this paper. The text below Eq. (2.13) and between Eqs. (2.33) and (2.36) has been considerably changed.Comment: 64 pages, LaTeX, 16 Postscript figure

Arachidonic acid, arachidonic/eicosapentaenoic acid ratio, stearidonic acid and eicosanoids are involved in dietary-induced albinism in Senegal sole (Solea senegalensis)

Senegal sole larvae were fed live prey enriched with different amounts of arachidonic acid (ARA, 20:4n-6) and eicosapentaenoic acid (EPA, 20:5n-3) to re-evaluate the effect of these two fatty acids on flatfish pigmentation. Echium oil, a plant derived oil rich in gamma-linolenic acid (GLA, 18:3n-6) and stearidonic acid (SDA, 18:4n-3) was also used as a component of one of the enrichment emulsions. Although ARA content did not have any effect on growth there was a clear influence on pigmentation that correlated clearly with prostaglandin production. Inclusion of Echium oil, on the contrary, exerted a positive effect on pigmentation rate even though dietary ARA levels were as high as in the other emulsions. The relationships between dietary ARA levels and dietary ARA/EPA ratio, prostaglandin production and pigmentation are discussed

Tau neutrino deep inelastic charged current interactions

The nu_mu -> nu_tau oscillation hypothesis will be tested through nu_tau production of tau in underground neutrino telescopes as well as long-baseline experiments. We provide the full QCD framework for the evaluation of tau neutrino deep inelastic charged current (CC) cross sections, including next-leading-order (NLO) corrections, charm production, tau threshold, and target mass effects in the collinear approximation. We investigate the violation of the Albright-Jarlskog relations for the structure functions F_4,5 which occur only in heavy lepton (tau) scattering. Integrated CC cross sections are evaluated naively over the full phase space and with the inclusion of DIS kinematic cuts. Uncertainties in our evaluation based on scale dependence, PDF errors and the interplay between kinematic and dynamical power corrections are discussed and/or quantified.Comment: 28 pages, 10 figure

Topological Charged Black Holes in High Dimensional Spacetimes and Their Formation from Gravitational Collapse of a Type II Fluid

Topological charged black holes coupled with a cosmological constant in $R^{2}\times X^{D-2}$ spacetimes are studied, where $X^{D-2}$ is an Einstein space of the form ${}^{(D-2)}R_{AB} = k(D-3) h_{AB}$. The global structure for the four-dimensional spacetimes with $k = 0$ is investigated systematically. The most general solutions that represent a Type $II$ fluid in such a high dimensional spacetime are found, and showed that topological charged black holes can be formed from the gravitational collapse of such a fluid. When the spacetime is (asymptotically) self-similar, the collapse always forms black holes for $k = 0, -1$, in contrast to the case $k = 1$, where it can form either balck holes or naked singularities.Comment: 14 figures, to appear in Phys. Rev.

Limit theorems for weakly subcritical branching processes in random environment

For a branching process in random environment it is assumed that the offspring distribution of the individuals varies in a random fashion, independently from one generation to the other. Interestingly there is the possibility that the process may at the same time be subcritical and, conditioned on nonextinction, 'supercritical'. This so-called weakly subcritical case is considered in this paper. We study the asymptotic survival probability and the size of the population conditioned on non-extinction. Also a functional limit theorem is proven, which makes the conditional supercriticality manifest. A main tool is a new type of functional limit theorems for conditional random walks.Comment: 35 page

Compressibility and Electronic Structure of MgB2 up to 8 GPa

The lattice parameters of MgB2 up to pressures of 8 GPa were determined using high-resolution x-ray powder diffraction in a diamond anvil cell. The bulk modulus, B0, was determined to be 151 +-5 GPa. Both experimental and first-principles calculations indicate nearly isotropic mechanical behavior under pressure. This small anisotropy is in contrast to the 2 dimensional nature of the boron pi states. The pressure dependence of the density of states at the Fermi level and a reasonable value for the average phonon frequency account within the context of BCS theory for the reduction of Tc under pressure.Comment: REVTeX file. 4 pages, 4 figure

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure