39,500 research outputs found
DNALinux Virtual Desktop Edition
The new version of DNALinux (VDE) is presented. DNALinux VDE is a departure from traditional distributions since it uses a virtual machine to bundle together the operating system and bioinformatics applications. The main advantage of this approach is that a virtualized environment doesn't affect a installed system. With a virtual machine a Linux system can be run under a Windows system, provided that the virtual machine player is installed. The included programs are listed and specifications to add more programs are explained. We believe that DNALinux could be used as a standardized virtual machine for learning, using, developing and testing bioinformatics applications
Line-of-sight velocity distributions of elliptical galaxies from collisionless mergers
We analyse the skewness of the line-of-sight velocity distributions in model
elliptical galaxies built through collisionless galaxy mergers. We build the
models using large N-body simulations of mergers between either two spiral or
two elliptical galaxies. Our aim is to investigate whether the observed ranges
of skewness coefficient (h3) and the rotational support (V/sigma), as well as
the anticorrelation between h3 and V, may be reproduced through collisionless
mergers. Previous attempts using N-body simulations failed to reach V/sigma ~
1-2 and corresponding high h3 values, which suggested that gas dynamics and
ensuing star formation might be needed in order to explain the skewness
properties of ellipticals through mergers. Here we show that high V/sigma and
high h3 are reproduced in collisionless spiral-spiral mergers whenever a
central bulge allows the discs to retain some of their original angular
momentum during the merger. We also show that elliptical-elliptical mergers,
unless merging from a high-angular momentum orbit, reproduce the strong
skewness observed in non-rotating, giant, boxy ellipticals. The behaviour of
the h3 coefficient therefore associates rapidly-rotating disky ellipticals to
disc-disc mergers, and associates boxy, slowly-rotating giant ellipticals to
elliptical-elliptical mergers, a framework generally consistent with the
expectations of hierarchical galaxy formation.Comment: 5 pages, 4 figures, MNRAS Letters, in pres
Statistical tests of sterile neutrinos using cosmology and short-baseline data
In this paper we revisit the question of the information which cosmology
provides on the scenarios with sterile neutrinos invoked to describe the SBL
anomalies using Bayesian statistical tests. We perform an analysis of the
cosmological data in CDM cosmologies for different
cosmological data combinations, and obtain the marginalized cosmological
likelihood in terms of the two relevant parameters, the sterile neutrino mass
and its contribution to the energy density of the early Universe . We then present an analysis to quantify at which level a model with one
sterile neutrino is (dis)favoured with respect to a model with only three
active neutrinos, using results from both short-baseline experiments and
cosmology. We study the dependence of the results on the cosmological data
considered, in particular on the inclusion of the recent BICEP2 results and the
SZ cluster data from the Planck mission. We find that only when the cluster
data is included the model with one extra sterile neutrino can become more
favoured that the model with only the three active ones provided the sterile
neutrino contribution to radiation density is suppressed with respect to the
fully thermalized scenario. We have also quantified the level of
(in)compatibility between the sterile neutrino masses implied by the
cosmological and SBL results.Comment: 23 pages, 4 figure
Scattering processes could distinguish Majorana from Dirac neutrinos
It is well known that Majorana neutrinos have a pure axial neutral current
interaction while Dirac neutrinos have the standard vector-axial interaction.
In spite of this crucial difference, usually Dirac neutrino processes differ
from Majorana processes by a term proportional to the neutrino mass, resulting
in almost unmeasurable observations of this difference. In the present work we
show that once the neutrino polarization evolution is considered, there are
clear differences between Dirac and Majorana scattering on electrons. The
change of polarization can be achieved in astrophysical environments with
strong magnetic fields. Furthermore, we show that in the case of unpolarized
neutrino scattering onto polarized electrons, this difference can be relevant
even for large values of the neutrino energy.Comment: 12 pages, 5 figure
Ground State Properties of Anderson Impurity in a Gapless Host
Using the Bethe ansatz method, we study the ground state properties of a
Anderson impurity in a ``gapless'' host, where a density of band
states vanishes at the Fermi level as . As
in metals, the impurity spin is proven to be screened at arbitrary parameters
of the system. However, the impurity occupancy as a function of the bare
impurity energy is shown to acquire novel qualitative features which
demonstrate a nonuniversal behavior of the system. The latter explains why the
Kondo screening is absent (or exists only at quite a large electron-impurity
coupling) in earlier studies based on scaling arguments.Comment: 5 pages, no figure, RevTe
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