200 research outputs found
Specific heat at the transition in a superconductor with fluctuating magnetic moments
In the heavy-fermion materials CeCoIn and UBe, the superconducting
order parameter is coupled to flucutating magnetization of the uncompensated
part of the localized -moments. We find that this coupling decreases the
superconducting transition temperature and increases the jump of the
specific-heat coefficient, which indicates entropy transfer from the magnetic
to the superconducting degree of freedom at the transition temperature. Below
the transition, we find that the magnetic fluctuations are suppressed. We
discuss the relation of our results to experiments on CeCoIn under
pressure.Comment: 4 pages, 1 figur
The Gradient Expansion for the Free-Energy of a Clean Superconductor
We describe a novel method for obtaining the gradient expansion for the free
energy of a clean BCS superconductor. We present explicit results up to fourth
order in the gradients of the order parameter.Comment: 33 pages, Late
Cryopreservation and cryotherapy of grapevine (Vitis vinifera L.)
This study aimed at testing the efficiency of a droplet-vitrification cryopreservation protocol in eliminating selected grapevine viruses. The cryopreservation protocol led to approximately 50 % recovery with cultivar 'Portan' and five international cultivars tested, but very low recovery was noted with Croatian cultivars. GFLV and GLRaV-3, two (economically important grapevine) viruses were eliminated in a high percentage (up to 100 %) of plants regenerated from cryopreserved shoot tips. Virus sanitation was observed as well in samples before liquid nitrogen exposure. Genetic stability of plants regenerated after cryopreservation was studied using AFLP markers. Polymorphic fragments were observed in non-cryopreserved and cryopreserved samples treated with PVS2 solution, the number of which increased with increasing durations of exposure to PVS2 solution
Free Energy of an Inhomogeneous Superconductor: a Wave Function Approach
A new method for calculating the free energy of an inhomogeneous
superconductor is presented. This method is based on the quasiclassical limit
(or Andreev approximation) of the Bogoliubov-de Gennes (or wave function)
formulation of the theory of weakly coupled superconductors. The method is
applicable to any pure bulk superconductor described by a pair potential with
arbitrary spatial dependence, in the presence of supercurrents and external
magnetic field. We find that both the local density of states and the free
energy density of an inhomogeneous superconductor can be expressed in terms of
the diagonal resolvent of the corresponding Andreev Hamiltonian, resolvent
which obeys the so-called Gelfand-Dikii equation. Also, the connection between
the well known Eilenberger equation for the quasiclassical Green's function and
the less known Gelfand-Dikii equation for the diagonal resolvent of the Andreev
Hamiltonian is established. These results are used to construct a general
algorithm for calculating the (gauge invariant) gradient expansion of the free
energy density of an inhomogeneous superconductor at arbitrary temperatures.Comment: REVTeX, 28 page
The circumburst density profile around GRB progenitors: a statistical study
According to our present understanding, long GRBs originate from the collapse
of massive stars while short bursts are due to the coalescence of compact
stellar objects. Since the afterglow evolution is determined by the circumburst
density profile, n(r), traversed by the fireball, it can be used to distinguish
between a so-called ISM profile, n(r) = const., and a free stellar wind, . Our goal is to derive the most probable circumburst density
profile for a large number of Swift-detected bursts using well-sampled
afterglow light curves in the optical and X-ray bands. We combined all publicly
available optical and Swift/X-ray afterglow data from June 2005 to September
2009 to find the best-sampled late-time afterglow light curves. After applying
several selection criteria, our final sample consists of 27 bursts, including
one short burst. The afterglow evolution was then studied within the framework
of the fireball model. We find that the majority (18) of the 27 afterglow light
curves are compatible with a constant density medium (ISM case). Only 6 of the
27 afterglows show evidence for a wind profile at late times. In particular, we
set upper limits on the wind termination-shock radius, , for GRB fireballs
which are propagating into an ISM profile and lower limits on for those
which were found to propagate through a wind medium. Observational evidence for
ISM profiles dominates in GRB afterglow studies, implying that most GRB
progenitors might have relatively small wind termination-shock radii. A smaller
group of progenitors, however, seems to be characterised by notably more
extended wind regions.Comment: A&A, accepted (Oct 26, 2010); 20 pages in journal format; 6 pages
main text, 13 pages Appendix, 1 page references, 6 tables and 2 figures;
included comments by the referee and language editor; removed grey colouring
of the table
Quantitative trait loci affecting pathogen resistance and ripening of grapevines
Grapevines (Vitis vinifera L.) form the basis of
viticulture, and are susceptible to diseases such as downy
mildew (Plasmopara viticola) and powdery mildew (Erysiphe necator). Therefore, successful viticulture programs
require the use of pesticides. Breeding for resistance is the
only eco-friendly solution. Marker-assisted selection is currently widely used for grapevine breeding. Consequently,
traits of interest must be tagged with molecular markers
linked to quantitative trait loci (QTL). We herein present
our findings regarding genetic mapping and QTL analysis of resistance to downy and powdery mildew diseases
in the progenies of the GF.GA-47-42 (‘Bacchus’ × ‘Seyval’) × ‘Villard blanc’ cross. Simple sequence repeats and
single nucleotide polymorphisms of 151 individuals were
analyzed. A map consisting of 543 loci was screened for
QTL analyses based on phenotypic variations observed in
plants grown in the field or under controlled conditions. A
major QTL for downy mildew resistance was detected on
chromosome 18. For powdery mildew resistance, a QTL was identified on chromosome 15. This QTL was replaced
by a novel QTL on chromosome 18 in 2003 (abnormally
high temperatures) and 2004. Subsequently, both QTLs
functioned together. Additionally, variations in the timing of the onset of veraison, which is a crucial step during
grape ripening, were studied to identify genomic regions
affecting this trait. A major QTL was detected on linkage
group 16, which was supplemented by a minor QTL on
linkage group 18. This study provides useful information
regarding novel QTL-linked markers relevant for the breeding of disease-resistant grapevines adapted to current climatic conditions
Author Correction: A consensus-based transparency checklist.
An amendment to this paper has been published and can be accessed via a link at the top of the paper
A possible bright blue SN in the afterglow of GRB 020305
We report on ground-based and HST(+STIS) imaging of the afterglow and host
galaxy of the Gamma-Ray Burst (GRB) of March 5 2002. The GRB occurred in a
R=25.17+/-0.14 galaxy, which apparently is part of an interacting system. The
lightcurve of the optical afterglow shows a rebrightening, or at least a
plateau, 12--16 days after the gamma-ray event. UBVRIK' multi-band imaging of
the afterglow ~12 days after the GRB reveals a blue spectral energy
distribution (SED). The SED is consistent with a power-law with a spectral
index of \beta=-0.63+/-0.16, but there is tentative evidence for deviations
away from a power-law. Unfortunately, a spectroscopic redshift has not been
secured for GRB020305. From the SED we impose a redshift upper limit of z ~<
2.8, hence excluding the pseudo redshift of 4.6 reported for this burst. We
discuss the possibilities for explaining the lightcurve, SED and host galaxy
properties for GRB 020305. The most natural interpretation of the lightcurve
and the SED is an associated supernova (SN). Our data can not precisely
determine the redshift of the GRB. The most favoured explanation is a low
redshift (z~0.2) SN, but a higher redshift (z>0.5) SN can not be excluded. We
also discuss less likely scenarios not based on SNe, like a burst occurring in
a z=2.5 galaxy with an extinction curve similar to that of the Milky Way.Comment: Accepted for publication in A&A. 8 pages, 5 figure
A consensus-based transparency checklist
We present a consensus-based checklist to improve and document the transparency of research reports in social and behavioural research. An accompanying online application allows users to complete the form and generate a report that they can submit with their manuscript or post to a public repository
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