4,561 research outputs found
Chandra Observation of the X-Ray Source Population of NGC 6946
We present the results of a study of discrete X-ray sources in NGC 6946 using
a deep Chandra ACIS observation. Based on the slope of the log N-log S
distribution and the general correlation of sources with the spiral arms, we
infer that the overall discrete source sample in NGC 6946 is dominated by high
mass X-ray binaries, in contrast to the source distributions in M31 and the
Milky Way. This is consistent with the higher star formation rate in NGC 6946
than in those galaxies. We find that the strong X-ray sources in the region of
the galactic center do not correlate in detail with images of the region in the
near-IR, although one of them may be coincident with the galactic center. The
non-central ultra-luminous X-ray source in NGC 6946, previously identified with
a supernova remnant, has an X-ray spectrum and luminosity that is inconsistent
with either a traditional pulsar wind nebula or a blast wave remnant.Comment: accepted Ap
Chandra Detection of the Forward and Reverse Shocks in Cassiopeia-A
We report the localization of the forward and reversed shock fronts in the
young supernova remnant Cas-A using X-ray data obtained with the Chandra
Observatory. High resolution X-ray maps resolve a previously unseen X-ray
feature encompassing the extremity of the remnant. This feature consists of
thin, tangential wisps of emission bordering the outer edge of the thermal
X-ray and radio remnant, forming a circular rim, approx. 2.7 in radius. Radio
images show a sharp rise in brightness at this X-ray rim, along with a large
jump in the synchrotron polarization angle. These characteristics suggest that
these wisps are the previously unresolved signature of the forward, or outer,
shock. Similarly, we identify the sharp rise in emissivity of the bright shell
for both the radio and X-ray line emission associated with the reverse shock.
The derived ratio of the averaged forward and reverse shock radii of approx.
3:2 constrains the remnant to have swept up roughly the same amount of mass as
was ejected; this suggests that Cas-A is just entering the Sedov phase.
Comparison of the X-ray spectra from the two shock regions shows that the
equivalent widths of prominent emission lines are significantly lower exterior
to the bright shell, as expected if they are respectively identified with the
shocked circumstellar material and shocked ejecta. Furthermore, the spectrum of
the outer rim itself is dominated by power-law emission, likely the counterpart
of the non-thermal component previously seen at energies above 10 keV.Comment: 7 pages with 5 figures, LaTex, emulateapj.sty. To appear in the
Astrophysical Journal Letter
BPEX Pig Health Scheme: a useful monitoring system for respiratory disease control in pig farms?
<p>Abstract</p> <p>Background</p> <p>Respiratory diseases account for significant economic losses to the UK pig industry. Lesions indicative of respiratory disease in pig lungs at slaughter e.g. pneumonia and pleuritis are frequently recorded to assess herd health or provide data for epidemiological studies. The BPEX Pig Health Scheme (BPHS) is a monitoring system, which informs producers of gross lesions in their pigs' carcasses at slaughter, enabling farm-level decisions to be made. The aim of the study was to assess whether information provided by the BPHS regarding respiratory lesions was associated with respiratory pathogens in the farm, farm management practices and each other.</p> <p>Results</p> <p>BPHS reports were obtained from a subset of 70 pig farms involved in a cross-sectional study conducted in 2008-09 investigating the epidemiology of post-weaning multi-systemic wasting syndrome. The reports were combined with data regarding the presence/absence of several pathogens in the herd and potential farm-level risk factors for respiratory disease. Principal component analysis (PCA) performed on BPHS reports generated three principal components, explaining 71% of the total variance. Enzootic pneumonia score, severe pleurisy and acute pleuropneumonia had the highest loadings for the principal component which explained the largest percentage of the total variance (35%) (BPHS component 1), it was thought that this component identifies farms with acute disease. Using the factor loadings a score for each farm for BPHS component 1 was obtained. As farms' score for BPHS component 1 increased, average carcass weight at slaughter decreased. In addition, farms positive for H1N2 and porcine reproductive and respiratory disease virus (PRRSV) were more likely to have higher levels of severe and mild pleurisy reported by the BPHS, respectively.</p> <p>Conclusions</p> <p>The study found statistical associations between levels of pleurisy recorded by BPHS at slaughter and the presence H1N2 and PRRSV in the herd. There is also some evidence that farms which submit pigs with these lesions may have reduced productivity. However, more research is needed to fully validate the scheme.</p
D 3.1 Guidance for scoring levels of risk supplied via hypertext links within each component of the web-based EPPO PRA scheme
Positive youth development in swimming: clarification and consensus of key psychosocial assets
The purpose of this study was to gain a more cohesive understanding of the assets considered necessary to develop in young swimmers to ensure both individual and sport specific development. This two stage study involved (a) a content analysis of key papers to develop a list of both psychosocial skills for performance enhancement and assets associated with positive youth development, and (b) in-depth interviews involving ten expert swim coaches, practitioners and youth sport scholars. Five higher order categories containing seventeen individual assets emerged. These results are discussed in relation to both existing models of positive youth development and implications for coaches, practitioners and parents when considering the psychosocial development of young British swimmers
Liver-Targeting of Interferon-Alpha with Tissue-Specific Domain Antibodies
PMCID: PMC3581439This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Precision mass measurements of magnesium isotopes and implications on the validity of the Isobaric Mass Multiplet Equation
If the mass excess of neutron-deficient nuclei and their neutron-rich mirror
partners are both known, it can be shown that deviations of the Isobaric Mass
Multiplet Equation (IMME) in the form of a cubic term can be probed. Such a
cubic term was probed by using the atomic mass of neutron-rich magnesium
isotopes measured using the TITAN Penning trap and the recently measured
proton-separation energies of Cl and Ar. The atomic mass of
Mg was found to be within 1.6 of the value stated in the Atomic
Mass Evaluation. The atomic masses of Mg were measured to be both
within 1, while being 8 and 34 times more precise, respectively. Using
the Mg mass excess and previous measurements of Cl we uncovered a
cubic coefficient of = 28(7) keV, which is the largest known cubic
coefficient of the IMME. This departure, however, could also be caused by
experimental data with unknown systematic errors. Hence there is a need to
confirm the mass excess of S and the one-neutron separation energy of
Cl, which have both come from a single measurement. Finally, our results
were compared to ab initio calculations from the valence-space in-medium
similarity renormalization group, resulting in a good agreement.Comment: 7 pages, 3 figure
Family of Hermitian Low-Momentum Nucleon Interactions with Phase Shift Equivalence
Using a Schmidt orthogonalization transformation, a family of Hermitian
low-momentum NN interactions is derived from the non-Hermitian Lee-Suzuki (LS)
low-momentum NN interaction. As special cases, our transformation reproduces
the Hermitian interactions for Okubo and Andreozzi. Aside from their common
preservation of the deuteron binding energy, these Hermitian interactions are
shown to be phase shift equivalent, all preserving the empirical phase shifts
up to decimation scale Lambda. Employing a solvable matrix model, the Hermitian
interactions given by different orthogonalization transformations are studied;
the interactions can be very different from each other particularly when there
is a strong intruder state influence. However, because the parent LS
low-momentum NN interaction is only slightly non-Hermitian, the Hermitian
low-momentum nucleon interactions given by our transformations, including the
Okubo and Andreozzi ones, are all rather similar to each other. Shell model
matrix elements given by the LS and several Hermitian low-momentum interactions
are compared.Comment: 10 pages, 7 figure
Recurrent De Novo NAHR Reciprocal Duplications in the ATAD3 Gene Cluster Cause a Neurogenetic Trait with Perturbed Cholesterol and Mitochondrial Metabolism.
Recent studies have identified both recessive and dominant forms of mitochondrial disease that result from ATAD3A variants. The recessive form includes subjects with biallelic deletions mediated by non-allelic homologous recombination. We report five unrelated neonates with a lethal metabolic disorder characterized by cardiomyopathy, corneal opacities, encephalopathy, hypotonia, and seizures in whom a monoallelic reciprocal duplication at the ATAD3 locus was identified. Analysis of the breakpoint junction fragment indicated that these 67 kb heterozygous duplications were likely mediated by non-allelic homologous recombination at regions of high sequence identity in ATAD3A exon 11 and ATAD3C exon 7. At the recombinant junction, the duplication allele produces a fusion gene derived from ATAD3A and ATAD3C, the protein product of which lacks key functional residues. Analysis of fibroblasts derived from two affected individuals shows that the fusion gene product is expressed and stable. These cells display perturbed cholesterol and mitochondrial DNA organization similar to that observed for individuals with severe ATAD3A deficiency. We hypothesize that the fusion protein acts through a dominant-negative mechanism to cause this fatal mitochondrial disorder. Our data delineate a molecular diagnosis for this disorder, extend the clinical spectrum associated with structural variation at the ATAD3 locus, and identify a third mutational mechanism for ATAD3 gene cluster variants. These results further affirm structural variant mutagenesis mechanisms in sporadic disease traits, emphasize the importance of copy number analysis in molecular genomic diagnosis, and highlight some of the challenges of detecting and interpreting clinically relevant rare gene rearrangements from next-generation sequencing data
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