5,422 research outputs found
Cassiopeia A: dust factory revealed via submillimetre polarimetry
If Type-II supernovae - the evolutionary end points of short-lived, massive
stars - produce a significant quantity of dust (>0.1 M_sun) then they can
explain the rest-frame far-infrared emission seen in galaxies and quasars in
the first Gyr of the Universe. Submillimetre observations of the Galactic
supernova remnant, Cas A, provided the first observational evidence for the
formation of significant quantities of dust in Type-II supernovae. In this
paper we present new data which show that the submm emission from Cas A is
polarised at a level significantly higher than that of its synchrotron
emission. The orientation is consistent with that of the magnetic field in Cas
A, implying that the polarised submm emission is associated with the remnant.
No known mechanism would vary the synchrotron polarisation in this way and so
we attribute the excess polarised submm flux to cold dust within the remnant,
providing fresh evidence that cosmic dust can form rapidly. This is supported
by the presence of both polarised and unpolarised dust emission in the north of
the remnant, where there is no contamination from foreground molecular clouds.
The inferred dust polarisation fraction is unprecedented (f_pol ~ 30%) which,
coupled with the brief timescale available for grain alignment (<300 yr),
suggests that supernova dust differs from that seen in other Galactic sources
(where f_pol=2-7%), or that a highly efficient grain alignment process must
operate in the environment of a supernova remnant.Comment: In press at MNRAS, 10 pages, print in colou
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Draft Genome Sequences of Four Saccharibacter sp. Strains Isolated from Native Bees.
The genus Saccharibacter is currently understudied, with only one described species, Saccharibacter floricola, isolated from a flower. In an effort to better understand the microbes that come in contact with native bee pollinators, we isolated and sequenced four additional strains of Saccharibacter from native bees in the genera Melissodes and Anthophora These genomes range in size from 2,104,494 to 2,316,791 bp (mean, 2,246,664 bp) and contain between 1,860 and 2,167 (mean, 2,060) protein-coding genes
Particle Impact Analysis of Bulk Powder During Pneumatic Conveyance
Fragmentation of powders during transportation is a common problem for manufacturers of food and pharmaceutical products. We illustrate that the primary cause of breakage is due to inter-particle collisions, rather than particle-wall impacts, and provide a statistical mechanics model giving the number of collisions resulting in fragmentation
Cystic fibrosis mice carrying the missense mutation G551D replicate human genotype phenotype correlations
We have generated a mouse carrying the human G551D mutation in the cystic fibrosis transmembrane conductance regulator gene (CFTR) by a one-step gene targeting procedure. These mutant mice show cystic fibrosis pathology but have a reduced risk of fatal intestinal blockage compared with 'null' mutants, in keeping with the reduced incidence of meconium ileus in G551D patients. The G551D mutant mice show greatly reduced CFTR-related chloride transport, displaying activity intermediate between that of cftr(mlUNC) replacement ('null') and cftr(mlHGU) insertional (residual activity) mutants and equivalent to approximately 4% of wild-type CFTR activity. The long-term survival of these animals should provide an excellent model with which to study cystic fibrosis, and they illustrate the value of mouse models carrying relevant mutations for examining genotype-phenotype correlations
Time Variability in the X-ray Nebula Powered by Pulsar B1509-58
We use new and archival Chandra and ROSAT data to study the time variability
of the X-ray emission from the pulsar wind nebula (PWN) powered by PSR B1509-58
on timescales of one week to twelve years. There is variability in the size,
number, and brightness of compact knots appearing within 20" of the pulsar,
with at least one knot showing a possible outflow velocity of ~0.6c (assuming a
distance to the source of 5.2 kpc). The transient nature of these knots may
indicate that they are produced by turbulence in the flows surrounding the
pulsar. A previously identified prominent jet extending 12 pc to the southeast
of the pulsar increased in brightness by 30% over 9 years; apparent outflow of
material along this jet is observed with a velocity of ~0.5c. However, outflow
alone cannot account for the changes in the jet on such short timescales.
Magnetohydrodynamic sausage or kink instabilities are feasible explanations for
the jet variability with timescale of ~1.3-2 years. An arc structure, located
30"-45" north of the pulsar, shows transverse structural variations and appears
to have moved inward with a velocity of ~0.03c over three years. The overall
structure and brightness of the diffuse PWN exterior to this arc and excluding
the jet has remained the same over the twelve year span. The photon indices of
the diffuse PWN and possibly the jet steepen with increasing radius, likely
indicating synchrotron cooling at X-ray energies.Comment: accepted to ApJ, 14 pages, 8 figure
Adapting primary care for new migrants: a formative assessment
Background: Immigration rates have increased recently in the UK. Migrant patients may have
particular needs that are inadequately met by existing primary care provision. In the absence of
national guidance, local adaptations are emerging in response to these new demands.
Aim: To formatively assess the primary care services offered to new migrants and the ways in which
practitioners and practices are adapting to meet need.
Design & setting: Online survey and case studies of current practice across primary care in the UK.
Case studies were selected from mainstream and specialist general practice as well as primary care
provision in the third sector.
Method: Non-probability sample survey of primary care practitioners (n = 70) with descriptive
statistical analysis. Qualitative case studies (n = 8) selected purposively; in-depth exploration of
organisational and practitioner adaptations to services. Analysis is structured around the principles
of equitable care.
Results: Survey results indicated that practitioners focused on working with communities and
external agencies and adapting processes of, for example, screening, vaccination, and health
checks. Lack of funding was cited most frequently as a barrier to service development (n = 51;
73%). Case studies highlighted the prominence partnership working and of an organisational and
practitioner focus on equitable care. Adaptations centred on addressing wider social determinants,
trauma, and violence, and additional individual needs; and on delivering culturally-competent care.
Conclusion: Despite significant resource constraints, some primary care services are adapting to
the needs of new migrants. Many adapted approaches can be characterised as equity-oriented
The Identification of Infrared Synchrotron Radiation from Cassiopeia A
We report the discovery of polarized flux at 2.2 micron from the bright shell
of the approximately 320 year old supernova remnant Cas A. The fractional
polarizations are comparable at 6 cm and 2.2 micron, and the polarization
angles are similar, demonstrating that synchrotron radiation from the same
relativistic plasma is being observed at these widely separated wavebands. The
relativistic electrons radiating at 2.2 micron have an energy of ~ 150 GeV,
(gamma ~ 3e5), assuming an ~500 microGauss magnetic field. The total intensity
at 2.2 micron lies close to the power law extrapolation from radio frequencies,
showing that relativistic particle acceleration is likely an ongoing process;
the infrared emitting electrons were accelerated no longer than ~80 years ago.
There is a small but significant concave curvature to the spectrum, as expected
if the accelerating shocks have been modified by the back pressure of the
cosmic rays; given calibration uncertainties, this conclusion must be
considered tentative at present. The 2.2 micron polarization angles and the
emission-line filaments observed by HST are both offset from the local radial
direction by 10 - 20 degrees, providing evidence that the magnetic fields in
Cas A are generated by Rayleigh-Taylor instabilities in the decelerating
ejecta.Comment: 11 pages, 3 figures, accepted for publication Ap
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