5,335 research outputs found

    Field monitoring of expansive soil behaviour in the Newcastle-Hunter region

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    Cassiopeia A: dust factory revealed via submillimetre polarimetry

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    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

    Cystic fibrosis mice carrying the missense mutation G551D replicate human genotype phenotype correlations

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    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

    Particle Impact Analysis of Bulk Powder During Pneumatic Conveyance

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    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

    Time Variability in the X-ray Nebula Powered by Pulsar B1509-58

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    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

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    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

    New Migrants in Primary Healthcare - How are services adapting? Summary and Mini Case Book

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    The Identification of Infrared Synchrotron Radiation from Cassiopeia A

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    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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