7,214 research outputs found
The ATLAS-SPT Radio Survey of Cluster Galaxies
Using a high-performance computing cluster to mosaic 4,787 pointings, we have
imaged the 100 sq. deg. South Pole Telescope (SPT) deep-field at 2.1 GHz using
the Australian Telescope Compact Array to an rms of 80 Jy and a resolution
of 8". Our goal is to generate an independent sample of radio-selected galaxy
clusters to study how the radio properties compare with cluster properties at
other wavelengths, over a wide range of redshifts in order to construct a
timeline of their evolution out to . A preliminary analysis of the
source catalogue suggests there is no spatial correlation between the clusters
identified in the SPT-SZ catalogue and our wide-angle tail galaxies.Comment: 9 pages, 4 figures. Submitted to Proceedings of Science for "The many
facets of extragalactic radio surveys: towards new scientific challenges",
Bologna, Italy 20-23 October 2015 (EXTRA-RADSUR2015
The Spatial Correlation of Bent-Tail Galaxies and Galaxy Clusters
We have completed a deep radio continuum survey covering 86 square degrees of
the Spitzer-South Pole Telescope deep field to test whether bent-tail galaxies
are associated with galaxy clusters. We present a new catalogue of 22 bent-tail
galaxies and a further 24 candidate bent-tail galaxies. Surprisingly, of the 8
bent-tail galaxies with photometric redshifts, only two are associated with
known clusters. While the absence of bent-tail sources in known clusters may be
explained by effects such as sensitivity, the absence of known clusters
associated with most bent-tail galaxies casts doubt upon current models of
bent-tail galaxies.Comment: Accepted by MNRA
Elastic moduli approximation of higher symmetry for the acoustical properties of an anisotropic material
The issue of how to define and determine an optimal acoustical fit to a set
of anisotropic elastic constants is addressed. The optimal moduli are defined
as those which minimize the mean squared difference in the acoustical tensors
between the given moduli and all possible moduli of a chosen higher material
symmetry. The solution is shown to be identical to minimizing a Euclidean
distance function, or equivalently, projecting the tensor of elastic stiffness
onto the appropriate symmetry. This has implications for how to best select
anisotropic constants to acoustically model complex materials.Comment: 20 page
Infrared-Faint Radio Sources: A New Population of High-redshift Radio Galaxies
We present a sample of 1317 Infrared-Faint Radio Sources (IFRSs) that, for
the first time, are reliably detected in the infrared, generated by
cross-correlating the Wide-Field Infrared Survey Explorer (WISE) all-sky survey
with major radio surveys. Our IFRSs are brighter in both radio and infrared
than the first generation IFRSs that were undetected in the infrared by the
Spitzer Space Telescope. We present the first spectroscopic redshifts of IFRSs,
and find that all but one of the IFRSs with spectroscopy has z > 2. We also
report the first X-ray counterparts of IFRSs, and present an analysis of radio
spectra and polarization, and show that they include Gigahertz-Peaked Spectrum,
Compact Steep Spectrum, and Ultra-Steep Spectrum sources. These results,
together with their WISE infrared colours and radio morphologies, imply that
our sample of IFRSs represents a population of radio-loud Active Galactic
Nuclei at z > 2. We conclude that our sample consists of lower-redshift
counterparts of the extreme first generation IFRSs, suggesting that the fainter
IFRSs are at even higher redshift.Comment: 23 pages, 17 figures. Submitted to MNRA
Hysteretic ac losses in a superconductor strip between flat magnetic shields
Hysteretic ac losses in a thin, current-carrying superconductor strip located
between two flat magnetic shields of infinite permeability are calculated using
Bean's model of the critical state. For the shields oriented parallel to the
plane of the strip, penetration of the self-induced magnetic field is enhanced,
and the current dependence of the ac loss resembles that in an isolated
superconductor slab, whereas for the shields oriented perpendicular to the
plane of the strip, penetration of the self-induced magnetic field is impaired,
and the current dependence of the ac loss is similar to that in a
superconductor strip flanked by two parallel superconducting shields. Thus,
hysteretic ac losses can strongly augment or, respectively, wane when the
shields approach the strip.Comment: 9 pages, 5 figures, submitted to PR
Radio galaxies and their magnetic fields out to z <= 3
We present polarisation properties at GHz of two separate
extragalactic source populations: passive quiescent galaxies and luminous
quasar-like galaxies. We use data from the {\it Wide-Field Infrared Survey
Explorer} data to determine the host galaxy population of the polarised
extragalactic radio sources. The quiescent galaxies have higher percentage
polarisation, smaller radio linear size, and GHz luminosity of
W Hz, while the quasar-like
galaxies have smaller percentage polarisation, larger radio linear size at
radio wavelengths, and a GHz luminosity of W Hz, suggesting that the environment of the
quasar-like galaxies is responsible for the lower percentage polarisation. Our
results confirm previous studies that found an inverse correlation between
percentage polarisation and total flux density at GHz. We suggest that
the population change between the polarised extragalactic radio sources is the
origin of this inverse correlation and suggest a cosmic evolution of the space
density of quiescent galaxies. Finally, we find that the extragalactic
contributions to the rotation measures (RMs) of the nearby passive galaxies and
the distant quasar-like galaxies are different. After accounting for the RM
contributions by cosmological large-scale structure and intervening Mg\,{II}
absorbers we show that the distribution of intrinsic RMs of the distant
quasar-like sources is at most four times as wide as the RM distribution of the
nearby quiescent galaxies, if the distribution of intrinsic RMs of the
WISE-Star sources itself is at least several rad m wide.Comment: 12 pages, 8 figures, accepted for publication into MNRA
Orbital flight effects on calcium kinetics and fracture healing Final report
Orbital flight effects on calcium kinetics and fracture healin
Severe Antiretroviral Therapy-Induced Toxic Epidermal Necrolysis in a Child
Toxic epidermal necrolysis (TEN) is a rare and life-threatening condition characterised by extensive epidermal detachment and mucosal erosion. Adverse drug reaction is a strongly correlated causative factor and TEN is currently considered the most severe end of a spectrum of drug-induced mucocutaneous diseases, including Stevens-Johnson syndrome. Attaining an accurate and detailed patient history is critical for identifying potential causative agents, which can prove challenging; particularly in cultures such as that of Malawi. TEN lacks definitive management and the use of immunomodulation, such as with corticosteroids and intravenous immunoglobulin, remains controversial. We report a fascinating case of TEN associated with antiretroviral therapy. A 10-year-old female was given a combination of antiretroviral drugs (lamivudine, nevirapine and stavudine) as postexposure prophylaxis, having been raped. The child subsequently developed TEN and presented to our remote hospital in Malawi, where she was treated entirely with supportive therapy. This is an excellent example of difficult disease management in a limited-resource setting and provides reassuring evidence to clinicians of similar circumstance. To our knowledge, this is the first case report of antiretroviral therapy-induced TEN in a child
Twenty eight years of ICP Vegetation: an overview of its activities
Here we look back at the activities and achievements in the 28 years of the International Cooperative Programme on the Effects of Air Pollution on Natural Vegetation and Crops (ICP Vegetation). The ICP Vegetation is a subsidiary body of the Working Group on Effects of the UNECE Convention on Long-range Transboundary Air Pollution (LTRAP), established in 1979. An important role of the ICP Vegetation is to provide evidence for air pollution impacts on vegetation in support of policy development and review of the LRTAP Convention and its Protocols. The activities and participation in the ICP Vegetation have grown over the years. The main activities include:
• Collate evidence of ozone impacts on vegetation, assess spatial patterns and temporal trends across Europe;
• Develop dose-response relationships, establish critical levels for vegetation and provide European risk maps of ozone impacts;
• Reviewing the literature on ozone impacts on vegetation and produce thematic scientific reports and policy-relevant brochures;
• Determine spatial patterns and temporal trends of heavy metals, nitrogen and persistent organic pollutants concentrations in mosses as a biomonitoring tool of atmospheric deposition of these compounds
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