248 research outputs found
Linearisation Instabilities of the Massive Nonsymmetric Gravitational Theory
The massive nonsymmetric gravitational theory is shown to posses a
linearisation instability at purely GR field configurations, disallowing the
use of the linear approximation in these situations. It is also shown that
arbitrarily small antisymmetric sector Cauchy data leads to singular evolution
unless an ad hoc condition is imposed on the initial data hypersurface.Comment: 14 pages, IOP style for submission to CQG. Minor changes and
additional background material adde
The effect of lutein intake on macular pigment density
Age related macular degeneration (AMD) is a sight-threatening retinal disease found predominately in men and women over 65 years of age. AMD is thought to result from oxidative damage to the retina triggered by UV and blue light. Recent studies have suggested the onset and progression of AMD may be delayed by diet supplementation with antioxidants like lutein and zeaxanthin which are found in the macular area as the macular pigments. The density of the macular pigments can be quantified using heterochromic flicker photometry. In this study, 29 optometry students, between the ages of 22 and 30, were divided into groups. Group one, the control group, experienced no intervention, group two took 4 mg of lutein daily for 30 days and group three ingested 0.75 ounces of spinach daily for 30 days. The macular pigment density was assessed at baseline before any intervention, after 30 days of supplementation and again 30 days after discontinuing supplementation. Neither lutein nor spinach increased the macular pigment density in this study
Chemical Residue in Irish Farmed Finfish, 2011
The following organisations and people within them, made valuable contributions in assisting with the delivery of 2011 residue monitoring programme for farmed finfish: Department of Agriculture, Food & Marine; Food Safety Authority of Ireland; Sea-Fisheries Protection Authority; The ongoing co-operation of the aquaculture industry.On behalf of the Department of Agriculture, Food and Marine (DAFM), the Marine Institute carries out monitoring of chemical residues in aquaculture in accordance with Council Directive 96/23/EC of 29 April 1996, on measures to monitor certain substances
and residues thereof in animals and animal products. The main objectives of the Aquaculture National Residue Control Plan (NRCP) is to ensure farmed fish are fit for
human consumption, to provide a body of data showing that Irish farmed fish is of high
quality, to promote good practices in aquaculture and to comply with EU Directive
96/23.
In 2011, in excess of 630 tests and 1,566 individual measurements for substances were
carried out on 140 samples of farmed finfish taken on farms and at processing plants for a range of residues. In accordance with Council Directive 96/23/EC, the following
species were sampled and tested: Atlantic salmon (Salmo salar), freshwater and seareared trout (Oncorhynchus mykiss). Tests were carried out for banned substances such
as growth promoters, and other unauthorised substances such as malachite green, which should not be present. Harvested fish were also tested for authorised veterinary
treatments such as antibiotics and sea lice treatments, environmental contaminants such as trace metals, polychlorinated biphenyls and organochlorine pesticides, to check for compliance with Maximum Residue Levels (MRL) where available.
As in previous years, no non-compliant results were reported in the surveillance
monitoring programme for farmed finfish. Overall, in recent years the outcome for
aquaculture remains one of consistently low occurrence of residues in farmed finfish,
with 0.23% non-compliant results from routine targeted monitoring in 2004, 0.09% in
2005 and 0% for the period 2006-2011.Funder: Marine Institut
The Wolf-Rayet population of the nearby barred spiral galaxy NGC 5068 uncovered by the Very Large Telescope and Gemini
We present a narrow-band Very Large Telescope/Focal Reduced Low-dispersion Spectrograph #1 imaging survey of the SAB(rs)cd spiral galaxy NGC 5068, located at a distance of 5.45 Mpc, from which 160 candidate Wolf–Rayet sources have been identified, of which 59 cases possess statistically significant λ4686 excesses. Follow-up Gemini Multi-Object Spectrograph spectroscopy of 64 candidates, representing 40 per cent of the complete photometric catalogue, confirms Wolf–Rayet signatures in 30 instances, corresponding to a 47 per cent success rate. 21 out of 22 statistically significant photometric sources are spectroscopically confirmed. Nebular emission detected in 30 per cent of the Wolf–Rayet candidates spectrally observed, which enable a re-assessment of the metallicity gradient in NGC 5068. A central metallicity of log (O/H) + 12 ∼ 8.74 is obtained, declining to 8.23 at R25. We combine our spectroscopy with archival Hα images of NGC 5068 to estimate a current star formation rate of Graphic, and provide a catalogue of the 28 brightest H ii regions from our own continuum subtracted Hα images, of which ∼17 qualify as giant H ii regions. Spectroscopically, we identify 24 WC- and 18 WN-type Wolf–Rayet stars within 30 sources since emission-line fluxes indicate multiple Wolf–Rayet stars in several cases. We estimate an additional ∼66 Wolf–Rayet stars from the remaining photometric candidates, although sensitivity limits will lead to an incomplete census of visually faint WN stars, from which we estimate a global population of ∼170 Wolf–Rayet stars. Based on the Hα-derived O star population of NGC 5068 and N(WR)/N(O) ∼ 0.03, representative of the Large Magellanic Cloud, we would expect a larger Wolf–Rayet population of 270 stars. Finally, we have compared the spatial distribution of spectroscopically confirmed WN and WC stars with Sloan Digital Sky Survey derived supernovae, and find both WN and WC stars to be most consistent with the parent population of Type Ib supernovae
A Very Large Telescope imaging and spectroscopic survey of the Wolf-Rayet population in NGC 7793
We present a VLT/FORS1 imaging and spectroscopic survey of the Wolf-Rayet
(WR) population in the Sculptor group spiral galaxy NGC 7793. We identify 74
emission line candidates from archival narrow-band imaging, from which 39 were
observed with the Multi Object Spectroscopy (MOS) mode of FORS1. 85% of these
sources displayed WR features. Additional slits were used to observe HII
regions, enabling an estimate of the metallicity gradient of NGC 7793 using
strong line calibrations, from which a central oxygen content of log (O/H) + 12
= 8.6 was obtained, falling to 8.25 at R_25. We have estimated WR populations
using a calibration of line luminosities of Large Magellanic Cloud stars,
revealing ~27 WN and ~25 WC stars from 29 sources spectroscopically observed.
Photometric properties of the remaining candidates suggest an additional ~27 WN
and ~8 WC stars. A comparison with the WR census of the LMC suggests that our
imaging survey has identified 80% of WN stars and 90% for the WC subclass.
Allowing for incompleteness, NGC 7793 hosts ~105 WR stars for which
N(WC)/N(WN)~0.5. From our spectroscopy of HII regions in NGC 7793, we revise
the global Halpha star formation rate of Kennicutt et al. upward by 50% to 0.45
M_sun/yr. This allows us to obtain N(WR)/N(O)~0.018, which is somewhat lower
than that resulting from the WR census by Schild et al. of another Sculptor
group spiral NGC 300, whose global physical properties are similar to NGC 7793.
Finally, we also report the fortuitous detection of a bright (m_V = 20.8 mag)
background quasar Q2358-32 at z~2.02 resulting from CIV 1548-51 redshifted to
the 4684 passband.Comment: 17 pages, 13 figures, accepted for MNRAS (detailed finding charts
omitted)
Chemical Residues in Irish Farmed Finfish, 2012-2014
The Marine Institute carries out monitoring of chemical residues in aquaculture in accordance with Council Directive 96/23/EC of 29 April 1996, on measures to monitor certain substances and residues thereof in animals and animal products, also known as the Residues Directive. This is carried out on behalf of the Department of Agriculture, Food and the Marine (DAFM). For the aquaculture sector, the Sea Fisheries Protection Authority (SFPA) with technical support from the Institute is responsible for residue controls on farmed finfish on behalf of the national residue monitoring plan. Annually, the National Residues Control Plan (NRCP) for Aquaculture is prepared by the Institute and this sets out the monitoring requirements for residues in animal products in required by the directive. The main objectives of the National Residue Control Plan for Aquaculture is to ensure farmed fish are fit for human consumption; to provide a body of data showing that Irish farmed fish is of high quality; to promote good practices in aquaculture; and to comply with EU Directive 96/23/EC. Based on production tonnage, the following species for the period of 2012 to 2014 were sampled and tested: Atlantic salmon (Salmo salar), freshwater and sea reared trout (Oncorhynchus mykiss & Salmo trutta). In excess of 2,141 tests and a total of 4,972 residue measurements were carried out over this three year period. Tests were carried out for banned substances such as growth promoters and other unauthorised substances such as malachite green, which should not be present. Harvest fish were also tested for authorised veterinary treatments such as antibiotics and sea lice treatments, environmental contaminants such as trace metals, polychlorinated biphenyls and organochlorine pesticides, to check for compliance with Maximum Residue Levels (MRL) where available. As in previous years, no non-compliant results were reported in the surveillance monitoring programme for farmed finfish during the period 2012 to 2014. Overall, in recent years the outcome for aquaculture remains one of consistently low occurrence of residues in farmed finfish, with 0.23% non-compliant results from routine targeted monitoring in 2004, 0.09% in 2005 and one of full compliance with 0% non-compliant target residue results for the period 2006-2014
Runaway stars as progenitors of supernovae and gamma-ray bursts
When a core collapse supernova occurs in a binary system, the surviving star
as well as the compact remnant emerging from the SN, may reach a substantial
space velocity. With binary population synthesis modelling at solar and one
fifth of solar metallicity, we predict the velocities of such runaway stars or
binaries. We compile predictions for runaway OB stars, red supergiants and
Wolf-Rayet stars. For those stars or binaries which undergo a second stellar
explosion we compute their further evolution and the distance travelled until a
Type II or Type Ibc SN or a long or short gamma-ray burst occurs. We find our
predicted population of OB runaway stars broadly matches the observed
population of stars but, to match the fastest observed WR runaway stars, we
require that black holes receive an asymmetric kick upon formation. We find
that at solar metallicity Type Ic SN progenitors travel shorter distances than
the progenitors of other SN types because they are typically more massive and
thus have shorter lifetimes. Those of Type IIP SN can fly farthest about 48 pc
on average at solar metallicity. In considering the consequences of assuming
that the progenitors of long GRBs are spun-up secondary stars that experience
quasi-homogeneous evolution, we find that such evolution has a dramatic effect
on the population of runaway WR stars and that some 30 per cent of GRBs could
occur a hundred parsecs or more from their initial positions. We also consider
mergers of double compact object binaries consisting of neutron stars and/or
black holes. We find the most common type of visible mergers are neutron
star--black hole mergers that are roughly ten times more common than neutron
star--neutron star mergers. We also find that there may be a population of
low-velocity neutron stars that are ejected from a binary rather than by their
own natal kick.Comment: Accepted for publication in MNRAS, 23 pages, 17 figures and 11
tables. Abstract was editted to fit within arXiv.org submission requirement
The SARS-CoV-2 Spike protein has a broad tropism for mammalian ACE2 proteins.
SARS Coronavirus 2 (SARS-CoV-2) emerged in late 2019, leading to the Coronavirus Disease 2019 (COVID-19) pandemic that continues to cause significant global mortality in human populations. Given its sequence similarity to SARS-CoV, as well as related coronaviruses circulating in bats, SARS-CoV-2 is thought to have originated in Chiroptera species in China. However, whether the virus spread directly to humans or through an intermediate host is currently unclear, as is the potential for this virus to infect companion animals, livestock, and wildlife that could act as viral reservoirs. Using a combination of surrogate entry assays and live virus, we demonstrate that, in addition to human angiotensin-converting enzyme 2 (ACE2), the Spike glycoprotein of SARS-CoV-2 has a broad host tropism for mammalian ACE2 receptors, despite divergence in the amino acids at the Spike receptor binding site on these proteins. Of the 22 different hosts we investigated, ACE2 proteins from dog, cat, and cattle were the most permissive to SARS-CoV-2, while bat and bird ACE2 proteins were the least efficiently used receptors. The absence of a significant tropism for any of the 3 genetically distinct bat ACE2 proteins we examined indicates that SARS-CoV-2 receptor usage likely shifted during zoonotic transmission from bats into people, possibly in an intermediate reservoir. Comparison of SARS-CoV-2 receptor usage to the related coronaviruses SARS-CoV and RaTG13 identified distinct tropisms, with the 2 human viruses being more closely aligned. Finally, using bioinformatics, structural data, and targeted mutagenesis, we identified amino acid residues within the Spike-ACE2 interface, which may have played a pivotal role in the emergence of SARS-CoV-2 in humans. The apparently broad tropism of SARS-CoV-2 at the point of viral entry confirms the potential risk of infection to a wide range of companion animals, livestock, and wildlife
Performing the Anglo-Scottish Border: Cultural Landscapes, Heritage and Borderland Identities
Recent times have seen much reflection on the nature of the Anglo-Scottish border region; its past, present and potential future. Political concerns have rightly absorbed much of the attention, but at the same time important light has been shed on the legacy of cultural engagements and forms of interaction that might be said to perform and produce this border over time and render it particularly distinctive. A soft, internal border, the territory considered in this article is one with an ancient feudal past and a heavily conserved, preserved and, in parts, still militarized present. It is predominantly rural and characterized by large swathes of forestry, agriculture, and moorland, all of which raise issues of aesthetic and environmental, as well as social and economic sustainability. The concern in the case studies presented in this article is how, through the relational and processual perspectives of border studies and cultural landscapes, we might comprehend the over layered and sedimented histories, the nature of identities, heritage and experience of place here. I consider too the ways in which recent forms of creative practice are contributing to a wider investigation of this region and re-conceptualizing the cultural significance of the border
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