239 research outputs found
The Predatory Bird Monitoring Scheme (PBMS) Report 2006-7
The Predatory Bird Monitoring Scheme (PBMS) examines the levels of certain pollutants in selected wildlife species in Britain. It started in the 1960s to assess the impact of organochlorine pesticides on raptor populations, and the scheme is now the longest-running of its kind in the
world. The aims of the PBMS are to monitor the levels of contaminants to determine how and why they vary between species and regions, how they are changing over time, and the risks they may have on individual birds and on their populations. Dead predatory birds are submitted to the
PBMS by the public and by wildlife hospitals, veterinarian and zoological organisations. Eggs are collected, under licence, from a range of nests. The majority of these eggs are addled or deserted, although for some species, e.g. northern gannets, fresh egg are sampled.
Second generation anticoagulant rodenticides (SGARs) are potentially toxic to all mammals and birds, and predators that feed upon rodents are particularly likely to be exposed to these compounds. Since 1983 the PBMS has monitored SGAR residues in barn owls, while kestrels
have been monitored since 2001. The proportion of barn owls which have one or more SGARs in their liver increased from less than 10% in the 1980s to approximately 40% in the early 2000s. However, there has been a small decrease in this percentage in the last few years. A higher proportion of kestrels have detectable residues of SGARs in their liver than barn owls with 60% of birds received in the years 2001 to 2006 having one or more SGAR in their liver. There is no evidence of a change over time in the proportion ok kestrels with detectable liver SGAR residues.
Overall, the high incidence of exposure amongst monitored species remains of concern.
Sparrowhawk livers are analysed for a range of persistent organic pollutants (POPs) and heavy metals. Sparrowhawks are studied because they have a wide distribution across the Britain and can be used as a sentinel species for the terrestrial environment. Following restrictions on its use as an agricultural pesticide, mercury concentrations have declined in sparrowhawks. However, despite PCBs being banned in 1981, there has not been any long-term change in polychlorinated biphenyl (PCB) liver concentrations in sparrowhawks during the period 1968-2006. In herons, used as a sentinel species for freshwater habitats, both PCB and mercury concentrations have declined. In 2006, mean PCB and mercury concentrations in both species were below those thought to have an adverse effect on individual birds.
Pollutants, such as mercury and PCBs, can affect development and hatchability.. Therefore, the PBMS monitors the levels of contaminants in the eggs of a range of species including those of conservation concern such as golden eagle and the re-introduced white-tailed sea eagle.
Other species that are monitored are the northern gannet, which are used as a monitor of the marine environment, and merlin that hunt in upland habitats. In general, and specifically in 2006, the residues measured in the eggs of golden eagle and gannets are below those thought to have an
adverse effect on bird eggs, but some residues in individual merlin eggs were at concentrations associated with effects in other species. Few white-tailed see eagle eggs are received for analysis by the PBMS but a large proportion of those eggs that have been analysed, including the egg collected in 2006, have DDE, PCB and mercury concentrations above levels associated with adverse effects on bird embryos and the hatching success of eggs.
Despite the withdrawal of PCBs from manufacturing over 20 years ago, the evidence for declining PCB concentrations in predatory birds is equivocal, with declines in liver or egg residues in some species but not in others. Mercury concentrations in most species have not significantly changed during the monitoring period
On the equivalence of the self-dual and Maxwell-Chern-Simons models coupled to Fermions
We study the exact equivalence between the self-dual model minimally coupled
with a Dirac field and the Maxwell-Chern-Simons model with non-minimal magnetic
coupling to fermions. We show that the fermion sectors of the models are
equivalent only if a Thirring like interaction is included. Using functional
methods we verify that, up to renormalizations, the equivalence persists at the
quantum level.Comment: 8 pages, revte
szinmü 4 felvonásban - írta Victorien Sardou - fordították Fai J. Béla és Makó Lajos - rendező Bihari
Vigszinház Debreczen, 1919 julius 25-én pénteken. Előadás kezdete 7 1/2 órakor.Debreceni Egyetem Egyetemi és Nemzeti Könyvtá
Equivalence between supersymmetric self-dual and Maxwell-Chern-Simons models coupled to a matter spinor superfield
We study the duality of the supersymmetric self-dual and Maxwell-Chern-Simons
theories coupled to a fermionic matter superfield, using a master action. This
approach evades the difficulties inherent to the quartic couplings that appear
when matter is represented by a scalar superfield. The price is that the
spinorial matter superfield represents a unusual supersymmetric multiplet,
whose main physical properties we also discuss.Comment: v2, 16 pages, elsarticle.cls, accepted for publication in PL
Oxidised cosmic acceleration
We give detailed proofs of several new no-go theorems for constructing flat
four-dimensional accelerating universes from warped dimensional reduction.
These new theorems improve upon previous ones by weakening the energy
conditions, by including time-dependent compactifications, and by treating
accelerated expansion that is not precisely de Sitter. We show that de Sitter
expansion violates the higher-dimensional null energy condition (NEC) if the
compactification manifold M is one-dimensional, if its intrinsic Ricci scalar R
vanishes everywhere, or if R and the warp function satisfy a simple limit
condition. If expansion is not de Sitter, we establish threshold
equation-of-state parameters w below which accelerated expansion must be
transient. Below the threshold w there are bounds on the number of e-foldings
of expansion. If M is one-dimensional or R everywhere vanishing, exceeding the
bound implies the NEC is violated. If R does not vanish everywhere on M,
exceeding the bound implies the strong energy condition (SEC) is violated.
Observationally, the w thresholds indicate that experiments with finite
resolution in w can cleanly discriminate between different models which satisfy
or violate the relevant energy conditions.Comment: v2: corrections, references adde
A Massive Renormalizable Abelian Gauge Theory in 2+1 Dimensions
The standard formulation of a massive Abelian vector field in
dimensions involves a Maxwell kinetic term plus a Chern-Simons mass term; in
its place we consider a Chern-Simons kinetic term plus a Stuekelberg mass term.
In this latter model, we still have a massive vector field, but now the
interaction with a charged spinor field is renormalizable (as opposed to super
renormalizable). By choosing an appropriate gauge fixing term, the Stuekelberg
auxiliary scalar field decouples from the vector field. The one-loop spinor
self energy is computed using operator regularization, a technique which
respects the three dimensional character of the antisymmetric tensor
. This method is used to evaluate the vector self
energy to two-loop order; it is found to vanish showing that the beta function
is zero to two-loop order. The canonical structure of the model is examined
using the Dirac constraint formalism.Comment: LaTeX, 17 pages, expanded reference list and discussion of
relationship to previous wor
The purified extract from the medicinal plant Bacopa monnieri, bacopaside II, inhibits growth of colon cancer cells in vitro by inducing cell cycle arrest and apoptosis
Published: 21 July 2018Aquaporin-1 (AQP1), a transmembrane pore-forming molecule, facilitates the rapid movement of water and small solutes across cell membranes. We have previously shown that bacopaside II, an extract from the medicinal herb Bacopa monnieri, blocks the AQP1 water channel and impairs migration of cells that express AQP1. The aim of this study was to further elucidate the anti-tumour potential of bacopaside II in colon cancer cells. Expression of AQP1 in HT-29, SW480, SW620 and HCT116 was determined by quantitative PCR and western immunoblot. Cells were treated with bacopaside II, and morphology, growth, autophagy, cell cycle and apoptosis assessed by time-lapse microscopy, crystal violet, acridine orange, propidium iodide (PI) and annexin V/PI staining respectively. AQP1 expression was significantly higher in HT-29 than SW480, SW620 and HCT116. Bacopaside II significantly reduced growth at ≥20 µM for HT-29 and ≥15 µM for SW480, SW620 and HCT116. Inhibition of HT-29 at 20 µM was primarily mediated by G0/G1 cell cycle arrest, and at 30 µM by G2/M arrest and apoptosis. Inhibition of SW480, SW620 and HCT116 at ≥15 µM was mediated by G2/M arrest and apoptosis. These results are the first to show that bacopaside II inhibits colon cancer cell growth by inducing cell cycle arrest and apoptosis.Eric Smith, Helen M. Palethorpe, Yoko Tomita, Jinxin V. Pei, Amanda R. Townsend, Timothy J. Price, Joanne P. Young, Andrea J. Yool and Jennifer E. Hardingha
Design of the PET–MR system for head imaging of the DREAM Project
NOTICE: this is the author’s version of a work that was accepted for publication in Nuclear Instruments and Methods in Physics Research Section A. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Nuclear Instruments and Methods in Physics Research Section A, Volume 702, 21 February 2013, Pages 94–97
DOI 10.1016/j.nima.2012.08.028In this paper we describe the overall design of a PET–MR system for head imaging within the
framework of the DREAM Project as well as the first detector module tests. The PET system design
consists of 4 rings of 16 detector modules each and it is expected to be integrated in a head dedicated
radio frequency coil of an MR scanner.
The PET modules are based on monolithic LYSO crystals coupled by means of optical devices to an
array of 256 Silicon Photomultipliers. These types of crystals allow to preserve the scintillation light
distribution and, thus, to recover the exact photon impact position with the proper characterization of
such a distribution. Every module contains 4 Application Specific Integrated Circuits (ASICs) which
return detailed information of several light statistical momenta. The preliminary tests carried out on
this design and controlled by means of ASICs have shown promising results towards the suitability of
hybrid PET–MR systems.This work was supported by the Centre for Industrial Technological Development co-funded by FEDER through the Technology Fund (DREAM Project, IDI-20110718), the Spanish Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica (I + D + I) under Grant no. FIS2010-21216-CO2-01 and the Valencian Local Government under Grant PROMETEO 2008/114.González Martínez, AJ.; Conde, P.; Hernández Hernández, L.; Herrero Bosch, V.; Moliner Martínez, L.; Monzó Ferrer, JM.; Orero Palomares, A.... (2013). Design of the PET–MR system for head imaging of the DREAM Project. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 702:94-97. https://doi.org/10.1016/j.nima.2012.08.028S949770
Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation
BACKGROUND: Any hypothesis in longitudinal studies may be affected by attrition and poor response rates. The MRC Cognitive Function and Ageing study (MRC CFAS) is a population based longitudinal study in five centres with identical methodology in England and Wales each recruiting approximately 2,500 individuals. This paper aims to identify potential biases in the two-year follow-up interviews. METHODS: Initial non-response: Those not in the baseline interviews were compared in terms of mortality to those who were in the baseline interviews at the time of the second wave interviews (1993–1996). Longitudinal attrition: Logistic regression analysis was used to examine baseline differences between individuals who took part in the two-year longitudinal wave compared with those who did not. RESULTS: Initial non-response: Individuals who moved away after sampling but before baseline interview were 1.8 times more likely to die by two years (95% Confidence interval(CI) 1.3–2.4) compared to respondents, after adjusting for age. The refusers had a slightly higher, but similar mortality pattern to responders (Odds ratio 1.2, 95%CI 1.1–1.4). Longitudinal attrition: Predictors for drop out due to death were being older, male, having impaired activities of daily living, poor self-perceived health, poor cognitive ability and smoking. Similarly individuals who refused were more likely to have poor cognitive ability, but had less years of full-time education and were more often living in their own home though less likely to be living alone. There was a higher refusal rate in the rural centres. Individuals who moved away or were uncontactable were more likely to be single, smokers, demented or depressed and were less likely to have moved if in warden-controlled accommodation at baseline. CONCLUSIONS: Longitudinal estimation of factors mentioned above could be biased, particularly cognitive ability and estimates of movements from own home to residential homes. However, these differences could also affect other investigations, particularly the estimates of incidence and longitudinal effects of health and psychiatric diseases, where the factors shown here to be associated with attrition are risk factors for the diseases. All longitudinal studies should investigate attrition and this may help with aspects of design and with the analysis of specific hypotheses
Cosmological Spacetimes from Negative Tension Brane Backgrounds
We identify a time-dependent class of metrics with potential applications to
cosmology, which emerge from negative-tension branes. The cosmology is based on
a general class of solutions to Einstein-dilaton-Maxwell theory, presented in
{hep-th/0106120}. We argue that solutions with hyperbolic or planar symmetry
describe the gravitational interactions of a pair of negative-tension
-branes. These spacetimes are static near each brane, but become
time-dependent and expanding at late epoch -- in some cases asymptotically
approaching flat space. We interpret this expansion as being the spacetime's
response to the branes' presence. The time-dependent regions provide explicit
examples of cosmological spacetimes with past horizons and no past naked
singularities. The past horizons can be interpreted as S-branes. We prove that
the singularities in the static regions are repulsive to time-like geodesics,
extract a cosmological `bounce' interpretation, compute the explicit charge and
tension of the branes, analyse the classical stability of the solution (in
particular of the horizons) and study particle production, deriving a general
expression for Hawking's temperature as well as the associated entropy.Comment: 43 pages, 8 figures. Published versio
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