19,884 research outputs found
Quasars in the 2MASS Second Incremental Data Release
Using the 2MASS Second Incremental Data Release, we have searched for near
infrared counterparts to 13214 quasars from the Veron-Cetty & Veron(2000)
catalog. We have detected counterparts within 4 arcsec for 2277 of the
approximately 6320 quasars within the area covered by the 2MASS Second
Incremental Data Release. Only 1.6% of these are expected to be chance
coincidences. Though this sample is heterogeneous, we find that known
radio-loud quasars are more likely to have large near-infrared-to-optical
luminosity ratios than radio-quiet quasars are, at a statistically significant
level. This is consistent with dust-reddened quasars being more common in
radio-selected samples than in optically-selected samples, due to stronger
selection effects against dust-reddened quasars in the latter. We also find a
statistically significant dearth of optically luminous quasars with large
near-infrared-to-optical luminosity ratios. This can be explained in a dust
obscuration model but not in a model where synchrotron emission extends from
the radio into the near-infrared and creates such large ratios. We also find
that selection of quasar candidates from the B-J/J-K color-color diagram,
modelled on the V-J/J-K selection method of Warren, Hewett & Foltz (2000), is
likely to be more sensitive to dust-obscured quasars than selection using only
infrared-infrared colors.Comment: To be published in May issue of Astronomical Journal (26 pages, 8
figures, 2 tables) Replaced Figure 6 and
Rings in the Planetesimal Disk of Beta Pic
The nearby main sequence star Beta Pictoris is surrounded by an edge-on disk
of dust produced by the collisional erosion of larger planetesimals. Here we
report the discovery of substructure within the northeast extension of the disk
midplane that may represent an asymmetric ring system around Beta Pic. We
present a dynamical model showing that a close stellar flyby with a quiescient
disk of planetesimals can create such rings, along with previously unexplained
disk asymmetries. Thus we infer that Beta Pic's planetesimal disk was highly
disrupted by a stellar encounter in the last hundred thousand years.Comment: Accepted by ApJ Letters. LaTeX, 13 pages, 4 figures, full PostScript
file available from http://www.maths.qmw.ac.uk/~jdl
Toward a Framework for Outcome-Based Analytical Performance Specifications: A Methodology Review of Indirect Methods for Evaluating the Impact of Measurement Uncertainty on Clinical Outcomes
Background: For medical tests that have a central role in clinical decision-making, current guidelines advocate outcome-based analytical performance specifications. Given that empirical (clinical-trial style) analyses are often impractical or unfeasible in this context, the ability to set such specifications is expected to rely on indirect studies to calculate the impact of test measurement uncertainty on downstream clinical, operational and economic outcomes. Currently however, a lack of awareness and guidance concerning available alternative indirect methods is limiting the production of outcome-based specifications. Our aim therefore was to review available indirect methods and present an analytical framework to inform future outcome-based performance goals.
Content: A methodology review consisting of database searches and extensive citation tracking was conducted to identify studies using indirect methods to incorporate or evaluate the impact of test measurement uncertainty on downstream outcomes (including clinical accuracy, clinical utility and/or costs). Eighty-two studies were identified, most of which evaluated the impact of imprecision and/or bias on clinical accuracy. A common analytical framework underpinning the various methods was identified, consisting of three key steps: (1) calculation of “true” test values; (2) calculation of measured test values (incorporating uncertainty); and (3) calculation of the impact of discrepancies between (1) and (2) on specified outcomes. A summary of the methods adopted is provided, and key considerations discussed.
Conclusions: Various approaches are available for conducting indirect assessments to inform outcome-based performance specifications. This study provides an overview of methods and key considerations to inform future studies and research in this area
Inter-cultural differences in response to a computer-based anti-bullying intervention
Background and purpose: Many holistic anti-bullying interventions have been attempted, with mixed success, while little work has been done to promote a 'self-help' approach to victimisation. The rise of the ICT curriculum and computer support in schools now allows for approaches that benefit from technology to be implemented. This study evaluates the cross-cultural effects of a computer-based anti-bullying intervention on primary school-aged children's knowledge about bullying and relevant coping strategies.
Programme description: FearNot! is an interactive computer-based virtual learning environment designed for use as an anti-bullying intervention. It includes interactive virtual agents who assume the most common participant roles found in episodes of bullying. FearNot! was used by children over three consecutive weeks to allow its effectiveness to be evaluated in a longitudinal in situ programme.
Sample: Two comparable samples were drawn from the UK and Germany. In the UK, 651 participants (aged 8-11) were recruited from primary schools in Hertfordshire, Coventry and Warwickshire, whereas the 535 German participants (aged 7-10) were sourced from Grundschulen in the Bayern and Hessen regions. Because of lack of parental consent, late joiners and absences/missing responses, data from 908 participants (UK 493; Germany 415) were analysed.
Design and methods: A quasi-experimental, pre/post-tests control group design employed pre-published and bespoke questionnaires to collect data. Descriptive and inferential analyses were conducted.
Results: UK students possessed higher coping strategy knowledge scores than German participants, but German children's scores improved over time and as a result of the FearNot! intervention.
Conclusions: Overall, while not effective at increasing children's coping strategy knowledge in this study, the FearNot! intervention could prove a useful classroom tool to approach the issue of bullying as part of a wider initiative. Cultural differences at baseline and reactions to the intervention are discussed
Metabolome Analysis of the Interaction Between Perennial Ryegrass (\u3cem\u3eLolium Perenne\u3c/em\u3e) and the Fungal Endophyte \u3cem\u3eNeotyphodium Lolii\u3c/em\u3e
Perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) frequently contain endophytic fungi (Neotyphodium lolii in perennial ryegrass and N. coenophialum in tall fescue). The presence of the endophyte has been shown to improve seedling vigour, persistence and drought tolerance in marginal environments as well as provide protection against some insect pests. Endophyte-infected grasses also produce a wide range of metabolites, including ergopeptine alkaloids, indole-isoprenoid lolitrems, pyrrolizidine alkaloids, and pyrrolopyrazine alkaloids. In contrast to information on alkaloids and animal toxicosis, the beneficial physiological aspects of the endophyte/grass interactions have not been well characterised. The physiological mechanisms which lead to increased plant vigour and enhanced tolerance to abiotic stresses unrelated to the reduction in pest damage to endophyte-infected grasses are unknown. Recent technological advances in metabolomics enable dynamic changes in the metabolome of an organism under varying experimental conditions to be studied. This provides opportunities for the investigation and validation of each and every detected metabolite, investigation of known metabolic pathways through searching of databases of known metabolites, molecular formula determination of unknown metabolites and creation of pathways from novel metabolites
The contested and contingent outcomes of Thatcherism in the UK
The death of Margaret Thatcher in April 2013 sparked a range of discussions and debates about the significance of her period in office and the political project to which she gave her name: Thatcherism. This article argues that Thatcherism is best understood as a symbolically important part of the emergence of first-phase neoliberalism. It engages with contemporary debates about Thatcherism among Marxist commentators and suggests that several apparently divergent positions can help us now reach a more useful analysis of Thatcherism’s short- and long-term outcomes for British political economy. The outcomes identified include: an initial crisis in the neoliberal project in the UK; the transformation of the party political system to be reflective of the politics of neoliberalism, rather than its contestation; long-term attempts at the inculcation of the neoliberal individual; de-industrialisation and financial sector dependence; and a fractured and partially unconscious working class. In all long-term outcomes, the contribution of Thatcherism is best understood as partial and largely negative, in that it cleared the way for a longer-term and more constructive attempt to embed neoliberal political economy. The paper concludes by suggesting that this analysis can inform current debates on the left of British politics about how to oppose and challenge the imposition of neoliberal discipline today
New -ray Transitions Observed in Ne with Implications for the O(,)Ne Reaction Rate
The O(,)Ne reaction is responsible for breakout
from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of
resonances between and 5 MeV in Ne is crucial in the
calculation of this reaction rate. The spins and parities of these states are
well known, with the exception of the 4.14- and 4.20-MeV states, which have
adopted spin-parities of 9/2 and 7/2, respectively. Gamma-ray
transitions from these states were studied using triton--
coincidences from the F(He,)Ne reaction measured
with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure
Studies) at Argonne National Laboratory. The observed transitions from the
4.14- and 4.20-MeV states provide strong evidence that the values are
actually 7/2 and 9/2, respectively. These assignments are consistent
with the values in the F mirror nucleus and in contrast to previously
accepted assignments
Key Ne states identified affecting -ray emission from F in novae
Detection of nuclear-decay rays provides a sensitive thermometer of
nova nucleosynthesis. The most intense -ray flux is thought to be
annihilation radiation from the decay of F, which is destroyed
prior to decay by the F(,)O reaction. Estimates of
F production had been uncertain, however, because key near-threshold
levels in the compound nucleus, Ne, had yet to be identified. This
Letter reports the first measurement of the
F(He,)Ne reaction, in which the placement of two
long-sought 3/2 levels is suggested via triton--
coincidences. The precise determination of their resonance energies reduces the
upper limit of the rate by a factor of at nova temperatures and
reduces the average uncertainty on the nova detection probability by a factor
of 2.1.Comment: 6 pages, 4 figure
Contextualizing entrepreneurial identity amongst Syrian refugees in Jordan: the emergence of a destabilized habitus?
This paper aims to contextualise the entrepreneurial identity of Syrian refugees living
outside refugee camps in Jordan. The research adopts a social lens to consider the situation
Syrians find themselves in by drawing on the work of Bourdieu. A qualitative design is
applied to explore the different experiences and perceptions that pervade refugee stories and
the work of refugee aid agencies. By contextualising entrepreneurial identity in the
Jordanian context, the paper reveals how a destabilized refugee habitus based on an
embodied disposition of survivability is emerging. The paper makes an empirical and
conceptual contribution by highlighting how the entrepreneurial activities of Syrian refugees
are driven by their experiences of the harsh social conditions they find themselves in
A method for determining venous contribution to BOLD contrast sensory activation
While BOLD contrast reflects haemodynamic changes within capillaries serving neural tissue, it also has a venous component. Studies that have determined the relation of large blood vessels to the activation map indicate that veins are the source of the largest response, and the most delayed in time. It would be informative if the location of these large veins could be extracted from the properties of the functional responses, since vessels are not visible in BOLD contrast images. The present study describes a method for investigating whether measures taken from the functional response can reliably predict vein location, or at least be useful in down-weighting the venous contribution to the activation response, and illustrates this method using data from one subject. We combined fMRI at 3 Tesla with high-resolution anatomical imaging and MR venography to test whether the intrinsic properties of activation time courses corresponded to tissue type. Measures were taken from a gamma fit to the functional response. Mean magnitude showed a significant effect of tissue type (P veins ≈ grey matter > white matter. Mean delays displayed the same ranking across tissue types (P grey matter. However, measures for all tissue types were distributed across an overlapping range. A logistic regression model correctly discriminated 72% of the veins from grey matter in the absence of independent information of macroscopic vessels (ROC=0.72). Whilst tissue classification was not perfect for this subject, weighting the T contrast by the predicted probabilities materially reduced the venous component to the activation map
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