19,884 research outputs found

    Quasars in the 2MASS Second Incremental Data Release

    Full text link
    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

    Full text link
    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

    Get PDF
    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

    Get PDF
    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

    Get PDF
    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

    Get PDF
    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 γ\gamma-ray Transitions Observed in 19^{19}Ne with Implications for the 15^{15}O(α\alpha,γ\gamma)19^{19}Ne Reaction Rate

    Get PDF
    The 15^{15}O(α\alpha,γ\gamma)19^{19}Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between Ex=4E_x = 4 and 5 MeV in 19^{19}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-γ\gamma-γ\gamma coincidences from the 19^{19}F(3^{3}He,tγt\gamma)19^{19}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 JπJ^\pi values are actually 7/2^- and 9/2^-, respectively. These assignments are consistent with the values in the 19^{19}F mirror nucleus and in contrast to previously accepted assignments

    Key 19^{19}Ne states identified affecting γ\gamma-ray emission from 18^{18}F in novae

    Get PDF
    Detection of nuclear-decay γ\gamma rays provides a sensitive thermometer of nova nucleosynthesis. The most intense γ\gamma-ray flux is thought to be annihilation radiation from the β+\beta^+ decay of 18^{18}F, which is destroyed prior to decay by the 18^{18}F(pp,α\alpha)15^{15}O reaction. Estimates of 18^{18}F production had been uncertain, however, because key near-threshold levels in the compound nucleus, 19^{19}Ne, had yet to be identified. This Letter reports the first measurement of the 19^{19}F(3^{3}He,tγt\gamma)19^{19}Ne reaction, in which the placement of two long-sought 3/2+^+ levels is suggested via triton-γ\gamma-γ\gamma coincidences. The precise determination of their resonance energies reduces the upper limit of the rate by a factor of 1.5171.5-17 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?

    Get PDF
    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

    Get PDF
    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
    corecore