6,430 research outputs found

    Anomalous isotopic predissociation in the F³Πu(v=1) state of O₂

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    Using a tunable, narrow-bandwidth vacuum-ultraviolet source based on third-harmonic generation from excimer-pumped dye-laser radiation, the F³Πu←X³Σg-(1,0)photoabsorption cross sections of ¹⁶O₂ and ¹⁸O₂ have been recorded in high resolution. Rotational analyses have been performed and the resultant F(v=1) term values fitted to the ³Π Hamiltonian of Brown and Merer [J. Mol. Spectrosc. 74, 488 (1979)]. A large rotationless isotope effect is observed in the F(v=1)predissociation, wherein the Lorentzian linewidth component for ¹⁸O₂ is a factor of ∼50 smaller than the corresponding ¹⁶O₂linewidth. This effect, a consequence of the nonadiabatic rotationless predissociation mechanism, is described using a coupled-channel treatment of the strongly Rydberg-valence-mixed 3Πu states. Significant J, e/f-parity, and sublevel dependencies observed in the isotopic F(v=1) rotational widths are found to derive from an indirect predissociation mechanism involving an accidental degeneracy with the E³Σ−u(v=3) level, itself strongly predissociated by ³Σ−u Rydberg-valence interactions, together with L-uncoupling (rotational) interactions between the Rydberg components of the F and E states. Transitions into the E(v=3) level are observed directly for the first time, specifically in the ¹⁸O₂ spectrumPartial support was provided by an NSF International Opportunities for Scientists and Engineers Program Grant No. INT-9513350, and Visiting Fellowships for G.S. and J.B.W. at the Australian National University

    他臓器癌の現病歴あるいは既往歴が大腸腫瘍の危険因子となるか?大腸内視鏡検査を行った患者を対象にした解析結果

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    We present an algorithm for computing one-dimensional stable and unstable manifolds of saddle periodic orbits in a, Poincaré section. The computation is set up as a, boundary value problem by restricting both end points of orbit segments to the section. Starting from the periodic orbit itself, we use collocation routines from AUTO to continue the solutions of the boundary value problem such that one end point of the orbit segment varies along a part of the manifold that was already computed. In this way, the other end point of the orbit segment traces out a new piece of the manifold. As opposed to standard methods that use shooting to compute the Poincaré map as the kth return map, our approach defines the Poincaré map as the solution of a boundary value problem. This enables us to compute global manifolds through points where the flow is tangent to the section - a situation that is typically encountered unless one is dealing with a periodically forced system. Another major advantage of our approach is that it deals effectively with the problem of extreme sensitivity of the Poincaré map to its argument, which is a typical feature in the important class of slow-fast systems. We illustrate and test our algorithm by computing stable and unstable manifolds for three examples: the forced Van der Pol oscillator, a model of a semiconductor laser with optical injection, and a slow-fast chemical oscillator. All examples are accompanied by animations demonstrating how the manifolds grow during the computation. © 2005 Society for Industrial and Applied Mathematics

    Flying Raggedy

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    Concealment, communication and stigma: The perspectives of HIV-positive immigrant Black African men and their partners living in the United Kingdom

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    This study explored the perspectives of Black men, originally from East Africa, living in the United Kingdom and their families on what it means to live with diagnosed HIV. This article reports on concealment of HIV-positive status as a strategy adopted by the affected participants to manage the flow of information about their HIV-positive status. Analysis of the data, collected using in-depth interviews involving 23 participants, found widespread selective concealment of HIV-positive status. However, a few respondents had ‘come out’ publicly about their condition. HIV prevention initiatives should recognise concealment as a vital strategy in managing communication about one’s HIV-positive status

    Trusted Energy-Efficient Cloud-based Services Brokerage Platform

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    The use of cloud computing can increase service efficiency and service level agreements for cloud users, by linking them to an appropriate cloud service provider, using the cloud services brokerage paradigm. Cloud service brokerage represents a promising new layer which is to be added to the cloud computing network, which manages the use, performance and delivery of cloud services, and negotiates relationships between cloud service providers and cloud service consumers. The work presented in this paper studies the research related to cloud service brokerage systems along with the weaknesses and vulnerabilities associated with each of these systems, with a particular focus on the multicloud-based services environment. In addition, the paper will conclude with a proposed multi-cloud framework that overcomes the weaknesses of other listed cloud brokers. The new framework aims to find the appropriate data centre in terms of energy efficiency, QoS and SLA. Moreover, it presents a security model aims to protect the proposed multicloud framework and highlights the key features that must be available in multi-cloud-based brokerage systems

    Reviewing research evidence and the case of participation in sport and physical recreation by black and minority ethnic communities

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    The paper addresses the implications of using the process of systematic review in the many areas of leisure where there is a dearth of material that would be admitted into conventional Cochrane Reviews. This raises important questions about what constitutes legitimate knowledge, questions that are of critical import not just to leisure scholars, but to the formulation of policy. The search for certainty in an area that lacks conceptual consensus results in an epistemological imperialism that takes a geocentric form. While clearly, there is a need for good research design whatever the style of research, we contend that the wholesale rejection of insightful research is profligate and foolhardy. A mechanism has to be found to capitalise on good quality research of whatever form. In that search, we draw upon our experience of conducting a review of the material available on participation in sport and physical recreation by people from Black and minority ethnic groups. The paper concludes with a proposal for a more productive review process that makes better use of the full panoply of good quality research available. © 2012 © 2012 Taylor & Francis

    The Leadership Role of Psychiatrists in the NHS

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    This article explores leadership in the context of psychiatry in the NHS. It identifies considerable policy challenges facing psychiatry such as recent attempts to upgrade mental health services and bring them up to par with other services. It suggests it will become increasingly necessary for the profession to respond to such challengers by engaging with leadership at various levels. The article suggests there may be merit in exploring one particular approach to leadership, namely transformational leadership, given its emphasis on dealing with change. Psychiatrists may find the behaviours associated with this approach of particular relevance. However, it suggests that there may need to adopt a particular variant of transformational leadership that acknowledges both the achievement of objectives and showing genuine concern for followers. The latter is important given the on going problem of clinical engagement in the NHS. The article concludes with the developmental implications in adopting this leadership approach
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