53,014 research outputs found

    BPS black holes, the Hesse potential, and the topological string

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    The Hesse potential is constructed for a class of four-dimensional N=2 supersymmetric effective actions with S- and T-duality by performing the relevant Legendre transform by iteration. It is a function of fields that transform under duality according to an arithmetic subgroup of the classical dualities reflecting the monodromies of the underlying string compactification. These transformations are not subject to corrections, unlike the transformations of the fields that appear in the effective action which are affected by the presence of higher-derivative couplings. The class of actions that are considered includes those of the FHSV and the STU model. We also consider heterotic N=4 supersymmetric compactifications. The Hesse potential, which is equal to the free energy function for BPS black holes, is manifestly duality invariant. Generically it can be expanded in terms of powers of the modulus that represents the inverse topological string coupling constant, gsg_s, and its complex conjugate. The terms depending holomorphically on gsg_s are expected to correspond to the topological string partition function and this expectation is explicitly verified in two cases. Terms proportional to mixed powers of gsg_s and gˉs\bar g_s are in principle present.Comment: 28 pages, LaTeX, added comment

    Organisational and occupational risk factors associated with work related injuries among public hospital employees in Costa Rica

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    Aims: To explore the relation between occupational and organisational factors and work related injuries (WRI) among public hospital employees in Costa Rica.Methods: A cross-sectional survey was conducted among a stratified random sample of 1000 employees from 10 of the 29 public hospitals in Costa Rica. A previously validated, self-administered questionnaire which included occupational and organisational factors and sociodemographic variables was used. From the final eligible sample ( n = 859), a total of 842 ( response rate 98%) questionnaires were returned; 475 workers were analysed after excluding not-at-risk workers and incomplete questionnaires. WRI were computed for the past six months.Results: Workers exposed to chemicals (RR = 1.36) and physical hazards ( RR = 1.26) had higher WRI rate ratios than non-exposed workers. Employees reporting job tasks that interfered with safety practices ( RR = 1.46), and a lack of safety training ( RR = 1.41) had higher WRI rate ratios than their counterparts. Low levels of safety climate ( RR = 1.51) and safety practices ( RR = 1.27) were individually associated with an increased risk of WRI. Also, when evaluated jointly, low levels of both safety climate and safety practices showed the highest association with WRI ( RR = 1.92).Conclusions: When evaluated independently, most of the occupational exposures and organisational factors investigated were significantly correlated with an increased injury risk. As expected, some of these associations disappeared when evaluated jointly. Exposure to chemical and physical hazards, lack of safety training, and low levels of safety climate and safety practices remained significant risk factors for WRI. These results will be important to consider in developing future prevention interventions in this setting

    Cyber-pseudepigraphy: A New Challenge for Higher Education Policy and Management

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    There is no lack of critical literature dealing with cyber-plagiarism and the implications for assessment in higher education. The practice of the selling of academic papers through the Internet is generally included under the category of plagiarism, although it is suggested that this ought to be considered under the separate category of cyber-pseudepigraphy. Pseudepigraphy is defined in this essay as the deliberate ascription of false authorship to a piece of writing, and cyber-pseudepigraphy is defined as using the Internet to have another person write an academic essay or paper, without this authorship being acknowledged. It is suggested that cyber-pseudepigraphy has widespread implications, and five critical issues are discussed. The essay finally raises the prospect of a return to some form of unseen examination as a method of student assessment as a way of dealing with this problem

    Iginio Tansini revisited

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    The origin of the muscolocutaneous latissimus dorsi flap dates back to 1906 when Igino Tansini, an Italian surgeon, described a procedure to reconstruct the mastectomy defect. After a detailed study of Tansini's original description and drawings, new insights about the pedicle of its compound flap have been found, showing that it has the same pedicle of the scapular flap. In the end, Tansini's flap should be more correctly considered as a compound musculocutaneous scapular flap

    PMS14 MODELING THE PROGRESSION OF RHEUMATOID ARTHRITIS IN ITALY: BUDGET IMPACT ANALYSIS FOR BIOLOGIC AGENTS

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    The discovery, monitoring and environment of SGR J1935+2154

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    We report on the discovery of a new member of the magnetar class, SGR J1935+2154, and on its timing and spectral properties measured by an extensive observational campaign carried out between July 2014 and March 2015 with Chandra and XMM-Newton (11 pointings). We discovered the spin period of SGR J1935+2154 through the detection of coherent pulsations at a period of about 3.24s. The magnetar is slowing-down at a rate of 1.43(1)x10^{-11} s/s and with a decreasing trend due to a negative second period derivative of -3.5(7)x10^{-19} s/s^2. This implies a surface dipolar magnetic field strength of about 2.2x10^{14} G, a characteristic age of about 3.6kyr and, a spin-down luminosity L_{sd} of about 1.7x10^{34} erg/s. The source spectrum is well modelled by a blackbody with temperature of about 500eV plus a power-law component with photon index of about 2. The source showed a moderate long-term variability, with a flux decay of about 25\% during the first four months since its discovery, and a re-brightening of the same amount during the second four months. The X-ray data were also used to study the source environment. In particular, we discovered a diffuse emission extending on spatial scales from about 1" up to at least 1' around SGR J1935+2154 both in Chandra and XMM-Newton data. This component is constant in flux (at least within uncertainties) and its spectrum is well modelled by a power-law spectrum steeper than that of the pulsar. Though a scattering halo origin seems to be more probable we cannot exclude that part, or all, of the diffuse emission is due to a pulsar wind nebula.Comment: To appear in MNRAS; 10 pages, 3 color figures, 4 table
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