295 research outputs found

    Meissner response of anisotropic superconductors

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    The response field of a half-space anisotropic superconductor is evaluated for an arbitrary weak external field source. Example sources of a point magnetic moment and a circular current are considered in detail. For the penetration depth λL\lambda \ll L with LL being any other relevant distance (the source size, or the distance between the source and the superconductor), the major contribution to the response is the λ\lambda independent field of the source image. It is shown that the absolute value of λ\lambda cannot be extracted from the response field with a better accuracy than that for the source position. Similar problems are considered for thin films.Comment: 8 pages, 0 figures. 7 pages: section removed, refs. adde

    Vortices in magnetically coupled superconducting layered systems

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    Pancake vortices in stacks of thin superconducting films or layers are considered. It is stressed that in the absence of Josephson coupling topological restrictions upon possible configurations of vortices are removed and various examples of structures forbidden in bulk superconductors are given. In particular, it is shown that vortices may skip surface layers in samples of less than a certain size R_c which might be macroscopic. The Josephson coupling suppresses R_c estimates

    Symmetry breaking due to Dzyaloshinsky-Moriya interactions in the kagome lattice

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    Due to the particular geometry of the kagom\'e lattice, it is shown that antisymmetric Dzyaloshinsky-Moriya interactions are allowed and induce magnetic ordering. The symmetry of the obtained low temperature magnetic phases are studied through mean field approximation and classical Mont\'e Carlo simulations. A phase diagram relating the geometry of the interaction and the ordering temperature has been derived. The order of magnitude of the anisotropies due to Dzyaloshinsky-Moriya interactions are more important than in non-frustrated magnets, which enhances its appearance in real systems. Application to the jarosites compounds is proposed. In particular, the low temperature behaviors of the Fe and Cr-based jarosites are correctly described by this model.Comment: 6 (revtex4) twocolumn pages, 6 .eps figures. Submitted to Phys. Rev.

    Development and psychometric testing of the clinical leadership needs analysis (CLeeNA) instrument for nurses and midwives

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    Aim: The aim of this study is to report the development and psychometric testing of the clinical leadership needs analysis instrument (CLeeNA). Background: Limited emphasis is placed on the clinical leadership needs of nurses and midwives that are fundamental to supporting the delivery of high quality, safe patient care. Methods: A development and validation study of CLeeNA was undertaken using cross-sectional data. A sample of 324 registered nurses and midwives completed the questionnaire using a 7-point adjectival scale. Principal component analysis was conducted to explore scale grouping of items (n = 103 items). Results: Principal component analysis, item reduction and parallel analysis on the items of the instrument resulted in seven factors consisting of 56 items. These factors were identified as: Staff and Care Delivery; Technology and Care Initiatives; Self and Team Development; Standards of Care; Financial and Service Management; Leadership and Clinical Practice; Patient Safety and Risk Management. Conclusion: The identified factors are reflective of an ever-changing health care environment. Implications for Nursing Management: Potentially, after further testing, this instrument could be used by nursing management and educators to measure clinical leadership needs, inform the design of clinical leadership training programmes and provide valuable information about health care leadership development

    The Japanese model in retrospective : industrial strategies, corporate Japan and the 'hollowing out' of Japanese industry

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    This article provides a retrospective look at the Japanese model of industrial development. This model combined an institutional approach to production based around the Japanese Firm (Aoki's, J-mode) and strategic state intervention in industry by the Japanese Ministry of International Trade and Industry (MITI). For a long period, the alignment of state and corporate interests appeared to match the wider public interest as the Japanese economy prospered. However, since the early 1990s, the global ambitions of the corporate sector have contributed to a significant 'hollowing out' of Japan's industrial base. As the world today looks for a new direction in economic management, we suggest the Japanese model provides policy-makers with a salutary lesson in tying the wider public interest with those of the corporate sector

    Pinned Balseiro-Falicov Model of Tunneling and Photoemission in the Cuprates

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    The smooth evolution of the tunneling gap of Bi_2Sr_2CaCu_2O_8 with doping from a pseudogap state in the underdoped cuprates to a superconducting state at optimal and overdoping, has been interpreted as evidence that the pseudogap must be due to precursor pairing. We suggest an alternative explanation, that the smoothness reflects a hidden SO(N) symmetry near the (pi,0) points of the Brillouin zone (with N = 3, 4, 5, or 6). Because of this symmetry, the pseudogap could actually be due to any of a number of nesting instabilities, including charge or spin density waves or more exotic phases. We present a detailed analysis of this competition for one particular model: the pinned Balseiro-Falicov model of competing charge density wave and (s-wave) superconductivity. We show that most of the anomalous features of both tunneling and photoemission follow naturally from the model, including the smooth crossover, the general shape of the pseudogap phase diagram, the shrinking Fermi surface of the pseudogap phase, and the asymmetry of the tunneling gap away from optimal doping. Below T_c, the sharp peak at Delta_1 and the dip seen in the tunneling and photoemission near 2Delta_1 cannot be described in detail by this model, but we suggest a simple generalization to account for inhomogeneity, which does provide an adequate description. We show that it should be possible, with a combination of photoemission and tunneling, to demonstrate the extent of pinning of the Fermi level to the Van Hove singularity. A preliminary analysis of the data suggests pinning in the underdoped, but not in the overdoped regime.Comment: 18 pages LaTeX, 26 ps. figure

    Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

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    A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

    America's Rural Hospitals: A Selective Review of 1980s Research

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    We review 1980s research on American rural hospitals within the context of a decade of increasing restrictiveness in the reimbursement and operating environments. Areas addressed include rural hospital definitions, organizational and financial performance, and strategic management activities. The latter category consists of hospital closure, diversification and vertical integration, swing-bed conversion, sole community provider designation, horizontal integration and multihospital system affiliation, marketing, and patient retention. The review suggests several research needs, including: developing more meaningful definitions of rural hospitals, engaging in methodologically sound work on the effects of innovative programs and strategic management activities—including conversion of the facility itself—on rural hospital performance, and completing studies of the effects of rural hospital closure or conversion on the health of the communities served.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74857/1/j.1748-0361.1990.tb00682.x.pd

    Collaborative meta-analysis finds no evidence of a strong interaction between stress and 5-HTTLPR genotype contributing to the development of depression

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    The hypothesis that the S allele of the 5-HTTLPR serotonin transporter promoter region is associated with increased risk of depression, but only in individuals exposed to stressful situations, has generated much interest, research, and controversy since first proposed in 2003. Multiple meta-analyses combining results from heterogeneous analyses have not settled the issue. To determine the magnitude of the interaction and the conditions under which it might be observed, we performed new analyses on 31 datasets containing 38 802 European-ancestry subjects genotyped for 5-HTTLPR and assessed for depression and childhood maltreatment or other stressful life events, and meta-analyzed the results. Analyses targeted two stressors (narrow, broad) and two depression outcomes (current, lifetime). All groups that published on this topic prior to the initiation of our study and met the assessment and sample size criteria were invited to participate. Additional groups, identified by consortium members or self-identified in response to our protocol (published prior to the start of analysis1) with qualifying unpublished data were also invited to participate. A uniform data analysis script implementing the protocol was executed by each of the consortium members. Our findings do not support the interaction hypothesis. We found no subgroups or variable definitions for which an interaction between stress and 5-HTTLPR genotype was statistically significant. In contrast, our findings for the main effects of life stressors (strong risk factor) and 5-HTTLPR genotype (no impact on risk) are strikingly consistent across our contributing studies, the original study reporting the interaction, and subsequent meta-analyses. Our conclusion is that if an interaction exists in which the S allele of 5-HTTLPR increases risk of depression only in stressed individuals, then it is not broadly generalizable, but must be of modest effect size and only observable in limited situations
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