12,411 research outputs found

    New tests of the pp-wave correspondence.

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    The pp-wave/SYM correspondence is an equivalence relation, H string = Δ-J , between the hamiltonian H string of string field theory in the pp-wave background and the dilatation operator Δ in = 4 Super Yang-Mills in the double scaling limit. We calculate matrix elements of these operators in string field theory and in gauge theory. In the string theory Hilbert space we use the natural string basis, and in the gauge theory we use the basis which is isomorphic to it. States in this basis are specific linear combinations of the original BMN operators, and were constructed previously for the case of two scalar impurities. We extend this construction to incorporate BMN operators with vector and mixed impurities. This enables us to verify from the gauge theory perspective two key properties of the three-string interaction vertex of Spradlin and Volovich: (1) the vanishing of the three-string amplitude for string states with one vector and one scalar impurity; and (2) the relative minus sign in the string amplitude involving states with two vector impurities compared to that with two scalar impurities. This implies a spontaneous breaking of the 2 symmetry of the string field theory in the pp-wave background. Furthermore, we calculate the gauge theory matrix elements of Δ-J for states with an arbitrary number of scalar impurities. In all cases we find perfect agreement with the corresponding string amplitudes derived from the three-string vertex

    Thinking territory historically.

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    BACKGROUND: While the randomised controlled trial (RCT) is generally regarded as the design of choice for assessing the effects of health care, within the social sciences there is considerable debate about the relative suitability of RCTs and non-randomised studies (NRSs) for evaluating public policy interventions. // OBJECTIVES: To determine whether RCTs lead to the same effect size and variance as NRSs of similar policy interventions; and whether these findings can be explained by other factors associated with the interventions or their evaluation. // METHODS: Analyses of methodological studies, empirical reviews, and individual health and social services studies investigated the relationship between randomisation and effect size of policy interventions by: 1) Comparing controlled trials that are identical in all respects other than the use of randomisation by 'breaking' the randomisation in a trial to create non-randomised trials (re-sampling studies). 2) Comparing randomised and non-randomised arms of controlled trials mounted simultaneously in the field (replication studies). 3) Comparing similar controlled trials drawn from systematic reviews that include both randomised and non-randomised studies (structured narrative reviews and sensitivity analyses within meta-analyses). 4) Investigating associations between randomisation and effect size using a pool of more diverse RCTs and NRSs within broadly similar areas (meta-epidemiology). // RESULTS: Prior methodological reviews and meta-analyses of existing reviews comparing effects from RCTs and nRCTs suggested that effect sizes from RCTs and nRCTs may indeed differ in some circumstances and that these differences may well be associated with factors confounded with design. Re-sampling studies offer no evidence that the absence of randomisation directly influences the effect size of policy interventions in a systematic way. No consistent explanations were found for randomisation being associated with changes in effect sizes of policy interventions in field trials

    Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations

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    We have carried out an extensive survey of magnetic field strengths toward dark cloud cores in order to test models of star formation: ambipolar-diffusion driven or turbulence driven. The survey involved 500\sim500 hours of observing with the Arecibo telescope in order to make sensitive OH Zeeman observations toward 34 dark cloud cores. Nine new probable detections were achieved at the 2.5-sigma level; the certainty of the detections varies from solid to marginal, so we discuss each probable detection separately. However, our analysis includes all the measurements and does not depend on whether each position has a detection or just a sensitive measurement. Rather, the analysis establishes mean (or median) values over the set of observed cores for relevant astrophysical quantities. The results are that the mass-to-flux ratio is supercritical by 2\sim 2, and that the ratio of turbulent to magnetic energies is also 2\sim 2. These results are compatible with both models of star formation. However, these OH Zeeman observations do establish for the first time on a statistically sound basis the energetic importance of magnetic fields in dark cloud cores at densities of order 103410^{3-4} cm3^{-3}, and they lay the foundation for further observations that could provide a more definitive test.Comment: 22 pages, 2 figures, 2 table

    'It's a Form of Freedom': The experiences of people with disabilities within equestrian sport

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    This paper explores the embodied, gendered experiences of disabled horse‐riders. Drawing on data from five in‐depth interviews with paradressage riders, the ways in which their involvement in elite disability sport impacts upon their sense of identity and confidence are explored, as well as the considerable health and social benefits that this involvement brings. Social models of disability are employed and the shortcomings of such models, when applied to disability sport, are highlighted. The data presented here demonstrates the necessity of seeing disability sport as an embodied experience and acknowledging the importance of impairment to the experiences of disabled athletes. Living within an impaired body is also a gendered experience and the implications of this when applied to elite disability sport are considered

    From Photodriven Charge Accumulation to Fueling Enzyme Cascades in Molecular Factories

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    In a multi-disciplinary team effort we gather experts on light-to-chemical energy conversion, artificial metalloenzymes, and bio-inspired polymer vesicles in order to construct molecular factories which produce added-value chemicals in an overall process fueled by solar energy. We outline our long-term vision and discuss specific challenges associated with this endeavor

    The “We” in Cyber Bullying: Response 1

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    This practical text explores contemporary case scenarios that arise in school counseling with children and adolescents. Throughout 30 chapters on a diverse range of topics, several school counseling experts analyze and discuss each incident from a best practices perspective. Topics are organized around the CACREP Standards and incidents include a list of related supplemental readings, online resources, and suggested learning activities. Issues explored include trauma, drug use, pregnancy, cyberbullying, suicide, gangs, parental conflicts, sexual orientation, third-culture students, student career development, and ethical and professional dilemmas. Tarrell Awe Agahe Portman, PhD, is the dean of the College of Education at Winona State University. Chris Wood, PhD, is an associate professor in the Counselor Education program at the University of Nevada, Las Vegas. Heather J. Fye, PhD, is an assistant professor in the Counselor Education program at the University of Alabama
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