504 research outputs found

    Photon-Neutrino Interactions in Magnetic Field through Neutrino Magnetic Moment

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    We study the neutrino-photon processes like γγ→ννˉ\gamma\gamma\to\nu\bar{\nu} in the presence of uniform external magnetic field for the case when neutrinos can couple to the electromagnetic field directly through their dipole magnetic moment and obtain the stellar energy loss. The process would be of special relevance in astrophysical situations where standard left-handed neutrinos are trapped and the right handed neutrinos produced through the spin flip interaction induced by neutrino magnetic moment alone can freely stream out.Comment: LaTex2e file, 9 page

    Relevance of the purity level in a MetalOrganic Vapour Phase Epitaxy reactor environment for the growth of high quality pyramidal sitecontrolled Quantum Dots

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    We report in this work on the spectral purity of pyramidal site-controlled InGaAs/AlGaAs Quantum Dots grown by metalorganic vapour phase epitaxy on(111)B oriented GaAs substrates. Extremely sharp emission peaks were found, showing linewidths surprisingly narrow (~27{\mu}eV) and comparable to those which can be obtained by Molecular Beam Epitaxy in an ultra-high vacuum environment. A careful reactor handling is regarded as a crucial step toward the fabrication of high optical quality systems.Comment: ICMOVPE 2010 Proceedin

    DISPARITIES OF ENTREPRENEURIAL ACTIVITIES AMONG URBAN INDUSTRIES -- AN EXPLORATORY APPROACH

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    The results of an on-going exploratory study focused on disparities in entrepreneurial activities across 203 Metropolitan Statistical Areas among 18 industries in the US showed that there existed variations in the path of entrepreneurial development among MSAs and different industries. Resource allocation, market, policies, and supportive organizations could lead to these variations.MSA, Entrepreneurship, urban, disparity, Gini coefficient, Community/Rural/Urban Development,

    OpenCL + OpenSHMEM Hybrid Programming Model for the Adapteva Epiphany Architecture

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    There is interest in exploring hybrid OpenSHMEM + X programming models to extend the applicability of the OpenSHMEM interface to more hardware architectures. We present a hybrid OpenCL + OpenSHMEM programming model for device-level programming for architectures like the Adapteva Epiphany many-core RISC array processor. The Epiphany architecture comprises a 2D array of low-power RISC cores with minimal uncore functionality connected by a 2D mesh Network-on-Chip (NoC). The Epiphany architecture offers high computational energy efficiency for integer and floating point calculations as well as parallel scalability. The Epiphany-III is available as a coprocessor in platforms that also utilize an ARM CPU host. OpenCL provides good functionality for supporting a co-design programming model in which the host CPU offloads parallel work to a coprocessor. However, the OpenCL memory model is inconsistent with the Epiphany memory architecture and lacks support for inter-core communication. We propose a hybrid programming model in which OpenSHMEM provides a better solution by replacing the non-standard OpenCL extensions introduced to achieve high performance with the Epiphany architecture. We demonstrate the proposed programming model for matrix-matrix multiplication based on Cannon's algorithm showing that the hybrid model addresses the deficiencies of using OpenCL alone to achieve good benchmark performance.Comment: 12 pages, 5 figures, OpenSHMEM 2016: Third workshop on OpenSHMEM and Related Technologie

    The Effects of Single Mothers' Welfare Participation and Work Decisions on Children's Attainments

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    This research examines the effects of mothers' welfare and work decisions on their children's attainments using two types of estimation methods in Stata: (1) an instrumental variables (IV) and (2) a nonlinear simultaneous equation estimation. The estimator employs sibling comparisons in a random effect framework and an instrumental variables approach to address the unobserved heterogeneity that may influence mothers' work and welfare decisions. We use the popular Stata command -ivreg2- to estimate the coefficients. Since production function of a child's ability can be written as a nonlinear function in a mother's decisions, we can also use the -nlsur- command to simulatneously estimate the production function as well as the (first-stage) IV projections. We focus on children who were born to single mothers with twelve or fewer years of schooling. IVs in this study are a mother's expected years of work and welfare use during childhood. The identification comes from the variation in mothers' different economic incentives that arises from the AFDC benefit structures across U.S. states. The estimates imply that, relative to no welfare participation, participating in welfare for one to three years provides up to a 5 percentage point gain in a child's Picture Individual Achievement Test (PIAT) scores. The negative effect of childhood welfare participation on adult earnings found by others is not significant if one accounts for mothers' work decisions. At the estimated values of the model parameters, a mother's number of years of work contributes between 3,000and3,000 and 7,000 1996 dollars to her child's labor income, but has no significant effect on the child's PIAT test scores. Finally, children's number of years of schooling is relatively unresponsive to mothers' work and welfare participation choices.

    Social media and news media: Building new publics or fragmenting audiences?

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    Kathryn Bow

    ‘Where else is the money? A study of innovation in online business models at newspapers in Britain’s 66 cities’

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    Much like their counterparts in the United States and elsewhere, British newspaper publishers have seen a sharp decline in revenues from traditional sources—print advertising and copy sales—and many are intensifying efforts to generate new income by expanding their online offerings. A study of the largest circulation newspapers in the 66 cities in England, Scotland, Wales and Northern Ireland showed that while only a small minority did not have companion websites, many of the publishers who do have an online presence have transferred familiar revenue models. It has also been recognised that income from these sources is not enough to sustain current operations and innovative publishers have diversified into additional broad categories of Web business models. Significantly, this study did not only compare the approaches of various news publishers with each other, but it also considered how active newspaper publishers were in taking advantage of the variety of business models generally being employed on the Web—and which opportunities were ignored
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