140,722 research outputs found

    The response of the moderate wing of the Civil Rights Movement to the war in Vietnam

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    This article explores the response of the moderate wing of the civil rights movement to the war in Vietnam. The moderates, made up of the National Association for the Advancement of Colored People (NAACP), the National Urban League, and leaders such as Bayard Rustin and A. Philip Randolph, were initially opposed to the civil rights movement taking a stand against the war. This reluctance was the result of a number of factors, including anti-communism and their own closeness with the administration of President Lyndon Johnson. Crucially, it also resulted from their own experiences of the black freedom struggle itself. The article also documents and analyses the growing anti-war dissent amongst the moderates, culminating in the decision of both the NAACP and the Urban League to adopt an anti-war stance at the end of the 1960s. Despite this, they remained unenthusiastic about participating in peace movement activities, and the reasons for this are explained. Finally, the article suggests that the war was important in exposing existing divisions within the civil rights movement, as well as in generating new ones

    The principle of equivalence and projective structure in space-times

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    This paper discusses the extent to which one can determine the space-time metric from a knowledge of a certain subset of the (unparametrised) geodesics of its Levi-Civita connection, that is, from the experimental evidence of the equivalence principle. It is shown that, if the space-time concerned is known to be vacuum, then the Levi-Civita connection is uniquely determined and its associated metric is uniquely determined up to a choice of units of measurement, by the specification of these geodesics. It is further demonstrated that if two space-times share the same unparametrised geodesics and only one is assumed vacuum then their Levi-Civita connections are again equal (and so the other metric is also a vacuum metric) and the first result above is recovered.Comment: 23 pages, submitted to Classical and Quantum Gravit

    Resource Letter BEC-1: Bose-Einstein Condensates in Trapped Dilute Gases

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    This Resource Letter provides a guide to the literature on Bose-Einstein condensation in trapped dilute gases. Journal articles and books are cited for the following topics: history, technological advances, condensates as quantum fluids, effects of interatomic interactions, condensates as matter waves, condensate optics, multiple condensates, lower dimensions, spectroscopy and precision measurement, entanglement, and cosmology.Comment: 12 pages, 0 figure

    Evaluation program for secondary spacecraft cells: Initial evaluation tests of General Electric Company 40.0 ampere hour nickel cadmium spacecraft cells for the tracking data relay satellite system

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    Average end of charge voltages and pressures, and capacity output in ampere hours are presented. Test limits specify those values at which a cell is to be terminated from charge or discharge. Requirements are based on past cell performance data. The requirement does not constitute a limit for discontinuance from testing. The nickel cadmium batteries were screened for internal shorts, low capacity, electrolyte leakage, or inability of any cell to recover its open circuit voltage above 1.150 volts during the internal short test

    MHD Disc Winds and Linewidth Distributions

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    We study AGN emission line profiles combining an improved version of the accretion disc-wind model of Murray & Chiang with the magneto-hydrodynamic model of Emmering et al. We show how the shape, broadening and shift of the C IV line depend not only on the viewing angle to the object but also on the wind launching angle, especially for small launching angles. We have compared the dispersions in our model C IV linewidth distributions to observational upper limit on that dispersion, considering both smooth and clumpy torus models. As the torus half-opening angle (measured from the polar axis) increases above about 18? degrees, increasingly larger wind launching angles are required to match the observational constraints. Above a half-opening angle of about 47? degrees, no wind launch angle (within the maximum allowed by the MHD solutions) can match the observations. Considering a model that replaces the torus by a warped disc yields the same constraints obtained with the two other models

    Holonomy and Projective Equivalence in 4-Dimensional Lorentz Manifolds

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    A study is made of 4-dimensional Lorentz manifolds which are projectively related, that is, whose Levi-Civita connections give rise to the same (unparameterised) geodesics. A brief review of some relevant recent work is provided and a list of new results connecting projective relatedness and the holonomy type of the Lorentz manifold in question is given. This necessitates a review of the possible holonomy groups for such manifolds which, in turn, requires a certain convenient classification of the associated curvature tensors. These reviews are provided.Comment: Comments: 23 pages, LaTeX; typos corrected, page 9 last line corrected to $g'=e^{2\chi}a^{-1}
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