2,741 research outputs found

    White Ethnic: A Social Concept

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    Why such a term as white ethnic or ethnic developed and what purposes it served guides this inquiry. Its origins in the wake of the Civil Rights Movement in a context of American immigration history are explored together with its adoption as a sociological concept. A survey of textbooks most likely to use such a term, particularly texts concerning race and ethnicity, intergroup relations, and sociology of minorities, together with related literature illustrates both its usage and the basis of such usage

    The Welfare Reservation: A Worst Case Scenario For A Federal Role In Homeless Assistance

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    The purpose of the little-known Stewart B. McKinney Homeless Assistance Act of 1987 is stated as ... States, units of local government, and private voluntary organizations have been unable to meet the basic human needs of all the homeless and, in the absence of greater Federal Assistance, will be unable to protect the lives and safety of all the homeless in need of assistance: and the Federal Government has a clear responsibility and an existing capacity to fulfill a more effective and responsible role to meet the basic human needs and to engender respect for the human dignity of the homeless (U.S. Congress, 1987) Recent developments and policies could imply an increased use of surplus and underutilized federal facilities for programs for the homeless

    Optimal frequency conversion in the nonlinear stage of modulation instability

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    We investigate multi-wave mixing associated with the strongly pump depleted regime of induced modulation instability (MI) in optical fibers. For a complete transfer of pump power into the sideband modes, we theoretically and experimentally demonstrate that it is necessary to use a much lower seeding modulation frequency than the peak MI gain value. Our analysis shows that a record 95 % of the input pump power is frequency converted into the comb of sidebands, in good quantitative agreement with analytical predictions based on the simplest exact breather solution of the nonlinear Schr\"odinger equation

    Modulational instability in dispersion-kicked optical fibers

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    We study, both theoretically and experimentally, modulational instability in optical fibers that have a longitudinal evolution of their dispersion in the form of a Dirac delta comb. By means of Floquet theory, we obtain an exact expression for the position of the gain bands, and we provide simple analytical estimates of the gain and of the bandwidths of those sidebands. An experimental validation of those results has been realized in several microstructured fibers specifically manufactured for that purpose. The dispersion landscape of those fibers is a comb of Gaussian pulses having widths much shorter than the period, which therefore approximate the ideal Dirac comb. Experimental spontaneous MI spectra recorded under quasi continuous wave excitation are in good agreement with the theory and with numerical simulations based on the generalized nonlinear Schr\"odinger equation

    A theorem of Truemper

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