1,855 research outputs found

    Legacies in Black and White: The Racial Composition of the Legacy Pool

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    Selective universities regularly employ policies that favor children of alumni (known as legacies') in undergraduate admissions. Since alumni from selective colleges and universities have, historically, been disproportionately white, admissions policies that favor legacies have disproportionately benefited white students. For this reason, legacy policies lead to additional costs in terms of reductions in racial diversity. As larger numbers of minority students graduate from colleges and universities and have children, however, the potential pool of legacy applicants will change markedly in racial composition. This analysis begins with a review of the history and objectives of the preference for children of alumni in undergraduate admissions. We then consider the specific case of the University of Virginia and employ demographic techniques to predict the racial composition of the pool of potential legacy applicants to the University. Significant changes in the racial composition of classes that graduated from the University of Virginia from the late 1960s through the 1970s foreshadow similar changes in the characteristics of alumni children maturing through the next two decades.

    Closing the Gap or Widening the Divide: The Effects of the G.I. Bill and World War II on the Educational Outcomes of Black Americans

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    The effects of the G.I. Bill on collegiate attainment may have differed for black and white Americans owing to differential returns to education and differences in opportunities at colleges and universities, with men in the South facing explicitly segregated colleges. The empirical evidence suggests that World War II and the availability of G.I. benefits had a substantial and positive impact on the educational attainment of white men and black men born outside the South. However, for those black veterans likely to be limited to the South in their educational choices, the G.I. Bill had little effect on collegiate outcomes, resulting in the exacerbation of the educational differences between black and white men from southern states.

    Protostellar Disk Evolution Over Million-Year Timescales with a Prescription for Magnetized Turbulence

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    Magnetorotational instability (MRI) is the most promising mechanism behind accretion in low-mass protostellar disks. Here we present the first analysis of the global structure and evolution of non-ideal MRI-driven T-Tauri disks on million-year timescales. We accomplish this in a 1+1D simulation by calculating magnetic diffusivities and utilizing turbulence activity criteria to determine thermal structure and accretion rate without resorting to a 3-D magnetohydrodynamical (MHD) simulation. Our major findings are as follows. First, even for modest surface densities of just a few times the minimum-mass solar nebula, the dead zone encompasses the giant planet-forming region, preserving any compositional gradients. Second, the surface density of the active layer is nearly constant in time at roughly 10 g/cm2, which we use to derive a simple prescription for viscous heating in MRI-active disks for those who wish to avoid detailed MHD computations. Furthermore, unlike a standard disk with constant-alpha viscosity, the disk midplane does not cool off over time, though the surface cools as the star evolves along the Hayashi track. The ice line is firmly in the terrestrial planet-forming region throughout disk evolution and can move either inward or outward with time, depending on whether pileups form near the star. Finally, steady-state mass transport is a poor description of flow through an MRI-active disk. We caution that MRI activity is sensitive to many parameters, including stellar X-ray flux, grain size, gas/small grain mass ratio and magnetic field strength, and we have not performed an exhaustive parameter study here.Comment: Accepted for publication in Astrophysical Journal. 19 pages, including 8 figure

    Coding Geographic Areas Across Census Years: Creating Consistent Definitions of Metropolitan Areas

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    This paper presents suggested matches for the geographical coding (geocoding) of metropolitan areas in the 1970, 1980, and 1990 Censuses. The Census Bureau used different definitions and taxonomies to describe the geography of metropolitan areas in these three Census years. As a result, the geographical areas referred to by the standard Census Bureau definitions differ among the three Census data sets. The geographic matching scheme explained in this paper attempts to maximize consistency over time for metropolitan areas in the U.S.

    Returning to Learning: Adults' Success in College Is Key to America's Future

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    Provides an overview of research on adult learners' characteristics, risk factors, and needs at four-year institutions and in for-credit and non-credit courses, and what changes institutions and governments can implement to help adult students succeed

    Beyond Nanopore Sequencing in Space: Identifying the Unknown

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    Astronaut Kate Rubins sequenced DNA on the International Space Station (ISS) for the first time in August 2016 (Figure 1A). A 2D sequencing library containing an equal mixture of lambda bacteriophage, Escherichia coli, and Mus musculus was prepared on the ground with a SQK_MAP006 kit and sent to the ISS frozen and loaded into R7.3 flow cells. After a total of 9 on-orbit sequencing runs over 6 months, it was determined that there was no decrease in sequencing performance on-orbit compared to ground controls (1). A total of ~280,000 and ~130,000 reads generated on-orbit and on the ground, respectively, identified 90% of reads that were attributed to 30% lambda bacteriophage, 30% Escherichia coli, and 30% M. musculus (Figure 1B). Extensive bioinformatics analysis determined comparable 2D and 1D read accuracies between flight and ground runs (Figure 1C), and data collected from the ISS were able to construct directed assemblies of E.coli and lambda genomes at 100% and M. musculus mitochondrial genome at 96.7%. These findings validate sequencing as a viable option for potential on-orbit applications such as environmental microbial monitoring and disease diagnosis. Current microbial monitoring of the ISS applies culture-based techniques that provide colony forming unit (CFU) data for air, water, and surface samples. The identity of the cultured microorganisms in unknown until sample return and ground-based analysis, a process that can take up to 60 days. For sequencing to benefit ISS applications, spaceflight-compatible sample preparation techniques are required. Subsequent to the testing of the MinION on-orbit, a sample-to-sequence method was developed using miniPCR and basic pipetting, which was only recently proven to be effective in microgravity. The work presented here details the in- flight sample preparation process and the first application of DNA sequencing on the ISS to identify unknown ISS-derived microorganisms
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