9,118 research outputs found

    The Impact of Social Policy and Economic Activity Throughout the Fertility Decision Tree

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    This paper considers the impact of changes in abortion and welfare policies along with economic conditions over the 1985 to 1996 period at each stage of the fertility decision tree, including sexual activity, contraception, pregnancy, abortion, and birth. Examining the impact of policy at each stage of the decision tree represents a useful approach because consistent findings provide stronger evidence of a causal link than focusing on just one stage. The abortion policies considered are parental involvement laws and mandatory waiting periods; welfare policies include benefit generosity as well as state-level welfare waivers as a whole and the 'family cap.' State-level data over this period are used to examine abortion, birth, and pregnancy outcomes, while microdata from the 1988 and 1995 National Surveys of Family Growth are employed to examine sexual activity and contraception. For those policies that target certain subgroups of the population, estimates are provided separately for each group and compared to help further identify causality. I find that parental involvement laws increase contraception use among minors, leading to fewer pregnancies and, therefore, fewer abortions; teen births do not rise in response. Evidence regarding welfare policies does not consistently support any impact throughout the decision tree.

    Design and calibration of a vacuum compatible scanning tunneling microscope

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    A vacuum compatible scanning tunneling microscope was designed and built, capable of imaging solid surfaces with atomic resolution. The single piezoelectric tube design is compact, and makes use of sample mounting stubs standard to a commercially available surface analysis system. Image collection and display is computer controlled, allowing storage of images for further analysis. Calibration results from atomic scale images are presented

    Fortran Program for X-Ray Photoelectron Spectroscopy Data Reformatting

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    A FORTRAN program has been written for use on an IBM PC/XT or AT or compatible microcomputer (personal computer, PC) that converts a column of ASCII-format numbers into a binary-format file suitable for interactive analysis on a Digital Equipment Corporation (DEC) computer running the VGS-5000 Enhanced Data Processing (EDP) software package. The incompatible floating-point number representations of the two computers were compared, and a subroutine was created to correctly store floating-point numbers on the IBM PC, which can be directly read by the DEC computer. Any file transfer protocol having provision for binary data can be used to transmit the resulting file from the PC to the DEC machine. The data file header required by the EDP programs for an x ray photoelectron spectrum is also written to the file. The user is prompted for the relevant experimental parameters, which are then properly coded into the format used internally by all of the VGS-5000 series EDP packages

    Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

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    The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (?0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting

    Analysis of analysis: importance of different musical parameters for Schenkerian analysis

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    While criteria for Schenkerian analysis have been much discussed, such discussions have generally not been informed by data. Kirlin [Kirlin, Phillip B., 2014 “A Probabilistic Model of Hierarchical Music Analysis.” Ph.D. thesis, University of Massachusetts Amherst] has begun to fill this vacuum with a corpus of textbook Schenkerian analyses encoded using data structures suggested byYust [Yust, Jason, 2006 “Formal Models of Prolongation.” Ph.D. thesis, University of Washington] and a machine learning algorithm based on this dataset that can produce analyses with a reasonable degree of accuracy. In this work, we examine what musical features (scale degree, harmony, metrical weight) are most significant in the performance of Kirlin's algorithm.Accepted manuscrip

    Identification of a Novel 81-kDa Component of the Xenopus Origin Recognition Complex

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    The Xenopus origin recognition complex is essential for chromosomal DNA replication in cell-free extracts. We have immunopurified the Xenopus origin recognition complex with anti-Xorc2 antibodies and analyzed its composition and properties. Xorc2 (p63) is specifically associated with Xorc1 (p115) and up to four additional polypeptides (p81, p78, p45, and p40). The cDNA encoding p81 is highly homologous to various expressed sequence tags from humans and mice encoding a protein of previously unknown function. Immunodepletion of p81 from Xenopus egg extracts, which also results in the removal of Xorc2, completely abolishes chromosomal DNA replication. Thus, p81 appears to play a crucial role at S phase in higher eukaryotes
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