1,223 research outputs found

    Beyond crime quantites: a multilevel analysis of the relative prevalence of interracial violence

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    Prior research examining between community variations in violent crime has largely been guided by the social disorganization perspective and the systemic model of community attachment. This literature supports a strong relation between structural resource deprivation, residential instability, and rates of violent crime. In communities where poverty, unemployment, and broken families are geographically concentrated and home ownership and length of residence are relatively low, levels of violent crime are exacerbated. This dissertation extends prior research by focusing on variation in the nature or quality of violence rather than crime rates or quantities. While many analyses explore variations in rates of crime, few have focused on understanding the contextual level predictors of variation in the relative prevalence of race specific forms of violence. The current study addresses this gap by elaborating a theoretical model that links characteristics of the contextual environment to variations in the prevalence of intra and interracial violence. It is proffered that concentrated disadvantage and residential stability decrease opportunities for fortuitous interracial associations which, in turn, reduce the likelihood that violent crime will involve actors from different race groups. Further, it is predicted that residential racial heterogeneity will increase opportunities for interracial contact and will thus be associated with an increase in the likelihood that violence will be interracial. The model is tested by merging crime data from the National Incident Based Reporting System with data on county characteristics culled from the U.S. Census. Nonlinear multilevel regression analyses provide strong support for the predicted pattern of relations between structural features of communities and the relative prevalence of race specific forms of violence. In communities with higher levels of structural disadvantage and residential stability violent crimes are relatively less likely to be interracial in nature. Conversely, violence that occurs in racially heterogeneous residential environments has an increased probability of being interracial. Analyses also reveal significant disparities in the contextual level correlates of black as compared to white intra-racial violence. The relevance of these findings and implications for criminological theory, future empirical research, and public policy are discussed in the concluding chapter

    PkANN - II. A non-linear matter power spectrum interpolator developed using artificial neural networks

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    In this paper we introduce PkANN, a freely available software package for interpolating the non-linear matter power spectrum, constructed using Artificial Neural Networks (ANNs). Previously, using Halofit to calculate matter power spectrum, we demonstrated that ANNs can make extremely quick and accurate predictions of the power spectrum. Now, using a suite of 6380 N-body simulations spanning 580 cosmologies, we train ANNs to predict the power spectrum over the cosmological parameter space spanning 3σ3\sigma confidence level (CL) around the concordance cosmology. When presented with a set of cosmological parameters (Ωmh2,Ωbh2,ns,w,σ8,mν\Omega_{\rm m} h^2, \Omega_{\rm b} h^2, n_s, w, \sigma_8, \sum m_\nu and redshift zz), the trained ANN interpolates the power spectrum for z2z\leq2 at sub-per cent accuracy for modes up to k0.9hMpc1k\leq0.9\,h\textrm{Mpc}^{-1}. PkANN is faster than computationally expensive N-body simulations, yet provides a worst-case error <1<1 per cent fit to the non-linear matter power spectrum deduced through N-body simulations. The overall precision of PkANN is set by the accuracy of our N-body simulations, at 5 per cent level for cosmological models with mν<0.5\sum m_\nu<0.5 eV for all redshifts z2z\leq2. For models with mν>0.5\sum m_\nu>0.5 eV, predictions are expected to be at 5 (10) per cent level for redshifts z>1z>1 (z1z\leq1). The PkANN interpolator may be freely downloaded from http://zuserver2.star.ucl.ac.uk/~fba/PkANNComment: 21 pages, 14 figures, 2 table

    Excess Clustering on Large Scales in the MegaZ DR7 Photometric Redshift Survey

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    We observe a large excess of power in the statistical clustering of luminous red galaxies in the photometric SDSS galaxy sample called MegaZ DR7. This is seen over the lowest multipoles in the angular power spectra C-l in four equally spaced redshift bins between 0: 45 <= z <= 0: 65. However, it is most prominent in the highest redshift band at similar to 4 sigma and it emerges at an effective scale k less than or similar to 0: 01 h Mpc(-1). Given that MegaZ DR7 is the largest cosmic volume galaxy survey to date (3.3(Gpch(-1))(3)) this implies an anomaly on the largest physical scales probed by galaxies. Alternatively, this signature could be a consequence of it appearing at the most systematically susceptible redshift. There are several explanations for this excess power that range from systematics to new physics. We test the survey, data, and excess power, as well as possible origins

    Using Common Gardens and AFLP Analyses to Identify Metapopulations of Indigenous Plant Materials for Rangeland Revegetation in Western USA

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    Past mismanagement, overgrazing, invasive weedy species, wildfires, marginal crop production, mineral and energy extraction, recreation and global climate change are challenges currently facing rangelands (Pierson et al. 2011). These disturbances may lead to long-term reductions in biodiversity, altered nutrient and water cycling, diminished forage production for livestock and wildlife, increased wildfire frequency and increased soil erosion and stream sedimentation (Sheley et al. 2008). Rangeland revegetation with desirable plant materials may be required to improve degraded conditions, speed recovery, and prevent further erosion and degradation. There is a critical need for plant materials to restore and revegetate rangeland ecosystems. Legumes indigenous to western North America are of particular interest for revegetation because they provide biologically fixed nitrogen, increase plant production, enhance forage quality and provide food sources for grazing animals and pollinators. Some land managers in the USA are concerned with the genetic identity of populations used for revegetation. To balance concerns of genetic identity, ecological adaptation, and economical seed production, we assessed genetic variation and its phenotypic expression in Astragalus filipes Torr. ex A. Gray (basalt milkvetch), Dalea ornata (Douglas) Eaton & Wright (western prairie clover) and D. searlsiae (A. Gray) Barneby (Searls’ prairie clover) using common-garden and AFLP (amplified fragment length polymorphism) techniques. These data were used to define population structures (genetically differentiated groups) within each species, which served as a basis for commercial release and rangeland revegetation (Johnson et al. 2012)

    Validating Phasing and Geometry of Large Focal Plane Arrays

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    The Kepler Mission is designed to survey our region of the Milky Way galaxy to discover hundreds of Earth-sized and smaller planets in or near the habitable zone. The Kepler photometer is an array of 42 CCDs (charge-coupled devices) in the focal plane of a 95-cm Schmidt camera onboard the Kepler spacecraft. Each 50x25-mm CCD has 2,200 x 1,024 pixels. The CCDs accumulate photons and are read out every six seconds to prevent saturation. The data is integrated for 30 minutes, and then the pixel data is transferred to onboard storage. The data is subsequently encoded and transmitted to the ground. During End-to-End Information System (EEIS) testing of the Kepler Mission System (KMS), there was a need to verify that the pixels requested by the science team operationally were correctly collected, encoded, compressed, stored, and transmitted by the FS, and subsequently received, decoded, uncompressed, and displayed by the Ground Segment (GS) without the outputs of any CCD modules being flipped, mirrored, or otherwise corrupted during the extensive FS and GS processing. This would normally be done by projecting an image on the focal plane array (FPA), collecting the data in a flight-like way, and making a comparison between the original data and the data reconstructed by the science data system. Projecting a focused image onto the FPA through the telescope would normally involve using a collimator suspended over the telescope opening. There were several problems with this approach: the collimation equipment is elaborate and expensive; as conceived, it could only illuminate a limited section of the FPA (.25 percent) during a given test; the telescope cover would have to be deployed during testing to allow the image to be projected into the telescope; the equipment was bulky and difficult to situate in temperature-controlled environments; and given all the above, test setup, execution, and repeatability were significant concerns. Instead of using this complicated approach of projecting an optical image on the FPA, the Kepler project developed a method using known defect features in the CCDs to verify proper collection and reassembly of the pixels, thereby avoiding the costs and risks of the optical projection approach. The CCDs composing the Kepler FPA, as all CCDs, had minor defects. At ambient temperature, some pixels look far brighter than they should. These ghot h pixels have a higher rate of charge leakage than the others due to manufacturing variations. They are usually stable over time, and appear at temperatures above 5 oC. The hot pixels on the Kepler FPA were mapped before photometer assembly during module testing. Selected hot pixels were used as target gstars h for the purposes of EEIS testing. gDead h pixels are permanently off, producing a permanently black pixel. These can also be used if there is some illumination of the FPA. During EEIS testing, Dark Current Full Frame Images (FFIs) taken at room temperature were used to create the hot pixel maps for all 84 Kepler photometer CCD channels. Data from two separate nights were used to create two hot pixel maps per channel, which were cross-correlated to remove cosmic ray events which appear to be hot pixels. These hot pixel maps obtained during EEIS testing were compared to the maps made during module testing to verify that the end-to-end data flow was correct

    Treatment of abdominal aortic anastomotic pseudoaneurysm with percutaneous coil embolization

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    AbstractIntraabdominal anastomotic pseudoaneurysms continue to be a late complication of aortic reconstructive procedures. Early surgical repair is critical but is associated with high operative mortality rates. We present a patient who was diagnosed with a distal anastomotic pseudoaneurysm 13 months after transabdominal repair of a symptomatic abdominal aortic aneurysm. Because of the poor operative risk, the patient was considered for a less invasive approach and underwent coil embolization of the abdominal aortic anastomotic pseudoaneurysm. The patient remains without recurrence of pseudoaneurysm 3.5 years later. (J Vasc Surg 2002;35:811-4.

    What makes for prize-winning television?

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    We investigate the determinants of success in four international television awards festivals between 1994 and 2012. We find that countries with larger markets and greater expenditure on public broadcasting tend to win more awards, but that the degree of concentration in the market for television and rates of penetration of pay-per-view television are unrelated to success. These findings are consistent with general industrial organisation literature on quality and market size, and with media policy literature on public service broadcasting acting as a force for quality. However, we also find that ‘home countries’ enjoy a strong advantage in these festivals, which is not consistent with festival success acting as a pure proxy for television quality

    Stabilization of Pd3−xIn1+x polymorphs with Pd-like crystal structure and their superior performance as catalysts for semi-hydrogenation of alkynes

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    Selective hydrogenation (semi-hydrogenation) reactions of alkynes rely on Pd-based catalysts to provide the correct pathway to favour formation of double bonds and avoid full hydrogenation to single bonds. Here, we present the preparation and characterisation of "Pd3In"/TiO2 nanocatalysts, which show improved activity and selectivity compared to pure Pd catalysts, towards the liquid phase semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE), a fundamental step in the preparation of pharmaceuticals, and other industrially produced substances, as well as a model reaction for the semi-hydrogenation of alkynes. For both the supported and unsupported "Pd3In" alloys (later redefined as Pd3-xIn1+x), we stabilised two new cubic polymorphs with a Pd-like structure, instead of the tetragonal structure as reported so far in the literature. The stabilisation of these new polymorphs was made possible by using a solution-based synthesis and, thanks to the use of different solvents, the reaction was 2 carried out at different temperatures and the Pd/In ratio could be tuned. The same synthetic approach was adapted to prepare two "Pd3In"/TiO2 catalysts by adding the TiO2 support to the reaction mixture, in a practical one-step, one-pot reaction. HREM and X-Ray maps show that the cubic crystal structure of "Pd3In" is maintained when prepared in the presence of the support, however, the support seems to influence the Pd/In ratio
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