3,908 research outputs found

    ALPyNA: Acceleration of Loops in Python for Novel Architectures

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    We present ALPyNA, an automatic loop parallelization framework for Python, which analyzes data dependences within nested loops and dynamically generates CUDA kernels for GPU execution. The ALPyNA system applies classical dependence analysis techniques to discover and exploit potential parallelism. The skeletal structure of the dependence graph is determined statically (if possible) or at runtime; this is combined with type and bounds information discovered at runtime, to auto-generate high-performance kernels for offload to GPU. We demonstrate speedups of up to 1000x relative to the native CPython interpreter across four array-intensive numerical Python benchmarks. Performance improvement is related to both iteration domain size and dependence graph complexity. Nevertheless, this approach promises to bring the benefits of manycore parallelism to application developers

    The Revised TESS Input Catalog and Candidate Target List

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    We describe the catalogs assembled and the algorithms used to populate the revised TESS Input Catalog (TIC), based on the incorporation of the Gaia second data release. We also describe a revised ranking system for prioritizing stars for 2-minute cadence observations, and assemble a revised Candidate Target List (CTL) using that ranking. The TIC is available on the Mikulski Archive for Space Telescopes (MAST) server, and an enhanced CTL is available through the Filtergraph data visualization portal system at the URL http://filtergraph.vanderbilt.edu/tess_ctl.Comment: 30 pages, 16 figures, submitted to AAS Journals; provided to the community in advance of publication in conjunction with public release of the TIC/CTL on 28 May 201

    HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Star

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    Quantifying the evolution of stellar extreme ultraviolet (EUV, 100 -- 1000 A∘\overset{\circ}{A}) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at various stages of a stellar lifetime through photometric measurements from the Galaxy Evolution Explorer (GALEX). The results revealed increased levels of short-wavelength emission that remain elevated for hundreds of millions of years. The trend for EUV flux as a function of age could not be determined empirically because absorption by the interstellar medium prevents access to the EUV wavelengths for the vast majority of stars. In this paper, we model the evolution of EUV flux from early M stars to address this observational gap. We present synthetic spectra spanning EUV to infrared wavelengths of 0.4 ±\pm 0.05 M⊙_{\odot} stars at five distinct ages between 10 and 5000 Myr, computed with the PHOENIX atmosphere code and guided by the GALEX photometry. We model a range of EUV fluxes spanning two orders of magnitude, consistent with the observed spread in X-ray, FUV, and NUV flux at each epoch. Our results show that the stellar EUV emission from young M stars is 100 times stronger than field age M stars, and decreases as t−1^{-1} after remaining constant for a few hundred million years. This decline stems from changes in the chromospheric temperature structure, which steadily shifts outward with time. Our models reconstruct the full spectrally and temporally resolved history of an M star's UV radiation, including the unobservable EUV radiation, which drives planetary atmospheric escape, directly impacting a planet's potential for habitability.Comment: 23 pages, 15 figures, accepted to Ap

    Understanding police officer resistance to body-worn cameras

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    Purpose Body-worn cameras (BWCs) have been adopted in police agencies across the USA in efforts to increase police transparency and accountability. This widespread implementation has occurred despite some notable resistance to BWCs from police officers in some jurisdictions. This resistance poses a threat to the appropriate implementation of this technology and adherence to BWC policies. The purpose of this paper is to examine factors that could explain variation in officer receptivity to BWCs. Design/methodology/approach The authors assess differences between officers who volunteered to wear a BWC and officers who resisted wearing a BWC as part of a larger randomized controlled trial of BWCs in the Phoenix Police Department. The authors specifically examine whether officer educational attainment, prior use of a BWC, attitudes toward BWCs, perceptions of organizational justice, support for procedural justice, noble cause beliefs, and official measures of officer activity predict receptivity to BWCs among 125 officers using binary logistic regression. Findings The findings indicate limited differences between BWC volunteers and resistors. Volunteers did have higher levels of educational attainment and were more likely to agree that BWCs improve citizen behaviors, relative to their resistant counterparts. Interestingly, there were no differences in perceptions of organizational justice, self-initiated activities, use of force, or citizen complaints between these groups. Originality/value Though a growing body of research has examined the impact of BWCs on officer use of force and citizen complaints, less research has examined officer attitudes toward the adoption of this technology. Extant research in this area largely focusses on general perceptions of BWCs, as opposed to officer characteristics that could predict receptivity to BWCs. This paper addresses this limitation in the research

    A Multi-City Comparison of Front and Backyard Differences in Plant Species Diversity and Nitrogen Cycling in Residential landscapes

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    We hypothesize that lower public visibility of residential backyards reduces households’ desire for social conformity, which alters residential land management and produces differences in ecological composition and function between front and backyards. Using lawn vegetation plots (7 cities) and soil cores (6 cities), we examine plant species richness and evenness and nitrogen cycling of lawns in Boston, Baltimore, Miami, Minneapolis-St. Paul, Phoenix, Los Angeles (LA), and Salt Lake City (SLC). Seven soil nitrogen measures were compared because different irrigation and fertilization practices may vary between front and backyards, which may alter nitrogen cycling in soils. In addition to lawn-only measurements, we collected and analyzed plant species richness for entire yards—cultivated (intentionally planted) and spontaneous (self-regenerating)—for front and backyards in just two cities: LA and SLC. Lawn plant species and soils were not different between front and backyards in our multi-city comparisons. However, entire-yard plant analyses in LA and SLC revealed that frontyards had significantly fewer species than backyards for both cultivated and spontaneous species. These results suggest that there is a need for a more rich and social-ecologically nuanced understanding of potential residential, household behaviors and their ecological consequences
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