7,016 research outputs found

    Developing landscape-scaled habitat selection functions for forest wildlife from Landsat data: judging black bear habitat quality in Louisiana

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    Understanding habitat needs of animal populations is critical for their effective management. In recent years, technological advances have increased the range of methods available to examine habitat selection patterns. However, available habitat data are often either limited to small geographic areas or are of coarse resolution, resulting in a gap in data to model habitat selection at landscape scales. I explored a method of processing Landsat data, the at-satellite reflectance tasseled cap, to address this data gap using black bears in south central Louisiana as a case study. As I showed, this case was particularly instructive because these bears occupy two very different habitat matrices. I examined the information content of resource measures derived from tasseled caps and determined that they contain substantially more information than is represented in coarse habitat maps such as available from the USGS GAP program. Additionally, this process could be applied over large areas and time frames, during different times of the year, and across sensors to produce consistent results that avoid the need to categorize land cover/habitats. I used logistic regression and the information theoretic approach to examine: the spatial scale at which habitat measures were derived, model complexity, and the relative value of groups of derived habitat measures. I grouped derived habitat measures to examine the information content in: images captured in two seasons, measures based on mean and standard deviation filters, and combinations of tasseled cap functions. My work suggests that researchers should consider multiple summary statistics derived over a range of scales, use multi-temporal data, and use all three tasseled cap functions to derive habitat measures. I calculated resource selection functions (RSF) for black bears in south central Louisiana and examined model calibration and discrimination. Mahalanobis distance has been proposed as an alternative to RSF because it does not require delineation of available resources, although results from the two approaches have not been compared. In this study, habitat quality predictions from RFS models more accurately depicted bear habitat preference than those of Mahalanobis. I propose an alternative use of Mahalanobis distance to direct model extrapolation beyond the boundaries of modeled populations

    Experimental studies of hypersonic boundary-layer transition and effects of wind tunnel disturbances

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    Boundary layer transition data on cones and free stream disturbance levels were measured in a hypersonic wind tunnel and Mach 8 variable density hypersonic tunnel. Transition data were obtained by using different conical models and techniques for detecting the location of transition. The disturbance levels were measured by using hot wire anemometry and pressure transducers. The transition Reynolds numbers obtained from the tests correlated well when the fluctuating pressures measured at the surface of conical models were used as a correlating parameter

    The future of global sugar markets: Policies, reforms, and impact

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    "Sugar is one of the most highly protected agricultural commodities worldwide. This protection depresses trade opportunities and the prices received by exporters without preferential market access. For this reason, dialogues about sugar policy are often polarized and short sound bites caustic. Yet today's sugar markets are being driven by a complex array of dynamic and emerging supply, demand, and policy forces that need to be understood. A number of these forces have the potential to reshape the global market scene. Recent sugar policy reforms in the European Union (EU) have received little attention in North America but may turn the EU into a net importer, with substantial compensation paid to its farmers and displaced processing facilities. High oil prices and the related ethanol boom place Brazil at the fulcrum of new market developments. In the United States, corn sweetener and sugar markets are being integrated with Mexican markets under the North American Free Trade Agreement (NAFTA), raising the question of whether the EU reforms provide a template for new policies. And among developing countries in Africa and elsewhere there are low-cost producers that would benefit from more open trade but others who would be disadvantaged by the loss of preferential markets. This discussion paper presents the proceedings of a one-day conference that served as a forum for the discussion of these and other critical issues affecting global sugar markets, policies, and reform options. The conference was attended by 60 representatives of governments, research institutions, producers and processors from the sugar sector, and other groups interested in sugar markets and policies. The four papers were presented by internationally recognized experts from the EU, Brazil, the United States, and South Africa. Discussion openers and general discussion at the conference added further policy insights, and the papers were edited and revised after the conference to reflect the dialogue that had occurred." from authors' abstractsugar, Ethanol, NAFTA, WTO, Trade policy,

    Task-related functional connectivity in autism spectrum conditions: an EEG study using wavelet transform coherence.

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    BACKGROUND: Autism Spectrum Conditions (ASC) are a set of pervasive neurodevelopmental conditions characterized by a wide range of lifelong signs and symptoms. Recent explanatory models of autism propose abnormal neural connectivity and are supported by studies showing decreased interhemispheric coherence in individuals with ASC. The first aim of this study was to test the hypothesis of reduced interhemispheric coherence in ASC, and secondly to investigate specific effects of task performance on interhemispheric coherence in ASC. METHODS: We analyzed electroencephalography (EEG) data from 15 participants with ASC and 15 typical controls, using Wavelet Transform Coherence (WTC) to calculate interhemispheric coherence during face and chair matching tasks, for EEG frequencies from 5 to 40 Hz and during the first 400 ms post-stimulus onset. RESULTS: Results demonstrate a reduction of interhemispheric coherence in the ASC group, relative to the control group, in both tasks and for all electrode pairs studied. For both tasks, group differences were generally observed after around 150 ms and at frequencies lower than 13 Hz. Regarding within-group task comparisons, while the control group presented differences in interhemispheric coherence between faces and chairs tasks at various electrode pairs (FT7-FT8, TP7-TP8, P7-P8), such differences were only seen for one electrode pair in the ASC group (T7-T8). No significant differences in EEG power spectra were observed between groups. CONCLUSIONS: Interhemispheric coherence is reduced in people with ASC, in a time and frequency specific manner, during visual perception and categorization of both social and inanimate stimuli and this reduction in coherence is widely dispersed across the brain.Results of within-group task comparisons may reflect an impairment in task differentiation in people with ASC relative to typically developing individuals.Overall, the results of this research support the value of WTC in examining the time-frequency microstructure of task-related interhemispheric EEG coherence in people with ASC.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

    Anatomical network analysis of the musculoskeletal system reveals integration loss and parcellation boost during the fins-to-limbs transition

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    Tetrapods evolved from within the lobe-finned fishes around 370 Ma. The evolution of limbs from lobe-fins entailed a major re-organization of the skeletal and muscular anatomy of appendages in early tetrapods. Concurrently, a degree of similarity between pectoral and pelvic appendages also evolved. Here, we compared the anatomy of appendages in extant lobe-finned fishes (Latimeria and Neoceratodus) and anatomically plesiomorphic amphibians (Ambystoma, Salamandra) and amniotes (Sphenodon) to trace and reconstruct the musculoskeletal changes that took place during the fins-to-limbs transition. We quantified the anatomy of appendages using network analysis. First, we built network models—in which nodes represent bones and muscles, and links represent their anatomical connections—and then we measured network parameters related to their anatomical integration, heterogeneity, and modularity. Our results reveal an evolutionary transition toward less integrated, more modular appendages. We interpret this transition as a diversification of muscle functions in tetrapods compared to lobe-finned fishes. Limbs and lobe-fins show also a greater similarity between their pectoral and pelvic appendages than ray-fins do. These findings on extant species provide a basis for future quantitative and comprehensive reconstructions of the anatomy of limbs in early tetrapod fossils, and a way to better understand the fins-to-limbs transition

    CryptOpt: Verified Compilation with Random Program Search for Cryptographic Primitives

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    Most software domains rely on compilers to translate high-level code to multiple different machine languages, with performance not too much worse than what developers would have the patience to write directly in assembly language. However, cryptography has been an exception, where many performance-critical routines have been written directly in assembly (sometimes through metaprogramming layers). Some past work has shown how to do formal verification of that assembly, and other work has shown how to generate C code automatically along with formal proof, but with consequent performance penalties vs. the best-known assembly. We present CryptOpt, the first compilation pipeline that specializes high-level cryptographic functional programs into assembly code significantly faster than what GCC or Clang produce, with mechanized proof (in Coq) whose final theorem statement mentions little beyond the input functional program and the operational semantics of x86-64 assembly. On the optimization side, we apply randomized search through the space of assembly programs, with repeated automatic benchmarking on target CPUs. On the formal-verification side, we connect to the Fiat Cryptography framework (which translates functional programs into C-like IR code) and extend it with a new formally verified program-equivalence checker, incorporating a modest subset of known features of SMT solvers and symbolic-execution engines. The overall prototype is quite practical, e.g. producing new fastest-known implementations for the relatively new Intel i9 12G, of finite-field arithmetic for both Curve25519 (part of the TLS standard) and the Bitcoin elliptic curve secp256k1

    Proximity to Sports Facilities and Sports Participation for Adolescents in Germany

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    Objectives - To assess the relationship between proximity to specific sports facilities and participation in the corresponding sports activities for adolescents in Germany. Methods - A sample of 1,768 adolescents aged 11–17 years old and living in 161 German communities was examined. Distances to the nearest sports facilities were calculated as an indicator of proximity to sports facilities using Geographic Information Systems (GIS). Participation in specific leisure-time sports activities in sports clubs was assessed using a self-report questionnaire and individual-level socio-demographic variables were derived from a parent questionnaire. Community-level socio-demographics as covariates were selected from the INKAR database, in particular from indicators and maps on land development. Logistic regression analyses were conducted to examine associations between proximity to the nearest sports facilities and participation in the corresponding sports activities. Results - The logisitic regression analyses showed that girls residing longer distances from the nearest gym were less likely to engage in indoor sports activities; a significant interaction between distances to gyms and level of urbanization was identified. Decomposition of the interaction term showed that for adolescent girls living in rural areas participation in indoor sports activities was positively associated with gym proximity. Proximity to tennis courts and indoor pools was not associated with participation in tennis or water sports, respectively. Conclusions - Improved proximity to gyms is likely to be more important for female adolescents living in rural areas

    Deep Chandra X-ray Imaging of a Nearby Radio Galaxy 4C+29.30: X-ray/Radio Connection

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    We report results from our deep Chandra X-ray observations of a nearby radio galaxy, 4C+29.30 (z=0.0647). The Chandra image resolves structures on sub-arcsec to arcsec scales, revealing complex X-ray morphology and detecting the main radio features: the nucleus, a jet, hotspots, and lobes. The nucleus is absorbed (N(H)=3.95 (+0.27/-0.33)x10^23 atoms/cm^2) with an unabsorbed luminosity of L(2-10 keV) ~ (5.08 +/-0.52) 10^43 erg/s characteristic of Type 2 AGN. Regions of soft (<2 keV) X-ray emission that trace the hot interstellar medium (ISM) are correlated with radio structures along the main radio axis indicating a strong relation between the two. The X-ray emission beyond the radio source correlates with the morphology of optical line-emitting regions. We measured the ISM temperature in several regions across the galaxy to be kT ~ 0.5 with slightly higher temperatures (of a few keV) in the center and in the vicinity of the radio hotspots. Assuming these regions were heated by weak shocks driven by the expanding radio source, we estimated the corresponding Mach number of 1.6 in the southern regions. The thermal pressure of the X-ray emitting gas in the outermost regions suggest the hot ISM is slightly under-pressured with respect to the cold optical-line emitting gas and radio-emitting plasma, which both seem to be in a rough pressure equilibrium. We conclude that 4C+29.30 displays a complex view of interactions between the jet-driven radio outflow and host galaxy environment, signaling feedback processes closely associated with the central active nucleus.Comment: ApJ in pres
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