1,813 research outputs found

    Observational data formats and identification of supplementary documentation for the National Geodetic Satellite Program

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    Observational formats for geodetic tracking data and supporting documentation for data reductio

    Multi-core computation of transfer matrices for strip lattices in the Potts model

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    The transfer-matrix technique is a convenient way for studying strip lattices in the Potts model since the compu- tational costs depend just on the periodic part of the lattice and not on the whole. However, even when the cost is reduced, the transfer-matrix technique is still an NP-hard problem since the time T(|V|, |E|) needed to compute the matrix grows ex- ponentially as a function of the graph width. In this work, we present a parallel transfer-matrix implementation that scales performance under multi-core architectures. The construction of the matrix is based on several repetitions of the deletion- contraction technique, allowing parallelism suitable to multi-core machines. Our experimental results show that the multi-core implementation achieves speedups of 3.7X with p = 4 processors and 5.7X with p = 8. The efficiency of the implementation lies between 60% and 95%, achieving the best balance of speedup and efficiency at p = 4 processors for actual multi-core architectures. The algorithm also takes advantage of the lattice symmetry, making the transfer matrix computation to run up to 2X faster than its non-symmetric counterpart and use up to a quarter of the original space

    The Effect of Nutritional Education Programs on Serum Cholesterol Values

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    The three objectives of this study were: 1. To test a simplified nutritional education program and it\u27s effectiveness on lowering serum cholesterol values. 2. To compare the effectiveness of two (partial vs. intense) nutritional education programs on the post serum cholesterol values. 3. To determine which demographic data influences a change in serum cholesterol values in response to a simplified nutritional program

    Nest-site resources for cavity-nesting birds in the southern Allegheny Mountain forests of West Virginia

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    Cavity-nesting birds may be negatively impacted by a lack of proper nesting sites. Southern Allegheny Mountain forests of West Virginia are unique due to the juxtaposition and diversity of forest cover types. Management must focus on monitoring wildlife population levels as well as habitat requirements within each cover type. Cavity tree abundance significantly differed among central hardwood (x¯ = 16.4; SE = 5.3), northern hardwood (x¯ =12.7; SE = 6.8), and boreal forest cover types (x¯ = 7.2; SE = 3.6) ( P \u3c 0.0001). Black locust (Robinia pseudoacacia) and American beech (Fagus grandifolia) were most likely to have tree cavities, yet beech may be influenced by increased mortality from recent outbreaks of beech bark disease initiated by the beech scale insect (Cryptacoccus fagisuga). Nesting bird community density, richness, and abundance do not differ among mature forests of the 3 cover types. Cavity-nesting species dependent on available tree holes were found most in the central hardwoods (P = 0.009). Forest managers should consider landscape level effects, as well as forest stand composition, when recommending silvicultural treatments

    Comparisons of high latitude <i>E</i> > 20 MeV proton geomagnetic cutoff observations with predictions of the SEPTR model

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    International audienceRadiation effects from solar energetic proton (SEP) events are a concern when the International Space Station reaches high latitudes accessible to SEPs. We use data from the 20?29 and 29?64 MeV proton channels of the Proton/Electron Telescope on the SAMPEX satellite during nine large SEP events to determine the experimental geographic cutoff latitudes for the two energy ranges. These are compared with calculated cutoff latitudes based on a computer model, SEPTR (solar energetic particle tracer). The observed cutoff latitudes are systematically equatorward of the latitudes calculated by the SEPTR program using a Tsyganenko field model, but that model produces mean values of ~ 2° for latitudinal differences with observations, DLat, which are ~ 3 times smaller than those using the 1995 International Geomagnetic Reference Field model alone. The number distributions of DLat are peaked near 0° and decline toward higher values. With the Tsyganenko model, we find no significant trend in either the DLat or their variances with increasing Kp

    Continuing data analysis of the AS/E grazing incidence X-ray telescope experiment on the OSO-4 satellite

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    The work to correct and extend the calculation of the theoretical solar X-ray spectrum produced during earlier OSO-4 data analysis is reported along with the work to formulate models of active regions, and compare these models with the experimental values. An atlas of solar X-ray photographs is included, and solar X-ray observations are correlated with the solar wind

    The Host-Pathogen Interactions and Epicellular Lifestyle of Neisseria meningitidis

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    Neisseria meningitidis is a gram-negative diplococcus and a transient commensal of the human nasopharynx. It shares and competes for this niche with a number of other Neisseria species including N. lactamica, N. cinerea and N. mucosa. Unlike these other members of the genus, N. meningitidis may become invasive, crossing the epithelium of the nasopharynx and entering the bloodstream, where it rapidly proliferates causing a syndrome known as Invasive Meningococcal Disease (IMD). IMD progresses rapidly to cause septic shock and meningitis and is often fatal despite aggressive antibiotic therapy. While many of the ways in which meningococci survive in the host environment have been well studied, recent insights into the interactions between N. meningitidis and the epithelial, serum, and endothelial environments have expanded our understanding of how IMD develops. This review seeks to incorporate recent work into the established model of pathogenesis. In particular, we focus on the competition that N. meningitidis faces in the nasopharynx from other Neisseria species, and how the genetic diversity of the meningococcus contributes to the wide range of inflammatory and pathogenic potentials observed among different lineages

    The chiral and flavour projection of Dirac-Kahler fermions in the geometric discretization

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    It is shown that an exact chiral symmetry can be described for Dirac-Kahler fermions using the two complexes of the geometric discretization. This principle is extended to describe exact flavour projection and it is shown that this necessitates the introduction of a new operator and two new structures of complex. To describe simultaneous chiral and flavour projection, eight complexes are needed in all and it is shown that projection leaves a single flavour of chiral field on each.Comment: v2: 17 pages, Latex. 5 images eps. Added references, reformatted and clarification of some point

    Size dependence of solar X-ray flare properties

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    Non-thermal and thermal parameters of 85 solar flares of GOES class B1 to M6 (background subtracted classes A1 to M6) have been compared to each other. The hard X-ray flux has been measured by RHESSI and a spectral fitting provided flux and spectral index of the non-thermal emission, as well as temperature and emission measure of the thermal emission. The soft X-ray flux was taken from GOES measurements. We find a linear correlation in a double logarithmic plot between the non-thermal flux and the spectral index. The higher the acceleration rate of a flare, the harder the non-thermal electron distribution. The relation is similar to the one found by a comparison of the same parameters from several sub-peaks of a single flare. Thus small flares behave like small subpeaks of large flares. Thermal flare properties such as temperature, emission measure and the soft X-ray flux also correlate with peak non-thermal flux. A large non-thermal peak flux entails an enhancement in both thermal parameters. The relation between spectral index and the non-thermal flux is an intrinsic feature of the particle acceleration process, depending on flare size. This property affects the reported frequency distribution of flare energies.Comment: Astronomy and Astrophysics, in pres
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