1,375 research outputs found

    Astrophysical limitations to the identification of dark matter: indirect neutrino signals vis-a-vis direct detection recoil rates

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    A convincing identification of dark matter (DM) particles can probably be achieved only through a combined analysis of different detections strategies, which provides an effective way of removing degeneracies in the parameter space of DM models. In practice, however, this program is made complicated by the fact that different strategies depend on different physical quantities, or on the same quantities but in a different way, making the treatment of systematic errors rather tricky. We discuss here the uncertainties on the recoil rate in direct detection experiments and on the muon rate induced by neutrinos from dark matter annihilations in the Sun, and we show that, contrarily to the local DM density or overall cross section scale, irreducible astrophysical uncertainties affect the two rates in a different fashion, therefore limiting our ability to reconstruct the parameters of the dark matter particle. By varying within their respective errors astrophysical parameters such as the escape velocity and the velocity dispersion of dark matter particles, we show that the uncertainty on the relative strength of the neutrino and direct-detection signal is as large as a factor of two for typical values of the parameters, but can be even larger in some circumstances.Comment: 12 pages, 3 figures. Improved presentation and Fig.3; clarifications, references and an appendix added; conclusions unchanged. Matches version published in PR

    WIMP astronomy and particle physics with liquid-noble and cryogenic direct-detection experiments

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    Once weakly-interacting massive particles (WIMPs) are unambiguously detected in direct-detection experiments, the challenge will be to determine what one may infer from the data. Here, I examine the prospects for reconstructing the local speed distribution of WIMPs in addition to WIMP particle-physics properties (mass, cross sections) from next-generation cryogenic and liquid-noble direct-detection experiments. I find that the common method of fixing the form of the velocity distribution when estimating constraints on WIMP mass and cross sections means losing out on the information on the speed distribution contained in the data and may lead to biases in the inferred values of the particle-physics parameters. I show that using a more general, empirical form of the speed distribution can lead to good constraints on the speed distribution. Moreover, one can use Bayesian model-selection criteria to determine if a theoretically-inspired functional form for the speed distribution (such as a Maxwell-Boltzmann distribution) fits better than an empirical model. The shape of the degeneracy between WIMP mass and cross sections and their offset from the true values of those parameters depends on the hypothesis for the speed distribution, which has significant implications for consistency checks between direct-detection and collider data. In addition, I find that the uncertainties on theoretical parameters depends sensitively on the upper end of the energy range used for WIMP searches. Better constraints on the WIMP particle-physics parameters and speed distribution are obtained if the WIMP search is extended to higher energy (~ 1 MeV).Comment: 25 pages, 27 figures, matches published versio

    Bioenergy Co-products as Swine Feed Ingredients: Combining DDGS and Glycerol

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    Bioenergy production generates two major coproducts—distillers dried grains with solubles (DDGS) from ethanol plants and crude glycerol from biodiesel plants. We need to evaluate whether these co-products, DDGS and glycerol, can be fed in combination to partially meet the feed energy needs of growing pigs. If successful, the diet with 25% DDGS and 10% glycerol has the potential to reduce corn feeding to market pigs by 40+%. The objective was to evaluate feeding crude glycerol and DDGS in combination to market swine. At the processing plant, a fat sample was taken from the jowl of each pig. The fat sample was analyzed for fatty acids. Pig performance and carcass traits did not differ between diets. Fatty acid composition showed differences based on the dietary treatments. Saturated fatty acids were highest for diets with the most corn and least DDGS – the corn-soy and 10% glycerol diets (P \u3c 0.01). Mono unsaturated fatty acids were highest for the 10% glycerol diet and decreased as DDGS was added with the lowest value for the 25% DDGS diet (P \u3c 0.01). Poly-unsaturated fats were lowest for the corn-soy and 10% glycerol diets and highest for the 25% DDGS diets (P \u3c 0.001). The results of this study show that pig performance was not affected by the addition of DDGS and crude glycerol. The amount of corn fed can be reduced by the addition of DDGS and glycerol. DDGS increases the unsaturated fatty acids in pork fat. Crude glycerol addition partially offsets the DDGS fatty acid effect by reducing polyunsaturated fatty acid content

    Evolutionary History and Attenuation of Myxoma Virus on Two Continents

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    The attenuation of myxoma virus (MYXV) following its introduction as a biological control into the European rabbit populations of Australia and Europe is the canonical study of the evolution of virulence. However, the evolutionary genetics of this profound change in host-pathogen relationship is unknown. We describe the genome-scale evolution of MYXV covering a range of virulence grades sampled over 49 years from the parallel Australian and European epidemics, including the high-virulence progenitor strains released in the early 1950s. MYXV evolved rapidly over the sampling period, exhibiting one of the highest nucleotide substitution rates ever reported for a double-stranded DNA virus, and indicative of a relatively high mutation rate and/or a continually changing selective environment. Our comparative sequence data reveal that changes in virulence involved multiple genes, likely losses of gene function due to insertion-deletion events, and no mutations common to specific virulence grades. Hence, despite the similarity in selection pressures there are multiple genetic routes to attain either highly virulent or attenuated phenotypes in MYXV, resulting in convergence for phenotype but not genotype. © 2012 Kerr et al

    Feeding Bioenergy Coproducts to Swine: Crude Glycerol

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    Biodiesel can be produced from a variety of fats and oils. Soybean oil is the primary feedstock in Iowa. In general, soybean oil is mixed with an alcohol (usually methanol) and a catalyst. The action of the alcohol and catalyst cause the oil (triacylglyceride) molecules to be broken down into methyl esters (biodiesel) and crude glycerol. Crude glycerol is the principal co-product of biodiesel production. For every gallon of biodiesel produced, 0.7 pounds of crude glycerol are co-generated. Biodiesel sales in the United States have increased rapidly since 1999 and annual production capacity in the U.S. is nearly 1.4 billion gallons. Iowa has 11 operating plants with 3 additional plants expected to be operational by December 2007. Production capacity in Iowa for biodiesel is 318.5 million gallons. Approximately 110,000 tons of crude glycerol could be generated annually by the biodiesel plants within Iowa

    Growth and Performance of Nursery Pigs Fed Crude Glycerol

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    The growth and performance of 96 nursery pigs fed crude glycerol was evaluated in a 33 d trial. Pigs were weaned at 21 d of age and had an average start weight of 7.9±1.2 kg (17.4±2.6 lb). Pigs were provided ad libitum access to corn soybean diets containing three levels of crude glycerol, 0, 5, or 10%. Diets were formulated to be ioscaloric and isolysinic. There was no difference in pig performance based on dietary treatment. Crude glycerol can be fed to young pigs as an energy source without growth or performance effects

    Construction and testing of a novel host-range defective myxoma virus vaccine with the M063 gene inactivated that is non-permissive for replication in rabbit cells

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    Deletion of the M063 gene from myxoma virus produces a virus that is unable to replicate in rabbit cells in vitro or in live rabbits but can be propagated in non-rabbit cell lines. A targeted M063 deletion mutant was constructed in the attenuated Uriarra strain of myxoma virus and the ability of this virus to act as a safe, non-transmissible vaccine against myxomatosis was tested in outbred laboratory rabbits. Immunization with the M063 deletion vaccine provided good short-term protection against lethal challenge with virulent myxoma virus. Long-term protection was similar to reported results with heterologous live virus, with some rabbits protected but others succumbing to challenge. Replication-deficient poxvirus vaccines, like the Modified Vaccinia Virus Ankara (MVA) in man and the myxoma virus vaccine described here in rabbits, are very attractive from a safety perspective. Seasonal boosting would be predicted to provide long-term protection. Targeted host-range gene deletions could have potential for rapid development of poxvirus vaccines in general.This study was funded by the Pest Animal Control Cooperative Research Centre. Grant McFadden is an International Scholar of the Howard Hughes Medical Institute

    Magneto-optical Kerr Effect Studies of Square Artificial Spin Ice

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    We report a magneto-optical Kerr effect study of the collective magnetic response of artificial square spin ice, a lithographically-defined array of single-domain ferromagnetic islands. We find that the anisotropic inter-island interactions lead to a non-monotonic angular dependence of the array coercive field. Comparisons with micromagnetic simulations indicate that the two perpendicular sublattices exhibit distinct responses to island edge roughness, which clearly influence the magnetization reversal process. Furthermore, such comparisons demonstrate that disorder associated with roughness in the island edges plays a hitherto unrecognized but essential role in the collective behavior of these systems.Comment: Physical Review B, Rapid Communications (in press

    Growth Performance of Growing Pigs Fed Crude Glycerol-Supplemented Diets

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    Growth performance of growing pigs fed crude glycerol was determined in a 138-d feeding trial. Crude glycerol utilized in the trial contained 84.51% glycerol, 11.95% water, 2.91% sodium chloride, and 0.32% methanol. Eight days post-weaning, 96 pigs (48 barrows, 48 gilts) with an average BW of 7.9 ± 0.4 kg were allotted to 24 pens (4 pigs/pen), with gender and pen weight balanced at the start of the experiment. Dietary regimes were randomly assigned to each pen. Dietary treatments were 0, 5, and 10% crude glycerol inclusion in corn-soybean meal based diets. Diets were offered ad libitum in meal form and formulated to be equal in metabolizable energy (ME), sodium, chloride, and Lys, with other amino acids (AA) balanced on an ideal AA basis. Every two weeks, pigs and feeders were weighed and G:F calculated. Pig growth, feed intake, and G:F were not affected by dietary treatment. Crude glycerol is a viable source of dietary energy that is well utilized by pigs. Inclusion of crude glycerol in pig diets may be determined by relative availability and price of other dietary energy sources
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