82,223 research outputs found

    Improving Sensitivity to Weak Pulsations with Photon Probability Weighting

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    All gamma-ray telescopes suffer from source confusion due to their inability to focus incident high-energy radiation, and the resulting background contamination can obscure the periodic emission from faint pulsars. In the context of the Fermi Large Area Telescope, we outline enhanced statistical tests for pulsation in which each photon is weighted by its probability to have originated from the candidate pulsar. The probabilities are calculated using the instrument response function and a full spectral model, enabling powerful background rejection. With Monte Carlo methods, we demonstrate that the new tests increase the sensitivity to pulsars by more than 50% under a wide range of conditions. This improvement may appreciably increase the completeness of the sample of radio-loud gamma-ray pulsars. Finally, we derive the asymptotic null distribution for the H-test, expanding its domain of validity to arbitrarily complex light curves.Comment: 10 pages, 11 figures, published by ApJ; v2 fixes an error in Eq.

    Solutions to polynomial congruences in well shaped sets

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    We use a generalization of Vinogradov's mean value theorem of S. Parsell, S. Prendiville and T. Wooley and ideas of W. Schmidt to give nontrivial bounds for the number of solutions to polynomial congruences, for arbitrary polynomials, when the solutions lie in a very general class of sets, including all convex sets

    Establishment of, and running, a comprehensive organic seed information database and communication network OF0195

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    The Scientific Objectives 1. To request and collate information from seed companies and organic sector certification bodies throughout the EU on the production of organic seed. Regular Organic Seed Working Group meetings were held throughout this period and information on EU regulations and techniques of organic seed production discussed and minuted on COSI. 2. To produce an up-to-date list of organic seed availability of varieties of field vegetable, cereals and potatoes within the EU. Where possible the list will provide an indication of seed quantity as well as variety availability. Contact was made with all seed companies and lists compiled of varieties available as organic seed. Over 1000 varieties were eventually added to the European OrganicXseeds database. 3. Establish an effective communication system linking the seed industry, organic growers, UKROFS and certification bodies. COSI web site was set up with the capability of exchanging information on organic topics and keeping abreast of legislation changes. 4. Where possible to provide an indication of the suitability of the varieties listed for UK growing and marketing. Where UK tests have not been carried out a comparison with known controls will be made. The COSI database lists comprehensive results for organic variety trial data carried out by NIAB, HDRA, Elm Farm and other centres. In addition, data for organic or conventional trial performance has been added for all varieties where information is available. The extent to which the objectives have been met. The COSI web site was created and launched in 2001 and the objectives have been fully met. Methods used Consultation with all interested representatives was carried out by post, telephone and twice-yearly meetings with each crop sector. Regular updates and progress reports were given at NIAB, HDRA and Soil Association open days and committee meetings. The web site was developed by Soil Association IT specialists. Results Several seed companies attempted organic seed production and most varieties produced were listed on the COSI/OrganicXseeds web sites. Some seed companies were discouraged by the extension of the derogation allowance of EU Regulation 2092/91 which meant that untreated conventional seed could still be used for vegetable crops. Access to lists of varieties available as organic seed through COSI and OrganicXseeds has been successful but seed companies were unwilling to list quantities of seed available. However a "red/green traffic light" system was set up to indicate whether seed is currently available and for vegetables the option of listing as "available in small packets only" is available. Every variety listed has been researched to enable organic and conventional performance data to be added. All known organic trial results have been added. Implications The web site has been successfully established and support is growing with time. Possible future work Maintain support for the site especially the time consuming addition of performance data for each variety. This project successfully set up a web site called COSI (Centre for Organic Seed Information) address: www.COSI.org.uk In addition, the site included the following areas: Latest news of interest to organic growers Information on organic standards An organic discussion forum Organic grower survey result

    Viking Force: Canada’s Unknown Commandos

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    Most people interested in Canadian military history know about hte elite first Special Battalion, formed in July 1942 as the Canadian element of the largely American First Sepcial Service Force.1 Few, however, have ever heard of Viking Force, Canada’s first attempt at creating an elite Commando unit in the Second World War. Viking Force does not appear in any Canadian Army Order of Battle, and did not even last long enough for its members to put on the unit’s horned-helmet shoulder patch, yet it played an important role in the sad story of the Dieppe fiasco. Acknowledgment of that role is long overdue

    Review of The Lamb and the Tiger: From Peacekeepers to Peacewarriors in Canada by Stanley R. Barrett

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    Review of The Lamb and the Tiger: From Peacekeepers to Peacewarriors in Canada by Stanley R. Barret
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