4,549 research outputs found

    General Volume-Preserving Mechanical Systems

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    In this letter, we present the general form of equations that generate a volume-preserving flow on a symplectic manifold (M, \omega). It is shown that every volume-preserving flow has some 2-forms acting the role of the Hamiltonian functions in the Hamiltonian mechanics and the ordinary Hamilton equations are included as a special case with a 2-form \frac{1}{n-1} H \omega where H is the corresponding Hamiltonian.Comment: Plain LaTeX, 13 pages, no figure

    On Torsion and Nieh-Yan Form

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    Using the well-known Chern-Weil formula and its generalization, we systematically construct the Chern-Simons forms and their generalization induced by torsion as well as the Nieh-Yan (N-Y) forms. We also give an argument on the vanishing of integration of N-Y form on any compact manifold without boundary. A systematic construction of N-Y forms in D=4n dimension is also given.Comment: 7 pages, latex, no figure

    Dublin City University at CLEF 2007: Cross-Language Speech Retrieval Experiments

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    The Dublin City University participation in the CLEF 2007 CL-SR English task concentrated primarily on issues of topic translation. Our retrieval system used the BM25F model and pseudo relevance feedback. Topics were translated into English using the Yahoo! BabelFish free online service combined with domain-specific translation lexicons gathered automatically from Wikipedia. We explored alternative topic translation methods using these resources. Our results indicate that extending machine translation tools using automatically generated domainspecific translation lexicons can provide improved CLIR effectiveness for this task

    Glycoprotein Synthesis and Signal Transduction in Schistosoma mansoni

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    Schistosomes are metazoan parasites which live within the blood vessels of man and his livestock. Infection results in a debilitating disease known as schistosomiasis or bilharzia. Over 200 million people in numerous tropical and sub-tropical countries are believed to harbour the parasite and effective long-term control has proved difficult. During my three years of research, I have concentrated on glycoprotein synthesis and signal transduction in S. mansoni
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