6,776 research outputs found

    A New Experiment to Study Hyperon CP Violation and the Charmonium System

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    Fermilab operates the world's most intense antiproton source, now exclusively dedicated to serving the needs of the Tevatron Collider. The anticipated 2009 shutdown of the Tevatron presents the opportunity for a world-leading low- and medium-energy antiproton program. We summarize the status of the Fermilab antiproton facility and review physics topics for which a future experiment could make the world's best measurements.Comment: 16 pages, 3 figures, to appear in Proceedings of CTP symposium on Supersymmetry at LHC: Theoretical and Experimental Perspectives, The British University in Egypt, Cairo, Egypt, 11-14 March 200

    Microwave Remote Sensing of Ocean Surface Wind Speed and Rain Rates over Tropical Storms

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    The value of using narrowly spaced frequencies within a microwave band to measure wind speeds and rain rates over tropical storms with radiometers is reviewed. The technique focuses on results obtained in the overflights of Hurricane Allen during 5 and 8 of August, 1980

    Multilevel semantic analysis and problem-solving in the flight domain

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    A computer based cockpit system which is capable of assisting the pilot in such important tasks as monitoring, diagnosis, and trend analysis was developed. The system is properly organized and is endowed with a knowledge base so that it enhances the pilot's control over the aircraft while simultaneously reducing his workload

    Directly immobilized DNA sensor for label-free detection of herpes virus

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    This paper reports the direct immobilization of deoxyribonucleic acid (DNA) sequences of Herpes simplex virus (5'-AT CAC CGA CCC GGA GAG GGA C-3') on the surface of DNA sensor by using the cyclic voltammetric method with the presence of pyrrole. The potential was scanned from -0.7 volt to + 0.6 volt, the scanning rate was at 100 mV/s....This kind of DNA sensor was developed to detect Herpes virus DNA in samples. The FTIR was applied to verify specific binding of DNA sequence and conducting polymer, the morphology of conducting polymer doped with DNA strands was investigated by using a field emission scanning electron microscope (FESEM). The results showed that output signal given by coimmobilized DNA/PPy membrane sensor was better than that given by APTS immobilized membrane sensors. The sensor can detect as low as 2 nM of DNA target in real samples.</p

    Sum rule for the optical Hall angle

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    We consider the optical Hall conductivity of a general electronic medium and prove that the optical Hall angle obeys a new sum rule. This sum rule governs the response of an electronic fluid to a Lorentz electric field and can thought of as the transverse counterpart to the f-sum rule in optical conductivity. The physical meaning of this sum rule is discussed, giving a number of examples of its application to a variety of of electronic media.Comment: Four pages. Latex file with two postscript figure

    The Anomalous Hall Effect in YBa2_2Cu3_3O7_7

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    The temperature dependence of the normal state Hall effect and magnetoresistance in YBa2_2Cu3_3O7_7 is investigated using the Nearly Antiferromagnetic Fermi Liquid description of planar quasiparticles. We find that highly anisotropic scattering at different regions of the Fermi surface gives rise to the measured anomalous temperature dependence of the resistivity and Hall coefficient while yielding the universal temperature dependence of the Hall angle observed for both clean and dirty samples. This universality is shown to arise from the limited momentum transfers available for the anomalous, spin fluctuation scattering and is preserved for any system with strong antiferromagnetic correlations.Comment: REVTeX, 10 pages + 4 figures in a single (compressed/uuencoded) PostScript fil

    Towards a Robuster Interpretive Parsing

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    The input data to grammar learning algorithms often consist of overt forms that do not contain full structural descriptions. This lack of information may contribute to the failure of learning. Past work on Optimality Theory introduced Robust Interpretive Parsing (RIP) as a partial solution to this problem. We generalize RIP and suggest replacing the winner candidate with a weighted mean violation of the potential winner candidates. A Boltzmann distribution is introduced on the winner set, and the distribution’s parameter TT is gradually decreased. Finally, we show that GRIP, the Generalized Robust Interpretive Parsing Algorithm significantly improves the learning success rate in a model with standard constraints for metrical stress assignment

    Quantum rotor theory of spinor condensates in tight traps

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    In this work, we theoretically construct exact mappings of many-particle bosonic systems onto quantum rotor models. In particular, we analyze the rotor representation of spinor Bose-Einstein condensates. In a previous work it was shown that there is an exact mapping of a spin-one condensate of fixed particle number with quadratic Zeeman interaction onto a quantum rotor model. Since the rotor model has an unbounded spectrum from above, it has many more eigenstates than the original bosonic model. Here we show that for each subset of states with fixed spin F_z, the physical rotor eigenstates are always those with lowest energy. We classify three distinct physical limits of the rotor model: the Rabi, Josephson, and Fock regimes. The last regime corresponds to a fragmented condensate and is thus not captured by the Bogoliubov theory. We next consider the semiclassical limit of the rotor problem and make connections with the quantum wave functions through use of the Husimi distribution function. Finally, we describe how to extend the analysis to higher-spin systems and derive a rotor model for the spin-two condensate. Theoretical details of the rotor mapping are also provided here.Comment: 10 pages, 2 figure
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