321 research outputs found

    Resultados da experimentação de genótipos de trigo para aptidão a duplo propósito no Paraná, em 2000.

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    Tritiation of amorphous and crystalline silicon using T <inf>2</inf> gas

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    Incorporation of tritium in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) at 250 °C using tritium (T 2) gas at pressures of up to 120 atm is reported. The tritium is stored in a surface layer which is approximately 150 and 10 nm for a-Si:H and c-Si, respectively. The concentration of tritium occluded in planar and textured c-Si is linearly dependent on the total surface area. The tritium is stable and the dominant tritium evolution occurs at temperatures above 300 °C. The concentration of tritium locked in a-Si:H and c-Si was 20 and 4 at. %, respectively. Self-catalysis appears to be important in the tritiation process. © 2006 American Institute of Physics

    Protective effect and economic impact of insecticide application methods on barley.

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    Avalia o efeito protetor de diferentes formas de aplicação de inseticida sobre a transmissão do nanismo amarelo em cultivares de cevada, bem como determina os custos de produção e o lucro líquido destes manejos. Os experimentos foram realizados durante as safras 2011 e 2012, tendo-se utilizado os seguintes manejos nas parcelas principais: T1, tratamento de sementes com inseticida (TS) + inseticida na parte aérea aplicado quinzenalmente; T2, apenas TS; T3, inseticida aplicado à parte aérea, quando foi atingido o nível de controle de afídeos (NC); T4, sem inseticida; e T5, TS + inseticida na parte aérea, quando o NC foi atingido. As subparcelas foram constituídas de diferentes cultivares de cevada: BRS Cauê, BRS Brau e MN 6021. Foram utilizados os inseticidas lambda&#8209;cialotrina (piretroide) e thiametoxam (neonicotinoide). Houve diferenças no índice de doença do nanismo amarelo em ambas as safras para os diferentes manejos, enquanto o dano ao rendimento de grãos foi influenciado pelo ano e pela população de afídeos. Os custos de produção e lucro líquido diferiram entre os tratamentos. Constatou-se que o tratamento de sementes com inseticida é suficiente para reduzir a epidemia do nanismo&#8209;amarelo em anos com baixa pressão populacional de afídeos; porém, em anos com maiores populações, a aplicação de inseticida à parte aérea também se torna necessária

    Hadroproduction and Polarization of Charmonium

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    In the limit of heavy quark mass, the production cross section and polarization of quarkonia can be calculated in perturbative QCD. We study the pp_\perp-averaged production of charmonium states in πN\pi N collisions at fixed target energies. The data on the relative production rates of \jp and χJ\chi_J is found to disagree with leading twist QCD. The polarization of the \jp indicates that the discrepancy is not due to poorly known parton distributions nor to the size of higher order effects (KK-factors). Rather, the disagreement suggests important higher twist corrections, as has been surmised earlier from the nuclear target AA-dependence of the production cross section.Comment: 19 page

    Quarkonium Suppression

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    I discuss quarkonium suppression in equilibriated strongly interacting matter. After a brief review of basic features of quarkonium production I discuss the application of recent lattice data on the heavy quark potential to the problem of quarkonium dissociation as well as the problem of direct lattice determination of quarkonium properties in finite temperature lattice QCD.Comment: Invited plenary talk presented on 4th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP-2001), November 26-30, 2001, Jaipur; 12 pp, LaTeX, uses pramana.st

    Anomalous J/psi suppression and charmonium dissociation cross sections

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    We study J/ψJ/\psi suppression in Pb+Pb collisions at CERN-SPS energies in hadronic matter with energy- and temperature-dependent charmonium dissociation cross sections calculated in the quark-interchange model of Barnes and Swanson. We find that the variation of J/ψ\psi survival probability from peripheral to central collisions can be explained as induced by hadronic matter absorption in central collisions.Comment: 30 pages, 8 figures, LaTex, changed for the latest NA50 dat

    Properties of heavy quarkonia and B_c mesons in the relativistic quark model

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    The mass spectra and electromagnetic decay rates of charmonium, bottomonium and B_c mesons are comprehensively investigated in the relativistic quark model. The presence of only heavy quarks allows the expansion in powers of their velocities. All relativistic corrections of order v^2/c^2, including retardation effects and one-loop radiative corrections, are systematically taken into account in the computations of the mass spectra. The obtained wave functions are used for the calculation of radiative magnetic dipole (M1) and electric dipole (E1) transitions. It is found that relativistic effects play a substantial role. Their account and the proper choice of the Lorentz structure of the quark-antiquark interaction in a meson is crucial for bringing theoretical predictions in accord with experimental data. A detailed comparison of the calculated decay rates and branching fractions with available experimental data for radiative decays of charmonium and bottomonium is presented. The possibilities to observe the currently missing spin-singlet S and P states as well as D states in bottomonium are discussed. The results for B_c masses and decays are compared with other quark model predictions.Comment: 31 pages, 2 figures, minor correction
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