20,391 research outputs found

    Coupling vortex dynamics with collective excitations in Bose-Einstein Condensates

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    Here we analyze the collective excitations as well as the expansion of a trapped Bose-Einstein condensate with a vortex line at its center. To this end, we propose a variational method where the variational parameters have to be carefully chosen in order to produce reliable results. Our variational calculations agree with numerical simulations of the Gross-Pitaevskii equation. The system considered here turns out to exhibit four collective modes of which only three can be observed at a time depending of the trap anisotropy. We also demonstrate that these collective modes can be excited using well established experimental methods such as modulation of the s-wave scattering length

    Avaliação de armadilhas com feromônio sexual e atrativo floral para monitoramento de Spodoptera frugiperda e Pseudoplusia includens em macieiras.

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    O presente trabalho teve como objetivos avaliar diferentes modelos de armadilhas e atrativos para o monitoramento de adultos de grandes lagartas e apresentar a distribuição temporal das espécies em macieira

    Levantamento da podridão do estipe da pupunha no litoral do Paraná.

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    Organizado por Patricia Póvoa de Mattos, Celso Garcia Auer, Rejane Stumpf Sberze, Katia Regina Pichelli e Paulo César Botosso

    Quantum Monte Carlo Study of Strongly Correlated Electrons: Cellular Dynamical Mean-Field Theory

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    We study the Hubbard model using the Cellular Dynamical Mean-Field Theory (CDMFT) with quantum Monte Carlo (QMC) simulations. We present the algorithmic details of CDMFT with the Hirsch-Fye QMC method for the solution of the self-consistently embedded quantum cluster problem. We use the one- and two-dimensional half-filled Hubbard model to gauge the performance of CDMFT+QMC particularly for small clusters by comparing with the exact results and also with other quantum cluster methods. We calculate single-particle Green's functions and self-energies on small clusters to study their size dependence in one- and two-dimensions.Comment: 14 pages, 18 figure

    Immunization and Aging: a Learning Process in the Immune Network

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    The immune system can be thought as a complex network of different interacting elements. A cellular automaton, defined in shape-space, was recently shown to exhibit self-regulation and complex behavior and is, therefore, a good candidate to model the immune system. Using this model to simulate a real immune system we find good agreement with recent experiments on mice. The model exhibits the experimentally observed refractory behavior of the immune system under multiple antigen presentations as well as loss of its plasticity caused by aging.Comment: 4 latex pages, 3 postscript figures attached. To be published in Physical Review Letters (Tentatively scheduled for 5th Oct. issue

    Avaliação de armadilhas com feromônio sexual e atrativo floral para monitoramento de Spodoptera frugiperda (J.E. Smith, 1797) e Pseudoplusia includens (Walter, 1857) (Lepidoptera: Noctuidae) em pomar de macieira.

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    O monitoramento de insetos-praga em pomares de macieira é um fator chave para elaboração de estratégias de controle. O presente trabalho teve como objetivo avaliar diferentes modelos de armadilhas e atrativos para o monitoramento de adultos de ?grandes lagartas?, e apresentar a distribuição temporal das espécies em macieira. O estudo foi realizado em pomar comercial de macieira (cultivar Cripps Pink), localizado na cidade de Vacaria, RS. Foram utilizados três modelos de armadilhas (Balde, Delta e Pet) e dois atrativos (feromônio sexual e atrativo floral a base de phenilacethaldeido). Foram capturados 350 exemplares de Spodoptera frugiperda e 370 de Pseudoplusia includens com maior ocorrência das espécies entre janeiro e março. O atrativo mais eficiente foi o feromônio sexual e o modelo de armadilha o Delta e Pet

    Estudo fitoquímico do extrato etanólico do caule de Solanum Stramonifolium Jacq. (Família: Solanaceae).

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    O objetivo deste trabalho foi realizar um estudo fitoquímico do extrato etanólico do caule de S. stramonifolium, visando identificar as classes de compostos secundários presentes
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