24,697 research outputs found

    On Duffin-Kemmer-Petiau particles with a mixed minimal-nonminimal vector coupling and the nondegenerate bound states for the one-dimensional inversely linear background

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    The problem of spin-0 and spin-1 bosons in the background of a general mixing of minimal and nonminimal vector inversely linear potentials is explored in a unified way in the context of the Duffin-Kemmer-Petiau theory. It is shown that spin-0 and spin-1 bosons behave effectively in the same way. An orthogonality criterion is set up and it is used to determine uniquely the set of solutions as well as to show that even-parity solutions do not exist.Comment: 10 page

    The peremptory influence of a uniform background for trapping neutral fermions with an inversely linear potential

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    The problem of neutral fermions subject to an inversely linear potential is revisited. It is shown that an infinite set of bound-state solutions can be found on the condition that the fermion is embedded in an additional uniform background potential. An apparent paradox concerning the uncertainty principle is solved by introducing the concept of effective Compton wavelength

    Bound states of bosons and fermions in a mixed vector-scalar coupling with unequal shapes for the potentials

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    The Klein-Gordon and the Dirac equations with vector and scalar potentials are investigated under a more general condition, Vv+Vs=constantV_{v}+V_{s}= \mathrm{constant}. These intrinsically relativistic and isospectral problems are solved in a case of squared hyperbolic potential functions and bound states for either particles or antiparticles are found. The eigenvalues and eigenfuntions are discussed in some detail and the effective Compton wavelength is revealed to be an important physical quantity. It is revealed that a boson is better localized than a fermion when they have the same mass and are subjected to the same potentials.Comment: 3 figure

    Alongamento de plantas de Dendrobium nobile Lindl. com pulverização de ácido giberélico.

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    Dendrobium nobile Lindl. (olho-de-boneca) é uma das orquídeas mais populares do Brasil, ocupando posição de destaque no mercado de plantas de corte e de vaso. Entretanto, o desenvolvimento muito lento da família Orchidaceae tem contribuído para o elevado valor unitário de suas plantas, sendo necessárias técnicas que promovam a obtenção mais rápida de plantas comercializáveis. Objetivando avaliar o efeito do ácido giberélico no alongamento de plantas de D. nobile, foi realizado experimento em delineamento inteiramente casualizado com cinco concentrações de GA3 (0, 50, 100, 200 e 400 mg.L-1) e treze repetições. Efetuaram-se quatro pulverizações com soluções de ácido giberélico a intervalos quinzenais e noventa dias após início dos tratamentos, avaliaram-se as seguintes características: altura e diâmetro do pseudobulbo, número de folhas, largura e comprimento das folhas. A aplicação do GA3 promoveu, em comparação às plantas testemunhas, incrementos de 64,08% em altura e 44,27% no comprimento das folhas e decréscimos de 50% no diâmetro do pseudobulbo e 56,09% na largura das folhas. Não houve diferença entre as concentrações de GA3 testadas. Portanto, o ácido giberélico nas concentrações de 50 a 400 mg.L-1 é igualmente eficiente no alongamento de plantas D. nobile

    Perfil fenólico de aceites de oliva vírgenes obtenidos de selecciones avanzadas en un programa de mejora

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    The evaluation of the phenolic composition in advanced selections in breeding programs constitutes the first approach for selecting genotypes with improved olive oil quality. In this work, the influence of genotype and ripening index on the phenolic profile of olive oils from advanced selections in comparison to their genitors was studied. Fruit samples were collected in genotypes from crosses between ‘Arbequina’ × ‘Picual’, ‘Picual’ × ‘Arbequina’ and ‘Frantoio’ × ‘Picual’ at five dates from 1st October to 26th November 2009. Characterization of the phenolic profile was performed by liquid–liquid extraction with 60:40 (v/v) methanol–water and subsequent chromatographic analysis with absorption and fluorescence detection in a sequential configuration. A dual effect of genotype and fruit ripening on the phenolic profile has been observed with more pronounced genetic influence in both total (34.73% and 20.45%, respectively) and individual phenols (16.99% to 49.25% and 1.58% to 23.77%, respectively). A higher degree of variability between genotypes at early ripening stages was also observed (p<0.05). The obtained results also allow identification of selections with high content of total and individual phenols. These results suggest a strategy based on early harvesting of fruits (at the first three ripening indexes) for better comparison and selection of genotypes in further crosses in olive breeding programs aiming at improving the quality of virgin olive oil.La evaluación de la composición fenolica en selecciones avanzadas en programas de mejora constituye el primer paso para la selección de genotipos cuyos aceites son de mejor calidad. Se ha estudiado la influencia del genotipo y del índice de madurez en el perfil fenólico del aceite de oliva de selecciones avanzadas en comparación con sus genitores. Se recogieron muestras de genotipos obtenidos de cruzamientos entre 'Arbequina' × 'Picual', 'Picual' × 'Arbequina' y 'Frantoio' × 'Picual' en cinco fechas entre el 1 de octubre y el 26 noviembre de 2009. Se realizó la caracterización del perfil fenólico por extracción líquido–líquido con metanol–agua al 60:40 (v/v) seguido de un análisis cromatográfico con detección por absorción y fluorescencia en una configuración secuencial. Los resultados obtenidos mostraron un mayor grado de variabilidad entre genotipos en las primeras etapas de maduración de los frutos (p<0.05), así como el efecto de la madurez de los frutos y del genotipo en el perfil fenólico, con una influencia genética más pronunciada tanto para fenoles totales (34.73% and 20.45%, respectivamente) como individuales (entre 16.99% y 49.25% y entre 1.58% y 23.77%, respectivamente). Los resultados obtenidos han permitido la identificación de selecciones con alto contenido en fenoles totales e individuales. Ambos resultados sugieren una estrategia basada en la evaluación de los fenoles totales e individuales en las primeras etapas de la maduración para comparar y seleccionar genotipos en programas de mejora por cruzamiento encaminados a mejorar la calidad del aceite de oliva virgen

    An effective singular oscillator for Duffin-Kemmer-Petiau particles with a nonminimal vector coupling: a two-fold degeneracy

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    Scalar and vector bosons in the background of one-dimensional nonminimal vector linear plus inversely linear potentials are explored in a unified way in the context of the Duffin-Kemmer-Petiau theory. The problem is mapped into a Sturm-Liouville problem with an effective singular oscillator. With boundary conditions emerging from the problem, exact bound-state solutions in the spin-0 sector are found in closed form and it is shown that the spectrum exhibits degeneracy. It is shown that, depending on the potential parameters, there may or may not exist bound-state solutions in the spin-1 sector.Comment: 1 figure. arXiv admin note: substantial text overlap with arXiv:1009.159

    Evolution of constrained layer damping using a cellular automaton algorithm

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    Constrained layer damping (CLD) is a highly effective passive vibration control strategy if optimized adequately. Factors controlling CLD performance are well documented for the flexural modes of beams but not for more complicated mode shapes or structures. The current paper introduces an approach that is suitable for locating CLD on any type of structure. It follows the cellular automaton (CA) principle and relies on the use of finite element models to describe the vibration properties of the structure. The ability of the algorithm to reach the best solution is demonstrated by applying it to the bending and torsion modes of a plate. Configurations that give the most weight-efficient coverage for each type of mode are first obtained by adapting the existing 'optimum length' principle used for treated beams. Next, a CA algorithm is developed, which grows CLD patches one at a time on the surface of the plate according to a simple set of rules. The effectiveness of the algorithm is then assessed by comparing the generated configurations with the known optimum ones

    Técnicas de preparação de amostras para estudos de insetos com microscópio eletrônico de varredura.

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