966 resultados para HILL-WHEELER EQUATION


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The climates of the central and southern regions of São Paulo state in Brazil favor pathogens such as Puccinia psidii Winter, which causes a common and severe disease in Eucalyptus plantations under 2 years old. We studied genetic parameters including genotype by environment interaction (G × E) of resistance to P. psidii rust in Eucalyptus grandis at nine sites in São Paulo State. Open-pollinated progeny from ten 'provenances' were established in a randomized complete block design; at individual sites there were from 134 to 160 progenies, from four to eight blocks, and five to six trees per plot. Significant provenance and progeny(provenance) differences were detected, as was G × E involving progeny(provenance). However, the G × E involved little if any rank changes, indicating that selection can be done efficiently at a single site, if the disease level is sufficient. The estimated coefficient of genetic variation among the progeny within provenances CVg was high and variable among the sites (ranging from 11 % to 36. 7 %), demonstrating different expression of genetic variability among the sites. The estimated heritability at the individual-tree level h2 and within a plot hw 2 ranged from low to intermediate (ranging from 0. 04 to 0. 46) and was high at the progeny-mean level hf 2 (ranging from 0. 30 to 0. 86). Our study shows good prospects of controlling this disease by selection among and within progenies in a single site. © 2012 Springer-Verlag Berlin Heidelberg.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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We derive the node structure of the radial functions which are solutions of the Dirac equation with scalar S and vector V confining central potentials, in the conditions of exact spin or pseudospin symmetry, i.e., when one has V=±S+C, where C is a constant. We show that the node structure for exact spin symmetry is the same as the one for central potentials which go to zero at infinity but for exact pseudospin symmetry the structure is reversed. We obtain the important result that it is possible to have positive energy bound solutions in exact pseudospin symmetry conditions for confining potentials of any shape, including naturally those used in hadron physics, from nuclear to quark models. Since this does not occur for potentials going to zero at large distances, which are used in nuclear relativistic mean-field potentials or in the atomic nucleus, this shows the decisive importance of the asymptotic behavior of the scalar and vector central potentials on the onset of pseudospin symmetry and on the node structure of the radial functions. Finally, we show that these results are still valid for negative energy bound solutions for antifermions. © 2013 American Physical Society.

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The dynamics of dissipative and coherent N-body systems, such as a Bose-Einstein condensate, which can be described by an extended Gross-Pitaevskii formalism, is investigated. In order to analyze chaotic and unstable regimes, two approaches are considered: a metric one, based on calculations of Lyapunov exponents, and an algorithmic one, based on the Lempel-Ziv criterion. The consistency of both approaches is established, with the Lempel-Ziv algorithmic found as an efficient complementary approach to the metric one for the fast characterization of dynamical behaviors obtained from finite sequences. © 2013 Elsevier B.V. All rights reserved.

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The Kaup-Newell (KN) hierarchy contains the derivative nonlinear Schrödinger equation (DNLSE) amongst others interesting and important nonlinear integrable equations. In this paper, a general higher grading affine algebraic construction of integrable hierarchies is proposed and the KN hierarchy is established in terms of an Ŝℓ2Kac-Moody algebra and principal gradation. In this form, our spectral problem is linear in the spectral parameter. The positive and negative flows are derived, showing that some interesting physical models arise from the same algebraic structure. For instance, the DNLSE is obtained as the second positive, while the Mikhailov model as the first negative flows. The equivalence between the latter and the massive Thirring model is also explicitly demonstrated. The algebraic dressing method is employed to construct soliton solutions in a systematic manner for all members of the hierarchy. Finally, the equivalence of the spectral problem introduced in this paper with the usual one, which is quadratic in the spectral parameter, is achieved by setting a particular automorphism of the affine algebra, which maps the homogeneous into principal gradation. © 2013 IOP Publishing Ltd.

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In this work we propose a new image inpainting technique that combines texture synthesis, anisotropic diffusion, transport equation and a new sampling mechanism designed to alleviate the computational burden of the inpainting process. Given an image to be inpainted, anisotropic diffusion is initially applied to generate a cartoon image. A block-based inpainting approach is then applied so that to combine the cartoon image and a measure based on transport equation that dictates the priority on which pixels are filled. A sampling region is then defined dynamically so as to hold the propagation of the edges towards image structures while avoiding unnecessary searches during the completion process. Finally, a cartoon-based metric is computed to measure likeness between target and candidate blocks. Experimental results and comparisons against existing techniques attest the good performance and flexibility of our technique when dealing with real and synthetic images. © 2013 Elsevier B.V. All rights reserved.

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Pós-graduação em Agronomia (Agricultura) - FCA

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Agronomia (Energia na Agricultura) - FCA

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Física - IFT

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Pós-graduação em Física - IFT

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)