1000 resultados para Cooper, V. A.
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Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)
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It is shown that the appearance of a fixed-point singularity in the kernel of the two-electron Cooper problem is responsible for the formation of the Cooper pair for an arbitrarily weak attractive interaction between two electrons. This singularity is absent in the problem of three and few superconducting electrons at zero temperature on the full Fermi sea. Consequently, such three- and few-electron systems on the full Fermi sea do not form Cooper-type bound states for an arbitrarily weak attractive pair interaction.
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Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)
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A search for pair production of third-generation scalar leptoquarks and supersymmetric top quark partners, top squarks, in final states involving tau leptons and bottom quarks is presented. The search uses events from a data sample of proton-proton collisions corresponding to an integrated luminosity of 19.7 fb(-1), collected with the CMS detector at the LHC with root s = 8 TeV. The number of observed events is found to be in agreement with the expected standard model background. Third-generation scalar leptoquarks with masses below 740 GeV are excluded at 95% confidence level, assuming a 100% branching fraction for the leptoquark decay to a tau lepton and a bottom quark. In addition, this mass limit applies directly to top squarks decaying via an R-parity violating coupling. lambda(') (333). The search also considers a similar signature from top squarks undergoing a chargino-mediated decay involving the Rparity violating coupling. lambda(')(3jk). Each top squark decays to a tau lepton, a bottom quark, and two light quarks. Top squarks in this model with masses below 580 GeV are excluded at 95% confidence level. The constraint on the leptoquark mass is the most stringent to date, and this is the first search for top squarks decaying via. lambda(')(3jk). (C) 2014 The Authors. Published by Elsevier B. V.
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The use of images as a mean of human knowledge transmission dates from the earliest records of visual communication with the cave paintings. Throughout history, the communicating function remained and was extended for a variety of approaches, including illustration, which plays an important role by transmitting a content to be communicated on a creative and unique way. The advertising area relies largely on the communicative power of illustration, using it as a visual aid on different ways and medias. The advertising pieces aimed at the automotive sector – especially those developed by BMW for the Mini Cooper model – broadly employs illustrations to spread the word about the product and its attributes, seeking to communicate it using an original way. With a qualitative approach to the case study, this article analyzes the illustrations produced by the South African design studio Am I Collective as part of a video prepared by South African advertising agency Blackriver FC as a celebration campaign for the fifty years of vehicle Mini Cooper, celebrated on 2009, and it aims to identify the illustrations visuals and compositions used in the construction of the covered temporal panorama.
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Published also, 1912, as v. 2 of the Publications of the Lincoln record society.
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Introd. to many v. by S.F. Cooper.
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We introduce a general Hamiltonian describing coherent superpositions of Cooper pairs and condensed molecular bosons. For particular choices of the coupling parameters, the model is integrable. One integrable manifold, as well as the Bethe ansatz solution, was found by Dukelsky et al. [J. Dukelsky, G.G. Dussel, C. Esebbag, S. Pittel, Phys. Rev. Lett. 93 (2004) 050403]. Here we show that there is a second integrable manifold, established using the boundary quantum inverse scattering method. In this manner we obtain the exact solution by means of the algebraic Bethe ansatz. In the case where the Cooper pair energies are degenerate we examine the relationship between the spectrum of these integrable Hamiltonians and the quasi-exactly solvable spectrum of particular Schrodinger operators. For the solution we derive here the potential of the Schrodinger operator is given in terms of hyperbolic functions. For the solution derived by Dukelsky et al., loc. cit. the potential is sextic and the wavefunctions obey PT-symmetric boundary conditions. This latter case provides a novel example of an integrable Hermitian Hamiltonian acting on a Fock space whose states map into a Hilbert space of PE-symmetric wavefunctions defined on a contour in the complex plane. (c) 2006 Elsevier B.V. All rights reserved.
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Practitioners assess performance of entities in increasingly large and complicated datasets. If non-parametric models, such as Data Envelopment Analysis, were ever considered as simple push-button technologies, this is impossible when many variables are available or when data have to be compiled from several sources. This paper introduces by the 'COOPER-framework' a comprehensive model for carrying out non-parametric projects. The framework consists of six interrelated phases: Concepts and objectives, On structuring data, Operational models, Performance comparison model, Evaluation, and Result and deployment. Each of the phases describes some necessary steps a researcher should examine for a well defined and repeatable analysis. The COOPER-framework provides for the novice analyst guidance, structure and advice for a sound non-parametric analysis. The more experienced analyst benefits from a check list such that important issues are not forgotten. In addition, by the use of a standardized framework non-parametric assessments will be more reliable, more repeatable, more manageable, faster and less costly. © 2010 Elsevier B.V. All rights reserved.
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A enzima nitrato redutase (NR) catalisa a redução do nitrato a nitrito e controla a taxa de assimilação do nitrato. O ensaio in vitro da nitrato redutase foi otimizado para a linhagem selvagem (marrom, MA) e para a linhagem deficiente em ficoeritrina (verde-clara, VC) de Hypnea musciformis. As duas linhagens foram cultivadas em temperatura de 23 ± 2°C, fotoperÃodo de 14 horas, irradiância de 60-90µmol fótons m-2s-1, e meio composto por água do mar esterilizada (30ups) enriquecida com a solução de von Stosch na concentração de 50% (VSES/2). As condições ótimas de ensaio para ambas as linhagens foram: 40µM de NADH; 10min de incubação do extrato bruto (EB) e 100µL de EB. A atividade ótima da NR ocorreu em 4 e 2mM de nitrato para a linhagem VC e MA, respectivamente. As linhagens VC e MA apresentaram, respectivamente, constante aparente de Michaelis-Menten (K M) para NADH de 0,2068 e 0,0837 µM, e K M para nitrato de 0,0492 e 0,0294mM. Os resultados indicam que a NR da linhagem MA tem maior afinidade pelo substrato do que a NR da linhagem VC de H. musciformis. Os experimentos para avaliar os efeitos da disponibilidade de nitrato (5 a 105µM) e nitrato e fosfato (0,5 a 25,5µM, com a relação N:P de 4:1) mostraram que a atividade da NR das linhagens VC e MA não aumentou com a adição de nitrato no meio, o que pode estar relacionado com o estado nutricional dessas algas. A atividade da NR foi maior nos tratamentos com adição de fosfato do que naqueles com adição de apenas nitrato, indicando que esse nutriente é importante para os processos metabólicos relacionados a atividade da NR.