72,977 research outputs found
Leituras críticas da obra de João Simões Lopes Neto: Província de São Pedro e Caderno de Sábado
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-graduação em LiteraturaEste trabalho tem como objetivo reunir e recuperar leituras críticas esparsas da obra de João Simões Lopes Neto publicadas na revista Província de São Pedro e no suplemento literário Caderno de Sábado, facilitando a pesquisa de outros estudiosos interessados em sua obra. O trabalho de transcrição foi realizado seguindo as normas padronizadas pela Filologia contemporânea, a fim de determinar os critérios adotados para a transcrição dos textos. Num primeiro momento, apresenta-se a apreciação da obra simoniana por parte dos críticos e, num segundo momento, são apresentados os vinte e oito textos selecionados para a transcrição
Avaliação do desempenho de produtos de cruzamentos entre Curraleiro Pé-duro e raças comerciais em sistemas silvipastoril e em pleno sol.
No full textAutoria: FROTA, M. [i.e. N. L.] da, MARCILIO [i.e. NILTON LOPES ] DA FROTA; CARVALHO, G. [i.e. M. C.], GERALDO [i.e. MAGELA CORTES] CARVALHO; LIMA NETO, A. [i.e. F.], ANISIO [i.e. FERREIRA] LIMA NETO
Field dependence of the magnetic spectrum in anisotropic and Dzyaloshinskii-Moriya antiferromagnets. I. Theory
No full textWe consider theoretically the effects of an applied uniform magnetic field on the magnetic spectrum of anisotropic two-dimensional and Dzyaloshinskii-Moriya layered quantum Heisenberg antiferromagnets. The former case is relevant for systems such as the two-dimensional square lattice antiferromagnet Sr2CuO2Cl2, while the latter is known to be relevant to the physics of the layered orthorhombic antiferromagnet La2CuO4. We first establish the correspondence between the low-energy spectrum obtained within the anisotropic nonlinear sigma model and by means of the spin-wave approximation for a standard easy-axis antiferromagnet. Then, we focus on the field-theory approach to calculate the magnetic-field dependence of the magnon gaps and spectral intensities for magnetic fields applied along the three possible crystallographic directions. We discuss the various possible ground states and their evolution with temperature for the different field orientations, and the occurrence of spin-flop transitions for fields perpendicular to the layers (transverse fields) as well as for fields along the easy axis (longitudinal fields). Measurements of the one-magnon Raman spectrum in Sr2CuO2Cl2 and La2CuO4 and a comparison between the experimental results and the predictions of the present theory will be reported in paper II of this research work [L. Benfatto Phys. Rev. B 74, 024416 (2006)]. (c) 2006 American Institute of Physics
Falsas anomalías de la función valor actual neto
No full textLas anomalías que surgen en el cálculo y la interpretación del Valor Actual Neto (VAN) y la Tasa Interna de Rendimiento son fácilmente superables, teniendo en cuenta las propiedades reales del VAN y redefiniendo adecuadamente lo que es una inversión y un crédit
Field dependence of the magnetic spectrum in anisotropic and Dzyaloshinskii-Moriya antiferromagnets. II. Raman spectroscopy
No full textWe compare the theoretical predictions of the previous paper on the field dependence of the magnetic spectrum in anisotropic two-dimensional and Dzyaloshinskii-Moriya layered antiferromagnets [L. Benfatto and M. B. Silva Neto, Phys. Rev. B 74, 024415 (2006)], with Raman spectroscopy experiments in Sr2CuO2Cl2 and untwinned La2CuO4 single crystals. We start by discussing the crystal structure and constructing the magnetic point group for the magnetically ordered phase of the two compounds, Sr2CuO2Cl2 and La2CuO4. We find that the magnetic point group in the ordered phase is the m_mm_ orthorhombic group, in both cases. Furthermore, we classify all the Raman active one-magnon excitations according to the irreducible co-representations for the associated magnetic point group. We find that the in-plane (or Dzyaloshinskii-Moriya) mode belongs to the DA(g) co-representation while the out-of-plane (XY) mode belongs to the DBg co-representation. We then measure and fully characterize the evolution of the one-magnon Raman energies and intensities for low and moderate magnetic fields along the three crystallographic directions. In the case of La2CuO4, a weak-ferromagnetic transition is observed for a magnetic field perpendicular to the CuO2 layers. We demonstrate that from the jump of the Dzyaloshinskii-Moriya gap at the critical magnetic field H-c similar or equal to 6.6 T one can determine the value of the interlayer coupling J(perpendicular to)/J similar or equal to 3.2x10(-5), in good agreement with previous estimates. We furthermore determine the components of the anisotropic gyromagnetic tensor as g(s)(a)=2.0, g(s)(b)=2.08, and the upper bound g(s)(c)=2.65, also in very good agreement with earlier estimates from magnetic susceptibility. For the case of Sr2CuO2Cl2, we compare the Raman data obtained in an in-plane magnetic field with previous magnon-gap measurements done by electron spin resonance (ESR). Using the very low magnon gap estimated by ESR (similar to 0.05 meV), the data for the one-magnon Raman energies agree reasonably well with the theoretical predictions for the case of a transverse field (only hardening of the gap). On the other hand, an independent fit of the Raman data provides an estimate for g(s)similar or equal to 1.98 and gives a value for the in-plane gap larger than the one measured by ESR. Finally, because of the absence of the Dzyaloshinskii-Moriya interaction in Sr2CuO2Cl2, no field-induced modes are observed for magnetic fields parallel to the CuO2 layers in the Raman geometries used, in contrast to the situation in La2CuO4. (c) 2006 American Institute of Physics
Distinção nutricional entre folhas de soja sadias e com sintoma de soja louca II utilizando a técnica espectroscopia de emissão óptica com plasma induzido por laser.
No full textEntrada padronizada: MARTIN-NETO, L
Caracterização da matéria orgânica de solos da região amazônica empregando a espectroscopia de fluorescência induzida por laser e a espectroscopia de emissão óptica com plasma induzido por laser.
No full textEntrada padronizada de BOAS, P. R. V.; MARTIN NETO, L
Impurity susceptibility and the fate of spin-flop transitions in lightly doped La2CuO4
No full textWe investigate the occurrence of a two-step spin-flop transition and spin reorientation when a longitudinal magnetic field is applied to lightly hole doped La2CuO4. We find that for large and strongly frustrating impurities, such as Sr in La2-xSrxCuO4, the huge enhancement of the longitudinal susceptibility suppresses the intermediate flop and the reorientation of spins is smooth and continuous. Contrarily, for small and weakly frustrating impurities, such as O in La2CuO4+y, a discontinuous spin reorientation (two-step spin-flop transition) takes place. Furthermore, we show that for La2-xSrxCuO4 the field dependence of the magnon gaps differs qualitatively from the La2CuO4 case, a prediction to be verified with Raman spectroscopy or neutron scattering
Differential Acquisition of m-Sequences using Recursive Soft Sequential Estimation
No full textIn this contribution a novel sequential estimation method is proposed for the acquisition of -sequences. This sequential estimation method exploits the principle of iterative soft-in-soft-out (SISO) decoding for enhancing the acquisition performance, and that of differential pre-processing for the sake of achieving an enhanced acquisition performance, when communicating over various communication environments. Hence the advocated acquisition arrangement is referred to as the Differential Recursive Soft Sequential Estimation (DRSSE) acquisition scheme. The DRSSE acquisition scheme exhibits a low complexity, which is similar to that of an -sequence generator, while achieving an acquisition time that is linearly dependent on the number of stages in the -sequence generator. A low acquisition time is achieved with the advent of the property that the proposed DRSSE scheme is capable of determining the real-time reliabilities associated with the decision concerning a set of, say , consecutive chips. This set of consecutive chips constitutes the sufficient initial condition for enabling the local -sequence generator to produce a synchronized local despreading -sequence replica. Owing to these attractive characteristics, the DRSSE acquisition scheme constitutes a promising initial synchronization scheme for acquisition of long -sequences, when communicating over various propagation environments
∑_(l+m=k,l,m≥0) ((α+l-1)¦l) ((β+m-1)¦m)=((α+β+k-1)¦k) and its application to negative binomial distribution
No full textWe prove here the following equation: ∑_(l+m=k,l,m≥0) ((α+l-1)¦l) ((β+m-1)¦m)=((α+β+k-1)¦k) and give its application to prove the reproductive property of the negative binomial distribution.
These finite sum equation involving binomial coefficients and proof of the reproductive property are not known as far as the author knows.論文(Article)departmental bulletin pape
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