7,476 research outputs found

    Noncommutativity due to spin

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    Using the Berezin-Marinov pseudoclassical formulation of spin particle we propose a classical model of spin noncommutativity. In the nonrelativistic case, the Poisson brackets between the coordinates are proportional to the spin angular momentum. The quantization of the model leads to the noncommutativity with mixed spacial and spin degrees of freedom. A modified Pauli equation, describing a spin half particle in an external e.m. field is obtained. We show that nonlocality caused by the spin noncommutativity depends on the spin of the particle; for spin zero, nonlocality does not appear, for spin half, őĒxőĒy‚Č•őł2/2\Delta x\Delta y\geq\theta^{2}/2, etc. In the relativistic case the noncommutative Dirac equation was derived. For that we introduce a new star product. The advantage of our model is that in spite of the presence of noncommutativity and nonlocality, it is Lorentz invariant. Also, in the quasiclassical approximation it gives noncommutativity with a nilpotent parameter.Comment: 11 pages, references adda

    Diretrizes para o desenvolvimento de especifica√ß√Ķes por desempenho para concretos no Brasil

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    Guidelines to develop performance specifications of concrete, including suggestions for performance requirements, are presented. This paper proposes changes to the Brazilian specifications and standards in order to follow the international trend and to move from prescription to performance. Although, the implementation of performance specifications may pose some challenges, it brings an opportunity to increase the service life of concrete structures. The strategic, tactic and operational aspects of performance specification's implementation in Brazil are presented, as well. These guidelines are based on specifications already adopted by other countries, on mathematical modeling and on experimental work.A implementa√ß√£o de especifica√ß√Ķes por desempenho, apesar de apresentarem alguns desafios, trazem uma oportunidade para o aumento da vida √ļtil das estruturas de concreto. Este trabalho apresenta sugest√Ķes para a modifica√ß√£o das especifica√ß√Ķes e normas brasileiras a fim de que sigam a tend√™ncia mundial e passem de prescri√ß√£o ao desempenho. S√£o tamb√©m apresentadas diretrizes para a cria√ß√£o de especifica√ß√Ķes por desempenho de concretos, incluindo sugest√Ķes para os requisitos de desempenho, bem como os aspectos estrat√©gicos, t√°ticos e operacionais de sua implementa√ß√£o no Brasil. Estas diretrizes t√™m como base especifica√ß√Ķes adotadas em outros pa√≠ses, modelagem matem√°tica e trabalhos experimentais.21922

    Performance and toolchain of a combined GPU/FPGA desktop

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    Low-power, high-performance computing nowadays relies on accelerator cards to speed up the calculations. Combining the power of GPUs with the flexibility of FPGAs enlarges the scope of problems that can be accelerated. We describe the performance analysis of a desktop equipped with a GPU Tesla 2050 and an FPGA Virtex- 6 LX 240T. The balance between the I/O and the raw peak performance is analyzed using the roofline model. A well-tuned accelerator- based codesign, identifying the parallelism, the computation and data patterns of different classes of algorithms, will enable to maximize the performance of the combined GPU/FPGA system

    Study of combining GPU/FPGA accelerators for high-performance computing

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    This contribution presents the performance modeling of a super desktop with GPU and FPGA accelerators, using OpenCL for the GPU and a high-level synthesis compiler for the FPGAs. The performance model is used to evaluate the different high-level synthesis optimizations, taking into account the resource usage, and to compare the compute power of the FPGA with the GP

    Inteligência artificial aplicada à predicação do ponto de abate de bovinos confinados.

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    O objetivo deste trabalho foi criar um software para realizar a predição do ponto de abate de bovinos por meio de características e medidas ultrassonográficas obtidas apenas no início do confinamento

    Coleta e prepara√ß√£o de material bot√Ęnico.

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    bitstream/item/50177/1/fd430001.pdf1 folder

    The Noncommutative Supersymmetric Nonlinear Sigma Model

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    We show that the noncommutativity of space-time destroys the renormalizability of the 1/N expansion of the O(N) Gross-Neveu model. A similar statement holds for the noncommutative nonlinear sigma model. However, we show that, up to the subleading order in 1/N expansion, the noncommutative supersymmetric O(N) nonlinear sigma model becomes renormalizable in D=3. We also show that dynamical mass generation is restored and there is no catastrophic UV/IR mixing. Unlike the commutative case, we find that the Lagrange multiplier fields, which enforce the supersymmetric constraints, are also renormalized. For D=2 the divergence of the four point function of the basic scalar field, which in D=3 is absent, cannot be eliminated by means of a counterterm having the structure of a Moyal product.Comment: 15 pages, 7 figures, revtex, minor modifications in the text, references adde

    Use of chemometrics to characterize tropical wines from different vintages and grape cultivars according to the 1H NMR spectroscopy data.

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    Tropical wines have been produced in Northeast of Brazil since 1980's, between the 8¬į and 9¬į S latitude, in a region called Sub-rniddle S√£o Francisco river Valley. This area presents an intra-annual climate variability and wines can be elaborated in different months of the year, according to the winery, with different analytical characteristics due to the climatic conditions. NMR spectroscopy is an interesting tool that allows to determine in a single analysis many analytical compounds of the wines. PCA and PLS rnultivariate statistical analyses applied on NMR data allow to discriminate samples and to identify the responsible compounds for the clustering. The aim of this work was to use chemometrics, PCA and PLS, applied on IH NMR spectroscopy data, to characterize tropical wines from different vintages and grape cultivars, in Northeast of Brazil. Wines were elaborated by using traditional winemaking process with control of the fermentations temperature and use of antioxidants. Before statistical analyses, IHNMR spectra were segmented, normalized, converted to Excel software format and further processed for PCA and PLS analyses. Statistical analyses applied on NMR spectra data were not satisfactory to discriminate between different vintages of white and red wines together, but they were able to separate each one according to different vintages and cultivars. Metabolic compounds were found to explain wine clusters, and fingerprints are discussed

    Aging increases susceptibility to high fat diet-induced metabolic syndrome in C57BL/6 mice: Improvement in glycemic and lipid profile after antioxidant therapy

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    Nonalcoholic fatty liver disease (NAFLD) has been considered a novel component of the metabolic syndrome (MetS), with the oxidative stress participating in its progression. This study aimed to evaluate the metabolic profile in young and old mice with MetS, and the effects of apocynin and tempol on glycemic and lipid parameters. Young and old C57BL/6 mice with high fat diet- (HFD-) induced MetS received apocynin and tempol 50 mg·kg(-1)/day in their drinking water for 10 weeks. After HFD, the young group showed elevated fasting glucose, worsened lipid profile in plasma, steatosis, and hepatic lipid peroxidation. Nevertheless, the old group presented significant increase in fasting insulin levels, insulin resistance, plasma and hepatic lipid peroxidation, and pronounced steatosis. The hepatic superoxide dismutase and catalase activity did not differ between the groups. Tempol and apocynin seemed to prevent hepatic lipid deposition in both groups. Furthermore, apocynin improved glucose tolerance and insulin sensitivity in old mice. In summary, old mice are more susceptible to HFD-induced metabolic changes than their young counterparts. Also, the antioxidant therapy improved insulin sensitivity and glucose tolerance, and in addition, apocynin seemed to prevent the HFD-induced hepatic fat deposition, suggesting an important role of oxidative stress in the induction of NAFLD
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