Weak decay constant of pseudoscalar mesons in a QCD-inspired model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

THE EFFECT of WEAK DISSIPATION IN TWO-DIMENSIONAL MAPPING

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Armazenagem em atmosfera modificada passiva de carambola azeda (Averrhoa carambola L.) cv. 'Golden Star'

Este trabalho avaliou o efeito das embalagens de polietileno de baixa densidade (PEBD), em diferentes espessuras, no prolongamento da vida útil pós-colheita de carambolas cv. 'Golden Star'. Os frutos foram colhidos fisiologicamente maturos, sendo selecionados pela ausência de defeitos e acondicionados nas embalagens de PEBD, constituindo os seguintes tratamentos: T1 - controle (sem embalagem); T2 - PEBD de 6 mim; T3 - PEBD de 10 mim; T4 - PEBD de 15 mim. Os frutos foram armazenados a 12 +/- 0,5 ºC e 95 +/- 5% de UR, por 45 dias, e mais 5 dias a 22 +/- 3ºC e 72 +/- 5% de UR. Vinte e quatro horas após a colheita e a cada nove dias, amostras eram retiradas do armazenamento refrigerado (AR), mantidas por 12 horas em condições ambiente (22 +/- 3ºC e 72 +/- 5% UR) e analisadas quanto à firmeza de polpa (FP), à perda de massa fresca, à coloração da epiderme, aos sólidos solúveis totais (SST), à acidez total titulável (ATT) e à ocorrência de distúrbios fisiológicos. Realizou-se também uma análise sensorial ao final do experimento. A maior firmeza de polpa e acidez total titulável, o melhor padrão de coloração, o menor conteúdo de sólidos solúveis totais, a ausência de manchas e podridões, e a melhor aceitabilidade pelos julgadores foram obtidos com os frutos acondicionados em embalagens de 10 mim.

Qualidade de carambolas azedas cv. 'Golden Star' tratadas com CaCl2 por imersão e armazenadas sob refrigeração

No presente trabalho, avaliou-se o efeito de diferentes concentrações de CaCl2 aplicadas na pós-colheita de carambolas cv. 'Golden Star, durante o armazenamento refrigerado (AR). Os frutos colhidos fisiologicamente maturos foram selecionados pela ausência de defeitos e imersos em soluções de CaCl2, em diferentes concentrações, em temperatura ambiente (22 °C) por 20 minutos. Após aplicação dos tratamentos T1 - controle (0% de CaCl2); T2 - CaCl2 a 1%; T3 - CaCl2 a 2%; T4 - CaCl2 a 3%, e T5 - CaCl2 a 4%, os frutos foram colocados em câmara frigorífica, por 35 dias, a 12 ± 0,5ºC e 95 ± 3%, e mais 3 dias a 22 ± 3°C e 72 ± 5% de umidade relativa (UR). 24 horas após a colheita e a cada sete dias, amostras foram retiradas da AR, mantidas por 12 horas em condições ambiente (22 ± 3°C e 72 ± 5% UR) e analisadas quanto ao teor de cálcio na polpa, perda de massa fresca, coloração da epiderme, firmeza de polpa (FP), sólidos solúveis totais (SST), acidez total titulável (ATT) e a ocorrência de distúrbios fisiológicos. Ao final do experimento, foi feita uma análise sensorial. Observou-se que os frutos imersos em solução de CaCl2 a 2% apresentaram menor perda de massa fresca e maior firmeza de polpa. As carambolas deste tratamento também não apresentaram manchas e podridões e foram preferidas pelos julgadores no teste de preferência. Os sólidos solúveis totais, a acidez total titulável e a coloração não apresentaram diferença estatística entre os tratamentos. Na análise de teores de cálcio adsorvido pelos frutos, determinou-se que quanto, maior a concentração da solução de CaCl2 aplicada, maior a concentração de cálcio presente na polpa.

Cultivar affects browning susceptibility of freshly cut star fruit slices

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Compositeness effects in the anomalous weak-magnetic moment of leptons

We investigate the effects induced by excited leptons, at the one-loop level, in the anomalous magnetic and weak-magnetic form factors of the leptons. In particular, we compute their contributions to the weak-magnetic moment of the tau lepton, which can be measured on the Z peak, and we compare it with the contributions to g(mu) - 2, measured at low energies.

Weak ferromagnetism in poly(3-methylthiophene)(PMTh)

Ferromagnetic behaviour at 300 K has been observed from SQUID experiments in ClO4- doped PMTh, the samples were prepared electrochemically at 25 degreesC in acetonitrile with 0.1M LiClO4 and then partially reduced. Atomic absorption analysis discards magnetic particles contamination. Hysteresis curves were observed for pressed pellets in ail range of temperatures (300K-2K). The remanence at 300 K and pressed at 250 bar was around 8.06x10(-4) emu/g with coercitivity of 130 Oe. The influence of water content in the solvent during the sample synthesis and the pressure is shown. We discuss a model that explains our data in terms of the anisotropic superexchange Dziatoshinski-Moriya interaction giving rise to weak ferromagnetism.

FERMION HELICITY FLIP IN WEAK GRAVITATIONAL-FIELDS

The helicity flip of a spin-1/2 Dirac particle interacting gravitationally with a scalar field is analyzed in the context of linearized quantum gravity. It is shown that massive fermions may have their helicity flipped by gravity, in opposition to massless fermions which preserve their helicity.

An alternative approach to solve convergence problems in the backpropagation algorithm

The multilayer perceptron network has become one of the most used in the solution of a wide variety of problems. The training process is based on the supervised method where the inputs are presented to the neural network and the output is compared with a desired value. However, the algorithm presents convergence problems when the desired output of the network has small slope in the discrete time samples or the output is a quasi-constant value. The proposal of this paper is presenting an alternative approach to solve this convergence problem with a pre-conditioning method of the desired output data set before the training process and a post-conditioning when the generalization results are obtained. Simulations results are presented in order to validate the proposed approach.

SOME CONSEQUENCES IN WEAK PROCESSES OF 3-GENERATION MIXING IN THE LEPTONIC SECTOR

We investigate the sensitivity of some weak processes to a Cabibbo-Kobayashi-Maskawa in the leptonic sector. Values for mixing angles and masses compatible with several experimental accelerator data were found. We discuss in this context neutrino oscillations and cosmological and astrophysical consequences as well.

Collective scattering of massive stars in higher order gravity

In the weak field approximation of higher order gravity theory a gravitational potential is described by a Newtonian plus a Yukawa-like term. This new term is used to explain some aspects of galactic dynamics, without considering dark matter. Its presence modifies the scattering probability of a massive intruder star and relaxation time of the stellar system.

Combining genetic algorithm and simulated annealing: A molecular geometry optimization study

We introduce a new hybrid approach to determine the ground state geometry of molecular systems. Firstly, we compared the ability of genetic algorithm (GA) and simulated annealing (SA) to find the lowest energy geometry of silicon clusters with six and 10 atoms. This comparison showed that GA exhibits fast initial convergence, but its performance deteriorates as it approaches the desired global extreme. Interestingly, SA showed a complementary convergence pattern, in addition to high accuracy. Our new procedure combines selected features from GA and SA to achieve weak dependence on initial parameters, parallel search strategy, fast convergence and high accuracy. This hybrid algorithm outperforms GA and SA by one order of magnitude for small silicon clusters (Si6 and Si10). Next, we applied the hybrid method to study the geometry of a 20-atom silicon cluster. It was able to find an original geometry, apparently lower in energy than those previously described in literature. In principle, our procedure can be applied successfully to any molecular system. © 1998 Elsevier Science B.V.

Transpressional tectonics and strain partitioning during oblique collision between three plates in the Precambrian of southeast Brazil

This paper is part of the special publication Continental transpressional and transtensional tectonics (eds R.E. Holdsworth, R.A. Strachan and J.F. Dewey). Two orogenic belts have been recognized in south- east Brazil, which are interpreted to have been formed as a product of diachronous collisions between three continental plates. Wide crustal-scale shear belts have developed both between and inboard of the collided and amalgamated plate borders. These shear belts record frontal, oblique or lateral displacements during oblique plate convergence and A-type subduction. The overall structural style of each belt depends on the angle subtended between the plate boundary and the convergence vector. The E-W branch between the Sao Paulo and Brasilia plates the Campo do Meio strike-slip shear belt, has undergone dominantly sinistral wrench dominated transpression along a set of folds and shear zones dipping southwards. The NE-SW branch between the Sao Paulo and Vitoria plates, the Paraiba do Sul strike-slip shear belt, has undergone a partitioned dextral transpression, whereas the north-south branch between the Brasilia and Vitoria plates is essentially a frontal thrust system with only a weak component of dextral strike-slip. These complex structural patterns, formed at deep to mid-crustal levels, reflect temporal and spatial partitioning at all scales between flattening and non- coaxial deformation, and down-dip and strike-slip shearing, in tangential as well as in transcurrent structural domains. Additionally, this area demonstrates that regional flower structures, lateral extrusion and other secondary deformations across the yz sections of transpressional belts are important in accommodating shortening in obliquely convergent orogens.

Weak decay of uniformly accelerated protons and related processes

We investigate the weak interaction emission of spin-1/2 fermions from accelerated currents. As particular applications, we analyze the decay of uniformly accelerated protons and neutrons, and the neutrino-antineutrino emission from uniformly accelerated electrons. The possible relevance of our results to astrophysics is also discussed.

Magnetic behavior of poly(3-methylthiophene): Metamagnetism and room-temperature weak ferromagnetism

A weak ferromagnetic phase is shown in pressed pellets of partially doped poly(3-methylthiophene) (P3MT) in the whole range from 1.8 to 300 K in magnetic measurements. Thermoremanence data have been used to estimate the suppression of this phase to be around 815 K. We also show that instead of the classical antiferromagnetism for the first-order interaction that gives weak ferromagnetism as a second-order effect, metamagnetic behavior is observed. X-band electron spin resonance (ESR) measurements and magnetization measurements allowed us to estimate that 8.1% of the total number of spins contributes to the weak ferromagnetism at room temperature. The doping level obtained from the ESR data is in good agreement with that estimated from electron dispersive spectroscopy measurements.