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Search Results: 1 - 10 of 390599 matches for " Margareth R?se L.;Barreiro "
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The synthesis of new isochromanylacetylarylhydrazones designed as probable non-addictive analgesic agents
Santos, Margareth Rse L.;Barreiro, Eliezer J.;Braz-Filho, Raimundo;Miranda, Ana Luisa P.;
Journal of the Brazilian Chemical Society , 1997, DOI: 10.1590/S0103-50531997000500007
Abstract: the synthesis and pharmacological profile as analgesic and anti-inflammatory agents of new isochromanylacetylarylhydrazone derivatives (3) are described in this paper. the synthetic route used in this work to construct the heterocyclic six member ring explored a lewis acid-catalyzed cyclization process as the key step, which represents a modified friedel-crafts reaction. these new derivatives (3) were obtained in ca. 85 % overall yields from the starting material safrole (4), an abundant natural product isolated from sassafras oil. the nmr spectral analysis of these new derivatives indicated, at the c=n double bond level, the diastereomeric nature in a 70:30 ratio, where the major compound is the (e)-isomer. the results obtained from the pharmacological evaluation of (3) using the carrageenan-induced rat paw edema test and the acetic acid solution-induced constrictions in mouse test, indicated the pharmacophoric nature of the acylarylhydrazone moiety to the analgesic activity observed in this series.the role of the aryl substituents in the bioactivity seems to indicate that the presence of hydrophobic groups may improve the analgesic profile. these new isochromanylacetylarylhydrazone derivatives (3) represent a new class of non-addictive analgesic agents.
A Generalized Smoluchowsky Equation: The Hydrodynamical and Thermodynamical Picture of Brownian Motion
L. A. Barreiro,J. R. Campanha,R. E. Lagos
Physics , 1999,
Abstract: We present a systematic expansion of Kramers equation in the high friction limit. The latter is expanded within an operator continued fraction scheme. The relevant operators include both temporal and spatial derivatives and a covariant derivate or gauge like operator associated to the potential energy. Trivially, the first order term yields the Smoluchowsky equation. The second order term is readily obtained, known as the corrected Smoluchowsky equation. Further terms are computed in compact and straightforward fashion. As an application, the nonequilibrium thermodynamics and hydrodynamical schemes for the one dimensional Brownian motion is presented.
The thermohydrodynamical picture of a charged Brownian particle
L. A. Barreiro,J. R. Campanha,R. E. Lagos
Physics , 2000,
Abstract: We study a charged Brownian gas with a non uniform bath temperature, and present a thermohydrodynamical picture. Expansion on the collision time probes the validity of the local equilibrium approach and the relevant thermodynamical variables. For the linear regime we present several applications (including some novel results). For the lowest nonlinear expansion and uniform bath temperature we compute the gradient corrections to the local equilibrium approach and the fundamental (Smoluchowsky) equation for the nonequilibrium particle density.
A QCD Sum Rule Approach to the $s\to dγ$ Contribution to the $Ω^-\to Ξ^-γ$ Radiative Decay
M. Nielsen,L. A. Barreiro,C. O. Escobar,R. Rosenfeld
Physics , 1995, DOI: 10.1103/PhysRevD.53.3620
Abstract: QCD sum rules are used to calculate the contribution of short-distance single-quark transition $s\rightarrow d \gamma$, to the amplitudes of the hyperon radiative decay, $\Omega^-\rightarrow \Xi^-\gamma$. We re-evaluate the Wilson coefficient of the effective operator responsible for this transition. We obtain a branching ratio which is comparable to the unitarity limit.
Can $Ω^- \to Ξ^- γ$ be sensitive to new physics beyond the Standard Model ?
R. Rosenfeld,L. A. Barreiro,C. O. Escobar,M. Nielsen
Physics , 1995, DOI: 10.1103/PhysRevD.54.3645
Abstract: We investigate the impact of new physics beyond the Standard Model to the $s \rightarrow d \gamma$ process, which is responsible for the short-distance contribution to the radiative decay $\Otogamma$. We study three representative extensions of the Standard Model, namely a one-family technicolor model, a two Higgs doublet model and a model containing scalar leptoquarks. When constraints arising from the observed $b \to s \gamma$ transition and the upper limit on $D^0 - \bar{D}^0$ mixing are taken into account, we find no significant contributions of new physics to the $s \to d \gamma$ process.
Geometrical estimators as a test of Gaussianity in the CMB
R. B. Barreiro,E. Martinez-Gonzalez,J. L. Sanz
Physics , 2000, DOI: 10.1046/j.1365-8711.2001.04139.x
Abstract: We investigate the power of geometrical estimators on detecting non-Gaussianity in the cosmic microwave background. In particular the number, eccentricity and Gaussian curvature of excursion sets above (and below) a threshold are studied. We compare their different performance when applied to non-Gaussian simulated maps of small patches of the sky, which take into account the angular resolution and instrumental noise of the Planck satellite. These non-Gaussian simulations are obtained as perturbations of a Gaussian field in two different ways which introduce a small level of skewness or kurtosis in the distribution. A comparison with a classical estimator, the genus, is also shown. We find that the Gaussian curvature is the best of our estimators in all the considered cases. Therefore we propose the use of this quantity as a particularly useful test to look for non-Gaussianity in the CMB.
Dieta e dispers?o de sementes por Cerdocyon thous (Linnaeus) (Carnívora, Canidae), em um fragmento florestal no Paraná, Brasil
Rocha, Vlamir J.;Reis, Nelio R. dos;Sekiama, Margareth L.;
Revista Brasileira de Zoologia , 2004, DOI: 10.1590/S0101-81752004000400022
Abstract: although the crab eating fox, cerdocyon thous (linnaeus, 1706), is a relatively common canidae, there isn't much information about its diet and its role as a seed disperser in the different habitats where it occurs. the aim of this work was to report the diet of the c. thous and its importance as a seed disperser and / or a seed predator and to test the rate of germination of the seeds after passing through the digestive tract of the animal. the work was carried out in a 680 ha fragment of the semidecidual seasonal forest in the parque estadual mata dos godoy, located in the city of londrina-paraná, south of brazil. the methodology consisted of the collection of excrement of c. thous which were analyzed in laboratory for identification of consumed items and seeds. in germination tests, the seeds were placed to germinate in petri dishes with wet cotton. ninety-three animal feces samples, with 219 animal and vegetable items were registered, being 36.52% remaining portions of small rodents, 24.19% of grasses, 13.24% of birds, 10.47% of insects, 6.39% of syagrus romanzoffiana (cham.) glassm., 4.6% of other items of animal origin and 4.54% of items vegetable origin. in addition, c. thous dispersed nine species of plants, with relevant importance to the germination of some seeds, which passed through the digestive tract, except for the most consumed of fruit, s. romanzoffiana, whith no seed germination at all in lab conditions. in conclusion, c. thous has a generalistc and opportunistc diet, surviving in degraded and anthropic areas and being able to act as a seed disperser.
Structural Biology by NMR: Structure, Dynamics, and Interactions
Phineus R. L. Markwick,Thérèse Malliavin,Michael Nilges
PLOS Computational Biology , 2008, DOI: 10.1371/journal.pcbi.1000168
Abstract: The function of bio-macromolecules is determined by both their 3D structure and conformational dynamics. These molecules are inherently flexible systems displaying a broad range of dynamics on time-scales from picoseconds to seconds. Nuclear Magnetic Resonance (NMR) spectroscopy has emerged as the method of choice for studying both protein structure and dynamics in solution. Typically, NMR experiments are sensitive both to structural features and to dynamics, and hence the measured data contain information on both. Despite major progress in both experimental approaches and computational methods, obtaining a consistent view of structure and dynamics from experimental NMR data remains a challenge. Molecular dynamics simulations have emerged as an indispensable tool in the analysis of NMR data.
Peripheral N$α$ Scattering: A Tool For Identifying The Two Pion Exchange Component Of The NN Potential
L. A. Barreiro,R. Higa,C. L. Lima,M. R. Robilotta
Physics , 1998, DOI: 10.1103/PhysRevC.57.2142
Abstract: We study elastic N$\alpha $ scattering and produce a quantitative correlation between the range of the effective potential and the energy of the system. This allows the identification of the waves and energies for which the scattering may be said to be peripheral. We then show that the corresponding phase shifts are sensitive to the tail of the NN potential, which is due to the exchange of two pions. However, the present uncertainties in the experimental phase shifts prevent the use of N$\alpha $ scattering to discriminate the existing models for the NN interaction.
Wavelets Applied to CMB Maps: a Multiresolution Analysis for Denoising
J. L. Sanz,F. Argueso,L. Cayon,E. Martinez-Gonzalez,R. B. Barreiro,L. Toffolatti
Physics , 1999, DOI: 10.1046/j.1365-8711.1999.02897.x
Abstract: Analysis and denoising of Cosmic Microwave Background (CMB) maps are performed using wavelet multiresolution techniques. The method is tested on $12^{\circ}.8\times 12^{\circ}.8$ maps with resolution resembling the experimental one expected for future high resolution space observations. Semianalytic formulae of the variance of wavelet coefficients are given for the Haar and Mexican Hat wavelet bases. Results are presented for the standard Cold Dark Matter (CDM) model. Denoising of simulated maps is carried out by removal of wavelet coefficients dominated by instrumental noise. CMB maps with a signal-to-noise, $S/N \sim 1$, are denoised with an error improvement factor between 3 and 5. Moreover we have also tested how well the CMB temperature power spectrum is recovered after denoising. We are able to reconstruct the $C_{\ell}$'s up to $l\sim 1500$ with errors always below $20% $ in cases with $S/N \ge 1$.
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