968 resultados para two-centre atomic orbital close coupling method


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Na gestação ocorrem adaptações que conduzem a um aumento da taxa metabólica basal, caracterizando um estado de alto nível de estresse oxidativo, tornando relevante a avaliação do consumo de nutrientes antioxidantes por mulheres grávidas. Este estudo teve como objetivo estimar a prevalência de consumo insuficiente das vitaminas C e E em gestantes assistidas em serviços públicos de saúde. Estudou-se amostra (n=107) representativa das mulheres no segundo trimestre gestacional atendidas durante o pré-natal nas unidades de atenção básica do município de Botucatu/SP. O consumo foi investigado mediante dois inquéritos recordatórios de 24 horas. Para estimar a prevalência de inadequação de consumo na população, foi utilizado o método EAR como ponto de corte. Diferenças de consumo (em tercis) em relação a fatores socioeconômicos, obstétricos e hábitos de vida foram pesquisadas mediante análise estratificada, adotando-se p<0.05 como nível de significância. As prevalências estimadas de consumo insuficiente das vitaminas C e E foram 60% e 91,5%, respectivamente. Houve associação inversa entre o consumo de vitamina E com paridade e o consumo de vitamina C foi menor nas adolescentes em relação às adultas. Estes resultados indicam a necessidade de intervenções individuais e coletivas de promoção e apoio ao consumo de alimentação saudável por mulheres em idade fértil. Conclui-se que a prevalência de inadequação do consumo das vitaminas C e E é elevada e sem contrastes socioeconômicos.

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For data obtained from horizontal soil column experiments, the determination of soil-water transport characteristics and functions would be aided by a single-form equation capable of objectively describing water content theta vs. time t at given position x(f). Our study was conducted to evaluate two such possible equations, one having the form of the Weibull frequency distribution, and the other being called a bipower form. Each equation contained three parameters, and was fitted by nonlinear least squares to the experimental data from three separate columns of a single soil. Across the theta range containing the measured data points obtained by gamma-ray attenuation, the two equations were in close agreement. The resulting family of theta(x(f),t) transients, as obtained from either equation, enabled the evaluation of exponent n in the t(n) dependence of the positional advance of a given theta. Not only was n found to be <0.5 at low theta values, but it also increased with theta and tended toward 0.5 as theta approached its sated (near-saturated) value. Some quantitative uncertainty in n(theta) does arise due to the reduced number of data points available at the higher water contents. Without claiming non-Boltzmann behavior (n < 0.5) as necessarily representative of all soils, we nonetheless consider n(theta) to be worthy of further study for evaluating its significance and implications.

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We present results for medium-energy elastic, inelastic [transition to He(1s2(1)s), He(1s2(1)p), He(1s3(1)s), and He(1s3(1)p) states], capture [to Ps(1s), Ps(2s), and Ps(2p) states of the positronium (Ps) atom] and total cross sections of positron-helium scattering in the close coupling approach using realistic wave functions.

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We study e+-Na, e+-K, and e+-Rb scattering using the close coupling approach in the static and coupled static expansion schemes. We calculate partial wave elastic scattering phase shifts and total elastic and Ps formation cross sections up to an incident positron energy of 100 eV. The effect of the positronium formation channel on the elastic channel is found to be strong in all cases up to an incident positron energy of 10 eV. We also make an estimate of the total cross section which exhibits a minimum as a function of energy at low energies.

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Positronium formation and target excitation in positron-helium scattering have been investigated using the close-coupling approximation with realistic wave functions for the positronium and helium atoms. The following eight states have been used in the close-coupling scheme: He(1s1s), He(1s2(1)s), He(1s2(1)p), He(1s3(1)s), He(1s3(1)p), Ps(1s), Ps(2s), and Ps(2p), where Ps stands for the positronium atom. Calculations are reported of differential cross sections for elastic scatering,, inelastic target excitation to He(1s2(1)s) and He(1s2(1)p) slates, and rearrangement transition to Ps(1s), Ps(2s), and Ps(2p) states for incident positron energies between 40 and 200 eV. The coincidence parameters for the transition to the He(1s2(1)p) state of helium are also reported and briefly discussed. [S1050-2947(98)05101-4].

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We studied e+-Li and e+-Na scattering using the close-coupling approximation in the static and coupled static expansion schemes. The effect of the positronium formation on the elastic channel is found to be strong in both cases. In the case of the lithium atom the effect is dramatic; the inclusion of the positronium formation channel transforms the purely repulsive effective e+-Li S wave (static) potential to a predominantly attractive (coupled static) potential. In this case, in the static model delta(0)-delta(infinity) = 0, whereas in the coupled static model delta(0)-delta(infinity)=pi. According to Levinson's theorem this suggests the presence of a S wave bound or continuum bound state in the e+-Li system.

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This article reports a theoretical study based on experimental results for barium zirconate, BaZrO3 (BZ) thin films, using periodic mechanic quantum calculations to analyze the symmetry change in a structural order-disorder simulation. Four periodic models were simulated using CRYSTAL98 code to represent the ordered and disordered BZ structures. The results were analyzed in terms of the energy level diagrams and atomic orbital distributions to explain and understand the BZ photoluminescence properties (PL) at room temperature for the disordered structure based on structural deformation and symmetry changes. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 694-701, 2011

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PANI films were deposited on glass substrates by in-situ polymerization and characterized by UV-VIS spectroscopy and atomic force microscopy. A method is developed to accurately analyze ellipsometric data obtained for transparent glass substrates before and after modification with absorbing polymer films. Surface modification was made with an overlayer such as polyaniline ( PANI), which exhibits different optical properties by varying its oxidation state. First, the issue of using transparent substrates for ellipsometry studies was examined and then, spectroscopic ellipsometry was used to characterize absorbing overlayers on transparent glasses. The same methodologies of data analysis can be also applied to other absorbing films on transparent substrates, and deposited by different techniques.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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A perturbative study of a class of nonsingular spiked harmonic oscillators defined by the Hamiltonian H= -d2/dr2 + r2 + λ/rα in the domain [0,∞] is carried out, in the two extremes of a weak coupling and a strong coupling regimes. A path has been found to connect both expansions for α near 2. © 1991 American Institute of Physics.

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We study positron-helium scattering using close coupling approximation (CCA) employing different combinations of the following basis functions: He(1s1s), He(1s2s), He(1s2p), Ps(1s). and Ps(2s), where Ps stands for the positronium atom. We observe a prominent S wave resonance of width 2 eV at about 30 eV, in excitation and rearrangement cross sections to He(1s2s), He(1s2p), Ps(1s) and Ps(2s) states. We also report results of differential cross sections for the excitation of helium and positronium formation.

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The muscular dystrophy of Golden Retriever (GRMD) is a degenerative miopaty caused by the absence of dystrophy and it is genetically homologue of the Duchenne muscular dystrophy in humans, so, these dogs are considerably experimental models for studies on cellular therapy. Their successful depends of the adequate immunosuppression. Cyclosporin A (CsA) is indicated for that and the monitoring of the blood concentration and adverse effects are essential to viabilise the therapy. It was studied GRMD dogs, and normal dogs from the same breed, submitted for therapy with CsA, associated, on GRMD, of cell transplantation. It was evaluated blood concentration of the drug, between two or tree days using the method of FPIA. In our results we found that the CsA blood concentrations oscillated too much on six than eight of our animals. We concluded that the doses varieties individually and the correct dosage as to important as the evaluation of the blood concentration of the drug and became viable for cell therapy.

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Continuous strip metal matrix composite (MMC) casting of 0.3 mm diameter hard-drawn stainless steel (316L) wire in a quasi-eutectic SnPb (64Sn36Pb) matrix was performed by a two-roll melt drag processing (TRMDping) method, with the wire being dragged through a semisolid puddle with a fibre contact time of approximately 0.2 s. A slag weir placed at the nozzle contained two wire guide holes: one located near the upper roll, and the other located between the rolls. A successful continuous composite strip casting with good fibre alignment was achieved by inserting and embedding the wire into the matrix using the guide hole between the rolls. Degeneration of eutectic/dendrite structures led to the formation of globular structures. The occurrence and formation mechanisms of cracks, de-lamination and voids in the matrix were discussed. TRMDping is economically viable and has significant benefits over other MMC fabrication methods. © (2013) Trans Tech Publications, Switzerland.