Nucleon-nucleon scattering within a multiple subtractive renormalization approach

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

A física da terapia de captura de nêutrons pelo boro

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

Desnutrição protéico-energética no paciente gastrectomizado

Racional - A gastrectomia traz conseqüências nutricionais inevitáveis mas atenuáveis, dependendo da dietoterapia pós-operatória. Embora observada, essa desnutrição protéico-energética é pouco dimensionada, provavelmente, pela falta de consenso metodológico. Objetivo - Avaliar o grau de desnutrição protéico-energética do paciente gastrectomizado, utilizando-se de indicadores isolados ou combinados. Pacientes e Métodos - Foram estudados 71 pacientes com gastrectomia parcial (n = 53) ou total (n =18) em pós-operatório de 6 a 24 meses e 24-60 meses. Os dados dietéticos, composição corporal e bioquímicos foram analisados de acordo com o tipo de gastrectomia e tempo pós-operatório. Resultados - A cirurgia foi conseqüência de complicações de úlcera péptica (68%) ou a câncer gástrico (32%). A perda de peso foi referida por 70% dos pacientes, sendo maior no grupo gastrectomia total (16 ± 5 kg) do que no grupo gastrectomia parcial (10 ± 6 kg). em geral, os pacientes apresentaram déficit antropométrico, albuminemia normal e baixa ingestão calórica, sugerindo deficiência energética crônica. A redução de hemoglobina, hematócrito e ferro ocorreu em maior intensidade e mais precocemente no grupo gastrectomia total. Assim, quando se associou hemoglobina aos indicadores albumina, linfócitos circunferência do braço e prega cutânea subescapular, a prevalência de desnutrição protéico-energética foi maior e em maior intensidade do que na ausência da hemoglobina. Conclusão - A gastrectomia resultou em desnutrição protéico-energética do tipo marasmática, acompanhada de anemia, mais intensa e precoce na gastrectomia total e gradativa na gastrectomia parcial, assemelhando-se à gastrectomia total no pós-operatório tardio.

Numerical study about natural escape and capture routes by the Moon via Lagrangian points L1 and L2

The lunar sphere of influence, whose radius is some 66,300 km, has regions of stable orbits around the Moon and also regions that contain trajectories which, after spending some time around the Moon, escape and are later recaptured by lunar gravity. Both the escape and the capture occur along the Lagrangian equilibrium points L1 and L2. In this study, we mapped out the region of lunar influence considering the restricted three-body Earth-Moon-particle problem and the four-body Sun-Earth-Moon-particle (probe) problem. We identified the stable trajectories, and the escape and capture trajectories through the L I and L2 in plots of the eccentricity versus the semi-major axis as a function of the time that the energy of the osculating lunar trajectory in the two-body Moon-particle problem remains negative. We also investigated the properties of these routes, giving special attention to the fact that they supply a natural mechanism for performing low-energy transfers between the Earth and the Moon, and can thus be useful on a great number of future missions. (C) 2007 Published by Elsevier Ltd on behalf of COSPAR.

Positron-helium scattering at medium energies

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.

RELATIVISTIC 3-PARTICLE DYNAMICAL EQUATIONS .2. APPLICATION TO THE TRINUCLEON SYSTEM

We calculate the contribution of relativistic dynamics on the neutron-deutron scattering length and triton binding energy employing five sets trinucleon potential models and four types of three-dimensional relativistic three-body equations suggested in the preceding paper. The relativistic correction to binding energy may vary a lot and even change sign depending on the relativistic formulation employed. The deviations of these observables from those obtained in nonrelativistic models follow the general universal trend of deviations introduced by off- and on-shell variations of two- and three-nucleon potentials in a nonrelativistic model calculation. Consequently, it will be difficult to separate unambiguously the effect of off- and on-shell variations of two- and three-nucleon potentials on low-energy three-nucleon observables from the effect of relativistic dynamics. (C) 1994 Academic Press, Inc.

Do all tannins have similar nutritional effects? A comparison of three Brazilian fodder legumes

Three tropical legumes, namely Leucaena leucocephala, Sesbania sesban and Cajanus cajan, were subjected to chemical analysis plus in vitro, in situ and in vivo evaluations. Three different assays were used to determine total tannins: adsorption to polyvinyl pyrrolidine (PVPP-tannins), radial diffusion (RD-tannins) and protein precipitation capacity (BSA-tannins). Total phenols, total tannins and condensed tannins were highest for Sesbania. RD-tannins were correlated with total phenols (r(2) = 0.93), PVPP-tannins (r(2) = 0.92) and condensed tannins (r(2) = 0.99). The protein precipitation capacity of Sesbania, Leucaena and Cajanus were 25.9, 6.13 and 4.05 mu g BSA/g DM, respectively.Gas production at 24h was negatively correlated with total phenols (r(2) = 0.99), PVPP-tannins (r(2) = 0.99) and condensed tannins (r(2) = 0.91). The RD-, PVPP-tannins and the response to polyethylene glycol (PEG) in the gas production assay appeared to be useful as a first screen for tannins.In situ degradability did not reflect any adverse effects of tannins. However, in vivo experiments showed that the apparent DM digestibility of Sesbania and Leucaena was lower than the basal diet. The apparent protein digestibility was lower for all legumes compared to the basal diet. Most treatments caused a negative nitrogen balance. The problems associated with browse feeding were not only related to tannin contents, other factors such as inherently poor digestibility and low energy intake may also have lead to the poor animal performance on these diets. We propose, given the limitations of current tannin assays, that it is not possible to predict beneficial or harmful nutritional effects from total tannin concentrations per se. (C) 2004 Elsevier B.V. All rights reserved.

MODEL INDEPENDENCE OF SCATTERING OF 3 IDENTICAL BOSONS IN 2 DIMENSIONS

Within the framework of scattering integral equations in momentum space, we present numerical results of scattering of three identical bosons at low energies in two dimensions for short-range separable potentials. An analysis of the present numerical results reveals the three-particle scattering observables to be independent of potential shape provided the low-energy two-particle binding energy and scattering length are held fixed throughout the investigation. We think that the present conclusion of model independence will be valid for any potential, local or nonlocal, whose range is much smaller than the size of the two-particle bound state.

Magnetic field release of trapped charges in poly(fluorenylenevinylene)s

We have measured the effect of an applied magnetic field on the current through thin films of two different organic conjugated polymers that have previously shown to exhibit magnetoresistance, poly(9,9-dioctyl-1,4-fluorenylenevinylene) and poly(9,9-dioctyl-2,7-fluorenylenevinylene). The results show that the magnetic field releases trapped charges from inside the material and enhances the current. We have also performed optical absorption experiments on these polymer films under applied voltage and magnetic field. The results show that the magnetic field produces a change in the optical absorption in the low-energy range associated with deep traps and only under conditions when these traps are likely charged. These two results provide a strong case for the release of trapped charges caused by the magnetic field as being the cause of the magneto resistance in these polymers and possibly in other organic materials where magnetoresistance was recently observed. (c) 2007 Elsevier B.V. All rights reserved.

Transient current effects on poly(o-methoxyaniline) films irradiated by pulsed electron beam

Fast transient current decay was recorded on POMA samples during current pulses (in the order of milliseconds) provided by a low energy electron beam under an applied field. The characteristic time decay depends on the electron beam energy and on the bias polarity. The results were explained taking into account the effect of space charge, the intrinsic conductivity of the non-irradiated region of the sample and the radiation-induced conductivity of the thin irradiated region. Fitting parameters may provide the value of both intrinsic and radiation-induced conductivities and the average electron range.

EFFECT OF THE HELIUM-NEON LASER ON THE HEALING OF EXTRACTION WOUNDS - A HISTOLOGICAL STUDY IN RATS

A histological study on the healing of extraction wounds following laser irradiation using a He-Ne laser, was carried out in rats. The results suggest that this mode of treatment has a beneficial effect on initial bony wound healing. Proliferation of fibroblasts and formation of trabecular osteoid tissue were found to be more prominent within the irradiated group. The deposition of led in the newly formed bone suggests swifter ossification within the irradiated group.

Electronic structure of Pb1-xLaxTiO3 ferroelectric materials from Ti 2p and O 1s soft x-ray absorption spectroscopy

The electronic structure of Pb1-xLaxTiO3 (PLT) compounds for x ranging from 0 to 30 at. % of La is investigated by means of soft x-ray absorption near edge structure (XANES) at the Ti L-3,L-2 and O K edges. The greatest modification in the structure of the Ti 2p XANES spectra of the PLT compounds is observed in the region of the high energy peak of the L-3 edge (e(g) states), which exhibits a splitting in the undoped sample. As the amount of lanthanum increases, this splitting becomes less pronounced. This modification is interpreted as a decrease in the degree of disorder of titanium atoms, which is correlated to the substitution of Pb by La atoms. The structural changes observed at the low energy peaks of the O K-edge XANES spectra of the PLT compounds may be interpreted in terms of hybridization between O 2p, Ti 3d, and Pb 6p orbitals. A decrease in the degree of hybridization observed as Pb atoms are replaced by La atoms may be related to the differences in the ferroelectric properties observed between x=0.0 and x=0.30 compounds. (c) 2006 American Institute of Physics.

CHIRAL SCHWINGER MODEL WITH A PODOLSKY TERM AT FINITE-TEMPERATURE

We study an exactly solvable two-dimensional model which mimics the basic features of the standard model. This model combines chiral coupling with an infrared behavior which resembles low energy QCD. This is done by adding a Podolsky higher-order derivative term in the gauge field to the Lagrangian of the usual chiral Schwinger model. We adopt a finite temperature regularization procedure in order to calculate the non-trivial fermionic Jacobian and obtain the photon and fermion propagators, first at zero temperature and then at finite temperature in the imaginary and real time formalisms. Both singular and non-singular cases, corresponding to the choice of the regularization parameter, are treated. In the nonsingular case there is a tachyonic mode as usual in a higher order derivative theory, however in the singular case there is no tachyonic excitation in the spectrum.

Using shifts in the electronic emission curve to evaluate polymer surface degradation

The polymer surface degradation and/or modification evolution of Teflon FEP and Mylar C films caused by a low energy electron beam were analyzed using a new method that consists in measuring the second crossover energy shift in the electronic emission curve. Upon prolonged irradiation, the second crossover energy shifts irreversibly to lower values in Teflon FEP but to higher values in Mylar C, indicating distinct mechanisms of surface degradation for the two polymers. The method represents a relatively inexpensive way to monitor early stages of surface degradation since the secondary electron emission comes from a maximum depth below the geometric surface of 100 mn in insulators. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Comparison of SRIM, MCNPX and GEANT simulations with experimental data for thick Al absorbers

Proton computerized tomography deals with relatively thick targets like the human head or trunk. In this case precise analytical calculation of the proton final energy is a rather complicated task, thus the Monte Carlo simulation stands out as a solution. We used the GEANT4.8.2 code to calculate the proton final energy spectra after passing a thick Al absorber and compared it with the same conditions of the experimental data. The ICRU49, Ziegler85 and Ziegler2000 models from the low energy extension pack were used. The results were also compared with the SRIM2008 and MCNPX2.4 simulations, and with solutions of the Boltzmann transport equation in the Fokker-Planck approximation. (C) 2009 Elsevier Ltd. All rights reserved.