Corrections to the Boltzmann mean free path in disordered systems with finite size scatterers

The mean free path is an essential characteristic length in disordered systems. In microscopic calculations, it is usually approximated by the classical value of the elastic mean free path. It corresponds to the Boltzmann mean free path when only isotropic scattering is considered, but it is different for anisotropic scattering. In this paper, we work out the corrections to the so called Boltzmann mean free path due to multiple scattering effects on finite size scatterers, in the s-wave approximation, ie. when the elastic mean free path is equivalent to the Boltzmann mean free path. The main result is the expression for the mean free path expanded in powers of the perturbative parameter given by the scatterer density.Comment: 12 page

Dynamical stability analysis of the HD202206 system and constraints to the planetary orbits

Long-term precise Doppler measurements with the CORALIE spectrograph revealed the presence of two massive companions to the solar-type star HD202206. Although the three-body fit of the system is unstable, it was shown that a 5:1 mean motion resonance exists close to the best fit, where the system is stable. We present here an extensive dynamical study of the HD202206 system aiming at constraining the inclinations of the two known companions, from which we derive possible ranges of value for the companion masses. We study the long term stability of the system in a small neighborhood of the best fit using Laskar's frequency map analysis. We also introduce a numerical method based on frequency analysis to determine the center of libration mode inside a mean motion resonance. We find that acceptable coplanar configurations are limited to inclinations to the line of sight between 30 and 90 degrees. This limits the masses of both companions to roughly twice the minimum. Non coplanar configurations are possible for a wide range of mutual inclinations from 0 to 90 degrees, although $\Delta\Omega = 0 [\pi]$ configurations seem to be favored. We also confirm the 5:1 mean motion resonance to be most likely. In the coplanar edge-on case, we provide a very good stable solution in the resonance, whose $\chi^2$ does not differ significantly from the best fit. Using our method to determine the center of libration, we further refine this solution to obtain an orbit with a very low amplitude of libration, as we expect dissipative effects to have dampened the libration.Comment: 14 pages, 18 figure

Effect of the curing time on the numerical modelling of the behaviour of a chemically stabilised soft soil

The ability of the Modified Cam Clay (MCC) model combined with the Von Mises (VM) model, considering the effect of curing time on the enhancement of the mechanical properties of a chemically stabilised soft soil is examined. The evolution of the strength and stiffness over time is based on the results of undrained compressive strength (UCS) tests carried out for different curing times (from 28 days to 360 days). Initially, the MCC/VM models associated with the effect of curing time are validated by CIU triaxial tests, for curing times of 28 and 90 days. Finally, the behaviour of an embankment built on a soft soil reinforced with deep mixing columns is predicted based on the previously validated models. The results show that the increase of curing time of the DMCs slightly decreases the settlement obtained with a curing time of 28 days

Transposição congenitamente corrigida das grandes artérias e coarctação da aorta: uma associação pouco comum

Congenitally corrected transposition of the great arteries, L-TGA, is a rare abnormality accounting for less than 0.5% of clinically apparent congenital heart disease. Age at time of diagnosis and survival rate are variable and depend mostly on associated anomalies. The authors present a clinical case of a twenty-four-year-old woman in whom, in a routine echocardiogram, congenitally corrected transposition of the great arteries and aortic coarctation were diagnosed, an unusual association. They describe the results of complementary exams (echocardiography, chest X-ray, electrocardiogram and cardiac angiography) that they believe to be useful for the correct diagnosis of this clinical situation. Additionally, the authors make a brief review of the literature relevant to the case

Ab-initio study of the relation between electric polarization and electric field gradients in ferroelectrics

The hyperfine interaction between the quadrupole moment of atomic nuclei and the electric field gradient (EFG) provides information on the electronic charge distribution close to a given atomic site. In ferroelectric materials, the loss of inversion symmetry of the electronic charge distribution is necessary for the appearance of the electric polarization. We present first-principles density functional theory calculations of ferroelectrics such as BaTiO3, KNbO3, PbTiO3 and other oxides with perovskite structures, by focusing on both EFG tensors and polarization. We analyze the EFG tensor properties such as orientation and correlation between components and their link with electric polarization. This work supports previous studies of ferroelectric materials where a relation between EFG tensors and polarization was observed, which may be exploited to study ferroelectric order when standard techniques to measure polarization are not easily applied.Comment: 9 pages, 6 figures, 5 tables, corrected typos, as published in Phys. Rev.

Analgesic interpatient variability of remifentanil assessed through pupillary dilation reflex

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Study of the processing and properties of mixtures of recycled plastics for outdoor applications

There is an industrial need for the study of the mechanical and physical properties of recycled polyolefins mixed with cellulose fibres from diapers, wood and packaging containing aluminium. The recycling of thermoplastic based residues is economically very interesting for the easy reprocessing of these materials and flexible shaping using conventional moulding processes as injection moulding or intrusion. Various mixtures of these materials were characterized in terms of their constituents and properties determined using 200 mm square mouldings of 10 mm and 5 mm thickness, in view of their potential application in urban furniture. These mouldings were processed by injection moulding and by intrusion that is a method which uses and extruder for delivering the melt directly into an injection mould. The mouldings were tested in terms of theirmechanical performance in impact and flexion. The intrusion process yielded mouldings with properties similar to injection moulding but appeared to be more attractive for requiring lower moulding pressure and thus lighter and cheaper tooling. The morphology of the mouldings, observed by bright field light microscopy showed some contamination and voiding associated to specific processing conditions and moulding size, the thinner mouldings having less voids than the 10 mm thick. The higher voiding in the thicker mouldings was detrimental to the flexural and impact performances of the parts. The coefficient of linear thermal expansion was determined and showed to be sensitive to the percentage of LDPE and fibres in the mixtures. The flexural stiffness of the moulded plates was assessed using the whole mouldings in the 3-point support test and showed the positive influence of the wood fibres and the diaper content in the mixtures. Conversely the impact performance assessed by the Charpy test was affected by the diaper content, but benefitted from the presence of aluminium from the recycled packaging. The prediction of these properties using the law of mixtures for predicting the overall density in the mouldings was not particularly accurate for the mixtures with recycled diapers.European Commission for Education and Training, Erasmus placement scholarship at Hogeschool Gen

Pupillary pain index correlates with postoperative pain scores in neurosurgical patients

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