The quantum Neumann model: refined semiclassical results

We extend the semiclassical study of the Neumann model down to the deep quantum regime. A detailed study of connection formulae at the turning points allows to get good matching with the exact results for the whole range of parameters.Comment: 10 pages, 5 figures Minor edit

The quantum Neumann model: asymptotic analysis

We use semi--classical and perturbation methods to establish the quantum theory of the Neumann model, and explain the features observed in previous numerical computations.Comment: 14 pages, 3 figure

Experimental and numerical investigation of the response of geocell-reinforced walls to horizontal localized impact

International audienceThe aim of this work is to study the effect of a localized impact on a wall made of soil reinforced with geocells. First, two structures were tested with an impacting remote-controlled car. Such experiments, carried out on 1/10th-scale model structures for practical reasons, are designed to mimic the mechanical response of an alveolar geocell reinforcement system. Two types of constitutive materials were considered for the geocells with very different mechanical properties. The test structures were dismantled after the tests to analyse the influence of the impact on the cell layers, especially within their bulk. Examining the video of the tests captured with two high-speed cameras also helped understanding the phenomena that occurred during impact. These experiments were completed by numerical simulations whose objective was to understand more clearly the causes of the phenomena observed either within the dismantled structures or in the videos

The INOVE ANR 2010 Blan 0308 project: Integrated approach for observation and control of vehicle dynamics

International audienceThis paper presents the INOVE "Integrated approach for observation and control of vehicle dynamics" project. The aim and organization of the project are described and we present some recent results on the proposed integrated approach to design new methodologies for the improvement of the vehicle dynamical behaviour

General Solution of the Consistency Equation

We produce the general solution of the Wess-Zumino consistency condition for gauge theories of the Yang-mills type, for any ghost number and form degree. We resolve the problem of the cohomological independence of these solutions. In other words we fully describe the local version of the cohomology of the BRS operator, modulo the differential on space--time. This in particular includes the presence of external fields and non--trivial topologies of space--time.Comment: 11 pages, Latex file, PAR-LPTHE 92/1

Nasal Carriage of Staphylococcus Aureus and Cross-Contamination in a Surgical Intensive Care Unit: Efficacy of Mupirocin Ointment

A six month prospective study was carried out in a surgical intensive care unit (SICU) of a university hospital to assess the incidence and routes of exogenous colonization by Staphylococcus aureus. A total of 157 patients were included in the study. One thousand one hundred and eleven specimens (nasal, surgical wound swabs, tracheal secretions obtained on admission and once a week thereafter, and all clinical specimens) were collected over a four month period from patients without nasal decontamination (A). They were compared with 729 specimens collected over a two month period from patients treated with nasal mupirocin ointment (B). All S. aureus strains were typed by restriction fragment length polymorphism (RFLP) pulsed-field gel electrophoresis after SmaI macrorestriction. The nasal colonization rates on admission were 25.5 and 32.7% in groups A and B, respectively. Thirty-one untreated patients (31.3%) and three patients (5.1%) treated with nasal ointment, acquired the nasal S. aureus in the SICU (P = 0.00027). Nasal carriers were more frequently colonized in the bronchopulmonary tract (Bp) and surgical wound (Sw) (62%) than patients who were not nasal carriers (14%) (P < 0.00001). The patterns were identical for nasal, Bp and Sw strains from the same patient. RFLP analysis characterized seven epidemic strains of methicillin-resistant S. aureus (MRSA) which colonized 60% of group A and 9% of group B patients (P < 0.00001). The bronchopulmonary tract infection rate was reduced in group B (P = 0.032). In conclusion, in an SICU, nasal carriage of S. aureus appeared to be the source of endogenous and cross- colonization. The use of nasal mupirocin ointment reduced the incidence of Bp and Sw colonization, as well as the MRSA infection rate

The effects of moderately fast shellular rotation on adiabatic oscillations

We investigate adiabatic oscillations for delta Scuti star models, taking into account a moderate rotation velocity ~100 \km/s. The resulting oscillation frequencies include corrections for rotation up to second order in the rotation rate including those of near degeneracy. Effects of either a uniform rotation or a rotation profile assuming local angular momentum conservation of the form Omega=Omega(r) on oscillation frequencies are compared. As expected, important differences (around 3 microHz) are obtained in the $g$ and mixed mode regions. For higher frequency p modes, differences range between 1 microHz and 3 microHz. Such differences are likely to be detectable with future space missions such as COROT, where precisions in frequency around 0.5 microHz will be reachable.Comment: A&A, in press (18 pag, 14 fig

Solar-like oscillations in a massive star

Seismology of stars provides insight into the physical mechanisms taking place in their interior, with modes of oscillation probing different layers. Low-amplitude acoustic oscillations excited by turbulent convection were detected four decades ago in the Sun and more recently in low-mass main-sequence stars. Using data gathered by the Convection Rotation and Planetary Transits mission, we report here on the detection of solar-like oscillations in a massive star, V1449 Aql, which is a known large-amplitude (b Cephei) pulsator.Comment: Published in Sience, 19 June 2009, vol. 324, p. 154

Mode excitation by turbulent convection in rotating stars. I. Effect of uniform rotation

We focus on the influence of the Coriolis acceleration on the stochastic excitation of oscillation modes in convective regions of rotating stars. Our aim is to estimate the asymmetry between excitation rates of prograde and retrograde modes. We extend the formalism derived for obtaining stellar $p$- and $g$-mode amplitudes (Samadi & Goupil 2001, Belkacem et al. 2008) to include the effect of the Coriolis acceleration. We then study the special case of uniform rotation for slowly rotating stars by performing a perturbative analysis. This allows us to consider the cases of the Sun and the CoRoT target HD 49933. We find that, in the subsonic regime, the influence of rotation as a direct contribution to mode driving is negligible in front of the Reynolds stress contribution. In slow rotators, the indirect effect of the modification of the eigenfunctions on mode excitation is investigated by performing a perturbative analysis of the excitation rates. It turns out that the excitation of solar $p$ modes is affected by rotation with excitation rates asymmetries between prograde and retrograde modes of the order of several percents. Solar low-order $g$ modes are also affected by uniform rotation and their excitation rates asymmetries are found to reach up to 10 %. The CoRoT target HD 49933 is rotating faster than the Sun ($\Omega / \Omega_\odot \approx 8$) and we show that the resulting excitation rates asymmetry is about 10 % for the excitation rates of $p$ modes. We have then demonstrated that $p$ and $g$ mode excitation rates are modified by uniform rotation through the Coriolis acceleration. Study of the effect of differential rotation is dedicated to a forthcoming paper.Comment: 9 pages, 4 figures, accepted in A&