Dislocation core field. I. Modeling in anisotropic linear elasticity theory

Aside from the Volterra field, dislocations create a core field, which can be modeled in linear anisotropic elasticity theory with force and dislocation dipoles. We derive an expression of the elastic energy of a dislocation taking full account of its core field and show that no cross term exists between the Volterra and the core fields. We also obtain the contribution of the core field to the dislocation interaction energy with an external stress, thus showing that dislocation can interact with a pressure. The additional force that derives from this core field contribution is proportional to the gradient of the applied stress. Such a supplementary force on dislocations may be important in high stress gradient regions, such as close to a crack tip or in a dislocation pile-up

F-02: Antibiothérapies anti-SARM dans le traitement probabiliste des bactériémies à Staphylococcus aureus au CHU d'Angers

Introduction – objectifs La résistance à la méticilline du Staphylococcus aureus (SA) ne cesse de diminuer en France. Nous avons évalué la prescription des antibiothérapies probabilistes dans les bactériémies à SA et leur impact clinique. Matériels et méthodes Il s’agit d’une étude rétrospective incluant les bactériémies à Staphylococcus aureus sur le CHU d’Angers entre novembre 2012 et septembre 2013 avec recueil de l’antibiothérapie prescrite au rendu « cocci gram (CG)+ », à J5, hospitalisation depuis plus de 5 jours ou dans les six derniers mois, signes de gravité clinique, mortalité à J5. Résultats Nous avons inclus 146 épisodes de bactériémies. A l’annonce de CG+, 10 patients étaient décédés, 38,2 % ont reçu un anti-SARM (n = 52), 54,4 % un anti-SASM (n = 74), 7,4 % aucun antibiotique (n = 10). Parmi les bactériémies à SARM (n = 23), 60,9 % (n = 14) ont reçu une antibiothérapie initiale à visée SARM contre 36,3 % (n = 41) pour les bactériémies à SASM (n = 113) (OR = 2,71, p = 0,03). Cette adaptation semble influencée par une hospitalisation récente (OR = 1,82 ; p = 0,33) et la présence de signes de gravité (OR = 1,87, p = 0,23). Dans 21,4 % (n = 6) des bactériémies à SASM, l’antibiothérapie anti-SARM n’a pas été désecaladée. La mortalité à J5 est 13 %. L’absence d’antibiothérapie dans les 24 premières heures (OR = 2,97 ; p = 0,046) et une prescription de C3G (OR = 5,2, p = 0,05) en monothérapie augmentent le risque de décès à J5. Conclusion L’antibiothérapie initale semble adaptée à l’histoire et la présentation des patients. L’initiation sans délai, la visée staphylococcique et la désescalade sont les éléments importants du traitement

An update on THORPEX-related research in data assimilation and observing strategies

International audienceThe international programme "THORPEX: a World Weather Research Programme" provides a framework in which to tackle the challenge of improving the forecast skill of high-impact weather through international collaboration between academic institutions, operational forecast centres, and users of forecast products. The objectives of the THORPEX Data Assimilation and Observation Strategy Working Group (DAOS-WG) are two-fold. The primary goal is to assess the impact of observations and various targeting methods to provide guidance for observation campaigns and for the configuration of the Global Observing System. The secondary goal is to setup an optimal framework for data assimilation, including aspects such as targeted observations, satellite data, background error covariances and quality control. The Atlantic THORPEX Regional campaign, ATReC, in 2003, has been very successful technically and has provided valuable datasets to test targeting issues. Various data impact experiments have been performed, showing a small but very slightly positive impact of targeted observations. Projects of the DAOS-WG include working on the AMMA field experiment, in the context of IPY and to prepare the future THORPEX-PARC field campaign in the Pacific by comparing sensitivity of the forecasts to observations between several groups

On some aspects of the geometry of differential equations in physics

In this review paper, we consider three kinds of systems of differential equations, which are relevant in physics, control theory and other applications in engineering and applied mathematics; namely: Hamilton equations, singular differential equations, and partial differential equations in field theories. The geometric structures underlying these systems are presented and commented. The main results concerning these structures are stated and discussed, as well as their influence on the study of the differential equations with which they are related. Furthermore, research to be developed in these areas is also commented.Comment: 21 page

Comparison between classical potentials and ab initio for silicon under large shear

The homogeneous shear of the {111} planes along the direction of bulk silicon has been investigated using ab initio techniques, to better understand the strain properties of both shuffle and glide set planes. Similar calculations have been done with three empirical potentials, Stillinger-Weber, Tersoff and EDIP, in order to find the one giving the best results under large shear strains. The generalized stacking fault energies have also been calculated with these potentials to complement this study. It turns out that the Stillinger-Weber potential better reproduces the ab initio results, for the smoothness and the amplitude of the energy variation as well as the localization of shear in the shuffle set

Comparison of cloud products within IASI footprints for the assimilation of cloudy radiances

This article compares different methods of deriving cloud properties in the footprint of the Infrared Atmospheric Sounding Interferometer (IASI), onboard the European MetOp satellite. Cloud properties produced by ten operational schemes are assessed and an intercomparison of the products for a 12 h global acquisition is presented. Clouds cover a large part of the Earth, contaminating most of the radiance data. The estimation of cloud top height and effective amount within the sounder footprint is an important step towards the direct assimilation of cloud-affected radiances. This study first examines the capability of all the schemes to detect and characterize the clouds for all complex situations and provides some indications of confidence in the data. Then the dataset is restricted to thick overcast single layers and the comparison shows a significant agreement between all the schemes. The impact of the retrieved cloud properties on the residuals between calculated cloudy radiances and observations is estimated in the long-wave part of the spectrum

Bioluminescence intensity modeling and sampling strategy optimization

Author Posting. © American Meteorological Society 2005. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 22 (2005): 1267–1281, doi:10.1175/JTECH1760.1.The focus of this paper is on the development of methodology for short-term (1–3 days) oceanic bioluminescence (BL) predictions and the optimization of spatial and temporal bioluminescence sampling strategies. The approach is based on predictions of bioluminescence with an advection–diffusion–reaction (tracer) model with velocities and diffusivities from a circulation model. In previous research, it was shown that short-term changes in some of the salient features in coastal bioluminescence can be explained and predicted by using this approach. At the same time, it was demonstrated that optimization of bioluminescence sampling prior to the forecast is critical for successful short-term BL predictions with the tracer model. In the present paper, the adjoint to the tracer model is used to study the sensitivity of the modeled bioluminescence distributions to the sampling strategies for BL. The locations and times of bioluminescence sampling prior to the forecast are determined by using the adjoint-based sensitivity maps. The approach is tested with bioluminescence observations collected during August 2000 and 2003 in the Monterey Bay, California, area. During August 2000, BL surveys were collected during a strong wind relaxation event, while in August 2003, BL surveys were conducted during an extended (longer than a week) upwelling-favorable event. The numerical bioluminescence predictability experiments demonstrated a close agreement between observed and model-predicted short-term spatial and temporal changes of the coastal bioluminescence.This work has been supported by the Ocean Optics and Biology and Physical Oceanography Programs of the Office of Naval Research. Shulman’s support is through the NRL “Use of a Circulation Model to Enhance Predictability of Bioluminescence in the Coastal Ocean” project sponsored by the Office of Naval Research

A case report of Mycoplasma hominis brain abscess identified by MALDI-TOF mass spectrometry

We report the case of a 43-year-old man with a Mycoplasma hominis brain abscess occurring after a cranial trauma, which was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The presence of colonies on classic blood agar plates and the use of MALDI-TOF MS, a valuable diagnostic tool that identified M. hominis due to its presence in the VITEK MS database, allowed the rapid diagnosis of this infection