Science & Mathematics

La détection d'objets enfouis dans les sédiments marins ou la détermination de certaines de leurs caractéristiques géotechniques peut se faire à partir d'ondes acoustiques générées et captées par des antennes multiéléments. Les auteurs se proposent d'appliquer des données, acquises en mer et à partir de sédiments artificiels, à un modèle numérique permettant de prévoir le comportement de la focalisation d'ondes en fonction de paramètres géoacoustiques des fonds marins. L'influence du sol sera prise en compte : — au niveau de l'interface, — dans le sédiment. Les paramètres acoustiques retenus dans le modèle (célérité et atténuation des ondes de compression — impédance acoustique des sédiments) influent sur la forme et les dimensions de la tache focale ainsi que sur les limites d'utilisation de ce procédé. Une trop forte atténuation des ondes interdit d'une part une bonne concentration de l'énergie acoustique à l'émission, d'autre part gêne le traitement du signal en réception (réduction trop importante des niveaux d'énergie des trajets les plus longs). Les auteurs présentent également des résultats obtenus sur un sédiment artificiel permettant : — d'une part de quantifier les paramètres acoustiques d'un site d'essais représentatif du comportement en milieu marin, — d'autre part de définir les limites d'utilisation d'une antenne multi-éléments basse fréquence.

Relevance of multilayer approach and isotopic signal in the understanding of soil respiration in forest ecosystem. Soil CO(2) efflux is one of the most important flux in carbon cycle. Its amplitude is estimated to 68 +/- 4 Pg C per year. In temperate forest, it represents approximately 60-80% of total CO(2) emissions from the ecosystem (ecosystem respiration). Given its magnitude and the consequences of any amplitude change on the atmosphere carbon dioxide content, it is essential to improve knowledge of the mechanisms that govern it and know precisely the influence of environmental variables (edaphic and climatic). This paper aims to show the interest of conducting multilayer analysis of the mechanisms causing this flow (transport and production) rather than restricting the study to the soil surface. In addition, this article highlights the isotopic tool benefits to improve the mechanistic understanding of this efflux.

Dystrophin and dystrophin-associated proteins (DAPs) form a complex around the sarcolemma, which gives stability to the sarcolemma and leads signal transduction. Recently, the nuclear presence of dystrophin Dp71 and DAPs has been revealed in different non-muscle cell types, opening the possibility that these proteins could also be present in the nucleus of muscle cells. In this study, we analyzed by Immunofluorescence assays and Immunoblotting analysis of cell fractions the subcellular localization of Dp71 and DAPs in the C(2)C(12) muscle cell line. We demonstrated the presence of Dp71, alpha-sarcoglycan, alpha-dystrobrevin, beta-dystroglycan and alpha-syntrophin not only in plasma membrane but also in the nucleus of muscle cells. In addition, we found by Immunoprecipitation assays that these proteins form a nuclear complex. Interestingly, myogenesis modulates the presence and/or relative abundance of DAPs in the plasma membrane and nucleus as well as the composition of the nuclear complex. Finally, we demonstrated the presence of Dp71, alpha-sarcoglycan, beta-dystroglycan, alpha-dystrobrevin and alpha-syntrophin in the C(2)C(12) nuclear envelope fraction. Interestingly, alpha-sarcoglycan and beta-dystroglycan proteins showed enrichment in the nuclear envelope, compared with the nuclear fraction, suggesting that they could function as inner nuclear membrane proteins underlying the secondary association of Dp71 and the remaining DAPs to the nuclear envelope. Nuclear envelope localization of Dp71 and DAPs might be involved in the nuclear envelope-associated functions, such as nuclear structure and modulation of nuclear processes. J. Cell. Biochem. 105: 735-745, 2008. (c) 2008 Wiley-Liss, Inc.

J'ai eu un bon point" ! Ce petit mot fièrement lancé au retour de l'école, c'est pour certains d'entre nous le souvenir nostalgique d'une enfance lointaine, composée de pupitres, de tabliers et de craies. Les bons points ont été mis en place dans le système scolaire dès le XVIIIe siècle pour encourager les meilleurs élèves. On ne reviendra pas ici sur la valeur pédagogique de ce système aujourd'hui critiqué et certainement critiquable, mais sur le 'bon point' en tant que support papier et les illustrations - en l'occurrence de nature entomologique - qui les accompagnaient parfois avec plus ou moins de précision comme le montre notre exemple.

The second International Symposium on Animal Genomics for Animal Health held in Paris, France 31 May-2 June, 2010, assembled more than 140 participants representing research organizations from 40 countries. The symposium included a roundtable discussion on critical needs, challenges and opportunities, and a forward look at the potential applications of animal genomics in animal health research. The aim of the roundtable discussion was to foster a dialogue between scientists working at the cutting edge of animal genomics research and animal health scientists. Importantly, stakeholders were included to provide input on priorities and the potential value of animal genomics to the animal health community. In an effort to facilitate the roundtable discussion, the organizers identified four priority areas to advance the use of genome-enabled technologies in animal health research. Contributions were obtained through open discussions and a questionnaire distributed at the start of the symposium. This report provides the outcome of the roundtable discussion for each of the four priority areas. For each priority, problems are identified, including potential solutions and recommendations. This report captures key points made by symposium participants during the roundtable discussion and serves as a roadmap to steer future research priorities in animal genomics research.

Measurements of CO2 emission spectra at high temperature in the 2.7 μm and 4.3 μm regions are presented and compared to predictions from the spectroscopic databases, CDSD-4000 (Tashkun SA, Perevalov VI. CDSD-4000: high-resolution, high-temperature carbon dioxide spectroscopic databank. Journal of Quantitative Spectroscopy and Radiative Transfer 2011;112:1403-10) and HITELOR (Scutaru D, Rosenmann L, Taine J. Approximate intensities of CO2 hot bands at 2.7, 4.3 and 12 μm for high temperature and medium resolution applications. Journal of Quantitative Spectroscopy and Radia- tive Transfer 1994;52:765-81). The measurements near 2.7 μm show that CDSD-4000 provides better agreement with experimental data, especially in the band wing corresponding to very hot band emission. In the 4.3 μm region, experimental intensities are generally lower than theoretical predictions but the measurements are more affected by the use of sapphire confinement tubes. The two spectroscopic databases provide closer results than in the 2.7 μm region although CDSD-4000 yields here also better agreement with experimental data in band wing. Analysis of the two spectro- scopic databases is carried out in terms of vibrational and rotational energy cutoff and total band emissivities.

Network densification via small cells is considered as a key step to cope with the data tsunami. Caching data at small cells or even user devices is also considered as a promising way to alleviate the backhaul congestion this densification might cause. However, the former suffers from high deployment and maintenance costs, and the latter from limited resources and privacy issues with user devices. We argue that an architecture with (public or private) vehicles acting as mobile caches and communication relays might be a promising middle ground. In this paper, we assume such a vehicular cloud is in place to provide video streaming to users, and that the operator can decide which content to store in the vehicle caches. Users can then greedily fill their playout buffer with video pieces of the streamed content from encountered vehicles, and turn to the infrastructure immediately when the playout buffer is empty, to ensure uninterrupted streaming. Our main contribution is to model the playout buffer in the user device with a queuing approach, and to provide a mathematical formulation for the idle periods of this buffer, which relate to the bytes downloaded from the cellular infrastructure. We also solve the resulting content allocation problem, and perform trace based simulations to finally show that up to 50% of the original traffic could be offloaded from the main infrastructure.

Nous décrivons ici un dispositif d'imagerie ultrasonore utilisant la méthode dite de « tomographie par diffraction ». Celle-ci permet de dresser la carte des sources secondaires induites dans l'objet par l'onde incidente, et ceci sans hypothèse a priori sur le mode de propagation de l'onde. Les caractéristiques du dispositif, ses performances et des exemples d'images de fantômes simples seront donnés. Parmi les utilisations possibles, nous présenterons les images, simulées, montrant la possibilité de détection des variations de température dans un processus d'hyperthermie.

En 2030 habrá en el planeta unos 8 500 millones de habitantes, y cerca de 10 000 millones en 2050, frente a los 7 700 millones de personas que lo habitamos hoy.

Mg alloys are promising lightweight structural materials due to their low density and excellent mechanical properties. However, their limited formability and ductility necessitate improvements in these properties, specifically through texture modification via grain boundary segregation. While significant efforts have been made, the segregation behavior in Mg polycrystals, particularly with basal texture, remains largely unexplored. In this study, we performed atomistic simulations to investigate grain boundary segregation in dilute and concentrated solid solution Mg-Al alloys. We computed the segregation energy spectrum of basal-textured Mg polycrystals, highlighting the contribution from specific grain boundary sites, such as junctions, and identified a newly discovered bimodal distribution which is distinct compared to the conventional skewnormal distribution found in randomly-oriented polycrystals. Using a hybrid molecular dynamics/Monte Carlo approach, we simulated segregation behavior at finite temperatures, identifying grain boundary structural transitions, particularly the varied fraction and morphology of topologically close-packed grain boundary phases when changing thermodynamic variables. The outcomes of this study offer crucial insights into basaltextured grain boundary segregation and phase formation, which can be extended to other relevant Mg alloys containing topologically close-packed intermetallics.

Les travaux de cette thèse s’inscrivent dans un projet de grande envergure, le projet 3D-IDEAS, financé par l’ANR. Le but de ce projet est d’établir la chaîne complète de l’intégration de circuits en technologie 3D. Les densités de puissance dans ces circuits sont telles que les problèmes liés à la température – électromigration, désappariement des courants et tensions de polarisation, etc. – sont susceptibles de remettre en cause la conception du circuit. Le coût élevé de la fabrication de ces circuits oblige le concepteur à valider le comportement électrothermique des circuits préalablement à l’envoi en fabrication. Pour répondre à ce besoin, un simulateur électrothermique précis et fiable doit être à disposition. En outre, en raison de la complexité extrême de ces circuits, il est judicieux que ce simulateur soit compatible avec l’approche de modélisation haut niveau. L’objectif de cette thèse est de développer un tel simulateur. La solution proposée intègre ce simulateur dans un environnement de développement CAO pour circuit intégré standard, Cadence®. La contrainte sur la précision des résultats nous a amené à développer une nouvelle méthodologie spécifique à la modélisation électrothermique haut-niveau. Ce manuscrit comporte deux grandes parties. Dans la première, la démarche adoptée pour concevoir le simulateur est détaillée. Ensuite, dans la seconde partie, le fonctionnement du simulateur ainsi que la méthode de modélisation haut-niveau mise en place sont présentées, puis validées.

24x36 mm, gélatine plan-film.

We consider the Hartree equation with a smooth kernel and an external potential, in the semiclassical regime. We analyze the propagation of two initial wave packets, and show different possible effects of the interaction, according to the size of the nonlinearity in terms of the semiclassical parameter. We show three different sorts of nonlinear phenomena. In each case, the structure of the wave as a sum of two coherent states is preserved. However, the envelope and the center (in phase space) of these two wave packets are affected by nonlinear interferences, which are described precisely.

24x36 mm, film.