Convergence Rates in L^2 for Elliptic Homogenization Problems

We study rates of convergence of solutions in L^2 and H^{1/2} for a family of elliptic systems {L_\epsilon} with rapidly oscillating oscillating coefficients in Lipschitz domains with Dirichlet or Neumann boundary conditions. As a consequence, we obtain convergence rates for Dirichlet, Neumann, and Steklov eigenvalues of {L_\epsilon}. Most of our results, which rely on the recently established uniform estimates for the L^2 Dirichlet and Neumann problems in \cite{12,13}, are new even for smooth domains.Comment: 25 page

VIDÉO-MICROSCOPIE SANS LENTILLE POUR LA BIOLOGIE CELLULAIRE 2D ET 3D

International audienceL'étude de l'évolution et de l'organisation de populations de cellules cultivées in vitro intéresse les biologistes depuis plusieurs dizaines d'années. À ces fins, d'importants progrès ont été réalisés dans les méthodes d'imagerie à l'échelle microscopique. Cependant, certaines informations demeurent inaccessibles, notamment à l'échelle mésoscopique, en raison du champ de vue réduit, ainsi que la complexité et le coût pour réaliser des acquisitions hors incubateur en temps réel sur de longues périodes. En réponse à ces limitations, nous avons développé la vidéo-microscopie sans lentille, en plaçant directement les cellules vivantes sur un capteur numérique en regard d'une illumination cohérente selon le principe de l'holographie en ligne. Cette technique permet l'observation d'une culture cellulaire sur un large champ de vue (24 mm² soit plusieurs dizaines de milliers de cellules), et ce à l'intérieur même de l'incubateur, autorisant de surcroît des acquisitions dynamiques couvrant des périodes allant de quelques jours à plusieurs semaines. À partir des images holographiques brutes acquises, nous pouvons remonter aux images refocalisées par reconstruction numérique jusqu'à une résolution de 2µm. Le traitement de ces images donne accès à des niveaux d'information quantifiables allant de la cellule unique à l'organisation inter-individus de la population. Avec des premières études sur des cultures standard de cellules sur substrat 2D, nous sommes aujourd'hui en mesure, avec notre dispositif et la force de l'imagerie holographique, d'explorer et d'étudier la vie cellulaire en 3D, nous rapprochant un peu plus de la réalité physiologique des phénomènes biologiques

Phi-Meson Production at RHIC, Strong Color Fields and Intrinsic Transverse Momenta

We investigate the effects of strong color fields and of the associated enhanced intrinsic transverse momenta on the phi-meson production in ultrarelativistic heavy ion collisions at RHIC. The observed consequences include a change of the spectral slopes, varying particle ratios, and also modified mean transverse momenta. In particular, the composition of the production processes of phi mesons, that is, direct production vs. coalescence-like production, depends strongly on the strength of the color fields and intrinsic transverse momenta and thus represents a sensitive probe for their measurement.Comment: 4 pages, 3 figure

Effect of Shot Peening Process on Rolling Contact Fatigue Performance of EN 31 Alloy Steel

This paper aims to study the effect of shot peening on the Rolling Contact Fatigue (RCF) life of EN 31 Steel subjected to a pure rolling condition. Tests were carried out under lubricated contact conditions using a two-disc on-cylinder test rig. The orthogonal stress distributions and depth of deformation zones under static loading conditions were calculated using an elastic model by Finite Element Analysis (FEA) method. Shot peening increased the surface hardness by 20 % and imparted residual stress, which resulted in a 2-fold improvement of life. The depth of origin of the crack from the sub-surface was found to be in good agreement with the depth of maximum shear region obtained from the finite element model

Microstructure and Phase Formation in a Rapidly Solidified Laser-Deposited Ni-Cr-B-Si-C Hardfacing Alloy

In this study, microstructural evolutions and phase selection phenomena during laser deposition of a hardfacing Ni-Cr-B-Si-C alloy at different processing conditions are experimentally investigated. The results show that even minor variations in the thermal conditions during solidification can modify the type and morphology of the phases. Higher undercoolings obtained at faster cooling rates suppressed the primary borides and encouraged floret-shape mixtures of Ni and Cr5B3 via a metastable reaction. Variations in the boride phases are discussed in terms of nucleation-and growth-controlled phase selection mechanisms. These selection processes also influenced the nature and proportion of the Ni-B-Si eutectics by changing the amount of the boron available for the final eutectic reactions. The results of this work emphasize the importance of controlling the cooling rate during deposition of these industrially important alloys using laser beam or other rapid solidification techniques. (C) The Minerals, Metals & Materials Society and ASM International 201

Towards a unified theory of Sobolev inequalities

We discuss our work on pointwise inequalities for the gradient which are connected with the isoperimetric profile associated to a given geometry. We show how they can be used to unify certain aspects of the theory of Sobolev inequalities. In particular, we discuss our recent papers on fractional order inequalities, Coulhon type inequalities, transference and dimensionless inequalities and our forthcoming work on sharp higher order Sobolev inequalities that can be obtained by iteration.Comment: 39 pages, made some changes to section 1

Spectroscopic and computational insights on catalytic synergy in bimetallic aluminophosphate catalysts

A combined electronic structure computational and X-ray absorption spectroscopy study was used to investigate the nature of the active sites responsible for catalytic synergy in Co-Ti bimetallic nanoporous frameworks. Probing the nature of the molecular species at the atomic level has led to the identification of a unique Co-O-Ti bond, which serves as the loci for the superior performance of the bimetallic catalyst, when compared with its analogous monometallic counterpart. The structural and spectroscopic features associated with this active site have been characterized and contrasted, with a view to affording structure property relationships, in the wider context of designing sustainable catalytic oxidations with porous solids

Genetic variation in Wnt/β-catenin and ER signalling pathways in female and male elite dancers and its associations with low bone mineral density: a cross-section and longitudinal study.

The association of genetic polymorphisms with low bone mineral density in elite athletes have not been considered previously. The present study found that bone mass phenotypes in elite and pre-elite dancers are related to genetic variants at the Wnt/β-catenin and ER pathways. Some athletes (e.g. gymnasts, dancers, swimmers) are at increased risk for low bone mineral density (BMD) which, if untreated, can lead to osteoporosis. To investigate the association of genetic polymorphisms in the oestrogen receptor (ER) and the Wnt/β-catenin signalling pathways with low BMD in elite and pre-elite dancers (impact sport athletes). The study included three phases: (1) 151 elite and pre-elite dancers were screened for the presence of low BMD and traditional osteoporosis risk factors (low body weight, menstrual disturbances, low energy availability); (2) a genetic association study was conducted in 151 elite and pre-elite dancers and age- and sex- controls; (3) serum sclerostin was measured in 101 pre-elite dancers and age- and sex-matched controls within a 3-year period. Eighty dancers revealed low BMD: 56.3% had at least one traditional osteoporosis risk factor, whereas 28.6% did not display any risk factor (37.2% revealed traditional osteoporosis risk factors, but had normal BMD). Body weight, menstrual disturbances and energy availability did not fully predict bone mass acquisition. Instead, genetic polymorphisms in the ER and Wnt/β-catenin pathways were found to be risk factors for low BMD in elite dancers. Sclerostin was significantly increased in dancers compared to controls during the 3-year follow-up (p < 0.05)