Three-dimensional separation in shock/boundary layer interaction

A Large-eddy simulation of a shock impinging on a turbulent boundary layer is carried out and demonstrates good agreement with the experiments. A special emphasis is put on the analysis of the three-dimensional modulation of the flow in order to clarify the origin of the mean vortices located in the separation region highlighted by the experimen

Computational identification of transcriptionally co-regulated genes, validation with the four ANT isoform genes.

International audienceABSTRACT: BACKGROUND: The analysis of gene promoters is essential to understand the mechanisms of transcriptional regulation required under the effects of physiological processes, nutritional intake or pathologies. In higher eukaryotes, transcriptional regulation implies the recruitment of a set of regulatory proteins that bind on combinations of nucleotide motifs. We developed a computational analysis of promoter nucleotide sequences, to identify co-regulated genes by combining several programs that allowed us to build regulatory models and perform a crossed analysis on several databases. This strategy was tested on a set of four human genes encoding isoforms 1 to 4 of the mitochondrial ADP/ATP carrier ANT. Each isoform has a specific tissue expression profile linked to its role in cellular bioenergetics. RESULTS: From their promoter sequence and from the phylogenetic evolution of these ANT genes in mammals, we constructed combinations of specific regulatory elements. These models were screened using the full human genome and databases of promoter sequences from human and several other mammalian species. For each of transcriptionally regulated ANT1, 2 and 4 genes, a set of co-regulated genes was identified and their over-expression was verified in microarray databases. CONCLUSIONS: Most of the identified genes encode proteins with a cellular function and specificity in agreement with those of the corresponding ANT isoform. Our in silico study shows that the tissue specific gene expression is mainly driven by promoter regulatory sequences located up to about a thousand base pairs upstream the transcription start site. Moreover, this computational strategy on the study of regulatory pathways should provide, along with transcriptomics and metabolomics, data to construct cellular metabolic networks

Un modèle pour les instationnarités basses fréquences dans les décollements compressibles.

Un modèle pour expliquer les instationnarités basses fréquences dans les décollements de couche limite induits par onde de chocs est proposé, dans les cas où l'écoulement recolle en aval. Ce modèle est basé sur les propriétés d'entraînement de la couche de mélange générée en aval du choc réfléchi, dont les mouvements basses fréquences sont liés aux contractions/dilatations successives du bulbe décollé. Ce modèle sera appliqué à différentes interactions, pour des nombres de Mach allant de 0 à 5

BASTA : a 95GHz FM-­‐CW Cloud radar

International audienceGround-based continuous observation of non-precipitating clouds and fo

Caractérisation d'un milieu poreux colmaté par la méthode du potentiel spontané

Laboratory experiments are performed on the physical clogging of a porous medium by injecting polydispersive suspended particles ranged from 1.7 to 40 μm in a column filled with sand (d50=715 µm). Three suspensions have been injected (2g/l, 3g/l and 5g/l) at constant flow velocity in a saturated porous medium. Hydrodynamic effects on particles deposition and porous medium damage were investigated. Particles retentions are significant at the inlet and decreases with depth which induces the drop of permeability and porosity. The coupling between electric and hydraulic flows is electrokinetic in nature, the second objective of this work is to test the sensitivity of the method of self-potential (SP) and to show the usefulness of this method to understand the controlling parameters of the electrical field associated with the filtration of suspended particles through a porous medium. Electrodes have been used to record the SP signal which detect and quantify the clay particles in the porous medium during injection tests. The variations of the SP signals are linearly correlated to the piezometric level changes. SP signals are directly sensitive to deposition particles distribution, and it is high at the inlet of the column where the deposit is large and decreases with depth. For the test injection with 2g/l the SP signal varies between +16 mv and +13 mv for the test with 3g/l it varies between +12 mv and +8mv and that with 5g/l it varies between - 22mv to-19mv. When the concentration of clay injected in the porous medium increases, the SP signal decreases and changes from a positive sign to a negative sign. SP method confirmed the behavior of the porous medium clogging obtained by the hydraulic measurements. The obtained results show that SP signal is sensitive to clay particles, their immediate passage to the inlet of the column and the amount deposited particles in each section of the porous medium

Cavitation Erosion Prediction on Francis Turbines Part 3 : Methodologies of Prediction

In the frame of a joint research program between EDF, Hydro Québec and IMHEF, different methods are investigated to predict cavitation erosion on Francis turbines from model. They are based on measurement of pitting, pressure fluctuations and acceleration. The measurement techniques have been detailed in Part I and Part 2. The present article describes essentially the theoretical and practical aspects of the methods and discusses the results obtained until now from the mode! and prototype tests. The first analysis shows that the methods proposed are suitable to measure cavitation aggressiveness on mode! and on prototype, and that the level on the mode! is several orders of magnitude smaller than on the prototype. To adjust transposition laws, a more complete set of data is needed

Symmetric microwave potentials for interferometry with thermal atoms on a chip

International audienceA trapped atom interferometer involving state-selective adiabatic potentials with two microwave frequencies on a chip is proposed. We show that this configuration provides a way to achieve a high degree of symmetry between the two arms of the interferometer, which is necessary for coherent splitting and recombination of thermal (i.e., noncondensed) atoms. The resulting interferometer holds promise to achieve high contrast and long coherence time, while avoiding the mean-field interaction issues of interferometers based on trapped Bose-Einstein condensates