Fragmentation and Limits to Dynamical Scaling in Viscous Coarsening: An Interrupted in situ X-Ray Tomographic Study

X-Ray microtomography was used to follow the coarsening of the structure of a ternary silicate glass experiencing phase separation in the liquid state. The volumes, surfaces, mean and Gaussian curvatures of the domains of minority phase were measured after reconstruction of the 3D images and segmentation. A linear growth law of the characteristic length scale $\ell \sim t$ was observed. A detailed morphological study was performed. While dynamical scaling holds for most of the geometrical observables under study, a progressive departure from scaling invariance of the distributions of local curvatures was evidenced. The latter results from a gradual fragmentation of the structure in the less viscous phase that also leads to a power-law size distribution of isolated domains

Exploiting technological synergies for future launch vehicles

Two launch vehicle concepts based on technologies available today or in a short term future in Western Europe are presented. The design of both launchers has the goal of exploiting synergies with current European programs to limit development and operational costs. Technologies of particular interest here are the high performance solid rocket motors with carbon-epoxy filament wound monolithic motor cases and the future high performance cryogenic expander cycle engine Vinci. The first concept dubbed ANGELA (A New GEneration LAuncher) is a study financed with funds of the German Ministry of Economics and managed by the DLR Space Administration. The project, which started in the summer of 2012 aims at designing a low cost versatile launcher able to place payloads between 2 and 5 tons into GTO. Three architectures have been considered during the first phase of the study. This phase was concluded in March 2013 with the preliminary stagings, which will be the starting point of more detailed analyses. The first architecture is made out of an H110 (stage with 110 tons of LOx/LH2) equipped with two Vulcain 2 engines with shortened nozzles and an H29 propelled by a Vinci engine. In addition the variation of the number of P36 solid rocket boosters allow to reach the entire range of payload performance. The second architecture differs from the first one only by the use of a new staged-combustion engine instead of two Vulcain 2 engines. The new engine, which should deliver 1800 kN in vacuum, allows a reduction of the size of the stages to H90-H24, enhanced with P34 boosters. The third and last architecture is a so called Multi PPH. The first stage is a bundle of 2 or 3 P120 solid rocket motors. The second stage is made out of one single P120, strictly similar to those used for the first stage. Finally the upper stage is an H23 equipped with a Vinci engine, the same as the two other architectures. The second launcher concept described in this paper is the small TSTO launch vehicle. It consists of a large solid rocket motor first stage P175 and a cryogenic upper stage propelled by the Vinci engine, H26. The preliminary design performed at DLR-SART considers two target performances. The light version of the small TSTO shall perform Galileo satellite replacement single launch missions to MTO corresponding to a payload performance of about 1400 kg in GTO. A heavy version of the launch vehicle shall be able to launch payloads up to 3000 kg in GTO. The performance increase for the heavy version is made possible by the addition of two pairs of P23 boosters, the second pair being ignited with a delay

On n’enseigne pas la langue à l’école : là est le problème

International audienceNous nous intéressons à la problématique de la didactique de la langue dite « maternelle » en France. Notre perspective se situant au carrefour des préoccupations sociolinguistiques et didactiques, nous tenterons de défendre l’hypothèse selon laquelle l’absence de reconnaissance de la réalité de la langue dans les apprentissages peut être à l’origine des difficultés constatées à l’école primaire. A partir de données issues de l’enregistrement de séquences de classe et d’un corpus de manuels scolaires, nous tenterons de mettre en évidence l’absence de prise en compte de la variation de la langue dans les enseignements et montrerons en quoi cet état de fait est un frein au bon déroulement de l’enseignement. Il s’agit, en arrière plan, de penser un enseignement de la langue commune qui contribue à la cohésion sociale, à la reconnaissance de la communauté, sans entraver le développement de la construction identitaire des élèves en tant qu’elle est la manifestation de l’individualité de chacu

Discovery of Escherichia coli methionyl-tRNA synthetase mutants for efficient labeling of proteins with azidonorleucine in vivo

Incorporation of noncanonical amino acids into cellular proteins often requires engineering new aminoacyl-tRNA synthetase activity into the cell. A screening strategy that relies on cell-surface display of reactive amino acid side-chains was used to identify a diverse set of methionyl-tRNA synthetase (MetRS) mutants that allow efficient incorporation of the methionine (Met) analog azidonorleucine (Anl). We demonstrate that the extent of cell-surface labeling in vivo is a good indicator of the rate of Anl activation by the MetRS variant harbored by the cell. By screening at low Anl concentrations in Met-supplemented media, MetRS variants with improved activities toward Anl and better discrimination against Met were identified

Exciton photon strong-coupling regime for a single quantum dot in a microcavity

We report on the observation of the strong coupling regime between a single GaAs quantum dot and a microdisk optical mode. Photoluminescence is performed at various temperatures to tune the quantum dot exciton with respect to the optical mode. At resonance, we observe an anticrossing, signature of the strong coupling regime with a well resolved doublet. The Vacuum Rabi splitting amounts to 400 μeV and is twice as large as the individual linewidths.Comment: submitted on November 7th 200

The mucin-degradation strategy of Ruminococcus gnavus:The importance of intramolecular trans-sialidases

We previously identified and characterized an intramolecular trans-sialidase (IT-sialidase) in the gut symbiont Ruminococcus gnavus ATCC 29149, which is associated to the ability of the strain to grow on mucins. In this work we have obtained and analyzed the draft genome sequence of another R. gnavus mucin-degrader, ATCC 35913, isolated from a healthy individual. Transcriptomics analyses of both ATCC 29149 and ATCC 35913 strains confirmed that the strategy utilized by R. gnavus for mucin-degradation is focused on the utilization of terminal mucin glycans. R. gnavus ATCC 35913 also encodes a predicted IT-sialidase and harbors a Nan cluster dedicated to sialic acid utilization. We showed that the Nan cluster was upregulated when the strains were grown in presence of mucin. In addition we demonstrated that both R. gnavus strains were able to grow on 2,7-anyhydro-Neu5Ac, the IT-sialidase transglycosylation product, as a sole carbon source. Taken together these data further support the hypothesis that IT-sialidase expressing gut microbes, provide commensal bacteria such as R. gnavus with a nutritional competitive advantage, by accessing and transforming a source of nutrient to their own benefit

Strontium isotope geochemistry of alluvial groundwater: a tracer for groundwater resources characterisation

International audienceThis study presents strontium isotope and major ion data of shallow groundwater and river water from the Ile du Chambon catchment, located on the Allier river in the Massif Central (France). There are large variations in the major-element contents in the surface- and groundwater. Plotting of Na vs. Cl contents and Ca, Mg, NO3, K, SO4, HCO3, Sr concentrations reflect water–rock interaction (carbonate dissolution for Ca, Mg, HCO3 and Sr because the bedrock contains marly limestones), agricultural input (farming and fertilising) and sewage effluents (for NO3, K, SO4), although some water samples are unpolluted. Sr contents and isotope ratios (87Sr/86Sr vary from 0.70892 to 0.71180 along the hydrological cycle) in the groundwater agree with previous work on groundwater in alluvial aquifers in the Loire catchment. The data plot along three directions in a 87Sr/86Sr v. 1/Sr diagram as a result of mixing, involving at least three geochemical signatures–Allier river water, and two distinct signatures that might be related to different water-rock interactions in the catchment. Mixing proportions are calculated and discussed. The alluvial aquifer of the Ile du Chambon catchment is considered, within the Sr isotope systematic, in a larger scheme that includes several alluvial aquifers of the Loire Allier catchment. Keywords: : Loire river, major and trace elements, Sr isotopic ratio, alluvial aquifer, hydrolog

Metabolic and Proteomic Profiling of Diapause in the Aphid Parasitoid Praon volucre

Background: Diapause, a condition of developmental arrest and metabolic depression exhibited by a wide range of animals is accompanied by complex physiological and biochemical changes that generally enhance environmental stress tolerance and synchronize reproduction. Even though some aspects of diapause have been well characterized, very little is known about the full range of molecular and biochemical modifications underlying diapause in non-model organisms. Methodology/Principal Findings: In this study we focused on the parasitic wasp, Praon volucre that exhibits a pupal diapause in response to environmental signals. System-wide metabolic changes occurring during diapause were investigated using GC-MS metabolic fingerprinting. Moreover, proteomic changes were studied in diapausing versus nondiapausing phenotypes using a combination of two-dimensional differential gel electrophoresis (2D-DIGE) and mass spectrometry. We found a reduction of Krebs cycle intermediates which most likely resulted from the metabolic depression. Glycolysis was galvanized, probably to favor polyols biosynthesis. Diapausing parasitoids accumulated high levels of cryoprotective polyols, especially sorbitol. A large set of proteins were modulated during diapause and these were involved in various functions such as remodeling of cytoskeleton and cuticle, stress tolerance, protein turnover, lipid metabolism and various metabolic enzymes. Conclusions/Significance: The results presented here provide some first clues about the molecular and biochemical events that characterize the diapause syndrome in aphid parasitoids. These data are useful for probing potential commonality of parasitoids diapause with other taxa and they will help creating a general understanding of diapause underpinnings and a background for future interpretations