Reliability approach in spacecraft structures

This paper presents an application of the probabilistic approach with reliability assessment on a spacecraft structure. The adopted strategy uses meta-modeling with first and second order polynomial functions. This method aims at minimizing computational time while giving relevant results. The first part focuses on computational tools employed in the strategy development. The second part presents a spacecraft application. The purpose is to highlight benefits of the probabilistic approach compared with the current deterministic one. From examples of reliability assessment we show some advantages which could be found in industrial applications

Tuning the DNA Reactivity of cis-Platinum: Conjugation to a Mismatch-Specific Metallointercalator

A novel bimetallic conjugate combining a rhodium intercalator that selectively binds DNA mismatches and a reactive cis-platinum analogue that targets DNA by coordination has been prepared. The site-selectivity of the bimetallic complex in forming coordination adducts is examined using mismatched and well-matched oligonucleotides of different sequences. The results indicate that through the bifunctional complex, the platinum center can be targeted near mismatched sites. Interestingly, with mismatched, DNA both intrastrand and the less common interstrand cross-linked adducts are formed. The recognition of a DNA mismatch by the bulky Rh intercalator appears to direct the Pt unit, depending upon steric constraints, to react preferentially with mismatched DNA at a site that may or may not be the preferred site of Pt coordination. Thus, the presence of a permanent link to a site-specific intercalator is able to tune the reactivity of the cis-platinum analogue

État des recherches en didactique du français

Ce numéro de Pratiques constitue, à la suite du numéro 145/146 de juin 2010, le second volet de notre enquête consacrée à l’état du champ des recherches en didactique du français. Il y a un an, nous écrivions que le contexte politique et institutionnel n’était pas favorable aux recherches en didactique, évoquant notamment l’effet de l’intégration des IUFM aux universités et les réformes régressives de la formation des maîtres. Dans l’intervalle, le contexte n’a pas changé, il s’est même aggra..

Application des surfaces de réponse pour l’analyse fiabiliste d’une structure spatiale

Cette communication présente une application des surfaces de réponse pour l’analyse de la fiabilité d’une structure satellite. Les méta-modèles sont construits par régression itérative où seul les termes significatifs sont sélectionnés parmi une liste de régresseurs potentiels préalablement déterminée par une analyse de sensibilité. Les méta-modèles sont ensuite vérifiés par une méthode de bootstrap où les variations observées sur les prédictions sont prises en compte dans le calcul des probabilités de défaillance afin de valider le résultat

Hydrologically driven seasonal changes in the sources and production mechanisms of dissolved organic carbon in a small lowland catchment

International audienceTo obtain better constraints on the control of seasonal hydrological variations on dissolved organic carbon (DOC) dynamics in headwater catchments, we combined hydrometric monitoring with high-frequency analyses of DOC concentration and DOC chemical composition (specific UV adsorption, 13C) in soil and stream waters during one complete hydrological cycle in a small lowland catchment of western France. We observed a succession of four hydrological periods, each corresponding to specific DOC signatures. In particular, the rise of the upland water table at the end of the rewetting period yielded to a strong increase of the specific UV absorbance (from 2.5 to 4.0 L mg C 1 m 1) and of the 13C values (from 29 to 27%) of the soil DOC. Another striking feature was the release of large amounts of DOC during reduction of soil Fe-oxyhydroxides at the end of the highflow period. Comparison of hydrometric data with DOC composition metrics showed that soils from the upland domains were rapidly DOC depleted after the rise of the water table in these domains, whereas wetland soils acted as quasi-infinite DOC sources. Results from this study showed that the composition and ultimate source of the DOC exported to the stream will depend on the period within the annual hydrological cycle. However, we found that the aromatic DOC component identified during the high-flow period will likely represent the dominant DOC component in stream waters on an annual basis, because most of the annual stream DOC flux is exported during such periods

Sources of dissolved organic matter during storm and inter-storm conditions in a lowland headwater catchment: constraints from high-frequency molecular data

International audienceThe transfer of dissolved organic matter (DOM) at soil–river interfaces controls the biogeochemistry of mi-cropollutants and the equilibrium between continental and oceanic C reservoirs. Understanding the mechanisms controlling this transfer is fundamental to ecology and geochem-istry. DOM delivery to streams during storms is assumed to come from the flushing of preexisting soil DOM reservoirs mobilized by the modification of water flow paths. We tested this hypothesis by investigating the evolution of the composition of stream DOM during inter-storm conditions and five storm events monitored with high-frequency sampling. The composition of DOM was analyzed using thermally assisted hydrolysis and methylation (THM) with tetramethylammo-nium hydroxide (TMAH) coupled to a gas chromatograph and mass spectrometer. In inter-storm conditions, stream DOM is derived from the flushing of soil DOM, while during storm events, the modification of the distribution of chemical biomarkers allows the identification of three additional mechanisms. The first one corresponds to the destabilization of microbial biofilms due to the increase in water velocity, resulting in the fleeting export of a microbial pool. The second mechanism corresponds to the erosion of soils and river banks, leading to a partition of organic matter between particulate and dissolved phases. The third mechanism is linked to the increase in water velocity in soils that could induce the erosion of macropore walls, leading to an in-soil partition between soil microparticles and dissolved phase. The contribution of this in-soil erosive process would be linked to the magnitude of the hydraulic gradient following the rise of the water table and could persist after the recession, which could explain why the return to inter-storm composition of DOM does not follow the same temporal scheme as the discharge. These results are the most important factors in understanding the transfer of nutrients and micropollutants at the soil–river interfaces during the hot moments that are storm events

Didactique de l’écriture en situation de raccrochage scolaire : une entrée par les compétences. Un début d’étude collaborative au micro lycée de Paris

International audienceDidactique de l'écriture en situation de raccrochage : une entrée par les compétences ? Un début d'étude collaborative au micro-lycée de Paris Régine Delamotte, Marie-Claude Penloup et Anne-Marie Petitjean, université de Rouen La question du passage à l'écriture s'avère peu traitée dans les travaux actuels sur le décrochage scolaire alors même que les enseignants des micro-lycées d'Évreux et de Paris ont une demande explicite concernant les difficultés que rencontrent leurs élèves pour passer à l'écriture acadé-mique, en même temps d'ailleurs qu'ils soulignent leurs compétences en écriture créative. Pour répondre à cette demande, l'étude diagnostique que nous présentons s'appuie sur des données diverses : observations, enquêtes auprès des acteurs, textes produits lors d'une séance d'écriture créative. Cet ensemble est construit à partir de positions théoriques sociolinguistiques et (so-cio)didactiques qui seront rappelées. Il nous amène à mettre en évidence l'existence effective de compétences en écriture créative chez les élèves du micro-lycée et à en évaluer les enjeux pour la didactique

PockDrug-Server : a new web server for predicting pocket druggability on holo and apo proteins

Predicting protein pocket's ability to bind drug-like molecules with high affinity, i.e. druggability, is of major interest in the target identification phase of drug discovery. Therefore, pocket druggability investigations represent a key step of compound clinical progression projects. Currently computational druggability prediction models are attached to one unique pocket estimation method despite pocket estimation uncertainties. In this paper, we propose 'PockDrug-Server' to predict pocket druggability, efficient on both (i) estimated pockets guided by the ligand proximity (extracted by proximity to a ligand from a holo protein structure) and (ii) estimated pockets based solely on protein structure information (based on amino atoms that form the surface of potential binding cavities). PockDrug-Server provides consistent druggability results using different pocket estimation methods. It is robust with respect to pocket boundary and estimation uncertainties, thus efficient using apo pockets that are challenging to estimate. It clearly distinguishes druggable from less druggable pockets using different estimation methods and outperformed recent druggability models for apo pockets. It can be carried out from one or a set of apo/holo proteins using different pocket estimation methods proposed by our web server or from any pocket previously estimated by the user. PockDrug-Server is publicly available at: http://pockdrug.rpbs.univ-paris-diderot.fr.Peer reviewe

Inflammatory control in AIDS-resistant non human primates

International audienceAfrican non human primates are natural hosts of SIV. The infection is non-pathogenic despite plasma viral load levels similar to those in HIV-1 infected humans and SIVmac-infected macaques (MAC) progressing towards AIDS. The most striking difference between non-pathogenic SIV and pathogenic HIV-1/SIVmac infections is the lack of chronic T cell activation in natural hosts. In HIV and SIVmac infections, chronic T cell activation is known to drive CD4+T cell depletion. Intense research efforts are worldwide put on the search of the mechanisms that can control chronic T cell activation in HIV/SIV infections. Innate immune responses play a determinant role in the regulation of T cell activation profiles. Type I interferons (IFN-I) are part of the first-wave response of the innate immune system in viral infections. We compared the IFN-I responses between pathogenic (MAC) and non-pathogenic SIV infections (African Green monkey, AGM) at the level of blood and lymph nodes (LN) during the early and chronic stage of infection. During the acute SIVagm infection, we detected high amounts of IFN-α in the plasma of AGMs, although the mean levels at the peak were three times lower than in MAC. The microarray data revealed a rapid and strong up-regulation of type I Interferon-Stimulated Genes (ISG) in AGMs during acute SIVagm infection. ISGs denote the in vivo activity of IFN-I. Using a functional assay, we demonstrated that low IFN-α concentrations (50 times lower than the IFN-α levels in plasma at the peak) were sufficient to induce strong ISG responses in AGM and MAC cells. Surprisingly, our direct comparison of blood and LNs showed that ISG induction was broader in blood of AGMs than in MAC, while in LN, it was the contrary. Thus, in AGMs, less ISG were induced in LNs as compared to MAC already during the acute phase of infection. Moreover, our tight kinetic analysis showed that this ISG expression was efficiently controlled after day 28 post-infection in AGMs, while in MAC the ISGs expression remained uncontrolled. Finally, we identified genes that were differentially expressed between the two species and which might be involved in the discriminating responses. Altogether, this shows that AGMs are capable to mount a well coordinated and efficient regulative response to innate immune activation