Low friction MoS2TiW Coatings Manufactured on X38CrMoV5-1 Steel Using PVD Method

In this article the friction coefficients and the wear resistances of MoS2TiW protective coatings manufactured on X38CrMoV5-1 steel samples by using PVD technology are studied. The investi- gations based on tribometer tests which were carried out in different temperature conditions. The process of deposition of PVD coatings was realized by using multisource, hybrid factory- scale equipment of type URM 079. This equipment allows for deposition of coatings by the phys- ical method. The tribological tests were performed using a precision high temperature tribome- ter under ambient and high temperature conditions with a steel and corundum balls as coun- ter-samples. In this paper the results of these tribological tests are presented. It is shown that the measured friction coefficient of steel samples with PVD coatings is significantly lower than the friction coefficient of uncoated steel. It is also shown that X38CrMoV5-1 steel samples with manufactured MoS2TiW coatings are characterized by very low friction coefficient and high wear resistance

Experimental discovery of small RNAs in Staphylococcus aureus reveals a riboregulator of central metabolism

Using an experimental approach, we investigated the RNome of the pathogen Staphylococcus aureus to identify 30 small RNAs (sRNAs) including 14 that are newly confirmed. Among the latter, 10 are encoded in intergenic regions, three are generated by premature transcription termination associated with riboswitch activities, and one is expressed from the complementary strand of a transposase gene. The expression of four sRNAs increases during the transition from exponential to stationary phase. We focused our study on RsaE, an sRNA that is highly conserved in the bacillales order and is deleterious when over-expressed. We show that RsaE interacts in vitro with the 5′ region of opp3A mRNA, encoding an ABC transporter component, to prevent formation of the ribosomal initiation complex. A previous report showed that RsaE targets opp3B which is co-transcribed with opp3A. Thus, our results identify an unusual case of riboregulation where the same sRNA controls an operon mRNA by targeting two of its cistrons. A combination of biocomputational and transcriptional analyses revealed a remarkably coordinated RsaE-dependent downregulation of numerous metabolic enzymes involved in the citrate cycle and the folate-dependent one-carbon metabolism. As we observed that RsaE accumulates transiently in late exponential growth, we propose that RsaE functions to ensure a coordinate downregulation of the central metabolism when carbon sources become scarce

Global Analysis of Extracytoplasmic Stress Signaling in Escherichia coli

The Bae, Cpx, Psp, Rcs, and σE pathways constitute the Escherichia coli signaling systems that detect and respond to alterations of the bacterial envelope. Contributions of these systems to stress response have previously been examined individually; however, the possible interconnections between these pathways are unknown. Here we investigate the dynamics between the five stress response pathways by determining the specificities of each system with respect to signal-inducing conditions, and monitoring global transcriptional changes in response to transient overexpression of each of the effectors. Our studies show that different extracytoplasmic stress conditions elicit a combined response of these pathways. Involvement of the five pathways in the various tested stress conditions is explained by our unexpected finding that transcriptional responses induced by the individual systems show little overlap. The extracytoplasmic stress signaling pathways in E. coli thus regulate mainly complementary functions whose discrete contributions are integrated to mount the full adaptive response

Evaluation of laboratory tests for cirrhosis and for alcohol use, in the context of alcoholic cirrhosis

International audienceLaboratory tests can play an important role in assessment of alcoholic patients, including for evaluation of liver damage and as markers of alcohol intake. Evidence on test performance should lead to better selection of appropriate tests and improved interpretation of results. We compared laboratory test results from 1578 patients between cases (with alcoholic cirrhosis; 753 men, 243 women) and controls (with equivalent lifetime alcohol intake but no liver disease; 439 men, 143 women). Comparisons were also made between 631 cases who had reportedly been abstinent from alcohol for over 60 days and 364 who had not. ROC curve analysis was used to estimate and compare tests' ability to distinguish patients with and without cirrhosis, and abstinent and drinking cases. The best tests for presence of cirrhosis were INR and bilirubin, with areas under the ROC curve (AUCs) of 0.91~\textpm~0.01 and 0.88~\textpm~0.01, respectively. Confining analysis to patients with no current or previous ascites gave AUCs of 0.88~\textpm~0.01 for INR and 0.85~\textpm~0.01 for bilirubin. GGT and AST showed discrimination between abstinence and recent drinking in patients with cirrhosis, including those without ascites, when appropriate (and for GGT, sex-specific) limits were used. For AST, a cut-off limit of 85~units/L gave 90% specificity and 37% sensitivity. For GGT, cut-off limits of 288~units/L in men and 138~units/L in women gave 90% specificity for both and 40% sensitivity in men, 63% sensitivity in women. INR and bilirubin show the best separation between patients with alcoholic cirrhosis (with or without ascites) and control patients with similar lifetime alcohol exposure. Although AST and GGT are substantially increased by liver disease, they can give useful information on recent alcohol intake in patients with alcoholic cirrhosis when appropriate cut-off limits are used

Genome-wide Association Study and Meta-analysis on Alcohol-Associated Liver Cirrhosis Identifies Genetic Risk Factors

International audienceBackground and aims - Only a minority of heavy drinkers progress to alcohol-associated cirrhosis (ALC). The aim of this study was to identify common genetic variants that underlie risk for ALC. Approach and results - We analyzed data from 1,128 subjects of European ancestry with ALC and 614 heavy-drinking subjects without known liver disease from Australia, the United States, the United Kingdom, and three countries in Europe. A genome-wide association study (GWAS) was performed, adjusting for principal components and clinical covariates (alcohol use, age, sex, body mass index, and diabetes). We validated our GWAS findings using UK Biobank. We then performed a meta-analysis combining data from our study, the UK Biobank, and a previously published GWAS. Our GWAS found genome-wide significant risk association of rs738409 in patatin-like phospholipase domain containing 3 (PNPLA3) (odds ratio [OR] = 2.19 [G allele], P = 4.93 × 10 ) and rs4607179 near HSD17B13 (OR = 0.57 [C allele], P = 1.09 × 10 ) with ALC. Conditional analysis accounting for the PNPLA3 and HSD17B13 loci identified a protective association at rs374702773 in Fas-associated factor family member 2 (FAF2) (OR = 0.61 [del(T) allele], P = 2.56 × 10 ) for ALC. This association was replicated in the UK Biobank using conditional analysis (OR = 0.79, P = 0.001). Meta-analysis (without conditioning) confirmed genome-wide significance for the identified FAF2 locus as well as PNPLA3 and HSD17B13. Two other previously known loci (SERPINA1 and SUGP1/TM6SF2) were also genome-wide significant in the meta-analysis. GeneOntology pathway analysis identified lipid droplets as the target for several identified genes. In conclusion, our GWAS identified a locus at FAF2 associated with reduced risk of ALC among heavy drinkers. Like the PNPLA3 and HSD17B13 gene products, the FAF2 product has been localized to fat droplets in hepatocytes. Conclusions - Our genetic findings implicate lipid droplets in the biological pathway(s) underlying ALC

The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article

Approches de théorie quantique des champs pour le transport quantique dans les nanostructures

Dans une jonction Josephson entre deux supraconducteurs séparés par deux points quantiques (dots), les paires de Cooper, qui sont les entités élémentaires du courant Josephson DC, peuvent être éventuellement scindées (processus CAR). Lorsqu'un champ magnétique est appliqué entre ces deux dots, la dépendance du courant critique renseigne sur ce processus de transport non local par une mesure à l'équilibre. Une efficacité de séparation des paires de Cooper a été définie et permet d'indiquer quels jeux de paramètres pourraient permettre à l'expérimentateur d'optimiser cette délocalisation spatiale d'électrons. Dans une jonction Josephson entre deux supraconducteurs polarisée, un courant alternatif apparaît avec une fréquence Josephson proportionnelle à la tension appliquée. Dans une jonction entre trois supraconducteurs, plusieurs fréquences Josephson cohabitent. Néanmoins, lorque la borne centrale est mise à la terre et les deux bornes latérales sont polarisées avec des tensions commensurables, un courant Josephson DC apparaît traduisant le transport effectif de paires de Cooper. Des résultats numériques pour la résonance quartet (intrication de deux paires de Cooper scindées par double CAR) sont présentés. Un calcul unifié basé sur les fonctions d'onde solutions de l'équation de Bogoliubov - de Gennes a permis de calculer courant et bruit dans une jonction entre deux supraconducteurs qu'ils soient conventionnels ou topologiques. Dans une jonction entre deux supraconducteurs topologiques, des quasiparticules d'énergie nulle aux propriétés de Majorana peuvent exister et le calcul entrepris permet de dégager de nouvelles signatures pour la présence de ces excitations.In a Josephson junction between two superconductors with two quantum dots in between, Cooper pairs which are the elementary charge carriers of the Josephson DC current can eventually be split (CAR process). If a magnetic flux threads the area enclosed by dots and superconductors, the critical current as a function of the Aharonov-Bohm phase can give information about this nonlocal process through an equilibrium measurement. A splitting efficiency has been defined so that experimental parameters optimizing Cooper pair splitting can be indicated to the experimentalist. In a Josephson junction between two superconductors, if a voltage is applied, an alternative current occurs with a Josephson frequency proportional to the voltage drop. In an all-superconducting three-terminal junction, several voltage drops and consequently different Josephson frequencies coexist. However, if the central electrode is grounded while the lateral gates are biased with commensurate voltages, then a DC Josephson current is recovered which translates the effective transport of Cooper pairs. Numerical results for the quartet resonance (production of two entangled Cooper pairs split by double CAR) are provided. Josephson current and thermal noise have been computed for a junction between conventional superconductors and a junction between topological superconductors (hosting zero-energy quasiparticules with Majorana properties) within a unified framework based on the Bogoliubov - de Gennes scattering approach. Such a calculation participates in the recent search of convincing signatures for the presence of Majorana modes

Effets Josephson et séparation de paires de Cooper dans des dispositifs hybrides modernes

Superconductors are natural sources for entangled states because of the intrinsic pairing of electrons in so-called Cooper pairs. Electronic transport in nanoscale devices containing such materials can give valuable information concerning this entanglement. Quantum information schemes in condensed matter settings benefit from the novel physics carried out by emergent collective excitations, e.g. the fault-tolerant topological quantum computer proposal which follows the discovery for the potential emergence of quasiparticles with Majorana properties in topological superconductors. While more and more convincing signatures compatible with the presence of Majorana zero-energy modes have been accumulated, transport properties in systems supporting such excitations can bring supplementary evidences. In a Josephson junction between two superconductors with two quantum dots in between, Cooper pairs which are the elementary charge carriers of the Josephson current driven by a difference in the superconducting phase can eventually be split (through the crossed Andreev reflection CAR process) and the constituent electrons can be spatially separated and pass through different dots. If a magnetic flux threads the area enclosed by dots and superconductors, the critical current (maximum of the Josephson current as a function of the superconducting phase) as a function of the Aharonov-Bohm phase can give information about this nonlocal process. This setup allows an equilibrium measurement for Cooper pair splitting unlike the early proposals relying on superconductor-normal junctions arranged in a fork geometry where the splitting of a Cooper pair originated from the injecting superconducting lead is probed by measuring cross correlations between the currents in the outgoing normal branches which flow in response to voltage drops. Based upon a path integral formulation of the partition function of the system, the calculation is performed in a non-perturbative way which is motivated by the experimental achievements of large couplings between superconductors and dots. A splitting efficiency has been defined so that experimental parameters (dot energies and Coulomb on-site interactions) optimizing Cooper pair splitting can be indicated to the experimentalist. In a Josephson junction between two superconductors, if a voltage is applied, an alternative current occurs with a Josephson frequency proportional to the voltage drop. In an all-superconducting three-terminal junction, several voltage drops and consequently different Josephson frequencies coexist. However, if the central electrode is grounded while the lateral gates are biased with commensurate voltages, then a DC Josephson current is recovered which translates the effective transport of Cooper pairs. The simplest case corresponds to opposite voltages and the production of two entangled Cooper pairs split by double CAR, the so-called quartet state. A path integral approach within the Keldysh formalism is adopted to compute non-perturbatively out-of-equilibrium current and noise and a frequency expansion relying on the voltage commensurability is conveniently used. Numerical results for the quartet resonance are provided. Josephson current and thermal noise have been computed for a junction between conventional superconductors and a junction between topological superconductors (hosting zero-energy quasiparticules with Majorana properties) within a unified framework based on the Bogoliubov - de Gennes scattering approach, the nature of the superconductors in contact being encoded in the matching condition. Such a calculation participates in the recent search of convincing signatures for the presence of Majorana modes.Les supraconducteurs sont des sources naturelles d'états intriqués de par la possibilité d'y apparier des électrons au sein de paires de Cooper et dans les dispositifs nanoscopiques contenant de tels matériaux, le transport électronique s'avère être un outil important de caractérisation. Les excitations collectives mises en jeu dans les systèmes mésoscopiques apportent une physique riche et les problématiques d'information quantique ont trouvé dans le monde de la matière condensée un domaine d'application stimulant, comme en témoigne la proposition de calcul quantique utilisant des qubits de Majorana protégés de la décohérence et qui peuvent être synthétisés dans les supraconducteurs topologiques. Alors que de plus en plus d'observations compatibles avec la présence de modes de Majorana s'accumulent, l'étude des propriétés de transport dans des systèmes abritant de telles excitations peut apporter des signatures complémentaires.Dans une jonction Josephson entre deux supraconducteurs séparés par deux points quantiques (dots), les paires de Cooper, qui sont les entités élémentaires du courant Josephson provoqué par une différence de phase supraconductrice, peuvent être éventuellement scindées (processus de réflection d'Andreev croisée CAR) et les électrons constituants peuvent être séparés spatialement pour transiter sur les deux dots. Lorsqu'un champ magnétique est appliqué entre ces deux dots, la dépendance du courant critique (maximum du courant Josephson en fonction de la phase supraconductrice) en fonction de la phase Aharonov-Bohm renseigne sur ce processus de transport non local. Ce dispositif permet une mesure à l'équilibre et constitue une alternative aux propositions hors-équilibre de jonctions en fourche avec un supraconducteur injecteur et des bornes métalliques collectrices, polarisées en tension. Le calcul basé sur une formulation en termes d'intégrale de chemin de la fonction de partition du système est non-perturbatif en le couplage entre supraconducteurs et dots, une telle approche s'avérant incontournable à la vue des avancées expérimentales. Une efficacité de séparation des paires de Cooper a été définie et permet d'indiquer quels jeux de paramètres (énergies et répulsions coulombiennes des dots) pourraient permettre à l'expérimentateur d'optimiser cette délocalisation spatiale d'électrons. Dans une jonction Josephson entre deux supraconducteurs polarisée, un courant alternatif apparaît avec une fréquence Josephson proportionnelle à la tension appliquée. Dans une jonction entre trois supraconducteurs, plusieurs différences de tension et donc plusieurs fréquences Josephson cohabitent. Néanmoins, lorque la borne centrale est mise à la terre et les deux bornes latérales sont polarisées avec des tensions commensurables, un courant Josephson DC apparaît traduisant le transport effectif de paires de Cooper. Le cas le plus simple correspond à des tensions opposées et au processus d'intrication de deux paires de Cooper scindées par double CAR, connu sous le nom de quartet. Une technique d'intégrale de chemin dans le formalisme de Keldysh a été adoptée pour calculer courant et bruit hors équilibre de manière non-perturbative et une représentation fréquentielle est permise par la commensurabilité des voltages. Des résultats numériques pour la résonance quartet sont présentés. Un calcul unifié basé sur les fonctions d'onde solutions de l'équation de Bogoliubov - de Gennes a permis de calculer courant et bruit dans une jonction entre deux supraconducteurs qu'ils soient conventionnels ou topologiques (la différence étant faite par l'équation de raccordement à la position du contact). Dans une jonction entre deux supraconducteurs topologiques, des quasiparticules d'énergie nulle aux propriétés de Majorana peuvent exister au niveau du contact et l'étude des statistiques du courant permet de dégager de nouvelles signatures pour la présence de ces excitations

Cyclodextrines hydrophiles : caractérisation et étude de leurs propriétés énantiosélective et complexante. Utilisation de la chromatographie en phase liquide et de la spectrométrie de masse.

Thank to their complexing and enantioselective properties, cyclodextrins (CDs) are widely used in pharmaceutical, cosmetic and food industries as well as in analytical chemistry. The present works concern different fields of CDs study : their characterisation, their use as chiral selectors and the analysis of their complexes.In the first part, a new methylated CD, slightly substituted, has been characterised by different analytical techniques, allowing the acquisition of complementary information leading to a better knowledge of the commercial mixture composition. In addition, the separation by liquid chromatography (LC) of the three isomers of the monosubstituted sulfobutylether-beta-CD was optimised on porous graphitic carbon (PGC) by increasing the column temperature.The second part concerned the evaluation of the chromatographic system PGC / methylated CDs for chiral separation in LC. In addition to its high physical and chemical resistance, the PGC appeared more selective than the grafted silica columns usually used for this type of separation and required smaller quantities of CDs in the mobile phase.At last, in the third part, complexes of different methylated CDs with test solutes were studied by liquid-liquid partition experiments and by electrospray ionisation mass spectrometry (ESI-MS). The comparison of the results obtained by these two methods showed that signals acquired in ESI-SM do not reflect the solution equilibria.De par leurs propriétés complexante et énantiosélective, les cyclodextrines (CDs) sont largement utilisées dans les industries pharmaceutique, cosmétique, agroalimentaire, etc. ainsi qu'en chimie analytique. Les travaux présentés dans ce manuscrit concernent différents domaines d'étude des CDs : leur caractérisation, leur utilisation en tant que sélecteurs chiraux et l'analyse de leurs complexes.Dans la première partie, une nouvelle CD méthylée faiblement substituée a été caractérisée par différentes techniques analytiques, permettant ainsi l'obtention d'informations complémentaires menant à une meilleure connaissance de la composition du mélange commercial. D'autre part, la séparation par chromatographie en phase liquide (CPL) des trois isomères de la sulfobutyléther-beta-CD monosubstituée a été optimisée sur carbone graphite poreux (PGC) en augmentant la température de la colonne.La deuxième partie a porté sur l'évaluation du système chromatographique PGC / CDs méthylées pour la séparation chirale en CPL. Outre sa grande résistance physique et chimique, le PGC s'est révélé plus sélectif que les colonnes de silice greffée habituellement employées pour ce type de séparation et a nécessité une quantité moindre de CDs dans la phase mobile.Enfin, dans la troisième partie, les complexes de différentes CDs méthylées avec des solutés test ont été étudiés par des expériences de partage liquide-liquide et par spectrométrie de masse à ionisation électrospray. La comparaison des résultats obtenus par ces deux méthodes a révélé que les signaux enregistrés en ESI-SM ne reflètent pas les équilibres existant en solution

Coopération des réseaux et garanties de qualité de service de bout-en-bout dans l'Internet

In the Internet, value-added services such as HD video, online gaming or cloud computing represent an ever-increasing share of the total traffic. Hence, it is essential to adapt the Internet to offer end-to-end (e2e) quality of service (QoS) for these services. However, a mechanism designed to offer quality of service at the inter-domain level must respect the three inter-domain communications properties: confidentiality and autonomy of the domains and the scalability. These properties made the problem of provisioning e2e QoS particularly difficult. In this thesis, we focus on the technical part of an e2e QoS mechanism by proposing an algorithm named SANP that computes e2e paths satisfying a set of QoS constraints. The idea of SANP is to construct a sub-graph between the destination and the source in which the latest can choose a path that satisfies its request. In a second part of the thesis we assume that the domains are ready to group together to form alliances. An alliance is defined as a group of domains that are ready to share business and/or technical policies. Thus, we propose a second algorithm named ACQA that computes e2e paths in a graph composed of alliances and independent domains. By simulations, we want to assess the quality and the quantity of the paths found by both SANP and ACQA.L'essor de nouvelles applications multimédia sur Internet tels que les vidéos à la demande ou la télévision a profondément changé le paysage économique et stratégique des acteurs de l'Internet. Ainsi, la nécessité d'avoir un réseau qui offre une qualité de service adaptée est devenue incontournable. Un mécanisme destiné à offrir de la qualité de service au niveau de l'inter-domaine doit respecter les propriétés de communications de l'inter-domaine qui sont la confidentialité et l'autonomie des domaines et la scalabilité. Ces propriétés rendent le problème de la qualité de service au niveau inter-domaine particulièrement difficile. La thèse se concentre essentiellement sur la partie technique d'un mécanisme offrant de la qualité de service au niveau inter-domaine notamment en proposant un algorithme nommé SANP calculant des chemins de bout-en-bout satisfaisant un ensemble de contraintes. Pour cela SANP fait l'hypothèse que chaque domaine annonce des offres de qualité de service entre ses points d'entrées et de sortie. L'idée de SANP est de construire un sous graphe entre la source et la destination dans lequel la source pourra choisir un chemin. Une deuxième algorithme nommé ACQA est proposé qui calcule des chemins de bout-en-bout satisfaisant un ensemble de contraintes dans un graphe de domaines et d'alliances. Une alliance est un groupe de domaines qui se sont regroupés pour différents intérêts. Nos simulations ont pour but de montrer la qualité et la quantité de chemins trouvés par SANP et ACQA