Conception, modélisation et dimensionnement d'un système de levé de soupape à trois positions discrètes pour un moteur essence automobile

Abstract : As the constraint on vehicle consumption tightens, variable valve lift strategies are used to increase engines efficiency. This thesis focuses on issues related to the design of a three-stage electromagnetic valve tappet. First of all, the tappet has to fit inside the engine and has to offer three different valve lifts: a full lift for high speed and torque requirements, a low lift for small loads and a lift allowing cylinder deactivation for medium loads. The tappet dimensioning includes, for example, cams feasibility, spring parameters and contact pressure between cams and tappets. Valve lift selection is made by two electromagnetic actuators in order to obtain a short transition time. Their size, however, hinders their integration. Hence, we realize an optimization aiming to reduce its volume and define the command profile and its return springs. This optimization requires a multi-physics model (electric, magnetic and dynamic) to simulate the actuator behavior. Due to the parameter number and the computational time needed per iteration, the optimization is expensive. Hence we suggest two metamodels algorithms to be used in the optimization. The first algorithm, off-line, is able to create iteratively a predictor precise in the entire domain studied with a lesser cost than Latin Hypercube Sample. The second, in-line, refines the predictor inside the optimization loops and uses it when the predicted error is small.La réduction de la consommation des véhicules est un enjeu majeur pour les constructeurs. Parmi les stratégies employées, l’utilisation de lois de levée de soupape variables est en voie de démocratisation.Le premier objectif de cette thèse est de présenter la recherche et le pré dimensionnement d’un mécanisme offrant à la soupape trois levées distinctes : une pour la pleine charge, une pour les faibles charges et une permettant de désactiver un ou plusieurs cylindres pour les charges intermédiaires. Le pré dimensionnement comprend notamment les conditions d’usinabilité des cames, le calcul des ressorts de distribution et la contrainte de pression de contact entre les cames et les poussoirs.Le mode de fonctionnement de ce mécanisme est piloté par la position de deux actionneurs électromagnétiques choisis pour leur temps de réponse faible. Le deuxième objectif de la thèse est de proposer une optimisation afin de réduire leurs dimensions et faciliter leur intégration. Cette optimisation nécessite une modélisation multi-physique (magnétique, électrique, mécanique) du comportement de l’actionneur et permet de définir le profil de commande et les ressorts.Compte tenu du nombre de paramètres d’entrée et du temps de calcul d’une itération, l’optimisation présente un coût de calcul important. Nous présentons donc deux algorithmes de création de modèles de substitution par krigeage. Le premier permet d’approximer une fonction fine dans tout le domaine d’étude à un coût limité. Le second est inclus dans une boucle d’optimisation et n’utilise le modèle fin que lorsque l’approximation n’est pas suffisamment fiable. Ils permettent tout deux de réduire le coût d’optimisation

Alteromonas fortis sp. nov., a non-flagellated bacterium specialized in the degradation of iota-carrageenan, and emended description of the genus Alteromonas

International audienceStrain 1T, isolated in the seventies from the thallus of the carrageenophytic red algae Eucheumaspinosum collected in Hawaii, USA, was retrospectively characterized using phenotypic,phylogenetic and genomic methods. Bacterial cells were Gram-stain-negative, strictly aerobic,non-flagellated, coccoid, ovoid or rod-shaped, and grew at 10-42 °C (optimum 20-25 °C), atpH 5.5-10 (optimum pH 6-9) and with 2-12 % NaCl (optimum 2-4 %). Strain 1T grew on theseaweed polysaccharides i-carrageenan, laminarin and alginic acid as sole carbon sources. Themajor fatty acids (>10 %) were C16:0, C18:1 ω7c and summed feature 3 (C16:1w7c and/or iso-C15:02OH) and significant amounts of C16:0 N alcohol (6.7 %) and 10 methyl C17:0 (8.6 %) were alsopresent. The only respiratory quinone was Q-8, and major polar lipids werephosphatidylethanolamine, phosphatidylglycerol and an unknown aminolipid. Phylogeneticanalyses based on 16S rRNA gene sequence comparisons showed that the bacterium is affiliatedto the genus Alteromonas (family Alteromonadaceae, class Gammaproteobacteria). Strain 1Texhibits 16S rRNA gene sequence similarity values of 98.8-99.2 % to the type strains ofAlteromonas mediterranea and Alteromonas australica respectively, and of 95.7-98.6 % tothose of the other species of the genus Alteromonas. The DNA G+C content of strain 1T is 43.9mol%. Based on the genome sequence of strain 1T, DNA-DNA hybridization predictions by theaverage nucleotide identity (ANI) and Genome-to-Genome Distance Calculations (GGDC)between strain 1T and other members of the genus Alteromonas showed values of 70-80 %, andbelow 26 %, respectively. The phenotypic, phylogenetic and genomic analyses show that strain 1T is distinct from species of the genus Alteromonas with validly published names and that itrepresents a novel species of the genus Alteromonas, for which the name Alteromonas fortis sp.nov. is proposed. The type strain is 1T (= ATCC 43554T = CIP XXXX)

Diversité génomique des espèces bactériennes du genre Flavobacterium

Les bactéries du genre Flavobacterium sont retrouvées dans des types d habitats très divers. Ce genre contient trois espèces ichtyopathogènes: columnare, branchiophilum et psychrophilum qui est responsable de pertes économiques importantes pour l élevage des salmonidés. Un projet de séquençage et de comparaison des génomes de plusieurs flavobactéries pathogènes de poissons ainsi qu isolées de différents environnements a été mis en place pour améliorer les connaissances sur ce genre. Les objectifs étaient l identification des déterminants de virulence et la caractérisation de différents marqueurs moléculaires des traits phénotypiques associés à leur mode de vie. L analyse des génomes de F. psychrophilum a permis de mettre en évidence une diversité des structures chromosomiques au sein de l espèce et d identifier des cibles moléculaires prometteuses pour le développement de tests de diagnostic ainsi que des cibles vaccinales potentielles. Le génome de F. branchiophilum a permis d identifier des mécanismes moléculaires de virulence originaux. Les caractéristiques du génome de F. indicum révèlent un mode de vie environnemental: sa petite taille et ses faibles capacités de dégradation des bio-polymères suggèrent que F. indicum est adapté à une niche écologique restreinte. Ces nouvelles données ont permis de caractériser in silico des marqueurs moléculaires de caractères phénotypiques. En particulier, un groupe de gènes (dnd) rare et responsable d une modification étonnante de la molécule d ADN a été décrit pour la première fois chez les Flavobacteriaceae. Ce projet a permis d enrichir les connaissances sur les bactéries du genre Flavobacterium et a contribué au développement d outils pour la santé animale.Flavobacterium species occur in a wide range of habitats. This genus includes three fish-pathogenic species, namely F. columnare, F. branchiophilum and F. psychrophilum. The latter is responsible for serious economic losses for salmonids farming in France and worlwide. A comparative genomics project including several fish-pathogenic flavobacteria as well as various environmental species has been set up in order to improve the knowledge on this poorly studied genus. Our aims were the identification of virulence determinants associated with pathogenicity and the characterization of various molecular elements reflecting phenotypes associated with their life-style. Analysis of the genomes of several F. psychrophilum isolates revealed the diversity of chromosomal structures within the species and identified in silico promising molecular targets for the development of diagnostic tests as well as potential vaccines targets. Analysis of the F. branchiophilum genome enabled to identify particular molecular virulence mechanisms. The features of the F. indicum genome reflected its environmental lifestyle: its small size and its limited bio-polymers degrading abilities suggested that F. indicum is adapted to a quite narrow ecological niche. These new data have allowed the in silico identification of many molecular elements reflecting phenotypic traits. In particular, a rare gene cluster (dnd) responsible for an unusual DNA structure modification was described for the first time within members of the family Flavobacteriaceae. This project enriched the knowledge on Flavobacterium species and contributed to the development of tools for animal health.EVRY-Bib. électronique (912289901) / SudocSudocFranceF

The electrical energy situation of French islands and focus on the Corsican situation

The present work aims to present the electrical energy situation of several French islands spread over the World. Various aspects are successively studied: repartition of energy means, renewable energy part in the production with a focus on the intermittent renewable sources, legal and financial aspect. The electrical situation of the islands is compared with the French mainland one. The electricity production cost in the islands are presented and the financial features for renewable energy in France are exposed. In a second part, a focus is realized on the Corsica Island situated in the Mediterranean Sea and partially connected to Italy. Successively, the energy mix, the objective of the new energy plan for 2023 and the renewable energy situation, present and future, are presented. Even if the integration of non-programmable renewable energy plants is more complex in small insular networks, the high cost of electricity generation in such territories encourages the introduction of wind and PV systems. The islands are good laboratories for the development of intermittent and stochastic renewable energy systems

Bacterial diseases of farmed fish

An overview of bacterial diseases in farmed fish is presented, including bacterial species involved, predisposing factors, routes of infection, modes of transmission, and control. INRA studies on the main bacterial pathogen of salmonid fish worldwide, Flavobacterium psychrophilum, are also presented. Once techniques of culture, identification, and molecular typing of isolates were defined, a reproducible model of experimental infection was developed using the rainbow trout. Molecular studies improved considerably the taxonomy and phylogeny of the whole Flavobacteriaceae family. The full genome of a F. psychrophilum strain has recently been sequenced. Its analysis has already identified many genes involved in the pathogen’s lifestyle, especially in its virulence towards the host.Un aperçu général des infections bactériennes chez les poissons d'élevage est d'abord présenté: espèces bactériennes en cause, facteurs favorisants, types d'infection, modes de transmission, et méthodes de lutte. Les études menées par l'INRA sur le principal pathogène bactérien des salmonidés dans le monde, Flavobacterium psychrophilum, sont ensuite passées en revue. Après les techniques de culture, d'identification et de typage moléculaire des souches, un modèle expérimental reproductible de la maladie sur la truite arc-en-ciel a été mis au point. Les études moléculaires ont considérablement affiné la taxonomie et la phylogénie de l'ensemble de la famille des Flavobacteriaceae. Le génome complet d'une souche de F. psychrophilum vient d'être séquencé. Son analyse a déjà révélé de nombreux gènes impliqués dans le mode de vie de la bactérie, en particulier dans sa virulence pour l'hôte

Evolutionary Evidence of Algal Polysaccharide Degradation Acquisition by Pseudoalteromonas carrageenovora 9T to Adapt to Macroalgal Niches

About half of seaweed biomass is composed of polysaccharides. Most of these complex polymers have a marked polyanionic character. For instance, the red algal cell wall is mainly composed of sulfated galactans, agars and carrageenans, while brown algae contain alginate and fucose-containing sulfated polysaccharides (FCSP) as cell wall polysaccharides. Some marine heterotrophic bacteria have developed abilities to grow on such macroalgal polysaccharides. This is the case of Pseudoalteromonas carrageenovora 9T (ATCC 43555T), a marine gammaproteobacterium isolated in 1955 and which was an early model organism for studying carrageenan catabolism. We present here the genomic analysis of P. carrageenovora. Its genome is composed of two chromosomes and of a large plasmid encompassing 109 protein-coding genes. P. carrageenovora possesses a diverse repertoire of carbohydrate-active enzymes (CAZymes), notably specific for the degradation of macroalgal polysaccharides (laminarin, alginate, FCSP, carrageenans). We confirm these predicted capacities by screening the growth of P. carrageenovora with a large collection of carbohydrates. Most of these CAZyme genes constitute clusters located either in the large chromosome or in the small one. Unexpectedly, all the carrageenan catabolism-related genes are found in the plasmid, suggesting that P. carrageenovora acquired its hallmark capacity for carrageenan degradation by horizontal gene transfer (HGT). Whereas P. carrageenovora is able to use lambda-carrageenan as a sole carbon source, genomic and physiological analyses demonstrate that its catabolic pathway for kappa- and iota-carrageenan is incomplete. This is due to the absence of the recently discovered 3,6-anhydro-D-galactosidase genes (GH127 and GH129 families). A genomic comparison with 52 Pseudoalteromonas strains confirms that carrageenan catabolism has been recently acquired only in a few species. Even though the loci for cellulose biosynthesis and alginate utilization are located on the chromosomes, they were also horizontally acquired. However, these HGTs occurred earlier in the evolution of the Pseudoalteromonas genus, the cellulose- and alginate-related loci being essentially present in one large, late-diverging clade (LDC). Altogether, the capacities to degrade cell wall polysaccharides from macroalgae are not ancestral in the Pseudoalteromonas genus. Such catabolism in P. carrageenovora resulted from a succession of HGTs, likely allowing an adaptation to the life on the macroalgal surface

Toxins and Secretion Systems of Photorhabdus luminescens

Photorhabdus luminescens is a nematode-symbiotic, gram negative, bioluminescent bacterium, belonging to the family of Enterobacteriaceae. Recent studies show the importance of this bacterium as an alternative source of insecticides, as well as an emerging human pathogen. Various toxins have been identified and characterized in this bacterium. These toxins are classified into four major groups: the toxin complexes (Tcs), the Photorhabdus insect related (Pir) proteins, the “makes caterpillars floppy” (Mcf) toxins and the Photorhabdus virulence cassettes (PVC); the mechanisms however of toxin secretion are not fully elucidated. Using bioinformatics analysis and comparison against the components of known secretion systems, multiple copies of components of all known secretion systems, except the ones composing a type IV secretion system, were identified throughout the entire genome of the bacterium. This indicates that Photorhabdus luminescens has all the necessary means for the secretion of virulence factors, thus it is capable of establishing a microbial infection

Transcriptional Responses of Resistant and Susceptible Fish Clones to the Bacterial Pathogen Flavobacterium psychrophilum

Flavobacterium psychrophilum is a bacterial species that represents one of the most important pathogens for aquaculture worldwide, especially for salmonids. To gain insights into the genetic basis of the natural resistance to F. psychrophilum, we selected homozygous clones of rainbow trout with contrasted susceptibility to the infection. We compared the transcriptional response to the bacteria in the pronephros of a susceptible and a resistant line by micro-array analysis five days after infection. While the basal transcriptome of healthy fish was significantly different in the resistant and susceptible lines, the transcriptome modifications induced by the bacteria involved essentially the same genes and pathways. The response to F. psychrophilum involved antimicrobial peptides, complement, and a number of enzymes and chemokines. The matrix metalloproteases mmp9 and mmp13 were among the most highly induced genes in both genetic backgrounds. Key genes of both pro- and anti-inflammatory response such as IL1 and IL10, were up-regulated with a greater magnitude in susceptible animals where the bacterial load was also much higher. While higher resistance to F. psychrophilum does not seem to be based on extensive differences in the orientation of the immune response, several genes including complement C3 showed stronger induction in the resistant fish. They may be important for the variation of susceptibility to the infection