Friedel oscillations in a Luttinger liquid with long-range interactions

We introduce a path-integral approach that allows to compute charge density oscillations in a Luttinger liquid with impurities. We obtain an explicit expression for the envelope of Friedel oscillations in the presence of arbitrary electron-electron potentials. As examples, in order to illustrate the procedure, we show how to use our formula for contact and Coulomb potentials.Comment: 11 pages, no figures, latex. Revised version to appear in PR

Structure-fonction des lipoglycanes et remodelage de l'enveloppe de mycobacterium tuberculosis dans les macrophages

La tuberculose est, encore aujourd'hui, responsable de 2 millions de morts et 9 millions de nouveaux cas chaque année et reste un problème sanitaire majeur notamment à cause de la recrudescence des cas de tuberculoses multi-résistantes aux antibiotiques. Il est donc nécessaire de développer de nouveaux antibiotiques ciblant les voies métaboliques de M. tuberculosis actives chez l'hôte infecté. Les données de la littérature montrent que dans le contexte intracellulaire, M. tuberculosis s'adapte à l'environnement phagosomal acide et hypoxique. Cette adaptation conduit, notamment, à des modifications de l'ultrastructure de l'enveloppe et de la structure de certains glycolipides. Dans ce contexte, nous avons cherché à déterminer quel impact pouvait avoir l'environnement intracellulaire sur la structure des lipoglycanes (LM, LAM), impliqués dans les interactions avec le système immunitaire inné, et de l'arabinogalactane (AG), jouant un rôle majeur dans la structure de l'enveloppe de l'enveloppe de M. tuberculosis (Chapitre IV). Pour cela, nous avons développé un protocole permettant de récupérer les mycobactéries intra-macrophagiques et d'éliminer un maximum de débris de macrophages. La mise au point du marquage 13C de M. tuberculosis intracellulaire et l'analyse de bactéries entières par RMN HR-MAS a permis d'étudier les structures du LAM et de l'AG et de caractériser une altération des signaux de résidus constitutifs des motifs Ara4 et Ara6 dans le contexte intramacrophagique. L'altération peut être due à des modifications de la structure et/ou de la dynamique des molécules au sein de l'enveloppe. Les analyses structurales des lipoglycanes purifiés indiquent une altération de leur structure. Ces modifications structurales pourraient avoir un impact sur l'organisation de l'enveloppe de M. tuberculosis et son interaction avec le système immunitaire inné. En parallèle de ces travaux, nous nous sommes intéressés à la contribution des lipoglycanes, dans le contexte physiologique d'une infection, à la détection des mycobactéries par le système immunitaire inné (Chapitre II). Jusqu'à présent, les études d'interaction lipoglycanes/TLR2 avaient été réalisées avec des composés purifiés. La construction et l'utilisation de mutants de l'organisme modèle Mycobacterium smegmatis présentant une altération de la production de lipoglycanes nous a permis de montrer que, comme les lipoprotéines, les lipoglycanes de l'enveloppe sont de véritables ligands physiologiques de TLR2 et participent à la détection des mycobactéries par le système immunitaire inné. Nous avons également étudié la relation structure/fonction de lipoglycanes dans leur détection par TLR2 et le rôle de l'ancre lipidique dans cette interaction (Chapitre III). Nous avons analysé la capacité de lipoglycanes produits par les Actinobactéries Micrococcus luteus Stomatococcus mucilaginosus et Corynebacterium glutamicum, dont l'ancre lipidique est basée sur un diacylglycérol glycocylé plutôt que sur un mannosyl-phosphatidyl-inositol comme chez les lipoglycanes mycobactériens, à être reconnus par TLR2. Nous avons montré que ces lipoglycanes activent TLR2 et induisent la production de cytokines et l'expression de marqueurs de surface par les macrophages. Ces travaux étendent le répertoire des ligands de TLR2 aux lipoglycanes à ancre lipidique à diacylglycérol glycosylé et confirment que les composés bactériens à ancre lipidique peuvent induire une réponse immunitaire dépendante de TLR2.Structure/function relationship of lipoglycans and remodeling of M. tuberculosis cell envelope in macrophages Abstract: Tuberculosis is still responsible for 2 million deaths and 9 million new cases each year and remains a major health problem, particularly due to the increase in multi-drug resistant TB cases. It is therefore necessary to develop new antibiotics targeting M. tuberculosis metabolic pathways active in the infected host. The literature data show that in the intracellular context, M. tuberculosis adapts to the acid and hypoxic phagosomal environment. This adaptation leads, particularly, to changes in the ultrastructure of the envelope and in the structure of some glycolipids. In this context, we sought to determine what could be the impact of the intracellular environment on the structure of lipoglycans (LM, LAM), involved in the interaction of with the innate immune system, and arabinogalactan (AG), playing a major in the M. tuberculosis envelope structure (Chapter IV). In this way, we developed a protocol to recover intramacrophage mycobacteria and remove the maximum of macrophages debris. The development of the 13C labeling of intracellular M. tuberculosis and whole bacteria analysis by HR-MAS NMR allowed us to study the LAM and AG structures and to characterize altered signals constitutive of Ara4 and Ara6 patterns in mycobacteria in cellulo. This alteration may be due to changes in the structure or different dynamics of the molecules in the envelope. Structural analyzes of purified lipoglycans show an alteration of their structure. These structural changes could have an impact on the organization of the envelope of M. tuberculosis and on its interaction with the innate immune system. Concurrently to this work, we were interested in the contribution of lipoglycans, in the physiological context of the infection, to the detection of mycobacteria by the innate immune system (Chapter II). Until now, lipoglycans/TLR2 studies were performed with purified compounds. The construction and use of mutants of the model organism Mycobacterium smegmatis with an altered lipoglycans production allowed us to show that, as lipoproteins, lipoglycans from the envelope are bona fide TLR2 ligands and participate in the detection of mycobacteria by the innate immune system. We also studied the structure/function relationship of lipoglycans in the detection by TLR2 and the lipid anchor role in this interaction. We analyzed the ability of Actinobacteria lipoglycans produced by Micrococcus luteus, Stomatococcus mucilaginosus and Corynbacterium glutamicum, whose lipid anchor is based on a glycosylated diacylglycerol rather than a mannosyl-phosphatidylinositol as in mycobacterial lipoglycans, to be recognized by TLR2 and to induce an immune response. We showed that these lipoglycans activate TLR2 and induce the production of cytokines and expression of surface markers by macrophages. This work extends the repertoire of TLR2 ligands to lipoglycans based on glycosylated diacylglycerol lipid anchor and confirm that bacterial compounds with a lipid anchor can induce TLR2-dependent immune response

Higgs self coupling measurement in e+e- collisions at center-of-mass energy of 500 GeV

Feasibility of the measurement of the trilinear self-couplings of the Higgs boson is studied. Such a measurement would experimentally determine the structure of the Higgs potential. Full hadronic and semi-leptonic final states of the double-Higgs strahlung have been investigated.Comment: 10 pages, 5 tables, 8 figure

Optimal Highway Maintenance Policies Under Uncertainty

International audienceWe develop an inspection and maintenance policy to minimize the cost of maintaining a given section of road or highway when there is a great deal of uncertainty in the degradation process. We propose to model the degradation of a section of road based on the proliferation and growth of cracks. We utilize a combination of a Poisson and gamma process to account for the tremendous amount of uncertainty and difficulty in predicting the proliferation of cracks. Our policy defines the optimal inspection interval as well as the minimum threshold at which to perform crack repairs. Furthermore, our policy contains a safety constraint to prevent the probability of a "catastrophic" failure from exceeding a pre-determined reliability value. Numerical calculations have shown that our model will extend the lifecycle of the road by performing preventive, conditioned-based maintenance to slow down the growth of cracks. Classical preventive maintenance policies usually shorten the lifecycle by forcing earlier renewals

What are the effects of the reliability model uncertainties in the maintenance decisions?

Most of the works proposed for the design of reliability test plans  are  devoted  to  the  guaranty  of  the  reliability performance  of  a  product  but  scarce  of  them  tackles maintenance  issues.  On  the  other  hand,  classical maintenance  optimization  criteria  rarely  take  into  account the variability of the failure parameters due to lack of data, especially when the data collection in the operating phase is expensive.  The  objective  of  this  paper  is  to  highlight through a numerical experiment the impact of the test plan design  defined  here  by  the  number  of  the  products  to  be tested and the test duration on the performance of a classical condition-based maintenance (CBM) policy

Optimal Resurfacing Decisions for Road Maintenance : A POMDP Perspective

International audienceWe develop an optimal maintenance policy for a road section to minimize the total maintenance cost over the infinite horizon when some deterioration and decision parameters are not observable. Both perfect and imperfect maintenance actions are possible through the application of various thicknesses of resurfacing layers. We use a two-phase deterioration process based on two parameters: the longitudinal cracking percentage and the deterioration growth rate. Our deterioration model is a state-based model based on the state-dependent Gamma process for the longitudinal cracking percentage and the Bilateral Gamma process for the deterioration growth rate. Moreover the maintenance decision is constrained by a maximum road thickness that makes the maintenance decisions more complex as it becomes how much surface layer to add as well as to remove. Because only one of the two deterioration parameters is observable, we formulate the problem as a partially observed Markov decision process and solve it using a grid-based value iteration algorithm. Numerical examples have shown that our model provides a preventive maintenance policy that slows down the initiation as well as the propagation of longitudinal cracks and that may ameliorate the road state to a better than as-good-as-new one by altering its composition through additive resurfacing layers

Optimisation de la politique de maintenance pour un système à dégradation graduelle stressé

International audienceThis paper investigates a maintenance policy allowing the maintenance cost optimization per unit of time combining statistical process control (SPC) and condition-based maintenance (CBM) policy. We consider a single-unit system with two failure modes which can be partially explained by several covariates. Failure modes are a continuous-state deterioration and a stress. A CBM policy is used for inspecting and replacing the system in order to balance the impacts of an excessive deterioration level whereas a control a classical control chart is used to monitor the stress covariate. Sensitivity analysis based on numerical results is proposed

Acquisition of new technology information for maintenance and replacement policies

In this paper, we propose the first model that considers the option to acquire information on the profitability of a new technology that is not yet available on the market for asset maintenance and replacement decisions. We consider the uncertainty of future asset characteristics by incorporating information acquisition decisions into a non-stationary Markov decision process framework. Using this framework, we optimise asset maintenance and replacement decisions as well as the optimal timing of new technology adoption. Through mathematical analyses, the monotone properties and convexity of the value function and optimal policy are deduced. Deeper numerical analyses highlight the importance of considering the acquisition of information on future technology when formulating a maintenance and replacement policy for the asset. We also deduce a non-intuitive result: an increase in the arrival probability of new technology does not necessarily make the acquisition of additional information more attractive

Optimizing Road Milling and Resurfacing Actions

International audienceA condition-based maintenance optimization approach is developed for the road-cracking problem in order to derive optimal maintenance policies that minimize a total discounted maintenance cost. The approach is based on a Markov decision process that takes into ac- count multiple actions with varying effects on future road performance. Maintaining the road consists of adding a new asphalt layer; however, as resurfacing actions are constrained by a maximum total road thickness, the maintenance decision is not only how thick a layer to apply, but also how much old road to remove. Each combination of these actions leads to different maintenance costs and different future degradation behaviours. The road state is modelled by a dependent bivariate deterioration variable (the longitudinal cracking percentage and the deterioration growth rate), for taking these different changes in the cracking patterns into account. Moreover, the sensitivity to cracking for existing roads can be reduced with the addition of new layers, and thus actions that can lead to states better than good-as-new have to be considered. A numerical analysis is provided to illustrate the benefits of the introduction of the deterioration speed in the decision framework, as well as the belief that initially building a road to its maximum thickness is not optimal. The trade-offs in the design decisions and the exploitation/maintenance costs are also explored

Optimisation de la politique de maintenance pour un système à dégradation graduelle stressé

International audienceThis paper investigates a maintenance policy allowing the maintenance cost optimization per unit of time combining statistical process control (SPC) and condition-based maintenance (CBM) policy. We consider a single-unit system with two failure modes which can be partially explained by several covariates. Failure modes are a continuous-state deterioration and a stress. A CBM policy is used for inspecting and replacing the system in order to balance the impacts of an excessive deterioration level whereas a control a classical control chart is used to monitor the stress covariate. Sensitivity analysis based on numerical results is proposed