399 research outputs found
Estimation de la recharge de la nappe phréatique du Continental Terminal (Niamey, Niger) à partir des teneurs en tritium
Dans l'environnement typiquement sahélien de la région de Niamey, la réalimentation de la nappe phréatique du Continental Terminal est essentiellement due à l'infiltration de la pluie concentrée dans les mares endoréiques temporaires. Les teneurs en tritium sont un bon indicateur de l'intensité de la recharge. Un modÚle simple utilise une chronique reconstituée des teneurs de la pluie à Niamey depuis 40 ans et fournit les taux de renouvellement correspondant aux valeurs mesurées dans la nappe (25 mm/an). Ces résultats sont cohérents avec ceux de l'approche hydrodynamique. (Résumé d'auteur
Recombinant Human Adenovirus with Rat MIP-2 Gene Insertion Causes Prolonged PMN Recruitment to the Murine Brain
Single injections of recombinant cytokines/chemokines into tissue have provided insights into their possible roles during the inflammatory response. Adenoviral technology may allow us to mimic the in vivo situation more closely, with protein generated in a continuous but transient fashion. Replication-deficient human type 5 adenovirus containing a rat macrophage inflammatory protein-2 ( MIP-2 ) gene insertion and cytomegalovirus promoter was injected into the mouse brain to investigate the inflammatory response to continuous overproduction of MIP-2. Adenovirus with a LacZ gene insertion expressing Î-galactosidase was used as a control. At doses of 10 4 to 10 7 plaque-forming units, a minimal inflammatory response was detected to the LacZ virus, with leukocyte recruitment that was restricted to the injection site. A dose of 10 7 plaque-forming units of both the LacZ and the MIP-2 vector produced extensive transgene product expression that persisted for at least 7 days. Astrocytes, recognized by their morphology, were the predominant cell type expressing MIP-2 and Î-galactosidase. A dose of 10 7 plaque-forming units of MIP-2 vector caused dramatic polymorphonuclear leukocyte (PMN) recruitment to the brain parenchyma after 2 days. PMN recruitment was still observed after 4 and 7 days, but had become more localized to the injection site and was associated with numerous foam-like macrophages. At both 2 and 7 days the blood-brain barrier was breached in the region of leukocyte recruitment. Despite the extent of leukocyte recruitment there were no overt signs of neuronal degeneration or demyelination. Our findings demonstrate that continuous production of MIP-2 in the CNS results in persistent PMN recruitment to the brain parenchyma with no evidence of tachyphylaxis. The lack of PMN recruitment to the brain parenchyma following CNS injury may be a result of deficient production of PMN chemoattractants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75633/1/j.1460-9568.1996.tb01324.x.pd
Neuroprotective and neurodegenerative effects of the chronic expression of tumor necrosis factor α in the nigrostriatal dopaminergic circuit of adult mice
Co-localization of high-affinity neurotrophin receptors in nucleus basalis of Meynert neurons and their differential reduction in Alzheimer's disease
CAR-associated vesicular transport of an adenovirus in motor neuron axons.
Axonal transport is responsible for the movement of signals and cargo between nerve termini and cell bodies. Pathogens also exploit this pathway to enter and exit the central nervous system. In this study, we characterised the binding, endocytosis and axonal transport of an adenovirus (CAV-2) that preferentially infects neurons. Using biochemical, cell biology, genetic, ultrastructural and live-cell imaging approaches, we show that interaction with the neuronal membrane correlates with coxsackievirus and adenovirus receptor (CAR) surface expression, followed by endocytosis involving clathrin. In axons, long-range CAV-2 motility was bidirectional with a bias for retrograde transport in nonacidic Rab7-positive organelles. Unexpectedly, we found that CAR was associated with CAV-2 vesicles that also transported cargo as functionally distinct as tetanus toxin, neurotrophins, and their receptors. These results suggest that a single axonal transport carrier is capable of transporting functionally distinct cargoes that target different membrane compartments in the soma. We propose that CAV-2 transport is dictated by an innate trafficking of CAR, suggesting an unsuspected function for this adhesion protein during neuronal homeostasis
Quality and value of solar probabilistic forecasting
La prĂ©vision solaire est un Ă©lĂ©ment central de la plupart des solutions dâintĂ©gration Ă large Ă©chelle de lâĂ©nergie solaire au sein des mix Ă©lectriques. Lâobjectif de ce travail est de dĂ©montrer que lâutilisation de prĂ©visions probabilistes, encore peu frĂ©quente Ă lâĂ©chelle industrielle, est pertinente pour de nombreuses applications. Comme la littĂ©rature ayant trait Ă la valeur des prĂ©visions est peu fournie, au contraire de celle Ă©tudiant leur qualitĂ©,nous souhaitons Ă©tablir des liens entre qualitĂ© et valeur. Sâils peuvent ĂȘtre gĂ©nĂ©ralisĂ©s,ceux-ci permettraient de dĂ©montrer et de comprendre la valeur ajoutĂ©e des prĂ©visions probabilistes. Dans une premiĂšre Ă©tape, un cadre dâĂ©valuation de la qualitĂ© des prĂ©visions probabilistes est prĂ©sentĂ©. Il est constituĂ© dâun ensemble de mĂ©triques, dâoutils graphiques et de modĂšles de rĂ©fĂ©rence. Ă lâissue dâune revue bibliographique qui recense diffĂ©rentes mĂ©triques probabilistes, nous proposons un nouvel outil appelĂ© matrice dâespĂ©rance qui a pour but de comparer celles-ci. Il permet dans un premier temps de sĂ©lectionner les scores les plus adaptĂ©s pour rĂ©pondre aux questions de recherche, et dans un second temps de quantifier les gains potentiels de qualitĂ© que lâutilisation de prĂ©visions probabilistes permet thĂ©oriquement dâobtenir. Pour complĂ©ter ce cadre de rĂ©fĂ©rence, nous introduisons un nouveau modĂšle de rĂ©fĂ©rence que nous suggĂ©rons dâappeler CSD-CLIM. Il est construit sur lâidĂ©e dâutiliser au mieux toute lâinformation contenue dans les donnĂ©es historiques dâobservations dâun site pour concevoir une prĂ©vision fiable, de qualitĂ© supĂ©rieure Ă celle des modĂšles de rĂ©fĂ©rence communĂ©ment utilisĂ©s. Ensuite, les gains rĂ©ellement obtenus que lâon peut effectivement attribuer Ă lâutilisation de lâapproche probabiliste sont calculĂ©s pour plusieurs modĂšles de prĂ©vision probabiliste couramment utilisĂ©s et pour un ensemble de six sites prĂ©sentant diffĂ©rentes conditions climatologiques. Ce calcul est effectuĂ© Ă lâaide dâune nouvelle mĂ©thodologie nommĂ©e âMC-CRPSâ, pour des prĂ©visions J+1 construites par post-traitement statistique de prĂ©visions dâensemble.Une seconde Ă©tape est dĂ©diĂ©e Ă lâĂ©tude de la valeur des prĂ©visions du point de vue de lâutilisateur. La valeur dâune prĂ©vision dĂ©pend de son utilisation, il est donc nĂ©cessaire de choisir un cas dâapplication pratique pour la mesurer. Pour un acteur industriel,elle mesure le bĂ©nĂ©fice apportĂ© par lâutilisation de cette prĂ©vision dans un contexte de prise de dĂ©cision. Une recherche thĂ©orique est conduite sur la maniĂšre de modĂ©liser les coĂ»ts associĂ©s aux dĂ©cisions prises Ă lâaide de la prĂ©vision. On parvient Ă proposer une mĂ©thodologie dâĂ©valuation de la valeur dans un cadre dâutilisation bien dĂ©fini. Celle-ci recommande lâutilisation dâun graphique combinant deux informations indĂ©pendantes, Ă savoir la structure des coĂ»ts et les performances de la prĂ©vision pour tous les niveaux de probabilitĂ©. Cet outil permet donc de dĂ©corrĂ©ler les facteurs explicatifs provenant de la qualitĂ© de la prĂ©vision et du contexte du marchĂ©.Cette mĂ©thodologie est finalement utilisĂ©e pour expliquer les rĂ©sultats obtenus lors de lâutilisation de diffĂ©rentes prĂ©visions pour la valorisation de la production Ă©lectrique dâune centrale solaire sur trois marchĂ©s de lâĂ©lectricitĂ©. Les rĂ©sultats prouvent que la structure des prix du marchĂ© a bien un rĂŽle fondamental sur la valeur effective des prĂ©visions. Ă nouveau, les gains de lâapproche probabiliste par rapport Ă lâapproche dĂ©terministe sont Ă©valuĂ©s puis comparĂ©s aux gains de qualitĂ©. Les valeurs des prĂ©visions probabilistes surpassent celles des prĂ©visions dĂ©terministes. Dans un contexte dâutilisation industrielle oĂč la structure de coĂ»ts devient elle-mĂȘme incertaine, il est nĂ©cessaire de disposer Ă©galement dâune prĂ©vision des prix du marchĂ©. Une mĂ©thode simple a Ă©tĂ© implĂ©mentĂ©e. Cette incertitude supplĂ©mentaire entraĂźne une diminution de la diffĂ©rence de valeur entre prĂ©visions probabilites et dĂ©terministes.Solar forecasting is a major asset in many solutions for large-scale integration of solar power into electricity mixes. This work aims to prove that probabilistic forecasting, yet not frequently used at an industrial scale, is nonetheless for many applications. Since the scientific literature related to value of forecasts is rare, contrary to literature about quality, this work is devoted to establishing links between quality and value. If they can be generalized, they would demonstrate and help the understanding of added-value of probabilistic forecasting. In a first step, a framework for the assessment of quality of probabilistic forecasts is presented. It is constituted of metrics, graphic tools and reference benchmark models. After a bibliographiv review focused on probabilistic metrics, a new tool called âoutcome matrixâ designed for the comparison of probabilistic metrics is presented. It is firstly used to select the most appropriate scores for the research question, and then to quantify the potential benefits in terms of quality that the usage of probabilistic forecasting may bring. In order to complete the framework of quality assessment of probabilistic forecasts, we propose a new reference model to benchmark solar probabilistic forecasts called âCSDCLIMâ. The main idea is to use at best all knowledge contained in the historical data of a site to generate a reliable forecast. The quality of this model slightly outperforms those of commonly used reference models. Finally, the benefits really obtained from the use of probabilistic forecasts are calculated for several probabilistic forecasting models from the literature and on six sites facing very different climatologies. This calculation is made with a new methodology called âMC-CRPSâ, for day-ahead forecasts built by post-processing of ensemble forecasts provided by ECMWF. A second step is dedicated to the study of the value of forecasts from a user perspective. The value of a forecast depends on its usage, and it is then necessary to select a practical case study to quantify it. For industrials, it measures the gains brought by this forecast in a decision-making process. A theoretical research is contucted on the way to model the cost associated to decisions based on the forecast. A methodology for the evaluation of the value of a probabilistic forecast of continuous variables is proposed. It consists in the usage of a plot that combines two independant informations, namely the cost structure and the skills of the forecast for all the different probability levels. This methodology allows to consider separately the factors explicable by the quality of the forecast and by the market cost structure. Finally, this methodology is used for the analysis of the results obtained by different forecasting models for the economic optimization of the production of a solar powerplant on three different electricity markets. The results tend to prove that the cost structure has indeed a crucial role on the effective economic value of forecasts. Again, the gains of the probabilistic approach compared to the deterministic approach are evaluated and compared with quality gains. For an industrial usage, it must be noted that it is necessary to have also a forecasting model dedicated to market prices. A simple method of such a forecast has been implemented. On the considered cases, the values of the probabilistic forecasts outpace those of deterministic forecasts. However, the differences between these two approaches decrease as soon as the cost structure is itself uncertain
Qualité et valeur des prévisions solaires probabilistes
Solar forecasting is a major asset in many solutions for large-scale integration of solar power into electricity mixes. This work aims to prove that probabilistic forecasting, yet not frequently used at an industrial scale, is nonetheless for many applications. Since the scientific literature related to value of forecasts is rare, contrary to literature about quality, this work is devoted to establishing links between quality and value. If they can be generalized, they would demonstrate and help the understanding of added-value of probabilistic forecasting. In a first step, a framework for the assessment of quality of probabilistic forecasts is presented. It is constituted of metrics, graphic tools and reference benchmark models. After a bibliographiv review focused on probabilistic metrics, a new tool called âoutcome matrixâ designed for the comparison of probabilistic metrics is presented. It is firstly used to select the most appropriate scores for the research question, and then to quantify the potential benefits in terms of quality that the usage of probabilistic forecasting may bring. In order to complete the framework of quality assessment of probabilistic forecasts, we propose a new reference model to benchmark solar probabilistic forecasts called âCSDCLIMâ. The main idea is to use at best all knowledge contained in the historical data of a site to generate a reliable forecast. The quality of this model slightly outperforms those of commonly used reference models. Finally, the benefits really obtained from the use of probabilistic forecasts are calculated for several probabilistic forecasting models from the literature and on six sites facing very different climatologies. This calculation is made with a new methodology called âMC-CRPSâ, for day-ahead forecasts built by post-processing of ensemble forecasts provided by ECMWF. A second step is dedicated to the study of the value of forecasts from a user perspective. The value of a forecast depends on its usage, and it is then necessary to select a practical case study to quantify it. For industrials, it measures the gains brought by this forecast in a decision-making process. A theoretical research is contucted on the way to model the cost associated to decisions based on the forecast. A methodology for the evaluation of the value of a probabilistic forecast of continuous variables is proposed. It consists in the usage of a plot that combines two independant informations, namely the cost structure and the skills of the forecast for all the different probability levels. This methodology allows to consider separately the factors explicable by the quality of the forecast and by the market cost structure. Finally, this methodology is used for the analysis of the results obtained by different forecasting models for the economic optimization of the production of a solar powerplant on three different electricity markets. The results tend to prove that the cost structure has indeed a crucial role on the effective economic value of forecasts. Again, the gains of the probabilistic approach compared to the deterministic approach are evaluated and compared with quality gains. For an industrial usage, it must be noted that it is necessary to have also a forecasting model dedicated to market prices. A simple method of such a forecast has been implemented. On the considered cases, the values of the probabilistic forecasts outpace those of deterministic forecasts. However, the differences between these two approaches decrease as soon as the cost structure is itself uncertain.La prĂ©vision solaire est un Ă©lĂ©ment central de la plupart des solutions dâintĂ©gration Ă large Ă©chelle de lâĂ©nergie solaire au sein des mix Ă©lectriques. Lâobjectif de ce travail est de dĂ©montrer que lâutilisation de prĂ©visions probabilistes, encore peu frĂ©quente Ă lâĂ©chelle industrielle, est pertinente pour de nombreuses applications. Comme la littĂ©rature ayant trait Ă la valeur des prĂ©visions est peu fournie, au contraire de celle Ă©tudiant leur qualitĂ©,nous souhaitons Ă©tablir des liens entre qualitĂ© et valeur. Sâils peuvent ĂȘtre gĂ©nĂ©ralisĂ©s,ceux-ci permettraient de dĂ©montrer et de comprendre la valeur ajoutĂ©e des prĂ©visions probabilistes. Dans une premiĂšre Ă©tape, un cadre dâĂ©valuation de la qualitĂ© des prĂ©visions probabilistes est prĂ©sentĂ©. Il est constituĂ© dâun ensemble de mĂ©triques, dâoutils graphiques et de modĂšles de rĂ©fĂ©rence. Ă lâissue dâune revue bibliographique qui recense diffĂ©rentes mĂ©triques probabilistes, nous proposons un nouvel outil appelĂ© matrice dâespĂ©rance qui a pour but de comparer celles-ci. Il permet dans un premier temps de sĂ©lectionner les scores les plus adaptĂ©s pour rĂ©pondre aux questions de recherche, et dans un second temps de quantifier les gains potentiels de qualitĂ© que lâutilisation de prĂ©visions probabilistes permet thĂ©oriquement dâobtenir. Pour complĂ©ter ce cadre de rĂ©fĂ©rence, nous introduisons un nouveau modĂšle de rĂ©fĂ©rence que nous suggĂ©rons dâappeler CSD-CLIM. Il est construit sur lâidĂ©e dâutiliser au mieux toute lâinformation contenue dans les donnĂ©es historiques dâobservations dâun site pour concevoir une prĂ©vision fiable, de qualitĂ© supĂ©rieure Ă celle des modĂšles de rĂ©fĂ©rence communĂ©ment utilisĂ©s. Ensuite, les gains rĂ©ellement obtenus que lâon peut effectivement attribuer Ă lâutilisation de lâapproche probabiliste sont calculĂ©s pour plusieurs modĂšles de prĂ©vision probabiliste couramment utilisĂ©s et pour un ensemble de six sites prĂ©sentant diffĂ©rentes conditions climatologiques. Ce calcul est effectuĂ© Ă lâaide dâune nouvelle mĂ©thodologie nommĂ©e âMC-CRPSâ, pour des prĂ©visions J+1 construites par post-traitement statistique de prĂ©visions dâensemble.Une seconde Ă©tape est dĂ©diĂ©e Ă lâĂ©tude de la valeur des prĂ©visions du point de vue de lâutilisateur. La valeur dâune prĂ©vision dĂ©pend de son utilisation, il est donc nĂ©cessaire de choisir un cas dâapplication pratique pour la mesurer. Pour un acteur industriel,elle mesure le bĂ©nĂ©fice apportĂ© par lâutilisation de cette prĂ©vision dans un contexte de prise de dĂ©cision. Une recherche thĂ©orique est conduite sur la maniĂšre de modĂ©liser les coĂ»ts associĂ©s aux dĂ©cisions prises Ă lâaide de la prĂ©vision. On parvient Ă proposer une mĂ©thodologie dâĂ©valuation de la valeur dans un cadre dâutilisation bien dĂ©fini. Celle-ci recommande lâutilisation dâun graphique combinant deux informations indĂ©pendantes, Ă savoir la structure des coĂ»ts et les performances de la prĂ©vision pour tous les niveaux de probabilitĂ©. Cet outil permet donc de dĂ©corrĂ©ler les facteurs explicatifs provenant de la qualitĂ© de la prĂ©vision et du contexte du marchĂ©.Cette mĂ©thodologie est finalement utilisĂ©e pour expliquer les rĂ©sultats obtenus lors de lâutilisation de diffĂ©rentes prĂ©visions pour la valorisation de la production Ă©lectrique dâune centrale solaire sur trois marchĂ©s de lâĂ©lectricitĂ©. Les rĂ©sultats prouvent que la structure des prix du marchĂ© a bien un rĂŽle fondamental sur la valeur effective des prĂ©visions. Ă nouveau, les gains de lâapproche probabiliste par rapport Ă lâapproche dĂ©terministe sont Ă©valuĂ©s puis comparĂ©s aux gains de qualitĂ©. Les valeurs des prĂ©visions probabilistes surpassent celles des prĂ©visions dĂ©terministes. Dans un contexte dâutilisation industrielle oĂč la structure de coĂ»ts devient elle-mĂȘme incertaine, il est nĂ©cessaire de disposer Ă©galement dâune prĂ©vision des prix du marchĂ©. Une mĂ©thode simple a Ă©tĂ© implĂ©mentĂ©e. Cette incertitude supplĂ©mentaire entraĂźne une diminution de la diffĂ©rence de valeur entre prĂ©visions probabilites et dĂ©terministes
Corrosion, passivation et protection du cuivre en solutions aqueuses
SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79914 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
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