Thèse d'exercice : Pharmacie : Nantes : 2007. / Bibliogr.

L’exploration de la surface de Mars par le rover Curiosity, au niveau du cratère Gale, a permis de révéler la présence de conditions habitables par le passe, a travers l’observation de dépôts sédimentaires fluvio-lacustres attestant d'une activité hydrologique prolongée. Ces roches portent également les stigmates de l’évolution complexe des sédiments lors de la diagenèse, sous forme de veines, nodules et concrétions s'etant formes par la circulation de fluides en sub-surface. A bord du rover, la spectroscopie de plasma induit par laser (LIBS) de l’instrument ChemCam permet une mesure chimique a petite échelle, particulièrement adaptée a l'analyse de tels éléments géologiques. Cette étude démontre que les veines de Ca-sulfate, observées dans toutes les unités géologiques traversées par le rover, présentent des enrichissements ponctuels en Fe témoignant de conditions de formation oxydantes lors de la diagenèse tardive. Par ailleurs, l’une des structures sédimentaires du cratère est caractérisée par des signatures spectrales d’hématite depuis l'orbite, suggérant que sa formation est en partie liée a des processus d'oxydo-reduction, pendant et/ou après le dépôt des sédiments. A cet endroit, ChemCam a mis en évidence la mobilité du Fe lors de la diagenèse, ainsi que la formation d'oxyde de Fe en association avec les veines de Ca-sulfate. Pour conclure, ces travaux montrent l'importance des interactions fluides-roches, comme les réactions d’oxydoreduction, lors de l’enfouissement des sédiments martiens, processus devant être pris en compte pour éviter des erreurs d’interprétation sur l’environnement de dépôt et l’intérêt exo-biologique des sédiments étudiés. / The exploration of the Martian surface by the rover Curiosity, at Gale crater, has unveiled past habitable conditions on the planet with evidences for sustained period of surface aqueous activity recorded in fluvio-lacustrine sedimentary deposits. In addition, the rocks also bear traces of the complex post-depositional evolution of the sediments during diagenesis, in the form of small-scale fracture-fills, nodules, and concretions that formed by sub-surface fluid circulations. On board, the rover, the Laser-Induced Breakdown Spectroscopy (LIBS) performed by the ChemCam instrument provide remote fine-scale chemical measurements, especially suited to the analysis of such geological items. This study demonstrates that the Ca-sulfate-bearing veins, observed across all geological terrains, show enrichments in Fe at specific locations along the rover traverse, tracing localized oxidizing conditions at the time of their formation in the later stages of diagenesis. Additionally, a key sedimentary structure in Gale crater is characterized by hematite spectral signatures from orbit, suggesting the involvement of redox-driven processes in its formation, either related to primary deposition or post-depositional conditions. There, in situ ChemCam observations highlight the mobility of Fe during diagenesis and the authigenic formation of Fe-oxide in association with Ca-sulfate bearing features. As such, this work attests of significant fluid interactions, and notably redox-driven chemical reactions, affecting the Martian sediments after their deposition and burial, which need to be taken into account in order to avoid any misinterpretations on the environment of deposition and its habitability.

The sedimentary deposits in Gale crater may preserve one of the best records of the early Martian climate during the Late Noachian and Early Hesperian. Surface and orbital observations support the presence of two periods of lake stability in Gale craterprior to the formation of the sedimentary mound during the Late Noachian and after the formation and erosion of the mound to its present state in the Early Hesperian. Here we use hydrological models and late-stage lake levels at Gale, to reconstruct the climate of Mars after mound formation and erosion to its present state. Using Earth analog climates, we show that the late-stage lakes require wetter interludes characterized by semiarid climates after the transition to arid conditions in the Hesperian. These climates are much wetter than is thought to characterize much of the Hesperian and are more similar to estimates of the Late Noachian climate.

AN ABSTRACT OF THE THESIS OF ISMAIL GUNEYDAS, for the Master of Science degree in Computer Science, presented on 5th November 2008, at Southern Illinois University Carbondale. TITLE: ACTOR POSITIONING IN WIRELESS SENSOR AND ACTOR NETWORKS USING MATCHING THEORY. MAJOR PROFESSOR: Dr. KEMAL AKKAYA In most of the Wireless sensor and actor network (WSAN) applications, the locations for the actors are determined autonomously by the collaboration of actors and/or sensors in order to eliminate human intervention as much as possible. Particularly, sensors can collaborate in a distributed manner and elect cluster-heads (CHs) among them which will be taking into account the distribution of the sensors within the region. In such cases, the actors can then move to such sensor locations (i.e., replace them as cluster-heads) as they have the ability to move by talking to nearby sensors/actors. Such movement, however, should be done wisely in order to minimize the total distance that will be traveled by the actors so that their lifetimes can be extended. Nevertheless, this may not be possible since not all the actor and CH locations will be known to each actor. In addition, the actors may not be reachable to each other and thus conflicts in assignments can easily occur. In this thesis, we propose an actor-CH location matching algorithm which will detect the CH locations and assign the actors to such locations in a distributed manner with the minimized travel distance. We adapt the Gale-Shapley (G-S) stable matching algorithm from Matching Theory in order to prevent conflicts and minimize the travel distance. In this matching algorithm, actors are regarded as men and CHs are regarded as women. First, we detect the CH locations through running a quorum-based search within the sensor network. Later, G-S is run on actor and CH locations. Once the locations are determined, each actor moves to that location. We evaluated the performance of our approach through simulation and have shown that our approach can produce results very close to the brute force approach.

Despite promotion by well-known economists and supporting economic theory, econometric analyses of voucher systems often find that they have been unsuccessful in improving traditional measures of educational success. This paper examines a possible explanation of this phenomenon by comparing the drivers of educational achievement and of school popularity by examining private school choice. The findings of this paper indicate that there is a disconnect between school success and school popularity, which adversely effects both the demand and supply-side benefits of voucher systems. Additionally, this paper reviews matching mechanisms that seek to efficiently match students with schools based on both student and school preferences.

Thèses (M.Sc.)--Université de Sherbrooke (Canada), 2000. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / No Brasil, a busca pela reduÃÃo das ineficiÃncias observadas na alocaÃÃo de vagas em instituiÃÃes de ensino superior via o tradicional vestibular levou à formulaÃÃo e implantaÃÃo de um mecanismo alternativo de seleÃÃo para admissÃo superior: o Sistema de SeleÃÃo Unificada (SISU), criado em 2010. O mecanismo, tecnicamente falando, à um algoritmo de matching com as seguintes caracterÃsticas: i) cada estudante que recebe oferta de matrÃcula decide por aceitar ou rejeitar a oferta recebida; ii) rejeiÃÃes de ofertas provocam a realizaÃÃo de novas propostas; e iii) propostas sÃo aceitas temporariamente, podendo cada oferta aceita ser âtrocadaâ por uma oferta considerada âmelhorâ. Ou seja, o SISU à um mecanismo semelhante ao Algoritmo Deferred Acceptance (Algoritmo Gale-Shapley) com os cursos propondo. Apesar da importÃncia do SISU, a literatura econÃmica sobre o tema à basicamente inexistente. Nesse sentido, a presente dissertaÃÃo buscou, à luz da teoria dos jogos, entender e caracterizar os incentivos propiciados pelo SISU atravÃs de dois mecanismos teÃricos desenvolvidos, o SISUα e o SISUβ. Ambos sÃo modelados como mecanismos de matching dinÃmicos. Caracterizamos estratÃgias nÃo dominadas para o SISUβ e o SISUα. Utilizando o SISUα como a melhor aproximaÃÃo disponÃvel para o SISU, concluÃmos que a introduÃÃo do SISU apresentou um importante avanÃo em relaÃÃo ao vestibular em termos de ganhos de eficiÃncia do matching entre alunos e cursos. / In Brazil, the quest for reducing observed inefficiencies in the allocation of seats in higher education institutions through traditional examination (Vestibular) led to the formulation and implementation of an alternative mechanism of selection: the Unified Selection System (SISU), created in 2010. Technically speaking, the mechanism is a matching algorithm with the following characteristics: i) each student who receives an offer decides to accept or reject the received offer; ii) rejections of offers prompt new proposals; iii) proposals are accepted temporarily, and each offer can be âreplacedâ by an offer considered âbetterâ. That is, the SISU is a mechanism similar to the Deferred Acceptance Algorithm (Gale-Shapley Algorithm). Despite the importance of SISU, the economic literature on the subject is basically nonexistent. In this sense, this dissertation sought, in light of game theory, to understand and characterize the incentives provided by SISU through two developed theoretical mechanisms, the SISUα and SISUβ. Both are modeled as dynamic matching mechanisms. We characterize undominated strategies for SISUβ and SISUα. Using SISUα as the best approximation available to SISU, we conclude that the introduction of SISU showed a significant improvement on Vestibular in terms of gains of efficiency from matching between students and courses.

Streptomyces scabiei est l'agent causal de la gale commune de la pomme de terre. Les symptômes causés par cet agent pathogène sont surtout superficiels mais ils engendrent des pertes économiques très importantes pour l'industrie. Les stratégies pour lutter contre cette maladie sont surtout culturales puisqu'il n'existe pas de pesticide ciblé à S. scabiei. Le pouvoir pathogène de cette bactérie repose surtout sur la synthèse d'une phytotoxine, appelée thaxtomine A. Le tryptophane est l'un des deux précurseurs biosynthétiques de la thaxtomine A. Par contre, il a été démontré que l'ajout de tryptophane au milieu de culture de S. scabiei induit une forte diminution de synthèse de la phytotoxine. Ce type de répression de synthèse par les précurseurs semble être un phénomène unique, autant chez les procaryotes que chez les eucaryotes. Les bactéries du genre streptomycètes produisent aussi une foule d'autres composés, certains synthétisés aussi à partir de tryptophane. C'est le cas de l'auxine, une hormone de croissance végétale régulant divers phénomènes de croissance chez les plantes. Chez la majorité des bactéries du sol, la synthèse d'auxine est augmentée en présence de tryptophane, mais cela n'a pas été vérifié pour S. scabiei. L'objectif de notre travail a été d'évaluer l'influence du tryptophane sur l'expression des gènes de synthèse de thaxtomime A, sur la production ainsi que l'expression des gènes de synthèse de l'auxine et ensuite, sur le pouvoir pathogène de S. scabiei. Les résultats obtenus indiquent que le tryptophane réprime l'expression des gènes de synthèse de la thaxtomine A. Parallèlement, une forte augmentation de production d'auxine a été observée avec ajout exogène de tryptophane au milieu de culture, sans qu'il y ait modulation des gènes de synthèse de l'auxine. Le pouvoir pathogène de S. scabiei a été évalué en présence de tryptophane, avec un système in planta utilisant des plantules de radis, un hôte alternatif à S. scabiei. Les résultats obtenus ont permis d'affirmer que S. scabiei, en certaines conditions, pouvait agir comme promoteur de la croissance des végétaux. En effet, en présence de certaines concentrations de tryptophane, les plantes hôtes inoculées par S. scabiei avaient une meilleure croissance que des plantes non inoculées dans les mêmes conditions de tryptophane. Cette étude remet en question la classification de S. scabiei, considéré jusqu' ici comme un agent phytopathogène typique. Évidemment, cela ouvre la voie à des méthodes de luttes alternatives contre la gale commune. L'application de ces conditions aux champs est peu envisageable, à court terme, mais le développement de composés ayant un effet similaire à celui du tryptophane (au niveau de l'inhibition de synthèse de la thaxtomine A et de la promotion de synthèse de l'auxine) est une voie de recherche intéressante. De plus, une compréhension plus poussée du mécanisme d'inhibition de synthèse de la thaxtomine A par le tryptophane serait souhaitable.

Matroids capture an abstraction of independence in mathematics, and in doing so, connect discrete mathematical structures that arise in a variety of contexts. A matroid can be defined in several cryptomorphic ways depending on which perspective of a matroid is most applicable to the given context. Among the many important concepts in matroid theory, the concept of matroid duality provides a powerful tool when addressing difficult problems. The usefulness of matroid duality stems from the fact that the dual of a matroid is itself a matroid. In this thesis, we explore a matroid-like object called a flag matroid. In particular, we suggest a notion of duality for flag matroids and we investigate the implications of this notion.

The aim of the paper is to discuss the way that the online job banks send resumes to businesses for job seekers, and most businesses and job seekers have chosen online job banks as channel management for job wanted due to the rapid development of information technology for recent years. What businesses find employees and job seekers find jobs through the online job banks can be classified into two kinds, one is active candidates for the job, and another is matching pair by the online job banks. The online job banks help job seekers to send resumes to businesses by means of both ways, and how the online job banks send resumes to businesses for job seekers will affect the outcome. Therefore, this paper focuses on original way of sending resumes used by the online job banks, and also uses Gale-Shapley algorithm to devise different way of sending resumes which the online job banks possibly use in the future and consequently by comparing two ways of sending resumes, it can analyze what ways of sending resumes can be adopted by the online job banks under different situations.