La preuve par le beau (examen critique de l'ontologie mathématique)

La plupart des mathématiciens croit en l'existence d'un troisième monde. Or, ni l'analyse des mathématiques ni celle des philosophes des mathématiques ne permettent de choisir entre découverte et invention. Cavaillès a voulu démontrer que les inventions s'enchaînaient de manière nécessaire et imprévisible. Cela peut expliquer la croyance des chercheurs mais n'intègre pas les illuminations qu'ils sont nombreux (dont Dieudonné, Weil, Poincaré et Connes) à souligner. Damasio a montré que le cheminement de la pensée peut ne pas être mathématisable et Châtelet démontre que celui-ci n'est jamais donné par les mathématiciens. Une expertise de leur travail est donc entreprise. La première démarche est une enquête internationale par internet, qui apporte de très nombreuse réponses. La seconde cherche à établir le processus de l'invention. Il est démontré que les essais de Poincaré au début du XXe siècle (repris par Hadamard puis Choquet en 1994) sont les seuls disponibles. Il découpe le processus : préparation (souvent à partir de cas particuliers), incubation (phase inconsciente), illumination (suivant plusieurs formes), vérification (l'illumination peut être trompeuse). Poincaré (les chercheurs le confirment dans l'enquête par internet) pense que les idées s'associent dans l'inconscient du mathématicien pour en inventer de nouvelles. Et la sensation de beauté en est le lien systématique. Ce terme de beauté est adopté par tous les chercheurs (le questionnaire auquel ils ont répondu le montre). Ils en décrivent les propriétés mais ne le définissent pas. Cinq situations particulières où apparaît cette beauté (une enfant, un étudiant, un professeur, un exposé de Choquet et une lettre de Cantor) montre qu'elle dépend du niveau de culture mathématique de l'individu et permettent une définition : en mathématiques, est beau ce qui mène à la connaissance. La sensation de découverte que ressent le mathématicien lors de l'ivention est comprise.Most mathematicians believe in the existence of a third world. But neither the analysis of mathematics nor the one of the philosophers of mathematics allow to choose between discovery and invention. Cavaillès wanted to demonstrate that inventions were chained in a necessary but imprevisible way. This can explain the researchers' belief but does not take into account the "illuminations" [enlightenments] they are numerous (like Dieudonné, Weil, Poincaré and Connes) to highlight. Damasio shows that the functioning of thought cannot be put in formulas and Châtelet demonstrates that the way their thought works is never given by mathematicians. A careful checking of their work is done. First, an international [survey was sent to mathematicians through the Internet and returned a lot of answers]. Second, we try to establish the functioning of invention. It is showed that that Poincaré's works, made in the beginning of the 20th century, are the only ones [dealing with the functioning of invention]: they have been developped by Hadamard and Choquet in 1994. It analyses the steps of the process: preparation (often from a peculiar case), incubation (unconscious phase), illumination [enlightenment] (sveral ways), checking (because [enlightenment] can be erroneous). Poincaré (and so it is confirmed by the Internet survey) thinks ideas are associated in the mathematician's mind to make new other ones. The feeling of beauty is always the link between those ideas. The word "beauty" is adopted by all researchers, as the surveys shows. The properties are well described, but the word is not defined. Five different situations (a child, a student, a professor, a text of Choquet and a letter from Cantor) shows that this "beauty" depends on the mathematical background of the person and leads to this definition: in mathematics, "beauty" is what leads to knowledge.ST DENIS-BU PARIS8 (930662101) / SudocSudocFranceF

A partir d une étude ethnométhodologique du "bug de l'an 2000", intégration d un processus d amélioration continue de gestion de bugs, incidents, problèmes, changements et configurations pour les systèmes d information critiques

L objectif de la présente thèse est de contribuer au débat suivant : comment gérer bugs, incidents, problèmes et changements qui apparaissent dans les grands systèmes d informations critiques ? On revient d abord sur les évolutions théoriques et technologiques du domaine. On traite ensuite des méthodologies récentes autour des référentiels (CMMI, COBIT, ITIL) qui visent à améliorer les méthodes de gestion d incidents, proble mes, configurations dans les aspects techniques, organisationnels et stratégiques. Une analyse comparative est effectuée avant d adopter une posture pragmatique faisant intervenir les spécificités en matière d intégration de technologies, de management de processus et d intégration des démarches d amélioration continue. Le travail débouche alors sur des nouvelles propositions, basées sur un modèle de pilotage par la connaissance, en matière de modélisation et de conduite de la gestion des problèmes. On décrit alors la conception et le développement d un logiciel qui démontre la faisabilité du modèle de pilotage proposé. Sa mise en place et son utilisation sur le terrain sont évalués afin de mesurer l opportunité et les limites d un tel système.ST DENIS-BU PARIS8 (930662101) / SudocSudocFranceF

Communication des messages complexes par des séquences gestuelles (les kata dans les arts martiaux japonais)

ST DENIS-BU PARIS8 (930662101) / SudocSudocFranceF

Dispositif socio-technique d'information et de communication épistémique (DISTICE) (de l'élaboration communautaire d'informations vers la construction collaborative d'un dispositif de gestion de connaissances)

En proposant une analyse nouvelle des systèmes de gestion de connaissances, cette thèse participe aux débats sur l élaboration d outils conceptuels dans le cadre des sociétés du savoir et concourt à l exploration de futures voies de recherches pour les chercheurs en sciences de l Info-Com. Ainsi, je propose de contribuer au développement du domaine de la gestion de connaissances en définissant un nouveau modèle de circulation et de transmission de l information, élaboré à partir d une approche constructiviste, sociale et instrumentale des activités d échanges informationnels. Ce nouveau modèle incorpore les mécanismes de l interaction sociale dans la transmission et la création de connaissances, au sein de dispositifs de management de la connaissance, d apprentissage et d échanges épistémiques. Selon cette perspective, les digital habitats, construits à l aide des TIC, sont considérés comme des éléments participant à la mise en œuvre d espaces de médiation sociale et sémiotique, favorisant les dynamiques individuelles et collectives de gestion de connaissances. Tout en exploitant les apports de l approche de type connaissance-objet présents dans les démarches "knowledge as a possession", la réflexion exposée dans ce mémoire s appuie sur une approche située et incarnée de la connaissance, constitutive des démarches "knowing as a practice". Aussi, cette réflexion participe-t-elle aux débats visant le dépassement de la définition positiviste de la connaissance pour aller sur une définition anthropo-phénoménologique de celle-ci. L ensemble de ce travail est donc à considérer dans le cadre du grand débat humaniste qui vise à définir de nouvelles voies pour la construction de l apprenance.As the paradigms of Information and Communication Sciences evolve towards those of Knowing Society, the relation between individuals, society and ICT needs to be reassessed in a context of knowing. Within this framework, this dissertation aims at contributing to the development of the field of knowing management. I attempt to define a new model of information transmission and circulation, using a constructivist, social and instrumental approach of information exchanges. This new model integrates the mechanisms of social interaction in the transmission and creation of knowledge within the processes of knowledge management, learning and epistemic exchanges. In this perspective, the digital habitats, built using ICT, are viewed as participating elements in creating social and semiotic mediation spaces promoting the individual and collective dynamics of knowing management. This research dissertation thus contributes to the debates trying to go from a positivist to an anthropo-phenomenological definition of knowledge. Lastly, through a new analysis of the knowledge management systems, this dissertation enriches the debates on the elaboration of conceptual tools within the framework of "sociétés du savoir" (UNESCO, 2005) and contributes to exploring new research trails in ICS. This body of work is to be viewed as part of the great humanistic debate to define new paths for the construction of "knowing communities", integrating the cultural diversities and the contingent specificities of their components.ST DENIS-BU PARIS8 (930662101) / SudocSudocFranceF

Les attaques et la sécurité des systèmes informatiques

Le piratage informatique est apparu avec les premiers micro-ordinateurs vers 1980 et depuis n'a cessé de s'amplifier. Au début, cette pratique était essentiellement individuelle et ludique. Elle est désormais principalement constituée par les activités des personnes qui, individuellement ou en groupe, avec des motivations très diverses, piratent les ordinateurs des autres. Aujourd'hui, l'explosion des moyens de communications électroniques fait que la sécurité des données concerne sans cesse de nouvelles populations. Cette thèse examine dans un premier temps, d un point de vue technique et sociologique, les méthodes et procédures d attaques et de défense en matière de piratage informatique. Dans un second temps, elle expose une théorisation de ces mécanismes d attaques et de défense, avant de proposer une nouvelle conception de la sécurité qui n est plus seulement centrée sur des moyens techniques mais également sur la prise en compte de la dimension sociale des attaques et de défense.Hacking activities appeared around 1980 with first personal computers and since did not stop developing. At the beginning, this practice was primarily individual and playful. Now it is mainly made up by the activities of groups, with very various motivations. Today, due to the development of electronic means of communication, data security concerns a wider public. This thesis examines initially, from a technical and sociological point of view, attacks and defense mechanisms, and proposes a new concept of the security which is not only any centered on technical solutions but also takes in consideration the social dimension of the problem.ST DENIS-BU PARIS8 (930662101) / SudocSudocFranceF

Genetic polymorphism of glutamine synthetase and delta-9 desaturase in families of Pacific oyster Crassostrea gigas and susceptibility to summer mortality

International audienceLarge-scale mortality events have been observed in Pacific oyster Crassostrea gigas on the west coast of France since the early 1980s, particularly during summer. In order to understand the causes of this mortality, two generations of oysters from single-pair matings were studied in three sites on the French Atlantic coast (Baie-des-Veys, Auray and Ronce-les-Bains). The present paper examines the role of two candidate genes in the susceptibility of oysters to summer mortality, and the selective pressure exerted by such mortality on their polymorphism. Glutamine synthetase (amino-acid metabolism) and delta-9 desaturase (lipid metabolism) genes were studied in the successive generations, using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP). Observed and expected genotypic frequencies were compared. Three different alleles were detected for the glutamine synthetase gene and two for delta-9 desaturase. Allele C of glutamine synthetase seemed to be counter-selected in some second generation families. Allele B of delta-9 desaturase gene was potentially counter-selected at Auray in the families showing higher mortality, and strong selection against BB homozygotes was observed. These observations led us to conclude that any selective effect of summer mortality on allele C of glutamine synthetase gene or allele B of delta-9 desaturase gene could be mediated either directly or via linkage to other loci involved in physiological pathways affecting susceptibility

Characterisation of physiological and immunological differences between Pacific oysters (Crassostrea gigas) genetically selected for high or low survival to summer mortalities and fed different rations under controlled conditions

International audienceWithin the framework of a national scientific program named "MORtalités ESTivales de l'huître creuse Crassostrea gigas" (MOREST), a family-based experiment was developed to study the genetic basis of resistance to summer mortality in the Pacific oyster, Crassostrea gigas. As part of the MOREST project, the second generation of three resistant families and two susceptible families were chosen and pooled into two respective groups: "R" and "S". These two groups of oysters were conditioned for 6 months on two food levels (4% and 12% of oyster soft-tissue dry weight in algal dry weight per day) with a temperature gradient that mimicked the Marennes-Oléron natural cycle during the oyster reproductive period. Oyster mortality remained low for the first two months, but then rapidly increased in July when seawater temperature reached 19 °C and above. Mortality was higher in "S" oysters than in "R" oysters, and also higher in oysters fed the 12% diet than those fed 4%, resulting in a decreasing, relative order in cumulative mortality as follows; 12% "S" > 12% "R" > 4% "S" > 4% "R". Although the observed mortality rates were lower than those previously observed in the field, the mortality differential between "R" and "S" oysters was similar. Gonadal development, estimated by tissue lipid content, followed a relative order yielding a direct, positive relationship between reproductive effort and mortality as we reported precedently by quantitative histology. Regarding hemocyte parameters, one of the most striking observations was that reactive oxygen species (ROS) production was significantly higher in "S" oysters than in "R" oysters in May and June, regardless of food level. The absence of known environmental stress under these experimental conditions suggests that the ROS increase in "S" oyster could be related to their higher reproductive activity. Finally, a higher increase in hyalinocyte counts was observed for"S" oysters, compared to "R" oysters, in July, just before mortality. Taken together, our results suggest an association of genetically based resistance to summer mortality, reproductive strategy and hemocyte parameters

Genetically based resistance to summer mortality in the Pacific oyster (Crassostrea gigas) and its relationship with physiological, immunological characteristics and infection processes

International audienceSummer mortality of Pacific oysters is known in several countries. However no specific pathogen has been systematically associated with this phenomenon. A complex combination of environmental and biological parameters has been suggested as the cause and is now starting to be identified. A high genetic basis was found for survival in oysters when a first generation (G1) was tested in three sites during summer. This paper presents a synthesis on physiological characteristics of two selected groups (‘R' and ‘S', from families selected for resistance and susceptibility to summer mortality respectively), of the second and third generations. R and S showed improvement or reduction of survival compared with the control in both field and laboratory trials confirming the high heritability of survival of juveniles <1 year old. Interestingly, no correlation was observed between growth and survival. Comparison between the two selected groups showed that S oysters invested more energy in reproduction and stayed a longer time without spawning than R oysters which had high synchronous spawning. This was mainly shown with high rather than low dietary rations (respectively 12% and 4% DW algae/DW oyster) in a controlled experiment. Moreover, early partial spawning was detected in S oysters and not R ones in the high dietary ration. S showed a higher respiration rate and an earlier decrease in absorption efficiency than R during gametogenesis, but they were not significantly different in glycogen or ATP utilisation. Two months before a mortality episode, hemocytes from S oysters had a higher adhesive capacity than R hemocytes and significantly higher reactive oxygen species production capacity. One month before mortality, S oysters had the highest hyalinocyte concentration and their expression of genes coding for glucose metabolism enzymes (Hexokinase, GS, PGM, PEPCK) was significantly lower in the labial palps. After a thermal increase from 13 °C to 19 °C, during 8 days in normoxia, S oysters showed a large HSP70 increase under hypoxia contrary to R oysters, suggesting their high susceptibility to stress. Their catalase activity was lower than in R oysters and showed no further change to subsequent hypoxia and pesticide stresses, in contrast to R oysters. These observations suggest possible links between higher reproductive effort in S oysters, their specific stress response to temperature and hypoxia, ROS production, partial spawning, hyalinocyte increase and the infection process. To compare R and S oysters in a more integrated way, a suppression subtractive hybridisation (SSH) library and a micro-array strategy are being undertaken

Cooperation and cheating orchestrate Vibrio assemblages and polymicrobial synergy in oysters infected with OsHV-1 virus

Polymicrobial diseases significantly impact the health of humans and animals but remain understudied in natural systems. We recently described the Pacific Oyster Mortality Syndrome (POMS), a polymicrobial disease that impacts oyster production and is prevalent worldwide. Analysis of POMS-infected oysters on the French North Atlantic coast revealed that the disease involves co-infection with the endemic ostreid herpesvirus 1 (OsHV-1) and virulent bacterial species such asVibrio crassostreae. However, it is unknown whether consistentVibriopopulations are associated with POMS in different regions, howVibriocontribute to POMS, and how they interact with the OsHV-1 virus during pathogenesis. We resolved theVibriopopulation structure in oysters from a Mediterranean ecosystem and investigated their functions in POMS development. We find thatVibrio harveyiandVibrio rotiferianusare the predominant species found in OsHV-1-diseased oysters and show that OsHV-1 is necessary to reproduce the partition of theVibriocommunity observed in the field. By characterizing the interspecific interactions between OsHV-1,V. harveyiandV. rotiferianus, we find that onlyV. harveyisynergizes with OsHV-1. When co-infected, OsHV-1 andV. harveyibehave cooperatively by promoting mutual growth and accelerating oyster death.V. harveyishowed high virulence potential in oysters and dampened host cellular defenses, making oysters a more favorable niche for microbe colonization. We next investigated the interactions underlying the co-occurrence of diverseVibriospecies in diseased oysters. We found thatV. harveyiharbors genes responsible for the biosynthesis and uptake of a key siderophore called vibrioferrin. This important resource promotes the growth ofV. rotiferianus, a cheater that efficiently colonizes oysters during POMS without costly investment in host manipulation nor metabolite sharing. By connecting field-based approaches, laboratory infection assays and functional genomics, we have uncovered a web of interdependencies that shape the structure and function of the POMS pathobiota. We showed that cooperative behaviors contribute to synergy between bacterial and viral co-infecting partners. Additional cheating behaviors further shape the polymicrobial consortium. Controlling such behaviors or countering their effects opens new avenues for mitigating polymicrobial diseases

Cooperation and cheating orchestrate Vibrio assemblages and polymicrobial synergy in oysters infected with OsHV-1 virus

Polymicrobial infections threaten the health of humans and animals but remain understudied in natural systems. We recently described the Pacific Oyster Mortality Syndrome (POMS), a polymicrobial disease affecting oyster production worldwide. In the French Atlantic coast, the disease involves coinfection with ostreid herpesvirus 1 (OsHV-1) and virulent Vibrio . However, it is unknown whether consistent Vibrio populations are associated with POMS in different regions, how Vibrio contribute to POMS, and how they interact with OsHV-1 during pathogenesis. By connecting field-based approaches in a Mediterranean ecosystem, laboratory infection assays and functional genomics, we uncovered a web of interdependencies that shape the structure and function of the POMS pathobiota. We show that Vibrio harveyi and Vibrio rotiferianus are predominant in OsHV-1-diseased oysters and that OsHV-1 drives the partition of the Vibrio community observed in the field. However only V. harveyi synergizes with OsHV-1 by promoting mutual growth and accelerating oyster death. V. harveyi shows high-virulence potential and dampens oyster cellular defenses through a type 3 secretion system, making oysters a more favorable niche for microbe colonization. In addition, V. harveyi produces a key siderophore called vibrioferrin. This important resource promotes the growth of V. rotiferianus , which cooccurs with V. harveyi in diseased oysters, and behaves as a cheater by benefiting from V. harveyi metabolite sharing. Our data show that cooperative behaviors contribute to synergy between bacterial and viral coinfecting partners. Additional cheating behaviors further shape the polymicrobial consortium. Controlling cooperative behaviors or countering their effects opens avenues for mitigating polymicrobial diseases