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L'infection d'un organisme par un agent pathogène déclenche l'activation des lymphocytes T-CD8 et l'initiation de la réponse immunitaire. Il s'ensuit un programme complexe de prolifération et de différenciation des lymphocytes T-CD8, contrôlé par l'évolution de leur contenu moléculaire. Dans ce manuscrit, nous présentons deux modèles mathématiques de la réponse T-CD8. Le premier se présente comme une équation différentielle à impulsions grâce à laquelle nous étudions l'effet du partage inégal des protéines lors des divisions cellulaires sur la régulation de l'hétérogénéité moléculaire. Le second est un modèle à base d'agents couplant la description d'une population discrète de lymphocytes T-CD8 à celle du contenu moléculaire de ces derniers. Ce modèle s'avère capable de reproduire les différentes phases caractéristiques de la réponse T-CD8 aux échelle cellulaire et moléculaire. Ces deux travaux supportent l'hypothèse que la dynamique cellulaire observée in vivo est le reflet de l'hétérogénéité moléculaire qui structure la population de lymphocytes T-CD8 / Infection of an organism by a pathogen triggers the activation of the CD8 T-cells and the initiation of the immune response. The result is a complex program of proliferation and differentiation of the CD8 T-cells, controlled by the evolution of their molecular content. In this manuscript, we present two mathematical models of the CD8 T-cell response. The first one is presented as an impulsive differential equation by which we study the effect of unequal molecular partitioning at cell division on the regulation of molecular heterogeneity. The second one is an agent-based-model that couples the description of a discrete population of CD8 T-cells and that of their molecular content. This model can reproduce the different typical phases of the CD8 T-cell response at both the cellular and the molecular scales. These two studies support the hypothesis that the cell dynamics observed in vivo is a consequence of the molecular heterogeneity structuring the CD8 T-cell population

A evolução tecnológica das redes de telecomunicações sem fio permite que organizações de redes mais inteligentes sejam vislumbradas. É possível imaginar um sistema de telefonia formado por dispositivos móveis autônomos que não necessite de nenhuma infraestrutura pré-estabelecida para trocar informações com seus vizinhos, de acordo com o alcance do raio de transmissão. Assim, as informações poderiam ser repassadas de nó em nó, formando uma rede de múltiplos saltos. A ausência de uma entidade central também poderia melhorar a tolerância a falhas do sistema, principalmente por gerar uma redundância de caminhos possíveis entre os nós. Analisamos o desempenho desse sistema em diferentes cenários e a sensibilidade à variação de parâmetros como o raio de transmissão, interferências, a quantidade de nós e número de saltos máximo permitido (TTL), e testamos estratégias de comunicação com raio fixo, raio variável, número de vizinhos mínimo e etc., através de modelagem e simulação baseada em agentes. De maneira geral, a estratégia de transmissão com raio variável apresentou a melhor taxa de mensagens recebidas e a menor média de saltos até o destino, porém com maior nível de energia do sistema. A estratégia de raio fixo apresentou a menor energia total gasta pelo sistema para enviar as mensagens, porém, com uma taxa menor de mensagens recebidas. Além disso, avaliamos que as principais causas de perdas de pacotes estão associadas com o aumento da mobilidade, a redução do TTL e as interferências, sendo que cada uma contribui mais ou menos de acordo com o cenário estudado. / The technological development of Wireless Networks leads to more intelligent networks structures. One can imagine a mobile data system consisting of autonomous mobile devices that do not require any pre-established infrastructure to exchange information one with another, limited mainly by the transmission radius. Thus, data could be forwarded from node to node, forming a multihop network. The absence of a central entity could also improve fault tolerance by allowing redundant paths for nodes to communicate. We analyzed the performance of the system in different scenarios and system behavior regarding parameters variations such as transmission radius, interferences, the number of nodes and maximum allowed number of hops (TTL), and tested communication strategies with fixed radius, variable radius, minimum number of neighbors to transmit, etc., through modeling and simulation-based agents. In general, variable radius strategy had the best rate of incoming messages and the lowest average number of hops to the destination. However it presented the higher level of system energy. In one hand, fixed radius strategy presented the lowest total energy expended by the system to send messages, but, in the other hand, the rate of incoming messages was lower. Furthermore, we discovered the main causes of packet losses are associated with increased mobility, reducing the TTL and interference, each of which contributes more or less in accordance with the scenario.

This research address the problem of inferring, through Radio-Frequency Identification (RFID) tracking data, the graph structures underlying social interactions in a group of rhesus macaques (a species of monkey). These social interactions are considered as independent affiliative and dominative components and are characterized by a variety of visual and auditory displays and gestures. Social structure in a group is an important indicator of its members’ relative level of access to resources and has interesting implications for an individual’s health. Automatic inference of the social structure in an animal group enables a number of important capabilities, including: 1. A verifiable measure of how the social structure is affected by an intervention such as a change in the environment, or the introduction of another animal, and 2. A potentially significant reduction in person hours normally used for assessing these changes. The behaviors of interest in the context of this research are those definable using the macaques’ spatial (x,y,z) position and motion inside an enclosure. Periods of time spent in close proximity with other group members are considered to be events of passive interaction and are used in the calculation of an Affiliation Matrix. This represents the strength of undirected interaction or tie-strength between individual animals. Dominance is a directed relation that is quantified using a heuristic for the detection of withdrawal and displacement behaviors. The results of an analysis based on these approaches for a group of 6 male monkeys that were tracked over a period of 60 days at the Yerkes Primate Research Center are presented in this Thesis.

無論在電腦動畫、電玩或電影產業，利用電腦自動產生虛擬人群已逐漸成為不可或缺的要素之一。這些虛擬人群，往往是系統先賦與每個虛擬代理人(agent)基礎智能，然後藉由個體之間的互動法則所自動產生。然而，過去因為普遍未考量真實群體情境中的傳播與互動模式，使得虛擬人群所表現的群體行為與現實情況仍有些差距。因此，我們引用社會心理學文獻，建立一個具有溝通機制的人群模擬平台(IMCrowd)，以期自動產生與現實群眾動態更相似的模擬人群。IMCrowd是多代理人(Multi-agent)基礎的系統，其中每個虛擬代理人都具有區域的感知範圍與自主能力，因此他們能夠自動地與環境中的其它物件互動與反應。由於我們為IMCrowd所建立的溝通模型考量了社會心理學的理論，因此虛擬人群能浮現真實群體動態中的社會互動模式，如情緒傳染與從眾效應。本研究以IMCrowd執行了多種情境下群眾暴動與群眾控制的模擬，藉此展現本系統的應用將不僅可提升群體模擬的真實度，亦可做為社會心理學家研究群體行為的工具。 / Using computer to automatically generate simulated crowd has become a trend in animation, computer game, and film productions. Many of these works were produced by modeling the intelligence of the agents in a crowd and their interactions with other nearby agents and the environment. However, the perceived facts or elicited emotions usually do not propagate in the crowd as they should in the real life. In this work we attempt to build up a communication model to simulate a large variety of crowd behaviors including the course of crowd formation. The proposed crowd simulation system, IMCrowd, has been implemented with a multi-agent system in which each agent has a local perception and autonomous abilities to improvise their actions. The algorithms used in our communication model in IMCrowd are based heavily on sociology research. Therefore, the collective behaviors will emerge out of the social process such as emotion contagion and conformity effect among individual agents. Several elaborate riot simulations and riot control simulations are demonstrated and reported in this thesis as the application examples of IMCrowd. Thus, we claim that IMCrowd may not only benefit on enhancing realism of crowd animation but also be useful in studying crowd behaviors such as panic, gathering, and riots.

Techn. Univ., Diss--Berlin, 2007.

L'obiettivo della tesi è lo sviluppo e nell'analisi di un modello macro-finanziario con aspetti reali e finanziari dell'economia, nell'ottica di ottenere un quadro comprensivo per l'analisi del rischio sistemico e delle instabilità. Il primo capitolo verte sulla costruzione di un modello ad agenti che si caratterizza per la presenza del mercato dei beni, del credito, del lavoro e interbancario. Il modello riproduce fluttuazioni endogene ed è in grado di replicare alcuni fatti stilizzati riguardanti i cicli economici e creditizi, mentre il mercato interbancario ha un ruolo importante dal punto di vista della stabilità e dell'efficienza. In particolare la regolazione prudenziale combinata con le aspettative adattive può esacerbare il comportamento precauzionale delle banche durante una recessione, inducendo a trattenere liquidità anche le banche solide. Inoltre la connettività del mercato interbancario ha un duplice effetto: da un lato favorisce l'accesso al credito nell'economia reale, dall'altro accresce l'accumulo di liquidità. Il secondo capitolo si concentra su un insieme di esperimenti condotti tramite il modello precedentemente sviluppato. Lo scopo è di confrontare tra loro politiche macro-prudenziali in cui le banche sono soggette a requisiti minimi di capitale derivati da misure di rischio sistemico. Nello specifico gli indicatori di rischio sistemico sono suddivisi in misure di mercato e di rete. Ogni categoria è ulteriormente scomposta in misure di vulnerabilità e misure di impatto. I risultati rivelano che le politiche costruite su indicatori di vulnerabilità sono migliori di quelle basate sull'impatto, dato che riducono i fallimenti da contagio senza peggiorare la performance macroeconomica. / The purpose of the thesis is to develop and analyse a macro-financial model with real and financial aspects of the economy to obtain a comprehensive framework for the analysis of systemic risk and instabilities. The first chapter concerns the construction of an agent-based-model, whose characteristic is the presence of goods, credit, labour and interbank markets. The model reproduces endogenous business cycles and it is able to replicate some stylized facts about business and credit cycles, while the interbank market has an important role for stability and efficiency. In particular prudential regulation, combined with adaptive expectations can exacerbate the precautionary behaviour of banks during a recession, inducing liquidity hoarding by sound banks. Furthermore connectivity of the interbank market has a twofold effect: on one side it supports credit to the real economy, on the other it increases liquidity hoarding. The second chapter is focused on a set of policy experiments performed performed on the model previously developed. The aim is to compare different macroprudential policies where banks are subject to minimum capital requirements derived from systemic risk measures. In detail systemic risk indicators are divided in market-based and network based measures. Each class is further decomposed in measures of vulnerability and measures of impact. The results reveal that policies based on vulnerability indicators perform better than those based on impact, reducing contagious defaults without worsening the macroeconomic performance.

Nourrir une population mondiale croissante dans un contexte de changements globaux pose de nouveaux défis à l’agriculture en termes d’efficience de production et d’impacts environnementaux. Rendre les systèmes agro-alimentaires plus soutenables nécessite de mieux recycler la biomasse et les nutriments, c’est-à-dire de tendre vers des flux de fertilisants, de produits végétaux, d’aliments du bétail, de coproduits et de déchets plus circulaires. À ce titre, il est nécessaire de développer de nouveaux outils pour mieux explorer et évaluer les échanges de matières entre les fermes et leurs partenaires économiques amont et aval dans les territoires. Dans le travail présent, l’état de l’art concernant les méthodes d’analyse, de modélisation et d’évaluation environnementale des flux de biomasse et d’éléments minéraux à différentes échelles est réalisé. Le modèle multi-agents FAN (« Flows in Agricultural Network») qui simule les flux des matières entre les fermes et leurs partenaires économiques dans les territoires agricoles a été développé. Les processus de FAN sont expliqués en détail et une analyse de sensibilité des variables clefs est présentée. Par ailleurs, le modèle FAN a été appliqué à un cas d’études en France pour évaluer la performance des scénarios contrastés visant à améliorer l’efficience d’utilisation des éléments minéraux, développer le recyclage de la matière, favoriser la production du biogaz ou reconcevoir les systèmes de production. Les sorties de simulations des scénarios sont analysées en termes de production alimentaire et énergétique, de flux de matières et de logistique, de cycle des nutriments et d’émissions de gaz à effet de serre. Ce travail montre l’utilité des outils de prospective et modèles multi-agents pour améliorer la durabilité des systèmes agricoles et des chaines alimentaires, pour créer et évaluer des solutions collectives tendant vers l’économie circulaire et pour prendre en charge les interactions entre acteurs économiques au sein des chaines et filières alimentaires complexes. / Feeding the growing global population in a context of global change raises new challenges for agriculture regarding its production efficiency and impacts on natural resources. Solutions for towards farming sustainability require to improve nutrient and biomass recycling in agro-food systems, i.e. to move from linear to more circular flows of fertilizers, crop products, feedstuff, by-products and organic wastes. Innovative tools exploring material exchanges between farms and their upstream and downstream partners in agro-food systems at the local scale are needed. In the present work, the state of the art about analysis methods, models and environmental tools addressing nutrient and biomass flows at different scales is reviewed. The FAN (“Flows in Agricultural Network”) model, an agent-based model that simulates a range of material flows among farms and their partners within agricultural districts is developed. FAN processes are explained in details and a sensitivity analysis to some key variables is performed. In addition, the FAN model is applied to a French case-study to assess the performances of contrasted scenarios aiming to enhance nutrient use efficiency, recycling strategies, biogas production and system redesign. The outcomes from the scenario simulation are analyzed are assessed in terms of food provisioning, nutrient cycling and greenhouse gas emissions. This work shows the usefulness of prospective, agent-based tools for greater farming and food-chain sustainability, to design and evaluate collective solutions for circular economy and to account for interactions among economic actors within complex agro-food systems.

Die Arbeit beschreibt ein Modell, dass den Materialfluss in Transport- und Puffersystemen mit Hilfe eines agenten-basierten Ansatzes realistisch abbildet. Auf der Basis von Produktionsprogrammen werden individuelle Güter in beliebigen Netzwerkstrukturen mit Hilfe direkter und indirekter Interaktionen behinderungsvermeidend gesteuert. / The thesis describes a model that realistically illustrates the material flow in transport and buffer systems by means of an agent-based approach. Individual goods are steered hindrance-avoiding in arbitrary network structures based on production programs by means of direct and indirect interactions.

Choisir un partenaire sexuel est une décision importante pour un animal. Parce que cette décision va considérablement affecter son succès reproducteur, l’individu doit se baser sur un ensemble de traits qui reflètent la qualité du partenaire. Depuis peu, une attention particulière est portée sur l’importance de la cognition dans le contexte de choix de partenaire. En effet, la capacité à percevoir, intégrer, mémoriser et utiliser l’information disponible dans l’environnement permet aux individus de répondre de manière appropriée aux problèmes qu’ils rencontrent et d’ajuster leur comportement en conséquent. Si les femelles retirent un bénéfice à s’apparier avec des mâles capables de répondre aux changements de leur environnement, ces derniers pourraient avoir un accès privilégié à l’appariement lors du choix de partenaire des femelles. Certaines évidences appuient cette idée en démontrant notamment des relations positives entre les capacités cognitives des mâles et leur succès d’appariement et reproducteur et en révélant des préférences sexuelles femelles pour des traits cognitifs mâles. Cependant, ces résultats restent très contrastés, particulièrement chez les animaux non humains où l’importance du choix de partenaire dans l’évolution de la cognition n’est pas encore clairement définie. L’objectif de ma thèse était donc d’explorer le rôle du choix de partenaire dans l’évolution de la cognition mâle et femelle en combinant l’approche observationnelle sur une espèce d’oiseaux monogame et l’approche théorique en utilisant un modèle à base d’agents. Plus précisément, en réalisant des expériences en laboratoire sur le Diamant mandarin (Taeniopygia guttata), j’ai notamment testé si les femelles démontrent une préférence pour des mâles capables d’ajuster leur comportement d’approvisionnement en réponse à un changement environnemental. J’ai ensuite examiné, dépendamment de leurs propres capacités cognitives, si les femelles expriment des préférences pour des mâles performants dans quatre tests psychométriques différents. J’ai finalement exploré les rôles respectifs de la sélection naturelle et intersexuelle en simulant l’évolution de la cognition sous différents scénarios environnementaux. Les résultats de cette thèse ont révélé que les femelles diamants mandarin exprimaient une préférence pour les mâles capables d’ajuster leur comportement d’approvisionnement ainsi que les mâles performants dans certaines tâches cognitives. Cependant, ces préférences n’étaient pas unanimes et dépendaient des propres capacités cognitives des femelles à performer dans ces différentes situations. À l’échelle évolutive, la sélection intersexuelle à travers le choix de partenaire modifiait les patrons d’évolution de la cognition prédits lorsque la sélection naturelle opérait seule. En effet, elle favorisait l’évolution de bonnes capacités cognitives lorsque les contraintes environnementales étaient faibles, mais maintenait de la diversité cognitive lorsque ces contraintes étaient élevées. Dans l’ensemble, ces résultats suggèrent que le choix de partenaire jouerait un rôle important dans l’évolution et le maintien de diversité cognitive au sein des populations. Néanmoins, les conséquences évolutives du choix de partenaire sur les capacités cognitives des individus dépendraient de l’avantage adaptatif à s’apparier avec un mâle plus performant, c’est-à-dire de la capacité cognitive mâle considérée, des caractéristiques des femelles et de l’environnement dans lequel ce choix est fait. / Choosing a mate is an important decision for an animal. Because this decision significantly affects an individual’s reproductive success, it must base its choice according to different traits that reflect the quality of potential mates. Recently, a particular attention has been given to cognitive traits in mate choice context. Indeed, the ability to perceive, integrate, memorize and use the information available in the environment allows individuals to act properly when facing a problem and to adjust their behaviours accordingly. Given that females could benefit from choosing males capable of responding to environmental changes, those with good cognitive abilities should have privileged access to females in mate choice contexts. Some evidence supports this idea by revealing positive relationships between males’ cognitive abilities and their mating and reproductive success as well as female mating preference for male cognitive abilities. However, these results stay contrasted, particularly in non-human animals for which the importance of mate choice in the evolution of cognition is still not clearly defined. The objective of my PhD was to explore the role of mate choice in the evolution of male and female cognition by combining an observational approach using a monogamous bird species and a theoretical approach using an agent-based model. Specifically, by running laboratory experiments on zebra finches (Taeniopygia guttata), I tested whether females demonstrated a mate preference for males able to adjust their foraging behaviour following an environmental change. Then, I investigated whether females, depending on their own cognitive abilities, demonstrated a mate preference for better performers in four different psychometric tests. I finally explored the relative role of natural and sexual selection by simulating the evolution of cognition under different environmental scenarios. The results of this PhD project revealed that zebra finch females preferred males exhibiting greater behavioural plasticity in their foraging tactic use as well as males performing better in several cognitive tasks. However, females’ preference for cognitive abilities was not unanimous but depended on females’ own abilities to perform in these tasks. At the evolutionary scale, intersexual selection through mate choice changed the evolutive patterns observed under natural selection alone. In fact, intersexual selection promoted good cognitive abilities under most favourable environments but maintained cognitive diversity under the harsher ones. Taken together, these results suggest that mate choice plays an important role in the evolution and maintenance of cognitive diversity within populations. Nevertheless, the evolutive consequences of mate choice on individual cognitive abilities should depend on i) the adaptive value of mating with a male with better performance, and thus, on the cognitive ability considered, ii) the female characteristics and iii) the local environment during mate choice.