Em distintos momentos da história, pesquisadores investigaram e propuseram, com relativo sucesso, modelos locacionais que explicassem a origem e os processos dos crescimentos das cidades, mas, de modo frequente, esbarrando na complexidade desses sistemas. Recentemente, apoiados nas teorias sobre Sistemas Complexos, Nova Geografia Econômica e Modelos Configuracionais Urbanos, alguns conceitos proporcionam uma fundamentação mais consistente para a verificação das variáveis e suas interações espaciais, as quais identifiquem esses processos. Dentre os sistemas complexos, são representativos os conceitos sobre a resiliência e a criticalidade auto-organizada enquanto os conceitos do modelo centro-periferia, propostos pela nova geografia econômica, contribuem para compreensão das formações de aglomerações econômicas e populacionais. Tais abordagens conduzem ao desenvolvimento da hipótese de que a localização relativa dos serviços urbanos e dos moradores, no espaço intraurbano, estaria condicionada a duas forças que se contrapõem, “centrípeta e centrífuga”, que são geradoras de “tensões” as quais conduzem o sistema a atingir níveis críticos por determinados períodos até que novas condições movam o sistema, de maneira surpreendente, a um novo limiar. O processo de crescimento do sistema urbano seria, assim, sujeito às variações de densidades populacionais e das localizações dos diferentes serviços urbanos e suas externalidades econômicas existentes na cidade. A averiguação e os comportamentos destas forças foram testados em uma situação real, na cidade de Santa Maria – RS. Os dados populacionais e dos serviços urbanos foram espacializados recorrendo a um Sistema de Informação Geográfica – SIG e suas interações avaliadas com o uso de medidas configuracionais urbanas. Espera-se, com isso, contribuir para a consolidação do conhecimento da dinâmica urbana e das condições dos diversos estados do sistema urbano. / At different times, researchers have investigated and proposed, with relative success, locational models that explain the origin and the processes of urban growth, but, often, failing to account for the complexity of these systems. Recently, the theories of Complex Systems, New Economic Geography and Urban Configurational Models, have provided concepts with a more consistent rationale for checking variables and the spatial interactions that identify these processes. The Complex Systems framework has provided the concepts of resiliency and self-organized criticality, whereas New Economic Geography has furnished the center-periphery model, which aids in understanding economic and population agglomerations. These approaches support the hypothesis that the relative location of urban services and residents in the intraurban space is subject to centripetal and centrifugal forces, which generate tensions that lead the system toward critical levels for determined periods until new conditions move the system, unexpectedly, to a new threshold. The growth process of the urban system is thus subject to variations in population density and in localization of the different urban services and their economic externalities that exist in the city. The behaviors of these forces were tested in a real situation, in the city of Santa Maria, RS. Population and urban services data were spatialized using a Geographic Information System – GIS and their interactions were evaluated with the use of urban configurational measures to contribute to our knowledge of urban dynamics and the conditions of the various states of the urban system.

Em distintos momentos da história, pesquisadores investigaram e propuseram, com relativo sucesso, modelos locacionais que explicassem a origem e os processos dos crescimentos das cidades, mas, de modo frequente, esbarrando na complexidade desses sistemas. Recentemente, apoiados nas teorias sobre Sistemas Complexos, Nova Geografia Econômica e Modelos Configuracionais Urbanos, alguns conceitos proporcionam uma fundamentação mais consistente para a verificação das variáveis e suas interações espaciais, as quais identifiquem esses processos. Dentre os sistemas complexos, são representativos os conceitos sobre a resiliência e a criticalidade auto-organizada enquanto os conceitos do modelo centro-periferia, propostos pela nova geografia econômica, contribuem para compreensão das formações de aglomerações econômicas e populacionais. Tais abordagens conduzem ao desenvolvimento da hipótese de que a localização relativa dos serviços urbanos e dos moradores, no espaço intraurbano, estaria condicionada a duas forças que se contrapõem, “centrípeta e centrífuga”, que são geradoras de “tensões” as quais conduzem o sistema a atingir níveis críticos por determinados períodos até que novas condições movam o sistema, de maneira surpreendente, a um novo limiar. O processo de crescimento do sistema urbano seria, assim, sujeito às variações de densidades populacionais e das localizações dos diferentes serviços urbanos e suas externalidades econômicas existentes na cidade. A averiguação e os comportamentos destas forças foram testados em uma situação real, na cidade de Santa Maria – RS. Os dados populacionais e dos serviços urbanos foram espacializados recorrendo a um Sistema de Informação Geográfica – SIG e suas interações avaliadas com o uso de medidas configuracionais urbanas. Espera-se, com isso, contribuir para a consolidação do conhecimento da dinâmica urbana e das condições dos diversos estados do sistema urbano. / At different times, researchers have investigated and proposed, with relative success, locational models that explain the origin and the processes of urban growth, but, often, failing to account for the complexity of these systems. Recently, the theories of Complex Systems, New Economic Geography and Urban Configurational Models, have provided concepts with a more consistent rationale for checking variables and the spatial interactions that identify these processes. The Complex Systems framework has provided the concepts of resiliency and self-organized criticality, whereas New Economic Geography has furnished the center-periphery model, which aids in understanding economic and population agglomerations. These approaches support the hypothesis that the relative location of urban services and residents in the intraurban space is subject to centripetal and centrifugal forces, which generate tensions that lead the system toward critical levels for determined periods until new conditions move the system, unexpectedly, to a new threshold. The growth process of the urban system is thus subject to variations in population density and in localization of the different urban services and their economic externalities that exist in the city. The behaviors of these forces were tested in a real situation, in the city of Santa Maria, RS. Population and urban services data were spatialized using a Geographic Information System – GIS and their interactions were evaluated with the use of urban configurational measures to contribute to our knowledge of urban dynamics and the conditions of the various states of the urban system.

Modelos e teorias científicas surgem da necessidade do homem entender melhor o funcionamento do mundo em que vive. Constantemente, novos modelos e técnicas são criados com esse objetivo. Uma dessas teorias recentemente desenvolvida é a da Criticalidade Auto-Organizada. No Capítulo 2 desta tese, apresentamos uma breve introdução a Criticalidade Auto-Organizada. Tendo a criticalidade auto-organizada como pano de fundo, no Capítulo 3, estudamos a dinâmica Bak-Sneppen (e diversas variantes) e a comparamos com alguns algoritmos de otimização. Apresentamos no Capítulo 4, uma revisão histórica e conceitual das redes complexas. Revisamos alguns importantes modelos tais como: Erdös-Rényi, Watts-Strogatz, de configuração e Barabási-Albert. No Capítulo 5, estudamos o modelo Barabási-Albert não-linear. Para este modelo, obtivemos uma expressão analítica para a distribuição de conectividades P(k), válida para amplo espectro do espaço de parâmetros. Propusemos também uma forma analítica para o coeficiente de agrupamento, que foi corroborada por nossas simulações numéricas. Verificamos que a rede Barabási-Albert não-linear pode ser assortativa ou desassortativa e que, somente no caso da rede Barabási-Albert linear, ela é não assortativa. No Capítulo 6, utilizando dados coletados do CD-ROM da revista Placar, construímos uma rede bastante peculiar -- a rede do futebol brasileiro. Primeiramente analisamos a rede bipartida formada por jogadores e clubes. Verificamos que a probabilidade de que um jogador tenha participado de M partidas decai exponencialmente com M, ao passo que a probabilidade de que um jogador tenha marcado G gols segue uma lei de potência. A partir da rede bipartida, construímos a rede unipartida de jogadores, que batizamos de rede de jogadores do futebol brasileiro. Nessa rede, determinamos várias grandezas: o comprimento médio do menor caminho e os coeficientes de agrupamento e de assortatividade. A rede de jogadores de futebol brasileiro nos permitiu analisar a evolução temporal dessas grandezas, uma oportunidade rara em se tratando de redes reais. / Models and scientific theories arise from the necessity of the human being to better understand how the world works. Driven by this purpose new models and techniques have been created. For instance, one of these theories recently developed is the Self-Organized Criticality, which is shortly introduced in the Chapter 2 of this thesis. In the framework of the Self-Organized Criticality theory, we investigate the standard Bak-Sneppen dynamics as well some variants of it and compare them with optimization algorithms (Chapter 3). We present a historical and conceptual review of complex networks in the Chapter 4. Some important models like: Erdös-Rényi, Watts-Strogatz, configuration model and Barabási-Albert are revised. In the Chapter 5, we analyze the nonlinear Barabási-Albert model. For this model, we got an analytical expression for the connectivity distribution P(k), which is valid for a wide range of the space parameters. We also proposed an exact analytical expression for the clustering coefficient which corroborates very well with our numerical simulations. The nonlinear Barabási-Albert network can be assortative or disassortative and only in the particular case of the linear Barabási-Albert model, the network is no assortative. In the Chapter 6, we used collected data from a CD-ROM released by the magazine Placar and constructed a very peculiar network -- the Brazilian soccer network. First, we analyzed the bipartite network formed by players and clubs. We find out that the probability of a footballer has played M matches decays exponentially with M, whereas the probability of a footballer to score G gols follows a power-law. From the bipartite network, we built the unipartite Brazilian soccer players network. For this network, we determined several important quantities: the average shortest path length, the clustering coefficient and the assortative coefficient. We were also able to analise the time evolution of these quantities -- which represents a very rare opportunity in the study of real networks.

Em distintos momentos da história, pesquisadores investigaram e propuseram, com relativo sucesso, modelos locacionais que explicassem a origem e os processos dos crescimentos das cidades, mas, de modo frequente, esbarrando na complexidade desses sistemas. Recentemente, apoiados nas teorias sobre Sistemas Complexos, Nova Geografia Econômica e Modelos Configuracionais Urbanos, alguns conceitos proporcionam uma fundamentação mais consistente para a verificação das variáveis e suas interações espaciais, as quais identifiquem esses processos. Dentre os sistemas complexos, são representativos os conceitos sobre a resiliência e a criticalidade auto-organizada enquanto os conceitos do modelo centro-periferia, propostos pela nova geografia econômica, contribuem para compreensão das formações de aglomerações econômicas e populacionais. Tais abordagens conduzem ao desenvolvimento da hipótese de que a localização relativa dos serviços urbanos e dos moradores, no espaço intraurbano, estaria condicionada a duas forças que se contrapõem, “centrípeta e centrífuga”, que são geradoras de “tensões” as quais conduzem o sistema a atingir níveis críticos por determinados períodos até que novas condições movam o sistema, de maneira surpreendente, a um novo limiar. O processo de crescimento do sistema urbano seria, assim, sujeito às variações de densidades populacionais e das localizações dos diferentes serviços urbanos e suas externalidades econômicas existentes na cidade. A averiguação e os comportamentos destas forças foram testados em uma situação real, na cidade de Santa Maria – RS. Os dados populacionais e dos serviços urbanos foram espacializados recorrendo a um Sistema de Informação Geográfica – SIG e suas interações avaliadas com o uso de medidas configuracionais urbanas. Espera-se, com isso, contribuir para a consolidação do conhecimento da dinâmica urbana e das condições dos diversos estados do sistema urbano. / At different times, researchers have investigated and proposed, with relative success, locational models that explain the origin and the processes of urban growth, but, often, failing to account for the complexity of these systems. Recently, the theories of Complex Systems, New Economic Geography and Urban Configurational Models, have provided concepts with a more consistent rationale for checking variables and the spatial interactions that identify these processes. The Complex Systems framework has provided the concepts of resiliency and self-organized criticality, whereas New Economic Geography has furnished the center-periphery model, which aids in understanding economic and population agglomerations. These approaches support the hypothesis that the relative location of urban services and residents in the intraurban space is subject to centripetal and centrifugal forces, which generate tensions that lead the system toward critical levels for determined periods until new conditions move the system, unexpectedly, to a new threshold. The growth process of the urban system is thus subject to variations in population density and in localization of the different urban services and their economic externalities that exist in the city. The behaviors of these forces were tested in a real situation, in the city of Santa Maria, RS. Population and urban services data were spatialized using a Geographic Information System – GIS and their interactions were evaluated with the use of urban configurational measures to contribute to our knowledge of urban dynamics and the conditions of the various states of the urban system.

A presente tese tem como objetivo produzir subsídios para a construção de um referencial teórico-metodológico sobre a utilização dos objetos de aprendizagem no contexto das comunidades virtuais auto-organizadas para a produção de software livre e de código aberto. Utiliza-se como metodologia a etnografia virtual (HINE, 2000) em conjunto com a teoria analítica da ação mediada (WERTSCH, 1991) e a análise de conteúdo (BARDIN, 2000). A coleta de dados foi efetuada, em duas fases, nos fóruns de discussão de quatro (4) comunidades, além de uma comunidade incubadora de desenvolvimento de projetos de software livre e de código aberto. Constata-se que os objetos de aprendizagem mediam o processo de solução de problemas, uma vez que 100% dos problemas da amostra analisada foram resolvidos, apesar da ausência de um padrão de conformidade desses objetos. Esta limitação é superada em razão do perfil específico imperante dos membros ativos da comunidade, pois estes possuem elevado nível de comportamento colaborativo/cooperativo, iniciativa voluntária, desprendimento, obstinação, capacidade de autoaprendizagem, autonomia, independência, disciplina, responsabilidade e comprometimento com prazos, qualidade dos produtos e outras exigências estabelecidas pela comunidade. Outro fator de relevância é que as comunidades são ricas em interação humana, o que qualifica o processo do significado da mediação e o ambiente de colaboração, nas ações referentes à localização, montagem e contextualização dos objetos de aprendizagem. Os significativos resultados atingidos por estas comunidades têm impactado, sobremaneira, as grandes organizações de produção de software, levando-as a rever suas estratégias corporativas, boas práticas de desenvolvimento, gestão de pessoas, equipes e projetos. Por outro lado, infere-se que a sustentabilidade de tais comunidades não pode estar assentada somente em atributos e habilidades pessoais, principalmente pelo fato de que a localização dos objetos de aprendizagem para a solução de problemas baseia-se no conhecimento tácito de seus membros. Necessário se faz agregar inovações na forma e funcionalidade de tais comunidades (padrão de conformidade, métodos e ferramentas tecnológicas), com vistas a possibilitar uma efetiva e universal acessibilidade do conhecimento produzido para a solução mais eficiente dos problemas, bem como incorporar membros com comportamentos e habilidades diversos. Os resultados desta pesquisa contribuem para as inovações futuras, no campo teórico e prático, na definição de um padrão de conformidade para a especificação, indexação, uso, combinação e avaliação dos objetos de aprendizagem, além de motivar a mudança de comportamento, cultura e forma de aprender. / The present thesis aims to produce subsidies for the development of a theoreticalmethodological referential on the use of learning objects in the context of self-organized virtual communities for the development of free and open source software. The methodologies used were the virtual ethnography (HINE, 2000), together with the mediated action analytical theory (WERTSCH, 1991) and content analysis (BARDIN, 2000). Data was collected in two phases: from the discussion forums of (4) four communities, and from an incubator community for the development of free and open source software projects. The learning objects appear to mediate the problem solution processes, since all the problems of the analyzed sample were solved, despite the lack of a standard of compliance of those objects. This limitation is overcome due to the specific dominant profile of the active members of the community, who display a high level of collaborative behavior, voluntary initiative, detachment, obstinacy, auto-learning capacity, autonomy, independence, discipline, responsibility and commitment to deadlines, product quality and other requirements established by the community. Another relevant aspect is that the communities are abundant in human interaction, what qualifies the mediation significance process and the collaborative environment in the actions referring to location, assembling and contextualization of the learning objects. The meaningful results obtained by those communities have led great software production organizations to review their corporate strategies, good developmental practices, staff, people and project management. On the other hand, it is inferred that the sustainability of those communities can not be maintained only by personal attributes and abilities, specially because the location of the learning objects for problem solution is based on the tacit knowledge of their members. It is necessary to aggregate innovation into the nature and functionality of those communities (standard compliance, technological methods and tools), to not only enable an effective and universal accessibility to knowledge leading to more efficient problem solution, but also to incorporate members with diverse behavior and abilities. The results of the present research contribute to future innovation in both theoretical and practical fields in the definition of a pattern of conformity for the specification, indexation, use, combination and evaluation of learning objects, in addition to motivating a change of behavior, culture and way of learning.

No description available.

Life presents fascinating examples of self-organization and emergent phenomena. In multi-cellular organisms, a multitude of cells interact to form and maintain highly complex body plans. This requires reliable communication between cells on various length scales. First, there has to be the right number of cells to preserve the integrity of the body and its size. Second, there have to be the right types of cells at the right positions to result in a functional body layout. In this thesis, we investigate theoretical feedback mechanisms for both self-organized body plan patterning and size control. The thesis is inspired by the astonishing scaling and regeneration abilities of flatworms. These worms can perfectly regrow their entire body plan even from tiny amputation fragments like the tip of the tail. Moreover, they can grow and actively de-grow by more than a factor of 40 in length depending on feeding conditions, scaling up and down all body parts while maintaining their functionality. These capabilities prompt for remarkable physical mechanisms of pattern formation. First, we explore pattern scaling in mechanisms previously proposed to describe biological pattern formation. We systematically extract requirements for scaling and highlight the limitations of these previous models in their ability to account for growth and regeneration in flatworms. In particular, we discuss a prominent model for the spontaneous formation of biological patterns introduced by Alan Turing. We characterize the hierarchy of steady states of such a Turing mechanism and demonstrate that Turing patterns do not naturally scale. Second, we present a novel class of patterning mechanisms yielding entirely self-organized and self-scaling patterns. Our framework combines a Turing system with our derived principles of pattern scaling and thus captures essential features of body plan regeneration and scaling in flatworms. We deduce general signatures of pattern scaling using dynamical systems theory. These signatures are discussed in the context of experimental data. Next, we analyze shape and motility of flatworms. By monitoring worm motility, we can identify movement phenotypes upon gene knockout, reporting on patterning defects in the locomotory system. Furthermore, we adapt shape mode analysis to study 2D body deformations of wildtype worms, which enables us to characterize two main motility modes: a smooth gliding mode due to the beating of their cilia and an inchworming behavior based on muscle contractions. Additionally, we apply this technique to investigate shape variations between different flatworm species. With this approach, we aim at relating form and function in flatworms. Finally, we investigate the metabolic control of cell turnover and growth. We establish a protocol for accurate measurements of growth dynamics in flatworms. We discern three mechanisms of metabolic energy storage; theoretical descriptions thereof can explain the observed organism growth by rules on the cellular scale. From this, we derive specific predictions to be tested in future experiments. In a close collaboration with experimental biologists, we combine minimal theoretical descriptions with state-of-the-art experiments and data analysis. This allows us to identify generic principles of scalable body plan patterning and growth control in flatworms. / Die belebte Natur bietet uns zahlreiche faszinierende Beispiele für die Phänomene von Selbstorganisation und Emergenz. In Vielzellern interagieren Millionen von Zellen miteinander und sind dadurch in der Lage komplexe Körperformen auszubilden und zu unterhalten. Dies verlangt nach einer zuverlässigen Kommunikation zwischen den Zellen auf verschiedenen Längenskalen. Einerseits ist stets eine bestimmte Zellanzahl erforderlich, sodass der Körper intakt bleibt und seine Größe erhält. Anderseits muss für einen funktionstüchtigen Körper aber auch der richtige Zelltyp an der richtigen Stelle zu finden sein. In der vorliegenden Dissertation untersuchen wir beide Aspekte, die Kontrolle von Wachstum sowie die selbstorganisierte Ausbildung des Körperbaus. Die Dissertation ist inspiriert von den erstaunlichen Skalierungs- und Regenerationsfähigkeiten von Plattwürmern. Diese Würmer können ihren Körper selbst aus winzigen abgetrennten Fragmenten -wie etwa der Schwanzspitze- komplett regenerieren. Darüberhinaus können sie auch, je nach Fütterungsbedingung, um mehr als das 40fache in der Länge wachsen oder schrumpfen und passen dabei alle Körperteile entsprechend an, wobei deren Funktionalität erhalten bleibt. Diese Fähigkeiten verlangen nach bemerkenswerten physikalischen Musterbildungsmechanismen. Zunächst untersuchen wir das Skalierungsverhalten von früheren Ansätzen zur Beschreibung biologischer Musterbildung. Wir leiten daraus Voraussetzung für das Skalieren ab und zeigen auf, dass die bekannten Modelle nur begrenzt auf Wachstum und Regeneration von Plattwürmern angewendet werden können. Insbesondere diskutieren wir ein wichtiges Modell für die spontane Entstehung von biologischen Strukturen, das von Alan Turing vorgeschlagen wurde. Wir charakterisieren die Hierarchie von stationären Zuständen solcher Turing Mechanismen und veranschaulichen, dass diese Turingmuster nicht ohne weiteres skalieren. Daraufhin präsentieren wir eine neuartige Klasse von Musterbildungsmechanismen, die vollständig selbstorgansierte und selbstskalierende Muster erzeugen. Unser Ansatz vereint ein Turing System mit den zuvor hergeleiteten Prinzipien für das Skalieren von Mustern und beschreibt dadurch wesentliche Aspekte der Regeneration und Skalierung von Plattwürmern. Mit Hilfe der Theorie dynamischer Systeme leiten wir allgemeine Merkmale von skalierenden Mustern ab, die wir im Hinblick auf experimentelle Daten diskutieren. Als nächstes analysieren wir Form und Fortbewegung der Würmer. Die Auswertung des Bewegungsverhaltens, nachdem einzelne Gene ausgeschaltet wurden, ermöglicht Rückschlüsse auf die Bedeutung dieser Gene für den Bewegungsapparat. Darüber hinaus wenden wir eine Hauptkomponentenanalyse auf die Verformungen des zweidimensionalen Wurmkörpers während der natürlichen Fortbewegung an. Damit sind wir in der Lage, zwei wichtige Fortbewegungsstrategien der Würmer zu charakterisieren: eine durch den Zilienschlag angetriebene gleichmässige Gleitbewegung und eine raupenartige Bewegung, die auf Muskelkontraktionen beruht. Zusätzlich wenden wir diese Analysetechnik auch an, um Unterschiede in der Gestalt von verschiedenen Plattwurmarten zu untersuchen. Grundsätzlich zielen alle diese Ansätze darauf ab, das Aussehen der Plattwürmer mit den damit verbundenen Funktionen verschiedener Körperteile in Beziehung zu setzen. Schlussendlich erforschen wir den Einfluss des Stoffwechsels auf den Zellaustausch und das Wachstum. Dazu etablieren wir Messungen der Wachstumsdynamik in Plattwürmern. Wir unterscheiden drei Mechanismen für das Speichern von Stoffwechselenergie, deren theoretische Beschreibung es uns ermöglicht, das beobachtete makroskopische Wachstum des Organismus mit dem Verhalten der einzelnen Zellen zu erklären. Basierend darauf leiten wir Vorhersagen ab, die nun experimentell getestet werden. In enger Zusammenarbeit mit Kollegen aus der experimentellen Biologie führen wir minimale theoretische Beschreibungen mit modernsten Experimenten und Analysetechniken zusammen. Dadurch sind wir in der Lage, Grundlagen sowohl der skalierbaren Ausbildung des Körperbaus als auch der Wachstumskontrolle bei Plattwürmern herauszuarbeiten.

L’émergence de la complexité, et de la vie en particulier, demeure l’une des énigmes les plus complexes pour la science moderne. Des travaux récents ont souligné la pertinence d’un apport de la physique statistique et de la théorie des phénomènes critiques — et en particulier de la théorie des phénomènes à criticalité auto-régulée — relativement à ces champs d’intérêt, tout autant que du rôle des phénomènes de coopération biochimique dans les premiers instants du vivant. La description des mécanismes par lesquels la vie a pu apparaître est par ailleurs d’un intérêt pratique pour l’astrophysique, puisque notre compréhension de ceux-ci module la manière dont l’analyse de biosignatures s’effectue dans le cadre de la recherche de la vie ailleurs dans l’Univers. L’analyse proposée ici porte sur un modèle en théorie des jeux permettant d’étudier les phénomènes de coopération implémenté dans un contexte spatial servant à émuler la dynamique d’un système ayant pu voir apparaître la vie. Une analyse de l’espace des paramètres du modèle révèle que celui-ci affiche des phénomènes de transition de phase et d’auto-organisation de structures spatiales, ces éléments se révélant des adjuvants à l’émergence de la coopération entre joueurs a priori égoïstes, dans un contexte qui à prime abord n’est pas d’emblée favorable à l’apparition de comportements coopératifs. Les résultats obtenus ici semblent supporter que la coopération biochimique puisse apparaître via un phénomène de transition de phase et que le modèle sous-jacent de dilemme du prisonnier itéré sur réseau présenté ici agit comme un système à criticalité autorégulée. / The emergence of complexity, and of life more specifically, is still one of the most intractable conundrums for modern science. Recent work emphasized the relevance of statistical physics and critical phenomena theory’s contribution to those questions — especially of self-organized criticality theory — just as much as the role of biochemical cooperation in life’s first moments. Moreover, the description of the mechanisms by which life could have appeared is of particular interest for astrophysics, because our comprehension of those mechanisms influences how biosignatures are analyzed in the context of the search for life elsewhere in the Universe. The analysis presented here concerns a model in game theory that allows to study cooperation phenomena — implemented in spatial context as to emulate the dynamics of a system in which life could have appeared. An analysis of the model’s parameter space reveals that it displays phase transition and self-organization of spatial structures phenomenon, those elements being adjuvants to the emergence of cooperation between a priori egoist players, in a context that is initially not favorable to the emergence of cooperative behavior. The results obtained here thus seem to support the idea that both biochemical cooperation can emerge through phase transition phenomena, and that the underlying lattice iterated prisoner’s dilemma model used here behaves like a self-organized critical system.

La préservation de l’environnement et des ressources naturelles pour les prochaines générations est aujourd’hui considérée comme un des axes les plus prioritaires dans presque tous les secteurs économiques. Le secteur des Technologies de l’Information et de la Communication est loin d’être épargné de cette tendance écologique. Nous considérons dans cette thèse la problématique de la conservation d’énergie dans le contexte technologique actuel caractérisé par: • La coexistence d’une multitude de technologies d’accès sans fil offrant un environnement riche et dynamique • Des terminaux mobiles multimodaux • Limitations persistantes des sources d’énergie sur les terminaux mobiles. Dans ce contexte très riche, les possibilités offertes aux usagers sont à double tranchant. D’un côté, elles peuvent très bien améliorer la QoS en offrant toujours la meilleure connectivité en fonction du contexte de l’utilisateur. D’un autre côté, et sans une bonne optimisation de la consommation d’énergie sur le terminal, la disponibilité de celui-ci peut vite diminuer et donc faire baisser la QoE à cause de l’énergie nécessaire pour gérer plusieurs interfaces radio en parallèle. Nous considérons essentiellement les liens entre les stations de base (ou les point d’accès) et les terminaux mobiles. Notre objectif étant d’analyser la consommation d’énergie sur ces liens pour ensuite proposer des contributions permettant de mieux la maitriser. Nous focalisons essentiellement sur l’exploitation des multiples interfaces et du multi-flux pour étudier, analyser et proposer des solutions dynamiques et adaptatives d’ordonnancement, de sélection et de gestion d’interfaces minimisant la consommation d’énergie / Since the last decades, environmental issues are becoming among the major concerns for most human activities, including the Information and Communication Technologies sector. This will surely influence upcoming networking technologies, architectures and usage practices. New approaches and methodologies are required in order to evaluate and to reduce the Carbon Footprint toward what is commonly denoted as Green Networks. Within the ICT sector, the main efforts are related to energy saving techniques. These efforts started in early stages within wireless technologies, mainly because of energy limitations on mobile devices such as mobile phones and wireless sensors. Additionally, because of health considerations, standardization bodies and government had set stringent policies and limits on electromagnetic radiation levels that can be emitted by radio stations. For these reasons, many academic and industrial research and development activities had led to a number of relatively energy efficient solutions. In this thesis, we consider energy efficiency in the context of Heterogeneous Wireless Access Networks. These are composed of multi-standards wireless network solutions, with non uniform topologies and cell sizes and Multi-Modal mobile terminals able to manage simultaneously different connections. The main contributions of our studies include the proposal of new optimization solutions regarding user association and scheduling techniques at both flow and packet levels for multi-homed mobile terminals. An overall context-based solution is also proposed in order to provide end-to-end energy efficient networking solutions

Self-organization is a hot topic as it has the potential to create surface patterns on the nanoscale avoiding cost-intensive top-down approaches. Although chemists have promising results in this area, ion irradiation can create self-organized surface patterns in a more controlled manner. Different regimes of pattern formation under ion irradiation were described so far by 2D models. Here, two new regimes have been studied experimentally, which require modeling in 3D: subsurface point defect kinetics as well as ion impact-induced melt pool formation. This thesis deals with self-organized pattern formation on Ge and Si surfaces under normal incidence irradiation with heavy monatomic and polyatomic ions of energies up to several tens of keV. Irradiation has been performed using liquid metal ion sources in a focused ion beam facility with mass-separation as well as by conventional broad beam ion implantation. Irradiated samples have been analyzed mainly by scanning electron microscopy. Related to the specific irradiation conditions, investigation and discussion of pattern formation has been divided into two parts: (i) formation of Ge morphologies due to point defect kinetics and (ii) formation of Ge and Si morphologies due to melt pool dynamics. Point defect kinetics dominates pattern formation on Ge under irradiation with monatomic ions at room temperature. Irradiation of Ge with Bi and Ge ions at fluences up to 10^17 cm^(-2) has been performed. Comprehensive studies show for the first time that morphologies change from flat surfaces over hole to nanoporous, sponge-like patterns with increasing ion energy. This study is consistent with former irradiations of Ge with a few ion energies. Based on my studies, a consistent, qualitative 3D model of morphology evolution has been developed, which attributes the ion energy dependency of the surface morphology to the depth dependency of point defect creation and relaxation. This model has been proven by atomistic computer experiments, which reproduce the patterns found in real irradiation experiments. At extremely high energy densities deposited by very heavy ions another mechanism dominates pattern formation. The formation of Ge and Si dot patterns by very heavy, monatomic and polyatomic Bi ion irradiation has been studied in detail for the first time. So far, this formation of pronounced dot pattern cannot be explained by any model. Comprehensive, experimental studies have shown that pattern formation on Ge is related to extremely high energy densities deposited by each polyatomic ion locally. The simultaneous impact of several atoms leads to local energy densities sufficient to cause local melting. Heating of Ge substrates under ion irradiation increases the achievable energy density in the collision cascade substantially. This prediction has been confirmed experimentally: it has been found that the threshold for nanomelting can be lowered by substrate heating, which allows pattern formation also under heavy, monatomic ion irradiation. Extensive studies of monatomic Bi irradiation of heated Ge have shown that morphologies change from sponge-like over highly regular dot patterns to smooth surfaces with increasing substrate temperature. The change from sponge-like to dot pattern is correlated to the melting of the ion collision cascade volume, with energy densities sufficient for melt pool formation at the surface. The model of pattern formation on Ge due to extremely high deposited energy densities is not specific to a single element. Therefore, Si has been studied too. Dot patterns have been found for polyatomic Bi ion irradiation of hot Si, which creates sufficiently high energy densities to allow ion impact-induced melt pool formation. This proves that pattern formation by melt pool formation is a novel, general pattern formation mechanism. Using molecular dynamics simulations of project partners, the correlation between dot patterning and ion impact-induced melt pool formation has been proven. The driving force for dot pattern formation due to high deposited energy densities has been identified and approximated in a first continuum description.