Apesar de vários estudos terem demonstrado que a presença de abelhas resulta em aumento da produtividade de culturas agrícolas, os mecanismos que determinam a eficácia da polinização em escalas espaciais mais amplas ainda são desconhecidos. Avaliamos a influência da composição e configuração da paisagem sobre a composição da comunidade de abelhas e a polinização do café (Coffea arábica). Nosso estudo foi realizado em uma das regiões cafeeiras mais importantes do Brasil, em nove paisagens compostas de cafezais e diferentes quantidades de remanescentes de Mata Atlântica. Utilizando experimentos de exclusão floral, avaliamos a polinização em 15 pés de café por paisagem. A eficiência da polinização foi medida através da contagem e pesagem dos frutos formados. Também coletamos e identificamos os visitantes florais. Nossas análises foram feitas no nível de paisagem, com 1 e 2 km de raio, e no nível do pé de café, com 300 m de raio em torno de cada árvore. Foram coletados 241 indivíduos de abelhas e identificadas um total de 22 espécies. A abelha Apis mellifera (Apini) foi a espécie mais abundante, seguida de Trigona spinipes (Meliponini). A abundância A. mellifera foi afetada pela composição da matriz na paisagem e a composição da comunidade de abelhas nativas mudou com a distância ao fragmento florestal mais próximo. A presença das abelhas, por sua vez, resultou em um aumento 28% na produção de frutos. A abundância de A. mellifera afetou positivamente a frutificação, enquanto a composição da comunidade de abelhas nativas afetou a frutificação de modo diferente no nível da paisagem e do pé de café. Nossos resultados indicam que a estrutura da paisagem afeta a composição da comunidade de visitantes florais e que as flores expostas às abelhas apresentam um aumento na frutificação. Embora nossos resultados não permitam separar claramente os mecanismos responsáveis pelo aumento observado na frutificação, nosso trabalho mostra que o serviço de polinização das abelhas pode ser afetado pela estrutura da paisagem. Estes resultados podem ser utilizados na conservação e planejamento agrícola a fim de maximizar a produção de culturas e, ao mesmo tempo, conservar a biodiversidade e o serviço de polinização. / Although several studies have shown that the presence of bees results in increased crop yields, the mechanisms that determine pollination effectiveness on broader spatial scales are still largely unknown. We evaluated the influence of landscape composition and configuration over bee community composition and coffee (Coffea Arabica) pollination. Our study was undertaken in one of the most important coffee-producing regions of Brazil, and comprised nine landscapes of sun coffee plantations surrounded by different amounts of Atlantic Forest remnants. Using floral exclusion experiments we evaluated pollination effectiveness in 15 coffee trees per landscape. Pollination effectiveness was measured by counting and weighing the fruit set. We also sampled the bees visiting coffee flowers. Our analyses were made at the landscape level, with 1 and 2 km radii, and at the coffee tree level, with 300 m radius around each tree. We collected 241 bee individuals and identified a total of 22 species. The honeybee Apis mellifera (Apini) was the most abundant species followed by Trigona spinipes (Meliponini). Honeybee abundance was affected by landscape matrix composition while native bee community composition changed with distance to the nearest forest fragment. The presence of bees resulted in an increase in coffee fruit set of 28%. A. mellifera abundance positively affected fruit set at both levels, while the composition of the native bee community affected fruit set differently at the landscape level than at the tree level. Landscape structure was found to affect the community composition of floral visitors, and coffee flowers exposed to bees showed an increase in fruit set compared to flowers excluded from pollinators. Although our results do not allow disentangling the mechanisms responsible for the observed increase in fruit set, our work shows that bee pollination services can be affected by landscape structure. These findings can be used in conservation and agricultural planning to maximize crop production while safeguarding biodiversity and the provision of pollination services.

Le cancer est une pathologie caractérisée par la transformation de cellules de l'organisme, et leur prolifération incontrôlée aux dépens de l'organisme. Elle peut toucher tout tissu de l'organisme, et menacer la survie des patients à terme. Ce phénomène est souvent interprété comme une dégénérescence de l'organisme au cours du vieillissement, mais ce paradigme ne suffit pas à embrasser toute la complexité de cette maladie. En effet, la progression cancéreuse est basée sur des mutations qui nourrissent une prolifération différentielle des cellules, et elle peut donc être décrite par une dynamique écologique et évolutive. En outre, les manifestations du cancer sont extrêmement répandues dans tout le vivant, et peuvent être attribuées à l'émergence des organismes multicellulaires il y a un milliard d'années. Le cancer a donc toujours représenté une contrainte sur l'évolution des organismes. La compréhension globale du cancer nécessite donc d'élucider comment les dynamiques éco-évolutives intra- et inter-organisme s'influencent mutuellement au cours des temps évolutifs. A l'aide de conceptualisation et d'approches théoriques, nous montrons qu'une approche multi-échelle offre de nouvelles perspectives sur les processus écologiques et évolutifs impliqués dans le cancer. A l'échelle intra-tumorale, nous nous concentrons sur les interactions entre cellules cancéreuses et au rôle structurant que ces interactions peuvent avoir dans les écosystèmes tumoraux. Nous montrons notamment que la fréquence des interactions diminue la diversité clonale durant l'expansion tumorale. A l'échelle populationnelle, nous formulons et explorons une hypothèse sur l'origine de la forte fréquence des cancers héréditaires : les défenses anti-cancer sélectionnées dans les environnements cancérogènes pourraient compenser la progression cancéreuse, et donc autoriser la persistance d'allèles pro-oncogéniques à l'équilibre mutation-dérive. Nous considérons enfin les interactions réciproques entre évolution des organismes et évolution des cellules cancéreuses : spécifiquement l'évolution emboîtée de la résistance et de la tolérance au cancer, et l'évolution de stratégies de manipulation de l'hôte chez les cellules cancéreuses. Nous montrons notamment que l'évolution intra-individuelle favorise la tolérance, tandis que l'évolution inter-individuelle favorise la résistance. / Cancer is a pathology characterized by organism cell transformation and uncontrolled cell proliferation at the expense of the organism. It can affect any tissue in the organism, and can eventually threaten patient survival. This phenomenon is commonly viewed as the result of organism decay during ageing, yet this paradigm fails to embrace the whole complexity of this disease. Cancer progression indeed relies on mutations which fuel differential cell proliferation, and thus it can be described by ecological and evolutionary dynamics. Besides, cancer manifestations are widespread across living organisms, and may be due to the emergence of multicellularity a billion years ago. Cancer has thus always constrained the evolution of organisms. How intra- and inter-organism eco-evolutionary dynamics influence each other across evolutionary times must be investigated to fully understand cancer. Through conceptualization and theoretical approaches, we show that a multi-scale approach offers novel prospects on ecological and evolutionary processes involved in cancer. At intratumor scale, we focus on interactions between cancer cells and on how these interactions structure tumor ecosystems. We notably find that frequent interactions yields lower clonal diversity during tumor expansion. At the population scale, we aim to explain the origins of highly frequent hereditary cancers. We thus hypothesize that pro-oncogenic alleles may neutrally evolve in certain contexts: anti-cancer defenses that are selected in carcinogenic environments may actually compensate cancer progression, and thus allow pro-oncogenic alleles to persist at mutation-drift equilibrium. We finally explore the reciprocal interactions between organism evolution and cancer evolution: especially, we use a nested approach to predict the evolution of resistance and tolerance to cancer, and then we suggest that cancer cells may evolve host manipulation strategies. We notably find that intra-individual evolution favors tolerance over resistance, whereas inter-individual evolution rather favors resistance.

A Bacia Amazônica é compartilhada por sete países (Bolívia, Brasil, Colômbia, Equador, Guiana, Peru e Venezuela) e tem sido foco de diversos projetos de infraestrutura e de atividades de exploração econômica que causam contaminação e degradação, demonstrando a necessidade de governança e gestão de seus recursos hídricos. Este trabalho busca compreender a governança multi-escalar como forma de regulação do uso dos recursos hídricos transfronteiriços na Bacia Amazônica, por meio da análise das ações dos Estados e demais atores sociais em duas bacias compartilhadas: a Bacia do rio Acre e a Bacia do rio Napo. A governança de uma bacia transfronteiriça envolve diversos atores sociais na escala local, nacional e internacional que deveriam coordenar suas ações no intuito de regular o uso da água. Na escala local encontram-se as regiões de fronteira onde foram estudas a governança na bacia do rio Acre e na bacia do rio Napo. Na escala nacional buscou-se compreender o arcabouço institucional para a gestão dos recursos hídricos na Bolívia, no Brasil, no Equador e no Peru, pois são os países que compartilham as duas bacias estudadas. Na escala internacional foram analisadas as instituições regionais que abarcam os países amazônicos e desenvolvem projetos que influenciam a governança dos recursos hídricos transfronteiriços na Bacia Amazônica, em especial nas bacias do Acre e do Napo. Ao analisar a cooperação entre os Estados e entre os demais atores sociais envolvidos na regulação do uso dos recursos hídricos transfronteiriços nas diferentes escalas geográficas que se sobrepõem na Bacia Amazônica demonstrou-se que apesar da existência de cooperação nas bacias analisadas a governança ainda é incipiente. Portanto, a cooperação não é o único fator que garante a emergência de um processo de governança dos recursos hídricos transfronteiriços na Amazônia. / Amazon River Basin is shared by seven countries (Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela) and has been the focus of infrastructure projects and economic activities that cause contamination and degradation demonstrating need for water resources governance and management. This work aims to comprehend the multi-scalar governance, understood as a mean for regulating the use of transboundary water resources, in the Amazon Basin analyzing actions taken by states and other social actors in two shared basins: the Acre River Basin and the Napo River Basin. Transboundary river basin governance involves different social actors in local, national and international scales that must coordinate their actions in order to regulate water use. Border regions are located at the local scales where the Acre River Basin and the Napo River Basin were studied. At the national scale it was analyzed the institutional framework of water resources management in Bolivia, Brazil, Ecuador and Peru, which are the countries that share the two river basins studied. At the international scale it was analyzed the cooperation and regional institutions of Amazon countries that have projects in the Amazon Basin which influence water governance in the basin, especially in the Basins of Rivers Napo and Acre. By analyzing the cooperation among Amazon countries and other social actors involved in the regulation of transboundary water resources uses in different scales overlapped in the Amazon Basin, this study demonstrated that despite the existence of cooperation in the basins analyzed, water governance is still incipient. Therefore, cooperation is not the only factor that ensures the emergence of a process of transboundary water resources governance in the two River Basins studied.

Les propriétés effectives mécaniques et physiques des matériaux hétérogènes dépendent d'une part de leurs constituants, mais peuvent également être fortement modifiées par leur répartition géométrique à l'échelle de la microstructure. L'optimisation topologique a pour but de définir la répartition optimale de matière dans une structure en vue de maximiser un ou plusieurs objectifs tels que les propriétés mécaniques sous des contraintes telles que la masse de matière. Récemment, les développements rapides de l'impression 3D ou d'autres techniques de fabrication additive ont rendu possible la fabrication de matériaux avec des microstructures "à la demande", ouvrant de nouvelles perspectives inédites pour la conception de matériaux. Dans ce contexte, les objectifs de cette thèse sont de développer des outils de modélisation et de simulation numériques pour concevoir des matériaux et des structures hétérogènes ayant des propriétés optimisées basés sur l'optimisation topologique. Plus précisément, nous nous intéressons aux points suivants. Premièrement, nous proposons des contributions à l'optimisation topologique à une seule échelle. Nous présentons tout d'abord une nouvelle méthode d'optimisation topologique avec évolution pour la conception de structures continues par description lisse de bords. Nous introduisons également deux techniques d'homogénéisation topologique pour la conception de microstructures possédant des propriétés effectives extrêmes et des « méta propriétés » (coefficient de Poisson négatif).Dans une seconde partie, des techniques multi échelle basées sur l'optimisation topologique sont développées. Nous proposons d'une part une approche concourante de structures hétérogènes dont les microstructures peuvent posséder plus de deux matériaux. Nous développons ensuite une approche d'optimisation topologique dans un cadre d'homogénéisation pour des échelles faiblement séparées, induisant des effets de gradient. Enfin dans une troisième partie, nous développons l'optimisation topologique pour maximiser la résistance à la fracture de structures ou de matériaux hétérogènes. La méthode de champs de phase pour la fracture est combinée à la méthode BESO pour concevoir des microstructures permettant d'augmenter fortement la résistance à la rupture. La technique prend en compte l'initiation, la propagation et la rupture complète de la structure / Mechanical and physical properties of complex heterogeneous materials are determined on one hand by the composition of their constituents, but can on the other hand be drastically modified by their microstructural geometrical shape. Topology optimization aims at defining the optimal structural or material geometry with regards to specific objectives under mechanical constraints like equilibrium and boundary conditions. Recently, the development of 3D printing techniques and other additive manufacturing processes have made possible to manufacture directly the designed materials from a numerical file, opening routes for totally new designs. The main objectives of this thesis are to develop modeling and numerical tools to design new materials using topology optimization. More specifically, the following aspects are investigated. First, topology optimization in mono-scale structures is developed. We primarily present a new evolutionary topology optimization method for design of continuum structures with smoothed boundary representation and high robustness. In addition, we propose two topology optimization frameworks in design of material microstructures for extreme effective elastic modulus or negative Poisson's ratio. Next, multiscale topology optimization of heterogeneous materials is investigated. We firstly present a concurrent topological design framework of 2D and 3D macroscopic structures and the underlying three or more phases material microstructures. Then, multiscale topology optimization procedures are conducted not only for heterogeneous materials but also for mesoscopic structures in the context of non-separated scales. A filter-based nonlocal homogenization framework is adopted to take into account strain gradient. Finally, we investigate the use of topology optimization in the context of fracture resistance of heterogeneous structures and materials. We propose a first attempt for the extension of the phase field method to viscoelastic materials. In addition, Phase field methods for fracture able to take into account initiation, propagation and interactions of complex both matrix and interfacial micro cracks networks are adopted to optimally design the microstructures to improve the fracture resistance

La dentine est l’un des principaux éléments constitutifs de la dent humaine. Elle montre une structure hiérarchique. A l’échelle microscopique, la dentine est composée de tubules (porosité naturelle du tissu), de dentine péritubulaire et de dentine intertubulaire.L’organisation de ces structures détermine fortement ses propriétés mécaniques. La connaissance de sa structure, de ses propriétés mécaniques et de ses déformations dues aux variations de l’environnement extérieur peuvent être utiles afin d’améliorer les protocoles de restauration de la dentine. Dans ce travail, quatre techniques d’observation (µCT, microscope optique, ESEM et microscope confocal) ont été explorées et comparées. En particulier, la microscopie confocale a été utilisée afin de visualiser en 3D le réseau poreux dentinaire. Comparée à l’observation 2D, elle permet d’obtenir des informations supplémentaires. Par example, les tubules montrent des structures en arbre plus complexes près de l’email que la forme en Y déduite des observations 2D. Ces résultats peuvent également nous fournir des données d’entréespour une modélisation réaliste prenant en compte la structure poreuse complexe à l’intérieur de la dentine humaine.Par la suite, un test de compression associé à la correlation d’images numérique a été mis en place avec un système qui permet de commander simultanément l’humidité et la température de l’environnement. Grâce à ce dispositif, le module d’élasticité de la dentine humaine a été mesuré (16.7GPa avec un écart-type de 5.1GPa), et le coefficient de Poisson a été estimé à 0.31. Le comportement de dilatation de la dentine humaine avec l’humidité relative a été étudié. La spectroscopie par résonance ultrasonore (RUS) a été utilisée et ses résultats comparés au test de compression mécanique. À échelle microscopique, les propriétés mécaniquesde la dentine péritubulaire et de la dentine intertubulaire ont été caractérisées par nanoindentation. Les deux méthodes utilisées (méthode dynamique CSM et méthode de déchargement statique) indiquent les mêmes tendances en matière de module d’Young pour les deux composantes de la dentine. La dentine péritubulaire a un module d’élasticité plus élevé (26.7GPa avec un écart type de 3.1GPa) que la dentine intertubulaire (16.2GPa avec un écart type de 5.5GPa). De plus, le comportement en fluage de la dentine a été étudié par nanoindentation. Il se trouve qu’un modèle de Maxwell-Voigt à quatre éléments peut être utilisé pour évaluer le comportement en fluage de la dentine.Pour résumer, une étude morphologique et mécanique du tissu dentinaire a été effectuée. De nouvelles techniques, par example, la microscopie confocale ont été utilisées et ont montré leur utilité dans le but de donner un nouvel éclairage sur le tissu dentinaire. Les protocoles d’essais mécaniques qui ont été mis en place à différentes échelles permettront de mieux comprendre la relation structure-propriété en utilisant les outils d’observation validés dans ce travail. / Human dentin is one of the main components of human tooth. It shows a hierarchicalstructure from a multi-scale point of view. Generally speaking, dentin can be seen as a hard biomaterial consisting in 3 phases: the porous phase made of tubules, the inclusion phase made of peritubular dentin and the matrix phase made of intertubular dentin. These hierarchical structures strongly determine its mechanical properties. The knowledge of its structure, its mechanical property and its deformation behavior due to the variation of the external environment may be useful to improve the dentin restoration process. In this work, four observation techniques (µCT, optical microscope, ESEM and confocal microscope) have been used and compared. Particularly, confocal microscopy is proposed to allow 3D visualization of the complex dentin porous network. Compared with usual 2D observation tool, it may provide new information. For example, near the DEJ, tubules show a more complex treestructure than the Y-shaped deduced from 2D observations. These findings may also allow to achieve more realistic modeling considering the complex porous structure inside human dentin.Later on, compression test associated with DIC was carried out within an integrated system which can control simultaneously the humidity and the temperature of the environment. Using this system, the elastic modulus of human dentin was measured to be 16.7GPa with a standard deviation of 5.1GPa. And the Poisson’s ratio was found to be 0.31. The dilatation behavior of human dentin due to relative humidity was also explored. Furthermore, resonant ultrasound spectroscopy was performed in order to compare the results with these mechanical testing. At the micro-scale, the mechanical properties of peritubular dentin and intertubular dentin werecharacterized by nanoindentation. The two methods used in this work (dynamic CSM method and the static unload method) present the same trends of elastic moduli for the two components. Peritubular dentin has a higher elastic modulus (26.7GPa with a standard deviation of 3.1GPa) than intertubular dentin(16.2GPa with a standard deviation of 5.5GPa). Besides, the creep behavior of dentin was assessed by nanoindentation. Four elements Maxwell-Voigt model can be used to model dentin’s creep behavior.To sum up, a morphological and mechanical study of the dentinal tissue has been performed. New techniques, such as confocal microscopy have been used and showed their usefulness in order to give new insight into the dentinal tissue. The mechanical testing protocols that have been set up at different scales will enable to better understand the structure-property relationship by using them associated with the observation tools validated in this work.

The subject of this work is the development of accurate frameworks to describe the electrochemical promotion of catalysis (EPOC) phenomenon. EPOC, also known as non-Faradaic electrochemical modification of catalytic activity (NEMCA), refers to the enhancement of the catalytic performance by application of current or potential in a catalyst/support system. Although this technology is of increasing interest nowadays in the field of modern electrochemistry and exhibits a great industrial potential, there are still just a few commercial applications, partly because the addressed phenomenon is not fully understood and has not been modelled to allow robust system design and control. For this purpose, a systematic multi-dimensional, isothermal, dynamic model is developed to address the EPOC phenomenon using the electrochemical oxidation of CO over Pt/YSZ as an illustrative system. The formulated model is based on partial differential equations (PDEs) accounting for the simulation of the mass and charge transport as well as the electrochemical phenomena taking place at the triple phase boundaries (TPBs, where the gas phase, the catalyst and the support are all in contact) implemented through a commercial finite element method (FEM) software (COMSOL Multiphysics). The constructed model is used in conjunction with experimental data for parameter estimation purposes, and a validated model is obtained. The results demonstrate that the effect in such a system is strongly non-Faradaic, with Faradaic rates 3 orders of magnidute lower than the non-Faradaic ones. The formulated model is extended to describe the various processes taking place in the electrochemically promoted CO combustion system at their characteristic length-scales. The proposed framework couples a macroscopic model simulating charge transport as well as electrochemical phenomena occuring at the TPBs implemented through a FEM-package and an in-house developed efficient implementation of the kinetic Monte Carlo method (kMC) for the simulation of reaction-diffusion micro-processes on the catalyst. Dynamic communication of macro- and micro-scopic models at the TPBs results in the construction of an integrated multi-scale system. Comparison between the multi-scale framework and a fully macroscopic model is carried out for several sets of operating conditions and differences between the two models steady-state outputs are presented and discussed. A detailed FEM/kMC model, regardless of accurately simulating the several phenomena at their appropriate length-scales, might not be suitable for large system simulations due to the high computational demand. To address this limitation, a computationally efficient coarse-graining methodology, the so-called gap-tooth method, is implemented. In this scheme the catalytic surface is efficiently represented by a small subset of the spatial domain (tooth) separated by gaps. While kMC simulations within each individual tooth (micro-lattice) are used to predict the corresponding evolution of the micro-processes, intelligent interpolation rules are employed to allow for the exchange (diffusion) of species between consecutive micro-lattices. A validated gap-tooth/kMC scheme is obtained and it is exploited for FEM/gap-tooth/kMC electrochemically promoted CO oxidation simulations achieving high computational savings.

Flexible risers that carry hydrocarbon fuels from the subsea facilities to the floatation units above the sea surface are composed of multiple metallic and polymeric layers (in their wall). Among these layers, the tensile armour layer consists of several helically wound metallic wires; these tensile armour layers carry the weight of the riser, provide tensile stiffness & strength and maintain the structural integrity of the riser structure during harsh underwater currents. However, as the oil & gas fields in shallow waters are receding, the oil & gas industry is being forced to move towards deeper offshore waters, where the metallic tensile armour wires pose limitations (fatigue, corrosion, weight, etc.). In this thesis an alternative to metallic tensile armour wires will be presented in form of a flexible hybrid composite formed by stacking seven pultruded composite (carbon and vinyl-ester) circular rods in form of hexagonal pack, held together by an over-braid (Dyneema fibres) sleeve. The manufacturing process for hybrid composite tensile armour wires will be studied and their mechanical properties will be presented. A multi-scale finite element model developed for hybrid composite wires will be presented in this thesis to help further understand the mechanical properties of hybrid composite wires.

Plutonium Uranium Reduction EXtraction (PUREX) technology is a solvent extraction process used to recover plutonium and uranium from spent nuclear fuel. The solvent system is composed of an aqueous nitric acid phase in contact with an organic phase made up of tributyl phosphate in an organic diluent. During the separation process, the PUREX solvent system is subject to an intense multi-component radiation field (gamma rays, alpha particles, beta particles, neutrons, and fission fragments) rendering it susceptible to radiolytic degradation, which reduces its performance. Despite the PUREX process being used for over sixty years, a complete quantitative mechanistic understanding of the radiolytic degradation processes is not available. Nitrous acid is the most significant radiolytic degradation product of nitric acid, especially as its chemical and physical properties alter the formulation of the PUREX solvent system. Furthermore, nitrous acid exhibits complex redox relationships with a number of actinides, with plutonium being of greatest concern to the performance of the PUREX process. A combination of experimental and computational (stochastic and deterministic) techniques have been used to investigate the radiolysis of the PUREX solvent system's aqueous phase, specifically the radiolytic formation of nitrous acid, and its conjugate base nitrite, as a function of solvent system formulation, absorbed dose (up to 1.7 kGy), and radiation quality (cobalt-60 gamma rays and alpha particles from plutonium and americium alpha decay). The research presented in this thesis focuses on: (i) the experimental radiation chemistry of solutions of nitric acid and sodium nitrate over the range of concentrations 1 × 10-3 to 6 mol dm-3, and (ii) the development of a multi-scale modelling approach for evaluating the radiolysis of aqueous systems in terms of reaction mechanisms. The experimental and modelling studies provide insight into the radiation chemistry of the PUREX solvent system's aqueous phase, mechanistically demonstrating how the radiation chemical yield of nitrous acid and nitrite is dependent upon the interplay between non-homogeneous radiation track chemistry and secondary bulk homogeneous chemistry. This interplay is influenced by low pH, the presence of chemical scavengers and redox active metal ions, and radiation quality. These findings will act as a benchmark for the development of advanced reprocessing schemes, which must seriously consider how modifications in solvent system formulation and fuel composition may affect this dynamic interplay, and ultimately the generation of secondary highly active liquid waste.

La corrosion des aciers est l’une des principales causes de dégradation des ouvrages en béton armé, notamment en façade maritime. Cette dégradation est due à la diffusion d’ions chlorures qui peut se produire dans les ouvrages immergés dans l’eau de mer, ceux subissant des cycles de marnage et également ceux soumis aux embruns marins. La corrosion peut être également due au processus de carbonatation du béton, responsable de la baisse du pH et par conséquent de la dépassivation des aciers. Cette thèse propose un modèle physico-chimique pour décrire la penetration des agents agressifs dans la première phase de la corrosion des aciers. Cette phase dite « incubation » correspond à la phase pendant laquelle le transfert des espèces agressives se produit dans le béton. Afin d’identifier clairement les paramètres de transport de ce modèle macroscopique une démarche multi-échelle est mise en oeuvre pour rendre compte de la diffusion dans les bétons. Cette démarche repose sur une description détaillée de la microstructure du béton (constituants et morphologie) par des méthodes de changement d’échelle. Cette approche se veut la plus exhaustive possible avec la prise en compte explicite de l’influence du rapport eau sur liant de la pâte de ciment, des propriétés des granulats et de la zone de transition entre la pâte et les granulats. Après identification de tous les paramètres d’entrée, le modèle physico-chimique macroscopique est utilisé pour évaluer la durée de vie d’un béton soumis au couplage carbonatation -chlorures en milieu insaturé. Suite à une validation du modèle par comparaison à des résultats expérimentaux, plusieurs applications de ce modèle sont présentées. / The corrosion of steels is one of the principal causes of degradation of reinforced concrete structures, especially in front of the sea. This degradation is due to the diffusion of chloride ions that can occur in the structures immersed in the seawater, those undergoing tidal cycles and also those subjected to the sea spray. The corrosion can also be due to the carbonation process of the concrete, which is responsible for decreasing of the pH and consequently the depassivation of the steels. This thesis proposes a physicochemical model to describe the penetration of aggressive agents in the first period of steel corrosion. This so-called « incubation » period corresponds to the period during which the transfer of aggressive species occurs in the concrete. In order to clearly identify the transport parameters of thismacroscopic model, a multi-scale approach is implemented to consider the diffusion in concretes. This approach is based on taking into account the detailed description of the microstructure of the concrete (constituents and morphology) by upscaling methods. This multi-scale approach is intended to be the most comprehensive with the consideration of the influence of the water-to-binder ratio of the cement paste, the properties of the aggregates and the transition zone between the cement paste and the aggregates. After identifying all the input parameters, the macroscopic physico-chemical model is used to evaluate the service life of a concrete subjected to coupling carbonation -chlorides in unsaturated medium. Following a validation of the model compared to experimental results, several applications of this model are presented.

O controle biológico de pragas agrícolas é um dos serviços ecossistêmicos mais valorizados, dada sua importância para a produção agrícola. Embora vários estudos tenham demonstrado que a abundância e riqueza de predadores aumentam com a quantidade de floresta nativa, os mecanismos subjacentes que modulam a relação entre a cobertura florestal e provisão de controle biológico em diferentes escalas espaciais são ainda pouco conhecidos. Neste trabalho, utilizamos experimentos de exclusão de vertebrados voadores em oito paisagens cafeeiras na Mata Atlântica, num gradiente de cobertura florestal, e quantificamos as consequências para a perda foliar e para a frutificação. A perda foliar mostrou uma relação negativa com a cobertura florestal em paisagens com 2 km de raio, indicando que a herbivoria é melhor controlada em paisagens com alta cobertura florestal, especialmente na presença de aves e morcegos. No entanto, no nível local, 300 m ao redor das plantas de café, a perda foliar e a frutificação responderam diferentemente à cobertura florestal. Em unidades com baixa cobertura florestal local, a exclusão de aves e morcegos aumentou a perda foliar e diminuiu a frutificação em uma média de 13%. Por outro lado, em unidades com alta cobertura florestal local, a exclusão de aves e morcegos não teve efeitos significativos nem na perda foliar, nem na frutificação. Concluímos que os efeitos da exclusão de aves e morcegos na perda foliar e frutificação são modulados por diferentes processos que ocorrem no nível local e da paisagem. Sugerimos que quando a cobertura florestal local é alta (geralmente perto de fragmentos florestais), as aves e os morcegos não se alimentam apenas de herbívoros, mas também de mesopredadores. No entanto, quando a cobertura florestal local é baixa (e.g. longe de fragmentos florestais), os mesopredadores não ocorrem e aves e morcegos passam a prover serviço de controle biológico de pragas, alimentando-se principalmente de herbívoros. Destacamos a importância de empregar uma análise multiescalar em sistemas onde espécies com diferentes capacidades de dispersão proveem um serviço ecossistêmico. / Biological control of agricultural pests is one of the most important ecosystem services given its key role for agricultural production. Although several studies have shown that the abundance and richness of predators increase with the amount of native forest in the landscape, the underlying mechanisms relating forest cover at different spatial scales with the provision of biological control are still poorly understood. We experimentally excluded flying vertebrates (birds and bats) in eight coffee landscapes in the Brazilian Atlantic Forest, encompassing a gradient of forest cover and quantified the consequences for coffee leaf loss and fruit set. Leaf loss showed a negative relation with forest cover at landscape level, in landscapes with 2 km radius, indicating that herbivory is better controlled in landscapes with high forest cover, especially in the presence of birds and bats. However, at local level, 300 m around coffee plants, leaf loss and fruit set responded to forest cover differently. In units with low local forest cover exclusion of birds and bats increased leaf loss and reduced fruit set by 13% in mean. However, in units with high local forest cover, exclusion of birds and bats had no significant effect neither on leaf loss nor in fruit set. We concluded that the effects of birds and bats exclusion on leaf loss and fruit set are modulated by different processes occurring at landscape and local levels. We hypothesized that when local forest cover is high (usually near remnant forest fragments) birds and bats are not only controlling herbivores but may also be reducing mesopredators, while when local forest cover is low (e.g. far from forest fragments), mesopredators do not occur and birds and bats start providing biological pest control by feeding mainly on herbivores. We highlight the importance of employing a multiscale analysis in systems where species with different dispersal abilities are providing an ecosystem service.