In data-poor regions around the world, particularly in less-privileged countries, hydrologists cannot always take advantage of available hydrological models to simulate a hydrological system due to the lack of reliable measurements of hydrological variables, in particular rainfall and streamflows, needed to implement and evaluate these models. Rainfall estimates obtained with remotely deployed sensors constitute an excellent source of precipitation for these basins, however they are prone to errors that can potentially affect hydrologic simulations. Concurrently, limited access to streamflow measurements does not allow a detailed representation of the system's structure through parameter estimation techniques. This dissertation presents multiple studies that evaluate the usefulness of remotely sensed products for different hydrological applications and the sensitivity of simulated streamflow to parameter uncertainty across basins with different hydroclimatic characteristics with the ultimate goal of increasing the applicability of land surface models in ungauged basins, particularly in South America. Paper 1 presents a sensitivity analysis of daily simulated streamflows to changes in model parameters along a hydroclimatic gradient. Parameters controlling the generation of surface and subsurface flow were targeted for the study. Results indicate that the sensitivity is strongly controlled by climate and that a more parsimonious version of the model could be implemented. Paper 2 explores how errors in satellite-estimated precipitation, due to infrequent satellite measurements, propagate through the simulation of a basin's hydrological cycle and impact the characteristics of peak streamflows within the basin. Findings indicate that nonlinearities in the hydrological cycle can introduce bias in simulated streamflows with error-corrupted precipitation. They also show that some characteristics of peak discharges are not conditioned by errors in satellite-estimated precipitation at a daily time step. Paper 3 evaluates the dominant sources of error in three satellite products when representing convective storms and how shifts in the location of the storm affect simulated peak streamflows in the basin. Results indicate that satellite products show some deficiencies retrieving convective processes and that a ground bias correction can mitigate these deficiencies but without sacrificing the potential for real-time hydrological applications. Finally, spatially shifted precipitation fields affect the magnitude of the peaks, however, its impact on the timing of the peaks is dampened out by the system's response at a daily time scale.

Este trabalho busca demonstrar a influência da usina hidrelétrica de Itaipu nas relações de poder da Bacia do Prata, em especial entre Argentina, Brasil e Paraguai. Para isso se fez um regaste histórico dos acontecimentos mais relevantes nas relações internacionais dos três países. Também é apresentada a forma que a região platina se insere no contexto latino-americano, sobretudo no que diz respeito à política externa. O empreendimento de Itaipu é explorado em diversos âmbitos (político-diplomático, econômico, social etc.), desde sua ideia inicial, com a Ata das Cataratas, até sua operação no começo do século XXI está contemplado na pesquisa. Importantes mudanças de contextos políticos e econômicos ocorridos na região, como a transição democrática, também estão presente na análise enquanto elemento fundamental na mudança de paradigma observado. As relações platinas que historicamente foram marcadas pelo relativo equilíbrio na balança de poder, entre Argentina e Brasil, se deparam com o descolamento do Brasil enquanto país preponderante. Itaipu surge nesse contexto, acirrando ainda mais os conflitos, inicialmente. O empreendimento se mostra como elemento fundamental na consolidação da preponderância brasileira, e com o passar do tempo, é possível perceber a sua colaboração no movimento que se modificou, passando da confrontação para cooperação, e finalmente integração. / This paper wills to show the influence of the Itaipu hydroelectric plant in the power relations of the Plata Basin, particularly the relationsof Argentina, Brazil and Paraguay. For it is made a ransom of most relevant historical events in international relations of the three countries. Is also presented the way that the platinum region fits into the Latin American context, especially with regard to foreign policy.Itaipu is explored in various contexts (political-diplomatic, economic, social, etc.) and the project since its initial idea, with the Ata das Cataratas, until its operation in the beginning of the XXI century is included in the paper. Major changes in political and economic contexts that occurred in the region, such as the transition to democracy, are also present in the analysis as a fundamental factor of the paradigm shift observed.The Platinum Relations that were historically marked by relative equilibrium in the balance of power, between Argentina and Brazil, are faced with the detachment of Brazil as a predominant country. Itaipu arises in this context, increasing even more the conflicts, at first. The project is shown as a key element in the consolidation of Brazilian dominance and after is possible to see their collaboration in the movement that went from confrontation to cooperation, and finally integration.

Este trabalho busca demonstrar a influência da usina hidrelétrica de Itaipu nas relações de poder da Bacia do Prata, em especial entre Argentina, Brasil e Paraguai. Para isso se fez um regaste histórico dos acontecimentos mais relevantes nas relações internacionais dos três países. Também é apresentada a forma que a região platina se insere no contexto latino-americano, sobretudo no que diz respeito à política externa. O empreendimento de Itaipu é explorado em diversos âmbitos (político-diplomático, econômico, social etc.), desde sua ideia inicial, com a Ata das Cataratas, até sua operação no começo do século XXI está contemplado na pesquisa. Importantes mudanças de contextos políticos e econômicos ocorridos na região, como a transição democrática, também estão presente na análise enquanto elemento fundamental na mudança de paradigma observado. As relações platinas que historicamente foram marcadas pelo relativo equilíbrio na balança de poder, entre Argentina e Brasil, se deparam com o descolamento do Brasil enquanto país preponderante. Itaipu surge nesse contexto, acirrando ainda mais os conflitos, inicialmente. O empreendimento se mostra como elemento fundamental na consolidação da preponderância brasileira, e com o passar do tempo, é possível perceber a sua colaboração no movimento que se modificou, passando da confrontação para cooperação, e finalmente integração. / This paper wills to show the influence of the Itaipu hydroelectric plant in the power relations of the Plata Basin, particularly the relationsof Argentina, Brazil and Paraguay. For it is made a ransom of most relevant historical events in international relations of the three countries. Is also presented the way that the platinum region fits into the Latin American context, especially with regard to foreign policy.Itaipu is explored in various contexts (political-diplomatic, economic, social, etc.) and the project since its initial idea, with the Ata das Cataratas, until its operation in the beginning of the XXI century is included in the paper. Major changes in political and economic contexts that occurred in the region, such as the transition to democracy, are also present in the analysis as a fundamental factor of the paradigm shift observed.The Platinum Relations that were historically marked by relative equilibrium in the balance of power, between Argentina and Brazil, are faced with the detachment of Brazil as a predominant country. Itaipu arises in this context, increasing even more the conflicts, at first. The project is shown as a key element in the consolidation of Brazilian dominance and after is possible to see their collaboration in the movement that went from confrontation to cooperation, and finally integration.

Esta dissertação tem o objetivo de examinar o comportamento do estado brasileiro diante das manifestações de insatisfação do Paraguai com o Tratado de Itaipu que reivindicou renegociações sobre o uso da água e a distribuição da geração elétrica. Elas resultaram em revisões de partes do Tratado ao longo da década de 2000. O subsistema platino está dividido em dois tempos, o primeiro de ocupação da fronteira, no período da construção da usina em que a ordem regional rivalizava com a Argentina, e o segundo a partir da década de 2000, quando se consolida uma nova ordem regional voltada à integração. A Itaipu Binacional usa as águas transfronteiriças da bacia onde os dois Estados fazem fronteira e sua existência depende do alinhamento de interesses entre os Estados ribeirinhos no projeto binacional. Isto demonstrou a superação da função de separação política, no entanto tornou mais evidente as desigualdades entre as Partes. As assimetrias no uso das águas transfronteiriças revelam relações de poder entre os Estados ribeirinhos e sugere a existência de agente hidro-hegemônico. No diálogo entre Geografia Política, Geopolítica e Relações Internacionais, defende-se a ideia de que o uso compartilhado da água transfronteiriça impõe uma realidade de interdependente que adapta o comportamento dos Estados, a distribuição de poder e as suas fontes, mas, mesmo assim, mantém a racionalidade estratégica autointeressada. Para viabilizar a investigação foram analisados documentos elaborados pelo Itamaraty e pela Itaipu Binacional, além de fontes secundárias. / This dissertation aims to examine the behavior of the Brazilian state in face of the manifestations of dissatisfaction of Paraguay with the Treaty of Itaipu that demanded renegotiations on the use of water and the distribution of electricity generation. They resulted in revisions of parts of the Treaty throughout the 2000s. The Platinum subsystem is divided into two periods, the first to occupy the frontier, during the construction of the plant in which the regional order rivaled Argentina, and the second from the 2000s, when a new regional order for integration was consolidated. Itaipu Binacional uses the transboundary waters of the basin where the two States border and their existence depends on the alignment of interests among the riparian states in the binational project. This has demonstrated the overcoming of the political separation function, but has made more evident the inequalities between the Parties. Asymmetries in the use of transboundary waters reveal power relations among riparian states and suggests the existence of a hydrohegemonic agent. In the dialogue between Political Geography, Geopolitics and International Relations, the idea is defended that the shared use of transboundary water imposes an interdependent reality that adapts the behavior of States, the distribution of power and its sources, maintains the self-interested strategic rationality. In order to facilitate the investigation, documents prepared by Itamaraty and Itaipu Binacional were analyzed, as well as secondary sources.

Cette recherche est une approche sur les processus transfrontaliers dans la Triple FrontièreBrésil-Argentine-Paraguay. Initialement nous avons cherché à identifier les acteurs et les nouveaux usages du territoire, ainsi que le rôle des régions transfrontalières au sein des blocs commerciaux régionaux en Amérique du Sud et en Europe. Afin de utiliser l'expérience européenne dans les politiques pour les régions frontalières, on a analysés les initiatives d'intégration dans l’Union européenne et un travail de terrain dans la Grande Région a été réalisé, dont les résultats ont été utilisés pour la composition d'un chapitre de la recherche. Au cours du present étude l'importance de l'infrastructure routière, l'énergie et les télécommunications, le rôle du tourisme, les diverses initiatives de coopération et d'interaction dans le Triple Frontière, ainsi que les effets négatifs desprocessus transfrontaliersont été également analysé. Dans la recherche, les acteurs et les processus transfrontaliers ont été signalées par des coremas et des cartes. Les éléments énumérés ont servi à soutenir l'idée que actuellement une régiontransfrontalière se dessine au coeur du bassin de La Plata. / A presente pesquisa constitui uma abordagem acerca dos processos de transfronteirização na Tríplice Fronteira Brasil-Argentina-Paraguai. Inicialmente buscou-se identificar os atores e os novos usos do território, bem como o papel das regiões transfronteiriças dentro dos blocos regionais de comércio na América do Sul e na Europa. Com o intuito de aproveitar a experiência europeia no âmbito das políticas para regiões transfronteiriças, foram analisadas as iniciativas de integração e foi realizado um trabalho de campo na Grande Région, cujos resultados serviram para a composição de um capítulo da pesquisa. No decorrer da pesquisa também foram analisados a importância das infraestruturas viárias, energéticas e de telecomunicações, o papel do turismo, as diferentes iniciativas de cooperação e interação na Tríplice Fronteira, bem como os efeitos negativos da transfronteirização. Os atores e os processos de transfronteirização foram relatados através de coremas e mapas elaborados para a pesquisa. Os elementos elencados serviram para embasar a ideia de que está surgindo uma região transfronteiriça no coração da Bacia do Prata. / This research is an approach to cross-border processes in the Tri-Border Area, between Brazil, Argentina and Paraguay. Initially we sought to identify the actors, the new land uses and the role of cross-border regions within regional trading blocs in South America and Europe. To take advantage of the European experience in policies for border regions, we analyzed the integration initiatives in the European Union and a fieldwork in the Grande Région was conducted. The results of the fieldwork were used to compose a chapter of the research. In the present study the importance of road infrastructure, energy and telecommunications, the role of tourism, initiatives of cooperation and interaction in Tri-Border Area, as well as the negative effects of cross-border processes were also analyzed. In the present research, actors and border processes have been reported by graphic schemes and maps. The items listed were used to support the idea that, presently, a cross-border region is emerging in the heart of La Plata Basin.

Cette recherche est une approche sur les processus transfrontaliers dans la Triple FrontièreBrésil-Argentine-Paraguay. Initialement nous avons cherché à identifier les acteurs et les nouveaux usages du territoire, ainsi que le rôle des régions transfrontalières au sein des blocs commerciaux régionaux en Amérique du Sud et en Europe. Afin de utiliser l'expérience européenne dans les politiques pour les régions frontalières, on a analysés les initiatives d'intégration dans l’Union européenne et un travail de terrain dans la Grande Région a été réalisé, dont les résultats ont été utilisés pour la composition d'un chapitre de la recherche. Au cours du present étude l'importance de l'infrastructure routière, l'énergie et les télécommunications, le rôle du tourisme, les diverses initiatives de coopération et d'interaction dans le Triple Frontière, ainsi que les effets négatifs desprocessus transfrontaliersont été également analysé. Dans la recherche, les acteurs et les processus transfrontaliers ont été signalées par des coremas et des cartes. Les éléments énumérés ont servi à soutenir l'idée que actuellement une régiontransfrontalière se dessine au coeur du bassin de La Plata. / A presente pesquisa constitui uma abordagem acerca dos processos de transfronteirização na Tríplice Fronteira Brasil-Argentina-Paraguai. Inicialmente buscou-se identificar os atores e os novos usos do território, bem como o papel das regiões transfronteiriças dentro dos blocos regionais de comércio na América do Sul e na Europa. Com o intuito de aproveitar a experiência europeia no âmbito das políticas para regiões transfronteiriças, foram analisadas as iniciativas de integração e foi realizado um trabalho de campo na Grande Région, cujos resultados serviram para a composição de um capítulo da pesquisa. No decorrer da pesquisa também foram analisados a importância das infraestruturas viárias, energéticas e de telecomunicações, o papel do turismo, as diferentes iniciativas de cooperação e interação na Tríplice Fronteira, bem como os efeitos negativos da transfronteirização. Os atores e os processos de transfronteirização foram relatados através de coremas e mapas elaborados para a pesquisa. Os elementos elencados serviram para embasar a ideia de que está surgindo uma região transfronteiriça no coração da Bacia do Prata. / This research is an approach to cross-border processes in the Tri-Border Area, between Brazil, Argentina and Paraguay. Initially we sought to identify the actors, the new land uses and the role of cross-border regions within regional trading blocs in South America and Europe. To take advantage of the European experience in policies for border regions, we analyzed the integration initiatives in the European Union and a fieldwork in the Grande Région was conducted. The results of the fieldwork were used to compose a chapter of the research. In the present study the importance of road infrastructure, energy and telecommunications, the role of tourism, initiatives of cooperation and interaction in Tri-Border Area, as well as the negative effects of cross-border processes were also analyzed. In the present research, actors and border processes have been reported by graphic schemes and maps. The items listed were used to support the idea that, presently, a cross-border region is emerging in the heart of La Plata Basin.

New research in lowland South America is beginning to reveal a diversity of complex and unique cultural trajectories in a region that was long-considered marginal with respect to Andean and Mesoamerican civilizations. This paper summarizes new archaeological, paleoecological, and archaebotanical data from the Los Ajos site, southeastern Uruguay, showing that a changing and increasingly drier mid-Holocene climate was associated with significant cultural transformations, including early village formation, the adoption of a mixed economy, and the construction of the earliest public architecture known for the area. Collectively, this evidence indicates an early and unexpected development of social complexity that had not heretofore been recorded in this area of South America. Human-environment interactions, social processes related to the development of early village life, and the role of early public architecture are discussed with reference to the emergence of early Formative communities in the region. / Nuevas investigaciones en las tierras bajas de Sudamérica están comenzando a revelar una diversidad de trayectorias culturales complejas y únicas en una parte de Sudamérica que ha sido tradicionalmente considerada como un área marginal en comparación con las civilizaciones que se desarrollaron en los Andes centrales y Mesoamérica. Este artículo resume nuevos datos arqueológicos, arqueobotánicos y paleoecológicos del sitio Los Ajos, en el sureste de Uruguay. Dichos estudios revelaron que el Holoceno Medio, que se caracterizó por un clima cambiante que se tornó cada vez más seco, está asociado a transformaciones culturales significativas, incluyendo el proceso de formación de aldeas, la adopción de una economía mixta y la construcción de la arquitectura pública más temprana conocida en la región. Estos recientes trabajos evidencian un desarrollo de la complejidad social temprana e inesperada que no había sido registrada en esta parte del continente. El presente artículo discute las interacciones del hombre con el medioambiente, los procesos sociales relacionados con el desarrollo de la vida aldeana incipiente y el papel que tuvo la arquitectura pública en relación con el surgimiento de las sociedades del Formativo Temprano en la región.

Cette recherche est une approche sur les processus transfrontaliers dans la Triple FrontièreBrésil-Argentine-Paraguay. Initialement nous avons cherché à identifier les acteurs et les nouveaux usages du territoire, ainsi que le rôle des régions transfrontalières au sein des blocs commerciaux régionaux en Amérique du Sud et en Europe. Afin de utiliser l'expérience européenne dans les politiques pour les régions frontalières, on a analysés les initiatives d'intégration dans l’Union européenne et un travail de terrain dans la Grande Région a été réalisé, dont les résultats ont été utilisés pour la composition d'un chapitre de la recherche. Au cours du present étude l'importance de l'infrastructure routière, l'énergie et les télécommunications, le rôle du tourisme, les diverses initiatives de coopération et d'interaction dans le Triple Frontière, ainsi que les effets négatifs desprocessus transfrontaliersont été également analysé. Dans la recherche, les acteurs et les processus transfrontaliers ont été signalées par des coremas et des cartes. Les éléments énumérés ont servi à soutenir l'idée que actuellement une régiontransfrontalière se dessine au coeur du bassin de La Plata. / A presente pesquisa constitui uma abordagem acerca dos processos de transfronteirização na Tríplice Fronteira Brasil-Argentina-Paraguai. Inicialmente buscou-se identificar os atores e os novos usos do território, bem como o papel das regiões transfronteiriças dentro dos blocos regionais de comércio na América do Sul e na Europa. Com o intuito de aproveitar a experiência europeia no âmbito das políticas para regiões transfronteiriças, foram analisadas as iniciativas de integração e foi realizado um trabalho de campo na Grande Région, cujos resultados serviram para a composição de um capítulo da pesquisa. No decorrer da pesquisa também foram analisados a importância das infraestruturas viárias, energéticas e de telecomunicações, o papel do turismo, as diferentes iniciativas de cooperação e interação na Tríplice Fronteira, bem como os efeitos negativos da transfronteirização. Os atores e os processos de transfronteirização foram relatados através de coremas e mapas elaborados para a pesquisa. Os elementos elencados serviram para embasar a ideia de que está surgindo uma região transfronteiriça no coração da Bacia do Prata. / This research is an approach to cross-border processes in the Tri-Border Area, between Brazil, Argentina and Paraguay. Initially we sought to identify the actors, the new land uses and the role of cross-border regions within regional trading blocs in South America and Europe. To take advantage of the European experience in policies for border regions, we analyzed the integration initiatives in the European Union and a fieldwork in the Grande Région was conducted. The results of the fieldwork were used to compose a chapter of the research. In the present study the importance of road infrastructure, energy and telecommunications, the role of tourism, initiatives of cooperation and interaction in Tri-Border Area, as well as the negative effects of cross-border processes were also analyzed. In the present research, actors and border processes have been reported by graphic schemes and maps. The items listed were used to support the idea that, presently, a cross-border region is emerging in the heart of La Plata Basin.

Das erste Ziel dieser Arbeit ist eine umfassende Analyse der Wasserflüsse durchzuführen und Quellen und Senken des kontinentalen Niederschlags zu identifizieren. Als Analysemethode werden komplexe Netzwerke verwendet, ein Ansatz, mit dessen Hilfe das neuartige Konzept des “cascading moisture recycling'''' (CMR) eingeführt wird. CMR wird als vielfache Verdunstung von Niederschlag während des Feuchtigkeitstransports über bewaldeten Gebieten definiert. Dieses Verfahren ermöglicht es, den Anteil von CMR an der Menge des regionalen Niederschlags zu quantifizieren und Schlüsselregionen des CMR zu identifizieren. Die Analyse zeigt, dass der südliche Bereich des Amazonasbeckens nicht nur eine direkte Quelle für Niederschlag im La-Plata Becken ist, sondern auch als ``Brückenregion'''' dient, über die die verdunstete Feuchtigkeit des ganzen Amazonasbeckens auf dem Weg in die Subtropen transportiert wird. Die Ergebnisse zeigen, dass eine Neubewertung der Vulnerabilität des Amazonasregenwalds unter Umweltveränderungen unabdingbar ist. Dies ist das zweite Ziel der vorliegenden Arbeit. Durch diese Veränderungen könnten große Teile des Regenwaldes in eine Savanne umgewandelt werden. Dies würde wiederum den Niederschlag reduzieren, was sich negativ auf die Stabilität der verbleibenden Waldgebiete auswirken und ein Waldsterben verursachen kann. Für die Analyse dieser Zusammenhänge werden ebenfalls komplexe Netzwerke verwendet, um das Konzept der Ökosystem-Resilienz und CMR basierend auf Beobachtungsdaten zu kombinieren. Es werden die Schlüsselregionen, in denen Entwaldung zu einer Destabilisierung der verbleibenden Wald führt, identifiziert und die Möglichkeit eines großflächigen Absterben des Regenwaldes aufgrund von verlängerter Trockenzeit untersucht. Die Ergebnisse zeigen, dass die Diversität des Regenwaldes und die durch den Feuchtigkeitstransport gegebene Konnektivität der Waldgebiete eine wichtige Rolle für die Stabilität und ökologische Integrität dieses Ökosystems spielen. / The first aim of this thesis is to improve the understanding of vegetation-atmosphere interactions by means of complex network analysis of water fluxes from the sources to the sinks of rainfall in South America. This novel approach allows to introduce the concept of “cascading moisture recycling” defined as moisture recycling on the continent involving re-evaporation cycles along the way. A methodological framework is developed to quantify the importance of cascading moisture recycling and to identify key regions that sustain this process. It reveals, for instance, that the southern part of the Amazon basin is not only a direct source of rainfall for the La Plata basin as previously thought but also an intermediary region that re-distribute moisture evaporating from the entire Amazon basin towards the subtropics. This new concept lays the foundation for evaluating the vulnerability of the Amazon forest to environmental perturbations, which is the second aim of this thesis. Land-use and rainfall variability are expected to be intensified at the end of the twenty-first century and may push the south-eastern part of the Amazon forest towards a grass-dominated ecosystem. Such a forest loss would reduce local dry-season evapotranspiration and the resulting moisture supply for down-wind rainfall. In turn, this might erode the resilience of the remaining forest and lead to further forest losses. Using a complex network approach, the concepts of forest resilience and cascading moisture recycling are combined in a data-driven modeling framework. Key regions are identified where deforestation would greatly destabilize the remaining forest, as well as tipping points in dry-season intensification for large-scale self-amplified Amazon forest loss. The findings highlight the need to maintain the diversity and connectivity of forest patches in order to sustain the ecological integrity of the largest remaining tropical forest on Earth.

Made available in DSpace on 2014-06-11T19:26:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-05-24Bitstream added on 2014-06-13T18:30:29Z : No. of bitstreams: 1 yahnfilho_ag_me_mar.pdf: 1098522 bytes, checksum: cc35139cfe47067c82c3d101a3d160fa (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho tem por objetivo fazer uma análise das relações internacionais na Bacia do Prata, no que tange ao seu aproveitamento hídrico, com foco na geração de energia e na navegação fluvial, haja vista o caráter duplamente conflitivo destes dois usos dþágua. No plano físico, as barragens se tornam um empecilho à navegação e, na esfera política, a prioridade que cada país dá a um destes usos está condicionada ao seu grau de desenvolvimento econômico ou à sua situação geográfica. Se, por um lado, as relações hostis entre Brasil e Argentina, decorrentes da incompatibilização de seus projetos de aproveitamento hidrelétrico do Rio Paraná, duarante as décadas de 1960 e 1970, caracterizam uma fase predominantemente realista na Bacia do Prata, por outro, o projeto da Hidrovia Paraguai-Paraná, iniciado nos anos 1980 e concretizado na década seguinte, representa a afirmação de uma tendência multilateralista das relações internacionais na região, fundamentada na teoria da interdependência complexa. / The purpose of this work is to analyze the Plata Basin international relations, as to water use, focusing on energy generation and fluvial navigation, taking into account double conflicting feature of these two water uses. At physical level, dams impair navigation and, at political level, priority assigned by each country to one of these uses is conditioned by its economic development degree or geographical location. If, on one hand, hostile relationships between Brazil and Argentina, arising from their projects of Paraná River hydroelectric use incompatibility, during the 1960s and 1970s, feature a mainly realistic phase in Plata Basin, on the other hand, Paraguay-Paraná Waterway, started in the 1980s and achieved in the following decade, represents a multilateral trend strengthening to international relations, based on complex interdependence theory.