This thesis is composed of three chapters. Chapter 1 considers the existence of equilibria in games with complete information, where players may have non-ordered and discontinuous preferences. Chapter 2 studies the issues on the existence of pure and behavioral strategy equilibria in games with incomplete information and discontinuous payoffs. We consider the standard setting with Bayesian preferences as well as the case in which players may face ambiguity. Chapter 3 extends the classical results on the Walras-core existence and equivalence to an ambiguous asymmetric information economy, where agents maximize maximin expected utilities (MEU). These results are based on the papers He and Yannelis (2014, 2015a,b,c, 2016a,b). In the first chapter, we propose the condition of "continuous inclusion property" to handle the difficulty of discontinuous payoffs in various general equilibrium and game theory models. Such discontinuities arise naturally in economic situations, including auction, price competition of firms and also patent races. Based on the continuous inclusion property, we establish the equilibrium existence result in a very general framework with discontinuous payoffs. On one hand, this condition is sufficiently general from the methodological point of view, as it unifies almost all special conditions proposed in the literature. On the other hand, our condition is also potentially useful from the realistic point of view, as it could be applied to deal with many economic models which cannot be studied before because of the presence of the discontinuity. In the second chapter, I study the existence problem of pure and behavioral strategy equilibria in discontinuous games with incomplete information. The framework of games with incomplete information is standard as in the literature, except for that we allow players' payoffs to be discontinuous. We illustrate by examples that the Bayesian equilibria may not exist in such games and the previous results are not applicable to handle this problem. We propose some general conditions to retain the existence of both pure strategy and behavioral strategy Bayesian equilibrium, and show that our condition is tight. In addition, we study the equilibrium existence problem in discontinuous games under incomplete information and ambiguity, and show that the maximin framework solves the equilibrium existence issue without introducing any additional condition. In the last chapter, I study a general equilibrium model with incomplete information by adopting the maximin expected utilities. The model is powerful enough to describe the behaviors of risk averse agents that cannot be explained by the standard assumption of subjective expected utilities. I use this new formulation to extend many classical results in general equilibrium theory by incorporating ambiguity into the model. In addition, the desirable incentive compatibility property is shown in our model with maximin expected utilities, while this property will typically fail in the traditional setup. Specifically, the existence results are shown for various equilibrium notions in a general equilibrium model, and the incentives can be guaranteed when all agents use the maximin expected utilities.

This dissertation explores how natural ecosystem can be integrated with economic system through two case studies of multiple species interactions, or predator-prey relations. By the inclusion of biological, ecological and economic aspects, the integrated approaches aim at more clearly understanding of how regional ecosystem and economy interact with each other, given threats of resource extinction and environmental shock. I also explain strategies and policy regimes that can be considered to achieve efficient and sustainable ecosystem management in those circumstances. The first case study focuses on a predator-prey relation in the Pacific Ocean between the United States and Canada, where endangered/threatened predators feed primarily on commercially valuable species as prey. Accounting for the importance of those predators as critical natural resources for whale watching industry, this case study synthesizes the species biological and the regional economic systems, and analyzes possible management strategies for both ecosystem conservation and sustainable economic growth. A long-term drought and fragmented management has been one of the critical issues in the Great Salt Lake (GSL) ecosystem that is linked with its regional economy in Utah. For this issue, the second case study builds an integrated model for describing how the lakes main natural resources, such as water, brine shrimp, and migratory birds, are related to primary industries in the region including agriculture, mining, fishery, and recreation. With the model framework, the study presents how the prolonged drought affects both the GSL ecosystem and its rigional economy, and suggests economic management strategies for the lakes ecosystem recovery in the presence of drought.

O treinamento de respostas posturais reativas por perturbações posturais é um paradigma inovador para prevenir quedas. Entretanto, há carência de informação sobre como organizar a prática para obter os maiores benefícios. O objetivo deste experimento foi comparar os efeitos de sequências de perturbações posturais com baixa (BIC) versus alta (AIC) interferência contextual na aquisição de estabilidade de movimentos compensatórios de braços e pernas em indivíduos jovens saudáveis. Trinta e oito participantes foram distribuídos de forma pseudoaleatória em 3 grupos: AIC, BIC, e controle (CON). A tarefa consistiu em recuperar o equilíbrio corporal após perturbações imprevisíveis da base de apoio no sentido mediolateral, para ambos os lados em diferentes velocidades (20, 30 e 40 cm/s [o/s]). Os grupos experimentais realizaram sessão única com 24 tentativas de prática para cada uma das seguintes modalidades de perturbação postural: rotação, translação e combinação translação-rotação. O grupo CON permitiu a avaliação das primeiras respostas às perturbações posturais e foi usado como linha de base das respostas posturais sem treinamento para comparação com os grupos experimentais. Os participantes foram avaliados em pós-teste, retenção e transferência para os seguintes contextos: (1) tarefa dual de contagem regressiva durante perturbações, e (2) velocidade mais alta do que aquelas treinadas (50 cm/s [o/s]). Os movimentos compensatórios de braços e pernas foram avaliados utilizando a escala CALM e cinemática. Os resultados mostraram o seguinte: (a) o treinamento levou a escores de estabilidade mais altos; (b) os ganhos por treinamento perturbatório foram evidentes em perturbações mais desafiadoras à manutenção da postura ereta; (c) perturbações repetitivas induziram efeitos imediatos, porém não persistentes e generalizáveis; e (d) perturbações aleatorizadas induziram ganhos persistentes e generalizáveis de estabilidade de movimentos compensatórios. Como conclusão, o treinamento perturbatório do equilíbrio corporal com alta em comparação com baixa interferência contextual se mostrou mais efetivo em promover ganhos mais persistentes e transferíveis de estabilidade de movimentos compensatórios / Perturbation-based training of reactive postural responses is an innovative paradigm for preventing falls. However, there is scarce information on how to organize the practice to obtain the greatest benefits. The objective of this experiment was to compare different schedules of postural perturbations, with low (BIC) versus high (AIC) contextual interference, on the acquisition of stability of arm and leg compensatory movements in healthy young individuals. Thirty-eight participants were distributed pseudorandomly in three groups: AIC, BIC, and control (CON). The task consisted in recovering body balance after unpredictable perturbations through support base displacements in mediolateral direction, for both sides in different speeds (20, 30 e 40 cm/s [o/s]). The experimental groups performed a single session with 24 practice trials for each of the following modalities of postural perturbation: rotation, translation and combination translation-rotation. The CON group allowed the evaluation of the first responses to postural perturbations was used as a baseline of postural responses without training for comparison with the experimental groups. Participants were evaluated in post-test, retention and transfer to the following contexts: (1) dual task, of counting down during perturbations; and (2) speed higher than those trained (50 cm/s [o/s]). The compensatory arm and leg movements were evaluated using the CALM scale and kinematics. Results showed the following: (a) training led to higher stability scores; (b) gains from perturbation training were evident in the most challenging perturbations to stance; (c) repetitive perturbations induced immediate but not persistent and generalizable effects; and (d) random perturbations induced persistent and generalizable gains in stability of compensatory movements. In conclusion, perturbation-based balance training with high as compared to low contextual interference was shown to be more effective in promoting more persistent and transferable compensatory movement stability gains

The recently proposed and experimentally validated Equilibrium Model provides the most detailed description of temperature's effect on enzyme catalytic activity to date. By introducing an equilibrium between Eact, the active form of enzyme, and Einact, a reversibly inactivated form of enzyme, the Equilibrium Model explains apparent enzyme activity loss at high temperatures that cannot be accounted for by irreversible thermal denaturation. The Equilibrium Model describes enzyme behavior in the presence of substrates and under assay conditions; thus its associated parameters, deltaHeq and Teq, may have physiological significance. The Equilibrium Model parameters have been determined for twenty-one enzymes of diverse origins. The results demonstrated the wide applicability of the Equilibrium Model to enzymes of different types and temperature affinity. The study has also established deltaHeq as the first quantitative measure of enzyme eurythermalism and demonstrated the relationship between Teq and optimal growth temperature of organisms. The Equilibrium Model is therefore a useful tool for studying enzyme temperature adaptation and its role in adaptations to thermophily and eurythermalism. Moreover, it potentially enables a description of the originating environment from the properties of the enzymes. The Equilibrium Model has been employed to characterize enzymes isolated from bacterial episymbionts of Alvinella pompejana. A. pompejana inhabits one of the most extreme environments known to science and has been proposed as an extremely eurythermal organism. A metagenomic study of the A. pompejana episymbionts has unveiled new information related to the adaptive and metabolic properties of the bacterial consortium; the availability of metagenomic sequences has also enabled targeted retrieval and heterologous expression of A. pompejana episymbiont genes. By inspecting enzymes derived from the unique episymbiotic microbial consortium intimately associated with A. pompejana, the study has shed light on temperature adaptations in this unique symbiotic relationship. The findings suggested that eurythermal enzymes are one of the mechanisms used by the microbial consortium to achieve its adaptations. By combining metagenomic and enzymological studies, the research described in this thesis has lead to insights on the eurythermalism of a complex microbial system from an enzymological aspect. The findings have enhanced our knowledge on how life adapts to extreme environments, and the validation of the Equilibrium Model as a tool for studying enzyme temperature adaptation paves the way for future studies.

In this thesis I address several neglected issues relating to the theoretical and applied analysis of human capital and the impact of taxation. I begin with the problem of measuring the effective tax rate on human capital accumulation. I develop a forward-looking measure of the effective tax rate that is grounded in human capital theory, allowing for features that differentiate human capital formation from physical capital formation. These features include concavity of the earnings-investment frontier and adjustments in capital utilization through leisure. I argue that the few attempts that have been made to measure the effective tax rate on skill formation are either limited by the fact that they inherit assumptions applicable to the theory of the firm or have dubious theoretical foundations (Chapter Two). The new measure is used to derive the effective tax rate on human capital in 25 OECD countries, including Australia (Chapter Three). While there are numerous general equilibrium models which integrate nominal rigidities of one form or another, little attention has been devoted to nominal rigidities arising from partial indexation of income tax thresholds. No doubt one of the reasons for this gap in the literature is the difficulty associated with introducing a fully specified progressive tax regime into an applied general equilibrium model. I show that this hurdle can be overcome through a zero-profit condition for general equilibrium on the labour market. The condition is integrated into an aggregative model of the economy consisting of two sectors (consumption and education) and two factors of production (skilled and unskilled labour). Since skill formation is endogenous, the model allows us to reopen research into the optimal level of skill formation and the role of government (Chapter Four). An applied general equilibrium version of the model is used to evaluate the impact of recent tax reform proposals on skill formation (Chapter Five). A concluding chapter draws together these lines of enquiry with suggestions for future research (Chapter Six).

Thèse soutenue en Anglais

Objectives: To evaluate postural control in individuals with functional ankle instability using static, dynamic, and clinical balance tests. Also, to examine the relationships between the performances in each of these tests. Design: Postural control was evaluated with a single leg balance test, a balance test involving movement, and the star excursion balance test. Participants: A volunteer sample of 19 subjects with functional ankle instability and 19 uninjured control subjects. Main Outcome Measures: Center of pressure sway path length was calculated for the static and dynamic balance tests. Total reach distance was measured for the star excursion balance test. Results: Subjects with functional ankle instability demonstrated a significantly greater center of pressure sway path length in both the static and dynamic balance tests. Conclusions: Functional ankle instability may be associated with reduced postural control as demonstrated by decreased performance in static and dynamic balance tests. / Graduation date: 2003

Graduation date: 1997

This paper investigates the potential for a carbon tax to induce R&D, and for the consequent induced technical change (ITC) to lower the macroeconomic cost of abating carbon emissions. ITC is modelled within a general equilibrium simulation of the U.S. economy by the effects of emissions restrictions on the level and composition of aggregate R&D, the accumulation of the stock of knowledge, and the industry-level reallocation and substitution of intangible services derived therefrom. Contrary to other authors, I find that ITC's impact is large, positive and dominated by the latter "substitution effect," which mitigates most of the deadweight loss of the tax. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/). / This research was supported by the Offce of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-02ER63484, and by funding from the MIT Joint Program on the Science and Policy of Global Change, which is supported by a consortium of government, industry and foundation sponsors.

The calculation of path travel times is an essential component for the dynamic traffic assignment and equilibrium problems. This paper presents a simulation method for calculating actual path travel times for the traffic network with dynamic demands. The method is based on a path-based macroscopic simulation model of network traffic dynamics. There is no need to explicitly model intersection delays in this method. Discontinuity in the travel time caused by traffic light control can be captured by this method. It's flexible in terms that the model is not limited to a specific velocity-density relationship. Some numerical results for signalized and unsignalized networks are reported. / Singapore-MIT Alliance (SMA)