abstract: The overall goal of this research project was to assess the feasibility of investigating the effects of microgravity on mineralization systems in unit gravity environments. If possible to perform these studies in unit gravity earth environments, such as earth, such systems can offer markedly less costly and more concerted research efforts to study these vitally important systems. Expected outcomes from easily accessible test environments and more tractable studies include the development of more advanced and adaptive material systems, including biological systems, particularly as humans ponder human exploration in deep space. The specific focus of the research was the design and development of a prototypical experimental test system that could preliminarily meet the challenging design specifications required of such test systems. Guided by a more unified theoretical foundation and building upon concept design and development heuristics, assessment of the feasibility of two experimental test systems was explored. Test System I was a rotating wall reactor experimental system that closely followed the specifications of a similar test system, Synthecon, designed by NASA contractors and thus closely mimicked microgravity conditions of the space shuttle and station. The latter includes terminal velocity conditions experienced by both innate material systems, as well as, biological systems, including living tissue and humans but has the ability to extend to include those material test systems associated with mineralization processes. Test System II is comprised of a unique vertical column design that offered more easily controlled fluid mechanical test conditions over a much wider flow regime that was necessary to achieving terminal velocities under free convection-less conditions that are important in mineralization processes. Preliminary results indicate that Test System II offers distinct advantages in studying microgravity effects in test systems operating in unit gravity environments and particularly when investigating mineralization and related processes. Verification of the Test System II was performed on validating microgravity effects on calcite mineralization processes reported earlier others. There studies were conducted on calcite mineralization in fixed-wing, reduced gravity aircraft, known as the `vomit comet' where reduced gravity conditions are include for very short (~20second) time periods. Preliminary results indicate that test systems, such as test system II, can be devised to assess microgravity conditions in unit gravity environments, such as earth. Furthermore, the preliminary data obtained on calcite formation suggest that strictly physicochemical mechanisms may be the dominant factors that control adaptation in materials processes, a theory first proposed by Liu et al. Thus the result of this study may also help shine a light on the problem of early osteoporosis in astronauts and long term interest in deep space exploration. / Dissertation/Thesis / M.S. Bioengineering 2013

by Lai Chi Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves [104]-107). / Text in English; abstract also in Chinese. / by Lai Chi Wai. / Abstract --- p.i / Acknowledgment --- p.iv / List of Figures --- p.xi / List of Tables --- p.xii / Chapter 1 --- Introduction to Numerical Relativity --- p.1 / Chapter 1.1 --- The need for numerical approach --- p.2 / Chapter 1.2 --- A brief history of numerical relativity --- p.3 / Chapter 1.3 --- What this thesis concern --- p.4 / Chapter 2 --- Mathematical Formulation --- p.6 / Chapter 2.1 --- The initial value problem --- p.6 / Chapter 2.2 --- The space-plus-time (3+1) formalism --- p.8 / Chapter 3 --- Methods in Numerical Relativity --- p.17 / Chapter 3.1 --- General numerical methods --- p.17 / Chapter 3.2 --- Consistency and stability --- p.18 / Chapter 3.3 --- Difficulties and limitations --- p.20 / Chapter 3.4 --- Strategies specific to numerical relativity --- p.21 / Chapter 3.5 --- Boundary conditions --- p.27 / Chapter 4 --- Detweiler's Scheme --- p.29 / Chapter 4.1 --- Constrainted evolution in numerical relativity --- p.29 / Chapter 4.2 --- Detweiler's Scheme --- p.31 / Chapter 5 --- Constraint Enforcement in Plane Waves --- p.36 / Chapter 5.1 --- General solution for a linearized plane wave --- p.36 / Chapter 5.2 --- Code test --- p.40 / Chapter 5.3 --- Comparison of results with and without Detweiler's scheme --- p.41 / Chapter 5.4 --- Stability of evolution --- p.46 / Chapter 5.5 --- Comparison of Detweiler's scheme and simple diffusion method --- p.50 / Chapter 5.6 --- Two parameter extension of Detweiler's scheme --- p.55 / Chapter 5.7 --- Long time behavior --- p.59 / Chapter 5.8 --- Comparison of Hamiltonian and momentum constraint --- p.63 / Chapter 5.9 --- Indicator of Detweiler's scheme --- p.67 / Chapter 5.10 --- The maximal slicing condition --- p.70 / Chapter 5.11 --- The leaking problem --- p.73 / Chapter 5.12 --- The near-linear plane waves --- p.75 / Chapter 6 --- Constraint Enforcement in MTW Waves --- p.83 / Chapter 6.1 --- MTW waves --- p.83 / Chapter 6.2 --- Linear regime --- p.85 / Chapter 6.3 --- Comparison of results with and without Detweiler's scheme --- p.85 / Chapter 6.4 --- The indicator --- p.90 / Chapter 6.5 --- A comparison of simple diffusion method and Detweiler's scheme with a large amplitude wave --- p.92 / Chapter 7 --- Summary and Conclusion --- p.97 / Chapter A --- The Numerical Scheme of the Code --- p.98 / Chapter B --- Convergence Test --- p.100 / Chapter B.1 --- Plane wave --- p.100 / Chapter B.2 --- MTW wave --- p.102 / Bibliography --- p.104

Submitted by Gizele Lima (gizele.lima@inpa.gov.br) on 2017-06-19T13:53:15Z No. of bitstreams: 2 2016_10_18_Dissertação_LuizaCosme.pdf: 1416222 bytes, checksum: 54f85e213133bb0455bb2a8d4098f181 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-06-19T13:53:15Z (GMT). No. of bitstreams: 2 2016_10_18_Dissertação_LuizaCosme.pdf: 1416222 bytes, checksum: 54f85e213133bb0455bb2a8d4098f181 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-05-31 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Environmental filters act directly on the distribution and composition of species. However, it is not known how soil and belowground hydric conditions are related to hydraulic characteristics of the xylem, branches and of the whole plant on a local scale. We examined wood density and anatomy, height, leaf area, specific leaf area, and the leaf area:sapwood area ratio at the branch level in valleys and plateaus of the terra-firme forest in Central Amazonia. These environments present contrasting table water depths and soil textures. We measure 20 traits related to branches, stem, and whole plant in 28 congeneric species pairs from 12 genera, each containing one valley and one plateau species. Species associated with the plateaus or valleys showed trait differences that indicate distinct investments in prevention against hydraulic failure and driving efficiency, respectively. On plateaus, species had higher wood density, lower averages of vessel size and hydraulic diameter of the vessel, smaller stem sapwood area and smaller specific leaf area. Some correlations between traits change according to the contrasting environmental conditions, demonstrating that species have different investments in traits according to the water conditions in the soil. The maximum adult stature in contrast environments was associated with different investing in conductivity efficiency through the xylem anatomy.We conclude that even in a fine scale, with few meters separating contrasting soil texture and water table depth conditions, environmental filters may impose ecological restrictions on trees that could explain species complementary distribution in Central Amazonia. These filter may be stronger in phylogenetically closely related species, which show more similarities and compete for the same resources. Thus, contrasting soil texture and water table depth conditions may be important determinants of species composition and diversity . Thus, we suggest that hydraulic attributes and their relationships with the environment must be better understood, especially on a local level. / Filtros ambientais atuam diretamente sobre a distribuição e composição de espécies. No entanto, não se sabe como solo e as condições hídricas abaixo do solo estão relacionados às características hidráulicas do xilema. Nós examinamos a densidade da madeira e anatomia da madeira, altura, área foliar, área foliar específica e a razão entre área foliar:área de xilema ativo no nível do ramo em espécies de árvore que ocorrem no baixio e platôs em uma floresta de terra-firme. Esses ambientes apresentam diferenças na profundidade do lençol freático e textura do solo. Nós medimos 20 traços funcionais em 28 pares de espécies congenéricas de 12 gêneros. Cada par com uma espécie associada a baixio e uma espécie associada platô. Espécies associadas aos platô ou baixios mostraram diferenças que indicam investimentos distintos na prevenção contra a falha hidráulica e eficiência de condução, respectivamente. Em platôs, as espécies apresentaram maior densidade da madeira, as médias mais baixas de diâmetro do vaso e diâmetro hidráulico do vaso, menor área de xilema ativo no caule e menor área foliar específica. A relação entre alguns atributos se alterou nas condições ambientais contrastantes, e espécies de diferentes alturas nos diferentes ambientes parecem investir em eficiencia e segurança hidráulica de maneiras distintas. Concluímos que mesmo em uma escala fina, com poucos metros separando ambientes com condições contrastantes de textura do solo e profundidade do lençol freático, filtros ambientais podem impor restrições ecológicas em árvores que poderiam explicar espécies de distribuição complementar na Amazônia Central. Estas restrições podem ser mais fortes em espécies filogeneticamente relacionadas, que mostram mais semelhanças e competem pelos mesmos recursos. Sugerimos que os atributos hidráulicos e suas relações com o meio ambiente devem ser melhor compreendidos, especialmente a nível local.

This dissertation considers the interconnections between trade and transportation. Through various theoretical and empirical analyses, I provide novel evidence of the simultaneity of trade and transportation, of spillover effects across integrated transport markets, and of the influence of the international transport sector on trade policy effectiveness and natural disaster induced trade disruptions. In the first substantive chapter, I develop a model of international trade and transportation. Accounting for the joint-production present in the international container shipping industry, I illustrate that freight rates adjust to differences in the international demands for transport and can result in balanced or imbalanced equilibrium trade in the presence of asymmetric freight rates. The empirical results exhibit the simultaneity of international trade and transportation costs and show that the dependence of transport costs on the trade imbalance can lead to spillover effects across bilateral export and import markets. In the second substantive chapter, I investigate the effects of maritime trade policy on bilateral trade in the presence of trade imbalances. Using the previously developed model, I show that the trade elasticities with respect to carrier costs vary systematically across transport markets, bilateral trade imbalances and differentiated products. Empirically, I estimate the varying effects of an EU environmental policy on U.S.-EU trade and provide strong evidence in support of the theoretical results. In the third substantive chapter, I analyze the dynamics and spatial distribution of the trade effects induced by natural disasters. I develop a spatial gravity model of international trade and apply the model to monthly US port level trade data. Empirically, I estimate the dynamic evolution of trade effects caused by Hurricane Katrina differentiating trade disruptions at the local port level. The estimates point to the static and dynamic resilience of international trade. While ports closest to Katrina's epicenter experience significant short-run reductions that can be of permanent nature, international trade handled by nearby ports rises in response to this disaster, both in the short- and in the long-run. Overall, the analysis underlines the significance of local infrastructure networks to reduce the devastation inflicted by natural disasters. This dissertation includes previously unpublished co-authored material.

Um estudo gravimétrico comparativo das bacias do Chaco-Paraná (BCP) e Paraná (BP) foi efetuado utilizando o modelo global EGM08 e os dados da missão GOCE. A feição gravimétrica mais notável é um gradiente gravimétrico de 0,25 mGal/km, de direção norte-sul e que contorna a borda oeste da Bacia do Paraná e inflexiona para leste na latitude 30º S. Esse gradiente separa as duas bacias em províncias gravimétricas com características distintas. A BCP é caracterizada por anomalias gravimétricas positivas entre 10 e 20 mGal e de direção norte-sul, enquanto que na BP as anomalias variam entre -50 a -90 mGal na direção NE-SW. A análise gravimétrica foi efetuada de duas formas. Inicialmente removeu-se o efeito gravitacional devido aos sedimentos e basaltos e a anomalia devido às fontes mais profundas foi invertida para determinar o relevo da interface crosta-manto. Posteriormente efetuou-se uma análise isostática estimando a profundidade de compensação para a topografia observada nos modelos de Airy e flexural de placa contínua. Esses modelos, considerando a topografia observada como a única carga, não preveem a profundidade da Moho qualquer que seja o valor da espessura elástica. Dados de profundidade da Moho por métodos sismológicos, onde existentes, foram confrontados com os fornecidos pela inversão gravimétrica, estimando assim o valor do contraste de densidade (300 kg/m³) para o qual as profundidades da Moho e da interface crosta-manto obtida pela gravimetria melhor se ajustam. A inversão gravimétrica indica que a crosta da BCP é em média 7 km menos espessa do que a crosta da BP. Os resultados deste estudo sugerem a existência de uma descontinuidade crustal, e possivelmente uma sutura litosférica ao longo do gradiente gravimétrico entre as bacias do Chaco-Paraná e do Paraná. / A comparative gravity study of the Chaco-Paraná (CPB) and the Paraná (PB) basins was carried out using the EGM08 and GOCE global geopotential models. The most prominent gravity feature in the study area is a gradient of 0.25 mGal/km, extending from north to south alongside the western border of the Paraná basin and continuing eastward towards the Atlantic coast at the latitude 30º S. This gradient separates both basins into two gravity provinces with distinct characteristics. The CPB is marked by positive Bouguer anomalies of about 10 to 20 mGal in amplitude with north-south trending, whereas in the PB the Bouguer anomalies range from -50 to -90 mGal and trend along the NE-SW direction. The gravity analysis was carried out in two ways. Firstly, the gravity effect from basalts and sediments was calculated and removed and the gravity anomaly due to deeper sources was inverted in order to determine the crust-mantle interface relief. Secondly, an isostatic analysis was carried out in order to estimate the compensation depth due to the observed topography using both Airy and continuous plate flexural models. These isostatic models, considering the observed topography as the only load, cannot account for the observed Moho regardless of the effective elastic thickness value. Moho depth provided by seismological studies, where available, were compared with the results of the gravity inversion, thus estimating the density contrast (300 kg/m3) for which the Moho and crust-mantle interface depths are in agreement. The gravity inversion indicates that, in average, the CPB crust is 7 km thinner than the PB crust. This study suggests the existence of a crustal discontinuity, and perhaps even a lithospheric suture along the gravity gradient between the Chaco-Paraná and the Paraná basins.

Neste trabalho dedicamo-nos à análise da presença de curvas fechadas tipo tempo em espaços-tempos cilindricamente simétricos e estacionários Ct. A equação de movimento que descreve a evolução de um campo escalar massivo nos espaços-tempos Ct é apresentada. Uma classe de espaços-tempos descrevendo cordas e cilindros cósmicos que admitem a presença de curvas fechadas tipo tempo é estudada em detalhes. A região não-causal desses espaços-tempos se revela acessível tanto a partículas massivas quanto a fótons. Curvas geodésicas e curvas fechadas tipo tempo são obtidas e investigadas. Essencialmente, dois tipos de órbitas descritas por partículas massivas e fótons foram observadas: órbitas confinadas e órbitas espalhadas. Os cones de luz evidenciaram claramente a intersecção de futuro e passado na região não-causal. Soluções exatas das equações de movimento do campo escalar se propagando nos espaçcos-tempos das cordas e cilindros são apresentadas. No caso dos cilindros estático e em rotação os modos quasinormais de oscilação do campo escalar foram calculados. A presença de modos instáveis foi observada em alguns casos. Observamos, também, que tanto na corda estática quanto na corda em rotação o campo escalar não apresentam modos quasinormais de oscilação. Concluimos com a proposta de uma conjectura relacionando curvas fechadas tipo tempo e instabilidades do espaço-tempo. / This work deals with the analysis of cylindrically symmetric and stationary space-times Ct with closed timelike curves. The equation of motion describing the evolution of a massive scalar field in a Ct space-time is obtained. A class of space-times with closed timelike curves describing cosmic strings and cylinders is studied in detail. In such space-times, both massive particles as well as photons can reach the non-causal region. Geodesics and closed timelike curves are calculated and investigated. We have observed that massive particles and photons describe, essentially, two kinds of trajectories: confined orbits and scattering states. The analysis of the light cones show us clearly the intersection between future and past inside the non-causal region. Exact solutions for the equation of motion of massive scalar field propagating in cosmic strings and cylinder space-times are presented. Quasinormal modes for the scalar field have been calculated in static and rotating cosmic cylinders. We found unstable modes in the rotating cases. Rotating as well as static cosmic strings, i.e., without regular interior solutions, do not display quasinormal modes for the scalar field. We conclude presenting a conjecture relating closed timelike curves and space-time instability.

In the construction of Canonical Loop Quantum Gravity, General Relativity is rewritten in terms of the Ashtekar variables to simplify its quantisation. They consist of a densitised triad and a connection terms. The latter depends by definition and by construction on a free parameter β, called the Barbero–Immirzi parameter. This freedom is passed on to the quantum theory as it appears in the expressions of certain operators. Their discreet spectra depend on the arbitrary value of this parameter β, meaning that the scale of those spectra is not uniquely defined. To get around this ambiguity, we propose to consider a theory of Conformal Loop Quantum Gravity, by imposing a local conformal symmetry through the addition of a scalar field. We construct our theory starting from the usual Einstein–Hilbert action for General Relativity to which we add the action for the massless scalar field and rewrite it in terms of a new set of Ashtekar-like variables. They are constructed through a set of canonical transformations, which allow to move the Barbero–Immirzi parameter from the connection to the scalar variable. We then show that the theory can be quantised by fulfilling the conditions for a Dirac quantisation. Finally, we present some first elements of the quantum formalism. It is expected that with such a scalar-tensor theory, the quantum operators should not depend on the free parameter directly but rather on the dynamical scalar field, solving therefore the ambiguity.

It is now a consolidated fact that our Universe is undergoing an accelerated expansion. According to Einstein's General Relativity, if the main constituents of our Universe were ordinary and cold dark matter, then we would expect it to be contracting and collapsing due to matter's attractive nature. The simplest explanation we have for this acceleration is in the form of a component with a negative ratio of pressure to density equal to -1 known as cosmological constant, Λ , presently dominating over baryonic and cold dark matter. However, the Λ Cold Dark Matter (Λ CDM) model suffers from a well known fine tuning problem. This led to the formulation of dark energy and modified gravity theories as alternatives to the problem of cosmic acceleration. These theories either include additional degrees of freedom, higher-order equations of motion, extra dimensionalities or imply non-locality. In this thesis we focus on single field scalar tensor theories embedded within Horndeski gravity. Even though there is currently doubt on their ability to explain cosmic acceleration without having a bare cosmological constant on their action, the degree of freedom they introduce mediates an additional fifth force. And while this force has to suppressed on Solar system scales, it can have interesting and observable effects on cosmological scales. Over the next decade there is a surge of surveys that will improve the understanding of our Universe on the largest scales. Hence, in this work, we take several different modified gravity theories and study their impact on cosmological observables. We will analyze the dynamics of linear perturbations on these theories and clearly highlight how they deviate from Λ CDM, allowing to break the degeneracy at the background level. We will also study the evolution of the gravitational potentials on sub horizon scales and provide simplified expressions at this regime and, for some models, obtain constraints using the latest data.

The probability of a fire occurring in space vehicles and facilities is amplified by the amounts of electrical equipment used. Additionally, the lack of egress for space personnel and irreplaceable resources used aboard space vehicles and facilities require a rapid response of a suppression system and quick extinguishment. Current experimental means that exist to gather data in space vehicles and facilities are limited by both size of the experiment and cost. Thus, more economical solutions must be considered. The aim of this research was to develop a reliable and inexpensive methodology for the prediction of flame extinction and suppression in any three-dimensional environment. This project was split into two parts. Part one included the identification and validation of a computational model for the prediction of gas dispersion. Part two involved the development of an analytical parameter for predicting flame extinction. For model validation, an experimental apparatus was constructed. The experimental apparatus was one-eighth of the volume of electronics racks found aboard typical space facilities. The experimental apparatus allowed for the addition of parallel plates to increase the complexity of the geometry. Data acquisition consisted of gas concentration measurements through planar laser induced fluorescence (PLIF) of nitrogen dioxide and velocity field measurements through particle image velocimetry (PIV). A theoretical framework for a generalized Damköhler number for the prediction of local flame extinction was also developed. Based on complexities in this parameter, the computational code FLUENT was determined to be the ideal means for predicting this quantity. The concentration and velocity field measurements provided validation data for the modelling analysis. Comparison of the modelling analysis with experimental data demonstrated that the FLUENT code adequately predicted the transport of gas to a remote location. The 5 FLUENT code was also used to predict gas transport at microgravity conditions. The model demonstrated that buoyancy decreases the time to achieve higher gas concentrations between the parallel plates. As an example of the use of this methodology for a combustion scenario, the model was used to predict flame extinction in a blow-off case (i.e., rapid increase in strain rate) and localized flame extinction (i.e., flame shrinking) in a low-strain dilution case with carbon dioxide over time. The model predictions demonstrated the potential of this methodology with a Damköhler number for the prediction of extinction in three-dimensional environments.

Um estudo gravimétrico comparativo das bacias do Chaco-Paraná (BCP) e Paraná (BP) foi efetuado utilizando o modelo global EGM08 e os dados da missão GOCE. A feição gravimétrica mais notável é um gradiente gravimétrico de 0,25 mGal/km, de direção norte-sul e que contorna a borda oeste da Bacia do Paraná e inflexiona para leste na latitude 30º S. Esse gradiente separa as duas bacias em províncias gravimétricas com características distintas. A BCP é caracterizada por anomalias gravimétricas positivas entre 10 e 20 mGal e de direção norte-sul, enquanto que na BP as anomalias variam entre -50 a -90 mGal na direção NE-SW. A análise gravimétrica foi efetuada de duas formas. Inicialmente removeu-se o efeito gravitacional devido aos sedimentos e basaltos e a anomalia devido às fontes mais profundas foi invertida para determinar o relevo da interface crosta-manto. Posteriormente efetuou-se uma análise isostática estimando a profundidade de compensação para a topografia observada nos modelos de Airy e flexural de placa contínua. Esses modelos, considerando a topografia observada como a única carga, não preveem a profundidade da Moho qualquer que seja o valor da espessura elástica. Dados de profundidade da Moho por métodos sismológicos, onde existentes, foram confrontados com os fornecidos pela inversão gravimétrica, estimando assim o valor do contraste de densidade (300 kg/m³) para o qual as profundidades da Moho e da interface crosta-manto obtida pela gravimetria melhor se ajustam. A inversão gravimétrica indica que a crosta da BCP é em média 7 km menos espessa do que a crosta da BP. Os resultados deste estudo sugerem a existência de uma descontinuidade crustal, e possivelmente uma sutura litosférica ao longo do gradiente gravimétrico entre as bacias do Chaco-Paraná e do Paraná. / A comparative gravity study of the Chaco-Paraná (CPB) and the Paraná (PB) basins was carried out using the EGM08 and GOCE global geopotential models. The most prominent gravity feature in the study area is a gradient of 0.25 mGal/km, extending from north to south alongside the western border of the Paraná basin and continuing eastward towards the Atlantic coast at the latitude 30º S. This gradient separates both basins into two gravity provinces with distinct characteristics. The CPB is marked by positive Bouguer anomalies of about 10 to 20 mGal in amplitude with north-south trending, whereas in the PB the Bouguer anomalies range from -50 to -90 mGal and trend along the NE-SW direction. The gravity analysis was carried out in two ways. Firstly, the gravity effect from basalts and sediments was calculated and removed and the gravity anomaly due to deeper sources was inverted in order to determine the crust-mantle interface relief. Secondly, an isostatic analysis was carried out in order to estimate the compensation depth due to the observed topography using both Airy and continuous plate flexural models. These isostatic models, considering the observed topography as the only load, cannot account for the observed Moho regardless of the effective elastic thickness value. Moho depth provided by seismological studies, where available, were compared with the results of the gravity inversion, thus estimating the density contrast (300 kg/m3) for which the Moho and crust-mantle interface depths are in agreement. The gravity inversion indicates that, in average, the CPB crust is 7 km thinner than the PB crust. This study suggests the existence of a crustal discontinuity, and perhaps even a lithospheric suture along the gravity gradient between the Chaco-Paraná and the Paraná basins.