The formation of dissolved gaseous mercury (DGM) can be an important pathway for mercury removal from an aquatic environment. DGM evasional fluxes from an aquatic system can account for up to 95% of atmospheric Hg and its deposition pathways. While this makes DGM an important species of mercury to investigate, the difficulty of accurately analyzing DGM has prevented many from studying it. In this study, DGM was measured in two different types of estuarine environments and with two different methods, discrete and continuous analysis. The discrete technique works reasonably well and is reproducible, but it does not allow one to observe rapid changes in DGM concentration due to long analysis times (~2 hr per sample). When used in this study, the discrete sampling technique agreed well with the continuous technique for Offatts Bayou, Galveston, Texas, and Georgiana Slough in the California Bay-Delta region. The average DGM concentration during the March continuous study at Offatts Bayou was 25.3 + 8.8 pg L-1. This is significantly higher than the average DGM concentration from Georgiana Slough during late March 2006 (9.6 + 6.6 pg L-1). DGM seemed to correlate best with photosynthetically active radiation (PAR) data in every study, suggesting that the primary control of its formation is solar irradiation. Stronger positive correlations with PAR were seen when DGM data was shifted back one hour, indicating that mercury photoreactions take time to complete. DGM also correlated positively with wind speed in most instances. However, increased wind speed should enhance air to water transfer of elemental mercury, thus one would expect a negative correlation. DGM co-varied negatively with salinity during the continuous studies, suggesting that the DGM pool is reduced in surface waters by chloride mediated oxidation. Three predictive flux models were used in the study to assess the potential for DGM water to air transfer. For both the Georgiana Slough and Offatts Bayou studies, the predicted flux dropped to or below zero after sunset. This study does contribute to the understanding of DGM cycling in aquatic environments as there are few studies that have made continuous DGM measurements in estuarine environments.

The formation of dissolved gaseous mercury (DGM) can be an important pathway for mercury removal from an aquatic environment. DGM evasional fluxes from an aquatic system can account for up to 95% of atmospheric Hg and its deposition pathways. While this makes DGM an important species of mercury to investigate, the difficulty of accurately analyzing DGM has prevented many from studying it. In this study, DGM was measured in two different types of estuarine environments and with two different methods, discrete and continuous analysis. The discrete technique works reasonably well and is reproducible, but it does not allow one to observe rapid changes in DGM concentration due to long analysis times (~2 hr per sample). When used in this study, the discrete sampling technique agreed well with the continuous technique for Offatts Bayou, Galveston, Texas, and Georgiana Slough in the California Bay-Delta region. The average DGM concentration during the March continuous study at Offatts Bayou was 25.3 ± 8.8 pg L-1. This is significantly higher than the average DGM concentration from Georgiana Slough during late March 2006 (9.6 ± 6.6 pg L-1). DGM seemed to correlate best with photosynthetically active radiation (PAR) data in every study, suggesting that the primary control of its formation is solar irradiation. Stronger positive correlations with PAR were seen when DGM data was shifted back one hour, indicating that mercury photoreactions take time to complete. DGM also correlated positively with wind speed in most instances. However, increased wind speed should enhance air to water transfer of elemental mercury, thus one would expect a negative correlation. DGM co-varied negatively with salinity during the continuous studies, suggesting that the DGM pool is reduced in surface waters by chloride mediated oxidation. Three predictive flux models were used in the study to assess the potential for DGM water to air transfer. For both the Georgiana Slough and Offatts Bayou studies, the predicted flux dropped to or below zero after sunset. This study does contribute to the understanding of DGM cycling in aquatic environments as there are few studies that have made continuous DGM measurements in estuarine environments.

Biogeochemical reactions and vadose zone transport, in particular gas phasetransport, are inherently coupled processes. To explore feedback mechanisms between these processes in a quantitative manner, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described based on the Dusty Gas Model, which provides the most generally applicable description for gas diffusion.Gas advection is described by Darcy's Law, which in the current formulation, is directly substituted into the transport equations. The model is used to investigate the interactions between geochemical reactions and transport processes with an emphasis to quantify reaction-induced gas migration in the vadose zone. Simulations of pyrite oxidation in mine tailings, gas attenuation in partially saturated landfill soil covers, and methane production and oxidation in aquifers contaminated by organic compounds demonstrate how biogeochemical reactions drive diffusive and advective transport of reactive and non-reactive gases. Pyrite oxidation in mine tailings causes a pressure reduction in the reaction zone and drives advective gas flow into the sediment column, enhancing the oxidation process. Release of carbondioxide by carbonate mineral dissolution partly offsets pressure reduction, and illustrates the role of water-rock interaction on gas transport. Microbially mediated methane oxidation in landfill covers reduces the existing upward pressure gradient, there by decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, both generation of CH⁴ in the methanogenic zone and oxidation of CH⁴ in the methanotrophic zone contribute to drive advective and diffusive fluxes. The model confirmed that non-reactive gases tend to accumulate in zones of gas consumption and become depleted in zones of gas production. In most cases, the model was able to quantify existing conceptual models, but also proved useful to identify data gaps, sensitivity, and inconsistencies in conceptual models. The formulation of the model is general and can be applied to other vadose zone systems in which reaction-induced gas transport is of importance.

Biogeochemical reactions and vadose zone transport, in particular gas phasetransport, are inherently coupled processes. To explore feedback mechanisms between these processes in a quantitative manner, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described based on the Dusty Gas Model, which provides the most generally applicable description for gas diffusion.Gas advection is described by Darcy's Law, which in the current formulation, is directly substituted into the transport equations. The model is used to investigate the interactions between geochemical reactions and transport processes with an emphasis to quantify reaction-induced gas migration in the vadose zone. Simulations of pyrite oxidation in mine tailings, gas attenuation in partially saturated landfill soil covers, and methane production and oxidation in aquifers contaminated by organic compounds demonstrate how biogeochemical reactions drive diffusive and advective transport of reactive and non-reactive gases. Pyrite oxidation in mine tailings causes a pressure reduction in the reaction zone and drives advective gas flow into the sediment column, enhancing the oxidation process. Release of carbondioxide by carbonate mineral dissolution partly offsets pressure reduction, and illustrates the role of water-rock interaction on gas transport. Microbially mediated methane oxidation in landfill covers reduces the existing upward pressure gradient, there by decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, both generation of CH⁴ in the methanogenic zone and oxidation of CH⁴ in the methanotrophic zone contribute to drive advective and diffusive fluxes. The model confirmed that non-reactive gases tend to accumulate in zones of gas consumption and become depleted in zones of gas production. In most cases, the model was able to quantify existing conceptual models, but also proved useful to identify data gaps, sensitivity, and inconsistencies in conceptual models. The formulation of the model is general and can be applied to other vadose zone systems in which reaction-induced gas transport is of importance.

Quantitative Magnetic Resonance has become more and more accepted for clinical trial in many fields. This technique not only can generate qMRI maps (such as T1/T2/PD) but also can be used for further postprocessing including segmentation of brain and characterization of different brain tissue. Another main application of qMRI is to measure the volume of the brain tissue such as the deep Grey Matter (dGM). The deep grey matter serves as the brain's "relay station" which receives and sends inputs between the cortical brain regions. An abnormal volume of the dGM is associated with certain diseases such as Fetal Alcohol Spectrum Disorders (FASD). The goal of this study is to investigate the effect of age on the volume change of the dGM using qMRI. Thirteen patients (mean age= 26.7 years old and age range from 0.5 to 72.5 years old) underwent imaging at a 1.5T MR scanner. Axial images of the entire brain were acquired with the mixed Turbo Spin-echo (mixed -TSE) pulse sequence. The acquired mixed-TSE images were transferred in DICOM format image for further analysis using the MathCAD 2001i software (Mathsoft, Cambridge, MA). Quantitative T1 and T2-weighted MR images were generated. The image data sets were further segmented using the dual-space clustering segmentation. Then volume of the dGM matter was calculated using a pixel counting algorithm and the spectrum of the T1/T2/PD distribution were also generated. Afterwards, the dGM volume of each patient was calculated and plotted on scatter plot. The mean volume of the dGM, standard deviation, and range were also calculated. The result shows that volume of the dGM is 47.5 ±5.3ml (N=13) which is consistent with former studies. The polynomial tendency line generated based on scatter plot shows that the volume of the dGM gradually increases with age at early age and reaches the maximum volume around the age of 20, and then it starts to decrease gradually in adulthood and drops much faster in elderly age. This result may help scientists to understand more about the aging of the brain and it can also be used to compare with the results from former studies using different techniques.

In this thesis, software adgfem is extended to be capable of calculation of non- linear magnetic field in complex geometry. Software adgfem implements discontinuous Galerkin method and so far has been used mainly to solve convection-diffusion problems and lacked streamlined approach to computational mesh generation. This thesis contains step-by-step guideline to creation of complex geometry using software SALOME. This mesh is then converted to format suitable for adgfem using newly written convertor datToAdgfem. Mesh created in this way is then used for calculation of non-linear static magnetic field.

Biogeochemical reactions and vadose zone transport, in particular gas phasetransport, are inherently coupled processes. To explore feedback mechanisms between these processes in a quantitative manner, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described based on the Dusty Gas Model, which provides the most generally applicable description for gas diffusion.Gas advection is described by Darcy's Law, which in the current formulation, is directly substituted into the transport equations. The model is used to investigate the interactions between geochemical reactions and transport processes with an emphasis to quantify reaction-induced gas migration in the vadose zone. Simulations of pyrite oxidation in mine tailings, gas attenuation in partially saturated landfill soil covers, and methane production and oxidation in aquifers contaminated by organic compounds demonstrate how biogeochemical reactions drive diffusive and advective transport of reactive and non-reactive gases. Pyrite oxidation in mine tailings causes a pressure reduction in the reaction zone and drives advective gas flow into the sediment column, enhancing the oxidation process. Release of carbondioxide by carbonate mineral dissolution partly offsets pressure reduction, and illustrates the role of water-rock interaction on gas transport. Microbially mediated methane oxidation in landfill covers reduces the existing upward pressure gradient, there by decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, both generation of CH⁴ in the methanogenic zone and oxidation of CH⁴ in the methanotrophic zone contribute to drive advective and diffusive fluxes. The model confirmed that non-reactive gases tend to accumulate in zones of gas consumption and become depleted in zones of gas production. In most cases, the model was able to quantify existing conceptual models, but also proved useful to identify data gaps, sensitivity, and inconsistencies in conceptual models. The formulation of the model is general and can be applied to other vadose zone systems in which reaction-induced gas transport is of importance. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

This thesis deals with solving stationary magnetic field in material with non-constant magnetic reluctivity in realistic geometry. To this end, we extended adgfem software. Software adgfem implements discontinuous Galerkin method and so far has been used mainly to solve convection- diffusion problems and lacked streamlined approach to computational mesh generation. This thesis contains step-by-step guideline to creation of complex geometry using software SALOME. This mesh is then converted to format suitable for adgfem using newly written convertor datToAdgfem. Mesh created in this way is then used for calculation of non-linear static magnetic field.

L’exposition foetale à l’hyperglycémie maternelle (HGM), ainsi qu’un poids à la naissance aux deux extrémités du spectre (petit ou grand poids en fonction de l’âge gestationnel) sont deux conditions associées à un risque accru de développer des maladies cardiovasculaires et/ou métaboliques, tels l’obésité ou le diabète de type II, plus tard dans la vie. Le système IGF {Insulin-like growth factor) est un important régulateur du métabolisme et de la croissance foeto-placentaire. Une perturbation moléculaire précoce du système IGF pourrait donc être impliquée dans la programmation métabolique foetale. Les objectifs de cette étude étaient donc d’évaluer l’impact d’une exposition foetale à l’HGM sur le profil de méthylation de l’ADN et d’ARNm des gènes IGF1R {Insulin-like growth factor 1 receptor), IGFBP3 {Insulin-like growth factor binding protein 3), IGFI {Insulin-like growth factor 1) et INSR {Insulin receptor) dans le placenta, puis d’évaluer les possibles associations entre le profil épigénétique des gènes de ce système et les indices de développement foeto-placentaire. L’HGM (incluant l’intolérance au glucose et le DGM) a été diagnostiquée selon les critères de l'Organisation Mondiale de la Santé (OMS; HGM: n=34; normo-glycémie matemelle (NGM): n=106). Une hypométhylation de l’ADN des gènes IGF1R et IGFBP3 a été démontrée dans les placentas exposés à l’HGM comparé à ceux exposés à la NGM (respectivement -4,3%; p=0,02 et -2,5%; p= 0,01). Les niveaux de méthylation de l’ADN d’IGFIR et d'1GFBP3 étaient aussi corrélés négativement à la glycémie 2h post-HGOP (respectivement r=-0,23; p= 0,01 et r=-0,20; p= 0,03). Le poids du nouveau-né à la naissance était associé au niveau d’ARNm d’IGFIR dans le placenta (r=0,20; p=0,03). Ces résultats supportent la fonction régulatrice de croissance du système IGF au cours du développement foeto-placentaire et suggèrent une dérégulation du profil de méthylation de l’ADN des gènes IGF1R et d'IGFBP3 dans les placentas exposés à l'HGM. Cette étude suggère également un effet compensatoire du système IGF placentaire pouvant contribuer à limiter les effets promoteurs de croissance liés à l’hyperinsulinémie foetale associé à l’HGM. Les gènes IGF1R et IGFBP3 pourraient être impliqués dans la programmation foetale des maladies métaboliques chroniques.

L'objectif de ce travail est de construire une machine d'essai pour la prothèse. La machine doit être capable de reproduire les mêmes conditions dynamiques et cinématiques appliquées sur la prothèse pendant l'utilisation normale.Le nombre d'amputation et les causes d'amputation ont été recueillis. Différents types de prothèses ont été classés selon la prothèse de jambe par hauteur d'amputation, prothèse passive et active, différenciées par la nature de leur actionneur. La plupart des machines d'essai pour la prothèse ont été étudiées à partir de la prospective technologique et capacitaire. Déterminer toutes les limitations de la plupart des machines d'essai existantes, et les besoins de développer une nouvelle machine pour remplir complètement ces besoins ont été développés.Ensuite, nous avons étudié et analysé la dynamique de la marche et de la course humaines. Les équations du mouvement en prenant en considération les masses et les moments d'inertie des segments squelettiques. La plupart des paramètres de la démarche ont été extraits. En conclusion, nous avons les exigences cinématiques du centre de gravité humain pour générer 6 DOF que la machine d'essai devrait effectuer pour imiter la démarche humaine normale et courir.Trois conceptions ont été proposées pour implanter la machine d'essai; Bras de robot articulé, manipulateur cartésien et Stewart Platform (SP). Après la mise en œuvre des trois solutions, nous avons trouvé la solution la plus appropriée est le SP attaché avec une hanche active artificielle. Nous avons choisi la puissance hydraulique car c'est la technique d'actionnement la plus appropriée pour notre solution, connaissant les forces d'actionnement requises.Pour aider à contrôler le mouvement de SP, une nouvelle solution de modèle géométrique direct pour la planeuse et la plate-forme Stewart 6-6 a été développée en utilisant les capteurs rotatifs au lieu de capteurs de revêtement comme voulu pour les actionneurs hydrauliques. L'analyse de sensibilité a été étudiée pour cette solution, et un calcul analytique pour le calcul de l'espace de travail a également été développé.La conclusion de cette machine d'essai est que nous pouvons créer toute la dynamique du corps humain, c'est-à-dire marcher ou courir ou monter et descendre des escaliers. La solution développée peut porter des procédures d'essai pour la prothèse passive ou active. / The objective of this work is to build a testing machine for prosthesis. The machine should be able to reproduce the same dynamic and kinematics conditions applied on the prosthesis during the normal use.Numbers of amputation, and causes of amputation were collected. Different types of prosthesis were classified according to the leg prosthesis per amputation height, passive and active prosthesis, differentiated by the nature of their actuator. Most of the testing machine for the prosthesis were studied form the technological and capability prospective. Determining all the limitations of most of existing testing machines, and the needs to develop a new machine to full fill these needs were developed.Then we studied and analyzed the dynamics of the human gait and run. The equations of motion by taking into consideration the masses and moments of inertia of skeletal segments. Most of the parameters of gait were extracted. In conclusion, we have the kinematic requirements of the human center of gravity to generate 6 DOF that the testing machine should carry out to emulate the normal human gait and run.Three designs were proposed to implement the testing machine; Articulated robot arm, Cartesian manipulator, and Stewart Platform (SP). After implementing the three solutions we found the most suitable solution is the SP attached with it an artificial active hip. We have chosen the hydraulic power as it is the most suitable actuation technique for our solution knowing the required actuation forces.To help in controlling the SP motion, a novel Closed-form solution of direct Geometric model for planer and 6-6 Stewart Platform using the rotary sensors instead of liner sensors as wanted to the hydraulic actuators was developed. Sensitivity analysis was studied for that solution, and analytical calculation for computing the workspace was also developed.The conclusion from this testing machine is that we can create all the dynamics of the human body, i.e. walking or running or going up and down stairs. The developed solution can carry testing procedures for either passive or active prothesis.