Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Les interactions plasma-paroi représentent l'un des principaux problèmes à résoudre pour avancer dans la recherche sur la fusion contrôlée. Ce travail de thèse a pour objectif de développer une source d'hydrogène atomique à basse pression (< Torr) dans un réacteur à configuration hélicon en mélange H2/Ar pour étudier la gravure chimique du graphite et de composites à fibres de carbone utilisés dans le tokamak Tore Supra. Selon les conditions expérimentales, le réacteur peut générer les modes de couplages capacitif, inductif, Trivelpiece-Gould et hélicon à bas champ. Leur caractérisation a montré que le mode inductif est, dans ce cas, celui présentant le plus grand intérêt pour la source d'hydrogène atomique. Les études en mode inductif ont révélé un phénomène de décroissance de la densité relative de deux niveaux métastables de l'ion Ar+ et d'un niveau métastable de l'argon neutre lors de l'augmentation du champ magnétique de confinement. Un modèle simple a confirmé que ces niveaux métastables sont détruits par collisions électroniques vers des niveaux de plus grande énergie. La gravure du graphite par la source d'hydrogène atomique est relativement efficace (jusqu'à 3 µm/h) à 10 mTorr et diminue avec la pression. Une analyse qualitative de la cinétique de l'hydrogène atomique a permis de conclure que cette baisse de la vitesse de gravure est due au flux d'hydrogène atomique arrivant sur l'échantillon qui décroît lorsque la pression augmente. Les premières observations de la surface après gravure ont mis en évidence la présence de structures carbonées (agglomérats de nanoparticules et dépôts). Ces structures ressemblent à celles observées dans différents tokamaks / Plasma-wall interactions are one of the main issues in fusion research and must be thoroughly studied to progress in this topic. The objective of this work is to develop an atomic hydrogen source at low pressure (< Torr) in a helicon configuration reactor working in H2/Ar gas mixture. This source is then used to study the chemical etching of graphite and carbon fiber composites composing the limiter of the Tore Supra tokamak. Depending on the experimental conditions, the RF power coupling of the reactor can be in capacitive, inductive, Trivelpiece-Gould or low field helicon mode. The characterization of these modes determined that in this case the inductive one presents the greatest interest for the atomic hydrogen source. Further studies in inductive mode showed that increasing the confinement magnetic field leads to a decrease of measured relative densities of two metastable levels of argon ion and one metastable state of neutral argon. A simple model simulating neutral metastable state behavior confirmed that these levels are destroyed by electronic collisions towards upper levels. The chemical etching of graphite exposed to the atomic hydrogen source is relatively efficient (up to 3 µm/h) at 10 mTorr and drops with the pressure. A qualitative analysis of atomic hydrogen kinetics concluded that this behavior is due to the decrease of atomic hydrogen flux on the sample with increasing pressure. Finally, first observations of the etched surface underlined different structures (nanoparticles clusters and deposits). These can be compared to the ones observed in different tokamaks

Testicular stem cells (TSCs) are relatively accessible potential source of pluripotent cells, which are particularly important for their application in regenerative medicine. Xenopus tropicalis is a useful model organism to study the migration and differentiation potential of stem cells. This amphibian is characteristic by outer fecundation and embryonic development of a great amount of embryos after fertilization. Oocytes and embryos are large enough (about 1 mm) to be suitable for micromanipulation micromanipulations. Laboratory of Developmental Biology, Faculty of Science, Charles University in Prague succeeded in the establishment of a mixed cell culture of TSCs growing on feeder layer of pre- Sertoli cells. This culture was derived from the testes of juvenile Xenopus tropicalis male. In the study of their differentiation potential it was found, that leukemia inhibitory factor (LIF) is the decisive factor allowing rapid proliferation of stem cells and their forming into characteristic colonies. This protein is produced by both types of cells which are present in the culture. The mouse LIF has the same positive effect on the proliferative potential of stem cells, which points at the evolutionary conservation of metabolic pathways associated with the maintenance of the stemness. RT-PCR analysis...

Made available in DSpace on 2017-07-24T19:38:13Z (GMT). No. of bitstreams: 1 celiamara.pdf: 1566129 bytes, checksum: 2e28de921736868a8a537a38f3f5b6fb (MD5) Previous issue date: 2007-07-30 / Soil organic matter is essential for its quality and productivity, being its process of humification affected by the climate, soil type and soil management, resulting in the formation of fluorescent groups that can be measured through Laser- Induced Fluorescence Spectroscopy, a recent technique that has been showing efficient for analysis of whole soil, that is, soil without any physical or chemical treatment. This technique was used to determine the humification degree of the Organic Matter of a whole soil, as well as the physical fraction for particle size. It can also be used to relate the results of the quantification of the humification organic matter with the depth of the soil and planting systems. On the surface of the soil, No-Tillage got the smallest humification in comparison with the conventional tillage and the reduced tillage, whereas the fractions of the superficial layer of the soil (0-20 cm), indicated larger humification in the fraction (20-53) and the smallest in the fraction (2 ), in all treatments. / RESUMO A matéria orgânica é essencial para a qualidade e produtividade do solo, sendo seu processo de humificação afetado pelo clima, tipo de solo e sistemas de manejo do solo, resultando na formação de grupos fluorescentes que podem ser avaliados por espectroscopia de Fluorescência Induzida por Laser (FIL), uma técnica recente que tem se mostrado eficiente para análise da matéria orgânica (MO) de solos inteiros, isto é, solos sem nenhum tratamento físico ou químico. Esta técnica foi utilizada para determinar a humificação da MO de um Latossolo inteiro, como também o fracionamento físico por tamanho de partículas e relacionar os resultados da quantificação da MO humificada com a profundidade do solo e sistemas de manejo. Na superfície do solo, o plantio direto possui a menor humificação em comparação com o preparo convencional e o preparo mínimo, enquanto que as frações da camada superficial do solo (0-20 cm) indicaram maior humificação na fração (20-53) e a menor na fração (2 ), em todos os sistemas de manejo.

Doctor of Philosophy(PhD) / This body of research uses numerical and experimental investigative techniques to further the understanding of autoignition. Hydrogen/nitrogen and methane/air fuel configurations of turbulent lifted flames in a vitiated coflow burner are used as model flames for this investigation. Characterisation was undertaken to understand the impact of controlling parameters and the overall behaviour of the flames, and to provide a body of data for modelling comparisons. Modelling of the flames was conducted using the PDF-RANS technique with detailed chemistry incorporated using In-situ Adaptive Tabulation (ISAT) within the commercial CFD package, FLUENT 6.2. From these investigations, two numerical indicators for autoignition were developed: convection-reaction balance in the species transport budget at the mean flame base; and the build-up of ignition precursors prior to key ignition species. These indicators were tested in well defined autoignition and premixed flame cases, and subsequently used with the calculated turbulent lifted flames to identify if these are stabilised through autoignition. Based on learnings from the modelling, a quantitative, high-resolution simultaneous imaging experiment was designed to investigate the correlations of an ignition precursor (formaldehyde: CH2O) with a key flame radical (OH) and temperature. Rayleigh scattering was used to measure temperature, while Laser Induced Fluorescence (LIF) was used to measure OH and CH2O concentrations. The high resolution in the Rayleigh imaging permitted the extraction of temperature gradient data, and the product of the OH and CH2O images was shown to be a valid and useful proxy for peak heat release rate in autoigniting and transient flames. The experimental data confirmed the presence of formaldehyde as a precursor for autoignition in methane flames and led to the identification of other indicators. Sequenced images of CH2O, OH and temperature show clearly that formaldehyde exists before OH and peaks when autoignition occurs, as confirmed by images of heat release. The CH2O peaks decrease later while those of OH remain almost unchanged in the reaction zone.

<p>ABSTRACT</p><p>A defect implantation process is the major reason for unexplained infertility. Estrogen andprogesterone are steroid hormones preparing the endometrium for implantation. They mediatetheir effect through their receptors: estrogen receptor alpha and beta and progesteronereceptor A and B, respectively. Leukemia inhibitory factor (LIF), which is also important forimplantation, mediates its effect through LIF receptor and the coreceptor, gp130, and is downregulated by suppressors of cytokine signaling 1. The aim of the study was to compare thelevels of the steroid hormone receptors and LIF related factors in the endometrium of twogroups of women with the diagnosis unexplained infertility: one that became pregnant afterassisted reproduction and one that did not become pregnant. Before treatment of thesewomen, endometrial mRNA was collected during the window of implantation in themenstrual cycle. The levels of specific mRNAs were measured with real-time PCR. Womenwho had become pregnant had a significantly higher level of steroid hormone receptors. Thus,these proteins seem to be important for a pregnancy and may be suitable as receptivitymarkers.</p>

Over the last decade our understanding of mercury cycling has dramatically changed. Evidence of rapid atmospheric oxidation has been observed in the Arctic, Antarctic, the MBL, coastal environments, saline lakes, and the upper troposphere/lower stratosphere. These results show that, Hg0, can undergo rapid gas-phase oxidation under standard atmospheric conditions. However, the mechanism and importance of this transformation is still unclear. The goal of this work was two-fold: to investigate of the kinetics of potential pathway for the gas phase oxidation of atmospheric mercury and to develop new laser based techniques, which can be employed for both laboratory and field studies of Hg(0) and the products of mercury oxidation. First and foremost, this work determined kinetic rate coefficients for the potentially important mercury reactions. Rate coefficients were determined using a Pulse Laser Photolysis - Laser Induced Fluorescence (PLP-LIF) technique monitoring one or more of the following species, Hg(0), Cl, Br, HgCl, and HgBr. The concentrations of these species were measured by LIF as the reaction occurred and a concentration vs. time profile was generated. From these profiles a rate coefficient for the reaction can be obtained. In the course of this work kinetic rate coefficients for the following mercury reactions were measured. Hg(0) + Cl + M --> HgCl + M Hg(0) + Br + M --> HgBr + M HgBr + M --> Hg(0) + Br + M HgBr + Br --> products HgCl + O2 --> products This work is the first direct measurement of a kinetic rate coefficient for these reactions, and the first work which employed one photon LIF to monitor the HgCl and HgBr products. The second aspect of this work was the development of new laser based techniques to detect atmospheric mercury and its oxidation products for both laboratory and field application. In this work a LIF technique was develop to detect HgCl and HgBr. In addition, a two photon LIF technique initially developed by Bauer et al., 2002 was verified and expanded. The two photon LIF technique was used to directly monitor Hg(0) atoms in-situ, to monitor Hg(0) evolving form a gold tube, and to monitor the Hg(0) evolving from the thermal decomposition of reactive gaseous mercury collected on a KCl coated or uncoated denuder. This work represents a significant advance in the development of a viable method the detect mercury and the mercury oxidation products in the laboratory and in the field and is the first study to observe clear differences in the characteristic desorption profiles of HgO and HgX2. This work has broad implications, it enhanced our current knowledge concerning the biogeochemical cycling of mercury, broadened our understanding of the mercury chemistry in high halogen environment, and provided new techniques which can be applied in future field and laboratory studies.

Ephemeral patches of hydrodynamic and chemical sensory cues at fine scales are fundamentally important to the life success of plankton populations and thus the overall health and vitality of nearshore marine ecosystems. We employed various tools from experimental fluid mechanics to create ecologically-relevant hydrodynamic and chemical conditions in a recirculating flume system for zooplankton behavioral assays. The goal was to quantify and correlate changes in zooplankton behavior with coincident sensory cues. A laminar, planar free jet (the Bickley jet) was used to create finescale, free shear layers with targeted hydrodynamic characteristics as well as finescale, sharp-edged layers of both beneficial and toxic ("red tide") phytoplankton species. Planar particle image velocimetry (PIV) and laser-induced fluorescence (LIF) were used to quantify the flow and concentration fields, respectively. Behavioral assays with a variety of crustacean zooplankton species including Antarctic krill (Euphausia superba), estuarine crab larvae (Panopeus herbstii), and calanoid copepods (Temora longicornis and Acartia tonsa), each unique in its ecology, morphology, and life history, show clear and statistically-significant behavioral responses to relevant hydrodynamic and chemical cues. Estuarine crab larvae optimize short term and long term behavioral needs (foraging and habitat selection) by sensing and exploiting the information contained in multi-directional free shear flows. In the presence of thin layers of toxic algal exudates (Karenia brevis), T. longicornis and A. tonsa exhibit explicit avoidance behaviors through significant increases in swimming speed and overall behavioral variability resulting in a conspicuous hydrodynamic signature in a risk/benefit behavioral response. Finally, Antarctic krill exploit the hydrodynamic cues contained in a free shear layer to modify swimming behaviors and ultimately graze in a thin phytoplankton layer (Tetraselmis spp.). Each species is able to sense and exploit the information contained in coherent hydrodynamic and chemical sensory cues to change swimming kinematics and alter macroscale trajectory characteristics. Quantifying changes in zooplankton behavior in response to ecologically-relevant sensory cues is a crucial step towards modeling (e.g. via biophysically-coupled individual-based ecosystem models) and managing sustainable marine fisheries.

ABSTRACT A defect implantation process is the major reason for unexplained infertility. Estrogen andprogesterone are steroid hormones preparing the endometrium for implantation. They mediatetheir effect through their receptors: estrogen receptor alpha and beta and progesteronereceptor A and B, respectively. Leukemia inhibitory factor (LIF), which is also important forimplantation, mediates its effect through LIF receptor and the coreceptor, gp130, and is downregulated by suppressors of cytokine signaling 1. The aim of the study was to compare thelevels of the steroid hormone receptors and LIF related factors in the endometrium of twogroups of women with the diagnosis unexplained infertility: one that became pregnant afterassisted reproduction and one that did not become pregnant. Before treatment of thesewomen, endometrial mRNA was collected during the window of implantation in themenstrual cycle. The levels of specific mRNAs were measured with real-time PCR. Womenwho had become pregnant had a significantly higher level of steroid hormone receptors. Thus,these proteins seem to be important for a pregnancy and may be suitable as receptivitymarkers.

Atmospheric nitrous acid (HONO) is a significant and sometimes dominant OH source at polar region. An improved method of detecting HONO is developed using photo-fragmentation and laser-induced fluorescence (LIF). The detection limit of this method is 2-3 pptv for ten-minute integration time with 35% uncertainty. The abundance of laser-induced fluorescence (LIF) HONO measurements during ANTCI (Antarctic troposphere chemistry investigation) 2003 exceeds the pure gas phase model predictions by a factor of 1.92±0.67, which implies snow emission of HONO. A 1D air-snowpack model of HONO was developed and constrained by observed chemistry and meteology data. The 1D model includes pure gas phase chemical mechanisms, molecular diffusion and mechanical dispersion, windpumping in snow, gas phase to quasi-liquid layer phase HONO transfer and quasi-liquid layer nitrate photolysis. Based on the air-snowpack model, snow emission of HONO is highly likely and will be transported to place of the measurements. The pH, thickness of quasi liquid layer and contineous nitrite measurement are key factors to calibrate and validate the air snowpack model.