The properties of RNiSb compounds were studied from various points of view: Magnetism, transport, electronic structure. The compounds with a light rare earth are metallic, while the cubic phases with a heavy rare earth element have the semi-Heusler structure and are narrow gap semiconductors. A giant magnetoresistance effect was found at low temperatures, the larger as the density of charge carriers is weak. It was explained by the polarisation of the impurity levels situated within the band gap of the semiconductor under the field of the magnetic moment of the 4f shell. The crystal field, as well as the magnetic order at low temperatures, were studied by neutron scattering and diffraction. Particular magnetic properties (absence of magnetic order in the Pr compound, antiferromagnetic structure in the second group, orientation of the moments) have been explained, at least qualitatively. CeNiSb is a Kondo-type compound with a Kondo temperature of about 8 K. Photoemission measurements have allowed to analyse the electronic structure in the valence band of these compounds, in agreement with band structure calculations. By resonant photoemission of TbNiSb and GdCu, different resonance channels have been resolved, which depend on the spin configuration of the excited states.

Arundo donax (Giant Reed) is quickly being developed as a rapidly-growing, robust, and highly productive bioenergy crop, with large scale cultivation of this species planned for the Columbia River basin of the Pacific Northwest (USA). Despite its potential as a next generation biomass crop, relatively few studies have examined the physiological performance of A. donax under agricultural conditions. Unlike traditional crops, A. donax is known to be a high-emitter of the volatile compound isoprene, which may significantly impact regional air quality, but it has not been widely cultivated in North America and little is known about how this species will perform in the Pacific Northwest. Over two field seasons, we measured isoprene fluxes from A. donax plants in both greenhouse conditions and in an agricultural field setting under a variety of conditions and fertilizer treatments. We also measured several other attributes of A. donax productivity and leaf physiology including chlorophyll content, photosynthesis rate, stomatal conductance, specific leaf mass, water use efficiency and gas exchange. We found that A. donax physiologically performs well under cultivation in the Columbia River basin, but that it also emits isoprene at significantly higher rates than previous reports indicate. We also found that both isoprene emission and leaf physiology were highly affected by agricultural management decisions, including nitrogen and irrigation management. Our findings indicate that crop management strategies can be developed that simultaneously seek to minimize isoprene emission while maximizing biomass production in this newly emerging bioenergy crop.

BACKGROUND: Netarsudil, a Rho kinase and norepinephrine transport (NET) inhibitor, is a new FDA approved drug used for decreasing raised intraocular pressure (IOP) in ocular hypertensive and primary open-angle glaucoma (POAG) patients. Previous studies reported that netarsudil increased outflow facility and lowered IOP by increasing active outflow areas around the circumference of the eye and dilating the episcleral veins (ESV; Kiel and Kopczynski, 2015; Ren et al., 2016). However, the mechanisms by which netarsudil increases outflow facility have not yet been fully elucidated. Moreover, the effects of netarsudil on the inner wall (IW) endothelium I-pores and B-pores of the Schlemm’s canal (SC) have also not been investigated yet. AIM: The goal was to determine if netarsudil-treatment increased the effective filtration areas (EFA) by increasing pore density in both high- and non-flow type areas, compared to untreated control eyes. METHODS: In this study, the effects of netarsudil on the pore densities on IW of SC were investigated by serial block-face scanning electron microscopy (SBF-SEM). Two pairs of eyes were perfused with green fluorescent tracers in order to determine the outflow pattern prior to treatment. Then, one eye of each pair was perfused with netarsudil, while the fellow eye of each pair was perfused with vehicle solution. All eyes were then perfused with red fluorescent tracers in order to determine the outflow pattern once they were treated with netarsudil. Both pairs of eyes were perfused and fixed at 15 mmHg. Global imaging was performed for all eyes to visualize high- and non- flow areas in the trabecular meshwork (TM) and ESV’s. A SBF-SEM was used to image eight wedges of tissue including the IW of SC and TM (high- and non-flow areas from four eyes) for a total of 16,378 images. The study analyzed the percentage of pore-types (GV-associated I-pores, Non-GV associated I-pores, B-pores), the median pore spans, the GV-associated I-pore locations, and the pore densities (per IW nuclei and IW area) between the equivalent control and netarsudil-treated flow areas. RESULTS: In global images, an increase in high-flow areas were observed in netarsudil-treated eyes due to recruitment from low-flow and non-flow areas. A greater percentage of GV-associated I-pores, B-pores, and total pores were found in high-flow in contrast to non-flow areas in both control and netarsudil-treated eyes (all P ≤ 0.05). However, the percentage of GV-associated I-pores in non-flow areas were significantly greater in treated compared to control eyes (P ≤ 0.05). Qualitative observations from two pairs of eyes showed a trend of greater I-pore, B-pore, and total pore density/per IW nucleus and density/per IW surface area in high-flow in contrast to non-flow areas for both treated and control eyes. No difference in I-pore, B-pore, and total pore density/per IW nucleus and density /per IW surface area were observed in equivalent flow-type areas when comparing control and netarsudil-treated eyes. In addition, there was a significant greater percentage of I-pores located on the side of GVs than the top of GVs in all cases (P ≤ 0.05). CONCLUSIONS: Netarsudil increased high-flow areas. A greater pore density was found in high-flow in contrast to non-flow areas. Netarsudil also significantly increased the proportion of GV-associated I-pores in non-flow areas when compared to control eyes. Our results suggests that one mechanism of netarsudil increasing outflow facility is acting through recruiting the high-flow areas around the circumference of the eye, which is associated with higher pore density and increasing the proportion of GV-associated I-pores in non-flow areas.

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L’objectif de ce mémoire est de quantifier la diagenèse de l’arsenic (As) dans les sédiments, d'utiliser ceux-ci comme archive environnementale et d’identifier les réactions clés de l’As. Huit lacs ont été visités en juin 2018 et mai 2019, le long d’un transect de 80 km au nord-ouest de la mine d’or Giant, à Yellowknife, dans les Territoires du Nord-Ouest, Canada, pour y prélever de l’eau de surface, des carottes de sédiments et de l’eau porale. Ces échantillons ont été analysés afin d’obtenir les concentrations dissoutes et solides de carbone organique, d’As, de fer (Fe), manganèse (Mn) et d'aluminium (Al) et des anions nitrate, sulfate, sulfure et chlorures. Les concentrations d’As dans l’eau porales ont été interprété à l’aide de la modélisation diagenétique inverse et de calculs thermodynamiques. L'historique des flux d’As solide déposés au fond des lacs a été calculé après correction pour l'influence de la diagenèse. Les flux diffusifs d’As à l’interface eau-sédiment en réponse à la contamination causée par l’activité minière ont été calculés pour les deux années d'échantillonnage. Les résultats montrent que la diagenèse est plus importante dans les lacs avec des taux de sédimentation plus faibles. Après correction, les données indiquent que les flux d'As maximaux coïncident avec la période d'activité de la mine. Néanmoins, les lacs près de la mine sont toujours sous l’influence d’apports importants d’As dissous depuis leur bassin versant, et montrent des flux diffusifs élevés d’As vers la colonne d’eau. Les calculs thermodynamiques de spéciation et des indices de saturations suggèrent que la mobilité de l'As est liée à celle des oxydes de fer et au soufre. Le sulfure de fer amorphe se forme dans les sédiments et l’As co-précipite ou s’adsorbe sur cette phase minérale. Enfin, le moment de la fonte du couvert de glace, qui permet l’arrivée de l’oxygène, semble déterminer la mobilité de l’As auprintemps. Dans le contexte où les changements climatiques influencent la durée du couvert de glace, une étude approfondie de l’effet du couvert de glace sur les conditions d’oxydoréduction est souhaitable. / The goal of this thesis is to quantify the diagenesis of arsenic (As) in the sediments, using them as environmental archives and identify the key reactions of As. Eight lakes have been visited in June 2018 and May 2019, along an 80 km transect northwest from the gold mine Giant, near Yellowknife in the Northwest Territories, Canada to collect surface water, sediment cores and porewater. These samples have been analyzed to obtain the dissolved and solid concentration of organic carbon, As, iron (Fe), manganese (Mn) and aluminium (Al) and anions (nitrate, sulfate, sulfide and chloride). As concentrations in porewater were interpreted using inverse diagenetic modeling and thermodynamics calculations. The history of the fluxes of solid As deposited at the bottom of the lakes was calculated after correction for the influence of diagenesis. Diffusive fluxes of As at the sediment-water interface in response to contamination from mining activity were calculated for the two years of sampling. The results show that diagenesis is greater in lakes with lower sedimentation rates. After correction, the data indicates that the maximum As fluxes coincide with the period of mine activity. Nonetheless, lakes near the mine are still influenced by large inputs of dissolved As from their watersheds, and show high diffusive fluxes of As to the water column. Thermodynamic calculations of speciation and saturation index suggest that the mobility of Asis related to that of iron oxides and sulfur. Amorphous iron sulfide forms in the sediment and As coprecipitates or adsorbs to this mineral phase. Finally, the timing of the melting of the ice cover, which allows the arrival of oxygen, seems to determine the mobility of As in the spring. In the context of climate change shortening the duration of ice cover, an in-depth study of the effect of ice cover on redox conditions is desirable.