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No / Numerous factors may influence the incidence of diabetes in the population. The production of reactive oxygen species (ROS) is elevated in diabetes patients. Based on the reported involvement of reactive species and nitrate/nitrite in diabetes, this present study has examined in the alkaline Comet assay, the effect of different levels of NaNO2 in the presence of the oxygen radical generating agent, hydrogen peroxide (H2O2). Peripheral lymphocytes from diabetic and non-diabetic Caucasians and Asians of both sexes were studied in vitro. Endogenous factors (e.g., sex, age, body mass index-BMI) and exogenous factors (lifestyle factors e.g., smoking and drinking habits, diet) were taken into account. A preliminary study in two individuals showed that DNA damage remained constant over a wide dose range of NaNO2 (1-75 mM), but when H2O2 was added at a constant concentration of 50 ¿M per dose of NaNO2, there was an increase in DNA damage corresponding with the varying levels of NaNO2 investigated. This was also seen with the 44 individuals (non-diabetic, n = 24; type 1 diabetic, n = 11; type 2 diabetic, n = 9) investigated. NaNO2 was capable of inducing a significant level of DNA damage in lymphocytes (p<0.001), but only with the addition of H2O2. When levels of DNA damage were analysed in terms of the different variables there were few significant differences in damage between diabetic and non-diabetic subjects, or other sub-population groups, and no statistically significant differences in susceptibility were observed between subject covariates using regression techniques.

Mycobacterium avium is human and animal opportunistic pathogen responsible for disseminated disease in immunocompromised patients. Mycobacteria have a capacity to adapt to the environmental conditions by inducing enzyme activities and altering their metabolism. M. avium A5 cells were grown in a defined minimal medium (Nitrogen Test Medium) with glutamine, nitrite, nitrate, or ammonia as sole nitrogen source at a concentration of 2 mM at 370C aerobically. The strain grew well on all the nitrogen sources except nitrite. It grew slowly on nitrite with a generation time of 6 days and cultures were not viable after 4 weeks of storage. These data confirm that M. avium can utilize a single nitrogen source in a defined minimal medium as documented by McCarthy (1987). M. avium genome has been sequenced and contains genes sharing sequence similarities to respiratory nitrate reductase and dissimilatory nitrite reductases. Because, M. avium can use nitrate or nitrite as sole nitrogen source for growth (McCarthy, 1987), it must have assimilatory nitrate- and nitrite-reductases. Nitrate- and nitrite-reductase activities of M. avium cells growing aerobically or undergoing anaerobic shift in the presence of ammonia, nitrate or ammonia and nitrate in combination were measured. M. avium produced nitrate- as well as nitrite-reductase activity. Nitrite- and nitrate-reductases used either NADH or NADPH as an electron donor. Nitrite reductase activity was greater than nitrate reductase activity. This observation supports the rapid reduction of nitrite and slow reduction of nitrate in M. avium as documented by McCarthy (1987) and explained why M. avium gives a negative result by the standard nitrate reductase test. In addition to assimilatory enzyme activity, M. avium A5 also produced dissimilatory nitrate- and nitrite-reductase activities. / Master of Science

Les ligands β-diiminates sont des plateformes intéressantes utilisées en chimie de coordination en particulier pour la catalyse homogène, leurs paramètres électroniques et géométriques facilement ajustables les rendant particulièrement attractifs. Toutefois, ces modifications sont limitées à l’introduction de bases de Lewis neutres (éthers, amines tertiaires) sur les substituants portés par les atomes d’azote du squelette β-diiminate. L’objectif principal de ce travail de thèse porte sur le dépassement de telles limitations avec la synthèse de nouveaux ligands β-diiminates fonctionnalisés par un ou deux groupements phénolates anioniques et l’étude de leur chimie de coordination avec des ions lanthanides et actinides. Un intérêt particulier a été apporté à l’élucidation du mécanisme de formation de ces ligands, qui a mis en lumière la sensibilité des fonctions imines vis-à-vis des fonctions phénols, à l’origine des limitations décrites ci-dessus. Deux nouveaux ligands N-aryloxy-β-diiminates ont été synthétisés à l’échelle de plusieurs grammes avec de très bons rendements. Ces ligands diffèrent par leur encombrement stérique, qui influe sur leur coordination aux ions lanthanides et actinides. La réactivité de trois des complexes N-aryloxy-β-diiminate a été explorée. Un complexe du Ce(III) possède des propriétés de réduction intéressantes, sa sphère de coordination permettant un abaissement significatif du potentiel d’oxydation du couple Ce(III)/Ce(IV). La présence d’une lacune de coordination dans un complexe du Th(IV) a été mise àprofit pour stabiliser différents adduits de bases de Lewis. Deux types de réarrangement du complexe de thorium ont été mis à jour, qui sont contrôlés par la minimisation de répulsions inter-ligands. La réactivité rédox d’un complexe N-aryloxy-β-diiminate de l’U(IV) a été exploitée pour préparer un exemple rare de complexe monooxo terminal d’uranium. Cette espèce possède une chimie rédox riche et sa réduction a permis la synthèse des analogues de l’U(V) et de l’U(IV), formant ainsi la première série de complexes monooxo terminaux d’uranium stables à trois degrés d’oxydation successifs. Cette série représente une opportunité unique d’étudier l’influence des électrons f sur le phénomène d’influence trans inverse (ITI) observés dans les complexes oxo de l’uranium. Des calculs DFT préliminaires ont été réalisés pour rationaliser les comportements expérimentaux. / Β-Diketiminate ligands have received increased interest in coordination chemistry, especially for homogeneous catalysis. Their successful applications arise from an easy and fine tuning of the ligand electronic and geometric properties. However, these modifications are limited to the introduction of neutral donors (ethers or amines), on the nitrogen substituents of the β-diketiminate skeleton. The main focus of this research project is to overcome this limitation by synthesizing new β-diketiminate ligands functionalized by one or two anionic aryloxide groups, and to study their coordination chemistry with lanthanide and actinide ions. Access to these species relies on a fine understanding of the mechanism underlying their formation, and the sensitivity of the β-diiminium skeleton towards nucleophiles (phenols) has been identified as the limiting side reaction in the synthetic route. Addition of reactants in well defined order allowed the formation of two new N-aryloxy-β-diketiminate dianions on a multi-gram scale. The two ligands differ by their steric bulk and exhibit different coordination behaviors towards lanthanides and actinide ions, which were rationalized on geometric considerations. The reactivity of three of these new complexes has been investigated. A Ce(III) N-aryloxy-β-diketiminate complex exhibits interesting reduction properties, due to the shift of its oxidation potential to negative values by its coordination environment. A Th(IV) complex presents a vacant coordination site, which has been probed with different Lewis bases, emphasizing two spatial arrangements ruled by inter-ligand repulsion. It has been compared to its U(IV) analogue, which can be oxidized to a rare terminal monooxo uranium(VI) species. The latter was reversibly reduced to its U(V) and U(IV) derivatives, creating the first series of terminal monooxo uranium complexes with three successive oxidation states. These compounds represent an opportunity to better understand the influence of f-electrons on the inverse trans influence (ITI) in uranium oxo complexes. Preliminary DFT calculations have been carried out to explore geometric and energetic aspects at play in this interaction.

Les travaux présentés dans cette thèse s’inscrivent dans une thématique de modification de surfaces par le biais de monocouches auto-assemblées post-fonctionnalisables. L’objectif principal consiste à élaborer une méthode générique de modification de monocouches par des motifs moléculaires variés. Pour cela, les travaux se concentrent sur la mise au point d’une plateforme générique facilement fonctionnalisable par un motif d’intérêt et greffable sur électrode modifiée. La voie retenue consiste à utiliser deux réactions de "click chemistry" de type "CuAAC". La première réaction de CuAAC s’effectue en solution et permet de solidariser plateforme et motifs d’intérêt (principalement des dérivés ferrocényles). Les ligands ainsi obtenus ont été utilisés pour la complexation d’ions métalliques (Cu2+, Zn2+). Les ligands et les complexes ont été étudiés en solution par électrochimie ainsi que par spectroscopies UV-Visibles et RPE. La seconde réaction de CuAAC permet l’immobilisation des différents complexes de cuivre sur des électrodes pré-modifiées par des fonctions azoture, généralement à l’aide de monocouches auto-assemblées. Ce greffage s’effectue selon le mode opératoire de l’"électroclick auto-induite", c'est-à-dire que le complexe de cuivre à immobiliser est également catalyseur de la réaction de CuAAC. Les systèmes ainsi immobilisés (mono-, bi- ou tri-métalliques) ont pu être étudiés en terme de cinétique d’immobilisation, de cinétique de transfert d’électrons et en réactivité. Ce dernier point a par ailleurs fait l’objet d’une attention particulière pour le cas de la réduction électro-catalytique des ions nitrite par les complexes de cuivre (I), en solution et sur surface. / This work depends on functionalized surface theme using modification of selfassembled monolayers (SAMs). The main objective consists to elaborate a new general pathway to modify monolayers with miscellaneous objects of interest. For this, we decide to focus our work to synthesize a versatile platform handling two ethynyl arms. These functions are available to operate two CuAAC reactions. The first one is use for linking platform with object of interest (in general ferrocenyl derivatives). Ligands obtained by that way were used for complexation of Cu2+ and Zn2+ ions. Electrochemical and spectroscopic (UV-Visible and EPR) studies were performed on these compounds. The second CuAAC reaction is used to immobilize copper complexes on azide modified electrode (azide derivatives SAMs on gold and ITO or direct functionnalization of glassy carbon surface). The grafting is operating through “self-induced electroclick” method; this means the CuAAC reaction is catalysed by the copper complex which is immobilized. Functionalized electrodes were characterized by cyclic voltammetry. It appears that similar complexes have closed grafting kinetic. These studies also demonstrate the both influence of copper and spacer on a second electroactive site (ferrocene moieties). The reactivity of copper centre is evaluated for complexes in solution and immobilized on surface with electrocatalytic reduction of nitrite ions by copper (I) species. The catalytic efficiency strongly depends on potential of copper reduction. Also, similar complexes show a loss of catalytic power with immobilization on surface.

Research was performed at a pilot-scale wastewater treatment plant operating an adsorption/bio-oxidation (A/B) process at 20C. The study compared B-Stage performance under DO Control, Ammonia Based Aeration Control (ABAC), and Ammonia vs. NOx (AvN) control. AvN in 1) fully-intermittent and 2) intermittently-aerated MLE configurations was compared to DO Control and ABAC, each with continuous aeration, in an MLE configuration. The study also examined operation of each aeration strategy with two different feed types: A-Stage effluent (ASE) and primary clarifier effluent (PCE). Operating modes were compared on the basis of nitrogen removal performance, COD utilization efficiency for denitrification, and alkalinity consumption. AvN was found to provide comparable nitrogen removal performance to DO Control and ABAC. The highest nitrogen removal performance was seen when operating DO Control (81.4 ± 1.2%) and ABAC (81.1 ± 1.2%) with PCE. High nitrogen removal efficiency (77.5 ± 6.1%) was seen when fully-intermittent AvN operation was fed ASE containing a high particulate COD fraction. A high effluent nitrite accumulation ratio (NAR = NO2-/(NO2-+NO3-)) was seen during this period (46 ± 15%) accompanied by the out-selection of Nitrospira. Feeding effluent from AvN control to an Anammox MBBR improved removal efficiency. Increased soluble COD loading resulted in greater nitrogen removal with strategies operating in an MLE configuration while particulate COD was found to be important for processes where removal was designed to occur in downstream reactors. Efficiency of COD for denitrification was found to vary based on the amount and type of influent COD; however AvN in an MLE configuration was found to use COD more efficiently than fully-intermittent AvN. In either configuration, AvN required less alkalinity addition than DO Control or ABAC. High sCOD concentrations in PCE led to increased nutrient removal as compared to ASE but increased heterotrophic growth and mixed liquor concentrations in the B-Stage making the A-Stage an attractive option for its ability to control the C/N ratio fed to BNR processes. / Master of Science

No description available.

This thesis reports on the research outcome of corrosion mechanism and corrosion rate of mild steel in different environments (saline, alkaline solutions and concrete media) using potentiodynamic polarization technique. The study also included the effect of corrosion on bond strength between reinforcing steel and concrete using pull-out test. Corrosion of mild steel and 316L stainless steel with different surface conditions in 1, 3 and 5% saline (NaCl + Distilled water) was investigated. Specimens ground with 200 and 600 grit silicon carbide grinding paper as well as 1μm surface finish (polished with 1μm diamond paste) were tested. In case of mild steel specimens, reduction in surface roughness caused increase in corrosion rate, while in 316L stainless steel corrosion rate decreased as the surface roughness improved. Metallographic examination of corroded specimens confirmed breakdown of passive region due to pitting corrosion. Corrosion of mild steel was also investigated in alkaline solution (saturated calcium hydroxide, pH =12.5) contaminated with 1, 3 and 5% saline. A series of corrosion experiments were also conducted to examine the efficiency of various concentrations of calcium nitrite (CN) on corrosion behaviour of both as-received and polished mild steel in alkaline solution containing 3% saline after 1 hour and 28 days of exposure. Corrosion rate was higher for the as-received than polished mild steel surface under the same testing conditions in NaCl alkaline solution with and without nitrites due to the effect of surface roughness. Morphology investigation of mild steel specimens in alkaline solution ii containing chlorides and nitrites showed localized pits even at nitrite concentration equal to chloride concentration. Corrosion of steel bars embedded in concrete having compressive strengths of 20, 30 and 46MPa was also investigated. The effect of 2 and 4% CN by weight of cement on corrosion behaviour of steel bar in low and high concrete strengths specimens were also studied. All reinforced concrete specimens were immersed in 3% saline solution for three different periods of 1, 7 and 15 days. In order to accelerate the chemical reactions, an external current of 0.4A was applied. Corrosion rate was measured by retrieving electrochemical information from polarization tests. Pull-out tests of reinforced concrete specimens were then conducted to assess the corroded steel/concrete bond characteristics. Experimental results showed that corrosion rate of steel bars and bond strength were dependent on concrete strength, amount of CN and acceleration corrosion period. As concrete strength increased from 20 to 46MPa, corrosion rate of embedded steel decreased. First day of corrosion acceleration showed a slight increase in steel/concrete bond strength, whereas severe corrosion due to 7 and 15 days corrosion acceleration significantly reduced steel/concrete bond strength. Addition of only 2% CN did not give corrosion protection for steel reinforcement in concrete with 20MPa strength at long time of exposure. However, the combination of good quality concrete and addition of CN appear to be a desirable approach to reduce the effect of chloride induced corrosion of steel reinforcement. At less time of exposure, specimens without CN showed higher bond strength in both concrete mixes than those with CN. After 7 days of corrosion acceleration, the higher concentration of CN gave higher bond strength in both concrete mixes. The same trend was observed at 15 days of corrosion acceleration except for the specimen with 20MPa compressive strength and 2% CN which recorded the highest deterioration in bond strength.

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