Recent successful drilling operations at Lake El'gygytgyn, NE Russia have recovered sediment cores back to 3.6Ma, representing the longest time-continuous sediment record of past climate change in the terrestrial Arctic. Analysis of the hydrogen isotopic ratio (δD) of specific organic biomarkers allows reconstruction of past hydrological conditions, thereby providing a powerful tool for reconstructing past Arctic climate changes. Compound specific isotopic analysis of sedimentary lipids from this remote basin provides new insights into the climate evolution of the Arctic, capturing the mechanisms and dynamics of the last two glacial-interglacial transitions, potentially enhancing the accuracy of modeled future climate change projections and presenting an opportunity to estimate past polar amplification of climate change. The results of this research document the first continuous, high fidelity continental record of reconstructed δD in precipitation from terrestrial plant leaf waxes in the High Arctic spanning the last 120 ka. The hydrogen isotopic composition of lipid biomarkers were determined from previously obtained Lake El'gygytgyn sediment cores and compared with other multi-proxy evidence of past climate change within the lake basin. The modern isotope hydrology and controls on the δD lipid signal were first established within the El'gygytgyn Basin from modern precipitation, stream and lake waters, ice cover as well as modern vegetation, water column and lake bottom surface sediments in order to provide a modern context to properly constrain and interpret paleoclimatic proxy data. Reconstructed δD records of paleoprecipitation and temperature at Lake El'gygytgyn lead other northern hemisphere climate records (e.g. North Greenland Ice Core Project, NGRIP δ18O records) and are in phase with other continental and Antarctic climate records, suggesting early high northern latitude continental warming prior to established glacial-interglacial transitions. The data set generated here leads to multiple avenues of future work and provides critical insights into Arctic paleoclimate and paleohydrology, contributing to our understanding of high latitude environmental change over geological timescales. Collectively, the results of this dissertation research will provide a context for paleoclimate reconstructions and future organic geochemical and stable isotope analysis. Future application of compound-specific H isotope analyses to long drill cores (recovered in 2009; ~315m of sediment) will potentially provide a quantitative high-resolution record of paleoclimatic and paleoenvironmental changes spanning the last 3.6 Ma.

The mass spectra of some monomethylquinolines, dimethylquinolines, monoethylquinolines and monopropylquinolines have been determined. In addition, the spectra of 1,2,3,4-tetrahydroquinoline, 5,6,7,8-tetrahydroquinoline and some monomethyl-1,2,3,4-tetrahydroquinolines have also been studied. Fragmentation mechanisms are proposed to account for the most important peaks in the spectra of these compounds. Deuterium labelled analogues of many of the compounds have been prepared and their spectra support the proposed fragmentation mechanisms. / Thesis / Doctor of Philosophy (PhD)

<p> Several ketones in the bicyclo{2.2.1.}heptane system, many of them previously unknown, have been prepared and characterized; these included monoketones, enones and diones. They are listed in Fig. II-1.</p> <p> The conformations of norbornane-2,5-dione (27) and 3,3-dimethyl-norbornane-2,5-dione (26) have been carefully examined by nuclear magnetic resonance spectroscopy. These compounds have been found to exist in two different synchro twist conformations.^76</p> <p> The stereochemistry of base-catalyzed protium-deuterium exchange of the diones 25, 26 and 27 has been examined and has been found to be similar to the stereochemistry of exchange in monoketones previously observed in these systems, viz exo exchange is considerably more rapid than endo exchange.</p> <p> The rates of NaOD-catalyzed protium-deuterium exchange of the ketones, enones and diones have been measured in 60 % dioxane-D2O at 25°. The rate data is shown in Table II-4. Kinetic analysis showed that these rate constants represent the true reactivity of the hydrogen for which the rate of exchange was measured.</p> <p> A study of the 13C chemical shift of highly substituted bicyclo{2.2.1.}heptanes has been undertaken, and also a study of the 13C-H coupling constants of many of these compounds has been made. The results are listed in Tables II-6 and II-8. They suggest that there are no unusual hybridization effects at the enolizable carbon in the diones and enones under study.</p> <p> The rate data, together with some literature data, shows that hybridization effects, torsional effects, conformational effects and strain effects are of minor importance in the exchange reactions. The rate acceleration observed in the dione systems is almost entirely accountable by an inductive effect of the second carbonyl group, with very little homoconjugative participation.</p> <p> The kinetic results suggest that an enol is the intermediate in the enolization reaction, and that the transition state occurs relatively early along the reaction coordinate.</p> / Thesis / Doctor of Philosophy (PhD)

No description available.

<p> Deuterium tracer studies, kinetic isotope effect measurements and product composition studies in both ammonia and ammonia-d3 have been used to elucidate the mechanism of the y-elimination reaction of 3-phenylpropyltrimethylammonium iodide with potassium amide in liquid ammonia at -55°. Deuterium tracer studies involving the products from the reaction of 3,3-dideutero-3-phenylpropyltrimethylammonium iodide have excluded the carbene and ylide mechanism. A deuterium exchange test involving the deuterated quaternary salt in ammonia demonstrated that a y-carbanion is formed during the reaction. In addition, a large y-hydrogen isotope effect (kH/kD > 22) and a large nitrogen isotope effect (k^14/K^15 = 1.022) were observed for the reaction. These results are consistent with either an Elcb mechanism in which the rates of ring closure and of return of the carbanion are of comparable magnitudes or a concerted mechanism accompanied by an irrelevant exchange reaction at the y-carbon. The latter has been eliminated on the basis of a deuterium exchange test involving the undeuterated quaternary salt in ammonia-d3 and the relative rates of y- and aelimination of the deuterated and undeuterated quaternary salts in both ammonia and ammonia-d3. </p> / Thesis / Doctor of Philosophy (PhD)

The parkinsonian inducing drug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is bioactivated in a reaction catalyzed by the flavoenzyme monoamine oxidase B (MAO-B) to form the corresponding dihydropyridinium (MPDP+) subsequently pyridinium (MPP+) metabolites. As part of our ongoing studies to characterize the structural features responsible for this unexpected biotransformation, we have synthesized and examined the MAO-B substrate properties of a variety of MPTP analogs bearing various heteroaryl groups at the 4-position of the tetrahydropyridinyl ring. The results of these SAR studies indicate that electronic features, steric features and polar interactions can contribute to the substrate activities. Additionally, isotope effects have been examined to investigate the mechanism and stereoselectivity of the MAO-B catalytic pathway. The synthesis and characterization of regio and stereoselectively deuterated MPTP analogs have been achieved. The results indicate that the catalytic step occurs exclusively at the allylic C-6 position and is rate-determining for both good and poor substrates. The two enantiomers of MPTP bearing a deuterium atom at C-6 have been prepared via chiral aminooxazolinyl derivatives and have been characterized by 2H NMR in a chiral liquid crystal matrix. These enantiomers were used to determine the selectivity of the MAO-B catalyzed a C-H bond cleavage reaction leading to the dihydropyridinium metabolite MPDP+. Some of the cyclopropyl analogs of MPTP have also been synthesized as the potential inhibitors. / Ph. D.

Nitrate (NO⁻3) export can vary widely among forested watersheds with similar nitrogen loading, geology, and vegetation, which suggests the importance of understanding differing internal retention mechanisms. Transport should be studied at the hillslope scale because the hillslope is the smallest unit with spatial and temporal resolution to reflect many relevant NO⁻3 retention and transport (flow-generation) processes, and headwater forested watersheds are largely comprised of sections of hillslopes. I conducted two experiments to elucidate subsurface flow dynamics and NO⁻3 transport and retention mechanisms on a constructed experimental hillslope model. In the first experiment, I tested whether decadal pedogenetic changes in soil properties in the experimental hillslope used by Hewlett and Hibbert (1963) would lead to changes in recession flow. I repeated (twice) their seminal experiment, whose results led to the development of the Variable Source Area paradigm, by also saturating, covering, and allowing the experimental hillslope to drain until it no longer yielded water. In the historical experiment there was fast drainage for 1.5 d, followed by slow drainage for ~140 d, which led the authors to conclude that recession flow in unsaturated soil could sustain baseflow throughout droughts. This long, slow drainage period was not reproduced in my experiments. Shapes of the drainage curves in my experiments were similar to the historical curve, but slow drainage was truncated, ending after 17 and 12 d, due likely to a leak in the boundary conditions, rather than to pedogenetic changes since the historical experiment. Leakage to bedrock, analogous to the leak in the hillslope model, is a commonly observed phenomenon and this study highlights how that can reduce drainage duration and the contribution of moisture from soils to support baseflow. In the second experiment, I tested whether movement of NO⁻3, which is considered a mobile ion, would be delayed relative to movement of water through a hillslope. I added concentrated pulses of ¹⁵NO⁻3 and a conservative tracer (²H₂O) on the same experimental hillslope, which was devegetated and irrigated at hydrologic steady state. Retention of the ¹⁵NO⁻3 tracer was high in the soil surface (0–10 cm) layer directly where the tracer was added. The portion of the ¹⁵NO⁻3 tracer that passed through this surface layer was further retained/removed in deeper soil. The reduction in the peaks in δ¹⁵N breakthrough was an order of magnitude larger than in δ₂H breakthrough at the outlet 5 m downslope of the tracer addition. The peaks in δ¹⁵N were also delayed relative to the peaks in δ₂H by 1, 6, 9 and 18.5 d for slope distances of 0, 2, 4, and 5 m, respectively, from tracer addition to the outlet. The excess mass of ¹⁵NO⁻3 recovered at the outlet was less than 3% of the original tracer mass injected. Nitrification and denitrification were estimated to be roughly 1:1 and were large fluxes relative to lateral transport into and out of the riparian zone. This tracer experiment shows that bedrock leakage, coupled with multiple retention/removal mechanisms can significantly delay export of added NO⁻3 with implications of additional NO⁻3 sink strength at the watershed scale. / Ph. D. / Nitrate (NO₃⁻) export can vary widely among forested watersheds with similar nitrogen loading, geology, and vegetation, which suggests the importance of understanding differing internal process mechanisms. I conducted two experiments to illustrate how water and NO₃⁻ moved on a constructed hillslope model. In the first experiment, I quantified differences in soil properties in the hillslope model used by Hewlett and Hibbert (1963). Then I repeated (twice) the seminal drainage experiment described in Hewlett and Hibbert (1963). The same hillslope (21.8°; 40%) was wetted up, covered, and allowed to drain until water stopped exiting at the outlet. In the historical experiment there was fast drainage for 1.5 d, followed by slow drainage for ~140 d, which led the authors to hypothesize that slow drainage in surface soil could continually contribute water to streams even during droughts. This long, slow drainage period was not reproduced in my experiments. Drainage was similar at the beginning of drainage between my experiments and the historical experiment, but in my experiment the slow drainage ended earlier (after 17 and 12 d) due likely to a leak in the constructed hillslope model, rather than to significant changes that occurred in the soil itself since the original experiment. This leak in the hillslope model is similar to leakage to bedrock, which is commonly observed in natural hillslopes. In the second experiment, I tested whether NO₃⁻ and water would move through a hillslope at the same rate. I added concentrated pulses of NO₃⁻ (as ¹⁵NO₃⁻ and water (as ²H₂O) on the same devegetated experimental hillslope. Retention of the ¹⁵NO₃⁻ tracer was high in the surface (0–10 cm) where the tracer was added, with little change in the immediately surrounding soil, despite high rates of water input immediately after tracer addition and throughout the experiment. The portion of the ¹⁵NO₃⁻ tracer that passed through the surface layer was further processed by microbes in deeper soil as it traveled downslope. This body of work shows that bedrock leakage, coupled with multiple retention mechanisms throughout the soil profile, can significantly delay export of added NO₃⁻ at the watershed scale.

La formation et l'étude structurale de bicouches planes formées à partir de lipides synthétiques et d'extraits lipidiques naturels sont décrites. Les bicouches ont été utilisées comme modèles membranaires pour étudier et quantifier les mécanismes d’action du médicament antifongique Amphotéricine B, principalement par réflectométrie des neutrons. Différents modèles membranaires de complexités croissantes, qui intègrent de l’ergostérol ou du cholestérol afin d’imiter respectivement des systèmes fongiques ou mammifères, ont été étudiés. L'extraction, l'analyse chimique et la préparation des mélanges de lipides hydrogénés et deutérés issus de levures sont présentés en même temps que l'optimisation du procédé de déposition sur des substrats de silicium, initialement contrôlés avec une microbalance à quartz et mesure de la dissipation, qui permet d'accéder à des modèles de membranes naturelles pertinentes pour les techniques de diffusion neutronique. Les effets de la deutération sur la composition lipidique de la levure méthylotrophe Pichia pastoris ou de la levure pathogène Candida glabrata, sont détaillés et utiles pour comprendre la modulation des lipides obtenus de ces micro-organismes. Les modèles membranaires basés sur le lipide synthétique 1-palmitoyl-2-oléoyl-sn-glycéro-3-phosphocholine ont d'abord été caractérisés et comparés à ceux formés des phospholipides ou des lipides totaux extraits des levures, principalement par réflectométrie des neutrons, mais aussi par diffraction de membrane. Enfin, la relation entre la composition lipidique et les réponses des modèles à l'Amphotéricine B ont été étudiées et quantifiées. Bien que différents comportements soient observés pour les systèmes fongiques et mammifères, les différents degrés de complexité des modèles utilisés a montré une incidence sur les résultats et l'interprétation des mécanismes impliqués lors de l'interaction du médicament avec les membranes. Les différences observées entre les systèmes lipidiques synthétiques et naturels démontrent la pertinence des modèles membranaires nouvellement développés à partir des lipides extraits de biomasse. / The formation and structural investigation of planar bilayers from synthetic lipids and natural extracts is described. The bilayers were used as model membrane systems for the investigation and quantification of the molecular mechanisms of the membrane-binding antifungal drug Amphotericin B, primarily by neutron reflectometry. Different membrane models of increasing complexity were investigated, with ergosterol or cholesterol included to mimic fungal and mammalian cell membranes, respectively. The extraction, chemical analysis and preparation of hydrogenous and deuterated lipid mixtures from yeasts are presented together with the optimization of the deposition process of supported lipid bilayers on silicon substrates using Quartz Crystal Microbalance with Dissipation monitoring to create relevant natural model membranes for the neutron scattering experiments. The effects of deuteration on the lipid composition in two different yeasts, the methylotrophic Pichia pastoris and the pathogenic Candida glabrata are detailed and is shown to be useful for understanding the modulation of the lipids accessible from these microorganisms. Model membranes from the synthetic lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine were initially characterized and compared to those formed by the phospholipids or the total lipids extracted from the yeasts, mainly using neutron reflectometry but also membrane diffraction. Finally, the relationship between the lipid composition and the response to Amphotericin B was investigated. Although different behavior of the drug is observed in fungal and mammal membrane mimics, the composition and degree of complexity of the model systems employed were shown to affect the findings and the interpretation of the mechanisms involved in the interaction of the drug with the membranes. The differences found between synthetic and natural lipid systems demonstrate the relevance of the newly developed model membranes from lipids extracted from biomass.

There are four distinguishable groundwater systems in the Boise area, Idaho, U.S.A., identified as modern batholith, thermal batholith, Boise frontal fault, and Nampa-Caldwell systems (Figure 1). Modern batholith and thermal batholith groundwaters are located in Tertiary to Cretaceous aged granites and granodiorites of the Atlanta lobe of the Idaho Batholith. The frontal fault system near Boise, ID defines the southeastern edge of the Idaho Batholith, and divides the batholith from the western Snake River Plain. The Nampa-Caldwell system is in the volcanic, fluvial and pluvial sediments of the western Snake River Plain. Groundwater ages for these systems are modern, 5-15 ka, 10-20 ka, and 20-40 ka respectively. Local meteoric water lines (LMWL) using the delta 2H and delta 18O composition of the groundwater were defined for each system using linear regression techniques. LMWL had variable and defined single slopes of 6.94 and 8. Deuterium excess values (d) were found for each system for each linear regression method. Relative differences of the deuterium excess value assuming the two single slope methods were similar. Changes in moisture source humidity and temperature, and Boise area recharge temperatures calculated from stable isotopic data and the deuterium excess factor agree with other published data. At the moisture source there was a 9% humidity increase and a 7-6 °C decrease of sea surface temperature between the present and the last glacial maximum (LGM). The local temperature decreased 4-5 °C from the present to the LGM for the Boise area.

In the atomic energy pile at Chalk River, heavy water (deuterium oxide, D2O) is to be used as a moderator. Early in 1944, it became evident that frequent determinations of the isotopic composition of D2O samples would be required. For this purpose, there was obtained from the American authorities a mass spectrometer specially designed for routine hydrogen isotope analysis. This instrument was assembled and put into operation at McMaster in the summer of 1944. During the course of subsequent work, two other deuterium mass spectrometers were built in this laboratory, following the design of the instrument sent from the United States; one of these has now been installed at the plant site, and a second is to follow at an early date. The studies reported below involved the determination of operating conditions, the measurement of grid leaks, of the order of 10^10 ohms, and the investigation of further applications of the deuterium mass spectrometer. / Thesis / Master of Science (MSc)