<p>The Alnö complex on the central Swedish east coast is composed of a main composite intrusion (the main intrusion) and four smaller satellite intrusions (Söråker, Sälskär, Långharsholmen and Båräng) distributed around the main intrusion on Alnö Island and on the mainland north of the island. The major rock types exposed within the complex are melilitolite, pyroxenite, ijolite series (melteigite-ijolite-urtite), nepheline syenite, carbonatite and alnöite dykes. Melilitolite is only exposed within the Söråker intrusion. The intrusive sequence is melilitolite → pyroxenite → ijolite series → nepheline syenite → carbonatite → alnöite.</p><p>Mineralogical, whole rock geochemical and radiogenic isotope (Nd-Sr-Pb) studies of exposed rocks from the Alnö alkaline complex, east central Sweden, were performed in order to investigate the genetic relationships between the diverse rock-types, and to evaluate the contributions from mantle and crustal components in the genesis of the complex. Most analysed samples fall within the depleted quadrant in a eNd-eSr diagram, similar to carbonatites and alkaline silicate rocks from other complexes, indicating derivation of parental magma(s) from a source that had experienced time-integrated depletion in LIL elements. Contamination by local crust is indicated by Sr and Pb isotope data, but is geographically restricted to samples collected from the outer parts of the main intrusion and from satellite intrusions. This localized contamination is attributed to selective hydrothermal element leaching of surrounding bedrock during fenitization. Nd- and Sr-isotope data separates the carbonatites into two groups (group I and II), each related to a specific set of silicate rock types. The overlap of group II carbonatites with ijolite and nepheline syenite could indicate a common origin through liquid immiscibility but this hypothesis cannot be confirmed by trace element data because initial concentrations are obscured by fractionation processes. Interestingly, results from AFC-modelling suggest that production of ijolite residual magma requires addition of a small volume (2.4 %) of carbonatite component to the parental magma, whereas formation of nepheline syenite residuals requires removal of an almost equal amount of carbonatite (1.5 %) to yield a statistically significant result. AFC-modelling further suggests that the various silicate rock types exposed within the complex are related to the same parental olivine-melilitite magma through crystal fractionation of olivine, melilite, clinopyroxene, nepheline, Ti-andradite and minor phases. These results agree with compositional trends exhibited by clinopyroxene and Ti-andradite from the silicate rocks of the main intrusion, which suggests co-genesis of pyroxenite, ijolite series rocks and nepheline syenite. Production of ijolite-like residual liquids can be achieved by <40% fractionation whereas production of nepheline syenite residuals requires >80% fractionation.</p><p>An investigation of the origin of silicate minerals in carbonatites suggest that most silicate minerals observed in the carbonatites on Alnö Island are derived from surrounding wall-rock and/or produced through corrosive interaction between carbonatite liquid and assimilated phases. This leads to ambiguities when addressing the possible genetic link between carbonatites and associated silicate rocks as occurrences of identical “liquidus” phases in inferred immiscible liquids may not actually be such.</p>

The present day Bahamian archipelago was deposited during sea level highstands when carbonate production was high enough to overfill accommodation space. This study unravels the complex stratigraphy and heterogeneity created by island accretion during and across the most recent Pleistocene highstands (MIS 5e, 9, and 11) using New Providence Island as a case study. Building upon the work of previous researchers, field based mapping was completed to understand the spatial relationships between ages, environments of deposition, and grainstone compositions across the island. Using the vertical and lateral relationships gained from detailed mapping, the depositional history of New Providence Island has been reconstructed for the Pleistocene MIS 5e, 9, and 11 sea level highstands. To map all of the environments of deposition, detailed criteria were created to recognize each environment observed on New Providence Island. Ages were estimated with field techniques and confirmed with dating done in previous studies and in this study, including both U-series techniques and amino acid racemization (AAR). Hand samples and short (< 1 m) cores were collected in the field and were used for petrographic analyses in the laboratory as well as whole rock AAR sampling for age determination. Detailed outcrop drawings were created, showing the lateral and vertical relationships of environments within outcrops. Meanwhile, maps and cross-sections were drafted to better understand island-wide relationships of environments, ages, and compositions. Based on age maps, New Providence formed by vertical and lateral accretion during the last three Pleistocene highstands (MIS 5e, 9, and 11), with a majority of deposition occurring during the most recent interglacial (MIS 5e, ~125 ka). Environment of deposition mapping revealed that island deposition occurred within shallow marine to eolian environments. Because of the abundance of MIS 5e deposits, the sedimentological complexity of an individual highstand (MIS 5e) reveals sub-orbital scale sea level changes. With mid-highstand sea level fluctuations apparent within the MIS 5e deposits on New Providence Island, a high level of lithofacies complexity could be expected within any individual sea level highstand. This study documents the complex vertical and lateral facies patterns associated with island building between and within sea level highstands.

The use of stable nitrogen isotope data in ecological and physiological studies is based in the assumption that nitrogen fractionates predictably during metabolism, leading to a broadly conserved pattern whereby consumers are isotopically enriched with respect to their diets. The application of stable isotope data to such studies is limited is by our understanding of the factors in that cause variability in the Δ15N values of consumers. In particular, parasites and fluid-feeders have been shown to demonstrate isotopic depletion with respect to their food sources. One factor that has been suggested to influence the Δ15N values seen in fluid-feeding consumers is the presence of endosymbionts and their contribution to nitrogen metabolism. The experiments described in this thesis directly test the hypothesis that the endosymbiotic bacteria Buchnera aphidicola is influencing the Δ15N value of the pea aphid on host alfalfa plants. Here I find that although aphids cured of their bacterial symbionts are less isotopically depleted than untreated aphids, they are still not enriched with respect to their phloem sap diet, indicating that endosymbiont metabolism alone is not responsible for the isotopic depletion observed in pea aphids. Metabolism of nitrogen in the pea aphid-Buchnera symbiosis has been well described with decades of physiological studies and with the publication of the pea aphid and Buchnera genomes. The two key features of metabolism in the pea aphid-Buchnera symbiosis are the recycling of waste ammonia by the aphid and the upgrading of the nonessential amino acids found in phloem sap to essential amino acids through collaborative metabolism between the pea aphid and Buchnera. Consistent with the described role of Buchnera in nitrogen metabolism, amino acid analyses of symbiotic and aposymbiotic aphids demonstrates an accumulation of the nonessential amino acids glutamine and glutamate and lower amounts of essential amino acids in the aposymbiotic aphids. I tested the influence of dietary amino acid profile on the Δ15N value of pea aphids and found that aphids are only isotopically depleted when they feed on diets with unbalanced amino acid compositions and are isotopically enriched when fed on a diet with a balanced profile of amino acids. I used isotopically labeled fructose to determine whether the difference in Δ15N value of pea aphids on diets of varying amino acid profiles is correlated to the amount of de novo amino acid synthesis occurring in the aphid. I found that there was a significantly higher incorporation of the labeled carbon backbone in the protein of pea aphids feeding on the unbalanced diets, supporting the idea that increased de novo amino acid synthesis are responsible for the differences in Δ15N values among aphids feeding on the two diets. The findings of this study highlight the influence of endosymbionts on the Δ15N values for pea aphids, demonstrate that dietary amino acid composition can influence the Δ15N value of pea aphids through the demand for metabolic upgrading of amino acids, and provide a model for the study of Δ15N values in systems where metabolism has been well characterized by experimental and genomic data.

Here, I evaluate biospheric evolution during the Ordovician using high-resolution inorganic carbon and sulfur (carbonate-associated sulfate and pyrite) isotope profiles for Early Ordovician to early Late Ordovician strata from geographically distant sections in Western Newfoundland and the Argentine Precordillera. Additionally, I present new, high-resolution U-Pb ages for volcanic ash beds within strata of the Argentine Precordillera. Carbon isotope data record subdued variation that is typical of Early- to Middle Ordovician strata worldwide. By contrast, sulfur-isotopic compositions of carbonate-associated sulfate reveal a complex signal of short-term, rhythmic variation superimposed over a longer-term signal. This short-term, rhythmic variation occurs in all sections and appears to be unrelated to lithology or depositional environment, suggesting preservation of an oceanographic signal. I interpret this signal to reflect a combination of a marine sulfate reservoir that was likely much smaller than the modern, the persistence of a substantial deep-ocean hydrogen sulfide reservoir, and the episodic oxidation of a portion of the deep-ocean euxinic reservoir. Persistent euxinia likely resulted from decreased solubility of oxygen in warmer water and/or sluggish oceanic circulation during greenhouse conditions that reduced vertical ventilation. A dramatic change in the behavior of carbonate-associated sulfate and pyrite in the Middle Ordovician is interpreted to reflect a major oceanographic event that records the initial transition from Ordovician greenhouse to icehouse states. I suggest that the initiation of downwelling of increasingly cool, oxygen-rich surface water resulted in widespread oxidation of much of the deep ocean hydrogen sulfide reservoir and concomitant limitation of marine pyrite formation. It is unknown, however, why sea surface temperatures declined through the Early to Middle Ordovician. Explosive volcanism does not appear to be a primary climate driver, based on the timing of Argentinian K-bentonite formations relative to marine records of sea surface temperature, carbon and strontium isotopic composition. Rather, long-term positive feedback between organic carbon burial rates and productivity may have increased carbon dioxide drawdown, ultimately driving a gradual decrease in sea surface temperatures in the Early to Middle Ordovician.

In order to assess the benefit or toxicity of chromium in dietary supplements, trivalent chromium and hexavalent chromium must be measured and verified with mass balance (sum of both species equaling total chromium). This is necessary because dietary supplements report trivalent chromium, an essential trace element, as an ingredient, but hexavalent chromium, a toxic carcinogen, may also be present. Because trivalent chromium is stable in acidic conditions and hexavalent chromium in alkaline conditions, interconversions between species occur and increase the difficulty of quantification. Therefore, EPA Method 3060A was first performed to extract hexavalent chromium. Then, EPA Method 3052 was performed on the residue to digest the remaining trivalent chromium. Speciated Isotope Dilution Mass Spectrometry (SIDMS) with Ion-Exchange Chromatography-Inductively Coupled Plasma-Mass Spectrometry (IC-ICP-MS) was used to account for interconversions as well as determination of trivalent and hexavalent chromium concentrations in the studied samples. Mass balance indicated that the analyzed supplements contained hexavalent chromium ranging from 0 to 16% of the total chromium content. / Bayer School of Natural and Environmental Sciences / Environmental Science and Management (ESM) / MS / Thesis

Four separate but complimentary studies investigated the role of grain sorghum as a predator source for Southern Rolling Plains cotton in 2001 and 2002. Objectives were to: (1) determine the timing and magnitude of predator movement between crops, (2) test putative causes of movement by manipulating prey levels at different stages of crop phenology, (3) explore the feeding and reproductive behavior of a common predator colonizing cotton, and (4) examine the effects of grain sorghum and uncultivated areas on cotton predator abundance at an area-wide scale. Rubidium mark-recapture experiments indicated grain sorghum fields produced a net predator gain for adjacent cotton. Analysis suggested two coccinellids, Hippodamia convergens Guérin-Méneville and Scymnus loewii Mulsant, were responsible for the overall pattern of predator movement. Predator movement into cotton did not appear to be concentrated at specific stages of sorghum phenology. Manipulations of aphid levels in field cages were used to determine if prey abundance or phenology influenced the movement of H. convergens into cotton. In both years, more lady beetle adults were collected on cotton during the latest stages of sorghum phenology. In the second year, relatively low aphid densities (15 per plant) appeared to influence the movement of beetles onto caged cotton. Carbon isotope ratios of H. convergens were used to assess adult feeding behavior after colonizing cotton and to determine if prey consumed in sorghum contributed to egg production in cotton. Though aphids were absent 2001, H. convergens adults stayed in cotton, did not produce eggs and apparently consumed few prey. Cotton aphids were present in 2002 and H. convergens isotope ratios changed from prey consumed in cotton. The isotope ratios of egg masses collected in 2002 indicated prey consumed in grain sorghum contributed very little to egg production in cotton. An area-wide pattern analysis suggested the abundance of grain sorghum and uncultivated areas both positively influenced cotton predator levels. While these landscape effects were less important overall than prey levels and cotton planting dates, in some sampling periods landscape composition appeared to be the most important factor in determining cotton predator levels.

Les molécules marquées aux isotopes stables, dont on peut assurer la traçabilité biologique grâce aux progrès récents des techniques analytiques, apportent de nouveaux moyens d’investigation du métabolisme. De nouveaux tests de diagnostics cliniques non invasifs sont, à ce jour, de pratique courante (ex. breath test à l’urée 13C). L’intérêt majeur des isotopes stables est évidemment leur innocuité vis-à-vis de l’organisme humain, contrairement aux produits radioactifs. Pour des raisons éthiques bien compréhensibles, l’usage de ces derniers est actuellement proscrit dans les essais in vivo chez l’homme ; dès lors, le développement de méthodes alternatives d’investigations métaboliques ou de diagnostics s’est révélé pertinent. L’objectif principal de notre étude est la mise au point d’un nouvel outil de suivi du métabolisme thyroïdien basé sur la double dilution de marqueurs isotopiques avec l’emploi de molécules marquées régio-sélectivement au carbone 13 (l’une est la sonde métabolique, la seconde le standard de quantification absolue). Les étapes développées sont les suivantes : 1.Biosynthèse du précurseur : la L-tyrosine contenant de 1 à 9 carbone 13 ; 2.Synthèse des hormones thyroïdiennes servant de traceurs biologiques ou de standards internes d’analyse (la thyroxine : 13C9 et 13C6-T4 ; la 3,3’,5-triiodothyronine : 13C9-T3) : optimisation de la voie de synthèse de façon à minimiser les pertes en réactifs marqués ; 3.Ingestion ou injection du traceur (13C6-T4) par l’animal ou par l’homme et collecte d’échantillons de plasma sur une période de temps donnée ; 4.Ajout du standard interne au plasma (13C9-T4 ou 13C9-T3) ; 5.Extraction par solvants, purification et dérivation des hormones thyroïdiennes (endogène, exogène et standard) du plasma ; 6.Analyse et quantification par chromatographie gazeuse couplée à la spectrométrie de masse (par suivi des ions spécifiques de chaque entité moléculaire). L’optimisation instrumentale du protocole analytique GC-MS - à savoir la séparation chromatographique et la gestion des ions de masse en mode SIR - a été maîtrisée pour l’analyse de traces de T3 et T4 ; les limites de détection actuelles sont de l’ordre de 20 pg pour chacune des hormones. Une mise en œuvre de tests in vivo de 13C9-T4 comme traceur métabolique a été réalisée sur animaux sous contrôle vétérinaire avec la collaboration du Département de Biochimie Clinique de la « Royal Infirmary » d’Edinbourg. Ils nous ont permis de démontrer la faisabilité de la méthodologie (incorporation de la sonde et son suivi temporel) et la possibilité d’utiliser ces traceurs comme sondes chez l’homme. The principal objective of this thesis is the development of a new tool for the study of the thyroid metabolism based on double isotopic dilution technique with the use of two isotopomers of the same hormone enriched with distinct carbon 13 contents (one as metabolic tracer, the second as internal standard). The successive stages of the methodology are described below: 1.Biosynthesis of the starting material (L-tyrosine) enriched with 1 to 9 carbon 13; 2.Optimized synthesis of the thyroid hormones being used as biological tracers or analytical internal standards (thyroxine : 13C9 and 13C6-T4; 3,3',5-triiodothyronine : 13C9-T3); 3.Incorporation of the tracer (13C6-T4) by the patient and collect of samples of plasma over a given period of time; 4.Internal standard addition to plasma (13C9-T4 or 13C9-T3); 5.Solvent extraction, purification of the thyroid hormones (endogenous, tracer and standard) of the plasma; and derivatization of the thyroid hormones; 6.Analysis and quantification by gas chromatography coupled with mass spectrometry (by follow-up of the specific ions of each isotopomer), monitoring of (m/z) values 970/979 and 976/979 for thyroxine. The instrumental optimization of GC-MS analytical protocol - namely chromatographic separation and management of the ions of mass in SIR mode - was worked out for the analysis of traces of T3 and T4. The limit of detection is 20 pg for each molecule. A first implementation in in vivo tests of 13C9-T4 as a metabolic tracer was carried out under veterinary control on cats and rabbits thanks to the collaboration of the Clinical Department of Biochemistry of Royal Infirmary of Edinburgh. They enabled us to prove the feasibility of the methodology (incorporation of the probe and its temporal follow-up) and the possibility of using these tracers as probes for human beings.

The Alnö complex on the central Swedish east coast is composed of a main composite intrusion (the main intrusion) and four smaller satellite intrusions (Söråker, Sälskär, Långharsholmen and Båräng) distributed around the main intrusion on Alnö Island and on the mainland north of the island. The major rock types exposed within the complex are melilitolite, pyroxenite, ijolite series (melteigite-ijolite-urtite), nepheline syenite, carbonatite and alnöite dykes. Melilitolite is only exposed within the Söråker intrusion. The intrusive sequence is melilitolite → pyroxenite → ijolite series → nepheline syenite → carbonatite → alnöite. Mineralogical, whole rock geochemical and radiogenic isotope (Nd-Sr-Pb) studies of exposed rocks from the Alnö alkaline complex, east central Sweden, were performed in order to investigate the genetic relationships between the diverse rock-types, and to evaluate the contributions from mantle and crustal components in the genesis of the complex. Most analysed samples fall within the depleted quadrant in a eNd-eSr diagram, similar to carbonatites and alkaline silicate rocks from other complexes, indicating derivation of parental magma(s) from a source that had experienced time-integrated depletion in LIL elements. Contamination by local crust is indicated by Sr and Pb isotope data, but is geographically restricted to samples collected from the outer parts of the main intrusion and from satellite intrusions. This localized contamination is attributed to selective hydrothermal element leaching of surrounding bedrock during fenitization. Nd- and Sr-isotope data separates the carbonatites into two groups (group I and II), each related to a specific set of silicate rock types. The overlap of group II carbonatites with ijolite and nepheline syenite could indicate a common origin through liquid immiscibility but this hypothesis cannot be confirmed by trace element data because initial concentrations are obscured by fractionation processes. Interestingly, results from AFC-modelling suggest that production of ijolite residual magma requires addition of a small volume (2.4 %) of carbonatite component to the parental magma, whereas formation of nepheline syenite residuals requires removal of an almost equal amount of carbonatite (1.5 %) to yield a statistically significant result. AFC-modelling further suggests that the various silicate rock types exposed within the complex are related to the same parental olivine-melilitite magma through crystal fractionation of olivine, melilite, clinopyroxene, nepheline, Ti-andradite and minor phases. These results agree with compositional trends exhibited by clinopyroxene and Ti-andradite from the silicate rocks of the main intrusion, which suggests co-genesis of pyroxenite, ijolite series rocks and nepheline syenite. Production of ijolite-like residual liquids can be achieved by &lt;40% fractionation whereas production of nepheline syenite residuals requires &gt;80% fractionation. An investigation of the origin of silicate minerals in carbonatites suggest that most silicate minerals observed in the carbonatites on Alnö Island are derived from surrounding wall-rock and/or produced through corrosive interaction between carbonatite liquid and assimilated phases. This leads to ambiguities when addressing the possible genetic link between carbonatites and associated silicate rocks as occurrences of identical “liquidus” phases in inferred immiscible liquids may not actually be such.

No description available.

The results of kinetic isotope determination and computational studies on Noyori-type catalytic systems for the hydrogenation of ketones are presented. The catalysts examined include RuH2(NHCMe2CMe2NH2)(R-binap) and RuH(NHCMe2CMe2NH2)(PPh3)2. These complexes are active catalysts for ketone hydrogenation in benzene without addition of an external base. The kinetic isotope effect (KIE) for catalysis by RuH2(NHCMe2CMe2NH2)(R-binap) was determined to be 2.0 ± (0.1). The calculated KIE for the model system RuH(NHCH2CH2NH2)(PH3)2 was 1.3, which is smaller than the experimentally observed value but does not include tunneling effects. The complex OsH(NHCMe2CMe2NH2)(PPh3)2 is known to display autocatalytic behaviour when it catalyzes the hydrogenation of acetophenone in benzene. Pseudo first-order reaction conditions are obtained via addition of the product alcohol at the beginning of each kinetic experiment. The KIE determined using various combinations of deuterium-labeled gas, alcohol and ketone was found to be 1.1 ± (0.2). DFT calculations were used to explore the effect of the alcohol and the KIE. An induction period is observed at the start of the hydrogenation that is attributed to the formation of an alkoxide complex. A novel, diamine-orchestrated hydrogen-bonding network is proposed based on DFT calculations to explain how the alkoxide is converted back to the active catalyst. The tetradentate complexes trans-RuHCl[PPh2(ortho-C6H4)CH2NHCH2)]2 and RuHCl[PPh2(ortho-C6H4)CH2NHCMe2)]2 are known to be catalysts for the hydrogenation of acetophenone and benzonitrile in toluene when activated by KOtBu/KH. DFT studies were performed and a mechanism is proposed. The calculated rate limiting step for acetone hydrogenation was found to be heterolytic splitting of dihydrogen, which agrees well with experiment. The novel outer-sphere sequential hydrogenation of a CN triple bond and then a C=N double bond is proposed. A mechanism is proposed, which is supported by DFT studies, to explain the selectivity observed in the nucleophilic attack of amines or aziridines on palladium -prenyl phosphines complexes. Calculations on based on a palladium complex with two phosphorus donor ligands indicated that the observed selectivity would not be produced. Using two new model intermediates with either THF or aziridine substituted for a phosphine ligand trans to the unhindered side of the prenyl ligand did predict the experimentally observed selectivity.