Teses / dissertações sobre o tema "Isotopes calcium"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Isotopes calcium".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
Valdes, Maria. "Geochemistry and Cosmochemistry of Calcium Stable Isotopes". Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/276866.
Texto completo da fonteDoctorat en Sciences
info:eu-repo/semantics/nonPublished
Tacail, Théo. "Physiologie isotopique du Calcium chez les mammifères". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN071/document.
Texto completo da fonteEnvironment influences the isotope compositions of body Ca and vertebrate physiology affects these compositions in turn. These observations have allowed recognition of possible applications for Ca isotopes, in the field of medical biology, with the assessment of bone mineral balance in human, and in (palaeo-)ecology for the study of past and present day diets in vertebrates. These applications depend on a better fundamental understanding of causes for these variations. This thesis aims at identifying the main mechanisms responsible for variability of Ca isotope compositions in mammals and human. A solution mode analysis protocol was first developed for MC-ICP-MS. Two methods for microsampling of tooth enamel were then compared in order to increase spatial resolution of mineralized tissues analysis. The influence of dietary Ca sources has been discussed. Isotope composition of human diet is variable because of the diversity of Ca primary sources but also due to variations in dairy products proportions in diet. Early dietary transitions, such as weaning, can be studied using the Ca isotope compositions of human deciduous tooth enamel.Based on observations in human and other mammals, the mechanisms responsible for Ca isotope fractionations are discussed. A mathematical model was developed, allowing the identification of some mechanisms responsible for Ca isotope distribution across organism reservoirs, and sheds light on the crucial role of kidney in determination of bone isotope compositions
Ramos, João Pedro Fernandes. "Effect of calcium oxide microstructure on the diffusion of isotopes". Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/8187.
Texto completo da fonteCalcium oxide (CaO) powder targets have been successfully used at CERN-ISOLDE to produce neutron deficient exotic argon and carbon isotopes under proton irradiation at high temperatures (>1000oC). These targets outperform the other related targets for the production of the same beams. However, they presented either slow release rates (yields) from the beginning or a rapid decrease over time. This problem was believed to come from the target microstructure degradation, justifying the material investigation. In order to do so, the synthesis, reactivity in ambient air and sintering kinetics of CaO were studied, through surface area determination by N2 adsorption, X-ray diffraction for crystalline phase identification and crystallite size determination, and scanning and transmission electron microscopy to investigate the microstructure. The synthesis studies revealed that a nanometric material is obtained from the decarbonation of CaCO3 in vacuum at temperatures higher than 550oC, which is very reactive in air. This reactivity was studied, and it was observed that the CaO powder microstructure is changed through the reaction with air (hydration and carbonation of the oxide) and that this change is not completely reversible after thermal decomposition of the reaction products. Therefore, special care was taken in the target handling at CERN-ISOLDE. From the sintering kinetics, studied in the range of 1000-1200oC, it was determined that this material’s microstructure degrades, with the reduction of the specific surface area and decrease of the powder porosity. At 1200oC, the specific surface area reduction is accentuated, reaching values of 50% of surface area reduction in 10h. These results suggest that the use of high temperatures, equal or higher than 1000oC must be avoided, if the microstructural characteristics of the targets are to be preserved. At CERN-ISOLDE, selected conditions for synthesis, handling of the target and target operation temperatures were chosen, based on the previous material research, and the obtained target material was tested under proton irradiation. From the online studies, the newly developed target proved to show better initial and stable over time release rates of almost all isotopes investigated and especially the exotic ones. These results are essentially due to the nanometric characteristics of the produced target and to the use of operation and handling conditions that decreased the degradation of the microstructural characteristics. Diffusion studies of Ar and Ne were also done in CaO through the application of a mathematical model, to the release curves of the respective isotopes at different temperatures, which enables the determination of the respective diffusion coefficients and activation energies.
Alvos de pós de oxido de cálcio (CaO) têm sido usados, com sucesso, no CERN-ISOLDE para produzir isótopos de Árgon (com défice de neutrões) e de carbono, sob irradiação com protões a alta temperatura (>1000oC). Estes alvos têm mostrado um desempenho superior a outros alvos usados para produzir os mesmos feixes. Contudo, apresentam baixas taxas de libertação de isótopos desde o início de operação ou uma redução rápida com o tempo. Suspeitou-se que este problema se devia à degradação da microestrutura do material, justificando a sua investigação. Assim, a síntese, reatividade em ar ambiente e a cinética de sinterização do CaO foram estudadas, nomeadamente através da determinação da área superficial especifica por adsorção de N2, difração de raios-X para identificação de fases e determinação do tamanho de cristalite e microscopia eletrónica de varrimento e transmissão para o estudo da microestrutura. Os estudos de síntese do CaO revelaram que um material nanométrico, e muito reativo em ar, é obtido através da descarbonatação do CaCO3 em vácuo a temperaturas superiores a 550oC. Esta reatividade foi estudada e observou-se que a microestrutura do pó de CaO é alterada por reação com o ar (hidratação e carbonatação do óxido) e que esta alteração não é totalmente reversível após decomposição térmica dos produtos de reação. Assim, foram tomados cuidados especiais no manuseamento dos alvos de CaO. Da cinética de sinterização, estudada na gama de 1000-1200oC, foi concluído que a microestrutura deste material se degrada com redução da área superficial específica e diminuição da porosidade do pó. A 1200oC, a redução da área superficial específica é acentuada, atingindo-se valores de 50% de redução em cerca de 10h. Estes resultados indicam que a utilização de temperaturas elevadas, iguais ou superiores a 1000oC, devem ser evitadas se se pretendem preservar as características microestruturais dos alvos. No CERN-ISOLDE, as condições de síntese, de manuseamento do material e temperatura de operação do alvo foram escolhidas, com base nos estudos anteriores, e o material resultante foi testado sobre irradiação de protões. Dos estudos online, o alvo desenvolvido provou ter melhores taxas de libertação iniciais e que se mantêm ao longo do tempo de libertação, comparativamente a outros alvos de CaO previamente usados no CERN-ISOLDE. Isto verificou-se em praticamente todos os isótopos estudados, especialmente nos exóticos. Estes resultados foram atribuídos às caraterísticas nanométricas do alvo produzido e à utilização de condições de manuseamento e de operação, tais que a degradação das características microestruturais do alvo é reduzida. Estudos de difusão de Árgon e Néon foram feitos no CaO através da aplicação de um modelo matemático às curvas de libertação dos respetivos isótopos a diferentes temperaturas de operação, que permitiram a determinação dos respetivos coeficientes de difusão e energias de ativação.
Schmitt, Anne-Désirée. "Les isotopes du calcium : Développements analytiques.Application au bilan océanique présent et passé". Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13077.
Texto completo da fonteFirst, a measurement protocol was developed at the Centre de Géochimie de la Surface to avoid instrumental fractionation. After chemical separation on ion exchanging resins, the Ca isotopic compositions were measured on a thermo-ionisation mass spectrometer, using a double-spike technique. The Ca isotopic ratios were expressed in a delta notation. To do this, a reference material is needed. No international standard presently exists for Ca isotopes. For that reason, we proposed to use the SRM 915a carbonaceous standard from the NIST. Seawater, the only common sample of most of previous studies has also been used: it was calibrated against the carbonaceous standard and used in present study. This protocol was then applied to study the Ca oceanic budget. The isotope data of continental waters allowed to constrain the Ca flux to the ocean. A limited variability of d44Ca (0. 5 ) was recorded at the outlet of main rivers or for hydrothermal vents. Moreover, no relationship was observed between d44Ca and the lithology or the climate of the studied watersheds. This allowed to determine the mean Ca isotopic composition of the Ca flux to the ocean (-1. 1 ± 0. 2 ) and to suggest that this value remains rather constant through time. A consequence of this value is that present-day seawater is at steady-state with regard to Ca isotopes. The d44Ca study of marine phosphates from Miocene and Pleistocene, which reflect the paleo-seawater variations through time, has shown that this was not necessarily the case in the past. At 22 Ma, a deviation in d44Ca through more positive values suggests that the intensity of the incoming and outcoming fluxes changed, but not their isotopic composition
Bradbury, Harold John. "Calcium isotope insight into the global carbon cycle". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273425.
Texto completo da fontePerez, Fernandez Andrea. "Etude expérimentale sur l'échange isotopique dans le système eau-roches carbonatées". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30398.
Texto completo da fonteThe isotopic signatures of carbonate minerals have been applied to illuminate a plethora of natural geochemical processes. This thesis is aimed to assess the rates and or conditions at which such isotope signatures might be altered by fluid-mineral interaction through a series of systematic experimental studies performed with dolomite (CaMg(CO3)2) magnesite (MgCO3) and calcite (Ca-CO3). Ca and Mg isotopic compositions were measured as a function of time during closed-system stoichiometric dolomite dissolution experiments at 50 to 126°C. Although identical to that of the original dolomite at low temperatures, at temperatures >120 °C, the calcium isotopic signature of fluid phase (delta(44/42)Ca fluid) became 0.6±0.1‰ higher than that of the dissolving dolomite over a 4-week period. In contrast, the delta(26/24)Mg fluid, remained equal to that of the dolo-mite both at low and high temperatures. This set of experiments evidences the two-way transfer of calcium in and out of the dolomite structure at elevated temperatures. The results suggest that the inhability of dolomite to precipitate at these conditions is due to the difficulty of Mg to be reincorporated in the dolomite structure. In a follow-up study, magnesite was dissolved at 25°C in the presence of fluids with distinct pH and CO2 pressures. The isotopic compositions of the fluid differed from that of the solid at near-to chemical equilibrium indicating the two-way transfer of magnesium into this mineral at ambient temperatures. A single fractionation mechanism cannot explain the distinct Mg isotope behaviors observed. Further work on carbon isotope exchanges in the calcite water system shows a slow by steady evolution of the carbon isotopic composition towards the accepted equilibrium fractionation factor over the course of nearly year-long experiments after the system had attained bulk chemical equilibrium. Carbon isotope reequilibration rates were found to be approximately four orders of magnitude slower than that of bulk calcite dissolution, suggesting that the rate limiting step to the carbon isotope reequilibration process is the transport of carbon into and out of the bulk mineral after it has exchanged on the surface. The results of this thesis suggest that the Mg, Ca and C isotopic signatures in carbonate minerals are not invariant over geological time-frames and can be readily altered by water-mineral interaction. Such results indicate that the preservation of carbonate mineral signatures require low permeability rock formations or some inhibitory mechanism limiting metal and carbon exchange
Brazier, Jean-Michel. "Rôle des phases minérales des sols en tant que réservoirs de nutriments : approche expérimentale (abiotique), en milieu naturel et multi-isotopique (isotopes stables Ca-Sr)". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAH005/document.
Texto completo da fonteThis PhD thesis examined the mechanisms of storage and release, from and elementary and isotopically point of view, of calcium (Ca) and strontium (Sr) onto or into mineral phases commonly encountered within soils (primary minerals, clay minerals, oxy-hydroxides, pedogenic carbonate). A robust δ88Sr measurements method had to be developed in the laboratory and validated by the measurement of international reference materials, mostly never measured in the literature. The results of this work show that Ca adsorption onto phyllosilicate minerals generates a quantifiable isotopic fractionation by preferential uptake of the light isotope (40Ca) under our experimental conditions when the minerals have a significant structural charge and specific surface area and/or an interlayer space open to hydrated cations adsorption. A study on rhizoliths in natural environment has also highlighted that the combination of Ca and Sr isotopes allows an effective tracing of sources and mechanisms in the problematic related to the storage of these two elements within soils
Blättler, Clara L. "Applications of calcium isotopes in marine carbonates in the Recent and Phanerozoic". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:9f2ce280-c7b9-43cc-8aaf-4aaac058d350.
Texto completo da fonteGriffith, Elizabeth Morris. "Seawater calcium isotopes and the cenozoic carbonate depositional history of the oceans /". May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Texto completo da fonteDrouet, Thomas. "Etude de l'origine du calcium dans les écosystèmes forestiers par les méthodes de géochimie et de dendrochime isotopiques du strontium". Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210940.
Texto completo da fonteSchmitt, Anne-Désirée. "Les isotopes du Calcium: Développements analytiques. Application au bilan océanique présent et passé". Phd thesis, Université Louis Pasteur - Strasbourg I, 2003. http://tel.archives-ouvertes.fr/tel-00376191.
Texto completo da fonteUn protocole de mesure permettant de s'affranchir du fractionnement instrumental a tout d'abord été développé au Centre de Géochimie de la Surface. Après séparation chimique sur résine échangeuse d'ions, les compositions isotopiques en Ca ont été déterminées au spectromètre de masse à thermo-ionisation par une technique employant un double spike. L'expression des rapports isotopiques du Ca sous forme de delta requiert l'emploi d'un matériel de référence. Aucun standard international n'existant pour les isotopes du Ca, le standard carbonaté SRM 915a du NIST a été proposé. L'eau de mer, seul échantillon commun à la majorité des études antérieures, a été calibré en fonction de ce standard carbonaté et utilisé pour ce travail.
Ce protocole a ensuite été appliqué à l'étude du bilan océanique du Ca. L'étude d'eaux continentales a permis de contraindre le flux de Ca arrivant aux océans. Il en résulte une variabilité limitée de δ44Ca (0,5 ‰) à l'embouchure des grands fleuves et pour les eaux hydrothermales. Aucune relation n'a en outre été observée entre δ44Ca et la lithologie ou le climat des bassins versants étudiés. Ceci a permis de calculer une composition isotopique moyenne en Ca arrivant aux océans égale à -1,1 ± 0,2 ‰ et de suggérer sa constance au cours du temps. Il résulte de cette valeur que l'océan actuel est à l'état stationnaire par rapport aux isotopes du calcium. L'étude du δ44Ca de phosphates marins du Miocène et du Pléistocène, qui reflètent la paléo-variation de l'eau de mer au cours du temps, a montré que cela n'a pas toujours été le cas par le passé. Ainsi, à 22 Ma, une incursion du δ44Ca vers des valeurs plus positives suggère que l'intensité des flux entrants et sortants a varié, mais non leur signature isotopique.
Gentry, David Keith. "Seasonal isotope and trace-metal profiles of serially-sampled Conus gastropods: proxies for paleoenvironmental change". Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/3871.
Texto completo da fonteTarits, Corinne. "Etude des variations de composition isotopique du carbone et de l'oxygène dans le domaine de la précipitation spontanée homogène du carbonate de calcium : modélisation du comportement isotopique du carbone dans ce domaine". Paris 5, 1990. http://www.theses.fr/1990PA05P617.
Texto completo da fonteCobert, Florian. "Processus et mécanismes physico-chimiques et biologiques responsables du fractionnement des isotopes du calcium". Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00762532.
Texto completo da fontePullyottum, Kavil Sarath. "Isotopic tracing (Si, Ca, Sr, H and O) of biogeochemical processes in Indian groundwater along the land-to-ocean continuum". Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS053.pdf.
Texto completo da fonteGroundwater forms a dynamic system exhibiting spatial and temporal heterogeneity, and acts as an intermediate between surface processes occurring in critical zone and the riverine systems, which ultimately delivers solutes from continents to ocean. Recent studies reveal that the submarine groundwater discharge (SGD) is a dominant pathway for nutrient delivery to the coastal ocean, often exceeding riverine nutrient fluxes, thus forming a significant component of oceanic biogeochemical cycling. However, SGD remains overlooked in coastal nutrient budgets and is difficult to quantify given large spatial and temporal variability. Among the elements delivered to the coast through SGD, silicon (Si) forms a key nutrient for diatoms, one of the dominant primary producers in freshwaters, estuary and coastal ecosystems. Tropical humid watersheds with seasonal monsoonal precipitation, commonly found in Indian subcontinent, favors intense silicate weathering resulting in high Si fluxes to surface and groundwaters. However, anthropogenic activities including agriculture and damming can significantly modulate Si cycling and requires further evaluation, particularly in groundwater. The present research investigates three major aspects of groundwater Si cycling: i) the impact of land use alterations (such as agriculture) and monsoon precipitation in groundwater dissolved silicon (DSi) and silicon isotopic signature (δ30Si) by comparing an agricultural (Berambadi) and forested (Mule Hole) watersheds across two seasons, ii) elucidating groundwater-surface water interactions in the largest monsoonal estuarine system in India (Godavari) and, iii) quantify the fresh submarine groundwater derived Si fluxes to Indian Ocean using a series of coastal groundwaters along Indian coastline. We employ multiple isotopic tracers to understand biogeochemical processes in groundwater including water isotopes and 87Sr/86Sr to understand sources and mixing, δ30Si and Ge/Si ratios to trace Si cycling, and δ44/40Ca to decipher carbonate weathering in critical zone. The present work increased the δ30Si average of global groundwater from 0.49±0.9‰ (1SD, n=66) to 0.81±0.9‰ (1SD, n=224), lower than the river water and seawater δ30Si. We show that the δ30Si signatures of groundwater are not impacted by land use alterations and seasonal monsoon, and are primarily driven by silicate weathering and secondary clay formation in soil and saprolite. Groundwater system generally exhibits a steady state behavior with a dynamic equilibrium between Si supply and formation of secondary phases. We conclude that Si isotopic signatures of weathering, adsorption, and plant uptake occurring in the shallow soil and saprolite horizons are partly overprinted and homogenized by the regolith weathering in the deep critical zone. In the second part of the thesis, we study Godavari estuary and adjacent groundwater to discern sources vs. mixing vs. processes along this land-to-ocean interface. The δ30Si signatures of estuary exhibit significant temporal variability, primarily driven by diatom uptake and some heterogeneous groundwater discharge during dry season while silicate weathering and secondary clay formation in the basin dominate during wet season. We note that estuaries can act as significant filters for Si supply to ocean, removing ~15% of the total DSi supplied by the Godavari river. The δ44/40Ca composition in Godavari estuary (1.3±0.5‰, 1SD, n=16) and groundwaters (1.6±0.7‰, 1SD, n=15) are highly heterogenous. The Ca isotopic fractionation in both estuary and groundwater are primarily driven by precipitation of secondary carbonates, a process that would require further study. Finally, the dissolved silicon and δ30Si of coastal groundwater all over India indicates that fresh SGD discharge contributes to <1% of the total Si flux of the rivers and is considered to have insignificant impact on oceanic Si and isotopic budgets in North Indian Ocean
Heuser, Alexander. "Variations of calcium isotopes (d44Ca) [delta 44 Ca] in foraminifers over the past 24 Ma". [S.l.] : [s.n.], 2002. http://e-diss.uni-kiel.de/diss_713/d713.pdf.
Texto completo da fonteWright, Carrie Carlota. "Calcium isotopes in sheep dental enamel : a new approach to studying weaning and dairying in the archaeological record". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6f7d5179-594a-41c3-a06d-478a811b818a.
Texto completo da fontePerrot, Frédéric. "Etude spectroscopique des isotopes 51,52,53Ca par décroissance β des noyaux riches en neutrons 51,52,53K et interaction effective dans la couche fp". Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/PERROT_Frederic_2004.pdf.
Texto completo da fonteThe study of neutron rich nuclei is a powerful tool to observe shell evolution with isospin far from stability. Recent experimental studies have pointed out a new magic number at N=32 with strong features for 52Ca. Indeed neutron rich calcium isotopes (N>29) are key nuclei to fix the effective neutron-neutron interaction in fp shell due to the simplicity of the Z=20 wave function. The study of 51,52,53Ca isotopes has been performed at the CERN-ISOLDE mass separator facility by beta-decay of 51,52,53K. The experimental set-up was composed of the TONNERRE and the LEND detector array dedicated to the observation of the delayed neutrons and of two MINIBALL clusters for gamma detection. A new method has been developed to determine the absolute decay number of K isotopes by modelling the time evolution of the ions extraction from the target-ion-source ensemble. Moreover, a lot of new bound and unbound states have been observed in 51,52,53Ca in a wide energy range up to 11 MeV. Shell model calculations have been performed in the fp shell and some monopole corrections in the T=1 isospin channel have been done, giving rise to a new KB3Gm effective interaction. Calculations with this interaction well agree with new spectroscopic results on 51,52,53Ca and predict a 2+ state around 2 MeV in 54Ca. Such a future experimental observation would sign the non appearence of a new magic number at N=34
Court, Mélanie. "Étude des cycles du Ca et Mg dans cinq hêtraies du nord de la France et des modifications induites par un amendement calco-magnésien : utilisation combinée des approches élémentaires et isotopiques (δ26/24Mg, δ44/40Ca et 87Sr/86Sr)". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0248/document.
Texto completo da fonteIn France, many forest ecosystems grow on acidic and nutrient poor soils. In numerous cases, the chemical fertility of forest soils is slowly degrading due to increasing external pressures (e.g. decreasing atmospheric inputs, increasing biomass exportations) and is a growing concern in the international forest community. Forest management often must resort to restauration/remediation practices to ensure the sustainability of the ecosystem. Forest liming with a carbonate product is a known practice to reduce soil acidity, globally improve the ecosystem functioning and compensate nutrient losses caused by biomass harvest and exportation. However, our understanding of the effects of liming on magnesium and calcium biogeochemical processes and cycling in forest ecosystems is still incomplete. This study focuses on the fate of magnesium and calcium originating from the dissolution of liming products in the soils and trees of five beech forests located in Northern France over a period up to 45 years. In order to do so, “conventional” total-element approaches were combined with a multi-isotopic approach (26/24Mg, 44/40Ca et 87/86Sr). At all five sites, the data measured in control plots throughout the study period suggest that the exchangeable pools of nutrient cations in the soil has decreased over the last several decades and that this trend, together with the low chemical fertility level of the soil, was reflected in foliar nutrition (Ca, Mg, K, P). Compared to the control plots, soil exchangeable pools of Mg and Ca in the 0-40cm layer in the limed plots increased during the first decade after liming but differences were no longer observable in soil pools after 20 to 30 years. However, the effect of liming on tree nutrition was still observed after 40 years, most probably because the biological cycling of these elements was enhanced by the lime input. The ecosystem response to the lime input varied between sites depending on the nature of the liming product (CaCO3 or Ca-MgCO3) and the initial chemical fertility level of the soil, the poorest sites showing the strongest responses. The natural variations of Mg, Ca and Sr isotopic ratios combined with conventional approaches highlight the importance of the BIO component of the biogeochemical cycling of Mg and Ca in the studied low chemical fertility beech forests. These isotopic tools also enabled to show the long-lasting incorporation of the Mg and Ca released from the liming product in the biological cycle and highlight the changes in the biogeochemical functioning of these forest ecosystems after the liming operation
Darnton, Susan Meacham. "The effects of boron supplementation on bone mineral density, blood and urinary calcium, magnesium, phosphorous and urinary boron in female athletes". Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134658/.
Texto completo da fonteChandler, Catherine. "Spectroscopy of exotic f - p - g nuclei using projectile fragmentation and fusion evaporation reactions". Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/843034/.
Texto completo da fontePoszwa, Anne. "Utilisation des isotopes du strontium pour évaluer la dynamique des éléments minéraux dans des écosystèmes forestiers sous climat boréal, tempéré et tropical". Nancy, 2000. http://docnum.univ-lorraine.fr/public/SCD_T_2000_0128_POSZWA.pdf.
Texto completo da fonteEvans, Nicholas Philip. "Isotope systematics of gypsum and its hydration water". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290136.
Texto completo da fonteNottingham, Mark. "Resonance photo-ionisation mass spectrometry techniques for the analysis of heavy noble gas isotopes in extra-terrestrial samples". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/resonance-photoionisation-mass-spectrometry-techniques-for-the-analysis-of-heavy-noble-gas-isotopes-in-extraterrestrial-samples(93bc14bd-d13f-4d91-ad16-e264754a6e79).html.
Texto completo da fonteWienholtz, Frank [Verfasser], Lutz [Gutachter] Schweikhard e Michael [Gutachter] Block. "Measurements of exotic calcium isotopes by multi-reflection time-of-flight mass spectrometry and further developments and applications / Frank Wienholtz ; Gutachter: Lutz Schweikhard, Michael Block". Greifswald : Universität Greifswald, 2019. http://d-nb.info/1191369668/34.
Texto completo da fonteWogsland, Brittan Valhalla. "Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a 42Ca-43Ca double spike". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554.
Texto completo da fonteRollion-Bard, Claire. "Variabilité des isotopes de l'oxygène dans les coraux Porites : développement et implications des microanalyses d'isotopes stables (B, C ET O) par sonde ionique". Nancy 1, 2001. http://docnum.univ-lorraine.fr/public/INPL_T_2001_ROLLION-BARD_C.pdf.
Texto completo da fonteCastillo, Alvarez Maria Cristina Castillo. "Fractionnement des isotopes de nickel lors de l'adsorption à la surface de la calcite et coprécipitation avec la calcite". Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30047.
Texto completo da fonteThe chemical and isotopic compositions of trace elements in calcite are the basis for most past temperature, atmospheric CO2, and ocean pH paleo reconstructions. The isotope compositions of divalent metals incorporated into the calcite structure also have the ability to record valuable information that reflects the geochemical conditions of formation (Galy et al., 2002; Chang et al., 2004; Beard et al., 2012; Mavromatis et al., 2013; Fantle and Tipper, 2014; Mavromatis et al., 2015; Mavromatis et al., 2019). Moreover, as the equilibrium and kinetic partition of divalent metals between calcite and fluid exhibit contrasting behaviors, it can be expected that their isotope composition in calcite exhibits distinct trends (Schott et al., 2014). Because Ni aqueous speciation strongly depends on fluid pH and alkalinity, the isotopic composition of Ni adsorbed on calcite surface and/or incorporated into the calcite lattice could provide information on the chemical environment in which this mineral originally formed. To calibrate this potentially useful tool, experiments were performed at 25°C to determine Ni isotope fractionation during 1) Ni adsorption on calcite surface as a function of solution pH (from 7.5 to 8.7) and 2) Ni coprecipitation with calcite at pH = 6.2, pCO2 = 1 atm as a function of calcite growth rates (ranging from 10-8.2 to 10-7.3 mol m-2 s-1). Results show that the equilibrium fractionation factor, Δ60Nisolid-solution, for Ni adsorption on calcite is equal to -0.49 ± 0.16‰ and is pH - independent. Light Ni isotopes are also preferentially incorporated in calcite during its coprecipitation. The extent of Ni isotope fractionation decreases from -0.3 to -1 ‰ as the calcite precipitation rate increases from 10-8.2 to 10-7.3 .mol m-2 s-1. This behavior, due to the strong hydration of the Ni2+ aqua ion, may serve to approximate calcite precipitation rates and pCO2 in past oceans
Carey, Amy Dawn. "Calcium isotope dynamics in the Hubbard Brook sandbox experiments". Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/summer2006/a%5Fcarey%5F072806.pdf.
Texto completo da fonteMarriott, Caedmon. "Lithium and calcium isotope fractionation and Li/Ca ratio incorporation into calcium carbonate as potential geochemical proxies". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418477.
Texto completo da fonteAlkhatib, Mahmoud [Verfasser]. "Trace element and isotope measurement on artificially precipitated calcium carbonate / Mahmoud Alkhatib". Kiel : Universitätsbibliothek Kiel, 2016. http://d-nb.info/1107010764/34.
Texto completo da fonteHippler, Dorothee. "Assessing the potentials of calcium isotope thermometry in tropical and polar oceans /". [S.l.] : [s.n.], 2004. http://www.zb.unibe.ch/download/eldiss/04hippler_d.pdf.
Texto completo da fonteSime, Neil Graham. "Calcium isotope variations in marine and terrestrial carbonates over the past 20 Ma". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614206.
Texto completo da fonteSaulnier, Ségolène. "Exploration des compositions isotopiques en magnésium des carbonates marins comme traceurs paléoenvironnementaux". Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0267/document.
Texto completo da fonteStudying the Mg isotopic composition in marine carbonate can help to understand the biogeochemical cycle of this element. Indeed, carbonates may record seawater Mg isotopic composition during their precipitation. However, it is necessary to understand the possible control of some environmental factors (e.g. temperature, pH, Mg/Ca of the solution) on those compositions. Therefore, the first goal of this thesis was to determine parameters impacting carbonate Mg isotopic composition with experimental precipitations under controlled conditions. Thus, it has been shown, in restricted ranges, that temperature, pH and solution Mg/Ca have no influence on Mg isotopic fractionation during calcite precipitation. Equilibrium Mg isotopic fractionation between solution and calcite has been evaluated to -2.13 ± 0.24 per thousand (2sigma) from this study, combined with published data. These results were then applied to a study of Mg isotopic compositions in modern and past brachiopod shells. For this, a quantification of vital effects with respect to Mg isotopes during the brachiopod growth was realized. The zones in isotopic equilibrium for Mg, O and C, and thus susceptible to be used for paleoenvironnemental reconstruction, are in the inner calcite at the edge of the shell. The first measurements of Mg isotopic compositions for the last 60 Ma suggest variations of Mg isotopic compositions of the seawater which could be linked to changes of carbonate flux in the ocean
Baker, Evan. "Carbon and Oxygen Isotope Fractionation in Laboratory-Precipitated, Inorganic Calcite". Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19311.
Texto completo da fonteDavenport, Jesse. "Isotopic tracing of silicate and carbonate weathering in the Himalayan erosional system". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0241.
Texto completo da fonteWeathering of Himalayan lithologies has had a potential impact on the global carbon cycle. To be able to constrain and understand the processes that occurred in the Himalayas that affected these cycles, we must be able to distinguish the signatures of silicate and carbonate weathering in the dissolved load of Himalayan rivers. Previous studies have attempted to do this using a variety of methods but there is still not a clear consensus on the magnitude and flux of silicate weathering in the Himalaya. This thesis proposes the use of 40Ca as a tracer that could improve the quantification of the silicate and carbonate weathering flux in the dissolved load of Himalayan rivers. Previous work has shown that the 40Ca budget of seawater is dominated by a mantle source, such that marine carbonates have a homogeneous 40Ca signature indistinguishable from the mantle value. In contrast, the upper silicate crust is expected to have developed a radiogenic composition. The difference between the radiogenic Ca signature of carbonate and silicate lithologies can be therefore used to differentiate between carbonate and silicate weathering in the dissolved load of rivers. Here, we present a geochemical survey, including radiogenic Ca analyses, of rivers draining the main lithological units of the Himalaya, as well as results from sediments, bedrock, soil and gravel. Our results show that Himalayan carbonates exhibit no radiogenic 40Ca excesses despite highly variable 87Sr/86Sr signatures, whereas sediments are variably radiogenic (+0.9 to +4). This suggests that for Ca, unlike for Sr, isotopic exchange between the silicate and carbonate lithologies has been minimal. The radiogenic Ca composition of river water ranges from +0.1 in carbonate dominated catchments to +11 in rivers draining silicate catchments. For large rivers, silicate and carbonate weathering budget estimates based on major elements and radiogenic Ca compositions tend to agree. However, for some smaller rivers, especially those draining silicate dominated basins in the HHC and LH formations, some discrepancies are observed. These cannot be attributed to poor definition of the chemical or radiogenic Ca composition of the endmembers used for budget modeling, as the values required to bring the estimates into agreement are unreasonable. They also cannot be explained by precipitation of secondary carbonates in the rivers as the non-radiogenic composition of the carbonate fraction of sediments suggests that this process is only minor. Rather, these discrepancies may be due to the dissolution/weathering of trace amounts of radiogenic calcite contained within HHC and LH silicate lithologies. The weathering of such material, which represents only a tiny fraction of the area of the silicate catchment, could yield a substantial proportion of the radiogenic Ca and may thus have a significant influence on the isotopically based weathering budgets of these basins. Nevertheless, as this effect is observed primarily in basins with low silicate erosion rates, its influence on estimates of the overall silicate weathering flux will be minor. More generally, the results of this thesis imply that the 40K–40Ca system can resolve issues that cannot be successfully addressed using Sr isotopes in the Himalaya. Further work is needed to define the full range of radiogenic Ca compositions in the Himalaya in order to clearly answer questions regarding silicate weathering fluxes
Ogliore, Ryan Christopher Stone Edward Stone Edward. "The sulfur, argon, and calcium isotopic composition of the galactic cosmic ray source /". Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-02082007-175902.
Texto completo da fonteTanaka, Yuuki. "Deciphering the physiological codes of bone using elemental and isotopic data obtained by ICP-mass spectrometry". Kyoto University, 2017. http://hdl.handle.net/2433/228224.
Texto completo da fonteHeuvel, Elisabeth Gertruda Hendrika Maria van den. "Application of dual stable isotope techniques to measure absorption of calcium, magnesium and iron in man". [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1998. http://arno.unimaas.nl/show.cgi?fid=8251.
Texto completo da fonteAl-Aasm, Ihsan Shakir. "Stabilization of aragonite to low-Mg calcite trace elements and stable isotopes in rudists". Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4677.
Texto completo da fonteGebert, Florian [Verfasser]. "Precision measurement of the isotopic shift in calcium ions using photon recoil spectroscopy / Florian Gebert". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1072060299/34.
Texto completo da fonteMutchler, Scott R. "Oxygen stable isotopic analysis of calcite by Raman microprobe spectrometry". Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-05092009-040655/.
Texto completo da fonteTipper, Edward Thomas. "The isotopic fingerprint of calcium and magnesium : from the alteration of the continental crust to global budgets". Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614219.
Texto completo da fonteMéheut-Le, Quéau Merlin. "Calcul prédictif du facteur de partage isotopique entre minéraux dans le cadre de la théorie de la fonctionnelle de la densité". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00231076.
Texto completo da fontedesquelles on déduit ses propriétés de partage. Notre but est de valider une approche ab initio, i.e. libre de tout paramètre issu de l'expérience, permettant la prédiction du partage entre deux matériaux. On s'est intéressé aux matériaux: quartz, vapeur d'eau, glace, kaolinite, lizardite, enstatite, forstérite, brucite et gibbsite. Certains ont fait l'objet d'études expérimentales précises de leurs différentes propriétés physiques, ce qui nous permet de valider notre approche, et tous sont de grand intérêt en sciences de la Terre, ce qui nous permet de proposer de nouvelles lois de partage en fonction de la température, et de vérifier la validité de celles déjà proposées. C'est la première fois qu'une telle étude systématique est réalisée à partir d'une approche ab initio, et sur autant de systèmes différents. On a donc procédé à une étude la plus complète possible des sources d'erreur susceptibles d'influencer le résultat final. Par ailleurs, cette approche nous permet d'analyser de façon plus détaillée les processus physiques à l'origine du partage isotopique dans ces différents matériaux.
Giuffre, Anthony J. "Biomolecular Controls on Calcium Carbonate Formation by Amorphous and Classical Pathways: Insights from Measurements of Nucleation Rates and Isotope Tracers". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51821.
Texto completo da fontePh. D.
Owen, Richard John. "Partitioning of stable isotopes between scallop shell calcite and sea water and factors influencing shell growth and microgrowth patterns". Thesis, Bangor University, 1998. https://research.bangor.ac.uk/portal/en/theses/partitioning-of-stable-isotopes-between-scallop-shell-calcite-and-sea-water-and-factors-influencing-shell-growth-and-microgrowth-patterns(33ab8f1a-0cc4-41cb-be1e-d9a30fd34d7e).html.
Texto completo da fonteMeynard, Karina. "Polymérisation radio-induite : calcul de dose et modélisation dans le cas d'irradiations prolongées de sources non-scellées". Toulouse 3, 2009. http://thesesups.ups-tlse.fr/649/.
Texto completo da fonteThis work is meant for improving dosimetry in internal targeted radiotherapy by using MAGIC polymer gels. The Monte Carlo PENELOPE code was used to simulate the trajectory of particles down to an incident energy of 100 eV. In a preliminary study the code was validated by calculating the absorbed-dose distributions around point sources and volume ones in liquid water. This study was completed by estimating the equivalences or non-equivalences of the MAGIC gel to water, soft and adipose tissues, muscle, thyroid and cartilage. For this purpose, cross sections and physical interaction quantities (stopping power, attenuation coefficient. . . ) concerning these media are compared. The overall result set allowed us to adapt the PENELOPE code for modelling different irradiation configurations of source/target which describe the main clinical treatments in internal targeted radiotherapy
Maskenskaya, Olga M. "Abundance and fractionation of rare earth elements in calcite and other secondary minerals in fractures in the upper kilometre of crystalline bedrock, SE Sweden". Doctoral thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-37547.
Texto completo da fonteTécourt, Jean-Pierre. "Sur le calcul effectif de la topologie de courbes et surfaces implicites". Nice, 2005. http://www.theses.fr/2005NICE4057.
Texto completo da fonteIn this thesis, we got interested into the effective computation of the topology of implicit curves and surfaces. One can distinguish four different works: In a first part, we present an algorithm for computing the topology of a curve of R3 defined as the intersection of two implicit surfaces. More precisely, we compute a graph of points isotopic to the original curve. Then we detail a sweeping algorithm to compute an arrangement of quadrics based on a ``trapezoidal'' decomposition of the sweeping plane. The third part is devoted to an algorithm of triangulation of algebraic surfaces. This algorithm based on the computation of a Whitney stratification of the surface is the first one providing an isotopic meshing of the original surface even for singular surfaces. Finally, we study a family of parametrized surfaces, the Steiner surfaces, providing answers to the problems of effective classification, implicitization and search of preimages
Van, der Heijden Gregory. "Apport du multi-traçage isotopique (26Mg, 44Ca et 2H) à la connaissance des flux d'éléments minéraux dans les écosystèmes forestiers". Phd thesis, AgroParisTech, 2013. http://pastel.archives-ouvertes.fr/pastel-01058253.
Texto completo da fonte