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1
Nilsson, Lino. "Nitrogen transformations at the Kiruna mine : The use of stable nitrogen isotopes to trace nitrogen-transforming processes". Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-209419.
Testo completoAbstract (sommario):
Release of different nitrogen compounds can cause eutrophication in lakes and rivers whichcan lead to oxygen-free environments in bottom water and in the sediment and can in turnlead to fish-deaths. Ammonium can be toxic to biota and nitrate can in high concentrationeven be toxic to humans. WHO has released a limit for nitrate concentration in drinking waterof 10mg/l. The LKAB mine in Kiruna is the largest underground iron mine in the world and isprospecting, mining and refining iron ore, with an annual production of around 28 milliontons. Release of different nitrogen compounds as a result of the explosives used during themining operations has been a known problem for some time; however the processes affectingnitrogen during the water transport have never been fully investigated. The main objective of this MSc thesis is to determine if changes in nitrogen and oxygenisotope composition can be used as a tracer for nitrogen transformation processes in the minewater at LKABs underground mine in Kiruna. Water samples were collected at key points in the water transport system and were analyzedfor isotopic composition. Isotopic and chemical data revealed two different sources of nitrateand ammonium, undetonated explosives and leachate from waste rocks. Three differentnitrogen changing processes affecting concentration of nitrate and ammonium were found:ammonium volatilization, nitrification and sorption. It was not possible to quantify theseprocesses individually. No processes which decrease the nitrate concentration were found.
2
Dubeau, Jacques. "Isotope shift measurements of the stable krypton isotopes in natural and enriched concentrations". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66154.
Testo completo
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Vaiglova, Petra. "Neolithic agricultural management in the Eastern Mediterranean : new insight from a multi-isotope approach". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:c8824136-da35-43b2-a700-f458d0cc2fdf.
Testo completoAbstract (sommario):
The work presented in this dissertation explores the nature of agro-pastoral strategies developed by Neolithic farmers as a way to understand how early food production was inter-twined with environmental and socio-economic opportunities and constraints. Towards this end, a multi-isotope approach is used to address questions of scale and intensity of crop cultivation and animal management at the archaeological sites of Kouphovouno, southern Greece, Makriyalos, northern Greece, and Çatalhöyük, south-central Turkey. Measurements of stable carbon, nitrogen, oxygen and strontium isotope values of carbonized plant remains, human and animal bone collagen and animal tooth enamel are used to examine the similarities and differences in the types of treatments that individual species of plants and animals received during the agricultural cycle at the distinct locations. The results show that farmers at the three sites developed variable methods for exploiting the arable and pastoral landscape and catering to their economic and culinary needs. The discussion considers the implications of these findings to our understanding of the complexity and adaptability of early farming systems.
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Móri, Cleusa [UNESP]. "Rastreabilidade de farinhas de origem animal em tecidos de codornas de corte pela técnica dos isótopos estáveis de carbono ('intpot.13C'/'intpot.12C') e nitrogênio ('intpot.15N'/'intpot.14N')". Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/104988.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-06-11T19:33:34Z (GMT). No. of bitstreams: 0
Previous issue date: 2007-05Bitstream added on 2014-06-13T18:45:25Z : No. of bitstreams: 1
mori_c_dr_botfmvz.pdf: 326000 bytes, checksum: 0ec30e51a3d43636409c064480add1c6 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Universidade Estadual Paulista (UNESP)
Estudos para detecção de subprodutos de origem animal em carne de aves são escassos e, em se tratando de codornas são inexistentes. O trabalho teve por objetivo a detecção de farinha de vísceras de aves (FVA) em dietas de codornas de corte no músculo peitoral quilha e tíbia pela técnica dos isótopos estáveis de carbono (13C/12C) e nitrogênio (15N/14N). Foram utilizadas 64 codornas de corte macho de um dia de idade advindas de granja comercial. As aves foram divididas em sete grupos distintos distribuídos aleatoriamente em relação às dietas experimentais que continham diferentes percentagens de FVA: 0; 1,5; 3,0; 4,5; 6,0; 7,5 e 15. As dietas foram formuladas de forma a serem isoenergéticas, isoprotéicas e isoaminoacídicas. Quatro aves de cada tratamento foram abatidas aos 42 dias de idade para colheita do músculo peitoral (Pectoralis major), quilha e tíbia para posteriormente serem analisadas. Observou-se enriquecimento isotópico de d13C e d15N nos três tecidos analisados. Em codornas de corte com 42 dias de idade, o nível de inclusão de farinha de vísceras de aves detectado compreende o intervalo de 3,0 a 4,5%.
Detection of animal origin by-products studies in poultry meat are rare and inexistent when related to quail meat. This paper aims the detection of increasing levels of poultry visceral meal (FVA) in quail meat, using carbon (13C/12C) and nitrogen (15N/14N) stable isotopes technique. Sixty four male quails aging one day originally from a commercial producer were divided in seven different groups in a random distribution. Those groups received different experimental diets containing 0; 1,5; 3,0; 4,5; 6,0; 7,5 e 15% of FVA. Those diets were formulated to be isoenergetic, isoproteic and to have the same level of amino-acids. Four individuals per treatment were sacrificed at the 42nd day for breast muscle (Pectoralis major), keel and tibia collection to later analysis. Isotopic enrichment of d13C and d15N were observed in all analyzed tissues. In 42 day old quail were detect a 3,0 and 4,5% poultry visceral meal inclusion in its diet.
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Móri, Cleusa 1974. "Rastreabilidade de farinhas de origem animal em tecidos de codornas de corte pela técnica dos isótopos estáveis de carbono ('intpot.13C'/'intpot.12C') e nitrogênio ('intpot.15N'/'intpot.14N') /". Botucatu : [s.n.], 2007. http://hdl.handle.net/11449/104988.
Testo completoAbstract (sommario):
Orientador: Edivaldo Antônio GarciaBanca: Ricardo de Albuquerque
Banca: Carla Cachoni Pizzolante
Banca: Carlos Ducatti
Banca: Ariel Antonio Mendes
Resumo: Estudos para detecção de subprodutos de origem animal em carne de aves são escassos e, em se tratando de codornas são inexistentes. O trabalho teve por objetivo a detecção de farinha de vísceras de aves (FVA) em dietas de codornas de corte no músculo peitoral quilha e tíbia pela técnica dos isótopos estáveis de carbono (13C/12C) e nitrogênio (15N/14N). Foram utilizadas 64 codornas de corte macho de um dia de idade advindas de granja comercial. As aves foram divididas em sete grupos distintos distribuídos aleatoriamente em relação às dietas experimentais que continham diferentes percentagens de FVA: 0; 1,5; 3,0; 4,5; 6,0; 7,5 e 15. As dietas foram formuladas de forma a serem isoenergéticas, isoprotéicas e isoaminoacídicas. Quatro aves de cada tratamento foram abatidas aos 42 dias de idade para colheita do músculo peitoral (Pectoralis major), quilha e tíbia para posteriormente serem analisadas. Observou-se enriquecimento isotópico de d13C e d15N nos três tecidos analisados. Em codornas de corte com 42 dias de idade, o nível de inclusão de farinha de vísceras de aves detectado compreende o intervalo de 3,0 a 4,5%.
Abstract: Detection of animal origin by-products studies in poultry meat are rare and inexistent when related to quail meat. This paper aims the detection of increasing levels of poultry visceral meal (FVA) in quail meat, using carbon (13C/12C) and nitrogen (15N/14N) stable isotopes technique. Sixty four male quails aging one day originally from a commercial producer were divided in seven different groups in a random distribution. Those groups received different experimental diets containing 0; 1,5; 3,0; 4,5; 6,0; 7,5 e 15% of FVA. Those diets were formulated to be isoenergetic, isoproteic and to have the same level of amino-acids. Four individuals per treatment were sacrificed at the 42nd day for breast muscle (Pectoralis major), keel and tibia collection to later analysis. Isotopic enrichment of d13C and d15N were observed in all analyzed tissues. In 42 day old quail were detect a 3,0 and 4,5% poultry visceral meal inclusion in its diet.
Doutor
6
Petitat, Manuel. "Cr isotopes in carbonaceous chondrites : 53Mn-53Cr systematics and Cr isotopic anomalies". Paris, Muséum national d'histoire naturelle, 2010. http://www.theses.fr/2010MNHN0017.
Testo completoAbstract (sommario):
Cette thèse comporte deux parties distinctes. Dans la première partie, la systématique 53Mn-53Cr a été développée sur une NanoSIMS 50 et une CAMECA IMS 1270 pour dater la formation de carbonates dans les météorites Orgueil, Alais, Boriskino et Kaidun. Dans chaque grain, les excès en 53Cr mesurés corrèlent linéairement avec leurs rapports élémentaires 55Mn/52Cr ratios mesurés, indiquant la décroissance in-situ de 53Mn et donc la présence de 53Mn lorsque le grain a cristallisé. Dans la deuxième partie, un fragment de Tagish Lake et d’Orgueil ont été dissouts en 5 étapes afin d’identifier les phases minérales porteuses d’anomalies en Cr. Nos résultats montrent que Tagish Lake présente les plus grands excès et déficits en 54Cr par rapport au standard terrestre de toutes les chondrites carbonées analysées à ce jour faisant de cette météorite une des moins métamorphisée ainsi qu’une candidate idéale pour trouver la phase porteuse de l’anomalie en 54Cr, elle encore inconnueThis thesis has 2 distinct parts. In part I, the 53Mn-53Cr systematics was developed on a NanoSIMS and a CAMECA IMS 1270 to date the formation of carbonates in Orgueil, Alais, Boriskino and Kaidun. For each grain, the 53Cr excesses measured linearly correlated with their respective 55Mn/52Cr ratios, indicating the in-situ decay of 53Mn and showing that 53Mn was still extent at the time of formation of the respective carbonate. In part II, fragments of Tagish Lake and of Orgueil were dissolved in 5 different steps by using reagents with increasing acid strength to identify the different mineral phases carrying the Cr anomalies. Our results show that Tagish Lake displays both the highest excess and the highest deficit in 54Cr relative to a terrestrial standard of all groups of carbonaceous chondrite meteorites. This makes this meteorite one of the least metamorphic meteorite present in the collections worldwide and a particular target for deciphering the carrier phase of the 54Cr anomaly
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Perez, Fernandez Andrea. "Etude expérimentale sur l'échange isotopique dans le système eau-roches carbonatées". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30398.
Testo completoAbstract (sommario):
Les signatures isotopiques des minéraux carbonatés sont utilisées pour caractériser de nombreux processus géochimiques. Cette thèse a pour but de déterminer les vitesses auxquelles ces signatures isotopiques peuvent être altérées lors des interactions entre les fluides et les minéraux. A cette fin, une série d'études expérimentales a été conduite avec la dolomite (CaMg(CO3)2), la magnésite (MgCO3) et la calcite (CaCO3). On a mesuré l'évolution temporelle des compositions isotopiques de Ca et Mg pendant une série d'expériences de dissolution en réacteur fermé de la dolomite à des températures de 50°C à 126°C. A T < 120°C la composition isotopique du calcium dans la phase fluide est identique à celle de la dolomite initiale, mais au-delà de cette température, la signature isotopique du calcium dans le fluide (delta(44/42)Ca fluid) après 4 semaines était 0.6±0.1‰ plus lourde que l'originale. En revanche, le rapport delta(26/24)Mg du fluide reste égal à celui de la dolomite à toutes les températures étudiées. Ces résultats indiquent un double transfert de calcium vers et depuis la structure de la dolomite à T > 120°C. En outre, ces résultats suggèrent que la difficulté de la dolomite à précipiter à température ambiante doit être la conséquence de l'incapacité de Mg à s'incorporer dans la structure du minéral. Dans une autre étude on a conduit des expériences de dissolution de la magnésite à 25°C en solution aqueuses pour différents pH et pression de CO2. On a trouvé que la composition isotopique du fluide à proximité de l'équilibre chimique était différente de celle du solide, ce qui reflète un double transfert de Mg en direction et hors du minéral à température ambiante. Cependant, un seul mécanisme de fractionnement ne peut expliquer le comportement isotopique de Mg observé. La dernière partie de ce travail, consacrée au fractionnement isotopique du carbone dans le système calcite-eau, montre une évolution du fractionnement isotopique de cet élément vers le fractionnement isotopique à l'équilibre d'une durée d'une année après l'atteinte de l'équilibre chimique entre la calcite et l'eau. Les vitesses de rééquilibrage des isotopes de carbone sont ainsi quatre ordres de grandeurs plus lentes que la vitesse d'équilibrage de la calcite avec la solution. Ceci suggère que l'étape limitante dans le processus de rééquilibrage des isotopes du carbone est le transport de cet élément dans le cristal après l'échange isotopique à la surface de ce dernier. Les résultats de cette thèse indiquent que la signature isotopique de Mg, Ca et C des carbonates n'est pas invariante à l'échelle des temps géologiques et qu'elle peut être altérée durant l'interaction de ces minéraux avec l'eau. Ainsi, la préservation des signatures isotopiques des carbonates requiert d'une faible perméabilité des roches ou bien quelque mécanisme inhibant les échanges des métaux et du carbone à la surface des cristauxThe 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
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Suzuki, Rafael Massami. "Aminoácidos marcados aplicados aos estudos de nutrição e fisiologia em frangos de corte /". Jaboticabal, 2019. http://hdl.handle.net/11449/191289.
Testo completoAbstract (sommario):
Orientador: Nilva Kazue SakomuraResumo: RESUMO: A evolução das análises, considerando especificamente a nutrição e fisiologia de frangos de corte, permitiram rastrear nutrientes a níveis nucleares, permitindo que novas metodologias fossem desenvolvidas e novos objetivos alcançados. Algumas das análises que merecem destaque considerando estudos voltados a exigências de aminoácidos e metabolismo proteico foram: determinação de nitrogênio total/proteína, análise da composição aminoacídica e análise isotópica, sendo que a associação destas análises permite um potencial ainda maior. O uso de compostos enriquecidos é uma excelente ferramenta para estudos fisiológicos, uma vez que as respostas obtidas são inerentes ao composto de interesse, sendo possível o rastreamento do isótopo. Contudo, esta tecnologia ainda apresenta um alto custo, parte devido à baixa produção destes produtos e devido o sigilo da tecnologia da produção de tais compostos. Deste modo, no capítulo 2 foi padronizado uma metodologia para avaliar a adição de aminoácido marcado na dieta de aves e sua incorporação nos tecidos. A seguir, no capítulo 3 é apresentado um estudo com o objetivo de fracionar a utilização dos aminoácidos sulfurados com a utilização de metionina e cistina marcadas, avaliando-se diferentes proporções de ambos aminoácidos e diferentes fontes de metionina. Por fim, no capitulo 4 foi avaliado o efeito da idade sob a incorporação da L-(15N) treonina em diferentes tecidos de frangos de corte. Portanto, os objetivos desta tese foram a padr... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: ABSTRACT: The evolution of the analyzes, specifically regarding nutrition and physiology of broiler chickens, allowed to track nutrients to nuclear levels, resulting in the development of new methodologies and new objectives were achieved. Some of the analyzes that deserve to be highlighted considering amino acid requirements and protein metabolism studies were: total nitrogen/protein determination, amino acid composition analysis and isotopic analysis, and the association of these analyzes allows an even greater potential. The use of enriched compounds is an excellent tool for physiological studies, since the responses obtained are inherent to the compound of interest, and it is possible to track the tracer. However, the cost of such technology is still high, partly due to the low production of these products and also due to the secrecy of the technology of the production of such compounds. Thus, in chapter 2, a methodology was standardized in order to evaluate the addition of labeled amino acid in the broiler diet and its incorporation into tissues. In addition, chapter 3 presents a study in order to fractionate the use of sulfur amino acids using labeled methionine and cystine, and evaluating different proportions of both amino acids and different sources of methionine. Finally, in chapter 4, the effect of age on the incorporation of L-(15N) threonine into different broiler tissues was evaluated. Therefore, the objectives of this thesis were the standardization and applica... (Complete abstract click electronic access below)
Doutor
9
Swift, Benjamin. "The use of radio-isotopes in forensic science : the development of the isotope fingerprint analysis". Thesis, University of Leicester, 2004. http://hdl.handle.net/2381/29475.
Testo completoAbstract (sommario):
It is generally accepted that remains should be no more than 75 years old to warrant police interest. Therefore any reliable dating method should distinguish bones from within this interval accurately from those lying outside of it. Although archaeologists have reliable tools for dating material, pathologists have been unable to devise a method that caters for their specific needs. Previous work has focused upon the physiochemical properties of bone or its organic constituents, though the results have failed to produce a workable calibration system. The first hypothesis of this thesis has confirmed the existence of a predictable and measurable relationship between specific radioisotope concentrations in human bone and the post-mortem interval (PMI). It is predicted that the relationship is such that, once a calibration system has been created, it is possible to accurately estimate the PMI in a set of remains of unknown antiquity. Though concentrating upon 210Pb activities, the study also evaluated additional commonly occurring nuclides, both natural and man-made, the latter being subsequent to nuclear experimentation. The second confirmed hypothesis is that the geographical region an individual lived within becomes imprinted within their skeletal system, such that recognisable relationships between isotopes exist, creating a radio-isotope fingerprint. Examination of these relationships allows identification of the country in which a decedent lived.
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Huckle, David Martyn. "Characterizing U-series Isotope Signatures in Soils and Headwater Streams in a Complex Volcanic Terrain: Jemez River Critical Zone Observatory, Valles Caldera, NM". Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/305863.
Testo completoAbstract (sommario):
Uranium-series isotopes are an emerging tool to characterize weathering and soil forming processes in the Critical Zone, the dynamic region of earth's surface where bedrock, water, soil, and life chemically and physically interact to support ecosystems. Understanding controls on the U-series composition of soils across a range of lithologies and climate is critical to applying existing mass balance models of U-series isotopes to calculate soil formation rates in these systems. This study seeks to understand the behavior of U-series isotopes in soil profiles in the semi-arid complex volcanic terrain of the Valles Caldera, NM. (²³⁴U/²³⁸U) measured in soils ranged from 0.90 to 1.56 and (²³⁰Th/²³⁸U) values ranged from 0.48 to 1.39. Significant ²³⁰Th enrichment in upper soil profiles was interpreted as evidence of mixing with ²³⁰Th-enriched volcanic ash and significant ²³⁴U enrichment in one soil profile was interpreted as evidence of addition of U to soils from ²³⁴U-enriched soil solutions. A simple U isotope mass balance model was applied to estimate soil residence time based on U addition, which yielded a minimum residence time of ~10ka. Evidence of past episodic mixing of volcanic ash in these soils suggests modeling soil formation using a mass balance approach is problematic, and future applications of existing models in other heterogeneous volcanic soils should be applied cautiously. U-series isotopes have also shown promise as a tracer of residence time in shallow groundwater and streams. In this study, (²³⁴U/²³⁸U) in dissolved U is used to trace seasonal variation in source water contributions to streamflow in a small (3.29km²), headwater catchment in the Jemez River Basin Critical Zone Observatory within the Valles Caldera. Systematically lower (²³⁴U/²³⁸U) values in dissolved U were observed in spring and stream waters in conjunction with greater contributions of longer residence time waters during snowmelt ((²³⁴U/²³⁸U) ranged 1.7 to 2.8) vs. dry seasons ((²³⁴U/²³⁸U) ranged 1.9 to 3.1). The lower (²³⁴U/²³⁸U) values in longer residence time waters were attributed to progressive depletion of easily-weathered ²³⁴U with increasing duration of water rock interaction. Further studies with more quantitative age tracers, such as ³H, could help to establish (²³⁴U/²³⁸U) values as a powerful tracer of water sources and residence time in streamwaters at the catchment scale.
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Jones, Charles Edward. "Strontium isotopes in Jurassic and Early Cretaceous seawater". Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:fe3733bd-8e31-4bba-a78b-6d8275a0075f.
Testo completoAbstract (sommario):
The collection and analysis of a large number of belemnites and oysters with excellent biostratigraphic and diagenetic control has resulted in a highly detailed determination of the seawater Sr-isotope curve through the Jurassic and Early Cretaceous. The new data confirm the broad trends established by previous work, but the much sharper resolution of the new data allows the application of Sr-isotope stratigraphy with an optimal stratigraphic resolution of ± 1 to 4 ammonite subzones (± 0.5 to 2 Ma). The data show a general decline from the Hettangian (Early Jurassic) to a minimum in the Callovian and Oxfordian (Middle/Late Jurassic). This is followed by an increase through the Kimmeridgian (Late Jurassic) to a plateau reached in the Barremian (Early Cretaceous). In addition, there are major negative excursions in the Pliensbachian/Toarcian (Early Jurassic) and Aptian/Albian (Early Cretaceous). Stable isotope data collected from belemnites and oysters have resulted in the most extensive Jurassic δ13C and δ18O database to date. While both the carbon and oxygen data appear to give reasonable marine signals, the scatter in the data suggests that future research must document possible biological fractionation effects and develop better indicators for the diagenetic alteration of 613C and 6i 8O. The final chapter documents an unexpected correlation between sudden shifts in the Sr-isotope curve, the occurrence of positive 513C excursions, and the eruption of flood basalts. In the Jurassic and Cretaceous there is a correlation in time between sudden downward shifts in the Sr-isotope curve (Pliensbachian, Aptian, Cenomanian/Turonian), the occurance of positive 613C excursions, and the eruption of flood basalts. Each of these major downward shifts in the Sr-isotope curve is followed by a sudden upward shift, which although associated with a positive 613C excursion is not associated with an episode of flood basalt volcanism. In the Cenozoic the Sr-isotope curve no longer displays downward shifts, but the correlation continues between the occurrence of flood basalts and positive 513C excursions. Several lines of evidence suggest that the eruption of flood basalts is associated with pulses of hydrothermal activity, and that this hydrothermal activity brings about the conditions necessary for the genesis of carbon-burial events.
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Churchill, Layne Russell. "Trapping triply ionized thorium isotopes". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37161.
Testo completoAbstract (sommario):
Cold trapped ions have many applications in quantum information science and precision metrology. In this thesis, we present progress toward two objectives involving ions confined to linear RF traps: the strong coupling of Ba+ ions with a high finesse optical cavity, and the observation of an optical nuclear transition in 229Th3+. In pursuit of the first objective, a novel high-temperture vapor cell for the spectroscopy of neutral barium was constructed. Using this vapor cell, a new technique for isotope-selective photoionization loading of Ba+ in an ion trap was developed. In pursuit of the second objective, techniques ultimately to be used in creating, trapping, and observing 229Th3+ are studied using 232Th3+. Ion traps are loaded with 232Th3+ via laser ablation of thorium targets. 232Th3+ is detected optically using laser-induced fluorescence and electronically using a channel electron multiplier. A technique for creating ablation targets from trace quantities of thorium nitrate is presented. The primary loss mechanisms of Th3+, charge exchange and chemical reactions, are studied.
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Brown, S. A. "Condition monitoring using stable isotopes". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38246.
Testo completo
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Babikov, Mark. "Alternative Algebras and Their Isotopes /". The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933245539266.
Testo completo
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Jentoft-Nilsen, Kristi Lynette. "Deformation and the search for shape coexistence in odd-mass neutron-deficient iridium isotopes : studies of the B+/EC-decay of ¹⁸³Pt and ¹⁸¹Pt". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/29447.
Testo completo
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Semmes, Paul Barksdale. "Core-quasiparticle coupling model calculations as a test of IBA core descriptions of the even-mass Hg isotopes : decay of mass-separated [superscript]203At". Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/30906.
Testo completo
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Lowles, Ian Michael. "Decay scheme data of neptunium isotopes". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46897.
Testo completo
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Buesseler, Ken O. "Plutonium isotopes in the North Atlantic". Online version, 1986. http://hdl.handle.net/1912/3484.
Testo completo
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Audet, Daniel. "Spectroscopie de polarisation : isotopes du krypton". Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63319.
Testo completo
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England, J. G. "Laser resonance spectroscopy of samarium isotopes". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374792.
Testo completo
21
Buesseleer, Ken O. "Plutonium isotopes in the North Atlantic". Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/55309.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1986.Microfiche copy available in Archives and Science.
Vita. Chapter 5: ²³⁹,̳²⁴⁰Pu and excess ²¹⁰Pb inventories along the shelf and slope of the northeast U.S.A. / Ken O. Buesseler, Hugh D. Livingston and Edward R. Sholkovitz, reprinted from Earth and Planetary Science Letters, 76 (1985/86) 10-22, Elsevier Science Publishers, B. V. Amsterdam. The underscored comma in the above note is superscript on the source.
Bibliography: leaves 193-207.
by Ken O. Buesseler.
Ph.D.
22
Moos, Simone Beatrice. "The marine biogeochemistry of chromium isotopes". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115788.
Testo completoAbstract (sommario):
Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018.Cataloged from PDF version of thesis.
Includes bibliographical references.
In the ocean, chromium (Cr) is a redox-sensitive trace metal. The reduction of Cr(VI) to Cr(III) occurs in oxygen deficient zones (ODZs), and Cr reduction in general has been identified as a significant Cr isotope fractionation mechanism. This thesis presents the first Cr isotope variations (653 Cr) in ODZs of the ocean and adds to the sparse Cr isotope data published for modern seawater. I developed a precise and accurate Cr isotope method for seawater samples. Seawater acidification converts total Cr to Cr(III) which is preconcentrated by Mg(OH) 2 coprecipitation. A three-column anion exchange chromatography scheme separates Cr from isobaric and polyatomic interferences present in the seawater and reagent matrixes. Isotope analysis is performed on a MC-ICP-MS IsoProbe. The addition of a 50Cr-54Cr double spike allows for accurate correction of procedural and instrumental Cr mass fractionations. The first Cr isotope ratio data for a full water column profile in the Pacific Ocean is presented. This station serves as a fully oxic counterpart to stations located within the ODZ of the Eastern Tropical North Pacific. At one station, Cr concentrations are lower and [delta]53Cr values are heavier within the ODZ. This is consistent with Cr reduction resulting in isotopically lighter, particle-reactive Cr(III), which is scavenged and exported from the water column. A strong correlation of [delta]53Cr and [delta]15 NNo3- at this station suggests that Cr reduction may be microbially mediated instead of simply being a product of thermodynamic equilibrium. Alternatively, Cr may be reduced by Fe(II). In the anoxic bottom waters of the Santa Barbara Basin a strong Cr reduction signal (lower [Cr], heavier [delta]53Cr) is observed, which may result from the same aforementioned Cr reduction mechanisms. A shift to the heaviest seawater Cr isotope signatures yet observed was detected in the oxic bottom waters of the shallow Arctic Chukchi shelf, while Cr concentrations decreased. This extreme isotope signal may result from Cr reduction by a reduced species (e.g. Fe(II)), which was released from the underlying anoxic shelf sediments. Cr in the Atlantic layer and in the bottom water of a central Arctic station appears to be shaped by a novel, unidentified process.
by Simone Beatrice Moos.
Ph. D.
23
John, Seth G. "The marine biogeochemistry of zinc isotopes". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40968.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007.Includes bibliographical references.
Zinc (Zn) stable isotopes can record information about important oceanographic processes. This thesis presents data on Zn isotopes in anthropogenic materials, hydrothermal fluids and minerals, cultured marine phytoplankton, natural plankton, and seawater. By measuring Zn isotopes in a diverse array of marine samples, we hope to understand how Zn isotopes are fractionated in the oceans and how Zn isotopes may be used as tracers of marine biogeochemical processes. Common forms of anthropogenic Zn had [delta]66Zn from +0.08 %o to +0.32 %o, a range similar to Zn ores and terrigenous materials. Larger variations were discovered in hydrothermal fluids and minerals, with hydrothermal fluids ranging in 666Zn from 0.02 %o to +0.93 %o, and chimney minerals ranging from -0.09 %o to +1.17 %o. Lower-temperature vent systems had higher [delta]666Zn values, suggesting that precipitation of isotopically light Zn sulfides drives much of the Zn isotope fractionation in hydrothermal systems. In cultured diatoms, a relationship was discovered between Zn transport by either high-affinity or low-affinity uptake pathways, and the magnitude of Zn isotope fractionation. We established isotope effects of [delta]66Zn = -0.2 %o for high-affinity uptake and [delta]66Zn = -0.8 %o for low-affinity uptake. This work is the first to describe the molecular basis for biological fractionation of transition metals. Biological fractionation of Zn isotopes under natural conditions was investigated by measuring Zn isotopes in plankton collected in the Peru Upwelling Region and around the world.
(cont.) Seawater dissolved Zn isotopes also reflect the chemical and biological cycling of Zn. The [delta]66Zn of deep seawater in the North Pacific and North Atlantic is about 0.5%0, and the dissolved [delta]66Zn gets lighter in the upper water column. This is unexpected based our observations of a biological preference for uptake of light Zn isotopes, and suggests that Zn transport to deep waters may occur by Zn adsorption to sinking particles rather than as primary biological Zn. The thesis, by presenting data on several important aspects of Zn isotope cycling in the oceans, lays the groundwork for further use of Zn isotopes as a marine biogeochemical tracer.
by Seth Greeley John.
Ph.D.
24
Vogl, Gero, Marcus Rennhofer, Bogdan Sepiol, Manfred Smolik, Franz Essl e Ingrid Kleinbauer. "Invasions of isotopes and of neobiota". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194174.
Testo completoAbstract (sommario):
We report on invasions with low diffusivity: one in materials science and one in ecology. What is interesting in materials science is to describe diffusivities in order to model technological important materials. In ecology on the other hand predictions into the future appear the most challenging issue.
25
Glowa, Dominika Aleksandra. "Neutron skin measurement of tin isotopes". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20451.
Testo completoAbstract (sommario):
Heavy atomic nuclei are thought to have proton and neutron radial distributions which have different extents. This difference is usually quantified in terms of a neutron skin (rnp), defined as the difference between the root mean square radii of the neutron and proton radial distributions (rnp = rn - rp). The nature, or even existence, of the neutron skin is currently not well established for many nuclei. Different nuclear theories give different predictions for the neutron skin thickness ranging for a typical heavy nucleus from 0.05 to 0.35 fm. Accurate measurement of the properties of the neutron skin would be a powerful constraint to differentiate between models of nuclear structure, improving our knowledge of the basic Equation Of State (EOS) for neutron rich matter. Particularly, the rate at which the neutron skin thickness changes across an isotopic chain of nuclei gives a tight constraint on the EOS and is also amenable to experimental determination with small systematic error. Improving our knowledge of the EOS for neutron rich matter is a crucial step towards gaining a deeper understanding of nuclear structure and nuclear matter in general. These results will also impact our knowledge of compact astrophysical objects such as neutron stars. This thesis describes the first measurement of neutron skin thicknesses along an isotopic chain using an electromagnetic probe. The neutron skin is measured through the study of the coherent photoproduction of neutral π mesons emitted from nuclei. This experiment was carried out in the A2 hall of the MAMI facility in Mainz, Germany in October 2012. The incident photon beam comprised of energy tagged photons in the range of Eγ=150-800 MeV with an intensity of 10⁸ photons per second. Experimental data was obtained for three different tin targets, 116Sn, 120Sn and 124Sn. The products from the resulting photoreactions were measured in the Crystal Ball detector and in the TAPS calorimeter systems, with track and particle identification information for charged particles provided by a multi wire proportional chamber (MWPC) and a particle identification detector (PID). The experiment provides the first information on the evolution of the neutron skin thickness along an isotopic chain using an electromagnetic probe. The results are compared with a range of theoretical models and previous data from strongly interacting probes. The new data will provide an important new experimental constraint on the basic properties of the EOS in atomic nuclei.
26
Vogl, Gero, Marcus Rennhofer, Bogdan Sepiol, Manfred Smolik, Franz Essl e Ingrid Kleinbauer. "Invasions of isotopes and of neobiota". Diffusion fundamentals 6 (2007) 76, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14256.
Testo completoAbstract (sommario):
We report on invasions with low diffusivity: one in materials science and one in ecology. What is interesting in materials science is to describe diffusivities in order to model technological important materials. In ecology on the other hand predictions into the future appear the most challenging issue.
27
Gengelbach, Aila. "Collectivity in Neutron-Rich Erbium Isotopes". Licentiate thesis, Uppsala universitet, Kärnfysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-442208.
Testo completoAbstract (sommario):
Neutron-rich rare-earth nuclei around the maximum of collectivity are predicted to exist with an extremely stable intrinsic configuration in their ground-state structure. Due to the high degree of axial symmetry and large deformation, these nuclei are also excellent candidates for having long-lived high-K isomers. The present work concerns a study of the structure of the yrast bands and a search for isomers in the neutron-rich 68Er isotopes. Excited states of 68Er isotopes were populated via multi-nucleon transfer reactions. A 859 MeV 136Xe-beam was used to bombard a 170Er-target. The experimental setup consisted of the high-resolution γ-ray spectrometer AGATA coupled to the heavy-ion magnetic spectrometer PRISMA. The experiment collected 2 TB of useful data corresponding to 3 days of effective beam time. Beam-like fragments were identified by the PRISMA specrometer placed at the grazing angle of 44 degrees. PRISMA allows for Z, A and q identification as well as TOF and velocity vector determination. This is required for the Doppler correction of the emitted γ rays detected in time coincidence with AGATA. A good Z and very clean A separation has been achieved in PRISMA. Making use of two-body kinematics, Doppler corrected γ-ray spectra for target-like fragments were obtained as well. Due to the novel techniques of PSA and γ-ray tracking, AGATA provided high-quality γ-ray spectra for both beam-like xenon and target-like erbium isotopes. Known yrast bands and isomeric states in neutron-rich erbium isotopes were observed. A candidate for the decay of an isomeric state with Eγ=184 keV in 173Er, which has no previously known excited states, was identified.
28
PORZIO, CARLOTTA. "CONFIGURATION MIXING INVESTIGATION IN GERMANIUM ISOTOPES". Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/886195.
Testo completoAbstract (sommario):
Protons and neutrons of atomic nuclei can arrange in both spherical and non-spherical configurations. Nuclei can also exhibit configurations which lie close in energy, yet present different deformations. Such phenomenon is referred to as shape coexistence and its occurrence in nuclei is thought to pervade the entire nuclear chart. Excited states with similar energies and same spin and parity can also mix, so that the observed states are the result of mixing of different configurations.
In this context, the structure of Ge isotopes has been widely investigated over the years. Previous transfer reaction experiments pointed to the occurrence of configuration mixing between the ground state and first excited 0+ state in 72Ge (N = 40). Furthermore, they indicated a weakening of such mixing moving away from N = 40, in correspondence with the increase of the excitation energy of the 0+[2] state. However, the nature of the configurations that mix and their evolution along the Ge isotopic chain is still elusive.
In this thesis, a study of configuration mixing in the even-even Ge isotopes at and near stability (A = 72, 74, 76, 78) has been carried out through the measurement of electric monopole (E0) transition strengths, which have been identified as a sensitive probe of configuration mixing. In particular, the focus has been set on the transitions with I = 2, 2+[2]→2+[1].
The experiments presented in this thesis have been performed at the TRIUMF laboratory (Vancouver, Canada). The isotopes of interest have been populated via the β decay of radioactive ion beams of 72,74,76,78Ga, which were implanted at the center of the GRIFFIN decay station. The GRIFFIN spectrometer, combined with the PACES silicon array, enabled us to perform both γ-ray and electron spectroscopic investigations, to measure E0 strengths between states with I = 2.
29
Bordinhon, André Moreira [UNESP]. "Autobalanceamento da energia e da proteína da dieta pela tilápia do Nilo por meio de isótopos estáveis de carbono e do consumo de matéria seca". Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/104115.
Testo completoAbstract (sommario):
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Universidade Estadual Paulista (UNESP)
O objetivo deste trabalho foi avaliar a capacidade da tilápia do Nilo em 5 balancear sua dieta, quando fornecidas duas misturas de ingredientes, utilizando os 6 isótopos estáveis de carbono. Foram utilizados 225 juvenis de tilápia (peso: 5,0 ± 0,5 g), 7 distribuídos em cinco tanques. Os indivíduos alocados em um dos tanques eram 8 alimentados com uma mistura de alta proteína (MAP; δ13C = -22,62‰), os alocados em 9 um segundo tanque eram alimentados com uma mistura de baixa proteína (MBP; δ13C = 10 -14,34‰) e os animais dos outros tanques tinham acesso livre a ambas, quatro vezes ao 11 dia. Foram realizadas coletas de músculo, fígado e sangue a cada cinco dias por 86 dias, 12 exceto para o grupo alimentado com MBP (alimentado por 120 dias). As amostras 13 foram analisadas em espectrômetro de massa e as proporções consumidas das misturas 14 foram estimadas a partir do enriquecimento isotópico do carbono (δ13C). O 15 balanceamento realizado indicou redução no consumo relativo de proteína. Contudo, 16 esta relação não apresentou padrão definido em relação ao peso dos indivíduos, ou seja: 17 o balanceamento de proteína e energia para tilápia do Nilo está relacionado 18 principalmente à idade dos animais e não é claro se este processo está relacionado 19 também ao seu peso. As estimativas de consumo de um grupo animais desta espécie por 20 meio dos isótopos estáveis de carbono são semelhantes aos obtidos por outras técnicas, 21 portanto este método permite observação da diversidade deste comportamento no 22 autobalanceamento entre os indivíduos que compõe tal grupo.
This study aimed to assess the Nile tilapia ability to balance its own diet, 6 when two ingredient mixes were offered, using carbon stable isotopes. In order to 7 accomplish that, 225 Nile tilapia juveniles (average initial weight 5.0g ± 0.5g) were 8 distributed in five tanks, each containing a group of 45 fish. One group of fish were fed 9 exclusively a high protein mix (HPM; δ13C = -22.62‰), a second one fed only a low 10 protein mix (LPM; δ13C = -14.34‰). The other groups had free access to both mixes 11 (free choice system). The fish from all tanks were fed four times a day. Muscle, liver 12 and blood samples were collected at each five days (from 2 fish/tank/collection) for 86 13 days, except for the fish fed with MBP (fed for a 120 days period). The samples were 14 analyzed in a mass spectrometer and proportions of the mixes consumed were estimated 15 through its carbon isotope enrichment (δ13C). The fish diminished their protein intake 16 along the time. However, consumption did not present a clear pattern in relation to the 17 individual weight, i.e.: protein consumption patterns are mainly related to the age of the 18 individuals and it is not clear if it is also correlated to their weight. The consumption 19 estimative through stable isotopes of carbon did not conflict other studies reported in the 20 literature. Additionally this technique allowed observation of consumption among the 21 individuals from an experimental group 22.
30
Bueno, Juliana Finoto. "Geoquimica e cronologia de alojamento de granitos colisionais na Faixa Sergipana, Nordeste do Brasil". [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287312.
Testo completoAbstract (sommario):
Orientador: Elson Paiva de OliveiraTese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias
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Resumo: A Faixa Sergipana é uma das mais significantes faixas móveis neoproterozóicas do nordeste do Brasil, porque ela contém diversas estruturas e domínios litológicos que permitem que ela seja comparada a orógenos fanerozóicos como os Himalaias, por exemplo. A Faixa Sergipana foi formada durante a colisão entre o Cráton São Francisco-Congo e o Maciço Pernambuco-Alagoas durante a orogênese Brasiliano/Pan-Africano é formada por cinco domínios litoestruturais (Canindé, Poço Redondo-Marancó, Macururé, Vaza Barris e Estância) e é um orógeno chave para a reconstrução de parte da história do Gondwana Oeste. São reconhecidos três eventos de deformação principais (D1-D3) nas rochas supracrustais da Faixa Sergipana, sendo que o evento D2 é o principal evento colisional na faixa e associado a ele tem-se a geração de grande parte dos granitos presentes nos domínios Macururé e Poço Redondo-Marancó. Os granitos presentes nestes domínios foram divididos em dois grupos principais: (1) os granitos com ~ 625 Ma compostos pelos: (i) granitos com características de arco no Domínio Poço Redondo-Marancó (Granodiorito Queimada Grande) e no Domínio Macururé (Tonalito Camará e Granodiorito Coronel João Sá) e (ii) granitos com características crustais do Domínio Poço Redondo- Marancó (granitos Sítios Novos e Poço Redondo) e (2) os granitos colisionais do Domínio Macururé de ~ 580 Ma. Os granitos Queimada Grande, Camará e Coronel João Sá são plutons de alto potássio, cálcioalcalinos, metaluminosos, magnesianos, tipo-I de arco vulcânico. Estes granitos foram originados por fusão parcial de rochas derivadas do manto ou de crosta inferior de composição basáltica com proporções variáveis de contaminação com crosta continental. Os granitos Sítios Novos e Poço Redondo foram gerados pela fusão dos migmatitos locais e os granitos colisionais do Domínio Macururé por alta taxa de fusão dos micaxistos encaixantes. A abundância de granitos colisionais no Domínio Macururé indica que este domínio pode ter funcionado como um conduto dúctil, durante o neoproterozóico, limitado por zonas de cisalhamento regionais. Para delimitar a duração da colisão que resultou na formação da Faixa Sergipana foi utilizada a idade obtida para o Tonalito Camará pré- D2 de 628±12 Ma, que marca a idade máxima para o início do evento D2, e a idade do Granito Pedra Furada sin a tardi- D2 de 571±9 Ma, que marca a idade mínima para o final do evento D2; utilizando estes dados tem-se que o principal evento colisional (D2) na Faixa Sergipana durou pelo menos 57 Ma. Os granitos Queimada Grande, Camará e Coronel João Sá são o registro de arco continental na Faixa Sergipana formado durante a colisão neoproterozóica e a sua presença indica que o Domínio Macururé estava conectado ao Domínio Poço Redondo-Marancó antes do início da orogênese Brasiliana.
Abstract: The Sergipano Belt is one of the most significant Precambrian orogenic belts of Northeastern Brazil because it contains several structural and lithologic domains that allow it to be compared with Phanaerozoic orogens, like Himalayas. The Sergipano Belt was formed through continental collision between the Congo- São Francisco Craton and the Pernambuco-Alagoas Massif during the Brasiliano/Pan-African Orogeny and it comprises five lithostructural domains: Canindé, Poço Redondo-Marancó, Macururé, Vaza Barris and Estância and it is a key belt for reconstructing part of the history of West Gondwana. Three main events of regional deformation (D1-D3) are recognized in the supracrustal rocks of the belt and the D2 event is the main collision event in the belt, most granites were emplaced during this event in the Macururé and Poço Redondo-Marancó domains. Granites found in these domains can be divided into two groups: (1) ~ 625 Maold granites formed by: (i) arc-type granites in the Poço Redondo-Marancó domain (Queimada Grande Granodiorite) and in the Macururé Domain (Camará tonalite and Coronel João Sá granodiorite) and (ii) crustal granites in the Poço Redondo-Marancó domain (Sítios Novos and Poço Redondo granites) and (2) ~ 580 Ma-old collision-related granites in the Macururé domain. The Queimada Grande, Camará and Coronel João Sá granites are plutons of high-K calc-alkaline, metaluminous, magnesian, I-type volcanic arc granites. These granites were originated by partial melting of basic crustal sources derived from mantle or lower crust of basaltic composition with variable ratios of continental crust contamination. The Poço Redondo and Sítios Novos granites were generated by partial melting of local migmatites and the collisional granites of the Macururé domain by high degree of partial melting of the Macururé micaschists. The abundance of collisional granites in the Macururé domain indicates that this domain acted as a ductile channel flow during the Neoproterozoic limited by regional. To delimit the collision duration that results in the formation of Sergipano belt was used the 628±12 Ma age obtained for the pre-D2 Camará Tonalite, which mark the maximum age for beginning of D2 event, and the 571±9 Ma age obtained for the syn- to tardi- D2 Pedra Furada granite that mark the minimum age for end of the D2 event; using these numbers without the associated errors, we conclude that the main Neoproterozoic collisional (D2) event in the Sergipano Belt may have lasted at least 57 million years. The Queimada Grande, Camará and Coronel João Sá granites are the record of continental arc in the Sergipano belt formed during the Neoproterozoic collision and its presence indicates that the Macururé domain was connected in the Poço Redondo-Marancó domain before the beginning of the Brasiliano orogeny.
Doutorado
Metalogenese
Doutor em Ciências
31
Bordinhon, André Moreira 1978. "Autobalanceamento da energia e da proteína da dieta pela tilápia do Nilo por meio de isótopos estáveis de carbono e do consumo de matéria seca /". Botucatu : [s.n.], 2008. http://hdl.handle.net/11449/104115.
Testo completoAbstract (sommario):
Orientador: Luiz Edivaldo PezzatoBanca: Wilson Massamitu Furuya
Banca: José Fernando Machado Menten
Banca: Carlos Ducatti
Banca: José Roberto Sartori
Resumo: O objetivo deste trabalho foi avaliar a capacidade da tilápia do Nilo em 5 balancear sua dieta, quando fornecidas duas misturas de ingredientes, utilizando os 6 isótopos estáveis de carbono. Foram utilizados 225 juvenis de tilápia (peso: 5,0 ± 0,5 g), 7 distribuídos em cinco tanques. Os indivíduos alocados em um dos tanques eram 8 alimentados com uma mistura de alta proteína (MAP; δ13C = -22,62‰), os alocados em 9 um segundo tanque eram alimentados com uma mistura de baixa proteína (MBP; δ13C = 10 -14,34‰) e os animais dos outros tanques tinham acesso livre a ambas, quatro vezes ao 11 dia. Foram realizadas coletas de músculo, fígado e sangue a cada cinco dias por 86 dias, 12 exceto para o grupo alimentado com MBP (alimentado por 120 dias). As amostras 13 foram analisadas em espectrômetro de massa e as proporções consumidas das misturas 14 foram estimadas a partir do enriquecimento isotópico do carbono (δ13C). O 15 balanceamento realizado indicou redução no consumo relativo de proteína. Contudo, 16 esta relação não apresentou padrão definido em relação ao peso dos indivíduos, ou seja: 17 o balanceamento de proteína e energia para tilápia do Nilo está relacionado 18 principalmente à idade dos animais e não é claro se este processo está relacionado 19 também ao seu peso. As estimativas de consumo de um grupo animais desta espécie por 20 meio dos isótopos estáveis de carbono são semelhantes aos obtidos por outras técnicas, 21 portanto este método permite observação da diversidade deste comportamento no 22 autobalanceamento entre os indivíduos que compõe tal grupo.
Abstract: This study aimed to assess the Nile tilapia ability to balance its own diet, 6 when two ingredient mixes were offered, using carbon stable isotopes. In order to 7 accomplish that, 225 Nile tilapia juveniles (average initial weight 5.0g ± 0.5g) were 8 distributed in five tanks, each containing a group of 45 fish. One group of fish were fed 9 exclusively a high protein mix (HPM; δ13C = -22.62‰), a second one fed only a low 10 protein mix (LPM; δ13C = -14.34‰). The other groups had free access to both mixes 11 (free choice system). The fish from all tanks were fed four times a day. Muscle, liver 12 and blood samples were collected at each five days (from 2 fish/tank/collection) for 86 13 days, except for the fish fed with MBP (fed for a 120 days period). The samples were 14 analyzed in a mass spectrometer and proportions of the mixes consumed were estimated 15 through its carbon isotope enrichment (δ13C). The fish diminished their protein intake 16 along the time. However, consumption did not present a clear pattern in relation to the 17 individual weight, i.e.: protein consumption patterns are mainly related to the age of the 18 individuals and it is not clear if it is also correlated to their weight. The consumption 19 estimative through stable isotopes of carbon did not conflict other studies reported in the 20 literature. Additionally this technique allowed observation of consumption among the 21 individuals from an experimental group 22.
Doutor
32
Brito, Adriano Leal de. "Oxigênio-18 e deutério traçadores do sistema de aqüíferos na Bacia Sedimentar do Araripe". reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/13703.
Testo completoAbstract (sommario):
BRITO, Adriano Leal de. Oxigênio-18 e deutério traçadores do sistema de aqüíferos na Bacia Sedimentar do Araripe. 2012. 96 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-10-21T21:30:43Z No. of bitstreams: 1 2012_dis_albrito.pdf: 1763548 bytes, checksum: 4fe45ca63d81b9f56baf5d804acb37a4 (MD5)
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The natural tracers deuterium and oxygen-18 were used to identify the dynamic characteristics of the groundwater reserves in the Araripe Sedimentary Basin, through the analysis of water samples collected in 40 wells in January, April, July and October 2011. The sampling points are located in 08 municipalities and electrical conductivity measurements, which expresses water salinity, were also performed. The results show spatial and temporal variation of the parameters analyzed, but the average values of δ18O in samples from 33 wells is -3.22 ± 0.05 (‰) which is the average rainfall in the region today. Samples of the remaining seven wells showed higher fluctuations and four had values below -3.2 ‰. The meteoric lines that express measures of deuterium versus oxygen-18, constructed with values of each sample show a mean slope of 7.87 ± 0.60 ‰ about the value of the World Meteoric Line. The excess of deuterium in the sample period increased from 7.26 to 9.38 ‰ reflecting internal processes in the aquifer. Samples with values of δ18O in meteoric waters below the current mix of show paleowater already identified with modern recharge water, the samples with these values are not distinguishable by their electrical conductivities that are current in the range of samples characterizing the importance of isotopic tracers
Os traçadores naturais oxigênio-18 e deutério foram utilizados para identificar características dinâmicas das reservas hídricas subterrâneas na Bacia Sedimentar do Araripe, através da análise de amostras de água coletadas em 40 poços nos meses de janeiro, abril, julho e outubro de 2011. Os pontos de amostragem localizam-se em 08 municípios e medidas de condutividade elétrica, que expressa salinidade das águas, também foram realizadas. Os resultados mostram variação espacial e temporal dos parâmetros analisados, mas a média dos valores de δ18O em amostras de 33 poços é de -3,22 ± 0,05 (‰) que é o valor médio das chuvas atuais na região. As amostras dos sete poços restantes apresentaram maiores flutuações e quatro deles apresentaram valores abaixo de -3,2‰. As retas meteóricas, que expressam medidas de deutério versus oxigênio-18, construídas com valores de cada coleta mostram coeficiente angular com média de 7,87 ± 0,60 ‰ cerca do valor da Reta Meteórica Mundial. O excesso de deutério cresceu no período de amostragem de 7,26 a 9,38 ‰ refletindo processos internos no aquífero. As amostras com valores de δ18O em abaixo do das águas meteóricas atuais mostram mistura de paleoáguas já identificadas com águas de recargas modernas; as amostras com estes valores não são distinguíveis pelas suas condutividades elétricas que estão na faixa das amostras atuai caracterizando a importância dos traçadores isotópicos.
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Costa, Gelcirene de Albuquerque [UNESP]. "Rastreabilidade de camarão amazônico proveniente de cultivo e ambiente natural utilizando a técnica de isótopos estáveis". Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/86669.
Testo completoAbstract (sommario):
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costa_ga_me_jabo.pdf: 398423 bytes, checksum: bc07b3e5f98d29910cf30e3b83eff7eb (MD5)A globalização no comércio de pescado tem aumentado à oferta do produto, mas tem favorecido a prática de fraudes, como por exemplo, a substituição de espécies nobres por espécies de menor valor comercial. Por outro lado, consumidores cada vez mais exigentes têm demonstrado preferências por produtos de sistemas agroalimentares diferenciados. No Brasil, a regulamentação para as indicações geográficas tem crescido em ritmo acelerado nos últimos dois anos, exigindo o desenvolvimento de ferramentas analíticas para comprovação dos atributos de qualidades destes produtos diferenciados. Neste trabalho foi verificada a eficiência das análises de composição química (carne) e isótopos estáveis de carbono e nitrogênio (carne e carapaça) como ferramentas para autenticação e rastreabilidade do camarão da Amazônia. Foram analisados camarões de ambiente natural provenientes de lagos do Amazonas (Rei e Catalão); Lagoa Bahiazinha, Pantanal de Miranda, MS; Ilhas próximas ao estuário no Pará. As amostras de camarão cultivado foram coletadas no CAUNESP, Jaboticabal, São Paulo. Amostras do Lago Rei foram coletadas em julho e dezembro para avaliar o efeito sazonal nos componentes analíticos. Os resultados mostraram que a análise fatorial exploratória (AFE) permitiu diferenciar camarões em função da origem geográfica e modo de produção tanto para a composição de isótopos estáveis como para composição química
Globalization and increasing international trade in fish and fisheries products, but has favored the practice of fraud, such as the replacement of noble species by species of lower commercial value. Furthermore, consumers are demanding have demonstrated preference for agrifood systems. In Brazil, the rules for geographical indications has grown at a fast pace in the past two years, requiring the development of analytical tools to prove the attributes of these qualities differentiated products. This study evaluated the efficiency of chemical composition analyzes (meat) and stable isotopes of carbon and nitrogen analyzes (meat and shells) as tools for authentication and traceability of Amazon River prawn. Prawns of natural environment came of the Amazonas from lakes (Rei and Catalão); Bahiazinha pond, Pantanal of Miranda, MS; Islands near the estuary on Para state. Farmed prawn samples were collected in CAUNESP, Jaboticabal, São Paulo. Samples were collected from Lake Rei in July and December to evaluate the seasonal effect in the analytical components. The results showed that the exploratory factor analysis (EFA) allowed differentiation shrimp depending on geographical origin and method of production for both the composition of stable isotopes as chemical composition
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Costa, Gelcirene de Albuquerque. "Rastreabilidade de camarão amazônico proveniente de cultivo e ambiente natural utilizando a técnica de isótopos estáveis /". Jaboticabal, 2013. http://hdl.handle.net/11449/86669.
Testo completoAbstract (sommario):
Orientador: Léa Silvia Sant'AnaBanca: Juliana Célia Denadai
Banca: Maria Márcia Pereira Sartori
Resumo: A globalização no comércio de pescado tem aumentado à oferta do produto, mas tem favorecido a prática de fraudes, como por exemplo, a substituição de espécies nobres por espécies de menor valor comercial. Por outro lado, consumidores cada vez mais exigentes têm demonstrado preferências por produtos de sistemas agroalimentares diferenciados. No Brasil, a regulamentação para as indicações geográficas tem crescido em ritmo acelerado nos últimos dois anos, exigindo o desenvolvimento de ferramentas analíticas para comprovação dos atributos de qualidades destes produtos diferenciados. Neste trabalho foi verificada a eficiência das análises de composição química (carne) e isótopos estáveis de carbono e nitrogênio (carne e carapaça) como ferramentas para autenticação e rastreabilidade do camarão da Amazônia. Foram analisados camarões de ambiente natural provenientes de lagos do Amazonas (Rei e Catalão); Lagoa Bahiazinha, Pantanal de Miranda, MS; Ilhas próximas ao estuário no Pará. As amostras de camarão cultivado foram coletadas no CAUNESP, Jaboticabal, São Paulo. Amostras do Lago Rei foram coletadas em julho e dezembro para avaliar o efeito sazonal nos componentes analíticos. Os resultados mostraram que a análise fatorial exploratória (AFE) permitiu diferenciar camarões em função da origem geográfica e modo de produção tanto para a composição de isótopos estáveis como para composição química
Abstract: Globalization and increasing international trade in fish and fisheries products, but has favored the practice of fraud, such as the replacement of noble species by species of lower commercial value. Furthermore, consumers are demanding have demonstrated preference for agrifood systems. In Brazil, the rules for geographical indications has grown at a fast pace in the past two years, requiring the development of analytical tools to prove the attributes of these qualities differentiated products. This study evaluated the efficiency of chemical composition analyzes (meat) and stable isotopes of carbon and nitrogen analyzes (meat and shells) as tools for authentication and traceability of Amazon River prawn. Prawns of natural environment came of the Amazonas from lakes (Rei and Catalão); Bahiazinha pond, Pantanal of Miranda, MS; Islands near the estuary on Para state. Farmed prawn samples were collected in CAUNESP, Jaboticabal, São Paulo. Samples were collected from Lake Rei in July and December to evaluate the seasonal effect in the analytical components. The results showed that the exploratory factor analysis (EFA) allowed differentiation shrimp depending on geographical origin and method of production for both the composition of stable isotopes as chemical composition
Mestre
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Goedert, Jean. "Écologie des premiers tétrapodes dévoilée par la composition isotopique du soufre (34S/32S) de leurs squelettes". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1337.
Testo completoAbstract (sommario):
La dichotomie environnementale qui caractérise la Terre, à savoir la présence de milieux aquatiques et de terres émergées, a joué un rôle important au cours de l’évolution de la vie. L’histoire évolutive des vertébrés, par exemple, a continuellement été ponctuée d’épisodes de sorties des eaux et de retours aux milieux aquatiques, souvent soulignés dans le registre fossile par des radiations biologiques majeures. L’exemple le plus célèbre concerne probablement les épisodes de sorties des eaux des premiers tétrapodes qui bouleversent les écosystèmes terrestres il y a environ 360 millions d’années, au moment de la transition Dévonien-Carbonifère. A l’échelle des temps géologiques, ces transitions écologiques ont pu revêtir un caractère soudain ; une instantanéité apparente résultant cependant, bien souvent, de l’incomplétude du registre fossile. Au fur et à mesure que les données paléontologiques s’étoffent ces transitions écologiques nous content des histoires d’une grande complexité, s’inscrivant dans des durées de l’ordre du million, voire de la dizaine de millions d’années ! La compréhension de toutes ces histoires nécessite de connaître avec précision les milieux de vie de leurs principaux acteurs, les espèces éteintes de vertébrés. Traditionnellement, l’étude des environnements de vie des espèces fossiles s’appuie sur les analyses morpho-fonctionnelles et sédimentaires. Cependant, ces deux méthodes permettent seulement de reconstruire un environnement fonctionnel et un environnement de dépôt, qui peuvent être différents de l’environnement de vie. L’objectif principal de cette thèse est de démontrer l’intérêt de l’analyse de la composition isotopique du soufre dans les apatites de vertébrés afin de reconstituer leurs milieux de vie. Nous avons tout d’abord démontré la capacité du système VarioPyrocube©, couplé en flux continu à un spectromètre de masse à ratio isotopique, à analyser avec précision la composition isotopique du soufre dans les apatites biogènes. Nous avons ensuite démontré que l’analyse conjointe des isotopes de l’oxygène et du soufre de l’apatite de nombreuses espèces de vertébrés actuels permettait de tracer leur environnement de vie. Nous avons ensuite appliqué ce nouvel outil isotopique aux assemblages de vertébrés du Dévonien supérieur et mis en évidence l’enregistrement d’une influence marine dans les apatites de ces espèces généralement considérées comme dulçaquicoles. En guise de perspectives, nous avons souligné une première piste diagénétique susceptible de perturber la composition isotopique originelle. Face à ce problème, nous suggérons finalement d’adopter une démarche empirique, consistant à analyser la composition isotopique du soufre de nombreuses apatites fossiles afin d’obtenir une vision exhaustive de son potentiel en tant que marqueur environnemental-
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Cruz, Steffen James. "Single particle structure of exotic strontium isotopes". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61928.
Testo completoAbstract (sommario):
The sudden onset of ground state deformation and the emergence of shape-coexisting states in the vicinity of N~60 and Z~40 has been a subject of substantial interest for many years. It has been shown that the emergence of deformed low-energy configurations can be explained in the shell model by the evolution of single particle structure and the interaction between protons and neutrons in certain valence orbitals. However, the numerous theoretical models that have been developed for this transitional region are limited by the experimental data that is available. In particular, a description of the underlying single particle configurations of low energy states is essential for a detailed description of this region.
In this work, the single particle structure of states in ⁹⁵Sr and ⁹⁶Sr has been investigated through the one-neutron transfer reactions ⁹⁵ ⁹⁶Sr(d,p) in inverse kinematics at TRIUMF. In each of these experiments, a 5.5 MeV/u Sr beam was impinged on a 5.0 mg/cm² CD₂ target, and emitted particles and γ-rays were detected using the SHARC and TIGRESS detector arrays, respectively. Using an angular distribution analysis, firm spin assignments have been made for the first time of the low-lying 352 keV, 556 keV and 681 keV excited states in ⁹⁵Sr from ⁹⁴Sr(d,p), and a constraint has been made on the spin of the higher-lying 1666 keV excited state in ⁹⁵Sr. Similarly, angular distributions have been extracted for 14 states in 96Sr from ⁹⁵Sr(d,p), and new experimental constraints have been assigned to the spins and parities of 8 states in ⁹⁶Sr. Additionally, two new states in ⁹⁶Sr have been identified in this work. A measurement of the mixing strength between the 1229 keV and 1465 keV shape-coexisting states in ⁹⁶Sr was also made, which was found to be a²=0.48(17).Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Lhomme, Nicolas. "Modelling water isotopes in polar ice sheets". Thesis, Université Joseph Fourier (Grenoble), 2004. http://hdl.handle.net/2429/17134.
Testo completoAbstract (sommario):
Concentrations of water isotopes in marine sediments and ice cores are a key indicator for estimating
global and regional fluctuations of past temperatures. Interpreting these concentrations requires an
understanding of the storage capacity and exchanges among the ocean, atmosphere and cryosphere
as well as an understanding of the dynamical behaviour of these reservoirs. The contribution of
the latter remains poorly established because of the paucity of deep ice cores in Greenland and
Antarctica and the difficulty of interpreting these cores.
To obtain the water isotope composition of polar ice sheets and gain an understanding of their
stratigraphy, I develop a tracer transport method first proposed by Clarke and Marshall (2002) and
significantly improve it by introducing an interpolation technique that accounts for the particular
age-depth relationship of ice sheets. I combine the tracers with numerical models of ice dynamics
to predict the fine layering of polar ice masses such that it is locally validated at ice core sites, hence
setting a new method to constrain reconstructions of ice sheets' climatic and dynamic histories.
This framework is first applied and tested with the UBC Ice Sheet Model of Marshall and Clarke
(1997). I predict the three-dimensional time-evolving stratigraphy of the Greenland Ice Sheet and
use the ice core records predicted at GRIP, Dye 3 and Camp Century to better determine the minimal
ice extent during the Eemian, 127 kyr ago, when the Earth's climate was somewhat similar to the
present. I suggest that 3.5-4.5 m of sea level rise could be attributed to melting in Greenland.
Tracers are also applied to Antarctica with the LGGE Ice Sheet Model of Ritz et al. (2001). The
three-dimensional model is compared to simple flow models at the deep ice core sites of Dome C,
Vostok and Dome Fuji to test the hypotheses on depositional and dynamical conditions used for
interpreting ice cores. These studies lead to a well-constrained stratigraphic reconstruction of the
Greenland and Antarctic Ice Sheets and allow me to produce the first-ever self-consistent prediction
of their bulk isotopic composition, hence closing the global water isotope budget of the Earth.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Gallagher, Andrew James. "Modelling barium isotopes in metal-poor stars". Thesis, University of Hertfordshire, 2012. http://hdl.handle.net/2299/9224.
Testo completoAbstract (sommario):
The principal theory concerning the origin of the elements heavier than the Fe-peak, such as Ba, strongly suggest that for old, metal-poor environments, the rapid (r-) process is the most likely path taken in their synthesis, while the slow (s-) process becomes more substantial in younger, more metal-rich stellar populations. In this work I test this theory by evaluating the isotope ratios of Ba. It is understood that Ba consists of seven stable isotopes, five of which are synthesised by the two neutron-capture processes. The two odd isotopes, 135,137Ba, as well as 138Ba are synthesised via both the r- and s-processes while two of the even isotopes, 134,136Ba are synthesised via the s-process only. The relative contribution of the r- and s-process to these isotopes can be understood via nucleosynthesis calculations and is described using the parameter fodd, where fodd = [N (135Ba) + N (137Ba)] /N (Ba). Low values of fodd (~0.11) indicate an s-process regime, while high values of fodd (~0.46) indicate an r-process regime. In the Ba II 4554 A line the even isotopes lie close to the line centre, while the odd isotopes, which are hyperfine split because of their non-zero nuclear spin, lie in the wings of the line. From an analysis of the line profile shape, one can determine whether Ba has been synthesised primarily through the r-process or s-process; a broad, asymmetric line would indicate a high r-process contribution, while a line with a deeper core and shallower wings would indicate a high s-process contribution. Using the radiative transfer code ATLAS, which assumes local thermodynamic equilibrium (LTE) and employs 1-dimensional (1D) KURUCZ06 model atmospheres, I synthesised line profiles for six metal-poor stars: HD140283, HD122563, HD88609, HD84937, BD-04 3208 and BD+26 3578 - for a range of isotope ratios. All six are of sufficiently low metallicity that Ba was expected to have an r-process origin. These were fit to high resolution (R\equiv \lamda/\Delta\lamda = 90 000 - 95 000), high signal-to-noise to the Ba II 4554 A line which has multiple components. In the first test, synthetic spectra were computed using the non local thermodynamic equilibrium (NLTE) radiative transfer code MULTI. The synthetic line profiles were fit to a number of lines in HD140283. Although this technique might have improved the fit in the line core, it was found that such a treatment did not improve upon fitting errors associated with the best fit 1D LTE synthetic profiles. The second test used a 3-dimensional (3D) radiative transfer code (LINFOR3D) that employed 3D, time-dependent atmospheres produced with CO5BOLD. The 3D synthetic pro les were fit to a selection of Fe lines and improvements over the poor fits produced by the 1D LTE synthesis were seen. It was found that the 3D synthesis could almost completely reproduce the line asymmetries seen in the observed stellar spectrum. This result suggests that further work to refine the 3D calculations and synthesis code would be valuable.
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Chapman, John Branson. "Iron isotopes in hydrothermal ore-forming systems". Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582584.
Testo completoAbstract (sommario):
Column chemistry element purification methods were optimised for separation of Cu, Fe and Zn from geological samples taken from hydrothermal ore-forming systems. The method presented produces high-purity elemental separates at -100% recovery, ensuring absence of column-induced isotopic fractionation. Variation of Fe isotope ratios within two different mineral deposit types was investigated. In the West Cumbrian hematite, isotopic variability due to intermineral, redox and biological fractionation is likely absent, allowing identification of fluid flow and mineral precipitation effects. Isotopic ratios span >2.4%, with a trend toward lower values in primary mineralisation close to fluid conduits. This is interpreted to reflect Rayleigh-type distillation during kinetically-controlled hematite precipitation, with ∆56Fefluid-hematite ≈ 0.90%0. Secondary hematite, containing Fe sourced by dissolution of primary mineralisation, showed similar light isotope enrichment. Iron sulfide samples from the Lisheen Zn-Pb deposit, Ireland, were studied to assess the potential of Fe isotope analysis for tracing Fe source and mineralisation influences in a complex massive-sulfide deposit. Here, Fe isotope variation is correlated to paragenetic stage. Preore sulfides retain diagenetic compositions, locally overprinted by red sandstone-derived Fe. Main stage sulfides have a silicate-derived Fe signature, modified by kinetic mineral precipitation, reflecting evolution of the hydrothermal system from shallow to deep flow through time. Laboratory experiments were conducted to better understand the behaviour of Fe isotopes during transfer of Fe from silicate rocks into hydrothermal solutions. Basalt and granite powders were leached with HCI or oxalic acid solutions, with supernatant aliquots retrieved over a 7 day period. Initial aliquots showed significant enrichment of light isotopes, commonly ∆56Ferock-fluid >1.50%0. Fractionation magnitudes decreased over time, to apparent steady-state at ∆56Ferock-fluid ≈ 1.0 - 0.5%0. This study demonstrates the importance of kinetic processes during mineral precipitation, and the potential for future Fe isotope studies for gaining fundamental insight into many aspects of hydrothermal ore genesis.
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Chael, Bradley. "Laser spectroscopy of cerium and yttrium isotopes". Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422322.
Testo completo
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Thayer, Hazel Louise. "Collinear laser spectroscopy of radioactive zirconium isotopes". Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398683.
Testo completo
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Fawcett, M. J. "High sensitivity collinear spectroscopy on strontium isotopes". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233278.
Testo completo
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Miller, Christian Alexander. "Surface-cycling of rhenium and its isotopes". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53548.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2009.Includes bibliographical references.
The application of elemental and isotopic metal palaeoredox tracers to the geologic past rests on an understanding of modern metal cycles. This study reevaluates the surface-cycling of Mo and Re in near-surface reservoirs. Revised river averages of Mo and Re are 1.8- and 7.9-fold larger than previous estimates. The river concentrations of 8.0 nmol Mo kg-1 and 11.2 pmol Re kg- (pre-anthropogenic), result in shorter seawater response times of 4.4 x 105 yr ([Tau]Mo) and 1.3 x 105 yr ([Tau]Re pre-anthropogenic). These metals, especially Re, are more sensitive to changing source and sink fluxes than previously thought. Evaluation of Mo and Re concentrations in high temperature fluids from the Manus Basin indicate that Re is essentially absent from the hydrothermal end member and Mo is present at concentrations considerably lower than ambient seawater. The sink fluxes represented by hydrothermal circulation are negligible in comparison to the revised river source fluxes. Anthropogenic contributions to the Re flux to seawater are seen in the high concentrations of certain impacted water samples such as those associated with mining sites. It may also be seen in a significant, variable, Re enrichment feature in the Hudson River estuary. This Re enrichment feature is not the result of estuarine mixing or the remobilization of sediment-hosted Re. On the basis of a Re - SO2- correlation we are able to quantify and correct for the anthropogenic Re, which corresponds to ~33% of the modern river average. This study documents the development of an analytical method for stable Re isotopes.
(cont.) Though complicated by analyte requirements and 187Re 1870s decay, Re isotope measurements have a reproducibility of ±0.05%o for analyte concentrations of 20 ng Re mL-1. Total Re isotopic variability to date is 0.9%o. This includes 0.3%0 across five commercially available Re products, and 0.5%0 across a black shale weathering profile. 6187Re variability across the weathering profile was systematic with the most weathered samples showing the most significant [delta]187Re depletions. The Re isotopic weathering profile is well described by both two-component mixing and Rayleigh fractionation. There are currently insufficient data to discriminate between the two models.
by Christian Alexander Miller.
Ph.D.
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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.
Testo completoAbstract (sommario):
Calcium (Ca) is the fifth most abundant element in the rocky planets. As a lithophile, refractory element, Ca does not partition into planetary cores nor is it volatilized during planetary accretion. These characteristics make Ca ideal for investigating the earliest stages of planetary formation and the subsequent chemical evolution of planetary mantles and crusts. This thesis presents observations of and explores the mechanisms involved in high-temperature mass-dependent Ca isotope fractionation in terrestrial, lunar, and meteoritic material. Chapter 1 reports Ca isotope fractionation among a co-genetic suite of samples from the Guelb el Azib ultramafic-mafic-anorthosite complex, which represents the fractional crystallization sequence of a terrestrial igneous magma chamber. The measurements imply that Ca isotope fractionation in an evolving crystallizing magma is mineralogically controlled and that the degree of fractionation can vary according to the Ca composition of the residual magma. Chapter 2 investigates ureilites, a distinctive group of achondritic meteorites, widely regarded to be mantle remnants of a disrupted asteroidal parent body. To date, it is not clear which of their features were inherited from the original chondritic body and which were created during post-accretionary igneous processes such as partial melting. This chapter presents evidence that partial melting on the ureilite parent body is responsible for two such ambiguous characteristics, Ca isotopic and magnesium number (MgDoctorat en Sciences
info:eu-repo/semantics/nonPublished
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Nigron, Etienne. "Isotopes radioactifs produits par voies non conventionnelles". Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4032.
Testo completoAbstract (sommario):
La médecine nucléaire utilise des radionucléides pour le diagnostic et pour la thérapie. La tendance suivie par la médecine nucléaire est de s'adapter de plus en plus à chaque patient. Pour arriver à cet objectif, une large gamme de radionucléides doit être disponible pour répondre aux besoins des médecins. Une approche théranostique (thérapie et diagnostic) peut être mise en place dès la conception du médicament permettant d'orienter la médecine vers une médecine personnalisée. Dans cette optique, des études de production de radionucléides innovants par voies non conventionnelles (faisceaux de deutons, matériaux cibles non usuels : cibles enrichies ou produits de fission) ont été menées durant cette thèse. Les voies de réaction ¹⁹⁷ Au(d,2n)¹⁹⁷ᵐHg et ⁷⁰Zn(d,x)⁶⁷Cu ont été identifiées comme intéressantes et des mesures de leur section efficace ont été effectuées. Des paramètres de production permettant de limiter la production de contaminants sont proposés et des courbes de rendement pour ces réactions d'intérêt ont été calculées. Pour effectuer ces mesures de sections efficaces, un nouveau dispositif expérimental a été mis en place permettant la mesure directe du flux de particules. Une étude approfondie sur les conditions optimales de fonctionnement a été effectuée et une incertitude sur la mesure a été définie à 2%. Ce dispositif permet l'obtention de valeurs de sections efficaces avec des incertitudes amoindries comparés à la méthode, communément utilisée, des réactions moniteurs qui possèdent des incertitudes de l'ordre de 10%. Une étude sur la possibilité de valoriser une partie des produits de fission légers du cycle électronucléaire a été explorée. En effet ces produits de fission peuvent être utilisés comme cible pour produire des radionucléides d'intérêt pour la médecine. Des noyaux, pouvant être créés à partir de ces produits de fission, ont été identifiés et leurs voies de production, à partir de la connaissance des sections efficaces, ont été étudiées dans le détail. Les courbes de rendement ont été calculées pour les voies de réaction reconnues comme potentiellement intéressantes/réalisablesNuclear medicine uses radionuclides for diagnosis and therapy. Nowadays, the nuclear medicine tends to adapt more efficiently to each patient. To achieve this goal, a wide range of radionuclides must be available for the physician's requirements. A theranostic approach (therapy and diagnosis) can be implemented from drug's design in order to guide medicine towards a personalised medicine. ln this sense, studies on the production of innovative radionuclides using unconventional pathways (deuteron beams, non-standard target materials: enriched targets or fission products) were conducted during this thesis. Reaction pathways¹⁹⁷ Au(d,2n) ¹⁹⁷ᵐHg and ⁷⁰Zn(d,x)⁶⁷ Cu were identified as relevant and their cross section were measured. The production parameters limiting the production of contaminants were proposed and yields were calculated for the highlighted reactions. For the measurements of these cross sections, a new experimental device has been designed to directly measure the particle flow. An intensive study on the optimal operational conditions was performed by defining an uncertainty of measurements of 2%. This device allows obtaining cross-section values with diminished uncertainties in comparison with the commonly used method of monitor reactions which have uncertainties of the order of 10%. The possibility of recovering light fission products from spent nuclear fuel was also explored. These fission products can be considered as a target to produce radionuclides of medical interest. Some nuclei, which can be created from these fission products, have been identified and their production pathways, based on their cross sections, have been studied in detail. The yield curves were calculated for the reaction paths were recognised as potentially interesting/feasible for this mean
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Varhelyi, Aron. "Quaternary Arctic foraminiferal isotopes: species reliability and palaeoceanographic application". Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-158047.
Testo completoAbstract (sommario):
To investigate whether foraminiferal stable isotope (δ18O/δ13C) variations have potential as a chronostratigraphic tool in the Arctic Ocean, this thesis presents new δ18O/δ13C data from five marine sediment cores. Three of those are downcore analyses (PS92/54-1; TC/PC-03; PC-07) and the remaining two are core top analyses (PC-04; PC-08). Seven species of benthic foraminifera (Cassidulina neoteretis, Cibicides lobatulus, Cibicidoides wuellerstorfi, Oridorsalis tener, Quinqueloculina arctica, Stainforthia concava and Triloculina sp.) and one planktic (Neogloboquadrina pachyderma sinistral) were compared against physical properties data, foraminifera counts and existing age models. The stable isotopic data reveal species-specific niches, resulting from vital effects and habitat preferences. As changes in δ13C mainly are related to palaeoproductivity and ocean/atmosphere gas exchange, and has limited use as a dating tool, the focus has been to create high-resolution downcore δ18O records that can be compared to a global benthic stack. Cibicidoides wuellerstorfi is found to be the most common benthic foraminiferal species in the central Lomonosov Ridge cores (TC/PC-03 and PC-07) whereas C. neoteretis and N. pachyderma are most common at the Yermak Plateau (PS92/54-1). Usefulness of C. wuellerstorfi in the central Lomonosov Ridge cores is limited due to low amplitude changes in δ18O over periods interpreted to cover several Marine Isotope Stages. A similar issue was observed in C. neoteretis δ18O on the Yermak Plateau (PS92/54-1). There, C. neoteretis abundances were low during interglacials. Instead, planktic N. pachyderma δ18O at the Yermak Plateau site (PS92/54-1), more closely than any analysed benthic species, resembled the global benthic δ18O stack. This implies potential of N. pachyderma δ18O as a chronostratigraphic tool in this region of the Arctic. Using N. pachyderma δ18O to correlate distal cores in the Arctic Ocean would demand addressing the issues of regional differences in pelagic δ18O, varying calcification depths and poor preservation. Addressing why the range of variability differs between sites in the same MISs is crucial, before attempting to stack downcore δ18O from the relatively abundant Arctic benthic species C. neoteretis.Med siktet på att undersöka huruvida variationer i stabila isotopvärden (δ18O/δ13C) hos foraminiferer har potential som dateringsredskap i Arktiska Oceanen, presenteras härmed ny δ18O/δ13C data från fem marina sedimentkärnor. Tre kärnor analyseras på längden (PS92/54-1; LOMROG III TC/PC-03 och PC-07) medan två analyser begränsas till kärnornas toppskikt (LOMROG I PC-04 och PC-08). Resultat från sju olika arter av bentoniska foraminiferer (Cassidulina neoteretis, Cibicides lobatulus, Cibicidoides wuellerstorfi, Oridorsalis tener, Quinqueloculina arctica, Stainforthia concava and Triloculina sp.) och en planktonisk (Neogloboquadrina pachyderma sinistral) har jämförts mot data som baserats på kärnornas fysiska egenskaper, mängden foraminiferer och befintliga åldersberäkningar. De nya isotopresultaten avslöjar nischer som är specifika för varje art och som, förutom isotopvärdena i det omkringliggande havsvattnet, är beroende av varierande fraktioneringseffekter samt habitatpreferenser. Förändringar i δ13C är mestadels avhängigt paleoproduktivitet och gasutbyte mellan atmosfär och hav. Det har därför begränsad användning som dateringsredskap. Fokus har istället legat på att skapa högupplöst δ18O data som kan jämföras med en global δ18O ’stack’. Cibicidoides wuellerstorfi är den vanligast förekommande arten i TC/PC-03 och PC-07 medan C. neoteretis och N. pachyderma har flest förekomster i PS92/54-1. I den senare kärnan saknas C. neoteretis under perioder där förändringar i δ18O antas vara stora (interglacialer). Istället är det δ18O hos planktoniska N. pachyderma som i högst grad efterliknar en global bentonisk ’stack’. Dessa resultat antyder att N. pachyderma potentiellt kan användas som lokalt dateringsverktyg. För att kunna korrelera mot mer avlägsna sedimentkärnor i Arktiska Oceanen med hjälp av δ18O från N. pachyderma, så behöver hänsyn tas till regionala skillnader i pelagial δ18O, varierande kalcifieringsdjup och dålig bevaring av foraminifererna. Det är viktigt att adressera varför det finns en amplitudskillnad mellan olika sedimentkärnor för samma tidsperioder, innan försök görs att sammanfoga δ18O resultat från den vanligt förekommande Arktiska bentoniska arten C. neoteretis.
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Brown, Daniel Edward. "Low temperature nuclear orientation studies of nuclei far from stability". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257942.
Testo completo
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Ritz, P. "An appraisal of the doubly labelled water method for energy expenditure measurements". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319821.
Testo completo
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Hannachi, Fazia. "Étude des isotopes de mercure de la région de transition A ~ 186". Paris 11, 1987. http://www.theses.fr/1987PA112475.
Testo completoAbstract (sommario):
Les états de haut spin des noyaux ¹⁸⁵,¹⁸⁷,¹⁸⁸Hg produits dans les réactions ¹⁶¹,¹⁶³,¹⁶⁴Dy (²⁸Si (135-151 MeV, xn) ont été étudiés à l’aide d’un multidétecteur 4π « Château de Cristal » en ligne sur le tandem du C. R. N. Strasbourg. Des mesures de distribution angulaire, de polarisation linéaire des transitions et de coïncidences ont été effectuées. Les schémas de niveaux ainsi établis ont permis de mettre en évidence la coexistence de ¹⁸⁵Hg et ¹⁸⁷Hg de deux formes d’équilibre « oblate » et « prolate » toutes deux stabilisées par le nucléon impair dans la couche sphérique νil3/2 ainsi que les bandes construits sur les états 1/2⁻[521] (fondamental) et 7/2⁻[514] de ¹⁸⁵Hg préalablement observés en radioactivité. Dans ¹⁸⁸Hg, outre le développement à plus haut spin des deux bandes de parité positive précédemment rapportées, quatre nouvelles bandes de parité négative ont été identifiées. L’interprétation de ces résultats a été réalisée à l’aide du modèle de « cranking » décrivant les mouvements de quasi-particules indépendantes dans le champ moyen du noyau déformé en rotation. Les propriétés des structures peu déformées dans ces isotopes sont bien reproduites en considérant l’excitation de neutrons il3/2 tandis qu’il est plus difficile de conclure sur l’origine des particules impliquées dans les structures plus déformées qui coexistent dans ces mêmes noyauxHigh-spin states in ¹⁸⁵⁻¹⁸⁷⁻¹⁸⁸Hg have been investigated via the ¹⁶¹-¹⁶⁴Dy (²⁸Si, xn) reactions by in-beam γ-ray spectroscopic techniques using the “Chateau de Cristal” 4π-multidetector array. Level schemes have been established. Spins and parities of the states have been deduced from transitions multipolarities obtained from measurements of the angular distribution and linear polarization of the γ-rays. The shape coexistence of both prolate and oblate band structures built on states originating from νil3/2 subshell, has been observed for the first time in ¹⁸⁵⁻¹⁸⁷Hg as well as the rotational bands built on the 1/2⁻[521] and 7/2⁻[514] states in ¹⁸⁵Hg. In ¹⁸⁸Hg negative-parity bands are well developed. The various band structures are interpreted within the framework of the cranked shell model. The oblate structures are well reproduced by considering νil3/2 excitations while it is more difficult to conclude about the nature of the particle involved in the prolate ones
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Breitenbach, Jϋrgen Bernhard. "Deformation in the neutron-deficient rare earth isotopes : radioactive decay scheme studies in the neodymium, promethium, and samarium isotopes". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/30070.
Testo completo