abstract: Isotope ratios of some trace metals have proven useful for tracking Earth’s ocean oxygenation history. As the limitations of some of these isotope systems are realized, it becomes increasingly important to develop new and complementary systems. This dissertation examines the utility of molybdenum (98Mo) and thallium (205Tl) isotope compositions preserved in ancient marine shales to track past ocean oxygenation. My approach is as follows: (1) as an initial exercise, apply the well-established Mo isotope system to a set of ancient shales; (2) validate the use of the newly developed Tl isotope system; and finally (3) examine the potential of applying Mo and Tl isotopes in tandem. Increasingly heavier 98Mo are found in shales deposited during the Neoarchean (2,800 to 2,500 million years ago, or Ma), which would be a predicted consequence of progressive ocean oxygenation across this timeframe. Increasingly heavier 205Tl across a well-documented Mesozoic Oceanic Anoxic Event (~94 Ma), on the other hand, would be a predicted consequence of progressive ocean de-oxygenation. An anti-correlation in the first combined application of Mo and Tl isotopes in ancient shales provides a strong fingerprint for previously unrecognized levels of ocean oxygenation at ~2,500 Ma. Lastly, neither 98Mo or 205Tl behave as predicted in shales deposited during three Ediacaran Ocean Oxygenation Events (~635 Ma, ~580 Ma, and ~560 Ma). These unexpected trends are due, at least in part, to local-scale overprints that must be taken into consideration when pairing together Mo and Tl isotopes in shales. The ability of the Mo and Tl isotope systems to track changes in past ocean oxygenation is confirmed in this dissertation. Both isotope systems have the potential to track these changes independently, but their combined utility is particularly powerful. Under ideal conditions, their combined application can provide an even more robust fingerprint for changes in past ocean oxygenation. Even under non-ideal conditions, their combined application makes it possible to decipher local-scale overprints from signals of past ocean oxygenation. It is therefore ideal, whenever possible, to measure both 98Mo and 205Tl in the same shale samples to assess past changes in ocean oxygenation. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2020

Orientador: Nilva Kazue Sakomura / Resumo: 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

The Térapa fossil vertebrate site, northcentral Sonora, Mexico, provides a rare opportunity to study the paleoenvironmental conditions present in northwestern Mexico during mid-Oxygen Isotope Stage (OIS) 3. Ostracode faunal assemblages and stable oxygen (δ18O) and stable carbon (δ13C) isotope values from ostracode calcite were used to reconstruct the seasonality of precipitation and vegetation cover at Térapa at 40-43 ka. The ostracode fauna was a non-analogue mix of temperate and tropical ostracode species composed of 13 species from 12 genera. The nearctic ostracodes Fabaeformiscandona caudata, Physocypria pustulosa, Cypridopsis vidua and the cosmopolitan ostracode Darwinula stevensoni dominate the assemblage. Two tropical ostracode genera, Chlamydotheca arcuata and Stenocypris sp., were present throughout the deposit and indicate that mean monthly summer temperatures were probably no more than 4°C to 6°C cooler than at present, based on available ecological information. Winter precipitation dominated the hydrologic cycle as evidenced by low ostracode δ18O values (-6‰ to -8‰ VPDB). Low ostracode δ13C values (-7‰ to -8‰ VPDB) suggest that local vegetation was dominated by C3 plants. A previous tooth enamel-based paleoenvironmental reconstruction at the same site favored a summer-dominated or evaporative hydrology and abundant C4 vegetation. The Térapa megafauna site exemplifies the need for multi-indicator paleoclimate reconstructions in desert environments where marked differences in the seasonality of precipitation and vegetation cover may occur.

We report here a sample of 5 cheek teeth of a primitive hipparion from the early late Miocene Ethiopian locality of Chorora. This sample represents the oldest hipparion known from Ethiopia, and probably East and South Africa. The sample exhibits a number of distinctly primitive characters that suggest its provisional referral to "Cormohipparion" sp. The Chorora hipparion has none of the more advanced features typical of the latest Miocene-Pleistocene African hipparionine lineage Eurygnathohippus, maintaining a low crown height, lack of ectostylids and pli caballinids. The Chorora hipparion does exhibit a mesowear signal, suggesting that it was a mixed-feeder. The carbon isotope signal also suggests that it was a mixed-feeder that included both browse and C4 grass in its diet.

No description available.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, School of Physics. Johannesburg, 2017. / Accelerator Mass Spectrometry (AMS) is an ultra-sensitive isotopic analysis technique that allows for the determination of isotopic ratios of rare long-lived radionuclides such as radiocarbon. AMS has become an important tool in many scientific disciplines, due to its sensitivity of detecting isotopic ratios at the level of 10-15 by making use of nuclear physics techniques and methods. The objective of the present work was to design and implement a new AMS system at iThemba LABS, the first of its kind on the African continent. The system is described in detail along with the relevant ion optics simulations using TRACE-3D. Beam optics calculations were performed for carbon isotopes, using the TRACE-3D code, in order to optimize the design of the new spectrometer and assess its overall performance. The AMS technique was applied in two unique South African research projects in relation to archaeology and environmental air pollution studies. The AMS technique, combined with the Proton-Induced X-Ray Emission (PIXE) technique, was also applied in an environmental study with respect to the contribution of contemporary and fossil carbon in air pollution in the Lephalale District, close to both the newly built Medupi coal-fired power station (~5 GW, the largest ever build in South Africa), and the existing Matimba coal-fired power station. The discrimination of contemporary carbon and fossil carbon is accomplished by using the AMS technique in measurements of the 14C/C ratios of aerosol particulate matter. The absence of 14C in fossil carbon material and the known 14C/C ratio levels in contemporary carbon material allows us to distinguish between contemporary carbon and fossil carbon and decipher in this manner different anthropogenic contributions. iv The contemporary carbon throughout our sampling campaign in the Lephalale District has been measured to be approximately 53% of carbon aerosol. As many studies have been performed of contemporary carbon and fossil carbon, no other contemporary and fossil carbon source assessment method provides the definitive results that can be obtained from radiocarbon measurements. PIXE analysis for the determination of the elemental composition of particulate matter in samples near the Medupi coal-fired power station in the Lephalale District was also performed for 6 elements, namely, K, Ca, Ti, Mn, Fe, and Zn. In the samples that were analyzed the particulate matter concentrations did not exceed the air quality standards regulation at Lephalale. The recommended daily limit air quality standard by South African legislation is 75 µg/m3. Enrichment Factor (EF) analysis of soil with respect to Fe shows anomalously high values for Zn. AMS was also applied to archaeological studies of early herding camps of the khoe khoe people at Kasteelberg, situated on the southwest coast in South Africa, and are among the best preserved sites of their kind in the world. Sea-shell samples from the Kasteelberg B (KBB) site have been dated with AMS at Lawrence Livermore National Laboratory (LLNL) in an effort to elucidate the relationship between the herder-foragers of the inland and shoreline sites in terms of migration patterns. The radiocarbon dates obtained are in general agreement with the other studies that have been performed on the site, and show that the ages of artifacts are less than 2000 years. The samples for this study originate from various well defined stratigraphic-levels at square A3 at KBB. It was evident from excavation that the artefacts seem to be of the same period and there is no evidence of mixing from different stratigraphic layers. v Radiocarbon dates were calibrated using Calib 6.1 and each was corrected for marine reservoir effect. The date range between the earliest and most recent dates that were obtained span gap is approximately 400 years from AD 825 to AD 1209. The majority of the radiocarbon dates of the KBB site belong to dates of 1002-1100 AD, the other few belong to 825-958 AD, and the last single date of 1209 AD. The new AMS dates from this work suggest the high probability that indeed there was a hiatus between the two occupations designated as lower and the upper KBB. The significant changes seen in material culture styles as well as in the nature of occupation and change in accumulation rate of deposits therefore do not necessarily indicate a cultural replacement caused by the arrival of a new population. This implies that the occupants of lower KBB may also have been Khoe-speakers, and not local San. / GR2018

Three different methods were developed to evaluate nutritional status: stable isotopes, near infra-red reflectance spectroscopy (NIRS), and microbial populations. In the first method, hair samples were collected, analyzed, stable isotope content greatly differed (P < 0.01) between pre- and post-weaning samples. The second method used NIRS spectral patterns and analyzed fecal samples, and a difference was found around 2100 to 2250 nm where diets containing milk showed a peak, and non-milk diets showed a plateau. Finally, the third method involved profiling microbial populations from fecal samples as calves experienced dietary shifts. Total anaerobes, enterics, and clostridium were different (P<0.05) from pre to post-weaning states. Total anaerobe samples differed (P < 0.005) from milk, milk-grain diets to grain and grain-hay diets. Total aerobes, streptococci, and clostridium samples differed (P <0.001) from the milk diet to the other diets. In summary, all three methods showed differences when comparing pre- to post-weaning states.

Mg/Ca and d18O derived from marine biogenic carbonates have been widely used as reliable paleoenvironmental proxy for seawater temperature, salinity and water mass circulation reconstructions. The use of Mg/Ca is based on long residence time in seawater and uniform distribution with habitat depth of planktonic foraminifera. Fluid Mg/Ca affects mineralogy of CaCO3, thus high seawater Mg/Ca favors precipitation of aragonite instead of calcite. The records of d18O in carbonates yield strong correlation with seawater temperature, salinity and d18O. Distribution of d18O in water is highly heterogeneous within longitude, latitude and depth. Therefore a combination of foraminieral d18O and Mg/Ca could resolve temperature, d118Owater, and hence salinity, which is linked to variability in fresh water balance and glacial ice volume throughout geologic history. In this work we study the effects of important seawater/fluid parameters on Mg/Ca in inorganic and d18O in natural samples and provide data for improving paleoceanographic reconstructions.

No description available.

<p> The large double focusing mass spectrometer operating at its theoretical resolving power of more than 100,000 at the base of the peaks has been used to measure five mass spectral doublets. The resulting single and double neutron separation energies for some cadmium nuclides are much more precise than those from previous work. It is noted that striking regularities occur amongst these energies. </p> / Thesis / Master of Science (MSc)