Literatura científica selecionada sobre o tema "Isotopes"
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Artigos de revistas sobre o assunto "Isotopes"
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Musich, О., A. Zubko e О. Demyanуuk. "Isotopic effect of macro- and microelements in ecosystems". Balanced nature using, n.º 4 (18 de agosto de 2020): 132–38. http://dx.doi.org/10.33730/2310-4678.4.2020.226644.
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Isotopic effects occurring in living organisms due to metabolism are analyzed. The phenomenon of metabolism is considered in the classical sense as a combination of biochemical reactions (mainly enzymatic) that take place in the cells of living beings and provide the cleavage, synthesis and interconversion of complex compounds. The scope of use of natural isotopes is wide and diverse. Isotopes are carriers of information about the birth and transformation of molecules, and isotope fractionation is a chemical characteristic of a substance. Isotope metabolism consists in the intermolecular fractionation of isotopes at separate stages of biochemical reactions, namely the cleavage, synthesis and interconversion of complex compounds caused by differences in the structure and fundamental properties of isotope nuclei. It is proved that the fractionation of isotopes in chemical and biochemical reactions due to isotopic effects is based on two fundamental properties of atomic nuclei — mass and magnetic moment. The kinetic (mass-depen dent) isotopic effect distributes the isotopic nuclei by their masses, and the magnetic one fractionates the nuclei by their magnetic moments. The kinetic isotopic effect depends on the magnitude of the difference in the masses of isotopic molecules, temperature and the difference in the activation energies of isotopic forms. The magnetic isotope effect depends on the reaction rate in a single cell, its projection, magnetic moment and energy of electron-nuclear interaction. It is determined that the fractionation of isotopes in living organisms is that the relative content of one of the isotopes in this compound increases by reducing its content in the other. As a result, there is a fractionation of isotopes within one biological object.
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Li, Xiangnan, Baisha Weng, Denghua Yan, Tianling Qin, Kun Wang, Wuxia Bi, Zhilei Yu e Batsuren Dorjsuren. "Anthropogenic Effects on Hydrogen and Oxygen Isotopes of River Water in Cities". International Journal of Environmental Research and Public Health 16, n.º 22 (12 de novembro de 2019): 4429. http://dx.doi.org/10.3390/ijerph16224429.
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Stable hydrogen and oxygen isotopes are important indicators for studying water cycles. The isotopes are not only affected by climate, but are also disturbed by human activities. Urban construction has changed the natural attributes and underlying surface characteristics of river basins, thus affecting the isotopic composition of river water. We collected urban river water isotope data from the Global Network for Isotopes in Rivers (GNIR) database and the literature, and collected river water samples from the Naqu basin and Huangshui River basin on the Tibetan Plateau to measure hydrogen and oxygen isotopes. Based on 13 pairs of urban area and non-urban area water samples from these data, the relationship between the isotopic values of river water and the artificial surface area of cities around rivers was analyzed. The results have shown that the hydrogen and oxygen isotope (δD and δ18O) values of river water in urban areas were significantly higher than those in non-urban areas. The isotopic variability of urban and non-urban water was positively correlated with the artificial surface area around the rivers. In addition, based on the analysis of isotope data from 21 rivers, we found that the cumulative effects of cities on hydrogen and oxygen isotopes have led to differences in surface water line equations for cities with different levels of development. The combined effects of climate and human factors were the important reasons for the variation of isotope characteristics in river water in cities. Stable isotopes can not only be used to study the effects of climate on water cycles, but also serve as an important indicator for studying the degree of river development and utilization.
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Pollard, A. M. "Isotopes and impact: a cautionary tale". Antiquity 85, n.º 328 (maio de 2011): 631–38. http://dx.doi.org/10.1017/s0003598x00068034.
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There can be no doubt that isotopic studies have made a huge contribution to archaeology in recent years, so much so that isotope archaeology is now seen as an essential subdiscipline of archaeology in much the same way as isotope geochemistry is a key subdiscipline of geochemistry. Ignoring for current purposes the contribution made by the measurement of a particular radioactive isotope of carbon (14C) since 1950, we can date the beginnings of isotope archaeology to the mid 1960s with the first measurements of lead isotopes in archaeological metals and slags by Brill and Wampler (1965, 1967). This was followed by carbon stable isotopes in human bone collagen in the late 1970s, building on previous work measuring σ13C in archaeological bone for radiocarbon determinations (Vogel & Van der Merwe 1977; Van der Merwe & Vogel 1978). Other isotopes followed rapidly, such as nitrogen, oxygen, sulphur and hydrogen for archaeological, palaeoecological or palaeoclimatological purposes and, more recently, the heavier radiogenic isotopes of strontium and neodymium for determining the provenance of organic and inorganic materials (Pollard & Heron 2008).
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Miljević, Nada, e Dušan Golobočanin. "Potential Use of Environmental Isotopes in Pollutant Migration Studies". Archives of Industrial Hygiene and Toxicology 58, n.º 2 (1 de junho de 2007): 251–62. http://dx.doi.org/10.2478/v10004-007-0015-5.
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Potential Use of Environmental Isotopes in Pollutant Migration StudiesThis article presents the use of natural abundance stable isotope (hydrogen, carbon, nitrogen, oxygen, chlorine) analysis data as a tool for providing important information about the origin of contaminants, the contribution of different sources to a multi-source plume, characterisation of their complex transport (rate and mechanisms) and for evaluating the success of contaminated site remediation. Isotopic signatures of contaminants are useful tracers of their sources, while isotopic fractionation can be used to quantitatively assess the progress of an environmental process such as biodegradation. This new isotopic approach is reliable and can offer more information than traditional techniques in pollutant migration studies, particularly after waste disposal. During biological degradation of any organic compound, molecules containing lighter isotopes are degraded, and the portion of heavier isotopes in the substrate is increased, identifying specific microbial roles in biogeochemical cycling. Since isotopic fractionation is proportional to degradation, depending on the type of contamination, a microbial degradation of 50% to 99% of the initial concentration can be quantified using isotope ratio measurements.
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Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews e F. von Blanckenburg. "A preliminary study of iron isotope fractionation in marine invertebrates (chitons, Mollusca) in near-shore environments". Biogeosciences 11, n.º 19 (8 de outubro de 2014): 5493–502. http://dx.doi.org/10.5194/bg-11-5493-2014.
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Abstract. Chitons (Mollusca) are marine invertebrates that produce radulae (teeth or rasping tongues) containing high concentrations of biomineralized magnetite and other iron-bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radulae might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radulae collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from −1.90 to 0.00 ‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae in the sublittoral zone, has a mean δ56Fe of −0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds on both green and red algae in the eulittoral zone, shows lighter isotopic values with a mean δ56Fe of −1.47 ± 0.98‰ (2σ, 5 specimens). Three possible pathways are proposed to account for the different isotopic signatures: (i) physiologically controlled processes within the chitons that lead to species-dependent fractionation; (ii) diet-controlled variability due to different Fe isotope fractionation in the red and green algal food sources; and (iii) environmentally controlled fractionation that causes variation in the isotopic signatures of bioavailable Fe in the different tidal regions. Our preliminary results suggest that while chitons are not simple recorders of the ambient seawater Fe isotopic signature, Fe isotopes provide valuable information concerning Fe biogeochemical cycling in near-shore environments, and may potentially be used to probe sources of Fe recorded in different organisms.
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Jensen, Alexandria, William Ford, James Fox e Admin Husic. "Improving In-Stream Nutrient Routines in Water Quality Models Using Stable Isotope Tracers: A Review and Synthesis". Transactions of the ASABE 61, n.º 1 (2018): 139–57. http://dx.doi.org/10.13031/trans.12545.
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Abstract. Water quality models serve as an economically feasible alternative to quantify fluxes of nutrient pollution and to simulate effective mitigation strategies; however, their applicability is often questioned due to broad uncertainties in model structure and parameterization, leading to uncertain outputs. We argue that reduction of uncertainty is partially achieved by integrating stable isotope data streams within the water quality model architecture. This article outlines the use of stable isotopes as a response variable within water quality models to improve the model boundary conditions associated with nutrient source provenance, constrain model parameterization, and elucidate shortcomings in the model structure. To assist researchers in future modeling efforts, we provide an overview of stable isotope theory; review isotopic signatures and applications for relevant carbon, nitrogen, and phosphorus pools; identify biotic and abiotic processes that impact isotope transfer between pools; review existing models that have incorporated stable isotope signatures; and highlight recommendations based on synthesis of existing knowledge. Broadly, we find existing applications that use isotopes have high efficacy for reducing water quality model uncertainty. We make recommendations toward the future use of sediment stable isotope signatures, given their integrative capacity and practical analytical process. We also detail a method to incorporate stable isotopes into multi-objective modeling frameworks. Finally, we encourage watershed modelers to work closely with isotope geochemists to ensure proper integration of stable isotopes into in-stream nutrient fate and transport routines in water quality models. Keywords: Isotopes, Nutrients, Uncertainty analysis, Water quality modeling, Watershed.
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Orlowski, N., P. Kraft e L. Breuer. "Exploring water cycle dynamics through sampling multitude stable water isotope pools in a small developed landscape of Germany". Hydrology and Earth System Sciences Discussions 12, n.º 2 (6 de fevereiro de 2015): 1809–53. http://dx.doi.org/10.5194/hessd-12-1809-2015.
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Abstract. Conducting a dual stable water isotope (δ2H and δ18O) study in the developed landscape of the Schwingbach catchment (Germany) helped to unravel connectivity and disconnectivity between the different water cycle components. The two-year weekly to biweekly measurements of precipitation, stream, and groundwater isotopes revealed that surface and groundwater are decoupled from the annual precipitation cycle but showed bidirectional interactions between each other. Seasonal variations based on temperature effects were observed in the precipitation signal but neither reflected in stream nor in groundwater isotopic signatures. Apparently, snowmelt played a fundamental role for groundwater recharge explaining the observed differences to precipitation δ-values. A spatially distributed snapshot sampling of soil water isotopes in two soil depths at 52 sampling points across different land uses (arable land, forest, and grassland) revealed that top soil isotopic signatures were similar to the precipitation input signal. Preferential water flow paths occurred under forested soils explaining the isotopic similarities between top and subsoil isotopic signatures. Due to human-impacted agricultural land use (tilling and compression) of arable and grassland soils, water delivery to the deeper soil layers was reduced, resulting in significant different isotopic signatures. However, the land use influence smoothed out with depth and soil water approached groundwater δ-values. Seasonally tracing stable water isotopes through soil profiles showed that the influence of new percolating soil water decreased with depth as no remarkable seasonality in soil isotopic signatures was obvious at depth > 0.9 m and constant values were observed through space and time. Little variation in individual isotope time series of stream and groundwater restricted the use of classical isotope hydrology techniques e.g. mean transit time estimation or hydrograph separation. Still, tracing stable water isotopes through the water cycle was valuable for determining interactions between different water cycle components and gaining catchment specific process understanding in a developed, human-impacted landscape.
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Emmanuel, S., J. A. Schuessler, J. Vinther, A. Matthews e F. von Blanckenburg. "Iron isotope fractionation in marine invertebrates in near shore environments". Biogeosciences Discussions 11, n.º 4 (11 de abril de 2014): 5533–55. http://dx.doi.org/10.5194/bgd-11-5533-2014.
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Abstract. Chitons (Mollusca) are marine invertebrates that produce radula (teeth or rasping tongue) containing high concentrations of biomineralized magnetite and other iron bearing minerals. As Fe isotope signatures are influenced by redox processes and biological fractionation, Fe isotopes in chiton radula might be expected to provide an effective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a pilot study to measure Fe isotopes in marine invertebrates, we examine Fe isotopes in modern marine chiton radula collected from different locations in the Atlantic and Pacific oceans to assess the range of isotopic values, and to test whether or not the isotopic signatures reflect seawater values. Furthermore, by comparing two species that have very different feeding habits but collected from the same location, we infer a possible link between diet and Fe isotopic signatures. Values of δ56Fe (relative to IRMM-014) in chiton teeth range from −1.90 to 0.00‰ (±0.05‰ (2σ) uncertainty in δ56Fe), probably reflecting a combination of geographical control and biological fractionation processes. Comparison with published local surface seawater Fe isotope data shows a consistent negative offset of chiton teeth Fe isotope compositions relative to seawater. Strikingly, two different species from the same locality in the North Pacific (Puget Sound, Washington, USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red algae, has a mean δ56Fe of −0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia muscosa, which feeds primarily on green algae, shows lighter isotopic values with a mean δ56Fe of −1.47 ± 0.98‰ (2σ, 5 specimens). Although chitons are not simple recorders of the ambient seawater Fe isotopic signature, these preliminary results suggest that Fe isotopes provide information concerning Fe biogeochemical cycling in near shore environments, and might be used to probe sources of Fe in the diets of different organisms.
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Fujii, T., F. Moynier, A. Agranier, E. Ponzevera e M. Abe. "Isotope fractionation of palladium in chemical exchange reaction". Proceedings in Radiochemistry 1, n.º 1 (1 de setembro de 2011): 339–44. http://dx.doi.org/10.1524/rcpr.2011.0060.
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Abstract Palladium isotopes were fractionated by the solvent extraction technique with a crown ether. After purification by ion-exchange chemistry, the isotopic ratios of 105Pd/106Pd, 108Pd/106Pd, and 110Pd/106Pd were determined by multiple-collector inductively coupled plasma mass spectrometry. Isotope fractionations between the two phases were found to be larger than 0.1‰. The isotope fractionation of the odd atomic mass isotope (105Pd) showed a deviation from that estimated from the even atomic mass isotopes (106Pd, 108Pd, and 110Pd). The mass-independent isotope fractionation found was attributable to the nuclear field shift effect. The quantum chemical calculations for the different Pd species supported the validity of the isotope fractionation factors obtained.
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Passey, Benjamin H. "Reconstructing Terrestrial Environments Using Stable Isotopes in Fossil Teeth and Paleosol Carbonates". Paleontological Society Papers 18 (novembro de 2012): 167–94. http://dx.doi.org/10.1017/s1089332600002606.
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Carbon isotopes in Neogene-age fossil teeth and paleosol carbonates are commonly interpreted in the context of past distributions of C3 and C4 vegetation. These two plant types have very different distributions in relation to climate and ecology, and provide a robust basis for reconstructing terrestrial paleoclimates and paleoenvironments during the Neogene. Carbon isotopes in pre-Neogene fossil teeth are usually interpreted in the context of changes in the δ13C value of atmospheric CO2, and variable climate-dependent carbon-isotope discrimination in C3 plants. Carbon isotopes in pre-Neogene soil carbonates can be used to estimate past levels of atmospheric CO2. Oxygen isotopes in fossil teeth and paleosol carbonates primarily are influenced by the oxygen isotopic compositions of ancient rainfall and surface waters. The oxygen isotopic composition of rainfall is has a complex, but tractable, relationship with climate, and variably relates to temperature, elevation, precipitation amount, and other factors. Mammal species that rely on moisture in dietary plant tissues to satisfy their water requirements (rather than surface drinking water) may have oxygen isotopic compositions that track aridity. Thus, oxygen isotopes of fossil mammals can place broad constraints on paleoaridity. Carbonate clumped isotope thermometry allows for reconstruction of soil temperatures at the time of pedogenic carbonate mineralization. The method is unique because it is the only thermodynamically based isotopic paleothermometer that does not require assumptions about the isotopic composition of the fluid in which the archive mineral formed. Soil temperature reflects a complex interplay of air temperature, solar radiative heating, latent heat effects, soil thermal diffusivity, and seasonal variations of these parameters. Because plants and most animals live in and/or near the soil, soil temperature is an important aspect of terrestrial (paleo)climate.
Teses / dissertações sobre o assunto "Isotopes"
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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.
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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.
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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.
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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.
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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.
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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.
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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
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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.
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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.
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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.
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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
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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.
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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.
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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.
Livros sobre o assunto "Isotopes"
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Arnikar, Hari Jeevan. Isotopes in the atomic age. New Delhi: Wiley Eastern, 1989.
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Marschall, Horst, e Gavin Foster, eds. Boron Isotopes. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-64666-4.
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Tom, Edwards, Kull Christoph e Alverson Keith, eds. Stable isotopes. Bern, Switzerland: PAGES International Project Office, 2002.
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M, Andreev B., ed. Separation of isotopes of biogenic elements in two-phase systems. Amsterdam: Elsevier, 2007.
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Symons, E. A. Lithium isotope separation: A review of possible techniques. Mississauga: CFFTP, 1985.
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Faure, Gunter. Principles of isotope geology. 2a ed. New York: Wiley, 1986.
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Spivack, Arthur J. Boron isotope geochemistry. Woods Hole, Mass: Woods Hole Oceanographic Institution, 1986.
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William, Walker F., Parrington Josef R, Feiner Frank e General Electric Company, eds. Nuclides and isotopes. San Jose, Calif: General Electric Co., 1989.
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Firestone, Richard B. Table of isotopes. Editado por Baglin Coral M. 1939-. 8a ed. New York: Wiley, 1998.
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Bowen, Robert. Isotopes and climates. London: Elsevier Applied Science, 1991.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Isotopes"
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Mathur, Ryan, e Yun Zhao. "Copper Isotopes Used in Mineral Exploration". In Isotopes in Economic Geology, Metallogenesis and Exploration, 433–50. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_14.
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AbstractThe use of copper isotopes related to ore deposit location and genesis has greatly expanded over the past twenty years. The isotope values in ores, rocks, soils, and water range greater than 10‰ and provide ample isotopic variation to identify and interpret complex geological process. From an exploration standpoint, the copper isotope values in waters, sulfides and weathered rocks vector to mineralization at depth. Ground and surface waters display the greatest potential for both green and brownfields exploration, whereas Fe-oxides and other related ore minerals isotope compositions for exploration are nascent. From an ore genesis perspective, the copper isotopes serve as a redox proxy to aid in unraveling magmatic and hydrothermal processes related to metal sulfide precipitation. In summary, the use of copper isotopic approaches by the mining industry are ideal as they point to processes directly related to the metal of economic interest and should be employed in all stages of the mine life from exploration to extraction, and to environmental monitoring post-mining activities.
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Werner, Roland A., e Marc-André Cormier. "Isotopes—Terminology, Definitions and Properties". In Stable Isotopes in Tree Rings, 253–89. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_8.
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AbstractThe intention of this chapter is to give insight into the properties and peculiarities of the stable isotopes of the bioelements. Following an overview about the terminology and ʻtechnical jargonʼ used in stable isotope sciences, methods to calculate and express isotopic abundances are presented. Subsequently, a short description of the physicochemical basis of equilibrium and kinetic (mass-dependent) isotope effects (EIEs and KIEs) as origin of isotope fractionation in chemical and biological systems is given. Further, measures for calculation and presentation of isotope fractionation are introduced and the corresponding properties of these quantities are critically discussed. Finally, examples for equilibrium and kinetic isotope fractionation in biochemical reactions are presented in more details and subsequent effects and consequences including the relationship between EIEs and KIEs are reviewed.
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Pfahler, V., J. Adu-Gyamfi, D. O’Connell e F. Tamburini. "The Use of the δ18OP to Study P Cycling in the Environment". In Oxygen Isotopes of Inorganic Phosphate in Environmental Samples, 1–15. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-97497-8_1.
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AbstractPhosphorus (P) fertilizers are known to increase crop productivity; however, when applied in excess, it can cause serious environment pollution. Monitoring P pollution in natural environments using stable isotopes has been difficult because P has only one stable isotope (31P) making the use of P stable isotope tracing not an option. Radioactive P isotopes (32P and 33P) have been used but its drawbacks are the short half-life, health risks and safety procedures required to apply them in agricultural catchments. Phosphorus in organic and inorganic P forms is strongly bonded to oxygen (O), which has three stable isotopes, providing a system to track P cycling in agricultural catchments and environment using the stable isotopes of O in phosphate (δ18O-PO4). In recent years, various studies have indicated that the analysis of the stable isotopic composition of oxygen (O) bound to P (δ18Op) to better understand P cycling in the environment, has become a promising tracer (surrogate) to investigate soil P transformation, plant P uptake and to trace the sources of P from the soil to water bodies and the environment. The chapter outlines the background and examples of δ18Op studies in sediments, soils, fresh water, mineral fertilizers and plants.
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Huston, David L., Ian Lambert e Jens Gutzmer. "Isotopes in Economic Geology, Metallogeny and Exploration—An Introduction". In Isotopes in Economic Geology, Metallogenesis and Exploration, 1–13. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_1.
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AbstractAlthough (Soddy, Nature 92:399–400, 1913) inferred the existence of isotopes early last century, it was not until the discovery of the neutron by (Chadwick, Nature 129:312, 1932) that isotopes were understood to result from differing numbers of neutrons in atomic nuclei. (Urey, J Chem Soc 1947:562–581, 1947) predicted that different isotopes would behave slightly differently in chemical (and physical) reactions due to mass differences, leading to the concept of isotopic fractionation. The discovery that some elements transformed into other elements by radioactive decay happened even before the recognition of isotopes (Rutherford and Soddy, Lond Edinb Dublin Philos Mag 4:370–396, 1902), although the role that different isotopes played in this process was discovered later. The twin, and related, concepts of isotopes and radioactive decay have been used by geoscience and other scientific disciplines as tools to understand geochemical processes such as mineralization, and also the age and duration of these processes. This book is a review of how isotope geoscience has developed to better understand the processes of ore formation and metallogenesis, and thereby improve mineral system models used in exploration.
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Wilkinson, Jamie J. "The Potential of Zn Isotopes in the Science and Exploration of Ore Deposits". In Isotopes in Economic Geology, Metallogenesis and Exploration, 451–63. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_15.
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AbstractSince the turn of the Century, the growth in development and application of zinc isotopes to multiple fields in terrestrial and planetary sciences has been exponential. The potential for the application of zinc isotope systematics to ore deposit formation processes was obvious from the outset, given that they represent the most significant concentrations of zinc on Earth and because this approach allowed, for the first time, direct assessment of zinc metal origins and transport. This contribution presents a brief summary of the notation and analytical procedures for analysis of zinc isotopes and summarizes the terrestrial data reported to date. These results show that the variation in zinc isotope composition in rocks and ore systems is in fact rather small (< 2 ‰), linked, at least in part, to the single oxidation state in which zinc occurs in nature. Based on an assessment of the literature, the principal mechanisms for causing isotopic fractionation are all relatively low temperature processes: (i) biogenic; (ii) supergene dissolution-reprecipitation; (iii) adsorption–desorption reactions; and (iv) hydrothermal precipitation. High temperature igneous processes do not appear to produce significant isotopic variations. In ore deposit studies, it currently appears unlikely that zinc isotopes can be used to constrain potential metal sources, apart from zinc derived from carbonate host rocks which tends to be isotopically heavy. However, there are a number of systems in which systematic variation in δ66Zn of sulfides suggests that Rayleigh-type fractionation during ore mineral precipitation occurs, opening up the possibility of using zinc isotopes to trace flow paths and vector in towards mineralized centers. Modeling of such hydrothermal processes is currently hindered by a paucity of experimentally-determined fractionation factors, but as such work is done, our ability to better understand and utilize zinc isotopic zonation patterns for the purposes of mineral exploration will be progressively enhanced.
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Kagawa, Akira, e Giovanna Battipaglia. "Post-photosynthetic Carbon, Oxygen and Hydrogen Isotope Signal Transfer to Tree Rings—How Timing of Cell Formations and Turnover of Stored Carbohydrates Affect Intra-annual Isotope Variations". In Stable Isotopes in Tree Rings, 429–62. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_15.
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AbstractIn this chapter, we discuss post-photosynthetic processes that affect intra-annual variation in the stable isotopes of tree rings, such as timing of cell formations and turnover of stored carbohydrates, by combining research findings gained by using either natural-abundance or artificially-enriched carbon, oxygenand hydrogen isotopes. We focus on within-ring variation in stable isotope ratios, with an emphasis on aligning observed ratios in whole wood or extracted cellulose to seasonal dynamics in climate and phenology. We also present a discussion of isotopic fractionation that operates within the scope of observed variations across individual rings. We then introduce a model that traces the seasonal partitioning of photosynthate into tree rings via storage pool, which is based on experimental data gained from labeling studies using artificially enriched 13CO2 gas. Finally, we will describe our current understanding of post-photosynthetic signal transfer processes of oxygenand hydrogen isotopes from leaves to tree rings, such as exchange of oxygen and hydrogen between storage carbohydrates and local cambial water, and possible causes of difference in oxygen and hydrogen isotope fractionations. Finally, we discuss mechanisms behind how oxygen and hydrogen from foliar-absorbed liquid water is then incorporated into wood biomass, by introducing results gained from recent H218O and HDO pulse-labeling experiments.
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Kagawa, Akira, e Giovanna Battipaglia. "Post-photosynthetic Carbon, Oxygen and Hydrogen Isotope Signal Transfer to Tree Rings—How Timing of Cell Formations and Turnover of Stored Carbohydrates Affect Intra-annual Isotope Variations". In Stable Isotopes in Tree Rings, 429–62. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_15.
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AbstractIn this chapter, we discuss post-photosynthetic processes that affect intra-annual variation in the stable isotopes of tree rings, such as timing of cell formations and turnover of stored carbohydrates, by combining research findings gained by using either natural-abundance or artificially-enriched carbon, oxygenand hydrogen isotopes. We focus on within-ring variation in stable isotope ratios, with an emphasis on aligning observed ratios in whole wood or extracted cellulose to seasonal dynamics in climate and phenology. We also present a discussion of isotopic fractionation that operates within the scope of observed variations across individual rings. We then introduce a model that traces the seasonal partitioning of photosynthate into tree rings via storage pool, which is based on experimental data gained from labeling studies using artificially enriched 13CO2 gas. Finally, we will describe our current understanding of post-photosynthetic signal transfer processes of oxygenand hydrogen isotopes from leaves to tree rings, such as exchange of oxygen and hydrogen between storage carbohydrates and local cambial water, and possible causes of difference in oxygen and hydrogen isotope fractionations. Finally, we discuss mechanisms behind how oxygen and hydrogen from foliar-absorbed liquid water is then incorporated into wood biomass, by introducing results gained from recent H218O and HDO pulse-labeling experiments.
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Andreu-Hayles, Laia, Mathieu Lévesque, Rossella Guerrieri, Rolf T. W. Siegwolf e Christian Körner. "Limits and Strengths of Tree-Ring Stable Isotopes". In Stable Isotopes in Tree Rings, 399–428. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_14.
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AbstractThis chapter aims at summarizing strengths and caveats on the suitability of stable carbon and oxygen isotopes in tree rings as recorders for fingerprints of environmental influences. First, environmental constraints limiting tree growth and shaping tree species distribution worldwide are discussed. Second, examples are presented for environmental conditions under which tree-ring isotopes record environmental signals particularly well, but also cases where physiological processes can mask climate signals. Third, the link between leaf-level carbon assimilation and the investment of assimilates in the stem during the annual ring formation are discussed in light of the resulting deviations of the isotopic values between leaves and tree rings. Finally, difficulties and pitfalls in the interpretation of stable isotope signals in tree rings are reviewed. These problems often result from a poor understanding of when and how the tree canopy, stems and roots are physiologically interconnected. Current literature suggests that photosynthesis and radial growth are only loosely coupled, if at all, challenging the interpretation of environmental signals recorded in tree-ring isotopes. Harsh environmental conditions (e.g. low temperatures, drought) often result in a decoupling of carbon assimilation and growth. The chapter closes by providing possible solutions on how to improve the detection of environmental information from stable isotope signals by integrating scales and different methodological approaches.
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Huston, David L., Robert B. Trumbull, Georges Beaudoin e Trevor Ireland. "Light Stable Isotopes (H, B, C, O and S) in Ore Studies—Methods, Theory, Applications and Uncertainties". In Isotopes in Economic Geology, Metallogenesis and Exploration, 209–44. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-27897-6_8.
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AbstractVariations in the abundances of light stable isotopes, particularly those of hydrogen, boron, carbon, oxygen and sulfur, were essential in developing mineralization models. The data provide constraints on sources of hydrothermal fluids, carbon, boron and sulfur, track interaction of these fluids with the rocks at both the deposit and district scales, and establish processes of ore deposition. In providing such constraints, isotopic data have been integral in developing genetic models for porphyry-epithermal, volcanic-hosted massive sulfide, orogenic gold, sediment-hosted base metal and banded-iron formation-hosted iron ore systems, as discussed here and in other chapters in this book. After providing conventions, definitions and standards used to present stable isotope data, this chapter summarizes analytical methods, both bulk and in situ, discusses processes that fractionate stable isotopes, documents the isotopic characteristics of major fluid and rock reservoirs, and then shows how stable isotope data have been used to better understand ore-forming processes and to provide vectors to ore. Analytical procedures, initially developed in the 1940s for carbon–oxygen analysis of bulk samples of carbonate minerals, have developed so that, for most stable isotopic systems, spots as small as a few tens of μm are routinely analyzed. This precision provides the paragenetic and spatial resolution necessary to answer previously unresolvable genetic questions (and create new questions). Stable isotope fractionation reflects geological and geochemical processes important in ore formation, including: (1) phase changes such as boiling, (2) water–rock interaction, (3) cooling, (4) fluid mixing, (5) devolatilization, and (6) redox reactions, including SO2 disproportionation caused by the cooling of magmatic-hydrothermal fluids and photolytic dissociation in the atmosphere. These processes commonly produce gradients in isotopic data, both in time and in space. These gradients, commonly mappable in space, provide not only evidence of process but also exploration vectors. Stable isotope data can be used to estimate the conditions of alteration or mineralization when data for coexisting minerals are available. These estimates use experimentally- or theoretically-determined fractionation equations to estimate temperatures of mineral formation. If the temperature is known from isotopic or other data (e.g., fluid inclusion data or chemical geothermometers), the isotopic composition of the hydrothermal fluid components can be estimated. If fluid inclusion homogenization and compositional data exist, the pressure and depth of mineralization can be estimated. One of the most common uses of stable isotope data has been to determine, or more correctly delimit, fluid and sulfur sources. Estimates of the isotopic compositions of hydrothermal fluids, in most cases, do not define unequivocal sources, but, rather, eliminate sources. As an example, the field of magmatic fluids largely overlap that of metamorphic fluids in δ18O-δD space, but are significantly different to the fields of meteoric waters and seawater. As such, a meteoric or seawater origin for a fluid source may be resolvable, but a magmatic source cannot be resolved from a metamorphic source. Similarly, although δ34S ~ 0‰ is consistent with a magmatic-hydrothermal sulfur source, the signature can also be produced by leaching of an igneous source. Recent analytical and conceptual advances have enabled gathering of new types of isotopic data and application of these data to resolve new problems in mineral deposit genesis and geosciences in general. Recent developments such as rapid isotopic analysis of geological materials or clumped isotopes will continue to increase the utility of stable isotope data in mineral deposit genesis and metallogeny, and, importantly, for mineral exploration.
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Helle, Gerhard, Maren Pauly, Ingo Heinrich, Karina Schollän, Daniel Balanzategui e Lucas Schürheck. "Stable Isotope Signatures of Wood, its Constituents and Methods of Cellulose Extraction". In Stable Isotopes in Tree Rings, 135–90. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_5.
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AbstractIn this chapter, we give some basic information on the chemical and isotopic properties of wood constituents and describe their relative contribution to the isotopic signature of wood. Based on these considerations we review studies that have compared stable isotope signals of wood with those of corresponding cellulose. We exemplify how relationships of wood-based tree-ring stable isotope sequences with climate can be affected by varying proportions of wood constituents like cellulose, lignin and extractives. A majority of benchmarking studies suggests that cellulose extraction may not be necessary. However, based upon existing research, a general statement cannot be made on the necessity of cellulose extraction. Changes in wood composition can particularly influence environmental signal strength during periods of low isotope variability. Cellulose extraction removes any effects from changing wood composition. We present the three established chemical approaches of extraction, outline how to test the purity of isolated cellulose and present user-friendly efficient experimental setups allowing to simultaneously process hundreds of samples in one batch. Further, we briefly address the analysis of stable isotopes of lignin methoxyl groups because of easy sample preparation and its potential additional value for studies on fossil wood.
Trabalhos de conferências sobre o assunto "Isotopes"
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Bunsen, James, Harsh Desai, Jacob Matthews e Patrick Snouffer. "Radioisotope Power System Isotopes Review". In Nuclear and Emerging Technologies for Space (NETS 2024), 489–94. Illinois: American Nuclear Society, 2024. http://dx.doi.org/10.13182/nets24-43989.
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Travis, J. C., T. B. Lucatorto, J. Wen, J. D. Fassett e C. W. Clark. "Doppler-Free Resonance Ionization Mass Spectrometry of Beryllium". In Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/laca.1987.tub2.
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As originally conceived, resonance ionization mass spectrometry (RIMS) combined the elemental selectivity of resonance ionization (1) with the isotopic selectivity of mass spectrometry to improve the accuracy and sensitivity of conventional mass spectrometry (2). For many applications, especially quantitation by isotope dilution (3) , it is important that no isotopic selectivity accompany the resonance ionization process. This condition is easily met for all but a few elements of the periodic table (4), since the great majority of optical isotope shifts are small with respect to typical dye laser bandwidths and Doppler-broadened linewidths in common atom reservoirs. However, another class of problem exists for which it is desirable to achieve isotopically selective resonance ionization. These applications involve the detection of extremely, rare stable or radioactive isotopes in the presence of the major isotopic species of an element. Miller et al. (5) have explored the optical isotopic selectivity of the isotopes of Lu using a RIMS spectrometer equipped with a high-resolution (single-mode) continuous-wave (cw) laser. Cannon et al. (6) have measured an optical selectivity (defined below) of 800 for isotopes of Ba, using a RIMS spectrometer with two cw lasers. We have proposed the use of pulsed, two-photon, Doppler-free resonance ionization to extend the capability of conventional mass spectrometers to measure isotope ratios in excess of 1012 (7). Initial experimental results using this approach, for the isotopes 9Be and 10Be, are reported here.
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Wunderlich, R. K., G. J. Wasserburg, I. D. Hutcheon e G. A. Black. "Laser-induced mass selectivity in resonance ionization mass spectrometry of Os". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.wp1.
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Measurements of isotope ratios by resonance ionization mass spectrometry depend critically on knowledge of isotopic-specific effects in the laser excitation-ionization process. Reports of odd-even isotope selectivity in RIMS studies of Mo, Sn,1 and Ti have led us to investigate isotope shifts in a RIMS study of Os. We identify three sources of laser-induced mass selectivity: (i) wavelength and bandwidth effects, (ii) selection rule and polarization effects, and (iii) dynamic effects.2 (i) In the presence of optical isotope shifts and hyperfine structure the finite laser bandwidth and reproducibility of wavelength setting produce isotope shifts as a result of the incomplete overlap of the laser spectrum with the absorption maxima of the Os isotopes and their HFS components.
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Koksalan, T., K. A. Khan, R. S. Alwaeel, N. M. Aljneibi e M. N. A. Alblooshi. "Innovative Isotopes Tracking: A Cost-Effective Approach for Monitoring of Injected CO2 Flood Advancement in Oil Reservoirs". In ADIPEC. SPE, 2024. http://dx.doi.org/10.2118/222173-ms.
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Abstract Assessing sweep efficiency and recognizing the point of breakthrough are critical for evaluating an Enhanced Oil Recovery (EOR) effort employing miscible CO2 Gas injection. This study aimed to employ CO2 carbon isotope composition and molar concentration to monitor sweep efficiency and breakthrough in production wells of an ADNOC Onshore field to optimize the project, such as adjusting injector and future production well placements. The integration of CO2 molar concentration data along with carbon and oxygen isotope readings, helped to assess the influence of CO2 Injection EOR. The project relied on the premise that using a distinct isotopic signature for injected CO2-deriving from a steel mill and notably lighter in comparison to CO2 associated with the oil-would aid in determining sweep efficiency and breakthrough levels. CO2 is injected through specific horizontal injectors in the north area of the field. Initial values of oil-associated CO2 carbon and oxygen isotope served as a benchmark to evaluate the progress of sweep efficiency and breakthrough. Frequently, compositions and isotopic values of injected CO2 are recorded. Subsequent periodic analyses of these components’ composition and isotopes in oil and water producing wells indicate the degree of breakthrough. Findings from CO2 molar and isotope measurements in both injector and producer wells demonstrate that injected CO2 tends to breakthrough preferentially in certain regions, signifying a varied reservoir quality across the field with superior reservoir quality, and CO2 injection distribution experiencing faster breakthrough. These compositional and isotopic metrics have proven sensitive enough to detect changes in producer wells. It is intriguing to note that the CO2 δ13C isotope signals a breakthrough sooner than the CO2 molar concentration. Data also indicates that CO2 WAG is a much more efficient EOR process compared with continues CO2 injection.
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Pyrayev, A. N., e A. A. Maksimova. "ISOTOPIC COMPOSITION OF GROUNDWATER IN OIL AND GAS DEPOSITS IN THE CENTRAL PART OF THE TRANS-URAL MEGAMONOCLISE". In All-Russian Youth Scientific Conference with the Participation of Foreign Scientists Trofimuk Readings - 2021. Novosibirsk State University, 2021. http://dx.doi.org/10.25205/978-5-4437-1251-2-117-120.
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The article presents the first results of complex isotope-hydrogeochemical studies of reservoir waters of the Upper Jurassic deposits of the central regions of the Zaural megamonoclysis. It was shown that most waters have a narrow distribution of oxygen and hy-drogen isotopes (δD from 103,2 to –85,6 % and δ18O from –15,4 to –12,9 %). Some of them have pronounced excursions on the isotopic composition, which indicates a difference in their genesis: from condensate to mixed with ancient infiltrogenic. The isotopic composition of car-bon of water-dissolved carbon dioxide (δ13СDIC from –41,6 to –16,3 %) indicates its biogenic origin and the possibility of interstratal flows from overlying horizons.
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Miller, C. M., R. Engleman e R. A. Keller. "Resonance ionization mass spectrometry for high-resolution mass-resolved spectra of rare isotopes". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.tha2.
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Previous isotope ratio measurements using resonance ionization mass spectrometry (RIMS) have used element selective photoionization with isotope ratios measured by dispersion of ions in a mass spectrometer. To increase the accuracy and dynamic range of isotope ratio measurements, it may be necessary to use isotopically selective ionization. To be successful in this task it is necessary to know isotope shifts and hyperfine structures of the optical transition(s) used for the isotopes of interest. We are particularly interested in rare and sometimes highly radioactive elements for which this information is not readily available. We demonstrate that the sensitivity and mass selectivity of the RIMS technique itself can be used to obtain the needed spectra. With this goal in mind, RIMS was used to acquire high-resolution optical spectra of rare isotopes. To demonstrate the potential of this technique, hyperfine spectra of the 2 D 3 / 2 0 ← 2 D 3 / 2 lutetium transition at 22,125 cm–1 are presented for 176Lu, 175Lu, 174Lu, and 173Lu. The latter two are rare isotopes with half-lives of 3.3 and 1.4 yr whose optical spectroscopy has not previously been explored. Sensitivity is documented by the fact that the total amount of these rare isotopes in our sample was 2 × 10–10 g and 3 × 10–11 g. Analysis of the spectra confirms that the spin of 174Lu is unity and yields values for the hyperfine constants and isotope shifts of these nuclei.
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Liepa, Sindija, Dace Butenaite, Jovita Pilecka-Ulcugaceva, Kristaps Siltumens e Inga Grinfelde. "FORMATION OF N2O ISOTOPES IN AGRICULTURAL SOILS". In 23rd SGEM International Multidisciplinary Scientific GeoConference 2023. STEF92 Technology, 2023. http://dx.doi.org/10.5593/sgem2023/4.1/s19.36.
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Agricultural activity accounts for two-thirds of the total anthropogenic nitrogen oxide (N2O) emissions worldwide. Most of the N2O emissions from agricultural soils come from the use of inorganic fertilizers and/or manure. As agricultural activity intensifies worldwide, N2O emissions are currently increasing by 0.25% per year. In order to investigate the feedback of soil N2O emissions with changes in environmental conditions, an improved understanding based on the wider use of isotopic tracer methods is needed. The aim of this study is to find out the formation of N2O in agricultural soils, as well as to find out other significant influencing factors that influence the formation of isotopes. To perform the experiment in laboratory conditions, 16 mixed soil samples from different experimental plots were collected. The fields have different types of management, there are both conventional and organic fields. For each experimental plot, two soil samples were created with different moisture regimes, one container with normal moisture regime and the other with over moistened conditions, such soil regimes were chosen to create both moist aerobic and moist anaerobic conditions. Soil samples were also measured for ph. N2O isotope measurements were performed using a Picarro G5131-i instrument. Measurement data were collected, processed and further analyzed. The formation of N2O isotopes in the soil is influenced by several factors, both soil moisture and physical properties of the soil, soil ph. level and microbiological activity in the soil.
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Lu, Feng Hu. "Using Isotope Technology to Identify Oil and Gas Reservoir Sweet Spots". In SPE Reservoir Characterisation and Simulation Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212642-ms.
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Abstract Porosity and permeability of rocks are crucial parameters utilized to assess the quality of oil and gas reservoirs. Diagenesis in carbonate reservoirs commonly results in dissolution, and creates secondary porosity and permeability. At the same time, geochemical records (e.g., isotopes and elements) in the carbonate rocks are diagenetically altered. This study is to utilize the isotope technology to evaluate diagenesis and its impact on oil and gas reservoirs. Micro-samples were collected from marine carbonate rocks in a studied reservoir for carbon and oxygen isotope analyses, plus analyses of Sr isotopes and element concentrations. The analytical results show outstanding negative shifts of oxygen isotopes in some intervals, whereas carbon and strontium isotopes have a minor or little change. These intervals also contain lower element contents including strontium. It is believed that these intervals experienced diagenetic dissolution with abundant secondary porosity, and are the best potential for oil and gas reservoirs. Petrographic study indicates minor cements but higher porosity developed within these intervals. This is confirmed by high porosity measured within these intervals by using other methods including gas injection and well logging. Furthermore, the degrees of water-rock interaction were quantitively assessed by modeling covariations of isotope pairs, which can help evaluate the quality of reservoirs relating to the intensity of diagenesis. Intensive diagenesis with a high water-rock ratio particularly in a closed system may result in additional cementation, alteration of most geochemical parameters, and also reduce porosity and permeability. Thus, the isotope technology can be utilized as an effective method to assess reservoir potential and determine reservoir sweet spots. Note that carbonate cementation and recrystallization commonly occur during diagenesis, and commonly show negative oxygen isotope values. If sampling happens to contain a certain amount of cements and recrystallized carbonate minerals, the analytical results will show lower oxygen isotopes and trace elements than their primary values in the studied marine carbonates. Petrographic study was conducted to help micro-sampling, and verify that cements were not collected in the studied carbonate rocks for isotope analysis. The implementation of this study is that the isotope results obtained from one studied well can be applied in the whole field or/and the region, as diagenesis rarely occurs only around one well. This will save cost for repeatedly measurements from different wells and fields by using other methods.
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Eerkens, Jeff W., Jay F. Kunze e Leonard J. Bond. "Laser Isotope Enrichment for Medical and Industrial Applications". In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89767.
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Use of lasers for isotope separation has been considered for many decades. None of the proposed methods have attained sufficient proof of principal status to be economically attractive to pursue commercially. Some of the authors have succeeded in separating sulfur isotopes using a rather new and different method, known as condensation repression. In this scheme, a gas of the selected isotopes for enrichment is irradiated with a laser at a particular wavelength that would excite only one of the isotopes. The entire gas is subjected to low temperatures sufficient to cause condensation on a cold surface or coagulation in the gas. Those molecules in the gas that the laser excited are not as likely to condense or dimerize (coagulate into a double molecule, called a dimer) as unexcited molecules. Hence in cold-wall condensation, gas drawn out of the system is enriched in the isotope that was laser-excited. We have evaluated the relative energy required in this process if applied on a commercial scale. We estimate the energy required for laser isotope enrichment is about 30% of that required in centrifuge separations, and 2% of that required by use of “calutrons”.
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Jia Yi, Xu, Ma Xu Bo, Shen Jing Wen, Liu Jia Yi e Chen Yi Xue. "A New Method to Evaluate the Correlation Coefficients Between Nuclides in Uncertainty and Sensitivity Analysis". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-66777.
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Uncertainty and sensitivity analysis is an essential component of nuclear engineering calculations. Uncertainties in the cross-section input data directly affect uncertainties in the results. The covariance values between different types of cross-sections are considered in the NJOY covariance library. However, the correlation coefficient between isotopes can depend on the specific problem. The correlation coefficient between 235U and 238U in a pressurized water reactor (PWR) might be different from that in a fast reactor. In this study, a new Monte Carlo-based method is proposed for calculating this effect. The correlation coefficients between different isotopes are calculated using a problem-dependent fraction parameter. The correlation coefficients between the capture cross-sections of 235U, 238U, 239Pu, and 241Pu are calculated. The same method can be extended to other reaction types. The correlation coefficients as a function of the isotopic atomic density uncertainty and the average one-group microscopic cross-section uncertainty are also studied. It is shown that the correlation coefficients vary very little with the uncertainty in the average one-group microscopic cross-section. The correlation coefficient of an isotope pair changes slightly over the course of a cycle because of atomic density and microscopic cross-section changes.
Relatórios de organizações sobre o assunto "Isotopes"
1
Fitzsimmons, Jonathan. Fishing for isotopes in the Brookhaven Lab Isotope Producer (BLIP) cooling water. Office of Scientific and Technical Information (OSTI), abril de 2016. http://dx.doi.org/10.2172/1340357.
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Nielsen, D. L. Transportation of medical isotopes. Office of Scientific and Technical Information (OSTI), novembro de 1997. http://dx.doi.org/10.2172/362356.
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Author, Not Given. Isotopes: Products and services. Office of Scientific and Technical Information (OSTI), março de 1989. http://dx.doi.org/10.2172/5992318.
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McIntyre, Justin I., Ted W. Bowyer, James C. Hayes, Tom R. Heimbigner, Scott J. Morris, Mark E. Panisko, W. K. Pitts, Sharon L. Pratt, Paul L. Reeder e Charles W. Thomas. Generation of Radixenon Isotopes. Office of Scientific and Technical Information (OSTI), junho de 2003. http://dx.doi.org/10.2172/15020775.
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Jacques, I. J., A. J. Anderson e S. G. Nielsen. The geochemistry of thallium and its isotopes in rare-element pegmatites. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328983.
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The Tl isotopic and trace element composition of K-feldspar, mica, pollucite and pyrite from 13 niobium-yttrium-fluorine (NYF)-type and 14 lithium-cesium-tantalum (LCT)-type rare-element pegmatites was investigated. In general, the epsilon-205Tl values for K-feldspar in NYF- and LCT-type pegmatites increases with increasing magmatic fractionation. Both NYF and LCT pegmatites display a wide range in epsilon-205Tl (-4.25 to 9.41), which complicates attempts to characterize source reservoirs. We suggest 205Tl-enrichment during pegmatite crystallization occurs as Tl partitions between the residual melt and a coexisting aqueous fluid or flux-rich silicate liquid. Preferential association of 205Tl with Cl in the immiscible aqueous fluid may influence the isotopic character of the growing pegmatite minerals. Subsolidus alteration of K-feldspar by aqueous fluids, as indicated by the redistribution of Cs in K-feldspar, resulted in epsilon-205Tl values below the crustal average (-2.0 epsilon-205Tl). Such low epsilon-205Tl values in K-feldspar is attributed to preferential removal and transport of 205Tl by Cl-bearing fluids during dissolution and reprecipitation. The combination of thallium isotope and trace element data may be used to examine late-stage processes related to rare-element mineralization in some pegmatites. High epsilon-205Tl and Ga in late-stage muscovite appears to be a favorable indicator of rare-element enrichment LCT pegmatites and may be a useful exploration vector.
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Brown, D., e J. Pruet. Updated Evaluations for Americium Isotopes. Office of Scientific and Technical Information (OSTI), setembro de 2005. http://dx.doi.org/10.2172/887268.
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Stehney, A. F., e H. F. Lucas. Thorium isotopes in human tissues. Office of Scientific and Technical Information (OSTI), dezembro de 1991. http://dx.doi.org/10.2172/10173422.
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Hayes, John. An Introduction to Isotopic Calculations. Woods Hole Oceanographic Insitution, setembro de 2004. http://dx.doi.org/10.1575/1912/27058.
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Berman, R. G., B. E. Taylor, W. J. Davis, M. Sanborn-Barrie e J B Whalen. Crustal architecture and evolution of the central Thelon tectonic zone, Nunavut: insights from Sm-Nd and O isotope analysis, U-Pb zircon geochronology, and targeted bedrock mapping. Natural Resources Canada/CMSS/Information Management, 2024. http://dx.doi.org/10.4095/332497.
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New isotopic analyses (Sm-Nd, O, and U-Pb), targeted geological mapping, and previously published whole-rock geochemical data and high-resolution aeromagnetic surveys define ten crustal domains across the central Thelon tectonic zone. In the eastern Slave Craton, granitoid rocks in the Overby Lake domain are more isotopically evolved than in the Tinney Hills domain and include tonalite dated at 2.71 Ga. The 400 km long main leucogranite belt separates most early (ca. 2.07-1.95 Ga) Thelon tectonic zone plutonic belts from the Queen Maud Block. Oxygen isotopes support its formation via melting of a sedimentary source during peak metamorphism, which coincides with three, new 1.925-1.91 Ga leucogranite ages. Modelling of Nd-Sm isotopes indicates Neoarchean crust as basement to early Thelon tectonic zone plutonic belts. Detrital zircon geochronology suggests a 2.5 Ga basement component that is not recognized in exposed crustal domains, but is compatible with the Dharwar Craton, which can be paleomagnetically reconstructed adjacent to the Slave Craton at 2.2 Ga. Two tectonic models are discussed for the evolution of the Thelon tectonic zone in the convergent margin tectonic setting indicated by the whole-rock geochemistry and mantle-like oxygen isotopic compositions of plutonic rocks. In one model, ca. 2.1 Ga extension precedes east-dipping subduction, which leads to 1.97 Ga collision of the Slave Craton with a composite Thelon tectonic zone basement-Rae Craton, upper plate. The second model proposes a ca. 2.05 Ga Slave-microcontinent (Thelon tectonic zone basement) collision, followed by a polarity flip with west-dipping subduction, leading to ca. 1.95 Ga collision of the Rae Craton.
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Pruet, J., D. McNabb e W. Ormand. Cross Section Evaluations for Arsenic Isotopes. Office of Scientific and Technical Information (OSTI), março de 2005. http://dx.doi.org/10.2172/15015183.
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