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Brown, Shaun T., Anirban Basu, Xin Ding, John N. Christensen i Donald J. DePaolo. "Uranium isotope fractionation by abiotic reductive precipitation". Proceedings of the National Academy of Sciences 115, nr 35 (16.08.2018): 8688–93. http://dx.doi.org/10.1073/pnas.1805234115.
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Significant uranium (U) isotope fractionation has been observed during abiotic reduction of aqueous U, counter to the expectation that uranium isotopes are only fractionated by bioassociated enzymatic reduction. In our experiments, aqueous U is removed from solution by reductive precipitation onto the surfaces of synthetic iron monosulfide. The magnitude of uranium isotopic fractionation increases with decreasing aqueous U removal rate and with increasing amounts of neutrally charged aqueous Ca–U–CO3 species. Our discovery means that abiotic U isotope fractionation likely occurs in any reducing environment with aqueous Ca ≥ 1 mM, and that the magnitude of isotopic fractionation changes in response to changes in aqueous major ion concentrations that affect U speciation. Our results have implications for the study of anoxia in the ancient oceans and other environments.
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Han, Guilin, Anton Eisenhauer, Jie Zeng i Man Liu. "Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions". Forests 12, nr 6 (25.05.2021): 666. http://dx.doi.org/10.3390/f12060666.
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In order to better constrain calcium cycling in natural soil and in soil used for agriculture, we present the δ44/40Ca values measured in rainwater, groundwater, plants, soil, and bedrock samples from a representative karst forest in SW China. The δ44/40Ca values are found to differ by ≈3.0‰ in the karst forest ecosystem. The Ca isotope compositions and Ca contents of groundwater, rainwater, and bedrock suggest that the Ca of groundwater primarily originates from rainwater and bedrock. The δ44/40Ca values of plants are lower than that of soils, indicating the preferential uptake of light Ca isotopes by plants. The distribution of δ44/40Ca values in the soil profiles (increasing with soil depth) suggests that the recycling of crop-litter abundant with lighter Ca isotope has potential effects on soil Ca isotope composition. The soil Mg/Ca content ratio probably reflects the preferential plant uptake of Ca over Mg and the difference in soil maturity. Light Ca isotopes are more abundant in mature soils than nutrient-depleted soils. The relative abundance in the light Ca isotope (40Ca) is in the following order: farmland > burnt grassland > forests > grassland > shrubland. Our results further indicate that biological fractionation in a soil–plant system is a vital factor for Ca–geochemical transformations in soil surface systems.
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Antonelli, Michael A., Tushar Mittal, Anders McCarthy, Barbara Tripoli, James M. Watkins i Donald J. DePaolo. "Ca isotopes record rapid crystal growth in volcanic and subvolcanic systems". Proceedings of the National Academy of Sciences 116, nr 41 (23.09.2019): 20315–21. http://dx.doi.org/10.1073/pnas.1908921116.
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Kinetic calcium isotope effects can be used as growth-rate proxies for volcanic and subvolcanic minerals. Here, we analyze Ca isotopic compositions in experimental and natural samples and confirm that large kinetic effects (>2‰) can occur during magmatic plagioclase crystallization. Experiments confirm theoretical predictions that disequilibrium isotope effects depend mainly on the rates for crystal growth relative to liquid phase Ca diffusivity (R/D). Plagioclase phenocrysts from the 1915 Mount Lassen rhyodacite eruption, the ∼650-y-old Deadman Creek Dome eruption, and several mafic subvolcanic orbicules and plagioclase comb layers from Northern California have disequilibrium Ca isotopic compositions that suggest rapid crystal growth rates (>1 cm/y to 15 cm/y). The Ca isotope results, combined with complementary crystal-size distribution analyses, suggest that magmatic rejuvenation (and eruption) events, as reflected in crystal growth times, can be as short as ∼10−3 y. Although mafic systems are predicted to have shorter magmatic rejuvenation periods, we find similarly short timescales in both mafic and silicic systems. These results are consistent with a growing body of evidence suggesting that dominantly crystalline volcanic magma reservoirs can be rapidly reactivated by the injection of fresh magma prior to eruption. By focusing on a common mineral such as plagioclase, this approach can be applied across all major magmatic compositions, suggesting that Ca isotopes can be used as a tool for investigating the dynamics and timing of volcanic eruptions.
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Merrett, Deborah C., Christina Cheung, Christopher Meiklejohn i Michael P. Richards. "Stable isotope analysis of human bone from Ganj Dareh, Iran, ca. 10,100 calBP". PLOS ONE 16, nr 3 (2.03.2021): e0247569. http://dx.doi.org/10.1371/journal.pone.0247569.
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We report here on stable carbon, nitrogen, and sulfur isotope values from bone collagen of human (n = 20) and faunal (n = 11) remains from the Early Neolithic site of Ganj Dareh, Iran, dating to ca. 10,100 cal. BP. Our focus explores how isotope values of human bone vary by age and sex, and evaluates dietary practices at this site. It also provides a baseline for future studies of subsistence in the early Holocene Central Zagros Mountains, from the site with the first evidence for human ovicaprid management in the Near East. Human remains include individuals of all age groups for dietary reconstruction, as well two Ottoman intrusive burials for temporal and cultural comparison. All analyzed individuals exhibited δ13C and δ15N values consistent with a diet based heavily on C3 terrestrial sources. There is no statistically significant difference between the isotopic compositions of the two sexes, though males appear to show larger variations compared to females. Interesting patterns in the isotopic compositions of the subadults suggested weaning children may be fed with supplements with distinctive δ13C values. Significant difference in sulfur isotope values between humans and fauna could be the earliest evidence of transhumance and could identify one older adult male as a possible transhumant shepherd. Both Ottoman individuals had distinctively different δ13C, δ15N, and δ34S values compared to the Neolithic individuals. This is the first large scale analysis of human stable isotopes from the eastern end of the early Holocene Fertile Crescent. It provides a baseline for future intersite exploration of stable isotopes and insight into the lifeways, health, and processes of neolithisation associated with the origins of goat domestication at Ganj Dareh and the surrounding Central Zagros.
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Adloff, Markus, Andy Ridgwell, Fanny M. Monteiro, Ian J. Parkinson, Alexander J. Dickson, Philip A. E. Pogge von Strandmann, Matthew S. Fantle i Sarah E. Greene. "Inclusion of a suite of weathering tracers in the cGENIE Earth system model – muffin release v.0.9.23". Geoscientific Model Development 14, nr 7 (5.07.2021): 4187–223. http://dx.doi.org/10.5194/gmd-14-4187-2021.
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Abstract. The metals strontium (Sr), lithium (Li), osmium (Os) and calcium (Ca), together with their isotopes, are important tracers of weathering and volcanism – primary processes which shape the long-term cycling of carbon and other biogeochemically important elements at the Earth's surface. Traditionally, because of their long residence times in the ocean, isotopic shifts in these four elements observed in the geologic record are almost exclusively interpreted with the aid of isotope-mixing, tracer-specific box models. However, such models may lack a mechanistic description of the links between the cycling of the four metals to other geochemically relevant elements, particularly carbon, or climate. Here we develop and evaluate an implementation of Sr, Li, Os and Ca isotope cycling in the Earth system model cGENIE. The model offers the possibility to study the dynamics of these metal systems alongside other more standard biogeochemical cycles, as well as their relationship with changing climate. We provide examples of how to apply this new model capability to investigate Sr, Li, Os and Ca isotope dynamics and responses to environmental change, for which we take the example of massive carbon release to the atmosphere.
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Martin, Jeremy E., Derek Vance i Vincent Balter. "Magnesium stable isotope ecology using mammal tooth enamel". Proceedings of the National Academy of Sciences 112, nr 2 (22.12.2014): 430–35. http://dx.doi.org/10.1073/pnas.1417792112.
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Geochemical inferences on ancient diet using bone and enamel apatite rely mainly on carbon isotope ratios (δ13C) and to a lesser extent on strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) elemental ratios. Recent developments in nontraditional stable isotopes provide an unprecedented opportunity to use additional paleodietary proxies to disentangle complex diets such as omnivory. Of particular relevance for paleodietary reconstruction are metals present in large quantity in bone and enamel apatite, providing that biologically mediated fractionation processes are constrained. Calcium isotope ratios (δ44Ca) meet these criteria but exhibit complex ecological patterning. Stable magnesium isotope ratios (δ26Mg) also meet these criteria but a comprehensive understanding of its variability awaits new isotopic data. Here, 11 extant mammal species of known ecology from a single locality in equatorial Africa were sampled for tooth enamel and, together with vegetation and feces, analyzed for δ26Mg, δ13C, Sr/Ca, and Ba/Ca ratios. The results demonstrate that δ26Mg incorporated in tooth enamel becomes heavier from strict herbivores to omnivores/faunivores. Using data from experimentally raised sheep, we suggest that this26Mg enrichment up the trophic chain is due to a26Mg enrichment in muscle relative to bone. Notably, it is possible to distinguish omnivores from herbivores, using δ26Mg coupled to Ba/Ca ratios. The potential effects of metabolic and dietary changes on the enamel δ26Mg composition remain to be explored but, in the future, multiproxy approaches would permit a substantial refinement of dietary behaviors or enable accurate trophic reconstruction despite specimen-limited sampling, as is often the case for fossil assemblages.
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Mirosław-Grabowska, Joanna. "Isotope record of environmental changes at the Skaliska Basin during the Late Glacial and Holocene". Acta Palaeobotanica 53, nr 1 (1.06.2013): 105–14. http://dx.doi.org/10.2478/acpa-2013-0008.
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ABSTRACT The results of isotopic investigations of the Skaliska Basin sediments are presented. Stable isotope analyses were done for authigenic carbonates from three profiles: W1 - Piotrowo-Ławniki, W2 - Sąkieły Małe, and W4 - Budzewo. The profiles contain carbonate silts at the bottom, then calcareous detritus gyttja and organic silts and peat at the top. Palynological data indicate that sediment were accumulated in the Skaliska Basin from the final phase of the Younger Dryas to the Subboreal period. The values δ18O change from ca −9.4 to −4.5‰, and δ13C values varies from −5.1 to +0.1‰. Such a large range of isotopic data reflects changing conditions in the basin during accumulation of deposits (different water levels, water temperatures, and bioproduction). Based on the results of stable isotope analyses of the carbonates, isotopic zones (Is) were defined and characterized for each profile. The results of isotopic analysis enabled reconstruction of varying environmental conditions connected with lake deepening and/or influx of water enriched in light isotopes, climatic warming, and increase of biological activity. The Late Glacial deposits are characterized by δ18O values of ca −6.5-6‰ and δ13C of ca −1‰. In the transitional time between the Late Glacial and the Holocene, δ18O systematically falls below −8‰, reflecting a substantial change in the isotopic composition of the lake water, likely caused by to inflow of melt water. During the Preboreal period the δ18O as well as the δ13C values systematically decrease and reach minima (−8.4-9.4‰ for δ18O and ca −3.5-4.7‰ for δ13C). At the beginning of the Boreal period, an increase of ca 2‰ in δ18O is noted and is associated with climatic warming. During the Atlantic period the varying trends in the δ18O record are likely connected with changing precipitation/evaporation ratios, causing changes in the isotope composition of the water. The fluctuations of the isotopic values in the upper parts of the successions probably point to shallowing of the lake due to sedimentary infill.
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Li, Chaofeng, Huiqian Wu, Xuance Wang, Zhuyin Chu, Youlian Li i Jinghui Guo. "Determination of Lead Elemental Concentration and Isotopic Ratios in Coal Ash and Coal Fly Ash Reference Materials Using Isotope Dilution Thermal Ionization Mass Spectrometry". International Journal of Environmental Research and Public Health 16, nr 23 (28.11.2019): 4772. http://dx.doi.org/10.3390/ijerph16234772.
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The rapid expansion of coal-fired power plants around the world has produced a huge volume of toxic elements associated with combustion residues such as coal fly ash (CFA) and coal ash (CA), which pose great threats to the global environment. It is therefore crucial for environmental science to monitor the migration and emission pathway of toxic elements such as CFA and CA. Lead isotopes have proved to be powerful tracers capable of dealing with this issue. Unfortunately, up to now, few high precision lead isotope data of CFA and CA certified reference materials (CRMs) determined by using the double spike technique have been reported. Hence, to facilitate the application of lead isotopes in environmental science, it is indispensable and urgent to determine a suite of high precision Pb isotope ratios and Pb elemental contents for CFA and CA CRMs. Here, we measured lead isotope ratios from four CFA and CA CRMs using thermal ionization mass spectrometry (TIMS) combined with the 204Pb–207Pb double spike method. Lead isotope ratios values of CRMs (GBW11124, GBW08401, GBW11125d, and JCFA-1) covered wide variation ranges from 17.993 to 19.228 for 206Pb/204Pb, from 15.513 to 15.675 for 207Pb/204Pb, and from 38.184 to 39.067 for 208Pb/204Pb. Lead isotope ratios of these CRMs, except for GBW11124, show good external reproducibility (2 RSD, n = 8), which is better than 0.05% for 206Pb/204Pb and 207Pb/204Pb, 0.07% for 208Pb/204Pb, 0.04% for 206Pb/207Pb, and 0.05% for 208Pb/206Pb. The Pb concentrations of these CRMs were determined using 207Pb single spike method. The reproducibility (1 RSD, n = 4) of Pb elemental content was <0.60%. This indicates the distribution of Pb elements in these CRMs is homogeneous. With the exception of GBW11124, the suite of CRMs can be used for determining CFA and CA matrix composition for quality control of Pb isotope analyses.
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Heydarizad, Mojtaba, i Rogert Sorí. "Application of Statistical Techniques to Study Stable Isotopes (18O and 2H) Characteristics of Precipitation in Iran (Southwest Asia)". Environmental Sciences Proceedings 8, nr 1 (1.06.2021): 5. http://dx.doi.org/10.3390/ecas2021-10298.
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Various climatic and geographic parameters influence precipitation in Iran, which makes the interpretation of stable isotope signatures in precipitation very complicated. Thus, precipitation sampling stations for stable isotope analyses in Iran have been classified by cluster analysis (CA) into 10 clusters, based on their stable isotope characteristics. The classification of stations by CA also has a close correlation with the Koppen climatic zones across Iran. Finally, the stations in each cluster were plotted on the GMWL and EMMWL. This study shows that classifying precipitation sampling stations can simplify the interpretation of stable isotopes in the precipitation of regions with complicated climatic systems.
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Griffin, Ian J., i Steven A. Abrams. "Methodological considerations in measuring human calcium absorption: relevance to study the effects of inulin-type fructans". British Journal of Nutrition 93, S1 (kwiecień 2005): S105—S110. http://dx.doi.org/10.1079/bjn20041344.
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During the last 50 years, a variety of methods have been developed to estimate Ca absorption in man. Mass balances were initially used, but these were unable to accurately measure fractional Ca absorption because they cannot distinguish unabsorbed dietary Ca from endogenous faecal Ca excretion (excretion of previously absorbed Ca back into the gut). A number of isotopic methods have been developed that can measure true fractional Ca absorption, employing radioisotopes, stable isotopes, or both. Different methods involve collection of urine, faecal or plasma samples. Of the currently available methods, the dual isotope tracer method with a timed urine collection is probably the most precise and reliable. It is also relatively straightforward to carry out and avoids the need for a faecal collection. The purpose of the present paper is to discuss the general advantages and disadvantages of the different methods of Ca absorption. In addition, the limitations the different methods have in examining the possible effects of non-digestible oligosaccharides on Ca absorption will be discussed.
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Gordon, Gwyneth W., Jorge Monge, Melanie B. Channon, Qing Wu, Joseph L. Skulan, Ariel D. Anbar i Rafael Fonseca. "Calcium Isotopic Composition and Its Association With Multiple Myeloma Disease Activity". Blood 122, nr 21 (15.11.2013): 3157. http://dx.doi.org/10.1182/blood.v122.21.3157.3157.
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Abstract Multiple myeloma (MM) is characterized by clonal proliferation of a neoplastic plasma cell and its production of a monoclonal immunoglobulin; evolving from an asymptomatic pre-malignant stage named monoclonal gammopathy of undetermined significance (MGUS). At the time of diagnosis with MM, lytic lesions are present in approximately 70-80% of patients. Lytic lesions increase the risk for skeletal related events as well as treatment costs, while lowering quality of life and overall survival. Metastatic bone surveys underestimate bone disease since plain radiographs demonstrate abnormalities until at least 30% of trabecular bone has been lost and cannot provide information about ongoing bone remodeling. Bone scintigraphy lacks usefulness in following bone disease due to decreased osteoblast activity in MM, while Dual-energy X-ray absorptiometry scans produce heterogeneous local bone mineral density changes and are not recommended to evaluate bone disease in these patients. Biomarkers (eg, N- and C-terminal telopeptides of type I collagen) have been used to assess bone metabolism balance (BMB; ie, the difference between bone formation and resorption) in MM prior and subsequent to specific therapies, however, consensus is still lacking and their clinical utility is uncertain. Calcium in nature consists of six isotopes, and the relative abundance of the isotopes varies measurably. The strength of molecular bonds depends on atomic weight of the participating atoms. Calcium (Ca) containing compounds react at different rates depending on atomic mass. Bone formation favors lighter isotopes of Ca, depleting soft tissue of light Ca isotopes, while bone resorption releases this isotopically light Ca back into soft tissue with little or no selectivity. As a result of this difference in isotope fractionation, Ca isotopic composition in soft tissue should shift to heavier Ca isotope values in positive BMB and lighter values in negative BMB. In order to identify whether Ca isotopic composition can be used as a marker of myeloma-induced bone disease, we first set out to determine its association with MM disease activity. Using multiple collector inductively coupled plasma mass spectrometry, we determined the Ca isotopic composition in 108 peripheral blood samples from 54 patients with monoclonal gammopathies. Ca isotopic composition was determined as the ratio between the naturally occurring 44Ca and 42Ca isotopes (δ44/42Ca) relative to a standard in parts per ten thousand units, as previously described by Morgan et al. Disease activity was determined at the time of δ44/42Ca determination by assessing disease status and response to treatment, as described by the International Myeloma Working Group uniform response criteria, defining progressive or relapsed disease as active disease, and stable or responsive disease as non-active. Categorical variables were analyzed using chi squared or Fisher’s exact test, interval variables were analyzed using a one-tailed t-test. A repeated measures logistic regression model was developed using a cross-sectional time-series generalized estimating equation. All statistical analysis was done using Stata/SE 12.0. Fifty-four adult patients (61% male) diagnosed with monoclonal gammopathy, ranging from MGUS (n=1) to SMM (n=4) to MM (n=49), were assessed at different time points, with 7 patients being assessed once, 41 were assessed twice, 5 were assessed 3 times, while 1 patient was assessed 4 times. Mean age at the time of first assessment was 66, ranging from 45 to 84. Mean δ44/42Ca was statistically lower in the active disease group as compared to the non-active group (-0.7536 vs -0.6564, p=0.0466). In a statistically significant repeated measurement logistic regression model (p= 0.0239), δ44/42Ca is associated with active disease (OR=0. 054, p=0.031, 95% CI=0.004-0.765) after adjusting for age, gender, presence of anemia, serum creatinine, free light chain ratio, current bisphosphonate and current anti-myeloma therapy. A lower δ44/42Ca in the active disease group might suggest a link between a more intense level of bone resorption and myeloma activity. Ca isotopic composition can become part of the clinician’s arsenal to determine disease status in a patient with MM. In order to further characterize δ44/42Ca to specifically infer myeloma-induced bone disease activity, further studies that include serum biomarkers and dynamic imaging should be performed. Disclosures: Gordon: Arizona State University: “Application of Ca isotope analysis to the early detection of metastatic cancer” (AzTE reference number M13-117) Patents & Royalties; Arizona State University: “Isotopic biomarkers for rapid assessment of bone mineral balance in biomedical applications” (US Application #PCT/US2011/039780; AzTE reference number M10-102L), “Isotopic biomarkers for rapid assessment of bone mineral balance in biomedical applications” (US Application #PCT/US2011/039780; AzTE reference number M10-102L) Patents & Royalties. Skulan:AZTE: “Application of Ca isotope analysis to the early detection of metastatic cancer” (AzTE reference number M13-117) Patents & Royalties; AZTE: “Isotopic biomarkers for rapid assessment of bone mineral balance in biomedical applications” (US Application #PCT/US2011/039780; AzTE reference number M10-102L), “Isotopic biomarkers for rapid assessment of bone mineral balance in biomedical applications” (US Application #PCT/US2011/039780; AzTE reference number M10-102L) Patents & Royalties. Anbar:Arizona State University: “Isotopic biomarkers for rapid assessment of bone mineral balance in biomedical applications” (US Application #PCT/US2011/039780; AzTE reference number M10-102L), “Isotopic biomarkers for rapid assessment of bone mineral balance in biomedical applications” (US Application #PCT/US2011/039780; AzTE reference number M10-102L) Patents & Royalties; Arizona State University: “Application of Ca isotope analysis to the early detection of metastatic cancer” (AzTE reference number M13-117) Patents & Royalties. Fonseca:AMGEN: Consultancy; Millennium: Consultancy; Binding Site: Consultancy; Onyx: Consultancy, Research Funding; Lilly: Consultancy; BMS: Consultancy; Genzyme: Consultancy; Celgene: Consultancy; Medtronic: Consultancy; Otsuka: Consultancy; Cylene: Research Funding; Prognostication of MM based on genetic categorization of the disease: Patents & Royalties.
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Gaigalas, Algirdas, i Stanislaw Halas. "Stable Isotopes (H, C, S) and the Origin of Baltic Amber". Geochronometria 33, nr -1 (1.01.2009): 33–36. http://dx.doi.org/10.2478/v10003-009-0001-9.
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Stable Isotopes (H, C, S) and the Origin of Baltic Amber New results of isotope analysis of light elements (H, C and S) of a dozen Baltic amber samples are described and discussed. Carbon isotope composition was nearly constant (ca. -23‰), whereas sulphur and hydrogen varied in their isotope compositions from +4 to -28‰ and from -171 to -213‰, respectively. The formation and subsequent evolution of this material since its origin in Paleogene time until present is outlined.
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Pessôa, G. S., i M. A. Z. Arruda. "Incorporation of67Zn and68Zn into carbonic anhydrase: effects on isotope enrichment and enzymatic aspects". Journal of Analytical Atomic Spectrometry 32, nr 8 (2017): 1473–80. http://dx.doi.org/10.1039/c7ja00061h.
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Fantle, M. S. "Evaluating the Ca isotope proxy". American Journal of Science 310, nr 3 (1.03.2010): 194–230. http://dx.doi.org/10.2475/03.2010.03.
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Yakovlev, O. I., i S. I. Shornikov. "Theoretical analyses of chemical and magnesium and silica isotope fractionation during vaporization of ca-al-inclusion of chondrite". Геохимия 64, nr 8 (3.09.2019): 777–93. http://dx.doi.org/10.31857/s0016-7525648777-793.
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Experimental study of changes in the composition of Ca-Al-inclusions of chondrites during evaporation indicates a close relationship of chemical and isotopic fractionation of this substance. The theoretical description of the coupling is carried out using the equations of the evaporation rate of the melt component (the Hertz-Knudsen equation) and isotope Rayleigh fractionation. The form of Rayleigh equation taken in foreign literature, derived from the Hertz-Knudsen equation, faces difficulties in interpreting experimental data. The discrepancy between the experimental and model data is explained by the fact that the «ideal» isotope fractionation factor used in the Rayleigh equation does not take into account its dependence on the temperature and composition of the evaporating melt. The article presents an alternative expression of the Rayleigh equation and a new expression of the rate of evaporation of Hertz-Knudsen, taking into account the activity of the melt component. The activity of the component is determined by the acidity-basicity index of the melt Ca-Al-inclusion, which, in turn, affects the evaporative fractionation of magnesium and silicon isotopes.
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Tacail, Théo, Philippe Télouk i Vincent Balter. "Precise analysis of calcium stable isotope variations in biological apatites using laser ablation MC-ICPMS". Journal of Analytical Atomic Spectrometry 31, nr 1 (2016): 152–62. http://dx.doi.org/10.1039/c5ja00239g.
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Taylor, Holly L., Isaac J. Kell Duivestein, Juraj Farkas, Martin Dietzel i Anthony Dosseto. "Technical note: Lithium isotopes in dolostone as a palaeo-environmental proxy – an experimental approach". Climate of the Past 15, nr 2 (4.04.2019): 635–46. http://dx.doi.org/10.5194/cp-15-635-2019.
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Abstract. Lithium (Li) isotopes in marine carbonates have considerable potential as a proxy to constrain past changes in silicate weathering fluxes and improve our understanding of Earth's climate. To date the majority of Li isotope studies on marine carbonates have focussed on calcium carbonates. The determination of the Li isotope fractionation between dolomite and a dolomitizing fluid would allow us to extend investigations to deep times (i.e. Precambrian) when dolostones were the most abundant marine carbonate archives. Dolostones often contain a significant proportion of detrital silicate material, which dominates the Li budget; thus, pretreatment needs to be designed so that only the isotope composition of the carbonate-associated Li is measured. This study aims to serve two main goals: (1) to determine the Li isotope fractionation between Ca–Mg carbonates and solution, and (2) to develop a method for leaching the carbonate-associated Li out of dolostone while not affecting the Li contained within the detrital portion of the rock. We synthesized Ca–Mg carbonates at high temperatures (150 to 220 ∘C) and measured the Li isotope composition (δ7Li) of the precipitated solids and their respective reactive solutions. The relationship of the Li isotope fractionation factor with temperature was obtained: 103lnαprec-sol=-(2.56±0.27)106(1)/T2+(5.8±1.3) Competitive nucleation and growth between dolomite and magnesite were observed during the experiments; however, there was no notable effect of their relative proportion on the apparent Li isotope fractionation. We found that Li isotope fractionation between the precipitated solid and solution is higher for Ca–Mg carbonates than for Ca carbonates. If the temperature of a precipitating solution is known or can be estimated independently, the above equation could be used in conjunction with the Li isotope composition of dolostones to derive the composition of the solution and hence make inferences about the past Li cycle. In addition, we also conducted leaching experiments on a Neoproterozoic dolostone and a Holocene coral. Results show that leaching with 0.05 M hydrochloric acid (HCl) or 0.5 % acetic acid (HAc) at room temperature for 60 min releases Li from the carbonate fraction without a significant contribution of Li from the siliciclastic detrital component. These experimental and analytical developments provide a basis for the use of Li isotopes in dolostones as a palaeo-environmental proxy, which will contribute to further advance our understanding of the evolution of Earth's surface environments.
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Letulle, Thomas, Danièle Gaspard, Mathieu Daëron, Florent Arnaud-Godet, Arnauld Vinçon-Laugier, Guillaume Suan i Christophe Lécuyer. "Multi-proxy assessment of brachiopod shell calcite as a potential archive of seawater temperature and oxygen isotope composition". Biogeosciences 20, nr 7 (12.04.2023): 1381–403. http://dx.doi.org/10.5194/bg-20-1381-2023.
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Abstract. Most of our knowledge of past seawater temperature history is based on δ18O values of calcium carbonate fossil shells. However, the determination of past temperatures using this proxy requires the knowledge of past seawater δ18O values, which is generally poorly constrained. Other paleothermometers using carbonate archives, such as Mg/Ca ratios and clumped isotopes (Δ47), have been developed to allow for paleotemperatures to be estimated independently and to allow past ocean δ18O values to be calculated using various groups of calcifying organisms. Articulated brachiopod shells are some of the most commonly used archives in studies of past oceanic geochemistry and temperature. They are abundant in the fossil record since the Cambrian, and for decades, their low Mg–calcite mineralogy has been considered relatively resistant to diagenetic alteration. Here, we investigate the potential of brachiopod shells as recorders of seawater temperatures and seawater δ18O values using new brachiopod shell geochemical data by testing multiple well-established or suggested paleothermometers applied to carbonate archives. Modern articulated brachiopod shells covering a wide range of temperatures (−1.9 to 25.5 ∘C), depths (5 to 3431 m) and salinities (33.4 to 37.0 PSU) were analysed for their stable isotope compositions (δ13C, δ18O and Δ47) and their elemental ratios (Mg/Ca, Sr/Ca, Na/Ca and Li/Ca). Our data allowed us to propose a revised oxygen isotope fractionation equation between modern-brachiopod shell calcite and seawater: (1) T = - 5.0 ( ± 0.2 ) ( δ 18 O c - δ 18 O sw ) + 19.4 ( ± 0.4 ) , where δ18Oc is in ‰ VPDB, δ18Osw is in ‰ VSMOW, and T is in ∘C. Our results strongly support the use of clumped isotopes as an alternative temperature proxy but confirm significant offsets relative to the canonical relationship established for other biogenic and abiogenic calcium carbonate minerals. Brachiopod shell Mg/Ca ratios show no relationship with seawater temperatures, indicating that this ratio is a poor recorder of past changes in temperatures, an observation at variance with several previous studies. Despite significant correlations with brachiopod living temperature, brachiopod shell Sr/Ca, Na/Ca and Li/Ca values indicate the influence of environmental and biological factors unrelated to temperature, which undermines their potential as alternative temperature proxies. Kinetic effects (growth rates) could explain most of the deviation of brachiopod shell calcite from expected isotopic equilibrium with seawater and part of the distribution of Sr/Ca, Na/Ca and Li/Ca ratios.
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Vezinet, Adrien, Emilie Thomassot, Yan Luo, Chiranjeeb Sarkar i D. Graham Pearson. "Diachronous Redistribution of Hf and Nd Isotopes at the Crystal Scale—Consequences for the Isotopic Evolution of a Poly-Metamorphic Crustal Terrane". Geosciences 12, nr 1 (12.01.2022): 36. http://dx.doi.org/10.3390/geosciences12010036.
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In metamorphic rocks, mineral species react over a range of pressure–temperature conditions that do not necessarily overlap. Mineral equilibration can occur at varied points along the metamorphic pressure–temperature (PT) path, and thus at different times. The sole or dominant use of zircon isotopic compositions to constrain the evolution of metamorphic rocks might then inadvertently skew geological interpretations towards one aspect or one moment of a rock’s history. Here, we present in-situ U–Pb/Sm–Nd isotope analyses of the apatite crystals extracted from two meta-igneous rocks exposed in the Saglek Block (North Atlantic craton, Canada), an Archean metamorphic terrane, with the aim of examining the various signatures and events that they record. The data are combined with published U–Pb/Hf/O isotope compositions of zircon extracted from the same hand-specimens. We found an offset of nearly ca. 1.5 Gyr between U-Pb ages derived from the oldest zircon cores and apatite U–Pb/Sm–Nd isotopic ages, and an offset of ca. 200 Ma between the youngest zircon metamorphic overgrowths and apatite. These differences in metamorphic ages recorded by zircon and apatite mean that the redistribution of Hf isotopes (largely hosted in zircon) and Nd isotopes (largely hosted in apatite within these rocks), were not synchronous at the hand-specimen scale (≤~0.001 m3). We propose that the diachronous redistribution of Hf and Nd isotopes and their parent isotopes was caused by the different PT conditions of growth equilibration between zircon and apatite during metamorphism. These findings document the latest metamorphic evolution of the Saglek Block, highlighting the role played by intra-crustal reworking during the late-Archean regional metamorphic event.
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Eerkens, Jelmer W., Eric J. Bartelink, Laura Brink, Richard T. Fitzgerald, Ramona Garibay, Gina A. Jorgenson i Randy S. Wiberg. "Trophy Heads or Ancestor Veneration? A Stable Isotope Perspective on Disassociated and Modified Crania in Precontact Central California". American Antiquity 81, nr 1 (styczeń 2016): 114–31. http://dx.doi.org/10.7183/0002-7316.81.1.114.
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AbstractFew items in the archaeological record capture the imagination more than human heads separated from their bodies. Such items are sometimes assumed to indicate warfare practices, where “trophy heads” display power and fighting prowess. Other times, they are interpreted as representing ancestor veneration. Isolated crania are not uncommon in the Early period (ca. 4500–2500 B.P.) in Central California. Some anthropologists interpret them as trophy heads, but isotopie analyses at CA-CCO-548 suggest an alternative interpretation. Strontium isotope analyses on one modified cranium produced values consistent with local individuals, and both headless burials and people buried with extra skulls overlap in carbon and nitrogen isotopes. Further, teeth from two individuals who were buried with extra skulls suggest both were weaned at early ages (before age 2), much earlier than other individuals at the site. Together with contextual information, we argue that the isotopie data are more consistent with the hypothesis that extra skulls and headless burials represent ancestor veneration rather than trophies, shedding new light on Early-period societies in Central California.
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Fiket, Željka, Martina Furdek Turk, Maja Ivanić i Goran Kniewald. "Non-traditional stable isotope signatures in geological matrices as a tool for interpreting environmental changes – a review". Geologia Croatica 74, nr 2 (30.06.2021): 177–87. http://dx.doi.org/10.4154/gc.2021.12.
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The development of new analytical techniques enabled the precise determination of the expanded set of stable isotopes and provided new insight into existing geological issues. This review outlines recent studies of non-traditional isotope signatures in geological matrices, summarizing in one place, new data for the stable isotopes of Ca, Mg, Sr, Li, Ni, Cr, and Cu and their application in the interpretation of environmental processes. Although some, such as δ44Ca and δ26Mg, have previously been used to track changes in seawater chemistry throughout geological history, recent studies report their application as geochemical proxies of post-depositional processes. Similarly, isotopic signatures of strontium, previously used in radioactive isotope chronology, and δ7Li, used in tracing plate subduction and crust/mantle material cycling, found a new application in studies of weathering patterns. The use of δ53Cr and δ 65Cu isotope signatures, on the other hand, reflects their fractionation under different redox conditions, whereas δ60Ni, due to its adsorption and co-precipitation with sulfide species and Fe-Mn phases, is used in interpreting the contributions of different material sources. And while the isotopic signatures of all these elements indicate certain environmental conditions and processes (e.g. post-depositional processes, redox conditions, organic matter input, the contribution of sources, etc.), by combining them a more comprehensive insight into the investigated environment can be achieved.
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Hassler, A., J. E. Martin, R. Amiot, T. Tacail, F. Arnaud Godet, R. Allain i V. Balter. "Calcium isotopes offer clues on resource partitioning among Cretaceous predatory dinosaurs". Proceedings of the Royal Society B: Biological Sciences 285, nr 1876 (11.04.2018): 20180197. http://dx.doi.org/10.1098/rspb.2018.0197.
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Large predators are overabundant in mid-Cretaceous continental dinosaur assemblages of North Africa. Such unbalanced ecosystem structure involves, among predatory dinosaurs, typical abelisaurid or carcharodontosaurid theropods co-occurring with long-snouted spinosaurids of debated ecology. Here, we report calcium (Ca) isotope values from tooth enamel (expressed as δ 44/42 Ca) to investigate resource partitioning in mid-Cretaceous assemblages from Niger (Gadoufaoua) and Morocco (Kem Kem Beds). In both assemblages, spinosaurids display a distinct isotopic signature, the most negative in our dataset. This distinct taxonomic clustering in Ca isotope values observed between spinosaurids and other predators provides unambiguous evidence for niche partitioning at the top of the trophic chains: spinosaurids foraged on aquatic environments while abelisaurid and carcharodontosaurid theropods relied almost exclusively on terrestrial resources.
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Herbert, Timothy D., Rocio Caballero-Gill i Joseph B. Novak. "A revised mid-Pliocene composite section centered on the M2 glacial event for ODP Site 846". Climate of the Past 17, nr 3 (23.06.2021): 1385–94. http://dx.doi.org/10.5194/cp-17-1385-2021.
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Abstract. The composite section from ODP Site 846 has provided key data sets for Pliocene stable isotope and paleoclimatic time series. We document here apparent outliers in previously published data sets for stable isotopes and alkenone-derived sea surface temperature (SST) estimates in the Pliocene interval containing the M2 glaciation (ca. 3.290–3.3 Ma) by tying high-resolution core measurements to a continuous downhole conductivity log. We generate a revised sequence of new stable isotopic and alkenone measurements across the M2 event that correlate well to the revised splices of color reflectance and gamma ray attenuation porosity evaluator data from Site 846, and to a new composite section produced at equatorial Pacific ODP Site 850. A new composite splice for Site 846 is proposed, along with composite isotope and alkenone time series that should be integrated into revised Pliocene paleoclimatic stacks.
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Rossete, Alexssandra Luiza Rodrigues Molina, Josiane Meire Toloti Carneiro, José Albertino Bendassolli, Claudineia Raquel Oliveira Tavares i Carlos Roberto Sant'Ana Filho. "Production of single superphosphate labeled with 34S". Scientia Agricola 65, nr 1 (luty 2008): 91–94. http://dx.doi.org/10.1590/s0103-90162008000100013.
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Single superphosphate is currently one of the mostly used fertilizers as an alternative source for phosphorus and sulphur. Sulphur presents four stable isotopes (32S, 33S, 34S, and 36S) with natural abundances of 95.00; 0.76; 4.22; and 0.014% in atoms, respectively. Single superphosphate labeled with the 34S isotope was obtained from a chemical reaction in stoichiometric amounts between Ca(H2PO4)2 and Ca34SO4.2H2O. Calcium sulphate (Ca34SO4.2H2O) was enriched with 5.85 ± 0.01 atoms % of 34S. The Ca(H2PO4)2 reagent was obtained from a reaction between CaCl2.2H2O and H3PO4. The reaction between the Ca(H2PO4)2 thus produced and the labeled Ca34SO4.2H2O compound was then performed to obtain the 34S-labeled single surperphosphate. The thermal decomposition of the labeled superphosphate for the production of gaseous 34SO2 was carried out under a vacuum line at 900ºC in the presence of NaPO3. The isotopic determination of S (atoms % of 34S) was carried out on an ATLAS-MAT model CH-4 mass spectrometer. The production yield of Ca(H2PO4)2 and labeled single superphosphate were approximately 97 and 99% respectively, and the purity level of the labeled single superphosphate was estimated as 96%. No isotopic fractionation was observed in the production process of 34S-labeled single superphosphate.
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Blättler, C. L., S. M. Stanley, G. M. Henderson i H. C. Jenkyns. "Identifying vital effects in <i>Halimeda</i> algae with Ca isotopes". Biogeosciences Discussions 11, nr 3 (5.03.2014): 3559–80. http://dx.doi.org/10.5194/bgd-11-3559-2014.
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Abstract. Geochemical records of biogenic carbonates provide some of the most valuable records of the geological past, but are often difficult to interpret without a mechanistic understanding of growth processes. In this experimental study, Halimeda algae are used as a test organism to untangle some of the specific factors that influence their skeletal composition, in particular their Ca-isotope composition. Algae were stimulated to precipitate both calcite and aragonite by growth in artificial Cretaceous seawater. The Ca-isotope fractionation of the algal calcite is much smaller than that for the algal aragonite, similar to the behaviour observed in inorganic precipitates. However, the carbonate from Halimeda is isotopically heavier than inorganic forms, likely due to Rayleigh distillation within the algal intercellular space. In identifying specific vital effects and the magnitude of their influence on Ca-isotope ratios, this study suggests that mineralogy has a first-order control on the Ca-isotope budget of the carbonate sink and the Ca-isotope composition of seawater.
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Fantle, Matthew S., i Edward T. Tipper. "Calcium isotopes in the global biogeochemical Ca cycle: Implications for development of a Ca isotope proxy". Earth-Science Reviews 129 (luty 2014): 148–77. http://dx.doi.org/10.1016/j.earscirev.2013.10.004.
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Fujii, Y., J. Hoshi, H. Iwamoto, M. Okamoto i H. Kakihana. "Calcium Isotope Effects in Ion Exchange Electromigration and Calcium Isotope Analysis by Thermo-Ionization Mass Spectrometry". Zeitschrift für Naturforschung A 40, nr 8 (1.08.1985): 843–48. http://dx.doi.org/10.1515/zna-1985-0807.
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Calcium ions were made to electromigrate along a cation exchange membrane. The abundance ratios of the calcium isotopes (Ca-40, 42, 43, 44, 48) in the migrated bands were measured by thermo-ionization mass spectrometry. The lighter isotopes were enriched in the front part of the migrated band. The increments in the isotope abundance ratios were found to be proportional to the mass differences of the isotopes. The observed e-values per unit mass difference (ε/ΔM) were 1.26 x 10-4 (at 20 °C), 1.85 x 10-4 (at 25 °C) and 2.4 x 10-4 (at 40 °C). The mass spectrometry was improved by using a low temperature for the evaporation of CaI2.
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Blättler, C. L., S. M. Stanley, G. M. Henderson i H. C. Jenkyns. "Identifying vital effects in <i>Halimeda</i> algae with Ca isotopes". Biogeosciences 11, nr 24 (17.12.2014): 7207–17. http://dx.doi.org/10.5194/bg-11-7207-2014.
Pełny tekst źródłaStreszczenie:
Abstract. Geochemical records of biogenic carbonates provide some of the most valuable records of the geological past, but are often difficult to interpret without a mechanistic understanding of growth processes. In this experimental study, Halimeda algae are used as a test organism to untangle some of the specific factors that influence their skeletal composition, in particular their Ca-isotope composition. Algae were stimulated to precipitate both calcite and aragonite by growth in artificial Cretaceous seawater, resulting in experimental samples with somewhat malformed skeletons. The Ca-isotope fractionation of the algal calcite (−0.6‰) appears to be much smaller than that for the algal aragonite (−1.4‰), similar to the behaviour observed in inorganic precipitates. However, the carbonate from Halimeda has higher Ca-isotope ratios than inorganic forms by approximately 0.25‰, likely because of Rayleigh distillation within the algal intercellular space. In identifying specific vital effects and the magnitude of their influence on Ca-isotope ratios, this study suggests that mineralogy has a first-order control on the marine Ca-isotope cycle.
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Feng, Lianjun, Hongwei Li i Tiejun Li. "Potential Reference Materials for Hematite Oxygen Isotope Analysis". Minerals 10, nr 11 (6.11.2020): 987. http://dx.doi.org/10.3390/min10110987.
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Hematite is a potential mineral for reconstructing the oxygen isotope composition and paleotemperature of paleowater. A highly accurate analysis of oxygen isotopes is essential. However, relative to other oxygenated minerals, we lack hematite reference materials that allow for internationally comparable analyses between different laboratories. To address this issue, we attempted to perform bulk rock oxygen isotope analysis on five hematite reference materials (GBW07223a, GBW07825, YSBC28740-95, YSBC28756-2008, Harvard 92649). Meanwhile, the oxygen isotope ratios of iron oxides (GBW07223a, GBW07825, YSBC28740-95, YSBC28756-2008) were obtained by mass balance involving other oxygen-bearing minerals such as quartz and silicates. In addition, the oxygen isotope ratios of iron oxides in an oolitic hematite (ca. 1.65 billion years ago) are consistent with the results of previous analyses of this class of minerals.
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Wang, Peng, Ting Liang, HongJun Jiang, XinKui Xiang i Bo Zhong. "Trace Elements and Pb-O Isotopes of Scheelite: Metallogenic Implications for the Shimensi W-Polymetallic Deposit in South China". Minerals 12, nr 11 (18.11.2022): 1461. http://dx.doi.org/10.3390/min12111461.
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The world-class Shimensi tungsten (W)-polymetallic deposit is located in Jiangnan Orogen, with an estimated reserve of 742.5 kt WO3 @ 0.195% W, 403.6 kt Cu and 28 kt Mo. In this paper, the trace elements and Pb-O isotopes of scheelite (the main ore mineral) are presented to study the ore-forming material source and ore-forming fluid evolution. The results show that the REE distribution in scheelite is mainly controlled by the substitution mechanism of 3Ca2+ = 2REE3+ + □Ca (where □Ca is the Ca-site vacancy). Oxygen isotope data indicate that the scheelite mineralization occurred under high-temperature oxygen isotope equilibrium conditions, and that the ore-forming fluid has a magmatic–hydrothermal origin. The variation in scheelite Eu anomalies and the wide range of scheelite Y/Ho ratio indicate that the ore-forming fluid evolves from reducing to oxidizing, and the early-stage and late-stage ore-forming fluid may have been relatively rich in F− and HCO3−, respectively. The significant Mo decrease in scheelite from the early to late stage that are opposite to the influence of fO2 variation may have resulted from the crystallization of molybdenite and Mo-rich scheelite. Lead isotopes of the ore minerals of scheelite, wolframite, molybdenite and chalcopyrite can be divided into three groups, similar to these of feldspars in different granites. Both the Mesozoic porphyritic and fine-grained biotite granites have Pb isotope ratios similar to the ores, which suggests that the former two are the main ore material source.
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Aladejana, Jamiu A., Robert M. Kalin, Ibrahim Hassan, Philippe Sentenac i Moshood N. Tijani. "Origin and Residence Time of Groundwater in the Shallow Coastal Aquifer of Eastern Dahomey Basin, Southwestern Nigeria, Using δ18O and δD Isotopes". Applied Sciences 10, nr 22 (10.11.2020): 7980. http://dx.doi.org/10.3390/app10227980.
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This study employed stable isotopes of δ18O and δ2H in conjunction with other hydrological parameters to understand the origin, inferred residence time, and seasonal effect of groundwater in the shallow aquifers of the eastern Dahomey Basin. A total of 230 groundwater samples (97 in the wet season and 133 in the dry season) were collected from the borehole and shallow aquifer between May 2017 and April 2018. Groundwater analysis included major ions and δ18O and δ2H, isotopes data in precipitation from three selected Global Network of Isotope in Precipitation (GNIP) stations across West Africa, Douala in Cameroon, Cotonou in Republic of Benin, and Kano in Nigeria were used in comparative analysis. Results of the hydrochemical model revealed Ca-HCO3 and Na-Cl as dominant water types with other mixing water types such as Ca–SO4, Ca–Cl, Na–SO4, and K–Mg–HCO3, which characterised early stage of groundwater transformation as it infiltrates through vadose zone into the aquifer. δ18O and δ2H precipitation data from the three stations plotted along with the groundwater samples indicate recent meteoric water origin, with little effect of evaporation during the dry season. The plot of Total Dissolved Solids (TDS) against δ18O showed clustering of the water samples between the recharge and the evaporation zone with dry season samples trending towards increased TDS, which is an indication of the subtle effect of evaporation during this period. Tracing groundwater types along the flow paths within the basin is problematic and attributed to the heterogeneity of the aquifer with anthropogenic influences. Moreover, a comparison of the δ18O and δ2H isotopic compositions of groundwater and precipitation in the three selected stations, with their respective deuterium excess (D-excess) values established low evapotranspiration induced isotope enrichment, which could be due to higher precipitation and humidity in the region resulting in low isotope fractionation; hence, little effect of seasonal variations. The study, therefore, suggested groundwater recharge in the shallow aquifer in the eastern Dahomey Basin is of meteoric origin with a short residence time of water flows from soils through the vadose zone to the aquifers.
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LIU, J. Y., HUAN FENG HAO, YONG ZHONG XING, WEI ZUO i XI GUO LEE. "INFLUENCES OF THE ISOSPIN-DEPENDENCE OF IN-MEDIUM NUCLEON–NUCLEON CROSS-SECTION AND MOMENTUM DEPENDENT INTERACTION ON ISOSCALING PARAMETER". International Journal of Modern Physics E 17, nr 04 (kwiecień 2008): 645–53. http://dx.doi.org/10.1142/s0218301308010052.
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Influences of the isospin-dependent in-medium nucleon–nucleon cross-section [Formula: see text] and momentum-dependent interaction (MDI) on the isoscaling parameter α are investigated for two central collisions 40 Ca + 40 Ca and 60 Ca + 60 Ca . These collisions are with isospin dependent quantum molecular dynamics in the beam energy region from 40 to 60 MeV/nucleon. The isotope yield ratio R21(N, Z) for the above two central collisions depends exponentially on the neutron number N and proton number Z of isotopes, with an isoscaling. In particular, the isospin-dependent [Formula: see text] and MDI induce an obvious decrease of the isoscaling parameter α. The mechanism of the decreases of α by both [Formula: see text] and MDI are studied respectively.
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von Quadt, A., D. Gallhofer, M. Guillong, I. Peytcheva, M. Waelle i S. Sakata. "U–Pb dating of CA/non-CA treated zircons obtained by LA-ICP-MS and CA-TIMS techniques: impact for their geological interpretation". J. Anal. At. Spectrom. 29, nr 9 (2014): 1618–29. http://dx.doi.org/10.1039/c4ja00102h.
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Chemical Abrasion Isotope-Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS) is known as a high precision technique for resolving lead loss and improving the interpretation of U–Pb zircon age data.
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Caemmerer, Susanne von, Martha Ludwig, Anthony Millgate, Graham D. Farquhar, Dean Price, Murray Badger i Robert T. Furbank. "Carbon Isotope Discrimination during C4 Photosynthesis: Insights from Transgenic Plants". Functional Plant Biology 24, nr 4 (1997): 487. http://dx.doi.org/10.1071/pp97031.
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We have measured the discrimination against 13C during CO2 assimilation in Flaveria bidentis wild type plants and in transgenic Flaveria bidentis plants transformed (1) with an antisense RNA construct targeted to the nuclear encoded gene for the small subunit of Rubisco—these plants had reduced amounts of Rubisco, decreased CO2 assimilation rates and increased carbon isotope discrimination, which was also evident in the carbon isotope discrimination of leaf dry matter; and (2) transformed with the mature coding region of carbonic anhydrase, CA, from tobacco (Nicotiana tabacum) in the sense direction under the control of the cauliflower mosaic virus 35S promoter—these plants had slightly increased CA activity in the mesophyll as well as a 2–4-fold increase in CA activity in the bundle-sheath cells. The introduction of tobacco CA manifested itself by a reduction in CO2 assimilation rate and an increase in carbon isotope discrimination. We suggest that the increased carbon isotope discrimination is a result of increased bicarbonate leakage out of the bundle sheath.
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Vigier, N., C. Rollion-Bard i S. Spezzaferri. "In situ Ca isotope measurements in foraminifera". Geochimica et Cosmochimica Acta 70, nr 18 (sierpień 2006): A672. http://dx.doi.org/10.1016/j.gca.2006.06.1257.
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Sharma, Manish, Daniel Sethio, Vincenza D’Anna, Juan C. Fallas, Pascal Schouwink, Radovan Černý i Hans Hagemann. "Isotope Exchange Reactions in Ca(BH4)2". Journal of Physical Chemistry C 119, nr 1 (17.12.2014): 29–32. http://dx.doi.org/10.1021/jp5082609.
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Holmden, Chris, i Nicolas Bélanger. "Ca isotope cycling in a forested ecosystem". Geochimica et Cosmochimica Acta 74, nr 3 (luty 2010): 995–1015. http://dx.doi.org/10.1016/j.gca.2009.10.020.
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Mennekes, David, Michael Rinderer, Stefan Seeger i Natalie Orlowski. "Ecohydrological travel times derived from in situ stable water isotope measurements in trees during a semi-controlled pot experiment". Hydrology and Earth System Sciences 25, nr 8 (23.08.2021): 4513–30. http://dx.doi.org/10.5194/hess-25-4513-2021.
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Abstract. Tree water uptake processes and ecohydrological travel times have gained more attention in recent ecohydrological studies. In situ measurement techniques for stable water isotopes offer great potential to investigate these processes but have not been applied much to tree xylem and soils so far. Here, we used in situ probes for stable water isotope measurements to monitor the isotopic signatures of soil and tree xylem water before and after two deuterium-labeled irrigation experiments. To show the potential of the method, we tested our measurement approach with 20-year-old trees of three different species (Pinus pinea, Alnus incana and Quercus suber). They were planted in large pots with homogeneous soil in order to have semi-controlled experimental conditions. Additional destructive sampling of soil and plant material allowed for a comparison between destructive (cryogenic vacuum extraction and direct water vapor equilibration) and in situ isotope measurements. Furthermore, isotope-tracer-based ecohydrological travel times were compared to travel times derived from sap flow measurements. The time to first arrival of the isotope tracer signals at 15 cm stem hight were ca. 17 h for all tree species and matched well with sap-flow-based travel times. However, at 150 cm stem height tracer-based travel times differed between tree species and ranged between 2.4 and 3.3 d. Sap-flow-based travel times at 150 cm stem hight were ca. 1.3 d longer than tracer-based travel times. The isotope signature of destructive and in situ isotope measurements differed notably, which suggests that the two types of techniques sampled water from different pools. In situ measurements of soil and xylem water were much more consistent between the three tree pots (on average standard deviations were smaller by 8.4 ‰ for δ2H and by 1.6 ‰ for δ18O for the in situ measurements) and also among the measurements from the same tree pot in comparison to the destructive methods (on average standard deviations were smaller by 7.8 ‰ and 1.6 ‰ for δ2H and δ18O, respectively). Our study demonstrates the potential of semi-controlled large-scale pot experiments and very frequent in situ isotope measurements for monitoring tree water uptake and ecohydrological travel times. It also shows that differences in sampling techniques or sensor types need to be considered when comparing results of different studies and within one study using different methods.
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Ito, Emi, Patrick De Deckker i Stephen M. Eggins. "Ostracodes and Their Shell Chemistry: Implications for Paleohydrologic and Paleoclimatologic Applications". Paleontological Society Papers 9 (listopad 2003): 119–52. http://dx.doi.org/10.1017/s1089332600002187.
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The shell chemistry of ostracodes is a useful indicator of past environmental conditions especially when the chemistry data are considered along with other proxy data. The complexities involved with the chemical and isotopic changes accompanying hydrologic change, solute evolution, and the autoecology of ostracodes all point to the need to exercise caution when interpreting shell chemistry. Nevertheless, the stable-isotope values and cation ratios (e.g., Mg/Ca, Sr/Ca) as well as the species assemblage of ostracodes can provide powerful tools for the reconstruction of paleoclimate and paleohydrology. In particular, the changes in Mg/Ca and Sr/Ca of well-calcified ostracodes shells record the qualitative changes in solute composition, and when the dissolved Mg/Ca remains relatively constant, the Mg/Ca in the ostracode shell is proportional to water temperature.
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Dwyer, Gary S., i Mark A. Chandler. "Mid-Pliocene sea level and continental ice volume based on coupled benthic Mg/Ca palaeotemperatures and oxygen isotopes". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, nr 1886 (14.10.2008): 157–68. http://dx.doi.org/10.1098/rsta.2008.0222.
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Ostracode magnesium/calcium (Mg/Ca)-based bottom-water temperatures were combined with benthic foraminiferal oxygen isotopes in order to quantify the oxygen isotopic composition of seawater, and estimate continental ice volume and sea-level variability during the Mid-Pliocene warm period, ca 3.3–3.0 Ma. Results indicate that, following a low stand of approximately 65 m below present at marine isotope stage (MIS) M2 ( ca 3.3 Ma), sea level generally fluctuated by 20–30 m above and below a mean value similar to present-day sea level. In addition to the low-stand event at MIS M2, significant low stands occurred at MIS KM2 (−40 m), G22 (−40 m) and G16 (−60 m). Six high stands of +10 m or more above present day were also observed; four events (+10, +25,+15 and +30 m) from MIS M1 to KM3, a high stand of +15 m at MIS K1, and a high stand of +25 m at MIS G17. These results indicate that continental ice volume varied significantly during the Mid-Pliocene warm period and that at times there were considerable reductions of Antarctic ice.
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Lu, Zhongying, Chengying Hai, Simin Yan, Lu Xu, Daowang Lu, Yixin Sou, Hengye Chen, Xiaolong Yang, Haiyan Fu i Jian Yang. "Chemistry Combining Elemental Profile, Stable Isotopic Ratios, and Chemometrics for Fine Classification of a Chinese Herb Licorice (Glycyrrhiza uralensis Fisch.) from 37 Producing Area". Journal of Analytical Methods in Chemistry 2022 (18.08.2022): 1–9. http://dx.doi.org/10.1155/2022/8906305.
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A method based on elemental fingerprint, stable isotopic analysis and combined with chemometrics was proposed to trace the geographical origins of Licorice (Glycyrrhiza uralensis Fisch) from 37 producing areas. For elemental fingerprint, the levels of 15 elements, including Ca, Cu, Mg, Pb, Zn, Sr, Mn, Se, Cd, Fe, Na, Al, Cr, Co, and K, were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Three stable isotopes, including δ13C, δ15N, and δ18O, were measured using an isotope-ratio mass spectrometer (IRMS). For fine classification, three multiclass strategies, including the traditional one-versus-rest (OVR) and one-versus-one (OVO) strategies and a new ensemble strategy (ES), were combined with two binary classifiers, partial least squares discriminant analysis (PLSDA) and least squares support vector machines (LS-SVM). As a result, ES-PLSDA and ES-LS-SVM achieved 0.929 and 0.921 classification accuracy of GUF samples from the 37 origins. The results show that element fingerprint and stable isotope combined with chemometrics is an effective method for GUF traceability and provides a new idea for the geographical traceability of Chinese herbal medicine.
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Schöne, Bernd R., Aliona E. Meret, Sven M. Baier, Jens Fiebig, Jan Esper, Jeffrey McDonnell i Laurent Pfister. "Freshwater pearl mussels from northern Sweden serve as long-term, high-resolution stream water isotope recorders". Hydrology and Earth System Sciences 24, nr 2 (17.02.2020): 673–96. http://dx.doi.org/10.5194/hess-24-673-2020.
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Abstract. The stable isotope composition of lacustrine sediments is routinely used to infer Late Holocene changes in precipitation over Scandinavia and, ultimately, atmospheric circulation dynamics in the North Atlantic realm. However, such archives only provide a low temporal resolution (ca. 15 years), precluding the ability to identify changes on inter-annual and quasi-decadal timescales. Here, we present a new, high-resolution reconstruction using shells of freshwater pearl mussels, Margaritifera margaritifera, from three streams in northern Sweden. We present seasonally to annually resolved, calendar-aligned stable oxygen and carbon isotope data from 10 specimens, covering the time interval from 1819 to 1998. The bivalves studied formed their shells near equilibrium with the oxygen isotope signature of ambient water and, thus, reflect hydrological processes in the catchment as well as changes, albeit damped, in the isotope signature of local atmospheric precipitation. The shell oxygen isotopes were significantly correlated with the North Atlantic Oscillation index (up to 56 % explained variability), suggesting that the moisture that winter precipitation formed from originated predominantly in the North Atlantic during NAO+ years but in the Arctic during NAO− years. The isotope signature of winter precipitation was attenuated in the stream water, and this damping effect was eventually recorded by the shells. Shell stable carbon isotope values did not show consistent ontogenetic trends, but rather oscillated around an average that ranged from ca. −12.00 to −13.00 ‰ among the streams studied. Results of this study contribute to an improved understanding of climate dynamics in Scandinavia and the North Atlantic sector and can help to constrain eco-hydrological changes in riverine ecosystems. Moreover, long isotope records of precipitation and streamflow are pivotal to improve our understanding and modeling of hydrological, ecological, biogeochemical and atmospheric processes. Our new approach offers a much higher temporal resolution and superior dating control than data from existing archives.
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Yoshimura, T., A. Suzuki i N. Iwasaki. "Mechanism of O and C isotope fractionation in magnesian calcite skeletons of <i>Octocorallia</i> corals and an implication on their calcification response to ocean acidification". Biogeosciences Discussions 12, nr 1 (8.01.2015): 389–412. http://dx.doi.org/10.5194/bgd-12-389-2015.
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Abstract. Coral calcification is strongly dependent on both the pH and the dissolved inorganic carbon (DIC) of the calcifying fluid. Skeletal oxygen and carbon isotope fractionation of high-Mg calcite skeletons of \\textit{Octocorallia} corals directly record the biological manipulation on sources of DIC in response to environmental changes. The coral skeletons were enriched in light isotopes (16O and 12C) relative to the expected values based on habitat environmental parameters and Mg/Ca of the skeletons. The differences between the expected and observed values ranged from −4.66 to −1.53 for δ18O and from −7.34 to −1.75 for δ13C. The large variability cannot be explained by the ambient environment, the contribution of metabolic carbon, or the precipitation rate of the skeleton. Therefore, the most plausible explanation for the observed O and C isotope differences in high-Mg calcite coral skeletons is the existence of two carbon sources, aqueous carbon dioxide in the calcifying fluid and dissolved inorganic carbon in seawater. Positive correlations of B/Ca with δ18O and δ13C suggest that skeletal isotopic compositions are enriched in light isotopes when conditions are less alkaline. Therefore, the relative contribution of isotopically heavy DIC from seawater through the skeleton and pericellular channels decreases under the reduced pH of the extracytoplasmic calcifying fluid. Our data suggest an even stronger biological effect under lower pH. Skeletal δ18O and δ13C values record the response of the sources of DIC in the coral calcifying fluids to ambient seawater pH. These changes give insight into how ocean acidification impacts the physiological mechanisms as well as the pH offset between calcifying fluid and seawater in response to ocean acidification.
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Lynott, Mark J., Thomas W. Boutton, James E. Price i Dwight E. Nelson. "Stable Carbon Isotopic Evidence for Maize Agriculture in Southeast Missouri and Northeast Arkansas". American Antiquity 51, nr 1 (styczeń 1986): 51–65. http://dx.doi.org/10.2307/280393.
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Analysis of bone collagen extracted from human skeletal remains from archaeological sites dating from the Archaic period through Euro-American settlement provides evidence for the introduction of maize into regional subsistence patterns. Stable carbon isotope ratios of samples from both the eastern Ozarks and the Mississippi River alluvial valley indicate that human populations living prior to ca. A.D. 1000 consumed little or no C4 plant material. In populations dating after ca. A.D. 1000, stable carbon isotope ratios indicate that maize represented a significant part of the human diet throughout the region. The change in dietary patterns coincides with a shift in settlement patterns from dispersed hamlets and small villages to civic-ceremonial centers with associated villages, hamlets, and farmsteads. This isotopic evidence indicates that Emergent Mississippian diets did not include substantial quantities of maize or other C4 plant material.
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Tanaka, Yu-ki, Nobuyuki Yajima, Yusuke Higuchi, Hideyuki Yamato i Takafumi Hirata. "Calcium isotope signature: new proxy for net change in bone volume for chronic kidney disease and diabetic rats". Metallomics 9, nr 12 (2017): 1745–55. http://dx.doi.org/10.1039/c7mt00255f.
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Herein, we measure the Ca isotope ratios (44Ca/42Ca and 43Ca/42Ca) in serum and bone samples collected from rats with chronic kidney disease (CKD) or diabetes mellitus (DM).
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Uno, Kevin T., Pratigya J. Polissar, Emma Kahle, Craig Feibel, Sonia Harmand, Hélène Roche i Peter B. deMenocal. "A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya". Philosophical Transactions of the Royal Society B: Biological Sciences 371, nr 1698 (5.07.2016): 20150235. http://dx.doi.org/10.1098/rstb.2015.0235.
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Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial–lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure ( ca 5–100% C 4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C 4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25–30% more C 4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C 3 –C 4 to C 4 -dominated ecosystems. The proportion of C 4 -based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C 4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61–97% C 4 vegetation on the landscape. This article is part of the themed issue ‘Major transitions in human evolution’.
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Frisia, Silvia, Andrea Borsato, Augusto Mangini, Christoph Spötl, Giuliana Madonia i Ugo Sauro. "Holocene Climate Variability in Sicily from a Discontinuous Stalagmite Record and the Mesolithic to Neolithic Transition". Quaternary Research 66, nr 3 (listopad 2006): 388–400. http://dx.doi.org/10.1016/j.yqres.2006.05.003.
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AbstractFabric and stable isotopic composition of a Holocene stalagmite (CR1) from a cave in northern Sicily record changes in paleorainfall in the early Holocene. High δ13C stable isotope values in the calcite deposited from ca. 8500 to ca. 7500 yr ago are interpreted as reflecting periods of high rainfall. The wet phase was interrupted by two periods of multi-century duration characterized by relatively cool and dry winters centered at ca. 8200 and ca. 7500 yr ago, highlighted by low δ13C and δ18O values. A high variability of δ13C values is recorded from ca. 7500 to ca. 6500 yr ago and indicates that the transition from a pluvial early Holocene to the present-day climate conditions was punctuated by decadal-scale periods of relatively dry winters. In northern Sicily, the traditional elements of the Neolithic appear at ca. 7700 yr ago. It is possible that changes in rainfall influenced the passage from hunter-gathering to farming and sheep-herding economies.
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Grubb, B. R., i P. J. Bentley. "Calcium exchange in isolated cutaneous epithelium of toad Bufo marinus". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 249, nr 2 (1.08.1985): R172—R178. http://dx.doi.org/10.1152/ajpregu.1985.249.2.r172.
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The Ca content of isolated cutaneous epithelium of toads (Bufo marinus) was 5 mmol/kg wet wt (compared with approximately 300 mmol/kg wet wt for intact skin), of which approximately 1.7 mM is not readily exchangeable with external 45Ca. After incubation in a solution containing 45Ca, loss of the accumulated isotope in an isotope-free medium is almost complete in 2 h. This efflux or washout is reduced by the presence of external Ca- and Na-free media and by La. Loss of Ca from the epithelium may thus reflect the presence of several mechanisms including a Ca-Ca exchange and a Ca-Na exchange. The effect of La (2 mM) was greater than that of a Na- and Ca-free medium, possibly reflecting the presence of an uncoupled Ca extrusion or extrusion by a Ca-ATPase (pump) mechanism. Drugs (ouabain and amiloride) that, respectively, increase or decrease levels of internal Na had no significant effects on efflux or accumulation of Ca. Vasopressin was also without such effects on Ca.
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Mondal, Surajit, i Ramananda Chakrabarti. "A novel sample loading method and protocol for monitoring sample fractionation for high precision Ca stable isotope ratio measurements using double-spike TIMS". Journal of Analytical Atomic Spectrometry 33, nr 1 (2018): 141–50. http://dx.doi.org/10.1039/c7ja00322f.
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The external reproducibility (2σSD) of Ca stable isotope ratio measurements (δ44/40Ca) using double-spike (43Ca–48Ca) thermal ionization mass spectrometry (TIMS) is better than 0.08 ‰ using our proposed loading technique.
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Khan, W. R., M. Nazre, S. Z. Zulkifli, K. A. Kudus, M. Zimmer, M. K. Roslan, A. Mukhtar, R. Mostapa i S. Gandaseca. "Reflection of stable isotopes and selected elements with the inundation gradient at the Matang Mangrove Forest Reserve (MMFR), Malaysia". International Forestry Review 19, nr 3 (1.12.2017): 1–10. http://dx.doi.org/10.1505/146554817828562314.
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Multi-elemental and isotopic fingerprints could help to track changes in mangrove forest productivity and development. This study aims to identify elemental concentrations and stable isotope ratios in inter- and intra-mangrove species along the inundation gradient of the Matang mangrove forest. Matured sun leaves of different mangrove species, namely, Avicennia alba, Rhizophora apiculata, Bruguiera parviflora, and Sonneratia ovata, were collected from the Matang Mangrove Forest Reserve (MMFR). After samples preparation, determination of elemental concentrations and stable isotope ratios were carried out using an Atomic Absorption Spectrometer (AAS) and Isotope Ratio Mass Spectrometry (IRMS) respectively. Trace elements (Mn, Fe, Cu, Zn), cations (Na, K, Ca, Mg) and stable isotope (δ13C and δ15N) ratios were found to follow different patterns along the inundation gradient in the leaves of the sampled plant species. Elemental concentrations of Na, K, Fe, Cu, Zn and Mn along with stable istopic ratio differed significantly within similar and different mangrove species. The results of Rhizophora apiculata elemental concentrations and stable isotope ratios can potentially serve as a baseline to further the research in the MMFR compartments.