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Journal articles on the topic 'Isotopes calcium'

Author: Grafiati

Published: 25 May 2024

Last updated: 31 July 2025

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1

Chandra, Subhash. "Imaging transported and endogenous calcium independently at a subcellular resolution: ion microscopy imaging of calcium stable isotopes." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (1992): 1604–5. http://dx.doi.org/10.1017/s0424820100132650.

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Ion microscopy, based on secondary ion mass spectrometry (SIMS), is a unique isotopic imaging technique. The use of stable isotopes as tracers and their SIMS localization at a subcellular resolution has introduced a significant new approach for molecular localization and ion transport studies. A molecule of interest may be tagged with stable 2H, 13C, 15N, etc. and imaged with SIMS for its intracellular location. Stable isotopes of physiologically important elements such as calcium and magnesium provide excellent tracers for ion transport imaging studies with SIMS. in a recent study with 44Ca,

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2

Fujii, Y., J. Hoshi, H. Iwamoto, M. Okamoto, and H. Kakihana. "Calcium Isotope Effects in Ion Exchange Electromigration and Calcium Isotope Analysis by Thermo-Ionization Mass Spectrometry." Zeitschrift für Naturforschung A 40, no. 8 (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 temp

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3

Yergey, Alfred L., Steven A. Abrams, Nancy E. Vieira, Richard Eastell, Laura S. Hillman, and David G. Covell. "Recent studies of human calcium metabolism using stable isotopic tracers." Canadian Journal of Physiology and Pharmacology 68, no. 7 (1990): 973–76. http://dx.doi.org/10.1139/y90-147.

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Stable isotopes of calcium are used safely as tracers for calcium in human populations ranging in age from infants to postmenopausal women. Thermal ionization mass spectrometry is used to measure calcium isotope ratios with relative accuracies of about 1% for natural abundance ratios at precisions of about 1% relative to the mean. Perturbations of natural abundance ratios are determined for the calcium in blood, urine, and feces with a limit of detection of about 2 Δ% excess. The mathematical rationale for clinical studies of fractional absorption of dietary calcium and the kinetics of calcium

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4

Zhao, Hongyu, and Junhua Huang. "Characteristics of Calcium Isotopes at Different Water Depths and Their Palaeoenvironmental Significance for Carbonate Rocks of the Permian-Triassic Boundary in Chibi, Southern China." Minerals 12, no. 11 (2022): 1440. http://dx.doi.org/10.3390/min12111440.

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Calcium isotopes of carbonate rocks can trace calcium cycles and record changes in the marine environment. As published calcium isotope profiles of carbonate rocks at the Permian-Triassic boundary are rare, comparative studies on deep-water profiles were lacking for the major extinction event that occurred during this time. We present sections of different water depths in the Chibi area of southern China that we have selected for a comparative study. We analyzed carbon isotopes, calcium isotopes, as well as major and trace elements of carbonates from two sections (Chibi North and Chibi West) t

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Han, Guilin, Anton Eisenhauer, Jie Zeng, and Man Liu. "Calcium Biogeochemical Cycle in a Typical Karst Forest: Evidence from Calcium Isotope Compositions." Forests 12, no. 6 (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 is

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Chalk, Thomas B., and Claire Rollion-Bard. "Boron Proxies: From Calcification Site pH to Cenozoic pCO2." Elements 21, no. 2 (2025): 98–104. https://doi.org/10.2138/gselements.21.2.98.

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The atmospheric partial pressure of CO2 (pCO2) is the key driver of climate variability. Boron isotopic compositions (δ11B) of marine calcium carbonates reveal pCO2 of the geologic past because boron isotope incorporation is sensitive to seawater pH, which closely reflects atmospheric pCO2. Biocarbonate δ11B values record environmental pH through a metabolic prism (so called “vital effects”), sometimes complicating interpretations. However, biocarbonate boron isotopes, coupled with boron concentrations (B/Ca), can also reveal the processes of calcification. Here, we review the link between sea

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7

Gordon, Gwyneth W., Jorge Monge, Melanie B. Channon, et al. "Calcium Isotopic Composition and Its Association With Multiple Myeloma Disease Activity." Blood 122, no. 21 (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 abnormali

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8

Oi, Takao, Kunihiko Sato, and Kazuki Umemoto. "Oxygen and Hydrogen Isotopic Preference in Hydration Spheres of Magnesium and Calcium Ions." Zeitschrift für Naturforschung A 68, no. 5 (2013): 362–70. http://dx.doi.org/10.5560/zna.2012-0122.

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Molecular orbital calculations were performed to estimate the 18O/16O and D/H isotopic reduced partition function ratios (rpfrs) of water molecules around magnesium and calcium ions. As model for water molecules in the ith hydration sphere of the cation in aqueous solutions containing that cation, we considered water molecules in the ith hydration sphere that were surrounded by water molecules in the (i+1)th hydration sphere in clusters, M2+(H2O)n (M = Mg or Ca; n up to 100). The calculations indicated that the decreasing order of the 18O preference over 16O in the primary hydration sphere is

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9

Schwarzschild, Bertram M. "Weighing exotic calcium isotopes." Physics Today 66, no. 9 (2013): 15–17. http://dx.doi.org/10.1063/pt.3.2104.

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10

Amsellem, Elsa, Frédéric Moynier, Hervé Bertrand, et al. "Calcium isotopic evidence for the mantle sources of carbonatites." Science Advances 6, no. 23 (2020): eaba3269. http://dx.doi.org/10.1126/sciadv.aba3269.

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The origin of carbonatites—igneous rocks with more than 50% of carbonate minerals—and whether they originate from a primary mantle source or from recycling of surface materials are still debated. Calcium isotopes have the potential to resolve the origin of carbonatites, since marine carbonates are enriched in the lighter isotopes of Ca compared to the mantle. Here, we report the Ca isotopic compositions for 74 carbonatites and associated silicate rocks from continental and oceanic settings, spanning from 3 billion years ago to the present day, together with O and C isotopic ratios for 37 sampl

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11

Kumar, P. V. Kiran, M. Sankari, and M. V. Suryanarayana. "Isotope selective near-resonant two-photon ionization of calcium isotopes." Journal of Physics D: Applied Physics 40, no. 1 (2006): 288–93. http://dx.doi.org/10.1088/0022-3727/40/1/028.

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12

Jahn, A., K. Lindsay, X. Giraud, et al. "Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)." Geoscientific Model Development 8, no. 8 (2015): 2419–34. http://dx.doi.org/10.5194/gmd-8-2419-2015.

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Abstract. Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized data set, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while

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13

Jahn, A., K. Lindsay, X. Giraud, et al. "Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)." Geoscientific Model Development Discussions 7, no. 6 (2014): 7461–503. http://dx.doi.org/10.5194/gmdd-7-7461-2014.

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Abstract. Carbon isotopes in the ocean are frequently used as paleo climate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized dataset, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while

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14

Nörtershäuser, W., N. Trautmann, K. Wendt, and B. A. Bushaw. "Isotope shifts and hyperfine structure in the transitions of stable calcium isotopes and calcium-41." Spectrochimica Acta Part B: Atomic Spectroscopy 53, no. 5 (1998): 709–21. http://dx.doi.org/10.1016/s0584-8547(98)00108-6.

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15

Antonelli, Michael A., Tushar Mittal, Anders McCarthy, Barbara Tripoli, James M. Watkins, and Donald J. DePaolo. "Ca isotopes record rapid crystal growth in volcanic and subvolcanic systems." Proceedings of the National Academy of Sciences 116, no. 41 (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 subvol

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16

Gibbs, W. R., and J. P. Dedonder. "Neutron radii of the calcium isotopes." Physical Review C 46, no. 5 (1992): 1825–33. http://dx.doi.org/10.1103/physrevc.46.1825.

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17

REYNARD, L. M., J. A. PEARSON, G. M. HENDERSON, and R. E. M. HEDGES. "CALCIUM ISOTOPES IN JUVENILE MILK-CONSUMERS." Archaeometry 55, no. 5 (2012): 946–57. http://dx.doi.org/10.1111/j.1475-4754.2012.00715.x.

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18

Chen, Zhensheng, Ian J. Griffin, Yana L. Kriseman, Lily K. Liang, and Steven A. Abrams. "Inductively Coupled Plasma Mass Spectrometric Analysis of Calcium Isotopes in Human Serum: A Low-Sample-Volume Acid-Equilibration Method." Clinical Chemistry 49, no. 12 (2003): 2050–55. http://dx.doi.org/10.1373/clinchem.2003.025692.

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Abstract Background: Analytical methods for measuring the calcium isotope distribution in enriched human serum samples that use low blood volumes, simple preparation methods, and rapid analysis are important in clinical studies of calcium kinetics. Previously, sample preparation by oxalate precipitation typically required 500 μL of serum. This method was time-consuming, and the blood volume required was limiting in circumstances when only a small amount of serum could be obtained. Methods: Serum was collected from humans who were administered 42Ca, and 20 μL of serum was mixed with 2 mL of 0.2

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19

Humphrey, John D., and C. Reid Ferring. "Stable Isotopic Evidence for Latest Pleistocene and Holocene Climatic Change in North-Central Texas." Quaternary Research 41, no. 2 (1994): 200–213. http://dx.doi.org/10.1006/qres.1994.1022.

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AbstractA paleoclimatic record for a southern Great Plains locality (the Aubrey Clovis site in north-central Texas) has been established using stable carbon and oxygen isotopes. Detailed composite stratigraphic sections, constrained by 14 C ages, place the age of these deposits between 14,200 and 1600 yr B.P. Calcium carbonate samples of lacustrine and pedogenic origin were analyzed. Oxygen isotopic compositions of most of these in situ carbonates reflect equilibrium precipitation from local meteoric waters. Oxygen isotope values reflect changes in the composition of meteoric waters tied to ch

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20

Schulze, Kerry J., Kimberly O. O’Brien, Emily L. Germain-Lee, Sarah L. Booth, Amanda Leonard, and Beryl J. Rosenstein. "Calcium Kinetics Are Altered in Clinically Stable Girls with Cystic Fibrosis." Journal of Clinical Endocrinology & Metabolism 89, no. 7 (2004): 3385–91. http://dx.doi.org/10.1210/jc.2003-031879.

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Abstract Reduced bone mass in individuals with cystic fibrosis (CF) may result from alterations in calcium metabolism. Bone calcium deposition and resorption rates, calcium balance, and markers of bone turnover were assessed using stable isotopes of calcium in 22 prepubertal and pubertal girls with CF. Bone calcium deposition was associated with the availability of dietary calcium, total serum osteocalcin, and leptin concentrations. Reduced bone mass in individuals with CF may result from inadequate bone calcium (Ca) deposition, and excessive resorption, although these parameters have not been

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21

Martin, Jeremy E., Derek Vance, and Vincent Balter. "Magnesium stable isotope ecology using mammal tooth enamel." Proceedings of the National Academy of Sciences 112, no. 2 (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 isotop

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22

Tacail, Théo, Béatrice Thivichon-Prince, Jeremy E. Martin, Cyril Charles, Laurent Viriot, and Vincent Balter. "Assessing human weaning practices with calcium isotopes in tooth enamel." Proceedings of the National Academy of Sciences 114, no. 24 (2017): 6268–73. http://dx.doi.org/10.1073/pnas.1704412114.

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Weaning practices differ among great apes and likely diverged during the course of human evolution, but behavioral inference from the fossil record is hampered by a lack of unambiguous biomarkers. Here, we show that early-life dietary transitions are recorded in human deciduous tooth enamel as marked variations in Ca isotope ratios (δ44/42Ca). Using a sequential microsampling method along the enamel growth axis, we collected more than 150 enamel microsamples from 51 deciduous teeth of 12 different modern human individuals of known dietary histories, as well as nine enamel samples from permanen

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23

Hassler, A., J. E. Martin, R. Amiot, et al. "Calcium isotopes offer clues on resource partitioning among Cretaceous predatory dinosaurs." Proceedings of the Royal Society B: Biological Sciences 285, no. 1876 (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 data

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24

Liu, Zhanmin, Congqiang Liu, Guilin Han, et al. "Environmental geochemistry of calcium isotopes: Applications of a new stable isotope approach." Chinese Journal of Geochemistry 25, no. 2 (2006): 184–94. http://dx.doi.org/10.1007/bf02872181.

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25

Griffin, Ian J., and 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 (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

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26

Ali, Ahmed H. "Investigation of the Quadrupole Moment and Form Factors of Some Ca Isotopes." Baghdad Science Journal 17, no. 2 (2020): 0502. http://dx.doi.org/10.21123/bsj.2020.17.2.0502.

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Nuclear shell model is adopted to calculate the electric quadrupole moments for some Calcium isotopes 20Ca (N = 21, 23, 25, and 27) in the fp shell. The wave function is generated using a two body effective interaction fpd6 and fp space model. The one body density matrix elements (OBDM) are calculated for these isotopes using the NuShellX@MSU code. The effect of the core-polarizations was taken through the theory microscopic by taking the set of the effective charges. The results for the quadrupole moments by using Bohr-Mottelson (B-M) effective charges are the best. The behavior of the form f

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27

MA, CHUN-WANG, HUI-LING WEI, and YU-QI LI. "THE SYSTEMATIC BEHAVIOR IN THE FRAGMENTS OF THE CALCIUM ISOTOPES PROJECTILE FRAGMENTATION." International Journal of Modern Physics E 19, no. 08n09 (2010): 1545–52. http://dx.doi.org/10.1142/s0218301310015941.

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We have calculated the cross sections of the fragments produced in the projectile fragmentation of the even 36–52 Ca isotopes using the statistical abrasion-ablation model. The isospin effect in the projectile fragmentation are studied by investigating the peak positions and the widths of the fragment isotopic cross section distributions. The peak positions of the fragments isotopic cross section distributions have good linear correlation to the Z of the fragments and the correlations are fitted using the linear function. The correlations between slopes b and the binding energies of the neutro

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28

Chambers, J., E. Zaremba, J. P. Adams, and B. Castel. "Pygmy dipole resonances in the calcium isotopes." Physical Review C 50, no. 6 (1994): R2671—R2674. http://dx.doi.org/10.1103/physrevc.50.r2671.

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29

Cheng-Rui, Ching, Ho Tso-Hsiu, and Zou Bing-Song. "Pion double-charge-exchange on calcium isotopes." Journal of Physics G: Nuclear and Particle Physics 17, no. 8 (1991): 1203–8. http://dx.doi.org/10.1088/0954-3899/17/8/010.

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30

Antonelli, Michael A., and Justin I. Simon. "Calcium isotopes in high-temperature terrestrial processes." Chemical Geology 548 (August 2020): 119651. http://dx.doi.org/10.1016/j.chemgeo.2020.119651.

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31

Smith, David L., Curtis Atkin, and Christof Westenfelder. "Stable isotopes of calcium as tracers: methodology." Clinica Chimica Acta 146, no. 1 (1985): 97–101. http://dx.doi.org/10.1016/0009-8981(85)90129-9.

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32

Zhu, Peng, and J. Douglas Macdougall. "Calcium isotopes in the marine environment and the oceanic calcium cycle." Geochimica et Cosmochimica Acta 62, no. 10 (1998): 1691–98. http://dx.doi.org/10.1016/s0016-7037(98)00110-0.

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33

Reynard, L. M., C. C. Day, and G. M. Henderson. "Large fractionation of calcium isotopes during cave-analogue calcium carbonate growth." Geochimica et Cosmochimica Acta 75, no. 13 (2011): 3726–40. http://dx.doi.org/10.1016/j.gca.2011.04.010.

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34

Skulan, Joseph, Thomas Bullen, Ariel D. Anbar, et al. "Natural Calcium Isotopic Composition of Urine as a Marker of Bone Mineral Balance." Clinical Chemistry 53, no. 6 (2007): 1155–58. http://dx.doi.org/10.1373/clinchem.2006.080143.

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Abstract Background: We investigated whether changes in the natural isotopic composition of calcium in human urine track changes in net bone mineral balance, as predicted by a model of calcium isotopic behavior in vertebrates. If so, isotopic analysis of natural urine or blood calcium could be used to monitor short-term changes in bone mineral balance that cannot be detected with other techniques. Methods: Calcium isotopic compositions are expressed as δ44Ca, or the difference in parts per thousand between the 44Ca/40Ca of a sample and the 44Ca/40Ca of a standard reference material. δ44Ca was

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35

Davidsson, Lena, Jill Mackenzie, Peter Kastenmayer, Peter J. Aggett, and Richard F. Hurrell. "Zinc and calcium apparent absorption from an infant cereal: a stable isotope study in healthy infants." British Journal of Nutrition 75, no. 2 (1996): 291–300. http://dx.doi.org/10.1017/bjn19960131.

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AbstractFractional apparent absorption of Zn and Ca from a wheat-milk-based infant cereal was studied in six healthy infants (18-30 weeks old). Mineral absorption was measured by a stable-isotope technique based on faecal excretion of the isotopes. Each test meal (40 g cereal) was extrinsically labelled with 70Zn and 42Ca before intake. All faecal material passed during the 21 d following intake of the labelled test meal was collected on trace-element-free nappies. Individual stool samples were analysed for their content of ‘OZn and 42Ca by thermal ionization mass spectrometry. Apparent absorp

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Adloff, Markus, Andy Ridgwell, Fanny M. Monteiro, et al. "Inclusion of a suite of weathering tracers in the cGENIE Earth system model – muffin release v.0.9.23." Geoscientific Model Development 14, no. 7 (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 bet

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Malikov, Sh R., M. B. Yuldashev, and O. O. Amanov. "Prospects for the application of nuclear reactor with homogeneous solution fuel for the production of medical radioisotopes." Journal of Physics: Conference Series 2642, no. 1 (2023): 012006. http://dx.doi.org/10.1088/1742-6596/2642/1/012006.

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Abstract The use of isotopes in medicine has opened up new possibilities for the diagnosis and treatment of many diseases. One of the effective radiopharmaceuticals is the strontium-89 isotope, which is used to treat many cancers, including bone cancer. Spreading and sorbing in the bone tissue (as an analog of calcium), strontium has both therapeutic and long-term analgesic effects. This allows you to do without drugs and saves the patient from severe drug addiction. Therefore, obtaining the radioisotope strontium-89 is a very serious task.

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38

Dill, Harald G., and Friedhelm Henjes-Kunst. "Strontium (87Sr/86Sr) and calcium isotope ratios (44Ca/40Ca-44Ca/42Ca) of the Miocene Dam Formation in Qatar: tools for stratigraphic correlation and environment analysis." GeoArabia 12, no. 3 (2007): 61–76. http://dx.doi.org/10.2113/geoarabia120361.

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ABSTRACT The Dam Formation in Qatar is a series consisting of calcareous (calcite, dolomite) and evaporitic sediments (gypsum, celestite) that developed under subtidal through supratidal conditions passing towards younger and older series in an environment of deposition more akin to modern beach deposits. In the present study 87Sr/86Sr ratios, δ44/40Ca and δ44/42Ca data are discussed together with δ13C and δ18O values obtained during an environmental analysis carried out previously. Rather uniform isotope curves of the Sr, Ca and O isotopes for tidal deposits are replaced by more oscillating o

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Lindau, Filipe G. L., Jefferson C. Simões, Barbara Delmonte, et al. "Giant dust particles at Nevado Illimani: a proxy of summertime deep convection over the Bolivian Altiplano." Cryosphere 15, no. 3 (2021): 1383–97. http://dx.doi.org/10.5194/tc-15-1383-2021.

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Abstract. A deeper understanding of past atmospheric circulation variability in the Central Andes is a high-priority topic in paleoclimatology mainly because of the necessity to validate climate models used to predict future precipitation trends and to develop mitigation and/or adaptation strategies for future climate change scenarios in this region. Within this context, we here investigate an 18-year firn core drilled at Nevado Illimani in order to interpret its mineral dust record in relation to seasonal processes, in particular atmospheric circulation and deep convection. The core was dated

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Beazley, Melanie J., Richard D. Rickman, Debra K. Ingram, Thomas W. Boutton, and Jon Russ. "Natural Abundances of Carbon Isotopes (14C, 13C) in Lichens and Calcium Oxalate Pruina: Implications for Archaeological and Paleoenvironmental Studies." Radiocarbon 44, no. 3 (2002): 675–83. http://dx.doi.org/10.1017/s0033822200032124.

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Radiocarbon ages of calcium oxalate that occurs naturally on rock surfaces have been used recently in archaeological and paleoenvironmental studies. Oxalate rock coatings are found globally, with most appearing to be residues from epilithic lichens. To explore the source(s) of carbon used by these organisms for the production of oxalate we measured the natural abundances of 14C and 13C in 5 oxalate-producing lichen species, 3 growing on limestone in southwestern Texas and 2 on sandstone in Arkansas. We also examined the distribution of the isotopes between the calcium oxalate and lichen tissue

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Gussone, Nikolaus, Anne-Sofie C. Ahm, Kimberly V. Lau, and Harold J. Bradbury. "Calcium isotopes in deep time: Potential and limitations." Chemical Geology 544 (June 2020): 119601. http://dx.doi.org/10.1016/j.chemgeo.2020.119601.

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In, Eun Jin, Youngman Kim, Panagiota Papakonstantinou, and Seung-Woo Hong. "Shape Coexistence in Isotopes from Oxygen to Calcium." Journal of the Korean Physical Society 77, no. 11 (2020): 966–70. http://dx.doi.org/10.3938/jkps.77.966.

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Throwe, T. G., S. E. Vigdor, W. W. Jacobs та ін. "Near-threshold (p→,π−) reactions on calcium isotopes". Physical Review C 35, № 3 (1987): 1083–98. http://dx.doi.org/10.1103/physrevc.35.1083.

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Oi, Takao, Norio Morioka, Hideki Ogino, Hidetake Kakihana, and Morikazu Hosoe. "Fractionation of Calcium Isotopes in Cation-Exchange Chromatography." Separation Science and Technology 28, no. 11-12 (1993): 1971–83. http://dx.doi.org/10.1080/01496399308016727.

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Gui, Jianye, and Wei Zou. "A New Sample Processing Protocol for Separation and Purification Enabling Precise Analysis of Various Non-Traditional Isotopes in Geological Samples with Low Concentrations." Separations 10, no. 9 (2023): 497. http://dx.doi.org/10.3390/separations10090497.

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Many non-traditional isotopes, such as chlorine, magnesium, calcium, etc., are widely used as groundwater tracers. A new sample processing protocol of purification and concentration for isotopic analysis is presented to overcome many of the major drawbacks of existing methods. Contemporary sample preparation often requires several laborious off-line procedures in a ultra clean laboratory prior to instrumental determination; additionally, interference ions in real samples are difficult to completely remove, especially when the concentration of those ions is equal to that of the target ions. The

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Whiticar, Michael J., Erwin Suess, Gerold Wefer, and Peter J. Müller. "Calcium Carbonate Hexahydrate (Ikaite): History of Mineral Formation as Recorded by Stable Isotopes." Minerals 12, no. 12 (2022): 1627. http://dx.doi.org/10.3390/min12121627.

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Calcium carbonate hexahydrate (ikaite) is a rare mineral that forms as metastable species in the organic-carbon-rich sediments of the King George Basin, Bransfield Strait, Antarctica, as a consequence of early diagenetic decomposition of organic matter under cold water (−1.4 °C) and high pressure (200 bar) conditions. Large crystals grow in the sediment immediately below the diagenetic transition between microbial sulfate reduction and methanogenesis at ~320 cm below sea floor (bsf). This process is reflected in the dissolved sulfate, total carbon dioxide, and methane concentrations, as well a

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Rasbury, E. Troy, and N. Gary Hemming. "Boron Isotopes: A “Paleo-pH Meter” for Tracking Ancient Atmospheric CO2." Elements 13, no. 4 (2017): 243–48. http://dx.doi.org/10.2138/gselements.13.4.243.

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The boron isotope composition of calcium carbonate shells of marine organisms has the unique potential to record surface ocean pH, allowing the calculation of atmospheric pCO2 due to the established relationship between pH and the partial pressure of (atmospheric) CO2 (pCO2). This “paleo-pH meter” allows scientists to produce a record of the natural fluctuations of atmospheric pCO2 over geologic time, which will help us better understand the impacts of the recent anthropogenic addition of CO2 to Earth's atmosphere. Towards this end, a tremendous effort to understand the systematics of boron up

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Shatalov, Oleg A., Maxim E. Grigoryev, Alexander A. Bukhvostov, and Dmitry A. Kuznetsov. "A Nuclear Spin Selective Control over the DNA Repair Key Enzyme Might Renovate the Cancer–Fight Paradigm. DNA Polymerase Beta to Engage with a Magnetic Isotope Effect." JOURNAL OF ADVANCES IN CHEMISTRY 4, no. 3 (2008): 554–62. http://dx.doi.org/10.24297/jac.v4i3.953.

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DNA Polymerase Beta (EC 2.7.7.7) is found to be operated by magnetic isotope effect (MIE) of Calcium once the Mg2+ ions replaced with the stable 43Ca2+ isotopes inside the enzyme catalytic sites. The isotope mentioned is the only paramagnetic species of the Calcium isotopic set with a 0.135 natural abundance value and the negative 7/2 nuclear spin providing a nuclear magnetic moment equal to 1.317 Bohr magnetons. As compared to the Mg/40Ca substitution, a 2.25-fold enzyme inhibition has been shown to provethe43Ca-MIE dependent mode of the catalysis turning down.An ion-radical mechanism based o

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Al-Paruany, Kamal B., Saadi Al-Naseri, and Al-Hassen F. Al-Ajena. "DISTRIBUTION OF ENVIRONMENTAL ISOTOPES IN THE EUPHRATES RIVER BETWEEN QAIM – FALLUJA, WESTERN IRAQ." Iraqi Geological Journal 50, no. 1 (2017): 12–27. http://dx.doi.org/10.46717/igj.50.1.2ms-2017-06-24.

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The environmental isotopes composition of water (δ18O, δ2Hand 3H) and hydrochemistry concentration were measured seasonally at eight stations along Euphrates River within the study area for two periods (January–Augustm, 2014) to study temporal special variations of these isotopes. The results of isotopes values showed there is a little difference between the periods due to the seasonal change and the trend of distribution can be attributed to evaporation and drainage flow. Generally the river water has positive d-excess, which indicates the vapor source of the Mediterranean moisture sources in

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Kilian, Krzysztof, Łukasz Cheda, Mateusz Sitarz, Katarzyna Szkliniarz, Jarosław Choiński, and Anna Stolarz. "Separation of 44Sc from Natural Calcium Carbonate Targets for Synthesis of 44Sc-DOTATATE." Molecules 23, no. 7 (2018): 1787. http://dx.doi.org/10.3390/molecules23071787.

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The rapid increase in applications of scandium isotopes in nuclear medicine requires new efficient production routes for these radioisotopes. Recently, irradiations of calcium in cyclotrons by α, deuteron, and proton beams have been used. Therefore, effective post-irradiation separation and preconcentration of the radioactive scandium from the calcium matrix are important to obtain the pure final product in a relatively small volume. Nobias resin was used as a sorbent for effective separation of 44Sc from calcium targets. Separation was performed at pH 3 using a column containing 10 mg of resi

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