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1
Chen, Ke, Bai Song, Navaneetha K. Ravichandran, Qiye Zheng, Xi Chen, Hwijong Lee, Haoran Sun, et al. "Ultrahigh thermal conductivity in isotope-enriched cubic boron nitride." Science 367, no. 6477 (January 9, 2020): 555–59. http://dx.doi.org/10.1126/science.aaz6149.
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Materials with high thermal conductivity (κ) are of technological importance and fundamental interest. We grew cubic boron nitride (cBN) crystals with controlled abundance of boron isotopes and measured κ greater than 1600 watts per meter-kelvin at room temperature in samples with enriched 10B or 11B. In comparison, we found that the isotope enhancement of κ is considerably lower for boron phosphide and boron arsenide as the identical isotopic mass disorder becomes increasingly invisible to phonons. The ultrahigh κ in conjunction with its wide bandgap (6.2 electron volts) makes cBN a promising material for microelectronics thermal management, high-power electronics, and optoelectronics applications.
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Barrick, Reese E., and William J. Showers. "Oxygen isotope variability in juvenile dinosaurs (Hypacrosaurus): evidence for thermoregulation." Paleobiology 21, no. 4 (1995): 552–60. http://dx.doi.org/10.1017/s0094837300013531.
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Small terrestrial vertebrates are not capable of maintaining a constant body temperature (±2°C) without a relatively high metabolism. The amount of temperature variability during bone growth can be determined using oxygen isotopes from bone phosphate because fractionation of oxygen isotopes between body fluid and bone phosphate is dependent upon temperature. Fluctuation of body temperature during the early phase of growth in juvenile ectotherms should result in high intra- and interbone isotopic variability, whereas juvenile endotherms should have low isotopic variability resulting from the maintenance of homeothermy. Analyses of juvenile Hypacrosaurus individuals indicate a pattern of low isotopic heterogeneity suggestive of endothermy.
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Ford, William, Mark R. Williams, Megan B. Young, Kevin W. King, and Eric Fischer. "Assessing Intra-Event Phosphorus Dynamics in Drainage Water Using Phosphate Stable Oxygen Isotopes." Transactions of the ASABE 61, no. 4 (2018): 1379–92. http://dx.doi.org/10.13031/trans.12804.
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Abstract. Quantifying fluxes and pathways of dissolved reactive phosphorus (DRP) in tile-drained landscapes has been hampered by a lack of measurements that are sensitive to P fate and transport processes. One potential tool to help understand these dynamics is the oxygen isotope signature of phosphate (d18OPO4); however, its potential benefits and limitations are not well understood for intra-event dynamics at the field scale. The objectives of this study were to quantify intra-event variability of d18OPO4 signatures in tile drainage water and assess the efficacy of d18OPO4 to elucidate mechanisms and flow pathways controlling DRP transport to tile drains. We collected water samples during a summer storm event from a subsurface (tile)-drained field located in west-central Ohio and analyzed for d18OPO4 of DRP. Supplementary water quality measurements, hydrologic modeling, and soil temperature data were used to help understand intra-event d18OPO4 dynamics. Results of the soil extraction analysis from our study site highlight that the soil water-extractable P (WEP) pool was not in equilibrium with long-term, temperature-dependent water isotope values. This result suggests that P-rich soils may, at least partially, retain their original source signature, which has significant implications for identifying hotspots of P delivery in watershed-scale applications. Results of the storm event analysis highlight that equilibration of leached DRP in soil water creates a gradient between isotopic compositions of pre-event shallow subsurface sources, pre-event deep subsurface sources, and the WEP tied up in surface soils. The current study represents the first intra-event analysis of d18OPO4 and highlights the potential for phosphate oxygen isotopes as a novel tool to improve understanding of P fate and transport in artificially drained agroecosystems. Keywords: Agriculture, Edge-of-field, Macropores, Phosphate oxygen isotopes, Tile-drainage.
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Navarro, Nicolas, Christophe Lécuyer, Sophie Montuire, Cyril Langlois, and François Martineau. "Oxygen isotope compositions of phosphate from arvicoline teeth and Quaternary climatic changes, Gigny, French Jura." Quaternary Research 62, no. 2 (September 2004): 172–82. http://dx.doi.org/10.1016/j.yqres.2004.06.001.
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Oxygen isotope compositions of biogenic phosphates from mammals are widely used as proxies of the isotopic compositions of meteoric waters that are roughly linearly related to the air temperature at high- and mid-latitudes. An oxygen isotope fractionation equation was determined by using present-day European arvicoline (rodents) tooth phosphate: δ18Op = 20.98(±0.59) + 0.572(±0.065) δ18Ow. This fractionation equation was applied to the Late Pleistocene karstic sequence of Gigny, French Jura. Comparison between the oxygen isotope compositions of arvicoline tooth phosphate and Greenland ice core records suggests to reconsider the previously established hypothetical chronology of the sequence. According to the δ18O value of meteoric water–mean air temperature relationships, the δ18O value of arvicoline teeth records variations in mean air temperatures that range from 0° to 15°C.
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Lisowska-Gaczorek, Aleksandra, Krzysztof Szostek, Jacek Pawlyta, and Beata Cienkosz-Stepańczak. "Oxygen isotopic fractionation in rat bones as a result of consuming thermally processed water – bioarchaeological applications." Geochronometria 47, no. 1 (May 4, 2020): 1–12. http://dx.doi.org/10.2478/geochr-2020-0001.
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AbstractStable isotope analyses of oxygen are used in anthropology for such purposes as determination of origin of individuals, tracking migration routes or dynamics of human community relocation. The methodology related to oxygen isotope analysis has been founded on the relationship between its isotopic composition within phosphate groups of bone tissue (δ18Op) in individuals being analysed and the water consumed by such individuals (δ18Ow). Such a relationship has been observed in many species of mammals, including humans. However, the influence of culinary practices on the isotopic delta values of apatite phosphates of individuals has not yet been researched. The present study, which was conducted using laboratory rats, is an investigation of the influence of the thermal processing of water drank by such rats on the isotopic composition (δ18Op) of bone apatite. Increasing the value of the isotopic composition of water by about 6.1 ‰ during boiling resulted in an increase in the oxygen isotopic value δ18Op of rats drinking the water by about 4 ‰ (29%). It can be expected that regular consumption of heavily isotopic drinks and foods by humans may cause the δ18Op of individuals to exceed the range of isotopic environmental variability, even by a few per mille.
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Vickers, J. D., and J. F. Mustard. "The phosphoinositides exist in multiple metabolic pools in rabbit platelets." Biochemical Journal 238, no. 2 (September 1, 1986): 411–17. http://dx.doi.org/10.1042/bj2380411.
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The labelling of the phosphoinositides and phosphatidic acid in washed rabbit platelets incubated with [32P]phosphate or [3H]glycerol was studied in the presence of isotope and after unincorporated isotope had been removed. With both isotopes the increase in the specific radioactivity of phosphatidylinositol 4,5-bisphosphate (PIP2) lagged behind that of phosphatidylinositol 4-phosphate (PIP) but the specific radioactivity remained higher after unincorporated isotope had been removed. This result was consistent with the presence of a second pool of PIP2, which interconverted slowly with the pool of PIP2 which was in direct equilibrium with PIP, proposed to explain the increase in specific radioactivity of PIP2 which accompanies the decrease in amount of PIP2 at 10 s in ADP-stimulated platelets. In platelets labelled with [3H]glycerol, the specific radioactivity of PIP2 became higher than that of PIP and the specific radioactivity of PIP became higher than that of phosphatidylinositol (PI). These results were interpreted to indicate that there were two pools of PIP; of these the pool with the higher specific radioactivity was the precursor of PIP2. Similarly, two pools of PI were proposed. The presence of pools of the phosphoinositides with different specific radioactivities necessitates the measurement of chemical amount of these compounds when studying the effect of stimulation of the platelets, since changes in labelling may not accurately reflect changes in the amount of the phosphoinositides.
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Nagatsuka, Naoko, Nozomu Takeuchi, Ki-Cheol Shin, and Takanori Nakano. "Spatial variations of Sr–Nd isotopic ratios, mineralogical and elemental compositions of cryoconite in an Alaskan glacier." Annals of Glaciology 59, no. 77 (December 2018): 147–58. http://dx.doi.org/10.1017/aog.2019.2.
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ABSTRACTTo understand the geological origins of minerals in cryoconite and the nutrients sources for microbes on glaciers, we analyzed the Sr–Nd isotopic ratios of the four mineral fractions in cryoconites including saline, carbonate, phosphate, silicate and the organic fraction obtained from Gulkana Glacier in Alaska. The isotopes in the silicate mineral fraction exhibited spatial variation within the glacier (87Sr/86Sr: 0.704533–0.709563, εNd (0): −16.0 to 0.5), which can be explained by the different mixing ratios of the two distinct sources: one of the sources is lateral and terminal moraines or soil, and the other is the medial moraine of the glacier. The minerals in the cryoconite at the lower sites in the glacier are likely derived from the former source, whereas those at the upper sites are from latter sources. The mineralogical and elemental compositions also support mixing of the silicate minerals from the two local sources. The Sr isotopic ratios of the organic fraction also showed spatial variation on the glacier in the middle sites – a trend similar to those of the phosphate fraction. The results suggest that the organic matter is mostly the byproducts of microbes using the phosphate minerals as a nutrient source.
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v. Sperber, C., F. Tamburini, B. Brunner, S. M. Bernasconi, and E. Frossard. "The oxygen isotope composition of phosphate released from phytic acid by the activity of wheat and <i>Aspergillus niger</i> phytase." Biogeosciences Discussions 12, no. 6 (March 30, 2015): 5055–77. http://dx.doi.org/10.5194/bgd-12-5055-2015.
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Abstract. Phosphorus (P) is an essential nutrient for living organisms. Under P-limiting conditions plants and microorganisms can exude extracellular phosphatases that release inorganic phosphate (Pi) from organic phosphorus compounds (Porg). Phytic acid (IP6) is an important form of Porg in many soils. The enzymatic hydrolysis of IP6 by phytase yields plant available inorganic phosphate (Pi) and less phosphorylated inositol derivates as products. The hydrolysis of organic P-compounds by phosphatases leaves an isotopic imprint on the oxygen isotope composition (δ18O) of released Pi, which might be used to trace P in the environment. This study aims at determining the effect of phytase on the oxygen isotope composition of released Pi. For this purpose, enzymatic assays with histidine acid phytases from wheat and Aspergillus niger were prepared using IP6, adenosine 5'monophosphate (AMP) and glycerophosphate (GPO4) as substrates. For a comparison to the δ18O of Pi released by other extracellular enzymes, enzymatic assays with acid phosphatases from potato and wheat germ with IP6 as substrate were prepared. During the hydrolysis of IP6 by phytase, four Pi are released, and one oxygen atom from water is incorporated into each Pi. This incorporation of oxygen from water into Pi is subject to an apparent inverse isotopic fractionation (&varepsilon; ∼ 6 to 10‰), which is similar to that imparted by acid phosphatase from potato during the hydrolysis of IP6 (&varepsilon; ∼ 7‰) where less than three Pi are released. The incorporation of oxygen from water into Pi during the hydrolysis of AMP and GPO4 by phytase yielded a normal isotopic fractionation (&varepsilon; ∼ −12‰), again similar to values reported for acid phosphatases from potato and wheat germ. We attribute this similarity in ε to the same amino acid sequence motif (RHGXRXP) at the active site of these enzymes, which leads to similar reaction mechanisms. We suggest that the striking substrate-dependency of the isotopic fractionation could be attributed to a difference in the δ18O-values of the C-O-P bridging and non-bridging oxygen atoms in organic phosphate compounds.
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Matveyeva, Ilona, Fatima Meiirman, Nurgul Nursapina, Bagdat Satybaldiyev, Tamara Tuzova, Zhandos Shalabayev, and Balnur Shynybek. "Concentration of uranium isotopes by in-situ coprecipitation on activated coal and iron (III) hydroxide." Chemical Bulletin of Kazakh National University, no. 1 (March 29, 2019): 4–11. http://dx.doi.org/10.15328/cb1000.
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The use of the method of nonequilibrium uranium in various branches of science led to the necessity to determine its isotopic composition. The content of uranium isotopes in natural waters is often extremely low, therefore, it is necessary to collect significant volumes of samples in order to obtain reliable results of analysis. In this paper, it is proposed to concentrate uranium isotopes from water in-situ. Two alternative methods of uranium coprecipitation in field conditions (on activated carbon and iron (III) hydroxide) are considered. The desorbed uranium isotopes are determined by an alpha-spectrometric method with preliminary radiochemical preparation in laboratory conditions, including extraction with tributyl phosphate and electrodeposition on a steel disc. It was found that when concentrating on activated carbon the chemical yield was from 2 to 32%, and when concentrating on iron (III) hydroxide it is from 15 to 62%. For the second case, the chemical yield is acceptable for radiochemical work, and the proposed method for concentrating of uranium isotopes is recommended for usage in field conditions. Approbation of the method was carried out within the framework of the PEER454 project in 2017 in the valley of the river Ziddy, Pamir-Alay, Republic of Tajikistan. Work in the field conditions showed high efficiency of the method and its full feasibility even in the absence of acceptable laboratory conditions.
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Sauze, Joana, Sam P. Jones, Lisa Wingate, Steven Wohl, and Jérôme Ogée. "The role of soil pH on soil carbonic anhydrase activity." Biogeosciences 15, no. 2 (January 30, 2018): 597–612. http://dx.doi.org/10.5194/bg-15-597-2018.
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Abstract. Carbonic anhydrases (CAs) are metalloenzymes present in plants and microorganisms that catalyse the interconversion of CO2 and water to bicarbonate and protons. Because oxygen isotopes are also exchanged during this reaction, the presence of CA also modifies the contribution of soil and plant CO18O fluxes to the global budget of atmospheric CO18O. The oxygen isotope signatures (δ18O) of these fluxes differ as leaf water pools are usually more enriched than soil water pools, and this difference is used to partition the net CO2 flux over land into soil respiration and plant photosynthesis. Nonetheless, the use of atmospheric CO18O as a tracer of land surface CO2 fluxes requires a good knowledge of soil CA activity. Previous studies have shown that significant differences in soil CA activity are found in different biomes and seasons, but our understanding of the environmental and ecological drivers responsible for the spatial and temporal patterns observed in soil CA activity is still limited. One factor that has been overlooked so far is pH. Soil pH is known to strongly influence microbial community composition, richness and diversity in addition to governing the speciation of CO2 between the different carbonate forms. In this study we investigated the CO2–H2O isotopic exchange rate (kiso) in six soils with pH varying from 4.5 to 8.5. We also artificially increased the soil CA concentration to test how pH and other soil properties (texture and phosphate content) affected the relationship between kiso and CA concentration. We found that soil pH was the primary driver of kiso after CA addition and that the chemical composition (i.e. phosphate content) played only a secondary role. We also found an offset between the δ18O of the water pool with which CO2 equilibrates and total soil water (i.e. water extracted by vacuum distillation) that varied with soil texture. The reasons for this offset are still unknown.
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Ellwood, Michael J., Robert Strzepek, Xiaoyu Chen, Thomas W. Trull, and Philip W. Boyd. "Some observations on the biogeochemical cycling of zinc in the Australian sector of the Southern Ocean: a dedication to Keith Hunter." Marine and Freshwater Research 71, no. 3 (2020): 355. http://dx.doi.org/10.1071/mf19200.
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In this study we investigated the distribution of dissolved and particulate zinc (dZn and pZn respectively) and its isotopes in the Subantarctic Zone as part of a Geotraces Process voyage. dZn and pZn depth profiles contrasted each other, with dZn showing depletion within the euphotic zone while pZn profiles showed enrichment. Fitting a power law equation to the pZn profiles produced an attenuation factor of 0.82, which contrasted values for particulate phosphorus, cadmium and copper. The results indicate that zinc has a longer regeneration length scale than phosphorus and cadmium, but shorter than copper. The differential regeneration of pZn relative to that of particulate phosphorus likely explains why dZn appears to have a deeper regeneration profile than that of phosphate. The dZn isotope (δ66Zndissolved) profiles collected across the Subantarctic Zone showed differing profile structures. For one station collected within an isolated cold-core eddy (CCE), δ66Zndissolved showed surface enrichment relative to deep waters. The corresponding pZn isotope profiles within the CCE did not show enrichment; rather, they were subtly depleted in surface waters and then converged to similar values at depth. Zinc isotope fractionation can be explained through a combination of fractionation processes associated with uptake by phytoplankton, zinc complexation by natural organic ligands and zinc regeneration from particulate matter.
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Sharma, Shikha, Michael M. Joachimski, Heinz J. Tobschall, Indra B. Singh, Devi P. Tewari, and Rakesh Tewari. "Oxygen isotopes of bovid teeth as archives of paleoclimatic variations in archaeological deposits of the Ganga plain, India." Quaternary Research 62, no. 1 (July 2004): 19–28. http://dx.doi.org/10.1016/j.yqres.2004.03.003.
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Oxygen isotope analysis was performed on enamel phosphate of mammalian teeth from archaeological sites Kalli Pachchhim and Dadupur in the central Ganga plain and Charda in the northern Ganga plain. The bulk oxygen isotopic compositions of enamel phosphate from third molars (M3) of Bos indicus individuals belonging to different cultural periods were used to understand the climatic changes during the past 3600 cal yr B.P. Oxygen isotope ratios indicate humid conditions around 3600 cal yr B.P., followed by a trend toward drier conditions until around 2800 cal yr B.P. Then from 2500 to 1500 cal yr B.P. there is a trend toward higher humidity, followed by the onset of a dry period around 1300 cal yr B.P. The study of intratooth δ18O variations in teeth from different periods demonstrates that the monsoon seasonality was prominent. Spatial changes in the amount of annual rainfall are also reflected in the δ18O values. Teeth derived from areas with intense rainfall have lighter isotope ratios compared to teeth from regions receiving less rain, but they show similar seasonal patterns. The long-term paleoclimatic variations reflected by fluctuations in bulk δ18Op values from M3 teeth match well with the regional paleoenvironmental records and show a good correlation to the cultural changes that took place during this time span in Ganga plain.
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von Sperber, C., F. Tamburini, B. Brunner, S. M. Bernasconi, and E. Frossard. "The oxygen isotope composition of phosphate released from phytic acid by the activity of wheat and <i>Aspergillus niger</i> phytase." Biogeosciences 12, no. 13 (July 14, 2015): 4175–84. http://dx.doi.org/10.5194/bg-12-4175-2015.
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Abstract. Phosphorus (P) is an essential nutrient for living organisms. Under P-limiting conditions plants and microorganisms can exude extracellular phosphatases that release inorganic phosphate (Pi) from organic phosphorus compounds (Porg). Phytic acid (myo-inositol hexakisphosphate, IP6) is an important form of Porg in many soils. The enzymatic hydrolysis of IP6 by phytase yields available Pi and less phosphorylated inositol derivates as products. The hydrolysis of organic P compounds by phosphatases leaves an isotopic imprint on the oxygen isotope composition (δ18O) of released Pi, which might be used to trace P in the environment. This study aims at determining the effect of phytase on the oxygen isotope composition of released Pi. For this purpose, enzymatic assays with histidine acid phytases from wheat and Aspergillus niger were prepared using IP6, adenosine 5'-monophosphate (AMP) and glycerophosphate (GPO4) as substrates. For a comparison to the δ18O of Pi released by other extracellular enzymes, enzymatic assays with acid phosphatases from potato and wheat germ with IP6 as a substrate were prepared. During the hydrolysis of IP6 by phytase, four of the six Pi were released, and one oxygen atom from water was incorporated into each Pi. This incorporation of oxygen from water into Pi was subject to an apparent inverse isotopic fractionation (&varepsilon; ~ 6 to 10 ‰), which was similar to that imparted by acid phosphatase from potato during the hydrolysis of IP6 (&varepsilon; ~ 7 ‰), where less than three Pi were released. The incorporation of oxygen from water into Pi during the hydrolysis of AMP and GPO4 by phytase yielded a normal isotopic fractionation (&varepsilon; ~ −12 ‰), similar to values reported for acid phosphatases from potato and wheat germ. We attribute this similarity in &varepsilon; to the same amino acid sequence motif (RHGXRXP) at the active site of these enzymes, which leads to similar reaction mechanisms. We suggest that the striking substrate dependency of the isotopic fractionation could be attributed to a difference in the δ18O values of the C–O–P bridging and non-bridging oxygen atoms in organic phosphate compounds.
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Hasenour, Clinton M., Martha L. Wall, D. Emerson Ridley, Curtis C. Hughey, Freyja D. James, David H. Wasserman, and Jamey D. Young. "Mass spectrometry-based microassay of 2H and 13C plasma glucose labeling to quantify liver metabolic fluxes in vivo." American Journal of Physiology-Endocrinology and Metabolism 309, no. 2 (July 15, 2015): E191—E203. http://dx.doi.org/10.1152/ajpendo.00003.2015.
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Mouse models designed to examine hepatic metabolism are critical to diabetes and obesity research. Thus, a microscale method to quantitatively assess hepatic glucose and intermediary metabolism in conscious, unrestrained mice was developed. [13C3]propionate, [2H2]water, and [6,6-2H2]glucose isotopes were delivered intravenously in short- (9 h) and long-term-fasted (19 h) C57BL/6J mice. GC-MS and mass isotopomer distribution (MID) analysis were performed on three 40-μl arterial plasma glucose samples obtained during the euglycemic isotopic steady state. Model-based regression of hepatic glucose and citric acid cycle (CAC)-related fluxes was performed using a comprehensive isotopomer model to track carbon and hydrogen atom transitions through the network and thereby simulate the MIDs of measured fragment ions. Glucose-6-phosphate production from glycogen diminished, and endogenous glucose production was exclusively gluconeogenic with prolonged fasting. Gluconeogenic flux from phospho enolpyruvate (PEP) remained stable, whereas that from glycerol modestly increased from short- to long-term fasting. CAC flux [i.e., citrate synthase ( V CS)] was reduced with long-term fasting. Interestingly, anaplerosis and cataplerosis increased with fast duration; accordingly, pyruvate carboxylation and the conversion of oxaloacetate to PEP were severalfold higher than V CS in long-term fasted mice. This method utilizes state-of-the-art in vivo methodology and comprehensive isotopomer modeling to quantify hepatic glucose and intermediary fluxes during physiological stress in mice. The small plasma requirements permit serial sampling without stress and the affirmation of steady-state glucose kinetics. Furthermore, the approach can accommodate a broad range of modeling assumptions, isotope tracers, and measurement inputs without the need to introduce ad hoc mathematical approximations.
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Spence, Michael W., Karyn Olsen, M. Oralia Cabrera Cortés, and Fred J. Longstaffe. "San José 520: An Unusual Teotihuacan Settlement System." Latin American Antiquity 31, no. 4 (August 20, 2020): 720–32. http://dx.doi.org/10.1017/laq.2020.59.
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San José 520 is a Classic period hamlet of single-family residences in the urban periphery of Teotihuacan, just beyond the southeast edge of the city. Three burial features were associated with one of the residences, AF2. One of the features contained the burial of a single adult, another the successive burials of eight adults and one neonate, and the third held a neonate. We analyzed 29 bone and enamel samples from the adults for bioapatite phosphate oxygen-isotope composition; we also considered isotopic data for another five bone samples analyzed in a separate project. The isotopic results suggest a pattern of birth in the Teotihuacan region and then movement in early childhood to a “relocation” region, the geographic location of which is unknown. Later, probably in adolescence, the individuals returned to live, and eventually die, in San José 520. Without knowing more about the occupation of the relocation region, it is difficult to say what concerns or beliefs underlay this unusual but long-established settlement system.
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Fisher, T. R., and D. R. S. Lean. "Interpretation of Radiophosphate Dynamics in Lake Waters." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 2 (February 1, 1992): 252–58. http://dx.doi.org/10.1139/f92-029.
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Models of planktonic phosphorus dynamics over the last 30–40 yr depend on the steady-state distribution of isotope for the determination of compartment size. Radiophosphate data for P-deficient lakes in summer have shown a steady-state distribution of 1–15% of 32P in the filtrate within 0.5–5 h. To explain this, a phosphate back-flux term from the particulate fraction has been widely accepted (phosphate is believed to be released from the internal pools of phosphate consumers and by excretion from herbivores and bacterivores). We show that dialysis of lake water at isotopic steady state provides values for the dissolved [32P]PO4 compartment up to an order of magnitude lower than those obtained by membrane filtration and gel filtration chromatography. This apparently occurs as a result of minor cell damage during filtration when most of the [32P]PO4 is in the particulate pool. Consequently, the size of the phosphate pool and the magnitudes of phosphate uptake and back-flux may have been overestimated by up to a factor of 10. Furthermore, the turnover time of the particulate compartment lengthens from ~ 40 min to > 1 d, which is more consistent with models describing P fluxes between functional components of the plankton.
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Chervyatsova, O. Ya, S. S. Potapov, L. V. Leonova, J. Baker, and R. S. Dbar. "Mineral sediments of the Kholodnyy grotto cave(Bzyb Gorge, Abkhazia) and d13C carbon and d18O oxygenisotope composition of karstogenic carbonates." Vestnik of Geosciences 10 (2020): 12–21. http://dx.doi.org/10.19110/geov.2020.10.2.
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The article is devoted to the results of the study of the mineral and isotopic composition of speleothems of the of the Kholodnyy Grotto cavein the Bzyb gorge of Abkhazia. The cavity was mapped and various types of secondary mineral deposits were recorded. The following mineral formations (speleothems) have been established in the cave: Mondmilch, corallites, guhrs, carbonate breccias, biogenic phosphates. Attention is drawn to the abundance of allogeneic mineral inclusions in drip calcite associated with the weathering products of igneous rocks (zircon, potassium feldspar, ilmenite, rutile, monazite, apatite). The source of these minerals is presumably the weathering crust of the Middle Jurassic volcanics. The oxygen isotope composition of all studied carbonates reflects the participation of meteoric waters. Moreover, the isotopic composition of carbon is subject to significant variations associated with kinetic fractionation (CO2 degassing). Based on the results of petrographic and isotopic studies, an attempt was made to typify speleothems according to the nature of their feeding and the characteristics of crystallization. Also, the cave revealed phosphate mineralization in the form of dark brown thin-layered crusts of hydroxylapatite, formed in place of old guano deposits.
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Lottermoser, Bernd G. "Trace metal enrichment in sugarcane soils due to the long-term application of fertilisers, North Queensland, Australia: geochemical and Pb, Sr, and U isotopic compositions." Soil Research 47, no. 3 (2009): 311. http://dx.doi.org/10.1071/sr06178.
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This study aimed to determine whether >80 years of fertiliser application has led to recognisable changes in the trace metal (Cd, Cu, Mo, Ni, Pb, Sr, Th, U, Zn) chemistry of topsoils (0–0.10 m) from sugarcane land, northern Queensland, Australia. The metal concentrations of commercial nitrogen (N) and potassium (K) fertilisers currently used in northern Queensland were generally lower than those of phosphate fertilisers and fertiliser blends. Composite topsoil samples (0–0.10 m depth) taken from canelands had higher median Cd, Mo, Pb, Sr, Th, U, and Zn concentrations than topsoils from forested areas of the catchment. Niobium, Ta, and Ti were confirmed as refractory immobile elements and used as reference elements for the evaluation of trace metal enrichments. Bivariate plots of trace metal/immobile element ratios verified that Cd, Mo, Pb, Sr, Th, U, and Zn are enriched in sugarcane soils compared with background forest soils. Isotopic ratios for Pb, Sr, and U highlight that fertilisers, cane soils, and forest soils have isotopically distinct compositions. Phosphate fertilisers currently used in the agricultural industry possess the most radiogenic 87Sr/86Sr, 234U/238U, 207Pb/206Pb, and 208Pb/206Pb ratios. Background forest soils have the highest 87Sr/86Sr, 207Pb/206Pb, and 208Pb/206Pb and lowest 234U/238U ratios. By contrast, cane soils exhibit 207Pb/206Pb and 208Pb/206Pb ratios that appear on a mixing line between the isotopically distinct background soils and phosphate fertilisers. Also, cane soils possess 234U/238U ratios similar to phosphate fertilisers. Thus, the application of phosphate fertilisers to canelands has resulted in higher Cd, Mo, Pb, Sr, Th, U, and Zn concentrations and more radiogenic Pb, Sr, and U isotope ratios in cane soils. Trace metal ratios and the Pb, Sr, and U isotopic composition of topsoils and fertilisers are useful tools to recognise fertiliser-derived trace metals in agricultural landscapes.
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Preuß, Andrea, Rolf Schauder, Georg Fuchs, and Willibald Stichler. "Carbon Isotope Fractionation by Autotrophic Bacteria with Three Different C02 Fixation Pathways." Zeitschrift für Naturforschung C 44, no. 5-6 (June 1, 1989): 397–402. http://dx.doi.org/10.1515/znc-1989-5-610.
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Abstract Carbon isotope fractionation during autotrophic growth o f different bacteria which possess different autotrophic CO2 fixation pathways has been studied. 13C /12C -Ratios in the cell carbon of the following bacteria were determined (CO2 fixation pathway suggested or proven in parentheses): Alkaligenes eutrophus (reductive pentose phosphate cycle), Desulfobacterium autotrophicum and Acetobacterium woodii (reductive acetyl-CoA pathway), Desulfobacter hydrogenophilus and Thermoproteus neutrophilus (reductive citric acid cycle). The Δδ13C values, which indicate the per mille deviation of the 13C content of cell carbon from that of the CO : used as the sole carbon source, range from - 10%° (reductive citric acid cycle) over - 26%° (reductive pentose phosphate cycle) to -36%° (reductive acetyl-CoA pathway). Acetate formed via the acetyl-CoA pathway by the acetogenic Acetobacterium woodii showed a Δδ13C = -40%°. These data are discussed in view of the different CO2 fixation reactions used by the bacteria and especially with regard to the isotopic composition of sedimentary carbon through time.
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Harms, Natalie C., Niko Lahajnar, Birgit Gaye, Tim Rixen, Kirstin Dähnke, Markus Ankele, Ulrich Schwarz-Schampera, and Kay-Christian Emeis. "Nutrient distribution and nitrogen and oxygen isotopic composition of nitrate in water masses of the subtropical southern Indian Ocean." Biogeosciences 16, no. 13 (July 12, 2019): 2715–32. http://dx.doi.org/10.5194/bg-16-2715-2019.
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Abstract. The Indian Ocean subtropical gyre (IOSG) is one of five extensive subtropical gyres in the world's ocean. In contrast to those of the Atlantic and Pacific oceans, the IOSG has been sparsely studied. We investigate the water mass distributions based on temperature, salinity and oxygen data, and the concentrations of water column nutrients and the stable isotope composition of nitrate, using water samples collected between ∼30∘ S and the Equator during two expeditions: MSM 59/2 in 2016 and SO 259 in 2017. Our results are the first from this oceanic region and provide new information on nitrogen sources and transformation processes. We identify the thick layer of nutrient-depleted surface waters of the oligotrophic IOSG with nitrate (NO3-) and phosphate (PO43-) concentrations of < 3 and < 0.3 µmol kg−1, respectively (< 300 m; σ < 26.4 kg−1 m−3). Increased nutrient concentrations towards the Equator represent the northern limb of the gyre, which is characterized by typical strong horizontal gradients of the outcropping nutriclines. The influx of the Subantarctic Mode Water (SAMW) from the Southern Ocean injects oxygen-saturated waters with preformed nutrients, indicated by the increased N and O isotope composition of nitrate (δ15N > 7 ‰; δ18O > 4 ‰) at 400–500 m (26.6–26.7 kg−1 m−3), into the subtropical thermocline. These values reflect partial N assimilation in the Southern Ocean. Moreover, in the northern study area, a residue of nitrate affected by denitrification in the Arabian Sea is imported into intermediate and deep water masses (> 27.0 kg−1 m−3) of the gyre, indicated by an N deficit (N* ∼-1 to −4 µmol kg−1) and by elevated isotopic ratios of nitrate (δ15N > 7 ‰; δ18O > 3 ‰). Remineralization of partially assimilated organic matter, produced in the subantarctic, leads to a decoupling of N and O isotopes in nitrate and results in a relatively low Δ(15–18) value of < 3 ‰ within the SAMW. In contrast, remineralization of 15N-enriched organic matter from the Arabian Sea indicates higher Δ(15–18) values of > 4 ‰ within the Red Sea–Persian Gulf Intermediate Water (RSPGIW). Thus, the subtropical southern Indian Ocean is supplied by preformed nitrate from the lateral influx of water masses from regions exhibiting distinctly different N-cycle processes documented in the dual isotope composition of nitrate. Additionally, a significant contribution of N2 fixation between 20.36 and 23.91∘ S is inferred from reduced δ15N–NO3- values towards surface waters (upward decrease of δ15N ∼2.4 ‰), N* values of > 2 µmol kg−1 and a relatively low Δ(15–18) value of < 3 ‰. A mass and isotope budget implies that at least 32 %–34 % of the nitrate in the upper ocean between 20.36 and 23.91∘ S is provided from newly fixed nitrogen, whereas N2 fixation appears to be limited by iron or temperature south of 26∘ S.
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Szostek, Krzysztof, Beata Stepańczak, Anita Szczepanek, Małgorzata Kępa, Henryk Głąb, Paweł Jarosz, Piotr Włodarczak, et al. "Diagenetic signals from ancient human remains - bioarchaeological applications." Mineralogia 42, no. 2-3 (January 1, 2011): 93–112. http://dx.doi.org/10.2478/v10002-011-0009-4.
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Diagenetic signals from ancient human remains - bioarchaeological applications This preliminary study examines the potential effects of diagenetic processes on the oxygen-isotope ratios of bone and tooth phosphate (δ18O) from skeletal material of individuals representing the Corded Ware Culture (2500-2400 BC) discovered in Malżyce (Southern Poland). Intra-individual variability of Ca/P, CI, C/P, collagen content (%) and oxygen isotopes was observed through analysis of enamel, dentin and postcranial bones. Using a variety of analytical techniques, it was found that, despite the lack of differences in soil acidity, not all the parts of a skeleton on a given site had been equally exposed to diagenetic post mortem changes. In a few cases, qualitative changes in the FTIR spectrum of analysed bones were observed. The data suggest that apart from quantitative analyses, i.e., the calculation of Ca/P, CI, C/P and collagen content, qualitative analyses such as examination of the absorbance line are recommended. The degree to which a sample is, contaminated on the basis of any additional, non-biogenic peaks, deemed to be contaminated should also be specified.
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HUANG, Ter-Mei, Hui-Chih HUNG, Tsu-Chung CHANG, and Gu-Gang CHANG. "Solvent kinetic isotope effects of human placental alkaline phosphatase in reverse micelles." Biochemical Journal 330, no. 1 (February 15, 1998): 267–75. http://dx.doi.org/10.1042/bj3300267.
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Human placental alkaline phosphatase was embedded in a reverse micellar system prepared by dissolving the surfactant sodium bis(2-ethylhexyl) sulphosuccinate (Aerosol-OT) in 2,2,4-trimethylpentane. This microemulsion system provides a convenient instrumental tool to study the possible kinetic properties of the membranous enzyme in an immobilized form. The pL (pH/p2H) dependence of hydrolysis of 4-nitrophenyl phosphate has been examined over a pL range of 8.5-12.5 in both aqueous and reverse micellar systems. Profiles of log V versus pL were Ha-bell shaped in the acidic region but reached a plateau in the basic region in which two pKa values of 9.01-9.71 and 9.86-10.48, respectively, were observed in reverse micelles. However, only one pKa value of 9.78-10.27 in aqueous solution was detected. Profiles of log V/K versus pL were bell-shaped in the acidic region. However, they were wave-shaped in the basic region in which a residue of pKa 9.10-9.44 in aqueous solution and 8.07-8.78 in reverse micelles must be dehydronated for the reaction to reach an optimum. The V/K value shifted to a lower value upon dehydronation of a pKa value of 9.80-10.62 in aqueous solution and 11.23-12.17 in reverse micelles. Solvent kinetic isotope effects were measured at three pL values. At pL 9.5, the observed isotope effect was a product of equilibrium isotope effect and a kinetic isotope effect; at pL 10.4, the log V/K value was identical in water and deuterium. The deuterium kinetic isotope effect on V/K was 1.14 in an aqueous solution and 1.16 in reverse micelles. At pL 11.0 at which the log V values reached a plateau in either solvent system, the deuterium kinetic isotope effect on V was 2.08 in an aqueous solution and 0.62 in reverse micelles. Results from a proton inventory experiment suggested that a hydron transfer step is involved in the transition state of the catalytic reaction. The isotopic fractionation factor (ϕ) for deuterium for the transition state (ϕT) increased when the pH of the solution was raised. At pL 11.0, the ϕT was 1.07 in reverse micelles, which corresponds to the inverse-isotope effect of the reaction in this solvent system. Normal viscosity effects on kcat and kcat/Km were observed in aqueous solution, corresponding to a diffusional controlled physical step as the rate-limiting step. We propose that the rate-limiting step of the hydrolytic reaction changes from phosphate releasing in aqueous solution to a covalent phosphorylation or dephosphorylation step in reverse micelles.
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White, Christine D., Michael W. Spence, Fred J. Longstaffe, Hilary Stuart-Williams, and Kimberley R. Law. "Geographic Identities of the Sacrificial Victims from the Feathered Serpent Pyramid, Teotihuacan: Implications for the Nature of State Power." Latin American Antiquity 13, no. 2 (June 2002): 217–36. http://dx.doi.org/10.2307/971915.
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This study addresses the political and military structure of early Teotihuacan through the analysis of oxygen-isotope ratios in skeletal phosphate from 41 victims of a sacrifice associated with the Feathered Serpent Pyramid. Oxygen-isotope ratios are markers of geographic identity. A comparison of bone and enamel values, which provides a contrast between environments experienced during growth and those of adulthood, illustrates that at least four different regions are represented in this sample. Those identified as soldiers had either lived locally since childhood or had moved to Teotihuacan from several foreign locations. Most had lived in Teotihuacan for a prolonged period before their death. This pattern suggests foreign “recruitment” or mercenary behavior. The women had either lived all their lives in Teotihuacan or had moved from there to a foreign location. Most of the individuals in the center of the pyramid (burial 14) did not come from Teotihuacan, nor had they lived in the city long before their deaths. We suggest that the choice of victims was meant to demonstrate Teotihuacan's powerful ideology to the rest of the Mesoamerican world. Notably, this isotopic evidence of physical interaction between Teotihuacan and foreign regions considerably predates the currently existing archaeological evidence.
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Mikhailova, Vasileva, Fedorov, Ershova, Vereshchagin, Rogov, and Pokrovsky. "Glendonite-Like Carbonate Aggregates from the Lower Ordovician Koporye Formation (Russian Part of the Baltic Klint): Detailed Mineralogical and Geochemical Data and Paleogeographic Implications." Minerals 9, no. 9 (August 29, 2019): 524. http://dx.doi.org/10.3390/min9090524.
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Stellate and plate-like carbonate bodies, traditionally called anthraconites, are found throughout the Baltic-Ladoga Klint in bituminous shale of the Koporye Formation (Tremadocian, Lower Ordovician). Although this time interval is usually considered as a greenhouse, there is some evidence for the existence of at least temporary cold conditions during the Cambrian–Ordovician. However, the origin of anthraconites is still strongly debated. We studied the mineralogical, petrographic, cathodoluminescence, geochemical, and isotopic characteristics of anthraconites from five sections of the Russian part of the Baltic paleobasin. A close similarity between the morphological, petrographic, cathodoluminescence, and isotopic characteristics of the studied anthraconites with those of glendonites allow us to suggest that these bodies formed in a similar paleo-environment and should be considered as pseudomorphs of the mineral ikaite. The oxygen and carbon isotope ratios reveal that ikaite precipitation occurred in low-temperature conditions on the seafloor. The carbon isotopic values reveal influence of inorganic seawater carbon along with organic matter decomposition and/or methane oxidation during ikaite-glendonite transformations. The oxygen isotopic composition significantly changed after deposition due to meteoric diagenesis. We propose that the studied Tremadocian anthraconites formed under a region of upwelling, where cold phosphate-rich deep waters rose to the relatively shallow part of the Baltic paleobasin, providing favorable conditions for ikaite precipitation. Based on our cathodoluminescence study, we suggest that ikaite was transformed to calcite over several stages during diagenesis. Mineralogical studies also reveal that primary calcite was transformed to sulfate (gypsum) or dolomite during late superimposed processes.
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Anderson, T. F., B. N. Popp, L. Z. HO, and A. C. Williams. "The carbon and oxygen isotopic records of fossils from the Lower Oxford Clay." Paleontological Society Special Publications 6 (1992): 7. http://dx.doi.org/10.1017/s2475262200005670.
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The excellent preservation of calcareous invertebrates and phosphatic vertebrates in the Lower Oxford Clay provides a good opportunity for paleooceanographic reconstruction based on stable isotopic abundances. We present here our initial results and interpretations on carbon and oxygen isotopic analyses on fossils of different depth habitats. Benthic fossils include epifaunal oysters and infaunal nuculacean bivalves. We also analyzed “pendant” bivalves whose depth habitat is uncertain. Fossil nekton are represented by ammonites and belemnites. Organisms that inhabited the uppermost part of the water column are represented by marine reptiles, such as icthyosaurs and plesiosaurs, and probable pelagic fish.The oxygen isotopic compositions of calcareous benthos and nekton overlap substantially (δ180 = −2 to +1 permil vs. PDB). The wide scatter in δ180 values probably reflects physiological (non-equilibrium) effects in calcification rather than paleoenvironmental variations. Mean δ180 values for oysters, pendant bivalves, and belemnites (all calcitic) and nuculacean bivalves (aragonitic) correspond to precipitation at isotopic equilibrium with non-glacial seawater at temperatures of 15°-18°. The mean isotopic paleotemperature for ammonites (aragonitic) is slightly higher (20°) but is probably not significantly different from those for other calcareous macro-invertebrates. Preliminary oxygen isotopic results on phosphate extracted from bones, teeth, and gill rays correspond to paleotemperatures of 20°–25°.Carbon isotopic results are limited to data from calcareous benthos and nekton. δ 13C values for individual taxa are quite variable (+2 to +5 permil for aragonitic fossils, 0 to +3 permil for calcitic fossils), suggesting physiological isotope effects. Nonetheless, mean δ 13C values are consistent with calcification in seawater having a carbon isotopic composition similar to that of modern average seawater. The presumably high flux of 13C-depleted CO2 into bottom waters from the diagenesis of sedimentary organic matter is not recorded in the carbon isotopic composition of benthic fossils.Thermal stratification implied by the oxygen isotopic record suggests the penetration of cool, nutrient-rich waters into the Lower Oxford Clay sea. Upward advection of deep waters together with runoff from adjacent landmasses must have provided sufficient nutrients to maintain the inferred high productivity of surface waters. The influence of productivity on the carbon isotopic composition of surface waters will be tested by the analysis of calcareous phytoplankton.
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Missimer, Thomas M., Christopher Teaf, Robert G. Maliva, Ashley Danley-Thomson, Douglas Covert, and Michael Hegy. "Natural Radiation in the Rocks, Soils, and Groundwater of Southern Florida with a Discussion on Potential Health Impacts." International Journal of Environmental Research and Public Health 16, no. 10 (May 21, 2019): 1793. http://dx.doi.org/10.3390/ijerph16101793.
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Southern Florida is underlain by rocks and sediments that naturally contain radioactive isotopes. The primary origin of the radioactive isotopes is Miocene-aged phosphate deposits that can be enriched in uranium-238 and its daughter isotopes. Nodular phosphate containing radionuclides from the Miocene has been reworked into younger formations and is ubiquitous in southern Florida. When the nodular phosphate is exposed to groundwater with geochemical conditions favorable for its dissolution, uranium, radium, and radon may be released into the groundwater system. Uranium concentrations have been measured above the 30 µg/L drinking water standard at only one location in Lee County. Radium226/228 exceedances of the drinking water standard have been documented in numerous wells in Sarasota County. Indoor radon activities have exceeded the 4 piC/L guideline in five southern Florida counties. The exceedance of radioactivity standards in drinking water does not occur in municipal drinking water supplies, but rather only in some domestic self-supply wells. Health risks for exposure to radiation from domestic self-supply wells could be mitigated by testing of well water and, if necessary, switching to the use of a different aquifer or treatment process. While the risk of exposure to radon in indoor air in southern Florida is generally low, some areas are enriched in soil radon that migrates into structures, which could be addressed by improved ventilation.
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Luz, Boaz, and Yehoshua Kolodny. "Oxygen isotope variation in bone phosphate." Applied Geochemistry 4, no. 3 (May 1989): 317–23. http://dx.doi.org/10.1016/0883-2927(89)90035-8.
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Visser, Anna-Neva, Scott D. Wankel, Pascal A. Niklaus, James M. Byrne, Andreas A. Kappler, and Moritz F. Lehmann. "Impact of reactive surfaces on the abiotic reaction between nitrite and ferrous iron and associated nitrogen and oxygen isotope dynamics." Biogeosciences 17, no. 16 (August 28, 2020): 4355–74. http://dx.doi.org/10.5194/bg-17-4355-2020.
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Abstract. Anaerobic nitrate-dependent Fe(II) oxidation (NDFeO) is widespread in various aquatic environments and plays a major role in iron and nitrogen redox dynamics. However, evidence for truly enzymatic, autotrophic NDFeO remains limited, with alternative explanations involving the coupling of heterotrophic denitrification with the abiotic oxidation of structurally bound or aqueous Fe(II) by reactive intermediate nitrogen (N) species (chemodenitrification). The extent to which chemodenitrification is caused (or enhanced) by ex vivo surface catalytic effects has not been directly tested to date. To determine whether the presence of either an Fe(II)-bearing mineral or dead biomass (DB) catalyses chemodenitrification, two different sets of anoxic batch experiments were conducted: 2 mM Fe(II) was added to a low-phosphate medium, resulting in the precipitation of vivianite (Fe3(PO4)2), to which 2 mM nitrite (NO2-) was later added, with or without an autoclaved cell suspension (∼1.96×108 cells mL−1) of Shewanella oneidensis MR-1. Concentrations of nitrite (NO2-), nitrous oxide (N2O), and iron (Fe2+, Fetot) were monitored over time in both set-ups to assess the impact of Fe(II) minerals and/or DB as catalysts of chemodenitrification. In addition, the natural-abundance isotope ratios of NO2- and N2O (δ15N and δ18O) were analysed to constrain the associated isotope effects. Up to 90 % of the Fe(II) was oxidized in the presence of DB, whereas only ∼65 % of the Fe(II) was oxidized under mineral-only conditions, suggesting an overall lower reactivity of the mineral-only set-up. Similarly, the average NO2- reduction rate in the mineral-only experiments (0.004±0.003 mmol L−1 d−1) was much lower than in the experiments with both mineral and DB (0.053±0.013 mmol L−1 d−1), as was N2O production (204.02±60.29 nmol L−1 d−1). The N2O yield per mole NO2- reduced was higher in the mineral-only set-ups (4 %) than in the experiments with DB (1 %), suggesting the catalysis-dependent differential formation of NO. N-NO2- isotope ratio measurements indicated a clear difference between both experimental conditions: in contrast to the marked 15N isotope enrichment during active NO2- reduction (15εNO2=+10.3 ‰) observed in the presence of DB, NO2- loss in the mineral-only experiments exhibited only a small N isotope effect (<+1 ‰). The NO2--O isotope effect was very low in both set-ups (18εNO2 <1 ‰), which was most likely due to substantial O isotope exchange with ambient water. Moreover, under low-turnover conditions (i.e. in the mineral-only experiments as well as initially in experiments with DB), the observed NO2- isotope systematics suggest, transiently, a small inverse isotope effect (i.e. decreasing NO2- δ15N and δ18O with decreasing concentrations), which was possibly related to transitory surface complexation mechanisms. Site preference (SP) of the 15N isotopes in the linear N2O molecule for both set-ups ranged between 0 ‰ and 14 ‰, which was notably lower than the values previously reported for chemodenitrification. Our results imply that chemodenitrification is dependent on the available reactive surfaces and that the NO2- (rather than the N2O) isotope signatures may be useful for distinguishing between chemodenitrification catalysed by minerals, chemodenitrification catalysed by dead microbial biomass, and possibly true enzymatic NDFeO.
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Kumar, Ravinder, Pardeep Singh, and Rajiv Kumar. "Analysis of longitudinal momentum distribution data of 26–29P isotopes in stripping reactions." Modern Physics Letters A 32, no. 06 (February 14, 2017): 1750021. http://dx.doi.org/10.1142/s0217732317500213.
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The orbital occupancy of the stripped proton in the phosphors isotopes with mass number 26–29 have been determined through the analysis of longitudinal momentum distributions (LMDs) of [Formula: see text] core fragments coming from [Formula: see text] and [Formula: see text] stripping reactions at high energies. It has been found that the probability of occupying [Formula: see text]-orbital by the stripped proton is 40–60%, 30–50%, 30–50% and 0–20% in [Formula: see text] isotopes, respectively. The effects of Coulomb barrier for the possibility of halo structure in proton-rich nuclei has also been examined and found that it decreases the chance of possessing halo structure in proton-rich nuclei.
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White, Christine D., Fred J. Longstaffe, and Kimberley R. Law. "REVISITING THE TEOTIHUACAN CONNECTION AT ALTUN HA." Ancient Mesoamerica 12, no. 1 (January 2001): 65–72. http://dx.doi.org/10.1017/s0956536101121103.
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An analysis of oxygen-isotope ratios in skeletal phosphate was used to assess the possibility that the Early Classic period (a.d. 280–550) Maya elite male in Tomb F/8-1 from the eastern Belizean site of Altun Ha had originally come from Teotihuacan, Mexico. When compared with four other individuals used as controls for spatial and temporal variability in δ18Op values at Altun Ha, this individual falls at the high end of the expected range of local intrasite variation but does not have a δ18Op value consistent with that of Teotihuacan. The mortuary and isotopic data have been compared with those from the previously analyzed Maya site of Kaminaljuyu, Guatemala, in order to examine regional and temporal differences in the influence of the powerful state of Teotihuacan. It appears that Teotihuacan was not the homeland of any of the tomb individuals analyzed from either site. Thus, models of ideological or symbolic power are supported over those of political or military imperialism.
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Lis, Hagar, Tal Weiner, Frances D. Pitt, Nir Keren, and Alon Angert. "Phosphate Uptake by Cyanobacteria Is Associated with Kinetic Fractionation of Phosphate Oxygen Isotopes." ACS Earth and Space Chemistry 3, no. 2 (December 27, 2018): 233–39. http://dx.doi.org/10.1021/acsearthspacechem.8b00099.
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Barrick, Reese E., William J. Showers, Alfred G. Fischer, and Bernard Genna. "The thermal physiology of the Dinosauria: direct evidence from oxygen isotopes." Paleontological Society Special Publications 6 (1992): 17. http://dx.doi.org/10.1017/s2475262200005773.
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The thermal physiology of extinct reptiles has been a hotly debated topic for the last two decades, with no direct evidence available to help solve the debate. Oxygen isotopes are fractionated with respect to temperature between an animal's body water and bone phosphate, thus providing avenues for deriving the first direct evidence of dinosaur thermal physiology.Multiple samples from both cortical and cancellous areas from individual bones were sampled in order to determine the heterogeneity of δ18O values within single bones. Bones from both the body core (ribs and vertebrae) and the extremities (limbs and caudal vertebrae) of known individual dinosaurs were sampled in this method. This allows for a comparison of isotopic heterogeneity from bones of all body regions. In ectothermic heterotherms or mass homeotherms the δ18O values from the extremities are expected to generally be heavier than those from ribs or dorsal vertebrae. It is also expected that there would be a greater degree of heterogeneity of δ18O values from bones in the extremities than those in the body core for these individuals. This relationship would result from the greater degree of heat loss from the extremities than body cores due to greater surface areas and distance from the heart. This relationship has been seen in analyses on bones from the modern Varanus komodoensis. On the other hand, true endothermic homeotherms should show a very narrow range of hetergeneity of δ18O values both within individual bones and between bones within single individuals as seen in modern mammals.Dinosaurs analyzed indicate isotopic heterogeneities within individual bones intermediate between modern mammals and Varanus, with the Tyrannosaurus showing the greatest isotopic variability. However, this isotopic heterogeneity is relatively small and is not significantly different for bones from the body core and extremities. This indicates that heterogeneity of the δ18O values is most likely the result of variations in drinking water δ18O values throughout an individual's lifetime rather than daily or seasonal variations in body temperatures.
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UCHIYAMA, Yoshichika, Hiroaki TAKAHASHI, Takao OI, and Morikazu HOSOE. "Selectivity of Lithium Isotopes on Semicrystalline Titanium(IV) Phosphate." Journal of Nuclear Science and Technology 38, no. 1 (January 2001): 85–87. http://dx.doi.org/10.1080/18811248.2001.9715010.
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D'Angela, D., and A. Longinelli. "Oxygen isotopes in living mammal's bone phosphate: Further results." Chemical Geology: Isotope Geoscience section 86, no. 1 (December 1990): 75–82. http://dx.doi.org/10.1016/0168-9622(90)90007-y.
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Reverdin, Gilles, Nicolas Metzl, Solveig Olafsdottir, Virginie Racapé, Taro Takahashi, Marion Benetti, Hedinn Valdimarsson, et al. "SURATLANT: a 1993–2017 surface sampling in the central part of the North Atlantic subpolar gyre." Earth System Science Data 10, no. 4 (October 18, 2018): 1901–24. http://dx.doi.org/10.5194/essd-10-1901-2018.
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Abstract. This paper presents the SURATLANT data set (SURveillance ATLANTique). It consists of individual data of temperature, salinity, parameters of the carbonate system, nutrients, and water stable isotopes (δ18O and δD) collected mostly from ships of opportunity since 1993 along transects between Iceland and Newfoundland (https://doi.org/10.17882/54517). We discuss how the data are validated and qualified, their accuracy, and the overall characteristics of the data set. The data are used to reconstruct seasonal cycles and interannual anomalies, in particular of sea surface salinity (SSS); inorganic nutrients; dissolved inorganic carbon (DIC); and its isotopic composition δ13CDIC, total alkalinity (At), and water isotope concentrations. Derived parameters such as fCO2 and pH are also estimated. The relation between salinity and At is estimated from these data to investigate the possibility to replace missing At when estimating other parameters of the carbonate system. When examining the average seasonal cycle in the deep ocean, in both these data with other climatologies, we find a period of small seasonal change between January and late April. On the Newfoundland shelf and continental slope, changes related with spring stratification and blooms occur earlier. The data were collected in a period of multi-decennial variability associated with the Atlantic multi-decadal variability with warming between 1994 and 2004–2007, and with the recent cooling having peaked in 2014–2016. We also observe strong salinification in 2004–2009 and fresher waters in 1994–1995 as well as since 2010 south of 54° N and in 2016–2017 north of 54° N. Indication of multi-decadal variability is also suggested by other variables, such as phosphate or DIC, but cannot be well resolved seasonally with the discrete sampling and in the presence of interannual variability. As a whole, over the 24 years, the ocean fCO2 trend (+1.9 µatm yr−1) is close to the atmospheric trend and associated with an increase in DIC (+0.77 µmol kg−1 yr−1). The data also revealed a canonical pH decrease of −0.0021 yr−1. There is also a decrease in δ13CDIC between 2005 and 2017 (in winter, −0.014 ‰ yr−1, but larger in summer, −0.042 ‰ yr−1), suggesting a significant anthropogenic carbon signal at play together with other processes (mixing, biological activity).
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Bryan, Clinton D., K. Barbara Schowen, and Richard L. Schowen. "Solvent isotope effects as a probe of general catalysis and solvation in phosphoryl transfer." Canadian Journal of Chemistry 74, no. 6 (June 1, 1996): 931–38. http://dx.doi.org/10.1139/v96-102.
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Phosphoryl transfer to methanol from tris(p-nitrophenyl) phosphate (PNNN), methyl bis(p-nitrophenyl) phosphate (PMNN), and dimethyl p-nitrophenyl phosphate (PMMN) exhibits general base catalysis by acetate ion but no detectable catalysis by acetic acid. For PNNN, acetate catalysis produces normal solvent isotope effects kROH/kROD of 1.68 ± 0.01 at high ionic strength (0.475) and 1.77 ± 0.04 at low ionic strength (0.048). A linear proton inventory indicates most simply that the isotope effect arises from a one-proton catalytic bridge in the transition state, although this model cannot strongly be distinguished from a generalized solvation effect. Reactions of methoxide ions produce slight inverse isotope effects kROD/kROH of 1.1–1.2, far smaller than the inverseeffect of about 2.5 expected for complete and uncompensated desolvation of the reactant-state methoxide ion. The transition state is thus stabilized by substantial interaction with the solvent. The proton inventory for the least reactive substrate PMMN (relative rate constant 1) is suggestive of transition-state stabilization by a combination of one-proton catalytic bridge(s) and distributed sites, while the proton inventory for the most reactive substrate PNNN (relative rate constant 1388) suggests only generalized transition-state solvation (many distributed sites); the proton inventory for PMNN, a substrate of intermediate reactivity (relative rate constant 60), suggests an intermediate situation. The data are consistent with a model in which transition states with exterior concentrations of charge favor stabilization of the charge by isotope-fractionating one-proton bridges, while transition states with distributed charge favor stabilization of the charge by many distributed sites. Key words: phosphoryl transfer, proton inventories, solvent isotope effects.
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Nagatsuka, Naoko, Nozomu Takeuchi, Takanori Nakano, Emi Kokado, and Zhongqin Li. "Sr, Nd and Pb stable isotopes of surface dust on Ürümqi glacier No. 1 in western China." Annals of Glaciology 51, no. 56 (2010): 95–105. http://dx.doi.org/10.3189/172756411795931895.
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AbstractStable-isotopic ratios of strontium (Sr), neodymium (Nd) and lead (Pb) provide a means of identifying a geological source of substances and are used as tracers of elements in biological and geochemical processes. We analyzed these isotopic ratios of surface dust (cryoconite) collected on Ürümqi glacier No. 1 , Tien Shan, China. The dust was separated chemically into five fractions (four minerals and organic matter), and the isotopic ratios of each fraction were measured. The Sr and Nd isotopic ratios in the fractions extracted with ultrapure water (saline minerals), hydrogen peroxide solution (organic matter) and acetic acid (carbonate minerals) were low and invariable, whereas those extracted by hydrochloric acid (phosphate minerals) and the residual fraction (silicate minerals) were higher. The difference was likely due to the original source of each fraction. The isotopic ratios of the surface dust collected from different sites showed no significant difference, suggesting that they were spatially uniform across the glacier. The isotopic ratios of the silicate fraction were closer to those of desert sand reported in China than those of the soil and bedrock around the glacier. This suggests that the silicate minerals on the glacier were derived from distant deserts. The isotopic ratios in saline, carbonate and phosphate fractions were also close to those of evaporites and apatite in that desert region, suggesting that these minerals were also derived from that source. The Sr isotopic ratios in the organic fraction were closer to ratios in the saline and carbonate fractions rather than the silicate or phosphate fractions and may therefore reflect the isotopic ratios of the elements when they are incorporated into living microbes on the glacier.
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Liang, Y., and R. E. Blake. "Oxygen isotope composition of phosphate in organic compounds: Isotope effects of extraction methods." Organic Geochemistry 37, no. 10 (October 2006): 1263–77. http://dx.doi.org/10.1016/j.orggeochem.2006.03.009.
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Angert, Alon, Tal Weiner, Shunit Mazeh, and Marcelo Sternberg. "Soil Phosphate Stable Oxygen Isotopes across Rainfall and Bedrock Gradients." Environmental Science & Technology 46, no. 4 (February 2, 2012): 2156–62. http://dx.doi.org/10.1021/es203551s.
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Luz, Boaz, Allison B. Cormie, and Henry P. Schwarcz. "Oxygen isotope variations in phosphate of deer bones." Geochimica et Cosmochimica Acta 54, no. 6 (June 1990): 1723–28. http://dx.doi.org/10.1016/0016-7037(90)90403-8.
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Crowson, Ronald A., William J. Showers, Ellen K. Wright, and Thomas C. Hoering. "Preparation of phosphate samples for oxygen isotope analysis." Analytical Chemistry 63, no. 20 (October 15, 1991): 2397–400. http://dx.doi.org/10.1021/ac00020a038.
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Bigio, Laura, and Alon Angert. "Oxygen Isotope Signatures of Phosphate in Wildfire Ash." ACS Earth and Space Chemistry 3, no. 5 (March 18, 2019): 760–69. http://dx.doi.org/10.1021/acsearthspacechem.8b00216.
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Amiot, Romain, Christophe Lécuyer, Gilles Escarguel, Jean-Paul Billon-Bruyat, Eric Buffetaut, Cyril Langlois, Samuel Martin, François Martineau, and Jean-Michel Mazin. "Oxygen isotope fractionation between crocodilian phosphate and water." Palaeogeography, Palaeoclimatology, Palaeoecology 243, no. 3-4 (January 2007): 412–20. http://dx.doi.org/10.1016/j.palaeo.2006.08.013.
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Kumashiro, Y., Y. Okada, and H. Okumura. "Isotope effects on boron phosphide single-crystal wafers." Journal of Crystal Growth 132, no. 3-4 (September 1993): 611–13. http://dx.doi.org/10.1016/0022-0248(93)90090-j.
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Rodionov, Andrei, Sara L. Bauke, Christian von Sperber, Carmen Hoeschen, Ellen Kandeler, Jens Kruse, Hans Lewandowski, et al. "Biogeochemical cycling of phosphorus in subsoils of temperate forest ecosystems." Biogeochemistry 150, no. 3 (October 2020): 313–28. http://dx.doi.org/10.1007/s10533-020-00700-8.
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Abstract Tree roots penetrate the soil to several meters depth, but the role of subsoils for the supply of nutrient elements such as phosphorus (P) to the trees is poorly understood. Here, we tested the hypothesis that increased P deficiency in the topsoil results in an increased microbial recycling of P from the forest subsoil. We sampled soils from four German temperate forest sites representing a gradient in total P stocks. We analyzed the oxygen isotopic composition of HCl-extractable phosphate (δ18OP) and identified differences in P speciation with increasing soil depth using X-ray absorption near-edge structure (XANES) spectroscopy. We further determined microbial oxygen demand with and without nutrient supply at different soil depths to analyse nutrient limitation of microbial growth and used nanoscale secondary ion mass spectrometry (NanoSIMS) to visualize spatial P gradients in the rhizosphere. We found that δ18OP values in the topsoil of all sites were close to the isotopic signal imparted by biological cycling when oxygen isotopes in phosphate are exchanged by enzymatic activity. However, with increasing soil depth and increasing HCl-P concentrations, δ18Ο values continuously decreased towards values expected for primary minerals in parent material at depths below 60 cm at sites with high subsoil P stocks and below more than 2 m at sites with low subsoil P stocks, respectively. For these depths, XANES spectra also indicated the presence of apatite. NanoSIMS images showed an enrichment of P in the rhizosphere in the topsoil of a site with high P stocks, while this P enrichment was absent at a site with low P stocks and in both subsoils. Addition of C, N and P alone or in combination revealed that microbial activity in subsoils of sites with low P stocks was mostly P limited, whereas sites with high P stocks indicated N limitation or N and P co-limitation. We conclude that subsoil P resources are recycled by trees and soil microorganisms. With continued weathering of the bedrock and mobilisation of P from the weathered rocks, P cycling will proceed to greater depths, especially at sites characterised by P limitation.
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Conrad, Ralf, Melanie Klose, and Peter Claus. "Phosphate Inhibits Acetotrophic Methanogenesis on Rice Roots." Applied and Environmental Microbiology 66, no. 2 (February 1, 2000): 828–31. http://dx.doi.org/10.1128/aem.66.2.828-831.2000.
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ABSTRACT The contribution of acetate- and H2/CO2-dependent methanogenesis to total CH4 production was determined in excised washed rice roots by radiolabeling, methyl fluoride inhibition, and stable carbon isotope fractionation. Addition of ≥20 mM phosphate inhibited methanogenesis, which then was exclusively from H2/CO2. Otherwise, acetate contributed about 50 to 60% of the total methanogenesis, demonstrating that phosphate specifically inhibited acetotrophic methanogens on rice roots.
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Conrad, Jacy, and Peter R. Tremaine. "Third dissociation constant of phosphoric acid in H2O and D2O from 75 to 300 °C at p = 20.4 MPa using Raman spectroscopy and a titanium-sapphire flow cell." Physical Chemistry Chemical Physics 23, no. 17 (2021): 10670–85. http://dx.doi.org/10.1039/d0cp06266a.
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Yu, Chan, Fei Wang, Sae Jung Chang, Jun Yao, and Ruth Elaine Blake. "Phosphate oxygen isotope evidence for methylphosphonate sources of methane and dissolved inorganic phosphate." Science of The Total Environment 644 (December 2018): 747–53. http://dx.doi.org/10.1016/j.scitotenv.2018.06.382.
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Cochrane, A. R., C. Idziak, W. J. Kerr, B. Mondal, L. C. Paterson, T. Tuttle, S. Andersson, and G. N. Nilsson. "Practically convenient and industrially-aligned methods for iridium-catalysed hydrogen isotope exchange processes." Org. Biomol. Chem. 12, no. 22 (2014): 3598–603. http://dx.doi.org/10.1039/c4ob00465e.
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The use of alternative solvents in the iridium-catalysed hydrogen isotope exchange reaction with developing phosphine/NHC Ir(i) complexes has identified reaction media which are more widely applicable than the commonly employed chlorinated solvent, dichloromethane.
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Fabre, Magali, Christophe Lécuyer, Jean-Philip Brugal, Romain Amiot, François Fourel, and François Martineau. "Late Pleistocene climatic change in the French Jura (Gigny) recorded in the δ18O of phosphate from ungulate tooth enamel." Quaternary Research 75, no. 3 (May 2011): 605–13. http://dx.doi.org/10.1016/j.yqres.2011.03.001.
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AbstractOxygen isotope compositions of phosphate in tooth enamel from large mammals (i.e. horse and red deer) were measured to quantify past mean annual air temperatures and seasonal variations between 145 ka and 33 ka in eastern France. The method is based on interdependent relationships between the δ18O of apatite phosphate, environmental waters and air temperatures. Horse (Equus caballus germanicus) and red deer (Cervus elaphus) remains have δ18O values that range from 14.2‰ to 17.2‰, indicating mean air temperatures between 7°C and 13°C. Oxygen isotope time series obtained from two of the six horse teeth show a sinusoidal-like signal that could have been forced by temperature variations of seasonal origin. Intra-tooth oxygen isotope variations reveal that at 145 ka, winters were colder (− 7 ± 2°C) than at present (3 ± 1°C) while summer temperatures were similar. Winter temperatures mark a well-developed West–East thermal gradient in France of about − 9°C, much stronger than the −4°C difference recorded presently. Negative winter temperatures were likely responsible for the extent and duration of the snow cover, thus limiting the food resources available for large ungulates with repercussions for Neanderthal predators.