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Sample records for evolution isotopic chemical

  1. Isotopic anomalies - chemical memory of Galactic evolution

    International Nuclear Information System (INIS)

    Clayton, D.D.

    1988-01-01

    New mechanisms for the chemical memory of isotopic anomalies are proposed which are based on the temporal change during the chemical evolution of the Galaxy of the isotopic composition of the mean ejecta from stars. Because of the differing temporal evolution of primary and secondary products of nucleosynthesis, the isotopic composition of the bulk interstellar medium changes approximately linearly with time, and thus any dust component having an age different from that of average dust will be isotopically anomalous. Special attention is given to C, O, Mg, Si, and isotopically heavy average-stellar condensates of SiC. 20 references

  2. The isotopic and chemical evolution of Mount St. Helens

    Science.gov (United States)

    Halliday, A.N.; Fallick, A.E.; Dickin, A.P.; Mackenzie, A.B.; Stephens, W.E.; Hildreth, W.

    1983-01-01

    Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000-2500 years ago: eruptions of dacite with ??{lunate}Nd = +5, ??{lunate}Sr = -10, variable ??18O, 206Pb/204Pb ??? 18.76, Ca/Sr ??? 60, Rb/Ba ??? 0.1, La/Yb ??? 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with ??{lunate}Nd = +4 to +8, ??{lunate}Sr = -7 to -22, variable ??18O (thought to represent melting of differing mantle-crust reservoirs), 206Pb/204Pb = 18.81-18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with ??{lunate}Nd = +6, ??{lunate}Sr = -13, ??18O ???6???, variable 206Pb/204Pb, Ca/Sr ??? 77, Rb/Ba = 0.1, La/Yb ??? 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between 87Sr/86Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region. ?? 1983.

  3. The isotopic and chemical evolution of Mount St. Helens

    International Nuclear Information System (INIS)

    Halliday, A.N.; Fallick, A.E.; Dickin, A.P.; Mackenzie, A.B.; Stephens, W.E.

    1983-01-01

    Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000-2500 years ago: eruptions of dacite with epsilonsub(Nd) = +5, epsilonsub(Sr) = -10, variable delta 18 O, 206 Pb/ 204 Pb approx.= 18.76, Ca/Sr approx.= 60, Rb/Ba- approx.= 0.1, La/Yb approx.= 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with epsilonsub(Nd) = +4 to + 8, epsilonsub(Sr) = -7 to -22, variable delta 18 O (thought to represent melting of differing mantle-crust reservoirs), 206 Pb/ 204 Pb = 18.81-18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with epsilonsub(Nd) = + 6, epsilonsub(Sr) = -13, delta 18 O approx.= 6per mille, variable 206 Pb/ 204 Pb, Ca/Sr approx.= 77, Rb/Ba = 0.1, La/Yb approx.= 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between 87 Sr/ 86 Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region. (orig.)

  4. CAN GALACTIC CHEMICAL EVOLUTION EXPLAIN THE OXYGEN ISOTOPIC VARIATIONS IN THE SOLAR SYSTEM?

    International Nuclear Information System (INIS)

    Lugaro, Maria; Liffman, Kurt; Ireland, Trevor R.; Maddison, Sarah T.

    2012-01-01

    A number of objects in primitive meteorites have oxygen isotopic compositions that place them on a distinct, mass-independent fractionation line with a slope of one on a three-isotope plot. The most popular model for describing how this fractionation arose assumes that CO self-shielding produced 16 O-rich CO and 16 O-poor H 2 O, where the H 2 O subsequently combined with interstellar dust to form relatively 16 O-poor solids within the solar nebula. Another model for creating the different reservoirs of 16 O-rich gas and 16 O-poor solids suggests that these reservoirs were produced by Galactic chemical evolution (GCE) if the solar system dust component was somewhat younger than the gas component and both components were lying on the line of slope one in the O three-isotope plot. We argue that GCE is not the cause of mass-independent fractionation of the oxygen isotopes in the solar system. The GCE scenario is in contradiction with observations of the 18 O/ 17 O ratios in nearby molecular clouds and young stellar objects. It is very unlikely for GCE to produce a line of slope one when considering the effect of incomplete mixing of stellar ejecta in the interstellar medium. Furthermore, the assumption that the solar system dust was younger than the gas requires unusual timescales or the existence of an important stardust component that is not theoretically expected to occur nor has been identified to date.

  5. Chemical and isotopic evolution of a layered eastern U.S. snowpack and its relation to stream-water composition

    Science.gov (United States)

    Shanley, J.B.; Kendall, C.; Albert, M.R.; Hardy, J.P.

    1995-01-01

    The chemical, isotopic, and morphologic evolution of a layered snowpack was investigated during the winter of 1993-94 at Sleepers River Research Watershed in Danville, Vermont. The snowpack was monitored at two small basins: a forested basin at 525 m elevation, and an agricultural basin at 292 m elevation. At each site, the snowpack morphology was characterized and individual layers were sampled seven times during the season. Nitrate and 8d18O profiles in the snowpack remained relatively stable until peak accumulation in mid-March, except near the snow surface, where rain-on-snow events caused water and nitrate movement down to impeding ice layers. Subsequently, water and nitrate moved more readily through the ripening snowpack. As the snowpack evolved, combined processes of preferential ion elution, isotopic fractionation, and infiltration of isotopically heavy rainfall caused the pack to become depleted in solutes and isotopically enriched. The release of nitrate and isotopically depleted water was reflected in patterns of nitrate concentrations and ??18O of meltwater and stream water. Results supported data from the previous year which suggested that streamflow in the forested basin during snowmelt was dominated by groundwater discharge.

  6. CHEMICAL EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Calvin, Melvin

    1965-06-01

    How did life come to be on the surface of the earth? Darwin himself recognized that his basic idea of evolution by variation and natural selection must be a continuous process extending backward in time through that period in which the first living things arose and into the period of 'Chemical Evolution' which preceded it. We are approaching the examination of these events by two routes. One is to seek for evidence in the ancient rocks of the earth which were laid down prior to that time in which organisms capable of leaving their skeletons in the rocks to be fossilized were in existence. This period is sometime prior to approximately 600 million years ago. The earth is believed to have taken its present form approximately 4700 million years ago. We have found in rocks whose age is about 1000 million years certain organic molecules which are closely related to the green pigment of plants, chlorophyll. This seems to establish that green plants were already fluorishing prior to that time. We have now found in rocks of still greater age, namely, 2500 million years, the same kinds of molecules mentioned above which can be attributed to the presence of living organisms. If these molecules are as old as the rocks, we have thus shortened the time available for the generation of the complex biosynthetic sequences which give rise to these specific hydrocarbons (polyisoprenoids) to less than 2000 million years.

  7. Re-Os Isotopic Constraints on the Chemical Evolution and Differentiation of the Martian Mantle

    Science.gov (United States)

    Brandon, Alan D.; Walker, Richard J.

    2002-01-01

    The (187)Re-187Os isotopic systematics of SNC meteorites, thought to be from Mars, provide valuable information regarding the chemical processes that affected the Martian mantle, particularly with regard to the relative abundances of highly siderophile elements (HSE). Previously published data (Birck and Allegre 1994, Brandon et al. 2000), and new data obtained since these studies, indicate that the HSE and Os isotopic composition of the Martian mantle was primarily set in its earliest differentiation history. If so, then these meteorites provide key constraints on the processes that lead to variation in HSE observed in not only Mars, but also Earth, the Moon and other rocky bodies in the Solar System. Processes that likely have an effect on the HSE budgets of terrestrial mantles include core formation, magma ocean crystallization, development of juvenile crust, and the addition of a late veneer. Each of these processes will result in different HSE variation and the isotopic composition of mantle materials and mantle derived lavas. Two observations on the SNC data to present provide a framework for which to test the importance of each of these processes. First, the concentrations of Re and Os in SNC meteorites indicate that they are derived from a mantle that has similar concentrations to the Earth's mantle. Such an observation is consistent with a model where a chondritic late veneer replenished the Earth and Martian mantles subsequent to core formation on each planet. Alternative models to explain this observation do exist, but will require additional data to test the limitations of each. Second, Re-Os isotopic results from Brandon et al. (2000) and new data presented here, show that initial yos correlates with variations in the short-lived systems of (182)Hf- (182)W and (142)Sm-142Nd in the SNC meteorites (epsilon(sub W) and epsilon(sub 142Nd)). These systematics require an isolation of mantle reservoirs during the earliest differentiation history of Mars, and

  8. Isotopes of C, N and O and chemical evolution of galaxies. Pt. 2

    Energy Technology Data Exchange (ETDEWEB)

    Vigroux, L; Audouze, J; Lequeux, J [Centre National de la Recherche Scientifique, 91 - Orsay (France). Lab. Rene Bernas; Observatoire de Paris, Section de Meudon, 92 (France). Dept. de Radioastronomie)

    1976-10-01

    The most recent progresses in the CNO abundance determinations are reported. They are still consistent with an enrichment of /sup 13/C relative to /sup 12/C with time and with the existence of spatial gradients of N and O abundances. An improved formalism has been used to study the evolution of these abundances: this formalism which can be applied to rather general problems relaxes the assumption of instant recycling approximation which in spite of its general use does not take properly into account the evolution of low mass stars. With this method the evolution of the gas content, the rate of supernova explosions and planetary nebulae and the evolution of the abundances have been studied in models sketching the galactic center and the solar neighborhood and these models take into account various evolution parameters such as the rate of infall of external matter and/or the possibility of a prompt initial enrichment in metals.

  9. Chemical evolution of galaxies

    CERN Document Server

    Matteucci, Francesca

    2012-01-01

    The term “chemical evolution of galaxies” refers to the evolution of abundances of chemical species in galaxies, which is due to nuclear processes occurring in stars and to gas flows into and out of galaxies. This book deals with the chemical evolution of galaxies of all morphological types (ellipticals, spirals and irregulars) and stresses the importance of the star formation histories in determining the properties of stellar populations in different galaxies. The topic is approached in a didactical and logical manner via galaxy evolution models which are compared with observational results obtained in the last two decades: The reader is given an introduction to the concept of chemical abundances and learns about the main stellar populations in our Galaxy as well as about the classification of galaxy types and their main observables. In the core of the book, the construction and solution of chemical evolution models are discussed in detail, followed by descriptions and interpretations of observations of ...

  10. Chemical separation of boron isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Palko, A.A.

    1978-06-01

    This is the final report of the research performed at ORNL on the chemical fractionation of boron isotopes between BF/sub 3/ gas and the liquid molecular addition compounds of BF/sub 3/. Thirty compounds were studied, ten of them in detail. Graphs and equations are given for variation of isotopic equilibrium constant, vapor pressure, and BF/sub 3/ solubility as a function of temperature. Rate of isotopic exchange and melting points were determined. Several of the compounds are likely candidates for use in a gas-liquid countercurrent exchange system for large-scale separation of boron isotopes. 23 figs, 53 tables, 39 references.

  11. Chemical separation of boron isotopes

    International Nuclear Information System (INIS)

    Palko, A.A.

    1978-06-01

    This is the final report of the research performed at ORNL on the chemical fractionation of boron isotopes between BF 3 gas and the liquid molecular addition compounds of BF 3 . Thirty compounds were studied, ten of them in detail. Graphs and equations are given for variation of isotopic equilibrium constant, vapor pressure, and BF 3 solubility as a function of temperature. Rate of isotopic exchange and melting points were determined. Several of the compounds are likely candidates for use in a gas-liquid countercurrent exchange system for large-scale separation of boron isotopes. 23 figs, 53 tables, 39 references

  12. Chemical evolution and life

    Directory of Open Access Journals (Sweden)

    Malaterre Christophe

    2015-01-01

    Full Text Available In research on the origins of life, the concept of “chemical evolution” aims at explaining the transition from non-living matter to living matter. There is however strong disagreement when it comes to defining this concept more precisely, and in particular with reference to a chemical form of Darwinian evolution: for some, chemical evolution is nothing but Darwinian evolution applied to chemical systems before life appeared; yet, for others, it is the type of evolution that happened before natural selection took place, the latter being the birthmark of living systems. In this contribution, I review the arguments defended by each side and show how both views presuppose a dichotomous definition of “life”.

  13. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Matteucci, F.; Consiglio Nazionale delle Ricerche, Frascati

    1989-01-01

    In principle, a good model of galactic chemical evolution should fulfil the majority of well established observational constraints. The goal of this paper is to review the observational data together with the existing chemical evolution models for the Milky Way (the disk), Blue Compact and Elliptical galaxies and to show how well the models can account for the observations. Some open problems and future prospects are also discussed. (author)

  14. Insights into magmatic evolution and recharge history in Capraia Volcano (Italy) from chemical and isotopic zoning in plagioclase phenocrysts

    DEFF Research Database (Denmark)

    Gagnevin, D.; Waight, Tod Earle; Daly, J.S.

    2007-01-01

    Plagioclase phenocrysts in dacites from the high-K calc-alkaline CapraiaVolcano were investigated for major, trace element and Sr isotope variations in order to gain better insight into the proposed open-system behaviour of the volcano. Repeated dissolution zone in plagioclases from the early-eru...

  15. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Vigroux, Laurent

    1979-01-01

    This research thesis addresses theories on the chemical evolution of galaxies which aim at explaining abundances of different elements in galaxies, and more particularly aims at improving the model by modifying hypotheses. After a description of the simple model and of its uncertainties, the author shows how it is possible to understand the evolution of the main elements. Predictions obtained with this model are then compared with the present knowledge on galaxies by considering them according to an increasing complexity: Sun's neighbourhood, our galaxy, other spiral galaxies, elliptical galaxies, and finally galaxy clusters. A specific attention is given to irregular galaxies which are the simplest systems [fr

  16. The {sup 12}C/{sup 13}C Ratio in Sgr B2(N): Constraints for Galactic Chemical Evolution and Isotopic Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Halfen, D. T.; Ziurys, L. M. [Department of Chemistry and Biochemistry, University of Arizona, 1305 E. 4th Street, Tucson, AZ 85719 (United States); Woolf, N. J., E-mail: halfend@email.arizona.edu [Department of Astronomy, Arizona Radio Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2017-08-20

    A study has been conducted of {sup 12}C/{sup 13}C ratios in five complex molecules in the Galactic center. H{sub 2}CS, CH{sub 3}CCH, NH{sub 2}CHO, CH{sub 2}CHCN, and CH{sub 3}CH{sub 2}CN and their {sup 13}C-substituted species have been observed in numerous transitions at 1, 2, and 3 mm, acquired in a spectral-line survey of Sgr B2(N), conducted with the telescopes of the Arizona Radio Observatory (ARO). Between 22 and 54 individual, unblended lines for the {sup 12}C species and 2–54 for {sup 13}C-substituted analogs were modeled in a global radiative transfer analysis. All five molecules were found to consistently exhibit two velocity components near V {sub LSR} ∼ 64 and 73 km s{sup −1}, with column densities ranging from N {sub tot} ∼ 3 × 10{sup 14} − 4 × 10{sup 17} cm{sup −2} and ∼2 × 10{sup 13} − 1 × 10{sup 17} cm{sup −2} for the {sup 12}C and {sup 13}C species, respectively. Based on 14 different isotopic combinations, ratios were obtained in the range {sup 12}C/{sup 13}C = 15 ± 5 to 33 ± 13, with an average value of 24 ± 7, based on comparison of column densities. These measurements better anchor the {sup 12}C/{sup 13}C ratio at the Galactic center, and suggest a slightly revised isotope gradient of {sup 12}C/{sup 13}C = 5.21(0.52) D {sub GC} + 22.6(3.3). As indicated by the column densities, no preferential {sup 13}C enrichment was found on the differing carbon sites of CH{sub 3}CCH, CH{sub 2}CHCN, and CH{sub 3}CH{sub 2}CN. Because of the elevated temperatures in Sgr B2(N), {sup 13}C isotopic substitution is effectively “scrambled,” diminishing chemical fractionation effects. The resulting ratios thus reflect stellar nucleosynthesis and Galactic chemical evolution, as is likely the case for most warm clouds.

  17. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Pagel, B.E.J.

    1990-01-01

    Initial conditions are probably set by results of Big Bang nucleosynthesis (BBNS) without intervening complications affecting the composition of visible matter so that extrapolation of observed abundances to BBNS products seems fairly secure. Primordial helium and deuterium abundances deduced in this way place upper and lower limits on baryonic density implying that both baryonic and non-baryonic dark matter exist and predicting no more than 3 neutrino flavours as recently confirmed in accelerator experiments. The validity of simple galactic chemical evolution models assumed in extrapolating back to the Big Bang is examined in the light of the frequency distribution of iron or oxygen abundances in the Galactic halo, bulge and disk. (orig.)

  18. Chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Pagel, B.E.J.

    1979-01-01

    The chemical evolution of disk galaxies is discussed with special reference to results obtained from studies of the oxygen abundance in H II regions. Normal spirals (including our own) display the by now well known radial abundance gradient, which is discussed on the basis of the simple enrichment model and other models. The Magellanic Clouds, on the other hand, and the barred spiral NGC 1365, have been found to have little or no abundance gradient, implying a very different sort of evolution that may involve large-scale mixing. Finally, the simple model is tested against a number of results in H II regions where the ratio of total mass to mass of residual gas can be estimated. It turns out to fit adequately the Magellanic Clouds and a number of H II regions in the outer parts of spiral galaxies, but in more inner parts it fails, as do more sophisticated models involving infall during the formation of galactic disks that have proved very successful in other respects. (Auth.)

  19. Isotope effects on chemical equilibria

    International Nuclear Information System (INIS)

    Golding, P.D.

    1974-01-01

    The thermodynamic equilibrium constants of three deuterated substituted acetic acids are reported. The calculation of secondary isotope effects of the second kind for the three isotopic acid pairs has been accomplished by the appropriate comparison of thermodynamic equilibrium constants, and by the comparison of isotopic slopes. The effect of substituent variation on the isotope effects reported here disqualifies the simple inductive model as a legitimate description of secondary isotope effects of the second kind. The correlation of diminishing isotope effect per deuterium atom with increasing acidity is also invalidated by the present results. The syntheses of 9-thia-9,10-dihydrophenanthrene-9-oxide and thioxanthene-10-oxide are described. These compounds have been partially deuterated at their respective methylene positions. Spectral evidence indicates stereoselectivity of the methylene protons in the exchange reactions of both compounds. (author)

  20. Evolution of Ore Deposits and Technology Transfer Project: Isotope and Chemical Methods in Support of the U.S. Geological Survey Science Strategy, 2003-2008

    Science.gov (United States)

    Rye, Robert O.; Johnson, Craig A.; Landis, Gary P.; Hofstra, Albert H.; Emsbo, Poul; Stricker, Craig A.; Hunt, Andrew G.; Rusk, Brian G.

    2010-01-01

    its natural-resources and natural-science needs. This circular presents an overview of the Project. Descriptions of the Project laboratories are given first including descriptions of the types of chemical or isotopic analyses that are made and the utility of the measurements. This is followed by summaries of select measurements that were carried out by the Project scientists. The studies are grouped by science direction. Virtually all of them were collaborations with USGS colleagues or with scientists from other governmental agencies, academia, or the private sector.

  1. Isotopic evolution of Mauna Loa volcano

    International Nuclear Information System (INIS)

    Kurz, M.D.; Kammer, D.P.

    1991-01-01

    In an effort to understand the temporal helium isotopic variations in Mauna Loa volcano, we have measured helium, strontium and lead isotopes in a suite of Mauna Loa lavas that span most of the subaerial eruptive history of the volcano. The lavas range in age from historical flows to Ninole basalt which are thought to be several hundred thousand years old. Most of the samples younger than 30 ka in age (Kau Basalt) are radiocarbon-dated flows, while the samples older than 30 ka are stratigraphically controlled (Kahuku and Ninole Basalt). The data reveal a striking change in the geochemistry of the lavas approximately 10 ka before present. The lavas older than 10 ka are characterized by high 3 He/ 4 He (≅ 16-20 times atmospheric), higher 206 Pb/ 204 Pb (≅ 18.2), and lower 87 Sr/ 86 Sr(≅ 0.70365) ratios than the younger Kau samples (having He, Pb and Sr ratios of approximately 8.5 x atmospheric, 18.1 and 0.70390, respectively). The historical lavas are distinct in having intermediate Sr and Pb isotopic compositions with 3 He/ 4 He ratios similar to the other young Kau basalt (≅ 8.5 x atmospheric). The isotopic variations are on a shorter time scale (100 to 10,000 years) than has previously been observed for Hawaiian volcanoes, and demonstrate the importance of geochronology and stratigraphy to geochemical studies. The data show consistency between all three isotope systems, which suggests that the variations are not related to magma chamber degassing processes, and that helium is not decoupled from the other isotopes. However, the complex temporal evolution suggests that three distinct mantle sources are required to explain the isotopic data. Most of the Mauna Loa isotopic variations could be explained by mixing between a plume type source, similar to Loihi, and an asthenospheric source with helium isotopic composition close to MORB and elevated Sr isotopic values. (orig./WL)

  2. The chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Chiosi, Cesare

    1986-01-01

    The chemical evolution of galaxies is reviewed with particular attention to the theoretical interpretation of the distribution and abundances of elements in stars and the interstellar medium. The paper was presented to the conference on ''The early universe and its evolution'', Erice, Italy, 1986. The metallicity distribution of the solar vicinity, age metallicity relationship, abundance gradients in the galaxy, external galaxies, star formation and evolution, major sites of nucleosynthesis, yields of chemical elements, chemical models, and the galactic disk, are all discussed. (U.K.)

  3. A stochastic approach to chemical evolution

    International Nuclear Information System (INIS)

    Copi, C.J.

    1997-01-01

    Observations of elemental abundances in the Galaxy have repeatedly shown an intrinsic scatter as a function of time and metallicity. The standard approach to chemical evolution does not attempt to address this scatter in abundances since only the mean evolution is followed. In this work, the scatter is addressed via a stochastic approach to solving chemical evolution models. Three simple chemical evolution scenarios are studied using this stochastic approach: a closed box model, an infall model, and an outflow model. These models are solved for the solar neighborhood in a Monte Carlo fashion. The evolutionary history of one particular region is determined randomly based on the star formation rate and the initial mass function. Following the evolution in an ensemble of such regions leads to the predicted spread in abundances expected, based solely on different evolutionary histories of otherwise identical regions. In this work, 13 isotopes are followed, including the light elements, the CNO elements, a few α-elements, and iron. It is found that the predicted spread in abundances for a 10 5 M circle-dot region is in good agreement with observations for the α-elements. For CN, the agreement is not as good, perhaps indicating the need for more physics input for low-mass stellar evolution. Similarly for the light elements, the predicted scatter is quite small, which is in contradiction to the observations of 3 He in HII regions. The models are tuned for the solar neighborhood so that good agreement with HII regions is not expected. This has important implications for low-mass stellar evolution and on using chemical evolution to determine the primordial light-element abundances in order to test big bang nucleosynthesis. copyright 1997 The American Astronomical Society

  4. Evolution of chemical and isotopic composition of inorganic carbon in a complex semi-arid zone environment: Consequences for groundwater dating using radiocarbon

    Science.gov (United States)

    Meredith, K. T.; Han, L. F.; Hollins, S. E.; Cendón, D. I.; Jacobsen, G. E.; Baker, A.

    2016-09-01

    Estimating groundwater age is important for any groundwater resource assessment and radiocarbon (14C) dating of dissolved inorganic carbon (DIC) can provide this information. In semi-arid zone (i.e. water-limited environments), there are a multitude of reasons why 14C dating of groundwater and traditional correction models may not be directly transferable. Some include; (1) the complex hydrological responses of these systems that lead to a mixture of different ages in the aquifer(s), (2) the varied sources, origins and ages of organic matter in the unsaturated zone and (3) high evaporation rates. These all influence the evolution of DIC and are not easily accounted for in traditional correction models. In this study, we determined carbon isotope data for; DIC in water, carbonate minerals in the sediments, sediment organic matter, soil gas CO2 from the unsaturated zone, and vegetation samples. The samples were collected after an extended drought, and again after a flood event, to capture the evolution of DIC after varying hydrological regimes. A graphical method (Han et al., 2012) was applied for interpretation of the carbon geochemical and isotopic data. Simple forward mass-balance modelling was carried out on key geochemical processes involving carbon and agreed well with observed data. High values of DIC and δ13CDIC, and low 14CDIC could not be explained by a simple carbonate mineral-CO2 gas dissolution process. Instead it is suggested that during extended drought, water-sediment interaction leads to ion exchange processes within the top ∼10-20 m of the aquifer which promotes greater calcite dissolution in saline groundwater. This process was found to contribute more than half of the DIC, which is from a mostly 'dead' carbon source. DIC is also influenced by carbon exchange between DIC in water and carbonate minerals found in the top 2 m of the unsaturated zone. This process occurs because of repeated dissolution/precipitation of carbonate that is dependent on

  5. Thermal and chemical evolution in the early solar system as recorded by FUN CAIs: Part I - Petrology, mineral chemistry, and isotopic composition of Allende FUN CAI CMS-1

    Science.gov (United States)

    Williams, C. D.; Ushikubo, T.; Bullock, E. S.; Janney, P. E.; Hines, R. R.; Kita, N. T.; Hervig, R. L.; MacPherson, G. J.; Mendybaev, R. A.; Richter, F. M.; Wadhwa, M.

    2017-03-01

    Detailed petrologic, geochemical and isotopic analyses of a new FUN CAI from the Allende CV3 meteorite (designated CMS-1) indicate that it formed by extensive melting and evaporation of primitive precursor material(s). The precursor material(s) condensed in a 16O-rich region (δ17O and δ18O ∼ -49‰) of the inner solar nebula dominated by gas of solar composition at total pressures of ∼10-3-10-6 bar. Subsequent melting of the precursor material(s) was accompanied by evaporative loss of magnesium, silicon and oxygen resulting in large mass-dependent isotope fractionations in these elements (δ25Mg = 30.71-39.26‰, δ29Si = 14.98-16.65‰, and δ18O = -41.57 to -15.50‰). This evaporative loss resulted in a bulk composition similar to that of compact Type A and Type B CAIs, but very distinct from the composition of the original precursor condensate(s). Kinetic fractionation factors and the measured mass-dependent fractionation of silicon and magnesium in CMS-1 suggest that ∼80% of the silicon and ∼85% of the magnesium were lost from its precursor material(s) through evaporative processes. These results suggest that the precursor material(s) of normal and FUN CAIs condensed in similar environments, but subsequently evolved under vastly different conditions such as total gas pressure. The chemical and isotopic differences between normal and FUN CAIs could be explained by sorting of early solar system materials into distinct physical and chemical regimes, in conjunction with discrete heating events, within the protoplanetary disk.

  6. Concrete Chemical Evolution

    Energy Technology Data Exchange (ETDEWEB)

    D.H. Tang

    1998-07-31

    The objectives of this analysis are to discuss and evaluate testing results that were performed for the M&O by the Pennsylvania State University (PSU) to evaluate the potential long-term evolution of organic admixtures in cementitious materials at elevated temperatures. The testing was designed to help provide a basis for a determination by the Performance Assessment group (PA) of the long-term acceptability and longevity of cementitious materials for repository use. The main purpose of the testing was to assess the evolution of gases (especially CO{sub 2}) from hydrated cement paste at elevated temperatures and to determine the impact on alkalinity, i.e., the pH value of cement paste pore solution. This information in turn can be used as scoping information to determine if further tests of this nature are needed to support PA. As part of this discussion and evaluation of the PSU results, an assessment of alkalinity in a ''cementitious repository'' and an evaluation of organic materials are presented.

  7. Concrete Chemical Evolution

    International Nuclear Information System (INIS)

    D.H. Tang

    1998-01-01

    The objectives of this analysis are to discuss and evaluate testing results that were performed for the M andO by the Pennsylvania State University (PSU) to evaluate the potential long-term evolution of organic admixtures in cementitious materials at elevated temperatures. The testing was designed to help provide a basis for a determination by the Performance Assessment group (PA) of the long-term acceptability and longevity of cementitious materials for repository use. The main purpose of the testing was to assess the evolution of gases (especially CO 2 ) from hydrated cement paste at elevated temperatures and to determine the impact on alkalinity, i.e., the pH value of cement paste pore solution. This information in turn can be used as scoping information to determine if further tests of this nature are needed to support PA. As part of this discussion and evaluation of the PSU results, an assessment of alkalinity in a ''cementitious repository'' and an evaluation of organic materials are presented

  8. Isotopic and chemical composition of groundwater in the Bolivian Altiplano, present space evolution records hydrologic conditions since 11,000 Yr

    International Nuclear Information System (INIS)

    Coudrain, A.; Talbi, A.; Loubet, M.; Gallaire, R.; Jusserand, C.; Ramirez, E.; Ledoux, E.

    1999-01-01

    The phreatic aquifer of the central Altiplano shows a Cl concentration that increases from 0.5 meq l -1 upstream to 150 meq l -1 downstream. The main outflow process from the aquifer is the upward flow E into the unsaturated zone associated to evaporation close to soil surface. A relation has been established for any arid zone areas on the base of isotopic profiles: E (mm yr -1 ) = 63 Z -1.5 where Z (m) is the water table depth under soil surface. The aquifer under study may have acquired its high chlorine content during last lacustrine phase (Tauca, 12 ka BP). Arguments for this hypothesis are: (i) maximum level of the lake (3780 m) higher than present soil elevation in the area, (ii) same order of salinity in the paleolake and in the more saline groundwater, (iii) weak molar ratio of Li/Cl in saline groundwater and in the Tauca, (iv) modelling of Cl transport over 11,000 years consistent with observed spatial evolution of Cl in groundwater. To this scenario, might be superimposed the assumption of a delay for the convective transfer of salt towards south by the coupled effects of accumulation of salt in the unsaturated zone by evaporation from the aquifer during thousand or so years, and of the subsequent return of this salt downwards to the aquifer during some short rainy periods. The 87 Sr/ 86 Sr, major and trace element compositions of surface and groundwater support this proposed scenario. (author)

  9. Chemical stability of levoglucosan: An isotopic perspective

    Science.gov (United States)

    Sang, X. F.; Gensch, I.; Kammer, B.; Khan, A.; Kleist, E.; Laumer, W.; Schlag, P.; Schmitt, S. H.; Wildt, J.; Zhao, R.; Mungall, E. L.; Abbatt, J. P. D.; Kiendler-Scharr, A.

    2016-05-01

    The chemical stability of levoglucosan was studied by exploring its isotopic fractionation during the oxidation by hydroxyl radicals. Aqueous solutions as well as mixed (NH4)2SO4-levoglucosan particles were exposed to OH. In both cases, samples experiencing different extents of processing were isotopically analyzed by Thermal Desorption-Gas Chromatography-Isotope Ratio Mass Spectrometry (TD-GC-IRMS). From the dependence of levoglucosan δ13C and concentration on the reaction extent, the kinetic isotope effect (KIE) of the OH oxidation reactions was determined to be 1.00187±0.00027 and 1.00229±0.00018, respectively. Both show good agreement within the uncertainty range. For the heterogeneous oxidation of particulate levoglucosan by gas-phase OH, a reaction rate constant of (2.67±0.03)·10-12 cm3 molecule-1S-1 was derived. The laboratory kinetic data, together with isotopic source and ambient observations, give information on the extent of aerosol chemical processing in the atmosphere.

  10. THE CHEMICAL EVOLUTION OF PHOSPHORUS

    International Nuclear Information System (INIS)

    Jacobson, Heather R.; Thanathibodee, Thanawuth; Frebel, Anna; Roederer, Ian U.; Cescutti, Gabriele; Matteucci, Francesca

    2014-01-01

    Phosphorus is one of the few remaining light elements for which little is known about its nucleosynthetic origin and chemical evolution, given the lack of optical absorption lines in the spectra of long-lived FGK-type stars. We have identified a P I doublet in the near-ultraviolet (2135/2136 Å) that is measurable in stars of low metallicity. Using archival Hubble Space Telescope-Space Telescope Imaging Spectrograph spectra, we have measured P abundances in 13 stars spanning –3.3 ≤ [Fe/H] ≤ -0.2, and obtained an upper limit for a star with [Fe/H] ∼ -3.8. Combined with the only other sample of P abundances in solar-type stars in the literature, which spans a range of –1 ≤ [Fe/H] ≤ +0.2, we compare the stellar data to chemical evolution models. Our results support previous indications that massive-star P yields may need to be increased by a factor of a few to match stellar data at all metallicities. Our results also show that hypernovae were important contributors to the P production in the early universe. As P is one of the key building blocks of life, we also discuss the chemical evolution of the important elements to life, C-N-O-P-S, together

  11. Isotope effects of sulfur in chemical reactions

    International Nuclear Information System (INIS)

    Mikolajczuk, A.

    1999-01-01

    Sulfur is an important component of organic matter because it forms compounds with many elements. Due to high chemical activity of sulfur, it takes part in biological and geological processes in which isotope effects are occurring. It has been shown during last years research of isotope effects that we have take into account not only mass difference but also many other physical properties of nuclides e.g. even or odd number of neutrons in nuclei, shape and distribution of charge, turn of nuclear spin etc. The factor remains that new theoretical ideas have been formed on the base of data, being obtained in fractionation processes of heavy element isotope, particularly uranium. Now it is being well known that effects unconnected with vibration energy have also caused an effect on fractionation of considerably lighter elements like iron and magnesium. The important question is, if these effects would come to light during the separation of sulfur isotopes. Sulfur have three even isotopes M = (32, 34, 36) and one odd M 33). This problem is still open. (author)

  12. The Chemical Evolution of Phosphorus

    Science.gov (United States)

    Jacobson, Heather R.; Thanathibodee, Thanawuth; Frebel, Anna; Roederer, Ian U.; Cescutti, Gabriele; Matteucci, Francesca

    2014-12-01

    Phosphorus is one of the few remaining light elements for which little is known about its nucleosynthetic origin and chemical evolution, given the lack of optical absorption lines in the spectra of long-lived FGK-type stars. We have identified a P I doublet in the near-ultraviolet (2135/2136 Å) that is measurable in stars of low metallicity. Using archival Hubble Space Telescope-Space Telescope Imaging Spectrograph spectra, we have measured P abundances in 13 stars spanning -3.3 production in the early universe. As P is one of the key building blocks of life, we also discuss the chemical evolution of the important elements to life, C-N-O-P-S, together. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is supported through program AR-13246. Other portions of this work are based on data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and the McDonald Observatory of the University of Texas at Austin.

  13. Chlorine isotopes potential as geo-chemical tracers

    Digital Repository Service at National Institute of Oceanography (India)

    Shirodkar, P.V.; Pradhan, U.K.; Banerjee, R.

    The potential of chlorine isotopes as tracers of geo-chemical processes of earth and the oceans is highlighted based on systematic studies carried out in understanding the chlorine isotope fractionation mechanism, its constancy in seawater and its...

  14. Isotope dependence of chemical erosion of carbon

    International Nuclear Information System (INIS)

    Reinhold, C.O.; Krstic, P.S.; Stuart, S.J.; Zhang, H.; Harris, P.R.; Meyer, F.W.

    2010-01-01

    We study the chemical erosion of hydrogen-supersaturated carbon due to bombardment by hydrogen isotopes H, D, and T at energies of 1-30 eV using classical molecular dynamics simulations. The chemical structure at the hydrogen-saturated interface (the distribution of terminal hydrocarbon moieties, in particular) shows a weak dependence on the mass of the impinging atoms. However, the sputtering yields increase considerably with increasing projectile mass. We analyze the threshold energies of chemical sputtering reaction channels and show that they are nearly mass independent, as expected from elementary bond-breaking chemical reactions involving hydrocarbons. Chemical sputtering yields for D impact are compared with new experimental data. Good agreement is found for small hydrocarbons but the simulations overestimate the production of large hydrocarbons for energies larger than 15 eV. We present a thorough analysis of the dependence of our simulations on the parameters of the bombardment schemes and discuss open questions and possible avenues for development.

  15. Evolution of single-particle structure of silicon isotopes

    Science.gov (United States)

    Bespalova, O. V.; Fedorov, N. A.; Klimochkina, A. A.; Markova, M. L.; Spasskaya, T. I.; Tretyakova, T. Yu.

    2018-01-01

    New data on proton and neutron single-particle energies E_{nlj} of Si isotopes with neutron number N from 12 to 28 as well as occupation probabilities N_{nlj} of single-particle states of stable isotopes 28, 30Si near the Fermi energy were obtained by the joint evaluation of the stripping and pick-up reaction data and excited state decay schemes of neighboring nuclei. The evaluated data indicate the following features of single-particle structure evolution: persistence of Z = 14 subshell closure with N increase, the new magicity of the number N = 16, and the conservation of the magic properties of the number N = 20 in Si isotopic chain. The features were described by the dispersive optical model. The calculation also predicts the weakening of N = 28 shell closure and demonstrates evolution of a bubble-like structure of the proton density distributions in neutron-rich Si isotopes.

  16. Evolution of single-particle structure of silicon isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Bespalova, O.V.; Klimochkina, A.A.; Spasskaya, T.I.; Tretyakova, T.Yu. [Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics, Moscow (Russian Federation); Fedorov, N.A.; Markova, M.L. [Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation)

    2018-01-15

    New data on proton and neutron single-particle energies E{sub nlj} of Si isotopes with neutron number N from 12 to 28 as well as occupation probabilities N{sub nlj} of single-particle states of stable isotopes {sup 28,30}Si near the Fermi energy were obtained by the joint evaluation of the stripping and pick-up reaction data and excited state decay schemes of neighboring nuclei. The evaluated data indicate the following features of single-particle structure evolution: persistence of Z = 14 subshell closure with N increase, the new magicity of the number N = 16, and the conservation of the magic properties of the number N = 20 in Si isotopic chain. The features were described by the dispersive optical model. The calculation also predicts the weakening of N = 28 shell closure and demonstrates evolution of a bubble-like structure of the proton density distributions in neutron-rich Si isotopes. (orig.)

  17. Chemical evolution coefficients for the study of galactic evolution

    Energy Technology Data Exchange (ETDEWEB)

    Mallik, D C.V. [Indian Inst. of Astrophysics, Bangalore

    1980-05-01

    A new evaluation of chemical evolution coefficients has been made using recent stellar evolution and nucleosynthesis data. The role of the low and intermediate mass stars in galactic nucleosynthesis has been emphasized. A significant amount of /sup 4/He, /sup 12/C and neutron-rich species is found to be contributed by these stars. Comparison with observed abundances suggests a primary origin of /sup 14/N. The simple model of galactic evolution with the new coefficients has been used to derive the ratio of helium to heavy element enrichment in the Galaxy. The new stellar evolution data do not explain the large value of this ratio that has been determined observationally.

  18. Chemical evolution coefficients for the study of galactic evolution

    International Nuclear Information System (INIS)

    Mallik, D.C.V.

    1980-01-01

    A new evaluation of chemical evolution coefficients has been made using recent stellar evolution and nucleosynthesis data. The role of the low and intermediate mass stars in galactic nuclosynthesis has been emphasized. A significant amount of 4 He, 12 C and neutron-rich species is found to be contributed by these stars. Comparison with observed abundances suggests a primary origin of 14 N. The simple model of galactic evolution with the new coefficients has been used to derive the ratio of helium to heavy element enrichment in the Galaxy. The new stellar evolution data do not explain the large value of this ratio that has been determined observationally. (orig.)

  19. Isotope and chemical tracers in groundwater hydrology

    International Nuclear Information System (INIS)

    Kendall, C.; Stewart, M.K.; Morgenstern, U.; Trompetter, V.

    1999-01-01

    The course sessions cover: session 1, Fundamentals of stable and radioactive isotopes; session 2, Stable oxygen and hydrogen isotopes in hydrology: background, examples, sampling strategy; session 3, Catchment studies using oxygen and hydrogen isotopes: background - the hydrologic water balance, evapotranspiration - the lion's share, runoff generation - new water/old water fractions, groundwater recharge - the crumbs; session 4, Isotopes in catchment hydrology: survey of applications, future developments; session 5, Applications of tritium in hydrology: background and measurement, interpretation, examples; session 6, Case studies using mixing models: Hutt Valley groundwater system, an extended mixing model for simulating tracer transport in the unsaturated zone; session 7, Groundwater dating using CFC concentrations: background, sampling and measurement, use and applications; session 8, Groundwater dating with carbon-14: background, sampling and measurement, use and applications; session 9, NZ case studies: Tauranga warm springs, North Canterbury Plains groundwater; session 10, Stable carbon and nitrogen isotopes: background and examples, biological applications of C-N-S isotopes; session 11, New developments in isotope hydrology: gas isotopes, compound specific applications, age dating of sediments etc; session 12, NZ case studies: North Canterbury Plains groundwater (continued), Waimea Plains groundwater. (author). refs., figs

  20. Pb, Sr and Nd isotope geological characteristics and its evolution of Jianchaling rock

    International Nuclear Information System (INIS)

    Pang Chunyong; Chen Minyang; Xu Wenxin

    2003-01-01

    It has been a long time debatable subject on the raw material source and its genesis of Jianchaling ultrabasic rock, because the original rock phases, the original mineral compositions, texture and structure, even part of the chemical components of the rocks had been changed completely after many periods and phases of metamorphism. According to the content of Pb, Rb, Sr, Nd elements and their Pb, Sr, Nd isotope compositions of the rocks, together with the isotope geological age of late magmatic activities, the authors analyze the evolution of Pb, Sr, Nd isotope compositions, The inferred initiate Nd isotope ratio of ultrabasic rocks is 0.510233, lower than that of meteorite unity at a corresponding period, its ε Nd(T)>O; The initiate Sr ratios inferred by the isotope geological age ranges from 0.702735 to 0.719028; Projecting the lead isotope compositions on the Pb tectonic evolution model, the result indicates that the raw material of Jianchaling ultrabasic rock coming from the deplete upper mantle. The ultrabasic magma which enrich of Mg, Ni and less S intruded the crust and formed the Jianchaling ultrabasic rock at late Proterozoic era (927 Ma±). The forming time of serpentinite is mostly equal to the granitoid intruding time, showing the intrusion o flate acidic magma caused a large scale alteration of the ultrabasic rocks and formed the meta-ultrabasic phase rock observed today. (authors)

  1. Antibodies and isotopes, a chemical approach to tumour targeting

    International Nuclear Information System (INIS)

    Vaughan, A.T.M.; Yankuba, S.C.S.; Anderson, P.

    1986-01-01

    In this study, scandium-47 and yttrium-90 have been used as representatives of potential cytotoxic labels. Both isotopes have a high yield of energetic beta particles and half-lives of the same order as indium-111. In addition they are both members of Group III and so may be used as a base for chemical comparisons in the future with radiotoxic isotopes from other chemical groups

  2. Isotopic and chemical investigations on Angra dos Reis

    International Nuclear Information System (INIS)

    Wasserburg, G.J.; Tera, F.; Papanastassiou, D.A.; Huneke, J.C.

    1977-01-01

    Extensive isotopic studies of Pb, Sr and Xe and chemical abundance measurements of K, Rb, Sr, Ba, Nd, Sm, U and Th for total meteorite and mineral separates of the Angra dos Reis achondrite are reported on. U-Pb, Th-Pb and Pb-Pb ages are concordant at 4.54 AE for the total meteorite and for high-purity whitlockite in Angra dos Reis. This establishes Angra dos Reis as an early planetary differentiate which has not been disturbed for these systems since 4.54 AE ago. Measured 87 Sr/ 86 Sr in pyroxene and whitlockite for Angra dos Reis (ADOR) are distinctly below BABI by two parts in 10 4 and only one part in 10 4 above the lowest 87 Sr/ 86 Sr (ALL) measured in an Allende inclusion. The difference in ADOR-ALL corresponds to an interval of condensation in the solar nebula of approximately 3 m.y. If 26 Al was the heat source for the magmatism on the parent planets of Angra dos Reis and the basaltic achondrites (BABI) then the relatively large difference in 87 Sr/ 86 Sr, BABI - ALL, must be the result of planetary evolution rather than condensation over approximately 10 m.y. Xe isotopic measurements confirm the presence of large amounts of 244 Pu-produced fission Xe and show that 244 Pu was enriched in the whitlockite relative to the pyroxene by a factor of approximately 18. Chemical element enrichment factors between the whitlockite and the fassaitic pyroxene in Angra dos Reis are presented. The enrichment factors demonstrate close analogy between the rare earth elements and their actinide analogs. The enrichment factor for Pu is intermediate to the enrichment factors of Nd and Sm. (Auth.)

  3. CHEMICAL EVOLUTION LIBRARY FOR GALAXY FORMATION SIMULATION

    International Nuclear Information System (INIS)

    Saitoh, Takayuki R.

    2017-01-01

    We have developed a software library for chemical evolution simulations of galaxy formation under the simple stellar population (SSP) approximation. In this library, all of the necessary components concerning chemical evolution, such as initial mass functions, stellar lifetimes, yields from Type II and Type Ia supernovae, asymptotic giant branch stars, and neutron star mergers, are compiled from the literature. Various models are pre-implemented in this library so that users can choose their favorite combination of models. Subroutines of this library return released energy and masses of individual elements depending on a given event type. Since the redistribution manner of these quantities depends on the implementation of users’ simulation codes, this library leaves it up to the simulation code. As demonstrations, we carry out both one-zone, closed-box simulations and 3D simulations of a collapsing gas and dark matter system using this library. In these simulations, we can easily compare the impact of individual models on the chemical evolution of galaxies, just by changing the control flags and parameters of the library. Since this library only deals with the part of chemical evolution under the SSP approximation, any simulation codes that use the SSP approximation—namely, particle-base and mesh codes, as well as semianalytical models—can use it. This library is named “CELib” after the term “Chemical Evolution Library” and is made available to the community.

  4. CHEMICAL EVOLUTION LIBRARY FOR GALAXY FORMATION SIMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Saitoh, Takayuki R., E-mail: saitoh@elsi.jp [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro, Tokyo, 152-8551 (Japan)

    2017-02-01

    We have developed a software library for chemical evolution simulations of galaxy formation under the simple stellar population (SSP) approximation. In this library, all of the necessary components concerning chemical evolution, such as initial mass functions, stellar lifetimes, yields from Type II and Type Ia supernovae, asymptotic giant branch stars, and neutron star mergers, are compiled from the literature. Various models are pre-implemented in this library so that users can choose their favorite combination of models. Subroutines of this library return released energy and masses of individual elements depending on a given event type. Since the redistribution manner of these quantities depends on the implementation of users’ simulation codes, this library leaves it up to the simulation code. As demonstrations, we carry out both one-zone, closed-box simulations and 3D simulations of a collapsing gas and dark matter system using this library. In these simulations, we can easily compare the impact of individual models on the chemical evolution of galaxies, just by changing the control flags and parameters of the library. Since this library only deals with the part of chemical evolution under the SSP approximation, any simulation codes that use the SSP approximation—namely, particle-base and mesh codes, as well as semianalytical models—can use it. This library is named “CELib” after the term “Chemical Evolution Library” and is made available to the community.

  5. Stable isotope evolution and paleolimnology of ancient Lake Creede

    Science.gov (United States)

    Rye, Robert O.; Bethke, Philip M.; Finkelstein, David B.

    2000-01-01

    gypsum or ikaite (CaCO3 ·6H2O) crystals grown displacively in the muds and silts near the water-sediment interface (rice grains). Other studies indicate that aragonite was the original CaCO3 precipitate forming the microsparite and peloidal laminae and that it converted to calcite during burial diagenesis. Samples from CCM-2 and nearby outcrop do not appear to have undergone significant isotope exchange during recrystallization. Samples from CCM-1 and nearby outcrop, however, appear to have undergone extensive oxygen isotope exchange with meteoric water-dominated fluids possibly during a local 17.6 Ma hydrothermal event.The δ18O-δ13C data set produced by microsampling of individual carbonate lamellae and rice grains is exceptional in several aspects and provides important clues concerning the evolution of limnologic structure of the lake and its chemical and isotopic composition. Travertine and ikaite pseudomorphs in travertine deposits extend the record an additional 330 m above the collar of CCM-2. The δ18O values on CCM-2 samples range from 10.4‰ to 37.3‰ and δ13C values range from –10.8‰ to 9.6‰. The data fall into two distinct groups, a covariant group and an invariant group. The covariant group shows a strong negative covariance and a large range of δ18O and δ13C values. The negative covariance is opposite that normally reported for lacustrine carbonates. The large range of δ18O and δ13C values requires that the carbonates precipitated from waters have a large range of temperature and carbon and oxygen isotopic composition. The invariant group has a narrow range of large δ18O values (35‰ ± 2‰) and a wide range of δ13C values (–10.8‰ to 9.6‰), indicating precipitation from waters with a narrow range of temperature and δ18O but a wide range in δ13C of aqueous carbon. The ranges of isotope values for microsparite and peloid samples are virtually identical; two-thirds are in the covariant group. By contrast, the values for almost all

  6. Chemical evolution of the galactic disk

    International Nuclear Information System (INIS)

    Wyse, R.F.G.; Gilmore, G.

    1987-01-01

    The distribution of enriched material in the stars and gas of their Galaxy contains information pertaining to the chemical evolution of the Milky Way from its formation epoch to the present day, and provides general constraints on theories of galaxy formation. The separate stellar components of the Galaxy cannot readily be understood if treated in isolation, but a reasonably self-consistent model for Galactic chemical evolution may be found if one considers together the chemical properties of the extreme spheroid, thick disk and thin disk populations of the Galaxy. The three major stellar components of the Galaxy are characterized by their distinct spatial distributions, metallicity structure, and kinematics, with the newly-identified thick disk being approximately three times more massive than the classical metal-poor, non-rotating extreme spheroid. Stellar evolution in the thick disk straightforwardly provides the desired pre-enrichment for resolution of the thin disk G dwarf problem

  7. Chemical evolution of the early Martian hydrosphere

    International Nuclear Information System (INIS)

    Schaefer, M.W.

    1990-01-01

    The chemical evolution of the early Martian hydrosphere is discussed. The early Martian ocean can be modeled as a body of relatively pure water in equilibrium with a dense carbon dioxide atmosphere. The chemical weathering of lavas, pyroclastic deposits, and impact melt sheets would have the effect of neutralizing the acidity of the juvenile water. As calcium and other cations are added to the water by chemical weathering, they are quickly removed by the precipitation of calcium carbonate and other minerals, forming a deposit of limestone beneath the surface of the ocean. As the atmospheric carbon dioxide pressure and the temperature decrease, the Martian ocean would be completely frozen. Given the scenario for the chemical evolution of the northern lowland plains of Mars, it should be possible to draw a few conclusions about the expected mineralogy and geomorphology of this regions

  8. Mo isotope fractionation during hydrothermal evolution of porphyry Cu systems

    Science.gov (United States)

    Shafiei, Behnam; Shamanian, GholamHossein; Mathur, Ryan; Mirnejad, Hassan

    2015-03-01

    We present Mo isotope compositions of molybdenite types from three successive stages of ore deposition in several porphyry copper deposits of the Kerman region, Iran. The data provide new insights into controlling processes on Mo isotope fractionation during the hydrothermal evolution of porphyry systems. The Mo isotope compositions of 27 molybdenite samples show wide variations in δ97Mo ranging from -0.37 to +0.92 ‰. The data reveal that molybdenites in the early and transitional stages of mineralization (preferentially 2H polytypes; δ97Mo mean = 0.35 ‰) have higher δ97Mo values than late stage (mainly 3R polytypes; δ97Mo mean = 0.02 ‰) molybdenites. This trend suggests that fractionation of Mo isotopes occurred in high-temperature stages of mineralization and that hydrothermal systems generally evolve towards precipitation of molybdenite with lower δ97Mo values. Taking into account the genetic models proposed for porphyry Cu deposits along with the temperature-dependent fractionation of Mo isotope ratios, it is proposed that large variations of Mo isotopes in the early and the transitional stages of ore deposition could be controlled by the separation of the immiscible ore-forming fluid phases with different density, pH, and ƒO2 properties (i.e., brine and vapor). The fractionation of Mo isotopes during fluid boiling and Rayleigh distillation processes likely dominates the Mo isotope budget of the remaining ore-forming fluids for the late stage of mineralization. The lower δ97Mo values in the late stage of mineralization can be explained by depletion of the late ore-forming hydrothermal solutions in 97Mo, as these fluids have moved to considerable distance from the source. Finally, the relationship observed between MoS2 polytypes (2H and 3R) and their Mo isotopic compositions can be explained by the molecular vibration theory, in which heavier isotopes are preferentially partitioned into denser primary 2H MoS2 crystals.

  9. Laser isotope separation - a new class of chemical process

    International Nuclear Information System (INIS)

    Woodall, K.B.; Mannik, L.; O'Neill, J.A.; Mader, D.L.; Nickerson, S.B.; Robins, J.R.; Bartoszek, F.E.; Gratton, D.

    1983-01-01

    Lasers may soon find several applications in chemical processing. The applications that have attracted the most research funding to date involve isotope separation for the nuclear industry. These isotopes have an unusually high value (≥$1000/kg) compared to bulk chemicals (∼$1/kg) and are generally required in very large quantities. In a laser isotope separation process, light is used to convert a separation that is very difficult or even impossible by conventional chemical engineering techniques to one that is readily handled by conventional separation technology. For some isotopes this can result in substantial capital and energy savings. A uranium enrichment process developed at the Lawrence Livermore National Laboratory is the closest to commercialization of the large scale laser isotope separation processes. Of particular interest to the Canadian nuclear industry are the laser separation of deuterium, tritium, zirconium-90 and carbon-14. In this paper, the basic principles behind laser isotope separation are reviewed and brief dscriptions of the more developed processes are given

  10. Isotopic evolution of aqueous sulphate in northern Chile water

    International Nuclear Information System (INIS)

    Aravena, R.; Suzuki, O.; Fritz, P.; Pena, H.; Rauert, W.

    1987-01-01

    Full text: The extremely arid condition of northern Chile is the main obstacle to the present and future development of urban centres and economic activities in the region. The existing water resources are scarce. During the last decade, isotope techniques have been applied to investigate aspects such as the origin and residence time of the groundwater, these being extremely important for water development and water management. This paper presents 18 O and 34 S data in aqueous sulphate, as well as 18 O, 2 H, and 3 H from springs, rivers and groundwater samples of the Pampa del Tamarugal and Salar de Llamara basins. The principal aim of this study was to investigate the isotope evolution of the sulphate, the origin of the sulphur, the groundwater flow path, and the possibility of using the 18 O of the sulphate as a tracer for estimation of the residence time of the groundwater. Springs that have their recharge area in the high Altiplano (Salar del Huasco basin) show δ values between +5.0 per mille and +6.0 per mille for the 18 O and +5.0 per mille and +9.0 per mille for the 34 S isotope. Springs from lower altitude, show an isotope content between + 8.6 per mille and + 10.6 per mille for 18 O and +7.4 per mille and + 11.7 per mille for 34 S. The groundwaters in the Pampa aquifers, based on their hydrogen and oxygen isotope composition, are associated with different recharge areas. However, these waters show an isotope range for the sulphate similar to .he one of the springs, and no clear relationships are observed between isotope content, flow path and residence time. This pattern could be related to the poorly defined aquifer systems present in the Pampa. The Llamara groundwaters have a uniform isotope content and are the most enriched in the region (δ 18 O = -6.0 per mille and δ 2 H = -50 per mille). The isotope composition of their sulphate compares well with the Pampa groundwater, indicating a similar sulphate source. The isotope composition of gypsum

  11. Isotopic Abundance and Chemical Purity Analysis of Stable Isotope Deuterium Labeled Sudan I

    Directory of Open Access Journals (Sweden)

    CAI Yin-ping;LEI Wen;ZHENG Bo;DU Xiao-ning

    2014-02-01

    Full Text Available It is important that to analysis of the isotopic abundance and chemical purity of Sudan I-D5, which is the internal standard of isotope dilution mass spectrometry. The isotopic abundance of Sudan I-D5 is detected by “mass cluster” classification method and LC-MS. The repeatability and reproducibility experiments were carried out by using different mass spectrometers and different operators. The RSD was less than 0.1%, so the repeatability and reproducibility were satisfactory. The accuracy and precision of the isotopic abundance analysis method was good with the results of F test and t test. The high performance liquid chromatography (HPLC had been used for detecting the chemical purity of Sudan I-D5 as external standard method.

  12. Mass-independent isotope effects in chemical exchange reaction

    International Nuclear Information System (INIS)

    Nishizawa, Kazushige

    2000-01-01

    Isotope effects of some elements in chemical exchange reaction were investigated by use of liquid-liquid extraction, liquid membrane or chromatographic separation. Cyclic polyether was used for every method. All polyethers used in a series of the studies were made clear that they distinguished the isotopes not only by their nuclear masses but also by their nuclear sizes and shapes. Chromium isotopes, for example, were recognized to have enrichment factors being proportional to δ 2 > which is a parameter to show field shift or the nuclear size and shape of the isotope. It follows that the chromium isotopes are separated not by their masses but by their field shift effects. Nuclear spin also played a great role to separate odd mass number isotopes from even mass number isotopes in even atomic number elements. Contribution of the nuclear spin (I=3/2) of 53 Cr to total enrichment factor, ε 53/52 = -0.00028, for 53 Cr to 52 Cr was observed to be, ε spin = -0.0025. (author)

  13. Influence of chemical structure on carbon isotope composition of lignite

    Science.gov (United States)

    Erdenetsogt, Bat-Orshikh; Lee, Insung; Ko, Yoon-Joo; Mungunchimeg, Batsaikhan

    2017-04-01

    During the last two decades, a number of studies on carbon isotopes in terrestrial organic matter (OM) have been carried out and used to determine changes in paleoatmospheric δ13C value as well as assisting in paleoclimate analysis. Coal is abundant terrestrial OM. However, application of its δ13C value is very limited, because the understanding of changes in isotopic composition during coalification is relatively insufficient. The purpose of this study was to examine the influence of the chemical structure on the carbon isotope composition of lignite. Generally, lignite has more complex chemical structures than other higher rank coal because of the existence of various types of oxygen-containing functional groups that are eliminated at higher rank level. A total of sixteen Lower Cretaceous lignite samples from Baganuur mine (Mongolia) were studied by ultimate, stable carbon isotope and solid-state 13C CP/MAS NMR analyses. The carbon contents of the samples increase with increase in depth, whereas oxygen content decreases continuously. This is undoubtedly due to normal coalification process and also consistent with solid state NMR results. The δ13C values of the samples range from -23.54‰ to -21.34‰ and are enriched in 13C towards the lowermost samples. Based on the deconvolution of the NMR spectra, the ratios between carbons bonded to oxygen (60-90 ppm and 135-220 ppm) over carbons bonded to carbon and hydrogen (0-50 ppm and 90-135 ppm) were calculated for the samples. These correlate well with δ13C values (R2 0.88). The results indicate that the δ13C values of lignite are controlled by two mechanisms: (i) depletion in 13C as a result of loss of isotopically heavy oxygen-bounded carbons and (ii) enrichment in 13C caused by a loss of isotopically light methane from aliphatic and aromatic carbons. At the rank of lignite, coal is enriched in 13C because the amount of isotopically heavy CO2 and CO, released from coal as a result of changes in the chemical

  14. Galactic chemical evolution in hierarchical formation models

    Science.gov (United States)

    Arrigoni, Matias

    2010-10-01

    The chemical properties and abundance ratios of galaxies provide important information about their formation histories. Galactic chemical evolution has been modelled in detail within the monolithic collapse scenario. These models have successfully described the abundance distributions in our Galaxy and other spiral discs, as well as the trends of metallicity and abundance ratios observed in early-type galaxies. In the last three decades, however, the paradigm of hierarchical assembly in a Cold Dark Matter (CDM) cosmology has revised the picture of how structure in the Universe forms and evolves. In this scenario, galaxies form when gas radiatively cools and condenses inside dark matter haloes, which themselves follow dissipationless gravitational collapse. The CDM picture has been successful at predicting many observed properties of galaxies (for example, the luminosity and stellar mass function of galaxies, color-magnitude or star formation rate vs. stellar mass distributions, relative numbers of early and late-type galaxies, gas fractions and size distributions of spiral galaxies, and the global star formation history), though many potential problems and open questions remain. It is therefore interesting to see whether chemical evolution models, when implemented within this modern cosmological context, are able to correctly predict the observed chemical properties of galaxies. With the advent of more powerfull telescopes and detectors, precise observations of chemical abundances and abundance ratios in various phases (stellar, ISM, ICM) offer the opportunity to obtain strong constraints on galaxy formation histories and the physics that shapes them. However, in order to take advantage of these observations, it is necessary to implement detailed modeling of chemical evolution into a modern cosmological model of hierarchical assembly.

  15. Age and isotope evidence for the evolution of continental crust

    International Nuclear Information System (INIS)

    Moorbath, S.

    1978-01-01

    Irreversible chemical differentiation of the mantle's essentially infinite reservoir for at least the past 3800 Ma has produced new continental, sialic crust during several relatively short (ca. 100-300 Ma) episodes which were widely separated in time and may have been of global extent. During each episode (termed 'accretion-differentiation superevent'), juvenile sial underwent profound igneous, metamorphic and geochemical differentiation, resulting in thick (ca. 25-40 km), stable, compositionally gradational, largely indestructible, continental crust exhibiting close grouping of isotopic ages of rock formation, as well as mantle-type initial Sr and Pb isotopic ratios for all major constituents. Isotopic evidence suggests that within most accretion-differentiation superevents - and especially during the earlier ones - continental growth predominated over reworking of older sialic crust. Reworking of older sialic crust can occur in several types of geological environment and appears to have become more prevalent with the passage of geological time. It is usually clearly distinguishable from continental growth, by application of appropriate age and isotope data. (author)

  16. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    Abou Zakhem, B.; Hafez, R.

    2008-01-01

    13 meteoric stations were selected in syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the syrian or local meteoric line (SMWL) was estimated with a slope of 6.63 and that of both syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude was determined by 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14% and - 0.84%/100 m elevation respectively). The spatial variability of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content of precipitation, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern mediterranean climate type over this region. (author)

  17. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    Abou Zakhem, B.; Hafez, R.

    2007-05-01

    The objective of this study is to determine isotopic characteristics of precipitation, the climatic and geographical conditions affecting isotopic composition in order to obtain the input function of groundwater to evaluate the water resources.13 meteoric stations were selected in Syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the Syrian meteoric line (SMWL) was estimated with a slope of 6.62 and that of both Syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude of 18 O was about 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14 % and -0.84% /100m respectively). The spatial distribution of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern Mediterranean climate type over this region.(author)

  18. Method for separating the isotopes of a chemical element

    International Nuclear Information System (INIS)

    Devienne, F.M.

    1977-01-01

    A beam of positive or negative primary ions of at least one compound of a chemical element is accelerated in order to pass through collision boxes placed in series. As a result of inelastic collisions of the ions with the molecules of a neutral target gas within each collision box, a given percentage of primary ions is dissociated into at least two fragments, one of which is a secondary ion in the form of at least two isotopic species. The collision boxes are brought to a potential V 2 so as to trap preferentially one isotopic species which is condensed within each box. 15 claims, 4 figures

  19. Isotopes and the early evolution of the earth

    International Nuclear Information System (INIS)

    Russell, R.D.

    1980-01-01

    The observed isotopic ratios of lead, strontium, neodymium, helium, and argon contain information about the chemical abundances of selected parent and daughter elements in the outer parts of the Earth. By necessity, we observe these isotopic ratios at the Earth's surface, which is a small, highly evolved part of the Earth. The studies of such isotopic ratios permit inferences to be made about interactions between this crust and the upper mantle. Helium has been especially valuable for demonstrating that primordial materials are still being outgassed from the earth. Models based on the observed argon isotopic ratios have lead to contradictory conclusions about the existence of an early period of extensive outgassing of the Earth. Lead has been a particularly interesting element because the ratio of the parents, 235 U/ 238 U, was very different in the Earth's early history than it is now. Therefore there is the potential for determining constraints on the early history of the Earth. A number of recently published papers offering lead isotope interpretations that reflect on the Earth's early history are reviewed, with special reference to models that are based upon uni-directional and bi-directional exchange between a protocrust and a residual mantle. Geochemical parameters for uranium, thorium and lead can be inferred for two evolving systems, as well as rate constants for differentiation. The principal conclusions are that the differentiation process extended beyond the first quarter of the Earth's history, and that it is possible to reproduce exactly the apparent oceanic basalt isochron by a simple two-reservoir model. In particular, such a model can explain quantitatively the observed lead-207 deficiency in the oceanic basalts

  20. Plutonium isotopes in the atmosphere of Central Europe: Isotopic composition and time evolution vs. circulation factors

    Energy Technology Data Exchange (ETDEWEB)

    Kierepko, Renata, E-mail: Renata.Kierepko@ifj.edu.pl [Institute of Nuclear Physics, Polish Academy of Sciences, Krakow (Poland); Mietelski, Jerzy W. [Institute of Nuclear Physics, Polish Academy of Sciences, Krakow (Poland); Ustrnul, Zbigniew [Jagiellonian University, Krakow (Poland); Institute of Meteorology and Water Management, National Research Institute, Krakow (Poland); Anczkiewicz, Robert [Institute of Geological Sciences, Polish Academy of Sciences, Krakow (Poland); Wershofen, Herbert [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Holgye, Zoltan [National Radiation Protection Institute, Prague (Czech Republic); Kapała, Jacek [Medical University of Bialystok (Poland); Isajenko, Krzysztof [Central Laboratory for Radiological Protection, Warsaw (Poland)

    2016-11-01

    This paper reports evidence of Pu isotopes in the lower part of the troposphere of Central Europe. The data were obtained based on atmospheric aerosol fraction samples collected from four places in three countries (participating in the informal European network known as the Ring of Five (Ro5)) forming a cell with a surface area of about 200,000 km{sup 2}. We compared our original data sets from Krakow (Poland, 1990–2007) and Bialystok (Poland, 1991–2007) with the results from two other locations, Prague (Czech Republic; 1997–2004) and Braunschweig (Germany; 1990–2003) to find time evolution of the Pu isotopes. The levels of the activity concentration for {sup 238}Pu and for {sup (239} {sup +} {sup 240)}Pu were estimated to be a few and some tens of nBq m{sup −} {sup 3}, respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of {sup 238}Pu in the atmosphere. The achieved complex data sets were used to test a new approach to the problem of solving mixing isotopic traces from various sources (here up to three) in one sample. Results of our model, supported by mesoscale atmospheric circulation parameters, suggest that Pu from nuclear weapon accidents or tests and nuclear burnt-up fuel are present in the air. - Highlights: • Evidence of Pu isotopes in the lower part of the troposphere of Central Europe • The effective annual doses associated with Pu inhalation • New approach to the problem of solving mixed Pu origins in one sample (3SM) • Relationship between Pu isotopes activity concentration and circulation factors.

  1. Thermal and Chemical Evolution of Collapsing Filaments

    Energy Technology Data Exchange (ETDEWEB)

    Gray, William J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Scannapieco, Evan [Arizona State Univ., Mesa, AZ (United States). School of Earth and Space Exploration

    2013-01-15

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, Z ≈ 0.1Z filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10-3Z filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253, but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

  2. Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

    Science.gov (United States)

    Rudnick, R. L.; Liu, X. M.

    2012-04-01

    The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" that is the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems point to the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 1×10^10 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

  3. Chemical evolution of the Magellanic Clouds

    Science.gov (United States)

    Barbuy, B.; de Freitas Pacheco, J. A.; Idiart, T.

    We have obtained integrated spectra for 14 clusters in the Magellanic Clouds, on which the spectral indices Hβ, Mg2, Fe5270, Fe5335 were measured. Selecting indices whose behaviour depends essentially on age and metallicity (Hβ and ), together with (B-V) and (V-K) colours, we were able to determine age and metallicities for these clusters, using calibrations based on single stellar population models (Borges et al. 1995). A chemical evolution model which follows a star formation history as indicated by the field population is checked with the age and metallicity data for our sample star clusters.

  4. Chemical Evolution of a Protoplanetary Disk

    Science.gov (United States)

    Semenov, Dmitry A.

    2011-12-01

    In this paper we review recent progress in our understanding of the chemical evolution of protoplanetary disks. Current observational constraints and theoretical modeling on the chemical composition of gas and dust in these systems are presented. Strong variations of temperature, density, high-energy radiation intensities in these disks, both radially and vertically, result in a peculiar disk chemical structure, where a variety of processes are active. In hot, dilute and heavily irradiated atmosphere only the most photostable simple radicals and atoms and atomic ions exist, formed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich ion-molecule and radical-radical chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex polyatomic (organic) species are synthesized. Dynamical processes affect disk chemical composition by enriching it in abundances of complex species produced via slow surface processes, which will become detectable with ALMA.

  5. Evolution of uranium isotope separation methods in France

    International Nuclear Information System (INIS)

    Frejacques, C.; Gelee, M.; Massignon, D.; Plurien, P.

    This paper examines the various processes studied in France from the dual standpoint of evolution of their technical-economic performances and the proliferation risks involved. Estimates of investments, energy consumptions, and operating and maintenance expenses are compared. The gaseous diffusion process is used as a reference; centrifuging, aerodynamic processes, chemical exchange, photochemical excitation, and ionic processes are considered. It is concluded that, from the standpoint of dissemination, while chemical exchange can provide a satisfactory solution for countries desiring an independent nuclear fuel supply, centrifuging and laser processes pose serious problems

  6. Galactic chemical evolution: perspectives and prospects

    International Nuclear Information System (INIS)

    Trimble, V.

    1987-01-01

    The first modern, quantitative models of galactic chemical evolution appeared exactly 20 years ago in the PhD dissertation of the late Beatrice M. Tinsley. Such models represent a synthesis of the behavior of the 10 11 or more stars that form over the 10 10 year age of a galaxy like their Milky Way and are vital both for understanding how and why galaxies have the luminosities, colors, and chemical compositions they see now and for interpreting observations of distant galaxies to answer cosmological questions about the size, age, density, inhomogeneities, and geometry of the universe. Since my last status report on the subject, some issues have become much clearer (the distinctness of nucleosynthesis in Type I, low mass, supernovae, from that in Type II's that make pulsars; the importance of galaxy mergers and interactions in triggering bursts of star formation), while others have remained puzzling (the sites of the r and p processes) or newly-surfaced (the nucleosynthetic contributions of pre-galactic massive objects; the nature and roll of dark matter in galaxies). The talk will touch briefly on the past, present, and future of galactic evolution studies

  7. UNCERTAINTIES IN GALACTIC CHEMICAL EVOLUTION MODELS

    International Nuclear Information System (INIS)

    Côté, Benoit; Ritter, Christian; Herwig, Falk; O’Shea, Brian W.; Pignatari, Marco; Jones, Samuel; Fryer, Chris L.

    2016-01-01

    We use a simple one-zone galactic chemical evolution model to quantify the uncertainties generated by the input parameters in numerical predictions for a galaxy with properties similar to those of the Milky Way. We compiled several studies from the literature to gather the current constraints for our simulations regarding the typical value and uncertainty of the following seven basic parameters: the lower and upper mass limits of the stellar initial mass function (IMF), the slope of the high-mass end of the stellar IMF, the slope of the delay-time distribution function of Type Ia supernovae (SNe Ia), the number of SNe Ia per M ⊙ formed, the total stellar mass formed, and the final mass of gas. We derived a probability distribution function to express the range of likely values for every parameter, which were then included in a Monte Carlo code to run several hundred simulations with randomly selected input parameters. This approach enables us to analyze the predicted chemical evolution of 16 elements in a statistical manner by identifying the most probable solutions, along with their 68% and 95% confidence levels. Our results show that the overall uncertainties are shaped by several input parameters that individually contribute at different metallicities, and thus at different galactic ages. The level of uncertainty then depends on the metallicity and is different from one element to another. Among the seven input parameters considered in this work, the slope of the IMF and the number of SNe Ia are currently the two main sources of uncertainty. The thicknesses of the uncertainty bands bounded by the 68% and 95% confidence levels are generally within 0.3 and 0.6 dex, respectively. When looking at the evolution of individual elements as a function of galactic age instead of metallicity, those same thicknesses range from 0.1 to 0.6 dex for the 68% confidence levels and from 0.3 to 1.0 dex for the 95% confidence levels. The uncertainty in our chemical evolution model

  8. Evolution of uranium isotope separation methods in France

    International Nuclear Information System (INIS)

    Frejacques, C.; Gelee, M.; Massignon, D.; Plurien, P.

    This paper examines the various processes for producing enriched U, from the dual standpoint of evolution of their technical-economic performances and the proliferation risks involved. The gaseous diffusion process is first examined as a reference; then centrifugation, aerodynamic processes, chemical exchange processes, photochemical excitation processes, and ionic processes are considered. It is concluded that the first four methods may be competitive in the next decade

  9. Stochastic evolution of refractory interstellar dust during the chemical evolution of a two-phase interstellar medium

    International Nuclear Information System (INIS)

    Liffman, K.; Clayton, D.D.

    1989-01-01

    The evolution course of refractory interstellar dust during the chemical evolution of a two-phase interstellar medium (ISM) is studied using a simple model of the chemical evolution of ISM. It is assumed that, in this medium, the stars are born in molecular clouds, but new nucleosynthesis products and stellar return are entered into a complementary diffuse medium; the well-mixed matter of each interstellar phase is repeatedly cycled stochastically through the complementary phase and back. The dust is studied on a particle-by-particle bases as it is sputtered by shock waves in the diffuse medium, accretes an amorphous mantle of gaseous refractory atoms while its local medium joins the molecular cloud medium, and encounters the possibility of astration within molecular clouds. Results are presented relevant to the size spectrum of accreted mantles, its age spectrum and the distinction among its several lifetimes, depletion factors of refractory atoms in the diffuse gas, and isotopic anomalies. 26 refs

  10. Stable isotope paleoaltimetry and the evolution of landscapes and life

    Science.gov (United States)

    Mulch, Andreas

    2016-01-01

    circulation and associated teleconnections in the global climate system that affect δ18O or δD of precipitation; (2) Evaluating on a case-by-case basis if temporal and spatial changes in isotope lapse rates influence interpretations of paleoelevation; (3) Interfacing with phylogenetic techniques to evaluate competing hypotheses with respect to the timing of surface uplift and the diversification of lineages; (4) Characterizing feedbacks between changes in surface elevation and atmospheric circulation as these are likely to be equally important to the diversification of lineages than changes in surface elevation alone. Tackling these challenges will benefit from the accelerating pace of improved data-model comparisons and rapidly evolving geochemical techniques for reconstructing precipitation patterns. Most importantly, stable isotope paleoaltimetry has the potential to develop into a truly interdisciplinary field if innovative tectonic/paleoclimatic and evolutionary biology/phylogenetic approaches are integrated into a common research framework. It therefore, opens new avenues to study the long-term evolution of landscapes and life. article>

  11. Chemical and isotopic fingerprinting of ancient Chinese porcelains

    International Nuclear Information System (INIS)

    Zhao, J.-X.; Li, B.-P.; Greig, A.; Collerson, K.D.; Feng, Y.-X.

    2005-01-01

    We have obtained unequivocal fingerprinting for many Chinese porcelains of utmost significance, based on high-precision multi-element and isotopic analysis by inductively-coupled mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS) in our laboratory. As most ancient Chinese kilns used raw materials mined from local areas, differences in the geochemistry and mineralogy of these raw materials are expected to be preserved as distinctive geochemical and isotopic signatures in finished products and this may be useful for identifying their sources. Production techniques, such as purifying and mixing of different raw materials, may also vary from kiln to kiln, or may even change over time. All of that could also potentially leave a characteristic chemical and isotopic signature in a kiln's finished products. Using a tiny amount (often a few tens milligrams) of porcelain material, more than 40 element concentrations and Sr-Nd isotopic compositions can be rapidly and precisely determined on the ICP-MS and TIMS, respectively. The analytical results show that visibly similar Chinese porcelains made in different places and/or dynasties are strikingly distinctive. The data also allow modern fakes to be readily distinguished from antique porcelains. (author). 4 refs., 7 figs

  12. Chemical Evolution and the Evolutionary Definition of Life.

    Science.gov (United States)

    Higgs, Paul G

    2017-06-01

    Darwinian evolution requires a mechanism for generation of diversity in a population, and selective differences between individuals that influence reproduction. In biology, diversity is generated by mutations and selective differences arise because of the encoded functions of the sequences (e.g., ribozymes or proteins). Here, I draw attention to a process that I will call chemical evolution, in which the diversity is generated by random chemical synthesis instead of (or in addition to) mutation, and selection acts on physicochemical properties, such as hydrolysis, photolysis, solubility, or surface binding. Chemical evolution applies to short oligonucleotides that can be generated by random polymerization, as well as by template-directed replication, and which may be too short to encode a specific function. Chemical evolution is an important stage on the pathway to life, between the stage of "just chemistry" and the stage of full biological evolution. A mathematical model is presented here that illustrates the differences between these three stages. Chemical evolution leads to much larger differences in molecular concentrations than can be achieved by selection without replication. However, chemical evolution is not open-ended, unlike biological evolution. The ability to undergo Darwinian evolution is often considered to be a defining feature of life. Here, I argue that chemical evolution, although Darwinian, does not quite constitute life, and that a good place to put the conceptual boundary between non-life and life is between chemical and biological evolution.

  13. Volcanic degassing at Somma-Vesuvio (Italy) inferred by chemical and isotopic signatures of groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Caliro, S. [Osservatorio Vesuviano sezione di Napoli dell' Istituto, Nazionale Geofisica Vulcanologia, Via Diocleziano 328, 80124 Naples (Italy)]. E-mail: caliro@ov.ingv.it; Chiodini, G. [Osservatorio Vesuviano sezione di Napoli dell' Istituto, Nazionale Geofisica Vulcanologia, Via Diocleziano 328, 80124 Naples (Italy); Avino, R. [Osservatorio Vesuviano sezione di Napoli dell' Istituto, Nazionale Geofisica Vulcanologia, Via Diocleziano 328, 80124 Naples (Italy); Cardellini, C. [Dipartimento di Scienze della Terra, Universita di Perugia (Italy); Frondini, F. [Dipartimento di Scienze della Terra, Universita di Perugia (Italy)

    2005-06-15

    A geochemical model is proposed for water evolution at Somma-Vesuvio, based on the chemical and isotopic composition of groundwaters, submarine gas emission and chemical composition of the dissolved gases. The active degassing processes, present in the highest part of the volcano edifice, strongly influence the groundwater evolution. The geological-volcanological setting of the volcano forces the waters infiltrating at Somma-Vesuvio caldera, enriched in volcanic gases, to flow towards the southern sector to an area of high pCO{sub 2} groundwaters. Reaction path modelling applied to this conceptual model, involving gas-water-rock interaction, highlights an intense degassing process in the aquifer controlling the chemical and isotopic composition of dissolved gases, total dissolved inorganic C (TDIC) and submarine gas emission. Mapping of TDIC shows a unique area of high values situated SSE of Vesuvio volcano with an average TDIC value of 0.039 mol/L, i.e., one order of magnitude higher than groundwaters from other sectors of the volcano. On the basis of TDIC values, the amount of CO{sub 2} transported by Vesuvio groundwaters was estimated at about 150 t/d. This estimate does not take into account the fraction of gas loss by degassing, however, it represents a relevant part of the CO{sub 2} emitted in this quiescent period by the Vesuvio volcanic system, being of the same order of magnitude as the CO{sub 2} diffusely degassed from the crater area.

  14. Volcanic degassing at Somma-Vesuvio (Italy) inferred by chemical and isotopic signatures of groundwater

    International Nuclear Information System (INIS)

    Caliro, S.; Chiodini, G.; Avino, R.; Cardellini, C.; Frondini, F.

    2005-01-01

    A geochemical model is proposed for water evolution at Somma-Vesuvio, based on the chemical and isotopic composition of groundwaters, submarine gas emission and chemical composition of the dissolved gases. The active degassing processes, present in the highest part of the volcano edifice, strongly influence the groundwater evolution. The geological-volcanological setting of the volcano forces the waters infiltrating at Somma-Vesuvio caldera, enriched in volcanic gases, to flow towards the southern sector to an area of high pCO 2 groundwaters. Reaction path modelling applied to this conceptual model, involving gas-water-rock interaction, highlights an intense degassing process in the aquifer controlling the chemical and isotopic composition of dissolved gases, total dissolved inorganic C (TDIC) and submarine gas emission. Mapping of TDIC shows a unique area of high values situated SSE of Vesuvio volcano with an average TDIC value of 0.039 mol/L, i.e., one order of magnitude higher than groundwaters from other sectors of the volcano. On the basis of TDIC values, the amount of CO 2 transported by Vesuvio groundwaters was estimated at about 150 t/d. This estimate does not take into account the fraction of gas loss by degassing, however, it represents a relevant part of the CO 2 emitted in this quiescent period by the Vesuvio volcanic system, being of the same order of magnitude as the CO 2 diffusely degassed from the crater area

  15. Chemical composition of HAL, an isotopically-unusual Allende inclusion

    International Nuclear Information System (INIS)

    Davis, A.M.; Tanaka, T.; Grossman, L.; Lee, T.; Wasserburg, G.J.

    1982-01-01

    Thirty-seven major, minor and trace elements were determined by INAA and RNAA in samples of hibonite, black rim and portions of friable rim from an unusual Allende inclusion, HAL. The peculiar isotopic, mineralogical and textural properties of HAL are accompanied by very unusual trace element abundances. The most striking feature of the chemistry is the virtual absence of Ce from an inclusion otherwise highly enriched in REE compared to C1 chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os and Ir, relative to other refractory elements. Of the lithophile elements determined which are normally considered to be refractory in a gas of solar composition, Sr, Ba, Ce, U and V are the most volatile in oxidizing gases. The distribution of REE between hibonite and rims seems to have been established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. On the basis of HAL's chemical and isotopic composition, possible locations for the chemical and mass dependent isotopic fractionation are discussed. (author)

  16. Temperature evolution and the oxygen isotope composition of Phanerozoic oceans from carbonate clumped isotope thermometry

    Science.gov (United States)

    Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Yancey, Thomas E.; Pérez-Huerta, Alberto

    2018-05-01

    Surface temperature is among the most important parameters describing planetary climate and habitability, and yet there remains considerable debate about the temperature evolution of the Earth's oceans during the Phanerozoic Eon (541 million years ago to present), the time during which complex metazoan life radiated on Earth. Here we critically assess the emerging record of Phanerozoic ocean temperatures based on carbonate clumped isotope thermometry of fossil brachiopod and mollusk shells, and we present new data that fill important gaps in the Late Paleozoic record. We evaluate and reject the hypothesis that solid-state reordering of 13C-18O bonds has destroyed the primary clumped isotope temperature signal of most fossils during sedimentary burial at elevated temperatures. The resulting Phanerozoic record, which shows a general coupling between tropical seawater temperatures and atmospheric carbon dioxide (CO2) levels since the Paleozoic, indicates that tropical temperatures during the icehouse climate of the Carboniferous period were broadly similar to present (∼25-30 °C), and suggests that benthic metazoans were able to thrive at temperatures of 35-40 °C during intervals of the early and possibly the latest Paleozoic when CO2 levels were likely 5-10× higher than present-day values. Equally important, there is no resolvable trend in seawater oxygen isotope ratios (δ18 O) over the past ∼500 million years, indicating that the average temperature of oxygen exchange between seawater and the oceanic crust has been high (∼270 °C) since at least the early Paleozoic, which points to mid-ocean ridges as the dominant locus of water-rock interaction over the past half-billion years.

  17. Chemical and environmental isotope study of the basaltic aquifer systems of Yarmouk Basin (Syria)

    International Nuclear Information System (INIS)

    Kattan, Z.

    1994-08-01

    The water in the fissured basalt aquifer system, the Upper Jurassic aquifer of the Yarmouk Basin and the atmospheric precipitation have been investigated using chemical and environmental isotope techniques. The groundwaters flowing through the different aquifers are differentiated by their chemical ratios and their isotopic compositions. The evolution of chemical facies of groundwater from the recharge area towards the basin outlet is characterized by increasing of sodium and magnesium contents as a result of silicate leaching. The stable isotope compositions of precipitation and mountainous spring waters match the Mediterranean Meteoric Water Line, while the groundwaters from the central zone and from the major springs of the Yarmouk Basin are mixtures of freshwater, which is isotopically depleted and salty groundwater of Laja plateau area. The interpretations of tritium and radiocarbon ( 14 C) data indicate that the recharge zones of the groundwater in the Yarmouk Basin occur on the high-land of more than 1000 m of altitude. The residence time of the mountainous springs is short (of about 40 years or less). However, water ages corrected by Vogel's concept and Gonfiantini's Model show, in general, a range from 1000 to 11000 years for the central zone groundwater. The groundwater moves from the Mt. Hermon and Mt. Arab towards the central zone and from the north-east (i.e. the Laja plateau) towards south-west (i.e. the major springs). The radiometric flow velocities range from 20 to 60 m/year within the central zone, while the flow velocities from both sides of Mt. Hermon and Mt. Arab are lower (1-7 m/year). (author). 43 refs., 37 figs., 6 tabs

  18. Chemical composition of HAL, an isotopically-unusual Allende inclusion

    Science.gov (United States)

    Davis, A. M.; Tanaka, T.; Grossman, L.; Lee, T.; Wasserburg, G. J.

    1982-01-01

    Samples of hibonite, black rim, and portions of friable rim from an unusual Allende inclusion, named HAL, were analyzed by INAA and RNAA for 37 major, minor, and trace elements. An unusually low amount of Ce was found in HAL, although it otherwise was highly enriched in REE compared to C1 chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os, and Ir relative to other refractory elements. It is concluded that the distribution of REE between hibonite and rims was established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. Possible locations for the chemical and mass dependent isotopic fractionation are considered to be in ejecta from the low temperature helium-burning zone of a supernova and in the locally oxidizing environment generated by evaporation of interstellar grains of near-chondritic chemical composition.

  19. Chemical and environmental isotopes study of precipitation in Syria

    International Nuclear Information System (INIS)

    Al-Charideh, A.; Abou Zakhem, B.

    2009-02-01

    Chemical and isotopic compositions of monthly precipitation were monitored at 12 stations distributed over the entire region in Syria for a period of 4 years from December 1999 to April 2003. Amount of precipitation and mean air temperature of rain monthly were also recorded. The conductivity of rain waters varies between 35 μ/cm in the mountainous stations and 336 μ/cm at Deir Az-Zor station. Excepted Tartous station, the mean value of Cl in the rainfall in all station is 3.8 mg/l. The seasonal variations in δ 18 O are smaller at west stations than to the east stations due to low seasonal temperature variations. All stations are characterized by water lines with slopes significantly lower than GMWL, except Bloudan, suggesting the influence of local factors on the isotopic composition of the precipitation. d-excess values decrease from 19% in the western part to 13% in the eastern part of Syria, indicating the influence of the precipitation generated by the air masses coming from the Mediterranean Sea over Syria. A reliable altitude effect represent by depletion of heavy stable isotopes of about -0.21, and -1.47, per 100 m elevation of 18 O and δ 2 H, respectively. Monthly tritium activity and seasonal variations pattern are low in the west stations than at the east stations. The weighted mean tritium values are between 3 to 9 TU during 2000-2003, and it is increasing with distance from the Syrian coast by 1 TU /100 Km. (author)

  20. Chemical and environmental isotope study of precipitation in Syria

    International Nuclear Information System (INIS)

    Kattan, Z.

    1999-01-01

    Waters from a network of rainfall collection covering mine meteorological stations distributed mainly in the western part of Syria have been assayed using chemical and environmental isotope techniques for a period of 5 months from Dec. 1989 to Apr. 1990. The chemistry of rain waters falling over the mountainous stations shows a low solute concentration (20-105 mg 1 -1 ) compared with those falling over the coastal and anterior stations (50-210 mg 1 -1 ). The rain waters was generally characterized by a high deuterium excess (d=19%) compared with that of typical global meteoric waters (d=10%). The estimated deuterium excess is lower than that for the eastern Mediterranean meteoric waters (d=22%). The altitude effect is shown up by a depletion of heavy stable isotopes of about - 0.23% and -1.65% per 100 m elevation of δ 1 8 O and δD, respectively. The spatial distribution pattern of tritium contents shows a gradual build up with increasing distance from the Syrian coast. The weighted mean tritium content in rain waters falling over the country is estimated to amount to 9.5 tritium units (TU) during the period of observation. (author)

  1. Chemical reaction on solid surface observed through isotope tracer technique

    International Nuclear Information System (INIS)

    Tanaka, Ken-ichi

    1983-01-01

    In order to know the role of atoms and ions on solid surfaces as the partners participating in elementary processes, the literatures related to the isomerization and hydrogen exchanging reaction of olefines, the hydrogenation of olefines, the metathesis reaction and homologation of olefines based on solid catalysts were reviewed. Various olefines, of which the hydrogen atoms were substituted with deuterium at desired positions, were reacted using various solid catalysts such as ZnO, K 2 CO 3 on C, MoS 2 (single crystal and powder) and molybdenum oxide (with various carriers), and the infra-red spectra of adsorbed olefines on catalysts, the isotope composition of reaction products and the production rate of the reaction products were measured. From the results, the bonding mode of reactant with the atoms and ions on solid surfaces, and the mechanism of the elementary process were considered. The author emphasized that the mechanism of the chemical reaction on solid surfaces and the role of active points or catalysts can be made clear to the considerable extent by combining isotopes suitably. (Yoshitake, I.)

  2. Isotope separation by chemical exchange process: Final technical report

    International Nuclear Information System (INIS)

    Schneider, A.

    1987-02-01

    The feasibility of a chemical exchange method for the separation of the isotopes of europium was demonstrated in the system EuCl 2 -EuCl 3 . The single stage separation factor, α, in this system is 1.001 or 1.0005 per mass unit. This value of α is comparable to the separation factors reported for the U 4+ - U 6 and U 3+ - Y 4+ systems. The separation of the ionic species was done by precipitation of the Eu 2+ ions or by extraction of the Eu 3+ ions with HDEHP. Conceptual schemes were developed for a countercurrent reflux cascades consisting of solvent extraction contractors. A regenerative electrocel, combining simultaneous europium reduction, europium oxidation with energy generation, and europium stripping from the organic phase is described. 32 refs., 22 figs., 6 tabs

  3. Stable isotope analysis of precipitation samples obtained via crowdsourcing reveals the spatiotemporal evolution of Superstorm Sandy.

    Directory of Open Access Journals (Sweden)

    Stephen P Good

    Full Text Available Extra-tropical cyclones, such as 2012 Superstorm Sandy, pose a significant climatic threat to the northeastern United Sates, yet prediction of hydrologic and thermodynamic processes within such systems is complicated by their interaction with mid-latitude water patterns as they move poleward. Fortunately, the evolution of these systems is also recorded in the stable isotope ratios of storm-associated precipitation and water vapor, and isotopic analysis provides constraints on difficult-to-observe cyclone dynamics. During Superstorm Sandy, a unique crowdsourced approach enabled 685 precipitation samples to be obtained for oxygen and hydrogen isotopic analysis, constituting the largest isotopic sampling of a synoptic-scale system to date. Isotopically, these waters span an enormous range of values (> 21‰ for δ(18O, > 160‰ for δ(2H and exhibit strong spatiotemporal structure. Low isotope ratios occurred predominantly in the west and south quadrants of the storm, indicating robust isotopic distillation that tracked the intensity of the storm's warm core. Elevated values of deuterium-excess (> 25‰ were found primarily in the New England region after Sandy made landfall. Isotope mass balance calculations and Lagrangian back-trajectory analysis suggest that these samples reflect the moistening of dry continental air entrained from a mid-latitude trough. These results demonstrate the power of rapid-response isotope monitoring to elucidate the structure and dynamics of water cycling within synoptic-scale systems and improve our understanding of storm evolution, hydroclimatological impacts, and paleo-storm proxies.

  4. Stable isotope analysis of precipitation samples obtained via crowdsourcing reveals the spatiotemporal evolution of Superstorm Sandy.

    Science.gov (United States)

    Good, Stephen P; Mallia, Derek V; Lin, John C; Bowen, Gabriel J

    2014-01-01

    Extra-tropical cyclones, such as 2012 Superstorm Sandy, pose a significant climatic threat to the northeastern United Sates, yet prediction of hydrologic and thermodynamic processes within such systems is complicated by their interaction with mid-latitude water patterns as they move poleward. Fortunately, the evolution of these systems is also recorded in the stable isotope ratios of storm-associated precipitation and water vapor, and isotopic analysis provides constraints on difficult-to-observe cyclone dynamics. During Superstorm Sandy, a unique crowdsourced approach enabled 685 precipitation samples to be obtained for oxygen and hydrogen isotopic analysis, constituting the largest isotopic sampling of a synoptic-scale system to date. Isotopically, these waters span an enormous range of values (> 21‰ for δ(18)O, > 160‰ for δ(2)H) and exhibit strong spatiotemporal structure. Low isotope ratios occurred predominantly in the west and south quadrants of the storm, indicating robust isotopic distillation that tracked the intensity of the storm's warm core. Elevated values of deuterium-excess (> 25‰) were found primarily in the New England region after Sandy made landfall. Isotope mass balance calculations and Lagrangian back-trajectory analysis suggest that these samples reflect the moistening of dry continental air entrained from a mid-latitude trough. These results demonstrate the power of rapid-response isotope monitoring to elucidate the structure and dynamics of water cycling within synoptic-scale systems and improve our understanding of storm evolution, hydroclimatological impacts, and paleo-storm proxies.

  5. Uranium Isotopes as a Tracer of Groundwater Evolution in the Complexe Terminal Aquifer of Southern Tunisia

    Energy Technology Data Exchange (ETDEWEB)

    Hadj Ammar, F. [Laboratory of Radio-Analysis and Environment, National School of Engineering of Sfax, Sfax (Tunisia); Centre Europeen de Recherche et d' Enseignement de Geosciences de l' Environnement, Aix en Provence (France); Deschamps, P.; Hamelin, B. [Centre Europeen de Recherche et d' Enseignement de Geosciences de l' Environnement, Aix en Provence (France); Chkir, N.; Zouari, K. [Laboratory of Radio-Analysis and Environment, National School of Engineering of Sfax, Sfax (Tunisia)

    2013-07-15

    The Complexe Terminal (CT) aquifer system is the main water supply for remote areas of southern Tunisia. Its exploitation has resulted in significant draw-down of the water table. The CT aquifer is a multilayered aquifer lodged in Miocene sand deposits, Senonian limestones and Turonian carbonates. Little is known about the relationships and exchanges between the different layers. Here, uranium isotopic measurements carried out in groundwater samples from the CT aquifer are presented in order to constrain models for mixing of water masses, water-rock interaction and groundwater flow. Analyses were performed using a VG54 (TIMS) at the CEREGE. Results indicate a range in {sup 238}U concentration and {sup 234}U/{sup 238}U activity ratios of 1.5 to 8 ppb and 1.1 to 3.2 respectively. Together with major and trace analyses, uranium isotopic compositions provide important insights into the factors controlling the chemical evolution of groundwater and shows very distinct patterns between carbonate and sandstone layers. (author)

  6. Chemical exchange equilibria in isotope separation. Part I : Evaluation of separation factors

    International Nuclear Information System (INIS)

    Dave, S.M.

    1980-01-01

    The theory of chemical exchange equilibria as applied to the isotope separation processes and the isotope effects on equilibrium constants of different exchange reactions has come a long way since its inception by Urey and Rittenberg. An attempt has been made to bring relevant information together and present a unified approach to isotopic chemical exchange equilibrium constant evaluation and its implications to separation processes. (auth.)

  7. Deuterium isotope effects on 13C chemical shifts of 10-Hydroxybenzo[h]quinolines

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Kamounah, Fadhil S.; Gryko, Daniel T.

    2013-01-01

    Deuterium isotope effects on 13C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ’s) The OH proton is deuteriated. The isotope effects on 13C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be nega...

  8. Chemical effects of ionizing radiation and sonic energy in the context of chemical evolution

    International Nuclear Information System (INIS)

    Negron Mendoza, A.; Albarran, G.

    1992-01-01

    Ionizing radiation and sonic energy are considered as sources for chemical evolution processes. These sources have still a modest place in the interdisciplinary approach for the prebiological synthesis of organic compounds. Studies in Radiation Chemistry and Sonochemistry can provide a deeper insight into the chemical processes that may have importance for prebiotic chemistry. The present work concerns the analysis of some chemical reactions induced by ionizing radiation or cavitation in aqueous media that may be relevant to chemical evolution studies. (author)

  9. Neon and xenon isotopes in MORB: Implications for the earth-atmosphere evolution

    International Nuclear Information System (INIS)

    Marty, B.

    1989-01-01

    The isotopic composition of neon and xenon measured in MORB glasses confirm significant deviations from atmospheric values. There are 1. 21 Ne excesses with are attributed to nucleogenic reactions in the mantle; 2. 20 Ne/ 22 Ne ratios higher than the air ratio interpreted as an evidence for the occurrence of solar-type Ne at depth; 3. 129 Xe and 131-136 Xe excesses, attributed to both extinct ( 129 I and 244 Pu) and present ( 238 U) radioactivities. Ne and Xe isotopic signatures in the mantle can hardly be explained in the framework of classical models for the atmospheric evolution (which postulate a mantle origin for atmospheric gases) and appeal for at least two sources of gases. Ne isotopic differences between air and MORB appear too large to be accounted for by any reasonable fractionation process in the mantle. They imply either fractionation of neon during hydrodynamic escape of a primary atmosphere or different degrees of mixing between primordial Ne components, which, in turn imply isolation of the surface reservoir (air) and deep reservoir (mantle) from the accretional period (except for mantle outgassing through volcanism, the contribution of which is 41% at best for 20 Ne). 129 I- 129 Xe, 244 Pu- 238 U- 136 Xe systematics for atmospheric and MORB-type xenon suggest that either atmospheric gases derived from a source whose formation was delayed (≥ 17 Ma) with respect to the mean accretion time of the mantle source and/or atmospheric gases and MORB-type gases derived from chemically distinct sources. These features are consistent with heterogeneous accretion models for the Earth. Volatile degassing was probably contemporaneous to accretional events, following impact degassing, and might have been most efficient during the late stages of Earth formation. (orig.)

  10. Flood of new isotopes offers keys to stellar evolution

    International Nuclear Information System (INIS)

    Normile, D.

    1996-01-01

    Germany's heavy-ion accelerator laboratory, GSI, is renowned for giving researchers the tools needed to create the six heaviest elements in the periodic table. But the facility is also helping scientist fill gaps at an unprecedented rate in another important atomic listing - a chart of unstable isotopes. Measuring the mass and lifetimes of those isotopes, in turn, could help scientist confirm theories about how supernovae produce heavy elements and distribute them throughout the universe. This article describes both the research process and some of the isotopes

  11. Conference on chemical evolution and the origin of life

    International Nuclear Information System (INIS)

    1992-10-01

    This report contains 19 summaries of papers presented at the Conference on Chemical Evolution and the Origin of Life held at the International Centre for Theoretical Physics. A separate indexing is provided for each summary

  12. On the transition period from chemical to biological evolution

    International Nuclear Information System (INIS)

    Chela-Flores, J.

    1991-06-01

    We discuss the consequences of the hypothesis that biological evolution was contemporary with an important event in chemical evolution, namely, the induction of a small chiral bias by the electroweak neutral interaction, amplified by the Salam enhancement factor, which we discuss in terms of familiar crystallographic terms. (author). 18 refs, 3 tabs

  13. Isotopic fractionation and profile evolution of a melting snowcover

    Institute of Scientific and Technical Information of China (English)

    周石硚; 中尾正义; 桥本重将; 坂井亚规子; 成田英器; 石川信敬

    2001-01-01

    Successive snow pits were dug intensively in a melting snowcover. Water was successfully separated from snow grains in the field for the first time. By measuring δ18O values of water and snow grain samples as well as comparing isotopic profiles, it is found that meltwater percolating down in snow develops quick and clear isotopic fractionation with snow grains, but exerts no clear impact on the δ18O profile of the snowcover through which the meltwater percolates.

  14. Molybdenum and technetium cycle in the environment. Physical chemical evolution and mobility in soils and plants

    International Nuclear Information System (INIS)

    Saas, A.; Denardi, J.L.; Colle, C.; Quinault, J.M.

    1980-01-01

    Molybdenum 99 and technetium 99 from liquid discharges of base nuclear installations (reactors, reprocessing plants, UF 6 treatment, etc.) can reach the environment via irrigation waters and atmospheric deposits. The contribution to the soil by irrigation results in a physical-chemical transformation, the results of which, in the case of technetium 99, could be volatilization via microbes. The changes in the physical-chemical forms of technetium in different soils reveals the preponderant effect of the initial amount deposited. The determination of the rate of technetium and molybdenum assimilation shows a certain similarity in behaviour; yet the localization of these isotopes is not the same. The transfer of molybdenum and technetium via the root system is different in its intensity; this is mainly due to different physical-chemical forms. Finally, each isotope has an optimum assimilation threshold and a toxicity threshold. The study of the physical-chemical evolution and the mobility in the soil-plant-water table system of these two isotopes shows a new aspect with respect to certain transfer channels to the human being [fr

  15. Evolution of triaxial shapes at large isospin: Rh isotopes

    Directory of Open Access Journals (Sweden)

    A. Navin

    2017-04-01

    Full Text Available The rotational response as a function of neutron–proton asymmetry for the very neutron-rich isotopes of Rh (116–119Rh has been obtained from the measurement of prompt γ rays from isotopically identified fragments, produced in fission reactions at energies around the Coulomb barrier. The measured energy “signature” splitting of the yrast bands, when compared with the Triaxial Projected Shell Model (TPSM calculations, shows the need for large, nearly constant, triaxial deformations. The present results are compared with global predictions for the existence of non axial shapes in the periodic table in the case of very neutron-rich nuclei Rh isotopes. The predicted trend of a second local maximum for a triaxial shape around N∼74 is not found.

  16. Evaluating the influence of chemical weathering on the composition of the continental crust using lithium and its isotopes

    Science.gov (United States)

    Rudnick, R. L.; Liu, X.

    2011-12-01

    The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" of the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems document the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 8×10^9 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

  17. Primordial nucleosynthesis and chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Audouze, J.; Delbourgo-Salvador, P.

    1986-07-01

    Simple or canonical Big Bang models are claimed to account properly for the abundances of the lightest elements D, 3 He, 4 He and 7 Li if the baryonic cosmological parameter of the Universe is Ω B B is lower than 0.06 i.e. significantly smaller than in the simplest framework. Moreover this hypothesis of significant D destruction during the galactic evolution could be observationally tested

  18. Early history of chemical exchange isotope enrichment and lessons we learn

    International Nuclear Information System (INIS)

    Ishida, Takanobu; Ono, Yuriko

    2006-01-01

    The chemical exchange isotope enrichment process has an advantage over other isotope separation methods in that it involves two chemicals rather than one and, consequently, relatively large separation factors can be obtained. However, the chemical exchange method requires a chemical conversion of the substance enriched in the target isotope into the second substance. The idiosyncrasies of the isotope separation process by this method are pointed out using McCabe-Thiele diagram and, from them, the difficulties involved in the chemical exchange methods are itemized. Examples of the points being made are taken from the pioneering works of this field carried out by Harold C. Urey, his contemporaries, the students and the students' students. Lessons we learn from these works are discussed. (author)

  19. Coupled sulfur isotopic and chemical mass transfer modeling: Approach and application to dynamic hydrothermal processes

    International Nuclear Information System (INIS)

    Janecky, D.R.

    1988-01-01

    A computational modeling code (EQPSreverse arrowS) has been developed to examine sulfur isotopic distribution pathways coupled with calculations of chemical mass transfer pathways. A post processor approach to EQ6 calculations was chosen so that a variety of isotopic pathways could be examined for each reaction pathway. Two types of major bounding conditions were implemented: (1) equilibrium isotopic exchange between sulfate and sulfide species or exchange only accompanying chemical reduction and oxidation events, and (2) existence or lack of isotopic exchange between solution species and precipitated minerals, parallel to the open and closed chemical system formulations of chemical mass transfer modeling codes. All of the chemical data necessary to explicitly calculate isotopic distribution pathways is generated by most mass transfer modeling codes and can be input to the EQPS code. Routines are built in to directly handle EQ6 tabular files. Chemical reaction models of seafloor hydrothermal vent processes and accompanying sulfur isotopic distribution pathways illustrate the capabilities of coupling EQPSreverse arrowS with EQ6 calculations, including the extent of differences that can exist due to the isotopic bounding condition assumptions described above. 11 refs., 2 figs

  20. Isotope effects in gas-phase chemical reactions and photodissociation processes: Overview

    International Nuclear Information System (INIS)

    Kaye, J.A.

    1992-01-01

    The origins of isotope effects in equilibrium and non-equilibrium chemical processes are reviewed. In non-equilibrium processes, attention is given to isotope effects in simple bimolecular reactions, symmetry-related reactions, and photodissociation processes. Recent examples of isotope effects in these areas are reviewed. Some indication of other scientific areas for which measurements and/or calculations of isotope effects are used is also given. Examples presented focus on neutral molecule chemistry and in many cases complement examples considered in greater detail in the other chapters of this volume

  1. Archean evolution of Enderby Land (Antarctica) and isotope-geochronological evidences for its ancient history

    International Nuclear Information System (INIS)

    Krylov, D.P.; Belyatskij, B.V.

    1987-01-01

    Revew of published isotope-geochronological data on Ender by Land (Antarctica), which is the region of highly metamorphic formations predominant development which includes ancient rock relicts, is presented. Three tectonic-thermal events present the Archeau evolution in the region. Correlation of isotope-geochronological (U-Pb, Rb-Sr, Sm-Nd) data with micro textural processing allows to estimate tectonic-thermal events age: 3000-3100 about 2900 and about 2500 million years. Metamorphism of 3000-3100 million years age has essentially modified all the isotope systems, while model calculations for evolution of U-Pb, Rb-Sr, Sm-Nd systems have shown that rocks primary formation accurred 3500-3900 million years ago

  2. Xenia: A Probe of Cosmic Chemical Evolution

    Science.gov (United States)

    Kouveliotou, Chryssa; Piro, L.; Xenia Collaboration

    2008-03-01

    Xenia is a concept study for a medium-size astrophysical cosmology mission addressing the Cosmic Origins key objective of NASA's Science Plan. The fundamental goal of this objective is to understand the formation and evolution of structures on various scales from the early Universe to the present time (stars, galaxies and the cosmic web). Xenia will use X-and γ-ray monitoring and wide field X-ray imaging and high-resolution spectroscopy to collect essential information from three major tracers of these cosmic structures: the Warm Hot Intergalactic Medium (WHIM), Galaxy Clusters and Gamma Ray Bursts (GRBs). Our goal is to trace the chemo-dynamical history of the ubiquitous warm hot diffuse baryon component in the Universe residing in cosmic filaments and clusters of galaxies up to its formation epoch (at z =0-2) and to map star formation and galaxy metal enrichment into the re-ionization era beyond z 6. The concept of Xenia (Greek for "hospitality") evolved in parallel with the Explorer of Diffuse Emission and GRB Explosions (EDGE), a mission proposed by a multinational collaboration to the ESA Cosmic Vision 2015. Xenia incorporates the European and Japanese collaborators into a U.S. led mission that builds on the scientific objectives and technological readiness of EDGE.

  3. Xenia: A Probe of Cosmic Chemical Evolution

    Science.gov (United States)

    Kouveliotou, Chryssa; Piro, L.

    2008-01-01

    Xenia is a concept study for a medium-size astrophysical cosmology mission addressing the Cosmic Origins key objective of NASA's Science Plan. The fundamental goal of this objective is to understand the formation and evolution of structures on various scales from the early Universe to the present time (stars, galaxies and the cosmic web). Xenia will use X-and y-ray monitoring and wide field X-ray imaging and high-resolution spectroscopy to collect essential information from three major tracers of these cosmic structures: the Warm Hot Intergalactic Medium (WHIM), Galaxy Clusters and Gamma Ray Bursts (GRBs). Our goal is to trace the chemo-dynamical history of the ubiquitous warm hot diffuse baryon component in the Universe residing in cosmic filaments and clusters of galaxies up to its formation epoch (at z =0-2) and to map star formation and galaxy metal enrichment into the re-ionization era beyond z 6. The concept of Xenia (Greek for "hospitality") evolved in parallel with the Explorer of Diffuse Emission and GRB Explosions (EDGE), a mission proposed by a multinational collaboration to the ESA Cosmic Vision 2015. Xenia incorporates the European and Japanese collaborators into a U.S. led mission that builds on the scientific objectives and technological readiness of EDGE.

  4. Isotopic and chemical characterization of coal in Pakistan

    International Nuclear Information System (INIS)

    Qureshi, R.M.; Hasany, S.M.; Javed, T.; Sajjad, M.I.; Shah, Z.; Rehman, H.

    1993-11-01

    Stable carbon isotope ratios (delta/sup 13/C PDB) and toxic/trace element concentration levels are determined for Tertiary coal samples collected from seven coal fields in Pakistan. No systematic isotope effects are found in the process of coal liquefaction from peat to Tertiary lignites and sub bituminous coal. Similarly, no age effects are observed during the Tertiary regime. The observed variations in the carbon isotopic composition of coal obtained from 'Sharigh coal field' and the 'Sor-Range/Degari coal field' in Baluchistan are attributed to the depositional environments. More sampling of stable carbon isotope analysis are required to validate these observations. Significant concentrations of toxic elements such as S, Cr, Cd and Pb in Makarwal coal may pose environmental and engineering/operational problems for thermal power plants. (author)

  5. Characteristics of isotope-selective chemical reactor with gas-separating device

    International Nuclear Information System (INIS)

    Gorshunov, N.M.; Kalitin, S.A.; Laguntsov, N.I.; Neshchimenko, Yu.P.; Sulaberidze, G.A.

    1988-01-01

    A study was made on characteristics of separating stage, composed of isotope-selective chemical (or photochemical) reactor and membrane separating cascade (MSC), designated for separation of isotope-enriched products from lean reagents. MSC represents the counterflow cascade for separation of two-component mixtures. Calculations show that for the process of carton isotope separation the electric power expences for MSC operation are equal to 20 kWxh/g of CO 2 final product at 13 C isotope content in it equal to 75%. Application of the membrane gas-separating cascade at rather small electric power expenses enables to perform cascading of isotope separation in the course of nonequilibrium chemical reactions

  6. Fluorine in the solar neighborhood: Chemical evolution models

    Science.gov (United States)

    Spitoni, E.; Matteucci, F.; Jönsson, H.; Ryde, N.; Romano, D.

    2018-04-01

    Context. In light of new observational data related to fluorine abundances in solar neighborhood stars, we present chemical evolution models testing various fluorine nucleosynthesis prescriptions with the aim to best fit those new data. Aim. We consider chemical evolution models in the solar neighborhood testing various nucleosynthesis prescriptions for fluorine production with the aim of reproducing the observed abundance ratios [F/O] versus [O/H] and [F/Fe] versus [Fe/H]. We study in detail the effects of various stellar yields on fluorine production. Methods: We adopted two chemical evolution models: the classical two-infall model, which follows the chemical evolution of halo-thick disk and thin disk phases; and the one-infall model, which is designed only for thin disk evolution. We tested the effects on the predicted fluorine abundance ratios of various nucleosynthesis yield sources, that is, asymptotic giant branch (AGB) stars, Wolf-Rayet (W-R) stars, Type II and Type Ia supernovae, and novae. Results: The fluorine production is dominated by AGB stars but the W-R stars are required to reproduce the trend of the observed data in the solar neighborhood with our chemical evolution models. In particular, the best model both for the two-infall and one-infall cases requires an increase by a factor of 2 of the W-R yields. We also show that the novae, even if their yields are still uncertain, could help to better reproduce the secondary behavior of F in the [F/O] versus [O/H] relation. Conclusions: The inclusion of the fluorine production by W-R stars seems to be essential to reproduce the new observed ratio [F/O] versus [O/H] in the solar neighborhood. Moreover, the inclusion of novae helps to reproduce the observed fluorine secondary behavior substantially.

  7. Late Guadalupian evolution of the Delaware Basin: insights from stable isotope and trace element geochemistry

    Science.gov (United States)

    Smith, B.; Kerans, C.

    2017-12-01

    Accurate characterization of mixed carbonate and evaporite deposits requires an understanding of basin-scale physical, chemical, and biological processes. In these settings, carbonate geochemistry often responds to changes in the prevailing conditions in the water column. It follows that the geochemical record presents a potential aid for interpretation of depositional systems provided that it is relatively free of diagenetic overprint. This is seldom the case in shallow-water settings as processes such as meteoric diagenesis and early dolomitization obscure or erase the original geochemical signal. Fine grained deep-water sediments are more likely to retain their original geochemical characteristics. If reliable shelf-to-basin correlations can be established, then basinal deposits provide critical data not only for the interpretation of deep water environments, but overall basin evolution as well. This study examines variations in trace element and stable isotope geochemistry from the Delaware Basin of West Texas and New Mexico. Interpretation of geochemical data within a pre-existing shelf-to-basin stratigraphic framework suggests a link between basin water chemistry and sea level changes during the entirety of the Guadalupian. This link is supported analogies to modern silled basins where changes in sea level and thus recharge across the sill can control nutrient input, circulation, and bottom water oxygenation. In light of these relationships, the filling of the Delaware Basin with basin-centered evaporites at the end of the Guadalupian likely represents the culmination of a more gradual, cyclic evolution towards basin restriction. Ongoing work will continue to focus on tying regional-scale changes in basin water chemistry to the combined geochemical and physical sedimentological records.

  8. Chemical and Isotopic Diversity of Organic Particles in Chondrites: Parent Body vs. Nebular Processes

    OpenAIRE

    Remusat, L.; Guan, Y.; Eiler, J. M.

    2009-01-01

    Insoluble organic matter (IOM), the main organic constituent in chondrites, has been extensively studied after HF/HCl isolation techniques. Bulk isotopic compositions and elemental ratios show variations between chondrite groups, whereas they are quite homogeneous within each class [1]. Recent isotopic measurements by ion probes have revealed that IOM is heterogeneous at the sub-micron scale [2,3]. Does this heterogeneity reflect parent body evolution or reactions in the gas...

  9. Evolution of the hafnium isotopic composition in the RBMK reactor

    International Nuclear Information System (INIS)

    Jurkevicius, A.; Remeikis, V.

    2002-01-01

    The isotopic composition of hafnium in the radial neutron flux sensor of the RBMK-1500 reactor, the rates of the neutron absorption on Hf isotopes and the neutron spectrum in the sensor were numerically modeled. The sequence SAS2 (Shielding Analysis Sequence) program from the package SCALE 4.4A and the HELIOS code system were used for calculations. It has been obtained that the overall neutron absorption rates in hafnium for the sensors located in the 2.4 % and 2.6 % enrichment uranium-erbium nuclear fuel assemblies are by 16 % and 19 % lower than in the 2.0 % enrichment uranium nuclear fuel assemblies. The overall neutron absorption rate in hafnium decreases 2.70-2.75 times due to the sensor burnup to 5800 MW d. The sensitivity of the Hf sensors to the thermal neutron flux increases twice due to the nuclear fuel assembly burnup to 3000 MW d. The corrective factors ξ d (I) at the different integral current I of the sensors and ξ td (E) at the different burnup E of the nuclear fuel assemblies were calculated. The obtained dependence ξ d (I) calculated numerically was compared to the experimental one determined by comparing signals of the fresh sensor and the sensor with the integral current I and by processing repeated calibration results of Hf sensors in RBMK-1500 reactors. The relative relationship coefficients K T (T FA ) were found for all RBMK-1500 nuclear fuel types. (author)

  10. Xe-135 and Sm-149 Isotopic Evolution Analysis Xesamo code

    International Nuclear Information System (INIS)

    Caro, R.; Gallego, J.; Martinez Fanegas, R.

    1977-01-01

    In this report the time evolution analysis of the nuclides concentration Xe-135 and Sm-149 as a function of the neutron flux is carried out. The neutron flux may be any function of time. It is analyzed as well the reactivity changes associated with the xenon and samarium concentration variations. (Author) 5 refs

  11. Fractionation of sulfur isotopes in the chemical and biochemical oxidation of sulfide to sulfate

    International Nuclear Information System (INIS)

    Maass, I.; Wetzel, K.; Weise, G.; Heyer, J.

    1983-01-01

    The behaviour of sulfur isotopes in the chemical and biochemical oxidation of marcasite (FeS 2 ) to sulfate has been investigated in rest and shaker cultures at 30 0 C. The microbiological oxidation was carried out using a mixed culture of Thiobacillus. The results show a considerably faster formation of sulfate in the biochemical oxidation in comparison with the chemical oxidation. Isotope analyses of the formed sulfates indicate no or only very small isotope fractionations depending on experimental conditions. The highest enrichment of 32 S in the sulfate is 1.7 per mille. In accordance with the results of other authors it is concluded that in both chemical and biochemical weathering of sedimentary sulfides resulting in the formation of sulfates isotope effects are not of importance. (author)

  12. Isotopic chemical weathering behaviour of Pb derived from a high-Alpine Holocene lake-sediment record

    Science.gov (United States)

    Gutjahr, Marcus; Süfke, Finn; Gilli, Adrian; Anselmetti, Flavio; Glur, Lukas; Eisenhauer, Anton

    2017-04-01

    Several studies assessing the chemical weathering systematics of Pb isotopes provided evidence for the incongruent release of Pb from source rocks during early stages of chemical weathering, resulting in runoff compositions more radiogenic (higher) than the bulk source-rock composition [e.g. 1]. Deep NW Atlantic seawater Pb isotope records covering the last glacial-interglacial transition further support these findings. Clear excursions towards highly radiogenic Pb isotopic input in the deep NW Atlantic seen during the early Holocene, hence after the large-scale retreat of the Laurentide Ice Sheet in North America, are interpreted to be controlled by preferential release of radiogenic Pb from U- and Th-rich mineral phases during early stages of chemical weathering that are less resistant to chemical dissolution than other rock-forming mineral phases [2-4]. To date, however, no terrestrial Pb isotope record exists that could corroborate the evidence from deep marine sites for efficient late deglacial weathering and washout of radiogenic Pb. We present a high-resolution adsorbed Pb isotope record from a sediment core retrieved from Alpine Lake Grimsel (1908 m.a.s.l.) in Switzerland, consisting of 117 Pb compositions over the past 10 kyr. This high-Alpine study area is ideally located for incipient and prolonged chemical weathering studies. The method used to extract the adsorbed lake Pb isotope signal is identical to previous marine approaches targeting the authigenic Fe-Mn oxyhydroxides fraction within the lake sediments [5, 6]. The Pb isotope compositions are further accompanied by various elemental ratios derived from the same samples that equally trace climatic boundary conditions in the Grimsel Lake area. The Pb isotopic composition recorded in Lake Grimsel is remarkably constant throughout the majority of the Holocene until ˜2.5 ka BP, despite variable sediment composition and -age, and isotopically relatively close to the signature of the granitic source rock

  13. Signatures of Chemical Evolution in Protostellar Nebulae

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha

    2011-01-01

    A decade ago observers began to take serious notice of the presence of crystalline silicate grains in the dust flowing away from some comets. While crystallinity had been seen in such objects previously, starting with the recognitions by Campins and Ryan (1990) that the 10 micron feature of Comet Halley resembled that of the mineral forsterite, most such observations were either ignored or dismissed as no path to explain such crystalline grains was available in the literature. When it was first suggested that an outward flow must be present to carry annealed silicate grains from the innermost regions of the Solar Nebula out to the regions where comets could form (Nuth, 1999; 2001) this suggestion was also dismissed because no such transport mechanism was known at the time. Since then not only have new models of nebular dynamics demonstrated the reality of long distance outward transport (Ciesla, 2007; 2008; 2009) but examination of older models (Boss, 2004) showed that such transport had been present but had gone unrecognized for many years. The most unassailable evidence for outward nebular transport came with the return of the Stardust samples from Comet Wild2, a Kuiper-belt comet that contained micron-scale grains of high temperature minerals resembling the Calcium-Aluminum Inclusions found in primitive meteorites (Zolensky et aI., 2006) that formed at T > 1400K. Now that outward transport in protostellar nebulae has been firmly established, a re-examination of its consequences for nebular gas is in order that takes into account both the factors that regulate both the outward flow as well as those that likely control the chemical composition of the gas. Laboratory studies of surface catalyzed reactions suggest that a trend toward more highly reduced carbon and nitrogen compounds in the gas phase should be correlated with a general increase in the crystallinity of the dust (Nuth et aI., 2000), but is such a trend actually observable? Unlike the Fischer-Tropsch or

  14. Isotope and trace element models of crustal evolution

    International Nuclear Information System (INIS)

    O'Nions, R.K.; Hamilton, P.J.

    1981-01-01

    Some of the isotopic constraints on the development of continental crust from about 3.8 Ga ago are reviewed. Particularly it is noted that Archaean granitic (sensu lato) rocks have initial 143 Nd/ 144 Nd ratios close to predicted values for the bulk Earth at the time before emplacement, whereas those Phanerozoic granites investigated so far diverge considerably from the bulk Earth and betray the existence of later continental crust in their provenance. Geochemical evidence for recycling of some continent-derived elements into the mantle is examined and the important distinction between selected element recycling and bulk return of continental material is emphasized. Various transport models that have been proposed to model the development of continental crust are examined and some of their differences and similarities, particularly with respect to implications for continental recycling, are highlighted. (author)

  15. Experimental study of the Mg and Sr isotopic evolution of seawater interacting with basalt between 150 and 300 ° C.

    Science.gov (United States)

    Voigt, Martin; Pearce, Christopher R.; Oelkers, Eric H.

    2016-04-01

    potential for combined radiogenic and stable isotope analysis to track solid-fluid reactions in the oceanic crust. Further characterisation of the extent of isotopic fractionation in these systems will help establish how such processes have affected the long-term chemical evolution of the oceans. [1] H. Elderfield and A. Schultz, "Mid-Ocean Ridge Hydrothermal Fluxes and the Chemical Composition of the Ocean," Annu Rev Earth Planet Sci, vol. 24, pp. 191-224, 1996. [2] W. E. Seyfried Jr and J. L. Bischoff, "Experimental seawater-basalt interaction at 300° C, 500 bars, chemical exchange, secondary mineral formation and implications for the transport of heavy metals," Geochim. Cosmochim. Acta, vol. 45, no. 2, pp. 135-147, 1981. [3] J. A. Higgins and D. P. Schrag, "The Mg isotopic composition of Cenozoic seawater - evidence for a link between Mg-clays, seawater Mg/Ca, and climate," Earth Planet. Sci. Lett., vol. 416, pp. 73-81, 2015.

  16. Isotopic composition of chemical elements in natural cycles

    International Nuclear Information System (INIS)

    Wetzel, K.

    1977-12-01

    Mathematical models developed for planning and evaluating tracer experiments have been applied in investigations of the isotopic composition of carbon in its natural cycle through various periods of the last billion years. The influence on the natural isotope ratio due to industrial combustion of fossil fuels is shown. In order to describe regional differences from the global behaviour of carbon a parameter has been introduced, which represents the time needed for one total exchange of the atmosphere in a certain region with the global atmosphere

  17. Isotope effects in interstellar molecules by chemical hyperfine interaction

    International Nuclear Information System (INIS)

    Haberkorn, R.; Michel-Beyerle, M.E.

    1977-01-01

    If free radicals recombine on grain surfaces, not only the different masses of isotopes but also their differing nuclear spin moments (e.g. 12 C/ 13 C, 14 N/ 15 N, 17 O/ 18 O) may imply variations in the recombination probability due to hyperfine interaction. This mechanism has not been accounted for so far. (orig.) [de

  18. Separation and sampling technique of light element isotopes by chemical exchange process

    International Nuclear Information System (INIS)

    Kato, Shunsaku; Oi, Kenta; Takagi, Norio; Hirotsu, Takafumi; Kano, Hirofumi; Sonoda, Akinari; Makita, Yoji

    2000-01-01

    Lithium and boron isotope separation technique were studied. Granulation of lithium isotope separation agent was carried out by cure covering in solution. Separation of lithium isotope was stepped up by ammonium carbonate used as elusion agent. Styrene and ester resin derived three kinds of agents such as 2-amino-1, 3-propanediol (1, 3-PD), 2-amino-2-methyl-1, 3-propanediol (Me-1,3-PD) and tris(2-hydroxyethyl)amine (Tris) were used as absorbent.The ester resin with Tris showed larger amount of adsorption (1.4 mmol/g) than other resins. However, all resins with agent indicated more large adsorption volume of boron than the objective value (0.5 mmol/g). Large isotope shift was shown by the unsymmetrical vibration mode of lithium ion on the basis of quantum chemical calculation of isotope effect on dehydration of hydrated lithium ion. (S.Y.)

  19. A comparison of chemical compositions of reported altered oceanic crusts and global MORB data set: implication for isotopic heterogeneity of recycled materials

    Science.gov (United States)

    Shimoda, G.; Kogiso, T.

    2017-12-01

    Chemical composition of altered oceanic crust is one of important constraints to delineate chemical heterogeneity of the mantle. Accordingly, many researchers have been studied to determine bulk chemical composition of altered oceanic crust mainly based on chemical compositions of old oceanic crusts at Site 801 and Site 417/418, and young crust at Site 504 (e.g., Staudigel et al., 1996; Bach et al. 2003; Kuo et al., 2016). Their careful estimation provided reliable bulk chemical compositions of these Sites and revealed common geochemical feature of alteration. To assess effect of recycling of altered oceanic crust on chemical evolution of the mantle, it might be meaningful to discuss whether the reported chemical compositions of altered oceanic crusts can represent chemical composition of globally subducted oceanic crusts. Reported chemical compositions of fresh glass or less altered samples from Site 801, 417/418 and 504 were highly depleted compared to that of global MORB reported by Gale et al. (2013), suggesting that there might be sampling bias. Hence, it could be important to consider chemical difference between oceanic crusts of these three Sites and global MORB to discuss effect of recycling of oceanic crust on isotopic heterogeneity of the mantle. It has been suggested that one of controlling factors of chemical variation of oceanic crust is crustal spreading rate because different degree of partial melting affects chemical composition of magmas produced at a mid-ocean ridge. Crustal spreading rate could also affect intensity of alteration. Namely, oceanic crusts produced at slow-spreading ridges may prone to be altered due to existence of larger displacement faults compared to fast spreading ridges which have relatively smooth topography. Thus, it might be significant to evaluate isotopic evolution of oceanic crusts those were produced at different spreading rates. In this presentation, we will provide a possible chemical variation of altered oceanic

  20. Chemical evolution with rotating massive star yields - I. The solar neighbourhood and the s-process elements

    Science.gov (United States)

    Prantzos, N.; Abia, C.; Limongi, M.; Chieffi, A.; Cristallo, S.

    2018-05-01

    We present a comprehensive study of the abundance evolution of the elements from H to U in the Milky Way halo and local disc. We use a consistent chemical evolution model, metallicity-dependent isotopic yields from low and intermediate mass stars and yields from massive stars which include, for the first time, the combined effect of metallicity, mass loss, and rotation for a large grid of stellar masses and for all stages of stellar evolution. The yields of massive stars are weighted by a metallicity-dependent function of the rotational velocities, constrained by observations as to obtain a primary-like 14N behaviour at low metallicity and to avoid overproduction of s-elements at intermediate metallicities. We show that the Solar system isotopic composition can be reproduced to better than a factor of 2 for isotopes up to the Fe-peak, and at the 10 per cent level for most pure s-isotopes, both light ones (resulting from the weak s-process in rotating massive stars) and the heavy ones (resulting from the main s-process in low and intermediate mass stars). We conclude that the light element primary process (LEPP), invoked to explain the apparent abundance deficiency of the s-elements with A values of ^{12}C/^{13}C in halo red giants, which is rather due to internal processes in those stars.

  1. Chemical and sulphur isotope compositions of pyrite in the ...

    Indian Academy of Sciences (India)

    sulphide mineralization and their chemical evo- lution in relative .... properties and chemical compositions. Electron ..... from the sulphide lode provide clues to the chang- ing fluid ..... Raymond O L 1996 Pyrite composition and ore geneis in.

  2. Reduction of chemical formulas from the isotopic peak distributions of high-resolution mass spectra.

    Science.gov (United States)

    Roussis, Stilianos G; Proulx, Richard

    2003-03-15

    A method has been developed for the reduction of the chemical formulas of compounds in complex mixtures from the isotopic peak distributions of high-resolution mass spectra. The method is based on the principle that the observed isotopic peak distribution of a mixture of compounds is a linear combination of the isotopic peak distributions of the individual compounds in the mixture. All possible chemical formulas that meet specific criteria (e.g., type and number of atoms in structure, limits of unsaturation, etc.) are enumerated, and theoretical isotopic peak distributions are generated for each formula. The relative amount of each formula is obtained from the accurately measured isotopic peak distribution and the calculated isotopic peak distributions of all candidate formulas. The formulas of compounds in simple spectra, where peak components are fully resolved, are rapidly determined by direct comparison of the calculated and experimental isotopic peak distributions. The singular value decomposition linear algebra method is used to determine the contributions of compounds in complex spectra containing unresolved peak components. The principles of the approach and typical application examples are presented. The method is most useful for the characterization of complex spectra containing partially resolved peaks and structures with multiisotopic elements.

  3. Adding geochemical and isotope tracers to models of hillslope evolution: valuable constraints or monumental headache?

    Science.gov (United States)

    Mudd, S. M.; Yoo, K.; Hurst, M. D.; Weinman, B. A.; Maher, K.

    2011-12-01

    Landscapes evolve through time, both in terms of their geomorphology and their geochemistry. Past studies have highlighted that topography suffers from the problem of equifinality: the topographic configuration of landscapes can be the result of many different, yet equally plausible, erosion histories. In hillslope soils the properties and chemistry of the soils themselves could provide additional constraints on landscape evolution. Here we present results from a combination of modelling and field studies that seek to quantify the co-evolution of hillslope morphology and the solid state chemistry of hillslope soils. The models follow large numbers of individual particles as they are entrained into a physically mobile soil layer, weathered, and accumulate isotopes such as 10Be and 21Ne. We demonstrate that multiple hillslope properties mitigate (but do not eliminate) the problem of equifinality and demonstrate the importance of accounting for individual particle residence times and ages in interpretation of both isotope and weathering data.

  4. Mg-Fe Isotope Systems of Mantle Xenoliths: Constrains on the Evolution of Siberian Craton

    Science.gov (United States)

    An, Y.; Kiseeva, E. S.; Sobolev, N. V.; Zhang, Z.

    2017-12-01

    Mantle xenoliths bring to the surface a variety of lithologies (dunites, lherzolites, harzburgites, wehrlites, eclogites, pyroxenites, and websterites) and represent snapshots of the geochemical processes that occur deep within the Earth. Recent improvements in the precision of the MC-ICP-MS measurements have allowed us to expand the amount of data on Mg and Fe isotopes for mantle-derived samples. For instance, to constrain the isotopic composition of the Earth based on the study of spinel and garnet peridotites (An et al., 2017; Teng et al., 2010), to trace the origin and to investigate the isotopic fractionation mechanism during metamorphic process using cratonic or orogenic eclogites (Li et al., 2011; Wang et al., 2012) and to reveal the metasomatism-induced mantle heterogeneity by pyroxenites (Hu et al., 2016). Numerous multi-stage modification events and mantle layering are detected in the subcontinental lithospheric mantle under the Siberian craton (Ashchepkov et al., 2008a; Sobolev et al., 1975, etc). Combined analyses of Mg and Fe isotopic systems could provide new constraints on the formation and evolution of the ancient cratonic mantle. In order to better constrain the magnitude and mechanism of inter-mineral Mg and Fe isotopic fractionations at high temperatures, systematic studies of mantle xenoliths are needed. For example, theoretical calculations and natural samples measurements have shown that large equilibrium Mg isotope fractionations controlled by the difference in coordination number of Mg among minerals could exist (Huang et al., 2013; Li et al., 2011). Thus, the Mg isotope geothermometer could help us trace the evolution history of ancient cratons. In this study we present Mg and Fe isotopic data for whole rocks and separated minerals (clinopyroxene (cpx) and garnet (grt)) from different types of mantle xenoliths (garnet pyroxenites, eclogites, grospydites and garnet peridotites) from a number of kimberlite pipes in Siberian craton (Udachnaya

  5. Isotopic and chemical variation of organic nanoglobules in primitive meteorites

    Science.gov (United States)

    de Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.; Alexander, Conel M. O'd.; Bassim, Nabil D.; Cody, George D.; Kilcoyne, A. L. David; Sandford, Scott A.; Milam, Stefanie N.; Nuevo, Michel; Zega, Thomas J.

    2013-05-01

    Organic nanoglobules are microscopic spherical carbon-rich objects present in chondritic meteorites and other astromaterials. We performed a survey of the morphology, organic functional chemistry, and isotopic composition of 184 nanoglobules in insoluble organic matter (IOM) residues from seven primitive carbonaceous chondrites. Hollow and solid nanoglobules occur in each IOM residue, as well as globules with unusual shapes and structures. Most nanoglobules have an organic functional chemistry similar to, but slightly more carboxyl-rich than, the surrounding IOM, while a subset of nanoglobules have a distinct, highly aromatic functionality. The range of nanoglobule N isotopic compositions was similar to that of nonglobular 15N-rich hotspots in each IOM residue, but nanoglobules account for only about one third of the total 15N-rich hotspots in each sample. Furthermore, many nanoglobules in each residue contained no 15N enrichment above that of bulk IOM. No morphological indicators were found to robustly distinguish the highly aromatic nanoglobules from those that have a more IOM-like functional chemistry, or to distinguish 15N-rich nanoglobules from those that are isotopically normal. The relative abundance of aromatic nanoglobules was lower, and nanoglobule diameters were greater, in more altered meteorites, suggesting the creation/modification of IOM-like nanoglobules during parent-body processing. However, 15N-rich nanoglobules, including many with highly aromatic functional chemistry, likely reflect preaccretionary isotopic fractionation in cold molecular cloud or protostellar environments. These data indicate that no single formation mechanism can explain all of the observed characteristics of nanoglobules, and their properties are likely a result of multiple processes occurring in a variety of environments.

  6. Isotope ratios and chemical fractionation of CO in Lynds 134

    International Nuclear Information System (INIS)

    Dickman, R.L.; Langer, W.D.

    1977-01-01

    Mahoney, McCutcheon and Shuter (1976) reported observations of the J = 1 → 0 transition of three isotopes of CO in the dust cloud Lynds 134 using the 4.6 m telescope at Aerospace Corporation. In this paper a new observation of 12 C 17 O is discussed and the question of the ratio 13 C 16 O/ 12 C 18 O across the dust cloud is considered further. (Auth.)

  7. Abundance gradients in disc galaxies and chemical evolution models

    International Nuclear Information System (INIS)

    Diaz, A.I.

    1989-01-01

    The present state of abundance gradients and chemical evolution models of spiral galaxies is reviewed. An up to date compilation of abundance data in the literature concerning HII regions over galactic discs is presented. From these data Oxygen and Nitrogen radial gradients are computed. The slope of the Oxygen gradient is shown to have a break at a radius between 1.5 and 1.75 times the value of the effective radius of the disc, i.e. the radius containing half of the light of the disc. The gradient is steeper in the central parts of the disc and becomes flatter in the outer parts. N/O gradients are shown to be rather different from galaxy to galaxy and only a weak trend of N/O with O/H is found. The existing chemical evolution models for spiral galaxies are reviewed with special emphasis in the interpretation of numerical models having a large number of parameters. (author)

  8. The Impact of Modeling Assumptions in Galactic Chemical Evolution Models

    Science.gov (United States)

    Côté, Benoit; O'Shea, Brian W.; Ritter, Christian; Herwig, Falk; Venn, Kim A.

    2017-02-01

    We use the OMEGA galactic chemical evolution code to investigate how the assumptions used for the treatment of galactic inflows and outflows impact numerical predictions. The goal is to determine how our capacity to reproduce the chemical evolution trends of a galaxy is affected by the choice of implementation used to include those physical processes. In pursuit of this goal, we experiment with three different prescriptions for galactic inflows and outflows and use OMEGA within a Markov Chain Monte Carlo code to recover the set of input parameters that best reproduces the chemical evolution of nine elements in the dwarf spheroidal galaxy Sculptor. This provides a consistent framework for comparing the best-fit solutions generated by our different models. Despite their different degrees of intended physical realism, we found that all three prescriptions can reproduce in an almost identical way the stellar abundance trends observed in Sculptor. This result supports the similar conclusions originally claimed by Romano & Starkenburg for Sculptor. While the three models have the same capacity to fit the data, the best values recovered for the parameters controlling the number of SNe Ia and the strength of galactic outflows, are substantially different and in fact mutually exclusive from one model to another. For the purpose of understanding how a galaxy evolves, we conclude that only reproducing the evolution of a limited number of elements is insufficient and can lead to misleading conclusions. More elements or additional constraints such as the Galaxy’s star-formation efficiency and the gas fraction are needed in order to break the degeneracy between the different modeling assumptions. Our results show that the successes and failures of chemical evolution models are predominantly driven by the input stellar yields, rather than by the complexity of the Galaxy model itself. Simple models such as OMEGA are therefore sufficient to test and validate stellar yields. OMEGA

  9. Isotopic and chemical investigations of quaternary aquifer in sinai peninsula

    International Nuclear Information System (INIS)

    Sadek, M.A.; Ahmed, M.A.; Awad, M.A.

    2001-01-01

    The present study has been conducted to investigate the renewal activity and mineralization potential of the quaternary aquifer in Sinai peninsula using environmental isotopes and hydrochemistry. The quaternary aquifer is vital for development processes as it has a wide extension and shallow water table. The total dissolved salts vary greatly from one location to another and range widely between 510-7060 mg/1, reflecting all categories from fresh to saline water. The change in salinity all over Sinai can be attributed to variations in the rate of evaporation. Leaching and dissolution of terrestrial salts during floods as well as the effects of sea spray and saline water intrusion. The main sources of groundwater recharge are the infiltration of Local precipitation and surface runoff as well as lateral flow through hydraulic connection with fractured aquifers. Snow melt also contributes to aquifer recharge in some areas in the central part of southern Sinai. The environmental stable isotopic contents of the ground water in the quaternary aquifer in Sinai reflect the isotopic composition of rain water from continental and east Mediterranean precipitation and monsonal air mass which comes from Indian ocean as well as the seepage of partly evaporated floodwater. The southern samples are more suitable for drinking and irrigation purposes due to its lower salinity and sodium hazard

  10. Titan's Carbon Isotopic Ratio: A Clue To Atmospheric Evolution?

    Science.gov (United States)

    Nixon, C. A.; Jennings, D. E.; Romani, P. N.; Jolly, A.; Teanby, N. A.; Irwin, P. G.; Bézard, B.; Vinatier, S.; Coustenis, A.; Flasar, F. M.

    2009-12-01

    In this presentation we describe the latest results to come from Cassini CIRS and ground-based telescopic measurements of Titan's 12C/13C ratio in atmospheric molecules, focusing on hydrocarbons. Previously, the Huygens GCMS instrument measured 12CH4/13CH4 to be 82±1 (Niemann et al., Nature, 438, 779-784, 2005), substantially and significantly lower than the VPDB inorganic Earth standard of 89.4. It is also at odds with measurements for the giant planets. Cassini CIRS infrared spectra have confirmed this enhancement in 13CH4, but also revealed that the ratio in ethane, the major photochemical product of methane photolysis, does not appear enhanced (90±7) (Nixon et al.. Icarus, 195, 778-791, 2008) and is compatible with the terrestrial and combined giant planet value (88±7, Sada et al., Ap. J., 472, p. 903-907, 1996). Recently-published results from spectroscopy using the McMath-Pierce telescope at Kitt Pitt (Jennings et al., JCP, 2009, in press) have confirmed this deviation between methane and ethane, and an explanation has been proposed. This invokes a kinetic isotope effect (KIE) in the abstraction of methane by ethynyl, a major ethane formation pathway, to preferentially partition 12C into ethane and leave an enhancement in atmospheric 13CH4 relative to the incoming flux from the reservoir. Modeling shows that a steady-state solution exists where the 12C/13C methane is decreased from the reservoir value by exactly the KIE factor (the ratio of 12CH4 to 13CH4 abstraction reaction rates): which is plausibly around 1.08, very close to the observed amount. However, a second solution exists in which we are observing Titan about ~1 methane lifetime after a major injection of methane into the atmosphere which is rapidly being eliminated. Updated measurements by Cassini CIRS of both the methane and ethane 12C/13C ratios will be presented, along with progress in interpreting this ratio. In addition, we summarize the 12C/13C measurements by CIRS in multiple other Titan

  11. Enrichment of {sup 15}N and {sup 10}B isotopes by chemical exchange process

    Energy Technology Data Exchange (ETDEWEB)

    D` Souza, A B; Sonwalkar, A S; Subrahmanyam, B V; Valladares, B A [Chemical Engineering Division, Bhabha Atomic Research Centre, Mumbai (India)

    1994-06-01

    Many processes are available for separation of stable isotopes like distillation, chemical exchange, thermal diffusion, gaseous diffusion, centrifuge etc. Chemical exchange process is eminently suitable for separation of isotopes of light elements. Work done on separation and enrichment of two of the stable isotopes viz. {sup 15}N and {sup 10}B in Chemical Engineering Division is presented. {sup 15}N is widely used as a tracer in agricultural research and {sup 10}B is used in nuclear industry as control rod material, soluble reactor poison, neutron detector etc. The work on {sup 15}N isotope resulted in a pilot plant, which was the only source of this material in the country for many years and later it was translated into a production plant as M/s. RCF Ltd. The work done on the ion-exchange process for enrichment of {sup 10}B isotope which is basically a chemical exchange process, is now being updated into a pilot plant to produce enriched {sup 10}B to be used as soluble reactor poison. (author). 5 refs., 2 figs., 3 tabs.

  12. Enrichment of 15N and 10B isotopes by chemical exchange process

    International Nuclear Information System (INIS)

    D'Souza, A.B.; Sonwalkar, A.S.; Subrahmanyam, B.V.; Valladares, B.A.

    1994-01-01

    Many processes are available for separation of stable isotopes like distillation, chemical exchange, thermal diffusion, gaseous diffusion, centrifuge etc. Chemical exchange process is eminently suitable for separation of isotopes of light elements. Work done on separation and enrichment of two of the stable isotopes viz. 15 N and 10 B in Chemical Engineering Division is presented. 15 N is widely used as a tracer in agricultural research and 10 B is used in nuclear industry as control rod material, soluble reactor poison, neutron detector etc. The work on 15 N isotope resulted in a pilot plant, which was the only source of this material in the country for many years and later it was translated into a production plant as M/s. RCF Ltd. The work done on the ion-exchange process for enrichment of 10 B isotope which is basically a chemical exchange process, is now being updated into a pilot plant to produce enriched 10 B to be used as soluble reactor poison. (author)

  13. The temporal evolution of magnesium isotope fractionation during hydromagnesite dissolution, precipitation, and at equilibrium

    Science.gov (United States)

    Oelkers, Eric H.; Berninger, Ulf-Niklas; Pérez-Fernàndez, Andrea; Chmeleff, Jérôme; Mavromatis, Vasileios

    2018-04-01

    This study provides experimental evidence of the resetting of the magnesium (Mg) isotope signatures of hydromagnesite in the presence of an aqueous fluid during its congruent dissolution, precipitation, and at equilibrium at ambient temperatures over month-long timescales. All experiments were performed in batch reactors in aqueous sodium carbonate buffer solutions having a pH from 7.8 to 9.2. The fluid phase in all experiments attained bulk chemical equilibrium within analytical uncertainty with hydromagnesite within several days, but the experiments were allowed to continue for up to 575 days. During congruent hydromagnesite dissolution, the fluid first became enriched in isotopically light Mg compared to the dissolving hydromagnesite, but this Mg isotope composition became heavier after the fluid attained chemical equilibrium with the mineral. The δ26Mg composition of the fluid was up to ∼0.35‰ heavier than the initial dissolving hydromagnesite at the end of the dissolution experiments. Hydromagnesite precipitation was provoked during one experiment by increasing the reaction temperature from 4 to 50 °C. The δ26Mg composition of the fluid increased as hydromagnesite precipitated and continued to increase after the fluid attained bulk equilibrium with this phase. These observations are consistent with the hypothesis that mineral-fluid equilibrium is dynamic (i.e. dissolution and precipitation occur at equal, non-zero rates at equilibrium). Moreover the results presented in this study confirm (1) that the transfer of material from the solid to the fluid phase may not be conservative during stoichiometric dissolution, and (2) that the isotopic compositions of carbonate minerals can evolve even when the mineral is in bulk chemical equilibrium with its coexisting fluid. This latter observation suggests that the preservation of isotopic signatures of carbonate minerals in the geological record may require a combination of the isolation of fluid-mineral system

  14. Topology in isotopic multispace and origin of mantle chemical heterogeneities

    International Nuclear Information System (INIS)

    Allegre, C.J.; Hamelin, B.; Provost, A.; Dupre, B.

    1987-01-01

    In this paper we present a simple technique for multidimensional treatment of isotopic data, which allows a global and rigorous correlation between the various radiogenic tracers. This technique is based on the determination of eigenvectors of the data matrix, allowing a geometric description of the inertia ellipsoid corresponding to the cluster of experimental data points. The relationships between the various sets of samples can be analyzed using the projections on the main elongation planes. When processing the Pb-Sr-Nd data for the oceanic mantle (OIB+MORB) with this technique we find that at least four different end-members are needed to define the 'mantle array' which thus cannot be a plane surface. Samples from island arcs (IAB) show the contribution of a component clearly out of the oceanic domain and very similar to terrigenous sediments. Continental tholeiites (CFB) also show some sort of contamination (but distinct from that of IAB) by the continental crust. They also show a domain overlapping with that of the oceanic islands corresponding to the compositions of the 'Dupal anomaly'. Multispace analysis also permits a rigorous comparison of relationships between the various isotopic tracers. In particular, we demonstrate that a U-Pb fractionation independent from the correlated Sr-Nd, Th-U and Th-Sr ones does exist. Consequently, a three-dimensional analysis performed only with lead isotopes yields by itself the main information that can be inferred from the five Pb-Sr-Nd dimensions. Helium also yields independent information decoupled with respect to the other tracers, adding one fifth end-member (Loihi, Hawaii islands) to the OIB+MORB array. (orig.)

  15. Osmium Isotopic Evolution of the Mantle Sources of Precambrian Ultramafic Rocks

    Science.gov (United States)

    Gangopadhyay, A.; Walker, R. J.

    2006-12-01

    The Os isotopic composition of the modern mantle, as recorded collectively by ocean island basalts, mid- oceanic ridge basalts (MORB) and abyssal peridotites, is evidently highly heterogeneous (γ Os(I) ranging from +25). One important question, therefore, is how and when the Earth's mantle developed such large-scale Os isotopic heterogeneities. Previous Os isotopic studies of ancient ultramafic systems, including komatiites and picrites, have shown that the Os isotopic heterogeneity of the terrestrial mantle can be traced as far back as the late-Archean (~ 2.7-2.8 Ga). This observation is based on the initial Os isotopic ratios obtained for the mantle sources of some of the ancient ultramafic rocks determined through analyses of numerous Os-rich whole-rock and/or mineral samples. In some cases, the closed-system behavior of these ancient ultramafic rocks was demonstrated via the generation of isochrons of precise ages, consistent with those obtained from other radiogenic isotopic systems. Thus, a compilation of the published initial ^{187}Os/^{188}Os ratios reported for the mantle sources of komatiitic and picritic rocks is now possible that covers a large range of geologic time spanning from the Mesozoic (ca. 89 Ma Gorgona komatiites) to the Mid-Archean (e.g., ca. 3.3 Ga Commondale komatiites), which provides a comprehensive picture of the Os isotopic evolution of their mantle sources through geologic time. Several Precambrian komatiite/picrite systems are characterized by suprachondritic initial ^{187}Os/^{188}Os ratios (e.g., Belingwe, Kostomuksha, Pechenga). Such long-term enrichments in ^{187}Os of the mantle sources for these rocks may be explained via recycling of old mafic oceanic crust or incorporation of putative suprachondritic outer core materials entrained into their mantle sources. The relative importance of the two processes for some modern mantle-derived systems (e.g., Hawaiian picrites) is an issue of substantial debate. Importantly, however, the

  16. Chemical equilibria relating the isotopic hydrogens at low temperatures

    International Nuclear Information System (INIS)

    Pyper, J.W.; Souers, P.C.

    1976-01-01

    Hydrogen fusion will require a fuel mixture of liquefied or frozen D 2 and T 2 . The composition of this fuel mixture is described by the equilibrium constant K/sub DT/. The theory of isotopic exchange reactions is discussed as applied to the hydrogen isotopes. A literature survey of the values of K/sub HD/, K/sub HT/, and K/sub DT/ found no values of K/sub DT/ for temperatures below 25 0 K and no values of K/sub HD/ and K/sub HT/ for temperatures below 50 0 K. The existing data are critically evaluated, and simplified formulas for the three equilibrium constants in the temperature range 50 to 300 0 K are derived from them. Harmonic approximation theory with rotational correction was used to calculate values of K/sub HD/, K/sub HT/, and K/sub DT/ in the temperature range 4.2 to 50 0 K. It is found that K/sub DT/ = 2.995 exp(-10.82/T) in the temperature range 16.7 to 33.3 0 K to an accuracy of 1%. Tables, graphs, and equations of K/sub HD/, K/sub HT/, and K/sub DT/ are given for the temperature range 4.2 to 50 0 K. 27 references, 14 tables, 8 figures

  17. On the enrichment of low-abundant isotopes of light chemical elements by gas centrifuges

    International Nuclear Information System (INIS)

    Borisevich, V.D.; Morozov, O.E.; Zaozerskiy, Yu.P.; Shmelev, G.M.; Shipilov, Yu.D.

    2000-01-01

    A brief review of the main areas for the application of the isotopes 15 N and 13 C is made. Separation of the nitrogen isotopes in a single gas centrifuge in the form of pure nitrogen, ammonia, and trifluoride of nitrogen as well as the carbon isotopes in the form of carbon dioxide has been studied by means of numerical simulation. The parameters of the centrifugal machine investigated were close to the parameters of the Iguassu machine. The dependence of the efficiency criterion versus the basic parameters of the separation process has been explored in the computational experiments. Comparisons of the calculated results with the experimental data have shown good agreement. The results obtained have demonstrated the possibility of using gas centrifuge technology to enrich successfully the low-abundant isotopes of light chemical elements

  18. Stable isotope and hydro chemical variability along the Calueque-Oshakati Canal in the Cuvelai-Etosha Basin, Namibia

    Science.gov (United States)

    Koeniger, Paul; Beyer, Matthias; Gaj, Marcel; Hamutoko, Josefina; Uugulu, Shoopi; Wanke, Heike; Huber, Markus; Lohe, Christoph; Quinger, Martin; Himmelsbach, Thomas

    2014-05-01

    Since 1973 Kunene River water (currently between 47 and 63 Million m3 per year [1]) is carried from the Calueque Dam in Angola along a 150 km concrete canal to Oshakati in the Cuvelai-Etosha Basin which supplies the most densely populated area of Namibia with drinking water. Backup storage is held in the Olushandja Dam and in water towers at Ogongo, Oshakati and Ondangwa and about 4,000 km of pipelines radiate out from purification schemes and supply most of the people and the livestock [2, 3]. The canal is open along most of its course to Oshakati, allowing livestock and people living nearby to make free use of the water. During the rainy season, flood water from the vast Oshana drainage system swashes into the canal bearing a potential health risk when consumed untreated. Within the SASSCAL project (Southern African Science Service Centre for Climate Change and Adaptive Land Management - www.sasscal.org) water samples were collected during a field campaign from 18th to 20th November 2013 right before the onset of the rainy season 2013/14, to gain information on water evolution, evaporation and mixing influences as well as to characterize input concentrations for indirect recharge in this area. Water samples were collected at 14 sites along the canal (about every 10 km) and the Kunene River for stable water isotopes (deuterium and oxygen-18) and hydro chemical analyzes. Coordinates and altitude, temperature, conductivity, pH-value, and oxygen content were measured in the field. Hydro chemical and stable isotope analyzes were conducted later on in the laboratory. For stable isotopes a Picarro L2120-i water vapor analyzer was used with accuracies of 0.2o and 0.8o for δ18O and δ2H, respectively. Further campaigns within and after the rainy season are planned. A discussion of isotope and hydro chemical evolution of canal water in comparison to local rain and available groundwater composition will be presented. [1] Directorate of Rural Water Supply (2004

  19. Survey of knowledge of hazards of chemicals potentially associated with the advanced isotope separation processes

    International Nuclear Information System (INIS)

    Chester, R.O.; Kirkscey, K.A.; Randolph, M.L.

    1979-09-01

    Hazards of chemical potentially associated with the advanced isotope separation processes are estimated based on open literature references. The tentative quantity of each chemical associated with the processes and the toxicity of the chemical are used to estimate this hazard. The chemicals thus estimated to be the most potentially hazardous to health are fluorine, nitric acid, uranium metal, uranium hexafluoride, and uranium dust. The estimated next most hazardous chemicals are bromine, hydrobromic acid, hydrochloric acid, and hydrofluoric acid. For each of these chemicals and for a number of other process-associated chemicals the following information is presented: (1) any applicable standards, recommended standards and their basis; (2) a brief discussion to toxic effects including short exposure tolerance, atmospheric concentration immediately hazardous to life, evaluation of exposures, recommended control procedures, chemical properties, and a list of any toxicology reviews; and (3) recommendations for future research

  20. Survey of knowledge of hazards of chemicals potentially associated with the advanced isotope separation processes

    Energy Technology Data Exchange (ETDEWEB)

    Chester, R.O.; Kirkscey, K.A.; Randolph, M.L.

    1979-09-01

    Hazards of chemical potentially associated with the advanced isotope separation processes are estimated based on open literature references. The tentative quantity of each chemical associated with the processes and the toxicity of the chemical are used to estimate this hazard. The chemicals thus estimated to be the most potentially hazardous to health are fluorine, nitric acid, uranium metal, uranium hexafluoride, and uranium dust. The estimated next most hazardous chemicals are bromine, hydrobromic acid, hydrochloric acid, and hydrofluoric acid. For each of these chemicals and for a number of other process-associated chemicals the following information is presented: (1) any applicable standards, recommended standards and their basis; (2) a brief discussion to toxic effects including short exposure tolerance, atmospheric concentration immediately hazardous to life, evaluation of exposures, recommended control procedures, chemical properties, and a list of any toxicology reviews; and (3) recommendations for future research.

  1. Isotopic shifts in chemical exchange systems. 1. Large isotope effects in the complexation of Na+ isotopes by macrocyclic polyethers

    International Nuclear Information System (INIS)

    Knoechel, A.; Wilken, R.D.

    1981-01-01

    The complexation of 24 Na + and 22 Na + by 18 of the most widely used macrocyclic polyethers (crown ethers and monocyclic and bicyclic aminopolyethers) has been investigated in view of possible equilibrium isotope shifts. Solvated salts and polyether complexes were distributed differently into two phases and isotope ratios determined in both phases. Chloroform/water systems were shown to be particularly suitable to the investigations allowing favorable distribution for Na + and 13 of the 18 polyethers employed. With crown ethers 24 Na + enrichment varied from nonsignficant values (for large crown ethers) up to 3.1 +- 0.4% (18-crown-6). In the case of bicyclic aminopolyethers, ligands with cages of optimum size to accommodate Na + showed 24 Na + enrichment between O (nonsignificant) (2.2/sub B/2./sub B/) and 5.2 +- 1.8% (2.2.1). In contrast, for 2.2.2. and its derivatives, being too large for Na + , 22 Na + enrichment varying from O (nonsignificant) (2.2.2.p) up to 5.4 +- 0.5% (2.2.2.) has been observed. These values are remarkably high. They are explained by different bonding in solvate structure and polyether complex by using the theoretical approach of Bigeleisen

  2. Identifying stereoisomers by ab-initio calculation of secondary isotope shifts on NMR chemical shieldings.

    Science.gov (United States)

    Böhm, Karl-Heinz; Banert, Klaus; Auer, Alexander A

    2014-04-23

    We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2H)ethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T) level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

  3. Identifying Stereoisomers by ab-initio Calculation of Secondary Isotope Shifts on NMR Chemical Shieldings

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Böhm

    2014-04-01

    Full Text Available We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2Hethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

  4. Enrichment: CRISLA [chemical reaction by isotope selective activation] aims to reduce costs

    International Nuclear Information System (INIS)

    Eerkens, J.W.

    1989-01-01

    Every year, more than $3 billion is spent on enriching uranium. CRISLA (Chemical Reaction by Isotope Selective Activation) uses a laser-catalyzed chemical reaction which, its proponents claim, could substantially reduce these costs. In CRISLA, an infrared CO laser illuminates the intracavity reaction cell (IC) at a frequency tuned to excite primarily UF 6 . When UF 6 and co-reactant RX are passed through the IC, the tuned laser photons preferentially enhance the reaction of UF 6 with RX ten-thousand-fold over the thermal reaction rate. Thus the laser serves as an activator and the chemical energy for separation is largely chemical. (author)

  5. Lead isotope evolution across the Neoproterozoic boundary between craton and juvenile crust, Bayuda Desert, Sudan

    Science.gov (United States)

    Evuk, David; Lucassen, Friedrich; Franz, Gerhard

    2017-11-01

    Metaigneous mafic and ultramafic rocks from the juvenile Neoproterozoic Arabian Nubian Shield (ANS) and the Proterozoic, reworked Saharan Metacraton (SMC) have been analysed for major- and trace elements and Sr, Nd, and Pb isotopes. Most of the rocks are amphibolites metamorphosed at amphibolite facies conditions, some with relicts of a granulite facies stage. The other rocks are metapyroxenites, metagabbros, and some ultramafic rocks. Trace element compositions of the metabasaltic (dominantly tholeiitic) rocks resemble the patterns of island arcs and primitive lavas from continental arcs. Variable Sr and Nd isotope ratios indicate depleted mantle dominance for most of the samples. 207Pb/204Pb signatures distinguish between the influence of high 207Pb/204Pb old SMC crust and depleted mantle signatures of the juvenile ANS crust. The Pb isotope signatures for most metabasaltic rocks, metapyroxenites and metagabbros from SMC indicate an autochthonous formation. The interpretation of the new data together with published evidence from mafic xenoliths on SMC and ophiolite from ANS allows an extrapolation of mantle evolution in time. There are two lines of evolution in the regional mantle, one, which incorporates potential upper crust material during Neoproterozoic, and a second one with a depleted mantle signature since pre-Neoproterozoic that still is present in the Red Sea and Gulf of Aden spreading centres.

  6. Dissolution of barite for the analysis of strontium isotopes and other chemical and isotopic variations using aqueous sodium carbonate

    Science.gov (United States)

    Breit, G.N.; Simmons, E.C.; Goldhaber, M.B.

    1985-01-01

    A simple procedure for preparing barite samples for chemical and isotopic analysis is described. Sulfate ion, in barite, in the presence of high concentrations of aqueous sodium carbonate, is replaced by carbonate. This replacement forms insoluble carbonates with the cations commonly in barite: Ba, Sr, Ca and Pb. Sulfate is released into the solution by the carbonate replacement and is separated by filtration. The aqueous sulfate can then be reprecipitated for analysis of the sulfur and oxygen isotopes. The cations in the carbonate phase can be dissolved by acidifying the solid residue. Sr can be separated from the solution for Sr isotope analysis by ion-exchange chromatography. The sodium carbonate used contains amounts of Sr which will affect almost all barite 87Sr 86Sr ratios by less than 0.00001 at 1.95?? of the mean. The procedure is preferred over other techniques used for preparing barite samples for the determination of 87Sr 86Sr ratios because it is simple, rapid and enables simultaneous determination of many compositional parameters on the same material. ?? 1985.

  7. Primordial and Stellar Nucleosynthesis Chemical Evolution of Galaxies

    International Nuclear Information System (INIS)

    Chiosi, Cesare

    2010-01-01

    Following a brief introduction to early Universe cosmology, we present in some detail the results of primordial nucleosynthesis. Then we summarize the basic theory of nuclear reactions in stars and sketch the general rules of stellar evolution. We shortly review the subject of supernova explosions both by core collapse in massive stars (Type II) and carbon-deflagration in binary systems when one of the components is a White Dwarf accreting mass from the companion (Type Ia). We conclude the part dedicated to nucleosynthesis with elementary notions on the s- and r-process. Finally, we shortly address the topic of galactic chemical evolution and highlight some simple solutions aimed at understanding the main observational data on abundances and abundance ratios.

  8. A new cascade method for studying isotope effect in chemical exchange system without valance change

    International Nuclear Information System (INIS)

    Wen Xiaoning; Luo Wenzong

    1987-01-01

    A new cascade method for studying isotope effect in chemical exchange system without valance change is developed and described. This method is simple to use and consumes less extractant as compared with the commonly used Woodward method. It is also convenient for unstable systems

  9. The importance of glyceraldehyde radiolysis in chemical evolution

    International Nuclear Information System (INIS)

    Cruz-Castaneda, J.; Melendez-Lopez, A.; Buhse, T.; Ramos-Bernal, S.; Camargo-Raya, C.; Negron-Mendoza, A.; Fuentes-Carreon, C.; Universidad Nacional Autonoma de Mexico, Mexico City

    2017-01-01

    Studies in chemical evolution are intended to demonstrate how compounds of biological importance are generated from substances that could have been found in abiotic conditions on the primitive Earth or in extraterrestrial environments. In this context, the aim of the present work was to examine the behavior of DL-glyceraldehyde in both aqueous solution and solid samples under gamma irradiation. We irradiated dl-glyceraldehyde at different doses and temperatures with a gamma source; even at low doses and temperature (77 K), free radicals were detected. Among the products formed were ethylene glycol and glycolaldehyde. Some sugar-like compounds were also detected. (author)

  10. Pair phase transition and its evolution on even 64-68Ge isotopes

    International Nuclear Information System (INIS)

    Tong Hong; Shi Zhuyi

    2004-01-01

    By using a microscopic sdIBM-2+2q . p . approach which is the phenomenological core plus two-quasi-particle model and the experimental single-particle energies, the levels of the ground-band, β-band, γ-band, and partial two-quasi-particle states on 64-68 Ge isotopes are successfully reproduced. Based on the phenomenological model and microscopic approach, it has been deduced that no s-boson in the nucleus is breaking up and aligning; and that when one d-boson does, the minimum aligned energy can be calculated. This paper explicitly indicates that, with the increase of neutron number, an evolution process of PPT objects, i.e. from the two-quasi-proton states (on 64 Ge nucleus) to the two-quasi-neutron states (on 68 Ge nucleus) may take place in even Ge isotopes. (authors)

  11. Evolution of a chemically reacting plume in a ventilated room

    Science.gov (United States)

    Conroy, D. T.; Smith, Stefan G. Llewellyn; Caulfield, C. P.

    2005-08-01

    The dynamics of a second-order chemical reaction in an enclosed space driven by the mixing produced by a turbulent buoyant plume are studied theoretically, numerically and experimentally. An isolated turbulent buoyant plume source is located in an enclosure with a single external opening. Both the source and the opening are located at the bottom of the enclosure. The enclosure is filled with a fluid of a given density with a fixed initial concentration of a chemical. The source supplies a constant volume flux of fluid of different density containing a different chemical of known and constant concentration. These two chemicals undergo a second-order non-reversible reaction, leading to the creation of a third product chemical. For simplicity, we restrict attention to the situation where the reaction process does not affect the density of the fluids involved. Because of the natural constraint of volume conservation, fluid from the enclosure is continually vented. We study the evolution of the various chemical species as they are advected by the developing ventilated filling box process within the room that is driven by the plume dynamics. In particular, we study both the mean and vertical distributions of the chemical species as a function of time within the room. We compare the results of analogue laboratory experiments with theoretical predictions derived from reduced numerical models, and find excellent agreement. Important parameters for the behaviour of the system are associated with the source volume flux and specific momentum flux relative to the source specific buoyancy flux, the ratio of the initial concentrations of the reacting chemical input in the plume and the reacting chemical in the enclosed space, the reaction rate of the chemicals and the aspect ratio of the room. Although the behaviour of the system depends on all these parameters in a non-trivial way, in general the concentration within the room of the chemical input at the isolated source passes

  12. Chemical evolution of the Earth: Equilibrium or disequilibrium process?

    Science.gov (United States)

    Sato, M.

    1985-01-01

    To explain the apparent chemical incompatibility of the Earth's core and mantle or the disequilibrium process, various core forming mechanisms have been proposed, i.e., rapid disequilibrium sinking of molten iron, an oxidized core or protocore materials, and meteorite contamination of the upper mantle after separation from the core. Adopting concepts used in steady state thermodynamics, a method is devised for evaluating how elements should distribute stable in the Earth's interior for the present gradients of temperature, pressure, and gravitational acceleration. Thermochemical modeling gives useful insights into the nature of chemical evolution of the Earth without overly speculative assumptions. Further work must be done to reconcile siderophile elements, rare gases, and possible light elements in the outer core.

  13. Isotopic and chemical features of hot springs in Akita Prefecture

    International Nuclear Information System (INIS)

    Matsubaya, Osamu

    1997-01-01

    All over the Akita Prefecture, many hot springs are located. Most of them are of meteoric water, fossil sea water and volcanic gas origins. In the Ohdate-Kazuno area, moderate temperature hot springs of meteoric water origin are found, which may exist as rather shallow formation water in the Green Tuff formations. On the contrary, high temperature geothermal waters of meteoric origin, which are used for power generation, are obtained in two volcanic area of Hachimantai and Oyasu. Those geothermal waters are expected to come up through vertical fissures from depth deeper than 2 km. The difference of these two manners of meteoric water circulation should be necessarily explained to understand the relationship of shallow and deep geothermal systems. About some hot springs of fossil sea water origin, the relationships of δ D and Cl - don't agree to the mixing relation of sea water and meteoric water. This may be explained by two different processes, one of which is mixing of sea water with saline meteoric water (Cl - ca. 12 g/kg). The other is modification of δD by hydrogen isotopic exchange with hydrous minerals underground, or by exchange with atmospheric vapor during a relic lake before burying. (author)

  14. Chemical and isotopic investigation of warm springs associated with normal faults in Utah

    Science.gov (United States)

    Cole, David R.

    1983-04-01

    Thermal springs associated with normal faults in Utah have been analyzed for major cations and anions, and oxygen and hydrogen isotopes. Springs with measured temperatures averaging greater than 40°C are characterized by Na + K- and SO 4 + Cl-rich waters containing 10 3 to 10 4 mg/l of dissolved solids. Lower temperature springs, averaging less than 40°C, are more enriched in Ca + Mg relative to Na + K. Chemical variations monitored through time in selected thermal springs are probably produced by mixing with non-thermal waters. During the summer months at times of maximum flow, selected hot springs exhibit their highest temperatures and maximum enrichments in most chemical constituents. Cation ratios and silica concentrations remain relatively constant through time for selected Utah thermal springs assuring the applicability of the geothermometer calculations regardless of the time of year. Geothermometer calculations utilizing either the quartz (no steam loss), chalcedony or Mg-corrected Na/K/Ca methods indicate that most thermal springs in Utah associated with normal faults have subsurface temperatures in the range of 25 to less than 120°C. This temperature range suggests fluid circulation is restricted to depths less than about three kilometers assuming an average thermal gradient of about 40°C/km. Thermodynamic calculations suggest that most thermal springs are oversaturated with respect to calcite, quartz, pyrophyllite, (Fe, Mg)-montmorillonite, microcline and hematite, and undersaturated with respect to anhydrite, gypsum, fluorite and anorthite. Chalcedony and cristobalite appear to be the only phases consistently at or near saturation in most waters. Theoretical evaluation of mixing on mineral saturation trends indicates that anhydrite and calcite become increasingly more undersaturated as cold, dilute groundwater mixes with a hot (150°C), NaCl-rich fluid. The evolution of these thermal waters issuing from faults appears to be one involving the

  15. Monitoring of chemical and isotopic composition of the Euphrates river in Syria

    International Nuclear Information System (INIS)

    Kattan, Z.

    2008-11-01

    The ratios of stable isotopes ( 18 O and 2 H), tritium content, together with the chemical composition of major ions of the Euphrates and Balikh (Euphrates tributary) Rivers, and the groundwaters of four wells drilled close to the Euphrates River course, were measured on a monthly basis. The Euphrates River water was monitored at twelve stations along its course in Syria during the period from January 2004 to December 2006, whereas those of the Balikh and groundwaters were only investigated during 2005. Although, the spatial variations of heavy stable isotope concentrations are moderated with respect to other large rivers in the world, the concentrations of these isotopes increase generally downstream the Euphrates River, with a sharp enrichment at Al-Assad Lake. This sharp increase could be explained by the effect of direct evaporation from the river and its tributaries; and the effect of drainage return flows of irrigation waters, isotopically more enriched. Enrichment of stable isotopes in the Euphrates River water was used as a direct indicator of evaporation. Based on an experimental evaporation result of a Euphrates water sample and the integral enrichment of heavy stable isotopes in the Euphrates River system, the amount of water losses by evaporation from Al-Assad Lake was estimated to be about 1.26 to 1.62 billion m''3, according to 18 O and deuterium ( 2 H), respectively. This amount represents about 12-16% of the renewable surface water resources in the country. (author)

  16. Chemical Ligation and Isotope Labeling to Locate Dynamic Effects during Catalysis by Dihydrofolate Reductase.

    Science.gov (United States)

    Luk, Louis Y P; Ruiz-Pernía, J Javier; Adesina, Aduragbemi S; Loveridge, E Joel; Tuñón, Iñaki; Moliner, Vincent; Allemann, Rudolf K

    2015-07-27

    Chemical ligation has been used to alter motions in specific regions of dihydrofolate reductase from E. coli and to investigate the effects of localized motional changes on enzyme catalysis. Two isotopic hybrids were prepared; one with the mobile N-terminal segment containing heavy isotopes ((2) H, (13) C, (15) N) and the remainder of the protein with natural isotopic abundance, and the other one with only the C-terminal segment isotopically labeled. Kinetic investigations indicated that isotopic substitution of the N-terminal segment affected only a physical step of catalysis, whereas the enzyme chemistry was affected by protein motions from the C-terminal segment. QM/MM studies support the idea that dynamic effects on catalysis mostly originate from the C-terminal segment. The use of isotope hybrids provides insights into the microscopic mechanism of dynamic coupling, which is difficult to obtain with other studies, and helps define the dynamic networks of intramolecular interactions central to enzyme catalysis. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  17. Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us?

    Directory of Open Access Journals (Sweden)

    K. R. Lassey

    2007-01-01

    Full Text Available Little is known about how the methane source inventory and sinks have evolved over recent centuries. New and detailed records of methane mixing ratio and isotopic composition (12CH4, 13CH4 and 14CH4 from analyses of air trapped in polar ice and firn can enhance this knowledge. We use existing bottom-up constructions of the source history, including "EDGAR"-based constructions, as inputs to a model of the evolving global budget for methane and for its carbon isotope composition through the 20th century. By matching such budgets to atmospheric data, we examine the constraints imposed by isotope information on those budget evolutions. Reconciling both 12CH4 and 13CH4 budgets with EDGAR-based source histories requires a combination of: a greater proportion of emissions from biomass burning and/or of fossil methane than EDGAR constructions suggest; a greater contribution from natural such emissions than is commonly supposed; and/or a significant role for active chlorine or other highly-fractionating tropospheric sink as has been independently proposed. Examining a companion budget evolution for 14CH4 exposes uncertainties in inferring the fossil-methane source from atmospheric 14CH4 data. Specifically, methane evolution during the nuclear era is sensitive to the cycling dynamics of "bomb 14C" (originating from atmospheric weapons tests through the biosphere. In addition, since ca. 1970, direct production and release of 14CH4 from nuclear-power facilities is influential but poorly quantified. Atmospheric 14CH4 determinations in the nuclear era have the potential to better characterize both biospheric carbon cycling, from photosynthesis to methane synthesis, and the nuclear-power source.

  18. Chemical and Oxygen Isotopic Composition of Roman and Late Antique Glass from Northern Greece

    Directory of Open Access Journals (Sweden)

    Alberta Silvestri

    2017-01-01

    Full Text Available The present paper emphasizes the importance of measuring the oxygen isotopic and chemical compositions of ancient glass, in order to constrain some features such as age, raw materials, and production technologies and to identify the “fingerprint” of local productions. In this context, thirty-nine Roman and late Antique glass samples and eight chert samples from northern Greece were selected and analysed for their oxygen isotopic and chemical compositions. Results show that the majority of glass samples are produced using natron as flux and have δ18O values of about 15.5‰, plus or minus a few tenths of one per mil, suggesting that raw materials probably come from Levantine area. Four samples are heavily enriched in 18O, and their chemical composition clearly shows that they were made with soda plant ash as flux. Isotopic and chemical data of Greek chert samples support the hypothesis of local production of the above samples. About half of the glass samples have chemical compositions, which allow their age to be constrained to the late Antique period. For the remaining glass, similarities with literature compositional groups are reported and discussed.

  19. Boninite petrogenesis: Chemical and Nd-Sr isotopic constraints

    International Nuclear Information System (INIS)

    Cameron, W.E.; Walker, D.A.; McCulloch, M.T.

    1983-01-01

    Major and trace element abundances and Nd and Sr isotopic compositions have been determined for boninites from the Bonin Islands, Cape Vogel (Papua New Guinea) and New Caledonia and for similar lavas from Cyprus and New Zealand. SiO 2 , CaO, incompatible element abundances and epsilonsub(Nd) values are shown to vary systematically with the degree of light rare earth element (LREE) enrichment. Lasub(N)/Ybsub(N) varies from 5.4 to 0.3. The range of epsilonsub(Nd) values is from +8.0 to +1.9. These features are interpreted in terms of mixing of two components: a LREE-depleted magma, derived by partial melting of an already-depleted peridotite source, and a hydrous. LREE-enriched fluid. If La for the fluid is taken as 100 x chondrites, REE abundances observed in boninites can be reproduced by 1-15% addition of the LREE-enriched component. Using a LREE-depleted component inferred from the Cyprus samples (Lasub(N)/Ybsub(N)=0.10), the LREE-enriched component for Tertiary boninites has been calculated to have a Lasub(N)/Ybsub(N) approx.= 20. The LREE-depleted component contains most of the CaO, Sc, HREE and TiO 2 , and has an epsilonsub(Nd) of >= +8. The enriched component contains H 2 O and most of the Zr, Nb and LREE, and has an epsilonsub(Nd) ranging from +6 to at least -5. Origins for the LREE-enriched fluid include derivation from mantle sources similar to those proposed for ocean islands or, more likely, from subducted oceanic or continental crust in island-arc settings. (orig.)

  20. Isotopic and chemical studies of geothermal waters of Northern Areas in Pakistan

    Energy Technology Data Exchange (ETDEWEB)

    Dildar Hussain, S; Ahmad, M; Akram, W; Sajjad, M I [Pakistan Inst. of Nuclear Science and Technology, Islamabad (Pakistan); Gonfiantini, R [International Atomic Energy Agency, Vienna (Austria). Isotope Hydrology Section; Tasneem, M A

    1995-02-01

    Northern Areas is one of the major thermal fields of Pakistan with more than two dozen known hot springs having discharge temperature ranging from 35 deg. C to 94 deg. C. Isotopic and chemical techniques applied to study the geothermal fields show that thermal waters are of meteoric origin and can be classified as Na-HCO{sub 3}, Na-SO{sub 4} and mixed type on the basis of their chemical contents. At some places cooling of thermal waters seems to be due to steam separation whereas mixing with fresh cold water is prominent at the remaining sites. The temperatures estimated by isotopic and chemical geothermometers for the two major fields i.e. Tatta Pani and Murtazabad are 83-257 deg. C and 65-296 deg. C respectively. (author). 24 refs, 11 figs, 3 tabs.

  1. A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

    Directory of Open Access Journals (Sweden)

    Yuan Zhen

    2016-01-01

    Full Text Available Fornax is the brightest Milky Way (MW dwarf spheroidal galaxy and its star formation history (SFH has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH usinga simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass Mx of the gas to mix with the ejecta from each SN. The choice of Mx depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = tsat. Our results indicate that due to the global gas outflow at t > tsat, part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.

  2. Non-equilibrium mass transfer absorption model for the design of boron isotopes chemical exchange column

    International Nuclear Information System (INIS)

    Bai, Peng; Fan, Kaigong; Guo, Xianghai; Zhang, Haocui

    2016-01-01

    Highlights: • We propose a non-equilibrium mass transfer absorption model instead of a distillation equilibrium model to calculate boron isotopes separation. • We apply the model to calculate the needed column height to meet prescribed separation requirements. - Abstract: To interpret the phenomenon of chemical exchange in boron isotopes separation accurately, the process is specified as an absorption–reaction–desorption hybrid process instead of a distillation equilibrium model, the non-equilibrium mass transfer absorption model is put forward and a mass transfer enhancement factor E is introduced to find the packing height needed to meet the specified separation requirements with MATLAB.

  3. Stable isotope and chemical compositions of European and Australasian ciders as a guide to authenticity.

    Science.gov (United States)

    Carter, James F; Yates, Hans S A; Tinggi, Ujang

    2015-01-28

    This paper presents a data set derived from the analysis of bottled and canned ciders that may be used for comparison with suspected counterfeit or substitute products. Isotopic analysis of the solid residues from ciders (predominantly sugar) provided a means to determine the addition of C4 plant sugars. The added sugars were found to comprise cane sugar, high-fructose corn syrup, glucose, or combinations. The majority of ciders from Australia and New Zealand were found to contain significant amounts of added sugar, which provided a limited means to distinguish these ciders from European ciders. The hydrogen and oxygen isotopic compositions of the whole ciders (predominantly water) were shown to be controlled by two factors, the water available to the parent plant and evaporation. Analysis of data derived from both isotopic and chemical analysis of ciders provided a means to discriminate between regions and countries of manufacture.

  4. Chempy: A flexible chemical evolution model for abundance fitting. Do the Sun's abundances alone constrain chemical evolution models?

    Science.gov (United States)

    Rybizki, Jan; Just, Andreas; Rix, Hans-Walter

    2017-09-01

    Elemental abundances of stars are the result of the complex enrichment history of their galaxy. Interpretation of observed abundances requires flexible modeling tools to explore and quantify the information about Galactic chemical evolution (GCE) stored in such data. Here we present Chempy, a newly developed code for GCE modeling, representing a parametrized open one-zone model within a Bayesian framework. A Chempy model is specified by a set of five to ten parameters that describe the effective galaxy evolution along with the stellar and star-formation physics: for example, the star-formation history (SFH), the feedback efficiency, the stellar initial mass function (IMF), and the incidence of supernova of type Ia (SN Ia). Unlike established approaches, Chempy can sample the posterior probability distribution in the full model parameter space and test data-model matches for different nucleosynthetic yield sets. It is essentially a chemical evolution fitting tool. We straightforwardly extend Chempy to a multi-zone scheme. As an illustrative application, we show that interesting parameter constraints result from only the ages and elemental abundances of the Sun, Arcturus, and the present-day interstellar medium (ISM). For the first time, we use such information to infer the IMF parameter via GCE modeling, where we properly marginalize over nuisance parameters and account for different yield sets. We find that 11.6+ 2.1-1.6% of the IMF explodes as core-collapse supernova (CC-SN), compatible with Salpeter (1955, ApJ, 121, 161). We also constrain the incidence of SN Ia per 103M⊙ to 0.5-1.4. At the same time, this Chempy application shows persistent discrepancies between predicted and observed abundances for some elements, irrespective of the chosen yield set. These cannot be remedied by any variations of Chempy's parameters and could be an indication of missing nucleosynthetic channels. Chempy could be a powerful tool to confront predictions from stellar

  5. Isotopic evolution of the protoplanetary disk and the building blocks of Earth and the Moon

    Science.gov (United States)

    Schiller, Martin; Bizzarro, Martin; Fernandes, Vera Assis

    2018-03-01

    Nucleosynthetic isotope variability among Solar System objects is often used to probe the genetic relationship between meteorite groups and the rocky planets (Mercury, Venus, Earth and Mars), which, in turn, may provide insights into the building blocks of the Earth–Moon system. Using this approach, it has been inferred that no primitive meteorite matches the terrestrial composition and the protoplanetary disk material from which Earth and the Moon accreted is therefore largely unconstrained. This conclusion, however, is based on the assumption that the observed nucleosynthetic variability of inner-Solar-System objects predominantly reflects spatial heterogeneity. Here we use the isotopic composition of the refractory element calcium to show that the nucleosynthetic variability in the inner Solar System primarily reflects a rapid change in the mass-independent calcium isotope composition of protoplanetary disk solids associated with early mass accretion to the proto-Sun. We measure the mass-independent 48Ca/44Ca ratios of samples originating from the parent bodies of ureilite and angrite meteorites, as well as from Vesta, Mars and Earth, and find that they are positively correlated with the masses of their parent asteroids and planets, which are a proxy of their accretion timescales. This correlation implies a secular evolution of the bulk calcium isotope composition of the protoplanetary disk in the terrestrial planet-forming region. Individual chondrules from ordinary chondrites formed within one million years of the collapse of the proto-Sun reveal the full range of inner-Solar-System mass-independent 48Ca/44Ca ratios, indicating a rapid change in the composition of the material of the protoplanetary disk. We infer that this secular evolution reflects admixing of pristine outer-Solar-System material into the thermally processed inner protoplanetary disk associated with the accretion of mass to the proto-Sun. The identical calcium isotope composition of Earth

  6. Evolution of deformation in neutron-rich Ba isotopes up to A =150

    Science.gov (United States)

    Licǎ, R.; Benzoni, G.; Rodríguez, T. R.; Borge, M. J. G.; Fraile, L. M.; Mach, H.; Morales, A. I.; Madurga, M.; Sotty, C. O.; Vedia, V.; De Witte, H.; Benito, J.; Bernard, R. N.; Berry, T.; Bracco, A.; Camera, F.; Ceruti, S.; Charviakova, V.; Cieplicka-Oryńczak, N.; Costache, C.; Crespi, F. C. L.; Creswell, J.; Fernandez-Martínez, G.; Fynbo, H.; Greenlees, P. T.; Homm, I.; Huyse, M.; Jolie, J.; Karayonchev, V.; Köster, U.; Konki, J.; Kröll, T.; Kurcewicz, J.; Kurtukian-Nieto, T.; Lazarus, I.; Lund, M. V.; Mǎrginean, N.; Mǎrginean, R.; Mihai, C.; Mihai, R. E.; Negret, A.; Orduz, A.; Patyk, Z.; Pascu, S.; Pucknell, V.; Rahkila, P.; Rapisarda, E.; Regis, J. M.; Robledo, L. M.; Rotaru, F.; Saed-Samii, N.; Sánchez-Tembleque, V.; Stanoiu, M.; Tengblad, O.; Thuerauf, M.; Turturica, A.; Van Duppen, P.; Warr, N.; IDS Collaboration

    2018-02-01

    The occurrence of octupolar shapes in the Ba isotopic chain was recently established experimentally up to N =90 . To further extend the systematics, the evolution of shapes in the most neutron-rich members of the Z =56 isotopic chain accessible at present, Ba,150148, has been studied via β decay at the ISOLDE Decay Station. This paper reports on the first measurement of the positive- and negative-parity low-spin excited states of 150Ba and presents an extension of the β -decay scheme of 148Cs. Employing the fast timing technique, half-lives for the 21+ level in both nuclei have been determined, resulting in T1 /2=1.51 (1 ) ns for 148Ba and T1 /2=3.4 (2 ) ns for 150Ba. The systematics of low-spin states, together with the experimental determination of the B (E 2 :2+→0+) transition probabilities, indicate an increasing collectivity in Ba-150148, towards prolate deformed shapes. The experimental data are compared to symmetry conserving configuration mixing (SCCM) calculations, confirming an evolution of increasingly quadrupole deformed shapes with a definite octupolar character.

  7. Isotopic and Chemical Evidence for Primitive Aqueous Alteration in the Tagish Lake Meteorite

    Science.gov (United States)

    Sakuma, Keisuke; Hidaka, Hiroshi; Yoneda, Shigekazu

    2018-01-01

    Aqueous alteration is one of the primitive activities that occurred on meteorite parent bodies in the early solar system. The Tagish Lake meteorite is known to show an intense parent body aqueous alteration signature. In this study, quantitative analyses of the alkaline elements and isotopic analyses of Sr and Ba from acid leachates of TL (C2-ungrouped) were performed to investigate effects of aqueous alteration. The main purpose of this study is to search for isotopic evidence of extinct 135Cs from the Ba isotopic analyses in the chemical separates from the Tagish Lake meteorite. Barium isotopic data from the leachates show variable 135Ba isotopic anomalies (ε = ‑2.6 ∼ +3.6) which correlatewith 137Ba and 138Ba suggesting a heterogeneous distribution of s- and r-rich nucleosynthetic components in the early solar system. The 87Rb–87Sr and 135Cs–135Ba decay systems on TL in this study do not provide any chronological information. The disturbance of the TL chronometers is likely a reflection of the selective dissolution of Cs and Rb given the relatively higher mobility of Cs and Rb compared to Ba and Sr, respectively, during fluid mineral interactions.

  8. Chemical and isotopic properties of groundwater along the coastal plain of the aqaba gulf, (EG)

    International Nuclear Information System (INIS)

    Awad, M.A.A

    1999-01-01

    Isotopic and hydrochemical studies were undertaken along the coastal plain of aqaba gulf in taba, dahab and sharm El-Sheikh to ascertain the role of precipitation (via floods), local water and sea water intrusion as replenishment sources for available groundwater resources in these areas. From the isotopic point of view, it can be concluded that groundwater in nuweiba wells appears to have been recharged from continental and mediterranean participation, while in dahab wells and sharm El-Sheikh Nubian well, recent precipitation via monsoonal air masses which comes from indian ocean plays a considerable role in recharging of these wells. In Taba wells, seepage of partly evaporated flood water represents the main source of their recharge. The fractured nature of the studied area has an effect on the occurrence of groundwater. The variation in chemical water type is due to leaching of terrestrial salts and impact of marine faces (i.e. evaporites and sea spray). Sea water intrusion via over pumping and/ or during tide and ebb duration shows an affect-to some extent-on the chemical composition of some localized wells. Construction of meteorological stations in scattered sites all over sinai is necessary to collect rainwater and floods samples periodically, to study the modification of the isotopic composition of rainwater by processes which occur before groundwater recharge using environmental isotopes

  9. Carbonate and carbon isotopic evolution of groundwater contaminated by produced water brine with hydrocarbons

    International Nuclear Information System (INIS)

    Atekwana, Eliot A.; Seeger, Eric J.

    2015-01-01

    The major ionic and dissolved inorganic carbon (DIC) concentrations and the stable carbon isotope composition of DIC (δ"1"3C_D_I_C) were measured in a freshwater aquifer contaminated by produced water brine with petroleum hydrocarbons. Our aim was to determine the effects of produced water brine contamination on the carbonate evolution of groundwater. The groundwater was characterized by three distinct anion facies: HCO_3"−-rich, SO_4"2"−-rich and Cl"−-rich. The HCO_3"−-rich groundwater is undergoing closed system carbonate evolution from soil CO_2_(_g_) and weathering of aquifer carbonates. The SO_4"2"−-rich groundwater evolves from gypsum induced dedolomitization and pyrite oxidation. The Cl"−-rich groundwater is contaminated by produced water brine and undergoes common ion induced carbonate precipitation. The δ"1"3C_D_I_C of the HCO_3"−-rich groundwater was controlled by nearly equal contribution of carbon from soil CO_2_(_g_) and the aquifer carbonates, such that the δ"1"3C of carbon added to the groundwater was −11.6‰. In the SO_4"2"−-rich groundwater, gypsum induced dedolomitization increased the "1"3C such that the δ"1"3C of carbon added to the groundwater was −9.4‰. In the produced water brine contaminated Cl"−-rich groundwater, common ion induced precipitation of calcite depleted the "1"3C such that the δ"1"3C of carbon added to the groundwater was −12.7‰. The results of this study demonstrate that produced water brine contamination of fresh groundwater in carbonate aquifers alters the carbonate and carbon isotopic evolution. - Highlights: • We studied carbonate and δ"1"3C evolution in groundwater contaminated by produced water brine. • Multiple processes affect the carbonate and δ"1"3C evolution of the groundwater. • The processes are carbonate weathering, dedolomitization and common ion induce calcite precipitation. • The δ"1"3C added to DIC was −11.6‰ for weathering, −9.4‰ for dedolomitization

  10. Chemical evolution of two-component galaxies. II

    International Nuclear Information System (INIS)

    Caimmi, R.

    1978-01-01

    In order to confirm and refine the results obtained in a previous paper the chemical evolution of two-component (spheroid + disk) galaxies is derived rejecting the instantaneous recycling approximation, by means of numerical computations, accounting for (i) the collapse phase of the gas, assumed to be uniform in density and composition, and (ii) a birth-rate stellar function. Computations are performed relatively to the solar neighbourhood and to model galaxies which closely resemble the real morphological sequence: in both cases, numerical results are compared with analytical ones. The numerical models of this paper constitute a first-order approximation, while higher order approximations could be made by rejecting the hypothesis of uniform density and composition, and making use of detailed dynamical models. (Auth.)

  11. Chemical evolution, stellar nucleosynthesis and a variable star formation rate

    International Nuclear Information System (INIS)

    Olive, K.A.; Thielemann, F.K.; Truran, J.W.

    1986-04-01

    The effects of a decreasing star formation rate (SFR) on the galactic abundances of elements produced in massive stars (M ≥ 10 Msub solar). On the basis of a straightforward model of galactic evolution, a relation between the upper mass limit of type II supernovae (M/sub SN/) contributing to chemical evolution and the decline of the SFR (tau) is derived, when the oxygen abundance is determined only by massive stars. The additional requirement that all intermediate mass elements (Ne-Ti), which are also predominantly due to nucleosynthesis in massive stars, are produced in solar proportions leads to a unique value of M/sub SN/ and tau. The application of this method with abundance yields from Arnett (1978) and Woosley and Weaver (1986) resuults, however, in contradicting solutions: M/sub SN/ ≅ 45 Msub solar, tau = ∞, and M/sub SN/ ≅ 15 Msub solar, tau = 3 x 10 9 y. Thus, in order that this approach provide an effective probe of the SFR over the history of our galaxy it is essential that converging and more accurate predictions of the consequences of stellar and supernova nucleosynthesis will be forthcoming. 54 refs., 2 figs., 2 tabs

  12. Chemical evolution of formation waters in the Palm Valley gas field, Northern Territory

    International Nuclear Information System (INIS)

    Andrew, A.S.; Giblin, A.M.

    2000-01-01

    The chemical composition and evolution of formation waters associated with gas production in the Palm Valley field, Northern Territory, has important implications for reservoir management, saline water disposal, and gas reserve calculations. Historically, the occurrence of saline formation water in gas fields has been the subject of considerable debate. A better understanding of the origin, chemical evolution and movement of the formation water at Palm Valley has important implications for future reservoir management, disposal of highly saline water and accurate gas reserves estimation. Major and trace element abundance data suggest that a significant component of the highly saline water from Palm Valley has characteristics that may have been derived from a modified evaporated seawater source such as an evaporite horizon. The most dilute waters probably represent condensate and the variation in the chemistry of the intermediate waters suggests they were derived from a mixture of the condensate with the highly saline brine. The chemical and isotopic results raise several interrelated questions; the ultimate source of the high salinity and the distribution of apparently mixed compositions. In this context several key observation are highlighted. Strontium concentrations are extremely high in the brines; although broadly similar in their chemistry, the saline fluids are neither homogeneous nor well mixed; the 87 Sr/ 86 Sr ratios in the brines are higher than the signatures preserved in the evaporitic Bitter Springs Formation, and all other conceivably marine-related evaporites (Strauss, 1993); the 87 Sr/ 86 Sr ratios in the brines are lower than those measured from groundmass carbonates in the host rocks, and that the 87 Sr/ 86 Sr ratios of the brines are similar, but still somewhat higher than those measured in vein carbonates from the reservoir. It is concluded that the high salinity brine entered the reservoir during the Devonian uplift and was subsequently

  13. General constraints on the effect of gas flows in the chemical evolution of galaxies

    International Nuclear Information System (INIS)

    Edmunds, M.G.

    1990-01-01

    The basic equations for the chemical evolution of galaxies in which the 'simple' closed box model is modified to allow any form of inflow or outflow are examined. It is found that there are quite general limiting constraints on the effects that such flows can have. Some implications for the actual chemical evolution of galaxies are discussed, and the constraints should also be useful in understanding the behaviour of detailed numerical models of galactic chemical evolution involving gas flows. (author)

  14. Application of isotopic and chemical methods to the study of hydrological problems in Brazilian northeastern areas

    International Nuclear Information System (INIS)

    Ponte, J.H.

    1979-01-01

    Hydrological studies are reported with samples of ground water from several region of northern - and northeastern Brazil: Marajo Island (State of Para), State of Piaui, Ceara and Rio Grande do Norte. A description is given of the utilization of chemical and isotopic methods, in particular measurements of tritium concentration and 14 C- counting techniques for the determination of the origin and residence time of water. (I.C.R.) [pt

  15. Chemical methods for Sm-Nd separation and its application in isotopic geological dating

    International Nuclear Information System (INIS)

    Guo Qifeng.

    1990-01-01

    Three chemical methods for Sm-Nd separation are mainly desribed: low chromatography of butamone-ammonium thiocyanate for hight concentration Sm and Nd separation, P 240 column chromatography for medium concentration Sm-Nd separation, and pressure ion exchange for low concentration Sm-Nd. The first Sm-Nd synchrone obtained in China with Sm-Nd methods is introduced and Sm-Nd isotopic geological dating in Early Archaean rocks in eastern Hebei has been determined

  16. The effect of natural weathering on the chemical and isotopic composition of biotites

    International Nuclear Information System (INIS)

    Clauer, N.; Bonnot-Courtois, C.

    1982-01-01

    The effect of progressive natural weathering on the isotopic (Rb-Sr, K-Ar, deltaD, delta 18 O) and chemical (REE, H 2 O + ) compositions of biotite has been studied on a suite of migmatitic biotites from the Chad Republic. During the early stages of weathering the Rb-Sr system is strongly affected, the hydrogen and oxygen isotope compositions change markedly, the minerals are depleted in light REE, the water content increases by a factor of two, and the K-Ar system is relatively little disturbed. During intensive weathering the K-Ar system is more strongly disturbed than the Rb-Sr system. Most of the isotopic and chemical modifications take place under nonequilibrium conditions and occur before newly formed kaolinite and/or smectite can be detected. These observations suggest that (a) 'protominerals' may form within the biotite structure during the initial period of weathering, and (b) only when chemical equilibrium is approached in the weathering profile are new minerals able to form. (author)

  17. Environmental isotopes, chemical composition and groundwater sources in Al-Maghara area, Sinai, Egypt

    International Nuclear Information System (INIS)

    Nada, A.A.; Awad, M.A.; Froehlich, K.; El Behery, M.

    1991-01-01

    Groundwater samples collected from a number of localities, in Al-Maghara area, north central part of Sinai, were subject to various chemical and isotopic analysis. The purpose of the study is to determine whether the groundwaters are recently recharged or not in order to adopt an efficient water management policy. The hydrochemical results indicate that they are mainly of primary marine origin, dilution of this water by meteoric water changes its chemical composition to be mixed water type, which has the major chemical components: KCl, NaCl, Na 2 SO 4 , MgSO 4 , Mg(HCO 3 ) 2 and Ca(HCO 3 ) 2 . The tritium content confirm the meteoric water recharge recently especially for wells with high tritium content. The stable environmental isotopic composition of the groundwater reflects the isotopic composition of precipitation and flooding with some evaporation enrichment prior to infiltration. There is also mixing with palaeowater (water recharge in the past cooler climate periods), by leaking through faulting in the area. (orig.) [de

  18. Features of adsorbed chemical elements and their isotopes distribution in iodine air filters AU-1500 of nuclear power plant

    International Nuclear Information System (INIS)

    Neklyudov, I.M.; Dovbnya, A.N.; Dikiy, N.P.; Ledenyov, O.P.; Lyashko, Yu.V.

    2013-01-01

    The main aim of research is to investigate the physical features of spatial distribution of the adsorbed chemical elements and their isotopes in the granular filtering medium in the iodine air filters of the type of AU-1500 in the forced-exhaust ventilation at the nuclear power plant. The ?-activation analysis method is applied to accurately characterize the distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the AU-1500 iodine air filter after its long term operation at the nuclear power plant. The typical spectrum of the detected chemical elements and their isotopes in the AU-1500 iodine air filter, which was exposed by the irradiation of bremsstrahlung gamma-quantum producing by the accelerating electrons in the tantalum target, are obtained. The spatial distributions of the detected chemical element 127 I and some other chemical elements and their isotopes in the layer of absorber, which was made of the cylindrical coal granules of the type of SKT-3, in the AU-1500 iodine air filter are also researched. The possible influences by the standing wave of air pressure in the iodine air filter on the spatial distribution of the chemical elements and their isotopes in the iodine air filter are discussed. The comprehensive analysis of obtained research results on the distribution of the adsorbed chemical elements and their isotopes in the absorber of iodine air filter is performed.

  19. Anglo-Saxon animal husbandry techniques revealed though isotope and chemical variations in cattle teeth

    International Nuclear Information System (INIS)

    Evans, J.A.; Tatham, S.; Chenery, S.R.; Chenery, C.A.

    2007-01-01

    The Sr concentration and isotope composition of tooth enamel from domesticated animals from two neighbouring Anglo-Saxon settlements, at Empingham (6-7th century) and Ketton (10-12th century) in Rutland, central England, are compared both with each other, and with associated human populations. Data from the Empingham II site form discrete fields in Sr concentration and isotope composition space for cattle, pig and sheep with a partial overlap of the human and pig fields. By contrast there is significant overlap in all the animal and human data fields from the Ketton site. The differences in data distribution between the two sites are attributed to animal husbandry techniques, as the surface geology of the two areas is very similar, implying geological factors are an unlikely cause of the difference. It is suggested that the grazing and feeding patterns of animals at the Empingham II site were controlled and restricted, whereas at the Ketton site the animals grazed and foraged freely over a common area. Strontium isotope variation within cattle molars from the two settlements show marked differences that reflect the nature of their feeding and rearing. The enamel from a cattle molar from the Empingham II site has a well-defined, systematic variation of Sr isotope composition with Sr concentration, whereas no such patterns exist in a comparable cattle molar from Ketton. Chemical and O isotope variations in the cattle tooth from Empingham II show sympathetic variation of Sr and Ba concentrations with Sr isotope composition from cusp to cervix. The cusp has higher Sr and Ba concentrations log (Sr/Ca) ratio of -3.1 and 87 Sr/ 86 Sr ratio of 0.71151 where as the cervical region of the enamel has log (Sr/Ca) = -3.3 and 87 Sr/ 86 Sr = 0.71061

  20. Anglo-Saxon animal husbandry techniques revealed though isotope and chemical variations in cattle teeth

    Energy Technology Data Exchange (ETDEWEB)

    Evans, J.A. [NERC Isotope Geosciences Laboratory, BGS, Keyworth, Nottingham NG12 5GG (United Kingdom)], E-mail: je@nigl.nerc.ac.uk; Tatham, S. [School of Archaeology and Ancient History, University of Leicester, Leicester LE1 7RH (United Kingdom); Chenery, S.R. [British Geological Survey, Keyworth, Nottingham NG12 5GG (United Kingdom); Chenery, C.A. [NERC Isotope Geosciences Laboratory, BGS, Keyworth, Nottingham NG12 5GG (United Kingdom)

    2007-09-15

    The Sr concentration and isotope composition of tooth enamel from domesticated animals from two neighbouring Anglo-Saxon settlements, at Empingham (6-7th century) and Ketton (10-12th century) in Rutland, central England, are compared both with each other, and with associated human populations. Data from the Empingham II site form discrete fields in Sr concentration and isotope composition space for cattle, pig and sheep with a partial overlap of the human and pig fields. By contrast there is significant overlap in all the animal and human data fields from the Ketton site. The differences in data distribution between the two sites are attributed to animal husbandry techniques, as the surface geology of the two areas is very similar, implying geological factors are an unlikely cause of the difference. It is suggested that the grazing and feeding patterns of animals at the Empingham II site were controlled and restricted, whereas at the Ketton site the animals grazed and foraged freely over a common area. Strontium isotope variation within cattle molars from the two settlements show marked differences that reflect the nature of their feeding and rearing. The enamel from a cattle molar from the Empingham II site has a well-defined, systematic variation of Sr isotope composition with Sr concentration, whereas no such patterns exist in a comparable cattle molar from Ketton. Chemical and O isotope variations in the cattle tooth from Empingham II show sympathetic variation of Sr and Ba concentrations with Sr isotope composition from cusp to cervix. The cusp has higher Sr and Ba concentrations log (Sr/Ca) ratio of -3.1 and {sup 87}Sr/{sup 86}Sr ratio of 0.71151 where as the cervical region of the enamel has log (Sr/Ca) = -3.3 and {sup 87}Sr/{sup 86}Sr = 0.71061.

  1. Chemical Evolution of Groundwater Near a Sinkhole Lake, Northern Florida: 2. Chemical Patterns, Mass Transfer Modeling, and Rates of Mass Transfer Reactions

    Science.gov (United States)

    Katz, Brian G.; Plummer, L. Niel; Busenberg, Eurybiades; Revesz, Kinga M.; Jones, Blair F.; Lee, Terrie M.

    1995-06-01

    Chemical patterns along evolutionary groundwater flow paths in silicate and carbonate aquifers were interpreted using solute tracers, carbon and sulfur isotopes, and mass balance reaction modeling for a complex hydrologic system involving groundwater inflow to and outflow from a sinkhole lake in northern Florida. Rates of dominant reactions along defined flow paths were estimated from modeled mass transfer and ages obtained from CFC-modeled recharge dates. Groundwater upgradient from Lake Barco remains oxic as it moves downward, reacting with silicate minerals in a system open to carbon dioxide (CO2), producing only small increases in dissolved species. Beneath and downgradient of Lake Barco the oxic groundwater mixes with lake water leakage in a highly reducing, silicate-carbonate mineral environment. A mixing model, developed for anoxic groundwater downgradient from the lake, accounted for the observed chemical and isotopic composition by combining different proportions of lake water leakage and infiltrating meteoric water. The evolution of major ion chemistry and the 13C isotopic composition of dissolved carbon species in groundwater downgradient from the lake can be explained by the aerobic oxidation of organic matter in the lake, anaerobic microbial oxidation of organic carbon, and incongruent dissolution of smectite minerals to kaolinite. The dominant process for the generation of methane was by the CO2 reduction pathway based on the isotopic composition of hydrogen (δ2H(CH4) = -186 to -234‰) and carbon (δ13C(CH4) = -65.7 to -72.3‰). Rates of microbial metabolism of organic matter, estimated from the mass transfer reaction models, ranged from 0.0047 to 0.039 mmol L-1 yr-1 for groundwater downgradient from the lake.

  2. Second Symposium on Chemical Evolution and the Origin of Life

    International Nuclear Information System (INIS)

    Devincenzi, D.L.; Dufour, P.A.

    1986-05-01

    Recent findings by NASA Exobiology investigators are reported. Scientific papers are presented in the following areas: cosmic evolution of biogenic compounds, prebiotic evolution (planetary and molecular), early evolution of life (biological and geochemical), evolution of advanced life, solar system exploration, and the Search for Extraterrestrial Intelligence (SETI)

  3. Cyril Ponnamperuma Memorial. Trieste conference on chemical evolution, 4: Physics of the origin and evolution of life. Summaries

    International Nuclear Information System (INIS)

    1995-08-01

    The document includes 19 summaries of papers presented at the Trieste Conference on Chemical Evolution, 4: Physics of the Origin and Evolution of Life (Cyril Ponnamperuma Memorial), Miramare, Trieste, 4-8 September 1995. The abstracts have been indexed individually. 3 refs, 1 fig

  4. Changes in Chemical and Isotopic Composition of Groundwater During a Long Term Pumping Test in Brestovica Karst Aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Mezga, K.; Urbanc, J. [Geological Survey of Slovenia, Department of Hydrogeology, Ljubljana (Slovenia)

    2013-07-15

    A pumping test of the Klarici water supply near Brestovica was performed in August 2008, in order to determine the karst groundwater resource capacity. Groundwater was pumped for a month with a total capacity of 470 L/s. During the experiment, sampling for chemical and isotopic composition of groundwater and surface water was carried out. Intensive pumping in dry meteorological conditions caused a lowering of the water table and changes in the chemical and isotopic composition of pumped water. Local meteoric waters are infiltrated into the aquifer at a lower mean altitude; therefore the {delta}{sup 18}O is enriched with the heavy oxygen isotope. The duration of pumping resulted in changes in the isotopic composition of oxygen due to a greater impact of the intergranular Soca River aquifer on the karst aquifer. On the basis of isotope composition it was possible to quantify the impact of the Soca River on the karst aquifer. (author)

  5. Wet deposition at the base of Mt Everest: Seasonal evolution of the chemistry and isotopic composition

    Science.gov (United States)

    Balestrini, Raffaella; Delconte, Carlo A.; Sacchi, Elisa; Wilson, Alana M.; Williams, Mark W.; Cristofanelli, Paolo; Putero, Davide

    2016-12-01

    The chemistry of wet deposition was investigated during 2012-2014 at the Pyramid International Laboratory in the Upper Khumbu Valley, Nepal, at 5050 m a.s.l., within the Global Atmosphere Watch (GAW) programme. The main hydro-chemical species and stable isotopes of the water molecule were determined for monsoon rain (July-September) and snow samples (October-June). To evaluate the synoptic-scale variability of air masses reaching the measurement site, 5 day back-trajectories were computed for the sampling period. Ion concentrations in precipitation during the monsoon were low suggesting that they represent global regional background concentrations. The associations between ions suggested that the principal sources of chemical species were marine aerosols, rock and soil dust, and fossil fuel combustion. Most chemical species exhibited a pattern during the monsoon, with maxima at the beginning and at the end of the season, partially correlated with the precipitation amount. Snow samples exhibited significantly higher concentrations of chemical species, compared to the monsoon rainfall observations. Particularly during 2013, elevated concentrations of NO3-, SO42- and NH4+ were measured in the first winter snow event, and in May at the end of the pre-monsoon season. The analysis of large-scale circulation and wind regimes as well as atmospheric composition observations in the region indicates the transport of polluted air masses from the Himalayan foothills and Indian sub-continent up to the Himalaya region. During the summer monsoon onset period, the greater values of pollutants can be attributed to air-mass transport from the planetary boundary layer (PBL) of the Indo-Gangetic plains. Isotopic data confirm that during the monsoon period, precipitation occurred from water vapor that originated from the Indian Ocean and the Bay of Bengal; by contrast during the non-monsoon period, an isotopic signature of more continental origin appeared, indicating that the higher

  6. Multiple sulfur isotopes monitor fluid evolution of an Archean orogenic gold deposit

    Science.gov (United States)

    LaFlamme, Crystal; Sugiono, Dennis; Thébaud, Nicolas; Caruso, Stefano; Fiorentini, Marco; Selvaraja, Vikraman; Jeon, Heejin; Voute, François; Martin, Laure

    2018-02-01

    The evolution of a gold-bearing hydrothermal fluid from its source to the locus of gold deposition is complex as it experiences rapid changes in thermochemical conditions during ascent through the crust. Although it is well established that orogenic gold deposits are generated during time periods of abundant crustal growth and/or reworking, the source of fluid and the thermochemical processes that control gold precipitation remain poorly understood. In situ analyses of multiple sulfur isotopes offer a new window into the relationship between source reservoirs of Au-bearing fluids and the thermochemical processes that occur along their pathway to the final site of mineralisation. Whereas δ34S is able to track changes in the evolution of the thermodynamic conditions of ore-forming fluids, Δ33S is virtually indelible and can uniquely fingerprint an Archean sedimentary reservoir that has undergone mass independent fractionation of sulfur (MIF-S). We combine these two tracers (δ34S and Δ33S) to characterise a gold-bearing laminated quartz breccia ore zone and its sulfide-bearing alteration halo in the (+6 Moz Au) structurally-controlled Archean Waroonga deposit located in the Eastern Goldfields Superterrane of the Yilgarn Craton, Western Australia. Over 250 analyses of gold-associated sulfides yield a δ34S shift from what is interpreted as an early pre-mineralisation phase, with chalcopyrite-pyrrhotite (δ34S = +0.7‰ to +2.9‰) and arsenopyrite cores (δ34S = ∼-0.5‰), to a syn-mineralisation stage, reflected in Au-bearing arsenopyrite rims (δ34S = -7.6‰ to +1.5‰). This shift coincides with an unchanging Δ33S value (Δ33S = +0.3‰), both temporally throughout the Au-hosting hydrothermal sulfide paragenesis and spatially across the Au ore zone. These results indicate that sulfur is at least partially recycled from MIF-S-bearing Archean sediments. Further, the invariant nature of the observed MIF-S signature demonstrates that sulfur is derived from a

  7. Isotope effects on chemical shifts in tautomeric systems with double proton transfer. Citronin

    International Nuclear Information System (INIS)

    Hansen, P.E.; Langgard, M.; Bolvig, S.

    1998-01-01

    Primary and secondary deuterium isotope effects on 1 H and 13 C chemical shifts are measured in citrinin, a tautomeric compound with an unusual doubly intramolecularly hydrogen bonded structure. The isotope effects are to a large extent dominated by equilibrium contributions and deuteration leads to more of the deuterated enol forms rather than the deuterated acid form. 1 H 13 C and 17 O nuclear shieldings are calculated using density functional ab initio methods. A very good correlation between calculated nuclear shieldings and experimental 1 H and 13 C chemical shifts is obtained. The tautomeric equilibrium can be analyzed based on the isotope effects on B-6 and C-8 carbons and shows an increase in the o-quinone form on lowering the temperature. Furthermore, upon deuteration the largest equilibrium shift is found for deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration is increasing at lower temperature. (author)

  8. Chemical analyses and calculation of isotopic compositions of high-burnup UO{sub 2} fuels and MOX fuels

    Energy Technology Data Exchange (ETDEWEB)

    Matsumura, Tetsuo; Sasahara, Akihiro [Central Research Inst. of Electric Power Industry, Tokyo (Japan)

    2001-08-01

    Chemical analysis activities of isotopic compositions of high-burnup UO{sub 2} fuels and MOX fuels in CRIEPI and calculation evaluation are reviewed briefly. C/E values of ORIGEN2, in which original libraries and JENDL-3.2 libraries are used, and other codes with chemical analysis data are reviewed and evaluated. Isotopic compositions of main U and Pu in fuels can be evaluated within 10% relative errors by suitable libraries and codes. Void ratio is effective parameter for C/E values in BWR fuels. JENDL-3.2 library shows remarkable improvement compared with original libraries in isotopic composition evaluations of FP nuclides. (author)

  9. New Zealand guidelines for the collection of groundwater samples for chemical and isotopic analyses

    International Nuclear Information System (INIS)

    Rosen, M.R.; Cameron, S.G.; Reeves, R.R.; Taylor, C.B.

    1999-01-01

    Chemical and isotopic analyses of groundwater are important tools for differentiating between the natural composition and human-induced contaminants of groundwater. A comprehensive suite of inorganic water chemical analyses is necessary to characterise waters. The geology of New Zealand is diverse, so it is impractical to characterise a ''typical'' groundwater chemical composition. Each aquifer system should be evaluated individually because the major dissolved species contain useful information about the pathways of water through the soil zone into the aquifer. Analyses of major ions such as chloride, nitrate, potassium and sulphate often give indication of septic systems and agricultural contamination. The minor ions, while most are not considered contaminants, are often indicators of human activity. Iron and manganese are good indicators of Eh potential, which is an important control on the mobility of many heavy metals. The inexpensive inorganic chemical analytical suite should be used as a guide to advisability of more expensive contaminant testing. The purpose of this manual is to provide consistent groundwater sampling guidelines for use throughout New Zealand. Sinton's (1998) guide to groundwater sampling techniques provided a sound basis for the accurate collection of groundwater samples. However Sinton did not address sampling materials and techniques for the collection of samples for ultra trace component analysis or the collection of environmental isotope samples. These important aspects of groundwater sampling have been included in this updated manual. (author). 30 refs., 12 figs., 5 tabs., 1 appendix

  10. Evolution of nuclear chemical industry in France; Evolution de l'industrie chimique nucleaire en France

    Energy Technology Data Exchange (ETDEWEB)

    Fould, M H [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The present characteristics can be summarized in one word: expansion. Impelled by the CEA, but also by such organisations as the Electricite de France and the Merchant Marine, the French nuclear effort for the years 1957-1961 reaches about 600 thousand millions francs; over half this sum will be spent by chemical industry on research, pilot installations, construction of plants and delivery. The aim is to work efficiently, quickly and profitably. This is achieved through close collaboration between the big state organisations and private industry. It is chiefly along the following lines that this large scale effort is carried on: - thorough chemical treatment of increasing tonnages of ores from the French Union, with the aim of producing pure, plentiful and cheap uranium. - careful preparation of nuclear fuels, economical and perfectly adapted to the various types of reactor in operation or under construction. - Further treatment of irradiated fuels to extract the plutonium completely, as well as the uranium and certain fission products. industrial manufacture of material of nuclear purity or corrosion resistant required by the technology of energy producing or research reactors. - Supply to the many foreign or French users of isotopes and radioactive tracers required by medicine, industry and agriculture in ever-increasing numbers. - Meticulous chemical treatment of gaseous or liquid effluent in strictly controlled stations in order that reactors and their annexes will be perfectly safe to use. This account shows the great extent of the effort laid out by a young, energetic chemical industry in full swing. Having made sure of its techniques and set up numerous installations it is fully in a position to confront the French atomic programme. In addition it is able and anxious to associate with the developments of foreign atomic industry, especially EURATOM and Eurochemic. (author) [French] Un mot en resume les caracteristiques presentes: l'expansion. Sous l

  11. Physico-chemical reactions in the underground movement of radioactive isotopes

    International Nuclear Information System (INIS)

    Gailledreau, C.

    The physico-chemical state of the radioelements moving underground can influence considerably their migration velocity. In the case of 90 Sr--held on by monmorillonites, apatites, activated aluminum oxide--the occurrence of electronegative colloids, sorbing selectively 90 Sr results in an immediate break-through of this isotope. This phenomenon has been demonstrated in the case of the calcite phosphate reaction. A high pH is generally favorable to 90 Sr sorption (apatite, aluminum oxide). The occurrence of Ca 2+ ions acts very unfavorably on 90 Sr sorption by minerals specifics of this isotope (apatite, aluminum oxide). The same thing occurs with organic matters 137 Cs sorption, attributed to illitic clays, is little sensitive to the nature of the solution. Ruthenium-106 seems to move underground chiefly as a nitrosylruthenium hydroxide complex. This complex would be weakly sorbed on soil colloids by London--Van der Waals forces

  12. Chemical and Isotopic Study of the Groundwater of Jeffara Plain of Medenine and Tataouine (Southern Tunisia)

    International Nuclear Information System (INIS)

    Trabelsi, R.; Kalled, M; Zouari, K.; Abidi, B.; Yahyaoui, H.

    2007-01-01

    The study area constitutes the major part of the plain of Jeffara, located at the south-east of Tunisia. This plain is characterized by an arid climate with rare and irregular pluviometry. The hydrochemical approach is used to define the chemical characteristics of the water in these aquifer systems. Indeed, the water salinity varies between 0.6g/? and 9g/?, and increases from the Daher mountains in the west to the Mediterranean Sea. The groundwaters are homogeneous and characterized by a Cl-(SO 4 ) and Na-(Ca-Mg) water type. The isotopic approach shows that the carbone-14 activities, measured in groundwater, evolve in the same direction of groundwater flow. These activities suggest a recent recharge area in eastern piedmont of the Dahar mountains, as well as the zone of the Sahel Abebsa and Zeuss-Koutine. The isotopic values confirm, also, the communication between the various major levels through the existing faults and discontinuities in this area

  13. Chemical investigations of isotope separation on line target units for carbon and nitrogen beams

    CERN Document Server

    Franberg, H; Gäggeler, H W; Köster, U

    2006-01-01

    Radioactive ion beams (RIBs) are of significant interest in a number of applications. Isotope separation on line (ISOL) facilities provide RIB with high beam intensities and good beam quality. An atom that is produced within the ISOL target will first diffuse out from the target material. During the effusion towards the transfer line and into the ion source the many contacts with the surrounding surfaces may cause unacceptable delays in the transport and, hence, losses of the shorter-lived isotopes. We performed systematic chemical investigations of adsorption in a temperature and concentration regime relevant for ISOL targets and ion source units, with regard to CO/sub x/ and NOmaterials are potential construction materials for the above-mentioned areas. Off-line and on-line tests have been performed using a gas thermochromatography setup with radioactive tracers. The experiments were performed at the production of tracers for atmospheric chemistry (PROTRAC) facility at the Paul Schener Institute in Villigen...

  14. Environmental isotopes, chemical composition and groundwater recharge in ataqa-north galala region, Egypt

    International Nuclear Information System (INIS)

    Shohaib, R.EL-SH.; Nada, A.; Safie El-Din, A.

    1991-01-01

    Groundwater samples collected from a number of localities in ataqa-north galala region were subjected to various chemical and isotopic analyses. The seasonal fluctuations in hydrochemical composition reveal that the marin Mg Cl 2 type is dominant in the aquifer through-out the year. The Ca Cl 2 water type of marine origin appears in January in wells W 3 and W 7 which lie close to sukhna fault. Recharge to the aquifer is reflected by fluctuation in the water level and fluctuations of the hydrochemical composition of the water. The results of the isotopic content of the water samples indicate that the connate marine water has been subjected to dilution and mixing by the meteoric water invasion since the pliestocene pluvial period (paleowater) and recent meteoric water precipitation. The bulk of the stored water ( about 80%) is paleowater and the recent water (20%) are percolate ones derived from the rain-fall at high latitudes.4 fig. 1 tab

  15. A study of chemical equilibrium of tri-component mixtures of hydrogen isotopes

    International Nuclear Information System (INIS)

    Cristescu, Ioana; Cristescu, I.; Peculea, M.

    1998-01-01

    In this paper we present a model for computing the equilibrium constants for chemical reactions between hydrogen's isotopes as function of temperature. The equilibrium constants were expressed with the aid of Gibbs potential and the partition function of the mixture. We assessed the partition function for hydrogen's isotopes having in view that some nuclei are fermions and other bosons. As results we plotted the values of equilibrium constants as function of temperature. Knowing these values we determined the deuterium distribution on species (for mixture H 2 -HD-D 2 ) as function of total deuterium concentration and the tritium distribution on species (for mixtures D 2 -DT-T 2 and H 2 -HT-T 2 ) as function of total tritium concentration. (authors)

  16. Thermal and chemical evolution in the early Solar System as recorded by FUN CAIs: Part II - Laboratory evaporation of potential CMS-1 precursor material

    Science.gov (United States)

    Mendybaev, Ruslan A.; Williams, Curtis D.; Spicuzza, Michael J.; Richter, Frank M.; Valley, John W.; Fedkin, Alexei V.; Wadhwa, Meenakshi

    2017-03-01

    We present the results of laboratory experiments in which a forsterite-rich melt estimated to be a potential precursor of Allende CMS-1 FUN CAI was evaporated into vacuum for different lengths of time at 1900 °C. The evaporation of this melt resulted in residues that define trajectories in chemical as well as magnesium, silicon and oxygen isotopic composition space and come very close to the measured properties of CMS-1. The isotopic composition of the evaporation residues was also used to determine the kinetic isotopic fractionation factors [α2,1 (vapor-melt) defined as the ratio of isotopes 2 and 1 of a given element in the evaporating gas divided by their ratio in the evaporating source] for evaporation of magnesium (α25,24 for 25Mg/24Mg), silicon (α29,28 for 29Si/28Si) and oxygen (α18,16 for 18O/16O) from the forsterite-rich melt at 1900 °C. The values of α25,24 = 0.98383 ± 0.00033 and α29,28 = 0.99010 ± 0.00038 are essentially independent of change in the melt composition as evaporation proceeds. In contrast, α18,16 changes from 0.9815 ± 0.0016 to ∼0.9911 when the residual melt composition changes from forsteritic to melilitic. Using the determined values of α25,24 and α29,28 and present-day bulk chemical composition of the CMS-1, the composition of the precursor of the inclusion was estimated to be close to the clinopyroxene + spinel + forsterite assemblage condensed from a solar composition gas. The correspondence between the chemical composition and isotopic fractionation of experimental evaporation residues and the present-day bulk chemical and isotopic compositions of CMS-1 is evidence that evaporation played a major role in the chemical evolution of CMS-1.

  17. The chemical evolution of white dwarf atmospheres: Diffusion and accretion

    International Nuclear Information System (INIS)

    Vauclair, G.; Vauclair, S.; Greenstein, J.L.

    1979-01-01

    A study of diffusion processes in white dwarfs is presented. We are especially interested in the estimate of the diffusion time scales for C, N, O, Mg, and Ca along the cooling sequence. The effect of the radiative acceleration is important in hot white dwarfs while in cooler ones the thermal diffusion dominates the gravitational settling. In hot white dwarfs, there should be an observable amount of CNO elements unless they have previously left the stars by a selective wind. Observational tests of this result are discussed. The diffusion time scales are always short compared to the evolutionary time scales. It is shown that in both hydrogen and helium envelopes, the convection zone, even at its maximum depth, is not able to bring back to the stellar surface the metals which have previously diffused downwards. The diffusion alone predicts a complete absence of metals in white dwarf atmospheres and envelopes. As metals are observed in white dwarfs, at least at effective temperatures lower than 15,000 K, there must be some mechanism competing with diffusion. We investigate the competition between diffusion and accretion and propose a general scheme for the chemical evolution of white dwarf atmospheres along the cooling sequence. (orig.)

  18. The evolution of the global selenium cycle: Secular trends in Se isotopes and abundances

    Science.gov (United States)

    Stüeken, E. E.; Buick, R.; Bekker, A.; Catling, D.; Foriel, J.; Guy, B. M.; Kah, L. C.; Machel, H. G.; Montañez, I. P.; Poulton, S. W.

    2015-08-01

    The Earth's surface has undergone major transitions in its redox state over the past three billion years, which have affected the mobility and distribution of many elements. Here we use Se isotopic and abundance measurements of marine and non-marine mudrocks to reconstruct the evolution of the biogeochemical Se cycle from ∼3.2 Gyr onwards. The six stable isotopes of Se are predominantly fractionated during redox reactions under suboxic conditions, which makes Se a potentially valuable new tool for identifying intermediate stages from an anoxic to a fully oxygenated world. δ82/78Se shows small fractionations of mostly less than 2‰ throughout Earth's history and all are mass-dependent within error. In the Archean, especially after 2.7 Gyr, we find an isotopic enrichment in marine (+0.37 ± 0.27‰) relative to non-marine samples (-0.28 ± 0.67‰), paired with increasing Se abundances. Student t-tests show that these trends are statistically significant. Although we cannot completely rule out the possibility of volcanic Se addition, these trends may indicate the onset of oxidative weathering on land, followed by non-quantitative reduction of Se oxyanions during fluvial transport. The Paleoproterozoic Great Oxidation Event (GOE) is not reflected in the marine δ82/78Se record. However, we find a major inflection in the secular δ82/78Se trend during the Neoproterozoic, from a Precambrian mean of +0.42 ± 0.45‰ to a Phanerozoic mean of -0.19 ± 0.59‰. This drop probably reflects the oxygenation of the deep ocean at this time, stabilizing Se oxyanions throughout the water column. Since then, reduction of Se oxyanions has likely been restricted to anoxic basins and diagenetic environments in sediments. In light of recent Cr isotope data, it is likely that oxidative weathering before the Neoproterozoic produced Se oxyanions in the intermediate redox state SeIV, whereas the fully oxidized species SeVI became more abundant after the Neoproterozoic rise of

  19. A combined chemical, isotopic and microstructural study of pyrite from roll-front uranium deposits, Lake Eyre Basin, South Australia

    Science.gov (United States)

    Ingham, Edwina S.; Cook, Nigel J.; Cliff, John; Ciobanu, Cristiana L.; Huddleston, Adam

    2014-01-01

    The common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, Lake Eyre Basin, South Australia. Combined chemical, isotopic and microstructural analysis of pyrite indicates variation in fluid composition, sulfur source and precipitation conditions during a protracted mineralization event. The results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low-temperature hydrothermal systems. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated broad-scale isotopic heterogeneity (δ34S = -43.9 to +32.4‰VCDT), indicative of complex, multi-faceted pyrite evolution, and sulfur derived from more than a single source. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic pyrite underwent prolonged evolution and recrystallization, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displays hyper-enrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types. Irregular variation in δ34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization. A late-stage oxidizing fluid may have mobilized selenium from pre-existing pyrite. Subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re-crystallization and precipitation of selenium as native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insights into

  20. Lithium isotope effects in chemical exchange with (2,2,1) cryptand

    International Nuclear Information System (INIS)

    Jepson, B.E.; Cairns, G.A.

    1979-01-01

    Equilibrium single-stage separation factors were determined for three lithium - (2,2,1) cryptand two-phase chemical exchange systems. The equilibrated phases consisted of an aqueous solution of a lithium salt and a chloroform solution of lithium cryptate salt complex. Lithium-6 concentrated in the organic phase in all cases, and the lithium isotope exchange rate with (2,2,1) cryptand was rapid. The separation factors were α = 1.026 +- 0.006 (LiBr exchange), α = 1.035 +- 0.003 (LiTFA), and α = 1.041 +- 0.006 (LiTFA + HTFA), where TFA represents trifluoroacetate. These values were compared with separation factors of other lithium chemical exchange systems. This work has shown that separation factors are influenced by the choice of chemical species and parameters. It has also demonstrated that significant lithium isotope effects can be obtained without a valence change of the metal exchanging between the aquo and cryptate complexes

  1. Physico-Chemical Evolution of Organic Aerosol from Wildfire Emissions

    Science.gov (United States)

    Croteau, P.; Jathar, S.; Akherati, A.; Galang, A.; Tarun, S.; Onasch, T. B.; Lewane, L.; Herndon, S. C.; Roscioli, J. R.; Yacovitch, T. I.; Fortner, E.; Xu, W.; Daube, C.; Knighton, W. B.; Werden, B.; Wood, E.

    2017-12-01

    Wildfires are the largest combustion-related source of carbonaceous emissions to the atmosphere; these include direct emissions of black carbon (BC), primary organic aerosol (POA) and semi-volatile, intermediate-volatility, and volatile organic compounds (SVOCs, IVOCs, and VOCs). However, there are large uncertainties surrounding the evolution of these carbonaceous emissions as they are physically and chemically transformed in the atmosphere. To understand these transformations, we performed sixteen experiments using an environmental chamber to simulate day- and night-time chemistry of gas- and aerosol-phase emissions from 6 different fuels at the Fire Laboratory in Missoula, MT. Across the test matrix, the experiments simulated 2 to 8 hours of equivalent day-time aging (with the hydroxyl radical and ozone) or several hours of night-time aging (with the nitrate radical). Aging resulted in an average organic aerosol (OA) mass enhancement of 28% although the full range of OA mass enhancements varied between -10% and 254%. These enhancement findings were consistent with chamber and flow reactor experiments performed at the Fire Laboratory in 2010 and 2012 but, similar to previous studies, offered no evidence to link the OA mass enhancement to fuel type or oxidant exposure. Experiments simulating night-time aging resulted in an average OA mass enhancement of 10% and subsequent day-time aging resulted in a decrease in OA mass of 8%. While small, for the first time, these experiments highlighted the continuous nature of the OA evolution as the wildfire smoke cycled through night- and day-time processes. Ongoing work is focussed on (i) quantifying bulk compositional changes in OA, (ii) comparing the near-field aging simulated in this work with far-field aging simulated during the same campaign (via a mini chamber and flow tube) and (iii) integrating wildfire smoke aging datasets over the past decade to examine the relationship between OA mass enhancement ratios, modified

  2. Magnetic isotope effect and theory of atomic orbital hybridization to predict a mechanism of chemical exchange reactions.

    Science.gov (United States)

    Epov, Vladimir N

    2011-08-07

    A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl(2) species and with several Ru(III) chloro-species, and highly positive for reactions of this ether with TeCl(6)(2-), and with several Cd(II) and Pd(II) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d(n)5s(m) electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions. This journal is © the Owner Societies 2011

  3. Chemical compositions and lead isotope ratios of ancient lead-barium glasses found in Japan

    International Nuclear Information System (INIS)

    Yamasaki, Kazuo.

    1991-01-01

    Six lead-barium glasses found in the archaeological sites of the Yayoi period in the northern part of Kyushu, Japan were chemically analysed and their lead isotope ratios were determined. These data agreed with those of the glasses of the Pre-Han period found in China, suggesting the presence of possible trade between China in the Pre-Han Period (ca. fourth-third centuries B.C.) and Japan in the earlier Yayoi period (ca. first century B.C.). (author)

  4. Associated chemical and carbon isotopic composition variations in diamonds from Finsch and Premier kimberlite, South Africa

    International Nuclear Information System (INIS)

    Deines, P.

    1984-01-01

    The carbon isotopic composition of 66 inclusion-containing diamonds from the Premier kimberlite, South Africa, 93 inclusion-containing diamonds and four diamonds of two diamond-bearing peridotite xenoliths from the Finsch kimberlite, South Africa was measured. The data suggest a relationship between the carbon isotopic composition of the diamonds and the chemical composition of the associated silicates. For both kimberlites similar trends are noted for diamonds containing peridotite-suite inclusions (P-type) and for diamonds containing eclogite-suite inclusions (E-type): Higher delta 13 C P-type diamonds tend to have inclusions lower in SiO 2 , Al 2 O 3 , Cr 2 O 3 , MgO, Mg/(Mg + Fe) and higher in FeO and CaO. Higher delta 13 C E-type diamonds tend to have inclusions lower in SiO 2 , Al 2 O 3 , MgO, Mg/(Mg + Fe), Na 2 O, K 2 O, TiO 2 and higher in CaO, Ca/(Ca + Mg). Consideration of a number of different models that have been proposed for the genesis of kimberlites, their zenoliths and diamonds shows that they are all consistent with the conclusion that in the mantle, regions exist that are characterized by different mean carbon isotopic compositions. (author)

  5. Isothermal and non-isothermal conditions of isotope separation by chemical exchange method

    International Nuclear Information System (INIS)

    Khoroshilov, A.V.; Andreev, B.M.; Katalnikov, S.G.

    1992-01-01

    The published data about the effect of temperature on thermodynamic and mass transfer parameters of isotope separation by the chemical exchange method were used to examine the influence of iso- and non-isothermal conditions on the effectiveness of the separation process. It has been shown that simultaneous fulfillment of several optimization criteria is impossible in optimization of the isothermal process. If the limitation that temperature must be constant in the whole range of concentrational changes for an isolated isotope is removed, then it is possible to solve the problem of optimization with simultaneous fulfillment of several optimization criteria. When the separation process is carried out with non-isothermal conditions, that is, in temperature cascade, then the maximum concentration change takes place at every theoretical separation plate, and whole cascade is characterised by maximum throughput, minimum height and volume, and minimum cost for the stream reflux. From the results of our study, it was concluded that in the optimum temperature cascade, the cost of production of unity quantity of isotope can be decreased at least by a factor of two as compared with the optimal isothermal version of the separation process. (author)

  6. The chemical and isotopic differentiation of an epizonal magma body: Organ Needle pluton, New Mexico

    Science.gov (United States)

    Verplanck, P.L.; Farmer, G.L.; McCurry, M.; Mertzman, S.A.

    1999-01-01

    Major and trace element, and Nd and Sr isotopic compositions of whole rocks and mineral separates from the Oligocene, alkaline Organ Needle pluton (ONP), southern New Mexico, constrain models for the differentiation of the magma body parental to this compositionally zoned and layered epizonal intrusive body. The data reveal that the pluton is rimmed by lower ??(Nd) (~-5) and higher 87Sr/86Sr (~0.7085) syenitic rocks than those in its interior (??(Nd) ~ 2, 87Sr/86Sr ~0.7060) and that the bulk compositions of the marginal rocks become more felsic with decreasing structural depth. At the deepest exposed levels of the pluton, the ??(Nd)~-5 lithology is a compositionally heterogeneous inequigranular syenite. Modal, compositional and isotopic data from separates of rare earth element (REE)-bearing major and accesory mineral phases (hornblende, titanite, apatite, zircon) demonstrate that this decoupling of trace and major elements in the inequigranular syenite results from accumulation of light REE (LREE)-bearing minerals that were evidently separated from silicic magmas as the latter rose along the sides of the magma chamber. Chemical and isotopic data for microgranular mafic enclaves, as well as for restite xenoliths of Precambrian granite wall rock, indicate that the isotopic distinction between the marginal and interior facies of the ONP probably reflects assimilation of the wall rock by ??(Nd) ~-2 mafic magmas near the base of the magma system. Fractional crystallization and crystal liquid separation of the crystally contaminated magma at the base and along the margins of the chamber generated the highly silicic magmas that ultimately pooled at the chamber top.

  7. Hydro-geochemical and isotopic fluid evolution of the Los Azufres geothermal field, Central Mexico

    International Nuclear Information System (INIS)

    Gonzalez-Partida, E.; Carrillo-Chavez, A.; Levresse, G.; Tello-Hinojosa, E.; Venegas-Salgado, S.; Ramirez-Silva, G.; Pal-Verma, M.; Tritlla, J.; Camprubi, A.

    2005-01-01

    Hydrothermal alteration at Los Azufres geothermal field is mostly propylitic with a progressive dehydration with depth and temperature increase. Argillic and advanced argillic zones overlie the propylitic zone owing to the activity of gases in the system. The deepest fluid inclusions (proto-fluid) are liquid-rich with low salinity, with NaCl dominant fluid type and ice melting temperatures (T mi ) near zero (0 deg C), and salinities of 0.8 wt% NaCl equivalent. The homogenization temperature (T h ) = 325 ± 5 deg C. The boiling zone shows T h = ±300 deg C and apparent salinities between 1 and 4.9 wt% NaCl equivalent, implying a vaporization process and a very important participation of non-condensable gases (NCGs), mostly CO 2 . Positive clathrate melting temperatures (fusion) with T h = 150 deg C are observed in the upper part of the geothermal reservoir (from 0 to 700 m depth). These could well be the evidence of a high gas concentration. The current water produced at the geothermal wells is NaCl rich (geothermal brine) and is fully equilibrated with the host rock at temperatures between T = 300 and 340 deg C. The hot spring waters are acid-sulfate, indicating that they are derived from meteoric water heated by geothermal steam. The NCGs related to the steam dominant zone are composed mostly of CO 2 (80-98% of all the gases). The gases represent between 2 and 9 wt% of the total mass of the fluid of the reservoir. The authors interpret the evolution of this system as deep liquid water boiling when ascending through fractures connected to the surface. Boiling is caused by a drop of pressure, which favors an increase in the steam phase within the brine ascending towards the surface. During this ascent, the fluid becomes steam-dominant in the shallowest zone, and mixes with meteoric water in perched aquifers. Stable isotope compositions (δ 18 O-δD) of the geothermal brine indicate mixing between meteoric water and a minor magmatic component. The enrichment in δ 18

  8. Concurrent reduction and distillation: an improved technique for the recovery and chemical refinement of the isotopes of cadmium and zinc

    International Nuclear Information System (INIS)

    Caudill, H.H.; McBride, L.E.; McDaniel, E.W.

    1982-01-01

    The Electromagnetic Isotope Separations Program of the Oak Ridge National Laboratory has been involved in the separation, chemical recovery, and refinement of the stable isotopes of cadmium and zinc since 1946. Traditionally, the chemical refinement procedures for these elements consisted of ion exchange separations using anion exchange resins followed by pH-controlled hydrogen sulfide precipitations. The procedures were quite time-consuming and made it difficult to remove trace quantities of sulfur which interferes in subsequent attempts to prepare rolled metal foils. As demands for 113 Cd and 68 Zn (a precursor for the production of the radiopharmaceutical 67 Ga) increased, it became evident that a quicker, more efficient refinement procedure was needed. Details of an improved method, which employs concurrent hydrogen reduction and distillation in the recovery and refinement of isotopically enriched zinc, are described. Modifications of the procedure suitable for the refinement of cadmium isotopes are also described. 3 figures, 1 table

  9. Groundwater recharge studies using isotope-chemical techniques in wadi gharandal, sinai peninsula(E G))

    International Nuclear Information System (INIS)

    Awad, M.A.A.; Salem, W.M.; Ezzeldin

    1999-01-01

    Wadi Gharandal lies on southwestern part of sinai peninsula with its outlets into the Gulf of suez. Eight groundwater samples were collected from quaternary aquifer in wadi gharandal to identify the sources of replenishment and evaluation of its water quality. The variation in chemical composition of water samples is due to water-rock interaction and the effect of sea spray. The distribution of chemical species in the examined groundwater samples is controlled by geography and climate conditions prevailing in the area of study. The salinity increase towards the gulf of suez. The isotopic data indicate that precipitation and floods are considered to be the main sources of recharge in this area. The investigated groundwater samples are found to be suitable for irrigation purposes based on sodium adsorption ratio (SAR) and unsuitable for domestic usages due to high salinity and hardness values

  10. Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

    Science.gov (United States)

    Cipollone, A.; Barbieri, C.; Navrátil, P.

    2015-07-01

    Background: Three-nucleon forces (3NFs) have nontrivial implications on the evolution of correlations at extreme proton-neutron asymmetries. Recent ab initio calculations show that leading-order chiral interactions are crucial to obtain the correct binding energies and neutron driplines along the O, N, and F chains [A. Cipollone, C. Barbieri, and P. Navrátil, Phys. Rev. Lett. 111, 062501 (2013), 10.1103/PhysRevLett.111.062501]. Purpose: Here we discuss the impact of 3NFs along the oxygen chain for other quantities of interest, such has the spectral distribution for attachment and removal of a nucleon, spectroscopic factors, and radii. The objective is to better delineate the general effects of 3NFs on nuclear correlations. Methods: We employ self-consistent Green's function (SCGF) theory which allows a comprehensive calculation of the single-particle spectral function. For the closed subshell isotopes, 14O, 16O, 22O, 24O, and 28O, we perform calculations with the Dyson-ADC(3) method, which is fully nonperturbative and is the state of the art for both nuclear physics and quantum chemistry applications. The remaining open-shell isotopes are studied using the newly developed Gorkov-SCGF formalism up to second order. Results: We produce complete plots for the spectral distributions. The spectroscopic factors for the dominant quasiparticle peaks are found to depend very little on the leading-order (NNLO) chiral 3NFs. The latter have small impact on the calculated matter radii, which, however, are consistently obtained smaller than experiment. Similarly, single-particle spectra tend to be too spread with respect to the experiment. This effect might hinder, to some extent, the onset of correlations and screen the quenching of calculated spectroscopic factors. The most important effect of 3NFs is thus the fine tuning of the energies for the dominant quasiparticle states, which governs the shell evolution and the position of driplines. Conclusions: Although present chiral

  11. Inferences of paleoenvironment from petrographic, chemical and stable-isotope studies of calcretes and fracture calcites

    International Nuclear Information System (INIS)

    Vaniman, D.T.; Whelan, J.F.

    1994-01-01

    Past research has indicated a genetic connection between calcite formed in calcretes at the surface of Yucca Mountain, Nevada, and calcites deposited in underlying fractures of the unsaturated zone. This common genesis suggests that paleoenvironmental information, as well as the timing and pathways of past recharge episodes, might be obtained from studies of the deposits in both the calcretes and the unsaturated fractures. Chemical and isotopic modification of calcite-precipitating fluids appears to begin at the surface, largely under the influence of plant roots and their decay products. Chemical characteristics of the deeper calcites are either initiated or largely defined within the first few meters of fluid migration into the unsaturated tuffs beneath the calcretes. However, petrographic and isotopic data indicate a very unique low-δ 13 C microenvironment that is localized at the upper surfaces of the calcretes. These surfaces form an interface in the soil horizon where infiltration may pond above the underlying carbonate ''plug.'' In order to decipher the chemistry and petrology of past recharge events, it is important to first understand microenvironments such as this that contribute to mineral precipitation/dissolution events in the pedogenic environment

  12. Ca isotopes, chemical weathering, and geomorphic controls on long-term climate

    Science.gov (United States)

    Moore, J.; Jacobson, A. D.; Holmden, C. E.; Craw, D.

    2009-12-01

    Calcium isotope geochemistry (δ44Ca) offers a unique opportunity to directly quantify proportions of riverine Ca originating from silicate versus carbonate weathering, which is essential for understanding how geomorphic processes affecting landscape evolution, such as tectonic uplift and glaciation, influence the long-term cycling of atmospheric CO2. We measured the elemental and δ44Ca chemistry of river and rock samples from the New Zealand Southern Alps. In combination with our geochemical data, we used runoff and suspended sediment fluxes to elucidate relationships between chemical weathering, mechanical erosion, and long-term climate. The S. Alps have uniform bedrock chemistry but significant tectonic and climatic gradients. West of the main topographic divide, watersheds drain schist and experience high runoff, uplift, and erosion rates. East of the main divide, watersheds drain greywacke or schist and experience lower runoff, uplift, and erosion rates. Glaciated watersheds with high erosion rates are present throughout the mountain range. Both schist and greywacke contain up to 3% metamorphic and hydrothermal calcite. Waters exhibit two-component mixing between calcite and silicate end-members when plotted as δ44Ca versus Ca/Sr. Scatter about the mixing curve is generally smaller than the analytical uncertainty of the measurements and likely reflects variability of the end-member compositions rather than fractionation. We used the mixing relationships to calculate percentages of Ca from silicate weathering. Rivers draining greywacke average 27.6% of Ca from silicate weathering with glaciated and non-glaciated watersheds yielding 41.8 and 19.5%, respectively. Rivers draining schist average 9.8% with glaciated and non-glaciated watersheds yielding 17.7 and 3.9%, respectively. Although Ca fluxes are larger west of the main divide where erosion and runoff are higher, the percentage of Ca from silicate weathering is smaller. Hence, long-term atmospheric CO2

  13. A geochemical and Pb, Sr isotopic study of the evolution of granite-gneisses from the Bastar craton, Central India

    International Nuclear Information System (INIS)

    Sarkar, G.; Paul, D.K.; Misra, V.P.; de Laeter, J.R.; Mc Naughton, N.J.

    1990-01-01

    Preliminary Pb-Pb and Rb-Sr geochronology of granitic and gneissic rocks from the Sukma area of the Bastar craton, Central India, provides important constraints on crustal evolution. Much of the craton is made up of felsic orthogneisses and younger granitic intrusives, compositionally ranging from tonalite to granite. Pb-Pb isotopic data suggest the presence of ca. 3.0 Ga old gneisses. Younger granitic intrusives have been dated at ca. 2.6 Ga which represents a widespread resetting and/or emplacement event. Comparison of the Pb-Pb and Rb-Sr whole rock ages suggests that the latter were more perturbed after the gneiss-forming or emplacement events. All rock suites show significant geological scatter of isotopic data probably because of sampling on a regional scale, and reflect multi-stage isotopic evolution in a complex terrain. The present isotopic data indicate the presence of Archaean rock in the Bastar craton and suggest temporal similarity with the oldest crustal rocks in the Singhbhum and Dharwar cratons. (author). 18 refs., 4 tabs., 8 figs

  14. Carbon Retention and Isotopic Evolution in Deeply Subducted Sediments: Evidence from the Italian Alps

    Science.gov (United States)

    Cook-Kollars, J.; Bebout, G. E.; Agard, P.; Angiboust, S.

    2012-12-01

    increasing grade, metapelitic carbonaceous matter shows an increase in δ13CVPDB, ranging from about -25‰ in low-grade Schistes Lustres samples to -16‰ in the highest-grade Cignana samples. Carbonate in the entire suite shows decrease in δ18OSMOW, from marine carbonate values > 25‰ to values of 17-22‰ independent of the carbonate content of the rocks. This shift could possibly be explained by isotopic exchange with silicate phases in the same rocks [Henry et al. (1996), Chem. Geol.]. Metapelitic rocks in this suite experienced moderate amounts of dehydration (20-50%) largely related to breakdown of chlorite and carpholite [Bebout et al. (in press), Chem. Geol. (abstract in this session); Angiboust and Agard (2010), Lithos], conceivably providing a source for infiltrating H2O-rich fluids producing negative shifts in calcite δ18O in interlayered metacarbonates. These results indicate that relatively little decarbonation occurred in carbonate-bearing sediments subducted to depths greater than 100 km, arguing against any model of extensive decarbonation driven by infiltration of the sediments by H2O-rich fluids released from mafic and ultramafic parts of the underlying subducting slab. This study provides field evidence for the efficient retention of C in subducting shale-carbonate sequences through forearc depths, potentially affecting the C budget and isotopic evolution of the deeper mantle.

  15. Groundwater evolution in the Continental Intercalaire aquifer of southern Algeria and Tunisia: trace element and isotopic indicators

    International Nuclear Information System (INIS)

    Edmunds, W.M.; Guendouz, A.H.; Mamou, A.; Moulla, A.; Shand, P.; Zouari, K.

    2003-01-01

    The geochemical processes taking place along an 800 km flow line in the non-carbonate Continental Intercalaire aquifer (CI) aquifer in North Africa are described using chemical (major and trace element) and isotopic indicators. The aquifer is hydraulically continuous from the Atlas Mountains in Algeria to the Chotts of Tunisia and the geochemical evidence corroborates this. The highest discharge temperature is 73 deg. C but silica geothermometry indicates a maximum temperature of 94 deg. C at depth. Chloride concentrations increase from 200 to 800 mg l -1 and the Br/Cl ratios confirm the dissolution of non-marine evaporites or interstitial waters as the main source of salinity. Fluoride concentrations are low and are likely to be derived from rainfall, recording oscillations in source. Radiocarbon ages, except near outcrop, are at or near detection limits and the δ 18 O and δ 2 H values indicate a cooler recharge regime with rainfall having lower primary evaporation than today. This is shown by the fact that mean isotope ratios of CI waters are around 3 per mille lighter than the present-day weighted mean value for rain. Major ion ratios and most trace elements indicate that despite the complex structure and stratigraphy, uniform evolution with continuous water-rock interaction takes place along the flow lines, which are only disturbed near the Tunisian Chotts by groundwater converging from additional flow lines. The ageing of the water can also be followed by the smooth increase in several indicator elements such as Li, K and Mn which are least affected by solubility controls. Similarly the influence of marine facies in the Tunisian sector may be recognised by the changing Mg/Ca and higher Br/Cl as well as trace element indicators. The groundwaters are oxidising up to 300 km from outcrop (dissolved O 2 has persisted for at least 20 ka) and within this zone the concentrations of several elements forming oxy-anions, such as U and Cr, increase and NO 3 remains

  16. Inhomogeneous Chemical Evolution of the Galaxy in the Solar ...

    Indian Academy of Sciences (India)

    The evolution of the galaxy is simulated by considering discrete .... The discrete nature of the simulations along with the high temporal resolution of 1 Myr ...... be revived again even if a major homogenizing event occurs over spatial dimensions.

  17. Experiments on chemical and physical evolution of interstellar grain mantles

    International Nuclear Information System (INIS)

    Greenberg, J.M.

    1984-01-01

    The Astrophysical Laboratory at the University of Leiden is the first to succeed in simulating the essential conditions in interstellar space as they affect the evolution of interstellar grains. (author)

  18. Correlated evolution of herbivory and food chemical discrimination in iguanian and ambush foraging lizards

    OpenAIRE

    William E. Cooper

    2003-01-01

    To efficiently locate and assess foods, animal sensory capacities and behavioral discriminations based on them must be appropriate for the diet and method of hunting. In lizards, actively foraging insectivores identify animal prey using lingually sampled chemical cues, but ambush foragers do not. Among plant eaters derived from active foragers, plant chemical discrimination is added to prey chemical discrimination, resulting in correlated evolution of plant diet and plant chemical discriminat...

  19. Crustal evolution of South American Platform based on Sm-Nd isotope geochemistry

    International Nuclear Information System (INIS)

    Sato, Kei

    1998-01-01

    Sm-Nd isotopic systematics is relevant to the topics of origin and evolution the of continental crust, where model ages refer to the time when crustal material was differentiated from the upper mantle. Alternative interpretations are due to a lack of adequate information on crustal processes and the variable composition of the mantle sources. The Sm-Nd methods are presented, and applied on rock materials from the South American Platform. The main conclusions indicate juvenile accretion with higher growth rates (peaks), around 3.7-3.5 Ga (∼ 0.5% in volume), 3.1 - 2.9 Ga (∼16%), 2.7 - 2.6 (∼ 9%), 2.2 - 1.9 (35%) and 1.3-1.0 (7%). The continental growth curve indicates that about 35 % of the crust was formed by 2.5 Ga, 88% by 1.8 Ga and 99% by 1.0 Ga, and the remaining ∼ 1 % was added in the Phanerozoic. Rapid crustal growth occurred between 2.2 and 1.9 Ga. The main period of continental crust formation occurred during the Paleoproterozoic, corresponding to 54 % in volume. Sm-Nd model ages, when compared with the crystallisation ages of granitoid rocks, furnish a rough estimate of juvenile vs. reworked material. Within the South American Platform about 45% of juvenile continental crust is still preserved within tectonic provinces of different ages. The remainder represents continental crust reworked in younger tectono-thermal events. In particular crustal reworking was predominating over juvenile accretion during Meso-Neoproterozoic. The Transbrasiliano Lineament is a megasuture, active in the Neoproterozoic, which separates a large northwestern mass, including the Amazonian and Sao Luis Cratons, from a southeastern mass, formed by a collage of cratonic fragments, of which the Sao Francisco and Rio de La Plata are the largest. The crustal evolutions of these two large continental masses are considered individually, and can be resumed following form: I - Old Archean rocks (>3.4 Ga) are found only within the south-eastern part (Gaviao Block, Contendas

  20. The origin of nitrogen and the chemical evolution of spiral galaxies

    OpenAIRE

    Díaz, Angeles I.; Tosi, M.

    1986-01-01

    This is an electronic version of an article published in Astronomy and Astrophysics. Diaz, A.I. and M. Tosi. The origin of nitrogen and the chemical evolution of spiral galaxies. Astronomy and Astrophysics 158 (1986): 60-66

  1. Coordinated Chemical and Isotopic Imaging of Bells (CM2) Meteorite Matrix

    Science.gov (United States)

    Clemett, S. J.; Messenger, S.; Naklamura-Messenger, K.; Thomas-Keprta, K. L.

    2014-01-01

    Meteoritic organic matter is a complex conglomeration of species formed in distinct environments and processes in circumstellar space, the interstellar medium, the Solar Nebula and asteroids. Consequently meteorites constitute a unique record of primordial organic chemical evolution. While bulk chemical analysis has provided a detailed description of the range and diversity of organic species present in carbonaceous chondrites, there is little information as to how these species are spatially distributed and their relationship to the host mineral matrix. The distribution of organic phases is nevertheless critical to understanding parent body processes. The CM and CI chondrites all display evidence of low temperature (chemical mapping study of the Bells meteorite using a newly developed two-step laser mass spectrometer (mu-L(sup 2)MS) capable of measuring a broad range of organic compounds.

  2. Petrography of isotopically-dated clasts in the Kapoeta howardite and petrologic constraints on the evolution of its parent body

    International Nuclear Information System (INIS)

    Dymek, R.F.; Albee, A.L.; Chodos, A.A.; Wasserburg, G.J.

    1976-01-01

    Detailed mineralogic and petrographic data are presented for four isotopically-dated basaltic rock fragments separated from the howardite Kapoeta. Clasts C and rho have been dated at approximately 4.55 AE and approximately 4.60 AE respectively, and Clast rho contains 244 Pu and 129 I decay products. These are both igneous rocks that preserve all the features of their original crystallization from a melt. They thus provide good evidence that the Kapoeta parent body produced basaltic magmas shortly after its formation ( 40 Ar/ 39 Ar age. This sample is extensively recrystallized, and the ages are interpreted as a time of recrystallization, and not the time of original crystallization from a melt. Clast B has yielded a Rb-Sr age of approximately 3.63 AE, and an 40 Ar/ 39 Ar age of > approximately 4.50 AE. This sample is moderately recrystallized, and the Rb-Sr age probably indicates a time of recrystallization, whereas the 40 Ar/ 39 Ar age more closely approaches the time of crystallization from a melt. Thus, there is no clearcut evidence for 'young' magmatism on the Kapeota parent body. The FeO and MnO contents of all pyroxenes in Kapeota fall near a line with FeO/MnO approximately 35, suggesting that the source rocks are fundamentally related. The FeO/MnO value in lunar pyroxenes (approximately 60) is distinct from that of the pyroxenes in Kapoeta. Anorthositic rocks were not observed in Kapoeta, suggesting that plagioclase was not important in the evolution of the Kapoeta parent body, in contrast to the Moon. Both objects appear to have originated in chemically-distinct portions of the solar system, and to have undergone differentiation on different time scales involving differing materials. (author)

  3. PALOMA : an isotope analyzer using static mass spectrometry, coupled with cryogenic and chemical trapping, for the MSL mission to Mars

    Science.gov (United States)

    Chassefiere, E.; Jambon, A.; Berthelier, J.-J.; Goulpeau, G.; Leblanc, F.; Montmessin, F.; Sarda, P.; Agrinier, P.; Fouchet, T.; Waite, H.

    The technique of GCMS analysis has to be completed by static mass spectrometry for precise in-situ measurements of the isotopic composition of planetary atmospheres (noble gases, stable isotopes), and volatile outgassed products from solid sample pyrolysis. Static mass spectrometry, coupled with gas separation by cryo-separation and gettering, is commonly used in the laboratory to study volatiles extracted from terrestrial and meteoritic samples. Such an instrument (PALOMA) is presently developed in our laboratories, and it will be coupled with a Pyr-GCMS analyzer (MACE), built by a US consortium of science laboratories and industrials (University of Michigan, Southwest Research Institute, JPL, Ball Aerospace). The MACE/PALOMA experiment will be proposed on the NASA Mars Science Laboratory mission, planned to be launched in 2009. The scientific objectives of PALOMA, coupled with MACE, may be listed as follows : (i) search for isotopic signatures of past life in atmosphere, rock, dust and ice samples, with emphasis on carbon, nitrogen and hydrogen; (ii) accurately measure isotopic composition of atmospheric noble gases, and stable isotopes, in order to better constrain past escape, surface interaction, outgassing history and climate evolution; (iii) precisely measure diurnal/ seasonal variations of isotopic ratios of H2O, CO2, and N2, for improving our understanding of present and past climate, and of the role of water cycle. Main measurement objectives are : (i) C, H, O, N isotopic composition in both organic evolved samples (provided by MACE pyrolysis system) and atmosphere with high accuracy (a few per mil at 1-s level); (ii) noble gas (He, Ne, Ar, Kr, Xe) and stable (C, H, O, N) isotope composition in atmosphere with high accuracy (a few per mil at 1-s level); (iii) molecular and isotopic composition of inorganic evolved samples (salts, hydrates, nitrates, {ldots}), including ices; (iv) diurnal and seasonal monitoring of D/H in water vapor, and water ice.

  4. Landscape Evolution Mechanisms in Gale Crater from In-Situ Measurement of Cosmogenic Noble Gas Isotopes

    Science.gov (United States)

    Martin, P.; Farley, K. A.; Mahaffy, P. R.; Malespin, C.; Vasconcelos, P. M.

    2017-12-01

    The Sample Analysis at Mars (SAM) instrument onboard the Curiosity rover can measure the noble gas isotopes contained in drilled rock samples on Mars by heating these samples to 930°C. In combination with bulk chemistry measured by the Alpha Particle X-ray Spectrometer (APXS), cosmogenic nuclide production rates can be determined and an exposure age may be calculated. Three cosmogenic nuclides are measured: 3He, and 21Ne, which are produced via spallation of mainly O, Mg, Si, and Al (held mostly in detrital grains); and 36Ar, which is produced from neutron capture of 35Cl (held mostly in secondary materials). To date, three samples have been measured: Cumberland (CB), Windjana (WJ), and Mojave 2 (MJ2). CB yielded 3He, 21Ne, and 36Ar ages of 72 ± 15, 84 ± 28, and 79 ± 24 Ma, respectively [Farley et al., 2014]. Two aliquots of WJ gave error-weighted mean ages of 30 ± 27 Ma (3He), 54 ± 19 Ma (21Ne), and 63 ± 84 Ma (36Ar) [Vasconcelos et al., 2016]. These relatively young ages were interpreted to suggest that a scarp-retreat mechanism is responsible for erosion at both the CB and WJ localities. The most recent measurements on MJ2 do not include the 21Ne isotope because of an instrument issue at this mass. 3He observed in MJ2 is the highest of any sample yet measured, suggesting an exposure age of approximately 1 Ga. In contrast, the calculated exposure age from 36Ar appears to be less than 100 Ma (despite a high uncertainty due to isobaric H35Cl). This discrepancy could be explained by 1) a contribution of extraterrestrial 3He from interplanetary dust or meteoritic fragments, or 2) approximately 1 Ga of prior exposure to the detrital grains. In the latter case 36Ar accumulates only after the Cl-bearing secondary minerals are formed and exposed at the surface. In either scenario the 36Ar measurement provides the better estimate of the recent exposure history. The young upper limit for 36Ar at MJ2 is consistent with the scarp-retreat mechanism observed at CB and

  5. Shallow nitrogen ion implantation: Evolution of chemical state and defect structure in titanium

    Energy Technology Data Exchange (ETDEWEB)

    Manojkumar, P.A., E-mail: manoj@igcar.gov.in [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Chirayath, V.A.; Balamurugan, A.K.; Krishna, Nanda Gopala; Ilango, S.; Kamruddin, M.; Amarendra, G.; Tyagi, A.K. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Raj, Baldev [National Institute of Advanced Studies, Bangalore 560 012 (India)

    2016-09-15

    Highlights: • Low energy nitrogen ion implantation in titanium was studied. • Chemical and defect states were analyzed using SIMS, XPS and PAS. • SIMS and depth resolved XPS data showed good agreement. • Depth resolved defect and chemical states information were revealed. • Formation of 3 layers of defect states proposed to fit PAS results. - Abstract: Evolution of chemical states and defect structure in titanium during low energy nitrogen ion implantation by Plasma Immersion Ion Implantation (PIII) process is studied. The underlying process of chemical state evolution is investigated using secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The implantation induced defect structure evolution as a function of dose is elucidated using variable energy positron annihilation Doppler broadening spectroscopy (PAS) and the results were corroborated with chemical state. Formation of 3 layers of defect state was modeled to fit PAS results.

  6. Chemical and isotopic compositions of water and dissolved sulfate from shallow wells on Vulcano Island, Aeolian Archipelago, Italy

    Energy Technology Data Exchange (ETDEWEB)

    Cortecci, G.; Dinelli, E.; Boschetti, T. [University of Bologna (Italy). Dept. of Earth and Geological Environmental Sciences; Bolognesi, L. [International Institute for Geothermal Research, Pisa (Italy); Ferrara, G. [University of Pisa (Italy). Dept. of Earth Sciences

    2001-02-01

    Twenty-two cold and thermal waters from shallow wells sampled in June 1995 in the Vulcano Porto area, Vulcano Island, were analyzed for major and minor chemical constituents, oxygen and hydrogen isotopes and tritium contents, and sulfur isotopes in the dissolved sulfate. The sulfur isotopic composition of the dissolved sulfate ranges between + 0.6 and + 6.5 per mille (mean + 3.7{+-}1.7 per mille), and is interpreted as deriving mainly from fumarolic SO{sub 2} undergoing oxidation in deep and shallow aquifers, with possible minor contributions from oxidation of H{sub 2}S. Dissolution of secondary anhydrite may have been a minor source of the isotopically heavy aqueous sulfate in the cold groundwaters. The chemical and isotopic features of the waters support previous interpretative hydrologic models of Vulcano Porto, which comprise a number of aquifers fed basically by two major end-members, i.e. meteoric water and crater-type fumarolic inputs, the latter in the form of absorbed emissions or condensate. These data, along with the sulfur isotopes of aqueous sulfate, exclude involvement of seawater in the recharge of the groundwater system of the island. (author)

  7. Identification of recharge sources of groundwater in the Joganjigawa Fan, Toyama, using isotopic and chemical data

    International Nuclear Information System (INIS)

    Mizutani, Yoshihiko; Sakurai, Kazuhiro

    1988-01-01

    The Joganjigawa Fan, an area of rice farming of 50 km 2 lies to the southeast of Toyama city and was formed in the Late Quarternary by terrestrial gravel deposition by the Joganji River. To identify sources of water in shallow aquifers (maximum depth 100 m) beneath the fan, studies of hydrogen and oxygen isotopes in the ground and surface waters of the fan have been made. Major rivers flowing onto the fan are from higher-altitude catchments (maximum altitude 3000 m) and have lower δ 18 D and δO values than rainfall on the fan. The isotopic measurements indicate that the aquifers are mainly recharged by infiltration of the irrigation water, which is derived from the Joganji River, and local precipitations from the surface. In narrow areas along the Jinzu and its tributary the Kumano Rivers, the aquifers are locally recharged from the Jinzu and Kumano Rivers, respectively. Chemical data support this identification of sources of water in the aquifers. (author)

  8. Chemical and isotopic methods for characterization of pollutant sources in rain water

    International Nuclear Information System (INIS)

    Verma, M.P.

    1996-01-01

    The acid rain formation is related with industrial pollution. An isotopic and chemical study of the spatial and temporary distribution of the acidity in the rain gives information about the acidity source. The predominant species in the acid rain are nitrates and sulfates. For the rain monitoring is required the determination of the anion species such as HCO 3 , Cl, SO 4 , NO 3 and p H. So it was analyzed the cations Na + , K + , Ca 2+ and Mg 2+ to determine the quality analysis. All of them species can be determined with enough accuracy, except HCO 3 by modern equipment such as, liquid chromatograph, atomic absorption, etc. The HCO 3 concentration is determined by traditional methods like acid-base titration. This work presents the fundamental concepts of the titration method for samples with low alkalinity (carbonic species), for rain water. There is presented a general overview over the isotopic methods for the characterization of the origin of pollutant sources in the rain. (Author)

  9. Application of isotope-labelled compounds in the study of the chemical stability of pesticides

    International Nuclear Information System (INIS)

    Roesseler, M.; Luther, D.; Abendroth, H.C.; Koch, H.

    1980-01-01

    The user of pesticides requires specific biological modes of action from the corresponding commercial products. Impurities and degradation products may cause uncontrollable toxicological reactions. Profound knowledge of the chemical stability of the effective substance in question and its formulations under storage conditions as well as under those of analytical sample preparation and detection is required. Radioisotope labelled effective substances dimethoate and 1-butyl-amino-cyclohexane-phosphonic acid dibutyl ester are used to study storage stability of the pure effective substance and its formulations; effects of selected impurities, such as technical by-products, moisture or water content, binding or carrier materials, organic solvents, chemical stabilizers and other formulation components on storage properties; temperature dependence of storage stability; selection of suitable analytical techniques for quantitative determination of the effective substance without interference effects from any by-product; reduction of the necessary analytical expense; disclosure of sources of error in the application of usual analytical techniques; improvement of possibilities of an immediate and clearer discrimination between types and amounts of compounds in a chemical system consisting of one pesticide and its degradation or reaction products at the beginning and at the end of an experimental or reaction period. Radiochemical analytical techniques, such as radio thin-layer chromatography (also combined with liquid scintillation counting), radio gas chromatography, autoradiography and isotope dilution analysis were used. Results are discussed, especially of experiments on dimethoate and its technical by-products

  10. Chemical Ligation of Folded Recombinant Proteins: Segmental Isotopic Labeling of Domains for NMR Studies

    Science.gov (United States)

    Xu, Rong; Ayers, Brenda; Cowburn, David; Muir, Tom W.

    1999-01-01

    A convenient in vitro chemical ligation strategy has been developed that allows folded recombinant proteins to be joined together. This strategy permits segmental, selective isotopic labeling of the product. The src homology type 3 and 2 domains (SH3 and SH2) of Abelson protein tyrosine kinase, which constitute the regulatory apparatus of the protein, were individually prepared in reactive forms that can be ligated together under normal protein-folding conditions to form a normal peptide bond at the ligation junction. This strategy was used to prepare NMR sample quantities of the Abelson protein tyrosine kinase-SH(32) domain pair, in which only one of the domains was labeled with 15N Mass spectrometry and NMR analyses were used to confirm the structure of the ligated protein, which was also shown to have appropriate ligand-binding properties. The ability to prepare recombinant proteins with selectively labeled segments having a single-site mutation, by using a combination of expression of fusion proteins and chemical ligation in vitro, will increase the size limits for protein structural determination in solution with NMR methods. In vitro chemical ligation of expressed protein domains will also provide a combinatorial approach to the synthesis of linked protein domains.

  11. The size-isotopic evolution connection among layered mafic instrusions: Clues from a Sr-Nd isotopic study of a small complex

    Science.gov (United States)

    Poitrasson, Franck; Pin, Christian; Duthou, Jean-Louis; Platevoet, Bernard

    1994-05-01

    Several theoretical and experimental works have focused on the processes occuring in continental mafic magma chambers. In contrast, systematic isotopic studies of natural remnants of these latter remain scarce, although they can give fundamental constraints for theoretical studies. This is especially true if different layered complex with contrasting characteristics (e.g., different size) are compared. For this reason, we present the results of a Sr-Nd isotopic profile across a small layered mafic intrusion of Permian age exposed near Fozzano (SW Corsica). In the main zone of the layered section, decreasing Sr-87/Sr(sub i)-86 and increasing Nd-143/Nd(sub i)-144 are observed from less evolved (bottom) to more evolved (top) rocks. This peculiar pattern precludes assimilation and fractional crystallization (AFC) as a dominant mechanism in the petrogenesis of this body. Instead, we interpret this trend as reflecting the dilution of an early stage contaminated magma by several reinjections of fresh basalt in the chamber. In agreement with mineralogical and structural data, every cyclic unit is interpreted as a new magmatic input. On the basis of rough refill and fractional crystallization (RFC) calculations, the average volume for each reinjection is estimated to have been about 0.04 cu km. The cumulative volume of these injections would amount to about 75% of the total volume of the layered complex. This implies that reinjections were accompanied by an important increase of the volume of the chamber or by magma withdrawal by surface eruptions. The RFC mechanism documented within this small layered body constrasts with the isotopic pattern observed between several intrusions at the regional scale in SW Corsica, and within large continental mafic magma chambers elsewhere. In these cases the isotopic evolution is dominated by AFC processes, and there is no clear isotopic evidence for reinjections, unless major influx of fresh magma occurred. It is suggested that there is

  12. Chemical and isotopic investigations of runoff in a mountainous watershed, Venezuelan Andes (Rio Bocono)

    International Nuclear Information System (INIS)

    Cornieles, M.; Moreau, A.; Valles, V.; Travi, Y.

    1999-01-01

    The Rio Bocono watershed, located in the Western part of Venezuela on the South western side of Andes is considered by the 'Ministerio de1 Ambiente y de los Recursos Naturales Renovables' (MARN) as a priority zone for environmental management. The studies of relation between flow, dissolved elements and solid transport are essential to estimate soil degradation and sediment deposition which provokes loss of depth in the dam reservoir at the Southern margin of the basin. Because of the large surface which reach 1540 km 2 , the lack of equipment and the flash flood character of the river do not enable the flow mechanisms and transit times to be determined using usual hydrologic methods; therefore this problem has been approached by the way of chemical and isotopic investigation

  13. Isotopic and chemical aspects of nitrate in the groundwater of the Springbok Flats

    Energy Technology Data Exchange (ETDEWEB)

    Heaton, T H.E.

    1985-10-01

    Increases in the concentration of nitrate in groundwater are becoming a world-wide problem and are commonly ascribe to one or more of three factors associated with modern farming methods: increased fertilization, increased animal waste and increased cultivation. A combined isotopic ( VN/ UN) and chemical study of the high nitrate groundwater in the basalts of the Springbok Flats (Transvaal, South Africa) indicates that the third factor is the only important source of nitrate. Nitrification of the 'black turf' soils, accelerated by the expansion of cultivation, has resulted in most of the shallow groundwater having nitrate concentrations higher than the 'maximum allowable' limit for domestic water supply and the concentrations are still increasing. Modification of farming practices has been suggested in some countries, as a means of controlling both the increase in groundwater nitrate and the attendant decrease in soil fertility.

  14. Isotopic and chemical aspects of nitrate in the groundwater of the Springbok Flats

    International Nuclear Information System (INIS)

    Heaton, T.H.E.

    1985-01-01

    Increases in the concentration of nitrate in groundwater are becoming a world-wide problem and are commonly ascribe to one or more of three factors associated with modern farming methods: increased fertilization, increased animal waste and increased cultivation. A combined isotopic ( 15 N/ 14 N) and chemical study of the high nitrate groundwater in the basalts of the Springbok Flats (Transvaal, South Africa) indicates that the third factor is the only important source of nitrate. Nitrification of the 'black turf' soils, accelerated by the expansion of cultivation, has resulted in most of the shallow groundwater having nitrate concentrations higher than the 'maximum allowable' limit for domestic water supply and the concentrations are still increasing. Modification of farming practices has been suggested in some countries, as a means of controlling both the increase in groundwater nitrate and the attendant decrease in soil fertility

  15. Coupled thermochemical, isotopic evolution and heat transfer simulations in highly irradiated UO{sub 2} nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Piro, M.H.A., E-mail: markuspiro@gmail.com [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Banfield, J. [Nuclear Engineering Department, University of Tennessee, Knoxville, TN (United States); Clarno, K.T., E-mail: clarnokt@ornl.gov [Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Simunovic, S. [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Besmann, T.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Lewis, B.J.; Thompson, W.T. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON (Canada)

    2013-10-15

    Predictive capabilities for simulating irradiated nuclear fuel behavior are enhanced in the current work by coupling thermochemistry, isotopic evolution and heat transfer. Thermodynamic models that are incorporated into this framework not only predict the departure from stoichiometry of UO{sub 2}, but also consider dissolved fission and activation products in the fluorite oxide phase, noble metal inclusions, secondary oxides including uranates, zirconates, molybdates and the gas phase. Thermochemical computations utilize the spatial and temporal evolution of the fission and activation product inventory in the pellet, which is typically neglected in nuclear fuel performance simulations. Isotopic computations encompass the depletion, decay and transmutation of more than 2000 isotopes that are calculated at every point in space and time. These computations take into consideration neutron flux depression and the increased production of fissile plutonium near the fuel pellet periphery (i.e., the so-called “rim effect”). Thermochemical and isotopic predictions are in very good agreement with reported experimental measurements of highly irradiated UO{sub 2} fuel with an average burnup of 102 GW d t(U){sup −1}. Simulation results demonstrate that predictions are considerably enhanced when coupling thermochemical and isotopic computations in comparison to empirical correlations. Notice: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

  16. Lead Isotopes in Olivine-Phyric Shergottite Tissint: Implications for the Geochemical Evolution of the Shergottite Source Mantle

    Science.gov (United States)

    Moriwaki, R.; Usui, T.; Simon, J. I.; Jones, J. H.; Yokoyama, T.

    2015-01-01

    Geochemically-depleted shergottites are basaltic rocks derived from a martian mantle source reservoir. Geochemical evolution of the martian mantle has been investigated mainly based on the Rb-Sr, Sm-Nd, and Lu-Hf isotope systematics of the shergottites [1]. Although potentially informative, U-Th- Pb isotope systematics have been limited because of difficulties in interpreting the analyses of depleted meteorite samples that are more susceptible to the effects of near-surface processes and terrestrial contamination. This study conducts a 5-step sequential acid leaching experiment of the first witnessed fall of the geochemically-depleted olivinephyric shergottite Tissint to minimize the effect of low temperature distrubence. Trace element analyses of the Tissint acid residue (mostly pyroxene) indicate that Pb isotope compositions of the residue do not contain either a martian surface or terrestrial component, but represent the Tissint magma source [2]. The residue has relatively unradiogenic initial Pb isotopic compositions (e.g., 206Pb/204Pb = 10.8136) that fall within the Pb isotope space of other geochemically-depleted shergottites. An initial µ-value (238U/204Pb = 1.5) of Tissint at the time of crystallization (472 Ma [3]) is similar to a time-integrated mu- value (1.72 at 472 Ma) of the Tissint source mantle calculated based on the two-stage mantle evolution model [1]. On the other hand, the other geochemically-depleted shergottites (e.g., QUE 94201 [4]) have initial µ-values of their parental magmas distinctly lower than those of their modeled source mantle. These results suggest that only Tissint potentially reflects the geochemical signature of the shergottite mantle source that originated from cumulates of the martian magma ocean

  17. A discussion for the evolution model of Pb isotope of the upper mantle in western Yunnan and its interpretation to the lead isotopic compositions of the regional alkali-rich porphyries and their related rocks

    International Nuclear Information System (INIS)

    Wu Kaixing; Hu Ruizhong; Bi Xianwu; Zhang Qian; Peng Jiantang

    2003-01-01

    Thirty Pb isotope data of the upper mantle in the area of western Yunnan have the similar trends with the Stacey-Kramers' two stage model growth curves but apparently deviate from it on the lead isotope composition programs, which may suggest Pb isotope of the upper mantle in the area of western Yunnan might have two stage evolution history though not fit very well to the Stacey-Kramers' two stage model growth curves. In this paper, a two-stage growth curves which can better fit the Pb isotope data was constructed based on the lead isotope data of the upper mantle in western Yunnan and the principle that Stacey and Kramers constructed the two-stage model and a reasonable interpretation was given to the lead isotopic compositions of the regional alkali-rich porphyries and their related rocks using the model. (authors)

  18. Hydro-geochemical and isotopic fluid evolution of the Los Azufres geothermal field, Central Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Partida, E. [Centro de Geociencias, UNAM, Campus Juriquilla, A.P. 15, Juriquilla, Qro., 76230 (Mexico)]. E-mail: egp@geociencias.unam.mx; Carrillo-Chavez, A. [Centro de Geociencias, UNAM, Campus Juriquilla, A.P. 15, Juriquilla, Qro., 76230 (Mexico); Levresse, G. [Centro de Geociencias, UNAM, Campus Juriquilla, A.P. 15, Juriquilla, Qro., 76230 (Mexico); Tello-Hinojosa, E. [Comision Federal de Electricidad, A.P. 31-7, C.P. 58090 Morelia, Mich. (Mexico); Venegas-Salgado, S. [Comision Federal de Electricidad, A.P. 31-7, C.P. 58090 Morelia, Mich. (Mexico); Ramirez-Silva, G. [Comision Federal de Electricidad, A.P. 31-7, C.P. 58090 Morelia, Mich. (Mexico); Pal-Verma, M. [Instituto de Investigaciones Electricas, A.P. 1-475, C.P. 62001 Cuernavaca, Morelos (Mexico); Tritlla, J. [Centro de Geociencias, UNAM, Campus Juriquilla, A.P. 15, Juriquilla, Qro., 76230 (Mexico); Camprubi, A. [Centro de Geociencias, UNAM, Campus Juriquilla, A.P. 15, Juriquilla, Qro., 76230 (Mexico)

    2005-01-01

    Hydrothermal alteration at Los Azufres geothermal field is mostly propylitic with a progressive dehydration with depth and temperature increase. Argillic and advanced argillic zones overlie the propylitic zone owing to the activity of gases in the system. The deepest fluid inclusions (proto-fluid) are liquid-rich with low salinity, with NaCl dominant fluid type and ice melting temperatures (T{sub mi}) near zero (0 deg C), and salinities of 0.8 wt% NaCl equivalent. The homogenization temperature (T{sub h}) = 325 {+-} 5 deg C. The boiling zone shows T{sub h} = {+-}300 deg C and apparent salinities between 1 and 4.9 wt% NaCl equivalent, implying a vaporization process and a very important participation of non-condensable gases (NCGs), mostly CO{sub 2}. Positive clathrate melting temperatures (fusion) with T{sub h} = 150 deg C are observed in the upper part of the geothermal reservoir (from 0 to 700 m depth). These could well be the evidence of a high gas concentration. The current water produced at the geothermal wells is NaCl rich (geothermal brine) and is fully equilibrated with the host rock at temperatures between T = 300 and 340 deg C. The hot spring waters are acid-sulfate, indicating that they are derived from meteoric water heated by geothermal steam. The NCGs related to the steam dominant zone are composed mostly of CO{sub 2} (80-98% of all the gases). The gases represent between 2 and 9 wt% of the total mass of the fluid of the reservoir. The authors interpret the evolution of this system as deep liquid water boiling when ascending through fractures connected to the surface. Boiling is caused by a drop of pressure, which favors an increase in the steam phase within the brine ascending towards the surface. During this ascent, the fluid becomes steam-dominant in the shallowest zone, and mixes with meteoric water in perched aquifers. Stable isotope compositions ({delta}{sup 18}O-{delta}D) of the geothermal brine indicate mixing between meteoric water and a

  19. The origin and evolution of chondrites recorded in the elemental and isotopic compositions of their macromolecular organic matter

    Science.gov (United States)

    Alexander, C. M. O.'D.; Fogel, M.; Yabuta, H.; Cody, G. D.

    2007-09-01

    Extraterrestrial organic matter in meteorites potentially retains a unique record of synthesis and chemical/thermal modification by parent body, nebular and even presolar processes. In a survey of the elemental and isotopic compositions of insoluble organic matter (IOM) from 75 carbonaceous, ordinary and enstatite chondrites, we find dramatic variations within and between chondrite classes. There is no evidence that these variations correlate with the time and/or location of chondrite formation, or with any primary petrologic or bulk compositional features that are associated with nebular processes (e.g., chondrule and volatile trace element abundances). Nor is there evidence for the formation of the IOM by Fischer-Tropsch-Type synthesis in the nebula or in the parent bodies. The elemental variations are consistent with thermal maturation and/or oxidation of a common precursor. For reasons that are unclear, there are large variations in isotopic composition within and between chondrite classes that do not correlate in a simple way with elemental composition or petrologic type. Nevertheless, because of the pattern of elemental variations with petrologic type and the lack of any correlation with the primary features of the chondrite classes, at present the most likely explanation is that all IOM compositional variations are the result of parent body processing of a common precursor. If correct, the range of isotopic compositions within and between chondrite classes implies that the IOM is composed of several isotopically distinct components whose relative stability varied with parent body conditions. The most primitive IOM is found in the CR chondrites and Bells (CM2). Isotopically, the IOM from these meteorites resembles the IOM in interplanetary dust particles. Chemically, their IOM resembles the CHON particles of comet Halley. Despite the large isotopic anomalies in the IOM from these meteorites, it is uncertain whether the IOM formed in the interstellar medium or

  20. Chemical and Isotopic Tracers of Groundwater Sustainability: an Overview of New Science Directions

    Science.gov (United States)

    Bullen, T.

    2002-12-01

    Groundwater sustainability is an emerging concept that is rapidly gaining attention from both scientists and water resource managers, particularly with regard to contamination and degradation of water quality in strategic aquifers. The sustainability of a groundwater resource is a complex function of its susceptibility to factors such as intrusion of poor-quality water from diverse sources, lack of sufficient recharge and reorganization of groundwater flowpaths in response to excessive abstraction. In theory the critical limit occurs when degradation becomes irreversible, such that remediative efforts may be fruitless on a reasonable human time scale. Chemical and isotopic tracers are proving to be especially useful tools for assessment of groundwater sustainability issues such as characterization of recharge, identification of potential sources, pathways and impacts of contaminants and prediction of how hydrology will change in response to excessive abstraction. A variety of relatively cost-efficient tracers are now available with which to assess the susceptibility of groundwater reserves to contamination from both natural and anthropogenic sources, and may provide valuable monitoring and regulatory tools for water resource managers. In this overview, the results of several ongoing groundwater studies by the U.S. Geological Survey will be discussed from the perspective of implications for new science directions for groundwater sustainability research that can benefit water policy development. A fundamental concept is that chemical and isotopic tracers used individually often provide ambiguous information, and are most effective when used in a rigorous "multi-tracer" context that considers the complex linkages between the hydrology, geology and biology of groundwater systems.

  1. Chemical Evolution of Mn in Three Dwarf Spheroidal Galaxies Men ...

    Indian Academy of Sciences (India)

    thesis and explosion rate of SNeIa and CCSNe, we studied Mn evolution for three local ... different types of supernovae and the time delay between the birth and death of supernovae .... We find the theory can explain most distribution of Mn.

  2. Zircon U-Pb and Hf isotopic constraints on the magmatic evolution of the Northern Luzon Arc

    Directory of Open Access Journals (Sweden)

    Yu-Ming Lai

    2018-01-01

    Full Text Available The complete volcanic sequences restored in the Coastal Range of Taiwan are key archives for better understanding the magmatic and tectonic evolution of the Northern Luzon Arc. This paper reports (1 new zircon U-Pb ages and Hf isotopic data of fourteen volcanic samples from different sequences of four major volcanoes in the Coastal Range, (2 Hf isotopic data of dated magmatic and detrital zircons from two offshore volcanic islands, Lutao and Lanyu. These data indicate that the arc magmatism in the Coastal Range started at ~15 Ma, most active at ~9 Ma, and ceased at ~4.2 Ma. Magmatic zircons from the arc rocks show a significant variation in Hf isotopic composition, with εHf(T values varying from +24.9 to +4.8. As pointed out by our previous studies, old continental zircons that show Cathaysian-type ages and Hf isotope features are common in samples from the Yuemei, Chimei, and Lanyu volcanoes, supporting the notion for the influence of the existence of an accreted micro-continent or continental fragment plays a role in the petrogenesis. Such inherited zircons are not observed in the Chengkuang’ao and Tuluanshan volcanoes and uncommon in Lutao, implying the discontinuity or a limited extent of the accreted continental fragment. The εHf(T values are high and positive from ~15 - 8 Ma (+25 to +15; ±5ε-unit variation, and became lower from ~6 to 4.2 Ma (+20 to +8; ±6ε units and the lowest from ~1.3 Ma (+19 to +5; ±7ε units. Such a temporal variation in zircon Hf isotopic ratios can be also identified in whole-rock Hf and Nd isotopic compositions, which decrease from ~6 Ma when the Northern Luzon Arc may have started colliding with the Eurasian continental margin.

  3. Modeling the isotopic evolution of snowpack and snowmelt: Testing a spatially distributed parsimonious approach.

    Science.gov (United States)

    Ala-Aho, Pertti; Tetzlaff, Doerthe; McNamara, James P; Laudon, Hjalmar; Kormos, Patrick; Soulsby, Chris

    2017-07-01

    Use of stable water isotopes has become increasingly popular in quantifying water flow paths and travel times in hydrological systems using tracer-aided modeling. In snow-influenced catchments, snowmelt produces a traceable isotopic signal, which differs from original snowfall isotopic composition because of isotopic fractionation in the snowpack. These fractionation processes in snow are relatively well understood, but representing their spatiotemporal variability in tracer-aided studies remains a challenge. We present a novel, parsimonious modeling method to account for the snowpack isotope fractionation and estimate isotope ratios in snowmelt water in a fully spatially distributed manner. Our model introduces two calibration parameters that alone account for the isotopic fractionation caused by sublimation from interception and ground snow storage, and snowmelt fractionation progressively enriching the snowmelt runoff. The isotope routines are linked to a generic process-based snow interception-accumulation-melt model facilitating simulation of spatially distributed snowmelt runoff. We use a synthetic modeling experiment to demonstrate the functionality of the model algorithms in different landscape locations and under different canopy characteristics. We also provide a proof-of-concept model test and successfully reproduce isotopic ratios in snowmelt runoff sampled with snowmelt lysimeters in two long-term experimental catchment with contrasting winter conditions. To our knowledge, the method is the first such tool to allow estimation of the spatially distributed nature of isotopic fractionation in snowpacks and the resulting isotope ratios in snowmelt runoff. The method can thus provide a useful tool for tracer-aided modeling to better understand the integrated nature of flow, mixing, and transport processes in snow-influenced catchments.

  4. Experimental evaporation of hyperacid brines: Effects on chemical composition and chlorine isotope fractionation

    Science.gov (United States)

    Rodríguez, Alejandro; van Bergen, Manfred J.; Eggenkamp, H. G. M.

    2018-02-01

    Hyperacid brines from active volcanic lakes are some of the chemically most complex aqueous solutions on Earth. Their compositions provide valuable insights into processes of elemental transfer from a magma body to the surface and interactions with solid rocks and the atmosphere. This paper describes changes in chemical and δ37Cl signatures observed in a 1750 h isothermal evaporation experiment on hyperacid (pH 0.1) sulphate-chloride brine water from the active lake of Kawah Ijen volcano (Indonesia). Although gypsum was the only evaporite mineral identified in the evolving brine, decreasing Si concentrations may ultimately result in amorphous silica precipitation. Geochemical simulations predict the additional formation of elemental sulphur at lower water activities (aH2O ≤ 0.65) that were not reached in the experiment. Absence of other sulphates and halides despite the high load of dissolved elements (initial TDS ca. 100 g/kg) can be attributed to increased solubility of metals, promoted by extensive formation of complexes between the variety of cations and the major anions (HSO4-, Cl-, F-) present. Chlorine deviations from a conservative behaviour point to losses of gaseous hydrogen chloride (HCl(g)) and consequently an increase in Br/Cl ratios. Chlorine isotope fractionation that accompanied the escape of HCl(g) showed a marked change in sign and magnitude in the course of progressive evaporation of the brine. The calculated factor of fractionation between HCl(g) and dissolved Cl for the initial interval (before 500 h) is positive (1000lnαHCl(g)-Cldiss. = + 1.55 ± 0.49‰to + 3.37 ± 1.11‰), indicating that, at first, the escaping HCl(g) was isotopically heavier than the dissolved Cl remaining in the brine. Conversely, fractionation shifted to the opposite direction in the subsequent interval (1000lnαHCl(g)-Cldiss. = 5.67 ± 0.17‰to - 5.64 ± 0.08‰), in agreement with values reported in literature. It is proposed that Cl isotopic fractionation in

  5. Chemical, physical and isotopic characterization of U3Si2, for nuclear forensics purposes

    International Nuclear Information System (INIS)

    Rosa, Daniele Scarpim

    2011-01-01

    In the early 1990's, the first illicit trafficking of nuclear and radioactive materials was observed mainly in Europe. A decade marked by numerous cases of seizures of these materials. As a result, these events have become the subject of criminal forensic investigations and develop from there, nuclear forensics. In Brazil there are no illicit trafficking official records of nuclear material, however, is widely known the extraction and illegal transportation of radioactive geological materials, and the materials pieces attachment used as shielding for radioactive sources. One of the main tools used in nuclear forensics is the nuclear materials databases establishment. These documents must contain the most information as possible about the physical, chemical and nuclear material seized, allowing the identification of their origin, manufacturing process or age. Thus, it sets characteristic composition standards of each material, called 'chemical signatures' (chemical finger print). In this work nuclear forensic protocol was adopted as well as the three stages of assessment suggested by International Atomic Energy Agency (IAEA) in identifying the origin of uranium silicide (U 3 Si 2 ). Assays were performed in order to make physical, chemical and isotopic characterization of the studied materials and compared the data with those obtained for other uranium compounds (Uranium tetrafluoride, UF 4 ; uranium oxide, UO 2 and U 3 O 8 ; Yellow cake) by establishing a characteristic signature for each one. Through the assays the uranium compounds were classify by origin groups, as far as they are from different manufactured process and/ or origin. It was also possible to show the importance of a nuclear forensic database during an investigation of a nuclear forensic event. (author)

  6. Impact of statistical uncertainty of the neutron spectrum in the isotopic evolution of fuel

    International Nuclear Information System (INIS)

    Ortega, P.

    2012-01-01

    The results obtained and presented in this study for different calculation conditions (number of stories, number of steps burning, etc.) and their simultaneous impact on neutron spectrum and isotopic composition and a methodology is proposed to determine the minimum parameters for calculation given uncertainty in the results of isotopic composition with high burnup, both UO 2 and MOX fuel.

  7. Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis.

    Science.gov (United States)

    Larsen, K K; Wielandt, D; Schiller, M; Bizzarro, M

    2016-04-22

    Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of these species can result in incomplete Cr recovery during chromatographic purification. Because of large mass-dependent inter-species isotope fractionation, incomplete recovery can affect the accuracy of high-precision Cr isotope analysis. Here, we demonstrate widely differing cation distribution coefficients of Cr(III)-species (Cr(3+), CrCl(2+) and CrCl2(+)) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr(3+), intermediates in CrCl(2+) and the lightest in CrCl2(+)/CrCl3°. Thus, for a typical reported loss of ∼25% Cr (in the form of Cr(3+)) through chromatographic purification, this translates into 185 ppm/amu offset in the stable Cr isotope ratio of the residual sample. Depending on the validity of the mass-bias correction during isotope analysis, this further results in artificial mass-independent effects in the mass-bias corrected (53)Cr/(52)Cr (μ(53)Cr* of 5.2 ppm) and (54)Cr/(52)Cr (μ(54)Cr* of 13.5 ppm) components used to infer chronometric and nucleosynthetic information in meteorites. To mitigate these fractionation effects, we developed strategic chemical sample pre-treatment procedures that ensure high and reproducible Cr recovery. This is achieved either through 1) effective promotion of Cr(3+) by >5 days exposure to HNO3H2O2 solutions at room temperature, resulting in >∼98% Cr recovery for most types of sample matrices tested using a cationic chromatographic retention strategy, or 2) formation of Cr(III)-Cl complexes through exposure to concentrated HCl at high temperature (>120 °C) for several hours, resulting in >97.5% Cr recovery using a

  8. Geochemical modelling of groundwater evolution using chemical equilibrium codes

    International Nuclear Information System (INIS)

    Pitkaenen, P.; Pirhonen, V.

    1991-01-01

    Geochemical equilibrium codes are a modern tool in studying interaction between groundwater and solid phases. The most common used programs and application subjects are shortly presented in this article. The main emphasis is laid on the approach method of using calculated results in evaluating groundwater evolution in hydrogeological system. At present in geochemical equilibrium modelling also kinetic as well as hydrologic constrains along a flow path are taken into consideration

  9. Evolution of quadrupole and octupole collectivity north-east of $^{132}$ Sn: the even Te and Xe isotopes

    CERN Multimedia

    We propose to study excited states in isotopes north-east of the doubly-magic $^{132}$Sn by $\\gamma$-ray spectroscopy following "safe" Coulomb excitation. The experiment aims to the determine B(E2) and B(E3) values to follow the evolution of quadrupole and octupole collectivity when going away from the shell closures at Z = 50 and N = 82. The B(E2; 0$^+_{gs}$ $\\rightarrow$ 2$^+_{1}$) values in the even isotopes $^{138-144}$Xe have been measured at REX-ISOLDE and the systematic trend towards neutron-rich nuclei is well described even by an empirical Grodzins-type formula. An increasing dipole moment observed for $^{140,142}$Xe is interpreted as indirect signature of increasing octupole correlations peaking at N = 88. So far, no B(E3) values are known. In contrast to the Xe isotopes, the Te ones, in particular $^{136}$Te, are known for their notoriously irregular behaviour. In order to understand the nuclear structure also on a microscopic basis, the isotope $^{136}$Te with just one pair of protons and neutrons...

  10. The measurement of the chemically mobile fraction of lead in soil using isotopic dilution analysis

    International Nuclear Information System (INIS)

    Kirchhoff, J.; Brand, J.; Schuettelkopf, H.

    1992-12-01

    The chemically available fraction of lead in eight soils measured by isotopic dilution analysis using 212 Pb ranged from 7 to 16% of the total content of lead in soil. The soluble fractions achieved values up to 63% of the total content in 1 M NH 4 NO 3 , 1 M MgCl 2 and 0.05 M DTPA solutions. Increasing the contact time between water and soil, the water-soil ratio from 1:1 to 5:1 and increasing the temperature of the soil-water suspension raised the chemically available fraction in soil. Comparing various soil parameters and the mobile fraction of lead, only pH shows a significant correlation. The amphoteric character of lead causes a minimum of mobility about pH 6; pH-values below are responsible for the higher mobility of lead as Pb 2+ , at pH-values above 6 soluble hydroxy and humic acid complexes are formed. (orig.) [de

  11. Investigation of Chemical and Physical Changes to Bioapatite During Fossilization Using Trace Element Geochemistry, Infrared Spectroscopy and Stable Isotopes

    Science.gov (United States)

    Suarez, C. A.; Kohn, M. J.

    2013-12-01

    Bioapatite in the form of vertebrate bone can be used for a wide variety of paleo-proxies, from determination of ancient diet to the isotopic composition of meteoric water. Bioapatite alteration during diagenesis is a constant barrier to the use of fossil bone as a paleo-proxy. To elucidate the physical and chemical alteration of bone apatite during fossilization, we analyzed an assortment of fossil bones of different ages for trace elements, using LA-ICP-MS, stable isotopes, and reflected IR spectroscopy. One set of fossil bones from the Pleistocene of Idaho show a diffusion recrystallization profile, however, rare earth element (REE) profiles indicate diffusion adsorption. This suggests that REE diffusion is controlled by changing (namely decreasing) boundary conditions (i.e. decreasing concentration of REE in surrounding pore fluids). Reflected IR analysis along this concentration profile reveal that areas high in U have lost type A carbonate from the crystal structure in addition to water and organics. Stable isotopic analysis of carbon and oxygen will determine what, if any, change in the isotopic composition of the carbonate component of apatite has occurred do to the diffusion and recrystallization process. Analysis of much older bone from the Cretaceous of China reveal shallow REE and U concentration profiles and very uniform reflected IR spectra with a significant loss of type A carbonate throughout the entire bone cortex. Analysis of stable isotopes through the bone cortex will be compared to the stable isotopes collected from the Pleistocene of Idaho.

  12. Chemical Evolution and the Galactic Habitable Zone of M31

    NARCIS (Netherlands)

    Carigi, Leticia; Garcia-Rojas, Jorge; Meneses-Goytia, Sofia

    2013-01-01

    We have computed the Galactic Habitable Zones (GHZs) of the Andromeda galaxy (M31) based on the probability of terrestrial planet formation, which depends on the metallicity (Z) of the interstellar medium, and the number of stars formed per unit surface area. The GHZ was obtained from a chemical

  13. Chemical and Isotopes study of pollutants transport through unsaturated zone in Damascus oasis (Syria)

    International Nuclear Information System (INIS)

    Abou Zakhem, B.; Hafez, R.

    2011-08-01

    The primary objectives of this study were to determine the hydrochemical and isotopic characteristics of groundwater and to study vertical transport processes for trace elements through the unsaturated zone, from the surface water into the groundwater system. A third objective is to identifying the importance of the unsaturated zone in protecting groundwater from contamination. Distribution of trace elements, including Cu, Pb, Cr, Cd, Zn and As in the soil with depth were studied. Mineralogy was investigated using X-Ray diffraction techniques and granulometry in three drilled soil profile (KA, KB and KS) in Damascus Oasis, which indicated that the soil consists mainly of calcite, a mineral that has the ability to bind some of the trace elements. Measurement of nitrate concentrations in groundwater permitted an investigation of the urban, industrial and agricultural pollution in the Oasis, in particular, in the eastern part of Damascus city and in the north of Oasis where the irrigation by treated wastewater is applied. Depending on the chemical characteristics of the studied trace elements and soil conditions, these elements have high concentrations in the upper part of the soil (20-30 cm depth), due to absorption by clay minerals and organic matter. These high concentrations represent pollution by leather industries (tannery) in the area. The trace element concentrations decrease towards the east in parallel with river flow direction. The lower part of profiles show low trace element concentrations, below the international permitted limit. The low concentrations of trace elements in groundwater which are also below the international limit, indicates no pollution is presented. The isotopic composition of shallow groundwater indicates the underground recharge, originated from the Anti-Lebanon Mountain, is more significant than the direct recharge through unsaturated zone. It is concluded the unsaturated zone and the decrease of groundwater levels have played an

  14. Metal Chemical and Isotope Characterisation in the Upper Loire River Basin, France

    Science.gov (United States)

    Widory, D.; Nigris, R.; Morard, A.; Gassama, N.; Poirier, A.; Bourrain, X.

    2016-12-01

    The Water Framework Directive (WFD) elaborated by the European Commission regulates water resources in the EC based on five years management plans. A new management plan that started in 2016 imposes strict water quality criteria to its member states, including good status thresholds for metallic contaminants. The Loire River, the most important river in France, flows through areas with lithologies naturally containing high metal concentrations in the upper part of its basin. Understanding these metal fluxes into the river is thus a prerequisite to understand their potential impact on the quality of its water in regards to the criteria defined by the WFD. The Massif Central, a residue of the Hercynian chain, is composed of granitic and volcanic rocks. Both its upstream position in the Loire basin and its numerous metal mineralizations made this region a good candidate for characterizing the natural metal geochemical background of its surface waters. To fulfill this objective we focused on the Pb, Cd and Zn chemical and isotope characteristics of selected non-anthropized small watersheds. The investigated small watersheds were selected for supposedly draining a single lithology and undergoing (as far as possible) negligible to no anthropogenic pressure. Results showed that although the high metal potential of the upper part of the Loire River basin has been highly exploited by humans for centuries, metal concentrations during the hydrological cycle are still under the guidelines defined by the WFD. Isotope compositions/ratios are strongly related to the corresponding lithologies along the rivers and help precisely define the local geochemical background that can then be used to identify and quantify any anthropogenic inputs downstream.

  15. Chemical and oxygen isotopic properties of ordinary chondrites (H5, L6) from Oman: Signs of isotopic equilibrium during thermal metamorphism

    Science.gov (United States)

    Ali, Arshad; Nasir, Sobhi J.; Jabeen, Iffat; Al Rawas, Ahmed; Banerjee, Neil R.; Osinski, Gordon R.

    2017-10-01

    Mean bulk chemical data of recently found H5 and L6 ordinary chondrites from the deserts of Oman generally reflect isochemical features which are consistent with the progressive thermal metamorphism of a common, unequilibrated starting material. Relative differences in abundances range from 0.5-10% in REE (Eu = 14%), 6-13% in siderophile elements (Co = 48%), and >10% in lithophile elements (exceptions are Ba, Sr, Zr, Hf, U = >30%) between H5 and L6 groups. These differences may have accounted for variable temperature conditions during metamorphism on their parent bodies. The CI/Mg-normalized mean abundances of refractory lithophile elements (Al, Ca, Sm, Yb, Lu, V) show no resolvable differences between H5 and L6 suggesting that both groups have experienced the same fractionation. The REE diagram shows subtle enrichment in LREE with a flat HREE pattern. Furthermore, overall mean REE abundances are 0.6 × CI with enriched La abundance ( 0.9 × CI) in both groups. Precise oxygen isotope compositions demonstrate the attainment of isotopic equilibrium by progressive thermal metamorphism following a mass-dependent isotope fractionation trend. Both groups show a slope-1/2 line on a three-isotope plot with subtle negative deviation in Δ17O associated with δ18O enrichment relative to δ17O. These deviations are interpreted as the result of liberation of water from phyllosilicates and evaporation of a fraction of the water during thermal metamorphism. The resultant isotope fractionations caused by the water loss are analogous to those occurring between silicate melt and gas phase during CAI and chondrule formation in chondrites and are controlled by cooling rates and exchange efficiency.

  16. Evolution of the mantle source in an evolving arc-backarc system (Torres del Paine, Patagonia): Evidence from Hf isotopes in zircon

    Science.gov (United States)

    Ewing, T. A.; Muntener, O.; Leuthold, J.; Baumgartner, L. P.; Putlitz, B.; d'Abzac, F. X.; Chiaradia, M.

    2015-12-01

    The Miocene Torres del Paine intrusive complex (TPIC) in Patagonia is a transitional alkaline backarc intrusion1 emplaced on short timescales of 162 ± 11 ka2. It is subdivided into two units with distinct ages of ~12.6 Ma and ~12.45 Ma1. Smaller intrusive bodies in the area record a change in chemistry from calc-alkaline at ~16 Ma, to transitional alkaline at ~12.5 Ma. Zircons from ~16 Ma intrusives and the 12.6 Ma part of the TPIC have remarkably consistent, slightly enriched Hf isotope compositions with ɛHf(i) of -1 to +2. An abrupt shift towards more juvenile Hf isotope compositions is observed in the ~12.45 Ma part of the TPIC, with ɛHf(i) of +3 to +6. Bulk rock Nd and Sr isotopes for the TPIC show the same shift towards more juvenile compositions at this time1. The long-term consistency of ɛHf(i) from 16 to 12.6 Ma is surprising, given that in the same period the bulk rock chemistry changes from calc-alkaline to transitional alkaline. Conversely, the major shift in ɛHf(i) is not correlated with any change in bulk rock chemistry, which remains transitional alkaline from 12.6 to 12.45 Ma. The decoupling of major element chemical evolution and Hf isotope signatures suggests that the subsequent rapid influx of juvenile material recorded by our Hf isotope data must have occurred by renewed mantle melting. Subduction of the Chile ridge at ~12.5 Ma in this area caused arc magmatism to move westwards and back-arc extension to initiate. We propose that the first TPIC magmas (12.6 Ma) came from a mantle wedge with a residual subduction signature. Subsequent melting of more juvenile mantle, less contaminated by a subduction component, generated the 12.45 Ma TPIC magmas. These results demonstrate that magmatic complexes such as the TPIC may tap distinct mantle sources even on very short timescales, fingerprinting arc-backarc transition processes. 1Leuthold et al., 2013, JPET, 54: 273-303 2Leuthold et al., 2012, EPSL, 325: 85-92

  17. The evolution of ethylene signaling in plant chemical ecology.

    Science.gov (United States)

    Groen, Simon C; Whiteman, Noah K

    2014-07-01

    Ethylene is a key hormone in plant development, mediating plant responses to abiotic environmental stress, and interactions with attackers and mutualists. Here, we provide a synthesis of the role of ethylene in the context of plant ecology and evolution, and a prospectus for future research in this area. We focus on the regulatory function of ethylene in multi-organismal interactions. In general, plant interactions with different types of organisms lead to reduced or enhanced levels of ethylene. This in turn affects not only the plant's response to the interacting organism at hand, but also to other organisms in the community. These community-level effects become observable as enhanced or diminished relationships with future commensals, and systemic resistance or susceptibility to secondary attackers. Ongoing comparative genomic and phenotypic analyses continue to shed light on these interactions. These studies have revealed that plants and interacting organisms from separate kingdoms of life have independently evolved the ability to produce, perceive, and respond to ethylene. This signature of convergent evolution of ethylene signaling at the phenotypic level highlights the central role ethylene metabolism and signaling plays in plant interactions with microbes and animals.

  18. Evolution of the Campanian Ignimbrite Magmatic System II: Trace Element and Th Isotopic Evidence for Open-System Processes

    Science.gov (United States)

    Bohrson, W. A.; Spera, F. J.; Fowler, S.; Belkin, H.; de Vivo, B.

    2005-12-01

    The Campanian Ignimbrite, a large volume (~200 km3 DRE) trachytic to phonolitic ignimbrite was deposited at ~39.3 ka and represents the largest of a number of highly explosive volcanic events in the region near Naples, Italy. Thermodynamic modeling of the major element evolution using the MELTS algorithm (see companion contribution by Fowler et al.) provides detailed information about the identity of and changes in proportions of solids along the liquid line of descent during isobaric fractional crystallization. We have derived trace element mass balance equations that explicitly accommodate changing mineral-melt bulk distribution coefficients during crystallization and also simultaneously satisfy energy and major element mass conservation. Although major element patterns are reasonably modeled assuming closed system fractional crystallization, modeling of trace elements that represent a range of behaviors (e.g. Zr, Nb, Th, U, Rb, Sm, Sr) yields trends for closed system fractionation that are distinct from those observed. These results suggest open-system processes were also important in the evolution of the Campanian magmatic system. Th isotope data yield an apparent isochron that is ~20 kyr younger than the age of the deposit, and age-corrected Th isotope data indicate that the magma body was an open-system at the time of eruption. Because open-system processes can profoundly change isotopic characteristics of a magma body, these results illustrate that it is critical to understand the contribution that open-system processes make to silicic magma bodies prior to assigning relevance to age or timescale information derived from isotope systematics. Fluid-magma interaction has been proposed as a mechanism to change isotopic and elemental characteristics of magma bodies, but an evaluation of the mass and thermal constraints on such a process suggest large-scale fluid-melt interaction at liquidus temperatures is unlikely. In the case of the magma body associated with

  19. Process for improving the separation efficiency in the isolation of radioactive isotopes in elementary or chemically bonded form from liquids and gases

    International Nuclear Information System (INIS)

    Schmidberger, R.; Kirch, R.; Kock, W.

    1986-01-01

    In the process for the improvement of the separation efficiency in the isolation of radioactive isotopes in elementary or chemically bonded form from liquids or gases by ion exchange and adsorption, non-radioactive isotopes of the element to be isolated are added to the fluid before the isolation, whereas at the same time a large surplus of the non-radioactive isotopes to the radioactive isotopes is achieved by addition of only small quantities of compounds of the non-radioactive isotopes. (orig./RB) [de

  20. Method and apparatus for controlling gas evolution from chemical reactions

    Science.gov (United States)

    Skorpik, James R.; Dodson, Michael G.

    1999-01-01

    The present invention is directed toward monitoring a thermally driven gas evolving chemical reaction with an acoustic apparatus. Signals from the acoustic apparatus are used to control a heater to prevent a run-away condition. A digestion module in combination with a robotic arm further automate physical handling of sample material reaction vessels. The invention is especially useful for carrying out sample procedures defined in EPA Methods SW-846.

  1. Chemical Evolution in the Interstellar Medium: From Astrochemistry to Astrobiology

    Science.gov (United States)

    Allamandola, Louis J.

    2009-01-01

    Great strides have been made in our understanding of interstellar material thanks to advances in infrared astronomy and laboratory astrophysics. Ionized polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by earlier astrochemical standards, are widespread and very abundant throughout much of the Universe. In cold molecular clouds, the birthplace of planets and stars, interstellar molecules freeze onto dust and ice particles forming mixed molecular ices dominated by simple species such as water, methanol, ammonia, and carbon monoxide. Within these clouds, and especially in the vicinity of star and planet forming regions, these ices and PAHs are processed by ultraviolet light and cosmic rays forming hundreds of far more complex species, some of biogenic interest. Eventually, these are delivered to primordial planets by comets and meteorites. Astrochemical evolution, highlights of this field from a chemist's perspective, and the astronomer's infrared toolbox will be reviewed.

  2. Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates

    Science.gov (United States)

    2014-09-01

    function of heating rate. The FWHM of the Ill PZT texture components is sim 2978 Journal of the American Ceramic Society Mhin et al. Vol. 97, No. 9...Z39.18 ABSTRACT Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates Report Title The crystallization of lead zirconate...phase influencing texture evolution. The results suggest that PZT nucleates directly on Pt, which explains the observation of a more highly oriented

  3. Temperatures and isotopic evolution of silicic magmas, Taupo Volcanic Zone and Coromandel, New Zealand

    International Nuclear Information System (INIS)

    Blattner, P.; Rui-Zhong H.; Graham, I.J.; Houston-Eleftheriadis, C.

    1996-01-01

    A new set of oxygen and strontium isotope data on rhyolitic lavas and ignimbrites of the Taupo Volcanic Zone (TVZ) and the Coromandel Peninsula provides new limits for petrogenic models. For oxygen isotopes, the rock matrix is frequently altered, so that values for magma need to be phenocryst based. Within TVZ a trend towards more negative δ 1 8O values for more recent magmas appears likely (average before about 1 Ma and for Coromandel near 8.0 per mille; after 1 Ma near 7.5 per mille). This could indicate the gradual removal of supracrustal contaminants from the zones of magma accumulation and extrusion. Similar trends within Coromandel cannot yet be resolved. A generally positive correlation is found for oxygen and strontium isotopes of magmas. Most magmas have a limited range of isotopic values, which then becomes a fingerprint (e.g., the Mamaku, Matahina, and Waiotapu Ignimbrites). A narrow range of eruption temperatures of 880 ± 60 o C is derived from quartz-plagioclase fractionations of 0.98 ± 0.25 per mille δ 1 8O values of quartz and feldspar phenocrysts are sufficiently low to suggest interaction between surface water and magma. However, large negative oxygen isotope anomalies (such as known from Yellowstone), could be no more than partially concealed by the isotopically less depleted meteoric water of New Zealand, and have not yet been found in New Zealand. (authors). 45 refs., 6 figs., 3 tabs

  4. Recent advances in chemical evolution and the origins of life

    Science.gov (United States)

    Oro, John; Lazcano, Antonio

    1992-01-01

    Consideration is given to the ideas of Oparin and Haldane who independently suggested more than 60 years ago that the first forms of life were anaerobic, heterotrophic bacteria that emerged as the result of a long period of chemical abiotic synthesis of organic compounds. It is suggested that at least some requirements for life are met in the Galaxy due to the cosmic abundance of carbon, nitrogen, oxygen, and other biogenic elements; the existence of extraterrestrial organic compounds; and the processes of stellar and interstellar planetary formation.

  5. Relation between separation factor of carbon isotope and chemical reaction of CO2 with amine in nonaqueous solvent

    International Nuclear Information System (INIS)

    Takeshita, Kenji; Kitamoto, Asashi

    1989-01-01

    The separation factor for carbon isotope exchange reaction between CO 2 and amine in nonaqueous solvent was related to absorption reaction of CO 2 in a solution. The test solutions were mixtures of primary amine (such as butylamine and tert-butylamine) or secondary amine (such as diethylamine, dipropylamine and dibutylamine) diluted with nonpolar solvent (octane or triethyalmine) or polar solvent (methanol), respectively. The isotope exchange reaction consists of three steps related to chemical reaction of CO 2 in amine and nonaqueous solvent mixture, namely the reaction between CO 2 and carbamic acid, that between CO 2 and amine carbamate, and that between CO 2 and carbamic ion. Above all, the isotope separation factor between CO 2 and carbamic acid had the highest value. The overall separation factor can be higher in amine-nonaqueous solvent mixture where the concentration of carbamic acid becomes higher. (author)

  6. The next generation of galaxy evolution models: A symbiosis of stellar populations and chemical abundances

    Science.gov (United States)

    Kotulla, Ralf

    2012-10-01

    Over its lifespan Hubble has invested significant effort into detailed observations of galaxies both in the local and distant universe. To extract the physical information from the observed {spectro-}photometry requires detailed and accurate models. Stellar population synthesis models are frequently used to obtain stellar masses, star formation rate, galaxy ages and star formation histories. Chemical evolution models offer another valuable and complementary approach to gain insight into many of the same aspects, yet these two methods have rarely been used in combination.Our proposed next generation of galaxy evolution models will help us improve our understanding of how galaxies form and evolve. Building on GALEV evolutionary synthesis models we incorporate state-of-the-art input physics for stellar evolution of binaries and rotating stars as well as new spectral libraries well matched to the modern observational capabilities. Our improved chemical evolution model allows us to self-consistently trace abundances of individual elements, fully accounting for the increasing initial abundances of successive stellar generations. GALEV will support variable Initial Mass Functions {IMF}, enabling us to test recent observational findings of a non-universal IMF by predicting chemical properties and integrated spectra in an integrated and consistent manner.HST is the perfect instrument for testing this approach. Its wide wavelength coverage from UV to NIR enables precise SED fitting, and with its spatial resolution we can compare the inferred chemical evolution to studies of star clusters and resolved stellar populations in nearby galaxies.

  7. Rheological, structural and chemical evolution of bitumen under gamma irradiation

    International Nuclear Information System (INIS)

    Mouazen, M.; Poulesquen, A.; Bart, F.; Masson, J.; Charlot, M.; Vergnes, B.

    2013-01-01

    Bitumen derived from crude oil by fractional distillation has been used in the nuclear industry as a radioactive waste encapsulation matrix. When subjected to α, β and γ self-irradiation, this organic matrix undergoes radiolysis, generating hydrogen bubbles and modifying the physical and chemical properties of the material. In this paper, the effects of irradiation on bitumen materials, especially in terms of its physical, chemical, structural and rheological properties, were characterized at radiation doses ranging from 1 to 7 MGy. An increase in the shear viscosity and melt yield stress was observed with increasing doses. Similarly, the elastic and viscous moduli (G' and G'') increase with the dose, with a more pronounced increase for G' that reflects enhanced elasticity arising from radiation-induced cross-linking. In addition, a low-frequency plateau is observed for G', reflecting pseudo-solid behavior and leading to an increase of the complex viscosity. This behavior is due to increased interactions between asphaltene particles, and to aromatization of the bitumen by γ-radiations. Cross-linking of bitumen enhances its strength, as confirmed by various techniques (modulated DSC, DTA/TGA, SEC, FTIR and XRD). (authors)

  8. Chemical Evolution of Strongly Interacting Quark-Gluon Plasma

    International Nuclear Information System (INIS)

    Pan, Ying-Hua; Zhang, Wei-Ning

    2014-01-01

    At very initial stage of relativistic heavy ion collisions a wave of quark-gluon matter is produced from the break-up of the strong color electric field and then thermalizes at a short time scale (~1 fm/c). However, the quark-gluon plasma (QGP) system is far out of chemical equilibrium, especially for the heavy quarks which are supposed to reach chemical equilibrium much late. In this paper a continuing quark production picture for strongly interacting QGP system is derived, using the quark number susceptibilities and the equation of state; both of them are from the results calculated by the Wuppertal-Budapest lattice QCD collaboration. We find that the densities of light quarks increase by 75% from the temperature T=400 MeV to T=150 MeV, while the density of strange quark annihilates by 18% in the temperature region. We also offer a discussion on how this late production of quarks affects the final charge-charge correlations

  9. Evolution of Uranium Isotopic Compositions of the Groundwater and Rock in a Sandy-Clayey Aquifer

    Directory of Open Access Journals (Sweden)

    Alexander I. Malov

    2017-11-01

    Full Text Available Uranium isotopes have been used as mechanistic or time scale tracers of natural processes. This paper describes the occurrence and redistribution of U in the Vendian aquifer of a paleo-valley in NW Russia. Forty-four rock samples were collected from nine boreholes with depths up to 160 m, and 25 groundwater samples were collected from 23 boreholes with depths up to 300 m. The U, Fe concentration, and 234U/238U activity ratio were determined in the samples. Estimations were made of the 14C and 234U-238U residence time of groundwater in the aquifer. It has been established that the processes of chemical weathering of Vendian deposits led to the formation of a strong oxidation zone, developed above 250 m.b.s.l. The inverse correlation between the concentrations of uranium and iron is a result of removal of U from paleo-valley slopes in oxidizing conditions, accumulation of U at the bottom of the paleo-valley in reducing conditions, and accumulation of Fe on the slopes and removal from the bottom of the paleo-valley. Almost all U on the slopes has been replaced by a newly formed hydrogenic U with a higher 234U/238U activity ratio. After, dissolution and desorption of hydrogenic U occurred from the slopes during periods with no glaciations and marine transgressions. Elevated concentrations of U are preserved in reduced lenses at the paleo-valley bottom. In these areas, the most dangerous aspect is the flow of groundwater from the underlying horizons, since during the operation of water supply wells it can lead to the creation of local zones of oxidizing conditions in the perforated screens zone and the transition of uranium into solution. For groundwater under oxidizing conditions, an increase in the concentration of uranium is characteristic of an increase in the residence time (age of water in the aquifer. Also, the 234U/238U activity ratio increases with increasing radioactivity of groundwater. Therefore, the most rational approach is to use

  10. CHEMICAL EVOLUTION OF RED MSX SOURCES IN THE SOUTHERN SKY

    International Nuclear Information System (INIS)

    Yu, Naiping; Xu, Jinlong

    2016-01-01

    Red Midcourse Space Experiment ( MSX ) Sources (RMSs) are regarded as excellent candidates of massive star-forming regions. In order to characterize the chemical properties of massive star formation, we made a systematic study of 87 RMSs in the southern sky, using archival data taken from the Atacama Pathfinder Experiment Telescope Large Area Survey of the Galaxy (ATLASGAL), the Australia Telescope Compact Array, and the Millimetre Astronomy Legacy Team Survey at 90 GHz (MALT90). According to previous multiwavelength observations, our sample could be divided into two groups: massive young stellar objects and H ii regions. Combined with the MALT90 data, we calculated the column densities of N 2 H + , C 2 H, HC 3 N, and HNC and found that they are not much different from previous studies made in other massive star-forming regions. However, their abundances are relatively low compared to infrared dark clouds (IRDCs). The abundances of N 2 H + and HNC in our sample are at least 1 mag lower than those found in IRDCs, indicating chemical depletions in the relatively hot gas. Besides, the fractional abundances of N 2 H + , C 2 H, and HC 3 N seem to decrease as a function of their Lyman continuum fluxes (N L ), indicating that these molecules could be destroyed by UV photons when H ii regions have formed inside. We also find that the C 2 H abundance decreases faster than HC 3 N with respect to N L . The abundance of HNC has a tight correlation with that of N 2 H + , indicating that it may be also preferentially formed in cold gas. We regard our RMSs as being in a relatively late evolutionary stage of massive star formation.

  11. Chemical Evolution of Red MSX Sources in the Southern Sky

    Science.gov (United States)

    Yu, Naiping; Xu, Jinlong

    2016-12-01

    Red Midcourse Space Experiment (MSX) Sources (RMSs) are regarded as excellent candidates of massive star-forming regions. In order to characterize the chemical properties of massive star formation, we made a systematic study of 87 RMSs in the southern sky, using archival data taken from the Atacama Pathfinder Experiment Telescope Large Area Survey of the Galaxy (ATLASGAL), the Australia Telescope Compact Array, and the Millimetre Astronomy Legacy Team Survey at 90 GHz (MALT90). According to previous multiwavelength observations, our sample could be divided into two groups: massive young stellar objects and H II regions. Combined with the MALT90 data, we calculated the column densities of N2H+, C2H, HC3N, and HNC and found that they are not much different from previous studies made in other massive star-forming regions. However, their abundances are relatively low compared to infrared dark clouds (IRDCs). The abundances of N2H+ and HNC in our sample are at least 1 mag lower than those found in IRDCs, indicating chemical depletions in the relatively hot gas. Besides, the fractional abundances of N2H+, C2H, and HC3N seem to decrease as a function of their Lyman continuum fluxes (N L ), indicating that these molecules could be destroyed by UV photons when H II regions have formed inside. We also find that the C2H abundance decreases faster than HC3N with respect to N L . The abundance of HNC has a tight correlation with that of N2H+, indicating that it may be also preferentially formed in cold gas. We regard our RMSs as being in a relatively late evolutionary stage of massive star formation.

  12. CHEMICAL EVOLUTION OF RED MSX SOURCES IN THE SOUTHERN SKY

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Naiping; Xu, Jinlong [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2016-12-20

    Red Midcourse Space Experiment ( MSX ) Sources (RMSs) are regarded as excellent candidates of massive star-forming regions. In order to characterize the chemical properties of massive star formation, we made a systematic study of 87 RMSs in the southern sky, using archival data taken from the Atacama Pathfinder Experiment Telescope Large Area Survey of the Galaxy (ATLASGAL), the Australia Telescope Compact Array, and the Millimetre Astronomy Legacy Team Survey at 90 GHz (MALT90). According to previous multiwavelength observations, our sample could be divided into two groups: massive young stellar objects and H ii regions. Combined with the MALT90 data, we calculated the column densities of N{sub 2}H{sup +}, C{sub 2}H, HC{sub 3}N, and HNC and found that they are not much different from previous studies made in other massive star-forming regions. However, their abundances are relatively low compared to infrared dark clouds (IRDCs). The abundances of N{sub 2}H{sup +} and HNC in our sample are at least 1 mag lower than those found in IRDCs, indicating chemical depletions in the relatively hot gas. Besides, the fractional abundances of N{sub 2}H{sup +}, C{sub 2}H, and HC{sub 3}N seem to decrease as a function of their Lyman continuum fluxes (N {sub L}), indicating that these molecules could be destroyed by UV photons when H ii regions have formed inside. We also find that the C{sub 2}H abundance decreases faster than HC{sub 3}N with respect to N{sub L}. The abundance of HNC has a tight correlation with that of N{sub 2}H{sup +}, indicating that it may be also preferentially formed in cold gas. We regard our RMSs as being in a relatively late evolutionary stage of massive star formation.

  13. H-O isotopic and chemical characteristics of a precipitation-lake water-groundwater system in a desert area

    Science.gov (United States)

    Jin, Ke; Rao, Wenbo; Tan, Hongbing; Song, Yinxian; Yong, Bin; Zheng, Fangwen; Chen, Tangqing; Han, Liangfeng

    2018-04-01

    The recharge mechanism of groundwater in the Badain Jaran Desert, North China has been a focus of research and still disputable in the past two decades. In this study, the chemical and hydrogen (H) and oxygen (O) isotopic characteristics of shallow groundwater, lake water and local precipitation in the Badain Jaran Desert and neighboring areas were investigated to reveal the relationships between various water bodies and the recharge source of shallow groundwater. Isotopic and hydrogeochemical results show that (1) shallow groundwater was associated with local precipitation in the Ayouqi and Yabulai regions, (2) lake water was mainly recharged by groundwater in the desert hinterland, (3) shallow groundwater of the desert hinterland, Yabulai Mountain and Gurinai Grassland had a common recharge source. Shallow groundwater of the desert hinterland had a mean recharge elevation of 1869 m a.s.l. on the basis of the isotope-altitude relationship and thus originated chiefly from lateral infiltration of precipitation in the Yabulai Mountain. It is further concluded that shallow groundwater flowed towards the Gurinai Grassland according to the groundwater table contour map. Along the flow pathway, the H-O isotopic variations were primarily caused by the evaporation effect but chemical variations of shallow groundwater were affected by multiple factors, e.g., evaporation effect, dilution effect of occasional heavy-precipitation and dissolution of aquifer evaporites. Our findings provide new insight into the groundwater cycle and benefit the management of the limited water resources in the arid desert area.

  14. Life from the stars?. [extraterrestrial sources contributing to chemical evolution on Earth

    Science.gov (United States)

    Pendleton, Yvonne J.; Cruikshank, Dale P.

    1994-01-01

    Scientists are now seriously considering the possibility that organic matter from interstellar space could have influenced, or even spurred, the origin of life on Earth. Various aspects of chemical evolution are discussed along with possible extraterrestrial sources responsible for contributing to Earth's life-producing, chemical composition. Specific topics covered include the following: interstellar matter, molecular clouds, asteroid dust, organic molecules in our solar system, interplanetary dust and comets, meteoritic composition, and organic-rich solar-system bodies.

  15. Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

    Science.gov (United States)

    Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, Charles N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

    2012-01-01

    The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

  16. Development of chemical isotope labeling liquid chromatography mass spectrometry for silkworm hemolymph metabolomics

    International Nuclear Information System (INIS)

    Shen, Weifeng; Han, Wei; Li, Yunong; Meng, Zhiqi; Cai, Leiming; Li, Liang

    2016-01-01

    Silkworm (Bombyx mori) is a very useful target insect for evaluation of endocrine disruptor chemicals (EDCs) due to mature breeding techniques, complete endocrine system and broad basic knowledge on developmental biology. Comparative metabolomics of silkworms with and without EDC exposure offers another dimension of studying EDCs. In this work, we report a workflow on metabolomic profiling of silkworm hemolymph based on high-performance chemical isotope labeling (CIL) liquid chromatography mass spectrometry (LC-MS) and demonstrate its application in studying the metabolic changes associated with the pesticide dichlorodiphenyltrichloroethane (DDT) exposure in silkworm. Hemolymph samples were taken from mature silkworms after growing on diet that contained DDT at four different concentrations (1, 0.1, 0.01, 0.001 ppm) as well as on diet without DDT as controls. They were subjected to differential "1"2C-/"1"3C-dansyl labeling of the amine/phenol submetabolome, LC-UV quantification of the total amount of labeled metabolites for sample normalization, and LC-MS detection and relative quantification of individual metabolites in comparative samples. The total concentration of labeled metabolites did not show any significant change between four DDT-treatment groups and one control group. Multivariate statistical analysis of the metabolome data set showed that there was a distinct metabolomic separation between the five groups. Out of the 2044 detected peak pairs, 338 and 1471 metabolites have been putatively identified against the HMDB database and the EML library, respectively. 65 metabolites were identified by the dansyl library searching based on the accurate mass and retention time. Among the 65 identified metabolites, 33 positive metabolites had changes of greater than 1.20-fold or less than 0.83-fold in one or more groups with p-value of smaller than 0.05. Several useful biomarkers including serine, methionine, tryptophan, asymmetric dimethylarginine, N

  17. Development of chemical isotope labeling liquid chromatography mass spectrometry for silkworm hemolymph metabolomics

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Weifeng [Key Laboratory of Detection for Pesticide Residues, Ministry of Agriculture (China); Sericultural Research Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou (China); Han, Wei; Li, Yunong [Department of Chemistry, University of Alberta, Edmonton, Alberta (Canada); Meng, Zhiqi [Sericultural Research Institute, Zhejiang Academy of Agricultural Sciences, Hangzhou (China); Cai, Leiming, E-mail: cailm@mail.zaas.ac.cn [Institute of Quality and Standard for Agro-products, Zhejiang Academy of Agricultural Sciences, Hangzhou (China); Li, Liang, E-mail: Liang.Li@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta (Canada)

    2016-10-26

    Silkworm (Bombyx mori) is a very useful target insect for evaluation of endocrine disruptor chemicals (EDCs) due to mature breeding techniques, complete endocrine system and broad basic knowledge on developmental biology. Comparative metabolomics of silkworms with and without EDC exposure offers another dimension of studying EDCs. In this work, we report a workflow on metabolomic profiling of silkworm hemolymph based on high-performance chemical isotope labeling (CIL) liquid chromatography mass spectrometry (LC-MS) and demonstrate its application in studying the metabolic changes associated with the pesticide dichlorodiphenyltrichloroethane (DDT) exposure in silkworm. Hemolymph samples were taken from mature silkworms after growing on diet that contained DDT at four different concentrations (1, 0.1, 0.01, 0.001 ppm) as well as on diet without DDT as controls. They were subjected to differential {sup 12}C-/{sup 13}C-dansyl labeling of the amine/phenol submetabolome, LC-UV quantification of the total amount of labeled metabolites for sample normalization, and LC-MS detection and relative quantification of individual metabolites in comparative samples. The total concentration of labeled metabolites did not show any significant change between four DDT-treatment groups and one control group. Multivariate statistical analysis of the metabolome data set showed that there was a distinct metabolomic separation between the five groups. Out of the 2044 detected peak pairs, 338 and 1471 metabolites have been putatively identified against the HMDB database and the EML library, respectively. 65 metabolites were identified by the dansyl library searching based on the accurate mass and retention time. Among the 65 identified metabolites, 33 positive metabolites had changes of greater than 1.20-fold or less than 0.83-fold in one or more groups with p-value of smaller than 0.05. Several useful biomarkers including serine, methionine, tryptophan, asymmetric dimethylarginine, N

  18. Temperatures and isotopic evolution of silicic magmas, Taupo Volcanic Zone and Coromandel, New Zealand

    International Nuclear Information System (INIS)

    Blattner, P.; Rui-Zhong, Hu; Graham, I.J.; Houston-Eleftheriadis, C.

    1996-01-01

    A new set of oxygen and strontium isotope data on rhyolitic lavas and ignimbrites of the Taupo Volcanic Zone (TVZ) and the Coromandel Peninsula provides new limits for petrogenetic models. For oxygen isotopes, the rock matrix is frequently altered, so that values for magma need to be phenocryst based. Within TVZ a trend towards more negative delta 1 8 O values for more recent magmas appears likely (average before about 1 Ma and for Coromandel near 8.0 per thousand; after 1 Ma near 7.5 per thousand). This could indicate the gradual removal of supracrustal contaminants from the zones of magma accumulation and extrusion. Similar trends within Coromandel cannot yet be resolved. A generally positive correlation is found for oxygen and strontium isotopes of magmas. Most magmas have a limited range of isotopic values, which then becomes a useful fingerprint (e.g., the Mamaku, Matahina, and Waiotapu Ignimbrites). A narrow range of eruption temperatures of 880 plus or minus 60degC is derived from quartz-plagioclase fractionations of 0.98 plus or minus 0.25 per thousand delta 1 8 O for 15 magmas. Some delta 1 8 O values of quartz and feldspar phenocrysts are sufficiently low to suggest interaction between surface water and magma. However, large negative oxygen isotope anomalies (such as known from Yellowstone), could be no more than partially concealed by the isotopically less depleted meteoric water of New Zealand, and have not yet been found in New Zealand. (author). 45 refs., 3 tabs., 6 figs

  19. A model for osmium isotopic evolution of metallic solids at the core-mantle boundary

    Science.gov (United States)

    Humayun, Munir

    2011-03-01

    Some plumes are thought to originate at the core-mantle boundary, but geochemical evidence of core-mantle interaction is limited to Os isotopes in samples from Hawaii, Gorgona (89 Ma), and Kostomuksha (2.7 Ga). The Os isotopes have been explained by physical entrainment of Earth's liquid outer core into mantle plumes. This model has come into conflict with geophysical estimates of the timing of core formation, high-pressure experimental determinations of the solid metal-liquid metal partition coefficients (D), and the absence of expected 182W anomalies. A new model is proposed where metallic liquid from the outer core is partially trapped in a compacting cumulate pile of Fe-rich nonmetallic precipitates (FeO, FeS, Fe3Si, etc.) at the top of the core and undergoes fractional crystallization precipitating solid metal grains, followed by expulsion of the residual metallic liquid back to the outer core. The Os isotopic composition of the solids and liquids in the cumulate pile is modeled as a function of the residual liquid remaining and the emplacement age using 1 bar D values, with variable amounts of oxygen (0-10 wt %) as the light element. The precipitated solids evolve Os isotope compositions that match the trends for Hawaii (at an emplacement age of 3.5-4.5 Ga; 5%-10% oxygen) and Gorgona (emplacement age < 1.5 Ga; 0%-5% oxygen). The Fe-rich matrix of the cumulate pile dilutes the precipitated solid metal decoupling the Fe/Mn ratio from Os and W isotopes. The advantages to using precipitated solid metal as the Os host include a lower platinum group element and Ni content to the mantle source region relative to excess iron, miniscule anomalies in 182W (<0.1 ɛ), and no effects for Pb isotopes, etc. A gradual thermomechanical erosion of the cumulate pile results in incorporation of this material into the base of the mantle, where mantle plumes subsequently entrain it. Fractional crystallization of metallic liquids within the CMB provides a consistent explanation of

  20. Precambrian continental crustal evolution of Southeastern Sao Paulo state - Brazil: based on isotopic evidences

    International Nuclear Information System (INIS)

    Tassinari, C.C.G.

    1988-01-01

    The isotopic studies on granitic intrusions, orthogneissic rocks and migmatitic terranes in the Southeastern Sao Paulo are presented, indicating the age and the geochemical nature of the continental crust of this area. Approximately 300 Ar, Sr and Pb isotopic age determinations are included in this paper, categorized as to their reliability and significance. Looking for the continental crust growth related to the geological time, at the end of the lower Proterozoic, at least 85% of the continental crust has already accreted and differentiated. (C.G.C.)

  1. Investigation of correlations in some chemical impurities and isotope ratios for nuclear forensic purposes

    International Nuclear Information System (INIS)

    Wallenius, M.; Mayer, K.; Nicholl, A.; Horta, J.

    2002-01-01

    Full text: Institute for Transuranium Elements (ITU) has worked in the area of nuclear forensic science since 1992 when the first seized sample was analysed. From the beginning the analytical tools for seized materials were adapted from safeguards measurements and from materials science. Especially in the view of the origin determination the spectrum of parameters to be taken into account had to be widened. In addition to the development of a comprehensive database on nuclear materials for power reactor fuels, experimental investigations were started to identify characteristic parameters. These systematic investigations comprised the development of methodologies for age determination of Pu and highly enriched uranium, surface roughness determination of UO 2 pellets and n( 18 O)/n( 16 O) measurements in uranium oxides. However, a more profound understanding on the nature of the characteristic chemical impurities and their propagation throughout the entire process appeared necessary in particular for uranium materials. Therefore a systematic research programme was launched in order to better understand which chemical impurities might be considered as characteristic for the origin of the base material. On the other hand some impurities are introduced intentionally during the processing of the material. These impurities might be characteristic for the process used or for the plant where the material was processed. We carried out impurity measurements on uranium ores, on intermediate products (Ammoniumdiuranate or yellow cake) and on (natural) uranium oxides, hence 'vertically' throughout the process in individual facilities. n( 18 O)/n( 16 O) ratio measurements have been proven to provide useful additional information on the geographic origin of the materials. We therefore investigated the n( 18 O)/n( 16 O) isotope ratios in these different compounds, in order to obtain further experimental evidence for a consistent set of materials reportedly originating from the same

  2. Polyamorphic Transformations in Fe-Ni-C Liquids: Implications for Chemical Evolution of Terrestrial Planets: Fe-Ni-C liquid structural change

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Xiaojing [Department of Geology and Geophysics, University of Hawai‘i at Mānoa, Honolulu HI USA; Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu HI USA; Chen, Bin [Hawaii Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu HI USA; Wang, Jianwei [Department of Geology and Geophysics, Center for Computation and Technology, Louisiana State University, Baton Rouge LA USA; Kono, Yoshio [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne IL USA; Zhu, Feng [Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor MI USA

    2017-12-01

    During the formation of the Earth's core, the segregation of metallic liquids from silicate mantle should have left behind evident geochemical imprints on both the mantle and the core. Some distinctive geochemical signatures of the mantle-derived rocks likely own their origin to the metal-silicate differentiation of the primitive Earth, setting our planet apart from undifferentiated meteorites as well as terrestrial planets or moons isotopically and compositionally. Understanding the chemical evolution of terrestrial planetary bodies requires knowledge on properties of both liquid iron alloys and silicates equilibrating under physicochemical conditions pertinent to the deep magma ocean. Here we report experimental and computational results on the pressure-induced structural evolution of iron-nickel liquids alloyed with carbon. Our X-ray diffraction experiments up to 7.3 gigapascals (GPa) demonstrate that Fe-Ni (Fe90Ni10) liquids alloyed with 3 and 5 wt % carbon undergo a polyamorphic liquid structure transition at approximately 5 GPa. Corroborating the experimental observations, our first-principles molecular dynamic calculations reveal that the structural transitions result from the marked prevalence of three-atom face-sharing polyhedral connections in the liquids at >5 GPa. The structure and polyamorphic transitions of liquid iron-nickel-carbon alloys govern their physical and chemical properties and may thus cast fresh light on the chemical evolution of terrestrial planets and moons.

  3. SURFACE AND LIGHTNING SOURCES OF NITROGEN OXIDES OVER THE UNITED STATES: MAGNITUDES, CHEMICAL EVOLUTION, AND OUTFLOW

    Science.gov (United States)

    We use observations from two aircraft during the ICARTT campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of regional sources, chemical evolution...

  4. Galactic chemical evolution in hierarchical formation models - I. Early-type galaxies in the local Universe

    NARCIS (Netherlands)

    Arrigoni, Matías; Trager, Scott C.; Somerville, Rachel S.; Gibson, Brad K.

    We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for

  5. Galactic chemical evolution in hierarchical formation models : I. Early-type galaxies in the local Universe

    NARCIS (Netherlands)

    Arrigoni, Matias; Trager, Scott C.; Somerville, Rachel S.; Gibson, Brad K.

    2010-01-01

    We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for

  6. Investigation of geothermal fields in himalayan range in pakistan using isotope and chemical techniques

    International Nuclear Information System (INIS)

    Ahmad, M.; Sheikh, M.R.; Akram, W.; Tasneem, M.A.; Iqbal, N.; Latif, Z.

    2007-07-01

    /sub 4/-H/sub 2/O) geothermometer indicates equilibrium temperatures around 150 degree C. For the Tato springs, the isotope and chemical geothermometers (except for the K-Mg) agree on equilibrium temperature of about 170-200 degree C. Thermal waters of Kotli are immature having meteoric origin. They are of sodium bicarbonate type. The thermal water seems to be young or significant component of fresh water is mixing. Reservoir temperatures estimated by K-Mg and Na-K-Ca-Mg thermometers have similar range (122-l25 degree C). Geothermometer based on dissolved silica gives reservoir temperature about 100 degree C. (author)

  7. Isotopic and chemical dilution effects on the vibrational relaxation rate of some totally symmetric motions of liquid acetonitrile

    International Nuclear Information System (INIS)

    Marri, E.; Morresi, A.; Paliani, G.; Cataliotti, R.S.; Giorgini, M.G.

    1999-01-01

    The vibrational dephasing of the ν 1 (C-H, C-D stretching) and ν 3 (C-H, C-D bending) symmetric motions of liquid acetonitrile in its light and fully deuterated forms has been studied in the frame of the vibrational time correlation functions obtained as Fourier transforms of the isotropic Raman spectral distributions and interpreted within the Kubo theory. In addition, the experimental isotropic profiles have been analysed within the bandshape approach formulated by analytical Fourier transformation of the Kubo vibrational time correlation functions in order to derive the relaxation parameters in the frequency domain. The effects of the isotopic (CH 3 CN/CD 3 CN and vice versa) and chemical (CCl 4 ) dilution on the bandshapes and on the vibrational relaxation parameters have been studied. It was observed that the decay rate of ν 1 mode is insensitive to the isotopic dilution but varies appreciably with chemical (CCl 4 ) dilution. The vibrational dephasing of ν 3 mode is qualitatively, but not quantitatively, affected in the same way by chemical dilution and shows a slower modulation regime than that exhibited by the stretching mode. Unlikely from the latter, the ν 3 mode results are slightly affected by the isotopic dilution. Phase relaxation mechanisms of these two motions of acetonitrile in the liquid state are proposed on the basis of these data, and a comparison is made with the results earlier published. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  8. Contribution to isotopic and chemical study of the aquifers in the area of Frecheirinha, State of Ceara, Brazil

    International Nuclear Information System (INIS)

    Siqueira, H.B. de; Santiago, M.M.F.

    1982-01-01

    The isotopic and chemical characteristics of the aquifers in the area of Frecheirinha (State of Ceara) have been analyzed. In a area of 3,000 scquare Kilometers three aquifers has been identified. Oxygen-18 measurements show that during the rainy season the piezometric level rises until reaching the surface. Thus the flow-water is a mixture of rainwater with stored under-groundwater. Chemical analysis shows all waters (except for samples 1, 2 and 3) are potable. (L.H.L.L.) [pt

  9. The multifaceted role of amino acids in chemical evolution

    Science.gov (United States)

    Strasdeit, Henry; Fox, Stefan; Dalai, Punam

    We present an overview of recent ideas about α-amino acids on the Hadean / early Archean Earth and Noachian Mars. Pertinent simulation experiments are discussed. Electrical dis-charges in early Earth's bulk, probably non-reducing atmosphere [1, 2] and in volcanic ash-gas clouds [3] are likely to have synthesized amino acids abiotically. In principle, this may have been followed by the synthesis of peptides. Different kinds of laboratory simulations have, however, revealed severe difficulties with the condensation process under presumed prebiotic conditions. It therefore appears that peptides on the early Earth were mainly di-, tri-and tetramers and slightly longer only in the case of glycine homopeptides. But even such short peptides may have shown primitive catalytic activity after complexation of metal ions to form proto-metalloenzymes. L-enantiomeric excesses (L-ee) of meteoritic amino acids were possibly involved in the origin of biohomochirality [4, 5]. This idea also faces some problems, mainly dilution of the amino acids on Earth and a resulting low overall L-ee. However, as yet unknown reactions might exist that are highly enantioselective even under such unfavorable conditions, perhaps by a combination of autocatalysis and inhibition (compare the Soai reaction). Primor-dial volcanic islands are prebiotically interesting locations. At their hot coasts, solid sea salt probably embedded amino acids [6]. Our laboratory experiments showed that further heating of the salt crusts, simulating the vicinity of lava streams, produced pyrroles among other prod-ucts. Pyrroles are building blocks of biomolecules such as bilins, chlorophylls and heme. Thus, an abiotic route from amino acids to the first photoreceptor and electron-transfer molecules might have existed. There is no reason to assume that the chemical evolutionary processes described above were singular events restricted to Earth and Mars. In fact, they might take place even today on terrestrial exoplanets

  10. Using Star Clusters as Tracers of Star Formation and Chemical Evolution: The Chemical Enrichment History of the Large Magellanic Cloud

    Science.gov (United States)

    Chilingarian, Igor V.; Asa’d, Randa

    2018-05-01

    The star formation (SFH) and chemical enrichment (CEH) histories of Local Group galaxies are traditionally studied by analyzing their resolved stellar populations in a form of color–magnitude diagrams obtained with the Hubble Space Telescope. Star clusters can be studied in integrated light using ground-based telescopes to much larger distances. They represent snapshots of the chemical evolution of their host galaxy at different ages. Here we present a simple theoretical framework for the chemical evolution based on the instantaneous recycling approximation (IRA) model. We infer a CEH from an SFH and vice versa using observational data. We also present a more advanced model for the evolution of individual chemical elements that takes into account the contribution of supernovae type Ia. We demonstrate that ages, iron, and α-element abundances of 15 star clusters derived from the fitting of their integrated optical spectra reliably trace the CEH of the Large Magellanic Cloud obtained from resolved stellar populations in the age range 40 Myr age–metallicity relation. Moreover, the present-day total gas mass of the LMC estimated by the IRA model (6.2× {10}8 {M}ȯ ) matches within uncertainties the observed H I mass corrected for the presence of molecular gas (5.8+/- 0.5× {10}8 {M}ȯ ). We briefly discuss how our approach can be used to study SFHs of galaxies as distant as 10 Mpc at the level of detail that is currently available only in a handful of nearby Milky Way satellites. .

  11. Reconnaissance isotopic investigations in the Namaqua mobile belt and implications for proterozoic crustal evolution - Namaqualand geotraverse

    International Nuclear Information System (INIS)

    Barton, E.S.

    1983-01-01

    Fourteen rock units in the western portion of the Namaqua mobile belt were investigated by some or all of the following isotopic methods: Rb-Sr, Pb-Pb, Th-Pb total-rock and Rb-Sr mineral age measurements. Two major tectogenetic events are recongnised. The early Orange River event is represented by the emplacement and metamorphism of the volcanic rocks of the Haib Subgroup and the emplacement of granitoids of the Vioolsdrif and Gladkop suites in the regions of the Richtersveld Province and the Steinkopf domain. The later Namaqua event is represented mainly by extensive granitoid emplacement and high-grade granulite facies metamorphism in the Okiep Copper District, with minor granitoid and dyke emplacement taking place in the Steinkopf domain. The polymetamorphism associated with these tectonic events had far-reaching effects in the form of long continued isotopic resetting of rock and mineral systems. In the instances where the regression of the total-rock isotopic data define errorchron results, geological disturbance is inferred. The Sr-isotopic results indicate substrantial crustal reworking and two periods of mantle differentiation producing continental crust at approximately 2 000 and approximately 1 200 Ma ago. The Pb-isotopic data for these rocks indicate μ 2 values for the source regions that are compatible with crustal reworking for the felsic rocks or a significant amount of crustal recycling into the mantle for the mafic rocks. On this basis a magmatic arc environment is envisaged for the rocks generated during the Orange River event. The deformation fabrics associated with the Orange River and Namaqua tectogenetic episodes are dated by the time of emplacement of syn- and post-tectonic granitic rocks. The regional fabric observed in the Steinkopf domain and in the Okiep Copper District was not synchronously developed

  12. Nitrate source apportionment using a combined dual isotope, chemical and bacterial property, and Bayesian model approach in river systems

    Science.gov (United States)

    Xia, Yongqiu; Li, Yuefei; Zhang, Xinyu; Yan, Xiaoyuan

    2017-01-01

    Nitrate (NO3-) pollution is a serious problem worldwide, particularly in countries with intensive agricultural and population activities. Previous studies have used δ15N-NO3- and δ18O-NO3- to determine the NO3- sources in rivers. However, this approach is subject to substantial uncertainties and limitations because of the numerous NO3- sources, the wide isotopic ranges, and the existing isotopic fractionations. In this study, we outline a combined procedure for improving the determination of NO3- sources in a paddy agriculture-urban gradient watershed in eastern China. First, the main sources of NO3- in the Qinhuai River were examined by the dual-isotope biplot approach, in which we narrowed the isotope ranges using site-specific isotopic results. Next, the bacterial groups and chemical properties of the river water were analyzed to verify these sources. Finally, we introduced a Bayesian model to apportion the spatiotemporal variations of the NO3- sources. Denitrification was first incorporated into the Bayesian model because denitrification plays an important role in the nitrogen pathway. The results showed that fertilizer contributed large amounts of NO3- to the surface water in traditional agricultural regions, whereas manure effluents were the dominant NO3- source in intensified agricultural regions, especially during the wet seasons. Sewage effluents were important in all three land uses and exhibited great differences between the dry season and the wet season. This combined analysis quantitatively delineates the proportion of NO3- sources from paddy agriculture to urban river water for both dry and wet seasons and incorporates isotopic fractionation and uncertainties in the source compositions.

  13. ISOTOPE-DILUTION AMMONIA CHEMICAL-IONIZATION MASS FRAGMENTOGRAPHIC ANALYSIS OF URINARY 3-O-METHYLATED CATECHOLAMINE METABOLITES - RAPID SAMPLE CLEANUP BY DERIVATIZATION AND EXTRACTION OF LYOPHILIZED SAMPLES

    NARCIS (Netherlands)

    KEMA, IP; MEIBORG, G; NAGEL, GT; STOB, GJ; MUSKIET, FAJ

    1993-01-01

    We developed a method for simultaneous quantification of the urinary 3-O-methylated catecholamine metabolites 3-methoxytyramine, normetanephrine and metanephrine by stable isotope-dilution ammonia chemical ionization mass fragmentography. Prepurification of lyophilized samples was done by

  14. Structural and chemical evolution in neutron irradiated and helium-injected ferritic ODS PM2000 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hee Joon [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Edwards, Dan J., E-mail: dan.edwards@pnnl.gov [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Kurtz, Richard J. [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Yamamoto, Takuya; Wu, Yuan [Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106 (United States); Odette, G. Robert [Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106 (United States); Materials Department, University of California, Santa Barbara, CA 93106 (United States)

    2017-02-15

    An investigation of the influence of helium on damage evolution under neutron irradiation of an 11 at% Al, 19 at% Cr ODS ferritic PM2000 alloy was carried out in the High Flux Isotope Reactor (HFIR) using a novel in situ helium injection (ISHI) technique. Helium was injected into adjacent TEM discs from thermal neutron {sup 58}Ni(n{sub th},γ) {sup 59}Ni(n{sub th},α) reactions in a thin NiAl layer. The PM2000 undergoes concurrent displacement damage from the high-energy neutrons. The ISHI technique allows direct comparisons of regions with and without high concentrations of helium since only the side coated with the NiAl experiences helium injection. The corresponding microstructural and microchemical evolutions were characterized using both conventional and scanning transmission electron microscopy techniques. The evolutions observed include formation of dislocation loops and associated helium bubbles, precipitation of a variety of phases, amorphization of the Al{sub 2}YO{sub 3} oxides (which also variously contained internal voids), and several manifestations of solute segregation. Notably, high concentrations of helium had a significant effect on many of these diverse phenomena. These results on PM2000 are compared and contrasted to the evolution of so-called nanostructured ferritic alloys (NFA).

  15. Reassessment of the origin of the Dun Mountain Ophiolite, New Zealand : Nd-isotopic and geochemical evolution of magma suites

    International Nuclear Information System (INIS)

    Sivell, W.J.; McCulloch, M.T.

    2000-01-01

    Magmatic suites with contrasting isotopic and geochemical compositions, sequentially emplaced in different tectonic regimes, comprise the Dun Mountain Ophiolite Belt (DMOB), New Zealand. At D'Urville Island, the northernmost exposure of the DMOB, earliest erupted (stage 1) pillow basalts ε Nd (T) = +6.3 to +7.5, and are incompatible element enriched, like basalts from geochemically anomalous ridge segments. Overlying stage 2 basalts (sheeted flows) show a narrow range of ε Nd (T) = +8.3 + or -0.2, with chemical characteristics of depleted backarc basin basalts. These rocks are intruded by mafic to silicic stage 3 magmas, which have high uniform initial 143 Nd/ 144 Nd ratios (ε Nd (T) = +9.3 + or -0.2) over a wide range of 147 Sm/ 144 Nd values (yielding a precise Early Permian Nd-isotope age of 278 ± 4 Ma (MSWD = 0.48)). Stage 3 magmas show pronounced subduction-related geochemical signatures similar to island arc tholeiites (IAT) from immature arcs. They are closely analogous to some (boninite)-IAT magmas which characterise 'infant arc' eruptive activity in forearc basins of present-day Western Pacific island arc systems. A wide variety of stage 3 magma compositions, ranging from near-primary basaltic dikes (Mg = 74) to extremely fractionated silicic plagiogranites with uniformly very depleted isotopic ratios, is consistent with slow spreading rates which gave rise to polybaric, closed-system fractionation of magmas and periodic chamber abandonment. Some stage 3 rocks with SiO 2 levels in the andesite range have low-TiO 2 contents and high Mg, and may be fractionated equivalents of boninites. High ε Nd (T) values of stage 3 magmas indicate a lack of subducted sediment with inherited crustal residence signatures, and reflect the extent of supra-subduction zone (SSZ) mantle wedge depletion. DMOB stage 3 magmas may represent foreac magmatism that was the precursor to normal subduction-related volcanism established by c. 265 Ma in the Brook Street Arc and derived

  16. The evolution of plant chemical defence - new roles for hydroxynitrile glucosides in Lotus japonicus

    DEFF Research Database (Denmark)

    Knudsen, Camilla

    Plants are sessile organisms well-known to produce a vast array of chemical compounds of which many are used in chemical defence against herbivores and pathogens. The biosynthesis of these plant chemical defence compounds poses a considerable risk of self-toxicity for the plant itself. Several...... on hydroxynitrile glucoside metabolism in the legume model plant Lotus japonicus. Lotus japonicus produces both cyanogenic and non-cyanogenic hydroxynitrile glucosides as chemical defence compounds. The cyanogenic glucosides linamarin and lotaustralin are stored in the cell vacuole as inactive glycosides and, upon...... function and evolution. Further, it contributes to our understanding of the formation and role of biosynthetic gene clusters in plant chemical defence. The bifurcation in hydroxynitrile glucoside biosynthesis and catabolism observed in Lotus japonicus makes it a very suitable model system to study...

  17. The Role of Sexual Selection in the Evolution of Chemical Signals in Insects

    Directory of Open Access Journals (Sweden)

    Sandra Steiger

    2014-06-01

    Full Text Available Chemical communication is the most ancient and widespread form of communication. Yet we are only beginning to grasp the complexity of chemical signals and the role they play in sexual selection. Focusing on insects, we review here the recent progress in the field of olfactory-based sexual selection. We will show that there is mounting empirical evidence that sexual selection affects the evolution of chemical traits, but form and strength of selection differ between species. Studies indicate that some chemical signals are expressed in relation to an individual’s condition and depend, for example, on age, immunocompetence, fertility, body size or degree of inbreeding. Males or females might benefit by choosing based on those traits, gaining resources or “good genes”. Other chemical traits appear to reliably reflect an individual’s underlying genotype and are suitable to choose a mating partner that matches best the own genotype.

  18. Determination of isotope ratio of elements by mass distribution in molecules of varied chemical compounds

    International Nuclear Information System (INIS)

    Gladkikh, I.S.; Babichev, A.P.

    1999-01-01

    The procedure and program for calculation of isotope ratio of elements involving in the compound being studied using data of mass spectrometry were elaborated. The methods developed for the O 2 , SiH 4 , Cd(CH 3 ) 2 molecules were demonstrated for the illustration. The results of calculation provide support for the efficiency of the program and satisfactory reliability of the results during calculation of the isotope and complex compound concentrations. The program may be used for the estimation of the degree of nonequilibrium isotope distributions, it may indicate on the errors of the mass spectroscopy results [ru

  19. Contributions of type II and Ib/c supernovae to Galactic chemical evolution

    International Nuclear Information System (INIS)

    Sahijpal Sandeep

    2014-01-01

    Type II and Ib/c supernovae (SNe II and Ib/c) have made major stellar nucleosynthetic contributions to the inventories of stable nuclides during chemical evolution of the Galaxy. A case study is performed here with the help of recently developed numerical simulations of Galactic chemical evolution in the solar neighborhood to understand the contributions of SNe II and Ib/c by comparing the stellar nucleosynthetic yields obtained by two leading groups in this field. These stellar nucleosynthetic yields differ in terms of their treatment of stellar evolution and nucleosynthesis. The formulation describing Galactic chemical evolution is developed with the recently revised solar metallicity of ∼0.014. Furthermore, the recent nucleosynthetic yields of stellar models based on the revised solar metallicity are also used. The analysis suggests that it could be difficult to explain, in a self-consistent manner, the various features associated with the elemental evolutionary trends over Galactic timescales by any single adopted stellar nucleosynthetic model that incorporates SNe II and Ib/c

  20. Chemical evolution and the origin of life: cumulative keyword subject index 1970-1986

    Science.gov (United States)

    Roy, A. C.; Powers, J. V.; Rummel, J. D. (Principal Investigator)

    1990-01-01

    This cumulative subject index encompasses the subject indexes of the bibliographies on Chemical Evolution and the Origin of Life that were first published in 1970 and have continued through publication of the 1986 bibliography supplement. Early bibliographies focused on experimental and theoretical material dealing directly with the concepts of chemical evolution and the origin of life, excluding the broader areas of exobiology, biological evolution, and geochemistry. In recent years, these broader subject areas have also been incorporated as they appear in literature searches relating to chemical evolution and the origin of life, although direct attempts have not been made to compile all of the citations in these broad areas. The keyword subject indexes have also undergone an analogous change in scope. Compilers of earlier bibliographies used the most specific term available in producing the subject index. Compilers of recent bibliographies have used a number of broad terms relating to the overall subject content of each citation and specific terms where appropriate. The subject indexes of these 17 bibliographies have, in general, been cumulatively compiled exactly as they originally appeared. However, some changes have been made in an attempt to correct errors, combine terms, and provide more meaningful terms.

  1. Isotopic evolution of the protoplanetary disk and the building blocks of Earth and the Moon

    DEFF Research Database (Denmark)

    Schiller, Martin; Bizzarro, Martin; Fernandes, Vera Assis

    2018-01-01

    Nucleosynthetic isotope variability among Solar System objects is often used to probe the genetic relationship between meteorite groups and the rocky planets (Mercury, Venus, Earth and Mars), which, in turn, may provide insights into the building blocks of the Earth-Moon system. Using this approach......, it has been inferred that no primitive meteorite matches the terrestrial composition and the protoplanetary disk material from which Earth and the Moon accreted is therefore largely unconstrained. This conclusion, however, is based on the assumption that the observed nucleosynthetic variability of inner...... into the thermally processed inner protoplanetary disk associated with the accretion of mass to the proto-Sun. The identical calcium isotope composition of Earth and the Moon reported here is a prediction of our model if the Moon-forming impact involved protoplanets or precursors that completed their accretion near...

  2. Magma source evolution beneath the Caribbean oceanic plateau: New insights from elemental and Sr-Nd-Pb-Hf isotopic studies of ODP Leg 165, Site 1001 basalts

    Science.gov (United States)

    Kerr, A. C.; Pearson, G.; Nowell, G.

    2008-12-01

    Ocean Drilling Project Leg 165 sampled 38m of the basaltic basement of the Caribbean plate at Site 1001 on the Hess Escarpment. The recovered section consists of 12 basaltic flow units which yield a weighted mean Ar-Ar age of 80.9±0.9 Ma (Sinton et al., 2000). The basalts (6.4-8.5 wt.% MgO) are remarkably homogeneous in composition and are more depleted in incompatible trace elements than N-MORB. Markedly, depleted initial radiogenic isotope ratios reveal a long-term history of depletion. Although the Site 1001 basalts are superficially similar to N-MORB, radiogenic isotopes in conjunction with incompatible trace element ratios show that the basalts have more similarity to the depleted basalts and komatiites of Gorgona Island. This chemical composition strongly implies that the Site 1001 basalts are derived from a depleted mantle plume component and not from depleted ambient upper mantle. Therefore the Site 1001 basalts are, both compositionally and tectonically, a constituent part of the Caribbean oceanic plateau. Mantle melt modelling suggests that the Site 1001 lavas have a composition which is consistent with second-stage melting of compositionally heterogeneous mantle plume source material which had already been melted, most likely to form the 90Ma basalts of the plateau. The prolonged residence (>10m.y.) of residual mantle plume source material below the region, confirms computational model predictions and places significant constraints on tectonic models of Caribbean evolution in the late Cretaceous, and the consequent environmental impact of oceanic plateau volcanism. Reference Sinton, C.W., et al., 2000. Geochronology and petrology of the igneous basement at the lower Nicaraguan Rise, Site 1001. Proceedings of the Ocean Drilling Program, Scientific Results. Leg 165. pp. 233-236.

  3. Evolution of Single Particle and Collective properties in the Neutron-Rich Mg Isotopes

    CERN Multimedia

    Reiter, P; Wiens, A; Fitting, J; Lauer, M; Van duppen, P L E; Finke, F

    2002-01-01

    We propose to study the single particle and collective properties of the neutron-rich Mg isotopes in transfer reactions and Coulomb excitation using REX-ISOLDE and MINIBALL. From the Coulomb excitation measurement precise and largely model independent B( E2 ; 0$^{+}_{g.s.}\\rightarrow$ 2$^{+}_{1}$ ) will be determined for the even-even isotopes. For the odd isotopes the distribution of the E2 strength over a few low-lying states will be measured. The sign of the M1/E2 mixing ratio, extracted from angular distributions, is characteristic of the sign of the deformation, as is the resulting level scheme. The neutron-pickup channel in the transfer reactions will allow for a determination of the single particle properties (spin, parity, spectroscopic factors) of these nuclei. This information will give new insights in changes of nuclear structure in the vicinity of the island of deformation around $^{32}$Mg. A total of 24 shifts of REX beam time is requested.

  4. Evolution of nuclear structure in neutron-rich odd-Zn isotopes and isomers

    Directory of Open Access Journals (Sweden)

    C. Wraith

    2017-08-01

    Full Text Available Collinear laser spectroscopy was performed on Zn (Z=30 isotopes at ISOLDE, CERN. The study of hyperfine spectra of nuclei across the Zn isotopic chain, N=33–49, allowed the measurement of nuclear spins for the ground and isomeric states in odd-A neutron-rich nuclei up to N=50. Exactly one long-lived (>10 ms isomeric state has been established in each 69–79Zn isotope. The nuclear magnetic dipole moments and spectroscopic quadrupole moments are well reproduced by large-scale shell–model calculations in the f5pg9 and fpg9d5 model spaces, thus establishing the dominant term in their wave function. The magnetic moment of the intruder Iπ=1/2+ isomer in 79Zn is reproduced only if the νs1/2 orbital is added to the valence space, as realized in the recently developed PFSDG-U interaction. The spin and moments of the low-lying isomeric state in 73Zn suggest a strong onset of deformation at N=43, while the progression towards 79Zn points to the stability of the Z=28 and N=50 shell gaps, supporting the magicity of 78Ni.

  5. Isotope and chemical techniques in assessing groundwater contamination from Metro Manila landfill

    International Nuclear Information System (INIS)

    Castaneda, Soledad S.; Almoneda, Rosalina V.; Ascano, Luz; Del Castillo, Lorena A.; Fernandez, Lourdes G.; Sucgang, Raymond J.; Iblan, Cynthia L.; Baui, Daniel G.

    2007-01-01

    The first objective of the investigations is establishing benchmark isotopic characteristics of water sources and baseline concentrations of main environmental parameters related to contamination from the landfill. Water samples were collected from the production wells and surface water in the municipalities in proximity of the landfill, in Rodriguez and in San Mateo. Stable isotope characterization of the deep groundwater and rivers shows isotopic values clustering along the LMWL with ae 18 O ranging from -7.5 promille to -6.5 promille and ae 2 H ranging from - 53.59 promille to -42.91. The shallow groundwater are more isotopically enriched trending towards the evaporation line, with mean ae 18 O and aeD values of -6.46 promille and -44.14 promille, respectively. The mean isotopic signatures of surface water, with mean ae 18 O of -7.19 promille and deep groundwater, with mean ae 18 O of -6.67 promille, in Rodriguez are significantly distinct. San Mateo groundwater appear to be more isotopically enriched, indicating recharge different from that of Rodriguez groundwater. Leachate from the landfill exhibits a distinct isotopic composition from the freshwaters, with ae 18 O and aeD values of -5.58 promille and -31.66 promille. The significant differences in the isotopic signatures of the different water sources in the study area would facilitate detection of contamination from leachate run-off to the surface water, and eventually, to the groundwater. Trace metals in the water samples collected, generally, were below the regulatory limits for drinking water and surface water. Results of elemental determination in the sediment samples obtained from rivers showed that aside from the major crustal elements, Zn, Cu, and Ni were also present in significant amount. (author)

  6. Limited Influence of Oxygen on the Evolution of Chemical Diversity in Metabolic Networks

    Directory of Open Access Journals (Sweden)

    Kazuhiro Takemoto

    2013-10-01

    Full Text Available Oxygen is thought to promote species and biomolecule diversity. Previous studies have suggested that oxygen expands metabolic networks by acquiring metabolites with different chemical properties (higher hydrophobicity, for example. However, such conclusions are typically based on biased evaluation, and are therefore non-conclusive. Thus, we re-investigated the effect of oxygen on metabolic evolution using a phylogenetic comparative method and metadata analysis to reduce the bias as much as possible. Notably, we found no difference in metabolic network expansion between aerobes and anaerobes when evaluating phylogenetic relationships. Furthermore, we showed that previous studies have overestimated or underestimated the degrees of differences in the chemical properties (e.g., hydrophobicity between oxic and anoxic metabolites in metabolic networks of unicellular organisms; however, such overestimation was not observed when considering the metabolic networks of multicellular organisms. These findings indicate that the contribution of oxygen to increased chemical diversity in metabolic networks is lower than previously thought; rather, phylogenetic signals and cell-cell communication result in increased chemical diversity. However, this conclusion does not contradict the effect of oxygen on metabolic evolution; instead, it provides a deeper understanding of how oxygen contributes to metabolic evolution despite several limitations in data analysis methods.

  7. SIMS chemical and isotopic analysis of impact features from LDEF experiments AO187-1 and AO187-2

    Science.gov (United States)

    Stadermann, Frank J.; Amari, Sachiko; Foote, John; Swan, Pat; Walker, Robert M.; Zinner, Ernst

    1995-01-01

    Previous secondary ion mass spectrometry (SIMS) studies of extended impact features from LDEF capture cell experiment AO187-2 showed that it is possible to distinguish natural and man-made particle impacts based on the chemical composition of projectile residues. The same measurement technique has now been applied to specially prepared gold target impacts from experiment AO187-1 in order to identify the origins of projectiles that left deposits too thin to be analyzed by conventional energy-dispersive x-ray (EDX) spectroscopy. The results indicate that SIMS may be the method of choice for the analysis of impact deposits on a variety of sample surfaces. SIMS was also used to determine the isotopic compositions of impact residues from several natural projectiles. Within the precision of the measurements all analyzed residues show isotopically normal compositions.

  8. The chemical composition of red giants in 47 Tucanae. II. Magnesium isotopes and pollution scenarios

    Science.gov (United States)

    Thygesen, A. O.; Sbordone, L.; Ludwig, H.-G.; Ventura, P.; Yong, D.; Collet, R.; Christlieb, N.; Melendez, J.; Zaggia, S.

    2016-04-01

    Context. The phenomenon of multiple populations in globular clusters is still far from understood, with several proposed mechanisms to explain the observed behaviour. The study of elemental and isotopic abundance patterns are crucial for investigating the differences among candidate pollution mechanisms. Aims: We derive magnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC 104) to provide new, detailed information about the nucleosynthesis that has occurred within the cluster. For the first time, the impact of 3D model stellar atmospheres on the derived Mg isotopic ratios is investigated. Methods: Using both tailored 1D atmospheric models and 3D hydrodynamical models, we derive magnesium isotopic ratios from four features of MgH near 5135 Å in 13 giants near the tip of the red giant branch, using high signal-to-noise, high-resolution spectra. Results: We derive the magnesium isotopic ratios for all stars and find no significant offset of the isotopic distribution between the pristine and the polluted populations. Furthermore, we do not detect any statistically significant differences in the spread in the Mg isotopes in either population. No trends were found between the Mg isotopes and [Al/Fe]. The inclusion of 3D atmospheres has a significant impact on the derived 25Mg/24Mg ratio, increasing it by a factor of up to 2.5, compared to 1D. The 26Mg/24Mg ratio, on the other hand, essentially remains unchanged. Conclusions: We confirm the results seen from other globular clusters, where no strong variation in the isotopic ratios is observed between stellar populations, for observed ranges in [Al/Fe]. We see no evidence for any significant activation of the Mg-Al burning chain. The use of 3D atmospheres causes an increase of a factor of up to 2.5 in the fraction of 25Mg, resolving part of the discrepancy between the observed isotopic fraction and the predictions from pollution models. Based on observations made with the ESO Very Large Telescope

  9. Variations of geothermometry and chemical-isotopic compositions of hot spring fluids in the Rehai geothermal field, southwestern China

    Science.gov (United States)

    Du, Jianguo; Liu, Congqiang; Fu, Bihong; Ninomiya, Yoshiki; Zhang, Youlian; Wang, Chuanyuan; Wang, Hualiu; Sun, Zigang

    2005-04-01

    Geothermal variations, origins of carbon-bearing components and reservoir temperatures in the Rehai geothermal field (RGF) of Tengchong volcanic area, Yunnan Province, southwestern China, are discussed on the basis of carbon isotope compositions, combined with helium isotope ratios and geothermal data from 1973 to 2000. δ 13C values of CO 2, CH 4, HCO 3-, CO 3= and travertine in the hot springs range from -7.6‰ to -1.18‰, -56.9‰ to -19.48‰, -6.7‰ to -4.2‰, -6.4‰ to -4.2‰ and -27.1‰ to +0.6‰, respectively. The carbon dioxide probably has a mantle/magma origin, but CH 4 and He have multiple origins. HCO 3- and CO 3= in RGF thermal fluids are predominantly derived from igneous carbon dioxide, but other ions originate from rocks through which the fluids circulate. The 13C values of CO 2, HCO 3- (aq) and CO 3= (aq) illustrate that isotopic equilibriums between CO 2 and HCO 3- (aq), and CO 3= (aq) and between DIC and travertine were not achieved, and no carbon isotope fractionation between HCO 3- (aq) and CO 3= (aq) of the hot springs in RGF was found. Using various geothermometers, temperatures of the geothermal reservoirs are estimated in a wide range from 69 °C to 450 °C that fluctuated from time to time. The best estimate of subsurface reservoir temperature may be 250-300 °C. Contributions of mantle fluids and shallow crust fluids in Rehai geothermal field varied with time, which resulted in variations of chemical and isotopic compositions and reservoir temperatures.

  10. Nitrogen and triple oxygen isotopes in near-road air samples using chemical conversion and thermal decomposition.

    Science.gov (United States)

    Smirnoff, Anna; Savard, Martine M; Vet, Robert; Simard, Marie-Christine

    2012-12-15

    The determination of triple oxygen (δ(18)O and δ(17)O) and nitrogen isotopes (δ(15)N) is important when investigating the sources and atmospheric paths of nitrate and nitrite. To fully understand the atmospheric contribution into the terrestrial nitrogen cycle, it is crucial to determine the δ(15)N values of oxidised and reduced nitrogen species in precipitation and dry deposition. In an attempt to further develop non-biotic methods and avoid expensive modifications of the gas-equilibration system, we have combined and modified sample preparation procedures and analytical setups used by other researchers. We first chemically converted NO(3)(-) and NH(4)(+) into NO(2)(-) and then into N(2)O. Subsequently, the resulting gas was decomposed into N(2) and O(2) and analyzed by isotope ratio mass spectrometry (IRMS) using a pre-concentration system equipped with a gold reduction furnace. The δ(17)O, δ(18)O and δ(15)N values of nitrate and nitrite samples were acquired simultaneously in one run using a single analytical system. Most importantly, the entire spectrum of δ(17)O, δ(18)O and/or δ(15)N values was determined from atmospheric nitrate, nitric oxide, ammonia and ammonium. The obtained isotopic values for air and precipitation samples were in good agreement with those from previous studies. We have further advanced chemical approaches to sample preparation and isotope analyses of nitrogen-bearing compounds. The proposed methods are inexpensive and easily adaptable to a wide range of laboratory conditions. This will substantially contribute to further studies on sources and pathways of nitrate, nitrite and ammonium in terrestrial nitrogen cycling. Copyright © 2012 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.

  11. No oxygen isotope exchange between water and APS-sulfate at surface temperature: Evidence from quantum chemical modeling and triple-oxygen isotope experiments

    Science.gov (United States)

    Kohl, Issaku E.; Asatryan, Rubik; Bao, Huiming

    2012-10-01

    In both laboratory experiments and natural environments where microbial dissimilatory sulfate reduction (MDSR) occurs in a closed system, the δ34S ((34S/32S)sample/(34S/32S)standard - 1) for dissolved SO42- has been found to follow a typical Rayleigh-Distillation path. In contrast, the corresponding δ18O ((18O/16O)sample/(18O/16O)standard) - 1) is seen to plateau with an apparent enrichment of between 23‰ and 29‰ relative to that of ambient water under surface conditions. This apparent steady-state in the observed difference between δ18O and δ18OO can be attributed to any of these three steps: (1) the formation of adenosine-5'-phosphosulfate (APS) from ATP and SO42-, (2) oxygen exchange between sulfite (or other downstream sulfoxy-anions) and water later in the MDSR reaction chain and its back reaction to APS and sulfate, and (3) the re-oxidation of produced H2S or precursor sulfoxy-anions to sulfate in environments containing Fe(III) or O2. This study examines the first step as a potential pathway for water oxygen incorporation into sulfate. We examined the structures and process of APS formation using B3LYP/6-31G(d,p) hybrid density functional theory, implemented in the Gaussian-03 program suite, to predict the potential for oxygen exchange. We conducted a set of in vitro, enzyme-catalyzed, APS formation experiments (with no further reduction to sulfite) to determine the degree of oxygen isotope exchange between the APS-sulfate and water. Triple-oxygen-isotope labeled water was used in the reactor solutions to monitor oxygen isotope exchange between water and APS sulfate. The formation and hydrolysis of APS were identified as potential steps for oxygen exchange with water to occur. Quantum chemical modeling indicates that the combination of sulfate with ATP has effects on bond strength and symmetry of the sulfate. However, these small effects impart little influence on the integrity of the SO42- tetrahedron due to the high activation energy required for

  12. Evolution of the Ar isotopic chain: the N=28 shell gap south of {sup 48}Ca

    Energy Technology Data Exchange (ETDEWEB)

    Mengoni, D., E-mail: Daniele.Mengoni@uws.ac.u [Dipartimento di Fisica dell' Universita and INFN Sezione di Padova, Padova (Italy); Valiente-Dobon, J.J. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy); Gadea, A. [Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia (Spain); Lenzi, S.M.; Lunardi, S. [Dipartimento di Fisica dell' Universita and INFN Sezione di Padova, Padova (Italy); Broda, R. [Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Dewald, A.; Pissulla, T. [Institut fuer Kernphysik der Universtaet zu Koeln, Koeln (Germany); Angus, L. [School of Engineering and Science, University of Paisley, Paisley, Scotland (United Kingdom); Aydin, S.; Bazzacco, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova (Italy); Benzoni, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano (Italy); Bizzeti, P.G.; Bizzeti-Sona, A.M. [Dipartimento di Fisica dell' Universita and INFN Sezione di Firenze, Firenze (Italy); Corradi, L. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy); Crespi, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Milano (Italy); Angelis, G. de [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy); Farnea, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova (Italy); Fioretto, E. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro (Italy); Goergen, A. [CEA Saclay, Daphnia/SphN, Gif-sur-Yvette Cedex (France)

    2010-03-01

    The lifetimes of the first excited states of the Z = 18 {sup 44}Ar and {sup 46}Ar isotopes have been determined using a novel technique that combines the Recoil Distance Doppler Shift method with the CLARA-PRISMA spectrometers for Multinucleon Transfer Reactions. The B(E2) values extracted for the 2{sup +}->0{sup +} transitions in both nuclei, as well as for higher excites states in {sup 44}Ar, are discussed and compared with the available experimental results and with the new large-scale shell-model calculations.

  13. Chromium stable isotope systematic – implications for the redox evolution of the earth

    DEFF Research Database (Denmark)

    Døssing, Lasse Nørbye

    and thus indicate the presence of oxidizing redox species. To track paleo-redox processes deep in the Earth’s history, a number of ancient soil horizons (e.g. the Drakenstein and Nsuze paleosols) formed ~2.2 and ~3.0 billion years ago have been analyzed. These horizons document similar behavior of Cr...... isotopes as modern soil profiles and indicate that oxidative weathering in the terrestrial environment started well before and after the Great Oxidation Event ~2.3 billion years ago. The signals of oxidative weathering on land are traceable in contemporaneous marine sediments such as Banded Iron Formations...

  14. Chemical Evolution of Interstellar Methanol Ice Analogs upon Ultraviolet Irradiation: The Role of the Substrate

    Science.gov (United States)

    Ciaravella, A.; Jiménez-Escobar, A.; Cosentino, G.; Cecchi-Pestellini, C.; Peres, G.; Candia, R.; Collura, A.; Barbera, M.; Di Cicca, G.; Varisco, S.; Venezia, A. M.

    2018-05-01

    An important issue in the chemistry of interstellar ices is the role of dust materials. In this work, we study the effect of an amorphous water-rich magnesium silicate deposited onto ZnSe windows on the chemical evolution of ultraviolet-irradiated methanol ices. For comparison, we also irradiate similar ices deposited onto bare ZnSe windows. Silicates are produced at relatively low temperatures exploiting a sol–gel technique. The chemical composition of the synthesized material reflects the forsterite stoichiometry. Si–OH groups and magnesium carbonates are incorporated during the process. The results show that the substrate material does affect the chemical evolution of the ice. In particular, the CO2/CO ratio within the ice is larger for methanol ices deposited onto the silicate substrate as a result of concurrent effects: the photolysis of carbonates present in the adopted substrate as a source of CO2, CO, and carbon and oxygen atoms; reactions of water molecules and hydroxyl radicals released from the substrate with the CO formed in the ice by the photolysis of the methanol ice; and changes in the structure and energy of the silicate surface by ultraviolet irradiation, leading to more favorable conditions for chemical reactions or catalysis at the grain surface. The results of our experiments allow such chemical effects contributed by the various substrate material components to be disentangled.

  15. The mineralogic evolution of the Martian surface through time: Implications from chemical reaction path modeling studies

    Science.gov (United States)

    Plumlee, G. S.; Ridley, W. I.; Debraal, J. D.; Reed, M. H.

    1993-01-01

    Chemical reaction path calculations were used to model the minerals that might have formed at or near the Martian surface as a result of volcano or meteorite impact driven hydrothermal systems; weathering at the Martian surface during an early warm, wet climate; and near-zero or sub-zero C brine-regolith reactions in the current cold climate. Although the chemical reaction path calculations carried out do not define the exact mineralogical evolution of the Martian surface over time, they do place valuable geochemical constraints on the types of minerals that formed from an aqueous phase under various surficial and geochemically complex conditions.

  16. Abundance anomalies in RGB stars as probes of galactic chemical evolution

    Science.gov (United States)

    Charbonnel, C.; Palacios, A.

    During the last two decades, extensive spectroscopic studies have revealed chemical abundance anomalies exhibited by low mass RGB stars which bring a new light on some important aspects of stellar nucleosynthesis and chemical evolution. We underline the differences between field and globular cluster populations and discuss their possible origin both in terms of primordial pollution and stellar internal nucleosynthesis and mixing. We suggest some tests to help to understand the influence of metallicity and of a dense environment on abundance anomalies in connection with the second parameter problem and with the stellar yields.

  17. Chemical evolution studies: the radiolysis and thermal decomposition of malonic acid

    International Nuclear Information System (INIS)

    Cruz-Castaneda, J.; Negron-Mendoza, A.; Heredia, A.; Ramos-Bernal, S.; Villafane-Barajas, S.; Frias, D.; Colin-Garcia, M.

    2015-01-01

    In the context of chemical evolution a simulation of a hydrothermal vent was performed. The thermolysis and radiolysis of malonic acid in aqueous solution were studied. The thermolysis was done by heating the samples (95 deg C) and radiolysis using gamma radiation. Products were identified by gas chromatography and gas chromatography-mass spectrometry. The thermal treatment produced acetic acid and CO 2 . The radiolysis experiments yield carbon dioxide, acetic acid, and di- and tricarboxylic acids. A theoretical model of the chemical process occurring under irradiation was developed; this was able to reproduce formation of products and the consumption of malonic acid. (author)

  18. Evolution of weak perturbations in gas-solid suspension with chemical reaction

    Energy Technology Data Exchange (ETDEWEB)

    Sharypov, O.V. [Russian Academy of Sciences, Novosibirsk (Russian Federation). Inst. of Thermophysics; Novosibirsk State Univ. (Russian Federation); Anufriev, I.S. [Novosibirsk State Univ. (Russian Federation)

    2013-07-01

    Dynamics of weak finite-amplitude perturbations in two-phase homogeneous medium (gas + solid particles) with non-equilibrium chemical reaction in gas is studied theoretically. Non-linear model of plane perturbation evolution is substantiated. The model takes into account wave-kinetic interaction and dissipation effects, including inter-phase heat and momentum transfer. Conditions for uniform state of the system are analyzed. Non-linear equation describing evolution of plane perturbation is derived under weak dispersion and dissipation effects. The obtained results demonstrate self-organization in the homogeneous system: steady-state periodic structure arises, its period, amplitude and velocity depends on the features of the medium. The dependencies of these parameters on dissipation and chemical kinetics are analyzed.

  19. Chemical Evolution of Ozone and Its Precursors in Asian Pacific Rim Outflow During TRACE-P

    Science.gov (United States)

    Hamlin, A.; Crawford, J.; Olson, J.; Pippin, M.; Avery, M.; Sachse, G.; Barrick, J.; Blake, D.; Tan, D.; Sandholm, S.; Kondo, Y.; Singh, H.; Eisele, F.; Zondlo, M.; Flocke, F.; Talbot, R.

    2002-12-01

    During NASA's GTE/TRACE-P (Transport and Chemical Evolution over the Pacific) mission, a widespread stagnant pollution layer was observed between 2 and 4 km over the central Pacific. In this region, high levels of O3 (70~ppbv), CO (210~ppbv), and NOx (130~pptv) were observed. Back trajectories suggest this airmass had been rapidly transported from the Asian coast near the Yellow Sea to the central Pacific where it underwent subsidence. The chemical evolution of ozone and its precursors for this airmass is examined using lagrangian photochemical box model calculations. Simulations are conducted along trajectories which intersect the flight path where predicted mixing ratios are compared to measurements. An analysis of the photochemical processes controlling the cycling of nitrogen oxides and ozone production and destruction during transport will be presented.

  20. Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars

    OpenAIRE

    Bensby, T.; Johnson, J. A.; Cohen, J.; Feltzing, S.; Udalski, A.; Gould, A.; Huang, W.; Thompson, I.; Simmerer, J.; Adén, D.

    2009-01-01

    Aims. Our aims are twofold. First we aim to evaluate the robustness and accuracy of stellar parameters and detailed elemental abundances that can be derived from high-resolution spectroscopic observations of microlensed dwarf and subgiant stars. We then aim to use microlensed dwarf and subgiant stars to investigate the abundance structure and chemical evolution of the Milky Way Bulge. Contrary to the cool giant stars, with their extremely crowded spectra, the dwarf stars are hotter, their spe...

  1. (S, C, O, Sr) isotopic constraints on the diagenetic evolution of the COX clay formations at the Bure URL site, Paris Basin)

    Science.gov (United States)

    Lerouge, C.; Gaucher, E. C.; Tournassat, C.; Agrinier, P.; Widory, D.; Guerrot, C.; Buschaert, S.

    2009-04-01

    The Underground Research Laboratory of Bure, located in the Eastern part of the Paris Basin, was selected by ANDRA (French Agency for Nuclear Management) in order to study the feasibility of a nuclear waste disposal in the Callovian-Oxfordian thick clayey formation at 400 meters depth. Since 1994's, numerous investigations have been initiated to understand and predict the behaviour of the clay formation in time and in space, by constraining its stability, the chemical evolution of the porewaters, and solution transfers between the clayey formation and its adjacent limestone sequences during geological times (ANDRA, 2005). In that way, this study presents combined new mineralogical and isotopic data of the diagenetic mineral sequence to constrain the porewater chemistry of the rock at different stages of the sedimentary then burial history of the clayey formation. The petrological study of Callovian-Oxfordian claystones provided evidence of the following diagenetic mineral sequence: 1) Framboïdal pyrite ± micritic calcite in replacement of carbonate bioclasts and in bioturbations, 2) Iron-rich euhedral carbonates (ankerite, sideroplesite), Glauconite, 3) Sparry dolomite, celestite in residual porosity, 4) Chalcedony 5) quartz/calcite. Pyrite in bioturbations shows a wide range of δ34S (-38 to +74 permil/CDT), providing evidence of bacterial sulphate reduction processes. The lowest negative values (-38 to -22 permil) indicate precipitation of pyrite in a marine environment with a permanent recharge in sulphate, whereas the higher pyrite δ34S values (-14 up to +74 permil) show that pyrite precipitated in a system that closed for sulphate. Consequently the variations of pyrite δ34S in bioturbations along the lithostratigraphic profil indicate a change of sedimentation conditions from a deep marine environment to an environment with alternative recharge of marine sulphates; that is consistent with the transgression/regression cycle observed in the middle sequence

  2. Devonian climate and reef evolution: Insights from oxygen isotopes in apatite

    Science.gov (United States)

    Joachimski, M. M.; Breisig, S.; Buggisch, W.; Talent, J. A.; Mawson, R.; Gereke, M.; Morrow, J. R.; Day, J.; Weddige, K.

    2009-07-01

    Conodonts, microfossils composed of carbonate-fluor apatite, are abundant in Palaeozoic-Triassic sediments and have a high potential to preserve primary oxygen isotope signals. In order to reconstruct the palaeotemperature history of the Devonian, the oxygen isotope composition of apatite phosphate was measured on 639 conodont samples from sequences in Europe, North America and Australia. The Early Devonian (Lochkovian; 416-411 Myr) was characterized by warm tropical temperatures of around 30 °C. A cooling trend started in the Pragian (410 Myr) with intermediate temperatures around 23 to 25 °C reconstructed for the Middle Devonian (397-385 Myr). During the Frasnian (383-375 Myr), temperatures increased again with temperatures to 30 °C calculated for the Frasnian-Famennian transition (375 Myr). During the Famennian (375-359 Myr), surface water temperatures slightly decreased. Reconstructed Devonian palaeotemperatures do not support earlier views suggesting the Middle Devonian was a supergreenhouse interval, an interpretation based partly on the development of extensive tropical coral-stromatoporoid communities during the Middle Devonian. Instead, the Devonian palaeotemperature record suggests that Middle Devonian coral-stromatoporoid reefs flourished during cooler time intervals whereas microbial reefs dominated during the warm to very warm Early and Late Devonian.

  3. Hydro-geochemical and isotopic fluid evolution of the Los Azufres caldera geothermal field, Central Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Partida, E [Centro de Geociencias, Campus Juriquilla-UNAM, Queretaro (Mexico); Viggiano-Guerra, J C [Subgerencia de Estudios C.F.E., Morelia. Michocan (Mexico); Perez, R J [Universidad de Calgary (Canada)], E-mail: egp@geociencias.unam.mx, E-mail: cesar.viggiano@cfe.gob.mx, E-mail: rene@geochemicalengineering.com

    2008-10-01

    Hydrothermal alteration at Los Azufres geothermal held is mostly propylitic showing progressive dehydration with depth, and temperature increase. The evolution of this system is inferred to be related to deep liquid water, boiling when ascending through fractures connected to the surface.

  4. Hydro-geochemical and isotopic fluid evolution of the Los Azufres caldera geothermal field, Central Mexico

    International Nuclear Information System (INIS)

    Gonzalez-Partida, E; Viggiano-Guerra, J C; Perez, R J

    2008-01-01

    Hydrothermal alteration at Los Azufres geothermal held is mostly propylitic showing progressive dehydration with depth, and temperature increase. The evolution of this system is inferred to be related to deep liquid water, boiling when ascending through fractures connected to the surface.

  5. IsoMS: automated processing of LC-MS data generated by a chemical isotope labeling metabolomics platform.

    Science.gov (United States)

    Zhou, Ruokun; Tseng, Chiao-Li; Huan, Tao; Li, Liang

    2014-05-20

    A chemical isotope labeling or isotope coded derivatization (ICD) metabolomics platform uses a chemical derivatization method to introduce a mass tag to all of the metabolites having a common functional group (e.g., amine), followed by LC-MS analysis of the labeled metabolites. To apply this platform to metabolomics studies involving quantitative analysis of different groups of samples, automated data processing is required. Herein, we report a data processing method based on the use of a mass spectral feature unique to the chemical labeling approach, i.e., any differential-isotope-labeled metabolites are detected as peak pairs with a fixed mass difference in a mass spectrum. A software tool, IsoMS, has been developed to process the raw data generated from one or multiple LC-MS runs by peak picking, peak pairing, peak-pair filtering, and peak-pair intensity ratio calculation. The same peak pairs detected from multiple samples are then aligned to produce a CSV file that contains the metabolite information and peak ratios relative to a control (e.g., a pooled sample). This file can be readily exported for further data and statistical analysis, which is illustrated in an example of comparing the metabolomes of human urine samples collected before and after drinking coffee. To demonstrate that this method is reliable for data processing, five (13)C2-/(12)C2-dansyl labeled metabolite standards were analyzed by LC-MS. IsoMS was able to detect these metabolites correctly. In addition, in the analysis of a (13)C2-/(12)C2-dansyl labeled human urine, IsoMS detected 2044 peak pairs, and manual inspection of these peak pairs found 90 false peak pairs, representing a false positive rate of 4.4%. IsoMS for Windows running R is freely available for noncommercial use from www.mycompoundid.org/IsoMS.

  6. The dimensionality of stellar chemical space using spectra from the Apache Point Observatory Galactic Evolution Experiment

    Science.gov (United States)

    Price-Jones, Natalie; Bovy, Jo

    2018-03-01

    Chemical tagging of stars based on their similar compositions can offer new insights about the star formation and dynamical history of the Milky Way. We investigate the feasibility of identifying groups of stars in chemical space by forgoing the use of model derived abundances in favour of direct analysis of spectra. This facilitates the propagation of measurement uncertainties and does not pre-suppose knowledge of which elements are important for distinguishing stars in chemical space. We use ˜16 000 red giant and red clump H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and perform polynomial fits to remove trends not due to abundance-ratio variations. Using expectation maximized principal component analysis, we find principal components with high signal in the wavelength regions most important for distinguishing between stars. Different subsamples of red giant and red clump stars are all consistent with needing about 10 principal components to accurately model the spectra above the level of the measurement uncertainties. The dimensionality of stellar chemical space that can be investigated in the H band is therefore ≲10. For APOGEE observations with typical signal-to-noise ratios of 100, the number of chemical space cells within which stars cannot be distinguished is approximately 1010±2 × (5 ± 2)n - 10 with n the number of principal components. This high dimensionality and the fine-grained sampling of chemical space are a promising first step towards chemical tagging based on spectra alone.

  7. Modelling of chemical evolution of low pH cements at long term

    International Nuclear Information System (INIS)

    El Bitouri, Y.; Buffo-Lacarriere, L.; Sellier, A.; Bourbon, X.

    2015-01-01

    In the context of the underground radioactive waste repository, low-pH cements were developed to reduce interactions between concrete and clay barrier. These cements contain high proportions of mineral additions like silica fume, fly ash or blast furnace slag for example. The high ratio of cement replacement by pozzolanic additions allows to reduce the pH by a global reduction of Ca/Si ratio of the hydrates (according to the one observed on CEM I pastes). In order to predict the short term development of the hydration for each component of this cement, a multiphasic hydration model, previously developed, is used. The model predicts the evolution of hydration degree of each anhydrous phase and consequently the quantity of each hydrate in paste (CH, aluminates, CSH with different Ca/Si ratios). However, this model is not suitable to determine the long term mineralogical and chemical evolution of the material, due to the internal change induced by chemical imbalance between initial hydrates. In order to evaluate the chemical characteristics of low pH cement based materials, and thus assess its chemical stability in the context of radioactive waste storage, a complementary model of chemical evolution at long term is proposed. This original model is based on 'solid-solution' principles. It assumes that the microdiffusion of calcium plays a major role to explain how the different Ca/Si ratio of initial C-S-H tends together toward a medium stabilized value. The main mechanisms and full development of the model equations are presented first. Next, a comparison of the model with experimental data issue from EDS (Energy Dispersive X-ray Spectroscopy) analysis on low pH cement allows to test the model. (authors)

  8. Identification of chlorinated solvents degradation zones in clay till by high resolution chemical, microbial and compound specific isotope analysis

    DEFF Research Database (Denmark)

    Damgaard, Ida; Bjerg, Poul Løgstrup; Bælum, Jacob

    2013-01-01

    subsampling of the clay till cores. The study demonstrates that an integrated approach combining chemical analysis, molecular microbial tools and compound specific isotope analysis (CSIA) was required in order to document biotic and abiotic degradations in the clay till system. © 2013 Elsevier B.V.......The degradation of chlorinated ethenes and ethanes in clay till was investigated at a contaminated site (Vadsby, Denmark) by high resolution sampling of intact cores combined with groundwater sampling. Over decades of contamination, bioactive zones with degradation of trichloroethene (TCE) and 1...

  9. Strontium isotope evolution of pore water and calcite in the Topopah Spring Tuff, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Marshall, Brian D.; Futa, Kiyoto

    2001-01-01

    Pore water in the Topopah Spring Tuff has a narrow range of (delta) 87 Sr values that can be calculated from the (delta) 87 Sr values of the rock considering advection through and reaction with the overlying nonwelded tuffs of the PTn. This model can be extended to estimate the variation of (delta) 87 Sr in the pore water through time; this approximates the variation of (delta) 87 Sr measured in calcite fracture coatings. In samples of calcite where no silica can be dated by other methods, strontium isotope data may be the only method to determine ages. In addition, other Sr-bearing minerals in the calcite and opal coatings, such as fluorite, may be dated using the same model

  10. Diagenetic evolution and stable isotopes of Lower Permian platform marginal carbonates (Trogkofel Limestone, Carnic Alps, Austria)

    Science.gov (United States)

    Schaffhauser, Maria; Krainer, Karl; Sanders, Diethard Gerald; Spötl, Christoph

    2010-05-01

    and filling of fractures. Closely below the erosional surface at the top of the Trogkofel Limestone, the dolomite is characterized by vuggy porosity. The Tarvis Breccia, which represents coarse alluvial fan deposits, in turn, is thick-bedded, poorly sorted, typically clast-supported, and consists of angular lithoclasts embedded in a matrix of former lime mudstone. Both, matrix as well as lithoclasts, are dolomitized. Various types of cement (isopachous, botryoidal, microbialite, calcite spar), karstic cavity fills (isopachous cements, internal sediments), and replacement dolomites of the Trogkofel section, as well as of the Tarvis Breccia were analysed for their stable isotopic composition. δ18O and δ13C data produced so far allow to differentiate between replacement dolomites and saddle dolomite of the Trogkofel Limestone and the Tarvis Breccia. Saddle dolomite shows the most depleted oxygen isotope values, suggesting formation during relatively high temperatures. Carbon isotope values are invariably positive in all dolomite types indicating lacking influence of organic diagenesis on the alkalinity of the deep-burial pore water. Matrix dolomite from the Tarvis Breccia shows slightly positive δ18O values. Calcite cements show a wide range in δ18O values (ca. -1 to -7 permil VPDB), which overlaps the composition of unaltered brachiopod shells (ca. -3 permil VPDB). Oxygen isotope values of calcite cements reveal a trend towards depleted δ18O values. This trend is reflecting most likely increasing temperature.

  11. THE INFLUENCE OF RADIAL STELLAR MIGRATION ON THE CHEMICAL EVOLUTION OF THE MILKY WAY

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yue; Zhao Gang, E-mail: gzhao@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2013-05-20

    Stellar migration is an important dynamical process in the Galactic disk. Here we model radial stellar migration in the Galactic disk with an analytical method, then add it to a detailed Galactic chemical evolution model to study the influence of radial stellar migration on the chemical evolution of the Milky Way, especially for the abundance gradients. We found that the radial stellar migration in the Galactic disk can make the profile of the G-dwarf metallicity distribution of the solar neighborhood taller and narrower, and thus it becomes another solution to the ''G-dwarf problem''. It can also scatter the age-metallicity relation. However, after migration, the abundance distributions along the Galactic radius do not change much; namely, the abundance gradients would not be flattened by the radial stellar migration, which is different from the predictions of many theoretical works. However, it can flatten the radial gradients of the mean chemical abundance of stars, and older stars possess flatter abundance gradients than younger stars. The most significant effect of radial stellar migration on the chemical abundance is that at a certain position it scatters the abundance of stars from a relatively concentrated value to a range.

  12. Chemical and isotopic composition of secondary organic aerosol generated by alpha-pinene ozonolysis

    NARCIS (Netherlands)

    Meusinger, Carl; Dusek, Ulrike; King, Stephanie M.; Holzinger, Rupert; Rosenorn, Thomas; Sperlich, Peter; Julien, Maxime; Remaud, Gerald S.; Bilde, Merete; Rockmann, Thomas; Johnson, Matthew S.

    2017-01-01

    Secondary organic aerosol (SOA) plays a central role in air pollution and climate. However, the description of the sources and mechanisms leading to SOA is elusive despite decades of research. While stable isotope analysis is increasingly used to constrain sources of ambient aerosol, in many cases

  13. Chemically modified glasses for analysis of hydrogen isotopes by gas-chromatography

    International Nuclear Information System (INIS)

    Stanciu, Vasile; Stefanescu, Doina

    1999-01-01

    Hydrogen isotope separation process by such methods as cryogenic distillation or thermal diffusion method is one of the key technologies of the tritium separation from heavy water of CANDU reactors and in the tritium fuel cycle for a thermonuclear fusion reactor. In each process, the analytical techniques for measuring contents of hydrogen isotope mixture are necessary. An extensive experimental research has been carried out in order to produce the most suitable absorbent and define the best operating conditions for selective separation and analysis of hydrogen isotope by gas-chromatography. This paper describes the preparation of adsorbent materials utilised as stationary phase in the gas-chromatographic column for hydrogen isotope separation and treatment (activation) of stationary phase. Modified thermo-resisting glass with Fe(NH 4 ) 2 (SO 4 ) 2 6H 2 O and Cr 2 O 3 , respectively, have been experimentally investigated at 77 K for H 2 , HD and D 2 separation and the results of chromatographic runs are also reported and discussed. The gas-chromatographic apparatus used is composed of a Hewlett-Packard 7620A gas-chromatograph equipped with a gas carrier flow rate controller and a thermal conductivity detector (TCD). The apparatus comprises also a Dewar vessel containing the separation column. The hydrogen isotopes H 2 , HD, D 2 and their mixture have been obtained in our laboratories. The best operating conditions of the adsorbent column Fe (III)/glass and Cr 2 O 3 /glass, i.e. granulometry, column length, pressure-drop along the column, carrier gas flow rate, sample volume have been studied by means of the analysis of the retention times, separation factors and HETP. (authors)

  14. Stable isotopes

    International Nuclear Information System (INIS)

    Brazier, J.L.; Guinamant, J.L.

    1995-01-01

    According to the progress which has been realised in the technology of separating and measuring isotopes, the stable isotopes are used as preferable 'labelling elements' for big number of applications. The isotopic composition of natural products shows significant variations as a result of different reasons like the climate, the seasons, or their geographic origins. So, it was proved that the same product has a different isotopic composition of alimentary and agriculture products. It is also important in detecting the pharmacological and medical chemicals. This review article deals with the technology, like chromatography and spectrophotometry, adapted to this aim, and some important applications. 17 refs. 6 figs

  15. Chemical and isotopic study of thermal springs and gas discharges from Sierra de Chiapas, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nencetti, A; Tassi, F; Vaselli, O [Department of Earth Sciences, Florence (Italy); Macias, J. L [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D.F. (Mexico); Magro, G [CNR-Institute of Geosciences and Earth Resources, Pisa (Italy); Capaccioni, B [Institute of Volcanology and Geochemistry, Urbino (Italy); Minissale, A [CNR-Institute of Geosciences and Earth Resources, Florence (Italy); Mora, J. C [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D.F. (Mexico)

    2005-01-15

    Thermal water and gas discharges south-east of El Chichon volcano, Mexico are associated mainly with NW-SE oriented fault systems. Spring discharges include i) waters with Na-Cl composition and TDS>3000 mg/L; ii) waters with Ca-SO{sub 4} composition and TDS values between 1400 and 2300 mg/L; iii) waters with Na-Cl composition and TDS of 800 to 2400 mg/L and sulphate content up to 650 mg/L and iv) waters with Ca-HCO{sub 3} composition and low salinity (TDS <250mg/L). Most of these waters are associated with free-gas discharges of N{sub 2} (up to 93 % by vol.), CO{sub 2} (2.4 to 31.2 % by vol.) and Ar (up to 1.25 % by vol.) with a predominant meteoric origin. H{sub 2}S is present only in gas samplers collected at El Azufre (up to 1.1 % by vol.). The {delta}13C CO{sub 2} values are always below -9.7% (PDB) and suggest a partially biogenic origin for CO{sub 2}. Chemical and isotopic features of spring discharges indicate that fluid circulation in the Sierra de Chiapas is mainly regulated by meteoric waters that tend to infiltrate the upper and middle-Cretaceous carbonate units up to the lower Cretaceous-upper Jurassic evaporitic formations (by Lopez-Ramos, 1982). The latter provide the main source of the species in solution. No evidence for high-to-medium enthalpy systems at depth beneath the Sierra de Chiapas has been found. [Spanish] La Sierra de Chiapas localizada en el Sureste de Mexico, se caracteriza por la presencia de descargas de gas y agua. La mayoria de los manantiales termales se asocian a rocas volcanicas Terciarias a lo largo de fallas regionales con orientacion NOSE. Las descargas termales se dividen en cuatro grupos: i) aguas con composicion Na-Cl y Solidos Disueltos Totales (SDT) >3000 mg/L; ii) aguas con composicion Ca-SO{sub 4} y valores de SDT entre 1400 y 2300 mg/L; iii) aguas con composicion Na-Cl, bajos contenidos de SDT (800 2400 mg/L) y un contenido de sulfato alto (hasta 650 mg/L) y iv) aguas con una composicion Ca-HCO{sub 3} y salinidad baja

  16. Formation and Evolution of the Continental Lithospheric Mantle: Perspectives From Radiogenic Isotopes of Silicate and Sulfide Inclusions in Macrodiamonds

    Science.gov (United States)

    Shirey, S. B.; Richardson, S. H.

    2007-12-01

    Silicate and sulfide inclusions that occur in diamonds comprise the oldest (>3 Ga), deepest (>140 km) samples of mantle-derived minerals available for study. Their relevance to the evolution of the continental lithosphere is clear because terrestrial macrodiamonds are confined to regions of the Earth with continental lithospheric mantle keels. The goals of analytical work on inclusions in diamond are to obtain paragenesis constraints, radiogenic ages, and initial isotopic compositions. The purpose is to place diamond formation episodes into the broader framework of the geological processes that create and modify the continental lithosphere and to relate the source of the C and N in diamond-forming fluids to understanding the Earth's C and N cycles in the Archean. Although sulfide and silicate inclusions rarely occur in the same diamond, they both can be grouped according to their geochemical similarity with the chief rock types that comprise the mantle keel: peridotite and eclogite. Silicate inclusions are classified as harzburgitic (depleted; olivine > Fo91, garnet Cr2O3 > 3 wt% and CaO from 0 to 5 wt%), lherzolitic (fertile), or eclogitic (basaltic; garnet Cr2O3 14 wt%; Os > 2 ppm) versus eclogitic (Ni bearing kimberlites, and the generosity of mining companies because of the extreme rarity of inclusions in suites of mostly gem-quality diamonds. Most isotopic work has been on the Kaapvaal-Zimbabwe craton with lesser work on the Slave, Siberian, and Australian cratons. Sm-Nd ages on silicate suites and Re-Os ages on sulfide suites confirm diamond formation from the Mesoarchean though the Neoproterozoic. Most important are the systematics across cratons in the context of crustal geology that lead to generalities about craton evolution. Inclusion suites date mantle keels as Mesoarchean and clearly point to subduction as the major process to form the earliest continental nuclei and to amalgamate the cratons in their present form. This is evident from the elevated

  17. Determination of mixing characteristics of the river Kabul and the river Indus using physico-chemical and stable isotope parameters

    International Nuclear Information System (INIS)

    Qureshi, R.M.; Hussain, Q.M.; Sajjad, M.I.; Hussain, S.D.; Latif, Z.

    1990-11-01

    This report presents a comparative study on the usefulness of stable isotope parameters (hydrogen and oxygen) versus the physico-chemical parameters (electrical conductivity, temperature, pH value) of water to determine the extent of mixing of the river Kabul with the river Indus near Attock. In view of the sampling techniques employed in the present investigations, electrical conductivity and temperature are found to be the best field parameters for a quick estimate of mixing path length. However, the stable isotopes of the water molecule, due to their greater sensitivity and measuring accuracy, provide a better scenario of mixing characteristics as compared to the physico-chemical parameters. It appears that under normal flow condition, it takes about 5 km channel distance for complete mixing of the Kabul river water in the Indus river channel. A computer code MIXABC is developed to determine the percentage contribution of one river water along a mixing channel in the other river. Details of the source programs are presented. The code can be used on any IBM-compatible microsystem. (author)

  18. Physico-Chemical Study of the Separation of Calcium Isotopes by Chemical Exchange Between Amalgam and Salt Solutions

    International Nuclear Information System (INIS)

    Duie, P.; Dirian, G.

    1962-01-01

    In a preliminary study of the isotopic exchange between Ca amalgam and aqueous or organic solutions of Ca salts, the main parameters governing the feasibility of a separation process based on these systems such as separation factor, exchange kinetics, rate of decomposition of the amalgam were investigated. The separation factor between 40 Ca and 46 Ca was found to be of the order of 1.02. The rate of the exchange reaction is rather low for aqueous solutions, extremely low for organic solutions. The amalgam seems not to be attacked by dimethyl-formamide solutions; but it is rapidly decomposed by aqueous solutions of Ca halides. This decomposition is slow in the case of aqueous solutions of calcium formate and still slower for Ca(OH) 2 ; however, except in particular conditions, the observed rate is often much higher, owing to interfering reactions between amalgam and water vapor contained in H 2 bubbles. (authors) [fr

  19. Isotopic constraints on the genesis and evolution of basanitic lavas at Haleakala, Island of Maui, Hawaii

    Science.gov (United States)

    Phillips, Erin H.; Sims, K.W.W.; Sherrod, David R.; Salters, Vincent; Blusztajn, Jurek; Dulaiova, Henrieta

    2016-01-01

    To understand the dynamics of solid mantle upwelling and melting in the Hawaiian plume, we present new major and trace element data, Nd, Sr, Hf, and Pb isotopic compositions, and 238U–230Th–226Ra and 235U–231Pa–227Ac activities for 13 Haleakala Crater nepheline normative basanites with ages ranging from ∼900 to 4100 yr B.P. These basanites of the Hana Volcanics exhibit an enrichment in incompatible trace elements and a more depleted isotopic signature than similarly aged Hawaiian shield lavas from Kilauea and Mauna Loa. Here we posit that as the Pacific lithosphere beneath the active shield volcanoes moves away from the center of the Hawaiian plume, increased incorporation of an intrinsic depleted component with relatively low 206Pb/204Pb produces the source of the basanites of the Hana Volcanics. Haleakala Crater basanites have average (230Th/238U) of 1.23 (n = 13), average age-corrected (226Ra/230Th) of 1.25 (n = 13), and average (231Pa/235U) of 1.67 (n = 4), significantly higher than Kilauea and Mauna Loa tholeiites. U-series modeling shows that solid mantle upwelling velocity for Haleakala Crater basanites ranges from ∼0.7 to 1.0 cm/yr, compared to ∼10 to 20 cm/yr for tholeiites and ∼1 to 2 cm/yr for alkali basalts. These modeling results indicate that solid mantle upwelling rates and porosity of the melting zone are lower for Hana Volcanics basanites than for shield-stage tholeiites from Kilauea and Mauna Loa and alkali basalts from Hualalai. The melting rate, which is directly proportional to both the solid mantle upwelling rate and the degree of melting, is therefore greatest in the center of the Hawaiian plume and lower on its periphery. Our results indicate that solid mantle upwelling velocity is at least 10 times higher at the center of the plume than at its periphery under Haleakala.

  20. Geochemical investigation of groundwater in the Tono area, Japan. Chemical characteristics and groundwater evolution

    International Nuclear Information System (INIS)

    Iwatsuki, Teruki; Hama, Katsuhiro; Yoshida, Hidekazu

    1997-01-01

    Geochemical investigations form an important part of the R and D program at the Tono study site, central Japan. Detailed geological structure and groundwater chemistry have been studied to understand the geochemical environment in the sedimentary and crystalline rocks distributed in this area. The chemical evolution of the groundwater in the sedimentary rocks is characterized with the variation in Na + , Ca 2+ and HCO 3 - concentrations, and ion exchange and dissolution of calcite are dominant reactions in the evolution of groundwater. Geological investigation shows that a fracture system of crystalline rock can be classified into:intact zone, moderately fractured zone and intensely fractured zone, according to the frequency and the width of fractures and fractured zones. The groundwater in the intact and fractured zones of crystalline rock are characterized by Na + -Ca 2+ -HCO 3 - or Na + -HCO 3 - dominated water, and Na + -Ca 2+ -Fe 2+ -HCO 3 - dominated water. The chemical evolution of groundwater is, generally, controlled by water-rock interaction between plagioclase, iron minerals and groundwater. The groundwater at depth of G.L.-186m in the crystalline rock at the Tono area is characterized by the mixture between the oxidized surface water and the reduced groundwater. The investigation based on correlation between geological structures and groundwater chemistry can be applied to understand the geochemical environment in deep crystalline rock, and will support the development of a realistic hydrogeochemical model. (author)

  1. Beverton-Holt discrete pest management models with pulsed chemical control and evolution of pesticide resistance

    Science.gov (United States)

    Liang, Juhua; Tang, Sanyi; Cheke, Robert A.

    2016-07-01

    Pest resistance to pesticides is usually managed by switching between different types of pesticides. The optimal switching time, which depends on the dynamics of the pest population and on the evolution of the pesticide resistance, is critical. Here we address how the dynamic complexity of the pest population, the development of resistance and the spraying frequency of pulsed chemical control affect optimal switching strategies given different control aims. To do this, we developed novel discrete pest population growth models with both impulsive chemical control and the evolution of pesticide resistance. Strong and weak threshold conditions which guarantee the extinction of the pest population, based on the threshold values of the analytical formula for the optimal switching time, were derived. Further, we addressed switching strategies in the light of chosen economic injury levels. Moreover, the effects of the complex dynamical behaviour of the pest population on the pesticide switching times were also studied. The pesticide application period, the evolution of pesticide resistance and the dynamic complexity of the pest population may result in complex outbreak patterns, with consequent effects on the pesticide switching strategies.

  2. The questa magmatic system: Petrologic, chemical and isotopic variations in cogenetic volcanic and plutonic rocks of the latir volcanic field and associated intrusives, northern New Mexico

    International Nuclear Information System (INIS)

    Johnson, C.M.

    1986-01-01

    Field, chemical and isotopic data demonstrate that nearly all igneous rocks at Questa resulted from interactions between mantle-derived parental magmas and the crust. Strontium, neodymium and lead isotope ratios of early andesites to rhyolites (28 to 26 Ma) indicate that these magmas assimilated > 25% lower crust. Injection of basaltic magmas extensively modified the strontium and neodymium but not the lead isotope compositions of the lower crust. Eruption of comendite magmas and the peralkaline Amalia Tuff 26 Ma is correlated with inception of regional extension. Lead isotope ratios identify different sources for the metaluminous granites and the peralkaline rocks. 26 Ma metaluminous granite to granodiorite intrusions have chemical and isotopic compositions to those of the precaldera intermediate-composition rocks, and are interpreted as representing the solidified equivalents of the precaldera magmatic episode. However, both conventional and ion-microprobe isotopic data prohibit significant assimilation of crustal rocks at the level of exposure, suggesting that the plutons were emplaced a relatively crystal-rich mushes which did not have sufficient heat to assimilate country rocks. This suggest that in some cases plutonic rocks are better than volcanic rocks in representing the isotopic compositions of their source regions, because the assimilation potential of crystal-rich magmas is significantly less than that of largely liquid magmas

  3. Stable Isotope Evidence for a Complex Fluid Evolution of the Northwestern British Columbia Coast Ranges Related to Terrane Accretion

    Science.gov (United States)

    Moertle, J.; Holk, G. J.

    2015-12-01

    Stable isotope geochemistry reveals a complex fluid evolution for the Western Metamorphic Belt (WMB), Coast Ranges Batholith (CRB), Central Gneiss Complex (CGC) and Coast Ranges Megalineament (CRM). These fluids are a product of a complex tectonic history related to terrane accretion that includes oblique convergence, metamorphism, magmatism, and orogenic collapse. From W-to-E, these fluid systems are as follows. High-pressure greenschist-to-amphibolite facies metasedimentary rocks of the WMB record variable mineral δD (-61 to -104‰) and δ18O (e.g., quartz +9.6 to +13.4‰) values with multiple minerals in apparent isotopic equilibrium (T ~ 450-550°C) suggest a low W/R system dominated by metamorphic fluids. Variable and non-equilibrium δD (-53 to -143‰) and δ18O (e.g., biotite +2.3 to +5.3‰) values from diorites of the Quottoon pluton affected by the ductile CRM suggest a complex evolution that involved both metamorphic and meteoric-hydrothermal fluids in this dextral shear zone; these results differ from those 300 km along strike to the north that documented only metamorphic fluids in the CRM (Goldfarb et al., 1988). Our data and those of Magaritz and Taylor (1976) from granulite facies metasediments of the CGC and plutons of the western CRB reveal homogeneous δD values (-62 to -78‰) and a restricted range of δ18O values (e.g., quartz +8.5 to +11.5‰) with all minerals in equilibrium at T > 570°C indicate a system dominated by magmatic fluids. Calculated whole-rock δ18O values (~ +7‰) for the Quottoon pluton and CRB intrusive rocks suggest a mantle origin for these magmas. Reinterpretation of very low δD (< -150‰) and quartz-feldspar δ18O pairs that display extreme disequilibrium (feldspar δ18O values as low as -5‰) from the Ponder pluton, eastern CRB, and Hazelton Group point reveals that the major meteoric-hydrothermal system that affected these rocks was related to Eocene detachment faulting along the Shames Lake fault system, a

  4. Nd isotopes in French Phanerzoic shales: external vs. internal aspects of crustal evolution

    International Nuclear Information System (INIS)

    Michard, A.; Gurriet, P.; Soudant, M.; Alberede, F.; Ecole Nationale Superieure de Geologie Appliquee et de Prospection Miniere, 54 - Nancy

    1985-01-01

    Nd isotopic composition has been determined on shales of Paleozoic (Brittany and Languedoc) and Mesozoic (Lorraine) age. epsilonsub(Nd)(T) values range from -6 to -12 while Nd crustal residence ages are typically in excess over their stratigraphic ages by some 1.4 Ga. Exceptions to this rule are the sediments coeval with Hercynian, Caledonian and Cadomian orogenic events, the epsilonsub(Nd)(T) values of which suggest addition of mantle material to the sediment in the form of volcanoclastic detritus. In Brittany, this is confirmed by the local zircon chronology which provides upper intercepts of Concordia up to 800 m.y. in excess of Nd crustal residence ages. Comparison of crustal residence ages with stratigraphic ages through geologic time suggests a three stage history: a) for rocks older than 2 Ga, stratigraphic and crustal residence ages coincide, b) from 2 to 1 Ga, crustal residence ages level off at ca. 2 Ga and then c) decrease down to 1.4 Ga in recent sediments. Two extreme models can account for the observed variations: an internally driven model, in which variable quantities of mantle material are added to the crust, and an externally driven model, in which the rate of crustal recycling is low in the Archean but increases rapidly at the onset of the atmospheric oxygen buildup. (author)

  5. Chemical and isotopic composition of secondary organic aerosol generated by α-pinene ozonolysis

    DEFF Research Database (Denmark)

    Meusinger, Carl; Dusek, Ulrike; King, Stephanie M.

    2017-01-01

    -NOx conditions, with OH scavengers and in the absence of seed particles. The excess of ozone and long residence time in the flow chamber ensured that virtually all α-pinene had reacted. Product SOA was collected on two sequential quartz filters. The filters were analysed offline by heating them stepwise from 100...... it is difficult to apply because neither the isotopic composition of aerosol precursors nor the fractionation of aerosol forming processes is well characterised. In this paper, SOA formation from ozonolysis of α-pinene - an important precursor and perhaps the best-known model system used in laboratory studies...... - was investigated using position-dependent and average determinations of 13C in α-pinene and advanced analysis of reaction products using thermal-desorption proton-transfer-reaction mass spectrometry (PTR-MS). The total carbon (TC) isotopic composition δ13C of the initial α-pinene was measured, and the δ13C...

  6. Real-time isotope monitoring network at the Biosphere 2 Landscape Evolution Observatory resolves meter-to-catchment scale flow dynamics

    Science.gov (United States)

    Volkmann, T. H. M.; Van Haren, J. L. M.; Kim, M.; Harman, C. J.; Pangle, L.; Meredith, L. K.; Troch, P. A.

    2017-12-01

    Stable isotope analysis is a powerful tool for tracking flow pathways, residence times, and the partitioning of water resources through catchments. However, the capacity of stable isotopes to characterize catchment hydrological dynamics has not been fully exploited as commonly used methodologies constrain the frequency and extent at which isotopic data is available across hydrologically-relevant compartments (e.g. soil, plants, atmosphere, streams). Here, building upon significant recent developments in laser spectroscopy and sampling techniques, we present a fully automated monitoring network for tracing water isotopes through the three model catchments of the Landscape Evolution Observatory (LEO) at the Biosphere 2, University of Arizona. The network implements state-of-the-art techniques for monitoring in great spatiotemporal detail the stable isotope composition of water in the subsurface soil, the discharge outflow, and the atmosphere above the bare soil surface of each of the 330-m2 catchments. The extensive valving and probing systems facilitate repeated isotope measurements from a total of more than five-hundred locations across the LEO domain, complementing an already dense array of hydrometric and other sensors installed on, within, and above each catchment. The isotope monitoring network is operational and was leveraged during several months of experimentation with deuterium-labelled rain pulse applications. Data obtained during the experiments demonstrate the capacity of the monitoring network to resolve sub-meter to whole-catchment scale flow and transport dynamics in continuous time. Over the years to come, the isotope monitoring network is expected to serve as an essential tool for collaborative interdisciplinary Earth science at LEO, allowing us to disentangle changes in hydrological behavior as the model catchments evolve in time through weathering and colonization by plant communities.

  7. Conference on chemical evolution and the origin of life: Self-organization of the macromolecules of life

    International Nuclear Information System (INIS)

    1993-10-01

    The formation of biomolecules was a necessary step in the evolution of life on earth. This interdisciplinary conference emphasized the role of replication in processes of self-organization of biological macromolecules. The present document contains abstracts of the 26 contributions to the conference on chemical evolution. The individual contributions have been indexed separately for the database

  8. Structural, chemical and isotopic examinations of interstellar organic matter extracted from meteorites and interstellar dust particles

    Science.gov (United States)

    Busemann, Henner; Alexander, Conel M. O'D.; Nittler, Larry R.; Stroud, Rhonda M.; Zega, Tom J.; Cody, George D.; Yabuta, Hikaru; Kilcoyne, A. L. David

    2008-10-01

    Meteorites and Interplanetary Dust Particles (IDPs) are supposed to originate from asteroids and comets, sampling the most primitive bodies in the Solar System. They contain abundant carbonaceous material. Some of this, mostly insoluble organic matter (IOM), likely originated in the protosolar molecular cloud, based on spectral properties and H and N isotope characteristics. Together with cometary material returned with the Stardust mission, these samples provide a benchmark for models aiming to understand organic chemistry in the interstellar medium, as well as for mechanisms that secured the survival of these fragile molecules during Solar System formation. The carrier molecules of the isotope anomalies are largely unknown, although amorphous carbonaceous spheres, so-called nanoglobules, have been identified as carriers. We are using Secondary Ion Mass Spectrometry to identify isotopically anomalous material in meteoritic IOM and IDPs at a ~100-200 nm scale. Organics of most likely interstellar origin are then extracted with the Focused-Ion-Beam technique and prepared for synchrotron X-ray and Transmission Electron Microscopy. These experiments yield information on the character of the H- and N-bearing interstellar molecules: While the association of H and N isotope anomalies with nanoglobules could be confirmed, we have also identified amorphous, micron-sized monolithic grains. D-enrichments in meteoritic IOM appear not to be systematically associated with any specific functional groups, whereas 15N-rich material can be related to imine and nitrile functionality. The large 15N- enrichments observed here (δ15N > 1000 ‰) cannot be reconciled with models using interstellar ammonia ice reactions, and hence, provide new constraints for understanding the chemistry in cold interstellar clouds.

  9. Chemical and isotopic variations of precipitation in the Los Alamos Region, New Mexico

    International Nuclear Information System (INIS)

    Adams, A.I.; Goff, F.; Counce, D.

    1995-02-01

    Precipitation collectors were installed at 14 locations on the Pajarito Plateau and surrounding areas to study variations in chemistry, stable isotopes and tritium for the years 1990 to 1993. The volume of precipitation was measured and samples were collected and analyzed every three to four months. All precipitation samples contain 18 O) results record seasonal variations in precipitation as the weather patterns shift from sources in the Pacific Ocean to sources in the Gulf of Mexico. The stable isotope results also show isotopic variations due to elevation differences among the collection points. The tritium contents ( 3 H) in rain samples vary from 6.54 T.U. to 141 T.U. Contouring of high tritium values (e.g. >20 T.U.) from each collection period clearly shows that Laboratory activities release some tritium to the atmosphere. The effect of these releases are well below the limits set by the Environmental Protection Agency for drinking water (about 6200 T.U.). The magnitude of the releases is apparently greatest during the summer months. However, anomalous tritium values are detected as far north as Espahola, New Mexico for many collection periods. Tritium releases by the Laboratory are not constant; thus, the actual amount of tritium in each release has been diluted in the composite samples of our three to four month collection periods

  10. Chemical Evolution and the Formation of Dwarf Galaxies in the Early Universe

    Science.gov (United States)

    Cote, Benoit; JINA-CEE, NuGrid, ChETEC

    2018-06-01

    Stellar abundances in local dwarf galaxies offer a unique window into the nature and nucleosynthesis of the first stars. They also contain clues regarding how galaxies formed and assembled in the early stages of the universe. In this talk, I will present our effort to connect nuclear astrophysics with the field of galaxy formation in order to define what can be learned about galaxy evolution using stellar abundances. In particular, I will describe the current state of our numerical chemical evolution pipeline which accounts for the mass assembly history of galaxies, present how we use high-redshift cosmological hydrodynamic simulations to calibrate our models and to learn about the formation of dwarf galaxies, and address the challenge of identifying the dominant r-process site(s) using stellar abundances.

  11. Carbon isotope systematics of the Cambrian–Vendian aquifer system in the northern Baltic Basin: Implications to the age and evolution of groundwater

    International Nuclear Information System (INIS)

    Raidla, Valle; Kirsimäe, Kalle; Vaikmäe, Rein; Kaup, Enn; Martma, Tõnu

    2012-01-01

    Groundwater in the Cambrian–Vendian aquifer system has a strongly depleted stable isotope composition (δ 18 O values of about −22‰) and a low radiocarbon concentration, which suggests that the water is of glacial origin from the last Ice Age. The aim of this paper was to elucidate the timing of infiltration of glacial waters and to understand the geochemical evolution of this groundwater. The composition of the dissolved inorganic C (DIC) in Cambrian–Vendian groundwater is influenced by complex reactions and isotope exchange processes between water, organic materials and rock matrix. The δ 13 C composition of dissolved inorganic C in Cambrian–Vendian water also indicates a bacterial modification of the isotope system. The corrected radiocarbon ages of groundwater are between 14,000 and 27,000 radiocarbon years, which is coeval with the advance of the Weichselian Glacier in the area.

  12. Isotopic ratios in the solar system

    International Nuclear Information System (INIS)

    1985-01-01

    This colloquium is aimed at presentation of isotope ratio measurements in different objects of solar system and surrounding interstellar space and evaluation of what information on composition and structure of primitive solar nebula and on chemical evolution of interstellar space in this part of the galaxy can be deduced from it. Isotope ratio in solar system got from laboratory study of extraterrestrial materials is a subject of this colloquium. Then isotope ratio measured in solar wind, planets and comets. Measurements either are made in-situ by mass spectrometry of ions in solar wind or planetery atmosphere gases either are remote measurements of spectra emitted by giant planets and comets. At last, planetology and astrophysics implications are presented and reviewed. Consraints for solar system formation model can be deduced from isotope ratio measurement. Particularly, isotope anomalies are marks of the processes, which have influenced the primitive solar nebula contraction [fr

  13. Tracing the Chemical Evolution of Metal-rich Galactic Bulge Globular Clusters

    Science.gov (United States)

    Munoz Gonzalez, Cesar; Saviane, Ivo; Geisler, Doug; Villanova, Sandro

    2018-01-01

    We present in this poster the metallicity characterization of the four metal rich Bulge Galactic Gobular Clusters, which have controversial metallicities. We analyzed our high-resolution spectra (using UVES-580nm and GIRAFFE-HR13 setups) for a large sample of RGB/AGB targets in each cluster in order to measure their metallicity and prove or discard the iron spread hypothesis. We have also characterized chemically stars with potentially different iron content by measuring light (O, Na, Mg, Al), alpha (Si, Ca, Ti), iron–peak (V, Cr, Ni, Mn) and s and r process (Y, Zr, Ba, Eu) elements. We have identified possible channels responsible for the chemical heterogeneity of the cluster populations, like AGB or massive fast-rotating stars contamination, or SN explosion. Also, we have analyzed the origin and evolution of these bulge GCs and their connection with the bulge itself.

  14. Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka [Laser Physics Application Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, MP (India)

    2014-07-07

    We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8–16 min. Mixture of metastable oxides like InAsO{sub 4,} As{sub 2}O{sub 3} are formed upon oxidation, which are reflected as sharp Raman peaks at ∼240–254 and 180–200 cm{sup −1}. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

  15. Chemical (Cl) and isotopic (18O, 2H, 3H) study of the unsaturated zone in the arid region of Nefta (South Tunisia)

    International Nuclear Information System (INIS)

    Zouari, K.; Maliki, My.A.; Moumni, L.; Aranyossy, J.F.

    2001-01-01

    A chemical and isotopic study of the unsaturated zone in Nefta, southwestern Tunisia was initiated to gain an improved understanding of the recharge and evaporation processes in the shallow 'Continental Terminal' (CT) sandy aquifer outcropping in the region of Nefta, which constitutes the most important water resource for agriculture and domestic uses in the region. A single 13.5-m core was extracted and subsampled from the unsaturated zone at the end of the 'rainy season' (23-24 April 1998) using a hand auger to avoid fluid contamination. Estimated recharge rates based on isotope and chemical profiles, uncertainties, and recommendations for future research are discussed. (author)

  16. Quantitative analysis of deuterium using the isotopic effect on quaternary {sup 13}C NMR chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Tamim A., E-mail: tamim.darwish@ansto.gov.au [National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Locked Bag 21, Kirrawee DC, NSW 2232 (Australia); Yepuri, Nageshwar Rao; Holden, Peter J. [National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Locked Bag 21, Kirrawee DC, NSW 2232 (Australia); James, Michael [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168 (Australia)

    2016-07-13

    Quantitative analysis of specifically deuterated compounds can be achieved by a number of conventional methods, such as mass spectroscopy, or by quantifying the residual {sup 1}H NMR signals compared to signals from internal standards. However, site specific quantification using these methods becomes challenging when dealing with non-specifically or randomly deuterated compounds that are produced by metal catalyzed hydrothermal reactions in D{sub 2}O, one of the most convenient deuteration methods. In this study, deuterium-induced NMR isotope shifts of quaternary {sup 13}C resonances neighboring deuterated sites have been utilized to quantify the degree of isotope labeling of molecular sites in non-specifically deuterated molecules. By probing {sup 13}C NMR signals while decoupling both proton and deuterium nuclei, it is possible to resolve {sup 13}C resonances of the different isotopologues based on the isotopic shifts and the degree of deuteration of the carbon atoms. We demonstrate that in different isotopologues, the same quaternary carbon, neighboring partially deuterated carbon atoms, are affected to an equal extent by relaxation. Decoupling both nuclei ({sup 1}H, {sup 2}H) resolves closely separated quaternary {sup 13}C signals of the different isotopologues, and allows their accurate integration and quantification under short relaxation delays (D1 = 1 s) and hence fast accumulative spectral acquisition. We have performed a number of approaches to quantify the deuterium content at different specific sites to demonstrate a convenient and generic analysis method for use in randomly deuterated molecules, or in cases of specifically deuterated molecules where back-exchange processes may take place during work up. - Graphical abstract: The relative intensities of quaternary {sup 13}C {"1H,"2H} resonances are equal despite the different relaxation delays, allowing the relative abundance of the different deuterated isotopologues to be calculated using NMR fast

  17. The isotopic chemical and dissolved gas concentrations in groundwater near Venterstad, Cape Province

    International Nuclear Information System (INIS)

    Vogel, J.C.; Talma, A.S.; Heaton, T.H.E.

    1980-01-01

    Groundwater was collected for a multi parameter investigation from 27 boreholes within a radius of 120 km from Venterstad (Cape Province). The samples were analysed for the isotopes carbon-14, carbon-13, oxygen-18, tritium and radon-222, for the dissolved gases nitrogen, oxygen, argon, methane and helium and for the major ionic species. These data, with those collected during previous investigations of the flooding of the Orange Fish tunnel, are used to discuss the geohydrology of the area. Three water types of different origin were delineated

  18. Boron isotopes in brachiopods during the end-Permian mass extinction: constraints on pH evolution and seawater chemistry

    Science.gov (United States)

    Jurikova, Hana; Gutjahr, Marcus; Liebetrau, Volker; Brand, Uwe; Posenato, Renato; Garbelli, Claudio; Angiolini, Lucia; Eisenhauer, Anton

    2017-04-01

    The global biogeochemical cycling of carbon is fundamental for life on Earth with the ocean playing a key role as the largest and dynamically evolving CO2 reservoir. The boron isotope composition (commonly expressed in δ11B) of marine calcium carbonate is considered to be one of the most reliable paleo-pH proxies, potentially enabling us to reconstruct past ocean pH changes and understand carbon cycle perturbations along Earth's geological record (e.g. Foster et al., 2008; Clarkson et al., 2015). Brachiopods present an advantageous and largely underutilised archive for Phanerozoic carbon cycle reconstructions considering their high abundance in the geological record and its origin dating back to the early Cambrian. Moreover, their shell made of low-magnesium calcite makes these marine calcifiers more resistant to post-depositional diagenetic alteration of primary chemical signals. We have investigated the δ11B using MC-ICP-MS (Neptune Plus) and B/Ca and other elemental ratios (Mg/Ca, Sr/Ca, Al/Ca, Li/Ca, Ba/Ca, Na/Ca and Fe/Ca) using ICP-MS-Quadrupole (Agilent 7500cx) from the same specimens in pristine brachiopod shells from two sections from northern Italy during the Late Permian. These sections cover the δ13C excursion in excess of ˜4 ‰ (Brand et al., 2012) and are associated with major climate and environmental perturbations that lead to the mass extinction event at the Permian-Triassic boundary. Particular emphasis will be placed on the implications of our new paleo-pH estimates on the seawater chemistry during the Late Permian. Brand, U., Posenato, R., Came, R., Affek, H., Angiolini, L., Azmy, K. and Farabegoli, E.: The end-Permian mass extinction: A rapid volcanic CO2 and CH4-climatic catastrophe, Chemical Geology 323, 121-144, doi:10.1016/j.chemgeo.2012.06.015, 2012. Clarkson, M.O., Kasemann, S.A., Wood, R.A., Lenton, T.M., Daines, S.J., Richoz, S., Ohnemueller, F., Meixner, A., Poulton, S.W. and Tipper, E.T.: Ocean acidification and the Permo

  19. Geochemistry and Nd-isotope systematics of chemical and terrigenous sediments from the Dun Mountain Ophiolite, New Zealand

    International Nuclear Information System (INIS)

    Sivell, W.J.

    2002-01-01

    . Metalliferous contributions to red and green TA in the overlying terrigenous sedimentary sequence also link these facies to early DMOB back-arc eruptives. The red and green TA pass upwards into ungraded Atomodesmid-bearing grey TA, implying turbidite deposition in a shallowing marine environment. The (mainly andesitic) TA show systematic trends of decreasing Eu/Eu* and ε Nd (T) with increasing Ε-REE, La/Y, Th/Sc, and SiO 2 . Th abundances and Th/Sc ratios (up to 1.6) in the TA are akin to those of calc-alkaline magmas in continental arcs, and are significantly greater than island-arc or ophiolitic volcanics. A narrow range of positive ε Nd (T) values (+0.5 to +2.0) for the TA suggests a young differentiated continental arc source, less dissected than the quartzofeldspathic plutonic provenance for the Torlesse (ε Nd (T) N /Yb N = 2.5-2.8) in the sandstones resemble island-arc tholeiites (IAT). The breccias have low Eu/Eu* (c. 0.72), Ce N /Yb N = 1.6, Th/Sc (0.1-0.2), and Tb N /Yb N c. 1.0, features transitional between the sandstones and DMOB plagiogranites. Importantly, the sandstones and breccias show high positive initial Nd ratios (ε Nd (T) = +5 to +8) akin to values for Brook Street IAT (ε Nd (T) = +9). This implies juvenile (mantle-derived) source rocks for both the mafic and felsic younger terrigenous sediments, compatible with crustal residence (mean provenance) ages less than for the TA. Little continental input is permitted by Nd-isotopic data for these rocks. Whereas the early DMOB pillow basalt - chemical sediment - TA assemblage was emplaced in a back-arc setting, with influx of detritus in part from an active continental margin (possibly within the New England Orogen), the younger DMOB terrigenous sediment association shows a close kinship with bimodal DMOB magmatism related to infant arc volcanic centres in an extensional forearc regime. Turbidite sands and mass-flow deposits were shed into proximal fault-bound basins isolated from continental clastic

  20. Identification of Groundwater Nitrate Contamination from Explosives Used in Road Construction: Isotopic, Chemical, and Hydrologic Evidence.

    Science.gov (United States)

    Degnan, James R; Böhlke, J K; Pelham, Krystle; Langlais, David M; Walsh, Gregory J

    2016-01-19

    Explosives used in construction have been implicated as sources of NO3(-) contamination in groundwater, but direct forensic evidence is limited. Identification of blasting-related NO3(-) can be complicated by other NO3(-) sources, including agriculture and wastewater disposal, and by hydrogeologic factors affecting NO3(-) transport and stability. Here we describe a study that used hydrogeology, chemistry, stable isotopes, and mass balance calculations to evaluate groundwater NO3(-) sources and transport in areas surrounding a highway construction site with documented blasting in New Hampshire. Results indicate various groundwater responses to contamination: (1) rapid breakthrough and flushing of synthetic NO3(-) (low δ(15)N, high δ(18)O) from dissolution of unexploded NH4NO3 blasting agents in oxic groundwater; (2) delayed and reduced breakthrough of synthetic NO3(-) subjected to partial denitrification (high δ(15)N, high δ(18)O); (3) relatively persistent concentrations of blasting-related biogenic NO3(-) derived from nitrification of NH4(+) (low δ(15)N, low δ(18)O); and (4) stable but spatially variable biogenic NO3(-) concentrations, consistent with recharge from septic systems (high δ(15)N, low δ(18)O), variably affected by denitrification. Source characteristics of denitrified samples were reconstructed from dissolved-gas data (Ar, N2) and isotopic fractionation trends associated with denitrification (Δδ(15)N/Δδ(18)O ≈ 1.31). Methods and data from this study are expected to be applicable in studies of other aquifers affected by explosives used in construction.

  1. Exploring the ground ice recharge near permafrost table on the central Qinghai-Tibet Plateau using chemical and isotopic data

    Science.gov (United States)

    Wang, Weihua; Wu, Tonghua; Zhao, Lin; Li, Ren; Zhu, Xiaofan; Wang, Wanrui; Yang, Shuhua; Qin, Yanhui; Hao, Junmin

    2018-05-01

    Thawing permafrost on the Qinghai-Tibet Plateau (QTP) has great impacts on the local hydrological process by way of causing ground ice to thaw. Until now there is little knowledge on ground ice hydrology near permafrost table under a warming climate. This study applied stable tracers (isotopes and chloride) and hydrograph separation model to quantify the sources of ground ice near permafrost table in continuous permafrost regions of the central QTP. The results indicated that the ground ice near permafrost table was mainly supplied by active layer water and permafrost water, accounting for 58.9 to 87.0% and 13.0 to 41.1%, respectively, which implying that the active layer was the dominant source. The contribution rates from the active layer to the ground ice in alpine meadow (59 to 69%) was less than that in alpine steppe (70 to 87%). It showed well-developed hydrogeochemical depth gradients, presenting depleted isotopes and positive chemical gradients with depth within the soil layer. The effects of evaporation and freeze-out fractionation on the soil water and ground ice were evident. The results provide additional insights into ground ice sources and cycling near permafrost table in permafrost terrain, and would be helpful for improving process-based detailed hydrologic models under the occurring global warming.

  2. Water movements in the unsaturated zone and recharge of the aquifer in the Champagne Chalk (France): Isotopic and chemical approaches

    International Nuclear Information System (INIS)

    Vachier, P.; Dever, L.; Fontes, J.C.

    1987-01-01

    Water from the unsaturated zone in the chalk, obtained from porous plugs, was subjected to chemical and isotope analyses over a three-year period. Tensiometric and volumetric water content measurements were carried out at the same time. The results obtained make it possible to establish an outline of the hydrodynamics of this porous, fissured chalk medium. Matrix porosity was 0.42 while fissure porosity was in the region of 0.01. The tritium and nitrate concentrations in the water fix the mean residence time in the 20-metre unsaturated zone at about 30 years. The isotope profiles ( 18 O and 3 H) and their downward displacements make it possible to estimate the mean annual recharge into the unconfined groundwater in the chalk (200 to 300 mm, depending on plant cover). The vertical movement of the solution in the porous matrix is dominated by the piston effect. Variations in 18 O concentration can be correlated with local climatic fluctuations. The recharge period runs from November to March, with summer rainfall playing no part. A comparison of 2 H and 18 O concentrations shows that even winter rainfall is partially removed by evaporation. (author). 17 refs, 11 figs, 1 tab

  3. A recursive microfluidic platform to explore the emergence of chemical evolution

    Directory of Open Access Journals (Sweden)

    David Doran

    2017-08-01

    Full Text Available We propose that a chemically agnostic approach to explore the origin of life, using an automated recursive platform based on droplet microfluidics, could be used to induce artificial chemical evolution by iterations of growth, speciation, selection, and propagation. To explore this, we set about designing an open source prototype of a fully automated evolution machine, comprising seven modules. These modules are a droplet generator, droplet transfer, passive and active size sorting, splitter, incubation chamber, reservoir, and injectors, all run together via a LabVIEWTM program integration system. Together we aim for the system to be used to drive cycles of droplet birth, selection, fusion, and propagation. As a proof of principle, in addition to the working individual modules, we present data showing the osmotic exchange of glycylglycine containing and pure aqueous droplets, showing that the fittest droplets exhibit higher osomolarity relative to their neighbours, and increase in size compared to their neighbours. This demonstrates the ability of our platform to explore some different physicochemical conditions, combining the efficiency and unbiased nature of automation with our ability to select droplets as functional units based on simple criteria.

  4. Observing the metal-poor solar neighbourhood: a comparison of galactic chemical evolution predictions*†

    Science.gov (United States)

    Mishenina, T.; Pignatari, M.; Côté, B.; Thielemann, F.-K.; Soubiran, C.; Basak, N.; Gorbaneva, T.; Korotin, S. A.; Kovtyukh, V. V.; Wehmeyer, B.; Bisterzo, S.; Travaglio, C.; Gibson, B. K.; Jordan, C.; Paul, A.; Ritter, C.; Herwig, F.; NuGrid Collaboration

    2017-08-01

    Atmospheric parameters and chemical compositions for 10 stars with metallicities in the region of -2.2 LTE) and non-LTE (NLTE) approaches. In particular, differences by assuming LTE or NLTE are about 0.10 dex; depending on [Fe/H], Teff, gravity and element lines used in the analysis. We find that the O abundance has the largest error, ranging from 0.10 and 0.2 dex. The best measured elements are Cr, Fe, and Mn; with errors between 0.03 and 0.11 dex. The stars in our sample were included in previous different observational work. We provide a consistent data analysis. The data dispersion introduced in the literature by different techniques and assumptions used by the different authors is within the observational errors, excepting for HD103095. We compare these results with stellar observations from different data sets and a number of theoretical galactic chemical evolution (GCE) simulations. We find a large scatter in the GCE results, used to study the origin of the elements. Within this scatter as found in previous GCE simulations, we cannot reproduce the evolution of the elemental ratios [Sc/Fe], [Ti/Fe], and [V/Fe] at different metallicities. The stellar yields from core-collapse supernovae are likely primarily responsible for this discrepancy. Possible solutions and open problems are discussed.

  5. A simple multistage closed-(box+reservoir model of chemical evolution

    Directory of Open Access Journals (Sweden)

    Caimmi R.

    2011-01-01

    Full Text Available Simple closed-box (CB models of chemical evolution are extended on two respects, namely (i simple closed-(box+reservoir (CBR models allowing gas outflow from the box into the reservoir (Hartwick 1976 or gas inflow into the box from the reservoir (Caimmi 2007 with rate proportional to the star formation rate, and (ii simple multistage closed-(box+reservoir (MCBR models allowing different stages of evolution characterized by different inflow or outflow rates. The theoretical differential oxygen abundance distribution (TDOD predicted by the model maintains close to a continuous broken straight line. An application is made where a fictitious sample is built up from two distinct samples of halo stars and taken as representative of the inner Galactic halo. The related empirical differential oxygen abundance distribution (EDOD is represented, to an acceptable extent, as a continuous broken line for two viable [O/H]-[Fe/H] empirical relations. The slopes and the intercepts of the regression lines are determined, and then used as input parameters to MCBR models. Within the errors (-+σ, regression line slopes correspond to a large inflow during the earlier stage of evolution and to low or moderate outflow during the subsequent stages. A possible inner halo - outer (metal-poor bulge connection is also briefly discussed. Quantitative results cannot be considered for applications to the inner Galactic halo, unless selection effects and disk contamination are removed from halo samples, and discrepancies between different oxygen abundance determination methods are explained.

  6. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Directory of Open Access Journals (Sweden)

    E. C. Apel

    2010-03-01

    Full Text Available The volatile organic compound (VOC distribution in the Mexico City Metropolitan Area (MCMA and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs but with a substantial contribution from oxygenated volatile organic compounds (OVOCs, predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry model and MOZART (Model for Ozone and Related chemical Tracers were able to approximate the observed MCMA daytime patterns and absolute values of the VOC OH reactivity. The MOZART model is also in agreement with observations showing that NMHCs dominate the reactivity distribution except in the afternoon hours. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height.

    A northeast transport event was studied in which air originating in the MCMA was intercepted aloft with the Department of Energy (DOE G1 on 18 March and downwind with the National Center for Atmospheric Research (NCAR C130 one day later on 19 March. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind; ozone was shown to be photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial extent and temporal evolution of the plume

  7. {sup 37}Cl, {sup 15}N, {sup 13}C isotopic analysis of common agro-chemicals for identifying non-point source agricultural contaminants

    Energy Technology Data Exchange (ETDEWEB)

    Annable, W.K. [Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada)]. E-mail: wkannabl@uwaterloo.ca; Frape, S.K. [Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Shouakar-Stash, O. [Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Shanoff, T. [Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Drimmie, R.J. [Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Harvey, F.E. [School of Natural Resources, University of Nebraska, Lincoln, NE 68588-0517 (United States)

    2007-07-15

    The isotopic compositions of commercially available herbicides were analyzed to determine their respective {sup 15}N, {sup 13}C and {sup 37}Cl signatures for the purposes of developing a discrete tool for tracing and identifying non-point source contaminants in agricultural watersheds. Findings demonstrate that of the agrochemicals evaluated, chlorine stable isotopes signatures range between {delta}{sup 37}Cl = -4.55 per mille and +3.40 per mille , whereas most naturally occurring chlorine stable isotopes signatures, including those of road salt, sewage sludge and fertilizers, vary in a narrow range about the Standard Mean Ocean Chloride (SMOC) between -2.00 per mille and +1.00 per mille . Nitrogen stable isotope values varied widely from {delta}{sup 15}N = -10.86 per mille to +1.44 per mille and carbon stable isotope analysis gave an observed range between {delta}{sup 13}C = -37.13 per mille and -21.35 per mille for the entire suite of agro-chemicals analyzed. When nitrogen, carbon and chlorine stable isotope analyses were compared in a cross-correlation analysis, statistically independent isotopic signatures exist suggesting a new potential tracer tool for identifying herbicides in the environment.

  8. Kinetics of isotope exchange reactions involving intra- and intermolecular reactions: 1. Rate law for a system with two chemical compounds and three exchangeable atoms

    International Nuclear Information System (INIS)

    Xuelei Chu; Ohmoto, Hiroshi

    1991-01-01

    For an isotopic exchange reaction between two compounds (X and AB) in a homogeneous system, such as a gaseous or aqueous system, where one (AB) of them possesses two exchangeable atoms in non-equivalent positions and where one intramolecular isotope exchange (A ↔ B) and two intermolecular isotope exchange reactions (X ↔ A and X ↔ B) may occur, its rate law no longer obeys a pseudo-first order rate equation described for simple two-component systems by many previous investigators. The change with time of the δ value of each of the three components (X, A, and B) in a closed and homogeneous system is a complicated function of the initial δ values of the three components, the chemical concentrations of the two compounds, and the overall rate constants of the forward and reverse reactions involving the two intermolecular and one intramolecular reactions of isotope exchanges. Also, for some one of the three components, the change of its δ value with time may not be monotonic, and the relationship of 1n (1 - F) with time may be non-linear in a plot of 1n (1 - F) vs. t. In addition, the rate law of the isotope exchange reaction in this system also provides a quantitative method to estimate the overall rate constants for the one-intra-and two intermolecular isotope exchanges and the equilibrium isotopic fractionation factors among the three components

  9. Development of routines for simultaneous in situ chemical composition and stable Si isotope ratio analysis by femtosecond laser ablation inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Frick, Daniel A., E-mail: dfrick@gfz-potsdam.de [GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Schuessler, Jan A. [GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Blanckenburg, Friedhelm von [GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Institute of Geological Science, Freie Universität Berlin, 12249 Berlin (Germany)

    2016-09-28

    Stable metal (e.g. Li, Mg, Ca, Fe, Cu, Zn, and Mo) and metalloid (B, Si, Ge) isotope ratio systems have emerged as geochemical tracers to fingerprint distinct physicochemical reactions. These systems are relevant to many Earth Science questions. The benefit of in situ microscale analysis using laser ablation (LA) over bulk sample analysis is to use the spatial context of different phases in the solid sample to disclose the processes that govern their chemical and isotopic compositions. However, there is a lack of in situ analytical routines to obtain a samples' stable isotope ratio together with its chemical composition. Here, we evaluate two novel analytical routines for the simultaneous determination of the chemical and Si stable isotope composition (δ{sup 30}Si) on the micrometre scale in geological samples. In both routines, multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is combined with femtosecond-LA, where stable isotope ratios are corrected for mass bias using standard-sample-bracketing with matrix-independent calibration. The first method is based on laser ablation split stream (LASS), where the laser aerosol is split and introduced simultaneously into both the MC-ICP-MS and a quadrupole ICP-MS. The second method is based on optical emission spectroscopy using direct observation of the MC-ICP-MS plasma (LA-MC-ICP-MS|OES). Both methods are evaluated using international geological reference materials. Accurate and precise Si isotope ratios were obtained with an uncertainty typically better than 0.23‰, 2SD, δ{sup 30}Si. With both methods major element concentrations (e.g., Na, Al, Si, Mg, Ca) can be simultaneously determined. However, LASS-ICP-MS is superior over LA-MC-ICP-MS|OES, which is limited by its lower sensitivity. Moreover, LASS-ICP-MS offers trace element analysis down to the μg g{sup −1}-range for more than 28 elements due to lower limits of detection, and with typical uncertainties better than 15%. For in situ

  10. Development of routines for simultaneous in situ chemical composition and stable Si isotope ratio analysis by femtosecond laser ablation inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Frick, Daniel A.; Schuessler, Jan A.; Blanckenburg, Friedhelm von

    2016-01-01

    Stable metal (e.g. Li, Mg, Ca, Fe, Cu, Zn, and Mo) and metalloid (B, Si, Ge) isotope ratio systems have emerged as geochemical tracers to fingerprint distinct physicochemical reactions. These systems are relevant to many Earth Science questions. The benefit of in situ microscale analysis using laser ablation (LA) over bulk sample analysis is to use the spatial context of different phases in the solid sample to disclose the processes that govern their chemical and isotopic compositions. However, there is a lack of in situ analytical routines to obtain a samples' stable isotope ratio together with its chemical composition. Here, we evaluate two novel analytical routines for the simultaneous determination of the chemical and Si stable isotope composition (δ 30 Si) on the micrometre scale in geological samples. In both routines, multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is combined with femtosecond-LA, where stable isotope ratios are corrected for mass bias using standard-sample-bracketing with matrix-independent calibration. The first method is based on laser ablation split stream (LASS), where the laser aerosol is split and introduced simultaneously into both the MC-ICP-MS and a quadrupole ICP-MS. The second method is based on optical emission spectroscopy using direct observation of the MC-ICP-MS plasma (LA-MC-ICP-MS|OES). Both methods are evaluated using international geological reference materials. Accurate and precise Si isotope ratios were obtained with an uncertainty typically better than 0.23‰, 2SD, δ 30 Si. With both methods major element concentrations (e.g., Na, Al, Si, Mg, Ca) can be simultaneously determined. However, LASS-ICP-MS is superior over LA-MC-ICP-MS|OES, which is limited by its lower sensitivity. Moreover, LASS-ICP-MS offers trace element analysis down to the μg g −1 -range for more than 28 elements due to lower limits of detection, and with typical uncertainties better than 15%. For in situ

  11. Significance of the molecular diffusion for chemical and isotopic separation during the formation and degradation of natural gas reservoirs

    International Nuclear Information System (INIS)

    Hermichen, W.D.; Schuetze, H.

    1987-01-01

    Investigations at natural gas fields as well as modelling experiments have pointed out that changes of the chemical and isotopic composition occur in the course of migration, accumulation and dispersion of natural gas. Dissolution and sorption processes as well as in particular the diffusion process are considered to be the elementary separation processes. The influences on dissolved and freely flowing gases and on stationary gas accumulation are described by differential equations. The simulation of the following phenomena is shown: (1) immigration of gas into the pore space which is hydrodynamically passive, (2) diffusive migration of gas into the environment of the accumulation, and (3) diffusive 'decompression' into the roof and the floor of a gas bed and a gas containing subsoil water stratum, respectively. (author)

  12. Effects of main-sequence mass loss on stellar and galactic chemical evolution

    International Nuclear Information System (INIS)

    Guzik, J.A.

    1988-01-01

    L.A. Willson, G.H. Bowen and C. Struck-Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10 -9 M mass of sun/yr, diminishing over several times 10 8 years. The author attempts to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M 0 , and mass-loss rates decreasing exponentially over 2-3 x 10 8 years. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 M mass of sun and mass loss timescales 0.2 to 2.0 Gry. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M mass of sun and a metallicity-dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus-remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main sequence to the present

  13. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    International Nuclear Information System (INIS)

    Andrews, Brett H.; Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A.

    2017-01-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

  14. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, Brett H. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A., E-mail: andrewsb@pitt.edu [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

    2017-02-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

  15. A global survey of the stable isotope and chemical compositions of bottled and canned beers as a guide to authenticity.

    Science.gov (United States)

    Carter, J F; Yates, H S A; Tinggi, U

    2015-01-01

    This study presents a dataset, derived from the analysis of 162 bottled and canned beers from around the globe, which may be used for comparison with suspected counterfeit or substitute products. The data comprise δ2H and δ18O compositions of the whole beer and δ13C compositions of the dry residue (mostly sugar) together with the concentrations of five anions (F, Cl, NO3, SO4, PO4) and seven cations (Ca, K, Mg, SiO2, V, Mn, Sr). A strong correlation, consistent with natural waters but offset from the Global Meteoric Water Line, was observed between the δ2H/δ18O composition of the beers. The extent of the offset could be explained by the brewing process and the alcohol and sugars present in the beers. Correlations between inorganic analytes were consistent with the addition of salts in the brewing process. Beers were classified as follows: ale, lager, stout or wheat-beer and the chemical composition was found to be characteristic of the assigned type, with lagers being the most readily classified. A combination of chemical and isotopic data was found to be characteristic of the geographical origin (on a continental scale) and could most easily identify beers from Australasia or Europe. A global map of δ18O data revealed a geo-spatial distribution that mirrored existing maps of the isotopic composition of annual precipitation. This confirmed a commonsense view that local precipitation will be the primary source for the water used in brewing. Using this isoscape (or alcoscape) it may be possible to assess the geographical origins of samples for which genuine comparative samples cannot be obtained. Copyright © 2014 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

  16. Chemical, physical, and optical evolution of biomass burning aerosols: a case study

    Science.gov (United States)

    Adler, G.; Flores, J. M.; Abo Riziq, A.; Borrmann, S.; Rudich, Y.

    2011-02-01

    In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB) event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (HR-RES-TOF-AMS) was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While these types of extensive BB events are not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI) was derived using a white light optical particle counter (WELAS). The average EBRI for a mixed population of aerosols dominated by open fires was m = 1.53(±0.03) + 0.07i(±0.03), during the smoldering phase of the fires we found the EBRI to be m = 1.54(±0.01) + 0.04i(±0.01) compared to m = 1.49(±0.01) + 0.02i(±0.01) of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs) were detected during the entire event, which suggest possible implications for human health during such extensive event.

  17. Chemical evolution of Titan’s aerosol analogues under VUV irradiation

    Science.gov (United States)

    Carrasco, Nathalie; Gavilan, Lisseth; Tigrine, Sarah; Vettier, Ludovic; Nahon, Laurent; Pernot, Pascal

    2017-10-01

    Since the Cassini-CAPS measurements, organic aerosols are known to be present and formed at high altitudes in the diluted and partially ionized medium that is Titan’s ionosphere [1].After production in the ionosphere, Titan’s aerosols evolve through microphysics during their sedimentation down to Titan’s surface [2]. Starting with a few nanomers size in the upper atmosphere, they reach a fractal structure of a few hundreds nanometers close to the surface [3]. During sedimentation, aerosols are also submitted to solar irradiation. As laboratory analogs of Titan’s atmospheric aerosols (tholins) show a strong UV absorption [4], we suspect that VUV irradiation could also induce a chemical evolution of Titan’s aerosols during their descent in Titan’s atmosphere.The aim of this work ist to simulate the irradiation process occuring on the aerosols in Titan’s atmosphere and to address whether this irradiation impacts the chemical composition of the organic solids. First aerosol analogues were produced in a N2-CH4 plasma discharge as thin organic films of a few hundreds of nanometers thick [5]. Then those were irradiated at Lyman-α wavelength, the strongest VUV line in the solar spectrum, with a high photon flux on a synchrotron VUV beamline. We will present and discuss the significant chemical evolutions observed on the analogues after VUV irradiation by mid-IR absorption spectroscopy.[1] Waite et al. (2009) Science , 316, p. 870[2] Lavvas et al. (2011) Astrophysical Journal, 728:80[3] Tomasko et al. (2008) Planetary and Space Science, 56, p. 669[4] Mahjoub et al. (2012) Icarus 221, P. 670[5] Carrasco et al. (2016) Planetary and Space Science, 128, p. 52

  18. STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF THE SEXTANS DWARF SPHEROIDAL GALAXY

    International Nuclear Information System (INIS)

    Lee, Myung Gyoon; Yuk, In-Soo; Park, Hong Soo; Harris, Jason; Zaritsky, Dennis

    2009-01-01

    We present the star formation history (SFH) and chemical evolution of the Sextans dSph galaxy as a function of a galactocentric distance. We derive these from the VI photometry of stars in the 42' x 28' field using the SMART model developed by Yuk and Lee and adopting a closed-box model for chemical evolution. For the adopted age of Sextans 15 Gyr, we find that >84% of the stars formed prior to 11 Gyr ago, significant star formation extends from 15 to 11 Gyr ago (∼ 65% of the stars formed 13-15 Gyr ago, while ∼ 25% formed 11-13 Gyr ago), detectable star formation continued to at least 8 Gyr ago, the SFH is more extended in the central regions than the outskirts, and the difference in star formation rates between the central and outer regions is most marked 11-13 Gyr ago. Whether blue straggler stars are interpreted as intermediate-age main-sequence stars affects conclusions regarding the SFH for times 4-8 Gyr ago, but this is at most only a trace population. We find that the metallicity of the stars increased rapidly up to [Fe/H] = -1.6 in the central region and to [Fe/H] = -1.8 in the outer region within the first Gyr, and has varied slowly since then. The abundance ratios of several elements derived in this study are in good agreement with the observational data based on the high-resolution spectroscopy in the literature. We conclude that the primary driver for the radial gradient of the stellar population in this galaxy is the SFH, which self-consistently drives the chemical enrichment history.

  19. Groundwater recharge and chemical evolution in the southern High Plains of Texas, USA

    Science.gov (United States)

    Fryar, Alan; Mullican, William; Macko, Stephen

    2001-11-01

    The unconfined High Plains (Ogallala) aquifer is the largest aquifer in the USA and the primary water supply for the semiarid southern High Plains of Texas and New Mexico. Analyses of water and soils northeast of Amarillo, Texas, together with data from other regional studies, indicate that processes during recharge control the composition of unconfined groundwater in the northern half of the southern High Plains. Solute and isotopic data are consistent with a sequence of episodic precipitation, concentration of solutes in upland soils by evapotranspiration, runoff, and infiltration beneath playas and ditches (modified locally by return flow of wastewater and irrigation tailwater). Plausible reactions during recharge include oxidation of organic matter, dissolution and exsolution of CO2, dissolution of CaCO3, silicate weathering, and cation exchange. Si and 14C data suggest leakage from perched aquifers to the High Plains aquifer. Plausible mass-balance models for the High Plains aquifer include scenarios of flow with leakage but not reactions, flow with reactions but not leakage, and flow with neither reactions nor leakage. Mechanisms of recharge and chemical evolution delineated in this study agree with those noted for other aquifers in the south-central and southwestern USA. Résumé. L'aquifère libre des Hautes Plaines (Ogallala) est le plus vaste aquifère des états-Unis et la ressource de base pour l'eau potable de la région semi-aride du sud des Hautes Plaines du Texas et du Nouveau-Mexique. Des analyses de l'eau et des sols prélevés au nord-est d'Amarillo (Texas), associées à des données provenant d'autres études dans cette région, indiquent que des processus intervenant au cours de l'infiltration contrôlent la composition de l'eau de la nappe libre dans la moitié septentrionale du sud des Hautes Plaines. Les données chimiques et isotopiques sont compatibles avec une séquence de précipitation épisodique, avec la reconcentration en solut

  20. The effects of early diagenesis on the chemical and stable carbon isotopic composition of wood

    International Nuclear Information System (INIS)

    Spiker, E.C.; Hatcher, P.G.

    1987-01-01

    Studies of modern and ancient buried wood show that there is a linear correlation between carbohydrate content and the stable carbon isotope composition as carbohydrates are preferentially degraded during early diagenesis. As the carbohydrate content decreases, the delta 13 C value of the degraded wood decreases 1 to 2 per mil, approaching the value of the residual lignin. These results indicate that carbohydrate degradation products are lost and not incorporated into the aromatic structure as lignin is selectively preserved during early diagenesis of wood. These results also indicate that attempts to quantify terrestrial inputs to modern sedimentary organic matter based on delta 13 C values should consider the possibility of a 1 to 2 per mil decrease in the delta 13 C value of degraded wood. (author)

  1. Chemical and isotopic composition of marine organic matter as indicators of its origin

    International Nuclear Information System (INIS)

    Malej, A.

    1989-07-01

    The present study was carried out to evaluate the relative importance of marine and terrestrial sources of Particulate Organic Matter (POM) in the Northern Adriatic Sea. Samples of POM were obtained from the water column at 14 stations using Niskin bottles at 4 depths and sediment traps (placed near the sea floor). Additional samples were obtained of likely source organic matter: sewage, river POM, phytoplankton bloom material, zooplankton, jelly-fish and bethic macrophytes. All samples were analyzed for total carbon and nitrogen and the delta C-13/C-12 ratio (by mass spectrometry). Marine and terrestrial sources of POM were clearly distinguished by their isotopic ratios. A linear model was set up to evaluate the relative importance of these sources at each sampling station. Except in the immediate vicinity of river sources, the marine component appears to dominate. 7 refs, 5 figs, 1 tab

  2. Isotopic separation

    International Nuclear Information System (INIS)

    Chen, C.L.

    1979-01-01

    Isotopic species in an isotopic mixture including a first species having a first isotope and a second species having a second isotope are separated by selectively exciting the first species in preference to the second species and then reacting the selectively excited first species with an additional preselected radiation, an electron or another chemical species so as to form a product having a mass different from the original species and separating the product from the balance of the mixture in a centrifugal separating device such as centrifuge or aerodynamic nozzle. In the centrifuge the isotopic mixture is passed into a rotor where it is irradiated through a window. Heavier and lighter components can be withdrawn. The irradiated mixture experiences a large centrifugal force and is separated in a deflection area into lighter and heavier components. (UK)

  3. Development of high-performance chemical isotope labeling LC-MS for profiling the human fecal metabolome.

    Science.gov (United States)

    Xu, Wei; Chen, Deying; Wang, Nan; Zhang, Ting; Zhou, Ruokun; Huan, Tao; Lu, Yingfeng; Su, Xiaoling; Xie, Qing; Li, Liang; Li, Lanjuan

    2015-01-20

    Human fecal samples contain endogenous human metabolites, gut microbiota metabolites, and other compounds. Profiling the fecal metabolome can produce metabolic information that may be used not only for disease biomarker discovery, but also for providing an insight about the relationship of the gut microbiome and human health. In this work, we report a chemical isotope labeling liquid chromatography-mass spectrometry (LC-MS) method for comprehensive and quantitative analysis of the amine- and phenol-containing metabolites in fecal samples. Differential (13)C2/(12)C2-dansyl labeling of the amines and phenols was used to improve LC separation efficiency and MS detection sensitivity. Water, methanol, and acetonitrile were examined as an extraction solvent, and a sequential water-acetonitrile extraction method was found to be optimal. A step-gradient LC-UV setup and a fast LC-MS method were evaluated for measuring the total concentration of dansyl labeled metabolites that could be used for normalizing the sample amounts of individual samples for quantitative metabolomics. Knowing the total concentration was also useful for optimizing the sample injection amount into LC-MS to maximize the number of metabolites detectable while avoiding sample overloading. For the first time, dansylation isotope labeling LC-MS was performed in a simple time-of-flight mass spectrometer, instead of high-end equipment, demonstrating the feasibility of using a low-cost instrument for chemical isotope labeling metabolomics. The developed method was applied for profiling the amine/phenol submetabolome of fecal samples collected from three families. An average of 1785 peak pairs or putative metabolites were found from a 30 min LC-MS run. From 243 LC-MS runs of all the fecal samples, a total of 6200 peak pairs were detected. Among them, 67 could be positively identified based on the mass and retention time match to a dansyl standard library, while 581 and 3197 peak pairs could be putatively

  4. Identification of volatile and semivolatile compounds in chemical ionization GC-MS using a mass-to-structure (MTS) Search Engine with integral isotope pattern ranking.

    Science.gov (United States)

    Liao, Wenta; Draper, William M

    2013-02-21

    The mass-to-structure or MTS Search Engine is an Access 2010 database containing theoretical molecular mass information for 19,438 compounds assembled from common sources such as the Merck Index, pesticide and pharmaceutical compilations, and chemical catalogues. This database, which contains no experimental mass spectral data, was developed as an aid to identification of compounds in atmospheric pressure ionization (API)-LC-MS. This paper describes a powerful upgrade to this database, a fully integrated utility for filtering or ranking candidates based on isotope ratios and patterns. The new MTS Search Engine is applied here to the identification of volatile and semivolatile compounds including pesticides, nitrosoamines and other pollutants. Methane and isobutane chemical ionization (CI) GC-MS spectra were obtained from unit mass resolution mass spectrometers to determine MH(+) masses and isotope ratios. Isotopes were measured accurately with errors of Search Engine and details performance testing with over 50 model compounds.

  5. Deposition of carbon nanotubes by a marine suspension feeder revealed by chemical and isotopic tracers

    Energy Technology Data Exchange (ETDEWEB)

    Hanna, Shannon K., E-mail: hanna.shannonk@gmail.com [Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106 (United States); Miller, Robert J. [Marine Science Institute, University of California, Santa Barbara, CA 93106 (United States); Lenihan, Hunter S. [Bren School of Environmental Science and Management, University of California, Santa Barbara, CA 93106 (United States)

    2014-08-30

    Highlights: • CNTs decrease the filtration rate of mussels by as much as 24%. • Metals in CNTs and their δ{sup 13}C can be used to quantify CNTs in biological samples. • Mussels exposed to CNTs deposit high concentrations of them in biodeposits. • CNTs accumulate mainly in gut tissue of mussels during exposure. - Abstract: Carbon nanotubes (CNTs) are one of the few truly novel nanomaterials and are being incorporated into a wide range of products, which will lead to environmental release and potential ecological impacts. We examined the toxicity of CNTs to marine mussels and the effect of mussels on CNT fate and transport by exposing mussels to 1, 2, or 3 mg CNTs l{sup −1} for four weeks and measuring mussel clearance rate, shell growth, and CNT accumulation in tissues and deposition in biodeposits. We used metal impurities and carbon stable isotope ratios of the CNTs as tracers of CNT accumulation. Mussels decreased clearance rate of phytoplankton by 24% compared with control animals when exposed to CNTs. However, mussel growth rate was unaffected by CNT concentrations up to 3 mg l{sup −1}. Based on metal concentrations and carbon stable isotope values, mussels deposited most CNTs in biodeposits, which contained >110 mg CNTs g{sup −1} dry weight, and accumulated about 1 mg CNTs g{sup −1} dry weight of tissue. We conclude that extremely high concentrations of CNTs are needed to illicit a toxic response in mussels but the ability of mussels to concentrate and deposit CNTs in feces and pseudofeces may impact infaunal organisms living in and around mussel beds.

  6. 2H isotope effect on 13C chemical shifts of Nitro-Benzo-9-Crown-3

    International Nuclear Information System (INIS)

    Moghimi, A.; Rastegar, M.; Ghandi, M.; Bijanzadeh, H. R.

    2002-01-01

    Deuterium substitution on two ortho-substituted-OCH 2 fragments in Nitro-Benzo-9 Crown-3 induces low frequency shifts, positive m ''nΔC j, in all 13 C NMR resonances which is an indication of the increased shielding in this crown ether. The magnitude of these shifts vary from 15 ΔC 7=716 to 54 ΔC 3=15 ppb for C 7 and C 3 carbons directly attached to 2 H, respectively. The influences of concentration and solvent, CDCl 3 CD 3 COCD 3 , and C 6 D 6 , on mn ΔC j values were investigated. The mn ΔC j values depended more on the nature of the solvent than on the concentration. The order of induced isotope shifts is 15 Δ, 51 Δ > 24 Δ, 42 Δ> 34 Δ, 43 Δ > 56 Δ, 65 Δ> 45 Δ, 54 Δ. The isotope shifts observed are suggested to be a sum of contributions from low frequency shift due to inductive-type and negative hyperconjugation perturbations. The C-D bond, as a poorer electron acceptor than a C-H bond induced less positive charge on directly attached oxygens O 1 and O 2. This, in turn, causes shielding of C 1 and C 2 in C1O1CD 2 and C 2 0 2 CD 2 fragments. The difference in 34 ΔC 1 and 43 ΔC 2 values is attributed to the conformational dependence of the negative hyperconjugation. The C 1 and C 2, are in fact, not equally affected by the two CD 2 groups by negative hyperconjugation because of the existence of NO 2 group attached to the benzene ring

  7. A chemically selective laser ion source for the on-line isotope separation

    International Nuclear Information System (INIS)

    Scheerer, F.

    1993-03-01

    In this thesis a laser ion source is presented. In a hot chamber the atoms of the elements to be studied are resonantly by light of pulsed dye lasers, which are pumped by pulsed copper-vapor lasers with extremely high pulse repetition rate (ν rep ∼ 10 kHz), stepwise excited and ionized. By the storage of the atoms in a hot chamber and the high pulse repetition rate of the copper-vapor lasers beyond the required high efficiency (ε ∼ 10%) can be reached. First preparing measurements were performed at the off-line separator at CERN with the rare earth elements ytterbium and thulium. Starting from the results of these measurements further tests of the laser ion source were performed at the on-line separator with in a thick tantalum target produced neutron-deficient ytterbium isotopes. Under application of a time-of-flight mass spectrometer in Mainz an efficient excitation scheme on the resonance ionization of tin was found. This excitation scheme is condition for an experiment at the GSI for the production of the extremely neutron-deficient, short-lived nucleus 102 Sn. In the summer 1993 is as first application of the newly developed laser ion source at the PSB-ISOLDE at CERN an astrophysically relevant experiment for the nuclear spectroscopy of the neutron-rich silver isotopes 124-129 Ag is planned. This experiment can because of the lacking selectivity of conventional ion sources only be performed by means of the here presented laser ion source. The laser ion source shall at the PSB-ISOLDE 1993 also be applied for the selective ionization of manganese. (orig./HSI) [de

  8. Evolution of chemical composition of fogwater in winter in Chengdu, China.

    Science.gov (United States)

    Yin, Hongling; Ye, Zhixiang; Yang, Yingchun; Yuan, Wei; Qiu, Changyan; Yuan, Huawei; Wang, Min; Li, Shiping; Zou, Changwu

    2013-09-01

    Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon (TOC) > total nitrogen (TN) > total inorganic carbon (TIC) was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes (C11-C37) at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57-21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog (393.12 ng/mL) which was more than ten times that in the fog formation period (27.83 ng/mL) and the fog dissipation period (14.87 ng/mL). Concentrations of Sigma15PAHs were in the range of 7.27-38.52 ng/mL at the urban site and 2.59-22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog (27.15 ng/mL) > fog dissipation period (11.59 ng/mL) > fog formation period (6.42 ng/mL). Concentrations of dicarboxylic acids (C5-C9) ranged from 10.92 to 40.78 ng/mL, with glutaric acid (C5) as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.

  9. Effects of different water storage procedures on the dissolved Fe concentration and isotopic composition of chemically contrasted waters from the Amazon River Basin.

    Science.gov (United States)

    Mulholland, Daniel S; Poitrasson, Franck; Boaventura, Geraldo R

    2015-11-15

    Although recent studies have investigated the Fe isotopic composition of dissolved, colloidal and particulate phases from continental and oceanic natural waters, few efforts have been made to evaluate whether water sample storage and the separation of different pore-size fractions through filtration can cause any change to the Fe isotopic compositions. The present study investigates the possible biases introduced by different water storage conditions on the dissolved Fe concentration and isotopic composition of chemically different waters. Water samples were collected from an organic-rich river and from mineral particulate-rich rivers. Filtered and unfiltered water samples were stored either at room temperature or frozen at -18°C in order to assess possible biases due to (i) different water storage temperature, and (ii) storage of bulk (unfiltered) vs filtered water. Iron isotope measurements were performed by Multicollector Inductively Coupled Plasma Mass Spectrometry with a Thermo Electron Neptune instrument, after Fe purification using anion-exchange resins. Our data reveal that bulk water storage at room temperature without filtration produces minor changes in the dissolved Fe isotopic composition of mineral particulate-rich waters, but significant isotopic composition changes in organic-rich waters. In both cases, however, the impact of the different procedures on the Fe concentrations was strong. On the other hand, the bulk water stored frozen without filtration produced more limited changes in the dissolved Fe concentrations, and also on isotopic compositions, relative to the samples filtered in the field. The largest effect was again observed for the organic-rich waters. These findings suggest that a time lag between water collection and filtration may cause isotopic exchanges between the dissolved and particulate Fe fractions. When it is not possible to filter the samples in the field immediately after collection, the less detrimental approach is to

  10. A transformation theory of stochastic evolution in Red Moon methodology to time evolution of chemical reaction process in the full atomistic system.

    Science.gov (United States)

    Suzuki, Yuichi; Nagaoka, Masataka

    2017-05-28

    Atomistic information of a whole chemical reaction system, e.g., instantaneous microscopic molecular structures and orientations, offers important and deeper insight into clearly understanding unknown chemical phenomena. In accordance with the progress of a number of simultaneous chemical reactions, the Red Moon method (a hybrid Monte Carlo/molecular dynamics reaction method) is capable of simulating atomistically the chemical reaction process from an initial state to the final one of complex chemical reaction systems. In the present study, we have proposed a transformation theory to interpret the chemical reaction process of the Red Moon methodology as the time evolution process in harmony with the chemical kinetics. For the demonstration of the theory, we have chosen the gas reaction system in which the reversible second-order reaction H 2 + I 2  ⇌ 2HI occurs. First, the chemical reaction process was simulated from the initial configurational arrangement containing a number of H 2 and I 2 molecules, each at 300 K, 500 K, and 700 K. To reproduce the chemical equilibrium for the system, the collision frequencies for the reactions were taken into consideration in the theoretical treatment. As a result, the calculated equilibrium concentrations [H 2 ] eq and equilibrium constants K eq at all the temperatures were in good agreement with their corresponding experimental values. Further, we applied the theoretical treatment for the time transformation to the system and have shown that the calculated half-life τ's of [H 2 ] reproduce very well the analytical ones at all the temperatures. It is, therefore, concluded that the application of the present theoretical treatment with the Red Moon method makes it possible to analyze reasonably the time evolution of complex chemical reaction systems to chemical equilibrium at the atomistic level.

  11. Method for separating isotopes

    International Nuclear Information System (INIS)

    Jepson, B.E.

    1976-01-01

    The invention comprises a method for separating different isotopes of elements from each other by contacting a feed solution containing the different isotopes with a macrocyclic polyether to preferentially form a macrocyclic polyether complex with the lighter of the different isotopes. The macrocyclic polyether complex is then separated from the lighter isotope depleted feed solution. A chemical separation of isotopes is carried out in which a constant refluxing system permits a continuous countercurrent liquid-liquid extraction. (LL)

  12. Evolution of chemical specifications following the working group of international inter-comparison

    International Nuclear Information System (INIS)

    Leduc-Brunet, Murielle; Gressier, F.; Mole, D.; Massias, O.; Marescot, O.; Bretelle, Jean Luc

    2012-09-01

    As part of a continuous improvement process and the inclusion of Experience Feedback, EDF has launched a working group to analyse its reference of Chemical Specifications with regard to the guidelines of EPRI and VGB.. As a result of the analysis of over 1000 lines of specifications, a large number of recommendations were issued, referring either to control of new chemical parameters or to an enhancement of measurement frequencies. These recommendations are to be developed by preliminary studies which will provide supporting evidence for future decisions. To implement these recommendations, EDF launched a dedicated project in 2011, whose main objectives were to: - raise the requirements of chemical specifications in line with international standards and compare the technical basis of the different international standards, - strengthen monitoring and anticipation of corrective actions in the field of plant chemistry with a view to extending nuclear plant lifetime to 60 years. This project, scheduled for 2011 to 2016, covers the following activities: - studies on the technical background of the specifications (2011-14), - study of the possibility of adopting an 'Actions Levels' approach in EDF's own specifications (2012-14), - new propositions evolution of the specifications (2015-16). (authors)

  13. Evolution and variation of the Tsushima warm current during the late Quaternary: Evidence from planktonic foraminifera, oxygen and carbon isotopes

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The evolution and variation history of the Tsushima warm current during the late Quaternary was reconstructed based on the quantitative census data of planktonic foraminiferal fauna, together with oxygen and carbon isotope records of mixed layer dweller G. ruber and thermocline dweller N. dutertrei in piston core CSH1 and core DGKS9603 collected separately from the Tsushima warm current and the Kuroshio dominated area. The result showed that the Tsushima warm current vanished in the lowstand period during 40―24 cal ka BP, while the Kuroshio still flowed across the Okinawa Trough, arousing strong upwelling in the northern Trough. Meanwhile, the influence of freshwater greatly increased in the northern Okinawa Trough, as the broad East China Sea continental shelf emerged. The freshwater reached its maximum during the last glacial maximum (LGM), when the upwelling obviously weakened for the lowest sea-level and the depression of the Kuroshio. The modern Tsushima warm current began its development since 16 cal ka BP, and the impact of the Kuroshio increased in the middle and north- ern Okinawa Trough synchronously during the deglaciation and gradually evolved as the main water source of the Tsushima current. The modern Tsushima current finally formed at about 8.5 cal ka BP, since then the circulation structure has been relatively stable. The water of the modern Tsushima cur- rent primarily came from the Kuroshio axis. A short-term wiggle of the current occurred at about 3 cal ka BP, probably for the influences from the enhancement of the winter monsoon and the depression of the Kuroshio. The cold water masses greatly strengthened during the wiggle.

  14. Si and C isotopic ratios in AGB stars: SiC grain data, models, and the galactic evolution of the Si Isotopes

    NARCIS (Netherlands)

    Zinner, E.; Nittler, L.R.; Gallino, R.; Karakas, A.I.; Lugaro, M.A.; Straniero, O.; Lattanzio, J.C.

    2006-01-01

    Presolar grains of the mainstream, Y and Z type are believed to have an origin in carbon stars. We compared the C and Si isotopic ratios of these grains [1] with the results of theoretical models for the envelope compositions of AGB stars. Two sets of models (FRANEC, Monash) use a range of stellar

  15. High mass isotope separation arrangement

    International Nuclear Information System (INIS)

    Eerkens, J.W.

    1980-01-01

    This invention relates to the isotope separation art and, more particularly, to a selectively photon-induced energy level transition of an isotopic molecule containing the isotope to be separated and a chemical reaction with a chemically reactive agent to provide a chemical compound containing atoms of the isotope desired. In particular a description is given of a method of laser isotope separation applied to the separation of 235 UF 6 from 238 UF 6 . (U.K.)

  16. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

    Apel, Eric; Emmons, L.; Karl, Thomas G.; Flocke, Frank M.; Hills, A. J.; Madronich, Sasha; Lee-Taylor, J.; Fried, Alan; Weibring, P.; Walega, J.; Richter, Dirk; Tie, X.; Mauldin, L.; Campos, Teresa; Weinheimer, Andrew J.; Knapp, David; Sive, B.; Kleinman, Lawrence I.; Springston, S.; Zaveri, Rahul A.; Ortega, John V.; Voss, Paul B.; Blake, D. R.; Baker, Angela K.; Warneke, Carsten; Welsh-Bon, Daniel; de Gouw, Joost A.; Zheng, J.; Zhang, Renyi; Rudolph, Jochen; Junkermann, W.; Riemer, D.

    2010-01-01

    The volatile organic compound (VOC) distribution in the Mexico City Metropolitan Area (MCMA) and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs) but with a substantial contribution from oxygenated volatile organic compounds (OVOCs), predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry) model and MOZART (Model for Ozone and Related chemical Tracers) were able to reproduce the general features of the daytime cycle of the VOC OH reactivity distribution showing that NMHCs dominate the distribution except in the afternoon hours and that the VOC OH reactivity peaks in the early morning due to high morning emissions from the city into a shallow boundary layer. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height. In addition, a plume was studied in which air was advected out of the MCMA and intercepted downwind with the DOE G1 on March 18 and the NCAR C130 one day later on March 19. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind. Ozone and many OVOCs were photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial and temporal extent of the March 19 plume and to help interpret the OH

  17. Chemical evolution of volatile organic compounds in the outflow of the Mexico City Metropolitan area

    Energy Technology Data Exchange (ETDEWEB)

    Apel, E.; Springston, S.; Karl, T.; Emmons, L.; Flocke, F.; Hills, A. J.; Madronich, S.; Lee-Taylor, J.; Fried, A.; Weibring, P.; Walega, J.; Richter, D., Tie, X.; Mauldin, L.; Campos, T.; Sive, B.; Kleinman, L.; Springston, S., Zaveri, R.; deGouw, J.; Zheng, J.; Zhang, R.; Rudolph, J.; Junkermann, W.; Riemer, D. D.

    2009-11-01

    The volatile organic compound (VOC) distribution in the Mexico City Metropolitan Area (MCMA) and its evolution as it is uplifted and transported out of the MCMA basin was studied during the 2006 MILAGRO/MIRAGE-Mex field campaign. The results show that in the morning hours in the city center, the VOC distribution is dominated by non-methane hydrocarbons (NMHCs) but with a substantial contribution from oxygenated volatile organic compounds (OVOCs), predominantly from primary emissions. Alkanes account for a large part of the NMHC distribution in terms of mixing ratios. In terms of reactivity, NMHCs also dominate overall, especially in the morning hours. However, in the afternoon, as the boundary layer lifts and air is mixed and aged within the basin, the distribution changes as secondary products are formed. The WRF-Chem (Weather Research and Forecasting with Chemistry) model and MOZART (Model for Ozone and Related chemical Tracers) were able to reproduce the general features of the daytime cycle of the VOC OH reactivity distribution showing that NMHCs dominate the distribution except in the afternoon hours and that the VOC OH reactivity peaks in the early morning due to high morning emissions from the city into a shallow boundary layer. The WRF-Chem and MOZART models showed higher reactivity than the experimental data during the nighttime cycle, perhaps indicating problems with the modeled nighttime boundary layer height. In addition, a plume was studied in which air was advected out of the MCMA and intercepted downwind with the DOE G1 on 18 March and the NCAR C130 one day later on 19 March. A number of identical species measured aboard each aircraft gave insight into the chemical evolution of the plume as it aged and was transported as far as 1000 km downwind. Ozone and many OVOCs were photochemically produced in the plume. The WRF-Chem and MOZART models were used to examine the spatial and temporal extent of the 19 March plume and to help interpret the OH

  18. Chemical and oxygen isotope zonings in garnet from subducted continental crust record mineral replacement and metasomatism

    Science.gov (United States)

    Vho, Alice; Rubatto, Daniela; Regis, Daniele; Baumgartner, Lukas; Bouvier, Anne-Sophie

    2017-04-01

    Garnet is a key mineral in metamorphic petrology for constraining pressure, temperature and time paths. Garnet can preserve multiple growth stages due to its wide P-T stability field and the relatively slow diffusivity for major and trace elements at sub-solidus temperatures. Pressure-temperature-time-fluid paths of the host rock may be reconstructed by combining metamorphic petrology with microscale trace element and oxygen isotope measurements in garnet. Subduction zones represent relevant geological settings for geochemical investigation of element exchanges during aqueous fluid-rock interactions. The Sesia Zone consists of a complex continental sequence containing a variety of mono-metamorphic and poly-metamorphic lithologies such as metagranitoids, sediments and mafic boudins. The precursor Varisican-Permian amphibolite-facies basement (6-9 kbar 650-850°C; Lardeaux and Spalla, 1991; Robyr et al., 2013) experienced high pressure metamorphism (15-22 kbar 500-550°C; Regis, et al. 2014; Robyr et al., 2013) during Alpine subduction. In different lithologies of the Internal Complex (Eclogitic Micaschist Complex), including metabasites from the Ivozio Complex, Ti-rich metasediments from Val Malone and pre-Alpine Mn-quartzites associated to metagabbros from Cima Bonze, garnet is abundant and shows a variety of complex textures that cannot be reconciled with typical growth zoning, but indicate resorption and replacement processes and possible metasomatism. In-situ, microscale oxygen isotopes analysis of garnet zones was performed by ion microprobe with the SwissSIMS Cameca IMS 1280-HR at University of Lausanne and SHRIMP-SI at the Australian National University. Each sample has a distinct δ18O composition, and the δ18O values show different degrees of variation between domains. Homogeneously low values of < 5‰ are measured in the garnets from the Ivozio Complex metagabbro. Intragrain variations of up to 3.5‰ in the porphyroblasts from Val Malone metasediments

  19. Experimental evaporation of hyperacid brines : Effects on chemical composition and chlorine isotope fractionation

    NARCIS (Netherlands)

    Rodríguez, Alejandro; van Bergen, Manfred J.; Eggenkamp, H. G.M.

    2018-01-01

    Hyperacid brines from active volcanic lakes are some of the chemically most complex aqueous solutions on Earth. Their compositions provide valuable insights into processes of elemental transfer from a magma body to the surface and interactions with solid rocks and the atmosphere. This paper

  20. Long time-series of chemical and isotopic compositions of Vesuvius fumaroles: evidence for deep and shallow processes

    Directory of Open Access Journals (Sweden)

    Berardino Bocchino

    2011-06-01

    Full Text Available Long time-series of chemical and isotopic compositions of Vesuvius fumaroles were acquired in the framework of the volcanic surveillance in the 1998-2010 period. These allow the identification of processes that occur at shallow levels in the hydrothermal system, and variations that are induced by deep changes in volcanic activity. Partial condensation processes of fumarolic water under near-discharge conditions can explain the annual 18O and deuterium variabilities that are observed at Vesuvius fumaroles. Significant variations in the chemical compositions of fumaroles occurred over the 1999-2002 period, which accompanied the seismic crisis of autumn 1999, when Vesuvius was affected by the most energetic earthquakes of its last quiescence period. A continuous increase in the relative concentrations of CO2 and He and a general decrease in the CH4 concentrations are interpreted as the consequence of an increment in the relative amount of magmatic fluids in the hydrothermal system. Gas equilibria support this hypothesis, showing a PCO2 peak that culminated in 2002, increasing from values of ~40 bar in 1998 to ~55-60 bar in 2001-2002. We propose that the seismic crisis of 1999 marked the arrival of the magmatic fluids into the hydrothermal system, which caused the observed geochemical variations that started in 1999 and culminated in 2002.

  1. Long-term fertilization alters chemically-separated soil organic carbon pools: Based on stable C isotope analyses

    Science.gov (United States)

    Dou, Xiaolin; He, Ping; Cheng, Xiaoli; Zhou, Wei

    2016-01-01

    Quantification of dynamics of soil organic carbon (SOC) pools under the influence of long-term fertilization is essential for predicting carbon (C) sequestration. We combined soil chemical fractionation with stable C isotope analyses to investigate the C dynamics of the various SOC pools after 25 years of fertilization. Five types of soil samples (0-20, 20-40 cm) including the initial level (CK) and four fertilization treatments (inorganic nitrogen fertilizer, IN; balanced inorganic fertilizer, NPK; inorganic fertilizer plus farmyard manure, MNPK; inorganic fertilizer plus corn straw residue, SNPK) were separated into recalcitrant and labile fractions, and the fractions were analysed for C content, C:N ratios, δ13C values, soil C and N recalcitrance indexes (RIC and RIN). Chemical fractionation showed long-term MNPK fertilization strongly increased the SOC storage in both soil layers (0-20 cm = 1492.4 gC m2 and 20-40 cm = 1770.6 gC m2) because of enhanced recalcitrant C (RC) and labile C (LC). The 25 years of inorganic fertilizer treatment did not increase the SOC storage mainly because of the offsetting effects of enhanced RC and decreased LC, whereas no clear SOC increases under the SNPK fertilization resulted from the fast decay rates of soil C.

  2. Variations in chemical and isotopic compositions of groundwaters from the Otobaru landslide in the area of hydrothermal alteration, Beppu City

    Energy Technology Data Exchange (ETDEWEB)

    Yoshioka, Ryuma; Kitaoka, Koichi; Kamiyama, Kokichi [Kyoto Univ., Uji (Japan). Disaster Prevention Research Inst.

    1989-10-01

    The landslide at the Otobaru area, Beppu City, occurred twice in 1943 and 1969. A part of this area, even now, is affected considerably by thermal activities. Variations in chemical and isotopic compositions of waters from the Otobaru area and its vicinity were investigated from 1977 to 1983 and 1986 to 1987. The results are as follows: (1) electric conductivity data suggest that the two kinds of low-concentration water and high-concentration water exist in the landslide area, (2) the existence-of two groundwater aquifer in the landslide area and its vicinity is inferred from tritium data, (3) variations chemical composition of waters from the horizontal borehole are accompanied by the rise and decline of water table, (4) the waters from the landslide area and its vicinity are in equilibrium with montmorillonite, (5) the most waters under 10{sup -1} atm. of P{sub co2} are saturated or supersaturated with calcite, and (6) there is no detectable contribution of geothermal water to the waters from the landslide and its vicinity. And our hypothesis on the mechanism for the formation of calcium sulfate type water is also presented. (author).

  3. Variations in chemical and isotopic compositions of groundwaters from the Otobaru landslide in the area of hydrothermal alteration, Beppu City

    International Nuclear Information System (INIS)

    Yoshioka, Ryuma; Kitaoka, Koichi; Kamiyama, Kokichi

    1989-01-01

    The landslide at the Otobaru area, Beppu City, occurred twice in 1943 and 1969. A part of this area, even now, is affected considerably by thermal activities. Variations in chemical and isotopic compositions of waters from the Otobaru area and its vicinity were investigated from 1977 to 1983 and 1986 to 1987. The results are as follows: (1) electric conductivity data suggest that the two kinds of low-concentration water and high-concentration water exist in the landslide area, (2) the existence-of two groundwater aquifer in the landslide area and its vicinity is inferred from tritium data, (3) variations chemical composition of waters from the horizontal borehole are accompanied by the rise and decline of water table, (4) the waters from the landslide area and its vicinity are in equilibrium with montmorillonite, (5) the most waters under 10 -1 atm. of P co2 are saturated or supersaturated with calcite, and (6) there is no detectable contribution of geothermal water to the waters from the landslide and its vicinity. And our hypothesis on the mechanism for the formation of calcium sulfate type water is also presented. (author)

  4. Evolution of E. coli on [U-13C] Glucose Reveals a Negligible Isotopic Influence on Metabolism and Physiology

    DEFF Research Database (Denmark)

    Sandberg, Troy E.; Long, Christopher P.; Gonzalez, Jacqueline E.

    2016-01-01

    13C-Metabolic flux analysis (13C-MFA) traditionally assumes that kinetic isotope effects from isotopically labeled compounds do not appreciably alter cellular growth or metabolism, despite indications that some biochemical reactions can be non-negligibly impacted. Here, populations of Escherichia...

  5. Morphology evolution and nanostructure of chemical looping transition metal oxide materials upon redox processes

    International Nuclear Information System (INIS)

    Qin, Lang; Cheng, Zhuo; Guo, Mengqing; Fan, Jonathan A.; Fan, Liang-Shih

    2017-01-01

    Transition metal are heavily used in chemical looping technologies because of their high oxygen carrying capacity and high thermal reactivity. These oxygen activities result in the oxide formation and oxygen vacancy formation that affect the nanoscale crystal phase and morphology within these materials and their subsequent bulk chemical behavior. In this study, two selected earlier transition metals manganese and cobalt as well as two selected later transition metals copper and nickel that are important to chemical looping reactions are investigated when they undergo cyclic redox reactions. We found Co microparticles exhibited increased CoO impurity presence when oxidized to Co_3O_4 upon cyclic oxidation; CuO redox cycles prefer to be limited to a reduced form of Cu_2O and an oxidized form of CuO; Mn microparticles were oxidized to a mixed phases of MnO and Mn_3O_4, which causes delamination during oxidation. For Ni microparticles, a dense surface were observed during the redox reaction. The atomistic thermodynamics methods and density functional theory (DFT) calculations are carried out to elucidate the effect of oxygen dissociation and migration on the morphological evolution of nanostructures during the redox processes. Our results indicate that the earlier transition metals (Mn and Co) tend to have stronger interaction with O_2 than the later transition metals (Ni and Cu). Also, our modified Brønsted−Evans−Polanyi (BEP) relationship for reaction energies and total reaction barriers reveals that reactions of earlier transition metals are more exergonic and have lower oxygen dissociation barriers than those of later transition metals. In addition, it was found that for these transition metal oxides the oxygen vacancy formation energies increase with the depth. The oxide in the higher oxidation state of transition metal has lower vacancy formation energy, which can facilitate forming the defective nanostructures. The fundamental understanding of these metal

  6. Stable isotope, chemical, and mineral compositions of the Middle Proterozoic Lijiaying Mn deposit, Shaanxi Province, China

    Science.gov (United States)

    Yeh, Hsueh-Wen; Hein, James R.; Ye, Jie; Fan, Delian

    1999-01-01

    The Lijiaying Mn deposit, located about 250 km southwest of Xian, is a high-quality ore characterized by low P and Fe contents and a mean Mn content of about 23%. The ore deposit occurs in shallow-water marine sedimentary rocks of probable Middle Proterozoic age. Carbonate minerals in the ore deposit include kutnahorite, calcite, Mn calcite, and Mg calcite. Carbon (−0.4 to −4.0‰) and oxygen (−3.7 to −12.9‰) isotopes show that, with a few exceptions, those carbonate minerals are not pristine low-temperature marine precipitates. All samples are depleted in rare earth elements (REEs) relative to shale and have negative Eu and positive Ce anomalies on chondrite-normalized plots. The Fe/Mn ratios of representative ore samples range from about 0.034 to deep ocean-floor during the Cenozoic. Because the Lijiaying precursor mineral formed in a shallow-water marine environment, the atmospheric oxygen content during the Middle Proterozoic may have been lower than it has been during the Cenozoic.

  7. Tracing of aerosol sources in an urban environment using chemical, Sr isotope, and mineralogical characterization.

    Science.gov (United States)

    Duarte, Regina M B O; Matos, João T V; Paula, Andreia S; Lopes, Sónia P; Ribeiro, Sara; Santos, José Francisco; Patinha, Carla; da Silva, Eduardo Ferreira; Soares, Rosário; Duarte, Armando C

    2017-04-01

    In the framework of two national research projects (ORGANOSOL and CN-linkAIR), fine particulate matter (PM 2.5 ) was sampled for 17 months at an urban location in the Western European Coast. The PM 2.5 samples were analyzed for organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), major water-soluble inorganic ions, mineralogical, and for the first time in this region, strontium isotope ( 87 Sr/ 86 Sr) composition. Organic matter dominates the identifiable urban PM 2.5 mass, followed by secondary inorganic aerosols. The acquired data resulted also in a seasonal overview of the carbonaceous and inorganic aerosol composition, with an important contribution from primary biomass burning and secondary formation processes in colder and warmer periods, respectively. The fossil-related primary EC seems to be continually present throughout the sampling period. The 87 Sr/ 86 Sr ratios were measured on both the labile and residual PM 2.5 fractions as well as on the bulk PM 2.5 samples. Regardless of the air mass origin, the residual fractions are more radiogenic (representative of a natural crustal dust source) than the labile fractions, whose 87 Sr/ 86 Sr ratios are comparable to that of seawater. The 87 Sr/ 86 Sr ratios and the mineralogical composition data further suggest that sea salt and mineral dust are important primary natural sources of fine aerosols throughout the sampling period.

  8. Chemical and boron isotopic composition of tourmaline from the Mariinsky emerald deposit, Central Urals, Russia

    Science.gov (United States)

    Baksheev, Ivan A.; Trumbull, Robert B.; Popov, Mikhail P.; Erokhin, Yuri V.; Kudryavtseva, Olesya E.; Yapaskurt, Vasily O.; Khiller, Vera V.; Vovna, Galina M.; Kiselev, Vladimir I.

    2018-04-01

    Tourmaline is abundant at the Mariinsky schist-hosted emerald deposit in the Central Urals, Russia, both in emerald-bearing phlogopite veins (type 1) and later, emerald-free pockets, lenses, and veinlets cutting the phlogopite veins (type 2). The Ca content in tourmaline is influenced by the host rocks (ultramafic and mafic rocks), associated minerals, and minerals crystallized before tourmaline (amphibole, fluorite, margarite). The Na concentration in tourmaline depends on the presence or absence of paragonite, and the association with micas also strongly influences the contents of Li, Zn, Ni, and Co in tourmaline. Type 1 tourmalines associated with phlogopite are relatively depleted in these elements, whereas type 2 tourmalines associated with margarite or paragonite are enriched. Some differences in isomorphic substitutions along with the trace element composition (Zn, V, Sr, Co, REE) may have value in exploration of emerald-bearing and emerald-free veins in schist-hosted emerald deposits. The δ11B values in tourmaline of all types fall in a narrow total range from -11.3 to -8.4‰. These values, combined with a mineralization temperature of 420-360 °C, yield an estimated δ11B fluid composition of -7.4 to -6.8‰ suggesting a mixed source of boron, likely dominated from the granitic rocks surrounding the emerald belt. The narrow range of B-isotope compositions in tourmaline from throughout the Mariinsky deposit suggests a well-mixed hydrothermal system.

  9. THE STAR FORMATION HISTORY AND CHEMICAL EVOLUTION OF STAR-FORMING GALAXIES IN THE NEARBY UNIVERSE

    International Nuclear Information System (INIS)

    Torres-Papaqui, J. P.; Coziol, R.; Ortega-Minakata, R. A.; Neri-Larios, D. M.

    2012-01-01

    We have determined the metallicity (O/H) and nitrogen abundance (N/O) of a sample of 122,751 star-forming galaxies (SFGs) from the Data Release 7 of the Sloan Digital Sky Survey. For all these galaxies we have also determined their morphology and obtained a comprehensive picture of their star formation history (SFH) using the spectral synthesis code STARLIGHT. The comparison of the chemical abundance with the SFH allows us to describe the chemical evolution of the SFGs in the nearby universe (z ≤ 0.25) in a manner consistent with the formation of their stellar populations and morphologies. A high fraction (45%) of the SFGs in our sample show an excess abundance of nitrogen relative to their metallicity. We also find this excess to be accompanied by a deficiency of oxygen, which suggests that this could be the result of effective starburst winds. However, we find no difference in the mode of star formation of the nitrogen-rich and nitrogen-poor SFGs. Our analysis suggests that they all form their stars through a succession of bursts of star formation extended over a period of few Gyr. What produces the chemical differences between these galaxies seems therefore to be the intensity of the bursts: the galaxies with an excess of nitrogen are those that are presently experiencing more intense bursts or have experienced more intense bursts in their past. We also find evidence relating the chemical evolution process to the formation of the galaxies: the galaxies with an excess of nitrogen are more massive, and have more massive bulges and earlier morphologies than those showing no excess. Contrary to expectation, we find no evidence that the starburst wind efficiency decreases with the mass of the galaxies. As a possible explanation we propose that the loss of metals consistent with starburst winds took place during the formation of the galaxies, when their potential wells were still building up, and consequently were weaker than today, making starburst winds more

  10. Modeling risk evolution of digestive tract functional violations when exposed to chemical environmental factors

    Directory of Open Access Journals (Sweden)

    M.R. Kamaltdinov

    2015-06-01

    Full Text Available Modern methods of health risk assessment are based on the representation of individual and public health as a dynamic process of “evolution”, which describes a continuous course of negative (and positive changes in the condition of the body. The article presents a conceptual diagram of multilevel health risk evolution modeling under the influence of environmental factors. The main aspects associated with the simulation of digestive processes in the “meso level” are considered. Some results of solving the problem of the flow in the digestive tract antroduodenal area taken into account tract motility. Further development ways of the model are outlines – account of biochemical reactions, secretory and absorptive functions tract. The proposed approach will enable not only to predict the risk of digestive system functional disorders, but also take into account basic physiological processes, mechanisms of income, distribution, excretion of chemicals.

  11. Role of Metal Oxides in Chemical Evolution: Interaction of Ribose Nucleotides with Alumina

    Science.gov (United States)

    Arora, Avnish Kumar; Kamaluddin

    2009-03-01

    Interaction of ribonucleotides—namely, 5‧-AMP, 5‧-GMP, 5‧-CMP, and 5‧-UMP—with acidic, neutral, and basic alumina has been studied. Purine nucleotides showed higher adsorption on alumina in comparison with pyrimidine nucleotides under acidic conditions. Adsorption data obtained followed Langmuir adsorption isotherm, and Xm and KL values were calculated. On the basis of infrared spectral studies of ribonucleotides, alumina, and ribonucleotide-alumina adducts, we propose that the nitrogen base and phosphate moiety of the ribonucleotides interact with the positive charge surface of alumina. Results of the present study may indicate the importance of alumina in concentrating organic molecules from dilute aqueous solutions in primeval seas in the course of chemical evolution on Earth.

  12. General constraints on the age and chemical evolution of the Galaxy

    International Nuclear Information System (INIS)

    Meyer, B.S.; Schramm, D.N.

    1986-05-01

    The formalism of Schramm and Wasserburg (1970) for determining the mean age of the elements is extended. Model-independent constraints (constraints that are independent of a specific form for the effective nucleosynthesis rate and Galactic chemical evolution over time) are derived on the first four terms in the expansion giving the mean age of the elements, and from these constraints limits are derived on the total duration of nucleosynthesis. These limits require only input of the Schramm-Wasserburg parameter Δ/sup max/ and of the ratio of the mean time for formation of the elements to the total duration of nucleosynthesis, t/sub nu//T. The former quantity is a function of nuclear input parameters. Limits on the latter are obtained from constraints on the relative rate of nucleosynthesis derived from the 232 Th/ 238 U, 235 U/ 238 U, and shorter-lived chronometric pairs. 65 refs

  13. Identifying the origins of local atmospheric deposition in the steel industry basin of Luxembourg using the chemical and isotopic composition of the lichen Xanthoria parietina.

    Science.gov (United States)

    Hissler, Christophe; Stille, Peter; Krein, Andreas; Geagea, Majdi Lahd; Perrone, Thierry; Probst, Jean-Luc; Hoffmann, Lucien

    2008-11-01

    Trace metal atmospheric contamination was assessed in one of the oldest European industrial sites of steel production situated in the southern part of the Grand-Duchy of Luxembourg. Using elemental ratios as well as Pb, Sr, and Nd isotopic compositions as tracers, we found preliminary results concerning the trace metal enrichment and the chemical/isotopic signatures of the most important emission sources using the lichen Xanthoria parietina sampled at 15 sites along a SW-NE transect. The concentrations of these elements decreased with increasing distance from the historical and actual steel-work areas. The combination of the different tracers (major elements, Rare Earth Element ratios, Pb, Sr and Nd isotopes) enabled us to distinguish between three principal sources: the historical steel production (old tailings corresponding to blast-furnace residues), the present steel production (industrial sites with arc electric furnace units) and the regional background (baseline) components. Other anthropogenic sources including a waste incinerator and major roads had only weak impacts on lichen chemistry and isotopic ratios. The correlation between the Sr and Nd isotope ratios indicated that the Sr-Nd isotope systems represented useful tools to trace atmospheric emissions of factories using scrap metal for steel production.

  14. Simulation of the evolution of fused silica's surface defect during wet chemical etching

    Science.gov (United States)

    Liu, Taixiang; Yang, Ke; Li, Heyang; Yan, Lianghong; Yuan, Xiaodong; Yan, Hongwei

    2017-08-01

    Large high-power-laser facility is the basis for achieving inertial confinement fusion, one of whose missions is to make fusion energy usable in the near future. In the facility, fused silica optics plays an irreplaceable role to conduct extremely high-intensity laser to fusion capsule. But the surface defect of fused silica is a major obstacle limiting the output power of the large laser facility and likely resulting in the failure of ignition. To mitigate, or event to remove the surface defect, wet chemical etching has been developed as a practical way. However, how the surface defect evolves during wet chemical etching is still not clearly known so far. To address this problem, in this work, the three-dimensional model of surface defect is built and finite difference time domain (FDTD) method is developed to simulate the evolution of surface defect during etching. From the simulation, it is found that the surface defect will get smooth and result in the improvement of surface quality of fused silica after etching. Comparatively, surface defects (e.g. micro-crack, scratch, series of pinholes, etc.) of a typical fused silica at different etching time are experimentally measured. It can be seen that the simulation result agrees well with the result of experiment, indicating the FDTD method is valid for investigating the evolution of surface defect during etching. With the finding of FDTD simulation, one can optimize the treatment process of fused silica in practical etching or even to make the initial characterization of surface defect traceable.

  15. Effect of increasing helium content and disk dwarfs evolution on the chemical enrichment of the galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Caimmi, R [Padua Univ. (Italy). Ist. di Astronomia

    1979-07-01

    The author deals with two main effects: First the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood, and second, the theoretical possibility of (i) an increased helium content as the Galaxy evolves, and (ii) the presence of evolutionary effects in disk dwarfs (i.e., the age of some or all stars considered up to the subgiant phase is not necessarily longer than the age of the galactic disk). Account is taken of a linear increase of helium content with metal content, and some constraints are imposed relative to initial, solar and present-day observed values of Y and Z, and to observed relative helium to heavy element enrichment, ..delta..Y/..delta..Z. In this way, little influence is found on the empirical metal abundance distribution in the range 0<=..delta..Y/..delta..Z<=3, while larger values of ..delta..Y/..delta..Zwould lead to a more significant influence. 'Evolved' and 'unevolved' theoretical metal abundance distributions are derived by accounting for a two-phase model of chemical evolution of galaxies and for a linear mass dependence of star lifetimes in the spectral range G2V-G8V and are compared with the empirical distribution. All are in satisfactory agreement due to systematic shift data by different observations; several values of collapse time Tsub(c) and age of the Galaxy T are also considered. Finally, models of chemical evolution invoking homogeneous collapse without infall and inhomogeneous collapse with infall, are briefly discussed relative to the empirical metal abundance distribution in Main Sequence disk dwarfs of the solar neighbourhood.

  16. Radiation-induced chemical evolution of glycine to (Gly)2, (Gly)3, and (Gly)4

    International Nuclear Information System (INIS)

    Matsui, T.; Izumi, Y.; Kamohara, M.; Nakagawa, K.; Yokoya, A.

    2006-01-01

    Recently amino acids were detected from some meteorites. Since these amino acids were found after hydrolysis, some oligopeptides were possibly formed in space. A simulation experiment of chemical evolution from Glycine (Gly) to Glycylglycine ((Gly)2) was reported by Kaneko et al. In this work, we irradiated (Gly)2 with 8 eV vacuum ultraviolet photons or with 530 eV soft X-ray photons and examined absolute values of quantum yield of radiation-induced chemical evolution from Gly2 to Glycylglycylglycine ((Gly)3) and Glycylglycylglycylglycine ((Gly)4). Thin films of (Gly)2 were prepared on quartz plate or CuBe plate with a vacuum evaporation technique. These samples were irradiated by 8 eV photons from a Xe 2 * excimer lamp or by 530 eV soft X-ray photons at SPring-8 Synchrotron Radiation Facility. Irradiated samples were analyzed with a high performance liquid chromatography HPLC. Decomposition of (Gly)2 and production of Gly, (Gly)3 and (Gly)4 were observed. Quantum yield Y was defined to be N = Y N 0 , where N is the number of produced or decomposed molecule, and N 0 is the number of (Gly)2 molecules excited by photons. Obtained results by 8 eV irradiation were summarized in Table 1. The similar magnitude of decomposition of (Gly)2 may show that yield of the primary breaking reaction upon photo-excitation is of similar magnitude. It should be noted that (Gly)3 and (Gly)4 was produced by irradiation with the yield of 10 -4 without any catalysis. For soft X-ray irradiation, yield of Gly was tentatively determined to be about 40. This largervalue than that for 8 eV irradiation may originate from large energy of incident soft X-ray photons just like a result reported by Simakov et al. We will discuss in detail at the conference. (authors)

  17. Directed evolution strategies for enantiocomplementary haloalkane dehalogenases: from chemical waste to enantiopure building blocks.

    Science.gov (United States)

    van Leeuwen, Jan G E; Wijma, Hein J; Floor, Robert J; van der Laan, Jan-Metske; Janssen, Dick B

    2012-01-02

    We used directed evolution to obtain enantiocomplementary haloalkane dehalogenase variants that convert the toxic waste compound 1,2,3-trichloropropane (TCP) into highly enantioenriched (R)- or (S)-2,3-dichloropropan-1-ol, which can easily be converted into optically active epichlorohydrins-attractive intermediates for the synthesis of enantiopure fine chemicals. A dehalogenase with improved catalytic activity but very low enantioselectivity was used as the starting point. A strategy that made optimal use of the limited capacity of the screening assay, which was based on chiral gas chromatography, was developed. We used pair-wise site-saturation mutagenesis (SSM) of all 16 noncatalytic active-site residues during the initial two rounds of evolution. The resulting best R- and S-enantioselective variants were further improved in two rounds of site-restricted mutagenesis (SRM), with incorporation of carefully selected sets of amino acids at a larger number of positions, including sites that are more distant from the active site. Finally, the most promising mutations and positions were promoted to a combinatorial library by using a multi-site mutagenesis protocol with restricted codon sets. To guide the design of partly undefined (ambiguous) codon sets for these restricted libraries we employed structural information, the results of multiple sequence alignments, and knowledge from earlier rounds. After five rounds of evolution with screening of only 5500 clones, we obtained two strongly diverged haloalkane dehalogenase variants that give access to (R)-epichlorohydrin with 90 % ee and to (S)-epichlorohydrin with 97 % ee, containing 13 and 17 mutations, respectively, around their active sites. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Development of a fully automated open-column chemical-separation system—COLUMNSPIDER—and its application to Sr-Nd-Pb isotope analyses of igneous rock samples

    Science.gov (United States)

    Miyazaki, Takashi; Vaglarov, Bogdan Stefanov; Takei, Masakazu; Suzuki, Masahiro; Suzuki, Hiroaki; Ohsawa, Kouzou; Chang, Qing; Takahashi, Toshiro; Hirahara, Yuka; Hanyu, Takeshi; Kimura, Jun-Ichi; Tatsumi, Yoshiyuki

    A fully automated open-column resin-bed chemical-separation system, named COLUMNSPIDER, has been developed. The system consists of a programmable micropipetting robot that dispenses chemical reagents and sample solutions into an open-column resin bed for elemental separation. After the initial set up of resin columns, chemical reagents, and beakers for the separated chemical components, all separation procedures are automated. As many as ten samples can be eluted in parallel in a single automated run. Many separation procedures, such as radiogenic isotope ratio analyses for Sr and Nd, involve the use of multiple column separations with different resin columns, chemical reagents, and beakers of various volumes. COLUMNSPIDER completes these separations using multiple runs. Programmable functions, including the positioning of the micropipetter, reagent volume, and elution time, enable flexible operation. Optimized movements for solution take-up and high-efficiency column flushing allow the system to perform as precisely as when carried out manually by a skilled operator. Procedural blanks, examined for COLUMNSPIDER separations of Sr, Nd, and Pb, are low and negligible. The measured Sr, Nd, and Pb isotope ratios for JB-2 and Nd isotope ratios for JB-3 and BCR-2 rock standards all fall within the ranges reported previously in high-accuracy analyses. COLUMNSPIDER is a versatile tool for the efficient elemental separation of igneous rock samples, a process that is both labor intensive and time consuming.

  19. Shape-coexistence and shape-evolution studies for bismuth isotopes by insource laser spectroscopy and $\\beta$-delayed fission in $^{188}$Bi

    CERN Multimedia

    The proposal aims at the two main goals: \\\\ \\\\1) the studies of shape-coexistence and shape-evolution phenomena in the long chain of bismuth isotopes (Z=83) by in-source laser spectroscopy measurements of isotopic shifts (IS) and hyperfine structures (hfs), and \\\\ 2) $\\beta$-delayed fission ($\\beta$DF) of two isomeric states in $^{188}$Bi. \\\\ \\\\Isomer-selective $\\beta$DF studies for $^{188m1, 188m2}$Bi isomers will enable us for the first time to investigate the spin-dependence of the $\\beta$DF process and to check theoretical predictions of asymmetrical fission fragment mass-distribution in this region of nuclei. The measurements will be performed with the well-proven Windmill and MR-TOF MS/Penning Trap techniques.

  20. Effects of Main-Sequence Mass Loss on Stellar and Galactic Chemical Evolution.

    Science.gov (United States)

    Guzik, Joyce Ann

    1988-06-01

    L. A. Willson, G. H. Bowen and C. Struck -Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10^{-9}M o/yr, diminishing over several times 10^8 years. We attempted to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M o, and mass-loss rates decreasing exponentially over 2-3 times 10^8 years. Compared to a constant -mass model, these models require a reduced initial ^4He abundance, have deeper envelope convection zones and higher ^8B neutrino fluxes. Early processing of present surface layers at higher interior temperatures increases the surface ^3He abundance, destroys Li, Be and B, and decreases the surface C/N ratio following first dredge-up. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 Mo and mass loss timescales 0.2 to 2.0 Gyr. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M o and a metallicity -dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus -remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main

  1. Using environmental isotopes along with major hydro-geochemical compositions to assess deep groundwater formation and evolution in eastern coastal China

    Science.gov (United States)

    Xu, Naizheng; Gong, Jianshi; Yang, Guoqiang

    2018-01-01

    Hydrochemical analysis and environmental isotopic tracing are successfully applied to study groundwater evolution processes. Located in eastern China, the Jiangsu Coastal Plain is characterized by an extensively exploited deep groundwater system, and groundwater salinization has become the primary water environmental problem. This paper provides a case study on the use of a hydrochemical and environmental isotopic approach to assess possible mixing and evolution processes at Yoco Port, Jiangsu Province, China. Hydrochemical and isotopic patterns of deep groundwater allow one to distinguish different origins in deep water systems. HCO3- is the dominant anion in the freshwater samples, whereas Na+ and Cl- are the dominant major ions in the saline samples. According to δ18O, δ2H and 14C dating, the fresh water is derived from precipitation under a colder climate during the Glacial Maximum (Dali Glacial), while the saline groundwater is influenced by glacial-interglacial cycles during the Holocene Hypsithermal. The δ18O, δ2H and 3H data confirm that deep groundwater in some boreholes is mixed with overlying saline water. The deep groundwater reservoir can be divided into a saline water sector and a fresh water sector, and each show distinct hydrochemical and isotopic compositions. The saline groundwater found in the deep aquifer cannot be associated with present seawater intrusion. Since the Last Glacial Maximum in the Late Pleistocene, the deep groundwater flow system has evolved to its current status with the decrease in ice cover and the rising of sea level. However, the hydraulic connection is strengthened by continuous overexploitation, and deep groundwater is mixed with shallow groundwater at some points.

  2. Chromium isotope variations (δ53/52Cr) in mantle-derived sources and their weathering products: Implications for environmental studies and the evolution of δ53/52Cr in the Earth’s mantle over geologic time

    Czech Academy of Sciences Publication Activity Database

    Farkaš, J.; Chrastný, V.; Novák, M.; Čadková, E.; Pašava, J.; Chakrabarti, R.; Jacobsen, S. B.; Ackerman, Lukáš; Bullen, T. D.

    2013-01-01

    Roč. 123, 15 December 2013 (2013), s. 74-92 ISSN 0016-7037 Keywords : chemical weathering * chromite * chromium * isotopic composition * isotopic fractionation * mantle chemistry * mantle source * serpentine * serpentinization * ultramafic rock Subject RIV: DD - Geochemistry Impact factor: 4.250, year: 2013

  3. Contribution of chemical and isotopic tools to the knowledge of the Carboniferous limestone aquifer - final report

    International Nuclear Information System (INIS)

    Gourcy, L.; Crastes de Paulet, F.

    2012-05-01

    Based on two sampling, analysis and interpretation campaigns, this study aimed at revealing hydro-chemical phenomena occurring within the Carboniferous and interactions between water and rock (ionic exchanges, oxido-reduction, dissolution, precipitation...), at characterizing underground flows (origins, circulation timing, mixing of different waters...), at identifying sources and at understanding phenomena related to the occurrence of high contents of sulphates (SO 4 ) in some drilling in the Carboniferous. The report presents the adopted methodology (analysis of underground and ground waters, selection of sampling points) and comments the obtained results

  4. The Diversity of Chemical Composition and the Effects on Stellar Evolution and Planetary Habitability

    Science.gov (United States)

    Truitt, Amanda R.

    2017-08-01

    I present a catalog of 1,794 stellar evolution models for solar-type and low-mass stars, which is intended to help characterize real host-stars of interest during the ongoing search for potentially habitable exoplanets. The main grid is composed of 904 tracks, for 0.5-1.2 M solar masses at scaled metallicity values of 0.1-1.5 Z solar masses and specific elemental abundance ratio values of 0.44-2.28 O/Fe solar masses, 0.58-1.72 C/Fe solar masses, 0.54-1.84 Mg/Fe solar masses, and 0.5-2.0 Ne/Fe solar masses. The catalog includes a small grid of late stage evolutionary tracks (25 models), as well as a grid of M-dwarf stars for 0.1-0.45 M solar masses (856 models). The time-dependent habitable zone evolution is calculated for each track, and is strongly dependent on stellar mass, effective temperature, and luminosity parameterizations. I have also developed a subroutine for the stellar evolution code TYCHO that implements a minimalist coupled model for estimating changes in the stellar X-ray luminosity, mass loss, rotational velocity, and magnetic activity over time; to test the utility of the updated code, I created a small grid (9 models) for solar-mass stars, with variations in rotational velocity and scaled metallicity. Including this kind of information in the catalog will ultimately allow for a more robust consideration of the long-term conditions that orbiting planets may experience. In order to gauge the true habitability potential of a given planetary system, it is extremely important to characterize the host-star's mass, specific chemical composition, and thus the timescale over which the star will evolve. It is also necessary to assess the likelihood that a planet found in the "instantaneous" habitable zone has actually had sufficient time to become "detectably" habitable. This catalog provides accurate stellar evolution predictions for a large collection of theoretical host-stars; the models are of particular utility in that they represent the real

  5. The chemical evolution of a travertine-depositing stream: Geochemical processes and mass transfer reactions

    Science.gov (United States)

    Lorah, Michelle M.; Herman, Janet S.

    1988-01-01

    This field study focuses on quantitatively defining the chemical changes occurring in Falling Spring Creek, a travertine-depositing stream located in Alleghany County, Virginia. The processes of CO2outgassing and calcite precipitation or dissolution control the chemical evolution of the stream. The observed chemical composition of the water was used with the computerized geochemical model WATEQF to calculate aqueous speciation, saturation indices, and CO2 partial pressure values. Mass balance calculations were performed to obtain mass transfers of CO2 and calcite. Reaction times, estimated from stream discharge, were used with the mass transfer results to calculate rates of CO2, outgassing and calcite precipitation between consecutive sampling points. The stream, which is fed by a carbonate spring, is supersaturated with respect to CO2 along the entire 5.2-km flow path. Outgassing of CO2 drives the solution to high degrees of supersaturation with respect to calcite. Metabolic uptake of CO2 by photosynthetic plants is insignificant, because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic CO2 outgassing to occur. Calcite precipitation is kinetically inhibited until near the crest of a 20-m vertical waterfall. Calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of CO2. Physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1.0 km below the falls. Net calcite precipitation occurs at all times of the year but is greatest during low-flow conditions in the summer and early fall.

  6. Chemical and radiological toxicity of iodine isotopes. Experimental study on the rat at the perinatal stage

    International Nuclear Information System (INIS)

    Bourahla, K.

    2000-01-01

    The recommended prophylactic measure in the case of an exposure to radio-iodine is an excess take of stable iodine. During the perinatal stage, the thyroid is radio-sensible but also fragile with respect to an excess of iodine. This work performed on the rat, treats of the potential thyroidal toxicity of the prophylaxy and analyzes the early radio-lesions induced by 131 I. On the basis of microscopic (optical, electronic, ionic) and dosimetric studies (TSH, T4), four aspects are considered: 1 - the perinatal morpho-functional evolution (F18, J1, J4, J10, J21, J35); 2 - the consequences of an iodine overburden at three moments of the thyroid maturation (F16, F20 and J4); 3 - the effects on the thyroid cells growth of different iodine overburdens (4 g, 20 g, 100 g); and 4 - the radio-toxic effects (after 48 h) of 131 I taken at J5 (30 Gy) and at J35 (900 Gy). This work evidences the following points: 1 - the perinatal evolution of the thyroid tissue of the rat shows ultra-structural and follicular modifications and physiological follicular destructions; 2 - the variability of the iodine overburden effects: hyperactivity for overburdens at F16, tissue destruction with compensated hypothyroidism for overburdens at J5, no recognized thyroidal anomaly for the overburden at J20; 3 - the iodated overburden inhibits the start-up of the S-phase of the cellular cycle at a lower level (1/20); 4 - the 131 I taken at J5 (30 Gy) induces a lysis of the nucleic acids content, while 131 I taken at J35 (900 Gy) induces an important inflammatory reaction and some apoptosis phenomena. In summary, the stable iodine prophylactic measure can have two conjugated effects on the rat: an interesting action of thyroid cells growth inhibition, and a toxic action leading to an hyperactivity or a follicular destruction without hypothyroidism, depending on the maturation stage. The early effects of 131 I seem to be linked with the age. (J.S.)

  7. An Isotopic Perspective into the Magmatic Evolution and Architecture of the Rift Zones of Kīlauea Volcano

    Science.gov (United States)

    Pietruszka, A. J.; Marske, J. P.; Garcia, M. O.; Heaton, D. E.; Rhodes, M. M.

    2016-12-01

    We present Pb, Sr, and Nd isotope ratios for Kīlauea's historical rift zone lavas (n=50) to examine the magmatic evolution and architecture of the volcano's East Rift Zone (ERZ) and Southwest Rift Zone (SWRZ). Our results show that Kīlauea's historical eruptive period was preceded by the delivery of a major batch of magma from the summit reservoir to the ERZ. The timing of this intrusion, most likely in the late 17th century, was probably related to the 300-yr period of explosive eruptions that followed the formation of the modern caldera (Swanson et al., 2012; JVGR). This rift-stored magma was a component in lavas from lower ERZ (LERZ) eruptions in 1790(?), 1840, 1955, and 1960. The only other components in these LERZ lavas are related to summit lavas erupted (1) after the 1924 collapse of Halemáumáu and (2) during episodes of high fountaining at Kīlauea Iki in 1959. Thus, the intrusion of magma from the summit reservoir into the LERZ is a rare occurrence that is tied to major volcanological events. Intrusions from the summit reservoir in the 1960s likely flushed most older, stored magma from the upper ERZ (UERZ) and middle ERZ (MERZ), leaving large pockets of 1960s-era magma to serve as a dominant component in many subsequent rift lavas. An increase in the duration of pre-eruptive magma storage from the UERZ ( 0-7 yr) to the MERZ ( 0-19 yr) to the LERZ (up to 335 yr) is likely controlled by a decrease in the rate of magma supply to the more distal portions of the ERZ. Lavas from several UERZ eruptions in the 1960s and 1970s have a component of mantle-derived magma that bypassed the summit reservoir. There is no evidence for a summit bypass into the MERZ, LERZ, or the volcanically active portion of the SWRZ. These results support a recent model for Kīlauea's plumbing system (Poland et al., 2014; USGS Prof. Pap. 1801): the ERZ is connected to the deeper "South Caldera" magma body and the volcanic SWRZ is connected to the shallower Halemáumáu magma body.

  8. Chemical Evolution and Star Formation History of the Disks of Spirals in Local Group

    Science.gov (United States)

    Yin, J.

    2011-05-01

    Milky Way (MW), M31 and M33 are the only three spiral galaxies in our Local group. MW and M31 have similar mass, luminosity and morphology, while M33 is only about one tenth of MW in terms of its baryonic mass. Detailed theoretical researches on these three spirals will help us to understand the formation and evolution history of both spiral galaxies and Local group. Referring to the phenomenological chemical evolution model adopted in MW disk, a similar model is established to investigate the star formation and chemical enrichment history of these three local spirals. Firstly, the properties of M31 disk are studied by building a similar chemical evolution model which is able to successfully describe the MW disk. It is expected that a simple unified phenomenological chemical evolution model could successfully describe the radial and global properties of both disks. Comparing with the former work, we adopt an extensive data set as model constraints, including the star formation profile of M31 disk derived from the recent UV data of GALEX. The comparison among the observed properties of these two disks displays very interesting similarities in their radial profiles when the distance from the galactic center is expressed in terms of the corresponding scale length. This implies some common processes in their formation and evolution history. Based on the observed data of the gas mass surface density and SFR surface density, the SFR radial profile of MW can be well described by Kennicutt-Schmidt star formation law (K-S law) or modified K-S law (SFR is inversely proportional to the distance from the galactic center), but this is not applicable to the M31 disk. Detailed calculations show that our unified model describes fairly well all the main properties of the MW disk and most properties of M31 disk, provided that the star formation efficiency of M31 disk is adjusted to be twice as large as that of MW disk (as anticipated from the lower gas fraction of M31). However, the

  9. Method for the detection of Tc in seaweed samples coupling the use of Re as a chemical tracer and isotope dilution inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Mas, Jose Luis; Tagami, Keiko; Uchida, Shigeo

    2004-01-01

    Analysis of the artificial radionuclide 99 Tc in environmental samples requires a chemical separation due to its low concentration, and therefore the use of a chemical yield tracer is peremptory. From a practical viewpoint, Re can be used for this purpose, due to its chemical similarities with Tc. Thus, the use of a radioactive tracer for Tc recovery calculation can be avoided. However, results from a recent intercomparison exercise showed that using of Re as a chemical yield tracer appears to underestimate the Tc concentration relative to the result obtained with isotopes of Tc. In the present work, the methodology used to design a simple separation method for the measurement of 99 Tc in environmental samples is described. Tc recovery is estimated throughout the Re recovery calculation by the isotope dilution technique coupled with ICP-MS (ID-ICP-MS) technique. For chemical separation, a chromatographic resin is used. Interfering elements are removed using a resin washing step carefully designed to avoid any element fractionation between Re and Tc; the care taken in this step is of major importance to assure the equivalence of the chemical recoveries for both elements. Agreement is tested using five replicates of five seaweed samples. The average recoveries for 95m Tc and Re were 93±6 and 95±7%, respectively, those are within the uncertainty intervals for each other. The results explained here demonstrate the possibility of applying Re chemical recoveries to calculate the Tc concentrations with the advantage of not introducing systematic errors

  10. Reactive transport modeling of chemical and isotope data to identify degradation processes of chlorinated ethenes in a diffusion-dominated media

    DEFF Research Database (Denmark)

    Chambon, Julie Claire Claudia; Damgaard, Ida; Jeannottat, Simon

    . Degradation and transport processes of chlorinated ethenes are not well understood in such geological settings, therefore risk assessment and remediation at these sites are particularly challenging. In this work, a combined approach of chemical and isotope analysis on core samples, and reactive transport...... the source zone (between 6 and 12 mbs). Concentrations and stable isotope ratios of the mother compounds and their daughter products, as well as redox parameters, fatty acids and microbial data, were analyzed with discrete sub-sampling along the cores. More samples (each 5 mm) were collected around...... of dechlorination and degradation pathways (biotic reductive dechlorination or abiotic β-elimination with iron minerals) in three core profiles. The model includes diffusion in the matrix, sequential reductive dechlorination, abiotic degradation, isotope fractionation due to degradation and due to diffusion...

  11. Chemical and isotopic seismic precursory signatures in deep groundwater: Cause and effect

    International Nuclear Information System (INIS)

    Reddy, D.V.; Nagabhushanam, P.

    2012-01-01

    Exploratory hydrochemical studies were initiated in Koyna, India, to examine the chemical changes in the deep groundwater due to seismic activity, 2 months before the occurrence of a M 5.1 earthquake on 14th March 2005. A few deep wells (100–250 m), out of a dozen, recorded hydrochemical anomalies induced by this earthquake, and the anomalies continued for the next 3 months. Periodical hydrochemical data of one of the wells indicated a linear increase in Cl − , SO 4 2- , F − and depleted δ 18 O from August 2006 to March 2009, though there is no long term change in groundwater level (except short duration seasonal change). The observed linear change is hypothesised as an effect of aquifer response to seismic stress related to an impending earthquake of M ⩾ 5. The observed temporal change in different chemical concentrations projected linearly to the levels of March 2005 and estimated the time of the impending earthquake (the same as that of March 2005 event) as 2011/12. Further, the time projection also made based on exponential increase in hydrochemistry after 3/2009, advanced the possible time window to 2010/11. This hypothesis was realized on 12 December 2009 with an earthquake of M 5.1. Even the simple arithmetic mean of the 45-a earthquake (M > 5) history of Koyna indicates a recurrence time of ∼5.4 a. To account for the observed temporal hydrochemical changes, a model, based on mixing of two aquifer waters caused by seismic stress, was proposed. Hourly monitoring of electrical conductivity (EC) of groundwater also recorded conductivity changes induced by the M 5.1 earthquake on 12th December 2009. A very important observation that emerges from this study is that the cyclic change in subsurface stress leads to earthquakes. Continuous monitoring of EC may be helpful in visualizing the effect of tectonic forces on groundwater chemistry.

  12. Evolution of camel CYP2E1 and its associated power of binding toxic industrial chemicals and drugs.

    Science.gov (United States)

    Kandeel, Mahmoud; Altaher, Abdullah; Kitade, Yukio; Abdelaziz, Magdi; Alnazawi, Mohamed; Elshazli, Kamal

    2016-10-01

    Camels are raised in harsh desert environment for hundreds of years ago. By modernization of live and the growing industrial revolution in camels rearing areas, camels are exposed to considerable amount of chemicals, industrial waste, environmental pollutions and drugs. Furthermore, camels have unique gene evolution of some genes to withstand living in harsh environments. In this work, the camel cytochrome P450 2E1 (CYP2E1) is compromised to detect its evolution rate and its power to bind with various chemicals, protoxins, procarcinogens, industrial toxins and drugs. In comparison with human CYP2E1, camel CYP2E1 more efficiently binds to small toxins as aniline, benzene, catechol, amides, butadiene, toluene and acrylamide. Larger compounds were more preferentially bound to the human CYP2E1 in comparison with camel CYP2E1. The binding of inhalant anesthetics was almost similar in both camel and human CYP2E1 coinciding with similar anesthetic effect as well as toxicity profiles. Furthermore, evolutionary analysis indicated the high evolution rate of camel CYP2E1 in comparison with human, farm and companion animals. The evolution rate of camel CYP2E1 was among the highest evolution rate in a subset of 57 different organisms. These results indicate rapid evolution and potent toxin binding power of camel CYP2E1. Copyright © 2016. Published by Elsevier Ltd.

  13. Elucidating Adverse Nutritional Implications of Exposure to Endocrine-Disrupting Chemicals and Mycotoxins through Stable Isotope Techniques.

    Science.gov (United States)

    Owino, Victor O; Cornelius, Carolin; Loechl, Cornelia U

    2018-03-23

    Multiple drivers of the double burden of malnutrition (DBM) include a rapid shift from predominantly plant-based diets to energy-dense foods based on meats, milk, animal fats and vegetable oils. The shift to overweight and obesity is driven by increased exposure to mass media, urbanization, technological advances in food processing, rising income and increased population density associated with increased access to cheap foods. At the same time, undernutrition persists mainly due to food insecurity and lack of access to safe water, sanitation and adequate health care. All known nutrition interventions result in only one third reduction in stunting. Little consideration has been given to hazardous exposure to endocrine disrupting chemicals (EDCs) and microbial toxins as major components of the malnutrition-causal framework. These hazards include microbial toxins, for example, mycotoxins, and environmental pollutants such as persistent organic pollutants (POPs), some of which are known to disrupt the endocrine system. These hazards sit at the cross road of undernutrition and overweight and obesity since the exposure cuts across the critical window of opportunity (the first 1000 days). In this review, we update on the role of food and environmental contaminants, especially EDCs and aflatoxins, in child growth and on the implications for metabolic dysfunction and disease risk in later life, and discuss potential applications of nuclear and isotopic techniques to elucidate the underlying biological mechanisms, outcome indicators, as well as occurrence levels.

  14. Isotope and chemical investigation of geothermal springs and thermal water produced by oil wells in potwat area, Pakistan

    International Nuclear Information System (INIS)

    Ahmad, M.; Rafique, M.; Tariq, J.A; Choudhry, M.A.; Hussain, Q.M.

    2008-10-01

    Isotopes and geochemical techniques were applied to investigate the origin, subsurface history and reservoir temperatures of geothermal springs in Potwar. Two sets of water samples were collected. Surface temperatures of geothermal springs ranges from 52 to 68.3 C. Waters produced by oil wells in Potwar area were also investigated. Geothermal springs of Potwar area are Na-HCO/sub 3/ type, while the waters produced by oil wells are Na-Cl and Ca-Cl types. Source of both the categories of water is meteoric water recharged from the outcrops of the formations in the Himalayan foothills. These waters undergo very high /sup 18/O-shift (up to 18%) due to rock-water interaction at higher temperatures. High salinity of the oil field waters is due to dissolution of marine evaporites. Reservoir temperatures of thermal springs determined by the Na-K geo thermometers are in the range of 56-91 deg. C, while Na-K-Ca, Na-K-Mg, Na-K-Ca-Mg and quartz geo thermometers give higher temperatures up to 177 C. Reservoir temperature determined by /sup 18/O(SO/Sub 4/-H/sub 2/O) geo thermometer ranges from 112 to 138 deg. C. There is wide variation in reservoir temperatures (54-297 deg. C) of oil fields estimated by different chemical geo thermometers. Na-K geo thermometer seems more reliable which gives close estimates to real temperature (about 100 deg. C) determined during drilling of oil wells. (author)

  15. Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

    Science.gov (United States)

    Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

    2008-01-01

    A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

  16. Mechanism of Microwave-Assisted Pyrolysis of Glucose to Furfural Revealed by Isotopic Tracer and Quantum Chemical Calculations.

    Science.gov (United States)

    Bao, Liwei; Shi, Lei; Luo, Hu; Kong, Lingzhao; Li, Shenggang; Wei, Wei; Sun, Yuhan

    2017-08-10

    Glucose labeled with 13 C or 18 O was used to investigate the mechanism of its conversion into furfural by microwaveassisted pyrolysis. The isotopic content and location in furfural were determined from GC-MS and 13 C NMR spectroscopic measurements and data analysis. The results suggest that the carbon skeleton in furfural is mainly derived from C1 to C5 of glucose, whereas the C of the aldehyde group and the O of the furan ring in furfural primarily originate from C1 and O5 of glucose, respectively. For the first time, the source of O in the furan ring of furfural was elucidated directly by experiment, providing results that are consistent with predictions from recent quantum chemical calculations. Moreover, further theoretical calculations indicate substantially lower energy barriers than previous predictions by considering the potential catalytic effect of formic acid, which is one of the pyrolysis products. The catalytic role of formic acid is further confirmed by experimental evidence. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Investigation of short-lived neutron-rich palladium and silver isotopes after fast chemical separation from fission fragments

    International Nuclear Information System (INIS)

    Bruechle, W.

    1976-01-01

    In this paper, chemical separation processes are described permitting fast and neat isolation of short-lived palladium and silver nuclides from fusion product mixtures. The process for palladium is based on the stability of palladium diethyldithiophosphate. From fission products of the reactions 238 U(n,f) and 249 Cf(nth,f), the following palladium niclides could be studied for the first time by gamma spectroscopy: 1.66 min 113 Pd, 2.45 min 114 Pd, 29 sec sup(115a)Pd, 54 sec sup(115b)Pd, 12.5 sec 116 Pd. 113 Pd could also be indentified according to the reaction 116 Cd(n,α) 113 Pd. The separation of silver is based on the fast isotopic exchange on AgCl. With this process, the following nuclides have been separated from fission product mixtures and studied by gamma spectroscopy: 70 sec sup(113m)Ag, 5.0 sec 114 Ag, 19.2 sec sup(115m)Ag, 2.65 min sup(116g)Ag, 10.5 sec sup(116m)Ag, 1.3 min sup(117g)Ag, 6.0 sec sup(117m)Ag, 4.0 sec 118 Ag. (orig./WL) [de

  18. Radiocarbon and stable carbon isotope compositions of chemically fractionated soil organic matter in a temperate-zone forest

    International Nuclear Information System (INIS)

    Koarashi, Jun; Iida, Takao; Asano, Tomohiro

    2005-01-01

    To better understand the role of soil organic matter in terrestrial carbon cycle, carbon isotope compositions in soil samples from a temperate-zone forest were measured for bulk, acid-insoluble and base-insoluble organic matter fractions separated by a chemical fractionation method. The measurements also made it possible to estimate indirectly radiocarbon ( 14 C) abundances of acid- and base-soluble organic matter fractions, through a mass balance of carbon among the fractions. The depth profiles of 14 C abundances showed that (1) bomb-derived 14 C has penetrated the first 16 cm mineral soil at least; (2) Δ 14 C values of acid-soluble organic matter fraction are considerably higher than those of other fractions; and (3) a significant amount of the bomb-derived 14 C has been preserved as the base-soluble organic matter around litter-mineral soil boundary. In contrast, no or little bomb-derived 14 C was observed for the base-insoluble fraction in all sampling depths, indicating that this recalcitrant fraction, accounting for approximately 15% of total carbon in this temperate-zone forest soil, plays a role as a long-term sink in the carbon cycle. These results suggest that bulk soil organic matter cannot provide a representative indicator as a source or a sink of carbon in soil, particularly on annual to decadal timescales

  19. The effects of the initial mass function on the chemical evolution of elliptical galaxies

    Science.gov (United States)

    De Masi, Carlo; Matteucci, F.; Vincenzo, F.

    2018-03-01

    We describe the use of our chemical evolution model to reproduce the abundance patterns observed in a catalogue of elliptical galaxies from the Sloan Digital Sky Survey Data Release 4. The model assumes ellipticals form by fast gas accretion, and suffer a strong burst of star formation followed by a galactic wind, which quenches star formation. Models with fixed initial mass function (IMF) failed in simultaneously reproducing the observed trends with the galactic mass. So, we tested a varying IMF; contrary to the diffused claim that the IMF should become bottom heavier in more massive galaxies, we find a better agreement with data by assuming an inverse trend, where the IMF goes from being bottom heavy in less massive galaxies to top heavy in more massive ones. This naturally produces a downsizing in star formation, favouring massive stars in largest galaxies. Finally, we tested the use of the integrated Galactic IMF, obtained by averaging the canonical IMF over the mass distribution function of the clusters where star formation is assumed to take place. We combined two prescriptions, valid for different SFR regimes, to obtain the Integrated Initial Mass Function values along the whole evolution of the galaxies in our models. Predicted abundance trends reproduce the observed slopes, but they have an offset relative to the data. We conclude that bottom-heavier IMFs do not reproduce the properties of the most massive ellipticals, at variance with previous suggestions. On the other hand, an IMF varying with galactic mass from bottom heavier to top heavier should be preferred.

  20. Chemical evolution of the Galaxy at the initial rapid-collapse phase

    Energy Technology Data Exchange (ETDEWEB)

    Caimmi, R [Padua Univ. (Italy). Istituto di Astronomia

    1978-04-01

    Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(..cap alpha..) is sufficiently high; moreover, the super metallic effect (SME) takes place for ..cap alpha.. greater than a given value (..cap alpha.. > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data.

  1. Chemical evolution of the Galaxy at the initial rapid-collapse phase

    International Nuclear Information System (INIS)

    Caimmi, R.

    1978-01-01

    Equations for the chemical evolution of the Galaxy are derived, accounting for (i) the dynamical evolution of the Galaxy (i.e. the collapse of the proto-galaxy) and (ii) either a variable mass-spectrum in the birth-rate stellar function of the type B(m,t) = psi(t)phi(m,t), or a constant mass-spectrum with variable lower mass limit for star birth: msub(mf) = msub(mf)(Z). Simple equations are adopted for the collapse of the proto-galaxy, accounting for the experimental data (i.e. axial ratio and major semi-axis) relative to the halo and to the disk, and best fitted for a rapid collapse; gas density is assumed to be always uniform. Numerical computations of several cases show that there is qualitative agreement with the experimental data relative to the Z(t) function when: (i) the mass-spectrum is nearly constant in time: phi(m,t) approximately phi(m) = msup(-2.35); (ii) the efficiency phi(t) proportional to rhosup(α) is sufficiently high; moreover, the super metallic effect (SME) takes place for α greater than a given value (α > approximately 1.5); (iii) the shorter the collapse time Tsub(c), the more rapid is the initial increase of metallicity, the asymptotic value being left nearly unaltered. The theoretical results are not in complete agreement with the observed data bearing on the Nsub(n)(Z) function (Nsub(n) is the number of stars whose Main-Sequence lifetime is not less than the age of the Galaxy), while a hypothesis of star formation with different efficiencies in different zones of the Galaxy, and successive stellar mixing from zone to zone, is not inconsistent with such data. (Auth.)

  2. Nano-scale chemical evolution in a proton-and neutron-irradiated Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Harte, Allan, E-mail: allan.harte@manchester.ac.uk [The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Topping, M.; Frankel, P. [The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom); Jädernäs, D. [Studsvik Nuclear AB, SE 611 82, Nyköping (Sweden); Romero, J. [Westinghouse Electric Company, Columbia, SC (United States); Hallstadius, L. [Westinghouse Electric Sweden AB, SE 72163 Västerås (Sweden); Darby, E.C. [Rolls Royce Plc., Nuclear Materials, Derby (United Kingdom); Preuss, M. [The University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)

    2017-04-15

    Proton-and neutron-irradiated Zircaloy-2 are compared in terms of the nano-scale chemical evolution within second phase particles (SPPs) Zr(Fe,Cr){sub 2} and Zr{sub 2}(Fe,Ni). This is accomplished through ultra-high spatial resolution scanning transmission electron microscopy and the use of energy-dispersive X-ray spectroscopic methods. Fe-depletion is observed from both SPP types after irradiation with both irradiative species, but is heterogeneous in the case of Zr(Fe,Cr){sub 2}, predominantly from the edge region, and homogeneously in the case of Zr{sub 2}(Fe,Ni). Further, there is evidence of a delay in the dissolution of the Zr{sub 2}(Fe,Ni) SPP with respect to the Zr(Fe,Cr){sub 2}. As such, SPP dissolution results in matrix supersaturation with solute under both irradiative species and proton irradiation is considered well suited to emulate the effects of neutron irradiation in this context. The mechanisms of solute redistribution processes from SPPs and the consequences for irradiation-induced growth phenomena are discussed. - Highlights: •Protons emulate the effects of neutron irradiation in the evolution of chemistry and morphology of second phase particles. •Detailed energy-dispersive X-ray spectroscopy reveals heterogeneity in Zr-Fe-Cr SPPs both before and after irradiation. •Zr-Fe-Ni SPPs are delayed in irradiation-induced dissolution due to their better self-solubility with respect to Zr-Fe-Cr.

  3. Role of Short-Range Chemical Ordering in (GaN) 1–x (ZnO) x for Photodriven Oxygen Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Dennis P. [Department; Neuefeind, Joerg C. [Chemical; Koczkur, Kallum M. [Department; Bish, David L. [Department; Skrabalak, Sara E. [Department

    2017-07-21

    (GaN)1–x(ZnO)x (GZNO) is capable of visible-light driven water splitting, but its bandgap at x ≤ 0.15 (>2.7 eV) results in poor visible-light absorption. Unfortunately, methods to narrow its bandgap by incorporating higher ZnO concentrations are accompanied by extensive Urbach tailing near the absorption-edge, which is indicative of structural disorder or chemical inhomogeneities. We evaluated whether this disorder is intrinsic to the bond-length distribution in GZNO or is a result of defects introduced from the loss of Zn during nitridation. Here, the synthesis of GZNO derived from layered double hydroxide (LDH) precursors is described which minimizes Zn loss and chemical inhomogeneities and enhances visible-light absorption. The average and local atomic structures of LDH-derived GZNO were investigated using X-ray and neutron scattering and are correlated with their oxygen evolution rates. An isotope-contrasted neutron-scattering experiment was conducted in conjunction with reverse Monte Carlo (RMC) simulations. We showed that a bond-valence bias in the RMC refinements reproduces the short-range ordering (SRO) observed in structure refinements using isotope-contrasted neutron data. The findings suggest that positional disorder of cation–anion pairs in GZNO partially arises from SRO and influences local bond relaxations. Furthermore, particle-based oxygen evolution reactions (OERs) in AgNO3 solution reveal that the crystallite size of GZNO correlates more than positional disorder with oxygen evolution rate. These findings illustrate the importance of examining the local structure of multinary photocatalysts to identify dominant factors in particulate-based photodriven oxygen evolution.

  4. Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis

    DEFF Research Database (Denmark)

    Larsen, Kirsten Kolbjørn; Wielandt, Daniel Kim Peel; Schiller, Martin

    2016-01-01

    Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of ...

  5. Deuterium isotope effects on 13C and 15N chemical shifts of intramolecularly hydrogen-bonded enaminocarbonyl derivatives of Meldrum’s and Tetronic acid

    Science.gov (United States)

    Ullah, Saif; Zhang, Wei; Hansen, Poul Erik

    2010-07-01

    Secondary deuterium isotope effects on 13C and 15N nuclear shieldings in a series of cyclic enamino-diesters and enamino-esters and acyclic enaminones and enamino-esters have been examined and analysed using NMR and DFT (B3LYP/6-31G(d,p)) methods. One-dimensional and two-dimensional NMR spectra of enaminocarbonyl and their deuterated analogues were recorded in CDCl 3 and CD 2Cl 2 at variable temperatures and assigned. 1JNH coupling constants for the derivatives of Meldrum's and tetronic acids reveal that they exist at the NH-form. It was demonstrated that deuterium isotope effects, for the hydrogen bonded compounds, due to the deuterium substitution at the nitrogen nucleus lead to large one-bond isotope effects at nitrogen, 1Δ 15N(D), and two-bond isotope effects on carbon nuclei, 2ΔC(ND), respectively. A linear correlations exist between 2ΔC(ND) and 1Δ 15N(D) whereas the correlation with δNH is divided into two. A good agreement between the experimentally observed 2ΔC(ND) and calculated dσ 13C/dR NH was obtained. A very good correlation between calculated NH bond lengths and observed NH chemical shifts is found. The observed isotope effects are shown to depend strongly on Resonance Assisted Hydrogen bonding.

  6. Ages of the solar system: Isotopic dating

    International Nuclear Information System (INIS)

    Turner, G.

    1982-01-01

    The major concern of this section will be to outline the ways in which measurements of isotope abundances have been used to determine the chronology of the origin and evolution of the solar system. In passing it should be remembered that the use of isotopic information is by no means restricted simply to the measurement of time scales and, particularly in recent years, isotope abundances have been used to investigate problems as diverse as the heat sources in the early solar nebula and the chemical evolution of the Earth's mantle. The fundamental property of isotopes which makes them especially useful for dating and other applications is the fact that, apart from a limited amount of mass fractionation, the composition of an isotopic mixture is unaffected by chemical processes. In those cases where mass fractionation does occur this effect may itself be useful, particularly as a source of information on temperatures. Since our main theme is time the events discussed in this section will be most conveniently presented as a chronological sequence, progressing from some time before the solar system existed down to the present day. (orig./WL)

  7. Chemical preparation of biological materials for accurate chromium determination by isotope dilution mass spectrometry

    International Nuclear Information System (INIS)

    Dunstan, L.P.; Garner, E.L.

    1977-01-01

    The current interest in trace elements in biological materials has created a need for accurate methods of analysis. The source of discrepancies and variations in chromium concentration determinations is often traceable to inadequate methods of sample preparation. Any method of Cr analysis that requires acid digestion of a biological matrix must take into consideration the existence or formation of a volatile Cr component. In addition, because Cr is often present at concentrations less than 1 μg/g, the analytical blank becomes a potential source of error. Chemical procedures have been developed for the digestion of the biological matrix and the separation of Cr without either large analytical blanks or significant losses by volatilization. These procedures have been used for the analysis of NBS Standard Reference Material (SRM) 1569 Brewers Yeast; SRM 1577 Bovine Liver; SRM 1570 Spinach and other biological materials including human hair and nails. At this time, samples containing 1 μg of Cr can be determined with an estimated accuracy of 2 percent

  8. Carbon-14, tritium, stable isotope and chemical measurements on thermal waters from the Tauranga region

    International Nuclear Information System (INIS)

    Stewart, M.K.; McGill, R.C.; Taylor, C.B.; Whitehead, N.E.; Downes, C.J.

    1984-03-01

    The chemical compositions of groundwater from the Tauranga region are affected to varying degrees by reducing conditions due to buried organic matter. The levels of some dissolved constituents are also affected by mixing with sea water contained within the rocks and by rock-water interaction. Dissolved gas compositions range from oxygen-bearing to methane-bearing reflecting the varying redox conditions. Excess air may be present but further experiments are necessary to confirm this. Apparent ages deduced from carbon-14 measurements (corrected using 12C dilution and 13C fractionation methods) range from 2-25,000 years, suggesting that some of the waters were recharged during late Pleistocene or early Holocene time. ΔD and Δ18 O values of the oldest waters are slightly more negative than those of younger samples; this may indicate recharge during a cooler climate, in agreement with the 14C ages. Very low but significantly non-zero tritium contents (TR=(0.007-0.059)+-0.007) were measured using the high tritium-enrichment facilities at INS and the very low-background counters at the University of Bern. The tritium is thought to derive from contamination or nuclear reactions in the aquifer rocks rather than from recharge water

  9. Modification degrees at specific sites on heparan sulphate: an approach to measure chemical modifications on biological molecules with stable isotope labelling

    Science.gov (United States)

    Wu, Zhengliang L.; Lech, Miroslaw

    2005-01-01

    Chemical modification of biological molecules is a general mechanism for cellular regulation. A quantitative approach has been developed to measure the extent of modification on HS (heparan sulphates). Sulphation on HS by sulphotransferases leads to variable sulphation levels, which allows cells to tune their affinities to various extracellular proteins, including growth factors. With stable isotope labelling and HPLC-coupled MS, modification degrees at various O-sulphation sites could be determined. A bovine kidney HS sample was first saturated in vitro with 34S by an OST (O-sulphotransferase), then digested with nitrous acid and analysed with HPLC-coupled MS. The 34S-labelled oligosaccharides were identified based on their unique isotope clusters. The modification degrees at the sulphotransferase recognition sites were obtained by calculating the intensities of isotopic peaks in the isotope clusters. The modification degrees at 3-OST-1 and 6-OST-1 sites were examined in detail. This approach can also be used to study other types of chemical modifications on biological molecules. PMID:15743272

  10. The role of neutron star mergers in the chemical evolution of the Galactic halo

    Science.gov (United States)

    Cescutti, G.; Romano, D.; Matteucci, F.; Chiappini, C.; Hirschi, R.

    2015-05-01

    Context. The dominant astrophysical production site of the r-process elements has not yet been unambiguously identified. The suggested main r-process sites are core-collapse supernovae and merging neutron stars. Aims: We explore the problem of the production site of Eu. We also use the information present in the observed spread in the Eu abundances in the early Galaxy, and not only its average trend. Moreover, we extend our investigations to other heavy elements (Ba, Sr, Rb, Zr) to provide additional constraints on our results. Methods: We adopt a stochastic chemical evolution model that takes inhomogeneous mixing into account. The adopted yields of Eu from merging neutron stars and from core-collapse supernovae are those that are able to explain the average [Eu/Fe]-[Fe/H] trend observed for solar neighbourhood stars, the solar abundance of Eu, and the present-day abundance gradient of Eu along the Galactic disc in the framework of a well-tested homogeneous model for the chemical evolution of the Milky Way. Rb, Sr, Zr, and Ba are produced by both the s- and r-processes. The r-process yields were obtained by scaling the Eu yields described above according to the abundance ratios observed in r-process rich stars. The s-process contribution by spinstars is the same as in our previous papers. Results: Neutron star binaries that merge in less than 10 Myr or neutron star mergers combined with a source of r-process generated by massive stars can explain the spread of [Eu/Fe] in the Galactic halo. The combination of r-process production by neutron star mergers and s-process production by spinstars is able to reproduce the available observational data for Sr, Zr, and Ba. We also show the first predictions for Rb in the Galactic halo. Conclusions: We confirm previous results that either neutron star mergers on a very short timescale or both neutron star mergers and at least a fraction of Type II supernovae have contributed to the synthesis of Eu in the Galaxy. The r

  11. Hydrogen evolution under visible light over LaCoO3 prepared by chemical route

    International Nuclear Information System (INIS)

    Meziani, D.; Reziga, A.; Rekhila, G.; Bellal, B.; Trari, M.

    2014-01-01

    Highlights: • Visible-light hydrogen evolution is achieved on the hetero-system LaCoO 3 /SnO 2 . • The crystal field splits the Co 3+ : 3d orbital by a value of 2.05 eV. • The capacitance plot shows p-type conduction with flat band potential of 0 V SCE. • The photo-electrochemistry yields a valence and conduction bands of 3d parentage. - Abstract: The semiconducting properties of the perovskite LaCoO 3 , prepared by nitrate route, are investigated for the first time by the photo-electrochemical technique. The oxide shows a direct optical transition at 1.33 eV, due to Co 3+ : 3d orbital splitting in octahedral site and possesses a chemical stability over a fair pH range (4–14). The conductivity follows an exponential type law with a hole mobility (8.3 × 10 −2 cm 2 V −1 s −1 ), thermally activated. The Mott–Schottky plot in KOH medium is characteristic of p type conduction with a flat band potential of 0 V SCE and a holes density of 1.35 × 10 17 cm −3 . The electrochemical impedance spectroscopy reveals the predominance of the bulk and grains boundaries contributions with a constant phase element and a multi-relaxation type nature. As application, the hydrogen evolution upon visible light is demonstrated on the hetero-junction LaCoO 3 /SnO 2 . The best performance occurs at pH ∼ 12.8 with an evolution rate of 0.25 cm 3 min −1 (mg LaCoO 3 ) −1 and a quantum yield of 0.11%. The improved activity is attributed to the wide depletion width of ∼10 nm and the potential of the conduction band of LaCoO 3 (−1.34 V SCE ), more negative than that of SnO 2 , the latter acts as electrons bridge for the interfacial water reduction. The relevance of 3d orbital of the performance of semi conducting photoelectrode is discussed

  12. Rates of carbonate soil evolution from carbon, U- and Th-series isotope studies: Example of the Astian sands (SE France)

    Science.gov (United States)

    Barbecot, Florent; Ghaleb, Bassam; Hillaire-Marcel, Claude

    2015-04-01

    In carbonate rich soils, C-isotopes (14C, 13C) and carbonate mass budget may inform on centennial to millennial time scale dissolution/precipitation processes and weathering rates, whereas disequilibria between in the U- and Th-decay series provide tools to document high- (228Ra-228Th-210Pb) to low- (234U, 230Th, 231Pa, 226Ra) geochemical processes rate, covering annual to ~ 1Ma time scales, governing both carbonate and silicate soil fractions. Because lithology constitutes a boundary condition, we intend to illustrate the behavior of such isotopes in soils developed over Astian sands formation (up to ~ 30% carbonate) from the Béziers area (SE France). A >20 m thick unsaturated zone was sampled firstly along a naturally exposed section, then in a cored sequence. Geochemical and mineralogical analyses, including stable isotopes and 14C-measurements, were complemented with 228U, 234U, 230Th, 226Ra, 210Pb and 228Th, 232Th measurements. Whereas the upper 7 m depict geochemical and isotopic features forced by dissolution/precipitation processes leading to variable radioactive disequilibria, but overall deficits in more soluble elements of the decay series, the lower part of the sequence shows strong excesses in 234U and 230Th over parent isotopes (i.e., 238U and 234U, respectively). These features might have been interpreted as the result of successive phases of U-loss and gains. However, 226Ra and 230Th are in near-equilibrium, thus leading to conclude at a more likely slow enrichment process in both 234Th(234U) and 230Th, which we link to dissolved U-decay during groundwater recharge events. In addition, 210Pb deficits (vs parent 226Ra) are observed down to 12 m along the natural outcropping section and below the top-soil 210Pb-excess in the cored sequence, due to gaseous 222Rn-diffusion over the cliff outcrop. Based on C-isotope and chemical analysis, reaction rates at 14C-time scale are distinct from those estimates at the short- or long-lived U-series isotopes

  13. Responses of soil physical and chemical properties to karst rocky desertification evolution in typical karst valley area

    Science.gov (United States)

    Chen, Fei; Zhou, Dequan; Bai, Xiaoyong; zeng, Cheng; Xiao, Jianyong; Qian, Qinghuan; Luo, Guangjie

    2018-01-01

    In order to reveal the differences of soil physical and chemical properties and their response mechanism to the evolution of KRD. The characteristics of soil physical and chemical properties of different grades of KRD were studied by field sampling method to research different types of KRD in the typical karst valley of southern China. Instead of using space of time, to explore the response and the mechanisms of the soil physical and chemical properties at the different evolution process. The results showed that: (1) There were significant differences in organic matter, pH, total nitrogen, total phosphorus, total potassium, sediment concentration, clay content and AWHC in different levels of KRD environment. However, these indicators are not with increasing desertification degree has been degraded, but improved after a first degradation trends; (2) The correlation analysis showed that soil organic matter, acid, alkali, total nitrogen, total phosphorus, total potassium and clay contents were significantly correlated with other physical and chemical factors. They are the key factors of soil physical and chemical properties, play a key role in improving soil physical and chemical properties and promoting nutrient cycling; (3) The principal component analysis showed that the cumulative contribution rate of organic matter, pH, total nitrogen, total phosphorus, total potassium and sediment concentration was 80.26%, which was the key index to evaluate rocky desertification degree based on soil physical and chemical properties. The results have important theoretical and practical significance for the protection and restoration of rocky desertification ecosystem in southwest China.

  14. Interpretation of chemical and isotopic data from boreholes in the unsaturated zone at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Yang, I.C.; Rattray, G.W.; Yu, P.

    1996-01-01

    Analyses of pore water from boreholes at Yucca Mountain indicate that unsaturated-zone pore water has significantly larger concentrations of chloride and dissolved solids than the saturated-zone water or perched-water bodies. Chemical compositions are of the calcium sulfate or calcium chloride types in the Paintbrush Group (Tiva Canyon, Yucca Mountain, Pah Canyon, and bedded tuffs), and sodium carbonate or bicarbonate type water in the Calico Hills Formation. Tritium profiles from boreholes at Yucca Mountain indicate tritium-concentration inversions (larger tritium concentrations are located below the smaller tritium concentration in a vertical profile) occur in many places. These inversions indicate preferential flow through fractures. Rock-gas compositions are similar to that of atmospheric air except that carbon dioxide concentrations are generally larger than those in the air. The delta carbon-13 values of gas are fairly constant from surface to 365.8 meters, indicating little interaction between the gas CO 2 and caliche in the soil. Model calculations indicate that the gas transport in the unsaturated zone at Yucca Mountain agrees well with the gas-diffusion process. Tritium-modeling results indicate that the high tritium value of about 100 tritium units in the Calico Hills Formation of UZ-16 is within limits of a piston-flow model with a water residence time of 32 to 35 years. The large variations in tritium concentrations with narrow peaks imply piston flow or preferential fracture flow rather than matrix flow. In reality, the aqueous-phase flow in the unsaturated zone is between piston and well-mixed flows but is closer to a piston flow

  15. Near-surface clay authigenesis in exhumed fault rock of the Alpine Fault Zone (New Zealand); O-H-Ar isotopic, XRD and chemical analysis of illite and chlorite

    Science.gov (United States)

    Boles, Austin; Mulch, Andreas; van der Pluijm, Ben

    2018-06-01

    Exhumed fault rock of the central Alpine Fault Zone (South Island, New Zealand) shows extensive clay mineralization, and it has been the focus of recent research that aims to describe the evolution and frictional behavior of the fault. Using Quantitative X-ray powder diffraction, 40Ar/39Ar geochronology, hydrogen isotope (δD) geochemistry, and electron microbeam analysis, we constrain the thermal and fluid conditions of deformation that produced two predominant clay phases ubiquitous to the exposed fault damage zone, illite and chlorite. Illite polytype analysis indicates that most end-member illite and chlorite material formed in equilibrium with meteoric fluid (δD = -55 to -75‰), but two locations preserve a metamorphic origin of chlorite (δD = -36 to -45‰). Chlorite chemical geothermometry constrains crystal growth to T = 210-296 °C. Isotopic analysis also constrains illite growth to T < 100 °C, consistent with the mineralogy, with Ar ages <0.5 Ma. High geothermal gradients in the study area promoted widespread, near-surface mineralization, and limited the window of clay authigenesis in the Alpine Fault Zone to <5 km for chlorite and <2 km for illite. This implies a significant contrast between fault rock exposed at the surface and that at depth, and informs discussions about fault strength, clays and frictional behavior.

  16. Molecular corridors and parameterizations of volatility in the chemical evolution of organic aerosols

    Directory of Open Access Journals (Sweden)

    Y. Li

    2016-03-01

    Full Text Available The formation and aging of organic aerosols (OA proceed through multiple steps of chemical reaction and mass transport in the gas and particle phases, which is challenging for the interpretation of field measurements and laboratory experiments as well as accurate representation of OA evolution in atmospheric aerosol models. Based on data from over 30 000 compounds, we show that organic compounds with a wide variety of functional groups fall into molecular corridors, characterized by a tight inverse correlation between molar mass and volatility. We developed parameterizations to predict the saturation mass concentration of organic compounds containing oxygen, nitrogen, and sulfur from the elemental composition that can be measured by soft-ionization high-resolution mass spectrometry. Field measurement data from new particle formation events, biomass burning, cloud/fog processing, and indoor environments were mapped into molecular corridors to characterize the chemical nature of the observed OA components. We found that less-oxidized indoor OA are constrained to a corridor of low molar mass and high volatility, whereas highly oxygenated compounds in atmospheric water extend to high molar mass and low volatility. Among the nitrogen- and sulfur-containing compounds identified in atmospheric aerosols, amines tend to exhibit low molar mass and high volatility, whereas organonitrates and organosulfates follow high O : C corridors extending to high molar mass and low volatility. We suggest that the consideration of molar mass and molecular corridors can help to constrain volatility and particle-phase state in the modeling of OA particularly for nitrogen- and sulfur-containing compounds.

  17. Origins and evolution of rhyolitic magmas in the central Snake River Plain: insights from coupled high-precision geochronology, oxygen isotope, and hafnium isotope analyses of zircon

    Science.gov (United States)

    Colón, Dylan P.; Bindeman, Ilya N.; Wotzlaw, Jörn-Frederik; Christiansen, Eric H.; Stern, Richard A.

    2018-02-01

    We present new high-precision CA-ID-TIMS and in situ U-Pb ages together with Hf and O isotopic analyses (analyses performed all on the same grains) from four tuffs from the 15-10 Ma Bruneau-Jarbidge center of the Snake River Plain and from three rhyolitic units from the Kimberly borehole in the neighboring 10-6 Ma Twin Falls volcanic center. We find significant intrasample diversity in zircon ages (ranges of up to 3 Myr) and in δ18O (ranges of up to 6‰) and ɛHf (ranges of up to 24 ɛ units) values. Zircon rims are also more homogeneous than the associated cores, and we show that zircon rim growth occurs faster than the resolution of in situ dating techniques. CA-ID-TIMS dating of a subset of zircon grains from the Twin Falls samples reveals complex crystallization histories spanning 104-106 years prior to some eruptions, suggesting that magma genesis was characterized by the cyclic remelting of buried volcanic rocks and intrusions associated with previous magmatic episodes. Age-dependent trends in zircon isotopic compositions show that rhyolite production in the Yellowstone hotspot track is driven by the mixing of mantle-derived melts (normal δ18O and ɛHf) and a combination of Precambrian basement rock (normal δ18O and ɛHf down to - 60) and shallow Mesozoic and Cenozoic age rocks, some of which are hydrothermally altered (to low δ18O values) by earlier stages of Snake River Plain magmatism. These crustal melts hybridize with juvenile basalts and rhyolites to produce the erupted rhyolites. We also observe that the Precambrian basement rock is only an important component in the erupted magmas in the first eruption at each caldera center, suggesting that the accumulation of new intrusions quickly builds an upper crustal intrusive body which is isolated from the Precambrian basement and evolves towards more isotopically juvenile and lower-δ18O compositions over time.

  18. Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures

    Energy Technology Data Exchange (ETDEWEB)

    McCarthy, Michael C., E-mail: mccarthy@cfa.harvard.edu; Martinez, Oscar; Crabtree, Kyle N.; Martin-Drumel, Marie-Aline [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA and School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138 (United States); McGuire, Brett A. [National Radio Astronomy Observatory, Charlottesville, Virginia 22901 (United States); Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA and School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138 (United States); Stanton, John F. [Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712-0165 (United States)

    2016-03-28

    HOCO is an important intermediate in combustion and atmospheric processes because the OH + CO → H + CO{sub 2} reaction represents the final step for the production of CO{sub 2} in hydrocarbon oxidation, and theoretical studies predict that this reaction proceeds via various intermediates, the most important being this radical. Isotopic investigations of trans- and cis-HOCO have been undertaken using Fourier transform microwave spectroscopy and millimeter-wave double resonance techniques in combination with a supersonic molecular beam discharge source to better understand the formation, chemical bonding, and molecular structures of this radical pair. We find that trans-HOCO can be produced almost equally well from either OH + CO or H + CO{sub 2} in our discharge source, but cis-HOCO appears to be roughly two times more abundant when starting from H + CO{sub 2}. Using isotopically labelled precursors, the OH + C{sup 18}O reaction predominately yields HOC{sup 18}O for both isomers, but H{sup 18}OCO is observed as well, typically at the level of 10%-20% that of HOC{sup 18}O; the opposite propensity is found for the {sup 18}OH + CO reaction. DO + C{sup 18}O yields similar ratios between DOC{sup 18}O and D{sup 18}OCO as those found for OH + C{sup 18}O, suggesting that some fraction of HOCO (or DOCO) may be formed from the back-reaction H + CO{sub 2}, which, at the high pressure of our gas expansion, can readily occur. The large {sup 13}C Fermi-contact term (a{sub F}) for trans- and cis-HO{sup 13}CO implicates significant unpaired electronic density in a σ-type orbital at the carbon atom, in good agreement with theoretical predictions. By correcting the experimental rotational constants for zero-point vibration motion calculated theoretically using second-order vibrational perturbation theory, precise geometrical structures have been derived for both isomers.

  19. Crustal evolution of granitoids and gneisses from the Cambaizinho belt, southern Brazil: Review zircon Pb-Pb evaporation ages and Pb-Nd-Sr isotopes

    International Nuclear Information System (INIS)

    Remus, M.V.D; Macambira, M.B; Hartmann, L.A.; Beilfuss, M

    2001-01-01

    Deformed granitoids and gneisses from the Cambai Complex (900-700 Ma) along Cambaizinho Creek and in the Vila Nova do Sul region, state of Rio Grande do Sul, Brazil, were formed in a remarkably short time, about 10 m.y., between 704±13 and 697±3 Ma. The data base of this work includes eighteen zircon Pb/Pb evaporation analyses, five Pb isotope in feldspar and whole rock. The oldest known rocks in the region are polydeformed dioritic gneisses dated by conventional U-Pb zircon at 704±13 Ma. New Pb-Pb zircon evaporation data on the late transcurrent, less deformed and more evolved granitoids (Sanga do Jobim Granitoids) yield a 697± Ma age and indicates that the evolution of the plutonic magmatism in the area was nearly contemporaneous. These data contrast with previous interpretations based on Rb-Sr data which considered that these rock associations were formed during a longer time period (700-640 Ma). All these granitoids intruded the supracrustal sequence. These granitoids yield a minimum age of about 700 Ma for the formation of the supracrustal sequence and its regional dynamothermal metamorphism. Lead isotope composition of K-feldspar from Sanga do Jobim Granitoids plot close to, but slightly below the lead isotope evolution curve of orogeny in the Zartmann and Doe model (1981). This indicates that the setting for these granitoids was that of a juvenile magmatic arc. These new data plus previous data in the region also corroborate that the crustal evolution involved juvenile crust accreted between 760-700 Ma. In contrast, the Cacapava and Sao Sepe Granites intruded the supracrustal sequences along the eastern side of the Sao Gabriel Block at 562 Ma and 550 Ma, respectively, and show Pb and Nd isotope signatures from an old basement. This evidence suggests that the juvenile terrane was thrusted over the older basement situated along the eastern part of the shield during the Dom Feliciano collisional orogeny at about 620-590 Ma (au)

  20. High mass isotope separation arrangement

    International Nuclear Information System (INIS)

    Eerkens, J.W.

    1976-01-01

    An isotope separation arrangement for separating a preselected isotope from a mixture of chemically-identical but isotopically-different molecules by either photon-induced pure revibrational or vibronic selective excitation of the molecules containing the atoms of the isotope to be separated from a lower to a higher energy state, and a chemical reaction of the higher energy state molecules with a chemically-reactive agent to form a chemical compound containing primarily the atoms of the isotope to be separated in a physicochemical state different from the physicochemical state of the mixture of chemically-identical but isotopically-different molecules. The chemical compound containing the atoms of the isotope to be separated may be subsequently processed to obtain the isotope. The laser configuration used to generate the photon beam is fully described

  1. Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

    Science.gov (United States)

    Paswan, A.; Omar, A.; Jaiswal, S.

    2018-02-01

    The optical spectroscopic and radio interferometric H I 21 cm-line observations of the blue compact dwarf galaxy Mrk 22 are presented. The Wolf-Rayet (WR) emission-line features corresponding to high ionization lines of He II λ4686 and C IV λ5808 from young massive stars are detected. The ages of two prominent star-forming regions in the galaxy are estimated as ∼10 and ∼ 4 Myr. The galaxy has non-thermal radio deficiency, which also indicates a young starburst and lack of supernovae events from the current star formation activities, consistent with the detection of WR emission-line features. A significant N/O enrichment is seen in the fainter star-forming region. The gas-phase metallicities [12 + log(O/H)] for the bright and faint regions are estimated as 7.98±0.07 and 7.46±0.09, respectively. The galaxy has a large diffuse H I envelop. The H I images reveal disturbed gas kinematics and H I clouds outside the optical extent of the galaxy, indicating recent tidal interaction or merger in the system. The results strongly indicate that Mrk 22 is undergoing a chemical and morphological evolution due to ongoing star formation, most likely triggered by a merger.

  2. H2-dependent attachment kinetics and shape evolution in chemical vapor deposition graphene growth

    Science.gov (United States)

    Meca, Esteban; Shenoy, Vivek B.; Lowengrub, John

    2017-09-01

    Experiments on graphene growth through chemical vapor deposition (CVD) involving methane (CH4) and hydrogen (H2) gases reveal a complex shape evolution and a non-monotonic dependence on the partial pressure of H2 ({{p}{{\\text{H}2}}} ). To explain these intriguing observations, we develop a microkinetic model for the stepwise decomposition of CH4 into mobile radicals and consider two possible mechanisms of attachment to graphene crystals: CH radicals to hydrogen-decorated edges of the crystals and C radicals to bare crystal edges. We derive an effective mass flux and an effective kinetic coefficient, both of which depend on {{p}{{\\text{H}2}}} , and incorporate these into a phase field model. The model reproduces both the non-monotonic dependence on {{p}{{\\text{H}2}}} and the characteristic shapes of graphene crystals observed in experiments. At small {{p}{{\\text{H}2}}} , growth is limited by the kinetics of attachment while at large {{p}{{\\text{H}2}}} growth is limited because the effective mass flux is small. We also derive a simple analytical model that captures the non-monotone behavior, enables the two mechanisms of attachment to be distinguished and provides guidelines for CVD growth of defect-free 2D crystals.

  3. Evolution of microbiological and physico-chemical quality of pasteurized milk

    Directory of Open Access Journals (Sweden)

    Natalia Gonzaga

    2015-11-01

    Full Text Available Milk quality is defined, among other parameters, by a reduced number of spoilage microorganisms, low somatic cell count and the absence of pathogens and chemical waste. Several studies conducted in different regions of the country have emphasized the high percentage of samples not complying with the standard. The purpose of this study was to evaluate the evolution of microbiological and physicochemical quality of pasteurized milk produced in the State of Paraná over 7 years. A total of 457 samples of pasteurized milk were analyzed, 104 samples in 2008, 269 samples in 2011 and 84 samples in 2014. The samples were subjected to physicochemical analysis of cryoscopy and enzyme search for alkaline phosphatase and peroxidase. Regarding microbiological tests, coliform counts were performed at 30°C and 45°C and count plate pattern. In the laboratory, physicochemical analysis were performed according to the Normative 68 and microbiological as normative instruction 62, both of the Brazilian Ministry of Agriculture, Livestock and Food Supply. The results showed that over the years the microbiological quality of milk decreased, with an increase of non-standard samples. For enzymes alkaline phosphatase, peroxidase, the pasteurization temperature has been observed over time and the overheating of the milk was more frequent in 2011. Fraud by addition of water in milk has either decreased or become more sophisticated, making its detection difficult.

  4. Gas Removal in the Ursa Minor Galaxy: Linking Hydrodynamics and Chemical Evolution Models

    Energy Technology Data Exchange (ETDEWEB)

    Caproni, Anderson; Lanfranchi, Gustavo Amaral; Baio, Gabriel Henrique Campos; Kowal, Grzegorz [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Falceta-Gonçalves, Diego, E-mail: anderson.caproni@cruzeirodosul.edu.br [Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, Rua Arlindo Bettio 1000, CEP 03828-000 São Paulo (Brazil)

    2017-04-01

    We present results from a non-cosmological, three-dimensional hydrodynamical simulation of the gas in the dwarf spheroidal galaxy Ursa Minor. Assuming an initial baryonic-to-dark-matter ratio derived from the cosmic microwave background radiation, we evolved the galactic gas distribution over 3 Gyr, taking into account the effects of the types Ia and II supernovae. For the first time, we used in our simulation the instantaneous supernovae rates derived from a chemical evolution model applied to spectroscopic observational data of Ursa Minor. We show that the amount of gas that is lost in this process is variable with time and radius, being the highest rates observed during the initial 600 Myr in our simulation. Our results indicate that types Ia and II supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and probably in other similar dwarf galaxies), but it is ultimately the combination of galactic winds powered by these supernovae and environmental effects (e.g., ram-pressure stripping) that results in the complete removal of the gas content.

  5. Robust numerical simulation of porosity evolution in chemical vapor infiltration III: three space dimension

    CERN Document Server

    Jin Shi

    2003-01-01

    Chemical vapor infiltration (CVI) process is an important technology to fabricate ceramic matrix composites (CMC's). In this paper, a three-dimension numerical model is presented to describe pore microstructure evolution during the CVI process. We extend the two-dimension model proposed in [S. Jin, X.L. Wang, T.L. Starr, J. Mater. Res. 14 (1999) 3829; S. Jin. X.L. Wang, T.L. Starr, X.F. Chen, J. Comp. Phys. 162 (2000) 467], where the fiber surface is modeled as an evolving interface, to the three space dimension. The 3D method keeps all the virtue of the 2D model: robust numerical capturing of topological changes of the interface such as the merging, and fast detection of the inaccessible pores. For models in the kinetic limit, where the moving speed of the interface is constant, some numerical examples are presented to show that this three-dimension model will effectively track the change of porosity, close-off time, location and shape of all pores.

  6. Ground water chemical evolution of Pocos de Caldas - Minas Gerais State -Brazil

    International Nuclear Information System (INIS)

    Cruz, W.B.; Peixoto, C.A.M.

    1991-01-01

    The chemical