Now showing items 10137-10156 of 20719

    • Isotopes, Inc. Radiocarbon Measurements V

      Trautman, Milton A.; Willis, Eric H. (American Journal of Science, 1966-01-01)
    • Isotopes, Plants, and Reservoir Effects: Case Study from the Caspian Steppe Bronze Age

      Shishlina, Natalia Ivanovna; Zazovskaya, E.; van der Plicht, J.; Sevastyanov, V. (Department of Geosciences, The University of Arizona, 2012-10-15)
      Bronze Age human and animal bone collagen from several steppe Bronze Age cultures (i.e. Early Catacomb, East and West Manych Catacomb, and Lola cultures) shows large variations in δ13C and δ15N values. In general, we observed that the older the sample, the lower the δ13C and δ15N values. We hypothesize that more positive values of δ13C and δ15N are caused by change in diet and a more arid climate. For ancient sheep during drier periods of the Early Catacomb, East and West Manych Catacomb, and Lola cultures, we observed 2 groups with different C and N isotopic compositions, reflecting consumption of different types of fodder. During periods of aridization, C4 and C3 plants with high δ15N values appeared in the vegetation, also influencing bone collagen values. Human bones show reservoir effects, caused by aquatic diet components. These effects can be quantified by paired dating of human bone and associated terrestrial samples. Reservoir corrections have revised chronologies for the region. Some paired dates do not reveal reservoir effects. This can be explained in 2 alternative ways. One is that the human diet did not include aquatic components; rather, the diet was based on C3 vegetation with high δ15N values (13–15‰), and flesh/milk of domesticated animals. An alternative explanation is that humans consumed food from freshwater resources without reservoir effects.
    • Isotopic Analysis and Cycling of Dissolved Inorganic Carbon at Lake Biwa, Central Japan

      Nakamura, Toshio; Kojima, Sadao; Ohta, Tomoko; Oda, Hirotaka; Ikeda, Akiko; Okuno, Mitsuru; Yokota, Ki-Ichiro; Mizutani, Yoshihiko; Kretschmer, Wolfgang (Department of Geosciences, The University of Arizona, 1998-01-01)
      This paper reports on concentrations and carbon isotopic results of dissolved inorganic carbon (DIC) in water samples collected at four locations and from several depths in Lake Biwa, central Japan, covering every season of the year, starting in the spring of 1995. Depth profiles of DIC concentration and DIC delta-13C showed a strong seasonal pattern, as a result of vertical mixing of the lake water in winter and early spring, or lack of mixing in the other seasons. No seasonal change in DIC Delta-14C depth profiles was recognizable, mainly owing to the wide scatter of DIC Delta-14C. Values typically ranged from 0.47 to 0.65 mmol kg-1 for DIC concentration, and from -4 to -8 per mil from +10 to +80 per mil for DIC delta-13C and DIC Delta-14C, respectively, for the Lake Biwa water.
    • Isotopic Analysis of Groundwater and Carbonate System in the Surdulica Geothermal Aquifer

      Hadžišehović, Munevera; Miljević, Nada; Šipka, Vojislava; Golobočanin, Dušan; Popović, Radule (Department of Geosciences, The University of Arizona, 1993-01-01)
      We present here results of our investigation of the isotopic chemical composition of groundwater and carbonates in the Surdulica geothermal aquifer, Serbia. We considered the effects of carbonate dissolution and measured 13C, 14C, D, 18O, 3H, field pH, temperature, Na+, Ca2+, Mg2+, HCO-3 and other aqueous species from 30 springs and boreholes. Geothermal waters are supersaturated with calcite. Carbon isotope compositions vary with carbonate mineral dissolution. The delta-D and delta-18O of groundwater samples fit the meteoric water line, and indicate that groundwater is recharged mainly from higher altitudes and the cold season. Different groundwater residence times point out two mechanisms for their formation; fissure flow for young waters and standard diffusion processes for old ones.
    • Isotopic Fractionation in Corn

      Lowdon, J. A. (American Journal of Science, 1969-01-01)
    • Isotopic Fractionation of Carbon During CO2 Absorption by Mortar

      Pachiaudi, Christiane; Marechal, Joelle; Van Strydonck, Mark; Dupas, Michel; Dauchot-Dehon, Michele (American Journal of Science, 1986-01-01)
    • Isotopic Fractionation of NBS Oxalic 14C Standard and Its Effect on Calculated Age of Materials

      Nehmi, Victor A. (American Journal of Science, 1980-01-01)
      There is much controversy about the significance to radiocarbon dating of isotopic fractionation during the oxidation to CO2 of NBS oxalic acid, the carbon-14 dating standard. To check the effect of fractionation, 30 routine potassium permanganate oxidations of oxalic acid were performed. The isotopic composition of resulting CO2 was determined mass-spectrometrically. delta-13C results ranged between -17.7 and -21.2, with an average of -18.9 per mil wrt PDB. The effect of not applying an isotopic fractionation correction to NBS oxalic acid when performing age calculations is evaluated.
    • Isotopic Fractionation of Norwegian Materials for Radiocarbon Dating

      Gulliksen, Steinar (American Journal of Science, 1980-01-01)
      To improve reporting of radiocarbon dates, Stuiver and Polach (1977) recommend that reported standard errors should include the error in the applied delta-13C value, and suggest estimated mean values for delta-13C to be applied when not measured. Based on delta-13C data for ca 250 samples measured during 1975-1979, mean values for different materials dated by the Trondheim radiocarbon laboratory have been compiled. All material is from Norway and Svalbard (marine bone collagen). For peat, gyttja, and terrestrial bone material, delta-13C should be measured to obtain optimal precision in the dates. For shell, wood, charcoal, and marine bones, the standard error in an estimated delta-13C value will only increase uncertainty of a date from +/- 50 years to ca +/- 55 years.
    • Isotopic Fractionation of Oxygen and Carbon in Lime Mortar Under Natural Environmental Conditions

      Van Strydonck, M. J. Y.; Dupas, Michel; Kippens, Edward (Department of Geosciences, The University of Arizona, 1989-01-01)
      The rate of calcite formation and the isotopic fractionation in lime mortar during the process of mortar setting were examined. The diffusion rate of atmospheric CO2 in the sample is the rate-controlling step of the chemical reaction. A Rayleigh diffusion in the mortar causes an enrichment of 13C and 18O in the samples.
    • Isotopic Investigation of the Surdulica Geothermal System

      Milovanović, Branislav; Stanković, Svetislav; Komatina, Miomir M.; Hadžišehović, Munevera; Župančić, Mladen; Miljević, Nada; Stepić, Rista; Obelić, Bogomil (Department of Geosciences, The University of Arizona, 1989-01-01)
      The object of our investigation was to study a mechanism of water formation in the Surdulica geothermal system (recharge area, age and homogeneity of the waters). We collected 56 samples to determine the chemical, stable isotope, 14C and tritium content of the waters. We found large stable isotope variations in precipitation collected at different altitudes, whereas the geothermal waters are largely homogeneous and seasonally independent. Data on springs and rivers, the local meteoric water line and recharge; area were obtained. Three groups of groundwater were identified by age modern from natural springs, old from mines and very old from the Vranjska Banja. Because the initial 14C activity of infiltrated waters from the recharge area is unknown, the age of thermal waters can only be inferred, from HCO3-, 14C and 3H content, to be 10,000 to 28,000 years old.
    • Israel and Anticipatory Self Defense [Article]

      Beres, Louis Rene (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1991)
    • Israel, Lebanon, and Hizbullah: A Jurisprudental Assessment [Article]

      Beres, Louis Rene (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1997)
    • An Issue Devoted To Southeastern Dendrochronology Editor's Note

      Leavitt, Steven W.; Tree-Ring Society (Tree-Ring Society, 2009-01)
    • Issue Paper: Biodiversity of Rangelands

      Society for Range Management, 2003-12-01
    • Issues Involved in the Taking of Evidence in Mexico by U.S. Litigants [Article]

      Low, Lucinda A. (The University of Arizona James E. Rogers College of Law (Tucson, AZ), 1986)
    • It All Happened In Tombstone

      Clum, John P. (Arizona State Historian (Phoenix, AZ), 1929-10)
    • It May Be Utilization, But Is It Management?

      McKinney, Earl (Society for Range Management, 1997-06-01)
    • It Pays to Organize Kitchen Space

      Books, Alice; School of Home Economics (College of Agriculture, University of Arizona (Tucson, AZ), 1955)
    • It Takes Price and Pounds To Make Dollars

      Gray, Robert G.; Cable, C. Curtis; Gila County Extension Service; Cooperative Extension Service (College of Agriculture, University of Arizona (Tucson, AZ), 1968)
    • It's All Mine

      Cook, Barbara; School of Home Economics (College of Agriculture, University of Arizona (Tucson, AZ), 1974)