Science.gov

Sample records for berkelium isotopes

  1. Berkelium

    NASA Astrophysics Data System (ADS)

    Hobart, David E.; Peterson, Joseph R.

    As was the case for the previously discovered transuranium elements, element 97 was first produced via a nuclear bombardment reaction. In December 1949 ion-exchange separation of the products formed by the bombardment of 241Am with accelerated alpha particles provided a new electron-capture activity eluting just ahead of curium (Thompson et al., 1950a,b). This activity was assigned to an isotope (mass number 243) of element 97. The new element was named berkelium after Berkeley, California, USA, the city of its discovery, in a manner parallel to the naming of its lanthanide analog, terbium, after Ytterby, Sweden. The initial investigations of the chemical properties of berkelium were limited to tracer experiments (ion exchange and coprecipitation), and these were sufficient to establish the stability of Bk(III) and the accessibility of Bk(IV) in aqueous solution and to estimate the electrochemical potential of the Bk(IV)/Bk(III) couple (Thompson et al., 1950b,c). Because a complete study of the chemistry of an element is not possible by tracer methods alone, a program for long-term neutron irradiation of about 8 g of 239Pu was initiated in 1952 in the Materials Testing Reactor (Arco, Idaho, USA) to provide macroquantities of berkelium (Cunningham, 1959). In 1958 about 0.6 mg of 249Bk was separated, purified, and used in experiments to determine the absorption spectrum of Bk(III) in aqueous solution and to measure the magnetic susceptibility of Bk(III) (Cunningham, 1959). No Bk(III) absorption was observed over the wavelength range 450-750 nm, but an upper limit of about 20 was set for the molar absorptivity of any Bk(III) absorption in this wavelength region. The magnetic susceptibility, measured from 77 to 298 K with the Bk(III) ions sorbed in a single bead of cation-exchange resin, was found to conform to the Curie-Weiss law with an effective moment of 8.7 mB, suggesting a 5f8 electronic configuration for the Bk(III) ion. The first structure determination of a

  2. Chemistry of berkelium

    SciTech Connect

    Peterson, J.R.; Hobart, D.E.

    1984-01-01

    The possibility of studying the physical and chemical properties of Bk(II) in bulk is intriguing. It has been suggested that this new oxidation state of berkelium is produced by nature via the ..cap alpha.. decay of einsteinium-253 dihalides; however, in these absorption spectrophotometric studies, only the divalent parent species and the divalent californium-249 granddaughter species have been directly identified. Other work has shown that the ..beta.. decay of berkelium-249 in the bulk-phase solid state results in the production of daughter californium-249 species exhibiting the same oxidation state and structural environment as those of the berkelium parent. Direct synthesis of Bk(II) via the reaction Bk + 2BkBr/sub 3/ ..-->.. 3BkBr/sub 2/ should be attempted to establish with certainty the existence of Bk(II) in the bulk-phase solid state and to characterize it via absorption spectrophotometry and X-ray powder diffraction. Studies of berkelium metal under pressure should be continued to determine more precisely its bulk modulus and to search for the existence of a distorted face-centered cubic (fcc) modification between the known fcc and ..cap alpha..-uranium-type orthorhombic phases. An interesting extension of this research would be to investigate the behavior of BkN under pressure to see if it might undergo a sudden volume collapse corresponding to a change in metallic valence from three to four. The preparation and characterization of intermetallic compounds and alloys of berkelium should be pursued, as well as the determination of the stability constants of Bk(IV) complexes. The range of oxidation states accessible to berkelium might be expanded by stabilizing Bk(II) and/or Bk(V) in highly complexing aqueous, nonaqueous, or even molten salt media and/or in appropriate solid-state matrices. 240 references, 9 figures, 5 tables.

  3. The New Element Berkelium (Atomic Number 97)

    DOE R&D Accomplishments Database

    Seaborg, G. T.; Thompson, S. G.; Ghiorso, A.

    1950-04-26

    An isotope of the element with atomic number 97 has been discovered as a product of the helium-ion bombardment of americium. The name berkelium, symbol Bk, is proposed for element 97. The chemical separation of element 97 from the target material and other reaction products was made by combinations of precipitation and ion exchange adsorption methods making use of its anticipated (III) and (IV) oxidation states and its position as a member of the actinide transition series. The distinctive chemical properties made use of in its separation and the equally distinctive decay properties of the particular isotope constitute the principal evidence for the new element.

  4. Characterization of berkelium(III) dipicolinate and borate compounds in solution and the solid state.

    PubMed

    Silver, Mark A; Cary, Samantha K; Johnson, Jason A; Baumbach, Ryan E; Arico, Alexandra A; Luckey, Morgan; Urban, Matthew; Wang, Jamie C; Polinski, Matthew J; Chemey, Alexander; Liu, Guokui; Chen, Kuan-Wen; Van Cleve, Shelley M; Marsh, Matthew L; Eaton, Teresa M; van de Burgt, Lambertus J; Gray, Ashley L; Hobart, David E; Hanson, Kenneth; Maron, Laurent; Gendron, Frédéric; Autschbach, Jochen; Speldrich, Manfred; Kögerler, Paul; Yang, Ping; Braley, Jenifer; Albrecht-Schmitt, Thomas E

    2016-08-26

    Berkelium is positioned at a crucial location in the actinide series between the inherently stable half-filled 5f(7) configuration of curium and the abrupt transition in chemical behavior created by the onset of a metastable divalent state that starts at californium. However, the mere 320-day half-life of berkelium's only available isotope, (249)Bk, has hindered in-depth studies of the element's coordination chemistry. Herein, we report the synthesis and detailed solid-state and solution-phase characterization of a berkelium coordination complex, Bk(III)tris(dipicolinate), as well as a chemically distinct Bk(III) borate material for comparison. We demonstrate that berkelium's complexation is analogous to that of californium. However, from a range of spectroscopic techniques and quantum mechanical calculations, it is clear that spin-orbit coupling contributes significantly to berkelium's multiconfigurational ground state. PMID:27563098

  5. METHOD FOR THE RECOVERY AND PURIFICATION OF BERKELIUM

    DOEpatents

    Hulet, E.K.

    1959-10-20

    A solvent extraction process is described for the separation of berkelium from a mixture of elements in the lanthanum and actinium series of the periodic table. In particular, the mixture of elements is dissolved in 1.0N nitric acid, and the resulting solution is extracted with n-tributyl phosphate containlng a stoichiometric excess of solid sodium bismuthate. The berkelium present in the nitric acid solution is oxidized to the IV oxidation state and is preferentially- extracted into the n-tributyl phosphate. The organic phase, containing berkelium in an oxidized state, is extracted with 0.1N hydrochloric acid solution containing a small quantity- of a reducing agent such as yvdrazine hydrochloride. The berkelium is reduced to the III oxidation state and is extracted into the aqueous phase. The berkelium is then recovered from the aqueous phase.

  6. Possible stabilization of the tetravalent oxidation state of berkelium and californium in acetonitrile with triphenylarsine oxide

    SciTech Connect

    Payne, G.F.; Peterson, J.R.

    1987-01-01

    It appears that we may have prepared Bk(IV) nitrate.nTPAs0 and Bk(IV) perchlorate.nTPAs0 complexes which formed the corresponding Cf(IV) complexes through the beta decay of Bk-249. Definitive proof should come from similar experiments with quantities of Bk-249 large enough to allow spectrophotometric detection of the characteristic f..-->..f transitions in these berkelium and californium species. It is clear, however, that TPAs0 and acetonitrile can play a pivotal role in the stabilization of lanact(IV) species.

  7. Discovery of isotopes of the transuranium elements with 93≤Z≤98

    SciTech Connect

    Fry, C.; Thoennessen, M.

    2013-01-15

    One hundred and five isotopes of the transuranium elements neptunium, plutonium, americium, curium, berkelium, and californium have been observed so far; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  8. Discovery of isotopes of the transuranium elements with 93≤Z≤98

    NASA Astrophysics Data System (ADS)

    Fry, C.; Thoennessen, M.

    2013-01-01

    One hundred and five isotopes of the transuranium elements neptunium, plutonium, americium, curium, berkelium, and californium have been observed so far; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  9. Reactor production of sup 252 Cf and transcurium isotopes

    SciTech Connect

    Alexander, C.W.; Halperin, J.; Walker, R.L.; Bigelow, J.E.

    1990-01-01

    Berkelium, californium, einsteinium, and fermium are currently produced in the High Flux Isotope Reactor (HFIR) and recovered in the Radiochemical Engineering Development Center (REDC) at the Oak Ridge National Laboratory (ORNL). All the isotopes are used for research. In addition, {sup 252}Cf, {sup 253}Es, and {sup 255}Fm have been considered or are used for industrial or medical applications. ORNL is the sole producer of these transcurium isotopes in the western world. A wide range of actinide samples were irradiated in special test assemblies at the Fast Flux Test Facility (FFTF) at Hanford, Washington. The purpose of the experiments was to evaluate the usefulness of the two-group flux model for transmutations in the special assemblies with an eventual goal of determining the feasibility of producing macro amounts of transcurium isotopes in the FFTF. Preliminary results from the production of {sup 254g}Es from {sup 252}Cf will be discussed. 14 refs., 5 tabs.

  10. Separation of berkelium (IV) from trivalent transplutonium elements on ion-exchangers in solutions of phosphoric acid

    SciTech Connect

    Guseva, L.I.; Stepushkina, V.V.; Tikhomirova, G.S.

    1985-01-01

    The dependences of Am, Cm, Bk, Cf and Es behavior on anion- and cation-exchangers in solutions of 0.1-8.0 M H/sub 3/PO/sub 4/ on acid concentration and oxidant content in solution (KBrO/sub 3/) or in resin (PbO/sub 2/) have been studied. Significant differences in distribution coefficients of Bk and other transplutonium elements (TPE) have been found that can be explained by Bk oxidation to the tetravalent state. A simple and effective method of Bk (IV) separation from trivalent TPE has been developed. The method was applied to the isolation of isotopes Bk-249 and Bk-250; the purification factor of Bk (IV) from other TPE is 10/sup 4/-10/sub 6/ per cycle. The possibility of Bk separation from bromate and phosphate ions by its sorption on a cation-exchanger from diluted H/sub 3/PO/sub 4/ solutions with subsequent desorption by the mineral acid has been shown. 20 references, 8 figures.

  11. Decay Properties of New Isotopes 234Bk and 230Am, and Even-Even Nuclides 234Cm and 230Pu

    NASA Astrophysics Data System (ADS)

    Kaji, Daiya; Morimoto, Kouji; Haba, Hiromitsu; Ideguchi, Eiji; Koura, Hiroyuki; Morita, Kosuke

    2016-01-01

    A neutron-deficient berkelium isotope of 234Bk produced via 197Au(40Ar,3n) reaction and the daughter product of 230Am were newly identified. Alpha-decay energies of eleven 234Bk were found at 7.62-7.96 MeV, and six fission events that correlated with the α-decay of 234Bk were observed. The half-lives of 234Bk and 230Am were determined to be 19 - 4 + 6 s and 32 - 9 + 22 s, respectively. The 234Cm followed by the β-decay of 234Bk was also identified.

  12. FUEL CYCLE ISOTOPE EVOLUTION BY TRANSMUTATION DYNAMICS OVER MULTIPLE RECYCLES

    SciTech Connect

    Samuel Bays; Steven Piet; Amaury Dumontier

    2010-06-01

    Because all actinides have the ability to fission appreciably in a fast neutron spectrum, these types of reactor systems are usually not associated with the buildup of higher mass actinides: curium, berkelium and californium. These higher actinides have high specific decay heat power, gamma and neutron source strengths, and are usually considered as a complication to the fuel manufacturing and transportation of fresh recycled transuranic fuel. This buildup issue has been studied widely for thermal reactor fuels. However, recent studies have shown that the transmutation physics associated with "gateway isotopes" dictates Cm-Bk-Cf buildup, even in fast burner reactors. Assuming a symbiotic fuel relationship with light water reactors (LWR), Pu-242 and Am-243 are formed in the LWRs and then are externally fed to the fast reactor as part of its overall transuranic fuel supply. These isotopes are created much more readily in a thermal than in fast spectrum systems due to the differences in the fast fission (i.e., above the fission threshold for non-fissile actinides) contribution. In a strictly breeding fast reactor this dependency on LWR transuranics would not exist, and thus avoids the introduction of LWR derived gateway isotopes into the fast reactor system. However in a transuranic burning fast reactor, the external supply of these gateway isotopes behaves as an external driving force towards the creation and build-up of Cm-Bk-Cf in the fuel cycle. It was found that though the Cm-Bk-Cf concentration in the equilibrium fuel cycle is dictated by the fast neutron spectrum, the time required to reach that equilibrium concentration is dictated by recycle, transmutation and decay storage dynamics.

  13. Isotopic Biogeochemistry

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.

    1985-01-01

    An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon isotopic records; isotopic studies of banded iron formations; isotope effects in microbial systems; studies of organic compounds in ancient sediments; and development in isotopic geochemistry and analysis.

  14. Isotope separation

    DOEpatents

    Bartlett, Rodney J.; Morrey, John R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated.

  15. Isotopic chirality

    SciTech Connect

    Floss, H.G.

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  16. Transuranium isotopes

    SciTech Connect

    Hoffman, D.C.

    1985-12-01

    The needs of the research community for the production of transuranium isotopes, the quantities required, the continuity of production desired, and what a new steady state neutron source would have to provide to satisfy these needs are discussed. Examples of past frontier research which need these isotopes as well as an outline of the proposed Large Einsteinium Activation Program, LEAP, which requires roughly ten times the current production of /sup 254/Es are given. 15 refs., 5 figs., 4 tabs.

  17. ISOTOPE SEPARATORS

    DOEpatents

    Bacon, C.G.

    1958-08-26

    An improvement is presented in the structure of an isotope separation apparatus and, in particular, is concerned with a magnetically operated shutter associated with a window which is provided for the purpose of enabling the operator to view the processes going on within the interior of the apparatus. The shutier is mounted to close under the force of gravity in the absence of any other force. By closing an electrical circuit to a coil mouated on the shutter the magnetic field of the isotope separating apparatus coacts with the magnetic field of the coil to force the shutter to the open position.

  18. Joint Institute for Nuclear Research Data Analysis Guide - Berkelium Edition

    SciTech Connect

    Henderson, R A

    2009-07-23

    This is a data analysis guide to the JINR system developed by Roger Henderson. It is intended as a complete guide to the data format and the calibration parameters utilized for the analysis of the data. This guide will provide the basic structure of the data files, the description of the individual data items, and the basic equations developed for the calculation of the results. Currently (7/17/2009), calculation of the calibration parameters is not a covered topic. It is intended that this will be covered in a future update.

  19. Method for separating isotopes

    DOEpatents

    Jepson, B.E.

    1975-10-21

    Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether.

  20. Stable isotope studies

    SciTech Connect

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  1. Isotope separation by photochromatography

    DOEpatents

    Suslick, Kenneth S.

    1977-01-01

    An isotope separation method which comprises physically adsorbing an isotopically mixed molecular species on an adsorptive surface and irradiating the adsorbed molecules with radiation of a predetermined wavelength which will selectively excite a desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thereby separate them from the unexcited undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes.

  2. Isotope separation by photochromatography

    DOEpatents

    Suslick, K.S.

    1975-10-03

    A photochromatographic method for isotope separation is described. An isotopically mixed molecular species is adsorbed on an adsorptive surface, and the adsorbed molecules are irradiated with radiation of a predetermined wavelength which will selectively excite desired isotopic species. Sufficient energy is transferred to the excited molecules to desorb them from the surface and thus separate them from the undesired isotopic species. The method is particularly applicable to the separation of hydrogen isotopes. (BLM)

  3. METHOD OF ISOTOPE CONCENTRATION

    DOEpatents

    Spevack, J.S.

    1957-04-01

    An isotope concentration process is described which consists of exchanging, at two or more different temperature stages, two isotopes of an element between substances that are physically separate from each other and each of which is capable of containing either of the isotopes, and withdrawing from a point between at least two of the temperatare stages one of the substances containing an increased concentration of the desired isotope.

  4. Cosmic ray isotopes

    NASA Technical Reports Server (NTRS)

    Stone, E. C.

    1973-01-01

    The isotopic composition of cosmic rays is studied in order to develop the relationship between cosmic rays and stellar processes. Cross section and model calculations are reported on isotopes of H, He, Be, Al and Fe. Satellite instrument measuring techniques separate only the isotopes of the lighter elements.

  5. Statistical clumped isotope signatures

    PubMed Central

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  6. Zirconium isotope separation

    SciTech Connect

    Siddall, M.B.

    1984-12-11

    A method of separating zirconium isotopes by converting the zirconium to its iodide salt prior to separation by usual isotope methods is disclosed. After separation the desired isotopes are converted from the salt to the metal by the van Arkel-de Boer iodide process.

  7. Statistical clumped isotope signatures.

    PubMed

    Röckmann, T; Popa, M E; Krol, M C; Hofmann, M E G

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  8. ISOTOPE CONVERSION DEVICE

    DOEpatents

    Wigner, E.P.; Young, G.J.; Ohlinger, L.A.

    1957-12-01

    This patent relates to nuclear reactors of tbe type utilizing a liquid fuel and designed to convert a non-thermally fissionable isotope to a thermally fissionable isotope by neutron absorption. A tank containing a reactive composition of a thermally fissionable isotope dispersed in a liquid moderator is disposed within an outer tank containing a slurry of a non-thermally fissionable isotope convertible to a thermally fissionable isotope by neutron absorption. A control rod is used to control the chain reaction in the reactive composition and means are provided for circulating and cooling the reactive composition and slurry in separate circuits.

  9. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2001-12-21

    Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

  10. Hybrid isotope separation scheme

    DOEpatents

    Maya, Jakob

    1991-01-01

    A method of yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus.

  11. HYDROGEN ISOTOPE TARGETS

    DOEpatents

    Ashley, R.W.

    1958-08-12

    The design of targets for use in the investigation of nuclear reactions of hydrogen isotopes by bombardment with accelerated particles is described. The target con struction eomprises a backing disc of a metal selected from the group consisting of molybdenunn and tungsten, a eoating of condensed titaniunn on the dise, and a hydrogen isotope selected from the group consisting of deuterium and tritium absorbed in the coatiag. The proeess for preparing these hydrogen isotope targets is described.

  12. Hybrid isotope separation scheme

    DOEpatents

    Maya, J.

    1991-06-18

    A method is described for yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which a scavenger, radiating the gas with a wave length or frequency characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photochemical reaction between the scavenger, and collecting the specific isotope-containing chemical by using a recombination surface or by a scooping apparatus. 2 figures.

  13. The DOE Isotopes Program

    NASA Astrophysics Data System (ADS)

    Gillo, Jehannes

    2015-10-01

    The DOE Isotope Program is a small federal program with a great deal of impact and is managed by the DOE Office of Nuclear Physics. The Isotope Program has been managed by the Office of Nuclear Physics since 2009, and since that time, has been re-defined in terms of mission, scope and operations. The program produces critical isotopes that are in short supply or simply unavailable from elsewhere to facilitate research and applications. Research is also supported to develop or improve production techniques that will increase availability of isotopes in high demand, such as alpha emitters for cancer therapy.

  14. Isotopically engineered semiconductors

    NASA Astrophysics Data System (ADS)

    Haller, E. E.

    1995-04-01

    Scientific interest, technological promise, and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This review of mostly recent activities begins with an introduction to some past classical experiments which have been performed on isotopically controlled semiconductors. A review of the natural isotopic composition of the relevant elements follows. Some materials aspects resulting in part from the high costs of enriched isotopes are discussed next. Raman spectroscopy studies with a number of isotopically pure and deliberately mixed Ge bulk crystals show that the Brillouin-zone-center optical phonons are not localized. Their lifetime is almost independent of isotopic disorder, leading to homogeneous Raman line broadening. Studies with short period isotope superlattices consisting of alternating layers of n atomic planes of 70Ge and 74Ge reveal a host of zone-center phonons due to Brillouin-zone folding. At n≳40 one observes two phonon lines at frequencies corresponding to the bulk values of the two isotopes. In natural diamond, isotope scattering of the low-energy phonons, which are responsible for the thermal conductivity, is very strongly affected by small isotope disorder. Isotopically pure 12C diamond crystals exhibit thermal conductivities as high as 410 W cm-1 K-1 at 104 K, leading to projected values of over 2000 W cm-1 K-1 near 80 K. The changes in phonon properties with isotopic composition also weakly affect the electronic band structures and the lattice constants. The latter isotope dependence is most relevant for future standards of length based on crystal lattice constants. Capture of thermal neutrons by isotope nuclei followed by nuclear decay produces new elements, resulting in a very large number of possibilities for isotope selective doping of semiconductors. This neutron transmutation of isotope nuclei, already used

  15. Intracellular Cadmium Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

    2011-12-01

    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  16. Discovery of the krypton isotopes

    SciTech Connect

    Heim, M.; Fritsch, A.; Schuh, A.; Shore, A.; Thoennessen, M.

    2010-07-15

    Thirty-two krypton isotopes have been observed so far and the discovery of these isotopes is discussed here. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  17. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  18. Detecting isotopic ratio outliers

    SciTech Connect

    Bayne, C.K.; Smith, D.H.

    1985-01-01

    An alternative method is proposed for improving isotopic ratio estimates. This method mathematically models pulse-count data and uses iterative reweighted Poisson regression to estimate model parameters to calculate the isotopic ratios. This computer-oriented approach provides theoretically better methods than conventional techniques to establish error limits and to identify outliers. 6 refs., 3 figs., 3 tabs.

  19. Laser isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Boyer, Keith; Greiner, Norman R.

    1988-01-01

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  20. Photochemical isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

    1987-01-01

    A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

  1. Discovery of Isotopes

    NASA Astrophysics Data System (ADS)

    May, Erin; Thoennessen, Michael

    2011-10-01

    To date, no comprehensive study has been undertaken regarding the initial detection and identification of isotopes. At NSCL, a project has been initiated to catalog and report the initial observation of every isotope. The conditions characterizing the successful discovery of an isotope include a clear and unambiguous mass and element identification through decay curves, mass spectroscopy, gamma-ray spectra, and/or relationships to other isotopes, as well as the publication of such findings in a refereed journal. I will present the documentation for eight elements: cesium, lanthanum, praseodymium, promethium, samarium, europium, gadolinium, and terbium. The year and author of each initial publication along with the location and methods of production and identification will be shown. A summary and overview of all ~3000 isotopes documented so far as a function of discovery year, method and place will also be presented.

  2. Photochemical isotope separation

    DOEpatents

    Robinson, C.P.; Jensen, R.J.; Cotter, T.P.; Greiner, N.R.; Boyer, K.

    1987-04-28

    A process is described for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium. 8 figs.

  3. Laser isotope separation

    DOEpatents

    Robinson, C.P.; Reed, J.J.; Cotter, T.P.; Boyer, K.; Greiner, N.R.

    1975-11-26

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light is described. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  4. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2006-06-19

    The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

  5. ISOTOPE SEPARATING APPARATUS

    DOEpatents

    Kudravetz, M.K.; Greene, H.B.

    1958-09-16

    This patent relates to control systems for a calutron and, in particular, describes an electro-mechanical system for interrupting the collection of charged particles when the ratio between the two isotopes being receivcd deviates from a predetermined value. One embodiment of the invention includes means responsive to the ratio between two isotopes being received for opening a normally closed shutter over the receiver entrance when the isotope ratio is the desired value. In another form of the invention the collection operation is interrupted by changing the beam accelerating voltage to deflect the ion beam away from the receiver.

  6. Carbon isotope techniques

    SciTech Connect

    Coleman, D.C. ); Fry, B. )

    1991-01-01

    This book is a hands-on introduction to using carbon isotope tracers in experimental biology and ecology. It is a bench-top reference with protocols for the study of plants, animals, and soils. The {sup 11}C, {sup 12}C, {sup 13}C, and {sup 14}C carbon isotopes are considered and standard techniques are described by established authors. The compilation includes the following features: specific, well-established, user-oriented techniques; carbon cycles in plants, animals, soils, air, and water; isotopes in ecological research; examples and sample calculations.

  7. Stable isotopes in mineralogy

    USGS Publications Warehouse

    O'Neil, J.R.

    1977-01-01

    Stable isotope fractionations between minerals are functions of the fundamental vibrational frequencies of the minerals and therefore bear on several topics of mineralogical interest. Isotopic compositions of the elements H, C, O, Si, and S can now be determined routinely in almost any mineral. A summary has been made of both published and new results of laboratory investigations, analyses of natural materials, and theoretical considerations which bear on the importance of temperature, pressure, chemical composition and crystal structure to the isotopic properties of minerals. It is shown that stable isotope studies can sometimes provide evidence for elucidating details of crystal structure and can be a powerful tool for use in tracing the reaction paths of mineralogical reactions. ?? 1977 Springer-Verlag.

  8. Perchlorate isotope forensics

    USGS Publications Warehouse

    Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Horita, J.; Brown, G.M.; Jackson, W.A.; Batista, J.; Hatzinger, P.B.

    2005-01-01

    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses ( 37Cl/35Cl and 18O/17O/ 16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. ?? 2005 American Chemical Society.

  9. Rare Isotope Accelerators

    NASA Astrophysics Data System (ADS)

    Savard, Guy

    2002-04-01

    The next frontier for low-energy nuclear physics involves experimentation with accelerated beams of short-lived radioactive isotopes. A new facility, the Rare Isotope Accelerator (RIA), is proposed to produce large amount of these rare isotopes and post-accelerate them to energies relevant for studies in nuclear physics, astrophysics and the study of fundamental interactions at low energy. The basic science motivation for this facility will be introduced. The general facility layout, from the 400 kW heavy-ion superconducting linac used for production of the required isotopes to the novel production and extraction schemes and the highly efficient post-accelerator, will be presented. Special emphasis will be put on a number of technical breakthroughs and recent R&D results that enable this new facility.

  10. Isotopically controlled semiconductors

    SciTech Connect

    Haller, E.E.

    2004-11-15

    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  11. Oxygen isotope cosmothermometer.

    NASA Technical Reports Server (NTRS)

    Onuma, N.; Clayton, R. N.; Mayeda, T. K.

    1972-01-01

    Variations in oxygen isotopic abundances of meteoritic minerals, chondrules, whole meteorites, and planets are discussed in terms of a model involving isotopic exchange between primordial dust and a cooling solar nebular gas. From the temperature-dependence of the isotopic fractionation factors, temperatures have been assigned to the processes of initial condensation, chondrule formation, and planetary accretion. Separated phases from carbonaceous chondrites fall into three isotopic groups representing widely differing conditions of formation: (1) low-iron olivine and pyroxene, and calcium-aluminum silicates condensed at temperatures above 1000 K; (2) high-iron olivine and pyroxene melted to form chondrules after prior cooling and exchange to temperatures of 530-620 K; and (3) hydrous silicates condensed at temperatures below 400 K.

  12. Oxygen Isotopes in Meteorites

    NASA Astrophysics Data System (ADS)

    Clayton, R. N.

    2003-12-01

    Oxygen isotope abundance variations in meteorites are very useful in elucidating chemical and physical processes that occurred during the formation of the solar system (Clayton, 1993). On Earth, the mean abundances of the three stable isotopes are 16O: 99.76%, 17O: 0.039%, and 18O: 0.202%. It is conventional to express variations in abundances of the isotopes in terms of isotopic ratios, relative to an arbitrary standard, called SMOW (for standard mean ocean water), as follows:The isotopic composition of any sample can then be represented by one point on a "three-isotope plot," a graph of δ17O versus δ18O. It will be seen that such plots are invaluable in interpreting meteoritic data. Figure 1 shows schematically the effect of various processes on an initial composition at the center of the diagram. Almost all terrestrial materials lie along a "fractionation" trend; most meteoritic materials lie near a line of "16O addition" (or subtraction). (4K)Figure 1. Schematic representation of various isotopic processes shown on an oxygen three-isotope plot. Almost all terrestrial materials plot along a line of "fractionation"; most primitive meteoritic materials plot near a line of "16O addition." The three isotopes of oxygen are produced by nucleosynthesis in stars, but by different nuclear processes in different stellar environments. The principal isotope, 16O, is a primary isotope (capable of being produced from hydrogen and helium alone), formed in massive stars (>10 solar masses), and ejected by supernova explosions. The two rare isotopes are secondary nuclei (produced in stars from nuclei formed in an earlier generation of stars), with 17O coming primarily from low- and intermediate-mass stars (<8 solar masses), and 18O coming primarily from high-mass stars (Prantzos et al., 1996). These differences in type of stellar source result in large observable variations in stellar isotopic abundances as functions of age, size, metallicity, and galactic location ( Prantzos

  13. The isotopic distribution conundrum.

    PubMed

    Valkenborg, Dirk; Mertens, Inge; Lemière, Filip; Witters, Erwin; Burzykowski, Tomasz

    2012-01-01

    Although access to high-resolution mass spectrometry (MS), especially in the field of biomolecular MS, is becoming readily available due to recent advances in MS technology, the accompanied information on isotopic distribution in high-resolution spectra is not used at its full potential, mainly because of lack of knowledge and/or awareness. In this review, we give an insight into the practical problems related to calculating the isotopic distribution for large biomolecules, and present an overview of methods for the calculation of the isotopic distribution. We discuss the key events that triggered the development of various algorithms and explain the rationale of how and why the various isotopic-distribution calculations were performed. The review is focused around the developmental stages as briefly outlined below, starting with the first observation of an isotopic distribution. The observations of Beynon in the field of organic MS that chlorine appeared in a mass spectrum as two variants with odds 3:1 lie at the basis of the first wave of algorithms for the calculation of the isotopic distribution, based on the atomic composition of a molecule. From here on, we explain why more complex biomolecules such as peptides exhibit a highly complex isotope pattern when assayed by MS, and we discuss how combinatorial difficulties complicate the calculation of the isotopic distribution on computers. For this purpose, we highlight three methods, which were introduced in the 1980s. These are the stepwise procedure introduced by Kubinyi, the polynomial expansion from Brownawell and Fillippo, and the multinomial expansion from Yergey. The next development was instigated by Rockwood, who suggested to decompose the isotopic distribution in terms of their nucleon count instead of the exact mass. In this respect, we could claim that the term "aggregated" isotopic distribution is more appropriate. Due to the simplification of the isotopic distribution to its aggregated counterpart

  14. Physicochemical isotope anomalies

    SciTech Connect

    Esat, T.M.

    1988-06-01

    Isotopic composition of refractory elements can be modified, by physical processes such as distillation and sputtering, in unexpected patterns. Distillation enriches the heavy isotopes in the residue and the light isotopes in the vapor. However, current models appear to be inadequate to describe the detailed mass dependence, in particular for large fractionations. Coarse- and fine-grained inclusions from the Allende meteorite exhibit correlated isotope effects in Mg both as mass-dependent fractionation and residual anomalies. This isotope pattern can be duplicated by high temperature distillation in the laboratory. A ubiquitous property of meteoritic inclusions for Mg as well as for most of the other elements, where measurements exist, is mass-dependent fractionation. In contrast, terrestrial materials such as microtektites, tektite buttons as well as lunar orange and green glass spheres have normal Mg isotopic composition. A subset of interplanetary dust particles labelled as chondritic aggregates exhibit excesses in {sup 26}Mg and deuterium anomalies. Sputtering is expected to be a dominant mechanism in the destruction of grains within interstellar dust clouds. An active proto-sun as well as the present solar-wind and solar-flare flux are of sufficient intensity to sputter significant amounts of material. Laboratory experiments in Mg show widespread isotope effects including residual {sup 26}Mg excesses and mass dependent fractionation. It is possible that the {sup 26}Mg excesses in interplanetary dust is related to sputtering by energetic solar-wind particles. The implication if the laboratory distillation and sputtering effects are discussed and contrasted with the anomalies in meteoritic inclusions the other extraterrestrial materials the authors have access to.

  15. Isotopic geochemistry and cosmochemistry

    NASA Astrophysics Data System (ADS)

    Shchukoliukov, Iu. A.

    The book includes recent information on isotope geology, geochemistry, and cosmochemistry, discussed at a recent Soviet-Japanese symposium (at Irkutsk, USSR). Attention is given to numerical modeling of geochronometric systems, a classification of noble-gas components in the earth's interior, the feasibility of using ion microprobe for local isotope analysis of zircons for the purpose of deriving the early history of the earth (on the example of the Novopavlovsk complex from the Ukranian shield), a geological and geochronological study of the Ganalski complex of Kamchatka, and strontium isotopes as a criterion of the nature of acid melts (i.e., mantle- or crust-related). Other papers are on the geochronology and geology of Siberian kimberlites, the nature of sulfur from effusive rocks of the Kamchatka-Kuril-Japan island arc, mass-spectrometric studies of volatile components in exocontact rocks of alkaline-basic intrusions, and an analytical method for stable-isotope analysis in ultrasmall amounts of CO2 and its application to studies of the microscale isotopic zoning in calcite and graphite crystals in marble.

  16. Separation of sulfur isotopes

    DOEpatents

    DeWitt, Robert; Jepson, Bernhart E.; Schwind, Roger A.

    1976-06-22

    Sulfur isotopes are continuously separated and enriched using a closed loop reflux system wherein sulfur dioxide (SO.sub.2) is reacted with sodium hydroxide (NaOH) or the like to form sodium hydrogen sulfite (NaHSO.sub.3). Heavier sulfur isotopes are preferentially attracted to the NaHSO.sub.3, and subsequently reacted with sulfuric acid (H.sub.2 SO.sub.4) forming sodium hydrogen sulfate (NaHSO.sub.4) and SO.sub.2 gas which contains increased concentrations of the heavier sulfur isotopes. This heavy isotope enriched SO.sub.2 gas is subsequently separated and the NaHSO.sub.4 is reacted with NaOH to form sodium sulfate (Na.sub.2 SO.sub.4) which is subsequently decomposed in an electrodialysis unit to form the NaOH and H.sub.2 SO.sub.4 components which are used in the aforesaid reactions thereby effecting sulfur isotope separation and enrichment without objectionable loss of feed materials.

  17. Transportation of medical isotopes

    SciTech Connect

    Nielsen, D.L.

    1997-11-19

    A Draft Technical Information Document (HNF-1855) is being prepared to evaluate proposed interim tritium and medical isotope production at the Fast Flux Test Facility (FFTF). This assessment examines the potential health and safety impacts of transportation operations associated with the production of medical isotopes. Incident-free and accidental impacts are assessed using bounding source terms for the shipment of nonradiological target materials to the Hanford Site, the shipment of irradiated targets from the FFTF to the 325 Building, and the shipment of medical isotope products from the 325 Building to medical distributors. The health and safety consequences to workers and the public from the incident-free transportation of targets and isotope products would be within acceptable levels. For transportation accidents, risks to works and the public also would be within acceptable levels. This assessment is based on best information available at this time. As the medical isotope program matures, this analysis will be revised, if necessary, to support development of a final revision to the Technical Information Document.

  18. Isotope separation apparatus

    DOEpatents

    Arnush, Donald; MacKenzie, Kenneth R.; Wuerker, Ralph F.

    1980-01-01

    Isotope separation apparatus consisting of a plurality of cells disposed adjacent to each other in an evacuated container. A common magnetic field is established extending through all of the cells. A source of energetic electrons at one end of the container generates electrons which pass through the cells along the magnetic field lines. Each cell includes an array of collector plates arranged in parallel or in tandem within a common magnetic field. Sets of collector plates are disposed adjacent to each other in each cell. Means are provided for differentially energizing ions of a desired isotope by applying energy at the cyclotron resonant frequency of the desired isotope. As a result, the energized desired ions are preferentially collected by the collector plates.

  19. Atomic Weights and Isotopic Compositions

    National Institute of Standards and Technology Data Gateway

    SRD 144 Atomic Weights and Isotopic Compositions (Web, free access)   The atomic weights are available for elements 1 through 111, and isotopic compositions or abundances are given when appropriate.

  20. Nonbiological fractionation of iron isotopes

    NASA Technical Reports Server (NTRS)

    Anbar, A. D.; Roe, J. E.; Barling, J.; Nealson, K. H.

    2000-01-01

    Laboratory experiments demonstrate that iron isotopes can be chemically fractionated in the absence of biology. Isotopic variations comparable to those seen during microbially mediated reduction of ferrihydrite are observed. Fractionation may occur in aqueous solution during equilibration between inorganic iron complexes. These findings provide insight into the mechanisms of iron isotope fractionation and suggest that nonbiological processes may contribute to iron isotope variations observed in sediments.

  1. DEEP WATER ISOTOPIC CURRENT ANALYZER

    DOEpatents

    Johnston, W.H.

    1964-04-21

    A deepwater isotopic current analyzer, which employs radioactive isotopes for measurement of ocean currents at various levels beneath the sea, is described. The apparatus, which can determine the direction and velocity of liquid currents, comprises a shaft having a plurality of radiation detectors extending equidistant radially therefrom, means for releasing radioactive isotopes from the shaft, and means for determining the time required for the isotope to reach a particular detector. (AEC)

  2. Method for separating boron isotopes

    DOEpatents

    Rockwood, Stephen D.

    1978-01-01

    A method of separating boron isotopes .sup.10 B and .sup.11 B by laser-induced selective excitation and photodissociation of BCl.sub.3 molecules containing a particular boron isotope. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BCl.sub.3, thus effecting the desired separation of the boron isotopes.

  3. Uranium Isotopic Analysis with the FRAM Isotopic Analysis Code

    SciTech Connect

    Duc T. Vo; Thomas E. Sampson

    1999-05-01

    FRAM is the acronym for Fixed-energy Response-function Analysis with Multiple efficiency. This software was developed at Los Alamos National Laboratory originally for plutonium isotopic analysis. Later, it was adapted for uranium isotopic analysis in addition to plutonium. It is a code based on a self-calibration using several gamma-ray peaks for determining the isotopic ratios. The versatile-parameter database structure governs all facets of the data analysis. User editing of the parameter sets allows great flexibility in handling data with different isotopic distributions, interfering isotopes, and different acquisition parameters such as energy calibration and detector type.

  4. Forensic Stable Isotope Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Cerling, Thure E.; Barnette, Janet E.; Bowen, Gabriel J.; Chesson, Lesley A.; Ehleringer, James R.; Remien, Christopher H.; Shea, Patrick; Tipple, Brett J.; West, Jason B.

    2016-06-01

    Stable isotopes are being used for forensic science studies, with applications to both natural and manufactured products. In this review we discuss how scientific evidence can be used in the legal context and where the scientific progress of hypothesis revisions can be in tension with the legal expectations of widely used methods for measurements. Although this review is written in the context of US law, many of the considerations of scientific reproducibility and acceptance of relevant scientific data span other legal systems that might apply different legal principles and therefore reach different conclusions. Stable isotopes are used in legal situations for comparing samples for authenticity or evidentiary considerations, in understanding trade patterns of illegal materials, and in understanding the origins of unknown decedents. Isotope evidence is particularly useful when considered in the broad framework of physiochemical processes and in recognizing regional to global patterns found in many materials, including foods and food products, drugs, and humans. Stable isotopes considered in the larger spatial context add an important dimension to forensic science.

  5. Carbon Isotope Ratiometer

    SciTech Connect

    Dr. Anthony O'Keefe

    2001-05-07

    This Report details the design of a optical analyzer capable of measuring and recording the carbon 13/12 isotope ratio in atmospheric carbon dioxide. The system can operate in remote modes for long duration and will transmit real-time data via wireless contact.

  6. Sulfur isotopic data

    SciTech Connect

    Rye, R.O.

    1987-01-01

    Preliminary sulfur isotope data have been determined for samples of the Vermillion Creek coal bed and associated rocks in the Vermillion Creek basin and for samples of evaporites collected from Jurassic and Triassic formations that crop out in the nearby Uinta Mountains. The data are inconclusive, but it is likely that the sulfur in the coal was derived from the evaporites.

  7. Water isotopes in desiccating lichens

    PubMed Central

    Cuntz, Matthias; Máguas, Cristina; Lakatos, Michael

    2009-01-01

    The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition. PMID:19888598

  8. Water isotopes in desiccating lichens.

    PubMed

    Hartard, Britta; Cuntz, Matthias; Máguas, Cristina; Lakatos, Michael

    2009-12-01

    The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition. PMID:19888598

  9. Iron isotope biosignatures

    NASA Technical Reports Server (NTRS)

    Beard, B. L.; Johnson, C. M.; Cox, L.; Sun, H.; Nealson, K. H.; Aguilar, C.

    1999-01-01

    The (56)Fe/(54)Fe of Fe-bearing phases precipitated in sedimentary environments varies by 2.5 per mil (delta(56)Fe values of +0.9 to -1. 6 per mil). In contrast, the (56)Fe/(54)Fe of Fe-bearing phases in igneous rocks from Earth and the moon does not vary measurably (delta(56)Fe = 0.0 +/- 0.3 per mil). Experiments with dissimilatory Fe-reducing bacteria of the genus Shewanella algae grown on a ferrihydrite substrate indicate that the delta(56)Fe of ferrous Fe in solution is isotopically lighter than the ferrihydrite substrate by 1.3 per mil. Therefore, the range in delta(56)Fe values of sedimentary rocks may reflect biogenic fractionation, and the isotopic composition of Fe may be used to trace the distribution of microorganisms in modern and ancient Earth.

  10. Selenium isotope analysis

    SciTech Connect

    Webster, C.L. Jr.; Warren, C.G.

    1981-01-01

    The isotope ratio of selenium-80 to selenium-74 was determined on an isotope ratio mass spectrometer. Samples of 2 to 4 mg of selenium were fluorinated with CoF/sub 3/ in a small disposable copper bomb. The product, SeF/sub 6/, was purified in a vacuum line by distillation. The /sup 80/Se//sup 74/Se ratio was determined on a double-collector mass spectrometer that was modified to collect either /sup 82/Se-/sup 80/Se or /sup 80/Se-/sup 74/Se ion pairs. The standard deviation of the difference between two individually fluorinated samples was about 1 per mil. Because essentially all the error was associated with the fluorination step, comparisons between a standard of SeF/sub 6/ and individually fluorinated samples can be expected to have a standard deviation of about 0.5 per mil.

  11. New Isotope 263Hs

    SciTech Connect

    Dragojevic, I.; Gregorich, K.E.; Dullmann, Ch.E.; Dvorak, J.; Ellison, P.A.; Gates, J.M.; Nelson, S.L.; Stavsetra, L.; Nitsche, H.

    2010-03-16

    A new isotope of Hs was produced in the reaction 208Pb(56Fe, n)263Hs at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. Six genetically correlated nuclear decay chains have been observed and assigned to the new isotope 263Hs. The measured cross section was 21+13-8.4 pb at 276.4 MeV lab-frame center-of-target beam energy. 263Hs decays with a half-life of 0.74 ms by alpha-decay and the measured alpha-particle energies are 10.57 +- 0.06, 10.72 +- 0.06, and 10.89 +- 0.06 MeV. The experimental cross section is compared to a theoretical prediction based on the Fusion by Diffusion model [W. J. Swiatecki et al., Phys. Rev. C 71, 014602 (2005)].

  12. Isotope shift in chromium

    NASA Astrophysics Data System (ADS)

    Furmann, B.; Jarosz, A.; Stefańska, D.; Dembczyński, J.; Stachowska, E.

    2005-01-01

    Thirty-three spectral lines of chromium atom in the blue-violet region (425-465 nm) have been investigated with the method of laser-induced resonance fluorescence on an atomic beam. For all the lines, the isotope shifts for every pair of chromium isotopes have been determined. The lines can be divided into six groups, according to the configuration of the upper and lower levels. Electronic factors of the field shift and the specific mass shift ( Fik and MikSMS, respectively) have been evaluated and the values for each pure configuration involved have been determined. Comparison of the values Fik and MikSMS to the ab initio calculations results has been performed. The presence of crossed second order (CSO) effects has been observed.

  13. Stable isotope laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Becker, J. F.; Yaldaei, Ramil; Mckay, Christopher P.

    1989-01-01

    Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.

  14. Stable isotope laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Becker, J. F.; Yaldaei, Ramil; McKay, Christopher P.

    1989-03-01

    Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.

  15. ISOTOPE SEPARATING APPARATUS CONTROL

    DOEpatents

    Barnes, S.W.

    1959-08-25

    An improved isotope separating apparatus of the electromagnetic type, commonly referred to as a calutron, is described. Improvements in detecting and maintaining optimum position and focus of the ion beam are given. The calutron collector is provided with an additional electrode insulated from and positioned between the collecting pockets. The ion beams are properly positioned and focused until the deionizing current which flows from ground to this additional electrode ts a minimum.

  16. ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

    SciTech Connect

    BULLOCK,R.M.; BENDER,B.R.

    2000-12-01

    The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.

  17. Electrochemically controlled iron isotope fractionation

    NASA Astrophysics Data System (ADS)

    Black, Jay R.; Young, Edward D.; Kavner, Abby

    2010-02-01

    Variations in the stable isotope abundances of transition metals have been observed in the geologic record and trying to understand and reconstruct the physical/environmental conditions that produced these signatures is an area of active research. It is clear that changes in oxidation state lead to large fractionations of the stable isotopes of many transition metals such as iron, suggesting that transition metal stable isotope signatures could be used as a paleo-redox proxy. However, the factors contributing to these observed stable isotope variations are poorly understood. Here we investigate how the kinetics of iron redox electrochemistry generates isotope fractionation. Through a combination of electrodeposition experiments and modeling of electrochemical processes including mass-transport, we show that electron transfer reactions are the cause of a large isotope separation, while mass transport-limited supply of reactant to the electrode attenuates the observed isotopic fractionation. Furthermore, the stable isotope composition of electroplated transition metals can be tuned in the laboratory by controlling parameters such as solution chemistry, reaction overpotential, and solution convection. These methods are potentially useful for generating isotopically-marked metal surfaces for tracking and forensic purposes. In addition, our studies will help interpret stable isotope data in terms of identifying underlying electron transfer processes in laboratory and natural samples.

  18. Laser isotope separation of erbium and other isotopes

    DOEpatents

    Haynam, C.A.; Worden, E.F.

    1995-08-22

    Laser isotope separation is accomplished using at least two photoionization pathways of an isotope simultaneously, where each pathway comprises two or more transition steps. This separation method has been applied to the selective photoionization of erbium isotopes, particularly for the enrichment of {sup 167}Er. The hyperfine structure of {sup 167}Er was used to find two three-step photoionization pathways having a common upper energy level. 3 figs.

  19. Laser isotope separation of erbium and other isotopes

    DOEpatents

    Haynam, Christopher A.; Worden, Earl F.

    1995-01-01

    Laser isotope separation is accomplished using at least two photoionization pathways of an isotope simultaneously, where each pathway comprises two or more transition steps. This separation method has been applied to the selective photoionization of erbium isotopes, particularly for the enrichment of .sup.167 Er. The hyperfine structure of .sup.167 Er was used to find two three-step photoionization pathways having a common upper energy level.

  20. Oxygen isotope studies and compilation of isotopic dates from Antarctica

    SciTech Connect

    Grootes, P.M.; Stuiver, M.

    1986-01-01

    The Quaternary Isotope Laboratory, alone or in collaboration with other investigators, is currently involved in a number of oxygen-isotope studies mainly in Antarctica. Studies of a drill core from the South Pole, seasonal oxygen-18 signals preserved in the Dominion Range, isotope dating of the Ross Ice Shelf, oxygen-18 profiles of the Siple Coast, McMurdo Ice Shelf sampling, and a data compilation of radiometric dates from Antarctica are discussed.

  1. Nickel isotopes and methanogens

    NASA Astrophysics Data System (ADS)

    Neubeck, A.; Ivarsson, M.

    2013-12-01

    Methanogens require Ni for their growth and as a consequence the microbial fractionation of Ni isotopes can be used as a biomarker for activity of methanogenic communities1. Anaerobic laboratory experiments was performed using methanogens to investigate methanogenic growth in a modified nutrient media2 with olivine Fo91 (5g/l) added as an additional mineral nutrient source and as the only H2 provider. One of the investigated methanogens showed an increased growth in the experiments with added olivine. There were also a close relationship between the mobilized Ni and the growth of the methanogen. Ni is an element that previously has been neglected in the study of fossilized microorganisms and their interaction with mineral substrates and, thus, there are no records or published data of Ni in association with microfossils. However, we have detected enrichments of Ni in fossilized microorganisms and ichno-fossils, respectively, from three separate locations. Ni is not present in the host rock in any of the samples. Thus, Ni is present in association with fossilized microorganisms from environments and more extensive analysis is required to understand the magnitude, uptake, preservation and fractionation of Ni in microfossils. In order to analyze Ni isotope fractionation from microbe-mineral interaction, we plan to use a high-resolution Laser-Ablation Time-of-Flight Mass Spectrometer (LMS)3. In situ profile ablation will provide detailed and localized data on fractionation patterns between microfossils and their host rock. Also, this technique will allow us to identify the change in Ni isotopic fractionation in rock samples caused by abiotic and biogenic processes in a faster and easier way and with less risk for contamination compared to the wet chemistry analyses of Ni isotopes. 1. Cameron, V., Vance, D., Archer, C. & House, C. H. A biomarker based on the stable isotopes of nickel. Proceedings of the National Academy of Sciences 106, 10944-10948 (2009). 2. Schn

  2. Laser Ablation Molecular Isotopic Spectrometry

    NASA Astrophysics Data System (ADS)

    Russo, Richard E.; Bol'shakov, Alexander A.; Mao, Xianglei; McKay, Christopher P.; Perry, Dale L.; Sorkhabi, Osman

    2011-02-01

    A new method of performing optical isotopic analysis of condensed samples in ambient air and at ambient pressure has been developed: Laser Ablation Molecular Isotopic Spectrometry (LAMIS). The technique uses radiative transitions from molecular species either directly vaporized from a sample or formed by associative mechanisms of atoms or ions in a laser ablation plume. This method is an advanced modification of a known atomic emission technique called laser-induced breakdown spectroscopy (LIBS). The new method — LAMIS — can determine not only chemical composition but also isotopic ratios of elements in the sample. Isotopic measurements are enabled by significantly larger isotopic shifts found in molecular spectra relative to atomic spectra. Analysis can be performed from a distance and in real time. No sample preparation or pre-treatment is required. Detection of the isotopes of hydrogen, boron, carbon, and oxygen are discussed to illustrate the technique.

  3. Isotopic anomalies in extraterrestrial grains.

    PubMed

    Ireland, T R

    1996-03-01

    Isotopic compositions are referred to as anomalous if the isotopic ratios measured cannot be related to the terrestrial (solar) composition of a given element. While small effects close to the resolution of mass spectrometric techniques can have ambiguous origins, the discovery of large isotopic anomalies in inclusions and grains from primitive meteorites suggests that material from distinct sites of stellar nucleosynthesis has been preserved. Refractory inclusions, which are predominantly composed of the refractory oxides of Al, Ca, Ti, and Mg, in chondritic meteorites commonly have excesses in the heaviest isotopes of Ca, Ti, and Cr which are inferred to have been produced in a supernova. Refractory inclusions also contain excess 26Mg from short lived 26Al decay. However, despite the isotopic anomalies indicating the preservation of distinct nucleosynthetic sites, refractory inclusions have been processed in the solar system and are not interstellar grains. Carbon (graphite and diamond) and silicon carbide grains from the same meteorites also have large isotopic anomalies but these phases are not stable in the oxidized solar nebula which suggests that they are presolar and formed in the circumstellar atmospheres of carbon-rich stars. Diamond has a characteristic signature enriched in the lightest and heaviest isotopes of Xe, and graphite shows a wide range in C isotopic compositions. SiC commonly has C and N isotopic signatures which are characteristic of H-burning in the C-N-O cycle in low-mass stars. Heavier elements such as Si, Ti, Xe, Ba, and Nd, carry an isotopic signature of the s-process. A minor population of SiC (known as Grains X, ca. 1%) are distinct in having decay products of short lived isotopes 26Al (now 26Mg), 44Ti (now 44Ca), and 49V (now 49Ti), as well as 28Si excesses which are characteristic of supernova nucleosynthesis. The preservation of these isotopic anomalies allows the examination of detailed nucleosynthetic pathways in stars. PMID

  4. ISOTOPE FRACTIONATION PROCESS

    DOEpatents

    Clewett, G.H.; Lee, DeW.A.

    1958-05-20

    A new method is described for isotopic enrichment of uranium. It has been found that when an aqueous acidic solution of ionic tetravalent uraniunn is contacted with chelate complexed tetravalent uranium, the U/sup 238/ preferentially concentrates in the complexed phase while U/sup 235/ concentrates in the ionic phase. The effect is enhanced when the chelate compound is water insoluble and is dissolved in a water-immiscible organic solvent. Cupferron is one of a number of sultable complexing agents, and chloroform is a suitable organic solvent.

  5. Tank waste isotope contributions

    SciTech Connect

    VANKEUREN, J.C.

    1999-08-26

    This document presents the results of a calculation to determine the relative contribution of selected isotopes to the inhalation and ingestion doses for a postulated release of Hanford tank waste. The fraction of the dose due to {sup 90}Sr, {sup 90}Y, {sup 137}Cs and the alpha emitters for single shell solids and liquids, double shell solids and liquids, aging waste solids and liquids and all solids and liquids. An effective dose conversion factor was also calculated for the alpha emitters for each composite of the tank waste.

  6. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, F.T.

    Intermetallic compounds with the CaCu/sub 5/ type of crystal structure, particularly LaNiCo/sub 4/ and CaNi/sub 5/, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen cn produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  7. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, Frederick T.

    1981-01-01

    Intermetallic compounds with the CaCu.sub.5 type of crystal structure, particularly LaNiCo.sub.4 and CaNi.sub.5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  8. Quantitative Determination of Isotope Ratios from Experimental Isotopic Distributions

    PubMed Central

    Kaur, Parminder; O’Connor, Peter B.

    2008-01-01

    Isotope variability due to natural processes provides important information for studying a variety of complex natural phenomena from the origins of a particular sample to the traces of biochemical reaction mechanisms. These measurements require high-precision determination of isotope ratios of a particular element involved. Isotope Ratio Mass Spectrometers (IRMS) are widely employed tools for such a high-precision analysis, which have some limitations. This work aims at overcoming the limitations inherent to IRMS by estimating the elemental isotopic abundance from the experimental isotopic distribution. In particular, a computational method has been derived which allows the calculation of 13C/12C ratios from the whole isotopic distributions, given certain caveats, and these calculations are applied to several cases to demonstrate their utility. The limitations of the method in terms of the required number of ions and S/N ratio are discussed. For high-precision estimates of the isotope ratios, this method requires very precise measurement of the experimental isotopic distribution abundances, free from any artifacts introduced by noise, sample heterogeneity, or other experimental sources. PMID:17263354

  9. Mass-independent isotope effects.

    PubMed

    Buchachenko, Anatoly L

    2013-02-28

    Three fundamental properties of atomic nuclei-mass, spin (and related magnetic moment), and volume-are the source of isotope effects. The mostly deserved and popular, with almost hundred-year history, is the mass-dependent isotope effect. The first mass-independent isotope effect which chemically discriminates isotopes by their nuclear spins and nuclear magnetic moments rather than by their masses was detected in 1976. It was named as the magnetic isotope effect because it is controlled by magnetic interaction, i.e., electron-nuclear hyperfine coupling in the paramagnetic species, the reaction intermediates. The effect follows from the universal physical property of chemical reactions to conserve angular momentum (spin) of electrons and nuclei. It is now detected for oxygen, silicon, sulfur, germanium, tin, mercury, magnesium, calcium, zinc, and uranium in a great variety of chemical and biochemical reactions including those of medical and ecological importance. Another mass-independent isotope effect was detected in 1983 as a deviation of isotopic distribution in reaction products from that which would be expected from the mass-dependent isotope effect. On the physical basis, it is in fact a mass-dependent effect, but it surprisingly results in isotope fractionation which is incompatible with that predicted by traditional mass-dependent effects. It is supposed to be a function of dynamic parameters of reaction and energy relaxation in excited states of products. The third, nuclear volume mass-independent isotope effect is detected in the high-resolution atomic and molecular spectra and in the extraction processes, but there are no unambiguous indications of its importance as an isotope fractionation factor in chemical reactions. PMID:23301791

  10. ENVIRONMENTAL ISOTOPES FOR RESOLUTION OF HYDROLOGY PROBLEMS

    EPA Science Inventory

    The use of environmental isotopes as tracers in the hydrosphere is increasing as analytical instrumentation improves and more applications are discovered. There exists still misconceptions on the role of isotopes in resolving hydrology problems. Naturally occurring isotopes in th...

  11. Si Isotopes of Brownleeite

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Messenger, Scott R.; Ito, M.; Keller, L. P.; Clemett, S. J.; Jones, J. H.; Tatsuoka, H.; Zolensky, M. E.; Tatsuoka, H.

    2010-01-01

    Brownleeite is a manganese silicide, ideally stoichiometric MnSi, not previously observed in nature until its discovery within an interplanetary dust particle (IDP) that likely originated from a comet [1]. Three discrete brownleeite grains in the IDP L2055 I3 (4 microns in size, hereafter IDP I3) were identified with maximum dimensions of 100, 250 and 600 nm and fully analyzed using scanning-transmission electron microscopy (STEM) [1]. One of the grains (100 nm in size) was poikilitically enclosed by low-Fe, Mn-enriched (LIME) olivine. LIME olivine is epitaxial to the brownleeite with the brownleeite (200) parallel to the olivine c* [1]. LIME olivine is an enigmatic phase first reported from chondritic porous IDPs and some unequilibrated ordinary chondrites [ 2], that is commonly observed in chondritic-porous IDPs. Recently, LIME olivine has been also found in comet Wild-2 (Stardust) samples [3], indicating that LIME olivine is a common mineral component of comets. LIME olivine has been proposed to form as a high temperature condensate in the protosolar nebula [2]. Brownleeite grains also likely formed as high-temperature condensates either in the early Solar System or in the outflow of an evolved star or supernova explosion [1]. The isotopic composition of the brownleeite grains may strongly constrain their ultimate source. To test this hypothesis, we performed isotopic analyses of the brownleeite and the associated LIME olivine, using the NASA/JSC NanoSIMS 50L ion microprobe.

  12. Phonon coherence in isotopic silicon superlattices

    SciTech Connect

    Frieling, R.; Radek, M.; Eon, S.; Bracht, H.; Wolf, D. E.

    2014-09-29

    Recent experimental and theoretical investigations have confirmed that a reduction in thermal conductivity of silicon is achieved by isotopic silicon superlattices. In the present study, non-equilibrium molecular dynamics simulations are performed to identify the isotope doping and isotope layer ordering with minimum thermal conductivity. Furthermore, the impact of isotopic intermixing at the superlattice interfaces on phonon transport is investigated. Our results reveal that the coherence of phonons in isotopic Si superlattices is prevented if interfacial mixing of isotopes is considered.

  13. Calcium isotopes in wine

    NASA Astrophysics Data System (ADS)

    Holmden, C. E.

    2011-12-01

    The δ 44/40Ca values of bottled wine vary between -0.76% to -1.55% on the seawater scale and correlate weakly with inverse Ca concentration and Mg/Ca ratio, such that the lowest δ 44/40Ca values have the highest Ca concentrations and lowest Mg/Ca ratios. The correlation is notable in the sense that the measured wines include both whites and reds sampled from different wine growing regions of the world, and cover a wide range of quality. Trends among the data yield clues regarding the cause of the observed isotopic fractionation. White wines, and wines generally perceived to be of lower quality, have lower δ 44/40Ca values compared to red wines and wines of generally perceived higher quality. Quality was assessed qualitatively through sensory evaluation, price, and scores assigned by critics. The relationship between δ 44/40Ca and wine quality was most apparent when comparing wines of one varietal from one producer from the same growing region. In the vineyard, wine quality is related to factors such as the tonnage of the crop and the ripeness of the grapes at the time of harvesting, the thickness of the skins for reds, the age of the vines, as well as the place where the grapes were grown (terroir). Quality is also influenced by winemaking practices such as fermentation temperature, duration of skin contact, and barrel ageing. Accordingly, the relationship between δ 44/40Ca and wine quality may originate during grape ripening in the vineyard or during winemaking in the cellar. We tested the grape ripening hypothesis using Merlot grapes sampled from a vineyard in the Okanagan, British Columbia, using sugar content (degrees Brix) as an indicator of ripeness. The grapes were separated into pulp, skin, and pip fractions and were analyzed separately. Thus far, there is no clear evidence for a systematic change in δ 44/40Ca values associated with progressive ripening of grapes in the vineyard. On the day of harvesting, the δ 44/40Ca value of juice squeezed from

  14. Aleutian terranes from Nd isotopes

    NASA Technical Reports Server (NTRS)

    Kay, R. W.; Kay, S. M.; Rubenstone, J. L.

    1986-01-01

    Nd isotope ratios substantiate the identification of oceanic crustal terranes within the continental crustal basement of the Aleutian island arc. The oceanic terranes are exposed in the westernmost Aleutians, but to the east, they are completely buried by isotopically distinct arc-volcanic rocks. Analogous oceanic terranes may be important components of the terrane collages that comprise the continents.

  15. The straight dope on isotopes

    NASA Astrophysics Data System (ADS)

    Thornton, Brett F.; Burdette, Shawn C.

    2013-12-01

    A century ago this month, Frederick Soddy described and named isotopes in the pages of Nature. Brett F. Thornton and Shawn C. Burdette discuss how chemists have viewed and used isotopes since then -- either as chemically identical or chemically distinct species as the need required and technology allowed.

  16. Method of separating boron isotopes

    DOEpatents

    Jensen, R.J.; Thorne, J.M.; Cluff, C.L.

    1981-01-23

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)-dichloroborane as the feed material. The photolysis can readily by achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

  17. Method of separating boron isotopes

    DOEpatents

    Jensen, Reed J.; Thorne, James M.; Cluff, Coran L.; Hayes, John K.

    1984-01-01

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO.sub.2 laser radiation and using fluences significantly below those required to dissociate BCl.sub.3.

  18. Isotope separation by laser means

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

    1982-06-15

    A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

  19. Correlated optical and isotopic nanoscopy

    NASA Astrophysics Data System (ADS)

    Saka, Sinem K.; Vogts, Angela; Kröhnert, Katharina; Hillion, François; Rizzoli, Silvio O.; Wessels, Johannes T.

    2014-04-01

    The isotopic composition of different materials can be imaged by secondary ion mass spectrometry. In biology, this method is mainly used to study cellular metabolism and turnover, by pulsing the cells with marker molecules such as amino acids labelled with stable isotopes (15N, 13C). The incorporation of the markers is then imaged with a lateral resolution that can surpass 100 nm. However, secondary ion mass spectrometry cannot identify specific subcellular structures like organelles, and needs to be correlated with a second technique, such as fluorescence imaging. Here, we present a method based on stimulated emission depletion microscopy that provides correlated optical and isotopic nanoscopy (COIN) images. We use this approach to study the protein turnover in different organelles from cultured hippocampal neurons. Correlated optical and isotopic nanoscopy can be applied to a variety of biological samples, and should therefore enable the investigation of the isotopic composition of many organelles and subcellular structures.

  20. Container for hydrogen isotopes

    DOEpatents

    Solomon, David E.

    1977-01-01

    A container for the storage, shipping and dispensing of hydrogen isotopes such as hydrogen, deuterium, tritium, or mixtures of the same which has compactness, which is safe against fracture or accident, and which is reusable. The container consists of an outer housing with suitable inlet and outlet openings and electrical feed elements, the housing containing an activated sorber material in the form, for example, of titanium sponge or an activated zirconium aluminate cartridge. The gas to be stored is introduced into the chamber under conditions of heat and vacuum and will be retained in the sorber material. Subsequently, it may be released by heating the unit to drive off the stored gas at desired rates.

  1. Cometary Isotopic Measurements

    NASA Astrophysics Data System (ADS)

    Bockelée-Morvan, Dominique; Calmonte, Ursina; Charnley, Steven; Duprat, Jean; Engrand, Cécile; Gicquel, Adeline; Hässig, Myrtha; Jehin, Emmanuël; Kawakita, Hideyo; Marty, Bernard; Milam, Stefanie; Morse, Andrew; Rousselot, Philippe; Sheridan, Simon; Wirström, Eva

    2015-12-01

    Isotopic ratios in comets provide keys for the understanding of the origin of cometary material, and the physical and chemical conditions in the early Solar Nebula. We review here measurements acquired on the D/H, 14N/15N, 16O/18O, 12C/13C, and 32S/34S ratios in cometary grains and gases, and discuss their cosmogonic implications. The review includes analyses of potential cometary material available in collections on Earth, recent measurements achieved with the Herschel Space Observatory, large optical telescopes, and Rosetta, as well as recent results obtained from models of chemical-dynamical deuterium fractionation in the early solar nebula. Prospects for future measurements are presented.

  2. Microbes: Agents of Isotopic Change

    NASA Astrophysics Data System (ADS)

    Fogel, M. L.

    2012-12-01

    Microbes drive many of the important oxidation and reduction reactions on Earth; digest almost all forms of organic matter; and can serve as both primary and secondary producers. Because of their versatile biochemistry and physiology, they impart unique isotopic signatures to organic and inorganic materials, which have proven to be key measurements for understanding elemental cycling now and throughout Earth's history. Understanding microbial isotope fractionations in laboratory experiments has been important for interpreting isotopic patterns measured in natural settings. In fact, the pairing of simple experiment with natural observation has been the pathway for interpreting the fingerprint of microbial processes in ancient sediments and rocks. Examples of how key experiments have explained stable isotope fractionations by microbes and advanced the field of microbial ecology will be presented. Learning the isotopic signatures of Earth's microbes is a valuable exercise for predicting what isotopic signatures could be displayed by possible extant or extinct extraterrestrial life. Given the potential for discovery on Mars, Enceladus, and other solar system bodies, new methods and techniques for pinpointing what is unique about microbial isotope signatures is particularly relevant.

  3. Isotopic analysis of planetary solids

    NASA Astrophysics Data System (ADS)

    Tulej, M.; Riedo, A.; Neuland, M.; Meyer, S.; Wurz, P.

    2013-09-01

    Isotopic analysis of planetary surfaces is of considerable interest for planetology. Studies of isotope composition can deliver information on radio-isotope chronology of planetary soil/regolith, an insight to processes that altered planetary surface (space weathering) or on possible biogenic processes that occurred or still occur on the planet. Mass spectrometry is a well-suited method that delivers accurate and precise isotope composition. Among other instruments (LAZMA and LAMS), the miniature laser ablation/ionisation mass analyser, LMS developed in Bern for in situ space research can be used to measure the elemental and isotopic composition of planetary solids. LMS support mass spectrometric investigation with a mass resolution of m/Δm≈500-1500, dynamic range of at least 8 decades and detection sensitivity of ~10 ppb. Current studies of various solid materials and standard reference materials show that isotope composition can be conducted with an accuracy and precision at per mill level if the isotope concentration exceeds 10-100 ppm. Implications of the studies for in situ application are discussed.

  4. Compelling Research Opportunities using Isotopes

    SciTech Connect

    2009-04-23

    Isotopes are vital to the science and technology base of the US economy. Isotopes, both stable and radioactive, are essential tools in the growing science, technology, engineering, and health enterprises of the 21st century. The scientific discoveries and associated advances made as a result of the availability of isotopes today span widely from medicine to biology, physics, chemistry, and a broad range of applications in environmental and material sciences. Isotope issues have become crucial aspects of homeland security. Isotopes are utilized in new resource development, in energy from bio-fuels, petrochemical and nuclear fuels, in drug discovery, health care therapies and diagnostics, in nutrition, in agriculture, and in many other areas. The development and production of isotope products unavailable or difficult to get commercially have been most recently the responsibility of the Department of Energy's Nuclear Energy program. The President's FY09 Budget request proposed the transfer of the Isotope Production program to the Department of Energy's Office of Science in Nuclear Physics and to rename it the National Isotope Production and Application program (NIPA). The transfer has now taken place with the signing of the 2009 appropriations bill. In preparation for this, the Nuclear Science Advisory Committee (NSAC) was requested to establish a standing subcommittee, the NSAC Isotope Subcommittee (NSACI), to advise the DOE Office of Nuclear Physics. The request came in the form of two charges: one, on setting research priorities in the short term for the most compelling opportunities from the vast array of disciplines that develop and use isotopes and two, on making a long term strategic plan for the NIPA program. This is the final report to address charge 1. NSACI membership is comprised of experts from the diverse research communities, industry, production, and homeland security. NSACI discussed research opportunities divided into three areas: (1) medicine

  5. Neodymium isotopic variations in seawater

    NASA Technical Reports Server (NTRS)

    Piepgras, D. J.; Wasserburg, G. J.

    1980-01-01

    Direct measurement of the isotopic composition of Nd in the Atlantic agree with the Nd content in ferromanganese sediments and differ from the observed amounts in the Pacific samples. These data indicate the existence of distinctive differences in the isotopic composition of Nd in the waters of major oceans; the average values determined from seawater and ferromanganese sediments are considerably lower than in sources with oceanic mantle affinities showing that the REE in the oceans is dominated by continental sources. The Nd isotopic variations in seawater are applied to relate the residence time of Nd and mixing rates between the oceans.

  6. Nucleon pairing in Sn isotopes

    NASA Astrophysics Data System (ADS)

    Imasheva, L.; Ishkhanov, B.; Stepanov, M.; Tretyakova, T.

    2016-01-01

    The systematics of excited states in Sn isotopes are discussed on basis of pairing interaction in nuclei. Nucleon paring leads to formation of excited states multiplets. The estimation of multiplet splitting based on experimental nuclear masses allows one to calculate the position of excited states with different seniority in δ-approximation. The wide systematics of the spectra of Sn isotopes gives a possibility to check the pairing interaction for different subshells and consider the multiplets of excited states in the neutron-rich isotopes far from stability.

  7. Carbon isotope geochemistry and geobiology

    NASA Technical Reports Server (NTRS)

    Desmarais, D.

    1985-01-01

    Carbon isotope fractionation values were used to understand the history of the biosphere. For example, plankton analyses confirmed that marine extinctions at the end of the Cretaceous period were indeed severe (see Hsu's article in Sundquist and Broeker, 1984). Variations in the isotopic compositions of carbonates and evaporitic sulfates during the Paleozoic reflect the relative abundances of euxinic (anoxic) marine environments and organic deposits from terrestrial flora. The carbon isotopic composition of Precambrian sediments suggest that the enzyme ribulose bisphosphate carboxylase has existed for perhaps 3.5 billion years.

  8. Magnesium isotopic composition of achondrites

    NASA Astrophysics Data System (ADS)

    Sedaghatpour, Fatemeh; Teng, Fang-Zhen

    2016-02-01

    Magnesium isotopic compositions of 22 well-characterized differentiated meteorites including 7 types of achondrites and pallasite meteorites were measured to estimate the average Mg isotopic composition of their parent bodies and evaluate Mg isotopic heterogeneity of the solar system. The δ26Mg values are -0.236‰ and -0.190‰ for acapulcoite-lodranite and angrite meteorites, respectively and vary from -0.267‰ to -0.222‰ in the winonaite-IAB-iron silicate group, -0.369‰ to -0.292‰ in aubrites, -0.269‰ to -0.158‰ in HEDs, -0.299‰ to -0.209‰ in ureilites, -0.307‰ to -0.237‰ in mesosiderites, and -0.303‰ to -0.238‰ in pallasites. Magnesium isotopic compositions of most achondrites and pallasite meteorites analyzed here are similar and reveal no significant isotopic fractionation. However, Mg isotopic compositions of D‧Orbigny (angrite) and some HEDs are slightly heavier than chondrites and the other achondrites studied here. The slightly heavier Mg isotopic compositions of angrites and some HEDs most likely resulted from either impact-induced evaporation or higher abundance of clinopyroxene with the Mg isotopic composition slightly heavier than olivine and orthopyroxene. The average Mg isotopic composition of achondrites (δ26Mg = -0.246 ± 0.082‰, 2SD, n = 22) estimated here is indistinguishable from those of the Earth (δ26Mg = -0.25 ± 0.07‰; 2SD, n = 139), chondrites (δ26Mg = -0.28 ± 0.06‰; 2SD, n = 38), and the Moon (δ26Mg = -0.26 ± 0.16‰; 2SD, n = 47) reported from the same laboratory. The chondritic Mg isotopic composition of achondrites, the Moon, and the Earth further reflects homogeneity of Mg isotopes in the solar system and the lack of Mg isotope fractionation during the planetary accretion process and impact events.

  9. Method for laser induced isotope enrichment

    DOEpatents

    Pronko, Peter P.; Vanrompay, Paul A.; Zhang, Zhiyu

    2004-09-07

    Methods for separating isotopes or chemical species of an element and causing enrichment of a desired isotope or chemical species of an element utilizing laser ablation plasmas to modify or fabricate a material containing such isotopes or chemical species are provided. This invention may be used for a wide variety of materials which contain elements having different isotopes or chemical species.

  10. Isotope separation using metallic vapor lasers

    NASA Technical Reports Server (NTRS)

    Russell, G. R.; Chen, C. J.; Harstad, K. G. (Inventor)

    1977-01-01

    The isotope U235 is separated from a gasified isotope mixture of U235 and U238 by selectively exciting the former from the ground state utilizing resonant absorption of radiation from precisely tuned lasers. The excited isotope is then selectively ionized by electron bombardment. It then is separated from the remaining isotope mixture by electromagnetic separation.

  11. Apparatus and process for separating hydrogen isotopes

    DOEpatents

    Heung, Leung K; Sessions, Henry T; Xiao, Xin

    2013-06-25

    The apparatus and process for separating hydrogen isotopes is provided using dual columns, each column having an opposite hydrogen isotopic effect such that when a hydrogen isotope mixture feedstock is cycled between the two respective columns, two different hydrogen isotopes are separated from the feedstock.

  12. Raman scattering method and apparatus for measuring isotope ratios and isotopic abundances

    DOEpatents

    Harney, Robert C.; Bloom, Stewart D.

    1978-01-01

    Raman scattering is used to measure isotope ratios and/or isotopic abundances. A beam of quasi-monochromatic photons is directed onto the sample to be analyzed, and the resulting Raman-scattered photons are detected and counted for each isotopic species of interest. These photon counts are treated mathematically to yield the desired isotope ratios or isotopic abundances.

  13. Isotope dilution mass spectrometry

    NASA Astrophysics Data System (ADS)

    Heumann, Klaus G.

    1992-09-01

    In the past isotope dilution mass spectrometry (IDMS) has usually been applied using the formation of positive thermal ions of metals. Especially in calibrating other analytical methods and for the certification of standard reference materials this type of IDMS became a routine method. Today, the progress in this field lies in the determination of ultra trace amounts of elements, e.g. of heavy metals in Antarctic ice and in aerosols in remote areas down to the sub-pg g-1 and sub-pg m-3 levels respectively, in the analysis of uranium and thorium at concentrations of a few pg g-1 in sputter targets for the production of micro- electronic devices or in the determination of sub-picogram amounts of230Th in corals for geochemical age determinations and of226Ra in rock samples. During the last few years negative thermal ionization IDMS has become a frequently used method. The determination of very small amounts of selenium and technetium as well as of other transition metals such as vanadium, chromium, molybdenum and tungsten are important examples in this field. Also the measurement of silicon in connection with a re-determination of Avogadro's number and osmium analyses for geological age determinations by the Re/Os method are of special interest. Inductively-coupled plasma mass spectrometry is increasingly being used for multi-element analyses by the isotope dilution technique. Determinations of heavy metals in samples of marine origin are representative examples for this type of multi-element analysis by IDMS. Gas chromatography-mass spectrometry systems have also been successfully applied after chelation of metals (for example Pt determination in clinical samples) or for the determination of volatile element species in the environment, e.g. dimethyl sulfide. However, IDMS--specially at low concentration levels in the environment--seems likely to be one of the most powerful analytical methods for speciation in the future. This has been shown, up to now, for species of

  14. Isotopic Analysis and Evolved Gases

    NASA Technical Reports Server (NTRS)

    Swindle, Timothy D.; Boynton, William V.; Chutjian, Ara; Hoffman, John H.; Jordan, Jim L.; Kargel, Jeffrey S.; McEntire, Richard W.; Nyquist, Larry

    1996-01-01

    Precise measurements of the chemical, elemental, and isotopic composition of planetary surface material and gases, and observed variations in these compositions, can contribute significantly to our knowledge of the source(s), ages, and evolution of solar system materials. The analyses discussed in this paper are mostly made by mass spectrometers or some other type of mass analyzer, and address three broad areas of interest: (1) atmospheric composition - isotopic, elemental, and molecular, (2) gases evolved from solids, and (3) solids. Current isotopic data on nine elements, mostly from in situ analysis, but also from meteorites and telescopic observations are summarized. Potential instruments for isotopic analysis of lunar, Martian, Venusian, Mercury, and Pluto surfaces, along with asteroid, cometary and icy satellites, surfaces are discussed.

  15. Isotopic Changes During Digestion: Protein

    NASA Astrophysics Data System (ADS)

    Tuross, N.

    2013-12-01

    Nutrient and hydrological inputs traverse a complicated route of pH, enzymatic and cellular processes in digestion in higher animals. The end products of digestion are the starting products for biosynthesis that are often used to interpret past life-ways. Using an artificial gut system, the isotopic changes (dD, d18O, d13C and d15N) of protein are documented. Three separate protein sources are subjected to the conditions, chemical and enzymatic, found in the stomach and upper small intestine with only a small shift in the oxygen isotopic composition of the proteins observed. Middle to lower small intestine parameters produced both greater isotopic effects and significantly lower molecular weight products. The role of the gastric enterocyte and the likely involvement of the internal milieu of this cell in the isotopic composition of amino acids that are transported to the liver are reported.

  16. Selective photoionisation of lutetium isotopes

    SciTech Connect

    D'yachkov, Aleksei B; Kovalevich, S K; Labozin, Valerii P; Mironov, Sergei M; Panchenko, Vladislav Ya; Firsov, Valerii A; Tsvetkov, G O; Shatalova, G G

    2012-10-31

    A three-stage laser photoionisation scheme intended for enriching the {sup 176}Lu isotope from natural lutetium was considered. An investigation was made of the hyperfine structure of the second excited state 5d6s7s {yields} {sup 4}D{sub 3/2} with an energy of 37194 cm{sup -1} and the autoionisation state with an energy of 53375 cm{sup -1} of the {sup 176}Lu and {sup 175}Lu isotopes. The total electron momentum of the autoionisation level and the constant A of hyperfine magnetic interaction were determined. Due to a small value of the isotopic shift between {sup 176}Lu and {sup 175}Lu, appreciable selectivity of their separation may be achieved with individual hyperfine structure components. The first tentative enrichment of the 176Lu isotope was performed to a concentration of 60 % - 70 %. (laser applications and other topics in quantum electronics)

  17. Titanium isotopic anomalies in meteorites

    NASA Astrophysics Data System (ADS)

    Neimeyer, S.; Lugmair, G. W.

    1984-07-01

    Studies of Ti isotopic compositions have shown that virtually every Ca-Al-rich Allende inclusion contains anomalous Ti. The present investigation is concerned with the results of a study of Ti isotopic compositions in meteorites. One objective of the study is to evaluate the possibility of a relation between oxygen and Ti anomalies, while another objective is to explore questions regarding the origin of the Ti anomalies. A summary of the major experimental findings of the study of Ti isotopic compositions is also presented. It is noted that an assessment of the implications of the Ti results favors a chemical memory type of model in which products from various nucleosynthetic sources survive in mineral grains. Isotopic heterogeneities are then preserved due to incomplete mixing and/or equilibriation with the bulk of solar system matter. Strong arguments are found to exist against a pure late supernova injection model.

  18. Physics with isotopically controlled semiconductors

    SciTech Connect

    Haller, E. E.

    2010-07-15

    This paper is based on a tutorial presentation at the International Conference on Defects in Semiconductors (ICDS-25) held in Saint Petersburg, Russia in July 2009. The tutorial focused on a review of recent research involving isotopically controlled semiconductors. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, is the most prominent effect for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples.

  19. Titanium isotopic anomalies in meteorites

    NASA Technical Reports Server (NTRS)

    Niemeyer, S.; Lugmair, G. W.

    1984-01-01

    Studies of Ti isotopic compositions have shown that virtually every Ca-Al-rich Allende inclusion contains anomalous Ti. The present investigation is concerned with the results of a study of Ti isotopic compositions in meteorites. One objective of the study is to evaluate the possibility of a relation between oxygen and Ti anomalies, while another objective is to explore questions regarding the origin of the Ti anomalies. A summary of the major experimental findings of the study of Ti isotopic compositions is also presented. It is noted that an assessment of the implications of the Ti results favors a chemical memory type of model in which products from various nucleosynthetic sources survive in mineral grains. Isotopic heterogeneities are then preserved due to incomplete mixing and/or equilibriation with the bulk of solar system matter. Strong arguments are found to exist against a pure late supernova injection model.

  20. Clumped isotope thermometry and catagenesis

    NASA Astrophysics Data System (ADS)

    Eiler, J. M.; Clog, M. D.; Dallas, B.; Douglas, P. M.; Piasecki, A.; Sessions, A. L.; Stolper, D. A.

    2014-12-01

    Clumped- and site-specific isotopic compositions of organic compounds can constrain their formation temperatures, sources, and chemical reaction histories. The large number of isotopologues of organic molecules may allow for the isotopic composition of a single compound to illuminate many processes. For example, it is possible that clumping or site specific effects in different parts of the same molecule will differ in blocking temperature, such that a molecule's full isotopic structure could simultaneously constrain conditions of biosynthesis, catagenic 'cracking', and storage in the crust. Recent innovations in high-resolution mass spectrometry and methods of IR and NMR spectroscopy make it possible to explore these questions. Methane is the first organic molecule to have its clumped isotope geochemistry analyzed in a variety of natural environments and controlled experiments. Methane generated through catagenic cracking of kerogen and other organic matter forms in equilibrium with respect to isotopic clumping, and preserves that state through later storage or migration, up to temperatures of ~250 ˚C. This kinetic behavior permits a variety of useful geological applications. But it is unexpected because the bulk stable isotope composition of thermogenic methane is thought to reflect kinetic isotope effects on irreversible reactions. Our observations imply a new interpretation of the chemical physics of catagenic methane formation. Additional instrument and methods developments are currently extending the measurement of isotopic clumping and position specific effects to larger alkanes, other hydrocarbon compounds, and amino acids. These measurements will ultimately expand our capacity to understand the formational conditions and fates of organic molecules in high- and low-temperature environments through geological time.

  1. Isotope-Identifying neutron reflectometry

    SciTech Connect

    Nikitenko, Yu. V. Petrenko, A. V.; Gundorin, N. A.; Gledenov, Yu. M.; Aksenov, V. L.

    2015-07-15

    The possibilities of an isotope-indentifying study of layered structures in different regimes of a neutron wave field are considered. The detection of specularly reflected neutrons and secondary radiation (caused by neutron capture) in the form of charged particles, γ quanta, and nuclear fission fragments, as well as neutrons spin-flipped in a noncollinear magnetic field and on nuclei of elements with spin, makes it possible to implement isotope-indentifying neutron reflectometry.

  2. Novel hybrid isotope separation scheme and apparatus

    DOEpatents

    Maya, Jakob

    1991-01-01

    A method of yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which the specific isotope is to be isolated, radiating the gas with frequencies characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photoionization reaction of the desired isotope, and collecting the specific isotope ion by suitable ion collection means.

  3. Novel hybrid isotope separation scheme and apparatus

    DOEpatents

    Maya, J.

    1991-06-18

    A method is described for yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which the specific isotope is to be isolated, radiating the gas with frequencies characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photoionization reaction of the desired isotope, and collecting the specific isotope ion by suitable ion collection means. 3 figures.

  4. Photo-induced isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Miller, Charles E.; Yung, Yuk L.

    2000-12-01

    This paper presents a systematic method for the analysis of photo-induced isotopic fractionation. The physical basis for this fractionation mechanism centers on the fact that isotopic substitution alters the energy levels, molecular symmetries, spin statistical weights and other fundamental molecular properties, producing spectroscopic signatures distinguishable from that of the parent isotopomer. These mass-dependent physical properties are identical to those invoked by Urey to explain stable isotope fractionation in chemical systems subject to thermodynamic equilibrium. Photo-induced isotopic fractionation is a completely general phenomenon and should be observable in virtually all gas phase photochemical systems. Water photo-induced isotopic fractionation has been examined in detail using experimental and theoretical data. These results illustrate the salient features of this fractionation mechanism for molecules possessing continuous UV absorption spectra and unit photodissociation quantum yields. Using the photo-induced isotopic fractionation methodology in conjunction with standard photochemical models, we predict substantial deuterium enrichment of water vapor in the planetary atmospheres of Earth and Mars.

  5. Isotope separation apparatus and method

    DOEpatents

    Feldman, Barry J.

    1985-01-01

    The invention relates to an improved method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferably substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. Because the molecules in the beam occupy various degenerate energy levels, if the laser beam comprises chirped pulses comprising selected wavelengths, the laser beam will very efficiently excite substantially all unexcited molecules and will cause stimulated emission of substantially all excited molecules of a selected one of the isotopes in the beam which such pulses encounter. Excitation caused by first direction chirped pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning chirped pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement of essentially all the molecules containing the one isotope is accomplished by a large number of chirped pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam.

  6. Isotopic Compositions of Evaporative Fluxes

    NASA Astrophysics Data System (ADS)

    Feng, X.; Lauder, A. M.; Kopec, B. G.; Dade, W. B.; Virginia, R. A.; Posmentier, E. S.

    2013-12-01

    The isotopic fluxes of evaporation from a water surface are typically computed using a one-dimensional model, originally conceptualized by Craig and Gordon (1965) and further developed and adapted to different natural settings (such as transpiration, open surface evaporation, etc.) by various investigators. These models have two distinguishing characteristics. First, there exists a laminar layer where molecular diffusion away from the water-air interface causes kinetic isotopic fractionation. The magnitude of this fractionation is controlled by the diffusion/transport coefficient of each vapor isotopologue in air and their concentration gradients, the latter being controlled by relative humidity, isotopic ratios of ambient air, and turbulent conditions (such as wind and surface roughness). Second, the horizontal variations are ignored. In particular, the effect of horizontal advection on isotopic variations in the ambient air is not considered. The research reported here addresses the effects of relinquishing the simplifying assumptions in both of these areas. We developed a model, in which the simplification of a purely laminar layer is dropped. Instead, we express the vertical transport coefficient as the sum of the molecular diffusivity, that differs for each water isotopologue, and the turbulent diffusivity that increases linearly with height but does not vary among water isotopologues. With this model, the kinetic isotopic effect reduces with height in the vicinity of the water surface, and the net isotopic fractionation through the boundary layer can be integrated. The advantage of this conceptualization is that the magnitude of kinetic isotopic fractionation can be assessed directly with changing environmental conditions, such as humidity and wind speed, rather than approximated by discontinuous empirical functions of the environmental conditions, as in the conventional models mentioned above. To address the effect of lateral heterogeneity, we expanded the

  7. Photodisintegration of Lithium Isotopes

    NASA Astrophysics Data System (ADS)

    Wurtz, Ward Andrew

    We have performed a measurement of the photodisintegration of the lithium isotopes, 6Li and 7Li, using a monochromatic, polarised photon beam and a segmented neutron detector array which covers approximately ¼ of 4pi srad. Using time-of-flight and scintillator light-output spectra we separate the data into individual reaction channels. This work is motivated by the need to compare with recent theoretical predictions and to provide data for future theoretical work. For the photodisintegration of 6Li we took data at 12 photon energies between 8 and 35 MeV. We describe the data using a model consisting of two-body reaction channels and obtain angular distributions and absolute cross sections for many of these reaction channels. We compare our results with a recent Lorentz integral transform calculation (Bacca et al. Phys. Rev. C 69, 057001 (2004)). Our results are in reasonable agreement with the calculation, in contradiction with previous experimental results. For the photodisintegration of 7Li, we took data at 9 photon energies between 10 and 35 MeV. We obtain cross sections for the reaction channel 7Li + gamma → n + 6 Li(g.s.) at all photon energies with angular distributions at all but the highest energy. We obtain angular distributions and total cross sections for reaction channels involving excited states of the daughter nucleus, 6Li, at select energies. We hope that these measurements will provide incentive for new theoretical calculations. We observe neutrons that can only be described by the reaction channel 7Li + gamma → n + 6Li(10.0) which necessitates an excited state of 6Li with excitation energy Ex = 10.0 +/- 0.5 MeV that is not in the standard tables of excited states. ii

  8. Isotope shifts in francium isotopes Fr-213206 and 221Fr

    NASA Astrophysics Data System (ADS)

    Collister, R.; Gwinner, G.; Tandecki, M.; Behr, J. A.; Pearson, M. R.; Zhang, J.; Orozco, L. A.; Aubin, S.; Gomez, E.; FrPNC Collaboration

    2014-11-01

    We present the isotope shifts of the 7 s1 /2 to 7 p1 /2 transition for francium isotopes 206 -213Fr with reference to 221Fr collected from two experimental periods. The shifts are measured on a sample of atoms prepared within a magneto-optical trap by a fast sweep of radio-frequency sidebands applied to a carrier laser. King plot analysis, which includes literature values for 7 s1 /2 to 7 p3 /2 isotope shifts, provides a field shift constant ratio of 1.0520(10) and a difference between the specific mass shift constants of 170(100) GHz amu between the D1 and D2 transitions, of sufficient precision to differentiate between ab initio calculations.

  9. Isotope separation apparatus and method

    DOEpatents

    Cotter, Theodore P.

    1982-12-28

    The invention relates to a method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferable substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. The laser beam comprises .pi.-pulses of a selected wavelength which excite unexcited molecules, or cause stimulated emission of excited molecules of one of the isotopes. Excitation caused by first direction .pi.-pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning .pi.-pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement is accomplished by a large number of .pi.-pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam.

  10. Isotopic Randomness and Maxwell's Demon

    NASA Astrophysics Data System (ADS)

    Berezin, Alexander A.

    2005-03-01

    Isotopic disorder in crystals can lead to suppression of thermal conductivity, mobility variations and (weak) Anderson localization on isotopic fluctuations. The latter (AAB, J.ChemPhys.1984) is akin to polaron effect (self-localization due polarization). Possibility of isotopic patterning (IP) increases near melting point (thermally activated isotopic hopping swaps). Crystal near melting threshold become “informationally sensitive” as if its IP is operated by some external Maxwell’s Demon, MD (AAB, URAM J, 2002). At this state short range (e.g. electrostatic inverse square) forces evolve into long-range interactions (due to divergence of order parameter) and information sensitivity can be further amplified by (say) a single fast electron (e.g. beta-particle from decay of 14-C or other radioactive isotope) which may result in cascade of impact ionization events and (short time-scale) enhancement of screening by impact-generated non-equilibrium (non-thermal) electrons. In this state informationally driven (MD-controlled) IP (Eccles effect) can result in decrease of positional entropy signifying emergence of physical complexity out of pure information, similar to peculiar “jinni effect” on closed time loops in relativistic cosmology (R.J.Gott, 2001) or Wheeler’s “it from bit” metaphor. By selecting special IP, MD modifies ergodicity principle in favor of info rich states.

  11. Opportunities for isotope discoveries at FRIB

    NASA Astrophysics Data System (ADS)

    Baumann, T.; Hausmann, M.; Sherrill, B. M.; Tarasov, O. B.

    2016-06-01

    Expected production yields of the Facility for Rare Isotope Beams (FRIB) were calculated for a wide range of rare isotopes using the code LISE++ and planned performance parameters (Tarasov and Bazin, 2008; Bollen et al., 2011 [2]). A comparison between isotope discoveries of the last decade and expected particle yields indicates the range of isotopes that can likely be detected at FRIB. This paper will highlight recent isotope discoveries at NSCL's Coupled Cyclotron Facility and deduce how far the limits could be pushed with the Facility for Rare Isotope Beams.

  12. Isotope specific arbitrary material sorter

    SciTech Connect

    Barty, Christopher P.J.

    2015-12-08

    A laser-based mono-energetic gamma-ray source is used to provide a rapid and unique, isotope specific method for sorting materials. The objects to be sorted are passed on a conveyor in front of a MEGa-ray beam which has been tuned to the nuclear resonance fluorescence transition of the desired material. As the material containing the desired isotope traverses the beam, a reduction in the transmitted MEGa-ray beam occurs. Alternately, the laser-based mono-energetic gamma-ray source is used to provide non-destructive and non-intrusive, quantitative determination of the absolute amount of a specific isotope contained within pipe as part of a moving fluid or quasi-fluid material stream.

  13. Photonuclear reactions on titanium isotopes

    SciTech Connect

    Belyshev, S. S.; Dzhilavyan, L. Z.; Ishkhanov, B. S.; Kapitonov, I. M.; Kuznetsov, A. A. Orlin, V. N.; Stopani, K. A.

    2015-03-15

    The photodisintegration of titanium isotopes in the giant-dipole-resonance energy region is studied by the photon-activation method. Bremsstrahlung photons whose spectrum has the endpoint energy of 55 MeV is used. The yields and integrated cross sections are determined for photoproton reactions on the titanium isotopes {sup 47,48,49,50}Ti. The respective experimental results are compared with their counterparts calculated on the basis of the TALYS code and a combined photonucleon-reaction model. The TALYS code disregards the isospin structure of the giant dipole resonance and is therefore unable to describe the yield of photoproton reactions on the heavy titanium isotopes {sup 49,50}Ti.

  14. The terrestrial uranium isotope cycle

    NASA Astrophysics Data System (ADS)

    Andersen, Morten B.; Elliott, Tim; Freymuth, Heye; Sims, Kenneth W. W.; Niu, Yaoling; Kelley, Katherine A.

    2015-01-01

    Changing conditions on the Earth's surface can have a remarkable influence on the composition of its overwhelmingly more massive interior. The global distribution of uranium is a notable example. In early Earth history, the continental crust was enriched in uranium. Yet after the initial rise in atmospheric oxygen, about 2.4 billion years ago, the aqueous mobility of oxidized uranium resulted in its significant transport to the oceans and, ultimately, by means of subduction, back to the mantle. Here we explore the isotopic characteristics of this global uranium cycle. We show that the subducted flux of uranium is isotopically distinct, with high 238U/235U ratios, as a result of alteration processes at the bottom of an oxic ocean. We also find that mid-ocean-ridge basalts (MORBs) have 238U/235U ratios higher than does the bulk Earth, confirming the widespread pollution of the upper mantle with this recycled uranium. Although many ocean island basalts (OIBs) are argued to contain a recycled component, their uranium isotopic compositions do not differ from those of the bulk Earth. Because subducted uranium was probably isotopically unfractionated before full oceanic oxidation, about 600 million years ago, this observation reflects the greater antiquity of OIB sources. Elemental and isotope systematics of uranium in OIBs are strikingly consistent with previous OIB lead model ages, indicating that these mantle reservoirs formed between 2.4 and 1.8 billion years ago. In contrast, the uranium isotopic composition of MORB requires the convective stirring of recycled uranium throughout the upper mantle within the past 600 million years.

  15. The terrestrial uranium isotope cycle.

    PubMed

    Andersen, Morten B; Elliott, Tim; Freymuth, Heye; Sims, Kenneth W W; Niu, Yaoling; Kelley, Katherine A

    2015-01-15

    Changing conditions on the Earth's surface can have a remarkable influence on the composition of its overwhelmingly more massive interior. The global distribution of uranium is a notable example. In early Earth history, the continental crust was enriched in uranium. Yet after the initial rise in atmospheric oxygen, about 2.4 billion years ago, the aqueous mobility of oxidized uranium resulted in its significant transport to the oceans and, ultimately, by means of subduction, back to the mantle. Here we explore the isotopic characteristics of this global uranium cycle. We show that the subducted flux of uranium is isotopically distinct, with high (238)U/(235)U ratios, as a result of alteration processes at the bottom of an oxic ocean. We also find that mid-ocean-ridge basalts (MORBs) have (238)U/(235)U ratios higher than does the bulk Earth, confirming the widespread pollution of the upper mantle with this recycled uranium. Although many ocean island basalts (OIBs) are argued to contain a recycled component, their uranium isotopic compositions do not differ from those of the bulk Earth. Because subducted uranium was probably isotopically unfractionated before full oceanic oxidation, about 600 million years ago, this observation reflects the greater antiquity of OIB sources. Elemental and isotope systematics of uranium in OIBs are strikingly consistent with previous OIB lead model ages, indicating that these mantle reservoirs formed between 2.4 and 1.8 billion years ago. In contrast, the uranium isotopic composition of MORB requires the convective stirring of recycled uranium throughout the upper mantle within the past 600 million years. PMID:25592542

  16. Development of an "Isotopic" Pulser

    SciTech Connect

    Luke, S J; Schmid, G; Beckedahl, D; Pohl, B; White, G

    2002-06-04

    We have developed a pulser that is able to generate a simulated signal from a high-purity germanium (HPGe) detector for various plutonium isotopes. In this paper we describe the development of an ''isotopics'' pulser for the simulation of signals that are produced by an HPGe detector. The present pulser generates the waveforms that are produced by an HPGe detector both before and after the preamplifier. These signals have been input into a normal MCA and the result closely simulates a genuine pulse-height distribution.

  17. Feasibility of Isotopic Measurements: Graphite Isotopic Ratio Method

    SciTech Connect

    Wood, Thomas W.; Gerlach, David C.; Reid, Bruce D.; Morgan, W. C.

    2001-04-30

    This report addresses the feasibility of the laboratory measurements of isotopic ratios for selected trace constituents in irradiated nuclear-grade graphite, based on the results of a proof-of-principal experiment completed at Pacific Northwest National Laboratory (PNNL) in 1994. The estimation of graphite fluence through measurement of isotopic ratio changes in the impurity elements in the nuclear-grade graphite is referred to as the Graphite Isotope Ratio Method (GIRM). Combined with reactor core and fuel information, GIRM measurements can be employed to estimate cumulative materials production in graphite moderated reactors. This report documents the laboratory procedures and results from the initial measurements of irradiated graphite samples. The irradiated graphite samples were obtained from the C Reactor (one of several production reactors at Hanford) and from the French G-2 Reactor located at Marcoule. Analysis of the irradiated graphite samples indicated that replicable measurements of isotope ratios could be obtained from the fluence sensitive elements of Ti, Ca, Sr, and Ba. While these impurity elements are present in the nuclear-grade graphite in very low concentrations, measurement precision was typically on the order of a few tenths of a percent to just over 1 percent. Replicability of the measurements was also very good with measured values differing by less than 0.5 percent. The overall results of this initial proof-of-principal experiment are sufficiently encouraging that a demonstration of GIRM on a reactor scale basis is planned for FY-95.

  18. Oxygen and silicon isotopes in ALHA 81005

    NASA Astrophysics Data System (ADS)

    Mayeda, T. K.; Clayton, R. N.; Molini-Velsko, C. A.

    1983-09-01

    The Antarctic meteorite ALHA81005 has oxygen and silicon isotopic compositions identical with lunar highland rocks. The oxygen is distinctly unlike that in calcium-rich achondrites. The isotopic data are entirely consistent with a lunar origin for the meteorite.

  19. Cosmology: Rare isotopic insight into the Universe

    NASA Astrophysics Data System (ADS)

    Prantzos, Nikos

    2016-01-01

    Light isotopes of hydrogen and helium formed minutes after the Big Bang. The study of one of these primordial isotopes, helium-3, has now been proposed as a useful strategy for constraining the physics of the standard cosmological model.

  20. Isotopic microanalysis of returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Zinner, Ernst

    1989-01-01

    If isotopic measurements of interplanetary dust particles (IDPs) and primitive meteorites can serve as a guide to the isotopic analysis of returned comet nucleus material, an essential requirement will be the capability for microanalysis. The reason is that in both types of extraterrestrial samples large isotopic heterogeneities on a small spatial scale have become apparent once it was possible to measure isotopes in small samples. In the discovery of large isotopic anomalies the ion microprobe has played a significant role because of its high spatial resolution for isotopic ratio measurements. The largest isotopic anomalies in C, N, O, Mg, Si, Ca and Ti found to date were measured by ion microprobe mass spectrometry. The most striking examples are D/H measurements in IDPs and isotopic measurements of C, N and Si in SiC from the CM chondrites Murray and Murchison.

  1. APPLICATIONS OF ENVIRONMENTAL ISOTOPES FOR WATERSHED INVESTIGATIONS

    EPA Science Inventory

    Environmental isotopes include naturally-occurring nuclides that can be applied as tracers within watersheds (Sidle, 1998). Recent advances in mass spectroscopy may supplant many traditional and costly hydrometric techniques. It is now possible, for example, to utilize isotopes a...

  2. Online Catalog of Isotope Products from DOE's National Isotope Development Center

    DOE Data Explorer

    The National Isotope Development Center (NIDC) interfaces with the User Community and manages the coordination of isotope production across the facilities and business operations involved in the production, sale, and distribution of isotopes. A virtual center, the NIDC is funded by the Isotope Development and Production for Research and Applications (IDPRA) subprogram of the Office of Nuclear Physics in the U.S. Department of Energy Office of Science. The Isotope subprogram supports the production, and the development of production techniques of radioactive and stable isotopes that are in short supply for research and applications. Isotopes are high-priority commodities of strategic importance for the Nation and are essential for energy, medical, and national security applications and for basic research; a goal of the program is to make critical isotopes more readily available to meet domestic U.S. needs. This subprogram is steward of the Isotope Production Facility (IPF) at Los Alamos National Laboratory (LANL), the Brookhaven Linear Isotope Producer (BLIP) facility at BNL, and hot cell facilities for processing isotopes at ORNL, BNL and LANL. The subprogram also coordinates and supports isotope production at a suite of university, national laboratory, and commercial accelerator and reactor facilities throughout the Nation to promote a reliable supply of domestic isotopes. The National Isotope Development Center (NIDC) at ORNL coordinates isotope production across the many facilities and manages the business operations of the sale and distribution of isotopes.

  3. Separating Isotopes With Laser And Electron Beams

    NASA Technical Reports Server (NTRS)

    Trajmar, Sandor

    1989-01-01

    Need for second laser eliminated. In scheme for separation of isotopes, electrons of suitable kinetic energy ionize specific isotope excited by laser beam in magnetic field. Ionization by electron beams cheap and efficient in comparison to ionization by laser beams, and requires no special technical developments. Feasibility of new scheme demonstrated in selective ionization of Ba138, making possible separation of isotope from Ba isotopes of atomic weight 130, 132, 134, 135, 136, and 137.

  4. ICP-MS for isotope ratio measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of stable isotopes in mineral nutrition research has become a fundamental aspect of conducting this research. A gradual transition has occurred, now virtually complete, from radioactive isotope studies to those using stable isotopes. Although primarily used in human research, mineral stable ...

  5. Isotope Cancer Treatment Research at LANL

    SciTech Connect

    Weidner, John; Nortier, Meiring

    2012-04-11

    Los Alamos National Laboratory has produced medical isotopes for diagnostic and imaging purposes for more than 30 years. Now LANL researchers have branched out into isotope cancer treatment studies. New results show that an accelerator-based approach can produce clinical trial quantities of actinium-225, an isotope that has promise as a way to kill tumors without damaging surrounding healthy cells.

  6. Substitution of stable isotopes in Chlorella

    NASA Technical Reports Server (NTRS)

    Flaumenhaft, E.; Katz, J. J.; Uphaus, R. A.

    1969-01-01

    Replacement of biologically important isotopes in the alga Chlorella by corresponding heavier stable isotopes produces increasingly greater deviations from the normal cell size and changes the quality and distribution of certain cellular components. The usefulness of isotopically altered organisms increases interest in the study of such permuted organisms.

  7. Isotope Cancer Treatment Research at LANL

    ScienceCinema

    Weidner, John; Nortier, Meiring

    2014-06-02

    Los Alamos National Laboratory has produced medical isotopes for diagnostic and imaging purposes for more than 30 years. Now LANL researchers have branched out into isotope cancer treatment studies. New results show that an accelerator-based approach can produce clinical trial quantities of actinium-225, an isotope that has promise as a way to kill tumors without damaging surrounding healthy cells.

  8. Dry phase reactor for generating medical isotopes

    DOEpatents

    Mackie, Thomas Rockwell; Heltemes, Thad Alexander

    2016-05-03

    An apparatus for generating medical isotopes provides for the irradiation of dry-phase, granular uranium compounds which are then dissolved in a solvent for separation of the medical isotope from the irradiated compound. Once the medical isotope is removed, the dissolved compound may be reconstituted in dry granular form for repeated irradiation.

  9. Isotopic Fractionation in Interstellar Chemistry

    NASA Technical Reports Server (NTRS)

    Charnley, Steven

    2009-01-01

    Isotopically fractionated material is found in many solar system objects, including meteorites and comets. It is thought, in some cases, to trace interstellar material that was incorporated into the solar sys tem without undergoing significant processing. In this poster, we sho w the results of several models of the nitrogen, oxygen, and carbon f ractionation in proto-stellar cores.

  10. A NICHE FOR ISOTOPIC ECOLOGY

    EPA Science Inventory

    Fifty years ago, GE Hutchinson defined the ecological niche as a hypervolume in n-dimensional space with environmental variables as axes. Ecologists have recently developed renewed interest in the concept, and technological advances now allow us to use stable isotope analyses to ...

  11. Bayesian stable isotope mixing models

    EPA Science Inventory

    In this paper we review recent advances in Stable Isotope Mixing Models (SIMMs) and place them into an over-arching Bayesian statistical framework which allows for several useful extensions. SIMMs are used to quantify the proportional contributions of various sources to a mixtur...

  12. Isotope separation by laser technology

    NASA Astrophysics Data System (ADS)

    Stoll, Wolfgang

    2002-03-01

    Isotope separation processes operate on very small differences, given either by the Quotient of masses with the same number of electrons or by their mass difference. When separating isotopes of light elements in mass quantities, thermodynamic processes accounting for the quotient, either in diffusion, chemical reactivity or distillation are used. For heavy elements those quotients are very small. Therefore they need a large number of separation steps. Large plants with high energy consumption result from that. As uranium isotope separation is the most important industrial field, alternatives, taking account for the mass difference, as e.g. gas centrifuges, have been developed. They use only a fraction of the energy input, but need a very large number of machines, as the individual throughput is small. Since it was discovered, that molecules of high symmetry like Uranium-Hexafluoride as a deep-cooled gas stream can be ionized by multiple photon excitation, this process was studied in detail and in competition to the selective ionization of metal vapors, as already demonstrated with uranium. The paper reports about the principles of the laser excitation for both processes, the different laboratory scale and prototypical plants built, the difficulties with materials, as far as the metal vapor laser separation is concerned, and the difficulties experienced in the similarity in molecular spectra. An overview of the relative economic merits of the different processes and the auspices in a saturated market for uranium isotope separation, together with other potential markets for molecular laser separation, is contained in the conclusions.

  13. Isotope geochemistry in 1990s

    SciTech Connect

    Billo, S.M.

    1995-12-31

    The intense interest in radioactive minerals as a source of atomic energy, and their application in searching for ore deposits and also in gamma-ray and neutron logging oil wells, have opened new vistas in every science. Many minerals containing elements of high atomic weight are radioactive, and emit a radiation which affects a photographic plate and may be detected by means of a sensitive phosphorescent screen. Most of the elements as found in nature are a mixture of isotopes. isotopes are atoms of one element which have different masses. Uranium, thorium, potassium, and rubidium isotopes are also used to date minerals and rocks. Organic materials that have been in equilibrium with CO{sub 2}-photosynthetic cycle during the past 50,000 years are dated by carbon-14 method. The stable isotopes of H{sub 2}, C, N{sub 2}, O{sub 2}, and S are intimately associated with the atmosphere, hydrosphere, and lithosphere and are used in probing water resources.

  14. Deformation properties of lead isotopes

    NASA Astrophysics Data System (ADS)

    Tolokonnikov, S. V.; Borzov, I. N.; Lutostansky, Yu. S.; Saperstein, E. E.

    2016-01-01

    The deformation properties of a long lead isotopic chain up to the neutron drip line are analyzed on the basis of the energy density functional (EDF) in the FaNDF0 Fayans form. The question of whether the ground state of neutron-deficient lead isotopes can have a stable deformation is studied in detail. The prediction of this deformation is contained in the results obtained on the basis of the HFB-17 and HFB-27 Skyrme EDF versions and reported on Internet. The present analysis reveals that this is at odds with experimental data on charge radii and magnetic moments of odd lead isotopes. The Fayans EDF version predicts a spherical ground state for all light lead isotopes, but some of them (for example, 180Pb and 184Pb) prove to be very soft—that is, close to the point of a phase transition to a deformed state. Also, the results obtained in our present study are compared with the predictions of some other Skyrme EDF versions, including SKM*, SLy4, SLy6, and UNE1. By and large, their predictions are closer to the results arising upon the application of the Fayans functional. For example, the SLy4 functional predicts, in just the same way as the FaNDF0 functional, a spherical shape for all nuclei of this region. The remaining three Skyrme EDF versions lead to a deformation of some light lead isotopes, but their number is substantially smaller than that in the case of the HFB-17 and HFB-27 functionals. Moreover, the respective deformation energy is substantially lower, which gives grounds to hope for the restoration of a spherical shape upon going beyond the mean-field approximation, which we use here. Also, the deformation properties of neutron-rich lead isotopes are studied up to the neutron drip line. Here, the results obtained with the FaNDF0 functional are compared with the predictions of the HFB-17, HFB-27, SKM*, and SLy4 Skyrme EDF versions. All of the EDF versions considered here predict the existence of a region where neutron-rich lead isotopes undergo

  15. Oxygen isotope geochemistry of zircon

    NASA Astrophysics Data System (ADS)

    Valley, John W.; Chiarenzelli, Jeffrey R.; McLelland, James M.

    1994-09-01

    The high-temperature and small sample size of an I.R. laser system has allowed the first detailed study of oxygen isotope ratios in zircon. Low-magnetism zircons that have grown during metamorphism in the Adirondack Mts., N.Y. preserve primary delta (O-18) values and low magnetism igneous zircons are likewise primary, showing no significant affect due to subsequent granulite facies metamorphism. The measured fractionation between zircon and garnet is delta (Gt-Zrc) = 0.0 + or - 0.2/mil (1(sigma)) for most low-magnetism zircons in meta-igneous rocks. The consistency of this value indicates equilibration at temperatures of 700 - 1100 C and little or no change in the equilibrium fractionation over this temperature range. In contrast, detrital low-magnetism zircons in quartzite preserve igneous compositions, up to 4/mil out of equilibrium with host quartz, in spite of granulite facies metamorphism. The oxygen isotope composition of zircon can be linked to U-Pb ages and can `see through' metamorphism, providing a new tool for deciphering complex igneous, metamorphic and hydrothermal histories. Zircons separated by magnetic susceptibility show a consistent correlation. Low-magnetism zircons have the lowest uranium contents, the most concordant U-Pb isotopic compositions, and primary delta (O-18) values. In contrast, high-magnetism zircons are up to 2/mil lower in delta (O-18) than low-magnetism zircons from the same rock. The resetting of oxygen isotope ratios in high-magnetism zircons is caused by radiation damage which creates microfractures and enhances isotopic exchange. Zircons from the metamorphosed anorthosite-mangerite-charnocite-granite (AMCG) suite of adirondacks have previously been dated (1125-1157 Ma) and classified as igneous, metamorphic or disturbed based on their physical and U-Pb isotopic characteristics. Low-magnetism zircons from the AMCG suite have high, nearly constant values of delta (O-18) that average 8.1 + or - 0.4/mil(1 sigma) for samples

  16. Modeling equilibrium Fe isotope fractionation

    NASA Astrophysics Data System (ADS)

    Anbar, A.; Jarzecki, A.; Spiro, T.

    2003-04-01

    Research into the stable isotope biogeochemistry of Fe and other transition metals has been driven primarily by analytical innovations which have revealed significant isotope effects in nature and the laboratory. Further development of these new isotope systems requires complementary theoretical research to guide analytical efforts. The results of the first such studies show some discrepancies with experiments. For example, Johnson et al. (2002) report an experimentally-determined 56Fe/54Fe equilibrium fractionation factor between Fe(II) and Fe(III) aquo complexes of ˜1.0025. This effect is ˜50% smaller than predicted theoretically by Schauble et al. (2001). It is important to resolve such discrepancies. Equilibrium isotope fractionation factors can be predicted from vibrational spectroscopic data of isotopically-substituted complexes, or from theoretical predictions of some or all of these frequencies obtained using force field models. The pioneering work of Schauble et al. (2001) utilized a modified Urey-Bradley force field (MUBFF) model. This approach is limiting in at least three ways: First, it is not ab initio, requiring as input some measured vibrational frequencies. Such data are not always available, or may have significant uncertainties. Second, the MUBFF does not include potentially important effects of solvent interaction. Third, because it makes certain assumptions about molecular symmetry, the MUBFF-based approach is not able to model the spectra of mixed-ligand complexes. To address these limitations, we are evaluating the use of density functional theory (DFT) as an ab initio method to predict vibrational frequencies of isotopically-substituted complexes and, hence, equilibrium fractionation factors. In a preliminary examination of the frequency shift upon isotope substitution of the bending and asymmetric stretching modes of the tetrahedral FeCl_42- complex, we find substantial differences between MUBFF and DFT predictions. Results for other Fe

  17. Isotopic anomalies - Chemical memory of Galactic evolution

    NASA Technical Reports Server (NTRS)

    Clayton, Donald 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.

  18. Isotope hydrology of catchment basins: lithogenic and cosmogenic isotopic systems

    SciTech Connect

    Nimz, G. J., LLNL

    1998-06-01

    A variety of physical processes affect solute concentrations within catchment waters. The isotopic compositions of the solutes can indicate which processes have determined the observed concentrations. These processes together constitute the physical history of the water. Many solutes in natural waters are derived from the interaction between the water and the rock and/or soil within the system - these are termed `lithogenic` solutes. The isotopic compositions of these solutes provide information regarding rock-water interactions. Many other solutes have their isotopic compositions determined both within and outside of the catchment - i.e., in addition to being derived from catchment rock and soil, they are solutes that are also transported into the catchment. Important members of this group include solutes that have isotopic compositions produced by atomic particle interactions with other nuclides. The source of the atomic particles can be cosmic radiation (producing `cosmogenic` nuclides in the atmosphere and land surface), anthropogenic nuclear reactions (producing `thermonuclear` nuclides), or radioactive and fission decay of naturally-occurring elements, principally {sup 238}U (producing `in-situ` lithogenic nuclides in the deep subsurface). Current language usage often combines all of the atomic particle-produced nuclides under the heading `cosmogenic nuclides`, and for simplicity we will often follow that usage here, although always indicating which variety is being discussed. This paper addresses the processes that affect the lithogenic and cosmogenic solute concentrations in catchment waters, and how the isotopic compositions of the solutes can be used in integrative ways to identify these processes, thereby revealing the physical history of the water within a catchment system. The concept of a `system` is important in catchment hydrology. A catchment is the smallest landscape unit that can both participate in all of the aspects of the hydrologic cycle and

  19. Isotopic stack - measurement of heavy cosmic ray isotopes

    NASA Technical Reports Server (NTRS)

    Beaujean, R.

    1981-01-01

    Heavy cosmic ray nuclei with nuclear charge, Z, equal to or greater than 3 are to be measured using an isotopic stack consisting of passive visual track detectors which remain sensitive throughout the entire mission. The scientific data are stored in latent tracks which are produced by heavy ions and which can be revealed in the investigator's laboratory after recovery. During the mission, only housekeeping data have to be collected. The exposure onboard Spacelab 1 allows the study of the chemical composition and energy spectrum of articles which have energies in the range 20 to 100 million electron volts per atomic mass unit, as well as the isotopic composition of heavy galactic cosmic rays with energies in the range 100 to 1000 million electron volts per atomic mass unit.

  20. Developing a Clinically Useful Calcium Isotope Biomarker

    NASA Technical Reports Server (NTRS)

    Romaniello, Stephen J.; Anbar, Ariel D.; Gordon, Gwyneth W.; Skulan, Joseph L.; Smith, Scott M.; Zwart, Sara R.; Monge, Jorge; Fonseca, Rafael

    2016-01-01

    Naturally-occurring Ca is mixture of six isotopes Ca-40, Ca-42, Ca-43, Ca-44, Ca-46, Ca-48). Biological reaction rates and equilibrium constants depend slightly, but measurably, on atomic mass, causing the relative abundances of Ca isotopes to vary between different tissues. During bone formation, light isotopes of Ca are preferentially incorporated into bone, leaving soft tissue depleted in light isotopes. In contrast, bone resorption exhibits no isotopic preference, and thus transfers the light isotope signature of bone back to soft tissue. This balance makes the Ca isotope composition of soft tissue (e.g. serum, urine) a highly sensitive, quantitative tracer for whole-body bone mineral balance (BMB).

  1. Isotopic compositions of the elements, 2001

    USGS Publications Warehouse

    Böhlke, J.K.; De Laeter, J. R.; De Bievre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

    2005-01-01

    The Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope-ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and forms the basis of the table of the isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the "best measurement" of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element A r(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001. ?? 2005 American Institute of Physics.

  2. Measuring SNM Isotopic Distributions using FRAM

    SciTech Connect

    Geist, William H.

    2015-12-02

    The first group of slides provides background information on the isotopic composition of plutonium. It is shown that 240Pu is the critical isotope in neutron coincidence/multiplicity counting. Next, response function analysis to determine isotopic composition is discussed. The isotopic composition can be determined by measuring the net peak counts from each isotope and then taking the ratio of the counts for each isotope relative to the total counts for the element. Then FRAM (Fixed energy Response function Analysis with Multiple efficiencies) is explained. FRAM can control data acquisition, automatically analyze newly acquired data, analyze previously acquired data, provide information on the quality of the analysis, and facilitate analysis in unusual situations (non-standard energy calibrations, gamma rays from non-SNM isotopes, poor spectra (within limits)).

  3. Laser ablation molecular isotopic spectrometry of carbon isotopes

    NASA Astrophysics Data System (ADS)

    Bol‧shakov, Alexander A.; Mao, Xianglei; Jain, Jinesh; McIntyre, Dustin L.; Russo, Richard E.

    2015-11-01

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented: empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5-476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrum yielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies.

  4. Laser ablation molecular isotopic spectrometry of carbon isotopes

    SciTech Connect

    Bol'shakov, Alexander A.; Jain, Jinesh; Russo, Richard E.; McIntyre, Dustin; Mao, Xianglei

    2015-08-28

    Quantitative determination of carbon isotopes using Laser Ablation Molecular Isotopic Spectrometry (LAMIS) is described. Optical emission of diatomic molecules CN and C2 is used in these measurements. Two quantification approaches are presented:empirical calibration of spectra using a set of reference standards and numerical fitting of a simulated spectrum to the experimental one. Formation mechanisms of C2 and CN in laser ablation plasma are briefly reviewed to provide insights for implementation of LAMIS measurements. A simulated spectrum of the 12C2 Swan system was synthesized using four constituents within 473.5–476.5 nm. Simulation included three branches of 12C2 (1-0), branches R(0-0) and R(1-1), and branch P(9-8) of 12C2. Spectral positions of the tail lines in R(0-0) and R(1-1) were experimentally measured, since they were not accurately known before. The Swan band (1-0) of the isotopologue 13C12C was also simulated. Fitting to the experimental spectrumyielded the ratio 13C/12C = 1.08% in a good agreement with measurements by isotope ratio mass spectrometry. LAMIS promises to be useful in coal, oil and shale exploration, carbon sequestration monitoring, and agronomy studies

  5. Nitrogen isotope effects induced by anammox bacteria

    PubMed Central

    Brunner, Benjamin; Contreras, Sergio; Lehmann, Moritz F.; Matantseva, Olga; Rollog, Mark; Kalvelage, Tim; Klockgether, Gabriele; Lavik, Gaute; Jetten, Mike S. M.; Kartal, Boran; Kuypers, Marcel M. M.

    2013-01-01

    Nitrogen (N) isotope ratios (15N/14N) provide integrative constraints on the N inventory of the modern ocean. Anaerobic ammonium oxidation (anammox), which converts ammonium and nitrite to dinitrogen gas (N2) and nitrate, is an important fixed N sink in marine ecosystems. We studied the so far unknown N isotope effects of anammox in batch culture experiments. Anammox preferentially removes 14N from the ammonium pool with an isotope effect of +23.5‰ to +29.1‰, depending on factors controlling reversibility. The N isotope effects during the conversion of nitrite to N2 and nitrate are (i) inverse kinetic N isotope fractionation associated with the oxidation of nitrite to nitrate (−31.1 ± 3.9‰), (ii) normal kinetic N isotope fractionation during the reduction of nitrite to N2 (+16.0 ± 4.5‰), and (iii) an equilibrium N isotope effect between nitrate and nitrite (−60.5 ± 1.0‰), induced when anammox is exposed to environmental stress, leading to the superposition of N isotope exchange effects upon kinetic N isotope fractionation. Our findings indicate that anammox may be responsible for the unresolved large N isotope offsets between nitrate and nitrite in oceanic oxygen minimum zones. Irrespective of the extent of N isotope exchange between nitrate and nitrite, N removed from the combined nitrite and nitrate (NOx) pool is depleted in 15N relative to NOx. This net N isotope effect by anammox is superimposed on the N isotope fractionation by the co-occurring reduction of nitrate to nitrite in suboxic waters, possibly enhancing the overall N isotope effect for N loss from oxygen minimum zones. PMID:24191043

  6. Isotopic ratios in planetary atmospheres.

    PubMed

    de Bergh, C

    1995-03-01

    Recent progress on measurements of isotopic ratios in planetary or satellite atmospheres include measurements of the D/H ratio in the methane of Uranus, Neptune and Titan and in the water of Mars and Venus. Implications of these measurements on our understanding of the formation and evolution of the planets and satellite are discussed. Our current knowledge of the carbon, nitrogen and oxygen isotopic ratios in the atmospheres of these planets, as well as on Jupiter and Saturn, is also reviewed. We finally show what progress can be expected in the very near future due to some new ground-based instrumentation particularly well suited to such studies, and to forthcoming space missions. PMID:11539257

  7. Interstellar Isotopes: Prospects with ALMA

    NASA Technical Reports Server (NTRS)

    Charnley Steven B.

    2010-01-01

    Cold molecular clouds are natural environments for the enrichment of interstellar molecules in the heavy isotopes of H, C, N and O. Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets, that may trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. Models of the fractionation chemistry of H, C, N and O in dense molecular clouds, particularly in cores where substantial freeze-out of molecules on to dust has occurred, make several predictions that can be tested in the near future by molecular line observations. The range of fractionation ratios expected in different interstellar molecules will be discussed and the capabilities of ALMA for testing these models (e.g. in observing doubly-substituted isotopologues) will be outlined.

  8. Measuring Oxygen Isotopes with COSIMA

    NASA Astrophysics Data System (ADS)

    Paquette, J. A.; Engrand, C.; Stenzel, O.; Hilchenbach, M.

    2014-12-01

    Oxygen isotopes in a variety of solar system solids show non-mass-dependent fractionation, i.e. are fractionated along a slope = 1 line in a three isotope plot, rather than the equilibrium fractionation line whose slope is close to 0.5 (Clayton, 1973). Many models have been put forward to explain this observation, such as galactic chemical evolution (Clayton, 1988), photochemical self-shielding (Thiemens and Jackson, 1987; Clayton, 2002; Yurimoto and Kuramoto, 2004; Lyons and Young, 2005), quantum chemical explanations (Hathorn and Marcus, 1999, 2000; Gao and Marcus, 2002; Marcus, 2004), the processing of solids via nebular lightning (Nuth et al, 2011), and others. Some of the models were invalidated when the Genesis results showed that the oxygen isotopic fractionation of solar wind (and hence of the Sun) was relatively much richer in 16O than such bodies as the Earth or the Moon. Whatever the process that produced non-mass-dependent fractionation in some chondrules and calcium aluminum inclusions, its signature may also be detectable in other solar system solids. If at least some cometary dust was produced in the inner nebula and only later transported outward to be incorporated into comets, then such dust may also show some degree of non-mass-dependent fractionation. The COSIMA instrument on the Rosetta spacecraft (Kissel et al 2009) is a secondary ion mass spectrometer designed to measure the composition of cometary dust. Using calibration data from the COSIMA reference model and flight data if possible, measurement all three isotopes of oxygen will be attempted, and the results compared to other solar system bodies.

  9. Isotope Labeling in Mammalian Cells

    PubMed Central

    Dutta, Arpana; Saxena, Krishna; Klein-Seetharaman, Judith

    2011-01-01

    Isotope labeling of proteins represents an important and often required tool for the application of nuclear magnetic resonance (NMR) spectroscopy to investigate the structure and dynamics of proteins. Mammalian expression systems have conventionally been considered to be too weak and inefficient for protein expression. However, recent advances have significantly improved the expression levels of these systems. Here, we provide an overview of some of the recent developments in expression strategies for mammalian expression systems in view of NMR investigations. PMID:22167668

  10. Analysis of hydrogen isotope mixtures

    DOEpatents

    Villa-Aleman, Eliel

    1994-01-01

    An apparatus and method for determining the concentrations of hydrogen isotopes in a sample. Hydrogen in the sample is separated from other elements using a filter selectively permeable to hydrogen. Then the hydrogen is condensed onto a cold finger or cryopump. The cold finger is rotated as pulsed laser energy vaporizes a portion of the condensed hydrogen, forming a packet of molecular hydrogen. The desorbed hydrogen is ionized and admitted into a mass spectrometer for analysis.

  11. Rare Isotope Accelerator (RIA) Project

    NASA Astrophysics Data System (ADS)

    York, R. C.

    2006-07-01

    The proposed Rare Isotope Accelerator (RIA) Project will provide world-class intensities of radioactive beams created by any of the known production mechanisms. A driver linac will be used to accelerate any stable isotope from protons through uranium to energies of ⩾400 MeV/u and intensities of ⩾100 kW. Lighter elements will be used to produce radioactive ion beams by the isotope separation on line (ISOL) method. Typically heavier elements will be used to produce radioactive ion beams by the particle fragmentation (PF) method. A hybrid method of stopping radioactive ion beams produced by the PF method in a gas cell will also be employed. The RIA project has strong support from the nuclear science community as evidenced by RIA being the highest priority for major new construction in the most recent Nuclear Science Advisory Committee (NSAC) Long Range Plan [2002 NSAC Long-Range Plan: Opportunities in Nuclear Science, A long-range plan for the next decade, April 2002]. In addition, RIA is tied for third position for the near term priorities of the Department of Energy (DoE) 20-year plan [DOE Office of Science, Facilities for the future of science: a twenty-year outlook. http://www.sc.doe.gov/Sub/Facilities_for_future/facilities_future.htm]. The status of the RIA design is presented.

  12. Large Isotope Spectrometer for Astromag

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Klarmann, J.; Israel, M. H.; Garrard, T. L.; Mewaldt, R. A.; Stone, E. C.; Ormes, J. F.; Streitmatter, R. E.; Rasmussen, I. L.; Wiedenbeck, M. E.

    1990-01-01

    The Large Isotope Spectrometer for Astromag (LISA) is an experiment designed to measure the isotopic composition and energy spectra of cosmic rays for elements extending from beryllium through zinc. The overall objectives of this investigation are to study the origin and evolution of galactic matter; the acceleration, transport, and time scales of cosmic rays in the galaxy; and search for heavy antinuclei in the cosmic radiation. To achieve these objectives, the LISA experiment will make the first identifications of individual heavy cosmic ray isotopes in the energy range from about 2.5 to 4 GeV/n where relativistic time dilation effects enhance the abundances of radioactive clocks and where the effects of solar modulation and cross-section variations are minimized. It will extend high resolution measurements of individual element abundances and their energy spectra to energies of nearly 1 TeV/n, and has the potential for discovering heavy anti-nuclei which could not have been formed except in extragalactic sources.

  13. Discovery of Cadmium, Indium, and Tin Isotopes

    NASA Astrophysics Data System (ADS)

    Amos, Stephanie; Thoennessen, Michael

    2009-10-01

    As of today, no comprehensive study has been made covering the initial observations and identifications of isotopes. A project has been undertaken at MSU to document the discovery of all the known isotopes. The criteria defining discovery of a given isotope is the publication of clear mass and element assignment in a refereed journal. Prior to the current work the documentation of the discovery of eleven elements had been completed^1. These elements are cerium^2, arsenic, gold, tungsten, krypton, silver, vanadium, einsteinium, iron, barium, and cobalt. We will present the new documentation for the cadmium, indium, and tin isotopes. Thirty-seven cadmium isotopes, thirty-eight indium isotopes, and thirty-eight tin isotopes have been discovered so far. The description for each discovered isotope includes the year of discovery, the article published on the discovery, the article's author, the method of production, the method of identification, and any previous information concerning the isotope discovery. A summary and overview of all ˜500 isotopes documented so far as a function of discovery year, method and place will also be presented. ^1http://www.nscl.msu.edu/˜thoennes/2009/discovery.htm ^2J.Q. Ginepro, J. Snyder, and M. Thoennessen, At. Data Nucl. Data. Tables, in press (2009), doi:10.1016/j.adt.2009.06.002

  14. Unusual mercury isotopic compositions in aqueous environment

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hintelmann, H.; Zheng, W.; Feng, X.; Cai, H.; Wang, Z.; Yuan, S.

    2014-12-01

    Preliminary studies have demonstrated both mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes in natural samples. Laboratory experiments showed that photochemical reduction of inorganic mercury (iHg) and methylmercury (MMHg) and liquid-vapour evaporation could produce MIF of odd Hg isotopes. This was thought to cause the MIF actually observed in aquatic organisms. Although isotopic measurements of Hg in aqueous environment would give direct evidence, little data was reported for surface water samples. Recent work reported, unexpectedly, positive MIF of odd Hg isotopes in both precipitation and ambient air, in contrast with the prediction of laboratory experiments and measurements of Hg accumulated in lichens . Intriguingly, MIF of even-mass Hg isotope (200Hg) was also recently determined in the atmosphere. In contrast with the now mainstream observation of odd Hg isotope anomaly that has several theoretical explanations, the hitherto mysterious even Hg isotope anomalies were neither reported in laboratory experiments, nor predicted by isotope fractionation mechanisms, highlighting the importance of further study on Hg isotopes in variable systems. Our measurements of lichens and lake water samples from different countries show for the first time significant Δ200Hg in surface terrestrial reservoirs, realizing a direct connection of even Hg isotope anomaly in the terrestrial reservoirs to the atmospheric deposition, and fulfilling the gap of Δ200Hg between the atmosphere and the terrestrial receptors. The specific odd Hg isotope compositions determined in lake waters also support the atmosphere contribution, and may be directly linked to the high Δ199Hg values largely determined and manifested on the top of aqueous food web. Our data show that the watershed Hg input is another contributing source, rather than the in-lake processes, to explain the lacustrine Hg isotope anomalies. Interestingly, lake sediments are isotopically

  15. A novel methodology to investigate isotopic biosignatures

    NASA Astrophysics Data System (ADS)

    Horner, T. J.; Lee, R. B. Y.; Henderson, G. M.; Rickaby, R. E. M.

    2012-04-01

    An enduring goal of trace metal isotopic studies of Earth History is to find isotopic 'fingerprints' of life or of life's individual physiochemical processes. Generally, such signatures are sought by relating an isotopic effect observed in controlled laboratory conditions or a well-characterized environment to a more complex system or the geological record. However, such an approach is ultimately limited because life exerts numerous isotopic fractionations on any one element so it is hard to dissect the resultant net fractionation into its individual components. Further, different organisms, often with the same apparent cellular function, can express different isotopic fractionation factors. We have used a novel method to investigate the isotopic fractionation associated with a single physiological process-enzyme specific isotopic fractionation. We selected Cd isotopes since only one biological use of Cd is known, CdCA (a Cd/Zn carbonic anhydrase from the coastal diatom T. Weissflogii). Thus, our investigation can also inform the long standing mystery as to why this generally toxic element appears to have a nutrient-like dissolved isotopic and concentration profile in the oceans. We used the pET-15b plasmid to insert the CdCA gene into the E. coli genome. There is no known biochemical function for Cd in E. coli, making it an ideal vector for studying distinct physiological processes within a single organism. The uptake of Cd and associated isotopic fractionation was determined for both normal cells and those expressing CdCA. It was found that whole cells always exhibited a preference for the light isotopes of Cd, regardless of the expression of CdCA; adsorption of Cd to cell surfaces was not seen to cause isotopic fractionation. However, the cleaning procedure employed exerted a strong control on the observed isotopic composition of cells. Using existing protein purification techniques, we measured the Cd isotopic composition of different subcellular fractions of E

  16. Chromium isotopic anomalies in the Murchison meteorite

    NASA Astrophysics Data System (ADS)

    Esat, T. M.; Ireland, T. R.

    1989-02-01

    The abundances of chromium isotopes, in refractory inclusions from the Allende meteorite, show wide-spread anomalies. The chromium isotope anomalies are similar in pattern to the anomalies discovered in Ca and Ti. The largest effects occur at the neutron-rich isotopes Ca-48, Ti-50 and Cr-54. Individual Cr-rich pink spinels, from the Murchison meteorite, exhibit large and variable excesses in Cr-53 and Cr-54 including the largest Cr-53 anomaly so far reported. Magnesium isotopes, in Murchison Cr-poor blue spinels, also show variable anomalies in Mg-26 including mass-dependent fractionation favoring the lighter isotopes. The Cr-53, Cr-54 and Mg-26 anomalies in Murchison spinels are indicative of a heterogeneous distribution of magnesium and chromium isotopes in the early solar nebula and require a contribution from several nucleosynthetic components in addition to physicochemical processing.

  17. Possible isotopic fractionation effects in sputtered minerals

    NASA Technical Reports Server (NTRS)

    Haff, P. K.; Watson, C. C.; Tombrello, T. A.

    1980-01-01

    A model which makes definite predictions for the fractionation of isotopes in sputtered material is discussed. The fractionation patterns are nonlinear, and the pattern for a particular set of isotopes depends on the chemical matrix within which those isotopes are contained. Calculations are presented for all nonmonoisotopic elements contained in the minerals perovskite, anorthite, ackermanite, enstatite, and troilite. All isotopes are fractionated at the level of approximately 4-6 deg/o per atomic mass unit. Oxygen is always positively fractionated (heavier isotopes sputtered preferentially), and heavier elements are generally negatively fractioned (light isotopes sputtered preferentially). The value of Delta (O-18:O-16) is always less by about 1.8 deg/o than a linear extrapolation based upon the calculated delta (O-17:O-16) value would suggest. The phenomenon of both negative and positive fractionation patterns from a single target mineral are used to make an experimental test of the proposed model.

  18. Stable Isotope Signatures for Microbial Forensics

    SciTech Connect

    Kreuzer, Helen W.

    2012-01-03

    The isotopic distribution of the atoms composing the molecules of microorganisms is a function of the substrates used by the organisms. The stable isotope content of an organism is fixed so long as no further substrate consumption and biosynthesis occurs, while the radioactive isotopic content decays over time. The distribution of stable isotopes of C, N, O and H in heterotrophic microorganisms is a direct function of the culture medium, and therefore the stable isotope composition can be used to associate samples with potential culture media and also with one another. The 14C content depends upon the 14C content, and therefore the age, of the organic components of the culture medium, as well as on the age of the culture itself. Stable isotope signatures can thus be used for sample matching, to associate cultures with specific growth media, and to predict characteristics of growth media.

  19. Stable Isotope Enrichment Capabilities at ORNL

    SciTech Connect

    Egle, Brian; Aaron, W Scott; Hart, Kevin J

    2013-01-01

    The Oak Ridge National Laboratory (ORNL) and the US Department of Energy Nuclear Physics Program have built a high-resolution Electromagnetic Isotope Separator (EMIS) as a prototype for reestablishing a US based enrichment capability for stable isotopes. ORNL has over 60 years of experience providing enriched stable isotopes and related technical services to the international accelerator target community, as well as medical, research, industrial, national security, and other communities. ORNL is investigating the combined use of electromagnetic and gas centrifuge isotope separation technologies to provide research quantities (milligram to several kilograms) of enriched stable isotopes. In preparation for implementing a larger scale production facility, a 10 mA high-resolution EMIS prototype has been built and tested. Initial testing of the device has simultaneously collected greater than 98% enriched samples of all the molybdenum isotopes from natural abundance feedstock.

  20. Isotope exchange in oxide-containing catalyst

    NASA Technical Reports Server (NTRS)

    Brown, Kenneth G. (Inventor); Upchurch, Billy T. (Inventor); Hess, Robert V. (Inventor); Miller, Irvin M. (Inventor); Schryer, David R. (Inventor); Sidney, Barry D. (Inventor); Wood, George M. (Inventor); Hoyt, Ronald F. (Inventor)

    1989-01-01

    A method of exchanging rare-isotope oxygen for common-isotope oxygen in the top several layers of an oxide-containing catalyst is disclosed. A sample of an oxide-containing catalyst is exposed to a flowing stream of reducing gas in an inert carrier gas at a temperature suitable for the removal of the reactive common-isotope oxygen atoms from the surface layer or layers of the catalyst without damaging the catalyst structure. The reduction temperature must be higher than any at which the catalyst will subsequently operate. Sufficient reducing gas is used to allow removal of all the reactive common-isotope oxygen atoms in the top several layers of the catalyst. The catalyst is then reoxidized with the desired rare-isotope oxygen in sufficient quantity to replace all of the common-isotope oxygen that was removed.

  1. Absolute isotopic abundances of TI in meteorites

    NASA Astrophysics Data System (ADS)

    Niederer, F. R.; Papanastassiou, D. A.; Wasserburg, G. J.

    1985-03-01

    The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using 46Ti/48Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. The authors provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components.

  2. Quantitative microbial ecology through stable isotope probing.

    PubMed

    Hungate, Bruce A; Mau, Rebecca L; Schwartz, Egbert; Caporaso, J Gregory; Dijkstra, Paul; van Gestel, Natasja; Koch, Benjamin J; Liu, Cindy M; McHugh, Theresa A; Marks, Jane C; Morrissey, Ember M; Price, Lance B

    2015-11-01

    Bacteria grow and transform elements at different rates, and as yet, quantifying this variation in the environment is difficult. Determining isotope enrichment with fine taxonomic resolution after exposure to isotope tracers could help, but there are few suitable techniques. We propose a modification to stable isotope probing (SIP) that enables the isotopic composition of DNA from individual bacterial taxa after exposure to isotope tracers to be determined. In our modification, after isopycnic centrifugation, DNA is collected in multiple density fractions, and each fraction is sequenced separately. Taxon-specific density curves are produced for labeled and nonlabeled treatments, from which the shift in density for each individual taxon in response to isotope labeling is calculated. Expressing each taxon's density shift relative to that taxon's density measured without isotope enrichment accounts for the influence of nucleic acid composition on density and isolates the influence of isotope tracer assimilation. The shift in density translates quantitatively to isotopic enrichment. Because this revision to SIP allows quantitative measurements of isotope enrichment, we propose to call it quantitative stable isotope probing (qSIP). We demonstrated qSIP using soil incubations, in which soil bacteria exhibited strong taxonomic variations in (18)O and (13)C composition after exposure to [(18)O]water or [(13)C]glucose. The addition of glucose increased the assimilation of (18)O into DNA from [(18)O]water. However, the increase in (18)O assimilation was greater than expected based on utilization of glucose-derived carbon alone, because the addition of glucose indirectly stimulated bacteria to utilize other substrates for growth. This example illustrates the benefit of a quantitative approach to stable isotope probing. PMID:26296731

  3. METHOD AND APPARATUS FOR COLLECTING ISOTOPES

    DOEpatents

    Leyshon, W.E.

    1957-08-01

    A method and apparatus for collecting isotopes having a high vapor pressure, such as isotopes of mercury, in a calutron are described. Heretofore, the collected material would vaporize and escape from the ion receiver as fast as it was received. By making the receiver of pure silver, the mercury isotopes form a nonvolatile amalgam with the silver at the water cooled temperature of the receiver, and the mercury is thus retained.

  4. Method for isotope separation by photodeflection

    DOEpatents

    Bernhardt, Anthony F.

    1977-01-01

    In the method of separating isotopes wherein a desired isotope species is selectively deflected out of a beam of mixed isotopes by irradiating the beam with a directed beam of light of narrowly defined frequency which is selectively absorbed by the desired species, the improvement comprising irradiating the deflected beam with light from other light sources whose frequencies are selected to cause the depopulation of any metastable excited states.

  5. Theory of the Helium Isotope Shift

    NASA Astrophysics Data System (ADS)

    Pachucki, Krzysztof; Yerokhin, V. A.

    2015-09-01

    Theory of the isotope shift of the centroid energies of light few-electron atoms is reviewed. Numerical results are presented for the isotope shift of the 23P-23S and 21S-23S transition energies of 3He and 4He. By comparing theoretical predictions for the isotope shift with the experimental results, the difference of the squares of the nuclear charge radii of 3He and 4He, δR2, is determined with high accuracy.

  6. Normalization of oxygen and hydrogen isotope data

    USGS Publications Warehouse

    Coplen, T.B.

    1988-01-01

    To resolve confusion due to expression of isotopic data from different laboratories on non-corresponding scales, oxygen isotope analyses of all substances can be expressed relative to VSMOW or VPDB (Vienna Peedee belemnite) on scales normalized such that the ??18O of SLAP is -55.5% relative to VSMOW. H3+ contribution in hydrogen isotope ratio analysis can be easily determined using two gaseous reference samples that differ greatly in deuterium content. ?? 1988.

  7. Multiple linear regression for isotopic measurements

    NASA Astrophysics Data System (ADS)

    Garcia Alonso, J. I.

    2012-04-01

    There are two typical applications of isotopic measurements: the detection of natural variations in isotopic systems and the detection man-made variations using enriched isotopes as indicators. For both type of measurements accurate and precise isotope ratio measurements are required. For the so-called non-traditional stable isotopes, multicollector ICP-MS instruments are usually applied. In many cases, chemical separation procedures are required before accurate isotope measurements can be performed. The off-line separation of Rb and Sr or Nd and Sm is the classical procedure employed to eliminate isobaric interferences before multicollector ICP-MS measurement of Sr and Nd isotope ratios. Also, this procedure allows matrix separation for precise and accurate Sr and Nd isotope ratios to be obtained. In our laboratory we have evaluated the separation of Rb-Sr and Nd-Sm isobars by liquid chromatography and on-line multicollector ICP-MS detection. The combination of this chromatographic procedure with multiple linear regression of the raw chromatographic data resulted in Sr and Nd isotope ratios with precisions and accuracies typical of off-line sample preparation procedures. On the other hand, methods for the labelling of individual organisms (such as a given plant, fish or animal) are required for population studies. We have developed a dual isotope labelling procedure which can be unique for a given individual, can be inherited in living organisms and it is stable. The detection of the isotopic signature is based also on multiple linear regression. The labelling of fish and its detection in otoliths by Laser Ablation ICP-MS will be discussed using trout and salmon as examples. As a conclusion, isotope measurement procedures based on multiple linear regression can be a viable alternative in multicollector ICP-MS measurements.

  8. THEORETICAL AND EXPERIMENTAL ASPECTS OF ISOTOPIC FRACTIONATION.

    USGS Publications Warehouse

    O'Neil, James R.

    1986-01-01

    Essential to the interpretation of natural variations of light stable isotope ratios is knowledge of the magnitude and temperature dependence of isotopic fractionation factors between the common minerals and fluids. These fractionation factors are obtained in three ways: (1) Semi-empirical calculations using spectroscopic data and the methods of statistical mechanics. (2) Laboratory calibration studies. (3) Measurements of natural samples whose formation conditions are well-known or highly constrained. In this chapter methods (1) and (2) are evaluated and a review is given of the present state of knowledge of the theory of isotopic fractionation and the fraction that influence the isotopic properties of minerals.

  9. Atom trap trace analysis of krypton isotopes

    SciTech Connect

    Bailey, K.; Chen, C. Y.; Du, X.; Li, Y. M.; Lu, Z.-T.; O'Connor, T. P.; Young, L.

    1999-11-17

    A new method of ultrasensitive isotope trace analysis has been developed. This method, based on the technique of laser manipulation of neutral atoms, has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton gas sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. This method is free of contamination from other isotopes and elements and can be applied to several different isotope tracers for a wide range of applications. The demonstrated detection efficiency is 1 x 10{sup {minus}7}. System improvements could increase the efficiency by many orders of magnitude.

  10. Variable Carbon Isotopes in ALH84001 Carbonates

    NASA Astrophysics Data System (ADS)

    Niles, P. B.; Leshin, L. A.; Guan, Y.

    2002-12-01

    The Martian meteorite ALH84001 contains a small amount of carbonate that was deposited from aqueous fluids on the Martian surface approximately 3.9 Ga.. McKay et al. (1996) proposed evidence for the existence of life preserved within the carbonate grains. In order to determine the nature of the ancient Martian aqueous system we have combined previously collected oxygen isotopic data with new carbon isotopic measurements performed on the Cameca 6f ion microprobe at Arizona State University. Isotopic measurements were made at high mass resolution with a spot size of 10 microns. The measured carbon isotopic values range from 29.2‰ to 64.5‰ (PDB) with an average uncertainty of +/-1.6‰ (1σ ). These data agree very well with previous acid dissolution and stepped combustion experiments which range from a δ13C of +32‰ to +41‰ . As observed with the oxygen isotopic data, the carbon isotopic composition is correlated with the chemical composition of the carbonates. This allows us to establish that the earliest (Ca-rich) carbonates had the lightest carbon isotopic composition while the latest forming (Mg-rich) carbonates had the heaviest carbon isotopic composition. The large range of carbon isotopic compositions measured in this study cannot be explained by previously proposed models. Temperature change or a Rayleigh distillation process caused by progressive carbonate precipitation are insufficient to create the observed carbon isotopic compositions. Furthermore, processes such as evaporation or photosynthesis will not produce large carbon isotopic variations due to rapid isotopic equilibration with the atmosphere. We propose two possible models for the formation of the ALH84001 carbonates consistent with the isotopic data collected thus far. Carbonates could have formed from an evolving system where the carbon and oxygen isotopic composition of the carbonates reflects a mixing between magmatic hydrothermal fluids and fluids in equilibrium with an isotopically

  11. Carbon isotopic composition of Amazon shelf sediments

    SciTech Connect

    Showers, W.J.; Angle, D.G.; Nittrouer, C.A.; Demaster, D.J.

    1985-02-01

    The distribution of carbon isotopes in Amazon shelf sediment is controlled by the same processes that are forming the modern subaqueous delta. The terrestrial (-27 to -25 per thousand) isotopic carbon signal observed in surficial sediments near the river mouth extends over 400 km northwest along the shelf. Terrestrial carbon is associated with areas of rapid sediment accumulation (topset and foreset regions). A sharp boundary between terrestrial (-27 to -25 per thousand) and marine (-23 to -22 per thousand) isotopic carbon values in surficial sediments is associated with a change in depositional conditions (foreset to bottomset regions) and a decrease in sediment accumulation rate. POC water-column isotopic values (-27 per thousand) near the river mouth are similar to the underlying surficial-sediment TOC isotopic values, but POC water-column samples collected 20 km off the river mouth have marine carbon isotopic values (-22 to -19 per thousand) and differ from the underlying surficial-sediment TOC isotopic values. These water column observations are related to variations in turbidity and productivity. Down-core isotopic variation is only observed in cores taken in areas of lower sediment accumulation rates. These observations indicate that the organic carbon in Amazon shelf sediment is dominantly terrestrial in composition, and the location of deposition of this carbon is controlled by modern processes of sediment accumulation. The modern Amazon shelf is similar to large clinoform shale deposits of the Cretaceous in North America. Thus, the stratigraphic setting may help predict the isotopic variations of carbon in ancient deposits.

  12. Method for isotope enrichment by photoinduced chemiionization

    DOEpatents

    Dubrin, James W.

    1985-01-01

    Isotope enrichment, particularly .sup.235 U enrichment, is achieved by irradiating an isotopically mixed vapor feed with radiant energy at a wavelength or wavelengths chosen to selectively excite the species containing a desired isotope to a predetermined energy level. The vapor feed if simultaneously reacted with an atomic or molecular reactant species capable of preferentially transforming the excited species into an ionic product by a chemiionization reaction. The ionic product, enriched in the desired isotope, is electrostatically or electromagnetically extracted from the reaction system.

  13. Adsorption and isotopic fractionation of Xe

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Podosek, F. A.

    1986-01-01

    A theoretical description of the mechanisms of isotopic fractionation arising during adsorption of noble gases in a Henry's Law pressure regime is given. Experimental data on the isotopic composition of Xe adsorbed on activated charcoal in the temperature range 220 K to 350 K are presented. Both theoretical considerations and the experimental data indicate that equilibrium adsorption does not significantly alter the isotopic structure of adsorbed structure of adsorbed noble gases. Therefore, if adsorption is responsible for the elemental noble gas pattern in meteorites and the earth, the heavy noble gas isotopic fractionation between them must have been produced prior to and by a different process than equilibrium adsorption.

  14. Miniature Laser Spectrometer for Stable Isotope Measurements

    NASA Technical Reports Server (NTRS)

    Becker, J. F.; Kojiro, D. R.

    1999-01-01

    As a first step in successfully measuring carbon isotopes optically we have previously demonstrated the measurement of C-13/C-12 to a precision of 0.1% using a tunable diode laser and CO2 spectral lines in the 2300/cm spectral region. This precision of 0.1% (1 per mil) for carbon isotopes is a value sufficiently precise to provide important isotopic data of interest to astrobiologists. The precision presently attainable in gases is sufficient to permit our instrument to be used in the measurement of isotopic ratios of interest to astrobiologists as well as geologists and planetary scientists.

  15. Stable isotope labeling methods for DNA.

    PubMed

    Nelissen, Frank H T; Tessari, Marco; Wijmenga, Sybren S; Heus, Hans A

    2016-08-01

    NMR is a powerful method for studying proteins and nucleic acids in solution. The study of nucleic acids by NMR is far more challenging than for proteins, which is mainly due to the limited number of building blocks and unfavorable spectral properties. For NMR studies of DNA molecules, (site specific) isotope enrichment is required to facilitate specific NMR experiments and applications. Here, we provide a comprehensive review of isotope-labeling strategies for obtaining stable isotope labeled DNA as well as specifically stable isotope labeled building blocks required for enzymatic DNA synthesis. PMID:27573183

  16. Isotopic characteristics of Indian precipitation

    NASA Astrophysics Data System (ADS)

    Kumar, Bhishm; Rai, S. P.; Kumar, U. Saravana; Verma, S. K.; Garg, Pankaj; Kumar, S. V. Vijaya; Jaiswal, Rahul; Purendra, B. K.; Kumar, S. R.; Pande, N. G.

    2010-12-01

    Hydrogen (2H/1H) and oxygen (18O/16O) isotopic ratios were measured in precipitation (900 samples) collected from several locations in India during the period 2003-2006 (12 locations in 2003 and 18 locations in 2004-2006). The amount of rainfall along with air temperature and humidity were also measured. The meteoric water line developed for India using isotopic data of precipitation samples, namely, δ2H = 7.93(±0.06) × δ18O + 9.94(±0.51) (n = 272, r2 = 0.98), differs slightly from the global meteoric water line. Regional meteoric water lines were developed for several Indian regions (i.e., northern and southern regions of India, western Himalayas) and found to be different from each other (southern Indian meteoric water line, slope is 7.82, intercept or D excess is 10.23; northern Indian meteoric water line, slope is 8.15, intercept is 9.55) which is attributed to differences in their geographic and meteorological conditions and their associated atmospheric processes (i.e., ambient temperature, humidity, organ, and source of vapor masses). The local meteoric water lines developed for a number of locations show wide variations in the slope and intercept. These variations are due to different vapor sources such as the northeast (NE) monsoon that originates in the Bay of Bengal; the southwest monsoon (SW) that originates in the Arabian Sea; a mixture of NE and SW monsoons; retreat of NE and SW monsoons and western disturbances that originate in the Mediterranean Sea. The altitude effect in the isotopic composition of precipitation estimated for western Himalayan region also varies from month to month.

  17. Uranium isotopes fingerprint biotic reduction

    SciTech Connect

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J.; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-04-20

    Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. In addition, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium.

  18. Uranium isotopes fingerprint biotic reduction

    DOE PAGESBeta

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J.; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-04-20

    Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U),more » i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. In addition, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium.« less

  19. Uranium isotopes fingerprint biotic reduction.

    PubMed

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-05-01

    Knowledge of paleo-redox conditions in the Earth's history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth's crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. Additionally, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium. PMID:25902522

  20. Uranium isotopes fingerprint biotic reduction

    PubMed Central

    Stylo, Malgorzata; Neubert, Nadja; Wang, Yuheng; Monga, Nikhil; Romaniello, Stephen J.; Weyer, Stefan; Bernier-Latmani, Rizlan

    2015-01-01

    Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. Additionally, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium. PMID:25902522

  1. Spatial periphery of lithium isotopes

    SciTech Connect

    Galanina, L. I. Zelenskaja, N. S.

    2013-12-15

    The spatial structure of lithium isotopes is studied with the aid of the charge-exchange and (t, p) reactions on lithium nuclei. It is shown that an excited isobaric-analog state of {sup 6}Li (0{sup +}, 3.56MeV) has a halo structure formed by a proton and a neutron, that, in the {sup 9}Li nucleus, there is virtually no neutron halo, and that {sup 11}Li is a Borromean nucleus formed by a {sup 9}Li core and a two-neutron halo manifesting itself in cigar-like and dineutron configurations.

  2. Hydrogen-isotope permeation barrier

    DOEpatents

    Maroni, Victor A.; Van Deventer, Erven H.

    1977-01-01

    A composite including a plurality of metal layers has a Cu-Al-Fe bronze layer and at least one outer layer of a heat and corrosion resistant metal alloy. The bronze layer is ordinarily intermediate two outer layers of metal such as austenitic stainless steel, nickel alloys or alloys of the refractory metals. The composite provides a barrier to hydrogen isotopes, particularly tritium that can reduce permeation by at least about 30 fold and possibly more below permeation through equal thicknesses of the outer layer material.

  3. Updated Evaluations for Americium Isotopes

    SciTech Connect

    Brown, D A; Pruet, J

    2005-09-22

    Here we describe evaluations for Am isotopes that will be included in the next release of ENDL. Current ENDL99 evaluations for these isotopes are quite outdated and almost entirely undocumented. Because Am is important for several DNT applications, and because quality evaluations are either readily available or easily calculated, the effort to update ENDL seems warranted. Results from good existing evaluations are adopted whenever possible. To this end we devote the next section of this report to a consideration of the availability of evaluations The quality of different evaluations as well as comparisons against experiments are also presented and used to motivate our choice of adopted data sets. Plans for modifying and improving adopted evaluations are also discussed. For {sup 240}Am there are no existing evaluations. To fill this gap, we are providing a new Am evaluation based on calculations with the statistical model reaction codes TALYS and EMPIRE. This evaluation is described below. The ENDF/B-VI formatted file containing this evaluation is given in the appendix.

  4. Lithium and magnesium isotopes fractionation by zone melting

    NASA Astrophysics Data System (ADS)

    Akimov, D. V.; Egorov, N. B.; Dyachenko, A. N.; Pustovalova, M. P.; Podoinikov, I. R.

    2016-06-01

    The process of changing isotopic composition of the lithium and magnesium salts was studied by using the process of zone melting. It was founded in the paper that the process of separation of the lithium isotopes is more effective than for magnesium isotopes when the conditions of process were the same. The coefficients of isotopes separation were calculated and have the next value: α = 1.006 for 26Mg isotope and α = 1.0022 for 6Li isotope.

  5. Oxygen isotope geospeedometry by SIMS

    NASA Astrophysics Data System (ADS)

    Bonamici, C. E.; Valley, J. W.

    2013-12-01

    Geospeedometry, a discipline closely related and complimentary to thermochronology, exploits the phenomenon of diffusion in order to extract rate and duration information for segments of a rock's thermal history. Geospeedometry data, when anchored in absolute time by geochronologic data, allow for the construction of detailed temperature-time paths for specific terranes and geologic processes. We highlight the developing field of SIMS-based oxygen isotope geospeedometry with an application from granulites of the Adirondack Mountains (New York) and discuss potential future applications based on a recently updated and expanded modeling tool, the Fast Grain Boundary diffusion program (FGB; Eiler et al. 1994). Equilibrium oxygen isotope ratios in minerals are a function of temperature and bulk rock composition. In dynamic systems, intragrain oxygen isotope zoning can develop in response to geologic events that affect the thermal state of a rock and/or induce recrystallization, especially tectonic deformation and fluid infiltration. As an example, titanite grains from late-Grenville shear zones in the northwestern Adirondack Mountains exhibit a range of δ18O zoning patterns that record post-peak metamorphic cooling, episodic fluid infiltration, and deformation-facilitated recrystallization. Many titanite grains preserve smooth, core-to-rim decreasing, diffusional δ18O profiles, which are amenable to diffusion modeling. FGB models that best fit the measured δ18O profiles indicate cooling from ~700-500°C in just 2-5 m.y., a rapid thermal change signaling the final gravitational collapse of the late-Grenville orogen. Titanite can also be utilized as a U-Pb chronometer, and comparison of δ18O and U-Pb age zoning patterns within the Adirondack titanites pins the episode of rapid cooling inferred from the δ18O record to some time between 1054 and 1047 Ma. The expanded capabilities of FGB also allow for evaluation of a range of heating-cooling histories for the

  6. Advanced Mass Spectrometers for Hydrogen Isotope Analyses

    SciTech Connect

    Chastagner, P.

    2001-08-01

    This report is a summary of the results of a joint Savannah River Laboratory (SRL) - Savannah River Plant (SRP) ''Hydrogen Isotope Mass Spectrometer Evaluation Program''. The program was undertaken to evaluate two prototype hydrogen isotope mass spectrometers and obtain sufficient data to permit SRP personnel to specify the mass spectrometers to replace obsolete instruments.

  7. Iron Isotopic Diagnostics of Presolar Supernova Grains

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.; Meyer, B. S; The, L.-S.

    2002-01-01

    We study the abundance and isotopic composition of iron in a massive-star supernova to identify those isotopic characteristics that can identify the location of the condensing matter that is contained in the presolar supernova grains from meteorites. Additional information is contained in the original extended abstract.

  8. Xenon Isotope Releases from Buried Transuranic Waste

    NASA Astrophysics Data System (ADS)

    Dresel, P. E.; Waichler, S. R.; Kennedy, B. M.; Hayes, J. C.; McIntyre, J. I.; Giles, J. R.; Sondrup, A. J.

    2004-12-01

    Xenon is an inert rare gas produced as a fission product in nuclear reactors and through spontaneous fission of some transuranic isotopes. Thus, xenon will be released from buried transuranic waste. Two complementary methods are used to measure xenon isotopes: radiometric analysis for short-lived radioxenon isotopes and mass spectrometry for detection of stable xenon isotopes. Initial measurements near disposal facilities at the U.S. Department of Energy's Hanford Site show radioxenon and stable xenon isotopic signatures that are indicative of transuranic waste. Radioxenon analysis has greater sensitivity due to the lower background concentrations and indicates spontaneous fission due to the short half life of the isotopes. Stable isotope ratios may be used to distinguish irradiated fuel sources from pure spontaneous fission sources and are not as dependent on rapid release from the waste form. The release rate is dependent on the type of waste and container integrity and is the greatest unknown in application of this technique. Numerical multi-phase transport modeling of burial grounds at the Idaho National Engineering and Environmental Laboratory indicates that, under generalized conditions, the radioxenon isotopes will diffuse away from the waste and be found in the soil cap and adjacent to the burial ground at levels many orders of magnitude above the detection limit.

  9. Isotope separation by selective photodissociation of glyoxal

    DOEpatents

    Marling, John B.

    1976-01-01

    Dissociation products, mainly formaldehyde and carbon monoxide, enriched in a desired isotope of carbon, oxygen, or hydrogen are obtained by the selective photodissociation of glyoxal wherein glyoxal is subjected to electromagnetic radiation of a predetermined wavelength such that photon absorption excites and induces dissociation of only those molecules of glyoxal containing the desired isotope.

  10. [Carbon isotope fractionation inplants]. Final report

    SciTech Connect

    O`Leary, M.H.

    1990-12-31

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  11. Isotope effect of mercury diffusion in air

    PubMed Central

    Koster van Groos, Paul G.; Esser, Bradley K.; Williams, Ross W.; Hunt, James R.

    2014-01-01

    Identifying and reducing impacts from mercury sources in the environment remains a considerable challenge and requires process based models to quantify mercury stocks and flows. The stable isotope composition of mercury in environmental samples can help address this challenge by serving as a tracer of specific sources and processes. Mercury isotope variations are small and result only from isotope fractionation during transport, equilibrium, and transformation processes. Because these processes occur in both industrial and environmental settings, knowledge of their associated isotope effects is required to interpret mercury isotope data. To improve the mechanistic modeling of mercury isotope effects during gas phase diffusion, an experimental program tested the applicability of kinetic gas theory. Gas-phase elemental mercury diffusion through small bore needles from finite sources demonstrated mass dependent diffusivities leading to isotope fractionation described by a Rayleigh distillation model. The measured relative atomic diffusivities among mercury isotopes in air are large and in agreement with kinetic gas theory. Mercury diffusion in air offers a reasonable explanation of recent field results reported in the literature. PMID:24364380

  12. Amino acid isotopic analysis in agricultural systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A relatively new approach to stable isotopic analysis—referred to as compound-specific isotopic analysis (CSIA)—has emerged, centering on the measurement of 15N:14N ratios in amino acids (glutamic acid and phenylalanine). CSIA has recently been used to generate trophic position estimates among anima...

  13. Uses of stable isotopes in fish ecology

    EPA Science Inventory

    Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable i...

  14. Isotopic fractionation of cadmium into calcite

    NASA Astrophysics Data System (ADS)

    Horner, Tristan J.; Rickaby, Rosalind E. M.; Henderson, Gideon M.

    2011-12-01

    Cadmium mimics the distribution of the macronutrient phosphate in the oceans, and has uses as a palaeoproxy of past ocean circulation and nutrient utilization. Isotopic analyses of dissolved Cd in modern seawater show potential as a new tool for disentangling phytoplankton utilization of Cd from abiotic processes, such as ocean mixing. Extending this information into the past requires the Cd isotope signal to be captured and faithfully preserved in a suitable sedimentary archive. However, the role that environmental factors, such as temperature, may play in controlling Cd isotope fractionation into such archives has not been assessed. To this end, we have performed controlled inorganic CaCO 3 precipitation experiments in artificial seawater solutions. We grew calcite under different precipitation rates, temperatures, salinities, and ambient [Mg 2 + ], before measuring Cd isotopic compositions by double spike MC-ICPMS. We find that the isotopic fractionation factor for Cd into calcite ( α-C) in seawater is always less than one (i.e. light isotopes of Cd are preferred in calcite). The fractionation factor has a value of 0.99955 ± 0.00012 and shows no response to temperature, [Mg 2 + ], or precipitation rate across the range studied. The constancy of this fractionation in seawater suggests that marine calcites may provide a record of the local seawater composition, without the need to correct for effects due to environmental variables. We also performed CaCO 3 growth in freshwater and, in contrast to calcite precipitated from artificial seawater solutions, no isotopic offset was recorded between the growth solution and calcite ( α-Cd=1.0000±0.0001). Cadmium isotope fractionation during calcite growth can be explained by a kinetic isotope effect during the largely unidirectional incorporation of Cd at the mineral surface. Further, the rate of Cd uptake and isotopic fractionation can be modulated by increased ion blocking of crystal surface sites at high salinity

  15. Oxygen isotope fractionation in stratospheric CO2

    NASA Technical Reports Server (NTRS)

    Thiemens, M. H.; Jackson, T.; Mauersberger, K.; Schueler, B.; Morton, J.

    1991-01-01

    A new cryogenic collection system has been flown on board a balloon gondola to obtain separate samples of ozone and carbon dioxide without entrapping major atmospheric gases. Precision laboratory isotopic analysis of CO2 samples collected between 26 and 35.5 km show a mass-independent enrichment in both O-17 and O-18 of about 11 per mil above tropospheric values. Ozone enrichment in its heavy isotopes was 9 to 16 percent in O3-50 and 8 to 11 percent in O3-49, respectively (Schueler et al., 1990). A mechanism to explain the isotope enrichment in CO2 has been recently proposed by Yung et al. (1991). The model is based on the isotope exchange between CO2 and O3 via O(1D), resulting in a transfer of the ozone isotope enrichment to carbon dioxide. Predicted enrichment and measured values agree well.

  16. Carbon isotope effects associated with aceticlastic methanogenesis

    NASA Technical Reports Server (NTRS)

    Gelwicks, J. T.; Risatti, J. B.; Hayes, J. M.

    1994-01-01

    The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems.

  17. Carbon isotope effects associated with aceticlastic methanogenesis.

    PubMed

    Gelwicks, J T; Risatti, J B; Hayes, J M

    1994-02-01

    The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems. PMID:11536629

  18. Device and method for separating oxygen isotopes

    DOEpatents

    Rockwood, Stephen D.; Sander, Robert K.

    1984-01-01

    A device and method for separating oxygen isotopes with an ArF laser which produces coherent radiation at approximately 193 nm. The output of the ArF laser is filtered in natural air and applied to an irradiation cell where it preferentially photodissociates molecules of oxygen gas containing .sup.17 O or .sup.18 O oxygen nuclides. A scavenger such as O.sub.2, CO or ethylene is used to collect the preferentially dissociated oxygen atoms and recycled to produce isotopically enriched molecular oxygen gas. Other embodiments utilize an ArF laser which is narrowly tuned with a prism or diffraction grating to preferentially photodissociate desired isotopes. Similarly, desired mixtures of isotopic gas can be used as a filter to photodissociate enriched preselected isotopes of oxygen.

  19. Carbon isotope effects associated with aceticlastic methanogenesis.

    PubMed Central

    Gelwicks, J T; Risatti, J B; Hayes, J M

    1994-01-01

    The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems. PMID:11536629

  20. Boron-isotope geochemistry. Doctoral thesis

    SciTech Connect

    Spivack, A.J.

    1986-01-01

    An investigation of the major aspects of the boron-isotope geochemical cycle was carried out. Particular emphasis was directed at developing a reproducible, high-precision method for the determination of boron isotope ratios in geologic materials and determining the processes that influence the boron-isotope composition of seawater. A method for the determination of the isotopic composition of boron by thermal ionization mass spectrometry of Cs/sub 2/B/sub 4/O/sub 7/ is described. Samples analyzed for boron content and isotopic composition included: seawater, unaltered mid-ocean ridge basalts (MORB), altered MORB (dredge and core samples), serpentinized periodotites, marine sediments, marine sedimentary pore waters, hydrothermally altered sediments, oceanic hydrothermal solutions, rainwater, river water and suspended sediments, island arc volcanics and a soil profile.

  1. Isotopic composition of gases from mud volcanoes

    SciTech Connect

    Valysaev, B.M.; Erokhin, V.E.; Grinchenko, Y.I.; Prokhorov, V.S.; Titkov, G.A.

    1985-09-01

    A study has been made of the isotopic composition of the carbon in methane and carbon dioxide, as well as hydrogen in the methane, in the gases of mud volcanoes, for all main mud volcano areas in the USSR. The isotopic composition of carbon and hydrogen in methane shows that the gases resemble those of oil and gas deposits, while carbon dioxide of these volcanoes has a heavier isotopic composition with a greater presence of ''ultraheavy'' carbon dioxide. By the chemical and isotopic composition of gases, Azerbaidzhan and South Sakhalin types of mud volcano gases have been identified, as well as Bulganak subtypes and Akhtala and Kobystan varieties. Correlations are seen between the isotopic composition of gases and the geological build of mud volcano areas.

  2. Atomic vapor laser isotope separation of lead-210 isotope

    DOEpatents

    Scheibner, Karl F.; Haynam, Christopher A.; Johnson, Michael A.; Worden, Earl F.

    1999-01-01

    An isotopically selective laser process and apparatus for removal of Pb-210 from natural lead that involves a one-photon near-resonant, two-photon resonant excitation of one or more Rydberg levels, followed by field ionization and then electrostatic extraction. The wavelength to the near-resonant intermediate state is counter propagated with respect to the second wavelength required to populate the final Rydberg state. This scheme takes advantage of the large first excited state cross section, and only modest laser fluences are required. The non-resonant process helps to avoid two problems: first, stimulated Raman Gain due to the nearby F=3/2 hyperfine component of Pb-207 and, second, direct absorption of the first transition process light by Pb-207.

  3. Atomic vapor laser isotope separation of lead-210 isotope

    DOEpatents

    Scheibner, K.F.; Haynam, C.A.; Johnson, M.A.; Worden, E.F.

    1999-08-31

    An isotopically selective laser process and apparatus for removal of Pb-210 from natural lead that involves a one-photon near-resonant, two-photon resonant excitation of one or more Rydberg levels, followed by field ionization and then electrostatic extraction. The wavelength to the near-resonant intermediate state is counter propagated with respect to the second wavelength required to populate the final Rydberg state. This scheme takes advantage of the large first excited state cross section, and only modest laser fluences are required. The non-resonant process helps to avoid two problems: first, stimulated Raman Gain due to the nearby F=3/2 hyperfine component of Pb-207 and, second, direct absorption of the first transition process light by Pb-207. 5 figs.

  4. Apparatus for storing hydrogen isotopes

    DOEpatents

    McMullen, John W.; Wheeler, Michael G.; Cullingford, Hatice S.; Sherman, Robert H.

    1985-01-01

    An improved method and apparatus for storing isotopes of hydrogen (especially tritium) are provided. The hydrogen gas(es) is (are) stored as hydrides of material (for example uranium) within boreholes in a block of copper. The mass of the block is critically important to the operation, as is the selection of copper, because no cooling pipes are used. Because no cooling pipes are used, there can be no failure due to cooling pipes. And because copper is used instead of stainless steel, a significantly higher temperature can be reached before the eutectic formation of uranium with copper occurs, (the eutectic of uranium with the iron in stainless steel forming at a significantly lower temperature).

  5. Laser system for isotope separation

    NASA Astrophysics Data System (ADS)

    Shirayama, Shimpey; Mikatsura, Takefumi; Ueda, Hiroaki; Konagai, Chikara

    1990-06-01

    Atomic vapor laser isotope separation (AVLIS) is regarded as the most promising method to obtain srightly enriched economical nuclear fuel for a nuclear power plant. However, achieving a high power laser seems to be the bottle neck in its industrialization. In 1985, after successful development of high power lasers, the U.S. announced that AVLIS would be used for future methods of uranium enrichment. In Japan , Laser Atomic Separation Enrichment Research Associates of Japan (LASER-J), a joint Japanese utility companies research organization, was founded in April, 1987, to push a development program for laser uranium enrichment. Based on research results obtained from Japanese National Labs, and Universities , Laser-J is now constructing an AVLIS experimental facility at Tokai-mura. It is planned to have a 1-ton swu capacity per year in 1991. Previous to the experimental facility construction , Toshiba proceeded with the preliminary testing of an isotope separation system, under contract with Laser-J. Since the copper vapor laser (CVL) and the dye laser (DL) form a good combination , which can obtain high power tunable visible lights ,it is suitable to resonate uranium atoms. The laser system was built and was successfully operated in Toshiba for two years. The system consist of three copper vapor lasers , three dye lasers and appropriate o Atomic vapor laser isotope separation (AVLIS) is regarded as the most promising method to obtain srightly enriched economical nuclear fuel for a nuclear power plant. However, achieving a high power laser seems to be the bottle neck in its industrialization. In 1985, after successful development of high power lasers, the U.S. announced that AVLIS would be used for future methods of uranium enrichment. In Japan , Laser Atomic Separation Enrichment Research Associates of Japan (LASER-J) , a joint Japanese utility companies research organization , was founded in April, 1987, to push a development program for laser uranium enrichment

  6. Isotopic signatures by bulk analyses

    SciTech Connect

    Efurd, D.W.; Rokop, D.J.

    1997-12-01

    Los Alamos National Laboratory has developed a series of measurement techniques for identification of nuclear signatures by analyzing bulk samples. Two specific applications for isotopic fingerprinting to identify the origin of anthropogenic radioactivity in bulk samples are presented. The first example is the analyses of environmental samples collected in the US Arctic to determine the impact of dumping of radionuclides in this polar region. Analyses of sediment and biota samples indicate that for the areas sampled the anthropogenic radionuclide content of sediments was predominantly the result of the deposition of global fallout. The anthropogenic radionuclide concentrations in fish, birds and mammals were very low. It can be surmised that marine food chains are presently not significantly affected. The second example is isotopic fingerprinting of water and sediment samples from the Rocky Flats Facility (RFP). The largest source of anthropogenic radioactivity presently affecting surface-waters at RFP is the sediments that are currently residing in the holding ponds. One gram of sediment from a holding pond contains approximately 50 times more plutonium than 1 liter of water from the pond. Essentially 100% of the uranium in Ponds A-1 and A-2 originated as depleted uranium. The largest source of radioactivity in the terminal Ponds A-4, B-5 and C-2 was naturally occurring uranium and its decay product radium. The uranium concentrations in the waters collected from the terminal ponds contained 0.05% or less of the interim standard calculated derived concentration guide for uranium in waters available to the public. All of the radioactivity observed in soil, sediment and water samples collected at RFP was naturally occurring, the result of processes at RFP or the result of global fallout. No extraneous anthropogenic alpha, beta or gamma activities were detected. The plutonium concentrations in Pond C-2 appear to vary seasonally.

  7. Isotopic composition of Silurian seawater

    SciTech Connect

    Knauth, L.P.; Kealy, S.; Larimer, S.

    1985-01-01

    Direct isotopic analyses of 21 samples of the Silurian hydrosphere preserved as fluid inclusions in Silurian halite deposits in the Michigan Basin Salina Group yield delta/sup 18/O, deltaD ranging from 0.2 to +5.9 and -26 to -73, respectively. delta/sup 18/O has the same range as observed for modern halite facies evaporite waters and is a few per thousand higher than 100 analyses of fluid inclusions in Permian halite. deltaD is about 20 to 30 per thousand lower than modern and Permian examples. The trajectory of evaporating seawater on a deltaD-delta/sup 18/O diagram initially has a positive slope of 3-6, but hooks strongly downward to negative values, the shape of the hook depending upon humidity. Halite begins to precipitate at delta values similar to those observed for the most /sup 18/O rich fluid inclusions. Subsequent evaporation yields progressively more negative delta values as observed for the fluid inclusions. The fluid inclusion data can be readily explained in terms of evaporating seawater and are consistent with the degree of evaporation deduced from measured bromide profiles. These data are strongly inconsistent with arguments that Silurian seawater was 5.5 per thousand depleted in /sup 18/O. delta/sup 18/O for evaporite waters is systematically related to that of seawater, and does not show a -5.5 per thousand shift in the Silurian, even allowing for variables which affect the isotope evaporation trajectory. The lower deltaD may indicate a component of gypsum dehydration waters or may suggest a D-depleted Silurian hydrosphere.

  8. Isotopic yield in cold binary fission of even-even 244-258Cf isotopes

    NASA Astrophysics Data System (ADS)

    Santhosh, K. P.; Cyriac, Annu; Krishnan, Sreejith

    2016-05-01

    The cold binary fission of even-even 244-258Cf isotopes has been studied by taking the interacting barrier as the sum of Coulomb and proximity potential. The favorable fragment combinations are obtained from the cold valley plot (plot of driving potential vs. mass number of fragments) and by calculating the yield for charge minimized fragments. It is found that for 244,246,248Cf isotopes highest yield is for the fragments with isotope of Pb (Z = 82) as one fragment, whereas for 250Cf and 252Cf isotopes the highest yield is for the fragments with isotope of Hg (Z = 80) as one fragment. In the case of 254,256,258Cf isotopes the highest yield is for the fragments with Sn (Z = 50) as one fragment. Thus, the fragment combinations with maximum yield reveal the role of doubly magic and near doubly magic nuclei in binary fission. It is found that asymmetric splitting is favored for Cf isotopes with mass number A ≤ 250 and symmetric splitting is favored for Cf isotopes with A > 252. In the case of Cf isotope with A = 252, there is an equal probability for asymmetric and symmetric splitting. The individual yields obtained for the cold fission of 252Cf isotope are compared with the experimental data taken from the γ- γ- γ coincidences technique using Gammasphere.

  9. A carbon isotope mass balance for an anoxic marine sediment: Isotopic signatures of diagenesis

    NASA Technical Reports Server (NTRS)

    Boehme, Susan E.

    1993-01-01

    A carbon isotope mass balance was determined for the sediments of Cape Lookout Bight, NC to constrain the carbon budgets published previously. The diffusive, ebullitive and burial fluxes of sigma CO2 and CH4, as well as the carbon isotope signatures of these fluxes, were measured. The flux-weighted isotopic signature of the remineralized carbon (-18.9 plus or minus 2.7 per mil) agreed with the isotopic composition of the remineralized organic carbon determined from the particulate organic carbon (POC) delta(C-13) profiles (-19.2 plus or minus 0.2), verifying the flux and isotopic signature estimates. The measured delta(C-13) values of the sigma CO2 and CH4 diffusive fluxes were significantly different from those calculated from porewater gradients. The differences appear to be influenced by methane oxidation at the sediment-water interface, although other potential processes cannot be excluded. The isotope mass balance provides important information concerning the locations of potential diagenetic isotope effects. Specifically, the absence of downcore change in the delta(C-13) value of the POC fraction and the identical isotopic composition of the POC and the products of remineralization indicate that no isotopic fractionation is expressed during the initial breakdown of the POC, despite its isotopically heterogeneous composition.

  10. Nitrogen isotope fractionation during archaeal ammonia oxidation: Coupled estimates from isotopic measurements of ammonium and nitrite

    NASA Astrophysics Data System (ADS)

    Mooshammer, Maria; Stieglmeier, Michaela; Bayer, Barbara; Jochum, Lara; Melcher, Michael; Wanek, Wolfgang

    2014-05-01

    Ammonia-oxidizing archaea (AOA) are ubiquitous in marine and terrestrial environments and knowledge about the nitrogen (N) isotope effect associated with their ammonia oxidation activity will allow a better understanding of natural abundance isotope ratios, and therefore N transformation processes, in the environment. Here we examine the kinetic isotope effect for ammonia oxidation in a pure soil AOA culture (Ca. Nitrososphaera viennensis) and a marine AOA enrichment culture. We estimated the isotope effect from both isotopic signatures of ammonium and nitrite over the course of ammonia oxidation. Estimates of the isotope effect based on the change in the isotopic signature of ammonium give valuable insight, because these estimates are not subject to the same concerns (e.g., accumulation of an intermediate) as estimates based on isotopic measurements of nitrite. Our results show that both the pure soil AOA culture and a marine AOA enrichment culture have similar but substantial isotope effect during ammonia consumption (31-34 per mill; based on ammonium) and nitrite production (43-45 per mill; based on nitrite). The 15N fractionation factors of both cultures tested fell in the upper range of the reported isotope effects for archaeal and bacterial ammonia oxidation (10-41 per mill) or were even higher than those. The isotope fractionation for nitrite production was significantly larger than for ammonium consumption, indicating that (1) some intermediate (e.g., hydroxylamine) of ammonia oxidation accumulates, allowing for a second 15N fractionation step to be expressed, (2) a fraction of ammonia oxidized is lost via gaseous N forms (e.g., NO or N2O), which is 15N-enriched or (3) a fraction of ammonium is assimilated into AOA biomass, biomass becoming 15N-enriched. The significance of these mechanisms will be explored in more detail for the soil AOA culture, based on isotope modeling and isotopic measurements of biomass and N2O.

  11. Canadian Network for Isotopes in Precipitation (CNIP)and Isotope Climatology and Hydroclimatology in Canada

    NASA Astrophysics Data System (ADS)

    Birks, S. J.; Edwards, T. W.; Gibson, J. J.

    2002-12-01

    The distribution of stable isotopes in precipitation provides fundamental information about the partitioning of the global atmospheric water budget, and hence about key aspects of Earth's climate, that cannot be discerned using other means. Although continuing demand exists for monitoring of isotopes in precipitation to define isotopic input functions for local hydrologic studies or for calibration of isotopic indicators of paleoclimate, based on longterm averages and climatological norms, awareness is also growing of the significant value of the monthly snapshots of the precipitation isotope field provided by the IAEA/WMO Global Network for Isotopes in Precipitation and its affiliated national networks as benchmark maps of the ongoing and dynamic evolution of the global water cycle. An initiative within the Canadian Network for Isotopes in Precipitation program includes development of a spatial and temporal database incorporating Canadian data to create a gridded isotope overlay compatible with gridded pressure and flux field data from the NCAR/CDAS Re-analysis Project. This database includes interpolated fields of our current best approximations of climatological isotopic means in addition to the original monthly data for the period 1997-2000. Studies are underway to test the sensitivity of the isotope-climate signal in precipitation to changes in these parameters utilizing perturbations in local climate arising from the El Nino/Southern Oscillation (ENSO). Intriguing results have been obtained from preliminary studies incorporating pressure and flux field data for the 1997-98 El Nino with CNIP isotope overlays. The strongest climate anomalies were found during the winter following the 1997 El Nino event, consistent with the expected strengthening of the Pacific North American pattern during this period. Comparisons of the isotopic fields with climate fields illustrate the complexity and dynamic nature of isotope climate not evident in time-series of data from

  12. Oxygen Isotopes in the Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Clayton, R. N.

    2004-12-01

    Mechanisms that may account for oxygen isotope heterogeneity in meteorites on the microscopic scale do not seem adequate for explaining the similarities and differences in isotopic composition on a planetary scale. In chondrites, most of the isotopic variability can be attributed to photochemical enrichment of the two rare heavy isotopes with respect to the 16O-rich solar composition In the CO, CM, CI, and CR chondrites, an additional low-temperature aqueous alteration leads to mass-dependent further enrichment of the heavy isotopes. If the photochemical origin of the isotopic variation in chondrites is correct, then only a small fraction, represented primarily in CAIs, has the solar oxygen isotopic composition, and all other meteoritic components must have undergone photochemical processing. In addition, since the bulk isotopic compositions of the terrestrial planets and of the achondrite parent bodies are similar to those of chondrites, they too must be made of photochemically enriched matter. The photochemical reactions produce a non-equilibrium assemblage of gases, probably leading to a non-equilibrium assemblage of solids, particularly with respect to their oxidation state. These issues emphasize the importance of the measurement of oxygen isotopes in the Genesis solar wind mission. Within the Earth, oxygen isotope variations are due almost entirely to mass-dependent fractionation effects, giving a line of slope 0.52 on the three-isotope plot. The average crustal composition is 3 to 4 permil higher in delta-18O than the upper mantle. This difference is too large to be due to igneous fractionation effects alone, and reflects the larger, low-temperature isotope fractionation associated with aqueous weathering reactions at the Earth's surface. Similar effects are not observed in the intraplanetary isotopic variations in the Moon or in the parent bodies of the HED and SNC meteorites. The bulk oxygen isotopic compositions of Earth and Mars (assumed to be the SNC

  13. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, Charles G. [Pleasanton, CA

    1978-08-29

    A method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, .sup.235 UF.sub.6 is separated from a UF.sub.6 mixture by selective excitation followed by dissociative electron capture into .sup.235 UF.sub.5 - and F.

  14. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, C.G.

    1978-08-29

    Disclosed is a method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, [sup 235]UF[sub 6] is separated from a UF[sub 6] mixture by selective excitation followed by dissociative electron capture into [sup 235]UF[sub 5]- and F. 2 figs.

  15. Deconstructing nitrate isotope dynamics in aquifers

    NASA Astrophysics Data System (ADS)

    Granger, J.

    2012-12-01

    The natural abundance N and O stable isotope ratios of nitrate provide an invaluable tool to differentiate N sources to the environment, track their dispersal, and monitor their attenuation by biological transformations. The interpretation of patterns in isotope abundances relies on knowledge of the isotope ratios of the source end-members, as well as on constraints on the isotope discrimination imposed on nitrate by respective biological processes. Emergent observations from mono-culture experiments of denitrifying bacteria reveal nitrate fractionation trends that appear at odds with trends ascribed to denitrification in soils and aquifers. This discrepancy raises the possibility that additional biological N transformations may be acting in tandem with denitrification. Here, the N and O isotope enrichments associated with nitrate removal by denitrification in aquifers are posited to bear evidence of coincident biological nitrate production - from nitrification and/or from anammox. Simulations are presented from a simple time-dependent one-box model of a groundwater mass ageing that is subject to net nitrate loss by denitrification with coincident nitrate production by nitrification or anammox. Within boundary conditions characteristic of freshwater aquifers, the apparent slope of the parallel enrichments in nitrate N and O isotopes associated with net N loss to denitrification can vary in proportion to the nitrate added simultaneous by oxidative processes. Pertinent observations from nitrate plumes in suboxic to anoxic aquifers are examined to validate this premise. In this perspective, nitrate isotope distributions suggest that we may be missing important N fluxes inherent to most aquifers.

  16. Si isotope homogeneity of the solar nebula

    SciTech Connect

    Pringle, Emily A.; Savage, Paul S.; Moynier, Frédéric; Jackson, Matthew G.; Barrat, Jean-Alix E-mail: savage@levee.wustl.edu E-mail: moynier@ipgp.fr E-mail: Jean-Alix.Barrat@univ-brest.fr

    2013-12-20

    The presence or absence of variations in the mass-independent abundances of Si isotopes in bulk meteorites provides important clues concerning the evolution of the early solar system. No Si isotopic anomalies have been found within the level of analytical precision of 15 ppm in {sup 29}Si/{sup 28}Si across a wide range of inner solar system materials, including terrestrial basalts, chondrites, and achondrites. A possible exception is the angrites, which may exhibit small excesses of {sup 29}Si. However, the general absence of anomalies suggests that primitive meteorites and differentiated planetesimals formed in a reservoir that was isotopically homogenous with respect to Si. Furthermore, the lack of resolvable anomalies in the calcium-aluminum-rich inclusion measured here suggests that any nucleosynthetic anomalies in Si isotopes were erased through mixing in the solar nebula prior to the formation of refractory solids. The homogeneity exhibited by Si isotopes may have implications for the distribution of Mg isotopes in the solar nebula. Based on supernova nucleosynthetic yield calculations, the expected magnitude of heavy-isotope overabundance is larger for Si than for Mg, suggesting that any potential Mg heterogeneity, if present, exists below the 15 ppm level.

  17. Stable Isotope Evidence for Planetary Differentiation

    NASA Astrophysics Data System (ADS)

    Shahar, A.; Mao, W. L.; Schauble, E. A.; Caracas, R.; Reagan, M. M.; Gleason, A. E.

    2015-12-01

    Planetary differentiation occurred at high temperature and varying oxygen fugacity, on bodies with varying compositions and internal pressures. The specific conditions at which bodies differentiated and the chemical fingerprints left by differentiation can be investigated by measuring stable isotope ratios in natural samples. Much can be learned by combining those data with experiments that systematically investigate the chemical and physical conditions within differentiating bodies. In this talk we focus on one variable in particular that has not been well defined with respect to stable isotope fractionation: pressure. We will present new iron isotope data on how pressure affects isotope fractionation factors for a number of iron compounds relative to silicate. The processes governing iron isotope fractionation in igneous rocks have been debated extensively over the past decade. Analyses of natural samples show that iron isotopes are fractionated at both the whole rock and mineral scales. This fractionation has been interpreted to be a result of several processes including a possible signature of high pressure core formation. We have collected new high pressure synchrotron nuclear resonant inelastic x-ray scattering data from Sector 16-ID-D at the Advanced Photon Source on 57Fe enriched Fe, FeO, FeHx and Fe3C. Our data show clear trends with pressure implying that not only does pressure have an effect on the iron isotope beta factors but also a fractionation amongst the alloys. This suggests that depending on the light element in the core, there will be a different resulting signature in the iron isotope record. We will discuss the likelihood of different light elements in the core based on these results, as well as the theoretical predictions for the same phases. Finally, we will present the fractionation expected between metal and silicate at high pressure and high temperature in order to determine if core formation would indeed leave an isotopic signature in

  18. Pb isotopic heterogeneity in basaltic phenocrysts

    SciTech Connect

    Bryce, Julia G.; DePaolo, Donald J.

    2002-06-01

    The Pb isotopic compositions of phenocrystic phases in young basaltic lavas have been investigated using the Getty-DePaolo method (Getty S. J. and DePaolo D. J. [1995] Quaternary geochronology by the U-Th-Pb method. Geochim. Cosmochim. Acta 59, 3267 3272), which allows for the resolution of small isotopic differences. Phenocryst, matrix, and whole rock analyses were made on samples from the 17 Myr-old Imnaha basalts of the Columbia River Group, a zero-age MORB from the Mid-Atlantic Ridge, and a ca. 260 kyr-old tholeiite from Mount Etna. Plagioclase feldspar phenocrysts have low-(U, Th)/Pb, and in each sample the plagioclase has significantly lower 206Pb/207Pb and 208Pb/207Pb values than whole rock, matrix, and magnetite-rich separates. The Pb isotopic contrast between plagioclase and matrix/whole rock is found in three samples with varying grain sizes (0.5 2 cm for the Imnaha basalt and MORB and <1 mm for the Etna sample) from different tectonic settings, suggesting that these results are not unique. The isotopic contrasts are only slightly smaller in magnitude than the variations exhibited by whole rock samples from the region. The Imnaha basalts also have Sr isotopic heterogeneity evident only in plagioclase phenocrysts, but the MORB and Etna lavas do not. The isotopic heterogeneities reflect magma mixing, and indicate that isotopically diverse magmas were mixed together just prior to eruption. The results reinforce indications from melt inclusion studies that magma source region isotopic heterogeneities have large amplitudes at short length scales, and that the isotopic variations imparted to the magmas are not entirely homogenized during segregation and transport processes.

  19. Stable isotope composition of Earth's large lakes

    NASA Astrophysics Data System (ADS)

    Jasechko, S.; Gibson, J. J.; YI, Y.; Birks, S. J.; Sharp, Z. D.

    2011-12-01

    Lakes cover about three percent of Earth's continental area. Large lakes can significantly influence lake shore and regional climates by increasing specific humidity during evaporation and by moderating air temperatures. Stable isotopes of oxygen and hydrogen can be used to quantify lake evaporation, providing a supplementary and often cost-advantageous alternative to conventional hydrologic approaches that require over lake monitoring. Further, stable isotopes in lake sediments are an established tool in paleolimnology; however, interpreting changes to a lake's past isotope composition requires a comprehensive understanding of contemporary controls. Here, δ18O and δ2H values of water in modern lakes exceeding roughly five hundred square kilometres are compiled (n > 35). Voluminous and seasonally mixed lakes - such as the North American Great Lakes - have the most homogenous stable isotope compositions, while perennially-stratified and shallow lakes show greater variability. A rudimentary stable isotope mass balance is used to assess evaporation fluxes from large lakes on Earth. The approach taken simultaneously constrains evaporation outputs for both oxygen and hydrogen stable isotopes by accounting for lake effects on the overlying atmosphere. Model development highlights important considerations such as isotopic stratification (Tanganyika), disequilibrium isotopic mass balances (Baikal), and non-steady hydrologic balances. Further, the isotope composition of Earth's continental surface water reservoir is calculated. This value - weighted to volume - is δ18O = -7.5±1.7 per mille relative to standard mean ocean water. The compiled data may be a useful tracer of continental evaporate in global atmospheric water cycle studies and could be coupled to climate models capable of incorporating oxygen-18 and deuterium tracers to improve or validate calculations of lake effects on regional water cycling.

  20. Isotopic CO2 Instrumentation for UAV Measurements

    NASA Astrophysics Data System (ADS)

    Gomez, A.; Silver, J.

    2013-12-01

    Carbon dioxide is the largest component of anthroprogenic green house gas emissions. Knowing atmospheric 13CO2/12CO2 ratios precisely is important for understanding biogenic and anthroprogenic sources and sinks for carbon. Instrumentation mounted on UAV aircraft would enable important spatial isotopic CO2 information. However, current isotopic CO2 instrumentation have unfavorable attributes for UAV use, such as high power requirements, high cost, high weight, and large size. Here we present the early development of a compact isotopic CO2 instrument that is designed to nullify effects of pressure, temperature and moisture, and will ultimately be suitable for UAV deployment.

  1. Isotopic Fractionation of Selenium Oxyanions in Wetlands

    NASA Astrophysics Data System (ADS)

    Clark, S. K.; Johnson, T. M.

    2004-05-01

    As oxic surface waters pass through aquatic macrophytes and over anoxic sediments in wetlands and lakes, the dissolved Se load often decreases; and, Se isotope ratio measurements can provide information about the mechanisms involved. Previous work on microbially induced isotopic fractionation of Se oxyanions under nearly natural conditions using wetland sediments shows consistent Se isotopic shifts during reduction of Se(VI) and Se(IV) to insoluble Se(0). However, previous isotopic studies of total dissolved selenium in wetlands found little to no isotopic shift as dissolved selenium concentrations decreased. This suggests that plant/algal uptake, followed by deposition and degradation, is the primary route of Se transfer into sediments. However, it is possible that the effective isotopic fractionation between Se in the surface water and Se deposited into sediments is somehow much less than the fractionation induced by the reduction reaction, or that cycling of organically bound Se is involved. In this study, we report Se isotope data for Se(VI), Se(IV) and total dissolved Se, Se(T), in surface waters from three wetland/lake sites: Sweitzer Lake, CO; 33-Mile Reservoir, WY; and, a small pond adjacent to Benton Lake, MT. We isolated Se(IV) via hydride generation, and Se(VI) via ion exchange. Se(T), including any organic components, was also analyzed. Isotope analysis was performed on an Isoprobe MC-ICPMS, using a method modified from that of Rouxel et al. (2002). We used the 82Se + 74Se double spike approach, and spiked samples before species separation. Our results for all three locations indicate similar trends in concentration changes and isotopic shifts between the inflow and outflow waters. Se(T) concentrations decrease by 45-70%, and Se(VI) concentrations decrease by 60-90%, whereas Se(IV) concentrations increase by 60-150%. Concomitant 80Se/76Se shifts are +0.5-0.8‰ for Se(T); -0.1-0.5‰ for Se(VI); and +0.4-6.5‰ for Se(IV). These data provide greater

  2. Theory of the Helium Isotope Shift

    SciTech Connect

    Pachucki, Krzysztof; Yerokhin, V. A.

    2015-09-15

    Theory of the isotope shift of the centroid energies of light few-electron atoms is reviewed. Numerical results are presented for the isotope shift of the 2{sup 3}P-2{sup 3}S and 2{sup 1}S-2{sup 3}S transition energies of {sup 3}He and {sup 4}He. By comparing theoretical predictions for the isotope shift with the experimental results, the difference of the squares of the nuclear charge radii of {sup 3}He and {sup 4}He, δR{sup 2}, is determined with high accuracy.

  3. Isotope effects on desorption kinetics of hydrogen isotopes implanted into stainless steel by glow discharge

    SciTech Connect

    Matsuyama, M.; Kondo, M.; Noda, N.; Tanaka, M.; Nishimura, K.

    2015-03-15

    In a fusion device the control of fuel particles implies to know the desorption rate of hydrogen isotopes by the plasma-facing materials. In this paper desorption kinetics of hydrogen isotopes implanted into type 316L stainless steel by glow discharge have been studied by experiment and numerical calculation. The temperature of a maximum desorption rate depends on glow discharge time and heating rate. Desorption spectra observed under various experimental conditions have been successfully reproduced by numerical simulations that are based on a diffusion-limited process. It is suggested, therefore, that desorption rate of a hydrogen isotope implanted into the stainless steel is limited by a diffusion process of hydrogen isotope atoms in bulk. Furthermore, small isotope effects were observed for the diffusion process of hydrogen isotope atoms. (authors)

  4. Short course on St-02 applications of isotope dilutions and isotopic measurements

    SciTech Connect

    Miller, P.

    1998-01-05

    This short course includes information on these topics and subtopics: (I) Nuclear Properties: (A) Historic roots; (B) Nomenclature; (C) Nuclear Stability and abundance; (D) Uses of isotopic techniques; (II) Instrumentation: (A) Sources; (B) Mass resolving elements; (C) Detectors; (III) Making Isotopic Measurements by ICP-MS: (A) Deadtime Correction; (B) Mass Discrimination; (C) Signal /Noise considerations; (IV) Applications and examples: (A) Isotope dilution; (B) Double Spike; (C) Biological Application; (D) Environmental Application; (E) Geological.

  5. Synthetic isotope mixtures for the calibration of isotope amount ratio measurements of carbon

    NASA Astrophysics Data System (ADS)

    Russe, K.; Valkiers, S.; Taylor, P. D. P.

    2004-07-01

    Synthetic isotope mixtures for the calibration of carbon isotope amount ratio measurements have been prepared by mixing carbon tetrafluoride highly enriched in 13C with carbon tetrafluoride depleted in 13C. Mixing procedures based on volumetry and gravimetry are described. The mixtures served as primary measurement standards for the calibration of isotope amount ratio measurements of the Isotopic Reference Materials PEF1, NBS22 and USGS24. Thus SI-traceable measurements of absolute carbon isotope amount ratios have been performed for the first time without any hypothesis needed for a correction of oxygen isotope abundances, such as is the case for measurements on carbon dioxide. As a result, "absolute" carbon isotope amount ratios determined via carbon tetrafluoride have smaller uncertainties than those published for carbon dioxide. From the measurements of the Reference Materials concerned, the absolute carbon isotope amount ratio of Vienna Pee Dee Belemnite (VPDB)--the hypothetical material upon which the scale for relative carbon isotope ratio measurements is based--was calculated to be R13(VPDB) = (11 101 +/- 16) × 10-6.

  6. Isotope pattern deconvolution as rising tool for isotope tracer studies in environmental research

    NASA Astrophysics Data System (ADS)

    Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

    2014-05-01

    During the last decade stable isotope tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' isotope tracers caused by the natural variation of isotopes, the intentional introduction of 'extrinsic' enriched stable isotope tracers into biological systems has gained significant interest. Hereby the induced change in the natural isotopic composition of an element allows amongst others for studying the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of isotope (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some isotope systems like the natural Sr isotopic system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the isotope dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. Isotope pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike isotope dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the isotope pattern in a spiked sample without knowing the quantities of enriched isotope tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer

  7. Evaluating chlorine isotope effects from isotope ratios and mass spectra of polychlorinated molecules.

    PubMed

    Elsner, Martin; Hunkeler, Daniel

    2008-06-15

    Compound-specific chlorine isotope analysis receives much interest to assess the fate of chlorinated hydrocarbons in contaminated environments. This paper provides a theoretical basis to calculate isotope ratios and quantify isotope fractionation from ion-current ratios of molecular- and fragment-ion multiplets. Because both (35)Cl and (37)Cl are of high abundance, polychlorinated hydrocarbons consist of molecules containing different numbers of (37)Cl denoted as isotopologues. We show that, during reactions, the changes in isotopologue ratios are proportional to changes in the isotope ratio assuming a nonselective isotope distribution in the initial compound. This proportionality extents even to fragments formed in the ion source of a mass spectrometer such as C 2Cl 2 (double dechlorinated fragment of perchloroethylene, PCE). Fractionation factors and kinetic isotope effects (KIE) may, therefore, be evaluated from isotope, isotopologue or even fragment ratios according to conventional simple equations. The proportionality is exact with symmetric molecules such as dichloroethylene (DCE) and PCE, whereas it is approximately true with molecules containing nonreactive positions such as trichloroethylene (TCE). If in the latter case isotope ratios are derived from dechlorinated fragments, e.g., C 2HCl 2, it is important that fragmentation in the ion source affect all molecular positions alike, as otherwise isotopic changes in reactive positions may be underrepresented. PMID:18484745

  8. Variation in Atmospheric Helium Isotopes

    NASA Astrophysics Data System (ADS)

    Mabry, J. C.; Marty, B.; Burnard, P.; Blard, P.

    2010-12-01

    Anthropogenic activity such as oil and gas exploitation releases crustal helium, which has excess 4He compared to atmospheric helium. This may give rise to both spatial and temporal variations in the atmospheric 3He/4He. Helium is present in trace quantities in the air (5 ppm) and has a very low ratio (3He/4Heair = 1.38 x 10-6), consequently high precision measurements of atmospheric He presents a significant analytical challenge. Recent work by Sano et al. [1] has endeavored to experimentally quantify these potential variations in the atmospheric 3He/4He by measuring the helium isotopes from air samples collected around the globe and from samples of ancient trapped atmosphere. Their results indicate an increase in the atmospheric 3He/4He from northern to southern latitudes of the order 2 - 4 ‰, which they attribute to greater use of fossil fuels in the northern hemisphere. However, since most of their data points overlap at the 2-3 ‰ (2σ) level, additional measurements (with increased precision if possible) are needed. We have constructed an automated extraction line dedicated to measuring He in samples of air which can rapidly switch between measuring aliquots of sample with standards. It additionally features an adjustable bellows on the sample aliquot volume that enables us to adjust the size of a sample aliquot to precisely match the standard, eliminating biases arising from nonlinear pressure effects in the mass spectrometer. The measurements are made using a Helix SFT multi-collector mass spectrometer. At present, repeat measurements of 3He/4He from our standard (purified air) have a reproducibility of 2‰ (2σ), while measurements of local (Nancy, France) air samples have a reproducibility of 3He/4He of 3‰ (2σ), which are at a similar level to the uncertainties reported by Sano. Modifications are underway to improve 3He measurements which are the principal source of error. We have collected atmospheric samples from around the globe over a wide

  9. The seawater Sr isotopic evolution

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. B.; Gorokhov, I. M.; Semikhatov, M. A.; Maslov, A. V.; Krupenin, M. T.; Melnikov, N. N.

    2003-04-01

    Progress toward a reconstruction of the 87Sr/86Sr variations in Proterozoic seawater is still deficient compared to the Phanerozoic. There is no universally recognized curve, and some of its versions are in conflict. The construction of a reference curve should be based on: (1) the study of several thick carbonate-bearing successions within single paleobasin, (2) the reliable isotope dating of these successions, (3) the geochemical screening of least-altered carbonate samples, (4) a selective dissolution of samples to enrich them in primary carbonate generations. This approach was applied to study Late Proterozoic marine carbonate successions of the South Urals and East Siberia. Three comprehensive fragments of 87Sr/86Sr seawater curve were obtained: (1) the descending trend from 0.70562-0.70596 to 0.70519-0.70523 at 1050-1000 Ma, (2) the ascending trend from 0.70525-0.70535 to 0.70611-70625 at 850-750 Ma, and (3) the area of minor fluctuations from 0.70540 to 0.70610 at 680-660 Ma. The Sr- and C-isotope data for the South Urals allow us to revise the current stratigraphic correlations and impose some constraints on the age of the classic Upper Proterozoic successions of North Canada (Shaler Gr) and Svalbard (Akademikerbreen Gr): (1) the carbonate formations in middle part of the Shaler Gr appear to have been deposited after 800 Ma, (2) the rate of sedimentation of the Akademikerbreen succession was likely to be higher than it was proposed. The data from East Siberia postulate predominance of the low 87Sr/86Sr ratio during culmination stage of the Grenville orogenic cycle and decrease in this ratio in post-Grenvillian ocean. This fact markedly distinguishes the Grenville orogeny from the Pan-African orogeny which resulted in rise of seawater 87Sr/86Sr ratio up to 0.7085. The following factors were responsible for the low 87Sr/86Sr ratio in Grenvillian and post-Grenvillian oceans: a high role of mantle rocks in the exhumed orogens, a sea-level rise and partial

  10. Carbon isotope effects associated with autotrophic acetogenesis

    USGS Publications Warehouse

    Gelwicks, J.T.; Risatti, J.B.; Hayes, J.M.

    1989-01-01

    The carbon kinetic isotope effects associated with synthesis of acetate from CO2 and H2 during autotrophic growth of Acetobacterium woodii at 30??C have been measured by isotopic analyses of CO2, methyl-carbon, and total acetate. Closed systems allowing construction of complete mass balances at varying stages of growth were utilized, and the effects of the partitioning of carbon between CO2 and HCO3- were taken into account. For the overall reaction, total carbonate ??? total acetate, isotope effects measured in replicate experiments ranged from -59.0 ?? 0.9% to - 57.2 ?? 2.3z%. Taking into account all measurements, the weighted mean and standard deviation are -58.6 ?? 0.7%. There is no evidence for intramolecular ordering in the acetate. The carbon isotopic composition of sedimentary acetate, otherwise expected to be near that of sedimentary organic carbon, is likely to be depleted in environments in which autotrophic acetogenesis is occurring. ?? 1989.

  11. Applications of stable isotopes in clinical pharmacology

    PubMed Central

    Schellekens, Reinout C A; Stellaard, Frans; Woerdenbag, Herman J; Frijlink, Henderik W; Kosterink, Jos G W

    2011-01-01

    This review aims to present an overview of the application of stable isotope technology in clinical pharmacology. Three main categories of stable isotope technology can be distinguished in clinical pharmacology. Firstly, it is applied in the assessment of drug pharmacology to determine the pharmacokinetic profile or mode of action of a drug substance. Secondly, stable isotopes may be used for the assessment of drug products or drug delivery systems by determination of parameters such as the bioavailability or the release profile. Thirdly, patients may be assessed in relation to patient-specific drug treatment; this concept is often called personalized medicine. In this article, the application of stable isotope technology in the aforementioned three areas is reviewed, with emphasis on developments over the past 25 years. The applications are illustrated with examples from clinical studies in humans. PMID:21801197

  12. Water isotope systematics: Improving our palaeoclimate interpretations

    NASA Astrophysics Data System (ADS)

    Jones, M. D.; Dee, S.; Anderson, L.; Baker, A.; Bowen, G.; Noone, D. C.

    2016-01-01

    The stable isotopes of oxygen and hydrogen, measured in a variety of archives, are widely used proxies in Quaternary Science. Understanding the processes that control δ18O change have long been a focus of research (e.g. Shackleton and Opdyke, 1973; Talbot, 1990; Leng, 2006). Both the dynamics of water isotope cycling and the appropriate interpretation of geological water-isotope proxy time series remain subjects of active research and debate. It is clear that achieving a complete understanding of the isotope systematics for any given archive type, and ideally each individual archive, is vital if these palaeo-data are to be used to their full potential, including comparison with climate model experiments of the past. Combining information from modern monitoring and process studies, climate models, and proxy data is crucial for improving our statistical constraints on reconstructions of past climate variability.

  13. Isotope effects of hydrogen and atom tunnelling

    NASA Astrophysics Data System (ADS)

    Buchachenko, A. L.; Pliss, E. M.

    2016-06-01

    The abnormally high mass-dependent isotope effects in liquid-phase hydrogen (deuterium) atom transfer reactions, which are customarily regarded as quantum effects, are actually the products of two classical effects, namely, kinetic and thermodynamic ones. The former is determined by the rate constants for atom transfer and the latter is caused by nonbonded (or noncovalent) isotope effects in the solvation of protiated and deuterated reacting molecules. This product can mimic the large isotope effects that are usually attributed to tunnelling. In enzymatic reactions, tunnelling is of particular interest; its existence characterizes an enzyme as a rigid molecular machine in which the residence time of reactants on the reaction coordinate exceeds the waiting time for the tunnelling event. The magnitude of isotope effect becomes a characteristic parameter of the internal dynamics of the enzyme catalytic site. The bibliography includes 61 references.

  14. The Most Useful Actinide Isotope: Americium-241.

    ERIC Educational Resources Information Center

    Navratil, James D.; And Others

    1990-01-01

    Reviewed is the discovery, nuclear and chemical properties, and uses of an isotope of Americium (Am-241). Production and separation techniques used in industry are emphasized. Processes are illustrated in flow sheets. (CW)

  15. Atomic vapor laser isotope separation process

    DOEpatents

    Wyeth, R.W.; Paisner, J.A.; Story, T.

    1990-08-21

    A laser spectroscopy system is utilized in an atomic vapor laser isotope separation process. The system determines spectral components of an atomic vapor utilizing a laser heterodyne technique. 23 figs.

  16. Possible application of laser isotope separation

    NASA Technical Reports Server (NTRS)

    Delionback, L. M.

    1975-01-01

    The laser isotope separation process is described and its special economic features discussed. These features are its low cost electric power operation, capital investment costs, and the costs of process materials.

  17. The Palladium Isotopic Composition in Iron Meteorites

    NASA Technical Reports Server (NTRS)

    Chen, J. H.; Papanastassiou, D. A.

    2005-01-01

    Ru, Mo and Pd are very useful indicators for the identification of nucleosynthetic components. We have developed techniques for Pd isotopes, in an effort to check the extent of isotopic effects in this mass region and for a Pt-group element which is less refractory than Ru. Stable Pd isotopes are produced by the process only (102Pd), the s-process only (104Pd), the process only (Pd-110) and by both the r- and s-processes (Pd-105, Pd-106, Pd-108). Kelly and Wasserburg reported a hint of a shift in 102Pd (approx. 25(epsilon)u; 1(epsilon)u (triple bonds) 0.01%) in Santa Clara. Earlier searches for Mo and Ru isotopic anomalies were either positive or negative.

  18. Stable isotope investigations of chlorinated aliphatic hydrocarbons.

    SciTech Connect

    Abrajano, T.; Heraty, L. J.; Holt, B. D.; Huang, L.; Sturchio, N. C.

    1999-06-01

    Stable isotope ratio measurements for carbon (C) and chlorine (Cl) can be used to elucidate the processes affecting transformation and transportation of chlorinated aliphatic hydrocarbons (CAHs) in the environment. Methods recently developed in our laboratory for isotopic analysis of CAHs have been applied to laboratory measurements of the kinetic isotope effects associated with aerobic degradation of dichloromethane (DCM) and with both anaerobic and aerobic cometabolic degradation of trichlomethene (TCE) in batch and column microbial cultures. These experimental determinations of fractionation factors are crucial for understanding the behavior of CAHs in complex natural systems, where the extent of biotransformation can be masked by dispersion and volatilization. We have also performed laboratory investigations of kinetic isotope effects accompanying evaporation of CAHs, as well as field investigations of natural attenuation and in situ remediation of CAHs in a number of contaminated shallow aquifers at sites operated by the federal government and the private sector.

  19. Quantification of isotopic turnover in agricultural systems

    NASA Astrophysics Data System (ADS)

    Braun, A.; Auerswald, K.; Schnyder, H.

    2012-04-01

    The isotopic turnover, which is a proxy for the metabolic rate, is gaining scientific importance. It is quantified for an increasing range of organisms, from microorganisms over plants to animals including agricultural livestock. Additionally, the isotopic turnover is analyzed on different scales, from organs to organisms to ecosystems and even to the biosphere. In particular, the quantification of the isotopic turnover of specific tissues within the same organism, e.g. organs like liver and muscle and products like milk and faeces, has brought new insights to improve understanding of nutrient cycles and fluxes, respectively. Thus, the knowledge of isotopic turnover is important in many areas, including physiology, e.g. milk synthesis, ecology, e.g. soil retention time of water, and medical science, e.g. cancer diagnosis. So far, the isotopic turnover is quantified by applying time, cost and expertise intensive tracer experiments. Usually, this comprises two isotopic equilibration periods. A first equilibration period with a constant isotopic input signal is followed by a second equilibration period with a distinct constant isotopic input signal. This yields a smooth signal change from the first to the second signal in the object under consideration. This approach reveals at least three major problems. (i) The input signals must be controlled isotopically, which is almost impossible in many realistic cases like free ranging animals. (ii) Both equilibration periods may be very long, especially when the turnover rate of the object under consideration is very slow, which aggravates the first problem. (iii) The detection of small or slow pools is improved by large isotopic signal changes, but large isotopic changes also involve a considerable change in the input material; e.g. animal studies are usually carried out as diet-switch experiments, where the diet is switched between C3 and C4 plants, since C3 and C4 plants differ strongly in their isotopic signal. The

  20. Carbon isotopic fractionation in heterotrophic microbial metabolism

    NASA Technical Reports Server (NTRS)

    Blair, N.; Leu, A.; Munoz, E.; Olsen, J.; Kwong, E.; Des Marais, D.

    1985-01-01

    Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4 percent depleted in C-13 relative to the glucose used as the carbon source, whereas the acetate was 12.3 percent enriched in C-13. The acetate C-13 enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6 percent depleted in C-13, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7 percent, respectively. Aspartic and glutamic acids were -1.6 and +2.7 percent, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.

  1. Zinc Isotope Anomalies in bulk Chondrites

    NASA Astrophysics Data System (ADS)

    Savage, P. S.; Boyet, M.; Moynier, F.

    2014-09-01

    This study is the first to demonstrate that Zn isotope anomalies are present in bulk primitive meteorites, consistent with the injection of material derived from a neutron-rich supernova source into the solar nebula.

  2. Barium Isotopes in Single Presolar Grains

    NASA Technical Reports Server (NTRS)

    Pellin, M. J.; Davis, A. M.; Savina, M. R.; Kashiv, Y.; Clayton, R. N.; Lewis, R. S.; Amari, S.

    2001-01-01

    Barium isotopic compositions of single presolar grains were measured by laser ablation laser resonant ionization mass spectrometry and the implications of the data for stellar processes are discussed. Additional information is contained in the original extended abstract.

  3. Carbon isotopic fractionation in heterotrophic microbial metabolism.

    PubMed Central

    Blair, N; Leu, A; Muñoz, E; Olsen, J; Kwong, E; Des Marais, D

    1985-01-01

    Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4% depleted in 13C relative to the glucose used as the carbon source, whereas the acetate was 12.3% enriched in 13C. The acetate 13C enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6% depleted in 13C, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7%, respectively. Aspartic and glutamic acids were -1.6 and +2.7%, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle. PMID:2867741

  4. Mercury Isotopes in Earth and Environmental Sciences

    NASA Astrophysics Data System (ADS)

    Blum, Joel D.; Sherman, Laura S.; Johnson, Marcus W.

    2014-05-01

    Virtually all biotic, dark abiotic, and photochemical transformations of mercury (Hg) produce Hg isotope fractionation, which can be either mass dependent (MDF) or mass independent (MIF). The largest range in MDF is observed among geological materials and rainfall impacted by anthropogenic sources. The largest positive MIF of Hg isotopes (odd-mass excess) is caused by photochemical degradation of methylmercury in water. This signature is retained through the food web and measured in all freshwater and marine fish. The largest negative MIF of Hg isotopes (odd-mass deficit) is caused by photochemical reduction of inorganic Hg and has been observed in Arctic snow and plant foliage. Ratios of MDF to MIF and ratios of 199Hg MIF to 201Hg MIF are often diagnostic of biogeochemical reaction pathways. More than a decade of research demonstrates that Hg isotopes can be used to trace sources, biogeochemical cycling, and reactions involving Hg in the environment.

  5. Nucleosynthesis and the Isotopic Composition of Stardust

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. M.

    1997-01-01

    Various components have been isolated from carbonaceous meteorites with an isotopically anomalous elemental composition. Several of these are generally thought to represent stardust containing a nucleosynthetic record of their birthsites. This paper discusses the expected isotopic composition of stardust based upon astronomical observations and theoretical studies of their birthsites: red giants and supergiants, planetary nebulae, C-rich Wolf-Rayet stars, novae and supernovae. Analyzing the stardust budget, it is concluded that about 15% of the elements will be locked up in stardust components in the interstellar medium. This stardust will be isotopically heterogenous on an individual grain basis by factors ranging from 2 to several orders of magnitude. Since comets may have preserved a relatively unprocessed record of the stardust entering the solar nebula, isotopic studies of returned comet samples may provide valuable information on the nucleosynthetic processes taking place in the interiors of stars and the elemental evolution of the Milky Way.

  6. Carbon isotope effects associated with autotrophic acetogenesis.

    PubMed

    Gelwicks, J T; Risatti, J B; Hayes, J M

    1989-01-01

    The carbon kinetic isotope effects associated with synthesis of acetate from CO2 and H2 during autotrophic growth of Acetobacterium woodii at 30 degrees C have been measured by isotopic analyses of CO2, methyl-carbon, and total acetate. Closed systems allowing construction of complete mass balances at varying stages of growth were utilized, and the effects of the partitioning of carbon between CO2 and HCO3- were taken account. For the overall reaction, total carbonate --> total acetate, isotope effects measured in replicate experiments ranged from -59.0 +/- 0.9% to -57.2 +/- 2.3%. Taking into account all measurements, the weighted mean and standard deviation are -58.6 +/- 0.7%. There is no evidence for intramolecular ordering in the acetate. The carbon isotopic composition of sedimentary acetate, otherwise expected to be near that of sedimentary organic carbon, is likely to be depleted in environments in which autotrophic acetogenesis is occurring. PMID:11542159

  7. Carbon isotope effects associated with autotrophic acetogenesis

    NASA Technical Reports Server (NTRS)

    Gelwicks, J. T.; Risatti, J. B.; Hayes, J. M.

    1989-01-01

    The carbon kinetic isotope effects associated with synthesis of acetate from CO2 and H2 during autotrophic growth of Acetobacterium woodii at 30 degrees C have been measured by isotopic analyses of CO2, methyl-carbon, and total acetate. Closed systems allowing construction of complete mass balances at varying stages of growth were utilized, and the effects of the partitioning of carbon between CO2 and HCO3- were taken account. For the overall reaction, total carbonate --> total acetate, isotope effects measured in replicate experiments ranged from -59.0 +/- 0.9% to -57.2 +/- 2.3%. Taking into account all measurements, the weighted mean and standard deviation are -58.6 +/- 0.7%. There is no evidence for intramolecular ordering in the acetate. The carbon isotopic composition of sedimentary acetate, otherwise expected to be near that of sedimentary organic carbon, is likely to be depleted in environments in which autotrophic acetogenesis is occurring.

  8. Carbon isotopic fractionation in heterotrophic microbial metabolism

    SciTech Connect

    Blair, N.; Leu, A.; Munoz, E.; Olsen, J.; Kwong, E.; Des Marais, D.

    1985-10-01

    Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4 percent depleted in C-13 relative to the glucose used as the carbon source, whereas the acetate was 12.3 percent enriched in C-13. The acetate C-13 enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6 percent depleted in C-13, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7 percent, respectively. Aspartic and glutamic acids were -1.6 and +2.7 percent, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle. 38 references.

  9. Photodisintegration of the isotope {sup 116}Cd

    SciTech Connect

    Belyshev, S. S.; Ishkhanov, B. S.; Orlin, V. N.; Stopani, K. A.; Khankin, V. V.; Shvedunov, N. V.

    2013-08-15

    The results obtained by measuring the yields of photodisintegration of the isotope {sup 116}Cd irradiated with bremsstrahlung photons whose spectrum had an endpoint energy of 55 MeV are presented and compared with the results of theoretical calculations.

  10. Magnesium isotopic composition of the mantle

    NASA Astrophysics Data System (ADS)

    Teng, F.; Li, W.; Ke, S.; Marty, B.; Huang, S.; Dauphas, N.; Wu, F.; Helz, R. L.

    2009-12-01

    Studies of Mg isotopic composition of the Earth not only are important for understanding its geochemistry but also can shed light on the accretion history of the Earth as well as the evolution of the Earth-Moon system. However, to date, the Mg isotopic composition of the Earth is still poorly constrained and highly debated. There is uncertainty in the magnitude of Mg isotope fractionation at mantle temperatures and whether the Earth has a chondritic Mg isotopic composition or not. To constrain further the Mg isotopic composition of the mantle and investigate the behavior of Mg isotopes during igneous differentiation, we report >200 high-precision (δ26Mg < 0.1‰, 2SD) analyses of Mg isotopes on 1) global mid-ocean ridge basalts covering major ridge segments of the world and spanning a broad range in latitudes, chemical and radiogenic isotopic compositions; 2) ocean island basalts from Hawaiian (Koolau, Kilauea and Loihi) and French Polynesian volcanoes (Society island and Cook Austral chain); 3) olivine grains from Hawaiian volcanoes (Kilauea, Koolau and Loihi) and 4) peridotite xenoliths from Australia, China, France, Tanzania and USA. Global oceanic basalts and peridotite xenoliths have a limited (<0.2 ‰) variation in Mg isotopic composition, with an average δ26Mg = -0.25 relative to DSM3. Olivines from Hawaiian lavas have δ26Mg ranging from -0.43 to +0.03, with most having compositions identical to basalts and peridotites. Therefore, the mantle’s δ26Mg value is estimated to be ~ -0.25 ± 0.1 (2SD), different from that reported by Wiechert and Halliday (2007; δ26Mg = ~ 0) but similar to more recent studies (δ26Mg = -0.27 to -0.33) (Teng et al. 2007; Handler et al. 2009; Yang et al., 2009). Moreover, we suggest the Earth, as represented by the mantle, has a Mg isotopic composition similar to chondrites (δ26Mg = ~-0.33). The need for a model such as that of Wiechert and Halliday (2007) that involves sorting of chondrules and calcium

  11. Isotopic fractionation of zinc in tektites

    NASA Astrophysics Data System (ADS)

    Moynier, Frederic; Beck, Pierre; Jourdan, Fred; Yin, Qing-Zhu; Reimold, Uwe; Koeberl, Christian

    2009-01-01

    Tektites are terrestrial natural glasses produced during a hypervelocity impact of an extraterrestrial projectile onto the Earth's surface. The similarity between the chemical and isotopic compositions of tektites and terrestrial upper continental crust implies that the tektites formed by fusion of such target rock. Tektites are among the driest rocks on Earth. Although volatilization at high temperature may have caused this extreme dryness, the exact mechanism of the water loss and the behavior of other volatile species during tektite formation are still debated. Volatilization can fractionate isotopes, therefore, comparing the isotope composition of volatile elements in tektites with that of their source rocks may help to understand the physical conditions during tektite formation. For this study, we have measured the Zn isotopic composition of 20 tektites from four different strewn fields. Almost all samples are enriched in heavy isotopes of Zn compared to the upper continental crust. On average, the different groups of tektites are isotopically distinct (listed from the isotopically lightest to the heaviest): Muong-Nong type indochinites ( δ66/64Zn = 0.61 ± 0.30‰); North American bediasites ( δ66/64Zn = 1.61 ± 0.49‰); Ivory Coast tektites ( δ66/64Zn = 1.66 ± 0.18‰); the Australasian tektites (others than the Muong Nong-type indochinites) ( δ66/64Zn = 1.84 ± 0.42‰); and Central European moldavites ( δ66/64Zn = 2.04 ± 0.19‰). These results are contrasted with a narrow range of δ66/64Zn = 0-0.7‰ for a diverse spectrum of upper continental crust materials. The elemental abundance of Zn is negatively correlated with δ66/64Zn, which may reflect that isotopic fractionation occurred by evaporation during the heating event upon tektite formation. Simple Rayleigh distillation predicts isotopic fractionations much larger than what is actually observed, therefore, such a model cannot account for the observed Zn isotope fractionation in tektites. We

  12. Sulfur Isotope Effects of Dissimilatory Sulfite Reductase

    PubMed Central

    Leavitt, William D.; Bradley, Alexander S.; Santos, André A.; Pereira, Inês A. C.; Johnston, David T.

    2015-01-01

    The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major (34S/32S) and minor (33S/32S, 36S/32S) sulfur isotope fractionations imparted by a central enzyme in the energy metabolism of sulfate reducers, dissimilatory sulfite reductase (DsrAB). Results from in vitro sulfite reduction experiments allow us to calculate the in vitro DsrAB isotope effect in 34S/32S (hereafter, 34εDsrAB) to be 15.3 ± 2‰, 2σ. The accompanying minor isotope effect in 33S, described as 33λDsrAB, is calculated to be 0.5150 ± 0.0012, 2σ. These observations facilitate a rigorous evaluation of the isotopic fractionation associated with the dissimilatory MSR pathway, as well as of the environmental variables that govern the overall magnitude of fractionation by natural communities of sulfate reducers. The isotope effect induced by DsrAB upon sulfite reduction is a factor of 0.3–0.6 times prior indirect estimates, which have ranged from 25 to 53‰ in 34εDsrAB. The minor isotope fractionation observed from DsrAB is consistent with a kinetic or equilibrium effect. Our in vitro constraints on the magnitude of 34εDsrAB is similar to the median value of experimental observations compiled from all known published work, where 34εr−p = 16.1‰ (r–p indicates reactant vs. product, n = 648). This value closely matches those of MSR operating at high sulfate reduction rates in both laboratory chemostat experiments (34εSO4−H2S =  17.3 ± 1.5‰, 2σ) and in modern marine sediments (34εSO4−H2S =  17.3 ± 3.8‰). Targeting the direct isotopic consequences of a specific enzymatic processes is a fundamental step toward a biochemical foundation for reinterpreting the biogeochemical and geobiological sulfur isotope records in

  13. Diffusive Fractionation of Lithium Isotopes in Olivine

    NASA Astrophysics Data System (ADS)

    Homolova, V.; Richter, F. M.; Watson, E. B.; Chaussidon, M.

    2014-12-01

    Systematic lithium isotope variations along concentration gradients found in olivine and pyroxene grains from terrestrial, lunar and martian rocks have been attributed to diffusive isotopic fractionation [Beck et al., 2006; Tang et al., 2007]. In some cases, these isotopic excursions are so large that a single grain may display isotopic variability that spans almost the entire range of documented terrestrial values [Jeffcoate et al., 2007]. In this study, we present the results of experiments to examine diffusive isotopic fractionation of lithium in olivine. The experiments comprised crystallographically oriented slabs of San Carlos olivine juxtaposed with either spodumene powder or a lithium rich pyroxene crystal. Experiments were conducted at 1 GPa and 0.1MPa over a temperature range of 1000 to 1125⁰C. Oxygen fugacity in the 0.1MPa experiments was controlled using the wustite-magnetite and nickel-nickel oxide solid buffer assemblages. Lithium concentrations generally decrease smoothly away from the edges of the grains; however, experiments involving diffusion parallel to the a-axis consistently show peculiar wavy or segmented concentration profiles. Lithium diffusivity parallel to the c-axis is on the order of 1E-14m2/s at 1100⁰C. The diffusivity parallel to the c-axis is more than an order of magnitude faster than diffusion parallel to the b-axis and correlates positively with oxygen fugacity. The lithium isotopic composition, δ7Li = 1000‰ * ((δ7Lisample- δ7Ligrain center)/ δ7Ligrain center), shows a decrease away from the edge of the grain to a minimum value (up to 70‰ lighter) and then an abrupt increase back to the initial isotopic composition of the olivine grain. This isotopic profile is similar to those found in natural grains and an experimental study on diffusive fractionation of lithium isotopes in pyroxene [Richter et al., 2014]. Results from the present study are modeled using the approach of Dohmen et al. [2010], which assumes lithium

  14. Sulfur Isotope Effects of Dissimilatory Sulfite Reductase.

    PubMed

    Leavitt, William D; Bradley, Alexander S; Santos, André A; Pereira, Inês A C; Johnston, David T

    2015-01-01

    The precise interpretation of environmental sulfur isotope records requires a quantitative understanding of the biochemical controls on sulfur isotope fractionation by the principle isotope-fractionating process within the S cycle, microbial sulfate reduction (MSR). Here we provide the only direct observation of the major ((34)S/(32)S) and minor ((33)S/(32)S, (36)S/(32)S) sulfur isotope fractionations imparted by a central enzyme in the energy metabolism of sulfate reducers, dissimilatory sulfite reductase (DsrAB). Results from in vitro sulfite reduction experiments allow us to calculate the in vitro DsrAB isotope effect in (34)S/(32)S (hereafter, [Formula: see text]) to be 15.3 ± 2‰, 2σ. The accompanying minor isotope effect in (33)S, described as [Formula: see text], is calculated to be 0.5150 ± 0.0012, 2σ. These observations facilitate a rigorous evaluation of the isotopic fractionation associated with the dissimilatory MSR pathway, as well as of the environmental variables that govern the overall magnitude of fractionation by natural communities of sulfate reducers. The isotope effect induced by DsrAB upon sulfite reduction is a factor of 0.3-0.6 times prior indirect estimates, which have ranged from 25 to 53‰ in (34)εDsrAB. The minor isotope fractionation observed from DsrAB is consistent with a kinetic or equilibrium effect. Our in vitro constraints on the magnitude of [Formula: see text] is similar to the median value of experimental observations compiled from all known published work, where (34)ε r-p = 16.1‰ (r-p indicates reactant vs. product, n = 648). This value closely matches those of MSR operating at high sulfate reduction rates in both laboratory chemostat experiments ([Formula: see text] 17.3 ± 1.5‰, 2σ) and in modern marine sediments ([Formula: see text] 17.3 ± 3.8‰). Targeting the direct isotopic consequences of a specific enzymatic processes is a fundamental step toward a biochemical foundation for reinterpreting the

  15. Chromium stable isotope fractionation during adsorption

    NASA Astrophysics Data System (ADS)

    Ellis, A.; Johnson, T.; Bullen, T.

    2003-04-01

    Chromium is a common anthropogenic contaminant in ground water. It is redox-active; the two common valences in natural waters are Cr(VI), which is highly soluble and toxic, and Cr(III), which is relatively insoluble. Redox reactions control Cr mobility in aqueous solutions with Cr(VI) reduction to Cr(III) controlling the attenuation of Cr in groundwater. Our previous study demonstrated that abiotic Cr(VI) reduction causes an isotope fractionation of -3.5 permil (53Cr/52Cr) and isotopes can therefore be used to calculate the extent of reduction. In the present study, experiments were conducted to measure Cr isotope fractionation during Cr(VI) sorption on Al203. Sorption of Cr(VI) could be important as a small isotope fractionation may get amplified along the edges of a Cr(VI) contaminated plume. A previous study demonstrated a similar process with Fe isotopes on anion exchange resin. Initial solutions of 200 mg/l Cr(VI) (as K2Cr2O7) and 0.1 mM KCl were made up. Sufficient solid Al203 was added to achieve 50% sorption. After equilibration, the solution was extracted by centrifuging and filtering with a 0.2 micron filter. Al203 was then added again to result in a further 50% sorption of the remaining Cr(VI). This process was repeated 10 times to amplify any isotopic fractionation between dissolved and adsorbed Cr(VI). The instantaneous stable isotope fractionation was calculated based on the δ 53Cr values of the initial and final Cr(VI) solutions. The results show that the stable isotope values measured in the solutions after the ten steps were within the uncertainty of the isotope value of the initial solution. Therefore, no significant stable isotope fractionation occurred. We are presently conducting experiments with goethite and expect similar results. Therefore, any fractionation of chromium stable isotopes observed in contaminant plumes are a result of processes other than adsorption (i.e., reduction).

  16. Reactive transport modeling of Li isotope fractionation

    NASA Astrophysics Data System (ADS)

    Wanner, C.; Sonnenthal, E. L.

    2013-12-01

    The fractionation of Li isotopes has been used as a proxy for interaction processes between silicate rocks and any kind of fluids. In particular, Li isotope measurements are powerful because Li is almost exclusively found in silicate minerals. Moreover, the two stable Li isotopes, 6Li and 7Li, differ by 17% in mass introducing a large mass dependent isotope fractionation even at high temperature. Typical applications include Li isotope measurements along soil profiles and of river waters to track silicate weathering patterns and Li isotope measurements of geothermal wells and springs to assess water-rock interaction processes in geothermal systems. For this contribution we present a novel reactive transport modeling approach for the simulation of Li isotope fractionation using the code TOUGHREACT [1]. It is based on a 6Li-7Li solid solution approach similar to the one recently described for simulating Cr isotope fractionation [2]. Model applications include the simulation of granite weathering along a 1D flow path as well as the simulation of a column experiment related to an enhanced geothermal system. Results show that measured δ7Li values are mainly controlled by (i) the degree of interaction between Li bearing primary silicate mineral phases (e.g., micas, feldspars) and the corresponding fluid, (ii) the Li isotope fractionation factor during precipitation of secondary mineral phases (e.g., clays), (iii) the Li concentration in primary and secondary Li bearing mineral phases and (iv) the proportion of dissolved Li that adsorbs to negatively charged surfaces (e.g., clays, Fe/Al-hydroxides). To date, most of these parameters are not very well constrained. Reactive transport modeling thus currently has to rely on many assumptions. Nevertheless, such models are powerful because they are the only viable option if individual contributions of all potential processes on the resulting (i.e., measured) Li isotopic ratio have to be quantitatively assessed. Accordingly, we

  17. Isotopic quantum effects in liquid methanol.

    PubMed

    Ludwig, Ralf

    2005-07-11

    Density functional calculations (B3 LYP/6-31+G*) on molecular clusters and a quantum cluster equilibrium (QCE) model were used to calculate thermodynamic and structural properties of four isotopically labeled methanol species. The method allowed the reproduction of the characteristic differences in boiling points and heats of vaporization. Structural changes were also detected and related to recent experimental findings. It was shown that isotopic effects clearly have a quantum-mechanical origin. PMID:15991271

  18. Magnesium isotope geochemistry in arc volcanism

    PubMed Central

    Teng, Fang-Zhen; Hu, Yan

    2016-01-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from −0.25 to −0.10, in contrast to the narrow range that characterizes the mantle (−0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid−mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration. PMID:27303032

  19. Oxygen isotope relationships in iron meteorites

    NASA Technical Reports Server (NTRS)

    Clayton, R. N.; Mayeda, T. K.; Olsen, E. J.; Prinz, M.

    1983-01-01

    Iron meteorites with oxygen-bearing phases can be classified in terms of their oxygen isotopic abundances. These iron meteorite classes are isotopically similar to various stony meteorite classes, which may indicate a common origin. The group IAB and IIICD irons may be related to the winonaites; group IIE irons may be related to H chondrites; group IVA irons may be related to L or LL chondrites.

  20. Isotopic studies in returned lunar samples

    NASA Technical Reports Server (NTRS)

    Alexander, E. C., Jr.

    1971-01-01

    Analysis of lunar soil samples returned by Apollo 11 and 12 flights are discussed. Isotopic studies of the rare gases from Apollo 11 flight lunar samples are presented. The lunar soil analyses indicated the following: (1) high concentrations of solar wind rare gases, (2) isotopic match between solar wind gases and gas components in gas-rich meteorites, and (3) rare gases attributable to spallation reactions induced in heavier nuclides by cosmic ray particles.

  1. Isotope shortage triggers delays for patients

    NASA Astrophysics Data System (ADS)

    Gould, Paula

    2009-07-01

    An unplanned shutdown of a nuclear reactor in Canada is disrupting the supply of medical isotopes across North America and forcing some hospitals to cancel or postpone patients' tests. The closure of the National Research Universal (NRU) reactor in Chalk River, Ontario, has also embarrassed Canadian officials, including a senior government minister who was forced to apologize after calling the isotope shortage a "sexy" career challenge.

  2. IUPAC Periodic Table of the Isotopes

    USGS Publications Warehouse

    Holden, N.E.; Coplen, T.B.; Böhlke, J.K.; Wieser, M.E.; Singleton, G.; Walczyk, T.; Yoneda, S.; Mahaffy, P.G.; Tarbox, L.V.

    2011-01-01

    For almost 150 years, the Periodic Table of the Elements has served as a guide to the world of elements by highlighting similarities and differences in atomic structure and chemical properties. To introduce students, teachers, and society to the existence and importance of isotopes of the chemical elements, an IUPAC Periodic Table of the Isotopes (IPTI) has been prepared and can be found as a supplement to this issue.

  3. Magnesium isotope geochemistry in arc volcanism.

    PubMed

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-28

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ(26)Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ(26)Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration. PMID:27303032

  4. Magnesium isotope geochemistry in arc volcanism

    NASA Astrophysics Data System (ADS)

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from ‑0.25 to ‑0.10, in contrast to the narrow range that characterizes the mantle (‑0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid‑mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  5. Modeling Nitrogen Isotopes in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Somes, C.; Schmittner, A.

    2008-12-01

    The nitrogen isotopic signal measured in marine sediments has the potential to be a valuable paleoceanographic proxy. It captures the response of different biological processes in the marine ecosystem including photosynthesis, nitrogen fixation, denitrification as well as processes within the food chain. A simple marine ecosystem model that includes the interactive cycling of nitrogen, phosphorus, and oxygen is augmented to record nitrogen isotopes in the University of Victoria Earth System Climate Model. New nitrogen isotopic tracers are employed at all trophic levels of the ecosystem. This includes the δ15N of nitrate, both classes of phytoplankton (nitrogen fixers and all other phytoplankton), zooplankton, and detritus. Despite a few shortcomings, it is shown that the nitrogen isotope model can capture the major trends observed in the modern climate. The ability to model nitrogen isotopes in a global coupled ocean- atmosphere-sea ice-ecosystem model gives us a unique opportunity to directly infer what physical and biological changes in the climate system are driving the δ15N signal on spatial and temporal scales. This is a valuable tool giving us tremendous insight on how to interpret the nitrogen isotopic signal.

  6. Iron isotopic systematics of oceanic basalts

    NASA Astrophysics Data System (ADS)

    Teng, Fang-Zhen; Dauphas, Nicolas; Huang, Shichun; Marty, Bernard

    2013-04-01

    The iron isotopic compositions of 93 well-characterized basalts from geochemically and geologically diverse mid-ocean ridge segments, oceanic islands and back arc basins were measured. Forty-three MORBs have homogeneous Fe isotopic composition, with δ56Fe ranging from +0.07‰ to +0.14‰ and an average of +0.105 ± 0.006‰ (2SD/√n, n = 43, MSWD = 1.9). Three back arc basin basalts have similar δ56Fe to MORBs. By contrast, OIBs are slightly heterogeneous with δ56Fe ranging from +0.05‰ to +0.14‰ in samples from Koolau and Loihi, Hawaii, and from +0.09‰ to +0.18‰ in samples from the Society Islands and Cook-Austral chain, French Polynesia. Overall, oceanic basalts are isotopically heavier than mantle peridotite and pyroxenite xenoliths, reflecting Fe isotope fractionation during partial melting of the mantle. Iron isotopic variations in OIBs mainly reflect Fe isotope fractionation during fractional crystallization of olivine and pyroxene, enhanced by source heterogeneity in Koolau samples.

  7. Gluconeogenesis from labeled carbon: estimating isotope dilution

    SciTech Connect

    Kelleher, J.K.

    1986-03-01

    To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoA and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA.

  8. Iron isotopic fractionation during continental weathering

    SciTech Connect

    Fantle, Matthew S.; DePaolo, Donald J.

    2003-10-01

    The biological activity on continents and the oxygen content of the atmosphere determine the chemical pathways through which Fe is processed at the Earth's surface. Experiments have shown that the relevant chemical pathways fractionate Fe isotopes. Measurements of soils, streams, and deep-sea clay indicate that the {sup 56}Fe/{sup 54}Fe ratio ({delta}{sup 56}Fe relative to igneous rocks) varies from +1{per_thousand} for weathering residues like soils and clays, to -3{per_thousand} for dissolved Fe in streams. These measurements confirm that weathering processes produce substantial fractionation of Fe isotopes in the modern oxidizing Earth surface environment. The results imply that biologically-mediated processes, which preferentially mobilize light Fe isotopes, are critical to Fe chemistry in weathering environments, and that the {delta}{sup 56}Fe of marine dissolved Fe should be variable and negative. Diagenetic reduction of Fe in marine sediments may also be a significant component of the global Fe isotope cycle. Iron isotopes provide a tracer for the influence of biological activity and oxygen in weathering processes through Earth history. Iron isotopic fractionation during weathering may have been smaller or absent in an oxygen-poor environment such as that of the early Precambrian Earth.

  9. Oxygen isotope studies of ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Clayton, Robert N.; Mayeda, Toshiko K.; Olsen, Edward J.; Goswami, J. N.

    1991-01-01

    Several stages in the evolution of ordinary chondritic meteorites are recorded in the oxygen isotopic composition of the meteorites and their separable components (chondrules, fragments, clasts, and matrix). The whole-rock isotopic compositions reflect the iron-group of the meteorite (H, L, or LL). Isotopic uniformity of H3 to H6 and L3 to L6 are consistent with closed-system metamorphism within each parent body. LL3 chondrites differ slightly from LL4 to LL6, implying a small degree of open-system aqueous alteration and carbon reduction. On the scale of individual chondrules, the meteorites are isotopically heterogeneous, allowing recognition of the solar-nebular processes of chondrule formation. Chondrules for all classes of ordinary chondrites are derived from a common population, which was separate from the population of chondrules in carbonaceous or enstatite chondrites. Chondrules define an isotopic mixing line dominated by exchange between (O - 16)-rich and (O - 16)-poor reservoirs. The oxygen isotopic compositions of chondrites serve as 'fingerprints' for identification of genetic association with other meteorite types (achondrites and iron) and for recognition of source materials in meteoritic breccias.

  10. Isotopic tracing of perchlorate in the environment

    SciTech Connect

    Sturchio, N. C.; Bohlke, J. K.; Gu, Baohua; Hatzinger, Paul B.; Jackson, Andrew

    2011-01-01

    Isotopic data can be used for tracing the origin and behavior of ClO4- in the environment. Four independently varying parameters have been measured on individual ClO4- samples for this purpose: delta 37Cl, 18O, 17O, and 36Cl/Cl. At least three distinct types of ClO4- have been identified isotopically, and these distinctions have proven to be useful in forensic applications. Additional data for natural ClO4- are urgently needed, however, to obtain a global picture of its isotopic variations. Improved methods for sample preparation and isotopic analysis with much better sensitivity would be helpful for measuring ClO4- isotopic variations in some sample types such as aerosols and precipitation as well as foodstuffs and bodily fluids, which have been precluded by the impracticality of obtaining the currently-required milligram amounts of ClO4-.. Further experimental and theoretical investigations of atmospheric ClO4- production mechanisms may lead to improved explanations of observed isotopic variations in natural samples.

  11. Isotopic Dependence of GCR Fluence behind Shielding

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Wilson, John W.; Saganti, Premkumar; Kim, Myung-Hee Y.; Cleghorn, Timothy; Zeitlin, Cary; Tripathi, Ram K.

    2006-01-01

    In this paper we consider the effects of the isotopic composition of the primary galactic cosmic rays (GCR), nuclear fragmentation cross-sections, and isotopic-grid on the solution to transport models used for shielding studies. Satellite measurements are used to describe the isotopic composition of the GCR. For the nuclear interaction data-base and transport solution, we use the quantum multiple-scattering theory of nuclear fragmentation (QMSFRG) and high-charge and energy (HZETRN) transport code, respectively. The QMSFRG model is shown to accurately describe existing fragmentation data including proper description of the odd-even effects as function of the iso-spin dependence on the projectile nucleus. The principle finding of this study is that large errors (+/-100%) will occur in the mass-fluence spectra when comparing transport models that use a complete isotopic-grid (approx.170 ions) to ones that use a reduced isotopic-grid, for example the 59 ion-grid used in the HZETRN code in the past, however less significant errors (<+/-20%) occur in the elemental-fluence spectra. Because a complete isotopic-grid is readily handled on small computer workstations and is needed for several applications studying GCR propagation and scattering, it is recommended that they be used for future GCR studies.

  12. Isotopic composition of precipitation in Greece

    NASA Astrophysics Data System (ADS)

    Argiriou, Athanassios A.; Lykoudis, Spyros

    2006-08-01

    SummaryThe contribution of stable isotopes in meteorological, climatological and hydrological research is well known. Until this date and despite the fact that several hydrological studies of water sources in Greece have been published, no systematic isotopic study of precipitation has been performed in the country. This paper presents all the available isotopic data collected since 1960 in several Hellenic measurement stations. This data is divided in two periods: the first covers data that was collected in the past, in the frame of a preliminary survey of the isotope composition of precipitation in the Eastern Mediterranean Sea and specific hydrological studies; the second is the result of a three-year coordinated research project of the International Atomic Energy Agency, in which the authors participated, aiming at the systematic study of stable isotopes ( 2H and 18O) and 3H in precipitation around the Mediterranean basin. No statistically significant behavior between the two periods of data was found. The isotopic content of precipitation presents characteristics intermediate of those of the Eastern and Western Mediterranean. The tritium concentration in precipitation declines as expected towards the pre-bomb levels, however there is an indication that tritium concentrations are higher in Northern Greece.

  13. Grosnaja ABCs: Magnesium isotope compositions

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Srinivasan, G.; Ulyanov, A. A.

    1993-01-01

    Three CAI's from the Grosnaja CV3 chondrite were analyzed for their magnesium isotopic compositions by the ion microprobe. The selected CAI's represent three distinct types: GR4(compact Type A), GR7(Type B) and GR2(Type C). Petrographic studies indicate that all three Grosnaja inclusions were subjected to secondary alterations. The Type A CAI GR4 is primarily composed of melilite with spinel and pyroxene occurring as minor phases. The rim of the inclusion does not exhibit distinct layered structure and secondary alteration products (garnet, Fe-rich olivine and Na-rich plagioclase) are present in some localized areas near the rim region. The average major element compositions of different mineral phases in GR4 are given. Preliminary REE data suggest a depletion of HREE relative to LREE by about a factor of 3 without any clear indication of interelement fractionation. The CAI GR7 has textural and minerological characteristics similar to Type B inclusions. The REE data show a pattern that is similar to Group 6 with enrichment in Eu and Yb. In addition, a depletion of HREE compared to LREE is also evident in this object. Melilite composition shows a broad range of akermanite content (Ak(sub 15-55)). Detailed petrographic study is in progress. GR2 is a anorthite-rich Type C inclusion with large plagioclase laths intergrown with Ti-rich pyroxene. The average plagioclase composition is close to pure anorthite (An99).

  14. Purdue Rare Isotope Measurement Laboratory

    NASA Astrophysics Data System (ADS)

    Caffee, M.; Elmore, D.; Granger, D.; Muzikar, P.

    2002-12-01

    The Purdue Rare Isotope Measurement Laboratory (PRIME Lab) is a dedicated research and service facility for accelerator mass spectrometry. AMS is an ultra-sensitive analytical technique used to measure low levels of long-lived cosmic-ray-produced and anthropogenic radionuclides, and rare trace elements. We measure 10Be (T1/2 = 1.5 My), 26Al (.702 My), 36Cl (.301 My), and 129I (16 My), in geologic samples. Applications include dating the cosmic-ray-exposure time of rocks on Earth's surface, determining rock and sediment burial ages, measuring the erosion rates of rocks and soils, and tracing and dating ground water. We perform sample preparation and separation chemistries for these radio-nuclides for our internal research activities and for those external researchers not possessing this capability. Our chemical preparation laboratories also serve as training sites for members of the geoscience community developing these techniques at their institutions. Research at Purdue involves collaborators among members of the Purdue Departments of Physics, Earth and Atmospheric Sciences, Chemistry, Agronomy, and Anthropology. We also collaborate and serve numerous scientists from other institutions. We are currently in the process of modernizing the facility with the goals of higher precision for routinely measured radio-nuclides, increased sample throughput, and the development of new measurement capabilities for the geoscience community.

  15. Identification of isotopically primitive interplanetary dust particles: A NanoSIMS isotopic imaging study

    SciTech Connect

    Floss, C; Stadermann, F J; Bradley, J P; Dai, Z R; Bajt, S; Graham, G; Lea, A S

    2005-09-02

    We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O, S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in {sup 15}N, including the largest {sup 15}N enrichments ({approx}1300 {per_thousand}) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in {sup 15}N, leading to average bulk N isotopic compositions that are {sup 15}N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two {sup 15}N-rich N-hotspots have correlated {sup 13}C anomalies. CN{sup -}/C{sup -} ratios suggest that most of the {sup 15}N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in the IDPs. The O isotopic compositions of the grains are similar to those found in presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the {sup 17}O and {sup 18}O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being ''isotopically primitive'' and consists of those IDPs that have anomalous bulk N isotopic compositions. These

  16. The Lithium Isotopic Signature of Hawaiian Basalts

    NASA Astrophysics Data System (ADS)

    Harrison, L.; Weis, D.; Hanano, D. W.

    2013-12-01

    Recycling of oceanic crust and sediment is a common mechanism to account for the presence of chemical heterogeneities observed in oceanic island basalts (OIBs). On Hawai';i, a mantle plume-sourced OIB with a high mass flux, sampling of deep mantle heterogeneities accounts for the presence of two unique geochemical and geographical trends called the Loa and Kea trends. The Loa trend overlaps the Pacific large low shear velocity province and is distinctly more enriched [1] than the Kea trend with average Pacific mantle compositions [2]. Because of the sizeable fractionation of lithium isotopes in low temperature environments, lithium serves as a tracer for the presence of recycled material in OIB sources, including Hawai'i. In this study, we analyzed 87 samples of Hawaiian basalt from the pre-shield, shield, post-shield, and rejuvenated volcanic stages and 10 samples of altered oceanic crust from ODP Site 843 for lithium isotopes using a multi-collector inductively coupled plasma mass spectrometer. Correlations of lithium isotopes with the radiogenic isotopes Pb, Hf, Nd, and Sr indicate lithium isotopes may be used to trace components in mantle plumes such as Hawai';i. The measured range of lithium isotopes for shield stage lavas is δ7Li = 1.8 - 5.7‰ and for post-shield lavas is δ7Li = 0.8 - 4.7‰. Pre-shield stage lavas (Lo'ihi volcano only) and rejuvenated lavas are the least and most homogeneous volcanic stages, respectively, in lithium isotopes. The Loa and Kea geochemical trends have different lithium isotopic signatures, with Loa trend shield volcanoes exhibiting lighter lithium isotopic signatures (δ7Li = 3.5‰ [N=43]) than Kea trend shield volcanoes (δ7Li = 4.0‰ [N=31]) [3]. Similarly, post-shield lavas have systematically lighter δ7Li than shield lavas. The presence of systematic differences in lithium isotopic signatures may indicate: 1) the sampling of distinct components in the deep source, to account for variations between Kea and Loa trend

  17. Magnesium isotopic compositions of the Mesoproterozoic dolostones: Implications for Mg isotopic systematics of marine carbonates

    NASA Astrophysics Data System (ADS)

    Huang, Kang-Jun; Shen, Bing; Lang, Xian-Guo; Tang, Wen-Bo; Peng, Yang; Ke, Shan; Kaufman, Alan J.; Ma, Hao-Ran; Li, Fang-Bing

    2015-09-01

    Available Mg isotope data indicate that dolostones of different ages have overlapping range of Mg isotopic composition (δ26Mg) and there is no systematic difference among different types of dolomites. To further explore the Mg isotopic systematics of dolomite formation, we measured Mg isotopic compositions of Mesoproterozoic dolostones from the Wumishan Formation in North China Block, because dolomite formation in Mesoproterozoic might have been fundamentally different from the younger counterparts. Based on petrographic observations, three texturally-different dolomite phases (dolomicrite, subhedral dolomite and anhedral dolomite) are recognized in the Wumishan dolostones. Nevertheless, these three types of dolomites have similar δ26Mg values, ranging from -1.35‰ to -1.72‰, which are indistinguishable from Neoproterozoic and Phanerozoic dolostones. To explain δ26Mg values of dolostones, we simulate the Mg isotopic system during dolomite formation by applying the one-dimensional Diffusion-Advection-Reaction (1D-DAR) model, assuming that the contemporaneous seawater is the Mg source of dolostone. The 1D-DAR modeling results indicate that the degree of dolomitization is controlled by sedimentation rate, seawater Mg concentration, temperature, and reaction rate of dolomite formation, whereas Mg isotopic composition of dolostone is not only dependent on these factors, but also affected by δ26Mg of seawater and isotope fractionation during dolomite formation. Moreover, the 1D-DAR model predicts that dolomite formation within sediments has limited range of variation in δ26Mg with respect to limestones. Furthermore, the modeling results demonstrate that dolostone is always isotopically heavier than Ca-carbonate precipitated from seawater, explaining the systematic isotopic difference between dolostones and limestones. Finally, we can infer from the 1D-DAR model that early-formed dolostone at shallower depth of sediments is always isotopically lighter than that

  18. Chemical stability of levoglucosan: an isotopic perspective

    NASA Astrophysics Data System (ADS)

    Sang, Xuefang; Gensch, Iulia; Schlag, Patrick; Wildt, Juergen; Laumer, Werner; Kammer, Beatrix; Tillmann, Ralf; Chitwan, Ojha; Heinichen, Gesa; Kiendler-scharr, Astrid

    2014-05-01

    Levoglucosan, used in receptor models as a specific tracer of biomass burning aerosols, has long been considered chemically stable in the atmosphere. Recent laboratory investigations found significant chemical degradation of levoglucosan when exposed to OH radicals (Hennigan et al., 2010). Stable carbon isotopic analyses, complementarily to concentration measurements, can provide additional evidence for physical and chemical processing in the atmosphere, since chemical processing causes changes in the relative abundance between heavy and light isotopes due to kinetic isotope effect (KIE). In this study, the chemical stability of levoglucosan was studied by exploring the isotopic fractionation of the reactant during the oxidation by OH. Mixed particles with levoglucosan and ammonium sulfate were generated in a continuous-stirred flow reactor and exposed to different levels of OH. Levoglucosan chemical degradation as function of OH exposure was derived from the decrease of levoglucosan/(NH4)2SO4 concentration ratios using aerosol mass spectrometry (AMS). Filter samples were collected for off-line isotopic analyses. Liquid extraction - Gas Chromatography - Isotope Ratio Mass Spectrometry (LE-GC-IRMS) was applied to measure stable carbon isotope ratios of levoglucosan. The observed d13C became more positive with increasing OH exposure, showing isotopic fractionations up to 3 ‰ at a reactant conversion of 45%. From the dependence of levoglucosan d13C on the OH exposure, a KIE of 1.00451 was derived, being within the range of predicted values for alkanes and alkenes with the same number of carbon atoms. With known source isotopic composition of levoglucosan in biomass burning aerosol (Sang et al., 2012), ambient measurements of levoglucosan d13C composition can therefore be used to determine the extent of chemical processing at the observation site. Reference: Hennigan, C. J., et al. 2010. Levoglucosan stability in biomass burning particles exposed to hydroxyl radicals

  19. Isotopic Compositions of Uranium Reference Materials

    NASA Astrophysics Data System (ADS)

    Jacobsen, B.; Borg, L. E.; Williams, R. W.; Brennecka, G.; Hutcheon, I. D.

    2009-12-01

    Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in 238U/235U, as well as the minor isotopes of U. Differences of ~1.3‰ are now being observed in 238U/235U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The 238U/235U ratios were measured with a TRITON TIMS using a mixed 233U-236U isotopic tracer to correct for instrument fractionation. This tracer was extremely pure and resulted in only very minor corrections on the measured 238U/235U ratios of ~0.03. The values obtained for 238U/235U are: IRMM184 = 137.698 ± 0.020 (n=15), SRM950a = 137.870 ± 0.018 (n=8), and CRM112a = 137.866 ± 0.030 (n=16). Uncertainties represent 2 s.d. of the population. Our measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 ± 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified 238U/235U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for 234U/235U are: SRM950a = (7.437 ± 0.043)x10-3 (n=18), and CRM112a = (7.281 ± 0.050)x10-3 (n=16), both of which are in good agreement with published values. The value for 236U/235U in SRM950a was determined to be (8.48 ± 2.63)x10-6, whereas 236U was not detected in CRM112a. We are currently obtaining the U isotopic composition of

  20. A Cr Isotope Proxy For Ocean Deoxygenation

    NASA Astrophysics Data System (ADS)

    Holmden, C. E.; Scheiderich, K. D.; Amini, M.; Francois, R. H. G. M.; Bacconais, I.

    2015-12-01

    The concentration and distribution of Cr in the oceans is strongly controlled by its oxidation state. Cr(VI) (as soluble chromate) is the dominant oxidation state in oxygenated seawater. Chromate is typically greater than 70% of total dissolved Cr in the open ocean, consistent with thermodynamic predictions. However, lower than average chromate concentrations in coastal seas and oxygen minimum zones suggest that chromate is being removed in these settings by reduction to Cr(III), which favours particle reactive species. Cr is an element whose isotopes are fractionated by redox changes. Reduction of Cr(VI) causes light isotopes of Cr to be enriched in the product Cr(III). Accordingly, any local-scale increase in reductive Cr removal fluxes will cause the seawater Cr concentration to decrease and the δ53Cr value to increase. A recent study of Cr isotopes in the oceans1 supports this prediction. Cr isotopes show a range of δ53Cr values correlating inversely with Cr concentration. The fractionation factor deduced from this correlation is -0.80 ±0.03 ‰ (2s) on a global scale. The difference in solubility of oxidized and reduced Cr in seawater, and the isotopic fractionation between them, is the basis on which the Cr isotope proxy may be used for tracing ocean deoxygenation events in the geological past. More specifically, changes in the size of the chromate inventory of seawater, both locally and globally, should be traceable from reconstructions of seawater-derived Cr isotope variations in marine sedimentary successions. Geological records of Cr isotope changes in the oceans during past deoxygenation events may be used to gauge the impact of global warming on future deoxygenation of the oceans, particularly if proxy records of temperature and ocean pH are also reconstructed. However, study of the modern ocean Cr cycle is still in its early stages, and important knowledge gaps need to be filled going forward. In this talk, we present results of our seawater Cr

  1. Site-Specific Carbon Isotopes in Organics

    NASA Astrophysics Data System (ADS)

    Piasecki, A.; Eiler, J. M.

    2012-12-01

    Natural organic molecules exhibit a wide range of internal site-specific isotope variation (i.e., molecules with same isotopic substitution type but different site). Such variations are generally unconstrained by bulk isotopic measurements. If known, site-specific variations might constrain temperatures of equilibrium, mechanisms of formation or consumption reactions, and possibly other details. For example, lipids can exhibit carbon isotope differences of up to 30‰ between adjacent carbon sites as a result of fractionations arising during decarboxylation of pyruvate and other steps in lipid biosynthesis(1). We present a method for site-specific carbon isotope analysis of propane, based on high-resolution, multi-collector gas source mass spectrometry, using a novel prototype instrument - the Thermo MAT 253 Ultra. This machine has an inlet system and electron bombardment ion source resembling those in conventional stable isotope gas source mass spectrometers, and the energy filter, magnet, and detector array resembling those in multi-collector ICPMS and TIMS. The detector array has 7 detector positions, 6 of which are movable, and each of which can collect ions with either a faraday cup (read through amplifiers ranging from 107-1012 ohms) or an SEM. High mass resolving power (up to 27,000, MRP = M/dM definition) is achieved through a narrow entrance slit, adjustable from 250 to 5 μm. Such resolution can cleanly separate isobaric interferences between isotopologues of organic molecules having the same cardinal mass (e.g., 13CH3 and 12CH2D). We use this technology to analyze the isotopologues and fragments of propane, and use such data to solve for the site-specific carbon isotope fractionation. By measuring isotopologues of both the one-carbon (13CH3) and the two-carbon (13C12CH4) fragment ion, we can solve for both bulk δ13C and the difference in δ13C between the terminal and central carbon position. We tested this method by analyzing mixtures between natural

  2. Isotopically pure magnesium isotope-24 is prepared from magnesium-24 oxide

    NASA Technical Reports Server (NTRS)

    Chellew, N. R.; Schilb, J. D.; Steunenberg, R. K.

    1968-01-01

    Apparatus is used to prepare isotopically pure magnesium isotope-24, suitable for use in neutron scattering and polarization experiments. The apparatus permits thermal reduction of magnesium-24 oxide with aluminum and calcium oxide, and subsequent vaporization of the product metal in vacuum. It uses a resistance-heated furnace tube and cap assembly.

  3. Analytical techniques in biomedical stable isotope applications: (isotope ratio) mass spectrometry or infrared spectrometry?

    PubMed

    Stellaard, Frans; Elzinga, Henk

    2005-12-01

    An overview is presented of biomedical applications of stable isotopes in general, but mainly focused on the activities of the Center for Liver, Digestive and Metabolic Diseases of the University Medical Center Groningen. The aims of metabolic studies in the areas of glucose, fat, cholesterol and protein metabolism are briefly explained, as well as the principle of breath testing and the techniques to study body composition and energy expenditure. Much attention is paid to the analytical considerations based upon metabolite concentrations, sample size restrictions, the availability of stable isotope labelled substrates and dose requirements in relation to compound-specific isotope analysis. The instrumental advantages and limitations of the generally used techniques gas chromatography/reaction/isotope ratio mass spectrometry and gas chromatography/mass spectrometry are described as well as the novelties of the recently commercialised liquid chromatography/combustion/isotope ratio mass spectrometry. The present use and future perspective of infrared (IR) spectrometry for clinical and biomedical stable isotope applications are reviewed. In this respect, the analytical demands on IR spectrometry are discussed to enable replacement of isotope ratio mass spectrometry by IR spectrometry, in particular, for the purpose of compound-specific isotope ratio analysis in biological matrices. PMID:16543190

  4. Iron Isotopic Fractionation in Early Planetary Crusts

    NASA Astrophysics Data System (ADS)

    Wang, K.; Moynier, F.; Dauphas, N.; Barrat, J.; Day, J. M.; Sio, C.; Korotev, R. L.; Zeigler, R. A.

    2012-12-01

    Differentiated meteorites (achondrites) derive from planetary bodies that experienced variable degrees of melting and silicate-metal segregation. The oldest achondrites, such as eucrites, angrites, brachinites and the oligoclase-rich meteorites Graves Nunataks 06128/06129 (GRA 06128/9), were formed ~2-5 Ma after the first Solar System solids. They represent the oldest differentiated silicate samples known in the Solar System and the study of these samples provides insight on the origins and conditions of formation of the first planetary crusts. Here, we present new high-precision data for the Fe isotopic compositions of eucrites, angrites, brachinites and GRA 06128/9 and interpret these results in terms of magmatism during formation of these samples. We find that most eucrites and brachinites are not fractionated compared to undifferentiated chondritic meteorites (δ56Fe = 0.00±0.01, 2se), while the rare Stannern-trend eucrites are slightly enriched in the heavier isotopes of Fe. Angrites are also enriched in the heavier isotopes (δ56Fe = 0.12±0.01, 2se), similar to what is observed for terrestrial basalts, reflecting the relatively high oxidation states of the angrite parent body(ies). Contrastingly to the 'basaltic' achondrites, GRA 06128/9 are enriched in light isotopes of Fe (δ56Fe = -0.08±0.02, 2se). Evidence for light Fe isotope enrichments may be the consequence of the segregation of magma rich in sulphide (usually enriched in light isotopes of Fe compared to silicate and metal in undifferentiated meteorites). If correct, this result not only confirms that GRA 06128/9 represent products from <30% partial melting of an asteroidal body, prior to core formation, but also indicates complementary Fe isotope systematics between GRA 06128/9 and brachinites.

  5. Calcium isotopic composition of mantle peridotites

    NASA Astrophysics Data System (ADS)

    Huang, F.; Kang, J.; Zhang, Z.

    2015-12-01

    Ca isotopes are useful to decipher mantle evolution and the genetic relationship between the Earth and chondrites. It has been observed that Ca isotopes can be fractionated at high temperature [1-2]. However, Ca isotopic composition of the mantle peridotites and fractionation mechanism are still poorly constrained. Here, we report Ca isotope composition of 12 co-existing pyroxene pairs in 10 lherzolites, 1 harzburgite, and 1 wehrlite xenoliths collected from Hainan Island (South Eastern China). Ca isotope data were measured on a Triton-TIMS using the double spike method at the Guangzhou Institute of Geochemistry, CAS. The long-term external error is 0.12‰ (2SD) based on repeated analyses of NIST SRM 915a and geostandards. δ44Ca of clinopyroxenes except that from the wehrlite ranges from 0.85‰ to 1.14‰, while opx yields a wide range from 0.98‰ up to 2.16‰. Co-existing pyroxene pairs show large ∆44Caopx-cpx (defined as δ44Caopx-δ44Cacpx) ranging from 0 to 1.23‰, reflecting equilibrium fractionation controlled by variable Ca contents in the opx. Notably, clinopyroxene of wehrlite shows extremely high δ44Ca (3.22‰). δ44Ca of the bulk lherzolites and harzburgites range from 0.86‰ to 1.14‰. This can be explained by extracting melts with slightly light Ca isotopic compositions. Finally, the high δ44Ca of the wehrlite (3.22‰) may reflect metasomatism by melt which has preferentially lost light Ca isotopes due to chemical diffusion during upwelling through the melt channel. [1] Amini et al (2009) GGR 33; [2] Huang et al (2010) EPSL 292.

  6. Modeling nuclear volume isotope effects in crystals

    PubMed Central

    Schauble, Edwin A.

    2013-01-01

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac–Hartree–Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor–crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium

  7. The Cu isotopic composition of iron meteorites

    NASA Astrophysics Data System (ADS)

    Bishop, Matthew Cole; Moynier, Frederic; Weinstein, Charlotte; Fraboulet, Jean-Gabriel; Wang, Kun; Foriel, Julien

    2012-02-01

    High-precision Cu isotopic compositions have been measured for the metal phase of 29 iron meteorites from various groups and for four terrestrial standards. The data are reported as the δ65Cu permil deviation of the 65Cu/63Cu ratio relative to the NIST SRM 976 standard. Terrestrial mantle rocks have a very narrow range of variations and scatter around zero. In contrast, iron meteorites show δ65Cu approximately 2.3‰ variations. Different groups of iron meteorites have distinct δ65Cu values. Nonmagmatic IAB-IIICD iron meteorites have similar δ65Cu (0.03 ± 0.08 and 0.12 ± 0.10, respectively), close to terrestrial values (approximately 0). The other group of nonmagmatic irons, IIE, is isotopically distinct (-0.69 ± 0.15). IVB is the iron meteorite group with the strongest elemental depletion in Cu and samples in this group are enriched in the lighter isotope (δ65Cu down to -2.26‰). Evaporation should have produced an enrichment in 65Cu over 63Cu (δ65Cu >0) and can therefore be ruled out as a mechanism for volatile loss in IVB meteorites. In silicate-bearing iron meteorites, Δ17O correlates with δ65Cu. This correlation between nonmass-dependent and mass-dependent parameters suggests that the Cu isotopic composition of iron meteorites has not been modified by planetary differentiation to a large extent. Therefore, Cu isotopic ratios can be used to confirm genetic links. Cu isotopes thus confirm genetic relationships between groups of iron meteorites (e.g., IAB and IIICD; IIIE and IIIAB); and between iron meteorites and chondrites (e.g., IIE and H chondrites). Several genetic connections between iron meteorites groups are confirmed by Cu isotopes, (e.g., IAB and IIICD; IIIE and IIIAB); and between iron meteorites and chondrites (e.g., IIE and H chondrites).

  8. Modeling nuclear volume isotope effects in crystals.

    PubMed

    Schauble, Edwin A

    2013-10-29

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac-Hartree-Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor-crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from (119)Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium. PMID

  9. Modeling nuclear volume isotope effects in crystals

    NASA Astrophysics Data System (ADS)

    Schauble, Edwin A.

    2013-10-01

    Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac-Hartree-Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor-crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium.

  10. Nuclear Volume Effects in Equilibrium Stable Isotope Fractionations of Hg, Tl and Pb Isotope Systems

    NASA Astrophysics Data System (ADS)

    Yang, S.; Liu, Y.

    2014-12-01

    Many evidences showed that heavy isotope systems could be significantly fractionated as the consequence of the nuclear volume effect (NVE) or so-called nuclear field shift effect. Here we investigate NVEs of Hg, Tl and Pb isotope systems by using quantum chemistry computational methods with careful evaluation on quantum relativistic effects via the Dirac's formalism of full-electron wavefunction. Our results generally agree with previous studies but with noticeable differences in many cases. With the unique NVE driving force, equilibrium 202Hg/198Hg and 205Tl/203Tl isotopes can be fractionated up to 3.94‰ and 2.78‰ at 0℃, respectively, showing potentially large equilibrium isotope fractionations can be expected for future studies of these two isotope systems. Moreover, the NVE causes large mass-independent fractionations (MIF) for odd-mass isotopes (e.g., ∆199NVHg and ∆201NVHg) and small MIFs for even-mass isotopes (e.g., ∆200NVHg). For Pb isotope system, NVEs induce isotope fractionations up to 1.62‰ (207Pb/206Pb) and 4.06‰ (208Pb/206Pb) at 0℃. However, contributions from classical mass-dependent driving force are small, about 0.1-0.5‰ for 207Pb/206Pb and 0.2-0.9‰ for 208Pb/206Pb. We find that Pb4+-bearing species can be significantly enriched heavy isotopes than Pb2+-bearing species. Comparing to Pb0, Pb2+-bearing species even enrich lighter Pb isotopes. A very strange and interesting thing is that the beta value of Pb2+-bearing species can be smaller than the unity (1.000). Similar thing has been found on Tl+-bearing species. This is an impossible and unexplained situation if only based on classical mass-dependent isotope fractionation theory (e.g., Bigeleisen-Mayer equation). The consequence is that the different direction of beta values of Pb2+-bearing species will let the Pb isotope fractionation even larger when they fractionate with Pb4+-bearing species. Moreover, NVEs also cause mass-independent fractionation (MIF) of odd 207Pb

  11. Isotopic inferences of ancient biochemistries - Carbon, sulfur, hydrogen, and nitrogen

    NASA Technical Reports Server (NTRS)

    Schidlowski, M.; Hayes, J. M.; Kaplan, I. R.

    1983-01-01

    In processes of biological incorporation and subsequent biochemical processing sizable isotope effects occur as a result of both thermodynamic and kinetic fractionations which take place during metabolic and biosynthetic reactions. In this chapter a review is provided of earlier work and recent studies on isotope fractionations in the biogeochemical cycles of carbon, sulfur, hydrogen, and nitrogen. Attention is given to the biochemistry of carbon isotope fractionation, carbon isotope fractionation in extant plants and microorganisms, isotope fractionation in the terrestrial carbon cycle, the effects of diagenesis and metamorphism on the isotopic composition of sedimentary carbon, the isotopic composition of sedimentary carbon through time, implications of the sedimentary carbon isotope record, the biochemistry of sulfur isotope fractionation, pathways of the biogeochemical cycle of nitrogen, and the D/H ratio in naturally occurring materials.

  12. LANL-IPF responses to isotopes workshop background information survey

    SciTech Connect

    Nortier, Francois Meiring

    2008-01-01

    Responses to the following are provided: (A) Which isotopes do you (company, agency, university, community) currently use in your activities or distribute (repackage) to end-users? (B) Describe generally what these isotopes are used for, i.e. the science or application. (C) Which isotope(s) do you anticipate may have significant future increase in demand. Identify the isotope(s), its priority, possible chemical form and for what purpose it would be used. (D) Are there other isotopes that you might use but are currently unavilable or not available in difficient quantities? If so, please identify this isotope, from whom have you tired to obtain it and for what prupose would it be used. (E) Do you have any specific issues with respect to the purity, availability, reliability of supply, etc. of isotopes at present?

  13. Isotope Ratios of Cellulose from Plants Having Different Photosynthetic Pathways

    PubMed Central

    Sternberg, Leonel O.; Deniro, Michael J.; Johnson, Hyrum B.

    1984-01-01

    Hydrogen and carbon isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from C3, C4, and Crassulacean acid metabolism (CAM) plants were determined for plants growing within a small area in Val Verde County, Texas. Plants having CAM had distinctly higher deuterium/hydrogen (D/H) ratios than plants having C3 and C4 metabolism. When hydrogen isotope ratios are plotted against carbon isotope ratios, each photosynthetic mode separates into a distinct cluster of points. C4 plants had many D/H ratios similar to those of C3 plants, so that hydrogen isotope ratios cannot be used to distinguish between these two photosynthetic modes. Portulaca mundula, which may have a modified photosynthetic mode between C4 and CAM, had a hydrogen isotope ratio between those of the C4 and CAM plants. When oxygen isotope ratios are plotted against carbon isotope ratios, no distinct clustering of the C4 and CAM plants occurs. Thus, oxygen isotope ratios are not useful in distinguishing between these metabolic modes. A plot of hydrogen isotope ratios versus oxygen isotope ratios for this sample set shows considerable overlap between oxygen isotope ratios of the different photosynthetic modes without a concomitant overlap in the hydrogen isotope ratios of CAM and the other two photosynthetic modes. This observation is consistent with the hypothesis that higher D/H ratios in CAM plants relative to C3 and C4 plants are due to isotopic fractionations occurring during biochemical reactions. PMID:16663460

  14. Molybdenum Isotopic Composition of Iron Meteorites, Chondrites and Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Becker, H.; Walker, R. J.

    2003-01-01

    Recent Mo isotopic studies of meteorites reported evidence for differences in isotopic compositions for whole rocks of some primitive and differentiated meteorites relative to terrestrial materials. Enrichments of r- and p-process isotopes of up to 3-4 units (e unit = parts in 10(exp 4) over s-process dominated isotopes are the most prominent features. Certain types of presolar grains show large enrichments in s-process isotopes, however, it was concluded on grounds of mass balance that incomplete digestion of such grains cannot explain the enrichments of r- and p-process isotopes in whole rocks of primitive chondrites. If the reported variability in r- and p-process isotope enrichments reflects the true isotopic characteristics of the whole rocks, the implications are quite profound. It would suggest the presence of large scale Mo isotopic heterogeneity within the solar accretion disk with likely collateral effects for other elements. However, such effects were not found for Ru isotopes, nor for Zr isotopes. Another recent Mo isotopic study by multi collector ICP-MS could not confirm the reported deviations in Allende, Murchison or iron meteorites. Here, we present new results for the Mo isotopic composition of iron meteorites, chondrites and CAIs obtained by negative thermal ionization mass spectrometry (NTIMS). We discuss analytical aspects and the homogeneity of Mo isotopic compositions in solar system materials.

  15. Determining Clumped Isotope (Δ47) Signatures of CO2 During Ion-Molecule Isotopic Exchange Reactions

    NASA Astrophysics Data System (ADS)

    Sarna, J.; Priyadarshi, A.; Pourmorady, P.; Tripati, A.; Estaris, J.

    2015-12-01

    The abundance of multiply-substituted isotopologues such as 13C16O18O can be used to understand fundamental mechanisms that controls isotopic fractionation in chemical reactions. Knowledge of the energy-dependent ion-molecule isotopic exchange rate for 13C16O18O may also provide important insights into the CO2 ion-molecular exchange that occurs in the source of the mass spectrometer. It may offer an explanation for the recently observed nonlinearities associated with clumped isotope measurements. We designed a controlled set of laboratory experiments to investigate variations in the abundance of 13C16O18O associated with different ion-molecular isotopic exchange reactions. In our experiments, we characterize the effects of changing ionization energy, reaction time, CO2 amount, the presence of different compounds, and reaction chamber temperature on the clumped isotopic composition of CO2.

  16. Resolving the stellar sources of isotopically rare presolar silicate grains through Mg and Fe isotopic analyses

    SciTech Connect

    Nguyen, Ann N.; Messenger, Scott

    2014-04-01

    We conducted multi-element isotopic analyses of 11 presolar silicate grains from the Acfer 094 meteorite having unusual O isotopic compositions. Eight grains are {sup 18}O-rich, one is {sup 16}O-rich, and two are extremely {sup 17}O-rich. We constrained the grains' stellar sources by measuring their Si and Mg isotopic ratios, and also the {sup 54}Fe/{sup 56}Fe and {sup 57}Fe/{sup 56}Fe ratios for five grains. The Mg and Fe isotopic measurements were conducted after surrounding matrix grains were removed for more accurate ratios. Most of the {sup 18}O-rich silicates had anomalous Mg isotopic ratios, and their combined isotopic constraints are consistent with origins in low-mass Type II supernovae (SNe II) rather than high-metallicity stars. The isotopic ratios of the {sup 16}O-rich silicate are also consistent with an SN origin. Mixing small amounts of interior stellar material with the stellar envelope replicated all measured isotopic ratios except for {sup 29}Si/{sup 28}Si and {sup 54}Fe/{sup 56}Fe in some grains. The {sup 29}Si/{sup 28}Si ratios of all SN-derived grains are matched by doubling the {sup 29}Si yield in the Ne- and Si-burning zones. The {sup 54}Fe/{sup 56}Fe ratios of the grains imply elemental fractionation in the Si/S zone, or introduction of isotopically solar Fe by secondary processing. The two highly {sup 17}O-rich silicates exhibited significant {sup 25}Mg and/or {sup 26}Mg enrichments and their isotopic ratios are best explained by strong dilution of 1.15 M {sub ☉} CO nova matter. We estimate that ∼12% and 1% of presolar silicates have SN and nova origins, respectively, similar to presolar SiC and oxides. This implies that asymptotic giant branch stars are the dominant dust producers in the galaxy.

  17. Palladium Isotopic Evidence for Nucleosynthetic and Cosmogenic Isotope Anomalies in IVB Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Mayer, Bernhard; Wittig, Nadine; Humayun, Munir; Leya, Ingo

    2015-08-01

    The origin of ubiquitous nucleosynthetic isotope anomalies in meteorites may represent spatial and/or temporal heterogeneity in the sources that supplied material to the nascent solar nebula, or enhancement by chemical processing. For elements beyond the Fe peak, deficits in s-process isotopes have been reported in some (e.g., Mo, Ru, W) but not all refractory elements studied (e.g., Os) that, among the iron meteorites, are most pronounced in IVB iron meteorites. Palladium is a non-refractory element in the same mass region as Mo and Ru. In this study, we report the first precise Pd isotopic abundances from IVB irons to test the mechanisms proposed for the origin of isotope anomalies. First, this study determined the existence of a cosmogenic neutron dosimeter from the reaction 103Rh(n, β-)104Pd in the form of excess 104Pd, correlated with excess 192Pt, in IVB irons. Second, all IVB irons show a deficit of the s-process only isotope 104Pd (\\varepsilon 104Pd = -0.48 ± 0.24), an excess of the r-only isotope 110Pd (\\varepsilon 110Pd = +0.46 ± 0.12), and no resolvable anomaly in the p-process 102Pd (\\varepsilon 102Pd = +1 ± 1). The magnitude of the Pd isotope anomaly is about half that predicted from a uniform depletion of the s-process yields from the correlated isotope anomalies of refractory Mo and Ru. The discrepancy is best understood as the result of nebular processing of the less refractory Pd, implying that all the observed nucleosynthetic anomalies in meteorites are likely to be isotopic relicts. The Mo-Ru-Pd isotope systematics do not support enhanced rates of the 22Ne(α,n)25Mg neutron source for the solar system s-process.

  18. Myths of Isotopic Reference Materials Busted

    NASA Astrophysics Data System (ADS)

    Coplen, T.

    2007-12-01

    During the past several years, the determination of the isotopic abundances of elements including H, Li, B, C, N, O, Mg, Si, S, Cl, Ca, Cr, Fe, Cu, Zn, Tl, and Se has substantially increased because of expanded use in hydrology, environmental studies, microbiology, forensic investigations, atmospheric investigations, oceanography, etc. Improvements in instrumentation enable increasingly precise isotope-amount-ratio measurements in these fields, but these improvements in precision commonly do not lead to improvements in accuracy because of the lack or improper use of isotopic reference materials. When properly used, these critically important materials enable any laboratory worldwide to measure the same homogeneous sample and report the same isotopic abundance within analytical uncertainty. For example, for stable isotopic analysis of gaseous hydrogen samples, the agreement among 36 laboratories worldwide before normalization to any hydrogen gas reference material was 11.8 per mill. After normalization to anchors (gaseous H isotopic reference materials) at each end of the delta H-2 scale, the agreement was 0.85 per mill, an improvement of more than an order of magnitude. Consistency of delta C-13 measurements often can be improved by nearly 50 percent by anchoring the delta C-13 scale with two isotopic reference materials differing substantially in C-13 mole fraction, namely NBS 19 calcite and L-SVEC lithium carbonate. Agreement of delta C-13 values of four expert laboratories analyzing USGS40 L- glutamic acid by CF-IRMS methods improved from 0.084 to 0.015 per mill with use of the two scale anchors (NBS 19 and L-SVEC). Solid oxygen isotopic reference materials (IAEA-600 caffeine, IAEA-601 and IAEA-602 benzoic acids, IAEA-NO-3, USGS32, USGS34, and USGS35 nitrates, NBS-127, IAEA-SO-5, and IAEA-SO-6 barium sulfates) are poorly calibrated. Calibrating these solids to the VSMOW-SLAP reference water scale has been very difficult because both the solids and reference

  19. Stable isotopes in Lithuanian bioarcheological material

    NASA Astrophysics Data System (ADS)

    Skipityte, Raminta; Jankauskas, Rimantas; Remeikis, Vidmantas

    2015-04-01

    Investigation of bioarcheological material of ancient human populations allows us to understand the subsistence behavior associated with various adaptations to the environment. Feeding habits are essential to the survival and growth of ancient populations. Stable isotope analysis is accepted tool in paleodiet (Schutkowski et al, 1999) and paleoenvironmental (Zernitskaya et al, 2014) studies. However, stable isotopes can be useful not only in investigating human feeding habits but also in describing social and cultural structure of the past populations (Le Huray and Schutkowski, 2005). Only few stable isotope investigations have been performed before in Lithuanian region suggesting a quite uniform diet between males and females and protein intake from freshwater fish and animal protein. Previously, stable isotope analysis has only been used to study a Stone Age population however, more recently studies have been conducted on Iron Age and Late medieval samples (Jacobs et al, 2009). Anyway, there was a need for more precise examination. Stable isotope analysis were performed on human bone collagen and apatite samples in this study. Data represented various ages (from 5-7th cent. to 18th cent.). Stable carbon and nitrogen isotope analysis on medieval populations indicated that individuals in studied sites in Lithuania were almost exclusively consuming C3 plants, C3 fed terrestrial animals, and some freshwater resources. Current investigation demonstrated social differences between elites and country people and is promising in paleodietary and daily life reconstruction. Acknowledgement I thank prof. dr. G. Grupe, Director of the Anthropological and Palaeoanatomical State Collection in Munich for providing the opportunity to work in her laboratory. The part of this work was funded by DAAD. Antanaitis-Jacobs, Indre, et al. "Diet in early Lithuanian prehistory and the new stable isotope evidence." Archaeologia Baltica 12 (2009): 12-30. Le Huray, Jonathan D., and Holger

  20. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    NASA Astrophysics Data System (ADS)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  1. Isotopic imprints of mountaintop mining contaminants.

    PubMed

    Vengosh, Avner; Lindberg, T Ty; Merola, Brittany R; Ruhl, Laura; Warner, Nathaniel R; White, Alissa; Dwyer, Gary S; Di Giulio, Richard T

    2013-09-01

    Mountaintop mining (MTM) is the primary procedure for surface coal exploration within the central Appalachian region of the eastern United States, and it is known to contaminate streams in local watersheds. In this study, we measured the chemical and isotopic compositions of water samples from MTM-impacted tributaries and streams in the Mud River watershed in West Virginia. We systematically document the isotopic compositions of three major constituents: sulfur isotopes in sulfate (δ(34)SSO4), carbon isotopes in dissolved inorganic carbon (δ(13)CDIC), and strontium isotopes ((87)Sr/(86)Sr). The data show that δ(34)SSO4, δ(13)CDIC, Sr/Ca, and (87)Sr/(86)Sr measured in saline- and selenium-rich MTM impacted tributaries are distinguishable from those of the surface water upstream of mining impacts. These tracers can therefore be used to delineate and quantify the impact of MTM in watersheds. High Sr/Ca and low (87)Sr/(86)Sr characterize tributaries that originated from active MTM areas, while tributaries from reclaimed MTM areas had low Sr/Ca and high (87)Sr/(86)Sr. Leaching experiments of rocks from the watershed show that pyrite oxidation and carbonate dissolution control the solute chemistry with distinct (87)Sr/(86)Sr ratios characterizing different rock sources. We propose that MTM operations that access the deeper Kanawha Formation generate residual mined rocks in valley fills from which effluents with distinctive (87)Sr/(86)Sr and Sr/Ca imprints affect the quality of the Appalachian watersheds. PMID:23909446

  2. Stable Isotope Spectroscopy for Diagnostic Medicine

    NASA Astrophysics Data System (ADS)

    Murnick, D. E.

    2000-06-01

    Isotopic tracers have been used in medical research for more than fifty years. Radioactive isotopes have been most used because of the high detection efficiencies possible. With increased awareness of the effects of low level radiation and radioactive waste management problems, the need for safe non radioactive tracers has become apparent. Rare stable isotopes of biologically active elements can be used for metabolic and pharmacokinetic studies provided that both sufficient detection sensitivity can be achieved and reliable cost effective instruments can be developed. High resolution optical spectroscopic methods which can determine isotopic ratios with high precision and accuracy are viable for research and clinical use. The study of 13C/12C ratios in CO2 for breath test diagnostics will be described in detail. Using the laser optogalvonic effect with isotopic lasers a specific medical diagnostic for h-pylori infection, has recently received FDA approval. Opportunities exist to study D/H ratios in water and 18O/16O ratios in CO2 and water for basic metabolism diagnostics and 15N/14N ratios in urine for liver function and related studies.

  3. Laser Isotope Separation Employing Condensation Repression

    SciTech Connect

    Eerkens, Jeff W.; Miller, William H.

    2004-09-15

    Molecular laser isotope separation (MLIS) techniques using condensation repression (CR) harvesting are reviewed and compared with atomic vapor laser isotope separation (AVLIS), gaseous diffusion (DIF), ultracentrifuges (UCF), and electromagnetic separations (EMS). Two different CR-MLIS or CRISLA (Condensation Repression Isotope Separation by Laser Activation) approaches have been under investigation at the University of Missouri (MU), one involving supersonic super-cooled free jets and dimer formation, and the other subsonic cold-wall condensation. Both employ mixtures of an isotopomer (e.g. {sup i}QF{sub 6}) and a carrier gas, operated at low temperatures and pressures. Present theories of VT relaxation, dimerization, and condensation are found to be unsatisfactory to explain/predict experimental CRISLA results. They were replaced by fundamentally new models that allow ab-initio calculation of isotope enrichments and predictions of condensation parameters for laser-excited and non-excited vapors which are in good agreement with experiment. Because of supersonic speeds, throughputs for free-jet CRISLA are a thousand times higher than cold-wall CRISLA schemes, and thus preferred for large-quantity Uranium enrichments. For small-quantity separations of (radioactive) medical isotopes, the simpler coldwall CRISLA method may be adequate.

  4. Tin isotope fractionation in terrestrial cassiterites

    SciTech Connect

    McNaughton, N.J. ); Rosman, K.J.R. )

    1991-02-01

    The isotopic composition of tin has been measured in a range of cassiterites and pure reagents to assess the extent to which this element is isotopically fractionated in natural processes. Only two samples showed evidence of isotopic fractionation, and it is concluded that natural Sn isotope fractionation is small and uncommon. This feature reflects the world dominance of Sn-oxide ores Sn-sulfide ores, and the highly efficient processes of Sn dissolution and precipitation which negate equilibrium and kinetic fractionation of Sn isotopes, respectively. The two samples which show slight fractionation are a highly purified and cassiterite from the Archaean Greenbushes pegmatite, Western Australia. The latter Sn is 0.15{per thousand} per mass unit heavier than the authors laboratory standard, whereas the former is 0.12{per thousand} per mass unit lighter. Although the cassiterite fractionation is considered to result from natural geological processes, the fractionation of purified Sn may be either natural or relate to the purification process, the fractionation of this magnitude has a negligible effect on the current best estimate of the atomic weight of Sn, but it does place a lower limit on its associated accuracy.

  5. Carbon isotope composition of Antarctic plants

    NASA Astrophysics Data System (ADS)

    Galimov, E. M.

    2000-05-01

    Carbon isotope compositions of Antarctic land plants are first reported. The most interesting feature is the isotope specificity of the species. For example Usnea antarctica from different locations shows relatively narrow range of the δ 13C-values from -22.44 to -21.29‰ (7 samples), Drepanocladus sp. from -24.86 to -23.49‰ (8 samples), and Andreaea depressincrvis from -23.87 to -23.23‰ (3 samples) etc. Usually, in inhabited lands and parts of the world with rich flora and developed soil, isotopic specificity of species is masked by variations of carbon isotope composition of CO 2. In Antarctic conditions influence of local sources of CO 2 on the isotope composition of CO 2 is appeared to be minimal. Therefore the δ 13C-variations inherent to individual plant physiology and biochemistry can be distinguished on the background of the stable level of the atmospheric CO 2 δ 13C-value. The latter is best to reflect the global state of the carbon cycle.

  6. New Stable Isotope Tropical Paleoclimate Proxies

    NASA Astrophysics Data System (ADS)

    Lawrence, J. R.

    2005-05-01

    Organized tropical rain systems such as tropical cyclones (TC) and mesoscale convective systems (MCS) produce both water vapor and rainfall with distinctly low isotope ratios. This lowering is caused by recyling of water in organized systems. Therefore, fresh water carbonate organisms have considerable potential to act as proxy recorders of these systems. Ostracoda are ephemeral making them especially attractive candidates. Tropical trees offer another opportunity because the low isotopic spikes produced in both soil waters when heavy rains result and ambient water vapor surronding the trees may be recorded in the tree cellulose. Ostracoda living in the surface waters derived from Tropical Storm Allison (2001) document the passage of the storm in their oxygen isotope ratios. The stable isotopic composition of water vapor along the southwest coast of Mexico shows considerable variation in response to TC and MCS activity offshore even when no rain falls in the region. Potentially a long-term record of this activity may be found in the stable isotopic composition of trees providing low elevation trees of sufficient longevity can be found.

  7. Chemical stability of levoglucosan: An isotopic perspective

    NASA Astrophysics Data System (ADS)

    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.

  8. Molybdenum isotope systematics in subduction zones

    NASA Astrophysics Data System (ADS)

    König, Stephan; Wille, Martin; Voegelin, Andrea; Schoenberg, Ronny

    2016-08-01

    This study presents Mo isotope data for arc lavas from different subduction zones that range between δ 98 / 95 Mo = - 0.72 and + 0.07 ‰. Heaviest isotope values are observed for the most slab fluid dominated samples. Isotopically lighter signatures are related to increasing relevance of terrigenous sediment subduction and sediment melt components. Our observation complements previous conclusions that an isotopically heavy Mo fluid flux likely mirrors selective incorporation of isotopically light Mo in secondary minerals within the subducting slab. Analogue to this interpretation, low δ 98 / 95 Mo flux that coincides with terrigenous sediment subduction and sediment melting cannot be simply related to a recycled input signature. Instead, breakdown of the controlling secondary minerals during sediment melting may release the light component and lead to decreasing δ 98 / 95 Mo influx into subarc mantle sources. The natural range between slab dehydration and hydrous sediment melting may thus cause a large spread of δ 98 / 95 Mo in global subduction zone magmas.

  9. Hydrogen isotope composition of magmatic water

    SciTech Connect

    Taylor, B.E. )

    1992-01-01

    Isotopic tracing of H[sub 2]O degassing in both small and very large rhyolitic magmas in continental tectonic settings (USA and New Zealand), and isotopic studies of high-temperature fumaroles (USA, Japan, and elsewhere) indicate that the hydrogen isotope compositions of magmatic waters vary primarily with the composition of source material and tectonic setting. Water from felsic magmas in volcanic arc settings has a mean [delta]D value off [minus]25 [+-] 5 permil, whereas water from volcanic and plutonic magmas in continental settings has a slightly lower mean [delta]D of [minus]40 [+-] 10 permil. These differences reflect the variation in composition of source materials: hydrated oceanic crust and marine sediments for the arc volcanoes, and largely metamorphic crust for magmas in continental settings. The isotopic record in certain ore deposits associated with felsic magmas (e.g., W skarns, Sn-W veins) and geothermal systems records the influx at critical times of magmatic water with a [delta]D value of [minus]35 to [minus]45 permil. This is best documented where isotopic contrast between magmatic and meteoric waters is large. The [delta]D of MORB H[sub 2]O presumably lies between the mean [delta]D for MORB glass ([minus]75 permil), the [delta]D of H[sub 2]O in equilibrium with this glass ([delta]D ca. [minus]35; assuming closed-system degassing).

  10. The calcium isotope systematics of Mars

    NASA Astrophysics Data System (ADS)

    Magna, Tomáš; Gussone, Nikolaus; Mezger, Klaus

    2015-11-01

    New Ca isotope data from a suite of Martian meteorites provide constraints on the Ca isotope composition of the Martian mantle and possible recycling of surface materials back into the mantle. A mean δ44/40Ca of 1.04 ± 0.09 ‰ (2SD) is estimated for the Martian mantle which can also be taken as an approximation for Bulk Silicate Mars. This value is identical with the estimates for Bulk Silicate Earth, and the inner Solar System planets can therefore be considered homogeneous with respect to Ca isotopes. The Ca isotope composition of two Martian dunites varies by ∼ 0.3 ‰ despite strong chemical and mineralogical similarities and this difference can be caused by the presence of carbonate, probably of pre-terrestrial origin, implying a protracted period of the existence of CaCO3-rich fluids and sufficient amounts of CO2 on the surface of Mars. The variability of δ44/40Ca within the groups of shergottites and nakhlites (clinopyroxene cumulates) cannot be related to partial melting and fractional crystallization in any simple way. However, there is no necessity of incorporating surface lithologies with isotopically light Ca into the mantle sources of Martian meteorites. These inferences are consistent with the absence of large scale crust-mantle recycling and thus of plate tectonics on Mars.

  11. Oxygen isotope fractionation in double carbonates.

    PubMed

    Zheng, Yong-Fei; Böttcher, Michael E

    2016-01-01

    Oxygen isotope fractionations in double carbonates of different crystal structures were calculated by the increment method. Synthesis experiments were performed at 60 °C and 100 °C to determine oxygen and carbon isotope fractionations involving PbMg[CO3]2. The calculations suggest that the double carbonates of calcite structure are systematically enriched in (18)O relative to those of aragonite and mixture structures. Internally consistent oxygen isotope fractionation factors are obtained for these minerals with respect to quartz, calcite and water at a temperature range of 0-1200 °C. The calculated fractionation factors for double carbonate-water systems are generally consistent with the data available from laboratory experiments. The experimentally determined fractionation factors for PbMg[CO3]2, BaMg[CO3]2 and CaMg[CO3]2 against H2O not only fall between fractionation factors involving pure carbonate end-members but are also close to the calculated fractionation factors. In contrast, experimentally determined carbon isotope fractionation factors between PbMg[CO3]2 and CO2 are much closer to theoretical predictions for the cerussite-CO2 system than for the magnesite-CO2 system, similar to the fractionation behavior for BaMg[CO3]2. Therefore, the combined theoretical and experimental results provide insights into the effects of crystal structure and exchange kinetics on oxygen isotope partitioning in double carbonates. PMID:25393769

  12. Oxygen isotopes in deep sea spherules

    NASA Technical Reports Server (NTRS)

    Mayeda, T. K.; Clayton, R. N.; Brownlee, D. E.

    1984-01-01

    The determination of the genetic relationships between the dust and small particles in the solar system, and the meteorites and larger bodies are examined. Oxygen isotopes proved useful in the identification of such relationships between one meteorite group and another. Of the various samples of submillimeter extraterrestrial particles available for laboratory study, only the deep sea spherules are abundant enough for precise oxygen isotope analysis using existing techniques. Complications arise in interpretation of the isotopic data, since these particles were melted during passage through the Earth's atmosphere, and have been in contact with seawater for prolonged periods. Spherules that were originally silicates are considered with the originally metallic ones to deduce their preterrestrial isotopic compositions. The type 1 spherules which enter the atmosphere as metallic particles, contain only atmospheric oxygen. The type S spherules contain a mixture of atmospheric oxygen and their original extraterrestrial oxygen. It is suggested that the Earth's mesosphere is strongly enriched in heavy isotopes of oxygen at altitudes near 90 km at which the iron particles are oxidized. Fractionation due to the combined diffusion of O atoms and O2 molecules may be responsible.

  13. Highly tritiated water processing by isotopic exchange

    SciTech Connect

    Shu, W.M.; Willms, R.S.; Glugla, M.; Cristescu, I.; Michling, R.; Demange, D.

    2015-03-15

    Highly tritiated water (HTW) is produced in fusion machines and one of the promising technologies to process it is isotopic exchange. 3 kinds of Pt-catalyzed zeolite (13X-APG, CBV-100-CY and HiSiv-1000) were tested as candidates for isotopic exchange of highly tritiated water (HTW), and CBV-100-CY (Na-Y type with a SiO{sub 2}/Al{sub 2}O{sub 3} ratio of ∼ 5.0) shows the best performance. Small-scale tritium testing indicates that this method is efficient for reaching an exchange factor (EF) of 100. Full-scale non-tritium testing implies that an EF of 300 can be achieved in 24 hours of operation if a temperature gradient is applied along the column. For the isotopic exchange, deuterium recycled from the Isotope Separation System (deuterium with 1% T and/or 200 ppm T) should be employed, and the tritiated water regenerated from the Pt-catalyzed zeolite bed after isotopic exchange should be transferred to Water Detritiation System (WDS) for further processing.

  14. Carbon isotopes in mollusk shell carbonates

    NASA Astrophysics Data System (ADS)

    McConnaughey, Ted A.; Gillikin, David Paul

    2008-10-01

    Mollusk shells contain many isotopic clues about calcification physiology and environmental conditions at the time of shell formation. In this review, we use both published and unpublished data to discuss carbon isotopes in both bivalve and gastropod shell carbonates. Land snails construct their shells mainly from respired CO2, and shell δ13C reflects the local mix of C3 and C4 plants consumed. Shell δ13C is typically >10‰ heavier than diet, probably because respiratory gas exchange discards CO2, and retains the isotopically heavier HCO3 -. Respired CO2 contributes less to the shells of aquatic mollusks, because CO2/O2 ratios are usually higher in water than in air, leading to more replacement of respired CO2 by environmental CO2. Fluid exchange with the environment also brings additional dissolved inorganic carbon (DIC) into the calcification site. Shell δ13C is typically a few ‰ lower than ambient DIC, and often decreases with age. Shell δ13C retains clues about processes such as ecosystem metabolism and estuarine mixing. Ca2+ ATPase-based models of calcification physiology developed for corals and algae likely apply to mollusks, too, but lower pH and carbonic anhydrase at the calcification site probably suppress kinetic isotope effects. Carbon isotopes in biogenic carbonates are clearly complex, but cautious interpretation can provide a wealth of information, especially after vital effects are better understood.

  15. New approaches to the Moon's isotopic crisis

    PubMed Central

    Melosh, H. J.

    2014-01-01

    Recent comparisons of the isotopic compositions of the Earth and the Moon show that, unlike nearly every other body known in the Solar System, our satellite's isotopic ratios are nearly identical to the Earth's for nearly every isotopic system. The Moon's chemical make-up, however, differs from the Earth's in its low volatile content and perhaps in the elevated abundance of oxidized iron. This surprising situation is not readily explained by current impact models of the Moon's origin and offers a major clue to the Moon's formation, if we only could understand it properly. Current ideas to explain this similarity range from assuming an impactor with the same isotopic composition as the Earth to postulating a pure ice impactor that completely vaporized upon impact. Several recent proposals follow from the suggestion that the Earth–Moon system may have lost a great deal of angular momentum during early resonant interactions. The isotopic constraint may be the most stringent test yet for theories of the Moon's origin. PMID:25114301

  16. New approaches to the Moon's isotopic crisis.

    PubMed

    Melosh, H J

    2014-09-13

    Recent comparisons of the isotopic compositions of the Earth and the Moon show that, unlike nearly every other body known in the Solar System, our satellite's isotopic ratios are nearly identical to the Earth's for nearly every isotopic system. The Moon's chemical make-up, however, differs from the Earth's in its low volatile content and perhaps in the elevated abundance of oxidized iron. This surprising situation is not readily explained by current impact models of the Moon's origin and offers a major clue to the Moon's formation, if we only could understand it properly. Current ideas to explain this similarity range from assuming an impactor with the same isotopic composition as the Earth to postulating a pure ice impactor that completely vaporized upon impact. Several recent proposals follow from the suggestion that the Earth-Moon system may have lost a great deal of angular momentum during early resonant interactions. The isotopic constraint may be the most stringent test yet for theories of the Moon's origin. PMID:25114301

  17. Stable oxygen and hydrogen isotopes of brines - comparing isotope ratio mass spectrometry and isotope ratio infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahrens, Christian; Koeniger, Paul; van Geldern, Robert; Stadler, Susanne

    2013-04-01

    Today's standard analytical methods for high precision stable isotope analysis of fluids are gas-water equilibration and high temperature pyrolysis coupled to isotope ratio mass spectrometers (IRMS). In recent years, relatively new laser-based analytical instruments entered the market that are said to allow high isotope precision data on nearly every media. This optical technique is referred to as isotope ratio infrared spectroscopy (IRIS). The objective of this study is to evaluate the capability of this new instrument type for highly saline solutions and a comparison of the analytical results with traditional IRMS analysis. It has been shown for the equilibration method that the presence of salts influences the measured isotope values depending on the salt concentration (see Lécuyer et al, 2009; Martineau, 2012). This so-called 'isotope salt effect' depends on the salt type and salt concentration. These factors change the activity in the fluid and therefore shift the isotope ratios measured by the equilibration method. Consequently, correction factors have to be applied to these analytical data. Direct conversion techniques like pyrolysis or the new laser instruments allow the measurement of the water molecule from the sample directly and should therefore not suffer from the salt effect, i.e. no corrections of raw values are necessary. However, due to high salt concentrations this might cause technical problems with the analytical hardware and may require labor-intensive sample preparation (e.g. vacuum distillation). This study evaluates the salt isotope effect for the IRMS equilibration technique (Thermo Gasbench II coupled to Delta Plus XP) and the laser-based IRIS instruments with liquid injection (Picarro L2120-i). Synthetic salt solutions (NaCl, KCl, CaCl2, MgCl2, MgSO4, CaSO4) and natural brines collected from the Stassfurt Salt Anticline (Germany; Stadler et al., 2012) were analysed with both techniques. Salt concentrations ranged from seawater salinity

  18. Diffusion in silicon isotope heterostructures

    SciTech Connect

    Silvestri, Hughes Howland

    2004-05-14

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly positively charged P

  19. Oxygen isotopes in nitrite: Analysis, calibration, and equilibration

    USGS Publications Warehouse

    Casciotti, K.L.; Böhlke, J.K.; McIlvin, M.R.; Mroczkowski, S.J.; Hannon, J.E.

    2007-01-01

    Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (NO3-), nitrite (NO2-), and nitrous oxide (N2O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because nitrite interferes with most methods of nitrate isotopic analysis, accurate isotopic analysis of nitrite is essential for correct measurement of nitrate isotopes in a sample that contains nitrite. In this study, nitrite salts with varying oxygen isotopic compositions were prepared and calibrated and then used to test the denitrifier method for nitrite oxygen isotopic analysis. The oxygen isotopic fractionation during nitrite reduction to N2O by Pseudomonas aureofaciens was lower than for nitrate conversion to N2O, while oxygen isotopic exchange between nitrite and water during the reaction was similar. These results enable the extension of the denitrifier method to oxygen isotopic analysis of nitrite (in the absence of nitrate) and correction of nitrate isotopes for the presence of nitrite in "mixed" samples. We tested storage conditions for seawater and freshwater samples that contain nitrite and provide recommendations for accurate oxygen isotopic analysis of nitrite by any method. Finally, we report preliminary results on the equilibrium isotope effect between nitrite and water, which can play an important role in determining the oxygen isotopic value of nitrite where equilibration with water is significant. ?? 2007 American Chemical Society.

  20. Advanced diffusion studies with isotopically controlled materials

    SciTech Connect

    Bracht, Hartmut A.; Silvestri, Hughes H.; Haller, Eugene E.

    2004-11-14

    The use of enriched stable isotopes combined with modern epitaxial deposition and depth profiling techniques enables the preparation of material heterostructures, highly appropriate for self- and foreign-atom diffusion experiments. Over the past decade we have performed diffusion studies with isotopically enriched elemental and compound semiconductors. In the present paper we highlight our recent results and demonstrate that the use of isotopically enriched materials ushered in a new era in the study of diffusion in solids which yields greater insight into the properties of native defects and their roles in diffusion. Our approach of studying atomic diffusion is not limited to semiconductors and can be applied also to other material systems. Current areas of our research concern the diffusion in the silicon-germanium alloys and glassy materials such as silicon dioxide and ion conducting silicate glasses.

  1. Atomic line emission analyzer for hydrogen isotopes

    DOEpatents

    Kronberg, J.W.

    1993-03-30

    Apparatus for isotopic analysis of hydrogen comprises a low pressure chamber into which a sample of hydrogen is introduced and then exposed to an electrical discharge to excite the electrons of the hydrogen atoms to higher energy states and thereby cause the emission of light on the return to lower energy states, a Fresnel prism made at least in part of a material anomalously dispersive to the wavelengths of interest for dispersing the emitted light, and a photodiode array for receiving the dispersed light. The light emitted by the sample is filtered to pass only the desired wavelengths, such as one of the lines of the Balmer series for hydrogen, the wavelengths of which differ slightly from one isotope to another. The output of the photodiode array is processed to determine the relative amounts of each isotope present in the sample. Additionally, the sample itself may be recovered using a metal hydride.

  2. Apparatus for separating and recovering hydrogen isotopes

    DOEpatents

    Heung, Leung K.

    1994-01-01

    An apparatus for recovering hydrogen and separating its isotopes. The apparatus includes a housing bearing at least a fluid inlet and a fluid outlet. A baffle is disposed within the housing, attached thereto by a bracket. A hollow conduit is coiled about the baffle, in spaced relation to the baffle and the housing. The coiled conduit is at least partially filled with a hydride. The hydride can be heated to a high temperature and cooled to a low temperature quickly by circulating a heat transfer fluid in the housing. The spacing between the baffle and the housing maximizes the heat exchange rate between the fluid in the housing and the hydride in the conduit. The apparatus can be used to recover hydrogen isotopes (protium, deuterium and tritium) from gaseous mixtures, or to separate hydrogen isotopes from each other.

  3. Isotopes in the Arctic atmospheric water cycle

    NASA Astrophysics Data System (ADS)

    Bonne, Jean-Louis; Werner, Martin; Meyer, Hanno; Kipfstuhl, Sepp; Rabe, Benjamin; Behrens, Melanie; Schönicke, Lutz; Steen Larsen, Hans Christian; Masson-Delmotte, Valérie

    2016-04-01

    The ISO-ARC project aims at documenting the Arctic atmospheric hydrological cycle, by assessing the imprint of the marine boundary conditions (e.g. temperature variations, circulation changes, or meltwater input) to the isotopic composition of the atmospheric water cycle (H218O and HDO) with a focus on North Atlantic and Arctic oceans. For this purpose, two continuous monitoring water vapour stable isotopes cavity ring-down spectrometers have been installed in July 2015: on-board the Polarstern research vessel and in the Siberian Lena delta Samoylov research station (N 72° 22', E 126° 29'). The Polarstern measurements cover the summer 2015 Arctic campaign from July to mid-October, including six weeks in the Fram Strait region in July- August, followed by a campaign reaching the North Pole and a transect from the Norwegian Sea to the North Sea. These vapour observations are completed by water isotopic measurements in samples from the surface ocean water for Polarstern and from precipitation in Samoylov and Tiksi (120 km south-east of the station). A custom-made designed automatic calibration system has been implemented in a comparable manner for both vapour instruments, based on the injection of different liquid water standards, which are completely vaporised in dry air at high temperature. Subsequent humidity level can be adjusted from 2000 to at least 30000 ppm. For a better resilience, an independent calibration system has been added on the Samoylov instrument, allowing measurements of one standard at humidity levels ranging from 2000 to 15000 ppm: dry air is introduced in a tank containing a large amount of liquid water standard, undergoing evaporation under a controlled environment. The measurement protocol includes an automatic calibration every 25 hours. First instrument characterisation experiments depict a significant isotope-humidity effect at low humidity, dependant on the isotopic composition of the standard. For ambient air, our first isotope

  4. Separation of isotopes by cyclical processes

    DOEpatents

    Hamrin, Jr., Charles E.; Weaver, Kenny

    1976-11-02

    Various isotopes of hydrogen are separated by a cyclic sorption process in which a gas stream containing the isotopes is periodically passed through a high pressure column containing a palladium sorbent. A portion of the product from the high pressure column is passed through a second column at lower pressure to act as a purge. Before the sorbent in the high pressure column becomes saturated, the sequence is reversed with the stream flowing through the former low-pressure column now at high pressure, and a portion of the product purging the former high pressure column now at low pressure. The sequence is continued in cyclic manner with the product being enriched in a particular isotope.

  5. Oxidation of hydrogen isotopes over honeycomb catalysts

    NASA Astrophysics Data System (ADS)

    Munakata, Kenzo; Wajima, Takaaki; Hara, Keisuke; Wada, Kohei; Shinozaki, Yohei; Katekari, Kenichi; Mochizuki, Kazuhiro; Tanaka, Masahiro; Uda, Tatsuhiko

    2011-10-01

    In the process of development of D-T fusion power reactors, recovery of tritium released into the last confinement system would be a key issue related to safety. If an accidental leakage of tritium takes place in a fusion power plant, a large volume of air should be detritiated with an air cleanup system (ACS). In ACS, tritium gas is converted to tritiated water vapor with a catalyst bed, and then which is recovered with an adsorption bed. In this study, the authors examined the applicability of honeycomb-type catalysts to ACS. A screening test of catalysts for oxidation of hydrogen and deuterium was performed using various honeycomb-type and pebble-type catalysts. Experimental results reveal that a honeycomb-type catalyst possesses a high oxidation performance for oxidation of hydrogen isotopes. Furthermore, the isotope effect on the oxidation of hydrogen isotopes over the honeycomb-type catalyst was thoroughly examined and quantified using tritium.

  6. Atomic line emission analyzer for hydrogen isotopes

    DOEpatents

    Kronberg, J.W.

    1991-05-08

    Apparatus for isotopic analysis of hydrogen comprises a low pressure chamber into which a sample of hydrogen is introduced and then exposed to an electrical discharge to excite the electrons of the hydrogen atoms to higher energy states and thereby cause the emission of light on the return to lower energy states, a Fresnel prism made at least in part of a material anomalously dispersive to the wavelengths of interest for dispersing the emitted light, and a photodiode array for receiving the dispersed light. The light emitted by the sample is filtered to pass only the desired wavelengths, such as one of the lines of the Balmer series for hydrogen, the wavelengths of which differ slightly from one isotope to another. The output of the photodiode array is processed to determine the relative amounts of each isotope present in the sample. Additionally, the sample itself may be recovered using, a metal hydride.

  7. Carbon isotopes in bulk carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Halbout, J.; Mayeda, T. K.; Clayton, R. N.

    1985-01-01

    The chemical and physical processes involved in the formation of the solar system are examined. Primitive matter has been found on a microscopic scale in a variety of meteorites: fragments of small solar system bodies that were never part of a large planet. This primitive matter has, in most cases, been identified by the presence of anomalous abundances of some isotopes of the chemical elements. Of particular interest for carbon isotope studies are the primitive meteorites known as carbonaceous chondrites. Using a selective oxidation technique to sort out the carbon contained in different chemical forms (graphite, carbonates, and organic matter), four carbonaceous chondrites are analyzed. The presence of the (13) C-rich component was confirmed and additional carbon components with different, but characteristic, isotopic signatures were resolved.

  8. Oxygen isotopes implanted in the LDEF spacecraft

    NASA Technical Reports Server (NTRS)

    Saxton, J. M.; Lyon, I. C.; Chatzitheodoridis, E.; Vanlierde, P.; Gilmour, J. D.; Turner, G.

    1993-01-01

    Secondary ion mass spectrometry was used to study oxygen implanted in the surface of copper from the Long Duration Exposure Facility (LDEF). Oxidation that occurred in orbit shows a characteristic oxygen isotope composition, depleted in O-18. The measured depletion is comparable to the predicted depletion (45 percent) based on a model of the gravitational separation of the oxygen isotopes. The anomalous oxygen was contained within 10nm of the surface. Tray E10 was calculated to have received 5.14 x 10(exp 21) atoms of oxygen cm(sup -2) during the LDEF mission and so there is sufficient anomalous implanted oxygen present in the surface to obtain a reliable isotopic profile.

  9. Earth Processes: Reading the Isotopic Code

    NASA Astrophysics Data System (ADS)

    Basu, Asish; Hart, Stan

    Publication of this monograph will coincide, to a precision of a few per mil, with the centenary of Henri Becquerel's discovery of "radiations actives" (C. R. Acad. Sci., Feb. 24, 1896). In 1896 the Earth was only 40 million years old according to Lord Kelvin. Eleven years later, Boltwood had pushed the Earth's age past 2000 million years, based on the first U/Pb chemical dating results. In exciting progression came discovery of isotopes by J. J. Thomson in 1912, invention of the mass spectrometer by Dempster (1918) and Aston (1919), the first measurement of the isotopic composition of Pb (Aston, 1927) and the final approach, using Pb-Pb isotopic dating, to the correct age of the Earth: close—2.9 Ga (Gerling, 1942), closer—3.0 Ga (Holmes, 1949) and closest—4.50 Ga (Patterson, Tilton and Inghram, 1953).

  10. The rare isotope accelerator (RIA) facility project

    SciTech Connect

    Christoph Leemann

    2000-08-01

    The envisioned Rare-Isotope Accelerator (RIA) facility would add substantially to research opportunities for nuclear physics and astrophysics by combining increased intensities with a greatly expanded variety of high-quality rare-isotope beams. A flexible superconducting driver linac would provide 100 kW, 400 MeV/nucleon beams of any stable isotope from hydrogen to uranium onto production targets. Combinations of projectile fragmentation, target fragmentation, fission, and spallation would produce the needed broad assortment of short-lived secondary beams. This paper describes the project's background, purpose, and status, the envisioned facility, and the key subsystem, the driver linac. RIA's scientific purposes are to advance current theoretical models, reveal new manifestations of nuclear behavior, and probe the limits of nuclear existence [3]. Figures 1 and 2 show, respectively, examples of RIA research opportunities and the yields projected for pursuing them. Figure 3 outlines a conceptual approach for delivering the needed beams.

  11. The HEAO-3 Cosmic Ray Isotope spectrometer

    NASA Technical Reports Server (NTRS)

    Bouffard, M.; Engelmann, J. J.; Koch, L.; Soutoul, A.; Lund, N.; Peters, B.; Rasmussen, I. L.

    1982-01-01

    This paper describes the Cosmic Ray Isotope instrument launched aboard the HEAO-3 satellite on September 20, 1979. The primary purpose of the experiment is to measure the isotopic composition of cosmic ray nuclei from Be-7 to Fe-58 over the energy range 0.5 to 7 GeV/nucleon. In addition charge spectra will be measured between beryllium and tin over the energy range 0.5 to 25 GeV/nucleon. The charge and isotope abundances measured by the experiment provide essential information needed to further our understanding of the origin and propagation of high energy cosmic rays. The instrument consists of 5 Cerenkov counters, a 4 element neon flash tube hodoscope and a time-of-flight system. The determination of charge and energy for each particle is based on the multiple Cerenkov technique and the mass determination will be based upon a statistical analysis of particle trajectories in the geomagnetic field.

  12. Isotopic ratio measurements with ICP-MS

    SciTech Connect

    Russ, G.P. III; Bazan, J.M.

    1986-06-03

    An inductively-coupled-plasma source mass spectrometer (ICP-MS) has been used to measure the isotopic composition of U, Pb, Os, and B standards. Particular emphasis has been placed on uranium because of its nuclear and environmental interest and because of the availability of a well-characterized set of standards with a wide range of isotopic compositions. The precision and accuracy obtainable in isotope ratio measurements by ICP-MS depend on many factors including background, interferences, dead time, mass fractionation (bias), abundance sensitivity, and counting statistics. Which, if any, of these factors controls accuracy and precision depends on the type of sample being analyzed and the characteristics of the mass spectrometer. These issues are discussed in detail.

  13. Stable isotope and elemental analysis in ants.

    PubMed

    Smith, Chris R; Tillberg, Chadwick V

    2009-07-01

    Over the past 20 yr, the use of stable isotopes to infer feeding ecology and the examination of how energetic and elemental exchanges are affected by and affect life (ecological stoichiometry) have gained momentum. The ecological diversity of ants makes them interesting models to explore dietary ecology and their role in food webs. Moreover, their ecological dominance in most habitats facilitates sampling. The protocol described here will produce samples adequate for submission to most labs that specialize in high-throughput analysis of stable isotopes; one should check with any particular lab for specific submission instructions. Note, however, that this protocol is designed specifically for the quantification of the natural abundance of stable isotopes; it does not cover the preparation of trace samples. PMID:20147207

  14. Isotopic fractionation of stratospheric nitrous oxide

    SciTech Connect

    Yung, Yuk L.; Miller, C.L.

    1997-12-05

    An isotopic fractionation mechanism is proposed, based on photolytic destruction to explain the {sup 15}N/{sup 14}N and {sup 18}O/{sup 16}O fractionation of stratospheric nitrous oxide (N{sub 2}O) and reconcile laboratory experiments with atmospheric observations. The theory predicts that (i) the isotopomers {sup 15}N{sup 14}N{sup 16}O and {sup 14}N{sup 15}N{sup 16}O have very different isotopic fractionations in the stratosphere, and (ii) laboratory photolysis experiments conducted at 205 nanometers should better simulate the observed isotopic fractionation of stratospheric N{sub 2}O. Modeling results indicate that there is no compelling reason to invoke a significant chemical source of N{sub 2}O in the middle atmosphere and that individual N{sub 2}O isotopomers might be useful tracers of stratospheric air parcel motion. 32 refs., 2 figs., 1 tab.

  15. Atomic line emission analyzer for hydrogen isotopes

    DOEpatents

    Kronberg, James W.

    1993-01-01

    Apparatus for isotopic analysis of hydrogen comprises a low pressure chamber into which a sample of hydrogen is introduced and then exposed to an electrical discharge to excite the electrons of the hydrogen atoms to higher energy states and thereby cause the emission of light on the return to lower energy states, a Fresnel prism made at least in part of a material anomalously dispersive to the wavelengths of interest for dispersing the emitted light, and a photodiode array for receiving the dispersed light. The light emitted by the sample is filtered to pass only the desired wavelengths, such as one of the lines of the Balmer series for hydrogen, the wavelengths of which differ slightly from one isotope to another. The output of the photodiode array is processed to determine the relative amounts of each isotope present in the sample. Additionally, the sample itself may be recovered using a metal hydride.

  16. Analysing Groundwater Using the 13C Isotope

    NASA Astrophysics Data System (ADS)

    Awad, Sadek

    The stable isotope of the carbon atom (13C) give information about the type of the mineralisation of the groundwater existing during the water seepage and about the recharge conditions of the groundwater. The concentration of the CO2(aq.) dissolved during the infiltration of the water through the soil's layers has an effect on the mineralisation of this water. The type of the photosynthesis's cycle (C-3 or C-4 carbon cycle) can have a very important role to determine the conditions (closed or open system) of the mineralisation of groundwater. The isotope 13C of the dissolved CO2 in water give us a certain information about the origin and the area of pollution of water. The proportion of the biogenic carbon and its percentage in the mineralisation of groundwater is determined by using the isotope 13C.

  17. The State of the Ca Isotope Proxy

    NASA Astrophysics Data System (ADS)

    Fantle, M. S.; Tipper, E.

    2012-12-01

    At the Earth's surface, Ca is a critical element at a variety of scales. It is both a biological nutrient and water-soluble, and is a major constituent of the dominant mineral sink for carbon in the ocean. Additionally, the 5‰ range in the stable isotope ratios of Ca (44Ca/40Ca) suggests that Ca isotopes may be a promising tracer of the Ca cycle, specifically the oceanic budget over time. Despite ~15 years of concentrated effort on high-precision Ca isotope measurements, the utility of Ca isotopes as a proxy remains far from clear. A variety of basic questions have yet to be resolved, both in the marine and terrestrial realms. To provide perspective, the current work presents a data compilation of over 60 published Ca isotope studies. The compilation includes δ44/40CaSRM-915a measurements of the modern Ca cycle, including rivers and groundwater, dust, soils and soil pore fluids, vegetation, rainwater, silicate minerals/rocks, and marine carbonates. The focus of this work is to quantify the leverage of inputs to change the isotopic composition of the ocean. One of the tenets of the weathering proxy is that there is little isotopic leverage to change seawater. If this assumption is valid, then significant variations in the isotopic composition of seawater can be explained to some extent by mass flux imbalances between Ca inputs and outputs, requiring the Ca cycle to be out of steady state for significant periods of time. Despite evidence that Ca fractionates in the modern system during continental cycling, the δ44Ca range of riverine inputs to the ocean is very narrow (especially when compared to the spread in marine carbonates). Thus, there appears to be minimal isotopic leverage amongst inputs to shift the ocean δ44Ca. In order to develop our understanding of the Ca isotope proxy, we identify two probable mechanisms for shifting ocean δ44Ca and evaluate them using a series of simple box models. In the terrestrial realm, plants exhibit a wide range of

  18. The isotopic homogeneity in the early solar system: Revisiting the CAI oxygen isotopic anomaly

    NASA Astrophysics Data System (ADS)

    Ozima, M.; Yamada, A.

    2009-12-01

    Since the first discovery of the mass-independently fractionated oxygen isotopes in anhydrous, high temperature Ca-Al rich inclusion minerals in carbonaceous meteorites (CAIs) by Clayton et al. (1), their common occurrence in primitive meteorites has generally been regarded to reflect some fundamental process prevalent in the early solar nebula. The CAI oxygen isotopic composition is uniquely characterized by (i) large mass independent isotopic fractionation and (ii) their isotopic data in an oxygen three isotope plot (δ17O - δ18O (δ17O ≡ {(17O/16O)/(17O/16O)SMOW - 1} × 1000) yield nearly a straight line with a slope 1.0. In establishing these characteristics, ion microprobe analyses has played a central role, especially an isotopic mapping technique (isotopography) was crucial (e.g., 2). The extraordinary oxygen isotopic ratio in CAIs is widely attributed to the self-shielding absorption of UV radiation in CO, one of the dominant chemical compounds in the early solar nebula (3). However, the self-shielding scenario necessarily leads to the unusual prediction that a mean solar oxygen isotopic composition differs from most of planetary bodies including Earth, Moon, and Mars. If the self-shielding process were indeed responsible to the CAI oxygen isotopic anomaly, this would require a fundamental revision of the current theory of the origin of the solar system, which generally assumes the initial total vaporization of nebula material to give rise to isotopic homogenization. The GENESIS mission launched in 2001(4), which collected oxygen in the solar wind was hoped to resolve the isotopic composition of the Sun. However, because of difficulties in correcting for instrumental and more importantly for intrinsic isotopic fractionation between the SW and the Sun, a final answer is yet to be seen (5). Here, we show on the basis of the oxygen isotopic fractionation systematics that the self shielding hypothesis cannot explain the key characteristics of the CAI oxygen

  19. Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth

    USGS Publications Warehouse

    Chen, Heng; Savage, Paul S.; Teng, Fang-Zehn; Helz, Rosalind T.; Moynier, Frédéric

    2013-01-01

    he zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic fractionation induced by magmatic differentiation. In this study we present high-precision Zn isotope analyses of two sets of chemically diverse, cogenetic samples from Kilauea Iki lava lake, Hawaii, and Hekla volcano, Iceland, which both show clear evidence of having undergone variable and significant degrees of magmatic differentiation. The Kilauea Iki samples display small but resolvable variations in Zn isotope composition (0.26‰66Zn66Zn defined as the per mille deviation of a sample's 66Zn/64Zn compositional ratio from the JMC-Lyon standard), with the most differentiated lithologies exhibiting more positive δ66Zn values. This fractionation is likely a result of the crystallization of olivine and/or Fe–Ti oxides, which can both host Zn in their crystal structures. Samples from Hekla have a similar range of isotopic variation (0.22‰66Zn66Zn=0.28±0.05‰ (2s.d.).

  20. Oxygen and carbon isotope disequilibria in Galapagos corals: isotopic thermometry and calcification physiology

    SciTech Connect

    McConnaughey, T.A.

    1986-01-01

    Biological carbonate skeletons are built largely from carbon dioxide, which reacts to form carbonate ion within thin extracellular solutions. The light isotopes of carbon and oxygen react faster than the heavy isotopes, depleting the resulting carbonate ions in /sup 13/C and /sup 18/O. Calcium carbonate precipitation occurs sufficiently fast that the skeleton remains out of isotopic equilibrium with surrounding fluids. This explanation for isotopic disequilibrium in biological carbonates was partially simulated in vitro, producing results similar to those seen in non-photosynthetic corals. Photosynthetic corals have higher /sup 13/C//sup 12/C ratios due to the preferential removal of /sup 12/C (as organic carbon) from the reservoir of dissolved inorganic carbon. The oxygen isotopic variations in corals can be used to reconstruct past sea surface temperatures to an accuracy of about 0.5/sup 0/C. The carbon isotopic content of photosynthetic corals provides an indication of cloudiness. Using isotopic data from Galapagos corals, it was possible to construct proxy histories of the El Nino phenomenon. The physiology of skeletogenesis appears to be surprisingly similar in calcium carbonate, calcium phosphate, and silica precipitating systems.

  1. Isotope shift measurements on the D1 line in francium isotopes at TRIUMF

    NASA Astrophysics Data System (ADS)

    Collister, R.; Tandecki, M.; Gwinner, G.; Behr, J. A.; Pearson, M. R.; Gomez, E.; Aubin, S.; Zhang, J.; Orozco, L. A.

    2013-05-01

    Francium is the heaviest alkali and has no stable isotopes. The longest-lived among them, with half-lives from seconds to a few minutes, are now available in the new Francium Trapping Facility at TRIUMF, Canada, for future weak interaction studies. We present isotope shift measurements on the 7S1 / 2 --> 7P1 / 2 (D 1) transition on three isotopes, 206, 207 and 213 in a magneto-optical trap. The shifts are measured using a c.w. Ti:sapphire laser locked to a stabilized cavity at the mid-point between two hyperfine transitions of the reference isotope 209Fr. Scanning tunable microwave sidebands locate transitions in the other isotopes. In combination with the D 2 isotope shifts, analysis can provide a separation of the field shift, due to a changing nuclear charge radius, and specific mass shift, due to changing electron correlations, in these isotopes. Work supported by NSERC and NRC from Canada, NSF and DOE from USA, CONYACT from Mexico.

  2. Carbonate clumped isotope thermometry in continental tectonics

    NASA Astrophysics Data System (ADS)

    Huntington, Katharine W.; Lechler, Alex R.

    2015-04-01

    Reconstructing the thermal history of minerals and fluids in continental environments is a cornerstone of tectonics research. Paleotemperature constraints from carbonate clumped isotope thermometry have provided important tests of geodynamic, structural, topographic and basin evolution models. The thermometer is based on the 13C-18O bond ordering in carbonates (mass-47 anomaly, Δ47) and provides estimates of the carbonate formation temperature independent of the δ18O value of the water from which the carbonate grew; Δ47 is measured simultaneously with conventional measurements of carbonate δ13C and δ18O values, which together constrain the isotopic composition of the parent water. Depending on the geologic setting of carbonate growth, this information can help constrain paleoenvironmental conditions or basin temperatures and fluid sources. This review examines how clumped isotope thermometry can shed new light on problems in continental tectonics, focusing on paleoaltimetry, basin evolution and structural diagenesis applications. Paleoaltimetry is inherently difficult, and the precision in carbonate growth temperature estimates is at the limit of what is useful for quantitative paleoelevation reconstruction. Nevertheless, clumped isotope analyses have enabled workers to address previously intractable problems and in many settings offer the best chance of understanding topographic change from the geologic record. The portion of the shallow crust residing at temperatures up to ca. 200 °C is important as host to economic resources and records of tectonics and climate, and clumped isotope thermometry is one of the few proxies that can access this critical range with sensitivity to temperature alone. Only a handful of studies to date have used clumped isotopes to investigate diagenesis and other sub-surface processes using carbonate crystallization temperatures or the sensitivity of Δ47 values to a sample's thermal history. However, the thermometer is

  3. Isotope geochemistry of caliche developed on basalt

    NASA Astrophysics Data System (ADS)

    Knauth, L. Paul; Brilli, Mauro; Klonowski, Stan

    2003-01-01

    Enormous variations in oxygen and carbon isotopes occur in caliche developed on < 3 Ma basalts in 3 volcanic fields in Arizona, significantly extending the range of δ 18O and δ 13C observed in terrestrial caliche. Within each volcanic field, δ 18O is broadly co-variant with δ 13C and increases as δ 13C increases. The most 18O and 13C enriched samples are for subaerial calcite developed on pinnacles, knobs, and flow lobes that protrude above tephra and soil. The most 18O and 13C depleted samples are for pedogenic carbonate developed in soil atmospheres. The pedogenic caliche has δ 18O fixed by normal precipitation in local meteoric waters at ambient temperatures and has low δ 13C characteristic of microbial soil CO 2. Subaerial caliche has formed from 18O-rich evapoconcentrated meteoric waters that dried out on surfaces after local rains. The associated 13C enrichment is due either to removal of 12C by photosynthesizers in the evaporating drops or to kinetic isotope effects associated with evaporation. Caliche on basalt lava flows thus initially forms with the isotopic signature of evaporation and is subsequently over-layered during burial by calcite carrying the isotopic signature of the soil environment. The large change in carbon isotope composition in subsequent soil calcite defines an isotopic biosignature that should have developed in martian examples if Mars had a "warm, wet" early period and photosynthesizing microbes were present in the early soils. The approach can be similarly applied to terrestrial Precambrian paleocaliche in the search for the earliest record of life on land. Large variations reported for δ 18O of carbonate in Martian meteorite ALH84001 do not necessarily require high temperatures, playa lakes, or flood runoff if the carbonate is an example of altered martian caliche.

  4. Titan's Isotopic Menagerie: The Cassini CIRS Perspective

    NASA Astrophysics Data System (ADS)

    Nixon, Conor A.; Achterberg, R. K.; Bezard, B.; Bjoraker, G. L.; Coustenis, A.; de Kok, R.; Flasar, F. M.; Hewagama, T.; Irwin, P. G. J.; Jennings, D. E.; Jolly, A.; Romani, P. N.; Teanby, N. A.; Vinatier, S.; CIRS Team

    2008-09-01

    Saturn's long-mysterious moon Titan is gradually yielding up its secrets under the intense scrutiny of the Cassini spacecraft, which has just completed a 4-year prime mission including 45 close flybys of the giant satellite. We here focus on the isotopic composition of the stratosphere, which since Voyager 1 in 1980 has been known to comprise a surprisingly rich mixture of hydrocarbons, nitriles and several oxygen species. These molecules are now understood to originate in the upper atmosphere by chemical processes initiated by the dissociation of the most abundant native species - methane and nitrogen - with some oxygen added from externally-supplied water. Measurements of isotopic ratios in these compounds are important and can provide valuable information on the formation and evolution of Titan's atmosphere. E.g. Chemical processes can cause isotopic fractionation via the 'kinetic isotope effect' (KIE). Cassini's Composite Infrared Spectrometer (CIRS), which is sensitive to thermal infrared radiation from 10-1500 cm-1 (7-1000 micron), is an ideal tool for measuring molecular concentrations and can distinguish between isotopologues due to the shifts in the molecular bands. CIRS has now identified at least eleven isotopologue species in our spectra, with multiple new detections in the past year (13CO2, CO18O, HC13CCCN). CIRS has measured the ratios 12C/13C in a total of seven species, D/H in two species, and 14N/15N and 16O/18O each in one species - the best measurement so far of the important ratio 16O/18O on Titan (346±110). In this presentation we will summarize all our results to date on isotopic ratios, including comparison with Huygens GCMS and other determinations, a discussion of possible isotopic separation in hydrocarbon chains, and formation/evolution implications of these measurements for Titan.

  5. Position-specific measurement of oxygen isotope ratios in cellulose: Isotopic exchange during heterotrophic cellulose synthesis

    NASA Astrophysics Data System (ADS)

    Waterhouse, John S.; Cheng, Shuying; Juchelka, Dieter; Loader, Neil J.; McCarroll, Danny; Switsur, V. Roy; Gautam, Lata

    2013-07-01

    We describe the first reported method for the measurement of oxygen isotope ratios at each position in the glucose units of the cellulose molecule. The overall process comprises a series of synthetic organic sequences, by which α-cellulose is hydrolysed to glucose, and oxygen atoms at specific positions in the glucose molecule are removed in samples of benzoic acid for measurement of δ18O. Values of δ18O at specific positions in cellulose are calculated from these δ18O values and the overall δ18O value of the cellulose. We apply the method to determine the degree to which oxygen atoms at each position undergo isotopic exchange with water during heterotrophic cellulose synthesis, such as occurs in the cambium of trees. To do this we extract α-cellulose from wheat seedlings germinated in the dark in aqueous media of differing oxygen isotope ratios. Results indicate that oxygen atoms at positions 5 and 6 (O-5 and O-6 respectively) undergo around 80% exchange with medium water, O-3 undergoes around 50% exchange, and O-2 and O-4 do not undergo isotopic exchange. The results have important implications for extracting palaeoclimatic records from oxygen isotope time series obtained from tree ring cellulose. As O-5 and O-6 undergo significant exchange with medium water during heterotrophic cellulose synthesis, oxygen isotopes at these positions in tree ring cellulose should carry a predominantly trunk (source) water signal. On the other hand, O-2 and O-4 should retain the isotopic signature of leaf water in tree ring cellulose. Our method therefore potentially enables the separate reconstruction of past temperature and humidity data from oxygen isotope ratios of tree ring cellulose - something that has hitherto not been possible. The measured degrees of isotopic exchange are to some extent unexpected and cannot be fully explained using current biochemical mechanisms, suggesting that knowledge of these processes is incomplete.

  6. Hitting the moving target: modelling ontogenetic shifts with stable isotopes reveals the importance of isotopic turnover.

    PubMed

    Hertz, Eric; Trudel, Marc; El-Sabaawi, Rana; Tucker, Strahan; Dower, John F; Beacham, Terry D; Edwards, Andrew M; Mazumder, Asit

    2016-05-01

    Ontogenetic niche shifts are widely prevalent in nature and are important in shaping the structure and dynamics of ecosystems. Stable isotope analysis is a powerful tool to assess these shifts, with δ(15) N providing a measure of trophic level and δ(13) C a measure of energy source. Previous applications of stable isotopes to study ontogenetic niche shifts have not considered the appreciable time lag between diet and consumer tissue associated with isotopic turnover. These time lags introduce significant complexity into field studies of ontogenetic niche shifts. Juvenile Chinook salmon (Oncorhynchus tshawytscha) migrate from freshwater to marine ecosystems and shift their diet from feeding primarily on invertebrates to feeding primarily on fish. This dual ontogenetic habitat and diet shift, in addition to the long time lag associated with isotopic turnover, suggests that there is potential for a disconnect between the prey sources that juvenile salmon are consuming, and the inferred prey sources from stable isotopes. We developed a model that considered ontogenetic niche shifts and time lags associated with isotopic turnover, and compared this 'ontogeny' model to one that considered only isotopic turnover. We used a Bayesian framework to explicitly account for parameter uncertainty. Data showed overwhelming support for the ontogeny model relative to the isotopic turnover model. Estimated variables from best model fits indicate that the ontogeny model predicts a much greater reliance on fish prey than does the stomach content data. Overall, we found that this method of quantifying ontogenetic niche shifts effectively accounted for both isotopic turnover and ontogenetic diet shifts; a finding that could be widely applicable to a variety of systems. PMID:26880007

  7. Isotope fractionation and isotope decoupling during nitrate reduction in marine sediments

    NASA Astrophysics Data System (ADS)

    Dähnke, Kirstin; Thamdrup, Bo

    2015-04-01

    In summer 2010, we sampled marine sediments in the Skagerrak, covering a gradient of reactivity, oxygen consumption, and manganese concentration in the sediment. Along this gradient, we aimed to evaluate links between nitrogen cycling and sediment properties. The focus of the study was the interplay of nitrate and nitrite reduction rates and concomitant nitrate and nitrite isotope changes in sediment incubations. As expected, nitrate reduction was fastest in sediments with highest sediment reactivity and oxygen consumption. At the shallower sampling sites, denitrification was the main removal pathway of nitrate and nitrite, but acetylene inhibition experiments pointed towards significant importance of anammox at the deepest site in the Skagerrak. The N-isotope of denitrification effect varied with depth, with stronger N-isotope fractionation at deeper, and less reactive, sites, and ranged from -12 to -16o. At the deepest site in the Skagerrak, anammox was the dominant N2 production pathway. For this site, we calculated the intrinsic isotope effect of anammox in marine sediments, and found that it is ~-15o, which is in accordance with recent culture studies. The isotope effect of oxygen, however, was not consistent pattern along the gradient of sediment reactivity. The oxygen isotope effect of nitrate reduction was entirely decoupled from the nitrogen isotope effect. Surprisingly, this variability in oxygen isotope fractionation was not linked to the occurrence of anammox, but rather to intermediate nitrite accumulation in the anoxic incubations. Consequently, the ratio of 18ɛ / 15ɛ was highly variable in all sediments we investigated. We presume that such decoupling of oxygen and nitrogen isotopes is due to anoxic nitrite oxidation, which rises in turn with nitrite accumulation in the sediment incubations. These findings suggest that the ratio of 18ɛ / 15ɛ in marine environments is highly flexible, and might, especially in regions with considerable nitrite

  8. Neutron multiplicities for the transplutonium nuclides

    SciTech Connect

    Holden, N.E.; Zucker, M.S.

    1985-01-01

    This paper continues, with respect to the transplutonium nuclides, earlier efforts to collate and evaluate data from the scientific literature on the prompt neutron multiplicity distribution from fission and its first moment = ..sigma..nuPnu. The isotopes considered here for which P/sub nu/ and or data (or both) were found in the literature are of americium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), and nobelium (No).

  9. Isotope Separation in Concurrent Gas Centrifuges

    NASA Astrophysics Data System (ADS)

    Bogovalov, S. V.; Borman, V. D.

    An analytical equation defining separative power of an optimized concurrent gas centrifuge is obtained for an arbitrary binary mixture of isotopes. In the case of the uranium isotopes the equation gives δU= 12.7(V/700 m/s)2(300 K/T)L, kg SWU/yr, where L and V are the length and linear velocity of the rotor of the gas centrifuge, T is the temperature. This formula well agrees with an empirical separative power of counter current gas centrifuges.

  10. Chromium isotopic anomalies in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.

    1986-01-01

    Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

  11. Cross Section Evaluations for Arsenic Isotopes

    SciTech Connect

    Pruet, J; McNabb, D P; Ormand, W E

    2005-03-10

    The authors present an evaluation of cross sections describing reactions with neutrons incident on the arsenic isotopes with mass numbers 75 and 74. Particular attention is paid to (n,2n) reactions. The evaluation for {sup 75}As, the only stable As isotope, is guided largely by experimental data. Evaluation for {sup 74}As is made through calculations with the EMPIRE statistical-model reaction code. Cross sections describing the production and destruction of the 26.8 ns isomer in {sup 74}As are explicitly considered. Uncertainties and covariances in some evaluated cross sections are also estimated.

  12. Modified Sigmund sputtering theory: isotopic puzzle

    NASA Astrophysics Data System (ADS)

    Zhang, Z. L.; Zhang, L.

    2005-05-01

    The theory of anisotropic sputtering proposed by Zhang [Z.L. Zhang, Phys. Rev. B 71 026101 (2005).] and [Z.L. Zhang and L. Zhang, Radiat. Eff. Defects Solids 159(5) 301 (2004).] has been generalized to sputtering of isotopic mixtures. The present theory (modified Sigmund theory) has been shown to fit numerous simulations and experimental measurements, including energy and angular distribution of sputtered atoms. In particular, the theory has successfully solved the isotope puzzle of sputtering induced by low energy and heavy ion bombardment.

  13. [Stable isotopes in biomedical diagnosis and research].

    PubMed

    Martínez, J A; Hellerstein, M K; Monreal, I; Neese, R A; Viteri, F E

    1995-01-01

    Atoms that are chemically identical but that differed slightly in weight due to the number of nuclear neutrons are called isotopes stables, meaning that do not degrade spontaneously. Mass spectrometry is the analytical technique to evaluate the enrichment on these isotopes with a variety of applications in the clinical diagnosis of pathological processes and the quantitation of metabolic events such as bacterial growth (Helicobacter pylorii), Phenylketonuria, lactose intolerance, liver and pancreatic function, body composition and energy expenditure, cholesterogenesis, glucose utilization, etc. in an easy, non-invasive and specific way as mass spectrometers develop. PMID:8552917

  14. Laser isotope separation by multiple photon absorption

    DOEpatents

    Robinson, C. Paul; Rockwood, Stephen D.; Jensen, Reed J.; Lyman, John L.; Aldridge, III, Jack P.

    1987-01-01

    Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, is the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO.sub.2 laser light may be used to highly enrich .sup.34 S in natural SF.sub.6 and .sup.11 B in natural BCl.sub.3.

  15. Laser isotope separation by multiple photon absorption

    DOEpatents

    Robinson, C. Paul; Rockwood, Stephen D.; Jensen, Reed J.; Lyman, John L.; Aldridge, III, Jack P.

    1977-01-01

    Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, in the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO.sub.2 laser light may be used to highly enrich .sup.34 S in natural SF.sub.6 and .sup.11 B in natural BCl.sub.3.

  16. Laser isotope separation by multiple photon absorption

    DOEpatents

    Robinson, C.P.; Rockwood, S.D.; Jensen, R.J.; Lyman, J.L.; Aldridge, J.P. III.

    1987-04-07

    Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, is the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO[sub 2] laser light may be used to highly enrich [sup 34]S in natural SF[sub 6] and [sup 11]B in natural BCl[sub 3]. 8 figs.

  17. Atomic balm: Finding hope in isotopes

    SciTech Connect

    Carlson, K.

    1996-12-31

    This article provides a glimpse of the research program at ORNL carried out as part of the nuclear medicine group, aimed at the application of radioisotopes for medical applications. These can be either diagnostic or treatment based applications. Faced with shrinking research budgets, the department focuses primarily on applications of reactor produced isotopes because of the continued availability of a reactor for producing such isotopes. This paper describes collaborative work to use rhenium-188 and iodine-123 for cancer and pain treatments, and for diagnosing Alzheimer`s disease.

  18. Isotope separation and advanced manufacturing technology

    NASA Astrophysics Data System (ADS)

    Carpenter, J.; Kan, T.

    This is the fourth issue of a semiannual report for the Isotope Separation and Advanced Materials Manufacturing (ISAM) Technology Program at Lawrence Livermore National Laboratory. Primary objectives include: (1) the Uranium Atomic Vapor Laser Isotope Separation (UAVLIS) process, which is being developed and prepared for deployment as an advanced uranium enrichment capability; (2) Advanced manufacturing technologies, which include industrial laser and E-beam material processing and new manufacturing technologies for uranium, plutonium, and other strategically important materials in support of DOE and other national applications. This report features progress in the ISAM Program from October 1993 through March 1994.

  19. Cadmium isotope variations in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Xue, Zichen; Rehkämper, Mark; Horner, Tristan J.; Abouchami, Wafa; Middag, Rob; van de Flierd, Tina; de Baar, Hein J. W.

    2013-11-01

    Cadmium concentrations and isotope compositions were determined for 47 seawater samples from the high nutrient low chlorophyll (HNLC) zone of the Atlantic sector of the Southern Ocean. The samples include 13 surface waters from a transect of the Weddell Gyre and 3 depth profiles from the Weddell Sea and Drake Passage. The Southern Ocean mixed layer samples from this study and Abouchami et al. (2011) define a clear but broad ‘HNLC trend’ in a plot of εCd114/110 versus [Cd], which is primarily a consequence of isotopic fractionation associated with biological uptake (εCd114/110 is the deviation of the 114Cd/110Cd ratio of a sample from NIST SRM 3108 Cd in parts per 10,000). The trend is especially apparent in comparison to the large range of values shown by a global set of seawater Cd data for shallow depths. The Southern Ocean samples are also distinguished by their relatively high Cd concentrations (typically 0.2 to 0.6 nmol/kg) and moderately fractionated εCd114/110 (generally between +4 and +8) that reflect the limited biological productivity of this region. Detailed assessment reveals fine structure within the ‘HNLC trend’, which may record differences in the biological fractionation factor, different scenarios of closed and open system isotope fractionation, and/or distinct source water compositions. Southern Ocean seawater from depths ⩾1000 m has an average εCd114/110 of +2.5±0.2 (2se, n=16), and together with previous results this establishes a relatively constant εCd114/110 value of +3.0±0.3 (2se, n=27) for global deep waters. Significant isotopic variability was observed at intermediate depths in the Southern Ocean. Seawater from 200 m to 400 m in Weddell Sea has high Cd concentrations and εCd114/110 as low as +1, presumably due to remineralization of Cd from biomass that records incomplete nutrient utilization. Antarctic Intermediate Water, which was sampled at 150 to 750 m depth in the Drake Passage, features a distinct Cd isotope

  20. Isotopic abundance in atom trap trace analysis

    DOEpatents

    Lu, Zheng-Tian; Hu, Shiu-Ming; Jiang, Wei; Mueller, Peter

    2014-03-18

    A method and system for detecting ratios and amounts of isotopes of noble gases. The method and system is constructed to be able to measure noble gas isotopes in water and ice, which helps reveal the geological age of the samples and understand their movements. The method and system uses a combination of a cooled discharge source, a beam collimator, a beam slower and magneto-optic trap with a laser to apply resonance frequency energy to the noble gas to be quenched and detected.

  1. Isotope shifts in methane near 6000/cm

    NASA Technical Reports Server (NTRS)

    Fox, K.; Halsey, G. W.; Jennings, D. E.

    1976-01-01

    Isotope shifts for cleanly resolved vibrational-rotational absorption lines of CH4-12 and CH4-13 were measured by a 5-m focal length Littrow spectrometer in the 6000/cm range. The methane isotopes were held in separate absorption cells: 20 torr of CH4-13 in a 1-m cell, and 5 torr of CH4-12 in a White cell of 4-m optical path length. Measured shifts for the cleanly resolved singlets R(0), R(1), Q(1) and P(1) are summarized in tabular form.

  2. Zinc isotope anomalies. [in Allende meteorite

    NASA Technical Reports Server (NTRS)

    Volkening, J.; Papanastassiou, D. A.

    1990-01-01

    The Zn isotope composition in refractory-element-rich inclusions of the Allende meteorite are determined. Typical inclusions contain normal Zn. A unique inclusion of the Allende meteorite shows an excess for Zn-66 of 16.7 + or - 3.7 eu (1 eu = 0.01 percent) and a deficit for Zn-70 of 21 + or - 13 eu. These results indicate the preservation of exotic components even for volatile elements in this inclusion. The observed excess Zn-66 correlates with excesses for the neutron-rich isotopes of Ca-48, Ti-50, Cr-54, and Fe-58 in the same inclusion.

  3. Zinc isotope anomalies in Allende meteorite inclusions

    NASA Technical Reports Server (NTRS)

    Loss, R. D.; Lugmair, G. W.

    1990-01-01

    The isotopic compositions of Zn, Cr, Ti, and Ca have been measured in a number of CAIs from the Allende meteorite. The aim was to test astrophysical models which predict large excesses of Zn-66 to accompany excesses in the neutron-rich isotopes of Ca, Ti, Cr, and Ni. Some of the CAIs show clearly resolved but small excesses for Zn-66 which are at least an order of magnitude smaller than predicted. This result may simply reflect the volatility and chemical behavior of Zn as compared to the other (more refractory) anomalous elements found in these samples. Alternatively, revision of parameters and assumptions used for the model calculations may be required.

  4. Iron isotopes in an Archean ocean analogue

    NASA Astrophysics Data System (ADS)

    Busigny, Vincent; Planavsky, Noah J.; Jézéquel, Didier; Crowe, Sean; Louvat, Pascale; Moureau, Julien; Viollier, Eric; Lyons, Timothy W.

    2014-05-01

    Iron isotopes have been extensively used to trace the history of microbial metabolisms and the redox evolution of the oceans. Archean sedimentary rocks display greater variability in iron isotope ratios and more markedly negative values than those deposited in the Proterozoic and Phanerozoic. This increased variability has been linked to changes in either water column iron cycling or the extent of benthic microbial iron reduction through time. We tested these contrasting scenarios through a detailed study of anoxic and ferruginous Lac Pavin (France), which can serve as a modern analogue of the Archean ocean. A depth-profile in the water column of Lac Pavin shows a remarkable increase in dissolved Fe concentration (0.1-1200 μM) and δ56Fe values (-2.14‰ to +0.31‰) across the oxic-anoxic boundary to the lake bottom. The largest Fe isotope variability is found at the redox boundary and is related to partial oxidation of dissolved ferrous iron, leaving the residual Fe enriched in light isotopes. The analysis of four sediment cores collected along a lateral profile (one in the oxic layer, one at the redox boundary, one in the anoxic zone, and one at the bottom of the lake) indicates that bulk sediments, porewaters, and reactive Fe mostly have δ56Fe values near 0.0 ± 0.2‰, similar to detrital iron. In contrast, pyrite δ56Fe values in sub-chemocline cores (60, 65, and 92 m) are highly variable and show significant deviations from the detrital iron isotope composition (δ56Fepyrite between -1.51‰ and +0.09‰; average -0.93‰). Importantly, the pyrite δ56Fe values mirror the δ56Fe of dissolved iron at the redox boundary—where near quantitative sulfate and sulfide drawdown occurs—suggesting limited iron isotope fractionation during iron sulfide formation. This finding has important implications for the Archean environment. Specifically, this work suggests that in a ferruginous system, most of the Fe isotope variability observed in sedimentary pyrites can

  5. New isotopic clues to solar system formation

    NASA Technical Reports Server (NTRS)

    Lee, T.

    1979-01-01

    The presence of two new extinct nuclides Al-26 and Pd-107 with half lives of approximately one million years in the early solar system implies that there were nucleosynthetic activities involving a great many elements almost at the instant of solar system formation. Rate gas and oxygen isotopic abundance variations ('anomalies') relative to the 'cosmic' composition were observed in a variety of planetary objects, which indicates that isotopic heterogeneities caused by the incomplete mixing of distinct nucleosynthesis components permeate the entire solar system. These new results have major implications for cosmochronology, nucleosynthesis theory, star formation, planetary heating, and the genetic relationship between different planetary bodies

  6. Discovery of new superheavy element isotopes

    NASA Astrophysics Data System (ADS)

    Gates, Jacklyn

    2011-04-01

    The first confirmation of element 114 production and decay was performed in 2009 with the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. The 48 Ca + 242Pu reaction was used. Compound nucleus evaporation residues were separated from beam and other reaction products with the Berkeley Gas-filled separator and implanted in the focal plane detector system. Production and decay of one atom each of 287 114 (via the 242Pu(48 Ca, 3n)287 114 reaction) and 286 114(via the 242Pu(48 Ca,4n)286 114 reaction) were observed. Production cross sections, decay modes, decay energies, and half-lives and for these element 114 isotopes and their daughters were consistent with those reported by the Dubna Gas Filled Recoil Separator Group (Yuri Oganessian , J. Phys. G: Nucl. Part. Phys. 34 (2007) R165--R242). In 2010, the 48 Ca + 242Pu reaction was used again, at an increased beam energy to optimize the production of new isotope, 285 114, by the 242Pu(48 Ca,5n)285 114 reaction. The production and decay of one atom of 286 114 (via the 242Pu(48 Ca,4n)286 114 reaction) was observed, re-confirming the properties of this isotope. In addition, a single event corresponding to the production and decay of 285 114 (via the 242Pu(48 Ca,5n)285 114 reaction) was observed. The implantation of 285 114 in the detector was followed by five α-decays and a spontaneous fission event, indicating the α-decays of new isotopes, 285 114, 281Cp, 277Ds, 273Hs, 269Sg, and the spontaneous fission of new isotope, 265Rf. The decay properties of all these new isotopes match expectations based on microscopic-macroscopic mass models supplemented with extrapolations of previously reported superheavy element isotope decay properties. However, some systematic differences between observed and predicted α-decay Q-values may be used to refine models of nuclear shell effects in heavy element isotopes. Financial support was provided by the Office of High Energy and Nuclear Physics

  7. Overview of the U.S. Department of Energy's Isotope Programs

    SciTech Connect

    Carty, J.

    2004-10-05

    This presentation provides an overview of the U.S. Department of Energy's Isotopes Program. The charter of the Isotope Programs covers the production and sale of radioactive and stable isotopes, associated byproducts, surplus materials, and related isotope services.

  8. Inter-isotope effects in optimal dual-isotope loading into a shallow optical trap

    NASA Astrophysics Data System (ADS)

    Hamilton, M. S.; Gorges, A. R.; Roberts, J. L.

    2012-05-01

    Examination of loading the isotopes 85Rb and 87Rb simultaneously into a shallow far-off-resonance trap (FORT) has revealed an unexpected decrease in maximum atom number loaded as compared to loading either isotope alone. The simultaneous loading of the FORT will be affected by additional homonuclear and heteronuclear light-assisted collisional losses. However, these losses are measured and found to be insufficient to explain the observed drop in the total number of atoms loaded into the FORT. We find that our observations are consistent with a decrease in loading rate caused by inter-isotope disruptions of the efficient laser cooling required to load atoms into the optical trap.

  9. Nitrogen Isotope Tracing of Eutrophication Sources on a Watershed Scale: Nitrogen and Oxygen Isotopes of Nitrate

    NASA Astrophysics Data System (ADS)

    Showers, W. J.; Genna, B.; Karr, J.

    2001-05-01

    Nitrate contamination of shallow aquifers and surface waters associated with agricultural activities has become a major concern in river basins, like the Neuse, where significant agricultural land use is coupled with growing numbers of intensive animal operations (ILO's). The development of effective management practices to preserve water quality, or remediation strategies for basins already polluted requires source identification. The stable isotopes of nitrogen and oxygen in nitrate has been used as tracers to evaluate nitrogen sources on small scales, such as agricultural fields, or small watersheds with one dominate land use. This discrimination is possible because of the large fractionation associated with the volatilization of ammonia from animal wastes. Using stable isotopes on larger scales to evaluate nutrient sources is complicated by multiple sources, overlapping point and non-point sources, and co-existing biogeochemical processes that alter nitrate concentrations. To evaluate the potential of stable isotopes to determine the character of nutrient fluxes on larger scales, the isotopic/discharge relationship was examined for a watershed with little agricultural activity, an urban watershed, a watershed with mixed urban and agricultural land use, a watershed dominated by swine ILO's, and a watershed dominated by poultry ILO's. The watershed with little agricultural activity and the poultry watershed have similar isotope/discharge relationships with isotopic values at natural background levels and no change in concentration or isotopic composition in different discharge states. The urban watershed is dominated by point source isotopic values at all flow levels, the mixed urban and agricultural watershed is dominated by point source values during low flow conditions, and fertilizer non-point source values during high flow conditions. In this watershed nutrient concentrations also increase during low flow conditions. The swine watershed is dominated by

  10. Silicon Isotopes in Achondrites and Planetary Accretion and Differentiation

    NASA Astrophysics Data System (ADS)

    Pringle, E. A.; Savage, P. S.; Badro, J.; Barrat, J.-A.; Moynier, F.

    2015-07-01

    We present new high-precision Si isotope data for an extended suite of achondrites to assess the processes affecting the Si isotope system during the accretion and early geochemical modification of planetesimals.

  11. STABLE ISOTOPES IN ECOLOGICAL STUDIES: NEW DEVELOPMENTS IN MIXING MODELS

    EPA Science Inventory

    Stable isotopes are increasingly being used as tracers in ecological studies. One application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include food sources for animals, water sources for plants, pollution sources...

  12. Ion laser isotope enrichment by photo-predissociation of formaldehyde

    DOEpatents

    Marling, John B.

    1977-06-17

    Enrichment of carbon, hydrogen and/or oxygen isotopes by means of isotopically selective photo-predissociation of formaldehyde is achieved by irradiation with a fixed frequency ion laser, specifically, a neon, cadmium, or xenon ion laser.

  13. Method for production of an isotopically enriched compound

    DOEpatents

    Watrous, Matthew G.

    2012-12-11

    A method is presented for producing and isolating an isotopically enriched compound of a desired isotope from a parent radionuclide. The method includes forming, or placing, a precipitate containing a parent radionuclide of the desired daughter isotope in a first reaction zone and allowing sufficient time for the parent to decay into the desired gaseous daughter radioisotope. The method further contemplates collecting the desired daughter isotope as a solid in a second reaction zone through the application of temperatures below the freezing point of the desired isotope to a second reaction zone that is connected to the first reaction zone. Specifically, a method is presented for producing isotopically enriched compounds of xenon, including the radioactive isotope Xe-131m and the stable isotope Xe-131.

  14. Characterising Redox-Related Isotope Effects

    NASA Astrophysics Data System (ADS)

    Black, J. R.; John, S.; Young, E. D.; Kavner, A.

    2008-12-01

    Redox processes have played a pivotal role in shaping Earth's interior and surface and making life possible. A record of this evolution is found within stable isotope signatures arising from chemical redox changes occurring in our continents, oceans and atmosphere over time. Experimental and theoretical studies of redox- related transition metal isotope fractionation provide a physical basis to understand how isotopes are fractionated under natural conditions, relating geochemical signatures to earth processes from which they arise. Here we present experimental evidence that charge transfer processes drive the fractionation of stable isotopes of Fe and Zn, and the magnitude of fractionation can be tuned as a function of redox potential and other physical variables. To quantitatively evaluate isotopic signatures of redox processes, we have conducted electrochemical experiments measuring the fractionation of Fe and Zn isotopes during their electrodeposition from aqueous solution: M2+ + 2e- = M(s). The electrochemical cell consisted of anodic and cathodic half- cells separated by a salt bridge, and connected to a potentiostat which applied an adjustable constant voltage (vs. Ag/AgCl). Metallic Fe and Zn plated on glassy carbon electrodes was recovered in acid for analysis of the stable isotope composition on a Thermo-Finnigan Neptune MC-ICP-MS. Results are reported as a large delta difference between the isotopic composition (56Fe/54Fe and 66Zn/64Zn) of plated metal relative to the stock solution. The results show some clear trends; fractionation is a function of applied voltage (overpotential: η = E- E0 Volts), ranging from Δ56Fe ~ -4 to -0.9 ‰, and Δ66Zn ~ - 5.5 to -4 ‰ at η = -0.5 to -1.25 V and -0.1 to -0.5 V, respectively. Temperature affects fractionation in a counter-intuitive manner, with fractionation increasing with increasing temperature (at η = -1.0 V: Δ56Fe ~ -1.25 ‰ at 0°C and -1.62 ‰ at 35°C). The results can be explained in terms of two

  15. Clumped isotope thermometry of cryogenic cave carbonates

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; Affek, Hagit P.; Zhang, Yi Ge; Dublyansky, Yuri; Spötl, Christoph; Immenhauser, Adrian; Richter, Detlev K.

    2014-02-01

    Freezing of cave pool water that is increasingly oversaturated with dissolved carbonate leads to precipitation of a very specific type of speleothems known as cryogenic cave carbonates (CCC). At present, two different environments for their formation have been proposed, based on their characteristic carbon and oxygen isotope ratios. Rapidly freezing thin water films result in the fast precipitation of fine-grained carbonate powder (CCCfine). This leads to rapid physicochemical changes including CO2 degassing and CaCO3 precipitation, resulting in significantly 13C-enriched carbonates. Alternatively, slow carbonate precipitation in ice-covered cave pools results in coarse crystalline CCC (CCCcoarse) yielding strongly 18O-depleted carbonate. This is due to the formation of relatively 18O-enriched ice causing the gradual depletion of 18O in the water from which the CCC precipitates. Cryogenic carbonates from Central European caves were found to have been formed primarily during the last glacial period, specifically during times of permafrost thawing, based on the oxygen isotope ratios and U-Th dating. Information about the precise conditions of CCCcoarse formation, i.e. whether these crystals formed under equilibrium or disequilibrium conditions with the parent fluid, however, is lacking. An improved understanding of CCCcoarse formation will increase the predictive value of this paleo-permafrost archive. Here we apply clumped isotopes to investigate the formation conditions of cryogenic carbonates using well-studied CCCcoarse from five different cave systems in western Germany. Carbonate clumped isotope measurements yielded apparent temperatures between 3 and 18 °C and thus exhibit clear evidence of isotopic disequilibrium. Although the very negative carbonate δ18O values can only be explained by gradual freezing of pool water accompanied by preferential incorporation of 18O into the ice, clumped isotope-derived temperatures significantly above expected freezing

  16. Stable isotope deltas: tiny, yet robust signatures in nature.

    PubMed

    Brand, Willi A; Coplen, Tyler B

    2012-09-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including (14)C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. (13)C, (2)H, and (18)O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as-25 per mil can be written as-25 mUr (or-2.5 cUr or-0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg 'units' are easily included (e.g. either+0.015 ‰ or+15 per meg

  17. Relativistic calculations of isotope shifts in highly charged ions

    SciTech Connect

    Tupitsyn, I.I.; Shabaev, V.M.; Crespo Lopez-Urrutia, J.R.; Soria Orts, R.; Ullrich, J.; Draganic, I.

    2003-08-01

    The isotope shifts of forbidden transitions in Be- and B-like argon ions are calculated. It is shown that only using the relativistic recoil operator can provide a proper evaluation of the mass isotope shift, which strongly dominates over the field isotope shift for the ions under consideration. Comparing the isotope shifts calculated with the current experimental uncertainties indicates very good perspectives for a first test of the relativistic theory of the recoil effect in middle-Z ions.

  18. Stable isotope deltas: Tiny, yet robust signatures in nature

    USGS Publications Warehouse

    Brand, Willi A.; Coplen, Tyler B.

    2012-01-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including 14C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. 13C, 2H, and 18O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as−25 per mil can be written as−25 mUr (or−2.5 cUr or−0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg ‘units’ are easily included (e.g. either+0.015 ‰ or+15 per meg

  19. Final Report on Isotope Ratio Techniques for Light Water Reactors

    SciTech Connect

    Gerlach, David C.; Gesh, Christopher J.; Hurley, David E.; Mitchell, Mark R.; Meriwether, George H.; Reid, Bruce D.

    2009-07-01

    The Isotope Ratio Method (IRM) is a technique for estimating the energy or plutonium production in a fission reactor by measuring isotope ratios in non-fuel reactor components. The isotope ratios in these components can then be directly related to the cumulative energy production with standard reactor modeling methods.

  20. Discovery of tantalum, rhenium, osmium, and iridium isotopes

    SciTech Connect

    Robinson, R.; Thoennessen, M.

    2012-09-15

    Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  1. Discovery of samarium, europium, gadolinium, and terbium isotopes

    SciTech Connect

    May, E.; Thoennessen, M.

    2013-01-15

    Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  2. INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS

    EPA Science Inventory

    Stable isotopes are often used as natural labels to quantify the contributions of multiple sources to a mixture. For example, C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source li...

  3. INCORPORATING CONCENTRATION DEPENDENCE IN STABLE ISOTOPE MIXING MODELS

    EPA Science Inventory

    Stable isotopes are frequently used to quantify the contributions of multiple sources to a mixture; e.g., C and N isotopic signatures can be used to determine the fraction of three food sources in a consumer's diet. The standard dual isotope, three source linear mixing model ass...

  4. Discovery of actinium, thorium, protactinium, and uranium isotopes

    NASA Astrophysics Data System (ADS)

    Fry, C.; Thoennessen, M.

    2013-05-01

    Thirty-one actinium, thirty-one thorium, twenty-eight protactinium, and twenty-three uranium isotopes have so far been observed; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  5. Discovery of gallium, germanium, lutetium, and hafnium isotopes

    SciTech Connect

    Gross, J.L.; Thoennessen, M.

    2012-09-15

    Currently, twenty-eight gallium, thirty-one germanium, thirty-five lutetium, and thirty-six hafnium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  6. Discovery of the Isotopes with 11{<=}Z{<=}19

    SciTech Connect

    Thoennessen, M.

    2012-09-15

    A total of 194 isotopes with 11{<=}Z{<=}19 have been identified to date. The discovery of these isotopes which includes the observation of unbound nuclei, is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  7. 21 CFR 886.1670 - Ophthalmic isotope uptake probe.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ophthalmic isotope uptake probe. 886.1670 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1670 Ophthalmic isotope uptake probe. (a) Identification. An ophthalmic isotope uptake probe is an AC-powered device intended to...

  8. 21 CFR 886.1670 - Ophthalmic isotope uptake probe.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ophthalmic isotope uptake probe. 886.1670 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1670 Ophthalmic isotope uptake probe. (a) Identification. An ophthalmic isotope uptake probe is an AC-powered device intended to...

  9. 21 CFR 886.1670 - Ophthalmic isotope uptake probe.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic isotope uptake probe. 886.1670 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1670 Ophthalmic isotope uptake probe. (a) Identification. An ophthalmic isotope uptake probe is an AC-powered device intended to...

  10. 21 CFR 886.1670 - Ophthalmic isotope uptake probe.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ophthalmic isotope uptake probe. 886.1670 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1670 Ophthalmic isotope uptake probe. (a) Identification. An ophthalmic isotope uptake probe is an AC-powered device intended to...

  11. 21 CFR 886.1670 - Ophthalmic isotope uptake probe.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ophthalmic isotope uptake probe. 886.1670 Section... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1670 Ophthalmic isotope uptake probe. (a) Identification. An ophthalmic isotope uptake probe is an AC-powered device intended to...

  12. Discovery of palladium, antimony, tellurium, iodine, and xenon isotopes

    SciTech Connect

    Kathawa, J.; Fry, C.; Thoennessen, M.

    2013-01-15

    Currently, thirty-eight palladium, thirty-eight antimony, thirty-nine tellurium, thirty-eight iodine, and forty xenon isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  13. Temperature measurements from oxygen isotope ratios of fish otoliths.

    PubMed

    Devereux, I

    1967-03-31

    Measurements have shown that the temperature of a fish's habitat can be deduced from the Oxygen isotope ratio of its otoliths (ear bones). Isotope ratios Obtained from fossil otoliths indicate a water temperature which agrees wiht that found by isotope measurements on associated benthonic foraminifera. PMID:6020293

  14. Discovery of scandium, titanium, mercury, and einsteinium isotopes

    SciTech Connect

    Meierfrankenfeld, D.; Bury, A.; Thoennessen, M.

    2011-03-15

    Currently, 23 scandium, 25 titanium, 40 mercury, and 17 einsteinium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  15. Discovery of scandium, titanium, mercury, and einsteinium isotopes

    NASA Astrophysics Data System (ADS)

    Meierfrankenfeld, D.; Bury, A.; Thoennessen, M.

    2011-03-01

    Currently, 23 scandium, 25 titanium, 40 mercury, and 17 einsteinium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  16. Sulfur Isotope Composition of Putative Primary Troilite in Chondrules

    NASA Technical Reports Server (NTRS)

    Tachibana, Shogo; Huss, Gary R.

    2002-01-01

    Sulfur isotope compositions of putative primary troilites in chondrules from Bishunpur were measured by ion probe. These primary troilites have the same S isotope compositions as matrix troilites and thus appear to be isotopically unfractionated. Additional information is contained in the original extended abstract.

  17. Discovery of cesium, lanthanum, praseodymium and promethium isotopes

    SciTech Connect

    May, E.; Thoennessen, M.

    2012-09-15

    Currently, forty-one cesium, thirty-five lanthanum, thirty-two praseodymium, and thirty-one promethium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  18. Discovery of the astatine, radon, francium, and radium isotopes

    SciTech Connect

    Fry, C.; Thoennessen, M.

    2013-09-15

    Thirty-nine astatine, thirty-nine radon, thirty-five francium, and thirty-four radium isotopes have so far been observed; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  19. Discovery of the astatine, radon, francium, and radium isotopes

    NASA Astrophysics Data System (ADS)

    Fry, C.; Thoennessen, M.

    2013-09-01

    Thirty-nine astatine, thirty-nine radon, thirty-five francium, and thirty-four radium isotopes have so far been observed; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  20. Impact of cell density on microbially induced stable isotope fractionation.

    PubMed

    Kampara, Makeba; Thullner, Martin; Harms, Hauke; Wick, Lukas Y

    2009-01-01

    Quantification of microbial contaminant biodegradation based on stable isotope fractionation analysis (SIFA) relies on known, invariable isotope fractionation factors. The microbially induced isotope fractionation is caused by the preferential cleavage of bonds containing light rather than heavy isotopes. However, a number of non-isotopically sensitive steps preceding the isotopically sensitive bond cleavage may affect the reaction kinetics of a degradation process and reduce the observed (i.e., the macroscopically detectable) isotope fractionation. This introduces uncertainty to the use of isotope fractionation for the quantification of microbial degradation processes. Here, we report on the influence of bacterial cell density on observed stable isotope fractionation. Batch biodegradation experiments were performed under non-growth conditions to quantify the toluene hydrogen isotope fractionation by exposing Pseudomonas putida mt-2(pWWO) at varying cell densities to different concentrations of toluene. Observed isotope fractionation depended significantly on the cell density. When the cell density rose from 5 x 10(5) to 5 x 10(8)cells/mL, the observed isotope fractionation declined by 70% and went along with a 55% decrease of the degradation rates of individual cells. Theoretical estimates showed that uptake-driven diffusion to individual cells depended on cell density via the overlap of the cells' diffusion-controlled boundary layers. Our data suggest that biomass effects on SIFA have to be considered even in well-mixed systems such as the cell suspensions used in this study. PMID:19015849

  1. Discovery of dysprosium, holmium, erbium, thulium, and ytterbium isotopes

    SciTech Connect

    Fry, C.; Thoennessen, M.

    2013-09-15

    Currently, thirty-one dysprosium, thirty-two holmium, thirty-two erbium, thirty-three thulium, and thirty-one ytterbium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  2. Discovery of the thallium, lead, bismuth, and polonium isotopes

    NASA Astrophysics Data System (ADS)

    Fry, C.; Thoennessen, M.

    2013-05-01

    Forty-two thallium, forty-two lead, forty-one bismuth, and forty-two polonium isotopes have so far been observed; the discovery of these isotopes is described. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  3. Discovery of rubidium, strontium, molybdenum, and rhodium isotopes

    SciTech Connect

    Parker, A.M.; Thoennessen, M.

    2012-07-15

    Currently, 31 rubidium, 35 strontium, 35 molybdenum, and 38 rhodium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  4. Isotopic phonon effects in β-rhombohedral boron—non-statistical isotope distribution

    NASA Astrophysics Data System (ADS)

    Werheit, H.; Filipov, V.; Kuhlmann, U.; Schwarz, U.; Armbrüster, M.; Antadze, M.

    2012-05-01

    On the basis of the spectra of IR- and Raman-active phonons, the isotopic phonon effects in β-rhombohedral boron are analysed for polycrystalline 10B- and 11B-enriched samples of different origin and high-purity natB single crystals. Intra- and inter-icosahedral B-B vibrations are harmonic, hence meeting the virtual crystal approximation (VCA) requirements. Deviations from the phonon shift expected according to the VCA are attributed to the anharmonic share of the lattice vibrations. In the case of icosahedral vibrations, the agreement with calculations on α-rhombohedral boron by Shirai and Katayama-Yoshida is quite satisfactory. Phonon shifts due to isotopic disorder in natB are separated and determined. Some phonon frequencies are sensitive to impurities. The isotopic phonon effects yield valuable specific information on the nature of the different phonon modes. The occupation of regular boron sites by isotopes deviates significantly from the random distribution.

  5. Cosmic ray produced isotopes in terrestrial systems.

    NASA Astrophysics Data System (ADS)

    Lal, D.

    1998-12-01

    Continuing improvements in the sensitivity of measurement of cosmic ray produced isotopes in environmental samples have progressively broadened the scope of their applications to characterise and quantify a wide variety of processes in Earth and planetary sciences. In this article, the author concentrates on the new developments in the field of nuclear geophysics, based on isotopic changes produced by cosmic rays in the terrestrial systems. This field, which is best described as cosmic ray geophysics, has roots with the discovery of cosmogenic 14C on the Earth by Willard Libby in 1948, and grew rapidly at first, but slowed down during the '60s and '70s. In the '80s, there was a renaissance in cosmic ray produced isotope studies, thanks mainly to the developments of the accelerator mass spectrometry technique capable of measuring minute amounts of radioactivity in terrestrial samples. This technological advance has considerably enhanced the applications of cosmic ray produced isotopes and today one finds them being used to address diverse problems in Earth and planetary sciences. The author discusses the present scope of the field of cosmic ray geophysics with an emphasis on geomorphology. It is stressed that this is the decade in which this field, which has been studied passionately by geographers, geomorphologists and geochemists for more than five decades, has at its service nuclear methods to introduce numeric time controls in the range of centuries to millions of years.

  6. UNCERTAINTY IN SOURCE PARTITIONING USING STABLE ISOTOPES

    EPA Science Inventory

    Stable isotope analyses are often used to quantify the contribution of multiple sources to a mixture, such as proportions of food sources in an animal's diet, C3 vs. C4 plant inputs to soil organic carbon, etc. Linear mixing models can be used to partition two sources with a sin...

  7. STABLE ISOTOPE DILUTION FOR HAZARDOUS WASTE INCINERATION

    EPA Science Inventory

    The report gives results of a project to determine if a proposed catalytic exchange procedure could be adapted to produce the labeled analog materials necessary for isotope dilution gas chromatography/mass spectrometry (GC/MS) analysis. It is related to a general evaluation of th...

  8. Review of hydrogen isotope permeability through materials

    SciTech Connect

    Steward, S.A.

    1983-08-15

    This report is the first part of a comprehensive summary of the literature on hydrogen isotope permeability through materials that do not readily form hydrides. While we mainly focus on pure metals with low permeabilities because of their importance to tritium containment, we also give data on higher-permeability materials such as iron, nickel, steels, and glasses.

  9. INSTRUMENTS AND METHODS OF INVESTIGATION: Isotope engineering

    NASA Astrophysics Data System (ADS)

    Plekhanov, Vladimir G.

    2000-11-01

    Major applications of the novel and extremely promising technology of isotope engineering are reviewed which, along with basic research, also include — by no means exhaustively — optical fibers, optoelectronics, tunable solid-state lasers, neutron transmutation doping, and information storage.

  10. The Chlorine Isotope Composition of Martian Meteorites

    NASA Astrophysics Data System (ADS)

    Sharp, Z. D.; Shearer, C. K.; Agee, C.; Burger, P. V.; McKeegan, K. D.

    2014-11-01

    The Cl isotope composition of martian meteorites range from -3.8 to +8.6 per mil. Ol-phyric shergottites are lightest; crustally contaminated samples are heaviest, basaltic shergottites are in-between. The system is explained as two component mixing.

  11. Progress towards trapping of atomic hydrogen isotopes

    NASA Astrophysics Data System (ADS)

    Chavez, Isaac; Libson, Adam; Mazur, Tom; Majors, Julia; Raizen, Mark

    2009-05-01

    Using a series of pulsed electromagnetic coils (atomic coilgun) we can stop supersonic beams of paramagnetic atoms and molecules. We will employ the coilgun method to stop and trap supersonic beams of hydrogen isotopes. The slowed atoms will be trapped in a quadrupole magnetic trap where single-photon atomic cooling will be applied. Further applications will be discussed.

  12. Seabird Modulations of Isotopic Nitrogen on Islands

    PubMed Central

    Caut, Stéphane; Angulo, Elena; Pisanu, Benoit; Ruffino, Lise; Faulquier, Lucie; Lorvelec, Olivier; Chapuis, Jean-Louis; Pascal, Michel; Vidal, Eric; Courchamp, Franck

    2012-01-01

    The transport of nutrients by migratory animals across ecosystem boundaries can significantly enrich recipient food webs, thereby shaping the ecosystems’ structure and function. To illustrate the potential role of islands in enabling the transfer of matter across ecosystem boundaries to be gauged, we investigated the influence of seabirds on nitrogen input on islands. Basing our study on four widely differing islands in terms of their biogeography and ecological characteristics, sampled at different spatial and temporal intervals, we analyzed the nitrogen isotopic values of the main terrestrial ecosystem compartments (vascular plants, arthropods, lizards and rodents) and their relationship to seabird values. For each island, the isotopic values of the ecosystem were driven by those of seabirds, which ultimately corresponded to changes in their marine prey. First, terrestrial compartments sampled within seabird colonies were the most enriched in δ15N compared with those collected at various distances outside colonies. Second, isotopic values of the whole terrestrial ecosystems changed over time, reflecting the values of seabirds and their prey, showing a fast turnover throughout the ecosystems. Our results demonstrate that seabird-derived nutrients not only spread across the terrestrial ecosystems and trophic webs, but also modulate their isotopic values locally and temporally on these islands. The wealth of experimental possibilities in insular ecosystems justifies greater use of these model systems to further our understanding of the modalities of trans-boundary nutrient transfers. PMID:22723945

  13. Unsupervised Identification of Isotope-Labeled Peptides.

    PubMed

    Goldford, Joshua E; Libourel, Igor G L

    2016-06-01

    In vivo isotopic labeling coupled with high-resolution proteomics is used to investigate primary metabolism in techniques such as stable isotope probing (protein-SIP) and peptide-based metabolic flux analysis (PMFA). Isotopic enrichment of carbon substrates and intracellular metabolism determine the distribution of isotopes within amino acids. The resulting amino acid mass distributions (AMDs) are convoluted into peptide mass distributions (PMDs) during protein synthesis. With no a priori knowledge on metabolic fluxes, the PMDs are therefore unknown. This complicates labeled peptide identification because prior knowledge on PMDs is used in all available peptide identification software. An automated framework for the identification and quantification of PMDs for nonuniformly labeled samples is therefore lacking. To unlock the potential of peptide labeling experiments for high-throughput flux analysis and other complex labeling experiments, an unsupervised peptide identification and quantification method was developed that uses discrete deconvolution of mass distributions of identified peptides to inform on the mass distributions of otherwise unidentifiable peptides. Uniformly (13)C-labeled Escherichia coli protein was used to test the developed feature reconstruction and deconvolution algorithms. The peptide identification was validated by comparing MS(2)-identified peptides to peptides identified from PMDs using unlabeled E. coli protein. Nonuniformly labeled Glycine max protein was used to demonstrate the technology on a representative sample suitable for flux analysis. Overall, automatic peptide identification and quantification were comparable or superior to manual extraction, enabling proteomics-based technology for high-throughput flux analysis studies. PMID:27145348

  14. Delayed neutrons in fission of polonium isotopes

    SciTech Connect

    Ramazanov, R.; Urikbaev, Z.S.; Maksyutenko, B.P.; Ignat'ev, S.V.

    1988-06-01

    A strong difference is found in the relative yields of delayed neutrons in the production of compound nuclei of polonium isotopes in reactions in which bismuth and lead are bombarded by various charged particles. The effect can be partially explained by the different lengths of the ..beta..-decay chains of the light and heavy fission products.

  15. Quadrupole Collectivity in Neutron Deficient Sn Isotopes

    NASA Astrophysics Data System (ADS)

    Gade, Alexandra

    2014-03-01

    One of the overarching goals of nuclear physics is the development of a comprehensive model of the atomic nucleus with predictive power across the nuclear chart. Of particular importance for the development of nuclear models is experimental data that consistently track the effect of isospin and changed binding, for example. The chain of Sn isotopes has been a formidable testing ground for nuclear models as some spectroscopic data is available from N = Z = 50 100Sn in the proximity of the proton dripline to 134Sn, beyond the very neutron-rich doubly magic nucleus 132Sn. In even-even nuclei, the electromagnetic quadrupole excitation strength is a measure of quadrupole collectivity, sensitive to the presence of shell gaps, nuclear deformation, and nucleon-nucleon correlations, for example. In the Sn isotopes, this transition strength has been reported from 104Sn to 130Sn, spanning a chain of 14 even-even Sn isotopes. The trend is asymmetric with respect to midshell and not even the largest-scale shell-model calculations have been able to describe the evolution of transition strength across the isotopic chain without varying effective charges. Implications will be discussed. This work was supported by the National Science Foundation under Grant No. PHY-1102511.

  16. Present Status of KEK Isotope Separation System

    NASA Astrophysics Data System (ADS)

    Hirayama, Y.; Jeong, S. C.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Miyatake, H.; Oyaizu, M.; Kim, Y. H.; Mukai, M.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

    2014-03-01

    KISS (KEK Isotope Separation System) has been constructed at Nishina Re-search Center (NRC) of RIKEN to study the decay properties of heavy neutron-rich iso-topes with mass number around A˜200 along the neutron magic number of N = 126 for the astrophysical interest. The isotopes of interest will be produced by multi-nucleon transfer reactions in neutron-rich heavy ion collisions (e.g. 136Xe projectile on 198Pt target). KISS consists of a gas-cell system for thermalizing (stopping and neutralizing) and fast-transporting reaction products to the gas cell exit hole, a laser system for the res-onant ionization, and a mass-separator system followed by a detection system for the decay spectroscopy. KISS will allow us to study unknown isotopes produced in weak re-action channels under low background conditions. The off-line test of the KISS has been finished. As a next step, on-line test experiments have been performed to investigate the overall efficiency and selectivity of the system as a function of the injected 56Fe beam intensity from the RIKEN Ring Cyclotron (RRC).

  17. Isotopic Study of Silicon Carbide in Semarkona

    NASA Astrophysics Data System (ADS)

    Smith, J. B.; Huss, G. R.

    2002-03-01

    We have measured Si and C isotopes for individual SiC grains from Semarkona. Our results are compared with those of previous studies on SiC from Murchison and Orgueil. Metamorphism and grain-size distribution can affect these comparisons.

  18. Laser Isotope Enrichment for Medical and Industrial Applications

    SciTech Connect

    Leonard Bond

    2006-07-01

    Laser Isotope Enrichment for Medical and Industrial Applications by Jeff Eerkens (University of Missouri), Jay Kunze (Idaho State University), and Leonard Bond (Idaho National Laboratory) The principal isotope enrichment business in the world is the enrichment of uranium for commercial power reactor fuels. However, there are a number of other needs for separated isotopes. Some examples are: 1) Pure isotopic targets for irradiation to produce medical radioisotopes. 2) Pure isotopes for semiconductors. 3) Low neutron capture isotopes for various uses in nuclear reactors. 4) Isotopes for industrial tracer/identification applications. Examples of interest to medicine are targets to produce radio-isotopes such as S-33, Mo-98, Mo-100, W-186, Sn-112; while for MRI diagnostics, the non-radioactive Xe-129 isotope is wanted. For super-semiconductor applications some desired industrial isotopes are Si-28, Ga-69, Ge-74, Se-80, Te-128, etc. An example of a low cross section isotope for use in reactors is Zn-68 as a corrosion inhibitor material in nuclear reactor primary systems. Neutron activation of Ar isotopes is of interest in industrial tracer and diagnostic applications (e.g. oil-logging). . In the past few years there has been a sufficient supply of isotopes in common demand, because of huge Russian stockpiles produced with old electromagnetic and centrifuge separators previously used for uranium enrichment. Production of specialized isotopes in the USA has been largely accomplished using old ”calutrons” (electromagnetic separators) at Oak Ridge National Laboratory. These methods of separating isotopes are rather energy inefficient. Use of lasers for isotope separation has been considered for many decades. None of the proposed methods have attained sufficient proof of principal status to be economically attractive to pursue commercially. Some of the authors have succeeded in separating sulfur isotopes using a rather new and different method, known as condensation

  19. Zinc isotope fractionation during magmatic differentiation and the isotopic composition of the bulk Earth

    NASA Astrophysics Data System (ADS)

    Chen, Heng; Savage, Paul S.; Teng, Fang-Zhen; Helz, Rosalind T.; Moynier, Frédéric

    2013-05-01

    The zinc stable isotope system has been successfully applied to many and varied fields in geochemistry, but to date it is still not completely clear how this isotope system is affected by igneous processes. In order to evaluate the potential application of Zn isotopes as a proxy for planetary differentiation and volatile history, it is important to constrain the magnitude of Zn isotopic fractionation induced by magmatic differentiation. In this study we present high-precision Zn isotope analyses of two sets of chemically diverse, cogenetic samples from Kilauea Iki lava lake, Hawaii, and Hekla volcano, Iceland, which both show clear evidence of having undergone variable and significant degrees of magmatic differentiation. The Kilauea Iki samples display small but resolvable variations in Zn isotope composition (0.26‰<δ66Zn<0.36‰; δ66Zn defined as the per mille deviation of a sample's 66Zn/64Zn compositional ratio from the JMC-Lyon standard), with the most differentiated lithologies exhibiting more positive δ66Zn values. This fractionation is likely a result of the crystallization of olivine and/or Fe-Ti oxides, which can both host Zn in their crystal structures. Samples from Hekla have a similar range of isotopic variation (0.22‰<δ66Zn<0.33‰), however, the degree of fractionation caused by magmatic differentiation is less significant (only 0.07‰) and no correlation between isotope composition and degree of differentiation is seen. We conclude that high temperature magmatic differentiation can cause Zn isotope fractionation that is resolvable at current levels of precision, but only in compositionally-evolved lithologies. With regards to primitive (ultramafic and basaltic) material, this signifies that the terrestrial mantle is essentially homogeneous with respect to Zn isotopes. Utilizing basaltic and ultramafic sample analyses, from different geologic settings, we estimate that the average Zn isotopic composition of Bulk Silicate Earth is δ66Zn=0.28

  20. What can one sample tell us? Stable isotopes can assess complex processes in national assessments of lakes, rivers and streams.

    EPA Science Inventory

    Stable isotopes can be very useful in large-scale monitoring programs because samples for isotopic analysis are easy to collect, and isotopes integrate information about complex processes such as evaporation from water isotopes and denitrification from nitrogen isotopes. Traditi...

  1. Constructing a Neoproterozoic Seawater Strontium Isotope Curve

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Shields-Zhou, G. A.; Manning, C. J.; Thirlwall, M.; Thurow, J. W.; Zhu, M.; Ling, H.

    2014-12-01

    The strontium isotopic composition of seawater has varied throughout Earth history in response to the balance between Sr isotopic exchange with ocean crust and input of riverine Sr derived from continental weathering. Because of this, seawater 87Sr/86Sr highs are interpreted to reflect erosion events, related to mountain building, while 87Sr/86Sr lows are considered to result from low weathering rates or increased seafloor spreading. Seawater 87Sr/86Sr also responds to changes in the isotopic composition of material undergoing weathering. The largest ever increase in seawater 87Sr/86Sr took place sometime from approximately 900 Ma to 500 Ma, and was associated with a permanent step shift in baseline 87Sr/86Sr composition. The unprecedented size of this increase, its timing and causation remains unconstrained. This study attempts firstly to reconstruct global seawater 87Sr/86Sr trends through this increase, using well-preserved carbonate rock samples from the North China craton, calibrated against additional 87Sr/86Sr and δ13C data from Neoproterozoic samples collected from other sections around the world. Sample preparation techniques for bulk carbonate Sr isotope stratigraphy are being honed during the course of this study. Other stable isotope systems (δ13C and δ18O) and trace elements, including REE have been investigated on the same samples to identify pristine samples for Sr isotope analysis and help in interpretation. The newly obtained data from this study (mainly Huaibei group of Huaibei area), using the excellently preserved early marine calcite cements and some bulk rock samples, confirm that the carbonate strata across the Jiao-Liao-Xu-Huai stratigraphic realm of the North China Craton exhibit the moderately positive δ13C values and low 87Sr/86Sr values that are characteristic of the early Neoproterozoic (Tonian).The results help to recreate the global curve by linking negative excursions in the Shijia (Xuzhou) (Xiao et al., 2014, Precambr. Res., 246

  2. ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS

    SciTech Connect

    Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

    2009-09-03

    Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for

  3. Stable Vanadium Isotope Fractionation at High Temperatures

    NASA Astrophysics Data System (ADS)

    Prytulak, J.; Parkinson, I. J.; Savage, P. S.; Nielsen, S. G.; Halliday, A. N.

    2011-12-01

    Vanadium is a redox sensitive transition metal existing in multiple valence states at terrestrial conditions. Stable vanadium isotopes (reported as δ51V in % relative to an Alfa Aesar standard [1]) are a potentially powerful tracer of oxidation-reduction processes. However, the determination of δ51V is analytically challenging, primarily due to the extreme abundance ratio between the only two stable isotopes (51V/50V ~ 400) and, also, significant isobaric interferences of 50Ti and 50Cr on the minor 50V isotope. We have developed the first method able to determine δ51V to a precision (2 s.d. ~ 0.15%, [1,2]) that enables application of this isotope system to geological processes. To usefully investigate high temperature processes using vanadium isotopes, knowledge of the isotope composition and range of values present in the ambient mantle is required. Here we discuss the first δ51V measured in igneous materials encompassing peridotites, MORB, and primitive mantle-derived melts such as picrites. This first dataset provides a preliminary reconnaissance of the magnitude of natural fractionation. We find little isotope fractionation in suites of peridotites and MORB (< 0.5 %). However, the small but analytically significant variation appears to be related to secondary processes, with extremely altered peridotites consistently displaying slightly heavier isotope compositions. We find no resolvable δ51V variation between fresh MORB glass and fresh peridotite. Intriguingly, a suite of subduction-related peridotites from the Mariana forearc, previously characterized for fO2 [3], do not display the predicted co-variation between δ51V and fO2, but instead also have compositions identical to MORB glass. This nominally supports recent indications that there is limited difference in the oxygen fugacity of the MORB source and the subarc mantle wedge [e.g., 4, 5]. Finally, we observe large δ51V variations (~ 2 %) in a suite of evolving lavas from Hekla volcano, Iceland

  4. Carbonate abundances and isotopic compositions in chondrites

    NASA Astrophysics Data System (ADS)

    Alexander, C. M. O'd.; Bowden, R.; Fogel, M. L.; Howard, K. T.

    2015-04-01

    We report the bulk C abundances, and C and O isotopic compositions of carbonates in 64 CM chondrites, 14 CR chondrites, 2 CI chondrites, LEW 85332 (C2), Kaba (CV3), and Semarkona (LL3.0). For the unheated CMs, the total ranges of carbonate isotopic compositions are δ13C ≈ 25-75‰ and δ18O ≈ 15-35‰, and bulk carbonate C contents range from 0.03 to 0.60 wt%. There is no simple correlation between carbonate abundance and isotopic composition, or between either of these parameters and the extent of alteration. Unless accretion was very heterogeneous, the uncorrelated variations in extent of alteration and carbonate abundance suggests that there was a period of open system behavior in the CM parent body, probably prior to or at the start of aqueous alteration. Most of the ranges in CM carbonate isotopic compositions can be explained by their formation at different temperatures (0-130 °C) from a single fluid in which the carbonate O isotopes were controlled by equilibrium with water (δ18O ≈ 5‰) and the C isotopes were controlled by equilibrium with CO and/or CH4 (δ13C ≈ -33‰ or -20‰ for CO- or CH4-dominated systems, respectively). However, carbonate formation would have to have been inefficient, otherwise carbonate compositions would have resembled those of the starting fluid. A quite similar fluid composition (δ18O ≈ -5.5‰, and δ13C ≈ -31‰ or -17‰ for CO- or CH4-dominated systems, respectively) can explain the carbonate compositions of the CIs, although the formation temperatures would have been lower (~10-40 °C) and the relative abundances of calcite and dolomite may play a more important role in determining bulk carbonate compositions than in the CMs. The CR carbonates exhibit a similar range of O isotopes, but an almost bimodal distribution of C isotopes between more (δ13C ≈ 65-80‰) and less altered samples (δ13C ≈ 30-40‰). This bimodality can still be explained by precipitation from fluids with the same isotopic

  5. The CN isotopic ratios in comets

    NASA Astrophysics Data System (ADS)

    Manfroid, J.; Jehin, E.; Hutsemékers, D.; Cochran, A.; Zucconi, J.-M.; Arpigny, C.; Schulz, R.; Stüwe, J. A.; Ilyin, I.

    2009-08-01

    Our aim is to determine the isotopic ratios 12C/13C and 14N/15N in a variety of comets and link these measurements to the formation and evolution of the solar system. The 12C/13C and 14N/15N isotopic ratios are measured for the CN radical by means of high-resolution optical spectra of the R branch of the B-X (0, 0) violet band. 23 comets from different dynamical classes have been observed, sometimes at various heliocentric and nucleocentric distances, in order to estimate possible variations of the isotopic ratios in parent molecules. The 12C/13C and 14N/15N isotopic ratios in CN are remarkably constant (average values of, respectively, 91.0 ± 3.6 and 147.8 ± 5.7) within our measurement errors, for all comets whatever their origin or heliocentric distance. While the carbon isotopic ratio does agree with the terrestrial value (89), the nitrogen ratio is a factor of two lower than the terrestrial value (272), indicating a fractionation in the early solar system, or in the protosolar nebula, common to all the comets of our sample. This points towards a common origin of the comets independently of their birthplaces, and a relationship between HCN and CN. Appendices and Table [see full textsee full textsee full text] are only available in electronic form at http://www.aanda.org Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes ID 268.C-5570, 270.C-5043, 073.C-0525, 274.C-5015 and 075.C-0355(A).

  6. Deciphering Ecohydrological Interactions Using Stable Isotopes

    NASA Astrophysics Data System (ADS)

    McDonnell, J.; Evaristo, J. A.; Jasechko, S.

    2014-12-01

    Deciphering the nature of ecohydrological interconnections and scaling that knowledge gained at single points to watersheds is challenging. One tool that that has proved useful in this regard is stable isotope tracing. Single isotope studies have been used recently to quantify landuse change effects on streamflow source apportionment and ecological effects on transit time distributions of water at the catchment scale. However, most work to date has assumed that plant transpiration, groundwater recharge and streamflow are all sourced or mediated by the same well mixed reservoir—the soil. Recent work in Oregon and Mexico has shown evidence of ecohydrological separation, whereby different subsurface compartmentalized pools of water supply either plant transpiration fluxes or the combined fluxes of groundwater recharge and streamflow. However, these findings have not yet been widely tested. Here we assemble the first dual isotope database for δ2H and δ18O extracted from 47 globally-distributed stable isotopic datasets. We use these data to test the ecohydrological separation hypothesis. We combine this dual isotope dataset with global precipitation, streamwater, groundwater and soil water datasets. Our results show that precipitation, streamwater and groundwater from the 47 sites plot approximately along the δ2H/δ18O slope of eight, suggesting that local precipitation inputs supply streamwater and groundwater. Soil waters extracted from the 47 studies plot below the regression of local streamwater and groundwater with a slope of 6.6±0.05 ‰. Local plant xylem waters from our matched dataset plot on a slope 6.6±0.07 ‰ consistent with local soil waters. The tight association of soil water slopes and not that of local groundwater or streamflow suggests that plants use soil water that does not itself contribute to groundwater recharge or stream water. This ubiquity of subsurface water compartmentalization is surprising and has important implications for how we

  7. Isotopic evidence of early hominin diets

    NASA Astrophysics Data System (ADS)

    Sponheimer, Matt; Alemseged, Zeresenay; Cerling, Thure E.; Grine, Frederick E.; Kimbel, William H.; Leakey, Meave G.; Lee-Thorp, Julia A.; Kyalo Manthi, Fredrick; Reed, Kaye E.; Wood, Bernard A.; Wynn, Jonathan G.

    2013-06-01

    Carbon isotope studies of early hominins from southern Africa showed that their diets differed markedly from the diets of extant apes. Only recently, however, has a major influx of isotopic data from eastern Africa allowed for broad taxonomic, temporal, and regional comparisons among hominins. Before 4 Ma, hominins had diets that were dominated by C3 resources and were, in that sense, similar to extant chimpanzees. By about 3.5 Ma, multiple hominin taxa began incorporating 13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their diets and had highly variable carbon isotope compositions which are atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern Africa diverged toward C4/CAM specialization and occupied an isotopic niche unknown in catarrhine primates, except in the fossil relations of grass-eating geladas (Theropithecus gelada). At the same time, other taxa (e.g., Australopithecus africanus) continued to have highly mixed and varied C3/C4 diets. Overall, there is a trend toward greater consumption of 13C-enriched foods in early hominins over time, although this trend varies by region. Hominin carbon isotope ratios also increase with postcanine tooth area and mandibular cross-sectional area, which could indicate that these foods played a role in the evolution of australopith masticatory robusticity. The 13C-enriched resources that hominins ate remain unknown and must await additional integration of existing paleodietary proxy data and new research on the distribution, abundance, nutrition, and mechanical properties of C4 (and CAM) plants.

  8. Oxygen isotope composition of trinitite postdetonation materials.

    PubMed

    Koeman, Elizabeth C; Simonetti, Antonio; Chen, Wei; Burns, Peter C

    2013-12-17

    Trinitite is the melt glass produced subsequent the first nuclear bomb test conducted on July 16, 1945, at White Sands Range (Alamagordo, NM). The geological background of the latter consists of arkosic sand that was fused with radioactive debris and anthropogenic materials at ground zero subsequent detonation of the device. Postdetonation materials from historic nuclear weapon test sites provide ideal samples for development of novel forensic methods for attribution and studying the chemical/isotopic effects of the explosion on the natural geological environment. In particular, the latter effects can be evaluated relative to their spatial distribution from ground zero. We report here δ(18)O(‰) values for nonmelted, precursor minerals phases (quartz, feldspar, calcite), "feldspathic-rich" glass, "average" melt glass, and bulk (natural) unmelted sand from the Trinity site. Prior to oxygen isotope analysis, grains/crystals were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine their corresponding major element composition. δ(18)O values for bulk trinitite samples exhibit a large range (11.2-15.5‰) and do not correlate with activity levels for activation product (152)Eu; the latter levels are a function of their spatial distribution relative to ground zero. Therefore, the slow neutron flux associated with the nuclear explosion did not perturb the (18)O/(16)O isotope systematics. The oxygen isotope values do correlate with the abundances of major elements derived from precursor minerals present within the arkosic sand. Hence, the O isotope ratios documented here for trinitite melt glass can be attributed to a mixture of the respective signatures for precursor minerals at the Trinity site prior to the nuclear explosion. PMID:24304329

  9. Quantifying uncertainty in stable isotope mixing models

    NASA Astrophysics Data System (ADS)

    Davis, Paul; Syme, James; Heikoop, Jeffrey; Fessenden-Rahn, Julianna; Perkins, George; Newman, Brent; Chrystal, Abbey E.; Hagerty, Shannon B.

    2015-05-01

    Mixing models are powerful tools for identifying biogeochemical sources and determining mixing fractions in a sample. However, identification of actual source contributors is often not simple, and source compositions typically vary or even overlap, significantly increasing model uncertainty in calculated mixing fractions. This study compares three probabilistic methods, Stable Isotope Analysis in R (SIAR), a pure Monte Carlo technique (PMC), and Stable Isotope Reference Source (SIRS) mixing model, a new technique that estimates mixing in systems with more than three sources and/or uncertain source compositions. In this paper, we use nitrate stable isotope examples (δ15N and δ18O) but all methods tested are applicable to other tracers. In Phase I of a three-phase blind test, we compared methods for a set of six-source nitrate problems. PMC was unable to find solutions for two of the target water samples. The Bayesian method, SIAR, experienced anchoring problems, and SIRS calculated mixing fractions that most closely approximated the known mixing fractions. For that reason, SIRS was the only approach used in the next phase of testing. In Phase II, the problem was broadened where any subset of the six sources could be a possible solution to the mixing problem. Results showed a high rate of Type I errors where solutions included sources that were not contributing to the sample. In Phase III some sources were eliminated based on assumed site knowledge and assumed nitrate concentrations, substantially reduced mixing fraction uncertainties and lowered the Type I error rate. These results demonstrate that valuable insights into stable isotope mixing problems result from probabilistic mixing model approaches like SIRS. The results also emphasize the importance of identifying a minimal set of potential sources and quantifying uncertainties in source isotopic composition as well as demonstrating the value of additional information in reducing the uncertainty in calculated

  10. Isotopic and chemical systematics of river waters

    SciTech Connect

    Goldstein, S.J.

    1987-01-01

    The isotopic composition of Nd and Sr and the concentration of the rare earth elements (REE), Rb, and Sr are reported for the dissolved and suspended load of rivers from North America, Australia, Japan, the Philippines, South America, and Pakistan. Nd and light REE are mobilized in solution in rivers of low pH, whereas Sr concentrations are generally determined by the degree of chemical weathering of source rocks. The REE pattern of the dissolved load of rivers is sensitive to pH, with heavy REE enrichments and negative Ce anomalies for alkaline rivers. The isotopic composition of Nd and Sr in the dissolved load of rivers is mainly controlled by the age of materials in a drainage basin and preferential weathering of marine precipitates. Rivers appear to be the dominant source of these elements in the oceans. Estuarine removal processes lower the actual river flux of dissolved REE to the oceans by 70% for the light REE and 40% for the heavy REE. A Sr isotopic mass balance for modern seawater yields a hydrothermal water of 2.9 x 10/sup 16/ g/yr. Suspended load data directly reflect the Sm-Nd isotopic systematics and REE systematics of upper continental crust exposed to weathering. Average Sm-Nd parameters estimated for the upper crust are: Sm = 5.7 ppm. Nd = 30.0 ppm, epsilon/sub Nd/ = -15.4, and T/sub DM//sup Nd/ = 2.0 Ga. An overall relationship between epsilon/sub Nd/ and /sup 87/Sr//sup 86/Sr in river suspended loads directly reflects the relationship of these parameters in upper crust and suggests that crustal additions have become progressively depleted in incompatible elements through time. The implications of these data for interpretation of the record of Nd and Sr isotopes and REE abundances in ancient erosion products are briefly discussed.

  11. Isotopic Fractionation of Atmospheric Nitrous Oxide

    NASA Astrophysics Data System (ADS)

    Morgan, C. G.; Yung, Y. L.; Allen, M. A.; Blake, G. A.; Liang, N. C.

    2002-05-01

    Nitrous oxide (N2O) is an important greenhouse gas in the Earth's atmosphere, with both natural and anthropogenic sources. Much effort has been made in using isotopic signatures as a way to constrain the magnitudes of the various sources of N2O. A necessary part of this task is to understand what effect the atmosphere, which is the major sink of N2O, has on these isotopic signatures. Using a two-dimensional (2-D) chemical transport model, we investigated the isotopic fractionation of N2O in the Earth's atmosphere, and we compared the results of our model with laboratory experiments and atmospheric observations. Isotopic fractionation of N2O can occur through photolytic destruction and through a reaction with singlet oxygen. We used three different methods of calculating photolytic cross-sections for each of the major isotopomers of N2O. We found that although the Yung and Miller approach (Science, 278, 1778 (1997)), which postulates that changes in the zero point energies between the isotopomers causes shifts in their respective absorption profiles, can model the pattern of enrichment factors for each isotopomer relative to each other, this approach underestimates the magnitude of the enrichment factors. The ab initio approach by Johnson et al. (JPCA, 105, 8672 (2001)) provided a better fit to the magnitudes of the enrichment factors, with the notable exception of the 15N14N16O isotopomer. A simpler, semi-empirical approach by Blake et al. (2002, in preparation) was able to model the magnitude of all the enrichment factors, including the one for the 15N14N16O isotopomer. We also explored the contributions and effects that the singlet oxygen reaction, climatology and transport have on atmospheric isotopic fractionation.

  12. Isotopic evidence of early hominin diets

    PubMed Central

    Sponheimer, Matt; Alemseged, Zeresenay; Cerling, Thure E.; Grine, Frederick E.; Kimbel, William H.; Leakey, Meave G.; Lee-Thorp, Julia A.; Manthi, Fredrick Kyalo; Reed, Kaye E.; Wood, Bernard A.; Wynn, Jonathan G.

    2013-01-01

    Carbon isotope studies of early hominins from southern Africa showed that their diets differed markedly from the diets of extant apes. Only recently, however, has a major influx of isotopic data from eastern Africa allowed for broad taxonomic, temporal, and regional comparisons among hominins. Before 4 Ma, hominins had diets that were dominated by C3 resources and were, in that sense, similar to extant chimpanzees. By about 3.5 Ma, multiple hominin taxa began incorporating 13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their diets and had highly variable carbon isotope compositions which are atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern Africa diverged toward C4/CAM specialization and occupied an isotopic niche unknown in catarrhine primates, except in the fossil relations of grass-eating geladas (Theropithecus gelada). At the same time, other taxa (e.g., Australopithecus africanus) continued to have highly mixed and varied C3/C4 diets. Overall, there is a trend toward greater consumption of 13C-enriched foods in early hominins over time, although this trend varies by region. Hominin carbon isotope ratios also increase with postcanine tooth area and mandibular cross-sectional area, which could indicate that these foods played a role in the evolution of australopith masticatory robusticity. The 13C-enriched resources that hominins ate remain unknown and must await additional integration of existing paleodietary proxy data and new research on the distribution, abundance, nutrition, and mechanical properties of C4 (and CAM) plants.

  13. Sulfur isotope homogeneity of lunar mare basalts

    NASA Astrophysics Data System (ADS)

    Wing, Boswell A.; Farquhar, James

    2015-12-01

    We present a new set of high precision measurements of relative 33S/32S, 34S/32S, and 36S/32S values in lunar mare basalts. The measurements are referenced to the Vienna-Canyon Diablo Troilite (V-CDT) scale, on which the international reference material, IAEA-S-1, is characterized by δ33S = -0.061‰, δ34S ≡ -0.3‰ and δ36S = -1.27‰. The present dataset confirms that lunar mare basalts are characterized by a remarkable degree of sulfur isotopic homogeneity, with most new and published SF6-based sulfur isotope measurements consistent with a single mass-dependent mean isotopic composition of δ34S = 0.58 ± 0.05‰, Δ33S = 0.008 ± 0.006‰, and Δ36S = 0.2 ± 0.2‰, relative to V-CDT, where the uncertainties are quoted as 99% confidence intervals on the mean. This homogeneity allows identification of a single sample (12022, 281) with an apparent 33S enrichment, possibly reflecting cosmic-ray-induced spallation reactions. It also reveals that some mare basalts have slightly lower δ34S values than the population mean, which is consistent with sulfur loss from a reduced basaltic melt prior to eruption at the lunar surface. Both the sulfur isotope homogeneity of the lunar mare basalts and the predicted sensitivity of sulfur isotopes to vaporization-driven fractionation suggest that less than ≈1-10% of lunar sulfur was lost after a potential moon-forming impact event.

  14. Carbon isotope ratios and isotopic correlations between components in fruit juices

    NASA Astrophysics Data System (ADS)

    Wierzchnicki, Ryszard

    2013-04-01

    Nowadays food products are defined by geographical origin, method of production and by some regulations concerning terms of their authenticity. Important data for confirm the authenticity of product are providing by isotopic methods of food control. The method checks crucial criteria which characterize the authenticity of inspected product. The European Union Regulations clearly show the tendency for application of the isotopic methods for food authenticity control (wine, honey, juice). The aim of the legislation steps is the protection of European market from possibility of the commercial frauds. Method of isotope ratio mass spectrometry is very effective tool for the use distinguishably the food products of various geographical origin. The basic problem for identification of the sample origin is the lack of databases of isotopic composition of components and information about the correlations of the data. The subject of the work was study the isotopic correlations existing between components of fruits. The chemical and instrumental methods of separation: water, sugars, organic acids and pulp from fruit were implemented. IRMS technique was used to measure isotopic composition of samples. The final results for original samples of fruits (apple, strawberry etc.) will be presented and discussed. Acknowledgement: This work was supported by the Polish Ministry of Science and Higher Education under grant NR12-0043-10/2010.

  15. Isotopically distinct reservoirs in the solar nebula: Isotope anomalies in Vigarano meteorite inclusions

    NASA Technical Reports Server (NTRS)

    Loss, R. D.; Lugmair, G. W.; Davis, A. M.; Macpherson, G. J.

    1994-01-01

    The isotopic compositions of Mg, Ca, Ti, Cr, Zn, Sr, Ba, Nd, and Sm were measured in four relatively unaltered refractory inclusions from the Vigarano carbonaceous chondrite meteorite. Three of the inclusions (USNM 1623-2, 1623-3, and 1623-8) show similar Mg, Ca, Ti, and Cr isotopic compositions to those found in most inclusions in the Allende carbonaceous chondrite. This indicates that these Vigarano inclusions sampled the same isotopic reservoirs as the majority of the Allende inclusions that isotope signatures in the latter were not significantly modified by the secondary alteration that permeates most Allende inclusions. In contrast, inclusion 1623-5 has large deficits in Mg-26, Ca-48, and Ti-50 and small but distinct Cr-54, Zn-66, Sr-84, Ba-135, Ba-137, and Sm-144 anomalies. The magnitudes of these unusual anomalies in the refractory elements are within analytical uncertainty of those found in the Allende 'FUN" inclusion C1, yet 1623-5 has a very different bulk chemical composition from C1. The fact that 1623-5 and C1 have identical isotopic anomalies yet have significantly distinct major and trace element contents provide convincing evidence for the presence of isotopically distinct reservoirs in the early solar system.

  16. Oxygen isotope exchange and isotopic fractionation during N2O production by denitrification

    NASA Astrophysics Data System (ADS)

    Lewicka-Szczebak, Dominika; Well, Reinhard; Kaiser, Jan

    2014-05-01

    Stable isotopic analyses of N2O may help in quantification of soil denitrification processes. N2O reduction to N2 during denitrification is associated with significant isotopic fractionation. Theoretically, this would allow the product ratio (N2O/(N2+N2O)) to be calculated based on the isotopic signature of the remaining N2O if the isotopic signature of the produced N2O were precisely predictable. Oxygen isotopes are especially useful, in particular the 17O excess, Δ(17O), to quantify any oxygen isotope exchange between soil water and intermediate products (NO2-, NO). This significantly influences the δ(18O) values of the N2O produced. Previous studies showed this exchange to be nearly complete, up to 90% 1,2. However, there are very few studies on the associated oxygen isotopic fractionation and its potential coupling to the magnitude of oxygen isotope exchange with soil water 2,3. We hypothesize that for high oxygen exchange, the oxygen isotopic fractionation will show little variability. In previous experiments, an 18O-enriched tracer was applied to quantify the magnitude of oxygen exchange 1,2. Such an approach does not permit determining any oxygen isotope fractionation. Here, we applied two novel experimental approaches: (1) waters of two different δ(18O) values within the natural range (-1.5 and -14.8 o relative to VSMOW) were used for rewetting the incubated soils and the oxygen exchange was calculated from comparing the relative isotope ratio difference between N2O and H2O for these two water treatments; (2) soils were amended with Chile Saltpeter characterized by a high 17O excess (20.2 o ) and the 17O excess of the N2O product was measured. Both approaches were applied simultaneously on the same soil samples, which allowed quantifying the oxygen isotope exchange with two independent methods at the same time. The N2O reduction was inhibited with acetylene method and δ(18O) values of the N2O produced were measured to determine the oxygen fractionation

  17. Vapor Pressure Isotope Effects and the Stable Isotope Geochemistry of the Martian Surface

    NASA Astrophysics Data System (ADS)

    Eiler, J. M.

    2002-12-01

    The stable isotope geochemistry of light elements (H, C, N, O and S) is a tool in the search for evidence of life on bodies other than the earth for several reasons: the elements in question are used by all known or easily imagined life forms; several mass spectrometric and spectroscopic methods for measuring their isotopic compositions exist and are appropriate for in situ analysis on other planets; it is known that 'vital effects' generate large (percent) isotopic fractionations; and studies of extant and former life on earth provide models for interpreting such data. However, the evidence stable isotope geochemistry provides is generally interpretable as a signature for life only in the context of a rich understanding of isotopic variations produced by non biological processes in the same environments. Several candidates in the search for extra-terrestrial life (Mars and the Jovian satellites) are bodies having volatile-element geochemical cycles that operate at lower temperatures than the earth's surface and involve phase-changes that do not occur on the earth (e.g., condensation/sublimation of CO2). We review new experimental data (both recently published and unpublished) describing isotopic fractionations accompanying phase changes of CO2, H2O below 240 K, NH3 and CO, compile them with previous data to derive general principles of low-temperature stable isotope fractionations, and discuss their significance for the stable isotope geochemistry of the surface of Mars. One example of the issues constrained by these data (the Martian CO2 cycle) is discussed here. The Martian surface is strongly influenced by condensation/sublimation and adsorption/desorption of CO2. The isotopic consequences of these processes are an attractive goal for in situ observations of atmosphere, ice and/or adsorbed gas because they provide a record of Martian atmospheric dynamics and atmosphere-surface interactions over a range of time-scales. Furthermore, these isotopic signals

  18. Method of enhancing selective isotope desorption from metals

    DOEpatents

    Knize, Randall J.; Cecchi, Joseph L.

    1984-01-01

    A method of enhancing the thermal desorption of a first isotope of a diatomic gas from a metal comprises the steps of (a) establishing a partial pressure of a second isotope of the diatomic gas in vicinity of the metal; heating the metal to a temperature such that the first isotope is desorbed from the metal; and reducing the partial pressure of the desorbed first isotope while maintaining the partial pressure of the second isotope substantially constant. The method is especially useful for enhancing the desorption of tritium from the Zr-Al getter in a plasma confinement device.

  19. Uranium Isotope Systematic in Saanich Inlet

    NASA Astrophysics Data System (ADS)

    Amini, M.; Holmden, C.; Francois, R.

    2008-12-01

    As a redox-sensitive element Uranium has become the focus of stable isotope studies. Based on the nuclear field shift effect [1], U isotope fractionation was predicted as a function of U(IV)-U(VI) exchange reactions with the insoluble reduced U(IV) species being heavier than the soluble oxidized U(VI) species. Recently, variations in 238U/235U were reported in low temperature aqueous and sedimentary environments [2,3] indicating that U deposited in well-oxygenated environments is characterized by light isotopic composition, whereas suboxic and anoxic deposits tend towards a heavy isotopic signature. U isotope fractionation has been hence proposed as a promising new paleo-redox proxy. In order to test the efficacy of U isotope fractionation to record oxidation states in marine systems, we are investigating sediment samples deposited over a range of redox conditions in the seasonally anoxic Saanich Inlet, on the east coast of Vancouver Island. We have also made δ238U measurements for water samples from above and below the redoxcline. The measurements were carried out by MC-ICPMS using 233U/236U-double spike technique. The data are reported as δ238U relative to NBL 112a with a 238U/235U ratio of 137.88 (2sd). External precision is better than 0.10 permil (2sd). Eleven analyses of seawater performed over the course of this work yielded δ238U of -0.41±0.07 permil (2sd). No clear difference in δ238U values has been found, thus far, in water samples collected at 10m (O2~380μM) and 200m (O2~1μM) depths from a single location in the middle of the inlet. The mean of two measurements of the deepwater sample yielded -0.43±0.01 permil (2sd). Two measurements of the shallow water sample yielded a mean value of -0.38±0.03 permil (2sd). The δ238U values for HF-HNO3 digestions of the organic rich sediments, one taken in the middle of the basin (3.11% organic carbon) below seasonally anoxic bottom waters (-0.22±0.01 permil, n=2), and the other taken from the sill (1

  20. Lithium Isotope Systematics in Azores Basalts

    NASA Astrophysics Data System (ADS)

    Yu, H.; Widom, E.; Qiu, L.; Rudnick, R.; Gelinas, A.; Franca, Z.

    2009-05-01

    Basalts from the Azores archipelago and MORB from the nearby Azores Platform exhibit extreme chemical and isotopic variations attributed to the influence of a heterogeneous mantle plume, with compositions ranging from depleted mantle (DMM) to strong HIMU, EMI and EMII signatures. In order to assess the utility of Li isotopes as a mantle source tracer and to better constrain the origin of heterogeneous mantle beneath the Azores, we have analyzed Li isotopes in a suite of young, fresh, MgO-rich basalts from São Miguel and three Central Group islands including Pico, Faial and Terceira. Despite large variations in radiogenic isotope signatures (e.g. 206Pb/204Pb = 19.3 to 20.1), δ7Li varies only slightly (3.1-4.7‰), and is within the range for global and North Atlantic MORB [1, 2]. More extreme δ7Li values such as those reported previously for some EMII, EMI and HIMU ocean island basalts (-17‰ to +10‰; [3-5]) were not observed. Nevertheless, basalts from the Central Group islands with EMI-type signatures are, on average, slightly heavier in δ7Li than the São Miguel samples, and they exhibit positive correlations with 87Sr/86Sr and negative correlations with 206Pb/204Pb, Nd, and Hf isotopes. Li isotopes do not correlate with indices of fractionation such as MgO, suggesting that the δ7Li correlations with radiogenic isotopes may represent subtle variations in mantle source signatures. Positive and negative correlations of δ7Li with 87Sr/86Sr and 206Pb/204Pb, respectively, and relatively unradiogenic Os (187Os/188Os = 0.1244-0.1269), may reflect old, slab-fluid metasomatized mantle beneath the Central Group islands. In contrast, δ7Li signatures in the São Miguel basalts do not correlate with radiogenic isotopes. Rather, δ7Li is essentially constant despite extremely high 87Sr/86Sr and 206Pb/204Pb and low ΔɛHf signatures that have been attributed to 3.5 Ga recycled E-MORB or evolved oceanic crust [6; 7]. This suggests either that the São Miguel source

  1. Molybdenum Isotopes in Some Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Qi, L.; Masuda, A.

    1992-07-01

    Measurement of all seven stable Mo isotopes in iron meteorites has been continued for study of possible direct evidences for processes of nucleosynthesis in the pre-solar stage and information on extinct radioactive nuclides. Mo in iron meteorite was extracted by using recently developed chemical separation method [1], then loaded on 5 pass zone refined Re ribbon. Molybdenum isotope analysis was performed [2] in a VG SECTOR 54-30 thermal ionization mass spectrometer using a Faraday collector in peak jumping mode. The measured ratios of Mo were normalized provisionally to ^94Mo/^98Mo = 0.3802. Particular caution was drawn on the isobaric interferences of Zr, Ru, etc., which were negligible as a result. A small but distinct anomaly of Mo isotopes was found in Acuna iron meteorite. The normalized data show a growth trend from ^92Mo to ^97Mo, and this increment decreased suddenly at ^98Mo, then slightly increased at ^100Mo. The isotope variations might be explained as a result of excess s-process component (^95Mo to ^98Mo) contained in the sample. Gibeon suggested that isotopic anomalies at ^92Mo, ^95Mo, and ^97Mo are about -3-epsilon, -1.2-epsilon, and -0.5-epsilon respectively. It is difficult to give a perfect explanation to the observed data at present. However, it is interesting to note that ^92Mo (N=50) has a closed shell and only ^95Mo and ^97Mo are even-odd nuclides in all seven stable Mo isotopes and the 30-keV Maxwellian-averaged neutron capture cross sections for ^95Mo and ^97Mo are about 3 times bigger than others [3]. The depletions at ^95Mo and ^97Mo might be attributed to the higher cross section for their destruction by (n, gamma) reaction. The apparent opposite aberrations are found for Odessa iron. We reported anomalies of Mo isotopes in a specimen of Sikhote-Alin iron meteorite [4,5]. Further investigations have shown that the isotopic compositions of Mo in this iron are heterogeneous and that the "general anomaly" of Mo isotopes is related with the

  2. Zinc isotope fractionation during adsorption on calcite

    NASA Astrophysics Data System (ADS)

    Dong, S.; Wasylenki, L. E.

    2013-12-01

    Zinc is an important element as a nutrient in the marine biosphere. However, our understanding of its biogeochemical cycling in the oceans is relatively limited. The Zn stable isotope system holds the promise of providing novel insights, since published Zn isotopic values for various natural samples reveal significant fractionations in the marine environment. Surface seawater, basalts, shales, deep-sea clay sediments, sediment trap material, bulk plankton and zooplankton samples, and eolian dust fall within a tight range (δ66/64Zn from -0.1 to 0.5‰), but modern ferromanganese crusts (δ66/64Zn from 0.5 to 1.2‰), as well as carbonates (δ66/64Zn from 0.3 to 1.4‰), are notably enriched in heavy Zn isotopes [1-4]. In this study we seek to constrain the mechanism by which carbonates are enriched in heavier isotopes. In particular, we have conducted experiments to quantify isotope fractionation during adsorption of Zn onto the surfaces of calcite crystals that are in equilibrium with solution. The adsorption experiments were carried out in a series of small-volume batch reactions in a clean laboratory environment, using high-purity reagents and calcite seed crystals. The calcite was equilibrated with the solution prior to addition of Zn at atmospheric CO2 pressure (i.e., in air) for 5 days until a stable pH of 8.3 was reached. Later, a small aliquot of dissolved ZnCl2 was added such that the solution remained undersaturated with respect to hydrozincite. Experimental duration varied among the replicates from 6 to 144 hours, and then all solids and solutions were separated by filtration, purified by ion exchange chromatography, and analyzed by MC-ICP-MS. Zn adsorbed on calcite is isotopically heavier than in the co-existing solutions, with Δ68/66Zncalcite-solution of approximately 0.3‰. The variation of Δ68/66Zncalcite-solution beyond 24 hours is insignificant, so we infer that isotopic equilibrium is reached by this time. Previous work strongly suggests that a

  3. Zn isotope fractionation during adsorption on birnessite

    NASA Astrophysics Data System (ADS)

    Bryan, A. L.; Dong, S.; Wasylenki, L. E.

    2013-12-01

    The biogeochemical cycling of zinc (Zn), an important micronutrient in the ocean, may influence primary productivity and species composition within surface waters. The chemical speciation and bioavailability of Zn is governed by diverse abiotic and biotic processes. These processes include adsorption reactions at mineral/water interfaces, as nanoparticles of oxyhydroxide minerals are known to adsorb significant amounts of Zn in surface waters (and during formation of ferromanganese crusts). Investigation of Zn isotope fractionation caused by adsorption onto birnessite, the dominant manganese oxide mineral in ferromanganese crusts, may help to explain the enrichment of heavy Zn isotopes in ferromanganese crusts. This will provide insight into the role of adsorption of Zn to nanoparticulate minerals in surface waters and into the overall biogeochemical cycling of Zn. This work aims to determine the mechanism and magnitude of Zn isotope fractionation during adsorption onto synthetic birnessite (KMn2O4.1.5H2O). Our simple-system experiments involve mixing solutions of 130 ppb Zn with aliquots of birnessite suspension (proportions varied to give a range of surface coverage) and a fixed pH near that of seawater at ~8.5. The mixtures react for 48 hours. The recovered dissolved Zn and adsorbed Zn are then separated, purified, and analyzed isotopically on a Nu Plasma MC-ICP-MS. Preliminary results show enrichment of light Zn isotopes on the mineral surfaces (Δ66/64Znsorbed-aqueous = -0.3‰). A time series will reveal whether this process is governed by equilibrium or Rayleigh fractionation. Contrary to our results, previously published studies led us to hypothesize that isotopically heavy Zn would adsorb compared to co-existing dissolved Zn. Maréchal et al. (2000) recorded ferromanganese crusts that were heavier than seawater with a mean δ66Zn value of 0.90‰. Dissolved Zn is octahedrally coordinated with oxygen atoms, but an EXAFS study by Manceau et al. (2002

  4. Oxygen isotope corrections for online δ34S analysis

    USGS Publications Warehouse

    Fry, B.; Silva, S.R.; Kendall, C.; Anderson, R.K.

    2002-01-01

    Elemental analyzers have been successfully coupled to stable-isotope-ratio mass spectrometers for online measurements of the δ34S isotopic composition of plants, animals and soils. We found that the online technology for automated δ34S isotopic determinations did not yield reproducible oxygen isotopic compositions in the SO2 produced, and as a result calculated δ34S values were often 1–3‰ too high versus their correct values, particularly for plant and animal samples with high C/S ratio. Here we provide empirical and analytical methods for correcting the S isotope values for oxygen isotope variations, and further detail a new SO2-SiO2 buffering method that minimizes detrimental oxygen isotope variations in SO2.

  5. THE ATOMIC WEIGHTS COMMISSION AND ISOTOPIC ABUNDANCE RATIO DETERMINATIONS.

    SciTech Connect

    HOLDEN, N.E.

    2005-08-07

    Following Thomson's discovery of stable isotopes in non-radioactive chemical elements, the derivation of atomic weight values from mass spectrometric measurements of isotopic abundance ratios moved very slowly. Forty years later, only 3 1/2 % of the recommended values were based on mass spectrometric measurements and only 38% in the first half century. It might be noted that two chemical elements (tellurium and mercury) are still based on chemical measurements, where the atomic weight value calculated from the relative isotopic abundance measurement either agrees with the value from the chemical measurement or the atomic weight value calculated from the relative isotopic abundance measurement falls within the uncertainty of the chemical measurement of the atomic weight. Of the 19 chemical elements, whose atomic weight is based on non-corrected relative isotopic abundance measurements, five of these are two isotope systems (indium, iridium, lanthanum, lutetium and tantalum) and one is a three-isotope system (oxygen).

  6. Method of preparing mercury with an arbitrary isotopic distribution

    DOEpatents

    Grossman, M.W.; George, W.A.

    1986-12-16

    This invention provides for a process for preparing mercury with a predetermined, arbitrary, isotopic distribution. In one embodiment, different isotopic types of Hg[sub 2]Cl[sub 2], corresponding to the predetermined isotopic distribution of Hg desired, are placed in an electrolyte solution of HCl and H[sub 2]O. The resulting mercurous ions are then electrolytically plated onto a cathode wire producing mercury containing the predetermined isotopic distribution. In a similar fashion, Hg with a predetermined isotopic distribution is obtained from different isotopic types of HgO. In this embodiment, the HgO is dissolved in an electrolytic solution of glacial acetic acid and H[sub 2]O. The isotopic specific Hg is then electrolytically plated onto a cathode and then recovered. 1 fig.

  7. Method of preparing mercury with an arbitrary isotopic distribution

    DOEpatents

    Grossman, Mark W.; George, William A.

    1986-01-01

    This invention provides for a process for preparing mercury with a predetermined, arbitrary, isotopic distribution. In one embodiment, different isotopic types of Hg.sub.2 Cl.sub.2, corresponding to the predetermined isotopic distribution of Hg desired, are placed in an electrolyte solution of HCl and H.sub.2 O. The resulting mercurous ions are then electrolytically plated onto a cathode wire producing mercury containing the predetermined isotopic distribution. In a similar fashion, Hg with a predetermined isotopic distribution is obtained from different isotopic types of HgO. In this embodiment, the HgO is dissolved in an electrolytic solution of glacial acetic acid and H.sub.2 O. The isotopic specific Hg is then electrolytically plated onto a cathode and then recovered.

  8. The identification of meteorite inclusions with isotope anomalies

    NASA Astrophysics Data System (ADS)

    Papanastassiou, D. A.; Brigham, C. A.

    1989-03-01

    Ca-Al refractory inclusions with characteristic chemical and mineralogical compositions show an enhanced occurrence of 20 pct of isotope anomalies reflecting unknown nucleosynthetic effects for O and Mg. The anomalies are characterized by large isotope fractionation in Mg, apparent deficits in Mg-26/Mg-24, and large correlated effects for isotopes of Ca, Ti, and Cr. These isotope patterns define exotic components depleted in the most neutron-rich isotopes of Ca, Ti, and Cr, or components depleted in isotopes produced in explosive O and Si burning. An opaque assemblage within one of the inclusions yields isotope anomalies in Cr similar to the bulk inclusion and must be intrinsically part of the inclusion and not a trapped, foreign grain aggregate.

  9. Effects of isotope selection on solution convergence in HZE transport

    NASA Technical Reports Server (NTRS)

    Kim, Myung-Hee Y.; Wilson, John W.; Kiefer, Richard L.; Thibeault, Sheila A.

    1994-01-01

    A fragmenting iron ion produces hundreds of isotopes during nuclear reactions. These isotopes are represented in the solution of the transport problem. A reduced set of isotopes is selected to minimize the computational burden but introduces error in the final result. A minimum list of 122 isotopes is required for adequate representation of the mass and charge distributions of the secondary radiation fields. A reduced set of 80 isotopes is sufficient to represent the charge distribution alone and represents reasonably well the linear energy transfer properties of the iron beam. Because iron fragmentation produces nearly every isotope lighter than iron, the resulting 122-isotope list should be adequate for ion beams with charges equal to or less than 26.

  10. Carbon isotopes as indicators of peatland growth?

    NASA Astrophysics Data System (ADS)

    Alewell, Christine; Krüger, Jan Paul; von Sengbusch, Pascal; Szidat, Sönke; Leifeld, Jens

    2016-04-01

    As undisturbed and/or growing peatlands store considerable amounts of carbon and are unique in their biodiversity and species assemblage, the knowledge of the current status of peatlands (growing with carbon sequestration, stagnating or degrading with carbon emissions) is crucial for landscape management and nature conservation. However, monitoring of peatland status requires long term measurements and is only feasible with expert knowledge. The latter determination is increasingly impeded in a scientific world, where taxonomic expert knowledge and funding of long term monitoring is rare. Stable carbon and nitrogen isotopes depth profiles in peatland soils have been shown to be a useful tool to monitor the degradation of peatlands due to permafrost thawing in Northern Sweden (Alewell et al., 2011; Krüger et al., 2014), drainage in Southern Finland (Krüger et al., 2016) as well as land use intensification in Northern Germany (Krüger et al., 2015). Here, we tackle the questions if we are able to differentiate between growing and degrading peats with the use of a combination of carbon stable (δ13C) and radiogenic isotope data (14C) with peat stratification information (degree of humification and macroscopic plant remains). Results indicate that isotope data are a useful tool to approximate peatland status, but that expert taxonomic knowledge will be needed for the final conclusion on peatland growth. Thus, isotope tools might be used for landscape screening to pin point sites for detailed taxonomic monitoring. As the method remains qualitative future research at these sites will need to integrate quantitative approaches to determine carbon loss or gain (soil C balances by ash content or C accumulation methods by radiocarbon data; Krüger et al., 2016). Alewell, C., R. Giesler, J. Klaminder, J. Leifeld, and M. Rollog. 2011. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats. Biogeosciences, 8, 1769-1778. Krüger, J. P., Leifeld, J

  11. Flux Partitioning by Isotopic Eddy Covariance

    NASA Astrophysics Data System (ADS)

    Wehr, R.; Munger, J. W.; Nelson, D. D.; McManus, J. B.; Zahniser, M. S.; Wofsy, S. C.; Saleska, S. R.

    2011-12-01

    Net ecosystem-atmosphere exchange of CO2 is routinely measured by eddy covariance at sites around the world, but studies of ecosystem processes are more interested in the gross photosynthetic and respiratory fluxes that comprise the net flux. The standard method of partitioning the net flux into these components has been to extrapolate nighttime respiration into daytime based on a relationship between nighttime respiration, temperature, and sometimes moisture. However, such relationships generally account for only a small portion of the variation in nighttime respiration, and the assumption that they can predict respiration throughout the day is dubious. A promising alternate method, known as isotopic flux partitioning, works by identifying the stable isotopic signatures of photosynthesis and respiration in the CO2 flux. We have used this method to partition the net flux at Harvard Forest, MA, based on eddy covariance measurements of the net 12CO2 and 13CO2 fluxes (as well as measurements of the sensible and latent heat fluxes and other meteorological variables). The CO2 isotopologues were measured at 4 Hz by an Aerodyne quantum cascade laser spectrometer with a δ13C precision of 0.4 % in 0.25 sec and 0.02 % in 100 sec. In the absence of such high-frequency, high-precision isotopic measurements, past attempts at isotopic flux partitioning have combined isotopic flask measurements with high-frequency (total) CO2 measurements to estimate the isoflux (the EC/flask approach). Others have used a conditional flask sampling approach called hyperbolic relaxed eddy accumulation (HREA). We 'sampled' our data according to each of these approaches, for comparison, and found disagreement in the calculated fluxes of ~10% for the EC/flask approach, and ~30% for HREA, at midday. To our knowledge, this is the first example of flux partitioning by isotopic eddy covariance. Wider use of this method, enabled by a new generation of laser spectrometers, promises to open a new window

  12. Isotopes in Western North American snowpack 1993 - 2013

    NASA Astrophysics Data System (ADS)

    Anderson, L.; Berkelhammer, M. B.; VanSistine, P.

    2013-12-01

    The interpretation of oxygen isotope-based climate proxies in the western North America, including those from lake sediment calcite, tree cellulose, leaf waxes, and speleothems, each depend on assumptions about the site-specific and regional patterns of the isotopic composition of seasonal precipitation. Here we explore isotopic ratios in the integrated Rocky Mountain snowpack (IRMS) since 1993 for >45 high-elevation locations per year between northern Montana and northern New Mexico. The isotopic network comprises the most extensive spatial and temporal effort to document snowpack isotopic values to be conducted beyond Polar Regions. The dataset provides new insight into the processes that influence the isotopic composition of Western North American winter precipitation. Preliminary assessments indicate a number of spatial features that are similar to those observed in existing isotopic networks from North America but with additional spatial and temporal detail over this topographically complex region. Lower isotopic ratios generally occur with higher latitude, a reflection of condensation at cooler temperatures associated with more common Arctic air mass incursions, which bring isotopically depleted vapor. Higher elevation sites also generally have lower isotopes ratios, but this is most likely as a consequence of orographic rainout. East-west isotopic gradients occur as a consequence of preferential rainout as air masses pass from west to east over the spine of the cordillera and when southern tracking lows generate east to west upslope flow. Previous studies have also indicated that isotopes in precipitation track interannual shifts in atmospheric regimes that lead to changes in jet stream strength and position and the frequency that Arctic, sub-tropical or Pacific air masses reach the Rockies. We hypothesize that these changes also yield distinct impacts on the isotopic ratio of the snowpack and use the unique spatial and temporal density of the IRMS dataset

  13. Combinatorial effects on clumped isotopes and their significance in biogeochemistry

    NASA Astrophysics Data System (ADS)

    Yeung, Laurence Y.

    2016-01-01

    The arrangement of isotopes within a collection of molecules records their physical and chemical histories. Clumped-isotope analysis interrogates these arrangements, i.e., how often rare isotopes are bound together, which in many cases can be explained by equilibrium and/or kinetic isotope fractionation. However, purely combinatorial effects, rooted in the statistics of pairing atoms in a closed system, are also relevant, and not well understood. Here, I show that combinatorial isotope effects are most important when two identical atoms are neighbors on the same molecule (e.g., O2, N2, and D-D clumping in CH4). When the two halves of an atom pair are either assembled with different isotopic preferences or drawn from different reservoirs, combinatorial effects cause depletions in clumped-isotope abundance that are most likely between zero and -1‰, although they could potentially be -10‰ or larger for D-D pairs. These depletions are of similar magnitude, but of opposite sign, to low-temperature equilibrium clumped-isotope effects for many small molecules. Enzymatic isotope-pairing reactions, which can have site-specific isotopic fractionation factors and atom reservoirs, should express this class of combinatorial isotope effect, although it is not limited to biological reactions. Chemical-kinetic isotope effects, which are related to a bond-forming transition state, arise independently and express second-order combinatorial effects related to the abundance of the rare isotope. Heteronuclear moeties (e.g., Csbnd O and Csbnd H), are insensitive to direct combinatorial influences, but secondary combinatorial influences are evident. In general, both combinatorial and chemical-kinetic factors are important for calculating and interpreting clumped-isotope signatures of kinetically controlled reactions. I apply this analytical framework to isotope-pairing reactions relevant to geochemical oxygen, carbon, and nitrogen cycling that may be influenced by combinatorial

  14. Complex Molybdenum Isotope Behavior During Weathering and Erosional Transport

    NASA Astrophysics Data System (ADS)

    Siebert, C.; Pett-Ridge, J. C.; Burton, K.; Halliday, A. N.

    2009-12-01

    The oceans play a major role in regulating global climate because they both react and drive changes in other geochemical reservoirs. Non-traditional stable isotope systems have become important proxies for changes in ocean chemistry making the quantification of these changes possible. Molybdenum isotopes have great potential as tracers of changes in the oxygenation of the oceans over geological time scales. Although significant progress has been made and the amount of data on the biogeochemical behaviour of Mo in the marine environment has been increasing rapidly over the last few years, some important aspects of Mo geochemistry remain poorly understood. These include diagenetic processes at continental margins and continental weathering. Mo isotope behaviour in these settings has a potentially large impact on the interpretation of the geological record. A recent study of Archer and Vance (2008) has shown that dissolved Mo in many of Earths major rivers has a heavy isotope composition relative to most magmatic rocks. A potential cause for this isotope composition in modern rivers is isotope fractionation during weathering and erosion processes. We investigated Mo isotope behaviour in weathering profiles from Hawaii and Puerto Rico. Results clearly show significant Mo isotope fractionation during chemical weathering. Mo retained in saprolithe samples from Hawaii has light isotope compositions of up to -0.5 permill. The extent of fractionation is dependent on redox-conditions in the investigated profiles. The particular setting of these profiles keeps other factors that might influence the Mo isotope composition to a minimum. The results also indicate the possible use of Mo isotope signals as paleoredox-proxy of weathering processes. However, a weathering profile with intermittent changes in redox, pH and porewater saturation show more variable Mo isotope signals with partly positive isotope values. Sequential extractions of saphrolite samples show a clear

  15. Calculation of individual isotope equilibrium constants for geochemical reactions

    USGS Publications Warehouse

    Thorstenson, D.C.; Parkhurst, D.L.

    2004-01-01

    Theory is derived from the work of Urey (Urey H. C. [1947] The thermodynamic properties of isotopic substances. J. Chem. Soc. 562-581) to calculate equilibrium constants commonly used in geochemical equilibrium and reaction-transport models for reactions of individual isotopic species. Urey showed that equilibrium constants of isotope exchange reactions for molecules that contain two or more atoms of the same element in equivalent positions are related to isotope fractionation factors by ?? = (Kex)1/n, where n is the number of atoms exchanged. This relation is extended to include species containing multiple isotopes, for example 13C16O18O and 1H2H18O. The equilibrium constants of the isotope exchange reactions can be expressed as ratios of individual isotope equilibrium constants for geochemical reactions. Knowledge of the equilibrium constant for the dominant isotopic species can then be used to calculate the individual isotope equilibrium constants. Individual isotope equilibrium constants are calculated for the reaction CO2g = CO2aq for all species that can be formed from 12C, 13C, 16O, and 18O; for the reaction between 12C18 O2aq and 1H218Ol; and among the various 1H, 2H, 16O, and 18O species of H2O. This is a subset of a larger number of equilibrium constants calculated elsewhere (Thorstenson D. C. and Parkhurst D. L. [2002] Calculation of individual isotope equilibrium constants for implementation in geochemical models. Water-Resources Investigation Report 02-4172. U.S. Geological Survey). Activity coefficients, activity-concentration conventions for the isotopic variants of H2O in the solvent 1H216Ol, and salt effects on isotope fractionation have been included in the derivations. The effects of nonideality are small because of the chemical similarity of different isotopic species of the same molecule or ion. The temperature dependence of the individual isotope equilibrium constants can be calculated from the temperature dependence of the fractionation

  16. Compilation of the Dakota Aquifer Project isotope data and publications: The Isotope Hydrology Program of the Isotope Sciences Division

    SciTech Connect

    Davisson, M.L.; Smith, D.K.; Hudson, G.B.; Niemeyer, S.; Macfarlane, P.A.; Whittemore, D.O.

    1995-01-01

    In FY92 the then Nuclear Chemistry Division embarked on a scientific collaboration with the Kansas Geological Survey (KGS) to characterize with isotope techniques groundwater of the Dakota Formation of Kansas. The Dakota Formation is a Cretaceous-aged marine sandstone hosting potable groundwater in most regions of Kansas whose use will serve to partially offset the severe overdraft problems in the overlying Ogallala Formation. The isotope characterization of the Dakota groundwater has generated data that delineates sources, ages, and subsurface controls on the water quality. Initial interpretations of the data have been published in abstract volumes of (1) the 1993 Geological Society of America National Meeting, (2) the 8th International Conference on Geochronology, Cosmochronology and Isotope Geology, and (3) the 1994 Dakota Aquifer Workshop and Clinic. Copies of all abstracts are included in this brief review. One report will focus on the sources and ages of the groundwater, and the other will focus on the subsurface controls on the natural water quality.

  17. Oxygen isotope fractionation in phosphates: the role of dissolved complex anions in isotope exchange.

    PubMed

    Zheng, Yong-Fei

    2016-01-01

    Oxygen isotope fractionation factors for phosphates were calculated by means of the increment method. The results suggest that Ag3PO4 and BiPO4 are enriched in (18)O relative to AgPO4, and the three phosphates are consistently depleted in (18)O relative to Ba3[PO4]2; fluorapatite and chlorapatite exhibit a similar behaviour of oxygen isotope fractionation with consistent enrichment of (18)O relative to hydroxyapatite. The valence, radii and coordination of metal cations play a quantitative role in dictating the (18)O/(16)O partitioning in these phosphates of different compositions. The calculated fractionation factors for the Ag3PO4-H2O system are in agreement with experimental determinations derived from enzyme-catalysed isotope exchange between dissolved inorganic phosphate and water at the longest reaction durations at low temperatures. This demonstrates that the precipitated Ag3PO4 has completely captured the oxygen isotope fractionation in the dissolved inorganic phosphate. The calculated fractionation factors for the F/Cl-apatite-water systems are in agreement with the enzyme-catalysed experimental fractionations for the dissolved phosphate-water system at the longest reaction durations but larger than fractionations derived from bacteria-facilitated exchange and inorganic precipitation experiments as well as natural observations. For the experimental calibrations of oxygen isotope fractionation involving the precipitation of dissolved phosphate species from aqueous solutions, the fractionation between precipitate and water is primarily dictated by the isotope equilibration between the dissolved complex anions and water prior to the precipitation. Therefore, the present results provide a quantitative means to interpret the temperature dependence of oxygen isotope fractionation in inorganic and biogenic phosphates. PMID:25587823

  18. Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

    NASA Astrophysics Data System (ADS)

    Ni, Yunyan; Ma, Qisheng; Ellis, Geoffrey S.; Dai, Jinxing; Katz, Barry; Zhang, Shuichang; Tang, Yongchun

    2011-05-01

    Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2 cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using δD values in ethane from several basins in the world are in close agreement with similar predictions based on the δ 13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that δD values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that δD values in ethane might be more suitable for modeling than comparable values in methane and propane.

  19. Fundamental studies on kinetic isotope effect (KIE) of hydrogen isotope fractionation in natural gas systems

    USGS Publications Warehouse

    Ni, Y.; Ma, Q.; Ellis, G.S.; Dai, J.; Katz, B.; Zhang, S.; Tang, Y.

    2011-01-01

    Based on quantum chemistry calculations for normal octane homolytic cracking, a kinetic hydrogen isotope fractionation model for methane, ethane, and propane formation is proposed. The activation energy differences between D-substitute and non-substituted methane, ethane, and propane are 318.6, 281.7, and 280.2cal/mol, respectively. In order to determine the effect of the entropy contribution for hydrogen isotopic substitution, a transition state for ethane bond rupture was determined based on density function theory (DFT) calculations. The kinetic isotope effect (KIE) associated with bond rupture in D and H substituted ethane results in a frequency factor ratio of 1.07. Based on the proposed mathematical model of hydrogen isotope fractionation, one can potentially quantify natural gas thermal maturity from measured hydrogen isotope values. Calculated gas maturity values determined by the proposed mathematical model using ??D values in ethane from several basins in the world are in close agreement with similar predictions based on the ??13C composition of ethane. However, gas maturity values calculated from field data of methane and propane using both hydrogen and carbon kinetic isotopic models do not agree as closely. It is possible that ??D values in methane may be affected by microbial mixing and that propane values might be more susceptible to hydrogen exchange with water or to analytical errors. Although the model used in this study is quite preliminary, the results demonstrate that kinetic isotope fractionation effects in hydrogen may be useful in quantitative models of natural gas generation, and that ??D values in ethane might be more suitable for modeling than comparable values in methane and propane. ?? 2011 Elsevier Ltd.

  20. A New Isotope Tracer for the Early Solar System Processes: Stable Chlorine Isotopes and Distribution of Cl-bearing Phases in Chondrites

    NASA Astrophysics Data System (ADS)

    Nakamura, N.; Fujitani, T.; Kimura, M.

    2007-03-01

    New results of stable chlorine isotope compositions and distribution of Cl-carriers in chondrites are reported. Each group shows unique Cl-isotope variations, suggeting that there existed several Cl-isotope reservoirs in the early solar system.

  1. Isotopically enhanced triple-quantum-dot qubit

    PubMed Central

    Eng, Kevin; Ladd, Thaddeus D.; Smith, Aaron; Borselli, Matthew G.; Kiselev, Andrey A.; Fong, Bryan H.; Holabird, Kevin S.; Hazard, Thomas M.; Huang, Biqin; Deelman, Peter W.; Milosavljevic, Ivan; Schmitz, Adele E.; Ross, Richard S.; Gyure, Mark F.; Hunter, Andrew T.

    2015-01-01

    Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking. PMID:26601186

  2. Oxygen isotope fractionation in divalent metal carbonates

    USGS Publications Warehouse

    O'Neil, J.R.; Clayton, R.N.; Mayeda, T.K.

    1969-01-01

    Equilibrium fractionation factors for the distribution of 18O between alkaline-earth carbonates and water have been measured over the temperature range 0-500??C. The fractionation factors ?? can be represented by the equations CaCO3-H2O, 1000 ln??=2.78(106 T-2)-3.39, SrCO3-H 2O, 1000 ln??=2.69(106 T-2)-3.74, BaCO3-H2O, 1000 ln??=2.57(106 T -2)-4.73. Measurements on MnCO3, CdCO3, and PbCO3 were made at isolated temperatures. A statistical-mechanical calculation of the isotopic partition function ratios gives reasonably good agreement with experiment. Both cationic size and mass are important in isotopic fractionation, the former predominantly in its effect on the internal vibrations of the anion, the latter in its effect on the lattice vibrations.

  3. (n,{gamma}) Experiments on tin isotopes

    SciTech Connect

    Baramsai, B.; Mitchell, G. E.; Walker, C. L.; Rusev, G.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Mosby, S.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Becvar, F.; Krticka, M.; Kroll, J.; Agvaanluvsan, U.; Dashdorj, D.; Erdenehuluun, B.; Tsend-Ayush, T.

    2013-04-19

    Neutron capture experiments on highly enriched {sup 117,119}Sn isotopes were performed with the DANCE detector array located at the Los Alamos Neutron Science Center. The DANCE detector provides detailed information about the multi-step {gamma}-ray cascade following neutron capture. Analysis of the experimental data provides important information to improve understanding of the neutron capture reaction, including a test of the statistical model, the assignment of spins and parities of neutron resonances, and information concerning the Photon Strength Function (PSF) and Level Density (LD) below the neutron separation energy. Preliminary results for the (n,{gamma}) reaction on {sup 117,119}Sn are presented. Resonance spins of the odd-A tin isotopes were almost completely unknown. Resonance spins and parities have been assigned via analysis of the multi-step {gamma}-ray spectra and directional correlations.

  4. Anomalous isotopic composition of cosmic rays

    SciTech Connect

    Woosley, S.E.; Weaver, T.A.

    1980-06-20

    Recent measurements of nonsolar isotopic patterns for the elements neon and (perhaps) magnesium in cosmic rays are interpreted within current models of stellar nucleosynthesis. One possible explanation is that the stars currently responsible for cosmic-ray synthesis in the Galaxy are typically super-metal-rich by a factor of two to three. Other possibilities include the selective acceleration of certain zones or masses of supernovas or the enhancement of /sup 22/Ne in the interstellar medium by mass loss from red giant stars and planetary nebulas. Measurements of critical isotopic ratios are suggested to aid in distinguishing among the various possibilities. Some of these explanations place significant constraints on the fraction of cosmic ray nuclei that must be fresh supernova debris and the masses of the supernovas involved. 1 figure, 3 tables.

  5. The Oxygen Isotopic Composition of the Sun

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.; Kallio, A.; Heber, V. S.; Jarzebinski, G.; Mao, P.; Coath, C.; Kunihiro, T.; Wiens, R. C.; Judith, A.; Burnett, D. S.

    2010-12-01

    An accurate and precise determination of the oxygen isotopic composition of the Sun is the highest priority scientific goal of the Genesis Mission [1] as such data would provide a baseline from which one could interpret the oxygen isotopic anomalies found at all spatial scales in inner solar system materials. We have measured oxygen isotope compositions of implanted solar wind in 40 spots along a radial traverse of the Genesis SiC target sample 60001 by depth profiling with the UCLA MegaSIMS [2]. Mass-dependent fractionation induced by the solar wind concentrator [3] ion optics was corrected by comparison of the concentrator 22Ne/20Ne with that measured in a bulk solar wind target (diamond-like carbon on Si, [4]). The solar wind captured at L1 has an isotopic composition of (δ18O, δ17O) ≈ (-99, -79)‰, a value which is far removed from the terrestrial mass fractionation line. Profiles from the central portion of the target, where solar concentrations are highest and background corrections minimal, yield a mean Δ17O = -28.3 ± 1.8 ‰ indicating that the Earth and other planetary materials from the inner solar system are highly depleted in 16O relative to the solar wind. A mass-dependent fractionation of ~ -20%/amu in the acceleration of solar wind is required if we hypothesize that the photospheric oxygen isotope value, which represents the bulk starting composition of the solar system, is on the 16O-mixing line characteristic of refractory phase in primitive meteorites [5]. With this assumption, our preferred value for the bulk solar oxygen isotope composition is δ18O ≈ δ17O ≈ -57‰. A mechanism is required to fractionate oxygen isotopes in a non-mass-dependent manner to deplete 16O by ~6 to 7% in the rocky materials of the solar nebula. As oxygen is the third most abundant element in the solar system, and the most abundant in the terrestrial planets, this mechanism must operate on a large scale. Isotope-selective photochemistry, for example as in

  6. Isotopic Composition of Oxygen in Lunar Zircons

    NASA Technical Reports Server (NTRS)

    Nemchin, A. A.; Whitehouse, M. J.; Pidgeon, R. T.; Meyer, C.

    2005-01-01

    The recent discovery of heavy oxygen in zircons from the Jack Hills conglomerates Wilde et al. and Mojzsis et al. was interpreted as an indication of presence of liquid water on the surface of Early Earth. The distribution of ages of Jack Hills zircons and lunar zircons appears to be very similar and therefore analysis of oxygen in the lunar grains may provide a reference frame for further study of the early history of the Earth as well as give additional information regarding processes that operated on the Moon. In the present study we have analysed the oxygen isotopic composition of zircon grains from three lunar samples using the Swedish Museum of Natural History CAMECA 1270 ion microprobe. The samples were selected as likely tests for variations in lunar oxygen isotopic composition. Additional information is included in the original extended abstract.

  7. Cadmium isotopic composition in the ocean

    NASA Astrophysics Data System (ADS)

    Lacan, Francois; Francois, Roger; Ji, Yongcheng; Sherrell, Robert M.

    2006-10-01

    The oceanic cycle of cadmium is still poorly understood, despite its importance for phytoplankton growth and paleoceanographic applications. As for other elements that are biologically recycled, variations in isotopic composition may bring unique insights. This article presents (i) a protocol for the measurement of cadmium isotopic composition (Cd IC) in seawater and in phytoplankton cells; (ii) the first Cd IC data in seawater, from two full depth stations, in the northwest Pacific and the northwest Mediterranean Sea; (iii) the first Cd IC data in phytoplankton cells, cultured in vitro. The Cd IC variation range in seawater found at these stations is not greater than 1.5 ɛCd/amu units, only slightly larger than the mean uncertainty of measurement (0.8 ɛCd/amu). Nevertheless, systematic variations of the Cd IC and concentration in the upper 300 m of the northwest Pacific suggest the occurrence of Cd isotopic fractionation by phytoplankton uptake, with a fractionation factor of 1.6 ± 1.4 ɛCd/amu units. This result is supported by the culture experiment data suggesting that freshwater phytoplankton ( Chlamydomonas reinhardtii and Chlorella sp.) preferentially take up light Cd isotopes, with a fractionation factor of 3.4 ± 1.4 ɛCd/amu units. Systematic variations of the Cd IC and hydrographic data between 300 and 700 m in the northwest Pacific have been tentatively attributed to the mixing of the mesothermal (temperature maximum) water ( ɛCd/amu = -0.9 ± 0.8) with the North Pacific Intermediate Water ( ɛCd/amu = 0.5 ± 0.8). In contrast, no significant Cd IC variation is found in the northwest Mediterranean Sea. This observation was attributed to the small surface Cd depletion by phytoplankton uptake and the similar Cd IC of the different water masses found at this site. Overall, these data suggest that (i) phytoplankton uptake fractionates Cd isotopic composition to a measurable degree (fractionation factors of 1.6 and 3.4 ɛCd/amu units, for the in situ and

  8. Isotopic And Geochemical Investigations Of Meteorites

    NASA Technical Reports Server (NTRS)

    Walker, Richard J.

    2005-01-01

    The primary goals of our research over the past four years are to constrain the timing of certain early planetary accretion/differentiation events, and to constrain the proportions and provenance of materials involved in these processes. This work was achieved via the analysis and interpretation of long- and short-lived isotope systems, and the study of certain trace elements. Our research targeted these goals primarily via the application of the Re-187, Os-187, Pt-190 Os-186 Tc-98 Ru-99 and Tc-99 Ru-99 isotopic systems, and the determination/modeling of abundances of the highly siderophile elements (HSE; including Re, Os, Ir, Ru, Pd, Pt, and maybe Tc). The specific events we examined include the segregation and crystallization histories of asteroidal cores, the accretion and metamorphic histories of chondrites and chondrite components, and the accretionary and differentiation histories of Mars and the Moon.

  9. High-purity, isotopically enriched bulk silicon

    SciTech Connect

    Ager III, J.W.; Beeman, J.W.; Hansen, W.L.; Haller, E.E.; Sharp, I.D.; Liao, C.; Yang, A.; Thewalt, M.L.W.; Riemann, H.

    2004-11-17

    The synthesis and characterization of dislocation-free, undoped, single crystals of Si enriched in all 3 stable isotopes is reported: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (89.8%). A silane-based process compatible with the relatively small amounts of isotopically enriched precursors that are practically available was used. The silane is decomposed to silicon on a graphite starter rod heated to 700-750 C in a recirculating flow reactor. A typical run produces 35 gm of polycrystalline Si at a growth rates of 5 {micro}m/min and conversion efficiency >95%. Single crystals are grown by the floating zone method and characterized by electrical and optical measurements. Concentrations of shallow dopants (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup 15} cm{sup -3}, respectively.

  10. Microturbulence study of the isotope effect

    SciTech Connect

    Bustos, A.; Bañón Navarro, A.; Görler, T.; Jenko, F.

    2015-01-15

    The influence of the ion mass on the dynamics of magnetized plasmas is an important challenge in fusion research. The discrepancies between the improvement of the magnetic confinement with the ion mass in tokamak experiments and diffusive turbulent transport predictions have remained unexplained for several decades. We refer to this phenomenon as the isotope effect. In this paper, we study this effect with gyrokinetic theory using the GENE code. We find several sets of plasma parameters that correspond to low wavenumber turbulence for which the isotope effect is present, although the intensity is smaller than the experimental observations. We also relate these results to the zonal flow intensity of the system, which is characterized by the average shear flow rate.

  11. Uranium isotope ratio measurements in field settings

    SciTech Connect

    Shaw, R.W.; Barshick, C.M.; Young, J.P.; Ramsey, J.M.

    1997-06-01

    The authors have developed a technique for uranium isotope ratio measurements of powder samples in field settings. Such a method will be invaluable for environmental studies, radioactive waste operations, and decommissioning and decontamination operations. Immediate field data can help guide an ongoing sampling campaign. The measurement encompasses glow discharge sputtering from pressed sample hollow cathodes, high resolution laser spectroscopy using conveniently tunable diode lasers, and optogalvanic detection. At 10% {sup 235}U enrichment and above, the measurement precision for {sup 235}U/({sup 235}U+{sup 238}U) isotope ratios was {+-}3%; it declined to {+-}15% for 0.3% (i.e., depleted) samples. A prototype instrument was constructed and is described.

  12. Radioactive isotopes in solid state physics

    NASA Astrophysics Data System (ADS)

    Forkel-Wirth, D.

    1996-04-01

    A wide range of solid state physics techniques is using radioactive ion beams, both from on-line and off-line separators. The different techniques can be roughly subdivided into two classes: one, including the hyperfine techniques like Mößbauer spectroscopy (MS), Perturbed Angular Correlation (PAC) spectroscopy, β-NMR and the ion-beam technique of Emission Channeling (EC). They all crucially depend on the availability of radioactive isotopes with very specific decay properties. The second group comprises radio-tracer techniques which combine radioactive probe atoms with conventional semiconductor physics methods like Deep Level Transient Spectroscopy (DLTS), Capacitance Voltage measurements (CV), Hall-effect measurements or Photoluminescence Spectroscopy (PL). They are perfectly feasible without any radioactive probe atom, however, using such isotopes enables the unambiguous chemical identification of impurities. The present paper gives an overview on the potential of nuclear techniques by describing some typical experiments.

  13. Water-hydrogen isotope exchange process analysis

    SciTech Connect

    Fedorchenko, O.; Alekseev, I.; Uborsky, V.

    2008-07-15

    The use of a numerical method is needed to find a solution to the equation system describing a general case of heterogeneous isotope exchange between gaseous hydrogen and liquid water in a column. A computer model of the column merely outputting the isotope compositions in the flows leaving the column, like the experimental column itself, is a 'black box' to a certain extent: the solution is not transparent and occasionally not fully comprehended. The approximate analytical solution was derived from the ZXY-diagram (McCabe-Thiele diagram), which illustrates the solution of the renewed computer model called 'EVIO-4.2' Several 'unusual' results and dependences have been analyzed and explained. (authors)

  14. Isotopic homojunction band engineering from diamond.

    PubMed

    Watanabe, H; Nebel, C E; Shikata, S

    2009-06-12

    Confinement of charge carriers in semiconductors by quantum wells is usually accomplished with layers that vary in elemental composition, such as aluminum gallium arsenide and gallium arsenide. We fabricated diamond superlattices by creating multilayer structures of isotopically pure carbon isotopes carbon-12 (12C) and carbon-13 (13C), which confine electrons by a difference in band-gap energy of 17 millielectron volts. Cathodoluminescence experiments performed at 80 kelvin showed that excitonic recombination in the higher-energy band of 13C vanishes in favor of increased recombination in the lower-energy 12C material. Carrier confinement was achieved in diamond superlattices made up of both thinner (30 nanometers) and thicker (up to 350 nanometers) layers. PMID:19520955

  15. Oxygen Isotope Systematics of Almahata Sitta

    NASA Technical Reports Server (NTRS)

    Kita, N. T.; Goodrich, C. A.; Herrin, J. S.; Shaddad, M. H.; Jenniskens, P.

    2011-01-01

    The Almahata Sitta (hereafter "AHS") meteorite was derived from an impact of asteroid 2008TC3 on Earth and is classified as an anomalous polymict ureilite. More than 600 meteorite fragments have been recovered from the strewnfield. Previous reports indicate that these fragments consist mainly of ureilitic materials with textures and compositions, while some fragments are found to be chondrites of a wide range of chemical classes. Bulk oxygen three isotope analyses of ureilitic fragments from AHS fall close to the CCAM (Carbonaceous Chondrite Anhydrous Mineral) line similar to ureilites. In order to further compare AHS with known ureilites, we performed high precision SIMS (Secondary Ion Mass Spectrometer) oxygen isotope analyses of some AHS samples

  16. Isotopically enhanced triple-quantum-dot qubit.

    PubMed

    Eng, Kevin; Ladd, Thaddeus D; Smith, Aaron; Borselli, Matthew G; Kiselev, Andrey A; Fong, Bryan H; Holabird, Kevin S; Hazard, Thomas M; Huang, Biqin; Deelman, Peter W; Milosavljevic, Ivan; Schmitz, Adele E; Ross, Richard S; Gyure, Mark F; Hunter, Andrew T

    2015-05-01

    Like modern microprocessors today, future processors of quantum information may be implemented using all-electrical control of silicon-based devices. A semiconductor spin qubit may be controlled without the use of magnetic fields by using three electrons in three tunnel-coupled quantum dots. Triple dots have previously been implemented in GaAs, but this material suffers from intrinsic nuclear magnetic noise. Reduction of this noise is possible by fabricating devices using isotopically purified silicon. We demonstrate universal coherent control of a triple-quantum-dot qubit implemented in an isotopically enhanced Si/SiGe heterostructure. Composite pulses are used to implement spin-echo type sequences, and differential charge sensing enables single-shot state readout. These experiments demonstrate sufficient control with sufficiently low noise to enable the long pulse sequences required for exchange-only two-qubit logic and randomized benchmarking. PMID:26601186

  17. A spectacular nitrogen isotope anomaly in Bencubbin

    NASA Technical Reports Server (NTRS)

    Prombo, C. A.; Clayton, R. N.

    1985-01-01

    Results of isotopic measurements on an unusual stony-iron meteorite named Bencubbin, which was found in Western Australia in 1930, are reported. Nitrogen from both the metallic and stony parts of the Bencubbin meteorite was analyzed, and in both materials large excesses of (15)N were found, resulting in values of the (14)N/(15)N abundance ratios as low as 137. That is, (15)N is enriched in Bencubbin by about a factor of two relative to terrestrial nitrogen. This is the largest (15)N enrichment of any known natural material. The effect is so large that chemical processes are probably inadequate to account for it. Nuclear processes which may be responsible for the anomalous isotope abundance are discussed.

  18. Simulating Isotope Enrichment by Gaseous Diffusion

    NASA Astrophysics Data System (ADS)

    Reed, Cameron

    2015-04-01

    A desktop-computer simulation of isotope enrichment by gaseous diffusion has been developed. The simulation incorporates two non-interacting point-mass species whose members pass through a cascade of cells containing porous membranes and retain constant speeds as they reflect off the walls of the cells and the spaces between holes in the membranes. A particular feature is periodic forward recycling of enriched material to cells further along the cascade along with simultaneous return of depleted material to preceding cells. The number of particles, the mass ratio, the initial fractional abundance of the lighter species, and the time between recycling operations can be chosen by the user. The simulation is simple enough to be understood on the basis of two-dimensional kinematics, and demonstrates that the fractional abundance of the lighter-isotope species increases along the cascade. The logic of the simulation will be described and results of some typical runs will be presented and discussed.

  19. Nitrogen isotopic signatures in the Acapulco meteorite

    NASA Technical Reports Server (NTRS)

    Sturgeon, G.; Marti, K.

    1991-01-01

    N isotopic abundances are reported for a bulk sample of the unique meteorite Acapulco. Although the mineral chemistry indicates a high degree of recrystallization under redox conditions between those of H and E chondrites (Palme et al., 1981), the presence of two distinct N isotopic signatures shows that the carriers of these N components were not equilibrated. In stepwise pyrolysis, the larger (65 percent) N component is released mostly below 1000 C and reveals a signature of delta(N-15) = 8.9 + or - 1.2 per mil, which is within the range observed in chondrites. A second 'light' component appears above 1000 C and has a signature of delta(N-15) less than or equal to -110.5 + or - 4.0 per mil (uncorrected for spallation N-15).

  20. BOREAS TE-5 Leaf Carbon Isotope Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

    2000-01-01

    The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. This documentation describes leaf carbon isotope data that were collected in 1993 and 1994 at the NSA and SSA OJP sites, the SSA OBS site, and the NSA UBS site. In addition, leaf carbon isotope data were collected in 1994 only at the NSA and SSA OA sites. These data was collected to provide seasonal integrated physiological information for 10 to 15 common species at these 6 BOREAS sites. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).