Science.gov

Sample records for isotope abundance measurements

  1. 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.

  2. LITERATURE SURVEY ON ISOTOPIC ABUNDANCE RATIO MEASUREMENTS - 2001-2005

    SciTech Connect

    HOLDEN, N.E.

    2005-08-13

    Along with my usual weekly review of the published literature for new nuclear data, I also search for new candidates for best measurements of isotopic abundances from a single source. Most of the published articles, that I previously had found in the Research Library at the Brookhaven Lab, have already been sent to the members of the Atomic Weights Commission, by either Michael Berglund or Thomas Walczyk. In the last few days, I checked the published literature for any other articles in the areas of natural variations in isotopic abundance ratios, measurements of isotopic abundance ratios on samples of extra-terrestrial material and isotopic abundance ratio measurements performed using ICPMS instruments. Hopefully this information will be of interest to members of the Commission, the sub-committee on isotopic abundance measurements (SIAM), members of the former sub-committee on natural isotopic fractionation (SNIF), the sub-committee on extra-terrestrial isotope ratios (SETIR), the RTCE Task Group and the Guidelines Task Group, who are dealing with ICPMS and TIMS comparisons. In the following report, I categorize the publications in one of four areas. Measurements performed using either positive or negative ions with Thermal Ionization Mass Spectrometer, TIMS, instruments; measurements performed on Inductively Coupled Plasma Mass Spectrometer, ICPMS, instruments; measurements of natural variations of the isotopic abundance ratios; and finally measurements on extra-terrestrial samples with instrumentation of either type. There is overlap in these areas. I selected out variations and ET results first and then categorized the rest of the papers by TIMS and ICPMS.

  3. Mass Spectrometric Measurement of Martian Krypton and Xenon Isotopic Abundance

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.; Mauersberger, K.

    1993-01-01

    The Viking gas chromatograph mass spectrometer experiment provided significant data on the atmospheric composition at the surface of Mars, including measurements of several isotope ratios. However, the limited dynamic range of this mass spectrometer resulted in marginal measurements for the important Kr and Xe isotopic abundance. The Xe-129 to Xe-132 ratio was measured with an uncertainty of 70%, but none of the other isotope ratios for these species were obtained. Accurate measurement of the Xe and Kr isotopic abundance in this atmosphere provides an important data point in testing theories of planetary formation and atmospheric evolution. The measurement is also essential for a stringent test for the Martian origin of the SNC meteorites, since the Kr and Xe fractionation pattern seen in gas trapped in glassy nodules of an SNC (EETA 79001) is unlike any other known solar system resevoir. Current flight mass spectrometer designs combined with the new technology of a high-performance vacuum pumping system show promise for a substantial increase in gas throughput and the dynamic range required to accurately measure these trace species. Various aspects of this new technology are discussed.

  4. Resonance ionization mass spectrometry for isotopic abundance measurements

    NASA Technical Reports Server (NTRS)

    Miller, C. M.

    1986-01-01

    Resonance ionization mass spectrometry (RIMS) is a relatively new laser-based technique for the determination of isotopic abundances. The resonance ionization process depends upon the stepwise absorption of photons from the laser, promoting atoms of the element of interest through progressively higher electronic states until an ion is formed. Sensitivity arises from the efficiency of the resonant absorption process when coupled with the power available from commercial laser sources. Selectivity derives naturally from the distinct electronic structure of different elements. This isobaric discrimination has provided the major impetus for development of the technique. Resonance ionization mass spectrometry was used for analysis of the isotopic abundances of the rare earth lutetium. Isobaric interferences from ytterbium severely effect the ability to measure small amounts of the neutron-deficient Lu isotopes by conventional mass spectrometric techniques. Resonance ionization for lutetium is performed using a continuous-wave laser operating at 452 nm, through a sequential two-photon process, with one photon exciting the intermediate resonance and the second photon causing ionization. Ion yields for microgram-sized quantities of lutetium lie between 10(6) and 10(7) ions per second, at overall ionization efficiencies approaching 10(-4). Discrimination factors against ytterbium greater than 10(6) have been measured. Resonance ionization for technetium is also being explored, again in response to an isobaric interference, molybdenum. Because of the relatively high ionization potential for Tc, three-photon, two-color RIMS processes are being developed.

  5. Measurement of isotope abundance variations in nature by gravimetric spiking isotope dilution analysis (GS-IDA).

    PubMed

    Chew, Gina; Walczyk, Thomas

    2013-04-01

    Subtle variations in the isotopic composition of elements carry unique information about physical and chemical processes in nature and are now exploited widely in diverse areas of research. Reliable measurement of natural isotope abundance variations is among the biggest challenges in inorganic mass spectrometry as they are highly sensitive to methodological bias. For decades, double spiking of the sample with a mix of two stable isotopes has been considered the reference technique for measuring such variations both by multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS) and multicollector-thermal ionization mass spectrometry (MC-TIMS). However, this technique can only be applied to elements having at least four stable isotopes. Here we present a novel approach that requires measurement of three isotope signals only and which is more robust than the conventional double spiking technique. This became possible by gravimetric mixing of the sample with an isotopic spike in different proportions and by applying principles of isotope dilution for data analysis (GS-IDA). The potential and principle use of the technique is demonstrated for Mg in human urine using MC-TIMS for isotopic analysis. Mg is an element inaccessible to double spiking methods as it consists of three stable isotopes only and shows great potential for metabolically induced isotope effects waiting to be explored.

  6. The Measurement of Iron-Group Isotopic Abundances in the Cosmic Rays Using the Magpie Detector

    NASA Astrophysics Data System (ADS)

    Yanasak, Nathan Eugene

    This thesis details the analysis of data from the MAGPIE detector, a balloon-borne detector designed to measure cosmic ray isotope abundances between 300 and 900 MeV/a μ in the Fe group. MAGPIE consists of a magnetic spectrometer for measuring particle rigidity, and nine stacks of CR-39 plastic nuclear track detectors for measuring charge and velocity. After an Antarctic flight in December of 1991 during which ~2000 Fe nuclei were collected, damage occurred to the spectrometer during the landing of the balloon payload, limiting the analysis to cosmic ray particles that stop in the plastic stack. This limited the energy range of data to between 100 MeV/a μ and 400 MeV/a μ for Fe group elements. The measurement of Fe group isotopes is an important one. Because nuclei from this group have the highest binding energy of all the elements, they represent the primary products during late stellar nucleosynthesis. This characteristic makes Fe group isotopes unique in their ability to probe the interior environment during the final stages of stellar evolution. In addition, the primary decay channel by e- capture for some of the Ni and Co isotopes makes these isotopes ideal for probing the time delay between production of cosmic rays and their acceleration. Finally, the radioactive isotope 54Mn has a mean lifetime that is comparable to residence time of lighter elements in the galaxy, which has been measured using the 10Be isotopic abundance. Both of these abundances are produced primarily through spallation during propagation, and Mn can measure the average density of the propagation medium and residence time for Fe group elements with isotopic abundance measurements of stable spallation products. After etching, the MAGPIE CR-39 plastic was scanned for tracks using an automated microscope and image processing system. This system offers a data acquisition method that is as efficient and much quicker than techniques using a microscope and reticle. Cosmic ray data were

  7. An investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.

    1977-01-01

    An instrument, the Caltech High Energy Isotope Spectrometer Telescope was developed to measure isotopic abundances of cosmic ray nuclei by employing an energy loss - residual energy technique. A detailed analysis was made of the mass resolution capabilities of this instrument. A formalism, based on the leaky box model of cosmic ray propagation, was developed for obtaining isotopic abundance ratios at the cosmic ray sources from abundances measured in local interstellar space for elements having three or more stable isotopes, one of which is believed to be absent at the cosmic ray sources. It was shown that the dominant sources of uncertainty in the derived source ratios are uncorrelated errors in the fragmentation cross sections and statistical uncertainties in measuring local interstellar abundances. These results were applied to estimate the extent to which uncertainties must be reduced in order to distinguish between cosmic ray production in a solar-like environment and in various environments with greater neutron enrichments.

  8. High Spatial Resolution Isotopic Abundance Measurements by Secondary Ion Mass Spectrometry: Status and Prospects

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.

    2007-12-01

    Secondary Ion Mass Spectrometry, SIMS or ion microprobe analysis, has become an important tool for geochemistry because of its ability study the distributions of elemental and isotopic abundances in situ on polished samples with high (typically a few microns to sub-micron) spatial resolution. In addition, SIMS exhibits high sensitivity for a wide range of elements (H to Pu) so that isotope analyses can sometimes be performed for elements that comprise only trace quantities of some mineral phase (e.g., Pb in zircon) or on major and/or minor elements in very small samples (e.g., presolar dust grains). Offsetting these positive attributes are analytical difficulties due to the complexity of the sputtering source of analyte ions: (1) relatively efficient production of molecular ion species (especially from a complex matrix such as most natural minerals) that cause interferences at the same nominal mass as atomic ions of interest, and (2) quantitation problems caused by variations in the ionization efficiencies of different elements and/or isotopes depending upon the chemical state of the sample surface during sputtering--the so-called "matrix effects". Despite the availability of high mass resolution instruments (e.g., SHRIMP II/RG, CAMECA 1270/1280/NanoSIMS), the molecular ion interferences effectively limit the region of the mass table that can be investigated in most samples to isotope systems at Ni or lighter or at Os or heavier. The matrix effects and the sensitivity of instrumental mass discrimination to the physical state of the sample surface can hamper reproducibility and have contributed to a view that SIMS analyses, especially for so- called stable isotopes, are most appropriate for extraterrestrial samples which are often small, rare, and can exhibit large magnitude isotopic effects. Recent improvements in instrumentation and technique have extended the scope of SIMS isotopic analyses and applications now range from geochronology to paleoclimatology to

  9. Preliminary report on isotope abundance measurements in groundwater samples from the Talbert Injection Barrier Area, Orange County Water District

    SciTech Connect

    Hudson, G.B.; Davisson, M.L.; Velsko, C.; Niemeyer, S.; Esser, B.; Beiriger, J.

    1995-02-01

    This report discusses isotope abundance measurements made on a collection of groundwater samples from the Orange County Water District. The water samples were collected in May, 1994 as part of a preliminary study conducted by LLNL to assess the feasibility of tracing and dating reclaimed water used in the Talbert Injection Barrier. A set of samples were collected both near to and far from the barrier and also at different depths in available monitoring wells. A variety of elements were selected for isotopic analysis; hydrogen (tritium), helium, neon, carbon, chlorine and strontium. The tritium abundance combined with the {sup 3}He and {sup 20}Ne abundance provides a method for age dating young (< 40 yr.) groundwater. The abundance of {sup 14}C provides an age dating technique for older (1,000--50,000 yr.) groundwater. The concentrations of {sup 36}Cl and {sup 87}Sr/{sup 86}Sr give information on sea water mixing and water-rock chemical interactions.

  10. Isotopic abundance measurements on solid nuclear-type samples by glow discharge mass spectrometry.

    PubMed

    Betti, M; Rasmussen, G; Koch, L

    1996-07-01

    A double-focusing Glow Discharge Mass Spectrometer (GDMS) installed in a glovebox for nuclear sample screening has been employed for isotopic measurements. Isotopic compositions of zirconium, silicon, lithium, boron, uranium and plutonium which are elements of nuclear concern have been determined. Interferences arising from the matrix sample and the discharge gas (Ar) for each of these elements are discussed. The GDMS results are compared with those from Thermal Ionization Mass Spectrometry (TIMS). For boron and lithium at microg/g-ng/g levels, the two methods gave results in good agreement. In samples containing uranium the isotopic composition obtained by GDMS was in agreement with those from TIMS independently of the enrichment. Attempts for the determination of plutonium isotopic composition were also made. In this case, due to the interferences of uranium at mass 238 and americium at mass 241, the GDMS raw data are complementary with those values obtained from physical non-destructive techniques.

  11. Study on strontium isotope abundance-ratio measurements by using a 13-MeV proton beam

    NASA Astrophysics Data System (ADS)

    Jeong, Cheol-Ki; Jang, Han; Lee, Goung-Jin

    2016-09-01

    The Rb-Sr dating method is used in dating Paleozoic and Precambrian rocks. This method measures the 87Rb and the 87Sr concentrations by using thermal ionization mass spectrometry (TIMS) [J. Hefne et al., Inter. J. Phys. Sci. 3(1), 28 (2008)]. In addition, it calculates the initial 87Sr/86Sr ratio to increase the reliability of Rb-Sr dating. In this study, the 87Sr/86Sr ratio was measured by using a 13-MeV proton accelerator. Proton kinetic energies are in the range of tens of megaelectronvolts, and protons have large absorption cross-sections for ( p, n) reactions with most substances. After absorbing a proton with such a high kinetic energy, an element is converted into a nuclide with its atomic number increased by one via nuclear transmutation. These nuclides usually have short half-lives and return to the original state through radioactive decay. When a strontium sample is irradiated with protons, nuclear transmutation occurs; thus, the strontium isotope present in the sample changes to a yttrium isotope, which is an activated radioisotope. Based on this, the 87Sr/86Sr ratio was calculated by analyzing the gamma-rays emitted by each yttrium isotope. The KIRAMS-13 cyclotron at the Cyclotron Center of Chosun University, where 13-MeV protons can be extracted, was utilized in our experiment. The 87Sr/86Sr isotope ratio was computed for samples irradiated with these protons, and the result was similar to the isotope ratio for the Standard Reference Material, i.e., 98.2 ± 3.4%. As part of the analysis, proton activation analyses were performed using 13-MeV protons, and the experimental results of this research suggest a possible approach for measuring the strontium-isotope abundance ratio of samples.

  12. Determination of the natural abundance δ15N of taurine by gas chromatography-isotope ratio measurement mass spectrometry.

    PubMed

    Tea, Illa; Antheaume, Ingrid; Besnard, Jorick; Robins, Richard J

    2010-12-15

    The measurement of the nitrogen isotope ratio of taurine (2-aminoethanesulphonic acid) in biological samples has a large number of potential applications. Taurine is a small water-soluble molecule which is notoriously difficult to analyze due to its polarity and functionality. A method is described which allows the determination of the natural abundance δ(15)N values of taurine and structural analogues, such as 3-amino-1-propanesulphonic acid (APSA), by isotope ratio mass spectrometry interfaced to gas chromatography (GC-irm-MS). The one-step protocol exploits the simultaneous derivatization of both functionalities of these aminosulphonic acids by reaction with triethylorthoacetate (TEOA). Conditions have been established which ensure quantitative reaction thus avoiding any nitrogen isotope fractionation during derivatization and workup. The differences in the δ(15)N values of derivatized and non-derivatized taurine and APSA all fall within the working range of 0.4‰ (-0.02 to 0.39‰). When applied to four sources of taurine with various δ(15)N values, the method achieved excellent reproducibility and accuracy. The optimized method enables the determination of the natural abundance δ(15)N values of taurine over the concentration range 1.5-7.84 µmol.mL(-1) in samples of biological origin.

  13. Sniffing for Clues to the Dinosaurs Demise: Measurement of Osmium Isotope Compositions and Platinum Group Element Abundances in Volcanic Emissions

    NASA Astrophysics Data System (ADS)

    Sims, K. W.; Peucker-Ehrenbrink, B.; Mather, T.; Pyle, D.; Martin, R.; Gauthier, P.; Aiuppa, A.

    2005-12-01

    Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of Deccan volcanism and the transient late Maastrichtian warming preceded the large extraterrestrial impact and the related KTB mass extinction by several hundred thousand years [Ravizza and Peucker-Ehrenbrink, 2003]. Distinguishing extraterrestrial from volcanic PGE sources has been difficult due to the similarity in Os isotopic compositions, complex PGE fractionations, and our lack of knowledge of the Os isotopic composition and PGE abundances in volcanic aerosols. These difficulties have fueled vigorous debate about extraterrestrial vs. volcanic triggers of mass extinctions in the geologic record. To assess the volcanic contribution to the global Re-Os-PGE cycle we have initiated a study of Os isotopic compositions and PGE abundances in volcanic emissions from volcanoes around the globe. Here we report preliminary data on PGE abundances and Os isotopes measured in gas and aerosol filter samples from Vulcan Masaya, Nicaragua and Mt Etna, Italy. Samples were analyzed by ID-ICPMS (ThermoFinnigan ELEMENT 2 and NEPTUNE) at the Woods Hole Oceanographic Institution. Osmium isotope compositions of the filters are unradiogenic (0.1272 to 0.187). Osmium concentrations range from 28 to 97 pg/cubic meter and are 3-4 orders of magnitude lower than those measured by Krahenbuhl et al. [1992] during the spring 1984 eruption of Mauna Loa just after the lava fountaining phase. Normalized PGE abundance patterns are fractionated relative to carbonaceous chondrites and two important features distinguish the pattern from other important PGE sources: 1) Os/Ir is much higher

  14. 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).

  15. Chromium-Isotope and iridium-Abundance Measurements for Late Eocene Impact-Derived Spherule Deposits

    NASA Astrophysics Data System (ADS)

    Kyte, F. T.; Shukolyukov, A.; Hildebrand, A. R.; Lugmair, G. W.; Hanova, J.

    2004-05-01

    The late Eocene (approx. 35 Ma) was a time of multiple large body impacts superimposed within an interval of dust accretion. At least two spherule layers are preserved in deep sea sediments: North American microtektites and the slightly older cpx spherules. The two largest impact structures in the Cenozoic, the 45 km Chesapeake Bay structure and the 100 km Popigai structure, are indicated as the respective spherule sources. Enhanced 3He concentrations extending across a 3 m.y. duration in upper Eocene sediments from the Massignano quarry in Italy indicate accretion of <50 micron dust over this time interval. To characterize one of the impactors we have analyzed splits from the 125-250 micron cpx spherules from ODP 709C, and two fractions from the Massignano layer. Splits of each sample were analyzed for minor and trace elements by instrumental activation analysis (INAA) including Ir, Cr, Fe, Ni, and Co. Additional splits were analyzed for their Cr-isotopic composition, using thermal ionization mass spectrometry. Significant concentrations of Ir were found in all samples, with the highest levels in the Massignano coarse sample and the lowest in the 709C sample. In all cases, element/Ir ratios are much higher than in chondritic meteorites; this may reflect elemental fractionation due to preferential concentration of Cr in spinel growing in the impact fireball. The Cr-isotopic compositions of the 709C and Massignano coarse samples are both non-terrestrial with a positive epsilon 53, indicating a 53Cr/52Cr ratio higher than in terrestrial materials. Microprobe surveys showed that the Massignano samples had significant fine grained oxide grains (mixed with the spherules in the coarse sample) that were not Ni- or Cr-rich, including Ti-rich spinels (likely terrestrial contaminants). In contrast, the ODP 709C sample is a pure extract of generally well-preserved cpx spherules composed of clinopyroxene in a glass matrix. Both the Massignano coarse and the 709C cpx samples

  16. Literature survey of isotopic abundance data for 1987-1989

    SciTech Connect

    Holden, N.E. )

    1989-08-09

    I have compiled all of the data on isotopic abundance measurements and their variation in nature for the time period since the last General Assembly. Most of the data deals with the variations in the abundances as given by per mil deviations from some standard. As such, they are not of major interest to the Atomic Weights Commission. However, there were some measurements which are of general interest in this list.

  17. Helium isotopic abundance variation in nature

    SciTech Connect

    Holden, N.E.

    1993-08-01

    The isotopic abundance of helium in nature has been reviewed. This atomic weight value is based on the value of helium in the atmosphere, which is invariant around the world and up to a distance of 100,000 feet. Helium does vary in natural gas, volcanic rocks and gases, ocean floor sediments, waters of various types and in radioactive minerals and ores due to {alpha} particle decay of radioactive nuclides.

  18. 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

  19. The abundance and isotopic composition of water in eucrites

    NASA Astrophysics Data System (ADS)

    Barrett, T. J.; Barnes, J. J.; TartèSe, R.; Anand, M.; Franchi, I. A.; Greenwood, R. C.; Charlier, B. L. A.; Grady, M. M.

    2016-06-01

    Volatile elements play a key role in the dynamics of planetary evolution. Extensive work has been carried out to determine the abundance, distribution, and source(s) of volatiles in planetary bodies such as the Earth, Moon, and Mars. A recent study showed that the water in apatite from eucrites has similar hydrogen isotopic compositions compared to water in terrestrial rocks and carbonaceous chondrites, suggesting that water accreted very early in the inner solar system given the ancient crystallization ages (~4.5 Ga) of eucrites. Here, the measurements of water (reported as equivalent H2O abundances) and the hydrogen isotopic composition (δD) of apatite from five basaltic eucrites and one cumulate eucrite are reported. Apatite H2O abundances range from ~30 to ~3500 ppm and are associated with a weighted average δD value of -34 ± 67‰. No systematic variations or correlations are observed in H2O abundance or δD value with eucrite geochemical trend or metamorphic grade. These results extend the range of previously published hydrogen isotope data for eucrites and confirm the striking homogeneity in the H-isotopic composition of water in eucrites, which is consistent with a common source for water in the inner solar system.

  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. Some isotopic abundances in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Young, J. S.; Freier, P. S.; Waddington, C. J.

    1980-01-01

    Cosmic ray nuclei with Z not less than 10 have been observed in a detector which measures charge with a double scintillator-Cherenkov array and mass by combining the Cherenkov signal with residual range measured in nuclear emulsions. Results are presented for the isotopic analyses of Al, Ca, Sc, Mn, Fe, Co, Ni and Cu in the energy range 300-800 MeV/amu.

  2. Evaluation of relative isotopic abundance measurements in a quadrupole time-of-flight mass spectrometer for elemental composition determination of natural products in traditional Chinese medicine.

    PubMed

    Wu, Zhi-Jun; Huo, Jia-Li; Chen, Jian-Zhong; Li, Na; Fang, Dong-Mei; Chen, Xiao-Zhen; Zhang, Guo-Lin; Wang, Jian-Hua; Xu, Xiao-Ying

    2013-01-01

    The relative isotopic abundance (RIA) measurement errors of a quadrupole time-of-flight (Q-ToF) instrument incorporating analog-to-digital converter detectors were systemically evaluated by stochastically collecting about 200 data in positive ion mass spectrometry (MS) mode. Errors varied with peak intensities at definite spectral acquisition rates but were very close, even if peak intensities changed sharply at different spectral acquisition rates with the same concentration. Intensity thresholds were systematically defined at 1 Hz of spectral acquisition rates. RIA measurement errors were also evaluated using peak area. It seemed that peak area was better adapted for the high-intensity ions while peak intensity was suited for very low-intensity ions. Several known compounds were selected for RIA measurements for product ions in tandem mass spectropmetry (MS/MS) mode. An extract of a representative traditional Chinese medicinal, Paederia scandens was analyzed with high-performance liquid chromatography-electrospray ionization-QToF-MS/MS. The unique elemental compositions of some compounds could not be identified even with exact masses and MS/MS spectra of measured and reference compounds. RIA errors, especially of (M+2)M(-1), provided vital information for determining the elemental composition. PMID:24261081

  3. Evaluation of relative isotopic abundance measurements in a quadrupole time-of-flight mass spectrometer for elemental composition determination of natural products in traditional Chinese medicine.

    PubMed

    Wu, Zhi-Jun; Huo, Jia-Li; Chen, Jian-Zhong; Li, Na; Fang, Dong-Mei; Chen, Xiao-Zhen; Zhang, Guo-Lin; Wang, Jian-Hua; Xu, Xiao-Ying

    2013-01-01

    The relative isotopic abundance (RIA) measurement errors of a quadrupole time-of-flight (Q-ToF) instrument incorporating analog-to-digital converter detectors were systemically evaluated by stochastically collecting about 200 data in positive ion mass spectrometry (MS) mode. Errors varied with peak intensities at definite spectral acquisition rates but were very close, even if peak intensities changed sharply at different spectral acquisition rates with the same concentration. Intensity thresholds were systematically defined at 1 Hz of spectral acquisition rates. RIA measurement errors were also evaluated using peak area. It seemed that peak area was better adapted for the high-intensity ions while peak intensity was suited for very low-intensity ions. Several known compounds were selected for RIA measurements for product ions in tandem mass spectropmetry (MS/MS) mode. An extract of a representative traditional Chinese medicinal, Paederia scandens was analyzed with high-performance liquid chromatography-electrospray ionization-QToF-MS/MS. The unique elemental compositions of some compounds could not be identified even with exact masses and MS/MS spectra of measured and reference compounds. RIA errors, especially of (M+2)M(-1), provided vital information for determining the elemental composition.

  4. Anatomy of a cluster IDP. Part 2: Noble gas abundances, trace element geochemistry, isotopic abundances, and trace organic chemistry of several fragments from L2008#5

    NASA Technical Reports Server (NTRS)

    Thomas, K. L.; Clemett, S. J.; Flynn, G. J.; Keller, L. P.; Mckay, David S.; Messenger, S.; Nier, A. O.; Schlutter, D. J.; Sutton, S. R.; Walker, R. M.

    1994-01-01

    The topics discussed include the following: noble gas content and release temperatures; trace element abundances; heating summary of cluster fragments; isotopic measurements; and trace organic chemistry.

  5. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.

    2004-01-01

    During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

  6. Study of the Role of Terrestrial Processes in the Carbon Cycle Based on Measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    SciTech Connect

    Piper, Stephen C; Keeling, Ralph F

    2012-01-03

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic ratios 13C/12C, 18O/16O, and 14C/12C. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. Using models of varying complexity, the concentration and isotopic measurements were used to study long-term change in the interhemispheric gradients in CO2 and 13C/12C to assess the magnitude and evolution of the northern terrestrial carbon sink, to study the increase in amplitude of the seasonal cycle of CO2, to use isotopic data to refine constraints on large scale changes in isotopic fractionation which may be related to changes in stomatal conductance, and to motivate improvements in terrestrial carbon cycle models. The original proposal called for a continuation of the new time series of 14C measurements but subsequent descoping to meet budgetary constraints required termination of measurements in 2007.

  7. Quantitative and In-Depth Survey of the Isotopic Abundance Distribution Errors in Shotgun Proteomics.

    PubMed

    Chang, Cheng; Zhang, Jiyang; Xu, Changming; Zhao, Yan; Ma, Jie; Chen, Tao; He, Fuchu; Xie, Hongwei; Zhu, Yunping

    2016-07-01

    Accuracy is an important metric when mass spectrometry (MS) is used in large-scale quantitative proteomics research. For MS-based quantification by extracting ion chromatogram (XIC), both the mass and intensity dimensions must be accurate. Although much research has focused on mass accuracy in recent years, less attention has been paid to intensity errors. Here, we investigated signal intensity measurement errors systematically and quantitatively using the natural properties of isotopic distributions. First, we defined a normalized isotopic abundance error model and presented its merits and demerits. Second, a comprehensive survey of the isotopic abundance errors using data sets with increasing sample complexities and concentrations was performed. We examined parameters such as error distribution, relationships between signal intensities within one isotopic cluster, and correlations between different peak errors in isotopic profiles. Our data demonstrated that the high resolution MS platforms might also generate large isotopic intensity measurement errors (approximately 20%). Meanwhile, this error can be reduced to less than 5% using a novel correction algorithm, which is based on the theoretical isotopic abundance distribution. Finally, a nonlinear relationship was observed as the abundance error decreased in isotopic profiles with higher intensity. Our findings are expected to provide insight into isotopic abundance recalibration in quantitative proteomics.

  8. Nitrogen isotope abundances in the recent solar wind.

    PubMed

    Kim, J S; Kim, Y; Marti, K; Kerridge, J F

    1995-06-01

    Although lunar crystalline rocks are essentially devoid of nitrogen, the same is not true of the lunar regolith. The nitrogen contents of individual regolith samples (which can be as high as 0.012% by mass) correlate strongly with abundances of noble gases known to be implanted in the lunar surface by solar radiation, indicating that lunar regolith nitrogen is also predominantly of solar origin. The large variability in 15N/14N ratios measured in different regolith samples may thus reflect long-term changes in the isotopic composition of the solar radiation. But attempts to explain these variations have been hampered by the lack of any firm constraint on 15N/14N in the present solar wind. Here we report measurements of nitrogen isotopes from two lunar samples that have had simple (and relatively recent) exposure histories. We find that nitrogen implanted in the lunar surface during the past 10(5) to 5 x 10(7) years has a 15N/14N ratio approximately 40% higher than that in the terrestrial atmosphere, which is substantially lower than most previous estimates. This isotopic signature probably represents the best measure of 15N/14N in the present-day solar wind.

  9. Measurement of Trace Uranium Isotopes

    SciTech Connect

    Matthew G. Watrous; James E. Delmore

    2011-05-01

    The extent to which thermal ionization mass spectrometry (TIMS) can measure trace quantities of 233U and 236U in the presence of a huge excess of natural uranium is evaluated. This is an important nuclear non-proliferation measurement. Four ion production methods were evaluated with three mass spectrometer combinations. The most favorable combinations are not limited by abundance sensitivity; rather, the limitations are the ability to generate a uranium ion beam of sufficient intensity to obtain the required number of counts on the minor isotopes in relationship to detector background. The most favorable situations can measure isotope ratios in the range of E10 if sufficient sample intensity is available. These are the triple sector mass spectrometer with porous ion emitters (PIE) and the single sector mass spectrometer with energy filtering.

  10. Isotope-abundance variations of selected elements (IUPAC technical report)

    USGS Publications Warehouse

    Coplen, T.B.; Böhlke, J.K.; De Bievre, P.; Ding, T.; Holden, N.E.; Hopple, J.A.; Krouse, H.R.; Lamberty, A.; Peiser, H.S.; Revesz, K.; Rieder, S.E.; Rosman, K.J.R.; Roth, E.; Taylor, P.D.P.; Vocke, R.D.; Xiao, Y.K.

    2002-01-01

    Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.

  11. The abundances of isotopes in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.

    1989-01-01

    Studies of the isotopic composition of nuclei in the cosmic radiation are reviewed, including abundances of the isotopes of elements from H to Ni, together with their implications for cosmic ray origin, acceleration, and transport in the Galaxy. The review focuses on determinations of the composition of cosmic ray source material, and the extent to which the isotopic composition of this material is different from, or similar to, typical solar system material and other samples of Galactic matter. Theoretical models that have been advanced to explain the observed overabundance of neutron-rich isotopes in cosmic rays are described. Also discussed are studies of various radioactive clocks that record the time-scales associated with the nucleosynthesis, acceleration, and transport of cosmic ray nuclei, and studies of the so-called anomalous cosmic ray component, thought to represent a sample of the neutral interstellar medium.

  12. Abundance coefficients, a new method for measuring microorganism relative abundance

    USGS Publications Warehouse

    Forester, R.M.

    1977-01-01

    A new method of measuring the relative abundance of microorganisms by using a set of interrelated coefficients, termed 'abundance coefficients' or 'AC', is proposed. These coefficients provide a means of recording abundance for geometric density categories, and each density measurement represents an approximation of the Poisson parameter ??t. The AC is the natural logarithm of a 'characteristic value,' which is a particular number for each geometric density category. The 'characteristic values' are based upon a probabilistic error statement derived from the Poisson formula, and they present evidence for separation of the geometric category boundaries by e = 2.71828. The proposed AC provide a means for recording species abundance in a manner suitable for arithmetic manipulation, for population structure studies, and for the determination of practical limits for defining the presence or absence of a species. Further, these coefficients provide for both intrasample and intersample abundance comparisons. ?? 1977 Plenum Publishing Corporation.

  13. 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.

  14. The isotopic and elemental abundances of neon nuclei accelerated in solar flares

    NASA Technical Reports Server (NTRS)

    Dietrich, W. F.; Simpson, J. A.

    1979-01-01

    The relative isotopic abundances of Ne-20 and Ne-22 in seven solar flares were determined from measurements of the satellite IMP 8, yielding the ratio Ne-20/Ne-22 = 7.7 (+2.3, -1.5) for solar chromospheric matter. This value is in agreement with the ratio for the component neon-A (the 'primordial' component) found in carbonaceous chondrites. An elemental abundance ratio Ne/O = 0.14 + or - 0.01 also has been obtained which agrees closely with earlier reported measurements. It is shown that the effects of preferential acceleration relative to solar-system abundances with increasing charge number observed for some solar flares - though biasing the elemental ratio - does not appear to influence the neon isotopic abundances.

  15. Natural abundances of carbon isotopes in acetate from a coastal marine sediment

    NASA Technical Reports Server (NTRS)

    Blair, N. E.; Martens, C. S.; Des Marais, D. J.

    1987-01-01

    Measurements of the natural abundances of carbon isotopes were made in acetate samples isolated from the anoxic marine sediment of Cape Lookout Bight, North Carolina. The typical value of the total acetate carbon isotope ratio (delta 13C) was -16.1 +/- 0.2 per mil. The methyl and carboxyl groups were determined to be -26.4 +/- 0.3 and -6.0 +/- 0.3 per mil, respectively, for one sample. The isotopic composition of the acetate is thought to have resulted from isotopic discriminations that occurred during the cycling of that molecule. Measurements of this type, which have not been made previously in the natural environment, may provide information about the dominant microbial pathways in anoxic sediments as well as the processes that influence the carbon isotopic composition of biogenic methane from many sources.

  16. Developing Model Constraints on Northern Extra-Tropical Carbon Cycling Based on measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    SciTech Connect

    Keeling, Ralph

    2014-12-12

    The objective of this project was to perform CO2 data syntheses and modeling activities to address two central questions: 1) how much has the seasonal cycle in atmospheric CO2 at northern high latitudes changed since the 1960s, and 2) how well do prognostic biospheric models represent these changes. This project also supported the continuation of the Scripps time series of CO2 isotopes and concentration at ten baseline stations distributed globally.

  17. Abundance measurements in stellar environments

    NASA Astrophysics Data System (ADS)

    Leone, F.

    2014-05-01

    Most of what we know about stars, and systems of stars, is derived from the analysis of their electromagnetic radiation. This lesson is an attempt to describe to Physicists, without any Astrophysical background, the framework to understand the present status of abundance determination in stellar environments and its limit. These notes are dedicated to the recently passed, November 21, 2013, Prof. Dimitri Mihalas who spent his life confuting the 19th century positivist philosopher Auguste Comte who stated that we shall not at all be able to determine the chemical composition of stars.

  18. Abundance measurements in stellar environments

    SciTech Connect

    Leone, F.

    2014-05-09

    Most of what we know about stars, and systems of stars, is derived from the analysis of their electromagnetic radiation. This lesson is an attempt to describe to Physicists, without any Astrophysical background, the framework to understand the present status of abundance determination in stellar environments and its limit. These notes are dedicated to the recently passed, November 21, 2013, Prof. Dimitri Mihalas who spent his life confuting the 19th century positivist philosopher Auguste Comte who stated that we shall not at all be able to determine the chemical composition of stars.

  19. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Blum, J. D.; Klaue, Bjorn

    2005-01-01

    During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

  20. Elemental and isotopic abundances in the solar wind

    NASA Technical Reports Server (NTRS)

    Geiss, J.

    1972-01-01

    The use of collecting foils and lunar material to assay the isotopic composition of the solar wind is reviewed. Arguments are given to show that lunar surface correlated gases are likely to be most useful in studying the history of the solar wind, though the isotopic abundances are thought to give a good approximation to the solar wind composition. The results of the analysis of Surveyor material are also given. The conditions leading to a significant component of the interstellar gas entering the inner solar system are reviewed and suggestions made for experimental searches for this fraction. A critical discussion is given of the different ways in which the basic solar composition could be modified by fractionation taking place between the sun's surface and points of observation such as on the Moon or in interplanetary space. An extended review is made of the relation of isotopic and elemental composition of the interplanetary gas to the dynamic behavior of the solar corona, especially processes leading to fractionation. Lastly, connection is made between the subject of composition, nucleosynthesis and the convective zone of the sun, and processes leading to modification of initial accretion of certain gases on the Earth and Moon.

  1. 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.

  2. Ion Mobility Mass Spectrometry Direct Isotope Abundance Analysis

    SciTech Connect

    Manuel J. Manard, Stephan Weeks, Kevin Kyle

    2010-05-27

    The nuclear forensics community is currently engaged in the analysis of illicit nuclear or radioactive material for the purposes of non-proliferations and attribution. One technique commonly employed for gathering nuclear forensics information is isotope analysis. At present, the state-of-the-art methodology for obtaining isotopic distributions is thermal ionization mass spectrometry (TIMS). Although TIMS is highly accurate at determining isotope distributions, the technique requires an elementally pure sample to perform the measurement. The required radiochemical separations give rise to sample preparation times that can be in excess of one to two weeks. Clearly, the nuclear forensics community is in need of instrumentation and methods that can expedite their decision making process in the event of a radiological release or nuclear detonation. Accordingly, we are developing instrumentation that couples a high resolution IM drift cell to the front end of a MS. The IM cell provides a means of separating ions based upon their collision cross-section and mass-to-charge ratio (m/z). Two analytes with the same m/z, but with different collision cross-sections (shapes) would exit the cell at different times, essentially enabling the cell to function in a similar manner to a gas chromatography (GC) column. Thus, molecular and atomic isobaric interferences can be effectively removed from the ion beam. The mobility selected chemical species could then be introduced to a MS for high-resolution mass analysis to generate isotopic distributions of the target analytes. The outcome would be an IM/MS system capable of accurately measuring isotopic distributions while concurrently eliminating isobaric interferences and laboratory radiochemical sample preparation. The overall objective of this project is developing instrumentation and methods to produce near real-time isotope distributions with a modular mass spectrometric system that performs the required gas-phase chemistry and

  3. 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.

  4. s-process studies - Xenon and krypton isotopic abundances

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.; Ward, R. A.

    1978-01-01

    We propose an analysis of the s-process contributions to the isotopes of xenon and krypton. The object is to aid studies of the possibility that meteorites may contain gas that was carried in presolar grains that were grown in stellar ejecta and that were not degassed prior to incorporation into parent bodies. That model suggests routine interstellar fractionation of s-isotopes from r-isotopes owing to differential incorporation into dust. We show that a deficiency of s-process nuclei cannot yield details of Xe-X, but the gross similarities are strong enough to lead one to think that such a deficiency may play a role in a more complicated explanation. We predict the existence of an s-rich complement somewhere if fractional separation of this type has played a role in Xe-X. We show that the analogous decomposition of krypton is more uncertain, and we call for measurements of neutron-capture cross sections to alleviate these uncertainties.

  5. Mercury Abundances and Isotopic Compositions in the Murchison (CM) and Allende (CV)Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.; Klaue, B.; Blum, J. D.; Buseck, P. R.

    2001-01-01

    The abundance and isotopic composition of Hg was determined in bulk samples of both the Murchison (CM) and Allende (CV) carbonaceous chondrites using single- and multi-collector inductively coupled plasma mass spectrometry (ICP-MS). The bulk abundances of Hg are 294 6 15 ng/g in Murchison and 30.0 6 1.5 ng/g in Allende. These values are within the range of previous measurements of bulk Hg abundances by neutron activation analysis (NAA). Prior studies suggested that both meteorites contain isotopically anomalous Hg, with d l 96/202Hg values for the anomalous, thermal-release components from bulk samples ranging from 2260 %o to 1440 9/00 in Murchison and from 2620 9/00 to 1540 9/00 in Allende (Jovanovic and Reed, 1976a; 1976b; Kumar and Goel, 1992). Our multi-collector ICP-MS measurements suggest that the relative abundances of all seven stable Hg isotopes in both meteorites are identical to terrestrial values within 0.2 to 0.5 9/00m. On-line thermal-release experiments were performed by coupling a programmable oven with the singlecollector ICP-MS. Powdered aliquots of each meteorite were linearly heated from room temperature to 900 C over twenty-five minutes under an Ar atmosphere to measure the isotopic composition of Hg released fiom the meteorites as a h c t i o n of temperature. In separate experiments, the release profiles of S and Se were determined simultaneously with Hg to constrain the Hg distribution within the meteorites and to evaluate the possibility of Se interferences in previous NAA studies. The Hg-release patterns differ between Allende and Murchison. The Hg-release profile for Allende contains two distinct peaks, at 225" and 343"C, whereas the profile for Murchison has only one peak, at 344 C. No isotopically anomalous Hg was detected in the thermal-release experiments at a precision level of 5 to 30 9/00, depending on the isotope ratio. In both meteorites the Hg peak at ;340"C correlates with a peak in the S-release profile. This correlation

  6. RELATIVE ABUNDANCE MEASUREMENTS IN PLUMES AND INTERPLUMES

    SciTech Connect

    Guennou, C.; Hahn, M.; Savin, D. W.

    2015-07-10

    We present measurements of relative elemental abundances in plumes and interplumes. Plumes are bright, narrow structures in coronal holes that extend along open magnetic field lines far out into the corona. Previous work has found that in some coronal structures the abundances of elements with a low first ionization potential (FIP) <10 eV are enhanced relative to their photospheric abundances. This coronal-to-photospheric abundance ratio, commonly called the FIP bias, is typically 1 for elements with a high-FIP (>10 eV). We have used Extreme Ultraviolet Imaging Spectrometer observations made on 2007 March 13 and 14 over a ≈24 hr period to characterize abundance variations in plumes and interplumes. To assess their elemental composition, we used a differential emission measure analysis, which accounts for the thermal structure of the observed plasma. We used lines from ions of iron, silicon, and sulfur. From these we estimated the ratio of the iron and silicon FIP bias relative to that for sulfur. From the results, we have created FIP-bias-ratio maps. We find that the FIP-bias ratio is sometimes higher in plumes than in interplumes and that this enhancement can be time dependent. These results may help to identify whether plumes or interplumes contribute to the fast solar wind observed in situ and may also provide constraints on the formation and heating mechanisms of plumes.

  7. Relative abundance of the helium isotopes He-3 and He-4 in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Jordan, S. P.; Meyer, P.

    1984-01-01

    The geomagnetic field near the equator is used to measure the He-3/He-4 abundance ratio near 6 GeV/nucleon. This ratio is found to be 0.24 + or - 0.05, under the assumption that the helium rigidity spectrum has the form dI/dR = about R exp(-2.65). If all He-3 is of secondary origin, this implies an interstellar mean escape-path length of about 15 g/sq cm, a value considerably larger than that determined from observations of heavier elements but compatible with measurements of the helium isotopic ratio at lower energies.

  8. OH vertical column abundance - Tropical measurements

    NASA Astrophysics Data System (ADS)

    Burnett, Clyde R.; Minschwaner, Kenneth R.; Burnett, Elizabeth B.

    1990-09-01

    Measurements of the vertical column abundance of atmospheric hydroxyl (OH) have been made during the period 1987-1989 at the National Weather Service (NWS) station at Moen, Truk, Federated States of Micronesia (7 deg N, 152 deg E). A total of 384 independent data sets was obtained. Tropical OH abundance levels average about 22 percent above corresponding mid-latitude values, with OH levels during late winter and early spring up to 50 percent above those observed at 40 deg N. Stratospheric wind and temperature data obtained from the daily NWS radiosonde data are examined for correlations with the OH results.

  9. OH vertical column abundance - Tropical measurements

    NASA Technical Reports Server (NTRS)

    Burnett, Clyde R.; Minschwaner, Kenneth R.; Burnett, Elizabeth B.

    1990-01-01

    Measurements of the vertical column abundance of atmospheric hydroxyl (OH) have been made during the period 1987-1989 at the National Weather Service (NWS) station at Moen, Truk, Federated States of Micronesia (7 deg N, 152 deg E). A total of 384 independent data sets was obtained. Tropical OH abundance levels average about 22 percent above corresponding mid-latitude values, with OH levels during late winter and early spring up to 50 percent above those observed at 40 deg N. Stratospheric wind and temperature data obtained from the daily NWS radiosonde data are examined for correlations with the OH results.

  10. ISO/GUM UNCERTAINTIES AND CIAAW (UNCERTAINTY TREATMENT FOR RECOMMENDED ATOMIC WEIGHTS AND ISOTOPIC ABUNDANCES)

    SciTech Connect

    HOLDEN,N.E.

    2007-07-23

    The International Organization for Standardization (ISO) has published a Guide to the expression of Uncertainty in Measurement (GUM). The IUPAC Commission on Isotopic Abundance and Atomic Weight (CIAAW) began attaching uncertainty limits to their recommended values about forty years ago. CIAAW's method for determining and assigning uncertainties has evolved over time. We trace this evolution to their present method and their effort to incorporate the basic ISO/GUM procedures into evaluations of these uncertainties. We discuss some dilemma the CIAAW faces in their present method and whether it is consistent with the application of the ISO/GUM rules. We discuss the attempt to incorporate variations in measured isotope ratios, due to natural fractionation, into the ISO/GUM system. We make some observations about the inconsistent treatment in the incorporation of natural variations into recommended data and uncertainties. A recommendation for expressing atomic weight values using a tabulated range of values for various chemical elements is discussed.

  11. Measurement of the Abundance of Radioactive Be-10 and Other Light Isotopes in Cosmic Radiation Up to 2 GeV /Nucleon with the Balloon-Borne Instrument Isomax

    NASA Technical Reports Server (NTRS)

    Hams, T.; Barbier, L. M.; Bremerich, M.; Christian, E. R.; deNolfo, G. A.; Geier, S.; Goebel, H.; Gupta, S. K.; Hof, M.; Menn, W.

    2004-01-01

    The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 les than or = Z less than or = 8) of cosmic radiation up to 4 GeV/nucleon with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive Be-10 with respect to its stable neighbor isotope Be-9, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4-5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g/sq cm. The isotopic ratio at the top of the atmosphere for Be-10/Be-9 was measured to be 0.195 +/- 0.036 (statistical) +/- 0.039 (systematic) between 0.26 and 1.03 GeV/nucleon and 0.317 +/- 0.109(statistical) +/- 0.042(systematic) between 1.13 and 2.03 GeV/nucleon. This is the first measurement of its kind above l GeV/nucleon. ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to approx. 1 GeV/nucleon). The lithium and boron ratios agree well with existing data and model predictions at similar energies.

  12. Nitrogen abundances and isotopic compositions in lunar samples

    NASA Technical Reports Server (NTRS)

    Becker, R. H.; Clayton, R. N.

    1975-01-01

    Isotopic analyses were carried out on soil separates as well as on bulk samples. Analyses of nitrogen fractions obtained by step-wise heating of the separates were also conducted. It was also attempted to obtain a value for the isotopic composition of indigenous lunar nitrogen from analyses of igneous rock samples. Several breccias were also analyzed for their nitrogen isotope ratios. The significance of the obtained results is discussed. Several lines of evidence point to the conclusion that the isotope ratio of the nitrogen being implanted into the lunar regolith has increased by some 15% over a period of at least 450 million years and possibly as long as 3,700 million years or more. This may be the result of changes in the nitrogen isotope ratio of the solar wind with time, or it may be due to outgassing and subsequent reimplantation of an isotopically light indigenous lunar nitrogen from the lunar interior in the early history of the moon.

  13. Variations in lead isotopic abundances in Sprague-Dawley rat tissues: possible reason of formation.

    PubMed

    Liu, Duojian; Wu, Jing; Ouyang, Li; Wang, Jingyu

    2014-01-01

    It has been reported in previous research that the lead isotopic composition of blood, urine and feces samples statistically differed from the given lead sources in Sprague-Dawley (SD) rats. However, the reason for this phenomenon is still unclear. An animal experiment was performed to investigate the lead isotope fractionation in diverse biological samples (i.e., lungs, liver, kidneys, bone) and to explore the possible reasons. SD rats were intratracheally instilled with lead acetate at the concentrations of 0, 0.02, 0.2, and 2 mg/kg body weight. Biological samples were collected for lead isotope analysis using an inductively coupled plasma mass spectrometry (ICP-MS). Significant differences are observed in lead isotope abundances among the diverse biological samples. The lead isotope abundances ((206)Pb, (207)Pb and (208)Pb) in diverse biological samples show different degrees and directions of departure from the given lead source. The results suggest that differences in enrichment or depletion capacity for each lead isotope in the various tissues might lead to the variation in lead isotopic abundances in tissues. Moreover, a nonlinear relationship between the blood lead level and the lead isotope abundances in liver and bone is observed. When the whole-blood level is higher than 50 ng/mL, the lead isotopic compositions of biological samples tend to be the same. Thus, the data support the speculation of a fractionation functional threshold.

  14. Variations in Lead Isotopic Abundances in Sprague-Dawley Rat Tissues: Possible Reason of Formation

    PubMed Central

    Liu, Duojian; Wu, Jing; Ouyang, Li; Wang, Jingyu

    2014-01-01

    It has been reported in previous research that the lead isotopic composition of blood, urine and feces samples statistically differed from the given lead sources in Sprague-Dawley (SD) rats. However, the reason for this phenomenon is still unclear. An animal experiment was performed to investigate the lead isotope fractionation in diverse biological samples (i.e., lungs, liver, kidneys, bone) and to explore the possible reasons. SD rats were intratracheally instilled with lead acetate at the concentrations of 0, 0.02, 0.2, and 2 mg/kg body weight. Biological samples were collected for lead isotope analysis using an inductively coupled plasma mass spectrometry (ICP-MS). Significant differences are observed in lead isotope abundances among the diverse biological samples. The lead isotope abundances (206Pb, 207Pb and 208Pb) in diverse biological samples show different degrees and directions of departure from the given lead source. The results suggest that differences in enrichment or depletion capacity for each lead isotope in the various tissues might lead to the variation in lead isotopic abundances in tissues. Moreover, a nonlinear relationship between the blood lead level and the lead isotope abundances in liver and bone is observed. When the whole-blood level is higher than 50 ng/mL, the lead isotopic compositions of biological samples tend to be the same. Thus, the data support the speculation of a fractionation functional threshold. PMID:24587048

  15. The isotopic abundances of neon, magnesium and silicon nuclei accelerated in solar flares

    NASA Technical Reports Server (NTRS)

    Dietrich, W. F.; Simpson, J. A.

    1980-01-01

    Direct measurements of the relative abundance of the isotopes Ne-20 and Ne-22 are reported along with a preliminary value for the Mg-26/Mg-24 ratio and an upper limit to the abundance of Si-30 in solar flare accelerated nuclei. A Ne-20/Ne-22 ratio of 7.7 plus 2.3 or minus 1.7 is in agreement with the ratio for the component Neon-A found in carbonaceous chondrites, while a preliminary value of 0.22 plus or minus 0.07 for Mg-26/Mg-24 is larger by approximately one standard deviation than the expected ratio of 0.14 given by Cameron (1973).

  16. Sims Analysis of Water Abundance and Hydrogen Isotope in Lunar Highland Plagioclase

    NASA Technical Reports Server (NTRS)

    Hui, Hejiu; Guan, Yunbin; Chen, Yang; Peslier, Anne H.; Zhang, Youxue; Liu, Yang; Rossman, George R.; Eiler, John M.; Neal, Clive R.

    2015-01-01

    The detection of indigenous water in mare basaltic glass beads has challenged the view established since the Apollo era of a "dry" Moon. Since this discovery, measurements of water in lunar apatite, olivine-hosted melt inclusions, agglutinates, and nominally anhydrous minerals have confirmed that lunar igneous materials contain water, implying that some parts of lunar mantle may have as much water as Earth's upper mantle. The interpretation of hydrogen (H) isotopes in lunar samples, however, is controversial. The large variation of H isotope ratios in lunar apatite (delta Deuterium = -202 to +1010 per mille) has been taken as evidence that water in the lunar interior comes from the lunar mantle, solar wind protons, and/or comets. The very low deuterium/H ratios in lunar agglutinates indicate that solar wind protons have contributed to their hydrogen content. Conversely, H isotopes in lunar volcanic glass beads and olivine-hosted melt inclusions being similar to those of common terrestrial igneous rocks, suggest a common origin for water in both Earth and Moon. Lunar water could be inherited from carbonaceous chondrites, consistent with the model of late accretion of chondrite-type materials to the Moon as proposed by. One complication about the sources of lunar water, is that geologic processes (e.g., late accretion and magmatic degassing) may have modified the H isotope signatures of lunar materials. Recent FTIR analyses have shown that plagioclases in lunar ferroan anorthosite contain approximately 6 ppm H2O. So far, ferroan anorthosite is the only available lithology that is believed to be a primary product of the lunar magma ocean (LMO). A possible consequence is that the LMO could have contained up to approximately 320 ppm H2O. Here we examine the possible sources of water in the LMO through measurements of water abundances and H isotopes in plagioclase of two ferroan anorthosites and one troctolite from lunar highlands.

  17. 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.

  18. Determination of lithium isotopes at natural abundance levels by atomic absorption spectrometry

    USGS Publications Warehouse

    Meier, A.L.

    1982-01-01

    The relationships of the absorption of 6Li and 7Li hollow cathode lamp emissions are used to determine lithium isotopic composition in the natural abundance range of geologic materials. Absorption was found to have a nonlinear dependence upon total lithium concentration and isotopic composition. A method using nonlinear equations to describe the relationship of the absorption of 6Li and 7Li lamp radiation is proposed as a means of calculating isotopic composition that is independent of total lithium concentration.

  19. Laser spectroscopic measurement of helium isotope ratios.

    SciTech Connect

    Wang, L.-B.; Mueller, P.; Holt, R. J.; Lu, Z.-T.; O'Connor, T. P.; Sano, Y.; Sturchio, N.; Univ. of Illinois; Univ. of Tokyo; Univ. of Illinois at Chicago

    2003-06-13

    A sensitive laser spectroscopic method has been applied to the quantitative determination of the isotope ratio of helium at the level of {sup 3}He/{sup 4}He = 10{sup -7}--10{sup -5}. The resonant absorption of 1083 nm laser light by the metastable {sup 3}He atoms in a discharge cell was measured with the frequency modulation saturation spectroscopy technique while the abundance of {sup 4}He was measured by a direct absorption technique. The results on three different samples extracted from the atmosphere and commercial helium gas were in good agreement with values obtained with mass spectrometry. The achieved 3{sigma} detection limit of {sup 3}He in helium is 4 x 10{sup -9}. This demonstration required a 200 {mu}L STP sample of He. The sensitivity can be further improved, and the required sample size reduced, by several orders of magnitude with the addition of cavity enhanced spectroscopy.

  20. Partitioning Respiration Between Plant and Microbial Sources Using Natural Abundance Stable Carbon Isotopes

    NASA Astrophysics Data System (ADS)

    Dawson, T. E.; Tu, K. P.

    2009-12-01

    Partitioning plant and microbial respiration is important for understanding the mechanistic basis of ecosystem respiration, as each can respond to changes in environmental conditions in different ways and at different timescales. In theory, natural abundance stable C isotopes can allow source partitioning when the isotopic difference between the sources can be resolved. The longstanding notion is that such differences do not exist, yet field measurements to support this conclusion are rare. The question remains as to how much isotopic difference exists between the plant and microbial respiration and whether or not this difference is sufficient for partitioning. We addressed this question by measuring the C isotope ratios (13C/12C) of plant, microbial, and whole ecosystem respiration from three contrasting ecosystems in California. We found significant variation in the 13C/12C ratios between plant and microbial sources. However, isotopic mass balance was not observed in more than half the cases. When isotopic mass balance was observed, the largest isotopic differences were always between CO2 evolved during leaf respiration and SOC decomposition, with leaf respiration more depleted by 1-8 per mil. Within plants, the leaf respiration was more depleted than rhizosphere respiration by 2-6 per mil. Among microbial sources, litter decomposition was more depleted than SOC decomposition by 1-5 per mil. The 13C/12C ratio of bulk C and respired CO2 exhibited similar trends, but bulk C values were clearly not a good surrogate for the 13C/12C ratios of respired CO2. Based on the 13C/12C ratios of respired CO2, belowground respiration accounted for 25% in the redwood forest, 37% in the grassland and 84% in the pine forest. Belowground respiration was further partitioned between rhizosphere, litter and SOC decomposition. Each contributed nearly equal amounts in the redwood forest (30/40/30) whereas litter respiration dominated in the grassland (20/70/10) and pine forest (15

  1. MEASUREMENTS OF ABSOLUTE ABUNDANCES IN SOLAR FLARES

    SciTech Connect

    Warren, Harry P.

    2014-05-01

    We present measurements of elemental abundances in solar flares with the EUV Variability Experiment (EVE) on the Solar Dynamics Observatory. EVE observes both high temperature Fe emission lines (Fe XV-Fe XXIV) and continuum emission from thermal bremsstrahlung that is proportional to the abundance of H. By comparing the relative intensities of line and continuum emission it is possible to determine the enrichment of the flare plasma relative to the composition of the photosphere. This is the first ionization potential or FIP bias (f). Since thermal bremsstrahlung at EUV wavelengths is relatively insensitive to the electron temperature, it is important to account for the distribution of electron temperatures in the emitting plasma. We accomplish this by using the observed spectra to infer the differential emission measure distribution and FIP bias simultaneously. In each of the 21 flares that we analyze we find that the observed composition is close to photospheric. The mean FIP bias in our sample is f = 1.17 ± 0.22. This analysis suggests that the bulk of the plasma evaporated during a flare comes from deep in the chromosphere, below the region where elemental fractionation occurs.

  2. Code System to Determine Pu Isotope Abundances from Multichannel Analyzer Gamma Spectra.

    2008-09-26

    Version 00 The MGA (Multiple Group Analysis) program determines the relative abundances of plutonium and other actinide isotopes in different materials. The program analyzes spectra taken of such samples using a 4096-channel germanium (Ge) gamma-ray spectrometer. The code can be run in a one or two detector mode. The first spectrum, which is required and must be taken at a gain of 0.075 Kev/channel with a high resolution planar detector, contains the 0-300Kev energy region.more » The second spectrum, which is optional, must be taken at a gain of 0.25 Kev/channel; it becomes important when analyzing high burnup samples (concentration of Pu241 greater than one percent). Isotopic analysis precisions of one percent or better can be obtained, and no calibrations are required. The system also measures the abundances of U235, U238, Np237, and Am241. A special calibration option is available to perform a one-time peak-shape characterization when first using a new detector system.« less

  3. The abundance of the radioactive isotope Al-26 in galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, M. E.

    1983-01-01

    Satellite observations of the isotopic composition of aluminum in low energy cosmic rays (E/M = 200 MeV/amu) have been used to determine the abundance of the unstable isotope Al-26 (T1/2 = 0.87 Myr). The observed abundance ratio, Al-26/Al-27 = 0.036 (+0.037, -0.022), is in good agreement with previous balloon observations and yields a cosmic ray confinement time consistent with values based on the abundance of Be-10.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  6. Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopes

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.; Andersson, B.-G.; Olofsson, H.; Ukita, N.; Young, K.

    1991-01-01

    Results are presented of millimeter- and submillimeter-wave observations of HCN and HCCCN that were made of the circmustellar envelopes of eight carbon stars, including the two protoplanetary nebulae CRL 618 and CRL 2688. The observations yield a measure of the double ratio (N-14)(C-13)/(N-15)(C-12). Measured C-12/C-13 ratios are used to estimate the N-14/N-15 abundance ratio, with the resulting lower limits in all eight envelopes and possible direct determinations in two envelopes. The two determinations and four of the remaining six lower limits are found to be in excess of the terrestrial value of N-14/N-15 = 272, indicating an evolution of the nitrogen isotope ratio, which is consistent with stellar CNO processing. Observations of thermal SiO (v = 0, J = 2-1) emission show that the Si-29/Si-28 ratio can be determined in carbon stars, and further observations are indicated.

  7. Atmospheric Trace Gas Abundances and Stable Isotope Ratios via IR-LIF

    NASA Technical Reports Server (NTRS)

    Blake, Geoffrey A.

    2004-01-01

    We propose to develop new technologies with support provided by PIDDP that will enable the in situ measurements of abundances and stable isotope ratios in important radiatively and biogenically active gases such as carbon dioxide, carbon monoxide, water, methane, nitrous oxide, and hydrogen sulfide to very high precision (0.1 per mil or better for the isotopic ratios, for example). Such measurements, impossible at present, could provide pivotal new constraints on the global (bio)geochemical budgets of these critical species, and could also be used to examine the dynamics of atmospheric transport on Mars, Titan, and other solar system bodies. We believe the combination of solid state light sources with imaging of the IR laser induced fluorescence (IR-LIF) via newly available detector arrays will make such in situ measurements possible for the first time. Even under ambient terrestrial conditions, the LIF yield from vibrational excitation of species such as water and carbon dioxide should produce emission measures well in excess of ten billion photons/sec from samples volumes of order 1 c.c. These count rates can, in principle, yield detection limits into the sub-ppt range that are required for the in situ isotopic study of atmospheric trace gases. While promising, such technologies are relatively immature, but developing rapidly, and there are a great many uncertainties regarding their applicability to in situ IR-LIF planetary studies. We therefore feel PIDDP support will be critical to developing these new tools, and propose a three-year program to combine microchip near-IR lasers with low background detection axes and state-of-the-art HgCdTe detectors developed for astronomical spectroscopy to investigate the sensitivity of IR-LIF under realistic planetary conditions, to optimize the optical pumping and filtering schemes for important species, and to apply the spectrometer to the non-destructive measurement of stable isotopes in a variety of test samples. These

  8. Practical Immunoaffinity-Enrichment LC-MS for Measuring Protein Kinetics of Low-Abundance Proteins

    PubMed Central

    Lassman, Michael E.; McAvoy, Thomas; Lee, Anita Y.H.; Chappell, Derek; Wong, Oitak; Zhou, Haihong; Reyes-Soffer, Gissette; Ginsberg, Henry N.; Millar, John S.; Rader, Daniel J.; Gutstein, David E.; Laterza, Omar

    2016-01-01

    BACKGROUND For a more complete understanding of pharmacodynamic, metabolic, and pathophysiologic effects, protein kinetics, such as production rate and fractional catabolic rate, can offer substantially more information than protein concentration alone. Kinetic experiments with stable isotope tracers typically require laborious sample preparation and are most often used for studying abundant proteins. Here we describe a practical methodology for measuring isotope enrichment into low-abundance proteins that uses an automated procedure and immunoaffinity enrichment (IA) with LC-MS. Low-abundance plasma proteins cholesteryl ester transfer protein (CETP) and proprotein convertase subtilisin/kexin type 9 (PCSK9) were studied as examples. METHODS Human participants (n = 39) were infused with [2H3]leucine, and blood samples were collected at multiple time points. Sample preparation and analysis were automated and multiplexed to increase throughput. Proteins were concentrated from plasma by use of IA and digested with trypsin to yield proteotypic peptides that were analyzed by microflow chromatography-mass spectrometry to measure isotope enrichment. RESULTS The IA procedure was optimized to provide the greatest signal intensity. Use of a gel-free method increased throughput while increasing the signal. The intra- and interassay CVs were <15% at all isotope enrichment levels studied. More than 1400 samples were analyzed in <3 weeks without the need for instrument stoppages or user interventions. CONCLUSIONS The use of automated gel-free methods to multiplex the measurement of isotope enrichment was applied to the low-abundance proteins CETP and PCSK9. PMID:24751376

  9. 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.

  10. A Methodology for Absolute Isotope Composition Measurement

    NASA Astrophysics Data System (ADS)

    Shen, J. J.; Lee, D.; Liang, W.

    2007-12-01

    Double spike technique was a well defined method for isotope composition measurement by TIMS of samples which have natural mass fractionation effect, but it is still a problem to define the isotope composition for double spike itself. In this study, we modified the old double spike technique and found that we could use the modified technique to solve the ¡§true¡¨ isotope composition of double spike itself. According the true isotope composition of double spike, we can measure the absolute isotope composition if the sample has natural fractionation effect. A new vector analytical method has been developed in order to obtain the true isotopic composition of a 42Ca-48Ca double spike, and this is achieved by using two different sample-spike mixtures combined with the double spike and the natural Ca data. Because the natural sample, the two mixtures, and the spike should all lie on a single mixing line, we are able to constrain the true isotopic composition of our double spike using this new approach. This method not only can be used in Ca system but also in Ti, Cr, Fe, Ni, Zn, Mo, Ba and Pb systems. The absolute double spike isotopic ratio is important, which can save a lot of time to check different reference standards. Especially for Pb, radiogenic isotope system, the decay systems embodied in three of four naturally occurring isotopes induce difficult to obtain true isotopic ratios for absolute dating.

  11. Empirical Solar Abundance Scaling Laws of Supernova {gamma} Process Isotopes

    SciTech Connect

    Hayakawa, Takehito; Iwamoto, Nobuyuki; Kajino, Toshitaka; Shizum, Toshiyuki; Umeda, Hideyuki; Nomoto, Ken'Ichi

    2008-11-11

    Analyzing the solar system abundances, we have found two empirical abundance scaling laws concerning the p- and s-nuclei with the same atomic number. They are evidence that the 27 p-nuclei are synthesized by the supernova {gamma}-process. The scalings lead to a novel concept of 'universality of {gamma}-process' that the s/p and p/p ratios of nuclei produced by individual {gamma}-processes are almost constant, respectively. We have calculated the ratios of materials produced by the {gamma}-process based on core-collapse supernova explosion models under various astrophysical conditions and found that the scalings hold for individual {gamma}-processes independent of the conditions assumed. The results further suggest an extended universality that the s/p ratios in the {gamma}-process layers are not only constant but also centered on a specific value of 3. With this specific value and the scaling of the s/p ratios, we estimate that the ratios of the s-process abundance contributions from the AGB stars to the massive stars are almost 6.7 for the s-nuclei of A>90 in the solar system.

  12. 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.

  13. Element distribution and noble gas isotopic abundances in lunar meteorite Allan Hills A81005

    NASA Technical Reports Server (NTRS)

    Kraehenbuehl, U.; Eugster, O.; Niedermann, S.

    1986-01-01

    Antarctic meteorite ALLAN HILLS A81005, an anorthositic breccia, is recognized to be of lunar origin. The noble gases in this meteorite were analyzed and found to be solar-wind implanted gases, whose absolute and relative concentrations are quite similar to those in lunar regolith samples. A sample of this meteorite was obtained for the analysis of the noble gas isotopes, including Kr(81), and for the determination of the elemental abundances. In order to better determine the volume derived from the surface correlated gases, grain size fractions were prepared. The results of the instrumental measurements of the gamma radiation are listed. From the amounts of cosmic ray produced noble gases and respective production rates, the lunar surface residence times were calculated. It was concluded that the lunar surface time is about half a billion years.

  14. 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)).

  15. On krypton isotopic abundances in the sun and in the solar wind

    NASA Technical Reports Server (NTRS)

    Marti, K.

    1980-01-01

    The Kr isotopic systematics in the meteorite Pesyanoe which is known to contain solar-type gases, are reported. Discrepancies in the isotopic data of fractions released at stepwise increasing temperatures cannot be reconciled with spallation Kr components, although spallation effects are significant. Fractionation mechanisms on the parent body and in the solar wind source region are considered and the implications for solar abundances discussed.

  16. 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.

  17. Calibrated sulfur isotope abundance ratios of three IAEA sulfur isotope reference materials and V-CDT with a reassessment of the atomic weight of sulfur

    NASA Astrophysics Data System (ADS)

    Ding, T.; Valkiers, S.; Kipphardt, H.; De Bièvre, P.; Taylor, P. D. P.; Gonfiantini, R.; Krouse, R.

    2001-09-01

    Calibrated values have been obtained for sulfur isotope abundance ratios of sulfur isotope reference materials distributed by the IAEA (Vienna). For the calibration of the measurements, a set of synthetic isotope mixtures were prepared gravimetrically from high purity Ag 2S materials enriched in 32S, 33S, and 34S. All materials were converted into SF 6 gas and subsequently, their sulfur isotope ratios were measured on the SF 5+ species using a special gas source mass spectrometer equipped with a molecular flow inlet system (IRMM's Avogadro II amount comparator). Values for the 32S/ 34S abundance ratios are 22.650 4(20), 22.142 4(20), and 23.393 3(17) for IAEA-S-1, IAEA-S-2, and IAEA-S-3, respectively. The calculated 32S/ 34S abundance ratio for V-CDT is 22.643 6(20), which is very close to the calibrated ratio obtained by Ding et al. (1999). In this way, the zero point of the VCDT scale is anchored firmly to the international system of units SI. The 32S/ 33S abundance ratios are 126.942(47), 125.473(55), 129.072(32), and 126.948(47) for IAEA-S-1, IAEA-S-2, IAEA-S-3, and V-CDT, respectively. In this way, the linearity of the V-CDT scale is improved over this range. The values of the sulfur molar mass for IAEA-S-1 and V-CDT were calculated to be 32.063 877(56) and 32.063 911(56), respectively, the values with the smallest combined uncertainty ever reported for the sulfur molar masses (atomic weights).

  18. Helium isotopes and heavier noble gas abundances of water in adjacent sea of Japan

    NASA Astrophysics Data System (ADS)

    Sano, Y.; Takahata, N.; Watanabe, T.; Shirai, K.; Nishizawa, M.

    2003-12-01

    We have measured helium isotopic ratios of water samples collected with various depths in adjacent sea of Japan. The 3He/4He ratios vary significantly from 0.989 Ratm to 1.242 Ratm where Ratm is the atmospheric ratio of 1.39x10-6. It is confirmed that all deep sea water (2000 - 2500 m) of western North Pacific is affected by the mantle helium with a high 3He/4He ratio. More precisely mid-depth (750 - 1500 m) profiles of 3He/4He ratios of northwestern Philippine Sea (Nansei Trench) and east of East China Sea (northeast and southwest of Okinawa Trough) are higher than those of western North Pacific (Off Joban) and comparable to those of northern Philippine Sea (Nankai Trough). Excess 3He of the mid-depth samples may be attributable to the subduction-type mantle helium originated from high-temperature hydrothermal sites in the Okinawa Trough. Noble gas abundances (neon, argon, krypton and xenon) were measured in water samples collected in western North Pacific and northwestern Philippine Sea. Neon abundances show slight excess relative to air saturated sea water at ambient temperature and salinity. This may be due to either air bubble effect or contamination during the sampling. When these effects are corrected using the neon anomaly, heavier noble gas abundances (argon, krypton and xenon) of samples with the temperature higher than 5° C (shallower than 500m) agree well with those of calculated air saturated seawater, while the lower temperature samples (deeper than 500 m) indicate anomaly of -7% to +10%.

  19. The Zn abundance and isotopic composition of diatom frustules, a proxy for Zn availability in ocean surface seawater

    NASA Astrophysics Data System (ADS)

    Andersen, Morten B.; Vance, Derek; Archer, Corey; Anderson, Robert F.; Ellwood, Michael J.; Allen, Claire S.

    2011-01-01

    We have developed cleaning methods for extracting diatomopal from bulk marine sediment samples, for measurement of both zinc (Zn) abundance and isotope composition. This cleaning technique was then applied to a set of Holocene core-top samples from the Southern Ocean. The measured δ66Zn (reported relative to the JMCLyon standard) and Zn/Si ratios from the Southern Ocean diatomopal samples range from 0.7 to 1.5‰, and from 14 to 0.9 μmol/mol, respectively. The Zn abundance and isotope composition data show a clear correlation with opal burial rates and other oceanographic parameters. In common with previous work, we interpret the systematic changes in the Zn/Si ratio to be linked to the variability in the concentrations of bioavailable Zn in the ambient surface seawater where the diatom opal is formed. This variability is likely to be primarily controlled by the degree to which Zn is taken up into phytoplankton biomass. The observed systematic pattern in the δ66Zn compositions of the diatomopal core-top samples is, similarly, likely to reflect changes in the δ66Zn composition of the ambient Zn in the surface waters above the core-top sites, which is progressively driven towards isotopically heavier values by preferential incorporation of the lighter isotopes into phytoplankton organic material. Thus, the systematic relationship between Zn isotopes and abundance observed in the core-top diatomopal samples suggests a potential tool for investigating the biogeochemical cycling of Zn in the past surface ocean for down-core diatomopal material. In this respect, it may be possible to test hypotheses that attribute variations in atmospheric CO2 on glacial-interglacial timescales to the degree to which trace metals limited primary productivity in HNLC zones.

  20. ANALYSIS OF RICIN TOXIN PREPARATIONS FOR CARBOHYDRATE AND FATTY ACID ABUNDANCE AND ISOTOPE RATIO INFORMATION

    SciTech Connect

    Wunschel, David S.; Kreuzer-Martin, Helen W.; Antolick, Kathryn C.; Colburn, Heather A.; Moran, James J.; Melville, Angela M.

    2009-12-01

    employing a quadrupole MS system for compound identification and an isotope ratio MS for measuring the stable isotope ratios of deuterium and hydrogen (D/H) in fatty acids. Finally, the method for analyzing the compound abundance data is included. This study indicates that removal of ricinoleic acid is a conserved consequence of each processing step we tested. Furthermore, the stable isotope D/H ratio of ricinoleic acid distinguished between two of the three castor seed sources. Concentrations of arabinose, xylose, mannose, glucosamine and myo-inositol differentiated between crude or acetone extracted samples and samples produced by protein precipitation. Taken together these data illustrate the ability to distinguish between processes used to purify a ricin sample as well as potentially the source seeds.

  1. Electrolytic recovery of mercury enriched in isotopic abundance

    DOEpatents

    Grossman, Mark W.

    1991-01-01

    The present invention is directed to a method of electrolytically extracting liquid mercury from HgO or Hg.sub.2 Cl.sub.2. Additionally there are disclosed two related techniques associated with the present invention, namely (1) a technique for selectively removing product from different regions of a long photochemical reactor (photoreactor) and (2) a method of accurately measuring the total quantity of mercury formed as either HgO or Hg.sub.2 Cl.sub.2.

  2. Column abundance measurements of atmospheric hydroxyl at 45 deg S

    NASA Technical Reports Server (NTRS)

    Wood, S. W.; Keep, D. J.; Burnett, C. R.; Burnett, E. B.

    1994-01-01

    The first Southern Hemisphere measurements of the vertical column abundance of atmospheric hydroxyl (OH) have been obtained at Lauder, New Zealand (45 deg S) with a PEPSIOS instrument measuring the absorption of sunlight at 308 nm. The variation of column OH with solar zenith angle is similar to that measured at other sites. However average annual abundances of OH are about 20% higher than those found by similar measurements at 40 deg N. Minimum OH abundances about 10% less than average levels at 40 deg N, are observed during austral spring. The OH abundance abruptly increases by 30% in early summer and remains at the elevated level until late the following winter.

  3. Interpretation of the carbon abundance in Saturn measured by Cassini

    NASA Astrophysics Data System (ADS)

    Hersant, Franck; Gautier, Daniel; Tobie, Gabriel; Lunine, Jonathan I.

    2008-06-01

    Spectral observations of Saturn from the far infrared spectrometer aboard the Cassini spacecraft [Flasar, F.M., et al., 2005. Temperatures, winds, and composition in the Saturnian system. Science 307, 1247-1251] have revealed that the C/H ratio in the planet is in fact about twice higher than previously derived from ground based observations and in agreement with the C/H value derived from Voyager IRIS by Courtin et al. [1984. The composition of Saturn's atmosphere at northern temperate latitudes from Voyager IRIS spectra - NH 3, PH 3, C 2H 2, C 2H 6, CH 3D, CH 4, and the Saturnian D/H isotopic ratio. Astrophys. J. 287, 899-916] . The implications of this measurement are reanalyzed in the present report on the basis that volatiles observed in cometary atmospheres, namely CO2, CH4, NH3 and H2S may have been trapped as solids in the feeding zone of the planet. CH4 and H2S may have been in the form of clathrate hydrates while CO2 presumably condensed in the cooling solar nebula. Carbon may also have been incorporated in organics. Conditions of temperature and pressure ease the hydratation of NH3. Such icy grains were included in planetesimals which subsequently collapsed into the hydrogen envelope of the planet, then resulting in C, N and S enrichments with respect to the solar abundance. Our calculations are consistent, within error bars, with observed elemental abundances on Saturn provided that the carbon trapped in planetesimals was mainly in the form of CH4 clathrate and CO2 ice (and maybe as organics) while nitrogen was in the form of NH3 hydrate. Our approach has implications on the possible pattern of noble gases in Saturn, since we predict that contrary to what is observed in Jupiter, Ar and Kr should be in solar abundance while Xe might be strongly oversolar. The only way to verify this scenario is to send a probe making in situ mass spectrometer measurements. Our scenario also predicts that the 14N/ 15N ratio should be somewhat smaller in Saturn than

  4. The Oxygen Isotopic Composition of MIL 090001: A CR2 Chondrite with Abundant Refractory Inclusions

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; McKeegan, K. D.; Sharp, Z. D.

    2012-01-01

    MIL 090001 is a large (>6 kg) carbonaceous chondrite that was classified as a member of the CV reduced subgroup (CVred) that was recovered during the 2009-2010 ANSMET field season [1]. Based on the abundance of refractory inclusions and the extent of aqueous alteration, Keller [2] suggested a CV2 classification. Here we report additional mineralogical and petrographic data for MIL 090001, its whole-rock oxygen isotopic composition and ion microprobe analyses of individual phases. The whole rock oxygen isotopic analyses show that MIL 090001 should be classified as a CR chondrite.

  5. Lunar Elemental Abundances from Gamma-Ray and Neutron Measurements

    NASA Astrophysics Data System (ADS)

    Reedy, R. C.; Vaniman, D. T.

    1999-01-01

    % , with Ti and Fe emitting more fast neutrons than light elements like O and Si. Most elements moderate neutrons to thermal energies at similar rates. The main exception is when neutrons scatter from H, in which case neutrons can be rapidly thermalized. The cross sections for the absorption of thermal neutrons can vary widely among elements, with major elements like Ti and Fe having high-capture cross sections. Some trace elements, such as Sm and Gd, have such large neutron-absorption cross sections that, despite their low abundances, can absorb significant amounts of thermal neutrons in the Moon. Because the processes affecting neutrons are complicated, good modeling is needed to properly extract elemental information from measured neutron fluxes. The LAHET Code System (LCS) can be use to calculate neutron fluxes from GCR interactions in the Moon. Lunar Gamma-Ray Spectroscopy: The main sources of planetary gamma-rays are the decay of the naturally occurring radioactive isotopes of K, Th, and U and the interactions of GCRs with atomic nuclei in the planet's surface. Most "cosmogenic" gamma-rays are produced by fast and thermal neutrons made in the planet's surface by GCRs, and their production rates can vary with time. Over 300 gamma-ray lines have been identified that can be emitted from planetary surfaces by a variety of production mechanisms. There exist nuclear databases that can be used to identify and quantify other gamma-ray lines. Use will be made of gamma-rays from major elements, particularly those from Si and O, that have not been routinely used in the past. The fluxes of gamma-rays from a given element can vary depending on many factors besides the concentration of that element. For example, the fluxes of neutron-capture gamma-rays in the planetary region of interest depend on (1) the total cross section for elements to absorb thermalized neutrons and (2) the H content of the top meter of the surface. The fluxes of the fast neutrons that induce inelastic

  6. Making an honest measurement scale out of the oxygen isotope delta-values.

    PubMed

    Gat, Joel R; DeBievre, Paul

    2002-01-01

    The differential measurement of the abundance of oxygen isotopes based on reference materials, such as VSMOW for the case of water, was used because the precision of the absolute mass-spectrometric determination of the abundance fell short of the differences to be measured. Since then these measurements have been much improved, so that a calibration scheme of the oxygen isotope abundance in water, carbonates, silica, phosphates, sulfates, nitrates and organic materials is suggested, based on an accredited primary standard of oxygen in air and using standard fluorination and O(2) to CO(2) conversion techniques. PMID:12442297

  7. Lithium isotopes and light lithophile element abundances in shergottites: Evidence for both magmatic degassing and subsolidus diffusion

    NASA Astrophysics Data System (ADS)

    Udry, Arya; McSween, Harry Y.; Hervig, Richard L.; Taylor, Lawrence A.

    2016-01-01

    Degassed magmatic water was potentially the major source of surficial water on Mars. We measured Li, B, and Be abundances and Li isotope profiles in pyroxenes, olivines, and maskelynite from four compositionally different shergottites—Shergotty, QUE 94201, LAR 06319, and Tissint—using secondary ion mass spectrometry (SIMS). All three light lithophile elements (LLE) are incompatible: Li and B are soluble in H2O-rich fluids, whereas Be is insoluble. In the analyzed shergottites, Li concentration decreases and Be concentration increases from cores to rims in pyroxenes. However, B concentrations do not vary consistently with Li and Be abundances, except in QUE 94201 pyroxenes. Additionally, abundances of these three elements in olivines show a normal igneous-fractionation trend consistent with the crystallization of olivine before magma ascent and degassing. We expect that kinetic effects would lead to fractionation of 6Li in the vapor phase compared to 7Li during degassing. The Li isotope profiles, with increasing δ7Li from cores to rims, as well as Li and B profiles indicate possible degassing of hydrous fluids only for the depleted shergottite QUE 94201, as also supported by degassing models. Conversely, Shergotty, LAR 06319, and Tissint appear to have been affected by postcrystallization diffusion, based on their LLE and Li isotope profiles, accompanied by diffusion models. This process may represent an overlay on a degassing pattern. The LLE profiles and isotope profiles in QUE 94201 support the hypothesis that degassing of some basaltic shergottite magmas provided water to the Martian surface, although evidence may be obscured by subsolidus diffusion processes.

  8. Boron abundances and isotopic ratios of olivine grains on Itokawa returned by the Hayabusa spacecraft

    NASA Astrophysics Data System (ADS)

    Fujiya, Wataru; Hoppe, Peter; Ott, Ulrich

    2016-07-01

    We report the B abundances and isotopic ratios of two olivine grains from the S-type asteroid Itokawa sampled by the Hayabusa spacecraft. Olivine grains from the Dar al Gani (DaG) 989 LL6 chondrite were used as a reference. Since we analyzed polished thin sections in both cases, we expect the contribution from the solar wind B (rich in 10B) to be minimal because the solar wind was implanted only within very thin layers of the grain surface. The Itokawa and DaG 989 olivine grains have homogeneous B abundances (~400 ppb) and 11B/10B ratios compatible with the terrestrial standard and bulk chondrites. The observed homogeneous B abundances and isotopic ratios of the Itokawa olivine grains are likely the result of thermal metamorphism which occurred in the parent asteroid of Itokawa, which had a similar composition as LL chondrites. The chondritic B isotopic ratios of the Itokawa samples suggest that they contain little cosmogenic B (from cosmic-ray spallation reactions) rich in 10B. This observation is consistent with the short cosmic-ray exposure ages of Itokawa samples inferred from the small concentrations of cosmogenic 21Ne. If other Itokawa samples have little cosmogenic B as well, the enrichment in 10B found previously on the surface of another Itokawa particle (as opposed to the bulk grain study here) may be attributed to implanted solar wind B.

  9. Boron abundances and isotopic ratios of olivine grains on Itokawa returned by the Hayabusa spacecraft

    NASA Astrophysics Data System (ADS)

    Fujiya, Wataru; Hoppe, Peter; Ott, Ulrich

    2016-09-01

    We report the B abundances and isotopic ratios of two olivine grains from the S-type asteroid Itokawa sampled by the Hayabusa spacecraft. Olivine grains from the Dar al Gani (DaG) 989 LL6 chondrite were used as a reference. Since we analyzed polished thin sections in both cases, we expect the contribution from the solar wind B (rich in 10B) to be minimal because the solar wind was implanted only within very thin layers of the grain surface. The Itokawa and DaG 989 olivine grains have homogeneous B abundances (~400 ppb) and 11B/10B ratios compatible with the terrestrial standard and bulk chondrites. The observed homogeneous B abundances and isotopic ratios of the Itokawa olivine grains are likely the result of thermal metamorphism which occurred in the parent asteroid of Itokawa, which had a similar composition as LL chondrites. The chondritic B isotopic ratios of the Itokawa samples suggest that they contain little cosmogenic B (from cosmic-ray spallation reactions) rich in 10B. This observation is consistent with the short cosmic-ray exposure ages of Itokawa samples inferred from the small concentrations of cosmogenic 21Ne. If other Itokawa samples have little cosmogenic B as well, the enrichment in 10B found previously on the surface of another Itokawa particle (as opposed to the bulk grain study here) may be attributed to implanted solar wind B.

  10. Comparison of the isotopic abundance of U235 and U238 and the radium activity ratios in Colorado Plateau uranium ores

    USGS Publications Warehouse

    Senftle, F.E.; Stieff, L.; Cuttitta, F.; Kuroda, P.K.

    1957-01-01

    The isotopic abundances of uranium and the radium activity ratios of eleven samples of uranium ore from the Colorado Plateau have been measured. No significant variation in the isotopic abundance of the uranium was noted; with'in the experimental error, the average U235/U238 ratio is 137.7. There is a significant variation in the Ra226/Ra223 activity ratios (0.048-0.143), which indicates a relatively recent alteration of the ore samples. The variations do not, however, explain the lead-uranium and lead-lead age discrepancies. ?? 1957.

  11. MGA: A gamma-ray spectrum analysis code for determining plutonium isotopic abundances. Volume 3, FORTRAN listing of the GA code

    SciTech Connect

    Gunnink, R

    1991-09-01

    Nondestructive measurements of x-ray and gamma-ray emissions can be used to determine the abundances of various actinides in a sample. Volume 1 of this report describes the methods and algorithms we have developed to determine the relative isotopic abundances of actinides in a sample, by analyzing gamma-ray spectra obtained using germanium detector systems. Volume 2 is a guide to using the MGA (Multiple Group Analysis) computer program we have written to perform plutonium isotopic analyses. This report contains a listing of the FORTRAN instructions of the code.

  12. Measurement of isotope shifts and hyperfine structure in Zr II

    NASA Astrophysics Data System (ADS)

    Rosner, S. D.; Holt, R. A.

    2016-06-01

    We have applied fast-ion-beam laser-fluorescence spectroscopy to measure the isotope shifts (IS) of 51 optical transitions in the wavelength range 420.6-461.4 nm and the hyperfine structures (hfs) of 11 even parity and 30 odd parity levels in Zr II. The IS and many of the hfs measurements are the first for these transitions and levels. These atomic data are very important for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines. They also provide important constraints on stellar diffusion modeling and provide a benchmark for theoretical atomic structure calculations.

  13. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  14. Zn Isotope Abundances of Lunar Soils 64801, 68841, 69941, and 69961

    NASA Astrophysics Data System (ADS)

    Xue, S.; Herzog, G. F.; Hall, G. S.

    1995-09-01

    Mass fractionation is well established for the isotopes of several elements in lunar soils, notably O, Si, K, Ca (to a lesser extent), and S (see [1,2]). Zinc is nearly as volatile as S and is associated with it in the coatings of pyroclastic deposits (see [3]). It therefore seemed plausible that zinc might also be fractionated and that the degree of fractionation might be correlated with that of sulfur. To test this inference, we have begun to measure Zn isotopic abundances in lunar soils. Here we report results for four Apollo 16 samples from which the magnetic fraction had been previously removed. The samples were ground, weighed, and dissolved in HF, HNO3 and HCl in a Teflon bomb. Zn was separated by anion exchange and analyzed isotopically by using ICP/MS. Only the data for 64Zn, 66Zn, and 68Zn are reported: The molecular ion ^35Cl^16O(sub)2+ interfered with the measurement of 67Zn and counting statistics for 70Zn gave only %-level precision. We used Zn atomic absorption solutions as standards with a known concentration of Ga added to control for instrumental drift. Measured elemental Zn contents are consistent with literature values [4-6]. The isotopic ratios of the samples were expressed as delta-values calculated relative to the corresponding isotopic ratios of the standards. No fractionation (i.e., < 0.2%/AMU) was observed for any of several ordinary chondrites, among them Suizhou and Dhajala. In all four lunar soils, however, we found delta 68Zn~2xdelta 66Zn and delta 66Zn>0 at the one-sigma level. These results indicate mass dependent fractionation. If we make the oversimplified assumption that the Zn isotopic fractionation reflects Rayleigh distillation from a single well-mixed reservoir of material from which Zn evaporated as the atom, then the fraction of Zn retained is given approximately by (1+delta ^YZn/1000)^(-2M(sub)Y/Delta M where Y=66 or 68, M is mass, and Delta M is the mass difference M(sub)Y - M(sub)64. The computations suggest that the

  15. Biological control of calcium isotopic abundances in the global calcium cycle

    SciTech Connect

    Skulan, J.; DePaolo, D.J.; Owens, T.L. |

    1997-06-01

    Measurements of {sup 44}Ca/{sup 40}Ca, expressed as {delta}{sup 44}Ca, were made on igneous rocks and on shell and bone material from modern organisms to investigate the magnitude and origins of calcium isotopic fractionation in nature. The results document a span of 4{per_thousand} in {delta}{sup 44}Ca, measured with the double spike technique to a precision of {+-}0.15{per_thousand}. Volcanic rocks, including basalt and rhyolite, show little variability and cluster near {delta}{sup 44}Ca = 0 {+-}0.2. Systematic analysis of biological samples indicates that biological processing of calcium discriminates against heavy isotopes, and that biological fractionation is the primary generator of calcium isotopic fractionation in nature. Preliminary data suggest that calcium becomes isotopically lighter as it moves through food chains. Calcium carbonate shells of marine microorganisms and deep-sea carbonate ooze have {delta}{sup 44}Ca about 1.0{per_thousand}, lower than seawater; this fractionation causes seawater to be enriched in heavy calcium ({delta}{sup 44}Ca = +0.9) relative to igneous rocks. Marine organisms consequently are isotopically heavier than their terrestrial counterparts at similar trophic level. The calcium isotopic composition of living and fossil organisms may record information on diet and environment. 22 refs., 3 figs., 2 tabs.

  16. 13C and 15N natural isotope abundance reflects breast cancer cell metabolism

    PubMed Central

    Tea, Illa; Martineau, Estelle; Antheaume, Ingrid; Lalande, Julie; Mauve, Caroline; Gilard, Francoise; Barillé-Nion, Sophie; Blackburn, Anneke C.; Tcherkez, Guillaume

    2016-01-01

    Breast cancer is the most common cancer in women worldwide. Despite the information provided by anatomopathological assessment and molecular markers (such as receptor expression ER, PR, HER2), breast cancer therapies and prognostics depend on the metabolic properties of tumor cells. However, metabolomics have not provided a robust and congruent biomarker yet, likely because individual metabolite contents are insufficient to encapsulate all of the alterations in metabolic fluxes. Here, we took advantage of natural 13C and 15N isotope abundance to show there are isotopic differences between healthy and cancer biopsy tissues or between healthy and malignant cultured cell lines. Isotope mass balance further suggests that these differences are mostly related to lipid metabolism, anaplerosis and urea cycle, three pathways known to be impacted in malignant cells. Our results demonstrate that the isotope signature is a good descriptor of metabolism since it integrates modifications in C partitioning and N excretion altogether. Our present study is thus a starting point to possible clinical applications such as patient screening and biopsy characterization in every cancer that is associated with metabolic changes. PMID:27678172

  17. Modeling stable isotope abundances in atmospheric nitrate using a photochemical box model

    NASA Astrophysics Data System (ADS)

    Mase, D. F.; Michalski, G. M.

    2012-12-01

    NOx is converted into HNO3 in the atmosphere through a complex series of chemical reactions and stable isotopes may be useful for understanding the relative importance of these reactions. Presented here are a series of relatively simple photochemical box model simulations of HNO3 production that utilize stable oxygen and nitrogen isotopes as a tool for understanding the specific chemistry of HNO3 production. These simulations are compared with observations in wet deposition NO3- at 8 National Atmospheric Deposition Program (NADP) sites in the Midwestern US and at several sites in the southwestern US. These comparisons help to address several unanswered questions, including which HNO3-production pathways are the most prevalent and how this prevalence varies in space and time. Additionally, these comparisons lend insights to the role of source and chemistry on nitrogen stable isotope abundances in atmospheric NO3-. The isotope chemical mechanisms can be incorporated into 2D and 3D chemical transport models such as the Community Scale Air Quality model to better understand the chemistry that generates air pollution.

  18. 13C and 15N natural isotope abundance reflects breast cancer cell metabolism

    NASA Astrophysics Data System (ADS)

    Tea, Illa; Martineau, Estelle; Antheaume, Ingrid; Lalande, Julie; Mauve, Caroline; Gilard, Francoise; Barillé-Nion, Sophie; Blackburn, Anneke C.; Tcherkez, Guillaume

    2016-09-01

    Breast cancer is the most common cancer in women worldwide. Despite the information provided by anatomopathological assessment and molecular markers (such as receptor expression ER, PR, HER2), breast cancer therapies and prognostics depend on the metabolic properties of tumor cells. However, metabolomics have not provided a robust and congruent biomarker yet, likely because individual metabolite contents are insufficient to encapsulate all of the alterations in metabolic fluxes. Here, we took advantage of natural 13C and 15N isotope abundance to show there are isotopic differences between healthy and cancer biopsy tissues or between healthy and malignant cultured cell lines. Isotope mass balance further suggests that these differences are mostly related to lipid metabolism, anaplerosis and urea cycle, three pathways known to be impacted in malignant cells. Our results demonstrate that the isotope signature is a good descriptor of metabolism since it integrates modifications in C partitioning and N excretion altogether. Our present study is thus a starting point to possible clinical applications such as patient screening and biopsy characterization in every cancer that is associated with metabolic changes.

  19. Isotopic Measurements of Organic Sulfonates From The Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Cooper, G. W.; Chang, S.; DeVincenzi, Donald L. (Technical Monitor)

    1995-01-01

    Organic sulfonates and phosphonates have been extracted from the Murchison meteorite for stable isotope measurements. Preliminary stable isotope measurements of individual alkyl sulfonates, R-SO3H (R=C(sub n)H(sub 2n+l)), are shown. These compounds were found in aqueous extracts of Murchison. Both groups show trends similar to other homologous series of organic compounds indigenous to Murchison. Molecular abundances decrease with increasing carbon number, and all possible isomers at each carbon number (through C-4) are present. Carbon isotope measurements of the sulfonates show a decrease in the C-13/C-12 ratio with increasing carbon number. The overall objectives of this project are to obtain dime element carbon, hydrogen, and sulfur - intramolecular isotopic analyses of individual sulfonates, and isotopic measurement of carbon and hydrogen of the phosphonates as a group. The Murchison meteorite is the best characterized carbonaceous chondrite with respect to organic chemistry. The finding of organic sulfonates and phosphonates in Murchison is of interest because they are the first well-characterized series of sulfur and phosphorus containing organic compounds found in meteorites. Also, meteorites, comets, and interplanetary dust particles may have been involved in chemical evolution on the early Earth. Because of the critical role of organic phosphorus and sulfur in all living systems, it is particularly interesting to see examples of abiotic syntheses of these classes of compounds. The study of the isotopic composition of the sulfonates and phosphonates can yield insight into their possible interstellar origin as well as their mechanisms of synthesis in the early solar system. Previous isotopic analyses of other classes of organic compounds indigenous to meteorites, e.g., amino acids, carboxylic acids, and hydrocarbons indicate the possibility that interstellar molecules were incorporated into meteorite parent bodies. In these compounds the ratios of heavy to

  20. (n,γ) measurements on radioactive isotopes for astrophysics

    NASA Astrophysics Data System (ADS)

    Reifarth, Rene; Herwig, Falk

    2004-10-01

    Almost all of the heavy elements are produced via neutron capture reactions in a multitude of stellar production sites. Stellar models yield the element production during the quiescent phase as well as the initial configuration for supernova simulations. Their predictive power is currently limited because they contain poorly constrained physics components such as convection, rotation or magnetic fields. With a neutron facility at RIA and a calorimetric γ-ray detector similar to DANCE at LANL we could largely improve these physics components. Neutron captures on heavy radioactive isotopes provide a unique opportunity to largely improve these physics components. The analysis of branch-points of the s-process path in combination with isotopic abundance information from pre-solar meteoritic grains offer a very powerful tool to address important questions of nuclear astrophysics. The astrophysical implications of recent measurements at DANCE and possibilities for future (n,γ) experiments at RIA will be presented during the talk.

  1. Using cosmogenic isotopes to measure basin-scale rates of erosion

    SciTech Connect

    Bierman, P.R.; Steig, E. . Dept. of Geology)

    1992-01-01

    The authors present a new and different approach to interpreting the abundance of in situ-produced cosmogenic nuclides such as [sup 36]Cl, [sup 26]Al, and [sup 10]Be. Unlike most existing models, which are appropriate for evaluating isotope concentrations on bedrock surfaces, this model can be used to interpret isotope concentration in fluvial sediment. Because sediment is a mixture of material derived from the entire drainage basin, measured isotope abundances can be used to estimate spatially-averaged rates of erosion and sediment transport. Their approach has the potential to provide geomorphologists with a relatively simple but powerful means by which to constrain rates of landscape evolution. The model considers the flux of cosmogenic isotopes into and out of various reservoirs. Implicit in model development are the assumptions that a geomorphic steady-state has been reached and that sampled sediment is spatially and temporally representative of all sediment leaving the basin. Each year, the impinging cosmic-ray flux produces a certain quantity of cosmogenic isotopes in the rock and soil of a drainage basin. For a basin in steady state, the outgoing isotope flux is also constant. They solve for the rate of mass loss as a function of isotope abundance in the sediment, the cosmic ray attenuation length, the isotope half life, and the effective isotope production rate. There are only a few published measurements of cosmogenic isotope abundance in sediment. They calculated model denudation rates for sediment samples from Zaire and central Texas. The denudation rates they calculated appear reasonable and are similar to those they have measured directly on granite landforms in Georgia and southeastern California and those calculated for the Appalachian Piedmont.

  2. 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.

  3. Carbon isotope analysis in urea at high 13C-abundances using the 13/12CO2-breath test device FANci2.

    PubMed

    Schmidt, G

    2002-09-01

    The increasing application of 13C-labelled urea in medicine requires simple and reasonable methods for measuring highly enriched C in urea. The combination: ultimate organic analysis--mass spectrometry so far prescribed is complicated and expensive. For medical diagnosis, however, isotope selective nondispersive infrared spectrometers (NDIRS) have been available for many years. One of these tools is FANci2 which is very reasonable and easily to be operated. By means of such devices also urea highly enriched in 13C can be analysed, provided that the samples are first diluted with a defined amount of urea of natural isotopic composition and then transformed into carbon dioxide by means of urease. The relative abundance of 13C in this carbon dioxide, measured by nondispersive infrared spectrometry, is then a measure of the 13C abundance in the initial urea sample. Comparison of results of such measurements with those attained by mass spectrometry proves that this procedure is feasible and yields precis results.

  4. Effectiveness of leaded petrol phase-out in Tianjin, China based on the aerosol lead concentration and isotope abundance ratio.

    PubMed

    Wang, Wan; Liu, Xiande; Zhao, Liwei; Guo, Dongfa; Tian, Xiaodan; Adams, Freddy

    2006-07-01

    The phase-out of leaded petrol has been a measure widely used to reduce atmospheric lead pollution. Since the 1980s, China began to promote unleaded petrol. In order to assess the effectiveness of the measure an isotope fingerprint technique was applied for aerosol samples in the city of Tianjin. After dilute acid leaching, the lead concentration and isotope abundance ratios were determined for 123 samples collected in Tianjin during eight years (1994-2001). The 206Pb/207Pb ratio was lower in summer, when coal combustion emission was low and vehicle exhaust became more important, indicating that the 206Pb/207Pb ratio of leaded petrol in Tianjin is lower than that of aerosol samples. The 206Pb/207Pb ratio gradually increased from 1994 to 2001, a trend that suggests that the contribution from vehicle exhaust was diminishing. Overall, the measurements matched well with national statistical data of leaded and unleaded petrol production. After the nationwide switch to unleaded gasoline, comprehensive control measures are urgently needed to reduce air lead pollution in China, as aerosol lead reduced slightly but remains at a relatively high level.

  5. BENCHMARKING ORTEC ISOTOPIC MEASUREMENTS AND CALCULATIONS

    SciTech Connect

    Dewberry, R; Raymond Sigg, R; Vito Casella, V; Nitin Bhatt, N

    2008-09-29

    This report represents a description of compiled benchmark tests conducted to probe and to demonstrate the extensive utility of the Ortec ISOTOPIC {gamma}-ray analysis computer program. The ISOTOPIC program performs analyses of {gamma}-ray spectra applied to specific acquisition configurations in order to apply finite-geometry correction factors and sample-matrix-container photon absorption correction factors. The analysis program provides an extensive set of preset acquisition configurations to which the user can add relevant parameters in order to build the geometry and absorption correction factors that the program determines from calculus and from nuclear g-ray absorption and scatter data. The Analytical Development Section field nuclear measurement group of the Savannah River National Laboratory uses the Ortec ISOTOPIC analysis program extensively for analyses of solid waste and process holdup applied to passive {gamma}-ray acquisitions. Frequently the results of these {gamma}-ray acquisitions and analyses are to determine compliance with facility criticality safety guidelines. Another use of results is to designate 55-gallon drum solid waste as qualified TRU waste3 or as low-level waste. Other examples of the application of the ISOTOPIC analysis technique to passive {gamma}-ray acquisitions include analyses of standard waste box items and unique solid waste configurations. In many passive {gamma}-ray acquisition circumstances the container and sample have sufficient density that the calculated energy-dependent transmission correction factors have intrinsic uncertainties in the range 15%-100%. This is frequently the case when assaying 55-gallon drums of solid waste with masses of up to 400 kg and when assaying solid waste in extensive unique containers. Often an accurate assay of the transuranic content of these containers is not required, but rather a good defensible designation as >100 nCi/g (TRU waste) or <100 nCi/g (low level solid waste) is required. In

  6. Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositions.

    PubMed

    Zhu, Renbin; Liu, Yashu; Li, Xianglan; Sun, Jianjun; Xu, Hua; Sun, Liguang

    2008-11-01

    Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using in situ field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean delta values of the soil-emitted N2O were delta15N = -13.5 +/- 3.2 per thousand and delta18O = 26.2 +/- 1.4 per thousand for the penguin colony, delta15N = -11.5 +/- 5.1 per thousand and delta18O = 26.4 +/- 3.5 per thousand for the skua colony and delta15N = -18.9 +/- 0.7 per thousand and delta18O = 28.8 +/- 1.3 per thousand for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93 microg N2O--N kg(-1)). Under N2 conditions, much more N2O was formed (9.74 microg N2O--N kg(-1)), and the mean delta15N and delta18O values of N2O were -19.1 +/- 8.0 per thousand and 21.3 +/- 4.3 per thousand, respectively, from penguin colony soils, and -17.0 +/- 4.2 per thousand and 20.6 +/- 3.5 per thousand, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the

  7. High resolution measurements of galactic cosmic-ray neon, magnesium, and silicon isotopes

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Spalding, J. D.; Stone, E. C.; Vogt, R. E.

    1980-01-01

    High-resolution measurements of the abundances of individual isotopes of neon, magnesium and silicon in galactic cosmic rays are reported. The Caltech Heavy Isotope Spectrometer Telescope on board the ISEE 3 spacecraft was used to obtain measurements in the range 30 to 180 MeV/n at an rms mass resolution of 0.20 amu. Results indicate excesses of Ne-22 as well as Mg-25 and Mg-26 in galactic cosmic rays with respect to their solar system abundances. Calculations of the effects of interstellar propagation and solar modulation on cosmic-ray isotope abundances also imply an Mg-25 + Mg-26 cosmic ray source fraction significantly greater than the solar system fraction, and it is suggested that the cosmic ray source material and solar system material were synthesized under different conditions.

  8. Abundance, distribution, and isotopic composition of particulate black carbon in the northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Guo, Laodong

    2014-11-01

    There exists increasing evidence supporting the important role of black carbon in global carbon cycles. Particulate black carbon (PBC) is allochthonous and has distinct reactivities compared to the bulk particulate organic carbon (tot-POC) in marine environments. However, the abundance, geochemical behavior of PBC and its importance in oceanic carbon budget remain poorly understood. Here we report the abundance, distribution, and stable isotopic signatures of BC derived from the chemo-thermal oxidation (CTO-375) method (BCCTO) in the Gulf of Mexico. Our results show that BCCTO abundance decreased from shelf to basin, and more than a half of riverine BCCTO could be removed over the shelf. Moreover, BCCTO is much more refractory compared to the tot-POC and has δ13C values lower than those of BC-excluded POC. These results highlight the significance of PBC in marine carbon cycles and potentially suggest the need for a new end-member term in quantifying POC sources in the ocean.

  9. Natural isotope correction of MS/MS measurements for metabolomics and (13)C fluxomics.

    PubMed

    Niedenführ, Sebastian; ten Pierick, Angela; van Dam, Patricia T N; Suarez-Mendez, Camilo A; Nöh, Katharina; Wahl, S Aljoscha

    2016-05-01

    Fluxomics and metabolomics are crucial tools for metabolic engineering and biomedical analysis to determine the in vivo cellular state. Especially, the application of (13)C isotopes allows comprehensive insights into the functional operation of cellular metabolism. Compared to single MS, tandem mass spectrometry (MS/MS) provides more detailed and accurate measurements of the metabolite enrichment patterns (tandem mass isotopomers), increasing the accuracy of metabolite concentration measurements and metabolic flux estimation. MS-type data from isotope labeling experiments is biased by naturally occurring stable isotopes (C, H, N, O, etc.). In particular, GC-MS(/MS) requires derivatization for the usually non-volatile intracellular metabolites introducing additional natural isotopes leading to measurements that do not directly represent the carbon labeling distribution. To make full use of LC- and GC-MS/MS mass isotopomer measurements, the influence of natural isotopes has to be eliminated (corrected). Our correction approach is analyzed for the two most common applications; (13)C fluxomics and isotope dilution mass spectrometry (IDMS) based metabolomics. Natural isotopes can have an impact on the calculated flux distribution which strongly depends on the substrate labeling and the actual flux distribution. Second, we show that in IDMS based metabolomics natural isotopes lead to underestimated concentrations that can and should be corrected with a nonlinear calibration. Our simulations indicate that the correction for natural abundance in isotope based fluxomics and quantitative metabolomics is essential for correct data interpretation.

  10. Preliminary results of oxygen isotope ratio measurement with a particle-gamma coincidence method

    NASA Astrophysics Data System (ADS)

    Borysiuk, Maciek; Kristiansson, Per; Ros, Linus; Abdel, Nassem S.; Elfman, Mikael; Nilsson, Charlotta; Pallon, Jan

    2015-04-01

    The possibility to study variations in the oxygen isotopic ratio with photon tagged nuclear reaction analysis (pNRA) is evaluated in the current work. The experiment described in the article was performed at Lund Ion Beam Analysis Facility (LIBAF) with a 2 MeV deuteron beam. Isotopic fractionation of light elements such as carbon, oxygen and nitrogen is the basis of many analytical tools in hydrology, geology, paleobiology and paleogeology. IBA methods provide one possible tool for measurement of isotopic content. During this experimental run we focused on measurement of the oxygen isotopic ratio. The measurement of stable isotopes of oxygen has a number of applications; the particular one driving the current investigation belongs to the field of astrogeology and specifically evaluation of fossil extraterrestrial material. There are three stable isotopes of oxygen: 16O, 17O and 18O. We procured samples highly enriched with all three isotopes. Isotopes 16O and 18O were easily detected in the enriched samples, but no significant signal from 17O was detected in the same samples. The measured yield was too low to detect 18O in a sample with natural abundances of oxygen isotopes, at least in the current experimental setup, but the spectral line from the reaction with 16O was clearly visible.

  11. Natural isotope correction of MS/MS measurements for metabolomics and (13)C fluxomics.

    PubMed

    Niedenführ, Sebastian; ten Pierick, Angela; van Dam, Patricia T N; Suarez-Mendez, Camilo A; Nöh, Katharina; Wahl, S Aljoscha

    2016-05-01

    Fluxomics and metabolomics are crucial tools for metabolic engineering and biomedical analysis to determine the in vivo cellular state. Especially, the application of (13)C isotopes allows comprehensive insights into the functional operation of cellular metabolism. Compared to single MS, tandem mass spectrometry (MS/MS) provides more detailed and accurate measurements of the metabolite enrichment patterns (tandem mass isotopomers), increasing the accuracy of metabolite concentration measurements and metabolic flux estimation. MS-type data from isotope labeling experiments is biased by naturally occurring stable isotopes (C, H, N, O, etc.). In particular, GC-MS(/MS) requires derivatization for the usually non-volatile intracellular metabolites introducing additional natural isotopes leading to measurements that do not directly represent the carbon labeling distribution. To make full use of LC- and GC-MS/MS mass isotopomer measurements, the influence of natural isotopes has to be eliminated (corrected). Our correction approach is analyzed for the two most common applications; (13)C fluxomics and isotope dilution mass spectrometry (IDMS) based metabolomics. Natural isotopes can have an impact on the calculated flux distribution which strongly depends on the substrate labeling and the actual flux distribution. Second, we show that in IDMS based metabolomics natural isotopes lead to underestimated concentrations that can and should be corrected with a nonlinear calibration. Our simulations indicate that the correction for natural abundance in isotope based fluxomics and quantitative metabolomics is essential for correct data interpretation. PMID:26479486

  12. Measurement of Plutonium Isotopic Composition - MGA

    SciTech Connect

    Vo, Duc Ta

    2015-08-21

    In this module, we will use the Canberra InSpector-2000 Multichannel Analyzer with a high-purity germanium detector (HPGe) and the MGA isotopic anlysis software to assay a variety of plutonium samples. The module provides an understanding of the MGA method, its attributes and limitations. You will assess the system performance by measuring a range of materials similar to those you may assay in your work. During the final verification exercise, the results from MGA will be combined with the 240Pueff results from neutron coincidence or multiplicity counters so that measurements of the plutonium mass can be compared with the operator-declared (certified) values.

  13. A Comparison of Stellar Elemental Abundance Techniques and Measurements

    NASA Astrophysics Data System (ADS)

    Hinkel, Natalie R.; Young, Patrick A.; Pagano, Michael D.; Desch, Steven J.; Anbar, Ariel D.; Adibekyan, Vardan; Blanco-Cuaresma, Sergi; Carlberg, Joleen K.; Delgado Mena, Elisa; Liu, Fan; Nordlander, Thomas; Sousa, Sergio G.; Korn, Andreas; Gruyters, Pieter; Heiter, Ulrike; Jofré, Paula; Santos, Nuno C.; Soubiran, Caroline

    2016-09-01

    Stellar elemental abundances are important for understanding the fundamental properties of a star or stellar group, such as age and evolutionary history, as well as the composition of an orbiting planet. However, as abundance measurement techniques have progressed, there has been little standardization between individual methods and their comparisons. As a result, different stellar abundance procedures determine measurements that vary beyond the quoted error for the same elements within the same stars. The purpose of this paper is to better understand the systematic variations between methods and offer recommendations for producing more accurate results in the future. We invited a number of participants from around the world (Australia, Portugal, Sweden, Switzerland, and the United States) to calculate 10 element abundances (C, O, Na, Mg, Al, Si, Fe, Ni, Ba, and Eu) using the same stellar spectra for four stars (HD 361, HD 10700, HD 121504, and HD 202206). Each group produced measurements for each star using (1) their own autonomous techniques, (2) standardized stellar parameters, (3) a standardized line list, and (4) both standardized parameters and a line list. We present the resulting stellar parameters, absolute abundances, and a metric of data similarity that quantifies the homogeneity of the data. We conclude that standardization of some kind, particularly stellar parameters, improves the consistency between methods. However, because results did not converge as more free parameters were standardized, it is clear there are inherent issues within the techniques that need to be reconciled. Therefore, we encourage more conversation and transparency within the community such that stellar abundance determinations can be reproducible as well as accurate and precise.

  14. Determining Mineral Types and Abundances from Reflectance Measurements

    NASA Technical Reports Server (NTRS)

    Smith, M. O.; Adams, J. B.

    1985-01-01

    Mineral types and their abundances were quantitatively determined from laboratory reflectance spectra using principal components analysis (PCA). PCA reduced the measured spectral dimensionality and allowed testing the uniqueness and validity of spectral mixing models. In addition to interpreting absorption bands, in this new approach we interpreted variations in the overall spectral curves in terms of physical processes, namely changes in mixtures of minerals, in particle size and in illumination geometry. Application of this approach to reflectances of planetary surfaces allows interpretation to be extended to quantitative determinations of mineral types and abundances.

  15. 4He abundances: Optical versus radio recombination line measurements

    NASA Astrophysics Data System (ADS)

    Balser, Dana S.; Rood, Robert T.; Bania, T. M.

    2010-04-01

    Accurate measurements of the 4He/H abundance ratio are important in constraining Big Bang nucleosynthesis, models of stellar and Galactic evolution, and H ii region physics. We discuss observations of radio recombination lines using the Green Bank Telescope toward a small sample of H ii regions and planetary nebulae. We report 4He/H abundance ratio differences as high as 15-20% between optical and ratio data that are difficult to reconcile. Using the H ii regions S206 and M17 we determine 4He production in the Galaxy to be dY/dZ = 1.71 ± 0.86.

  16. Nuclear abundance measurements inside MIR and ISS with Sileye experiments

    NASA Astrophysics Data System (ADS)

    Casolino, M.

    In this work we present measurements of cosmic ray nuclear abundances above 150 MeV/n performed inside Mir space station between 1998 and 2000. Data have been obtained with SilEye-2 detector, a 6 plane silicon strip detector telescope designed to measure environmental radiation and investigate on the Light Flash phenomenon. In standalone mode, SilEye-2 is capable to measure LET distribution spectra and identify nuclear species with energy above 100 MeV/n: a total of 100 sessions comprising more than 1000 hours of observation were perfomed in the years 1998-2000, recording also several Solar Energetic Particle (SEP) events. Cosmic ray abundances inside a spacecraft can differ from the primary component due to interaction with the interposed material of the hull and the instruments. We report on LET measurements and relative abundances from Boron to Iron measured in different regions and at different geomagnetic cutoffs, in solar quiet conditions and during SEP events, showing how the composition varies in these different situations. We also report on preliminary results on cosmic ray measurements inside ISS (27/4/2002 - 4/5/2002) obtained with Sileye-3/Alteino experiment.

  17. Measurement scale in maximum entropy models of species abundance

    PubMed Central

    Frank, Steven A.

    2010-01-01

    The consistency of the species abundance distribution across diverse communities has attracted widespread attention. In this paper, I argue that the consistency of pattern arises because diverse ecological mechanisms share a common symmetry with regard to measurement scale. By symmetry, I mean that different ecological processes preserve the same measure of information and lose all other information in the aggregation of various perturbations. I frame these explanations of symmetry, measurement, and aggregation in terms of a recently developed extension to the theory of maximum entropy. I show that the natural measurement scale for the species abundance distribution is log-linear: the information in observations at small population sizes scales logarithmically and, as population size increases, the scaling of information grades from logarithmic to linear. Such log-linear scaling leads naturally to a gamma distribution for species abundance, which matches well with the observed patterns. Much of the variation between samples can be explained by the magnitude at which the measurement scale grades from logarithmic to linear. This measurement approach can be applied to the similar problem of allelic diversity in population genetics and to a wide variety of other patterns in biology. PMID:21265915

  18. Mass spectrometric measurements of the isotopic anatomies of molecules (Invited)

    NASA Astrophysics Data System (ADS)

    Eiler, J. M.; Krumwiede, D.; Schlueter, H.

    2013-12-01

    Site-specific and multiple isotopic substitutions in molecular structures potentially provide an extraordinarily rich set of constraints on their sources, conditions of formation, reaction and transport histories, and perhaps other issues. Examples include carbonate ';clumped isotope' thermometry, clumped isotope measurements of CO2, O2, and, recently, methane, ethane and N2O; site-specific 15N measurements in N2O and 13C and D analyses of fatty acids, sugars, cellulose, food products, and, recently, n-alkanes. Extension of the principles behind these tools to the very large number of isotopologues of complex molecules could potentially lead to new uses of isotope chemistry, similar to proteomics, metabolomics and genomics in their complexity and depth of detail (';isotomics'?). Several technologies are potentially useful for this field, including ';SNIF-NMR', gas source mass spectrometry and IR absorption spectroscopy. However, all well established methods have restrictive limits in the sizes of samples, types of analyzes, and the sorts of isotopologues that can be measured with useful precision. We will present an overview of several emerging instruments and techniques of high-resolution gas source mass spectrometry that may enable study of a large proportion of the isotopologues of a wide range of volatile and semi-volatile compounds, including many organics, with precisions and sample sizes suitable for a range of applications. A variety of isotopologues can be measured by combining information from the Thermo 253 Ultra (a new high resolution, multi-collector gas source mass spectrometer) and the Thermo DFS (a very high resolution single collector, but used here on a novel mode to achieve ~per mil precision ratio measurements), sometimes supplemented by conventional bulk isotopic measurements. It is possible to design methods in which no one of these sources of data meaningfully constrain abundances of specific isotopologues, but their combination fully and

  19. DANCEing with the Stars: Measuring Neutron Capture on Unstable Isotopes with DANCE

    NASA Astrophysics Data System (ADS)

    Couture, A.; Agvaanluvsan, U.; Baker, J. D.; Bayarbadrahk, B.; Becker, J. A.; Bond, E.; Bredeweg, T. A.; Chyzh, A.; Dashdorj, D.; Fowler, M.; Haight, R. C.; Jandel, M.; Keksis, A. L.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.

    2009-03-01

    Isotopes heavier than iron are known to be produced in stars through neutron capture processes. Two major processes, the slow (s) and rapid (r) processes are each responsible for 50% of the abundances of the heavy isotopes. The neutron capture cross sections of the isotopes on the s process path reveal information about the expected abundances of the elements as well as stellar conditions and dynamics. Until recently, measurements on unstable isotopes, which are most important for determining stellar temperatures and reaction flow, have not been experimentally feasible. The Detector for Advance Neutron Capture Experiments (DANCE) located at the Los Alamos Neutron Science Center (LANSCE) was designed to perform time-of-flight neutron capture measurements on unstable isotopes for nuclear astrophysics, stockpile stewardship, and reactor development. DANCE is a 4-π BaF2 scintillator array which can perform measurements on sub-milligram samples of isotopes with half-lives as short as a few hundred days. These cross sections are critical for advancing our understanding of the production of the heavy isotopes.

  20. DANCEing with the Stars: Measuring Neutron Capture on Unstable Isotopes with DANCE

    SciTech Connect

    Couture, A.; Bond, E.; Bredeweg, T. A.; Fowler, M.; Haight, R. C.; Jandel, M.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Agvaanluvsan, U.; Becker, J. A.; Baker, J. D.; Bayarbadrahk, B.; Chyzh, A.; Dashdorj, D.; Reifarth, R.

    2009-03-10

    Isotopes heavier than iron are known to be produced in stars through neutron capture processes. Two major processes, the slow (s) and rapid (r) processes are each responsible for 50% of the abundances of the heavy isotopes. The neutron capture cross sections of the isotopes on the s process path reveal information about the expected abundances of the elements as well as stellar conditions and dynamics. Until recently, measurements on unstable isotopes, which are most important for determining stellar temperatures and reaction flow, have not been experimentally feasible. The Detector for Advance Neutron Capture Experiments (DANCE) located at the Los Alamos Neutron Science Center (LANSCE) was designed to perform time-of-flight neutron capture measurements on unstable isotopes for nuclear astrophysics, stockpile stewardship, and reactor development. DANCE is a 4-{pi}BaF{sub 2} scintillator array which can perform measurements on sub-milligram samples of isotopes with half-lives as short as a few hundred days. These cross sections are critical for advancing our understanding of the production of the heavy isotopes.

  1. Light Isotope Abundances in SEPS measured by NINA

    NASA Astrophysics Data System (ADS)

    Sparvoli, R.; Bidoli, V.; Casolino, M.; De Pascale, M.; Furano, G.; Iannucci, A.; Morselli, A.; Picozza, P.; Bakaldin, A.; Galper, A.; Koldashov, S.; Korotkov, M.; Leonov, A.; Mikhailov, V.; Murashov, A.; Voronov, S.; Boezio, M.; Bonvicini, V.; Cirami, R.; Vacchi, A.; Zampa, N.; Ambriola, M.; Bellotti, R.; Cafagna, F.; Ciacio, F.; Circella, M.; De Marzo, C.; Adriani, O.; Papini, P.; Spillantini, P.; Straulino, S.; Vannuccini, E.; Bartalucci, S.; Ricci, M.; Castellini, G.; Wizard-NINA Collaboration

    2001-08-01

    Observations of 9 Solar Energetic Particle events detected by the instrument NINA from November 1998 to April 1999 will be presented. NINA is a silicon-based space detector in orbit since July 1998 on board the Russian satellite Resurs-01-N4, which flies at low altitude (about 800 km) in polar inclination. For every SEP event we reconstructed the power-law 4 He spectrum in the energy interval 10-50 MeV/n, extracting spectral indexes from 1.8 to 6.8. Data of 3 He and 4 He were then employed to determine the 3 He/4 He ratio, that turned out to be high for some SEP events showing the enrichment in 3 He. For the 7 November 1998 event this ratio reached the maximum value of 0.33 ± 0.06, with spectral indexes 2.5 ± 0.6 and 3.7 ± 0.3 for 3 He and 4 He, respectively. The 3 He/4 He ratio averaged over the remaining events was 0.011 ± 0.004. For all events we determined the deuterium-to-proton ratio. The average value of the 2 H/1 H ratio, over all events, was (3.9±1.4)× 10-5 in the energy interval 9-12 MeV/n. During 24 November 1998 event, however, this ratio resulted about 10 times higher than normal coronal values.

  2. Abundance and isotopic composition of gases in the martian atmosphere from the Curiosity rover.

    PubMed

    Mahaffy, Paul R; Webster, Christopher R; Atreya, Sushil K; Franz, Heather; Wong, Michael; Conrad, Pamela G; Harpold, Dan; Jones, John J; Leshin, Laurie A; Manning, Heidi; Owen, Tobias; Pepin, Robert O; Squyres, Steven; Trainer, Melissa

    2013-07-19

    Volume mixing and isotope ratios secured with repeated atmospheric measurements taken with the Sample Analysis at Mars instrument suite on the Curiosity rover are: carbon dioxide (CO2), 0.960(±0.007); argon-40 ((40)Ar), 0.0193(±0.0001); nitrogen (N2), 0.0189(±0.0003); oxygen, 1.45(±0.09) × 10(-3); carbon monoxide, < 1.0 × 10(-3); and (40)Ar/(36)Ar, 1.9(±0.3) × 10(3). The (40)Ar/N2 ratio is 1.7 times greater and the (40)Ar/(36)Ar ratio 1.6 times lower than values reported by the Viking Lander mass spectrometer in 1976, whereas other values are generally consistent with Viking and remote sensing observations. The (40)Ar/(36)Ar ratio is consistent with martian meteoritic values, which provides additional strong support for a martian origin of these rocks. The isotopic signature δ(13)C from CO2 of ~45 per mil is independently measured with two instruments. This heavy isotope enrichment in carbon supports the hypothesis of substantial atmospheric loss.

  3. Abundance and isotopic composition of gases in the martian atmosphere from the Curiosity rover.

    PubMed

    Mahaffy, Paul R; Webster, Christopher R; Atreya, Sushil K; Franz, Heather; Wong, Michael; Conrad, Pamela G; Harpold, Dan; Jones, John J; Leshin, Laurie A; Manning, Heidi; Owen, Tobias; Pepin, Robert O; Squyres, Steven; Trainer, Melissa

    2013-07-19

    Volume mixing and isotope ratios secured with repeated atmospheric measurements taken with the Sample Analysis at Mars instrument suite on the Curiosity rover are: carbon dioxide (CO2), 0.960(±0.007); argon-40 ((40)Ar), 0.0193(±0.0001); nitrogen (N2), 0.0189(±0.0003); oxygen, 1.45(±0.09) × 10(-3); carbon monoxide, < 1.0 × 10(-3); and (40)Ar/(36)Ar, 1.9(±0.3) × 10(3). The (40)Ar/N2 ratio is 1.7 times greater and the (40)Ar/(36)Ar ratio 1.6 times lower than values reported by the Viking Lander mass spectrometer in 1976, whereas other values are generally consistent with Viking and remote sensing observations. The (40)Ar/(36)Ar ratio is consistent with martian meteoritic values, which provides additional strong support for a martian origin of these rocks. The isotopic signature δ(13)C from CO2 of ~45 per mil is independently measured with two instruments. This heavy isotope enrichment in carbon supports the hypothesis of substantial atmospheric loss. PMID:23869014

  4. Penning trap mass measurements on nobelium isotopes

    SciTech Connect

    Dworschak, M.; Block, M.; Ackermann, D.; Herfurth, F.; Hessberger, F. P.; Hofmann, S.; Vorobyev, G. K.; Audi, G.; Blaum, K.; Droese, C.; Marx, G.; Schweikhard, L.; Eliseev, S.; Ketter, J.; Fleckenstein, T.; Haettner, E.; Plass, W. R.; Scheidenberger, C.; Ketelaer, J.; Kluge, H.-J.

    2010-06-15

    The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes {sup 252-254}No were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a {sup 48}Ca beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

  5. Penning trap mass measurements on nobelium isotopes

    NASA Astrophysics Data System (ADS)

    Dworschak, M.; Block, M.; Ackermann, D.; Audi, G.; Blaum, K.; Droese, C.; Eliseev, S.; Fleckenstein, T.; Haettner, E.; Herfurth, F.; Heßberger, F. P.; Hofmann, S.; Ketelaer, J.; Ketter, J.; Kluge, H.-J.; Marx, G.; Mazzocco, M.; Novikov, Yu. N.; Plaß, W. R.; Popeko, A.; Rahaman, S.; Rodríguez, D.; Scheidenberger, C.; Schweikhard, L.; Thirolf, P. G.; Vorobyev, G. K.; Wang, M.; Weber, C.

    2010-06-01

    The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes No252-254 were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a Ca48 beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

  6. Evaluation of strontium isotope abundance ratios in combination with multi-elemental analysis as a possible tool to study the geographical origin of ciders.

    PubMed

    García-Ruiz, Silvia; Moldovan, Mariella; Fortunato, Giuseppino; Wunderli, Samuel; García Alonso, J Ignacio

    2007-05-01

    In order to evaluate alternative analytical methodologies to study the geographical origin of ciders, both multi-elemental analysis and Sr isotope abundance ratios in combination with multivariate statistical analysis were estimated in 67 samples from England, Switzerland, France and two Spanish regions (Asturias and the Basque Country). A methodology for the precise and accurate determination of the (87)Sr/(86)Sr isotope abundance ratio in ciders by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. Major elements (Na, K, Ca and Mg) were measured by ICP-AES and minor and trace elements (Li, Be, B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Sb, Cs, Ba, La, Ce, W, Tl, Pb, Bi, Th and U) were measured by ICP-MS using a collision cell instrument operated in multitune mode. An analysis of variance (ANOVA test) indicated that group means for B, Cr, Fe, Ni, Cu, Se, Cd, Cs, Ce, W, Pb, Bi and U did not show any significant differences at the 95% confidence level, so these elements were rejected for further statistical analysis. Another group of elements (Li, Be, Sc, Co, Ga, Y, Sn, Sb, La, Tl, Th) was removed from the data set because concentrations were close to the limits of detection for many samples. Therefore, the remaining elements (Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba) together with (87)Sr/(86)Sr isotope abundance ratio were considered for principal component analysis (PCA) and linear discriminant analysis (LDA). Finally, LDA was able to classify correctly 100% of cider samples coming from different Spanish regions, France, England and Switzerland when considering Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba and (87)Sr/(86)Sr isotope abundance ratio as original variables. PMID:17416223

  7. 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 ...

  8. Old Masters' lead white pigments: investigations of paintings from the 16th to the 17th century using high precision lead isotope abundance ratios.

    PubMed

    Fortunato, G; Ritter, A; Fabian, D

    2005-06-01

    White lead (2PbCO(3).Pb(OH)(2)), a common component in 17c. artists' painting materials, was singled out to investigate the potential of lead isotope abundance ratios in the field of authentication and origin assignment. Paintings by Peter Paul Rubens, Anthony van Dyck and other Old Masters of the Northern and Southern schools were chosen for this study. An interdisciplinary approach was chosen using both analytical instrumental methods, art technological and art historical knowledge. Minute samples taken from paintings from selected art collections worldwide were investigated using mass spectrometry, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The high precision lead isotope abundance ratios were measured by multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The determination of the calcium matrix influence with respect to possible bias effects to the isotope ratios gave clear decision support, to whether a result lies within the stated combined measurement uncertainty of the result, to eliminate time-consuming matrix separations. The scatter plots of the measured isotope abundance ratios for the painting pigments from P. P. Rubens, A. van Dyck and other Flemish painters exhibit a very narrow distribution forming a cluster. The range of the measured ratio (206)Pb/(204)Pb amounts to 0.55% and for the ratio (207)Pb/(204)Pb to 0.2%. The comparison of the data to cis-alpine (Italian) sample pigments from paintings from the same time period reveals a clear distinction between the two fields. With respect to the lead isotope data originating from the ores it is assumed that the pigment isotope ratio distribution can be explained by very distinct origin of raw materials. Presumably, no mixing of different lead ores from Europe took place. The comparison of the measured white lead isotope ratio values (Flemish paintings) and the data from ore samples led to the unexpected conclusion that local ores were not

  9. The Determination of the Natural Abundance of the Isotopes of Chlorine: An Introductory Experiment in Mass Spectrometry.

    ERIC Educational Resources Information Center

    O'Malley, Rebecca M.

    1982-01-01

    Describes a laboratory experiment which introduces basic principles and experimental techniques of mass spectrometry for fourth year undergraduate (B.Sc.) students. Laboratory procedures, background information, and discussion of results are provided for the experiment in which the natural isotopic abundance of chlorine is determined. (Author/JN)

  10. Siderophile and chalcophile element abundances in oceanic basalts, Pb isotope evolution and growth of the earth's core

    NASA Technical Reports Server (NTRS)

    Newsom, H. E.; White, W. M.; Jochum, K. P.; Hofmann, A. W.

    1986-01-01

    The hypothesis that the mantle Pb isotope ratios reflect continued extraction of Pb into the earth's core over geologic time is evaluated by studying the depeletion of chalcophile and siderophile elements in the mantle. Oceanic basalt samples are analyzed in order to determine the Pb, Sr, and Nd isotropic compositions and the abundances of siderophile and chalcophile elements and incompatible lithophile elements. The data reveal that there is no systematic variation of siderophile or chalcophile element abundances relative to abundances of lithophile elements and the Pb/Ce ratio of the mantle is constant. It is suggested that the crust formation involves nonmagmatic and magmatic processes.

  11. The origin of aubrites: Evidence from lithophile trace element abundances and oxygen isotope compositions

    NASA Astrophysics Data System (ADS)

    Barrat, J. A.; Greenwood, R. C.; Keil, K.; Rouget, M. L.; Boesenberg, J. S.; Zanda, B.; Franchi, I. A.

    2016-11-01

    We report the abundances of a selected set of "lithophile" trace elements (including lanthanides, actinides and high field strength elements) and high-precision oxygen isotope analyses of a comprehensive suite of aubrites. Two distinct groups of aubrites can be distinguished: (a) the main-group aubrites display flat or light-REE depleted REE patterns with variable Eu and Y anomalies; their pyroxenes are light-REE depleted and show marked negative Eu anomalies; (b) the Mount Egerton enstatites and the silicate fraction from Larned display distinctive light-REE enrichments, and high Th/Sm ratios; Mount Egerton pyroxenes have much less pronounced negative Eu anomalies than pyroxenes from the main-group aubrites. Leaching experiments were undertaken to investigate the contribution of sulfides to the whole rock budget of the main-group aubrites. Sulfides contain in most cases at least 50% of the REEs and of the actinides. Among the elements we have analyzed, those displaying the strongest lithophile behaviors are Rb, Ba, Sr and Sc. The homogeneity of the Δ17O values obtained for main-group aubrite falls [Δ17O = +0.009 ± 0.010‰ (2σ)] suggests that they originated from a single parent body whose differentiation involved an early phase of large-scale melting that may have led to the development of a magma ocean. This interpretation is at first glance in agreement with the limited variability of the shapes of the REE patterns of these aubrites. However, the trace element concentrations of their phases cannot be used to discuss this hypothesis, because their igneous trace-element signatures have been modified by subsolidus exchange. Finally, despite similar O isotopic compositions, the marked light-REE enrichments displayed by Mount Egerton and Larned suggest that they are unrelated to the main-group aubrites and probably originated from a distinct parent body.

  12. Measuring β-diversity with species abundance data.

    PubMed

    Barwell, Louise J; Isaac, Nick J B; Kunin, William E

    2015-07-01

    Baselga R turn , βBaselga B-C turn and βsim measured purely species turnover and were independent of nestedness. Among the other metrics, sensitivity to nestedness varied >4-fold. Our results indicate large amounts of redundancy among existing β-diversity metrics, whilst the estimation of unseen shared and unshared species is lacking and should be addressed in the design of new abundance-based metrics. PMID:25732937

  13. Measuring β-diversity with species abundance data.

    PubMed

    Barwell, Louise J; Isaac, Nick J B; Kunin, William E

    2015-07-01

    Baselga R turn , βBaselga B-C turn and βsim measured purely species turnover and were independent of nestedness. Among the other metrics, sensitivity to nestedness varied >4-fold. Our results indicate large amounts of redundancy among existing β-diversity metrics, whilst the estimation of unseen shared and unshared species is lacking and should be addressed in the design of new abundance-based metrics.

  14. Scale-dependent linkages between nitrate isotopes and denitrification in surface soils: implications for isotope measurements and models.

    PubMed

    Hall, Steven J; Weintraub, Samantha R; Bowling, David R

    2016-08-01

    Natural abundance nitrate (NO3 (-)) isotopes represent a powerful tool for assessing denitrification, yet the scale and context dependence of relationships between isotopes and denitrification have received little attention, especially in surface soils. We measured the NO3 (-) isotope compositions in soil extractions and lysimeter water from a semi-arid meadow and lawn during snowmelt, along with the denitrification potential, bulk O2, and a proxy for anaerobic microsites. Denitrification potential varied by three orders of magnitude and the slope of δ(18)O/δ(15)N in soil-extracted NO3 (-) from all samples measured 1.04 ± 0.12 (R (2) = 0.64, p < 0.0001), consistent with fractionation from denitrification. However, δ(15)N of extracted NO3 (-) was often lower than bulk soil δ(15)N (by up to 24 ‰), indicative of fractionation during nitrification that was partially overprinted by denitrification. Mean NO3 (-) isotopes in lysimeter water differed from soil extractions by up to 19 ‰ in δ(18)O and 12 ‰ in δ(15)N, indicating distinct biogeochemical processing in relatively mobile water versus soil microsites. This implies that NO3 (-) isotopes in streams, which are predominantly fed by mobile water, do not fully reflect terrestrial soil N cycling. Relationships between potential denitrification and δ(15)N of extracted NO3 (-) showed a strong threshold effect culminating in a null relationship at high denitrification rates. Our observations of (1) competing fractionation from nitrification and denitrification in redox-heterogeneous surface soils, (2) large NO3 (-) isotopic differences between relatively immobile and mobile water pools, (3) and the spatial dependence of δ(18)O/δ(15)N relationships suggest caution in using NO3 (-) isotopes to infer site or watershed-scale patterns in denitrification.

  15. [Humus composition and stable carbon isotope natural abundance in paddy soil under long-term fertilization].

    PubMed

    Ma, Li; Yang, Lin-Zhang; Ci, En; Wang, Yan; Yin, Shi-Xue; Shen, Ming-Xing

    2008-09-01

    Soil samples were collected from an experimental paddy field with long-term (26 years) fertilization in Taihu Lake region of Jiangsu Province to study the effects of different fertilization on the organic carbon distribution and stable carbon isotope natural abundance (delta 13C) in the soil profile, and on the humus composition. The results showed that long-term fertilization increased the organic carbon content in top soil significantly, and there was a significantly negative exponential correlation between soil organic carbon content and soil depth (P < 0.01). The organic carbon content in 10-30 cm soil layer under chemical fertilizations and in 20-40 cm soil layer under organic fertilizations was relatively stable. Soil delta 13C increased gradually with soil depth, its variation range being from -24% per thousand to -28 per thousand, and had a significantly negative linear correlation with soil organic carbon content (P < 0.05). In 0-20 cm soil layer, the delta 13C in treatments organic manure (M), M + NP, M + NPK, M + straw (R) + N, and R + N decreased significantly; while in 30-50 cm soil layer, the delta 13C in all organic fertilization treatments except R + N increased significantly. Tightly combined humus (humin) was the main humus composition in the soil, occupying 50% or more, and the rest were loosely and stably combined humus. Long-term fertilization increased the content of loosely combined humus and the ratio of humic acid (HA) to fulvic acid (FA).

  16. Airborne Measurements of Coarse Mode Aerosol Composition and Abundance

    NASA Astrophysics Data System (ADS)

    Froyd, K. D.; Murphy, D. M.; Brock, C. A.; Ziemba, L. D.; Anderson, B. E.; Wilson, J. C.

    2015-12-01

    Coarse aerosol particles impact the earth's radiative balance by direct scattering and absorption of light and by promoting cloud formation. Modeling studies suggest that coarse mode mineral dust and sea salt aerosol are the dominant contributors to aerosol optical depth throughout much of the globe. Lab and field studies indicate that larger aerosol particles tend to be more efficient ice nuclei, and recent airborne measurements confirm the dominant role of mineral dust on cirrus cloud formation. However, our ability to simulate coarse mode particle abundance in large scale models is limited by a lack of validating measurements above the earth's surface. We present airborne measurements of coarse mode aerosol abundance and composition over several mid-latitude, sub-tropical, and tropical regions from the boundary layer to the stratosphere. In the free troposphere the coarse mode constitutes 10-50% of the total particulate mass over a wide range of environments. Above North America mineral dust typically dominates the coarse mode, but biomass burning particles and sea salt also contribute. In remote environments coarse mode aerosol mainly consists of internally mixed sulfate-organic particles. Both continental and marine convection can enhance coarse aerosol mass through direct lofting of primary particles and by secondary accumulation of aerosol material through cloud processing.

  17. Constraints on Galactic Cosmic-Ray Origins from Elemental and Isotopic Composition Measurements

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Christian, E. R.; Cummings, A. C.; deNolfo, G. A.; Israel, M. H.; Leske, R. A.; Mewaldt, R. A,; Stone, E. C.; vonRosevinge, T. T.; Wiedenbeck, M. E.

    2013-01-01

    The most recent measurements by the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) satellite of ultra-heavy cosmic ray isotopic and elemental abundances will be presented. A range of isotope and element ratios, most importantly Ne-22/Ne-20, Fe-58/Fe-56, and Ga-31/Ge -32 show that the composition is consistent with source material that is a mix of approx 80% ISM (with Solar System abundances) and 20% outflow/ejecta from massive stars. In addition, our data show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to an approx 80%/20% mix rather than pure ISM, that the refractory and volatile elements have similar slopes, and that refractory elements are preferentially accelerated by a factor of approx 4. We conclude that these data are consistent with an OB association origin of GCRs.

  18. Uranium Isotopic Ratio Measurements of U3O8 Reference Materials by Atom Probe Tomography

    SciTech Connect

    Fahey, Albert J.; Perea, Daniel E.; Bartrand, Jonah AG; Arey, Bruce W.; Thevuthasan, Suntharampillai

    2016-01-01

    We report results of measurements of isotopic ratios obtained with atom probe tomography on U3O8 reference materials certified for their isotopic abundances of uranium. The results show good agreement with the certified values. High backgrounds due to tails from adjacent peaks complicate the measurement of the integrated peak areas as well as the fact that only oxides of uranium appear in the spectrum, the most intense of which is doubly charged. In addition, lack of knowledge of other instrumental parameters, such as the dead time, may bias the results. Isotopic ratio measurements can be performed at the nanometer-scale with the expectation of sensible results. The abundance sensitivity and mass resolving power of the mass spectrometer are not sufficient to compete with magnetic-sector instruments but are not far from measurements made by ToF-SIMS of other isotopic systems. The agreement of the major isotope ratios is more than sufficient to distinguish most anthropogenic compositions from natural.

  19. Uranium isotopic ratio measurements of U3O8 reference materials by atom probe tomography.

    PubMed

    Fahey, Albert J; Perea, Daniel E; Bartrand, Jonah; Arey, Bruce W; Thevuthasan, Suntharampillai

    2016-03-01

    We report results of measurements of isotopic ratios obtained with atom probe tomography on U3O8 reference materials certified for their isotopic abundances of uranium. The results show good agreement with the certified values. High backgrounds due to tails from adjacent peaks complicate the measurement of the integrated peak areas as well as the fact that only oxides of uranium appear in the spectrum, the most intense of which is doubly charged. In addition, lack of knowledge of other instrumental parameters, such as the dead time, may bias the results. Isotopic ratio measurements can be performed at the nanometer-scale with the expectation of sensible results. The abundance sensitivity and mass resolving power of the mass spectrometer are not sufficient to compete with magnetic-sector instruments but are not far from measurements made by ToF-SIMS of other isotopic systems. The agreement of the major isotope ratios is more than sufficient to distinguish most anthropogenic compositions from natural. PMID:26774651

  20. Improving precision in resonance ionization mass spectrometry : influence of laser bandwidth in uranium isotope ratio measurements.

    SciTech Connect

    Isselhardt, B. H.; Savina, M. R.; Knight, K. B.; Pellin, M. J.; Hutcheon, I. D.; Prussin, S. G.

    2011-03-01

    The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of {sup 235}U/{sup 238}U ratios by resonance ionization mass spectrometry (RIMS) to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a three-color, three-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from 10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation.

  1. Achievements in testing of the MGA and FRAM isotopic software codes under the DOE/NNSA-IRSN cooperation of gamma-ray isotopic measurement systems

    SciTech Connect

    Vo, Duc; Wang, Tzu - Fang; Funk, Pierre; Weber, Anne - Laure; Pepin, Nicolas; Karcher, Anna

    2009-01-01

    DOE/NNSA and IRSN collaborated on a study of gamma-ray instruments and analysis methods used to perform isotopic measurements of special nuclear materials. The two agencies agreed to collaborate on the project in response to inconsistencies that were found in the various versions of software and hardware used to determine the isotopic abundances of uranium and plutonium. IRSN used software developed internally to test the MGA and FRAM isotopic analysis codes for criteria used to stop data acquisition. The stop-criterion test revealed several unusual behaviors in both the MGA and FRAM software codes.

  2. The helium abundance of Uranus from Voyager measurements

    NASA Technical Reports Server (NTRS)

    Conrath, B.; Hanel, R.; Gautier, D.; Marten, A.; Lindal, G.

    1987-01-01

    Voyager radio-occultation and IR spectroscopy measurements are combined to infer an He mole fraction in the upper troposphere of Uranus of 0.152 + or - 0.033; the corresponding mass fraction is Y = 0.262 + or - 0.048. This value is in agreement with recent estimates of the solar He abundance, suggesting that He differentiation has not occurred on Uranus. Comparisons with values previously obtained for Jupiter and Saturn imply that migration of He toward the core began long ago on Saturn and may also have recently begun on Jupiter. The protosolar He abundance inferred from the Uranus measurements and from recent solar evolutionary models is used along with an assumed primordial He mass fraction of 0.23-0.24 to estimate a 3-4-percent enrichment of He in the interstellar medium between the big bang and the origin of the solar system. The result is in agreement with galactic chemical evolution models which include a substantial decrease in D during the evolutionary process.

  3. MeV He3/He4 isotope abundances in solar energetic particle events: SOHO/COSTEP observations

    NASA Astrophysics Data System (ADS)

    Bothmer, V.:; Sierks, H.; Böhm, E.; Kunow, H.

    2001-08-01

    We present first results based on a systematic survey of 4-41 MeV/N 3He/4He isotope abundances with ratios >0.01 detected by the COmprehensive SupraThermal and Energetic Particle analyzer (COSTEP) onboard the SOHO (SOlar and Heliospheric Observatory) spacecraft. More than about 25% of the identified events showed 3He/4He ratios in the range 0.1-1. For events with sufficiently high detector count rates the atomic mass plots can be resolved up to a time resolution of about 1 hour. These events are most suitable for comparisons with in situ solar wind plasma and magnetic field measurements and SOHO's optical white-light and extreme ultraviolet (EUV) observations of the Sun. The correlations show an association with passages of shock associated coronal mass ejections (CMEs) in the solar wind that inhibit high He/H plasma overabundances. It is likely that the CMEs have been released in strong magnetic reconfiguration processes at the solar source sites. Here we present a brief overview of such an event detected on October 30, 2000. 1. Introduction The SOHO/COSTEP instrument measures solar energetic particles (SEPs) at MeV energies in the interplanetary medium. The solid state detectors are capable to detect 3 He/4 He-enrichments at these energies (Müller-Mellin et al., 1995). Usually, the 3 He/4 He-ratio in the solar wind is at the order of 10-4 , but occasionally ratios up to about values of ~1 or even above have been observed in SEP events (e.g., Mason et al., 1999). The origin of these isotope abundances has commonly been attributed to impulsive solar flares and wave-particle interaction mechanisms (Temerin and Roth, 1992). However, fully satisfying physical explanations are still lacking. Here we present first results of a systematic survey of the He-measurements taken by COSTEP since launch in 1995 until the end of the year 2000. 2. Data For this study we have analyzed SOHO/COSTEP measurements of 4.3-40.9 MeV/N helium particles as well as COSTEP data covering

  4. {sup 39}Ar Detection at the 10{sup -16} Isotopic Abundance Level with Atom Trap Trace Analysis

    SciTech Connect

    Jiang, W.; Williams, W.; Bailey, K.; O'Connor, T. P.; Mueller, P.; Davis, A. M.; Hu, S.-M.; Sun, Y. R.; Lu, Z.-T.; Purtschert, R.; Sturchio, N. C.

    2011-03-11

    Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric {sup 39}Ar (half-life=269 yr), a cosmogenic isotope with an isotopic abundance of 8x10{sup -16}. In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

  5. Ground-based column abundance measurements of atmospheric hydroxyl

    NASA Technical Reports Server (NTRS)

    Burnett, Clyde R.

    1988-01-01

    The preliminary results of ground-based OH column abundance measurements from Truk, Federated States of Micronesia, are contained. These are the first OH column measurements from the tropics, and constitute a signficcant contribution to the OH data base. Comparisons of tropical OH behavior with the extensive mid-latitude observations serve as a critical test of the current understanding of the HO (sub x) photochemistry and its relationship to the other major chemical families. The quasi-biennial oscillation (QBO) in tropical stratospheric winds exerts a major influence on the Hadley cell vertical transport. Related QBOs in total O3 and in stratospheric H2O were identified, but QBO effects on other stratospheric species are still unknown. The solar tide in the tropics produces a diurnal surface pressure variation of 2 to 3 mb; its effect on OH photochemistry in the stratosphere may be significant.

  6. Ground-based column abundance measurements of atmospheric hydroxyl

    NASA Astrophysics Data System (ADS)

    Burnett, Clyde R.

    1988-04-01

    The preliminary results of ground-based OH column abundance measurements from Truk, Federated States of Micronesia, are contained. These are the first OH column measurements from the tropics, and constitute a signficcant contribution to the OH data base. Comparisons of tropical OH behavior with the extensive mid-latitude observations serve as a critical test of the current understanding of the HO (sub x) photochemistry and its relationship to the other major chemical families. The quasi-biennial oscillation (QBO) in tropical stratospheric winds exerts a major influence on the Hadley cell vertical transport. Related QBOs in total O3 and in stratospheric H2O were identified, but QBO effects on other stratospheric species are still unknown. The solar tide in the tropics produces a diurnal surface pressure variation of 2 to 3 mb; its effect on OH photochemistry in the stratosphere may be significant.

  7. Further carbon isotope measurements of LEW 88516

    NASA Technical Reports Server (NTRS)

    Wright, I. P.; Douglas, C.; Pillinger, C. T.

    1993-01-01

    Douglas et al. have previously analyzed the carbon content and isotopic composition of a crushed sample (sub-sample 13) of the shergottite, LEW 88516. The powder, which was from a relatively large portion of the meteorite in order to obtain a representative sample, was distributed amongst the scientific community. However, it is probable that the preparation procedure was not optimized for the purposes of carbon measurements. Indeed, it was found that LEW 88516,13 contained over 1200 ppm carbon, a concentration which is greater than that present in any other SNC meteorite. That a close relative, ALH A77005, contains only 141 ppm carbon seems to implicate the preparation procedure as being responsible for the apparently high carbon content of LEW 88516. However, it may also be the nature of the fine powder which has resulted in contamination. The observation of high carbon content in LEW 88516,13 highlights the extreme difficulty of trying to obtain representative samples of whole meteorites for this kind of investigation. Presented herein are some further measurements of LEW 88516 which should serve to clarify some of the issues raised by the previous investigation.

  8. A large detector for cosmic ray abundance and energy measurements

    NASA Astrophysics Data System (ADS)

    Alsop, C.

    A large aperture, balloon borne cosmic ray detector was designed to measure the energy spectra of individual cosmic ray species with Z greater than 8 in the energy range 0.3GeV/N to 400GeV/N. The energy dependence of the abundance spectrum extending up to such high energies will provide valuable data for determining the nature of the origin and propagation of cosmic rays in the Galaxy. The properties of cosmic ray nuclei and the interpretation of the energy dependence of the abundance spectrum are discussed. The design and response of the BUGS IV cosmic ray detector are described. The measurement techniques used are gas scintillation, gas proportional scintillation and Cerenkov radiation from both gases and solids. The light collection properties of the detector and several experimental investigations of the light collection efficiency of the drift chamber region are described. The expected signals from the gas scintillation and gas Cerenkov emissions are predicted and the choice of a suitable scintillating gas mixture for minimizing the uncertainty in the charge and energy measurements is considered. The theoretical aspects of electron drift and diffusion in gases and several experimental investigations on the electron drift in the BUGS IV drift chamber are given. Also some preliminary results from a uniform field drift chamber are included which demonstrate the sensitivity of the electron drift velocity in inert gas mixtures to water vapor contamination. The expected overall performance of BUGS IV and the results of an experimental simulation of the parachute landing of the detector are given.

  9. 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.

  10. Position-Specific Isotope Analysis of Xanthines: A (13)C Nuclear Magnetic Resonance Method to Determine the (13)C Intramolecular Composition at Natural Abundance.

    PubMed

    Diomande, Didier G; Martineau, Estelle; Gilbert, Alexis; Nun, Pierrick; Murata, Ariaki; Yamada, Keita; Watanabe, Naoharu; Tea, Illa; Robins, Richard J; Yoshida, Naohiro; Remaud, Gérald S

    2015-07-01

    The natural xanthines caffeine, theobromine, and theophylline are of major commercial importance as flavor constituents in coffee, cocoa, tea, and a number of other beverages. However, their exploitation for authenticity, a requirement in these commodities that have a large origin-based price-range, by the standard method of isotope ratio monitoring by mass spectrometry (irm-MS) is limited. We have now developed a methodology that overcomes this deficit that exploits the power of isotopic quantitative (13)C nuclear magnetic resonance (NMR) spectrometry combined with chemical modification of the xanthines to enable the determination of positional intramolecular (13)C/(12)C ratios (δ(13)Ci) with high precision. However, only caffeine is amenable to analysis: theobromine and theophylline present substantial difficulties due to their poor solubility. However, their N-methylation to caffeine makes spectral acquisition feasible. The method is confirmed as robust, with good repeatability of the δ(13)Ci values in caffeine appropriate for isotope fractionation measurements at natural abundance. It is shown that there is negligible isotope fractionation during the chemical N-methylation procedure. Thus, the method preserves the original positional δ(13)Ci values. The method has been applied to measure the position-specific variation of the (13)C/(12)C distribution in caffeine. Not only is a clear difference between caffeine isolated from different sources observed, but theobromine from cocoa is found to show a (13)C pattern distinct from that of caffeine. PMID:26067163

  11. Solar coronal and photospheric abundances from solar energetic particle measurements

    NASA Technical Reports Server (NTRS)

    Breneman, H. H.; Stone, E. C.

    1985-01-01

    Solar energetic particle (SEP) elemental abundance data from the cosmic ray subsystem (CRS) aboard the Voyager 1 and 2 spacecraft are used to derive unfractionated coronal and photospheric abundances for elements with Z = 6-30. It is found that the ionic charge-to-mass ratio (Q/M) is the principal organizing parameter for the fractionation of SEPs by acceleration and propagation processes and for flare-to-flare variability, making possible a single-parameter Q/M-dependent correction to the average SEP abundances to obtain unfractionated coronal abundances. A further correction based on first ionization potential allows the determination of unfractionated photospheric abundances.

  12. Solar Coronal and photospheric abundances from solar energetic particle measurements

    NASA Technical Reports Server (NTRS)

    Breneman, H.; Stone, E. C.

    1985-01-01

    Solar energetic particle (SEP) elemental abundance data from the cosmic ray subsystem (CRS) aboard the Voyager 1 and 2 spacecraft are used to derive unfractionated coronal and photospheric abundances for elements with 3 Z or = 30. It is found that the ionic charge-to-mass ratio (Q/M) is the principal organizing parameter for the fractionation of SEPs by acceleration and propagation processes and for flare-to-flare variability, making possible a single-parameter Q/M-dependent correction to the average SEP abundances to obtain unfractionated coronal abundances. A further correction based on first ionization potential allows the determination of unfractionated photospheric abundances.

  13. Solar coronal and photospheric abundances from solar energetic particle measurements

    NASA Technical Reports Server (NTRS)

    Breneman, H.; Stone, E. C.

    1985-01-01

    Solar energetic particle (SEP) elemental abundance data from the Cosmic Ray Subsystem (CRS) aboard the Voyager 1 and 2 spacecraft are used to derive unfractionated coronal and photospheric abundances for elements with 3 = or Z or = 30. The ionic charge-to-mass ratio (Q/M) is the principal organizing parameter for the fractionation of SEPs by acceleration and propagation processes and for flare-to-flare variability, making possible a single-parameter Q/M-dependent correction to the average SEP abundances to obtain unfractionated coronal abundances. A further correction based on first ionization potential allows the determination of unfractionated photospheric abundances.

  14. Guidelines and recommended terms for expression of stable-isotope-ratio and gas-ratio measurement results

    USGS Publications Warehouse

    Coplen, Tyler B.

    2011-01-01

    To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Système International d'Unités, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented.

  15. Field measurements of isotope fractionation during evaporation

    NASA Astrophysics Data System (ADS)

    Smith, R. B.; Williams, J. K.; Lee, X.

    2004-12-01

    The isotopic fractionation associated with evaporation from bodies of water is an important process for the interpretation of isotope data from the atmosphere and in the development of ice core climate records. Existing theories include the resistance model of Craig and Gordon [1965] summarized by Gat [1996], and the exchange model of Merlivat and Jouzel [1979, MJ79]. The MJ79 model was recently extended by He and Smith [1999, HS99] to include a limited exchange between the liquid at depth and the air-liquid interface. These theories are relatively complex as they must include not only equilibrium fractionation but also the kinetic effects of diffusion and the influence of the "back-flux" of water vapor to the surface. Laboratory experiments by Craig et al. (1963), Merlivat and Coantic [1975], Merlivat [1978] and Cappa et al. (2003) have added new insight and generated proposals for parameterizations. Field testing of these theories and parametrizations has received little attention however. The primary difficulty to be overcome is that water vapor collected near the liquid interface is not representative of the evaporative flux, as it contains a significant proportion of vapor from the free atmosphere above. We overcome this problem using a two-level sampling technique developed by Keeling [1960] for carbon isotopes and applied to water vapor by Yakir and Wang [1996], Gat [2000], and He and Smith [2003] among others. Vapor collections were carried out over the Hudson River in the summer 2003 at altitudes of 12 and 190 centimeters. Samples from the two levels showed systematic differences in specific humidity and isotope ratio, allowing the isotope ratio in the net flux to be determined. In general, flux isotope ratios were significantly lighter than the collected vapor. Furthermore, the flux ratios are significantly lighter than that in equilibrium with river water samples. This small data set provides an opportunity to evaluate existing theories of isotope

  16. Mass measurements of neutron-rich Rb and Sr isotopes

    NASA Astrophysics Data System (ADS)

    Klawitter, R.; Bader, A.; Brodeur, M.; Chowdhury, U.; Chaudhuri, A.; Fallis, J.; Gallant, A. T.; Grossheim, A.; Kwiatkowski, A. A.; Lascar, D.; Leach, K. G.; Lennarz, A.; Macdonald, T. D.; Pearkes, J.; Seeraji, S.; Simon, M. C.; Simon, V. V.; Schultz, B. E.; Dilling, J.

    2016-04-01

    We report on the mass measurements of several neutron-rich Rb and Sr isotopes in the A ≈100 region with the TITAN Penning-trap mass spectrometer. By using highly charged ions in the charge state q =10 + , the masses of Rb,9998 and Sr-10098 have been determined with a precision of 6-12 keV, making their uncertainty negligible for r -process nucleosynthesis network calculations. The mass of 101Sr has been determined directly for the first time with a precision eight times higher than the previous indirect measurement and a deviation of 3 σ when compared to the Atomic Mass Evaluation. We also confirm the mass of 100Rb from a previous measurement. Furthermore, our data indicate the existence of a low-lying isomer with 80 keV excitation energy in 98Rb. We show that our updated mass values lead to minor changes in the r process by calculating fractional abundances in the A ≈100 region of the nuclear chart.

  17. Precision measures of the primordial abundance of deuterium

    SciTech Connect

    Cooke, Ryan J.; Jorgenson, Regina A.; Murphy, Michael T.; Steidel, Charles C.

    2014-01-20

    We report the discovery of deuterium absorption in the very metal-poor ([Fe/H] = –2.88) damped Lyα system at z {sub abs} = 3.06726 toward the QSO SDSS J1358+6522. On the basis of 13 resolved D I absorption lines and the damping wings of the H I Lyα transition, we have obtained a new, precise measure of the primordial abundance of deuterium. Furthermore, to bolster the present statistics of precision D/H measures, we have reanalyzed all of the known deuterium absorption-line systems that satisfy a set of strict criteria. We have adopted a blind analysis strategy (to remove human bias) and developed a software package that is specifically designed for precision D/H abundance measurements. For this reanalyzed sample of systems, we obtain a weighted mean of (D/H){sub p} = (2.53 ± 0.04) × 10{sup –5}, corresponding to a universal baryon density 100 Ω{sub b,} {sub 0} h {sup 2} = 2.202 ± 0.046 for the standard model of big bang nucleosynthesis (BBN). By combining our measure of (D/H){sub p} with observations of the cosmic microwave background (CMB), we derive the effective number of light fermion species, N {sub eff} = 3.28 ± 0.28. We therefore rule out the existence of an additional (sterile) neutrino (i.e., N {sub eff} = 4.046) at 99.3% confidence (2.7σ), provided that the values of N {sub eff} and of the baryon-to-photon ratio (η{sub 10}) did not change between BBN and recombination. We also place a strong bound on the neutrino degeneracy parameter, independent of the {sup 4}He primordial mass fraction, Y {sub P}: ξ{sub D} = +0.05 ± 0.13 based only on the CMB+(D/H){sub p} observations. Combining this value of ξ{sub D} with the current best literature measure of Y {sub P}, we find a 2σ upper bound on the neutrino degeneracy parameter, |ξ| ≤ +0.062.

  18. Measurements of Isotopic Composition of Vapour on the Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Casado, M.; Landais, A.; Masson-Delmotte, V.; Genthon, C.; Prie, F.; Kerstel, E.; Kassi, S.; Arnaud, L.; Steen-Larsen, H. C.; Vignon, E.

    2015-12-01

    The oldest ice core records are obtained on the East Antarctic plateau. The composition in stable isotopes of water (δ18O, δD, δ17O) permits to reconstruct the past climatic conditions over the ice sheet and also at the evaporation source. Paleothermometer accuracy relies on good knowledge of processes affecting the isotopic composition of surface snow in Polar Regions. Both simple models such as Rayleigh distillation and global atmospheric models with isotopes provide good prediction of precipitation isotopic composition in East Antarctica but post deposition processes can alter isotopic composition on site, in particular exchanges with local vapour. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum water vapour - precipitation - surface snow - buried snow. While precipitation and snow sampling are routinely performed in Antarctica, climatic conditions in Concordia, very cold (-55°C in average) and very dry (less than 1000ppmv), impose difficult conditions to measure the water vapour isotopic composition. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces (down to 20ppmv). Here we present the results of a campaign of measurement of isotopic composition in Concordia in 2014/2015. Two infrared spectrometers have been deployed or the first time on top of the East Antarctic Plateau allowing a continuous vapour measurement for a month. Comparison of the results from infrared spectroscopy with cryogenic trapping validates the relevance of the method to measure isotopic composition in dry conditions. Identification of different behaviour of isotopic composition in the water vapour associated to turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction.

  19. Carbon Isotopic Measurements of Amino Acids in Stardust-Returned Samples

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie

    2009-01-01

    NASA's Stardust spacecraft returned to Earth samples from comet 81P/Wild 2 in January 2006. Preliminary examinations revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds could not be identified. Here, we present the carbon isotopic ratios of glycine and e-aminocaproic acid (EACA), the two most abundant amino acids, in Stardust-returned foil samples measured by gas chromatography-combustion-isotope ratio mass spectrometry coupled with quadrupole mass spectrometry (GC-CAMS/IRMS).

  20. Predicted CALET Measurements of Ultra-Heavy Cosmic Ray Abundances

    NASA Astrophysics Data System (ADS)

    Rauch, Brian

    2013-04-01

    The CALorimetric Electron Telescope (CALET), comprised of main calorimeter telescope (CAL) and Gamma-ray Burst Monitor (CGBM), is under construction for launch to the ISS in 2014. CAL consists of a Charge Detector (CHD) with two segmented planes of 1 cm thick plastic scintillator, an Imaging Calorimeter (IMC) with a total of 3 radiation lengths (X0) of tungsten plates read out with 8 planes of interleaved scintillating fibers, and a Total Absorption Calorimeter (TASC) with 27 X0 of lead tungstate (PWO) logs. The primary objectives of CAL are to measure electron energy spectra from 1GeV to 20 TeV, to detect gamma-rays above 10 GeV, and to measure the energy spectra of nuclei from protons through iron up to 1,000 TeV. In this paper we discuss the predicted abundance measurements CAL can make of rare ultra-heavy (UH) nuclei (30 <=Z <=40). In addition to the nuclei that pass within the full CAL geometry, UH nuclei can be resolved using the CHD and top IMC layers without requiring particle energy determination in the TASC in the portion of the ISS 51.6^o inclination orbit where the geomagnetic rigidity cutoffs are above minimum ionization in the scintillator. In 5-years CAL would collect 4-5 times the UH statistics of TIGER.

  1. Isotopic Resonance Hypothesis: Experimental Verification by Escherichia coli Growth Measurements

    NASA Astrophysics Data System (ADS)

    Xie, Xueshu; Zubarev, Roman A.

    2015-03-01

    Isotopic composition of reactants affects the rates of chemical and biochemical reactions. As a rule, enrichment of heavy stable isotopes leads to progressively slower reactions. But the recent isotopic resonance hypothesis suggests that the dependence of the reaction rate upon the enrichment degree is not monotonous. Instead, at some ``resonance'' isotopic compositions, the kinetics increases, while at ``off-resonance'' compositions the same reactions progress slower. To test the predictions of this hypothesis for the elements C, H, N and O, we designed a precise (standard error +/-0.05%) experiment that measures the parameters of bacterial growth in minimal media with varying isotopic composition. A number of predicted resonance conditions were tested, with significant enhancements in kinetics discovered at these conditions. The combined statistics extremely strongly supports the validity of the isotopic resonance phenomenon (p << 10-15). This phenomenon has numerous implications for the origin of life studies and astrobiology, and possible applications in agriculture, biotechnology, medicine, chemistry and other areas.

  2. On strontium isotopic anomalies and odd-A p-process abundances. [in solar system

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1978-01-01

    Several aspects of the nucleosynthesis of Sr isotopes are considered in an attempt to shed light on the problem of the Sr isotopic anomalies discovered in an inclusion of the Allende meteorite. Decomposition of the Sr isotopes into average r-, s-, and p-process nucleosynthetic classes is performed. It is suggested that the Allende inclusion most likely has an excess of s-process Sr and that the initial Sr-87/Sr-86 isotopic ratio is probably slightly more primitive than basaltic achondrites. The results also show that Sn-115 is mostly due to the r-process and that odd-A yields are very small. It is concluded that if the Sr anomaly in the inclusion is an average s enhancement, it argues somewhat in favor of a model of gas/dust fractionation of s and r isotopes during accumulation of the inclusion parent in the protosolar cloud.

  3. Using natural isotopic abundances to determine the source of nitrous oxide (N2O) emissions

    NASA Astrophysics Data System (ADS)

    Mothet, A.; Sebilo, M.; Laverman, A. M.; Vaury, V.; Mariotti, A.

    2012-04-01

    Numerous greenhouse gas studies have focused on carbon dioxide (CO2), whereas nitrous oxide (N2O) also plays a major role in global warming. Indeed, while nitrous oxide is 1000 times less concentrated than CO2 in the atmosphere, it is 300 times more efficient in terms of global warming potential. In addition, its atmospheric concentration increases with 0,3 % per year. According to the literature, nitrous oxide is produced, in soils and sediments, by two major processes: (1) Nitrification, mediated by autotrophic nitrifying bacteria under oxic conditions; (2) Denitrification, mediated by heterotrophic denitrifying bacteria under anoxic conditions. Denitrification induces intensive, localized and instantaneous fluxes. N2O emissions can be easily measured and modeled. In contrast, nitrification induces weak emissions, but spatially and temporally extended. Therefore, this process could represent a large potential of N2O emissions from soils and sediments. The study of isotopomer's isotopic composition of N2O, i.e. the intramolecular distribution or site preference (SP) determined by 15N measurement allows the determination of the origin of N2O emissions (nitrification vs. denitrification). Recent studies on pure cultures have showed that SP associated with nitrification is 35 ‰ while SP associated with denitrification is 0 ‰. The aim of this study was to determine SP associated with denitrification in soils and sediments, taking into account the environmental denitrifying bacterial communities, and under different environmental variables. To this end, flow-through reactors were used to determine denitrification rates at different temperatures and varying substrate (nitrate) concentrations. Site preference was measured for the different experiments. Different experiments of denitrification were realized in sediment flow through reactors under denitrifying conditions (anoxia, presence of organic matter and nitrate). We used acetylene (25°C) to block the enzyme

  4. A measurement of cosmic-ray beryllium isotopes from 200 to 1500 MeV per nucleon

    NASA Technical Reports Server (NTRS)

    Buffington, A.; Orth, C. D.; Mast, T. S.

    1978-01-01

    A balloon-borne superconducting magnetic spectrometer was used in the measurement of cosmic-ray isotopic abundances from lithium through oxygen in the energy range 200-1500 MeV per nucleon. Except for Be-7 all isotopic composition is essentially energy-independent. Be-10 is nearly absent, indicating a mean cosmic-ray age of 6(-3, +10) x 10 to the 6th years. Above about 500 MeV per nucleon, Be-7 drops dramatically in abundance relative to Be-9 and C. By 1500 MeV per nucleon, the relative abundance of Be-7 has become one-half of its lower-energy value. Since Be-7 is the only isotope measured which decays by electron capture, this result is interpreted as indicating that higher-energy Be-7 had an appreciable probability of not being stripped of all its electrons before entering interstellar space where electron pickup is negligible.

  5. Measurements of CFC Isotope Changes in Firn, Stratospheric and Tropospheric Air

    NASA Astrophysics Data System (ADS)

    Allin, S.; Laube, J.; Witrant, E.; Kaiser, J.; McKenna, E.; Dennis, P.; Mulvaney, R.; Capron, E.; Martinerie, P.; Blunier, T.; Schwander, J.; Fraser, P. J.; Sturges, W. T.

    2014-12-01

    The degradation of chlorofluorocarbons (CFCs) releases chlorine, which is a major contributor to the destruction of stratospheric ozone. Recent studies of CFC-12 (CCl2F2) have reported strong chlorine and carbon isotope fractionations in stratospheric and tropospheric samples, respectively. The δ(37Cl) variations were attributed to isotope dependent sink reactions, similar to effects seen in nitrous oxide (N2O), whereas adjustments to manufacturing processes were used to explain the δ(13C) changes. Using air archives to measure chlorine and carbon isotope ratios in CFCs could help to identify and quantify their sources and sinks. We analyse the three most abundant CFCs and show that CFC-11 (CCl3F) and CFC-113 (CClF2CCl2F) exhibit significant chlorine isotope fractionation in the stratosphere, in common with CFC-12. We then use a 2-box model to estimate the expected tropospheric isotope signature of these gases, based on their emissions and transport history, as well as their measured stratospheric isotope fractionation constants (ɛapp). We also present long-term δ(37Cl) and δ(13C) trends of all three CFCs, determined from background tropospheric samples from the Cape Grim air archive (1978 - 2010) and firn air samples from the Arctic (NEEM, Greenland) and Antarctica (Fletcher Promontory). These measurements are compared to our model trends, leading to an evaluation of long-term chlorine and carbon isotope changes. This study also extends the novel approach to measuring trace gas isotope ratios in small air volumes, using a single-detector gas chromatography-mass spectrometry system.

  6. Oxygen isotopic abundances in calcium- aluminum-rich inclusions from ordinary chondrites: implications for nebular heterogeneity.

    PubMed

    McKeegan, K D; Leshin, L A; Russell, S S; MacPherson, G J

    1998-04-17

    The oxygen isotopic compositions of two calcium-aluminum-rich inclusions (CAIs) from the unequilibrated ordinary chondrite meteorites Quinyambie and Semarkona are enriched in 16O by an amount similar to that in CAIs from carbonaceous chondrites. This may indicate that most CAIs formed in a restricted region of the solar nebula and were then unevenly distributed throughout the various chondrite accretion regions. The Semarkona CAI is isotopically homogeneous and contains highly 16O-enriched melilite, supporting the hypothesis that all CAI minerals were originally 16O-rich, but that in most carbonaceous chondrite inclusions some minerals exchanged oxygen isotopes with an external reservoir following crystallization.

  7. Cumulative fission yields of short-lived isotopes under natural-abundance-boron-carbide-moderated neutron spectrum

    SciTech Connect

    Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce; Wittman, Richard S.; Friese, Judah I.; Kephart, Rosara F.

    2015-04-09

    The availability of gamma spectroscopy data on samples containing mixed fission products at short times after irradiation is limited. Due to this limitation, data interpretation methods for gamma spectra of mixed fission product samples, where the individual fission products have not been chemically isolated from interferences, are not well-developed. The limitation is particularly pronounced for fast pooled neutron spectra because of the lack of available fast reactors in the United States. Samples containing the actinide isotopes 233, 235, 238U, 237Np, and 239Pu individually were subjected to a 2$ pulse in the Washington State University 1 MW TRIGA reactor. To achieve a fission-energy neutron spectrum, the spectrum was tailored using a natural abundance boron carbide capsule to absorb neutrons in the thermal and epithermal region of the spectrum. Our tailored neutron spectrum is unique to the WSU reactor facility, consisting of a soft fission spectrum that contains some measurable flux in the resonance region. This results in a neutron spectrum at greater than 0.1 keV with an average energy of 70 keV, similar to fast reactor spectra and approaching that of 235U fission. Unique fission product gamma spectra were collected from 4 minutes to 1 week after fission using single-crystal high purity germanium detectors. Cumulative fission product yields measured in the current work generally agree with published fast pooled fission product yield values from ENDF/B-VII, though a bias was noted for 239Pu. The present work contributes to the compilation of energy-resolved fission product yield nuclear data for nuclear forensic purposes.

  8. Transition Region Abundance Measurements During Impulsive Heating Events

    NASA Astrophysics Data System (ADS)

    Warren, Harry P.; Brooks, David H.; Doschek, George A.; Feldman, Uri

    2016-06-01

    It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona, low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper we report on measurements of plasma composition made during impulsive heating events observed at transition region temperatures with the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these events the intensities of O iv, v, and vi emission lines are enhanced relative to emission lines from Mg v, vi, and vii and Si vi and vii, and indicate a composition close to that of the photosphere. Long-lived coronal fan structures, in contrast, show an enrichment of low-FIP elements. We conjecture that the plasma composition is an important signature of the coronal heating process, with impulsive heating leading to the evaporation of unfractionated material from the lower layers of the solar atmosphere and higher-frequency heating leading to long-lived structures and the accumulation of low-FIP elements in the corona.

  9. Non-Gaussian error distribution of 7Li abundance measurements

    NASA Astrophysics Data System (ADS)

    Crandall, Sara; Houston, Stephen; Ratra, Bharat

    2015-07-01

    We construct the error distribution of 7Li abundance measurements for 66 observations (with error bars) used by Spite et al. (2012) that give A(Li) = 2.21 ± 0.065 (median and 1σ symmetrized error). This error distribution is somewhat non-Gaussian, with larger probability in the tails than is predicted by a Gaussian distribution. The 95.4% confidence limits are 3.0σ in terms of the quoted errors. We fit the data to four commonly used distributions: Gaussian, Cauchy, Student’s t and double exponential with the center of the distribution found with both weighted mean and median statistics. It is reasonably well described by a widened n = 8 Student’s t distribution. Assuming Gaussianity, the observed A(Li) is 6.5σ away from that expected from standard Big Bang Nucleosynthesis (BBN) given the Planck observations. Accounting for the non-Gaussianity of the observed A(Li) error distribution reduces the discrepancy to 4.9σ, which is still significant.

  10. Temporal variation in mycorrhizal diversity and carbon and nitrogen stable isotope abundance in the wintergreen meadow orchid Anacamptis morio.

    PubMed

    Ercole, Enrico; Adamo, Martino; Rodda, Michele; Gebauer, Gerhard; Girlanda, Mariangela; Perotto, Silvia

    2015-02-01

    Many adult orchids, especially photoautotrophic species, associate with a diverse range of mycorrhizal fungi, but little is known about the temporal changes that might occur in the diversity and functioning of orchid mycorrhiza during vegetative and reproductive plant growth. Temporal variations in the spectrum of mycorrhizal fungi and in stable isotope natural abundance were investigated in adult plants of Anacamptis morio, a wintergreen meadow orchid. Anacamptis morio associated with mycorrhizal fungi belonging to Tulasnella, Ceratobasidium and a clade of Pezizaceae (Ascomycetes). When a complete growing season was investigated, multivariate analyses indicated significant differences in the mycorrhizal fungal community. Among fungi identified from manually isolated pelotons, Tulasnella was more common in autumn and winter, the pezizacean clade was very frequent in spring, and Ceratobasidium was more frequent in summer. By contrast, relatively small variations were found in carbon (C) and nitrogen (N) stable isotope natural abundance, A. morio samples showing similar (15)N enrichment and (13)C depletion at the different sampling times. These observations suggest that, irrespective of differences in the seasonal environmental conditions, the plant phenological stages and the associated fungi, the isotopic content in mycorrhizal A. morio remains fairly constant over time.

  11. Measuring glass abundances in lunar agglutinates. [Abstract only

    NASA Technical Reports Server (NTRS)

    Strait, M. M.; Basu, A.; Mckay, D. S.; Robinson, R.

    1994-01-01

    The purpose of this study is to develop a standard method for measuring modal abundances of glass in single agglutinates in the lunar regolith. Not only does agglutinitic glass increase in single agglutinates as clasts of older agglutinates get incorporated into newer agglutinates with increasing maturity, but it is in this glassy phase that nanophase superparamagnetic Fe metal originates as a result of reduction reactions during the agglutination process. We report the results of two sets of independent measurements using two different methods to determine the proportion of glass in single agglutinates. We have used polished grain mounts (PGM) of five hand-picked single agglutinates from Apollo 16 soil 61181. The ISI Scanning Electron Microscope (SEM) fitted with a high-resolution Backscattered Electron (BSE) detector was used to collect high-contrast BSE images of the agglutinates. Several images were collected to represent each single agglutinate. The contrast, brightness, and focus were adjusted to optimize each image collected. Histograms of the grayscale range for all images produced four 'peaks' corresponding to epoxy, glass, crystalline phases, and metal grains. We analyzed every grid point for 12 elements with a less than 1 micron electron beam using a CAMECA SX-50 electron probe microanalyzer (EPM). If any analysis was not within about 10% of the stoichiometry of a known lunar mineral, we considered that point to be nonmineralic. Our results show that there is a remarkable correspondence in the glass percentages obtained by the two methods. The EPM method may overestimate glass because secondary fluorescence from dusty clasts in agglutinitic glass can give the appearance of nonmineralic targets. The BSE method may underestimate glass because the diversity of compositions of agglutinitic glass may not be contained under one grayscale 'peak' during image analysis.

  12. 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.

  13. 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.

  14. Natural-abundance stable carbon isotopes of small-subunit ribosomal RNA (SSU rRNA) from Guaymas Basin (Mexico)

    NASA Astrophysics Data System (ADS)

    MacGregor, B. J.; Mendlovitz, H.; Albert, D.; Teske, A. P.

    2012-12-01

    Small-subunit ribosomal RNA (SSU rRNA) is a phylogenetically informative molecule found in all species. Because it is poorly preserved in most environments, it is a useful marker for active microbial populations. We are using the natural-abundance stable carbon isotopic composition of specific microbial groups to help identify the carbon substrates contributing to microbial biomass in a variety of marine environments. At Guaymas Basin, hydrothermal fluids interact with abundant sedimentary organic carbon to produce natural gas and petroleum. Where this reaches the sediment surface, it can support dense patches of seafloor life, including Beggiatoa mats. We report here on the stable carbon isotopic composition of SSU rRNA from a Beggiatoa mat transect, a cold background site, a warm site with high oil concentration, and a second Beggiatoa mat. The central part of the transect mat overlay the steepest temperature gradient, and was visually dominated by orange Beggiatoa. This was fringed by white Beggiatoa mat and bare, but still warm, sediment. Methane concentrations were saturating beneath the orange and white mats and at the oily site, lower beneath bare sediment, and below detection at the background site. Our initial hypotheses were that rRNA isotopic composition would be strongly influenced by methane supply, and that archaeal rRNA might be lighter than bacterial due to contributions from methanogens and anaerobic methane oxidizers. We used biotin-labeled oligonucleotides to capture Bacterial and Archaeal SSU rRNA for isotopic determination. Background-site rRNA was isotopically heaviest, and bacterial RNA from below 2 cm at the oily site was lightest, consistent with control by methane. Within the transect mat, however, the pattern was more complicated; at some sediment depths, rRNA from the mat periphery was isotopically lightest. Part of this may be due to the spatially and temporally variable paths followed by hydrothermal fluid, which can include horizontal

  15. Isotopic Measurements: Interpretation and Implications of Plutonium Data

    SciTech Connect

    Luksic, Andrzej T.; Collins, Brian A.; Friese, Judah I.; Schwantes, Jon M.; Starner, Jason R.; Wacker, John F.

    2010-08-11

    One of the fundamental activities within the field of nuclear forensics is the laboratory analysis of nuclear material; one aspect is providing the isotopic composition of the material under investigation. For both plutonium and uranium, this includes a unique suite of isotopes that, individually and collectively (i.e. an isotopic vector), will help characterize these materials, and potentially provide insight into their mode of production, intended utilization, and processing history. A full understanding of how this information is used provides the basis for defining the need for these measurements and helps determine the precision and accuracy requirements for those measurements. This paper provides an overview of this process as it applies to plutonium, discussing how reactor design and operating parameters can impact the resultant plutonium vector, thereby giving us the ability to infer those reactor traits based on isotopic measurements.

  16. Simultaneous analysis of abundance and isotopic composition of nitrogen, carbon, and noble gases in lunar basalts: Insights into interior and surface processes on the Moon

    NASA Astrophysics Data System (ADS)

    Mortimer, J.; Verchovsky, A. B.; Anand, M.; Gilmour, I.; Pillinger, C. T.

    2015-07-01

    Simultaneous static-mode mass spectrometric measurements of nitrogen, carbon, helium, neon, and argon extracted from the same aliquot of sample by high-resolution stepped combustion have been made for a suite of six lunar basalts. Collecting abundance and isotopic data for several elements simultaneously from the same sample aliquot enables more detailed identification of different volatile components present in the basalts by comparing release patterns for volatiles across a range of temperature steps. This approach has yielded new data, from which new insights can be gained regarding the indigenous volatile inventory of the Moon. By taking into account N and C data for mid-temperature steps, unaffected by terrestrial contamination or cosmogenic additions, it is possible to determine the indigenous N and C signatures of the lunar basalts. With an average δ15N value of around +0.35‰, the indigenous N component seen in these samples is similar within error to other (albeit limited in number) isotopic measurements of indigenous lunar N. Average C/N ratios for indigenous volatiles in these six basalt samples are much lower than those of the terrestrial depleted mantle, or bulk silicate Earth, possibly suggesting much less C in the lunar interior, relative to N, than on Earth. Cosmogenic isotopes in these samples are well-correlated with published sample exposure ages, and record the rate of in situ production of spallogenic volatiles within material on the lunar surface.

  17. Measuring Isotope Ratios Across the Solar System

    NASA Technical Reports Server (NTRS)

    Webster, Chris R.; Mahaffy, Paul R.

    2012-01-01

    Stable isotope ratios in C, H, N, O and S are powerful indicators of a wide variety of planetary geophysical processes that can identify origin, transport, temperature history, radiation exposure, atmospheric escape, environmental habitability and biology [1]. For the Allan Hills 84001 meteorite, for example, the (sup 1)(sup 3)C/(sup 1)(sup 2)C ratio identifies it as a Mars (SNC) meteorite; the ??K/??Ar ratio tells us the last time the rock cooled to solid, namely 4 Gya; isotope ratios in (sup 3)He, (sup 2)(sup 1)Ne and (sup 3)?Ar show it was in space (cosmic ray exposure) for 10-20 million years; (sup 1)?C dating that it sat in Antarctica for 13,000 years before discovery; and clumped isotope analysis of (sup 1)?O(sup 1)(sup 3)C(sup 1)?O in its carbonate that it was formed at 18+/-4 ?C in a near-surface aqueous environment [2]. Solar System Formation

  18. Silicon isotopic abundance toward evolved stars and its application for presolar grains

    NASA Astrophysics Data System (ADS)

    Peng, T.-C.; Humphreys, E. M. L.; Testi, L.; Baudry, A.; Wittkowski, M.; Rawlings, M. G.; de Gregorio-Monsalvo, I.; Vlemmings, W.; Nyman, L.-A.; Gray, M. D.; de Breuck, C.

    2013-11-01

    Aims: Galactic chemical evolution (GCE) is important for understanding the composition of the present-day interstellar medium (ISM) and of our solar system. In this paper, we aim to track the GCE by using the 29Si/30Si ratios in evolved stars and tentatively relate this to presolar grain composition. Methods: We used the APEX telescope to detect thermal SiO isotopologue emission toward four oxygen-rich M-type stars. Together with the data retrieved from the Herschel science archive and from the literature, we were able to obtain the 29Si/30Si ratios for a total of 15 evolved stars inferred from their optically thin 29SiO and 30SiO emission. These stars cover a range of masses and ages, and because they do not significantly alter 29Si/30Si during their lifetimes, they provide excellent probes of the ISM metallicity (or 29Si/30Si ratio) as a function of time. Results: The 29Si/30Si ratios inferred from the thermal SiO emission tend to be lower toward low-mass oxygen-rich stars (e.g., down to about unity for W Hya), and close to an interstellar or solar value of 1.5 for the higher-mass carbon star IRC+10216 and two red supergiants. There is a tentative correlation between the 29Si/30Si ratios and the mass-loss rates of evolved stars, where we take the mass-loss rate as a proxy for the initial stellar mass or current stellar age. This is consistent with the different abundance ratios found in presolar grains. Before the formation of the Sun, the presolar grains indicate that the bulk of presolar grains already had 29Si/30Si ratios of about 1.5, which is also the ratio we found for the objects younger than the Sun, such as VY CMa and IRC+10216. However, we found that older objects (up to possibly 10 Gyr old) in our sample trace a previous, lower 29Si/30Si value of about 1. Material with this isotopic ratio is present in two subclasses of presolar grains, providing independent evidence of the lower ratio. Therefore, the 29Si/30Si ratio derived from the SiO emission of

  19. A stable isotope dilution method for measuring bioavailability of organic contaminants

    PubMed Central

    Delgado-Moreno, Laura; Gan, Jay

    2014-01-01

    Methods for determining bioavailability of organic contaminants suffer various operational limitations. We explored the use of stable isotope labeled references in developing an isotope dilution method (IDM) to measure the exchangeable pool (E) of pyrene and bifenthrin as an approximation of their bioavailability in sediments. The exchange of deuterated bifenthrin or pyrene with its native counterpart was completed within 48 h. The derived E was 38–82% for pyrene and 28–59% for bifenthrin. Regression between E and the sum of rapid and slow desorption fractions obtained from sequential desorption showed a slope close to 1.0. The ability of IDM to predict bioavailability was further shown from a strong relationship (r2 > 0.93) between E and bioaccumulation into Chironomus tentans. Given the abundance of stable isotope labeled references and their relatively easy analysis, the IDM has the potential to become a readily adoptable tool for estimating organic contaminants bioaccessibility in various matrices. PMID:23434573

  20. Abundances and isotopic compositions of rhenium and osmium in pyrite samples from the Huaibei coalfield, Anhui, China

    USGS Publications Warehouse

    Liu, Gaisheng; Chou, C.-L.; Peng, Z.; Yang, G.

    2008-01-01

    Two pyrite samples from the Shihezi Formation (Lower Permian), Huaibei coalfield, Anhui, China, have been analyzed for abundances and isotopic compositions of rhenium and osmium using negative thermal ion mass spectrometry. The Re-Os ages of the pyrites are 64.4 and 226 Ma, which are younger than the formation age of the coal seam. The pyrite samples may consist of pyrite formed at various stages during the history of coal formation. The ??Osvalues of the two pyrite samples are +17 and +18, respectively. Such high ??Osvalues are reported for the first time for recycles crustal materials from a sedimentary basin. ?? Springer-Verlag 2007.

  1. Food Resources of Stream Macronivertebrates Determined by Natural-Abundance stable C and N Isotopes and a 15N Tracer Addition

    SciTech Connect

    Mulholland, P. J.

    2000-01-01

    Trophic relationships were examined using natural-abundance {sup 13}C and {sup 15}N analyses and a {sup 15}N-tracer addition experiment in Walker Branch, a 1st-order forested stream in eastern Tennessee. In the {sup 15}N-tracer addition experiment, we added {sup 15}NH{sub 4} to stream water over a 6-wk period in early spring, and measured {sup 15}N:{sup 14}N ratios in different taxa and biomass compartments over distance and time. Samples collected from a station upstream from the {sup 15}N addition provided data on natural-abundance {sup 13}C:{sup 12}C and {sup 15}N:{sup 14}N ratios. The natural-abundance {sup 15}N analysis proved to be of limited value in identifying food resources of macroinvertebrates because {sup 15}N values were not greatly different among food resources. In general, the natural-abundance stable isotope approach was most useful for determining whether epilithon or detritus were important food resources for organisms that may use both (e.g., the snail Elimia clavaeformis), and to provide corroborative evidence of food resources of taxa for which the {sup 15}N tracer results were not definitive. The {sup 15}N tracer results showed that the mayflies Stenonema spp. and Baetis spp. assimilated primarily epilithon, although Baetis appeared to assimilate a portion of the epilithon (e.g., algal cells) with more rapid N turnover than the bulk pool sampled. Although Elimia did not reach isotopic equilibrium during the tracer experiment, application of a N-turnover model to the field data suggested that it assimilated a combination of epilithon and detritus. The amphipod Gammarus minus appeared to depend mostly on fine benthic organic matter (FBOM), and the coleopteran Anchytarsus bicolor on epixylon. The caddisfly Diplectrona modesta appeared to assimilate primarily a fast N-turnover portion of the FBOM pool, and Simuliidae a fast N-turnover component of the suspended particulate organic matter pool rather than the bulk pool sampled. Together, the

  2. Stable platinum isotope measurements in presolar nanodiamonds by TEAMS

    NASA Astrophysics Data System (ADS)

    Wallner, A.; Melber, K.; Merchel, S.; Ott, U.; Forstner, O.; Golser, R.; Kutschera, W.; Priller, A.; Steier, P.

    2013-01-01

    Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of 198Pt/195Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction.

  3. Stable platinum isotope measurements in presolar nanodiamonds by TEAMS

    PubMed Central

    Wallner, A.; Melber, K.; Merchel, S.; Ott, U.; Forstner, O.; Golser, R.; Kutschera, W.; Priller, A.; Steier, P.

    2013-01-01

    Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of 198Pt/195Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction. PMID:23565017

  4. Stable platinum isotope measurements in presolar nanodiamonds by TEAMS.

    PubMed

    Wallner, A; Melber, K; Merchel, S; Ott, U; Forstner, O; Golser, R; Kutschera, W; Priller, A; Steier, P

    2013-01-01

    Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of (198)Pt/(195)Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction.

  5. Stable platinum isotope measurements in presolar nanodiamonds by TEAMS.

    PubMed

    Wallner, A; Melber, K; Merchel, S; Ott, U; Forstner, O; Golser, R; Kutschera, W; Priller, A; Steier, P

    2013-01-01

    Nanodiamonds are stardust grains commonly found in primitive meteorites. They survived the formation of the solar system and kept their own individuality. Measurements of trace-element isotopic signatures in these grains will help understanding heavy element nucleosynthesis in massive stars and dust formation from their ejecta. We have continued previous attempts to search for stable Pt isotope anomalies in nanodiamonds via trace element accelerator mass spectrometry (TEAMS). The installation of a new injector beam line at the VERA facility allowed studying low traces of stable elements in different materials. Moreover, recent experiments showed that VERA provides the required measurement precision together with a low Pt machine background. Here, we observed for the first time an indication for enhancements of (198)Pt/(195)Pt isotope ratios in two diamond residues prepared by different chemical separation techniques from the Allende meteorite. Variations in other isotopic ratios were within analytical uncertainty, and no anomaly was identified in a third diamond fraction. PMID:23565017

  6. Trace Element Abundance Measurements on Cosmic Dust Particles

    NASA Technical Reports Server (NTRS)

    Flynn, George

    1996-01-01

    The X-Ray Microprobe on beamline X-26A at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory was used to determine the abundances of elements from Cr through Sr in individual interplanetary dust particles (IDPs) collected from the Earth's stratosphere and the Scanning Transmission X-ray Microscope (STXM) on beamline X-1A at the NSLS was used to determine the carbon abundances and spatial distributions in IDPs. In addition, modeling was performed in an attempt to associate particular types of IDPs with specific types of parent bodies, and thus to infer the chemistry, mineralogy, and structural properties of those parent bodies.

  7. MG Isotopic Measurement of FIB-Isolated Presolar Silicate Grains

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Nguyen, A.; Ito, M.; Rahman, Z.

    2010-01-01

    The majority of presolar oxide and silicate grains are ascribed to origins in low-mass red giant and asymptotic giant branch (AGB) stars based on their O isotopic ratios. However, a minor population of these grains (< 10%) has O isotopic ratios incompatible with these sources. Two principle alternative sources are higher-than-solar metallicity (Z) stars or, more likely, supernovae (SN) [1-3]. These rare (Group 4) grains [3] are characterized by enrichments in O-18, and typically also enrichments in O-17. An even rarer subset of grains with extremely large enrichments in O-17 and smaller depletions in O-18 were suggested to come from binary star systems [2]. To establish the origins of these isotopically unusual grains, it is necessary to examine isotopic systems in addition to O. Presolar silicates offer several elements diagnostic of their stellar sources and nuclear processes, including O, Si, Mg, Fe and Ca. However, the database for minor element isotopic compositions in silicates is seriously lacking. To date only two silicate grains have been analyzed for Mg [4] or Fe [5]. One major complicating factor is their small size (average 230 nm), which greatly limits the number of measurements that can be performed on any one grain and makes it more difficult to obtain statistically relevant data. This problem is compounded because the grains are identified among isotopically solar silicates, which contribute a diluting signal in isotopic measurements [1]. Thus, relatively small isotopic anomalies are missed due to this dilution effect. By applying focused ion beam (FIB) milling, we obtain undiluted Mg isotopic ratios of isolated rare presolar silicate grains to investigate their sources.

  8. Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

    SciTech Connect

    Horkley, J. J.; Carney, K. P.; Gantz, E. M.; Davies, J. E.; Lewis, R. R.; Crow, J. P.; Poole, C. A.; Grimes, T. S.; Giglio, J. J.

    2015-03-17

    Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure “spike” solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for “age” determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determine 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution, and the encapsulation of the materials will be described.

  9. Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

    SciTech Connect

    J.J. Horkley; K.P E.M. Gantz; J.E. Davis; R.R. Lewis; J.P. Crow; C.A. Poole; T.S. Grimes; J.J. Giglio

    2015-03-01

    t Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure ‘‘spike’’ solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for ‘‘age’’ determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determine 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution,

  10. Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

    DOE PAGES

    Horkley, J. J.; Carney, K. P.; Gantz, E. M.; Davies, J. E.; Lewis, R. R.; Crow, J. P.; Poole, C. A.; Grimes, T. S.; Giglio, J. J.

    2015-03-17

    Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure “spike” solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for “age” determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determinemore » 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution, and the encapsulation of the materials will be described.« less

  11. Effectiveness of mosquito traps in measuring species abundance and composition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mosquito species abundance and composition estimates provided by trapping devices are commonly used to guide control efforts, but knowledge of trap biases is necessary for accurately interpreting results. We compared the Mosquito Magnet – Pro, the Mosquito Magnet – X and the CDC Miniature Light Trap...

  12. Measurement of stable carbon isotope ratios of non-methane hydrocarbons and halocarbons

    NASA Astrophysics Data System (ADS)

    Zuiderweg, A. T.

    2012-09-01

    Within the realm of volatile organic compounds, hydrocarbons and halocarbons form a sizable proportion of carbon input to the atmosphere. Within these compound categories, the light non-methane hydrocarbons (NMHC, two to seven carbon atoms) and monocarbon halocarbons have a special place as these have strong, if not exclusive, anthropogenic (human-caused) sources. With common atmospheric molar mixing ratios in the parts-per-trillion (10-12 mole/mole) to parts-per-billion (10-9 mole/mole) range, these trace gases, though decidedly minor constituants of the atmosphere, have diverse consequences due to their atmospheric presence and their removal processes. Effects range from causing ground level air pollution and resulting hazards to health, to contributing to anthropogenic climate change and the destruction of the ozone layer in the stratosphere, among many others. The existance of stable isotopes (otherwise identical atoms with varying amounts of neutrons that do not spontaneously disintegrate) in several elements relevant to atmospheric chemistry and physics is a boon to research. Their presence in molecules is detectable by mass and cause small intra- and intermolecular property changes. These changes range from the physical (e.g. boiling point variation) to the chemical (reaction rate variation) and can influence external interactions as well. The measurement of the ratio of a minor stable isotope of an element to the major one (the stable isotope ratio) can be used to establish source fingerprints, trace the interaction dynamics, and refine the understanding of the relative contribution of sources and sinks to the atmosphere as a whole. The stable minor stable isotope of carbon, 13C, has a natural abundance of approximately 1.1 %. It has a sufficient fractional mass difference from its major isotope as to cause significant effects, making it ideal for measuring the ratios and properties of hydro- and halocarbons. In order to enable a better understanding of the

  13. Guide to plutonium isotopic measurements using gamma-ray spectrometry

    SciTech Connect

    Lemming, J.F.; Rakel, D.A.

    1982-08-26

    Purpose of this guide is to assist those responsible for plutonium isotopic measurements in the application of gamma-ray spectrometry. Objectives are to promote an understanding of the measurement process, including its limitations and applicability, by reviewing the general features of a plutonium spectrum and identifying the quantities which must be extracted from the data; to introduce state-of-the-art analysis techniques by reviewing four isotopic analysis packages and identifying their differences; to establish the basis for measurement control and assurance by discussing means of authenticating the performance of a measurement system; and to prepare for some specific problems encountered in plutonium isotopic analyses by providing solutions from the practical experiences of several laboratories. 29 references, 12 figures, 17 tables.

  14. Phosphoprotein Isotope-coded Affinity Tags: Application to the Enrichment and Identification of Low-Abundance Phosphoproteins

    SciTech Connect

    Goshe, Michael; Veenstra, Timothy D. ); Panisko, Ellen A.; Conrads, Thomas P. ); Angell, Nicolas H.; Smith, Richard D. )

    2002-02-01

    A novel approach using different isotopic labeling and biotinylation has been developed for the enrichment and quantitation of phosphoseryl and phosphothreonyl-peptides. The phosphoprotein isotope-coded affinity tag (PhIAT) exploits the high affinity biotin-avidin interaction to isolate modified phosphopeptides from a complex mixture of peptides. The PhIAT strategy for quantifying and enriching mixtures for phosphopeptides was demonstrated using a commercially available sample of the phosphoprotein B-casein. A denatured solution of B-casein was labeled using the PhIAT method and after proteolytic digestion, the labeled peptides were isolated using immobilize avidin. The recovered peptides were separated by capillary reversed-phase liquid chromatography and identified by tandem mass spectrometry. PhIAT-labeled peptides corresponding to known O-phosphorylated peptides from B-casein were identified as were phosphorylated peptides from as1-casein and ase-casein, known low-level (< 5%) contaminants of commercially available B-casein. All of the identified phosphopeptides from these caseins have been previously documented to be phosphorylated at the sites elucidated by the PhIAT approach. The results illustrate the efficancy of the PhIAT-labeling strategy to enrich mixtures for phosphopeptides and permit the detection and identification of low abundance phosphopeptides. In addition, experiments using light and heavy isotopic version of the PhIAT reagents demonstrated that a 10% difference in phosphorylation state could be determined between phosphopeptides in comparative samples.

  15. Quantitative estimates of precision for molecular isotopic measurements.

    PubMed

    Jasper, J P

    2001-01-01

    At least three methods of calculating the random errors or variance of molecular isotopic data are presently in use. The major components of variance are differentiated and quantified here into least three to four individual components. The measurement of error of the analyte relative to a working (whether an internal or an external) standard is quantified via the statistical pooled estimate of error. A statistical method for calculating the total variance associated with the difference of two individual isotopic compositions from two isotope laboratories is given, including the variances of the laboratory (secondary) and working standards, as well as those of the analytes. An abbreviated method for estimation of of error typical for chromatographic/isotope mass spectrometric methods is also presented.

  16. CNO abundances and carbon isotope ratios in evolved stars of the open clusters NGC 2324, NGC 2477, and NGC 3960

    NASA Astrophysics Data System (ADS)

    Tautvaišienė, Gražina; Drazdauskas, Arnas; Bragaglia, Angela; Randich, Sofia; Ženovienė, Renata

    2016-10-01

    Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters NGC 2324, NGC 2477, and NGC 3960, which have turn-off masses of about 2 M⊙, and to compare them with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential synthetic spectrum method. Abundances of carbon were derived using the C2 Swan (0, 1) band heads at 5135 and 5635.5 Å. The wavelength interval 7940-8130 Å with strong CN features was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 Å. Results: The mean values of the CNO abundances are [C/Fe] = -0.35 ± 0.06 (s.d.), [N/Fe] = 0.28 ± 0.05, and [O/Fe] = -0.02 ± 0.10 in seven stars of NGC 2324; [C/Fe] = -0.26 ± 0.02, [N/Fe] = 0.39 ± 0.04, and [O/Fe] = -0.11 ± 0.06 in six stars of NGC 2477; and [C/Fe] = -0.39 ± 0.04, [N/Fe] = 0.32 ± 0.05, and [O/Fe] = -0.19 ± 0.06 in six stars of NGC 3960. The mean C/N ratio is equal to 0.92 ± 0.12, 0.91 ± 0.09, and 0.80 ± 0.13, respectively. The mean 12C /13C ratio is equal to 21 ± 1, 20 ± 1, and 16 ± 4, respectively. The 12C /13C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. Conclusions: The mean values of the 12C /13C and C/N ratios in NGC 2324 and NGC 2477 agree well with the first dredge-up and thermohaline-induced extra-mixing models, which are similar for intermediate turn-off mass stars. The 12C /13C ratios in the investigated clump stars of NGC 3960 span from 10 to 20. The mean carbon isotope and C/N ratios in NGC 3960 are close to predictions of the model in which the thermohaline- and rotation-induced (if rotation velocity at the zero-age main sequence was 30% of the critical velocity) extra-mixing act together. Based on observations collected at ESO telescopes under programmes 072.D-0550 and 074.D-0571.

  17. Carbon, nitrogen and sulfur in lunar fines 15012 and 15013 - Abundances, distributions and isotopic compositions

    NASA Technical Reports Server (NTRS)

    Chang, S.; Lawless, J.; Romiez, M.; Kaplan, I. R.; Petrowski, C.; Sakai, H.; Smith, J. W.

    1974-01-01

    Lunar fines 15012,16 and 15013,3 were analyzed by stepwise pyrolysis and acid hydrolysis as well as complete combustion in oxygen to determine carbon, nitrogen and sulfur. In addition, hydrogen was analysed during pyrolysis as well as during hydrolysis. By comparison of the distribution frequencies of C, N, S, H2 and Fe with He-4, considered to have arisen from solar wind contribution, it is concluded that nitrogen and hydrogen have largely a solar origin. Carbon has a significant solar contribution, and metallic iron may have resulted from solar wind interaction with ferrous minerals on the lunar surface. Sulfur probably has a predominantly lunar origin. There is no direct evidence for meteorotic contribution to these samples. Solar wind interaction also has a marked effect on the stable isotope distribution of C-13/C-12, N-15/N-14, and S-34/S-32. In all cases, the heavy isotope was most enriched in the smallest grain-size fraction.

  18. Theoretical effect of diffusion on isotopic abundance ratios in rocks and associated fluids

    USGS Publications Warehouse

    Senftle, F.E.; Bracken, J.T.

    1955-01-01

    Diffusion is considered as a possible process of isotope fractionation taking place throughout geologic time. Both diffusion in solids and diffusion in liquids are taken as possible mechanisms, the latter being more important. Arguments are presented to show that if significant fractionation takes place within a crystal by outward diffusion under solid-state conditions, enrichment will be evident only in elements of minor concentration. Similar conclusions are inferred for solid-state diffusion across a boundary or for diffusion in liquids. No isotopic enrichment can be expected in relatively large bodies of diffusion transported material. Although the necessary data to confirm these conclusions are scanty, it seems worth while to undertake further work in this direction. ?? 1955.

  19. Models of earth structure inferred from neodymium and strontium isotopic abundances

    PubMed Central

    Wasserburg, G. J.; DePaolo, D. J.

    1979-01-01

    A simplified model of earth structure based on the Nd and Sr isotopic characteristics of oceanic and continental tholeiitic flood basalts is presented, taking into account the motion of crustal plates and a chemical balance for trace elements. The resulting structure that is inferred consists of a lower mantle that is still essentially undifferentiated, overlain by an upper mantle that is the residue of the original source from which the continents were derived. PMID:16592688

  20. Continuous on-line water vapor isotope measurements in Antarctica

    NASA Astrophysics Data System (ADS)

    Landsberg, Janek; Romanini, Daniele; Holmen, Kim; Isaksson, Elisabeth; Meijer, Harro; Kerstel, Erik

    2010-05-01

    In the context of a globally warming climate it is crucial to study the climate variability in the past and to understand the underlying mechanisms (1). Precipitation deposited on the polar ice caps provides a means to retrieve information on temperature changes (through the paleo-temperature dependence of the isotopic composition of the ice) and atmospheric composition (of gas stored in bubbles in the ice) on time scales from one to almost one million years, with sub-annual resolution in the most recent centuries. However, it is now widely recognized that the calibration of the paleo-thermometer is highly problematic. For this reason attempts to model the global water cycle, including the isotope signals, are ongoing with the aim of providing a more physical basis of the isotope - temperature relation. Currently, there is a large divergence in the results obtained by different modeling strategies. The missing link in these model studies is their forcing by experimental data on the pre-deposition isotopic composition of the vapor phase compartment of the hydrological cycle. We propose to measure the isotopic composition of moisture carried towards and deposited on Antarctica, in order to constrain the numerical models. In this context we are developing a modified, more sensitive and precise, version of a laser water vapor isotope spectrometer, originally designed for stratospheric studies (2, 3). This instrument, which will first be operated at the Norwegian station of Troll in Queen Maud Land, will enable the continuous, online measurement of all three stable isotope ratios of atmospheric water vapor. So far, such data is non-existent. Our data should improve the validity of the models and improve the understanding of the physical mechanisms at the basis of the isotope thermometer. This in turn will lead to an increased confidence in the predictions of (general circulation) models concerning climate variability. (1) International Panel on Climate Change (IPCC), 4

  1. A chart of cosmic ray isotopes. [showing radioactive decay, abundance and nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Waddington, C. J.

    1975-01-01

    A chart has been prepared that lists some of the properties relevant to cosmic ray studies of all the significant nuclides between lithium and nickel. On this chart there are shown all the possible decays that might be of interest in the unique conditions experienced by cosmic ray nuclei, various abundance figures and the probable nucleosynthesis processes of origin.

  2. Cosmic ray abundance measurements with the CAKE balloon experiment

    NASA Astrophysics Data System (ADS)

    Cecchini, S.; Chiarusi, T.; Giacomelli, G.; Manzoor, S.; Medinaceli, E.; Patrizii, L.; Togo, V.

    We present the results from the CAKE (Cosmic Abundance below Knee Energy) balloon experiment which uses nuclear track detectors. The final experiment goal is the determination of the charge spectrum of CR nuclei with Z > 30 in the primary cosmic radiation. The detector, which has a geometric acceptance of \\~ 1.7 m2 sr, was exposed in a trans-mediterranean stratospheric balloon flight. Calibrations of the detectors used (CR39 and Lexan), scanning strategies and algorithms for tracking particles in an automatic mode are presented. The present status of the results is discussed

  3. Isotopic Resonance Hypothesis: Experimental Verification by Escherichia coli Growth Measurements

    PubMed Central

    Zubarev, Roman A.

    2015-01-01

    Isotopic composition of reactants affects the rates of chemical and biochemical reactions. As a rule, enrichment of heavy stable isotopes leads to progressively slower reactions. But the recent isotopic resonance hypothesis suggests that the dependence of the reaction rate upon the enrichment degree is not monotonous. Instead, at some “resonance” isotopic compositions, the kinetics increases, while at “off-resonance” compositions the same reactions progress slower. To test the predictions of this hypothesis for the elements C, H, N and O, we designed a precise (standard error ±0.05%) experiment that measures the parameters of bacterial growth in minimal media with varying isotopic composition. A number of predicted resonance conditions were tested, with significant enhancements in kinetics discovered at these conditions. The combined statistics extremely strongly supports the validity of the isotopic resonance phenomenon (p ≪ 10−15). This phenomenon has numerous implications for the origin of life studies and astrobiology, and possible applications in agriculture, biotechnology, medicine, chemistry and other areas. PMID:25782666

  4. A hydrogen gas-water equilibration method produces accurate and precise stable hydrogen isotope ratio measurements in nutrition studies.

    PubMed

    Wong, William W; Clarke, Lucinda L

    2012-11-01

    Stable hydrogen isotope methodology is used in nutrition studies to measure growth, breast milk intake, and energy requirement. Isotope ratio MS is the best instrumentation to measure the stable hydrogen isotope ratios in physiological fluids. Conventional methods to convert physiological fluids to hydrogen gas (H(2)) for mass spectrometric analysis are labor intensive, require special reagent, and involve memory effect and potential isotope fractionation. The objective of this study was to determine the accuracy and precision of a platinum catalyzed H(2)-water equilibration method for stable hydrogen isotope ratio measurements. Time to reach isotopic equilibrium, day-to-day and week-to-week reproducibility, accuracy, and precision of stable hydrogen isotope ratio measurements by the H(2)-water equilibration method were assessed using a Thermo DELTA V Advantage continuous-flow isotope ratio mass spectrometer. It took 3 h to reach isotopic equilibrium. The day-to-day and week-to-week measurements on water and urine samples with natural abundance and enriched levels of deuterium were highly reproducible. The method was accurate to within 2.8 (o)/oo and reproducible to within 4.0 (o)/oo based on analysis of international references. All the outcome variables, whether in urine samples collected in 10 doubly labeled water studies or plasma samples collected in 26 body water studies, did not differ from those obtained using the reference zinc reduction method. The method produced highly accurate estimation on ad libitum energy intakes, body composition, and water turnover rates. The method greatly reduces the analytical cost and could easily be adopted by laboratories equipped with a continuous-flow isotope ratio mass spectrometer.

  5. A Hydrogen Gas-Water Equilibration Method Produces Accurate and Precise Stable Hydrogen Isotope Ratio Measurements in Nutrition Studies12

    PubMed Central

    Wong, William W.; Clarke, Lucinda L.

    2012-01-01

    Stable hydrogen isotope methodology is used in nutrition studies to measure growth, breast milk intake, and energy requirement. Isotope ratio MS is the best instrumentation to measure the stable hydrogen isotope ratios in physiological fluids. Conventional methods to convert physiological fluids to hydrogen gas (H2) for mass spectrometric analysis are labor intensive, require special reagent, and involve memory effect and potential isotope fractionation. The objective of this study was to determine the accuracy and precision of a platinum catalyzed H2-water equilibration method for stable hydrogen isotope ratio measurements. Time to reach isotopic equilibrium, day-to-day and week-to-week reproducibility, accuracy, and precision of stable hydrogen isotope ratio measurements by the H2-water equilibration method were assessed using a Thermo DELTA V Advantage continuous-flow isotope ratio mass spectrometer. It took 3 h to reach isotopic equilibrium. The day-to-day and week-to-week measurements on water and urine samples with natural abundance and enriched levels of deuterium were highly reproducible. The method was accurate to within 2.8 o/oo and reproducible to within 4.0 o/oo based on analysis of international references. All the outcome variables, whether in urine samples collected in 10 doubly labeled water studies or plasma samples collected in 26 body water studies, did not differ from those obtained using the reference zinc reduction method. The method produced highly accurate estimation on ad libitum energy intakes, body composition, and water turnover rates. The method greatly reduces the analytical cost and could easily be adopted by laboratories equipped with a continuous-flow isotope ratio mass spectrometer. PMID:23014490

  6. A Portable, Field-Deployable Analyzer for Isotopic Water Measurements

    NASA Astrophysics Data System (ADS)

    Berman, E. S.; Gupta, M.; Huang, Y. W.; Lacelle, D.; McKay, C. P.; Fortson, S.

    2015-12-01

    Water stable isotopes have for many years been used to study the hydrological cycle, catchment hydrology, and polar climate among other applications. Typically, discrete water samples are collected and transported to a laboratory for isotope analysis. Due to the expense and labor associated with such sampling, isotope studies have generally been limited in scope and time-resolution. Field sampling of water isotopes has been shown in recent years to provide dense data sets with the increased time resolution illuminating substantially greater short term variability than is generally observed during discrete sampling. A truly portable instrument also opens the possibility to utilize the instrument as a tool for identifying which water samples would be particularly interesting for further laboratory investigation. To make possible such field measurements of liquid water isotopes, Los Gatos Research has developed a miniaturized, field-deployable liquid water isotope analyzer. The prototype miniature liquid water isotope analyzer (mini-LWIA) uses LGR's patented Off-Axis ICOS (Integrated Cavity Output Spectroscopy) technology in a rugged, Pelican case housing for easy transport and field operations. The analyzer simultaneously measures both δ2H and δ18O from liquid water, with both manual and automatic water introduction options. The laboratory precision for δ2H is 0.6 ‰, and for δ18O is 0.3 ‰. The mini-LWIA was deployed in the high Arctic during the summer of 2015 at Inuvik in the Canadian Northwest Territories. Samples were collected from Sachs Harbor, on the southwest coast of Banks Island, including buried basal ice from the Lurentide Ice Sheet, some ice wedges, and other types of ground ice. Methodology and water analysis results from this extreme field deployment will be presented.

  7. Leaf water oxygen isotope measurement by direct equilibration.

    PubMed

    Song, Xin; Barbour, Margaret M

    2016-08-01

    The oxygen isotope composition of leaf water imparts a signal to a range of molecules in the atmosphere and biosphere, but has been notoriously difficult to measure in studies requiring a large number of samples as a consequence of the labour-intensive extraction step. We tested a method of direct equilibration of water in fresh leaf samples with CO2 , and subsequent oxygen isotope analysis on an optical spectrometer. The oxygen isotope composition of leaf water measured by the direct equilibration technique was strongly linearly related to that of cryogenically extracted leaf water in paired samples for a wide range of species with differing anatomy, with an R(2) of 0.95. The somewhat more enriched values produced by the direct equilibration method may reflect lack of full equilibration with unenriched water in the vascular bundles, but the strong relationship across a wide range of species suggests that this difference can be adequately corrected for using a simple linear relationship.

  8. Radioactive halos and ion microprobe measurement of Pb isotope ratios

    NASA Technical Reports Server (NTRS)

    Gentry, R. V.

    1974-01-01

    This investigation was to obtain, if possible, the Pb isotope ratios of both lunar and meteoritic troilite grains by utilizing ion microprobe techniques. Such direct in situ measurement of Pb isotope ratios would eliminate contamination problems inherent in wet chemistry separation procedures, and conceivably determine whether lunar troilite grains were of meteoritic origin. For comparison purposes two samples of meteoritic troilite were selected (one from Canyon Diablo) for analysis along with two very small lunar troilite grains (approximately 50-100 microns). It was concluded that the ion microprobe as presently operating, does not permit the in situ measurement of Pb isotope ratios in lunar or meteoritic troilite. On the basis of these experiments no conclusions could be drawn as to the origin of the lunar troilite grains.

  9. The Kaidun chondrite breccia: Petrology, oxygen isotopes, and trace element abundances

    NASA Astrophysics Data System (ADS)

    MacPherson, Glenn J.; Mittlefehldt, David W.; Lipschutz, Michael E.; Clayton, Robert N.; Bullock, Emma S.; Ivanov, Andrei V.; Mayeda, Toshiko K.; Wang, Ming-Sheng

    2009-09-01

    Oxygen isotope and trace element data for 13 samples of the Kaidun chondritic breccia reaffirm the complex polymict nature of this unique meteorite. Bulk Kaidun samples most closely resemble CR chondrites, but the matrix is CI-like. Two separated clasts are CR-like but have some properties that resemble CM, two clasts are enstatite chondrites (one EL and one EH), one clast is an aubrite-like metal-rich impact melt, and one clast is a unique layered olivine-bearing pyroxenite with the isotopic composition of an aubrite. Yet, although each clast resembles a known meteorite group, all deviate in some respect from the norms for those groups. Collectively, Kaidun has sampled materials not yet represented in the world meteorite collections and which greatly extend the definitions of known meteorite groups. Phyllosilicates in Kaidun span a very wide range in composition and vary from clast to clast, suggesting that the aqueous alteration experienced by the clasts predated assembly of the Kaidun parent body.

  10. Measuring sulfur isotopes by multicollector ICP-MS

    NASA Astrophysics Data System (ADS)

    Sessions, A. L.; Adkins, J. F.

    2011-12-01

    The stable isotopes of sulfur have traditionally been measured by converting analytes to SO2, which is then introduced to a gas-source isotope ratio mass spectrometer (IRMS). Recently, we and several other groups have begun measuring S isotopes using a multicollector inductively-coupled plasma mass spectrometer (MC-ICP-MS). The approach offers several advantages, including decreased reliance on preparatory chemical conversion (including combustion) of analytes, greater flexibility of sample introduction, and increased sensitivity. Sulfur is measured as monoatomic S+ ions produced in the plasma source, and can be introduced in a variety of forms including dissolved sulfate or sulfide, or as organosulfur compounds either in solution or in the gas phase. A primary requirement for accurate measurements is resolving isobaric interferences from O2+, which requires a mass analyzer with resolution > 4000. Using a Thermo Neptune system, we document accuracy and precision for δ34S near the shot-noise limit (ie, counting statistics) for both aqueous solutions and gas streams. For samples containing 50 pmol S (as gaseous SF6), this corresponds to ~0.3%; for 50 nmol S (as aqueous SO4) this is ~0.02%. One important application of this new analytical approach is the measurement of S isotopes in volatile and semivolatile organic compounds. No IRMS-based methods for measuring compound-specific S isotopes currently exist. We have demonstrated this capability by coupling a capillary gas chromatograph (GC) directly to the ICP-MS via a heated transfer line. Isotope ratios (δ34S values) are calculated relative to co-injected peaks of SF6 reference gas, in the same manner as is used by GC-combustion-IRMS approaches. As a demonstration of this capability, we measured the δ34S values of individual thiophene isomers separated by GC from a crude oil, which range over 20% for compounds from the same oil. A second application of ICP-MS to sulfur isotopes is the measurement of dissolved

  11. Apparent abundance and vertical profiles of ozone from OMEGA measurements

    NASA Astrophysics Data System (ADS)

    Altieri, F.; Zasova, L.; Grassi, D.; Bellucci, G.; Bibring, J.-P.; Formisano, V.; Ignatiev, N.; Drossart, P.; Encrenaz, T.; Fouchet, T.; OMEGA Team

    In this work we study the vertical and seasonal distribution of O2 by means the 1.27 micron day glow emission in the spectra acquired by OMEGA, the imaging spectrometer on board the ESA mission Mars Express. Limb OMEGA observations have been used to retrieve the vertical distribution of O3 up to 20 km, applying an "onion peeling" procedure. The quenching effect due to the collisions with the CO2 have been taken into account using simultaneously vertical CO2 profiles obtained by the PFS LWC data. OMEGA nadir observations have been used to map the latitude, local time and seasonal distribution of the apparent ozone abundance in the Martian atmosphere and results are discussed. We acknowledge the ESA Headquarters and IFSI-INAF for support to Russian CoIs and the Russian Foundation of Basic Research for grant RFFI 04-02-16856a.

  12. Measurement of Absolute Carbon Isotope Ratios: Mechanisms and Implications

    NASA Astrophysics Data System (ADS)

    Vogel, J. S.; Giacomo, J. A.; Dueker, S. R.

    2012-12-01

    An accelerator mass spectrometer (AMS) produced absolute isotope ratio measurements for 14C/13C as tested against >500 samples of NIST SRM-4990-C (OxII 14C standard) to an accuracy of 2.2±0.6‰ over a period of one year with measurements made to 1% counting statistics. The spectrometer is not maximized for 13C/12C, but measured ∂13C to 0.4±0.1‰ accuracy, with known methods for improvement. An AMS produces elemental anions from a sputter ion source and includes a charge-changing collision in a gas cell to isolate the rare 14C from the common isotopes and molecular isobars. Both these physical processes have been modeled to determine the parameters providing such absolute measures. Neutral resonant ionization in a cesium plasma produces mass-independent ionization, while velocity dependent charge-state distributions in gas collisions produce relative ion beam intensities that are linear in mass at specific collision energies. The mechanisms are not specific to carbon isotopes, but stand alone absolute IRMS (AIR-MS) instruments have not yet been made. Aside from the obvious applications in metrology, AIR-MS is particularly valuable in coupled separatory MS because no internal or external standards are required. Sample definition processes can be compared, even if no exact standard reference sample exists. Isotope dilution measurements do not require standards matching the dilution end-points and can be made over an extended, even extrapolated, range.

  13. Accurate experimental determination of the isotope effects on the triple point temperature of water. I. Dependence on the 2H abundance

    NASA Astrophysics Data System (ADS)

    Faghihi, V.; Peruzzi, A.; Aerts-Bijma, A. T.; Jansen, H. G.; Spriensma, J. J.; van Geel, J.; Meijer, H. A. J.

    2015-12-01

    Variation in the isotopic composition of water is one of the major contributors to uncertainty in the realization of the triple point of water (TPW). Although the dependence of the TPW on the isotopic composition of the water has been known for years, there is still a lack of a detailed and accurate experimental determination of the values for the correction constants. This paper is the first of two articles (Part I and Part II) that address quantification of isotope abundance effects on the triple point temperature of water. In this paper, we describe our experimental assessment of the 2H isotope effect. We manufactured five triple point cells with prepared water mixtures with a range of 2H isotopic abundances encompassing widely the natural abundance range, while the 18O and 17O isotopic abundance were kept approximately constant and the 18O  -  17O ratio was close to the Meijer-Li relationship for natural waters. The selected range of 2H isotopic abundances led to cells that realised TPW temperatures between approximately  -140 μK to  +2500 μK with respect to the TPW temperature as realized by VSMOW (Vienna Standard Mean Ocean Water). Our experiment led to determination of the value for the δ2H correction parameter of A2H  =  673 μK / (‰ deviation of δ2H from VSMOW) with a combined uncertainty of 4 μK (k  =  1, or 1σ).

  14. Precise measurement of chromium isotopes by MC-ICPMS

    PubMed Central

    Schiller, Martin; Van Kooten, Elishevah; Holst, Jesper C.; Olsen, Mia B.; Bizzarro, Martin

    2014-01-01

    We report novel analytical procedures allowing for the concurrent determination of the stable and mass-independent Cr isotopic composition of silicate materials by multiple collector inductively coupled mass spectrometry (MC-ICPMS). In particular, we focus on improved precision of the measurement of the neutron-rich isotope 54Cr. Because nitride and oxide interferences are a major obstacle to precise and accurate 54Cr measurements by MC-ICPMS, our approach is designed to minimize these interferences. Based on repeat measurements of standards, we show that the mass-independent 53Cr and 54Cr compositions can be routinely determined with an external reproducibility better than 2.5 and 5.8 ppm (2 sd), respectively. This represents at least a two-fold improvement compared to previous studies. Although this approach uses significantly more Cr (30–60 μg) than analysis by thermal ionization mass spectrometry (TIMS), our result indicate that it is possible to obtain an external reproducibility of 19 ppm for the μ54Cr when consuming amounts similar to that typically analyzed by TIMS (1 μg). In addition, the amount of time required for analysis by MC-ICPMS is much shorter thereby enabling a higher sample throughput. As a result of the improved analytical precision, we identified small apparent mass-independent differences between different synthetic Cr standards and bulk silicate Earth (BSE) when using the kinetic law for the mass bias correction. These differences are attributed to the Cr loss by equilibrium processes during production of the synthetic standards. The stable isotope data concurrently obtained have a precision of 0.05‰ Da −1, which is comparable to earlier studies. Comparison of the measured isotopic composition of four meteorites with published data indicates that Cr isotope data measured by the technique described here are accurate to stated uncertainties. The stable Cr composition of the Bilanga and NWA 2999 achondrites suggests that the

  15. Abundance and Isotopic Composition of Gases in the Martian Atmosphere: First Results from the Mars Curiosity Rover

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul; Webster, Chris R.; Atreya, Sushil K.; Franz, Heather; Wong, Michael; Conrad, Pamela G.; Harpold, Dan; Jones, John J.; Leshin, Laurie, A.; Manning, Heidi; Owen, Tobias; Pepin, Robert O.; Squyres, Steven; Trainer, Melissa

    2013-01-01

    Repeated measurements of the composition of the Mars atmosphere from Curiosity Rover yield a (40)Ar/N2 ratio 1.7 times greater and the (40)Ar/(36)Ar ratio 1.6 times smaller than the Viking Lander values in 1976. The unexpected change in (40)Ar/N2 ratio probably results from different instrument characteristics although we cannot yet rule out some unknown atmospheric process. The new (40)Ar/(36)Ar ratio is more aligned with Martian meteoritic values. Besides Ar and N2 the Sample Analysis at Mars instrument suite on the Curiosity Rover has measured the other principal components of the atmosphere and the isotopes. The resulting volume mixing ratios are: CO2 0.960(+/- 0.007); (40)Ar 0.0193(+/- 0.0001); N2 0.0189(+/- 0.0003); O2 1.45(+/- 0.09) x 10(exp -3); and CO 5.45(+/- 3.62) x 10(exp 4); and the isotopes (40)Ar/(36)Ar 1.9(+/- 0.3) x 10(exp 3), and delta (13)C and delta (18)O from CO2 that are both several tens of per mil more positive than the terrestrial averages. Heavy isotope enrichments support the hypothesis of large atmospheric loss. Moreover, the data are consistent with values measured in Martian meteorites, providing additional strong support for a Martian origin for these rocks.

  16. Petrology, trace element abundances and oxygen isotopic compositions of a compound CAI-chondrule object from Allende

    NASA Astrophysics Data System (ADS)

    Wakaki, S.; Itoh, S.; Tanaka, T.; Yurimoto, H.

    2013-02-01

    We report the petrology, trace element abundances and oxygen isotopic characteristics of a compound CAI-chondrule object, WI-025, found in the Allende CV3 chondrite. The WI-025 is an irregularly shaped inclusion consisting of three texturally and chemically distinct portions: the interior portion, the igneous rim and the intermediate zone located between these two portions. The interior portion consists of anorthite, spinel, olivine and Al-bearing low-Ca pyroxene. The major element chemistry of the interior portion corresponds to that of Al-rich chondrules and is of intermediate character between fine-grained spinel-rich CAIs and ferromagnesian chondrules. The interior portion has abundant 16O-rich spinel (Δ17O = -14.2 to -24.7) and displays a group II CAI-like REE composition. These observations indicate that the interior portion contains a CAI component formed by fractional condensation. The major and trace element chemistry of the interior portion indicate that the CAI had subsequently assimilated chondrule materials through partial melting. The maximum heating temperature of the partial melting is estimated at approximately 1400 °C, similar to the maximum heating temperature of Type-B CAIs. The oxygen isotopic compositions of the olivine and low-Ca pyroxene (Δ17O = -6.3) in the interior portion indicate that the partial melting and chondrule assimilation took place under a moderately 16O-poor nebular gas. The igneous rim is texturally and chemically similar to ferromagnesian chondrules and entirely surrounds the interior portion. The oxygen isotopic compositions of the olivine and low-Ca pyroxene in the igneous rim are indistinguishable from those of the interior olivine and Al-bearing low-Ca pyroxenes. These observations indicate that a chondrule material, which was melted in the same nebular gas as the interior portion, was accreted to the interior portion. The intermediate zone represents a reaction zone accompanying the igneous rim formation. The

  17. Highly accurate isotope composition measurements by a miniature laser ablation mass spectrometer designed for in situ investigations on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Riedo, A.; Meyer, S.; Heredia, B.; Neuland, M. B.; Bieler, A.; Tulej, M.; Leya, I.; Iakovleva, M.; Mezger, K.; Wurz, P.

    2013-10-01

    An experimental procedure for precise and accurate measurements of isotope abundances by a miniature laser ablation mass spectrometer for space research is described. The measurements were conducted on different untreated NIST standards and galena samples by applying pulsed UV laser radiation (266 nm, 3 ns and 20 Hz) for ablation, atomisation, and ionisation of the sample material. Mass spectra of released ions are measured by a reflectron-type time-of-flight mass analyser. A computer controlled performance optimiser was used to operate the system at maximum ion transmission and mass resolution. At optimal experimental conditions, the best relative accuracy and precision achieved for Pb isotope compositions are at the per mill level and were obtained in a range of applied laser irradiances and a defined number of accumulated spectra. A similar relative accuracy and precision was achieved in the study of Pb isotope compositions in terrestrial galena samples. The results for the galena samples are similar to those obtained with a thermal ionisation mass spectrometer (TIMS). The studies of the isotope composition of other elements yielded relative accuracy and precision at the per mill level too, with characteristic instrument parameters for each element. The relative accuracy and precision of the measurements is degrading with lower element/isotope concentration in a sample. For the elements with abundances below 100 ppm these values drop to the percent level. Depending on the isotopic abundances of Pb in minerals, 207Pb/206Pb ages with accuracy in the range of tens of millions of years can be achieved.

  18. Combustion influences on natural abundance nitrogen isotope ratio in soil and plants following a wildfire in a sub-alpine ecosystem.

    PubMed

    Huber, Edith; Bell, Tina L; Adams, Mark A

    2013-11-01

    This before-and-after-impact study uses the natural abundance N isotope ratio (δ(15)N) to investigate the effects of a wildfire on sub-alpine ecosystem properties and processes. We measured the (15)N signatures of soil, charred organic material, ash and foliage in three sub-alpine plant communities (grassland, heathland and woodland) in south-eastern Australia. Surface bulk soil was temporarily enriched in (15)N immediately after wildfire compared to charred organic material and ash in all plant communities. We associated the enrichment of bulk soil with fractionation of N during combustion and volatilization of N, a process that also explains the sequential enrichment of (15)N of unburnt leaves > ash > charred organic material in relation to duration and intensity of heating. The rapid decline in (15)N of bulk soil to pre-fire values indicates that depleted ash, containing considerable amounts of total N, was readily incorporated into the soil. Foliar δ(15)N also increased with values peaking 1 year post-fire. Foliar enrichment was foremost coupled with the release of enriched NH4(+) into the soil owing to isotopic discrimination during volatilization of soluble N and combustion of organic material. The mode of post-fire regeneration influenced foliar (15)N enrichment in two species indicating use of different sources of N following fire. The use of natural abundance of (15)N in soil, ash and foliage as a means of tracing transformation of N during wildfire has established the importance of combustion products as an important, albeit temporary source of inorganic N for plants regenerating after wildfire. PMID:23649752

  19. Combustion influences on natural abundance nitrogen isotope ratio in soil and plants following a wildfire in a sub-alpine ecosystem.

    PubMed

    Huber, Edith; Bell, Tina L; Adams, Mark A

    2013-11-01

    This before-and-after-impact study uses the natural abundance N isotope ratio (δ(15)N) to investigate the effects of a wildfire on sub-alpine ecosystem properties and processes. We measured the (15)N signatures of soil, charred organic material, ash and foliage in three sub-alpine plant communities (grassland, heathland and woodland) in south-eastern Australia. Surface bulk soil was temporarily enriched in (15)N immediately after wildfire compared to charred organic material and ash in all plant communities. We associated the enrichment of bulk soil with fractionation of N during combustion and volatilization of N, a process that also explains the sequential enrichment of (15)N of unburnt leaves > ash > charred organic material in relation to duration and intensity of heating. The rapid decline in (15)N of bulk soil to pre-fire values indicates that depleted ash, containing considerable amounts of total N, was readily incorporated into the soil. Foliar δ(15)N also increased with values peaking 1 year post-fire. Foliar enrichment was foremost coupled with the release of enriched NH4(+) into the soil owing to isotopic discrimination during volatilization of soluble N and combustion of organic material. The mode of post-fire regeneration influenced foliar (15)N enrichment in two species indicating use of different sources of N following fire. The use of natural abundance of (15)N in soil, ash and foliage as a means of tracing transformation of N during wildfire has established the importance of combustion products as an important, albeit temporary source of inorganic N for plants regenerating after wildfire.

  20. Continental-Scale Stable Isotope Measurements at NEON to Address Ecological Processes Across Systems

    NASA Astrophysics Data System (ADS)

    Luo, H.; Goodman, K. J.; Hinckley, E. S.; West, J. B.; Williams, D. G.; Bowen, G. J.

    2013-12-01

    The National Ecological Observatory Network (NEON) is a national-scale research platform. The overarching goal of NEON is to enable understanding and forecasting of the impacts of climate change, land use change, and invasive species on aspects of continental-scale ecology (such as biodiversity, biogeochemistry, infectious diseases, ecohydrology, etc.). NEON focuses explicitly on questions that relate to grand challenges in environmental science, are relevant to large regions, and would otherwise be very difficult to address with traditional ecological approaches. The use of stable isotope approaches in ecological research has grown steadily during the last two decades. Stable isotopes at natural abundances in the environment trace and integrate the interaction between abiotic and biotic components across temporal and spatial scales. In this poster, we will present the NEON data products that incorporate stable isotope measurements in atmospheric, terrestrial, and aquatic ecosystems in North America. We further outline current questions in the natural sciences community and how these data products can be used to address continental-scale ecological questions, such as the ecological impacts of climate change, terrestrial-aquatic system linkages, land-atmosphere exchange, landscape ecohydrological processes, and linking biogeochemical cycles across systems. Specifically, we focus on the use of stable isotopes to evaluate water availability and residence times in terrestrial systems, as well as nutrient sources to terrestrial systems, and cycling across ecosystem boundaries.

  1. Measurements of isotope effects in the photoionization of N2 and implications for Titan's atmosphere

    SciTech Connect

    Croteau, Philip; Randazzo, John B.; Kostko, Oleg; Ahmed, Musahid; Liang, Mao-Chang; Yung, Yuk L.; Boering, Kristie A.

    2010-12-30

    Isotope effects in the non-dissociative photoionization of molecular nitrogen (N2 + h nu -> N2+ + e-) may play a role in determining the relative abundances of isotopic species containing nitrogen in interstellar clouds and planetary atmospheres but have not been previously measured. Measurements of the photoionization efficiency spectra of 14N2, 15N14N, and 15N2 from 15.5 to 18.9 eV (65.6-80.0 nm) using the Advanced Light Source at Lawrence Berkeley National Laboratory show large differences in peak energies and intensities, with the ratio of the energy-dependent photoionization cross-sections, sigma(14N2)/sigma(15N14N), ranging from 0.4 to 3.5. Convolving the cross-sections with the solar flux and integrating over the energies measured, the ratios of photoionization rate coefficients are J(15N14N)/J(14N2)=1.00+-0.02 and J(15N2)/J(14N2)=1.00+-0.02, suggesting that isotopic fractionation between N2 and N2+ should be small under such conditions. In contrast, in a one-dimensional model of Titan's atmosphere, isotopic self-shielding of 14N2 leads to values of J(15N14N)/J(14N2) as large as ~;;1.17, larger than under optically thin conditions but still much smaller than values as high as ~;;29 predicted for N2 photodissociation. Since modeled photodissociation isotope effects overpredict the HC15N/HC14N ratio in Titan's atmosphere, and since both N atoms and N2+ ions may ultimately lead to the formation of HCN, estimates of the potential of including N2 photoionization to contribute to a more quantitative explanation of 15N/14N for HCN in Titan's atmosphere are explored.

  2. A natural abundance stable isotope tracer experiment to define SO2 oxidation pathways and their fractionation during heterogeneous oxidation

    NASA Astrophysics Data System (ADS)

    Amiri, N.; Norman, A. L.

    2015-12-01

    Sulfate aerosols have crucial direct and indirect effects on climate from radiative cooling to modifying clouds by formation of cloud condensation nuclei. Secondary sulfate aerosols are formed by oxidation of SO2 and subsequent nucleation and growth and the characteristics of primary aerosol sulfate can be modified by oxidation of SO2. There are several known oxidation pathways for SO2; gaseous phase OH oxidation and aqueous phase H2O2, O3 and transition metal oxides oxidation. The SO2 oxidation pathway affects the characteristics of the aerosols formed. Stable isotope techniques are useful in determining the oxidation pathway of SO2 due to unique fractionation patterns (Harris et al., 2012). However, there are still gaps in our understanding of the oxidation pathways and fractionations affecting SO2 and secondary sulfate. A tracer experiment to investigate the oxidation of SO2 and fractionation using size segregated aerosols in the presence of different compounds is described. Two high volume samplers situated to measure background sulfate upwind, and the results of a tracer experiment, downwind, is described. After sufficient size segregated aerosol sulfate has been collected, a source of SO2 with known isotopic composition is introduced to the second high volume sampler. Changes in the isotopic composition for size segregated aerosol sulfate in comparison to the first high volume sampler are investigated. The amount of fractionation during heterogeneous oxidation of SO2 on pre-existing aerosols is calculated using the concentrations and known isotopic composition and compared to data from laboratory and field experiments. The experiment is performed downwind of sources of organic compounds such as pine forests, and characterized using co-located canister samples, to determine the effects of SO2 oxidation on secondary aerosol sulfate.

  3. Stable isotope method to measure drug release from nanomedicines.

    PubMed

    Skoczen, Sarah; McNeil, Scott E; Stern, Stephan T

    2015-12-28

    Existing methods to measure nanomedicine drug release in biological matrices are inadequate. A novel drug release method utilizing a stable isotope tracer has been developed. Stable isotope-labeled drug is spiked into plasma containing nanomedicine. The labeled drug equilibrates with plasma components identical to the normoisotopic drug released from the nanomedicine formulation. Therefore, the ultrafilterable fraction of the isotope-labeled drug represents a reliable measure of free normoisotopic drug fraction in plasma, and can be used to calculate nanomedicine encapsulated and unencapsulated drug fractions. To demonstrate the utility of this method, we performed a plasma drug release study with both a fast releasing commercial docetaxel formulation, Taxotere®, and a delayed releasing nanomicellar formulation of a docetaxel prodrug, Procet 8. The instability of the unencapsulated prodrug in plasma allowed us to compare our calculated prodrug release and docetaxel conversion with the actual docetaxel concentration measured directly without fractionation. Drug release estimates for the fast releasing Taxotere formulation demonstrated accuracy deviation and precision (%CV) of <15%. For the controlled release Procet 8 formulation, we calculated a slow release and conversion of the prodrug in rat plasma that was highly correlated with the direct docetaxel measurement (R(2)=0.98). We believe that this method will have tremendous utility in the development and regulatory evaluation of nanomedicines, and aid in determination of generic bioequivalence.

  4. Odd isotope deficits in atmospheric Hg measured in lichens.

    PubMed

    Carignan, Jean; Estrade, Nicolas; Sonke, Jeroen E; Donard, Olivier F X

    2009-08-01

    Redox reactions govern mercury (Hg) concentrations in the atmosphere because fluxes (emissions and deposition), and residence times, are largely controlled by Hg speciation. Recent work on aquatic Hg photoreduction suggested that this reaction produces non-mass dependent fractionation (NMF) and that residual aquatic Hg(II)is characterized by positive delta199Hg and delta201Hg anomalies. Here, we show that atmospheric Hg accumulated in lichens is characterized by NMF with negative delta199Hg and delta201Hg values (-0.3 to -1 per thousand), making the atmosphere and the aquatic environment complementary reservoirs regarding photoreduction and NMF of Hg isotopes. Because few other reactions than aquatic Hg photoreduction induce NMF, photochemical reduction appears to be a key pathway in the global Hg cycle. Based on a NMF isotope mass balance, direct anthropogenic emissions may account for only 50 +/- 10% of atmospheric Hg deposition in an urban area of NE France. Furthermore, isotopic anomalies found in several polluted soils and sediments strongly suggests that an important part of Hg in these samples was affected by photoreactions and has cycled through the atmosphere before being stored in the geological environment. Thus, mercury isotopic anomalies measured in environmental samples may be used to trace and quantify the contribution of source emissions.

  5. Measurements of stable isotope ratios in milk samples from a farm placed in the mountains of Transylvania

    SciTech Connect

    Magdas, D. A. Cristea, G. Bot, A.; Puscas, R.; Radu, S.; Mirel, V.; Cordea, D. V.; Mihaiu, M.

    2013-11-13

    Product origin is of great importance for consumers especially because its association in consumer's perception with food quality, freedom from disease or pollution. Stable isotope ratio analysis is a powerful technique in food authenticity and traceability control which has been introduced within the European wine industry to ensure authenticity of wine provenance and to detect adulteration. Isotopic ratios measurements have also been successfully to other food commodities like: fruit juices, honey and dairy foods. The δ{sup 18}O and δ{sup 2}H content in milk water reflects the isotope composition of the ground water drunk by animals. Seasonal effects are also very important: in summer, milk water contains higher δ{sup 18}O and δ{sup 2}H values due to the fresh plants that are ate by animals. Relative carbon stable isotope abundances in total milk reflect the isotopic composition of the diet fed to the dairy cows. In this study the hydrogen, oxygen and carbon isotopic composition of 15 milk samples coming from a unit placed in the mountains of Transylvania was investigated. The distribution of the obtained isotopic values was than discussed taking into account that all the animals were feed with the same type of forage and consumed water was taken from the same source.

  6. Measurements of stable isotope ratios in milk samples from a farm placed in the mountains of Transylvania

    NASA Astrophysics Data System (ADS)

    Magdas, D. A.; Cristea, G.; Cordea, D. V.; Bot, A.; Puscas, R.; Radu, S.; Mirel, V.; Mihaiu, M.

    2013-11-01

    Product origin is of great importance for consumers especially because its association in consumer's perception with food quality, freedom from disease or pollution. Stable isotope ratio analysis is a powerful technique in food authenticity and traceability control which has been introduced within the European wine industry to ensure authenticity of wine provenance and to detect adulteration. Isotopic ratios measurements have also been successfully to other food commodities like: fruit juices, honey and dairy foods. The δ18O and δ2H content in milk water reflects the isotope composition of the ground water drunk by animals. Seasonal effects are also very important: in summer, milk water contains higher δ18O and δ2H values due to the fresh plants that are ate by animals. Relative carbon stable isotope abundances in total milk reflect the isotopic composition of the diet fed to the dairy cows. In this study the hydrogen, oxygen and carbon isotopic composition of 15 milk samples coming from a unit placed in the mountains of Transylvania was investigated. The distribution of the obtained isotopic values was than discussed taking into account that all the animals were feed with the same type of forage and consumed water was taken from the same source.

  7. Precise Re isotope ratio measurements by negative thermal ionization mass spectrometry (NTI-MS) using total evaporation technique

    NASA Astrophysics Data System (ADS)

    Suzuki, Katsuhiko; Miyata, Yoshiki; Kanazawa, Nobuyuki

    2004-06-01

    High precision rhenium isotope ratios, 187Re/185Re, have been determined by negative thermal ionization mass spectrometry (NTI-MS) using a total evaporation technique. The salient features of this method are evaporation of the entire sample and simultaneous integration of the signal from each isotope, which effectively eliminates isotope fractionation effects during the evaporation process. The 187Re/185Re ratio is obtained with a high reproducibility (1.6755+/-0.0014 (2[sigma]), R.S.D.=0.083%, n=28) for 50 pg-1 ng of a Re natural standard using the total evaporation with NTI-MS. This value is within analytical uncertainty of the previously reported accurate 187Re/185Re ratio (1.6740+/-0.0011) adopted by IUPAC as the Re isotopic composition, and is significantly more precise than the ratio obtained from conventional NTI-MS isotopic measurements in our laboratory (1.6772+/-0.0037 (2[sigma]), R.S.D.=0.22%, n=34). Based on these results, the total evaporation technique allows us to precisely determine Re isotope ratios, even for small sample amounts. In addition, this method is effective for highly precise Re abundance determinations using isotope dilution.

  8. Rate equation model of laser induced bias in uranium isotope ratios measured by resonance ionization mass spectrometry

    SciTech Connect

    Isselhardt, B. H.; Prussin, S. G.; Savina, M. R.; Willingham, D. G.; Knight, K. B.; Hutcheon, I. D.

    2015-12-07

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process between uranium atoms and potential isobars without the aid of chemical purification and separation. The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of the 235U/238U ratio to decrease laser-induced isotopic fractionation. In application, isotope standards are used to identify and correct bias in measured isotope ratios, but understanding laser-induced bias from first-principles can improve the precision and accuracy of experimental measurements. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variations in laser parameters on the measured isotope ratio. The model uses atomic data and empirical descriptions of laser performance to estimate the laser-induced bias expected in experimental measurements of the 235U/238U ratio. Empirical corrections are also included to account for ionization processes that are difficult to calculate from first principles with the available atomic data. As a result, development of this model has highlighted several important considerations for properly interpreting experimental results.

  9. Rate equation model of laser induced bias in uranium isotope ratios measured by resonance ionization mass spectrometry

    DOE PAGES

    Isselhardt, B. H.; Prussin, S. G.; Savina, M. R.; Willingham, D. G.; Knight, K. B.; Hutcheon, I. D.

    2015-12-07

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process between uranium atoms and potential isobars without the aid of chemical purification and separation. The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of the 235U/238U ratio to decrease laser-induced isotopic fractionation. In application, isotope standards are used to identify and correct bias in measured isotope ratios, but understanding laser-induced bias from first-principles can improve the precision and accuracy of experimental measurements. A rate equationmore » model for predicting the relative ionization probability has been developed to study the effect of variations in laser parameters on the measured isotope ratio. The model uses atomic data and empirical descriptions of laser performance to estimate the laser-induced bias expected in experimental measurements of the 235U/238U ratio. Empirical corrections are also included to account for ionization processes that are difficult to calculate from first principles with the available atomic data. As a result, development of this model has highlighted several important considerations for properly interpreting experimental results.« less

  10. Natural abundance stable carbon isotope evidence for the routing and de novo synthesis of bone FA and cholesterol.

    PubMed

    Jim, Susan; Ambrose, Stanley H; Evershed, Richard P

    2003-02-01

    This research reported in this paper investigated the relationship between diet and bone FA and cholesterol in rats raised on a variety of isotopically controlled diets comprising 20% C3 or C4 protein (casein) and C3 and/or C4 nonprotein or energy (sucrose, starch, and oil) macronutrients. Compound-specific stable carbon isotope analysis (delta13C) was performed on the FA (16:0, 18:0, 18:1, and 18:2) and cholesterol isolated from the diet (n = 4) and bone (n = 8) of these animals. The dietary signals reflected by the bone lipids were investigated using linear regression analysis. delta13C values of bone cholesterol and stearic (18:0) acid were shown to reflect whole-diet delta13C values, whereas the delta13C values of bone palmitic (16:0), oleic (18:1), and linoleic (18:2) acids reflected dietary FA delta13C values. Dietary signal differences are a result of the balance between direct incorporation (or routing) and de novo synthesis of each of these bone lipids. Estimates of the degree of routing of these bone lipids gleaned from correlations between delta13C(dlipid-wdiet) (= delta13C(diet lipid) - delta13C(whole diet)) spacings and delta13C(blipid-wdiet) (= delta13C(bone lipid) - delta13C(whole diet)) fractionations demonstrated that the extent of routing, where 18:2 > 16:0 > 18:1 > 18:0 > cholesterol, reflected the relative abundances of these lipids in the diet. These findings provide the basis for more accurate insights into diet when the delta13C analysis of bone fatty FA or cholesterol is employed.

  11. On the accuracy of gamma spectrometric isotope ratio measurements of uranium

    NASA Astrophysics Data System (ADS)

    Ramebäck, H.; Lagerkvist, P.; Holmgren, S.; Jonsson, S.; Sandström, B.; Tovedal, A.; Vesterlund, A.; Vidmar, T.; Kastlander, J.

    2016-04-01

    The isotopic composition of uranium was measured using high resolution gamma spectrometry. Two acid solutions and two samples in the form of UO2 pellets were measured. The measurements were done in close geometries, i.e. directly on the endcap of the high purity germanium detector (HPGe). Applying no corrections for count losses due to true coincidence summing (TCS) resulted in up to about 40% deviation in the abundance of 235U from the results obtained with mass spectrometry. However, after correction for TCS, excellent agreement was achieved between the results obtained using two different measurement methods, or a certified value. Moreover, after corrections, the fitted relative response curves correlated excellently with simulated responses, for the different geometries, of the HPGe detector.

  12. New Measurement of the Thermal-capture Cross Section for the Minor Isotope 180W

    NASA Astrophysics Data System (ADS)

    Hurst, A. M.; Firestone, R. B.; Szentmiklósi, L.; Révay, Zs.; Basunia, M. S.; Belgya, T.; Escher, J. E.; Krtička, M.; Summers, N. C.; Sleaford, B. W.

    2014-05-01

    Tungsten occurs naturally in five isotopic forms; four of them, 182,183,184,186W, contribute significantly to the overall elemental abundance (with each contribution between 14 and 30 %), whereas 180W only occurs at the 0.12 % level and is a minor isotope. Given its very low abundance, a precise measurement of the thermal neutron-capture cross section is extremely challenging. This work reports a new value of the thermal neutron-capture cross section from a direct 180W(n,γ) measurement using a guided-thermal beam at the Budapest Research Reactor, incident upon an 11.35 % enriched sample to induce prompt γ-ray activation within the sample. The thermal-capture cross section was determined as the sum of experimentally observed partial neutron-capture γ-ray cross sections feeding the ground state directly, and, the modeled contribution from the (unobserved) ground-state feeding predicted from statistical-model calculations using the Monte Carlo program DICEBOX. The preliminary value of the 180W(n,γ) thermal neutron-capture cross section is 20.5(42) b.

  13. A Widely Tunable Infrared Laser Spectrometer for Measurements of Isotopic Ratios of Carbon Cycle Gases

    SciTech Connect

    Joanne H. Shorter; J. Barry McManus; David D. Nelson; Charles E. Kolb; Mark S. Zahniser; Ray Bambha; Uwe Lehmann; Tomas Kulp; Stanley C. Tyler

    2005-01-31

    The atmospheric abundances of carbon dioxide and methane have increased dramatically during the industrial era. Measurements of the isotopic composition of these gases can provide a powerful tool for quantifying their sources and sinks. This report describes the development of a portable instrument for isotopic analysis CO{sub 2} and CH{sub 4} using tunable infrared laser absorption spectroscopy. This instrument combines novel optical design and signal processing methods with a widely tunable mid-infrared laser source based on difference frequency generation (DFG) which will can access spectral regions for all the isotopes of CO{sub 2} and CH{sub 4} with a single instrument. The instrument design compensates for the large difference in concentration between major and minor isotopes by measuring them with path lengths which differ by a factor of 100 within the same multipass cell. During Phase I we demonstrated the basic optical design and signal processing by determining {sup 13}CO{sub 2} isotopic ratios with precisions as small as 0.2{per_thousand} using a conventional lead salt diode laser. During Phase II, the DFG laser source was coupled with the optical instrument and was demonstrated to detect {sup 13}CH{sub 4}/{sup 12}CH{sub 4} ratios with a precision of 0.5{per_thousand} and an averaging time of 20 s using concentrated methane in air with a mixing ratio of 2700 ppm. Methods for concentrating ambient air for isotopic analysis using this technique have been evaluated. Extensions of this instrument to other species such as {sup 13}CO{sub 2}, C{sup 18}OO, and CH{sub 3}D are possible by substituting lasers at other wavelengths in the DFG source module. The immediate commercial application of this instrument will be to compete with existing mass spectrometric isotope instruments which are expensive, large and relatively slow. The novel infrared source developed in this project can be applied to the measurement of many other gas species and will have wide

  14. Secondary ion mass spectrometry combined with alpha track detection for isotope abundance ratio analysis of individual uranium-bearing particles.

    PubMed

    Esaka, Fumitaka; Magara, Masaaki

    2014-03-01

    Secondary ion mass spectrometry (SIMS) was used in combination with alpha track detection for the efficient analysis of uranium-bearing particles with higher (235)U abundances in environmental samples. A polycarbonate film containing particles was prepared and placed in contact with a CR-39 plastic detector. After exposure for 28 days, the detector was etched in a NaOH solution and each uranium-bearing particle was identified through observation of the alpha tracks recorded in the detector. A portion of the film containing each uranium-bearing particle was cut out and put onto a glassy carbon planchet. The films on the planchet were decomposed through plasma ashing for subsequent uranium abundance ratio analysis with SIMS. The alpha track-SIMS analysis of 10 uranium-bearing particles in a sample taken from a nuclear facility enabled n((235)U)/n((238)U) abundance ratios in the range 0.0072-0.25 to be detected, which were significantly higher than those obtained by SIMS without alpha track detection. The duration of the whole analytical process for analysis of 10 particles was about 32 days. The detection efficiency was calculated to be 27.1±6.5%, based on the analysis of the particles in uranium reference materials. The detection limits, defined as the diameter of the particle which produces alpha tracks more than one for a 28-days exposure, were estimated to be 0.8, 0.9, 1.1, 2.1 and 3.0 μm for the particles having the same uranium abundance ratios with NBL CRM U850, U500, U350, U050 and U010 reference materials, respectively. The use of alpha track detection for subsequent SIMS analysis is an inexpensive and an efficient way to measure uranium-bearing particles with higher (235)U abundances. PMID:24468381

  15. Millimeter-scale variations of stable isotope abundances in carbonates from banded iron-formations in the Hamersley Group of Western Australia.

    PubMed

    Baur, M E; Hayes, J M; Studley, S A; Walter, M R

    1985-01-01

    Several diamond drill cores from formations within the Hamersley Group of Western Australia have been studied for evidence of short-range variations in the isotopic compositions of the carbonates. For a set of 32 adjacent microbands analyzed in a specimen from the Marra Mamba Iron Formation, carbon isotope compositions of individual microbands ranged from -2.8 to -19.8 per mil compared to PDB and oxygen isotope compositions ranged from 10.2 to 20.8 per mil compared to SMOW. A pattern of alternating abundances was present, with the average isotopic contrasts between adjacent microbands being 3.0 per mil for carbon and 3.1 per mil for oxygen. Similar results were obtained for a suite of 34 microbands (in four groups) from the Bruno's Band unit of the Mount Sylvia Formation. Difficulties were experienced in preparing samples of single microbands from the Dales Gorge Member of the Brockman Iron Formation, but overall isotopic compositions were in good agreement with values reported by previous authors. Chemical analyses showed that isotopically light carbon and oxygen were correlated with increased concentrations of iron. The preservation of these millimeter-scale variations in isotopic abundances is interpreted as inconsistent with a metamorphic origin for the isotopically light carbon in the BIF carbonates. A biological origin is favored for the correlated variations in 13C and Fe, and it is suggested that the 13C-depleted carbonates may derive either from fermentative metabolism or from anaerobic respiration. A model is presented in which these processes occur near the sediment-water interface and are coupled with an initial oxidative precipitation of the iron. PMID:11539027

  16. Millimeter-scale variations of stable isotope abundances in carbonates from banded iron-formations in the Hamersley Group of Western Australia

    NASA Technical Reports Server (NTRS)

    Baur, M. E.; Hayes, J. M.; Studley, S. A.; Walter, M. R.

    1985-01-01

    Several diamond drill cores from formations within the Hamersley Group of Western Australia have been studied for evidence of short-range variations in the isotopic compositions of the carbonates. For a set of 32 adjacent microbands analyzed in a specimen from the Marra Mamba Iron Formation, carbon isotope compositions of individual microbands ranged from -2.8 to -19.8 per mil compared to PDB and oxygen isotope compositions ranged from 10.2 to 20.8 per mil compared to SMOW. A pattern of alternating abundances was present, with the average isotopic contrasts between adjacent microbands being 3.0 per mil for carbon and 3.1 per mil for oxygen. Similar results were obtained for a suite of 34 microbands (in four groups) from the Bruno's Band unit of the Mount Sylvia Formation. Difficulties were experienced in preparing samples of single microbands from the Dales Gorge Member of the Brockman Iron Formation, but overall isotopic compositions were in good agreement with values reported by previous authors. Chemical analyses showed that isotopically light carbon and oxygen were correlated with increased concentrations of iron. The preservation of these millimeter-scale variations in isotopic abundances is interpreted as inconsistent with a metamorphic origin for the isotopically light carbon in the BIF carbonates. A biological origin is favored for the correlated variations in 13C and Fe, and it is suggested that the 13C-depleted carbonates may derive either from fermentative metabolism or from anaerobic respiration. A model is presented in which these processes occur near the sediment-water interface and are coupled with an initial oxidative precipitation of the iron.

  17. Potassium Stable Isotopic Compositions Measured by High-Resolution MC-ICP-MS

    NASA Technical Reports Server (NTRS)

    Morgan, Leah E.; Lloyd, Nicholas S.; Ellam, Robert M.; Simon, Justin I.

    2012-01-01

    Potassium isotopic (K-41/K-39) compositions are notoriously difficult to measure. TIMS measurements are hindered by variable fractionation patterns throughout individual runs and too few isotopes to apply an internal spike method for instrumental mass fractionation corrections. Internal fractionation corrections via the K-40/K-39 ratio can provide precise values but assume identical K-40/K-39 ratios (e.g. 0.05% (1sigma) in [1]); this is appropriate in some cases (e.g. identifying excess K-41) but not others (e.g., determining mass fractionation effects and metrologically traceable isotopic abundances). SIMS analyses have yielded measurements with 0.25% precisions (1sigma) [2]. ICP-MS analyses are significantly affected by interferences from molecular species such as Ar-38H(+) and Ar-40H(+) and instrument mass bias. Single collector ICP-MS instruments in "cold plasma" mode have yielded uncertainties as low as 2% (1sigma, e.g. [3]). Although these precisions may be acceptable for some concentration determinations, they do not resolve isotopic variation in terrestrial materials. Here we present data from a series of measurements made on the Thermo Scientific NEPTUNE Plus multi-collector ICP-MS that demonstrate the ability to make K-41/K-39 ratio measurements with 0.07% precisions (1sigma). These data, collected on NIST K standards, indicate the potential for MC-ICP-MS measurements to look for K isotopic variations at the sub-permil level. The NEPTUNE Plus can sufficiently resolve 39K and 41K from the interfering 38ArH+ and 40ArH+ peaks in wet cold plasma and high-resolution mode. Measurements were made on small but flat, interference-free, plateaus (ca. 50 ppm by mass width for K-41). Although ICP-MS does not yield accurate K-41/K-39 values due to significant instrumental mass fractionation (ca. 6%), this bias can be sufficiently stable over the time required for several measurements so that relative K-41/K-39 values can be precisely determined via sample

  18. Precise and accurate isotopic measurements using multiple-collector ICPMS

    NASA Astrophysics Data System (ADS)

    Albarède, F.; Telouk, Philippe; Blichert-Toft, Janne; Boyet, Maud; Agranier, Arnaud; Nelson, Bruce

    2004-06-01

    New techniques of isotopic measurements by a new generation of mass spectrometers equipped with an inductively-coupled-plasma source, a magnetic mass filter, and multiple collection (MC-ICPMS) are quickly developing. These techniques are valuable because of (1) the ability of ICP sources to ionize virtually every element in the periodic table, and (2) the large sample throughout. However, because of the complex trajectories of multiple ion beams produced in the plasma source whether from the same or different elements, the acquisition of precise and accurate isotopic data with this type of instrument still requires a good understanding of instrumental fractionation processes, both mass-dependent and mass-independent. Although physical processes responsible for the instrumental mass bias are still to be understood more fully, we here present a theoretical framework that allows for most of the analytical limitations to high precision and accuracy to be overcome. After a presentation of unifying phenomenological theory for mass-dependent fractionation in mass spectrometers, we show how this theory accounts for the techniques of standard bracketing and of isotopic normalization by a ratio of either the same or a different element, such as the use of Tl to correct mass bias on Pb. Accuracy is discussed with reference to the concept of cup efficiencies. Although these can be simply calibrated by analyzing standards, we derive a straightforward, very general method to calculate accurate isotopic ratios from dynamic measurements. In this study, we successfully applied the dynamic method to Nd and Pb as examples. We confirm that the assumption of identical mass bias for neighboring elements (notably Pb and Tl, and Yb and Lu) is both unnecessary and incorrect. We further discuss the dangers of straightforward standard-sample bracketing when chemical purification of the element to be analyzed is imperfect. Pooling runs to improve precision is acceptable provided the pooled

  19. Leaf water oxygen isotope measurement by direct equilibration.

    PubMed

    Song, Xin; Barbour, Margaret M

    2016-08-01

    The oxygen isotope composition of leaf water imparts a signal to a range of molecules in the atmosphere and biosphere, but has been notoriously difficult to measure in studies requiring a large number of samples as a consequence of the labour-intensive extraction step. We tested a method of direct equilibration of water in fresh leaf samples with CO2 , and subsequent oxygen isotope analysis on an optical spectrometer. The oxygen isotope composition of leaf water measured by the direct equilibration technique was strongly linearly related to that of cryogenically extracted leaf water in paired samples for a wide range of species with differing anatomy, with an R(2) of 0.95. The somewhat more enriched values produced by the direct equilibration method may reflect lack of full equilibration with unenriched water in the vascular bundles, but the strong relationship across a wide range of species suggests that this difference can be adequately corrected for using a simple linear relationship. PMID:27147584

  20. Evaluating Nitrogen Isotope Measurements in Unconventional Hydrocarbon Reservoirs

    NASA Astrophysics Data System (ADS)

    Quan, T. M.; Rivera, K.; Adigwe, E.; Riedinger, N.; Puckette, J.

    2014-12-01

    Nitrogen isotope (δ15N) measurements from core samples taken from unconventional hydrocarbon reservoirs may provide important information on depositional environment, reservoir characterization, and post-depositional processes. In order to evaluate the potential of nitrogen isotopes as geochemical proxies for resource evaluation, we measured δ15Nbulk values for six Woodford Shale (Late Devonian-Early Mississippian) cores and three Caney Shale (Early Mississippian) cores and compared the profiles with other geochemical, lithological, maturation, and well-log data. The strongest correlation is between δ15Nbulk and redox-sensitive trace metals and other redox proxies, as predicted by previous research into δ15Nbulk values. This indicates that δ15Nbulk can be used in unconventional reservoirs as a proxy for depositional redox conditions. Unlike other redox proxies, δ15Nbulk reflects the redox state of the deep-water column, rather than that of the deposited sediment, providing a representation of water column processes during deposition. The δ15Nbulk proxy also appears not to be overprinted by catagenic processes. Associations of δ15Nbulk with thermal maturity, gamma ray response, and catagenesis and diagenesis proxies were found to be minimal. The δ15Nbulk profiles do not appear to be overprinted during catagenesis and therefore are not a reliable record of post-depositional processes. Including nitrogen isotope analyses in a geochemical assessment can provide valuable information about the original redox state of the reservoir unit, and assist in characterizing depositional environment.

  1. Guidelines and recommended terms for expression of stable-isotope-ratio and gas-ratio measurement results.

    PubMed

    Coplen, Tyler B

    2011-09-15

    To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Système International d'Unités, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented. PMID:21910288

  2. Abundance and isotope systematics of carbon in subglacial basalts, geothermal gases and fluids from Iceland's rift zones

    NASA Astrophysics Data System (ADS)

    Barry, P. H.; Hilton, D. R.; Fueri, E.; Halldorsson, S. A.; Fischer, T. P.; Gronvold, K.

    2010-12-01

    P. H. BARRY1*, D. R. HILTON1, E. FÜRI1, S.A. HALLDÓRSON1, T.P. FISCHER2, K. GRONVOLD3 1 Scripps Institution of Oceanography, UCSD, La Jolla, California 92093, USA (*Correspondence: pbarry@ucsd.edu). 2University of New Mexico, Albuquerque, NM 87131, USA. 3University of Iceland, Askja, Sturlugata 7, IS-101, Reykjavik, Iceland Carbon dioxide (CO2) is the dominant non-aqueous volatile species found in oceanic basalts and geothermal fluids and serves as the carrier gas for trace volatiles such as He and other noble gases. The aim of this study is to identify the superimposed effects of degassing and crustal contamination on the CO2 systematics of the Icelandic hotspot in order to reveal and characterize the carbon abundance and isotopic features of the underlying mantle source. Our approach involves coupling CO2 with He, utilizing the sensitivity of 3He/4He ratios to reveal mantle and crustal inputs. We report new C-isotope (δ13C) and abundance characteristics for a suite of 47 subglacial basalts and 50 geothermal gases and fluids from Iceland. CO2 contents in hyaloclastite glasses are extremely low (10-100 ppm) and likely residual following extensive degassing whereas geothermal fluids are dominated by CO2 (>90 %). C-isotopes range from -27.2 to -3.6 ‰ (vs. PDB) for basalts and from -18.8 to 2.86 ‰ (vs. PDB) for geothermal samples (mean = -4.2 ± 3.6 ‰). CO2/3He ratios range from 108 to 1012 for basalts and from 105 to 1012 for geothermal samples: In both cases, our results extend He-CO2 relationships over a much broader range than reported previously [1]. Taken together, these data suggest that several processes including mixing, degassing, and/or syn- or post-eruptive crustal contamination may act to modify CO2 source characteristics. Equilibrium degassing models are compatible with ~75 % of the basalt data, and preliminary results indicate that initial Icelandic source characteristics are ~500 ppm CO2 and δ13C ~ -5 ‰ (vs. PDB). These values are high

  3. Major and trace element abundances, and Sr and Nd isotopic composition of Carbonatites from Amba Dongar, Gujarat, India

    NASA Astrophysics Data System (ADS)

    Chandra, Jyoti; Paul, Debajyoti; Viladkar, Shrinivas G.; Sensarma, Sarajit

    2015-04-01

    Despite significant progress during the last decade, the petrogenesis of carbonatites is still highly debated regarding the exact mechanism of carbonatite magma generation (fractional crystallization of carbonated-silicate magmas, liquid immiscibility of carbonated-silicate magmas, partial melting of carbonated mantle peridotite or carbonated lherzolitic mantle) and its evolution. The Amba Dongar carbonatite complex in Chhota Udaipur district, Gujarat is the youngest Indian carbonatite complex, which intruded into the ~ 90 Ma Bagh sandstones and limestone and 68-65 Ma Deccan flood basalts. The emplacement age (40Ar/39Ar age of 65±0.3 Ma; Ray and Pande, 1999) coincides with the age of main pulse of Deccan flood basalts at ca. 65 Ma. We report new geochemical data (major oxide and trace element abundances, and Sr and Nd isotopic ratios) on 23 carbonatite samples from Amba Dongar. The Amba Dongar carbonatite complex consists of carbonatite (sövite, and ankerite), and associated nephelinite, phonolite, and both pre- and post-carbonatite basalts. Detailed minerology of carbonatite include dominant calcite along with pyrochlore, apatite, magnetite, aegirine-augite and accessory phases. Apatite crystals are observed in carbonatite as well as in nephelinite. In sövites, apatite occur in various forms including cumulus, clusters and scattered within and along the boundary of calcite crystals. Two generation of apatite crystals are commonly observed in sövite and nephelinite; textural changes suggest presence of different five pulses of sövitic magma during the emplacement of the sövite ring dike. Bulk major oxides and trace element (including REEs) compositions of carbonatites and associated silicate rocks are determined by WD-XRF and ICP-MS, respectively. Major oxides abundances are consistent with the already available data on the Amba Dongar carbonatite complex. Trace element concentrations for the sövite reveals high concentrations of Sr (929-7476 ppm), Ba (344

  4. Cross-Section Measurements with the Radioactive Isotope Accelerator (ria)

    NASA Astrophysics Data System (ADS)

    Stoyer, M. A.; Moody, K. J.; Wild, J. F.; Patin, J. B.; Shaughnessy, D. A.; Stoyer, N. J.; Harris, L. J.

    2003-10-01

    RIA will produce beams of exotic nuclei of unprecedented luminosity. Preliminary studies of the feasibility of measuring cross-sections of interest to the science based stockpile stewardship (SBSS) program will be presented, and several experimental techniques will be discussed. Cross-section modeling attempts for the A = 95 mass region will be shown. In addition, several radioactive isotopes could be collected for target production or medical isotope purposes while the main in-beam experiments are running. The inclusion of a broad range mass analyzer (BRAMA) capability at RIA will enable more effective utilization of the facility, enabling the performance of multiple experiments at the same time. This option will be briefly discussed.

  5. Cross-Section Measurements with the Radioactive Isotope Accelerator (RIA)

    SciTech Connect

    Stoyer, M A; Moody, K J; Wild, J F; Patin, J B; Shaughnessy, D A; Stoyer, N J; Harris, L J

    2002-11-19

    RIA will produce beams of exotic nuclei of unprecedented luminosity. Preliminary studies of the feasibility of measuring cross-sections of interest to the science based stockpile stewardship (SBSS) program will be presented, and several experimental techniques will be discussed. Cross-section modeling attempts for the A = 95 mass region will be shown. In addition, several radioactive isotopes could be collected for target production or medical isotope purposes while the main in-beam experiments are running. The inclusion of a broad range mass analyzer (BRAMA) capability at RIA will enable more effective utilization of the facility, enabling the performance of multiple experiments at the same time. This option will be briefly discussed.

  6. Evaluation of Affinity-Tagged Protein Expression Strategies using Local and Global Isotope Ratio Measurements

    SciTech Connect

    Hervey, IV, William Judson; Khalsa-Moyers, Gurusahai K; Lankford, Patricia K; Owens, Elizabeth T; McKeown, Catherine K; Lu, Tse-Yuan S; Foote, Linda J; Morrell-Falvey, Jennifer L; McDonald, W Hayes; Pelletier, Dale A; Hurst, Gregory {Greg} B

    2009-01-01

    Protein enrichments of engineered, affinity-tagged (or bait ) fusion proteins with interaction partners are often laden with background, non-specific proteins, due to interactions that occur in vitro as an artifact of the technique. Furthermore, the in vivo expression of the bait protein may itself affect physiology or metabolism. In this study, intrinsic affinity purification challenges were investigated in a model protein complex, DNA-dependent RNA polymerase (RNAP), encompassing chromosome- and plasmid-encoding strategies for bait proteins in two different microbial species: Escherichia coli and Rhodopseudomonas palustris. Isotope ratio measurements of bait protein expression strains relative to native, wild-type strains were performed by liquid chromatography tandem mass spectrometry (LC-MS-MS) to assess bait protein expression strategies in each species. Authentic interacting proteins of RNAP were successfully discerned from artifactual co-isolating proteins by the isotopic differentiation of interactions as random or targeted (I-DIRT) method (A. J. Tackett et al. J. Proteome Res. 2005, 4 (5), 1752-1756). To investigate broader effects of bait protein production in the bacteria, we compared proteomes from strains harboring a plasmid that encodes an affinity-tagged subunit (RpoA) of the RNAP complex with the corresponding wild-type strains using stable isotope metabolic labeling. The ratio of RpoA abundance in plasmid strains versus wild type was 0.8 for R. palustris and 1.7 for E. coli. While most other proteins showed no appreciable difference, proteins significantly increased in abundance in plasmid-encoded bait-expressing strains of both species included the plasmid encoded antibiotic resistance protein, GenR and proteins involved in amino acid biosynthesis. Together, these local, complex-specific and more global, whole proteome isotopic abundance ratio measurements provided a tool for evaluating both in vivo and in vitro effects of plasmid

  7. Changes in biomarker abundances and sulfur isotopes of pyrite across the Permian Triassic (P/Tr) Schuchert Dal section (East Greenland)

    NASA Astrophysics Data System (ADS)

    Fenton, Stephen; Grice, Kliti; Twitchett, Richard J.; Böttcher, Michael E.; Looy, Cindy V.; Nabbefeld, Birgit

    2007-10-01

    In this study, we report on biomarker abundances through parts of the Permian/Triassic boundary (PTB) of Schuchert Dal (East Greenland) that contains rich marine faunal records and excellent terrestrial palynological records. Biomarker abundances and sulfur isotopes are used to correlate the series of events (including changes in element cycling and associated redox conditions of the ocean) surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on Earth during a mass extinction episode. The Upper Schuchert Dal Formation contains a low diversity palynological assemblage, ascribed to arborescent cordiaite-conifer-pteridosperm vegetation. Samples from this pre-collapse interval are characterised by high abundances of dibenzofuran (DBF), dibenzothiophene (DBT) and biphenyl. Since these compounds have similar base structures, and show comparable abundance curves, it is plausible that they probably derive from a common source. We propose that phenolic compounds of lignin of the woody plants present during this period could be the source for DBF, DBT and biphenyl. The redox conditions during this period of time also support the formation of DBF and DBT. Just above the extinction interval, there is a dramatic decrease in the abundances of DBF and DBT which occurs at the same time as a sudden change in the stable sulfur isotopic composition ( δ34S) of pyrite, indicating a change in redox conditions from oxic to anoxic/euxinic conditions. δ34S values leading up to the extinction are highly depleted in the heavy sulfur isotope (about - 40‰ vs. VCDT), whilst shortly after the extinction interval much more positive isotope values are observed (about - 25‰). An inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections. It is suggested that two processes are operating closely here; 1) Changes in redox conditions and 2) extinction and/or transgression

  8. How much do carbon isotope measurements constrain glacial ocean circulation?

    NASA Astrophysics Data System (ADS)

    Schmittner, A.; Mix, A. C.

    2010-12-01

    Reconstructions of the isotopic composition of dissolved inorganic carbon in seawater (d13DIC) are often interpreted as a ventilation or circulation proxy in paleoceanography. The modern deep-sea distribution of d13C in dissolved inorganic carbon (d13DIC) is highly anti-correlated to macronutrient (PO4, NO3) and apparent oxygen utilization (AOU) patterns due to fractionation during photosynthetic carbon uptake by phytoplankton. Nutrient and AOU concentrations in freshly ventilated North Atlantic Deep Water, for example, are low (d13DIC is high), whereas older water masses contain more respired nutrients and (isotopically light) carbon and have high AOU. However, d13DIC is also influenced by fractionation during air sea gas exchange - a process that decouples d13DIC from changes in nutrients and AOU. Moreover, biological fractionation is not constant but spatially and temporally variable. Here we are using a new global three-dimensional model of stable carbon isotope cycling that includes variable biological and air-sea gas exchange fractionation effects in conjunction with modern and glacial d13C observations to reconstruct ocean circulation patterns. Model versions with different rates and patterns of ocean circulation are produced and the resulting d13C patterns are compared to a compilation of measurements from ocean sediment cores in a probabilistic approach. The method allows us to quantify the uncertainty of deep ocean mass fluxes given available d13C observations/reconstructions and provide a quantitative test of the assumption of d13C as a ventilation proxy.

  9. Endogenous surfactant turnover in preterm infants measured with stable isotopes.

    PubMed

    Bunt, J E; Zimmermann, L J; Wattimena, J L; van Beek, R H; Sauer, P J; Carnielli, V P

    1998-03-01

    We studied surfactant synthesis and turnover in vivo in preterm infants using the stable isotope [U-13C]glucose, as a precursor for the synthesis of palmitic acid in surfactant phosphatidylcholine (PC). Six preterm infants (birth weight, 916 +/- 244 g; gestational age, 27.7 +/- 1.7 wk) received a 24-h [U-13C]glucose infusion on the first day of life. The 13C-enrichment of palmitic acid in surfactant PC, obtained from tracheal aspirates, was measured by gas chromatography-combustion interface-isotope ratio mass spectrometry. We observed a significant incorporation of carbon-13 from glucose into surfactant PC palmitate. PC palmitate became enriched after 19.4 +/- 2.3 (16.5 to 22.3) h and reached maximum enrichment at 70 +/- 18 (48 to 96) h after the start of the label infusion. The fractional synthesis rate (FSR) of surfactant PC palmitate from glucose was 2.7 +/- 1.3%/d. We calculated the absolute production rate of surfactant PC to be 4.2 mg/kg/d, and the half-life to be 113 +/- 25 (87 to 144) h. Data on endogenous surfactant production and turnover were obtained for the first time in human infants with the use of stable isotopes. This novel and safe method could be applied to address many important issues concerning surfactant metabolism in preterm infants, children, and adults.

  10. (n, γ) measurements on radioactive isotopes with DANCE

    NASA Astrophysics Data System (ADS)

    Reifarth, R.; Esch, E.-I.; Alpizar-Vicente, A.; Bond, E. M.; Bredeweg, T. A.; Glover, S. E.; Greife, U.; Hatarik, R.; Haight, R. C.; Kronenberg, A.; O'Donnell, J. M.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.

    2005-12-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos National Laboratory (LANL) is designed as a high efficiency, highly segmented 4π BaF2 detector for calorimetrically detecting gamma rays following a neutron capture. Coupled with the neutron spallation source at the Los Alamos Neutron Science Center (LANSCE), DANCE measurements on unstable isotopes in the energy range between 10 meV and 500 keV will provide many of the missing key reactions that are needed to understand the nucleosynthesis of the heavy elements and will also provide vital information for the design of future reactor concepts.

  11. Mobile measurement of methane: plumes, isotopes and inventory verification

    NASA Astrophysics Data System (ADS)

    Lowry, D.; Zazzeri, G.; Fisher, R. E.; France, J.; Al-Shalaan, A.; Lanoisellé, M.; Nisbet, E. G.

    2015-12-01

    Since 2013 the RHUL group has been identifying methane plumes from major UK sources using a Picarro 2301 coupled to the A0941 mobile module. Once identified the plumes have been sampled by filling Tedlar or Flexfoil bags for later carbon isotopic analysis by high-precision IRMS. This method has ben successfully deployed to isotopically characterize the main anthropogenic methane emitters in the UK (natural gas, coal, landfill, wastewater treatment, cattle; Zazzeri et al., 2015) and during overseas campaigns in eastern Australia (coal, cattle, legacy gas wells) and Kuwait (landfill, wastewater treatment, oil refineries, cattle, camels). This has identified strong similarities of isotopic signature for some sources (landfill, cattle), but large variations for others (natural gas, coal), which must be isotopically resolved at regional scale. Both landfill and natural gas emissions in SE England have tightly-constrained δ13C signatures, averaging -58 ± 3‰ and -36 ± 2‰, respectively, the latter being characteristic of homogenised North Sea gas supply. In contrast, signatures for coal mines in England and Wales fall in a range of 51.2 ± 0.3‰ to 30.9 ± 1.4‰, but can be tightly constrained by region. On a local scale in west London, repeat surveys in the boroughs of Hounslow and Runnymede have been made for comparison with the latest 1x1 km grid UK inventories for 2009 and 2012, which are subdivided by UNECE categories. An excess methane map can be derived for comparison with inventory emissions maps by identifying daily background and binning the excess values from mobile measurements by grid-square. This shows that the spatial distribution of emissions in the UK 2012 inventory is a big improvement on that of 2009. It also suggests that there is an overestimation of emissions from old landfills (closed before 2000 and reliant on a topsoil cap for oxidation), and an underestimation on emissions from currently active landfill cells. Zazzeri, G. et al. (2015

  12. Measurements of the Fe-group abundance in energetic solar particles

    NASA Technical Reports Server (NTRS)

    Bertsch, D. L.; Fichtel, C. E.; Pellerin, C. J.; Reames, D. V.

    1972-01-01

    The abundance of Fe-group nuclei in the energetic solar particles was measured twice in the 24 January 1971 event and once in the 2 September 1971 event. Including earlier results from the 2 September 1966 event, the Fe-group abundance was found to be in the range from 3% to 6% of the oxygen nuclei in the energy interval from 21 to 50 MeV/nucleon, in those events where the Fe-group abundance could be measured. Fe-nuclei have a different charge-to-mass ratio from that of the C, N, O nuclei, so small variations in the Fe abundance in solar particles are expected. In the three exposures where the statistics were adequate to construct an energy spectrum, the Fe-group nuclei were seen to have an energy/nucleon spectrum similar to that of the C, N, O nuclei; however, the energy/nucleon range was limited. The abundance for the Fe-group nuclei is consistent with the present solar spectroscopic abundance estimates.

  13. Rb, Sr and strontium isotopic composition, K/Ar age and large ion lithophile trace element abundances in rocks and glasses from the Wanapitei Lake impact structure

    NASA Technical Reports Server (NTRS)

    Winzer, S. R.; Lum, R. K. L.; Schuhmann, S.

    1976-01-01

    Shock metamorphosed rocks and shock-produced melt glasses from the Wanapitei Lake impact structure have been examined petrographically and by electron microprobe. Eleven clasts exhibiting varying degrees of shock metamorphism and eight impact-produced glasses have been analyzed for Rb, Sr and Sr isotopic composition. Five clasts and one glass have also been analyzed for large ion lithophile (LIL) trace element abundances including Li, Rb, Sr, and Ba and the REE's. The impact event forming the Wanapitei Lake structure occurred 37 m.y. ago based on K/Ar dating of glass and glassy whole-rock samples. Rb/Sr isotopic dating failed to provide a meaningful whole-rock or internal isochron. The isotopic composition of the glasses can be explained by impact-produced mixing and melting of metasediments.

  14. Improving the Sensitivity of Uranium Isotope Ratio Measurements

    NASA Astrophysics Data System (ADS)

    Friedrich, J.; Snow, J.

    2003-12-01

    Accurate and precise measurements of natural and anthropogenic 235/238 U isotope ratios are important for a range of investigations where the amount of sample is extremely restricted and/or the analyte is only present in ultra-trace quantities. Examples include biological, cosmochemical, environmental, geological, and radiological studies. We have developed and validated a novel method using our Nu Instruments Nu Plasma Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS) and a 233U, 236U mixed double spike for the measurement of 235U/238U ratios. Our multi-dynamic technique employs the installed quadrupole zoom optics and fixed positioning of the ion counting detectors such that rather than the commonly used mass dispersion of 1 or 2, we utilize a mass dispersion of 1.5. Using this configuration, we can simultaneously monitor the 235U and 238U ion beams in the first cycle followed by a second cycle that simultaneously monitors the 233U and 236U beams. This innovative approach allows us to correct for the considerable, but consistent, instrumental mass fractionation and ion-counter amplification bias within each sequence. Since we were hesitant to use a U500 (235U, 238U equal atom) solution for spike calibration because of possible enriched U laboratory and instrumentation contamination, we used a U960 (terrestrial 235U/238U) solution for isotopic calibration of the spike. This standardization corrected for the small amounts of 235U and 238U in the spike solution by using a U960 standard solution. With a mean intraday 2-sigma precision of 1.5 permil and an overall 2-sigma precision of 2.25 permil using individual sample sizes of 350 pg (8.8 x10 E11 atoms), we are confident our technique will be useful for identifying U isotopic anomalies present in many sample types.

  15. Measurement of picosecond lifetimes in neutron-rich Xe isotopes

    NASA Astrophysics Data System (ADS)

    Ilieva, S.; Kröll, Th.; Régis, J.-M.; Saed-Samii, N.; Blanc, A.; Bruce, A. M.; Fraile, L. M.; de France, G.; Hartig, A.-L.; Henrich, C.; Ignatov, A.; Jentschel, M.; Jolie, J.; Korten, W.; Köster, U.; Lalkovski, S.; Lozeva, R.; Mach, H.; Mǎrginean, N.; Mutti, P.; Paziy, V.; Regan, P. H.; Simpson, G. S.; Soldner, T.; Thürauf, M.; Ur, C. A.; Urban, W.; Warr, N.

    2016-09-01

    Background: Lifetimes of nuclear excited states in fission fragments have been studied in the past following isotope separation, thus giving access mainly to the fragments' daughters and only to long-lived isomeric states in the primary fragments. For the first time now, short-lived excited states in the primary fragments, produced in neutron-induced prompt fission of 235U and 241Pu, were studied within the EXILL&FATIMA campaign at the intense neutron-beam facility of the Institute Laue-Langevin in Grenoble. Purpose: We aim to investigate the quadrupole collective properties of neutron-rich even-even 138,140,142Xe isotopes lying between the double shell closure N =82 and Z =50 and a deformed region with octupole collectivity. Method: The γ rays emitted from the excited fragments were detected with a mixed array consisting of 8 HPGe EXOGAM Clover detectors (EXILL) and 16 LaBr3(Ce) fast scintillators (FATIMA). The detector system has the unique ability to select the interesting fragment making use of the high resolution of the HPGe detectors and determine subnanosecond lifetimes using the fast scintillators. For the analysis the generalized centroid difference method was used. Results: We show that quadrupole collectivity increases smoothly with increasing neutron number above the closed N =82 neutron shell. Our measurements are complemented by state-of-the-art theory calculations based on shell-model descriptions. Conclusions: The observed smooth increase in quadrupole collectivity is similar to the evolution seen in the measured masses of the xenon isotopic chain and is well reproduced by theory. This behavior is in contrast to higher Z even-even nuclei where abrupt change in deformation occurs around N =90 .

  16. Evolution, Abundance and Biocalcification of Calcareous Nannoplankton During the Aptian (Early Cretaceous): Causes and Consequences for C Isotopic Anomalies, Climate Changes and the Carbon Cycle.

    NASA Astrophysics Data System (ADS)

    Erba, E.

    2005-12-01

    The mid Cretaceous is marked by extreme greenhouse conditions, coeval with emplacement of large igneous provinces, C isotopic anomalies, major changes in structure and composition of the oceans, and accelerated rates in the evolutionary history of calcareous plankton. The Aptian is a crucial interval to decipher links between biotic evolution and environmental pressure: it is appealing for understanding nannofloral biocalcification and feedbacks in the carbonate system and in the global carbon cycle. Ontong Java, Manihiki and Kerguelen Plateaus formed in the Aptian affecting the ocean-atmosphere system with excess CO2, changes in Ca2+ and Mg2+ concentrations, and varying nutrient cycling. Two large C isotopic anomalies are associated with episodes of prolonged high primary productivity, changes in alkality, global warming and cooling, anoxia, speciations and extinctions in planktonic communities. Nannofossil diversity, abundance and biocalcification are quantified in continuous, complete, pelagic sections to derive biosphere-geosphere interactions at short and long time scales. The early Aptian C isotopic anomaly interrupts a speciation episode in calcareous nannoplankton paralleled by a drastic reduction in nannofossil paleofluxes culminating in the nannoconid crisis preceding the Oceanic Anoxic Event 1a and the negative C isotopic spike linked to clathrate melting presumably triggered by the thermal maximum at the onset of the mid Cretaceous greenhouse climate. No extinctions are recorded. In the early late Aptian resumption of nannoconid production and appearance of several taxa are coeval with a return to normal C isotopic values. The occurrence of calpionellids and diversified planktonic foraminifers indicate successful biocalcification and restoration of the thermocline. In the late Aptian a drop in nannofossil abundance and accelerated extinction rates are associated with another C isotopic excursion under cool conditions possibly due to a prolonged volcanic

  17. Actinide abundances in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Hagee, B.; Bernatowicz, T. J.; Podosek, F. A.; Johnson, M. L.; Burnett, D. S.

    1990-01-01

    Measurements of actinide and light REE (LREE) abundances and of phosphate abundances in equilibrated ordinary chondrites were obtained and were used to define the Pu abundance in the solar system and to determine the degree of variation of actinide and LREE abundances. The results were also used to compare directly the Pu/U ratio with the earlier obtained ratio determined indirectly, as (Pu/Nd)x(Nd/U), assuming that Pu behaves chemically as a LREE. The data, combined with high-accuracy isotope-dilution data from the literature, show that the degree of gram-scale variability of the Th, U, and LREE abundances for equilibrated ordinary chondrites is a factor of 2-3 for absolute abundances and up to 50 percent for relative abundances. The observed variations are interpreted as reflecting the differences in the compositions and/or proportions of solar nebula components accreted to ordinary chondrite parent bodies.

  18. Iron and Nickel Isotopic Compositions of Presolar Silicon Carbide Grains from AGB Stars Measured with CHILI

    NASA Astrophysics Data System (ADS)

    Trappitsch, R.; Stephan, T.; Davis, A. M.; Pellin, M. J.; Savina, M. R.; Gyngard, F.; Bisterzo, S.; Gallino, R.; Dauphas, N.

    2016-08-01

    Simultaneous iron and nickel isotopic studies in presolar SiC mainstream grains measured on CHILI show the expected AGB star anomalies in the neutron-rich isotopes. Neutron-poor isotopes are dominated by GCE and show clear correlations with silicon.

  19. Beta-decay measurements of neutron-deficient cesium isotopes

    SciTech Connect

    Parry, R.F.

    1983-03-01

    Beta decay endpoint energy measurements of the neutron deficient cesium isotopes were done using an energy spectrum shape fitting technique. This was a departure from the typical method of endpoint energy analysis, the Fermi-Kurie plot. A discussion of the shape fitting procedure and its improved features are discussed. These beta endpoint measurements have led to total decay energies (Q/sub EC/) of the neutron deficient /sup 119/ /sup 123/Cs isotopes. The total decay energies of /sup 122m/Cs (Q/sub EC/ = 6.95 +- 0.25 MeV) and /sup 119/Cs (Q/sub EC/ = 6.26 +- 0.29 MeV) were new measurements. The total decay energies of /sup 123/Cs (Q/sub EC/ = 4.05 +- 0.18 MeV), /sup 122g/Cs (Q/sub EC/ = 7.05 +- 0.18 MeV), /sup 121/Cs (Q/sub EC/ = 5.21 +- 0.22 MeV), and /sup 120/Cs (Q/sub EC/ = 7.38 +- 0.23 MeV) were measurements with significantly improved uncertainties as compared to the literature. Further, a combination of the energy levels derived from previous literature gamma-gamma coincident measurements and the experimental beta-coincident gamma decay energies has supported an improved level scheme for /sup 121/Xe and the proposal of three new energy levels in /sup 119/Xe. Comparison of the experimental cesium mass excesses (determined with our Q/sub EC/ values and known xenon mass excesses) with both the literature and theoretical predicted values showed general agreement except for /sup 120/Cs. Possible explanations for this deviation are discussed.

  20. Highly accurate isotope measurements of surface material on planetary objects in situ

    NASA Astrophysics Data System (ADS)

    Riedo, Andreas; Neuland, Maike; Meyer, Stefan; Tulej, Marek; Wurz, Peter

    2013-04-01

    Studies of isotope variations in solar system objects are of particular interest and importance. Highly accurate isotope measurements provide insight into geochemical processes, constrain the time of formation of planetary material (crystallization ages) and can be robust tracers of pre-solar events and processes. A detailed understanding of the chronology of the early solar system and dating of planetary materials require precise and accurate measurements of isotope ratios, e.g. lead, and abundance of trace element. However, such measurements are extremely challenging and until now, they never have been attempted in space research. Our group designed a highly miniaturized and self-optimizing laser ablation time-of-flight mass spectrometer for space flight for sensitive and accurate measurements of the elemental and isotopic composition of extraterrestrial materials in situ. Current studies were performed by using UV radiation for ablation and ionization of sample material. High spatial resolution is achieved by focusing the laser beam to about Ø 20μm onto the sample surface. The instrument supports a dynamic range of at least 8 orders of magnitude and a mass resolution m/Δm of up to 800—900, measured at iron peak. We developed a measurement procedure, which will be discussed in detail, that allows for the first time to measure with the instrument the isotope distribution of elements, e.g. Ti, Pb, etc., with a measurement accuracy and precision in the per mill and sub per mill level, which is comparable to well-known and accepted measurement techniques, such as TIMS, SIMS and LA-ICP-MS. The present instrument performance offers together with the measurement procedure in situ measurements of 207Pb/206Pb ages with the accuracy for age in the range of tens of millions of years. Furthermore, and in contrast to other space instrumentation, our instrument can measure all elements present in the sample above 10 ppb concentration, which offers versatile applications

  1. Isotope-shift measurements of stable and short-lived lithium isotopes for nuclear-charge-radii determination

    SciTech Connect

    Noertershaeuser, W.; Sanchez, R.; Ewald, G.; Dax, A.; Goette, S.; Kluge, H.-J.; Kuehl, Th.; Wojtaszek, A.; Behr, J.; Bricault, P.; Dilling, J.; Dombsky, M.; Lassen, J.; Levy, C. D. P.; Pearson, M.; Bushaw, B. A.; Drake, G. W. F.; Pachucki, K.; Puchalski, M.; Yan, Z.-C.

    2011-01-15

    Changes in the mean square nuclear charge radii along the lithium isotopic chain were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. Nuclear charge radii of light elements are of high interest due to the appearance of the nuclear halo phenomenon in this region of the nuclear chart. During the past years we have developed a laser spectroscopic approach to determine the charge radii of lithium isotopes which combines high sensitivity, speed, and accuracy to measure the extremely small field shift of an 8-ms-lifetime isotope with production rates on the order of only 10 000 atoms/s. The method was applied to all bound isotopes of lithium including the two-neutron halo isotope {sup 11}Li at the on-line isotope separators at GSI, Darmstadt, Germany, and at TRIUMF, Vancouver, Canada. We describe the laser spectroscopic method in detail, present updated and improved values from theory and experiment, and discuss the results.

  2. Rapid accurate isotopic measurements on boron in boric acid and boron carbide.

    PubMed

    Duchateau, N L; Verbruggen, A; Hendrickx, F; De Bièvre, P

    1986-04-01

    A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry.

  3. Determining the Local Abundance of Martian Methane and its 13-C/l2-C and D/H Isotopic Ratios for Comparison with Related Gas and Soil Analysis on the 2011 Mars Science Laboratory (MSL) Mission

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; Mahaffy, Paul R.

    2011-01-01

    Understanding the origin of Martian methane will require numerous complementary measurements from both in situ and remote sensing investigations and laboratory work to correlate planetary surface geophysics with atmospheric dynamics and chemistry. Three instruments (Quadrupole Mass Spectrometer (QMS), Gas Chromatograph (GC) and Tunable Laser Spectrometer (TLS)) with sophisticated sample handling and processing capability make up the Sample Analysis at Mars (SAM) analytical chemistry suite on NASA s 2011 Mars Science Laboratory (MSL) Mission. Leveraging off the SAM sample and gas processing capability that includes methane enrichment, TLS has unprecedented sensitivity for measuring absolute methane (parts-per-trillion), water, and carbon dioxide abundances in both the Martian atmosphere and evolved from heated soil samples. In concert with a wide variety of associated trace gases (e.g. SO2, H2S, NH3, higher hydrocarbons, organics, etc.) and other isotope ratios measured by SAM, TLS will focus on determining the absolute abundances of methane, water and carbon dioxide, and their isotope ratios: 13C/12C and D/H in methane; 13C/12C and 18O/17O/16O in carbon dioxide; and 18O/17O/16O and D/H in water. Measurements near the MSL landing site will be correlated with satellite (Mars Express, Mars 2016) and ground-based observations.

  4. Simultaneous measurements of stable water isotopes in near-surface vapor and precipitation to constrain below-cloud processes

    NASA Astrophysics Data System (ADS)

    Graf, Pascal; Sodemann, Harald; Pfahl, Stephan; Schneebeli, Marc; Ventura, Jordi Figueras i.; Leuenberger, Andreas; Grazioli, Jacopo; Raupach, Tim; Berne, Alexis; Wernli, Heini

    2016-04-01

    Present-day observations of stable water isotopes (SWI) in precipitation on monthly time scales are abundant and the processes governing the variation of SWI on these time scales have been investigated by many studies. However, also on much shorter time scales of hours mesoscale meteorological processes lead to significant variations of SWIs, which are important to understand. There are only few studies investigating the variations of SWI on this short time scale, for which, e.g., frontal dynamics, convection and cloud microphysics play an essential role. In particular, the isotopic composition of both near-surface vapor and precipitation is significantly influenced by below-cloud processes that include precipitation evaporation and isotopic exchange between falling precipitation and surrounding vapor. In this study, simultaneous measurements of SWI in near-surface vapor and precipitation with high (sub-hourly) temporal resolution in combination with observational data from radars, disdrometers, radiosondes and standard meteorological instruments are used for a detailed analysis of the relative importance of below-cloud and in-cloud (i.e., precipitation formation) processes during the course of three rain events in Switzerland in spring 2014. Periods are identified when the isotopic composition of near-surface vapor and equilibrium vapor above liquid rain drops agree and when they differ due to either evaporation of precipitation or incomplete equilibration of precipitation with surrounding vapor. These findings are verified by the supporting observational data. In addition, calculations with a simple rain-shaft model fed with observational data are compared to the actual isotopic composition of precipitation. This combination of isotope measurements and model calculations allows us to test the sensitivity of the precipitation isotope signal to rain intensity, drop-size distribution and temperature and humidity profiles.

  5. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Hayes, J. M.; Trendel, J. M.; Albrecht, P.

    1990-01-01

    The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.

  6. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons.

    PubMed

    Freeman, K H; Hayes, J M; Trendel, J M; Albrecht, P

    1990-01-18

    The organic matter found in sedimentary rocks must derive from many sources; not only from ancient primary producers but also from consumers and secondary producers. In all of these organisms, isotope effects can affect the abundance and distribution of 13C in metabolites. Here, by using an improved form of a previously described technique in which the effluent of a gas chromatograph is continuously analysed isotopically, we report evidence of the diverse origins of sedimentary organic matter. The record of 13C abundances in sedimentary carbonate and total organic carbon can be interpreted in terms of variations in the global carbon cycle. Our results demonstrate, however, that isotope variations within sedimentary organic mixtures substantially exceed those observed between samples of total organic carbon. Resolution of isotope variations at the molecular level offers a new and convenient means of refining views both of localized palaeoenvironments and of control mechanisms within the global carbon cycle.

  7. New Half-lives of r-process Zn and Ga Isotopes Measured with Electromagnetic Separation

    NASA Astrophysics Data System (ADS)

    Madurga, M.; Surman, R.; Borzov, I. N.; Grzywacz, R.; Rykaczewski, K. P.; Gross, C. J.; Miller, D.; Stracener, D. W.; Batchelder, J. C.; Brewer, N. T.; Cartegni, L.; Hamilton, J. H.; Hwang, J. K.; Liu, S. H.; Ilyushkin, S. V.; Jost, C.; Karny, M.; Korgul, A.; Królas, W.; Kuźniak, A.; Mazzocchi, C.; Mendez, A. J., II; Miernik, K.; Padgett, S. W.; Paulauskas, S. V.; Ramayya, A. V.; Winger, J. A.; Wolińska-Cichocka, M.; Zganjar, E. F.

    2012-09-01

    The β decays of neutron-rich nuclei near the doubly magic Ni78 were studied at the Holifield Radioactive Ion Beam Facility using an electromagnetic isobar separator. The half-lives of Zn82 (228±10ms), Zn83 (117±20ms), and Ga85 (93±7ms) were determined for the first time. These half-lives were found to be very different from the predictions of the global model used in astrophysical simulations. A new calculation was developed using the density functional model, which properly reproduced the new experimental values. The robustness of the new model in the Ni78 region allowed us to extrapolate data for more neutron-rich isotopes. The revised analysis of the rapid neutron capture process in low entropy environments with our new set of measured and calculated half-lives shows a significant redistribution of predicted isobaric abundances strengthening the yield of A>140 nuclei.

  8. 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.

  9. Evaluating microbial carbon sources in Athabasca oil sands tailings ponds using natural abundance stable and radiocarbon isotopes

    NASA Astrophysics Data System (ADS)

    Ahad, J. M.; Pakdel, H.

    2013-12-01

    Natural abundance stable (δ13C) and radiocarbon (Δ14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate the carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. The absence of algal-specific PLFAs at three of the four sites investigated, in conjunction with δ13C signatures for PLFAs that were generally within ~3‰ of that reported for oil sands bitumen (~ -30‰), indicated that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. The Δ14C values of PLFAs ranged from -906 to -586‰ and pointed to a significant uptake of fossil carbon (up to ~90% of microbial carbon derived from petroleum), particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively higher levels of 14C in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population (~50-80% of microbial carbon derived from petroleum). Since the main carbon pools in tailings sediment were essentially 'radiocarbon dead' (i.e., no detectable 14C), the principal source for this modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential uptake of the minor amount of young and presumably more biodegradable material present in systems otherwise dominated by recalcitrant petroleum constituents has important implications for remediation strategies. On the one hand, it implies that mining-related organic contaminants could persist in the environment long after tailings pond reclamation has begun. Alternatively, it may be that the young, labile organic matter provided by the Athabasca River plays an important role in stimulating or supporting the microbial utilization of petroleum carbon in oil sands tailings ponds via co-metabolism or priming processes

  10. Anomalous 13C isotope abundances in C3S and C4H observed toward the cold interstellar cloud, Taurus Molecular Cloud-1.

    PubMed

    Sakai, Nami; Takano, Shuro; Sakai, Takeshi; Shiba, Shoichi; Sumiyoshi, Yoshihiro; Endo, Yasuki; Yamamoto, Satoshi

    2013-10-01

    We have studied the abundances of the (13)C isotopic species of C3S and C4H in the cold molecular cloud, Taurus Molecular Cloud-1 (Cyanopolyyne Peak), by radioastronomical observations of their rotational emission lines. The CCCS/(13)CCCS and CCCS/C(13)CCS ratios are determined to be >206 and 48 ± 15, respectively. The CC(13)CS line is identified with the aid of laboratory microwave spectroscopy, and the range of the CCCS/CC(13)CS ratio is found to be from 30 to 206. The abundances of at least two (13)C isotopic species of C3S are thus found to be different. Similarly, it is found that the abundances of the four (13)C isotopic species of C4H are not equivalent. The CCCCH/(13)CCCCH, CCCCH/C(13)CCCH, CCCCH/CC(13)CCH, and CCCCH/CCC(13)CH ratios are evaluated to be 141 ± 44, 97 ± 27, 82 ± 15, and 118 ± 23, respectively. Here the errors denote 3 times the standard deviation. These results will constrain the formation pathways of C3S and C4H, if the nonequivalence is caused during the formation processes of these molecules. The exchange reactions after the formation of these two molecules may also contribute to the nonequivalence. In addition, we have confirmed that the (12)C/(13)C ratio of some species are significantly higher than the interstellar elemental (12)C/(13)C ratio of 60-70. The observations of the (13)C isotopic species provide us with rich information on chemical processes in cold interstellar clouds.

  11. Measurement of the isotope enrichment of stable isotope-labeled proteins using high-resolution mass spectra of peptides.

    PubMed

    MacCoss, Michael J; Wu, Christine C; Matthews, Dwight E; Yates, John R

    2005-12-01

    Stable isotope-enriched molecules are used as internal standards and as tracers of in vivo substrate metabolism. The accurate conversion of measured ratios in the mass spectrometer to mole ratios is complicated because a polyatomic molecule containing enriched atoms will result in a combinatorial distribution of isotopomers depending on the enrichment and number of "labeled" atoms. This effect could potentially cause a large error in the mole ratio measurement depending on which isotope peak or peaks were used to determine the ratio. We report a computational method that predicts isotope distributions over a range of enrichments and compares the predicted distributions to experimental peptide isotope distributions obtained by Fourier transform ion cyclotron resonance mass spectrometry. Our approach is accurate with measured enrichments within 1.5% of expected isotope distributions. The method is also precise with 4.9, 2.0, and 0.8% relative standard deviations for peptides containing 59, 79, and 99 atom % excess (15)N, respectively. The approach is automated making isotope enrichment calculations possible for thousands of peptides in a single muLC-FTICR-MS experiment.

  12. Carbon Isotope Measurements of Experimentally-Derived Hydrothermal Mineral-Catalyzed Organic Products by Pyrolysis-Isotope Ratio Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.

    2011-01-01

    We report results of experiments to measure the C isotope composition of mineral catalyzed organic compounds derived from high temperature and high pressure synthesis. These experiments make use of an innovative pyrolysis technique designed to extract and measure C isotopes. To date, our experiments have focused on the pyrolysis and C isotope ratio measurements of low-molecular weight intermediary hydrocarbons (organic acids and alcohols) and serve as a proof of concept for making C and H isotope measurements on more complicated mixtures of solid-phase hydrocarbons and intermediary products produced during high temperature and high pressure synthesis on mineral-catalyzed surfaces. The impetus for this work stems from recently reported observations of methane detected within the Martian atmosphere [1-4], coupled with evidence showing extensive water-rock interaction during Martian history [5-7]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization reactions [8,9]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [10-12]. Further, recent experiments by Fu et al. [13] focus on examining detailed C isotope measurements of hydrocarbons produced by surface-catalyzed mineral reactions. Work described in this paper details the experimental techniques used to measure intermediary organic reaction products (alcohols and organic acids).

  13. A century of progress in the sciences due to atomic weight and isotopic composition measurements.

    PubMed

    De Laeter, J R; Peiser, H S

    2003-01-01

    Even before the 20th century, a consistent set of internationally accepted atomic weights was an important objective of the scientific community because of the fundamental importance of these values to science, technology and trade. As the 20th century progressed, physicists, geoscientists, and metrologists collaborated with chemists to revolutionize the science of atomic weights. At the beginning of the century, atomic weights were determined from mass relationships between chemical reactants and products of known stoichiometry. They are now derived from the measured isotopic composition of elements and the atomic masses of the isotopes. Accuracy in measuring atomic weights has improved continually, leading to the revelation of small but significant variations in the isotope abundances of many elements in their normal terrestrial occurrences caused by radioactivity and a variety of physicochemical and biochemical fractionation mechanisms. This atomic-weight variability has now been recognized as providing new scientific insights into and knowledge of the history of materials. Atomic weights, except those of the monoisotopic elements, are thus no longer regarded as "constants of nature". At the beginning of the 20th century, two scales for atomic weights were in common use: that based on the atomic weight of hydrogen being 1 and that based on the atomic weight of oxygen being 16. Atomic weights are now scaled to (12)C, which has the value 12 exactly. Accurate atomic weights of silicon, silver, and argon, have enabled the values of the Avogadro, Faraday and Universal Gas constants, respectively, to be established, with consequent effects on other fundamental constants.

  14. Nitrate dynamics in natural plants: insights based on the concentration and natural isotope abundances of tissue nitrate

    PubMed Central

    Liu, Xue-Yan; Koba, Keisuke; Makabe, Akiko; Liu, Cong-Qiang

    2014-01-01

    The dynamics of nitrate (NO−3), a major nitrogen (N) source for natural plants, has been studied mostly through experimental N addition, enzymatic assay, isotope labeling, and genetic expression. However, artificial N supply may not reasonably reflect the N strategies in natural plants because NO−3 uptake and reduction may vary with external N availability. Due to abrupt application and short operation time, field N addition, and isotopic labeling hinder the elucidation of in situ NO−3-use mechanisms. The concentration and natural isotopes of tissue NO−3 can offer insights into the plant NO−3 sources and dynamics in a natural context. Furthermore, they facilitate the exploration of plant NO−3 utilization and its interaction with N pollution and ecosystem N cycles without disturbing the N pools. The present study was conducted to review the application of the denitrifier method for concentration and isotope analyses of NO−3 in plants. Moreover, this study highlights the utility and advantages of these parameters in interpreting NO−3 sources and dynamics in natural plants. We summarize the major sources and reduction processes of NO−3 in plants, and discuss the implications of NO−3 concentration in plant tissues based on existing data. Particular emphasis was laid on the regulation of soil NO−3 and plant ecophysiological functions in interspecific and intra-plant NO−3 variations. We introduce N and O isotope systematics of NO−3 in plants and discuss the principles and feasibilities of using isotopic enrichment and fractionation factors; the correlation between concentration and isotopes (N and O isotopes: δ18O and Δ17O); and isotope mass-balance calculations to constrain sources and reduction of NO−3 in possible scenarios for natural plants are deliberated. Finally, we offer a preliminary framework of intraplant δ18O-NO−3 variation, and summarize the uncertainties in using tissue NO−3 parameters to interpret plant NO−3 utilization

  15. Oxygen isotope ratio measurements on carbon dioxide generated by reaction of microliter quantities of biological fluids with guanidine hydrochloride

    SciTech Connect

    Wong, W.W.; Lee, L.S.; Klein, P.D.

    1987-03-01

    Guanidine hydrochloride was used to convert water in biological fluids to carbon dioxide for oxygen isotope ratio measurements. Five 10-..mu..L aliquots each of five different saliva, urine, plasma, and human milk samples were allowed to react with 100 mg of guanidine hydrochloride at 260/sup 0/C to produce ammonia and carbon dioxide. Ammonia was removed with 100% phosphoric acid and carbon dioxide was cryogenically purified before isotope ratio measurement. At natural abundances, the delta/sup 18/O values of the biological fluids were reproducible to within 0.16% (standard deviation) and accurate to within 0.11 +/- 0.73% (x vector +/- SD) of the H/sub 2/O-CO/sub 2/ equilibration values. At a 250% enrichment level of /sup 18/O, the delta/sup 18/O values of the biological fluids were reproducible to within 0.95% and accurate to -1.27 +/- 2.25%.

  16. Nicotine, acetanilide and urea multi-level2H-,13C- and15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry

    USGS Publications Warehouse

    Schimmelmann, A.; Albertino, A.; Sauer, P.E.; Qi, H.; Molinie, R.; Mesnard, F.

    2009-01-01

    Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the S values of these reference materials should bracket the isotopic range of samples with unknown S values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW-SLAP) and carbonates (NBS 19 and L-SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). At present only L-glutamic acids USGS40 and USGS41 satisfy these requirements for ??13C and ??13N, with the limitation that L-glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on-line (i.e. continuous flow) hydrogen reductive gas chromatography-isotope ratio mass-spectrometry (GC-IRMS), (ii) five nicotines for oxidative C, N gas chromatography-combustion-isotope ratio mass-spectrometry (GC-C-IRMS, or GC-IRMS), and (iii) also three acetanilide and three urea reference materials for on-line oxidative EA-IRMS for C and N. Isotopic off-line calibration against international stable isotope measurement standards at Indiana University adhered to the 'principle of identical treatment'. The new reference materials cover the following isotopic ranges: ??2Hnicotine -162 to -45%o, ??13Cnicotine -30.05 to +7.72%, ?? 15Nnicotine -6.03 to +33.62%; ??15N acetanilide +1-18 to +40.57%; ??13Curea -34.13 to +11.71%, ??15Nurea +0.26 to +40.61% (recommended ?? values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as the first organic nitrogen stable isotope reference materials for GC-IRMS that are available with different ??13N

  17. Nicotine, acetanilide and urea multi-level 2H-, 13C- and 15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry.

    PubMed

    Schimmelmann, Arndt; Albertino, Andrea; Sauer, Peter E; Qi, Haiping; Molinie, Roland; Mesnard, François

    2009-11-01

    Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the delta values of these reference materials should bracket the isotopic range of samples with unknown delta values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW-SLAP) and carbonates (NBS 19 and L-SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). At present only L-glutamic acids USGS40 and USGS41 satisfy these requirements for delta13C and delta15N, with the limitation that L-glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on-line (i.e. continuous flow) hydrogen reductive gas chromatography-isotope ratio mass-spectrometry (GC-IRMS), (ii) five nicotines for oxidative C, N gas chromatography-combustion-isotope ratio mass-spectrometry (GC-C-IRMS, or GC-IRMS), and (iii) also three acetanilide and three urea reference materials for on-line oxidative EA-IRMS for C and N. Isotopic off-line calibration against international stable isotope measurement standards at Indiana University adhered to the 'principle of identical treatment'. The new reference materials cover the following isotopic ranges: delta2H(nicotine) -162 to -45 per thousand, delta13C(nicotine) -30.05 to +7.72 per thousand, delta15N(nicotine) -6.03 to +33.62 per thousand; delta15N(acetanilide) +1.18 to +40.57 per thousand; delta13C(urea) -34.13 to +11.71 per thousand, delta15N(urea) +0.26 to +40.61 per thousand (recommended delta values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as

  18. Water vapor isotopes measurements at Mauna Loa, Hawaii: Comparison of laser spectroscopy and remote sensing with traditional methods, and the need for ongoing monitoring

    NASA Astrophysics Data System (ADS)

    Galewsky, J.; Noone, D.; Sharp, Z.; Worden, J.

    2009-04-01

    The isotopic composition of water vapor (2H/1H and 18O/16 ratios) provides unique information on the transport pathways that link water sources to regional sinks, and thus proves useful in understanding large scale atmospheric humidity budgets. Recent advances in measurement technology allow the monitoring of water vapor isotope composition in ways which has can revolutionize investigations of atmospheric hydrology. Traditional measurement of isotopic composition requires trapping of samples with either large volume vacuum flasks or by trapping liquid samples with cryogens for later analyses using mass spectrometry, and are laborious and seldom span more than just short dedicated observational periods. On the other hand, laser absorption spectroscopy can provide almost continuous and autonomous in situ measurements of isotope abundances with precision almost that of traditional mass spectrometry, and observations from spacecraft can make almost daily maps of the global isotope distributions. In October of 2008 three laser based spectrometers were deployed at the Mauna Loa Laboratory in Hawaii to make continuous measurement of the 2H and 18O abundance of free tropospheric water vapor. These results are compared with traditional measurements and with measurements from two satellite platforms. While providing field validation of the new methodologies, the data show variability which captures the transport processes in the region. The data are used to characterize the role of large scale mixing of dry air, the influence of the boundary layer and the importance of moist convection in controlling the low humidity of subtropical air near Hawaii. Although the record is short, it demonstrates the usefulness of using robust isotope measurements to understand the budgets of the most important greenhouse gas. This work motivates establishing a continuous record of isotopes measurement at baseline sites, like Mauna Loa, such that the changes in water cycle can be understood and

  19. Water vapor isotopes measurements at Mauna Loa, Hawaii: Comparison of laser spectroscopy and remote sensing with traditional methods, and the need for ongoing monitoring

    NASA Astrophysics Data System (ADS)

    Noone, D.; Galewsky, J.; Sharp, Z.; Worden, J.

    2008-12-01

    The isotopic composition of water vapor (2H/1H and 18O/16 ratios) provides unique information on the transport pathways that link the water sources to regional sinks, and thus proves useful in understanding the large scale humidity budgets. Recent advances in measurement technology allow the monitoring of water vapor isotope composition in ways which has can revolutionize investigations of atmospheric hydrology. Traditional measurement of isotopic composition requires trapping of samples with either large volume vacuum flasks or by trapping liquid samples with cryogens for later analyses using mass spectrometry, and are laborious and seldom span more than just short dedicated observational periods. On the other hand, laser absorption spectroscopy can provide almost continuous and autonomous in situ measurements of isotope abundances with precision almost that of traditional mass spectrometry, and observations from spacecraft can make almost daily maps of the global isotope distributions. In October of 2008 three laser based spectrometers were deployed at the Mauna Loa Laboratory in Hawaii to make continuous measurement of the 2H and 18O abundance of free tropospheric water vapor. These results are compared with traditional measurements and with measurements from two satellite platforms. While providing field validation of the new methodologies, the data show variability which captures the transport processes in the region. The data are used to characterize the role of large scale mixing of dry air, the influence of the boundary layer and the importance of moist convection in controlling the low humidity of subtropical air near Hawaii. Although the record is short, it demonstrates the usefulness of using robust isotope measurements to understand the budgets of the most important greenhouse gas. This work motivates establishing a continuous record of isotopes measurement at baseline sites, like Mauna Loa, such that the changes in water cycle can be understood and

  20. Monte Carlo method for calculating oxygen abundances and their uncertainties from strong-line flux measurements

    NASA Astrophysics Data System (ADS)

    Bianco, F. B.; Modjaz, M.; Oh, S. M.; Fierroz, D.; Liu, Y. Q.; Kewley, L.; Graur, O.

    2016-07-01

    We present the open-source Python code pyMCZ that determines oxygen abundance and its distribution from strong emission lines in the standard metallicity calibrators, based on the original IDL code of Kewley and Dopita (2002) with updates from Kewley and Ellison (2008), and expanded to include more recently developed calibrators. The standard strong-line diagnostics have been used to estimate the oxygen abundance in the interstellar medium through various emission line ratios (referred to as indicators) in many areas of astrophysics, including galaxy evolution and supernova host galaxy studies. We introduce a Python implementation of these methods that, through Monte Carlo sampling, better characterizes the statistical oxygen abundance confidence region including the effect due to the propagation of observational uncertainties. These uncertainties are likely to dominate the error budget in the case of distant galaxies, hosts of cosmic explosions. Given line flux measurements and their uncertainties, our code produces synthetic distributions for the oxygen abundance in up to 15 metallicity calibrators simultaneously, as well as for E(B- V) , and estimates their median values and their 68% confidence regions. We provide the option of outputting the full Monte Carlo distributions, and their Kernel Density estimates. We test our code on emission line measurements from a sample of nearby supernova host galaxies (z < 0.15) and compare our metallicity results with those from previous methods. We show that our metallicity estimates are consistent with previous methods but yield smaller statistical uncertainties. It should be noted that systematic uncertainties are not taken into account. We also offer visualization tools to assess the spread of the oxygen abundance in the different calibrators, as well as the shape of the estimated oxygen abundance distribution in each calibrator, and develop robust metrics for determining the appropriate Monte Carlo sample size. The code

  1. The isotopes of hydrogen and helium in the Galactic cosmic radiation - Their source abundances and interstellar propagation

    NASA Technical Reports Server (NTRS)

    Beatty, James J.

    1986-01-01

    A self-consistent model describing the interstellar propagation of Galactic cosmic radiation is developed using low-energy measurements and calculations of the effects of interstellar propagation and solar modulation. The source ratio H-1/He-4 at constant energy per nucleon is determined to be 12.2 + or - 1.5, and the mean path length for an exponential path length weighting function required to account for the data is 7.2 + or - 1.0 g/sq cm. The measured H-2/He-4 and He-3/He-4 ratios do not vary by more than about 30 percent over the solar cycle. The behavior of the ratios during the solar cycle reflects the energy dependence of the local interstellar ratios, and leads to an energy dependence of the mean path length below 1 GeV per nucleon weaker than that inferred from boron/carbon. The source ratio H-1/He-4 inferred from the low-energy data is consistent both with the value inferred from high-energy cosmic ray data using a model of rigidity-dependent confinement and with the solar system abundance ratio.

  2. Attogram measurement of rare isotopes by CW resonance ionization mass spectrometry

    SciTech Connect

    Bushaw, B.A.

    1992-05-01

    Three-color double-resonance ionization mass spectrometry, using two single-frequency cw dye lasers and a cw carbon dioxide laser, has been applied to the detection of attogram quantities of rare radionuclides. {sup 210}Pb has been measured in human hair and brain tissue samples to assess indoor radon exposure. Measurements on {sup 90}Sr have shown overall isotopic selectivity of greater than 10{sup 9} despite unfavorable isotope shifts relative to the major stable isotope, {sup 88}Sr.

  3. The superTIGER instrument: Measurement of elemental abundances of ultra-heavy galactic cosmic rays

    SciTech Connect

    Binns, W. R.; Bose, R. G.; Braun, D. L.; Dowkontt, P. F.; Israel, M. H.; Moore, P.; Murphy, R. P.; Olevitch, M. A.; Rauch, B. F.; Brandt, T. J.; Daniels, W. M.; Fitzsimmons, S. P.; Hahne, D. J.; Hams, T.; Link, J. T.; Mitchell, J. W.; Sakai, K.; and others

    2014-06-10

    The SuperTIGER (Super Trans-Iron Galactic Element Recorder) instrument was developed to measure the abundances of galactic cosmic-ray elements from {sub 10}Ne to {sub 40}Zr with individual element resolution and the high statistics needed to test models of cosmic-ray origins. SuperTIGER also makes exploratory measurements of the abundances of elements with 40 < Z ≤ 60 and measures the energy spectra of the more abundant elements for Z ≤ 30 from about 0.8 to 10 GeV/nucleon. This instrument is an enlarged and higher resolution version of the earlier TIGER instrument. It was designed to provide the largest geometric acceptance possible and to reach as high an altitude as possible, flying on a standard long-duration 1.11 million m{sup 3} balloon. SuperTIGER was launched from Williams Field, McMurdo Station, Antarctica, on 2012 December 8, and made about 2.7 revolutions around the South Pole in 55 days of flight, returning data on over 50 × 10{sup 6} cosmic-ray nuclei with Z ≥ 10, including ∼1300 with Z > 29 and ∼60 with Z > 49. Here, we describe the instrument, the methods of charge identification employed, the SuperTIGER balloon flight, and the instrument performance.

  4. The use of molecular beacons to directly measure bacterial mRNA abundances and transcript degradation.

    PubMed

    Kuechenmeister, Lisa J; Anderson, Kelsi L; Morrison, John M; Dunman, Paul M

    2009-02-01

    The regulation of mRNA turnover is a dynamic means by which bacteria regulate gene expression. Although current methodologies allow characterization of the stability of individual transcripts, procedures designed to measure alterations in transcript abundance/turnover on a high throughput scale are lacking. In the current report, we describe the development of a rapid and simplified molecular beacon-based procedure to directly measure the mRNA abundances and mRNA degradation properties of well-characterized Staphylococcus aureus pathogenicity factors. This method does not require any PCR-based amplification, can monitor the abundances of multiple transcripts within a single RNA sample, and was successfully implemented into a high throughput screen of transposon mutant library members to detect isolates with altered mRNA turnover properties. It is expected that the described methodology will provide great utility in characterizing components of bacterial RNA degradation processes and can be used to directly measure the mRNA levels of virtually any bacterial transcript.

  5. THE SuperTIGER Instrument: Measurement of Elemental Abundances of Ultra-Heavy Galactic Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Bose, R. G.; Braun, D. L.; Brandt, T. J.; Daniels, W. M.; DowKonnt, P. F.; Fitzsimmons, S. P.; Hahne, D. J.; Hams, T.; Israel, M. H.; Klemic, J.; Labrador, A. W.; Link, J. T.; Mewaldt, R. A.; Mitchell, J. W.; Moore, P.; Murphy, R. P.; Olevitch, M. A.; Rauch, B. F.; Sakai, K.; San Sebastian, F.; Sasaki, M.; Simburger, G. E.; Stone, E. C.; Waddington, C. J.; Ward, J. E.; Wiedenbeck, M. E.

    2014-01-01

    The SuperTIGER (Super Trans-Iron Galactic Element Recorder) instrument was developed to measure the abundances of galactic cosmic-ray elements from Ne-10 to Zr-40 with individual element resolution and the high statistics needed to test models of cosmic-ray origins. SuperTIGER also makes exploratory measurements of the abundances of elements with 40 < Z < or = 60 and measures the energy spectra of the more abundant elements for Z < or = 30 from about 0.8 to 10 GeV/nucleon. This instrument is an enlarged and higher resolution version of the earlier TIGER instrument. It was designed to provide the largest geometric acceptance possible and to reach as high an altitude as possible, flying on a standard long-duration 1.11 million cu m balloon. SuperTIGER was launched from Williams Field, McMurdo Station, Antarctica, on 2012 December 8, and made about 2.7 revolutions around the South Pole in 55 days of flight, returning data on over 50 x 10(exp 6) cosmic-ray nuclei with Z > or = 10, including approx.1300 with Z > 29 and approx.60 with Z > 49. Here, we describe the instrument, the methods of charge identification employed, the SuperTIGER balloon flight, and the instrument performance.

  6. Determination of carbon isotopic measurement conditions for ceramide in skin using gas chromatography-combustion-isotope ratio mass spectrometry.

    PubMed

    Haraguchi, Hiroyuki; Yamada, Keita; Miyashita, Rumiko; Aida, Kazuhiko; Ohnishi, Masao; Gilbert, Alexis; Yoshida, Naohiro

    2014-01-01

    The ceramide (Cer) content of skin and glucosylceramide (GlcCer) intake affect skin moisture conditions, but their mutual relation in skin remains unclear. For clarification of that mutual relation, carbon stable isotopes ((12)C and (13)C) are useful as a tracer. However, carbon isotopic measurement has not been applied to the study of clarifying their skin moisturizing effects. Therefore, we used gas chromatography / combustion / isotope ratio mass spectrometry (GC-C-IRMS) to ascertain the appropriate conditions for carbon isotopic measurements using synthesized Cer (SCer) in substitution for very low concentrations of Cer in skin. SCer was derivatized to trimethylsilylated SCer (TMS-SCer) quantitatively using N-trimethylsilylimidazole (TMSI) depending on the amount of SCer. The derivatization rates were 75-85%. Excess TMSI was removed using three cycles of hexane-water distribution. Under these conditions, carbon isotopic measurements of TMS-SCer conducted using GC-C-IRMS showed high repeatability and good inter-day variation (S.D. < 0.3‰). The carbon stable isotope ratio value (δ(13)C) of SCer calculated using a mass balance equation was compared with δ(13)C of underivatized SCer, which was regarded as the actual δ(13)C of SCer obtained using sealed tube combustion method. The difference between the calculated δ(13)C of SCer and δ(13)C of the underivatized SCer depended on the TMSI reagent supplier and on the number of hydroxyl groups to be derivatized in SCer. For accurate δ(13)C of Cer in skin using GC-C-IRMS, the measured δ(13)C of a target TMS-Cer must be calculated using a correction factor representing the difference in δ(13)C of underivatized standard SCer from that of TMS-standard SCer having a structure resembling that of the target Cer in skin. In addition, we show that the same lot of TMSI reagent from a specific supplier must be used throughout the experiments.

  7. Existing and emerging technologies for measuring stable isotope labelled retinol in biological samples: isotope dilution analysis of body retinol stores.

    PubMed

    Preston, Tom

    2014-01-01

    This paper discusses some of the recent improvements in instrumentation used for stable isotope tracer measurements in the context of measuring retinol stores, in vivo. Tracer costs, together with concerns that larger tracer doses may perturb the parameter under study, demand that ever more sensitive mass spectrometric techniques are developed. GCMS is the most widely used technique. It has high sensitivity in terms of sample amount and uses high resolution GC, yet its ability to detect low isotope ratios is limited by background noise. LCMSMS may become more accessible for tracer studies. Its ability to measure low level stable isotope tracers may prove superior to GCMS, but it is isotope ratio MS (IRMS) that has been designed specifically for low level stable isotope analysis through accurate analysis of tracer:tracee ratios (the tracee being the unlabelled species). Compound-specific isotope analysis, where GC is interfaced to IRMS, is gaining popularity. Here, individual 13C-labelled compounds are separated by GC, combusted to CO2 and transferred on-line for ratiometric analysis by IRMS at the ppm level. However, commercially-available 13C-labelled retinol tracers are 2 - 4 times more expensive than deuterated tracers. For 2H-labelled compounds, GC-pyrolysis-IRMS has now become more generally available as an operating mode on the same IRMS instrument. Here, individual compounds are separated by GC and pyrolysed to H2 at high temperature for analysis by IRMS. It is predicted that GC-pyrolysis-IRMS will facilitate low level tracer procedures to measure body retinol stores, as has been accomplished in the case of fatty acids and amino acids. Sample size requirements for GC-P-IRMS may exceed those of GCMS, but this paper discusses sample preparation procedures and predicts improvements, particularly in the efficiency of sample introduction.

  8. Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Casado, Mathieu; Landais, Amaelle; Masson-Delmotte, Valérie; Genthon, Christophe; Kerstel, Erik; Kassi, Samir; Arnaud, Laurent; Picard, Ghislain; Prie, Frederic; Cattani, Olivier; Steen-Larsen, Hans-Christian; Vignon, Etienne; Cermak, Peter

    2016-07-01

    Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014-January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading

  9. A solvent extraction technique for the isotopic measurement of dissolved copper in seawater.

    PubMed

    Thompson, Claire M; Ellwood, Michael J; Wille, Martin

    2013-05-01

    Stable copper (Cu) isotope geochemistry provides a new perspective for investigating and understanding Cu speciation and biogeochemical Cu cycling in seawater. In this work, sample preparation for isotopic analysis employed solvent-extraction with amino pyrollidine dithiocarbamate/diethyl dithiocarbamate (APDC/DDC), coupled with a nitric acid back-extraction, to concentrate Cu from seawater. This was followed by Cu-purification using anion-exchange. This straightforward technique is high yielding and fractionation free for Cu and allows precise measurement of the seawater Cu isotopic composition using multi-collector inductively coupled plasma mass-spectrometry. A deep-sea profile measured in the oligotrophic north Tasman Sea shows fractionation in the Cu isotopic signature in the photic zone but is relatively homogenised at depth. A minima in the Cu isotopic profile correlates with the chlorophyll a maximum at the site. These results indicate that a range of processes are likely to fractionate stable Cu isotopes in seawater. PMID:23601981

  10. A solvent extraction technique for the isotopic measurement of dissolved copper in seawater.

    PubMed

    Thompson, Claire M; Ellwood, Michael J; Wille, Martin

    2013-05-01

    Stable copper (Cu) isotope geochemistry provides a new perspective for investigating and understanding Cu speciation and biogeochemical Cu cycling in seawater. In this work, sample preparation for isotopic analysis employed solvent-extraction with amino pyrollidine dithiocarbamate/diethyl dithiocarbamate (APDC/DDC), coupled with a nitric acid back-extraction, to concentrate Cu from seawater. This was followed by Cu-purification using anion-exchange. This straightforward technique is high yielding and fractionation free for Cu and allows precise measurement of the seawater Cu isotopic composition using multi-collector inductively coupled plasma mass-spectrometry. A deep-sea profile measured in the oligotrophic north Tasman Sea shows fractionation in the Cu isotopic signature in the photic zone but is relatively homogenised at depth. A minima in the Cu isotopic profile correlates with the chlorophyll a maximum at the site. These results indicate that a range of processes are likely to fractionate stable Cu isotopes in seawater.

  11. Advances in laser-based isotope ratio measurements: selected applications

    NASA Astrophysics Data System (ADS)

    Kerstel, E.; Gianfrani, L.

    2008-09-01

    Small molecules exhibit characteristic ro-vibrational transitions in the near- and mid-infrared spectral regions, which are strongly influenced by isotopic substitution. This gift of nature has made it possible to use laser spectroscopy for the accurate analysis of the isotopic composition of gaseous samples. Nowadays, laser spectroscopy is clearly recognized as a valid alternative to isotope ratio mass spectrometry. Laser-based instruments are leaving the research laboratory stage and are being used by a growing number of isotope researchers for significant advances in their own field of research. In this review article, we discuss the current status and new frontiers of research on high-sensitivity and high-precision laser spectroscopy for isotope ratio analyses. Although many of our comments will be generally applicable to laser isotope ratio analyses in molecules of environmental importance, this paper concerns itself primarily with water and carbon dioxide, two molecules that were studied extensively in our respective laboratories. A complete coverage of the field is practically not feasible in the space constraints of this issue, and in any case doomed to fail, considering the large body of work that has appeared ever since the review by Kerstel in 2004 ( Handbook of Stable Isotope Analytical Techniques, Chapt. 34, pp. 759-787).

  12. Heavy atom labeled nucleotides for measurement of kinetic isotope effects.

    PubMed

    Weissman, Benjamin P; Li, Nan-Sheng; York, Darrin; Harris, Michael; Piccirilli, Joseph A

    2015-11-01

    Experimental analysis of kinetic isotope effects represents an extremely powerful approach for gaining information about the transition state structure of complex reactions not available through other methodologies. The implementation of this approach to the study of nucleic acid chemistry requires the synthesis of nucleobases and nucleotides enriched for heavy isotopes at specific positions. In this review, we highlight current approaches to the synthesis of nucleic acids enriched site specifically for heavy oxygen and nitrogen and their application in heavy atom isotope effect studies. This article is part of a special issue titled: Enzyme Transition States from Theory and Experiment.

  13. Precision Oxygen Isotope Measurements of Two C-Rich Hydrated Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Snead, C. J.; Keller, L. P.; McKeegan, K. D.; Messenger, S.

    2016-01-01

    SMOW (minus 33 plus or minus 19 per mille, 1 plus or minus 14 per mille 1 sigma), several delta D-rich hotspots were also identified, reaching 2000 per mille. As shown in Fig. 1, these hotspots are clearly associated with discrete carbonaceous inclusions that are akin to nanoglobules found in many meteorites and other IDPs. Oxygen Isotopes. Results of the oxygen isotope measurements are shown in Figure 1. The oxygen isotope composition for L2079C35 was delta 18O equals plus11.6 plus or minus 1.9per mille, delta 17O equals plus 7.9 plus or minus 1.9per mille (2 standard errors). The oxygen isotope composition for L2083D46 was delta 18O equals minus 8.1 plus or minus 1.9 per mille, delta 17O equals minus 6.4 plus or minus 3.1 per mille (2 standard errors). The oxygen isotope composition for L2083E46 was delta 18O equals plus 12.0 plus or minus 1.9 per mille, delta 17O equals plus 9.2 plus or minus 2.0 per mille (2 standard errors). Discussion: Despite mineralogical similarities to highly aqueously altered carbonaceous chondrites, the hydrated IDPs we analyzed have oxygen isotopic compositions that are distinct from matrix materials in the CI, CM, and CR chondrites. The IDPs plot along the Young-Russell line, with delta 17O values for C35 and E46 suggestive of interaction with a 16O-poor reservoir. However, we have thus far not observed evidence of extreme 16O-poor reservoirs expected from self-shielding models and observed in Acfer 094 simplectite. The high carbon contents of the IDPs also set them apart from known meteoritic samples. The lack of atmospheric entry heating effects are consistent with low encounter velocities and suggest either an asteroidal source, or a low inclination, low eccentricity cometary origin. Conclusions: The unusual oxygen isotopic compositions, high carbon contents, and the abundance of Drich nanoglobules, together, suggest that the high-carbon, hydrated IDPs are derived from a primitive source that is not yet represent ed in meteorite

  14. The measurement of elemental abundances above 10 exp 15 eV at a lunar base

    NASA Astrophysics Data System (ADS)

    Swordy, S. P.

    1990-03-01

    At about 10 exp 15 eV the slope of the energy spectrum of cosmic rays becomes significantly steeper than at lower energies. The measurement of relative elemental abundances at these energies is expected to provide a means to resolve the origin of this feature and greatly contribute to the understanding of the sources of cosmic rays. A moon-based detector for making well-resolved elemental measurements at these energies is described using hadronic calorimetry. This detector is particularly well suited for a site on the lunar surface because there is no overlying layer of atmosphere and the large mass required can be provided by the lunar regolith.

  15. Airborne Measurements of Atmospheric Methane Column Abundance Made Using a Pulsed IPDA Lidar

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Numata, Kenji; Li, Steve; Wu, Stewart; Ramanathan, Anamd; Dawsey, Martha; Mao, Jianping; Kawa, Randolph; Abshire, James B.

    2012-01-01

    We report airborne measurements of the column abundance of atmospheric methane made over an altitude range of 3-11 km using a direct detection IPDA lidar with a pulsed laser emitting at 1651 nm. The laser transmitter was a tunable, seeded optical parametric amplifier (OPA) pumped by a Nd:YAG laser and the receiver used a photomultiplier detector and photon counting electronics. The results follow the expected changes with aircraft altitude and the measured line shapes and optical depths show good agreement with theoretical calculations.

  16. pyMCZ: Oxygen abundances calculations and uncertainties from strong-line flux measurements

    NASA Astrophysics Data System (ADS)

    Bianco, Federica B.; Modjaz, Maryam; Oh, Seung Man; Fierroz, David; Liu, Yuqian; Kewley, Lisa; Graur, Or

    2015-05-01

    pyMCZ calculates metallicity according to a number of strong line metallicity diagnostics from spectroscopy line measurements and obtain uncertainties from the line flux errors in a Monte Carlo framework. Given line flux measurements and their uncertainties, pyMCZ produces synthetic distributions for the oxygen abundance in up to 13 metallicity scales simultaneously, as well as for E(B-V), and estimates their median values and their 68% confidence regions. The code can output the full MC distributions and their kernel density estimates.

  17. First Measurement of the Nuclear Carge Radii of Short-Lived Lithium Isotopes

    SciTech Connect

    Nortershauser, W.; Dax, A ..; Ewald, G; Gotte, S; Kirchner, Rolf; Kluge, H J.; Kuhl, T H.; Sanchez, Rodolfo; Wojtaszek, A.; Bushaw, Bruce A.; Drake, Gordon W. F.; Yan, Z C.; Zimmerman, C.

    2006-04-01

    A novel method for the determination of nuclear charge radii of lithium isotopes is presented. Precise laser spectroscopic measurements of the isotope shift in the lithium 2s? 3s transition are combined with highly accurate atomic physics calculation of the mass dependent isotope shift to extract the charge-distribution-sensitive information. This approach has been used to determine the charge radii of 6,7,8,9Li.

  18. Using antibody arrays to measure protein abundance and glycosylation: considerations for optimal performance.

    PubMed

    Haab, Brian B; Partyka, Katie; Cao, Zheng

    2013-09-24

    Antibody arrays provide a valuable method for obtaining multiple protein measurements from small volumes of biological samples. Antibody arrays can be designed to target not only core protein abundances (relative or absolute abundances, depending on the availability of standards for calibration), but also posttranslational modifications, provided antibodies or other affinity reagents are available to detect them. Glycosylation is a common modification that has important and diverse functions in both normal and disease biology. Significant progress has been made in developing methods for measuring glycan levels on multiple specific proteins using antibody arrays and glycan-binding reagents. This unit describes practical approaches for developing, optimizing, and using antibody array assays to determine both protein abundance and glycosylation state. Low-volume arrays can be used to reduce sample consumption, and a new way to improve the binding strength of particular glycan-binding reagents through multimerization is discussed. These methods can be useful for a wide range of biological studies in which glycosylation may change and/or affect protein function.

  19. A PRECISE WATER ABUNDANCE MEASUREMENT FOR THE HOT JUPITER WASP-43b

    SciTech Connect

    Kreidberg, Laura; Bean, Jacob L.; Stevenson, Kevin B.; Désert, Jean-Michel; Line, Michael R.; Fortney, Jonathan J.; Madhusudhan, Nikku; Showman, Adam P.; Kataria, Tiffany; Charbonneau, David; McCullough, Peter R.; Seager, Sara; Burrows, Adam; Henry, Gregory W.; Williamson, Michael; Homeier, Derek

    2014-10-01

    The water abundance in a planetary atmosphere provides a key constraint on the planet's primordial origins because water ice is expected to play an important role in the core accretion model of planet formation. However, the water content of the solar system giant planets is not well known because water is sequestered in clouds deep in their atmospheres. By contrast, short-period exoplanets have such high temperatures that their atmospheres have water in the gas phase, making it possible to measure the water abundance for these objects. We present a precise determination of the water abundance in the atmosphere of the 2 M {sub Jup} short-period exoplanet WASP-43b based on thermal emission and transmission spectroscopy measurements obtained with the Hubble Space Telescope. We find the water content is consistent with the value expected in a solar composition gas at planetary temperatures (0.4-3.5 × solar at 1σ confidence). The metallicity of WASP-43b's atmosphere suggested by this result extends the trend observed in the solar system of lower metal enrichment for higher planet masses.

  20. Variations in Os- and Mo-isotope compositions and trace element abundances across the Permo-Triassic boundary, Meishan, China: Proxy evidence for large-scale oceanic anoxia?

    NASA Astrophysics Data System (ADS)

    Cohen, A. S.; Saunders, A.; Zhang, H.; Li, J.

    2009-12-01

    We have carried out Os-isotope analyses, and major and trace element determinations, on samples from the Permo-Triassic section at Meishan B sections, adjacent to the GSSP, China, to assess environmental change at the P-Tr boundary (Bed 27) and the underlying main extinction horizon (Bed 25). Major and trace element abundances were determined by XRF on 38 samples from a 2.3-metre interval of limestone, shale and dolomitic marl from Bed 24a to Bed 32. Re, Os and Mo abundances, and Os-isotope compositions, were determined on a subset of 26 samples, predominantly dark-coloured mudrocks; new Mo-isotope data will be presented. Initial 187Os/188Os(t=250Ma) ranges from 0.3 to 2, with no obvious pattern of change up-section. The data thus provide no unambiguous evidence at Meishan for major perturbation of seawater 187Os/188Os in this region of Palaeotethys, at least at the scale of the sampling. This is unlike early Jurassic and end-Cretaceous boundary sections, and mid-Cretaceous OAE intervals, which record substantial shifts in seawater 187Os/188Os that clearly reflect the influence of LIP emplacement. Major changes in elemental abundances occur between Beds 24 and Bed 27, accompanying the documented excursion in d13C. Redox- and biologically-sensitive elements such as Cu, Ni, P, V and Zn show strong fluctuations in abundance throughout Bed 24, even when abundances are normalised using Al2O3 to minimise the effects of carbonate dilution. In the lower part of Bed 27, however, the Al2O3-normalised concentrations of these elements decrease by an order of magnitude, and remain consistently low in the overlying Triassic marls. The relative decreases in Re and Os abundances throughout Bed 27 are even more substantial. Whilst these decreases are partly an artefact of Al-normalisation, the changes are accompanied by large increases in ratios involving lithogenous elements such as REE, Nb, Zr, Th and Ti. The data thus record a dramatic change in the marine depositional

  1. High Temporal Resolution Measurements and Modeling of the Isotopic Composition of Methane in Europe

    NASA Astrophysics Data System (ADS)

    Popa, E.; Röckmann, T.; Eyer, S.; van der Veen, C.; Tuzson, B.; Monteil, G.; Houweling, S.; Harris, E. J.; Brunner, D.; Fischer, H.; Fisher, R. E.; Lowry, D.; Nisbet, E. G.; Emmenegger, L.; Mohn, J.

    2015-12-01

    Isotope measurements can help constraining the atmospheric budget of methane because different sources emit methane with slightly different isotopic composition. In the past, high precision isotope measurements have primarily been carried out by isotope ratio mass spectrometry on flask samples that are usually collected at relatively low temporal resolution. During the EU project INGOS, we have deployed a fully automated gas chromatography - isotope ratio mass spectrometry system (GC-IRMS), together with two laser instruments, during a 4-months campaign in the field at the Cabauw Experimental Site for Atmospheric Research (CESAR). More than 1600 measurements for δ13C and δD were obtained with IRMS during this period. Measurements show clear isotope signals associated with methane elevations both on the diurnal as well as the synoptic scale. In order to assess the added value of such measurements for constraining the CH4 budget, we performed coupled simulations of CH4 and δ13C-CH4 using the chemistry transport model TM5. We specifically assessed the relative impact of uncertainties in i) CH4 emissions, ii) CH4 isotope source signatures and iii) methane transport and chemistry throughout the atmosphere. By randomly perturbing CH4 emissions and δ13C source signatures, we identified areas where simulated variations are dominated by uncertainties in the emission strength and areas where uncertainties in the isotope signatures dominate. At observation sites where the uncertainties in CH4 emissions dominate the other sources of uncertainty, isotope observations should provide useful additional constraints on CH4 emissions. At locations where uncertainties in the isotope signatures dominate, the isotope measurements will be useful to better constrain the source signatures themselves.

  2. Measuring and predicting abundance and dynamics of habitat for piping plovers on a large reservoir

    USGS Publications Warehouse

    Anteau, Michael J.; Wiltermuth, Mark T.; Sherfy, Mark H.; Shaffer, Terry L.

    2014-01-01

    Measuring habitat and understanding habitat dynamics have become increasingly important for wildlife conservation. Using remotely-sensed data, we developed procedures to measure breeding habitat abundance for the federally listed piping plover (Charadrius melodus) at Lake Sakakawea, North Dakota, USA. We also developed a model to predict habitat abundance based on past and projected water levels, vegetation colonization rates, and topography. Previous studies define plover habitat as flat areas (30% bare-substrate obstruction) were 76% correct and omission and commission errors were equal. Due to water level fluctuations, habitat abundance varied markedly among years (1986–2009) ranging from 9 to 5195 ha. The proportion bare substrate declined with the number of years since a contour was inundated until 5 years (β = -0.65, SE = 0.05), then it stabilized near zero, and the decline varied by shoreline segment (5, 50, and 95 percentile were β = -0.19, SE = 0.05, β = -0.63, SE = 0.05, and β = -0.91, SE = 0.05, respectively). Years since inundated predicted habitat abundance well at shoreline segments (R2 = 0.77), but it predicted better for the whole lake (R2 = 0.86). The vastness and dynamics of plover habitat on Lake Sakakawea suggest that this is a key area for conservation of this species. Model-based habitat predictions can benefit resource conservation because they can (1) form the basis for a sampling stratification, (2) help allocate monitoring efforts among areas, and (3) help inform management through simulations or what-if scenarios.

  3. A balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon and nitrogen. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F.

    1981-01-01

    The isotopic compositions of galactic cosmic ray boron, carbon, and nitrogen were measured at energies near 300 MeV amu, using a balloon-borne instrument at an atmospheric depth of approximately 5 g/sq cm. The calibrations of the detectors comprising the instrument are described. The saturation properties of the cesium iodide scintillators used for measurement of particle energy are studied in the context of analyzing the data for mass. The achieved rms mass resolution varies from approximately 0.3 amu at boron to approximately 0.5 amu at nitrogen, consistent with a theoretical analysis of the contributing factors. Corrected for detector interactions and the effects of the residual atmosphere the results are B-10/B=0.33 (+0.17, -0.11), C-13/C=0.06 (+0.13, -0.11), and N-15/N=0.42 (+0.19, -0.17). A model of galactic propagation and solar modulation is described. Assuming a cosmic ray source composition of solar-like isotopic abundances, the model predicts abundances near Earth consistent with the measurements.

  4. Hydrogen Isotope Measurements of Organic Acids and Alcohols by Pyrolysis-GC-MS-TC-IRMS

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.

    2011-01-01

    One possible process responsible for methane generation on Mars is abiotic formation by Fischer-Tropsch-type (FTT) synthesis during serpentinization reactions. Measurement of carbon and hydrogen isotopes of intermediary organic compounds can help constrain the origin of this methane by tracing the geochemical pathway during formation. Of particular interest within the context of this work is the isotopic composition of organic intermediaries produced on the surfaces of mineral catalysts (i.e. magnetite) during hydrothermal experiments, and the ability to make meaningful and reproducible hydrogen isotope measurements. Reported here are results of experiments to characterize the hydrogen isotope composition of low molecular weight organic acids and alcohols. The presence of these organic compounds has been suggested by others as intermeadiary products made during mineral surface catalyzed reactions. This work compliments our previous study characterizing the carbon isotope composition of similar low molecular weight intermediary organic compounds (Socki, et al, American Geophysical Union Fall meeting, Abstr. #V51B-2189, Dec., 2010). Our hydrogen isotope measurements utilize a unique analytical technique combining Pyrolysis-Gas Chromatograph-Mass Spectrometry-High Temperature Conversion-Isotope Ratio Mass Spectrometry (Py-GC-MS-TC-IRMS). Our technique is unique in that it carries a split of the pyrolyzed GC-separated product to a Thermo DSQ-II? quadrupole mass spectrometer as a means of making qualitative and semi-quantitative compositional measurements of separated organic compounds, therefore both chemical and isotopic measurements can be carried out simultaneously on the same sample.

  5. Hf sbnd Nd sbnd Sr isotopes and incompatible element abundances in island arcs: implications for magma origins and crust-mantle evolution

    NASA Astrophysics Data System (ADS)

    White, William M.; Patchett, Jonathan

    1984-02-01

    We present Hf, Nd and Sr isotopic data and abundances of K, Rb, Cs, Ba, Sr, Hf and REE for 32 samples from seven intra-oceanic island arcs. Samples from the Marianas, Izu, Aleutian and New Britain arcs have tightly grouped 176Hf/ 177Hf˜ 0.28320, 143Nd/ 144Nd˜ 0.51303 and 87Sr/ 86Sr˜ 0.7035 close to, but distinct from, mid-ocean ridge basalts (MORB) for 143Nd/ 144Nd and 87Sr/ 86Sr . In contrast, samples from the Sunda, Banda and Lesser Antilles arcs are much more variable towards lower 176Hf/ 177Hf and 143Nd/ 144Nd , and higher 87Sr/ 86Sr . Isotopically, island arcs on the whole are closely similar to ocean islands. Some commonly-occurring features of the trace element geochemistry of island arcs are apparent in our data: alkali and alkaline-earth elements, particularly Cs, have high abundance relative to LREE compared to oceanic basalts; negative Ce anomalies occur in six out of seven arcs. However, Hf does not appear underabundant relative to REE. The isotopic data require a continental component in all island arcs, in addition to probable mantle and oceanic crust contributions, even for the arcs with isotope ratios close to MORB. In the absence of continental crust, we can best explain this component by subducted pelagic sediment in the arc magma source region. The involvement of sediments in all arcs implies that there is an inherent recycling of older continent to island arcs, and potentially to new continent, of at least 1%. Conservative calculations show that the upper subducted slab (basalt + sediment) passes beyond the arc magma genesis zone and enters the deep mantle with a minimum of 500-1000 ppm K, and corresponding amounts of other incompatible elements. If this material is not completely homogenized with the mantle and later becomes part of the source of ocean island magmas, then the ocean island—island arc isotopic similarity is a result of their similar mix of source materials—mantle peridotite with trace element signatures from oceanic crust

  6. The {sup 13}C-pocket structure in AGB models: constraints from zirconium isotope abundances in single mainstream SiC grains

    SciTech Connect

    Liu, Nan; Davis, Andrew M.; Pellin, Michael J.; Gallino, Roberto; Bisterzo, Sara; Savina, Michael R.

    2014-06-20

    We present postprocess asymptotic giant branch (AGB) nucleosynthesis models with different {sup 13}C-pocket internal structures to better explain zirconium isotope measurements in mainstream presolar SiC grains by Nicolussi et al. and Barzyk et al. We show that higher-than-solar {sup 92}Zr/{sup 94}Zr ratios can be predicted by adopting a {sup 13}C-pocket with a flat {sup 13}C profile, instead of the previous decreasing-with-depth {sup 13}C profile. The improved agreement between grain data for zirconium isotopes and AGB models provides additional support for a recent proposal of a flat {sup 13}C profile based on barium isotopes in mainstream SiC grains by Liu et al.

  7. Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Assonov, Sergey S.

    2010-01-01

    Measurements of δ(13C) determined on CO2 with an isotope-ratio mass spectrometer (IRMS) must be corrected for the amount of 17O in the CO2. For data consistency, this must be done using identical methods by different laboratories. This report aims at unifying data treatment for CO2 IRMS by proposing (i) a unified set of numerical values, and (ii) a unified correction algorithm, based on a simple, linear approximation formula. Because the oxygen of natural CO2 is derived mostly from the global water pool, it is recommended that a value of 0.528 be employed for the factor λ, which relates differences in 17O and 18O abundances. With the currently accepted N(13C)/N(12C) of 0.011 180(28) in VPDB (Vienna Peedee belemnite) reevaluation of data yields a value of 0.000 393(1) for the oxygen isotope ratio N(17O)/N(16O) of the evolved CO2. The ratio of these quantities, a ratio of isotope ratios, is essential for the 17O abundance correction: [N(17O)/N(16O)]/[N(13C)/N(12C)] = 0.035 16(8). The equation [δ(13C) ≈ 45δVPDB-CO2 + 2 17R/13R (45δVPDB-CO2 – λ46δVPDB-CO2)] closely approximates δ(13C) values with less than 0.010 ‰ deviation for normal oxygen-bearing materials and no more than 0.026 ‰ in extreme cases. Other materials containing oxygen of non-mass-dependent isotope composition require a more specific data treatment. A similar linear approximation is also suggested for δ(18O). The linear approximations are easy to implement in a data spreadsheet, and also help in generating a simplified uncertainty budget.

  8. Comparative evaluation of quantitative glomerular filtration rate measured by isotopic and nonisotopic methods

    SciTech Connect

    Balachandran, S.; Toguri, A.G.; Petrusick, T.W.; Abbott, L.C.

    1981-04-01

    Good correlation of glomerular filtration rate measured isotopically from plasma disappearance of Tc-99m-DTPA was shown with inulin clearance, creatinine clearance, and graded radionuclide imaging. The isotopic GFR is a simple, urineless technique not requiring continuous infusion that enables one to perform simultaneous renal imaging with one radiotracer.

  9. Comparative evaluation of quantitative glomerular filtration rate measured by isotopic and nonisotopic methods

    SciTech Connect

    Balachandran, S.; Toguri, A.G.; Petrusick, T.W.; Abbott, L.C.

    1981-04-01

    Good correlation of glomerular filtration rate (GFR) measured isotopically from plasma disappearance of Tc-99m-DTPA (Sn) was shown with inulin clearance, creatinine clearance, and graded radionuclide imaging. The isotopic GFR is a simple, urineless technique not requiring continuous infusion that enables one to perform simultaneous renal imaging with one radiotracer.

  10. Abundance, stable isotopic composition, and export fluxes of DOC, POC, and DIC from the Lower Mississippi River during 2006-2008

    NASA Astrophysics Data System (ADS)

    Cai, Yihua; Guo, Laodong; Wang, Xuri; Aiken, George

    2015-11-01

    Sources, abundance, isotopic compositions, and export fluxes of dissolved inorganic carbon (DIC), dissolved and colloidal organic carbon (DOC and COC), and particulate organic carbon (POC), and their response to hydrologic regimes were examined through monthly sampling from the Lower Mississippi River during 2006-2008. DIC was the most abundant carbon species, followed by POC and DOC. Concentration and δ13C of DIC decreased with increasing river discharge, while those of DOC remained fairly stable. COC comprised 61 ± 3% of the bulk DOC with similar δ13C abundances but higher percentages of hydrophobic organic acids than DOC, suggesting its aromatic and diagenetically younger status. POC showed peak concentrations during medium flooding events and at the rising limb of large flooding events. While δ13C-POC increased, δ15N of particulate nitrogen decreased with increasing discharge. Overall, the differences in δ13C between DOC or DIC and POC show an inverse correlation with river discharge. The higher input of soil organic matter and respired CO2 during wet seasons was likely the main driver for the convergence of δ13C between DIC and DOC or POC, whereas enhanced in situ primary production and respiration during dry seasons might be responsible for their isotopic divergence. Carbon export fluxes from the Mississippi River were estimated to be 13.6 Tg C yr-1 for DIC, 1.88 Tg C yr-1 for DOC, and 2.30 Tg C yr-1 for POC during 2006-2008. The discharge-normalized DIC yield decreased during wet seasons, while those of POC and DOC increased and remained constant, respectively, implying variable responses in carbon export to the increasing discharge.

  11. Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Völkening, Joachim; Köppe, Manfred; Heumann, Klaus G.

    1991-07-01

    A precise determination of the isotopic abundances of tungsten with natural isotopic composition is presented. WO-3 ions are generated by negative thermal ionization (NTI) in a double-filament ion source. La2O3 is used as a chemical substance to reduce the electron work function of the rhenium filament material. An ionization efficiency of 1% is obtained for sample loadings of 100 ng. The isotopic abundances are measured with relative standard deviations of 0.2% for the least abundant 180W isotope and 0.02-0.004% for the other tungsten isotopes. These improved isotopic data are used to recalculate the atomic weight of tungsten as 183.8417 ± 0.0001. The new NTI technique is an ideal tool for the application of isotope dilution mass spectrometry to analyse tungsten traces and for the measurement of isotopic shifts of this element in meteorites produced by the decay of 182Hf.

  12. Relative elemental abundance and heating constraints determined for the solar corona from SERTS measurements

    NASA Technical Reports Server (NTRS)

    Falconer, David A.

    1994-01-01

    Intensities of EUV spectral lines were measured as a function of radius off the solar limb by two flights of Goddard's Solar EUV Rocket Telescope and Spectrograph (SERTS) for three quiet sun regions. The density scale height, line-ratio densities, line-ratio temperatures, and emission measures were determined. The line-ratio temperature determined from the ionization balances of Arnaud and Rothenflug (1985) were more self-consistent than the line-ratio temperatures obtained from the values of Arnaud and Raymond (1992). Limits on the filling factor were determined from the emission measure and the line-ratio densities for all three regions. The relative abundances of silicon, aluminum, and chromium to iron were determined. Results did agree with standard coronal relative elemental abundances for one observation, but did not agree for another. Aluminum was overabundant while silicon was underabundant. Heating was required above 1.15 solar radii for all three regions studied. For two regions, local nonconductive heating is needed for any filling factor, and in all three regions for filling factor of 0.1.

  13. Stable Isotope Measurements of Carbon Dioxide, Methane, and Hydrogen Sulfide Gas Using Frequency Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nowak-Lovato, K.

    2014-12-01

    Seepage from enhanced oil recovery, carbon storage, and natural gas sites can emit trace gases such as carbon dioxide, methane, and hydrogen sulfide. Trace gas emission at these locations demonstrate unique light stable isotope signatures that provide information to enable source identification of the material. Light stable isotope detection through surface monitoring, offers the ability to distinguish between trace gases emitted from sources such as, biological (fertilizers and wastes), mineral (coal or seams), or liquid organic systems (oil and gas reservoirs). To make light stable isotope measurements, we employ the ultra-sensitive technique, frequency modulation spectroscopy (FMS). FMS is an absorption technique with sensitivity enhancements approximately 100-1000x more than standard absorption spectroscopy with the advantage of providing stable isotope signature information. We have developed an integrated in situ (point source) system that measures carbon dioxide, methane and hydrogen sulfide with isotopic resolution and enhanced sensitivity. The in situ instrument involves the continuous collection of air and records the stable isotope ratio for the gas being detected. We have included in-line flask collection points to obtain gas samples for validation of isotopic concentrations using our in-house isotope ratio mass spectroscopy (IRMS). We present calibration curves for each species addressed above to demonstrate the sensitivity and accuracy of the system. We also show field deployment data demonstrating the capabilities of the system in making live dynamic measurements from an active source.

  14. Human baby hair amino acid natural abundance 15N-isotope values are not related to the 15N-isotope values of amino acids in mother's breast milk protein.

    PubMed

    Romek, Katarzyna M; Julien, Maxime; Frasquet-Darrieux, Marine; Tea, Illa; Antheaume, Ingrid; Hankard, Régis; Robins, Richard J

    2013-12-01

    Since exclusively breast-suckled infants obtain their nutrient only from their mother's milk, it might be anticipated that a correlation will exist between the (15)N/(14)N isotope ratios of amino acids of protein of young infants and those supplied by their mother. The work presented here aimed to determine whether amino nitrogen transfer from human milk to infant hair protein synthesized within the first month of life conserves the maternal isotopic signature or whether post-ingestion fractionation dominates the nitrogen isotope spectrum. The study was conducted at 1 month post-birth on 100 mother-infant pairs. Isotope ratios (15)N/(14)N and (13)C/(12)C were measured using isotope ratio measurement by Mass Spectrometry (irm-MS) for whole maternal milk, and infant hair and (15)N/(14)N ratios were also measured by GC-irm-MS for the N-pivaloyl-O-isopropyl esters of amino acids obtained from the hydrolysis of milk and hair proteins. The δ(15)N and δ(13)C (‰) were found to be significantly higher in infant hair than in breast milk (δ(15)N, P < 0.001; δ(13)C, P < 0.001). Furthermore, the δ(15)N (‰) of individual amino acids in infant hair was also significantly higher than that in maternal milk (P < 0.001). By calculation, the observed shift in isotope ratio was shown not to be accounted for by the amino acid composition of hair and milk proteins, indicating that it is not simply due to differences in the composition in the proteins present. Rather, it would appear that each pool-mother and infant-turns over independently, and that fractionation in infant N-metabolism even in the first month of life dominates over the nutrient N-content.

  15. Voyager measurements of the isotopic composition of cosmic-ray aluminum and implications for the propagation of cosmic rays

    NASA Technical Reports Server (NTRS)

    Lukasiak, A.; Mcdonald, F. B.; Webber, W. R.

    1994-01-01

    We report a new measurement of the cosmic-ray isotopic composition of aluminum in the low-energy range form 75 to 206 MeV per nucleon.This measurement was made using the high-energy telescope of the CRS experiment on the Voyager 1 and 2 spacecraft during the time period from 1977 to 1993 with an average solar modulation level about 497 MV, roughly the same as at Earth near sunspot minimum. We obtain approximately 430 Al events of which approximately 35 are Al-26 and 395 are Al-27. The Al isotopes were separated with an average mass resolution sigma of 0.35 amu. Our interpretation of the isotopic composition of cosmic-ray aluminum is based on a standard Leaky-Box model for the interstellar propagation of cosmic-ray nuclei using the latest cross sections of the New Mexico-Saclay collaboration as well as a disk-halo diffusion model. From our observed ratio Al-26/Al-27 of 8.3 +/- 2.4 % we deduce an average interstellar density of about 0.52 (+0.26, -0.2) atoms per cu cm. This density is larger than the value of 0.28 (+0.14, -0.11) atoms per cu cm we found from an analysis of the observed abundance of the longer lived Be-10 made using data from the Voyager detectors over almost the same time interval and using essentially the same propagation program.

  16. New method for the measurement of osmium isotopes applied to a New Zealand Cretaceous/Tertiary boundary shale

    USGS Publications Warehouse

    Lichte, F.E.; Wilson, S.M.; Brooks, R.R.; Reeves, R.D.; Holzbecher, J.; Ryan, D.E.

    1986-01-01

    The determination of osmium content and isotopic abundances in geological materials has received increasing attention in recent years following the proposal of Alvarez et al.1 that mass extinctions at the end of the Cretaceous period were caused by the impact of a large (???10km) meteorite which left anomalously high iridium levels as a geochemical signature in the boundary shales. Here we report a new and simple method for measuring osmium in geological materials, involving fusion of the sample with sodium peroxide, distillation of the osmium as the tetroxide using perchloric acid, extraction into chloroform, and absorption of the chloroform extract onto graphite powder before instrumental neutron activation analysis. In a variant of this technique, the chloroform extract is back-extracted into an aqueous phase and the osmium isotopes are determined by plasma-source mass spectrometry (ICPMS). We have used this method on the Woodside Creek (New Zealand) Cretaceous/Tertiary boundary clay and have obtained the first osmium content (6g ng g-1) for this material. The 187Os/186Os ratio is 1.12??0.16, showing a typical non-crustal signature. This combined distillation-extraction- ICPMS method will prove to be useful for measuring osmium isotopes in other geological materials. ?? 1986 Nature Publishing Group.

  17. Carbon-13 isotopic abundance and concentration of atmospheric methane for background air in the Southern and Northern Hemispheres from 1978 to 1989

    SciTech Connect

    Stevens, C.M.; Sepanski; Morris, L.J.

    1995-03-01

    Atmospheric methane (CH{sub 4}) may become an increasingly important contributor to global warming in future years. Its atmospheric concentration has risen, doubling over the past several hundred years, and additional methane is thought to have a much greater effect on climate, on a per molecule basis, than additional C0{sub 2} at present day concentrations (Shine et al. 1990). The causes of the increase of atmospheric CH{sub 4} have been difficult to ascertain because of a lack of quantitative knowledge of the fluxes (i.e., net emissions) from the numerous anthropogenic and natural sources. The goal of CH{sub 4} isotopic studies is to provide a constraint (and so reduce the uncertainties) in estimating the relative fluxes from the various isotopically distinct sources, whose combined fluxes must result in the measured atmospheric isotopic composition, after the fractionating effect of the atmospheric removal process is considered. In addition, knowledge of the spatial and temporal changes in the isotopic composition of atmospheric CH{sub 4}, along with estimates of the fluxes from some of the major sources, makes it possible to calculate growth rates for sources whose temporal emissions trends would be difficult to measure directly.

  18. On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions

    NASA Technical Reports Server (NTRS)

    Simpson, Janet P.; Rubin, Robert H.; Colgan, Sean W. J.; Erickson, Edwin F.; Haas, Michael R.

    2004-01-01

    Although abundance gradients in the Milky Way Galaxy certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in G333.6-0.2 with the Kuiper Airborne Observatory and reobserved the central position with the Infrared Space Observatory's Long Wavelength Spectrometer in far-infrared lines of S++, N++, N+, and O++. We also added the N+ lines at 122 and 205 microns to the suite of lines measured in W43 by Simpson et al.. The measured electron densities range from approx. 40 to over 4000 per cu cm in a single HII region, indicating that abundance analyses must consider density variations, since the critical densities of the observed lines range from 40 to 9000 per cu cm. We propose a method to handle density variations and make new estimates of the S/H and N/H abundance ratios. We find that our sulfur abundance estimates for G333.6-0.2 and W43 agree with the S/H abundance ratios expected for the gradient previously reported by Simpson et al., with the S/H values revised to be smaller owing to changes in collisional excitation cross sections. The estimated N/H, S/H, and N/S ratios are the most reliable because of their small corrections for unseen ionization states (< or approx. 10%). The estimated N/S ratios for the two sources are smaller than what would be calculated from the N/H and S/H ratios in our previous paper. If all low excitation H II regions had similar changes to their N/S ratios as a result of adding measurements of N+ to previous measurements of N++, there would be no or only a very small gradient in N/S. This is interesting because nitrogen is considered to be a secondary element and sulfur is a primary element in galactic chemical evolution calculations. We compute models of the two H II regions to estimate corrections for the other

  19. High-precision iron isotope measurements of terrestrial and lunar materials

    NASA Astrophysics Data System (ADS)

    Beard, Brian L.; Johnson, Clark M.

    1999-06-01

    We present the analytical methods that have been developed for the first high-precision Fe isotope analyses that clearly identify naturally-occurring, mass-dependent isotope fractionation. A double-spike approach is used, which allows rigorous correction of instrumental mass fractionation. Based on 21 analyses of an ultra pure Fe standard, the external precision (1-SD) for measuring the isotopic composition of Fe is ±0.14 ‰/mass; for demonstrated reproducibility on samples, this precision exceeds by at least an order of magnitude that of previous attempts to empirically control instrumentally-produced mass fractionation (Dixon et al., 1993). Using the double-spike method, 15 terrestrial igneous rocks that range in composition from peridotite to rhyolite, 5 high-Ti lunar basalts, 5 Fe-Mn nodules, and a banded iron formation have been analyzed for their iron isotopic composition. The terrestrial and lunar igneous rocks have the same isotopic compositions as the ultra pure Fe standard, providing a reference Fe isotope composition for the Earth and Moon. In contrast, Fe-Mn nodules and a sample of a banded iron formation have iron isotope compositions that vary over a relatively wide range, from δ 56Fe = +0.9 to -1.2 ‰; this range is 15 times the analytical errors of our technique. These natural isotopic fractionations are interpreted to reflect biological ("vital") effects, and illustrate the great potential Fe isotope studies have for studying modern and ancient biological processes.

  20. Abundance Anomaly of the 13C Isotopic Species of c-C3H2 in the Low-mass Star Formation Region L1527

    NASA Astrophysics Data System (ADS)

    Yoshida, Kento; Sakai, Nami; Tokudome, Tomoya; López-Sepulcre, Ana; Watanabe, Yoshimasa; Takano, Shuro; Lefloch, Bertrand; Ceccarelli, Cecilia; Bachiller, Rafael; Caux, Emmanuel; Vastel, Charlotte; Yamamoto, Satoshi

    2015-07-01

    The rotational spectral lines of c-C3H2 and two kinds of the 13C isotopic species, c-{}13{{CCCH}}2 ({C}2v symmetry) and c-{{CC}}13{{CH}}2 (Cs symmetry), have been observed in the 1–3 mm band toward the low-mass star-forming region L1527. We have detected 7, 3, and 6 lines of c-C3H2, c-{}13{{CCCH}}2, and c-{{CC}}13{{CH}}2, respectively, with the Nobeyama 45 m telescope and 34, 6, and 13 lines, respectively, with the IRAM 30 m telescope, where seven, two, and two transitions, respectively, are observed with both telescopes. With these data, we have evaluated the column densities of the normal and 13C isotopic species. The [c-C3H2]/[c-{}13{{CCCH}}2] ratio is determined to be 310 ± 80, while the [c-C3H2]/[c-{{CC}}13{{CH}}2] ratio is determined to be 61 ± 11. The [c-C3H2]/[c-{}13{{CCCH}}2] and [c-C3H2]/[c-{{CC}}13{{CH}}2] ratios expected from the elemental 12C/13C ratio are 60–70 and 30–35, respectively, where the latter takes into account the statistical factor of 2 for the two equivalent carbon atoms in c-C3H2. Hence, this observation further confirms the dilution of the 13C species in carbon-chain molecules and their related molecules, which are thought to originate from the dilution of 13C+ in the gas-phase C+ due to the isotope exchange reaction: {}13{{{C}}}++{CO}\\to {}13{CO}+{{{C}}}+. Moreover, the abundances of the two 13C isotopic species are different from each other. The ratio of c-{}13{{CCCH}}2 species relative to c-{{CC}}13{{CH}}2 is determined to be 0.20 ± 0.05. If 13C were randomly substituted for the three carbon atoms, the [c-{}13{{CCCH}}2]/[c-{{CC}}13{{CH}}2] ratio would be 0.5. Hence, the observed ratio indicates that c-{{CC}}13{{CH}}2 exists more favorably. Possible origins of the different abundances are discussed. Based on observations carried out with the IRAM 30 m Telescope and the NRO 45 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). NRO is a branch of the National Astronomical Observatory of Japan

  1. Carbon isotope and abundance systematics of Icelandic geothermal gases, fluids and subglacial basalts with implications for mantle plume-related CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Barry, P. H.; Hilton, D. R.; Füri, E.; Halldórsson, S. A.; Grönvold, K.

    2014-06-01

    We report new carbon dioxide (CO2) abundance and isotope data for 71 geothermal gases and fluids from both high-temperature (HT > 150 °C at 1 km depth) and low-temperature (LT < 150 °C at 1 km depth) geothermal systems located within neovolcanic zones and older segments of the Icelandic crust, respectively. These data are supplemented by CO2 data obtained by stepped heating of 47 subglacial basaltic glasses collected from the neovolcanic zones. The sample suite has been characterized previously for He-Ne (geothermal) and He-Ne-Ar (basalt) systematics (Füri et al., 2010), allowing elemental ratios to be calculated for individual samples. Geothermal fluids are characterized by a wide range in carbon isotope ratios (δ13C), from -18.8‰ to +4.6‰ (vs. VPDB), and CO2/3He values that span eight orders of magnitude, from 1 × 104 to 2 × 1012. Extreme geothermal values suggest that original source compositions have been extensively modified by hydrothermal processes such as degassing and/or calcite precipitation. Basaltic glasses are also characterized by a wide range in δ13C values, from -27.2‰ to -3.6‰, whereas CO2/3He values span a narrower range, from 1 × 108 to 1 × 1012. The combination of both low δ13C values and low CO2 contents in basalts indicates that magmas are extensively and variably degassed. Using an equilibrium degassing model, we estimate that pre-eruptive basaltic melts beneath Iceland contain ∼531 ± 64 ppm CO2 with δ13C values of -2.5 ± 1.1‰, in good agreement with estimates from olivine-hosted melt inclusions (Metrich et al., 1991) and depleted MORB mantle (DMM) CO2 source estimates (Marty, 2012). In addition, pre-eruptive CO2 compositions are estimated for individual segments of the Icelandic axial rift zones, and show a marked decrease from north to south (Northern Rift Zone = 550 ± 66 ppm; Eastern Rift Zone = 371 ± 45 ppm; Western Rift Zone = 206 ± 24 ppm). Notably, these results are model dependent, and selection of a lower

  2. Measurement error associated with surveys of fish abundance in Lake Michigan

    USGS Publications Warehouse

    Krause, Ann E.; Hayes, Daniel B.; Bence, James R.; Madenjian, Charles P.; Stedman, Ralph M.

    2002-01-01

    In fisheries, imprecise measurements in catch data from surveys adds uncertainty to the results of fishery stock assessments. The USGS Great Lakes Science Center (GLSC) began to survey the fall fish community of Lake Michigan in 1962 with bottom trawls. The measurement error was evaluated at the level of individual tows for nine fish species collected in this survey by applying a measurement-error regression model to replicated trawl data. It was found that the estimates of measurement-error variance ranged from 0.37 (deepwater sculpin, Myoxocephalus thompsoni) to 1.23 (alewife, Alosa pseudoharengus) on a logarithmic scale corresponding to a coefficient of variation = 66% to 156%. The estimates appeared to increase with the range of temperature occupied by the fish species. This association may be a result of the variability in the fall thermal structure of the lake. The estimates may also be influenced by other factors, such as pelagic behavior and schooling. Measurement error might be reduced by surveying the fish community during other seasons and/or by using additional technologies, such as acoustics. Measurement-error estimates should be considered when interpreting results of assessments that use abundance information from USGS-GLSC surveys of Lake Michigan and could be used if the survey design was altered. This study is the first to report estimates of measurement-error variance associated with this survey.

  3. Comparison of multifrequency acoustic and in situ measurements of zooplankton abundances in Knight Inlet, British Columbia.

    PubMed

    Trevorrow, Mark V; Mackas, David L; Benfield, Mark C

    2005-06-01

    An investigation of midwater zooplankton aggregations in a coastal fjord was conducted in November 2002. This study focused on quantitative comparisons between a calibrated, three-frequency (38, 120, and 200 kHz) vessel-based echo-sounder, a multinet towed zooplankton sampler (BIONESS), and a high-resolution underwater camera (ZOOVIS). Daytime layers of euphausiids and amphipods near 70-90-m depth were observed in lower parts of the inlet, especially concentrated by tidal flows around a sill. Quantitative backscatter measurements of euphausiids and amphipods, combined with in situ size and abundance estimates, and using an assumed tilt-angle distribution, were in agreement with averaged fluid-cylinder scattering models produced by Stanton and Chu [ICES J. Mar. Sci. 57, 793-807, (2000)]. Acoustic measurements of physonect siphonophores in the upper inlet were found to have a strong 38-kHz scattering strength, in agreement with a damped bubble scattering model using a diameter of 0.4 mm. In relatively dense euphausiid layers, ZOOVIS abundance estimates were found to be a factor of 2 to 4 higher than the acoustic estimates, potentially due to deviations from assumed euphausiid orientation. Nocturnal near-surface euphausiid scattering exhibited a strong (15 dB) and rapid (seconds) sensitivity to vessel lights, interpreted as due to changing animal orientation. PMID:16018461

  4. Oxygen Isotope Measurements of a Rare Murchison Type A CAI and Its Rim

    NASA Technical Reports Server (NTRS)

    Matzel, J. E. P.; Simon, J. I.; Hutcheon, I. D.; Jacobsen, B.; Simon, S. B.; Grossman, L.

    2013-01-01

    Ca-, Al-rich inclusions (CAIs) from CV chondrites commonly show oxygen isotope heterogeneity among different mineral phases within individual inclusions reflecting the complex history of CAIs in both the solar nebula and/or parent bodies. The degree of isotopic exchange is typically mineral-specific, yielding O-16-rich spinel, hibonite and pyroxene and O-16-depleted melilite and anorthite. Recent work demonstrated large and systematic variations in oxygen isotope composition within the margin and Wark-Lovering rim of an Allende Type A CAI. These variations suggest that some CV CAIs formed from several oxygen reservoirs and may reflect transport between distinct regions of the solar nebula or varying gas composition near the proto-Sun. Oxygen isotope compositions of CAIs from other, less-altered chondrites show less intra-CAI variability and 16O-rich compositions. The record of intra-CAI oxygen isotope variability in CM chondrites, which commonly show evidence for low-temperature aqueous alteration, is less clear, in part because the most common CAIs found in CM chondrites are mineralogically simple (hibonite +/- spinel or spinel +/- pyroxene) and are composed of minerals less susceptible to O-isotopic exchange. No measurements of the oxygen isotope compositions of rims on CAIs in CM chondrites have been reported. Here, we present oxygen isotope data from a rare, Type A CAI from the Murchison meteorite, MUM-1. The data were collected from melilite, hibonite, perovskite and spinel in a traverse into the interior of the CAI and from pyroxene, melilite, anorthite, and spinel in the Wark-Lovering rim. Our objectives were to (1) document any evidence for intra-CAI oxygen isotope variability; (2) determine the isotopic composition of the rim minerals and compare their composition(s) to the CAI interior; and (3) compare the MUM-1 data to oxygen isotope zoning profiles measured from CAIs in other chondrites.

  5. {beta}-delayed neutron emission measurements around the third r-process abundance peak

    SciTech Connect

    Caballero-Folch, R.; Cortes, G.; Calvino, F.; Gomez-Hornillos, M. B.; Riego, A.; Domingo-Pardo, C.; Tain, J. L.; Agramunt, J.; Rubio, B.; Algora, A.; Ameil, F.; Farinon, F.; Heil, M.; Knoebel, R.; Kojouharov, I.; Kurcewicz, J.; Kurz, N.; Litvinov, Y.; Mukha, I.; Nociforo, C.; and others

    2013-06-10

    This contribution summarizes an experiment performed at GSI (Germany) in the neutron-rich region beyond N=126. The aim of this measurement is to provide the nuclear physics input of relevance for r-process model calculations, aiming at a better understanding of the third r-process abundance peak. Many exotic nuclei were measured around {sup 211}Hg and {sup 215}Tl. Final ion identification diagrams are given in this contribution. For most of them, we expect to derive halflives and and {beta}-delayed neutron emission probabilities. The detectors used in this experiment were the Silicon IMplantation and Beta Absorber (SIMBA) detector, based on an array of highly segmented silicon detectors, and the BEta deLayEd Neutron (BELEN) detector, which consisted of 30 3He counters embedded in a polyethylene matrix.

  6. Measuring terrestrial subsidies to aquatic food webs using stable isotopes of hydrogen.

    PubMed

    Doucett, Richard R; Marks, Jane C; Blinn, Dean W; Caron, Melanie; Hungate, Bruce A

    2007-06-01

    Understanding river food webs requires distinguishing energy derived from primary production in the river itself (autochthonous) from that produced externally (allochthonous), yet there are no universally applicable and reliable techniques for doing so. We compared the natural abundance stable isotope ratios of hydrogen (deltaD) of allochthonous and autochthonous energy sources in four different aquatic ecosystems. We found that autochthonous organic matter is uniformly far more depleted in deuterium (lower deltaD values) than allochthonous: an average difference of approximately 100% per hundred. We also found that organisms at higher trophic levels, including both aquatic invertebrates and fish, have deltaD values intermediate between aquatic algae and terrestrial plants. The consistent differences between leaves and algae in deltaD among these four watersheds, along with the intermediate values in higher trophic levels, indicate that natural abundance hydrogen isotope signatures are a powerful tool for partitioning energy flow in aquatic ecosystems. PMID:17601150

  7. Evaluation of affinity-tagged protein expression strategies using local and global isotope ratio measurements.

    PubMed

    Hervey, W Judson; Khalsa-Moyers, Gurusahai; Lankford, Patricia K; Owens, Elizabeth T; McKeown, Catherine K; Lu, Tse-Yuan; Foote, Linda J; Asano, Keiji G; Morrell-Falvey, Jennifer L; McDonald, W Hayes; Pelletier, Dale A; Hurst, Gregory B

    2009-07-01

    Elucidation of protein-protein interactions can provide new knowledge on protein function. Enrichments of affinity-tagged (or "bait") proteins with interaction partners generally include background, nonspecific protein artifacts. Furthermore, in vivo bait expression may introduce additional artifacts arising from altered physiology or metabolism. In this study, we compared these effects for chromosome and plasmid encoding strategies for bait proteins in two microbes: Escherichia coli and Rhodopseudomonas palustris. Differential metabolic labeling of strains expressing bait protein relative to the wild-type strain in each species allowed comparison by liquid chromatography tandem mass spectrometry (LC-MS-MS). At the local level of the protein complex, authentic interacting proteins of RNA polymerase (RNAP) were successfully discerned from artifactual proteins by the isotopic differentiation of interactions as random or targeted (I-DIRT, Tackett, A. J.; et al. J. Proteome Res. 2005, 4, 1752-1756). To investigate global effects of bait protein production, we compared proteomes from strains harboring a plasmid encoding an affinity-tagged subunit (RpoA) of RNAP with the corresponding wild-type strains. The RpoA abundance ratios of 0.8 for R. palustris and 1.7 for E. coli in plasmid strains versus wild-type indicated only slightly altered expression. While most other proteins also showed no appreciable difference in abundance, several that did show altered levels were involved in amino acid metabolism. Measurements at both local and global levels proved useful for evaluating in vitro and in vivo artifacts of plasmid-encoding strategies for bait protein expression.

  8. Predicted CALET measurements of ultra-heavy cosmic ray relative abundances

    NASA Astrophysics Data System (ADS)

    Rauch, B. F.

    2014-05-01

    The CALorimetric Electron Telescope (CALET) is an imaging calorimeter under construction for launch to the ISS in 2014 for a planned 5 year mission. CALET consists of a charge detection module (CHD) with two segmented planes of 1 cm thick plastic scintillator, an imaging calorimeter (IMC) with a total of 3 radiation lengths (X∘) of tungsten plates read out with 8 planes of interleaved scintillating fibers, and a total absorption calorimeter (TASC) with 27 X∘ of lead tungstate (PWO) logs. The primary objectives of the instrument are to measure electron energy spectra from 1 GeV to 20 TeV, to detect gamma-rays above 10 GeV, and to measure the energy spectra of nuclei from protons through iron up to 1,000 TeV. In this paper we describe how the geomagnetic field at the 51.6° inclination orbit of the ISS can be used to allow CALET to measure the rare ultra-heavy (UH) cosmic ray (CR) abundances, which provide important clues for the CR source and acceleration mechanism. The CHD scintillator response is relatively insensitive to energy above minimum ionization, and the angle-dependent rigidity as a function of geomagnetic latitude can be exploited to discriminate particles above this energy threshold. Such events require corrections for trajectory in instrument that can be made with only the top 4 layers of the IMC, which allows for considerably greater geometric acceptance than for events that require passage through the TASC for energy determination. Using this approach CALET will be able to measure UH CR relative abundances over its expected mission with superior statistics to previous space instruments.

  9. Ion Microprobe Measurements of Carbon Isotopes in Martian Phosphates: Insights into the Martian Mantle

    NASA Astrophysics Data System (ADS)

    Goreva, J. S.; Leshin, L. A.; Guan, Y.

    2003-03-01

    In-situ measurements of C in the phosphates from meteorites Los Angeles, Zagami, QUE94201 and ALH84001 predict isotopically light martian magmatic C, heavier than previous estimates yet significantly lighter than the terrestrial value.

  10. Chemical and isotopic measurements of micrometeoroids by secondary ion mass spectrometry (A0187-2)

    NASA Technical Reports Server (NTRS)

    Foote, J. H.; Swan, P. D.; Walker, R. M.; Zinner, E. K.; Bahr, D.; Fechtig, H.; Jessberger, E.; Igenbergs, E.; Kreitmayr, U.; Kuczera, H.

    1984-01-01

    The objective of this experiment is to measure the chemical and isotopic composition of interplanetary dust particles of mass greater than 10 to the minus 10 power G for most of thermator elements expected to be present.

  11. Characterizing the Spatial and Temporal Variations in Organic Carbon Abundance and Stable Isotope Ratios in Lake Sediments Containing Evidence of Prehistoric Agriculture

    NASA Astrophysics Data System (ADS)

    Taylor, Z. P.; Finkelstein, D. B.; Horn, S. P.

    2009-12-01

    Intra-basin spatial variability in lake sediments has the potential to limit the utility of interpretations based on the analysis of a single sediment core. We analyzed a network of five sediment cores to assess geochemical and isotopic spatial variability across a lake in southern Costa Rica. Laguna Zoncho (8.813°N, 82.963°W) provides an excellent opportunity to detect spatial variability because it is a small lake (0.75 ha) with a known history of prehistoric maize agriculture in its watershed. During the agricultural period (1770-570 cal BP) at Zoncho, stable carbon isotope values in the five cores average -23 ‰ V-PDB; these values increase to -27 ‰ V-PDB during the subsequent period of forest recovery. In prior work at the lake, this forest recovery was assumed to have been initiated by the Spanish Conquest about AD 1500, but our new findings suggest it may have occurred earlier and have been driven by a different set of circumstances. We attribute the more positive values during the agricultural period to a greater abundance of C4 vegetation in the watershed as the result of agricultural activity that removed native C3 forest vegetation and created fields and disturbed environments that favor C4 plants. Organic carbon contents during the agricultural period average 5 % and increase to an average of 16 % post-Conquest. Molar C/N ratios range from 13 during the agricultural period to 16 after the cessation of agriculture in the watershed. The cores may indicate a non-simultaneous end to agriculture in the watershed. Stable carbon isotope values and organic carbon contents in three of the four cores collected closer to shore contain evidence of an abrupt end of agriculture around 1000 cal. BP. In these cores, stable carbon isotope values indicate a dramatic shift from C4 to C3 inputs and a rapid increase in organic contents. The fourth core shows this shift around 700 cal. BP. The core recovered from the center of the lake records a gradual end to

  12. HORMONE MEASUREMENT GUIDELINES: Tracing lipid metabolism: the value of stable isotopes.

    PubMed

    Umpleby, A Margot

    2015-09-01

    Labelling molecules with stable isotopes to create tracers has become a gold-standard method to study the metabolism of lipids and lipoproteins in humans. There are a range of techniques which use stable isotopes to measure fatty acid flux and oxidation, hepatic fatty synthesis, cholesterol absorption and synthesis and lipoprotein metabolism in humans. Stable isotope tracers are safe to use, enabling repeated studies to be undertaken and allowing studies to be undertaken in children and pregnant women. This review provides details of the most appropriate tracers to use, the techniques which have been developed and validated for measuring different aspects of lipid metabolism and some of the limitations of the methodology.

  13. Mass measurements on radioactive isotopes with a Penning trap mass spectrometer

    SciTech Connect

    Bollen, G.; Ames, F.; Schark, E.; Audi, G.; Lunney, D.; Saint Simon, M. de; Beck, D.; Herfurth, F.; Kluge, H.-J.; Kohl, A.; Schwarz, S.; Moore, R. B.; Szerypo, J.

    1999-01-15

    Penning trap mass measurements on short-lived isotopes are performed with the ISOLTRAP mass spectrometer at the radioactive beam facility ISOLDE/CERN. In the last years the applicability of the spectrometer has been considerably extended by the installation of an RFQ trap ion beam buncher and a new cooler Penning trap, which is operated as an isobar separator. These improvements allowed for the first time measurements on isotopes of rare earth elements and on isotopes with Z=80-85. In all cases an accuracy of {delta}m/m{approx_equal}1{center_dot}10{sup -7} was achieved.

  14. Carbon kinetic isotope effects at natural abundances during iron-catalyzed photolytic cleavage of Csbnd C bonds in aqueous phase α,ω-dicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Irei, Satoshi

    2016-09-01

    Carbon kinetic isotope effects (KIEs) at natural abundances during photolysis of Fe3+-oxalato, malonato, and succinato complexes in aqueous solution were studied to identify the Csbnd C bond cleaving mechanism of Fe3+-oxalato complexes under sunlight irradiation. Observed overall KIEs were 5.9‰, 11.5‰, and 8.4‰, respectively. This variation is inconsistent with secondary carbon KIEs for the Fesbnd O bond cleavage, but consistent with primary carbon KIEs for sequential cleavage of Fesbnd O and Csbnd C bonds. Position-specific probability of 13C content estimated KIEs of 5.9‰, 17.2‰, and 17‰ for 12Csbnd 13C bond cleavage, respectively, indicating the different KIEs for carboxyl-carboxyl and methyl-carboxyl cleavage.

  15. Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada - An alkaline, meromictic lake

    NASA Technical Reports Server (NTRS)

    Oremland, R. S.; Des Marais, D. J.

    1983-01-01

    The study of the distribution and isotopic composition of low molecular weight hydrocarbon gases at the Big Soda Lake, Nevada, has shown that while neither ethylene nor propylene were found in the lake, ethane, propane, isobutane and n-butane concentrations all increased with water column depth. It is concluded that methane has a biogenic origin in both the sediments and the anoxic water column, and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in delta C-13/CH4/ and CH4/(C2H6 + C3H8) with depth in the water column and sedimeents are probably due to bacterial processes, which may include anaerobic methane oxidation and different rates of methanogenesis, and C2-to-C4 alkane production by microorganisms.

  16. High Precision Ti stable Isotope Measurement of Terrestrial Rocks

    NASA Astrophysics Data System (ADS)

    Millet, M. A.; Dauphas, N.; Williams, H. M.; Burton, K. W.; Nowell, G. M.

    2014-12-01

    Advances in multi-collection plasma source mass spectrometry have allowed the determination of stable isotope composition of transition metals to address questions relevant to both high and low temperature geochemistry. However, titanium has received only very limited attention. Here we present a new technique allowing the determination of the stable isotope composition of titanium in geological samples (d49Ti or deviation of the 49Ti/47Ti ratio from the OL-Ti in-house standard of reference) using double-spike methodology and high-resolution MC-ICP-MS. We have carried out a range analytical tests for a wide spectrum of samples matrices to demonstrate a external reproducibility of ±0.02‰ on the d49Ti while using as little as 150ng of natural Ti for a single analysis. We have analysed a comprehensive selection of mantle-derived samples covering a range of geodynamic contexts (MORB, IAB, OIB, adakites, eclogites, serpentines) and geographical distribution (MORB: Mid-Atlantic Ridge, Southwest Indian Ridge and Eastern Pacific Ridge; IAB: New Britain reference suite and Marianas Arc). The samples show a very limited range from -0.06‰ to +0.04‰ with a main mode at +0.004‰ relative to the OL-Ti standard. Average values for MORB, IAB and eclogites are similar within uncertainty and thus argue for limited mobility of Ti during subduction zone processes and homogeneity of the Ti stable isotope composition of the upper mantle. However, preliminary data for more evolved igneous rocks suggest that they display heavier Ti stable isotope compositions, which may reflect the removal of isotopically light Ti as a function of Fe-Ti oxide crystallisation. This is in good agreement with Ti being present in 5-fold and 6-fold coordination in basaltic melts and preferential uptake of 6-folded Ti by Ti-bearing oxides [1]. This dataset will be complemented by analysis of abyssal peridotites to confirm the homogeneity of the mantle as well as data for a range of ferromanganese crusts

  17. Precise determination of the absolute isotopic abundance ratio and the atomic weight of chlorine in three international reference materials by the positive thermal ionization mass spectrometer-Cs2Cl+-graphite method.

    PubMed

    Wei, Hai-Zhen; Jiang, Shao-Yong; Xiao, Ying-Kai; Wang, Jun; Lu, Hai; Wu, Bin; Wu, He-Pin; Li, Qing; Luo, Chong-Guang

    2012-12-01

    Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise

  18. Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

    USGS Publications Warehouse

    Wanless, V.D.; Perfit, M.R.; Ridley, W.I.; Wallace, P.J.; Grimes, Craig B.; Klein, E.M.

    2011-01-01

    Most geochemical variability in MOR basalts is consistent with low- to moderate-pressure fractional crystallization of various mantle-derived parental melts. However, our geochemical data from MOR high-silica glasses, including new volatile and oxygen isotope data, suggest that assimilation of altered crustal material plays a significant role in the petrogenesis of dacites and may be important in the formation of basaltic lavas at MOR in general. MOR high-silica andesites and dacites from diverse areas show remarkably similar major element trends, incompatible trace element enrichments, and isotopic signatures suggesting similar processes control their chemistry. In particular, very high Cl and elevated H2O concentrations and relatively light oxygen isotope ratios (~ 5.8‰ vs. expected values of ~ 6.8‰) in fresh dacite glasses can be explained by contamination of magmas from a component of ocean crust altered by hydrothermal fluids. Crystallization of silicate phases and Fe-oxides causes an increase in δ18O in residual magma, but assimilation of material initially altered at high temperatures results in lower δ18O values. The observed geochemical signatures can be explained by extreme fractional crystallization of a MOR basalt parent combined with partial melting and assimilation (AFC) of amphibole-bearing altered oceanic crust. The MOR dacitic lavas do not appear to be simply the extrusive equivalent of oceanic plagiogranites. The combination of partial melting and assimilation produces a distinct geochemical signature that includes higher incompatible trace element abundances and distinct trace element ratios relative to those observed in plagiogranites.

  19. History of the paired lunar meteorites MAC88104 and MAC88105 derived from noble gas isotopes, radionuclides, and some chemical abundances

    SciTech Connect

    Eugster, O.; Burger, M.; Kraehenbuehl, U.; Michel, T. ); Beer, J. ); Finkel, R.C. ); Hofmann, H.J.; Synal, H.A.; Woelfli, W. )

    1991-11-01

    Noble gas isotopes, radionuclides, and chemical abundances were studied in the lunar meteorites MAC88104 and MAC88105 collected in the MacAlpine Hills area of Antarctica. The concentrations of the noble gas isotopes and the radionuclide activities in the two meteorites are essentially identical, proving that the two meteorites are paired. From {sup 40}K-{sup 40}Ar dating the authors obtain a gas retention age of 3,550 {plus minus} 400 Ma, typical for lunar surface material. Probably before breccia compaction the MAC88104/5 material resided for 630 {plus minus} 200 Ma at an average shielding depth of 85 g/cm{sup 2}, that is, about 50 cm below the lunar surface in the lunar regolith, as judged from the concentration of cosmic-ray produced Kr and Xe isotopes. Although this duration of lunar regolith residence is relatively long, MAC88104/5 represent immature regolith material: the concentration of solar wind implanted noble gases are two orders of magnitude lower than those in mature lunar soil. The {sup 40}Ar/{sup 36}Ar ratio of the trapped component is 5.7 {plus minus} 1.0, indicating an intermediate antiquity of the material; the authors estimate that the solar wind and lunar atmospheric particles were implanted about 2,000 Ma ago. The radionuclide activities allow a determination of the exposure history of the MAC88104/5 material. The duration of the Moon-Earth transfer was {much lt} 0.24 Ma. The exposure histories of the lunar meteorites discussed in this work indicate that at least two impact events are required for their ejection from the Moon. The authors first noble gas results for lunar meteorite Yamato-793274 show that it represents mature lunar regolith material with relatively high concentrations of solar wind implanted noble gas and a duration of several hundred million years of exposure to cosmic rays.

  20. Stratospheric BrO abundance measured by a balloon-borne submillimeterwave radiometer

    NASA Astrophysics Data System (ADS)

    Stachnik, R. A.; Millán, L.; Jarnot, R.; Monroe, R.; McLinden, C.; Kühl, S.; Puķīte, J.; Shiotani, M.; Suzuki, M.; Kasai, Y.; Goutail, F.; Pommereau, J. P.; Dorf, M.; Pfeilsticker, K.

    2013-03-01

    Measurements of mixing ratio profiles of stratospheric bromine monoxide (BrO) were made using observations of BrO rotational line emission at 650.179 GHz by a balloon-borne SIS (superconductor-insulator-superconductor) submillimeterwave heterodyne limb sounder (SLS). The balloon was launched from Ft. Sumner, New Mexico (34° N) on 22 September 2011. Peak mid-day BrO abundance varied from 16 ± 2 ppt at 34 km to 6 ± 4 ppt at 16 km. Corresponding estimates of total inorganic bromine (Bry), derived from BrO vmr (volume mixing ratio) using a photochemical box model, were 21 ± 3 ppt and 11 ± 5 ppt, respectively. Inferred Bry abundance exceeds that attributable solely to decomposition of long-lived methyl bromide and other halons, and is consistent with a contribution from bromine-containing very short lived substances, BryVSLS, of 4 ppt to 8 ppt. These results for BrO and Bry were compared with, and found to be in good agreement with, those of other recent balloon-borne and satellite instruments.

  1. Stratospheric BrO abundance measured by a balloon-borne submillimeterwave radiometer

    NASA Astrophysics Data System (ADS)

    Stachnik, R. A.; Millán, L.; Jarnot, R.; Monroe, R.; McLinden, C.; Kühl, S.; Pukīte, J.; Kasai, Y.; Goutail, F.; Pommereau, J. P.; Dorf, M.; Pfeilsticker, K.

    2012-11-01

    Measurements of mixing ratio profiles of stratospheric bromine monoxide (BrO) were made using observations of BrO otational line emission at 650.179 GHz by a balloon-borne SIS (superconductor-insulator-superconductor) submillimeterwave heterodyne receiver. The balloon was launched from Ft. Sumner, New Mexico (34°N) on 22 September 2011. Peak mid-day BrO abundance varied from 16 ± 2 ppt at 34 km to 6 ± 4 ppt at 16 km. Corresponding estimates of total inorganic bromine (Bry), derived from BrO vmr (volume mixing ratio) using a photochemical box model, were 21 ± 3 ppt and 11 ± 5 ppt, respectively. Inferred Bry abundance exceeds that attributable solely to decomposition of long-lived methyl bromide and other halons, and is consistent with a contribution from bromine-containing very short lived substances, BryVSLS, of 4 ppt to 8 ppt. These results for BrO and Bry were compared with, and found to be in good agreement with, those of other recent balloon-borne and satellite instruments.

  2. Infrared spectroscopic measurements of the vertical column abundance of sulfur hexafluoride, SF6, from the ground

    NASA Technical Reports Server (NTRS)

    Zander, R.; Demoulin, P.; Rinsland, C. P.

    1991-01-01

    The solar observations involved in the present monitoring evaluation were made at two facilities, using Fourier-transform spectrometers achieving spectral resolutions of 0.005/cm and signal-to-rms noise ratios for individual scans from near 500 to near 1000. The monthly mean total vertical-column abundances of SF6 above both facilities are reported for time intervals from June 1986 to June 1990 and from March 1981 to June 1990. It is found that the vertical-column abundances increased at mean rates of 6.9 +/- 2.8 pct above one station and 6.6 +/- 7.2 pct above the other. Since all the results were retrieved using the same spectroscopic parameters and similar nonlinear least-squares curve-fitting algorithms validated through intercomparison exercises, the large error reported for the second station is attributed to a larger measurement uncertainty due to stronger H2O and C2O interferences, and a greater variability during each month.

  3. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    NASA Astrophysics Data System (ADS)

    Cai, Mick Y.; Wang, Lixin; Parkes, Stephen D.; Strauss, Josiah; McCabe, Matthew F.; Evans, Jason P.; Griffiths, Alan D.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10 m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (∼1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  4. Measuring long-lived 13C2 state lifetimes at natural abundance

    NASA Astrophysics Data System (ADS)

    Claytor, Kevin; Theis, Thomas; Feng, Yesu; Warren, Warren

    2014-02-01

    Long-lived disconnected eigenstates (for example, the singlet state in a system with two nearly equivalent carbons, or the singlet-singlet state in a system with two chemically equivalent carbons and two chemically equivalent hydrogens) hold the potential to drastically extend the lifetime of hyperpolarization in molecular tracers for in vivo magnetic resonance imaging (MRI). However, a first-principles calculation of the expected lifetime (and thus selection of potential imaging agents) is made very difficult because of the large variety of relevant intra- and intermolecular relaxation mechanisms. As a result, all previous measurements relied on costly and time consuming syntheses of 13C labeled compounds. Here we show that it is possible to determine 13C singlet state lifetimes by detecting the naturally abundant doubly-labeled species. This approach allows for rapid and low cost screening of potential molecular biomarkers bearing long-lived states.

  5. Earthworm eco-physiological characteristics and quantification of earthworm feeding in vermifiltration system for sewage sludge stabilization using stable isotopic natural abundance.

    PubMed

    Li, Xiaowei; Xing, Meiyan; Yang, Jian; Dai, Xiaohu

    2014-07-15

    Previous studies showed that the presence of earthworm improves treatment performance of vermifilter (VF) for sewage sludge stabilization, but earthworm eco-physiological characteristics and effects in VF were not fully investigated. In this study, earthworm population, enzymatic activity, gut microbial community and stable isotopic abundance were investigated in the VF. Results showed that biomass, average weight, number and alkaline phosphatase activity of the earthworms tended to decrease, while protein content and activities of peroxidase and catalase had an increasing tendency as the VF depth. Earthworm gut microbial communities were dominated by Gammaproteobacteria, and the percentages arrived to 76-92% of the microbial species detected. (15)N and (13)C natural abundance of the earthworms decreased with operation time, and increased as the VF depth. Quantitative analysis using δ(15)N showed that earthworm feeding and earthworm-microorganism interaction were responsible for approximately 21% and 79%, respectively, of the enhanced volatile suspended solid reduction due to the presence of earthworm. The finding provides a quantitative insight into how earthworms influence on sewage sludge stabilization in vermifiltration system.

  6. Calcium isotope analysis by mass spectrometry.

    PubMed

    Boulyga, Sergei F

    2010-01-01

    The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. The present article discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. In Sections 2 and 3, mass spectrometric methods applied to precise stable isotope analysis and to the determination of (41)Ca are described. Section 4 contains a short summary of selected applications, and includes tracer experiments and the potential use

  7. Isotope fractionation studies of molybdenum

    NASA Astrophysics Data System (ADS)

    Wieser, M. E.; de Laeter, J. R.; Varner, M. D.

    2007-08-01

    Mass spectrometric studies of the isotopic composition of molybdenum have become an active area of research in stable isotope geochemistry, biogeochemistry and cosmochemistry. The redox chemistry of Mo, together with its proclivity for covalent bonding, indicates its importance in isotope fractionation studies such as palaeoceanography. The measurement of the magnitude of isotope fractionation of Mo in natural systems is a challenging task, in that natural fractionation has to be carefully distinguished from chemical and instrumental isotope fractionation. An ion exchange chemical separation procedure has been developed with high efficiency and low blank, to ensure that the isobaric elements Zr and Ru are removed from the samples before mass spectrometric analysis. The isotope fractionation resulting from this procedure is 0.14[per mille sign] per u. The isotopic composition of Mo of a Laboratory Standard has been measured by positive and negative thermal ionization mass spectrometry (P-TIMS and N-TIMS, respectively), to give an isotope fractionation of 6.4[per mille sign] and 0.5[per mille sign] per u, respectively, with respect to the absolute isotope abundances of Mo. In both cases the lighter isotopes are enhanced with respect to the heavier isotopes. An ascorbic acid activator has enabled the sensitivity of P-TIMS to be improved as compared to traditional methods. The same experiment was repeated using a multiple collector-inductively coupled plasma-mass spectrometer (MC-ICP-MS) to give an isotope fractionation of approximately 17.0[per mille sign] per u. In this case the heavier isotopes are enhanced with respect to the lighter isotopes. The strengths and weaknesses of these three mass spectrometric techniques are evaluated. We conclude that MC-ICP-MS is the optimum mass spectrometric method for accurately measuring the isotope fractionation of Mo in natural materials, provided chemical and instrumental isotope fractionation can be resolved from naturally

  8. Measurements of Cosmic-Ray Hydrogen and Helium Isotopes with the PAMELA Experiment

    NASA Astrophysics Data System (ADS)

    Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Mergè, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2016-02-01

    The cosmic-ray hydrogen and helium (1H, 2H, 3He, 4He) isotopic composition has been measured with the satellite-borne experiment PAMELA, which was launched into low-Earth orbit on board the Resurs-DK1 satellite on 2006 June 15. The rare isotopes 2H and 3He in cosmic rays are believed to originate mainly from the interaction of high-energy protons and helium with the galactic interstellar medium. The isotopic composition was measured between 100 and 1100 MeV/n for hydrogen and between 100 and 1400 MeV/n for helium isotopes using two different detector systems over the 23rd solar minimum from 2006 July to 2007 December.

  9. An isotopic approach to measuring nitrogen balance in caribou

    USGS Publications Warehouse

    Gustine, D.D.; Barboza, P.S.; Adams, L.G.; Farnell, R.G.; Parker, K.L.

    2011-01-01

    Nutritional restrictions in winter may reduce the availability of protein for reproduction and survival in northern ungulates. We refined a technique that uses recently voided excreta on snow to assess protein status in wild caribou (Rangifer tarandus) in late winter. Our study was the first application of this non-invasive, isotopic approach to assess protein status of wild caribou by determining dietary and endogenous contributions of nitrogen (N) to urinary urea. We used isotopic ratios of N (??15N) in urine and fecal samples to estimate the proportion of urea N derived from body N (p-UN) in pregnant, adult females of the Chisana Herd, a small population that ranged across the Alaska-Yukon border. We took advantage of a predator-exclosure project to examine N status of penned caribou in April 2006. Lichens were the primary forage (>40%) consumed by caribou in the pen and ?? 15N of fiber tracked the major forages in their diets. The ??15N of urinary urea for females in the pen was depleted relative (-1.3 ?? 1.0 parts per thousand [??], x?? ?? SD) to the ??15N of body N (2.7 ?? 0.7??). A similar proportion of animals in the exclosure lost core body mass (excluding estimates of fetal and uterine tissues; 55%) and body protein (estimated by isotope ratios; 54%). This non-invasive technique could be applied at various spatial and temporal scales to assess trends in protein status of free-ranging populations of northern ungulates. Intra- and inter-annual estimates of protein status could help managers monitor effects of foraging conditions on nutritional constraints in ungulates, increase the efficiency and efficacy of management actions, and help prepare stakeholders for potential changes in population trends. ?? 2010 The Wildlife Society.

  10. High-precision measurement of chlorine stable isotope ratios

    USGS Publications Warehouse

    Long, A.; Eastoe, C.J.; Kaufmann, R.S.; Martin, J.G.; Wirt, L.; Finley, J.B.

    1993-01-01

    We present an analysis procedure that allows stable isotopes of chlorine to be analyzed with precision sufficient for geological and hydrological studies. The total analytical precision is ?????0.09%., and the present known range of chloride in the surface and near-surface environment is 3.5???. As Cl- is essentially nonreactive in natural aquatic environments, it is a conservative tracer and its ??37Cl is also conservative. Thus, the ??37Cl parameter is valuable for quantitative evaluation of mixing of different sources of chloride in brines and aquifers. ?? 1993.

  11. Satellite measurements of the isotopic composition of galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Spalding, J. D.; Stone, E. C.; Vogt, R. E.

    1979-01-01

    The individual isotopes of galactic cosmic ray Ne, Mg, and Si at 100 MeV/nucleon were clearly resolved with an rms mass resolution of 0.20 amu. The results suggest the cosmic ray source is enriched in Ne-22, Mg-25, and Mg-26 when compared to the solar system. The ratio of (Mg-25)+(Mg-26) to Mg-24, which is approximately 0.49 compared to the solar system value of 0.27, suggest that the cosmic ray source and solar system material were synthesized under different conditions.

  12. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    NASA Astrophysics Data System (ADS)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    oxygen isotope composition of ambient CO2. This non-destructive approach was tested through laboratory incubations of air-dried soils that were re-wetted with water of known isotopic composition. Performance was assessed by comparing estimates of the soil water oxygen isotope composition derived from open chamber flux measurements with those measured in the irrigation water and soil water extracted following incubations. The influence of soil pH and bovine carbonic anhydrase additions on these estimates was also investigated. Coherent values were found between the soil water composition estimates obtained from the dual steady state approach and those measured for irrigation waters. Estimates of carbonic anhydrase activity made using this approach also reflected well artificial increases to the concentration of carbonic anhydrase and indicated that this activity was sensitive to soil pH.

  13. Acoustic measures of the abundance and size of pelagic planktivores in Lake Michigan

    USGS Publications Warehouse

    Brandt, Stephen B.; Mason, Doran M.; Patrick, E. Vincent; Argyle, Ray L.; Wells, L.; Unger, Philip A.; Stewart, Donald J.

    1991-01-01

    Based on acoustic data taken at night and vertically stratified by bottom depth (3–110 m only), the total number (± 95% Cl) of pelagic fishes in Lake Michigan was 43.4 ± 10.1 x 109 or 226.0 ± 55.2 kt in spring (mean density 0.7–3.8 fish·m-2 or 1.6–12.8 ga·m-2) and 115.8 ± 18.3 x 109 or 313.2 ± 74.3 kt in late summer, 1987 (mean density 1.1–7.0 fish·m-2 or 3.0–13.2 g·m-2); approximately 30% of this increase in numbers (35% of biomass) occurred within Green Bay. Abundance estimates from horizontally stratified (by water column depth) data were within 9-11% of vertically stratified estimates during spring but over 20% higher during summer. By extrapolation to all water depths, we estimated total pelagic biomass as 274.6 kt for spring and 410.8 kt for summer. During both seasons, smaller fishes were nearer to the surface and nearer shore than larger individuals, and acoustic measures of size approximated the sizes of fishes caught in trawls. Bioenergetic model simulations suggest that 60% of the available production of alewife (Alosa pseudoharengus) was either consumed by stocked salmonines (52.9%) or commercially harvested (7.1%) in 1987. Underwater acoustics proved a valuable tool for lakewide assessments of fish abundances in the Great Lakes.

  14. Hydroacoustic measures of Mysis relicta abundance and distribution in Lake Ontario

    USGS Publications Warehouse

    Rudstam, L. G.; Schaner, T.; Gal, G.; Boscarino, B.T.; O'Gorman, R.; Warner, D.M.; Johannsson, O.E.; Bowen, K.L.

    2008-01-01

    Mysis relicta can be observed on echograms as a sound scattering layer when they migrate into the water column at night to feed on zooplankton. However, quantitative measures of mysid abundance with hydroacoustics requires knowledge of mysid target strength (TS), a method of removing fish echoes and contribution from noise, and an understanding of the effect of range on the ability of hydroacoustics to detect mysids (the detection limit). Comparisons of paired net data and acoustics data from July 7, 2005 yielded a mysid TS of -86.3 dB (9 mm animal) and a biomass TS of -58.4 dB (g dry wt)-1. With ambient noise levels (Sv of -125 dB at 1 m depth) and this TS, we can detect a mysid density of 1 m-3 at 60 m depth with a signal to noise ratio of 3 dB. We present a method to remove backscattering from both noise and fish and apply this method and the new TS data to whole lake acoustic data from Lake Ontario collected in July 25-31, 2005 with a 120 kHz echosounder as part of the annual standard fish survey in that lake. Mysis abundance was strongly depth dependent, with highest densities in areas with bottom depth > 100 m, and few mysids in areas with bottom depth 100 m, 100-75 m, 75-50 m, 50-30 m, < 30 m), the whole-lake average mysid density was 118 m-2 (CV 21%) and the whole-lake average mysid biomass was 0.19 g dry wt m-2 (CV 22%) in July 2005. The CVs of these densities also account for uncertainty in the TS estimates. This is comparable to whole-lake density estimates using vertical net tows in November, 2005 (93 m-2, CV 16%). Copyright ?? 2008 AEHMS.

  15. Re-Os Abundance and Isotope Systematics of Al-undepleted Komatiites in the Kidd-Munro Assemblage: Results From Dundonald Beach, Abitibi Greenstone Belt, Canada

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, A.; Sproule, R. A.; Walker, R. J.; Lesher, C. M.

    2004-05-01

    Petrographic and geochemical studies suggest that all Precambrian komatiites have undergone variable degrees of weathering, hydrothermal alteration and metamorphism. The effects of these secondary processes in some suites have manifested into large-scale open-system behavior of Re-Os elemental and isotope systematics of whole rocks, which, in some cases, yield inaccurate age and large uncertainties in calculated initial Os isotopic compositions of the emplaced lavas. Thus, some of the previous Os isotopic studies of Precambrian komatiites for which the crystallization ages were known from other radiogenic isotope systematics (e.g., Sm-Nd, Pb-Pb) have relied on Os-rich, relatively well-preserved primary igneous minerals (e.g., olivine and chromite) in order to calculate the initial Os isotopic compositions of the host lavas. Consequently, the whole-rock concentrations of Re and Os in these altered komatiites can neither be used to infer their concentrations in the parental liquids nor their partitioning behaviors during generation and subsequent differentiation of komatiitic magmas. Here we report the Re-Os concentrations of whole rocks from a suite of ca. 2.7-Ga komatiitic rocks from the Dundonald Beach area, part of the Kidd-Munro volcanic assemblage in the Abitibi greenstone belt, Canada. We show that it is possible to calculate the original Re concentrations in the emplaced lavas, and to estimate the gain or loss of Re through comparison of their measured concentrations and those recalculated from their correlations with other incompatible, yet relatively immobile major oxide and trace elements (e.g., Al2O3, Zr, Hf, Yb). We also demonstrate the statistical significance of this scheme of correction with the reduced values of MSWD (by an order of magnitude) and respective uncertainties in slope (by 2-3 orders of magnitude) of regressions involving Re and the immobile elements. Based on the absence of a correlation between loss of Re and the Os isotopic

  16. Solar photospheric and coronal abundances from solar energetic particle measurements. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Breneman, H.

    1985-01-01

    Observations of solar energetic particles (SEP) from 22 solar flares in the 1977 to 1982 time period are reported. SEP abundances were obtained for all elements with 3 approximately less than Z approximately less than 30 except Li, Be, B, F, Sc, v, Co and Cu for which upper limits were obtained. Statistically meaningful abundances of several rare elements (P, Cl, K, Ti, and Mn) were determined for the first time, and the average abundance of the more abundant elements were determined with improved precision.

  17. Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada: An alkaline, meromictic lake

    USGS Publications Warehouse

    Oremland, R.S.; Des Marais, D.J.

    1983-01-01

    Distribution and isotopic composition (??13C) of low molecular weight hydrocarbon gases were studied in Big Soda Lake (depth = 64 m), an alkaline, meromictic lake with permanently anoxic bottom waters. Methane increased with depth in the anoxic mixolimnion (depth = 20-35 m), reached uniform concentrations (55 ??M/l) in the monimolimnion (35-64 m) and again increased with depth in monimolimnion bottom sediments (>400 ??M/kg below 1 m sub-bottom depth). The ??13C[CH4] values in bottom sediment below 1 m sub-bottom depth (<-70 per mil) increased with vertical distance up the core (??13C[CH4] = -55 per mil at sediment surface). Monimolimnion ??13C[CH4] values (-55 to -61 per mil) were greater than most ??13C[CH4] values found in the anoxic mixolimnion (92% of samples had ??13C[CH4] values between -20 and -48 per mil). No significant concentrations of ethylene or propylene were found in the lake. However ethane, propane, isobutane and n-butane concentrations all increased with water column depth, with respective maximum concentrations of 260, 80, 23 and 22 nM/l encountered between 50-60 m depth. Concentrations of ethane, propane and butanes decreased with depth in the bottom sediments. Ratios of CH4 [C2H6 + C3H8] were high (250-620) in the anoxic mixolimnion, decreased to ~161 in the monimolimnion and increased with depth in the sediment to values as high as 1736. We concluded that methane has a biogenic origin in both the sediments and the anoxic water column and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in ??13C[CH4] and CH4 (C2H6 + C3H8) with depth in the water column and sediments are probably caused by bacteria] processes. These might include anaerobic methane oxidation and different rates of methanogenesis and C2 to C4 alkane production by microorganisms. ?? 1983.

  18. Measurement of Relative Abundances of Ultra-Heavy Cosmic Rays with CALET on the ISS

    NASA Astrophysics Data System (ADS)

    Rauch, Brian; Calet Collaboration

    2016-03-01

    The CALorimetric Electron Telescope (CALET) is a Japanese-Italian-US astroparticle observatory that was launched from the Tanegashima Space Center on the H-IIB Launch Vehicle No.5 (H-IIB F5) aboard the KOUNOTORI5 (HTV5 cargo transfer vehicle) to the International Space Station (ISS) on August 19, 2015. The HTV5 arrived at the ISS on August 24, and CALET was installed on port 9 of the Japanese Experiment Module ``Kibo'' Exposed Facility (JEM-EF), where CALET underwent the planned turn on and checkout procedures. CALET has completed its commissioning phase and its main calorimeter (CAL) is observing the highest energy cosmic electrons from 1 GeV to 20 TeV, along with cosmic ray nuclei through iron up to 1,000 TeV and gamma-rays above 10 GeV. In a five-year mission CALET will also have the exposure to measure the relative abundances of the ultra-heavy (UH) cosmic rays with ~4 × the statistics of the TIGER instrument for the full CAL acceptance. Rigidity cutoffs based on the earth's geomagnetic field in the 51.6° inclination ISS orbit can provide an energy independent UH measurement with expanded acceptance with ~10 × the TIGER statistics. An overview of the anticipated performance and preliminary CALET UH analysis data will be presented. This research was supported by NASA at Washington University under Grant Number NNX11AE02G.

  19. Chlorine and carbon isotope measurements can help assessing the effectivenes of a zero valent iron barrier

    NASA Astrophysics Data System (ADS)

    Cretnik, S.; Audi, C.; Bernstein, A.; Palau, J.; Soler, A.; Elsner, M.

    2012-04-01

    Chlorinated aliphatic hydrocarbons (CAH's) such as trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinylchloride (VC) are extensively used in industrial applications. One of the most promising remediation techniques for CAH's in groundwater is their removal via abiotic reductive dechlorination using Zero Valent Iron (ZVI). This is applied for the treatment of contaminated sites by installing permeable reactive barriers (PRB). In this study, isotope fractionation of chlorinated ethylenes in transformation by cast iron has been investigated, because such types of iron are commonly used in PRBs. Batch experiments have been carried out in closed flasks, containing cast iron with aqueous solutions of TCE, cDCE and VC. These substrates and their respective products have been monitored by headspace samplings for their concentration (by GC-FID) and isotope fractionation of carbon and chlorine (by GC-IRMS). A decreasing reactivity trend was observed when compounds contain less chlorine atoms, with differences in rate constants of about one order of magnitude between each of the substances TCE > cDCE > VC. This resulted in the accumulation of products with fewer chlorine atoms. Therefore a similar observation can be expected if degradation in the field is incomplete, for example in the case of aged or improperly designed PRB. Pronounced carbon and chlorine isotope fractionation was measured for each of the compounds, and characteristic dual isotope plots (C, Cl) were obtained for TCE and cDCE. These results may serve as an important reference for the interpretation of isotope data from field sites, since stable isotope fractionation is widely recognized as robust indicator for such pollutant transformations. However, carbon isotope fractionation in a given parent compound may be caused by either abiotic or biotic degradation. In the field, it can therefore be difficult to delineate the contribution of abiotic transformation by PRB in the presence of ongoing

  20. The capabilities of ROSINA/DFMS to measure argon isotopes at comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Hässig, M.; Altwegg, K.; Berthelier, J. J.; Calmonte, U.; De Keyser, J.; Fiethe, B.; Fuselier, S. A.; Gombosi, T. I.; Le Roy, L.; Owen, T.; Rubin, M.

    2015-01-01

    Little is known about the noble gas abundances in comets. These highly volatile atoms are possible tracers of the history of cometary matter including the thermal evolution. They can help quantify the contribution of cometary impacts to terrestrial oceans and help elucidate on the formation history of comets and their role in the formation and evolution of planetary atmospheres. This paper focuses on argon and the capabilities to measure this noble gas with in situ mass spectrometry at comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's spacecraft Rosetta. Argon may have been detected by remote sensing in a single Oort cloud comet but to date nothing is known about the isotopic abundances of argon in comets. Furthermore, no detection of argon in a Jupiter-family comet has been reported. Comet 67P/Churyumov-Gerasimenko belongs to the group of Jupiter-family comets and originates most likely in the Kuiper belt. Onboard Rosetta is ROSINA/DFMS (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer). DFMS has unprecedented mass resolution and high sensitivity and is designed to measure isotopic ratios including argon (Balsiger et al., 2007). Argon measurements using the DFMS lab model (identical to the flight model) demonstrate this capability. At very least, this mass spectrometer has the resolution and sensitivity to reduce the upper limit on the argon outgassing rate relative to water by more than three orders of magnitude (for 38Ar). Most likely, ROSINA/DFMS will provide the first detection of argon in a Jupiter-family comet together with the first determination of the 36Ar/38Ar ratio at a comet.

  1. Ab initio calculations of the Fe(II) and Fe(III) isotopic effects in citrates, nicotianamine, and phytosiderophore, and new Fe isotopic measurements in higher plants

    NASA Astrophysics Data System (ADS)

    Moynier, Frédéric; Fujii, Toshiyuki; Wang, Kun; Foriel, Julien

    2013-05-01

    Iron is one of the most abundant transition metal in higher plants and variations in its isotopic compositions can be used to trace its utilization. In order to better understand the effect of plant-induced isotopic fractionation on the global Fe cycling, we have estimated by quantum chemical calculations the magnitude of the isotopic fractionation between different Fe species relevant to the transport and storage of Fe in higher plants: Fe(II)-citrate, Fe(III)-citrate, Fe(II)-nicotianamine, and Fe(III)-phytosiderophore. The ab initio calculations show firstly, that Fe(II)-nicotianamine is ˜3‰ (56Fe/54Fe) isotopically lighter than Fe(III)-phytosiderophore; secondly, even in the absence of redox changes of Fe, change in the speciation alone can create up to ˜1.5‰ isotopic fractionation. For example, Fe(III)-phytosiderophore is up to 1.5‰ heavier than Fe(III)-citrate2 and Fe(II)-nicotianamine is up to 1‰ heavier than Fe(II)-citrate. In addition, in order to better understand the Fe isotopic fractionation between different plant components, we have analyzed the iron isotopic composition of different organs (roots, seeds, germinated seeds, leaves and stems) from six species of higher plants: the dicot lentil (Lens culinaris), and the graminaceous monocots Virginia wild rye (Elymus virginicus), Johnsongrass (Sorghum halepense), Kentucky bluegrass (Poa pratensis), river oat (Uniola latifolia), and Indian goosegrass (Eleusine indica). The calculations may explain that the roots of strategy-II plants (Fe(III)-phytosiderophore) are isotopically heavier (by about 1‰ for the δ56Fe) than the upper parts of the plants (Fe transported as Fe(III)-citrate in the xylem or Fe(II)-nicotianamine in the phloem). In addition, we suggest that the isotopic variations observed between younger and older leaves could be explained by mixing of Fe received from the xylem and the phloem.

  2. Site-selective nitrogen isotopic ratio measurement of nitrous oxide using a TE-cooled CW-RT-QCL based spectrometer.

    PubMed

    Li, Jingsong; Zhang, Lizhu; Yu, Benli

    2014-12-10

    The feasibility of laser spectroscopic isotopic composition measurements of atmospheric N2O was demonstrated, although making them useful will require further improvements. The system relies on a thermoelectrically (TE) cooled continuous-wave (CW) room temperature (RT) quantum cascade laser source emitting wavelength of around 4.6μm, where strong fundamental absorption bands occur for the considered specie and its isotopomers. The analysis technique is based on wavelength modulation spectroscopy with second-harmonic detection and the combination of long-path absorption cell. Primary laboratory tests have been performed to estimate the achievable detection limits and the signal reproducibility levels in view of possible measurements of (15)N/(14)N and (18)O/(16)O isotope ratios. The experiment results showed that the site-selective (15)N/(14)N ratio can be measured with a precision of 3‰ with 90s averaging time using natural-abundance N2O sample of 12.7ppm.

  3. Constraints on nitrogen cycling at the subtropical North Pacific Station ALOHA from isotopic measurements of nitrate and particulate nitrogen

    NASA Astrophysics Data System (ADS)

    Casciotti, K. L.; Trull, T. W.; Glover, D. M.; Davies, D.

    2008-07-01

    Nitrogen supply to surface waters can play an important role in the productivity and ecology of subtropical ecosystems. As part of the Vertical Transport in the Global Ocean (VERTIGO) program, we examined the fluxes of nitrogen into and out of the euphotic zone at station ALOHA in the North Pacific Subtropical Gyre using natural abundance stable isotopic measurements of nitrate ( δN and δO), as well as sinking and suspended particulate nitrogen (δ 15N PN). Paralleling the steep gradient in nitrate concentration in the upper thermocline at ALOHA, we observed a steep gradient in δN, decreasing from a maximum of +7.1‰ at 500 meters (m) to +1.5-2.4‰ at 150 m. δO values also decreased from +3.0‰ at 300 m to +0.7-0.9‰ at 150 m. The decreases in both δN and δO require inputs of isotopically "light" nitrate to balance the upward flux of nitrate with high δN (and δO). We conclude that both nitrogen fixation and diagenetic alteration of the sinking flux contribute to the decrease in δN and δO in the upper thermocline at station ALOHA. While nitrogen fixation is required to explain the nitrogen isotope patterns, the rates of nitrogen fixation may be lower than previously estimated. By including high-resolution nitrate isotope measurements in the nitrogen isotope budget for the euphotic zone at ALOHA, we estimate that approximately 25%, rather than 50%, of export production was fueled by N 2 fixation during our study. On the other hand, this input of N 2-derived production accumulates in the upper thermocline over time, playing a significant role in subtropical nutrient cycling through maintenance of the subsurface nitrate pool. An increase in sinking δ 15N PN between 150 and 300 m, also suggests that fractionation during remineralization contributed to the low δN values observed in this depth range by introducing a subsurface nitrate source that is 0.5‰ lower in δ 15N than the particle flux exported from the euphotic zone. While the time scale of these

  4. The evolution of capturing reliable isotopic water vapor signatures: An intercomparison of measurement techniques (Invited)

    NASA Astrophysics Data System (ADS)

    Apodaca, R. L.; Simonin, K. A.; Tu, K. P.; Cohen, R. C.; Dawson, T. E.

    2009-12-01

    Stable isotope analysis of water is a proven tool for gaining insight into the processes that govern the hydrologic cycle. One of the most challenging aspects of characterizing the movement of water between the biosphere, hydrosphere, and the atmosphere has been capturing shifts in the isotope value of ambient water vapor. Traditional methods of cryogenically trapping ambient vapor for subsequent laboratory analysis using isotope ratio mass spectrometry (IRMS) are labor-intensive, difficult to calibrate, and are susceptible to incomplete trapping problems. Furthermore, cryogenic trapping is often insufficient for producing highly-resolved spatial and temporal observations that capture the evolution of isotope changes that occur in moving airmasses or on short timescales. The recent advent of laser-based isotope vapor analyzers promises to solve many issues related to real-time isotope analysis of ambient water vapor by providing capabilities for making reliable, high-accuracy, high-precision measurements faster than ever before. Because laser-based isotope analysis is still in its relative infancy, and for the validity of the science produced by using these tools, it is critically important that we understand exactly how reliable, accurate, and precise these analyzers are. Here, we present the results of an intercomparison between two commercially-available isotopic-water vapor analyzers (Picarro, Inc. and Los Gatos Research, Inc.) and cryogenic vapor trapping/IRMS analysis. The intercomparison, conducted at the University of California, Berkeley, was designed to simulate the rigors of real field-deployments by assessing the ability of each technique to faithfully capture isotope variations in ambient water vapor. We show characterizations of the temperature and concentration dependencies of each analyzer, compare accuracy and precision with IRMS results, and present observations made under variable ambient conditions during chamber and field deployments.

  5. Isotope composition of sulphate in acid mine drainage as measure of bacterial oxidation

    USGS Publications Warehouse

    Taylor, B.E.; Wheeler, M.C.; Nordstrom, D.K.

    1984-01-01

    The formation of acid waters by oxidation of pyrite-bearing ore deposits, mine tailing piles, and coal measures is a complex biogeochemical process and is a serious environmental problem. We have studied the oxygen and sulphur isotope geochemistry of sulphides, sulphur, sulphate and water in the field and in experiments to identify sources of oxygen and reaction mechanisms of sulphate formation. Here we report that the oxygen isotope composition of sulphate in acid mine drainage shows a large variation due to differing proportions of atmospheric- and water-derived oxygen from both chemical and bacterially-mediated oxidation. 18O-enrichment of sulphate results from pyrite oxidation facilitated by Thiobacillus ferrooxidans in aerated environments. Oxygen isotope analysis may therefore be useful in monitoring the effectiveness of abatement programmes designed to inhibit bacterial oxidation. Sulphur isotopes show no significant fractionation between pyrite and sulphate, indicating the quantitative insignificance of intermediate oxidation states of sulphur under acid conditions. ?? 1984 Nature Publishing Group.

  6. New Isotopic Water Analyzer for Hydrological Measurements of Both Liquid Water and Water Vapor

    NASA Astrophysics Data System (ADS)

    Owano, T.; Gupta, M.; Berman, E.; Baer, D.

    2012-04-01

    Measurements of the stable isotope ratios of liquid water allow determination of water flowpaths, residence times in catchments, and groundwater migration. Previously, discrete water samples have been collected and transported to an IRMS lab for isotope characterization. Due to the expense and labor associated with such sampling, isotope studies have thus been generally limited in scope and in temporal resolution. We report on the recent development of the first Isotopic Water Analyzer that simultaneously quantifies δ2H, δ17O and δ18O in liquid water or in water vapor from different natural water sources (e.g., rain, snow, streams and groundwater). In High-Throughput mode, the IWA can report measurements at the unprecedented rate of over 800 injections per day, which yields more than 140 total unknown and reference samples per day (still with 6 injections per measurement). This fast time response provides isotope hydrologists with the capability to study dynamic changes in δ values quickly (minutes) and over long time scales (weeks, months), thus enabling studies of mixing dynamics in snowmelt, canopy throughfall, stream mixing, and allows for individual precipitation events to be independently studied. In addition, the same IWA can also record fast measurements of isotopic water vapor (δ2H, δ17O, δ18O) in real time (2 Hz data rate or faster) over a range of mole fractions greater than 60000 ppm H2O in air. Changing between operational modes requires a software command, to enable the user to switch from measuring liquid water to measuring water vapor, or vice versa. The new IWA, which uses LGR's patented Off-axis ICOS technology, incorporates proprietary internal thermal control for stable measurements with essentially zero drift despite changes in ambient temperature (over the entire range from 0-45 degrees C). Measurements from recent field studies using the IWA will be presented.

  7. New Isotopic Water Analyzer for Hydrological Measurements of both Liquid Water and Water Vapor

    NASA Astrophysics Data System (ADS)

    Owano, T. G.; Gupta, M.; Dong, F.; Baer, D. S.

    2011-12-01

    Measurements of the stable isotope ratios of liquid water (δ2H and δ18O) allow determination of water flowpaths, residence times in catchments, and groundwater migration. In the past, discrete water samples have been collected and transported to an IRMS lab for isotope characterization. Due to the expense and labor associated with such sampling, isotope studies have thus been generally limited in scope and in temporal resolution. We report on the recent development of a new field-portable Isotopic Water Analyzer (IWA-35EP) that accurately quantifies δ2H and δ18O of different natural water sources (e.g., rain, snow, streams and groundwater) at the unprecedented rate of 1080 injections per day, which yields 180 total unknown and reference samples per day (150 unknown samples per day), or 1 measurement of an unknown sample in less than 10 minutes (with 6 injections per measurement). This fast time response provides isotope hydrologists with the capability to study dynamic changes in δ values quickly (minutes) and over long time scales (weeks, months), thus enabling studies of mixing dynamics in snowmelt, canopy throughfall, stream mixing, and allows for individual precipitation events to be independently studied. In addition, the same IWA can also record fast measurements of isotopic water vapor (δ18O and δ2H) in real time (2 Hz data rate or faster) over a range of mole fractions greater than 60000 ppm H2O in air. Changing between operational modes requires a software command, to enable the user to switch from measuring liquid water to measuring water vapor, or vice versa. The new IWA, which uses LGR's patented Off-axis ICOS technology, incorporates proprietary internal thermal control for stable measurements with essentially zero drift. Measurements from recent field studies using the IWA will be presented.

  8. Reporting and measurement of mass-dependent and mass-independent fractionation of mercury isotopes

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.

    2007-12-01

    Hg isotope analysis by MC-ICP-MS is an important new approach for fingerprinting Hg sources and monitoring Hg redox reactions and bioaccumulation, especially with the recent discovery of mass independent Hg isotope fractionation. Unfortunately research groups have adopted different standards, definitions of delta values, and methods of isotopic measurement. We suggest that a single standard, NIST SRM 3133, be adopted for reporting the isotopic variability of Hg isotopes. Isotope ratios should be determined by sample-standard bracketing (SSB) during analysis and reported as permil (‰) deviation from SRM 3133. For the highest precision and accuracy, a Tl internal standard along with SSB should be used to correct instrumental mass bias. Measurement routines should also include on-peak zero corrections and matching of concentration and matrix between the samples and bracketing standard. For samples that display mass-dependent fractionation (MDF), only one delta value needs to be reported (δ202/198Hg). Mass-independent fractionation (MIF) (Jackson et al., 2006; Bergquist et al., 2006; Bergquist and Blum, submitted) requires additional nomenclature, and we suggest reporting MIF as the deviation in isotope ratios from the theoretical mass dependent kinetic isotope fractionation (Δxxx/198Hg)¬. External reproducibility should be monitored by analysis of secondary standards. For studies of MDF, we use an in-house secondary standard solution made from metallic Hg mined from Almaden Spain and obtain a δ202Hg of -0.55 ±0.06‰ (2SD). For studies of MIF, we use NRCC CRM DORM-2 (dogfish muscle) and obtain a mean value of δ202Hg of +0.19 ±0.13‰ (2SD), Δ201Hg of +0.89 ±0.07‰ (2SD) , and Δ199Hg of +1.07 ±0.08‰ (2SD).

  9. An analytical system for the measurement of stable hydrogen isotopes in ambient volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Meisehen, T.; Bühler, F.; Koppmann, R.; Krebsbach, M.

    2015-10-01

    Stable isotope measurements in atmospheric volatile organic compounds (VOCs) are an excellent tool to analyse chemical and dynamical processes in the atmosphere. While up to now isotope studies of VOCs in ambient air have mainly focussed on carbon isotopes, we herein present a new measurement system to investigate hydrogen isotope ratios in atmospheric VOCs. This system, consisting of a gas chromatography pyrolysis isotope ratio mass spectrometer (GC-P-IRMS) and a pre-concentration system, was thoroughly characterised using a VOC test mixture. A precision of better than 9 ‰ (in δ 2H) is achieved for n-pentane, 2-methyl-1,3-butadiene (isoprene), n-heptane, 4-methyl-pentane-2-one (4-methyl-2-pentanone), methylbenzene (toluene), n-octane, ethylbenzene, m/p-xylene and 1,2,4-trimethylbenzene. A comparison with independent measurements via elemental analysis shows an accuracy of better than 9 ‰ for n-pentane, n-heptane, 4-methyl-2-pentanone, toluene and n-octane. Above a minimum required pre-concentrated compound mass the obtained δ 2H values are constant within the standard deviations. In addition, a remarkable influence of the pyrolysis process on the isotope ratios is found and discussed. Reliable measurements are only possible if the ceramic tube used for the pyrolysis is sufficiently conditioned, i.e. the inner surface is covered with a carbon layer. It is essential to verify this conditioning regularly and to renew it if required. Furthermore, influences of a necessary H3+ correction and the pyrolysis temperature on the isotope ratios are discussed. Finally, the applicability to measure hydrogen isotope ratios in VOCs at ambient levels is demonstrated with measurements of outside air on 5 different days in February and March 2015. The measured hydrogen isotope ratios range from -136 to -105 ‰ forn-pentane, from -86 to -63 ‰ for toluene, from -39 to -15 ‰ for ethylbenzene, from -99 to -68 ‰ for m/p-xylene and from -45 to -34 ‰ for o-xylene.

  10. An analytical system for the measurement of stable hydrogen isotopes in ambient volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Meisehen, T.; Bühler, F.; Koppmann, R.; Krebsbach, M.

    2015-07-01

    Stable isotope measurements in atmospheric volatile organic compounds (VOC) are an excellent tool to analyse chemical and dynamical processes in the atmosphere. While up to now isotope studies of VOC in ambient air mainly focus on carbon isotopes, we herein present a new measurement system to investigate hydrogen isotope ratios in atmospheric VOC. This system consisting of a GC-P-IRMS (Gas Chromatography Pyrolysis Isotope Ratio Mass Spectrometer) and a preconcentration system was thoroughly characterised using a working standard. A precision of better than 9 ‰ (in δD) is achieved for n-pentane, 2-methyl-1,3-butadiene (isoprene), n-heptane, 4-methyl-pentane-2-one (4-methyl-2-pentanone), methylbenzene (toluene), n-octane, ethylbenzene, m/p-xylene, and 1,2,4-trimethylbenzene. A comparison with independent measurements via elemental analysis shows an accuracy of better than 9 ‰ for n-pentane, n-heptane, 4-methyl-2-pentanone, toluene, and n-octane. Above a compound specific minimum peak area the obtained δD values are constant within the standard deviations. In addition, a remarkable influence of the pyrolysis process on the isotope ratios is found and discussed. Reliable measurements are only possible if the ceramic tube used for the pyrolysis is sufficiently conditioned, i.e. the inner surface is covered with a carbon layer. It is essential to verify this conditioning regularly and to renew it if required. Furthermore, influences of a necessary H3+ correction and the pyrolysis temperature on the isotope ratios are discussed. Finally, the applicability to measure hydrogen isotope ratios in VOC at ambient levels is demonstrated with measurements of outside air on five different days in February and March 2015. The measured hydrogen isotope ratios range from -136 to -105 ‰ for n-pentane, from -86 to -63 ‰ for toluene, from -39 to -15 ‰ for ethylbenzene, from -99 to -68 ‰ for m/p-xylene, and from -45 to -34 ‰ for o-xylene.

  11. Separation of copper, iron, and zinc from complex aqueous solutions for isotopic measurement

    USGS Publications Warehouse

    Borrok, D.M.; Wanty, R.B.; Ridley, W.I.; Wolf, R.; Lamothe, P.J.; Adams, M.

    2007-01-01

    The measurement of Cu, Fe, and Zn isotopes in natural samples may provide valuable information about biogeochemical processes in the environment. However, the widespread application of stable Cu, Fe, and Zn isotope chemistry to natural water systems remains limited by our ability to efficiently separate these trace elements from the greater concentrations of matrix elements. In this study, we present a new method for the isolation of Cu, Fe, and Zn from complex aqueous solutions using a single anion-exchange column with hydrochloric acid media. Using this method we are able to quantitatively separate Cu, Fe, and Zn from each other and from matrix elements in a single column elution. Elution of the elements of interest, as well as all other elements, through the anion-exchange column is a function of the speciation of each element in the various concentrations of HCl. We highlight the column chemistry by comparing our observations with published studies that have investigated the speciation of Cu, Fe, and Zn in chloride solutions. The functionality of the column procedure was tested by measuring Cu, Fe, and Zn isotopes in a variety of stream water samples impacted by acid mine drainage. The accuracy and precision of Zn isotopic measurements was tested by doping Zn-free stream water with the Zn isotopic standard. The reproducibility of the entire column separation process and the overall precision of the isotopic measurements were also evaluated. The isotopic results demonstrate that the Cu, Fe, and Zn column separates from the tested stream waters are of sufficient purity to be analyzed directly using a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS), and that the measurements are fully-reproducible, accurate, and precise. Although limited in scope, these isotopic measurements reveal significant variations in ??65Cu (- 1.41 to + 0.30???), ??56Fe (- 0.56 to + 0.34???), and ??66Zn (0.31 to 0.49???) among samples collected from different

  12. Evapotranspiration partitioning through in-situ oxygen isotope measurements in an oasis cropland

    NASA Astrophysics Data System (ADS)

    Wen, Xue-Fa

    2016-04-01

    The oxygen isotope compositions of ecosystem water pools and fluxes are useful tracers in the water cycle. As part of the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) program, high-frequency and near-continuous in situ measurements of 18O composition of atmospheric vapor (δv) and of evapotranspiration (δET) were made with the flux-gradient method using a cavity ring-down spectroscopy water vapor isotope analyzer. At the sub-daily scale, we found, in conjunction with intensive isotopic measurements of other ecosystem water pools, that the differences between 18O composition of transpiration (δT) and of xylem water (δx) were negligible in early afternoon (13:00-15:00 Beijing time) when ET approached the daytime maximum, indicating isotopic steady state. At the daily scale, for the purpose of flux partitioning, δT was approximated by δx at early afternoon hours, and the 18O composition of soil evaporation (δE) was obtained from the Craig-Gordon model with a moisture-dependent soil resistance. The relative contribution of transpiration to evapotranspiration ranged from 0.71 to 0.96 with a mean of 0.87 ± 0.052 for the growing season according to the isotopic labeling, which was good agreement with soil lysimeter measurements showing a mean transpiration fraction of 0.86 ± 0.058. At the growing season scale, the predicted18O composition of runoff water was within the range of precipitation and irrigation water according to the isotopic mass conservation. The 18O mass conservation requires that the decreased δ18O of ET should be balanced by enhanced δ18O of runoff water. (Wen, XF*, Yang, B, Sun, XM, Lee, X. 2015. Evapotranspiration partitioning through in-situ oxygen isotope measurements in an oasis cropland. Agricultural and Forest Meteorology , doi:10.1016/j.agrformet.2015.12.003).

  13. Using PLFA Biomarkers and Natural Abundance Stable and Radiocarbon Isotopes to Characterize the Microbial Ecology and Metabolism of Methane Cycling

    NASA Astrophysics Data System (ADS)

    Mills, C. T.; Mandernack, K. W.; Slater, G. F.; Dias, R. F.

    2008-12-01

    Methane generated in the subsurface is a major source of atmospheric CH4, but its release is mitigated by CH4-oxidizing bacteria (methanotrophs). Therefore, it is important to understand the ecology of methanotroph communities in various environments. Phospholipid fatty acid (PLFA) analyses are a particularly useful method for characterizing these communities for two reasons: (1) Many type I and II methanotrophs produce specific PLFA biomarkers that can be used to estimate their populations, and (2) because CH4 is often very depleted in 13C and sometimes 14C, natural abundance δ13CPLFA and Δ14CPLFA values can be used to trace the flow of CH4- derived carbon through microbial ecosystems. We used these tools to evaluate the role of methanotrophs in carbon flow in three different environments: (1) a soil column overlying a coal bed methane (CBM) seep in southwest CO, and pristine, oligotrophic groundwaters within (2) sedimentary and (3) granitic host rocks in Japan. In the soil column impacted by CBM seepage, concentrations of the biomarker PLFAs for type I (16:1ω8cis) and type II (18:1ω8cis) methanotrophs were as high as 13 and 18 nmoles (g dry soil)-1, respectively. Depth profiles of methanotroph PLFA concentrations varied over different sampling dates indicating dynamic populations. δ13CPLFA values of the CBM soils (-25.1 to - 66.9‰) were substantially more negative than those for the control soil (-14.5 to -32.5‰) indicating that CBM is an important carbon source for the CBM-impacted soil microbial community. Δ14CPLFA values (-351 to -936‰) indicate the importance of 14C-dead CBM as a carbon source to the microbial communities, contributing 32 to 66% of total carbon in PLFA structures isolated from shallow soils and 67 to 97% for those isolated from deeper soils. The biomarker for type II methanotrophs, comprised 3 and 18% of total PLFAs in sedimentary and granitic groundwaters, respectively. The Δ14C values determined for type II methanotroph PLFAs

  14. DERIVING PLASMA DENSITIES AND ELEMENTAL ABUNDANCES FROM SERTS DIFFERENTIAL EMISSION MEASURE ANALYSIS

    SciTech Connect

    Schmelz, J. T.; Kimble, J. A.; Saba, J. L. R.

    2012-09-20

    We use high-resolution spectral emission line data obtained by the SERTS instrument during three rocket flights to demonstrate a new approach for constraining electron densities of solar active region plasma. We apply differential emission measure (DEM) forward-fitting techniques to characterize the multithermal solar plasma producing the observed EUV spectra, with constraints on the high-temperature plasma from the Yohkoh Soft X-ray Telescope. In this iterative process, we compare line intensities predicted by an input source distribution to observed line intensities for multiple iron ion species, and search a broad range of densities to optimize {chi}{sup 2} simultaneously for the many available density-sensitive lines. This produces a density weighted by the DEM, which appears to be useful for characterizing the bulk of the emitting plasma over a significant range of temperature. This 'DEM-weighted density' technique is complementary to the use of density-sensitive line ratios and less affected by uncertainties in atomic data and ionization fraction for any specific line. Once the DEM shape and the DEM-weighted density have been established from the iron lines, the relative elemental abundances can be determined for other lines in the spectrum. We have also identified spectral lines in the SERTS wavelength range that may be problematic.

  15. Deriving Plasma Densities and Elemental Abundances from SERTS Differential Emission Measure Analysis

    NASA Technical Reports Server (NTRS)

    Schmelz, J. T.; Kimble, J. A.; Saba, J. L. R.

    2012-01-01

    We use high-resolution spectral emission line data obtained by the SERTS instrument during three rocket flights to demonstrate a new approach for constraining electron densities of solar active region plasma.We apply differential emission measure (DEM) forward-fitting techniques to characterize the multithermal solar plasma producing the observed EUV spectra, with constraints on the high-temperature plasma from the Yohkoh Soft X-ray Telescope. In this iterative process, we compare line intensities predicted by an input source distribution to observed line intensities for multiple iron ion species, and search a broad range of densities to optimize chi-square simultaneously for the many available density-sensitive lines. This produces a density weighted by the DEM, which appears to be useful for characterizing the bulk of the emitting plasma over a significant range of temperature. This "DEM-weighted density" technique is complementary to the use of density-sensitive line ratios and less affected by uncertainties in atomic data and ionization fraction for any specific line. Once the DEM shape and the DEM-weighted density have been established from the iron lines, the relative elemental abundances can be determined for other lines in the spectrum. We have also identified spectral lines in the SERTS wavelength range that may be problematic

  16. High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry.

    PubMed

    Paul, Maxence; Bridgestock, Luke; Rehkämper, Mark; van DeFlierdt, Tina; Weiss, Dominik

    2015-03-10

    A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a (207)Pb-(204)Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28±21 pg (1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12±4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700-1500 ppm and 1000-2000 ppm were achieved for (207)Pb/(206)Pb, (208)Pb/(206)Pb and (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor (204)Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the (206)Pb/(204)Pb ratios are well correlated

  17. Hydrogen isotope measurements of organic acids and alcohols by Pyrolysis-GC-MS-TC-IRMS

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Fu, Q.; Niles, P. B.

    2011-12-01

    One possible process responsible for methane generation on Mars is abiotic formation by Fischer-Tropsch-type (FTT) synthesis during serpentinization reactions. Measurement of carbon and hydrogen isotopes of intermediary organic compounds can help constrain the origin of this methane by tracing the geochemical pathway during formation. Of particular interest within the context of this work is the isotopic composition of organic intermediaries produced on the surfaces of mineral catalysts (i.e. magnetite) during hydrothermal experiments, and the ability to make meaningful and reproducible hydrogen isotope measurements. Reported here are results of experiments to characterize the hydrogen isotope composition of low molecular weight organic acids and alcohols. The presence of these organic compounds has been suggested by us and others as intermediary products made during mineral surface catalyzed reactions. This work compliments our previous study characterizing the carbon isotope composition of similar low molecular weight intermediary organic compounds (Socki, et al, American Geophysical Union Fall meeting, Abstr. #V51B-2189, Dec., 2010). Our hydrogen isotope measurements utilize a unique analytical technique combining Pyrolysis-Gas Chromatograph-Mass Spectrometry-High Temperature Conversion-Isotope Ratio Mass Spectrometry (Py-GC-MS-TC-IRMS). Our technique is unique in that it carries a split of the pyrolyzed GC-separated product to a Thermo DSQ-II° quadrupole mass spectrometer as a means of making qualitative and semi-quantitative compositional measurements of separated organic compounds, therefore both chemical and isotopic measurements can be carried out simultaneously on the same sample. Samples of carboxylic acid (C1 through C4) and alcohols (C1 through C4) were pyrolyzed at 200°C on a CDS Analytical. Inc. Model 5200° pyroprobe and passed through a Thermo Electron GC-MS-TC-IRMS system operating in continuous flow mode. The High Temperature Conversion step

  18. Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer

    NASA Astrophysics Data System (ADS)

    Hoegg, Edward D.; Barinaga, Charles J.; Hager, George J.; Hart, Garret L.; Koppenaal, David W.; Marcus, R. Kenneth

    2016-08-01

    In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs.

  19. Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer.

    PubMed

    Hoegg, Edward D; Barinaga, Charles J; Hager, George J; Hart, Garret L; Koppenaal, David W; Marcus, R Kenneth

    2016-08-01

    In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs. Graphical Abstract ᅟ.

  20. Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer.

    PubMed

    Hoegg, Edward D; Barinaga, Charles J; Hager, George J; Hart, Garret L; Koppenaal, David W; Marcus, R Kenneth

    2016-08-01

    In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs. Graphical Abstract ᅟ. PMID:27080006

  1. VAPOR PRESSURE ISOTOPE EFFECTS IN THE MEASUREMENT OF ENVIRONMENTAL TRITIUM SAMPLES.

    SciTech Connect

    Kuhne, W.

    2012-12-03

    Standard procedures for the measurement of tritium in water samples often require distillation of an appropriate sample aliquot. This distillation process may result in a fractionation of tritiated water and regular light water due to the vapor pressure isotope effect, introducing either a bias or an additional contribution to the total tritium measurement uncertainty. The magnitude of the vapor pressure isotope effect is characterized as functions of the amount of water distilled from the sample aliquot and the heat settings for the distillation process. The tritium concentration in the distillate is higher than the tritium concentration in the sample early in the distillation process, it then sharply decreases due to the vapor pressure isotope effect and becomes lower than the tritium concentration in the sample, until the high tritium concentration retained in the boiling flask is evaporated at the end of the process. At that time, the tritium concentration in the distillate again overestimates the sample tritium concentration. The vapor pressure isotope effect is more pronounced the slower the evaporation and distillation process is conducted; a lower heat setting during the evaporation of the sample results in a larger bias in the tritium measurement. The experimental setup used and the fact that the current study allowed for an investigation of the relative change in vapor pressure isotope effect in the course of the distillation process distinguish it from and extend previously published measurements. The separation factor as a quantitative measure of the vapor pressure isotope effect is found to assume values of 1.034 {+-} 0.033, 1.052 {+-} 0.025, and 1.066 {+-} 0.037, depending on the vigor of the boiling process during distillation of the sample. A lower heat setting in the experimental setup, and therefore a less vigorous boiling process, results in a larger value for the separation factor. For a tritium measurement in water samples, this implies that

  2. Measuring kinetic isotope effects in enzyme reactions using time-resolved electrospray mass spectrometry.

    PubMed

    Liuni, Peter; Olkhov-Mitsel, Ekaterina; Orellana, Arturo; Wilson, Derek J

    2013-04-01

    Kinetic isotope effect (KIE) measurements are a powerful tool for studying enzyme mechanisms; they can provide insights into microscopic catalytic processes and even structural constraints for transition states. However, KIEs have not come into widespread use in enzymology, due in large part to the requirement for prohibitively cumbersome experimental procedures and daunting analytical frameworks. In this work, we introduce time-resolved electrospray ionization mass spectrometry (TRESI-MS) as a straightforward, precise, and inexpensive method for measuring KIEs. Neither radioisotopes nor large amounts of material are needed and kinetic measurements for isotopically "labeled" and "unlabeled" species are acquired simultaneously in a single "competitive" assay. The approach is demonstrated first using a relatively large isotope effect associated with yeast alcohol dehydrogenase (YADH) catalyzed oxidation of ethanol. The measured macroscopic KIE of 2.19 ± 0.05 is consistent with comparable measurements in the literature but cannot be interpreted in a way that provides insights into isotope effects in individual microscopic steps. To demonstrate the ability of TRESI-MS to directly measure intrinsic KIEs and to characterize the precision of the technique, we measure a much smaller (12)C/(13)C KIE associated specifically with presteady state acylation of chymotrypsin during hydrolysis of an ester substrate.

  3. Distinguishing phosphate from fertilizers and wastewater treatment plant effluents in Western Canada using oxygen isotope measurements

    NASA Astrophysics Data System (ADS)

    Fau, Veronique; Nightingale, Michael; Tamburini, Frederica; Mayer, Bernhard

    2014-05-01

    The successful application of oxygen isotope ratios as a tracer for phosphate in aquatic ecosystems requires that different sources of phosphate are isotopically distinct. The objective of this study was to determine whether the oxygen isotope ratios of phosphate from fertilizers and effluents from wastewater treatment plants in Western Canada are isotopically distinct. Therefore, we carried out oxygen isotope analyses on phosphate in effluent from five different wastewater treatment plants (WWTP) in the Bow River watershed of Alberta, Canada. Samples were collected directly from the final effluent (post-UV) in Banff and Canmore upstream of Calgary, and from effluents of Calgary's WWTPs at Bonnybrook, Fish Creek and Pine Creek. We also carried out oxygen isotope analyses on a variety of phosphate-containing fertilizers that are widely used in Western Canada. Historically, most of the phosphate contained in manufactured fertilizers sold in Alberta came from two distinct deposits: 1) a weathered Pliocene igneous carbonatite located in eastern Canada, and 2) the Permian Phosphoria Formation in the western USA. Phosphate (PO43-) contained in the water or the fertilizer was concentrated and quantitatively converted to pure silver phosphate (Ag3PO4). The silver phosphate was then reduced with carbon in an oxygen free environment using a TC/EA pyrolysis reactor linked to a mass spectrometer where 18O/16O ratios of CO were measured in continuous flow mode. Preparation of samples for δ18OPO4 analyses was conducted using the Magnesium Induced Coprecipitation (MAGIC) method. Expected oxygen isotope ratios for phosphate in equilibrium with water (δ18Oeq) were calculated using the Longinelli and Nuti equation: T (° C) = 111.4 - 4.3 (δ18Oeq - δ18Owater). Measured δ18O values of phosphate for fertilizer samples varied from 8 to 25 oÈ®n average, fertilizer samples of sedimentary origin had higher δ18O values (15.8) than those of igneous origin (11.5). Phosphate isotopic

  4. Fate of Selenium in Soils at a Seleniferous Site Recorded by High Precision Se Isotope Measurements.

    PubMed

    Schilling, Kathrin; Johnson, Thomas M; Dhillon, Karaj S; Mason, Paul R D

    2015-08-18

    Selenium poisoning is a significant health problem in parts of Punjab, India, which is an area of intense agricultural productivity. To determine the complex soil dynamics that control distribution of Se in this area, we measured concentrations and δ(82/76)Se of bulk Se and individual Se pools in four soil profiles. This was compared against δ(82/76)Se of crops and groundwater used for irrigation. The isotopic composition of bulk Se and component Se pools reveal spatial heterogeneity. The bulk δ(82/76)Se show progressively lower values with increasing soil depth indicating the preferential migration of isotopically lighter Se downward through the soil profile. The δ(82/76)Se of water-soluble Se is isotopically heavier than δ(82/76)Se of adsorbed Se, suggesting Se isotope fractionation by reduction prior to scavenging by reactive minerals in the soil. The organically bound Se is isotopically lighter than water-soluble Se and correlates with the C/N ratio at different soil depths. Thus, Se immobilization by redox cycling controls the biogeochemical Se cycle in the soil. Se isotope ratios help to trace biochemical processes of Se in agricultural seleniferous soils and provide an important assessment for better soil management mitigating Se concentrations of ecotoxicological levels.

  5. Carbon and Hydrogen Isotope Measurements of Alcohols and Organic Acids by Online Pyroprobe-GC-IRMS

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.; Gibson, Everett K., Jr.

    2012-01-01

    The detection of methane in the atmosphere of Mars, combined with evidence showing widespread water-rock interaction during martian history, suggests that the production of methane on Mars may be the result of mineral surface-catalyzed CO2 and or CO reduction during Fisher-Tropsch Type (FTT) reactions. A better understanding of these reaction pathways and corresponding C and H isotope fractionations is critical to deciphering the synthesis of organic compounds produced under abiotic hydrothermal conditions. Described here is a technique for the extraction and analysis of both C and H isotopes from alcohols (C1-C4) and organic acids (C1-C6). This work is meant to provide a "proof of concept" for making meaningful isotope measurements on complex mixtures of solid-phase hydrocarbons and other intermediary products produced during high-temperature and high-pressure synthesis on mineral-catalyzed surfaces. These analyses are conducted entirely "on-line" utilizing a CDS model 5000 Pyroprobe connected to a Thermo Trace GC Ultra that is interfaced with a Thermo MAT 253 isotope ratio mass spectrometer operating in continuous flow mode. Also, this technique is designed to carry a split of the GC-separated product to a DSQ II quadrupole mass spectrometer as a means of making semi-quantitative compositional measurements. Therefore, both chemical and isotopic measurements can be carried out on the same sample.

  6. Effects of four different restoration treatments on the natural abundance of (15)n stable isotopes in plants.

    PubMed

    Temperton, Vicky M; Märtin, Lea L A; Röder, Daniela; Lücke, Andreas; Kiehl, Kathrin

    2012-01-01

    δ(15)N signals in plant and soil material integrate over a number of biogeochemical processes related to nitrogen (N) and therefore provide information on net effects of multiple processes on N dynamics. In general little is known in many grassland restoration projects on soil-plant N dynamics in relation to the restoration treatments. In particular, δ(15)N signals may be a useful tool to assess whether abiotic restoration treatments have produced the desired result. In this study we used the range of abiotic and biotic conditions provided by a restoration experiment to assess to whether the restoration treatments and/or plant functional identity and legume neighborhood affected plant δ(15)N signals. The restoration treatments consisted of hay transfer and topsoil removal, thus representing increasing restoration effort, from no restoration measures, through biotic manipulation to major abiotic manipulation. We measured δ(15)N and %N in six different plant species (two non-legumes and four legumes) across the restoration treatments. We found that restoration treatments were clearly reflected in δ(15)N of the non-legume species, with very depleted δ(15)N associated with low soil N, and our results suggest this may be linked to uptake of ammonium (rather than nitrate). The two non-legume species differed considerably in their δ(15)N signals, which may be related to the two species forming different kinds of mycorrhizal symbioses. Plant δ(15)N signals could clearly separate legumes from non-legumes, but our results did not allow for an assessment of legume neighborhood effects on non-legume δ(15)N signals. We discuss our results in the light of what the δ(15)N signals may be telling us about plant-soil N dynamics and their potential value as an indicator for N dynamics in restoration.

  7. Effects of Four Different Restoration Treatments on the Natural Abundance of 15N Stable Isotopes in Plants

    PubMed Central

    Temperton, Vicky M.; Märtin, Lea L. A.; Röder, Daniela; Lücke, Andreas; Kiehl, Kathrin

    2012-01-01

    δ15N signals in plant and soil material integrate over a number of biogeochemical processes related to nitrogen (N) and therefore provide information on net effects of multiple processes on N dynamics. In general little is known in many grassland restoration projects on soil–plant N dynamics in relation to the restoration treatments. In particular, δ15N signals may be a useful tool to assess whether abiotic restoration treatments have produced the desired result. In this study we used the range of abiotic and biotic conditions provided by a restoration experiment to assess to whether the restoration treatments and/or plant functional identity and legume neighborhood affected plant δ15N signals. The restoration treatments consisted of hay transfer and topsoil removal, thus representing increasing restoration effort, from no restoration measures, through biotic manipulation to major abiotic manipulation. We measured δ15N and %N in six different plant species (two non-legumes and four legumes) across the restoration treatments. We found that restoration treatments were clearly reflected in δ15N of the non-legume species, with very depleted δ15N associated with low soil N, and our results suggest this may be linked to uptake of ammonium (rather than nitrate). The two non-legume species differed considerably in their δ15N signals, which may be related to the two species forming different kinds of mycorrhizal symbioses. Plant δ15N signals could clearly separate legumes from non-legumes, but our results did not allow for an assessment of legume neighborhood effects on non-legume δ15N signals. We discuss our results in the light of what the δ15N signals may be telling us about plant–soil N dynamics and their potential value as an indicator for N dynamics in restoration. PMID:22645597

  8. The cosmic ray abundances of the platinum-lead elements as measured on HEAO-3

    NASA Technical Reports Server (NTRS)

    Fixsen, D. J.; Waddington, C. J.; Binns, W. R.; Israel, M. H.; Klarmann, J.; Garrard, T. L.; Newport, B. J.; Stone, E. C.

    1983-01-01

    The relative abundances of elements in the charge ranges of Z = 75-79 (platinum) and Z = 80-83 (lead) should be a sensitive indication of the contributions of the r- and s-processes in nucleosynthesis. Data from the HEAO 3 Heavy Nuclei Experiment are used to establish abundances, relative to iron, of these elements in the cosmic radiation, as well as the ratio of 'secondary' elements, in the Z = 62-74 range, to the primary lead-platinum elements. These results appear to suggest that either the source abundances are deficient in s-process elements or that they are not organized solely by first ionization potential. In addition, present propagation models can adequately represent the relative abundances of primary and secondary elements.

  9. Mass measurements of short-lived isotopes in a penning trap

    SciTech Connect

    Kern, F.; Egelhof, P.; Hilberath, T.; Kalinowsky, H.; Kluge, H.h.; Kunz, K.; Schweikhard, L.; Stolzenberg, H.; Moore, R.B.; Audi, G.; and others

    1987-12-10

    A mass spectrometer has been set up at the on-line isotope separator ISOLDE at CERN/Geneva. Mass-separated radioactive ions are stored in a Penning trap. Their mass is determined by a measurement of the cyclotron frequency in the magnetic field of a superconducting magnet. A resolving power of up to 300.000 and a precision of some 10 keV were determined in case of mass measurements of neutron-deficient RB and Cs isotopes. The resonance of the isobars /sup 88/Sr and /sup 88/Rb were clearly resolved and evidence was obtained for an isomer in /sup 122/Cs.

  10. Measurement of the Elemental Abundances in Four Rich Clusters of Galaxies. I. Observations

    NASA Astrophysics Data System (ADS)

    Mushotzky, R.; Loewenstein, M.; Arnaud, K. A.; Tamura, T.; Fukazawa, Y.; Matsushita, K.; Kikuchi, K.; Hatsukade, I.

    1996-08-01

    The elemental abundances of O, Ne, Mg, Si, S, Ca, Ar, and Fe for four clusters of galaxies (Abell 496, 1060, 2199, and AWM 7) are determined from X-ray spectra derived from Advanced Satellite for Cosmology and Astrophysics performance verification phase observations. Since the gas in the outer parts of the cluster is optically thin and virtually isothermal, the abundance analysis is very straightforward compared to the analysis of stellar or H II region spectra. We find that the abundance ratios of all four clusters are very similar. The mean abundances of O, Ne, Si, S, and Fe are 0.48, 0.62, 0.65, 0.25, and 0.32, respectively, relative to solar. The abundances of Si, S, and Fe are unaffected by the uncertainties in the atomic physics of the Fe L shell. The abundances of Ne and Mg and to a lesser extent O are affected by the present uncertainties in Fe L physics and are thus somewhat more uncertain. The Fe abundances derived from the Fe L lines agree well with those derived from the Fe K lines for these clusters. The observed ratio of the relative abundance of elements is consistent with an origin of all the metals in Type II supernovae. The presence of large numbers of Type II supernovae during the early stages of evolution of cluster galaxies is a very strong constraint on all models of galaxy and chemical evolution and implies either a very flat initial mass function or bimodal star formation during the period when most of the metals were created.

  11. Measuring fish abundance in a weir trap using an acoustical-optical platform.

    PubMed

    Miksis-Olds, Jennifer L; Stokesbury, Kevin D E

    2007-10-01

    Data recorded by a bottom mounted survey platform deployed within the opening of a fishing weir were used to calculate species specific abundance estimates for comparison to the weir catch. Abundance estimates were calculated from the combination of sonar and video information recorded by the Acoustical-Optical Platform (AOP). Echo counting was used to detect individual moving targets in the sonar images with the application of a background removal technique utilizing a moving average filter. Video images provided species identification of acoustic targets. Video images and differences in target strength distributions reflected a change in dominant species from each deployment which was confirmed with the weir catch. The algorithm used to calculate AOP abundance estimates was most accurate in predicting abundance for species comprising at least 13% of the overall catch by weight. Close agreement between the species specific AOP estimates and absolute abundances of each species suggests that the combination of acoustic and video data is a powerful combination for accurately identifying fish species and predicting abundance.

  12. 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

  13. Isotope-Shift Measurement of High-energy Highly Charged Ion Beams

    NASA Astrophysics Data System (ADS)

    Ozawa, S.; Ariga, T.; Inabe, N.; Kase, M.; Tanihata, I.; Wakasugi, M.; Yano, Y.

    2001-10-01

    Isotope-shift measurement by the laser spectroscopic method was aimed to apply for radioactive isotope beams up to uranium created by projectile fragmentation at RIKEN RI beam factory (T. Katayama, et al.,): Nucl. Phys., A626, 545c (1997).to make a systematic study of the mean square nuclear charge radii. The present work was started to verify the feasibility of the method. Projectile fragments are high-energy highly charged ions and weak currents. Therefore we designed ultralow-background photon-detection system (M. Wakasugi, et al.,): Nucl. Instr. and Meth., A419, 50 (1998).for collinear laser spectroscopy of such ion beams. To demonstrate isotope-shift measurement, we measured precisely the 1s2s ^3S_1-1s2p ^3P_0,1,2 transition energy of He-like ^12C ion accelerated up to 0.9 MeV/u and ^13C ion 0.6 MeV/u. For the precision measurement, the uncertainty coming from the ambiguity in the absolute ion beam velocity was suppressed by means of that the resonance energy was measured by two laser beams which propagate in parallel and anti-parallel directions to the ion beam. As the result, isotope shifts of these transitions were obtained with the accuracy of 10 %. The lower limit of the ion-beam intensity for the measurement is estimated to be 2000 ions/s.

  14. Interchange for Joint Research Entitled: Measurement of Stable Nitrogen and Sulfur Isotopes

    NASA Technical Reports Server (NTRS)

    Becker, Joseph F.; Valentin, Jose

    1997-01-01

    Viking measurements of the Martian atmosphere indicate a value of N-15/N-14 which is markedly greater than that found in Earth's atmosphere. These isotopic measurements provide a powerful diagnostic tool which may be used to derive valuable information regarding the past history of Mars and they have been used to place important constraints on the evolution of Mars' atmosphere. Initial partial pressures of nitrogen, outgassing rates, and integrated deposition of nitrogen into minerals have been calculated from this important atmospheric data (McElroy et al., 1976 and 1977; Fox and Dalgarno, 1983). The greater precision obtained in laser spectrometer isotopic measurements compared to the Viking data will greatly improve these calculated values. It has also been proposed that the N-15/N-14 value in Mars' atmosphere has increased monotonically over time (McElroy et al., 1977; Fox and Dalgarno, 1983; Wallis, 1989) owing to preferential escape of atmospheric 14N to space. Nitrogen isotopic ratios might be used to identify relatively ancient crustal rocks (R. Mancinelli, personal communication), and perhaps determine relative aces of surface samples. As a first step in successfully measuring nitrogen isotopes optically we have demonstrated the measurement of 15NI14N to a precision of 0.1% (See Figures 1-4) using a tunable diode laser and an available gas (N-,O) with spectral lines in the 2188 cm-1 region. The sample and reference gas cells contained gases of identical isotopic composition so that the 15NI14N absorption ratio determined from the sample cell, when divided by the 15NI14N absorption ratio determined from the reference cell, should yield an ideal value of unity. The average measured value of this "ratio of ratios" was 0.9983 with a standard deviation (20 values) of 0.0010. This corresponds to a precision of 0.1% (1 per mil) for nitrogen isotopes, a value sufficiently precise to provide important isotopic data of interest to exobiologists. The precision

  15. Interchange for Joint Research Entitled: 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. A small stable isotope laser spectrometer with a 10 cm path gas cell was designed and constructed. The cell was integrated with a liquid nitrogen cooled tunable diode laser and indium antimonide detector for evaluation. Using the small gas cell, preliminary measurements of 13C/12C in CO2 were made employing single-beam sequential acquisitions of the required spectral data. The results indicate an accuracy of 0.1% which is sufficiently high to make meaningful measurements of martian samples. In addition, improvements in the spectrometer gas handling system have been made to markedly reduce C-13/C-12 isotopic fractionation during sample gas cell loading which we expect will lead to further improvements in precision and accuracy. An important part of making isotopic ratio measurements in solid samples using diode lasers is the conversion of the elements of interest to molecules that have absorption spectra in the mid-ir spectral range accessible by tunable diode lasers. In this project we have investigated the necessary sample preparation procedures to extract carbon, an element of astrobiological importance, from model soil compounds and to convert it to CO2, a molecule with appropriate optical absorption characteristics for reliable laser spectrometer isotopic ratio measurements of 13C/12C. We have considered calcium carbonate as a model for a component of the martian regolith

  16. New attempts to identify core-mantle interactions in plume-derived materials using ultra-high precision tungsten isotope measurements

    NASA Astrophysics Data System (ADS)

    Touboul, M.; Puchtel, I. S.; Walker, R. J.

    2010-12-01

    Some mantle plume derived materials show coupled 187,186Os enrichments relative to upper-mantle materials that have been interpreted by some to reflect core-mantle interaction (Brandon et al., 1999, 2003, Puchtel et al., 2005). In addition to osmium, tungsten is another element whose isotopic composition can potentially be used to trace core-mantle interactions. Tungsten has one radiogenic isotope, 182W, a decay product of 182Hf, with a half-life of ~9 Myr. Like Os, W is siderophile, under reducing conditions, and, hence, is preferentially incorporated into Earth’s core, whereas Hf is lithophile and is retained in the mantle. Fractionation of Hf from W during core formation is predicted to have led to large differences in 182W/184W between the core and mantle. The use of W isotopes as tracers of core-mantle interaction has been hampered by limitations in the ability to measure W isotopic ratios at the level of ± 10 ppm or better. Within analytical uncertainty, MC-ICP-MS measurements of terrestrial rocks investigated so far show no resolvable 182W anomalies (Scherstén et al., 2004). Over the past year, we have developed a new ultra-high precision 182W/184W measurement protocol using a Triton thermal ionization mass spectrometer, allowing us to resolve 182W anomalies at a ± 6 ppm level (2σ, n=40). All W isotope measurements are performed in a negative ionization mode (WO3-) using a dynamic acquisition scheme. This precision improvement allows us to more rigorously interrogate the W isotopic compositions of materials with potentially deep mantle origins. A major problem in this application of W isotopes is the acquisition of mantle-derived materials that have not been contaminated with crustal W. Here we present W abundances, measured using isotope dilution, and corresponding ultra-high precision W isotopic composition measurements of Archean komatiites from the Kostomuksha greenstone belt (Baltic Shield), for which coupled 186Os-187Os enrichment has been

  17. Evaluation strategies for isotope ratio measurements of single particles by LA-MC-ICPMS.

    PubMed

    Kappel, S; Boulyga, S F; Dorta, L; Günther, D; Hattendorf, B; Koffler, D; Laaha, G; Leisch, F; Prohaska, T

    2013-03-01

    Data evaluation is a crucial step when it comes to the determination of accurate and precise isotope ratios computed from transient signals measured by multi-collector-inductively coupled plasma mass spectrometry (MC-ICPMS) coupled to, for example, laser ablation (LA). In the present study, the applicability of different data evaluation strategies (i.e. 'point-by-point', 'integration' and 'linear regression slope' method) for the computation of (235)U/(238)U isotope ratios measured in single particles by LA-MC-ICPMS was investigated. The analyzed uranium oxide particles (i.e. 9073-01-B, CRM U010 and NUSIMEP-7 test samples), having sizes down to the sub-micrometre range, are certified with respect to their (235)U/(238)U isotopic signature, which enabled evaluation of the applied strategies with respect to precision and accuracy. The different strategies were also compared with respect to their expanded uncertainties. Even though the 'point-by-point' method proved to be superior, the other methods are advantageous, as they take weighted signal intensities into account. For the first time, the use of a 'finite mixture model' is presented for the determination of an unknown number of different U isotopic compositions of single particles present on the same planchet. The model uses an algorithm that determines the number of isotopic signatures by attributing individual data points to computed clusters. The (235)U/(238)U isotope ratios are then determined by means of the slopes of linear regressions estimated for each cluster. The model was successfully applied for the accurate determination of different (235)U/(238)U isotope ratios of particles deposited on the NUSIMEP-7 test samples. PMID:23314620

  18. Carbon and Sulfur Isotopic Composition of Yellowknife Bay Sediments: Measurements by the Sample Analysis at Mars (SAM) Quadrupole Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Franz, H. B.; Mahaffy, P. R.; Stern, J. C.; Eigenbrode, J. L.; Steele, A.; Ming, D. W.; McAdam, A. C.; Freissinet, C.; Glavin, D. P.; Archer, P. D.; Brunner, A. E.; Grotzinger,J. P.; Jones, J. H.; Leshin, L. A.; Miller, K.; Morris, R. V.; Navarro-Gonzalez, R.; Niles, P. B.; Owen, T. C.; Summons, R. E.; Sutter, B.; Webster, C. R.

    2014-01-01

    Since landing at Gale Crater in Au-gust 2012, the Sample Analysis at Mars (SAM) instru-ment suite on the Mars Science Laboratory (MSL) “Curiosity” rover has analyzed solid samples from the martian regolith in three locations, beginning with a scoop of aeolian deposits from the Rocknest (RN) sand shadow. Curiosity subsequently traveled to Yellowknife Bay, where SAM analyzed samples from two separate holes drilled into the Sheepbed Mudstone, designated John Klein (JK) and Cumberland (CB). Evolved gas analysis (EGA) of all samples revealed the presence of H2O as well as O-, C- and S-bearing phas-es, in most cases at abundances below the detection limit of the CheMin instrument. In the absence of definitive mineralogical identification by CheMin, SAM EGA data can help provide clues to the mineralogy of volatile-bearing phases through examination of tem-peratures at which gases are evolved from solid sam-ples. In addition, the isotopic composition of these gas-es may be used to identify possible formation scenarios and relationships between phases. Here we report C and S isotope ratios for CO2 and SO2 evolved from the JK and CB mudstone samples as measured with SAM’s quadrupole mass spectrometer (QMS) and draw com-parisons to RN.

  19. Capabilities to measure isotopic ratios in water at comet 67P/Churyumov-Gerasimenko with ROSINA/DFMS

    NASA Astrophysics Data System (ADS)

    Hässig, Myrtha; Altwegg, K.; Balsiger, H.; Berthelier, J.; Calmonte, U.; Combi, M. R.; De Keyser, J.; Fiethe, B.; Fuselier, S. A.; Rubin, M.; ROSINA-Team

    2013-10-01

    The likelihood that comets may have delivered part of the water to Earth has been reinforced by the recent observation of the earth-like D/H ratio in Jupiter-family comet 103P/Hartley 2 by Hartogh et al. (2011). Prior to this observation, results from several Oort cloud comets indicated a factor of 2 enrichment of deuterium relative to the abundance at Earth. The European Space Agency’s Rosetta spacecraft will encounter comet 67P/Churyumov-Gerasimenko, another Jupiter-family comet of likely Kuiper belt origin, in 2014 and accompany it from almost aphelion to and past perihelion. Onboard Rosetta is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) which consists of two mass spectrometers and a pressure sensor [Balsiger et al. 2007]. With its unprecedented mass resolution, for a space-borne instrument, the Double Focusing Mass Spectrometer (DFMS), one of the major subsystems of ROSINA, will be able to obtain unambiguously the ratios of the isotopes in water from in situ measurements in the coma around the comet. We will discuss the performance of this sensor on the basis of measurements of the terrestrial hydrogen and oxygen isotopic ratios performed with the flight spare instrument in the lab. We also show that the instrument on Rosetta is capable of measuring the D/H even in the very low density water background released by the spacecraft. This capability demonstrates that ROSINA should obtain very sensitive measurements of these ratios in the cometary environment. These measurements will allow detection of fractionation as function of the distance from the nucleus as well as fractionation due to mechanisms that are correlated with heliocentric distance. References: H. Balsiger et al., Space Sci. Rev., 128, 745-801 P. Hartogh et al., Nature, 478, 218-220, 2011 M. Hässig et al., PSS, 84, 148-152, 2013

  20. D/H Isotope Ratio Measurements of Atmospheric Volatile Organic Compounds

    NASA Astrophysics Data System (ADS)

    Meisehen, Thomas; Bühler, Fred; Koppmann, Ralf; Krebsbach, Marc

    2015-04-01

    Analysis of isotope ratios in atmospheric volatile organic compounds (VOC) is a reliable method to allocate their sources, to estimate atmospheric residence times and investigate physical and chemical processes on various temporal and spatial scales. Most investigations yet focus on carbon isotope ratios. Certainly more detailed information can be gained by the ratio of deuterium (D) to hydrogen (H) in VOC, especially due to the high mass ratio. Combining measurements of carbon and hydrogen isotopes could lead to considerable improvement in our understanding of atmospheric processes. For this purpose we set up and thoroughly characterised a gas chromatograph pyrolysis isotope ratio mass spectrometer to measure the D/H ratio in atmospheric VOC. From a custom-made gas standard mixture VOC were adsorbed on Tenax®TA which has the advantage that CO2 is not preconcentrated when measuring ambient air samples. Our results show that the pyrolysis method has significant impact on the D/H ratios. A pyrolysis temperature of at least 1723 K and conditioning of the ceramic tube on a regular basis is essential to obtain reproducible D/H isotope ratios. For an independent comparison D/H ratios of the pure VOC used in the gas standard were determined using elemental analysis by Agroisolab (Jülich, Germany). Comparisons of 10 VOC show perfect agreement within the standard deviations of our measurements and the errors given by Agroisolab, e.g. for n-pentane, toluene, 4-methyl-2-pentanone and n-octane. A slight mean difference of 5.1 o was obtained for n-heptane while significant mean differences of 15.5 o and 20.3 o arose for 1,2,4-trimethylbenzene and isoprene, respectively. We further demonstrate the stability of our system and show that the sample preparation does not affect the isotope ratios. Moreover the applicability of our system to ambient air samples is demonstrated.

  1. Stable isotope ratio measurements of royal jelly samples for controlling production procedures: impact of sugar feeding.

    PubMed

    Daniele, Gaëlle; Wytrychowski, Marine; Batteau, Magali; Guibert, Sylvie; Casabianca, Hervé

    2011-07-30

    The carbon and nitrogen stable ratios of royal jelly (RJ) samples from various origins are determined using an elemental analyser linked online to an isotope ratio mass spectrometer to evaluate authenticity and adulteration. The (13)C/(12)C and (15)N/(14)N stable isotope ratios are measured in more than 500 RJs (domestic, imported and derived from feeding experiments) in order to obtain isotopic measurements that take into account seasonal, botanical and geographical effects. Authenticity intervals are established for traditional beekeeping practices, without feeding, in the range -22.48 to -27.90‰ for δ(13)C. For these samples, the δ(15)N values range from -1.58 to 7.98‰, depending on the plant sources of pollen and nectar. The δ(13)C values of the commercial samples vary from -18.54 to -26.58‰. High δ(13)C values are typical of sugar cane or corn syrups which have distinctive isotopic (13)C signatures because both plants use the C4 photosynthetic cycle, in contrast to most RJs which are derived from C3 plants. These differences in the (13)C-isotopic composition allow the detection of the addition of such sugars. RJs from traditional sources and from industrial production by sugar feeding are thus successfully distinguished. PMID:21698675

  2. Fast Scanning Single Collector ICP-MS for Low Level Isotope Ratio Measurements

    NASA Astrophysics Data System (ADS)

    Newman, K.; Georg, B.

    2010-12-01

    Multiple collector (MC)-ICP-MS is recognized as a workhorse in the field of isotope ratio measurements. With its unrivalled precision, high sample throughput and multi-element coverage, MC-ICPMS has opened up new areas of study in earth, environmental and biological sciences. However, SC-ICP-MS is fit for purpose for many applications where sample amount is limited and fractionations are relatively large. To compensate for the inherent ion beam instability associated with the ICP ion source, fast scanning magnetic sector instruments are used. Here, we describe and discuss the use of the Nu Attom SC-ICP-MS for low level isotope ratio measurements. The Nu Attom is a double focusing magnetic sector mass spectrometer with unique fast scanning capabilities. Deflectors located at the entrance and exit of the flight tube are used to alter the effective magnet radius by changing the ion trajectory. This enables a fast electrostatic scan over a mass range of approximately 40%. In contrast to other fast scanning magnetic sector instruments, there is no change in the ion energy which may introduce additional mass bias effects. The Nu Attom also has fully adjustable source and collector slits. This facilitates measurements in medium mass resolution (R=1500-2500), whilst maintaining a flat topped peak necessary for precise isotope ratio measurements. The potential applications of the Nu Attom in isotope ratio measurements will be explored.

  3. Tracing the dispersion of contaminated sediment with plutonium isotope measurements in coastal catchments of Fukushima Prefecture

    NASA Astrophysics Data System (ADS)

    Evrard, Olivier; Pointurier, Fabien; Onda, Yuichi; Chartin, Caroline; Hubert, Amélie; Lepage, Hugo; Pottin, Anne-Claire; Lefèvre, Irène; Bonté, Philippe; Laceby, J. Patrick; Ayrault, Sophie

    2015-04-01

    The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident led to important releases of radionuclides into the environment, and trace levels of plutonium (Pu) were detected in northeastern Japan. However, measurement of Pu isotopic atom and activity ratios is required to differentiate between the contributions of global nuclear test fallout and FDNPP emissions. In this study, we measured Pu isotopic ratios in recently deposited sediments along rivers draining the most contaminated part of the inland radioactive plume. To this end, we carried out a thorough chemical purification and concentration of Pu from sediment samples (5 g dry material) and precise isotopic measurements using a double-focusing sector field ICP-MS. Results showed that the entire range of measured Pu isotopes (i.e., 239Pu, 240Pu, 241Pu, and 242Pu) were detected in all samples, although in extremely low concentrations. The 241Pu/239Pu atom ratios measured in sediment deposits (0.0017-0.0884) were significantly higher than the corresponding values attributed to the global fallout (0.00113±0.00008 on average in the Northern Hemisphere between 31°-71°N). The results indicated the presence of Pu from FDNPP, in slight excess compared to the Pu background from global fallout, representing up to ca. 60% of Pu in the analyzed samples. These results demonstrate that this radionuclide has been transported relatively long distances (45 km) from FDNPP and deposited in rivers representing a potential source of Pu to the ocean.

  4. Natural Ca Isotope Composition of Urine as a Rapid Measure of Bone Mineral Balance

    NASA Astrophysics Data System (ADS)

    Skulan, J.; Gordon, G. W.; Morgan, J.; Romaniello, S. J.; Smith, S. M.; Anbar, A. D.

    2011-12-01

    Naturally occurring stable Ca isotope variations in urine are emerging as a powerful tool to detect changes in bone mineral balance. Bone formation depletes soft tissue of light Ca isotopes while bone resorption releases isotopically light Ca into soft tissue. Previously published work found that variations in Ca isotope composition could be detected at 4 weeks of bed rest in a 90-day bed rest study (data collected at 4, 8 and 12 weeks). A new 30-day bed rest study involved 12 patients on a controlled diet, monitored for 7 days prior to bed rest and 7 days post bed rest. Samples of urine, blood and food were collected throughout the study. Four times daily blood samples and per void urine samples were collected to monitor diurnal or high frequency variations. An improved chemical purification protocol, followed by measurement using multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) allowed accurate and precise determinations of mass-dependent Ca isotope variations in these biological samples to better than ±0.2% (δ44/42Ca) on <25 μg of Ca. Results from this new study show that Ca isotope ratios shift in a direction consistent with net bone loss after just 7 days, long before detectible changes in bone density by X-ray measurements occur. Consistent with this interpretation, the Ca isotope variations track changes observed in N-teleopeptide, a bone resorption biomarker. Bone-specific alkaline phosphatase, a bone formation biomarker, is unchanged over this period. Ca isotopes can in principle be used to quantify net changes in bone mass. Using a mass-balance model, our results indicate an average loss of 0.62 ± 0.16 % in bone mass over the course of this 30-day study. This is consistent with the rate of bone loss in longer-term studies as seen by X-ray measurements. This Ca isotope technique should accelerate the pace of discovery of new treatments for bone disease and provide novel insights into the dynamics of bone metabolism.

  5. Size-Based Hydroacoustic Measures of Within-Season Fish Abundance in a Boreal Freshwater Ecosystem

    PubMed Central

    Pollom, Riley A.; Rose, George A.

    2015-01-01

    Eleven sequential size-based hydroacoustic surveys conducted with a 200 kHz split-beam transducer during the summers of 2011 and 2012 were used to quantify seasonal declines in fish abundance in a boreal reservoir in Manitoba, Canada. Fish densities were sufficiently low to enable single target resolution and tracking. Target strengths converted to log2-based size-classes indicated that smaller fish were consistently more abundant than larger fish by a factor of approximately 3 for each halving of length. For all size classes, in both years, abundance (natural log) declined linearly over the summer at rates that varied from -0.067.day-1 for the smallest fish to -0.016.day-1 for the largest (R2 = 0.24–0.97). Inter-annual comparisons of size-based abundance suggested that for larger fish (>16 cm), mean winter decline rates were an order of magnitude lower (-0.001.day-1) and overall survival higher (71%) than in the main summer fishing season (mean loss rate -0.038.day-1; survival 33%). We conclude that size-based acoustic survey methods have the potential to assess within-season fish abundance dynamics, and may prove useful in long-term monitoring of productivity and hence management of boreal aquatic ecosystems. PMID:25875467

  6. Assessing the ceRNA hypothesis with quantitative measurements of miRNA and target abundance

    PubMed Central

    Denzler, Rémy; Agarwal, Vikram; Stefano, Joanna; Bartel, David P; Stoffel, Markus

    2014-01-01

    SUMMARY Recent studies have reported that competitive endogenous RNAs (ceRNAs) can act as sponges for a microRNA (miRNA) through their binding sites and that changes in ceRNA abundances from individual genes can modulate the miRNA’s activity. Consideration of this hypothesis would benefit from knowing the quantitative relationship between a miRNA and its endogenous target sites. Here, we altered intracellular target-site abundance through expression of a miR-122 target in hepatocytes and livers, and analyzed the effects on miR-122 target genes. Target repression was released in a threshold-like manner at high target-site abundance (≥1.5×105 added target sites per cell), and this threshold was insensitive to the effective levels of the miRNA. Furthermore, in response to extreme metabolic liver disease models, global target-site abundance of hepatocytes did not change sufficiently to affect miRNA-mediated repression. Thus, modulation of miRNA target abundance is unlikely to cause significant effects on gene expression and metabolism through a ceRNA effect. PMID:24793693

  7. The stability and calibration of water vapor isotope ratio measurements during long-term deployments

    NASA Astrophysics Data System (ADS)

    Bailey, A.; Noone, D.; Berkelhammer, M.; Steen-Larsen, H. C.; Sato, P.

    2015-10-01

    With the recent advent of commercial laser absorption spectrometers, field studies measuring stable isotope ratios of hydrogen and oxygen in water vapor have proliferated. These pioneering analyses have provided invaluable feedback about best strategies for optimizing instrumental accuracy, yet questions still remain about instrument performance and calibration approaches for multi-year field deployments. With clear scientific potential for using these instruments to carry out monitoring of the hydrological cycle, this study examines the long-term stability of the isotopic biases associated with three cavity-enhanced laser absorption spectrometers - calibrated with different systems and approaches - at two remote field sites: Mauna Loa Observatory, Hawaii, USA, and Greenland Environmental Observatory, Summit, Greenland. The analysis pays particular attention to the stability of measurement dependencies on water vapor concentration and also evaluates whether these so-called concentration dependences are sensitive to statistical curve-fitting choices or measurement hysteresis. The results suggest evidence of monthly-to-seasonal concentration-dependence variability - which likely stems from low signal-to-noise at the humidity-range extremes - but no long-term directional drift. At Mauna Loa, where the isotopic analyzer is calibrated by injection of liquid water standards into a vaporizer, the largest source of inaccuracy in characterizing the concentration dependence stems from an insufficient density of calibration points at low water vapor volume mixing ratios. In comparison, at Summit, the largest source of inaccuracy is measurement hysteresis associated with interactions between the reference vapor, generated by a custom dew point generator, and the sample tubing. Nevertheless, prediction errors associated with correcting the concentration dependence are small compared to total measurement uncertainty. At both sites, changes in measurement repeatability that are

  8. A New Technology for Elimination of Isobaric Interferences in Ultra-Sensitive Isotope Measurements

    NASA Astrophysics Data System (ADS)

    Eliades, J.; Zhao, X.; Litherland, T.; Kieser, L.; Cousins, L.; Ye, J.

    2009-05-01

    Accelerator Mass Spectrometry (AMS) is a technique used for ultra-sensitive abundance ratio measurements. Applications in the earth sciences typically involve the measurement of 10Be, 14C, 26Al, 36Cl, 41Ca and 129I, for example in exposure dating and ground water studies, sometimes yielding ratios of unstable to stable isotope at 10-15 or less. AMS is most effective when the stable atomic isobar does not form a stable negative ion. When this is not the case larger accelerators have been required. Here we report preliminary tests of a prototype radio-frequency quadrupole collision cell system for the removal of isobaric interferences for Accelerator Mass Spectrometry (AMS) and for studies of anion-gas interactions at low energy. A fully developed ISA could allow smaller AMS systems to handle a wider range of samples. This system, known as an Isobar Separator for Anions (ISA), decelerates a mass-analyzed beam of anions from an energy typically generated by an AMS ion source (˜20 keV) down to < 10 eV. Radiofrequency quardrupoles and electrostatic lenses then guide the ions through the collision cell where ion-gas reactions attenuate most of the unwanted isobars and ion-gas elastic collisions reduce the ion energy and energy spread of the ion beam (cool the ions). The anions are then reaccelerated to their original energy for injection into the rest of the AMS system. With the ISA installed on a full 3MV AMS system, attenuations of 32S-, 12C3-, and 39K- by six, seven, and > ten orders of magnitude respectively have been achieved using NO2 gas in the collision cell. Transmission of a non-reactive anion is approximately 10-20% through the ISA. Further measurements of four 36Cl standards (4 x 10-13 < 36Cl/Cl < 4 x 10-11) and an estimate of the attenuation of the interfering isobars 36S-and 12C3-is also described.

  9. Mass measurements of isotopes of Nb, Mo, Tc, Ru, and Rh along the νp- and rp-process paths using the Canadian Penning trap mass spectrometer

    NASA Astrophysics Data System (ADS)

    Fallis, J.; Clark, J. A.; Sharma, K. S.; Savard, G.; Buchinger, F.; Caldwell, S.; Chaudhuri, A.; Crawford, J. E.; Deibel, C. M.; Gulick, S.; Hecht, A. A.; Lascar, D.; Lee, J. K. P.; Levand, A. F.; Li, G.; Lundgren, B. F.; Parikh, A.; Russell, S.; Scholte-van de Vorst, M.; Scielzo, N. D.; Segel, R. E.; Sharma, H.; Sinha, S.; Sternberg, M. G.; Sun, T.; Tanihata, I.; van Schelt, J.; Wang, J. C.; Wang, Y.; Wrede, C.; Zhou, Z.

    2011-10-01

    The reaction paths of two proposed nucleosynthetic processes on the proton-rich side of stability, the rp and νp processes, pass through a region of isotopes between Mo and Pd where masses had long gone unmeasured. Precise knowledge of the paths and final abundances of these two processes has been limited by the corresponding lack of precision in the proton-separation energies Sp when derived from extrapolated masses. The masses of 18 neutron-deficient isotopes of Nb, Mo, Tc, Ru, and Rh have been measured using the Canadian Penning trap mass spectrometer. Three of the masses presented, 90Mo, 91Mo, and 93Tc, provide the first direct measurement of the masses of these nuclides, and the others provide confirmation of recent measurements using other Penning traps. Included in this work is a measurement of the mass of 87Mo, which differs by 3.7σ from the mass presented in the 2003 Atomic Mass Evaluation. This leads to a change in the Sp value of 88Tc which reduces the suppression of flow of the νp-process path through 87Mo(p,γ)88Tc reported following the mass measurement of 88Tc [C. Weber , Phys. Rev. CPRVCAN0556-281310.1103/PhysRevC.78.054310 78, 054310 (2008)]. This in turn affects the resulting νp-process abundances.

  10. Measurement of the isotopic composition of the iron-group elements in the galactic cosmic radiation

    NASA Technical Reports Server (NTRS)

    Tarle, G.; Ahlen, S. P.; Cartwright, B. G.

    1978-01-01

    With an average mass resolution of approximately 0.65 amu the isotopic composition of Cr, Mn, Fe, and Ni in the galactic cosmic radiation has been measured for energies of about 300 to 600 MeV/amu at the detector. Large deviations from solar-system source composition reported by other workers are not observed.

  11. Iron and Nickel Isotope Measurements on SiC X Grains with CHILI

    NASA Astrophysics Data System (ADS)

    Kodolányi, J.; Stephan, T.; Trappitsch, R.; Hoppe, P.; Pignatari, M.; Davis, A. M.; Pellin, M. J.

    2016-08-01

    New measurements with CHILI on SiC X grains provide more detailed Fe and Ni isotope data than previous NanoSIMS analyses. The new data suggest that Fe-Ni fractionation may occur in supernova ejecta before SiC condensation.

  12. Reconciling the Differences between the Measurements of CO2 Isotopes by the Phoenix and MSL Landers

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Mahaffy, P. R.; Atreya, S.; Pavlov, A. A.; Trainer, M.; Webster, C. R.; Wong, M.

    2014-01-01

    Precise stable isotope measurements of the CO2 in the martian atmosphere have the potential to provide important constraints for our understanding of the history of volatiles, the carbon cycle, current atmospheric processes, and the degree of water/rock interaction on Mars. There have been several different measurements by landers and Earth based systems performed in recent years that have not been in agreement. In particular, measurements of the isotopic composition of martian atmospheric CO2 by the Thermal and Evolved Gas Analyzer (TEGA) instrument on the Mars Phoenix Lander and the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) are in stark disagreement. This work attempts to use measurements of mass 45 and mass 46 of martian atmospheric CO2 by the SAM and TEGA instruments to search for agreement as a first step towards reaching a consensus measurement that might be supported by data from both instruments.

  13. High-accuracy mass measurements of neutron-rich Kr isotopes

    SciTech Connect

    Delahaye, P.; Kellerbauer, A.; Audi, G.; Lunney, D.; Blaum, K.; George, S.; Carrel, F.; Herfurth, F.; Yazidjian, C.; Herlert, A.; Schweikhard, L.; Kluge, H.-J.

    2006-09-15

    The atomic masses of the neutron-rich krypton isotopes {sup 84,86-95}Kr have been determined with the tandem Penning trap mass spectrometer ISOLTRAP with uncertainties ranging from 20 to 220 ppb. The masses of the short-lived isotopes {sup 94}Kr and {sup 95}Kr were measured for the first time. The masses of the radioactive nuclides {sup 89}Kr and {sup 91}Kr disagree by 4 and 6 standard deviations, respectively, from the present Atomic-Mass Evaluation database. The resulting modification of the mass surface with respect to the two-neutron separation energies as well as implications for mass models and stellar nucleosynthesis are discussed.

  14. Towards high precision measurements of nuclear g-factors for the Be isotopes

    NASA Astrophysics Data System (ADS)

    Takamine, A.; Wada, M.; Okada, K.; Ito, Y.; Schury, P.; Arai, F.; Katayama, I.; Imamura, K.; Ichikawa, Y.; Ueno, H.; Wollnik, H.; Schuessler, H. A.

    2016-06-01

    We describe the present status of future high-precision measurements of nuclear g-factors utilizing laser-microwave double and laser-microwave-rf triple resonance methods for online-trapped, laser-cooled radioactive beryllium isotope ions. These methods have applicability to other suitably chosen isotopes and for beryllium show promise in deducing the hyperfine anomaly of 11Be with a sufficiently high precision to study the nuclear magnetization distribution of this one-neutron halo nucleus in a nuclear-model-independent manner.

  15. Progress in AMS measurement of U isotope ratios in nanogram U samples

    NASA Astrophysics Data System (ADS)

    Dong, Kejun; He, Ming; Wang, Chen; Zhao, Xinhong; Li, Lili; Zhao, Yonggang; Wang, Xianggao; Shen, Hongtao; Wang, Xiaoming; Pang, Fangfang; Xu, Yongning; Zhao, Qingzhang; Dou, Liang; Yang, Xuran; Wu, Shaoyong; Lin, Deyu; Li, Kangning; You, Qubo; Bao, Yiwen; Hu, Yueming; Xia, Qingliang; Yin, Xinyi; Jiang, Shan

    2015-10-01

    The determination of uranium isotopic composition in ultra-trace U samples is very important in different fields, especially for the nuclear forensics. A new Accelerator Mass Spectrometry (AMS) technique has been developed for the measurement of uranium isotopic ratios in ng level uranium samples at China Institute of Atomic Energy (CIAE). Recently, the method was further optimized and developed by using a series of blank and standard samples. The results show that the 236U at the femtogram level can be determined in nanogram U samples by the newly developed AMS technique at CIAE. The experimental setup, performances and results will be detailed in this contribution.

  16. Equation of State measurements of hydrogen isotopes on Nova

    SciTech Connect

    Collins, G. W., LLNL

    1997-11-01

    High intensity lasers can be used to perform measurements of materials at extremely high pressures if certain experimental issues can be overcome. We have addressed those issues and used the Nova laser to shock-compress liquid deuterium and obtain measurements of density and pressure on the principal Hugoniot at pressures from 300 kbar to more than 2 Mbar. The data are compared with a number of equation of state models. The data indicate that the effect of molecular dissociation of the deuterium into a monatomic phase may have a significant impact on the equation of state near 1 Mbar.

  17. MEASUREMENTS OF THE RELATIVE ABUNDANCES OF HIGH-ENERGY COSMIC-RAY NUCLEI IN THE TeV/NUCLEON REGION

    SciTech Connect

    Ahn, H. S.; Ganel, O.; Han, J. H.; Kim, K. C.; Lee, M. H.; Malinin, A.; Allison, P. S.; Beatty, J. J.; Brandt, T. J.; Bagliesi, M. G.; Bigongiari, G.; Maestro, P.; Marrocchesi, P. S.; Barbier, L.; Childers, J. T.; DuVernois, M. A.; Conklin, N. B.; Coutu, S.; Jeon, J. A.; Lee, J.

    2010-06-01

    We present measurements of the relative abundances of cosmic-ray nuclei in the energy range of 500-3980 GeV/nucleon from the second flight of the Cosmic Ray Energetics And Mass balloon-borne experiment. Particle energy was determined using a sampling tungsten/scintillating-fiber calorimeter, while particle charge was identified precisely with a dual-layer silicon charge detector installed for this flight. The resulting element ratios C/O, N/O, Ne/O, Mg/O, Si/O, and Fe/O at the top of atmosphere are 0.919 {+-} 0.123{sup stat} {+-} 0.030{sup syst}, 0.076 {+-} 0.019{sup stat} {+-} 0.013{sup syst}, 0.115 {+-} 0.031{sup stat} {+-} 0.004{sup syst}, 0.153 {+-} 0.039{sup stat} {+-} 0.005{sup syst}, 0.180 {+-} 0.045{sup stat} {+-} 0.006{sup syst}, and 0.139 {+-} 0.043{sup stat} {+-} 0.005{sup syst}, respectively, which agree with measurements at lower energies. The source abundance of N/O is found to be 0.054 {+-} 0.013{sup stat} {+-} 0.009{sup syst+0.010esc} {sub -0.017}. The cosmic-ray source abundances are compared to local Galactic (LG) abundances as a function of first ionization potential and as a function of condensation temperature. At high energies the trend that the cosmic-ray source abundances at large ionization potential or low condensation temperature are suppressed compared to their LG abundances continues. Therefore, the injection mechanism must be the same at TeV/nucleon energies as at the lower energies measured by HEAO-3, CRN, and TRACER. Furthermore, the cosmic-ray source abundances are compared to a mixture of 80% solar system abundances and 20% massive stellar outflow (MSO) as a function of atomic mass. The good agreement with TIGER measurements at lower energies confirms the existence of a substantial fraction of MSO material required in the {approx}TeV per nucleon region.

  18. Carbon and Oxygen Stable Isotope Measurements of Martian Atmospheric CO2 by the Phoenix Lander

    NASA Technical Reports Server (NTRS)

    Niles, Paul B.; Boynton, W. V.; Hoffman, J. H.; Ming, D. W.; Hamara, D.

    2010-01-01

    Precise stable isotope measurements of the CO2 in the martian atmosphere have the potential to provide important constraints for our understanding of the history of volatiles, the carbon cycle, current atmospheric processes, and the degree of water/rock interaction on Mars [1]. The isotopic composition of the martian atmosphere has been measured using a number of different methods (Table 1), however a precise value (<1%) has yet to be achieved. Given the elevated Delta(sup 13)C values measured in carbonates in martian meteorites [2-4] it has been proposed that the martian atmosphere was enriched in 13C [8]. This was supported by measurements of trapped CO2 gas in EETA 79001[2] which showed elevated Delta(sup 13)C values (Table 1). More recently, Earth-based spectroscopic measurements of the martian atmosphere have measured the martian CO2 to be depleted in C-13 relative to CO2 in the terrestrial atmosphere[ 7, 9-11]. The Thermal and Evolved Gas Analyzer (TEGA) instrument on the Mars Phoenix Lander [12] included a magnetic-sector mass spectrometer (EGA) [13] which had the goal of measuring the isotopic composition of martian atmospheric CO2 to within 0.5%. The mass spectrometer is a miniature instrument intended to measure both the martian atmosphere as well as gases evolved from heating martian soils.

  19. Measurement of the intramolecular isotope effect on aliphatic hydroxylation by Chromobacterium violaceum phenylalanine hydroxylase.

    PubMed

    Panay, Aram J; Fitzpatrick, Paul F

    2010-04-28

    The non-heme iron enzyme phenylalanine hydroxylase from Chromobacterium violaceum has previously been shown to catalyze the hydroxylation of benzylic and aliphatic carbons in addition to the normal aromatic hydroxylation reaction. The intrinsic isotope effect for hydroxylation of 3-cyclochexylalanine by the enzyme was determined in order to gain insight into the reactivity of the iron center. With 3-[(2)H(11)-cyclohexyl]alanine as the substrate, the isotope effect on the k(cat) value was 1, consistent with an additional step in the overall reaction being significantly slower than hydroxylation. Consequently, the isotope effect was determined as an intramolecular effect by measuring the amount of deuterium lost in the hydroxylation of 3-[1,2,3,4,5,6-(2)H(6)-cyclohexyl]alanine. The ratio of 4-HO-cyclohexylalanine that retained deuterium to that which lost one deuterium atom was 2.8. This gave a calculated value of 12.6 for the ratio of the primary deuterium kinetic isotope effect to the secondary isotope effect. This value is consistent with hydrogen atom abstraction by an electrophilic Fe(O) center and a contribution of quantum-mechanical tunneling to the reaction.

  20. Osmium isotopic ratio measurements by inductively coupled plasma source mass spectrometry

    SciTech Connect

    Russ, G.P. III; Bazan, J.M.; Date, A.R.

    1987-04-01

    The isotopic composition of nanogram quantities of osmium was measured by using an inductively coupled plasma source mass spectrometer. Sensitivity was enhanced a factor of approx.100 by the use of an osmium tetraoxide vapor generator rather than nebulization of solution. For samples less than or equal to5 ng, the ratios /sup 190/Os//sup 192/Os, /sup 189/Os//sup 192/Os, and /sup 188/Os//sup 192/Os were determined to better than +/- 0.5% (1sigma/sub m/) precision. For the minor isotopes, the ratios /sup 187/Os//sup 192/Os and /sup 186/Os//sup 192/Os were determined to +/-1%, and /sup 184/Os//sup 192/Os (4 x 10/sup -4/) was determined to approx.10%. Isotope ratios for common osmium are reported.

  1. Measurement of helium isotopes in soil gas as an indicator of tritium groundwater contamination.

    PubMed

    Olsen, Khris B; Dresel, P Evan; Evans, John C; McMahon, William J; Poreda, Robert

    2006-05-01

    The focus of this study was to define the shape and extent of tritium groundwater contamination emanating from a legacy burial ground and to identify vadose zone sources of tritium using helium isotopes (3He and 4He) in soil gas. Helium isotopes were measured in soil-gas samples collected from 70 sampling points around the perimeter and downgradient of a burial ground that contains buried radioactive solid waste. The soil-gas samples were analyzed for helium isotopes using rare gas mass spectrometry. 3He/4He ratios, reported as normalized to the air ratio (RA), were used to locate the tritium groundwater plume emanating from the burial ground. The 3He (excess) suggested that the general location of the tritium source is within the burial ground. This study clearly demonstrated the efficacy of the 3He method for application to similar sites elsewhere within the DOE weapons complex.

  2. Tunable Diode Laser Measurements of Leaf-scale Carbon Isotope Discrimination and Ecosystem Respired Carbon and Oxygen Isotope Ratios in a Semi-arid Woodland

    NASA Astrophysics Data System (ADS)

    McDowell, N.; Chris, B.; Hanson, D.; Kern, S.; Meyer, C.; Pockman, W.; Powers, H.

    2005-12-01

    We present results and speculative interpretation of leaf-level carbon isotope discrimination and ecosystem respired carbon and oxygen isotope ratios from a semi-arid, C3/C4 woodland located in northern New Mexico, USA. Overstory leaf area index (LAI) is dominated by live juniper (Juniperus monosperma) trees with an LAI value of approximately 1.0 m2 per m2 ground area, and has a seasonally dynamic understory of mixed C3 forbs and C4 grasses and cacti, with a maximum LAI of 0.30 m2 per m2 ground area. Ecosystem respired carbon isotope ratios showed values characteristic of C3 dominated photosynthesis (Keeling plot intercepts of -35 to -22 per mil). Seasonal variation was typical of that found in wetter, C3 dominated forests, as was the dependence on climate (e.g. relationships with vapor pressure deficit, soil water content, and canopy conductance). Leaf-level carbon isotope discrimination of the junipers, measured by coupling a Li-Cor 6400 photosynthesis system to the TDL, provided discrimination-Ci and discrimination-vpd relationships consistent with measured ecosystem respired carbon isotope ratios. The oxygen isotope ratio of ecosystem respiration was dependent on rain water isotope composition, but was correlated with soil water content during rain-free periods. The cumulative effect of vapor pressure deficit after a rain event was tightly correlated with the oxygen isotope ratio of ecosystem respiration, suggesting the primary drivers are evaporative enrichment of soil water and perhaps nocturnal leaf enrichment. Instrument precision for carbon and oxygen isotope ratios of carbon dioxide is 0.06 to 0.18 per mil; however, overall precision is somewhat lower due to pressure and sampling effects.

  3. [Distribution characteristics of soil humus fractions stable carbon isotope natural abundance (delta 13C) in paddy field under long-term ridge culture].

    PubMed

    Tang, Xiao-hong; Luo, You-jin; Ren, Zhen-jiang; Lü, Jia-ke; Wei, Chao-fu

    2011-04-01

    A 16-year field experiment was conducted in a ridge culture paddy field in the hilly region of Sichuan Basin, aimed to investigate the distribution characteristics of stable carbon isotope natural abundance (delta 13C) in soil humus fractions. The soil organic carbon (SOC) content in the paddy field under different cultivation modes ranked in the order of wide ridge culture > ridge culture > paddy and upland rotation. In soil humus substances (HS), humin (HU) was the main composition, occupying 21% - 30% of the total SOC. In the extracted soil carbon, humic acid (HA) dominated, occupying 17% - 21% of SOC and 38% - 65% of HS. The delta 13C value of SOC ranged from -27.9 per thousand to -25.6 per thousand, and the difference of the delta 13C value between 0-5 cm and 20-40 cm soil layers was about 1.9 per thousand. The delta 13C value of HA under different cultivation modes was 1 per thousand - 2 per thousand lower than that of SOC, and more approached to the delta 13C value of rapeseed and rice residues. As for fulvic acid (FA), its delta 13C value was about 2 per thousand and 4 per thousand higher than that of SOC and HA, respectively. The delta 13C value of HU in plough layer (0-20 cm) and plow layer (20-40 cm) ranged from -23.7 per thousand - -24.9 per thousand and -22.6 per thousand - -24.2 per thousand, respectively, reflecting the admixture of young and old HS. The delta 13C value in various organic carbon fractions was HU>FA>SOC>rapeseed and rice residues>HA. Long-term rice planting benefited the increase of SOC content, and cultivation mode played an important role in affecting the distribution patterns of soil humus delta 13C in plough layer and plow layer. PMID:21774322

  4. [Distribution characteristics of soil humus fractions stable carbon isotope natural abundance (delta 13C) in paddy field under long-term ridge culture].

    PubMed

    Tang, Xiao-hong; Luo, You-jin; Ren, Zhen-jiang; Lü, Jia-ke; Wei, Chao-fu

    2011-04-01

    A 16-year field experiment was conducted in a ridge culture paddy field in the hilly region of Sichuan Basin, aimed to investigate the distribution characteristics of stable carbon isotope natural abundance (delta 13C) in soil humus fractions. The soil organic carbon (SOC) content in the paddy field under different cultivation modes ranked in the order of wide ridge culture > ridge culture > paddy and upland rotation. In soil humus substances (HS), humin (HU) was the main composition, occupying 21% - 30% of the total SOC. In the extracted soil carbon, humic acid (HA) dominated, occupying 17% - 21% of SOC and 38% - 65% of HS. The delta 13C value of SOC ranged from -27.9 per thousand to -25.6 per thousand, and the difference of the delta 13C value between 0-5 cm and 20-40 cm soil layers was about 1.9 per thousand. The delta 13C value of HA under different cultivation modes was 1 per thousand - 2 per thousand lower than that of SOC, and more approached to the delta 13C value of rapeseed and rice residues. As for fulvic acid (FA), its delta 13C value was about 2 per thousand and 4 per thousand higher than that of SOC and HA, respectively. The delta 13C value of HU in plough layer (0-20 cm) and plow layer (20-40 cm) ranged from -23.7 per thousand - -24.9 per thousand and -22.6 per thousand - -24.2 per thousand, respectively, reflecting the admixture of young and old HS. The delta 13C value in various organic carbon fractions was HU>FA>SOC>rapeseed and rice residues>HA. Long-term rice planting benefited the increase of SOC content, and cultivation mode played an important role in affecting the distribution patterns of soil humus delta 13C in plough layer and plow layer.

  5. Precise Measurement of Stable Neodymium Isotopes of Geological Materials by Using MC-ICP-MS

    NASA Astrophysics Data System (ADS)

    Ma, J.; Wei, G.; Liu, Y.; Ren, Z.; Xu, Y.

    2013-12-01

    A method has developed to determine high-precision high precision stable Nd isotopes in geological materials by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) using sample-standard-bracketing (SSB) mode. Nd was pre-concentrated and purifed and through a two column ion-exchange chromatographic procedure, yeilding a recovery of >96% for Nd with the interferences such as Ce and Sm being removed to cause little influence on the stable Nd isotopic compositions. The internal precision for the stable Nd isotopic compositions, ɛ142Nd, ɛ145Nd, ɛ146Nd and ɛ148Nd were generally better than ×0.2 (2SEM: standard error of the mean), and the external precision were generally better than ×0.2 (1SD: standard deviation) for ɛ142Nd, ɛ145Nd and ɛ146Nd, and better than ×0.5 (1SD) for ɛ148Nd estimated by the long-term results of the Nd standard solutions, such as La Jolla, Nd-GIG and NIST 3135a. Such precision id comparable to those by double spike method. Our measured ɛ142Nd, ɛ145Nd, ɛ146Nd and ɛ148Nd results of La Jolla are indentical to those by double spike method winthin analytical error. Thus, our method can provide comparable results for stable Nd isotopes to those by double spike method, but free from the inconvenience of calibrationg double spikes. This provides a more convenient means for studying stabe Nd isotopes in geological processes. By using this method, the stable Nd isotopic compositions for a series of international rock standard references were measured.

  6. Application of neodymium isotope ratio measurements for the origin assessment of uranium ore concentrates.

    PubMed

    Krajkó, Judit; Varga, Zsolt; Yalcintas, Ezgi; Wallenius, Maria; Mayer, Klaus

    2014-11-01

    A novel procedure has been developed for the measurement of (143)Nd/(144)Nd isotope ratio in various uranium-bearing materials, such as uranium ores and ore concentrates (UOC) in order to evaluate the usefulness and applicability of variations of (143)Nd/(144)Nd isotope ratio for provenance assessment in nuclear forensics. Neodymium was separated and pre-concentrated by extraction chromatography and then the isotope ratios were measured by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The method was validated by the measurement of standard reference materials (La Jolla, JB-2 and BCR-2) and the applicability of the procedure was demonstrated by the analysis of uranium samples of world-wide origin. The investigated samples show distinct (143)Nd/(144)Nd ratio depending on the ore type, deposit age and Sm/Nd ratio. Together with other characteristics of the material in question, the Nd isotope ratio is a promising signature for nuclear forensics and suggests being indicative of the source material, the uranium ore.

  7. Measurement of lithium isotope ratio in various concentration samples using degenerate four-wave mixing.

    PubMed

    Yin, Xunli; Cheng, Xuemei; Zhang, Ying; Chen, Haowei; Bai, Jintao; Ren, Zhaoyu

    2015-08-20

    Phase-conjugate degenerate four-wave mixing (PCDFWM), as a sub-Doppler spectroscopy technique, can be employed to selectively analyze Li isotopes. It is necessary to explore the optimal incident powers in order to measure the Li isotope ratio accurately. In this case, the power condition of PCDFWM signal is first investigated using samples with various concentrations. The results indicate that the power characteristic is intimately related to the sample concentration, and the optimal incident power conditions for different sample concentrations are different. Under their own optimized power conditions, we measured the Li7/Li6 isotope ratio in Li standard solutions of 500, 300, and 200 ng/ml. The corresponding results are, respectively, 11.571±0.003, 11.552±0.003, and 11.582±0.004, which are in good agreement with the value calculated by atomic absorption spectroscopy. The information obtained from this study suggests that PCDFWM can be used to measure isotope ratios accurately in samples with different concentrations under suitable power conditions.

  8. Neutron multiplicity measurements of Cf and Fm isotopes

    SciTech Connect

    Hoffman, D.C.; Ford, G.P.; Balagna, J.P.; Veeser, L.R.

    1980-02-01

    Prompt neutrons in coincidence with the fission fragments from the spontaneous fission of /sup 250,252,254/Cf and /sup 257/Fm were measured inside a 75-cm-diameter, Gd-loaded liquid scintillation counter having a neutron-detection efficiency of about 78%. Measurements for /sup 256/Fm were done just outside the counter with an efficiency of 31%. The kinetic energies of both fission fragments and the number of neutrons for each fission event were recorded. From these data, the fragment kinetic energies and masses and the neutron multiplicity distributions were determined for /sup 250,252,254/Cf and /sup 257/Fm. Variances of neutron multiplicity distributions as a function of total fragment kinetic energy and the ratio of fragment masses have been calculated and are presented for all the nuclides studied.

  9. High Frequency Measurements of Methane Concentrations and Carbon Isotopes at a Marsh and Landfill

    NASA Astrophysics Data System (ADS)

    Mortazavi, B.; Wilson, B.; Chanton, J.; Eller, K.; Dong, F.; Baer, D. S.; Gupta, M.; Dzwonkowski, B.

    2012-12-01

    High frequency measurements of methane concentrations and carbon isotopes can help constrain the source strengths of methane emitted to the atmosphere. We report here methane concentrations and 13C values measured at 0.5 Hz with cavity enhanced laser absorption spectrometers (Los Gatos Research) deployed at a saltmarsh in Alabama and a landfill in Florida. Methane concentrations and 13C at the saltmarsh were monitored over a 2.5 day time period at 2 m, 0.5 m above the ground as well as from the outflow of a flow-through (2 L) chamber placed on the Spartina alterniflora dominated marsh. A typical measurement cycle included regular samples from two tanks of known methane concentrations and isotopic values and from ambient air samples. Over the 2.5-day measurement period methane concentrations and isotopic ratios at 2 m averaged 1.85 ppm and -43.57‰ (±0.34, 1 SE), respectively. The concentration and isotopic values from the chamber outflow varied from 1.92 to 5.81 ppm and -38.5 to -59.3‰, respectively. Methane flux from the marsh ranged from undetectable to 3.6 mgC m-2hr-1, with high fluxes measured during low tide. The 13δCH4 of the emitted CH4 from the marsh, determined from a mass balance equation using the chamber inflow and outflow concentration and isotopic values ranged from -62.1 to -93.9‰ and averaged -77‰ (±1.25, 1SE). At the landfill ambient methane concentrations and 13C ratios measured over multiple days varied from 4.25 to 11.91 ppm and from -58.81 to -45.12‰, respectively. At higher methane concentrations the δ13C of CH4 was more depleted consistent with previously observed relationship at this site made by more traditional techniques. Over a 30-minute measurement period CH4 concentrations at the landfill could vary by as much as 15 ppm. The high frequency continuous optical measurements with field-deployed instruments provide us with an unprecedented temporal resolution of CH4 concentrations and isotopic ratios. These measurements will

  10. Ecosystem Carbon-13 Isoscapes and Uncertainty Estimates for Africa: Integrating Remote Sensing and Field Isotope Measurements

    NASA Astrophysics Data System (ADS)

    Powell, R. L.; Yoo, E.; Still, C. J.

    2012-12-01

    The carbon isotope composition (δ13C) of terrestrial vegetation and soils is required for a diverse set of carbon cycle research, including inversion studies that use global CO2 and δ13C atmospheric data, as well as work that requires the carbon isotope composition of biomass burning emissions. Spatial representation of plant photosynthetic pathways is also necessary for mapping plant functional types needed to accurately simulate biosphere-atmosphere exchanges and for understanding the response of vegetation to global change. Here, we present continental maps of leaf and soil δ13C for Africa corresponding to approximately the year 2000, based upon predictions of the abundance and distribution of C3 and C4 vegetation and the δ13C values of various plant leaf endmembers. Our approach is based on the near-universal restriction of C4 photosynthesis to the herbaceous growth form and the differing performance of C3 and C4 plants in various climates, along with land-cover and crop-type distributions. We predict the percentage of C3 and C4 vegetation in each 5-minute grid cell (~10 km) by merging freely available, global-scale datasets of vegetation-growth-form fractional cover, crop-area/crop-type distribution, and fine-spatial-resolution climate data. We develop a consistent set of rules to harmonize the different data layers. The δ13C of vegetation is then estimated based on the relative C3/C4 composition of each terrestrial grid cell, assuming constant mean δ13C values for closed tropical forest, open forest/shrub ecosystems, C3 herbaceous cover, and C4 herbaceous cover. By integrating the reported standard deviations for each vegetation category, we generate additional layers that represent the lower and upper values for expected leaf δ13C (μ ± 1σ). Soil δ13C is estimated for regions in C4-favored climates using two different approaches: the first is derived from our vegetation δ13C prediction, and the second is based on a previously published

  11. Simultaneous measurement of CO2 concentration and isotopic ratios in gas samples using IRMS

    NASA Astrophysics Data System (ADS)

    Yu, Eun-Ji; Lee, Dongho; Bong, Yeon-Sik; Lee, Kwang-Sik

    2014-05-01

    Isotopic methods are indispensable tools for studies on atmosphere-biosphere exchanges of CO2 and environmental monitoring such as CO2 leakage detection from subsurface carbon storages. CO2 concentration is an important variable in interpreting isotopic composition of CO2 especially in atmospheric applications (e.g., 'Keeling plot'). Optical methods such as CRDS (Cavity Ring Down Spectroscopy) are gaining attention recently because of its capability to simultaneously measure CO2 concentration and isotopic ratios with a short measurement interval (up to 1 sec.). On the other hand, IRMS (Isotope Ratio Mass Spectrometer) has been used only for isotopic measurements. In this study, we propose a method to measure CO2 concentration from gas samples along with isotopic ratios using conventional IRMS system. The system consists of Delta V Plus IRMS interfaced with GasBench II (Thermo Scientific, Germany). 12-mL vials with open top screw cap and rubber septum were used for both gas sampling and analysis. For isotopic analysis, gases in the vials were transferred into GasBench II by He carrier flow and CO2 was trapped by a single cryotrap (-180 ºC) after passing a water trap (Mg(ClO4)2). Upon release of the cryotrap, liberated CO2 was separated from N2O using gas chromatography column inside the GasBench II and introduced online into the IRMS. Isotopic ratios were measured for the masses of 44, 45 and 46, and the peak intensity (mV of mass 44 and peak area) was recorded for the concentration calculation. For the determination of CO2 concentration, a calibration curve relating the peak intensity with molar concentration of CO2 was constructed. By dissolving NaHCO3 in de-ionized water, solutions containing 0.05, 0.1, 0.25 and 0.5 µmol of inorganic carbon were prepared in 12 mL vials. Phosphoric acid was injected through rubber septum of the vials to acidify the solution and released CO2 was analyzed for the isotopic ratios and the corresponding peak intensity was recorded

  12. Spectral contaminant identifier for off-axis integrated cavity output spectroscopy measurements of liquid water isotopes

    NASA Astrophysics Data System (ADS)

    Brian Leen, J.; Berman, Elena S. F.; Liebson, Lindsay; Gupta, Manish

    2012-04-01

    Developments in cavity-enhanced absorption spectrometry have made it possible to measure water isotopes using faster, more cost-effective field-deployable instrumentation. Several groups have attempted to extend this technology to measure water extracted from plants and found that other extracted organics absorb light at frequencies similar to that absorbed by the water isotopomers, leading to δ2H and δ18O measurement errors (Δδ2H and Δδ18O). In this note, the off-axis integrated cavity output spectroscopy (ICOS) spectra of stable isotopes in liquid water is analyzed to determine the presence of interfering absorbers that lead to erroneous isotope measurements. The baseline offset of the spectra is used to calculate a broadband spectral metric, mBB, and the mean subtracted fit residuals in two regions of interest are used to determine a narrowband metric, mNB. These metrics are used to correct for Δδ2H and Δδ18O. The method was tested on 14 instruments and Δδ18O was found to scale linearly with contaminant concentration for both narrowband (e.g., methanol) and broadband (e.g., ethanol) absorbers, while Δδ2H scaled linearly with narrowband and as a polynomial with broadband absorbers. Additionally, the isotope errors scaled logarithmically with mNB. Using the isotope error versus mNB and mBB curves, Δδ2H and Δδ18O resulting from methanol contamination were corrected to a maximum mean absolute error of 0.93 ‰ and 0.25 ‰ respectively, while Δδ2H and Δδ18O from ethanol contamination were corrected to a maximum mean absolute error of 1.22 ‰ and 0.22 ‰. Large variation between instruments indicates that the sensitivities must be calibrated for each individual isotope analyzer. These results suggest that the properly calibrated interference metrics can be used to correct for polluted samples and extend off-axis ICOS measurements of liquid water to include plant waters, soil extracts, wastewater, and alcoholic beverages. The general technique

  13. Spectral contaminant identifier for off-axis integrated cavity output spectroscopy measurements of liquid water isotopes.

    PubMed

    Brian Leen, J; Berman, Elena S F; Liebson, Lindsay; Gupta, Manish

    2012-04-01

    Developments in cavity-enhanced absorption spectrometry have made it possible to measure water isotopes using faster, more cost-effective field-deployable instrumentation. Several groups have attempted to extend this technology to measure water extracted from plants and found that other extracted organics absorb light at frequencies similar to that absorbed by the water isotopomers, leading to δ(2)H and δ(18)O measurement errors (Δδ(2)H and Δδ(18)O). In this note, the off-axis integrated cavity output spectroscopy (ICOS) spectra of stable isotopes in liquid water is analyzed to determine the presence of interfering absorbers that lead to erroneous isotope measurements. The baseline offset of the spectra is used to calculate a broadband spectral metric, m(BB), and the mean subtracted fit residuals in two regions of interest are used to determine a narrowband metric, m(NB). These metrics are used to correct for Δδ(2)H and Δδ(18)O. The method was tested on 14 instruments and Δδ(18)O was found to scale linearly with contaminant concentration for both narrowband (e.g., methanol) and broadband (e.g., ethanol) absorbers, while Δδ(2)H scaled linearly with narrowband and as a polynomial with broadband absorbers. Additionally, the isotope errors scaled logarithmically with m(NB). Using the isotope error versus m(NB) and m(BB) curves, Δδ(2)H and Δδ(18)O resulting from methanol contamination were corrected to a maximum mean absolute error of 0.93 [per thousand] and 0.25 [per thousand] respectively, while Δδ(2)H and Δδ(18)O from ethanol contamination were corrected to a maximum mean absolute error of 1.22 [per thousand] and 0.22 [per thousand]. Large variation between instruments indicates that the sensitivities must be calibrated for each individual isotope analyzer. These results suggest that the properly calibrated interference metrics can be used to correct for polluted samples and extend off-axis ICOS measurements of liquid water to include plant

  14. Spectral contaminant identifier for off-axis integrated cavity output spectroscopy measurements of liquid water isotopes

    SciTech Connect

    Brian Leen, J.; Berman, Elena S. F.; Gupta, Manish; Liebson, Lindsay

    2012-04-15

    Developments in cavity-enhanced absorption spectrometry have made it possible to measure water isotopes using faster, more cost-effective field-deployable instrumentation. Several groups have attempted to extend this technology to measure water extracted from plants and found that other extracted organics absorb light at frequencies similar to that absorbed by the water isotopomers, leading to {delta}{sup 2}H and {delta}{sup 18}O measurement errors ({Delta}{delta}{sup 2}H and {Delta}{delta}{sup 18}O). In this note, the off-axis integrated cavity output spectroscopy (ICOS) spectra of stable isotopes in liquid water is analyzed to determine the presence of interfering absorbers that lead to erroneous isotope measurements. The baseline offset of the spectra is used to calculate a broadband spectral metric, m{sub BB}, and the mean subtracted fit residuals in two regions of interest are used to determine a narrowband metric, m{sub NB}. These metrics are used to correct for {Delta}{delta}{sup 2}H and {Delta}{delta}{sup 18}O. The method was tested on 14 instruments and {Delta}{delta}{sup 18}O was found to scale linearly with contaminant concentration for both narrowband (e.g., methanol) and broadband (e.g., ethanol) absorbers, while {Delta}{delta}{sup 2}H scaled linearly with narrowband and as a polynomial with broadband absorbers. Additionally, the isotope errors scaled logarithmically with m{sub NB}. Using the isotope error versus m{sub NB} and m{sub BB} curves, {Delta}{delta}{sup 2}H and {Delta}{delta}{sup 18}O resulting from methanol contamination were corrected to a maximum mean absolute error of 0.93 per mille and 0.25 per mille respectively, while {Delta}{delta}{sup 2}H and {Delta}{delta}{sup 18}O from ethanol contamination were corrected to a maximum mean absolute error of 1.22 per mille and 0.22 per mille . Large variation between instruments indicates that the sensitivities must be calibrated for each individual isotope analyzer. These results suggest that the

  15. Cd Isotopic Composition Measured by Plasma Source Mass Spectrometry on Natural and Anthropogenic Materials. A Preliminary Outline of Cd Isotope Systematics

    NASA Astrophysics Data System (ADS)

    Innocent, C.

    2004-05-01

    Cadmium is a trace metal that is used as a geochemical tracer of natural processes, like biological productivity and paleoproductivity, and also of anthropogenic pollution, as Cd is known to be a toxic heavy metal that has become a major environmental and health concern. For these purposes, an outstanding issue is to determine whether Cd, like a number of metallic elements (e.g. Fe, Cu, Zn, Mo, Tl), may display variable isotopic compositions in natural and/or industrial compounds. It is known that Cd may display variable isotopic composition. Indeed, isotopic fractionation processes have been documented in some meteorites and in lunar soils. Consequently, due to its relatively low boiling point (767\\deg C) and also to the large mass range covered by its isotopes (10 mass units), Cd might fractionate isotopically, for example during the outpouring of acidic volcanic magmas and/or the emplacement of granitoids. On another hand, isotopic fractionation could also occur during human activities like refuse incineration or industrial manufacturing, for instance. Finally, biologically-induced isotopic fractionation should not be ruled out, as it is clearly evidenced for other metals, like Fe. A high precision method has been developed for determining the isotopic composition of Cd by plasma source mass spectrometry (Neptune). This method holds on the standard-bracketing technique, owing to the availability of Cd solutions of known isotopic composition provided by the University of M\\H{u}nster. This allows to correct precisely for mass fractionation that occurs in the plasma source mass spectrometer. It is also critical for the analysis to be possible to work with Cd solutions of very high purity. Chemical isolation of Cd involves 3 steps, and may be also suitable for Cd isotopic measurements using solid source mass spectrometry. Preliminary results suggest that Cd is likely to fractionate during smelting activities, as indicated by measurements on mining waste. The

  16. Symbiotic nitrogen fixation in an arid ecosystem measured by sup 15 N natural abundance

    SciTech Connect

    Johnson, G.V. )

    1990-05-01

    Plants dependent on nitrogen fixation have an {sup 15}N abundance similar to the atmosphere, while non-nitrogen fixing plants usually are enriched in {sup 15}N and are similar to soil nitrogen values. The natural abundance of {sup 15}N in leaf tissues and soils was determined to evaluate symbiotic nitrogen fixation by several legumes and actinorhizal species in the Sevilleta Long-term Ecological Research area in central New Mexico. Comparison of {delta}{sup 15}N values for the legume Prosopis glandulosa (mesquite) to adjacent Atriplex canascens (fourwing saltbush) indicated that P. glandulosa obtained 66% of its nitrogen by fixation. The legume Hoffmanseggia jamesii was found to be utilizing soil nitrogen. The {delta}{sup 15}N values for the actinorhizal plants, Elaeagnus angustifolia and Cercocarpus montanus, while below values for soil nitrogen, did not differ from associated non-fixing plants.

  17. The Abundance of Lithium Measured for the First Time Beyond Our Galaxy

    NASA Astrophysics Data System (ADS)

    Mucciarelli, A.; Salaris, M.; Bonifacio, P.; Monaco, L.; Villanova, S.

    2014-12-01

    The discrepancy between the primordial lithium abundance derived from Population II dwarf stars and from the predictions of standard Big Bang nucleosynthesis is one of the most intriguing and challenging open questions in modern astrophysics. The use of lower red giant branch stars, instead of the usual method of observing dwarf stars, represents a new approach to attacking the problem. Lithium in distant, extragalactic stellar systems, for which observations of dwarf stars are precluded because of their faintness, becomes open for investigation. From observations with FLAMES at the VLT, we have been able to derive for the first time the initial lithium abundance in an extragalactic globular cluster, namely M54 in the Sagittarius galaxy.

  18. Tropospheric chlorine isotope measurements in CFC-11, CFC-12 and CFC-113

    NASA Astrophysics Data System (ADS)

    Allin, Sam; Kaiser, Jan; Laube, Johannes; Sturges, Bill

    2014-05-01

    In 2010, we reported the first measurements of chlorine isotope fractionation in stratospheric dichlorodifluoromethane (CF2Cl2, CFC-12) (Laube et al., Science 329:1167, 2010). We found an increase in the isotope delta, δ(37Cl), with altitude and a tight correlation between ln[1 + δ(37Cl)] and ln(mixing ratio). The derived apparent isotope fractionation was ɛapp = (-12 ± 2) o. The stratospheric isotopic fractionation should lead to a continuous increase of the tropospheric chlorine isotope delta while CFC-12 is still emitted into the atmosphere. Provided the source signature has not changed, we predict a 2.5 to 3 o increase since when CFC emissions started in the 1930s until 2010, with the strongest increase in recent years (about 1 o per decade since the mid-1990s). We have now measured the chlorine isotope delta of CFC-12 as well as CFC-11 (trichlorofluoromethane, CFCl3) and CFC-113 (1,1,2-trichloro-1,2,2-trifluoroethane, C2F3Cl3) in the Cape Grim Air Archive (1978 to 2010) and Arctic (NEEM, Greenland) and Antarctic firn samples (Fletcher, West Antarctica). The deepest firn samples include a significant proportion of older air from before 1978. The repeatability for individual samples was ±2.6o for CFC-12 and ±2.7o for CFC-11 and ±3.7o for CFC-113. The results show no significant trends in δ(37Cl) over the whole time period; however, there is a small positive trend for the latter period of the samples of (0.3 ± 0.1) o per decade for CFC-12 since 1997, which explains at third of the predicted trend. The discrepancy between observed and predicted trends may be due to offsetting changes in the source isotope signature: If the there was decrease in the isotope delta of the emissions over time, this would reduce the predicted increase caused by downward transport of 37Cl-enriched stratospheric air.

  19. Measuring marine fish biodiversity: temporal changes in abundance, life history and demography

    PubMed Central

    Hutchings, Jeffrey A; Baum, Julia K

    2005-01-01

    Patterns in marine fish biodiversity can be assessed by quantifying temporal variation in rate of population change, abundance, life history and demography concomitant with long-term reductions in abundance. Based on data for 177 populations (62 species) from four north-temperate oceanic regions (Northeast Atlantic and Pacific, Northwest Atlantic, North mid-Atlantic), 81% of the populations in decline prior to 1992 experienced reductions in their rate of loss thereafter; species whose rate of population decline accelerated after 1992 were predominantly top predators such as Atlantic cod (Gadus morhua), sole (Solea solea) and pelagic sharks. Combining population data across regions and species, marine fish have declined 35% since 1978 and are currently less than 70% of recorded maxima; demersal species are generally at historic lows, pelagic species are generally stable or increasing in abundance. Declines by demersal species have been associated with substantive increases in pelagic species, a pattern consistent with the hypothesis that increases in the latter may be attributable to reduced predation mortality. There is a need to determine the consequences to population growth effected by the reductions in age (21%) and size (13%) at maturity and in mean age (5%) and size (18%) of spawners, concomitant with population decline. We conclude that reductions in the rate of population decline, in the absence of targets for population increase, will be insufficient to effect a recovery of marine fish biodiversity, and that great care must be exercised when interpreting multi-species patterns in abundance. Of fundamental importance is the need to explain the geographical, species-specific and habitat biases that pervade patterns of marine fish recovery and biodiversity. PMID:15814348

  20. High-temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose.

    PubMed

    Woodley, Ewan J; Loader, Neil J; McCarroll, Danny; Young, Giles H F; Robertson, Iain; Heaton, Timothy H E; Gagen, Mary H; Warham, Joseph O

    2012-01-30

    Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree-ring α-cellulose samples are used to compare the stable carbon isotope ratios (δ(13)C) produced by high-temperature (1400°C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree-ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub-sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample. This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high-temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately.

  1. Stable isotope and high precision concentration measurements confirm that all humans produce and exhale methane.

    PubMed

    Keppler, Frank; Schiller, Amanda; Ehehalt, Robert; Greule, Markus; Hartmann, Jan; Polag, Daniela

    2016-01-29

    Mammalian formation of methane (methanogenesis) is widely considered to occur exclusively by anaerobic microbial activity in the gastrointestinal tract. Approximately one third of humans, depending on colonization of the gut by methanogenic archaea, are considered methane producers based on the classification terminology of high and low emitters. In this study laser absorption spectroscopy was used to precisely measure concentrations and stable carbon isotope signatures of exhaled methane in breath samples from 112 volunteers with an age range from 1 to 80 years. Here we provide analytical evidence that volunteers exhaled methane levels were significantly above background (inhaled) air. Furthermore, stable carbon isotope values of the exhaled methane unambiguously confirmed that this gas was produced by all of the human subjects studied. Based on the emission and stable carbon isotope patterns of various age groups we hypothesize that next to microbial sources in the gastrointestinal tracts there might be other, as yet unidentified, processes involved in methane formation supporting the idea that humans might also produce methane endogenously in cells. Finally we suggest that stable isotope measurements of volatile organic compounds such as methane might become a useful tool in future medical research diagnostic programs.

  2. Neutron unbound resonances cataloged by isotope and invariant mass measurements for nuclei Z = 1-12

    NASA Astrophysics Data System (ADS)

    Havens, Elizabeth; Finck, Joseph; Gueye, Paul; Thoennessen, Michael; MoNA Collaboration

    2015-10-01

    Prior to 2014, no comprehensive study had been undertaken to compile experimental results from neutron unbound spectroscopy using invariant mass measurements, gamma resolutions and half-lives. Through the collaborative efforts of Central Michigan University, Hampton University and the NSCL, a project was initiated to catalog all unbound resonances in light nuclei (Z = 1-12). Unbound resonances were characterized by having a confirmed neutron decay branch and/or an energy level greater than the neutron binding energy listed for that isotope, according to either the NNDC's ENSDF or XUNDL and the referred journals therein. This was initially compiled in July 2014 and presented in October of that year. Recent discoveries and updates to NNDC have added ten isotopes and their resonances. Additionally, various corrections to previously compiled resonances have been made and equivalent evaluated and unevaluated invariant mass measurements have been consolidated into single entries. The neutron separation energy is noted for each isotope. The isotopes in which unbound resonances occur have been identified and, if known, each unbound resonance's gamma resolution, half-life, method of production and journal reference were also determined.

  3. CF-IRMS method to measure the isotopic composition of very small/stratospheric water samples

    NASA Astrophysics Data System (ADS)

    Franz, P.; Roeckmann, T.

    2003-04-01

    Measurements of the isotopic composition of stratospheric water vapor are believed to provide further insight about sources of stratospheric water vapor, i.e. transport from the troposphere and in situ formation, and thus about the stratospheric water budget. Including the 17O signature in addition to the usually targeted 18O and D data is interesting, since water formed in the stratosphere may inherit a fraction of the oxygen isotope anomaly present in ozone in its photochemical production. Whereas several methods are being developed for in situ measurements with optical techniques, we attempt to obtain stratospheric water samples and analyze them in the laboratory with a novel high precision continuous-flow isotope ratio monitoring technique. The laboratory extraction and measurement parts have been setup and will be presented. For the measurement of the stable oxygen isotopes, the sample is injected into a heated tube filled with CoF_3, where water is chemically converted to oxygen. The O_2 sample is then injected into a multi-cup isotope ratio mass spectrometer, where δ17O and δ18O are determined. Due to the extremely small sample size requirement for continuous-flow isotope ratio mass spectrometry, many measurements can be made on the same sample. This is realized by flushing the sample out of its container with purified helium into a sample loop trap, and successively injecting many aliquots. Non-linearity effects and instrumental fractionation can then be taken into account by fitting an entire measurement series onto a mathematical model. At present, measurement errors are about 0.8 0/00 for δ17O and 0.5 0/00 for δ18O. Alternatively, a high temperature furnace (alumina tube filled with Ni-wires) can be used for the conversion to hydrogen gas. Carbon molecules can be deposited on the Ni by flushing the furnace with CH_4, hence allowing the later pyrolysis of water to H_2 and CO. Due to the somewhat more complicated analysis of H_2, this method has not

  4. Monitoring great ape and elephant abundance at large spatial scales: measuring effectiveness of a conservation landscape.

    PubMed

    Stokes, Emma J; Strindberg, Samantha; Bakabana, Parfait C; Elkan, Paul W; Iyenguet, Fortuné C; Madzoké, Bola; Malanda, Guy Aimé F; Mowawa, Brice S; Moukoumbou, Calixte; Ouakabadio, Franck K; Rainey, Hugo J

    2010-01-01

    Protected areas are fundamental to biodiversity conservation, but there is growing recognition of the need to extend beyond protected areas to meet the ecological requirements of species at larger scales. Landscape-scale conservation requires an evaluation of management impact on biodiversity under different land-use strategies; this is challenging and there exist few empirical studies. In a conservation landscape in northern Republic of Congo we demonstrate the application of a large-scale monitoring program designed to evaluate the impact of conservation interventions on three globally threatened species: western gorillas, chimpanzees and forest elephants, under three land-use types: integral protection, commercial logging, and community-based natural resource management. We applied distance-sampling methods to examine species abundance across different land-use types under varying degrees of management and human disturbance. We found no clear trends in abundance between land-use types. However, units with interventions designed to reduce poaching and protect habitats--irrespective of land-use type--harboured all three species at consistently higher abundance than a neighbouring logging concession undergoing no wildlife management. We applied Generalized-Additive Models to evaluate a priori predictions of species response to different landscape processes. Our results indicate that, given adequate protection from poaching, elephants and gorillas can profit from herbaceous vegetation in recently logged forests and maintain access to ecologically important resources located outside of protected areas. However, proximity to the single integrally protected area in the landscape maintained an overriding positive influence on elephant abundance, and logging roads--even subject to anti-poaching controls--were exploited by elephant poachers and had a major negative influence on elephant distribution. Chimpanzees show a clear preference for unlogged or more mature forests

  5. Monitoring great ape and elephant abundance at large spatial scales: measuring effectiveness of a conservation landscape.

    PubMed

    Stokes, Emma J; Strindberg, Samantha; Bakabana, Parfait C; Elkan, Paul W; Iyenguet, Fortuné C; Madzoké, Bola; Malanda, Guy Aimé F; Mowawa, Brice S; Moukoumbou, Calixte; Ouakabadio, Franck K; Rainey, Hugo J

    2010-01-01

    Protected areas are fundamental to biodiversity conservation, but there is growing recognition of the need to extend beyond protected areas to meet the ecological requirements of species at larger scales. Landscape-scale conservation requires an evaluation of management impact on biodiversity under different land-use strategies; this is challenging and there exist few empirical studies. In a conservation landscape in northern Republic of Congo we demonstrate the application of a large-scale monitoring program designed to evaluate the impact of conservation interventions on three globally threatened species: western gorillas, chimpanzees and forest elephants, under three land-use types: integral protection, commercial logging, and community-based natural resource management. We applied distance-sampling methods to examine species abundance across different land-use types under varying degrees of management and human disturbance. We found no clear trends in abundance between land-use types. However, units with interventions designed to reduce poaching and protect habitats--irrespective of land-use type--harboured all three species at consistently higher abundance than a neighbouring logging concession undergoing no wildlife management. We applied Generalized-Additive Models to evaluate a priori predictions of species response to different landscape processes. Our results indicate that, given adequate protection from poaching, elephants and gorillas can profit from herbaceous vegetation in recently logged forests and maintain access to ecologically important resources located outside of protected areas. However, proximity to the single integrally protected area in the landscape maintained an overriding positive influence on elephant abundance, and logging roads--even subject to anti-poaching controls--were exploited by elephant poachers and had a major negative influence on elephant distribution. Chimpanzees show a clear preference for unlogged or more mature forests

  6. 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).

  7. Validation of a simple isotopic technique for the measurement of global and separated renal function

    SciTech Connect

    Chachati, A.; Meyers, A.; Rigo, P.; Godon, J.P.

    1986-01-01

    Schlegel and Gates described an isotopic method for the measurement of global and separated glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) based on the determination by scintillation camera of the fraction of the injected dose (99mTc-DTPA-(/sup 131/I)hippuran) present in the kidneys 1-3 min after its administration. This method requires counting of the injected dose and attenuation correction, but no blood or urine sampling. We validated this technique by the simultaneous infusion of inulin and para-amino hippuric acid (PAH) in patients with various levels of renal function (anuric to normal). To better define individual renal function we studied 9 kidneys in patients either nephrectomized or with a nephrostomy enabling separated function measurement. A good correlation between inulin, PAH clearance, and isotopic GFR-ERPF measurement for both global and separate renal function was observed.

  8. Laser ablation inductively coupled plasma mass spectrometry measurement of isotope ratios in depleted uranium contaminated soils.

    PubMed

    Seltzer, Michael D

    2003-09-01

    Laser ablation of pressed soil pellets was examined as a means of direct sample introduction to enable inductively coupled plasma mass spectrometry (ICP-MS) screening of soils for residual depleted uranium (DU) contamination. Differentiation between depleted uranium, an anthropogenic contaminant, and naturally occurring uranium was accomplished on the basis of measured 235U/238U isotope ratios. The amount of sample preparation required for laser ablation is considerably less than that typically required for aqueous sample introduction. The amount of hazardous laboratory waste generated is diminished accordingly. During the present investigation, 235U/238U isotope ratios measured for field samples were in good agreement with those derived from gamma spectrometry measurements. However, substantial compensation was required to mitigate the effects of impaired pulse counting attributed to sample inhomogeneity and sporadic introduction of uranium analyte into the plasma.

  9. Laser ablation inductively coupled plasma mass spectrometry measurement of isotope ratios in depleted uranium contaminated soils.

    PubMed

    Seltzer, Michael D

    2003-09-01

    Laser ablation of pressed soil pellets was examined as a means of direct sample introduction to enable inductively coupled plasma mass spectrometry (ICP-MS) screening of soils for residual depleted uranium (DU) contamination. Differentiation between depleted uranium, an anthropogenic contaminant, and naturally occurring uranium was accomplished on the basis of measured 235U/238U isotope ratios. The amount of sample preparation required for laser ablation is considerably less than that typically required for aqueous sample introduction. The amount of hazardous laboratory waste generated is diminished accordingly. During the present investigation, 235U/238U isotope ratios measured for field samples were in good agreement with those derived from gamma spectrometry measurements. However, substantial compensation was required to mitigate the effects of impaired pulse counting attributed to sample inhomogeneity and sporadic introduction of uranium analyte into the plasma. PMID:14611049

  10. An Empirical Approach to Determining the Boundary Layer Bromine Monoxide (BrO) Abundance from Satellite Total Column Measurements

    NASA Astrophysics Data System (ADS)

    Simpson, W. R.; Donohoue, D.; Carlson, D. A.

    2009-12-01

    Unique chemistry in the Arctic boundary layer during springtime liberates bromine from sea salt, producing reactive halogen gases (e.g. atomic bromine and bromine monoxide radicals) that then drastically alter atmospheric oxidation pathways. This phenomenon causes ozone depletion events and affects mercury deposition to the snowpack. Satellite remote sensing (e.g. OMI and GOME2 observations) techniques can detect the total column abundance of BrO, which is generally the primary species of the reactive bromine family. However, BrO is also present in the stratosphere, so it is necessary to partition the satellite-observed BrO column abundance into boundary layer and non-boundary layer (primarily stratospheric) partial columns to be able to infer boundary layer abundances and hence chemical affects near the Earth's surface (i.e. ozone and mercury impacts). In this presentation, we describe an empirical method for partitioning the BrO total column and apply it globally during spring 2008. The method indicates that some BrO total column enhancements ("hotspots") are not actually enhancements in the boundary layer BrO abundance but occur aloft. Movies and a statistical analysis of the inferred boundary layer BrO abundance are presented. The method has been tested and performs well at the Barrow field site. However, in areas that lack routine ground truth BrO measurements (e.g. Hudson Bay, Canada), large tropospheric BrO abundances are indicated. It is not clear if these inferred boundary layer BrO events are real or if the simple empirical method described here is failing in those locations. Verification of this method over large spatial regions of the Arctic is needed.

  11. The exchange of acetaldehyde between plants and the atmosphere: Stable carbon isotope and flux measurements

    NASA Astrophysics Data System (ADS)

    Jardine, Kolby Jeremiah

    The exchange of acetaldehyde between plant canopies and the atmosphere may significantly influence regional atmospheric chemistry and plant metabolism. While plants are known to both produce and consume acetaldehyde, the exchange of this compound with forested ecosystems is complicated by physical, biological, and chemical processes that range from being poorly understood to completely unknown. This precludes a quantitative understanding of acetaldehyde exchange rates between the atmosphere and the biosphere. In this study, the processes controlling the exchange of acetaldehyde with plant canopies was investigated using concentration, flux, and natural abundance 13C measurements of gas phase acetaldehyde from individual plants, soils, and entire ecosystems. Although previously only considered important in anoxic tissues, it was discovered that acetaldehyde is produced and consumed in leaves through ethanolic fermentation coupled to the pyruvate dehydrogenase bypass system under normal aerobic conditions. These coupled pathways determine the acetaldehyde compensation point, a major factor controlling its exchange with the atmosphere. Carbon isotope analysis suggests a new pathway for acetaldehyde production from plants under stress involving the peroxidation of membrane fatty acids. This pathway may be a major source of acetaldehyde to the atmosphere from plants under biotic and abiotic stresses. Plant stomata were found to be the dominant pathway for the exchange of acetaldehyde with the atmosphere with stomatal conductance influencing both emission and uptake fluxes. In addition, increasing temperature and solar radiation was found to increase the compensation point by increasing the rates of acetaldehyde production relative to consumption. Under ambient conditions, bare soil was neutral to the exchange of acetaldehyde while senescing and decaying leaves were found to be strong source of acetaldehyde to the atmosphere due to increased decomposition processes and

  12. Measurement of CO{sub 2} and N{sub 2}O at nanomolar amounts using continuous-flow isotope-ratio mass spectrometry (CF-IRMS)

    SciTech Connect

    Patel, A; Downie, S.; Webster, E.; Hopkins, D.W.; Rennie, M.J.

    1994-12-01

    We are currently developing methods using Continuous Flow Isotope Ratio Mass Spectrometry (CF-IRMS) in conjunction with a thermal desorption purification unit to measure nanomolar levels of C0{sub 2} and N{sub 2}0. Samples of the pure gases diluted in He/air and transferred to septum capped Exetainers (Labco) provided a simple means to investigate the technique. We analyzed C0{sub 2} at natural abundance in the concentration range 50 to 5 nmoles and N{sub 2}0 at two concentrations between 25 and 5 nmoles. The technique was then used to measure C0{sub 2} (natural abundance and {sup 13}C-labeled) generated from the ninhydrin reaction. The results are summarized in a table; values are expressed in delta {sup 13}C notation relative to Pee Dee Belemnite. The data show that, provided care is taken to minimize or eliminate sources of contamination (air leaks, etc.), CF-IRMS coupled with a thermal desorption unit permits measurement of {sup 13}C enrichment in much smaller amounts of isolated amino acids than has been possible until now. The new methodology, including thermal desorption, should allow stable-isotope investigations on much smaller samples than are possible with other currently available techniques-while maintaining high precision.

  13. Neutron-Induced Fission Cross Section Measurements for Full Suite of Uranium Isotopes

    NASA Astrophysics Data System (ADS)

    Laptev, Alexander; Tovesson, Fredrik; Hill, Tony

    2010-11-01

    A well established program of neutron-induced fission cross section measurement at Los Alamos Neutron Science Center (LANSCE) is supporting the Fuel Cycle Research program (FC R&D). The incident neutron energy range spans energies from sub-thermal energies up to 200 MeV by measuring both the Lujan Center and the Weapons Neutron Research center (WNR). Conventional parallel-plate fission ionization chambers with actinide deposited foils are used as a fission detector. The time-of-flight method is implemented to measure neutron energy. Counting rate ratio from investigated and standard U-235 foils is translated into fission cross section ratio. Different methods of normalization for measured ratio are employed, namely, using of actinide deposit thicknesses, normalization to evaluated data, etc. Finally, ratios are converted to cross sections based on the standard U-235 fission cross section data file. Preliminary data for newly investigated isotopes U-236 and U-234 will be reported. Those new data complete a full suite of Uranium isotopes, which were investigated with presented experimental approach. When analysis of the new measured data will is completed, data will be delivered to evaluators. Having data for full set of Uranium isotopes will increase theoretical modeling capabilities and make new data evaluations much more reliable.

  14. Ion microprobe measurement of strontium isotopes in calcium carbonate with application to salmon otoliths

    USGS Publications Warehouse

    Weber, P.K.; Bacon, C.R.; Hutcheon, I.D.; Ingram, B.L.; Wooden, J.L.

    2005-01-01

    The ion microprobe has the capability to generate high resolution, high precision isotopic measurements, but analysis of the isotopic composition of strontium, as measured by the 87Sr/ 86Sr ratio, has been hindered by isobaric interferences. Here we report the first high precision measurements of 87Sr/ 86Sr by ion microprobe in calcium carbonate samples with moderate Sr concentrations. We use the high mass resolving power (7000 to 9000 M.R.P.) of the SHRIMP-RG ion microprobe in combination with its high transmission to reduce the number of interfering species while maintaining sufficiently high count rates for precise isotopic measurements. The isobaric interferences are characterized by peak modeling and repeated analyses of standards. We demonstrate that by sample-standard bracketing, 87Sr/86Sr ratios can be measured in inorganic and biogenic carbonates with Sr concentrations between 400 and 1500 ppm with ???2??? external precision (2??) for a single analysis, and subpermil external precision with repeated analyses. Explicit correction for isobaric interferences (peak-stripping) is found to be less accurate and precise than sample-standard bracketing. Spatial resolution is ???25 ??m laterally and 2 ??m deep for a single analysis, consuming on the order of 2 ng of material. The method is tested on otoliths from salmon to demonstrate its accuracy and utility. In these growth-banded aragonitic structures, one-week temporal resolution can be achieved. The analytical method should be applicable to other calcium carbonate samples with similar Sr concentrations. Copyright ?? 2005 Elsevier Ltd.

  15. Ptolemy an Instrument to Measure Stable Isotopic Ratios of Key Volatiles on a Cometary Nucleus

    NASA Astrophysics Data System (ADS)

    Wright, I. P.; Barber, S. J.; Morgan, G. H.; Morse, A. D.; Sheridan, S.; Andrews, D. J.; Maynard, J.; Yau, D.; Evans, S. T.; Leese, M. R.; Zarnecki, J. C.; Kent, B. J.; Waltham, N. R.; Whalley, M. S.; Heys, S.; Drummond, D. L.; Edeson, R. L.; Sawyer, E. C.; Turner, R. F.; Pillinger, C. T.

    2007-02-01

    A fundamental goal of cometary studies is to determine the exact relationship between these bodies and the Solar System the question(s) can be summarised as follows: did comets originate during the same events that spawned the Sun and planets, are they more primitive bodies that record a pre-solar history, or are they interstellar materials collected in relatively more recent times? Now, whatever the origin of comets, it is entirely possible that they could, in part, contain interstellar or pre-solar components indeed, it seems rather likely in light of the fact that primitive meteorites contain such entities. These particular components are likely to be refractory (dust, macromolecular organic complexes, etc.). Of more relevance to the issues above are the volatile constituents, which make up the bulk of a comet's mass. Since these materials, by their very nature, volatilise during perihelion passage of a comet they can, in some instances, be detected and measured spectroscopically. Perhaps the most useful species for isotopic investigations are C2, HCN and CN. Unfortunately, spectroscopic measurements can only currently be made with accuracies of ±10 to ±20%. As such it is very often not practical to conclude anything further than the fact that isotopic measurements are compatible with ‘`solar’' values, which tends to imply an origin from the margins of the solar accretion disk. But there is another problem with the spectroscopic measurements since these are made on gaseous species in the coma (and relatively minor species at that) it is impossible to be certain that these represent the true nuclear values. In other words, if the processes of sublimation, active jetting, and photochemistry in the coma impart isotopic fractionation, the spectroscopic measurements could give a false impression of the true isotope ratios. What is required is an experiment capable of measuring isotopic ratios at the very surface of a comet. Herein we describe the Ptolemy

  16. Solubility of krypton, xenon and radon in polycarbonates. Application for measurement of their radioactive isotopes

    NASA Astrophysics Data System (ADS)

    Pressyanov, D.; Mitev, K.; Dimitrova, I.; Georgiev, S.

    2011-02-01

    Bisphenol-A polycarbonates have a high absorption ability for noble gases that can be employed for sampling and measurement of radioactive isotopes of these gases. In this report the solubility of krypton, xenon and radon in the specified polycarbonates is determined by measurement of 85Kr, 133Xe and 222Rn absorbed in polycarbonate specimens. The found solubility is used to develop a general methodology for measurement of radioactive noble gases in air and water. The methodology is tested in pilot measurements of 133Xe in air under real conditions. The results demonstrate sufficient potential for practical applications.

  17. H2S interference on CO2 isotopic measurements using a Picarro G1101-i cavity ring-down spectrometer

    NASA Astrophysics Data System (ADS)

    Malowany, K.; Stix, J.; Van Pelt, A.; Lucic, G.

    2015-10-01

    Cavity ring-down spectrometers (CRDSs) have the capacity to make isotopic measurements of CO2 where concentrations range from atmospheric (~ 400 ppm) to 6000 ppm. Following field trials, it has come to light that the spectrographic lines used for CO2 have an interference with elevated (higher than ambient) amounts of hydrogen sulfide (H2S), which causes significant depletions in the δ13C measurement by the CRDSs. In order to deploy this instrument in environments with elevated H2S concentrations (i.e., active volcanoes), we require a robust method for eliminating this interference. Controlled experiments using a Picarro G1101-i optical spectrometer were done to characterize the H2S interference at varying CO2 and H2S concentrations. The addition of H2S to a CO2 standard gas reveals an increase in the 12CO2 concentration and a more significant decrease in the 13CO2 concentration, resulting in a depleted δ13C value. Reacting gas samples containing H2S with copper prior to analysis can eliminate this effect. Models post-dating the G1101-i carbon isotope analyzer have maintained the same spectral lines for CO2 and are likely to have a similar H2S response at elevated H2S concentrations. It is important for future work with CRDS, particularly in volcanic regions where H2S is abundant, to be aware of the H2S interference on the CO2 spectroscopic lines and to remove all H2S prior to analysis. We suggest employing a scrub composed of copper to remove H2S from all gas samples that have concentrations in excess of 1 ppb.

  18. Reformulated 17O correction of mass spectrometric stable isotope measurements in carbon dioxide and a critical appraisal of historic 'absolute' carbon and oxygen isotope ratios

    NASA Astrophysics Data System (ADS)

    Kaiser, Jan

    2008-03-01

    Mass-spectrometric stable isotope measurements of CO 2 use molecular ion currents at mass-to-charge ratios m/ z 44, 45 and 46 to derive the elemental isotope ratios n( 13C)/ n( 12C) and n( 18O)/ n( 16O), abbreviated 13C/ 12C and 18O/ 16O, relative to a reference. The ion currents have to be corrected for the contribution of 17O-bearing isotopologues, the so-called ' 17O correction'. The magnitude of this correction depends on the calibrated isotope ratios of the reference. Isotope ratio calibrations are difficult and are therefore a matter of debate. Here, I provide a comprehensive evaluation of the existing 13C/ 12C ( 13R), 17O/ 16O ( 17R) and 18O/ 16O ( 18R) calibrations of the reference material Vienna Standard Mean Ocean Water (VSMOW) and CO 2 generated from the reference material Vienna Pee Dee Belemnite (VPDB) by reaction with 100% H 3PO 4 at 25 °C (VPDB-CO 2). I find 17R/10-6=382.7-2.1+1.7, 18RVSMOW/10 -6 = 2005.20 ± 0.45, 13R/10-6= 11124 ± 45, 17R/10-6=391.1-2.1+1.7 and 18R/10-6=2088.37±0.90. I also rephrase the calculation scheme for the 17O correction completely in terms of relative isotope ratio differences ( δ values). This reveals that only ratios of isotope ratios (namely, 17R/ 13R and 13R17R/ 18R) are required for the 17O correction. These can be, and have been, measured on conventional stable isotope mass spectrometers. I then show that the remaining error for these ratios of isotope ratios can lead to significant uncertainty in the derived relative 13C/ 12C difference, but not for 18O/ 16O. Even though inter-laboratory differences can be corrected for by a common 'ratio assumption set' and/or normalisation, the ultimate accuracy of the 17O correction is hereby limited. Errors of similar magnitude can be introduced by the assumed mass-dependent relationship between 17O/ 16O and 18O/ 16O isotope ratios. For highest accuracy in the 13C/ 12C ratio, independent triple oxygen isotope measurements are required. Finally, I propose an experiment that

  19. Sensitivity of orbital neutron measurements to the thickness and abundance of surficial lunar water

    NASA Astrophysics Data System (ADS)

    Lawrence, D. J.; Hurley, D. M.; Feldman, W. C.; Elphic, R. C.; Maurice, S.; Miller, R. S.; Prettyman, T. H.

    2011-01-01

    Recent near-infrared spectral data have shown that surficial water (H2O/OH) exists over large expanses of the lunar surface. These results have led to a reexamination of the hydrogen abundance sensitivity limits of orbital neutron data to detect surficial hydrogen on the lunar surface. A wet-over-dry, two-layer stratigraphy is modeled for the first time using neutron transport codes. For thin layers (<30 g/cm2), the epithermal neutron flux increases with increasing hydrogen concentration. This behavior is in contrast to the standard behavior for a single layer or dry-over-wet stratigraphy where the epithermal neutron counting rate decreases with increasing hydrogen concentration. These neutron transport results are applied to a H2O/OH enhancement at Goldschmidt crater. The neutron behavior at Goldschmidt is mostly controlled by spatial variations in neutron absorbing elements. After accounting for variations from neutron absorbing elements, there remain residual neutron enhancements at Goldschmidt crater with marginal statistical significance. If these residual enhancements are due to hydrogen, then their magnitude implies the presence of an upper layer with thickness of ˜3-30 g/cm2 (or 1.7-17 cm for an assumed density of 1.8 g/cm3) having an enhanced hydrogen abundance of 0.1-1 wt % water equivalent hydrogen. However, more work needs to be done to understand systematic variations of neutron counting rates at the 1-3% signal contrast level before a definitive conclusion can be made that the residual neutron enhancement at Goldschmidt crater is due to enhanced hydrogen abundances.

  20. A precise few-nucleon size difference by isotope shift measurements of helium

    NASA Astrophysics Data System (ADS)

    Rezaeian, Nima Hassan

    We perform high precision measurements of an isotope shift between the two stable isotopes of helium. We use laser excitation of the 23 S1 -- 23P0 transition at 1083 .... in a metastable beam of 3He and 4He atoms. A newly developed tunable laser frequency selector along with our previous electro-optic frequency modulation technique provides extremely reliable, adaptable, and precise frequency and intensity control. The intensity control contributes negligibly to overall experimental uncertainty by selecting (t selection < 50 ) and stabilizing the intensity of the required sideband and eliminating (˜10-5) the unwanted frequencies generated during the modulation of 1083 nm laser carrier frequency. The selection technique uses a MEMS based fiber switch (tswitch ≈ 10 ms) and several temperature stabilized narrow band (˜3 GHz) fiber gratings. A fiber based optical circulator and an inline fiber amplifier provide the desired isolation and the net gain for the selected frequency. Also rapid (˜2 sec.) alternating measurements of the 23 S1 -- 23P0 interval for both species of helium is achieved with a custom fiber laser for simultaneous optical pumping. A servo-controlled retro-reflected laser beam eliminates residual Doppler effects during the isotope shift measurement. An improved detection design and software control makes negligible subtle potential biases in the data collection. With these advances, combined with new internal and external consistency checks, we are able to obtain results consistent with the best previous measurements, but with substantially improved precision. Our measurement of the 23S 1 -- 23P0 isotope shift between 3He and 4He is 31 097 535.2 (5)kHz. The most recent theoretic calculation combined with this measuremen. yields a new determination for nuclear size differences between 3He and 4He: Deltarc = 0.292 6 (1)exp (8)th(52)expfm, with a precision of less than a part in 104 coming from the experimental uncertainty (first parenthesis), and a

  1. The abundance of the actinides in the cosmic radiation as measured on HEAO 3

    NASA Technical Reports Server (NTRS)

    Binns, W. R.; Israel, M. H.; Klarmann, J.; Fickle, R. K.; Waddington, C. J.; Garrard, T. L.; Stone, E. C.

    1982-01-01

    The HEAO 3 detector of heavy cosmic-ray nuclei has observed one possible actinide nucleus and some 100 nuclei of the platinum-lead group of elements. The resulting upper limit of 3% for the abundance ratio of actinides to platinum-lead nuclides is significantly lower than previous results from other observations. This new limit is inconsistent with freshly synthesized, pure r-process sources for cosmic-ray nuclei in this charge interval but is consistent with a source having a composition similar to the solar system, or to aged r-process material. We observe no events with a charge greater than 96.

  2. Evapotranspiration Partitioning with Sub-Daily Isotopic Measurement in a Sub-Humid Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Sun, X.; Wilcox, B. P.; Zou, C.; Stebler, E.; West, J. B.

    2015-12-01

    Evapotranspiration (ET) interweaves water, energy, and biogeochemical interactions between the land surface and atmospheric system. Stable isotopic measurement, especially field deployable laser absorption spectrometers, provides a promising tool for ET partitioning with its direct and efficient measurement on isotopic components of water vapor. This isotopic approach, however, is still facing some uncertainties in quantifying ET and its constituents according to assumptions and empirical formula involved. In this study, we combined high-time resolution measurement with laser absorption spectrometers and eddy covariance techniques to quantify ET and its two components, namely soil water Evaporation (E) and plant transpiration (T) for a sub-humid grassland in southern US. Direct chamber measurement on these two end-members was compared with revised Craig-Gordon model for the quantification consistency assessment. Our results indicate the daily ratio of T/ET and its sub-daily dynamics for different soil moisture and micro-climate conditions. We investigated the controlling factors for ET and its partitioning dynamics for this grassland ecosystem. The uncertainties involved in the quantification were also assessed by comparison between direct chamber and empirical approaches.

  3. Separation Of Uranium And Plutonium Isotopes For Measurement By Multi Collector Inductively Coupled Plasma Mass Spectroscopy

    SciTech Connect

    Martinelli, R E; Hamilton, T F; Williams, R W; Kehl, S R

    2009-03-29

    Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with {sup 233}U and {sup 242}Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA{reg_sign} column coupled to a UTEVA{reg_sign} column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of {sup 234}U/{sup 235}U, {sup 238}U/{sup 235}U, {sup 236}U/{sup 235}U, and {sup 240}Pu/{sup 239}Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment.

  4. Charge-changing cross section measurement of neutron-rich carbon isotopes at 50 AMeV

    NASA Astrophysics Data System (ADS)

    Tran, D. T.; Nguyen, T. T.; Tanihata, I.; Ong, H. J.; Fukuda, M.; Aoi, N.; Ayyad, Y.; Sakaguchi, H.; Tanaka, J.; Chan, P. Y.; Hoang, T. H.; Hashimoto, T.; Ideguchi, E.; Inoue, A.; Kawabata, T.; Khiem, L. H.; Matsuta, K.; Mihara, M.; Momota, S.; Nagae, D.; Ozawa, A.; Ren, P. P.; Terashima, S.; Wada, R.; Lin, W. P.; Yamamoto, T.

    2016-05-01

    Charge Changing Cross Sections (CCCS or σCC) of neutron-rich carbon isotopes on carbon target were measured at low energy (50A MeV) for the first time. The consistency between Glauber calculation and experimental σCC of 12C isotope at low energy region shows that proton distribution radii can be derived from CCCS at low energy.

  5. Accurate measurement of the relative abundance of different DNA species in complex DNA mixtures.

    PubMed

    Jeong, Sangkyun; Yu, Hyunjoo; Pfeifer, Karl

    2012-06-01

    A molecular tool that can compare the abundances of different DNA sequences is necessary for comparing intergenic or interspecific gene expression. We devised and verified such a tool using a quantitative competitive polymerase chain reaction approach. For this approach, we adapted a competitor array, an artificially made plasmid DNA in which all the competitor templates for the target DNAs are arranged with a defined ratio, and melting analysis for allele quantitation for accurate quantitation of the fractional ratios of competitively amplified DNAs. Assays on two sets of DNA mixtures with explicitly known compositional structures of the test sequences were performed. The resultant average relative errors of 0.059 and 0.021 emphasize the highly accurate nature of this method. Furthermore, the method's capability of obtaining biological d