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Sample records for carbon-13 isotopic enrichment

  1. A report on the inter comparison of isotopic analyses by mass spectrometry for the laser enrichment of carbon-13

    International Nuclear Information System (INIS)

    A method has been standardized for the mass spectral analysis of (13C/12C) ratio in the isotopically enriched C2F4 photoproduct obtained by the CO2 laser photolysis of natural CF2HCI sample. For improving the quality of the spectra as well as enchancing the detection level of the product at very low concentrations, a pre-concentration technique has been developed by gas chromatography. Inter comparison of the results for analyses carried out with two different mass spectrometers, viz., a commercial instrument available at the Land PT Division and an indigenously built one by MS and ES, BARC showed a very good agreement. (author)

  2. Enhanced biosynthetically directed fractional carbon-13 enrichment of proteins for backbone NMR assignments.

    Science.gov (United States)

    Wenrich, Broc R; Sonstrom, Reilly E; Gupta, Riju A; Rovnyak, David

    2015-11-01

    Routes to carbon-13 enrichment of bacterially expressed proteins include achieving uniform or positionally selective (e.g. ILV-Me, or (13)C', etc.) enrichment. We consider the potential for biosynthetically directed fractional enrichment (e.g. carbon-13 incorporation in the protein less than 100%) for performing routine n-(D)dimensional NMR spectroscopy of proteins. First, we demonstrate an approach to fractional isotope addition where the initial growth media containing natural abundance glucose is replenished at induction with a small amount (e.g. 10%(w/w)u-(13)C-glucose) of enriched nutrient. The approach considered here is to add 10% (e.g. 200mg for a 2g/L culture) u-(13)C-glucose at the induction time (OD600=0.8), resulting in a protein with enhanced (13)C incorporation that gives almost the same NMR signal levels as an exact 20% (13)C sample. Second, whereas fractional enrichment is used for obtaining stereospecific methyl assignments, we find that (13)C incorporation levels no greater than 20%(w/w) yield (13)C and (13)C-(13)C spin pair incorporation sufficient to conduct typical 3D-bioNMR backbone experiments on moderate instrumentation (600 MHz, RT probe). Typical 3D-bioNMR experiments of a fractionally enriched protein yield expected backbone connectivities, and did not show amino acid biases in this work, with one exception. When adding 10% u-(13)C glucose to expression media at induction, there is poor preservation of (13)Cα-(13)Cβ spin pairs in the amino acids ILV, leading to the absence of Cβ signals in HNCACB spectra for ILV, a potentially useful editing effect. Enhanced fractional carbon-13 enrichment provides lower-cost routes to high throughput protein NMR studies, and makes modern protein NMR more cost-accessible.

  3. Selective carbon 13 enrichment of side chain carbons of ginkgo lignin traced by carbon 13 nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Although carbon 13 nuclear magnetic resonance spectroscopy (13C-NMR) is widely used in lignin structural studies, serious difficulties are encountered in the assignments of 13C signals because of their extensive overlaps resulting from the complex structure of lignin and of delicate detection of minor structures. To overcome these difficulties, specifically 13C-enriched precursors of lignin biosynthesis, coniferin-[side chain-β-13C] and coniferin-[side chain-γ-13C], were administered to growing stems of ginkgo (Ginkgo biloba). The NMR analysis of the milled wood lignins isolated from the newly formed xylem showed that selective enrichment of specific carbons of protolignin in the cell wall was achieved without seriously disturbing the lignin biosynthesis. The presence of saturated methylene side chains in the protolignin was shown for the first time by this selective enrichment technique in combination with NMR analysis. (authors). 23 refs., 3 figs., 1 tab

  4. Selective carbon 13 enrichment of side chain carbons of ginkgo lignin traced by carbon 13 nuclear magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Y. (Nagoya Univ. (Japan). Faculty of Agriculture); Robert, D.R. (CEA Centre d' Etudes de Grenoble, 38 (France). Dept. de Recherche Fondamentale sur la Matiere Condensee); Terashima, N. (Forest Products Lab., Madison, WI (United States))

    Although carbon 13 nuclear magnetic resonance spectroscopy ([sup 13]C-NMR) is widely used in lignin structural studies, serious difficulties are encountered in the assignments of [sup 13]C signals because of their extensive overlaps resulting from the complex structure of lignin and of delicate detection of minor structures. To overcome these difficulties, specifically [sup 13]C-enriched precursors of lignin biosynthesis, coniferin-[side chain-[beta]-[sup 13]C] and coniferin-[side chain-[gamma]-[sup 13]C], were administered to growing stems of ginkgo (Ginkgo biloba). The NMR analysis of the milled wood lignins isolated from the newly formed xylem showed that selective enrichment of specific carbons of protolignin in the cell wall was achieved without seriously disturbing the lignin biosynthesis. The presence of saturated methylene side chains in the protolignin was shown for the first time by this selective enrichment technique in combination with NMR analysis. (authors). 23 refs., 3 figs., 1 tab.

  5. Concomitant oxygen-18 enrichment in commercial carbon-13 labelled urea

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Katsumi; Chiyoda, Takeshi; Kajiwara, Masahiro [Meiji College of Pharmacy, Tokyo (Japan). Dept. of Medicinal Chemistry

    1996-12-01

    By mass spectroscopy, 50-fold oxygen-18 enrichment over natural abundance was observed in commercial {sup 13}C-urea (99 atom % {sup 13}C) synthesized from {sup 13}C-carbon monoxide that had been {sup 13}C-enriched by cryogenic distillation. In contrast, {sup 13}C-urea synthesized from {sup 13}C-potassium cyanide (a {sup 13}C-labelled compound having no oxygen atom) showed the natural abundance level of oxygen-18. (author).

  6. Isotopic composition of carbon-13 and oxygen-18 from authigenic carbonates, Black Sea region

    Science.gov (United States)

    Logvina, E.; Mazurenko, L.; Prasolov, E.

    2004-05-01

    Several types of authigenic carbonates related to the fluid discharge zones were sampled during the international expeditions onboard R/V "Professor Vodyanitskiy" (56th cruise) and R/V "Professor Logachev" (11th cruise of UNESCO-TTR) in the northwest part of the Black sea. These carbonates are represented as mounds, build-ups and chimney-like structures, cemented sediments, crusts and concretions. The isotope analyses of carbonates were conducted using mass-spectrometer MS-20 in the Laboratory of Isotope Geology (St.Petersburg State University). The obtained values of oxygen-18 varied from +0,6 to -1,9 per mille (up to C0.8 per mille on average). This value is corresponding to normal seawater oxygen-18 value (about 0 per mille); we suspect, that the source of oxygen for carbonate formation is the seawater. The carbonates are characterized by low carbon-13 (from -35,4 to -42,6 per mille) in comparison with normal marine carbonates (about 0 per mille). We have reason to suppose that carbonates associated with fluid venting were formed by light isotopic composition of carbon dioxide (carbon-13 -45 to -52 per mille), which forming under methane microbiologic oxidation with such isotopic composition. This is because of crossing fluid process of carbon dioxide to carbonate with 8~10 degrees temperature carbon became heaver to 10- 11 per mille. The isotopic composition study of carbonate build-ups is of interest because its association with the gas hydrate accumulations is quite often in the gas seeps. This work is financially supported by Russian Foundation for Basic Research, grant 02-05-64346.

  7. Kinetic isotope effect of carbon-13 in decarboxylation of phenylpropiolic acid in anhydrous formic acid

    International Nuclear Information System (INIS)

    Carbon-13 kinetic isotope effects in the decarboxylation of phenylpropiolic acid (carboxyl-13C) in formic acid medium and in the decarbonylation of liquid formic acid assisted with phenylpropiolic acid (PPA) and acetophenone (AP) have been studied in the 70-100oC temperature interval. The carboxyl-13C KIEs are in the range 1.0034 at 71.6oC and 1.0047 at 101.2oC respectively. The C-13C KIE, k-12/k-13, in the decarbonylation of liquid formic acid assisted with PPA were found to be of 1.0419 at 71.6oC and 1.0383 at 101.2oC. The C-13 KIE in the decarbonylation of pure formic acid are 1.0464 at 70.2oC and 1.0411 at 98oC respectively. The above experimental results have been discussed and interpreted as indicating that the formation of Cα-H bond preceded by the protonation of triple acetylenic bond of PPA is the rate determining step followed by carbon dioxide splitting. The 13-CO-KIE in the carbon monooxide generation assisted with PPA is much larger than the 13-CO-KIE generated in the presence of phenylacetylene. This shows that the decarboxylation of PPA and decarboxylation of FA are interrelated processes proceeding in the reaction cage. The formic acid involved in the formation of TS is decarbonylating directly avoiding probably largely the formic acid anhydride intermediate formation. (author)

  8. Phenotyping hepatocellular metabolism using uniformly labeled carbon-13 molecular probes and LC-HRMS stable isotope tracing.

    Science.gov (United States)

    Meissen, John K; Pirman, David A; Wan, Min; Miller, Emily; Jatkar, Aditi; Miller, Russell; Steenwyk, Rick C; Blatnik, Matthew

    2016-09-01

    Metabolite stable isotope tracing is a powerful bioanalytical strategy that has the potential to unravel phenotypic markers of early pharmaceutical efficacy by monitoring enzymatic incorporation of carbon-13 atoms into targeted pathways over time. The practice of probing biological systems with carbon-13 labeled molecules using broad MS-based screens has been utilized for many years in academic laboratories but has had limited application in the pharmaceutical R&D environment. The goal of this work was to establish a LCMS analytical workflow that was capable of monitoring carbon-13 isotope changes in glycolysis, the TCA and urea cycles, and non-essential amino acid metabolism. This work applies a standardized protein precipitation with 80% cold methanol and two distinct reverse-phase ion-pair liquid chromatography methods coupled to either a positive- or negative-ion mode high-resolution accurate mass spectrometry screening method. The data herein combines thousands of single-point peak integrations into a novel metabolite network map as a visualization aid to probe and monitor stable isotope incorporation in murine hepatocytes using uniformly labeled (13)C6 glucose, (13)C3 lactate, and (13)C5 glutamine. This work also demonstrates that nitrogen metabolism may have a large influence on the TCA cycle and gluconeogenic carbon fluxes in hepatocyte cell culture. PMID:27343766

  9. Studying biosphere-atmosphere exchange of CO2 through Carbon-13 stable isotopes

    NARCIS (Netherlands)

    Velde, van der I.R.

    2015-01-01

    Summary Thesis ‘Studying biosphere-atmosphere exchange of CO2 through carbon-13 stable isotopes’ Ivar van der Velde Making predictions of future climate is difficult, mainly due to large uncertainties in the carbon cycle. The rate at which carbon is stored in the oceans and terrestrial b

  10. Oak Ridge National Laboratory's isotope enrichment program

    International Nuclear Information System (INIS)

    The Isotope Enrichment Program (IEP) at Oak Ridge National Laboratory (ORNL) is responsible for the production and distribution of ∼225 enriched stable isotopes from 50 multi-isotopic elements. In addition, ORNL distributes enriched actinide isotopes and provides extensive physical- and chemical-form processing of enriched isotopes to meet customer requirements. For more than 50 yr, ORNL has been a major provider of enriched isotopes and isotope-related services to research, medical, and industrial institutions throughout the world. Consolidation of the Isotope Distribution Office (IDO), the Isotope Research Materials Laboratory (IRML), and the stable isotope inventories in the Isotope Enrichment Facility (IEF) have improved operational efficiencies and customer services. Recent changes in the IEP have included adopting policies for long-term contracts, which offer program stability and pricing advantages for the customer, and prorated service charges, which greatly improve pricing to the small research users. The former U.S. Department of Energy (DOE) Loan Program has been converted to a lease program, which makes large-quantity or very expensive isotopes available for nondestructive research at a nominal cost. Current efforts are being pursued to improve and expand the isotope separation capabilities as well as the extensive chemical- and physical-form processing that now exists. The IEF's quality management system is ISO 9002 registered and accredited in the United States, Canada, and Europe

  11. Differentiation of Pigment in Eggs Using Carbon ((13)C/(12)C) and Nitrogen ((15)N/(14)N) Stable Isotopes.

    Science.gov (United States)

    Sun, Feng M; Shi, Guang Y; Wang, Hui W

    2016-07-01

    Consumers prefer natural and healthy food, but artificial pigments are often abused in egg products. The study aimed at differentiating the origin of pigments in eggs by applying the technique of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope analysis. Five hundred sixty laying hens were randomly distributed into 14 treatments, which were divided into four groups: maize, carophyll red pigment, carophyll yellow pigment, and a mixture of carophyll red and yellow pigments. Eggs were collected and pretreated to determe the values of the Roche Yolk Color Fan (RCF), δ(13)C, and δ(15)N. With increasing maize content, the RCF and δ(13)C values of yolks increased. Moreover, the RCF values in the three pigment groups were significantly influenced by the artificial colors, but δ(13)C values were not significantly different, regardless of the existence of pigment. The δ(15)N values in all treatments did not vary as regularly as the carbon stable isotope. A strong positive correlation was found between RCF and δ(13)C in the maize group, but no such correlation was be observed in the pigment groups. It is concluded that carbon stable isotope ratio analysis (δ(13)C) of the yolk can be used to differentiate the origin of the pigment added to eggs.

  12. Differentiation of Pigment in Eggs Using Carbon ((13)C/(12)C) and Nitrogen ((15)N/(14)N) Stable Isotopes.

    Science.gov (United States)

    Sun, Feng M; Shi, Guang Y; Wang, Hui W

    2016-07-01

    Consumers prefer natural and healthy food, but artificial pigments are often abused in egg products. The study aimed at differentiating the origin of pigments in eggs by applying the technique of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) stable isotope analysis. Five hundred sixty laying hens were randomly distributed into 14 treatments, which were divided into four groups: maize, carophyll red pigment, carophyll yellow pigment, and a mixture of carophyll red and yellow pigments. Eggs were collected and pretreated to determe the values of the Roche Yolk Color Fan (RCF), δ(13)C, and δ(15)N. With increasing maize content, the RCF and δ(13)C values of yolks increased. Moreover, the RCF values in the three pigment groups were significantly influenced by the artificial colors, but δ(13)C values were not significantly different, regardless of the existence of pigment. The δ(15)N values in all treatments did not vary as regularly as the carbon stable isotope. A strong positive correlation was found between RCF and δ(13)C in the maize group, but no such correlation was be observed in the pigment groups. It is concluded that carbon stable isotope ratio analysis (δ(13)C) of the yolk can be used to differentiate the origin of the pigment added to eggs. PMID:27302905

  13. Carbon-13 and oxygen-18 kinetic isotope effects on methanolysis of p-nitrostyrene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Jacober, S.P.; Hanzlik, R.P.

    1986-04-02

    Kinetic isotope effects for the acid- and base-catalyzed methanolysis of (epoxide-/sup 18/O)- and (8-/sup 13/C)-p-nitrostyrene oxide have been measured at 30.0/sup 0/. In acid 94.7% of the reaction occurs at the benzylic carbon, while in base 83.5% occurs at the primary carbon (C(8)). In base the isotope effects kappa/sub 16//kappa/sub 1/( and kappa/sub 1/''/kappa /sub 1/number were 1.035 +/- 0.013 and 1.082 +/- 0.012, while in acid they were 1.012 +/- 0.011 and 0.995 +/- 0.012, respectively. These data complement previously determined deuterium isotope effects for the reaction in base. They suggest a late transition state in base with considerable ring opening via an S/sub N/2 mechanism. However, in acid, the data suggest a somewhat earlier transition state with less ring opening and weaker bonding to the nucleophile than in base.

  14. Engineering Studies of a Pilot Plant for Laser Isotope Separation of CARBON-13 by Multiphoton Dissociation of Chlorodifluoromethane

    Science.gov (United States)

    Mehmetli, Bulent Ahmet

    Recent research in laser isotope separation by multiphoton dissociation (LISMPD) of ^{13 }C suggests that an LISMPD commercial process is more economical than the cryogenic CO distillation technology currently used to meet most of the world's ^ {13}C demand. In this dissertation, experimental studies of an engineering process for LISMPD of polyatomic molecules is examined. The experimental results have been obtained by MPD of chlorodifluoromethane (CF_2 HCl) to yield ^{13}C -enriched tetrafluoroethylene rm(C_2F _4). Emphasis is on research leading to the development of a practical chemical plant for the preparation of stable isotopes by this method. The experimental program has achieved the design, construction, and operation of a laboratory-scale ^{13}C separation apparatus and parametric dependences of enrichment factors and dissociated fractions. In this experiment, the reactant gas, industrial grade CF_2HCl, flows continuously along the axis of a stainless steel reaction cell. The beam of a commercial CO_2 TEA laser, delivering up to 3 J/pulse at a single wavelength, is focused into the cell to induce isotope-selective multiphoton dissociation. The ^{13}C-enriched reaction product, rm C_2F_4, is analyzed by mass spectroscopy for its isotopic content. Typical production rates of the setup are about 10 g/year ^{13}C at an enrichment of 15% or 1 g/year at an enrichment of 65%. The results of a detailed cost analysis, which takes into account different reaction conditions and laser types, showed that at production rates of 7,000 kg per year, the cost of ^{13}C can be as low as 4/g. This figure is about an order of magnitude less than the cost of ^13 C obtained by cryogenic distillation of CO. The design, construction, and operation of a CO _2 MOPA (Master Oscillator/ Power Amplifier) laser is proposed because a MOPA combines the advantages of favorable isotope separation reaction conditions of TEA lasers and the cheaper photons of cw discharges. Analytical

  15. Coastal climate reflected in carbon-13/carbon-12 ratio of organic carbon in varved sediment from Santa Barbara basin

    OpenAIRE

    Schimmelmann, Arndt; Tegner, Mia J.

    1991-01-01

    A 1844-1987 time-series of carbon stable isotope ratios from dated sedimentary total organic carbon from the center of the Santa Barbara basin is compared with historical climate and oceanographic records. Carbon derived from carbon-13-depleted phytoplankton and carbon-13-enriched kelp appear responsible for a large part of the isotopic variance in sedimentary total organic carbon. El Niño/Southern Oscillation events are recorded by the isotopic response of marine organic carbon in sediments.

  16. Utilization of carbon 13-labelled stable isotopes for studying drug toxicity on cellular metabolism; Utilisation d`isotopes stables marques au carbone 13 pour etudier la toxicite de drogues au niveau du metabolisme cellulaire

    Energy Technology Data Exchange (ETDEWEB)

    Herve, M.; Wietzerbin, J.; Tran-Dinh, S. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Biologie Cellulaire et Moleculaire

    1994-12-31

    A new approach for studying the effects of two drugs, amphotericine B (AMB), an anti-fungal antibiotic, and 2-deoxy-D-glucose (DG), on the glucose metabolism in brewer yeast cells (Saccharomyces cerevisiae), is presented; AMB interacts with the membrane sterols, inducing formation of pores through which ions and small molecules can pass. DG may enter in the cytosol, where it is phosphoryled by hexokinase into deoxy-D-glucose 6-phosphate (DG6P) which disappears very slowly. DG slows down the glycolysis process and induces the formation of new substances. This paper shows the advantages of utilizing carbon 13-labelled substrates combined to the NMR-13C and NMR-1H techniques. 6 figs., 5 refs.

  17. Stable isotope enrichment using a plasma centrifuge

    Science.gov (United States)

    Krishnan, Mahadevan; Bures, Brian; Madden, Robert

    2012-10-01

    A primary goal of the Department of Energy's Isotope Development and Production for Research and Applications Program (Isotope Program) within the Office of Nuclear Physics (NP) is to produce isotopes that are in short supply in the U.S. and of which there exists no or insufficient domestic commercial production capability. A vacuum arc plasma centrifuge is a rigid rotor column of metal plasma in which centrifugal forces re-distribute ions radially according to their mass/charge ratio. Early work demonstrated rotation at 2 million rpm and separation of various stable isotopes. The spinning plasma column had a Gaussian flux profile, peaked on the rigid rotor axis. This work adopts a more efficient approach, with the plasma created as a hollow column, wherein the flux is concentrated at larger radii where the centrifugal action is highest. By tailoring the vacuum arc discharge geometry, the rotation rate can also be increased to ˜10 million rpm. Data from Cu, Al and other metal plasmas will be presented and discussed in light of enriched stable isotopes needed for research and medicine.

  18. Complementary constraints from carbon (13C) and nitrogen (15N) isotopes on the glacial ocean's soft-tissue biological pump

    Science.gov (United States)

    Schmittner, A.; Somes, C. J.

    2016-06-01

    A three-dimensional, process-based model of the ocean's carbon and nitrogen cycles, including 13C and 15N isotopes, is used to explore effects of idealized changes in the soft-tissue biological pump. Results are presented from one preindustrial control run (piCtrl) and six simulations of the Last Glacial Maximum (LGM) with increasing values of the spatially constant maximum phytoplankton growth rate μmax, which accelerates biological nutrient utilization mimicking iron fertilization. The default LGM simulation, without increasing μmax and with a shallower and weaker Atlantic Meridional Overturning Circulation and increased sea ice cover, leads to 280 Pg more respired organic carbon (Corg) storage in the deep ocean with respect to piCtrl. Dissolved oxygen concentrations in the colder glacial thermocline increase, which reduces water column denitrification and, with delay, nitrogen fixation, thus increasing the ocean's fixed nitrogen inventory and decreasing δ15NNO3 almost everywhere. This simulation already fits sediment reconstructions of carbon and nitrogen isotopes relatively well, but it overestimates deep ocean δ13CDIC and underestimates δ15NNO3 at high latitudes. Increasing μmax enhances Corg and lowers deep ocean δ13CDIC, improving the agreement with sediment data. In the model's Antarctic and North Pacific Oceans modest increases in μmax result in higher δ15NNO3 due to enhanced local nutrient utilization, improving the agreement with reconstructions there. Models with moderately increased μmax fit both isotope data best, whereas large increases in nutrient utilization are inconsistent with nitrogen isotopes although they still fit the carbon isotopes reasonably well. The best fitting models reproduce major features of the glacial δ13CDIC, δ15N, and oxygen reconstructions while simulating increased Corg by 510-670 Pg compared with the preindustrial ocean. These results are consistent with the idea that the soft-tissue pump was more efficient

  19. Traceability of animal byproducts in quail (Coturnix coturnix japonica tissues using carbon (13C/12C and nitrogen (15N/14N stable isotopes

    Directory of Open Access Journals (Sweden)

    C Móri

    2007-12-01

    Full Text Available Consistent information on meat products consumed by the public is essential. The technique of stable isotopes is a powerful tool to recover consumers' confidence, as it allows the detection of animal byproduct residues in poultry meat, particularly in quail meat. This study aimed at checking the presence of poultry byproduct mixtures in quail diets by applying the technique of carbon (13C/12C and nitrogen (15N/14N stable isotopes in quail breast muscle, keel, and tibia. Sixty four one-day-old male quails were obtained from a commercial farm. Birds were housed in an experimental house from one to 42 days of age, and were randomly distributed into 8 experimental treatments, and fed diets containing poultry offal meal (POM, bovine meat and bone meal (MBM or poultry feather meal (PFM, or their mixtures. Four birds per treatment were slaughtered at 42 days of age, and breast (Pectoralis major, keel, and tibia were collected for analyses. The inclusion of animal byproducts in quail diets was detected by 13C e 15N analyses in the tissues of the birds; however, it was not possible to specify which byproducts were used. It was concluded that quail meat can be certified by the technique of stable isotopes.

  20. Enriching stable isotopes: Alternative use for Urenco technology

    Energy Technology Data Exchange (ETDEWEB)

    Rakhorst, H.; de Jong, P.G.T.; Dawson, P.D. [URENCO-NL, Almelo (Netherlands)

    1996-12-31

    The International Urenco Group utilizes a technologically advanced centrifuge process to enrich uranium in the fissionable isotope {sup 235}U. The group operates plants in the United Kingdom, the Netherlands, and Germany and currently holds a 10% share of the multibillion dollar world enrichment market. In the early 1990s, Urenco embarked on a strategy of building on the company`s uniquely advanced centrifuge process and laser isotope separation (LIS) experience to enrich nonradioactive isotopes colloquially known as stable isotopes. This paper summarizes the present status of Urenco`s stable isotopes business.

  1. Enriching stable isotopes: Alternative use for Urenco technology

    International Nuclear Information System (INIS)

    The International Urenco Group utilizes a technologically advanced centrifuge process to enrich uranium in the fissionable isotope 235U. The group operates plants in the United Kingdom, the Netherlands, and Germany and currently holds a 10% share of the multibillion dollar world enrichment market. In the early 1990s, Urenco embarked on a strategy of building on the company's uniquely advanced centrifuge process and laser isotope separation (LIS) experience to enrich nonradioactive isotopes colloquially known as stable isotopes. This paper summarizes the present status of Urenco's stable isotopes business

  2. Carbon-13 isotope composition of the mean CO2 source in the urban atmosphere of Krakow, southern Poland

    Science.gov (United States)

    Zimnoch, Miroslaw; Jasek, Alina; Rozanski, Kazimierz

    2014-05-01

    Quantification of carbon emissions in urbanized areas constitutes an important part of the current research on the global carbon cycle. As the carbon isotopic composition of atmospheric carbon dioxide can serve as a fingerprint of its origin, systematic observations of δ13CO2 and/or Δ14CO2, combined with atmospheric CO2mixing ratio measurements can be used to better constrain the urban sources of this gas. Nowadays, high precision optical analysers based on absorption of laser radiation in the cavity allow a real-time monitoring of atmospheric CO2 concentration and its 13CO2/12CO2 ratio, thus enabling better quantification of the contribution of different anthropogenic and natural sources of this gas to the local atmospheric CO2load. Here we present results of a 2-year study aimed at quantifying carbon isotopic signature of the mean CO2 source and its seasonal variability in the urban atmosphere of Krakow, southern Poland. The Picarro G2101-i CRDS isotopic analyser system for CO2and 13CO2/12CO2 mixing ratio measurements has been installed at the AGH University of Science and Technology campus in July 2011. Air inlet was located at the top of a 20m tower mounted on the roof of the faculty building (ca. 42m a.g.l.), close to the city centre. While temporal resolution of the analyser is equal 1s, a 2-minute moving average was used for calculations of δ13CO2 and CO2 mixing ratio to reduce measurement uncertainty. The measurements were calibrated against 2 NOAA (National Oceanic and Atmospheric Administration) primary standard tanks for CO2 mixing ratio and 1 JRAC (Jena Reference Air Cylinder) isotope primary standard for δ13C. A Keeling approach based on two-component mass and isotope balance was used to derive daily mean isotopic signatures of local CO2 from individual measurements of δ13CO2 and CO2 mixing ratios. The record covers a 2-year period, from July 2011 to July 2013. It shows a clear seasonal pattern, with less negative and less variable δ13CO2 values

  3. Quantitative and mechanistic studies using the oxygen-18 isotope shift in carbon-13 nuclear magnetic resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Mega, T.L.

    1989-01-01

    The {sup 18}O-isotope shift in {sup 13}C NMR spectroscopy was used to study the kinetics of oxygen exchange at the anomeric carbon atoms of several ketoses and aldoses. At 25-26{degree}C and over the pH range from 2 to 10, the relative rates of oxygen exchange for the aldoses studied increased in the following sequence: D-glucose, D-mannose, D-ribose, D-2-deoxyribose. The hydration rates for the open chain forms of the sugars were calculated and the results were analyzed in terms of steric and inductive effects by drawing analogies with the hydration kinetics of simple aldehydes and ketones. Effective molarities associated with ring closure reactions of common monosaccharides are calculated. The position of bond cleavage in the acid-catalyzed hydrolysis of sucrose was elucidated by hydrolyzing the sugar in {sup 18}O-water and assaying the incorporation of {sup 18}O into the several anomeric products using {sup 13}C NMR. Independents supporting experimental evidence was obtained using {sup 1}H NMR. A detailed investigation was made of the complex {sup 13}C NMR spectrum arising from the various {sup 18}O-isotopomers in a solution of {sup 18}O-labeled (1,4-{sup 13}C{sub 2}) succinic acid. The quantitative use of the {sup 18}O isotope shift in {sup 13}C NMR was assessed.

  4. Availability of enriched isotopic material for accelerator targets

    International Nuclear Information System (INIS)

    The electromagnetic isotope enrichment facility at ORNL provides a broad spectrum of highly enriched stable isotopes to the worldwide scientific community. The continued timely availability of these materials is of vital importance in many areas of basic research and, in particular, as source material for the fabrication of accelerator targets. A brief description of the facility and its capabilities and limitations is presented

  5. Laser Isotope Enrichment for Medical and Industrial Applications

    Energy Technology Data Exchange (ETDEWEB)

    Leonard Bond

    2006-07-01

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

  6. Moss stable isotopes (carbon-13, oxygen-18) and testate amoebae reflect environmental inputs and microclimate along a latitudinal gradient on the Antarctic Peninsula.

    Science.gov (United States)

    Royles, Jessica; Amesbury, Matthew J; Roland, Thomas P; Jones, Glyn D; Convey, Peter; Griffiths, Howard; Hodgson, Dominic A; Charman, Dan J

    2016-07-01

    The stable isotope compositions of moss tissue water (δ(2)H and δ(18)O) and cellulose (δ(13)C and δ(18)O), and testate amoebae populations were sampled from 61 contemporary surface samples along a 600-km latitudinal gradient of the Antarctic Peninsula (AP) to provide a spatial record of environmental change. The isotopic composition of moss tissue water represented an annually integrated precipitation signal with the expected isotopic depletion with increasing latitude. There was a weak, but significant, relationship between cellulose δ(18)O and latitude, with predicted source water inputs isotopically enriched compared to measured precipitation. Cellulose δ(13)C values were dependent on moss species and water content, and may reflect site exposure to strong winds. Testate amoebae assemblages were characterised by low concentrations and taxonomic diversity, with Corythion dubium and Microcorycia radiata types the most cosmopolitan taxa. The similarity between the intra- and inter-site ranges measured in all proxies suggests that microclimate and micro-topographical conditions around the moss surface were important determinants of proxy values. Isotope and testate amoebae analyses have proven value as palaeoclimatic, temporal proxies of climate change, whereas this study demonstrates that variations in isotopic and amoeboid proxies between microsites can be beyond the bounds of the current spatial variability in AP climate. PMID:27003701

  7. Moss stable isotopes (carbon-13, oxygen-18) and testate amoebae reflect environmental inputs and microclimate along a latitudinal gradient on the Antarctic Peninsula.

    Science.gov (United States)

    Royles, Jessica; Amesbury, Matthew J; Roland, Thomas P; Jones, Glyn D; Convey, Peter; Griffiths, Howard; Hodgson, Dominic A; Charman, Dan J

    2016-07-01

    The stable isotope compositions of moss tissue water (δ(2)H and δ(18)O) and cellulose (δ(13)C and δ(18)O), and testate amoebae populations were sampled from 61 contemporary surface samples along a 600-km latitudinal gradient of the Antarctic Peninsula (AP) to provide a spatial record of environmental change. The isotopic composition of moss tissue water represented an annually integrated precipitation signal with the expected isotopic depletion with increasing latitude. There was a weak, but significant, relationship between cellulose δ(18)O and latitude, with predicted source water inputs isotopically enriched compared to measured precipitation. Cellulose δ(13)C values were dependent on moss species and water content, and may reflect site exposure to strong winds. Testate amoebae assemblages were characterised by low concentrations and taxonomic diversity, with Corythion dubium and Microcorycia radiata types the most cosmopolitan taxa. The similarity between the intra- and inter-site ranges measured in all proxies suggests that microclimate and micro-topographical conditions around the moss surface were important determinants of proxy values. Isotope and testate amoebae analyses have proven value as palaeoclimatic, temporal proxies of climate change, whereas this study demonstrates that variations in isotopic and amoeboid proxies between microsites can be beyond the bounds of the current spatial variability in AP climate.

  8. Method for production of an isotopically enriched compound

    Science.gov (United States)

    Watrous, Matthew G.

    2012-12-11

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

  9. Estimating groundwater mixing and origin in an overexploited aquifer in Guanajuato, Mexico, using stable isotopes (strontium-87, carbon-13, deuterium and oxygen-18).

    Science.gov (United States)

    Horst, Axel; Mahlknecht, Jürgen; Merkel, Broder J

    2007-12-01

    Stable Isotopes (strontium-87, deuterium and oxygen-18, carbon-13) have been used to reveal different sources of groundwater and mixing processes in the aquifer of the Silao-Romita Valley in the state of Guanajuato, Mexico. Calcite dissolution appeared to be the main process of strontium release leading to relatively equal (87)Sr/(86)Sr ratios of 0.7042-0.7062 throughout the study area which could be confirmed by samples of carbonate rocks having similar Sr ratios (0.7041-0.7073). delta(13)C values (-11.91- -6.87 per thousand VPDB) of groundwaters confirmed the solution of carbonates but indicated furthermore influences of soil-CO(2). Deuterium and (18)O contents showed a relatively narrow range of-80.1- -70.0 per thousand VSMOW and -10.2- -8.8 per thousand, VSMOW, respectively but are affected by evaporation and mixing processes. The use of delta(13)C together with (87)Sr/(86)Sr revealed three possible sources: (i) carbonate-controlled waters showing generally higher Sr-concentrations, (ii) fissure waters with low-strontium contents and (iii) infiltrating water which is characterized by low delta(13)C and (87)Sr/(86)Sr ratios. The third component is affected by evaporation processes taking place before and during infiltration which might be increased by extraction and reinfiltration (irrigation return flow). PMID:18041622

  10. Capability of the electromagnetic isotope-enrichment facility at ORNL

    International Nuclear Information System (INIS)

    The isotope separation program at Oak Ridge National Laboratory (ORNL) prepares and distributes electromagnetically enriched stable isotopes to the worldwide scientific community. Among the topics discussed in the present paper are the methods of enriching isotopes, the limitations that apply to the quantity and final assay of the separation products, and a generalized production flowsheet indicating the capability of the facility. A brief description of each of the production steps, from the selection and preparation of initial feedstock to the recovery and distribution of the isotopically enriched material, is presented. The future of the facility, the continued supply of enriched isotopes, and the response of the program to new and changing requirements are emphasized

  11. Proposal to realize a cost breakthrough in carbon-13 production by photochemical separation

    International Nuclear Information System (INIS)

    A cost breakthrough can now be made in photochemical production of the rare stable isotope carbon-13. This cost breakthrough is achieved by CO2 laser infrared multiple-photon dissociation of any of several halocarbons (Freon derivatives) such as CF3Cl, CF3Br, or CF2Cl2. The single-step carbon-13 enrichment factor for this process is approximately 50, yielding 30% pure C-13 in one step, or up to 97% pure C-13 in two steps. A three-fold carbon-13 cost reduction to below $20/gram is expected to be achieved in a small laboratory-scale demonstration facility capable of producing 4 to 8 kg/year of carbon-13, using presently available pulsed CO2 TEA lasers at an average power level of 50 watts. Personnel costs dominate the attainable C-13 production costs in a small photochemical enrichment facility. A price reduction to $2/gm carbon-13 is feasible at carbon-13 production levels of 100 to 1000 kg/year, dominated by the Freon raw material costs

  12. Isotope enrichment of metal in the process of zone melting

    International Nuclear Information System (INIS)

    The possibility of using the zone melting technique with the purpose of isotope enrichment of metal has been checked. The experiments have been carried out with zinc and cadmium wires. After the experiment the long wire has been sectioned by 15 mm and in such a state has been subjected to mass spectrometric and neutron activation analysis. The dependence of isotope enrichment with zone passage is shown. The light isotopes 64Zn in zinc and 106Cd and 108Cd in cadmium move following the zone enriching at the wire end

  13. Preparation and physico-chemical study of nitroxide radicals. Isotopic marking with carbon 13 and deuterium; Preparations et etudes physico-chimiques de radicaux nitroxydes. Marquage isotopique au carbone 13 et au deuterium

    Energy Technology Data Exchange (ETDEWEB)

    Chapelet-Letourneux, G. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1967-07-01

    N-t-butyl-N-phenyl nitroxide is obtained by: a) action of t-butyl-magnesium chloride on nitrobenzene, or of phenyl-magnesium bromide on nitro-t-butane, b) oxidation of N-t-butyl-N-phenylhydroxylamine, c) oxidation of N-t-butylaniline. In these latter two cases, it has been possible to isolate the pure radical and to study it using UV, IR and EPR. It decomposes to give N-t-butylaniline and the N-oxide of N-t-butyl-p-quinon-imine. The action of peracids such as p-nitro-perbenzoic or m-chloro-perbenzoic acids on amines or hydroxylamines leads to the formation of stable or unstable nitroxide radicals easily observable by EPR. Finally, with a view to obtaining definite values for the coupling between the free electron of a nitroxide and carbon 13, the preparation of such radicals marked with {sup 13}C in the {alpha} or {beta} position of the nitroxide function has been carried out. The coupling with an {alpha} carbon 13 is negative and does not appear to vary with the spin density on the nitrogen. The interaction with the p nuclei of the nitrogen depends on the nature of the substituents: the two benzyl protons have a hyperfine splitting a{sub H} which is always less than that of the ethyl. On the other hand, the {sup 13}C coupling is greater in the first case. The usually adopted conformations for the compounds having the carbonyl group cannot account for the observed values of the {beta} couplings. (author) [French] Le N-t-butyl-N-phenyl nitroxyde est obtenu par: a) action du chlorure de t-butylmagnesium sur le nitrobenzene, ou du bromure de phenylmagnesium sur le nitro-t-butane, b) oxydation de la N-t-butyl-N-phenylhydroxylamine, c) oxydation de la N-t-butylaniline. Dans ces deux derniers cas, le radical a pu etre isole pur et etudie par UV, IR et RPE. Il se decompose en N-t-butylaniline et N-oxyde de N-t-butyl-p-quinonimine. L'action de peracides (p-nitroperbenzoique ou m-chloroperbenzoique) sur des amines ou des hydroxylamines conduit a des radicaux nitroxydes

  14. Peculiarities of preparation of cadmium isotopes of high enrichment

    International Nuclear Information System (INIS)

    Cascade equipped by gas centrifuges with regard for requirements to structural materials operating with chemically active compounds (dimethylcadmium) was devised for preparation of high-enriched cadmium isotopes. Solutions of such problems as overcoming of isotope memory, compensation of the effect of isotope overlapping, operative analytical accompanying permitted to optimize separation process and to obtain cadmium isotopes of high enrichment degree: cadmium-116 ∼98.9 %, cadmium-114 ∼98.7 %, cadmium-113 ∼93.3 %, cadmium-112 ∼99.1 %, cadmium-110 ∼95.8 %

  15. Application of enriched stable isotopes as tracers in biological systems

    DEFF Research Database (Denmark)

    Stürup, Stefan; Hansen, Helle Rüsz; Gammelgaard, Bente

    2008-01-01

    The application of enriched stable isotopes of minerals and trace elements as tracers in biological systems is a rapidly growing research field that benefits from the many new developments in inorganic mass spectrometric instrumentation, primarily within inductively coupled plasma mass spectrometry...... (ICP-MS) instrumentation, such as reaction/collision cell ICP-MS and multicollector ICP-MS with improved isotope ratio measurement and interference removal capabilities. Adaptation and refinement of radioisotope tracer experiment methodologies for enriched stable isotope experiments......, and the development of new methodologies coupled with more advanced compartmental and mathematical models for the distribution of elements in living organisms has enabled a broader use of enriched stable isotope experiments in the biological sciences. This review discusses the current and future uses of enriched...

  16. Metabolism and transport studies of exogenous compounds thanks to 13C uniform isotopic enrichment

    International Nuclear Information System (INIS)

    The study of many exogenous compounds does not raise difficulties when they are isolated, purified and in quantities sufficient for the usual detection methods used in biology (Chromatography, NMR, Mass Spectrometry, etc). When they are found in a biological fluid (blood, urines,..), they are often in infinitesimal amount such as the effect of their biological matrices or the background noise that make their detection and their quantification very delicate. The use of internal standards uniformly enriched with carbon 13 and/or nitrogen 15 makes it possible to obtain a signal more easily recognizable and identifiable thanks to the presence of the isotopes (peaks shifted in a mass spectrum for example). This is why, complementary to the analytical and biochemical studies of zearalenone (ZEN) metabolism, we were interested in building mass spectra of molecules enriched (rates between 0 and 1) by various isotopes (13C, 15N, 18O and 2H). In parallel we studied the influence of the 13C enrichment on the reactivity of a given molecule, from a theoretical and an experimental point of view. (author)

  17. The role of enriched isotopes in fundamental physical investigations

    International Nuclear Information System (INIS)

    Development of physics of elementary particles, astrophysics and cosmology at present is characterized by continuous increase of a number of fundamental problems experimental investigation of which needs significant quantities of enriched isotopes of high purity. Study of solar neutrino radiation, search of nonluminous matter, detection of neutrino-free double beta-decay are the most priority investigations in the world at present. In the report the most actual experiments with enriched isotopes (136Xe, 100Mo, 76Ge, 116Cd, 82Se and some others) are discussed together with basic requirements for isotopes and possibilities on operating time of the Industrial Joining Electrochemical plant

  18. Stable Isotope (delta OXYGEN-18, Delta Deuterium, Delta CARBON-13) Dendroclimatological Studies in the Waterloo Region of Southern Ontario, Canada, Between AD 1610 and 1990.

    Science.gov (United States)

    Buhay, William Mark

    Oxygen (delta^{18} O), hydrogen (delta^2H) and carbon (delta^{13}C) isotopes were measured in wood cellulose from elm, white pine and maple trees that grew in southwestern Ontario, Canada. The measured oxygen and hydrogen isotopic data were used for model-based reconstructions of delta^{18}{O}_{meteoric water}, mean annual temperature (MAT) and relative humidity for a period, AD 1610 to 1880, that precedes instrumental records of climate. The carbon isotope measurements were compared with the Cellulose Model inferred climate data to reveal additional environmental information. Modifications made to the Cellulose Model focused on the dynamics of oxygen and hydrogen isotopic fractionation in plants during evapotranspiration and photosynthetic assimilation. For instance, kinetic fractionation of ^{18}O was found to be predictable from theoretical considerations of leaf energy balance and boundary layer dynamics. Kinetic fractionation during evapotranspiration is sensitive to the nature of the boundary layer, which is controlled by leaf size and morphology. Generally, plants with small segmented leaves have a lower component of turbidity in the leaf boundary layer, which results in higher kinetic fractionation values, than do plants having large simple leaves and more turbulent boundary layers. Kinetic ^2H enrichment in plant leaf water can also be rationalized in terms of leaf size and morphology when an apparent temperature-dependent isotope effect, acting in opposition to evaporative enrichment, is taken into account. Accounting for this temperature -dependent isotope effect helps to: (1) reconcile hydrogen kinetic fractionation inconsistencies for different leaves; (2) explain a temperature effect previously attributed to variable biochemical fractionation during cellulose synthesis, and; (3) verify hydrogen biochemical effects in plants. This improved characterization of the oxygen and hydrogen isotopic effects in plants, using the modified Cellulose Model, helped

  19. Isotopic enrichment of tritium by using host-guest chemistry

    International Nuclear Information System (INIS)

    The isotopic enrichment of tritium in the liquid-liquid extraction system, butylammonium/crownether was investigated using water solution of butylammonium iodide and chloroform solution of dicyclohexyl-18-crown-6. Tritium was enriched in the ammonium-crown complex which was extracted into the organic phase. Both the enthalpy and entropy changes were positive for the direction of negative free energy change. The value of entropy effect (TΔS) exceeded that of enthalpy change around room temperature. Single stage isotope separation factors obtained were 12 for n-butylammonium and 50 for tert-butylammonium as guest compounds at 550C. (orig./RK)

  20. Minor isotope measurements for safeguarding a uranium enrichment plant

    Energy Technology Data Exchange (ETDEWEB)

    Blumkin, S.; Levin, S.A.; Von Halle, E.

    1979-03-26

    A study of the behavior of the minor uranium isotopes in enrichment cascades indicates that the measurement of their concetrations in cascade feed and withdrawal streams can be used to confirm or deny material accountability results in safeguarding an enrichment plant. In further support of safeguard measures, an indirect non-intrusive method to measure cascade uranium inventory has been devised and tested satisfactorily in a gaseous diffusion cascade.

  1. Enrichment of rare isotopes using a quadrupole mass spectrometer

    International Nuclear Information System (INIS)

    A small quadrupole mass spectrometer was operated in the static mode to enrich selected rare gas isotopes. Memory effects in the apparatus were observed and attributed to the re-emission of atoms implanted by the electron-impact ion source. Studies of the pumping mechanism led to a practical means for reducing the rate of noble gas pumping. (author)

  2. Isotopic enrichment of 15N by ionic exchange cromatography

    International Nuclear Information System (INIS)

    The ionic exchange chromatographic method in columns of resin which is employed in the study of isotopic enrichment of 15N is presented. Determinations are made of the isotopic separation constant for the exchange of isotopes 15N and 14N in the equilibrium involving ammonium hidroxide in the solution phase and ions NH4+ adsorbed in cationic resins: Dowex 50W-X8 and X12, 100-200 mesh. Experiments are also conducted for determination of height of theoretical plates for situations of equilibrium of the NH4+ band in two systems of resin's columns aimed at estimating the experimental conditions used. The isotopic analyses of nitrogen are carried out by mass spectrometry

  3. The Enriched Background Isotope Study (EBIS)

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, Paul J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Trumbore, Susan [Univ. of California, Irvine, CA (United States); Swanston, Chris [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Torn, Margaret [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Jastrow, Julie [Argonne National Lab. (ANL), Argonne, IL (United States); Parton, William A [Colorado State Univ., Fort Collins, CO (United States); Century Ecosystems, Inc. (United States); Post, Wilfred M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Froberg, Mats J [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hainsworth, Laura J [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kleber, Markus [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kramer, Christiane [Univ. of California, Irvine, CA (United States); Matamala-Paradeda, Roser [Argonne National Lab. (ANL), Argonne, IL (United States); Garten, Jr, Charles T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2007-02-05

    A unique, large release of radiocarbon occurred near the Oak Ridge Reservation (ORR), Oak Ridge, TN in July/August 1999. Measurements of 14C in tree ring cellulose throughout the ORR area demonstrate that the 1999 release was unprecedented in its uptake by vegetation. We are taking advantage of the whole-ecosystem isotopic label generated by this release to address five outstanding issues in the terrestrial carbon cycle: (1) partitioning of soil respiration between autotrophic and heterotrophic sources, and quantification of that partitioning seasonally and inter-annually, (2) partitioning of heterotrophic respiration sources between above-ground litter decomposition and below-ground root detritus decomposition, (3) identification of pathways leading from leaf and root detritus to long-term stabilization of soil organic matter, including the role of soil fauna, (4) the role of dissolved organic carbon (DOC) transport in distributing carbon within the soil profile, and, (5) the longevity and turnover time of fine roots. The first four issues are being addressed through a reciprocal litter transplant experiment set up at four sites on the ORR encompassing two soil types and two levels of 14C exposure in 1999. The fifth issue, longevity and turnover of fine roots, is being addressed by tracing the radiocarbon label through the fine root pool over time. With a combination of incubation, soil surface chamber and soil CO2 profiles, and continuous measurements of soil temperature and moisture controls, we are tracking changes in soil respiration partitioning over several years. The nature and source of organic matter pools that reside in soils for years to decades are being tracked with differently labeled root and surface litter, and experiments to exclude soil fauna have been initiated to elucidate their role in vertical transport. Periodic sampling of soils and soil solutions and the use of inert tracers, allow us to investigate the chemical nature and form of DOC and

  4. Prospects of lithium enrichment on 7Li isotope by method of controlled ions electro-migration

    Science.gov (United States)

    Martoyan, G. A.; Kalugin, M. M.; Gabrielyan, A. V.; Martoyan, A. G.

    2016-01-01

    This paper deals with a new electro-membrane method of enrichment of 7Li isotope. The data are presented on the importance and application fields regarding the use of 7Li isotopes. Existing methods and criteria of separation of lithium isotopes are discussed. The principle of new technology, regimes of enrichment experiments, and analysis details of obtained products are briefly described.

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

    International Nuclear Information System (INIS)

    Atmospheric methane (CH4) 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 C02 at present day concentrations (Shine et al. 1990). The causes of the increase of atmospheric CH4 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 CH4 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 CH4, 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, C.M. [Argonne National Lab., IL (United States); Sepanski; Morris, L.J. [Univ. of Tennessee, Knoxville, TN (United States). Energy, Environment, and Resources Center

    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.

  7. Stable isotope enrichment techniques and ORNL separation status

    International Nuclear Information System (INIS)

    The isotope separation program is described, emphasizing present state-of-the-art techniques utilized to achieve specific isotopic requirements. An interesting problem addressed here is the calutron enrichment of rare-earth isotopes where small quantities of feed (<5g) are available, and the unresolved feed is to be recovered and recycled. Conventional ion-source units using graphite and stainless steel deteriorate in the halogenating atmosphere or are permeable to rare-earth compounds, reducing the process efficiency. An ion source has been developed using boron nitride for containing the halogenating agent and rare-earth compounds. Tests have been successfully conducted using Lu/sub 2/O/sub 3/ and the in situ chlorinating technique with CCl/sub 4/. Collectively, 166 mg of /sup 176/Lu were recovered from two runs using 2.95 and 1.10 g of 44.5% /sup 176/Lu. Process efficiency of 10.5% was achieved, and 1.2 g of the unresolved feed were recovered. Material compatibility of the boron nitride, carbon tetrachloride, and lutetium compounds has been established

  8. Status of stable isotope enrichment, products, and services at the Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    The Oak Ridge national laboratory (ORNL) has been supplying enriched stable and radioactive isotopes to the research, medical, and industrial communities for over 50 y. Very significant changes have occurred in this effort over the past several years, and, while many of these changes have had a negative impact on the availability of enriched isotopes, more recent developments are actually improving the situation for both the users and the producers of enriched isotopes. ORNL is still a major producer and distributor of radioisotopes, but future isotope enrichment operations to be conducted at the isotope enrichment facility (IEF)fwill be limited to stable isotopes. Among the positive changes in the enriched stable isotope area are a well-functioning, long-term contract program, which offers stability and pricing advantages; the resumption of calutron operations; the adoption of prorated conversion charges, which greatly improves the pricing of isotopes to small users; ISO 9002 registration of the IEF's quality management system; and a much more customer-oriented business philosophy. Efforts are also being made to restore and improve upon the extensive chemical and physical form processing capablities that once existed in the enriched stable isotope program. Innovative ideas are being pursued in both technical and administrative areas to encourage the beneficial use of enriched stable isotopes and the development of related technologies. (orig.)

  9. Status of stable isotope enrichment, products, and services at the Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    The Oak Ridge National Laboratory (ORNL) has been supplying enriched stable and radioactive isotopes to the research, medical, and industrial communities for over 50 years. Very significant changes have occurred in this effort over the past several years, and, while many of these changes have had a negative impact on the availability of enriched isotopes, more recent developments are actually improving the situation for both the users and the producers of enriched isotopes. ORNL is still a major producer and distributor of radioisotopes, but future isotope enrichment operations conducted at the Isotope Enrichment Facility (IEF) will be limited to stable isotopes. Among the positive changes in the enriched stable isotope area are a well-functioning, long-term contract program, which offers stability and pricing advantages; the resumption of calutron operations; the adoption of prorated conversion charges, which greatly improves the pricing of isotopes to small users; SIO 9002 registration of the IEF's quality management system; and a much more customer-oriented business philosophy. Efforts are also being made to restore and improve upon the extensive chemical and physical form processing capabilities that once existed in the enriched stable isotope program. Innovative ideas are being pursued in both technical and administrative areas to encourage the beneficial use of enriched stable isotopes and the development of related technologies

  10. Bringing hope to marginal and harsh environments: The use of carbon-13 isotope discrimination technique to evaluate and select food crops adapted to water and salt stress environments

    International Nuclear Information System (INIS)

    Many countries have weather patterns and soil characteristics that place major constraints on food production systems over large tracts of land. Thus a major challenge for making better use of these marginal lands is not only to select appropriate crops but also to evaluate and optimize their adaptability and crop productivity under extreme climatic conditions (high temperatures and low rainfall) or where soils suffer from salinity, acidity or low plant nutrient status. The carbon isotope discrimination technique (using the ratios of different carbon isotopes [12C/13C] in plants) commonly referred to as CID, has been proposed as a possible selection criterion for greater water use efficiency in breeding programmes for water limited and salt stress environments because it provides an integrative assessment of genotypic variation in leaf transpiration efficiency. Although the relationship between CID and water and/or salt stress have been well studied and documented for many crop plants, few studies have looked at the combined effects of salt, water and nutrient stresses on the potential use of this technique to select and evaluate crop plants adapted to harsh environments

  11. Study on atmospheric hydrogen enrichment by cryopump method and isotope separation by gas chromatography

    International Nuclear Information System (INIS)

    To obtain the information of source of atmospheric hydrogen tritium an analysis of tritium isotopes is thought to be effective. So an atmospheric hydrogen enrichment apparatus and a cryogenic gas chromatographic column were made. Experiments were carried out to study the performance of cryopump to enrich atmospheric hydrogen and the column to separate hydrogen isotopes that obtained by cryopump method. The cryopump was able to process about 1000 1 atmosphere and the column was able to separate hydrogen isotopes with good resolution. (author)

  12. High purity isotopically enriched 70Ge and 74Ge single crystals: Isotope separation, growth, and properties

    International Nuclear Information System (INIS)

    70Ge and 74Ge isotopes were successfully separated from natural Ge and zone purified. Several highly enriched, high purity 70Ge and 74Ge single crystals were grown by the vertical Bridgman method. The growth system was designed for reliable growth of low dislocation density, high purity Ge single crystals of very small weight (∼4g). A 70Ge and a 74Ge crystal were selected for complete characterization. In spite of the large surface to volume ratio of these ingots, both 70Ge and 74Ge crystals contain low electrically active chemical net-impurity concentrations of ∼2x1012 cm-3, which is two orders of magnitude better than that of 74Ge crystals previously grown by two different groups.1,2 Isotopic enrichment of the 70Ge and the 74Ge crystals is 96.3% and 96.8%, respectively. The residual donors and acceptors present in both crystals were identified as phosphorus and copper, respectively. In addition less than 1011 cm-3 gallium, aluminum, and indium were found in the 70Ge crystal

  13. Ultra-rapid targeted analysis of 40 drugs of abuse in oral fluid by LC-MS/MS using carbon-13 isotopes of methamphetamine and MDMA to reduce detector saturation.

    Science.gov (United States)

    Di Rago, Matthew; Chu, Mark; Rodda, Luke N; Jenkins, Elizabeth; Kotsos, Alex; Gerostamoulos, Dimitri

    2016-05-01

    The number of oral fluid samples collected by the road policing authority in Victoria, Australia, requiring confirmatory laboratory analysis for drugs proscribed under Victorian legislation (methamphetamine, MDMA and Δ9-tetrahydrocannabinol) has greatly increased in recent years, driving the need for improved analysis techniques to enable expedient results. The aim of this study was to develop an LC-MS/MS-based targeted oral fluid screening technique that covers a broad range of basic and neutral drugs of abuse that can satisfy increased caseload while monitoring other compounds of interest for epidemiological purposes. By combining small sample volume, simple extraction procedure, rapid LC-MS/MS analysis and automated data processing, 40 drugs of abuse including amphetamines, benzodiazepines, cocaine and major metabolites, opioids, cannabinoids and some designer stimulants were separated over 5 min (with an additional 0.5 min re-equilibration time). The analytes were detected using a Sciex® API 4500 Q-Trap LC-MS/MS system with positive ESI in MRM mode monitoring three transitions per analyte. The method was fully validated in accordance with international guidelines and also monitored carbon-13 isotopes of MDMA and MA to reduce detector saturation effects, allowing for confirmation of large concentrations of these compounds without the need for dilution or re-analysis. The described assay has been successfully used for analysis of oral fluid collected as part of law enforcement procedures at the roadside in Victoria, providing forensic results as well as epidemiological prevalence in the population tested. The fast and reliable detection of a broad range of drugs and subsequent automated data processing gives the opportunity for high throughput and fast turnaround times for forensic toxicology.

  14. Ultra-rapid targeted analysis of 40 drugs of abuse in oral fluid by LC-MS/MS using carbon-13 isotopes of methamphetamine and MDMA to reduce detector saturation.

    Science.gov (United States)

    Di Rago, Matthew; Chu, Mark; Rodda, Luke N; Jenkins, Elizabeth; Kotsos, Alex; Gerostamoulos, Dimitri

    2016-05-01

    The number of oral fluid samples collected by the road policing authority in Victoria, Australia, requiring confirmatory laboratory analysis for drugs proscribed under Victorian legislation (methamphetamine, MDMA and Δ9-tetrahydrocannabinol) has greatly increased in recent years, driving the need for improved analysis techniques to enable expedient results. The aim of this study was to develop an LC-MS/MS-based targeted oral fluid screening technique that covers a broad range of basic and neutral drugs of abuse that can satisfy increased caseload while monitoring other compounds of interest for epidemiological purposes. By combining small sample volume, simple extraction procedure, rapid LC-MS/MS analysis and automated data processing, 40 drugs of abuse including amphetamines, benzodiazepines, cocaine and major metabolites, opioids, cannabinoids and some designer stimulants were separated over 5 min (with an additional 0.5 min re-equilibration time). The analytes were detected using a Sciex® API 4500 Q-Trap LC-MS/MS system with positive ESI in MRM mode monitoring three transitions per analyte. The method was fully validated in accordance with international guidelines and also monitored carbon-13 isotopes of MDMA and MA to reduce detector saturation effects, allowing for confirmation of large concentrations of these compounds without the need for dilution or re-analysis. The described assay has been successfully used for analysis of oral fluid collected as part of law enforcement procedures at the roadside in Victoria, providing forensic results as well as epidemiological prevalence in the population tested. The fast and reliable detection of a broad range of drugs and subsequent automated data processing gives the opportunity for high throughput and fast turnaround times for forensic toxicology. PMID:26993306

  15. Molecular modelling guided experimental study for isotopic enrichment of Gadolinium

    International Nuclear Information System (INIS)

    Molecular modelling and experimental studies were performed to predict the feasibility of Gd isotope separation using crown ether grafted resin. BP and B3LYP functional - based DFT calculations foretell the complexation stability order of Gd3+ ion as DCH18C6>B15C5>DB18C6 as observed in the experiment. The calculated isotopic separation factor shows that DB18C6 is the promising candidate. Hence, CMPS grafted DB18C6 resin was chosen for the isotope separation of Gd. The adsorption capacity of the resin for Gd3+ ion was found to be 1mg/g. The separation coefficients (ε ×103) were found to be 6.3, 3.4, 9.7 and 11.1 for the isotopic pair of 155/158, 157/158, 155/160 and 157/160 respectively and shows promise for future study. (author)

  16. Stratospheric ozone isotope enrichment studied by submillimeter-wave heterodyne radiometry

    Science.gov (United States)

    Kasai, Y.; Urban, J.; Takahashi, K.; JEM/SMILES Science-Team,

    2002-05-01

    Since the discovery of the heavy isotope enrichment of ozone formation in the stratosphere in 1981, considerable progress has been made in understanding the processes that control the isotope enrichment by using mass spectrometry, spectrometric techniques, laboratory measurements, and so on. The detection limit of the mass spectrometers is enough to discuss these isotope enrichments, but symmetric and asymmetric ozone isotopes cannot be distinguished. It is important to observe symmetric and asymmetric ozone isotopes separately with enough accuracy to understand the mechanism of the ozone isotope enrichment for the ozone formation chemistry. Measurements of the ozone isotopes using a new technology of he superconducting submillimeter-wave limb emission spectrometer (SMILES) have been proposed. The instrument is planned to be aboard the Japanese Experiment Module (JEM) at the International Space Station. The SMILES instrument is planned to be launched in 2006. The SMILES instrument measures thermal emissions from ozone isotopes as well as ozone-depletion-related molecules such as ClO, HCl, HO2, HNO3 and BrO in the frequency bands at 624.32-626.32 GHz and 649.12-650.32 GHz. Overview of this experiment, such as new techniques for a high-sensitive sounding, measurement coverage, measurement frequency, is described. The scientific objective of the SMILES experiment, including a brief review on the controversial problem of stratospheric ozone isotope anomaly, is presented. The error analysis of the SMILES measurement is evaluated by using the SMILES simulator for all 5 isotopes of normal ozone, asymmetric-17-ozone, asymmetric-18-ozone, symmetric-17-ozone, symmetric-18-ozone. The evaluation suggests that the global distributions of symmetric-17-ozone, asymmetric-18-ozone, symmetric-17-ozone, as well as normal ozone can be obtained from the single profile, with the errors of less than about 1 % between 20 and 40 km with the partial column about 5 km.

  17. Enrichment of zinc isotopes by a liquid membrane system using a crown ether

    International Nuclear Information System (INIS)

    A liquid membrane system to enrich zinc isotope was investigated. The liquid membrane was composed of a solution of dicyclohexano-18-crown-6 in chloroform. Zinc chloride dissolved in diluted hydrochloric acid was used as a feed phase. A receiving phase was made of a 0.001 M HCl solution. The zinc isotopes were enriched (1) at the interface of the liquid-membrane/feed-phase and (2) at that of the liquid-membrane/receiving-phase. The separation factor attained in the system was α = 1.049 for the separation of 64Zn and 66Zn. The enrichment factor of 66Zn relative to 67Zn was ε = -0.053, which is in the inverse direction of enrichment by a liquid-liquid extraction. The enrichment factor of 64Zn to 66Zn showed a different value from that of 66Zn to 68Zn, regardless of their similar mass difference. The isotope effects in the Zn-crown complex were dominated by the field shift of electronic energy in the isotope atom. This is in contrast to the Bigeleisen-Mayer approximation for a chemical exchange reaction. Trace amounts of zinc are injected into the primary coolant of boiling water reactors in order to suppress 60Co build-up. The use of 64Zn-depleted zinc suppresses the production of 65Zn within the reactor. Zinc isotopes are also useful precursors of radiopharmaceuticals

  18. [Meta-analysis of stable carbon and nitrogen isotopic enrichment factors for aquatic animals].

    Science.gov (United States)

    Guo, Liang; Sun, Cui-ping; Ren, Wei-zheng; Zhang, Jian; Tang, Jian-iun; Hu, Liana-liang; Chen, Xin

    2016-02-01

    Isotopic enrichment factor (Δ, the difference between the δ value of food and a consumer tissue) is an important parameter in using stable isotope analysis (SIA) to reconstruct diets, characterize trophic relationships, elucidate patterns of resource allocation, and construct food webs. Isotopic enrichment factor has been considered as a constancy value across a broad range of animals. However, recent studies showed that the isotopic enrichment factor differed among various types of animals although the magnitude of variation was not clear. Here, we conducted a meta-analysis to synthesize and compare Δ13C and Δ15N among four types of aquatic animals (teleosts, crustaceans, reptiles and molluscs). We searched for papers published before 2014 on Web of Science and CNKI using the key words "stable isotope or isotopic fractionation or fractionation factor or isotopic enrichment or trophic enrichment". Forty-two publications that contain 140 studies on Δ13C and 159 studies on Δ15N were obtained. We conducted three parallel meta-analyses by using three types of weights (the reciprocal of variance as weights, the sample size as weights, and equal weights). The results showed that no significant difference in Δ13C among different animal types (teleosts 1.0 per thousand, crustaceans 1.3 per thousand, reptiles 0.5 per thousand, and molluscs 1.5 per thousand), while Δ15N values were significantly different (teleosts 2.4 per thousand, crustaceans 3.6 per thousand, reptiles 1.0 per thousand and molluscs 2.5 per thousand). Our results suggested that the overall mean of Δ13C could be used as a general enrichment factor, but Δ15N should be chosen according to the type of aquatic animals in using SIA to analyze trophic relationships, patterns of resource allocation and food webs.

  19. Synthesis of colchicine and isocolchicine labelled with carbon-11 or carbon-13

    Energy Technology Data Exchange (ETDEWEB)

    Kothari, P.J.; Finn, R.D.; Larson, S.M. [Memorial Sloan-Kettering Cancer Center, New York, NY (United States)

    1995-06-01

    The syntheses of isotopically labelled (-)-10-[{sup 11}C/{sup 13}C]-colchicine and (-)-9-[{sup 11}C/{sup 13}C]-isocolchicine have been achieved from the reaction of (-)desmethylcolchicine with [{sup 11}C/{sup 13}C]-iodomethane. The radiolabelled compounds, (-)-10-[{sup 11}C]-colchicine ({sup 11}C-n-colchicine) and (-)-9-[{sup 11}C]-isocolchicine ({sup 11}C-i-colchicine), were isolated by reversed phase HPLC. The total synthesis time was approximately 60 minutes for both radiolabelled compounds with an average specific activity of 240 mCi/{mu}mol calculated to EOB. Utilizing a similar synthetic strategy, we also reported the synthesis of milligram quantities of the carbon-13 enriched compounds and the magnetic resonance signal assignment for (-)-9-[{sup 13}C] isocolchicine. (Author).

  20. Stable-isotope-enrichment program at the Oak Ridge National Laboratory

    International Nuclear Information System (INIS)

    This paper has attempted to present a brief description of the production steps, from the selection and preparation of the initial feedstock to the recovery and distribution of the isotopically enriched materials. The facility suffers from the disadvantage of coping with utility and support systems that are rapidly becoming obsolescent and that the current operational level is insufficient to maintain sales inventory equilibrium. The electromagnetic isotope enrichment facility does, however, have the operational equipment and capability to almost triple the current production. This increased production can be achieved as rapidly as an expanded operational crew can be trained

  1. Water enriched in the rare stable isotopes: Preparation, measurement and applications

    OpenAIRE

    Faghihi, Vahideh

    2016-01-01

    The subject of this thesis is water with increased abundances of the rare stable isotopes 2H and 18O (and to some extent also 17O). Such artificially enriched (or "labelled") waters are often used in biomedicine, for establishing the total amount of body water (and thus body composition) of humans and animals and also for measuring their energy expenditure. These non-evasive totally harmless techniques offer great advantages, however they require accurate and precise "isotope ratio" measureme...

  2. Zinc absorption study using an enriched stable isotope (70Zn)

    International Nuclear Information System (INIS)

    A weaning food from fermented soybean was prepared for increasing the bioavailability of zinc. The zinc absorption was compared with that of a weaning food from non-fermented soybean and normal staple food. A stable isotope tracer technique (70Zn) and neutron activation were used for determining the absorption of zinc. Nine children aged 7 to 18 months were tested. Zinc bioavailability of weaning food from fermented soybean is higher than that of normal weaning food. The weight increment and zinc nutrition of children having weaning food from fermented soybean are improved by this diet. 5 tabs

  3. Water enriched in the rare stable isotopes : Preparation, measurement and applications

    NARCIS (Netherlands)

    Faghihi, Vahideh

    2016-01-01

    The subject of this thesis is water with increased abundances of the rare stable isotopes 2H and 18O (and to some extent also 17O). Such artificially enriched (or "labelled") waters are often used in biomedicine, for establishing the total amount of body water (and thus body composition) of humans a

  4. The application of atomic vapor laser isotope separation to the enrichment of mercury

    International Nuclear Information System (INIS)

    The authors discuss the results of recent work carried out at Lawrence Livermore National Laboratory to develop a process for enriching mercury. The discussion centers around the results of spectroscopic measurements of excited-state lifetimes, photoionization cross sections, and isotope shifts. (author)

  5. Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium.

    Science.gov (United States)

    Sigillito, A J; Jock, R M; Tyryshkin, A M; Beeman, J W; Haller, E E; Itoh, K M; Lyon, S A

    2015-12-11

    Germanium is a widely used material for electronic and optoelectronic devices and recently it has become an important material for spintronics and quantum computing applications. Donor spins in silicon have been shown to support very long coherence times (T_{2}) when the host material is isotopically enriched to remove any magnetic nuclei. Germanium also has nonmagnetic isotopes so it is expected to support long T_{2}'s while offering some new properties. Compared to Si, Ge has a strong spin-orbit coupling, large electron wave function, high mobility, and highly anisotropic conduction band valleys which will all give rise to new physics. In this Letter, the first pulsed electron spin resonance measurements of T_{2} and the spin-lattice relaxation (T_{1}) times for ^{75}As and ^{31}P donors in natural and isotopically enriched germanium are presented. We compare samples with various levels of isotopic enrichment and find that spectral diffusion due to ^{73}Ge nuclear spins limits the coherence in samples with significant amounts of ^{73}Ge. For the most highly enriched samples, we find that T_{1} limits T_{2} to T_{2}=2T_{1}. We report an anisotropy in T_{1} and the ensemble linewidths for magnetic fields oriented along different crystal axes but do not resolve any angular dependence to the spectral-diffusion-limited T_{2} in samples with ^{73}Ge. PMID:26705654

  6. Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium

    Science.gov (United States)

    Sigillito, A. J.; Jock, R. M.; Tyryshkin, A. M.; Beeman, J. W.; Haller, E. E.; Itoh, K. M.; Lyon, S. A.

    2015-12-01

    Germanium is a widely used material for electronic and optoelectronic devices and recently it has become an important material for spintronics and quantum computing applications. Donor spins in silicon have been shown to support very long coherence times (T2 ) when the host material is isotopically enriched to remove any magnetic nuclei. Germanium also has nonmagnetic isotopes so it is expected to support long T2's while offering some new properties. Compared to Si, Ge has a strong spin-orbit coupling, large electron wave function, high mobility, and highly anisotropic conduction band valleys which will all give rise to new physics. In this Letter, the first pulsed electron spin resonance measurements of T2 and the spin-lattice relaxation (T1) times for 75As and 31P donors in natural and isotopically enriched germanium are presented. We compare samples with various levels of isotopic enrichment and find that spectral diffusion due to 73Ge nuclear spins limits the coherence in samples with significant amounts of 73Ge. For the most highly enriched samples, we find that T1 limits T2 to T2=2 T1. We report an anisotropy in T1 and the ensemble linewidths for magnetic fields oriented along different crystal axes but do not resolve any angular dependence to the spectral-diffusion-limited T2 in samples with 73Ge.

  7. Isotopic enrichment of forming planetary systems from supernova pollution

    Science.gov (United States)

    Lichtenberg, Tim; Parker, Richard J.; Meyer, Michael R.

    2016-08-01

    Heating by short-lived radioisotopes (SLRs) such as 26Al and 60Fe fundamentally shaped the thermal history and interior structure of Solar System planetesimals during the early stages of planetary formation. The subsequent thermo-mechanical evolution, such as internal differentiation or rapid volatile degassing, yields important implications for the final structure, composition and evolution of terrestrial planets. SLR-driven heating in the Solar System is sensitive to the absolute abundance and homogeneity of SLRs within the protoplanetary disk present during the condensation of the first solids. In order to explain the diverse compositions found for extrasolar planets, it is important to understand the distribution of SLRs in active planet formation regions (star clusters) during their first few Myr of evolution. By constraining the range of possible effects, we show how the imprint of SLRs can be extrapolated to exoplanetary systems and derive statistical predictions for the distribution of 26Al and 60Fe based on N-body simulations of typical to large clusters (103-104 stars) with a range of initial conditions. We quantify the pollution of protoplanetary disks by supernova ejecta and show that the likelihood of enrichment levels similar to or higher than the Solar System can vary considerably, depending on the cluster morphology. Furthermore, many enriched systems show an excess in radiogenic heating compared to Solar System levels, which implies that the formation and evolution of planetesimals could vary significantly depending on the birth environment of their host stars.

  8. Establishing a Cost Basis for Converting the High Flux Isotope Reactor from High Enriched to Low Enriched Uranium Fuel

    International Nuclear Information System (INIS)

    Under the auspices of the Global Threat Reduction Initiative Reduced Enrichment for Research and Test Reactors Program, the National Nuclear Security Administration/Department of Energy (NNSA/DOE) has, as a goal, to convert research reactors worldwide from weapons grade to non-weapons grade uranium. The High Flux Isotope Reactor (HFIR) at Oak Ridge National Lab (ORNL) is one of the candidates for conversion of fuel from high enriched uranium (HEU) to low enriched uranium (LEU). A well documented business model, including tasks, costs, and schedules was developed to plan the conversion of HFIR. Using Microsoft Project, a detailed outline of the conversion program was established and consists of LEU fuel design activities, a fresh fuel shipping cask, improvements to the HFIR reactor building, and spent fuel operations. Current-value costs total $76 million dollars, include over 100 subtasks, and will take over 10 years to complete. The model and schedule follows the path of the fuel from receipt from fuel fabricator to delivery to spent fuel storage and illustrates the duration, start, and completion dates of each subtask to be completed. Assumptions that form the basis of the cost estimate have significant impact on cost and schedule.

  9. The reduction and distillation of isotopically enriched zinc oxides under high vacuum conditions

    International Nuclear Information System (INIS)

    Historically, enriched zinc (Zn) metal was produced at the Oak Ridge National Laboratory's Isotope Enrichment Facility (IEF) by either electrodeposition, followed by melting to produce a metal ingot, or purified by hydrogen reduction and distillation at atmospheric pressure in a tube furnace as a prelude to electroplating. Electroplated material was generally poor in quality, and losses were high during subsequent melting. Adapting the distillation purifying technique as an ultimate means of recovery of Zn metal proved to be difficult and inefficient. To resolve these problems, the well-established vacuum reduction/distillation process was adapted for the conversion of Zn oxide to metal

  10. An isotopic analysis system for plutonium samples enriched in 238Pu

    International Nuclear Information System (INIS)

    We have designed and built a gamma-ray spectrometer system that measures the relative plutonium isotopic abundances of plutonium oxide enriched in 238Pu. The first system installed at Westinghouse Savannah River Company was tested and evaluated on plutonium oxide in stainless steel EP60/61 containers. 238Pu enrichments ranged from 20% to 85%. Results show that 200 grams of plutonium oxide in an EP60.61 container can be measured with ±0.3% precision and better than ±1.0% accuracy in the specific power using a counting time of 50 minutes. 3 refs., 2 figs

  11. Centrifugal enrichment of zinc isotopes, their application in medicine and in increasing radiation safety in nuclear power plants

    International Nuclear Information System (INIS)

    This paper contains the results of our research on the complete cycle of centrifuge enrichment of all zinc isotopes. The centrifuge cascade that was used to obtain the world's first zinc isotope, 7Zn, with an enrichment of more than 99.3% in gram quantities, is described. As a result of this work, gram quantities of all highly enriched zinc isotopes and hundreds of grams of depleted zinc (in the form of ZnO) with concentrations of less than 0.5% 64Zn were obtained

  12. The thermal desorption of CO2 from amine carbamate solutions for the 13C isotope enrichment

    Science.gov (United States)

    Dronca, S.; Varodi, C.; Gligan, M.; Stoia, V.; Baldea, A.; Hodor, I.

    2012-02-01

    The CO2 desorption from amine carbamate in non-aqueous solvents is of major importance for isotopic enrichment of 13C. A series of experiments were carried out in order to set up the conditions for the CO2 desorption. For this purpose, a laboratory- scale plant for 13C isotope separation by chemical exchange between CO2 and amine carbamate was designed and used. The decomposition of the carbamate solution was mostly produced in the desorber and completed in the boiler. Two different-length desorbers were used, at different temperatures and liquid flow rates of the amine-non-aqueous solvent solutions. The residual CO2 was determined by using volumetric and gaschromatographic methods. These results can be used for enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvents.

  13. Preparation and characterisation of isotopically enriched Ta2O5 targets for nuclear astrophysics studies

    International Nuclear Information System (INIS)

    The direct measurement of reaction cross-sections at astrophysical energies often requires the use of solid targets of known thickness, isotopic composition, and stoichiometry that are able to withstand high beam currents for extended periods of time. Here, we report on the production and characterisation of isotopically enriched Ta2O5 targets for the study of proton-induced reactions at the Laboratory for Underground Nuclear Astrophysics facility of the Laboratori Nazionali del Gran Sasso. The targets were prepared by anodisation of tantalum backings in enriched water (up to 66% in 17O and up to 96% in 18O). Special care was devoted to minimising the presence of any contaminants that could induce unwanted background reactions with the beam in the energy region of astrophysical interest. Results from target characterisation measurements are reported, and the conclusions for proton capture measurements with these targets are drawn. (orig.)

  14. Preparation and characterisation of isotopically enriched Ta$_2$O$_5$ targets for nuclear astrophysics studies

    CERN Document Server

    Caciolli, A; Di Leva, A; Formicola, A; Aliotta, M; Anders, M; Bellini, A; Bemmerer, D; Broggini, C; Campeggio, M; Corvisiero, P; Depalo, R; Elekes, Z; Fülöp, Zs; Gervino, G; Guglielmetti, A; Gustavino, C; Gyürky, Gy; Imbriani, G; Junker, M; Marta, M; Menegazzo, R; Napolitani, E; Prati, P; Rigato, V; Roca, V; Rolfs, C; Alvarez, C Rossi; Somorjai, E; Salvo, C; Straniero, O; Strieder, F; Szücs, T; Terrasi, F; Trautvetter, H P; Trezzi, D

    2012-01-01

    The direct measurement of reaction cross sections at astrophysical energies often requires the use of solid targets of known thickness, isotopic composition, and stoichiometry that are able to withstand high beam currents for extended periods of time. Here, we report on the production and characterisation of isotopically enriched Ta$_2$O$_5$ targets for the study of proton-induced reactions at the Laboratory for Underground Nuclear Astrophysics facility of the Laboratori Nazionali del Gran Sasso. The targets were prepared by anodisation of tantalum backings in enriched water (up to 66% in $^{17}$O and up to 96% in $^{18}$O). Special care was devoted to minimising the presence of any contaminants that could induce unwanted background reactions with the beam in the energy region of astrophysical interest. Results from target characterisation measurements are reported, and the conclusions for proton capture measurements with these targets are drawn.

  15. Highly enriched isotope samples of uranium and transuranium elements for scientific investigation

    Science.gov (United States)

    Vesnovskii, Stanislav P.; Polynov, Vladimir N.; Danilin, Lev. D.

    1992-02-01

    The paper describes the production of highly enriched isotopes of uranium, plutonium, americium and curium by electromagnetic separation for scientific and applied researches in physics, chemistry, geology, medicine, biology and other fields. Using the equipment described, the isotopes are produced in quantities sufficient to set up nuclear physical experiments, to produce nuclear reference materials and standard sources for calibration of radiometrical and mass spectrometrical equipment, in radionuclide metrology, etc. For the following isotopes the indicated degrees of isotopic enrichment were achieved: 233U - 99.97%; 235U - 99.97%; 236U - 98.0%; 238U - 99.997%; 238Pu - 99.6%; 239Pu - 99.9977%; 240Pu - 99.9-100%; 241Pu - 96.998%; 242Pu - 97.8-99.96%; 244Pu - 96.7%; 241Am - 99.6%; 242Am - 73.6%; 243Am - 99.2-99.94%; 243Cm - 99.99%; 245Cm - 99.998%; 246Cm - 99.8%; 247Cm - 90%; 248Cm - 97%. Methods for preparing layers of highly enriched isotopes on various substances are presented: - electrochemical deposition of transuranic elements from aqueous-organic and organic media and vacuum spraying: - the method of foil and coating formation via compounds in the vapour phase; - the method of fabrication of layers of transuranic elements on superthin (1-2 μm) metal substrates with additional isolating polymer-metal coatings (0.2-0.4 μm), that substantially decrease material transfer from the active layer and increase safety of product handling.

  16. Russian ElectroKhimPribor integrated plant - producer and supplier of enriched stable isotopes

    International Nuclear Information System (INIS)

    Russian ElectroKhimPribor Integrated Plant, as well as ORNL, is a leading production which manufactures and supplied to the world market such specific products as stable isotopes. More than 200 isotopes of 44 elements can be obtained at its electromagnetic separator. Changes being underway for a few last years in Russia affected production and distribution of stable isotopes. There arose a necessity in a new approach to handling work in this field so as to create favourable conditions for both producers and customers. As a result, positive changes in calutron operation at ElectroKhimPribor has been reached; quality management system covering all stages of production has been set up; large and attractive stock of isotopes has been created; prospective scientific isotope-based developments are taken into account when planning separation F campaigns; executing the contracts is guaranteed; business philosophy has been changed to meet maximum of customer needs. For more than forty years ElectroKhimPribor have had no claim from customers as to quality of products or implementing contracts. Supplying enriched stable isotopes virtually to all the world's leading customers, ElectroKhimPribor cooperates successfully with Canadian company Trace Science since 1996

  17. Modeling study of vibrational photochemical isotope enrichment. [HBr + Cl/sub 2/; HCl + Br/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Badcock, C.C.; Hwang, W.C.; Kalsch, J.F.

    1978-09-29

    Chemical kinetic modeling studies of vibrational-photochemical isotope enrichment have been performed on two systems: Model (I), H/sup 79/Br(H/sup 81/Br) + Cl/sub 2/ and, Model (II), H/sup 37/Cl(H/sup 35/Cl) + Br. Pulsed laser excitation was modeled to the first excited vibrational level of H/sup 79/Br in Model I and the first and second excited vibrational levels of both HCl isotopes in Model II. These are prototype systems of exoergic (Model I) and endoergic (Model II) reactions. The effects on enrichment of varying the external parameters (pressure, laser intensity) and the internal parameters (rate constants for V-V exchange and excited-state reactions) were examined. Studies of these prototype systems indicate that a favorable reaction for enrichment, with isotopically-specific excitation and a significantly accelerated vibrationally-excited-state reaction should have the following properties: the reaction from v = 0 should be only moderately exoergic, and the most favorable coreactant should be a polyatomic species, such as alkyl radical. Direct excitation of the reacting vibrational level is at least an order of magnitude more favorable for enrichment than is population by energy transfer. Enrichment of the minor isotope by these processes is more effective than is major isotope enrichment. Within limits, increased laser intensity is beneficial. However, for sequential excitation of a second vibrational level, major isotope enrichment can be diminished by high populations of the first vibrational level.

  18. Diurnal variation of oxygen isotopic enrichment in asymmetric-18 ozone from the middle stratosphere to lower mesosphere

    Science.gov (United States)

    Sato, Tomohiro; Kasai, Yasuko; Yoshida, Naohiro

    2016-07-01

    Oxygen isotopic signature is a powerful tracer of chemical and physical processes in the earth's atmosphere. Ozone has the largest oxygen isotopic enrichment in other oxygen-included species and is a source of oxygen isotopic enrichment. The vertical profile of ozone isotopic enrichment has been measured; however its variation over time remains uninvestigated. As ozone isotopic enrichment is generated by the ozone formation reaction and ozone photolysis, ozone isotopic enrichment is expected to vary over the course of a day. In this paper, the diurnal variation in oxygen isotopic enrichment of asymmetric 18 heavy ozone (δ^{18}OOO) was reported from the middle stratosphere to the lower mesosphere for the first time. We used the Level 2 vertical profile data derived from the atmospheric limb emission spectra acquired by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) with the optimized retrieval algorithm for ozone isotopic ratio by SMILES (TOROROS). In the middle stratosphere, δ^{18}OOO increased during the day with amplitudes of approximately 3.5 % and 2.2 % at 32 and 37 km, respectively. No significant variation was observed in the upper stratosphere and lower mesosphere, although δ^{18}OOO tended to decrease during the day with increasing altitude. This trend is opposite to that observed in the stratosphere. We estimated the diurnal variation in δ^{18}OOO with isotopic fractionation of ozone photolysis calculated by the photolysis rates of major and minor ozones. The estimation reproduced the daytime increase in the stratosphere and daytime decrease in the mesosphere. The contributions of ozone photolysis to the daytime increase were approximately 70 % and 80 % at 32 and 37 km, respectively. The daytime increase at an altitude of 32 km was underestimated, which indicates possible contributions from other chemical reactions such as collision with NO_x species. We concluded that ozone photolysis plays a key role in determining the diurnal

  19. ForCent model development and testing using the Enriched Background Isotope Study experiment

    Energy Technology Data Exchange (ETDEWEB)

    Parton, W.J.; Hanson, P. J.; Swanston, C.; Torn, M.; Trumbore, S. E.; Riley, W.; Kelly, R.

    2010-10-01

    The ForCent forest ecosystem model was developed by making major revisions to the DayCent model including: (1) adding a humus organic pool, (2) incorporating a detailed root growth model, and (3) including plant phenological growth patterns. Observed plant production and soil respiration data from 1993 to 2000 were used to demonstrate that the ForCent model could accurately simulate ecosystem carbon dynamics for the Oak Ridge National Laboratory deciduous forest. A comparison of ForCent versus observed soil pool {sup 14}C signature ({Delta} {sup 14}C) data from the Enriched Background Isotope Study {sup 14}C experiment (1999-2006) shows that the model correctly simulates the temporal dynamics of the {sup 14}C label as it moved from the surface litter and roots into the mineral soil organic matter pools. ForCent model validation was performed by comparing the observed Enriched Background Isotope Study experimental data with simulated live and dead root biomass {Delta} {sup 14}C data, and with soil respiration {Delta} {sup 14}C (mineral soil, humus layer, leaf litter layer, and total soil respiration) data. Results show that the model correctly simulates the impact of the Enriched Background Isotope Study {sup 14}C experimental treatments on soil respiration {Delta} {sup 14}C values for the different soil organic matter pools. Model results suggest that a two-pool root growth model correctly represents root carbon dynamics and inputs to the soil. The model fitting process and sensitivity analysis exposed uncertainty in our estimates of the fraction of mineral soil in the slow and passive pools, dissolved organic carbon flux out of the litter layer into the mineral soil, and mixing of the humus layer into the mineral soil layer.

  20. Enrichment of hydrogen isotopes while decomposition of alkali metal amalgams (Preprint No. CA-11)

    International Nuclear Information System (INIS)

    Sodium amalgam was prepared by electrolyzing caustic soda solution in a cell with flowing mercury as cathode. On decomposition of amalgam with aqueous sodium hydroxide solution in a denuder column packed with graphite pieces, the resultant hydrogen gas was depleted in deuterium. The alkali solution was enriched in deuterium content. The separation of the isotopes of some amalgam forming metals while decomposition of the amalgam of these metals with water has already been described. The separation is due to differential reaction rates of alkali metal amalgams with water containing light and heavy isotopes of hydrogen. However in the present investigation, the separation factor obtained is considerably higher than earlier reported due to possible chemical exchange between resultant hydrogen and the alkali metal hydroxide in presence of graphite surface and/or exchange of water with nascent hydrogen catalysed by OH- ions. (author). 18 refs., 3 tabs., 1 fig

  1. PHYSICAL BASIS OF ISOTOPE-ENRICHED LAYERS FORMATION IN FIBER OPTICS

    Directory of Open Access Journals (Sweden)

    Myshkin V. F.

    2015-06-01

    Full Text Available It is known that transmission coefficient of quartz glass containing the same amount of 28Si and 30Si in the silicon optical fiber is lesser than in commercial LEDs for telecommunications. Therefore it is topical to develop the method of optical glass formation with specified isotope composition in the core and in the shell. The article provides an analysis of physical and chemical processes occurring at the formation of quartz optical fiber blanks by vapor deposition from the gas phase. It is shown that the part of the silicon tetrachloride oxidation stages passes through the radical processes. Therefore for quartz glass formation with specified isotope composition it is possible to use the paramagnetic phenomena caused by the external magnetic field in a high-temperature flow at the quartz glass chemical deposition from the vapor phase. In this case alloy additive using is not necessary. Alloy additives can form density inhomogeneities in the glass. Simultaneous silicon glass formation and silicon isotope separation process bring to significant reduction of the fiber cost in comparison with isotope-enriched materials using. The permanent magnets can be used for magnetic field formation at existing process units

  2. Establishing Specifications for Low Enriched Uranium Fuel Operations Conducted Outside the High Flux Isotope Reactor Site

    Energy Technology Data Exchange (ETDEWEB)

    Pinkston, Daniel [ORNL; Primm, Trent [ORNL; Renfro, David G [ORNL; Sease, John D [ORNL

    2010-10-01

    The National Nuclear Security Administration (NNSA) has funded staff at Oak Ridge National Laboratory (ORNL) to study the conversion of the High Flux Isotope Reactor (HFIR) from the current, high enriched uranium fuel to low enriched uranium fuel. The LEU fuel form is a metal alloy that has never been used in HFIR or any HFIR-like reactor. This report provides documentation of a process for the creation of a fuel specification that will meet all applicable regulations and guidelines to which UT-Battelle, LLC (UTB) the operating contractor for ORNL - must adhere. This process will allow UTB to purchase LEU fuel for HFIR and be assured of the quality of the fuel being procured.

  3. GAS CHROMATOGRAPHIC-MASS SPECTROMETRIC ANALYSIS OF HIGH PURITY SULFUR HEXAFLUORIDE ENRICHED WITH 32S ISOTOPE

    OpenAIRE

    Krylov, V. A.; Sozin, A. Iu.; Chernova, O. Iu.

    2016-01-01

    The method of gas chromatography-mass spectrometry was used for the first time to investigate the impurity composition of high-purity sulfur hexafluoride enriched with 32S isotope. For the separation of impurities an adsorption capillary column GS-GasPro of 60 m ´ 0.32 mm with a modified silica gel and a column of 25 m × 0.26 mm, df = 0.25 microns with  a poly trimethylsilyl propyne (PTMSP) were used. It was shown that GS-GasPro column allowed separating the impurity substances with low molec...

  4. Partial Safety Analysis for a Reduced Uranium Enrichment Core for the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Primm, Trent [ORNL; Gehin, Jess C [ORNL

    2009-04-01

    A computational model of the reactor core of the High Flux Isotope Rector (HFIR) was developed in order to analyze non-destructive accidents caused by transients during reactor operation. The reactor model was built for the latest version of the nuclear analysis software package called Program for the Analysis of Reactor Transients (PARET). Analyses performed with the model constructed were compared with previous data obtained with other tools in order to benchmark the code. Finally, the model was used to analyze the behavior of the reactor under transients using a different nuclear fuel with lower enrichment of uranium (LEU) than the fuel currently used, which has a high enrichment of uranium (HEU). The study shows that the presence of fertile isotopes in LEU fuel, which increases the neutron resonance absorption, reduces the impact of transients on the fuel and enhances the negative reactivity feedback, thus, within the limitations of this study, making LEU fuel appear to be a safe alternative fuel for the reactor core.

  5. Use of carbon-13 as a population marker for Anopheles arabiensis in a sterile insect technique (SIT context

    Directory of Open Access Journals (Sweden)

    Knols Bart GJ

    2006-01-01

    Full Text Available Abstract Background Monitoring of sterile to wild insect ratios in field populations can be useful to follow the progress in genetic control programmes such as the Sterile Insect Technique (SIT. Of the numerous methods for marking insects most are not suitable for use in mass rearing and mass release. Suitable ones include dye marking, genetic marking and chemical marking. Methods The feasibility of using the stable isotope of carbon, 13C, as a potential chemical marker for Anopheles arabiensis was evaluated in the laboratory. Labeled-13C glucose was incorporated into the larval diet in a powder or liquid form. The contribution of adult sugar feeding to the total mosquito carbon pool and the metabolically active carbon pool was determined by tracing the decline of the enrichment of the adult male mosquito as it switched from a labeled larval diet to an unlabeled adult diet. This decline in the adult was monitored by destructive sampling of the whole mosquito and analyzed using isotope ratio mass spectrometry. Results A two-pool model was used to describe the decline of the 13C-enrichment of adult mosquitoes. The proportion of the total adult carbon pool derived from the adult sugar diet over the life span of mosquitoes was determined and the ratio of structural carbon, with a low turnover rate to metabolically active non-structural carbon was assessed. The uptake and turnover of sugar in the metabolically active fraction suggests that after 3 days >70% of the active fraction carbon is derived from sugar feeding (increasing to >90% by day 7, indicating the high resource demand of male mosquitoes. Conclusion It was possible to "fix" the isotopic label in adult An. arabiensis and to detect the label at an appropriate concentration up to 21 days post-emergence. The optimum labeling treatment would cost around 250 US$ per million mosquitoes. Stable isotope marking may thus aid research on the fate of released insects besides other population

  6. In vivo trace element speciation study by using enriched stable isotopic tracer technique

    International Nuclear Information System (INIS)

    In contrast to the radioactive tracer method, the enriched stable isotopic technique used in life sciences will not cause radiation damage to cells and its operation will be no radioactive risk, In our laboratory, the enriched stable isotopes Cr-50, Hg-196 and Hg-198 combined with biochemical separation, neutron activation analysis (NAA) and inductively coupled plasma mass spectrometry (ICP-IVIS) have been used to investigate the element speciation in vivo. Chromium (Cr) is proposed to act as a potentiator of insulin action in animals and human beings. Its deficiency induces the symptoms resembling diabetes and its supplement can alleviate these symptoms. However, as the concentration of Cr in vivo is usually at ultratrace level(- ng/g), its speciation study is usually difficult, since it is almost impossible to avoid the exogenous Cr contamination caused by separation and determination processes. Therefore, in this study, 50Cr2O3 with 94.2% 50Cr was used as a tracer combined with gel chromatography to study the Cr speciation in serum, liver, urine and other tissues of healthy and diabetic rats. The Cr concentrations can be determined via 50Cr(n, γ)51Cr by NAA, which is ideally suited for the ultratrace element analyses due to its high precision, accuracy and sensitivity. Such research have found that the most quantity of chromium in vivo is mainly combined with high molecular weight proteins, which is later identified as transferrin and low molecular weight protein is mainly excreted from urine. Mercury is listed by the International Program of Chemical Safety as one of the six most dangerous chemicals in the global environment. Mercury compounds in the environment are often difficult to degrade. However, the mechanism on mercury toxicity to developing children following long term and low dose of mercury exposure is still not clear. Therefore, high sensitive method in vivo needs to be developed to study such low level mercury toxicity to fetus In this study, high

  7. In vivo synthesized 34S enriched amino acid standards for species specific isotope dilution of proteins

    DEFF Research Database (Denmark)

    Hermann, Gerrit; Moller, Laura Hyrup; Gammelgaard, Bente;

    2016-01-01

    with the concept of species specific isotope dilution analysis (IDA). The method relies on the determination of the two sulfur containing amino acids, cysteine and methionine by sulfur speciation analysis and is hence applicable to any protein containing sulfur. In vivo synthesis using 34S as sulfur source...... (ICP-MS) combined to anion exchange showed that very high concentrated spike material could be produced with [small mu ]mol amounts of proteinogenic sulfur containing amino acids per g cell dry weight. An enrichment of 34S to 96.3 +/- 0.4% (n = 3) and 98.5 +/- 0.4% (n = 3) for cysteic acid......A generic quantification approach was introduced addressing the characterization of protein standards while fulfilling the principles of metrology. Traceable absolute quantification was achieved combining a proven biochemical method, i.e. protein hydrolysis followed by amino acid quantification...

  8. Isotopic fingerprints of Pt-containing luminescence centers in highly enriched Si-28

    CERN Document Server

    Steger, M; Godisov, O N; Alves, E; Kaliteevskii, A K; Saeedi, K; Abrosimov, N V; Churbanov, M F; Gusev, A V; Johnston, K; Thewalt, M L W; Sekiguchi, T; Yang, A; Riemann, H; Henry, M O; Pohl, H -J; Wahl, U

    2010-01-01

    Recently we have shown that the reduction in the photoluminescence linewidth of many deep luminescence centers in highly enriched Si-28 results in well-resolved isotopic fingerprints. This allows for a better characterization of a defect center, as not only the involvement of a specific element but also the number of atoms of that element within the complex can be determined. Surprisingly, we have found that many well-known luminescence centers have a different composition than originally supposed. In addition, we have found a large number of four- and five-atom luminescence centers involving the elements Cu, Au, and Li. Here we introduce series of four- and five-atom deep luminescence centers involving a single Pt atom together with Cu and Li, similar to what has been seen previously for Au-containing luminescence centers.

  9. Application of enriched stable isotope technique to the study of copper bioavailability in Daphnia magna

    Institute of Scientific and Technical Information of China (English)

    Wenhong Fan; Chenguang Wu; Chunmei Zhao; Tao Yu; Yuan Zhang

    2011-01-01

    The biokinetics of Cu in Daphnia magna, including dissolved uptake, assimilation and efflux, has been determined using a gamma 67Cu radiotracer methodology.However, this gamma emitting radioisotope is not readily available due to its very short half-life.In the present study, we employed a stable isotope tracer (65Cu) to determine the Cu biokinetics and compared our results to those determined using 67Cu.The dissolved uptake rate constant of 65Cu was 3.36 L/(g·day), which is higher than that of 67Cu (1.32 L/(g·day)).With increasing food concentrations from 2×104 to 1×105 cells/mL, the Cu assimilation efficiency (AE) decreased from 46% to 11%,compared to a decrease from 27% to 16% when determined using 67Cu.The efflux of Cu from Daphnia magna was quantified following both dissolved and dietary uptake.The efflux of waterborne Cu was comparable to that of dietborne Cu and the efflux rate constant (0.32-0.52 day-1) was higher than that determined by 67Cu (0.19-0.20 day-1).By considering different water properties and handling procedure between the two experiments, we believe that these differences are reasonable.Overall, this study demonstrated that the enriched stable isotope tracer technique is a powerful tool to investigate metal bioavailability and maybe a good alternative to radioactive measurements.

  10. Yield and enrichment studies of C-13 isotope by multi-photon dissociation of Freon-22 at low temperatures

    Indian Academy of Sciences (India)

    Manoj Kumar; Anant Deshpande; Chintan Gupta; A K Nath

    2003-06-01

    Multi-photon dissociation of Freon-22 (CF2HCl) at low temperatures has been carried out to separate the C-13 isotope using a TEA CO2 laser. Yield and enrichment of C-13 isotope in the product C2F4 are studied at 9(22) laser line as a function of temperature (-50°C to 30°C). It is observed that at a given fluence when the temperature is lowered the yield decreases and the enrichment factor of C-13 increases. Room temperature irradiation of CF2HCl towards the blue edge of C-13 absorption (i.e. at 9(20) laser line) gives low yield of the product (C2F4) at a fluence, which produces the desired enrichment factor of 100. An increase in fluence gives very high yield of C2F4 but the enrichment factor is very low. Irradiating CF2HCl at a temperature of -10°C enhances the enrichment factor to 100 and the yield obtained is comparable to that towards the red edge of C-13 absorption (i.e. at 9(26) laser line). At a given enrichment factor higher enrichment efficiency is achieved when CF2HCl is irradiated at lower temperature.

  11. Determining metal assimilation efficiency in aquatic invertebrates using enriched stable metal isotope tracers

    International Nuclear Information System (INIS)

    We employ a novel approach that combines pulse-chase feeding and multi-labelled stable isotopes to determine gut passage time (GPT), gut retention time (GRT), food ingestion rate (IR) and assimilation efficiency (AE) of three trace elements for a freshwater gastropod. Lettuce isotopically enriched in 53Cr, 65Cu and 106Cd was fed for 2 h to Lymnaea stagnalis. The release of tracers in feces and water was monitored for 48 h, during which unlabelled lettuce was provided ad libidum. The first defecation of 53Cr occurred after 5 h of depuration (GPT), whereas 90% of the ingested 53Cr was recovered in the feces after 22.5 h of depuration (GRT). 53Chromium was not significantly accumulated in the soft tissues upon exposure. In contrast, 65Cu and 106Cd assimilation was detectable for most experimental snails, i.e., 65/63Cu and 106/114Cd ratios in exposed snails were higher than those for controls. Food IR during the labelled feeding phase was 0.16 ± 0.07 g g-1 d-1. IR was inferred from the amount of 53Cr egested in the feces during depuration and the concentration of 53Cr in the labelled lettuce. Assimilation efficiencies (±95% CI) determined using mass balance calculations were 84 ± 4% for Cu and 85 ± 3% for Cd. The ratio method yields similar AE estimates. Expanding the application of this novel stable isotope tracer technique to other metals in a wide variety of species will provide unique opportunities to evaluate the interplay between digestive processes and dietary influx of metals. Understanding the biological processes that modulate dietborne metal uptake is crucial to assess the toxicity of dietborne metals

  12. Determining metal assimilation efficiency in aquatic invertebrates using enriched stable metal isotope tracers

    Science.gov (United States)

    Croteau, M.-N.; Luoma, S.N.; Pellet, B.

    2007-01-01

    We employ a novel approach that combines pulse-chase feeding and multi-labelled stable isotopes to determine gut passage time (GPT), gut retention time (GRT), food ingestion rate (IR) and assimilation efficiency (AE) of three trace elements for a freshwater gastropod. Lettuce isotopically enriched in 53Cr, 65Cu and 106Cd was fed for 2 h to Lymnaea stagnalis. The release of tracers in feces and water was monitored for 48 h, during which unlabelled lettuce was provided ad libidum. The first defecation of 53Cr occurred after 5 h of depuration (GPT), whereas 90% of the ingested 53Cr was recovered in the feces after 22.5 h of depuration (GRT). 53Chromium was not significantly accumulated in the soft tissues upon exposure. In contrast, 65Cu and 106Cd assimilation was detectable for most experimental snails, i.e., 65/63Cu and 106/114Cd ratios in exposed snails were higher than those for controls. Food IR during the labelled feeding phase was 0.16 ?? 0.07 g g-1 d-1. IR was inferred from the amount of 53Cr egested in the feces during depuration and the concentration of 53Cr in the labelled lettuce. Assimilation efficiencies (??95% CI) determined using mass balance calculations were 84 ?? 4% for Cu and 85 ?? 3% for Cd. The ratio method yields similar AE estimates. Expanding the application of this novel stable isotope tracer technique to other metals in a wide variety of species will provide unique opportunities to evaluate the interplay between digestive processes and dietary influx of metals. Understanding the biological processes that modulate dietborne metal uptake is crucial to assess the toxicity of dietborne metals. ?? 2007 Elsevier B.V. All rights reserved.

  13. Chlorine isotope enrichment on a strong alkaline anion exchanger in dependence of type and concentration of the strange electrolytic solution

    International Nuclear Information System (INIS)

    Chlorine isotope enrichment for heterogenous ionexchange equilibria was studied. The dependence of element separation effects on the anion of the strange electrolyte (for same cation), on the cation of the strange electrolyte (for same anion), on the concentration of the strange electrolyte and also on the acetone: water ratio of the solvent was investigated. (orig./HBR)

  14. Lithium isotope evidence for subduction-enriched mantle in the source of mid-ocean-ridge basalts.

    Science.gov (United States)

    Elliott, Tim; Thomas, Alex; Jeffcoate, Alistair; Niu, Yaoling

    2006-10-01

    'Recycled' crustal materials, returned from the Earth's surface to the mantle by subduction, have long been invoked to explain compositional heterogeneity in the upper mantle. Yet increasingly, problems have been noted with this model. The debate can be definitively addressed using stable isotope ratios, which should only significantly vary in primitive, mantle-derived materials as a consequence of recycling. Here we present data showing a notable range in lithium isotope ratios in basalts from the East Pacific Rise, which correlate with traditional indices of mantle heterogeneity (for example, 143Nd/144Nd ratios). Such co-variations of stable and radiogenic isotopes in melts from a normal ridge segment provide critical evidence for the importance of recycled material in generating chemical heterogeneity in the upper mantle. Contrary to many models, however, the elevated lithium isotope ratios of the 'enriched' East Pacific Rise lavas imply that subducted ocean crust is not the agent of enrichment. Instead, we suggest that fluid-modified mantle, which is enriched during residency in a subduction zone, is mixed back into the upper mantle to cause compositional variability. PMID:17024091

  15. Re-enrichment of O-18 isotopic water used for the production of F-18 in a cyclotron

    International Nuclear Information System (INIS)

    Full text: The demand for and applications of stable isotopes in medicine, industry, and science in the modern era has increased and expanded significantly. Especially, 18O-enriched water (> 90%) is used as a target in a cyclotron for the production of the β -emitting radioisotope 18F, which is essential for PET (Positron Emission Tomography) pharmaceutical [18F]-labeled 2-deoxyglucose (FDG) synthesis. Currently, 18O is produced by a cold distillation of NO (Nitric Oxide) or a fractional distillation of water. These processes, however, are technically complicated and costly so as to limit the production of 18O. In this regard, it is essential to re-use the used target water as much as possible since the 18O-enriched water is so expensive (∼ $150/g). In order to recycle the used target water, it is necessary to purify the organic and inorganic impurities contaminated during the 18f-FDG production loop and to re-enrich the 18O isotope in the target water diluted during the purification process. For the development of a compact target water 18O re-enrichment system, the 18O isotope separation characteristics of MD (Membrane Distillation) were investigated. The 18O isotopic water permeation and separation characteristics of a hydrophobic PTFE membrane using Air Gap MD and Vacuum Enhanced MD were evaluated. Permeation fluxes were measured by weighing the collected membrane-permeated water vapor. 18O/ 16O of each water sample was analyzed by a Tunable Diode Laser Absorption Spectroscopy (TDLAS). We observed the effects of the air in the membrane pores and the temperature gradient applied to the membrane surfaces on the vapor permeation flux and the oxygen isotope separation for the first time. For both AGMD and VEMD, the permeation flux and the degree of 18O separation increased as the membrane interfacial temperature gradient increased. Even though the oxygen isotope separation and the permeation flux for the VEMD is slightly higher than the AGMD, the latter may be

  16. The separation nozzle method for enrichment of the light uranium isotope

    International Nuclear Information System (INIS)

    The history of the development of the separation nozzle method for enrichment of the light uranium isotope is described as a contribution to a memorandum published by Deutsche Forschungsgemeinschaft. The work was triggered off by an effect which had been observed in fundamental studies on gas kinetics. Development up to the technical maturity covered a period of more than 25 years. The implementation of the project at the Karlsruhe Nuclear Research Center provided an adequate financial and technical framework, the employment of senior staff without limitations in time being of major importance for the continuity of work. The links established between the Institute and the University and the resulting opportunity of having doctoral theses written, on the other hand, gave rise to a permanent flow of young, highly qualified scientists and engineers. Thus the Institut's requirements for junior staff could be satisfied in an optimum way. Although the Center offered a variety of possibilities of internal technical cooperation, important developments were performed jointly with industrial firms experienced in related fields. By this, not only a steady flow of know-how had been accumulated but also the large-scale applicability was ensured at a later date of results jointly obtained. (orig.)

  17. ESR Experiments on a Single Donor Electron in Isotopically Enriched Silicon

    Science.gov (United States)

    Tracy, Lisa; Luhman, Dwight; Carr, Stephen; Borchardt, John; Bishop, Nathaniel; Ten Eyck, Gregory; Pluym, Tammy; Wendt, Joel; Witzel, Wayne; Blume-Kohout, Robin; Nielsen, Erik; Lilly, Michael; Carroll, Malcolm

    In this talk we will discuss electron spin resonance experiments in single donor silicon qubit devices fabricated at Sandia National Labs. A self-aligned device structure consisting of a polysilicon gate SET located adjacent to the donor is used for donor electron spin readout. Using a cryogenic HEMT amplifier next to the silicon device, we demonstrate spin readout at 100 kHz bandwidth and Rabi oscillations with 0.96 visibility. Electron spin resonance measurements on these devices show a linewidth of 30 kHz and coherence times T2* = 10 us and T2 = 0.3 ms. We also discuss estimates of the fidelity of our donor electron spin qubit measurements using gate set tomography. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. ESR Experiments on a Single Donor Electron in Isotopically Enriched Silicon.

  18. ASTRONOMICAL OXYGEN ISOTOPIC EVIDENCE FOR SUPERNOVA ENRICHMENT OF THE SOLAR SYSTEM BIRTH ENVIRONMENT BY PROPAGATING STAR FORMATION

    International Nuclear Information System (INIS)

    New infrared absorption measurements of oxygen isotope ratios in CO gas from individual young stellar objects confirm that the solar system is anomalously high in its [18O]/[17O] ratio compared with extrasolar oxygen in the Galaxy. We show that this difference in oxygen isotope ratios is best explained by ∼1% enrichment of the protosolar molecular cloud by ejecta from Type II supernovae from a cluster having of order a few hundred stars that predated the Sun by at least 10-20 Myr. The likely source of exogenous oxygen was the explosion of one or more B stars during a process of propagating star formation.

  19. Production of stable isotope enriched antimicrobial peptides in Escherichia coli: An application to the production of a 15N-enriched fragment of lactoferrin

    International Nuclear Information System (INIS)

    A method is described for the production of recombinant isotopically enriched peptides in E. coli. Peptides are produced in high yield as fusion proteins with ketosteroid isomerase which form insoluble inclusion bodies. This insoluble form allows easy purification, stabilizes the peptide against degradation and prevents bactericidal activity of the peptide. Cyanogen bromide cleavage released peptide which was conjugated with alkylamines to form lipopeptide. An important advantage of this system is that it allows production of peptides that are toxic to bacteria, which we have demonstrated on a dodecapeptide based on residues 21-31 of human bactericidal protein lactoferrin

  20. Utilization of stable isotopes for the study of in vivo compartmental metabolism of poly-insaturate fatty acids; Utilisation des isotopes stables pour l`etude du metabolisme compartimental in vivo d`acides gras polyinsatures

    Energy Technology Data Exchange (ETDEWEB)

    Brossard, N.; Croset, M.; Lecerf, J.; Lagarde, M. [Institut National des Sciences Appliquees (INSA), 69 - Villeurbanne (France); Pachiaudi, C.; Normand, S.; Riou, J.P. [Faculte de Medecine, 69 - Lyon (France); Chirouze, V.; Tayot, J.L. [IMEDEX, 69 - Chaponost (France)

    1994-12-31

    In order to study the compartmental metabolism of the 22:6n-3 fatty acid, and particularly the role of the transport plasmatic forms for the tissue uptake (especially brain), a technique is developed using carbon 13 stable isotope and an isotopic mass spectrometry coupled to gaseous chromatography technique. This method has been validated in rat with docosahexaenoic acid enriched in {sup 13}C and esterified in triglycerides. The compartmental metabolism is monitored by measuring the variation of 22:6n-3 isotopic enrichment in the various lipoprotein lipidic fractions, in blood globules and in the brain. 1 fig., 1 tab., 12 refs.

  1. Design, construction, and operation of a laboratory scale reactorfor the production of high-purity, isotopically enriched bulksilicon

    Energy Technology Data Exchange (ETDEWEB)

    Ager III, J.W.; Beeman, J.W.; Hansen, W.L.; Haller, E.E.

    2004-12-20

    The design and operation of a recirculating flow reactor designed to convert isotopically enriched silane to polycrystalline Si with high efficiency and chemical purity is described. The starting material is SiF{sub 4}, which is enriched in the desired isotope by a centrifuge method and subsequently converted to silane. In the reactor, the silane is decomposed to silicon on the surface of a graphite starter rod (3 mm diameter) heated to 700-750 C. Flow and gas composition (0.3-0.5% silane in hydrogen) are chosen to minimize the generation of particles by homogeneous nucleation of silane and to attain uniform deposition along the length of the rod. Growth rates are 5 {micro}m/min, and the conversion efficiency is greater than 95%. A typical run produces 35 gm of polycrystalline Si deposited along a 150 mm length of the rod. After removal of the starter rod, dislocation-free single crystals are formed by the floating zone method. Crystals enriched in all 3 stable isotopes of Si have been made: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (88.25%). Concentrations of electrically active impurities (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup 15} cm{sup -3}, respectively.

  2. The use of stable isotopes to trace oil sands constituents

    Energy Technology Data Exchange (ETDEWEB)

    Farwell, A.J.; Nero, V.; Dixon, D.G. [Waterloo Univ., ON (Canada). Dept. of Biology

    2002-07-01

    A study was conducted to determine the biological effects of oil sands mining operations on aquatic ecosystems. The study focused on the Athabasca oil sand deposit, the largest of 4 deposits in northern Alberta. In particular, the study examined the cycling of oil sand constituents in Benthic invertebrates collected from test pits at Syncrude Canada Ltd.. The invertebrates were similar in size, but different in the quantity of process-affected water or mature fine tailings containing residual bitumen. Dragonflies and damselflies in particular, showed trends of depletion for the carbon 13 isotope and enrichment in nitrogen 15 isotope in pits where levels of process affected water was high. The depletion of carbon 13 isotope suggests that oil sand constituents assimilate into the benthic food chain. The greatest carbon 13 depletion, which was approximately 27 per cent, was found to be in test pits with high turbidity. This implies that oil sands constituents degrade microbially instead of by photosynthetic production. All benthic invertebrate group demonstrated an incremental enrichment in nitrogen 15 isotope from the control pit to the pit with greatest levels of mature fine tailings.

  3. Protein expression and isotopic enrichment based on induction of the Entner-Doudoroff pathway in Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Refaeli, Bosmat [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv (Israel); Goldbourt, Amir, E-mail: amirgo@post.tau.ac.il [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv (Israel)

    2012-10-12

    Highlights: Black-Right-Pointing-Pointer The Entner-Doudoroff pathway is induced during protein expression in E. coli. Black-Right-Pointing-Pointer 1-{sup 13}C-gluconate and {sup 15}NH{sub 4}Cl provide a carbonyl-amide protein backbone labeling scheme. Black-Right-Pointing-Pointer The enrichment pattern is determined by nuclear magnetic resonance. -- Abstract: The Entner-Doudoroff pathway is known to exist in many organisms including bacteria, archea and eukarya. Although the common route for carbon catabolism in Escherichia coli is the Embden-Meyerhof-Parnas pathway, it was shown that gluconate catabolism in E. coli occurs via the Entner-Doudoroff pathway. We demonstrate here that by supplying BL21(DE3) competent E.coli cells with gluconate in a minimal growth medium, protein expression can be induced. Nuclear magnetic resonance data of over-expressed ubiquitin show that by using [1-{sup 13}C]-gluconate as the only carbon source, and {sup 15}N-enriched ammonium chloride, sparse isotopic enrichment in the form of a spin-pair carbonyl-amide backbone enrichment is obtained. The specific amino acid labeling pattern is analyzed and is shown to be compatible with Entner-Doudoroff metabolism. Isotopic enrichment serves as a key factor in the biophysical characterization of proteins by various methods including nuclear magnetic resonance, mass spectrometry, infrared spectroscopy and more. Therefore, the method presented here can be applied to study proteins by obtaining sparse enrichment schemes that are not based on the regular glycolytic pathway, or to study the Entner-Doudoroff metabolism during protein expression.

  4. Influence of 15N enrichment on the net isotopic fractionation factor during the reduction of nitrate to nitrous oxide in soil

    DEFF Research Database (Denmark)

    Mathieu, O.; Levegue, J.; Henault, C.;

    2007-01-01

    Nitrous oxide, a greenhouse gas, is mainly emitted from soils during the denitrification process. Nitrogen stable-isotope investigations can help to characterise the N(2)O source and N(2)O production mechanisms. The stable-isotope approach is increasingly used with (15)N natural abundance...... or relatively low (15)N enrichment levels and requires a good knowledge of the isotopic fractionation effect inherent to this biological mechanism. This paper reports the measurement of the net and instantaneous isotopic fractionation factor (alpha(i)(s/p)) during the denitrification of NO(3)(-) to N(2)O over...... a range of (15)N substrate enrichments (0.37 to 1.00 atom% (15)N). At natural abundance level, the isotopic fractionation effect reported falls well within the range of data previously observed. For (15)N-enriched substrate, the value of alpha(i)(s/p) was not constant and decreased from 1.024 to 1...

  5. Sensitive, Efficient Quantitation of 13C-Enriched Nucleic Acids via Ultrahigh-Performance Liquid Chromatography–Tandem Mass Spectrometry for Applications in Stable Isotope Probing

    OpenAIRE

    Wilhelm, Roland; Szeitz, András; Klassen, Tara L; Mohn, William W.

    2014-01-01

    Stable isotope probing (SIP) of nucleic acids is a powerful tool for studying the functional traits of microbial populations within complex communities, but SIP involves a number of technical challenges. Many of the difficulties in DNA-SIP and RNA-SIP experiments can be effectively overcome with an efficient, sensitive method for quantitating the isotopic enrichment of nucleic acids. Here, we present a sensitive method for quantitating 13C enrichment of nucleic acids, requiring a few nanogram...

  6. Conversion of enriched isotopes of sulfur form SF6 to a suitable compound for feed to the electromagnetic calutron separators

    International Nuclear Information System (INIS)

    Enriched isotopes of sulfur are becoming attractive for use as tracers in a variety of environmental and scientific experiments. Small amounts of highly enriched sulfur isotopes can be provided by means of electro-magnetic separation in the calutrons. However, the cost is prohibitively high for enrichment of large amounts needed by many experiments. Thus, a two-stage process is planned to obtain large amounts using gas centrifuges for preenrichment, followed by final enrichment in the calutrons. Sulfur hexafluoride is the most efficient form for processing sulfur in the centrifuges; however, SF6 is unacceptable as feed to the calutrons because it has excellent insulating properties for the high-voltage apparatus used to ionize the feed. An efficient process is needed to convert the preenriched sulfur isotopes from SF6 to a suitable form for calutron feed. Development of a conversion process is difficult because of the relatively high stability of SF6. Reiner and Simmons (1) have successfully converted SF6 to SO2 in pilot studies using a propane/oxygen flame reactor. However, H2S is a more desirable intermediate for producing metal sulfides or sulfur halides. Thus, experiments have been made using direct hydrogenation at temperatures of >900 degree C. Conversion to cadmium sulfide has been accomplished by scrubbing the H2S product gas with 5% CdCl2, achieving product yields of > 90%. A development program to convert SF6 to CdS, or another more efficient form, is being carried out. Optimum conditions for the conversion are being determined, and the products are being evaluated in calutron test runs. 7 refs., 5 figs., 2 tabs

  7. Synthesis of carbon-13-labeled tetradecanoic acids.

    Science.gov (United States)

    Sparrow, J T; Patel, K M; Morrisett, J D

    1983-07-01

    The synthesis of tetradecanoic acid enriched with 13C at carbons 1, 3, or 6 is described. The label at the carbonyl carbon was introduced by treating 1-bromotridecane with K13CN (90% enriched) to form the 13C-labeled nitrile, which upon hydrolysis yielded the desired acid. The [3-13C]tetradecanoic acid was synthesized by alkylation of diethyl sodio-malonate with [1-13C]1-bromododecane; the acid was obtained upon saponification and decarboxylation. The label at the 6 position was introduced by coupling the appropriately labeled alkylcadmium chloride with the half acid chloride methyl ester of the appropriate dioic acid, giving the corresponding oxo fatty acid ester. Formation of the tosylhydrazone of the oxo-ester followed by reduction with sodium cyanoborohydride gave the labeled methyl tetradecanoate which, upon hydrolysis, yielded the desired tetradecanoic acid. All tetradecanoic acids were identical to unlabeled analogs as evaluated by gas-liquid chromatography and infrared or NMR spectroscopy. These labeled fatty acids were used subsequently to prepare the correspondingly labeled diacyl phosphatidylcholines. PMID:6631228

  8. Comparison of CdTe and CdZnTe Detectors for Field Determination of Uranium Isotopic Enrichments

    Energy Technology Data Exchange (ETDEWEB)

    Hofstetter, KJ

    2004-01-23

    A performance comparison of a CdTe and a CdZnTe detector when exposed to uranium samples of various isotopic enrichments has been performed. These high-resolution detectors can assist in the rapid determination of uranium isotopic content of illicit material. Spectra were recorded from these room temperature semiconductor detectors with a portable multi-channel analyzer, both in the laboratory and in a field environment. Both detectors were operated below ambient temperature using the vendor supplied thermoelectric coolers. Both detectors had nominally the same active volume (18 mm3 for the CdZnTe and 25 mm3 for the CdTe detector) and resolution. Spectra of samples of known isotopic content were recorded at fixed geometries. An evaluation of potential signature g rays for the detection of enriched uranium was completed. Operational advantages and disadvantages of each detector are discussed. There is a need to improve the detection sensitivity during the interdiction of special nuclear materials (SNM) for increased homeland protection. It is essential to provide additional tools to first responders and law enforcement personnel for assessing nuclear and radiological threats.

  9. Recycle of enriched Mo targets for economic production of 99Mo/99mTc medical isotope without use of enriched uranium

    International Nuclear Information System (INIS)

    A new recycle process for recovery of enriched 98Mo or 100Mo used for production of 99Mo/99mTc medical isotope was developed. In this process, Mo is precipitated from spent NorthStar Mo/Tc generator solution containing ∼200 g/L Mo as K2MoO4 in 5 M KOH using acetic acid and then washed with nitric acid. High purification factors from potassium were achieved, and typical Mo recovery yields were ∼95 %. The recycle process was performed with up to 260 g of Mo per batch and can be easily implemented for processing of up to 400 g of Mo. (author)

  10. Comparison of isotopic time-series partitioning analysis with an evaporative enrichment model in lake- and wetland-dominated river basins, Mackenzie basin, Canada

    International Nuclear Information System (INIS)

    The use of the water isotope tracers oxygen-18 and deuterium to partition the streamflow components into snowmelt, surface water and groundwater can provide fundamental information about the factors that influence water balance and runoff generation in cold regions. Defining the isotopic composition of surface water (lakes and wetlands) is a challenge with the partitioning strategy, since the surface water contribution to streamflow, which is influenced seasonally by inputs of snowpack in spring and evaporative enrichment in summer, is a mixture from different water sources. Furthermore, the isotopic composition of streams in cold climates, particularly in subarctic wetlands, is often skewed because of noncontributing water balance compartments that undergo evaporative enrichment. That is, streams tend to reflect lower isotopic enrichment, especially in wetland-dominated basins

  11. Calculated activities of some isotopes in the RA reactor highly enriched fuel significant for possible environmental contamination - Operational report

    International Nuclear Information System (INIS)

    This report contains calculation basis and obtained results of activities for three groups of isotopes in the RA reactor 80% enriched fuel element. The following isotopes are included: 1) 85mKr, 87Kr, 88Kr, 131J, 132J, 133J, 134J, 135J, 133Xe, 138Xe i 138Cs, 2) 89Sr, 90Sr, 91Sr, 92Sr, 95Zr, 97Zr, 103Ru, 105Ru, 106Ru, 129mTe, 134Cs, 137Cs, 140Ba, 144Ce, kao i 3) 238Pu, 239Pu i 240Pu. It was estimated that the fuel is exposed to mean neutron flux. The periodicity of reactor operation is taken into account. Calculation results are given dependent on the time of exposure. These results are to be used as source data for Ra reactor safety analyses

  12. Stable-isotope analysis of a deep-sea benthic-fish assemblage: evidence of an enriched benthic food web.

    Science.gov (United States)

    Boyle, M D; Ebert, D A; Cailliet, G M

    2012-04-01

    In this study, fishes and invertebrates collected from the continental slope (1000 m) of the eastern North Pacific Ocean were analysed using stable-isotope analysis (SIA). Resulting trophic positions (T(P) ) were compared to known diets and habitats from the literature. Dual isotope plots indicated that most species groups (invertebrates and fishes) sorted as expected along the carbon and nitrogen axes, with less intraspecific variability than interspecific variability. Results also indicated an isotopically distinct benthic and pelagic food web, as the benthic food web was more enriched in both nitrogen and carbon isotopes. Trophic positions from SIA supported this finding, resulting in the assignment of fishes to different trophic positions from those expected based on published dietary information. These differences can be explained largely by the habitat of the prey and the percentage of the diet that was scavenged. A mixing model estimated dietary contributions of prey similar to those of the known diet of Bathyraja trachura from stomach-content analysis (SCA). Linear regressions indicated that trophic positions calculated from SIA and SCA, when plotted against B. trachura total length for 32 individuals, exhibited similar variation and patterns. Only the T(P) from SCA yielded significant results (stomach content: P 0·05).

  13. Stable-isotope analysis of a deep-sea benthic-fish assemblage: evidence of an enriched benthic food web.

    Science.gov (United States)

    Boyle, M D; Ebert, D A; Cailliet, G M

    2012-04-01

    In this study, fishes and invertebrates collected from the continental slope (1000 m) of the eastern North Pacific Ocean were analysed using stable-isotope analysis (SIA). Resulting trophic positions (T(P) ) were compared to known diets and habitats from the literature. Dual isotope plots indicated that most species groups (invertebrates and fishes) sorted as expected along the carbon and nitrogen axes, with less intraspecific variability than interspecific variability. Results also indicated an isotopically distinct benthic and pelagic food web, as the benthic food web was more enriched in both nitrogen and carbon isotopes. Trophic positions from SIA supported this finding, resulting in the assignment of fishes to different trophic positions from those expected based on published dietary information. These differences can be explained largely by the habitat of the prey and the percentage of the diet that was scavenged. A mixing model estimated dietary contributions of prey similar to those of the known diet of Bathyraja trachura from stomach-content analysis (SCA). Linear regressions indicated that trophic positions calculated from SIA and SCA, when plotted against B. trachura total length for 32 individuals, exhibited similar variation and patterns. Only the T(P) from SCA yielded significant results (stomach content: P 0·05). PMID:22497394

  14. DESIGN STUDY FOR A LOW-ENRICHED URANIUM CORE FOR THE HIGH FLUX ISOTOPE REACTOR, ANNUAL REPORT FOR FY 2010

    Energy Technology Data Exchange (ETDEWEB)

    Cook, David Howard [ORNL; Freels, James D [ORNL; Ilas, Germina [ORNL; Jolly, Brian C [ORNL; Miller, James Henry [ORNL; Primm, Trent [ORNL; Renfro, David G [ORNL; Sease, John D [ORNL; Pinkston, Daniel [ORNL

    2011-02-01

    This report documents progress made during FY 2010 in studies of converting the High Flux Isotope Reactor (HFIR) from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum alloy. With axial and radial grading of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in performance to users from the current level. Studies are reported of support to a thermal hydraulic test loop design, the implementation of finite element, thermal hydraulic analysis capability, and infrastructure tasks at HFIR to upgrade the facility for operation at 100 MW. A discussion of difficulties with preparing a fuel specification for the uranium-molybdenum alloy is provided. Continuing development in the definition of the fuel fabrication process is described.

  15. Design Study for a Low-Enriched Uranium Core for the High Flux Isotope Reactor, Annual report for FY 2009

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, David [ORNL; Freels, James D [ORNL; Ilas, Germina [ORNL; Miller, James Henry [ORNL; Primm, Trent [ORNL; Sease, John D [ORNL; Guida, Tracey [University of Pittsburgh; Jolly, Brian C [ORNL

    2010-02-01

    This report documents progress made during FY 2009 in studies of converting the High Flux Isotope Reactor (HFIR) from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum alloy. With axial and radial grading of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in reactor performance from the current level. Results of selected benchmark studies imply that calculations of LEU performance are accurate. Studies are reported of the application of a silicon coating to surrogates for spheres of uranium-molybdenum alloy. A discussion of difficulties with preparing a fuel specification for the uranium-molybdenum alloy is provided. A description of the progress in developing a finite element thermal hydraulics model of the LEU core is provided.

  16. Low-Enriched Uranium Fuel Design with Two-Dimensional Grading for the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ilas, Germina [ORNL; Primm, Trent [ORNL

    2011-05-01

    An engineering design study of the conversion of the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) to low-enriched uranium (LEU) fuel is ongoing at Oak Ridge National Laboratory. The computational models developed during fiscal year 2010 to search for an LEU fuel design that would meet the requirements for the conversion and the results obtained with these models are documented and discussed in this report. Estimates of relevant reactor performance parameters for the LEU fuel core are presented and compared with the corresponding data for the currently operating HEU fuel core. The results obtained indicate that the LEU fuel design would maintain the current performance of the HFIR with respect to the neutron flux to the central target region, reflector, and beam tube locations under the assumption that the operating power for the reactor fueled with LEU can be increased from the current value of 85 MW to 100 MW.

  17. Monitoring degradation of oil sands constituents and foodweb dynamics in aquatic reclamation using stable isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Farwell, A.J.; Butler, B.J.; Dixon, D.G. [Waterloo Univ., ON (Canada). Dept. of Biology; Mackinnon, M.D. [Syncrude Canada Ltd., Edmonton, AB (Canada)

    2003-07-01

    The process of extracting bitumen from the Athabasca oil sands deposits in northern Alberta generates large volumes of process-affected water with highly toxic constituents such as naphthenic acids. Napthenic acids can biodegrade and become less toxic in reclaimed aquatic systems. This study used stable isotopes to examine the cycling of oil sands constituents in aquatic systems. Benthic invertebrates were collected from test pits at Syncrude Canada Ltd. Dragonflies and damselflies showed trends in carbon 13 depletion and nitrogen 15 enrichment in pits with high levels of process-affected water. Chironomids and amphipods showed only nitrogen 15 enrichment. Carbon 13 depletion suggests invertebrate assimilation and incorporation of oil sands constituents through the microbial foodweb. It is important to define the isotope pathway of naphthenic acid degradation because naphthenic acids could represent a major source of carbon in reclaimed systems.

  18. Identification of excitonic phonon sideband by photoluminescence spectroscopy of single-walled carbon-13 nanotubes

    OpenAIRE

    Miyauchi, Yuhei; Maruyama, Shigeo

    2005-01-01

    We have studied photoluminescence (PL) and resonant Raman scatterings of single-walled carbon nanotubes (SWNTs) consisting of carbon-13 (SW13CNTs) synthesized from a small amount of isotopically modified ethanol. There was almost no change in the Raman spectra shape for SW13CNTs except for a downshift of the Raman shift frequency by the square-root of the mass ratio 12/13. By comparing photoluminescence excitation (PLE) spectra of SW13CNTs and normal SWNTs, the excitonic phonon sideband due t...

  19. High-Precision Nd Isotopes in Picrites from Hawaii and Iceland - No Evidence for an Early-Formed Enriched Reservoir

    Science.gov (United States)

    Brandon, A. D.; Norman, M. D.; Debaille, V.

    2007-01-01

    New high-precision Nd isotope measurements have shown that the present-day Nd-142/Nd-144 for average chondrites is approximately 20 ppm lower than that for the terrestrial standard and all recent mantle-derived samples measured to date. One explanation for these differences is that an enriched missing reservoir with lower Nd-142/Nd-144 resides in the mantle to balance the bulk Earth to chondritic. Data from Archean Greenland rocks show anomalies in Nd-142/Nd-144 of up to 40 ppm higher than the proposed average for chondrites. This difference between the Archean Greenland rocks and present-day mantle-derived samples has been interpreted to result from remixing of an early-formed enriched reservoir into the convecting mantle during the Archean. If so, the implication from this is that remixing of the enriched reservoir largely shut down some time in the past such that it must at present reside in a region in the mantle that infrequently participates dynamically and leading to volcanism at the surface. Several studies have suggested that the missing reservoir may be present just above the coremantle boundary (CMB). Depending on the size of this reservoir it could potentially make up all of D or exist as distinct domains within it. If such a reservoir does exist, then mantle-derived samples from plume systems that are thought to come from the CMB may be the best opportunity to identify this component using high-precision Nd isotope measurements. To test this, picrites from Hawaii with coupled enrichments in Os-186-Os-187 that has been proposed to be a signature of core-mantle interaction were measured on the JSC Triton for high-precision Nd-142/Nd-144. For comparison, picrites from Hawaii and Iceland that do not show coupled enrichments in Os-186-Os-187 were measured. We have established an external precision for Nd-142/Nd-144 of 3.6 ppm (2 sigma) during the analytical campaign. The Iceland (n=5) and Hawaiian data (n=9) have Nd-142 ranging from -0.01 plus or minus 0

  20. NUCLEAR ISOTOPIC DILUTION OF HIGHLY ENRICHED URANIUM BY DRY BLENDING VIA THE RM-2 MILL TECHNOLOGY

    International Nuclear Information System (INIS)

    DOE has initiated numerous activities to focus on identifying material management strategies to disposition various excess fissile materials. In particular the INEEL has stored 1,700 Kg of offspec HEU at INTEC in CPP-651 vault facility. Currently, the proposed strategies for dispositioning are (a) aqueous dissolution and down blending to LEU via facilities at SRS followed by shipment of the liquid LEU to NFS for fabrication into LWR fuel for the TVA reactors and (b) dilution of the HEU to 0.9% for discard as a waste stream that would no longer have a criticality or proliferation risk without being processed through some type of enrichment system. Dispositioning this inventory as a waste stream via aqueous processing at SRS has been determined to be too costly. Thus, dry blending is the only proposed disposal process for the uranium oxide materials in the CPP-651 vault. Isotopic dilution of HEU to typically less than 20% by dry blending is the key to solving the dispositioning issue (i.e., proliferation) posed by HEU stored at INEEL. RM-2 mill is a technology developed and successfully tested for producing ultra-fine particles by dry grinding. Grinding action in RM-2 mill produces a two million-fold increase in the number of particles being blended in a centrifugal field. In a previous study, the concept of achieving complete and adequate blending and mixing (i.e., no methods were identified to easily separate and concentrate one titanium compound from the other) in remarkably short processing times was successfully tested with surrogate materials (titanium dioxide and titanium mono-oxide) with different particle sizes, hardness and densities. In the current project, the RM-2 milling technology was thoroughly tested with mixtures of natural uranium oxide (NU) and depleted uranium oxide (DU) stock to prove its performance. The effects of mill operating and design variables on the blending of NU/DU oxides were evaluated. First, NU and DU both made of the same oxide

  1. Temperature effect on leaf water deuterium enrichment and isotopic fractionation during leaf lipid biosynthesis: results from controlled growth of C3 and C4 land plants.

    Science.gov (United States)

    Zhou, Youping; Grice, Kliti; Chikaraishi, Yoshito; Stuart-Williams, Hilary; Farquhar, Graham D; Ohkouchi, Naohiko

    2011-02-01

    The hydrogen isotopic ratios ((2)H/(1)H) of land plant leaf water and the carbon-bound hydrogen of leaf wax lipids are valuable indicators for climatic, physiological, metabolic and geochemical studies. Temperature will exert a profound effect on the stable isotopic composition of leaf water and leaf lipids as it directly influences the isotopic equilibrium (IE) during leaf water evaporation and cellular water dissociation. It is also expected to affect the kinetics of enzymes involved in lipid biosynthesis, and therefore the balance of hydrogen inputs along different biochemical routes. We conducted a controlled growth experiment to examine the effect of temperature on the stable hydrogen isotopic composition of leaf water and the biological and biochemical isotopic fractionations during lipid biosynthesis. We find that leaf water (2)H enrichment at 20°C is lower than that at 30°C. This is contrary to the expectation that at lower temperatures leaf water should be more enriched in (2)H due to a larger equilibrium isotope effect associated with evapotranspiration from the leaf if all other variables are held constant. A hypothesis is presented to explain the apparent discrepancy whereby lower temperature-induced down-regulation of available aquaporin water channels and/or partial closure of transmembrane water channel forces water flow to "detour" to a more convoluted apoplastic pathway, effectively increasing the length over which diffusion acts against advection as described by the Péclet effect (Farquhar and Lloyd, 1993) and decreasing the average leaf water enrichment. The impact of temperature on leaf water enrichment is not reflected in the biological isotopic fractionation or the biochemical isotopic fractionation during lipid biosynthesis. Neither the biological nor biochemical fractionations at 20°C are significantly different from that at 30°C, implying that temperature has a negligible effect on the isotopic fractionation during lipid biosynthesis.

  2. Hydrogen isotope enrichment by hydrophobic Pt-catalyst in Japan and Western countries

    International Nuclear Information System (INIS)

    The activities of the studies on hydrogen isotope separation by hydrophobic Pt-catalyst in Japan and the Western countries between 1970 and 1990 were reviewed. The R and D of tritium separation from heavy water or light water by the H2/H2O-isotopic exchange system with the aid of hydrophobic Pt-catalyst at the CRNL in Canada, the Mound Facility in the USA, the University of Karlsruhe in Germany and the Nuclear Center of Mol in Belgium were technically successful, but the construction of a commercial H2/H2O-isotopic exchange plant was abandoned or suspended because of political or budgetary problems. On the other hand, the Fugen heavy water upgrader using hydrogen isotope exchange by hydrophobic Pt-catalyst was constructed commercially and is treating on the average of about 10 m3 degraded heavy water (about 30%D) a year since 1986. In Canada, the major thrust of the development program of a new heavy water production process is directed at the CIRCE process. The catalyst used in this process is based on AECL's structured-type hydrophobic screen Pt-catalysts which are about three times more active than the corresponding random-type. Recent advances have allowed a fourfold reduction in Pt-metal loading without affecting catalyst performance. The objective of AECL is to develop the catalyst technology to allow commitment of a prototype CIRCE plant in 1994. (author)

  3. Determination of the isotopic composition of natural and slightly enriched uranium by alpha-spectrometry

    DEFF Research Database (Denmark)

    Kunzendorf, Helmar

    1968-01-01

    Determinations of the isotope contents of 238U, 235U and 234U in five uranium samples containing 0–5 at% 235U were carried out on the basis of a least-squares fit of the α-spectra from the samples, measured with a semiconductor detector, to the theoretically expected α-spectra. With a simple source...

  4. Production and use of mycotoxins uniformly enriched with stable isotopes for their dosage in biological samples: (3) Tools for pharmacokinetics and as internal standards

    International Nuclear Information System (INIS)

    Pharmacological studies of exogenous compounds often encounter problems: these compounds are in such infinitesimal amount in their biological matrices, that they require particular detection method. We have implemented an alternative method to the usual radioactivity, based on incorporation of stable isotopes, through the example of biosynthesis of uniformly 13C enriched mycotoxins. The isotopic cluster obtained from a 10% 13C enrichment of several mycotoxins (and their metabolites) can be easily recovered from biological tissue samples by mass spectrometry allowing an easy discrimination from natural non-enriched compounds. We illustrate such pharmacological approaches by in vitro zearalenone metabolism. Such enriched compound can also be used as internal standard with high reliability in order to quantify mycotoxins in contaminated food samples. (authors)

  5. Production and use of mycotoxins uniformly enriched with stable isotopes for their dosage in biological samples: (3) Tools for pharmacokinetics and as internal standards

    Energy Technology Data Exchange (ETDEWEB)

    Bravin, F.; Delaforge, M.; Duca, R.C. [CNRS, URA 2096, F-91191 Gif Sur Yvette (France); Bravin, F.; Delaforge, M.; Duca, R.C. [CEA Saclay, DSV, DBJC, SBFM, F-91191 Gif Sur Yvette (France); Pean, M. [CEA Cadarache, DEVM, GRAP, St Paul Les Durance (France); Puel, O. [INRA, Lab Pharmacol Toxicol, UR 66, Toulouse (France)

    2007-07-01

    Pharmacological studies of exogenous compounds often encounter problems: these compounds are in such infinitesimal amount in their biological matrices, that they require particular detection method. We have implemented an alternative method to the usual radioactivity, based on incorporation of stable isotopes, through the example of biosynthesis of uniformly {sup 13}C enriched mycotoxins. The isotopic cluster obtained from a 10% {sup 13}C enrichment of several mycotoxins (and their metabolites) can be easily recovered from biological tissue samples by mass spectrometry allowing an easy discrimination from natural non-enriched compounds. We illustrate such pharmacological approaches by in vitro zearalenone metabolism. Such enriched compound can also be used as internal standard with high reliability in order to quantify mycotoxins in contaminated food samples. (authors)

  6. Use of carbon-13 as a population marker for Anopheles arabiensis in a sterile insect technique (SIT) context

    OpenAIRE

    Knols Bart GJ; Mayr Leo; Hood-Nowotny Rebecca

    2006-01-01

    Abstract Background Monitoring of sterile to wild insect ratios in field populations can be useful to follow the progress in genetic control programmes such as the Sterile Insect Technique (SIT). Of the numerous methods for marking insects most are not suitable for use in mass rearing and mass release. Suitable ones include dye marking, genetic marking and chemical marking. Methods The feasibility of using the stable isotope of carbon, 13C, as a potential chemical marker for Anopheles arabien...

  7. Hf and Nd Isotope Evidence for Production of an Incompatible Trace Element Enriched Crustal Reservoir in Early Earth (Invited)

    Science.gov (United States)

    Brandon, A. D.; Debaille, V.; Lapen, T. J.

    2010-12-01

    The final significant stage of accretion of the Earth was likely a collision between proto-Earth and a Mars sized impactor that formed the Moon. This event is thought to have produced enough thermal energy to melt all or most of the Earth, with a consequent magma ocean (MO). During subsequent cooling, the Earth would have formed its protocrust and corresponding mantle lithosphere, consisting of solidified basalt-komatiitic melt, in combination with buoyant cumulates and late stage residual melts from the MO. Relative to the convecting mantle, portions of this protolithosphere are likely to have been enriched in incompatible trace elements (ITE) in sufficient quantities to contain a significant amount of the bulk Earth’s budget for rare earth elements, U, Th, and Hf. If the protolithosphere was negatively buoyant, it may have overturned at or near the final stages of MO crystallization and a significant portion of that material may have been transported into the deep mantle where it resided and remixed into the convecting mantle over Earth history [1,2]. If the protolithosphere remained positively buoyant, its crust would have likely begun to erode from surface processes, and subsequently recycled back into the mantle over time as sediment and altered crust, once a subduction mechanism arose. The Nd and Hf isotopic compositions of Earth’s earliest rocks support the idea that an early-formed ITE-enriched reservoir was produced. The maxima in 142Nd/144Nd for 3.85 to 3.64 Ga rocks from Isua, Greenland decreases from +20 ppm to +12 ppm relative to the present day mantle value, respectively [3]. This indicates mixing of an early-formed ITE enriched reservoir back into the convecting mantle. In addition, zircons from the 3.1 Ga Jack Hills conglomerate indicate that material with an enriched 176Lu/177Hf of ~0.02 and an age of 4.4 Ga or greater was present at the Earth’s surface over the first 2 Ga of Earth history, supporting the scenario of a positively buoyant

  8. CdWO4 crystal scintillators from enriched isotopes for double beta decay experiments

    CERN Document Server

    Poda, D V; Belli, P; Bernabei, R; Boiko, R S; Brudanin, V B; Cappella, F; Caracciolo, V; Castellano, S; Cerulli, R; Chernyak, D M; Danevich, F A; d'Angelo, S; Degoda, V Ya; Di Vacri, M L; Dossovitskiy, A E; Galashov, E N; Incicchitti, A; Kobychev, V V; Konovalov, S I; Kovtun, G P; Laubenstein, M; Mikhlin, A L; Mokina, V M; Nikolaiko, A S; Nisi, S; Podviyanuk, R B; Polischuk, O G; Shcherban, A P; Shlegel, V N; Solopikhin, D A; Tretyak, V I; Umatov, V I; Vasiliev, Ya V; Virich, V D

    2013-01-01

    Cadmium tungstate crystal scintillators enriched in 106Cd and 116Cd were developed. The produced scintillators exhibit good optical and scintillation properties, and a low level of radioactive contamination. Experiments to search for double beta decay of 106Cd and 116Cd are in progress at the Gran Sasso National Laboratories of the INFN (Italy). Prospects to further improve the radiopurity of the detectors by recrystallization are discussed.

  9. Relationship among latest Miocene oxygen isotopic enrichment, antarctic ice volume, and the Messinian salinity crisis

    Energy Technology Data Exchange (ETDEWEB)

    Hodell, D.A.; Elmstrom, K.M.; Kennett, J.P.

    1985-01-01

    An interval of high variable, enriched benthic /sup 18/O values was found to bracket the Miocene/Pliocene boundary, between 5.6 and 5.1 Ma, in five sites from the Southwest Pacific and Atlantic Oceans. The duration of this enrichment event was less than 500,000 years, and is shown by paleomagnetic correlation to be equivalent in time with the deposition of Messinian evaporites. The /sup 18/O enrichment occurred in two main stages separated by a brief interval of relatively depleted /sup 18/O values. Between 5.5 and 5.3 Ma, glacioeustatic lowering of sea level due to increased Antarctic ice volume isolated the Mediterranean basin, and resulted in the deposition of the lower evaporite unit (Main Salt unit). A temporary decrease in ice volume occurred between 5.3 and 5.2 Ma, and corresponded to the intra-Messinian transgression where evaporite deposition ceased temporarily. Between 5.2 and 5.1 Ma, a second Antarctic glacial advance lowered sea level again and resulted in the deposition of the upper evaporite unit. A rapid decreased in delta/sup 18/O values occurred in all sites during the early Pliocene at 5.0 Ma. This depletion marks a glacial retreat and marine transgression, which refilled the Mediterranean Basin and permanently terminated evaporite deposition.

  10. Element enrichment and U-series isotopic characteristics of the hydrothermal sulfides at Jade site in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The geochemical and U-series isotopic characteristics of hydrothermal sulfide samples from the Jade site (127°04.5′E, 27°15′N, water depth 1300-1450 m) at Jade site in the Okinawa Trough were analyzed. In the hydrothermal sulfide samples bearing sulfate (samples HOK1 and HOK2), the LREEs are relatively enriched. All the hydrothermal sulfide samples except HOK1 belong to Zn-rich hydrothermal sulfide. In comparison with Zn-rich hydrothermal sulfides from other fields, the contents of Zn, Pb, Ag, Cd, Au and Hg are higher, the contents of Fe, Al, Cr, Co, Ni, Sr, Te, Cs, Ti and U lower, and the 210Pb radioactivity ratios and 210Pb/Pb ratios very low. In the hydrothermal sulfide mainly composed of sphalerite, the correlations between rare elements Hf and U, and Hf and Mn as well as that between dispersive elements Ga and Zn, are strongly positive; also the contents of Au and Ag are related to Fe-sulfide, because the low temperature promotes enrichment of Au and Ag. Meanwhile, the positive correlations between Fe and Bi and between Zn and Cd are not affected by the change of mineral assemblage. Based on the 210Pb/Pb ratios of hydrothermal sulfide samples (3.99×10-5-5.42×10?5), their U isotopic composition (238U content 1.15-2.53 ppm, 238U activity 1.07-1.87 dpm/g, 234U activity 1.15-2.09 dpm/g and 234U/238U ratio 1.07-1.14) and their 232Th and 230Th contents are at base level, and the chronological age of hydrothermal sulfide at Jade site in the Okinawa Trough is between 200 and 2000 yr.

  11. Element enrichment and U-series isotopic characteristics of the hydrothermal sulfides at Jade site in the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    ZENG ZhiGangi; YU ShaoXiong; YIN XueBo; WANG XiaoYuan; ZHANG GuoLiang; WANG XiaoMei; CHEN DaiGeng

    2009-01-01

    The geochemical and U-series isotopic characteristics of hydrothermal sulfide samples from the Jade site (127°04.5'E, 27°15'N, water depth 1300-1450 m) at Jade site in the Okinawa Trough were analyzed. In the hydrothermal sulfide samples bearing sulfate (samples HOK1 and HOK2), the LREEs are rela- tively enriched. All the hydrothermal sulfide samples except HOK1 belong to Zn-rich hydrothermal sul- fide. In comparison with Zn-rich hydrothermal sulfides from other fields, the contents of Zn, Pb, Ag, Cd, Au and Hg are higher, the contents of Fe, Al, Cr, Co, Ni, Sr, Te, Ca, Ti and U lower, and the 210Pb radio- activity ratios and 210Pb/Pb ratios very low. In the hydrothermal sulfide mainly composed of sphalerite, the correlations between rare elements Hf and U, and Hf and Mn as well as that between dispersive elements Ga and Zn, are strongly positive; also the contents of Au and Ag are related to Fe-aulfide, because the low temperature promotes enrichment of Au and Ag. Meanwhile, the positive correlations between Fe and Bi and between Zn and Cd are not affected by the change of mineral assemblage. Based on the 210Pb/Pb ratios of hydrothermal sulfide samples (3.99x10-5-.42x10-5), their U isotopic composition (238 U content 1.15-2.53 ppm, 238U activity 1.07-1.87 dpm/g, 234U activity 1.15-2.09 dpm/g and 234U/238U ratio 1.07-1.14) and their 222Th and 230Th contents are at base level, and the chronological age of hydrothermal sulfide at Jade site in the Okinawa Trough is between 200 and 2000 yr.

  12. High information throughput analysis of nucleotides and their isotopically enriched isotopologues by direct-infusion FTICR-MS.

    Science.gov (United States)

    Lorkiewicz, Pawel; Higashi, Richard M; Lane, Andrew N; Fan, Teresa W-M

    2012-01-01

    Fourier transform-ion cyclotron resonance-mass spectrometry (FTICR-MS) is capable of acquiring unmatched quality of isotopologue data for stable isotope resolved metabolomics (SIRM). This capability drives the need for a continuous ion introduction for obtaining optimal isotope ratios. Here we report the simultaneous analysis of mono and dinucleotides from crude polar extracts by FTICR-MS by adapting an ion-pairing sample preparation method for LC-MS analysis. This involves a rapid cleanup of extracted nucleotides on pipet tips containing a C(18) stationary phase, which enabled global analysis of nucleotides and their (13)C isotopologues at nanomolar concentrations by direct infusion nanoelectrospray FTICR-MS with 5 minutes of data acquisition. The resolution and mass accuracy enabled computer-assisted unambiguous assignment of most nucleotide species, including all phosphorylated forms of the adenine, guanine, uracil and cytosine nucleotides, NAD(+), NADH, NADP(+), NADPH, cyclic nucleotides, several UDP-hexoses, and all their (13)C isotopologues. The method was applied to a SIRM study on human lung adenocarcinoma A549 cells grown in [U-(13)C] glucose with or without the anti-cancer agent methylseleninic acid. At m/z resolving power of 400,000, (13)C-isotopologues of nucleotides were fully resolved from all other elemental isotopologues, thus allowing their (13)C fractional enrichment to be accurately determined. The method achieves both high sample and high information throughput analysis of nucleotides for metabolic pathway reconstruction in SIRM investigations.

  13. Low-Enriched Uranium Fuel Conversion Activities for the High Flux Isotope Reactor, Annual Report for FY 2011

    Energy Technology Data Exchange (ETDEWEB)

    Renfro, David G [ORNL; Cook, David Howard [ORNL; Freels, James D [ORNL; Griffin, Frederick P [ORNL; Ilas, Germina [ORNL; Sease, John D [ORNL; Chandler, David [ORNL

    2012-03-01

    This report describes progress made during FY11 in ORNL activities to support converting the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum (UMo) alloy. With both radial and axial contouring of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in performance to users from the current levels achieved with HEU fuel. Studies are continuing to demonstrate that the fuel thermal safety margins can be preserved following conversion. Studies are also continuing to update other aspects of the reactor steady state operation and accident response for the effects of fuel conversion. Technical input has been provided to Oregon State University in support of their hydraulic testing program. The HFIR conversion schedule was revised and provided to the GTRI program. In addition to HFIR conversion activities, technical support was provided directly to the Fuel Fabrication Capability program manager.

  14. The Supply of Medical Radioisotopes. Market impacts of converting to low-enriched uranium targets for medical isotope production

    International Nuclear Information System (INIS)

    The reliable supply of molybdenum-99 (99Mo) and its decay product, technetium-99m (99mTc), is a vital component of modern medical diagnostic practices. At present, most of the global production of 99Mo is from highly enriched uranium (HEU) targets. However, all major 99Mo-producing countries have recently agreed to convert to using low-enriched uranium (LEU) targets to advance important non-proliferation goals, a decision that will have implications for the global supply chain of 99Mo/99mTc and the long-term supply reliability of these medical isotopes. This study provides the findings and analysis from an extensive examination of the 99Mo/99mTc supply chain by the OECD/NEA High-level Group on the Security of Supply of Medical Radioisotopes (HLG-MR). It presents a comprehensive evaluation of the potential impacts of converting to the use of LEU targets for 99Mo production on the global 99Mo/99mTc market in terms of costs and available production capacity, and the corresponding implications for long-term supply reliability. In this context, the study also briefly discusses the need for policy action by governments in their efforts to ensure a stable and secure long-term supply of 99Mo/99mTc

  15. Analysis of isotope element by electrolytic enrichment method for ground water and surface water in Saurashtra region, Gujarat, India

    Directory of Open Access Journals (Sweden)

    Sajal Singh

    2016-12-01

    Full Text Available The present study has been aimed for the assessment of isotope element Tritium (3H. It is a great threat to human health and environment for lengthy duration. The tritium exists in earth in diverse forms such as (1 small amounts of natural tritium are produced by alpha decay of lithium-7, (2 natural atmospheric tritium is also generated by secondary neutron cosmic ray bombardment of nitrogen, (3 atmospheric nuclear bomb testing in the 1950s, although the contribution from nuclear power plants is small. Tritium or 3H is a radioactive isotope of hydrogen with a half-life of 12.32 ± 0.02 years. Water samples from ground water, surface water, and precipitation were collected from different locations in Gujarat area and were analyzed for the same. Distillation of samples was done to reduce the conductivity. Deuterium and Hydrogen were removed by the process of physico-chemical fractionation in the tritium enrichment unit. The basis of physico-chemical fractionation is the difference in the strength of bonds formed by the light vs. the heavier isotope of a given element. A total of 10 cycles (runs were executed using Quintals process. Tritium concentration files were created with help of WinQ and Quick start software in Quintals process (Liquid Scintillation Spectrometer. The concentration of tritium in terms of tritium units (TU of various samples has been determined. The TU values of the samples vary in the range of 0.90–6.62 TU.

  16. Lead and neodymium isotopic results from metabasalts of the Haveri Formation, southern Finland: evidence for Palaeoproterozoic enriched mantle

    Directory of Open Access Journals (Sweden)

    Vaasjoki, M.

    1999-06-01

    Full Text Available Tholeiitic metabasalts and coexisting sulphides have been analysed for their Pb and Nd isotopic compositions from the Proterozoic Haveri Formation, which forms the basal unit of the Tampere Schist Belt in southern Finland. Ten whole rock samples analysed for Pb isotopes form a sublinear array which yields rather uncertain age estimates in the 1900-2000 Ma range and lies on the 207Pb/204Pb vs. 206Pb/204Pb diagram well below the average global lead evolution curve. The initial lead isotopic composition inferred from the whole rock data and measured on chalcopyrite is the least radiogenic obtained from the Svecofennian domain, and precludes involvement of old upper crustal material in basalt genesis. This together with the geochemical composition and initial eNd (1900 of +0.5±0.6 suggest that the Haveri mafic metavolcanic rocks were not derived from convective MORB-type mantle. The source was rather a mantle, which had been enriched in LREE for a considerable time period. Some chalcopyrite trace leads plot close to the whole rock array while others lie above it. This is interpreted as indicating two distinct mineralisation processes. The primary and major process involved lead which was cogenetic with the basalts, while the second mineralising fluid introduced radiogenic (high 207Pb upper crustal lead scavenged from the adjacent sedimentary rocks. The least radiogenic leads at Haveri and in the Outokumpu ophiolite complex some 300 km NE are similar and the two occurrences can be coeval. The preservation of original mantle material at Haveri may be interpreted as suggesting that continental crust had formed in the Tampere area 1900-2000 Ma ago.

  17. Development of a computer systems for operational data acquisition of uranium isotopic enrichment pilot plant

    International Nuclear Information System (INIS)

    A pilot plant for uranium enrichment using the jet nozzle process was transfered from Federal Republic of Germany to Brazil, to train Brazilian technicist in its operation and to improve the process. This pilot plant is monitored by a data acquisition system and the possibility of faulty events would cause serious dificulties, as far as maintenance is concerned (for instance, unvailable special components). It is described the development of a new system, which is proposed in order to minimize difficulties with maintenance that utilizes in the assembling integrated circuits of large scale of integration. It is controlled by a microcomputer. (Author)

  18. Utilization of carbon isotope enrichments (ð¹³C) of alkanes as faecal markers to estimate diet composition of goats fed with heathland vegetation

    NARCIS (Netherlands)

    Ferreira, L.M.M.; Daniel, J.B.; Celaya, R.; Santos, A.S.; Osoro, K.; Rodrigues, M.A.M.; Pellikaan, W.F.

    2014-01-01

    This study aimed to evaluate the possible utilization of carbon isotope enrichments (d13C) of n-alkanes as faecal markers for estimating diet composition of goats fed with diets composed of different proportions of browse (Erica umbellata, Erica cinerea, Calluna vulgaris, Erica arborea, and Ulex gal

  19. Utilization of non-weapons-grade plutonium and highly enriched uranium with breeding of the 233U isotope in the VVER reactors using thorium and heavy water

    Science.gov (United States)

    Marshalkin, V. E.; Povyshev, V. M.

    2015-12-01

    A method for joint utilization of non-weapons-grade plutonium and highly enriched uranium in the thorium-uranium—plutonium oxide fuel of a water-moderated reactor with a varying water composition (D2O, H2O) is proposed. The method is characterized by efficient breeding of the 233U isotope and safe reactor operation and is comparatively simple to implement.

  20. Utilization of non-weapons-grade plutonium and highly enriched uranium with breeding of the 233U isotope in the VVER reactors using thorium and heavy water

    International Nuclear Information System (INIS)

    A method for joint utilization of non-weapons-grade plutonium and highly enriched uranium in the thorium–uranium—plutonium oxide fuel of a water-moderated reactor with a varying water composition (D2O, H2O) is proposed. The method is characterized by efficient breeding of the 233U isotope and safe reactor operation and is comparatively simple to implement

  1. Melt extraction and enrichment processes in the New Caledonia lherzolites: Evidence from geochemical and Sr-Nd isotope data

    Science.gov (United States)

    Secchiari, Arianna; Montanini, Alessandra; Bosch, Delphine; Macera, Patrizia; Cluzel, Dominique

    2016-09-01

    The New Caledonia ophiolite (Peridotite Nappe) is dominated by mantle lithologies, composed of forearc-related refractory harzburgites and minor lherzolites in both the spinel and plagioclase facies. In this study, a comprehensive geochemical data set (major, trace elements and Sr-Nd isotopes) is used to constrain the mantle evolution of the lherzolites and their relationships with the basalts from the Poya Terrane, which tectonically underlies the mantle rocks. The majority of the lherzolites are low-strain porphyroclastic tectonites. They likely record an asthenospheric origin followed by re-equilibration at lithospheric conditions, as supported by geothermometric estimates (T = 1100-940 °C and 920-890 °C for porphyroclastic and neoblastic spinel-facies assemblages, respectively). Olivine composition (Fo = 88.5-90.0 mol%), spinel Cr# ([molar 100 • Cr/(Cr + Al)] = 13-17) and relatively high amounts (7-8 vol%) of Al2O3- and Na2O-rich clinopyroxene (up to 0.5 and 6.5 wt.%, respectively) indicate a moderately depleted geochemical signature for the spinel lherzolites. Bulk rock and clinopyroxene rare earth elements (REE) patterns display a typical abyssal-type signature, i.e. steeply plunging LREE accompanied by nearly flat HREE to MREE. Clinopyroxene REE compositions of the spinel lherzolites may be reproduced by small amounts of fractional melting of a garnet lherzolite precursor (~ 4%), followed by 4%-5% melting in the spinel peridotite field. The plagioclase lherzolites show melt impregnation microstructures, Cr- and Ti-rich spinels and incompatible trace element enrichments (REE, Ti, Y, and Zr) in bulk rocks and clinopyroxenes. Impregnation modelling for these elements suggests that the plagioclase lherzolites originated from residual spinel lherzolites by entrapment of highly depleted (non-aggregated) MORB melt fractions in the shallow oceanic lithosphere. Nd isotope compositions of the investigated peridotites are consistent with derivation from an

  2. Determination of symbiotic nitrogen fixation by labelling the soil atmosphere with sup(15)N sub(2) at low isotope enrichment

    International Nuclear Information System (INIS)

    A direct method to determine the total symbiotic nitrogen fixation during the leguminous plants cycles has been, developed, by labelling the soil atmosphere with sup(15)N sub(2) at low isotope enrichment, of about 1 atom % excess. The soil explored by the root system of leguminous plants was confined by means of a chamber in the field and by sealed pots in greenhouse experiments in order to maintain the soil air labelled with sup(15)N sub(2). The average sup(15)N concentration in the soil atmosphere, necessary to calculate dinitrogen fixation, was obtained by integration of the exponential functions of isotope dilution. Those functions were obtained by periodic sampling and analysis of the N sub(2) in the soil atmosphere. The field experiment with labelled atmosphere was carried out from the 22 sup(nd) to the 31 sup(st) day of the bean crop cycle and 5.5 mg N/plant (24% of total plant N) was derived from fixation. In pot experiments, under greenhouse conditions, integrated determination of fixation was made in Phaseolus beans (from the 19 sup(th) to the 67 sup(th) day from planting) and in soybeans (from the 24 sup(th) to the 70 sup(th) day from planting). The soil atmosphere was labelled with sup(15)N sub(2) in both cases. Average fixation obtained for Phaseolus beans was 80 mg N/plant (65% of total plant N) and for soybeans 265 mg N/plant (71% of total plant N). Evaluation of the basic concept of the isotope dilution method to determine nitrogen fixation in pots experiments, as proposed by Fried and Middelboe (1977) has also been made in the present paper. Simultaneous determinations of fixation in soybeans, using the isotope dilution method of Fried and Middelboe, natural variation of the sup(15)N/ sup(14)N ratios, and total-N differences, indicated the same results for pot experiments, harvested at the end of the plant cycle. (author)

  3. A method for the determination of carbon 13 content in glucose and glycerol of blood plasma; Methode pour la determination de la teneur en carbone 13 du glucose et du glycerol dans les plasmas sanguins

    Energy Technology Data Exchange (ETDEWEB)

    Koziet, J. [Centre de Recherche Pernod-Ricard, 94 - Creteil (France)

    1994-12-31

    The coupled gaseous chromatography and isotope ratio mass spectrometry approach was first validated on beet and maize glucose and glycerol aqueous solutions containing variable carbon 13 content. Then human plasma was used to prepare samples where glucose and glycerol were labelled with small amounts of (1.3-{sup 13}C{sub 2})-glycerol and D-(U{sup 13}-C{sub 6})-glucose. The samples are then de-proteinized with acetone before lyophilization and acetylation in order to be able to measure them in the form of acetates. Carbon 13 content evaluation should then take into account the exogenous carbons from the acetyl radicals. This method appears well adapted to the simultaneous metabolic monitoring of glycerol and glucose in the blood plasma. 1 fig., 3 tabs., 5 refs.

  4. Carbon-13 variations in fluids from the Cerro Prieto geothermal system

    Energy Technology Data Exchange (ETDEWEB)

    Janik, C.J.; Nehring, N.L.; Huebner, M.A.; Truesdell, A.H.

    1982-08-10

    The carbon isotope compositions of CO/sub 2/ in steam from Cerro Prieto production well have been measured for 1977, 1979, and 1982. Variations in the delta/sup 13/C values are caused by production-related changes in the chemical and physical parameters of the geothermal system. In 1977, most CO/sub 2/ in the reservoir was isotopically light (delta/sup 13/C = -6.4 +/- 0.4). Heavier CO/sub 2/ was produced from wells in the center of the field (M5,M26,M27) due to deposition of isotopically light calcite caused by near-well boiling. In 1979 nearly all well showed relatively heavy CO/sub 2/, probably due to expansion of aquifer boiling and calcite precipitation. In 1982, many wells in the central part of the field were shut in. The amount of drawndown decreased and as temperatures and pressures near the wells increased, the boiling zones collapsed. The CO/sub 2/ in the fluid then exchanged with the precipitated calcite and became isotopically lighter. The sensitivity of carbon isotopes to calcite precipitations caused by aquifer boiling and to reequilibration with this deposited calcite upon decrease of boiling suggests use as an indicator of these aquifer processes. Surficial CO/sub 2/ of thermal origin was collected in 1981. Generally, the carbon-13 contents were close to CO/sub 2/ from production wells except for high-temperature mud pots and fumaroles containing isotopically light CO/sub 2/ derived from near surface alteration of organic matter.

  5. Field study of time-dependent selenium partitioning in soils using isotopically enriched stable selenite tracer.

    Science.gov (United States)

    Di Tullo, Pamela; Pannier, Florence; Thiry, Yves; Le Hécho, Isabelle; Bueno, Maïté

    2016-08-15

    A better understanding of selenium fate in soils at both short and long time scales is mandatory to consolidate risk assessment models relevant for managing both contamination and soil fertilization issues. The purpose of this study was thus to investigate Se retention processes and their kinetics by monitoring time-dependent distribution/speciation changes of both ambient and freshly added Se, in the form of stable enriched selenite-77, over a 2-years field experiment. This study clearly illustrates the complex reactivity of selenium in soil considering three methodologically defined fractions (i.e. soluble, exchangeable, organic). Time-dependent redistribution of Se-77 within solid-phases having different reactivity could be described as a combination of chemical and diffusion controlled processes leading to its stronger retention. Experimental data and their kinetic modeling evidenced that transfer towards less labile bearing phases are controlled by slow processes limiting the overall sorption of Se in soils. These results were used to estimate time needed for (77)Se to reach the distribution of naturally present selenium which may extend up to several decades. Ambient Se speciation accounted for 60% to 100% of unidentified species as function of soil type whereas (77)Se(IV) remained the more abundant species after 2-years field experiment. Modeling Se in the long-term without taking account these slow sorption kinetics would thus result in underestimation of Se retention. When using models based on Kd distribution coefficient, they should be at least reliant on ambient Se which is supposed to be at equilibrium. PMID:27100008

  6. Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

    Science.gov (United States)

    Friedman, I.; O'Neil, J.R.; Adami, L.H.; Gleason, J.D.; Hardcastle, K.

    1970-01-01

    The water content of the breccia is 150 to 455 ppm, with a ??D from -580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a ??D of -830 to -970 per mil. The CO2 is 290 to 418 ppm with S 13C = + 2.3 to + 5.1 per mil and ??18O = 14.2 to 19.1 per mil. Non-CO2 carbon is 22 to 100 ppm, ??18C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H2O (D = 80 ppm) and 188 ppm total carbon (??13C = -17.6 per mil). The 18O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100?? to 1300??C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.

  7. Development of particle induced gamma-ray emission methods for nondestructive determination of isotopic composition of boron and its total concentration in natural and enriched samples.

    Science.gov (United States)

    Chhillar, Sumit; Acharya, Raghunath; Sodaye, Suparna; Pujari, Pradeep K

    2014-11-18

    We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

  8. Mechanisms linking metabolism of Helicobacter pylori to (18)O and (13)C-isotopes of human breath CO2.

    Science.gov (United States)

    Som, Suman; De, Anulekha; Banik, Gourab Dutta; Maity, Abhijit; Ghosh, Chiranjit; Pal, Mithun; Daschakraborty, Sunil B; Chaudhuri, Sujit; Jana, Subhra; Pradhan, Manik

    2015-06-03

    The gastric pathogen Helicobacter pylori utilize glucose during metabolism, but the underlying mechanisms linking to oxygen-18 ((18)O) and carbon-13 ((13)C)-isotopic fractionations of breath CO2 during glucose metabolism are poorly understood. Using the excretion dynamics of (18)O/(16)O and (13)C/(12)C-isotope ratios of breath CO2, we found that individuals with Helicobacter pylori infections exhibited significantly higher isotopic enrichments of (18)O in breath CO2 during the 2h-glucose metabolism regardless of the isotopic nature of the substrate, while no significant enrichments of (18)O in breath CO2 were manifested in individuals without the infections. In contrast, the (13)C-isotopic enrichments of breath CO2 were significantly higher in individuals with Helicobacter pylori compared to individuals without infections in response to (13)C-enriched glucose uptake, whereas a distinguishable change of breath (13)C/(12)C-isotope ratios was also evident when Helicobacter pylori utilize natural glucose. Moreover, monitoring the (18)O and (13)C-isotopic exchange in breath CO2 successfully diagnosed the eradications of Helicobacter pylori infections following a standard therapy. Our findings suggest that breath (12)C(18)O(16)O and (13)C(16)O(16)O can be used as potential molecular biomarkers to distinctively track the pathogenesis of Helicobacter pylori and also for eradication purposes and thus may open new perspectives into the pathogen's physiology along with isotope-specific non-invasive diagnosis of the infection.

  9. Utilization of non-weapons-grade plutonium and highly enriched uranium with breeding of the {sup 233}U isotope in the VVER reactors using thorium and heavy water

    Energy Technology Data Exchange (ETDEWEB)

    Marshalkin, V. E., E-mail: marshalkin@vniief.ru; Povyshev, V. M. [Russian Federal Nuclear Center All-Russian Research Institute of Experimental Physics (Russian Federation)

    2015-12-15

    A method for joint utilization of non-weapons-grade plutonium and highly enriched uranium in the thorium–uranium—plutonium oxide fuel of a water-moderated reactor with a varying water composition (D{sub 2}O, H{sub 2}O) is proposed. The method is characterized by efficient breeding of the {sup 233}U isotope and safe reactor operation and is comparatively simple to implement.

  10. THE SYSTEM OF ENRICHMENT AND CHROMATOGRAPHIC SEPARATION OF METHANOL TNE NEW ANALYTE FOR DETERMINATION OF THE COMBINED ISOTOPIC COMPOSITION OF METHANE

    OpenAIRE

    Kudryavtsev, A; Makas, A.; Troshkov, M.

    2011-01-01

    This work is developing the new approach to mass-spectrometric determination of the combined isotopic composition of methane. The approach is based on the preliminary on-line conversion of methane to methanol in corona discharge and selective chemical ionization. One of the method's advantages is the possibility to concentrate the new analyte methanol on sorbents at ambient temperature. The system of enrichment and separation of methanol is reported. The simple system provides the rise in the...

  11. Comparison of isotopic time-series partitioning analysis with an evaporative enrichment model in lake- and wetland-dominated river basins, Mackenzie basin, Canada

    International Nuclear Information System (INIS)

    The use of the water isotope tracers oxygen-18 and deuterium to partition the streamflow components into snowmelt, surface water and groundwater can provide fundamental information about the factors that influence water balance and runoff generation in cold regions. Defining the isotopic composition of surface water (lakes and wetlands) is a challenge with the partitioning strategy, since the surface water contribution to streamflow, which is influenced seasonally by inputs of snowpack in spring and evaporative enrichment in summer, is a mixture from different water sources. Furthermore, the isotopic composition of streams in cold climates, particularly in subarctic wetlands, is often skewed because of non-contributing water balance compartments that undergo evaporative enrichment. That is, streams tend to reflect lower isotopic enrichment, especially in wetland-dominated basins. The streamflow partitioning strategy relies on 'set points' of low flow during late winter and fall leading to the development of a conceptual model for the isotopic variations in streamflow, which allow closure of the water balance over complete annual cycles. The isotopic variation in source waters for five subarctic basins near Fort Simpson, Northwest Territories, Canada is shown. The temporal changes in the volume of snowmelt, surface water, and groundwater contributions to streamflow from each river basin are displayed. Evaporation/inflow (E/I) ratios are obtained from isotope-mass balance calculations and the results are presented in the table below. Correspondingly, runoff contributions are calculated based on the water balance equation. The lowest level of the drainage hierarchy collects the maximum surface water accumulation, representing the corresponding isotopic signal (a value close to summer low-flow signal) integrated over the catchment area, and reflects the total water loss by evaporation. Hence, the evaporative enrichment model for E/I can be used to predict the net

  12. Human biokinetic data and a new compartmental model of zirconium - A tracer study with enriched stable isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Greiter, Matthias B., E-mail: matthias.greiter@helmholtz-muenchen.de; Giussani, Augusto, E-mail: AGiussani@BfS.de; Hoellriegl, Vera, E-mail: vera.hoellriegl@helmholtz-muenchen.de; Li Weibo, E-mail: wli@helmholtz-muenchen.de; Oeh, Uwe, E-mail: uwe.oeh@helmholtz-muenchen.de

    2011-09-01

    highlights: {yields} Data from adult human volunteer study with zirconium with 100 d follow-up period. {yields} Double tracer study with ingested and injected enriched stable isotopes. {yields} Evaluation of fractional absorption for two chemical forms of zirconium. {yields} Biokinetic compartmental model with recycling describes zirconium metabolism.

  13. Design Study for a Low-enriched Uranium Core for the High Flux Isotope Reactor, Annual Report for FY 2007

    Energy Technology Data Exchange (ETDEWEB)

    Primm, Trent [ORNL; Ellis, Ronald James [ORNL; Gehin, Jess C [ORNL; Ilas, Germina [ORNL; Miller, James Henry [ORNL; Sease, John D [ORNL

    2007-11-01

    This report documents progress made during fiscal year 2007 in studies of converting the High Flux Isotope Reactor (HFIR) from highly enriched uranium (HEU) fuel to low enriched uranium fuel (LEU). Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum alloy. A high volume fraction U/Mo-in-Al fuel could attain the same neutron flux performance as with the current, HEU fuel but materials considerations appear to preclude production and irradiation of such a fuel. A diffusion barrier would be required if Al is to be retained as the interstitial medium and the additional volume required for this barrier would degrade performance. Attaining the high volume fraction (55 wt. %) of U/Mo assumed in the computational study while maintaining the current fuel plate acceptance level at the fuel manufacturer is unlikely, i.e. no increase in the percentage of plates rejected for non-compliance with the fuel specification. Substitution of a zirconium alloy for Al would significantly increase the weight of the fuel element, the cost of the fuel element, and introduce an as-yet untried manufacturing process. A monolithic U-10Mo foil is the choice of LEU fuel for HFIR. Preliminary calculations indicate that with a modest increase in reactor power, the flux performance of the reactor can be maintained at the current level. A linearly-graded, radial fuel thickness profile is preferred to the arched profile currently used in HEU fuel because the LEU fuel media is a metal alloy foil rather than a powder. Developments in analysis capability and nuclear data processing techniques are underway with the goal of verifying the preliminary calculations of LEU flux performance. A conceptual study of the operational cost of an LEU fuel fabrication facility yielded the conclusion that the annual fuel cost to the HFIR would increase significantly from the current, HEU fuel cycle. Though manufacturing can be accomplished with existing technology

  14. Vacuum-arc plasma centrifuge applied to stable isotope separation

    International Nuclear Information System (INIS)

    This work describes the results of a vacuum-arc plasma centrifuge experiment. A plasma centrifuge is an apparatus where a plasma column is produced due to the interaction of an electric current with an externally applied magnetic field, sup(→)J x sup(→)B. Among the applications of a rotating plasma, this work deals particularly with its utilization in an isotope enrichment device. The main characteristics of the plasma produced in this experiment are presented, with special attention to the plasma column rotation and the isotope enrichment. The analysis of the results is performed using a fluid model for a completely ionized rigid body rotating plasma column in steady state equilibrium. The main results are: a) rotation frequency of the plasma column in the range 2 x 10 sup(4) to 3 x 10 sup(5) rad/s; b) enrichment of 10 to 30% for the magnesium isotopes, and of 290 to 490% for the carbon 13 isotope; c) rigid body rotation of the plasma column only for radii smaller than the characteristic radius of the plasma column. re; d) linear dependence of the rotation frequency upon the magnetic field strength only for r < re; e) existence of an optimum value of the magnetic field for maximum enrichment; and f) dependence of the rotation frequency upon the inverse of the atomic mass. (author)

  15. High dynamic orientation of protons, deuterons and carbon-13 nuclei

    International Nuclear Information System (INIS)

    The behaviour of hydrogen, deuterium, and carbon-13 nuclear spin systems have been studied in partially deuterated diols, doped with paramagnetic Crsup(V) complexes, between 0.1 and 0.5 K. Experimental evidence is given that the dynamic polarization in such samples comes from a cooling of the electron spin-spin interaction reservoir by off-resonance microwave irradiation; a strong thermal coupling between this reservoir and the nuclear Zeeman reservoirs cools these too, thus changing the polarizations. In a 25 kG magnetic field at a lattice temperature of 0.37 K we reached a common spin temperature for the nuclear Zeeman reservoirs of 1.1 mK in 1,2-propanediol-D6, which corresponds to a proton polarization of 98%, a deuteron polarization of 44%, and a carbon-13 polarization of 52%. A new way of dynamic orientation of the deuteron spin system was found. It allows one to vary the deuteron tensor polarization or alignment independently of its vector polarization. This can be done by slightly off-resonance RF irradiation of the polarized proton system, which cools the proton spin-spin interaction reservoir. It appeared that at the same time the RF field provides a thermal contract between this reservoir and the deuteron quadrupole interaction reservoir, which caused the observed alignment. Values around 60% were reached for some parts of the deuteron spin system, corresponding to a deuteron quadrupole spin temperature of 7 uK. The dependence of the alignment on RF frequency and initial proton polarization as well as thermal mixing rates are in good agreement with quantitative estimates from spin temperature theory. (author)

  16. GC/MS method for determining carbon isotope enrichment and concentration of underivatized short-chain fatty acids by direct aqueous solution injection of biogas digester samples.

    Science.gov (United States)

    Mulat, Daniel Girma; Feilberg, Anders

    2015-10-01

    In anaerobic digestion of organic matter, several metabolic pathways are involved during the simultaneous production and consumption of short-chain fatty acids (SCFA) in general and acetate in particular. Understanding the role of each pathway requires both the determination of the concentration and isotope enrichment of intermediates in conjunction with isotope labeled substrates. The objective of this study was to establish a rapid and simple GC/MS method for determining the isotope enrichment of acetate and concentration of underivatized short-chain fatty acids (SCFA) in biogas digester samples by direct liquid injection of acidified aqueous samples. Sample preparation involves only acidification, centrifugation and filtration of the aqueous solution followed by direct injection of the aqueous supernatant solution onto a polar column. With the sample preparation and GC/MS conditions employed, well-resolved and sharp peaks of underivatized SCFA were obtained in a reasonably short time. Good recovery (96.6-102.3%) as well as low detection (4-7 µmol/L) and quantification limits (14-22 µmol/L) were obtained for all the 6 SCFA studied. Good linearity was achieved for both concentration and isotope enrichment measurement with regression coefficients higher than 0.9978 and 0.9996, respectively. The method has a good intra- and inter-day precision with a relative standard deviation (RSD) below 6% for determining the tracer-to-tracee ratio (TTR) of both [2-(13)C]acetate and [U-(13)C]acetate. It has also a good intra- and inter-day precision with a RSD below 6% and 5% for determining the concentration of standard solution and biogas digester samples, respectively. Acidification of biogas digester samples with oxalic acid provided the low pH required for the protonation of SCFA and thus, allows the extraction of SCFA from the complex sample matrix. Moreover, oxalic acid was the source of formic acid which was produced in the injector set at high temperature. The produced

  17. New method for GC/FID and GC-C-IRMS analysis of plasma free fatty acid concentration and isotopic enrichment.

    Science.gov (United States)

    Kangani, Cyrous O; Kelley, David E; Delany, James P

    2008-09-15

    A simple, direct and accurate method for the determination of concentration and enrichment of free fatty acids (FFAs) in human plasma was developed. The validation and comparison to a conventional method are reported. Three amide derivatives, dimethyl, diethyl and pyrrolidide, were investigated in order to achieve optimal resolution of the individual fatty acids. This method involves the use of dimethylamine/Deoxo-Fluor to derivatize plasma free fatty acids to their dimethylamides. This derivatization method is very mild and efficient, and is selective only towards FFAs so that no separation from a total lipid extract is required. The direct method gave lower concentrations for palmitic acid and stearic acid and increased concentrations for oleic acid and linoleic acid in plasma as compared to methyl ester derivative after thin-layer chromatography. The [(13)C]palmitate isotope enrichment measured using direct method was significantly higher than that observed with the BF(3)/MeOH-TLC method. The present method provided accurate and precise measures of concentration as well as enrichment when analyzed with gas chromatography combustion-isotope ratio-mass spectrometry. PMID:18757250

  18. Quantitative amino acid profiling and stable isotopically labeled amino acid tracer enrichment used for in vivo human systemic and tissue kinetics measurements

    DEFF Research Database (Denmark)

    Bornø, Andreas; van Hall, Gerrit

    2014-01-01

    . The present study describes a new sensitive liquid chromatography tandem mass-spectrometry method quantifying 20 amino acids and their tracer(s) ([ring-(13)C6]/D5Phenylalanine) in human plasma and skeletal muscle specimens. Before analysis amino acids were extracted and purified via deprotonization...... curve correlations for amino acids were on average; r(2)=0.998. Interday accuracy for amino acids determined in spiked plasma was on average 97.3% and the coefficient of variation (CV) was 2.6%. The ([ring-(13)C6]/D5Phenylalanine) enrichment CV's for machine reproducibility in muscle tissue fluid......An important area within clinical functional metabolomics is in vivo amino acid metabolism and protein turnover measurements for which accurate amino acid concentrations and stable isotopically labeled amino acid enrichments are mandatory not the least when tissue metabolomics is determined...

  19. Assumptions and Criteria for Performing a Feasability Study of the Conversion of the High Flux Isotope Reactor Core to Use Low-Enriched Uranium Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Primm, R.T., III; Ellis, R.J.; Gehin, J.C.; Moses, D.L.; Binder, J.L.; Xoubi, N. (U. of Cincinnati)

    2006-02-01

    A computational study will be initiated during fiscal year 2006 to examine the feasibility of converting the High Flux Isotope Reactor from highly enriched uranium fuel to low-enriched uranium. The study will be limited to steady-state, nominal operation, reactor physics and thermal-hydraulic analyses of a uranium-molybdenum alloy that would be substituted for the current fuel powder--U{sub 3}O{sub 8} mixed with aluminum. The purposes of this document are to (1) define the scope of studies to be conducted, (2) define the methodologies to be used to conduct the studies, (3) define the assumptions that serve as input to the methodologies, (4) provide an efficient means for communication with the Department of Energy and American research reactor operators, and (5) expedite review and commentary by those parties.

  20. [Utilization of magnetic effects as a means of isotopic enrichment]: Technical progress report, January 1, 1987 to August 31, 1987

    International Nuclear Information System (INIS)

    A quantitative theory was developed. Structural variations that would enhance the efficiency of the 13C isotope separation were explored. Photolysis of substituted large ring cyclic ketones resulted in efficient separations

  1. Optical absorption of isotopically enriched Li{sub 2}B{sub 4}O{sub 7} single crystals irradiated by thermal neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Burak, Ya.V. E-mail: burak@ifo.lviv.ua; Adamiv, V.T.; Teslyuk, I.M.; Shevel, V.M

    2004-12-01

    Induced absorption spectra in the range 200-900 nm at 77 and 290 K for Li{sub 2}B{sub 4}O{sub 7} single crystals, isotopically Li and B enriched are presented after irradiation of these crystals by thermal neutrons with fluence 1.8x10{sup 16} cm{sup -2}. The dependence of induced absorption spectra on the isotope composition was revealed: for {sup 6}Li{sub 2}{sup 10}B{sub 4}O{sub 7} and {sup 7}Li{sub 2}{sup 10}B{sub 4}O{sub 7} crystals intensive band in the region of 280-294 nm was observed. Under substitution of {sup 7}Li isotope by {sup 6}Li in the lithium tetraborate lattice no changes in the absorption spectra were observed. The nuclear reaction {sup 10}B(n,{alpha}){sup 7}Li is proposed to be the main mechanism of formation of the radiation defects.

  2. Preliminary Assessment of the Impact on Reactor Vessel dpa Rates Due to Installation of a Proposed Low Enriched Uranium (LEU) Core in the High Flux Isotope Reactor (HFIR)

    Energy Technology Data Exchange (ETDEWEB)

    Daily, Charles R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-10-01

    An assessment of the impact on the High Flux Isotope Reactor (HFIR) reactor vessel (RV) displacements-per-atom (dpa) rates due to operations with the proposed low enriched uranium (LEU) core described by Ilas and Primm has been performed and is presented herein. The analyses documented herein support the conclusion that conversion of HFIR to low-enriched uranium (LEU) core operations using the LEU core design of Ilas and Primm will have no negative impact on HFIR RV dpa rates. Since its inception, HFIR has been operated with highly enriched uranium (HEU) cores. As part of an effort sponsored by the National Nuclear Security Administration (NNSA), conversion to LEU cores is being considered for future HFIR operations. The HFIR LEU configurations analyzed are consistent with the LEU core models used by Ilas and Primm and the HEU balance-of-plant models used by Risner and Blakeman in the latest analyses performed to support the HFIR materials surveillance program. The Risner and Blakeman analyses, as well as the studies documented herein, are the first to apply the hybrid transport methods available in the Automated Variance reduction Generator (ADVANTG) code to HFIR RV dpa rate calculations. These calculations have been performed on the Oak Ridge National Laboratory (ORNL) Institutional Cluster (OIC) with version 1.60 of the Monte Carlo N-Particle 5 (MCNP5) computer code.

  3. Characterization of recharge processes in shallow and deeper aquifers using isotopic signatures and geochemical behavior of groundwater in an arsenic-enriched part of the Ganga Plain

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Dipankar, E-mail: dsaha002@yahoo.com [Central Ground Water Board, Ministry of water Resources, Govt of India, Lok Nayak Bhawan, Patna 800001 (India); Sinha, U.K. [Isotope Application Division, Bhaba Atomic Research Center, Mumbai 400085 (India); Dwivedi, S.N. [Central Ground Water Board, Ministry of water Resources, Govt of India, Lok Nayak Bhawan, Patna 800001 (India)

    2011-04-15

    Research highlights: {yields} Sub-regional scale aquifers delineated in arsenic-enriched belt in the Ganga Plain. Isotopic fingerprint of the groundwater, from arsenic-enriched and arsenic-safe aquifers established for the first time in the Ganga Plain. {yields} Recharge processes and the water provenances of vertically separated Quaternary aquifers have been established. {yields} Mean residence time of groundwater in the deeper aquifers has been worked out using C-14 isotope. {yields} Water from the deeper aquifer has been correlated with the paleoclimatic model of the Middle Ganga Plain (Mid-Ganga Basin) for 6-2 ka. - Abstract: Arsenic concentrations in groundwater extracted from shallow aquifers in some areas of the Ganga Plain in the states of Bihar and Uttar Pradesh, exceed 50 {mu}g L{sup -1} and locally reach levels in the 400 {mu}g L{sup -1} range. The study covered 535 km{sup 2} of active flood plain of the River Ganga, in Bihar where a two-tier aquifer system has been delineated in a multi-cyclic sequence of Quaternary sand, clay, sandy clay and silty clay all {<=}{approx}250 m below ground surface. The research used isotopic signatures ({delta}{sup 18}O, {delta}{sup 2}{Eta}, {sup 3}H, {sup 14}C) and major chemical constituents (HCO{sub 3}{sup -},SO{sub 4}{sup 2-},NO{sub 3}{sup -},Cl{sup -},Ca{sup 2+},Mg{sup 2+},Na{sup +},K{sup +},As{sub total}) of groundwater to understand the recharge processes and groundwater circulation in the aquifers. Values of {delta}{sup 18}O and {delta}{sup 2}{Eta} combined with {sup 3}H data indicate that the recharge to the As-enriched top 40 m of the deposits is modern (<50 a), predominantly meteoric, with some evaporation during infiltration, and partly from tanks and other surface water bodies. The lower part of the upper aquifer is vulnerable to mobilization of As with increasing groundwater extraction. The low As lower aquifer (max. 5 {mu}g L{sup -1}) is hydrologically isolated from the upper aquifer and is characterized by

  4. Laser and gas centrifuge enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Heinonen, Olli [Senior Fellow, Belfer Center for Science and International Affairs, Harvard Kennedy School, Cambridge, Massachusetts (United States)

    2014-05-09

    Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future.

  5. Laser and gas centrifuge enrichment

    Science.gov (United States)

    Heinonen, Olli

    2014-05-01

    Principles of uranium isotope enrichment using various laser and gas centrifuge techniques are briefly discussed. Examples on production of high enriched uranium are given. Concerns regarding the possibility of using low end technologies to produce weapons grade uranium are explained. Based on current assessments commercial enrichment services are able to cover the global needs of enriched uranium in the foreseeable future.

  6. [Microbial synthesis of deuterium labelled L-phenylalanine with different levels of isotopic enrichment by facultative methylotrophic bacterium Brevibacterium methylicum with RMP assimilation of carbon].

    Science.gov (United States)

    Mosin, O V; Shvets, V I; Skladnev, D A; Ignatov, I

    2014-01-01

    The preparative microbial synthesis of amino acids labelled with stable isotopes, including deuterium ( 2 H), suitable for biomedical applications by methylotrophic bacteria was studied using L-phenylalanine as example. This amino acid is secreted by Gram-negative aerobic facultative methylotrophic bacteria Brevibacterium methylicum, assimilating methanol via ribulose-5-monophosphate (RMP) cycle of assimilation of carbon, The data on adaptation of L-phenylalanine secreted by methylotrophic bacterium В. methylicum to the maximal concentration of deuterium in the growth medium with 98% 2 Н 2 O and 2% [ 2 Н]methanol, and biosynthesis of deuterium labelled L-phenylalanine With different levels of enrichment are presented. The strain was adapted by means of plating initial cells on firm (2% agarose) minimal growth media with an increasing gradient of 2 Н 2 O concentration from 0; 24.5; 49.0; 73.5 up to 98% 2 Н 2 O followed by subsequent selection of separate colonies stable to the action of 2 Н 2 O. These colonies were capable to produce L-phenylalanine. L-phenylalanine was extracted from growth medium by extraction with isopropanol with the subsequent crystallization in ethanol (output 0.65 g/l). The developed method of microbial synthesis allows to obtain deuterium labelled L-phenylalanine with different levels of isotopic enrichment, depending on concentration of 2 Н 2 O in growth media, from 17% (on growth medium with 24,5% 2 Н 2 O) up to 75% (on growth medium with 98% 2 Н 2 O) of deuterium in the molecule that is confirmed with the data of the electron impact (EI) mass- spectrometry analysis of methyl ethers of N-dimethylamino(naphthalene)-5-sulfochloride (dansyl) phenylalanine in these experimental conditions.

  7. Quantitative amino acid profiling and stable isotopically labeled amino acid tracer enrichment used for in vivo human systemic and tissue kinetics measurements.

    Science.gov (United States)

    Bornø, Andreas; van Hall, Gerrit

    2014-03-01

    An important area within clinical functional metabolomics is in vivo amino acid metabolism and protein turnover measurements for which accurate amino acid concentrations and stable isotopically labeled amino acid enrichments are mandatory not the least when tissue metabolomics is determined. The present study describes a new sensitive liquid chromatography tandem mass-spectrometry method quantifying 20 amino acids and their tracer(s) ([ring-(13)C6]/D5Phenylalanine) in human plasma and skeletal muscle specimens. Before analysis amino acids were extracted and purified via deprotonization/ion exchange, derivatized using a phenylisothiocyanate reagent and each amino acid was quantitated with its own stable isotopically labeled internal standard (uniformly labeled-(13)C/(15)N). The method was validated according to general recommendations for chromatographic analytical methods. The calibration curve correlations for amino acids were on average; r(2)=0.998. Interday accuracy for amino acids determined in spiked plasma was on average 97.3% and the coefficient of variation (CV) was 2.6%. The ([ring-(13)C6]/D5Phenylalanine) enrichment CV's for machine reproducibility in muscle tissue fluid and plasma were 4.4 and 0.8%, and the interday variability was 3.4% and the recovery was 90.5%, respectively. In conclusion, we have developed and validated a method for quantitative amino acid profiling that meets the requirements for systemic and tissue human in vivo amino acid and protein turnover kinetics measurements. Moreover, citrulline, ornithine, π-methyl-histidine, τ-methyl-l-histidine, hydroxy-proline and carnitine were analysed but when similar precision and accuray are required an additional stable istopically labeled internal standard for these meatablites should be be added.

  8. [Microbial synthesis of deuterium labelled L-phenylalanine with different levels of isotopic enrichment by facultative methylotrophic bacterium Brevibacterium methylicum with RMP assimilation of carbon].

    Science.gov (United States)

    Mosin, O V; Shvets, V I; Skladnev, D A; Ignatov, I

    2014-01-01

    The preparative microbial synthesis of amino acids labelled with stable isotopes, including deuterium ( 2 H), suitable for biomedical applications by methylotrophic bacteria was studied using L-phenylalanine as example. This amino acid is secreted by Gram-negative aerobic facultative methylotrophic bacteria Brevibacterium methylicum, assimilating methanol via ribulose-5-monophosphate (RMP) cycle of assimilation of carbon, The data on adaptation of L-phenylalanine secreted by methylotrophic bacterium В. methylicum to the maximal concentration of deuterium in the growth medium with 98% 2 Н 2 O and 2% [ 2 Н]methanol, and biosynthesis of deuterium labelled L-phenylalanine With different levels of enrichment are presented. The strain was adapted by means of plating initial cells on firm (2% agarose) minimal growth media with an increasing gradient of 2 Н 2 O concentration from 0; 24.5; 49.0; 73.5 up to 98% 2 Н 2 O followed by subsequent selection of separate colonies stable to the action of 2 Н 2 O. These colonies were capable to produce L-phenylalanine. L-phenylalanine was extracted from growth medium by extraction with isopropanol with the subsequent crystallization in ethanol (output 0.65 g/l). The developed method of microbial synthesis allows to obtain deuterium labelled L-phenylalanine with different levels of isotopic enrichment, depending on concentration of 2 Н 2 O in growth media, from 17% (on growth medium with 24,5% 2 Н 2 O) up to 75% (on growth medium with 98% 2 Н 2 O) of deuterium in the molecule that is confirmed with the data of the electron impact (EI) mass- spectrometry analysis of methyl ethers of N-dimethylamino(naphthalene)-5-sulfochloride (dansyl) phenylalanine in these experimental conditions. PMID:25249528

  9. Uranium enrichment. Principles

    International Nuclear Information System (INIS)

    Uranium enrichment industry is a more than 60 years old history and has developed without practically no cost, efficiency or profit constraints. However, remarkable improvements have been accomplished since the Second World War and have led to the development of various competing processes which reflect the diversity of uranium compositions and of uranium needs. Content: 1 - general considerations: uranium isotopes, problem of uranium enrichment, first realizations (USA, Russia, Europe, Asia, other countries), present day situation, future needs and market evolution; 2 - principles of isotopic separation: processes classification (high or low enrichment), low elementary enrichment processes, equilibrium time, cascade star-up and monitoring, multi-isotopes case, uranium reprocessing; 3 - enrichment and proliferation. (J.S.)

  10. Circuit-quantum electrodynamics with direct magnetic coupling to single-atom spin qubits in isotopically enriched 28Si

    Directory of Open Access Journals (Sweden)

    Guilherme Tosi

    2014-08-01

    Full Text Available Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified 28Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.

  11. Laser Carbon-13 and Nitrogen-15 Isotope Analysis for Greenhouse Gases now available at the SWMCNL

    International Nuclear Information System (INIS)

    The Cosmic-Ray Neutron Probe (CRNP), a passive and non-invasive method to monitor soil water contents in the top 50 cm and covers an area of about 40 hectares. After the first field calibration in 2013, further calibration was carried out using the method of Desilets et al. (2010) modified by Bogena et al. (2013). For this purpose, soil sampling were collected for gravimetric water content in July, August and October 2015 from a field site located at the Petzenkirchen research station of the Federal Agency for Water Management and the Technical University, Vienna. This field site is located about 100 km west of Vienna. These campaigns aimed to calibrate the soil water content (SWC) for different soil wetness and cropping patterns

  12. Rate of uptake and distribution of Hg in dissolved organic carbon compounds in darkwater ecosystems by ICP-MS and enriched stable isotope spiking

    International Nuclear Information System (INIS)

    The role of natural organic acids on mercury binding, transportation, net uptake rates and possibly net methylation rates will be evaluated by tracing these processes with isotope enriched mercury and ICP-MS technology. The correlation between dissolved organic matter and Hg in waters is well documented. It appears that organic acids can react with mercury residing in or emitted from different sources such as soils (particularly hydromorphic soils), laterites, natural degassing, forest fires, fuel combustion, gold mining activities, etc. to form soluble Hg-organo-complexes. The formation of these complexes is believed to greatly enhance Hg transport and be an important preliminary step in the formation of Methyl-Hg and biological uptake. The rates of these reactions and the key organic compounds involved in mercury binding will be determined by reacting isotopically-enriched Hg with samples containing a variety of concentrations and types of organic acids and subsequently analysing both reactants and organisms exposed to the reactants (bioassays) for Hg isotopes by ICP-MS. The Hg spike will allow the precise determination of rates of uptake and the most active agents of uptake. Initially, the method will be used to examine total Hg uptake and distribution but if technological limitations are overcome, this same approach can be used to determine net rates of methylation and net MeHg uptake. After the method is validated the experimental design can be altered to test the relative effects of such things as the addition of CO2 (pH change), or adding a substrate such as Fe-Mn oxyhydroxides. The addition of synthetic materials such as mulched automobile tires, can also be tested with the goal developing a pragmatic remedial method for Hg containment. Ultimately, this research should contribute to an understanding of mercury mobilization, transport and bio-concentration mechanisms, and provide a basis for developing management and treatment strategies. Emphasis will be on

  13. Anthropogenic and natural lead isotopes in Fe-hydroxides and Fe-sulphates in a watershed associated with arsenic-enriched groundwater, Maine, USA

    Science.gov (United States)

    Ayuso, Robert A.; Foley, Nora K.

    2008-01-01

    A survey of the natural and anthropogenic sources of lead contributing to secondary minerals in sulphidic schists associated with arsenic-enriched groundwater in Coastal Maine shows that the most likely source is natural Pb, particularly from coexisting sulphide minerals. The secondary minerals also reflect notable contributions from anthropogenic Pb. The Pb isotopes establish pathways by which Pb, and by inference As, could have been transported from As-bearing minerals (arsenian pyrite, arsenopyrite, lollingite, orpiment, arsenic oxide and others), via sulphide oxidation or carbonation reactions into multiple generations of secondary minerals (goethite, hematite, jarosite, natrojarosite and others). Lead isotopic compositions of the sulphides and secondary minerals determined by thermal ionization mass spectrometry (n=53) range widely. Lead and As contents of the sulphides and secondary minerals overlap, and are generally positively correlated. Pyrite, the dominant sulphide in sulphidic schists associated with As-enriched groundwater in Coastal Maine, has values of 206Pb/204Pb from 18.186 to 18.391, 207Pb/204Pb from 15.617 to 15.657, 208Pb/204Pb from 38.052 to 38.210, 206Pb/207Pb from c. 1.1625 to 1.1760 and 208Pb/207Pb from c. 2.4276 to 2.4394. Mixtures of Fe-hydroxide and oxide minerals (predominantly goethite and hematite) and secondary Fe-sulphate minerals (jarosite, natrojarosite, rozenite and melanterite) in the sulphidic schists have overlapping but generally higher values of 206Pb/204Pb from 18.495 to 19.747 (one sample at 21.495), 207Pb/204Pb from 15.595 to 15.722 (one sample at 15.839), 208Pb/204Pb from 38.186 to 39.162,206Pb/207Pb from c.1.1860 to 1.2575 (one sample at 1.3855) and 208Pb/207Pb from c. 2.4441 to 2.4865 than the sulphides. Sulphides from Zn-Pb metal mines are somewhat less radiogenic than sulphides from the schists. Other sulphides (mostly pyrite) associated with pegmatites and granitic rocks are heterogeneous and more

  14. Determination of 13C isotopic enrichment of glutathione and glycine by gas chromatography/combustion/isotope ratio mass spectrometry after formation of the N- or N,S-ethoxycarbonyl methyl ester derivatives.

    Science.gov (United States)

    Tea, Illa; Ferchaud-Roucher, Véronique; Küster, Alice; Darmaun, Dominique; Robins, Richard J

    2007-01-01

    The depletion of glutathione (GSH) reported in very-low-birth-weight infants is implicated in several pathologies, especially if deficiency occurs during foetal development. The cause of this depletion is suggested to be modification of GSH turnover. To probe the role of GSH, a reliable non-invasive method adapted to very-low-birth-weight infants is required. In this paper, we report the preparation of the N,S-ethoxycarbonyl methyl ester derivatives of GSH and glycine and their application to the measurement of (13)C/(12)C ratios at natural abundance in erythrocyte samples by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The technique allowed the determination of (13)C/(12)C ratios at natural abundance with a precision synthesis rate (FSR) in human adult blood (approx. 300% day(-1)) using the low-enrichment (13)C-glycine/GC/C/IRMS protocol and that using highly enriched (13)C-glycine (99 atom %)/GC/MS with the same derivative. The GC/C/IRMS method was shown to be suitable to measure the in vitro GSH FSR (200-660% day(-1)) in human venous and arterial blood from the umbilical cord. This approach provides a good tool for studying the turnover of GSH in vitro in infants, allowing both the use of minimal amounts of tracer and negligible perturbation of endogenous precursor pools.

  15. Reduction of isotopically enriched 50Ti-dioxide for the production of high-intensity heavy-ion beam

    International Nuclear Information System (INIS)

    Titanium-50 (50Ti) is an important and often requested ion beam for nuclear physics' experiments. While natural titanium of very high purity is available in different forms; enriched material can only be bought as the dioxide or the tetrachloride. These compounds cannot be processed from currently available ion sources with a sufficient beam quality and sufficient beam intensity for a long time. We describe here the process of converting titanium dioxide into the metal, the material analysis of the starting material as well as of the reduced material. Despite varying contamination levels of silicon, chlorine, and tin in the primary materials, we obtained high yields of metallic titanium with different contamination levels. The obtained metallic 50Ti was applied at the accelerator UNILAC for the production of a high intensity ion beam for several month of beam time. (author)

  16. Sr, Nd, and Pb isotopes of ultramafic xenoliths in volcanic rocks of Eastern China: enriched components EMI and EMII in subcontinental lithosphere

    Science.gov (United States)

    Tatsumoto, M.; Basu, A.R.; Wankang, H.; Junwen, W.; Guanghong, X.

    1992-01-01

    The UThPb, SmNd, and RbSr isotopic systematics of mafic and ultramafic xenolithic rocks and associated megacrystic inclusions of aluminous augite and garnet, that occur in three alkalic volcanic suites: Kuandian in eastern Liaoning Province, Hanluoba in Hebei Province, and Minxi in western Fujian Province, China are described. In various isotopic data plots, the inclusion data invariably fall outside the isotopic ranges displayed by the host volcanic rocks, testifying to the true xenolithic nature of the inclusions. The major element partitioning data on Ca, Mg, Fe, and Al among the coexisting silicate minerals of the xenoliths establish their growth at ambient mantle temperatures of 1000-1100??C and possible depths of 70-80 km in the subcontinental lithosphere. Although the partitioning of these elements reflects equilibrium between coexisting minerals, equilibria of the Pb, Nd, and Sr isotopic systems among the minerals were not preserved. The disequilibria are most notable with respect to the 206Pb 204Pb ratios of the minerals. On a NdSr isotopic diagram, the inclusion data plot in a wider area than that for oceanic basalts from a distinctly more depleted component than MORB with higher 143Nd 144Nd and a much broader range of 87Sr 86Sr values, paralleling the theoretical trajectory of a sea-water altered lithosphere in NdSr space. The garnets consistently show lower ?? and ?? values than the pyroxenes and pyroxenites, whereas a phlogopite shows the highest ?? and ?? values among all the minerals and rocks studied. In a plot of ??207 and ??208, the host basalts for all three areas show lower ??207 and higher ??208 values than do the xenoliths, indicating derivation of basalts from Th-rich (relative to U) sources and xenoliths from U-rich sources. The xenolith data trends toward the enriched mantle components, EMI and EMII-like, characterized by high 87Sr 86Sr and ??207 values but with slightly higher 143Nd 144Nd. The EMI trend is shown more distinctly by the host

  17. Stable carbon and nitrogen isotope trophic enrichment factors for Steller sea lion vibrissae relative to milk and fish/invertebrate diets

    Science.gov (United States)

    Stricker, Craig A.; Christ, Aaron M.; Wunder, Michael B.; Doll, Andrew C.; Farley, Sean D.; Rea, Lorrie D.; Rosen, David A. S.; Scherer, R. D.; Tollit, Dominic J.

    2015-01-01

    Nutritional constraints have been proposed as a contributor to population declines in the endangered Steller sea lion Eumetopias jubatus in some regions of the North Pacific. Isotopic analysis of vibrissae (whiskers) is a potentially useful approach to resolving the nutritional ecology of this species because long-term (up to 8 yr) dietary information is sequentially recorded and metabolically inert once formed. Additionally, vibrissae are grown in utero, potentially offering indirect inference on maternal diet. However, diet reconstruction using isotopic techniques requires a priori knowledge of trophic enrichment factors (TEFs), which can vary relative to diet quality and among animal species. In this study, we provide new TEF estimates for (1) maternal relative to pup vibrissae during both gestation and nursing and (2) adult vibrissae relative to a complex diet. Further, we refine vibrissa-milk TEFs based on an additional 76 animals with an age distribution ranging from 1 to 20 mo. Mother-pup vibrissae TEF values during gestation and nursing were near zero for δ13C and averaged 0.8 and 1.6‰, respectively, for δ15N. In contrast, vibrissa-fish/invertebrate TEFs averaged 3.3 (± 0.3 SD) and 3.7‰ (±0.3) for lipid-free δ13C and δ15N, respectively. Average lipid-free δ13C and δ15N vibrissa-milk TEFs were 2.5 (±0.9) and 1.8‰ (±0.8), respectively, and did not differ among metapopulations. Empirically determined TEFs are critical for accurate retrospective diet modeling, particularly for evaluating the hypothesis of nutritional deficiency contributing to the lack of Steller sea lion population recovery in some regions of Alaska.

  18. Study of chromium-containing proteins in subcellular fractions of rat liver by enriched stable isotopic tracer technique and gel filtration chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Weiyue; Li, Bai; Liu, Jing; Chai, Zhifang; Zhang, Peiqun; Gao, Yuxi; Zhao, Jiujiang [Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918, 100039, Beijing (China)

    2003-02-01

    Ten male Wistar rats were intravenously injected with a single approximately physiological dose of enriched stable isotopic Cr-50 tracer solution (200 ng {sup 50}Cr{sup 3+}/100 g body wt). The fundamental distribution patterns of the chromium-containing proteins in the nucleic, mitochondrial, lysosomal, microsomal, and cytosolic subcellular fractions of the rat liver were investigated by means of Sephadex G-100 gel chromatography combined with neutron activation analysis via {sup 50}Cr (n, {gamma}) {sup 51}Cr reaction. In total, nine kinds of Cr-containing proteins were found in the five subcellular fractions, whose relative molecular masses were 96.6{+-}6.2, 68.2{+-}1.4, 57.9{+-}4.7, 36.6{+-}1.2, 24.2{+-}1.8, 14.0{+-}1.5, 8.8{+-}0.6, 6.9{+-}0.4, and 4.2{+-}0.4 kDa. Approximately 64.5% of Cr proteins accumulated in the cytosolic fraction. The second enriched part was the nucleic fraction; about 12.2% Cr proteins were stored in this section. The 4.2-kDa molecular mass might contain the so-called low molecular weight chromium-containing substance; however, in this research, it was only observed in the mitochondria, lysosome, and microsome. In the mitochondrial fraction, most of the Cr proteins were present as relatively low molecular weight substances: about 56% of chromium-containing proteins had molecular masses {<=}6.9 kDa. Nevertheless, more than 69% of Cr-containing proteins were observed with molecular masses {>=}57.9 kDa in the liver cytosolic fraction. (orig.)

  19. Feeding strategies of deep-sea sub-Arctic macrofauna of the Faroe-Shetland Channel: Combining natural stable isotopes and enrichment techniques

    Science.gov (United States)

    Gontikaki, E.; Mayor, D. J.; Narayanaswamy, B. E.; Witte, U.

    2011-02-01

    The response of a sub-arctic, deep-sea macrofaunal community to a simulated food sedimentation event was studied by means of a stable isotope "pulse-chase" experiment. A food pulse was simulated by adding 500 mg C m -2 of 13C-labelled diatoms, Chaetoceros radicans, to sediment cores retrieved from 1080 m in the Faroe-Shetland Channel. Carbon uptake by specific macrofaunal groups was quantified after 3 and 6 days of incubation. The carbon uptake of the dominant taxon (Polychaeta) was quantified at the genus-, and where possible, species-level, representing a data resolution that is rare in deep-sea tracer studies. The macrofaunal community reacted rapidly to the diatom addition, with 47% and 70% of the animals illustrating 13C-enrichment after 3 and 6 days, respectively. Approximately 95% of C uptake was located in the upper 2 cm due to the particularly shallow vertical distribution of the macrofaunal community and the nonexistent tracer subduction by burrowing species. Polychaetes of the families Ampharetidae and Cirratulidae were among the most heavily labelled with above background enrichment reaching 1300‰. Approximately 0.8 and 2.0 mg C m -2 were processed by the macrofauna after 3 and 6 days, representing 0.2% and 0.4% of the added carbon, respectively. It was not possible to differentiate sub-surface deposit-feeding polychaetes from predator/scavenger- and omnivorous polychaetes using their natural δ 15N signatures. However, the combination of natural abundance δ 15N data and 13C-labelling experiments proved to be useful for elucidating trophic relations in deep-sea food webs. This study confirms that macrofauna play an active role in the short-term carbon cycling at bathyal depths even at sub-zero temperatures and highlights the need for detailed knowledge of the community structure in understanding carbon processing patterns and early diagenesis of organic matter in marine sediments.

  20. The use of environmental monitoring as a technique to identify isotopic enrichment activities; O uso da monitoracao ambiental como tecnica de identificacao de atividades de enriquecimento isotopico

    Energy Technology Data Exchange (ETDEWEB)

    Buchmann, Jose Henrique

    2000-07-01

    The use of environmental monitoring as a technique to identify activities related to the nuclear fuel cycle has been proposed, by international organizations, as an additional measure to the safeguards agreements in force. The elements specific for each kind of nuclear activity, or nuclear signatures, inserted in the ecosystem by several transfer paths, can be intercepted with better or worse ability by different live organisms. Depending on the kind of signature of interest, the anthropogenic material identification and quantification require the choice of adequate biologic indicators and, mainly, the use of sophisticated techniques associated with elaborate sample treatments. This work demonstrates the technical viability of using pine needles as bioindicators of nuclear signatures associated with uranium enrichment activities. Additionally, it proposes the use of a technique widely diffused nowadays in the scientific community, the High Resolution Inductively Coupled Plasma Mass Spectrometer (HR-ICP-MS), to identify the signature corresponding to that kind of activities in the ecosystem. It can be also found a description of a methodology recently being applied in analytical chemistry,based on uncertainties estimates metrological concepts, used to calculate the uncertainties associated with the obtained measurement results. Nitric acid solutions with a concentration of 0.3 mol.kg{sup -1}, used to wash pine needles sampled near facilities that manipulate enriched uranium and containing only 0.1 {mu}g.kg{sup -1} of uranium, exhibit a {sup 235} U: {sup 238} U isotopic abundance ratio of 0.0092{+-}0.0002, while solutions originated from samples collected at places located more than 200 km far from activities related to the nuclear fuel cycle exhibit a value of 0.0074{+-}0.0002 for this abundance ratio. Similar results were obtained for samples collected in different places permit to confirm the presence of anthropogenic uranium and demonstrate the viability of using

  1. Determination of 13C isotopic enrichment of valine and threonine by GC-C-IRMS after formation of the N(O,S)-ethoxycarbonyl ethyl ester derivatives of the amino acids.

    Science.gov (United States)

    Godin, Jean-Philippe; Faure, Magali; Breuille, Denis; Hopfgartner, Gérard; Fay, Laurent-Bernard

    2007-06-01

    We describe a new method of assessing, in a single run, (13)C isotopic enrichment of both Val and Thr by gas chromatography-combustion-isotope-ratio mass spectrometry (GC-C-IRMS). This method characterised by a rapid one-step derivatisation procedure performed at room temperature to form the N(O,S)-ethoxycarbonyl ethyl ester derivatives, and a polar column for GC. The suitability of this method for Val and Thr in in-vivo samples (mucosal hydrolysate) was demonstrated by studying protein metabolism with two tracers ((13)C-valine or (13)C-threonine). The intra-day and inter-day repeatability were both assessed either with standards or with in-vivo samples at natural abundance and at low (13)C isotopic enrichment. For inter-day repeatability CVs were between 0.8 and 1.5% at natural abundance and lower than 5.5% at 0.112 and 0.190 atom% enrichment for Val and Thr, respectively. Overall isotopic precision was studied for eleven standard amino acid derivatives (those of Val, Ala, Leu, Iso, Gly, Pro, Asp, Thr, Ser, Met, and Phe) and was assessed at 0.32 per thousand. The (13)C isotopic measurement was then extended to the other amino acids (Ala, Val, Leu, Iso, Gly, Pro, Thr, and Phe) at natural abundance for in-vivo samples. The isotopic precision was better than 0.002 atom% per amino acid (for n = 4 rats). This analytical method was finally applied to an animal study to measure Thr utilization in protein synthesis. PMID:17468859

  2. Uranium enrichment

    International Nuclear Information System (INIS)

    This paper reports that in 1990 the Department of Energy began a two-year project to illustrate the technical and economic feasibility of a new uranium enrichment technology-the atomic vapor laser isotope separation (AVLIS) process. GAO believes that completing the AVLIS demonstration project will provide valuable information about the technical viability and cost of building an AVLIS plant and will keep future plant construction options open. However, Congress should be aware that DOE still needs to adequately demonstrate AVLIS with full-scale equipment and develop convincing cost projects. Program activities, such as the plant-licensing process, that must be completed before a plant is built, could take many years. Further, an updated and expanded uranium enrichment analysis will be needed before any decision is made about building an AVLIS plant. GAO, which has long supported legislation that would restructure DOE's uranium enrichment program as a government corporation, encourages DOE's goal of transferring AVLIS to the corporation. This could reduce the government's financial risk and help ensure that the decision to build an AVLIS plant is based on commercial concerns. DOE, however, has no alternative plans should the government corporation not be formed. Further, by curtailing a planned public access program, which would have given private firms an opportunity to learn about the technology during the demonstration project, DOE may limit its ability to transfer AVLIS to the private sector

  3. Accumulation of methylmercury in rice and flooded soil in experiments with an enriched isotopic Hg(II) tracer

    Science.gov (United States)

    Strickman, R. J.; Mitchell, C. P. J.

    2015-12-01

    Methylmercury (MeHg) is a neurotoxin produced in anoxic aquatic sediments. Numerous factors, including the presence of aquatic plants, alter the biogeochemistry of sediments, affecting the rate at which microorganisms transform bioavailable inorganic Hg (IHg) to MeHg. Methylmercury produced in flooded paddy soils and its transfer into rice has become an important dietary consideration. An improved understanding of how MeHg reaches the grain and the extent to which rice alters MeHg production in rhizosphere sediments could help to inform rice cultivation practices. We conducted a controlled greenhouse experiment with thirty rice plants grown in individual, flooded pots amended with enriched 200Hg. Unvegetated controls were maintained under identical conditions. At three plant growth stages (vegetative growth, flowering, and grain maturity), ten plants were sacrificed and samples collected from soil, roots, straw, panicle, and grain of vegetated and unvegetated pots, and assessed for MeHg and THg concentrations. We observed consistent ratios between ambient and tracer MeHg between soils (0.36 ±0.04 — 0.44 ± 0.09) and plant compartments (0.23 ± 0.07 -0.34 ± 0.05) indicating that plant MeHg contamination originates in the soil rather than in planta methylation. The majority of this MeHg was absorbed between the tillering (4.48 ± 2.38 ng/plant) and flowering (8.43 ± 5.12 ng/pl) phases, with a subsequent decline at maturity (2.87 ± 1.23 ng/pl) only partly explained by translocation to the developing grain, indicating that MeHg was demethylated in planta. In contrast, IHg was absorbed from both soil and air, as evidenced by the higher ambient IHg concentrations compared to tracer (3.76 ± 1.19 vs. 0.27 ± 0.40 ng/g). Surprisingly, MeHg accumulation was significantly (p= 0.042-- 0.003) lower in vegetated vs. unvegetated sediments at flowering (1.41 ± 0.26 vs. 1.57 ± 0.23) and maturity (1.27 ± 0.22 vs. 1.71 ± 0.25), suggesting that plant exudates bound Hg

  4. Carbon-13 magnetic resonance chemical shift additivity relationships of clinically used furocoumarins and furchromones

    International Nuclear Information System (INIS)

    The natural abundance carbon-13 nuclear magnetic resonance spectra of various clinically used furocoumarins and furochromones have been studied. The assignments of carbon chemical shift values were based on the theory of chemical shift, additivity rules, SFORD spectra and model compounds. (author)

  5. Research and Development of Multiphysics Models in Support of the Conversion of the High Flux Isotope Reactor to Low Enriched Uranium Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Bodey, Isaac T [ORNL; Curtis, Franklin G [ORNL; Arimilli, Rao V [ORNL; Ekici, Kivanc [ORNL; Freels, James D [ORNL

    2015-12-01

    ABSTRACT The findings presented in this report are results of a five year effort lead by the RRD Division of the ORNL, which is focused on research and development toward the conversion of the High Flux Isotope Reactor (HFIR) fuel from high-enriched uranium (HEU) to low-enriched uranium (LEU). This report focuses on the tasks accomplished by the University of Tennessee Knoxville (UTK) team from the Department of Mechanical, Aerospace, and Biomedical Engineering (MABE) that provided expert support in multiphysics modeling of complex problems associated with the LEU conversion of the HFIR reactor. The COMSOL software was used as the main computational modeling tool, whereas Solidworks was also used in support of computer-aided-design (CAD) modeling of the proposed LEU fuel design. The UTK research has been governed by a statement of work (SOW), which was updated annually to clearly define the specific tasks reported herein. Ph.D. student Isaac T. Bodey has focused on heat transfer and fluid flow modeling issues and has been aided by his major professor Dr. Rao V. Arimilli. Ph.D. student Franklin G. Curtis has been focusing on modeling the fluid-structure interaction (FSI) phenomena caused by the mechanical forces acting on the fuel plates, which in turn affect the fluid flow in between the fuel plates, and ultimately the heat transfer, is also affected by the FSI changes. Franklin Curtis has been aided by his major professor Dr. Kivanc Ekici. M.Sc. student Adam R. Travis has focused two major areas of research: (1) on accurate CAD modeling of the proposed LEU plate design, and (2) reduction of the model complexity and dimensionality through interdimensional coupling of the fluid flow and heat transfer for the HFIR plate geometry. Adam Travis is also aided by his major professor, Dr. Kivanc Ekici. We must note that the UTK team, and particularly the graduate students, have been in very close collaboration with Dr. James D. Freels (ORNL technical monitor and mentor

  6. Research and Development of Multiphysics Models in Support of the Conversion of the High Flux Isotope Reactor to Low Enriched Uranium Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Bodey, Isaac T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Curtis, Franklin G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Arimilli, Rao V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Ekici, Kivanc [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Freels, James D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-11-01

    ABSTRACT The findings presented in this report are results of a five year effort lead by the RRD Division of the ORNL, which is focused on research and development toward the conversion of the High Flux Isotope Reactor (HFIR) fuel from high-enriched uranium (HEU) to low-enriched uranium (LEU). This report focuses on the tasks accomplished by the University of Tennessee Knoxville (UTK) team from the Department of Mechanical, Aerospace, and Biomedical Engineering (MABE) that provided expert support in multiphysics modeling of complex problems associated with the LEU conversion of the HFIR reactor. The COMSOL software was used as the main computational modeling tool, whereas Solidworks was also used in support of computer-aided-design (CAD) modeling of the proposed LEU fuel design. The UTK research has been governed by a statement of work (SOW), which was updated annually to clearly define the specific tasks reported herein. Ph.D. student Isaac T. Bodey has focused on heat transfer and fluid flow modeling issues and has been aided by his major professor Dr. Rao V. Arimilli. Ph.D. student Franklin G. Curtis has been focusing on modeling the fluid-structure interaction (FSI) phenomena caused by the mechanical forces acting on the fuel plates, which in turn affect the fluid flow in between the fuel plates, and ultimately the heat transfer, is also affected by the FSI changes. Franklin Curtis has been aided by his major professor Dr. Kivanc Ekici. M.Sc. student Adam R. Travis has focused two major areas of research: (1) on accurate CAD modeling of the proposed LEU plate design, and (2) reduction of the model complexity and dimensionality through interdimensional coupling of the fluid flow and heat transfer for the HFIR plate geometry. Adam Travis is also aided by his major professor, Dr. Kivanc Ekici. We must note that the UTK team, and particularly the graduate students, have been in very close collaboration with Dr. James D. Freels (ORNL technical monitor and mentor

  7. A novel method for simultaneous measurement of concentration and enrichment of NO synthesis-specific amino acids in human plasma using stable isotopes and LC/MS ion trap analysis.

    Science.gov (United States)

    Oosterink, J Efraim; Buijs, Nikki; van Goudoever, Johannes B; Schierbeek, Henk

    2014-05-01

    Stable isotope studies offer the opportunity to study the in-depth metabolic pathway of glutamine, citrulline, and arginine amino acids involved in NO synthesis. The use of multiple stable isotopes can be used to elucidate the exact transformation of glutamine to citrulline and arginine de novo synthesis. This novel method provides a purification step using cation exchange resin in combination with a rapid and easy derivatization procedure for a precise and robust measurement of the concentration and isotopic enrichments of NO synthesis-specific amino acids using a liquid chromatography mass spectrometry (LC/MS) ion trap system with high sensitivity and selectivity. The ethyl chloroformate derivatization procedure is beneficial in terms of robustness, velocity, simplicity, and derivative stability. In addition, the ethyl chloroformate derivatization can be performed at room temperature in an aqueous environment without incubation and the isolation of the derivatives from the reaction mixture also serves as a purification step. The concentration and enrichment of NO synthesis-specific amino acids as well as phenylalanine and tyrosine to determine protein turnover, were measured with good inter-day precision for the concentration (glutamine-citrulline-arginine pathway by using stable isotope studies.

  8. Advanced uranium enrichment processes

    International Nuclear Information System (INIS)

    Three advanced Uranium enrichment processes are dealt with in the report: AVLIS (Atomic Vapour LASER Isotope Separation), MLIS (Molecular LASER Isotope Separation) and PSP (Plasma Separation Process). The description of the physical and technical features of the processes constitutes a major part of the report. If further presents comparisons with existing industrially used enrichment technologies, gives information on actual development programmes and budgets and ends with a chapter on perspectives and conclusions. An extensive bibliography of the relevant open literature is added to the different subjects discussed. The report was drawn up by the nuclear research Centre (CEA) Saclay on behalf of the Commission of the European Communities

  9. STUDIES OF MAIN CHAIN DYNAMICS OF FLUORINE-CONTAINING IONOMERS BY CARBON-13 NUCLEAR MAGNETIC RELAXATION

    Institute of Scientific and Technical Information of China (English)

    YANG Yanwu; WANG Dehua; QIU Jianqing; QIAN Baogong; WANG Hongzuo

    1992-01-01

    The carbon-13 spin-spin relaxation times of fluorine-containing ionomers are measured and motional correlation times τ0 and τd are calculated by using VJGM model. The results show that the motions of polymer main chain in ionomers become more difficult with increasing of ionization degree and contents of functional group, and depend on the fine structures and stability of ionic microdomains.

  10. NMR spectroscopy of lactate in the skeleton muscle: visibility, quantification and measurement of carbon 13 enrichment by double quantum edition

    International Nuclear Information System (INIS)

    The metabolism of skeleton muscles gave rise to numerous research works since the beginning of the century in order to make some reply about the muscle physiology with the will to improve the sport performances or the understanding of muscles diseases. This metabolism is complex and the lactate has an importance place; the purpose of this work is to answer these questions with some strategy studies by nuclear magnetic resonance spectroscopy. (N.C.)

  11. Renovação do carbono-13 em figueiras 'Roxo de Valinhos' Carbon-13 turnover in fig trees 'Roxo de Valinhos'

    Directory of Open Access Journals (Sweden)

    Andréa Carvalho da Silva

    2011-06-01

    Full Text Available O objetivo do trabalho foi determinar a taxa de renova��ão do carbono-13 ("turnover", dos diferentes órgãos da figueira 'Roxo de Valinhos'. O experimento foi conduzido no pomar da Faculdade de Ciências Agronômicas, FCA/UNESP, Câmpus de Botucatu-SP. Determinou-se previamente, através das trocas gasosas com um medidor aberto portátil de fotossíntese, IRGA, a principal folha fotossinteticamente ativa. Essa folha foi colocada em uma câmara onde ocorreu a injeção do gás enriquecido. O tempo de enriquecimento da folha foi de 30 minutos. Os tratamentos foram constituídos por sete plantas de figueira, que foram retiradas do solo após: 6; 24; 48; 72; 120; 168 e 360 horas do enriquecimento com 13C, e suas partes seccionadas em: gema apical, folha jovem, folhas adultas (fotossinteticamente ativas, brotações laterais, frutos e ramo. Os resultados obtidos permitiram o estabelecimento da sequência de metabolização do carbono-13 nas partições estudadas: Folhas novas > Frutos > Brotações > Folhas Adultas > Gema Apical > Ramo > Folha marcada. Plantas de figueira 'Roxo de Valinhos' apresentam reciclagem do 13C de 24 horas e um tempo de meia-vida de duração do carbono-13 inferior a 11 horas.The aim of this study was to assess carbon-13 turnover in different organs of the fig tree cultivar 'Roxo de Valinhos'. The experiment was carried out in an orchard at School of Agronomical Sciences, FCA/UNESP, Botucatu Campus, São Paulo State, Brazil. The main photosynthetically active leaf was previously determined based on gas exchanges by means of an open portable photosynthesis system, IRGA. That leaf was placed in a chamber where the enriched gas injection occurred. The leaf enrichment time was 30 minutes. Treatments were constituted of seven fig trees harvested of soil after: 6; 24; 48; 72; 120; 168 and 360 hours of enrichment using 13C, and their parts were sectioned into: apical bud, young leaves, adult leaves (photosynthetically active

  12. Laboratory measurement of the 2-centimeter, 2/11/-2/12/ transition of normal formaldehyde and its carbon-13 and oxygen-18 species.

    Science.gov (United States)

    Tucker, K. D.; Tomasevich, G. R.; Thaddeus, P.

    1972-01-01

    Beam-maser spectrometric measurements to an accuracy of about 100 Hz have been conducted of the 2(11)-2(12) transition for the isotopic species of greatest astronomical interest - i.e., H2CO, H2(13)CO, and H2C(18)O. The samples used were not isotopically enriched, monomeric formaldehyde vapors. For these species, all the coupling constants required to calculate the hyperfine structure of any rotational transition have been determined.

  13. 激光抽运极化原子束磁偏转铀浓缩方案%A Scheme of Uranium Isotope Enrichment via Magnetic Deflection of an Atomic Beam Polarized by Laser Pumping

    Institute of Scientific and Technical Information of China (English)

    黄学人; 朱熙文; 梅刚华; 钟达

    2001-01-01

    将激光抽运选择性极化原子束磁偏转方案用于铀同位素浓缩,考察了铀原子基态各子能级的磁偏转特性,提出了选择性光抽运极化的实验方案,讨论了可能得到的浓缩结果。%A scheme of magnetic deflection of an atomic beam polarized bylaser pumping applied to isotope enrichment of uranium is presented. The characteristics of magnetic deflection for all sub-levels in the ground state of uranium atoms were evaluated. An experimental method of selectively polarized uranium atoms by optical pumping was proposed. The available enrichment result in this scheme was discussed.

  14. Carbon-13 natural abundance signatures of long-chain fatty acids to determinate sediment origin: A case study in northeast Austria

    Science.gov (United States)

    Mabit, Lionel; Gibbs, Max; Meusburger, Katrin; Toloza, Arsenio; Resch, Christian; Klik, Andreas; Swales, Andrew; Alewell, Christine

    2016-04-01

    - Several recently published information from scientific research have highlighted that compound-specific stable isotope (CSSI) signatures of fatty acids (FAs) based on the measurement of carbon-13 natural abundance signatures showed great promises to identify sediment origin. The authors have used this innovative isotopic approach to investigate the sources of sediment in a three hectares Austrian sub-watershed (i.e. Mistelbach). Through a previous study using the Cs-137 technique, Mabit et al. (Geoderma, 2009) reported a local maximum sedimentation rate reaching 20 to 50 t/ha/yr in the lowest part of this watershed. However, this study did not identify the sources. Subsequently, the deposited sediment at its outlet (i.e. the sediment mixture) and representative soil samples from the four main agricultural fields - expected to be the source soils - of the site were investigated. The bulk delta carbon-13 of the samples and two long-chain FAs (i.e. C22:0 and C24:0) allowed the best statistical discrimination. Using two different mixing models (i.e. IsoSource and CSSIAR v1.00) and the organic carbon content of the soil sources and sediment mixture, the contribution of each source has been established. Results suggested that the grassed waterway contributed to at least 50% of the sediment deposited at the watershed outlet. This study, that will require further validation, highlights that CSSI and Cs-137 techniques are complementary as fingerprints and tracers for establishing land sediment redistribution and could provide meaningful information for optimized decision-making by land managers.

  15. Biosynthetic control of the natural abundance of carbon 13 at specific positions within fatty acids in Escherichia coli. Evidence regarding the coupling of fatty acid and phospholipid synthesis

    International Nuclear Information System (INIS)

    Stable carbon isotope ratios (13C/12C) at natural abundance levels have been determined for individual carbon atoms in each of the major phospholipid fatty acids of Escherichia coli grown on glucose as the sole carbon source. Two models were constructed for the isotope effects and carbon flow pathways which must be responsible for the observed isotopic fractionations. Both models incorporate a branch in the carbon flow at which fatty acyl-acyl carrier protein (acyl-ACP) is utilized either for complex lipid synthesis or for elongation by fatty acid synthetase. Depletion of carbon 13 in the carboxyl groups of myristic and palmitoleic acids (relative to carbonyl groups in precursor acyl-ACP's) was observed to occur at this branching site. Only one of the models was consistent both with this observation and with the observation that exogenous fatty acids are incorporated into phospholipids but are not elongated. The successful model has free fatty acid as the intermediate product coupling fatty acid biosynthesis to phospholipid synthesis. Essential to this pathway are those reactions catalyzed by thioesterases I and II as well as acyl-ACP synthetase, enzymes whose roles have previously been unknown in vivo

  16. Environmental isotope observations on Sishen ground waters

    International Nuclear Information System (INIS)

    Environmental isotope measurements have been conducted on the outputs of some of the main dewatering points in both north and south mining areas as well as on numerous other observation points in the Sishen compartment. The effect of the dykes bounding the compartment could be observed from the behaviour of the isotopic composition of ground waters in the conduit zone. Measurements were done on radiocarbon, tritium oxygen-18 and carbon-13

  17. Reactivity and isotopic composition of spent PWR [pressurized-water-reactor] fuel as a function of initial enrichment, burnup, and cooling time

    International Nuclear Information System (INIS)

    This study presents the reactivity loss of spent PWR fuel due to burnup in terms of the infinite lattice multiplications factor, k/sub ∞/. Calculations were performed using the SAS2 and CSAS1 control modules of the SCALE system. The k/sub ∞/ values calculated for all combinations of six enrichments, seven burnups, and five cooling times. The results are presented as a primary function of enrichment in both tabular and graphic form. An equation has been developed to estimate the tabulated values of k/sub ∞/'s by specifying enrichment, cooling time, and burnup. Atom densities for fresh fuel, and spent fuel at cooling times of 2, 10, and 20 years are included. 13 refs., 8 figs., 8 tabs

  18. 235U isotopic characterization of natural and enriched uranium materials by using multigroup analysis (MGA method at a defined geometry using different absorbers and collimators

    Directory of Open Access Journals (Sweden)

    Yücel Haluk

    2015-09-01

    Full Text Available Characterization of nuclear materials is an important topic within the context of nuclear safeguards, homeland security and nuclear forensics. This paper deals with the performance of multigroup gamma-ray analysis (MGA method using the X- and γ-rays in the 80-130 keV region and enrichment meter principle (EMP based on the analysis of 185.7 keV peak for a certain geometry using different absorbers and collimators. The results from MGA and those of EMP are compared. In particular, the effect of aluminum/lead absorbers and lead collimator on the enrichment determination of 235U in natural and low enriched samples is investigated in a given source-detector geometry. The optimum diameter/height ratio for the Pb-collimator is found to be Dc/Hc = 1.4-1.6 in the chosen geometry. In order to simulate the container walls, ten different thicknesses of Al-absorbers of 141 to 840 mg·cm-2 and six different thicknesses of Pb-absorbers of 1120-7367 mg·cm-2 are interposed between sample and detector. The calibration coefficients (% enrichment/cps are calculated for each geometry. The comparison of the MGA and EMP methods shows that the enrichment meter principle provides more accurate and precise results for 235U abundance than those of MGA method at the chosen geometrical conditions. The present results suggest that a two-step procedure should be used in analyses of uranium enrichment. Firstly MGA method can be applied in situ and then EMP method can be used at a defined geometry in laboratory.

  19. Carbon isotope signatures of latest Permian marine successions of the Southern Alps suggest a continental runoff pulse enriched in land plant material

    Directory of Open Access Journals (Sweden)

    S. H. Kraus

    2013-02-01

    Full Text Available The latest Permian mass extinction, the most severe Phanerozoic biotic crisis, is marked by dramatic changes in palaeoenvironments. These changes significantly disrupted the global carbon cycle, reflected by a prominent and well known negative carbon isotope excursion recorded in marine and continental sediments. Carbon isotope trends of bulk carbonate and bulk organic matter in marine deposits of the European Southern Alps near the low-latitude marine event horizon deviate from each other. A positive excursion of several permil in δ13Corg starts earlier and is much more pronounced than the short-term positive 13Ccarb excursion; both excursions interrupt the general negative trend. Throughout the entire period investigated, 13Corg values become lighter with increasing distance from the palaeocoastline. Changing 13Corg values may be due to the influx of comparatively isotopically heavy land plant material. The stronger influence of land plant material on the 13Corg during the positive isotope excursion indicates a temporarily enhanced continental runoff that may either reflect increased precipitation, possibly triggered by aerosols originating from Siberian Trap volcanism, or indicate higher erosion rate in the face of reduced land vegetation cover. doi:10.1002/mmng.201300004

  20. Use of environmental isotopes in organic contaminants research in groundwater systems

    International Nuclear Information System (INIS)

    The paper presents two case studies that explore the use of environmental isotopes (13Cl, 37Cl) in organic contaminants research in groundwater systems. Carbon-13 data on soil CO2 were collected at a gas plant site where the degradation of organic contaminants by bioventing is being investigated. The isotope study was done to contribute to the evaluation of biodegradation of organic contaminants, especially under field conditions where results obtained by standard techniques are not conclusive. The results show enriched δ13C values on soil CO2, in comparison with the natural gas condensate source, a by-product of gas plants. Degradation of the condensate in a controlled laboratory microcosm did not show any significant isotopic fractionation during degradation. These results suggest that preferential degradation of enriched 13C hydrocarbons is occurring during bioventing. This hypothesis is being tested under field and laboratory conditions. The isotope research on chlorinated solvents aims to evaluate the use of 37Cl and 13C as tracers to provide information about sources and transformation of chlorinated solvents in groundwater systems. Chlorine-37 and 13C data in chlorinated solvents, perchlorethylene (PCE), trichloroethylene (TCE) and 1,1,1, trichloroethane (TCA), supplied by different manufacturers range from -3.5 to +6.0 per mille for δ37Cl and from -37.2 to -23.3 per mille for δ13C. These results indicated that these compounds have a different and distinct isotopic composition, which results from the individual manufacturing practices. These results show the potential of 37Cl and 13Cl as tracers to provide information to identify source areas of chlorinated solvent plumes in groundwater. (author). 25 refs, 3 figs

  1. Selenium speciation and isotope composition in 77Se-enriched yeast using gradient elution HPLC separation and ICP-dynamic reaction cell-MS

    DEFF Research Database (Denmark)

    Larsen, Erik Huusfeldt; Sloth, Jens Jørgen; Hansen, M.;

    2003-01-01

    using the enriched Se-77-selenite as substrate, were released by enzymatic hydrolysis using (I), a beta-glucosidase followed by a protease mixture, and (II), a commercial protease preparation. For selenium speciation the chromatographic selectivity of the cation exchange HPLC system was adjusted...

  2. Toward microtesla MRI of hyperpolarized carbon-13 for real-time metabolic imaging

    CERN Document Server

    Zotev, V S; Savukov, I M; Matlashov, A N; Gómez, J J; Espy, M A

    2009-01-01

    Hyperpolarization of carbon-13 is a promising technique that has enabled MR angiography, perfusion mapping, and real-time metabolic imaging of C-13 labeled organic substances with unprecedented signal-to-noise levels. Because the hyperpolarization is performed outside an MRI scanner (using a special NMR-style hyperpolarizer), high magnetic fields of conventional MRI systems offer little advantage in terms of achievable C-13 polarization. Here we propose an ultimate low-field MRI scanner for imaging hyperpolarized C-13. It uses only microtesla-range magnetic fields and employs SQUID (superconducting quantum interference device) sensors for broadband reception of MRI signals. We present the first images acquired by SQUID-based microtesla MRI with dynamic nuclear polarization (Overhauser enhancement). We also report the first NMR spectra of C-13 at microtesla fields, including spectra of metabolically relevant sodium pyruvate, bicarbonate, and alanine. Our results demonstrate feasibility and potential of the pro...

  3. Determination of low isotopic enrichment of L-[1-C-13]valine by gas chromatography combustion isotope ratio mass spectrometry : a robust method for measuring protein fractional synthetic rates in vivo

    NARCIS (Netherlands)

    Reijngoud, DJ; Hellstern, G; Elzinga, H; de Sain-van der Velden, MG; Okken, A; Stellaard, F

    1998-01-01

    A method was developed for measuring protein fractional synthetic rates using the N-methoxycarbonylmethyl ester (MCM) derivative of L-[1-C-13]valine and on-line gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The derivatization procedure can be performed rapidly and GC sep

  4. Lead isotopic compositions of soil and near-surface till profiles from a watershed containing arsenic-enriched groundwater in coastal Maine

    Science.gov (United States)

    Ayuso, Robert; Foley, Nora; Wandless, Gregory; Dillingham, Jeremy; Colvin, Anna

    2005-01-01

    Lead isotope compositions of soils and near-surface tills from an area of coastal Maine known to have groundwater with anomalously high arsenic contents were measured in order to determine the source of the lead and, by inference, possible sources of arsenic. Five soil and till sites were selected for detailed chemical and isotopic analysis. To construct profiles of the soil and till horizons, five samples were collected at 10-cm intervals from the surface to the base of each horizon. Total lead and arsenic concentrations and lead isotopic compositions were measured for 48 leaches and bulk residues. The soils and tills are underlain by sulfidic schists of the Penobscot Formation. Several generations of minerals containing arsenic and lead exist in the regional bedrock, including rock-forming silicates (feldspar and micas), sulfide minerals formed during diagenesis (for example, arsenic-rich pyrite), and sulfide and oxide minerals that formed as a result of Silurian metamorphic and igneous events (for example, arsenopyrite, galena, iron-oxides, and arsenic-sulfides). A young group of secondary minerals (for example, iron-hydroxides, arsenic-hydroxides, lead-sulfate, and arsenic-jarosite) formed from recent weathering and pedogenic processes.

  5. Chlorine distribution and its isotopic composition in “rusty rock” 66095. Implications for volatile element enrichments of “rusty rock” and lunar soils, origin of “rusty” alteration, and volatile element behavior on the Moon

    Science.gov (United States)

    Shearer, C. K.; Sharp, Z. D.; Burger, P. V.; McCubbin, F. M.; Provencio, P. P.; Brearley, A. J.; Steele, A.

    2014-08-01

    An interesting characteristic of the pyroclastic glass bead deposits, select impact produced lithologies such as the “rusty rock” 66095, and unique lunar soils from the Apollo 16 landing site, is their unusual enrichments in 204Pb, Cd, Bi, Br, I, Ge, Sb, Tl, Zn, and Cl which indicates that portions of these sample contain a substantial volatile component. Sample 66095, a fine-grained, subophitic to ophitic polymict melt breccia, also hosts a pervasive low-temperature, volatile-rich, oxyhydrated mineral assemblage. The volatile element enrichments in these assorted lunar lithologies have been attributed to a variety of extra-lunar and lunar processes, whereas the oxyhydration in 66095 has long been thought to represent either terrestrial alteration of lunar chlorides and Fe-Ni metal to βFeO(OH,Cl) or indigenous lunar processes. In 66095, Cl is accommodated in FeO(OH,Cl), phosphates, and chlorides and is heterogeneously distributed. The low-temperature alteration occurs as rims around Fe-Ni metal and sulfide grains, and as dispersed grains in the adjacent matrix. Micro-Raman and transmission electron microscope (TEM) imaging indicate that akaganéite (βFeO(OH,Cl)) is the dominant FeO(OH) polymorph and is intergrown with goethite (αFeO(OH)) and hematite (αFe2O3). TEM observations indicate a well-defined “nanometer-scale” stratigraphy” to the alteration. For example, kamacite (body centered cubic) → face-centered cubic (fcc) Fe-Ni alloy → lawrencite (FeCl2) → akaganéite. The lunar lawrencite (Fe,Ni)Cl2 in 66095 does not react directly to akaganéite on Earth. Rather, lawrencite exposed to terrestrial conditions reacts to form an amorphous Fe- and Cl-bearing phase, nano-crystalline goethite, and hematite. The morphology of these terrestrial alteration products is significantly different than that of the akaganéite occurring in 66095. The chlorine isotopic compositions of these volatile-rich samples are enriched in heavy Cl. For 66095, the δ37Cl

  6. New method for GC/FID and GC-C-IRMS Analysis of plasma free fatty acid concentration and isotopic enrichment

    OpenAIRE

    Kangani, Cyrous O.; Kelley, David E.; DeLany, James P.

    2008-01-01

    A simple, direct and accurate method for the determination of concentration and enrichment of free fatty acids in human plasma was developed. The validation and comparison to a conventional method are reported. Three amide derivatives, dimethyl, diethyl and pyrrolidide, were investigated in order to achieve optimal resolution of the individual fatty acids. This method involves the use of dimethylamine/Deoxo-Fluor to derivatize plasma free fatty acids to their dimethylamides. This derivatizati...

  7. An enriched stable-isotope approach to determine the gill-zinc binding properties of juvenile rainbow trout (Oncorhynchus mykiss) during acute zinc exposures in hard and soft waters

    Science.gov (United States)

    Todd, A.S.; Brinkman, S.; Wolf, R.E.; Lamothe, P.J.; Smith, K.S.; Ranville, J.F.

    2009-01-01

    The objective of the present study was to employ an enriched stable-isotope approach to characterize Zn uptake in the gills of rainbow trout (Oncorhynchus mykiss) during acute Zn exposures in hard water (???140 mg/L as CaCO 3) and soft water (???30 mg/L as CaCO3). Juvenile rainbow trout were acclimated to the test hardnesses and then exposed for up to 72 h in static exposures to a range of Zn concentrations in hard water (0-1,000 ??g/L) and soft water (0-250 ??g/L). To facilitate detection of new gill Zn from endogenous gill Zn, the exposure media was significantly enriched with 67Zn stable isotope (89.60% vs 4.1% natural abundance). Additionally, acute Zn toxicity thresholds (96-h median lethal concentration [LC50]) were determined experimentally through traditional, flow-through toxicity tests in hard water (580 ??g/L) and soft water (110 ??g/L). Following short-term (???3 h) exposures, significant differences in gill accumulation of Zn between hard and soft water treatments were observed at the three common concentrations (75, 150, and 250 ??g/L), with soft water gills accumulating more Zn than hard water gills. Short-term gill Zn accumulation at hard and soft water LC50s (45-min median lethal accumulation) was similar (0.27 and 0.20 ??g/g wet wt, respectively). Finally, comparison of experimental gill Zn accumulation, with accumulation predicted by the biotic ligand model, demonstrated that model output reflected short-term (trout gills. Our results indicate that measurable differences exist in short-term gill Zn accumulation following acclimation and exposure in different water hardnesses and that short-term Zn accumulation appears to be predictive of Zn acute toxicity thresholds (96-h LC50s). ?? 2009 SETAC.

  8. Application of environmental isotopes in studies of biodegradation of organic contaminants in groundwater

    International Nuclear Information System (INIS)

    -DCE ) and 1,2-dichloroethane (1,2-DCA). In contrast small carbon isotope fractionation occurred during biodegradation of BTEX. Recent studies have shown deuterium can be more sensitive than carbon-13 for BTEX biodegradation studies. An example of microcosm studies is illustrated on Figure 1 that shows concentration and isotope pattern for biodegradation of cis-dichloroethene (cis-DCE) to vinyl chloride (VC) and final product, ethene. As the cis-DCE is transformed to VC, an enrichment trend is observed in the remaining cis-DCE. The formed VC is isotopically lighter than the primary product, but as the VC is transformed, the remaining VC becomes enriched in 13C. The ethene is lighter than the VC and its isotope composition tend to the isotope composition of the primary substrate, cis-DCE, at the end of the experiment. The laboratory results have been confirmed at field sites. This paper will present a state of the art review on the application of environmental isotopes in biodegradation studies of organic contaminants in groundwater. Laboratories and field studies, and potential new applications of environmental isotopes in contaminant hydrogeology will be discussed during this presentation

  9. Using Stable Isotopes of Carbon and Nitrogen to Mark Wild Populations of Anopheles and Aedes Mosquitoes in South-Eastern Tanzania

    Science.gov (United States)

    Opiyo, Mercy A.; Hamer, Gabriel L.; Lwetoijera, Dickson W.; Auckland, Lisa D.; Majambere, Silas; Okumu, Fredros O.

    2016-01-01

    Background Marking wild mosquitoes is important for understanding their ecology, behaviours and role in disease transmission. Traditional insect marking techniques include using fluorescent dyes, protein labels, radioactive labels and tags, but such techniques have various limitations; notably low marker retention and inability to mark wild mosquitoes at source. Stable isotopes are gaining wide spread use for non-invasive marking of arthropods, permitting greater understanding of mosquito dispersal and responses to interventions. We describe here a simple technique for marking naturally-breeding malaria and dengue vectors using stable isotopes of nitrogen (15N) and carbon (13C), and describe potential field applications. Methods We created man-made aquatic mosquito habitats and added either 15N-labelled potassium nitrate or 13C-labelled glucose, leaving non-adulterated habitats as controls. We then allowed wild mosquitoes to lay eggs in these habitats and monitored their development in situ. Pupae were collected promptly as they appeared and kept in netting cages. Emergent adults (in pools of ~4 mosquitoes/pool) and individually stored pupae were desiccated and analysed using Isotope Ratio Mass Spectrometry (IRMS). Findings Anopheles gambiae s.l and Aedes spp. from enriched 13C and enriched 15N larval habitats had significantly higher isotopic levels than controls (P = 0.005), and both isotopes produced sufficient distinction between marked and unmarked mosquitoes. Mean δ15N for enriched females and males were 275.6±65.1 and 248.0±54.6, while mean δ15N in controls were 2.1±0.1 and 3.9±1.7 respectively. Similarly, mean δ13C for enriched females and males were 36.08±5.28 and 38.5±6.86, compared to -4.3±0.2 and -7.9±3.6 in controls respectively. Mean δ15N and δ13C was significantly higher in any pool containing at least one enriched mosquito compared to pools with all unenriched mosquitoes, P<0.001. In all cases, there were variations in standardized

  10. Is Job Enrichment Really Enriching?

    OpenAIRE

    Robert D. Mohr; Cindy Zoghi

    2006-01-01

    This study uses a survey of Canadian workers with rich, matched data on job characteristics to examine whether “enriched” job design, with features like quality circles, feedback, suggestion programs, and task teams, affects job satisfaction. We identify two competing hypotheses on the relationship between enriched jobs and job satisfaction. The “motivation hypothesis,” implies that enrichment will generally increase satisfaction and the “intensification hypothesis,” implies that enrichment m...

  11. Uranium enrichment

    International Nuclear Information System (INIS)

    GAO was asked to address several questions concerning a number of proposed uranium enrichment bills introduced during the 100th Congress. The bill would have restructured the Department of Energy's uranium enrichment program as a government corporation to allow it to compete more effectively in the domestic and international markets. Some of GAO's findings discussed are: uranium market experts believe and existing market models show that the proposed DOE purchase of a $750 million of uranium from domestic producers may not significantly increase production because of large producer-held inventories; excess uranium enrichment production capacity exists throughout the world; therefore, foreign producers are expected to compete heavily in the United States throughout the 1990s as utilities' contracts with DOE expire; and according to a 1988 agreement between DOE's Offices of Nuclear Energy and Defense Programs, enrichment decommissioning costs, estimated to total $3.6 billion for planning purposes, will be shared by the commercial enrichment program and the government

  12. Monitoring of liver glycogen synthesis in diabetic patients using carbon-13 MR spectroscopy

    International Nuclear Information System (INIS)

    To investigate the relationship between liver glucose, glycogen, and plasma glucose in diabetic patients, in vivo liver carbon-13 magnetic resonance spectroscopy (13C MRS) with a clinical 3.0 T MR system was performed. Subjects were healthy male volunteers (n = 5) and male type-2 diabetic patients (n = 5). Pre- and during oral glucose tolerance tests (OGTT), 13C MR spectra without proton decoupling were acquired in a monitoring period of over 6 h, and in total seven spectra were obtained from each subject. For OGTT, 75 g of glucose, including 5 g of [1-13C]glucose, was administered. The MR signals of liver [1-13C]glucose and glycogen were detected and their time-course changes were assessed in comparison with the plasma data obtained at screening. The correlations between the fasting plasma glucose level and liver glycogen/glucose rate (Spearman: ρ = -0.68, p 13C MRS can perform noninvasive measurement of glycogen storage/degradation ability in the liver individually and can assist in tailor-made therapy for diabetes. In conclusion, 13C MRS has a potential to become a powerful tool in diagnosing diabetes multilaterally.

  13. Stable isotope metabolic labeling with a novel N-enriched bacteria diet for improved proteomic analyses of mouse models for psychopathologies.

    Directory of Open Access Journals (Sweden)

    Elisabeth Frank

    Full Text Available The identification of differentially regulated proteins in animal models of psychiatric diseases is essential for a comprehensive analysis of associated psychopathological processes. Mass spectrometry is the most relevant method for analyzing differences in protein expression of tissue and body fluid proteomes. However, standardization of sample handling and sample-to-sample variability are problematic. Stable isotope metabolic labeling of a proteome represents the gold standard for quantitative mass spectrometry analysis. The simultaneous processing of a mixture of labeled and unlabeled samples allows a sensitive and accurate comparative analysis between the respective proteomes. Here, we describe a cost-effective feeding protocol based on a newly developed (15N bacteria diet based on Ralstonia eutropha protein, which was applied to a mouse model for trait anxiety. Tissue from (15N-labeled vs. (14N-unlabeled mice was examined by mass spectrometry and differences in the expression of glyoxalase-1 (GLO1 and histidine triad nucleotide binding protein 2 (Hint2 proteins were correlated with the animals' psychopathological behaviors for methodological validation and proof of concept, respectively. Additionally, phenotyping unraveled an antidepressant-like effect of the incorporation of the stable isotope (15N into the proteome of highly anxious mice. This novel phenomenon is of considerable relevance to the metabolic labeling method and could provide an opportunity for the discovery of candidate proteins involved in depression-like behavior. The newly developed (15N bacteria diet provides researchers a novel tool to discover disease-relevant protein expression differences in mouse models using quantitative mass spectrometry.

  14. Uranium enrichment

    International Nuclear Information System (INIS)

    Canada is the world's largest producer and exporter of uranium, most of which is enriched elsewhere for use as fuel in LWRs. The feasibility of a Canadian uranium-enrichment enterprise is therefore a perennial question. Recent developments in uranium-enrichment technology, and their likely impacts on separative work supply and demand, suggest an opportunity window for Canadian entry into this international market. The Canadian opportunity results from three particular impacts of the new technologies: 1) the bulk of the world's uranium-enrichment capacity is in gaseous diffusion plants which, because of their large requirements for electricity (more than 2000 kW·h per SWU), are vulnerable to competition from the new processes; 2) the decline in enrichment costs increases the economic incentive for the use of slightly-enriched uranium (SEU) fuel in CANDU reactors, thus creating a potential Canadian market; and 3) the new processes allow economic operation on a much smaller scale, which drastically reduces the investment required for market entry and is comparable with the potential Canadian SEU requirement. The opportunity is not open-ended. By the end of the century the enrichment supply industry will have adapted to the new processes and long-term customer/supplier relationships will have been established. In order to seize the opportunity, Canada must become a credible supplier during this century

  15. Oxygen-18 and carbon-13 in the carbonates of the Salina formation of southwestern Ontario

    Energy Technology Data Exchange (ETDEWEB)

    O' Shea, K.J.; Miles, M.C.; Fritz, P.; Frape, S.K.; Lawson, D.E.

    1988-02-01

    The oxygen and carbon isotopic composition of the carbonates of the Upper Silurian Salina formation of the Michigan Basin was investigated to aid in interpretation of depositional environments. /sup 13/C results indicate that a change from generally anoxic bottom conditions to oxic conditions occurred during deposition of the salt and anhydrite evaporite unit. The lower organic-rich carbonate units were deposited in a shallow-water, evaporitic setting, most likely adjacent to a sabkha-type environment. A positive water balance maintained the anoxic conditions and buffered the carbon isotopes. Above the salt and anhydrite evaporite, the isotopic composition suggests that the development of a similar depositional environment, a sub-aerial prograding sabkha, occurred over wide areas of the basin. /sup 18/O results support the conclusion that Silurian oceans were depleted in /sup 18/O with respect to modern oceans by 5-6%. 56 refs., 13 figs., 4 tabs.

  16. Isotopes in environmental research

    International Nuclear Information System (INIS)

    Radioactive and stable isotopes have long been considered a very efficient tool for studying physical and biological aspects of how the global ecosystem functions. Their applications in environmental research are numerous, embracing research at all levels. This article looks at only a few of the approaches to environmental problems that involve the use of isotopes. Special attention is given to studies of the Amazon Basin. Environmental isotopes are very efficient tools in water cycle studies. Tritium, a radioactive tracer, is especially useful in studying dynamics of water movement in different compartments of the hydrosphere, both on the local and global scales. Heavy stable isotopes of hydrogen and oxygen (deuterium and oxygen-18) provide information about steady-state characteristics of the water cycle. Isotope methods, some relatively new, have a major role in site-specific studies. Some indicative examples include: Studying turnover of organic matter. Changes in the carbon-13/carbon-12 isotopic ratio of organic matter were used to determine the respective contributions of organic carbon derived from forest and pasture. Studying biological nitrogen fixation. One of the ways nitrogen levels in soil can be maintained for productivity is by biological nitrogen fixation. Studying nitrogen availability and losses. The experimental use of nitrogen-15 is invaluable for defining losses of soil nitrogen to the atmosphere and to groundwater. Studies can similarly be done with stable and radioactive sulphur isotopes. This article indicates some potential uses of isotopes in environmental research. While the major problem of global climate change has not been specifically addressed here, the clearing of the Amazon forest, one focus of the IAEA's environmental programme, may have serious consequences for the global climate. These include substantial reduction of the amount of latent heat transported to the regions outside the tropics and acceleration of the greenhouse

  17. Composition of Carbon-13 and Nitrogen-15 in Sediments of the Ha Long Bay

    International Nuclear Information System (INIS)

    The Ha Long Bay with beautiful landscape and rich ecosystems is being used by human to develop the economy. The Ha Long Bay is currently affected by human activities causing the sedimentary environment to be much changed. The change of the environment in the Bay was studied using the composition of carbon-13, nitrogen-15 (δ13C, δ15N) and the C/N ratio in sediment of seven cores collected within the Ha Long Bay. In the Ha Long Bay, sedimentary environment receives many source sediment supplies. The north-east of Ha Long bay receives sources from sea, it is characterized by δ13C in sediment from -8.79 to -18.01‰, value δ15N in sediment from 4.36 to 4.73 ‰ and ratio of C/N from 13 to 41, the source organic matter in sediment shows that affected by C4 plant. The centre of Ha Long Bay receives organic source from sea, it is characterized by δ13C in sediment from -16.72 to -21.58 ‰, value δ15N in sediment ranges 4.15 - 5.20 ‰, ratio of C/N in sediment from 7 to 23. The north-west of Ha Long Bay is affected by rivers, it is characterized by δ13C in sediment range from -13.64 to -25.77 ‰, value δ15N in sediment from 2.50 to 4.38 ‰, and ratio C/N from 9 to 19. (author)

  18. Oxygen and carbon isotopic signatures reveal a long-term effect of free-air ozone enrichment on leaf conductance in semi-natural grassland

    Science.gov (United States)

    Jäggi, M.; Fuhrer, J.

    The effect of ozone on leaf gas diffusion was investigated by analyzing the stable oxygen isotopic signatures (δ 18O) in leaves of Holcus lanatus L., Plantago lanceolata L., Ranunculus friesianus (Jord.), and Trifolium pratense L. grown in temperate, semi-natural grassland. Dried material from plants exposed to ambient or elevated ozone levels in a long-term free-air experiment was sampled in 2002 and 2003. A general increase in δ 18O in elevated ozone indicated increased limitation to gas diffusion, which was strongest during the driest and warmest period in 2003. In three out of four species, the increase in δ 18O paralleled an increase in δ 13C measured earlier in the same samples, meaning that the dominant effect of ozone was on gas diffusion and not on CO 2 fixation. Only in R. friesianus, ozone affected both processes simultaneously. It is concluded that elevated ozone not only affects productivity, but also the water status of important component species of grassland communities.

  19. Accurate Quantification of Selenoprotein P (SEPP1) in Plasma Using Isotopically Enriched Seleno-peptides and Species-Specific Isotope Dilution with HPLC Coupled to ICP-MS/MS.

    Science.gov (United States)

    Deitrich, Christian L; Cuello-Nuñez, Susana; Kmiotek, Diana; Torma, Frank Attila; Del Castillo Busto, Maria Estela; Fisicaro, Paola; Goenaga-Infante, Heidi

    2016-06-21

    A novel strategy for the absolute quantification of selenium (Se) included in selenoprotein P (SEPP1), an important biomarker for human nutrition and disease, including diabetes and cancer, is presented here for the first time. It is based on the use of species-specific double isotope dilution mass spectrometry (SSIDA) in combination with HPLC-ICP-MS/MS for the determination of protein bound Se down to the peptide level in a complex plasma matrix with a total content of Se of 105.5 μg kg(-1). The method enabled the selective Se speciation analysis of human plasma samples without the need of extensive cleanup or preconcentration steps as required for traditional protein mass spectrometric approaches. To assess the method accuracy, two plasma reference materials, namely, BCR-637 and SRM1950, for which literature data and a reference value for SEPP1 have been reported, were analyzed using complementary hyphenated methods and the species-specific approach developed in this work. The Se mass fractions obtained via the isotopic ratios (78)Se/(76)Se and (82)Se/(76)Se for each of the Se-peptides, namely, ENLPSLCSUQGLR (ENL) and AEENITESCQUR (AEE) (where U is SeCys), were found to agree within 2.4%. A relative expanded combined uncertainty (k = 2) of 5.4% was achieved for a Se (as SEPP1) mass fraction of approximately 60 μg kg(-1). This work represents a systematic approach to the accurate quantitation of plasma SEPP1 at clinical levels using SSIDA quantification. Such methodology will be invaluable for the certification of reference materials and the provision of reference values to clinical measurements and clinical trials. PMID:27108743

  20. Excitation function of the alpha particle induced nuclear reactions on enriched $^{116}$Cd, production of the theranostic isotope $^{117m}$Sn

    CERN Document Server

    Ditrói, F; Haba, H; Komori, Y; Aikawa, M; Szűcs, Z; Saito, M

    2016-01-01

    $^{117m}$Sn is one of the radioisotopes can be beneficially produced through alpha particle irradiation. The targets were prepared by deposition of $^{116}$Cd metal onto high purity 12 $\\mu$m thick Cu backing. The average deposited thickness was 21.9 $\\mu$m. The beam energy was thoroughly measured by Time of Flight (TOF) methods and proved to be 51.2 MeV. For the experiment the well-established stacked foil technique was used. In addition to the Cd targets, Ti foils were also inserted into the stacks for energy and intensity monitoring. The Cu backings were also used for monitoring and as recoil catcher of the reaction products from the cadmium layer. The activities of the irradiated foils were measured with HPGe detector for gamma-ray spectrometry and cross section values were determined. As a result excitation functions for the formation of $^{117m}$Sn, $^{117m,g}$In, $^{116m}$In, $^{115m}$In and $^{115m,g}$Cd from enriched $^{116}$Cd were deduced and compared with the available literature data and with the...

  1. Excitation function of the alpha particle induced nuclear reactions on enriched 116Cd, production of the theranostic isotope 117mSn

    Science.gov (United States)

    Ditrói, F.; Takács, S.; Haba, H.; Komori, Y.; Aikawa, M.; Szűcs, Z.; Saito, M.

    2016-10-01

    117mSn is one of the radioisotopes can be beneficially produced through alpha particle irradiation. The targets were prepared by deposition of 116Cd metal onto high purity 12 μm thick Cu backing. The average deposited thickness was 21.9 μm. The beam energy was thoroughly measured by Time of Flight (TOF) methods and proved to be 51.2 MeV. For the experiment the well-established stacked foil technique was used. In addition to the Cd targets, Ti foils were also inserted into the stacks for energy and intensity monitoring. The Cu backings were also used for monitoring and as recoil catcher of the reaction products from the cadmium layer. The activities of the irradiated foils were measured with HPGe detector for gamma-ray spectrometry and cross section values were determined. As a result excitation functions for the formation of 117mSn, 117m,gIn, 116mIn, 115mIn and 115m,gCd from enriched 116Cd were deduced and compared with the available literature data and with the results of the nuclear reaction model code calculations EMPIRE 3.2 and TALYS 1.8. Yield curves were also deduced for the measured nuclear reactions and compared with the literature.

  2. Measurement of forest ecosystem-atmosphere exchange of delta-carbon-13--carbon dioxide using Fourier transform infrared spectroscopy and disjunct eddy covariance

    Science.gov (United States)

    Cambaliza, Maria Obiminda L.

    The measurement of the stable isotopic content and isotopic flux of atmospheric carbon dioxide is important for understanding the carbon budget on ecosystem, regional, and global spatial scales. Conventional measurements of the isotopic composition of atmospheric CO2 involve laboratory mass spectrometry analysis of grab samples from the field, which limits the location, collection frequency and throughput of samples. More technologically advanced methods (e.g. tunable diode laser spectroscopy) suffer from interferences with other chemical species. We have developed a new measurement method based on Fourier-transform infrared spectroscopy (FTIR) and disjunct eddy covariance (DEC) for fast, continuous, real-time measurement of the carbon isotopic composition of atmospheric CO2. Molecular absorption is measured in the 2100 to 2500 cm -1 spectral region of the 13CO2 and 12CO2 vibration-rotation bands with concentrations of both isotopologues used to determine delta13C. We demonstrate the capability of this new technique in a managed poplar forest near Boardman, Oregon with measurements during the summers of 2005 and 2006 from a 22-meter tower in a 16-m forest canopy. Long-term calibration using reference gas cylinders yielded field accuracy and precision for the forest measurements of 0.5‰ and 0.8‰, respectively, for the 45-second cycle time between samples. The signature of ecosystem respiration derived from the nighttime vertical profile measurements of CO2-delta13C was --26.6‰, about 2‰ more enriched than the isotopic composition of measured bulk leaf samples from the forest. Ecosystem respired CO 2 was ˜1.6‰ more enriched than soil-respired CO2. A comparison of the FTIR -- DEC total CO2 fluxes against standard eddy covariance measurements showed excellent (10%) agreement. FTIR-DEC measurement of the CO2 isoflux enabled the estimation of the mean carbon isotope ratio of the photosynthetic flux (deltaP). The average deltaP (-24.9‰) was 13C-enriched

  3. Niche differentiation between sympatric alien aquatic crustaceans : An isotopic evidence

    OpenAIRE

    Rothhaupt, Karl-Otto; Hanselmann, Almut J.; Yohannes, Elizabeth

    2014-01-01

    Among the mechanisms that allow competing species to coexist are resource partitioning and dietary segregation. The current study uses multiple stable isotopes, carbon ( 13C), nitrogen ( 15N) and sulphur ( 34S), to test the hypothesis that dietary segregation in cohabiting invasive mysids (Limnomysis benedeni and Katamysis warpachowskyi) and gammarids (Dikerogammarus villosus and Gammarus roeselii) will be reflected by differences in isotope values. Furthermore, IsoError mixing models were us...

  4. 水中氯代烃单体碳同位素分析中预富集方法进展%Review on Pre-enrichment Methods in Compound Specific Carbon Isotope Analysis of Chlorinated Hydrocarbon in Water

    Institute of Scientific and Technical Information of China (English)

    凌媛; 黄毅; 尚文郁; 谢曼曼; 刘舒波; 孙青

    2011-01-01

    Highly accurate determination of Compound Specific Carbon Isotope Analysis ( CSIA ) of chlorinated hydrocarbons is of great significance in tracing the source and revealing the biodegradating progress of pollutants. The isotopic composition of organic contaminations may be stable or varied in the process of environmental transformation. We can trace the source of contaminations if the composition is stable and can evaluate the probability and degree of degradation of contaminations. This paper summarizes solid-phase microextraction, static headspace analysis, purge and trap method and compound specific isotope analyses of chlorinated hydrocarbon in water, using combinations of these pretreatment methods, Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry ( GC-C-IRMS ), and comparesthe three methods. Compared with liquid-liquid extraction, solid-phase micro extraction, static headspace analysis, purge and trap method are all solvent-free enrichment techniques, producing no secondary pollution, less interference, and the resolution and accuracy of the analysis of GC-C-IRMS is improved. No, or little, isotopic mass fractionation occurred during the isotope analysis of chlorinated hydrocarbon in water by combining these solvent-free enrichment techniques with GC-C-IRMS, of which the precision of the analysis is less than l%e. The detection limit decreased along with the methods of static headspace analysis, solid-phase micro extraction, purge and trap method. Purge and trap is the most popular method because of its good reproducibility and low detection limit for the compound specific isotope analysis of chlorinated hydrocarbon in Water. The combinations of in-needle microextraction, in-tube microextraction, stir bar sorptive extraction or headspace sorptive extraction with GC-C-IRMS have a bright future.%高精度准确测定氯代烃单体碳同位素对示踪污染物来源,了解污染物的生物降解过程具有重要意义.在环境转化过程中,

  5. Job Enrichment

    Science.gov (United States)

    Sanders, Rick

    1970-01-01

    Job enrichment means giving people more decision-making power, more responsibility, more grasp of the totality of the job, and a sense of their own importance in the company. This article presents evidence of the successful working of this approach (Donnelly Mirrors), and the lack of success with an opposing approach (General Motors). (NL)

  6. Isotopically controlled semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Haller, E.E.

    2004-11-15

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

  7. Isotope ratio mass spectrometry in oceanic studies

    International Nuclear Information System (INIS)

    Isotope ratio mass spectrometry (IRMS) is an important and well established method in many scientific fields as analytical chemistry (isotope dilution MS), physical chemistry, nuclear sciences and technology, environmental, agricultural, geological isotope dating, archaeometric, cosmic, bioavailability and nutrition studies, food authentication and adulteration control, elucidation of chemical reaction mechanism, isotope effect studies on chemical reactions and isotope enrichment/separation processes. This paper is aimed to provide a brief summary of IRMS contribution to sea and oceanic studies

  8. Uranium enrichment. 1980 annual report

    International Nuclear Information System (INIS)

    This report contains data and related information on the production of enriched uranium at the gaseous diffusion plants and an update on the construction and project control center for the gas centrifuge plant. Power usage at the gaseous diffusion plants is illustrated. The report contains several glossy color pictures of the plants and processes described. In addition to gaseous diffusion and the centrifuge process, three advanced isotope separation process are now being developed. The business operation of the enrichment plants is described; charts on revenue, balance sheets, and income statements are included

  9. Use of dual isotope tracers in biomedical research

    NARCIS (Netherlands)

    Stellaard, F

    2005-01-01

    Biomedical stable isotope studies involve administration of tracer and measurement of isotope enrichment in blood, urine, feces or breath. The aim of the studies is to gather quantitative information about a specific metabolic function. However, the measured isotope enrichment may be affected by oth

  10. Laser isotope separation of gadolinium

    International Nuclear Information System (INIS)

    Basic studies on laser isotope separation of gadolinium were performed. Spectroscopic data were obtained such as isotope shifts and hyperfine structures using an atomic beam. Enrichment of 157Gd up to 80% was observed by three-step photoionization experiment using linearly polarized dye lasers. Design of an separation system was discussed by the help of computer calculation of excitation dynamics. (author)

  11. Drought indicated in carbon-13/carbon-12 ratios of Southwestern tree rings

    International Nuclear Information System (INIS)

    Stomatal closure during periods of moisture deficiency should theoretically lead to elevated 13C/12C ratios as reduction of available CO2 leads to diminished photosynthetic discrimination against 13C in favor of 12C. Stable-carbon isotope ratio chronologies developed from 5-yr tree-ring groups at 17 sites in six southwestern states were tested for a drought relationship by first fitting a spline curve to each chronology to remove the long-term trend and calculating indices as the ratio of actual to spline curve value. The time series of “Del Indices” so developed are significantly correlated with 5-yr mean Palmer Hydrological Drought Indices (post-1930 period) and reconstructed July Palmer Drought Severity Indices from respective areas. Overall, in the period since 1790, the driest pentads were 1900–04 and 1960–64, whereas the wettest were 1980–84 and 1915–19. Maps of drought represented for two pentads seem to be reasonable representations, although spatial correlations of Del Indices with PHDI were generally not significant. These Del Index drought reconstructions may provide a useful measure of past physiological response to drought (stomatal closure), although the present cost of analysis would prevent this from being a routine method. (author)

  12. Developing high-resolution carbon-13 and silicon-29 MRI of solids in sedimentary rocks

    Science.gov (United States)

    Blum, Robert; Barrett, Sean; Viswanathan, Ravinath; Song, Yi-Qiao

    2014-03-01

    Mapping pore structure and flow properties of sedimentary rock is directly relevant to current challenges in geophysics like carbon sequestration and oil/gas exploration. Such applications require detailed information about both structure and composition of porous rocks. However, existing scanning methods tend to be limited to gathering one or the other type of information. MRI could be used to measure both composition and structure simultaneously, but conventional MRI in such systems, which targets the proton signal of interstitial fluid, is severely limited by signal losses due to magnetic susceptibility inhomogeneity. Our lab has recently made advances in obtaining high spatial resolution (sub-400 μm)3 three-dimensional 31P MRI of bone through use of the quadratic echo line-narrowing sequence (1). In this talk, we describe our current work applying these methods to sedimentary rock, targeting the isotopes 13C and 29Si. We describe the results of characterization of limestone and shale samples, and we discuss our progress with producing MRI of these systems. (1) M. Frey, et al. PNAS 109: 5190 (2012)

  13. Interannual variability in seagrass carbon and nitrogen stable isotopes from the Florida Keys National Marine Sanctuary, a preliminary study

    Science.gov (United States)

    Fourqurean, J. W.; Fourqurean, J. W.; Anderson, W. T.; Anderson, W. T.

    2001-12-01

    The shallow marine waters surrounding the southern tip of Florida provide an ideal environment for seagrasses, which are the most common benthic community in the region. Yet, these communities are susceptible to a variety of anthropogenic disturbances, especially changes in water quality caused by an increase the nutrient flux to the near shore environment. In order to better understand the carbon and nitrogen isotopic ratio in marine plants, an extensive times series analysis was constructed from quarterly sampling of Thalassia testudinum (the dominate species in the study area) from 1996 through 1998. Sites for study where selected from permanent stations within the Florida Keys National Marine Sanctuary (FKNMS), from both sides of the Florida Keys - two stations on the bay side and two stations on the reef side. These data will also help to constrain elements of the carbon and nitrogen cycles affecting this region. The data analyzed over the three year study period show unique cyclic trends associated with seasonal changes in primary productivity and potentially changes in the nitrogen and carbon pools. Additionally, the analysis of our time series indicates that isotope food web studies need to take into account spatial and temporal changes when evaluating trophic levels. The mean carbon and nitrogen isotope values of T. testudinum from all 4 stations vary respectively from -7.2 per mil to -10.41 and 1.1 per mil to 2.2 per mil (n = 48). However, certain stations displayed anonymously depleted nitrogen isotope values, values as low as -1.2 per mil. These values potentially indicated that biogeochmical processes like N fixation, ammonification and denitrification cause regional pattern in the isotopic composition of the source DIN. Both carbon and nitrogen isotopes displayed seasonal enrichment-depletion trends, with maximum enrichment occurring during the summer. The overall seasonal variation for carbon 13 from the different stations ranged from 1 per mil to

  14. Separation of sulfur isotopes

    Science.gov (United States)

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

    1976-06-22

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

  15. Origin of epigenetic calcite in coal from Antarctica and Ohio based on isotope compositions of oxygen, carbon and strontium

    Science.gov (United States)

    Faure, G.; Botoman, G.

    1984-01-01

    Isotopic compositions of oxygen, carbon and strontium of calcite cleats in coal seams of southern Victoria Land, Antarctica, and Tuscarawas County, Ohio, contain a record of the conditions a the time of their formation. The Antarctic calcites (?? 18O(SMOW) = +9.14 to +11.82%0) were deposited from waters enriched in 16O whose isotopic composition was consistent with that of meteoric precipitation at low temperature and high latitude. The carbon of the calcite cleats (?? 13C(PDB) = -15.6 to -16.9%0) was derived in part from the coal (?? 13C(PDB) = -23.5 to -26.7%0) as carbon dioxide and by oxidation of methane or other hydrocarbon gases. The strontium ( 87Sr 86Sr = 0.71318-0.72392) originated primarily from altered feldspar grains in the sandstones of the Beacon Supergroup. Calcite cleats in the Kittaning No. 6 coal seam of Ohio (?? 18O(SMOW) = +26.04 to +27.79%0) were deposited from waters that had previously exchanged oxygen, possibly with marine carbonate at depth. The carbon (?? 13C(PDB) = 0.9 to +2.4%0) is enriched in 13C even though that cleats were deposited in coal that is highly enriched in 12C and apparently originated from marine carbonates. Strontium in the cleats ( Sr 87 0.71182-0.71260) is not of marine origin but contains varying amounts of radiogenic 87Sr presumably derived from detrital Rb-bearing minerals in the adjacent sedimentary rocks. The results of this study suggest that calcite cleats in coal of southern Victoria Land, Antarctica, were deposited after the start of glaciation in Cenozoic time and that those in Ohio precipitated from formation waters derived from the underlying marine carbonate rocks, probably in the recent geologic past. ?? 1984.

  16. Isotopically controlled semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Haller, Eugene E.

    2006-06-19

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

  17. Isotope effects of hafnium in solvent extraction using crown ethers

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Toshiyuki; Moriyama, Hirotake [Research Reactor Institute, Kyoto University, Osaka (Japan); Hirata, Takafumi [Laboratory for Planetary Sciences, Tokyo Institute of Technology, Tokyo (Japan); Nishizawa, Kazushige [Department of Nuclear Engineering, Graduate School of Engineering, Osaka University, Osaka (Japan)

    2001-06-01

    Hafnium isotopes were fractionated in a liquid-liquid extraction system by using seven types of crown ethers, tributyl phosphate, or {omicron}-diethoxybenzene. The largest isotope effect was observed in the isotope pair of {sup 177}Hf-{sup 179}Hf with dibenzo-24-crown-8; the isotope enrichment factor was observed to be 0.0129{+-}0.0032. (author)

  18. Use of stable isotopes for testing aromas: vanillin as an example

    International Nuclear Information System (INIS)

    The determination of the origin, natural or synthetic, of vanillin is obtained by mass spectrometry of carbon 13. The depletion in 13C of the natural product is due to the photosynthesis mechanism (crassulacean acid metabolism). Deuterium is also a possible isotopic tracer and NMR an alternative analysis method but requires a more important sample

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

    OpenAIRE

    Xueshu Xie; 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 ...

  20. Isotopic Tracers for Delineating Non-Point Source Pollutants in Surface Water

    Energy Technology Data Exchange (ETDEWEB)

    Davisson, M L

    2001-03-01

    This study tested whether isotope measurements of surface water and dissolved constituents in surface water could be used as tracers of non-point source pollution. Oxygen-18 was used as a water tracer, while carbon-14, carbon-13, and deuterium were tested as tracers of DOC. Carbon-14 and carbon-13 were also used as tracers of dissolved inorganic carbon, and chlorine-36 and uranium isotopes were tested as tracers of other dissolved salts. In addition, large databases of water quality measurements were assembled for the Missouri River at St. Louis and the Sacramento-San Joaquin Delta in California to enhance interpretive results of the isotope measurements. Much of the water quality data has been under-interpreted and provides a valuable resource to investigative research, for which this report exploits and integrates with the isotope measurements.

  1. Assessing wine quality using isotopic methods

    International Nuclear Information System (INIS)

    Full text: The analytical methods used to determine the isotope ratios of deuterium, carbon-13 and oxygen-18 in wines have gained official recognition from the Office International de la Vigne et du Vin (OIV) and National Organisation of Vine and Wine. The amount of stable isotopes in water and carbon dioxide from plant organic materials and their distribution in sugar and ethanol molecules are influenced by geo-climatic conditions of the region, grape varieties and the year of harvest. For wine characterization, to prove the botanical and geographical origin of the raw material, the isotopic analysis by continuous flow mass spectrometry CF-IRMS has made a significant contribution. This paper emphasize the results of a study concerning the assessing of water adulterated wines and non-grape alcohol and sugar additions at different concentration levels, using CF-IRMS analytical technique. (authors)

  2. Technical status study of heavy water enrichment

    International Nuclear Information System (INIS)

    Technical status study of heavy water enrichment in Indonesia and also in the world has been done. Heavy water enrichment processes have been investigated were water distillation, hydrogen distillation, laser enrichment, electrolysis and isotop exchange. For the isotop exchange, the chemical pair can be used were water-hydrogen sulphite, ammonium-hydrogen, aminomethane-hydrogen, and water-hydrogen. For the isotope exchange, there was carried out by mono thermal or bi thermal. The highest producer of heavy water is Canada, and the other producer is USA, Norwegian and India. The processes be used in the world are isotope exchange Girdler Sulphide (GS), distillation and electrolysis. Research of heavy water carried out in Batan Yogyakarta, has a purpose to know the characteristic of heavy water purification. Several apparatus which has erected were 3 distillation column: Pyrex glass of 2 m tall, stainless steel column of 3 m tall and steel of 6 m tall. Electrolysis apparatus is 50 cell electrolysis and an isotope exchange unit which has catalyst: Ni- Cr2O3 and Pt-Carbon. These apparatus were not ready to operate. (author)

  3. Carbon dioxide effects research and assessment program. Proceedings of the International Meeting on Stable Isotopes in Tree-Ring Research, New Paltz, New York, May 22-25, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Jacoby, G [ed.

    1980-12-01

    Information about the past and present concentrations of CO/sub 2/ in the atmosphere and variations in climate can be obtained from measurements of stable isotopes in tree rings; specifically carbon-13, oxygen-18 and deuterium. The analysis of these stable isotopes in tree rings is a relatively new and rapidly developing field. This proceedings volume contains most of the papers presented at the meeting. The first paper gives an overview of the status of carbon-13 research. Papers relating to carbon-13 are in section I and grouped separately from the contributions on carbon-14. Although the meeting was primarily concerned with stable isotopes, all carbon isotopic analysis may be helpful in understanding the carbon-13 record in tree rings. The papers on hydrogen and oxygen isotope studies are in sections II and III respectively. The remaining sections contain papers that consider more than one isotope at a time, general topics related to isotopes, atmospheric changes and tree growth, and methods of isotopic analysis.

  4. Advances in uranium enrichment processes

    International Nuclear Information System (INIS)

    Advances in gas centrifuges and development of the atomic vapour laser isotope separation process promise substantial reductions in the cost of enriched uranium. The resulting reduction in LWR fuel costs could seriously erode the economic advantage of CANDU, and in combination with LWR design improvements, shortened construction times and increased operational reliability could allow the LWR to overtake CANDU. CANDU's traditional advantages of neutron economy and high reliability may no longer be sufficient - this is the challenge. The responses include: combining neutron economy and dollar economy by optimizing CANDU for slightly enriched uranium fuel; developing cost-reducing improvements in design, manufacture and construction; and reducing the cost of heavy water. Technology is a renewable resource which must be continually applied to a product for it to remain competitive in the decades to come. Such innovation is a prerequisite to Canada increasing her share of the international market for nuclear power stations. The higher burn-up achievable with enriched fuel in CANDU can reduce the fuel cycle costs by 20 to 40 percent for a likely range of costs for yellowcake and separative work. Alternatively, some of the benefits of a higher fissile content can take the form of a cheaper reactor core containing fewer fuel channels and less heavy water, and needing only a single fuelling machine. An opportunity that is linked to this need to introduce an enriched uranium fuel cycle into CANDU is to build an enrichment business in Canada. This could offer greater value added to our uranium exports, security of supply for enriched CANDUs, technological growth in Canada and new employment opportunities. AECL has a study in progress to define this opportunity

  5. Validation in an animal model of the carbon 13-labeled mixed triglyceride breath test for the detection of intestinal fat malabsorption

    NARCIS (Netherlands)

    Kalivianakis, M; Elstrodt, J; Havinga, R; Kuipers, F; Stellaard, F; Sauer, PJJ; Vonk, RJ; Verkade, HJ

    1999-01-01

    Objective: To determine, in a rat model of fat malabsorption, the potency of the carbon 13-labeled mixed triglyceride (C-13-MTG) breath test as a noninvasive, patient-friendly replacement for classic fat balance studies, Study design: Comparison of the percentage of Fat absorption, detected by fat b

  6. Rapid Stable Isotope Turnover of Larval Fish in a Lake Superior Coastal Wetland: Implications for Diet and Life History Studies

    Science.gov (United States)

    Trophic linkages of larval fish in Lake Superior coastal wetlands, rivers and embayments can be identified using naturally occurring differences in the stable isotope ratios of nitrogen (15N:14N, ?15N) and carbon (13C:12C, ?13C). We sampled pelagic fish larvae weekly during sprin...

  7. Lithium isotope separation

    International Nuclear Information System (INIS)

    Published methods for 6Li-7Li lithium isotope separation have been reviewed. Future demand for 6Li, whose main use will be as a tritium breeder in blankets surrounding the core of DT fusion power reactors, is likely to exceed 5 Mg/a in the next century. The applicability of the various available methods to such a large scale production rate has been assessed. Research on improving the effectiveness of current lithium isotope separation processes has been carried out worldwide in several major areas during the past decade; these include two-phase chemical exchange systems, ion exchange resin chromatography, highly isotope-selective techniques like laser photoactivation and radiofrequency spectroscopy. Chemical exchange systems appear to offer good potential in the near term for 6Li enrichment

  8. Traceability of poultry offal meal in broiler feeding using isotopic analysis (δ13C and δ15N of different tissues

    Directory of Open Access Journals (Sweden)

    RP Oliveira

    2010-03-01

    Full Text Available Our goal was to trace the inclusion of poultry offal meal (OM in diets by using carbon (13C/12C and nitrogen (15N/14N isotopic ratios of different tissues in order to contribute for the development of an independent technology for the certification of the feeding of broilers reared on diets with no addition of animal ingredients. Eighty one-day-old chicks were randomly distributed into five experimental treatments, that is, diets containing increasing levels of OM inclusion (0, 2, 4, 8 and 16% OM, with four replicates of four birds each. At 42 days of age, four birds per treatment (n=4 were randomly selected, weighed, and sacrificed to collect breast muscle (Pectoralis major, keel and tibia samples to determine their isotopic ratios (13C/12C e 15N/14N. It was observed that 13C and 15N enrichment increased as a function of increasing OM inclusion in all diets. The analyses of the Pectoralis major showed that that only treatments with 8 and 16% OM dietary inclusion were different form those in the control group (0% OM. On the other hand, when the keel and tibia were analyzed, in addition to 8 and 16% OM, the treatment with 4% OM inclusion was also different from the control group. The use of isotopic ratios of stable carbon and nitrogen isotopes is an alternative to trace OM inclusion in broiler diets as it is capable of tracing OM levels below those usually practiced by the poultry industry in Brazil.

  9. Full quantification of selenium species by RP and AF-ICP-qMS with on-line isotope dilution in serum samples from mercury-exposed people supplemented with selenium-enriched yeast

    DEFF Research Database (Denmark)

    Li, Yu-Feng; Hu, Liang; Li, Bai;

    2011-01-01

    and affinity chromatography (AF) hyphenated to inductively coupled plasma-(quadrupole) mass spectrometry (ICP-qMS) with post-column isotope dilution analysis (IDA) and a collision cell technique (CCT). Different Se species like inorganic Se (Se4+ and Se6+), selenocystine (SeCys), selenomethionine (Se...

  10. Oxygen and carbon isotopic growth record in a reef coral from the florida keys and a deep-sea coral from blake plateau

    Science.gov (United States)

    Emiliani, C.; Harold, Hudson J.; Shinn, E.A.; George, R.Y.

    1978-01-01

    Carbon and oxygen isotope analysis through a 30-year (1944 to 1974) growth of Montastrea annularis from Hen and Chickens Reef (Florida Keys) shows a strong yearly variation in the abundances of both carbon-13 and oxygen-18 and a broad inverse relationship between the two isotopes. Normal annual dense bands are formed during the summer and are characterized by heavy carbon and light oxygen. "Stress bands" are formed during particularly severe winters and are characterized by heavy carbon and heavy oxygen. The isotopic effect of Zooxanthellae metabolism dominates the temperature effect on the oxygen-18/oxygen-16 ratio. The isotopic results on the deep-sea solitary coral Bathypsammia tintinnabulum, where Zooxanthellae are nonexistent, indicates that the abundance of the heavy isotopes carbon-13 and oxygen-18 is inversely related to the growth rate, with both carbon and oxygen approaching equilibrium values with increasing skeletal age.

  11. Protein labelling with stable isotopes: strategies; Le marquage des proteines aux isotopes stables: strategies

    Energy Technology Data Exchange (ETDEWEB)

    Lirsac, P.N.; Gilles, N.; Jamin, N.; Toma, F.; Gabrielsen, O.; Boulain, J.C.; Menez, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Direction des Sciences du Vivant

    1994-12-31

    A protein labelling technique with stable isotopes has been developed at the CEA: a labelled complete medium has been developed, performing as well as the Luria medium, but differing from it because it contains not only free aminated acids and peptides, but also sugars (96% of D-glucopyrannose) and labelled nucleosides. These precursors are produced from a labelled photosynthetic micro-organisms biomass, obtained with micro-algae having incorporated carbon 13, nitrogen 15 and deuterium during their culture. Labelling costs are reduced. 1 fig., 1 tab., 3 refs.

  12. Quantitative microbial ecology through stable isotope probing.

    Science.gov (United States)

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

    2015-11-01

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

  13. Beyond Job Enrichment to Employment Enrichment

    Science.gov (United States)

    Werther, William B., Jr.

    1975-01-01

    Employment enrichment views the total work environment confronting employees as a system consisting of two overlapping areas: worker-job and worker-organization subsystems. Job enrichment has improved the worker-job subsystem. The focus of this article is on methods of improving the worker-organization relationship. (Author/JB)

  14. World enrichment services market 1990-2005

    International Nuclear Information System (INIS)

    Growth in world enrichment capacity, already in oversupply, will lead to a very competitive enrichment services market by the second half of the 1990s. Three of the four primary enrichment suppliers (USDOE, Eurodif, and Urenco) already have the capacity to produce 33 million SWU per year. Explorts from the Soviet Union and the People's Republic of China (PRC) currently make available an additional six million SWU per year, and that figure could rise substantially. With additional supply capability expected from China, the Soviet Union, Louisiana Energy Services (LES) and Isotope Technologies (ITI), and the increased capacity of Urenco, and possibly even AVLIS from DOE, enrichment supply capability could exceed 46 million SWU per year by the year 2000. Yet annual enrichment requirements are only estimated to grow from 23.5 million SWU in 1990, to 28.9 million SWU by 2000. Total unfilled enrichment requirements will rise significantly in the second half of the 1990s, particularly from US utilities, creating sales opportunities for which suppliers will compete aggressively. These factors foretell a very competitive market in which sellers will offer low prices and flexible contracts. The anticipation of such strong competition also raises the question of which enrichment technology will succeed, and puts tremendous pressure on all suppliers to find cost-effective means of production as quickly as possible

  15. Atlas of isotope hydrology - Africa

    International Nuclear Information System (INIS)

    Although there are abundant water resources in Africa - about 17 large rivers and 160 lakes greater than 27 km2 - most of these resources are located in the humid and sub-humid regions around the equator. The surface runoff in Africa, on average, is much lower than average precipitation as a result of high evaporation and evapotranspiration, resulting in endemic drought in parts of the continent. Consequently, groundwater is a very important resource for Africa, providing nearly two-thirds of drinking water on the continent, and an even greater proportion in northern Africa. Despite the importance of groundwater for many societies, there is a lack of corresponding public concern about its protection, perhaps because the extent and availability of groundwater are not easily measured. The impact of increasing degrees of temporal and spatial climatic variability on water resources is also an important consideration, and groundwater to some extent provides an opportunity to mitigate the impacts of climate change. Applications of isotopes in hydrology are based on the general concept of 'tracing', in which naturally occurring or environmental isotopes (either radioactive or stable) are used to study hydrological processes on large temporal and spatial scales through their natural distribution in a hydrological system. Thus, environmental isotope methodologies are unique in regional studies of water resources to obtain integrated characteristics of groundwater systems. The most frequently used environmental isotopes include those of the water molecule, hydrogen (2H or D, also called deuterium, and 3H, also called tritium) and oxygen (18O), as well as of carbon (13C and 14C, also called radiocarbon or carbon-14) occurring in water as constituents of dissolved inorganic and organic carbon compounds. 2H, 13C and 18O are stable isotopes of the respective elements, whereas 3H and 14C are radioactive isotopes. Among the most important areas where isotopes are useful in

  16. My academic life with isotopes

    International Nuclear Information System (INIS)

    The present article outlines investigations and experience made by the author in carrying out a variety of studies on isotopes since 1939. First, he was interested in transuranic elements and his studies on artificial radioactive isotopes covered the detection of plutonium at Nagasaki, chemical separation of plutomium from atmosphere at Tokyo, spectral analysis of alpha rays from plutomium, application of 113mIn to emission spectral analysis as a tracer, chemical enrichment of 76As hot atom, and non-destructive analysis of the chemical state of 119Sn produced through EC disintegration in solid material. His studies on natural radioactivity include measurement of the radium content in rock and mineral samples collected in the Korean Peninsula, investigation on the formation process of minerals found around hot springs and determination of the age of rock and mineral samples. He started investigations on isotope enrichment around 1965. Studies in this field cover the application of cataphoretic processes to separation of 23Na and 22Na, enrichment of 7Li and other alkali metals, enrichment of 6Li by isotope exchange, derivation of an empirical equation (Saito-Kanno Equation) for mass effect in couter-current cataphoresis of molten halides, etc. (Nogami, K.)

  17. Liquid chromatography-electrospray ionization tandem mass spectrometry for on-line characterization, monitoring and isotopic profiling of the main selenium-metabolite in human urine after consumption of Se-rich and Se-enriched food

    International Nuclear Information System (INIS)

    The metabolism of selenium (Se) in the human body has yet not completely been unravelled and hence, an efficient method for characterization and on-line monitoring of the main Se-compound in human urine after consumption of Se-rich food was developed. Total Se-concentration in human urine after consumption of several Se-rich products was measured with inductively coupled plasma mass spectrometry (ICP-MS). The highest Se concentration in urine was observed after 4-10 h. The urine samples were brought onto a reversed phase column and the Se was detected by ICP-MS. Parameters for liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) measurements were optimized by using commercially available sugars, because it is known that some of the urinary metabolites contain a sugar moiety. In order to characterize the predominant Se-metabolite, it was necessary to extensively clean-up the sample and preconcentrate the species. The main metabolite was measured on its precursor ion on three different m/z according to three isotopes of Se. Relative peak surfaces matched the relative abundances of the isotopes. The product ions could be measured in a human urine sample in accordance to the product ions of the commercially available sugars. Moreover, the evidence of a selenosugar was demonstrated by the use of the Se-isotopes when measuring the product ions. LC-ESI-MS-MS was proven to be very efficient for the characterization of the main urinary Se-metabolite and can be used for on-line monitoring of the compound in urine samples. The method can be extended for clinical screening after consumption of Se-(en)rich(ed) food by use of the Se-isotopic profile and/or of the typical product ions of (methyl)-N-acetyl-hexosamines

  18. Isotopic geology

    International Nuclear Information System (INIS)

    Born from the application to geology of nuclear physics techniques, the isotopic geology has revolutionized the Earth's sciences. Beyond the dating of rocks, the tracer techniques have permitted to reconstruct the Earth's dynamics, to measure the temperatures of the past (giving birth to paleoclimatology) and to understand the history of chemical elements thanks to the analysis of meteorites. Today, all domains of Earth sciences appeal more or less to the methods of isotopic geology. In this book, the author explains the principles, methods and recent advances of this science: 1 - isotopes and radioactivity; 2 - principles of isotope dating; 3 - radio-chronological methods; 4 - cosmogenic isotope chronologies; 5 - uncertainties and radio-chronological results; 6 - geochemistry of radiogenic isotopes; 7 - geochemistry of stable isotopes; 8 - isotopic geology and dynamical analysis of reservoirs. (J.S.)

  19. Isotopic clusters

    International Nuclear Information System (INIS)

    Spectra of isotopically mixed clusters (dimers of SF6) are calculated as well as transition frequencies. The result leads to speculations about the suitability of the laser-cluster fragmentation process for isotope separation. (Auth.)

  20. Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum

    OpenAIRE

    Tagliabue, A.; L. Bopp; Roche, D. M.; N. Bouttes; J.-C. Dutay; Alkama, R.; Kageyama, M.; Michel, E.; Paillard, D.

    2009-01-01

    We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO2 at the last glacial maximum (LGM). We examine 5 different realisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton ph...

  1. US developments in technology for uranium enrichment

    International Nuclear Information System (INIS)

    The purpose of this paper is to review recent progress and the status of the work in the United States on that part of the fuel cycle concerned with uranium enrichment. The United States has one enrichment process, gaseous diffusion, which has been continuously operated in large-scale production for the past 37 years; another process, gas centrifugation, which is now in the construction phase; and three new processes, molecular laser isotope separation, atomic vapor laser isotope separation, plasma separation process, in which the US has also invested sizable research and development efforts over the last few years. The emphasis in this paper is on the technical aspects of the various processes, but the important economic factors which will define the technological mix which may be applied in the next two decades are also discussed

  2. Isotope effect of potassium in an aqueous/amalgam system

    International Nuclear Information System (INIS)

    The isotope fractionation of potassium in an aqueous (KOH)/amalgam system has been studied. Two types of isotope effects with opposite isotope enrichment directions were observed in the electrolysis of potassium from the aqueous into the amalgam phase under constant electrolytic potentials. It was found that the first isotope effect causing the light isotope enriched in the amalgam is related to the kinetic process of the mass transfer through the aqueous/amalgam interface, while the second one leading to the enrichment of the heavy isotope in the amalgam phase is produced by the isotope-exchange equilibrium. The temperature dependence of the equilibrium isotope effect was also investigated using single-stage and multi-stage techniques. It was observed that the equilibrium isotope effect increases as the temperature increases in the range of 293-371 K. An empirical equation was used to fit the variations of the isotope effects with temperature for potassium together with the other alkaline and alkaline earth metals studied in the same system. The origin of the equilibrium isotope fractionation in the electron-exchange system was discussed. Furthermore, the mass dependence of the separation coefficients of the alkaline and alkaline earth metals observed in aqueous/amalgam and ion-exchange systems were compared. At 293 K the equilibrium isotope separation coefficient for the 39K/41K isotopes in the amalgam system was determined as (5.6 ± 0.6).10-3. (author)

  3. Environmental isotope studies of marine coastal pollution in Pakistan

    International Nuclear Information System (INIS)

    The International Atomic Energy Agency (the Agency), Vienna launched a five year (duration: 1998 - 2002) Joint Project on 'Better Management of the Environment and Industrial Growth Through Isotopes and Radiation Technology (RAS/97/030) in co-operation with the RCA (Regional Co-operative Agreement) office-Vienna, and UNDP (United Nations Development Programme). The Marine Sub-project entitled 'Management of Marine Coastal Environment and its Pollution (RAS/8/083)' is a key component of this joint project. Pakistan has significantly contributed in the marine sub-project by demonstrating the potential use of environmental isotope techniques such as stable isotope ratios of oxygen-18 in water molecules, carbon-13 in total dissolved inorganic carbon (TDIC), carbon-13 in total dissolved inorganic carbon as well as marine plant (leaves and tree rings), nitrogen-15 in marine plants and animal shells, and sulfur-34 in aqueous sulfate for tracking the transport of pollutants in marine coastal environment. This paper/poster highlights the innovative use of these environmental stable isotope techniques in relation to conventional physiochemical techniques for tracking fate and behaviour of land based domestic / industrial pollution inventory in the marine coastal environment of Pakistan

  4. Non-linear Isotope Effects

    DEFF Research Database (Denmark)

    Schmidt, Johan Albrecht

    The isotopic fractionation associated with photodissociation of N2O, OCS and CO2, at different altitudes in Earth’s atmosphere, is investigated theoretically using constructed quantum mechanical models of the dissociation processes (i.e. potential energy surfaces and relevant coupling elements...... or moderate, and overall sulfur fractionation in the stratosphere is very weak which does not exclude OCS from being an acceptable background the Stratospheric Sulfate Aerosol layer. (iii) CO2 photolysis in the upper stratosphere and lower mesosphere is highly fractionating in both isotopes, enriching...... the remaining CO2 and depleting the produced CO in heavy isotopes. But photolysis of CO2 is too slow to produce significant fractionation in the remaining CO2. In contrast, the produced CO is highly fractionated and possesses a significant non mass dependent perturbation and a clumped isotope signal. Given...

  5. ISOTOPE FRACTIONATION PROCESS

    Science.gov (United States)

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

    1958-05-20

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

  6. NRC licensing of uranium enrichment plants

    International Nuclear Information System (INIS)

    The US Nuclear Regulatory Commission (NRC) is preparing a rule making that establishes the licensing requirements for low-enriched uranium enrichment plants. Although implementation of this rule making is timed to correspond with receipt of a license application for the Louisiana Energy Services centrifuge enrichment plant, the rule making is applicable to all uranium enrichment technologies. If ownership of the US gaseous diffusion plants and/or atomic vapor laser isotope separation is transferred to a private or government corporation, these plants also would be licensable under the new rule making. The Safeguards Studies Department was tasked by the NRC to provide technical assistance in support of the rule making and guidance preparation process. The initial and primary effort of this task involved the characterization of the potential safeguards concerns associated with a commercial enrichment plant, and the licensing issues associated with these concerns. The primary safeguards considerations were identified as detection of the loss of special nuclear material, detection of unauthorized production of material of low strategic significance, and detection of production of uranium enriched to >10% 235U. The primary safeguards concerns identified were (1) large absolute limit of error associated with the material balance closing, (2) the inability to shutdown some technologies to perform a cleanout inventory of the process system, and (3) the flexibility of some technologies to produce higher enrichments. Unauthorized production scenarios were identified for some technologies that could prevent conventional material control and accounting programs from detecting the production and removal of 5 kg 235U as highly enriched uranium. Safeguards techniques were identified to mitigate these concerns

  7. Oxygen Isotopes in Meteorites

    Science.gov (United States)

    Clayton, R. N.

    2003-12-01

    , and C18O - absorb at different wavelengths, corresponding to the isotope shift in vibrational frequencies. Because of their different number densities, the abundant C16O becomes optically thick in the outermost part of the cloud (nearest to the external source of UV radiation), while the rare C17O and C18O remain optically thin, and hence dissociate at a greater rate in the cloud interior. The differences in chemical reactivity between C16O molecules and 17O and 18O atoms may lead to isotopically selective reaction products. This scenario has been suggested to explain meteoritic isotope patterns, as discussed below (Yurimoto and Kuramoto, 2002).Stable isotope abundances in meteoritic material provide an opportunity to evaluate the thoroughness of mixing of isotopes of diverse stellar sources. Molybdenum presents a good test case: it has seven stable isotopes, derived from at least three types of stellar sources, corresponding to the r-process, s-process, and p-process. Presolar silicon carbide grains, extracted from primitive meteorites, contain molybdenum that has been subject to s-process neutron capture in red-giant stars, resulting in large enrichments of isotopes at masses 95, 96, 97, 98, and severe depletions (up to 100%) of isotopes at masses 92 and 94 (p-process) and 100 (r-process) (Nicolussi et al., 1998). Complementary patterns have been found in whole-rock samples of several meteorites, with >1,000-fold smaller amplitude, suggesting the preservation of a small fraction of the initial isotopic heterogeneity ( Yin et al., 2002; Dauphas et al., 2002). Oxygen is another element for which primordial isotopic heterogeneity might be preserved. This is discussed further below.It would be highly desirable to have samples of oxygen-rich mineral grains that have formed in stellar atmospheres and have recorded the nucleosynthetic processes in individual stars. Similar samples are already available for carbon-rich grains, in the form of SiC and graphite, primarily from

  8. Basic characterization of highly enriched uranium by gamma spectrometry

    OpenAIRE

    Nguyen, Cong Tam; Zsigrai, Jozsef

    2005-01-01

    Gamma-spectrometric methods suitable for the characterization of highly enriched uranium samples encountered in illicit trafficking of nuclear materials are presented. In particular, procedures for determining the 234U, 235U, 238U, 232U and 236U contents and the age of highly enriched uranium are described. Consequently, the total uranium content and isotopic composition can be calculated. For determining the 238U and 232U contents a low background chamber was used. In addition, age dating of...

  9. Peak fitting applied to low-resolution enrichment measurements

    Energy Technology Data Exchange (ETDEWEB)

    Bracken, D.; McKown, T.; Sprinkle, J.K. Jr. [Los Alamos National Lab., NM (United States); Gunnink, R. [Lawrence Livermore National Lab., CA (United States); Kartoshov, M.; Kuropatwinski, J.; Raphina, G.; Sokolov, G. [Ulba Metallurgical Facility, Ust-Kamenogorsk (Kazakhstan)

    1998-12-01

    Materials accounting at bulk processing facilities that handle low enriched uranium consists primarily of weight and uranium enrichment measurements. Most low enriched uranium processing facilities draw separate materials balances for each enrichment handled at the facility. The enrichment measurement determines the isotopic abundance of the {sup 235}U, thereby determining the proper strata for the item, while the weight measurement generates the primary accounting value for the item. Enrichment measurements using the passive gamma radiation from uranium were developed for use in US facilities a few decades ago. In the US, the use of low-resolution detectors was favored because they cost less, are lighter and more robust, and don`t require the use of liquid nitrogen. When these techniques were exported to Europe, however, difficulties were encountered. Two of the possible root causes were discovered to be inaccurate knowledge of the container wall thickness and higher levels of minor isotopes of uranium introduced by the use of reactor returns in the enrichment plants. the minor isotopes cause an increase in the Compton continuum under the 185.7 keV assay peak and the observance of interfering 238.6 keV gamma rays. The solution selected to address these problems was to rely on the slower, more costly, high-resolution gamma ray detectors when the low-resolution method failed. Recently, these gamma ray based enrichment measurement techniques have been applied to Russian origin material. The presence of interfering gamma radiation from minor isotopes was confirmed. However, with the advent of fast portable computers, it is now possible to apply more sophisticated analysis techniques to the low-resolution data in the field. Explicit corrections for Compton background, gamma rays from {sup 236}U daughters, and the attenuation caused by thick containers can be part of the least squares fitting routine. Preliminary results from field measurements in Kazakhstan will be

  10. Short-term carbon and nitrogen cycling in urine patches assessed by combined carbon-13 and nitrogen-15 labelling

    DEFF Research Database (Denmark)

    Ambus, Per; Petersen, S.O.; Soussana, J.F.

    2007-01-01

    sources for C include the urine itself, increased solubility of soil C, lysis of microbial cells and leakage of C from scorched roots. The objective of this experiment was to test the hypothesis that: (i) urine deposition causes an increase in root-derived degradable C compounds in the soil, which (ii.......03), whereas HUN = HMN (P urea concentration and 0.15% for mineral N (NH4+). The N-15 isotopic data indicated that denitrification of soil NO3- was the sole source for N2O production in the urine-affected soil after 12...... of urea concentration, and 72% of the NH4+-was recovered after 6 weeks of incubation. This finding, in combination with the difference in the NO losses, emphasizes the potential to control N-emissions from urine patches through dietary control of the urine N-content. (c) 2006 Elsevier B.V. All rights...

  11. Determination of zinc stable isotopes in biological materials using isotope dilution inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    A method is described for using isotope dilution to determine both the amount of natural zinc and enriched isotopes of zinc in biological samples. Isotope dilution inductively coupled plasma mass spectrometry offers a way to quantify not only the natural zinc found in a sample but also the enriched isotope tracers of zinc. Accurate values for the enriched isotopes and natural zinc are obtained by adjusting the mass count rate data for measurable instrumental biases. Analytical interferences from the matrix are avoided by extracting the zinc from the sample matrix using diethylammonium diethyldithiocarbamate. The extraction technique separates the zinc from elements which form interfering molecular ions at the same nominal masses as the zinc isotopes. Accuracy of the method is verified using standard reference materials. The detection limit is 0.06 μg Zn per sample. Precision of the abundance ratios range from 0.3-0.8%. R.S.D. for natural zinc concentrations is about 200-600 μg g-1. The accuracy and precision of the measurements make it possible to follow enriched isotopic tracers of zinc in biological samples in metabolic tracer studies. (author). 19 refs.; 1 fig., 4 tabs

  12. A double-quadrature radiofrequency coil design for proton-decoupled carbon-13 magnetic resonance spectroscopy in humans at 7T

    OpenAIRE

    Serés Roig, Eulalia; Magill, Arthur W.; Donati, Guillaume; Meyerspeer, Martin; Xin, Lijing; Ipek, Ozlem; Gruetter, Rolf

    2015-01-01

    Purpose Carbon-13 magnetic resonance spectroscopy (13C-MRS) is challenging because of the inherent low sensitivity of 13C detection and the need for radiofrequency transmission at the 1H frequency while receiving the 13C signal, the latter requiring electrical decoupling of the 13C and 1H radiofrequency channels. In this study, we added traps to the 13C coil to construct a quadrature-13C/quadrature-1H surface coil, with sufficient isolation between channels to allow simultaneous operation at...

  13. Proton And Carbon-13 Nuclear Magnetic Resonance Of Some 4-Amino-3-Alkyl (Aryl)-5-Thio-1,2,4-Triazolines And Their Derivatives

    OpenAIRE

    El Toukhy, Ahmed [احمد الطوخي; Al-Kubaisi, Abdulla H.; Kenawy, Ibrahim

    1991-01-01

    The proton and carbon-13 NMR spectra of some 4-amino-3-alkyl(aryl)-5-thio-1,2,4-triazolines, some 3-alkyl-5-thio- 1,2,4-triazolines and some 4-amino-3-aryl-5-thio-l,2,4-triazoles were measured in DMSO-d6 as solvent. The chemical shift for each proton and carbon in these compounds were assigned. The 'H, chemical shift of N-H protons of the thioamide group and the "C chemical shift of C(3) in the triazolines were found to be sensitive to the substituent R (alkyi or aryl) at C(3), and correlated...

  14. Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism.

    Science.gov (United States)

    Kaufman, A J; Hayes, J M; Knoll, A H; Germs, G J

    1991-01-01

    Proterozoic seawater. Within the Damara basin, carbon-isotopic compositions of carbonates provide a potentially useful tool for the correlation of units between the Kalahari and Congo cratons. Carbonates depleted in 13C were deposited during and immediately following three separate glacial episodes in Namibia. The correspondence between ice ages and negative delta 13C excursions may reflect the effects of lowered sea levels; enhanced circulation of deep, cold, O2-rich seawater; and/or the upwelling of 13C-depleted deep water. Iron-formation is additionally associated with one of the glacial horizons, the Chuos tillite. Carbon-13 enriched isotopic abundances in immediately pre-glacial carbonates suggest that oceanographic conditions favored high rates of organic burial. It is likely that marine waters were stratified, with deep waters anoxic. A prolonged period of ocean stratification would permit the build-up of ferrous iron, probably from hydrothermal sources. At the onset of glaciation, upwelling would have brought 13C-depleted and iron-rich deep water onto shallow shelves where contact with cold, oxygenated surface waters led to the precipitation of ferric iron.

  15. A molecular organic carbon isotope record of Miocene climate changes

    OpenAIRE

    Schoell, M.; Schouten, S.; Sinninghe Damsté, J.S.; J. W. de Leeuw; Summons, R. E.

    1994-01-01

    The difference in carbon-13 (13C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in 18O (δ18O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (δ13C = 25.4 ± 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfu...

  16. Profile of World Uranium Enrichment Programs - 2007

    Energy Technology Data Exchange (ETDEWEB)

    Laughter, Mark D [ORNL

    2007-11-01

    It is generally agreed that the most difficult step in building a nuclear weapon is acquiring weapons grade fissile material, either plutonium or highly enriched uranium (HEU). Plutonium is produced in a nuclear reactor, while HEU is produced using a uranium enrichment process. Enrichment is also an important step in the civil nuclear fuel cycle, in producing low enriched uranium (LEU) for use in fuel for nuclear reactors. However, the same equipment used to produce LEU for nuclear fuel can also be used to produce HEU for weapons. Safeguards at an enrichment plant are the array of assurances and verification techniques that ensure uranium is only enriched to LEU, no undeclared LEU is produced, and no uranium is enriched to HEU or secretly diverted. There are several techniques for enriching uranium. The two most prevalent are gaseous diffusion, which uses older technology and requires a lot of energy, and gas centrifuge separation, which uses more advanced technology and is more energy efficient. Gaseous diffusion plants (GDPs) provide about 40% of current world enrichment capacity, but are being phased out as newer gas centrifuge enrichment plants (GCEPs) are constructed. Estimates of current and future enrichment capacity are always approximate, due to the constant upgrades, expansions, and shutdowns occurring at enrichment plants, largely determined by economic interests. Currently, the world enrichment capacity is approximately 53 million kg-separative work units (SWU) per year, with 22 million in gaseous diffusion and 31 million in gas centrifuge plants. Another 23 million SWU/year of capacity are under construction or planned for the near future, almost entirely using gas centrifuge separation. Other less-efficient techniques have also been used in the past, including electromagnetic and aerodynamic separations, but these are considered obsolete, at least from a commercial perspective. Laser isotope separation shows promise as a possible enrichment technique

  17. Assay of the deuterium enrichment of water via acetylene.

    Science.gov (United States)

    Previs, S F; Hazey, J W; Diraison, F; Beylot, M; David, F; Brunengraber, H

    1996-06-01

    A technique is presented for measuring the 2H enrichment of water in biological samples when this enrichment is greater than 0.2%. The sample is reacted with calcium carbide to form acetylene gas, which is determined by gas chromatography electron impact ionization mass spectrometry. Ion-molecule reactions, resulting in proton abstraction, are minimized by lowering the electron ionization energy from the usual 70 eV to 45 eV. This technique is much more rapid and economical than the classical isotope ratio mass spectrometric assay of the enrichment of hydrogen gas derived from reduction of water.

  18. Carbon isotopic fractionation in heterotrophic microbial metabolism

    Science.gov (United States)

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

    1985-01-01

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

  19. A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2: evidence from carbon isotope discrimination in paleo and CO2 enrichment studies

    Science.gov (United States)

    Voelker, Steven L.; Brooks, J. Renée; Meinzer, Frederick C.; Anderson, Rebecca D.; Bader, Martin K.-F.; Battipaglia, Giovanna; Becklin, Katie M.; Beerling, David; Bert, Didier; Betancourt, Julio L.; Dawson, Todd E.; Domec, Jean-Christophe; Guyette, Richard P.; Körner, Christian; Leavitt, Steven W.; Linder, Sune; Marshall, John D.; Mildner, Manuel; Ogée, Jérôme; Panyushkina, Irina P.; Plumpton, Heather J.; Pregitzer, Kurt S.; Saurer, Matthias; Smith, Andrew R.; Siegwolf, Rolf T.W.; Stambaugh, Michael C.; Talhelm, Alan F.; Tardif, Jacques C.; Van De Water, Peter K.; Ward, Joy K.; Wingate, Lisa

    2016-01-01

    Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO2], ci, a constant drawdown in CO2(ca − ci), and a constant ci/ca. These strategies can result in drastically different consequences for leaf gas-exchange. The accuracy of Earth systems models depends in part on assumptions about generalizable patterns in leaf gas-exchange responses to varying ca. The concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these strategies, provides a unifying framework for understanding leaf gas-exchange responses to ca. To assess leaf gas-exchange regulation strategies, we analyzed patterns in ci inferred from studies reporting C stable isotope ratios (δ13C) or photosynthetic discrimination (∆) in woody angiosperms and gymnosperms that grew across a range of ca spanning at least 100 ppm. Our results suggest that much of the ca-induced changes in ci/ca occurred across ca spanning 200 to 400 ppm. These patterns imply that ca − ci will eventually approach a constant level at high ca because assimilation rates will reach a maximum and stomatal conductance of each species should be constrained to some minimum level. These analyses are not consistent with canalization toward any single strategy, particularly maintaining a constant ci. Rather, the results are consistent with the existence of a broadly conserved pattern of stomatal optimization in woody angiosperms and gymnosperms. This results in trees being profligate water users at low ca, when additional water loss is small for each unit of C gain, and increasingly water-conservative at high ca, when photosystems are saturated and water loss is large for each unit C gain.

  20. Dye laser chain for laser isotope separation

    Science.gov (United States)

    Doizi, Denis; Jaraudias, Jean; Pochon, E.; Salvetat, G.

    1993-05-01

    Uranium enrichment by laser isotope separation uses a three step operation which requires four visible wavelengths to boost an individual U235 isotope from a low lying atomic energy level to an autoionizing state. The visible wavelengths are delivered by dye lasers pumped by copper vapor lasers (CVL). In this particular talk, a single dye chain consisting of a master oscillator and amplifier stages will be described and some of its performance given.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-09-02

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

  2. TRIGA low enrichment fuel

    International Nuclear Information System (INIS)

    Sixty TRIGA reactors have been sold and the earliest of these are now passing twenty years of operation. All of these reactors use the uranium-zirconium hydride fuel (UZrH) which provides certain unique advantages arising out of its large prompt negative temperature coefficient, very low fission product release, and high temperature capability. Eleven of these Sixty reactors are conversions from plate fuel to TRIGA fuel which were made as a result of these advantages. With only a few exceptions, TRIGA reactors have always used low-enriched-uranium (LEU) fuel with an enrichment of 19.9%. The exceptions have either been converted from the standard low-enriched fuel to the 70% enriched FLIP fuel in order to achieve extended lifetime, or are higher powered reactors which were designed for long life using 93%-enriched uranium during the time when the use and export of highly enriched uranium (HEU) was not restricted. The advent of international policies focusing attention on nonproliferation and safeguards made the HEU fuels obsolete. General Atomic immediately undertook a development effort (nearly two years ago) in order to be in a position to comply with these policies for all future export sales and also to provide a low-enriched alternative to fully enriched plate-type fuels. This important work was subsequently partially supported by the U.S. Department of Energy. The laboratory and production tests have shown that higher uranium densities can be achieved to compensate for reducing the enrichment to 20%, and that the fuels maintain the characteristics of the very thoroughly proven standard TRIGA fuels. In May of 1978, General Atomic announced that these fuels were available for TRIGA reactors and for plate-type reactors with power levels up to 15 MW with GA's standard commercial warranty

  3. TRIGA low enrichment fuel

    International Nuclear Information System (INIS)

    Sixty TRIGA reactors have been sold and the earliest of these are now passing twenty years of operation. All of these reactors use the uranium zirconium hydride fuel (UZrH) which provides certain unique advantages arising out of its large prompt negative temperature coefficient, very low fission product release, and high temperature capability. Eleven of these Sixty reactors are conversions from plate fuel to TRIGA fuel which were made as a result of these advantages. With only a few exceptions, TRIGA reactors have always used low-enriched uranium (LEU) fuel with an enrichment of 19.9%. The exceptions have either been converted from the standard low-enriched fuel to the 70% enriched FLIP fuel in order to achieve extended lifetime, or are higher powered reactors which were designed for long life using 93%-enriched uranium during the time when the use and export of highly enriched uranium (HEU) was not restricted. The advent of international policies focusing attention on nonproliferation and safeguards made the HEU fuels obsolete. General Atomic immediately undertook a development effort (nearly two years ago) in order to be in a position to comply with these policies for all future export sales and also to provide a low-enriched alternative to fully enriched plate-type fuels. This important work was subsequently partially supported by the U.S. Department of Energy. The laboratory and production tests have shown that higher uranium densities can be achieved to compensate for reducing the enrichment to 20%, and that the fuels maintain the characteristics of the very thoroughly proven standard TRIGA fuels. In May of 1978, General Atomic announced that these fuels were available for TRIGA reactors and for plate-type reactors with power levels up to 15 MW with General Atomic's standard commercial warranty

  4. Embryotoxicity of stable isotopes and use of stable isotopes in studies of teratogenetic mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Spielmann, H.; Nau, H.

    1986-07-01

    Experiments on teratogenic effects of stable isotopes from our own and other laboratories are evaluated. In the first series of investigations, the enrichment of the stable isotope /sup 13/C derived from U-/sup 13/C-glucose was studied in mouse embryos at various stages of development, including limb buds in organ culture. Preimplantation mouse embryos incubated in vitro in /sup 13/C-enriched medium for 48 hours showed normal development during subsequent differentiation in vitro and also in vivo after embryo transfer to faster mothers. These embryos were 15% to 20% enriched in /sup 13/C. Administration of U-13-C-glucose to pregnant mice during organogenesis led to an increase of the absolute /sup 13/C content of the embryo for several days after the end of isotope administration, whereas the enrichment in maternal tissue decreased. No alterations of embryonic development were detected due to stable isotope enrichment. Development of cultured mouse limb buds was unaffected by incubation with 82 mol% U-/sup 13/C-glucose as judged from morphologic and biochemical criteria. The second part of the article describes the value of deuterium-labeled drugs as probes into the mechanism of activation of teratogenic metabolites. A comparison of the pharmacokinetics as well as the teratogenicity between cyclophosphamide and some specific deuterium-labeled analogues showed that the isotope effect observed can be related to a particular metabolic pathway crucial for teratogenic activation by this drug.

  5. Leatherback Isotopes

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — SWFSC is currently working on a project identifying global marine isotopes using leatherback turtles (Dermochelys coriacea) as the indicator species. We currently...

  6. Insights Into Water-Soluble Organic Aerosol Sources From Carbon-13 Ratios of Size Exclusion Chromatography Fractions

    Science.gov (United States)

    Ruehl, C. R.; Chuang, P. Y.; McCarthy, M. D.

    2008-12-01

    Many sources of organic aerosols have been identified and quantified, and much of this work has used individual (mosty water-insoluble) compounds as tracers of primary sources. However, most organic aerosol cannot be molecularly characterized, and the water-soluble organic carbon (WSOC) in many aerosols is thought to originate from gaseous precursors (i.e., it is secondary in nature). It can therefore be difficult to infer aerosol sources, particularly of background (i.e., aged) aerosols, and of the relatively high-MW component of aerosols. The stable isotope ratios (δ13C) of organic aerosols have been used to distinguish between sources, with lighter values (-30‰ to -25‰) interpreted as having originated from fossil fuel combustion and C4 biogenic emission, and heavier values (-25‰ to - 20‰) indicating a marine or C3 biogenic source. Most published measurements were of either total suspended particulates or PM2.5, however, and it is unknown to what extent these fractions differ from submicron WSOC. We report δ13C for submicron WSOC collected at a variety of sites, ranging from marine to polluted to background continental. Bulk marine organic δ13C ranged from -30.4 to - 27.6‰, slightly lighter than previously published results. This could be due to the elimination of supermicron cellular material or other biogenic primary emissions from the sample. Continental WSOC δ13C ranged from -19.1 to -29.8‰, with heavier values (-19.8 ± 1.0‰) in Oklahoma and lighter values at Great Smoky Mountain National Park in Tennessee (-25.8 ± 2.6‰) and Illinois (-24.5 ± 1.0‰). This likely results from the greater proportional of C3 plant material in the Oklahoma samples. In addition to bulk samples, we used size exclusion chromatography (SEC) to report δ13C of organic aerosols as a function of hydrodynamic diameter. Variability and magnitude of hydrodynamic diameter was greatest at low SEC pH, indicative of the acidic character of submicron WSOC. Tennessee

  7. Isotopic chirality

    Energy Technology Data Exchange (ETDEWEB)

    Floss, H.G. [Univ. of Washington, Seattle, WA (United States)

    1994-12-01

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

  8. Isotopic Paleoclimatology

    Science.gov (United States)

    Bowen, R.

    Paleotemperature scales were calculated by H. C. Urey and others in the 1950s to assess past temperatures, and later work using the stable isotopes of oxygen, hydrogen, and carbon employed standards such as Peedee belemnite (PDB) and Standard Mean Ocean Water (SMOW). Subsequently, subjects as diverse as ice volume and paleotemperatures, oceanic ice and sediment cores, Pleistocene/Holocene climatic changes, and isotope chronostratigraphy extending back to the Precambrian were investigated.

  9. Stellar Origins of C-13 and N-15-Enriched Presolar SiC Grains

    Science.gov (United States)

    Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.; Wang, Jianhua; Pignatari, Marco; Jose, Jordi; Nguyen, Ann

    2016-01-01

    Extreme excesses of 13 C ( C (12 C/ 13 CSiC 20) in rare presolar SiClar SiC grains have been considered diagnostic of an origin in classical novae [1], though an origin in core-collapse supernovae (CCSNe) has also been proposed [2]. We report multi-element isotopic data for 19 13 C- and 15 N-enriched presolar SiC grains(12 C/13 C<16 and 14 N/ 15 N<150) from an acid resistant residue of the Murchison meteorite. These grains are enriched in 13 C and15 N, but with quite diverse Si isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures. Four grains with isotopic signatures.

  10. An ideal cascade for uranium 235 enrichment by centrifuge jet nozzle process

    International Nuclear Information System (INIS)

    The design of an ideal cascade for the process of isotope separation by centrifugation for the U235 enrichment, is presented. A selection of building materials used in fabrication of isotope separation plants, showing the importance of aluminium, due the bauxite mines in Northern Brazil, is done. (M.C.K.)

  11. A gas extraction system for the measurement of carbon dioxide and carbon isotopes in polar ice cores

    International Nuclear Information System (INIS)

    Knowledge of the distribution of Carbon 13 in the glacial ocean, atmosphere, and biosphere is important to understanding the causes of glacial/interglacial changes in atmospheric CO2 levels. Although deep-ocean Carbon 13 values are well-constrained by ocean sediment studies, model-based estimates of changes in the carbon budget for the biosphere and atmosphere vary considerably. Measurement of atmospheric Carbon 13 in CO2 in ice cores will provide additional constraints on this budget and will also improve estimates of changes in the ocean surface layer Carbon 13. Direct measurement of ancient atmospheric Carbon 13 can be accomplished through polar ice core studies. A gas-extraction line for ice cores has been designed and constructed with particular attention to the specific difficulties of measuring Carbon 13 in CO2. The ice is shaved, rather than crushed, to minimize fractionation effects resulting from gas travel through long air-paths in the ice. To minimize the risk of isotopic contamination and fractionation within the vacuum line, CO2 is separated immediately from the air; the CO2 concentration is then measured by a simple pressure/volume comparison rather than by gas chromatography or spectroscopy. Measurements from Greenland ice core samples give an average value of 280±2 ppM CO2 for preindustrial samples, demonstrating that the extraction system gives accurate, precise determinations Of CO2 concentrations. Measurement of δ13C from polar ice samples has not been achieved at this time. However, results on standard air samples demonstrate a precision for δ13C of less than 0.2 per-thousand at the 95% confidence level

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

    CERN Document Server

    Xie, Xueshu

    2014-01-01

    Isotopic composition of reactants affects the rates of chemical and biochemical reactions. As a rule, enrichment of heavy stable isotopes leads to 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 plus or minus 0.05%) experiment to measure the bacterial growth parameters in minimal media with varying isotopic compositions. A number of predicted resonance conditions were tested, which kinetic enhancements as strong as plus 3% discovered at these conditions. The combined evidence extremely strongly supports the existence of isotopic resonances. This phenomenon has numerous implications for the origin of life and astrobiology, and possible application...

  13. Isotopic paleoecology of Clovis mammoths from Arizona

    Science.gov (United States)

    Metcalfe, Jessica Z.; Longstaffe, Fred J.; Ballenger, Jesse A. M.; Vance Haynes, C., Jr.

    2011-11-01

    The causes of megafaunal extinctions in North America have been widely debated but remain poorly understood. Mammoths (Mammuthus spp.) in the American Southwest were hunted by Clovis people during a period of rapid climate change, just before the regional onset of Younger Dryas cooling and mammoth extirpation. Thus, these mammoths may provide key insights into late Pleistocene extinction processes. Here we reconstruct the seasonal diet and climatic conditions experienced by mammoths in the San Pedro Valley of Arizona, using the carbon (13C/12C) and oxygen (18O/16O) isotope compositions of tooth enamel. These records suggest that Clovis mammoths experienced a warm, dry climate with sufficient summer rainfall to support seasonal C4 plant growth. Monsoon intensity may have been reduced relative to the preceding time period, but there is no isotopic evidence for severe drought. However, it is possible that the "Clovis drought", inferred from stratigraphic evidence, occurred suddenly at the end of the animals' lives and thus was not recorded in the enamel isotopic compositions. Unlike mammoths that lived before the Last Glacial Maximum, Clovis mammoths regularly increased C4 grass consumption during summer, probably seeking seasonally green grasslands farther from the river valley. This predictable seasonal behavior may have made mammoths easier to locate by Clovis hunters. Furthermore, Clovis mammoths probably had no previous experience of such sudden climatic change as is believed to have occurred at the time of their extinction.

  14. High-purity enrichment of 84Sr

    International Nuclear Information System (INIS)

    High-purity 84Sr (i.e., >99 at %) is an important tool in many areas of basic and applied research, in particular for spikes used in isotopic dilution/mass spectrometer investigations in geochemistry, cosmochemistry, and paleoclimate-age studies. In nature, the 84Sr abundance is only 0.56%; however, it can be enriched to the specified requirements by using a high-resolution separator, such as the 180 deg. -sector separator, or by completing two passes through a high-production, lower-resolution machine, such as the calutron. The latter option was used for this enrichment to produce ∼1 g of strontium with a final 84Sr concentration of 99.64%. Three innage runs were made, vaporizing a total of ∼17 g of metal feed that had been pre-enriched in the calutron to ∼70% 84Sr. A partial recovery, followed by recycle of the unresolved feed, was made after the second innage run. A process efficiency of 8.44% was achieved, and 4.33 g of the unresolved feed material was recovered. A modified ion-source unit using materials compatible with strontium and the use of krypton as mass markers to aid in operations are described. Standard contamination analyses were performed to evaluate the enrichment and to compare measured results with predicted product purity

  15. A carbon-13 NMR spin-lattice relaxation study of the molecular conformation of the nootropic drug 2-oxopyrrolidin-1-ylacetamide

    Science.gov (United States)

    Baldo, M.; Grassi, A.; Guidoni, L.; Nicolini, M.; Pappalardo, G. C.; Viti, V.

    The spin-lattice relaxation times ( T1) of carbon-13 resonances of the drug 2-oxopyrrolidin- 1-ylacetamide ( 2OPYAC) were determined in CDCl 3 + DMSO and H 2O solutions to investigate the internal conformational flexibility. The measured T1s for the hydrogen-bearing carbon atoms of the 2-pyrrolidone ring fragment were diagnostic of a rigid conformation with respect to the acetamide linked moiety. The model of anisotropic reorientation of a rigid body was used to analyse the measured relaxation data in terms of a single conformation. Owing to the small number of T1 data available the fitting procedure for each of the possible conformations failed. The structure corresponding to the rigid conformation was therefore considered to be the one that is strongly stabilized by internal hydrogen bonding as predicted on the basis of theoretical MO ab initio quantum chemical calculations.

  16. Isotope effects in the gadolinium amalgam system

    International Nuclear Information System (INIS)

    Gadolinium is a good neutron absorbent used in uranium oxide nuclear fuel for LWR. The157 Gd has a very large cross section for neutron absorption, namely 254000 barn. One of the isotope separation method for gadolinium is the isotopic exchange in the Gd3+ - GdHg system. In this work, the separation elemental factors for this isotopic exchange reaction, determined experimentally, are presented. Gadolinium amalgam was prepared by electrolysis of aqueous solution of gadolinium acetate with lithium citrate as complexing agent ([Li+]/[Gd3+] = 12), in a glass electrolyzer with a Hg cathode and a Pt anode. The gadolinium amalgam was treated with HCl 1-2N and the extracted Gd3+ was precipitated as oxalate and converted in Gd2O3. Gadolinium in acetic solution was precipitated as oxalate and converted in Gd2O3. The isotopic ratios 154 Gd/160 Gd, 155 Gd/160 Gd, 156 Gd/160 Gd, 157 Gd/160 Gd and 158 Gd/160 Gd were determined in Gd2O3 samples by a mass spectrometer MAT 261 equipped with thermoionization ion source. After the isotopic exchange, GdHg enriches with the light Gd isotopes and the solution (Gd3+) enriches with 160 Gd. The dependence of separation elemental factor on mass difference between gadolinium isotopes is presented. (authors)

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

    Science.gov (United States)

    Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

    2014-05-01

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

  18. An ionic cyclotron resonance isotopic separation device

    International Nuclear Information System (INIS)

    Isotopes are separated using ion cyclotron resonance. The process takes place under vacuum in a vertical cylindrical vessel, with means for creating a plasma containing ions of the isotope to be separated. An electrical field is generated, perpendicular to a vertical magnetic field and oscillating at a frequency near to the cyclotron frequency of the isotope in question. Mixtures enriched and depleted in the isotopes in question are collected separately in the upper part of the vessel. The plasma generator includes a container for the element for treatment made of electro-conducting material which does not melt at operating temperature, open at the top. During operation part of the container is held at a high enough temperature to provoke evaporation or sublimation of the element being treated, while its upper part stays cooler. An ionizer is situated above the container. Isotopes of metals such as zinc, cadmium, tin, calcium and particularly gadolinium can be separated. 1 fig

  19. Obtaining Sulfur from Sulfur Hexafluoride and Studying the Sulfur Isotopes Properties by Using Vibrational Spectroscopy

    OpenAIRE

    Egorov, Nikolai Borisovich; Akimov, Dmitry Vasilievich; Zhuravlev, Nikolay

    2015-01-01

    Scheme of isotopically enriched SF[6] to elemental sulfur with orthorhombic modification conversion is offered. This scheme includes SF[6] reduction to Li2S by using lithium. The yield of isotopically enriched sulfur is not less than 97% with chemical purity not less than 99.9%. The results which show the dependence of the experimental frequencies in the vibrational spectra on the molecular weight of the sulfur isotope have been obtained.

  20. NMR spectroscopy of lactate in the skeleton muscle: visibility, quantification and measurement of carbon 13 enrichment by double quantum edition; Spectroscopie RMN du lactate dans le muscle squeletique: visibilite, quantification et mesure de l'enrichissement au carbone 13 par edition a double quantum

    Energy Technology Data Exchange (ETDEWEB)

    Jouvensal, L

    1997-12-18

    The metabolism of skeleton muscles gave rise to numerous research works since the beginning of the century in order to make some reply about the muscle physiology with the will to improve the sport performances or the understanding of muscles diseases. This metabolism is complex and the lactate has an importance place; the purpose of this work is to answer these questions with some strategy studies by nuclear magnetic resonance spectroscopy. (N.C.)

  1. Isotopic modeling of the sub-cloud evaporation effect in precipitation.

    Science.gov (United States)

    Salamalikis, V; Argiriou, A A; Dotsika, E

    2016-02-15

    In dry and warm environments sub-cloud evaporation influences the falling raindrops modifying their final stable isotopic content. During their descent from the cloud base towards the ground surface, through the unsaturated atmosphere, hydrometeors are subjected to evaporation whereas the kinetic fractionation results to less depleted or enriched isotopic signatures compared to the initial isotopic composition of the raindrops at cloud base. Nowadays the development of Generalized Climate Models (GCMs) that include isotopic content calculation modules are of great interest for the isotopic tracing of the global hydrological cycle. Therefore the accurate description of the underlying processes affecting stable isotopic content can improve the performance of iso-GCMs. The aim of this study is to model the sub-cloud evaporation effect using a) mixing and b) numerical isotope evaporation models. The isotope-mixing evaporation model simulates the isotopic enrichment (difference between the ground and the cloud base isotopic composition of raindrops) in terms of raindrop size, ambient temperature and relative humidity (RH) at ground level. The isotopic enrichment (Δδ) varies linearly with the evaporated raindrops mass fraction of the raindrop resulting to higher values at drier atmospheres and for smaller raindrops. The relationship between Δδ and RH is described by a 'heat capacity' model providing high correlation coefficients for both isotopes (R(2)>80%) indicating that RH is an ideal indicator of the sub-cloud evaporation effect. Vertical distribution of stable isotopes in falling raindrops is also investigated using a numerical isotope-evaporation model. Temperature and humidity dependence of the vertical isotopic variation is clearly described by the numerical isotopic model showing an increase in the isotopic values with increasing temperature and decreasing RH. At an almost saturated atmosphere (RH=95%) sub-cloud evaporation is negligible and the isotopic

  2. Enrichment: Dealing with overcapacity

    International Nuclear Information System (INIS)

    Today's surplus of enrichment capacity will continue until at least the end of this century. This will challenge the ingenuity of the separative work unit (SWU) suppliers as they attempt to keep market share and remain profitable in a very competitive marketplace. The utilities will be faced with attractive choices, but making the best choice will require careful analysis and increased attention to market factors. Current demand projections will probably prove too high to the extent that more reactors are canceled or delayed. The DOE has the vast majority of the unused capacity, so it will feel the most immediate impact of this large surplus in productive capacity. The DOE has responded to these market challenges by planning another reorganization of its enriching operations. Without a major agreement among the governments affected by the current surplus in enrichment capacity, the future will see lower prices, more competitive terms, and the gradual substitution of centrifuge or laser enrichment for the gaseous diffusion plants. The competition that is forcing the gaseous diffusion prices down to marginal cost will provide the long-term price basis for the enrichment industry

  3. COMPOUND-SPECIFIC CARBON AND HYDROGEN ISOTOPE ANALYSIS-FIELD EVIDENCE OF MTBE BIOREMEDIATION

    Science.gov (United States)

    Chemical reactions (including bio- and abiotic degradation) tend to favor molecules with the lighter isotopic species (e.g., 12C, 1H), resulting in enrichment of the heavier isotopic species (13C, D) in the unreacted substrate, referred to as isotopic fractionation. On the other ...

  4. A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings

    Science.gov (United States)

    Blashenkov, N. M.; Sheshenya, E. S.; Solov'ev, S. M.; Sachenko, V. D.; Gall, L. N.; Zarutskii, I. V.; Gall, N. R.

    2013-05-01

    A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings based on the carbon-13 isotope breath test has been designed and constructed. Important stages of the work included (i) calculating a low-aberration mass analyzer, (ii) manufacturing and testing special gas inlet system, and (iii) creating a small-size collector of ions. The proposed instrument ensures 13C/12C isotopic ratio measurement to within 1.7‰ (pro mille) accuracy, which corresponds to requirements for a diagnostic tool. Preliminary medical testing showed that the mass spectrometer is applicable to practical diagnostics. The instrument is also capable of measuring isotopic ratios of other light elements, including N, O, B (for BF2+ ions), Ar, Cl, and S.

  5. Copper isotope fractionation by desert shrubs

    Energy Technology Data Exchange (ETDEWEB)

    Navarrete, Jesica U., E-mail: jnavarrete2@miners.utep.edu [University of Texas at El Paso, Department of Geological Sciences, 500 W. University Ave, El Paso, TX 79968 (United States); Viveros, Marian; Ellzey, Joanne T. [University of Texas at El Paso, Department of Biological Sciences, El Paso, TX 79968 (United States); Borrok, David M. [University of Texas at El Paso, Department of Geological Sciences, 500 W. University Ave, El Paso, TX 79968 (United States)

    2011-06-15

    Copper has two naturally occurring stable isotopes of masses 63 and 65 which can undergo mass dependent fractionation during various biotic and abiotic chemical reactions. These interactions and their resulting Cu isotope fractionations can be used to determine the mechanisms involved in the cycling of Cu in natural systems. In this study, Cu isotope changes were investigated at the organismal level in the metal-accumulating desert plant, Prosopis pubescens. Initial results suggest that the lighter Cu isotope was preferentially incorporated into the leaves of the plant, which may suggest that Cu was actively transported via intracellular proteins. The roots and stems show a smaller degree of Cu isotope fractionation and the direction and magnitude of the fractionations was dependent upon the levels of Cu exposure. Based on this and previous work with bacteria and yeast, a trend is emerging that suggests the lighter Cu isotope is preferentially incorporated into biological components, while the heavier Cu isotope tends to become enriched in aqueous solutions. In bacteria, plants and animals, intracellular Cu concentrations are strictly regulated via dozens of enzymes that can bind, transport, and store Cu. Many of these enzymes reduce Cu(II) to Cu(I). These initial results seem to fit into a broader picture of Cu isotope cycling in natural systems where oxidation/reduction reactions are fundamental in controlling the distributions of Cu isotopes.

  6. Isotopic Measurement of Uranium by Mass Spectrometry

    International Nuclear Information System (INIS)

    The growing application of atomic energy creates a wider need for precise and accurate knowledge of the isotopic composition of uranium. This information is particularly of great importance in the accountability and transfer of enriched uranium for reactor and research applications involving millions of dollars worth of fissionable materials. Reliable isotopic measurements are also necessary to ensure compliance of fuel element compositions with the reactor design specifications and to permit calculation of process and fuel burn-up losses. Mass spectrometry methods, which far surpass the capabilities of other methods, Were developed for very precise isotopic determinations. These methods, ''Single Standard'' and ''Double Standard'', involve the comparison of measurements of an unknown sample to similar measurements on known standards. Use of the ''Double Standard'' method eliminates the effects of instrument bias, thus permitting isotopic determinations with precisions (95% limit of error) of the order of ± 0.02% of the values. Accuracies are limited only by the knowledge of the standard values used, which are referenced to the series of uranium isotopic standards available from the US National Bureau of Standards. The mass spectrometers are also useful for the absolute determination of isotopic composition of uranium, especially in forms other than UF6. Thermal ionization techniques using high-resolution (approximately 12-in. radius) spectrometers permit the absolute isotopic characterization of the minor isotopes (i.e. those less than 10 wt.%) with an accuracy and precision of about 0.5% of the values per analysis. These analyses are particularly useful in calibrating highly enriched and highly depleted uranium for subsequent use as blending materials in an isotopic standards programme. Both relative and absolute isotopic measurement methods are described as well as their application in the accountability and operational analytical programmes. These applications

  7. Oxygen enrichment incineration

    International Nuclear Information System (INIS)

    Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested

  8. Oxygen enrichment incineration

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Guk; Yang, Hee Chul; Park, Geun Il; Kim, Joon Hyung

    2000-10-01

    Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested.

  9. Isotope effect on the zero point energy shift upon condensation

    International Nuclear Information System (INIS)

    The various isotope-dependent and independent atomic and molecular properties that pertain to the isotopic difference between the zero point energy (ZPE) shifts upon condensation were derived. The theoretical development of the change of the ZPE associated with the internal molecular vibrations, due to the condensation of the gaseous molecules, is presented on the basis of Wolfsberg's second-order perturbation treatment of the isotope-dependent London dispersion forces between liquid molecules. The isotope effect on the ZPE shift is related to the difference between the sums of the integrated intensities of the infrared absorption bands of the two gaseous isotopic molecules. The effective atomic charges are also calculated from available experimental infrared intensity data. The effects of isotopic substitutions of carbon-13 for carbon-12 and/or deuterium for protium, in ethylene, methane, and the fluorinated methanes, CH3F, CH2F2, CHF3, and CF4, on the ZPE shift upon condensation are calculated. These results compare well with the Bigeleisen B-factors, which are experimentally obtained from vapor pressure measurements of the isotopic species. Each of the following molecular properties will tend to increase the isotopic difference between the ZPE shifts upon condensation: (1) large number of highly polar bonds, (2) high molecular weight, (3) non-polar (preferably) or massive molecule, (4) non-hydrogenous molecule, and (5) closely packed liquid molecules. These properties will result in stronger dispersion forces in the liquid phase between the lighter molecules than between the isotopically heavier molecules. 36 tables, 9 figures

  10. Isotope effect on the zero point energy shift upon condensation

    Energy Technology Data Exchange (ETDEWEB)

    Kornblum, Z.C.; Ishida, T.

    1977-07-01

    The various isotope-dependent and independent atomic and molecular properties that pertain to the isotopic difference between the zero point energy (ZPE) shifts upon condensation were derived. The theoretical development of the change of the ZPE associated with the internal molecular vibrations, due to the condensation of the gaseous molecules, is presented on the basis of Wolfsberg's second-order perturbation treatment of the isotope-dependent London dispersion forces between liquid molecules. The isotope effect on the ZPE shift is related to the difference between the sums of the integrated intensities of the infrared absorption bands of the two gaseous isotopic molecules. The effective atomic charges are also calculated from available experimental infrared intensity data. The effects of isotopic substitutions of carbon-13 for carbon-12 and/or deuterium for protium, in ethylene, methane, and the fluorinated methanes, CH/sub 3/F, CH/sub 2/F/sub 2/, CHF/sub 3/, and CF/sub 4/, on the ZPE shift upon condensation are calculated. These results compare well with the Bigeleisen B-factors, which are experimentally obtained from vapor pressure measurements of the isotopic species. Each of the following molecular properties will tend to increase the isotopic difference between the ZPE shifts upon condensation: (1) large number of highly polar bonds, (2) high molecular weight, (3) non-polar (preferably) or massive molecule, (4) non-hydrogenous molecule, and (5) closely packed liquid molecules. These properties will result in stronger dispersion forces in the liquid phase between the lighter molecules than between the isotopically heavier molecules. 36 tables, 9 figures.

  11. Principles of isotopic analysis by mass spectrometry

    International Nuclear Information System (INIS)

    The use of magnetic sector field mass spectrometers in isotopic analysis, especially for nitrogen gas, is outlined. Two measuring methods are pointed out: the scanning mode for significantly enriched samples and the double collector method for samples near the natural abundance of 15N. The calculation formulas are derived and advice is given for corrections. (author)

  12. Oxygen isotopic anomaly and solar nebular photochemistry

    International Nuclear Information System (INIS)

    At the cool periphery of the solar nebula, oxygen could photochemically be formed from water. The mixing of 17O and 18O enriched by the self-shielding effect of 16O2 to the dust grain melted by the shock waves there would explain the oxygen isotopic anomaly in the high-temperature mineral of the carbonaceous meteorites. (Auth.)

  13. Segal Enriched Categories I

    CERN Document Server

    Bacard, Hugo V

    2010-01-01

    We develop a theory of enriched categories over a (higher) category M equipped with a class W of morphisms called homotopy equivalences. We call them Segal M_W -categories. Our motivation was to generalize the notion of "up-to-homotopy monoids" in a monoidal category M, introduced by Leinster. The formalism adopted generalizes the classical Segal categories and extends the theory of enriched category over a bicategory. In particular we have a linear version of Segal categories which did not exist so far. Our goal in this paper is to present the theory and provide some examples. Applications are reserved for the future.

  14. Isotopic analysis of Bothrops atrox in Amazonian forest

    Science.gov (United States)

    Martinez, M. G.; Silva, A. M.; Chalkidis, H.; de Oliveira Júnior, R. C.; Camargo, P. B.

    2012-12-01

    The poisoning of snakes is considered a public health problem, especially in populations from rural areas of tropical and subtropical countries. In Brazil, the 26,000 snakebites, 90% are of the genus Bothrops, and Bothrops atrox species predominant in the Amazon region including all the Brazilian Amazon. Research shows that using stable isotopes, we can verify the isotopic composition of tissues of animals that depend mainly on food, water ingested and inhaled gases. For this study, samples taken from Bothrops atrox (B. atrox), in forest using pitfall traps and fall ("Pitt-fall traps with drift fence"). The analyzes were performed by mass spectrometry, where the analytical error is 0.3‰ for carbon and 0.5‰ to nitrogen. The results of the forest animals are significantly different from results of animal vivarium. The average values of the tissues and venoms of snakes of the forest for carbon-13 and nitrogen-15 are: δ13C = -24.68‰ and δ15N = 14.22‰ and mean values of tissue and poisons snakes vivarium (Instituto Butantan) to carbon-13 and nitrogen-15 are δ13C = -20.47‰ and δ15N = 8.36‰, with a significantly different due to different sources of food animals. Based on all results isotopic δ13C and δ15N, we can suggest that changes as the power of the serpent, (nature and captivity), changes occur in relation to diet and environment as the means of the isotopic data are quite distinct, showing that these changes can also cause metabolic changes in the body of the animal itself and the different periods of turnover of each tissue analyzed.

  15. Advanced uranium enrichment technologies

    International Nuclear Information System (INIS)

    The Advanced Gas Centrifuge and Atomic Vapor Laser Isotope Separation methods are described. The status and potential of the technologies are summarized, the programs outlined, and the economic incentives are noted. How the advanced technologies, once demonstrated, might be deployed so that SWV costs in the 1990s can be significantly reduced is described

  16. Multiple linear regression for isotopic measurements

    Science.gov (United States)

    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.

  17. Practical enrichment technique for 33S (34S)

    International Nuclear Information System (INIS)

    The successful preparation of a macroscopic sample of enriched 33S by laser-induced molecular dissociation is reported. Approach was to induce isotopically selective dissociation of SF6 with CO2-laser pulses and to separate the remaining SF6 from the sulfur-containing reaction products by cryogenic distillation. A 200 Hz, 0.75 J/pulse laser was used for photolysis of low-pressure (less than 1 torr) gas mixtures. The mixture of SF6 and scavenger recirculated continuously throughout the irradiation chamber where the laser pulses selectively dissociated 32SF6 to give the final products: SF4 or SOF2. The unreacted SF6 was enriched in the heavier isotopes: 33S, 34S, and 36S. A 1.3-g sample of SF6 was collected with a 33S enrichment factor of 1.96 and a 34S enrichment factor of 2.25. A similar size sample of depleted (32S) sulfur compounds was also collected. A scavenger was necessary to ensure high yield, and moist hydrogen was found to be best for our conditions. Removal of hydrogen fluoride was also necessary to prevent severe corrosion and to maintain high isotopic selectivity. 6 figures

  18. Enriching Number Knowledge

    Science.gov (United States)

    Mack, Nancy K.

    2011-01-01

    Exploring number systems of other cultures can be an enjoyable learning experience that enriches students' knowledge of numbers and number systems in important ways. It helps students deepen mental computation fluency, knowledge of place value, and equivalent representations for numbers. This article describes how the author designed her…

  19. Designing job enrichment projects.

    Science.gov (United States)

    Clakeley, G L

    1988-01-01

    This paper describes a management strategy for a job satisfaction program utilized in a large occupational therapy department. The goal of the program is to retain satisfied, productive employees and reduce attrition of therapists and assistants. The use of job enrichment projects for occupational therapy assistants will be presented with brief descriptions of two projects. PMID:23944880

  20. Job Enrichment in Extension.

    Science.gov (United States)

    Fourman, Louis S.; Jones, Jo

    1997-01-01

    Interviews with 10 participants in Ohio State University's job enrichment program for midcareer extension agents found that 5 returned to their same jobs after the experience but only 2 felt challenged/renewed. Part-time participation while working made it difficult to balance responsibilities. More information and a structured orientation were…

  1. Enriching the Catalog

    Science.gov (United States)

    Tennant, Roy

    2004-01-01

    After decades of costly and time-consuming effort, nearly all libraries have completed the retrospective conversion of their card catalogs to electronic form. However, bibliographic systems still are really not much more than card catalogs on wheels. Enriched content that Amazon.com takes for granted--such as digitized tables of contents, cover…

  2. Methodology for content enrichment

    NARCIS (Netherlands)

    Nederbragt, H.; Heerlien, M.

    2010-01-01

    The STERNA project mainly focuses on enrichment of existing content of content holding organisations in the natural history domain. Therefore, developing a methodology on how to best integrate one’s content into the STERNA information space is an essential part of the project. This document is the o

  3. Isotope Spectroscopy

    CERN Document Server

    Caffau, E; Bonifacio, P; Ludwig, H -G; Monaco, L; Curto, G Lo; Kamp, I

    2013-01-01

    The measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high-resolution, high-quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived $^6$Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non-LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced ...

  4. Isotopic constraints on the origin of meteoritic organic matter

    Science.gov (United States)

    Kerridge, J. F.

    1991-01-01

    Salient features of the isotopic distribution of H, C and N in the organic material found in carbonaceous meteorites are noted. Most organic fractions are strongly enriched in D with respect to the D/H ratio characteristic of H2 in the protosolar system; substantial variations in C-13/C-12 ratio are found among different molecular species, with oxidised species tending to be C-13 enriched relative to reduced species; some homologous series reveal systematic decrease in C-13/C-12 with increasing C number; considerable variation in N-15/N-14 ratio is observed within organic matter, though no systematic pattern to its distribution has yet emerged; no interelement correlations have been observed between isotope enrichments for the different biogenic elements. The isotopic complexity echoes the molecular diversity observed in meteoritic organic matter and suggests that the organic matter was formed by multiple processes and/or from multiple sources. However, existence of a few systematic patterns points towards survival of isotopic signatures characteristic of one or more specific processes. The widespread D enrichment implies either survival of many species of interstellar molecule or synthesis from a reservoir containing a significant interstellar component. Several of the questions raised above can be addressed by more detailed determination of the distribution of the H, C and N isotopes among different well-characterized molecular fractions. Thus, the present study is aimed at discovering whether the different amino acids have comparable D enrichments, which would imply local synthesis from a D-enriched reservoir, or very viable D enrichments, which would imply survival of some interstellar amino acids. The same approach is also being applied to polycyclic aromatic hydrocarbons. Because the analytical technique employed (secondary ion mass spectrometry) can acquire data for all three isotopic systems from each molecular fraction, any presently obscured interelement

  5. Nickel isotopes and methanogens

    Science.gov (United States)

    Neubeck, A.; Ivarsson, M.

    2013-12-01

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

  6. Si Isotopes of Brownleeite

    Science.gov (United States)

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

    2010-01-01

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

  7. Isotopic effect on thermal physical properties of isotopically modified boron single crystals

    International Nuclear Information System (INIS)

    The measurement of specific heat and thermal conductivity at low temperature for isotopically modified boron single crystals was performed between 0.5 and 100K using relaxation method and steady heat flow method, respectively. The results indicate that the specific heat has obvious divergences at T10B-enriched crystal is about 570 W/m·K, which is 40% larger than that of natural boron crystal. The influence of lattice vibration modes and the isotopic effect on specific heat and thermal conductivity for isotopically modified boron are discussed. (author)

  8. Study of groundwater recharge in Rechna Doab using isotope techniques

    International Nuclear Information System (INIS)

    Isotopic studies were performed in the Rechna Doab area to understand the recharge mechanism, investigate the relative contributions from various sources such as rainfall, rivers and canal system and to estimate the turn over times and replenishment rate of groundwater. The isotopic data suggest that the groundwater in the project area can be divided into different zones each having its own characteristic isotopic composition. The enriched isotopic values show rain recharge and depleted isotopic values are associated with river/canal system while the intermediate isotopic values show a mixing of two or more sources of water. The major contribution, however, comes from canal system. The isotopic data suggest that there is no quick movement of groundwater in the area. 18 figs. (author)

  9. Development of O-18 stable isotope separation technology using membrane

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Woo; Kim, Taek Soo; Choi, Hwa Rim; Park, Sung Hee; Lee, Ki Tae; Chang, Dae Shik

    2006-06-15

    The ultimate goal of this investigation is to develop the separation technology for O-18 oxygen stable isotope used in a cyclotron as a target for production of radioisotope F-18. F-18 is a base material for synthesis of [F-18]FDG radio-pharmaceutical, which is one of the most important tumor diagnostic agent used in PET (Positron Emission Tomography). More specifically, this investigation is focused on three categories as follow, 1) development of the membrane distillation isotope separation process to re-enrich O-18 stable isotope whose isotopic concentration is reduced after used in a cyclotron, 2) development of organic impurity purification technology to remove acetone, methanol, ethanol, and acetonitrile contained in a used cyclotron O-18 enriched target water, and 3) development of a laser absorption spectroscopic system for analyzing oxygen isotopic concentration in water.

  10. Enriched $^{82}$Se for the LUCIFER experiment

    CERN Document Server

    Beeman, J W; Benetti, P; Cardani, L; Casali, N; Chiesa, D; Clemenza, M; Dafinei, I; Di Domizio, S; Ferroni, F; Gironi, L; Giuliani, A; Gotti, C; Laubenstein, M; Maino, M; Nagorny, S; Nisi, S; Nones, C; Orio, F; Pagnanini, L; Pattavina, L; Pessina, G; Piperno, G; Pirro, S; Previtali, E; Rusconi, C; Schäffner, K; Tomei, C; Vignati, M

    2015-01-01

    The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of $^{82}$Se. The matrix which embeds the source is an array of ZnSe crystals, where enriched $^{82}$Se is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3% enriched $^{82}$Se metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of $^{232}$Th, $^{238}$U and $^{235}$U are respectively: $<$61 $\\mu$Bq/kg, $<$110 $\\mu$Bq/kg and $<$74 $\\mu$Bq/kg at 90% C.L.. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the $^{82}$...

  11. Numerical modelling of the jet nozzle enrichment process

    International Nuclear Information System (INIS)

    A numerical model was developed for the simulation of the isotopic enrichment produced by the jet nozzle process. The flow was considered stationary and under ideal gas conditions. The model calculates, for any position of the skimmer piece: (a) values of radial mass concentration profiles for each isotopic species and (b) values of elementary separation effect (Σ sub(A)) and uranium cut (theta). The comparison of the numerical results obtained with the experimental values given in the literature proves the validity of the present work as an initial step in the modelling of the process. (Author)

  12. Carbon and oxygen isotope separation by plasma chemical reactions in carbon monoxide glow discharge

    International Nuclear Information System (INIS)

    The separation of carbon and oxygen isotopes in CO glow discharge has been studied. The isotope enrichment in the products was measured by quadru-pole mass spectrometer. The reaction yield and empirical formula of solid phase products were determined by the gas-volumetric analysis. The stable products obtained in our experiment are CO2 and solid polymers formed on the discharge wall. The polymer consists of both carbon and oxygen and the oxygen/carbon mole ratio in the polymer is 0.35±0.05. Thi isotope enrichment coefficients show a strong negative dependence on discharge current though the relative reaction yields have an opposite tendency. Consequently, the maximum isotope enrichment coefficients for 13C in wall deposit of 2.31 and for 18O in CO2 of 1.37 are obtained when the discharge current and the reaction yields are minimum in our experimental range. The experimental results of isotope enrichment have been compared with theoretical values estimated by an analytical model of literature. The dilution mechanism of the isotope enrichment of stable products is inferred from the isotopic distributions of 13C and 18O in products and theoretical predictions for isotope enrichment. (author)

  13. Isotopic enrichment of forming planetary systems from supernova pollution

    CERN Document Server

    Lichtenberg, Tim; Meyer, Michael R

    2016-01-01

    Heating by short-lived radioisotopes (SLRs) such as aluminum-26 and iron-60 fundamentally shaped the thermal history and interior structure of Solar System planetesimals during the early stages of planetary formation. The subsequent thermo-mechanical evolution, such as internal differentiation or rapid volatile degassing, yields important implications for the final structure, composition and evolution of terrestrial planets. SLR-driven heating in the Solar System is sensitive to the absolute abundance and homogeneity of SLRs within the protoplanetary disk present during the condensation of the first solids. In order to explain the diverse compositions found for extrasolar planets, it is important to understand the distribution of SLRs in active planet formation regions (star clusters) during their first few Myr of evolution. By constraining the range of possible effects, we show how the imprint of SLRs can be extrapolated to exoplanetary systems and derive statistical predictions for the distribution of alumi...

  14. Profile of World Uranium Enrichment Programs-2009

    Energy Technology Data Exchange (ETDEWEB)

    Laughter, Mark D [ORNL

    2009-04-01

    It is generally agreed that the most difficult step in building a nuclear weapon is acquiring fissile material, either plutonium or highly enriched uranium (HEU). Plutonium is produced in a nuclear reactor, whereas HEU is produced using a uranium enrichment process. Enrichment is also an important step in the civil nuclear fuel cycle, in producing low enriched uranium (LEU) for use as fuel for nuclear reactors to generate electricity. However, the same equipment used to produce LEU for nuclear reactor fuel can also be used to produce HEU for weapons. Safeguards at an enrichment plant are the array of assurances and verification techniques that ensure uranium is not diverted or enriched to HEU. There are several techniques for enriching uranium. The two most prevalent are gaseous diffusion, which uses older technology and requires a lot of energy, and gas centrifuge separation, which uses more advanced technology and is more energy efficient. Gaseous diffusion plants (GDPs) provide about 40% of current world enrichment capacity but are being phased out as newer gas centrifuge enrichment plants (GCEPs) are constructed. Estimates of current and future enrichment capacity are always approximate, due to the constant upgrades, expansions, and shutdowns occurring at enrichment plants, largely determined by economic interests. Currently, the world enrichment capacity is approximately 56 million kilogram separative work units (SWU) per year, with 22.5 million in gaseous diffusion and more than 33 million in gas centrifuge plants. Another 34 million SWU/year of capacity is under construction or planned for the near future, almost entirely using gas centrifuge separation. Other less-efficient techniques have also been used in the past, including electromagnetic and aerodynamic separations, but these are considered obsolete, at least from a commercial perspective. Laser isotope separation shows promise as a possible enrichment technique of the future but has yet to be

  15. Standard specification for uranium metal enriched to more than 15 % and less Than 20 % 235U

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This specification covers nuclear grade uranium metal that has either been processed through an enrichment plant, or has been produced by the blending of highly enriched uranium with other uranium, to obtain uranium of any 235U concentration below 20 % (and greater than 15 %) and that is intended for research reactor fuel fabrication. The scope of this specification includes specifications for enriched uranium metal derived from commercial natural uranium, recovered uranium, or highly enriched uranium. Commercial natural uranium, recovered uranium and highly enriched uranium are defined in Section 3. The objectives of this specification are to define the impurity and uranium isotope limits for commercial grade enriched uranium metal. 1.2 This specification is intended to provide the nuclear industry with a standard for enriched uranium metal which is to be used in the production of research reactor fuel. In addition to this specification, the parties concerned may agree to other appropriate conditions. ...

  16. Isotope distribution program at the Oak Ridge National Laboratory with emphasis on medical isotopes

    International Nuclear Information System (INIS)

    The Isotope Distribution Program (IDP) is a group of individual activities with separate and diverse DOE sponsors which share the common mission of the production and distribution of isotope products and the performance of isotope-related services. Its basic mission is to provide isotope products and associated services to the user community by utilizing government-owned facilities that are excess to the primary mission of the DOE. The IDP is in its 41st year of operation. Initially, the program provided research quantities of radioactive materials, and through the 1950's it was the major supplier of radioisotopes for both research and commercial application. Distribution of enriched stable isotopes began in 1954. This paper discusses the use of radioisotopes in medicine and the role that ORNL plays in this field

  17. Synthesis of deleobuvir, a potent hepatitis C virus polymerase inhibitor, and its major metabolites labeled with carbon-13 and carbon-14.

    Science.gov (United States)

    Latli, Bachir; Hrapchak, Matt; Chevliakov, Maxim; Li, Guisheng; Campbell, Scot; Busacca, Carl A; Senanayake, Chris H

    2015-05-30

    Deleobuvir, (2E)-3-(2-{1-[2-(5-bromopyrimidin-2-yl)-3-cyclopentyl-1-methyl-1H-indole-6-carboxamido]cyclobutyl}-1-methyl-1H-benzimidazol-6-yl)prop-2-enoic acid (1), is a non-nucleoside, potent, and selective inhibitor of hepatitis C virus NS5B polymerase. Herein, we describe the detailed synthesis of this compound labeled with carbon-13 and carbon-14. The synthesis of its three major metabolites, namely, the reduced double bond metabolite (2) and the acyl glucuronide derivatives of (1) and (2), is also reported. Aniline-(13) C6 was the starting material to prepare butyl (E)-3-(3-methylamino-4-nitrophenyl-(13) C6 )acrylate [(13) C6 ]-(11) in six steps. This intermediate was then used to obtain [(13) C6 ]-(1) and [(13) C6 ]-(2) in five and four more steps, respectively. For the radioactive synthesis, potassium cyanide-(14) C was used to prepare 1-cylobutylaminoacid [(14) C]-(23) via Buchrer-Bergs reaction. The carbonyl chloride of this acid was then used to access both [(14) C]-(1) and [(14) C]-(2) in four steps. The acyl glucuronide derivatives [(13) C6 ]-(3), [(13) C6 ]-(4) and [(14) C]-(3) were synthesized in three steps from the acids [(13) C6 ]-(1), [(13) C6 ]-(2) and [(14) C]-(1) using known procedures. PMID:25964148

  18. Assessment of the specific absorption rate and calibration of decoupling parameters for proton decoupled carbon-13 MR spectroscopy at 3.0 T

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Moyoko [Biomedical Imaging Group, Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)]. E-mail: moyoko-saitou@aist.go.jp; Matsuda, Tsuyoshi [Imaging Application Tech. Center, GE Yokogawa Medical Systems Ltd., Tokyo (Japan); Tropp, James [General Electric Company, CA (United States); Inubushi, Toshiro [Molecular Neuroscience Research Center, Shiga University of Medical Science, Shiga (Japan); Nakai, Toshiharu [Biomedical Imaging Group, Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan) and Institute of Biomedical Research and Innovation, Kobe (Japan)]. E-mail: t-nakai@aist.go.jp

    2005-08-01

    A strategy for proton decoupled carbon-13 MR spectroscopy ({l_brace}{sup 1}H{r_brace}-{sup 13}C MRS) with a strong static magnetic field (3.0 T) in vivo was investigated. The proton decoupling improves the signal-to-noise ratio, however, the effect of the decoupling power on the human body, especially in strong magnetic fields, should be considered. In order to establish a technique for monitoring the metabolism of glucose in the liver using {l_brace}{sup 1}H{r_brace}-{sup 13}C MRS at 3.0 T, two phantom experiments were performed. To assess whether the decoupling energy conformed to SAR limits defined by the IEC, temperature rises inside an agar gel phantom were monitored during a {l_brace}{sup 1}H{r_brace}-{sup 13}C MRS experiment. Then, the decoupling conditions of a glucose solution phantom were systematically optimized with combinations of decoupling bandwidth and power. The reliability of this procedure was discussed in conjunction with IEC guidelines.

  19. Isotope effects of zinc in crown ether chromatography

    International Nuclear Information System (INIS)

    Isotope separation of zinc has been studied with a polymer-supported crown ether resin packed in glass columns. Chromatography was performed in a break-through manner by feeding a zinc chloride solution into the columns. The mass analysis revealed that the heavier isotope was enriched at the front part of the zinc adsorption band. This result means that the heavier isotopes are preferentially fractionated into the solution phase. The largest single-stage separation coefficient (ε) in the present work is 1.0 x 10-3 for the isotopic pair of 64Zn and 66Zn at 35degC. (author)

  20. Market of stable isotopes produced by gas centrifuges: status and prospects

    International Nuclear Information System (INIS)

    The major consumers on the market of enriched stable isotopes traditionally include nuclear industry, medicine and life sciences, and new technical and scientific applications. The beginning of new millennium has brought the wide application of enriched stable isotopes in fundamental physics experiments that needed tens and hundreds kilograms of various stable isotopes of middle and heavy masses. In addition, the needs of nuclear power industry to develop materials to be used in nuclear power plants capable to reduce formation of radioactive by-products and to prevent cracking in certain metallic components led to production of big amounts of different compounds of zinc depleted with the 64Zn isotope. All these problems have been solved successfully by means of the gas centrifuge technology applied for separation of isotopes other than uranium. As a result the market of enriched/depleted stable isotopes has changed radically in recent years. (authors)

  1. Hominin palaeoecology in Late Pliocene Malawi: First insights from isotopes (13C, 18O in mammal teeth

    Directory of Open Access Journals (Sweden)

    Ottmar Kullmer

    2011-03-01

    Full Text Available Carbon-13 and oxygen-18 abundances were measured in large mammal skeletal remains (tooth enamel, dentine and bone from the Chiwondo Beds in Malawi, which were dated by biostratigraphic correlation to ca. 2.5 million years ago. The biologic isotopic patterns, in particular the difference in carbon-13 abundances between grazers and browsers and the difference in oxygen-18 abundances between semi-aquatic and terrestrial herbivores, were preserved in enamel, but not in dentine and bone. The isotopic results obtained from the skeletal remains from the Chiwondo Beds indicate a dominance of savannah habitats with some trees and shrubs. This environment was more arid than the contemporaneous Ndolanya Beds in Tanzania. The present study confirms that robust australopithecines were able to live in relatively arid environments and were not confined to more mesic environments elsewhere in southern Africa.

  2. Italian activities in uranium enrichment

    International Nuclear Information System (INIS)

    The paper describes Italian activities in uranium enrichment, which have mainly developed along the lines of the two classical processes: gaseous diffusion and centrifuges. Research, development and industrial activities play different roles in the two methods, and a special working group, GIAU, was established by CNEN to help co-ordinate this activity. In the field of gaseous diffusion, R and D effort was, from the start of the programme in 1968, mainly devoted to barriers and compressors, with the object of fully understanding the process and of demonstrating that it was capable of overcoming the main problems in this technology. Isotope separation of UF6 was demonstrated in 1974 at experimental plant level. Cost-sharing contracts were signed between CNEN and industries to build prototypes and ''first-of-a-kind'' components; small production lines have been set up to evaluate economics and assess production quality. Eurodif is partially associated with the development of this activity. On the industrial level, AGIP Nucleare and CNEN were among the promoters of the Eurodif venture from the beginning in 1973 and now own 25% of the shares. In the field of ultracentrifugation, work is still devoted mainly to R and D on the machines. The separation process was demonstrated in 1973 at laboratory level with a Zippe type centrifuge. Later activities aimed at developing high-capacity machines; different solutions are under close scrutiny. Carbon fibres and multiplerotor machines have been mechanically tested, and the first reference design of a small cascade plant has been completed. In the field of laser separation, after a complete and critical survey of different processes under development in other countries, experimental research work is now being undertaken, and experiments on basic aspects of the process are in progress. (author)

  3. Preliminary study of the economics of enriching PWR fuel with a fusion hybrid reactor

    International Nuclear Information System (INIS)

    This study is a comparison of the economics of enriching uranium oxide for pressurized water reactor (PWR) power plant fuel using a fusion hybrid reactor versus the present isotopic enrichment process. The conclusion is that privately owned hybrid fusion reactors, which simultaneously produce electrical power and enrich fuel, are competitive with the gaseous diffusion enrichment process if spent PWR fuel rods are reenriched without refabrication. Analysis of irradiation damage effects should be performed to determine if the fuel rod cladding can withstand the additional irradiation in the hybrid and second PWR power cycle. The cost competitiveness shown by this initial study clearly justifies further investigations

  4. Enrichment marketplace - today (and tomorrow)

    International Nuclear Information System (INIS)

    The technologies and capacities of the four primary sources of enrichment services, the United States Department of Energy, Eurodif, Techsnabexport of the Soviet Union, and Urenco, were given. Forecasts of future capacities and prices of enriched uranium were also included

  5. Interstellar Isotopes: Prospects with ALMA

    Science.gov (United States)

    Charnley Steven B.

    2010-01-01

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

  6. Effects of low-level deuterium enrichment on bacterial growth.

    Directory of Open Access Journals (Sweden)

    Xueshu Xie

    Full Text Available Using very precise (±0.05% measurements of the growth parameters for bacteria E. coli grown on minimal media, we aimed to determine the lowest deuterium concentration at which the adverse effects that are prominent at higher enrichments start to become noticeable. Such a threshold was found at 0.5% D, a surprisingly high value, while the ultralow deuterium concentrations (≤0.25% D showed signs of the opposite trend. Bacterial adaptation for 400 generations in isotopically different environment confirmed preference for ultralow (≤0.25% D enrichment. This effect appears to be similar to those described in sporadic but multiple earlier reports. Possible explanations include hormesis and isotopic resonance phenomena, with the latter explanation being favored.

  7. The measurement of the isotope ratios and concentrations of zinc by thermal ionization mass spectrometry using double isotope dilution

    International Nuclear Information System (INIS)

    The isotope ratios and concentrations of zinc are measured by silicagel-thermal ionization mass spectrometry using the double isotope spikers. The double isotope spikers (70Zn and 67Zn-enriched isotopes) are used to correct the isotope mass fractionation for the zinc isotope ratios, and to certify the zinc concentrations in the unknown samples. The zinc concentrations of these double isotope spikers are surveyed by a spiker made of pure (99.99%) natural zinc metal powder. The correcting factors (fa, ft and fn) of the zinc isotope ratios in the spiked mixture, spike and unspiked samples for the isotope mass fractionation, and the spike-to-unspiked ratios (Xr) of the zinc isotope r in the spiked mixture samples can be obtained to solve the matrix equations by numerical approximation. The natural zinc isotope ratios are: 64Zn/67Zn = 11.8498, 66Zn/67Zn = 6.7977, 68Zn/67Zn = 4.5730 and 70Zn/67Zn = 0.1520. The uncertainties determined of the isotope ratios and concentrations of zinc are +- 0.16% and +-0.31%, respectively

  8. Laser system for isotope separation

    Science.gov (United States)

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

    1990-06-01

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

  9. Separation of uranium isotopes by gas centrifugation

    International Nuclear Information System (INIS)

    The uranium isotope enrichment is studied by means of the countercurrent gas centrifuge driven by thermal convection. A description is given of (a) the transfer and purification of the uranium hexafluoride used as process gas in the present investigation; (b) the countercurrent centrifuge ZG3; (c) the system designed for the introduction and extraction of the process gas from the centrifuge; (d) the measurement of the process gas flow rate through the centrifuge; (e) the determination of the uranium isotopic abundance by mass spectrometry; (f) the operation and mechanical behavior of the centrifuge and (g) the isotope separation experiments, performed, respectively, at total reflux and with production of enriched material. The results from the separation experiments at total reflux are discussed in terms of the enrichment factor variation with the magnitude and flow profile of the countercurrent given by the temperature difference between the rotor covers. As far as the separation experiments with production are concerned, the discussion of their results is presented through the variation of the enrichment factor as a function of the flow rate, the observed asymmetry of the process and the calculated separative power of the centrifuge. (Author)

  10. An evaluation of teeth of ringed seals (Phoca hispida) from Greenland as a matrix to monitor spatial and temporal trends of mercury and stable isotopes.

    OpenAIRE

    Aubail, Aurore; Dietz, Rune; Rigét, Frank; Simon-Bouhet, Benoit; Caurant, Florence

    2010-01-01

    International audience; Total mercury (Hg) concentrations were measured in teeth of ringed seals from Qeqertarsuaq, central West Greenland (1982 to 2006) and Ittoqqortoormiit, central East Greenland (1986 to 2006). Stable isotopic ratios of carbon (13C/12C) and nitrogen (15N/14N) were determined as well to provide insights into diet variations between regions or through time. Mercury concentrations decreased the first years of life of the animals suggesting that Hg had been transferred from t...

  11. Atomic vapor laser isotope separation

    Science.gov (United States)

    Paisner, J. A.

    1988-07-01

    Atomic Vapor Laser Isotope Separation (AVLIS) is a general and powerful technique applicable to many elements. A major present application to the enrichement of uranium for lightwater power reactor fuel has been under development at the Lawrence Livermore National Laboratory since 1973. In June 1985, the Department of Energy announced the selection of AVLIS as the technology to meet future U.S. needs for the internationally competitive production of uranium separative work. Major features of the AVLIS process will be discussed with consideration of the process figures of merit.

  12. Rapid photochemical equilibration of isotope bond ordering in O2

    Science.gov (United States)

    Yeung, Laurence Y.; Ash, Jeanine L.; Young, Edward D.

    2014-09-01

    The abundances of 18O18O and 17O18O in the atmosphere were recently found to be enriched relative to the stochastic distribution of isotopes in O2. The enrichment is believed to arise from O(3P) + O2 isotope exchange reactions, which reorder the isotopes in O2 to a distribution that favors bonds between heavy isotopes. Theoretical predictions and laboratory experiments suggest that the reordered distribution of isotopes should reflect internal isotopic equilibrium, but a laboratory test of this hypothesis for the complete O2 isotopologue system has not yet been realized. Here we use a simple photochemical experiment that reorders the isotopes in O2 at temperatures between 200 K and 350 K. Using simultaneous measurements of five O2 isotopologues, we show that O(3P) + O2 reorders the isotopes in O2 to isotopic equilibrium. Furthermore, we use this scheme to calibrate measurements of isotopic ordering in samples of O2, obtaining Δ36 and Δ35 values within ±0.1‰. Measurements of atmospheric O2 sampled at the University of California, Los Angeles, from 2012 to 2014 have mean values of Δ36 = 1.97 ± 0.07‰ and Δ35 = 1.0 ± 0.1‰ (2 SE; n = 23), with no detectable long-term trend. These measurements are consistent with values for air reported earlier, but with a threefold to fourfold improvement in precision. Together, the experiments and observations support the case that isotopic ordering in tropospheric O2 is altered by O(3P) + O2; however, they also suggest that tropospheric Δ36 and Δ35 values do not reflect complete isotopic equilibration in the troposphere. Isotopic ordering in atmospheric O2 likely reflects the decadal-scale balance of stratospheric and tropospheric air masses modulated by variations in tropospheric photochemistry and convection.

  13. Sulfur Isotopic Characteristics of Coal in China and Sulfur Isotopic Fractionation during Coal—burning Process

    Institute of Scientific and Technical Information of China (English)

    洪业汤; 张鸿斌; 等

    1993-01-01

    The determined results of the sulfur contents and isotopic composition of coal samples from major coal mines in 15 provinces and regions of China show that the coal mined in the north of China is characterized by higher 34S and lower sulfur content, but that in the south of China has lower 34S and higher sulfur content.During the coal-burning process in both indrstrial and daily use of coal as fuel the released sulfur dioxide is always enriched in lighter sulfur isotope relative to the corresponding coal;the particles are always enriched in heavier sulfur isotope.The discussion on the environmental geochemical significance of the above-mentioned results also has been made.

  14. Elementary excitations in isotope-mixed crystals

    International Nuclear Information System (INIS)

    Over the last five decades, the isotope effect has been one of the major research in solids. Most of the physical properties of a solid depend to a greater or lesser degree on its isotopic composition. Scientific interest, technological promise and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor and insulator crystals. A great number of stable isotopes and well-developed methods of their separation has made it possible to date to grow crystals of C, LiH, ZnO, ZnSe, CuCl, GaN, GaAs, CdS, Cu2O, Si, Ge and α-Sn with a controllable isotopic composition. The use of such objects allows the investigation of not only the isotope effects in lattice dynamics (vibrational, elastic and thermal properties) but also the influence of such effects on the electronic states via electron-phonon coupling (the renormalization of the band-to-band transition energy Eg, the exciton binding energy EB and the size of the longitudinal-transverse splitting ΔLT). The thermal conductivity enhancement in the isotopically enriched materials amounts (C; Ge; Si) to almost 10% at room temperature and is close to a factor of six at the thermal conductivity maximum around 20K (Si-case). The change in the lattice constant is Δa/a∼10-3-10-4, while the change δcik in the elastic constants amounts to several percent. The nonlinear dependence of the free exciton luminescence (especially Cx1312C1-x, LiHxD1-x) intensity on the excitation density allows to consider these crystals as potential solid-state lasers in the UV part of the spectrum. Isotopic information storage may consist in assigning the information 'zero' or 'one' to mono-isotopic microislands (or even to single atoms) within a bulk crystalline (or thin film) structure. Isotope information storage and isotope quantum computers are briefly discussed

  15. Investigation of Stable C and Cl Isotope Effects of Trichloroethene and Tetrachloroethylene during Evaporation at Different Temperatures

    Institute of Scientific and Technical Information of China (English)

    Tingting Yu; Yiqun Gan; Aiguo Zhou; Kai Yu; Yunde Liu

    2014-01-01

    There are variations of reported isotope enrichment factors of chlorinated organic contaminants in evaporation processes. Trichloroethene (TCE) and tetrachloroethylene (PCE) were chosen to study carbon and chlorine isotope effects during evaporation at different temperatures. Equilibrium vapor-liquid carbon and chlorine isotope effects experiments were also conducted. In the equilibrium liquid-vapor system, the 13C was enriched but 37Cl was depleted in the vapor phase, being consistent with previous results. For evaporation average carbon isotope enrichment factor εC were +0.28‰± 0.01‰ for TCE and +0.56‰±0.09‰ for PCE at temperature from 20 to 26 ºC. Meanwhile, average chlorine isotope enrichment factor εCl were -1.33‰±0.21‰ for TCE and -1.00‰±0.00‰ for PCE. The results indicate that during evaporation the equilibrium isotope effect attenuates the magnitude of carbon isotope fractionation whereas enhances the chlorine isotope effect. Isotope fractionation during evaporation is determined by both equilibrium and kinetic factors. Chlorine isotope fractionation is influenced by the evaporation rate which is linked to temperature. When using stable isotope to investigate the behavior of chlorinated organic contaminants in groundwater with slow biodegradation rate, the isotope fractionation resulted from evaporation should be taken into consideration. Furthermore, the environment conditions such as temperature are also factors to be considered.

  16. Current Status of the MLIS Uranium Enrichment Process

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Woo; Rhee, Chang Kyu; Kim, Whung Whoe [Nuclear Materials Research Division, Daejeon (Korea, Republic of); Yang, Maeng Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Eerkens, Jeff W. [Isotope Technologies Inc., Woodland (United States)

    2009-05-15

    Well-established energy security is extremely important for the national economy and future prosperity of the country. Many countries are trying to develop and use renewable energy sources such as solar, wind, and tidal power to keep the natural environment clean and safe. Although some have disputed calling nuclear power (which produces {approx}40% of domestic electricity) 'green energy', it deserves credit for this label because of its low CO{sub 2} emission and fuel efficiency. While fuel costs in nuclear power generation are less than 30% and uranium enrichment is only {approx}40% of front-end fuel loop, uranium enrichment is a critical step in nuclear power generation. It is also politically sensitive worldwide due to potential proliferation aspects. Currently, gaseous diffusion and centrifuge are the technologies for uranium enrichment. Since the 70s, many countries have been trying to develop a more advanced and economic technology after the gaseous diffusion process started to loose its economic viability. Among the developed laser-assisted technologies, MLIS (Molecular Laser Isotope Separation) is still under investigation for industrial application while most other laser uranium enrichment technologies have been terminated. In this regard it is worthwhile to review the MLIS processes being developed currently, SILEX (Separation of Isotopes by Laser EXcitation) and CRISLA (Condensation Repression by Isotope Selective Laser Activation). Recently the Canadian company Cameco joined the GE-Hitachi venture by paying $123.8M for a 24% holding, and GE-Hitachi- Cameco is now running the GLE (Global Laser Enrichment) facility using SILEX technology in Wilmington, North Carolina to evaluate commercialization of the process.

  17. Compound specific isotope analysis of organophosphorus pesticides.

    Science.gov (United States)

    Wu, Langping; Yao, Jun; Trebse, Polonca; Zhang, Ning; Richnow, Hans H

    2014-09-01

    Compound-specific isotope analysis (CSIA) has been established as a tool to study the environmental fate of a wide range of contaminants. In this study, CSIA was developed to analyse the stable carbon isotope signatures of the widely used organophosphorus pesticides: dichlorvos, omethoate and dimethoate. The linearity of the GC-C-IRMS system was tested for target pesticides and led to an acceptable isotope composition within the uncertainty of the instrument. In order to assess the accuracy of the developed method, the effect of the evaporation procedure on measured carbon isotope composition (δ(13)C) values was studied and showed that concentration by evaporation of solvents had no significant isotope effect. The CSIA was then applied to investigate isotope fractionation of the hydrolysis and photolysis of selected pesticides. The carbon isotope fractionation of tested pesticides was quantified by the Rayleigh model, which revealed a bulk enrichment factor (ε) of -0.2±0.1‰ for hydrolysis of dichlorvos, -1.0±0.1‰ and -3.7±1.1‰ for hydrolysis and photolysis of dimethoate respectively. This study is a first step towards the application of CSIA to trace the transport and degradation of organophosphorus pesticides in the environment.

  18. Liquid and gas chromatography coupled to isotope ratio mass spectrometry for the determination of 13C-valine isotopic ratios in complex biological samples.

    Science.gov (United States)

    Godin, Jean-Philippe; Breuillé, Denis; Obled, Christiane; Papet, Isabelle; Schierbeek, Henk; Hopfgartner, Gérard; Fay, Laurent-Bernard

    2008-10-01

    On-line gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is commonly used to measure isotopic ratios at natural abundance as well as for tracer studies in nutritional and medical research. However, high-precision (13)C isotopic enrichment can also be measured by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Indeed, LC-IRMS can be used, as shown by the new method reported here, to obtain a baseline separation and to measure (13)C isotopic enrichment of underivatised amino acids (Asp, Thr-Ser, Glu, Pro, Gly, Ala, Cys and Val). In case of Val, at natural abundance, the SD(delta(13)C) reported with this method was found to be below 1 per thousand . Another key feature of the new LC-IRMS method reported in this paper is the comparison of the LC-IRMS approach with the conventional GC-C-IRMS determination. To perform this comparative study, isotopic enrichments were measured from underivatised Val and its N(O, S)-ethoxycarbonyl ethyl ester derivative. Between 0.0 and 1.0 molar percent excess (MPE) (delta(13)C= -12.3 to 150.8 per thousand), the calculated root-mean-square (rms) of SD was 0.38 and 0.46 per thousand and the calculated rms of accuracy was 0.023 and 0.005 MPE, respectively, for GC-C-IRMS and LC-IRMS. Both systems measured accurately low isotopic enrichments (0.002 atom percent excess (APE)) with an SD (APE) of 0.0004. To correlate the relative (delta(13)C) and absolute (atom%, APE and MPE) isotopic enrichment of Val measured by the GC-C-IRMS and LC-IRMS devices, mathematical equations showing the slope and intercept of the curves were established and validated with experimental data between 0.0 to 2.3 MPE. Finally, both GC-C-IRMS and LC-IRMS instruments were also used to assess isotopic enrichment of protein-bound (13)C-Val in tibial epiphysis in a tracer study performed in rats. Isotopic enrichments measured by LC-IRMS and GC-C-IRMS were not statistically different (p>0.05). The results of this work indicate that

  19. Stable water isotope patterns in a climate change hotspot: the isotope hydrology framework of Corsica (western Mediterranean).

    Science.gov (United States)

    van Geldern, Robert; Kuhlemann, Joachim; Schiebel, Ralf; Taubald, Heinrich; Barth, Johannes A C

    2014-06-01

    The Mediterranean is regarded as a region of intense climate change. To better understand future climate change, this area has been the target of several palaeoclimate studies which also studied stable isotope proxies that are directly linked to the stable isotope composition of water, such as tree rings, tooth enamel or speleothems. For such work, it is also essential to establish an isotope hydrology framework of the region of interest. Surface waters from streams and lakes as well as groundwater from springs on the island of Corsica were sampled between 2003 and 2009 for their oxygen and hydrogen isotope compositions. Isotope values from lake waters were enriched in heavier isotopes and define a local evaporation line (LEL). On the other hand, stream and spring waters reflect the isotope composition of local precipitation in the catchment. The intersection of the LEL and the linear fit of the spring and stream waters reflect the mean isotope composition of the annual precipitation (δP) with values of-8.6(± 0.2) ‰ for δ(18)O and-58(± 2) ‰ for δ(2)H. This value is also a good indicator of the average isotope composition of the local groundwater in the island. Surface water samples reflect the altitude isotope effect with a value of-0.17(± 0.02) ‰ per 100 m elevation for oxygen isotopes. At Vizzavona Pass in central Corsica, water samples from two catchments within a lateral distance of only a few hundred metres showed unexpected but systematic differences in their stable isotope composition. At this specific location, the direction of exposure seems to be an important factor. The differences were likely caused by isotopic enrichment during recharge in warm weather conditions in south-exposed valley flanks compared to the opposite, north-exposed valley flanks.

  20. Uranium enrichment by gas centrifuge

    International Nuclear Information System (INIS)

    After recalling the physical principles and the techniques of centrifuge enrichment the report describes the centrifuge enrichment programmes of the various countries concerned and compares this technology with other enrichment technologies like gaseous diffusion, laser, aerodynamic devices and chemical processes. The centrifuge enrichment process is said to be able to replace with advantage the existing enrichment facilities in the short and medium term. Future prospects of the process are also described, like recycled uranium enrichment and economic improvements; research and development needs to achieve the economic prospects are also indicated. Finally the report takes note of the positive aspect of centrifuge enrichment as far as safeguards and nuclear safety are concerned. 27 figs, 113 refs

  1. Anomalous 13C enrichment in modern marine organic carbon

    Science.gov (United States)

    Arthur, M.A.; Dean, W.E.; Claypool, G.E.

    1985-01-01

    Marine organic carbon is heavier isotopically (13C enriched) than most land-plant or terrestrial organic C1. Accordingly, ??13C values of organic C in modern marine sediments are routinely interpreted in terms of the relative proportions of marine and terrestrial sources of the preserved organic matter2,3. When independent geochemical techniques are used to evaluate the source of organic matter in Cretaceous or older rocks, those rocks containing mostly marine organic C are found typically to have lighter (more-negative) ??13C values than rocks containing mostly terrestrial organic C. Here we conclude that marine photosynthesis in mid-Cretaceous and earlier oceans generally resulted in a greater fractionation of C isotopes and produced organic C having lighter ??13C values. Modern marine photosynthesis may be occurring under unusual geological conditions (higher oceanic primary production rates, lower PCO2) that limit dissolved CO2 availability and minimize carbon isotope fractionation4. ?? 1985 Nature Publishing Group.

  2. Isotope separation and advanced manufacturing technology

    Science.gov (United States)

    Carpenter, J.; Kan, T.

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

  3. OXYGEN ISOTOPE FRACTION ATION IN URANIUM OXIDES

    Institute of Scientific and Technical Information of China (English)

    郑永飞

    1995-01-01

    Thermodynamic oxygen isotope factors for uranium oxides have been calculated by means of the modified increment method.The sequence of 18O-enrichment in the uranium oxides with respect to the common rock-forming minerals is predicted as follows:spinelisotopic geothermometry of uranium ores when pairing with other gangue minerals in hydrothermal uranium deposits.

  4. Sulfate in the Palaeoarchean Ocean: Localized Enrichment or Variable Preservation?

    Science.gov (United States)

    Mason, P. R. D.; Roerdink, D. L.; Galic, A.; Martin, W.

    2015-12-01

    The Archean oceans are thought to have been depleted in sulfate, reflecting widespread anoxic conditions and limited input of oxidized sulfur species from atmospheric photolysis. This is supported by the paucity of sulfate-bearing minerals and the relatively limited mass-dependent sulfur isotope fractionation in the majority of the Archean geological record. An exception to this is the occurrence of barite deposits in the Palaeoarchean (3.5-3.2 Ga) which indicate spatial or temporal increases in sulfate concentration. The origin and extent of these enrichments remains controversial and has been difficult to assess due to limited and highly variable data. Here we compile an extensive new database of SIMS multiple sulfur isotope data for pyrite and barite from across the Barberton Greenstone Belt in South Africa in order to further investigate the extent and origin of any sulfate enrichment. Individual pyrites were measured with good stratigraphic and petrographic control. Pyrite δ56Fe was used to further delineate pyrite populations and pathways of pyrite formation. Our new sulfur isotope data support conventional models where a positive Δ33S was derived from heterogeneous photolytic elemental S, with negative Δ33S capturing a homogenized marine sulfate reservoir. Pyrite multiple S isotope data closely track the abundance of barite, suggesting that marine sulfate levels were generally low and that sulfate increases were sporadic and localized. We speculate that the subsequent Neoarchean scarcity was controlled by biological evolution.

  5. Oxygen-18 and carbon-13 records for the last 14,000 years from lacustrine carbonates of Siling-Co (lake) in the Qinghai-Tibetan Plateau

    Science.gov (United States)

    Morinaga, H.; Itota, C.; Isezaki, N.; Goto, H.; Yaskawa, K.; Kusakabe, M.; Liu, J.; Gu, Z.; Yuan, B.; Cong, S.

    1993-12-01

    To understand paleoenvironmental changes for the central Qinghai-Tibetan plateau, we analyzed stable isotopes of oxygen and carbon from calcium carbonates in a bottom sediment core collected from Siling-Co (lake). Five conventional and two Tandetron Acceleration Mass Spectrometry (TAMS) C-14 dates indicate that the core recovered sediments of the last 14,000 years. Calcium carbonates in the sediments seem to be primary carbonates precipitated chemically in the lake, and not clastic particles from limestones distributed around the lake, because of large variation of isotopic ratios, isotopic covariance since 6,000 yr BP and similarity between dates from total calcium carbonates and organic carbon. Their isotopic composition therefore reflects that of the lake water. We present the following paleoenvironmental history over the last 14,000 years in the central part of the plateau, from secular variations of delta O-18, delta C-13 and CaCO3 content throughout the core: (1) Desiccation was dominant during the latter part of the Last Glacial stage (14,000 to 11,000 yr BP). (2) The Last Glacial stage abruptly terminated at 11,000 yr BP. (3) A temperate and stable climate was dominant from 11,000 to 5,000 yr BP. (4) Climatic conditions fluctuated from 5,000 to the present, including two strong desiccation periods (5,000 to 4,000 yr BP and 3,000 to 2,000 yr BP) and an intermediate period of heavy rainfall (4,000 to 3,000 yr BP). This period is also characterized by a covariant O and C isotopic trend.

  6. Conceptualization of groundwater flow of a coastal arid aquifer using isotopic and chemical tools: La Paz, Baja California Sur, Mexico

    Science.gov (United States)

    Tamez-Melendez, Carol; Hernández-Antonio, Arturo; Mahlknecht, Jürgen

    2016-04-01

    Groundwater from the La Paz coastal aquifer in Baja California Sur, Mexico, is the main source of drinking water for the local population. Due to its proximity to the coast, sea water intrusion is the main factor of salinization of groundwater. Other geochemical processes also affect the quality of the aquifer threating its vulnerability. Forty-seven samples were analyzed for ion chemistry and isotopes. A hierarchical cluster analysis was performed for a better interpretation resulting in three main groups and proved for geographical correspondence. Deuterium and d18O ranged from -82 to -52.1 and from -11.6 to -7 permil, respectively, showing that the main recharge originates in the Sierra el Novillo, flowing toward SE-NW direction and in accordance to deuterium excess (d) high evaporation effects (d>10‰) are mostly in the middle portion of the study area and in El Centenario due to high kinetic isotope fractioning related to elevated temperatures. Hydrogeochemistry analyses demonstrated salinization mainly due to sea water intrusion and in second instance due water-rock interaction, where enrichment of Na+ (ranges from 35.7 to 1089 mg/L-1) was present in some samples probably due to weathering of silicates and/or cation exchange in soils with Ca2+ (27.7 to 658 mg/L-1) at clay-surfaces. High concentrations of NO3-2 (ranges from 1.4 to 48.8 mg/L-1), Cl- (ranges from 54.4 to 2960 mg/L-1) and Na+ show that anthropogenic input is mainly coming from an agricultural area (El Centenario-Chametla) where heavy groundwater extractions are made for irrigational purposes, lowering the groundwater table up to 10 m and consequently promoting upconing and salinity concentrations (NaCl). Carbon-13 and radiocarbon ranged from -12.3 to -9.1‰ and from 29.5 to 100.4 pmC, respectively. Distribution of ages (up to ~5000 years) indicates two flow trends (E-W and SE-NW).

  7. Isotopic compositions of cometary matter returned by Stardust.

    Science.gov (United States)

    McKeegan, Kevin D; Aléon, Jerome; Bradley, John; Brownlee, Donald; Busemann, Henner; Butterworth, Anna; Chaussidon, Marc; Fallon, Stewart; Floss, Christine; Gilmour, Jamie; Gounelle, Matthieu; Graham, Giles; Guan, Yunbin; Heck, Philipp R; Hoppe, Peter; Hutcheon, Ian D; Huth, Joachim; Ishii, Hope; Ito, Motoo; Jacobsen, Stein B; Kearsley, Anton; Leshin, Laurie A; Liu, Ming-Chang; Lyon, Ian; Marhas, Kuljeet; Marty, Bernard; Matrajt, Graciela; Meibom, Anders; Messenger, Scott; Mostefaoui, Smail; Mukhopadhyay, Sujoy; Nakamura-Messenger, Keiko; Nittler, Larry; Palma, Russ; Pepin, Robert O; Papanastassiou, Dimitri A; Robert, François; Schlutter, Dennis; Snead, Christopher J; Stadermann, Frank J; Stroud, Rhonda; Tsou, Peter; Westphal, Andrew; Young, Edward D; Ziegler, Karen; Zimmermann, Laurent; Zinner, Ernst

    2006-12-15

    Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single (17)O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is (16)O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.

  8. Stable isotopes of carbon and nitrogen in suspended matter and sediments from the Godavari estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.S.S.; Arya, J.; Subbaiah, Ch.V.; Naidu, S.A.; Gawade, L.; PraveenKumar, P.; Reddy, N.P.C.

    Spatial distribution of the carbon and nitrogen content and their isotopic enrichment in suspended matter and sediments were measured in the Godavari estuary to identify the sources and transformation mechanism of organic matter. Significant...

  9. MUICYCL and MUIFAP: models tracking minor uranium isotopes in the nuclear fuel cycle

    International Nuclear Information System (INIS)

    Two computer programs have been written to provide information on the buildup of minor uranium isotopes in the nuclear fuel cycle. The Minor Uranium Isotope Cycle Program, MUICYCL, tracks fuel through a multiyear campaign cycle of enrichment, reactor burnup, reprocessing, enrichment, etc. MUICYCL facilities include preproduction stockpiles, U235 escalation, and calculation of losses. The Minor Uranium Isotope Flowsheet Analyzer Program, MUIFAP, analyzes one minor isotope in one year of an enrichment operation. The formulation of the enrichment cascade, reactors, and reprocessing facility is presented. Input and output descriptions and sample cases are presented. The programs themselves are documented by short descriptions of each routine, flowcharts, definitions of common blocks and variables, and internal documentation. The programs are written in FORTRAN for use in batch mode

  10. MUICYCL and MUIFAP: models tracking minor uranium isotopes in the nuclear fuel cycle

    Energy Technology Data Exchange (ETDEWEB)

    Blum, S.R.; McLaren, R.A.

    1979-10-01

    Two computer programs have been written to provide information on the buildup of minor uranium isotopes in the nuclear fuel cycle. The Minor Uranium Isotope Cycle Program, MUICYCL, tracks fuel through a multiyear campaign cycle of enrichment, reactor burnup, reprocessing, enrichment, etc. MUICYCL facilities include preproduction stockpiles, U/sup 235/ escalation, and calculation of losses. The Minor Uranium Isotope Flowsheet Analyzer Program, MUIFAP, analyzes one minor isotope in one year of an enrichment operation. The formulation of the enrichment cascade, reactors, and reprocessing facility is presented. Input and output descriptions and sample cases are presented. The programs themselves are documented by short descriptions of each routine, flowcharts, definitions of common blocks and variables, and internal documentation. The programs are written in FORTRAN for use in batch mode.

  11. Transportable calorimeter measurements of highly enriched uranium

    Energy Technology Data Exchange (ETDEWEB)

    Rudy, C.; Bracken, D.S.; Staples, P.; Carrillo, L.

    1997-11-01

    A sensitive calorimeter has been combined with a small temperature-controlled water bath to compose a transportable system that is capable of measuring multikilogram quantities of highly enriched uranium (HEU). The sample chamber size, 5 in. in diameter by 10 in. high, is large enough to hold sufficient HEU metal or high-grade scrap to provide a measurable thermal signal. Calorimetric measurements performed on well-characterized material indicate that the thermal power generated by 93% {sup 235}U samples with 1.0% {sup 234}U can be measured with a precision of about 1% (1 sigma) for 4-kg samples. The transportable system consists of a twin-bridge calorimeter installed inside a 55-gal. stainless steel drum filled with water with heating and cooling supplied by a removable thermoelectric module attached to the side. Isotopic measurements using high-resolution gamma-ray measurements of the HEU samples and analysis with the FRAM code were used to determine the isotopic ratios and specific power of the samples. This information was used to transform the measured thermal power into grams of HEU. Because no physical standards are required, this system could be used for the verification of plutonium, {sup 238}Pu heat sources, or large quantities of metal or other high-grade matrix forms of HEU.

  12. Operating experience with the hydrogen isotope separation system at MOUND

    International Nuclear Information System (INIS)

    The Hydrogen Isotope Separation System (HISS) is a general-purpose tritium recovery and enrichment processor that uses low-temperature distillation as the separation process. HISS processes feed mixtures containing all three isotopes of hydrogen (H, D, T) and yields an enriched tritium product up to 99.95% tritium, while producing a discardable raffinate. The three-column system operates continuously with unattended overnight operation and limited operation during weekends. Production runs with a full still inventory were started in October 1987, with individual runs lasting up to seven weeks

  13. Isotopic Hg in an Allende carbon-rich residue

    Science.gov (United States)

    Reed, G. W., Jr.; Jovanovic, S.

    1990-01-01

    A carbon-rich residue from Allende subjected to stepwise heating yielded two isotopically resolvable types of Hg: one with an (Hg-196)/(Hg-202) concentration ratio the same as terrestrial (monitor) Hg; the other enriched in Hg-196 relative to Hg-202 by about 60 percent. Hg with the 202 isotope enriched relative to 196, as is found in bulk Allende, was not observed. Whether the result of mass fractionation or nucleosynthesis, the distinct types of Hg entered different carrier phases and were not thermally mobilized since the accretion of the Allende parent body.

  14. Atomic vapor laser isotope separation using resonance ionization

    International Nuclear Information System (INIS)

    In June 1985, the Department of Energy announced the selection of atomic vapor laser isotope separation [AVLIS] as the technology to meet the United States' future need for enriched uranium. Resonance photoionization is the heart of the AVLIS process. The authors discuss those fundamental atomic parameters that are necessary for describing isotope-selective resonant multistep photoionization along with the measurement techniques employed. The methodology adopted is illustrated with examples of other elements that are under study in the program. (author)

  15. Stellar condensates in meteorites - Isotopic evidence from noble gases

    Science.gov (United States)

    Lewis, R. S.; Alaerts, L.; Matsuda, J.-I.; Anders, E.

    1979-01-01

    The Murchison carbonaceous chondrite contains three isotopically anomalous noble-gas components of apparently presolar origin: two kinds of Ne-E, (Ne-20)/(Ne-22) less than 0.6, and s-process Kr + Xe (enriched in the even isotopes 82, 84, 86, 128, 130, 132). Their carriers are tentatively identified as spinel and two carbonaceous phases, the principal high-temperature stellar condensates at low and high C/O ratios, respectively.

  16. Electromagnetic isotope separation at the China Institute of Atomic Energy

    Energy Technology Data Exchange (ETDEWEB)

    Li Gongpan; Lin Zhizhou; Xiang Xuyang; Deng Jingting (China Inst. of Atomic Energy, Beijing, BJ (China))

    1992-08-01

    Electromagnetic isotope separation at the China Institute of Atomic Energy (CIAE) is described. Calutron, Nier-Bernas and Freeman ion sources were constructed for ion implantation systems. It was found that some enriched isotope samples were contaminated more by lighter than by heavier neighbors. This phenomenon may be explained if the sputtered particles consist of a considerable percentage of ions. A computer inspection system for recording and processing operation data has been designed. (orig.).

  17. A Segmented, Enriched N-type Germanium Detector for Neutrinoless Double Beta-Decay Experiments

    OpenAIRE

    Leviner, L. E.; Aalseth, C. E.; Ahmed, M. W.; Avignone III, F. T.; Back, H. O.; Barabash, A. S.; Boswell, M.(Los Alamos National Laboratory, Los Alamos, NM 87545, USA); L. De Braeckeleer(Washington U., Seattle); Brudanin, V. B.; Chan, Y-D.; Egorov, V. G.; Elliott, S. R.; Gehman, V. M.; Hossbach, T. W.; Kephart, J. D.

    2013-01-01

    We present data characterizing the performance of the first segmented, N-type Ge detector, isotopically enriched to 85% $^{76}$Ge. This detector, based on the Ortec PT6x2 design and referred to as SEGA (Segmented, Enriched Germanium Assembly), was developed as a possible prototype for neutrinoless double beta-decay measurements by the {\\sc Majorana} collaboration. We present some of the general characteristics (including bias potential, efficiency, leakage current, and integral cross-talk) fo...

  18. Short-Term Response of Soil Bacteria to Carbon Enrichment in Different Soil Microsites ▿

    OpenAIRE

    Monard, C; Binet, F.; Vandenkoornhuyse, P.

    2008-01-01

    The response of bacteria in bulk soil and earthworm casts to carbon enrichment was studied by an RNA stable-isotope probing/terminal restriction fragment length polymorphism strategy with 13C-labeled glucose and acetate. Both the soil microsite status and the carbon enrichment selected rapidly for different active bacterial communities, which resulted in different degradation kinetics. Our study clearly illustrates the biases that are generated by adding C substrates to detect metabolically a...

  19. A molecular organic carbon isotope record of miocene climate changes.

    Science.gov (United States)

    Schoell, M; Schouten, S; Damsté, J S; de Leeuw, J W; Summons, R E

    1994-02-25

    The difference in carbon-13 ((13)C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in (18)O (delta(18)O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (delta(13)C = 25.4 +/- 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C(35) hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing (13)C concentrations in Middle and Late Miocene samples (delta(13)C = -29.5 to -31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone. PMID:17831625

  20. Influence of organic carbon sources and isotope exchange processes between water and nitrate on the fractionation of the stable isotopes 15N/14N and 18O/16O in dissolved nitrate during microbial dentrification in groundwater

    International Nuclear Information System (INIS)

    Stable isotopes of nitrate are commonly used to determine sources and degradation of nitrate. In this study, nitrite oxidizing bacteria were found to promote an oxygen isotope exchange between water and nitrate under anoxic conditions. Also, different carbon sources were found to influence the enrichment of stable isotopes in nitrate during microbial denitrification. Both results refine the stable isotope model of nitrate in respect to nitrate source determination and microbial nitrate reduction.

  1. Stable isotope studies

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, T.

    1992-01-01

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

  2. Method for separating isotopes

    Science.gov (United States)

    Jepson, B.E.

    1975-10-21

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

  3. Stable isotope studies

    International Nuclear Information System (INIS)

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

  4. Metabolic studies in man using stable isotopes

    International Nuclear Information System (INIS)

    In this project, stable isotope compounds and stable isotope pharmaceuticals were used (with emphasis on the application of 15N) to study several aspects of nitrogen metabolism in man. Of the many methods available, the 15N stable isotope tracer technique holds a special position because the methodology for application and nitrogen isotope analysis is proven and reliable. Valid routine methods using 15N analysis by emission spectrometry have been demonstrated. Several methods for the preparation of biological material were developed during our participation in the Coordinated Research Programme. In these studies, direct procedures (i.e. use of diluted urine as a samples without chemical preparation) or rapid isolation methods were favoured. Within the scope of the Analytical Quality Control Service (AQCS) enriched stable isotope reference materials for medical and biological studies were prepared and are now available through the International Atomic Energy Agency. The materials are of special importance as the increasing application of stable isotopes as tracers in medical, biological and agricultural studies has focused interest on reliable measurements of biological material of different origin. 24 refs

  5. Wannier-Mott excitons in isotope-disordered crystals

    International Nuclear Information System (INIS)

    Most of the physical properties of a solid depend to a greater or lesser degree on its isotopic composition. Scientific interest, technological promise and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor and insulator crystals. A systematic analysis is for the first time presented of isotopic and disorder effects observed in crystals of various isotopic composition via low-temperature large-radius exciton spectroscopy. Substituting a light isotope with a heavy one increases the interband transition energy and the binding energy of the Wannier-Mott exciton as well as the magnitude of the longitudinal-transverse splitting. The nonlinear variation of these quantities with the isotope concentration is due to the isotopic disordering of the crystal lattice and is consistent with the concentration dependence of line half-widths in exciton reflection and luminescence spectra. The common nature of the isotopic and disorder effects in the crystals of C, LiH, ZnO, ZnSe, CuCl, CdS, Cu2O, GaAs, Si and Ge is emphasized. The review closes with an outlook on the exciting future possibilities offered through isotope control of a wide range of semiconductor and insulator crystals. (author)

  6. Stable isotopes in leaf water of terrestrial plants.

    Science.gov (United States)

    Cernusak, Lucas A; Barbour, Margaret M; Arndt, Stefan K; Cheesman, Alexander W; English, Nathan B; Feild, Taylor S; Helliker, Brent R; Holloway-Phillips, Meisha M; Holtum, Joseph A M; Kahmen, Ansgar; McInerney, Francesca A; Munksgaard, Niels C; Simonin, Kevin A; Song, Xin; Stuart-Williams, Hilary; West, Jason B; Farquhar, Graham D

    2016-05-01

    Leaf water contains naturally occurring stable isotopes of oxygen and hydrogen in abundances that vary spatially and temporally. When sufficiently understood, these can be harnessed for a wide range of applications. Here, we review the current state of knowledge of stable isotope enrichment of leaf water, and its relevance for isotopic signals incorporated into plant organic matter and atmospheric gases. Models describing evaporative enrichment of leaf water have become increasingly complex over time, reflecting enhanced spatial and temporal resolution. We recommend that practitioners choose a model with a level of complexity suited to their application, and provide guidance. At the same time, there exists some lingering uncertainty about the biophysical processes relevant to patterns of isotopic enrichment in leaf water. An important goal for future research is to link observed variations in isotopic composition to specific anatomical and physiological features of leaves that reflect differences in hydraulic design. New measurement techniques are developing rapidly, enabling determinations of both transpired and leaf water δ(18) O and δ(2) H to be made more easily and at higher temporal resolution than previously possible. We expect these technological advances to spur new developments in our understanding of patterns of stable isotope fractionation in leaf water.

  7. Earthquake forecast enrichment scores

    Directory of Open Access Journals (Sweden)

    Christine Smyth

    2012-03-01

    Full Text Available The Collaboratory for the Study of Earthquake Predictability (CSEP is a global project aimed at testing earthquake forecast models in a fair environment. Various metrics are currently used to evaluate the submitted forecasts. However, the CSEP still lacks easily understandable metrics with which to rank the universal performance of the forecast models. In this research, we modify a well-known and respected metric from another statistical field, bioinformatics, to make it suitable for evaluating earthquake forecasts, such as those submitted to the CSEP initiative. The metric, originally called a gene-set enrichment score, is based on a Kolmogorov-Smirnov statistic. Our modified metric assesses if, over a certain time period, the forecast values at locations where earthquakes have occurred are significantly increased compared to the values for all locations where earthquakes did not occur. Permutation testing allows for a significance value to be placed upon the score. Unlike the metrics currently employed by the CSEP, the score places no assumption on the distribution of earthquake occurrence nor requires an arbitrary reference forecast. In this research, we apply the modified metric to simulated data and real forecast data to show it is a powerful and robust technique, capable of ranking competing earthquake forecasts.

  8. Stable isotopes for heavy element production

    CERN Document Server

    Lommel, B; Hofmann, S; Kindler, B; Klemm, J; Steiner, J; Tinschert, K

    2003-01-01

    The synthesis of heavy elements and the search for new superheavy elements is one of the exciting fields in modern nuclear physics and chemistry. Heavy elements are produced by heavy-ion fusion reactions. Necessary prerequisites are intense heavy-ion beams from pure isotopic material and thin isotopically enriched targets. At GSI the elements from 107 to 112 were produced using targets of Pb and Bi and beams of the most neutron rich isotopes of Cr, Fe, Ni, and Zn. Experimental set-up consisting of target wheel, velocity filter SHIP (Separator for Heavy Ion Reaction Products), and detector system is presented. Status of the ion source techniques for delivering intense and stable beams for this kind of experiment is shortly described. The manufacturing and properties of various source - target combinations used for the synthesis of the elements by now are discussed in detail as well as the possibilities for extending the experiments into the region of superheavy elements.

  9. Isotopic analysis of bullet lead samples

    International Nuclear Information System (INIS)

    The possibility of using the isotopic composition of lead for the identification of bullet lead is investigated. Lead from several spent bullets were converted to lead sulphide and analysed for the isotopic abundances using an MS-7 mass spectrometer. The abundances are measured relative to that for Pb204 was too small to permit differentiation, while the range of variation of Pb206 and Pb207 and the better precision in their analyses permitted differentiating samples from one another. The correlation among the samples examined has been pointed out. The method is complementary to characterisation of bullet leads by the trace element composition. The possibility of using isotopically enriched lead for tagging bullet lead is pointed out. (author)

  10. The design of an automated electrolytic enrichment apparatus for tritium

    Energy Technology Data Exchange (ETDEWEB)

    Myers, J.L.

    1994-12-01

    The Radiation Analytical Sciences Section at Laboratory at Lawrence Livermore National Laboratory performs analysis of low-level tritium concentrations in various natural water samples from the Tri-Valley Area, DOE Nevada Test Site, Site 300 in Tracy, CA, and other various places around the world. Low levels of tritium, a radioactive isotope of hydrogen, which is pre-concentrated in the RAS laboratory using an electrolytic enrichment apparatus. Later these enriched waters are analyzed by liquid scintillation counting to determine the activity of tritium. The enrichment procedure and the subsequent purification process by vacuum distillation are currently undertaken manually, hence being highly labor-intensive. The whole process typically takes about 2 to 3 weeks to complete a batch of 30 samples, with a dedicated personnel operating the process. The goal is to automate the entire process, specifically having the operation PC-LabVIEW{trademark} controlled with real-time monitoring capability. My involvement was in the design and fabrication of a prototypical automated electrolytic enrichment cell. Work will be done on optimizing the electrolytic process by assessing the different parameters of the enrichment procedure. Hardware and software development have also been an integral component of this project.

  11. Seabird modulations of isotopic nitrogen on islands.

    Directory of Open Access Journals (Sweden)

    Stéphane Caut

    Full Text Available The transport of nutrients by migratory animals across ecosystem boundaries can significantly enrich recipient food webs, thereby shaping the ecosystems' structure and function. To illustrate the potential role of islands in enabling the transfer of matter across ecosystem boundaries to be gauged, we investigated the influence of seabirds on nitrogen input on islands. Basing our study on four widely differing islands in terms of their biogeography and ecological characteristics, sampled at different spatial and temporal intervals, we analyzed the nitrogen isotopic values of the main terrestrial ecosystem compartments (vascular plants, arthropods, lizards and rodents and their relationship to seabird values. For each island, the isotopic values of the ecosystem were driven by those of seabirds, which ultimately corresponded to changes in their marine prey. First, terrestrial compartments sampled within seabird colonies were the most enriched in δ(15N compared with those collected at various distances outside colonies. Second, isotopic values of the whole terrestrial ecosystems changed over time, reflecting the values of seabirds and their prey, showing a fast turnover throughout the ecosystems. Our results demonstrate that seabird-derived nutrients not only spread across the terrestrial ecosystems and trophic webs, but also modulate their isotopic values locally and temporally on these islands. The wealth of experimental possibilities in insular ecosystems justifies greater use of these model systems to further our understanding of the modalities of trans-boundary nutrient transfers.

  12. Zinc isotope fractionation on benzo-15-crown-5 resin by liquid chromatography

    International Nuclear Information System (INIS)

    Chromatographic fractionation of zinc isotopes was performed on the synthesized benzo-15-crown-5 resin as a column packing material at 323 K in the breakthrough manner for both a frontal and a rear bands. Zinc adsorption capacity was affected by anion chloride concentration and solvent dielectric constant. The heavier zinc isotopes were found enriched to the solution phase and the lighter zinc isotope was concentrated on the resin phase. The frontal maximum enrichment ratio for isotopic pair of 68Zn/64Zn was 1.0081. The isotope separation coefficients for isotopic pair of 68Zn/64Zn for frontal and rear band, were 5.3x10-4, 4.5x10-4, respectively. (author)

  13. Summary of the Effort to Use Active-induced Time Correlation Techniques to Measure the Enrichment of HEU

    Energy Technology Data Exchange (ETDEWEB)

    McConchie, Seth M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Crye, Jason Michael [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Pena, Kirsten [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Sword, Eric [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mihalczo, John T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-09-30

    This document summarizes the effort to use active-induced time correlation techniques to measure the enrichment of bulk quantities of enriched uranium. In summary, these techniques use an external source to initiate fission chains, and the time distribution of the detected fission chain neutrons is sensitive to the fissile material enrichment. The number of neutrons emitted from a chain is driven by the multiplication of the item, and the enrichment is closely coupled to the multiplication of the item. As the enrichment increases (decreases), the multiplication increases (decreases) if the geometry is held constant. The time distribution of fission chain neutrons is a complex function of the enrichment and material configuration. The enrichment contributes to the probability of a subsequent fission in a chain via the likelihood of fissioning on an even-numbered isotope versus an odd-numbered isotope. The material configuration contributes to the same probability via solid angle effects for neutrons inducing subsequent fissions and the presence of any moderating material. To simplify the ability to accurately measure the enrichment, an associated particle imaging (API) D-T neutron generator and an array of plastic scintillators are used to simultaneously image the item and detect the fission chain neutrons. The image is used to significantly limit the space of enrichment and material configuration and enable the enrichment to be determined unambiguously.

  14. Stereochemistry effect of dicyclohexano-18-crown-6 on zinc isotope separation

    International Nuclear Information System (INIS)

    Zinc isotope fractionation is reported with the pure cis-syn-cis and cis-anti-cis stereoisomers of dicyclohexano-18-crown-6. These structures contribute differently to the enrichment of the Zn isotopes, and the best fractionation was obtained with the cis-syn-cis derivative. (authors)

  15. Carbon and oxygen isotopes in apatite CO2 and co-existing calcite

    International Nuclear Information System (INIS)

    Carbon and oxygen isotopes were analyzed in carbonate apatite CO2 and in co-existing calcite. Both C and O in apatite CO2 are enriched in the respective light isotopes relative to calcite. These results confirm the proposition that carbonate is part of the apatite structure

  16. Oxygen and carbon isotopic composition of limestones and dolomites, bikini and eniwetok atolls

    Science.gov (United States)

    Grant, Gross M.; Tracey, J.I., Jr.

    1966-01-01

    Aragonitic, unconxolidated sediments from the borings on the Eniwetok and Bikini atolls are isotopically identical with unaltered skeletal fragments, whereas the recrystallized limestones exhibit isotopic variations resulting from alteration in meteoric waters during periods of emergence. Dolomites and associated calcites are enriched in O18, perhaps because of interaction with hypersaline brines.

  17. Reduced thermal conductivity of isotopically modulated silicon multilayer structures

    DEFF Research Database (Denmark)

    Bracht, H.; Wehmeier, N.; Eon, S.;

    2012-01-01

    We report measurements of the thermal conductivity of isotopically modulated silicon that consists of alternating layers of highly enriched silicon-28 and silicon-29. A reduced thermal conductivity of the isotopically modulated silicon compared to natural silicon was measured by means of time......-resolved x-ray scattering. Comparison of the experimental results to numerical solutions of the corresponding heat diffusion equations reveals a factor of three lower thermal conductivity of the isotope structure compared to natural Si. Our results demonstrate that the thermal conductivity of silicon can...

  18. Hydrogen-enriched fuels

    Energy Technology Data Exchange (ETDEWEB)

    Roser, R. [NRG Technologies, Inc., Reno, NV (United States)

    1998-08-01

    NRG Technologies, Inc. is attempting to develop hardware and infrastructure that will allow mixtures of hydrogen and conventional fuels to become viable alternatives to conventional fuels alone. This commercialization can be successful if the authors are able to achieve exhaust emission levels of less than 0.03 g/kw-hr NOx and CO; and 0.15 g/kw-hr NMHC at full engine power without the use of exhaust catalysts. The major barriers to achieving these goals are that the lean burn regimes required to meet exhaust emissions goals reduce engine output substantially and tend to exhibit higher-than-normal total hydrocarbon emissions. Also, hydrogen addition to conventional fuels increases fuel cost, and reduces both vehicle range and engine output power. Maintaining low emissions during transient driving cycles has not been demonstrated. A three year test plan has been developed to perform the investigations into the issues described above. During this initial year of funding research has progressed in the following areas: (a) a cost effective single-cylinder research platform was constructed; (b) exhaust gas speciation was performed to characterize the nature of hydrocarbon emissions from hydrogen-enriched natural gas fuels; (c) three H{sub 2}/CH{sub 4} fuel compositions were analyzed using spark timing and equivalence ratio sweeping procedures and finally; (d) a full size pick-up truck platform was converted to run on HCNG fuels. The testing performed in year one of the three year plan represents a baseline from which to assess options for overcoming the stated barriers to success.

  19. Silicon isotopes reveal recycled altered oceanic crust in the mantle sources of Ocean Island Basalts

    CERN Document Server

    Pringle, Emily A; Savage, Paul S; Jackson, Matthew G; Day, James M D

    2016-01-01

    The study of silicon (Si) isotopes in ocean island basalts (OIB) has the potential to discern between different models for the origins of geochemical heterogeneities in the mantle. Relatively large (several per mil per atomic mass unit) Si isotope fractionation occurs in low-temperature environments during biochemical and geochemical precipitation of dissolved Si, where the precipitate is preferentially enriched in the lighter isotopes relative to the dissolved Si. In contrast, only a limited range (tenths of a per mil) of Si isotope fractionation has been observed from high-temperature igneous processes. Therefore, Si isotopes may be useful as tracers for the presence of crustal material within OIB mantle source regions that experienced relatively low-temperature surface processes in a manner similar to other stable isotope systems, such as oxygen. Characterizing the isotopic composition of the mantle is also of central importance to the use of the Si isotope system as a basis for comparisons with other plan...

  20. Isotope-coded ATP Probe for Quantitative Affinity Profiling of ATP-binding Proteins

    OpenAIRE

    Xiao, Yongsheng; Guo, Lei; Wang, Yinsheng

    2013-01-01

    ATP-binding proteins play significant roles in numerous cellular processes. Here, we introduced a novel isotope-coded ATP-affinity probe (ICAP) as acylating agent to simultaneously enrich and incorporate isotope label to ATP-binding proteins. By taking advantage of the quantitative capability of this isotope-coded probe, we devised an affinity profiling strategy to comprehensively characterize ATP-protein interactions at the entire proteome scale. False-positive identification of ATP-binding ...

  1. Extreme Enrichment of Tellurium in Deep-Sea Sediments

    Institute of Scientific and Technical Information of China (English)

    LI Yanhe; WANG Yimin; SONG Hebin; YUE Guoliang

    2005-01-01

    Tellurium is a sort of scattered rare element on the earth.Its concentration is very low in earth's crust,only 1.0 ng/g.However,it has extremely high abundance in Co-rich crusts,marine polymetallic nodules,deep-sea sediments and aerolites.To find out the origin of tellurium enrichment in deep-sea sediments,we analyzed and compared tellurium concentrations and helium isotope compositions in the magnetic parts and those in the bulk parts of deep-sea sediments.The result indicates that the helium content,3He/4He ratio and tellurium concentration are obviously higher in the magnetic parts than those in the bulk parts.The 3He abundance varies synchronously with the tellurium concentration.3He and Te have a distinct positive correlation with each other.It is the first time that the paper brings forward that the extreme enrichment of tellurium in deep-sea sediments,like helium isotope anomalies,probably results from the input of interplanetary dust particles (IDPs).Similarly,the extreme enrichment of tellurium in marine polymetallic nodules and Co-rich crusts is possibly related to IDPs.

  2. Mg Isotopes of the Late Permian Evaporites, New Mexico, USA

    Science.gov (United States)

    Feng, C.; Gao, C. H.; Chang, S. C.

    2015-12-01

    Mg isotope holds promise to decipher the evaporative environment of evaporites. High-precision Mg isotope compositions of the late Permian langbeinites have been measured by using MC-ICPMS. The equilibrium Mg isotope fractionation factor between langbeinite and aqueous Mg2+ solutions has been determined using quantum chemistry calculations. All computations are employed at B3LYP/6-311++G(2d,2p) level and solvation effects are treated by solvent model ("water-droplet" approach), mineral structures are constructed using volume variable cluster models (VVCM). The Mg isotope compositions of the langbeinite samples, whose total formation thickness ranges up to 100 meters, are extremely isotopically lighter than that of modern seawater and relatively homogeneous (δ26MgDSM3 is from -4.12±0.03‰ to -3.81±0.07‰ v.s. -0.83‰ of modern seawater). The computed equilibrium Mg isotope fractionation factors between langbeinite and aqueous Mg2+ solutions are -2.73‰, -2.66‰ and -2.53‰ at 25, 30 and 40 ℃, respectively. These significant equilibrium fractionation factors indicate that a huge equilibrium Mg isotope fractionation between langbeinite and its parent brine can happen during langbeinite depositions, and langbeinites are enriched in isotopically light 24Mg comparing to the brine. Using the computed fractionation factors to simulate a Rayleigh fractionation process of langbeinite Mg precipitation, we find that a significant Mg isotope difference between langbeinite and its growing brine (seawater) is indeed present but the Mg isotope composition of langbeinite merely increase monotonically in a closed system. Because of that, the homogenous Mg isotope compositions of such a thick evaporite sequence suggest a disequlibrium effect rather than an equilibrium Mg isotope fractionation behavior during its formation. Combined with its prevailing Mg-bearing character, the homogenous Mg isotope compositions reveal that this the late Permian langbeinite sequence has

  3. Gradual enrichment of N-15 with humification of diets in a below-ground food web : relationship between N-15 and diet age determined using C-14

    OpenAIRE

    Hyodo, F.; I. Tayasu; Konate, S.; Tondoh, J.E.; Lavelle, Patrick; WADA, E.

    2008-01-01

    1. Stable nitrogen (N) isotope has been widely used to disentangle food webs and to infer trophic positions of organisms based on an assumption that the stepwise enrichment occurs along trophic levels. The enrichment of N-15 in soil organisms with diet humification has also been reported, but the underlying mechanism has not been fully examined. 2. To examine the effect of diet humification on N-15, we estimated the stable N isotope ratios and diet ages of earthworms and termites. These organ...

  4. High enrichment to low enrichment core's conversion. Technical securities

    International Nuclear Information System (INIS)

    This work presents the fulfillment of the technical securities subscribed by INVAP S.E. for the conversion of a high enriched uranium core. The reactor (of 5 thermal Mw), built in the 50's and 60's, is of the 'swimming pool' type, with light water and fuel elements of the curve plates MTR type, enriched at 93.15 %. These are neutronic and thermohydraulic securities. (Author)

  5. Gamma-ray spectrometric enrichment determination of a low enriched UF6 sample

    International Nuclear Information System (INIS)

    Non-destructive gamma-ray spectroscopic measurements have been done on a solid 80-gram UF6 sample in the framework of an interlaboratory measurement evaluation programme for isotopic abundance measurements on low enriched UF6. In the ECN measurements the photopeak areas of the 185.72 keV gamma-rays of 23'5U have been determined with different peak evaluation methods. In spite of the rather large spread in un-certainty values between the different methods, no statistically significant differences in the 235U atomic abundance values have been obtained. The average measured 235U atomic abundance in uranium is 3.480% with a relative uncertainty of 0.2% (2 σ confidence level). The certified value is 3.5001% with a relative uncertainty of 0.03% (2 σ). An explanation for this discrepancy has not been found. (author). 8 refs.; 7 figs.; 20 tabs

  6. Spatial distribution of stable water isotopes in alpine snow cover

    Directory of Open Access Journals (Sweden)

    N. Dietermann

    2013-07-01

    Full Text Available The aim of this study was to analyse and predict the mean stable water isotopic composition of the snow cover at specific geographic locations and altitudes. In addition, the dependence of the isotopic composition of the entire snow cover on altitude was analysed. Snow in four Swiss catchments was sampled at the end of the accumulation period in April 2010 and a second time during snowmelt in May 2010 and analysed for stable isotope composition of 2H and 18O. The sampling was conducted at both south-facing and north-facing slopes at elevation differences of 100 m, for a total altitude difference of approximately 1000 m. The observed variability of isotopic composition of the snow cover was analysed with stepwise multiple linear regression models. The analysis indicated that there is only a limited altitude effect on the isotopic composition when considering all samples. This is due to the high variability of the isotopic composition of the precipitation during the winter months and, in particular in the case of south-facing slopes, an enrichment of heavy isotopes due to intermittent melting processes. This enrichment effect could clearly be observed in the samples which were taken later in the year. A small altitudinal gradient of the isotopic composition could only be observed at some north-facing slopes. However, the dependence of snow depth and the day of the year were significant predictor variables in all models. This study indicates the necessity to further study the variability of water isotopes in the snow cover to increase prediction for isotopic composition of snowmelt and hence increase model performance of residence time models for alpine areas in order to better understand the accumulation processes and the sources of water in the snow cover of high mountains.

  7. Isotope label-aided mass spectrometry reveals the influence of environmental factors on metabolism in single eggs of fruit fly.

    Directory of Open Access Journals (Sweden)

    Te-Wei Tseng

    Full Text Available In order to investigate the influence of light/dark cycle on the biosynthesis of metabolites during oogenesis, here we demonstrate a simple experimental protocol which combines in-vivo isotopic labeling of primary metabolites with mass spectrometric analysis of single eggs of fruit fly (Drosophila melanogaster. First, fruit flies were adapted to light/dark cycle using artificial white light. Second, female flies were incubated with an isotopically labeled sugar ((13C(6-glucose for 12 h--either during the circadian day or the circadian night, at light or at dark. Third, eggs were obtained from the incubated female flies, and analyzed individually by matrix-assisted laser desorption/ionization (MALDI mass spectrometry (MS: this yielded information about the extent of labeling with carbon-13. Since the incorporation of carbon-13 to uridine diphosphate glucose (UDP-glucose in fruit fly eggs is very fast, the labeling of this metabolite was used as an indicator of the biosynthesis of metabolites flies/eggs during 12-h periods, which correspond to circadian day or circadian night. The results reveal that once the flies adapted to the 12-h-light/12-h-dark cycle, the incorporation of carbon-13 to UDP-glucose present in fruit fly eggs was not markedly altered by an acute perturbation to this cycle. This effect may be due to a relationship between biosynthesis of primary metabolites in developing eggs and an alteration to the intake of the labeled substrate - possibly related to the change of the feeding habit. Overall, the study shows the possibility of using MALDI-MS in conjunction with isotopic labeling of small metazoans to unravel the influence of environmental cues on primary metabolism.

  8. Cascades for natural water enrichment in deuterium and oxygen-18 using membrane permeation

    Energy Technology Data Exchange (ETDEWEB)

    Chmielewski, A.G.; Matuszak, A.; Zakrzewska-Trznadel, G. [Inst. of Nuclear Chemistry and Technology, Warsaw (Poland); Van Hook, W.A. [Univ. of Tenneseee, Knoxville (United States); Miljevic, N.R. [Inst. of Nuclear Science, Belgrade (Yugoslavia)

    1993-01-01

    Heavy isotope enrichment of water using a hydrophobic membrane permeation process is described. Simple and ordinary countercurrent cascades will not be of practical interest because of high energy demand. A better solution is to employ a double countercurrent cascade, reutilizing part of the heat of condensation.

  9. Isotopic signatures of lamproite dikes on the eastern Baltic shield

    International Nuclear Information System (INIS)

    The age values, coinciding by Rb-Sr and Sm-Nd, are obtained for lamproits in the eastern party of the Baltic Shield (the Kostamuksha Region): 1230±5 Ma and 1234±80 Ma correspondingly. The magnetic source of lamproites is depletary relative to the Sr isotope composition and enriched relative to the Nd composition

  10. Isotopic fractionation of zinc in tektites

    Science.gov (United States)

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

    2009-01-01

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

  11. Isotopic modeling of the sub-cloud evaporation effect in precipitation.

    Science.gov (United States)

    Salamalikis, V; Argiriou, A A; Dotsika, E

    2016-02-15

    In dry and warm environments sub-cloud evaporation influences the falling raindrops modifying their final stable isotopic content. During their descent from the cloud base towards the ground surface, through the unsaturated atmosphere, hydrometeors are subjected to evaporation whereas the kinetic fractionation results to less depleted or enriched isotopic signatures compared to the initial isotopic composition of the raindrops at cloud base. Nowadays the development of Generalized Climate Models (GCMs) that include isotopic content calculation modules are of great interest for the isotopic tracing of the global hydrological cycle. Therefore the accurate description of the underlying processes affecting stable isotopic content can improve the performance of iso-GCMs. The aim of this study is to model the sub-cloud evaporation effect using a) mixing and b) numerical isotope evaporation models. The isotope-mixing evaporation model simulates the isotopic enrichment (difference between the ground and the cloud base isotopic composition of raindrops) in terms of raindrop size, ambient temperature and relative humidity (RH) at ground level. The isotopic enrichment (Δδ) varies linearly with the evaporated raindrops mass fraction of the raindrop resulting to higher values at drier atmospheres and for smaller raindrops. The relationship between Δδ and RH is described by a 'heat capacity' model providing high correlation coefficients for both isotopes (R(2)>80%) indicating that RH is an ideal indicator of the sub-cloud evaporation effect. Vertical distribution of stable isotopes in falling raindrops is also investigated using a numerical isotope-evaporation model. Temperature and humidity dependence of the vertical isotopic variation is clearly described by the numerical isotopic model showing an increase in the isotopic values with increasing temperature and decreasing RH. At an almost saturated atmosphere (RH=95%) sub-cloud evaporation is negligible and the isotopic

  12. Meadow enriched ACP process algebras

    OpenAIRE

    J.A. Bergstra; Middelburg, C.A.

    2009-01-01

    We introduce the notion of an ACP process algebra. The models of the axiom system ACP are the origin of this notion. ACP process algebras have to do with processes in which no data are involved. We also introduce the notion of a meadow enriched ACP process algebra, which is a simple generalization of the notion of an ACP process algebra to processes in which data are involved. In meadow enriched ACP process algebras, the mathematical structure for data is a meadow.

  13. Isotopic geology; Geologie isotopique

    Energy Technology Data Exchange (ETDEWEB)

    Allegre, C. [Paris-7 Univ. Denis Diderot, 75 (France); Institut de physique du globe de Paris, 75 - Paris (France)

    2005-07-01

    Born from the application to geology of nuclear physics techniques, the isotopic geology has revolutionized the Earth's sciences. Beyond the dating of rocks, the tracer techniques have permitted to reconstruct the Earth's dynamics, to measure the temperatures of the past (giving birth to paleoclimatology) and to understand the history of chemical elements thanks to the analysis of meteorites. Today, all domains of Earth sciences appeal more or less to the methods of isotopic geology. In this book, the author explains the principles, methods and recent advances of this science: 1 - isotopes and radioactivity; 2 - principles of isotope dating; 3 - radio-chronological methods; 4 - cosmogenic isotope chronologies; 5 - uncertainties and radio-chronological results; 6 - geochemistry of radiogenic isotopes; 7 - geochemistry of stable isotopes; 8 - isotopic geology and dynamical analysis of reservoirs. (J.S.)

  14. High enriched lead-206 for small nuclear power plants

    International Nuclear Information System (INIS)

    In modern projects of perspective NPP the preference is returned to fast reactors (FR) with heavy liquid metal coolants. Internal self-hardening, absence of poisoning effects, compensation of uranium fuel burn-out by produced plutonium fuel and other positive features of FR will allow in the long term to lengthen operating campaign of the reactor till 10-12 of years, and service life of FR - till 30-60 of years. As is known, the coolant, circulating through the core of FR, is activated and accumulates long-lived radionuclides. Taking in account the masses of coolant materials in considered FR (20-200 tons) and the scales of an introduction of small NPP in the future, it can be problems with handling a completed coolant after FR removal from exploitation and at realization of repair and emergency activities. There, it is desirable to have a low-activation coolant with low contents of long-lived radionuclides - products of nuclear reactions. In paper, presented at the ICONE-8 conference, it is offered to use lead enriched with isotope Pb-206 as a low-activation coolant for FR. Its contents in a natural mix of lead isotopes make 24 %, and the demanded enrichment of isotope does not exceed 95-98 %. However, usage of a coolant from enriched lead can result in advancing the price of power, owing to what NPP can become noncompetitive in relation to other power sources. The purpose of the present paper - to point that interval of the prices of the product lead-206, at which one it can be demanded for nuclear engineering in large quantities. In the paper possible ways to ease the costs of obtaining the product lead-206 for the need of small nuclear engineering are also considered. (author)

  15. Optical isotope shifts for unstable samarium isotopes

    International Nuclear Information System (INIS)

    Using a tunable dye laser beam intersecting a thermal atomic beam, optical isotope shifts and hyperfine splittings have been measured for the four unstable samarium isotopes between 144Sm and 154Sm, covering the well known transition region from spherical to deformed shapes. (orig.)

  16. The Cascade Design For The Uranium Enrichment Plant Using Centrifuge Technique

    International Nuclear Information System (INIS)

    A cascade containing few number of stages is simply outlined by development of cascade theory. This technique is applied to determine the feed streams and isotopic mass balances calculations for each stage at a cascade using stage cut 1/2. The enriched streams is contacted with the depleted streams is a simple countercurrent mode. An example of the enriched and depleted streams determination and isotopic mass balances calculation at each stage is given to obtained 3% of U-235 as the product. The results show that the optimal number of stages is 13 where 2 stages at the stripping section and 11 stages at the enriching section. The large the number of stages at the stripping section the smaller the U-235 content in the tails, whilst the smaller the separation factor the large the number of stages required. This cascade design can also be used separate a gas mixture other than UF6 gas where its separation factor is large

  17. A status of progress for the Laser Isotope Separation (LIS) process

    Science.gov (United States)

    Delionback, L. M.

    1976-01-01

    An overview of the Laser Isotope Separation (LIS) methodology is given together with illustrations showing a simplified version of the LIS technique, an example of the two-photon photoionization category, and a diagram depicting how the energy levels of various isotope influence the LIS process. Applications were proposed for the LIS system which, in addition to enriching uranium, could in themselves develop into programs of tremendous scope and breadth. These include the treatment of radioactive wastes from light-water nuclear reactors, enriching the deuterium isotope to make heavy-water, and enriching the light isotopes of such elements as titanium for aerospace weight-reducing programs. Economic comparisons of the LIS methodology with the current method of gaseous diffusion indicate an overwhelming advantage; the laser process promises to be 1000 times more efficient. The technique could also be utilized in chemical reactions with the tuned laser serving as a universal catalyst to determine the speed and direction of a chemical reaction.

  18. Comments on proposed legislation to restructure DOE's uranium enrichment program

    International Nuclear Information System (INIS)

    This book focuses on H.R.145, H.R.788, and S.210. Each of the proposed bills would restructure DOE's enrichment program as a government corporation with private financing and would encourage the eventual sale of the corporation to the private sector. In doing so, the bills would, among other things, allow the corporation to set prices to maximize long-term returns; establish a fund to meet the costs of decontamination, decommissioning, and other environmental cleanup costs associated with uranium enrichment activities; transfer interest in DOE's new atomic vapor laser isotope separation (AVLIS) process to the new corporation; and, except for H.R. 145, require the government to pay its share of the costs to clean up mill tailings (mining wastes) generated under government contracts

  19. Magnesium isotope fractionation during carbonatite magmatism at Oldoinyo Lengai, Tanzania

    Science.gov (United States)

    Li, Wang-Ye; Teng, Fang-Zhen; Halama, Ralf; Keller, Jörg; Klaudius, Jurgis

    2016-06-01

    To investigate the behaviour of Mg isotopes during carbonatite magmatism, we analyzed Mg isotopic compositions of natrocarbonatites and peralkaline silicate rocks from Oldoinyo Lengai, Tanzania. The olivine melilitites from the vicinity of Oldoinyo Lengai have homogeneous and mantle-like Mg isotopic compositions (δ26Mg of -0.30 to -0.26‰), indicating limited Mg isotope fractionation during mantle melting. The highly evolved peralkaline silicate rocks not related to silicate-carbonatite liquid immiscibility, including phonolites from the unit Lengai I, combeite-wollastonite nephelinites (CWNs) from the unit Lengai II A and carbonated combeite-wollastonite-melilite nephelinites (carbCWMNs), have δ26Mg values (from -0.25 to -0.10‰) clustered around the mantle value. By contrast, the CWNs from the unit Lengai II B, which evolved from the silicate melts that were presumably generated by silicate-carbonatite liquid immiscibility, have heavier Mg isotopes (δ26Mg of -0.06 to +0.09‰). Such a difference suggests Mg isotope fractionation during liquid immiscibility and implies, based on mass-balance calculations, that the original carbonatite melts at Lengai were isotopically light. The variable and positive δ26Mg values of natrocarbonatites (from +0.13 to +0.37‰) hence require a change of their Mg isotopic compositions subsequent to liquid immiscibility. The negative correlations between δ26Mg values and contents of alkali and alkaline earth metals of natrocarbonatites suggest Mg isotope fractionation during fractional crystallization of carbonatite melts, with heavy Mg isotopes enriched in the residual melts relative to fractionated carbonate minerals. Collectively, significant Mg isotope fractionation may occur during both silicate-carbonatite liquid immiscibility and fractional crystallization of carbonatite melts, making Mg isotopes a potentially useful tracer of these processes relevant to carbonatite petrogenesis.

  20. Statistical clumped isotope signatures.

    Science.gov (United States)

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

    2016-01-01

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

  1. The isotope effect in gadolinium amalgam system

    International Nuclear Information System (INIS)

    Gadolinium is a neutron absorbing material and has been used as a burnable poison contained in the U fuel pellets for LWRs. Among the 7 isotopes of gadolinium, 157 Gd has a special large neutron absorption cross section of 254 000 barn (10 -24 cm2). In this paper gadolinium isotope separation factor for isotopic exchange between Gd 3+ (in solution) and gadolinium amalgam (GdHg) is determined. By electrolysis of aqueous solutions containing gadolinium acetate and lithium citrate, as complexing agent, using the ratio (Li +/Gd3+) = 12, gadolinium amalgam was prepared using a glass electrolyser with Hg as cathode and platinum as anode. The gadolinium amalgam was stirred with HCl solution 1-2N and Gd 3+ is precipitated as oxalate at weak acid pH and then converted to Gd2O3. The remained gadolinium in acetate solution (after electrolysis) was also precipitated as oxalate and converted to Gd2O3. On Gd2O3 samples the isotopic ratios 156 Gd/160 Gd were determined by mass spectrometry, using MAT 261 equipped with a thermal ionisation ion source. Between Gd3+ and Gadolinium amalgam there is an isotopic exchange, the heavy isotope 160 Gd was found to be enriched in Gd3+ while the lighter isotope, 156 Gd, was enriched in GdHg.. The single stage separation factor α (156 Gd/160 Gd) was determined in different experimental conditions: contact time between Gd3+ and GdHg, the yield of GdHg formation, current density. The range of the measured values of α was 1.0013 - 1.00456, average value being 1.0023 at 26 deg. C. The yield of GdHg formation has increased from 37-75.5% for the electrolyser of 40 mm i.d. (S = 12.56 cm2), to 89.6%, for electrolyser of 53 mm i.d. (S = 22 cm2).. After 30 minutes of contact (in electrolysis conditions) between Gd3+ and GdHg there is not an important passage of Gd between the two phases, in these conditions the isotopic exchange of Gd is studied. (authors)

  2. Seasonal variation in stable carbon and nitrogen isotope values of bats reflect environmental baselines.

    Directory of Open Access Journals (Sweden)

    Ana G Popa-Lisseanu

    Full Text Available The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers.

  3. Seasonal variation in stable carbon and nitrogen isotope values of bats reflect environmental baselines.

    Science.gov (United States)

    Popa-Lisseanu, Ana G; Kramer-Schadt, Stephanie; Quetglas, Juan; Delgado-Huertas, Antonio; Kelm, Detlev H; Ibáñez, Carlos

    2015-01-01

    The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers. PMID:25700080

  4. The IMCA: A field instrument for uranium enrichment measurements

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, G.H.; Koskelo, M.; Moeslinger, M. [Canberra Industries, Meriden, CT (United States); Mayer, R.L. II; McGinnis, B.R. [Lockheed Martin Utility Services, Piketon, OH (United States). Portsmouth Gaseous Diffusion Plant; Wishard, B. [International Atomic Energy Agency, Vienna (Austria)

    1996-12-31

    The IMCA (Inspection Multi-Channel Analyzer) is a portable gamma-ray spectrometer designed to measure the enrichment of uranium either in a laboratory or in the field. The IMCA consists of a Canberra InSpector Multi-Channel Analyzer, sodium iodide or a planar germanium detector, and special application software. The system possesses a high degree of automation. The IMCA uses the uranium enrichment meter principle, and is designed to meet the International Atomic Energy Agency (IAEA) requirements for the verification of enriched uranium materials. The IMCA is available with MGA plutonium isotopic analysis software or MGAU uranium analysis software as well. In this paper, the authors present a detailed description of the hardware and software of the IMCA system, as well as results from preliminary measurements testing compliance of IMCA with IAEA requirements using uranium standards and UF6 cylinders. Measurements performed on UF6 cylinders in the field under variable environmental conditions (temperatures ranging from 0 to 35 C) have shown that good results can be achieved. The enrichment of UF6 contained in the cylinder is determined by using calibration constants generated from an instrument calibration, using traceable uranium oxide standards, performed in the laboratory under controlled environmental conditions. The IMCA software is designed to make the necessary matrix and container corrections to ensure that accurate results are achieved in the field.

  5. Probing the Isotopic Composition of Surface Waters Across Isotopic Extremes of Cryogenian Carbonates

    Science.gov (United States)

    Bosak, T.; Matys, E. D.; Bird, L. R.; Macdonald, F. A.; Freeman, K. H.

    2012-12-01

    Neoproterozoic carbonate strata record unusually large and positive carbon isotope values (δ13Ccarb from 4 to 10 per mil), and stratigraphically extensive large negative carbon isotope excursions (δ13Ccarb isotopically extreme carbonates in Neoproterozoic successions remain poorly understood. Little is also known about organisms and metabolisms that cycled carbon in these carbonate strata, because they rarely contain well-preserved organic-rich fossils. To better understand the cycling of carbon during the deposition of the 715-635 Ma Tayshir member of the Tsagaan Oloom Formation, Mongolia, we analyzed δ13Cfossil of two types of organic fossils that occur in 13C- enriched carbonates (+ 5 to 9.9 per mil) and within 13C-depleted carbonates of the Tayshir anomaly (-3 to -6 per mil). Because these organic microfossils are remarkably similar to the tests of modern planktonic, herbivorous tintinnid ciliates and benthic macroscopic red algae, respectively, they can be used as tracers of organic matter production in surface waters. Fossil tests were extracted by acid maceration, cleaned and analyzed morphologically and microscopically. Their carbon isotopic composition was measured using a nano-scaled elemental analyzer inlet (nano-EA-IRMS), with ±1 per mil analytical precision. To date, we analyzed 12 samples of 100-150 organic tests, representing 3 different fossiliferous parts of the Tayshir anomaly (δ13Ccarb +5 per mil), respectively. More samples, including those of fossil algae and tests from the carbonate strata overlying the Tayshir anomaly, are currently being analyzed. Initial data reveal a rather constant isotopic composition of organic carbon in fossil tests (δ13Cfossil), with values of -23 ±1 per mil both within 13C-enriched and 13C-depleted carbonates. The isotopic difference between δ13Cfossil and 13C-enriched carbonates is 28 to 30 per mil, suggesting maximal isotopic fractionation by primary producers, and little environmental (or diagenetic

  6. Conversion and Blending Facility highly enriched uranium to low enriched uranium as uranyl nitrate hexahydrate. Revision 1

    International Nuclear Information System (INIS)

    This Conversion and Blending Facility (CBF) will have two missions: (1) convert HEU materials to pure HEU uranyl nitrate (UNH) and (2) blend pure HEU UNH with depleted and natural UNH to produce HEU UNH crystals. The primary emphasis of this blending operation will be to destroy the weapons capability of large, surplus stockpiles of HEU. The blended LEU product can only be made weapons capable again by the uranium enrichment process. To the extent practical, the chemical and isotopic concentrations of blended LEU product will be held within the specifications required for LWR fuel. Such blended LEU product will be offered to the United States Enrichment Corporation (USEC) to be sold as feed material to the commercial nuclear industry. Otherwise, blended LEU Will be produced as a waste suitable for storage or disposal

  7. Conversion and Blending Facility highly enriched uranium to low enriched uranium as uranyl nitrate hexahydrate. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-07-05

    This Conversion and Blending Facility (CBF) will have two missions: (1) convert HEU materials to pure HEU uranyl nitrate (UNH) and (2) blend pure HEU UNH with depleted and natural UNH to produce HEU UNH crystals. The primary emphasis of this blending operation will be to destroy the weapons capability of large, surplus stockpiles of HEU. The blended LEU product can only be made weapons capable again by the uranium enrichment process. To the extent practical, the chemical and isotopic concentrations of blended LEU product will be held within the specifications required for LWR fuel. Such blended LEU product will be offered to the United States Enrichment Corporation (USEC) to be sold as feed material to the commercial nuclear industry. Otherwise, blended LEU Will be produced as a waste suitable for storage or disposal.

  8. NOx cycle and tropospheric ozone isotope anomaly: an experimental investigation

    Directory of Open Access Journals (Sweden)

    G. Michalski

    2013-04-01

    Full Text Available The oxygen isotope composition of nitrogen oxides (NOx in the atmosphere may be a useful tool for understanding the oxidation of NOx into nitric acid/nitrate in the atmosphere. A set of experiments were conducted to examine changes in isotopic composition of NOx due to O3-NOx photochemical cycling. At low NO2/O2 mixing ratios, NO2 becomes progressively and nearly equally enriched in 17O and 18O over time until it reaches a steady state with Δ17O values of 40.6 ± 1.9‰ and δ18O values of 84.2 ± 4‰, relative to the isotopic composition of the O2 gas. As the mixing ratio increases, isotopic exchange between O atoms and O2 and NOx suppresses the isotopic enrichments. A kinetic model simulating the observed data shows that the isotope effects during ozone formation play a more dominant role compared to kinetic isotope effects during NO oxidation or exchange of NO2. The model results are consistent with the data when the NO + O3 reaction occurs mainly via the transfer of the terminal atom of O3. The model predicts that under tropospheric concentrations of the three reactants, the timescale of NOx isotopic equilibrium ranges from hours (ppbv mixing ratios to days/weeks (pptv and yields steady state Δ17O and δ18O values of 46‰ and 115‰ respectively with respect to Vienna Standard Mean Ocean Water. Interpretation of tropospheric nitrate isotope data can now be done with the derived rate coefficients of the major isotopologue reactions at various pressures.

  9. Isotopes in heterogeneous catalysis

    CERN Document Server

    Hargreaves, Justin SJ

    2006-01-01

    The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

  10. Isotopically controlled semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Haller, Eugene E.

    2001-12-21

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

  11. Isotopic fractionation in a large herbivorous insect, the Auckland tree weta.

    Science.gov (United States)

    Wehi, Priscilla M; Hicks, Brendan J

    2010-12-01

    Determining diet and trophic position of species with stable isotopes requires appropriate trophic enrichment estimates between an animal and its potential foods. These estimates are particularly important for cryptic foragers where there is little comparative dietary information. Nonetheless, many trophic enrichment estimates are based on related taxa, without confirmation of accuracy using laboratory trials. We used stable isotope analysis to investigate diet and to resolve trophic relationships in a large endemic insect, the Auckland tree weta (Hemideina thoracica White). Comparisons of isotopes in plant foods fed to captive wetas with isotope ratios in their frass provided variable results, so frass isotope values had limited usefulness as a proxy indicator of trophic level. Isotopic values varied between different tissues, with trophic depletion of (15)N highest in body fat and testes. Tissue fractionation was consistent in captive and wild caught wetas, and isotopic values were not significantly different between the two groups, suggesting that this weta species is primarily herbivorous. Whole-body values in captive wetas demonstrated trophic depletion (Δδ) for δ(15)N of about -0.77 ‰ and trophic enrichment of 4.28 ‰ for δ(13)C. These values differ from commonly estimated trophic enrichments for both insects and herbivores and indicate the importance of laboratory trials to determine trophic enrichment. Isotopic values for femur muscles from a number of local wild weta populations did not vary consistently with body weight or size, suggesting that juveniles eat the same foods as adults. Considerable variation among individuals within and between populations suggests that isotopic values are strongly influenced by food availability and individual foraging traits. PMID:20709068

  12. Experimental study on stable isotopic fractionation of evaporating water under varying temperature

    Institute of Scientific and Technical Information of China (English)

    Hai-ying HU; Wei-min BAO; Tao WANG; Si-min QU

    2009-01-01

    The variation of stable isotope ratios in natural waters provides valuable information that can be used to trace water movement. Evaporation plays a crucial role in determining the variation of stable isotopes. In this paper, several evaporation experiments were conducted in order to study the stable isotopic fractionation mechanism of water and analyze the influence of different temperatures on evaporation fractionation. Three group experiments of water evaporation under different temperatures and initial isotopic values were carried out. The results show that fractionation factors of hydrogen and oxygen may increase with temperature, and the average enrichment degree of hydrogen isotope D is 3.432 times that of oxygen isotope 18O. The results also show that the isotopic composition of the initial water has little influence on water evaporation fractionation, which is mainly affected by the state variables in the evaporation process, such as temperature. This research provides experimental data for further understanding the evaporation fractionation mechanism.

  13. A Metasomatic Origin for the Enriched Walvis Ridge Basalts

    Science.gov (United States)

    Salters, V. J.

    2008-12-01

    he isotopic composition of the EMI and HIMU are consistent with them containing a component of recycled crust. For HIMU it is suggested that subducted oceanic crust plays an important role and for EMI it is argued that pelagic sediments is present in small but important amounts. One of the "type localities" of the EMI source is the Walvis Ridge, and the most enriched basalts from this locality define the EMI endmember. Models that explain the isotopic composition of the Walvis Ridge basalts need in addition to subducted oceanic crust with sediment a component of subcontinental lithosphere (SCL) [1, 2]. New and more complete data on Walvis Ridge basalts allows a better constrain on its source evolution. The approach has been to explain both the isotopic composition as well as the trace element composition with an as-simple-as possible model. The parent-daughter ratios of the U-Th-Pb, Lu-Hf, Sm-Nd and Rb-Sr system provide a large part of the incompatible trace element pattern. Starting with a bulk silicate Earth composition the isotopic composition can be modeled by a three stage evolution: first as Bulk Silicate Earth which ended by an 4.2 Ga old addition of 1.5% of a low degree garnet melt (1%). This enrichment raised the μ of the system to 10 during the second stage of the sources' history. This enrichment was followed by a 3.9 Ga old depletion equivalent to the extraction of 0.5% melt, again in the garnet stability field. This source then melts to 10% partly in the garnet and partly in the spinel stability field to generate the trace element pattern of the basalts. Because the nuclides represent a large range in half-lives the age constraints are surprisingly strong and especially the early fractionation cannot be younger then 4.1 Ga. Similarly the duration of the second stage is constrained to plus or minus 0.1 Ga. This purely metasomatic origin explains the enriched Walvis ridge basalt source evolution from "cradle to grave" with garden variety processes

  14. Silicon isotopes in angrites and volatile loss in planetesimals

    Science.gov (United States)

    Moynier, Frédéric; Savage, Paul S.; Badro, James; Barrat, Jean-Alix

    2014-01-01

    Inner solar system bodies, including the Earth, Moon, and asteroids, are depleted in volatile elements relative to chondrites. Hypotheses for this volatile element depletion include incomplete condensation from the solar nebula and volatile loss during energetic impacts. These processes are expected to each produce characteristic stable isotope signatures. However, processes of planetary differentiation may also modify the isotopic composition of geochemical reservoirs. Angrites are rare meteorites that crystallized only a few million years after calcium–aluminum-rich inclusions and exhibit extreme depletions in volatile elements relative to chondrites, making them ideal samples with which to study volatile element depletion in the early solar system. Here we present high-precision Si isotope data that show angrites are enriched in the heavy isotopes of Si relative to chondritic meteorites by 50–100 ppm/amu. Silicon is sufficiently volatile such that it may be isotopically fractionated during incomplete condensation or evaporative mass loss, but theoretical calculations and experimental results also predict isotope fractionation under specific conditions of metal–silicate differentiation. We show that the Si isotope composition of angrites cannot be explained by any plausible core formation scenario, but rather reflects isotope fractionation during impact-induced evaporation. Our results indicate planetesimals initially formed from volatile-rich material and were subsequently depleted in volatile elements during accretion. PMID:25404309

  15. MULTIPLE ORIGINS OF NITROGEN ISOTOPIC ANOMALIES IN METEORITES AND COMETS

    International Nuclear Information System (INIS)

    Isotopic fractionation and mixing calculations compared with coupled hydrogen and nitrogen isotopic composition of organic molecules from primitive chondrites, interplanetary dust particles (IDPs), and comets C/1995 O1 (Hale-Bopp) and 81P/Wild2 reveal that meteoritic and cometary organic matter contains three different isotopic components of different origins. (1) A major component of carbonaceous chondrites, IDPs, and comets Hale-Bopp and Wild2 shows correlated H and N isotopic compositions attributable to isotope exchange between an organic matter of solar composition and a reservoir formed by ion-molecule reactions at T 15N-rich component having identical 15N and D enrichments relative to the protosolar gas. Temperatures > 100 K deduced from the low D/H ratio and an anti-correlation between the abundance of this component and meteoritic age indicate a late origin in the solar protoplanetary disk. N2 self-shielding and the non-thermal nucleosynthesis of 15N upon irradiation are possible but unlikely sources of this component, and a chemical origin is preferred. (3) An interstellar component with highly fractionated hydrogen isotopes and unfractionated nitrogen isotopes is present in ordinary chondrites. A dominantly solar origin of D and 15N excesses in primitive solar system bodies shows that isotopic anomalies do not necessarily fingerprint an interstellar origin and implies that only a very small fraction of volatile interstellar matter survived the events of solar system formation.

  16. Copper isotope fractionation during equilibration with natural and synthetic ligands.

    Science.gov (United States)

    Ryan, Brooke M; Kirby, Jason K; Degryse, Fien; Scheiderich, Kathleen; McLaughlin, Mike J

    2014-01-01

    As copper (Cu) stable isotopes emerge as a tool for tracing Cu biogeochemical cycling, an understanding of how Cu isotopes fractionate during complexation with soluble organic ligands in natural waters and soil solutions is required. A Donnan dialysis technique was employed to assess the isotopic fractionation of Cu during complexation with the soluble synthetic ligands ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA) and desferrioxamine B (DFOB), as well as with Suwannee River fulvic acid (SRFA). The results indicated enrichment of the heavy isotope ((65)Cu) in the complexes, with Δ(65)Cu complex-free values ranging from +0.14 to +0.84‰. A strong linear correlation was found between the logarithms of the stability constants of the Cu complexes and the magnitudes of isotopic fractionation. These results show that complexation of Cu by organic ligands can affect the isotopic signature of the free Cu ion. This free Cu is considered the most bioavailable species, and hence, our results highlight the importance of understanding fractionation processes in the uptake medium when using Cu isotopes to study the uptake mechanisms of organisms. These data contribute a vital piece to the emerging picture of Cu isotope cycling in the natural environment, as organic complexation plays a key role in the Cu cycle. PMID:24992660

  17. Uranium enrichment: technology, economics, capacity

    International Nuclear Information System (INIS)

    Large-scale enrichment of uranium has now been carried out for 40 years. While the gaseous diffusion process was the original choice of several countries and continues today to provide the major component of the world production of separative work, the last two decades have witnessed the development of a number of alternative processes for enrichment. These processes, which are being studied and deployed around the world, offer a wide range of technical and economic characteristics which will be useful in assuring adequate capacity to meet projected reactor fuel market needs through the rest of this century at competitive prices. With present uncertainties in future enriched uranium needs, it is apparent that flexibility in the deployment and operation of any enrichment process will be one of the prime considerations for the future. More economical production of separative work not only can have a beneficial impact on reactor fuel costs, but also tends to conserve natural uranium resources. This paper reviews the world scene in the enrichment component of the fuel cycle, including existing or planned commercial-scale facilities and announced R and D efforts on various processes

  18. Isotopic ratios at z=0.68 from molecular absorption lines toward B 0218+357

    CERN Document Server

    Wallstrom, S H J; Guelin, M

    2016-01-01

    Isotopic ratios of heavy elements are a key signature of the nucleosynthesis processes in stellar interiors. The contribution of successive generations of stars to the metal enrichment of the Universe is imprinted on the evolution of isotopic ratios over time. We investigate the isotopic ratios of carbon, nitrogen, oxygen, and sulfur through millimeter molecular absorption lines arising in the z=0.68 absorber toward the blazar B 0218+357. We find that these ratios differ from those observed in the Galactic interstellar medium, but are remarkably close to those in the only other source at intermediate redshift for which isotopic ratios have been measured to date, the z=0.89 absorber in front of PKS1830-211. The isotopic ratios in these two absorbers should reflect enrichment mostly from massive stars, and they are indeed close to the values observed toward local starburst galaxies. Our measurements set constraints on nucleosynthesis and chemical evolution models.

  19. The synthesis of [14C]-3S,4R-4-(4-fluorophenyl)-3-(3,4-methylenedioxyphenoxymethyl) piperidine hydrochloride (BRL 29060A), and mechanistic studies using carbon-13 labelling

    International Nuclear Information System (INIS)

    Paroxetine, BRL 29060A has been labelled with both carbon-14 and carbon-13. Hydroxymethylation of 4-(4-fluorophenyl)-1-methyl-1,2,5,6-tetrahydropyridine, using [14C]formaldehyde, produced an enantiomeric mixture of products which was taken without separation through a multistage sequence. Resolution of the mixture of stereoisomers at the penultimate step gave [14C]BRL 29060A with the required configuration. The overall radiochemical yield was 8%. At some stage in this process, as shown by C-13 labelling studies, scrambling of the label took place to give BRL 29060A with the majority of the label in the C-2 position of the piperidine ring and the remainder at the expected 7-methylene position. Further investigations of this route using carbon-13 as the label are described. When sesamol, (3,4-methylenedioxyphenol) was reacted with the O-benzene sulphonate of -cis-4-(4-fluorophenyl)-3-(hydroxy[13C]methyl-l-methylpiperidine, an inversion of configuration resulted via the previously described 1-aza[3.1.1]bicycloheptane ring system. It is also shown that the corresponding -trans-substituted piperidine, under similar conditions, does not undergo this inversion. (Author)

  20. The synthesis of [[sup 14]C]-3S,4R-4-(4-fluorophenyl)-3-(3,4-methylenedioxyphenoxymethyl) piperidine hydrochloride (BRL 29060A), and mechanistic studies using carbon-13 labelling

    Energy Technology Data Exchange (ETDEWEB)

    Willcocks, K.; Rustidge, D.C.; Tidy, D.J.D. (SmithKline Beecham Pharmaceuticals Research Div., Harlow (United Kingdom)); Barnes, R.D. (SmithKline Beecham Pharmaceuticals Div., Betchworth (United Kingdom). Chemotherapeutic Research Centre)

    1993-01-01

    Paroxetine, BRL 29060A has been labelled with both carbon-14 and carbon-13. Hydroxymethylation of 4-(4-fluorophenyl)-1-methyl-1,2,5,6-tetrahydropyridine, using [[sup 14]C]formaldehyde, produced an enantiomeric mixture of products which was taken without separation through a multistage sequence. Resolution of the mixture of stereoisomers at the penultimate step gave [[sup 14]C]BRL 29060A with the required configuration. The overall radiochemical yield was 8%. At some stage in this process, as shown by C-13 labelling studies, scrambling of the label took place to give BRL 29060A with the majority of the label in the C-2 position of the piperidine ring and the remainder at the expected 7-methylene position. Further investigations of this route using carbon-13 as the label are described. When sesamol, (3,4-methylenedioxyphenol) was reacted with the O-benzene sulphonate of -cis-4-(4-fluorophenyl)-3-(hydroxy[[sup 13]C]methyl-l-methylpiperidine), an inversion of configuration resulted via the previously described 1-aza[3.1.1]bicycloheptane ring system. It is also shown that the corresponding -trans-substituted piperidine, under similar conditions, does not undergo this inversion. (Author).

  1. Fractionation of stable isotopes and impurities during zone recrystallization of metals and preparation of single crystals rich in individual isotopes

    International Nuclear Information System (INIS)

    It is shown that a small number of zone melting (recrystallization) passes results in a periodical distribution of individual isotopes along the material. The effect is observed with the Zn64 and Sn119 isotopes in zinc and tin, respectively. An increase of the number of passes to about ten leads to some preferential final isotope distribution. In the case of Sn119, the tail portion of the material becomes enriched (the portion to which the zone movement is directed), provided that the recrystallization rate is high enough (3 mm/min), or the head portion is enriched if the rate is slow (about 0.5 mm/min). In the presence of bismuth impurities, the isotope Sn119 is in all cases displaced towards the head portion of the material, which suggests a complex nature of the behaviour of individual isotopes during zone melting and an effect of impurities on this process. The Zn64 and Cd119 isotopes may be characterized, in accordance with their respective behaviour in the course of zone melting, by some effective distribution coefficients which are less than unity (K 1) in the latter. (author)

  2. Assignment of congested NMR spectra: Carbonyl backbone enrichment via the Entner Doudoroff pathway

    Science.gov (United States)

    Goldbourt, Amir; Day, Loren A.; McDermott, Ann E.

    2007-12-01

    In NMR spectra of complex proteins, sparse isotope enrichment can be important, in that the removal of many 13C- 13C homonuclear J-couplings can narrow the lines and thereby facilitate the process of spectral assignment and structure elucidation. We present a simple scheme for selective yet extensive isotopic enrichment applicable for production of proteins in organisms utilizing the Entner-Doudoroff (ED) metabolic pathway. An enrichment scheme so derived is demonstrated in the context of a magic-angle spinning solid-state NMR (MAS SSNMR) study of Pf1 bacteriophage, the host of which is Pseudomonas aeruginosa, strain K (PAK), an organism that uses the ED pathway for glucose catabolism. The intact and infectious Pf1 phage in this study was produced by infected PAK cells grown on a minimal medium containing 1- 13C D-glucose ( 13C in position 1) as the sole carbon source, as well as 15NH 4Cl as the only nitrogen source. The 37 MDa Pf1 phage consists of about 93% major coat protein, 1% minor coat proteins, and 6% single-stranded, circular DNA. As a consequence of this composition and the enrichment scheme, the resonances in the MAS SSNMR spectra of the Pf1 sample were almost exclusively due to carbonyl carbons in the major coat protein. Moreover, 3D heteronuclear NCOCX correlation experiments also show that the amino acids leucine, serine, glycine, and tyrosine were not isotopically enriched in their carbonyl positions (although most other amino acids were), which is as expected based upon considerations of the ED metabolic pathway. 3D NCOCX NMR data and 2D 15N- 15N data provided strong verification of many previous assignments of 15N amide and 13C carbonyl shifts in this highly congested spectrum; both the semi-selective enrichment patterns and the narrowed linewidths allowed for greater certainty in the assignments as compared with use of uniformly enriched samples alone.

  3. Use of isotopic tracers in pesticide and environmental contamination research

    International Nuclear Information System (INIS)

    The era of synthetic organic pesticides, starting with DDT and the herbicide 2,4-D about 1940, coincides with that of rapid advances in radiotracer applications. This is indeed fortunate since isotopic experiments are an essential step in evaluating each new pesticide and in continually reassessing older compounds for safety and most efficient utilization. This research is carried out in all developed nations with important supplementation on local problems or use conditions from investigations in the developing countries. Several slides will help illustrate the sequence of studies for establishing the disposition and fate of pesticides and other environmental contaminants.It is clear that very little of the pesticide ever contacts the pest. Pesticide chemicals are generally applied at dosages of 0.2 to 2 kilogram per hectare from one to five or more times per crop season. Less than 0.01% of an insecticide is absorbed or ingested by the pest insect. The remaining amount, more than 99.99%, is an environmental contaminant, a portion of which is a potential residue in food, feed and fibre. Isotopic research is critical in understanding or solving several aspects of the problem. The isotopic label is introduced into the chemical by synthesis in a commercial or university laboratory or in a national or regional atomic research centre. The most common radioisotopes used are tritium, 14carbon, 32phosphorus, 35sulphur and 36chlorine. Stable isotopes are becoming increasingly important in pesticide research, particularly carbon 13, nitrogen 15 and oxygen 18. The initial studies usually involve administration of the 14 carbon-labelled pesticide to rats, which are then held in metabolism cages that allow separate collection of expired gases, urine and faeces. The products in the excreta are identified by various chromatographic and spectroscopic techniques. The persistence of the chemical and its metabolites in various tissues is also determined to make sure that the material

  4. Enrichment of light hydrocarbon mixture

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Dali (Los Alamos, NM); Devlin, David (Santa Fe, NM); Barbero, Robert S. (Santa Cruz, NM); Carrera, Martin E. (Naperville, IL); Colling, Craig W. (Warrenville, IL)

    2011-11-29

    Light hydrocarbon enrichment is accomplished using a vertically oriented distillation column having a plurality of vertically oriented, nonselective micro/mesoporous hollow fibers. Vapor having, for example, both propylene and propane is sent upward through the distillation column in between the hollow fibers. Vapor exits neat the top of the column and is condensed to form a liquid phase that is directed back downward through the lumen of the hollow fibers. As vapor continues to ascend and liquid continues to countercurrently descend, the liquid at the bottom of the column becomes enriched in a higher boiling point, light hydrocarbon (propane, for example) and the vapor at the top becomes enriched in a lower boiling point light hydrocarbon (propylene, for example). The hollow fiber becomes wetted with liquid during the process.

  5. Do birds of like feather flock together? The use of a novel 13C+D combustion isotope analyzer to track bird migration

    Science.gov (United States)

    Saad, N.

    2011-12-01

    Information on spring migration routes, geographic linkages among winter, spring, and breeding locations, and potential geographic effects on arrival body condition of a variety of avian species is so far little known. Stable isotope ratios are exquisitely sensitive to the biochemistry of living organisms and the nutrients available to them. Isotope ratios provide detailed knowledge useful in a variety of fields, including birds migration, through a combination of stable-isotope measurements of carbon (13C/12C) and hydrogen (D/H) isotopes of flight feathers and breast feathers of tissues representing different periods of dietary integration and body composition analyses. Associations among specific geographic areas, habitat use, and arrival condition can be elucidated through the measurement of these dual isotopes. We report here on the development of a novel laser spectroscopy based system for the simultaneous analysis of the stable isotope ratios of carbon (13C/12C) and hydrogen (D/H) that is robust, easy-to-use, and is the first stable isotope ratio analysis system to combine the measurement of 13C/12C and D/H in one simple analysis from a bulk organic sample with an application to bird migration. The system comprises a combustion module to convert the organic sample into CO2 and H2O and a Cavity Ring-Down Spectrometer (CRDS) that analyzes the combustion species inside an optical cavity based on the molecular absorption of individual isotopomers. This CRDS uses dual lasers to target the four isotpomers of interest: 12CO2, 13CO2, H2O and HDO. The system delivers a typical precision of 0.1 permil for δ13C and 1.5 permil for δD that parallels that achieved by IRMS, but with an unprecedented simplicity that allows ecologists to leverage the science and elucidate the avian migration patterns.

  6. A Systematic Approach to Marital Enrichment.

    Science.gov (United States)

    Dinkmeyer, Don; Carlson, Jon

    1986-01-01

    Presents a systematic approach to enriching marital relationships. The history and current status of marital enrichment is reviewed. An Adlerian approach to marital enrichment is described. Applications of the program in enrichment groups, marriage therapy and couple groups are included. (Author)

  7. Potassium isotopic evidence for a high-energy giant impact origin of the Moon

    Science.gov (United States)

    Wang, Kun; Jacobsen, Stein B.

    2016-10-01

    The Earth–Moon system has unique chemical and isotopic signatures compared with other planetary bodies; any successful model for the origin of this system therefore has to satisfy these chemical and isotopic constraints. The Moon is substantially depleted in volatile elements such as potassium compared with the Earth and the bulk solar composition, and it has long been thought to be the result of a catastrophic Moon-forming giant impact event. Volatile-element-depleted bodies such as the Moon were expected to be enriched in heavy potassium isotopes during the loss of volatiles; however such enrichment was never found. Here we report new high-precision potassium isotope data for the Earth, the Moon and chondritic meteorites. We found that the lunar rocks are significantly (>2σ) enriched in the heavy isotopes of potassium compared to the Earth and chondrites (by around 0.4 parts per thousand). The enrichment of the heavy isotope of potassium in lunar rocks compared with those of the Earth and chondrites can be best explained as the result of the incomplete condensation of a bulk silicate Earth vapour at an ambient pressure that is higher than 10 bar. We used these coupled constraints of the chemical loss and isotopic fractionation of K to compare two recent dynamic models that were used to explain the identical non-mass-dependent isotope composition of the Earth and the Moon. Our K isotope result is inconsistent with the low-energy disk equilibration model, but supports the high-energy, high-angular-momentum giant impact model for the origin of the Moon. High-precision potassium isotope data can also be used as a ‘palaeo-barometer’ to reveal the physical conditions during the Moon-forming event.

  8. Light element isotopic compositions of cometary matter returned by the STARDUST mission

    Energy Technology Data Exchange (ETDEWEB)

    McKeegan, K D; Aleon, J; Bradley, J; Brownlee, D; Busemann, H; Butterworth, A; Chaussidon, M; Fallon, S; Floss, C; Gilmour, J; Gounelle, M; Graham, G; Guan, Y; Heck, P R; Hoppe, P; Hutcheon, I D; Huth, J; Ishii, H; Ito, M; Jacobsen, S B; Kearsley, A; Leshin, L A; Liu, M; Lyon, I; Marhas, K; Marty, B; Matrajt, G; Meibom, A; Messenger, S; Mostefaoui, S; Nakamura-Messenger, K; Nittler, L; Palma, R; Pepin, R O; Papanastassiou, D A; Robert, F; Schlutter, D; Snead, C J; Stadermann, F J; Stroud, R; Tsou, P; Westphal, A; Young, E D; Ziegler, K; Zimmermann, L; Zinner, E

    2006-10-10

    Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild2 particle fragments, however extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Non-terrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is {sup 16}O-enriched like refractory inclusions in meteorites, suggesting formation in the hot inner solar nebula and large-scale radial transport prior to comet accretion in the outer solar system.

  9. Dating Cactus: Annual and Sub-annual Variations of Oxygen-18, Carbon-13 and Radiocarbon in Spines of a Columnar Cactus, Carnegiea gigantea.

    Science.gov (United States)

    Dettman, D. L.; English, N. B.; Sandquist, D. R.; Williams, D. G.

    2006-12-01

    , suggesting that isotopes in spine tissue are a good proxy of these climate anomalies. We found similar δ18O, δ13C and F14C variations and relationships in a longer record (172 spines) from a 4.1 m tall saguaro 30 km distant. Temporal isotopic records from saguaro and potentially other long-lived succulent plants may provide useful high-frequency records of ecological responses to climate variation in desert environments where other such records are lacking.

  10. Calcium and Titanium Isotope Fractionation in CAIS: Tracers of Condensation and Inheritance in the Early Solar Protoplanetary Disk

    Science.gov (United States)

    Simon, J. I.; Jordan, M. K.; Tappa, M. J.; Kohl, I. E.; Young, E. D.

    2016-01-01

    The chemical and isotopic compositions of calcium-aluminum-rich inclusions (CAIs) can be used to understand the conditions present in the protoplantary disk where they formed. The isotopic compositions of these early-formed nebular materials are largely controlled by chemical volatility. The isotopic effects of evaporation/sublimation, which are well explained by both theory and experimental work, lead to enrichments of the heavy isotopes that are often exhibited by the moderately refractory elements Mg and Si. Less well understood are the isotopic effects of condensation, which limits our ability to determine whether a CAI is a primary condensate and/or retains any evidence of its primordial formation history.

  11. Fuel preparation for use in the production of medical isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Policke, Timothy A.; Aase, Scott B.; Stagg, William R.

    2016-10-25

    The present invention relates generally to the field of medical isotope production by fission of uranium-235 and the fuel utilized therein (e.g., the production of suitable Low Enriched Uranium (LEU is uranium having 20 weight percent or less uranium-235) fuel for medical isotope production) and, in particular to a method for producing LEU fuel and a LEU fuel product that is suitable for use in the production of medical isotopes. In one embodiment, the LEU fuel of the present invention is designed to be utilized in an Aqueous Homogeneous Reactor (AHR) for the production of various medical isotopes including, but not limited to, molybdenum-99, cesium-137, iodine-131, strontium-89, xenon-133 and yttrium-90.

  12. Oxygen isotope correlation of cetacean bone phosphate with environmental water

    Science.gov (United States)

    Yoshida, Naohiro; Miyazaki, Nobuyuki

    1991-01-01

    The variation with time in the oxygen isotope ratio of the oceans is of prime interest in a variety of research fields. An excellent correlation between oxygen isotope ratios of cetacean (whales, dolphins, and porpoises) bone phosphate and their environmental water is found in this study. Bone phosphate samples of dolphins living in fresh waters are more depleted in oxygen 18 than those of cetaceans living in the oceans, reflecting the clear difference in the isotope composition of water. Cetaceans distributed in the higher latitudes in the oceans are more depleted in oxygen 18 than those distributed in the lower latitudes where seawater is slightly enriched in oxygen 18 relative to that in the higher latitudes. The present results provide a promising tool for estimating the oxygen isotope ratio of the oceanic water of the past without assuming water temperature.

  13. VARIATIONS IN ISOTOPIC COMPOSITIONS OF CHLORINE IN EVAPORATION-CONTROLLED SALT LAKE BRINES OF QAIDAM BASIN,CHINA

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The variations in the isotopic compositions of chlorine in evaporation-controlled saline lake brines were determined by using an improved procedure for precise measurement of chlorine isotopes based on Cs2Cl+ ion by thermal ionization mass spectrometry. The results showed that variation in δ37Cl values in these evaporation-controlled brines are attributable to evaporation of brine accompanied by the deposition of saline minerals. The isotopic fractionation of chlorine between the deposited saline mineral and the co-existing brine caused the variation of δ37Cl values in the brine. In general the isotopic fractionation of chlorine in nature indicates enrichment of 37Cl in the solid phase relative to 35Cl. The reverse isotopic fractionation of chlorine in which 35Cl is enriched in the solid phase, was observed to some extent during quick deposition under laboratory conditions as well as in nature. The mechanism of isotopic fractionation of chlorine during evaporation deposition was studied.

  14. Technical evaluation on some chemical exchange process for uranium enrichment

    International Nuclear Information System (INIS)

    In CEA in France, Asahi Chemical Industry Co., Ltd., in Japan and others, the industrialization of the uranium enrichment by chemical processes has been studied independently for ten years, using large amount of research expenses. In this study, technological examination was carried out on such processes and their separation characteristics, based on the published literatures. As the results, it was recognized that they have sufficient separation capability to aim at the industrialization, and the power required can be limited relatively low. However, very precise plant design and operation control system are required for them, and it is necessary to watch the future course to carry out the objective evaluation of the economic efficiency. The electric power has become a dominant factor in the production cost of enriched uranium. The separation of uranium isotopes with anion exchange resin being developed by Asahi Chemical Industry Co., Ltd., and the isotope separation by electron exchange using solvent extraction method being developed by CEA in France are introduced. Though the equilibrium separation factor is very small, they utilize reversible processes, and have the possibility of large power reduction and the cost reduction due to scaling-up. (Kako, I.)

  15. (n,γ) Experiments on tin isotopes

    International Nuclear Information System (INIS)

    Neutron capture experiments on highly enriched 117,119Sn isotopes were performed with the DANCE detector array located at the Los Alamos Neutron Science Center. The DANCE detector provides detailed information about the multi-step γ-ray cascade following neutron capture. Analysis of the experimental data provides important information to improve understanding of the neutron capture reaction, including a test of the statistical model, the assignment of spins and parities of neutron resonances, and information concerning the Photon Strength Function (PSF) and Level Density (LD) below the neutron separation energy. Preliminary results for the (n,γ) reaction on 117,119Sn are presented. Resonance spins of the odd-A tin isotopes were almost completely unknown. Resonance spins and parities have been assigned via analysis of the multi-step γ-ray spectra and directional correlations.

  16. Meadow enriched ACP process algebras

    NARCIS (Netherlands)

    J.A. Bergstra; C.A. Middelburg

    2009-01-01

    We introduce the notion of an ACP process algebra. The models of the axiom system ACP are the origin of this notion. ACP process algebras have to do with processes in which no data are involved. We also introduce the notion of a meadow enriched ACP process algebra, which is a simple generalization o

  17. Environmental Development Plan: uranium enrichment

    International Nuclear Information System (INIS)

    This Environmental Development Plan identifies and examines the environmental, health, safety, and socioeconomic concerns and corresponding requirements associated with the DOE research, development, demonstration, and operation of the Uranium Enrichment program, including the gaseous diffusion process, the centrifuge process, centrifuge rotor fabrication, and related research and development activities

  18. Do water isotopes reflect differences in timber harvest practices? Isotope ecohydrology in the Mica Creek watershed, Idaho, USA

    International Nuclear Information System (INIS)

    The impacts of timber harvesting techniques on the water balance and flow regime were studied at the catchment scale at the Mica Creek Experimental Watershed (97 km2, 975 - 1,750 m a.s.l.) in northwestern Idaho, USA. These studies relied on stable isotopic techniques to assess the variation in water isotope fluxes of clear-cut, partial-cut (thinned), and unimpacted forest sites. Precipitation, stream flow, soil water, and sap flow, and stable isotope concentrations (deuterium and oxygen-18) of these components were measured on a monthly basis starting in fall 2004. The isotopic composition of sap flow appeared to reflect differential canopy interception losses, with greater enrichment under the densest canopies. (author)

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

    International Nuclear Information System (INIS)

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

  20. Enantiospecific C(sp3)-H activation catalyzed by ruthenium nanoparticles : application to isotopic labeling of molecules of biological interest.

    OpenAIRE

    Taglang, Céline

    2015-01-01

    Isotopic labeling with deuterium and tritium is extensively used in chemistry, biology and pharmaceutical research.Numerous methods of labeling by isotopic exchange allow high isotopic enrichments but generally require harsh conditions (high temperatures, acidity). As a consequence, a general, regioselective and smooth labeling method that might be applicable to a wide diversity of substrates remains to develop. In the first part of this thesis, we demonstrated that the use of ruthenium nanop...

  1. Stable isotope separation in calutrons: Forty years of production and distribution

    International Nuclear Information System (INIS)

    The stable isotope separation program, established in 1945, has operated continually to provide enriched stable isotopes and selected radioactive isotopes, including the actinides, for use in research, medicine, and industrial applications. This report summarizes the first forty years of effort in the production and distribution of stable isotopes. Evolution of the program along with the research and development, chemical processing, and production efforts are highlighted. A total of 3.86 million separator hours has been utilized to separate 235 isotopes of 56 elements. Relative effort expended toward processing each of these elements is shown. Collection rates (mg/separator h), which vary by a factor of 20,000 from the highest to the lowest (205Tl to 46Ca), and the attainable isotopic purity for each isotope are presented. Policies related to isotope pricing, isotope distribution, and support for the enrichment program are discussed. Changes in government funding, coupled with large variations in sales revenue, have resulted in 7-fold perturbations in production levels

  2. Isotope separation principles

    Energy Technology Data Exchange (ETDEWEB)

    Benedict, Manson

    1963-03-15

    Isotope separation theory of ideal cascades is discussed. It is shown how the most important characteristics of an isotope separation process can be worked out from the compositions and flow rates of the feed and product streams. These characteristics include plant size, dependence of product rate on product purity, minimum power consumption, costs of isotope separation, minimum time for reaching steady production, and effect of third component on process performance and product costs. The concepts of value functions, separative power, and separative work are used to derive the characteristics, and the analogy between isotope separation theory and thermodynamics is emphasized. (D.L.C.)

  3. The isotope breathe test

    International Nuclear Information System (INIS)

    The foundations of the breath diagnostic test, based on application of the carbon compounds, labeled with the stable (13C) or radioactive isotope are presented. The methodology for conducting the breath isotope test and the apparatuses, making it possible to determine under clinical conditions the isotope composition of the carbon, contained in the expired air, depending on the introduced tracer type, is briefly described. The safety of the method and prospects of its application are discussed. The examples of the breath isotope test practical application are presented

  4. Zinc isotope fractionation during adsorption on calcite

    Science.gov (United States)

    Dong, S.; Wasylenki, L. E.

    2013-12-01

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

  5. Coupled isotopes of plant wax and hemicellulose markers record information on relative humidity and isotopic composition of precipitation

    Science.gov (United States)

    Tuthorn, M.; Zech, R.; Ruppenthal, M.; Oelmann, Y.; Kahmen, A.; del Valle, H. F.; Eglinton, T.; Zech, M.

    2015-02-01

    The δ2H isotopic composition of leaf waxes is used increasingly for paleohydrological and -climate reconstructions. However, it is challenging to disentangle past changes in the isotopic composition of precipitation and changes in evapotranspirative enrichment of leaf water. We analyzed δ2H on n-alkanes and fatty acids in topsoils along a climate transect in Argentina, for which we had previously measured δ18O on plant-derived sugars. Our results indicate that leaf wax biomarker δ2H values (δ2Hlipids) primarily reflect δ2Hsource water (precipitation), but are modulated by evapotranspirative enrichment. A mechanistic model is able to produce the main trends in δ2Hlipids along the transect, but seems to slightly underestimate evapotranspirative enrichment in arid regions and overestimate it in grass-dominated ecosystems. Furthermore, the (i) coupling of the δ2Hlipid and δ18Osugar biomarker results and (ii) application of biosynthetic fractionation factors allows calculating the δ2H-δ18O isotopic composition of leaf water along the transect. This also yields the deuterium excess (d excess) of leaf water, which mainly reflects evapotranspirative enrichment, and can be used to model relative air humidity (RH). The high correlation of modeled (reconstructed based on biomarker results) and measured RH, as well as the good agreement between modeled and actual δ2H and δ18O of precipitation along the transect lends support to the coupled δ2Hlipid and δ18Osugar biomarker approach for future paleoclimate research.

  6. Silicon Isotopic Fractionation of CAI-like Vacuum Evaporation Residues

    Energy Technology Data Exchange (ETDEWEB)

    Knight, K; Kita, N; Mendybaev, R; Richter, F; Davis, A; Valley, J

    2009-06-18

    Calcium-, aluminum-rich inclusions (CAIs) are often enriched in the heavy isotopes of magnesium and silicon relative to bulk solar system materials. It is likely that these isotopic enrichments resulted from evaporative mass loss of magnesium and silicon from early solar system condensates while they were molten during one or more high-temperature reheating events. Quantitative interpretation of these enrichments requires laboratory determinations of the evaporation kinetics and associated isotopic fractionation effects for these elements. The experimental data for the kinetics of evaporation of magnesium and silicon and the evaporative isotopic fractionation of magnesium is reasonably complete for Type B CAI liquids (Richter et al., 2002, 2007a). However, the isotopic fractionation factor for silicon evaporating from such liquids has not been as extensively studied. Here we report new ion microprobe silicon isotopic measurements of residual glass from partial evaporation of Type B CAI liquids into vacuum. The silicon isotopic fractionation is reported as a kinetic fractionation factor, {alpha}{sub Si}, corresponding to the ratio of the silicon isotopic composition of the evaporation flux to that of the residual silicate liquid. For CAI-like melts, we find that {alpha}{sub Si} = 0.98985 {+-} 0.00044 (2{sigma}) for {sup 29}Si/{sup 28}Si with no resolvable variation with temperature over the temperature range of the experiments, 1600-1900 C. This value is different from what has been reported for evaporation of liquid Mg{sub 2}SiO{sub 4} (Davis et al., 1990) and of a melt with CI chondritic proportions of the major elements (Wang et al., 2001). There appears to be some compositional control on {alpha}{sub Si}, whereas no compositional effects have been reported for {alpha}{sub Mg}. We use the values of {alpha}Si and {alpha}Mg, to calculate the chemical compositions of the unevaporated precursors of a number of isotopically fractionated CAIs from CV chondrites whose

  7. Biogeochemical and isotopic gradients in a BTEX/PAH contaminant plume: Model-based interpretation of a high-resolution field data set

    DEFF Research Database (Denmark)

    Prommer, H.; Anneser, B.; Rolle, Massimo;

    2009-01-01

    A high spatial resolution data set documenting carbon and sulfur isotope fractionation at a tar oil-contaminated, sulfate-reducing field site was analyzed with a reactive transport model. Within a comprehensive numerical model, the study links the distinctive observed isotope depth profiles with...... isotope signature of toluene, which is the most rapidly degrading compound and the most important reductant at the site. The resulting depth profiles at the observation well show distinct differences between the small isotopic enrichment in the contaminant plume core and the much stronger enrichment of up...

  8. Food webs of two intermittently open estuaries receiving 15N-enriched sewage effluent

    Science.gov (United States)

    Hadwen, Wade L.; Arthington, Angela H.

    2007-01-01

    Carbon and nitrogen stable isotope signatures were used to assess the response of food webs to sewage effluent discharged into two small intermittently open estuaries in northern New South Wales, Australia. One of these systems, Tallows Creek, has a history of direct sewage inputs, whilst the other, Belongil Creek, receives wastewater via an extensive wetland treatment system. The food webs of both systems were driven by algal sources of carbon, reflecting high autotrophic productivity in response to the nutrients entering the system from sewage effluent. All aquatic biota collected from Tallows Creek had significantly enriched δ15N signatures relative to their conspecifics from Belongil Creek, indicating that sewage nitrogen had been assimilated and transferred throughout the Tallows Creek food web. These δ15N values were higher than those reported from studies in permanently open estuaries receiving sewage effluent. We suggest that these enriched signatures and the transfer of nitrogen throughout the entire food web reflect differences in hydrology and associated nitrogen cycling processes between permanently open and intermittently open estuaries. Although all organisms in Tallows Creek were generally 15N-enriched, isotopically light (less 15N-enriched) individuals of estuary perchlet ( Ambassis marianus) and sea mullet ( Mugil cephalus) were also collected. These individuals were most likely recent immigrants into Tallows Creek, as this system had only recently been opened to the ocean. This isotopic discrimination between resident (enriched) and immigrant (significantly less enriched) individuals can provide information on fish movement patterns and the role of heavily polluted intermittently open estuaries in supporting commercially and recreationally valuable estuarine species.

  9. Temperature dependence of carbon isotope fractionation in CAM plants

    Energy Technology Data Exchange (ETDEWEB)

    Deleens, E.; Treichel, I.; O' Leary, M.H.

    1985-09-01

    The carbon isotope fractionation associated with nocturnal malic acid synthesis in Kalanchoe daigremontiana and Bryophyllum tubiflorum was calculated from the isotopic composition of carbon-4 of malic acid, after appropriate corrections. In the lowest temperature treatment (17/sup 0/C nights, 23/sup 0/C days), the isotope fractionation for both plants is -4% per thousand (that is, malate is enriched in /sup 13/C relative to the atmosphere). For K. daigremontiana, the isotope fractionation decreases with increasing temperature, becoming approximately 0% per thousand at 27/sup 0/C/33/sup 0/C. Detailed analysis of temperature effects on the isotope fractionation indicates that stomatal aperture decreases with increasing temperature and carboxylation capacity increases. For B. tubiflorum, the temperature dependence of the isotope fractionation is smaller and is principally attributed to the normal temperature dependences of the rates of diffusion and carboxylation steps. The small change in the isotopic composition of remaining malic acid in both species which is observed during deacidification indicates that malate release, rather than decarboxylation, is rate limiting in the deacidification process. 28 references, 1 figure, 4 tables.

  10. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    Science.gov (United States)

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2015-01-01

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, hypothesized to be the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs, while processes such as fractionating foliar metabolism and preferentially loading into phloem of 13C-enriched sugars may contribute to the overall autotrophic-heterotrophic difference in carbon isotope compositions.

  11. Separation of hydrogen and oxygen isotopes by membrane method

    International Nuclear Information System (INIS)

    Water enriched with deuterium or heavy oxygen plays an important role in research and technology. Heavy water (HDO, D2O) is used in nuclear technology and research and its role will become even more important should nuclear fusion ever be used for energy production. Over the past few years the world has witnessed a continuously increasing demand for enriched oxygen isotopes, especially 18O, due to a large consumption of H218O by positron emission tomography (PET), a new medical diagnostic technique used principally for tumour detection. PET uses short-lived positron emitters, like carbon-11, nitrogen-13, oxygen-15 and fluorine-18 incorporated into biochemically active tracer molecules absorbed preferentially by the tumour. Several different target materials are used for a production of these isotopes, among them water enriched in 18O. The methods of hydrogen and oxygen isotopes enrichment are expensive and energy-consuming; the separation processes are characterised by low separation factors, which very often introduce hazardous substances, poisonous or explosive (H2S, NH3, H2). There is a need to explore new methods, less energy-consuming and more safe. In this work, the unit H/D and 16O/18O separation factors in permeation of natural water with phase transition (membrane distillation) were determined and the influence of process parameters on their values was defined. Isotope effects of permeation were compared with vapour pressure isotope effects (VPIE). The experimental separation factors of H/D and 16O/18O in permeation through hydrophobic PTFE membrane were higher than those for water distillation. Since distillation is the only method for heavy oxygen production the process has particular importance for separation. The description of phenomena occurring in permeation of water isotopomers through porous PTFE membranes was presented. The isotope effect of permeation was performed as a combination of two effects: VPIE and the effect related to the transport of

  12. Comparison of the regiospecific distribution from triacylglycerols after chemical and enzymatic interesterification of high oleic sunflower oil and fully hydrogenated high oleic sunflower oil blend by carbon-13 nuclear magnetic resonance.

    Science.gov (United States)

    Lopes, Thiago I B; Ribeiro, Marilene D M M; Ming, Chiu C; Grimaldi, Renato; Gonçalves, Lireny A G; Marsaioli, Anita J

    2016-12-01

    The nutritional and organoleptic attributes of oils can proceed via interesterification of oils blends catalyzed by enzymes or chemicals. Enzymatic interesterification processes are preferred due the regiospecific outcome. Traditionally, monitoring of distribution of fatty acids (FA) in glycerol backbone is performed by enzymatic and chromatographic methods that are time-consuming, involving a series of chemical manipulations employing large volumes of organic solvents. Alternatively, carbon-13 nuclear magnetic resonance ((13)C NMR) is a fast and reliable technique that could be applied to determine the saturated and unsaturated FA distribution of the triacylglycerols (TAGs) present in high oleic sunflower oil (SO) and fully hydrogenated high oleic sunflower oil (HSO) blends and their interesterification products. The enzymatic interesterification was conducted employing the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM), the results show that the process was not completely regiospecific at sn-1,3 positions, due to the spontaneous acyl migration from position sn-2 to sn-1,3.

  13. Comparison of the regiospecific distribution from triacylglycerols after chemical and enzymatic interesterification of high oleic sunflower oil and fully hydrogenated high oleic sunflower oil blend by carbon-13 nuclear magnetic resonance.

    Science.gov (United States)

    Lopes, Thiago I B; Ribeiro, Marilene D M M; Ming, Chiu C; Grimaldi, Renato; Gonçalves, Lireny A G; Marsaioli, Anita J

    2016-12-01

    The nutritional and organoleptic attributes of oils can proceed via interesterification of oils blends catalyzed by enzymes or chemicals. Enzymatic interesterification processes are preferred due the regiospecific outcome. Traditionally, monitoring of distribution of fatty acids (FA) in glycerol backbone is performed by enzymatic and chromatographic methods that are time-consuming, involving a series of chemical manipulations employing large volumes of organic solvents. Alternatively, carbon-13 nuclear magnetic resonance ((13)C NMR) is a fast and reliable technique that could be applied to determine the saturated and unsaturated FA distribution of the triacylglycerols (TAGs) present in high oleic sunflower oil (SO) and fully hydrogenated high oleic sunflower oil (HSO) blends and their interesterification products. The enzymatic interesterification was conducted employing the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM), the results show that the process was not completely regiospecific at sn-1,3 positions, due to the spontaneous acyl migration from position sn-2 to sn-1,3. PMID:27374579

  14. Enrichment of the Superheavy Element Rg in Natural Au

    CERN Document Server

    Marinov, A; Kolb, D; Halicz, L; Segal, I; Tepliakov, N; Kashiv, Y; Brandt, R

    2010-01-01

    Based on the observation of the long-lived isotopes 261Rg and 265Rg (Z = 111, t(1/2) >= 10^(8) y) in natural Au, an experiment was performed to enrich Rg in 99.999% Au. 16 mg of Au were heated in vacuum for two weeks at a temperature of 1127 deg. C (63 deg. C above the melting point of Au). The content of 197Au and 261Rg in the residue was studied with high resolution inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The residue of Au was 3x10^(-6) of its original quantity. The recovery of Rg was a few percent. The abundance of Rg compared to Au in the enriched solution was about 2x10^(-6), which is a three to four orders of magnitude enrichment. It is concluded that the evaporation rate of Rg from an Au matrix in vacuum at 63 deg. C above the Au melting point is lower than that of Au. This experiment reinforces our first observation of Rg in a terrestrial material. As before it is concluded that a long-lived isomeric state exists in 261Rg and that it probably belongs to a new class of iso...

  15. Uranium isotope separation from 1941 to the present

    International Nuclear Information System (INIS)

    Uranium isotope separation was the key development for the preparation of highly enriched isotopes in general and thus became the seed for target development and preparation for nuclear and applied physics. In 1941 (year of birth of the author) large-scale development for uranium isotope separation was started after the US authorities were warned that NAZI Germany had started its program for enrichment of uranium and might have confiscated all uranium and uranium mines in their sphere of influence. Within the framework of the Manhattan Projects the first electromagnetic mass separators (Calutrons) were installed and further developed for high throughput. The military aim of the Navy Department was to develop nuclear propulsion for submarines with practically unlimited range. Parallel to this the army worked on the development of the atomic bomb. Also in 1941 plutonium was discovered and the production of 239Pu was included into the atomic bomb program. 235U enrichment starting with natural uranium was performed in two steps with different techniques of mass separation in Oak Ridge. The first step was gas diffusion which was limited to low enrichment. The second step for high enrichment was performed with electromagnetic mass spectrometers (Calutrons). The theory for the much more effective enrichment with centrifugal separation was developed also during the Second World War, but technical problems e.g. development of high speed ball and needle bearings could not be solved before the end of the war. Spying accelerated the development of uranium separation in the Soviet Union, but also later in China, India, Pakistan, Iran and Iraq. In this paper, the physical and chemical procedures are outlined which lead to the success of the project. Some security aspects and Non-Proliferation measures are discussed.

  16. Uranium isotope separation from 1941 to the present

    Energy Technology Data Exchange (ETDEWEB)

    Maier-Komor, Peter, E-mail: Peter@Maier-Komor.d [Retired from Physik-Department E12, Technische Universitaet Muenchen, D-85747 Garching (Germany)

    2010-02-11

    Uranium isotope separation was the key development for the preparation of highly enriched isotopes in general and thus became the seed for target development and preparation for nuclear and applied physics. In 1941 (year of birth of the author) large-scale development for uranium isotope separation was started after the US authorities were warned that NAZI Germany had started its program for enrichment of uranium and might have confiscated all uranium and uranium mines in their sphere of influence. Within the framework of the Manhattan Projects the first electromagnetic mass separators (Calutrons) were installed and further developed for high throughput. The military aim of the Navy Department was to develop nuclear propulsion for submarines with practically unlimited range. Parallel to this the army worked on the development of the atomic bomb. Also in 1941 plutonium was discovered and the production of {sup 239}Pu was included into the atomic bomb program. {sup 235}U enrichment starting with natural uranium was performed in two steps with different techniques of mass separation in Oak Ridge. The first step was gas diffusion which was limited to low enrichment. The second step for high enrichment was performed with electromagnetic mass spectrometers (Calutrons). The theory for the much more effective enrichment with centrifugal separation was developed also during the Second World War, but technical problems e.g. development of high speed ball and needle bearings could not be solved before the end of the war. Spying accelerated the development of uranium separation in the Soviet Union, but also later in China, India, Pakistan, Iran and Iraq. In this paper, the physical and chemical procedures are outlined which lead to the success of the project. Some security aspects and Non-Proliferation measures are discussed.

  17. Uranium isotope separation from 1941 to the present

    Science.gov (United States)

    Maier-Komor, Peter

    2010-02-01

    Uranium isotope separation was the key development for the preparation of highly enriched isotopes in general and thus became the seed for target development and preparation for nuclear and applied physics. In 1941 (year of birth of the author) large-scale development for uranium isotope separation was started after the US authorities were warned that NAZI Germany had started its program for enrichment of uranium and might have confiscated all uranium and uranium mines in their sphere of influence. Within the framework of the Manhattan Projects the first electromagnetic mass separators (Calutrons) were installed and further developed for high throughput. The military aim of the Navy Department was to develop nuclear propulsion for submarines with practically unlimited range. Parallel to this the army worked on the development of the atomic bomb. Also in 1941 plutonium was discovered and the production of 239Pu was included into the atomic bomb program. 235U enrichment starting with natural uranium was performed in two steps with different techniques of mass separation in Oak Ridge. The first step was gas diffusion which was limited to low enrichment. The second step for high enrichment was performed with electromagnetic mass spectrometers (Calutrons). The theory for the much more effective enrichment with centrifugal separation was developed also during the Second World War, but technical problems e.g. development of high speed ball and needle bearings could not be solved before the end of the war. Spying accelerated the development of uranium separation in the Soviet Union, but also later in China, India, Pakistan, Iran and Iraq. In this paper, the physical and chemical procedures are outlined which lead to the success of the project. Some security aspects and Non-Proliferation measures are discussed.

  18. Intracellular Cadmium Isotope Fractionation

    Science.gov (United States)

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

    2011-12-01

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

  19. Discovery of the Arsenic Isotopes

    CERN Document Server

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

    2009-01-01

    Twenty-nine arsenic isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  20. Discovery of the Scandium Isotopes

    CERN Document Server

    Meierfrankenfeld, D

    2010-01-01

    Twenty-three scandium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  1. Discovery of the Tungsten Isotopes

    OpenAIRE

    A. Fritsch; Ginepro, J. Q.; Heim, M.; Schuh, A.; SHORE, A.; Thoennessen, M

    2009-01-01

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

  2. Discovery of the Vanadium Isotopes

    OpenAIRE

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

    2009-01-01

    Twenty-four vanadium isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  3. Discovery of the Barium Isotopes

    OpenAIRE

    SHORE, A.; A. Fritsch; Ginepro, J. Q.; Heim, M.; Schuh, A.; Thoennessen, M

    2009-01-01

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

  4. Discovery of the Silver Isotopes

    OpenAIRE

    Schuh, A.; A. Fritsch; Ginepro, J. Q.; Heim, M.; SHORE, A.; Thoennessen, M

    2009-01-01

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

  5. Discovery of the Cadmium Isotopes

    OpenAIRE

    Amos, S.; Thoennessen, M

    2009-01-01

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

  6. Discovery of the Krypton Isotopes

    OpenAIRE

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

    2009-01-01

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

  7. Discovery of the Iron Isotopes

    OpenAIRE

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

    2009-01-01

    Twenty-eight iron isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  8. Discovery of the Gold Isotopes

    OpenAIRE

    Schuh, A.; A. Fritsch; Ginepro, J. Q.; Heim, M.; SHORE, A.; Thoennessen, M

    2009-01-01

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

  9. Discovery of the Cobalt Isotopes

    OpenAIRE

    Szymanski, T; Thoennessen, M

    2009-01-01

    Twenty-six cobalt isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  10. Standard specification for uranium hexafluoride enriched to less than 5 % 235U

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This specification covers nuclear grade uranium hexafluoride (UF6) that either has been processed through an enrichment plant, or has been produced by the blending of Highly Enriched Uranium with other uranium to obtain uranium of any 235U concentration below 5 % and that is intended for fuel fabrication. The objectives of this specification are twofold: (1) To define the impurity and uranium isotope limits for Enriched Commercial Grade UF6 so that, with respect to fuel design and manufacture, it is essentially equivalent to enriched uranium made from natural UF6; and (2) To define limits for Enriched Reprocessed UF6 to be expected if Reprocessed UF6 is to be enriched without dilution with Commercial Natural UF6. For such UF6, special provisions, not defined herein, may be needed to ensure fuel performance and to protect the work force, process equipment, and the environment. 1.2 This specification is intended to provide the nuclear industry with a standard for enriched UF6 that is to be used in the pro...

  11. Development of a new 48Ca enrichment method and the CANDLES experiment

    Science.gov (United States)

    Kishimoto, Tadafumi

    2015-10-01

    CANDLES is a project to study double beta decay of 48Ca. CANDLES could become the most competitive experiment if we could have an efficient method to enrich 48Ca. We developed a new method for enrichment of large amount of calcium isotopes. The method is called Multi-Channel Counter-Current Electrophoresis (MCCCE) which can be found elsewhre. Essential point is the increase of the power density in the migration path. In MCCCE, ions migrate in multi-channels on a boron nitride (BN) plate by which substantial increase of the power density was achieved. We made a tiny prototype instrument with a 10 mm thick BN plate and obtained 3 for an enrichment factor for the ratio of abundance of 48Ca to 43Ca over that of natural abundance. It corresponds to 6 for the enrichment factor of 48Ca to 40Ca. Recently we obtained 10 for the enrichment factor by using 20 mm BN plate. This remarkably large enrichment factor demonstrates that the MCCCE is a realistic and promising method for the enrichment of large amount of ions. This method can be applied to many other elements and compounds. I will describe MCCCE and its effect on the study of double beta decay and other fields.

  12. Survey on isotope effects and separation technologies

    International Nuclear Information System (INIS)

    This paper is a review of the main industrial processes and physical principles used for stable isotope separation on a production scale. It will be restricted to 'classical' industrial technologies. Roughly speaking, only three types of technologies have been contemplated for today's production (apart from uranium enrichment, outside the scope of this review). 1. Chemical exchange processes for the lighter isotopes (D, T, 7 Li, 10 B, 13 C, 15 N, 17 O). Operating processes such as exchange distillation and liquid-gas chemical exchange are based on isotope mass-differences in the free energy (vapour pressures, vibration frequencies) of molecular species.. Insight into statistical thermodynamics gives low enrichment factors (α ≤ 1.05), which have generally a (Δm/m2) ratio dependency. Although needing thousands of repetitive elementary operations, those low cost processes are well suited for large capacity production. Modern trends are now in solid-liquid chromatographic columns: polymer-crown complexes with large macro-cyclic rings have topological ability to pick up boron, lithium, or cesium isotopes. Detritiation (on a small scale) with palladium solid-gas interface is a special case. 2. Thermal Diffusion process for the production of light rare gases (3 He, 22 Ne, 36 Ar, 86 Kr). While having a low separation factor for each stage, this process is still of topical interest for production of the rare gases, with a high purity degree, and of 13 C H4 at the gram level of yearly production. 3. Ultra Gas Centrifuge (G.C.) for medium and heavy nuclei des. This process is based on an increase of a small mass diffusion flux by a pressure gradient. Several counter-current thermal diffusion effects are added to reach higher separation factors (α ∼ 1.5). The whole process results in a Δm dependency. That allowed low cost units to separate xenon as well as metallic isotopes. The trend at Oak-Ridge and at the Kurchatoff-Institute is to replace the electromagnetic

  13. Determination of U235 enrichment from nuclear fuel by neutronic activation

    International Nuclear Information System (INIS)

    The enrichment of 235U in UO2 pellets samples through the instrumental neutron activation analysis method (I.N.A.A.) was determined. By high resolution gamma-ray spectrometry (H.R.G.S.), from analysis of isotopic ratios between fission products peaks from 235U and 239Np different energies peaks from 238U, the enrichment was achieved. The 'Boatstrap' statistics technique for the analytical results, which is based in shaping results of an unknown distribution to the Gaussian distribution by B replications in interested statistics such as: the mean and its standard error, was introduced. (M.J.C.)

  14. Detection of interstellar DNC - Difficulties of chemical equilibrium hypothesis for enrichment

    Science.gov (United States)

    Godfrey, P. D.; Brown, R. D.; Gunn, H. I.; Blackman, G. L.; Storey, J. W. V.

    1977-01-01

    The J = 1-0 transition of DNC at 76.3058 GHz has been observed in emission in NGC 2264. Comparison with previous observations of HN(C-13) indicates that deuterium is enriched in DNC similarly to the enrichment reported for DCO(+) in this source. The DNC/HNC ratio is estimated to be about 1/24. The results cannot readily be interpreted in terms of chemical equilibria relating to the formation of DNC. It is suggested that the explanation must be sought in isotope effects on rates of formation of interstellar molecules.

  15. Molybdenum isotopic composition of single silicon carbides from supernovae.

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-02-03

    Presolar silicon carbide grains form in a variety of types of stars, including asymptotic giant branch red giant stars and supernovae. The dominant mechanisms of heavy element nucleosynthesis, the s-process and r-process, are thought to occur in AGB stars and supernovae, respectively. We have previously reported that mainstream SiC grains have strong enrichments in the s-process isotopes of Sr, Zr and Mo. We report here the first measurements of Mo isotopes in X-type SiC grains, which have previously been identified as having formed from supernova ejecta.

  16. Use of an isotope separator at the INEL

    International Nuclear Information System (INIS)

    An electromagnetic isotope separator with a retardation lens as a collector was used to prepare highly enriched samples of Nd-143, -144, -145, -146, -148, -150, Sm-147, -149; Eu-151, -152, -153, -154. The 50 μg to 75 μg samples, deposited on 1 mil nickel foil or 0.5 mil vanadium foil, are part of a sample set to be irradiated in EBR-II as part of an integral-capture cross-section measurement program at the INEL. The isotope separator and the apparatus used for the sample preparation are described

  17. Job enrichment in job design.

    Science.gov (United States)

    Bobeng, B J

    1977-03-01

    For optimal operation in labor-intensive industries, such as foodservice, not only scientific management principles but also behavioral aspects (the people) must be considered in designing job content. Three psychologic states--work that is meaningful, responsibility for outcomes, and knowledge of outcomes--are critical in motivating people. These, in turn encompass the core dimensions of skill variety, task identity, task significance, autonomy, and feedback. Job enrichment and job enlargement--related but not identical means of expanding job content--when combined, offer the likelihood of redesigned jobs in the core dimensions. Effective implementation of a job enrichment program hinges on diagnosing problems in the work system, actual changes in the work, and systematic evaluation of the changes. The importance of the contribution of the behavioral sciences to management cannot be neglected.

  18. Iron isotopes in an Archean ocean analogue

    Science.gov (United States)

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

    2014-05-01

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

  19. Boron Enrichment in Martian Clay

    OpenAIRE

    James D Stephenson; Lydia J Hallis; Kazuhide Nagashima; Freeland, Stephen J.

    2013-01-01

    We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest minera...

  20. Enrichment of lanthanides in aragonite

    Institute of Scientific and Technical Information of China (English)

    瞿成利; 路波; 刘刚

    2009-01-01

    Using the constant addition technique,the coprecipitation of lanthanum,gadolinium,and lutetium with aragonite in seawater was experimentally investigated at 25 ℃.Their concentrations in aragonite overgrowths were determined by inductive coupled plasma mass spectrometer.All these lanthanides were strongly enriched in aragonite overgrowths.The amount of lanthanum,gadolinium,and lutetium incorporated into aragonite accounted for 57%-99%,50%-89%,and 40%-91% of their initial total amount,respectively.With the in...