Covariance of oxygen and hydrogen isotopic composition in plant water: Species effects

Energy Technology Data Exchange (ETDEWEB)

Cooper, L.W.; DeNiro, M.J. (Univ. of California, Los Angeles (United States))

1989-12-01

Leaf water becomes enriched in the heavy isotopes of oxygen and hydrogen during evapotranspiration. The magnitude of the enrichment has been shown to be influenced by temperature and humidity, but the effects of species-specific factors on leaf water enrichment of D and {sup 18}O have not been studied for different plants growing together. To learn whether leaf water enrichment patterns and processes for D and {sup 18}O are different for individual species growing under the same environmental conditions the authors tested the proposal that leaf waters in plants with crassulacean acid metabolism (CAM) show high sloped (m in the leaf water equation {delta}D = m {delta}{sup 18}O + b) than in C{sub 3} plants. They determined the relationships between the stable hydrogen ({delta}D) and oxygen ({delta}{sup 18}O) isotope ratios of leaf waters collected during the diurnal cycle of evapotranspiration for Yucca schidigera, Ephedra aspera, Agave deserti, Prunus ilicifolia, Yucca whipplei, Heteromeles arbutifolia, Dyckia fosteriana, Simmondsia chinensis, and Encelia farinosa growing at two sites in southern California. The findings indicate that m in the aforementioned equation is related to the overall residence time for water in the leaf and proportions of water subjected to repeated evapotranspiration enrichments of heavy isotopes.

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

Science.gov (United States)

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

1998-04-17

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

Sulfur and Oxygen Isotope Fractionation During Bacterial Sulfur Disproportionation Under Anaerobic Haloalkaline Conditions

NARCIS (Netherlands)

Poser, Alexander; Vogt, Carsten; Knöller, Kay; Sorokin, Dimitry Y.; Finster, Kai W.; Richnow, Hans H.

2016-01-01

Sulfur and oxygen isotope fractionation of elemental sulfur disproportionation at anaerobic haloalkaline conditions was evaluated for the first time. Isotope enrichment factors of the strains Desulfurivibrio alkaliphilus and Dethiobacter alkaliphilus growing at pH 9 or 10 were −0.9‰ to −1‰ for

THz spectroscopy of the 29 cm{sup -1} oxygen vibrational line in natural silicon and isotopically enriched {sup 28}Si

Energy Technology Data Exchange (ETDEWEB)

Lassmann, Kurt; Dressel, Martin [1. Physikalisches Inst., Univ. Stuttgart (Germany); Gorshunov, Boris; Zhukova, E.S. [1. Physikalisches Inst., Univ. Stuttgart (Germany); A.M. Prokhorov Gen. Phys. Inst., RAS, Moscow (Russian Federation); Moscow Inst. Physics and Technology (Russian Federation); Korolev, P.S. [A.M. Prokhorov Gen. Phys. Inst., RAS, Moscow (Russian Federation); Lomonosov Moscow State Univ. (Russian Federation); Kalinsuhkin, V.P. [A.M. Prokhorov Gen. Phys. Inst., RAS, Moscow (Russian Federation); Abrosimov, N.V. [Leibniz Inst. Kristallzuechtung, Berlin (Germany); Sennikov, P.G. [Inst. Chem. High-Purity Substances, Nizhny Novgorod (Russian Federation); Pohl, H.J. [PTB, Braunschweig (Germany); Zakel, S. [VITCON-Projektconsult, Jena (Germany)

2012-07-01

Looking for a possible host-isotope effect on the low-energy two-dimensional motion of interstitial oxygen in silicon we have measured the resonance parameters of the lowest transition of the 30 cm{sup -1} band of the Si-O-Si complex in natural Si and in isotopically enriched {sup 28}Si at temperatures between 5 K and 22 K by means of coherent-source terahertz spectroscopy. At 5.5 K we obtain for the resonance maxima 29.24 {+-} 0.003 cm{sup -1} and 29.22 {+-} 0.003 cm{sup -1} and for the line widths 0.09 {+-} 0.01 cm{sup -1} and 0.11 {+-} 0.01 cm{sup -1} for {sup 28}Si and {sup nat}Si, respectively. Both lines can be fitted by single Lorentzians, so, no obvious isotopic structure or asymmetry of the line in {sup nat}Si due to the Si neighbors in the Si-O-Si complex is detected. We therefore conclude that down-shift and broadening of the {sup nat}Si-resonance is not due to the Si isotopes in the isolated Si-O-Si complex but to an average effect of the isotopically inhomogeneous lattice.

A route for oxygen isotope enrichment of α-COOH groups in amino acids

International Nuclear Information System (INIS)

Steinschneidner, A.; St Armour, T.; Valentine, B.; Burgar, M.I.; Fiat, D.

1981-01-01

Oxygen-17 was introduced into leucine, proline, phenylalanine and tyrosine. The corresponding tert-butyloxycarbonyl amino acids were first converted to their O-methyl esters. Following saponification with Na 17 OH, the tert-butyloxycarbonyl group was removed to yield free amino acid enriched with oxygen-17 by approximately 1000-fold. Oxygen-17 NMR revealed well-resolved peaks for the labelled amino acids. The chemical shifts are reported. (author)

Covariance of oxygen and hydrogen isotopic compositions in plant water: species effects

International Nuclear Information System (INIS)

Cooper, L.W.; DeNiro, M.J.

1989-01-01

Leaf water becomes enriched in the heavy isotopes of oxygen and hydrogen during evapotranspiration. The magnitude of the enrichment has been shown to be influenced by temperature and humidity, but the effects of species—specific factors on leaf water enrichment of D and 18 O have not been studied for different plants growing together. Accordingly, to learn whether leaf water enrichment patterns and processes for D and 18 O are different for individual species growing under the same environmental conditions we tested the proposal that leaf waters in plants with crassulacean acid metabolism (CAM) show higher slopes (m in the leaf water equation °D = m ° 18 O + b) than in C 3 plants. We determined the relationships between the stable hydrogen (°D) and oxygen (° 18 O) isotope ratios of leaf waters collected during the diurnal cycle of evapotranspiration for Yucca schidigera, Ephedra aspera, Agave deserti, Prunus ilicifolia, Yucca whipplei, Heteromeles arbutifolia, Dyckia fosteriana, Simmondsia chinensis, and Encelia farinosa growing at two sites in southern California. Slopes (m in the above leaf water equation) ranged from 1.50 to 3.21, compared to °8 for meteoric water, but differences in slope could not be attributed to carboxylation pathway (CAM vs. C 3 ) nor climate (coastal California vs. Sonoran Desert). Higher slopes were correlated with greater overall ranges of leaf water enrichment of D and 18 O. Water in plants with higher slopes also differed most from unaltered meteoric water. Leaf water isotope ratios in plants with lower slopes were better correlated with temperature and humidity. The findings indicate that m in the aforementioned equation is related to the overall residence time for water in the leaf and proportions of water subjected to repeated evapotranspiration enrichments of heavy isotopes

Laser photochemical studies on di-isopropyl ether for oxygen-18 enrichment

International Nuclear Information System (INIS)

Mathi, P.; Kumar, Awadhesh; Ghosh, Ayan; Nayak, A.K.; Parthasarathy, V.; Nataraju, V.; Jadhav, K.A.; Babu, K.Rajendra; Sarkar, S.K.

2013-05-01

Oxygen-18 is needed for the production of Fluorine-18 in medical cyclotron for use in positron emission tomography. This report deals with our work on Oxygen-18 selective photo dissociation of natural di-isopropyl ether under various conditions leading to various oxygen bearing products having different levels of 18 O enrichment. Apart from obtaining 18 O enrichment in products 2-propanol and acetaldehyde, we have observed unusually high enrichment (about 39%) in another photoproduct, acetone, as measured by mass spectrometry. This new finding is attributed to 18 O selective secondary reaction channels which is supported by molecular orbital calculations. The investigation required characterization and quantitative estimation of various chemical species, viz., di-isopropyl ether, acetaldehyde, acetone and isopropanol by various instrumental methods of analysis. These methods include gas chromatography, Fourier transform infrared spectrometry and quadrupole mass spectrometry. Detailed Gas Chromatographic (GC) studies summarize the interference problems encountered for quantitatively identifying different photo-products and establish the right experimental conditions for optimum separation. This exercise is extremely useful for an isotope enrichment scheme as it generates a valuable database to understand the processes involved for both selectivity enhancement and degradation. (author)

Enriching stable isotopes: Alternative use for Urenco technology

International Nuclear Information System (INIS)

Rakhorst, H.; de Jong, P.G.T.; Dawson, P.D.

1996-01-01

The International Urenco Group utilizes a technologically advanced centrifuge process to enrich uranium in the fissionable isotope 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

Do oxygen isotope values in collagen reflect the ecology and physiology of neotropical mammals?

Directory of Open Access Journals (Sweden)

Brooke eCrowley

2015-11-01

Full Text Available Stable isotope data provide insight into the foraging ecology of animals. Traditionally, carbon and nitrogen isotope values have been used to infer dietary and habitat preferences. Oxygen isotopes are used less frequently but may complement the ecological information provided by carbon and nitrogen, particularly in densely forested or arid environments. Additionally, because oxygen is preserved in both bioapatite and collagen, it is useful for paleoecological studies. To investigate the suitability of oxygen isotopes for complementing and building on ecological applications of carbon and nitrogen isotopes, we analyze all three isotopes in bone collagen for nearly identical assemblages of Costa Rican mammals in two ecologically distinct habitats - a evergreen rainforest and a seasonal dry forest. We assess the degree to which differences in habitat, activity pattern, diet, arboreality, and thermoregulation are revealed by each of the isotope systems. Our results highlight the potential of oxygen isotopes in modern and paleoecological contexts. In addition to reflecting habitat type, oxygen isotope values in collagen distinguish species on the basis of vertical habitat stratification and drinking behavior. Within a locality, individuals with low oxygen isotope values likely track meteoric water, whereas those with elevated values most likely consume evaporatively-enriched plant tissues, such as canopy leaves. These patterns will be useful in reconstructing paleoenvironments and interpreting ecological differences among taxa both extant and extinct.

Formation of chondrules in a moderately high dust enriched disk: Evidence from oxygen isotopes of chondrules from the Kaba CV3 chondrite

Science.gov (United States)

Hertwig, Andreas T.; Defouilloy, Céline; Kita, Noriko T.

2018-03-01

Oxygen three-isotope analysis by secondary ion mass spectrometry of chondrule olivine and pyroxene in combination with electron microprobe analysis were carried out to investigate 24 FeO-poor (type I) and 2 FeO-rich (type II) chondrules from the Kaba (CV) chondrite. The Mg#'s of olivine and pyroxene in individual chondrules are uniform, which confirms that Kaba is one of the least thermally metamorphosed CV3 chondrites. The majority of chondrules in Kaba contain olivine and pyroxene that show indistinguishable Δ17O values (= δ17O - 0.52 × δ18O) within analytical uncertainties, as revealed by multiple spot analyses of individual chondrules. One third of chondrules contain olivine relict grains that are either 16O-rich or 16O-poor relative to other indistinguishable olivine and/or pyroxene analyses in the same chondrules. Excluding those isotopically recognized relicts, the mean oxygen isotope ratios (δ18O, δ17O, and Δ17O) of individual chondrules are calculated, which are interpreted to represent those of the final chondrule melt. Most of these isotope ratios plot on or slightly below the primitive chondrule mineral (PCM) line on the oxygen three-isotope diagram, except for the pyroxene-rich type II chondrule that plots above the PCM and on the terrestrial fractionation line. The Δ17O values of type I chondrules range from ∼-8‰ to ∼-4‰; the pyroxene-rich type II chondrule yields ∼0‰, the olivine-rich type II chondrule ∼-2‰. In contrast to the ungrouped carbonaceous chondrite Acfer 094, the Yamato 81020 CO3, and the Allende CV3 chondrite, type I chondrules in Kaba only possess Δ17O values below -3‰ and a pronounced bimodal distribution of Δ17O values, as evident for those other chondrites, was not observed for Kaba. Investigation of the Mg#-Δ17O relationship revealed that Δ17O values tend to increase with decreasing Mg#'s, similar to those observed for CR chondrites though data from Kaba cluster at the high Mg# (>98) and the low Δ17O

Boron isotopic enrichment by displacement chromatography

International Nuclear Information System (INIS)

Mohapatra, K.K.; Bose, Arun

2014-01-01

10 B enriched boron is used in applications requiring high volumetric neutron absorption (absorption cross section- 3837 barn for thermal and 1 barn for 1 MeV fast neutron). It is used in fast breeder reactor (as control rod material), in neutron counter, in Boron Neutron Capture Therapy etc. Owing to very small separation factor, boron isotopic enrichment is a complex process requiring large number of separation stages. Heavy Water Board has ventured in industrial scale production of 10 B enriched boron using Exchange Distillation Process as well as Ion Displacement Chromatography Process. Ion Displacement Chromatography process is used in Boron Enrichment Plant at HWP, Manuguru. It is based on isotopic exchange between borate ions (B(OH) 4 - ) on anion exchange resin and boric acid passing through resin. The isotopic exchange takes place due to difference in zero point energy of 10 B and 11 B

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

Laser Isotope Enrichment for Medical and Industrial Applications

International Nuclear Information System (INIS)

Leonard Bond

2006-01-01

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

Method for the enrichment of isotopes

International Nuclear Information System (INIS)

Schuster, E.; Kersting, A.; Gebauhr, W.

1976-01-01

A method for the enrichment of isotopes, especially of uranium compounds, is described, working according to the principle of selective excitation by laser beams. As the starting compound, UF 6 is mentioned; the reaction partness are atomic gases (hydrogen, oxygen, nitrogen) or radicals (CH 3 , CHO). According to the invention, the gas mixture flows through the reaction space with a velocity so large that in leaving it, recombination of the reaction partner will already take place again. In this way, competing thermal reactions will be avoided and energy transfer fo excited 235 U molecules to non-excited 238 U molecules is eliminated to a large extent. A suitable equipment for implementing the method is described. (UWI) [de

Isotopic enrichment in a plasma centrifuge

International Nuclear Information System (INIS)

Del Bosco, E.; Dallaqua, R.S.; Ludwig, G.O.; Bittencourt, J.A.

1986-05-01

A rotating fully ionized plasma column was produced in a vacuum-arc centrifuge. The apparatus is described and new results for the rotational velocity and isotope enrichment of carbon and metal plasmas are shown. The ion rotation velocity is derived from electrostatic probes measurents and from the azimuthal displacement of the material deposited behind of a narrow slit. The isotope enrichment is measured with a modified quadrupole mass spectrometer, which determines, in situ, the relative abundance of the isotopes at the end of the plasm column at various radil positions. (Author) [pt

Sulfur cycling in contaminated aquifers: What can we learn from oxygen isotopes in sulfate? (Invited)

Science.gov (United States)

Knoeller, K.; Vogt, C.; Hoth, N.

2009-12-01

Bacterial reduction of dissolved sulfate (BSR) is a key process determining the natural attenuation in many contaminated aquifers. For example, in groundwater bodies affected by acid mine drainage (AMD) BSR reduces the contaminant load by producing alkalinity and facilitating a sustainable fixation of sulfur in the sediment. In aquifers contaminated with petroleum hydrocarbons sulfate may act as a terminal electron acceptor for the anaerobic oxidation of the organic contaminants to carbon dioxide and water. Due to the isotope selectivity of sulfate reducing bacteria, BSR shows the most pronounced isotope fractionation within the sulfur cycle. While sulfur displays a straightforward kinetic enrichment in the residual sulfate described by the enrichment factor epsilon (ɛ), the mechanism of oxygen isotope fractionation is still being discussed controversially. Nevertheless, it is agreed on that oxygen isotope exchange between ambient water and residual sulfate occurs during BSR in natural environments. With respect to this potential isotope exchange, the fractionation parameter theta (θ) is introduced instead of the kinetic enrichment factor epsilon (ɛ). The dual isotope system considering both sulfate-sulfur and sulfate-oxygen isotope fractionation and the respective fractionation parameters ɛ and θ provides an excellent tool for the recognition and quantification of BSR. Beyond that, the dual isotope approach may help identify and estimate interfering sulfur transformations such as re-oxidation and disproportionation processes which is especially vital for the understanding of the overall natural attenuation potential of the investigated aquifers. We present two examples from different field studies showing the benefits of applying the combination of sulfur and oxygen isotopes in dissolved sulfate to reveal the details of the sulfur cycle. The first case study is concerned with the evaluation of the potential for BSR in an AMD-affected aquifer close to an

Isotope anomalies in oxygen isotope exchange equilibrium systems

International Nuclear Information System (INIS)

Kotaka, M.

1997-01-01

The purpose of the present work is to elucidate the isotope anomalies in oxygen isotope exchange equilibrium systems, according to the calculations of the equilibrium constants for oxygen isotopic exchange reactions, and the calculations of the oxygen isotope separation factors between two phases. The equilibrium constants (K65, K67, K68 and K69) of 16 O- 15 O, 16 O 17 O, 16 O- 18 O, and 16 O- 19 O exchange reactions between diatomic oxides were calculated in a wide temperature range on the basis of quantum statistical mechanics. Many equilibrium constants showed the anomalous mass effects, and then had the crossover temperatures and the mass independent fractionation (MIF) temperatures which held K67 = K65, K67 = K68, or K67 = K69, etc. For example, the equilibrium constants for the reactions between OH and the other diatomic oxides (MO) showed the anomalous mass effects, when M was Li, Na, Mg, K, Fe, Al, Ge, Zr, Pt, etc. The 16 O 15 O, 16 O 17 O, 16 O- 18 O, and 16 O- 19 O oxygen isotope separation factors (S65, S67, S68 and S69) between two phases were calculated, when OH and CO were in the first phase, and SiO was in the second phase. Although the oxygen isotopic exchange equilibria in the two phases had no MIF and crossover temperatures, the separation factors showed the anomalous mass effects and had the temperatures. According to what is called the normal mass effects for the equilibrium constant of isotopic exchange reaction, the value of InK68/InK67 is 1.885. Therefore, the value of InS68/InS67 should be 1.885 too. The value calculated, however, widely changed. It can be concluded from the results obtained in the present work that some oxygen isotopic exchange equilibria cause the anomalous mass effects, the anomalous oxygen isotope separation factors, and then isotope anomalies

Fractionation of Nitrogen and Oxygen Isotopes and Roles of Bacteria during Denitrification

Science.gov (United States)

Kang, J.; Buyanjargal, A.; Jeen, S. W.

2017-12-01

Nitrate in groundwater can cause health and environmental problems when not properly treated. The purpose of this study was to develop a treatment method for nitrate in groundwater using organic carbon-based reactive mixtures (i.e., wood chips and gravel) through column experiments and to evaluate reaction mechanisms responsible for the treatment. The column experiments were operated for a total of 19 months. The results from the geochemical analyses for the experiments suggest that cultures of denitrifying bacteria used organic carbon while utilizing nitrate as their electron acceptor via denitrification process. Proteobacteria was the most abundant phylum in all samples, accounting for 45.7% of the bacterial reads, followed by Firmicutes (22.6%) and Chlorobi (10.6%). Bacilli, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria_c consisted of 32, 30, 23, 11, and 2% of denitrifying bacteria class. The denitrification process caused fractionation of nitrogen and oxygen isotopes of nitrate while nitrate concentration decreased. When fitted to the Rayleigh's fractionation model, enrichment factors (ɛ) were 11.5‰ and 5.6‰ for 15N and 18O isotopes, respectively. Previous studies suggested that nitrogen isotope enrichment factors of denitrification are within the range of 4.7 to 40‰ and oxygen isotopic enrichment factors are between 8 and 18.3‰. This study shows that nitrate in groundwater can be effectively treated using passive treatment systems, such as permeable reactive barriers (PRBs), and denitrificaton is the dominant process reponsible for the removal of nitrate.

Isotopically enriched structural materials in nuclear devices

Energy Technology Data Exchange (ETDEWEB)

Morgan, L.W.G., E-mail: Lee.Morgan@ccfe.ac.uk [CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Shimwell, J. [CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Gilbert, M.R. [CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom)

2015-01-15

Highlights: • C-B analysis of isotopic enrichment of structural materials is presented. • Some, previously, prohibited elements could be used as alloying elements in LAM's. • Adding enriched molybdenum and nickel, to EUROFER, could increase availability. • Isotope enrichment for EUROFER could be cost-effective. • Isotopically enriching copper, in CuCrZr, can reduce helium production by 50%. - Abstract: A large number of materials exist which have been labeled as low activation structural materials (LAM). Most often, these materials have been designed in order to substitute-out or completely remove elements that become activated and contribute significantly to shut-down activity after being irradiated by neutrons in a reactor environment. To date, one of the fundamental principles from which LAMs have been developed is that natural elemental compositions are the building blocks of LAMs. Thus, elements such as Co, Al, Ni, Mo, Nb, N and Cu that produce long-lived decay products are significantly reduced or removed from the LAM composition. These elements have an important part to play in the composition of steels and the removal/substitution can have a negative impact on materials properties such as yield stress and fracture toughness. This paper looks in more detail at whether using isotopic selection of the more mechanically desirable, but prohibited due to activation, elements can improve matters. In particular, this paper focuses on the activation of Eurofer. Carefully chosen isotopically enriched elements, which are normally considered to be on the prohibited element list, are added to EUROFER steel as potential alloying elements. The EUROFER activation results show that some prohibited elements can be used as alloying elements in LAM steels, providing the selected isotopes do not have a significant impact on waste disposal rating or shut-down dose. The economic implications of isotopically enriching elements and the potential implications for

Capability of the electromagnetic isotope-enrichment facility at ORNL

International Nuclear Information System (INIS)

Newman, E.

1982-01-01

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

Seasonal transfer of oxygen isotopes from precipitation and soil to the tree ring: source water versus needle water enrichment.

Science.gov (United States)

Treydte, Kerstin; Boda, Sonja; Graf Pannatier, Elisabeth; Fonti, Patrick; Frank, David; Ullrich, Bastian; Saurer, Matthias; Siegwolf, Rolf; Battipaglia, Giovanna; Werner, Willy; Gessler, Arthur

2014-05-01

For accurate interpretation of oxygen isotopes in tree rings (δ(18) O), it is necessary to disentangle the mechanisms underlying the variations in the tree's internal water cycle and to understand the transfer of source versus leaf water δ(18) O to phloem sugars and stem wood. We studied the seasonal transfer of oxygen isotopes from precipitation and soil water through the xylem, needles and phloem to the tree rings of Larix decidua at two alpine sites in the Lötschental (Switzerland). Weekly resolved δ(18) O records of precipitation, soil water, xylem and needle water, phloem organic matter and tree rings were developed. Week-to-week variations in needle-water (18) O enrichment were strongly controlled by weather conditions during the growing season. These short-term variations were, however, not significantly fingerprinted in tree-ring δ(18) O. Instead, seasonal trends in tree-ring δ(18) O predominantly mirrored trends in the source water, including recent precipitation and soil water pools. Modelling results support these findings: seasonal tree-ring δ(18) O variations are captured best when the week-to-week variations of the leaf water signal are suppressed. Our results suggest that climate signals in tree-ring δ(18) O variations should be strongest at temperate sites with humid conditions and precipitation maxima during the growing season. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

An isotope-enrichment unit and a process for isotope separation

International Nuclear Information System (INIS)

1981-01-01

A process and equipment for isotope enrichment using gas-centrifuge cascades are described. The method is described as applied to the separation of uranium isotopes, using natural-abundance uranium hexafluoride as the gaseous-mixture feedstock. (U.K.)

INVESTIGATION OF DISSOLVED SULPHATE IN VARIOUS GEOTHERMAL FIELDS OF SUMATRA USING OXYGEN AND SULPHUR ISOTOPES

Directory of Open Access Journals (Sweden)

E. Ristin Pujiindiyati

2010-06-01

Full Text Available There are at least 30 high temperature systems; eleven active volcanoes, five degassing volcanoes and one caldera volcano controlled by Sumatra Fault Zone over a length of 1700 km. To understand this geothermal field system, some information about geochemistry including isotope composition in its fluid is needed. Sulphur-34 and oxygen-18 isotopes in dissolved sulphate pair have been used to determine the origin of acidic fluid of sulphate and to evaluate the process involved. The fluids from eight hot springs, two fumaroles, four deep wells and crater have been collected in along Sumatra geothermal fields. Sulphur-34 (d 34S (SO4, 0/00 CDT and oxygen-18 (d 18O (SO4, 0/00 SMOW in sulphate is analyzed according to Robinson-Kusakabe and Rafter method, respectively. The d 34S (SO4 values from Sibayak wells are more enriched of 16.8 0/00 to 18.2 0/0 that may indicate the dissolution of anhydrite minerals or isotope partitioning in hydration of SO2. The d 34S (SO4 values from two fumaroles (Pusuk Bukit - North Sumatra and Rantau Dadap - South Sumatra are at depleted value of -0.150/00 and 1.80/00, those are close to d 34S from magmatic sulphur.  In general, the d 34S (SO4 of springs spread in a wide range of 5.250/00 to14.20/00 and show a mixing process between atmospheric sulphate and sulphate from deep wells. The d 18O (SO4 from wells exhibits depleted value around -3.60/00 suggesting that 87.5% of sulphate oxygen is derived from groundwater oxygen and 12.5% is derived from atmospheric molecular oxygen in sulphide oxidation reaction. In the other hand, hot springs (except Semurup, crater and fumaroles have enriched value of d 18O (SO4. These enriched values suggest that a higher percentage of atmospherically derived oxygen compared to those from the depth.   Keywords: isotope, geothermal, Sumatra

High-throughput simultaneous determination of plasma water deuterium and 18-oxygen enrichment using a high-temperature conversion elemental analyzer with isotope ratio mass spectrometry.

Science.gov (United States)

Richelle, M; Darimont, C; Piguet-Welsch, C; Fay, L B

2004-01-01

This paper presents a high-throughput method for the simultaneous determination of deuterium and oxygen-18 (18O) enrichment of water samples isolated from blood. This analytical method enables rapid and simple determination of these enrichments of microgram quantities of water. Water is converted into hydrogen and carbon monoxide gases by the use of a high-temperature conversion elemental analyzer (TC-EA), that are then transferred on-line into the isotope ratio mass spectrometer. Accuracy determined with the standard light Antartic precipitation (SLAP) and Greenland ice sheet precipitation (GISP) is reliable for deuterium and 18O enrichments. The range of linearity is from 0 up to 0.09 atom percent excess (APE, i.e. -78 up to 5725 delta per mil (dpm)) for deuterium enrichment and from 0 up to 0.17 APE (-11 up to 890 dpm) for 18O enrichment. Memory effects do exist but can be avoided by analyzing the biological samples in quintuplet. This method allows the determination of 1440 samples per week, i.e. 288 biological samples per week. Copyright 2004 John Wiley & Sons, Ltd.

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

Science.gov (United States)

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

2012-10-01

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

Availability of enriched stable isotopes: present status and future prospects

International Nuclear Information System (INIS)

Hoff, R.W.

1986-01-01

The Electromagnetic Isotope Enrichment Facility (EMIEF) is currently used to produce 225 enriched stable isotopes of 50 elements. Among these are included most of the known elements with stable isotopes except for the noble gases, certain light elements, monisotopic elements, etc. The EMIEF can also be used to produce enriched samples of radioactive species, most notably the isotopes of uranium and plutonium. These enriched materials are placed in either the Sales Inventory of in the Research Materials Collection (RMC). The materials in the Sales Inventory are for sale to anyone on a first come, first served basis. Prices in the most recent catalog range from $0.05/mg for 99.8% 140 Ce to $1,267/mg for 98.5% 176 Lu. The materials in the RMC are made available to US researchers (or groups that include a US investigator) on a loan basis for use in non-destructive experiments and applications. In addition, certain samples have been provided to European investigators for cross-section studies through the auspices of EURATOM and the European-American Nuclear Data Committee. The status of the enriched isotopes included in the Sales Inventory is tabulated where isotopes are listed that are either not available or are in insufficient quantity or quality to meet current requests, as of 6/30/86. These can be summarized in the following subcategories: isotopes with zero inventory (22), Isotopes of insufficient quantity (17), and isotopes with insufficient enrichment quality (10). Of these 49 species, the supplies of 10 will be replenished by the scheduled FY86 enrichments in process (isotopes of bromine, calcium, nickel, potassium, rubidium, and strontium). In Table 3 are listed isotopes where the current inventory is less than the average annual sales level for the past five years. There are 47 isotopes listed, representing 25 different elements. Thus, there exists considerable potential for a substantial increase in the number of isotopes with zero inventory

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

International Nuclear Information System (INIS)

Kim, J.; Kim, T.S.; Choi, H.; Jang, D.S.; Jeong, D.Y.

2004-01-01

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, 18 O-enriched water (> 90%) is used as a target in a cyclotron for the production of the β -emitting radioisotope 18 F, which is essential for PET (Positron Emission Tomography) pharmaceutical [ 18 F]-labeled 2-deoxyglucose (FDG) synthesis. Currently, 18 O 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 18 O. In this regard, it is essential to re-use the used target water as much as possible since the 18 O-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 18 f-FDG production loop and to re-enrich the 18 O isotope in the target water diluted during the purification process. For the development of a compact target water 18 O re-enrichment system, the 18 O isotope separation characteristics of MD (Membrane Distillation) were investigated. The 18 O 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. 18 O/ 16 O 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 18 O 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

Oxygen isotope regional pattern in granitoids from the Cachoeirinha Belt, northeast Brazil

International Nuclear Information System (INIS)

Sial, A.N.

1984-01-01

Four groups of granitoids are present within the Cachoeirinha belt and in the adjacent migmatitic basement, between 37 0 and 40 0 W long. and 7 0 and 8 0 15' S lat., States of Pernambuco and Paraiba: a) K 2 O - enriched, very porphyritic; b) a calc-alkalic slightly porphyritic group; c) group with trondjemitic affinities; and d) peralkalic group. Petrology and oxygen isotope geochemistry for over 100 samples from these groups were studied. Almost all plutons for which 5 or more samples were analyzed, exhibit a total range of gamma 18 O less than 2% o. A broad range of mean oxygen isotope composition is observed, varying from 6.93 to 12.79% o. There is a systematic regional trend in which the calc-alkalic granitoids (conceicao-type) found within the Cachoeirinha space are the most 18 O - enriched rocks (10.6 to 12.9% o) while the lowest mean gamma 18 O values (4.5 to 9.7% o) are found in the K 2 O - enriched granitoids (Itaporanga-type). Intermediate gamma 18 O values were recorded in the bodies with trondhjemitic affinities (8.9 to 9.8% o) which intruded metasediments of the Salgueiro Group and in the peralkalic granitoids of Catingueira (8.1 to 9.8% o) which intruded Cachoeirinha metamorphics. Among the potassic granitoids, mean gamma 18 O increases from Bodoco to Itaporanga (from west to east). As a whole, the W.R. gamma 18 O of these plutons correlate with the type of grade of metamorphism of the host rocks and, therefore, with the tectonic framework, increasing from those which intruded the gneiss-migmatites to those which intruded the low-grade metamorphics of the Cachoeirinha Group. The possible origin of each rock group is discussed in light of the oxygen isotope geochemistry. (Author) [pt

OXYGEN ISOTOPIC COMPOSITIONS OF SOLAR CORUNDUM GRAINS

International Nuclear Information System (INIS)

Makide, Kentaro; Nagashima, Kazuhide; Huss, Gary R.; Krot, Alexander N.

2009-01-01

Oxygen is one of the major rock-forming elements in the solar system and the third most abundant element of the Sun. Oxygen isotopic composition of the Sun, however, is not known due to a poor resolution of astronomical spectroscopic measurements. Several Δ 17 O values have been proposed for the composition of the Sun based on (1) the oxygen isotopic measurements of the solar wind implanted into metallic particles in lunar soil ( 2 O 3 ) is thermodynamically the first condensate from a cooling gas of solar composition. Corundum-bearing CAIs, however, are exceptionally rare, suggesting either continuous reaction of the corundum condensates with a cooling nebular gas and their replacement by hibonite (CaAl 12 O 19 ) or their destruction by melting together with less refractory condensates during formation of igneous CAIs. In contrast to the corundum-bearing CAIs, isolated micrometer-sized corundum grains are common in the acid-resistant residues from unmetamorphosed chondrites. These grains could have avoided multistage reprocessing during CAI formation and, therefore, can potentially provide constraints on the initial oxygen isotopic composition of the solar nebula, and, hence, of the Sun. Here we report oxygen isotopic compositions of ∼60 micrometer-sized corundum grains in the acid-resistant residues from unequilibrated ordinary chondrites (Semarkona (LL3.0), Bishunpur (LL3.1), Roosevelt County 075 (H3.2)) and unmetamorphosed carbonaceous chondrites (Orgueil (CI1), Murray (CM2), and Alan Hills A77307 (CO3.0)) measured with a Cameca ims-1280 ion microprobe. All corundum grains, except two, are 16 O-rich (Δ 17 O = -22.7 per mille ± 8.5 per mille, 2σ), and compositionally similar to the mineralogically pristine CAIs from the CR carbonaceous chondrites (-23.3 per mille ± 1.9 per mille, 2σ), and solar wind returned by the Genesis spacecraft (-27 per mille ± 6 per mille, 2σ). One corundum grain is highly 17 O-enriched (δ 17 O ∼ +60 per mille, δ 18 O �

The isotopic enrichment of uranium in 1979

International Nuclear Information System (INIS)

Baron, M.

1979-01-01

The Eurodif uranium enrichment plant built on the Tricastin site is described. The uranium isotope separation plants in service abroad are presented. The main characteristics of the international enrichment market are defined [fr

Laser-induced photochemical enrichment of boron isotopes

International Nuclear Information System (INIS)

Freund, S.M.; Ritter, J.J.

1976-01-01

A boron trichloride starting material containing both boron-10 isotopes and boron-11 isotopes is selectively enriched in one or the other of these isotopes by a laser-induced photochemical method involving the reaction of laser-excited boron trichloride with either H 2 S or D 2 S. The method is carried out by subjecting a low pressure gaseous mixture of boron trichloride starting material and the sulfide to infrared radiation from a carbon dioxide TE laser. The wave length of the radiation is selected so as to selectively excite one or the other of boron-10 BCl 3 molecules or boron-11 BCl 3 molecules, thereby making them preferentially more reactive with the sulfide. The laser-induced reaction produces both a boron-containing solid phase reaction product and a gaseous phase containing mostly unreacted BCl 3 and small amounts of sulfhydroboranes. Pure boron trichloride selectively enriched in one of the isotopes is recovered as the primary product of the method from the gaseous phase by a multi-step recovery procedure. Pure boron trichloride enriched in the other isotope is recovered as a secondary product of the method by the subsequent chlorination of the solid phase reaction product followed by separation of BCl 3 from the mixture of gaseous products resulting from the chlorination

Stable isotope enrichment by thermal diffusion

International Nuclear Information System (INIS)

Vasaru, Gheorghe

2003-01-01

Thermal diffusion (TD) in both gaseous and liquid phase has been the subject of extensive experimental and theoretical investigations, especially after the invention by K. Clusius and G. Dickel of the thermal diffusion column, sixty years ago. This paper gives a brief overview of the most important applications and developments of this transport phenomenon for enrichment of 13 C and of some noble gases isotopes in our institute. The results of calculations of the transport coefficients H and K for a concentric tube type TD column, operated with methane as process gas, are presented. Static separation factor at equilibrium vs gas pressure has been calculated for various molecular models. The experimental separation factors for different gas pressure were found to be consistent with those calculated for the inverse power repulsion model and the Lennard-Jones model. The most important characteristics of a seven-stage cascade consisting of 19 TD columns of concentric tube type are given. This system has been constructed and successfully operated at a temperature of 673 K and produces an enrichment of methane of natural isotopic 13 C abundance, up to the concentration of 25% 13 CH 4 . Enrichment of the noble gases isotopes implies: - a . Enrichment of 20 Ne and 22 Ne in a eight-stage cascade consisting of 8 TD columns; - b. enrichment of 46 Ar in a seven-stage cascade consisting of TD columns and finally; - c. enrichment of 78 Kr and 86 Kr in a fifteen-stage cascade, consisting of 35 TD columns. For all these installations we have adopted TD columns of hot wire type (4 m in length), operated at a temperature of 1073 K. (author)

Yttrium doped BSCF membranes for oxygen separation

DEFF Research Database (Denmark)

Haworth, P.; Smart, S.; Glasscock, Julie

2011-01-01

This work investigates the partial substitution of yttrium in place of iron in BSCF to form Ba0.5Sr0.5Co0.8Fe0.2−xYxO3−δ, where x varied between 0 and 0.2. X-ray diffraction patterns showed the formation of a perovskite cubic phase structure up to x = 0.15, whilst the full substitution of yttrium...

Calcium hydroxide isotope effect in calcium isotope enrichment by ion exchange

International Nuclear Information System (INIS)

Jepson, B.E.; Shockey, G.C.

1984-01-01

The enrichment of calcium isotopes has been observed in ion-exchange chromatography with an aqueous phase of calcium hydroxide and a solid phase of sulfonic acid resin. The band front was exceedingly sharp as a result of the acid-base reaction occuring at the front of the band. Single-stage separation coefficients were found to be epsilon( 44 Ca/ 40 Ca) = 11 x 10 -4 and epsilon( 48 Ca/ 40 Ca) = 18 x 10 -4 . The maximum column separation factors achieved were 1.05 for calcium-44 and 1.09 for calcium-48 with the heavy isotopes enriching in the fluid phase. The calcium isotope effect between fully hydrated aqueous calcium ions and undissociated aqueous calcium hydroxide was estimated. For the calcium-44/40 isotope pair the separation coefficient was 13 x 10 -4 . 20 references, 2 figures

Availability of enriched isotopic material for accelerator targets

International Nuclear Information System (INIS)

Newman, E.

1982-01-01

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

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...

Development of empirical relation for isotope of uranium in enriched uranium matrix

International Nuclear Information System (INIS)

Srivastava, S.K.; Vidyasagar, D.; Jha, S.K.; Tripathi, R.M.

2018-01-01

Uranium enriched in 235 U is required in commercial light water reactors to produce a controlled nuclear reaction. Enrichment allows the 235 U isotopes to be increased from 0.71% to a range between 2% to 5% depending upon requirement. The enriched uranium in the form of sintered UO 2 pellet is used for any commercially operating boiling light water reactors. The enriched uranium fuel bundle surface swipes sample is being analysed to assess the tramp uranium as a quality control parameter. It is known that the 234 U isotope also enriched along with 235 U isotope in conventional gaseous diffusion enrichment process. The information about enrichment percentage of 234 U helps to characterize isotopic properties of enriched uranium. A few reports provide the empirical equation and graphs for finding out the specific activity, activity percentage, activity ratio of 234 U isotopes for enriched uranium. Most of them have not provided the reference for the data used and their source. An attempt has been made to model the relationship between 234 U and 235 U as a function of uranium enrichment at low level

Status of the isotope enrichment program at Oak Ridge National Laboratory

Science.gov (United States)

Tracy, J. G.

1991-05-01

The objectives of the isotope enrichment program at the Oak Ridge National Laboratory are to prepare and distribute electromagnetically separated stable isotopes to the research, medical and industrial communities on a worldwide basis. Topics discussed in this presentation include (1) a review of facility modifications, (2) current facility capabilities, (3) enrichment processes, and (4) final product distribution. An update on alternative separations methods to augment the electromagnetic separations process is covered, as well as special services that are available for providing custom materials to meet special applications. Recent changes in U.S. Department of Energy policy that impact the nation's isotope and isotope-related programs are summarized, with special emphasis on the effects on isotope enrichment, radioisotope production, target fabrication, pricing, and marketing and distribution of stable isotopes.

Fractionation of hydrogen and oxygen isotopes between hydrated and free water molecules in aqueous urea solution

International Nuclear Information System (INIS)

Kakiuchi, M.; Matsuo, S.

1985-01-01

Ratios of D/H and 18 O/ 16 O in the vapor phase in equilibrium with aqueous urea solution with different urea molalities were measured at 15 and 25 0 C. Under the assumption that urea solutions consist of two species, i.e., the urea-water cluster and free water, the results are interpreted to give the average hydration number, i.e., the number of water molecules per urea molecule in the urea-water cluster. Good agreement was obtained for the hydration number estimated independently from hydrogen and oxygen isotopic fractions. On the basis of hydrogen isotopic data at 25 0 C, the average hydration number of urea in the cluster is 6.3 +/- 0.8 at 2.1 m and 2.75 +/- 0.08 at saturation (20.15 m). The corresponding average hydration numbers based on oxygen isotopic data were calculated to be 6.7 +/- 2.4 at 2.1 m and 2.75 +/- 0.25 at urea saturation. HD 16 O is enriched in the urea-water cluster and H 2 18 O is enriched in free water. Isotopic partitioning between the cluster and free water is markedly different from those between hydration spheres and free water in aqueous electrolyte solutions. 29 references, 6 figures, 5 tables

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

International Nuclear Information System (INIS)

Aaron, W.S.; Tracy, J.G.; Collins, E.D.

1997-01-01

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.)

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

Science.gov (United States)

Scott Aaron, W.; Tracy, Joe G.; Collins, Emory D.

1997-02-01

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) 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; 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.

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

International Nuclear Information System (INIS)

Aaron, W.S.; Tracy, J.G.; Collins, E.D.

1996-01-01

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

Research on aerodynamic means of isotope enrichment

International Nuclear Information System (INIS)

Cattolica, R.J.; Gallagher, R.J.; Talbot, L.; Willis, D.R.; Hurlbut, F.C.; Fiszdon, W.; Anderson, J.B.

1978-03-01

The results of a research program directed toward the understanding of the fundamental gas dynamics involved in aerodynamic isotope enrichment are summarized. The specific aerodynamic isotope enrichment method which was examined in this research is based on a velocity slip phenomenon which occurs in the rarefied hypersonic expansion of a heavy molecular weight gas and a light carrier gas in a nozzle or free jet. This particular aerodynamic method was chosen for study because it contains the fundamental molecular physics of other more complex techniques within the context of a one-dimensional flow without boundary effects. From both an experimental and theoretical modeling perspective this provides an excellent basis for testing the experimental and numerical tools with which to investigate more complex aerodynamic isotope enrichment processes. This report consists of three separate parts. Part I contains a theoretical analysis of the velocity slip effect in free jet expansions of binary and ternary gas mixtures. The analysis, based on a source flow model and using moment equations is derived from the Boltzmann equation using the hypersonic approximation. Part II contains the experimental measurements of velocity slip. The numerical simulation of the slip process was carried out by using a Monte-Carlo numerical technique. In addition, comparisons between the theoretical analysis of Part I and the experiments are presented. Part III describes impact pressure measurements of free jet expansions from slot shaped two dimensional nozzles. At least two methods of aerodynamic isotope enrichment (opposed jet and velocity slip) would depend on the use of this type of two dimensional expansion. Flow surveys of single free jet and the interferene of crossed free jets are presented

Size-dependent cytotoxicity of yttrium oxide nanoparticles on primary osteoblasts in vitro

Energy Technology Data Exchange (ETDEWEB)

Zhou, Guoqiang, E-mail: zhougq1982@163.com; Li, Yunfei; Ma, Yanyan; Liu, Zhu; Cao, Lili; Wang, Da; Liu, Sudan; Xu, Wenshi; Wang, Wenying [Hebei University, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Key Laboratory of Chemical Biology of Hebei Province, College of Chemistry and Environmental Science (China)

2016-05-15

Yttrium oxide nanoparticles are an excellent host material for the rare earth metals and have high luminescence efficiency providing a potential application in photodynamic therapy and biological imaging. In this study, the effects of yttrium oxide nanoparticles with four different sizes were investigated using primary osteoblasts in vitro. The results demonstrated that the cytotoxicity generated by yttrium oxide nanoparticles depended on the particle size, and smaller particles possessed higher toxicological effects. For the purpose to elucidate the relationship between reactive oxygen species generation and cell damage, cytomembrane integrity, intracellular reactive oxygen species level, mitochondrial membrane potential, cell apoptosis rate, and activity of caspase-3 in cells were then measured. Increased reactive oxygen species level was also observed in a size-dependent way. Thus, our data demonstrated that exposure to yttrium oxide nanoparticles resulted in a size-dependent cytotoxicity in cultured primary osteoblasts, and reactive oxygen species generation should be one possible damage pathway for the toxicological effects produced by yttrium oxide particles. The results may provide useful information for more rational applications of yttrium oxide nanoparticles in the future.

Measurement system analysis (MSA) of the isotopic ratio for uranium isotope enrichment process control

Energy Technology Data Exchange (ETDEWEB)

Medeiros, Josue C. de; Barbosa, Rodrigo A.; Carnaval, Joao Paulo R., E-mail: josue@inb.gov.br, E-mail: rodrigobarbosa@inb.gov.br, E-mail: joaocarnaval@inb.gov.br [Industrias Nucleares do Brasil (INB), Rezende, RJ (Brazil)

2013-07-01

Currently, one of the stages in nuclear fuel cycle development is the process of uranium isotope enrichment, which will provide the amount of low enriched uranium for the nuclear fuel production to supply 100% Angra 1 and 20% Angra 2 demands. Determination of isotopic ration n({sup 235}U)/n({sup 238}U) in uranium hexafluoride (UF{sub 6} - used as process gas) is essential in order to control of enrichment process of isotopic separation by gaseous centrifugation cascades. The uranium hexafluoride process is performed by gas continuous feeding in separation unit which uses the centrifuge force principle, establishing a density gradient in a gas containing components of different molecular weights. The elemental separation effect occurs in a single ultracentrifuge that results in a partial separation of the feed in two fractions: an enriched on (product) and another depleted (waste) in the desired isotope ({sup 235}UF{sub 6}). Industrias Nucleares do Brasil (INB) has used quadrupole mass spectrometry (QMS) by electron impact (EI) to perform isotopic ratio n({sup 235}U)/n({sup 238}U) analysis in the process. The decision of adjustments and change te input variables are based on the results presented in these analysis. A study of stability, bias and linearity determination has been performed in order to evaluate the applied method, variations and systematic errors in the measurement system. The software used to analyze the techniques above was the Minitab 15. (author)

Novel Membranes and Processes for Oxygen Enrichment

Energy Technology Data Exchange (ETDEWEB)

Lin, Haiqing

2011-11-15

The overall goal of this project is to develop a membrane process that produces air containing 25-35% oxygen, at a cost of $25-40/ton of equivalent pure oxygen (EPO2). Oxygen-enriched air at such a low cost will allow existing air-fueled furnaces to be converted economically to oxygen-enriched furnaces, which in turn will improve the economic and energy efficiency of combustion processes significantly, and reduce the cost of CO{sub 2} capture and sequestration from flue gases throughout the U.S. manufacturing industries. During the 12-month Concept Definition project: We identified a series of perfluoropolymers (PFPs) with promising oxygen/nitrogen separation properties, which were successfully made into thin film composite membranes. The membranes showed oxygen permeance as high as 1,200 gpu and oxygen/nitrogen selectivity of 3.0, and the permeance and selectivity were stable over the time period tested (60 days). We successfully scaled up the production of high-flux PFP-based membranes, using MTR's commercial coaters. Two bench-scale spiral-wound modules with countercurrent designs were made and parametric tests were performed to understand the effect of feed flow rate and pressure, permeate pressure and sweep flow rate on the membrane module separation properties. At various operating conditions that modeled potential industrial operating conditions, the module separation properties were similar to the pure-gas separation properties in the membrane stamps. We also identified and synthesized new polymers [including polymers of intrinsic microporosity (PIMs) and polyimides] with higher oxygen/nitrogen selectivity (3.5-5.0) than the PFPs, and made these polymers into thin film composite membranes. However, these membranes were susceptible to severe aging; pure-gas permeance decreased nearly six-fold within two weeks, making them impractical for industrial applications of oxygen enrichment. We tested the effect of oxygen-enriched air on NO{sub x} emissions

Shifts in rotifer life history in response to stable isotope enrichment: testing theories of isotope effects on organismal growth

Science.gov (United States)

2017-01-01

In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic interactions, nutrient budgets and biogeochemical processes. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism growth and metabolism. This assumption is, however, challenged by theoretical considerations and experimental studies on kinetic isotope effects in vivo. Here, I demonstrate profound changes in life histories of the rotifer Brachionus plicatilis fed 15N-enriched algae (0.4–5.0 at%); i.e. at the enrichment levels commonly used in ecological studies. These findings support theoretically predicted effects of heavy isotope enrichment on growth, metabolism and ageing in biological systems and underline the importance of accounting for such effects when using stable isotope labelling in experimental studies. PMID:28405367

Scandium, yttrium and the lanthanides

International Nuclear Information System (INIS)

Hart, F.A.

1987-01-01

This chapter on the chemistry of the coordination complexes of scandium, yttrium and the lanthanides includes sections on the nitrogen and oxygen donor ligands and complex halides of scandium, and the phosphorus and sulfur donor ligands of yttrium and the lanthanides. Complexes with the macrocylic ligands and with halides are also discussed. Sections on the NMR and electronic spectra of the lanthanides are also included. (UK)

Hydrogen Production from Cyclic Chemical Looping Steam Methane Reforming over Yttrium Promoted Ni/SBA-16 Oxygen Carrier

Directory of Open Access Journals (Sweden)

Sanaz Daneshmand-Jahromi

2017-09-01

Full Text Available In this work, the modification of Ni/SBA-16 oxygen carrier (OC with yttrium promoter is investigated. The yttrium promoted Ni-based oxygen carrier was synthesized via co-impregnation method and applied in chemical looping steam methane reforming (CL-SMR process, which is used for the production of clean energy carrier. The reaction temperature (500–750 °C, Y loading (2.5–7.4 wt. %, steam/carbon molar ratio (1–5, Ni loading (10–30 wt. % and life time of OCs over 16 cycles at 650 °C were studied to investigate and optimize the structure of OC and process temperature with maximizing average methane conversion and hydrogen production yield. The synthesized OCs were characterized by multiples techniques. The results of X-ray powder diffraction (XRD and energy dispersive X-ray spectroscopy (EDX of reacted OCs showed that the presence of Y particles on the surface of OCs reduces the coke formation. The smaller NiO species were found for the yttrium promoted OC and therefore the distribution of Ni particles was improved. The reduction-oxidation (redox results revealed that 25Ni-2.5Y/SBA-16 OC has the highest catalytic activity of about 99.83% average CH4 conversion and 85.34% H2 production yield at reduction temperature of 650 °C with the steam to carbon molar ratio of 2.

Yttrium and lanthanum recovery from low cerium carbonate, yttrium carbonate and yttrium concentrate; Aproveitamento de itrio e lantanio de um carbonato de terras raras de baixo teor em cerio, de um carbonato de itrio e de um oxido de terras itricas

Energy Technology Data Exchange (ETDEWEB)

Vasconcelos, Mari Estela de

2006-07-01

In this work, separation, enrichment and purification of lanthanum and yttrium were performed using as raw material a commercial low cerium rare earth concentrate named LCC (low cerium carbonate), an yttrium concentrate named 'yttrium carbonate', and a third concentrated known as 'yttrium earths oxide. The first two were industrially produced by the late NUCLEMON - NUCLEBRAS de Monazita e Associados Ltda, using Brazilian monazite. The 'yttrium earths oxide' come from a process for preparation of lanthanum during the course of the experimental work for the present thesis. The following techniques were used: fractional precipitation with urea; fractional leaching of the LCC using ammonium carbonate; precipitation of rare earth peroxycarbonates starting from the rare earth complex carbonates. Once prepared the enriched rare earth fractions the same were refined using the ion exchange chromatography with strong cationic resin without the use of retention ion and elution using the ammonium salt of ethylenediaminetetraacetic acid. With the association of the above mentioned techniques were obtained pure oxides of yttrium (>97,7%), lanthanum (99,9%), gadolinium (96,6%) and samarium (99,9%). The process here developed has technical and economic viability for the installation of a large scale unity. (author)

The role of enriched isotopes in fundamental physical investigations

International Nuclear Information System (INIS)

Gavrin, V.N.; Skorynin, G.M.; Shubin, A.N.

2002-01-01

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 ( 136 Xe, 100 Mo, 76 Ge, 116 Cd, 82 Se and some others) are discussed together with basic requirements for isotopes and possibilities on operating time of the Industrial Joining Electrochemical plant [ru

Oxygen isotopic fractionation during bacterial sulfate reduction

Science.gov (United States)

Balci, N.; Turchyn, A. V.; Lyons, T.; Bruchert, V.; Schrag, D. P.; Wall, J.

2006-12-01

Sulfur isotope fractionation during bacterial sulfate reduction (BSR) is understood to depend on a variety of environmental parameters, such as sulfate concentration, temperature, cell specific sulfate reduction rates, and the carbon substrate. What controls oxygen isotope fractionation during BSR is less well understood. Some studies have suggested that carbon substrate is important, whereas others concluded that there is a stoichiometric relationship between the fractionations of sulfur and oxygen during BSR. Studies of oxygen fractionation are complicated by isotopic equilibration between sulfur intermediates, particularly sulfite, and water. This process can modify the isotopic composition of the extracellular sulfate pool (δ18OSO4 ). Given this, the challenge is to distinguish between this isotopic equilibration and fractionations linked to the kinetic effects of the intercellular enzymes and the incorporation of sulfate into the bacterial cell. The δ18OSO4 , in concert with the sulfur isotope composition of sulfate (δ34SSO4), could be a powerful tool for understanding the pathways and environmental controls of BSR in natural systems. We will present δ18OSO4 data measured from batch culture growth of 14 different species of sulfate reducing bacteria for which sulfur isotope data were previously published. A general observation is that δ18OSO4 shows little isotopic change (kinetic effect during BSR and/or equilibration between sulfur intermediates and the isotopically light water (~-5‰) of the growth medium. Our present batch culture data do not allow us to convincingly isolate the magnitude and the controlling parameters of the kinetic isotope effect for oxygen. However, ongoing growth of mutant bacteria missing enzymes critical in the different steps of BSR may assist in this mission.

Theory of oxygen isotope exchange

NARCIS (Netherlands)

den Otter, M.W.; Boukamp, Bernard A.; Bouwmeester, Henricus J.M.

2001-01-01

Transients for oxygen molecular mass numbers 32, 34 and 36 are derived which can be used for the interpretation of oxygen isotope exchange data based on measurement of concentrations of 16O2, 16O18O and 18O2 in the gas phase. Key parameters in the theory are the rate at which oxygen molecules are

Biomedical research applications of electromagnetically separated enriched stable isotopes

International Nuclear Information System (INIS)

Lambrecht, R.M.

1982-01-01

The current and projected annual requirements through 1985 for stable isotopes enriched by electromagnetic separation methods were reviewed for applications in various types of biomedical research: (1) medical radiosotope production, labeled compounds, and potential radiopharmaceuticals; (2) nutrition, food science, and pharmacology; (3) metallobiochemistry and environmental toxicology; (4) nuclear magnetic resonance, electron paramagnetic resonance, and Moessbauer spectroscopy in biochemical, biophysical, and biomedical research; and (5) miscellaneous advances in radioactive and non-radioactive tracer technology. Radioisotopes available from commercial sources or routinely used in clinical nuclear medicine were excluded. Priorities and summaries are based on statements in the references and from answers to a survey conducted in the fall of 1981. Current requirements for enriched stable isotopes in biomedical research are not being satisfied. Severe shortages exist for 26 Mg, 43 Ca, 70 Zn, 76 Se, 78 Se, 102 Pd, 111 Cd, 113 Cd, and 190 Os. Many interesting and potentially important investigations in biomedical research require small quantities of specific elements at high isotopic enrichments

Method for enriching and separating heavy hydrogen isotopes from substance streams containing such isotopes by means of isotope exchange

International Nuclear Information System (INIS)

Knochel, A.; Eggers, I.; Klatte, B.; Wilken, R. D.

1985-01-01

A process for enriching and separating heavy hydrogen isotopes having a heavy hydrogen cation (deuterium and/or tritium) from substance streams containing them, wherein the respectively present hydrogen isotopes are exchanged in chemical equilibria. A protic, acid solution containing deuterium and/or tritium is brought into contact with a value material from the group of open-chained polyethers or aminopolyethers, macro-monocyclic or macro-polycyclic polyethers, macro-monocyclic or macro-polycyclic amino polyethers, and mixtures of these values, in their free or proton salt form to form a reaction product of the heavy hydrogen cation with the value or value salt and bring about enrichment of deuterium and/or tritium in the reaction product. The reaction product containing the value or value salt is separated from the solution. The separated reaction product is treated to release the hydrogen isotope(s) to be enriched in the form of deuterium oxide (HDO) and/or tritium oxide (HTO) by regenerating the value or its salt, respectively. The regenerated value is returned for reuse

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

Science.gov (United States)

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

2017-10-01

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

Ultrahigh thermal conductivity of isotopically enriched silicon

Science.gov (United States)

Inyushkin, Alexander V.; Taldenkov, Alexander N.; Ager, Joel W.; Haller, Eugene E.; Riemann, Helge; Abrosimov, Nikolay V.; Pohl, Hans-Joachim; Becker, Peter

2018-03-01

Most of the stable elements have two and more stable isotopes. The physical properties of materials composed of such elements depend on the isotopic abundance to some extent. A remarkably strong isotope effect is observed in the phonon thermal conductivity, the principal mechanism of heat conduction in nonmetallic crystals. An isotopic disorder due to random distribution of the isotopes in the crystal lattice sites results in a rather strong phonon scattering and, consequently, in a reduction of thermal conductivity. In this paper, we present new results of accurate and precise measurements of thermal conductivity κ(T) for silicon single crystals having three different isotopic compositions at temperatures T from 2.4 to 420 K. The highly enriched crystal containing 99.995% of 28Si, which is one of the most perfect crystals ever synthesized, demonstrates a thermal conductivity of about 450 ± 10 W cm-1 K-1 at 24 K, the highest measured value among bulk dielectrics, which is ten times greater than the one for its counterpart natSi with the natural isotopic constitution. For highly enriched crystal 28Si and crystal natSi, the measurements were performed for two orientations [001] and [011], a magnitude of the phonon focusing effect on thermal conductivity was determined accurately at low temperatures. The anisotropy of thermal conductivity disappears above 31 K. The influence of the boundary scattering on thermal conductivity persists sizable up to much higher temperatures (˜80 K). The κ(T) measured in this work gives the most accurate approximation of the intrinsic thermal conductivity of single crystal silicon which is determined solely by the anharmonic phonon processes and diffusive boundary scattering over a wide temperature range.

Simulating Isotope Enrichment by Gaseous Diffusion

Science.gov (United States)

Reed, Cameron

2015-04-01

A desktop-computer simulation of isotope enrichment by gaseous diffusion has been developed. The simulation incorporates two non-interacting point-mass species whose members pass through a cascade of cells containing porous membranes and retain constant speeds as they reflect off the walls of the cells and the spaces between holes in the membranes. A particular feature is periodic forward recycling of enriched material to cells further along the cascade along with simultaneous return of depleted material to preceding cells. The number of particles, the mass ratio, the initial fractional abundance of the lighter species, and the time between recycling operations can be chosen by the user. The simulation is simple enough to be understood on the basis of two-dimensional kinematics, and demonstrates that the fractional abundance of the lighter-isotope species increases along the cascade. The logic of the simulation will be described and results of some typical runs will be presented and discussed.

Oxygen isotopic ratio of the diatom siliceous valves: development of a new method in quantitative paleoclimatology

International Nuclear Information System (INIS)

Labeyrie, Laurent.

1979-07-01

This paper describes a new method allowing the measurement of the 18 O/ 16 O ratio of the biogenic silica oxygen, which takes into account the effects due to the organic matter and hydration water associated with this type of silica. By isotopic exchange with enriched water, we have been able to fix a treatment which eliminate all contamination and memory effects. This has permitted us to study the temperature dependance of the hydrated silica-water oxygen isotopic fractionation. As application, we present a study of the variations of the delta 18 O of fossil diatoms valves along an Equatorial Pacific sediment core covering the last 20.000 years. The results demonstrate the usefulness of the delta 18 O of the diatom silica for paleoclimatic investigations [fr

Atom probe microscopy of zinc isotopic enrichment in ZnO nanorods

Directory of Open Access Journals (Sweden)

C. N. Ironside

2017-02-01

Full Text Available We report on atomic probe microscopy (APM of isotopically enriched ZnO nanorods that measures the spatial distribution of zinc isotopes in sections of ZnO nanorods for natural abundance natZnO and 64Zn and 66Zn enriched ZnO nanorods. The results demonstrate that APM can accurately quantify isotopic abundances within these nanoscale structures. Therefore the atom probe microscope is a useful tool for characterizing Zn isotopic heterostructures in ZnO. Isotopic heterostructures have been proposed for controlling thermal conductivity and also, combined with neutron transmutation doping, they could be key to a novel technology for producing p-n junctions in ZnO thin films and nanorods.

A latitudinal study of oxygen isotopes within horsehair

Science.gov (United States)

Thompson, E.; Bronk Ramsey, C.; McConnell, J. R.

2016-12-01

This study aims to explore the hypothesis that 'if oxygen isotope ratios deplete with decreasing temperature then a study of oxygen isotope ratios within horsehair from Oxfordshire to Iceland will show a latitudinal depletion gradient'. By looking at oxygen isotope values at different geographical positions, we can track the relationship with latitude and with different regional climate features. This will provide a firmer understanding of how to compare climate records from different locations. Additionally, a comparison of the horse breeds from this study to those analysed within previous studies will create an even better understanding of the intra-species variation within the δ18O values of horsehair. A total of 24 horses were sampled on the 7th March from Thordale Stud in Shetland, the Icelandic Food And Veterinary Authority in Iceland, the Exmoor Pony Centre in Exmoor and the Pigeon House Equestrian Centre in Oxfordshire. By starting the sampling process from the most recent growth at the follicle, the sampling date becomes a chronological marker, temporally fixing the first sample within a sequential set of data points extending for one year or longer, depending on the length of each individual hair. The samples were analysed for oxygen isotope values using an IRMS coupled within a Sercon HTEA. Preliminary results show a latitudinal gradient is evident on comparison between the locations, consistent with the findings of Darling and Talbot's study of fresh water isotopes in the British Isles (2003). These results support the hypothesis, showing that a study of oxygen isotope ratios within horse hair from Oxfordshire to Iceland showing a latitudinal depletion gradient, consistent with a depletion of oxygen isotope ratios due to decreasing temperatures. Darling, W. and Talbot, J. (2003). The O and H stable isotope composition of freshwaters in the British Isles. 1. Rainfall. Hydrol. Earth System Science, 7(2), pp.163-181.

Thermoanalytical study of the formation mechanism of yttria from yttrium acetate

International Nuclear Information System (INIS)

Farjas, J.; Camps, J.; Roura, P.; Ricart, S.; Puig, T.; Obradors, X.

2011-01-01

Highlights: → Thermal decomposition of yttrium acetate: three endothermic stages. → Intermediates: yttrium hydroxide and carbonate. → Product: cubic yttria (the degree of transformation is at least 99%). → The decomposition does not depend on the oxygen partial pressure. - Abstract: The processes involved in the thermal decomposition of yttrium acetate tetrahydrate, Y(CH 3 COO) 3 .4H 2 O, in air and in an inert atmosphere have been analyzed by thermoanalytical techniques (thermogravimetry, differential thermal analysis and evolved gas analysis) and by the structural characterization (X-ray diffraction, infrared spectroscopy, elemental analysis and scanning electron microscopy) of intermediates and final products. Decomposition of yttrium acetate is an endothermic transformation that takes place in a temperature range between 350 and 900 o C. The evolution of the mass during the decomposition process is not affected by the presence of oxygen. The process is initiated by the rupture of the bond between the metallic cation and the acetate ligand. This initial step (350-450 o C) involves the formation of amorphous yttrium hydroxide and yttrium carbonate and is characterized by a fast mass loss rate. A sudden decrease of the mass loss rate indicates a change in the decomposition kinetics that continues with the decomposition of yttrium hydroxide and yttrium carbonate. The main effect of an oxygen atmosphere is an intense exothermic process due to the combustion of organic species in the gas phase.

The transport of oxygen isotopes in hydrothermal systems

International Nuclear Information System (INIS)

McKibbin, R.; Absar, A.; Blattner, P.

1986-01-01

As groundwater passes through porous rocks, exchange of oxygen between the fluid and the solid matrix causes a change in the oxygen isotope concentrations in both water and rock. If the rate at which the exchange takes place can be estimated (as a function of the isotope concentrations and temperature) then the time taken for a rock/water system to come to equilibrium with respect to isotope concentration might be calculated. In this paper, the equation for isotope transport is derived using conservation laws, and a simple equation to describe the rate of isotope exchange is proposed. These are combined with the equations for fluid flow in a porous medium, to produce a general set of equations describing isotope transport in a hydrothermal system. These equations are solved numerically, using typical parameters, for the one-dimensional case. Oxygen isotope data from the basement rocks underlying Kawerau geothermal field are modelled. The results indicate that the time taken for exchange of 18 O to present-day values is less than the postulated age of hydrothermal alteration in that field. This suggests that, although controlled by similar parameters, oxygen isotope exchange, in felsic rocks at least, is much faster than hydrothermal alteration. This conclusion is consistent with the petrographic observations from the Kawerau system as well as other geothermal fields

Isotopic exchange between CO2 and H2O and labelling kinetics of photosynthetic oxygen

International Nuclear Information System (INIS)

Gerster, Richard

1971-01-01

The reaction of carbon dioxide with water has been studied by measuring the rate of oxygen exchange between C 18 O 2 and H 2 16 O. The mathematical treatment of the kinetics allows to determine with accuracy the diffusion flow between the gas and the liquid phase, in the same way as the CO 2 hydration rate. The velocity constant of this last process, whose value gives the in situ enzymatic activity of carbonic anhydrase, has been established in the case of chloroplast and Euglena suspensions and of aerial leaves. The study of the isotopic exchange between C 18 O 2 and a vegetable submitted to alternations of dark and light has allowed to calculate the isotopic abundance of the metabolized CO 2 whose value has been compared to that of the intracellular water and that of photosynthetic oxygen. In addition, a new method using 13 C 18 O 2 gives the means to measure with accuracy eventual isotopic effects. The labelling kinetics of the oxygen evolved by Euglena suspensions whose water has been enriched with 18 O have been established at different temperatures. (author) [fr

Oxygen isotopic tracing study of the dry thermal oxidation of 6H SiC

International Nuclear Information System (INIS)

Vickridge, I.C.; Ganem, J.-J.; Battistig, G.; Szilagyi, E.

2000-01-01

The (0 0 0 1) and (0 0 0 1-bar) faces of 6H SiC have been oxidised sequentially at 1100 deg. C and 100 mbar in ultra-dry oxygen of natural isotopic concentration and in ultra-dry oxygen highly enriched in 18 O. Measurement of the 18 O isotopic concentration profiles by nuclear resonance profiling with the narrow resonance at 151 keV in 18 O(p,α) 15 N shows that on the carbon-terminated face (0 0 0 1-bar) the oxidation mechanism is rather similar to that observed on Si(1 0 0), but that on the silicon-terminated face (0 0 0 1) the surface isotopic exchange and oxide formation are superposed. The surface exchange observed during a third dry oxidation, in 16 O 2 , is very similar in magnitude and spatial extent on Si(1 0 0), and the two 6H SiC faces, suggesting that at least near the surface the nature and composition of the three oxides are very similar

Oxygen isotopic tracing study of the dry thermal oxidation of 6H SiC

Energy Technology Data Exchange (ETDEWEB)

Vickridge, I.C. E-mail: vickridge@gps.jussieu.fr; Ganem, J.-J.; Battistig, G.; Szilagyi, E

2000-03-01

The (0 0 0 1) and (0 0 0 1-bar) faces of 6H SiC have been oxidised sequentially at 1100 deg. C and 100 mbar in ultra-dry oxygen of natural isotopic concentration and in ultra-dry oxygen highly enriched in {sup 18}O. Measurement of the {sup 18}O isotopic concentration profiles by nuclear resonance profiling with the narrow resonance at 151 keV in {sup 18}O(p,{alpha}){sup 15}N shows that on the carbon-terminated face (0 0 0 1-bar) the oxidation mechanism is rather similar to that observed on Si(1 0 0), but that on the silicon-terminated face (0 0 0 1) the surface isotopic exchange and oxide formation are superposed. The surface exchange observed during a third dry oxidation, in {sup 16}O{sub 2}, is very similar in magnitude and spatial extent on Si(1 0 0), and the two 6H SiC faces, suggesting that at least near the surface the nature and composition of the three oxides are very similar.

Oxygen enriched air using membrane for palm oil wastewater treatment

Directory of Open Access Journals (Sweden)

Ramlah Mohd Tajuddin

2002-11-01

Full Text Available A research aimed to explore new method of aeration using oxygen enriched air performance on BOD reduction of palm oil wastewater was conducted. The oxygen enriched air was obtained from an Oxygen Enriched System (OES developed using asymmetric polysulfone hollow fiber membrane with composition consisting of PSF: 22%, DMAc: 31.8%, THF: 31.8%, EtOH: 14.4%. Palm oil wastewater samples were taken from facultative pond effluent. These samples were tested for its initial biochemical oxygen demand (BOD, total suspended solids (TSS, pH, conductivity, turbidity, dissolved oxygen (DO, suspended solids (SS, and total dissolved solids (TDS before being subjected to two modes of aeration system, that is diffused air and oxygen enriched air. These water quality concentrations were tested for every 20 minutes for two-hour period during the aeration process. Results of BOD, TSS, pH, conductivity, DO, SS and TDS concentrations against time of samples from the two modes of aeration were then compared. It was found that DO concentration achieved in oxygen enriched air aeration was better than aeration using diffused air system. Aeration using OES improve the DO concentration in the wastewater and thus improve the BOD reduction and also influence other physical characteristics of wastewater. This phenomenon indicates the advantage of using air with higher oxygen concentration for wastewater aeration instead of diffused air system.

The rise of metal radionuclides in medical imaging: copper-64, zirconium-89 and yttrium-86.

Science.gov (United States)

Ikotun, Oluwatayo F; Lapi, Suzanne E

2011-04-01

Positron emission tomography, with its high sensitivity and resolution, is growing rapidly as an imaging technology for the diagnosis of many disease states. The success of this modality is reliant on instrumentation and the development of effective and novel targeted probes. Initially, research in this area was focused on what we will define in this article as 'standard' PET isotopes (carbon-11, nitrogen-13, oxygen-15 and fluorine-18), but the short half-lives of these isotopes limit radiopharmaceutical development to those that probe rapid biological processes. To overcome these limitations, there has been a rise in nonstandard isotope probe development in recent years. This review focuses on the biological probes and processes that have been examined, in additiom to the preclinical and clinical findings with nonstandard radiometals: copper-64, zirconium-89, and yttrium-86.

Seasonality of Leaf Carbon Isotopic Composition and Leaf Water Isotopic Enrichment in a Mixed Evergreen Forest in Southern California

Science.gov (United States)

Santiago, L. S.; Sickman, J. O.; Goulden, M.; DeVan, C.; Pasquini, S. C.; Pivovaroff, A. L.

2011-12-01

Leaf carbon isotopic composition and leaf water isotopic enrichment reflect physiological processes and are important for linking local and regional scale processes to global patterns. We investigated how seasonality affects the isotopic composition of bulk leaf carbon, leaf sugar carbon, and leaf water hydrogen under a Mediterranean climate. Leaf and stem samples were collected monthly from four tree species (Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Quercus chrysolepis) at the James San Jacinto Mountain Reserve in southern California. Mean monthly bulk leaf carbon isotopic composition varied from -34.5 % in P. ponderosa to -24.7 % in P. lambertiana and became more depleted in 13C from the spring to the summer. Mean monthly leaf sugar varied from -29.3 % in P. ponderosa to -21.8 % in P. lambertiana and was enriched in 13C during the winter, spring and autumn, but depleted during the mid-summer. Leaf water hydrogen isotopic composition was 28.4 to 68.8 % more enriched in deuterium than source water and this enrichment was greater as seasonal drought progressed. These data indicate that leaf carbon and leaf water hydrogen isotopic composition provide sensitive measures that connect plant physiological processes to short-term climatic variability.

Oxygen isotope mapping and evaluation of paleo-hydrothermal systems associated with synvolcanic intrusion and VMS deposits

International Nuclear Information System (INIS)

Taylor, B.E

2001-01-01

Whole-rock oxygen isotope mapping provides a useful method for the delineation and quantitative evaluation of paleo-hydrothermal systems associated with syn-volcanic intrusions and volcanic-associated massive sulfide (VMS) deposits. During the course of a four-year study of regional alteration systems associated with VMS Deposits, four syn-volcanic intrusive complexes in Canada were mapped using stable isotope techniques. The complexes included Noranda, Quebec; Clifford-Ben Nevis, Ontario; Snow Lake, Manitoba, and Sturgeon Lake, Ontario. This study was regional in extent, involving large areas and large numbers of whole-rock samples: Noranda (625 km 2 ;≥600 samples, plus others (total = 1198); Sturgeon Lake (525 km 2 ; 452 samples); Clifford-Ben Nevis (160 km 2 ; 251 samples); and Snow Lake (84 km 2 ; 575 samples). Isotopic data on whole-rock carbonates and hydrous minerals were also collected. The regional isotopic studies were carried out in concert with other studies on mineral assemblages and mineral composition, and on associated intrusive and extrusive rocks. The Clifford-Ben Nevis area was selected as a control area, in as much as it contains no known VMS deposits; all other areas are well-known, productive VMS districts. Oxygen isotope maps are, in a sense, thermal maps, illustrating the paleo-distribution of heat and fluids, and offering a potential aid to exploration. The isotopic data may be contoured to reveal zones of 18 O depletion and enrichment, relative to unaltered rocks. Zones of δ 18 O≤60% comprise rocks that have reacted with seawater at high (e.g., 300+ o C) temperatures. The volume of foot-wall rocks isotopically-depleted by water/rock interaction during the life of one or more episodes of submarine hydrothermal activity is proportional to the amount of heat available from the syn-volcanic intrusive center. These altered rocks comprise the reaction zone often inferred to have supplied metals and other constituents for the VMS deposits

Isotopically Enriched C-13 Diamond Anvil as a Stress Sensor in High Pressure Experiments

Science.gov (United States)

Vohra, Yogesh; Qiu, Wei; Kondratyev, Andreiy; Velisavljevic, Nenad; Baker, Paul

2004-03-01

The conventional high pressure diamond anvils were modified by growing an isotopically pure C-13 diamond layer by microwave plasma chemical vapor deposition using methane/hydrogen/oxygen chemistry. The isotopically pure C-13 nature of the culet of the diamond anvil was confirmed by the Raman spectroscopy measurements. This isotopically engineered diamond anvil was used against a natural abundance diamond anvil for high pressure experiments in a diamond anvil cell. Spatial resolved Raman spectroscopy was used to measure the stress induced shift in the C-13 layer as well as the undelying C-12 layer to ultra high pressures. The observed shift and splitiing of the diamond first order Raman spectrum was correlated with the stress distribution in the diamond anvil cell. The experimental results will be compared with the finite element modeling results using NIKE-2D software in order to create a mathematical relationship between sets of the following parameters: vertical (z axis) distance; horizontal (r axis) distance; max shear stress, and pressure. The isotopically enriched diamond anvils offer unique opportunities to measure stress distribution in the diamond anvil cell devices.

Multiple stable isotope fronts during non-isothermal fluid flow

Science.gov (United States)

Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

2018-02-01

Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may

Isotopic enrichment in a plasma centrifuge

International Nuclear Information System (INIS)

Del Bosco, E.; Dallaqua, R.S.; Ludwig, G.O.; Bittencourt, J.A.

1987-01-01

High rotational velocity and centrifugal isotopic separation of carbon in a vacuum-arc plasma centrifuge are presented. Enrichments of up to 390% for 13 C are measured at 6 cm radius with angular rotation frequencies in excess of 1.0 x 10 5 rad/s in an axial magnetic field of 0.12 T

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

International Nuclear Information System (INIS)

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

1994-01-01

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

Primary study of ethyl cellulose nanofiber for oxygen-enrichment membrane

Directory of Open Access Journals (Sweden)

Shen Jing

2016-01-01

Full Text Available Ethyl cellulose is widely used for oxygen-enrichment membrane, however, its nanofiber membrane was rarely developed though it behaves more excellent performance. This paper gives a preliminary study to produce oxygen-enrichment membrane by bubbfil spinning.

Aerodynamic isotope separation processes for uranium enrichment: process requirements

International Nuclear Information System (INIS)

Malling, G.F.; Von Halle, E.

1976-01-01

The pressing need for enriched uranium to fuel nuclear power reactors, requiring that as many as ten large uranium isotope separation plants be built during the next twenty years, has inspired an increase of interest in isotope separation processes for uranium enrichment. Aerodynamic isotope separation processes have been prominently mentioned along with the gas centrifuge process and the laser isotope separation methods as alternatives to the gaseous diffusion process, currently in use, for these future plants. Commonly included in the category of aerodynamic isotope separation processes are: (a) the separation nozzle process; (b) opposed gas jets; (c) the gas vortex; (d) the separation probes; (e) interacting molecular beams; (f) jet penetration processes; and (g) time of flight separation processes. A number of these aerodynamic isotope separation processes depend, as does the gas centrifuge process, on pressure diffusion associated with curved streamlines for the basic separation effect. Much can be deduced about the process characteristics and the economic potential of such processes from a simple and elementary process model. In particular, the benefit to be gained from a light carrier gas added to the uranium feed is clearly demonstrated. The model also illustrates the importance of transient effects in this class of processes

High-Performance Pyrochlore-Type Yttrium Ruthenate Electrocatalyst for Oxygen Evolution Reaction in Acidic Media

Energy Technology Data Exchange (ETDEWEB)

Kim, Jaemin [Department; Shih, Pei-Chieh [Department; Tsao, Kai-Chieh [Department; Pan, Yung-Tin [Department; Yin, Xi [Department; Sun, Cheng-Jun [X-ray; Yang, Hong [Department

2017-08-17

Development of acid-stable electrocatalysts with low overpotential for oxygen evolution reaction (OER) is a major challenge for the production of hydrogen directly from water. We report in this paper a pyrochlore yttrium ruthenate (Y2Ru2O7-δ) electrocatalyst that has significantly enhanced performance towards OER in acid media over the best-known catalysts, with an onset overpotential of 190 mV and high stability in 0.1-M perchloric acid solution. X-ray absorption near-edge structure (XANES) indicates Y2Ru2O7-δ electrocatalyst had a low valence state that favors the high OER activity. Density functional theory (DFT) calculation shows this pyrochlore has lower band center energy for the overlap between Ru 4d and O 2p orbitals and therefore more stable Ru-O bond than RuO2, highlighting the effect of yttrium on the enhancement in stability. The Y2Ru2O7-δ pyrochlore is also free of expensive iridium metal, thus a cost-effective candidate for practical applications.

Centrifugation. A theoretical study of oxygen enrichment by centrifugation

Energy Technology Data Exchange (ETDEWEB)

Kierkegaard, P.; Raetz, E.

1998-12-01

In the present paper we first investigate what happens if we fill a cylinder with air, close it and rotate it. The results show that no matter which peripheral speed is used, it is not possible by means of the radial separation effect alone, to enrich the oxygen concentration from the previous 21% to more then 23.3%, which is of no practical value. In case of a too low enrichment in one centrifuge, the wanted material from this centrifuge can be used as an input for a second centrifuge and so on, in this way forming a cascade of centrifuges. Oxygen will be enriched in each step, until the desired concentration is reached. Cascading was the technology in the very beginning by enrichment plants for uraniumhexaflouride, used for atomic weapons and nuclear power plants. In this study we try to avoid cascading by aiming for higher separation factors. Therefore, we next investigate the possibilities of using a countercurrent centrifuge where in principle the enriched gas is subjected to several centrifugation in the same centrifuge. The calculations show, that in this way it is possible to produce nearly a 100% pure oxygen (polluted with some heavier molecules like argon) in one machine. Our third step was to calculate the amount of oxygen produced per hour. Using a countercurrent centrifuge of the Zippe type, 100 cm high and 20 cm in diameter, it is or will be possible in the near future to produce 17 g enriched air per hour enriched to 50% oxygen. That corresponds to processing 1 m{sup 3} atmospherical air in the period of approximately 24 hours. This is not very impressive. Our fourth step was to estimate the amount of power used for producing this amount of oxygen. A rough, but complicated, estimate shows that the power consumption at the production level will be about the double of the consumption used today. The overall conclusion is, that centrifugation as a production method for oxygen (or nitrogen) will not be competitive with the currently used method in the

Origin of the brines near WIPP from the drill holes ERDA-6 and WIPP-12 based on stable isotope concentrations of hydrogen and oxygen

International Nuclear Information System (INIS)

Spiegler, P.; Updegraff, D.

1983-03-01

Pathways which might alter the isotopic compositions of deuterium and oxygen-18 meteoric water, seawaters, and in hydration waters in gypsum to the isotopic compositions of brines encountered at ERDA-6 and WIPP-12 are discussed. Present geologic conditions do not favor the alteration of the isotopic compositions of waters that exist near the WIPP site to those of the brines by these pathways. It is concluded that the brines encountered at ERDA-6 and WIPP-12 are probably derived from ancient ocean waters that have been isotopically enriched in oxygen-18 by exchange interaction with rock. The dehydration of gypsum as a process of origin of these brines cannot be ruled out

Oxygen Isotope Composition of Nitrate Produced by Freshwater Nitrification

Science.gov (United States)

Boshers, D.; Granger, J.; Bohlke, J. K.

2016-12-01

Measurements of the naturally occurring nitrogen and oxygen stable isotope ratios of nitrate (NO3-), δ15N and δ18O, can be used to determine the source, dispersal, and fate of natural and contaminant NO3- in aquatic environments. To this end, it is necessary to know the extent to which NO3- isotopologues are modified by biological reactions, as heavy and light isotopes have different reaction rates. The purpose of this study was to determine the influence of the δ18O of ambient water on the isotope composition of NO3- produced during nitrification, the biological oxidation of ammonium (NH4+) to nitrite (NO2-) and then NO3-, which is poorly constrained in freshwater systems. To determine the δ18O of NO3- produced by nitrification in freshwater, we collected water from a stream in New England, which we amended with NH4+ and with increments of 18O-enriched water, to monitor the isotope composition of NO3- produced by a natural consortium of nitrifiers. Added NH4+ was completely oxidized to NO3- over 26 days. The final δ18O of nitrified NO3- revealed sensitivity to the δ18O of water mediated by (a) isotopic equilibration between water and NO2- and (b) kinetic isotope fractionation during O-atom incorporation from water into NO2- and NO3-. Our results concur with nitrifying culture experiments that have demonstrated analogous sensitivity of the δ18O of nitrified NO3- to equilibrium and kinetic O isotope effects (Buchwald et al. 2012), as well as show that these dynamics need to be considered to interpret NO3- isotope distribution in freshwater environments.

Sulfur Isotope Trends in Archean Microbialite Facies Record Early Oxygen Production and Consumption

Science.gov (United States)

Zerkle, A.; Meyer, N.; Izon, G.; Poulton, S.; Farquhar, J.; Claire, M.

2014-12-01

The major and minor sulfur isotope composition (δ34S and Δ33S) of pyrites preserved in ~2.65-2.5 billion-year-old (Ga) microbialites record localized oxygen production and consumption near the mat surface. These trends are preserved in two separate drill cores (GKF01 and BH1-Sacha) transecting the Campbellrand-Malmani carbonate platform (Ghaap Group, Transvaal Supergroup, South Africa; Zerkle et al., 2012; Izon et al., in review). Microbialite pyrites possess positive Δ33S values, plotting parallel to typical Archean trends (with a Δ33S/δ34S slope of ~0.9) but enriched in 34S by ~3 to 7‰. We propose that these 34S-enriched pyrites were formed from a residual pool of sulfide that was partially oxidized via molecular oxygen produced by surface mat-dwelling cyanobacteria. Sulfide, carrying the range of Archean Δ33S values, could have been produced deeper within the microbial mat by the reduction of sulfate and elemental sulfur, then fractionated upon reaction with O2 produced by oxygenic photosynthesis. Preservation of this positive 34S offset requires that: 1) sulfide was only partially (50­­-80%) consumed by oxidation, meaning H2S was locally more abundant (or more rapidly produced) than O2, and 2) the majority of the sulfate produced via oxidation was not immediately reduced to sulfide, implying either that the sulfate pool was much larger than the sulfide pool, or that the sulfate formed near the mat surface was transported and reduced in another part of the system. Contrastingly, older microbialite facies (> 2.7 Ga; Thomazo et al., 2013) appear to lack these observed 34S enrichments. Consequently, the onset of 34S enrichments could mark a shift in mat ecology, from communities dominated by anoxygenic photosynthesizers to cyanobacteria. Here, we test these hypotheses with new spatially resolved mm-scale trends in sulfur isotope measurements from pyritized stromatolites of the Vryburg Formation, sampled in the lower part of the BH1-Sacha core. Millimeter

Oxygen isotopic anomalies in Allende inclusion HAL

International Nuclear Information System (INIS)

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

1980-01-01

The oxygen isotopic composition has been measured on the constituent phases of Allende inclusion HAL, which has unusual mineralogical, chemical, and calcium isotopic compositions. The oxygen in HAL is heterogeneous, with the rim showing more ''normal'' composition and the hibonite core showing large deviation from both the terrestrial material and the usual inclusions. The observed pattern indicates that HAL is a bona fide and more devious member of the rare ''FUN'' family, whose isotopic composition is characterized by correlated nuclear effects and extreme mass fractionation. The data imply that HAL has suffered a large oxygen mass fractionation of 25% 0 per mass unit, followed by exchange with oxygen in a second reservoir. The present experiment supports the identification of two distinct reservoirs from which all refractory inclusions in carbonaceous meteorites derived their oxygen. The required fractionation process seems to operate according to the volatility of various elements and could have been caused by evaporation during a heating event. Nuclear anomalies can be produced in the same heating event if the progenitors of the refractory inclusions were macroscopic aggregates of tiny pre-solar interstellar dust grains and if these grains were destroyed differentially during the evaporation

Influence of oxygen enrichment on compression ignition engines using biodiesel blends

Directory of Open Access Journals (Sweden)

Vaiyapuri Senthil Murugan

2017-01-01

Full Text Available The influence of oxygen enrichment on performance and emission characteristics of a single cylinder diesel engine operated with biodiesel blends have been investigated in this work. The methyl ester of jatropha biodiesel was selected as bio-diesel and four blends (B10, B20, B30, and B40 were selected for experimental investigations. The performance and emission characteristics were obtained for the these blends along with three oxygen enrichment flow rates (1, 3, and 5 L per minute using an oxygen cylinder at the air intake in the diesel engine. The performance and emission characteristics were studied and compared with the diesel and biodiesel. It was observed that, oxygen enrichment enhances the brake thermal efficiency, HC, CO, and smoke. B10 biodiesel with 5 L per minute oxygen enrichment was found to be the best fuel for biodiesel operation.

Early history of chemical exchange isotope enrichment and lessons we learn

International Nuclear Information System (INIS)

Ishida, Takanobu; Ono, Yuriko

2006-01-01

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

Carbon and Oxygen isotopic composition in paleoenvironmental determination

International Nuclear Information System (INIS)

Silva, J.R.M. da.

1978-01-01

This work reports that the carbon and oxygen isotopic composition separate the mollusks from marine environment of the mollusks from continental environment in two groups isotopically different, making the biological control outdone by environment control, in the isotopic fragmentation mechanisms. The patterns from the continental environment are more rich in O 16 than the patterns from marine environments. The C 12 is also more frequent in the mollusks from continental environments. The carbon isotopic composition in paterns from continental environments is situated betwen - 10.31 and - 4,05% and the oxygen isotopic composition is situated between - 6,95 and - 2,41%. To the marine environment patterns the carbon isotopic composition is between - 2,08 and + 2,65% and the oxigen isotopic composition is between - 2,08 and + 0,45%. Was also analysed fossil marine mollusks shells and their isotopic composition permit the formulation of hypothesis about the environment which they lived. (C.D.G.) [pt

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

Directory of Open Access Journals (Sweden)

Alberta Silvestri

2017-01-01

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

235U isotope enrichment in the metastable levels of UI

International Nuclear Information System (INIS)

Gagne, J.M.; Demers, Y.; Dreze, C.; Pianarosa, P.

1983-01-01

We have used optical pumping to produce a substantial 235 U enrichment in the metastable levels of UI in the discharge afterglow of a hollow-cathode vapor generator. The measured isotope-enrichment factor for the level at 3800 cm -1 is approximately 20

Oxygen isotope fractionations across individual leaf carbohydrates in grass and tree species.

Science.gov (United States)

Lehmann, Marco M; Gamarra, Bruno; Kahmen, Ansgar; Siegwolf, Rolf T W; Saurer, Matthias

2017-08-01

Almost no δ 18 O data are available for leaf carbohydrates, leaving a gap in the understanding of the δ 18 O relationship between leaf water and cellulose. We measured δ 18 O values of bulk leaf water (δ 18 O LW ) and individual leaf carbohydrates (e.g. fructose, glucose and sucrose) in grass and tree species and δ 18 O of leaf cellulose in grasses. The grasses were grown under two relative humidity (rH) conditions. Sucrose was generally 18 O-enriched compared with hexoses across all species with an apparent biosynthetic fractionation factor (ε bio ) of more than 27‰ relative to δ 18 O LW , which might be explained by isotopic leaf water and sucrose synthesis gradients. δ 18 O LW and δ 18 O values of carbohydrates and cellulose in grasses were strongly related, indicating that the leaf water signal in carbohydrates was transferred to cellulose (ε bio  = 25.1‰). Interestingly, damping factor p ex p x , which reflects oxygen isotope exchange with less enriched water during cellulose synthesis, responded to rH conditions if modelled from δ 18 O LW but not if modelled directly from δ 18 O of individual carbohydrates. We conclude that δ 18 O LW is not always a good substitute for δ 18 O of synthesis water due to isotopic leaf water gradients. Thus, compound-specific δ 18 O analyses of individual carbohydrates are helpful to better constrain (post-)photosynthetic isotope fractionation processes in plants. © 2017 John Wiley & Sons Ltd.

Method and device for the enrichment of isotopes

International Nuclear Information System (INIS)

Stehle, H.

1976-01-01

A variation of a method for isotope enrichment by laser radiation is proposed which improves the selectivity and with it the economy of the method by eliminating undesired reactions caused by thermal activation. The method according to the invention is applied discontinuously in three steps: The isotope mixture and the reacting agents are fed to a vessel, a laser beam is passed through, and the contents are emptied into a vacuum tank while expanding adiabatically. The time steps are controlled. The method is explained using the example of separating an isotope mixture of UF 6 . (UWI) [de

Oxygen isotopic fractionation of O₂ during adsorption and desorption processes using molecular sieve at low temperatures.

Science.gov (United States)

Ahn, Insu; Kusakabe, Minoru; Lee, Jong Ik

2014-06-15

Cryogenic trapping using molecular sieves is commonly used to collect O2 extracted from silicates for (17)O/(16)O and (18)O/(16)O analyses. However, gases which interfere with (17)O/(16)O analysis, notably NF3, are also trapped and their removal is essential for accurate direct measurement of the (17)O/(16)O ratio. It is also necessary to identify and quantify any isotopic fractionation associated with the use of cryogenic trapping using molecular sieves. The oxygen isotopic compositions of O2 before and after desorption from, and adsorption onto, 13X and 5A molecular sieves (MS13X and MS5A) at 0°C, -78°C, -114°C, and -130°C were measured in order to determine the oxygen isotopic fractionation at these temperatures. We also investigated whether isotopic fractionation occurred when O2 gas was transferred sequentially into a second cold finger, also containing molecular sieve. It was confirmed that significant oxygen isotopic fractionation occurs between the gaseous O2 and that adsorbed onto molecular sieve, if desorption and adsorption are incomplete. As the fraction of released or untrapped O2 becomes smaller with decreasing trapping temperature (from 0 to -130°C), the isotopic fractionation becomes larger. Approximately half of the total adsorbed O2 is released from the molecular sieve during desorption at -114°C, which is the temperature recommended for separation from NF3 (retained on the molecular sieve), and this will interfere with (17)O/(16)O measurements. The use of a single cold finger should be avoided, because partial desorption is accompanied by oxygen isotopic fractionation, thereby resulting in inaccurate isotopic data. The use of a dual cold finger arrangement is recommended because, as we have confirmed, the transfer of O2 from the first trap to the second is almost 100%. However, even under these conditions, a small isotopic fractionation (0.18 ± 0.05‰ in δ(17)O values and 0.26 ± 0.06‰ in δ(18)O values) occurred, with O2 in

Attempts at treating rheumatoid arthritis with radioactive yttrium

International Nuclear Information System (INIS)

Scott, J.T.

1979-01-01

Two years' observations on 33 knee joints in 33 patients with rheumatoid arthritis did not prove a therapeutic effect of Y 90 , which was tested in a randomized study against non-radioactive yttrium. It was noticable that 9 knee joints of the isotope group but only one of the control group became unstable. Independent of the yttrium treatment, significant improvement was noticed in patients where fibrin clots had been washed out of the joints in the course of arthroscopies. (orig.) [de

Major events in Neogene oxygen isotopic records

International Nuclear Information System (INIS)

Kennett, J.P.; Hodell, D.A.

1986-01-01

Changes in oxygen isotopic ratios of foraminiferal calcite during the cainozoic have been one of the primary tools for investigating the history of Arctic and Antarctic glaciation, although interpretations of the oxygen isotopic record differ markedly. The ambiguity in interpretation results mainly from the partitioning of temperature from ice volume effects in delta 18 O changes. Oxygen isotopic records for the Cainozoic show an increase in delta 18 O values towards the present, reflecting gradual cooling and increased glaciation of the Earth's climate since the late Cretaceous. A variety of core material from the South Atlantic and South-west Pacific oceans are investigated. This composite data represents one of the most complete available with which to evaluate the evolution of glaciation during the Neogene. Expansion of ice shelves in Antarctica undoubtedly accompanied the increased glaciation of the northern hemisphere, since eustatic sea-level lowering would positively reinforce ice growth on Antarctica

Candidate processes for diluting the 235U isotope in weapons-capable highly enriched uranium

International Nuclear Information System (INIS)

Snider, J.D.

1996-02-01

The United States Department of Energy (DOE) is evaluating options for rendering its surplus inventories of highly enriched uranium (HEU) incapable of being used to produce nuclear weapons. Weapons-capable HEU was earlier produced by enriching uranium in the fissile 235 U isotope from its natural occurring 0.71 percent isotopic concentration to at least 20 percent isotopic concentration. Now, by diluting its concentration of the fissile 235 U isotope in a uranium blending process, the weapons capability of HEU can be eliminated in a manner that is reversible only through isotope enrichment, and therefore, highly resistant to proliferation. To the extent that can be economically and technically justified, the down-blended uranium product will be made suitable for use as commercial reactor fuel. Such down-blended uranium product can also be disposed of as waste if chemical or isotopic impurities preclude its use as reactor fuel

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

International Nuclear Information System (INIS)

Newman, E.

1982-01-01

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

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.

Relationship of leaf oxygen and carbon isotopic composition with transpiration efficiency in the C4 grasses Setaria viridis and Setaria italica.

Science.gov (United States)

Ellsworth, Patrick Z; Ellsworth, Patrícia V; Cousins, Asaph B

2017-06-15

Leaf carbon and oxygen isotope ratios can potentially provide a time-integrated proxy for stomatal conductance (gs) and transpiration rate (E), and can be used to estimate transpiration efficiency (TE). In this study, we found significant relationships of bulk leaf carbon isotopic signature (δ13CBL) and bulk leaf oxygen enrichment above source water (Δ18OBL) with gas exchange and TE in the model C4 grasses Setaria viridis and S. italica. Leaf δ13C had strong relationships with E, gs, water use, biomass, and TE. Additionally, the consistent difference in δ13CBL between well-watered and water-limited plants suggests that δ13CBL is effective in separating C4 plants with different availability of water. Alternatively, the use of Δ18OBL as a proxy for E and TE in S. viridis and S. italica was problematic. First, the oxygen isotopic composition of source water, used to calculate leaf water enrichment (Δ18OLW), was variable with time and differed across water treatments. Second, water limitations changed leaf size and masked the relationship of Δ18OLW and Δ18OBL with E. Therefore, the data collected here suggest that δ13CBL but not Δ18OBL may be an effective proxy for TE in C4 grasses. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Review of Membrane Oxygen Enrichment for Efficient Combustion

Science.gov (United States)

Ariono, Danu; Kusuma Wardani, Anita

2017-07-01

Oxygen enrichment from air is a simple way of increasing the efficiency of combustion process, as in oxy-combustion. Oxy-combustion has become one of the most attracting combustion technologies because of its potential to address both pollutant reduction and CO2 capture. In oxy-combustion, the fuel and recycled flue gas are combusted with oxygen enriched air (OEA). By using OEA, many benefits can be obtained, such as increasing available heat, improving ignition characteristics, flue gas reduction, increasing productivity, energy efficiency, turndown ratio, and flame stability. Membrane-based gas separation for OEA production becomes an attractive technology over the conventional technology due to the some advantages, including low capital cost, low energy consumption, compact size, and modularity. A single pass through membrane usually can enrich O2 concentration in the air up to 35% and a 50% concentration can be achieved with a double pass of membrane. The use of OEA in the combustion process eliminates the presence of nitrogen in the flue gas. Hence, the flue gas is mainly composed of CO2 and condensable water that can be easily separated. This paper gives an overview of oxy-combustion with membrane technology for oxygen enrichment process. Special attention is given to OEA production and the effect of OEA to the efficiency of combustion.

The Helikon technique for isotope enrichment

International Nuclear Information System (INIS)

Haarhoff, P.C.

1976-11-01

The separating element employed in the UCOR process for uranium enrichment has an enriched stream which is much smaller than the depleted stream. To deal with this small cut and to exploit the full potential of the process, a new cascade technique has been developed, the so-called helikon technique. It is based on the principle that an axial flow compressor can simultaneously compress a number of streams of different isotopic composition, which flow through it in parallel, without any significant mixing between them. The technique makes it possible to achieve the desired enrichment with a relatively small number of separating units, by making the best use of the high enrichment factor available. A further feature of the helikon technique is that a module yields an enrichment factor which is not constant, but can vary. In this way a cascade can be built up from modules of a fixed size, which is a great advantage when compared to conventional cascade arrangements where several unit sizes are required. A general theoretical treatment of the helikon technique is given and the similarity between helikon and conventional cascades is pointed out. Practical helikon cascades are subsequently discussed on the basis of the UCOR process

Decommissioning Combustible Waste Treatment using Oxygen-Enriched Incinerator

Energy Technology Data Exchange (ETDEWEB)

Min, Byungyoun; Lee, Yoonji; Yun, Gyoungsu; Lee, Kiwon; Moon, Jeikwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-05-15

The aim of the paper is current status of treatment for the decommissioning combustible waste in KAERI and for the purpose of the volume reduction and clearance for decommissioning combustible wastes generated by the decommissioning projects. The incineration technology has been selected for the treatment of combustible wastes. About 34 tons of decommissioning combustible waste has been treated using Oxygen Enriched incineration. Temperature, pressure of major components, stack gas concentration, i. e., SOx, NOx, CO, CO{sub 2} and HCl, and the residual oxygen were measured. Measured major parameters during normal operation were sustained on a stable status within a criteria operation condition. Oxygen enriched air, 22vol. % (dry basis) was used for stable incineration. The volume reduction ratio has achieved about 1/117. The incineration with decommissioning radioactive combustible waste is possible with moderate oxygen enrichment of 22 vol.% (dry basis) into the supply air. The incineration facility operated quite smoothly through the analysis major critical parameters of off-gas. The pressure, off-gas flow and temperature of major components remained constant within the range specified. The measures gases and particulate materials in stack were considerably below the regulatory limits. The achieved volume reduction ratio through incineration is about 1/117.

Enrichment of yttrium from rare earth concentrate by ammonium carbonate leaching and peroxide precipitation

International Nuclear Information System (INIS)

Vasconcellos, Mari E. de; Rocha, S.M.R. da; Pedreira, W.R.; Queiroz S, Carlos A. da; Abrao, Alcidio

2006-01-01

The rare earth elements (REE) solubility with ammonium carbonate vary progressively from element to element, the heavy rare earth elements (HRE) being more soluble than the light rare earth elements (LRE). Their solubility is function of the carbonate concentration and the kind of carbonate as sodium, potassium and ammonium. In this work, it is explored this ability of the carbonate for the dissolution of the REE and an easy separation of yttrium was achieved using the precipitation of the peroxide from complex yttrium carbonate. For this work is used a REE concentrate containing (%) Y 2 O 3 2.4, Dy 2 O 3 0.6, Gd 2 O 3 2.7, CeO 2 2.5, Nd 2 O 3 33.2, La 2 O 3 40.3, Sm 2 O 3 4.1 and Pr 6 O 11 7.5. The mentioned concentrate was produced industrially from the chemical treatment of monazite sand by NUCLEMON in Sao Paulo. The yttrium concentrate was treated with 200 g L -1 ammonium carbonate during 10 and 30 min at room temperature. The experiments indicated that a single leaching operation was sufficient to get a rich yttrium solution with about 60.3% Y 2 O 3 . In a second step, this yttrium solution was treated with an excess of hydrogen peroxide (130 volumes), cerium, praseodymium and neodymium peroxides being completely precipitated and separated from yttrium. Yttrium was recovered from the carbonate solution as the oxalate and finally as oxide. The final product is an 81% Y 2 O 3 . This separation envisages an industrial application. The work discussed the solubility of the REE using ammonium carbonate and the subsequent precipitation of the correspondent peroxides

Chlorine isotope fractionation during supergene enrichment of copper

Science.gov (United States)

Reich, M.; Barnes, J.; Barra, F.; Milojevic, C.; Drew, D.

2017-12-01

Supergene enrichment of Cu deposits in the Atacama Desert has played a critical role in making this the prime Cu-producing province of the world. The Cu-hydroxychloride atacamite is a major component of supergene zones in this region whereas in similar deposits elsewhere it is rare. Atacamite requires saline water to form and dissolves rapidly when exposed to fresh, meteoric water. Previous chlorine stable isotope data [1] for atacamite mineralization at the Radomiro Tomic, Chuquicamata and Mina Sur Cu deposits show δ37Cl values that range from -0.1 to +0.2‰, indicating a similar nonmagmatic source for the introduction of chloride. However, distal atacamite mineralization on the periphery of these orebodies show more fractionated and lighter δ37Cl values (-3.2 to -0.1‰). Although little disagreement currently exists about the involvement of saline groundwater during the formation of atacamite [2], no δ37Cl data are currently available for atacamite within a single deposit and/or supergene enrichment profile that allow explaining the aforementioned differences in the observed δ37Cl values. Furthermore, no experimental data for chlorine isotope fractionation between Cu-hydroxychloride minerals and water exist that help evaluate possible mechanisms of fractionation along the groundwater flow path. Here we present a new database that combines detailed mineralogical observations with δ37Cl data of atacamite along a thick ( 100 m) supergene enrichment profile at the Barreal Seco IOCG deposit in the Atacama Desert of northern Chile. Chlorine stable isotope data of atacamite vary between -0.62 and +2.1 ‰ and show a well-defined trend where δ37Cl values progressively decrease (become lighter) with depth. These data, when combined with new experimental determinations of chlorine isotope fractionation between atacamite and water, point to changes triggered by the progressive deepening of groundwater tables during Andean uplift and the extreme desiccation of

Reaction of yttrium polonides with carbon dioxide

International Nuclear Information System (INIS)

Abakumov, A.S.; Khokhlov, A.D.; Reznikova, N.F.

1986-01-01

It has been proved that heating of yttrium and tantalum in carbon dioxide to 500 and 800 0 C alters the gas phase composition, causing formation of carbon monoxide and reduction of oxygen content. A study of the thermal stability of yttrium polonides in carbon dioxide showed that yttrium sesqui- and monopolonides decompose at 400-430 0 C. The temperature dependence of the vapor pressure of polonium obtained upon decomposition of the referred polonides has been determined in a carbon dioxide environment radiotensometrically. The enthalpy of the process calculated from this dependence is close to the enthalpy of vaporization of elemental polonium in vacuo. The mechanism of the reactions has been suggested

Oxygen isotope systematics of chondrules in the Murchison CM2 chondrite and implications for the CO-CM relationship

Science.gov (United States)

Chaumard, Noël; Defouilloy, Céline; Kita, Noriko T.

2018-05-01

High-precision oxygen three-isotope measurements of olivine and pyroxene were performed on 29 chondrules in the Murchison CM2 chondrite by secondary ion mass spectrometry (SIMS). The oxygen isotope ratios of analyzed chondrules all plot very close to the primitive chondrule minerals (PCM) line. In each of 24 chondrules, the olivine and/or pyroxene grains analyzed show indistinguishable oxygen isotope ratios. Exceptions are minor occurrences of isotopically distinguished relict olivine grains, which were found in nine chondrules. The isotope homogeneity of these phenocrysts is consistent with a co-magmatic crystallization of olivine and pyroxene from the final chondrule melts and a significant oxygen isotope exchange between the ambient gas and the melts. Homogeneous type I chondrules with Mg#'s of 98.9-99.5 have host chondrule Δ17O values ranging from -6.0‰ to -4.1‰, with one exception (Δ17O: -1.2‰; Mg#: 99.6). Homogeneous chondrules with Mg#'s poor H2O ice (∼0.3-0.4× the CI dust; Δ17O > 0‰) and at dust enrichments of ∼300-2000×. Regarding the Mg# and oxygen isotope ratios, the chondrule populations sampled by CM and CO chondrites are similar and indistinguishable. The similarity of these 16O-rich components in CO and CM chondrites is also supported by the common Fe/Mn ratio of olivine in type II chondrules. Although they accreted similar high-temperature silicates, CO chondrites are anhydrous compared to CM chondrites, suggesting they derived from different parent bodies formed inside and outside the snow line, respectively. If chondrules in CO and CM chondrites formed at the same disk locations but the CM parent body accreted later than the CO parent body, the snow line might have crossed the common chondrule-forming region towards the Sun between the time of the CO and CM parent bodies accretion.

CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula.

Science.gov (United States)

Lyons, J R; Young, E D

2005-05-19

The abundances of oxygen isotopes in the most refractory mineral phases (calcium-aluminium-rich inclusions, CAIs) in meteorites have hitherto defied explanation. Most processes fractionate isotopes by nuclear mass; that is, 18O is twice as fractionated as 17O, relative to 16O. In CAIs 17O and 18O are nearly equally fractionated, implying a fundamentally different mechanism. The CAI data were originally interpreted as evidence for supernova input of pure 16O into the solar nebula, but the lack of a similar isotope trend in other elements argues against this explanation. A symmetry-dependent fractionation mechanism may have occurred in the inner solar nebula, but experimental evidence is lacking. Isotope-selective photodissociation of CO in the innermost solar nebula might explain the CAI data, but the high temperatures in this region would have rapidly erased the signature. Here we report time-dependent calculations of CO photodissociation in the cooler surface region of a turbulent nebula. If the surface were irradiated by a far-ultraviolet flux approximately 10(3) times that of the local interstellar medium (for example, owing to an O or B star within approximately 1 pc of the protosun), then substantial fractionation of the oxygen isotopes was possible on a timescale of approximately 10(5) years. We predict that similarly irradiated protoplanetary disks will have H2O enriched in 17O and 18O by several tens of per cent relative to CO.

Isotopic enrichment of 15N by ionic exchange cromatography

International Nuclear Information System (INIS)

Trivelin, P.C.O.; Matsui, E.; Salati, E.

1979-01-01

The ionic exchange chromatographic method in columns of resin which is employed in the study of isotopic enrichment of 15 N is presented. Determinations are made of the isotopic separation constant for the exchange of isotopes 15 N and 14 N in the equilibrium involving ammonium hidroxide in the solution phase and ions NH 4 + 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 NH 4 + 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 [pt

Rate of oxygen isotope exchange between selenate and water.

Science.gov (United States)

Kaneko, Masanori; Poulson, Simon R

2012-04-17

The rate of oxygen isotope exchange between selenate and water was investigated at conditions of 10 to 80 °C and pH -0.6 to 4.4. Oxygen isotope exchange proceeds as a first-order reaction, and the exchange rate is strongly affected by reaction temperature and pH, with increased rates of isotope exchange at higher temperature and lower pH. Selenate speciation (HSeO(4)(-) vs SeO(4)(2-)) also has a significant effect on the rate of isotope exchange. The half-life for isotope exchange at example natural conditions (25 °C and pH 7) is estimated to be significantly in excess of 10(6) years. The very slow rate of oxygen isotope exchange between selenate and water under most environmental conditions demonstrates that selenate-δ(18)O signatures produced by biogeochemical processes will be preserved and hence that it will be possible to use the value of selenate-δ(18)O to investigate the biogeochemical behavior of selenate, in an analogous fashion to the use of sulfate-δ(18)O to study the biogeochemical behavior of sulfate.

Oxygen and hydrogen isotope fractionation during cellulose metabolism in Lemna gibba L

International Nuclear Information System (INIS)

Yakir, D.; DeNiro, M.J.

1990-01-01

Lemna gibba L. B3 was grown under heterotrophic, photoheterotrophic, and autotrophic conditions in water having a variety of hydrogen and oxygen isotopic compositions. The slopes of the linear regression lines between the isotopic composition of water and leaf cellulose indicated that under the three growth conditions about 40, 70, and 100% of oxygens and carbon-bound hydrogens of cellulose exchanged with those of water prior to cellulose formation. Using the equations of the linear relationships, we estimated the overall fractionation factors between water and the exchanged oxygen and carbon bound-hydrogen of cellulose. At least two very different isotope effects must determine the hydrogen isotopic composition of Lemna cellulose. One reflects the photosynthetic reduction of NADP, while the second reflects exchange reactions that occur subsequent to NADP reduction. Oxygen isotopic composition of cellulose apparently is determined by a single type of exchange reaction with water. Under different growth conditions, variations in metabolic fluxes affect the hydrogen isotopic composition of cellulose by influencing the extent to which the two isotope effects mentioned above are recorded. The oxygen isotopic composition of cellulose is not affected by such changes in growth conditions

Isotope enrichment effect of gaseous mixtures in standing sound vibration

International Nuclear Information System (INIS)

Knesebeck, R.L.

1984-01-01

When standing acoustic waves are excited in a tube containing a mixture of two gases, a partial zonal fractioning of the components arises as consequence of mass transport by diffusion, driven by the thermal and pressure gradients which are associeted with the standing waves. This effect is present in each zone corresponding to a quarter wavelength, with the heavier component becoming enriched at the nodes fo the standing waves and deplected at the crests. The magnitude of the enrichment in one of the components of a binary gas mixture is given by Δω=ap 2 /lambda [b + (1-bω)] 2 . Where ω is the mass concentration of the component in the mixture, a and b are parameters which are related to molecular proprieties of the gases, p is the relative pressure amplitude of the standing wave and lambda is its wavelength. For a natural mixture of uranium hexafluorate, with 0.715% of the uranium isotope 340 an enrichment of about 2 x 10 -6 % in the concentration of this isotope is theorecticaly attainable per stage consisting of a quarter wavelenght, when a standing acoustical wave of relative pressure amplitude of 0,2 and wavelenght of 20 cm is used. Since standing acoustical waves are easely excited in gas columns, an isotope enrichment plant made of a cascade of tubes in which standing waves are excited, is presumably feasible with relatively low investment and operation costs. (Author) [pt

Normalization of oxygen and hydrogen isotope data

Science.gov (United States)

Coplen, T.B.

1988-01-01

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

Stable Oxygen-18 and Deuterium Isotopes

DEFF Research Database (Denmark)

Müller, Sascha

The application of stable Oxygen-18 (18O) and Deuterium (2H) isotopes, as a tracer for fluxes between different compartments of the water cycle was subject of the present PhD-thesis. During a three year period, temporal data from a wide range of water cycle constituents was collected from...... the Skjern River catchment, Denmark. The presented applications focused on studying the isotopic 'input signal' to the hydrosphere in the form of precipitation, the isotopic 'output signal' with its related dynamic processes at a coastal saltwater-freshwater interface (groundwater isotopes) and the temporal...... development within a given lowland headwater catchment (stream water isotopes). Based on our investigations on the precipitation isotopic composition a local meteoric water line (LMWL) was constructed and expressed as: δ2H=7.4 δ18O + 5.36‰. Moreover, we showed that under maritime temperature climate influence...

Analysis of Atmospheric Nitrate Deposition in Lake Tahoe Using Multiple Oxygen Isotopes

Science.gov (United States)

McCabe, J. R.; Michalski, G. M.; Hernandez, L. P.; Thiemens, M. H.; Taylor, K.; Kendall, C.; Wankel, S. D.

2002-12-01

Lake Tahoe in the Sierra Nevada Mountain Range is world renown for its depth and water clarity bringing 2.2 million visitors per year resulting in annual revenue of \\1.6 billion from tourism. In past decades the lake has suffered from decreased water clarity (from 32 m plate depth to less than 20), which is believed to be largely the result of algae growth initiated by increased nutrient loading. Lake nutrients have also seen a shift from a nitrogen limited to a phosphorous limited system indicating a large increase in the flux of fixed nitrogen. Several sources of fixed nitrogen of have been suggested including surface runoff, septic tank seepage from ground water and deposition from the atmosphere. Bio-available nitrogen in the form of nitrate (NO_{3}$-) is a main component of this system. Recent studies have estimated that approximately 50% of the nitrogen input into the lake is of atmospheric origin (Allison et al. 2000). However, the impact and magnitude of atmospheric deposition is still one of the least understood aspects of the relationship between air and water quality in the Basin (TRPA Threshold Assessment 2002). The utility of stable isotopes as tracers of nitrate reservoirs has been shown in several studies (Bohlke et al. 1997, Kendall and McDonnell 1998, Durka et al. 1994). Stable nitrogen (δ15N) and oxygen (δ18O) isotopes have been implemented in a dual isotope approach to characterize the various nitrate sources to an ecosystem. While δ18O distinguishes between atmospheric and soil sources of nitrate, processes such as denitrification can enrich the residual nitrate in δ18O leaving a misleading atmospheric signature. The benefit of δ15N as a tracer for NO3- sources is the ability to differentiate natural soil, fertilizer, and animal or septic waste, which contain equivalent δ18O values. The recent implementation of multiple oxygen isotopes to measure Δ17O in nitrate has proven to be a more sensitive tracer of atmospheric deposition. The

Ion Microprobe Measurements of Comet Dust and Implications for Models of Oxygen Isotope Heterogeneity in the Solar System

Science.gov (United States)

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

2017-01-01

The oxygen isotopic compositions of anhydrous minerals in carbonaceous chondrites reflect mixing between a O-16-rich and O-17, O18-rich reservoir. The UV photodissociation of CO (i.e. selfshielding) has been proposed as a mass-independent mechanism for producing these isotopically distinct reservoirs. Self-shielding models predict the composition for the CO gas reservoir to be O-16-rich, and that the accreting primordial dust was in isotopic equilibrium with the gaseous reservoir [1, 2]. Self-shielding also predicts that cometary water, presumed to represent the O-17, O-18-rich reservoir, should be enriched in O-17 and O-18, with compositions of 200 -1000per mille, and that the interaction with this O-17, O-18-rich H2O reservoir altered the compositions of the primordial dust toward planetary values. The bulk composition of the solar nebula, which may be an approximation to the 16O-rich gaseous reservoir, has been constrained by the Genesis results [3]. However, material representing the O-17, O-18-rich end-member is rare [4], and dust representing the original accreting primordial dust has been challenging to conclusively identify in current collections. Anhydrous dust from comets, which accreted in the distal cold regions of the nebula at temperatures below approximately 30K, may provide the best opportunity to measure the oxygen isotope composition of primordial dust. Chondritic porous interplanetary dust particles (CP-IDPs) have been suggested as having cometary origins [5]; however, until direct comparisons with dust from a known comet parent body were made, link between CP-IDPs and comets remained circumstantial. Oxygen isotope analyses of particles from comet 81P/Wild 2 collected by NASA's Stardust mission have revealed surprising similarities to minerals in carbonaceous chondrites which have been interpreted as evidence for large scale radial migration of dust components from the inner solar nebula to the accretion regions of Jupiter- family comets [6

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

International Nuclear Information System (INIS)

Taniyama, Yuki; Momoshima, Noriyuki

2001-01-01

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)

Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

Science.gov (United States)

Suchopár, M.; Wagner, V.; Svoboda, O.; Vrzalová, J.; Chudoba, P.; Tichý, P.; Kugler, A.; Adam, J.; Závorka, L.; Baldin, A.; Furman, W.; Kadykov, M.; Khushvaktov, J.; Solnyshkin, A.; Tsoupko-Sitnikov, V.; Tyutyunnikov, S.; Bielewicz, M.; Kilim, S.; Strugalska-Gola, E.; Szuta, M.

2017-03-01

The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW) performed intensive studies of several simple accelerator-driven system (ADS) setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

Directory of Open Access Journals (Sweden)

Suchopár M.

2017-01-01

Full Text Available The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW performed intensive studies of several simple accelerator-driven system (ADS setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

Oxygen enriched combustion system performance study. Phase 2: 100 percent oxygen enriched combustion in regenerative glass melters, Final report

Energy Technology Data Exchange (ETDEWEB)

Tuson, G.B.; Kobayashi, H.; Campbell, M.J.

1994-08-01

The field test project described in this report was conducted to evaluate the energy and environmental performance of 100% oxygen enriched combustion (100% OEC) in regenerative glass melters. Additional objectives were to determine other impacts of 100% OEC on melter operation and glass quality, and to verify on a commercial scale that an on-site Pressure Swing Adsorption oxygen plant can reliably supply oxygen for glass melting with low electrical power consumption. The tests constituted Phase 2 of a cooperative project between the United States Department of Energy, and Praxair, Inc. Phase 1 of the project involved market and technical feasibility assessments of oxygen enriched combustion for a range of high temperature industrial heating applications. An assessment of oxygen supply options for these applications was also performed during Phase 1, which included performance evaluation of a pilot scale 1 ton per day PSA oxygen plant. Two regenerative container glass melters were converted to 100% OEC operation and served as host sites for Phase 2. A 75 ton per day end-fired melter at Carr-Lowrey Glass Company in Baltimore, Maryland, was temporarily converted to 100% OEC in mid- 1990. A 350 tpd cross-fired melter at Gallo Glass Company in Modesto, California was rebuilt for permanent commercial operation with 100% OEC in mid-1991. Initially, both of these melters were supplied with oxygen from liquid storage. Subsequently, in late 1992, a Pressure Swing Adsorption oxygen plant was installed at Gallo to supply oxygen for 100% OEC glass melting. The particular PSA plant design used at Gallo achieves maximum efficiency by cycling the adsorbent beds between pressurized and evacuated states, and is therefore referred to as a Vacuum/Pressure Swing Adsorption (VPSA) plant.

Effect of oxygen enrichment in air on acid gas combustion under Claus conditions

KAUST Repository

Ibrahim, Salisu

2013-09-01

Results are presented to examine the combustion of acid gas (H2S and CO2) in hydrogen-fueled flames using a mixture of oxygen and nitrogen under Claus conditions (Φ = 3). Specifically the effect of oxygen enrichment in the above flames is examined. The compositions of acid gas examined are100% H2S and 50% H2S/50% CO2 with different percentages of oxygen enrichment (0%, 19.3% and 69.3%) in the oxygen/nitrogen mixtures. The results revealed that combustion of acid gas formed SO2 wherein the mole fraction of SO2 increased to an asymptotic value at all the oxygen concentrations examined. In addition, increase in oxygen enrichment of the air resulted in increased amounts of SO2 rather than the formation of more desirable elemental sulfur. In case of 50% H2S/50% CO2 acid gas, carbon monoxide mole fraction increased with oxygen enrichment which is an indicator to the availability of additional amounts of oxygen into the reaction pool. This gas mixture resulted in the formation of other sulfurous–carbonaceous compounds (COS and CS2) due to the presence of carbon monoxide. The results showed that the rate of COS formation increased with oxygen enrichment due to the availability of higher amounts of CO while that of CS2 reduced. The global reactions responsible for this observed phenomenon are presented.

High performance yttrium-doped BSCF hollow fibre membranes

DEFF Research Database (Denmark)

Haworth, P.; Smart, S.; Glasscock, Julie

2012-01-01

measurements in air was similar for both compositions, suggesting that the higher oxygen fluxes obtained for BSCFY hollow fibres could be attributed to the higher non-stoichiometry due to yttrium addition to the BSCF crystal structure. In addition, the improvement of oxygen fluxes for small wall thickness (∼0...

Method of deuterium isotope separation and enrichment

International Nuclear Information System (INIS)

Benson, S.W.

1980-01-01

A method of deuterium isotope separation and enrichment using infrared laser technology in combination with chemical processes for treating and recycling the unreacted and deuterium-depleted starting materials is described. Organic molecules of the formula RX (where R is an ethyl, isopropyl, t-butyl, or cyclopentenyl group and X is F, Cl, Br or OH) containing a normal abundance of hydrogen and deuterium are exposed to intense laser infrared radiation. An olefin containing deuterium (olefin D) will be formed, along with HX. The enriched olefin D can be stripped from the depleted stream of RX and HX, and can be burned to form enriched water or pyrolyzed to produce hydrogen gas with elevated deuterium content. The depleted RX is decomposed to olefins and RX, catalytically exchanged with normal water to restore the deuterium content to natural levels, and recombined to form RX which can be recycled. (LL)

Growth history of cultured pearl oysters based on stable oxygen isotope analysis

Science.gov (United States)

Nakashima, R.; Furuta, N.; Suzuki, A.; Kawahata, H.; Shikazono, N.

2007-12-01

We investigated the oxygen isotopic ratio in shells of the pearl oyster Pinctada martensii cultivated in embayments in Mie Prefecture, central Japan, to evaluate the biomineralization of shell structures of the species and its pearls in response to environmental change. Microsamples for oxygen isotope analysis were collected from the surfaces of shells (outer, middle, and inner shell layers) and pearls. Water temperature variations were estimated from the oxygen isotope values of the carbonate. Oxygen isotope profiles of the prismatic calcite of the outer shell layer reflected seasonal variations of water temperature, whereas those of nacreous aragonites of the middle and inner shell layers and pearls recorded temperatures from April to November, June to September, and July to September, respectively. Lower temperatures in autumn and winter might slow the growth of nacreous aragonites. The oxygen isotope values are controlled by both variations of water temperature and shell structures; the prismatic calcite of this species is useful for reconstructing seasonal changes of calcification temperature.

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

Energy Technology Data Exchange (ETDEWEB)

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

1994-06-01

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

Hanford isotope project strategic business analysis yttrium-90 (Y-90)

International Nuclear Information System (INIS)

1995-10-01

The purpose of this analysis is to address the short-term direction for the Hanford yttrium-90 (Y-90) project. Hanford is the sole DOE producer of Y-90, and is the largest repository for its source in this country. The production of Y-90 is part of the DOE Isotope Production and Distribution (IP and D) mission. The Y-90 is ''milked'' from strontium-90 (Sr-90), a byproduct of the previous Hanford missions. The use of Sr-90 to produce Y-90 could help reduce the amount of waste material processed and the related costs incurred by the clean-up mission, while providing medical and economic benefits. The cost of producing Y-90 is being subsidized by DOE-IP and D due to its use for research, and resultant low production level. It is possible that the sales of Y-90 could produce full cost recovery within two to three years, at two curies per week. Preliminary projections place the demand at between 20,000 and 50,000 curies per year within the next ten years, assuming FDA approval of one or more of the current therapies now in clinical trials. This level of production would incentivize private firms to commercialize the operation, and allow the government to recover some of its sunk costs. There are a number of potential barriers to the success of the Y-90 project, outside the control of the Hanford Site. The key issues include: efficacy, Food and Drug Administration (FDA) approval and medical community acceptance. There are at least three other sources for Y-90 available to the US users, but they appear to have limited resources to produce the isotope. Several companies have communicated interest in entering into agreements with Hanford for the processing and distribution of Y-90, including some of the major pharmaceutical firms in this country

Hanford isotope project strategic business analysis yttrium-90 (Y-90)

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-10-01

The purpose of this analysis is to address the short-term direction for the Hanford yttrium-90 (Y-90) project. Hanford is the sole DOE producer of Y-90, and is the largest repository for its source in this country. The production of Y-90 is part of the DOE Isotope Production and Distribution (IP and D) mission. The Y-90 is ``milked`` from strontium-90 (Sr-90), a byproduct of the previous Hanford missions. The use of Sr-90 to produce Y-90 could help reduce the amount of waste material processed and the related costs incurred by the clean-up mission, while providing medical and economic benefits. The cost of producing Y-90 is being subsidized by DOE-IP and D due to its use for research, and resultant low production level. It is possible that the sales of Y-90 could produce full cost recovery within two to three years, at two curies per week. Preliminary projections place the demand at between 20,000 and 50,000 curies per year within the next ten years, assuming FDA approval of one or more of the current therapies now in clinical trials. This level of production would incentivize private firms to commercialize the operation, and allow the government to recover some of its sunk costs. There are a number of potential barriers to the success of the Y-90 project, outside the control of the Hanford Site. The key issues include: efficacy, Food and Drug Administration (FDA) approval and medical community acceptance. There are at least three other sources for Y-90 available to the US users, but they appear to have limited resources to produce the isotope. Several companies have communicated interest in entering into agreements with Hanford for the processing and distribution of Y-90, including some of the major pharmaceutical firms in this country.

Application of atomic vapor laser isotope separation to the enrichment of mercury

International Nuclear Information System (INIS)

Crane, J.; Erbert, G.; Paisner, J.; Chen, H.; Chiba, Z.; Beeler, R.; Combs, R.; Mostek, S.

1986-09-01

Workers at GTE/Sylvania have shown that the efficiency of fluorescent lighting may be markedly improved using mercury that has been enriched in the 196 Hg isotope. A 5% improvement in the efficiency of fluorescent lighting in the United States could provide a savings of $450 million dollars in the corresponding reduction of electrical power consumption. We discuss the results of recent work done at our 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

Cascades for natural water enrichment in deuterium and oxygen-18 using membrane permeation

International Nuclear Information System (INIS)

Chmielewski, A.G.; Matuszak, A.; Zakrzewska-Trznadel, G.; Van Hook, A.

1991-01-01

The enrichment of water in heavy isotopes by permeation through a hydrophobic membrane is described. Simple counter - current cascades are of no practical interest because of their high energy demand. A better solution is to employ a double counter - current cascade re-utilizing part of the heat of condensation. Currently employed methods of natural water enrichment in heavy isotopes are compared to the proposed membrane process. (author). 18 refs, 14 tabs, 21 figs

The jet nozzle process for uranium 235 isotopic enrichment

International Nuclear Information System (INIS)

Jordan, I.; Umeda, K.; Brown, A.E.P.

1979-01-01

A general survey of the isotopic enrichment of Uranium - 235, principally by jet nozzle process, is made. Theoretical treatment of a single stage and cascade of separation stages of the above process with its development in Germany until 1976 is presented [pt

How the oxygen isotope ratio of rain water influences the isotope ratio of chicken eggshell carbonate

Science.gov (United States)

Price, Gregory; Grimes, Stephen

2015-04-01

The stable oxygen isotope ratio of chicken eggshell carbonate was analysed from chicken eggs laid under free range, and organic farming regimes from across the UK. The eggshell carbonate oxygen isotope data shows a clear depletion in delta18O distribution from the southwest to the northeast. Although consistently offset by around 1 permil, the same isotopic distribution as that seen in eggshell carbonate is observed in the delta18O ratio of rainfall and groundwater from across the UK. This distribution is related to the Rayleigh distillation of rainfall driven by westerly winds across the UK landmass. The clear relationship observed between eggshell delta18O values and that of rainwater presumably reflects the nature of free range chickens which must be drinking locally derived rainwater and supplementing their diet and water intake with locally derived food. These results suggest that the oxygen isotope value of chicken eggshells can be used as a forensic tool to identify the locality that free range and organic eggs were laid within the UK. Furthermore, if suitable material is preserved in the archaeological and geological record then such a relationship can potentially be used to establish the oxygen isotope value of rainwater from which ancient and / or ancestral birds lived.

Numeric Simulation of Oxygen Enriched Combustion in a Frit Melting Kiln

Directory of Open Access Journals (Sweden)

Bernardo A. Herrera-Múnera

2013-11-01

Full Text Available In this paper, a numerical study of air enriched combustion on a natural gas rotary furnace for frita melting is presented. This study was done with the aim of determining an oxygen concentration to ensure economic feasibility of the process without affecting quality requirements. The simulations were conducted using the commercial software ANSYS FLUENT as a design tool to predict the behavior of the thermal system and to establish operations conditions with different oxygen enrichment levels. Finite Rate / Eddy Dissipation model was used for combustion simulation, while k - ε Realizable and Discrete Ordinates models were utilized for turbulence and radiation simulation, respectively. It was found that an enrichment level close to 31% of oxygen in the air allows for reaching temperatures for frita melting larger than 1700 K. In this way, current consumption of high purity oxygen can be diminished without affecting the production levels and the quality of the product.

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.

Separation of isotopes of nitrogen and oxygen by low temperature distillation of nitrogen oxide

Energy Technology Data Exchange (ETDEWEB)

Isomura, Shohei; Tonooka, Yasuhiko; Kaetsu, Hayato

1987-02-01

In general, the distillation parameters, such as the number of theoretical plate (NTP) and the height equivalent to a theoretical plate (HETP), can be obtained from the operation at the steady state. However, it is time-consuming to achieve the steady state especially in the case of isotope separation. In this paper, with the purpose of simultaneous separation of isotopes of nitrogen and oxygen by NO distillation, we tried to determine the distillation parameters by an analytical method through the transient-state operation. It was confirmed that the results from the analysis were in good agreement with those observed for the operation at the steady state. Enrichment of the isotopes was carried out using a distillation column with a height of 1 m and inside diameter of 12 mm. The dependence of HETP on liquid flow rate was measured by the proposed method. The obtained HETP values were from 2 to 4 cm. The operation time of about 5 h was found to be long enough to determine the distillation parameters.

Separation of isotopes of nitrogen and oxygen by low temperature distillation of nitrogen oxide

International Nuclear Information System (INIS)

Isomura, Shohei; Tonooka, Yasuhiko; Kaetsu, Hayato

1987-01-01

In general, the distillation parameters, such as the number of theoretical plate (NTP) and the height equivalent to a theoretical plate (HETP), can be obtained from the operation at the steady state. However, it is time-consuming to achieve the steady state especially in the case of isotope separation. In this paper, with the purpose of simultaneous separation of isotopes of nitrogen and oxygen by NO distillation, we tried to determine the distillation parameters by an analytical method through the transient-state operation. It was confirmed that the results from the analysis were in good agreement with those observed for the operation at the steady state. Enrichment of the isotopes was carried out using a distillation column with a height of 1 m and inside diameter of 12 mm. The dependence of HETP on liquid flow rate was measured by the proposed method. The obtained HETP values were from 2 to 4 cm. The operation time of about 5 h was found to be long enough to determine the distillation parameters. (author)

Yttrium-enriched YBa2Cu3Ox thin films for coated conductors fabricated by pulsed laser deposition

International Nuclear Information System (INIS)

Khoryushin, Alexey V.; Mozhaev, Peter B.; Mozhaeva, Julia E.; Andersen, Niels H.; Grivel, Jean-Claude; Hansen, Jørn Bindslev; Jacobsen, Claus S.

2013-01-01

Highlights: ► YBCO films were fabricated by PLD from targets of various elemental compositions. ► The Y-enriched films contain yttria nanoparticles which provide efficient pinning. ► The best film has 5.5× higher j c (5 T,50 K) = 2.6MA/cm 2 comparing with a reference film. ► The Y-enriched films remain c-oriented up to 500 nm. ► Films demonstrate no j c suppression with thickness and remarkable stability with time. -- Abstract: The effects of excess yttria on the structural and electrical properties of the YBa 2 Cu 3 O x (YBCO) thin films are studied. The films were deposited on (LaAlO 3 ) 0.3 –(Sr 2 AlTaO 8 ) 0.7 substrates by pulsed laser ablation from targets with different elemental composition. An increase of yttrium content of the target leads to formation of porous films with significantly improved current-carrying capabilities. Structural studies of these films reveal presence of yttria nanoparticles embedded into the YBCO matrix. The highest obtained critical current density in an external magnetic field of 5 T was 2.6 MA/cm 2 at 50 K and 9.4 MA/cm 2 at 20 K. The fabricated Y-enriched YBCO films remain c-oriented at least up to 600 nm thickness with no significant suppression of the critical current density

The effect of phosphomonoesterases on the oxygen isotope composition of phosphate

Science.gov (United States)

von Sperber, Christian; Kries, Hajo; Tamburini, Federica; Bernasconi, Stefano M.; Frossard, Emmanuel

2014-01-01

Plants and microorganisms under phosphorus (P) stress release extracellular phosphatases as a strategy to acquire inorganic phosphate (Pi). These enzymes catalyze the hydrolysis of phosphoesters leading to a release of Pi. During the enzymatic hydrolysis an isotopic fractionation (ε) occurs leaving an imprint on the oxygen isotope composition of the released Pi which might be used to trace phosphorus in the environment. Therefore, enzymatic assays with acid phosphatases from wheat germ and potato tuber and alkaline phosphatase from Escherichia coli were prepared in order to determine the oxygen isotope fractionation caused by these enzymes. Adenosine 5‧ monophosphate and glycerol phosphate were used as substrates. The oxygen isotope fractionation caused by acid phosphatases is 20-30‰ smaller than for alkaline phosphatases, resulting in a difference of 5-7.5‰ in δ18O of Pi depending on the enzyme. We attribute the enzyme dependence of the isotopic fractionation to distinct reaction mechanisms of the two types of phosphatases. The observed difference is large enough to distinguish between the two enzymatic processes in environmental samples. These findings show that the oxygen isotope composition of Pi can be used to trace different enzymatic processes, offering an analytical tool that might contribute to a better understanding of the P-cycle in the environment.

Method for separation and enrichment of isotopes

International Nuclear Information System (INIS)

Kakihana, H.; Miyamatsu, T.

1977-01-01

Boron or uranium isotopes can be chemically separated and enriched with high speed and with high separating efficiency by using weakly basic anion exchange fibers having a diameter of not more than 100 μ, an aspect ratio of at least 5 and an exchange capacity of at least 2 meq/g-dry fiber, which are packed in a column at a specific volume of 2.0 to 20.0 ml/g-dry fiber

Gas phase adsorption technology for nitrogen isotope separation and its feasibility for highly enriched nitrogen gas production

International Nuclear Information System (INIS)

Inoue, Masaki; Asaga, Takeo

2000-04-01

Highly enriched nitrogen-15 gas is favorable to reduce radioactive carbon-14 production in reactor. The cost of highly enriched nitrogen-15 gas in mass production is one of the most important subject in nitride fuel option in 'Feasibility Study for FBR and Related Fuel Cycle'. In this work gas phase adsorption technology was verified to be applicable for nitrogen isotope separation and feasible to produce highly enriched nitrogen-15 gas in commercial. Nitrogen isotopes were separated while ammonia gas flows through sodium-A type zeolite column using pressure swing adsorption process. The isotopic ratio of eight samples were measured by high resolution mass spectrometry and Fourier transform microwave spectroscopy. Gas phase adsorption technology was verified to be applicable for nitrogen isotope separation, since the isotopic ratio of nitrogen-15 and nitrogen-14 in samples were more than six times as high as in natural. The cost of highly enriched nitrogen-15 gas in mass production were estimated by the factor method. It revealed that highly enriched nitrogen-15 gas could be supplied in a few hundred yen per gram in mass production. (author)

Isotopic enrichment of 15N by ionic exchange chromatography

International Nuclear Information System (INIS)

Trivelin, P.C.O.

1979-01-01

The present paper presents some studies on production of 15 N-enriched ammonium sulphate with 5% atoms by ionic exchange chromatography method. Two systems are described of columns of resin, where experiments were conducted by eluition of NH 4 + bands with sodium hydroxide solution. Analyses were made of the cost of production of 15 N-enriched ammonium sulphate 5% atoms and, based on the experiments developed, a cost was obtained which was compatible with the international price of the product. The isotopic analyses of nitrogen were made by mass spectrometry. (Author) [pt

Hydrogen and oxygen isotope exchange reactions over illuminated and nonilluminated TiO2

International Nuclear Information System (INIS)

Sato, S.

1987-01-01

Hydrogen isotope exchange between H 2 , gaseous H 2 O, and the surface hydroxyls of TiO 2 , and oxygen isotope exchange between O 2 , CO 2 , CO, H 2 O vapor, and the hydroxyls over TiO 3 were studied at room temperature in the dark and under illumination. Hydrogen isotope exchange between H 2 O and the hydroxyls occurred rapidly in the dark, but the exchange involving H 2 did not occur at all even under illumination. Oxygen isotope exchange among H 2 O vapor, CO 2 , and the hydroxyls easily took place in the dark, but the exchange involving O 2 required band-gap illumination. Dioxygen isotope equilibration was much faster than the other photoexchange reactions. Although the oxygen exchange between O 2 and illuminated TiO 2 has been considered to involve lattice-oxygen exchange, the present experiments revealed that the hydroxyls of TiO 2 mainly participate in the exchange reaction. The oxygen exchange between O 2 and H 2 O vapor was strongly inhibited by H 2 O vapor itself probably because oxygen adsorption was retarded by adsorbed water. Oxygen in CO was not exchanged with the other substrates under any conditions tested

A 2000-2010 years outlook of isotopic uranium enrichment

International Nuclear Information System (INIS)

Vasaru, G.

1998-01-01

The increase of the installed power in nuclear plants implies the following steps to be achieved: - developing a parallel industry for the nuclear fuel cycle able to ensure a rhythmic supply of natural uranium, possibly an isotopic enrichment of 235 U of around 1.2 - 3.2%, depending on the reactor system; - manufacturing the fuel elements and the operation of cycle back-end, which may, possibly, include a temporary storage of the irradiated fuel; - reprocessing the spend fuel; - radioactive waste processing in view of final disposal, as well as the recovery of un-spent uranium and of plutonium formed. The heavy water reactors of CANDU-PHW does not imply any isotopic enrichment but provides a lower burnup of only 7,000 MW day/tone. An enrichment to 1.2% in 235 U for this type of reactors could increase the burnup up to 20,000 MW day/tone. An advanced method of enriching 235 U is based on the Atomic Vapor Laser Isotop Separation (AVLIS). This procedure called AVLIS has several advantages which are pointed out in this paper, among which: a very high selectivity; high separation factors; a low energy consumption due to the fact that in the conditions of a selective photo ionization, the energy necessary to the process is only 6.2 eV for the separated 235 U atom vs 0.3 MeV in case of inertial separators or 3 MeV in case of gaseous diffusion procedure. With the current laser yields an energy consumption of 100 kWh/SWU is estimated for AVLIS procedures as compared with 2,400 kWh/SWU in case of gaseous diffusion; an almost entire extraction of 235 U, what ensures a more efficient utilisation of nuclear fuel. Due to its modular character and to potential improvement in the equipment which could be achieved, this procedure will ensure a reduction in the investment costs in the construction stage what will make AVLIS a substitute of the classical separation procedures

Isotopic analysis of uranium hexafluoride highly enriched in U-235

International Nuclear Information System (INIS)

Chaussy, L.; Boyer, R.

1968-01-01

Isotopic analysis of uranium in the form of the hexafluoride by mass-spectrometry gives gross results which are not very accurate. Using a linear interpolation method applied to two standards it is possible to correct for this inaccuracy as long as the isotopic concentrations are less than about 10 per cent in U-235. Above this level, the interpolations formula overestimates the results, especially if the enrichment of the analyzed samples is higher than 1.3 with respect to the standards. A formula is proposed for correcting the interpolation equation and for the extending its field of application to high values of the enrichment (≅2) and of the concentration. It is shown that by using this correction the results obtained have an accuracy which depends practically only on that of the standards, taking into account the dispersion in the measurements. (authors) [fr

The oxygen isotope composition of earth's oldest rocks and evidence of a terrestrial magma ocean

DEFF Research Database (Denmark)

Rumble, D.; Bowring, S.; Iizuka, T.

2013-01-01

Analysis of Hadean and Archean rocks for O-16-O-17-O-18 isotopes demonstrates that the Terrestrial Mass Fractionation Line of oxygen isotopes has had the same slope and intercept for at least the past 4.0 and probably for as long as 4.2Ga. The homogenization of oxygen isotopes required to produce....... But other sources of heat for global melting cannot be excluded such as bolide impacts during early accretion of proto-Earth, the decay of short-lived radioactive isotopes, or the energy released during segregation of core from mantle.......Analysis of Hadean and Archean rocks for O-16-O-17-O-18 isotopes demonstrates that the Terrestrial Mass Fractionation Line of oxygen isotopes has had the same slope and intercept for at least the past 4.0 and probably for as long as 4.2Ga. The homogenization of oxygen isotopes required to produce...... such long-lived consistency was most easily established by mixing in a terrestrial magma ocean. The measured identical oxygen isotope mass fractionation lines for Earth and Moon suggest that oxygen isotope reservoirs of both bodies were homogenized at the same time during a giant moon-forming impact...

Bulk Oxygen Isotopic Composition of Ultracarbonaceous Antarctic Micrometeorites with the NanoSIMS

Science.gov (United States)

Kakazu, Y.; Engrand, C.; Duprat, J.; Briani, G.; Bardin, N.; Mostefaoui, S.; Duhamel, R.; Remusat, L.

2014-09-01

We analyzed the carbon and oxygen isotope ratios of two UCAMMs with the NanoSIMS in order to understand the origin and formation of UCAMMs. One UCAMM has 16O-rich composition and a highly heterogeneous oxygen isotopic distribution.

Enhanced production and isotope enrichment of recombinant glycoproteins produced in cultured mammalian cells

Energy Technology Data Exchange (ETDEWEB)

Skelton, David; Goodyear, Abbey [Florida State University, Department of Chemistry and Biochemistry (United States); Ni, DaQun; Walton, Wendy J.; Rolle, Myron; Hare, Joan T. [Florida State University, Institute of Molecular Biophysics (United States); Logan, Timothy M., E-mail: tlogan@fsu.ed [Florida State University, Department of Chemistry and Biochemistry (United States)

2010-10-15

NMR studies of post-translationally modified proteins are complicated by the lack of an efficient method to produce isotope enriched recombinant proteins in cultured mammalian cells. We show that reducing the glucose concentration and substituting glutamate for glutamine in serum-free medium increased cell viability while simultaneously increasing recombinant protein yield and the enrichment of non-essential amino acids compared to culture in unmodified, serum-free medium. Adding dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, further improves cell viability, recombinant protein yield, and isotope enrichment. We demonstrate the method by producing partially enriched recombinant Thy1 glycoprotein from Lec1 Chinese hamster ovary (CHO) cells using U-{sup 13}C-glucose and {sup 15}N-glutamate as labeled precursors. This study suggests that uniformly {sup 15}N,{sup 13}C-labeled recombinant proteins may be produced in cultured mammalian cells starting from a mixture of labeled essential amino acids, glucose, and glutamate.

Enhanced production and isotope enrichment of recombinant glycoproteins produced in cultured mammalian cells

International Nuclear Information System (INIS)

Skelton, David; Goodyear, Abbey; Ni, DaQun; Walton, Wendy J.; Rolle, Myron; Hare, Joan T.; Logan, Timothy M.

2010-01-01

NMR studies of post-translationally modified proteins are complicated by the lack of an efficient method to produce isotope enriched recombinant proteins in cultured mammalian cells. We show that reducing the glucose concentration and substituting glutamate for glutamine in serum-free medium increased cell viability while simultaneously increasing recombinant protein yield and the enrichment of non-essential amino acids compared to culture in unmodified, serum-free medium. Adding dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, further improves cell viability, recombinant protein yield, and isotope enrichment. We demonstrate the method by producing partially enriched recombinant Thy1 glycoprotein from Lec1 Chinese hamster ovary (CHO) cells using U- 13 C-glucose and 15 N-glutamate as labeled precursors. This study suggests that uniformly 15 N, 13 C-labeled recombinant proteins may be produced in cultured mammalian cells starting from a mixture of labeled essential amino acids, glucose, and glutamate.

Sources and Contributions of Oxygen During Microbial Pyrite Oxidation: the Triple Oxygen Isotopes of Sulfate

Science.gov (United States)

Ziegler, K.; Coleman, M. L.; Mielke, R. E.; Young, E. D.

2008-12-01

The triple isotopes of oxygen (Δ17O' = δ17O'-0.528 × δ18O' using logarithmic deltas) can trace the oxygen sources of sulfate produced during sulfide oxidation, an important biogeochemical process on Earth's surface and possibly also on Mars [1]. δ18OSO4 compositions are determined by the isotopic selectivity of the mechanism(s) responsible for their changes, and the δ18O value of the reactants (O2 vs. H2O). The relative proportional importance and contribution of each of those sources and mechanisms, as well as their associated isotopic fractionations, are not well understood. We are investigating the use of Δ 17O as a quantitative and qualitative tracer for the different processes and oxygen sources involved in sulfate production. Δ17O signatures are distinct fingerprints of these reservoirs, independent of fractionation factors that can be ambiguous. We conducted controlled abiotic and biotic (Acidithiobacillus ferrooxidans, A.f.) laboratory experiments in which water was spiked with 18O, allowing us to quantify the sources of sulfate oxygen and therefore the processes attending sulfate formation. Results of this Δ17O tracer study show that A.f. microbes initiate pyrite S-oxidation within hours of exposure, and that sulfate is produced from ~90% atmospheric oxygen. This initial lag-phase (behavior in the initial lag-phase will aid in the understanding of the ecological conditions required for microbial populations to establish and survive. An exponential phase of growth, facilitated by microbial Fe2+-oxidation, follows. The source of sulfate rapidly switches to abiotic sulfide oxidation during exponential growth and the source of oxygen switches from atmospheric O2 to nearly ~100% water. Pending acquisition of complimentary chemistry data (in progress), we interpret our isotope data to indicate that the biotic fractionation factor ɛ18OSO4-O2 of at least ~ -25 to - 35‰ is augmented by microbially induced kinetic fractionation; it is larger than

Oxygen isotope exchange on palladium catalysts

International Nuclear Information System (INIS)

Kravchuk, L.S.; Beschetvertnaya, T.I.; Novorodskij, V.G.; Novikova, M.G.; Zaretskij, M.V.; Valieva, S.V.

1983-01-01

Oxygen heteromolecular isotope exchange on unreduced palladium catalysts, distingushing by metal content is studied. Content of 18 O in gaseous phase is eoual to 46%. Calculations of heteroexchange rates are conducted with decrease of the 18 O in the gaseous phase over solid sample. Method of oxygen thermodesorption has been used to establish that palladium, deposited on γ-Al 2 O 3 during exchange process is in oxidized state; in this case strength of Pd-O bond is determined by content dispersity) of the metal. It is shown that significant increase of exchange rate on the samples with Pd >> 0.5 mass.% content can be induced as by side decomposition reaction of its oxide and corresponding dilution of gaseous mixture by ''light'' oxygen so by possibility of exchange with oxygen of PdO phase

Hydrogen and oxygen isotope ratios of geothermal waters in the southern hachimantai area

International Nuclear Information System (INIS)

Matsubaya, Osamu; Etchu, Hiroshi; Takenaka, Teruo; Yoshida, Yutaka.

1985-01-01

Geothermal waters from the Matsukawa and Kakkonda Geothermal Plants, wells at Amihari-Motoyu, and Nyuto and Tazawako areas were isotopically studied. The geothermal waters from Mutsukawa, Kakkonda and Amihari-Motoyu have hydrogen isotope ratios similar to the local meteoric waters, while have higher oxygen isotope ratios than the local meteoric waters. This relationship of hydrogen and oxygen isotope ratios, that is called ''oxygen shift'', means that these geothermal waters are meteoric waters undergone the oxygen isotope exchange with rocks at high temperature of underground. The exygen shifts are 2 -- 3 per mil in Matsukawa and Kakkonda, and 7 per mil in Amihari-Motoyu. This difference may be important to understand the processe of water-rock interaction in this area. The geothermal waters at Nyuto and Tazawako areas also show 2 -- 3 per mil oxygen shift. The steam from the Tazawako-cho well and the hot spring water form the Tsurunoyu are estimated to be vapor and liquid phases separated form a single geothermal water of NaCl type, though the hot water from the Tsurunoyu is diluted with shallow meteoric water. (author)

High Temperature Oxidation of Steel in an Oxygen-enriched Low NOX Furnace Environment

Energy Technology Data Exchange (ETDEWEB)

Poirier, D.; Grandmaison, E.W. [Department of Chemical Engineering, Queen' s University, Kingston, ON K7L 3N6 (Canada); Matovic, M.D. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON K7L 3N6 (Canada); Barnes, K.R. [KB Technical Services, Inc (formerly) Stelco Inc, Research Manager, Stelco Inc., P.O. Box 2030, Hamilton, ON L8N 3T1 (Canada); Nelson, B.D. [Department of Chemical Engineering, Senior Researcher, Dofasco Inc., P.O. Box 2460, Hamilton, ON L8N 3J5 (Canada)

2006-09-15

Steel scaling tests have been performed in a research furnace utilizing an oxygen-enriched, low NOX, burner. This work was performed in conjunction with a study of the combustion characteristics for the Canadian Gas Research Institute (CGRI) low NOX burner. The furnace (a facility of the Centre for Advanced Gas Combustion Technology (CAGCT)) was fired with the burner mounted in a sidewall configuration similar to the geometry encountered in steel reheat furnaces. Scale habit, intactness, adhesion and oxidation rates were examined for five grades of steel over a range of stack oxygen concentrations ({approx}0.8% - {approx}4.3%) and oxygen enrichment levels (0-90%) at 1100C. Steel grade had the largest effect on scaling properties examined in this work. Within the tests for each grade, stack oxygen concentration had the largest effect on the scaling properties while oxygen enrichment level had only a small effect.

Oxygen isotope fractionation between bird eggshell calcite and body water: application to fossil eggs from Lanzarote (Canary Islands)

Science.gov (United States)

Lazzerini, Nicolas; Lécuyer, Christophe; Amiot, Romain; Angst, Delphine; Buffetaut, Eric; Fourel, François; Daux, Valérie; Betancort, Juan Francisco; Flandrois, Jean-Pierre; Marco, Antonio Sánchez; Lomoschitz, Alejandro

2016-10-01

Oxygen and carbon isotope compositions of fossil bird eggshell calcite (δ18Ocalc and δ13Ccalc) are regularly used to reconstruct paleoenvironmental conditions. However, the interpretation of δ18Ocalc values of fossil eggshells has been limited to qualitative variations in local climatic conditions as oxygen isotope fractionations between calcite, body fluids, and drinking water have not been determined yet. For this purpose, eggshell, albumen water, and drinking water of extant birds have been analyzed for their oxygen and carbon isotope compositions. Relative enrichments in 18O relative to 16O between body fluids and drinking water of +1.6 ± 0.9 ‰ for semi-aquatic birds and of +4.4 ± 1.9 ‰ for terrestrial birds are observed. Surprisingly, no significant dependence to body temperature on the oxygen isotope fractionation between eggshell calcite and body fluids is observed, suggesting that bird eggshells precipitate out of equilibrium. Two empirical equations relating the δ18Ocalc value of eggshell calcite to the δ18Ow value of ingested water have been established for terrestrial and semi-aquatic birds. These equations have been applied to fossil eggshells from Lanzarote in order to infer the ecologies of the Pleistocene marine bird Puffinus sp. and of the enigmatic giant birds from the Pliocene. Both δ13Ccalc and δ18Ocalc values of Puffinus eggshells point to a semi-aquatic marine bird ingesting mostly seawater, whereas low δ13Ccalc and high δ18Ocalc values of eggshells from the Pliocene giant bird suggest a terrestrial lifestyle. This set of equations can help to quantitatively estimate the origin of waters ingested by extinct birds as well as to infer either local environmental or climatic conditions.

Application of atomic vapor laser isotope separation to the enrichment of mercury

International Nuclear Information System (INIS)

Crane, J.K.; Erbert, G.V.; Paisner, J.A.; Chen, H.L.; Chiba, Z.; Beeler, R.G.; Combs, R.; Mostek, S.D.

1986-09-01

Workers at GTE/Sylvania have shown that the efficiency of fluorescent lighting may be markedly improved using mercury that has been enriched in the 196 Hg isotope. A 5% improvement in the efficiency of fluorescent lighting in the United States could provide a savings of ∼ 1 billion dollars in the corresponding reduction of electrical power consumption. We will discuss the results of recent work done at our laboratory to develop a process for enriching mercury. The discussion will center around the results of spectroscopic measurements of excited state lifetimes, photoionization cross sections and isotope shifts. In addition, we will discuss the mercury separator and supporting laser mesurements of the flow properties of mercury vapor. We will describe the laser system which will provide the photoionization and finally discuss the economic details of producing enriched mercury at a cost that would be attractive to the lighting industry

Energy consumption of chemical uranium enrichment

International Nuclear Information System (INIS)

Miyake, T.; Takeda, K.; Obanawa, H.

1987-01-01

A quantitative study of chemical separation energy for enriching uranium-235 by the redox chromatography was conducted. Isotope exchange reactions between U 4+ -UO 2 2+ ions in the enrichment column are maintained by the redox reactions. The chemical separation energy is ultimately supplied by hydrogen and oxygen gas for regenerating redox agents. The redox energy for the isotope separation is theoretically predicted as a function of the dynamic enrichment factor observed in the chromatographic development of uranium adsorption band. Thermodynamic treatments of the equilibrium reactions implies and inverse redox reaction which can be enhanced by the chemical potential of the ion-exchange reaction of oxidant. Experimental results showed 30 to 90% recovery of the redox energy by the inverse reaction. These results will devise a simplified redox chromatography process where a number of columns in one module is reduced

Analytical techniques for determination of framework oxygen isotope ratio of wairakite

International Nuclear Information System (INIS)

Noto, Masami; Kusakabe, Minoru; Uchida, Tetsuo.

1990-01-01

Dehydration techniques were developed for the analysis of isotopic ratios of framework oxygen of wairakite, one of calcium zeolites often encountered in geothermal systems. Channel water in wairakite were separated from aluminosilicate framework by dehydration in vacuum at 300 deg, 400 deg, 450 deg, 500 deg, 550 deg, 650 deg, 750 deg, 850 deg, and 950 degC, and by stepwise heating at temperatures from 300 deg to 700 degC. The oxygen isotopic analyses of the separated channel water and the residual aluminosilicate framework of wairakite indicated that dehydration at temperatures higher than 400 degC is accompanied by isotopic exchang between the framework oxygen and dehydrating water vapor. The isotopic exchange during the high temperature dehydration makes the δ 18 O of framework oxygen lower and that of channel water higher than those obtained by dehydration at 300 degC. These results are consistent with dehydration behavior of wairakite under vacuum that the maximum rate of dehydration of channel water is attained at about 400 degC. Consequently it is recommended to dehydrate wairakite at a temperature as low as possible in order to avoid the effect of the isotopic exchange. Time required to attain complete dehydration becomes longer with lowering the temperature of dehydration. To compromise these conflicting effects, the optimum conditions of dehydration have been found that most of the channel water is dehydrated at 300 degC for 24 hours, followed by stepwise heating for additional 17 hours up to 700 degC. We obtained a better than ± 0.1 reproducibility for the framework oxygen isotopic determinations with this technique. (author)

Sulfur isotope separation by anion exchange chromatography: 34 S isotope enrichment

International Nuclear Information System (INIS)

Bendassolli, Jose Albertino; Trivelin, Paulo Cesar O.; Carneiro Junior, Francisco

1995-01-01

The 34 S isotope separation was carried out by isotopic exchange reactions between sulphurous acid in solution and bisulphite anions adsorbed on an ammonium quaternary (Dowex 1 x 8 and Dowex 2 x 8, 100-200 mesh) anion exchange resin packed in columns. Each resin column had 130 cm length and 2.2 cm diameter. The columns were connected in series during displacement of bisulphite bands. For the experiments, a band of bisulphite was fixed to the anion resin, initially in the hydroxyl ion form, and subsequently eluted with 0.2 0.3, 0.4 and 0.6 mol L -1 HCL solution. The hydrochloric acid solution was kept under a nitrogen atmosphere at 245 KPa of pressure, in order to prevent the evolution of gases and also the oxidation of the bisulphite. The experiments showed that the best results were obtained with the elution of bisulphite with 0.2 mol.L -1 HCL, with the Dowex 1 x 8 resin. Enrichments in 34 S of 17.33 atoms% were obtained using Dowex 1 x 8 resin, 0.2 mol.L -1 HCL solution and band displacement of 50 m. Replacing the depleted portion of the band with natural bisulphite, for each 10 m of band displacement, produced 6.79 mmol of sulphurous acid enriched with approximately 17% of 34 S, after 14 m of band dislocation. (author). 7 refs., 1 fig., 2 tabs

Oxygen and U-Th isotopes and the timescales of hydrothermal exchange and melting in granitoid wall rocks at Mount Mazama, Crater Lake, Oregon

Science.gov (United States)

Ankney, Meagan E.; Bacon, Charles R.; Valley, John W.; Beard, Brian L.; Johnson, Clark M.

2017-01-01

We report new whole rock U-Th and in-situ oxygen isotope compositions for partially melted (0–50 vol% melt), low-δ18O Pleistocene granitoid blocks ejected during the ∼7.7 ka caldera-forming eruption of Mt. Mazama (Crater Lake, Oregon). The blocks are interpreted to represent wall rocks of the climactic magma chamber that, prior to eruption, experienced variable amounts of exchange with meteoric hydrothermal fluids and subsequent partial melting. U-Th and oxygen isotope results allow us to examine the timescales of hydrothermal circulation and partial melting, and provide an “outside in” perspective on the buildup to the climactic eruption of Mt. Mazama. Oxygen isotope compositions measured in the cores and rims of individual quartz (n = 126) and plagioclase (n = 91) crystals, and for transects across ten quartz crystals, document zonation in quartz (Δ18OCore-Rim ≤ 0.1–5.5‰), but show homogeneity in plagioclase (Δ18OCore-Rim ≤ ±0.8‰). We propose that oxygen isotope zonation in quartz records hydrothermal exchange followed by high-temperature exchange in response to partial melting caused by injection of basaltic to andesitic recharge magma into the deeper portions of the chamber. Results of modeling of oxygen diffusion in quartz indicates that hydrothermal exchange in quartz occurred over a period of ∼1000–63,000 years. Models also suggest that the onset of melting of the granitoids occurred a minimum of ∼10–200 years prior to the Mazama climactic eruption, an inference which is broadly consistent with results for magnetite homogenization and for Zr diffusion in melt previously reported by others.Uranium-thorium isotope compositions of most granitoid blocks are in 238U excess, and are in agreement with a 238U enriched array previously measured for volcanic rocks at Mt. Mazama. Uranium excess in the granitoids is likely due to enrichment via hydrothermal circulation, given their low δ18O values. The sample with the

Low-temperature, non-stoichiometric oxygen isotope exchange coupled to Fe(II)-goethite interactions

Energy Technology Data Exchange (ETDEWEB)

Frierdich, Andrew J. [Univ. of Wisconsin, Madison, WI (United States); Univ. of Iowa, Iowa City, IA (United States); Beard, Brian L. [Univ. of Wisconsin, Madison, WI (United States); Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Scherer, Michelle M. [Univ. of Iowa, Iowa City, IA (United States); Spicuzza, Michael J. [Univ. of Wisconsin, Madison, WI (United States); Valley, John W. [Univ. of Wisconsin, Madison, WI (United States); Johnson, Clark M. [Univ. of Wisconsin, Madison, WI (United States)

2015-07-01

The oxygen isotope composition of natural iron oxide minerals has been widely used as a paleoclimate proxy. Interpretation of their stable isotope compositions, however, requires accurate knowledge of isotopic fractionation factors and an understanding of their isotopic exchange kinetics, the latter of which informs us how diagenetic processes may alter their isotopic compositions. Prior work has demonstrated that crystalline iron oxides do not significantly exchange oxygen isotopes with pure water at low temperature, which has restricted studies of isotopic fractionation factors to precipitation experiments or theoretical calculations. Using a double three-isotope method (¹⁸O-¹⁷O-¹⁶O and ⁵⁷Fe-⁵⁶Fe-⁵⁴Fe) we compare O and Fe isotope exchange kinetics, and demonstrate, for the first time, that O isotope exchange between structural O in crystalline goethite and water occurs in the presence of aqueous Fe(II) (Fe(II)_aq) at ambient temperature (i.e., 22–50 °C). The three-isotope method was used to extrapolate partial exchange results to infer the equilibrium, mass-dependent isotope fractionations between goethite and water. In addition, this was combined with a reversal approach to equilibrium by reacting goethite in two unique waters that vary in composition by about 16‰ in ¹⁸O/¹⁶O ratios. Our results show that interactions between Fe(II)_aq and goethite catalyzes O isotope exchange between the mineral and bulk fluid; no exchange (within error) is observed when goethite is suspended in ¹⁷O-enriched water in the absence of Fe(II)_aq. In contrast, Fe(II)-catalyzed O isotope exchange is accompanied by significant changes in ¹⁸O/¹⁶O ratios. Despite significant O exchange, however, we observed disproportionate amounts of Fe versus O exchange, where Fe isotope exchange in goethite was roughly three times that of O. This disparity provides novel insight into the reactivity of oxide minerals in aqueous

Chromatographic enrichment of isotopes in hydrogen and water samples on palladium

International Nuclear Information System (INIS)

Andreev, B.M.; Polevoi, A.S.; Perevezentsev, A.N.

1987-01-01

Data on the isotopic enrichment of hydrogen and water samples by chromatography on palladium have been analyzed. Experimental data on the effect of temperature, hydrogen flow, volume of the enriched fraction, and length of the chromatographic column on the degree of separation attainable in the column have been obtained. It has been shown that the maximum separation achievable (regardless of the type of the isotope mixture) at 273 K falls with increase of hydrogen flow and volume of the enriched gas fraction recoverable from the column. A separation degree of ∼ 1040 has been achieved for a mixture of protium and deuterium in a 10-mm wide and 0.6-m long chromatographic column packed with palladium black with a grain size of 0.2-0.5 mm at 273 K and a specific hydrogen flow of 1.22 mole/m 2 x sec. For a protium-tritium mixture a separation degree of ∼ 90 has been reached in a similar column at 273 K and a specific hydrogen flow of 0.4 mole/m 2 x sec

The method of water enrichment in oxygen-18

International Nuclear Information System (INIS)

Chmielewski, A.G.; Zakrzewska-Trznadel, G.; Van Hook, A.; Milievic, N.R.

1996-01-01

The process of membrane distillation has been used for water enrichment in oxygen-18. The hydrophobic PTFE membranes has been used as a boundary for liquids being at different temperatures on the each side of membrane. Example of obtained results have been shown

Yield and enrichment studies of C-13 isotope by multi-photon ...

Indian Academy of Sciences (India)

Abstract. 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 9P(22) laser line as a function of temperature (–50°C to 30°C). It is observed that at a given fluence ...

Isotope separation by selective photodissociation of glyoxal

International Nuclear Information System (INIS)

Marling, J.B.

1976-01-01

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

Oxygen isotope exchange rate between dissolved sulfate and water at hydrothermal temperatures

International Nuclear Information System (INIS)

Chiba, H.; Sakai, H.

1985-01-01

Oxygen isotope exchange rate between dissolved sulfate and water was experimentally determined at 100, 200 and 300 deg C. The isotope exchange rate is strongly dependent on temperature and pH of the solution. Combining the temperature and pH dependence of the reaction rate, the exchange reaction was estimated to be first-order with respect to sulfate. The logarithm of apparent rate constant of exchange reaction at a given temperature is a function of the pH calculated at the experimental temperatures. From the pH dependence of the apparent rate constant, it was deduced that the isotope exchange reaction between dissolved sulfate and water proceeds through collision between H 2 SO 4 0 and H 2 O at low pH, and between HSO 4 - and H 2 O at intermediate pH. The isotope exchange rate obtained indicates that oxygen isotope geothermometry utilizing the studied isotope exchange is suitable for temperature estimation of geothermal reservoirs. The extrapolated half-life of this reaction to oceanic temperature is about 10 9 years, implying that exchange between oceanic sulfate and water cannot control the oxygen isotope ratio of oceanic sulfates. (author)

The Effect of Phytase on the Oxygen Isotope Composition of Phosphate

Science.gov (United States)

von Sperber, C.; Tamburini, F.; Bernasconi, S. M.; Frossard, E.

2013-12-01

Plants and microorganisms under phosphorus (P) stress release extracellular phosphatases as a strategy to acquire inorganic phosphate (Pi) (1-2). These enzymes catalyze the hydrolysis of phosphoesters leading to a release of Pi. The enzymatic hydrolysis leads, via a nucleophilic attack, to the incorporation of one oxygen atom from the water into the newly formed Pi molecule. During the incorporation, an isotopic fractionation occurs, which might be used to identify the origin of Pi in the environment (3-6). While the effect of phosphomonoesterases and phosphodiesterases on the oxygen isotope composition of phosphate has been examined, there are, so far, no studies dealing with the effect of phytases (4-6). Phytases catalyze the hydrolysis of myo-inositol-hexakis-phosphate (IP6), which is an important component of organic P in many ecosystems (7). Enzymatic assays with phytase from wheat germ and Aspergillus niger were prepared under sterile and temperature controlled conditions in order to determine the effect of phytases on the oxygen isotope composition of phosphate, which has been liberated from IP6 via enzymatic hydrolysis. Assays with phytase from wheat germ lead to a turnover of the substrate close to 100%, while assays with phytase from Aspergillus niger lead to a turnover of the substrate close to 80%. In the case of the assays with phytase from wheat germ, our results indicate that one sixth of the total 24 oxygen which are associated to the phosphates in IP6 are exchanged with oxygen from water. From this we conclude that the incorporation of one oxygen atom from water occurs only at four phosphate molecules of IP6, while two phosphate molecules do not experience an incorporation of oxygen. This suggests that during the enzymatic hydrolysis, four P-O bonds and two C-O bonds are broken. Provided that, the isotopic fractionation can be calculated with an isotopic mass balance resulting in -8.4‰ (×3.6 SD). This is a value very similar to those reported

OXYGEN ISOTOPIC COMPOSITIONS OF THE ALLENDE TYPE C CAIs: EVIDENCE FOR ISOTOPIC EXCHANGE DURING NEBULAR MELTING AND ASTEROIDAL THERMAL METAMORPHISM

Energy Technology Data Exchange (ETDEWEB)

Krot, A N; Chaussidon, M; Yurimoto, H; Sakamoto, N; Nagashima, K; Hutcheon, I D; MacPherson, G J

2008-02-21

Based on the mineralogy and petrography, coarse-grained, igneous, anorthite-rich (Type C) calcium-aluminum-rich inclusions (CAIs) in the CV3 carbonaceous chondrite Allende have been recently divided into three groups: (i) CAIs with melilite and Al,Ti-diopside of massive and lacy textures (coarse grains with numerous rounded inclusions of anorthite) in a fine-grained anorthite groundmass (6-1-72, 100, 160), (ii) CAI CG5 with massive melilite, Al,Ti-diopside and anorthite, and (iii) CAIs associated with chondrule material: either containing chondrule fragments in their peripheries (ABC, TS26) or surrounded by chondrule-like, igneous rims (93) (Krot et al., 2007a,b). Here, we report in situ oxygen isotopic measurements of primary (melilite, spinel, Al,Ti-diopside, anorthite) and secondary (grossular, monticellite, forsterite) minerals in these CAIs. Spinel ({Delta}{sup 17}O = -25{per_thousand} to -20{per_thousand}), massive and lacy Al,Ti-diopside ({Delta}{sup 17}O = -20{per_thousand} to -5{per_thousand}) and fine-grained anorthite ({Delta}{sup 17}O = -15{per_thousand} to -2{per_thousand}) in 100, 160 and 6-1-72 are {sup 16}O-enriched relative spinel and coarse-grained Al,Ti-diopside and anorthite in ABC, 93 and TS26 ({Delta}{sup 17}O ranges from -20{per_thousand} to -15{per_thousand}, from -15{per_thousand} to -5{per_thousand}, and from -5{per_thousand} to 0{per_thousand}, respectively). In 6-1-72, massive and lacy Al,Ti-diopside grains are {sup 16}O-depleted ({Delta}{sup 17}O {approx} -13{per_thousand}) relative to spinel ({Delta}{sup 17}O = -23{per_thousand}). Melilite is the most {sup 16}O-depleted mineral in all Allende Type C CAIs. In CAI 100, melilite and secondary grossular, monticellite and forsterite (minerals replacing melilite) are similarly {sup 16}O-depleted, whereas grossular in CAI 160 is {sup 16}O-enriched ({Delta}{sup 17}O = -10{per_thousand} to -6{per_thousand}) relative to melilite ({Delta}{sup 17}O = -5{per_thousand} to -3{per_thousand}). We infer

Purification in the interaction between yttria mould and Nb-silicide-based alloy during directional solidification: A novel effect of yttrium

International Nuclear Information System (INIS)

Ma, Limin; Tang, Xiaoxia; Wang, Bin; Jia, Lina; Yuan, Sainan; Zhang, Hu

2012-01-01

Nb-silicide-based alloys were directionally solidified in yttria moulds. As a result of thermal dissociation of yttria, the alloys were slightly contaminated with oxygen, which caused a competitive oxidation between yttrium and hafnium. The addition of 0.15 at.% yttrium reduced the oxygen increment by 42%, because the buoyant inclusions concentrated around the top surface. The yttrium addition caused a significant purification of the interaction between the yttria mould and the Nb-silicide-based alloys during the directional solidification.

Palaeotemperature estimation in the Holsteinian Interglacial (MIS 11) based on oxygen isotopes of aquatic gastropods from eastern Poland

Science.gov (United States)

Szymanek, Marcin

2017-12-01

For quantitative estimation of past water temperature of four Holsteinian (MIS 11) palaeolakes from eastern Poland, the oxygen isotope palaeothermometer was applied to shells of the aquatic gastropods Viviparus diluvianus and Valvata piscinalis. The δ18O composition of their shells demonstrated the average growth-season water temperatures during the mesocratic stage of the interglacial (Ortel Królewski Lake), during its climatic optimum - the Carpinus-Abies Zone (Ossówka-Hrud, Roskosz and Szymanowo Lakes), and in the post-optimum (Szymanowo Lake). The calculation was based on δ18OShell values and the δ18OWater assumed for the Holsteinian from the modern oxygen isotope composition of precipitation and the expected amount of evaporative enrichment. The mean oxygen isotope palaeotemperatures of Ortel Królewski lake waters were in the range of 18.1-21.9°C and were uniform for the Taxus and Pinus-Larix zones. Ossówka-Hrud and Roskosz Lakes had mean temperatures of 17.4-21.0°C during the climatic optimum, whereas the temperature of Szymanowo lake waters was estimated at 20.6-21.7°C at that time. These values are concordant with the pollen-inferred July air temperatures noted during the Holsteinian in eastern Poland. Relatively high values of 25°C in the post-optimum noted at Szymanowo were connected with the presence of a shallow and warm isolated bay indicated by pollen and mollusc records.

Oxygen isotope ratios of the Icelandic crust

International Nuclear Information System (INIS)

Hattori, K.; Muehlenbachs, K.

1982-01-01

Oxygen isotope ratios of hydrothermally altered basalts from depth of up to approx.3 km are reported from three localities in Iceland: International Research Drilling Project (IRDP) core at Reydarfjordur, eastern Iceland (Tertiary age); drill cuttings from Reykjavik (Plio-Pleistocene age); and Halocene drill cuttings from the active Krafla central volcano. Whole rock samples from these three localities have delta 18 O values averaging +3.9 +- 1.3, +2.4 +- 1.1, and -7.7 +- 2.4%, respectively. The observed values in the deeper samples from Krafla are as low as the values for any rocks previously reported. There seems to be a slight negative gradient in delta 18 O with depth at the former two localities and a more pronounced one at Krafla. Oxygen isotope fractionations between epidote and quartz and those between calcite and fluid suggests that the basalts were altered at temperatures of 300 0 --400 0 C. Low deltaD and delta 18 O of epidote and low delta 34 S of anhydrite indicate that the altering fluids in all three areas originated as meteoric waters and have undergone varied 'oxygen shifts'. Differences in the 18 O shift of the fluids are attributed to differences in hydrothermal systems; low water/rock ratios ( 5) at Krafla. The convective hydrothermal activity, which is probably driven by silicic magma beneath the central volcanoes, has caused strong subsolidus depletion of 18 O in the rocks. The primary-magnetic delta 18 O value of the rocks in the Tertiary IRDP core was about +3.9%, which is lower than that obtained for fresh basalt from other places. Such exceptionally low delta 18 O magmas are common in Iceland and may occur as the result of oxygen isotope exchange with or assimilation of altered rocks that form a thick sequence beneath the island due to isostatic subsidence

Growth and characterization of isotopically enriched 70Ge and 74Ge single crystals

International Nuclear Information System (INIS)

Itoh, K.

1992-10-01

Isotopically enriched 70 Ge and 74 Ge single crystals were successfully gown by a newly developed vertical Bridgman method. The system allows us to reliably grow high purity Ge single crystals of approximately 1 cm 3 volume. To our knowledge, we have grown the first 70 Ge single crystal. The electrically active chemical impurity concentration for both crystals was found to be ∼2 x cm -3 which is two order of magnitude better that of 74 Ge crystals previously grown by two different groups. Isotopic enrichment of the 70 Ge and the 74 Ge crystals is 96.3% and 96.8%, respectively. The residual chemical impurities present in both crystals were identified as phosphorus, copper, aluminum, and indium. A wide variety of experiments which take advantage of the isotopic purity of our crystals are discussed

Non-linear Isotope Effects

DEFF Research Database (Denmark)

Schmidt, Johan Albrecht

’s stratosphere is nearly mass dependent, and only a small fraction of the observed anomalous oxygen-17 excess can be attributed to N2O photolysis. In contrast, stratospheric photolysis produces a significant inverse clumped isotope effect.(ii) Stratospheric OCS photolysis significantly enrich the remaining OCS...

Stable isotope ratio measurements in hydrogen, nitrogen, and oxygen using Raman scattering

International Nuclear Information System (INIS)

Harney, R.C.; Bloom, S.D.; Milanovich, F.P.

1975-01-01

A method for measuring stable isotope ratios using laser Raman scattering was developed which may prove of significant utility and benefit in stable isotope tracer studies. Crude isotope ratio measurements obtained with a low-power laser indicate that with current technology it should be possible to construct an isotope ratio measurement system using laser Raman scattering that is capable of performing 0.1 percent accuracy isotope ratio measurements of 16 O/ 18 O in natural abundance oxygen gas or 14 N/ 15 N in natural abundance nitrogen gas in times less than two minutes per sample. Theory pertinent to the technique, designs of specific isotope ratio spectrometer systems, and data relating to isotope ratio measurements in hydrogen, nitrogen, and oxygen are presented. In addition, the current status of several studies utilizing this technique is discussed. (auth)

Isotopic labeling study of oxygen diffusion in amorphous LaScO3 high-κ films on Si(100) and its effects on the electrical characteristics

International Nuclear Information System (INIS)

Lopes, J.M.J.; Littmark, U.; Roeckerath, M.; Durgun Oezben, E.; Lenk, S.; Schubert, J.; Mantl, S.; Breuer, U.; Besmehn, A.; Staerk, A.; Grande, P.L.; Sortica, M.A.; Radtke, C.

2009-01-01

The influence of post-deposition oxygen anneals on the properties of amorphous LaScO 3 films on Si(100) is reported. The use of an isotopically ( 18 O 2 ) enriched atmosphere allowed to investigate the 16 O- 18 O exchange and the oxygen diffusion across the dielectric layer. Such effects are connected to the formation of an interfacial layer. Oxygen annealing leads to nearly ideal capacitance-voltage curves, lower leakage currents and interface trap densities, as well as to κ-values up to 33 for the LaScO 3 films. These results are attributed to the suppression of oxygen-related trap centers and the achievement of a stoichiometric oxygen content. (orig.)

A Plant-Based Proxy for the Oxygen Isotope Ratio of Atmospheric Water Vapor

Science.gov (United States)

Helliker, B.

2007-12-01

Atmospheric water vapor is a major component of the global hydrological cycle, but the isotopic balance of vapor is largely unknown. It is shown here that the oxygen isotope ratio of leaf water in the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides (Spanish Moss) is controlled by the oxygen isotope ratio of atmospheric water vapor in both field and lab studies. Assuming that the leaf-water isotopic signature (and hence the atmospheric water vapor signature) is recorded in plant organic material, the atmospheric water vapor oxygen isotope ratios for Miami, Florida (USA) were reconstructed for several years from 1878 to 2005 using contemporary and herbarium specimens. T. usneoides ranges from Virginia, USA southwards through the tropics to Argentina, and the CAM epiphytic lifeform is widespread in other species. Therefore, epiphytes may be used to reconstruct the isotope ratio of atmospheric water for spatial scales that span over 60° of latitude and temporal scales that cover the last century of global temperature increase.

Light Stable Isotopic Compositions of Enriched Mantle Sources: Resolving the Dehydration Paradox

Science.gov (United States)

Dixon, J. E.; Bindeman, I. N.; Kingsley, R. H.

2017-12-01

An outstanding puzzle in mantle geochemistry has been the origin and evolution of Earth's volatile components. The "dehydration paradox" refers to the following conundrum. Mantle compositions for some enriched mid-ocean ridge (MORB) and ocean island (OIB) basalts basalts require involvement of a mostly dehydrated slab component to explain the trace element ratios and radiogenic isotopic compositions, but a fully hydrated slab component to explain the stable isotopic compositions. Volatile and stable isotopic data on enriched MORB show a diversity of enriched components. Pacific PREMA-type basalts (H2O/Ce = 215 ± 30, δDSMOW = -45 ± 5 ‰) are similar to those in the north Atlantic (H2O/Ce = 220 ± 30; δDSMOW = -30 to -40 ‰). Basalts with EM-type signatures have regionally variable volatile compositions. North Atlantic EM-type basalts are wetter (H2O/Ce = 330 ± 30) and have isotopically heavier hydrogen (δDSMOW = -57 ± 5 ‰) than north Atlantic MORB. South Atlantic EM-type basalts are damp (H2O/Ce = 120 ± 10) with intermediate δDSMOW (-68 ± 2 ‰), similar to dDSMOW for Pacific MORB. North EPR EM-type basalts are dry (H2O/Ce = 110 ± 20) and isotopically light (δDSMOW = -94 ± 3 ‰). Boron and lithium isotopic ratios parallel the trends observed for dDSMOW. A multi-stage metasomatic and melting model accounts for the origin of the enriched components by extending the subduction factory concept down through the mantle transition zone, with slab temperature a key variable. The dehydration paradox is resolved by decoupling of volatiles from lithophile elements, reflecting primary dehydration of the slab followed by secondary rehydration and re-equilibration by fluids derived from subcrustal hydrous phases (e.g., antigorite) in cooler, deeper parts of the slab. The "expanded subduction factory" model includes melting at several key depths, including 1) 180 to 280 km, where EM-type mantle compositions are generated above slabs with average to hot thermal

Rapid measurement of plasma free fatty acid concentration and isotopic enrichment using LC/MS

Science.gov (United States)

Persson, Xuan-Mai T.; Błachnio-Zabielska, Agnieszka Urszula; Jensen, Michael D.

2010-01-01

Measurements of plasma free fatty acids (FFA) concentration and isotopic enrichment are commonly used to evaluate FFA metabolism. Until now, gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS) was the best method to measure isotopic enrichment in the methyl derivatives of 13C-labeled fatty acids. Although IRMS is excellent for analyzing enrichment, it requires time-consuming derivatization steps and is not optimal for measuring FFA concentrations. We developed a new, rapid, and reliable method for simultaneous quantification of 13C-labeled fatty acids in plasma using high-performance liquid chromatography-mass spectrometry (HPLC/MS). This method involves a very quick Dole extraction procedure and direct injection of the samples on the HPLC system. After chromatographic separation, the samples are directed to the mass spectrometer for electrospray ionization (ESI) and analysis in the negative mode using single ion monitoring. By employing equipment with two columns connected parallel to a mass spectrometer, we can double the throughput to the mass spectrometer, reducing the analysis time per sample to 5 min. Palmitate flux measured using this approach agreed well with the GC/C/IRMS method. This HPLC/MS method provides accurate and precise measures of FFA concentration and enrichment. PMID:20526002

Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition

International Nuclear Information System (INIS)

Zielinski, M.; Zielinska, A.; Papiernik-Zielinska, H.; McKenzie, J.A.; Bernasconi, S.; Paul, H.

1998-01-01

Carbon-13 and oxygen-18 isotope effects in the decarboxylation of nicotinic acid of natural isotopic composition above and below its melting temperature have been studied and compared with the primary (PKIE) and secondary kinetic isotope effects (SKIE) of 13 C and 18 O, respectively, in the decarboxylation of other heterocyclic acids. The temperature dependence of the secondary oxygen-18 isotope effects is negative in the total 221-255 deg C temperature interval investigated initially. The 13 C KIE measured above melting point of N.A. (temperature interval 235-270 deg C) are located in the range 1.007-1.009. Below melting point of nicotinic acid the 13 C KIE are larger and reveal the negative temperature dependence ( 13 C KIE decreases with decreasing the reaction temperature from 1.013/at 230 deg C to 1.0114/at 221 deg C). A discussion of the above isotopic results is presented. (author)

Boron-isotope fractionation in plants

Energy Technology Data Exchange (ETDEWEB)

Marentes, E [Univ. of Guelph, Dept. of Horticultural Science, Guelph, Ontario (Canada); Vanderpool, R A [USDA/ARS Grand Forks Human Nutrition Research Center, Grand Forks, North Dakota (United States); Shelp, B J [Univ. of Guelph, Dept. of Horticultural Science, Guelph, Ontario (Canada)

1997-10-15

Naturally-occurring variations in the abundance of stable isotopes of carbon, nitrogen, oxygen, and other elements in plants have been reported and are now used to understand various physiological processes in plants. Boron (B) isotopic variation in several plant species have been documented, but no determination as to whether plants fractionate the stable isotopes of boron, {sup 11}B and {sup 10}B, has been made. Here, we report that plants with differing B requirements (wheat, corn and broccoli) fractionated boron. The whole plant was enriched in {sup 11}B relative to the nutrient solution, and the leaves were enriched in {sup 10}B and the stem in {sup 11}B relative to the xylem sap. Although at present, a mechanistic role for boron in plants is uncertain, potential fractionating mechanisms are discussed. (author)

Boron-isotope fractionation in plants

International Nuclear Information System (INIS)

Marentes, E.; Vanderpool, R.A.; Shelp, B.J.

1997-01-01

Naturally-occurring variations in the abundance of stable isotopes of carbon, nitrogen, oxygen, and other elements in plants have been reported and are now used to understand various physiological processes in plants. Boron (B) isotopic variation in several plant species have been documented, but no determination as to whether plants fractionate the stable isotopes of boron, 11 B and 10 B, has been made. Here, we report that plants with differing B requirements (wheat, corn and broccoli) fractionated boron. The whole plant was enriched in 11 B relative to the nutrient solution, and the leaves were enriched in 10 B and the stem in 11 B relative to the xylem sap. Although at present, a mechanistic role for boron in plants is uncertain, potential fractionating mechanisms are discussed. (author)

Oxygen-enriched fermentation of sodium gluconate by Aspergillus niger and its impact on intracellular metabolic flux distributions.

Science.gov (United States)

Shen, Yuting; Tian, Xiwei; Zhao, Wei; Hang, Haifeng; Chu, Ju

2018-01-01

Different concentrations of oxygen-enriched air were utilized for sodium gluconate (SG) fermentation by Aspergillus niger. The fermentation time shortened from 20 to 15.5 h due to the increase of volumetric oxygen transfer coefficient (K L a) and the formation of more dispersed mycelia when inlet oxygen concentration ascended from 21 to 32%. According to metabolic flux analysis, during the growth phase, extracellular glucose for SG synthesis accounted for 79.0 and 85.3% with air and oxygen-enriched air (25%), respectively, whereas the proportions were 89.4 and 93.0% in the stationary phase. Intracellular glucose consumption decreased in oxygen-enriched fermentation, as cell respiration was more high-efficiently performed. Metabolic profiling indicated that most intermediates in TCA cycle and EMP pathway had smaller pool sizes in oxygen-enriched fermentations. Moreover, the main by-product of citric acid dramatically decreased from 1.36 to 0.34 g L -1 in oxygen-enriched fermentation. And the sodium gluconate yield increased from 0.856 to 0.903 mol mol -1 .

Role of stable isotope mass spectroscopy in hydrological sciences

International Nuclear Information System (INIS)

Keesari, Tirumalesh

2017-01-01

Isotope Ratio Mass Spectrometry (IRMS) is a specialized technique used to provide information about a given sample about its geographic, chemical, physical and biological origin. The ability to determine the source of water molecule stems from the relative isotopic abundances of its constituent elements, viz., hydrogen and oxygen or sometimes through its dissolved elements such as carbon, nitrogen and sulphur etc. Since the isotope ratios of carbon, hydrogen, oxygen, sulfur, and nitrogen can become locally enriched or depleted through a variety of kinetic and thermodynamic factors, measurement of the isotope ratios can be used to unravel the processes and differentiate water samples which otherwise exhibit similar chemical signatures. For brevity, this article focuses mainly on measurement of water isotopes, common notation for expressing isotope data and standards, theory of isotope hydrology, field applications and advances

Oxygen isotopic signature of CO2 from combustion processes

Directory of Open Access Journals (Sweden)

W. A. Brand

2011-02-01

Full Text Available For a comprehensive understanding of the global carbon cycle precise knowledge of all processes is necessary. Stable isotope (13C and 18O abundances provide information for the qualification and the quantification of the diverse source and sink processes. This study focuses on the δ18O signature of CO2 from combustion processes, which are widely present both naturally (wild fires, and human induced (fossil fuel combustion, biomass burning in the carbon cycle. All these combustion processes use atmospheric oxygen, of which the isotopic signature is assumed to be constant with time throughout the whole atmosphere. The combustion is generally presumed to take place at high temperatures, thus minimizing isotopic fractionation. Therefore it is generally supposed that the 18O signature of the produced CO2 is equal to that of the atmospheric oxygen. This study, however, reveals that the situation is much more complicated and that important fractionation effects do occur. From laboratory studies fractionation effects on the order of up to 26%permil; became obvious in the derived CO2 from combustion of different kinds of material, a clear differentiation of about 7‰ was also found in car exhausts which were sampled directly under ambient atmospheric conditions. We investigated a wide range of materials (both different raw materials and similar materials with different inherent 18O signature, sample geometries (e.g. texture and surface-volume ratios and combustion circumstances. We found that the main factor influencing the specific isotopic signatures of the combustion-derived CO2 and of the concomitantly released oxygen-containing side products, is the case-specific rate of combustion. This points firmly into the direction of (diffusive transport of oxygen to the reaction zone as the cause of the isotope fractionation. The original total 18O signature of the material appeared to have little influence, however, a contribution of specific bio

Oxygen isotope exchange with quartz during pyrolysis of silver sulfate and silver nitrate.

Science.gov (United States)

Schauer, Andrew J; Kunasek, Shelley A; Sofen, Eric D; Erbland, Joseph; Savarino, Joel; Johnson, Ben W; Amos, Helen M; Shaheen, Robina; Abaunza, Mariana; Jackson, Terri L; Thiemens, Mark H; Alexander, Becky

2012-09-30

Triple oxygen isotopes of sulfate and nitrate are useful metrics for the chemistry of their formation. Existing measurement methods, however, do not account for oxygen atom exchange with quartz during the thermal decomposition of sulfate. We present evidence for oxygen atom exchange, a simple modification to prevent exchange, and a correction for previous measurements. Silver sulfates and silver nitrates with excess (17)O were thermally decomposed in quartz and gold (for sulfate) and quartz and silver (for nitrate) sample containers to O(2) and byproducts in a modified Temperature Conversion/Elemental Analyzer (TC/EA). Helium carries O(2) through purification for isotope-ratio analysis of the three isotopes of oxygen in a Finnigan MAT253 isotope ratio mass spectrometer. The Δ(17)O results show clear oxygen atom exchange from non-zero (17)O-excess reference materials to zero (17)O-excess quartz cup sample containers. Quartz sample containers lower the Δ(17)O values of designer sulfate reference materials and USGS35 nitrate by 15% relative to gold or silver sample containers for quantities of 2-10 µmol O(2). Previous Δ(17)O measurements of sulfate that rely on pyrolysis in a quartz cup have been affected by oxygen exchange. These previous results can be corrected using a simple linear equation (Δ(17)O(gold) = Δ(17)O(quartz) * 1.14 + 0.06). Future pyrolysis of silver sulfate should be conducted in gold capsules or corrected to data obtained from gold capsules to avoid obtaining oxygen isotope exchange-affected data. Copyright © 2012 John Wiley & Sons, Ltd.

Biological fractionation of oxygen and carbon isotopes by recent benthic foraminifera

International Nuclear Information System (INIS)

Woodruff, F.; Douglas, R.G.

1980-01-01

Recent deep-sea benthic foraminifera from five East Pacific Rise box core tops have been analyzed for oxygen and carbon isotopic composition. The five equatorial stations, with water depths of between 3200 and 4600 m, yielded fourteen specific and generic taxonomic groups. Of the taxa analyzed, Uvigerina spp. most closely approaches oxygen isotopic equilibrium with ambient sea water. Pyrgo spp. was next closest to isotopic equilibrium, being on the average 0.59 per thousand depleted in 18 O relative to Uvigerina spp. Oridorsalis umbonatus also has relatively high delta 18 O values. Most other taxa were depleted in 18 O by large amounts. In no taxa was the carbon in the CaCO 3 secreted in carbon isotopic equilibrium with the dissolved HCO 3 - of ambient sea water. (Auth.)

Oxygen stable isotopes variation in water precipitation in Poland – anthropological applications

Directory of Open Access Journals (Sweden)

Lisowska-Gaczorek Aleksandra

2017-03-01

Full Text Available The main objective of oxygen isotope analysis is to determine the probable place of origin of an individual or the reconstruction of migration paths. The research are methodologically based on referencing oxygen isotope ratios of apatite phosphates (δ18Op to the range of environmental background δ18O, most frequently determined on the basis of precipitation.

The fractioning factor and the number of theorical plates in isotopic enrichment columns determined simultaneously

International Nuclear Information System (INIS)

Ducatti, Carlos

1997-01-01

Using an analytical approach and an analytical graphical method, it was determined simultaneously the fractioning factor and the number of theoretical plates in isotopic enrichment columns during the conditions of dinamical isotopic equilibrium. (author). 5 refs., 2 figs., 2 tabs

Stable-isotope composition of the water of apple juice

International Nuclear Information System (INIS)

Bricout, Jacques; Merlivat, Liliane

1973-01-01

By deuterium and oxygen 18 analysis, it was shown that apples' water is enriched in heavier isotopes as compared to rain water. The isotopic composition of the water of reconstituted apple juice is closed to the isotopic content of the rain water used for dilution. Thus, deuterium and oxyden 18 analysis allows a good analytical distinction between natural apple juice and reconstituted juices [fr

Characterization of oxygen dimer-enriched silicon detectors

CERN Document Server

Boisvert, V; Moll, M; Murin, L I; Pintilie, I

2005-01-01

Various types of silicon material and silicon p+n diodes have been treated to increase the concentration of the oxygen dimer (O2i) defect. This was done by exposing the bulk material and the diodes to 6 MeV electrons at a temperature of about 350 °C. FTIR spectroscopy has been performed on the processed material confirming the formation of oxygen dimer defects in Czochralski silicon pieces. We also show results from TSC characterization on processed diodes. Finally, we investigated the influence of the dimer enrichment process on the depletion voltage of silicon diodes and performed 24 GeV/c proton irradiations to study the evolution of the macroscopic diode characteristics as a function of fluence.

Interlaboratory determinations of isotopically enriched metals by field desorption mass spectroscopy

International Nuclear Information System (INIS)

Bahr, U.; Schulten, H.R.; Achenbach, C.; Ziskoven, R.

1982-01-01

The isotopic distribution of stable isotopes in six enriched metals (calcium, copper, barium, rubidium, strontium and thallium) has been determined by field desorption mass spectrometry. A first evaluation of the interlaboratory reproducibility of the application of this method for trace determination of metals was made using three different types of mass spectrometers in three different laboratories. The standard deviations for the most abundant isotopes of the metals investigated are between +-0.1 and +-0.5%. Within these standard deviations, the values obtained by the three mass spectrometry groups are the same. To support the accuracy of our quantification, thermal ionization mass spectrometry has been employed and confirms the results of the field desorption method. (orig.) [de

Determination of copper oxidizing power in superconducting yttrium ceramics

International Nuclear Information System (INIS)

Pontaler, R.P.; Lebed', N.B.

1989-01-01

A new photometric method for determining the formal copper degree of oxidation and oxygen deficiency in superconducting high-temperature oxides containing yttrium, barium and copper is developed. The method is based on oxidation of Co(2) complex with EDTA by Cu(3) ions in acetrate buffer solution with pH 4.2-4.7 and allows one to determine 1-10% of Cu(3). Relative standard deviation when determining Cu(3) makes up 0.03-0.05. Using a qualitative reaction with the application of sodium vanadate hydrochloride solution the absence of peroxide compound in superconducting yttrium ceramics is ascertained

The influence of annealing on yttrium oxide thin film deposited by reactive magnetron sputtering: Process and microstructure

Directory of Open Access Journals (Sweden)

Y. Mao

2017-01-01

Full Text Available Yttrium oxide thin films were prepared by reactive magnetron sputtering in different deposition condition with various oxygen flow rates. The annealing influence on the yttrium oxide film microstructure is investigated. The oxygen flow shows a hysteresis behavior on the deposition rate. With a low oxygen flow rate, the so called metallic mode process with a high deposition rate (up to 1.4µm/h was achieved, while with a high oxygen flow rate, the process was considered to be in the poisoned mode with an extremely low deposition rate (around 20nm/h. X-ray diffraction (XRD results show that the yttrium oxide films that were produced in the metallic mode represent a mixture of different crystal structures including the metastable monoclinic phase and the stable cubic phase, while the poisoned mode products show a dominating monoclinic phase. The thin films prepared in metallic mode have relatively dense structures with less porosity. Annealing at 600 °C for 15h, as a structure stabilizing process, caused a phase transformation that changes the metastable monoclinic phase to stable cubic phase for both poisoned mode and metallic mode. The composition of yttrium oxide thin films changed from nonstoichiometric to stoichiometric together with a lattice parameter variation during annealing process. For the metallic mode deposition however, cracks were formed due to the thermal expansion coefficient difference between thin film and the substrate material which was not seen in poisoned mode deposition. The yttrium oxide thin films that deposited in different modes give various application options as a nuclear material.

Fractionation of oxygen isotopes between mammalian bone-phosphate and environmental drinking water

International Nuclear Information System (INIS)

Luz, B.; Kolodny, V.; Horowitz, M.

1984-01-01

The delta 18 O of mammalian bone-phosphate varies linearly with delta 18 O of environmental water, but is not in isotopic equilibrium with that water. This situation is explained by a model of delta 18 O in body water in which the important fluxes of exchangeable oxygen through the body are taken into account. Fractionation of oxygen isotopes between body and environmental drinking water is dependent on the rates of drinking and respiration. Isotopic fractionation can be estimated from physiological data and the estimates correlate very well with observed fractionation. Species whose water consumption is large relative to its energy expenditure is sensitive to isotopic ratio changes in environmental water. (author)

A new high-quality set of singly (H-2) and doubly (H-2 and O-18) stable isotope labeled reference waters for biomedical and other isotope-labeled research

NARCIS (Netherlands)

Faghihi, V.; Verstappen-Dumoulin, B. M. A. A.; Jansen, H. G.; van Dijk, G.; Aerts-Bijma, A. T.; Kerstel, E. R. T.; Groening, M.; Meijer, H. A. J.

2015-01-01

RATIONALE: Research using water with enriched levels of the rare stable isotopes of hydrogen and/or oxygen requires well-characterized enriched reference waters. The International Atomic Energy Agency (IAEA) did have such reference waters available, but these are now exhausted. New reference waters

Expanding the isotopic toolbox: Applications of hydrogen and oxygen stable isotope ratios to food web studies

OpenAIRE

Hannah B Vander Zanden; David X Soto; Gabriel J Bowen; Keith A Hobson; Keith A Hobson

2016-01-01

The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H) and oxygen (δ18O) isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applicat...

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

OpenAIRE

Vander Zanden, Hannah B.; Soto, David X.; Bowen, Gabriel J.; Hobson, Keith A.

2016-01-01

The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotopes in tissues of organisms has formed the foundation of isotopic food web reconstructions, as these values directly reflect assimilated diet. In contrast, stable hydrogen (δ2H) and oxygen (δ18O) isotope measurements have typically been reserved for studies of migratory origin and paleoclimate reconstruction based on systematic relationships between organismal tissue and local environmental water. Recently, innovative applicatio...

Isotopic Generation and Confirmation of the PWR Application Model?

International Nuclear Information System (INIS)

L.B. Wimmer

2003-01-01

The objective of this calculation is to establish an isotopic database to represent commercial spent nuclear fuel (CSNF) from pressurized water reactors (PWRs) in criticality analyses performed for the proposed Monitored Geologic Repository at Yucca Mountain, Nevada. Confirmation of the conservatism with respect to criticality in the isotopic concentration values represented by this isotopic database is performed as described in Section 3.5.3.1.2 of the ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2000). The isotopic database consists of the set of 14 actinides and 15 fission products presented in Section 3.5.2.1.1 of YMP 2000 for use in CSNF burnup credit. This set of 29 isotopes is referred to as the principal isotopes. The oxygen isotope from the UO 2 fuel is also included in the database. The isotopic database covers enrichments of 235 U ranging from 1.5 to 5.5 weight percent (wt%) and burnups ranging from approximately zero to 75 GWd per metric ton of uranium (mtU). The choice of fuel assembly and operating history values used in generating the isotopic database are provided is Section 5. Tables of isotopic concentrations for the 29 principal isotopes (plus oxygen) as a function of enrichment and burnup are provided in Section 6.1. Results of the confirmation of the conservatism with respect to criticality in the isotopic concentration values are provided in Section 6.2

Production of yttrium

International Nuclear Information System (INIS)

Day, J.G.

1980-01-01

A process is described for the production of yttrium metal, or of an alloy comprising a major proportion of yttrium, in which calcium (metal) and yttrium fluoride are reacted together by use of a submerged electric arc in a molten slag. (author)

Paleoclimatic reconstruction in the Bolivian Andes from oxygen isotope analysis of lake sediment cellulose

International Nuclear Information System (INIS)

Wolfe, B.B.; Aravena, R.; Gibson, J.J.; Abbott, M.B.; Seltzer, G.O.

2002-01-01

Cellulose-inferred lake water δ 18 O (δ 18 O lw ) records from Lago Potosi, a seasonally-closed lake in a watershed that is not currently glaciated, and Lago Taypi Chaka Kkota, an overflowing lake in a glaciated watershed, provide the basis for late Pleistocene and Holocene paleoclimatic reconstruction in the Bolivian Andes. Deconvolution of the histories of changing evaporative isotopic enrichment from source water δ 18 O in the lake sediment records is constrained by comparison to the Sajama ice core oxygen isotope profile. At Lago Potosi, the δ 18 O lw record appears to be dominantly controlled by evaporative 18 O-enrichment, reflecting shifts in local effective moisture. Using an isotope-mass balance model, a preliminary quantitative reconstruction of summer relative humidity spanning the past 11,500 cal yr is derived from the Lago Potosi Π 18 O lw record. Results indicate that the late Pleistocene was moist with summer relative humidity values estimated at 10-20% greater than present. Increasing aridity developed in the early Holocene with maximum prolonged dryness spanning 7500 to 6000 cal yr BP at Lago Potosi, an interval characterized by summer relative humidity values that may have been 20% lower than present. Highly variable but dominantly arid conditions persist in the mid- to late Holocene, with average summer relative humidity values estimated at 15% below present, which then increase to about 10-20% greater than present by 2000 cal yr BP. Slightly more arid conditions characterize the last millennium with summer relative humidity values ranging from 5-10% lower than present. Similar long-term variations are evident in the Lago Taypi Chaka Kkota δ 18 O lw profile, except during the early Holocene when lake water evaporative 18 Oenrichment in response to low relative humidity appears to have been offset by enhanced inflow from 18 O-depleted snowmelt or groundwater from the large catchment. Close correspondence occurs between the isotope

Applications of stable Isotope ratios determinations in fruit juice authentication

International Nuclear Information System (INIS)

Magdas, Dana Alina; Dehelean, Adriana; Voica, Cezara; Puscas, Romulus

2010-01-01

Full text: Adulteration of a product consists in making it impure by fraudulent addition of a foreign or inferior substance. The result is either an alteration of the product and of its quality or a falsification. The falsification is a voluntary act with the intention of abuse. The falsification may be more or less sophisticated and its sophistication as well as its costs increases with the improvement of analytical methods. Vacuum concentration with aroma does not affect the chemical composition of fruit juices and therefore the determination of deuterium (D) and oxygen-18 content in waters is the most confident procedure for differentiating between a natural single strength juice and a juice rediluted from a concentrate. This technique is based on the fact that when absorbed by a plant, the rainwater or the irrigation water is fractionated by evapotranspiration, and enriched in the heavy isotopes (deuterium and oxygen-18) with respect to the light isotope (hydrogen and oxygen-16, respectively). It is known that climatic conditions affect the isotope content of rain waters and therefore that of fruit juices waters: the warmer climate, the higher the deuterium and oxygen-18 contents in water. Rainwater and tap water have nearly the same isotopic content and the water of fruit juices derived from concentrate by dilution with tap water has an isotopic content close to that of tap water. This makes it easy to distinguish diluted concentrates from the isotopically more enriched water of authentic single strength juice. In this study, single strength juice, in Romanian fruits, were investigated by mean of stable isotope measurements (oxygen, hydrogen and carbon) in order to offer a discussion basis for the authenticity of some fruit juices currently available on Romanian market. (authors)

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.

Origin of photosynthetic oxygen

International Nuclear Information System (INIS)

Gerster, Richard; Dupuy, Jacques; Guerin de Montgareuil, Pierre

From the comparison of isotopic exchange kinetics between C 18 O 2 and the water of algae suspensions or aerial leaves subjected to alternating darkness and light, it becomes possible to calculate the isotopic abundance of the CO 2 involved in the photochemical process; this value has been compared to those of the intracellular water and of the evolved O 2 . Kinetics of the appearance of 18 O in the oxygen produced by algae suspended in enriched water are also presented [fr

Oxygen Isotope Records in Modern Oyster Shells from Chi Ku, Tainan and Their Implication of Seasonality

Science.gov (United States)

Chen, Y. C.; Mii, H. S.; Li, K. T.

2015-12-01

To exam whether oxygen isotope records of Crassostrea gigasoysters can be used as proxies of environment, 133 cultivated oysters and 21 water samples were collected from Chi Ku area, Tainan City, southern Taiwan in December of 2012, and from March, 2013 to July, 2014. Instrumental air and water temperatures and precipitation records were obtained from a nearest Central Weather Bureau (CWB) station roughly 16 km north of Chi Ku. The oxygen and carbon isotope values of the ligamental area of the modern oyster shells are from -6.92‰ to -0.08‰ (-3.05 ± 1.17‰, N = 2280; 1σ; VPDB) and from -5.57‰ to 0.63‰ (-1.88 ± 0.81‰), respectively. Oxygen isotope values of the water samples are mainly between -0.28‰ and 0.74‰ (0.18 ± 0.29‰, N = 20; 1σ; VSMOW). However, water oxygen isotope value of -2.75‰ was observed for the water sample collected immediately after a typhoon heavy rainfall. Seasonal temperature fluctuation pattern of estimated oxygen isotope temperatures from modern shells is similar to that of CWB instrumental records. However, the oxygen isotope temperatures are respectively about 3 °C and 10°C higher than those of instrumental records for winter and summer. Higher estimated oxygen isotope temperatures are most likely caused by underestimated fraction of freshwater. We analyzed 5 archaeological oyster shells of Siraya culture (500~250B.P.) collected from Wu Chien Tuso North (WCTN) archaeological site of Tainan branch of Southern Taiwan Science Park to infer the harvest season of mollusks. Oxygen isotope values of the ligamental area of the archaeological oyster shells are between -5.98‰ and -1.26‰ (-3.34 ± 1.37‰, N = 60; 1σ), and carbon isotope values are between -3.21‰ and 0.60‰ (-2.04‰ ± 0.55‰). The oxygen isotope records of archaeological oyster shells also showed clear seasonality. Most of the oysters were collected in autumn and winter. Oxygen isotope values of archaeological oyster shells was 1‰ greater than that

[Research advances in identifying nitrate pollution sources of water environment by using nitrogen and oxygen stable isotopes].

Science.gov (United States)

Mao, Wei; Liang, Zhi-wei; Li, Wei; Zhu, Yao; Yanng, Mu-yi; Jia, Chao-jie

2013-04-01

Water body' s nitrate pollution has become a common and severe environmental problem. In order to ensure human health and water environment benign evolution, it is of great importance to effectively identify the nitrate pollution sources of water body. Because of the discrepant composition of nitrogen and oxygen stable isotopes in different sources of nitrate in water body, nitrogen and oxygen stable isotopes can be used to identify the nitrate pollution sources of water environment. This paper introduced the fractionation factors of nitrogen and oxygen stable isotopes in the main processes of nitrogen cycling and the composition of these stable isotopes in main nitrate sources, compared the advantages and disadvantages of five pre-treatment methods for analyzing the nitrogen and oxygen isotopes in nitrate, and summarized the research advances in this aspect into three stages, i. e. , using nitrogen stable isotope alone, using nitrogen and oxygen stable isotopes simultaneously, and combining with mathematical models. The future research directions regarding the nitrate pollution sources identification of water environment were also discussed.

Textural properties of chars as determined by petrographic analysis: comparison between air-blown, oxygen-blown and oxygen-enriched gasification

CSIR Research Space (South Africa)

Oboirien, BO

2012-11-01

Full Text Available In this study, the textural properties of chars generated from a vitrinite, high ash coal in a fluidised bed gasifier under air-blown, oxygen-blown and oxygen-enriched conditions were determined by detailed petrographic analysis. The char samples...

Examinations of the process of hard coal and biomass blend combustion in OEA (oxygen enriched atmosphere)

International Nuclear Information System (INIS)

Pawlak-Kruczek, Halina; Ostrycharczyk, Michał; Czerep, Michał; Baranowski, Marcin; Zgóra, Jacek

2015-01-01

The benefits of oxygen enrichment have been demonstrated in a variety of industrial combustion applications, but to date no implementation of oxygen enrichment in boilers has been reported, primarily due to their already high thermal efficiencies and a very large scale of such systems, which require significant amounts of oxygen. But recently, oxygen combustion in boilers has become one of the CCS technologies which can be an effective tool for reducing greenhouse gases emissions, and oxygen enriched combustion is suitable for low-calorific fuels, including biomass. This paper analyses the use of oxygen enrichment in a furnace for co-firing of different kinds of biomass with hard coal in terms of emission and burnout impact (LOI). As a part of this research, the effect of injection oxygen mode and total oxygen concentration on the flue gas emission (SO_2, NO_x) and burnout from co-firing of straw and wooden biomass in different proportions (20% and 40%) with hard coal were studied. The co-firing tests were carried out in an isothermal flow reactor. One of the benefits from the OEA (oxygen enriched atmosphere) technology is more effective separation of CO_2 owing to the higher CO_2 concentration in the flue gas. The additional advantage of the OEA combustion technology in comparison with oxy-fuel combustion is that the OEA process needs lower O_2 purities and therefore it is cost-effective. Experimental tests on co-firing of 20% straw-hard coal blend were conducted in oxygen enriched (up to 25 and 30%) atmospheres with three variants of O_2 injection modes. NO_x, SO_2 emissions and burnout for the various atmospheres in the combustion chamber were studied. Moreover, co-firing tests were performed with 40% share of wooden biomass to examine the effect of the biomass share and a type on emission of NO_x and SO_2 in OEA. The two O_2 injection modes were investigated. In each case, the emission of SO_2 increases alongside an increase of oxygen concentration in

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

Nitrogen and Oxygen Isotopic Studies of the Marine Nitrogen Cycle.

Science.gov (United States)

Casciotti, Karen L

2016-01-01

The marine nitrogen cycle is a complex web of microbially mediated reactions that control the inventory, distribution, and speciation of nitrogen in the marine environment. Because nitrogen is a major nutrient that is required by all life, its availability can control biological productivity and ecosystem structure in both surface and deep-ocean communities. Stable isotopes of nitrogen and oxygen in nitrate and nitrite have provided new insights into the rates and distributions of marine nitrogen cycle processes, especially when analyzed in combination with numerical simulations of ocean circulation and biogeochemistry. This review highlights the insights gained from dual-isotope studies applied at regional to global scales and their incorporation into oceanic biogeochemical models. These studies represent significant new advances in the use of isotopic measurements to understand the modern nitrogen cycle, with implications for the study of past ocean productivity, oxygenation, and nutrient status.

Magnetic and micellar effects on photoreactions. 1. 13C isotopic enrichment of dibenzyl ketone via photolysis in aqueous detergent solution

International Nuclear Information System (INIS)

Turro, N.J.; Chow, M.F.; Chung, C.J.; Kraeutler, B.

1981-01-01

The photolysis of dibenzyl ketone (DBK) in homogeneous organic solutions and in micelle-containing detergent solutions has been investigated from the standpoint of determining the extent and location of 13 C enrichment that occurs. In a series of experiments it is established that for incomplete conversions the residual, recovered DBK is enriched in 13 C relative to the initial unphotolyzed DBK. The efficiency of the 13 C/ 12 C separation is shown to be characterized by an isotope enrichment parameter, α, which is independent of the extent of conversion. A combination of mass spectrometry and nuclear magnetic resonance spectroscopy provides support for the primary location of the 13 C enrichment at C-1 (the carbonyl carbon) with a lesser but significant enrichment at C-2 (the methylene carbon). A very small but experimentally distinct enrichment of the aromatic rings is indicated by 13 C NMR analysis. An isomer of DBK, 1-phenyl-4'-methylacetophenone (PMAP) is formed as a minor product of photolysis in micellar solutions. PMAP, like the recovered, residual DBK, is found to be substantially enriched in 13 C relative to the starting DBK. The magnitude of α is found to be significantly influenced by the application of laboratory magnetic fields to the photolysis sample. The latter result, along with the unusually large magnitude of α, suggests that the mechanism involved in isotopic enrichment is not dominated by kinetic mass isotope effects but rather by nuclear magnetic moment and/or magnetic spin isotope effects

Application of carbon and oxygen stable isotopes to the study of Brazilian precambrian

International Nuclear Information System (INIS)

Torquato, J.R.F.

1980-01-01

Samples of carbonated rocks of precambrian age are studied. The stable carbon and oxygen isotopes are applied to the study of terrestrial materials considering the variations of some element isotopic composition in function of the environment of sedimentation. The isotopic analysis was done using mass spectrometers. The analytical results and the description of region geology of the site of each sample are presented. The isotopic data are interpreted aiming to the environment of sedimentation. New techniques for better improvement of carbon and oxygen ratios, are proposed, such as: to use the analysis of surface trend and the isotopic logging in mapping of surface and subsurface. A new method for approximated determination of the ages of precambrian carbonated rocks, considering the limitations of their new technique, is also presented. (M.C.K.) [pt

An isotopic analysis system for plutonium samples enriched in 238Pu

International Nuclear Information System (INIS)

Ruhter, W.D.; Camp, D.C.

1991-08-01

We have designed and built a gamma-ray spectrometer system that measures the relative plutonium isotopic abundances of plutonium oxide enriched in 238 Pu. The first system installed at Westinghouse Savannah River Company was tested and evaluated on plutonium oxide in stainless steel EP60/61 containers. 238 Pu 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

Isotope enrichment by electron spin resonance transitions of the intermediate radical pair

International Nuclear Information System (INIS)

Okazaki, M.; Shiga, T.; Sakata, S.; Konaka, R.; Toriyama, K.

1988-01-01

Microwave effects on the spin adduct yield were observed in the photoreduction of menadione in micellar solutions with ordinary sodium dodecyl sulfate (SDS), deuterium-labeled SDS, and a mixture of them. A large isotope effect was found in the microwave modulation of the spin adduct yield, which is due to the ESR transitions of the transient radical pair in the reaction. It is demonstrated for the first time that the microwave field can be used to enrich one of the isotopes which coexist in the system

Experimental study on isotope fractionation of evaporating water of different initial isotopic composition

International Nuclear Information System (INIS)

Pooja Devi; Jain, A.K.; Rao, M.S.; Kumar, B.

2014-01-01

The studies of evaporative isotopic fractionation in controlled conditions are of particular importance for understanding the mechanism of evaporation fractionation in natural conditions. We present the measurements of the average isotopic fractionation factors during the evaporation of water having different initial isotopic compositions at constant temperature. The results show that the isotopic composition of residual water become more enriched over the time and the initial isotopic composition of evaporating water has considerable effect on the average isotopic fractionation factors. The average isotopic fractionation factors in evaporation of Water A and Water B under the present experimental conditions were found to be 0.9817 ± 0.0044 and 0.9887 ± 0.0031 for oxygen and 0.9178 ± 0.0182 and 0.9437 ± 0.0169 for hydrogen, respectively. The findings of this work should lead to a better understanding and use of stable isotope techniques in isotope hydrology by using a simple technique of evaporation pan. (author)

Use of minor uranium isotope measurements as an aid in safeguarding a uranium enrichment cascade

International Nuclear Information System (INIS)

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

1979-01-01

Surveillance and containment, which are indispensable supporting measures for material accountability, do not provide those charged with safeguarding an installation with the assurance beyond the shadow of a doubt that all the input and output uranium will in fact be measured. Those who are concerned with developing non-intrusive techniques for safeguarding uranium enrichment plants under the Nuclear Non-Proliferation Treaty have perceived the possibility that data on the minor uranium isotope concentrations in an enrichment cascade withdrawal and feed streams may provide a means either to corroborate or to contradict the material accountability results. A basic theoretical study has been conducted to determine whether complete isotopic measurements on enrichment cascade streams may be useful for safeguards purposes. The results of the calculations made to determine the behaviour of the minor uranium isotopes ( 234 U and 236 U) in separation cascades, and the results of three plant tests made to substantiate the validity of the calculations, are reviewed briefly. Based on the fact that the 234 U and 236 U concentrations relative to that of 235 U in cascade withdrawal streams reflect the cascade flow-sheet, the authors conclude that the use of the minor isotope concentration measurements (MIST) in cascade withdrawal streams is a potentially valuable adjunct to material accounting for safeguarding a 235 U enrichment cascade. A characteristic of MIST, which qualifies it particularly for safeguards application under the NPT, is the fact that its use is entirely non-intrusive with regard to process technology and proprietary information. The usefulness of MIST and how it may be applied are discussed briefly. (author)

Radiogenic isotopes in enriched mid-ocean ridge basalts from Explorer Ridge, northeast Pacific Ocean

Science.gov (United States)

Cousens, Brian; Weis, Dominique; Constantin, Marc; Scott, Steve

2017-09-01

Extreme gradients in topography related to variations in magma supply are observed on the Southern Explorer Ridge (SER), part of the northern Juan de Fuca ridge system. We report radiogenic isotope (Pb, Sr, Nd, Hf) and geochemical data for twenty-four basalt whole-rock and glass samples collected from the length of the SER and from Explorer Deep, a rift to the north of the SER. Lavas from the SER form a north-south geochemical gradient, dominated by E-MORB at the northern axial high, and range from T-MORB to N-MORB towards the southern deepest part of the ridge. Linear relationships between incompatible element ratios and isotopic ratios in MORB along the ridge are consistent with mixing of magmas beneath the ridge to generate the geographic gradient from E- to N-MORB. The E-MORB have high Sr and Pb, and low Nd and Hf isotopic ratios, typical of enriched mantle that includes a FOZO or HIMU isotopic component. The West Valley and Endeavour segments of the northern Juan de Fuca ridge also include this isotopic component, but the proportion of the FOZO or HIMU component is more extreme in the SER basalts. The FOZO or HIMU component may be garnet-bearing peridotite, or a garnet pyroxenite embedded in peridotite. Recycled garnet pyroxenite better explains the very shallow SER axial high, high Nb/La and La/Sm, and the ;enriched; isotopic compositions.

Study on Characteristics of Co-firing Ammonia/Methane Fuels under Oxygen Enriched Combustion Conditions

Science.gov (United States)

Xiao, Hua; Wang, Zhaolin; Valera-Medina, Agustin; Bowen, Philip J.

2018-06-01

Having a background of utilising ammonia as an alternative fuel for power generation, exploring the feasibility of co-firing ammonia with methane is proposed to use ammonia to substitute conventional natural gas. However, improvement of the combustion of such fuels can be achieved using conditions that enable an increase of oxygenation, thus fomenting the combustion process of a slower reactive molecule as ammonia. Therefore, the present study looks at oxygen enriched combustion technologies, a proposed concept to improve the performance of ammonia/methane combustion. To investigate the characteristics of ammonia/methane combustion under oxygen enriched conditions, adiabatic burning velocity and burner stabilized laminar flame emissions were studied. Simulation results show that the oxygen enriched method can help to significantly enhance the propagation of ammonia/methane combustion without changing the emission level, which would be quite promising for the design of systems using this fuel for practical applications. Furthermore, to produce low computational-cost flame chemistry for detailed numerical analyses for future combustion studies, three reduced combustion mechanisms of the well-known Konnov's mechanism were compared in ammonia/methane flame simulations under practical gas turbine combustor conditions. Results show that the reduced reaction mechanisms can provide good results for further analyses of oxygen enriched combustion of ammonia/methane. The results obtained in this study also allow gas turbine designers and modellers to choose the most suitable mechanism for further combustion studies and development.

Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.

Science.gov (United States)

Loader, N J; Street-Perrott, F A; Daley, T J; Hughes, P D M; Kimak, A; Levanič, T; Mallon, G; Mauquoy, D; Robertson, I; Roland, T P; van Bellen, S; Ziehmer, M M; Leuenberger, M

2015-01-06

A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (δ(13)C, δ(18)O, δ(2)H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (δ(13)C 0.15‰, δ(18)O 0.30‰, δ(2)H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited.

Stable isotopes of authigenic minerals in variably-saturated fractured tuff

International Nuclear Information System (INIS)

Weber, D.S.; Evans, D.D.

1988-11-01

Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ( 18 O/ 16 O) and carbon ( 13 C/ 12 C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs

Stable isotopes of authigenic minerals in variably-saturated fractured tuff

Energy Technology Data Exchange (ETDEWEB)

Weber, D.S.; Evans, D.D.

1988-11-01

Identifying stable isotope variation and mineralogical changes in fractured rock may help establish the history of climatic and geomorphological processes that might affect the isolation properties of a waste repository site. This study examines the use of the stable isotope ratios of oxygen ({sup 18}O/{sup 16}O) and carbon ({sup 13}C/{sup 12}C) in authigenic minerals as hydrogeochemical tools tracing low-temperature rock-water interaction in variably-saturated fractured stuff. Isotopic compositions of fracture-filling and rock matrix minerals in the Apache Leap tuff, near Superior, Arizona were concordant with geothermal temperatures and in equilibrium with water isotopically similar to present-day meteoric water and groundwater. Oxygen and carbon isotope ratios of fracture-filling, in unsaturated fractured tuff, displayed an isotopic gradient believed to result from near-surface isotopic enrichment due to evaporation rather than the effects of rock-water interaction. Oxygen isotope ratios of rock matrix opal samples exhibited an isotopic gradient believed to result from, leaching and reprecipitation of silica at depth. Methods and results can be used to further define primary flowpaths and the movement of water in variably-saturated fractured rock. 71 refs., 23 figs., 3 tabs.

Organic photochemical reactions on solid surfaces: Enrichment and separation of isotopes. Final report. SBIR-1988, Phase 2

International Nuclear Information System (INIS)

Ruderman, W.; Fehlner, J.; Spencer, J.

1988-01-01

The objectives of the Phase II program were to: (1) investigate organic photochemical reactions on solid porous silica surfaces, (2) utilize the magnetic isotope effect to develop a (13)C enrichment process using a fluidized bed reactor, and (3) investigate the possibility of enrichment of heavier isotopes having a nuclear spin. Although researchers were able to demonstrate a continuous fluidized bed (13)C enrichment process, analysis showed that the process could not compete with low temperature distillation of CO because of the high cost of the starting material, dibenzylketone (DBK), and the difficulty of converting the photochemical decomposition products back to DBK. However, the process shows promise for the separation of heavier isotopes such as (29)Si. The photochemical studies led to the discovery that the selectivity for terminal chlorination of alkanes can be increased more than 25 fold by sorbing the alkanes on ZSM-5 zeolites in a fluidized bed. The selectivity is ascribed to the presence of interfaces within the crystals

Defining a stable water isotope framework for isotope hydrology application in a large trans-boundary watershed (Russian Federation/Ukraine).

Science.gov (United States)

Vystavna, Yuliya; Diadin, Dmytro; Huneau, Frédéric

2018-05-01

Stable isotopes of hydrogen ( 2 H) and oxygen ( 18 O) of the water molecule were used to assess the relationship between precipitation, surface water and groundwater in a large Russia/Ukraine trans-boundary river basin. Precipitation was sampled from November 2013 to February 2015, and surface water and groundwater were sampled during high and low flow in 2014. A local meteoric water line was defined for the Ukrainian part of the basin. The isotopic seasonality in precipitation was evident with depletion in heavy isotopes in November-March and an enrichment in April-October, indicating continental and temperature effects. Surface water was enriched in stable water isotopes from upstream to downstream sites due to progressive evaporation. Stable water isotopes in groundwater indicated that recharge occurs mainly during winter and spring. A one-year data set is probably not sufficient to report the seasonality of groundwater recharge, but this survey can be used to identify the stable water isotopes framework in a weakly gauged basin for further hydrological and geochemical studies.

Growth of the European abalone ( Haliotis tuberculata L.) in situ: Seasonality and ageing using stable oxygen isotopes

Science.gov (United States)

Roussel, Sabine; Huchette, Sylvain; Clavier, Jacques; Chauvaud, Laurent

2011-02-01

The ormer, Haliotis tuberculata is the only European abalone species commercially exploited. The determination of growth and age in the wild is an important tool for fisheries and aquaculture management. However, the ageing technique used in the past in the field is unreliable. The stable oxygen isotope composition ( 18O/ 16O) of the shell depends on the temperature and oxygen isotope composition of the ambient sea water. The stable oxygen isotope technique, developed to study paleoclimatological changes in shellfish, was applied to three H. tuberculata specimens collected in north-west Brittany. For the specimens collected, the oxygen isotope ratios of the shell reflected the seasonal cycle in the temperature. From winter-to-winter cycles, estimates of the age and the annual growth increment, ranging from 13 to 55 mm per year were obtained. This study shows that stable oxygen isotopes can be a reliable tool for ageing and growth studies of this abalone species in the wild, and for validating other estimates.

Positional enrichment by proton analysis (PEPA). A one-dimensional "1H-NMR approach for "1"3C stable isotope tracer studies in metabolomics

International Nuclear Information System (INIS)

Vinaixa, Maria; Yanes, Oscar; Rodriguez, Miguel A.; Capellades, Jordi; Aivio, Suvi; Stracker, Travis H.; Gomez, Josep; Canyellas, Nicolau

2017-01-01

A novel metabolomics approach for NMR-based stable isotope tracer studies called PEPA is presented, and its performance validated using human cancer cells. PEPA detects the position of carbon label in isotopically enriched metabolites and quantifies fractional enrichment by indirect determination of "1"3C-satellite peaks using 1D-"1H-NMR spectra. In comparison with "1"3C-NMR, TOCSY and HSQC, PEPA improves sensitivity, accelerates the elucidation of "1"3C positions in labeled metabolites and the quantification of the percentage of stable isotope enrichment. Altogether, PEPA provides a novel framework for extending the high-throughput of "1H-NMR metabolic profiling to stable isotope tracing in metabolomics, facilitating and complementing the information derived from 2D-NMR experiments and expanding the range of isotopically enriched metabolites detected in cellular extracts. (copyright 2017 The Authors. Published by Wiley-VCH Verlag GmbH and Co. KGaA.)

Oxygen isotope exchange in La2NiO(4±δ).

Science.gov (United States)

Ananyev, M V; Tropin, E S; Eremin, V A; Farlenkov, A S; Smirnov, A S; Kolchugin, A A; Porotnikova, N M; Khodimchuk, A V; Berenov, A V; Kurumchin, E Kh

2016-04-07

Oxygen surface exchange kinetics and diffusion have been studied by the isotope exchange method with gas phase equilibration using a static circulation experimental rig in the temperature range of 600-800 °C and oxygen pressure range of 0.13-2.5 kPa. A novel model which takes into account distributions of the dissociative adsorption and incorporation rates has been developed. The rates of the elementary stages have been calculated. The rate-determining stages for a La2NiO(4±δ) polycrystalline specimen have been discussed. The diffusion activation energies calculated using the gas phase equilibration method (1.4 eV) differ significantly from those calculated using isotope exchange depth profiling (0.5-0.8 eV), which was attributed to the influence of different oxygen diffusion pathways.

Studies of MHD generator performance with oxygen enriched coal combustion

Science.gov (United States)

Wormhoudt, J.; Yousefian, V.; Kolb, C. E.; Martinez-Sanchez, M.

1980-07-01

This paper presents calculations made using the Aerodyne PACKAGE (Plasma Analysis, Chemical Kinetics, and Generator Efficiency) computer code which bear on two questions which arise in connection with choices between oxygen enrichment and air preheating to attain the high combustion temperatures needed for open-cycle, coal-fired MHD power generation. The first question is which method produces the highest enthalpy extraction per unit channel length. The second is, in test facilities intended to study tradeoffs between oxygen enrichment and preheated air, can good generator performance be obtained from the same physical channel for different combustor compositions. The answer to the first question is found to depend on what combustor conditions are taken to be comparable. As for the second question, it is found that operation with channel input from off-design combustor conditions can cause serious problems, which can be partially alleviated by changing the channel load factors.

Coprecipitation of yttrium and aluminium hydroxide for preparation of yttrium aluminium garnet

NARCIS (Netherlands)

Vrolijk, J.W.G.A.; Willems, J.W.M.M.; Metselaar, R.

1990-01-01

Coprecipitation of yttrium and aluminium hydroxide for the preparation of pure yttrium aluminium garnet (YAG) powder with small grain size is the subject of this study. Starting materials are sulphates and chlorides of yttrium and aluminium. To obtain pure YAG (Y3Al5O12), the pH during flocculation

A 1000-year record of dry conditions in the eastern Canadian prairies reconstructed from oxygen and carbon isotope measurements on Lake Winnipeg sediment organics

Science.gov (United States)

Buhay, W.M.; Simpson, S.; Thorleifson, H.; Lewis, M.; King, J.; Telka, A.; Wilkinson, Philip M.; Babb, J.; Timsic, S.; Bailey, D.

2009-01-01

A short sediment core (162 cm), covering the period AD 920-1999, was sampled from the south basin of Lake Winnipeg for a suite of multi-proxy analyses leading towards a detailed characterisation of the recent millennial lake environment and hydroclimate of southern Manitoba, Canada. Information on the frequency and duration of major dry periods in southern Manitoba, in light of the changes that are likely to occur as a result of an increasingly warming atmosphere, is of specific interest in this study. Intervals of relatively enriched lake sediment cellulose oxygen isotope values (??18Ocellulose) were found to occur from AD 1180 to 1230 (error range: AD 1104-1231 to 1160-1280), 1610-1640 (error range: AD 1571-1634 to 1603-1662), 1670-1720 (error range: AD 1643-1697 to 1692-1738) and 1750-1780 (error range: AD 1724-1766 to 1756-1794). Regional water balance, inferred from calculated Lake Winnipeg water oxygen isotope values (??18Oinf-lw), suggest that the ratio of lake evaporation to catchment input may have been 25-40% higher during these isotopically distinct periods. Associated with the enriched d??18Ocellulose intervals are some depleted carbon isotope values associated with more abundantly preserved sediment organic matter (d??13COM). These suggest reduced microbial oxidation of terrestrially derived organic matter and/or subdued lake productivity during periods of minimised input of nutrients from the catchment area. With reference to other corroborating evidence, it is suggested that the AD 1180-1230, 1610-1640, 1670-1720 and 1750-1780 intervals represent four distinctly drier periods (droughts) in southern Manitoba, Canada. Additionally, lower-magnitude and duration dry periods may have also occurred from 1320 to 1340 (error range: AD 1257-1363), 1530-1540 (error range: AD 1490-1565 to 1498-1572) and 1570-1580 (error range: AD 1531-1599 to 1539-1606). ?? 2009 John Wiley & Sons, Ltd.

Effectiveness of oxygen enriched hydrogen-HHO gas addition on DI diesel engine performance, emission and combustion characteristics

Directory of Open Access Journals (Sweden)

Premkartikkumar S.R.

2014-01-01

Full Text Available Nowadays, more researches focus on protecting the environment. Present investigation concern with the effectiveness of Oxygen Enriched hydrogen- HHO gas addition on performance, emission and combustion characteristics of a DI diesel engine. Here the Oxygen Enriched hydrogen-HHO gas was produced by the process of water electrolysis. When potential difference is applied across the anode and cathode electrodes of the electrolyzer, water is transmuted into Oxygen Enriched hydrogen-HHO gas. The produced gas was aspirated into the cylinder along with intake air at the flow rates of 1 lpm and 3.3 lpm. The results show that when Oxygen Enriched hydrogen-HHO gas was inducted, the brake thermal efficiency of the engine increased by 11.06%, Carbon monoxide decreased by 15.38%, Unburned hydrocarbon decreased by 18.18%, Carbon dioxide increased by 6.06%, however, the NOX emission increased by 11.19%.

Uranium-isotope enrichment: application bounds of the separative power and separation work concepts

Energy Technology Data Exchange (ETDEWEB)

Novelli, P.

1981-05-01

The aim of this paper is a critical re-examination of the concepts of separative power, separation work and value function in order to understand if their extension to the new enrichment processes such as Laser Isotope Separation is possible.

Quantification of Stable Isotope Traces Close to Natural Enrichment in Human Plasma Metabolites Using Gas Chromatography-Mass Spectrometry.

Science.gov (United States)

Krämer, Lisa; Jäger, Christian; Trezzi, Jean-Pierre; Jacobs, Doris M; Hiller, Karsten

2018-02-14

Currently, changes in metabolic fluxes following consumption of stable isotope-enriched foods are usually limited to the analysis of postprandial kinetics of glucose. Kinetic information on a larger diversity of metabolites is often lacking, mainly due to the marginal percentage of fully isotopically enriched plant material in the administered food product, and hence, an even weaker 13 C enrichment in downstream plasma metabolites. Therefore, we developed an analytical workflow to determine weak 13 C enrichments of diverse plasma metabolites with conventional gas chromatography-mass spectrometry (GC-MS). The limit of quantification was increased by optimizing (1) the metabolite extraction from plasma, (2) the GC-MS measurement, and (3) most importantly, the computational data processing. We applied our workflow to study the catabolic dynamics of 13 C-enriched wheat bread in three human subjects. For that purpose, we collected time-resolved human plasma samples at 16 timepoints after the consumption of 13 C-labeled bread and quantified 13 C enrichment of 12 metabolites (glucose, lactate, alanine, glycine, serine, citrate, glutamate, glutamine, valine, isoleucine, tyrosine, and threonine). Based on isotopomer specific analysis, we were able to distinguish catabolic profiles of starch and protein hydrolysis. More generally, our study highlights that conventional GC-MS equipment is sufficient to detect isotope traces below 1% if an appropriate data processing is integrated.

Quantification of Stable Isotope Traces Close to Natural Enrichment in Human Plasma Metabolites Using Gas Chromatography-Mass Spectrometry

Science.gov (United States)

Krämer, Lisa; Jäger, Christian; Jacobs, Doris M.; Hiller, Karsten

2018-01-01

Currently, changes in metabolic fluxes following consumption of stable isotope-enriched foods are usually limited to the analysis of postprandial kinetics of glucose. Kinetic information on a larger diversity of metabolites is often lacking, mainly due to the marginal percentage of fully isotopically enriched plant material in the administered food product, and hence, an even weaker 13C enrichment in downstream plasma metabolites. Therefore, we developed an analytical workflow to determine weak 13C enrichments of diverse plasma metabolites with conventional gas chromatography-mass spectrometry (GC-MS). The limit of quantification was increased by optimizing (1) the metabolite extraction from plasma, (2) the GC-MS measurement, and (3) most importantly, the computational data processing. We applied our workflow to study the catabolic dynamics of 13C-enriched wheat bread in three human subjects. For that purpose, we collected time-resolved human plasma samples at 16 timepoints after the consumption of 13C-labeled bread and quantified 13C enrichment of 12 metabolites (glucose, lactate, alanine, glycine, serine, citrate, glutamate, glutamine, valine, isoleucine, tyrosine, and threonine). Based on isotopomer specific analysis, we were able to distinguish catabolic profiles of starch and protein hydrolysis. More generally, our study highlights that conventional GC-MS equipment is sufficient to detect isotope traces below 1% if an appropriate data processing is integrated. PMID:29443915

Quantification of Stable Isotope Traces Close to Natural Enrichment in Human Plasma Metabolites Using Gas Chromatography-Mass Spectrometry

Directory of Open Access Journals (Sweden)

Lisa Krämer

2018-02-01

Full Text Available Currently, changes in metabolic fluxes following consumption of stable isotope-enriched foods are usually limited to the analysis of postprandial kinetics of glucose. Kinetic information on a larger diversity of metabolites is often lacking, mainly due to the marginal percentage of fully isotopically enriched plant material in the administered food product, and hence, an even weaker 13C enrichment in downstream plasma metabolites. Therefore, we developed an analytical workflow to determine weak 13C enrichments of diverse plasma metabolites with conventional gas chromatography-mass spectrometry (GC-MS. The limit of quantification was increased by optimizing (1 the metabolite extraction from plasma, (2 the GC-MS measurement, and (3 most importantly, the computational data processing. We applied our workflow to study the catabolic dynamics of 13C-enriched wheat bread in three human subjects. For that purpose, we collected time-resolved human plasma samples at 16 timepoints after the consumption of 13C-labeled bread and quantified 13C enrichment of 12 metabolites (glucose, lactate, alanine, glycine, serine, citrate, glutamate, glutamine, valine, isoleucine, tyrosine, and threonine. Based on isotopomer specific analysis, we were able to distinguish catabolic profiles of starch and protein hydrolysis. More generally, our study highlights that conventional GC-MS equipment is sufficient to detect isotope traces below 1% if an appropriate data processing is integrated.

Synthesis and Use of Stable Isotope Enriched Retinals in the Field of Vitamin A

Directory of Open Access Journals (Sweden)

Johan Lugtenburg

2010-03-01

Full Text Available The role of vitamin A and its metabolites in the life processes starting with the historical background and its up to date information is discussed in the introduction. Also the role of 11Z-retinal in vision and retinoic acid in the biological processes is elucidated. The essential role of isotopically enriched systems in the progress of vision research, nutrition research etc. is discussed. In part B industrial commercial syntheses of vitamin A by the two leading companies Hoffmann-La Roche (now DSM and BASF are discussed. The knowledge obtained via these pioneering syntheses has been essential for the further synthetic efforts in vitamin A field by other scientific groups. The rest of the paper is devoted to the synthetic efforts of the Leiden group that gives an access to the preparation of site directed high level isotope enrichment in retinals. First the synthesis of the retinals with deuterium incorporation in the conjugated side chain is reviewed. Then, 13C-labeled retinals are discussed. This is followed by the discussion of a convergent synthetic scheme that allows a rational access to prepare any isotopomer of retinals. The schemes that provide access to prepare any possible isotope enriched chemically modified systems are discussed. Finally, nor-retinals and bridged retinals that give access to a whole (as yet incomplete library of possible isotopomers are reviewed.

A novel membrane inlet mass spectrometer method to measure ¹⁵NH4₄⁺ for isotope-enrichment experiments in aquatic ecosystems.

Science.gov (United States)

Yin, Guoyu; Hou, Lijun; Liu, Min; Liu, Zhanfei; Gardner, Wayne S

2014-08-19

Nitrogen (N) pollution in aquatic ecosystems has attracted much attention over the past decades, but the dynamics of this bioreactive element are difficult to measure in aquatic oxygen-transition environments. Nitrogen-transformation experiments often require measurement of (15)N-ammonium ((15)NH4(+)) ratios in small-volume (15)N-enriched samples. Published methods to determine N isotope ratios of dissolved ammonium require large samples and/or costly equipment and effort. We present a novel ("OX/MIMS") method to determine N isotope ratios for (15)NH4(+) in experimental waters previously enriched with (15)N compounds. Dissolved reduced (15)N (dominated by (15)NH4(+)) is oxidized with hypobromite iodine to nitrogen gas ((29)N2 and/or (30)N2) and analyzed by membrane inlet mass spectrometry (MIMS) to quantify (15)NH4(+) concentrations. The N isotope ratios, obtained by comparing the (15)NH4(+) to total ammonium (via autoanalyzer) concentrations, are compared to the ratios of prepared standards. The OX/MIMS method requires only small sample volumes of water (ca. 12 mL) or sediment slurries and is rapid, convenient, accurate, and precise (R(2) = 0.9994, p < 0.0001) over a range of salinities and (15)N/(14)N ratios. It can provide data needed to quantify rates of ammonium regeneration, potential ammonium uptake, and dissimilatory nitrate reduction to ammonium (DNRA). Isotope ratio results agreed closely (R = 0.998, P = 0.001) with those determined independently by isotope ratio mass spectrometry for DNRA measurements or by ammonium isotope retention time shift liquid chromatography for water-column N-cycling experiments. Application of OX/MIMS should simplify experimental approaches and improve understanding of N-cycling rates and fate in a variety of freshwater and marine environments.

A Quantitative, Time-Dependent Model of Oxygen Isotopes in the Solar Nebula: Step one

Science.gov (United States)

Nuth, J. A.; Paquette, J. A.; Farquhar, A.; Johnson, N. M.

2011-01-01

The remarkable discovery that oxygen isotopes in primitive meteorites were fractionated along a line of slope I rather than along the typical slope 0,52 terrestrial fractionation line occurred almost 40 years ago, However, a satisfactory, quantitative explanation for this observation has yet to be found, though many different explanations have been proposed, The first of these explanations proposed that the observed line represented the final product produced by mixing molecular cloud dust with a nucleosynthetic component, rich in O-16, possibly resulting from a nearby supernova explosion, Donald Clayton suggested that Galactic Chemical Evolution would gradually change the oxygen isotopic composition of the interstellar grain population by steadily producing O-16 in supernovae, then producing the heavier isotopes as secondary products in lower mass stars, Thiemens and collaborators proposed a chemical mechanism that relied on the availability of additional active rotational and vibrational states in otherwise-symmetric molecules, such as CO2, O3 or SiO2, containing two different oxygen isotopes and a second, photochemical process that suggested that differential photochemical dissociation processes could fractionate oxygen , This second line of research has been pursued by several groups, though none of the current models is quantitative,

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

International Nuclear Information System (INIS)

Bravin, F.

2008-12-01

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 ( 13 C, 15 N, 18 O and 2 H). In parallel we studied the influence of the 13 C enrichment on the reactivity of a given molecule, from a theoretical and an experimental point of view. (author)

Unactivated yttrium tantalate phosphor

International Nuclear Information System (INIS)

Reddy, V.B.; Cheung, H.K.

1992-01-01

This patent describes an unactivated yttrium tantalate phosphor having M prime monoclinic structure and containing one or more additives of Rb and Al in an amount of between about 0.001 to 0.1 moles per mole of yttrium tantalate to improve brightness under X-radiation. This patent also describes an unactivated yttrium tantalate phosphor having M prime monoclinic structure and containing additives of Sr in an amount of between 0.001 to 0.1 moles per mole of yttrium tantalate and one or more of Rb and Al in an amount of between 0.001 to 0.1 moles per mole of yttrium tantalate the phosphor exhibiting a greater brightness under X-radiation than the phosphor absent Rb and Al

Thermogravimetric analysis of rice and wheat straw catalytic combustion in air- and oxygen-enriched atmospheres

International Nuclear Information System (INIS)

Yu Zhaosheng; Ma Xiaoqian; Liu Ao

2009-01-01

By thermogravimetric analysis (TGA) study, the influences of different catalysts on the ignition and combustion of rice and wheat straw in air- and oxygen-enriched atmospheres have been investigated in this paper. Straw combustion is divided into two stages. One is the emission and combustion of volatiles and the second is the combustion of fixed carbon. The existence of catalysts in the first step enhances the emission of volatiles from the straw. The action of catalysts in the second step of straw combustion may be as a carrier of oxygen to the fixed carbon. Two parameters have been used to compare the characteristics of ignition and combustion of straw under different catalysts and in various oxygen concentrations. One is the temperature when the conversion degree combustible (CDC) of straw is 5%, the other is the CDC when the temperature is 900 deg. C. By comparing the different values of the two parameters, the different influences of the catalysts and oxygen concentration on the ignition and combustion of straw have been studied, the action of these catalysts for straw ignition and combustion in air and oxygen-enriched atmosphere is effective except the oxygen-enriched catalytic combustion of wheat straw fixed carbon

High Pressure and High Temperature State of Oxygen Enriched Ice

Science.gov (United States)

LI, M.; Zhang, S.; Jeanloz, R.; Militzer, B.

2016-12-01

Interior models for Uranus and Neptune include a hydrogen/helium/water outer envelope and a core of rock and metal at the center, with superionic water-rich ice proposed as comprising an intermediate layer. Here we consider an oxygen-enriched ice, such as H2O2 hydrogen peroxide (± water), that could form through chemical reaction between water-rich and underlying rocky (i.e., oxygen-rich) layers. As oxygen and its compounds (e.g., H2O, SiO2) form metallic fluids at pressures above 100-150 GPa, the problem amounts to considering oxygen alloying of semiconducting or metallic water. The density of H2O2 is 1.45 g/cc at ambient pressure and 0° C, increasing to 1.71 g/cc in the solid state at about -20° C. There are no Hugoniot data beyond 30 GPa, so we estimated Hugoniots for H2O2 with different initial densities, using both a mixing model based on Hugoniot data for H2O2 and 1/2 O2 (molar volume summation under pressure) and ab initio calculations for unreacted H2O2. The results agree with each other to pressures of about 200 GPa, and the ab initio calculations show evidence of a superionic state at temperatures as low as 500 K, much lower than for water ice. Hydrogen peroxide is expected to be liquid along planetary isentropes for Uranus and Neptune, suggesting that H2O2 may not be present as a pure compound in these planets. Instead, oxygen-enriched H2O ice may be the relevant form of water and oxygen, and might be produced in the laboratory by way of dynamic compression of H2O2 or laser-heating of statically compressed H2O + O2 and/or H2O2.

Positional enrichment by proton analysis (PEPA). A one-dimensional {sup 1}H-NMR approach for {sup 13}C stable isotope tracer studies in metabolomics

Energy Technology Data Exchange (ETDEWEB)

Vinaixa, Maria; Yanes, Oscar [Department of Electronic Engineering-Universitat Rovira i Virgili, Spanish Biomedical Research Center in Diabetes and Associated Metabolic Disorders (CIBERDEM), Reus (Spain); Rodriguez, Miguel A.; Capellades, Jordi [Universitat Rovira i Virgili, Spanish Biomedical Research Center in Diabetes and Associated Metabolic Disorders (CIBERDEM), Reus (Spain); Aivio, Suvi; Stracker, Travis H. [Institute for Research in Biomedicine (IRB Barcelona), Barcelona Institute of Science and Technology (Spain); Gomez, Josep; Canyellas, Nicolau [Department of Electronic Engineering-, Universitat Rovira i Virgili, Tarragona (Spain)

2017-03-20

A novel metabolomics approach for NMR-based stable isotope tracer studies called PEPA is presented, and its performance validated using human cancer cells. PEPA detects the position of carbon label in isotopically enriched metabolites and quantifies fractional enrichment by indirect determination of {sup 13}C-satellite peaks using 1D-{sup 1}H-NMR spectra. In comparison with {sup 13}C-NMR, TOCSY and HSQC, PEPA improves sensitivity, accelerates the elucidation of {sup 13}C positions in labeled metabolites and the quantification of the percentage of stable isotope enrichment. Altogether, PEPA provides a novel framework for extending the high-throughput of {sup 1}H-NMR metabolic profiling to stable isotope tracing in metabolomics, facilitating and complementing the information derived from 2D-NMR experiments and expanding the range of isotopically enriched metabolites detected in cellular extracts. (copyright 2017 The Authors. Published by Wiley-VCH Verlag GmbH and Co. KGaA.)

Oxygen and sulfur isotope systematics of sulfate produced during abiotic and bacterial oxidation of sphalerite and elemental sulfur

Science.gov (United States)

Balci, N.; Mayer, B.; Shanks, Wayne C.; Mandernack, K.W.

2012-01-01

Studies of metal sulfide oxidation in acid mine drainage (AMD) systems have primarily focused on pyrite oxidation, although acid soluble sulfides (e.g., ZnS) are predominantly responsible for the release of toxic metals. We conducted a series of biological and abiotic laboratory oxidation experiments with pure and Fe-bearing sphalerite (ZnS & Zn 0.88Fe 0.12S), respectively, in order to better understand the effects of sulfide mineralogy and associated biogeochemical controls of oxidation on the resultant ?? 34S and ?? 18O values of the sulfate produced. The minerals were incubated in the presence and absence of Acidithiobacillus ferrooxidans at an initial solution pH of 3 and with water of varying ?? 18O values to determine the relative contributions of H 2O-derived and O 2-derived oxygen in the newly formed sulfate. Experiments were conducted under aerobic and anaerobic conditions using O 2 and Fe(III) aq as the oxidants, respectively. Aerobic incubations with A. ferrooxidans, and S o as the sole energy source were also conducted. The ??34SSO4 values from both the biological and abiotic oxidation of ZnS and ZnS Fe by Fe(III) aq produced sulfur isotope fractionations (??34SSO4-ZnS) of up to -2.6???, suggesting the accumulation of sulfur intermediates during incomplete oxidation of the sulfide. No significant sulfur isotope fractionation was observed from any of the aerobic experiments. Negative sulfur isotope enrichment factors (??34SSO4-ZnS) in AMD systems could reflect anaerobic, rather than aerobic pathways of oxidation. During the biological and abiotic oxidation of ZnS and ZnS Fe by Fe(III) aq all of the sulfate oxygen was derived from water, with measured ?? 18OSO 4-H 2O values of 8.2??0.2??? and 7.5??0.1???, respectively. Also, during the aerobic oxidation of ZnS Fe and S o by A. ferrooxidans, all of the sulfate oxygen was derived from water with similar measured ?? 18OSO 4-H 2O values of 8.1??0.1??? and 8.3??0.3???, respectively. During biological oxidation

Oxygen isotopic composition of mammal bones as a new tool for studying ratios of paleoenvironmental water and paleoclimates

International Nuclear Information System (INIS)

Longinelli, A.

1984-04-01

The purpose of this study is to try to establish quantitative relationships between the average oxygen isotopic composition of local meteoric water, the oxygen isotopic composition of mammal body water and the oxygen isotopic composition of phosphate in mammal bones. These relationships, after calibration of the method on living specimens, would allow quantitative paleoclimatological research based on the measurement of delta 18 O(PO 4 3- ) of fossil mammal bones

Phosphorus dynamics in soils irrigated with reclaimed waste water or fresh water - A study using oxygen isotopic composition of phosphate

Science.gov (United States)

Zohar, I.; Shaviv, A.; Young, M.; Kendall, C.; Silva, S.; Paytan, A.

2010-01-01

Transformations of phosphate (Pi) in different soil fractions were tracked using the stable isotopic composition of oxygen in phosphate (??18Op) and Pi concentrations. Clay soil from Israel was treated with either reclaimed waste water (secondary, low grade) or with fresh water amended with a chemical fertilizer of a known isotopic signature. Changes of ??18Op and Pi within different soil fractions, during a month of incubation, elucidate biogeochemical processes in the soil, revealing the biological and the chemical transformation impacting the various P pools. P in the soil solution is affected primarily by enzymatic activity that yields isotopic equilibrium with the water molecules in the soil solution. The dissolved P interacts rapidly with the loosely bound P (extracted by bicarbonate). The oxides and mineral P fractions (extracted by NaOH and HCl, respectively), which are considered as relatively stable pools of P, also exhibited isotopic alterations in the first two weeks after P application, likely related to the activity of microbial populations associated with soil surfaces. Specifically, isotopic depletion which could result from organic P mineralization was followed by isotopic enrichment which could result from preferential biological uptake of depleted P from the mineralized pool. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with reclaimed waste water compared to the fertilizer treated soil. ?? 2010 Elsevier B.V.

Preparation of isotopically enriched mercury sulphide targets

Energy Technology Data Exchange (ETDEWEB)

Szerypo, J.; Friebel, H.U.; Frischke, D.; Grossman, R.; Maier, H.J. [Dept. fuer Physik, Univ. Muenchen (LMU) (Germany); Maier-Leibnitz-Lab. (MLL), Garching (Germany)

2007-07-01

The primary difficulty in performing nuclear reactions on mercury is to obtain a suitable target. The primary difficulty in performing nuclear reactions on mercury is to obtain a suitable target. The utilization of amalgam targets has been reported in early publications. These targets, however, were lacking homogeneity and in-beam stability. A thorough investigation of literature shows, that HgS, because of its comparatively high chemical and mechanical stability, is one of the more adequate Hg compounds for accelerator target applications. In this presentation we describe the production of HgS targets consisting of an enriched Hg isotope and S of natural isotopic abundance, starting up from HgO. Following the outline given in [3], in this special case HgS can be prepared by dissolving HgO in diluted HNO{sub 3} and subsequent precipitation of the black HgS modification with gaseous H{sub 2}S. Last step of the target production procedure is evaporation-condensation of HgS in vacuum. In the present case, HgS layers of 500 {mu}g/cm{sup 2} on a backing carbon foil of 26 {mu}g/cm{sup 2} with a protective carbon layer of about 20 {mu}g/cm{sup 2} thickness on top of the HgS layer were produced. (orig.)

Exploring Neutron-Rich Oxygen Isotopes with MoNA

International Nuclear Information System (INIS)

Frank, N.; Gade, A.; Peters, W. A.; Thoennessen, M.; Baumann, T.; Bazin, D.; Lecouey, J.-L.; Scheit, H.; Schiller, A.; Brown, J.; DeYoung, P. A.; Finck, J. E.; Hinnefeld, J.; Howes, R.; Luther, B.

2007-01-01

The Modular Neutron Array (MoNA) was used in conjunction with a large-gap dipole magnet (Sweeper) to measure neutron-unbound states in oxygen isotopes close to the neutron dripline. While no excited states were observed in 24 O, a resonance at 45(2) keV above the neutron separation energy was observed in 23 O

Influence of chemical structure on carbon isotope composition of lignite

Science.gov (United States)

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

2017-04-01

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

Use of enriched 74Se and 77Se in combination with isotope pattern deconvolution to differentiate and determine endogenous and supplemented selenium in lactating rats

International Nuclear Information System (INIS)

Gonzalez Iglesias, H.; Fernandez Sanchez, M.L.; Garcia Alonso, J.I.; Sanz-Medel, A.

2007-01-01

A quantitative methodology has been developed to differentiate between endogenous and supplemented selenium in lactating rats using two enriched selenium isotopes. Lactating rats were fed for 2 weeks with formula milk containing one enriched Se isotope, 77 Se, as the metabolic tracer. The isotopic composition of selenium in serum and urine samples was then measured by collision cell ICP-MS after the addition of a solution containing another enriched isotope, 74 Se, as quantitation tracer, before analysis. Isotope pattern deconvolution allowed the transformation of measured Se isotopic abundances into concentrations of natural abundance (endogenous) selenium and enriched 77 Se (supplemented) present in the samples. The proposed methodology was validated using serum and urine reference materials spiked with both 77 Se and 74 Se. The obtained results are discussed in terms of selenium exchange and half-life in lactating rats (11-12 days) and selenium levels in serum in comparison with non-supplemented rats and control rats after maternal feeding. (orig.)

Yttrium-enriched YBa{sub 2}Cu{sub 3}O{sub x} thin films for coated conductors fabricated by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Khoryushin, Alexey V., E-mail: khoryushin@ya.ru [Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Mozhaev, Peter B.; Mozhaeva, Julia E.; Andersen, Niels H. [Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Grivel, Jean-Claude [Department of Energy Conversion and Storage, Technical University of Denmark, DK-4000 Roskilde (Denmark); Hansen, Jørn Bindslev; Jacobsen, Claus S. [Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark)

2013-02-14

Highlights: ► YBCO films were fabricated by PLD from targets of various elemental compositions. ► The Y-enriched films contain yttria nanoparticles which provide efficient pinning. ► The best film has 5.5× higher j{sub c}(5 T,50 K) = 2.6MA/cm{sup 2} comparing with a reference film. ► The Y-enriched films remain c-oriented up to 500 nm. ► Films demonstrate no j{sub c} suppression with thickness and remarkable stability with time. -- Abstract: The effects of excess yttria on the structural and electrical properties of the YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) thin films are studied. The films were deposited on (LaAlO{sub 3}){sub 0.3}–(Sr{sub 2}AlTaO{sub 8}){sub 0.7} substrates by pulsed laser ablation from targets with different elemental composition. An increase of yttrium content of the target leads to formation of porous films with significantly improved current-carrying capabilities. Structural studies of these films reveal presence of yttria nanoparticles embedded into the YBCO matrix. The highest obtained critical current density in an external magnetic field of 5 T was 2.6 MA/cm{sup 2} at 50 K and 9.4 MA/cm{sup 2} at 20 K. The fabricated Y-enriched YBCO films remain c-oriented at least up to 600 nm thickness with no significant suppression of the critical current density.

Oxygen isotope fractionation in the CaCO3-DIC-H2O system

Science.gov (United States)

Devriendt, Laurent S.; Watkins, James M.; McGregor, Helen V.

2017-10-01

The oxygen isotope ratio (δ18O) of inorganic and biogenic carbonates is widely used to reconstruct past environments. However, the oxygen isotope exchange between CaCO3 and H2O rarely reaches equilibrium and kinetic isotope effects (KIE) commonly complicate paleoclimate reconstructions. We present a comprehensive model of kinetic and equilibrium oxygen isotope fractionation between CaCO3 and water (αc/w) that accounts for fractionation between both (a) CaCO3 and the CO32- pool (α c / CO32-) , and (b) CO32- and water (α CO32- / w) , as a function of temperature, pH, salinity, calcite saturation state (Ω), the residence time of the dissolved inorganic carbon (DIC) in solution, and the activity of the enzyme carbonic anhydrase. The model results suggest that: (1) The equilibrium αc/w is only approached in solutions with low Ω (i.e. close to 1) and low ionic strength such as in the cave system of Devils Hole, Nevada. (2) The sensitivity of αc/w to the solution pH and/or the mineral growth rate depends on the level of isotopic equilibration between the CO32- pool and water. When the CO32- pool approaches isotopic equilibrium with water, small negative pH and/or growth rate effects on αc/w of about 1-2‰ occur where these parameters covary with Ω. In contrast, isotopic disequilibrium between CO32- and water leads to strong (>2‰) positive or negative pH and growth rate effects on α CO32-/ w (and αc/w) due to the isotopic imprint of oxygen atoms derived from HCO3-, CO2, H2O and/or OH-. (3) The temperature sensitivity of αc/w originates from the negative effect of temperature on α CO32-/ w and is expected to deviate from the commonly accepted value (-0.22 ± 0.02‰/°C between 0 and 30 °C; Kim and O'Neil, 1997) when the CO32- pool is not in isotopic equilibrium with water. (4) The model suggests that the δ18O of planktic and benthic foraminifers reflects a quantitative precipitation of DIC in isotopic equilibrium with a high-pH calcifying fluid, leading

Potential benefits of oxygen-enriched intake air in a vehicle powered by a spark-ignition engine

Science.gov (United States)

Ng, H. K.; Sekar, R. R.

1994-04-01

A production vehicle powered by a spark-ignition engine (3.1-L Chevrolet Lumina, model year 1990) was tested. The test used oxygen-enriched intake air containing 25 and 28% oxygen by volume to determine (1) if the vehicle would run without difficulties and (2) if emissions benefits would result. Standard Federal Test Procedure (FTP) emissions test cycles were run satisfactorily. Test results of catalytic converter-out emissions (emissions out of the converter) showed that both carbon monoxide and hydrocarbons were reduced significantly in all three phases of the emissions test cycle. Test results of engine-out emissions (emissions straight out of the engine, with the converter removed) showed that carbon monoxide was significantly reduced in the cold phase. All emission test results were compared with those for normal air (21% oxygen). The catalytic converter also had an improved carbon monoxide conversion efficiency under the oxygen-enriched-air conditions. Detailed results of hydrocarbon speciation indicated large reductions in 1,3-butadiene, formaldehyde, acetaldehyde, and benzene from the engine with the oxygen-enriched air. Catalytic converter-out ozone was reduced by 60% with 25%-oxygen-content air. Although NO(x) emissions increased significantly, both for engine-out and catalytic converter-out emissions, we anticipate that they can be ameliorated in the near future with new control technologies. The automotive industry currently is developing exhaust-gas control technologies for an oxidizing environment; these technologies should reduce NO(x) emissions more efficiently in vehicles that use oxygen-enriched intake air. On the basis of estimates made from current data, several production vehicles that had low NO(x) emissions could meet the 2004 Tier 2 emissions standards with 25%-oxygen-content air.

Hydro-geochemical and isotopic composition of ground water in Helwan area

Directory of Open Access Journals (Sweden)

W.M. Salem

2015-12-01

The environmental stable isotopes oxygen and hydrogen (18O, and deuterium were studied and used to identify the sources of recharge. The studied ground waters are enriched in D and 18O and the isotopic features suggest that most of the ground water recharged indirectly after evaporation prior to infiltration from irrigation return water as well as the contribution from Nile water.

Crystallization history of enriched shergottites from Fe and Mg isotope fractionation in olivine megacrysts

Science.gov (United States)

Collinet, Max; Charlier, Bernard; Namur, Olivier; Oeser, Martin; Médard, Etienne; Weyer, Stefan

2017-06-01

Martian meteorites are the only samples available from the surface of Mars. Among them, olivine-phyric shergottites are basalts containing large zoned olivine crystals with highly magnesian cores (Fo 70-85) and rims richer in Fe (Fo 45-60). The Northwest Africa 1068 meteorite is one of the most primitive "enriched" shergottites (high initial 87Sr/86Sr and low initial ε143Nd). It contains olivine crystals as magnesian as Fo 77 and is a major source of information to constrain the composition of the parental melt, the composition and depth of the mantle source, and the cooling and crystallization history of one of the younger magmatic events on Mars (∼180 Ma). In this study, Fe-Mg isotope profiles analyzed in situ by femtosecond-laser ablation MC-ICP-MS are combined with compositional profiles of major and trace elements in olivine megacrysts. The cores of olivine megacrysts are enriched in light Fe isotopes (δ56FeIRMM-14 = -0.6 to -0.9‰) and heavy Mg isotopes (δ26MgDSM-3 = 0-0.2‰) relative to megacryst rims and to the bulk martian isotopic composition (δ56Fe = 0 ± 0.05‰, δ26Mg = -0.27 ± 0.04‰). The flat forsterite profiles of megacryst cores associated with anti-correlated fractionation of Fe-Mg isotopes indicate that these elements have been rehomogenized by diffusion at high temperature. We present a 1-D model of simultaneous diffusion and crystal growth that reproduces the observed element and isotope profiles. The simulation results suggest that the cooling rate during megacryst core crystallization was slow (43 ± 21 °C/year), and consistent with pooling in a deep crustal magma chamber. The megacryst rims then crystallized 1-2 orders of magnitude faster during magma transport toward the shallower site of final emplacement. Megacryst cores had a forsterite content 3.2 ± 1.5 mol% higher than their current composition and some were in equilibrium with the whole-rock composition of NWA 1068 (Fo 80 ± 1.5). NWA 1068 composition is thus close to a

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

Isotope Enrichment Detection by Laser Ablation - Laser Absorption Spectrometry: Automated Environmental Sampling and Laser-Based Analysis for HEU Detection

International Nuclear Information System (INIS)

Anheier, Norman C.; Bushaw, Bruce A.

2010-01-01

The global expansion of nuclear power, and consequently the uranium enrichment industry, requires the development of new safeguards technology to mitigate proliferation risks. Current enrichment monitoring instruments exist that provide only yes/no detection of highly enriched uranium (HEU) production. More accurate accountancy measurements are typically restricted to gamma-ray and weight measurements taken in cylinder storage yards. Analysis of environmental and cylinder content samples have much higher effectiveness, but this approach requires onsite sampling, shipping, and time-consuming laboratory analysis and reporting. Given that large modern gaseous centrifuge enrichment plants (GCEPs) can quickly produce a significant quantity (SQ ) of HEU, these limitations in verification suggest the need for more timely detection of potential facility misuse. The Pacific Northwest National Laboratory (PNNL) is developing an unattended safeguards instrument concept, combining continuous aerosol particulate collection with uranium isotope assay, to provide timely analysis of enrichment levels within low enriched uranium facilities. This approach is based on laser vaporization of aerosol particulate samples, followed by wavelength tuned laser diode spectroscopy to characterize the uranium isotopic ratio through subtle differences in atomic absorption wavelengths. Environmental sampling (ES) media from an integrated aerosol collector is introduced into a small, reduced pressure chamber, where a focused pulsed laser vaporizes material from a 10 to 20-(micro)m diameter spot of the surface of the sampling media. The plume of ejected material begins as high-temperature plasma that yields ions and atoms, as well as molecules and molecular ions. We concentrate on the plume of atomic vapor that remains after the plasma has expanded and then cooled by the surrounding cover gas. Tunable diode lasers are directed through this plume and each isotope is detected by monitoring absorbance

Carbon and oxygen isotope compositions of the carbonate facies

Indian Academy of Sciences (India)

The Vindhyan sedimentary succession in central India spans a wide time bracket from the Paleopro- terozoic to the Neoproterozoic period.Chronostratigraphic significance of stable carbon and oxygen isotope ratios of the carbonate phase in Vindhyan sediments has been discussed in some recent studies.However,the ...

Uranium enrichment

International Nuclear Information System (INIS)

Mohrhauer, H.

1982-01-01

The separation of uranium isotopes in order to enrich the fuel for light water reactors with the light isotope U-235 is an important part of the nuclear fuel cycle. After the basic principals of isotope separation the gaseous diffusion and the centrifuge process are explained. Both these techniques are employed on an industrial scale. In addition a short review is given on other enrichment techniques which have been demonstrated at least on a laboratory scale. After some remarks on the present situation on the enrichment market the progress in the development and the industrial exploitation of the gas centrifuge process by the trinational Urenco-Centec organisation is presented. (orig.)

Intercomparison of enriched stable isotope reference materials for medical and biological studies

International Nuclear Information System (INIS)

Parr, R.M.; Clements, S.A.

1991-01-01

This report summarizes the results of an intercomparison exercise organized by the IAEA during the latter part of 1988 and 1989. Data are presented for 13 different kinds of enriched stable isotope reference material containing 2 H, 13 C, 15 N and 18 O. Results were submitted by forty participants in twenty countries. 2 refs, 13 figs, 18 tabs

Controls of oxygen isotope ratios of nitrate formed during nitrification in soils

International Nuclear Information System (INIS)

Mayer, B.; Bollwerk, S.M.; Vorhoff, B.; Mansfeldt, T.; Veizer, J.

1999-01-01

The isotopic composition of nitrate is increasingly used to determine sources and transformations of nitrogen in terrestrial and aquatic ecosystems. Oxygen isotope ratios of nitrate appear to be particularly useful, since they allow the differentiation between nitrate from atmospheric deposition (δ 18 O nitrate between +25 and +70 per mille), nitrate from fertilizers (δ 18 O nitrate +23 per mille), and nitrate derived from nitrification processes in soils (δ 18 O nitrate 3 molecule derive from H 2 O (with negative δ 18 O values dependent upon location) and one oxygen derives from atmospheric O 2 (δ 18 O = +23.5 per mille).. The objective of this study was to experimentally determine the extent to which water oxygen controls the δ 18 O value of nitrate, which is formed during nitrification in soils

Theorical and experimental analysis of nitrogen-15 isotope enrichment by nitrogen monoxide and nitric acid system

International Nuclear Information System (INIS)

Ducatti, C.

1985-01-01

Nitrogen-15 isotope enrichment by chemical exchange in NO/HNO 3 system was studied using two different theories. The isotope fractionation factors obtained by the countercurrent theory was compared to those estimated by the isotope equipartition theory were confronted through a model. A column in countercurrent was built at laboratory scale and parameters such as: number of theoretical plates, height equivalent to a theoretical plate, type of packing, total height of column, production of H 15 NO 3 /week, obtained under isotope dynamic equilibrium conditions, were studied in comparison to those in the literature. (Author) [pt

Stable isotopes. Enriched wheat: a new chance for nutrition research

International Nuclear Information System (INIS)

Chagvardieff, P.

1996-01-01

The Department of Plant Eco-physiology (DEV) from the CEA/Life Sciences Department of Cadarache (France) has artificially produced two kg of carbon 13 labelled wheat for nutrition research. It is the first successful stable isotope labelling of complex nutriments with a 10% enrichment in carbon 13. This wheat has been used for the manufacturing of pastas to follow the assimilation of nutrients by the organism. This short paper gives some details about the experimental procedure of labelled wheat cultivation. (J.S.)

Effects of oxygen enriched combustion on pollution and performance characteristics of a diesel engine

Directory of Open Access Journals (Sweden)

P. Baskar

2016-03-01

Full Text Available Oxygen enriched combustion is one of the attractive combustion technologies to control pollution and improve combustion in diesel engines. An experimental test was conducted on a single cylinder direct injection diesel engine to study the impact of oxygen enrichment on pollution and performance parameters by increasing the oxygen concentration of intake air from 21 to 27% by volume. The tests results show that the combustion process was improved as there is an increase in thermal efficiency of 4 to 8 percent and decrease in brake specific fuel consumption of 5 to 12 percent. There is also a substantial decrease in unburned hydro carbon, carbon mono-oxide and smoke density levels to the maximum of 40, 55 and 60 percent respectively. However, there is a considerable increase in nitrogen oxide emissions due to increased combustion temperature and extra oxygen available which needs to be addressed.

Seasonal variation in kangaroo tooth enamel oxygen and carbon isotopes in southern Australia

Science.gov (United States)

Brookman, Tom H.; Ambrose, Stanley H.

2012-09-01

Serial sampling of tooth enamel growth increments for carbon and oxygen isotopic analyses of Macropus (kangaroo) teeth was performed to assess the potential for reconstructing paleoseasonality. The carbon isotope composition of tooth enamel apatite carbonate reflects the proportional intake of C3 and C4 vegetation. The oxygen isotopic composition of enamel reflects that of ingested and metabolic water. Tooth enamel forms sequentially from the tip of the crown to the base, so dietary and environmental changes during the tooth's formation can be detected. δ13C and δ18O values were determined for a series of enamel samples drilled from the 3rd and 4th molars of kangaroos that were collected along a 900 km north-south transect in southern Australia. The serial sampling method did not yield pronounced seasonal isotopic variation patterns in Macropus enamel. The full extent of dietary isotopic variation may be obscured by attenuation of the isotopic signal during enamel mineralisation. Brachydont (low-crowned) Macropus teeth may be less sensitive to seasonal variation in isotopic composition due to time-averaging during mineralisation. However, geographic variations observed suggest that there may be potential for tracking latitudinal shifts in vegetation zones and seasonal environmental patterns in response to climate change.

Influence of the enzyme dissimilatory sulfite reductase on stable isotope fractionation during sulfate reduction

Science.gov (United States)

Mangalo, Muna; Einsiedl, Florian; Meckenstock, Rainer U.; Stichler, Willibald

2008-03-01

The stable isotopes of sulfate are often used as a tool to assess bacterial sulfate reduction on the macro scale. However, the mechanisms of stable isotope fractionation of sulfur and oxygen at the enzymatic level are not yet fully understood. In batch experiments with water enriched in 18O we investigated the effect of different nitrite concentrations on sulfur isotope fractionation by Desulfovibrio desulfuricans. With increasing nitrite concentrations, we found sulfur isotope enrichment factors ranging from -11.2 ± 1.8‰ to -22.5 ± 3.2‰. Furthermore, the δ18O values in the remaining sulfate increased from approximately 50-120‰ when 18O-enriched water was supplied. Since 18O-exchange with ambient water does not take place in sulfate, but rather in intermediates of the sulfate reduction pathway (e.g. SO32-), we suggest that nitrite affects the steady-state concentration and the extent of reoxidation of the metabolic intermediate sulfite to sulfate during sulfate reduction. Given that nitrite is known to inhibit the production of the enzyme dissimilatory sulfite reductase, our results suggest that the activity of the dissimilatory sulfite reductase regulates the kinetic isotope fractionation of sulfur and oxygen during bacterial sulfate reduction. Our novel results also imply that isotope fractionation during bacterial sulfate reduction strongly depends on the cell internal enzymatic regulation rather than on the physico-chemical features of the individual enzymes.

Volume Reduction of Decommissioning Burnable Waste with Oxygen Enrich Incinerator

International Nuclear Information System (INIS)

Min, B. Y.; Yang, D. S.; Lee, K. W.; Choi, J. W.

2016-01-01

The incineration technology is an effective treatment method that contains hazardous chemicals as well as radioactive contamination. The volume reduction of the combustible wastes through the incineration technologies has merits from the view point of a decrease in the amount of waste to be disposed of resulting in a reduction of the disposal cost. Incineration is generally accepted as a method of reducing the volume of radioactive waste. The incineration technology is an effective treatment method that contains hazardous chemicals as well as radioactive contamination. This paper covers the general facility operation of an oxygen-enriched incinerator for the treatment of decommissioning wastes generated from a decommissioning project. The combustible wastes have been treated by the utilization of incinerator the capacity of the average 20 kg/hr. The decommissioning combustible waste of about 31 tons has been treated using Oxygen Enriched incinerator by at the end of 2016. The off-gas flow and temperature were maintained constant or within the desired range. The measured gases and particulate materials in the stack were considerably below the regulatory limits.

Volume Reduction of Decommissioning Burnable Waste with Oxygen Enrich Incinerator

Energy Technology Data Exchange (ETDEWEB)

Min, B. Y.; Yang, D. S.; Lee, K. W.; Choi, J. W. [KAERI, Daejeon (Korea, Republic of)

2016-05-15

The incineration technology is an effective treatment method that contains hazardous chemicals as well as radioactive contamination. The volume reduction of the combustible wastes through the incineration technologies has merits from the view point of a decrease in the amount of waste to be disposed of resulting in a reduction of the disposal cost. Incineration is generally accepted as a method of reducing the volume of radioactive waste. The incineration technology is an effective treatment method that contains hazardous chemicals as well as radioactive contamination. This paper covers the general facility operation of an oxygen-enriched incinerator for the treatment of decommissioning wastes generated from a decommissioning project. The combustible wastes have been treated by the utilization of incinerator the capacity of the average 20 kg/hr. The decommissioning combustible waste of about 31 tons has been treated using Oxygen Enriched incinerator by at the end of 2016. The off-gas flow and temperature were maintained constant or within the desired range. The measured gases and particulate materials in the stack were considerably below the regulatory limits.

Oxygen isotope fractionation and algal symbiosis in benthic foraminifera from the Gulf of Elat, Israel

International Nuclear Information System (INIS)

Buchardt, B.; Hansen, H.J.

1977-01-01

In order to investigate possible isotopic fractionations due to algal symbiosis the oxygen and carbon isotope compositions of shell carbonate from symbiont-free and symbiont-bearing benthic foraminifera have been compared to that of molluscs living at the same locality. The material was collected over a depth profile in the Gulf of Elat (Aqaba), Israel, covering the interval from 4 to 125 metres. After corrections variations for temperature with depth, characteristic 18 O-depletions were observed in the foraminiferal shell carbonate when compared to the molluscs. These depletions are interpreted as 1) a constant vital effect seen in all the foraminifera studied and 2) an additional, light-dependent vital effect observed in the symbiont-bearing forms only, caused by incorporation of photosynthetic oxygen formed by the symbiotic algae. This additional vital effect emphasizes the difficulties in applying foraminifera to oxygen isotope palaeotemperature analyses. No well-defined differences in carbon isotope compositions are observed between symbiont-bearing and symbiont-free foraminifera. (author)

Oxygen isotope fractionation and algal symbiosis in benthic foraminifera from the Gulf of Elat, Israel

Energy Technology Data Exchange (ETDEWEB)

Buchardt, B; Hansen, H J [Copenhagen Univ. (Denmark)

1977-01-01

In order to investigate possible isotopic fractionations due to algal symbiosis the oxygen and carbon isotope compositions of shell carbonate from symbiont-free and symbiont-bearing benthic foraminifera have been compared to that of molluscs living at the same locality. The material was collected over a depth profile in the Gulf of Elat (Aqaba), Israel, covering the interval from 4 to 125 metres. After correcting for variations of temperature with depth, characteristic /sup 18/O-depletions were observed in the foraminiferal shell carbonate when compared to the molluscs. These depletions are interpreted as 1) a constant vital effect seen in all the foraminifera studied and 2) an additional, light-dependent vital effect observed in the symbiont-bearing forms only, caused by incorporation of photosynthetic oxygen formed by the symbiotic algae. This additional vital effect emphasizes the difficulties in applying foraminifera to oxygen isotope palaeotemperature analyses. No well-defined differences in carbon isotope compositions are observed between symbiont-bearing and symbiont-free foraminifera.

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

International Nuclear Information System (INIS)

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

2000-01-01

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

Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica

Directory of Open Access Journals (Sweden)

J. Savarino

2007-01-01

Full Text Available Throughout the year 2001, aerosol samples were collected continuously for 10 to 15 days at the French Antarctic Station Dumont d'Urville (DDU (66°40' S, l40°0' E, 40 m above mean sea level. The nitrogen and oxygen isotopic ratios of particulate nitrate at DDU exhibit seasonal variations that are among the most extreme observed for nitrate on Earth. In association with concentration measurements, the isotope ratios delineate four distinct periods, broadly consistent with previous studies on Antarctic coastal areas. During austral autumn and early winter (March to mid-July, nitrate concentrations attain a minimum between 10 and 30 ng m−3 (referred to as Period 2. Two local maxima in August (55 ng m−3 and November/December (165 ng m−3 are used to assign Period 3 (mid-July to September and Period 4 (October to December. Period 1 (January to March is a transition period between the maximum concentration of Period 4 and the background concentration of Period 2. These seasonal changes are reflected in changes of the nitrogen and oxygen isotope ratios. During Period 2, which is characterized by background concentrations, the isotope ratios are in the range of previous measurements at mid-latitudes: δ18Ovsmow=(77.2±8.6‰; Δ17O=(29.8±4.4‰; δ15Nair=(−4.4±5.4‰ (mean ± one standard deviation. Period 3 is accompanied by a significant increase of the oxygen isotope ratios and a small increase of the nitrogen isotope ratio to δ18Ovsmow=(98.8±13.9‰; Δ17O=(38.8±4.7‰ and δ15Nair=(4.3±8.20‰. Period 4 is characterized by a minimum 15N/14N ratio, only matched by one prior study of Antarctic aerosols, and oxygen isotope ratios similar to Period 2: δ18Ovsmow=(77.2±7.7‰; Δ17O=(31.1±3.2‰; δ15Nair=(−32.7±8.4‰. Finally, during Period 1, isotope ratios reach minimum values for oxygen and intermediate values for nitrogen: δ18Ovsmow=63.2±2.5‰; Δ17O=24.0±1.1‰; δ15Nair=−17.9±4.0‰. Based on the measured

Laser Spectroscopic Analysis of Liquid Water Samples for Stable Hydrogen and Oxygen Isotopes

International Nuclear Information System (INIS)

2009-01-01

Stable isotope ratios of hydrogen and oxygen are tracers of choice for water cycle processes in hydrological, atmospheric and ecological studies. The use of isotopes has been limited to some extent because of the relatively high cost of isotope ratio mass spectrometers and the need for specialized operational skills. Here, the results of performance testing of a recently developed laser spectroscopic instrument for measuring stable hydrogen and oxygen isotope ratios of water samples are described, along with a procedure for instrument installation and operation. Over the last four years, the IAEA Water Resources Programme conducted prototype and production model testing of these instruments and this publication is the outcome of those efforts. One of the main missions of the IAEA is to promote the use of peaceful applications of isotope and nuclear methods in Member States and this publication is intended to facilitate the use of laser absorption based instruments for hydrogen and oxygen stable isotope analyses of liquid water samples for hydrological and other studies. The instrument uses off-axis integrated cavity output spectroscopy to measure absolute abundances of 2 HHO, HH 18 O, and HHO via laser absorption. Test results using a number of natural and synthetic water standards and samples with a large range of isotope values demonstrate adequate precision and accuracy (e.g. precisions of 1 per mille for δ 2 H and 0.2 per mille for δ 18 O). The laser instrument has much lower initial and maintenance costs than mass spectrometers and is substantially easier to operate. Thus, these instruments have the potential to bring about a paradigm shift in isotope applications by enabling researchers in all fields to measure isotope ratios by themselves. The appendix contains a detailed procedure for the installation and operation of the instrument. Using the procedure, new users should be able to install the instrument in less than two hours. It also provides step

Oxygen isotope variations in phosphate of biogenic apatites. Pt.1

International Nuclear Information System (INIS)

Kolodny, Y.; Luz, B.; Navon, O.

1983-01-01

The major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone (and teeth) building organisms are alive, and the record is nearly perfectly preserved after death. Fish from seven water bodies of different temperatures (3-23 0 C) and different delta 18 O (values - 16 to + 3) of the water were analysed. The delta 18 O values of the analysed PO 4 vary from 6 to 25. The system passed the following tests: (a) the temperature deduced from isotopic analyses of the sequence of fish from Lake Baikal are in good agreement with the temperatures measured in the thermally stratified lake; (b) the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish, but only by temperature and water composition. Isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates. (orig.)

Technical-and-Economic Efficiency of Draft Enriched with Oxygen in Small-Capacity Heating Boilers

Directory of Open Access Journals (Sweden)

P. Ratnikov

2013-01-01

Full Text Available Data on complex experimental and theoretical investigations pertaining to efficiency of oxygen-enriched draft in the small-capacity heating boilers as exemplified by the plant HEIZA (HW-S-10/K have been presented in the paper. The paper provides a calculation model of heating processes in heat generator burner (as exemplified by HEIZA plant. Simulation of heating processes in the operational zone has been executed in paper. The experimental data have proved model adequacy. The calculation scheme of the plant will be used in future for determination of power and ecological efficiency of draft enrichment with oxygen.

Oxygen Isotopes in Early Solar System Materials: A Perspective Based on Microbeam Analyses of Chondrules from CV Carbonaceous Chondrites

Science.gov (United States)

Jones, R. H.; Leshin, L. A.; Guan, Y.

2004-01-01

Some of the biggest challenges to understanding the early history of the solar system include determining the distribution of oxygen isotopes amongst materials that existed in the solar nebula, and interpreting the processes that might have resulted in the observed isotopic distributions. Oxygen isotope ratios in any individual mineral grain from a chondritic meteorite may be the cumulative product of a variety of processes, including stellar nucleosynthetic events, gas/solid interactions in the molecular cloud, mixing of independent isotopic reservoirs in the nebula, mass-independent processing in the nebula, and mass-dependent fractionation effects in various environments. It is not possible to unravel this complex isotopic record unless the distribution of oxygen isotope ratios in chondritic materials is fully understood.

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

International Nuclear Information System (INIS)

Tatarinov, A.N.; Polyakov, L.A.

1997-01-01

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

Scavenging of oxygen vacancies at modulation-doped oxide interfaces: Evidence from oxygen isotope tracing

DEFF Research Database (Denmark)

Chen, Yunzhong; Döbeli, M.; Pomjakushina, E.

2017-01-01

, the mechanisms underlying the extreme mobility enhancement remain elusive. Herein, we used 18O isotope exchanged SrTi18O3 as substrates to create 2DEG at room temperature with and without the LSMO buffer layer. By mapping the oxygen profile across the interface between STO18 and disordered LaAlO3 or yttria...

Effect of vanadium and yttrium doping on BSCCO superconductors

International Nuclear Information System (INIS)

Mohamed, S.B.; Halim, S.A.; Azhan, H.; Sidek, H.A.A; Tee, T.W.; Hassan, Z.A.

1999-01-01

The effect of vanadium and yttrium doping on the superconductivity is investigated. The doping was done on the calcium site ranging from x=0.00-0.10. The temperature dependence of electrical resistance and AC susceptibility measurements were made on these samples. The zero resistance for vanadium doped samples varied from 107 K (x = 0.00) to 68.5K (x = 0.10), whereas for yttrium doped samples it varied from 107 K (x = 0.00) to 54K (x 0.10). The volume fraction of the 2223 phase for both dopalit decreases witli increasing doping concentration. The nature of the temperature derivative of the resistance curves indicates the presence of a superconducting transition between grains coupled by weak links. The AC susceptibility data show enrichment of the volume fraction of the low Tc phase at higher compositions. The presence of low Tc phase (∼70 K) is visible in the susceptibility data. X-ray diffraction confirms the presence of mixed phases in the samples. (author)

Preparation and use of nitrogen (2) oxide of special purity for production of oxygen and nitrogen isotopes

International Nuclear Information System (INIS)

Polevoj, A.S.

1989-01-01

Problems related with production of oxygen and nitrogen isotopes by means of low-temperature rectification of nitrogen (2) oxide are analyzed. Special attention, in particular, is payed to the techniques of synthesis and high purification of initial NO, utilization of waste flows formed during isotope separation. Ways to affect the initial isotope composition of nitrogen oxide and the rate of its homogeneous-isotope exchange, which provide for possibility of simultaneous production of oxygen and nitrogen isotopes by means of NO rectification, are considered. Description of a new technique for high purification of nitrogen oxide, prepared at decomposition of nitric acid by sulfurous anhydride, suggested by the author is presented

Dual temperature effects on oxygen isotopic ratio of shallow-water coral skeleton: Consequences on seasonal and interannual records

Science.gov (United States)

Juillet-Leclerc, A.; Reynaud, S.

2009-04-01

Oxygen isotopic ratio from coral skeleton is regarded for a long time as promising climate archives at seasonal scale. Although in isotopic disequilibrium relative to seawater, it is supposed to obey to the isotope thermometer. Indeed, coral oxygen isotopic records are strongly temperature dependent, but d18O-temperature calibrations derived from different corals are highly variable. The isotope thermometer assumption does not take into account vital effects due to biogenic origin of the mineral. Corals are animals living in symbiosis with algae (zooxanthellae). Interactions between symbiont photosynthesis and coral skeleton carbonation have been abundantly observed but they remain poorly understood and the effects of photosynthesis on coral growth and skeleton oxygen ratio are ignored. Coral cultured under two light conditions enabled to relate metabolic parameters and oxygen isotopic variability with photosynthetic activity. By examining responses provided by each colony they revealed that photosynthesis significantly affected d18O, by an opposite sense compared with the sole temperature influence. Since temperature and light changes are associated during seasonal variations, this complicates the interpretation of seasonal record. Additionally, this complexity is amplified because photosynthetic activity is also directly impacted by temperature variability. Thus, the annual isotopic amplitude due to the "physical" temperature influence is partly compensated through photosynthesis. Similar opposite effect is also shown by extension rate of the cultured colonies. First, we will examine and quantify consequences of photosynthesis on growth rate and oxygen isotopic signature, from cultured corals. Second, we will consider the consequences of this vital effect on data series, at seasonal and interannual time scales.

A new route of oxygen isotope exchange in the solid phase: demonstration in CuSO4.5H2O.

Science.gov (United States)

Danon, Albert; Saig, Avraham; Finkelstein, Yacov; Koresh, Jacob E

2005-11-10

Temperature-programmed desorption mass spectrometry (TPD-MS) measurements on [(18)O]water-enriched copper sulfate pentahydrate (CuSO(4).5H(2)(18)O) reveal an unambiguous occurrence of efficient oxygen isotope exchange between the water of crystallization and the sulfate in its CuSO(4) solid phase. To the best of our knowledge, the occurrence of such an exchange was never observed in a solid phase. The exchange process was observed during the stepwise dehydration (50-300 degrees C) of the compound. Specifically, the exchange promptly occurs somewhere between 160 and 250 degrees C; however, the exact temperature could not be resolved conclusively. It is shown that only the fifth, sulfate-associated, anionic H(2)O molecule participates in the exchange process and that the exchange seems to occur in a preferable fashion with, at the most, one oxygen atom in SO(4). Such an exchange, occurring below 250 degrees C, questions the common conviction of unfeasible oxygen exchange under geothermic conditions. This new oxygen exchange phenomenon is not exclusive to copper sulfate but is unambiguously observed also in other sulfate- and nitrate-containing minerals.

Isotopic-spectral determination of hydrogen, nitrogen, oxygen and carbon in semiconductor materials

International Nuclear Information System (INIS)

Dudich, G.K.; Eremeev, V.A.; Li, V.N.; Nemets, V.M.

1981-01-01

Techniques of low-temperature isotopic-spectral determination of impurities of hydrogen, nitrogen, oxygen and carbon in semiconductor materials Bi, Ge, Pb tellurides are developed. The techniques include selection into special vessel with the known volume (exchanger) of sample analyzed, dosed introduction into exchanger of rare isotope of the element determined ( 2 H, 15 N, 18 O, 13 C) in the form of isotope-containing gas, balancing of the determined element isotopes in the system sample-isotope, containing gas, spectroscopic, determination of its isotope composition in gaseous phase of the system and calculation of the amount of the element determined in the sample. The lower boundaries of the amounts determined constitute 10 -7 , 10 -7 , 10 -6 and 10 -5 mass % respectively when sample of 20 g are used [ru

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.

Use of enriched {sup 74}Se and {sup 77}Se in combination with isotope pattern deconvolution to differentiate and determine endogenous and supplemented selenium in lactating rats

Energy Technology Data Exchange (ETDEWEB)

Gonzalez Iglesias, H.; Fernandez Sanchez, M.L.; Garcia Alonso, J.I.; Sanz-Medel, A. [University of Oviedo, Department of Physical and Analytical Chemistry, Faculty of Chemistry, Oviedo (Spain)

2007-10-15

A quantitative methodology has been developed to differentiate between endogenous and supplemented selenium in lactating rats using two enriched selenium isotopes. Lactating rats were fed for 2 weeks with formula milk containing one enriched Se isotope, {sup 77}Se, as the metabolic tracer. The isotopic composition of selenium in serum and urine samples was then measured by collision cell ICP-MS after the addition of a solution containing another enriched isotope, {sup 74}Se, as quantitation tracer, before analysis. Isotope pattern deconvolution allowed the transformation of measured Se isotopic abundances into concentrations of natural abundance (endogenous) selenium and enriched {sup 77}Se (supplemented) present in the samples. The proposed methodology was validated using serum and urine reference materials spiked with both {sup 77}Se and {sup 74}Se. The obtained results are discussed in terms of selenium exchange and half-life in lactating rats (11-12 days) and selenium levels in serum in comparison with non-supplemented rats and control rats after maternal feeding. (orig.)

Using Oxygen and Carbon Isotopic Signatures in Order to Infer Climatic and Dietary Information in Roman Edessa, Greece

Science.gov (United States)

Michael, Dimitra-Ermioni; Dotsika, Elissavet

2017-12-01

Even though many isotopic studies have been conducted on ancient populations from Greece for the purpose of dietary reconstruction; mostly through carbon and nitrogen isotopic signals of bone collagen, less attention has been given to the utility of apatite signatures (oxygen and carbon) as dietary and palaeoenvironmental tools. Moreover, until recently the isotopic signal of tooth enamel for both the purposes of environmental and dietary reconstructions has been rarely assessed in ancient Greek societies. Therefore, the present study aims to provide with novel isotopic information regarding Edessa; a town in Northern Greece, during the Roman period. The current study primarily aims to explore the possible differentiation between the present climatic conditions in Edessa in relation to those occurring at the Roman period. Secondly, this study aims to reveal the significant utility of enamel isotopic signatures (carbon and oxygen) in palaeoenvironmental and palaeodietary studies regarding ancient human remains. The isotopic analyses have been conducted at the Stable Isotope and Radiocarbon Unit of INN, NCSR “Demokritos”. The population of Roman Edessa (2nd-4th c. AD) consists of 22 individuals, providing with 19 bone samples and 16 enamel ones. The mean enamel oxygen value is at -7.7 ±1.1 %0, the bone apatite mean oxygen value at -9.2 ±1.9 %0, and finally the mean carbon enamel value is at -11.7 ±1.2 %0. Oxygen values probably indicate that Edessa had a cooler climate during the Roman times in relation to present conditions, even though more research should be carried out in order to be more certain. In addition, the possible existence of non-local individuals has been revealed through the oxygen teeth enamel-bone apatite spacing. Finally, the carbon enamel signature has pointed out possible differentiations between the adult and the juvenile diet. Based on Edessa’s findings, the stated study strongly encourages the enamel oxygen and carbon isotopic signals

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)

Wunderlich, Anja A.L.

2012-01-01

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.

Multiple taxon multiple locality approach to providing oxygen isotope evidence for warm-blooded theropod dinosaurs

Science.gov (United States)

Fricke, Henry C.; Rogers, Raymond R.

2000-09-01

Oxygen isotope ratios of fossil remains of coexisting taxa from several different localities can be used to help investigate dinosaur thermoregulation. Focusing on the Late Cretaceous, oxygen isotope ratios of crocodile tooth enamel from four separate localities exhibit less of a decrease with latitude than do ratios of tooth enamel from coexisting theropod dinosaurs. A shallower latitudinal gradient for crocodiles is consistent with how oxygen isotope ratios should vary for heterothermic animals having body temperatures coupled with their environments (“cold blooded”), while a steeper gradient for theropods is consistent with how these ratios should vary for homeothermic animals having constant body temperatures independent of their environments (“warm blooded”). This inferred homoethermy in theropods is likely due to higher rates of metabolic heat production relative to crocodiles and is not an artifact of body size.

Intracrystalline oxygen isotope effects in CuSO4.5H2O and their dependence on crystallization temperature

International Nuclear Information System (INIS)

Heinzinger, K.

1976-01-01

In copper sulphate pentahydrate the water molecules occupy three different sites, connected with different oxygen isotope ratios. Results of measurements of the change of these isotope ratios with crystallization temperature are reported. The temperature dependence found here provides the basis for the determination of crystallization temperatures of hydrated crystals from such intracrystalline oxygen isotope fractionation. Suppositions necessary for the application of this method are discussed. (author)

Oxygen isotope analysis of plant water without extraction procedure

International Nuclear Information System (INIS)

Gan, K.S.; Wong, S.C.; Farquhar, G.D.; Yong, J.W.H.

2001-01-01

Isotopic analyses of plant water (mainly xylem, phloem and leaf water) are gaming importance as the isotopic signals reflect plant-environment interactions, affect the oxygen isotopic composition of atmospheric O 2 and CO 2 and are eventually incorporated into plant organic matter. Conventionally, such isotopic measurements require a time-consuming process of isolating the plant water by azeotropic distillation or vacuum extraction, which would not complement the speed of isotope analysis provided by continuous-flow IRMS (Isotope-Ratio Mass Spectrometry), especially when large data sets are needed for statistical calculations in biological studies. Further, a substantial amount of plant material is needed for water extraction and leaf samples would invariably include unenriched water from the fine veins. To measure sub-microlitre amount of leaf mesophyll water, a new approach is undertaken where a small disc of fresh leaf is cut using a specially designed leaf punch, and pyrolysed directly in an IRMS. By comparing with results from pyrolysis of the dry matter of the same leaf, the 18 O content of leaf water can be determined without extraction from fresh leaves. This method is validated using a range of cellulose-water mixtures to simulate the constituents of fresh leaf. Cotton leaf water δ 18 O obtained from both methods of fresh leaf pyrolysis and azeotropic distillation will be compared. The pyrolysis technique provides a robust approach to measure the isotopic content of water or any volatile present in a homogeneous solution or solid hydrous substance

Oxygen diffusion in monazite

Science.gov (United States)

Cherniak, D. J.; Zhang, X. Y.; Nakamura, M.; Watson, E. B.

2004-09-01

We report measurements of oxygen diffusion in natural monazites under both dry, 1-atm conditions and hydrothermal conditions. For dry experiments, 18O-enriched CePO4 powder and monazite crystals were sealed in Ag-Pd capsules with a solid buffer (to buffer at NNO) and annealed in 1-atm furnaces. Hydrothermal runs were conducted in cold-seal pressure vessels, where monazite grains were encapsulated with 18O-enriched water. Following the diffusion anneals, oxygen concentration profiles were measured with Nuclear Reaction Analysis (NRA) using the reaction 18O(p,α)15N. Over the temperature range 850-1100 °C, the Arrhenius relation determined for dry diffusion experiments on monazite is given by: Under wet conditions at 100 MPa water pressure, over the temperature range 700-880 °C, oxygen diffusion can be described by the Arrhenius relationship: Oxygen diffusion under hydrothermal conditions has a significantly lower activation energy for diffusion than under dry conditions, as has been found the case for many other minerals, both silicate and nonsilicate. Given these differences in activation energies, the differences between dry and wet diffusion rates increase with lower temperatures; for example, at 600 °C, dry diffusion will be more than 4 orders of magnitude slower than diffusion under hydrothermal conditions. These disparate diffusivities will result in pronounced differences in the degree of retentivity of oxygen isotope signatures. For instance, under dry conditions (presumably rare in the crust) and high lower-crustal temperatures (∼800 °C), monazite cores of 70-μm radii will preserve O isotope ratios for about 500,000 years; by comparison, they would be retained at this temperature under wet conditions for about 15,000 years.

Control strategies for laser separation of carbon isotopes

Indian Academy of Sciences (India)

Laser isotope separation (LIS) by infrared laser chemistry of polyatomic molecules has come a long way since its discovery. The last decade has seen considerable efforts in scaling up of the process for light elements like carbon, oxygen and silicon. These efforts aim at ways to improve both the enrichment factor and the ...

Diffusion of hydrogen in yttrium

International Nuclear Information System (INIS)

Vorobyov, V.V.; Ryabchikov, L.N.

1966-01-01

In this work the diffusion coefficients of hydrogen in yttrium were determined from the rate at which the hydrogen was released from yttrium samples under a vacuum at temperatures of 450 to 850 0 C and from the quantity of hydrogen retained by yttrium at hydrogen pressures below 5 x 10 - 4 mm Hg in the same temperature range

Yttrium and lanthanides in human lung fluids, probing the exposure to atmospheric fallout

Energy Technology Data Exchange (ETDEWEB)

Censi, P., E-mail: censi@unipa.it [Dipartimento C.F.T.A., Universita di Palermo, Via Archirafi, 36 90123 - Palermo (Italy); I.A.M.C.-CNR - UOS di Capo Granitola, Via faro, 1 - 91026 Torretta Granitola, Campobello di Mazara (TP) (Italy); En.Bio.Tech. - Via Aquileia, 35 90100 Palermo (Italy); Tamburo, E. [Dipartimento C.F.T.A., Universita di Palermo, Via Archirafi, 36 90123 - Palermo (Italy); Speziale, S. [Deutsches GeoForschungsZentrum, Telegrafenberg, Potsdam, 14473 (Germany); Zuddas, P. [Institut Genie de l' Environnement et Ecodeveloppement and Departement Sciences de la Terre, UMR 5125, Universite Claude Bernard Lyon 1, 2 rue R. Dubois, Bat GEODE 69622 Villeurbanne Cedex (France); Randazzo, L.A. [Dipartimento C.F.T.A., Universita di Palermo, Via Archirafi, 36 90123 - Palermo (Italy); I.A.M.C.-CNR - UOS di Capo Granitola, Via faro, 1 - 91026 Torretta Granitola, Campobello di Mazara (TP) (Italy); En.Bio.Tech. - Via Aquileia, 35 90100 Palermo (Italy); Institut Genie de l' Environnement et Ecodeveloppement and Departement Sciences de la Terre, UMR 5125, Universite Claude Bernard Lyon 1, 2 rue R. Dubois, Bat GEODE 69622 Villeurbanne Cedex (France); Punturo, R. [Dipartimento di Scienze Geologiche, Universita di Catania, Corso Italia, 55 - 95129 Catania (Italy); Cuttitta, A. [I.A.M.C.-CNR - UOS di Capo Granitola, Via faro, 1 - 91026 Torretta Granitola, Campobello di Mazara (TP) (Italy); Arico, P. [Dipartimento C.F.T.A., Universita di Palermo, Via Archirafi, 36 90123 - Palermo (Italy)

2011-02-28

Inhalation of airborne particles can produce crystallization of phosphatic microcrysts in intraaveolar areas of lungs, sometimes degenerating into pulmonary fibrosis. Results of this study indicate that these pathologies are induced by interactions between lung fluids and inhaled atmospheric dust in people exposed to volcanic dust ejected from Mount Etna in 2001. Here, the lung solid-liquid interaction is evaluated by the distribution of yttrium and lanthanides (YLn) in fluid bronchoalveolar lavages on selected individuals according the classical geochemical approaches. We found that shale-normalised patterns of yttrium and lanthanides have a 'V shaped' feature corresponding to the depletion of elements from Nd to Tb when compared to the variable enrichments of heavy lanthanides, Y, La and Ce. These features and concurrent thermodynamic simulations suggest that phosphate precipitation can occur in lungs due to interactions between volcanic particles and fluids. We propose that patterns of yttrium and lanthanides can represent a viable explanation of some pathology observed in patients after prolonged exposure to atmospheric fallout and are suitable to become a diagnostic parameter of chemical environmental stresses.

Design of a formaldehyde photodissociation process for carbon and oxygen isotope separation

International Nuclear Information System (INIS)

Stern, R.C.; Scheibner, K.F.

1993-01-01

The current shortage of 18 O has revived interest in using one step UV photodissociation of formaldehyde to enrich 13 C, 17 O and 18 O. The frequency doubled output of the copper laser pumped dye laser system currently in operation at LLNL can be used to drive this dissociation. The authors use a simple kinetics model and their experience with Atomic Vapor Laser Isotope Separation (AVLIS) process design to examine the relative merits of different designs for a formaldehyde photodissociation process. Given values for the molecular photoabsorption cross section, partition function, spectroscopic selectivity, collisional exchange and quenching cross sections (all as parameters), they perform a partial optimization in the space of illuminated area, formaldehyde pressure in each stage, and formaldehyde residence time in each stage. They examine the effect of cascade design (heads and tails staging) on molecule and photon utilization for each of the three isotope separation missions, and look in one case at the system's response to different ratios of laser to formaldehyde costs. Finally, they examine the relative cost of enrichment as a function of isotope and product assay. Emphasis is as much on the process design methodology, which is general, as on the specific application to formaldehyde

Evaluation of the performance of high temperature conversion reactors for compound-specific oxygen stable isotope analysis.

Science.gov (United States)

Hitzfeld, Kristina L; Gehre, Matthias; Richnow, Hans-Hermann

2017-05-01

In this study conversion conditions for oxygen gas chromatography high temperature conversion (HTC) isotope ratio mass spectrometry (IRMS) are characterised using qualitative mass spectrometry (IonTrap). It is shown that physical and chemical properties of a given reactor design impact HTC and thus the ability to accurately measure oxygen isotope ratios. Commercially available and custom-built tube-in-tube reactors were used to elucidate (i) by-product formation (carbon dioxide, water, small organic molecules), (ii) 2nd sources of oxygen (leakage, metal oxides, ceramic material), and (iii) required reactor conditions (conditioning, reduction, stability). The suitability of the available HTC approach for compound-specific isotope analysis of oxygen in volatile organic molecules like methyl tert-butyl ether is assessed. Main problems impeding accurate analysis are non-quantitative HTC and significant carbon dioxide by-product formation. An evaluation strategy combining mass spectrometric analysis of HTC products and IRMS 18 O/ 16 O monitoring for future method development is proposed.

Stratigraphy on Oxygen and Carbon Isotope of Paciran Formation East Java

International Nuclear Information System (INIS)

Premonowati; R P Koesoemadinata; Harsono-Pringgoprawiro; Wahyoe-S-Hantoro

2004-01-01

Paleotemperature fluctuation in tropical zone (centennial and decad al scale) has been known. It's based on stable isotopic analysis from each of unconformity zones. Those boundaries have derived on reef units of shallows marine reef complex of Paciran Formation, Tuban area in Northeast Java Basin. From 25 samples have been choosen on undeformed calcite and analyzed by oxygen and carbon stable isotope. It used to validizing a sea level changes during the formation to Reef 1 to Reef 17 from Paciran formation with sea surface temperature (SST) since 4 Ma until now. On early forming of Reef 1 to Reef 3 (since 4 Ma - 2,88 Ma), sea level occurred marine flooding surface. Since the formation of reef 4 (2,59 Ma) to Reef 8 (1,4 Ma) occurred stagnant temperature and almost to warmer condition. Then, δ 18 O have arise up drastically to 5 0/00 and shows warmer condition to Reef 8 formation, in contrary, the sea level have been arised to Reef 10 formation (0,7 Ma). The temperature have been fluctuated between 0,5 o and 1 o C until the formation of Reef 17 (Early Holocene) and continued to Reef 17 formation at 2 o C based on the rapidity sampling of Po rites sp. Wholly, in centennial scale, since the formation of Reef 4 (2,59 Ma) to Reef 17 (1 Ma), the curve of oxygen stable isotope shows decrease or cooler condition. Those condition have conducted to sea level drop since the formation to Reef 7 and Reef 8. There are 4 periods of interglacial since the formation of Reef 4. The warmer condition indicated since the formation of Reef 9, Reef 11 and Reef 17. Recently, a curve of oxygen isotopes reveals warmer drastically or sea level have been arisen. (author)

Test Operation of Oxygen-Enriched Incinerator for Wastes From Nuclear Fuel Fabrication Facility

International Nuclear Information System (INIS)

Kim, J.-G.; Yang, H.cC.; Park, G.-I.; Kim, I.-T.; Kim, J.-K.

2002-01-01

The oxygen-enriched combustion concept, which can minimize off-gas production, has been applied to the incineration of combustible uranium-containing wastes from a nuclear fuel fabrication facility. A simulation for oxygen combustion shows the off-gas production can be reduced by a factor of 6.7 theoretically, compared with conventional air combustion. The laboratory-scale oxygen enriched incineration (OEI) process with a thermal capacity of 350 MJ/h is composed of an oxygen feeding and control system, a combustion chamber, a quencher, a ceramic filter, an induced draft fan, a condenser, a stack, an off-gas recycle path, and a measurement and control system. Test burning with cleaning paper and office paper in this OEI process shows that the thermal capacity is about 320 MJ/h, 90 % of design value and the off-gas reduces by a factor of 3.5, compared with air combustion. The CO concentration for oxygen combustion is lower than that of air combustion, while the O2 concentration in off-gas is kept above 25 vol % for a simple incineration process without any grate. The NOx concentration in an off-gas stream does not reduce significantly due to air incoming by leakage, and the volume and weight reduction factors are not changed significantly, which suggests a need for an improvement in sealing

Effect of administration of water enriched in O2 by injection or electrolysis on transcutaneous oxygen pressure in anesthetized pigs.

Science.gov (United States)

Charton, Antoine; Péronnet, François; Doutreleau, Stephane; Lonsdorfer, Evelyne; Klein, Alexis; Jimenez, Liliana; Geny, Bernard; Diemunsch, Pierre; Richard, Ruddy

2014-01-01

Oral administration of oxygenated water has been shown to improve blood oxygenation and could be an alternate way for oxygen (O2) supply. In this experiment, tissue oxygenation was compared in anesthetized pigs receiving a placebo or water enriched in O2 by injection or a new electrolytic process. Forty-two pigs randomized in three groups received either mineral water as placebo or water enriched in O2 by injection or the electrolytic process (10 mL/kg in the stomach). Hemodynamic parameters, partial pressure of oxygen in the arterial blood (PaO2), skin blood flow, and tissue oxygenation (transcutaneous oxygen pressure, or TcPO2) were monitored during 90 minutes of general anesthesia. Absorption and tissue distribution of the three waters administered were assessed using dilution of deuterium oxide. Mean arterial pressure, heart rate, PaO2, arteriovenous oxygen difference, and water absorption from the gut were not significantly different among the three groups. The deuterium to protium ratio was also similar in the plasma, skin, and muscle at the end of the protocol. Skin blood flow decreased in the three groups. TcPO2 slowly decreased over the last 60 minutes of the experiment in the three groups, but when compared to the control group, the values remained significantly higher in animals that received the water enriched in O2 by electrolysis. In this protocol, water enriched in O2 by electrolysis lessened the decline of peripheral tissue oxygenation. This observation is compatible with the claim that the electrolytic process generates water clathrates which trap O2 and facilitate O2 diffusion along pressure gradients. Potential applications of O2-enriched water include an alternate method of oxygen supply.

Research of catalysts for isotope enrichment of deuterium oxide in water - PX15-01/89 progress report

International Nuclear Information System (INIS)

1989-08-01

The information about the development of research project for producing concentrate deuterium oxide by isotope enrichment in hydrogen-water contact systems combined with electrolysis are described. (C.G.C.)

Sulphur isotope variations in the atmosphere

International Nuclear Information System (INIS)

Newman, L.; Krouse, H.R.; Grinenko, V.A.

1991-01-01

The measurement of the isotope ratios of sulphur and oxygen can in principal be used to assess sulphur inputs into, transformation within, and removal from the atmosphere. Major inputs arise from both anthropogenic and biogenic activities. Transformations arise from oxidation, neutralization, and other chemical reactions. Advection causes dilution and the main removal processes are dry deposition (governed by gravitation and diffusion) and rain. The admixture of sources can be discerned from their isotopic signatures whereas transformations and removal can be followed from the isotopic fractionation that might occur. In this chapter, the atmospheric sulphur cycle and the associated chemistry are summarized. Also presented is information on natural isotopic variations and fundamental concepts relating to the use of isotopic data to delineate anthropogenic S in the atmosphere. Examples of successful applications of these concepts are given. Finally, consideration is given to the potential of using isotopically enriched sulphur to study transport and transformation of atmospheric S compounds. Refs, figs and tabs

Influence of organic carbon sources and isotope exchange processes between water and nitrate on the fractionation of the stable isotopes {sup 15}N/{sup 14}N and {sup 18}O/{sup 16}O in dissolved nitrate during microbial dentrification in groundwater

Energy Technology Data Exchange (ETDEWEB)

Wunderlich, Anja A.L.

2012-11-02

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.

Technical note: Consistent calculation of aquatic gross production from oxygen triple isotope measurements

Directory of Open Access Journals (Sweden)

J. Kaiser

2011-07-01

Full Text Available Oxygen triple isotope measurements can be used to calculate aquatic gross oxygen production rates. Past studies have emphasised the appropriate definition of the ¹⁷O excess and often used an approximation to derive production rates from the ¹⁷O excess. Here, I show that the calculation can be phrased more consistently and without any approximations using the relative ¹⁷O/¹⁶O and ¹⁸O/¹⁶O isotope ratio differences (delta values directly. I call this the "dual delta method". The ¹⁷O excess is merely a mathematical construct and the derived production rate is independent of its definition, provided all calculations are performed with a consistent definition. I focus on the mixed layer, but also show how time series of triple isotope measurements below the mixed layer can be used to derive gross production.

In the calculation of mixed layer productivity, I explicitly include isotopic fractionation during gas invasion and evasion, which requires the oxygen supersaturation s to be measured as well. I also suggest how bubble injection could be considered in the same mathematical framework. I distinguish between concentration steady state and isotopic steady state and show that only the latter needs to be assumed in the calculation. It is even possible to derive an estimate of the net production rate in the mixed layer that is independent of the assumption of concentration steady state.

I review measurements of the parameters required for the calculation of gross production rates and show how their systematic uncertainties as well as the use of different published calculation methods can cause large variations in the production rates for the same underlying isotope ratios. In particular, the ¹⁷O excess of dissolved O₂ in equilibrium with atmospheric O₂ and the ¹⁷O excess of photosynthetic O₂ need to

Preliminary analysis of 500 MWt MHD power plant with oxygen enrichment

Science.gov (United States)

1980-04-01

An MHD Engineering Test Facility design concept is analyzed. A 500 MWt oxygen enriched MHD topping cycle integrated for combined cycle operation with a 400 MWe steam plant is evaluated. The MHD cycle uses Montana Rosebud coal and air enriched to 35 mole percent oxygen preheated to 1100 F. The steam plant is a 2535 psia/1000 F/1000 F reheat recycle that was scaled down from the Gilbert/Commonwealth Reference Fossil Plant design series. Integration is accomplished by blending the steam generated in the MHD heat recovery system with steam generated by the partial firing of the steam plant boiler to provide the total flow requirement of the turbine. The major MHD and steam plant auxiliaries are driven by steam turbines. When the MHD cycle is taken out of service, the steam plant is capable of stand-alone operation at turbine design throttle flow. This operation requires the full firing of the steam plant boiler. A preliminary feasibility assessment is given, and results on the system thermodynamics, construction scheduling, and capital costs are presented.

Constraining the Final Fates of Massive Stars by Oxygen and Iron Enrichment History in the Galaxy

Science.gov (United States)

Suzuki, Akihiro; Maeda, Keiichi

2018-01-01

Recent observational studies of core-collapse supernovae suggest that only stars with zero-age main-sequence masses smaller than 16–18 {M}ȯ explode when they are red supergiants, producing Type IIP supernovae. This may imply that more massive stars produce other types of supernovae or they simply collapse to black holes without giving rise to bright supernovae. This failed supernova hypothesis can lead to significantly inefficient oxygen production because oxygen abundantly produced in inner layers of massive stars with zero-age main-sequence masses around 20–30 {M}ȯ might not be ejected into the surrounding interstellar space. We first assume an unspecified population of oxygen injection events related to massive stars and obtain a model-independent constraint on how much oxygen should be released in a single event and how frequently such events should happen. We further carry out one-box galactic chemical enrichment calculations with different mass ranges of massive stars exploding as core-collapse supernovae. Our results suggest that the model assuming that all massive stars with 9–100 {M}ȯ explode as core-collapse supernovae is still most appropriate in explaining the solar abundances of oxygen and iron and their enrichment history in the Galaxy. The oxygen mass in the Galaxy is not explained when assuming that only massive stars with zero-age main-sequence masses in the range of 9–17 {M}ȯ contribute to the galactic oxygen enrichment. This finding implies that a good fraction of stars more massive than 17 {M}ȯ should eject their oxygen layers in either supernova explosions or some other mass-loss processes.

Quasi-free one nucleon knockout reactions on neutron-rich oxygen isotopes

Energy Technology Data Exchange (ETDEWEB)

Atar, Leyla; Aumann, Thomas [TU Darmstadt, Darmstadt (Germany); GSI, Darmstadt (Germany); Bertulani, Carlos [Texas A and M University-Commerce, Commerse (United States); Paschalis, Stefanos [TU Darmstadt, Darmstadt (Germany); Nociforo, Chiara [GSI, Darmstadt (Germany); Collaboration: R3B-Collaboration

2015-07-01

Recent experiments have shown a reduction of spectroscopic strengths to about 60-70% for stable nuclei. When going to drip lines this tendency is changing, loosely bound nucleons have spectroscopic strengths close unity while deeply bound nucleons have a large reduction of the strength. We aim to make a systematic study of spectroscopic factors (SF) of the Oxygen isotopes using quasi-free (p,2p) and (p,pn) knockout reactions in inverse kinematics. Quasi-free knockout reactions are a direct tool to study the occupancy and the location of valance and deeply bound single particle states. The Oxygen isotopes offer a large variation of separation energies which will allow us to obtain a qualitative and quantitative understanding of SF in a large variation of isospin asymmetry. For this we performed an experiment at the R3B-LAND setup at the GSI with secondary beams containing {sup 14-24}O. The {sup 16-18}O and {sup 21-23}O isotopes have been analyzed and the preliminary results will be presented. The results include the partial cross sections, gamma ray spectra of the residual fragments in coincidence, and the SF obtained via comparison with theory.

Stable isotope ratio measurements on highly enriched water samples by means of laser spectrometry

NARCIS (Netherlands)

van Trigt, R; Kerstel, E.R.T.; Visser, GH; Meijer, H.A.J.

2001-01-01

We demonstrate the feasibility of using laser spectrometry (LS) to analyze isotopically highly enriched water samples (i.e., delta H-2 less than or equal to 15000 parts per thousand, delta O-18 less than or equal to 1200 parts per thousand), as often used in the biomedical doubly labeled water (DLW)

Texture and deformation mechanism of yttrium

International Nuclear Information System (INIS)

Adamesku, R.A.; Grebenkin, S.V.; Stepanenko, A.V.

1992-01-01

X-ray pole figure analysis was applied to study texture and deformation mechanism in pure and commercial polycrystalline yttrium on cold working. It was found that in cast yttrium the texture manifected itself weakly enough both for pure and commercial metal. Analysis of the data obtained made it possible to assert that cold deformation of pure yttrium in the initial stage occurred mainly by slip the role of which decreased at strains higher than 36%. The texture of heavily deformed commercial yttrium contained two components, these were an 'ideal' basic orientation and an axial one with the angle of inclination about 20 deg. Twinning mechanism was revealed to be also possible in commercial yttrium

Scattering of polarized protons by yttrium, iron and nickel nuclei

International Nuclear Information System (INIS)

Melssen, J.P.M.G.

1978-01-01

Results are presented of scattering experiments performed on yttrium and some iron and nickel isotopes with polarized proton beams at energies around 20 MeV. The angular distributions of the differential cross sections and analyzing powers have been measured and comparison of these with predictions from theoretical models has led to information about excited nuclear states like spin, parity and details of the wavefunctions. The DWBA has been mostly used to describe the reaction at the bombarding energies and for the target nuclei investigated. (C.F.)

Oxygen isotope partitioning between rhyolitic glass/melt and CO2: An experimental study at 550-950 degrees C and 1 bar

International Nuclear Information System (INIS)

Palin, J.M.; Epstein, S.; Stolper, E.M.

1996-01-01

Oxygen isotope partitioning between gaseous CO 2 and a natural rhyolitic glass and melt (77.7 wt% SiO 2 , 0.16 wt% H 2 O total ) has been measured at 550-950 degrees C and approximately 1 bar. Equilibrium oxygen isotope fractionation factors (α CO2-rhyolite = ( 18 O/ 16 O) rhyolite ) determined in exchange experiments of 100-255 day duration. These values agree well with predictions based on experimentally determined oxygen isotope fractionation factors for CO 2 -silica glass and CO 2 -albitic glass/melt, if the rhyolitic glass is taken to be a simple mixture of normative silica and alkali feldspar components. The results indicate that oxygen isotope partitioning in felsic glasses and melts can be modeled by linear combinations of endmember silicate constituents. Rates of oxygen isotope exchange observed in the partitioning experiments are consistent with control by diffusion of molecular H 2 O dissolved in the glass/melt and are three orders of magnitude faster than predicted for rate control solely by diffusion of dissolved molecular CO 2 under the experimental conditions. Additional experiments using untreated and dehydrated (0.09 wt% H 2 O total ) rhyolitic glass quantatively support these interpretations. We conclude that diffusive oxygen isotope exchange in rhyolitic glass/melt, and probably other polymerized silicate materials, it controlled by the concentrations and diffusivities of dissolved oxygen-bearing volatile species rather than diffusion of network oxygen under all but the most volatile-poor conditions. 25 refs., 6 figs., 1 tab

Non-mass-dependent fractionation of sulfur and oxygen isotopes during UV photolysis of sulfur dioxide

Science.gov (United States)

Pen, Aranh

Since the discovery of anomalous sulfur isotope abundance in the geological record in sulfate and sulfide minerals (Farquhar et al., 2000), much effort has been put into understanding their origin to provide new insights into the environmental conditions on the early Earth (Farquhar et al., 2001; Pavlov and Kasting, 2002; Ono et al., 2003; Zahnle et al., 2006; Farquhar et al., 2007; Lyons, 2007; Lyons, 2008). This discovery gained immense interest because of its implications for both the lack of oxygen in the atmosphere during the Archean era 2.5-3.8 Gya (billion years ago), and for rise of oxygen, or the "Great Oxidation Event", that occurred 2.2-2.4 Gya (Holland, 2002). These signatures are believed to be produced in an anticorrelation to oxygen abundance in the early atmosphere, which will aid in quantifying the rate of oxygenation during the "Great Oxidation Event". According to Farquhar et al. (2000), the non-mass-dependent (NMD), or anomalous, fractionation signatures were produced by photochemical reactions of volcanic sulfur species in Earth's early atmosphere (> 2.3 Gya) due to the lack of an oxygen and ozone shield, resulting in an atmosphere transparent to solar ultraviolet (UV) radiation (Farquhar et al., 2001). Interpretation of the anomalous rock records, though, depends on the identification of (1) chemical reactions that can produce the NMD signature (Farquhar and Wing, 2003); and (2) conditions necessary for conversion of the gas-phase products into solid minerals (Pavlov and Kasting, 2002). The focus of my research addresses the first step, which is to determine whether the chemical reactions that occurred in Earth's early atmosphere, resulting in NMD fractionation of sulfur isotopes, were due to broadband UV photochemistry, and to test isotopic self-shielding as the possible underlying mechanism. In this project, our goals were to test isotopic self-shielding during UV photolysis as a possible underlying mechanism for anomalous sulfur isotopic

Investigation of mercury-containing proteins by enriched stable isotopic tracer and size-exclusion chromatography hyphenated to inductively coupled plasma-isotope dilution mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Shi Junwen [Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)]|[Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Feng Weiyue [Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)]. E-mail: fengwy@mail.ihep.ac.cn; Wang Meng [Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)]|[Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Zhang Fang [Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Li Bai [Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wang Bing; Zhu Motao [Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)]|[Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Chai Zhifang [Laboratory for Bio-Environmental Health Sciences of Nanoscale Materials and Key Laboratory of Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)]|[Institute of Nuclear Technology, Shenzhen University, Shenzhen 518060 (China)]|[Institute of Nanochemistry and Nanosafety, Shanghai University, Shanghai (China)

2007-01-30

In order to investigate trace mercury-containing proteins in maternal rat and their offspring, a method of enriched stable isotopic tracer ({sup 196}Hg and {sup 198}Hg) combined with size-exclusion chromatography (SEC) coupled to inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS) was developed. Prior to the analysis, {sup 196}Hg- and {sup 198}Hg-enriched methylmercury was administrated to the pregnant rats. Then the mercury-containing proteins in serum and brain cytosol of the dam and pup rats were separated by size-exclusion columns and the mercury was detected by ICP-MS. The ICP-MS spectrogram of the tracing samples showed significantly elevated {sup 196}Hg and {sup 198}Hg isotopic signals compared with the natural ones, indicating that the detection sensitivity could be increased by the tracer method. The contents of mercury in chromatographic fractions of the dam and pup rat brain cytosol were quantitatively estimated by post-column reverse ID-ICP-MS. The quantitative speciation differences of mercury in brain cytosol between the dam and pup rats were observed, indicating that such studies could be useful for toxicological estimation. Additionally, the isotopic ratio measurement of {sup 198}Hg/{sup 202}Hg in the tracing samples could be used to identify the artifact mercury species caused in the analytical procedure. The study demonstrates that the tracer method combined with high-performance liquid chromatography (HPLC)-ICP-IDMS could provide reliably qualitative and quantitative information on mercury-containing proteins in organisms.

Investigation of mercury-containing proteins by enriched stable isotopic tracer and size-exclusion chromatography hyphenated to inductively coupled plasma-isotope dilution mass spectrometry

International Nuclear Information System (INIS)

Shi Junwen; Feng Weiyue; Wang Meng; Zhang Fang; Li Bai; Wang Bing; Zhu Motao; Chai Zhifang

2007-01-01

In order to investigate trace mercury-containing proteins in maternal rat and their offspring, a method of enriched stable isotopic tracer ( 196 Hg and 198 Hg) combined with size-exclusion chromatography (SEC) coupled to inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS) was developed. Prior to the analysis, 196 Hg- and 198 Hg-enriched methylmercury was administrated to the pregnant rats. Then the mercury-containing proteins in serum and brain cytosol of the dam and pup rats were separated by size-exclusion columns and the mercury was detected by ICP-MS. The ICP-MS spectrogram of the tracing samples showed significantly elevated 196 Hg and 198 Hg isotopic signals compared with the natural ones, indicating that the detection sensitivity could be increased by the tracer method. The contents of mercury in chromatographic fractions of the dam and pup rat brain cytosol were quantitatively estimated by post-column reverse ID-ICP-MS. The quantitative speciation differences of mercury in brain cytosol between the dam and pup rats were observed, indicating that such studies could be useful for toxicological estimation. Additionally, the isotopic ratio measurement of 198 Hg/ 202 Hg in the tracing samples could be used to identify the artifact mercury species caused in the analytical procedure. The study demonstrates that the tracer method combined with high-performance liquid chromatography (HPLC)-ICP-IDMS could provide reliably qualitative and quantitative information on mercury-containing proteins in organisms

Pathways of CH3Hg and Hg ingestion in benthic organisms: an enriched isotope approach.

Science.gov (United States)

Taylor, Vivien F; Bugge, Deenie; Jackson, Brian P; Chen, Celia Y

2014-05-06

Mercury is a widespread contaminant in marine food webs, and identifying uptake pathways of mercury species, CH3Hg(+) and Hg(2+), into low trophic level organisms is important to understanding its entry into marine food webs. Enriched stable isotope tracers were used to study benthic vs. pelagic pathways of CH3Hg(+) and Hg(2+) uptake via food to the infaunal estuarine amphipod, Leptocheirus plumulosus. Algal cells differentially labeled with isotopically enriched CH3Hg(+) or Hg(2+) were added simultaneously to the sediment and water column of microcosms, and Hg species were monitored in amphipods and in sediment and water compartments. Methylation of Hg(2+) occurred during the course of the experiment, enhancing the uptake of Hg(2+) spikes. Trophic transfer of Hg from algae added to the water column was determined to be the major uptake route for amphipods, suggesting inputs of contaminated organic matter from the pelagic zone are important to mercury bioaccumulation even in organisms living in sediments.

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.

Leaf water 18 O and 2 H enrichment along vertical canopy profiles in a broadleaved and a conifer forest tree.

Science.gov (United States)

Bögelein, Rebekka; Thomas, Frank M; Kahmen, Ansgar

2017-07-01

Distinguishing meteorological and plant-mediated drivers of leaf water isotopic enrichment is prerequisite for ecological interpretations of stable hydrogen and oxygen isotopes in plant tissue. We measured input and leaf water δ 2 H and δ 18 O as well as micrometeorological and leaf morpho-physiological variables along a vertical gradient in a mature angiosperm (European beech) and gymnosperm (Douglas fir) tree. We used these variables and different enrichment models to quantify the influence of Péclet and non-steady state effects and of the biophysical drivers on leaf water enrichment. The two-pool model accurately described the diurnal variation of leaf water enrichment. The estimated unenriched water fraction was linked to leaf dry matter content across the canopy heights. Non-steady state effects and reduced stomatal conductance caused a higher enrichment of Douglas fir compared to beech leaf water. A dynamic effect analyses revealed that the light-induced vertical gradients of stomatal conductance and leaf temperature outbalanced each other in their effects on evaporative enrichment. We conclude that neither vertical canopy gradients nor the Péclet effect is important for estimates and interpretation of isotopic leaf water enrichment in hypostomatous trees. Contrarily, species-specific non-steady state effects and leaf temperatures as well as the water vapour isotope composition need careful consideration. © 2017 John Wiley & Sons Ltd.

Oxygen isotopic analyses of individual planktic foraminifera species: Implications for seasonality in the western Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

Naidu, P.D.; Niitsuma, N.; Naik, S.S.

The variation of stable isotopes between individual shells of planktic foraminifera of a given species and size may provide short-term seasonal insight on Paleoceanography. In this context, oxygen isotope analyses of individual Globigerinoides...

Fabrication of dense yttrium oxyfluoride ceramics by hot pressing and their mechanical, thermal, and electrical properties

Science.gov (United States)

Tahara, Ryuki; Tsunoura, Toru; Yoshida, Katsumi; Yano, Toyohiko; Kishi, Yukio

2018-06-01

Excellent corrosion-resistant materials have been strongly required to reduce particle contamination during the plasma process in semiconductor production. Yttrium oxyfluoride can be a candidate as highly corrosion-resistant material. In this study, three types of dense yttrium oxyfluoride ceramics with different oxygen contents, namely, YOF, Y5O4F7 and Y5O4F7 + YF3, were fabricated by hot pressing, and their mechanical, thermal, and electrical properties were evaluated. Y5O4F7 ceramics showed an excellent thermal stability up to 800 °C, a low loss factor, and volume resistivity comparable to conventional plasma-resistant oxides, such as Y2O3. From these results, yttrium oxyfluoride ceramics are strongly suggested to be used as electrostatic chucks in semiconductor production.

Measurement of infiltration rates in urban sewer systems by use of oxygen isotopes.

Science.gov (United States)

De Bénédittis, J; Bertrand-Krajewski, J L

2005-01-01

The paper presents the principle of a method to measure infiltration rates in sewer systems based on the use of oxygen isotopes and its application in Lyon (France). In the urban area of Lyon, significant differences in delta 18O that can reach 3 per thousand are observed between the oxygen isotopic compositions of groundwater originating from Rhone, Saone and from their associated alluvial aquifers. Drinking water supplying Lyon results mainly from pumping in the Rhone alluvial aquifer. Therefore, in some areas, the difference of isotopic composition between wastewater resulting from the consumption of drinking water and local groundwater can be used to measure infiltration in sewer systems. The application in the catchment of Ecully shows that the infiltration flow rate presents strong fluctuations at an hourly scale: it varies between 15 and 40 m3/h. This variability could be explained by non-constant discharges of pumping and by variations of the water level in the sewer.

Stable isotopes applied as water tracers for infiltration experiment

International Nuclear Information System (INIS)

Liu Xiaoyan; Chen Jiansheng; Sun Xiaoxu; Su Zhiguo

2011-01-01

The δD and δ 18 O vertical profiles of soil water were measured prior to and after a rainfall event. Mechanisms of soil water movement were deciphered by comparing the soil water isotope profiles with the isotopic composition of precipitation. The results show that evaporation at the upper depth led to enrichment of the heavy isotopes. Compared to the loess profile, the shallow soil water of sand profile is relatively enriched in D and 18 O due to macro-pore and low water-holding capacity. The precipitation is infiltrated into soil in piston mode, accompanied with significant mixing of older soil water. The preferential fluid flow in loess was observed at depths of 0-20 cm, caused by cracks in the depths. The hydrogen and oxygen isotopic compositions in outflow are close to the precipitation, which shows a mixing of the precipitation and old soil water, and indicates that the isotopic composition of outflow water is mainly controlled by that of the precipitation. The δD and δ 18 O in outflow decreased with time until stable δ values of outflow are close to those of the precipitation. (authors)

Triple oxygen isotope systematics of structurally bonded water in gypsum

Science.gov (United States)

Herwartz, Daniel; Surma, Jakub; Voigt, Claudia; Assonov, Sergey; Staubwasser, Michael

2017-07-01

The triple oxygen isotopic composition of gypsum mother water (gmw) is recorded in structurally bonded water in gypsum (gsbw). Respective fractionation factors have been determined experimentally for 18O/16O and 17O/16O. By taking previous experiments into account we suggest using 18αgsbw-gmw = 1.0037; 17αgsbw-gmw = 1.00195 and θgsbw-gmw = 0.5285 as fractionation factors in triple oxygen isotope space. Recent gypsum was sampled from a series of 10 ponds located in the Salar de Llamara in the Atacama Desert, Chile. Total dissolved solids (TDS) in these ponds show a gradual increase from 23 g/l to 182 g/l that is accompanied by an increase in pond water 18O/16O. Gsbw falls on a parallel curve to the ambient water from the saline ponds. The offset is mainly due to the equilibrium fractionation between gsbw and gmw. However, gsbw represents a time integrated signal biased towards times of strong evaporation, hence the estimated gmw comprises elevated 18O/16O compositions when compared to pond water samples taken on site. Gypsum precipitation is associated with algae mats in the ponds with lower salinity. No evidence for respective vital effects on the triple oxygen isotopic composition of gypsum hydration water is observed, nor are such effects expected. In principle, the array of δ18Ogsbw vs. 17Oexcess can be used to: (1) provide information on the degree of evaporation during gypsum formation; (2) estimate pristine meteoric water compositions; and (3) estimate local relative humidity which is the controlling parameter of the slope of the array for simple hydrological situations. In our case study, local mining activities may have decreased deep groundwater recharge, causing a recent change of the local hydrology.

Modeling the effects of late cycle oxygen enrichment on diesel engine combustion and emissions

International Nuclear Information System (INIS)

Mather, D. K.; Foster, D. E.; Poola, R. B.; Longman, D. E.; Chanda, A.; Vachon, T. J.

2002-01-01

A multidimensional simulation of Auxiliary Gas Injection (AGI) for late cycle oxygen enrichment was exercised to assess the merits of AGI for reducing the emissions of soot from heavy duty diesel engines while not adversely affecting the NO(sub x) emissions of the engine. Here, AGI is the controlled enhancement of mixing within the diesel engine combustion chamber by high speed jets of air or another gas. The engine simulated was a Caterpillar 3401 engine. For a particular operating condition of this engine, the simulated soot emissions of the engine were reduced by 80% while not significantly affecting the engine-out NO(sub x) emissions compared to the engine operating without AGI. The effects of AGI duration, timing, and orientation are studied to confirm the window of opportunity for realizing lower engine-out soot while not increasing engine out NO(sub x) through controlled enhancement of in-cylinder mixing. These studies have shown that this window occurs during the late combustion cycle, from 20 to 60 crank angle degrees after top-dead-center. During this time, the combustion chamber temperatures are sufficiently high that soot oxidation increases in response in increased mixing, but the temperature is low enough that NO(sub x) reactions are quenched. The effect of the oxygen composition of the injected air is studied for the range of compositions between 21% and 30% oxygen by volume. This is the range of oxygen enrichment that is practical to produce from an air separation membrane. Simulations showed that this level of oxygen enrichment is insufficient to provide an additional benefit by either increasing the level of soot oxidation or prolonging the window of opportunity for increasing soot oxidation through enhanced mixing

Simultaneous speciation of endogenous and exogenous elements by HPLC/ICP-MS with enriched stable isotopes

International Nuclear Information System (INIS)

Suzuki, K.T.

1996-01-01

High performance liquid chromatography (HPLC)/inductively coupled argon plasma-mass spectrometry (ICP-MS) was introduced to investigate the distributions of selenium (Se) in biological fluids. The method was to determine both the natural abundance of Se and an enriched stable isotope of Se used as a tracer. The distributions of Se in plasma and in urine specimens were determined in Wistar rats on various Se diets with and without an intravenous injection of 82 Se-selenite. Although the distribution of natural abundance Se (endogenous Se) in the plasma was affected little by the nutritional status of Se, that in the urine gave a Se peak depending on the nutritional status of Se, and the peak was identified as methylselenol. When 82 Se-selenite was injected in excess into rats given three different Se diets (Se-deficient, Se-adequate, Se-excessive), three Se peaks occurred in the HPLC chromatogram of the urine samples, corresponding to selenite, methylselenol and trimethylselenonium ion in the order of elution, and the intensities of the tracer peaks reflected the nutritional status. These results indicate that the HPLC/ICP-MS method is a powerful analytical tool for specifying Se-containing biological constituents, both natural abundance and enriched stable isotopes. Methylselenol in urine is proposed to be a sensitive and Se-specific biological indicator for diagnosing the nutritional status of Se. Furthermore, it was shown that an enriched stable isotope such as 82 Se-selenite was shown to be used for the same purpose, and that 82 Se-methylselenol and 82 Se-trimethylselenonium ion in urine were more sensitive indicators of the Se status of the rats. (author)

Triple oxygen isotopes in biogenic and sedimentary carbonates

Science.gov (United States)

Passey, Benjamin H.; Hu, Huanting; Ji, Haoyuan; Montanari, Shaena; Li, Shuning; Henkes, Gregory A.; Levin, Naomi E.

2014-09-01

The 17O anomaly (Δ17O) of natural waters has been shown to be sensitive to evaporation in a way analogous to deuterium excess, with evaporated bodies of water (e.g., leaf waters, lake waters, animal body waters) tending to have lower Δ17O than primary meteoric waters. In animal body water, Δ17O relates to the intake of evaporated waters, evaporative effluxes of water, and the Δ17O value of atmospheric O2, which itself carries signatures of global carbon cycling and photochemical reactions in the stratosphere. Carbonates have the potential to record the triple oxygen isotope compositions of parent waters, allowing reconstruction of past water compositions, but such investigations have awaited development of methods for high-precision measurement of Δ17O of carbonate. We describe optimized methods based on a sequential acid digestion/reduction/fluorination approach that yield Δ17O data with the high precision (∼0.010‰, 1σ) needed to resolve subtle environmental signals. We report the first high-precision Δ17O dataset for terrestrial carbonates, focusing on vertebrate biogenic carbonates and soil carbonates, but also including marine invertebrates and high-temperature carbonates. We determine apparent three-isotope fractionation factors between the O2 analyte derived from carbonate and the parent waters of the carbonate. These in combination with appropriate temperature estimates (from clumped isotope thermometry, or known or estimated body temperatures) are used to calculate the δ18O and Δ17O of parent waters. The clearest pattern to emerge is the strong 17O-depletion in avian, dinosaurian, and mammalian body water (from analyses of eggshell and tooth enamel) relative to meteoric waters, following expected influences of evaporated water (e.g., leaf water) and atmospheric O2 on vertebrate body water. Parent waters of the soil carbonates studied here have Δ17O values that are similar to or slightly lower than global precipitation. Our results suggest

The reactive element effect of yttrium and yttrium silicon on high temperature oxidation of NiCrAl coating

Science.gov (United States)

Ramandhany, S.; Sugiarti, E.; Desiati, R. D.; Martides, E.; Junianto, E.; Prawara, B.; Sukarto, A.; Tjahjono, A.

2018-03-01

The microstructure formed on the bond coat affects the oxidation resistance, particularly the formation of a protective oxide layer. The adhesion of bond coat and TGO increased significantly by addition of reactive element. In the present work, the effect of yttrium and yttrium silicon as reactive element (RE) on NiCrAl coating was investigated. The NiCrAl (without RE) and NiCrAlX (X:Y or YSi) bond coating were deposited on Hastelloy C-276 substrate by High Velocity Oxygen Fuel (HVOF) method. Isothermal oxidation was carried out at 1000 °C for 100 hours. The results showed that the addition of RE could prevent the breakaway oxidation. Therefore, the coating with reactive element were more protective against high temperature oxidation. Furthermore, the oxidation rate of NiCrAlY coating was lower than NiCrAlYSi coating with the total mass change was ±2.394 mg/cm2 after 100 hours of oxidation. The thickness of oxide scale was approximately 1.18 μm consisting of duplex oxide scale of spinel NiCr2O4 in outer scale and protective α-Al2O3 in inner scale.

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

Science.gov (United States)

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

2012-01-01

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

Bringing organic carbon isotopes and phytoliths to the table as additional constraints on paleoelevation

Science.gov (United States)

Sheldon, N. D.; Cotton, J. M.; Hren, M. T.; Hyland, E. G.; Smith, S. Y.; Strömberg, C. A. E.

2015-12-01

A commonly used tool in paleotectonic and paleoaltimetry studies is the oxygen isotopic composition of authigenic carbonates formed that formed in lakes or soils, with both spatial (e.g., shoreline to mountain top) or temporally resolved records potentially providing constraints. However, in many cases there is a substantial spread in the oxygen isotope data for a given time period, often to the point of allowing for essentially any interpretation of the data depending upon how they have been used by the investigator. One potential way of distinguishing between different potential paleotectonic or paleoaltimetric interpretations is to use carbon isotope and plant microfossil (phytolith) analyses from the same paleosols to screen the oxygen isotope data by looking for evidence of evaporative enrichment. For example, if both inorganic (carbonate) and organic carbon isotopes are measured from the same paleosol, then in it possible to determine if the two isotope record equilibrium conditions or if they record disequilibrium driven by kinetic effects. In the former case, the oxygen isotope results can be considered reliable whereas in the latter case, the oxygen isotope results can be considered unreliable and could be culled from the interpretation. Similarly, because the distribution of C4 plants varies as a function of temperature and elevation, the presence/absence or abundance of C4 plant phytoliths, or of carbon isotope compositions that require a component of C4 vegetation can also be used to constrain paleoelevation by providing a maximum elevation constraint. Worked examples will include the late Miocene-Pliocene of Catamarca, Argentina, where phytoliths and organic carbon isotopes provide a maximum elevation constraint and can be used to demonstrate that oxygen isotopes do not provide a locally useful constraint on paleoelevation, and Eocene-Miocene of southwestern Montana where organic matter and phytoliths can be used to select between different potential

MCrAlY bond coat with enhanced Yttrium layer

Science.gov (United States)

Jablonski, Paul D; Hawk, Jeffrey A

2015-04-21

One or more embodiments relates to an MCrAlY bond coat comprising an MCrAlY layer in contact with a Y--Al.sub.2O.sub.3 layer. The MCrAlY layer is comprised of a .gamma.-M solid solution, a .beta.-MAl intermetallic phase, and Y-type intermetallics. The Y--Al.sub.2O.sub.3 layer is comprised of Yttrium atoms coordinated with oxygen atoms comprising the Al.sub.2O.sub.3 lattice. Both the MCrAlY layer and the Y--Al.sub.2O.sub.3 layer have a substantial absence of Y--Al oxides, providing advantage in the maintainability of the Yttrium reservoir within the MCrAlY bulk. The MCrAlY bond coat may be fabricated through application of a Y.sub.2O.sub.3 paste to an MCrAlY material, followed by heating in a non-oxidizing environment.

Estimating of gas transfer velocity using triple isotopes of dissolved oxygen.

Digital Repository Service at National Institute of Oceanography (India)

Sarma, V.V.S.S.; Abe, O.; Honda, M.; Saino, T.

variations in oxygen isotopes are found to be higher than the direct estimations at low wind speed (<5 m s sup(-1)) and lower at high wind speeds (>13 m s sup(-1)) and showed significant spatial variability. The method presented here can be used to derive...

The Oxygen Isotopic Composition of Phosphate: A Tracer for Phosphate Sources and Cycling

Energy Technology Data Exchange (ETDEWEB)

Mclaughlin, K. [Southern California Coastal Water Research Project, Costa Mesa, University of California, CA (United States); Young, M. B.; Paytan, A.; Kendall, C. [U.S. Geological Survey, University of California, CA (United States)

2013-05-15

Phosphorus (P) is a limiting macro-nutrient for primary productivity and anthropogenic P-loading to aquatic ecosystems is one of the leading causes of eutrophication in many ecosystems throughout the world. Because P has only one stable isotope, traditional isotope techniques are not possible for tracing sources and cycling of P in aquatic systems. However, much of the P in nature is bonded to four oxygen (O) atoms as orthophosphate (PO{sub 4}{sup 3-}). The P-O bonds in orthophosphate are strongly resistant to inorganic hydrolysis and do not exchange oxygen with water without biological mediation (enzyme-mediated recycling). Thus, the oxygen isotopic composition of dissolved inorganic phosphate ({delta}{sup 18}O{sub p}) may be used as a tracer for phosphate sources and cycling in aquatic ecosystems. Recently, several studies have been conducted utilizing {delta}{sup 18}O{sub p} as a tracer for phosphate sources and cycling in various aquatic environments. Specifically, work to date indicates that {delta}{sup 18}O{sub p} is useful for determining sources of phosphate to aquatic systems if these sources have unique isotopic signatures and phosphate cycling within the system is limited compared to input fluxes. In addition, because various processes imprint specific fractionation effects, the {delta}{sup 18}O{sub p} tracer can be utilized to determine the degree of phosphorous cycling and processing through the biomass. This chapter reviews several of these studies and discusses the potential to utilize the {delta}{sup 18}O{sub p} of phosphate in rivers and streams. (author)

Comparison of interglacial warm events since the marine oxygen isotope stage 11

Digital Repository Service at National Institute of Oceanography (India)

Oba, T.; Banakar, V.K.

Large numbers of oxygen isotopic curves of benthic foraminifcral tests from deep-sea sediment cores have been published. The curves are well-established reliable proxies for past climate and relative sea level fluctuations. In order to understand...

EQUILIBRIUM AND KINETIC NITROGEN AND OXYGEN-ISOTOPE FRACTIONATIONS BETWEEN DISSOLVED AND GASEOUS N2O

NARCIS (Netherlands)

INOUE, HY; MOOK, WG

1994-01-01

Experiments were performed to determine the equilibrium as well as kinetic stable nitrogen and oxygen isotope fractionations between aqueous dissolved and gaseous N2O. The equilibrium fractionations, defined as the ratio of the isotopic abundance ratios (15R and 18R, respectively) of gaseous and

Forensic applications of nitrogen and oxygen isotopes in tracing nitrate sources in urban environments

Science.gov (United States)

Silva, S.R.; Ging, P.B.; Lee, R.W.; Ebbert, J.C.; Tesoriero, A.J.; Inkpen, E.L.

2002-01-01

Ground and surface waters in urban areas are susceptible to nitrate contamination from septic systems, leaking sewer lines, and fertilizer applications. Source identification is a primary step toward a successful remediation plan in affected areas. In this respect, nitrogen and oxygen isotope ratios of nitrate, in conjunction with hydrologic data and water chemistry, have proven valuable in urban studies from Austin, Texas, and Tacoma, Washington. In Austin, stream water was sampled during stremflow and baseflow conditions to assess surface and subsurface sources of nitrate, respectively. In Tacoma, well waters were sampled in adjacent sewered and un-sewered areas to determine if locally high nitrate concentrations were caused by septic systems in the un-sewered areas. In both studies, sewage was identified as a nitrate source and mixing between sewage and other sources of nitrate was apparent. In addition to source identification, combined nitrogen and oxygen isotopes were important in determining the significance of denitrification, which can complicate source assessment by reducing nitrate concentrations and increasing ??15N values. The two studies illustrate the value of nitrogen and oxygen isotopes of nitrate for forensic applications in urban areas. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

Carbon and oxygen isotope ratios in wood constituents of Pinus halepensis as indicators of precipitation, temperature and vapour pressure deficit

International Nuclear Information System (INIS)

Ferrio, J.P.; Voltas, J.

2005-01-01

Carbon and oxygen isotope compositions (δ 13 C, δ 18 O) in tree rings have been shown to bear relevant climatic signals. However, little is known about the interrelationship between both isotopes in wood constituents for species from other than relatively wet climates. We hypothesized that in a species adapted to temporary droughts (e.g. Pinus halepensis Mill.) the signal derived from δ 18 O in precipitation would be hidden by the strong variability in leaf transpirative enrichment. To test this assumption, we compared the effect of precipitation, temperature and vapour pressure deficit (VPD) on δ 18 O and δ 13 C along 23 sites covering the ecological range for this species. We extracted the cores from the south side of four to six adult dominant trees per aspect (north/south) within each site. For each aspect and site, fragments of the period 1975-1999 were pooled and milled to a fine powder. To further test the postulated need for cellulose purification in the assessment of climatic information, we studied these relationships in whole and extracted wood, holocellulose and lignin. In all wood fractions, δ 13 C was related to annual precipitation [r=0.58 (P 18 O only holocellulose showed consistent relationships with climatic data, being strongly significant for VPD [r=0.66 (P 18 O in precipitation, confirming that transpirative enrichment (driven by VPD) dampened the source signal in P. halepensis. The relationships between δ 13 C and δ 18 O were generally poor, regardless of the wood constituent, suggesting that although both variables were somewhat related to transpirative demand, they were relatively independent. This was further confirmed by building stepwise models using both isotopes to predict annual and seasonal precipitation [r 2 = 0.34 (P 2 = 0.15 (P 2 = 0.31 (P< 0.01) to 0.55 (P< 0.001)]. We concluded that, even when partially describing the same climate variables, the information underlying the two isotopes can be regarded as complementary

Cryogenic separation of an oxygen-argon mixture in natural air samples for the determination of isotope and molecular ratios.

Science.gov (United States)

Keedakkadan, Habeeb Rahman; Abe, Osamu

2015-04-30

The separation and purification of oxygen-argon mixtures are critical in the high-precision analysis of Δ(17) O and δ(O2 /Ar) for geochemical applications. At present, chromatographic methods are used for the separation and purification of oxygen-argon mixtures or pure oxygen, but these methods require the use of high-purity helium as a carrier gas. Considerable interest has been expressed in the development of a helium-free cryogenic separation of oxygen-argon mixtures in natural air samples. The precise and simplified cryogenic separation of oxygen-argon mixtures from natural air samples presented here was made possible using a single 5A (30/60 mesh) molecular sieve column. The method involves the trapping of eluted gases using molecular sieves at liquid nitrogen temperature, which is associated with isotopic fractionation. We tested the proposed method for the determination of isotopic fractionations during the gas exchange between water and atmospheric air at equilibrium. The dependency of fractionation was studied at different water temperatures and for different methods of equilibration (bubbling and stirring). Isotopic and molecular fractionations during gas desorption from molecular sieves were studied for different amounts and types of molecular sieves. Repeated measurements of atmospheric air yielded a reproducibility (±SD) of 0.021 ‰, 0.044 ‰, 15 per meg and 1.9 ‰ for δ(17) O, δ(18) O, Δ(17) O and δ(O2 /Ar) values, respectively. We applied the method to determine equilibrium isotope fractionation during gas exchange between air and water. Consistent δ(18) O and Δ(17) O results were obtained with the latest two studies, whereas there was a significant difference in δ(18) O values between seawater and deionized water. We have revised a helium-free, cryogenic separation of oxygen-argon mixtures in natural air samples for isotopic and molecular ratio analysis. The use of a single 13X (1/8" pellet) molecular sieve yielded the smallest isotopic

Unexpected variations in the triple oxygen isotope composition of stratospheric carbon dioxide

Science.gov (United States)

Wiegel, Aaron A.; Cole, Amanda S.; Hoag, Katherine J.; Atlas, Elliot L.; Schauffler, Sue M.; Boering, Kristie A.

2013-10-01

We report observations of stratospheric CO2 that reveal surprisingly large anomalous enrichments in 17O that vary systematically with latitude, altitude, and season. The triple isotope slopes reached 1.95 ± 0.05(1σ) in the middle stratosphere and 2.22 ± 0.07 in the Arctic vortex versus 1.71 ± 0.03 from previous observations and a remarkable factor of 4 larger than the mass-dependent value of 0.52. Kinetics modeling of laboratory measurements of photochemical ozone-CO2 isotope exchange demonstrates that non-mass-dependent isotope effects in ozone formation alone quantitatively account for the 17O anomaly in CO2 in the laboratory, resolving long-standing discrepancies between models and laboratory measurements. Model sensitivities to hypothetical mass-dependent isotope effects in reactions involving O3, O(1D), or CO2 and to an empirically derived temperature dependence of the anomalous kinetic isotope effects in ozone formation then provide a conceptual framework for understanding the differences in the isotopic composition and the triple isotope slopes between the laboratory and the stratosphere and between different regions of the stratosphere. This understanding in turn provides a firmer foundation for the diverse biogeochemical and paleoclimate applications of 17O anomalies in tropospheric CO2, O2, mineral sulfates, and fossil bones and teeth, which all derive from stratospheric CO2.

Palmyra Island Monthly Oxygen Isotope Data (delta 18O) for 1886-1998

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Palmyra Island Monthly Coral Oxygen Isotope Data. 112-yr, monthly-resolved coral record from Palmyra Island (5 deg 52 min N, 162 deg 8 min W). The coral was drilled...

LBA-ECO CD-02 Carbon, Nitrogen, Oxygen Stable Isotopes in Organic Material, Brazil

Data.gov (United States)

National Aeronautics and Space Administration — This data set reports the measurement of stable carbon, nitrogen, and oxygen isotope ratios in organic material (plant, litter and soil samples) in forest canopy...

LBA-ECO CD-02 Carbon, Nitrogen, Oxygen Stable Isotopes in Organic Material, Brazil

Data.gov (United States)

National Aeronautics and Space Administration — ABSTRACT: This data set reports the measurement of stable carbon, nitrogen, and oxygen isotope ratios in organic material (plant, litter and soil samples) in forest...

Influence of uncertainties of isotopic composition of the reprocessed uranium on effectiveness of its enrichment in gas centrifuge cascades

Science.gov (United States)

Smirnov, A. Yu; Mustafin, A. R.; Nevinitsa, V. A.; Sulaberidze, G. A.; Dudnikov, A. A.; Gusev, V. E.

2017-01-01

The effect of the uncertainties of the isotopic composition of the reprocessed uranium on its enrichment process in gas centrifuge cascades while diluting it by adding low-enriched uranium (LEU) and waste uranium. It is shown that changing the content of 232U and 236U isotopes in the initial reprocessed uranium within 15% (rel.) can significantly change natural uranium consumption and separative work (up to 2-3%). However, even in case of increase of these parameters is possible to find the ratio of diluents, where the cascade with three feed flows (depleted uranium, LEU and reprocessed uranium) will be more effective than ordinary separation cascade with one feed point for producing LEU from natural uranium.

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

International Nuclear Information System (INIS)

Primm, Trent; Guida, Tracey

2010-01-01

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.

Fractionation of oxygen and hydrogen isotopes at the hydrate gas forming in the sea sediments

International Nuclear Information System (INIS)

Pashkina, V.I.; Esikov, A.D.

1990-01-01

The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies show that heavy isotopes of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ 18 O=+1.99per mille, δD=+23per mille relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading. (orig.) [de

Dolomite clumped isotope constraints on the oxygen isotope composition of the Phanerozoic Sea

Science.gov (United States)

Ryb, U.; Eiler, J. M.

2017-12-01

The δ18O value of the Phanerozoic Sea has been debated several decades, largely motivated by an 8‰ increase in δ18O of sedimentary carbonates between the Cambrian and the present. Some previous studies have interpreted this increase to be a primary depositional signal, resulting from an increase in the 18O content of ocean water over time, or from a decrease in ocean temperature increasing the oxygen isotope fractionation between seawater and carbonates. In contrast, other studies have interpreted lower δ18O compositions as the products of diagenetic alteration at elevated burial temperatures. Here, we show that the Phanerozoic dolomite δ18O record overlaps with that of well-preserved calcite fossils, and use carbonate clumped isotope measurements of Cambrian to Pleistocene dolomites to calculate their formation temperatures and the isotopic compositions of their parent-waters. The observed variation in dolomite δ18O is largely explained by dolomite formation at burial temperatures of up to 158°C. The δ18O values of dolomite parent-waters range -2 to +12‰ and are correlated with formation temperatures. Such correlation is consistent with the modification of seawater (0±2‰, VSMOW) toward isotopically heavier compositions through water-rock reactions at elevated burial temperatures. The similarity between the dolomite and calcite δ18O records, and published clumped isotope-based calculations of water compositions, suggests that like dolomite, temporal variations of the calcite δ18O record may also be largely driven by diagenetic alteration. Finally, the relationship we observe between temperature of dolomitization and d18O of dolomite suggests platform carbonates generally undergo dolomitization through reaction with modified marine waters, and that there is no evidence those waters were ever significantly lower in d18O than the modern ocean.

Modelling and Mapping Oxygen-18 Isotope Composition of Precipitation in Spain for Hydrologic and Climatic Applications

Energy Technology Data Exchange (ETDEWEB)

Rodriguez-Arevalo, J.; Diaz-Teijeiro, M. F. [Centro de Estudios y Experimentacion de Obras Publicas (CEDEX), Madrid (Spain); Castano, S. [Geological Survey of Spain (IGME), Madrid (Spain)

2013-07-15

A simple multiple regression model based on two geographic factors (latitude and elevation) has been developed that reproduces reasonably well the spatial distribution of the current mean oxygen-18 isotope composition in precipitation over spain. In a preliminary analysis, additional geographic and climatic factors do not improve the performance of the model. A continuous digital map of oxygen-18 isotope composition in precipitation has been produced by combining the polynomial model with a digital elevation model using GIS tools. Application of the resulting map to several groundwater case studies in spain has shown it to be useful as a reference of the input function to recharge. Further validation of the model, and further testing of its usefulness in surface hydrology and climatic studies, is ongoing through comparison of model results with isotope data from the GNIP database and from isotope studies in hydrogeology and climate change taking place in spain. (author)

Stable sulfur and oxygen isotopes as geochemical tracers of sulfate in karst waters

Science.gov (United States)

Sun, Jing; Kobayashi, Tatsuaki; Strosnider, William H. J.; Wu, Pan

2017-08-01

Karst water resources, which are extremely sensitive to mining activities, are critical for the support of human societies and ecological systems in many regions worldwide. In order to determine the sources and fate of dissolved sulfate in low-pH karst waters, hydrochemical variations of karst waters with and without acid mine drainage (AMD) impacts were investigated along with stable isotope dynamics. As expected, hydrochemical characteristics and isotopic compositions of the AMD and AMD-downstream water (ADW) were dramatically different from that of the non-AMD-impacted water (NAW). The sources of sulfur isotopes in sulfate were predominantly pyrite oxidation for the AMD and ADW, and atmospheric deposition for the NAW. Based on the general isotope-balance model, the relative proportions of sulfate oxygen derived from water and air were calculated. The mean proportion of sulfate oxygen derived from water in ADW was roughly double that of AMD. This suggests that the sulfate associated with AMD is predominantly influenced by aerobic pyrite oxidation, while that of ADW is likely affected by the dissolution of pyrite under anaerobic conditions in reservoir sediment. This observation was coincident with the noted variations of hydrochemical characteristics and was supported by principal component analysis. These results provide a better understanding of how stable isotopes of sulfate and water can be used to track mining contamination in karst aquifers, which could benefit remediation planning for these distinctive systems.

Oxygen isotope geochemistry of The Geysers reservoir rocks, California

Energy Technology Data Exchange (ETDEWEB)

Gunderson, Richard P.; Moore, Joseph N.

1994-01-20

Whole-rock oxygen isotopic compositions of Late Mesozoic graywacke, the dominant host rock at The Geysers, record evidence of a large liquid-dominated hydrothermal system that extended beyond the limits of the present steam reservoir. The graywackes show vertical and lateral isotopic variations that resulted from gradients in temperature, permeability, and fluid composition during this early liquid-dominated system. All of these effects are interpreted to have resulted from the emplacement of the granitic "felsite" intrusion 1-2 million years ago. The {delta}{sup 18}O values of the graywacke are strongly zoned around a northwest-southeast trending low located near the center of and similar in shape to the present steam system. Vertical isotopic gradients show a close relationship to the felsite intrusion. The {delta}{sup 18}O values of the graywacke decrease from approximately 15 per mil near the surface to 4-7 per mil 300 to 600 m above the intrusive contact. The {delta}{sup 18}O values then increase downward to 8-10 per mil at the felsite contact, thereafter remaining nearly constant within the intrusion itself. The large downward decrease in {delta}{sup 18}O values are interpreted to be controlled by variations in temperature during the intrusive event, ranging from 150{degree}C near the surface to about 425{degree}C near the intrusive contact. The upswing in {delta}{sup 18}O values near the intrusive contact appears to have been caused by lower rock permeability and/or heavier fluid isotopic composition there. Lateral variations in the isotopic distributions suggests that the effects of temperature were further modified by variations in rock permeability and/or fluid-isotopic composition. Time-integrated water:rock ratios are thought to have been highest within the central isotopic low where the greatest isotopic depletions are observed. We suggest that this region of the field was an area of high permeability within the main upflow zone of the liquid

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

Science.gov (United States)

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

2018-05-01

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

Oxygen isotopes in garnet and accessory minerals to constrain fluids in subducted crust

Science.gov (United States)

Rubatto, Daniela; Gauthiez-Putallaz, Laure; Regis, Daniele; Rosa Scicchitano, Maria; Vho, Alice; Williams, Morgan

2017-04-01

Fluids are considered a fundamental agent for chemical exchanges between different rock types in the subduction system. Constraints on the sources and pathways of subduction fluids thus provide crucial information to reconstruct subduction processes. Garnet and U-Pb accessory minerals constitute some of the most robust and ubiquitous minerals in subducted crust and can preserve multiple growth zones that track the metamorphic evolution of the sample they are hosted in. Microbeam investigation of the chemical (major and trace elements) and isotopic composition (oxygen and U-Pb) of garnet and accessory minerals is used to track significant fluid-rock interaction at different stages of the subduction system. This approach requires consideration of the diffusivity of oxygen isotopes particularly in garnet, which has been investigated experimentally. The nature of the protolith and ocean floor alteration is preserved in relict accessory phases within eclogites that have been fully modified at HP conditions (e.g. Monviso and Dora Maira units in the Western Alps). Minerals in the lawsonite-blueschists of the Tavsanli zone in Turkey record pervasive fluid exchange between mafic and sedimentary blocks at the early stage of subduction. High pressure shear zones and lithological boundaries show evidence of intense fluid metasomatism at depth along discontinuities in Monviso and Corsica. In the UHP oceanic crust of the Zermatt-Saas Zone, garnet oxygen isotopes and tourmaline boron isotopes indicate multistage fluid infiltration during prograde metamorphism. Localized exchanges of aqueous fluids are also observed in the subducted continental crust of the Sesia-Lanzo Zone. In most cases analyses of distinct mineral zones enable identification of multiple pulses of fluids during the rock evolution.

A new feature in the internal heavy isotope distribution in ozone

International Nuclear Information System (INIS)

Bhattacharya, S. K.; Liang, Mao-Chang; Savarino, Joel; Michalski, G.

2014-01-01

Ozone produced by discharge or photolysis of oxygen has unusually heavy isotopic composition ( 18 O/ 16 O and 17 O/ 16 O ratio) which does not follow normal mass fractionation rule: δ 17 O ∼ 0.52 * δ 18 O, expressed as an anomaly Δ 17 O = δ 17 O − 0.52 * δ 18 O. Ozone molecule being an open isosceles triangle can have the heavy isotope located either in its apex or symmetric (s) position or the base or asymmetric (as) position. Correspondingly, one can define positional isotopic enrichment, written as δ 18 O (s) or δ 18 O (as) (and similarly for δ 17 O) as well as position dependent isotope anomaly Δ 17 O (s) and Δ 17 O (as). Marcus and co-workers have proposed a semi-empirical model based in principle on the RRKM model of uni-molecular dissociation but with slight modification (departure from statistical randomness assumption for symmetrical molecules) which explains many features of ozone isotopic enrichment. This model predicts that the bulk isotope anomaly is contained wholly in the asymmetric position and the Δ 17 O (s) is zero. Consequently, Δ 17 O (as) = 1.5 * Δ 17 O (bulk) (named here simply as the “1.5 rule”) which has been experimentally confirmed over a range of isotopic enrichment. We now show that a critical re-analysis of the earlier experimental data demonstrates a small but significant departure from this 1.5 rule at the highest and lowest levels of enrichments. This departure provides the first experimental proof that the dynamics of ozone formation differs from a statistical model constrained only by restriction of symmetry. We speculate over some possible causes for the departure

A new feature in the internal heavy isotope distribution in ozone

Science.gov (United States)

Bhattacharya, S. K.; Savarino, Joel; Michalski, G.; Liang, Mao-Chang

2014-10-01

Ozone produced by discharge or photolysis of oxygen has unusually heavy isotopic composition (18O/16O and 17O/16O ratio) which does not follow normal mass fractionation rule: δ17O ˜ 0.52*δ18O, expressed as an anomaly Δ17O = δ17O - 0.52*δ18O. Ozone molecule being an open isosceles triangle can have the heavy isotope located either in its apex or symmetric (s) position or the base or asymmetric (as) position. Correspondingly, one can define positional isotopic enrichment, written as δ18O (s) or δ18O (as) (and similarly for δ17O) as well as position dependent isotope anomaly Δ17O (s) and Δ17O (as). Marcus and co-workers have proposed a semi-empirical model based in principle on the RRKM model of uni-molecular dissociation but with slight modification (departure from statistical randomness assumption for symmetrical molecules) which explains many features of ozone isotopic enrichment. This model predicts that the bulk isotope anomaly is contained wholly in the asymmetric position and the Δ17O (s) is zero. Consequently, Δ17O (as) = 1.5 * Δ17O (bulk) (named here simply as the "1.5 rule") which has been experimentally confirmed over a range of isotopic enrichment. We now show that a critical re-analysis of the earlier experimental data demonstrates a small but significant departure from this 1.5 rule at the highest and lowest levels of enrichments. This departure provides the first experimental proof that the dynamics of ozone formation differs from a statistical model constrained only by restriction of symmetry. We speculate over some possible causes for the departure.

Calibration of an isotopically enriched carbon-13 layer pressure sensor to 156 GPa in a diamond anvil cell

International Nuclear Information System (INIS)

Qiu Wei; Baker, Paul A.; Velisavljevic, Nenad; Vohra, Yogesh K.; Weir, Samuel T.

2006-01-01

An isotopically enriched 13 C homoepitaxial diamond layer of 6±1 μm thickness was grown on top of a brilliant cut diamond anvil by a microwave plasma chemical vapor deposition process for application as a pressure sensor. This isotopically enriched diamond tip was then used in conjunction with a natural isotopic abundance diamond anvil to generate high pressure on the sample. We provide a calibration for the 13 C Raman mode of this extremely thin epitaxial layer to 156 GPa using ruby fluorescence and the equation of state of copper as secondary pressure standards. The nonlinear calibration of the 13 C Raman mode pressure sensor is compared with similar calibrations of 12 C Raman edge and a good agreement is obtained. The Raman signal from the 13 C epitaxial layer remained a distinct singlet to 156 GPa, and pressure calibration is independent of sample mechanical strength or the diamond anvil geometry. The use of even thinner layer would allow calibration further into ultrahigh pressure regime where the use of other optical sensors has proven to be difficult

Oxygen isotope signature of UV degradation of glyphosate and phosphonoacetate: Tracing sources and cycling of phosphonates

Energy Technology Data Exchange (ETDEWEB)

Sandy, Edward H. [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 (United States); Department of Chemistry, University of Sierra Leone, Freetown (Sierra Leone); Blake, Ruth E., E-mail: ruth.blake@yale.edu [Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 (United States); School of Civil and Environmental Engineering, and National “International Cooperation Base on Environment and Energy”, University of Science and Technology Beijing, Beijing 100084 (China); Chang, Sae Jung [Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 (United States); Jun, Yao, E-mail: yaojun@ustb.edu.cn [State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074 (China); Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 (United States); School of Civil and Environmental Engineering, and National “International Cooperation Base on Environment and Energy”, University of Science and Technology Beijing, Beijing 100084 (China); Yu, Chan [Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 (United States); School of Civil and Environmental Engineering, and National “International Cooperation Base on Environment and Energy”, University of Science and Technology Beijing, Beijing 100084 (China)

2013-09-15

Highlights: • Phosphonate (phon) hydrolysis by UVR (1.2 kW) attained ≥90% completion in 84 h. • Isotope study reveals both ambient H{sub 2}O and O{sub 2} involvements in phon C-P bond cleavage. • Mechanistic models proposed for phon C-P bond cleavage based on O-isotope analysis. • Model equations used to calculate δ{sup 18}O{sub P-org} of original phon P-moiety-useful as a tracer. • Study shows relevance in tracing phon sources and cycling in the environment. -- Abstract: The degradation of phosphonates in the natural environment constitutes a major route by which orthophosphate (Pi) is regenerated from organic phosphorus and recently implicated in marine methane production, with ramifications to environmental pollution issues and global climate change concerns. This work explores the application of stable oxygen isotope analysis in elucidating the C-P bond cleavage mechanism(s) of phosphonates by UV photo-oxidation and for tracing their sources in the environment. The two model phosphonates used, glyphosate and phosphonoacetic acid were effectively degraded after exposure to UV irradiation. The isotope results indicate the involvement of both ambient water and atmospheric oxygen in the C-P bond cleavage and generally consistent with previously posited mechanisms of UV-photon excitation reactions. A model developed to calculate the oxygen isotopic composition of the original phosphonate P-moiety, shows both synthetic phosphonates having distinctly lower values compared to naturally derived organophosphorus compounds. Such mechanistic models, based on O-isotope probing, are useful for tracing the sources and reactions of phosphonates in the environment.

Leaf water enrichment of stable water isotopes (δ18O and δD) in a mature oil palm plantation in Jambi province, Indonesia.

Science.gov (United States)

Bonazza, Mattia; Tjoa, Aiyen; Knohl, Alexander

2017-04-01

During the last few decades, Indonesia experienced rapid and large scale land-use change towards intensively managed crops, one of them is oil palm. This transition results in warmer and dryer conditions in microclimate. The impacts on the hydrological cycle and on water-use by plants are, however, not yet completely clear. Water stable isotopes are useful tracers of the hydrological processes and can provide means to partition evapotranspiration into evaporation and transpiration. A key parameter, however, is the enrichment of water stable isotope in plant tissue such as leaves that can provide estimates on the isotopic composition of transpiration. Here we present the results of a field campaign conducted in a mature oil palm plantation in Jambi province, Indonesia. We combined continuous measurements of water vapor isotopic composition and mixing ratio with isotopic analysis of water stored in different pools like oil palm leaves, epiphytes, trunk organic matter and soil collected over a three days period. Leaf enrichment varied from -2 ‰ to 10 ‰ relative to source (ground) water. The temporal variability followed Craig and Gordon model predictions for leaf water enrichment. An improved agreement was reached after considering the Péclet effect with an appropriate value of the characteristic length (L). Measured stomatal conductance (gs) on two different sets of leaves (top and bottom canopy) was mainly controlled by radiation (photosynthetically active radiation) and vapor pressure deficit. We assume that this control could be explained in conditions where soil water content is not representing a limiting factor. Understanding leaf water enrichment provides one step towards partitioning ET.

The mechanism of oxygen isotopic fractionation during fungal denitrification - A pure culture study

Science.gov (United States)

Wrage-Moennig, Nicole; Rohe, Lena; Anderson, Traute-Heidi; Braker, Gesche; Flessa, Heinz; Giesemann, Annette; Lewicka-Szczebak, Dominika; Well, Reinhard

2014-05-01

Nitrous oxide (N2O) from soil denitrification originates from bacteria and - to an unknown extent - also from fungi. During fungal denitrification, oxygen (O) exchange takes place between H2O and intermediates of the denitrification process as in bacterial exchange[1,2]. However, information about enzymes involved in fungal O exchanges and the associated fractionation effects is lacking. The objectives of this study were to estimate the O fractionation and O exchange during the fungal denitrifying steps using a conceptual model[2] adapted from concepts for bacterial denitrification[3], implementing controls of O exchange proposed by Aerssens, et al.[4] and using fractionation models by Snider et al.[5] Six different pure fungal cultures (five Hypocreales, one Sordariales) known to be capable of denitrification were incubated under anaerobic conditions, either with nitrite or nitrate. Gas samples were analyzed for N2O concentration and its isotopic signatures (SP, average δ15N, δ18O). To investigate O exchange, both treatments were also established with 18O-labelled water as a tracer in the medium. The Hypocreales strains showed O exchange mainly at NO2- reductase (Nir) with NO2- as electron acceptor and no additional O exchange at NO3- reductase (Nar) with NO3- as electron acceptor. The only Hypocreales species having higher O exchange with NO3- than with NO2- also showed O exchange at Nar. The Sordariales species tested seems capable of O exchange at NO reductase (Nor) additionally to O exchange at Nir with NO2-. The data will help to better interpret stable isotope values of N2O from soils. .[1] D. M. Kool, N. Wrage, O. Oenema, J. Dolfing, J. W. Van Groenigen. Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of NO?3- and N2O: a review. Rapid Commun. Mass Spec. 2007, 21, 3569. [2] L. Rohe, T.-H. Anderson, B. Braker, H. Flessa, A. Giesemann, N. Wrage-Mönnig, R. Well. Fungal Oxygen Exchange between

Heterogenous Oxygen Isotopic Composition of a Complex Wark-Lovering Rim and the Margin of a Refractory Inclusion from Leoville

Science.gov (United States)

Simon, J. I.; Matzel, J. E. P.; Simon, S. B.; Weber, P. K.; Grossman, L.; Ross, D. K.; Hutcheon, I. D.

2014-01-01

Wark-Lovering (WL) rims [1] surrounding many refractory inclusions represent marker events in the early evolution of the Solar System in which many inclusions were exposed to changes in pressure [2], temperature [3], and isotopic reservoirs [4-7]. The effects of these events can be complex, not only producing mineralogical variability of WL rims [2], but also leading to mineralogical [8-10] and isotopic [7, 11, 12] changes within inclusion interiors. Extreme oxygen isotopic heterogeneity measured in CAIs has been explained by mixing between distinct oxygen gas reservoirs in the nebula [13]. Some WL rims contain relatively simple mineral layering and/or are isotopically homogeneous [14, 15]. As part of a larger effort to document and understand the modifications observed in some CAIs, an inclusion (L6) with a complex WL rim from Leoville, a member of the reduced CV3 subgroup was studied. Initial study of the textures and mineral chemistry was presented by [16]. Here we present NanoSIMS oxygen isotopic measurements to complement these petrologic observations.

Method for separating isotopes

International Nuclear Information System (INIS)

Schlenker, R.F.

1978-01-01

A vortex tube for separating isotopes is described. A gas mixture containing the isotopic molecules enters the vortex tube under pressure and is separated into a hot discharge flow stream and a cold discharge flow stream. The hot discharge is enriched in lighter isotopic molecules whereas the cold discharge flow stream is enriched in the heavier isotopic molecules. The vortex tube can be used in a single stage or multistage isotope separation apparatus

Antibodies and isotopes, a chemical approach to tumour targeting

International Nuclear Information System (INIS)

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

1986-01-01

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

Nitrogen and Oxygen Isotope Effects of Ammonia Oxidation by Thermophilic Thaumarchaeota from a Geothermal Water Stream.

Science.gov (United States)

Nishizawa, Manabu; Sakai, Sanae; Konno, Uta; Nakahara, Nozomi; Takaki, Yoshihiro; Saito, Yumi; Imachi, Hiroyuki; Tasumi, Eiji; Makabe, Akiko; Koba, Keisuke; Takai, Ken

2016-08-01

Ammonia oxidation regulates the balance of reduced and oxidized nitrogen pools in nature. Although ammonia-oxidizing archaea have been recently recognized to often outnumber ammonia-oxidizing bacteria in various environments, the contribution of ammonia-oxidizing archaea is still uncertain due to difficulties in the in situ quantification of ammonia oxidation activity. Nitrogen and oxygen isotope ratios of nitrite (δ(15)NNO2- and δ(18)ONO2-, respectively) are geochemical tracers for evaluating the sources and the in situ rate of nitrite turnover determined from the activities of nitrification and denitrification; however, the isotope ratios of nitrite from archaeal ammonia oxidation have been characterized only for a few marine species. We first report the isotope effects of ammonia oxidation at 70°C by thermophilic Thaumarchaeota populations composed almost entirely of "Candidatus Nitrosocaldus." The nitrogen isotope effect of ammonia oxidation varied with ambient pH (25‰ to 32‰) and strongly suggests the oxidation of ammonia, not ammonium. The δ(18)O value of nitrite produced from ammonia oxidation varied with the δ(18)O value of water in the medium but was lower than the isotopic equilibrium value in water. Because experiments have shown that the half-life of abiotic oxygen isotope exchange between nitrite and water is longer than 33 h at 70°C and pH ≥6.6, the rate of ammonia oxidation by thermophilic Thaumarchaeota could be estimated using δ(18)ONO2- in geothermal environments, where the biological nitrite turnover is likely faster than 33 h. This study extended the range of application of nitrite isotopes as a geochemical clock of the ammonia oxidation activity to high-temperature environments. Because ammonia oxidation is generally the rate-limiting step in nitrification that regulates the balance of reduced and oxidized nitrogen pools in nature, it is important to understand the biological and environmental factors underlying the regulation of

Stable isotope fractionation during bacterial sulfate reduction is controlled by reoxidation of intermediates

Science.gov (United States)

Mangalo, Muna; Meckenstock, Rainer U.; Stichler, Willibald; Einsiedl, Florian

2007-09-01

Bacterial sulfate reduction is one of the most important respiration processes in anoxic habitats and is often assessed by analyzing the results of stable isotope fractionation. However, stable isotope fractionation is supposed to be influenced by the reduction rate and other parameters, such as temperature. We studied here the mechanistic basics of observed differences in stable isotope fractionation during bacterial sulfate reduction. Batch experiments with four sulfate-reducing strains ( Desulfovibrio desulfuricans, Desulfobacca acetoxidans, Desulfonatronovibrio hydrogenovorans, and strain TRM1) were performed. These microorganisms metabolize different carbon sources (lactate, acetate, formate, and toluene) and showed broad variations in their sulfur isotope enrichment factors. We performed a series of experiments on isotope exchange of 18O between residual sulfate and ambient water. Batch experiments were conducted with 18O-enriched (δ 18O water = +700‰) and depleted water (δ 18O water = -40‰), respectively, and the stable 18O isotope shift in the residual sulfate was followed. For Desulfovibrio desulfuricans and Desulfonatronovibrio hydrogenovorans, which are both characterized by low sulfur isotope fractionation ( ɛS > -13.2‰), δ 18O values in the remaining sulfate increased by only 50‰ during growth when 18O-enriched water was used for the growth medium. In contrast, with Desulfobacca acetoxidans and strain TRM1 ( ɛS factor ( ɛS exchange with water during sulfate reduction. However, this neither takes place in the sulfate itself nor during formation of APS (adenosine-5'-phosphosulfate), but rather in intermediates of the sulfate reduction pathway. These may in turn be partially reoxidized to form sulfate. This reoxidation leads to an incorporation of oxygen from water into the "recycled" sulfate changing the overall 18O isotopic composition of the remaining sulfate fraction. Our study shows that such incorporation of 18O is correlated with the

Preliminary study on the characteristics of carbon and oxygen isotopes in the Shiziping geothermal field groundwater in Emei Mountain

International Nuclear Information System (INIS)

Yu Xiujing; Jia Shuyuan

2000-01-01

Emei Mountain is a well-known scenic tourism spot in China. In order to promote the development of tourist trade, the authors have explored the hydrothermal water in Emei Mountain. At the beginning of 1998, the hydrothermal water was successfully drilled from the Shiziping geothermal field. In the process of prospecting the hydrothermal water, the authors adopted the geochemical method such as carbon and oxygen isotopes. The result indicates that the groundwater of different genetic types has different constitution characteristics of carbon and oxygen isotopes. This provides the important basis for finding out the forming conditions of underground hydrothermal water. So, it is prospective to study the growth characteristics of hydrothermal water with the carbon and oxygen isotopes of HCO 3 in groundwater

From nitrogen enrichment to oxygen depletion: a mechanistic model of coastal marine ecosystems response

DEFF Research Database (Denmark)

Cosme, Nuno Miguel Dias; Koski, Marja; Hauschild, Michael Zwicky

Nitrogen (N) emissions from anthropogenic sources may enrich coastal waters and lead to marine eutrophication impacts. Processes describing N-limited primary production (PP), zooplankton grazing, and bacterial respiration of sinking organic carbon, were modelled to quantify the potential dissolved...... oxygen (DO) consumption as a function of N input. Such indicator is the basis for an eXposure Factor (XF) applied in Life Cycle Impact Assessment (LCIA) to estimate impacts from N enrichment. The Large Marine Ecosystems (LME) biogeographical classification system was adopted to address the spatial...

Simultaneous gettering of oxygen and chlorine and homogenization of the β phase by rare earth hydride additions to a powder metallurgy Ti–2.25Mo–1.5Fe alloy

International Nuclear Information System (INIS)

Yan, M.; Liu, Y.; Liu, Y.B.; Kong, C.; Schaffer, G.B.; Qian, M.

2012-01-01

A detailed transmission electron microscopy analysis has revealed that small additions of yttrium hydride to a powder metallurgy Ti–2.25Mo–1.5Fe alloy resulted in the formation of both chlorine-free yttrium oxides and essentially oxygen-free yttrium chlorides. The oxides and chlorides showed distinctly different morphologies and spatial distribution. Yttrium acted as a potent getter for both oxygen and chlorine. Additionally, the β-Ti phase was free of nanoscaled α-Ti in the presence of yttrium. These microstructural changes contribute to the substantially increased ductility (∼90%).

Cerium and yttrium oxide nanoparticles are neuroprotective

International Nuclear Information System (INIS)

Schubert, David; Dargusch, Richard; Raitano, Joan; Chan, S.-W.

2006-01-01

The responses of cells exposed to nanoparticles have been studied with regard to toxicity, but very little attention has been paid to the possibility that some types of particles can protect cells from various forms of lethal stress. It is shown here that nanoparticles composed of cerium oxide or yttrium oxide protect nerve cells from oxidative stress and that the neuroprotection is independent of particle size. The ceria and yttria nanoparticles act as direct antioxidants to limit the amount of reactive oxygen species required to kill the cells. It follows that this group of nanoparticles could be used to modulate oxidative stress in biological systems

Oxygen isotopes in mammal bone phosphate: A new tool for paleohydrological and paleoclimatological research?

Science.gov (United States)

Longinelli, Antonio

1984-02-01

Oxygen isotope analyses of water in blood of humans and domestic pigs indicate that the oxygen isotope fractionation effects between ingested water and body water are the same in all specimens of the same species. The δ18O of body water has been shown to vary linearly with the mean δ18O of local meteoric water. This conclusion also holds for the bone phosphate. Thus, δ18O( PO3-4) values of unaltered fossil bones from humans and domestic pigs can be used to reconstruct the δ18O values of local meteoric waters during the life-times of the mammals. Such data can be used for paleohydrological and paleoclimatological studies both on land and at sea.

Characterization of phenols biodegradation by compound specific stable isotope analysis

Science.gov (United States)

Wei, Xi; Gilevska, Tetyana; Wenzig, Felix; Hans, Richnow; Vogt, Carsten

2015-04-01

Biodegradation of phenol and alkylphenols has been described under both oxic and anoxic conditions. In the absence of molecular oxygen, the degradation of phenolic compounds is initiated by microorganisms through carboxylation, fumarate addition to the methyl moiety or anoxic hydroxylation of the methyl moiety. Comparatively, under aerobic condition, the initiation mechanisms are revealed to be monoxygenation or dihydroxylation for phenol and ring hydroxylation or methyl group oxidation for cresols. While several studies biochemically characterized the enzymes and reaction mechanisms in the relevant degradation pathways, isotope fractionation patterns were rarely reported possibly due to constraints in current analytical methods. In this study, the carbon isotope fractionation patterns upon the degradation of phenol and cresols by several strains were analyzed by using isotope ratio mass spectrometry connected with liquid chromatography (LC-IRMS). The corresponding enrichment factors for carbon (ƐC) have been obtained. Cresols degradation by various strains showed generally moderate carbon isotope fractionation patterns with notable differences. For p-cresol degradation, five strains were examined. The aerobic strain Acinetobacter calcoaceticus NCIMB8250 exploits ring hydroxylation by molecular oxygen as initial reaction, and a ƐC value of -1.4±0.2‰ was obtained. Pseudomonas pseudoalcaligenes NCIMB 9867, an aerobic strain initiating cresols degradation via oxygen-dependent side chain hydroxylation, yielded a ƐC value of -2.3±0.2‰. Under nitrate-reducing conditions, Geobacter metallireducens DSM 7210 and Azoarcus buckelii DSM 14744 attacks p-cresol at the side chain by monohydroxylation using water as oxygen source; the two strains produced ƐC values of -3.6±0.4‰ and -2±0.1‰, accordingly. The sulfate-reducing Desulfosarcina cetonica DSM 7267 activating cresols by fumarate addition to the methyl moiety yielded ƐC values of -1.9±0.2‰ for p

Low-temperature aqueous alteration on the CR chondrite parent body: Implications from in situ oxygen-isotope analyses

Science.gov (United States)

Jilly-Rehak, Christine E.; Huss, Gary R.; Nagashima, Kazu; Schrader, Devin L.

2018-02-01

The presence of hydrated minerals in chondrites indicates that water played an important role in the geologic evolution of the early Solar System; however, the process of aqueous alteration is still poorly understood. Renazzo-like carbonaceous (CR) chondrites are particularly well-suited for the study of aqueous alteration. Samples range from being nearly anhydrous to fully altered, essentially representing snapshots of the alteration process through time. We studied oxygen isotopes in secondary-minerals from six CR chondrites of varying hydration states to determine how aqueous fluid conditions (including composition and temperature) evolved on the parent body. Secondary minerals analyzed included calcite, dolomite, and magnetite. The O-isotope composition of calcites ranged from δ18O ≈ 9 to 35‰, dolomites from δ18O ≈ 23 to 27‰, and magnetites from δ18O ≈ -18 to 5‰. Calcite in less-altered samples showed more evidence of fluid evolution compared to heavily altered samples, likely reflecting lower water/rock ratios. Most magnetite plotted on a single trend, with the exception of grains from the extensively hydrated chondrite MIL 090292. The MIL 090292 magnetite diverges from this trend, possibly indicating an anomalous origin for the meteorite. If magnetite and calcite formed in equilibrium, then the relative 18O fractionation between them can be used to extract the temperature of co-precipitation. Isotopic fractionation in Al Rais carbonate-magnetite assemblages revealed low precipitation temperatures (∼60 °C). Assuming that the CR parent body experienced closed-system alteration, a similar exercise for parallel calcite and magnetite O-isotope arrays yields "global" alteration temperatures of ∼55 to 88 °C. These secondary mineral arrays indicate that the O-isotopic composition of the altering fluid evolved upon progressive alteration, beginning near the Al Rais water composition of Δ17O ∼ 1‰ and δ18O ∼ 10‰, and becoming increasingly

Ras Umm Sidd Oxygen Isotope (delta 18O) Data for 1750 to 1995

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Ras Umm Sidd bimonthly coral oxygen isotope data (coral core RUS-95). Notes on the data: File (Ras Umm Sidd d18O.txt.) includes columns for Year AD (bimonthly...

Stable hydrogen, oxygen and sulfur isotopes composition in different tissues of cattle

International Nuclear Information System (INIS)

Sun Fengmei; Shi Guangyu; Wang Huiwen; Yang Shuming

2012-01-01

In order to research on stable hydrogen, oxygen, sulfur isotopes composition in different tissues of cattle, as well as the breed, δ 2 H and δ 34 S values of different defatted muscle, cattle tail hair, blood, liver, also δ 2h and δ 18 O values of water from muscle were determined by isotope ratio mass spectrometry. The stable sulfur isotope composition was not affected by cattle variety, meanwhile the hydrogen was uncertain; the δ 2 H and δ 34 S values between different defatted muscle, blood, liver, cattle hair were significantly different, at the same time the δ 34 S and δ 2 H values between each tissue were not significantly correlated; the δ 2 H values were strongly correlated with the δ 18 O values of muscle water. The above results indicated that stable sulfur and hydrogen isotopes fractionation in the various tissues were discrepant, thus the proper tissue should be selected according to the purpose and object in the beef traceability. (authors)

Carbon, hydrogen oxygen isotope studies on imbedded old tree ring and paleoclimate reconstruction

International Nuclear Information System (INIS)

Sun Yanrong; Mu Zhiguo; Cui Haiting

2002-01-01

Tree ring is a kind of natural archives, on which the isotopic analysis is important to study global climate and environmental change. The authors mainly provide a comprehensive introduction to the fractionation models of carbon, hydrogen and oxygen isotope in plants, their research technique and the extract methods from cellulose. That results show isotopic tracer can record the message of climatic variation and has become a powerful tool for paleoclimate reconstruction and for the modern environment changing research. Especially studying on PAGES. the cellulose isotopic analyses of imbedded old tree ring have become the mainly quantitative means of environmental evolvement. In addition, China is a typical monsoon country, research in tree ring stable isotope seasonal variation can give a lot of important information on that. Up to now, the research techniques and works on tree ring in China are still in its earlier stage, and remain many limitations. It needs further accumulate basic research materials, intensity regional contrast and intercross studies on relative subjects

Modelling and Mapping Oxygen-18 Isotope Composition of Precipitation in Spain for Hydrologic and Climatic Applications

International Nuclear Information System (INIS)

Rodriguez-Arevalo, J.; Diaz-Teijeiro, M.F.; Castano, S.

2011-01-01

A simple multiple regression model based on two geographic factors (latitude and elevation) has been developed that reproduces reasonably well the spatial distribution of the current mean oxygen-18 isotope composition in precipitation over Spain. In a preliminary analysis, additional geographic and climatic factors do not improve the performance of the model. A continuous digital map of oxygen-18 isotope composition in precipitation has been produced by combining the polynomial model with a Digital Elevation Model using GIS tools. Application of the resulting map to several case studies in Spain has shown it to be useful as a reference of the isotope input function to groundwater recharge and surface runoff. The results obtained so far show a good fit between modelled stable isotope values and those measured in surface and ground waters from different aquifers and recharge areas. The GIS tools applied to a continuous digital layer of spatial isotope are able to provide accurate information at detailed scales that are not affordable by other means. Further validation of the model, and further testing of its usefulness in surface hydrology and climatic studies, is going on.

Thallium isotopes track fluctuations in global manganese oxide burial during the Ediacaran Period

Science.gov (United States)

Ostrander, C. M.; Nielsen, S.; Owens, J. D.; Jiang, G.; Planavsky, N.; Sahoo, S. K.; Zhang, F.; Lyons, T. W.; Anbar, A. D.

2017-12-01

Complex marine ecosystems appear in the geologic record for the first time during the Ediacaran (635 - 541 Ma), after the Marinoan Glaciation but before the Cambrian Explosion. Much debate surrounds the redox-state of global oceans during this diversification, with some arguing for pervasive anoxic conditions and others for increased oxygenation, including the possibility of episodic oxygen increases. Here, we use thallium (Tl) isotopes preserved in organic-rich shales from a deep-water section at Wuhe, South China, to track large-scale perturbations in Mn oxide burial during the Ediacaran. Changes to the Tl isotope composition of seawater over geologic timescales are driven dominantly by fluctuations in global Mn oxide burial, which require persistent O2 at the sediment-water interface. Importantly, the suite of sedimentary rocks analyzed is thought to have been deposited beneath persistent localized euxinia, which is an environment shown to effectively capture the Tl isotope composition of seawater. Within samples previously suggested to host oceanic oxygenation episodes (OOEs) because of high redox-sensitive element (RSE) enrichments (Sahoo et al. 2016, Geobiology), we find Tl isotope values as light as -5 epsilon units, which are indicative of removal of heavy Tl by Mn oxides elsewhere in the Ediacaran ocean and in-line with the presence of deep-marine O2. Intriguingly, between these events, during periods previously viewed as dominantly anoxic, we find Tl isotope excursions to values that are even lighter than during the OOEs (less than -10 epsilon units). To first order, these results imply that an even larger Mn oxide sink was present between the OOEs, which would require pervasive oceanic oxygenation. This interpretation is in direct conflict with interpretations of low RSE enrichments in these same samples, which invoke reservoir drawdown due to widespread anoxia—as well as many other data that suggest dominantly anoxic deep marine conditions through the

Intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite measured by thermal dehydroxylation and partial fluorination

Science.gov (United States)

Girard, Jean-Pierre; Savin, Samuel M.

1996-02-01

Thermal dehydroxylation and partial fluorination techniques were used to measure intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite. Several aliquots of a well characterized, fine-grained (rates, and target temperatures. Measured δ18O values of both the liberated water and the dehydroxylated residue are consistent over a wide range of temperatures (550 850°C) when dehydroxylation is performed in a single-step fashion at a rapid heating rate (>50°C/min.). Similar dehydroxylation experiments indicate that brucite dehydroxylation occurs without any significant isotopic fractionation of the oxygen isotopes. By extrapolation we postulate that no significant fractionation occurs during single-step thermal dehydroxylation of fine-grained kaolinite, provided that dehydroxylation is performed under well controlled conditions. In contrast, gibbsite dehydroxylation is accompanied by substantial isotopic fractionation. This is probably the result of the complex, multi-pathway dehydroxylation reaction of this mineral. Similarly, thermal dehydroxylation of coarsegrained (>1 μm) kaolinites and dickites of weathering and hydrothermal origin yield results that are dependent on the temperature of dehydroxylation. We suggest that this effect may be caused by isotopic exchange during diffusion of water molecules through coarse particles. Partial fluorination of fine-grained kaolinite in the presence of excess F2 at low temperatures (rate of reaction of hydroxyl oxygen than of non-hydroxyl oxygen, but examination of the isotopic data as well as XRD and IR analyses of the residues after partial fluorination indicates that the separation between the two types of oxygen is not complete. The results, therefore, do not yield a reliable δ18O value of the hydroxyl oxygen. The results of this study suggest that the thermal dehydroxylation technique may be appropriate for analysis of OH groups in fine-grained kaolinite. The partial

Validation of chlorine and oxygen isotope ratio analysis to differentiate perchlorate sources and to document perchlorate biodegradation

Science.gov (United States)

Paul B. Hatzinger,; Böhlke, John Karl; Sturchio, Neil C.; Gu, Baohua

2013-01-01

Increased health concerns about perchlorate (ClO4-) during the past decade and subsequent regulatory considerations have generated appreciable interest in source identification. The key objective of the isotopic techniques described in this guidance manual is to provide evidence concerning the origin of ClO4- in soils and groundwater and, more specifically, whether that ClO4- is synthetic or natural. Chlorine and oxygen isotopic analyses of ClO4- provide the primary direct approach whereby different sources of ClO4- can be distinguished from each other. These techniques measure the relative abundances of the stable isotopes of chlorine (37Cl and 35Cl) and oxygen (18O, 17O, and 16O) in ClO4- using isotope-ratio mass spectrometry (IRMS). In addition, the relative abundance of the radioactive chlorine isotope 36Cl is measured using accelerator mass spectrometry (AMS). Taken together, these measurements provide four independent quantities that can be used to distinguish natural and synthetic ClO4- sources, to discriminate different types of natural ClO4-, and to detect ClO4- biodegradation in the environment. Other isotopic, chemical, and geochemical techniques that can be applied in conjunction with isotopic analyses of ClO4- to provide supporting data in forensic studies are also described.

The NNSA global threat reduction initiative's efforts to minimize the use of highly enriched uranium for medical isotope production

International Nuclear Information System (INIS)

Staples, Parrish

2010-01-01

The mission of the National Nuclear Security Administration's (NNSA) Office of Global Threat Reduction (GTRI) is to reduce and protect vulnerable nuclear and radiological materials located at civilian sites worldwide. GTRI is a key organization for supporting domestic and global efforts to minimize and, to the extent possible, eliminate the use of highly enriched uranium (HEU) in civilian nuclear applications. GTRI implements the following activities in order to achieve its threat reduction and HEU minimization objectives: Converting domestic and international civilian research reactors and isotope production facilities from the use of HEU to low enriched uranium (LEU); Demonstrating the viability of medical isotope production technologies that do not use HEU; Removing or disposing excess nuclear and radiological materials from civilian sites worldwide; and Protecting high-priority nuclear and radiological materials worldwide from theft and sabotage. This paper provides a brief overview on the recent developments and priorities for GTRI program activities in 2010, with a particular focus on GTRI's efforts to demonstrate the viability of non-HEU based medical isotope production technologies. (author)

Simultaneous Assay of Isotopic Enrichment and Concentration of Guanidinoacetate and Creatine by Gas Chromatography-Mass Spectrometry

Science.gov (United States)

Kasumov, Takhar; Gruca, Lourdes L.; Dasarathy, Srinivasan; Kalhan, Satish C.

2012-01-01

A gas chromatographic-mass spectrometric (GC-MS) method for the simultaneous measurement of isotopic enrichment and concentration of guanidinoacetic acid and creatine in plasma sample for kinetic studies is reported. The method, based on preparation of the bis(trifluoromethyl)-pyrimidine methyl ester derivatives of guanidinoacetic acid and creatine, is robust and sensitive. The lowest measurable m1 and m3 enrichment for guanidinoacetic acid and creatine, respectively, was 0.3%. The calibration curves for measurements of concentration were linear over a range of 0.5-250 μM guanidinoacetic acid and 2-500 μM for creatine. The method was reliable for inter-assay and intra-assay precision, accuracy and linearity. The technique was applied in a healthy adult to determine in vivo fractional synthesis rate of creatine using primed- constant rate infusion of [1-13C]glycine. It was found that isotopic enrichment of guanidinoacetic acid reached plateau by 30 min of infusion of [1-13C]glycine, indicating either a small pool size or a rapid turnover rate or both, of guanidinoacetic acid. In contrast, tracer appearance in creatin was slow (slope: 0.00097), suggesting a large pool size and a slow rate of synthesis of creatine. This method can be used to estimate rate of synthesis of creatine in-vivo in human and animal studies. PMID:19646413

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.

Application of oxygen and hydrogen isotopes of waters in Tengchong hydrothermal systems of China

International Nuclear Information System (INIS)

Shen Minzi; Hou Fagao; Lin Ruifen; Ni Baoling

1988-01-01

This paper summarizes the results obtained for hydrothermal systems in Tengchong by using deuterium, oxygen-18 and tritium as natural tracers. On the basis of deuterium and oxygen-18 analyses of 69 thermal springs and some other meteoric, surface and underground water samples it has been confirmed that all geothermal waters are originally meteoric, but the δD of hot spring waters is often lighter than that of local surface and underground waters. It seems that the recharging water is from higher elevations and far from the thermal areas. The differences in oxygen-18 and deuterium contents between thermal springs and deep thermal waters have been calculated for single-stage steam separation from 276 deg. C to 96 deg. C. The oxygen isotope shift of deep thermal water produced by water-rock reactions is of 1.57 per mille and part of the observed oxygen isotope shift of thermal springs seems to have occurred due to subsurface boiling. The tritium content ( 18 O three subsurface processes would have been distinguished, they are subsurface boiling, mixing-subsurface boiling and subsurface boiling-mixing. The springs formed by subsurface boiling have tritium content of less than 5 TU. The tritium content of 5-10 TU is for springs formed by mixing-subsurface boiling and 10-20 TU is for subsurface boiling-mixing. The tritium content of geothermal water in Hot Sea, geothermal field seems higher than that of the Geysers U.S.A. and Wairakei N.Z. It would show that the circulation time of the thermal water in Hot Sea geothermal system is not so long, the reservoir is quite good with percolation and the recharging water is sufficiently enough. The most important applications of oxygen and hydrogen isotopes of water in geothermal study are in two ways, as tracers of water origins and as tracers of reservoir processes. This paper discussed these two aspects of Tengchong hydrothermal systems. 6 refs, 6 figs, 5 tabs

18O isotopic tracer studies of silicon oxidation in dry oxygen

International Nuclear Information System (INIS)

Han, C.J.

1986-01-01

Oxidation of silicon in dry oxygen has been an important process in the integrated circuit industry for making gate insulators on metal-oxide-semiconductory (MOS) devices. This work examines this process using isotopic tracers of oxygen to determine the transport mechanisms of oxygen through silicon dioxide. Oxides were grown sequentially using mass-16 and mass-18 oxygen gas sources to label the oxygen molecules from each step. The resulting oxides are analyzed using secondary ion mass spectrometry (SIMS). The results of these analyses suggest two oxidant species are present during the oxidation, each diffuses and oxidizes separately during the process. A model from this finding using a sum of two linear-parabolic growth rates, each representing the growth rate from one of the oxidants, describes the reported oxidation kinetics in the literature closely. A fit of this relationship reveals excellent fits to the data for oxide thicknesses ranging from 30 A to 1 μm and for temperatures ranging from 800 to 1200 0 C. The mass-18 oxygen tracers also enable a direct observation of the oxygen solubility in the silicon dioxide during a dry oxidation process. The SIMS profiles establish a maximum solubility for interstitial oxygen at 1000 0 C at 2 x 10 20 cm -3 . Furthermore, the mass-18 oxygen profiles show negligible network diffusion during an 1000 0 C oxidation

Kinetics of yttrium dissolution from waste ceramic dust

OpenAIRE

STOPIC SRECKO R.; FRIEDRIH BERND G.

2016-01-01

Yttrium is a silvery transition metal and has similar chemical properties to lanthanoids. Because of this similarity, yttrium belongs to rare earth elements. Ytttrium and yttrium oxide are mostly used in fluoroscent lamps, production of electrodes, in electronic filters, lasers, superconductors and as additives in various materials to improve their properties. Yttrium is mainly recovered from the minerals monazite [(Ce,La,Th,Nd,Y)PO4] and xenotime YPO4.The presence of radioactive elements suc...