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Sample records for boron isotopic composition

  1. Isotopic compositions of boron in sediments and their implications

    Digital Repository Service at National Institute of Oceanography (India)

    Shirodkar, P.V.; Yingkai, X.

    The abundance and isotopic compositions of boron in sediments from the salt lakes of Qaidam Basin, China have been determined by thermal ionization mass spectrometry of cesium borate. The results show large variations in the isotopic compositions...

  2. Determination of isotopic composition of boron in boron carbide by TIMS and PIGE: an inter-comparison study

    International Nuclear Information System (INIS)

    The paper reports a comparison of results on the determination of isotopic composition of boron in boron carbide (B4C) samples by Thermal Ionisation Mass Spectrometry (TIMS) and Particle Induced Gamma ray Spectrometry (PIGE). B4C samples having varying boron isotopic composition (natural, enriched with respect to 10B) and their synthetic mixtures) have been analysed by both the techniques. The 10B atom% was found to be in the range of 20-67%. (author)

  3. Isotopic composition dependences of lattice constant and thermal expansion of β-rhombohedral boron

    International Nuclear Information System (INIS)

    Boron isotope substitution in boron-containing crystalline structures is important because many properties of these materials are structure sensitive. In the present work, we studied the unit cell expansion at the fixed temperature and temperature dependence of thermal expansion for the β-rhombohedral modification of boron, when 11B is replaced by 10B isotope. Theoretical analysis of experimental results associates the observed changes in structures of the β-rhombohedral boron samples of various isotope compositions with isotope effects rather than with technologically concomitant impurities.

  4. Authentication of bell peppers using boron and strontium isotope compositions

    Science.gov (United States)

    Rosner, Martin; Pritzkow, Wolfgang; Vogl, Jochen; Voerkelius, Susanne

    2010-05-01

    The wrong declaration of food in terms of geographical origin and production method is a major problem for the individual consumer and public regulatory authorities. The authentication of food matrices using H-C-N-O-S isotopic compositions is already well established. However, specific questions require additional isotopic systems, which are more diagonstic for the source reservoires involved or production methods used. Here we present B and Sr isotopic compositions of bell peppers from Europe (Germany, Austria, Netherlands, Spain) and Israel to verfiy their origin. The bell peppers' B isotopic compositions between different locations are highly variable (d11BNISTSRM951 -8 to +35 ‰), whereas the 87Sr/86Sr ratios are all close to modern seawater Sr isotopic composition of about 0.7092 (0.7078 to 0.7107), but still can reliably be distinguished. Distinct isotopically heavy and light B isotopic fingerprints are obtained for bell peppers from Israel and the Netherlands. Samples from Germany, Austria, and Spain display overlapping d11B values between 0 and +12 ‰. Bell peppers from Israel show high d11B values (+28 to +35 ‰) combined with 87Sr/86Sr ratios slightly more unradiogenic than modern seawater (ca 0.7079). Bell peppers from the Netherlands, however, show low d11B values (-8 ‰) combinded with 87Sr/86Sr ratios of modern seawater (approx. 0.7085). Mainly based on diagnostic B isotopic compositions bell peppers from Israel and the Netherlands can be related to a specific geographical growing environment (Israel) or production method (Netherlands). The isotope fingerprints of bell peppers from the Netherlands are consistent with growing conditions in greenhouses typical for the Netherlands vegetable farming. Using optimized production methods crops in greenhouses were supplied with nutritients by liquid fertilizers on artificial substrates. As most fertilizers derive from non-marine salt deposits, fertilization typically imprints invariant d11B values close

  5. Wich Parameter of the Carbonate System Influences the Boron Isotopic Composition and the Boron Calcium Ratio in Foraminiferal Tests?

    Science.gov (United States)

    Kaczmarek, K.; Nehrke, G.; Horn, I.; Langer, G.; Misra, S.; Bijma, J.

    2013-12-01

    We performed culture experiments with the benthic symbiont bearing foraminifer Amphistegina lessonii in order to determine which parameter of the marine carbonate system influences the boron isotopic composition (δ11B) and the boron calcium ratio (B/Ca) in the test. A. lessonii grew for two months in treatments of culture media with decoupled pH-carbonate chemistry. We measured δ11B and B/Ca simultaneously on single tests using a recently new developed mass spectrometric technique. Our results show a clear pH dependence on δ11B. The B/Ca in the shell show a positive correlation with aqueous B(OH)4-/HCO3-.

  6. The atomic weight and isotopic composition of boron and their variation in nature

    International Nuclear Information System (INIS)

    The boron isotopic composition and atomic weight value and their variation in nature are reviewed. Questions are raised about the previously recommended value and the uncertainty for the atomic weight. The problem of what constitutes an acceptable range for normal material and what should then be considered geologically exceptional is discussed. Recent measurements make some previous decisions in need of re-evaluation

  7. Boron isotope composition of geothermal fluids and borate minerals from salar deposits (central Andes/NW Argentina)

    Science.gov (United States)

    Kasemann, Simone A.; Meixner, Anette; Erzinger, Jörg; Viramonte, José G.; Alonso, Ricardo N.; Franz, Gerhard

    2004-06-01

    We have measured the boron concentration and isotope composition of regionally expansive borate deposits and geothermal fluids from the Cenozoic geothermal system of the Argentine Puna Plateau in the central Andes. The borate minerals borax, colemanite, hydroboracite, inderite, inyoite, kernite, teruggite, tincalconite, and ulexite span a wide range of δ11B values from -29.5 to -0.3‰, whereas fluids cover a range from -18.3 to 0.7‰. The data from recent coexisting borate minerals and fluids allow for the calculation of the isotope composition of the ancient mineralizing fluids and thus for the constraint of the isotope composition of the source rocks sampled by the fluids. The boron isotope composition of ancient mineralizing fluids appears uniform throughout the section of precipitates at a given locality and similar to values obtained from recent thermal fluids. These findings support models that suggest uniform and stable climatic, magmatic, and tectonic conditions during the past 8 million years in this part of the central Andes. Boron in fluids is derived from different sources, depending on the drainage system and local country rocks. One significant boron source is the Paleozoic basement, which has a whole-rock isotopic composition of δ11B=-8.9±2.2‰ (1 SD); another important boron contribution comes from Neogene-Pleistocene ignimbrites ( δ11B=-3.8±2.8‰, 1 SD). Cenozoic andesites and Mesozoic limestones ( δ11B≤+8‰) provide a potential third boron source.

  8. Boron contents and isotopic compositions of hog manure, selected fertilizers, and water in Minnesota

    Science.gov (United States)

    Komor, S.C.

    1997-01-01

    Boron-isotope (δ11B) values may be useful as surrogate tracers of contaminants and indicators of water mixing in agricultural settings. This paper characterizes the B contents and isotopic compositions of hog manure and selected fertilizers, and presents δ11B data for ground and surface water from two agricultural areas. Boron concentrations in dry hog manure averaged 61 mg/kg and in commercial fertilizers ranged from below detection limits in some brands of ammonium nitrate and urea to 382 mg/kg in magnesium sulfate. Values of δ11B of untreated hog manure ranged from 7.2 to 11.2o/oo and of N fertilizers were −2.0 to 0.7o/oo. In 22 groundwater samples from a sand-plain aquifer in east-central Minnesota, B concentrations averaged 0.04 mg/L and δ11B values ranged from 2.3 to 41.5o/oo. Groundwater beneath a hog feedlot and a cultivated field where hog manure was applied had B-isotope compositions consistent with the water containing hog-manure leachate. In a 775-km2 watershed with silty-loam soils in southcentral Minnesota: 18 samples of subsurface drainage from corn (Zea mays L.) and soybean (Glycine max L. Merr.) fields had average B concentrations of 0.06 mg/L and δ11B values of 5.3 to 15.1o/oo; 27 stream samples had average B concentrations of 0.05 mg/L and δ11B values of 1.0 to 19.0o/oo; and eight groundwater samples had average B concentrations of 0.09 mg/L and δ11B values of −0.3 to 23.0o/oo. Values of δ11B and B concentrations, when plotted against one another, define a curved mixing trend that suggests subsurface drainage and stream water contain mixtures of B from shallow and deep groundwater.

  9. Boron content and isotopic composition of tektites and impact glasses: Constraints on source regions

    Science.gov (United States)

    Chaussidon, Marc; Koeberl, Christian

    1995-02-01

    Abundances of Li, Be, and B, as well as boron isotopic compositions, were determined in twenty-seven tektite and impact glass samples, using an ion microprobe. Samples included tektites from the Australasian, North American, and Ivory Coast strewn fields, and Aouelloul and Darwin impact glasses. Variations of B abundance and isotopic composition in a flanged australite were also studied. δ 11B variations of only a few permil were found within the australite flange. The isotopic composition shows no correlation with the B contents or with the distance from the rim of the flange. The mean δ 11B value for the flanged australite is very similar to that of Muong-Nong type tektites (-1.9 ± 1.9‰). Thus, vapor fractionation has been unimportant during tektite formation. This is supported by the observation that B contents and the δ 11B values of the different samples from the Australasian tektite strewn field are not correlated with each other. Most tektites show a rather limited range of δ 11B values (-9.3 ± 1.5 to +2.7 ± 1.5%o), which is small compared to the range observed for common terrestrial rocks (-30 to +40‰). The B abundance and isotopic data can be used to place constraints on the tektite source rocks. Australasian tektites have high B and Li abundances; only clay-rich sediments, such as pelagic and neritic sediments, as well as river and deltaic sediments have B contents (up to 100 ppm) and δ 11B values that are in agreement with the range shown by Australasian tektites (-4.9 to + 1.4‰). 10Be and RbSr data indicate continental crustal source rocks and exclude pelagic and neritic sediments. However, deltaic sediments, e.g., from the Mekong river, which are of continental crustal origin, agree with 10Be, RbSr, and B data, and support a possible source locality close to the coast of SE Indochina in the South China Sea. On the other hand, one bediasite sample has a very high δ 11B value of +15.1 ± 2.1‰, requiring the presence of marine

  10. Determination of isotopic composition of boron in various neutron absorbers by a particle induced gamma-ray emission method

    International Nuclear Information System (INIS)

    A particle induced gamma-ray emission (PIGE) method was utilized for non-destructive determination of isotopic composition of boron (10B/11B atom ratio) in seven natural and two enriched boron based neutron absorber samples. Samples in pellet forms were irradiated with 4 MeV proton beam from FOlded Tandem Ion Accelerator (FOTIA) at BARC, Mumbai. The prompt gamma rays of 429, 718 and 2125 keV from 10B (p, αγ)7Be, 10B(p,p'γ)10B and 11B(p,p' γ)11B, respectively, were measured using high resolution gamma-ray spectrometry. Isotopic composition values were arrived by a relative method using corresponding peak areas of 10B and 11B. (author)

  11. Mass spectrometric determination of boron isotope in boron carbide

    International Nuclear Information System (INIS)

    Boron isotopes in boron carbide are measured by thermionic ionization mass spectrometry with no prior chemical separation. Boron is converted to sodium borate by fusion of the boron carbide with sodium hydroxide (or sodium carbonate) directly on the rhenium filament. The boron isotopic ratios are measured by using the Na2BO2+ ion

  12. Development and validation of a single collector ICPMS procedure to determine boron isotopeic compositions of water and food samples

    Science.gov (United States)

    Vogl, Jochen; Rosner, Martin; Pritzkow, Wolfgang

    2010-05-01

    Authenticity and provenance studies as well as issues in environmental- and geo-sciences are hot topics in nowadays isotope research. Elements being known for their natural isotopic variation, such as lead and strontium, are being used to assign the provenance of artefacts, food and other products. A recent study revealed the potential of boron (B) isotopes for delivering information on the provenance of crop plants. To offer alternative analytical instrumentations beside the classical TIMS procedures a single collector ICPMS procedure for B isotope analyses has been developed and validated. This procedure should enable more B isotope studies, as single collector ICPMS intruments are more widepread in the relevant laboratories compared to TIMS. The developed procedures for the determination of B isotopic compositions use a magnetic sector ICPMS and consist of one low resolution (LR) and one medium resolution (MR) procedure. The absolute standard deviation for the δ11B determination in three independently measured samples lies between 0.2 and 0.8 ‰ for the LR and between 0.3 and 1.5 ‰ for the MR. The expanded uncertainties with a coverage factor of k=2 range between 1.4 and 1.6 ‰ for the LR and between 2.9 and 3.2 ‰ for the MR. The trueness, expressed as average deviation from the reference values, is less than 1.1 ‰ for LR and 0.8 ‰ for MR. To test the practicability of the procedure the matrix tolerance has been investigated. Using a measurement solution containing 100 µg/kg boron a matrix of 2 mg/kg of alkaline and earth alkaline elements was found as a limit for stable instrumental mass discrimination. Thus a highly efficient matrix separation is required, similar to TIMS. The developed procedure is well suited for the for B isotope studies of various matrices and especially the LR procedure offers relatively small uncertainties combined with high sample throughput.

  13. Boron isotopes in geothermal systems

    International Nuclear Information System (INIS)

    Boron is a highly mobile element and during water-rock reactions, boron is leached out of rocks with no apparent fractionation. In geothermal systems where the water recharging the systems are meteoric in origin, the B isotope ratio of the geothermal fluid reflects the B isotope ratio of the rocks. Seawater has a distinctive B isotope ratio and where seawater recharges the geothermal system, the B isotope ratio of the geothermal system reflects the mixing of rock derived B and seawater derived B. Any deviations of the actual B isotope ratio of a mixture reflects subtle differences in the water-rock ratios in the cold downwelling limb of the hydrothermal system. This paper will present data from a variety of different geothermal systems, including New Zealand; Iceland; Yellowston, USA; Ibusuki, Japan to show the range in B isotope ratios in active geothermal systems. Some of these systems show well defined mixing trends between seawater and the host rocks, whilst others show the boron isotope ratios of the host rock only. In geothermal systems containing high amounts of CO2 boron isotope ratios from a volatile B source can also be inferred. (auth)

  14. Isotopic composition of dissolved boron and its geochemical behavior in a freshwater-seawater mixture at the estuary of the Changjiang (Yangtze) River

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The isotopic composition of dissolved boron, in combination with the elemental concentrations of B, Cl and salinities in freshwater-seawater mixed samples taken from the estuary of the Changjiang River, the largest one in China, was investigated in detail in this study. Brackish water and seawater samples from the estuary of the Changjiang River were collected during low water season in November, 1998. Boron isotopic compositions were determined by the Cs2BO2+-graphite technique with a analytical uncertainty of 0.2‰ for NIST SRM 951 and an average analytical uncertainty of 0.8‰ for the samples. The isotopic compositions of boron, expressed in δ11B, and boron concentrations in the Changjiang River at Nanjing and seawater from the open marine East Sea, China, are characterized by δ11B values of -5.4‰ and 40.0‰, as well as 0.0272 and 4.43 mg B/L, respectively. Well-defined correlations between δ11B values, B concentrations and Cl concentrations are interpreted in terms of binary mixing between river input water and East Sea seawater by a process of straightforward dilution. The offsets of δ11B values are not related to the contents of clastic sediment and to the addition of boron. These relationships favor a conservative behavior of boron at the estuarine of the Changjiang River.

  15. Boron, lithium and methane isotope composition of hyperalkaline waters (Northern Apennines, Italy): Terrestrial serpentinization or mixing with brine?

    International Nuclear Information System (INIS)

    Highlights: ► First data on boron and lithium isotope on waters from ophiolites are described. ► High boron and lithium isotope composition may be related to terrestrial serpentinization. ► Methane isotope data show unusual biotic signature. - Abstract: Spring waters issuing from serpentinized ultramafic rocks of the Taro-Ceno Valleys (Northern Apennine, Emilia-Romagna region, Italy) were analyzed for major element, trace element and dissolved gas concentrations and δ11B, δ7Li, δ18O(H2O), δ2H(H2O), δ13C(CH4) and δ2H(CH4) isotope compositions. Similar to other springs worldwide that issue from serpentinites, the chemical composition of the waters evolves with water–rock interaction from Ca-HCO3, through Mg-HCO3 and ultimately to a hyperalkaline Na-(Ca)-OH composition. Most of the Ca- and Mg-HCO3 springs have δ11B ranging between +16.3‰ and +23.7‰, consistent with the range of low P–T serpentinites. Very high δ11B in two springs from Mt. Prinzera (PR10: +39‰; PR01: +43‰) can be related to isotopic fractionation during secondary phase precipitation, as also inferred from δ7Li values. In contrast to typical abiogenic isotope signatures of CH4 from serpentinized rocks, dissolved CH4 from the Taro-Ceno hyperalkaline springs has an apparent biotic (thermogenic and/or mixed thermogenic-microbial) signature with δ13C(CH4) ranging from −57.5‰ to −40.8‰, which is similar to that of hydrocarbons from production wells and natural seeps in adjacent hydrocarbon systems. The data suggest that CH4 in the hyperalkaline springs investigated in this study may derive from organic matter of the sedimentary (flysch and arenaceous) formations underlying the ophiolite unit. However, small amounts of H2 were detected in one hyperalkaline spring (PR10), but for two springs with very low CH4 concentrations (PR01 and UM15) the δ2H value could not be measured, so the occurrence of some abiotic CH4 cannot be excluded. The occurrence of thermogenic CH4 in

  16. Boron nitride composites

    Energy Technology Data Exchange (ETDEWEB)

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  17. Effects of seawater-pH and biomineralization on the boron isotopic composition of deep-sea bamboo corals

    Science.gov (United States)

    Farmer, Jesse R.; Hönisch, Bärbel; Robinson, Laura F.; Hill, Tessa M.

    2015-04-01

    The ocean is currently absorbing excess carbon from anthropogenic emissions, leading to reduced seawater-pH (termed 'ocean acidification'). Instrumental records of ocean acidification are unavailable from well-ventilated areas of the deep ocean, necessitating proxy records to improve spatio-temporal understanding on the rate and magnitude of deep ocean acidification. Here we investigate boron, carbon, and oxygen isotopes on live-collected deep-sea bamboo corals (genus Keratoisis) from a pHtot range of 7.5-8.1. These analyses are used to explore the potential for using bamboo coral skeletons as archives of past deep-sea pH and to trace anthropogenic acidification in the subsurface North Atlantic Ocean (850-2000 m water depth). Boron isotope ratios of the most recently secreted calcite of bamboo coral skeletons are close to the calculated isotopic composition of borate anion in seawater (δ11Bborate) for North Atlantic corals, and 1-2‰ higher than δ11Bborate for Pacific corals. Within individual coral skeletons, carbon and oxygen isotopes correlate positively and linearly, a feature associated with vital effects during coral calcification. δ11B variability of 0.5-2‰ is observed within single specimens, which exceeds the expected anthropogenic trend in modern North Atlantic corals. δ11B values are generally elevated in Pacific corals relative to δ11Bborate, which may reflect pH-driven physiological processes aiding coral calcification in environments unfavorable for calcite precipitation. Elevated δ11B values are also observed proximal to the central axis in multiple Atlantic and Pacific specimens, relative to δ11Bborate, which might reflect ontogenetic variability in calcification rates. Although the observed boron isotope variability is too large to resolve the present anthropogenic ocean acidification signal at the studied depths in the North Atlantic (∼0.03-0.07 pH units), pH changes ⩾0.1 units might still be reconstructed using δ11B measurements in

  18. Geochemical evolution of tourmaline in the Darasun gold district, Transbaikal region, Russia: evidence from chemical and boron isotopic compositions

    Science.gov (United States)

    Baksheev, Ivan A.; Prokofiev, Vsevolod Yu.; Trumbull, Robert B.; Wiedenbeck, Michael; Yapaskurt, Vasilii O.

    2015-01-01

    The Darasun gold district, Transbaikal region, eastern Russia comprises three deposits: Teremkyn, Talatui, and Darasun, where gold-bearing quartz veins are hosted in metagabbro and granitoids. Tourmaline is a common gangue mineral in these deposits and a useful indicator of fluid source. The tourmaline compositions are oxy-dravite-povondraite, dravite, and schorl. We report here in situ B-isotope analyses by secondary ion mass spectrometry (SIMS) on tourmaline from veins in metagabbro and K-rich granodiorite, as well as from a breccia pipe at the margin of granodiorite porphyry. The B-isotope composition of tourmalines from the Darasun gold district as a whole covers a very wide range from -15.7 to +11.2 ‰, with distinctive differences among the three deposits. The δ11B values in the Teremkyn tourmalines are the most diverse, from -15.7 to +2.5 ‰. Tourmaline core compositions yield an inferred δ11B value of the initial fluid of ca. -12 ‰, suggesting granitic rocks as the B source, whereas the heavier rims and late-stage grains reflect Rayleigh fractionation. The δ11B values of tourmaline from Talatuiare -5.2 to -0.9 ‰. Taking into account fluid inclusion temperatures from vein quartz (ca. 400 °C), the inferred δ11B value of fluid is heavy (-2.5 to +2.2 ‰) suggesting a B source from the host metagabbro. At the Darasun deposit, tourmaline from the breccia pipe is isotopically uniform (δ11 B -6 to -5 ‰) and suggested to have precipitated from a 10B-depleted, residual fluid derived from granitic rocks. The Darasun vein-hosted tourmalines I and II (δ11B from -4.4 to +1.5 ‰) may have crystallized from strongly fractionated residual granitic fluid although mixing with heavy boron from the metagabbro rocks probably occurred as well; the boron isotopic composition of tourmaline III (-11.2 ‰) is attributed to a less-fractionated fluid, possibly a recharge from the same source.

  19. Geochemical and boron isotopic compositions of tourmalines from selected gold-mineralised and barren rocks in SW Finland

    Directory of Open Access Journals (Sweden)

    Matti Talikka

    2010-12-01

    Full Text Available Tourmaline-bearing rocks and a number of gold occurrences coexist in southwestern Finland, in a region where extensive magmatism and hydrothermal systems occurred during the Svecofennian orogeny, 1.9–1.8 Ga ago. Tourmalines investigated for this study were sampled from late-orogenic granite pegmatites (Eräjärvi, Kietyönmäki, quartztourmaline veins from gold occurrences (Kutemajärvi, Riukka, and the tourmalinised contact between a synorogenic intrusion and supracrustal rocks (Lepomäki Au occurrence, Ylöjärvi Cu-W-As-Ag-Au deposit. Major element compositions of the tourmalines are controlled by their host lithologies, whereas their boron isotopic compositions reflect the B reservoir(s and the magmatic hydrothermal processes of the B-bearing systems. The obtained δ11B values for granite pegmatite, vein, and intrusion-country rock contact-related tourmalines range between -10.2 ‰ and -13.2 ‰, -10.2 ‰ and -11.6 ‰, and -9.6 ‰ and -8.7 ‰, respectively, and are similar to tourmalines worldwide.The lighter B isotopic composition at Lepomäki gold and Ylöjärvi polymetallic occurrences indicate different B reservoirs and magmatic-hydrothermal processes between syn and late-orogenic tourmalines. Geological observations and geochemical data on tourmalinesalso suggest that B was a constituent in hydrothermal fluids at all localities, including the gold-mineralising fluids at Lepomäki, Ylöjärvi and Riukka.

  20. ISOBORDAT: An Online Data Base on Boron Isotopes

    International Nuclear Information System (INIS)

    From 1986, boron isotope data in natural substances increased sharply in scientific publications. Analytical difficulties derived from complex geochemical matrices have been faced and interlaboratory calibrations reported in the boron literature. Boron isotopes are nowdays applied to investigate boron origin and migration in natural waters, sources of boron contamination, water-rock interactions and also contribute to water resource management. This is especially important in those areas where boron content exceeds the local regulations for drinking water supply and boron sources need to be identified. ISOBORDAT, an interactive database on boron isotope composition and content in natural waters is presented to the wider community of boron isotope users. The database's structure, scope and applications are reported, along with a discussion on δ11B values obtained in Italian waters. In the database boron data are structured in the following categories: rainwater, rivers, lakes, groundwater and potential contaminants. New categories (medium and high enthalpy fluids from volcanic and geothermal areas) are anticipated. ISOBORDAT aims to be as interactive as possible and will be developed taking into account information and suggestions received. The database is continually undergoing revision to keep pace with continuous data publication. Indications of data that are missing at present are greatly appreciated. (author)

  1. Boron isotope method for study of seawater intrusion

    Institute of Scientific and Technical Information of China (English)

    肖应凯; 尹德忠; 刘卫国; 王庆忠; 魏海珍

    2001-01-01

    A distinct difference in boron isotopes between seawater and terrestrial water is emphasized by δ11B values reported for seawater and groundwater, with an average of 38.8‰ and in the range of -8.9‰ to 9.8‰, respectively. The isotopic composition of boron in groundwater can be used to quantify seawater intrusion and identify intrusion types, e.g. seawater or brine intrusions with different chemical and isotopic characteristics, by using the relation of δ11B and chloride concentration. The feasibility of utilizing boron isotope in groundwater for studying seawater intrusion in Laizhou Bay Region, China, is reported in this study, which shows that boron isotope is a useful and excellent tool for the study of seawater intrusion.

  2. Effects of foliar boron application on seed composition, cell wall boron, and seed δ15N and δ13C isotopes in water-stressed soybean plants

    OpenAIRE

    Bellaloui, Nacer; Hu, Yanbo; Mengistu, Alemu; Kassem, My A.; Abel, Craig A.

    2013-01-01

    Limited information is available on the effects of foliar boron (B) application on soybean seed composition. The objective of this research was to investigate the effects of foliar B on seed composition (protein, oil, fatty acids, and sugars). Our hypothesis was that since B is involved in nitrogen and carbon metabolism, it may impact seed composition. A repeated greenhouse experiment was conducted where half of the soybean plants was exposed to water stress (WS) and the other half was well-w...

  3. Boron isotope fractionation during brucite deposition from artificial seawater

    Directory of Open Access Journals (Sweden)

    J. Xiao

    2011-03-01

    Full Text Available Experiments involving boron incorporation into brucite (Mg(OH2 from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite. The results show that both concentration of boron in deposited brucite ([B]d and its boron partition coefficient (Kd between deposited brucite and final seawater are controlled by pH of the solution. The incorporation capacity of boron into brucite is much stronger than that into oxides and clay minerals. The isotopic compositions of boron in deposited brucite (δ11Bd are higher than those in the associated artificial seawater (δ11Bisw with fractionation factors ranging between 1.0177 and 1.0569, resulting from the preferential incorporation of B(OH3 into brucite. Both boron adsorptions onto brucite and precipitation reaction of H3BO3 with brucite exist during deposition of brucite from artificial seawater. The simultaneous occurrence of both processes determines the boron concentration and isotopic fractionation of brucite. The isotopic fractionation behaviors and mechanisms of boron incorporated into brucite are different from those into carbonates. Furthermore, the isotopic compositions of boron in modern corals might be affected by the existence of brucite in madrepore and the preferential incorporation of B(OH3 into brucite. An exploratory study for the influence of brucite on the boron isotopic composition in modern corals is justifiable.

  4. Boron isotopic enrichment by displacement chromatography

    International Nuclear Information System (INIS)

    10B 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 10B 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 10B and 11B

  5. Boron-isotope fractionation in plants

    International Nuclear Information System (INIS)

    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, 11B and 10B, has been made. Here, we report that plants with differing B requirements (wheat, corn and broccoli) fractionated boron. The whole plant was enriched in 11B relative to the nutrient solution, and the leaves were enriched in 10B and the stem in 11B relative to the xylem sap. Although at present, a mechanistic role for boron in plants is uncertain, potential fractionating mechanisms are discussed. (author)

  6. Laser Ablation Molecular Isotopic Spectrometry: Parameter influence on boron isotope measurements

    International Nuclear Information System (INIS)

    Laser Ablation Molecular Isotopic Spectrometry (LAMIS) was recently reported for optical isotopic analysis of condensed samples in ambient air and at ambient pressure. LAMIS utilizes molecular emissions which exhibit larger isotopic spectral shits than in atomic transitions. For boron monoxide 10BO and 11BO, the isotopic shifts extend from 114 cm-1 (0.74 nm) to 145-238 cm-1 (5-8 nm) at the B2Σ+ (v = 0) → X2Σ+ (v = 2) and A2Πi (v = 0) → X2Σ+ (v = 3) transitions, respectively. These molecular isotopic shifts are over two orders of magnitude larger than the maximum isotopic shift of approximately 0.6 cm-1 in atomic boron. This paper describes how boron isotope abundance can be quantitatively determined using LAMIS and how atomic, ionic, and molecular optical emission develops in a plasma emanating from laser ablation of solid samples with various boron isotopic composition. We demonstrate that requirements for spectral resolution of the measurement system can be significantly relaxed when the isotopic abundance ratio is determined using chemometric analysis of spectra. Sensitivity can be improved by using a second slightly delayed laser pulse arriving into an expanding plume created by the first ablation pulse.

  7. Reconstructing Ocean pH with Boron Isotopes in Foraminifera

    Science.gov (United States)

    Foster, Gavin L.; Rae, James W. B.

    2016-06-01

    In order to better understand the effect of CO2 on the Earth system in the future, geologists may look to CO2-induced environmental change in Earth's past. Here we describe how CO2 can be reconstructed using the boron isotopic composition (δ11B) of marine calcium carbonate. We review the chemical principles that underlie the proxy, summarize the available calibration data, and detail how boron isotopes can be used to estimate ocean pH and ultimately atmospheric CO2 in the past. δ11B in a variety of marine carbonates shows a coherent relationship with seawater pH, in broad agreement with simple models for this proxy. Offsets between measured and predicted δ11B may in part be explained by physiological influences, though the exact mechanisms of boron incorporation into carbonate remain unknown. Despite these uncertainties, we demonstrate that δ11B may provide crucial constraints on past ocean acidification and atmospheric CO2.

  8. Boron isotope fractionation during brucite deposition from artificial seawater

    Directory of Open Access Journals (Sweden)

    J. Xiao

    2011-07-01

    Full Text Available Experiments involving boron incorporation into brucite (Mg(OH2 from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite and the influence of it on Mg/Ca-SST proxy and δ11B-pH proxy. The results show that both the concentration of boron in deposited brucite ([B]d and its boron partition coefficient (Kd between deposited brucite and final seawater are controlled by the pH of the solution. The incorporation capacity of boron into brucite is almost the same as that into corals, but much stronger than that into oxides and clay minerals. The isotopic compositions of boron in deposited brucite (δ11Bd are higher than those in the associated artificial seawater (δ11Bisw with fractionation factors ranging between 1.0177 and 1.0569, resulting from the preferential incorporation of B(OH3 into brucite. Both boron adsorptions onto brucite and the precipitation reaction of H3BO3 with brucite exist during deposition of brucite from artificial seawater. The simultaneous occurrence of both processes determines the boron concentration and isotopic fractionation of brucite. The isotopic fractionation behaviors and mechanisms of boron incorporated into brucite are different from those into corals. The existence of brucite in corals can affect the δ11B and Mg/Ca in corals and influences the Mg/Ca-SST proxy and δ11B-pH proxy negatively. The relationship between δ11B and Mg/Ca in corals can be used to judge the existence of brucite in corals, which should provide a reliable method for better use of δ11B and Mg/Ca in corals to reconstruct paleo-marine environment.

  9. Tracing recycled volatiles in a heterogeneous mantle with boron isotopes

    Science.gov (United States)

    Walowski, Kristina; Kirstein, Linda; de Hoog, Cees-Jan; Elliot, Tim; Savov, Ivan; Devey, Colin

    2016-04-01

    Recycling of oceanic lithosphere drives the chemical evolution of the Earth's mantle supplying both solids and volatiles to the Earth's interior. Yet, how subducted material influences mantle composition remains unclear. A perfect tracer for slab recycling should be only fractionated at the Earth's surface, have a strong influence on mantle compositions but be resistant to perturbations en route back to the surface. Current understanding suggests that boron concentrations linked to B isotope determinations fulfil all these requirements and should be an excellent tracer of heterogeneity in the deep mantle. Here, we present the trace element, volatile and the B isotope composition of basaltic glasses and melt inclusions in olivine from distinct end-member ocean island basalts (OIB) to track the fate of recycled lithosphere and ultimately document how recycling contributes to mantle heterogeneity. The chosen samples represent the different end member OIB compositions and include: EMI (Pitcairn), EMII (MacDonald), HIMU (St. Helena), and FOZO (Cape Verde & Reunion). The data is derived from both submarine and subaerial deposits, with B isotope determination of both basaltic glass and melt inclusions from each locality. Preliminary results suggest OIB have B isotopic compositions that overlap the MORB array (-7.5‰±0.7; Marschall et al., 2015) but extend to both lighter and heavier values. These results suggest that B isotopes will be useful for resolving mantle source heterogeneity at different ocean islands and contribute to our understanding of the volatile budget of the deep mantle.

  10. Isotopic effects on the phonon modes in boron carbide.

    Science.gov (United States)

    Werheit, H; Kuhlmann, U; Rotter, H W; Shalamberidze, S O

    2010-10-01

    The effect of isotopes ((10)B-(11)B; (12)C-(13)C) on the infrared- and Raman-active phonons of boron carbide has been investigated. For B isotopes, the contributions of the virtual crystal approximation, polarization vector and isotopical disorder are separated. Boron and carbon isotope effects are largely opposite to one another and indicate the share of the particular atoms in the atomic assemblies vibrating in specific phonon modes. Some infrared-active phonons behave as expected for monatomic boron crystals. PMID:21403227

  11. Thermal conductivity of boron carbide-boron nitride composites

    International Nuclear Information System (INIS)

    This paper reports that because of their preferred orientation, the addition of boron nitride dispersions to hot-pressed boron carbide was found to result in a considerable degree of anisotropy in thermal conductivity of the resulting composite, indicated by an increase in the thermal conductivity perpendicular to the hot-pressing direction by as much as a factor of 3 at the highest boron nitride volume fractions of this study, and a decrease in the thermal conductivity parallel to the hot-pressing direction by as much as a factor of 2. The composite data were found to be below the values expected from composite theory, which may represent indirect evidence for the existence of an interfacial thermal barrier

  12. Fractionation of Boron Isotopes in Icelandic Hydrothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Aggarwal, J.K.; Palmer, M.R.

    1995-01-01

    Boron isotope ratios have been determined in a variety of different geothermal waters from hydrothermal systems across Iceland. Isotope ratios from the high temperature meteoric water recharged systems reflect the isotope ratio of the host rocks without any apparent fractionation. Seawater recharged geothermal systems exhibit more positive {delta}{sup 11}B values than the meteoric water recharged geothermal systems. Water/rock ratios can be assessed from boron isotope ratios in the saline hydrothermal systems. Low temperature hydrothermal systems also exhibit more positive {delta}{sup 11}B than the high temperature systems, indicating fractionation of boron due to adsorption of the lighter isotope onto secondary minerals. Fractionation of boron in carbonate deposits may indicate the level of equilibrium attained within the systems.

  13. Development of TIMS for isotopic ratio analysis of boron

    International Nuclear Information System (INIS)

    A magnetic sector based Thermal Ionisation Mass Spectrometer (TIMS) has been developed at Technical Physics Division, for high precision isotope ratio analysis of Boron (in the form of Sodium Meta-borate) at the Boron enrichment facility, Heavy Water Plant, Manuguru. The performance of this indigenously developed TIMS has been tested for sensitivity, isotope ratio precision and accuracy for different levels of enrichment in the plant samples. The sensitivity of this instrument was found to be 1 ion per 200 atoms. The internal and external precision for natural concentration levels Boron isotopes were better than 0.05%. (author)

  14. Determination of boron isotope ratios in boron carbide by mass spectrometry

    International Nuclear Information System (INIS)

    This paper introduces the direct determination of boron isotope ratios in the boron carbide powder by thermal ionization mass spectrometry. The technique for sample loading, the procedure for heating and the eliminating of effects induced by oxygen are studied. The study indicates that the preparing process for the sample will be shorted, and the time for determination and the exposure dose of the laboratory assistant will be reduced for the reason of directly determination of boron carbide. (authors)

  15. Ground-water pollution determined by boron isotope systematics

    International Nuclear Information System (INIS)

    Boron isotopic systematics as related to ground-water pollution is reviewed. We report isotopic results of contaminated ground water from the coastal aquifers of the Mediterranean in Israel, Cornia River in north-western Italy, and Salinas Valley, California. In addition, the B isotopic composition of synthetic B compounds used for detergents and fertilizers was investigated. Isotopic analyses were carried out by negative thermal ionization mass spectrometry. The investigated ground water revealed different contamination sources; underlying saline water of a marine origin in saline plumes in the Mediterranean coastal aquifer of Israel (δ11B=31.7 per mille to 49.9 per mille, B/Cl ratio ∼1.5x10-3), mixing of fresh and sea water (25 per mille to 38 per mille, B/Cl∼7x10-3) in saline water associated with salt-water intrusion to Salinas Valley, California, and a hydrothermal contribution (high B/Cl of ∼0.03, δ11B=2.4 per mille to 9.3 per mille) in ground water from Cornia River, Italy. The δ11B values of synthetic Na-borate products (-0.4 per mille to 7.5 per mille) overlap with those of natural Na-borate minerals (-0.9 per mille to 10.2 per mille). In contrast, the δ11B values of synthetic Ca-borate and Na/Ca borate products are significantly lower (-15 per mille to -12.1 per mille) and overlap with those of the natural Ca-borate minerals. We suggest that the original isotopic signature of the natural borate minerals is not modified during the manufacturing process of the synthetic products, and it is controlled by the crystal chemistry of borate minerals. The B concentrations in pristine ground-waters are generally low (11B=39 per mille), salt-water intrusion and marine-derived brines (40 per mille to 60 per mille) are sharply different from hydrothermal fluids (δ11B=10 per mille to 10 per mille) and anthropogenic sources (sewage effluent: δ11B=0 per mille to 10 per mille; boron-fertilizer: δ11B=-15 per mille to 7 per mille). some differences (up to 15

  16. Stable isotope ratio mass spectrometry of nanogram quantities of boron and sulfur

    Science.gov (United States)

    Wieser, Michael Eugene

    1998-09-01

    Instrumentation and analytical techniques were developed to measure isotope abundances from nanograms of sulfur and boron. Sulfur isotope compositions were determined employing continuous flow isotope ratio mass spectroscopy (CF-IRMS) procedures and AsS+ thermal ionization mass spectrometry techniques (AsS+-TIMS). Boron isotope abundances were determined by BO2/sp--TIMS. CF-IRMS measurements realized δ34S values from 10 μg sulfur with precisions of ±0.3/perthous. To extend sulfur isotope measurements to much smaller samples, a TIMS procedure was developed to measure 75As32S+ and 75As34S+ at masses 108 and 109 from 200 ng S on a Finnigan MAT 262 with an ion counter. This is possibly the smallest amount of sulfur which has been successfully analyzed isotopically. The internal precision of 32S/34S ratios measured by AsS+-TIMS was better than ±0.15 percent. δ34S-values calculated relative to the measured 32S/34S value of an IAEA AG2S standard (S-1) agreed with those determined by CF-IRMS to within ±3/perthous. The increasing sensitivity of S-isotope analyses permits hiterto impossible investigations e.g. sulfur in tree rings and ice cores. Boron isotope abundances were measured as BO2/sp- from 50 ng B using an older thermal ionization mass spectrometer which had been extensively upgraded including the addition of computer control electronics, sensitive ion current amplification and fiber optic data bus. The internal precisions of the measured 11B/10B ratios were ±0.15 percent and the precisions of δ11B values calculated relative to the accepted international standard (SRM-951) were ±3/perthous. Two applications of boron isotope abundance variations were initiated (1) ground waters of Northern Alberta and (2) coffee beans in different regions of the world. In the first it was demonstrated that boron isotopes could be used to trace boron released during steam injection of oil sands into the surrounding environment. Data from the second study suggest that boron

  17. Isotope effect on the spin resonance of boron in silicon

    International Nuclear Information System (INIS)

    The fourfold degeneracy of the boron acceptor ground state in silicon, which is easily lifted by any symmetry breaking perturbation, allows for a strong inhomogeneous broadening of the B-related electron paramagnetic resonance (EPR) lines, e.g. by randomly distributed, defect-induced local strain. In previous studies a number of fundamental questions concerning the line shape, the magnitude of the residual broadening, and the substructure of the B resonances have remained unsolved. We show that local fluctuations of the valence band edge due to the presence of different Si isotopes in the vicinity of the B acceptors can quantitatively account for all inhomogeneous broadening effects in high purity Si with a natural isotope composition. A comparison of our calculations with previous work investigating the B acceptor ground state in the absence of an external magnetic field, provides an independent verification of the energy offsets between the valence bands of 28Si, 29Si, and 30Si. Moreover, our calculations show that the isotopic perturbation also leads to a shift in the g-value of different B-related resonance lines, which could be verified in our experiments.

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

    International Nuclear Information System (INIS)

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

  19. Geochemical study of boron isotopes in the process of loess weathering

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Zhiqi; (

    2003-01-01

    [1]Palmer, M. R., Swihart, G. H., Boron isotope geochemistry: An overview, in Rev. Mineral 33, Boron Mineralogy, Petrology and Geochemistry (eds. Grew, E. S., Anovitz, L. M.), Washington, D. C.: Mineral Soc. Am., 1996, 709-744.[2]Chaussidon, M., Albarède, F., Secular boron isotope variations in the continental crust: An ion microprobe study, Earth Planet Sci. Lett., 1992, 108: 229-241.[3]Spivack, A. J., Edmond, J. M., Boron isotope exchange between seawater and the oceanic crust, Geochim. Cosmochim. Acta, 1987, 51: 1033-1043.[4]Vengosh, A., Chivas, A. R., Mcculloch, M. T. et al., Boron isotope geochemistry of Australian salt lakes, Geochim. Cosmochim. Acta, 1991, 55: 2591-2606.[5]Xiao, Y. K., Sun, D. P., Wang, Y. H. et al., Boron isotopic compositions of brine, sediments and source water in Da Qaidam Lake, Qinghai, China, Geochim Cosmochim Acta, 1992,56: 1561-1568.[6]Mcmullen, C. C., Cragg, C. B., Thode, H. G., Absolute rations of 11B/10B in Searles Lake borax, Geochim. Cosmochim. Acta, 1961, 23: 147-150.[7]Palmer, M. R., Sturchio, N. C., The boron isotope systematics of the Yellowstone National Park (Wyoming) hydrothermal system: A reconnaissance, Geochim. Cosmochim. Acta, 1990, 54: 2811-2815.[8]Arndsson, S., Andrèsdèttir, A., Processes controlling the distribution of boron and chlorine in natural waters in Iceland, Geochim. Cosmochim. Acta, 1995, 59: 4125-4146.[9]Aggarwal, J. K., Palmer, M. R., Bullen, T. D. et al., The boron isotope systematics of Iceland geothermal waters: 1. Meteoric water charged systems, Geochim. Cosmochim. Acta, 2000, 64: 579-585.[10]Spivack, A. J., Palmer, M. R., Edmond, J. M., The sedimentary cycle of the boron isotopes, Geochim. Cosmochim. Acta, 1987, 51: 1939-1949.[11]Liu Yingjun, Cao Liming, Li Zhaolin et al., Element Geochemistry (in Chinese), Beijing: Science Press, 1984, 422-428.[12]Schwarcz, H. P., Agyei, E. K., Mcmullen, C. C., Boron isotopic fractionation during clay adsorption

  20. Separation of boron isotopes using NMG type anion exchange resin

    International Nuclear Information System (INIS)

    Ion exchange separation of boron isotopes (B-10 and B-11) has been studied by using a special boron selective ion exchange resin; NMG (n-methyl glucamine)-type anion exchange resin. The resin has shown a large isotope separation coefficient of 1.02 at the experimental conditions of temperature, 80degC, and boric acid concentration, 0.2 M (mole/dm3). Enriched B-10 (92%) was obtained after the migration of 1149 m by a recyclic operation of ion exchange columns in a merry-go-round method. (author)

  1. A Preliminary experimental study of the boron concentration in vapor and the isotopic A preliminary experimental study of the boron concentrationin vapor and the isotopic fractionation of boron betweenseawater and vapor during evaporation of seawater

    Institute of Scientific and Technical Information of China (English)

    XIAO; Yingkai

    2001-01-01

    [1]Gast, J. A., Thompson, T. G., Evaporation of boric acid from seawater, Tellus, 1959, 6: 344-347.[2]Nishimura, M., Tanaka, K., Seawater may not be a source of boron in the atmosphere, J. Geoph. Res., 1972, 77: 5239-5242.[3]Fogg, T. R., Duce, R. A., Fasching, J. L., Sampling and determination of boron in the atmosphere, Anal. Chem., 1983, 55:2179-2184.[4]Fogg, T. R., Duce, R. A., Boron in the troposphere: Distribution and fluxes, J. Geoph. Res., 1985, 90: 3781-3796.[5]Spivack, A. J., Berndt, M. E., Seyfreid, W. E., Boron isotope fractionation during supercritical phase separation, Geochim.Cosmochim. Acta, 1990, 54: 2337-2339.[6]Palmer, M. R., London, D., Morgan, G. B. et al., Experimental determination of fractionation of 11B/10B between tourma-line and aqueous vapor: A temperature and pressure-dependent isotopic system, Chem. Geol., 1992, 101:123-129.[7]Hervig, R. L., London, D., Morgan, G. B. et al., Large boron isotope fractionation between hydrous vapor and silicate meltat igneous temperatures, in the Seventh Annual V. M. Goldschmidt Conf., LPI Contribution No. 921, Houston: Lunar and Planetary Institute, 1997, 93-94.[8]Vengosh, A., Starinsky, A., Kolodny, Y. et al., Boron isotope variations during fractional evaporation of seawater: New constraints on the marine vs. nonmarine debate, Geology, 1992, 20: 799-802.[9]Zhang, X. P., Shi, Y. E, Yao, T. D., The variation characteristics of δo18O in precipitation in Northeastern Qing-Zhang Plateau, Science in China, Series B (in Chinese), 1995, 25(5): 540-547.[10]Yu, J. S., Yu, E J., Liu, D. P., The hydrogen and oxygen of isotopic compositions of meteoric water in the eastern part of China, Geochimica (in Chinese), 1987, (1): 22-26.[11]Xiao, Y. K., Xiao, Y., Swihart, G. H. et al., Separation of boron by ion exchange with boron specific resin, Acta Geosci.Sinica (in Chinese), 1997, 18: 286-289.[12]Kiss, E., Ion-exchange separation and spectrophotometric determination of

  2. Pressure-dependent boron isotopic fractionation observed by column chromatography

    Science.gov (United States)

    Musashi, M.; Oi, T.; Matsuo, M.; Nomura, M.

    2007-12-01

    Boron isotopic fractionation factor ( S ) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25°C, using 0.1 mmol/L boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at atmospheric pressure at 25°C with the boron concentration of 10 mmol/L, but were larger than the values at the same condition with much higher concentration of 100 and 501 mmol/L, indicating that borate-polymerization reducing the isotopic fractionation was negligible. However, calculations based on the theory of isotope distribution between two phases estimated that 21% (5MPa) and 47% (17MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)3-form, instead of in the four-coordinated B(OH)4--form, at high pressures even with the very diluted solution. We discussed this discrepancy by introducing (1) hydration or (2) a partial molar volume difference between isotopic molecules. It was inferred that borate ions were partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Alternatively, it was likely that the S value decreased with increasing pressure, because the difference of the partial isotopic molar volumes between 10B(OH)3 and 11B(OH)3 was larger than that between 10B(OH)4- and 11B(OH)4-. If either will be the case, the influence of a pressure upon the isotope effect may not be negligible for boron isotopic exchange equilibrium. This knowledge is crucial for the principle of the boron isotopic pH-metry reconstructing a chemical variation at the paleo-deep oceanic environment where the early life may have been evolved.

  3. Boron and strontium isotopes in studying the high boron content of the alluvial aquifer of the Cecina River valley, Central Italy

    International Nuclear Information System (INIS)

    The Cecina River basin extends over 900 km2 in Western Tuscany and includes the Northern part of the Larderello geothermal field. In this work the isotopic composition and concentration of boron and strontium dissolved in ground water, in surface waters, and in bottom sediments were analysed

  4. Rapid mass-spectrometric determination of boron isotopic distribution in boron carbide.

    Science.gov (United States)

    Rein, J E; Abernathey, R M

    1972-07-01

    Boron isotopic ratios are measured in boron carbide by thermionic ionization mass spectrometry with no prior chemical separation. A powder blend of boron carbide and sodium hydroxide is prepared, a small portion is transferred to a tantalum filament, the filament is heated to produce sodium borate, and the filament is transferred to the mass spectrometer where the(11)B/(10)B ratio is measured, using the Na(2)BO(2)(+) ion. Variables investigated for their effect on preferential volatilization of (10)B include the sodium hydroxide-boron carbide ratio and the temperature and duration of filament heating. A series of boron carbide pellets containing natural boron, of the type proposed for the control rods of the Fast Flux Test Facility reactor, were analysed with an apparently unbiased result of 4.0560 for the (11)B/(10)B ratio (standard deviation 0.0087). The pellets contained over 3% metal impurities typically found in this material. Time of analysis is 45 min per sample, with one analyst. PMID:18961131

  5. Intra-Shell boron isotope ratios in benthic foraminifera: Implications for paleo-pH reconstructions

    Science.gov (United States)

    Rollion-Bard, C.; Erez, J.

    2009-12-01

    The boron isotope composition of marine carbonates is considered to be a seawater pH proxy. Nevertheless, the use of δ11B has some limitations: 1) the knowledge of fractionation factor (α4-3) between the two boron dissolved species (boric acid and borate ion), 2) the δ11B of seawater may have varied with time and 3) the amplitude of the "vital effects" of this proxy. Using secondary ion mass spectrometry (SIMS), we looked at the internal variability in the boron isotope ratio of the shallow water, symbionts bearing foraminiferan Amphistegina lobifera. Specimens were cultured at constant temperature (24±0.1 °C) in seawater with pH ranging between 7.90 and 8.45. We performed 6 to 8 measurements of δ11B in each foraminifera. Intra-shell boron isotopes show large variability with an upper threshold value of pH ~ 9. The ranges of the skeletal calculated pH values in different cultured foraminifera, show strong correlation with the culture pH values and may thus serve as proxy for pH in the past ocean.

  6. Geochemical study of boron isotopes in the process of loess weathering

    Institute of Scientific and Technical Information of China (English)

    赵志琦; 刘丛强; 肖应凯; 郎赟超

    2003-01-01

    In this paper the boron contents and boron isotopic composition of acid-soluble phases in loess and paleosol samples are determined for the first time. The boron contents of acid-soluble phases in the Luochuan loess section (S0 -S2) vary within the range of (0.8-2.7)×10-6 and theirδ11B values vary from -1.8‰ to +18.6‰, mostly within the range of 0-+10‰. The boron contents andδ11B values of paleosol layers are higher than those of loess layers, especially in the loess layer S1. Varying chemical weathering intensity and loess adsorption capability are the main factors leading to the variations of boron contents and δ11B values of acid-soluble phases in the loess section. The variation of chemical weathering intensity in response to the variation of climatic conditions seems to be the main factor leading to the variations of boron contents andδ11B values of acid-soluble phases in the loess section.

  7. Isotope geochemistry of boron in mantle rocks, tektites and meteorites

    International Nuclear Information System (INIS)

    Recent ion microprobe studies of fresh oceanic basalt glasses and chondrules from primitive meteorites give an overview of the distribution of boron isotopes in the mantle and in extra-terrestrial rocks. After removal of secondary boron isotope variations due to interactions between mantle melts and the oceanic crust, the primitive mantle is found to have a constant δ11B value of -10 ± 2 per mill, similar to that of the bulk continental crust. In contrast, large isotopic variations between -50 and +40 per mill are present at the micron scale in meteoritic chondrules which are among the most primitive objects of the solar system. These isotopic variations imply that a significant part of the boron of the solar system was synthesized in the presolar cloud, likely by spallation reactions between lo-energy cosmic rays and nebular hydrogen. These heterogeneities were partly preserved in chondrules which formed early in the evolution of the solar system but are not observed for the silicate Earth implying an efficient mixing just before or during the accretion of the Earth. (authors). 74 refs., 5 figs., 2 tabs

  8. Boron isotope ratios of surface waters in Guadeloupe, Lesser Antilles

    Energy Technology Data Exchange (ETDEWEB)

    Louvat, Pascale, E-mail: louvat@ipgp.fr [Geochimie et Cosmochimie, IPGP, Universite Paris Diderot, Sorbonne Paris Cite, UMR 7154 CNRS, 75005 Paris (France); Gaillardet, Jerome; Paris, Guillaume; Dessert, Celine [Geochimie et Cosmochimie, IPGP, Universite Paris Diderot, Sorbonne Paris Cite, UMR 7154 CNRS, 75005 Paris (France)

    2011-06-15

    Highlights: > Rivers outer of hydrothermal areas have d11B around 40 per mille and [B] of 10-31 {mu}g/L. > Thermal springs have d11B of 8-15 per mille and [B] between 250 and 1000 {mu}g/L. > With Na, SO{sub 4} and Cl, boron shows mixing of rain, low and high-T weathering inputs. > Guadeloupe rivers and thermal springs have d11B 20-40 per mille higher than the local rocks. > Solid-solution fractionation during weathering pathways may explain this gap of d11B. - Abstract: Large variations are reported in the B concentrations and isotopic ratios of river and thermal spring waters in Guadeloupe, Lesser Antilles. Rivers have {delta}{sup 11}B values around 40 per mille and B concentrations lower than 30 {mu}g/L, while thermal springs have {delta}{sup 11}B of 8-15 per mille and B concentrations of 250-1000 {mu}g/L. River samples strongly impacted by hydrothermal inputs have intermediate {delta}{sup 11}B and B contents. None of these surface water samples have {delta}{sup 11}B comparable to the local unweathered volcanic rocks (around 0 per mille), implying that a huge isotopic fractionation of 40 per mille takes place during rock weathering, which could be explained by preferential incorporation of {sup 10}B during secondary mineral formation and adsorption on clays, during rock weathering or in the soils. The soil-vegetation B cycle could also be a cause for such a fractionation. Atmospheric B with {delta}{sup 11}B of 45 per mille represents 25-95% of the river B content. The variety of the thermal spring chemical composition renders the understanding of B behavior in Guadeloupe hydrothermal system quite difficult. Complementary geochemical tracers would be helpful.

  9. Boron isotope fractionation in magma via crustal carbonate dissolution

    Science.gov (United States)

    Deegan, Frances M.; Troll, Valentin R.; Whitehouse, Martin J.; Jolis, Ester M.; Freda, Carmela

    2016-08-01

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ11B values down to ‑41.5‰, reflecting preferential partitioning of 10B into the assimilating melt. Loss of 11B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports 11B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ11B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  10. Development of a new TIMS for boron isotopic ratio analysis

    International Nuclear Information System (INIS)

    Thermal Ionization Mass Spectrometry is the widely used technique for precise isotopic ratio measurements of materials of interest in the fields of nuclear technology and geochronology. The basic evaluation of the instrument shows that the instrument is suitable for precise isotopic ratio measurements for Boron. It can be used for other masses falling in the mass range of 1-200 amu. The sensitivity and precision obtained are highly satisfactory for the analysis of Boron samples. Analysis time involved in measurement on one sample is 30-35 minutes. Moreover, the provision of turret with 12 filament assemblies increases the throughput of the system and makes it more useful for the plant where the operator has to routinely analyse more number of samples

  11. Studies on separation of boron isotopes by ion exchange

    International Nuclear Information System (INIS)

    Studies have been carried out for the enrichment of boron isotopes by the ion exchange method using various anion exchange resins available. The elementary separation factors and heights equivalent of theoretical plate were measured at different concentrations and flow rates. A number of experiments were performed to study the displacement of borate band on ion exchange columns. The problem of CO2 evolution during displacement was also studied and a solution was found. (author). 9 refs

  12. Boron carbide whisker and platelet reinforced ceramic matrix composites

    International Nuclear Information System (INIS)

    Boron carbide whisker and platelet-reinforced alumina and boron-carbide-whisker-reinforced silicon carbide composites were prepared by hot-pressing. The mechanical properties of hot-pressed boron carbide platelet and whisker-reinforced composites are better than the inherent ceramic matrix. A maximum fracture toughness, K(lc), of 9.5 MPa sq rt m is achieved for alumina/boron carbide whisker composites, 8.6 MPa sq rt m is achieved for alumina/boron carbide platelet composites, and 3.8 MPa sq rt m is achieved for silicon carbide/boron carbide whisker composites. The fracture toughness is dependent on the volume fraction of the platelets and whiskers. 12 refs

  13. Isotopic analysis of boron by thermal ionization mass spectrometry

    International Nuclear Information System (INIS)

    This paper presents a methodology for isotopic analysis of boron by thermal ionization mass spectrometry technique through the ion intensity measurement of Na2BO+2 in H3BO3, Bo and B4C. The samples were loaded on single tantalum filaments by different methods. In the case of H3BO3, the method of neutralization with NaOH was used. For B4C the alcaline fusion with Na2CO3 and for Bo dissolution with 1:1 nitric sulfuric acid mixture followed by neutralization with NaOH was used. The isotopic ratio measurements were obtained by the use of s Faraday cup detector with external precision of ±0,4% and accuracy of ±0,1%, relative to H3BO3 isotopic standard NBS 951. The effects of isotopic fractionation was studied in function of the time during the analyses and the different chemical forms of deposition. (author)

  14. Interlaboratory comparison for boron isotope ratio measurement with inductively coupled plasma-quadrupole mass spectrometer

    International Nuclear Information System (INIS)

    Boron isotope ratios were analyzed in seven domestic analytical labs for boric acid solutions with various compositions of boron isotope abundances, using an Inductively Coupled Plasma-Quadrupole Mass Spectrometer (ICP-QMS). Five sample solutions with different isotope abundances of 10B were prepared in the range of 10 to 20 % by mixing two boric acid solutions containing natural B and enriched 11B, respectively. Then, the 10B isotope abundances of each sample were certified by analyzing with thermal ionization mass spectrometry (TI-MS) according to ASTM-C791-04. Results obtained from each lab have indicated good coincidences with TI-MS results. Also, the relative standard deviations of results with ICP-QMS of seven analytical labs were 0.11 to 0.81 %. The measurement precision for ICP-QMS would be sufficient in terms of practical use, while taking into consideration a valid requirement required for verifying a depletion of the 10B isotope abundance in the PWR coolant, while this is greater than a nominal analytical error (relative value : 0.22 %) for TI-MS shown in ASTM-C791-04. (author)

  15. Short-Term Coral Bleaching Is Not Recorded by Skeletal Boron Isotopes

    OpenAIRE

    Schoepf, Verena; Malcolm T McCulloch; Mark E Warner; Stephen J Levas; Matsui, Yohei; Aschaffenburg, Matthew D.; Andréa G Grottoli

    2014-01-01

    Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (δ11B), carbon (δ1...

  16. A comparative study of boron isotopes and trace elements of the marine foraminifers during the last glacial maximum and Holocene

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Boron isotopic compositions in marine planktonic foraminifers can record changes in seawater pH and hence provide a new tool to reconstruct the changes of paleo-atmospheric PCO2.Here a comparative study was done on boron isotopes and trace element abundances of planktonic foraminifers,Globigerinoides sacculifer and Globigerinoides ruber from three tropical ODP sites,Site 806B,Site 664C and Site 999A.It is demonstrated here that G.ruber is a better species to be used for downcore boron isotope analyses on glacial-interglacial scales,particularly since G.sacculifer is prone to dissolution causing unexpectedly light boron isotopes during glacial times.It has been shown that the trace elements composition of foraminifers (i.e.,Mg/Ca,U/Ca,B/Ca,and Li/Ca) can reflect the variations of seawater temperature and/or [CO3 2-].However,all of these systems are highly species de-pendent and affected by other vital effects,and it is therefore important to perform necessary calibrations when applying them to the downcore analyses.

  17. Crystallographic control on the boron isotope paleo-pH proxy

    Science.gov (United States)

    Noireaux, J.; Mavromatis, V.; Gaillardet, J.; Schott, J.; Montouillout, V.; Louvat, P.; Rollion-Bard, C.; Neuville, D. R.

    2015-11-01

    When using the boron isotopic composition (δ11B) of marine carbonates as a seawater pH proxy, it is assumed that only the tetrahedral borate ion is incorporated into the growing carbonate crystals and that no boron isotope fractionation occurs during uptake. However, the δ11B of the calcium carbonate from most modern foraminifera shells or corals skeletons is not the same as the δ11B of seawater borate, which depends on pH, an observation commonly attributed to vital effects. In this study, we combined previously published high-field 11B MAS NMR and new δ11B measurements on the same synthetic calcite and aragonite samples precipitated inorganically under controlled environments to avoid vital effects. Our results indicate that the main controlling factors of δ11B are the solution pH and the mineralogy of the precipitated carbonate mineral, whereas the aqueous boron concentration of the solution, CaCO3 precipitation rate and the presence or absence of growth seeds all appear to have negligible influence. In aragonite, the NMR data show that boron coordination is tetrahedral (BO4), in addition, its δ11B is equal to that of aqueous borate, thus confirming the paleo-pH hypothesis. In contrast, both trigonal BO3 and tetrahedral BO4 are present in calcite, and its δ11B values are higher than that of aqueous borate and are less sensitive to solution pH variations compared to δ11B in aragonite. These observations are interpreted in calcite as a reflection of the incorporation of decreasing amounts of boric acid with increasing pH. Moreover, the fraction of BO3 measured by NMR in calcite is higher than that inferred from δ11B which indicates a coordination change from BO4 to BO3 upon boron incorporation in the solid. Overall, this study shows that although the observed differences in δ11B between inorganic and biological aragonite are compatible with a pH increase at calcification sites, the B speciation and isotope composition of biological calcites call for a

  18. Separation of boron isotopes by exchange distillation process

    International Nuclear Information System (INIS)

    Boron has two stable isotopes namely 10B and 11B with natural abundance of 19.9 % and 80.1 % respectively. Both the isotopes find extensive use in the nuclear industry and can be used for the production of two radioisotopes: 11C and 13N as well as tracers to study reaction mechanisms in biological systems. 10B has a large neutron capture cross-section and, therefore, used to assist control of nuclear reactors, a shield against radiation and in neutron detection. 10B is also used in boron neutron capture therapy (BNCT) of brain cancer patients. 11B is useful as a neutron reflector and largely immune to radiation damage so can be very useful in radiation hardened semiconductor designs to be used in spacecrafts. 11B is also an attractive candidate as a fuel for aneutronic fusion. The full potential of 11B is yet to be realized in the last two applications and its demand likely to pick up in future

  19. Effects of boron number per unit volume on the shielding properties of composites made with boron ores form China

    International Nuclear Information System (INIS)

    The total macroscopic removal cross sections, deposited energies and the absorbed doses of three new shielding composites loaded with specific boron-rich slag, boron concentrate ore and boron mud of China for 252Cf neutron source were investigated by experimental and Monte Carlo calculation. The results were evaluated by boron mole numbers per unit volume in composites. The half value layers of the composites were calculated and compared with that of Portland concrete, indicating that ascending boron mole numbers per unit volume in the composites can enhance the shielding properties of the composites for 252Cf neutron source. (authors)

  20. Microwave sintering of boron carbide composites

    International Nuclear Information System (INIS)

    Boron carbide is an important ceramic material because of its high hardness and low specific gravity. it is used for applications involving impact and wear resistance. The disadvantages of boron carbide materials are difficulty in fabrication and sensitivity to brittle fracture. These problems are significantly reduced by production of cermets based on boron carbide and aluminum or aluminum alloys. Microwave heating of boron carbide materials results in ultrarapid heating and high temperatures. Therefore, a finer microstructure is obtained. The objective of this work was to define a technology that would allow the manufacture of boron carbide ceramics having mechanical properties similar to those exhibited by hot-pressed specimens. microwave heating would be used for the densification step. Mixtures of boron carbide and aluminum were considered for this research because aluminum simultaneously acts as a sintering aid and introduces phases that contribute to toughness enhancement

  1. Highly thermal conductive carbon fiber/boron carbide composite material

    International Nuclear Information System (INIS)

    In a composite member for use in walls of a thermonuclear reactor, if carbon fibers and boron carbide are mixed, since they are brought into contact with each other directly, boron is reacted with the carbon fibers to form boron carbide to lower thermal conductivity of the carbon fibers. Then, in the present invention, graphite or amorphous carbon is filled between the carbon fibers to provide a fiber bundle of not less than 500 carbon fibers. Further, the surface of the fiber bundle is coated with graphite or amorphous carbon to suppress diffusion or solid solubilization of boron to carbon fibers or reaction of them. Then, lowering of thermal conductivity of the carbon fibers is prevented, as well as the mixing amount of the carbon fiber bundles with boron carbide, a sintering temperature and orientation of carbon fiber bundles are optimized to provide a highly thermal conductive carbon fiber/boron carbide composite material. In addition, carbide or boride type short fibers, spherical graphite, and amorphous carbon are mixed in the boron carbide to prevent development of cracks. Diffusion or solid solubilization of boron to carbon fibers is reduced or reaction of them if the carbon fibers are bundled. (N.H.)

  2. Boron carbide/carbon composite material and production process therefor

    International Nuclear Information System (INIS)

    The boron carbide/carbon composite material of the present invention comprises from 15 to 40% by volume of graphite and the balance of two kinds of powdery boron carbides X and Y having different average grain sizes. The average grain size of the powdery boron carbide X is less than 1/2 of the average grain size of the boron carbide Y, and the composite material comprises more than 10% by volume of the powdery boron carbide X and more than 30% by volume of the powdery boron carbide Y. They are press-molded under heating at a temperature range of 480 to 600degC, followed by sintering. A binder pitch of less evaporation ingredient melting upon heating is used as a binder. Since the pitch of satisfactory melting property is used, there is no worry that binding property lacks to reduce the lowering of the strength even if a great amount of powdery boron carbide is added. Further, since a carbonization yield is improved due to less evaporation content, density and strength of the composite material can be increased. (T.M.)

  3. Boron isotope separation by ion exchange chromatography using weakly basic anion exchange resin

    International Nuclear Information System (INIS)

    Isotopic plateau displacement chromatography, a useful method for isotope separation is presented. The boric acid band formed in a column of weakly basic anion exchange resin Diaion WA21 can be eluted with pure water. In order to obtain good accumulation of the isotope effect, a series of experiments with different migration length were carried out. The boron-10 enriched part of the boric acid absorbed band was always preceded by the isotopic plateau part, in which the atomic fraction of boron-10 was maintained at its original value. The atomic fraction of boron-10 at the end of the chromatogram increased with migration length, and in the case of 256-m migration, boron-10 was enriched from its original atomic fraction of 19.84 to 91.00%, the separation factor S being constant irrespective of migration length: S = 1.0100 +- 0.0005. (author)

  4. Separation of boron isotopes in anion exchange resin column. Isotopic enrichment of 10 B

    International Nuclear Information System (INIS)

    The separation of boron isotopes (10 B and 11 B) was carried out by isotopic exchange reaction between boric acid in solution and borate/poly borate anions adsorbed on an ammonium quaternary (Dowex 1 X 8 and 2 X 8) anion exchange resin packed in columns. Each resin column had 100 cm length and 1.4 cm in diameter. The columns were connected in series during displacement of boric bands. The enrichment line used pressure ranging from 2.5 to 3.0 Kg f.cm-2. N2 gas was used as in inert atmosphere in order to prevent C O2 formation. Enrichments in 10 B of 43% were obtained using Dowex 1 X 8 resin, 0.1 eq.L-1 H3 B O3 solution and band displacement of 1,876 cm. With Dowex 2 X 8 the enrichment was 40% with 1,330 cm of band displacement and 0.1 eq. L-1 H3 B O3. The boron isotopes were analysed, as methyl borate, by mass spectrometry. (author). 13 refs, 5 figs, 2 tabs

  5. Boron isotope fractionation during brucite deposition from artificial seawater

    OpenAIRE

    J. Xiao; Xiao, Y. K.; Liu, C. Q.; Z. D. Jin

    2011-01-01

    Experiments involving boron incorporation into brucite (Mg(OH)2) from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite. The results show that both concentration of boron in deposited brucite ([B]d) and its boron partition coefficient (Kd) between deposited brucite and final seawater are controll...

  6. Boron nitride nanosheets reinforced glass matrix composites

    Czech Academy of Sciences Publication Activity Database

    Saggar, Richa; Porwal, H.; Tatarko, P.; Dlouhý, Ivo; Reece, M. J.

    2015-01-01

    Roč. 114, SEP (2015), S26-S32. ISSN 1743-6753 R&D Projects: GA MŠk(CZ) 7AMB14SK155 EU Projects: European Commission(XE) 264526 Institutional support: RVO:68081723 Keywords : Boron nitride nanosheets * Borosilicate glass * Mechanical properties Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 1.163, year: 2014

  7. Polyethylene/boron-containing composites for radiation shielding

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Ji Wook [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Department of Chemical and Biological Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Lee, Jang-Woo; Yu, Seunggun; Baek, Bum Ki; Hong, Jun Pyo [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Seo, Yongsok [School of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Woo Nyon [Department of Chemical and Biological Engineering, Korea University, Seoul 136-701 (Korea, Republic of); Hong, Soon Man, E-mail: smhong@kist.re.kr [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of); Koo, Chong Min, E-mail: koo@kist.re.kr [Center for Materials Architecturing, Institute for Multi-Disciplinary Convergence of Materials, Korea Institute of Science and Technology (KIST), Seoul 136-791 (Korea, Republic of); Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 305-350 (Korea, Republic of)

    2014-06-01

    Graphical abstract: - Highlights: • HDPE/silane-treated boron nitride (mBN) composites were fabricated. • The HDPE/mBN composites revealed a strong adhesion behavior at the interface of matrix/filler. • The HDPE/mBN composites show superior radiation shielding, thermoconductive and mechanical properties to the composites containing pristine BN and B{sub 4}C fillers. - Abstract: High-density polyethylene (HDPE) composites with modified boron nitride (mBN) fillers, functionalized with an organosilane, were fabricated through conventional melt-extrusion processing techniques. The properties and performances of these composites were compared with those of the composites containing pristine BN and boron carbide (B{sub 4}C) fillers. The silane functionalization of the BN fillers strongly improved the interfacial adhesion between the polymer matrix and the filler. As a result, the HDPE/mBN composites showed a better dispersion state of the filler particles, larger tensile modulus, greater effective thermal conductivity, and better neutron shielding property compared with the HDPE/BN and HDPE/B{sub 4}C composites.

  8. Boron isotope fractionation during brucite deposition from artificial seawater

    OpenAIRE

    J. Xiao; Xiao, Y. K.; Liu, C. Q.; Z. D. Jin

    2011-01-01

    Experiments involving boron incorporation into brucite (Mg(OH)2) from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite and the influence of it on Mg/Ca-SST proxy and δ11B-pH proxy. The results show that both the concentration of boron in deposited brucite ([B]d) and its boron partition coefficient (

  9. Boron isotope fractionation during brucite deposition from artificial seawater

    OpenAIRE

    J. Xiao; Xiao, Y. K.; Liu, C. Q.; Z. D. Jin

    2011-01-01

    Experiments involving boron incorporation into brucite (Mg(OH)2) from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite and the influence of it on Mg/Ca-SST proxy and δ11B-pH proxy. The results show that both the concentration of boron in deposited brucite ([B]d) and its boron partition coefficient (Kd) between deposited brucite and final seawater are control...

  10. Measurements of the isotopic composition of galactic cosmic rays

    International Nuclear Information System (INIS)

    The galactic cosmic-ray boron and carbon isotopic composition has been measured. The boron measurement is the first ever made in nuclear emulsion. The carbon measurement has substantially improved the statistical assuracy in the determination of the 13C abundance as compared to an earlier measurement using the same technique. Mass-spectra of cosmic-ray carbon and oxygen in different zenith angle intervals have been compared with calculated spectra. The method makes it possible to study experimentally the atmospheric influence on the primary cosmic-ray isotopic composition. Photometric measurements on fragments from oxygen-induced interactions in nuclear emulsion have been made. Accurate charge assignments have been made on all heavy fragments which has made it possible to study the interaction exclusively event-by-event. Measurements on the isotopic composition of primary cosmic-ray neom have been made. The data are from the Danish-French instrument on the HEAO-3 satellite. The rigidity dependent filtering of the cosmic rays by the Earth's magnetic field has been used. The energy dependence of the 22Ne/20Ne-ratio and its astrophysical implications are discussed. (Author)

  11. Boron isotope variations in geothermal systems on Java, Indonesia

    Science.gov (United States)

    Purnomo, Budi Joko; Pichler, Thomas; You, Chen-Feng

    2016-02-01

    This paper presents δ11B data for hot springs, hot acid crater lakes, geothermal brines and a steam vent from Java, Indonesia. The processes that produce a large range of the δ11B values were investigated, including the possible input of seawater as well as the contrast δ11B compositions of acid sulfate and acid chloride crater lakes. The δ11B values of hot springs ranged from - 2.4 to + 28.7‰ and acid crater lakes ranged from + 0.6 to + 34.9‰. The δ11B and Cl/B values in waters from the Parangtritis and Krakal geothermal systems confirmed seawater input. The δ11B values of acid sulfate crater lakes ranged from + 5.5 to + 34.9‰ and were higher than the δ11B of + 0.6‰ of the acid chloride crater lake. The heavier δ11B in the acid sulfate crater lakes was caused by a combination of vapor phase addition and further enrichment due to evaporation and B adsorption onto clay minerals. In contrast, the light δ11B of the acid chloride crater lake was a result of acid water-rocks interaction. The correlations of δ11B composition with δ18O and δ2H indicated that the B isotope corresponded to their groundwater mixing sources, but not for J21 (Segaran) and J48 (Cikundul) that underwent 11B isotope enrichment by B adsorption into minerals.

  12. A Preliminary experimental study of the boron concentration in vapor and the isotopic A preliminary experimental study of the boron concentrationin vapor and the isotopic fractionation of boron betweenseawater and vapor during evaporation of seawater

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A laboratory experiment was undertaken to investigate the behaviour of boron at theseawater-air interface under air flow conditions. Dried air at 25 and 35℃ was passed over or bub-bled through seawater at the same temperature. A combination of ice-chilled condensers and KOHimpregnated cellulose fibre filters was used to collect boron from the reacted air. When air strippedof boron was passed over the seawater, boron was found in the reacted air, and its concentrationwas higher in the higher temperature test. In the tests where air was bubbled through seawater theconcentration of boron in the reacted air was directly proportional to the air flow rate. In this situa-tion the boron in the reacted air was mainly introduced as a spray of microdroplets. Isotopic analy-sis of the collected boron in the non-bubbled tests yields fractionation factors which demonstratethat the lighter isotope, 10B, is enriched in the reacted air. The size of the fractionation changeswith temperature, ruling out a purely kinetic effect.

  13. Phase and property studies of boron carbide-boron nitride composites

    International Nuclear Information System (INIS)

    This paper reports on boron carbide-boron nitride particulate composites that were fabricated by vacuum hot-pressing. Near-theoretical densities of B4C were obtained, but percent theoretical densities decreased with increasing amounts of BN. The grain size of B4C and BN was not affected by composition, but the amount of twinning in B4C decreased with increasing BN content. No third phase was found at the B4C-BN interface by analytical STEM analysis. Lattice parameter measurements indicated slight solubility of B4C in BN, but no solubility of BN in B4C for samples hot-pressed at 2250 degrees C. Room-temperature flexural strength measurements revealed a sharply decreasing strength with increasing BN content up to 40% BN, and then relatively constant values with greater amounts of BN

  14. Utilization of intrinsic boron isotopes as co-migrating tracers for identifying potential nitrate contamination sources

    International Nuclear Information System (INIS)

    The stable isotopes of the conservative element boron, 11B and 10B, have been employed as co-migrating isotopic tracers to trace potential sources of nitrate observed in ground water pumped from a large capacity 0.167 m3/s irrigation well in the Avra Valley of southeastern Arizona. The isotopic ratios provided an identifying signature for two nitrogen carrying source waters: municipal waste water and agricultural return flow. Additional chemical parameters were also examined to corroborate the isotopic indications. Boron isotopes provided a superior delineation of mixing processes in the system compared to the general inorganic chemical parameters. Findings of this investigation indicate that the water pumped by the study well at the beginning of the 1993 irrigation season was composed of a mixture of approximately 25% municipal waste water and 75% background ground water. As the irrigation season progressed, an increasing proportion of water was contributed by irrigation return flow from neighboring agricultural fields

  15. Short-term coral bleaching is not recorded by skeletal boron isotopes.

    Directory of Open Access Journals (Sweden)

    Verena Schoepf

    Full Text Available Coral skeletal boron isotopes have been established as a proxy for seawater pH, yet it remains unclear if and how this proxy is affected by seawater temperature. Specifically, it has never been directly tested whether coral bleaching caused by high water temperatures influences coral boron isotopes. Here we report the results from a controlled bleaching experiment conducted on the Caribbean corals Porites divaricata, Porites astreoides, and Orbicella faveolata. Stable boron (δ11B, carbon (δ13C, oxygen (δ18O isotopes, Sr/Ca, Mg/Ca, U/Ca, and Ba/Ca ratios, as well as chlorophyll a concentrations and calcification rates were measured on coral skeletal material corresponding to the period during and immediately after the elevated temperature treatment and again after 6 weeks of recovery on the reef. We show that under these conditions, coral bleaching did not affect the boron isotopic signature in any coral species tested, despite significant changes in coral physiology. This contradicts published findings from coral cores, where significant decreases in boron isotopes were interpreted as corresponding to times of known mass bleaching events. In contrast, δ13C and δ18O exhibited major enrichment corresponding to decreases in calcification rates associated with bleaching. Sr/Ca of bleached corals did not consistently record the 1.2°C difference in seawater temperature during the bleaching treatment, or alternatively show a consistent increase due to impaired photosynthesis and calcification. Mg/Ca, U/Ca, and Ba/Ca were affected by coral bleaching in some of the coral species, but the observed patterns could not be satisfactorily explained by temperature dependence or changes in coral physiology. This demonstrates that coral boron isotopes do not record short-term bleaching events, and therefore cannot be used as a proxy for past bleaching events. The robustness of coral boron isotopes to changes in coral physiology, however, suggests that

  16. Chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets

    Energy Technology Data Exchange (ETDEWEB)

    1981-01-01

    Aluminum oxide pellets are used in a reactor core as filler or spacers within fuel, burnable poison, or control rods. In order to be suitable for this purpose, the material must meet certain criteria for impurity content. The test methods in the standard are designed to show whether or not a given material meets these specifications. The following analytical procedures are described in detail: boron by titrimetry; separation of boron by mass spectrometry; isotopic composition by mass spectrometry; separation of halides by pyrohydrolysis; fluoride by ion-selective electrode; chloride, bromide, and iodide by amperometric microtitrimetry; trace elements by emission spectroscopy. (JMT)

  17. Preparation, structure and some properties of boron crystals with different content of 10B and 11B isotopes

    International Nuclear Information System (INIS)

    The present work deals with the analysis of data on preparation and investigation of boron with different content of 10B and 11B isotopes. It was established that influence of isotopes on the structure and physical-mechanical properties of boron varies with regard to the type and percentage of an applied isotope. Microhardness of the specimens was measured at room temperatures. Peculiarities of changes observed in the values of microhardness, thermal expansion coefficients and characteristics of the relaxation processes are discussed from the point of view of probable changes in inter-atomic forces created due to substitution of natural boron atoms with their isotopes

  18. Separation of boron isotopes at chemical isotopic exchange between, boron trifluoride and its complex with anisole in multitube mass-exchange column

    International Nuclear Information System (INIS)

    The results are given on continuous counterflow two-phase process of boron isotopes 10B and 11B separation at chemical isotopic exchange between gaseous BF3 and its liquid complex with anisole, the process is realized in the module of three packed columns with parallel operation; each of the columns in its bottom part is connected with the others by the common unit of flow reversal (desorber), has the diameter of 78 mm, height of 46.5 m, and is filled with wire spiral-prismatic pack with 3.5·3.5·0.2 mm element

  19. Zinc isotopic compositions of breast cancer tissue.

    OpenAIRE

    Larner, F; Woodley, LN; Shousha, S; Moyes, A; Humphreys-Williams, E; Strekopytov, S; Halliday, AN; Rehkämper, M; Coombes, RC

    2015-01-01

    An early diagnostic biomarker for breast cancer is essential to improve outcome. High precision isotopic analysis, originating in Earth sciences, can detect very small shifts in metal pathways. For the first time, the natural intrinsic Zn isotopic compositions of various tissues in breast cancer patients and controls were determined. Breast cancer tumours were found to have a significantly lighter Zn isotopic composition than the blood, serum and healthy breast tissue in both groups. The Zn i...

  20. Isotopic fractionation of boron in growing corals and its palaeoenvironmental implication

    Digital Repository Service at National Institute of Oceanography (India)

    Xiao, Y.K.; Shirodkar, P.V.; Zhang, C.G.; Wei, H.Z.; Liu, W.G.; Zhou, W.J.

    to be incorporated into corals. Based on the measured δ11B values of growing corals and coexisting sea water as well as the pH of co-existing sea water, a new isotopic fractionation factor α43 between two boron species, B(OH)4 – and B(OH)3, has been measured to be 0...

  1. Tracing the strength of the southwest monsoon using boron isotopes in the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, S.S.; Naidu, P.D.; Foster, G.L.; Martínez-Boti, M.A.

    Here we present the first boron isotope-based pCO2sw (pCO2 of seawater) reconstruction from the eastern Arabian Sea using the planktic foraminifera species Globigerinoides ruber. Our results from sediment core AAS9...

  2. Geochemistry of the Congo and Amazon river systems. Boron isotopic geochemistry in corals. Continental erosion and ocean pH

    International Nuclear Information System (INIS)

    Two main geological processes control the CO2 concentration in the atmosphere at a geological time scale: CO2 outgasing from the interior of the Earth and CO2 consumption by continental weathering. In the thesis, we initiate two different directions that can be useful to constraint the past climate evolution models. The first one is the extensive study of the largest rivers of the world using the classical geochemical analyses (major and trace elements, Sr-Nd-Pb isotopes) and modelling approaches. The study case of this thesis are the Congo and Amazon Basin. In particular, the coupling between chemical and physical erosion is examined and related to the hydrologic and tectonic parameters. Relief, thus tectonics appear to best control CO2 consumption by rock weathering. The second part of the work is devoted to the measurement of boron isotopic ratio in corals because it may be used as a proxy for paleo-ocean pH. It could thus bring important pieces of information on the global C cycle and climate evolution. The technical part is extensively described and the method applied to the corals from the last interglacial period. Our conclusion is that corals are likely to be influence by early diagenetic changes that modify the boron isotopic composition of corals. We thus propose a test to select the samples. (author)

  3. Irradiation Effects in Fortiweld Steel Containing Different Boron Isotopes

    International Nuclear Information System (INIS)

    Tensile specimens and miniature impact specimens of the low alloyed pressure vessel steel Fortiweld have been irradiated at 265 deg C in R2 to two neutron doses, 6.5 x 1018 n/cm2 (> 1 MeV) and 4 x 1019 n/cm2 (thermal) and also 9.0 x 1018 n/cm2 (> 1 MeV) and 6 x 1019 n/cm2 (thermal). Material from three laboratory melts, in which the boron consisted of 10B, 11B and natural boron respectively, were investigated. The results both of tensile tests and impact tests with miniature impact specimens show that the 10B-alloyed material was changed more and the 11B-alloyed material was changed less than the material containing natural boron. At the higher neutron dose the increase in yield strength (0.2 % offset yield strength) was 11 kg/mm in the 10B containing material compared to 5 kg/mm in the 11B-containing material. The decrease in total elongation was 5 and 0 percentage units respectively. The transition temperature was increased 190 deg C at the higher neutron dose in the 10B-alloyed material, 40 deg C in the 11B-alloyed material and 80 deg C in the material containing natural boron

  4. Irradiation Effects in Fortiweld Steel Containing Different Boron Isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Grounes, M.

    1967-07-15

    Tensile specimens and miniature impact specimens of the low alloyed pressure vessel steel Fortiweld have been irradiated at 265 deg C in R2 to two neutron doses, 6.5 x 10{sup 18} n/cm{sup 2} (> 1 MeV) and 4 x 10{sup 19} n/cm{sup 2} (thermal) and also 9.0 x 10{sup 18} n/cm{sup 2} (> 1 MeV) and 6 x 10{sup 19} n/cm{sup 2} (thermal). Material from three laboratory melts, in which the boron consisted of {sup 10}B, {sup 11}B and natural boron respectively, were investigated. The results both of tensile tests and impact tests with miniature impact specimens show that the {sup 10}B-alloyed material was changed more and the {sup 11}B-alloyed material was changed less than the material containing natural boron. At the higher neutron dose the increase in yield strength (0.2 % offset yield strength) was 11 kg/mm in the {sup 10}B containing material compared to 5 kg/mm in the {sup 11}B-containing material. The decrease in total elongation was 5 and 0 percentage units respectively. The transition temperature was increased 190 deg C at the higher neutron dose in the {sup 10}B-alloyed material, 40 deg C in the {sup 11}B-alloyed material and 80 deg C in the material containing natural boron.

  5. Ab initio prediction of equilibrium boron isotope fractionation between minerals and aqueous fluids at high P and T

    CERN Document Server

    Kowalski, Piotr M; Jahn, Sandro

    2012-01-01

    Over the last decade experimental studies have shown a large B isotope fractionation between materials carrying boron incorporated in trigonally and tetrahedrally coordinated sites, but the mechanisms responsible for producing the observed isotopic signatures are poorly known. In order to understand the boron isotope fractionation processes and to obtain a better interpretation of the experimental data and isotopic signatures observed in natural samples, we use first principles calculations based on density functional theory in conjunction with ab initio molecular dynamics and a new pseudofrequency analysis method to investigate the B isotope fractionation between B-bearing minerals (such as tourmaline and micas) and aqueous fluids containing H_3BO_3 and H_4BO_4- species. We confirm the experimental finding that the isotope fractionation is mainly driven by the coordination of the fractionating boron atoms and have found in addition that the strength of the produced isotopic signature is strongly correlated w...

  6. Fundamental studies on the ion-exchange separation of boron isotopes

    International Nuclear Information System (INIS)

    The single-stage separation factors for boron isotopes between an ion-exchange resin and an external solution were determined, using an ion-exchange breakthrough operation. The lighter isotope boron-10 was considerably enriched in the anion-exchange resin phase. The separation factor was very much influenced by the boric acid concentration in the external solution, but not as much influenced by the kind of the anion exchange resin used and operation temperature. The separation factor increased with a decrease in the boric acid concentration of external solution from 1.008 (0.501 mol/l) to 1.016 (0.010 mol/l). The value of the separation factors obtained experimentally were compared with those estimated on the basis of the theory of the two-phase distribution of isotopes. (auth.)

  7. Development of a boron-copper neutron absorber composite

    International Nuclear Information System (INIS)

    This report describes the fabrication of a new boron-copper neutron absorbing material that was developed to meet the upgrading needs of the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. To increase the intensity of the neutron beams from the IPNS, the target uranium was changed from depleted uranium to uranium enriched to 77.5% 235U. To keep the multiplication factor, keff (number of fissions in one generation/number of fissions in preceding generation) at a safe level, a new neutron absorber material was needed. The previous materials, boral and cadmium, could not meet the new requirements and a search of the literature showed that no currently available material was acceptable. With previous powder metallurgy used as a base, the composite was fabricated with 43 vol. % 10B (81% enriched 10B) and the balance copper and voids. The powder metallurgy techniques was followed by hot-rolling the composite to a sheet. The material composed of boron particles dispersed in a pure copper matrix and clad with pure copper on both sides, exhibits the following properties: Loadings up to 43 vol. % boron, with the balance copper and voids. A loading of 0.5 x 102210B atoms/cm2 in sections as thin as 0.067 in. (1.7 mm), with copper cladding as thin as 0.010 in. (0.25 mm). Formability to radii as small as 2.1 in. (53.3 mm). No observed reaction between boron and the copper matrix and cladding at temperatures up to 900 degrees C for times as long as 7 h. Retains structural integrity at 900 degrees C

  8. The effect of the boron source composition ratio on the adsorption performance of hexagonal boron nitride without a template

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ning, E-mail: zhangning5832@163.com; Zhang, Tong; Kan, Hongmin; Wang, Xiaoyang; Long, Haibo; Cui, Xingyu

    2015-08-01

    An inexpensive boric acid (H{sub 3}BO{sub 3}) and borax (Na{sub 2}B{sub 4}O{sub 7}·10H{sub 2}O) mix was used as a source of boron with different composition ratios, and urea was used as a nitrogen source, in flowing ammonia atmosphere, for the preparation of hexagonal boron nitride (h-BN) with different micro-morphologies. Under a certain synthesis process, the effects of the molar ratio of borax and boric acid (or simply the boron source composition ratio for short) on the phase composition of the sample were studied; the work also explored the effect of boron source composition ratio on the micro-morphology, adsorption desorption isotherm and specific surface area of the h-BN powder. The main purpose of this work was to determine the optimum composition ratio of preparing spherical mesoporous h-BN and ensure that the micro-mechanism underpinning the formation of spherical mesoporous h-BN was understood. The results showed that at the optimum boron source composition ratio of 1:1, globular mesoporous spheres with a diameter of approximately 600–800 nm could be obtained with the highest pore volume and specific surface area (230.2 m{sup 2}/g). - Graphical abstract: Display Omitted - Highlights: • Spherical h-BN was synthesized by controlling the boron source composition ratio. • Without extra spherical template, solid Na{sub 2}O was equal to a spherical template. • At boron source composition ratio of 1:1, h-BN had best adsorption performance.

  9. Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.

    Science.gov (United States)

    Musashi, Masaaki; Oi, Takao; Matsuo, Motoyuki; Nomura, Masao

    2008-08-01

    Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure. PMID:18585727

  10. Thermal conductivity of polymer composites with oriented boron nitride

    International Nuclear Information System (INIS)

    Highlights: • Thermal conductivity depended on the orientation of BN in the polymer matrices. • Hexagonal boron nitride (BN) particles were treated by C27H27N3O2 and C14H6O8. • Amphiphilic-agent-treated BN particles are more easily oriented in the composite. • BN/PVA composites with C14H6O8-treated BN showed the highest thermal conductivity. • Thermal conductivity of the composites was compared with several theoretical models. - Abstract: Thermal conductivity of boron nitride (BN) with polyvinyl alcohol (PVA) and/or polyvinyl butyral (PVB) was investigated as a function of the degree of BN orientation, the numbers of hydroxyl groups in the polymer matrices and the amphiphilic agents used. The composites with in-plane orientation of BN showed a higher thermal conductivity than the composites with out-of-plane orientation of BN due to the increase of thermal pathway. For a given BN content, the composites with in-plane orientation of BN/PVA showed higher thermal conductivity than the composites with in-plane orientation of BN/PVB. This result could be attributed to the improved degree of orientation of BN, caused by a larger number of hydroxyl groups being present. Those treated with C14H6O8 amphiphilic agent demonstrated a higher thermal conductivity than those treated by C27H27N3O2. The measured thermal conductivity of the composites was compared with that predicted by the several theoretical models

  11. Failure of unidirectional boron-reinforced aluminum composites in compression

    International Nuclear Information System (INIS)

    The authors examine a composite material consisting of an aluminum matrix with plastic properties, assuming that the stress and strain intensities are linked by a power dependence and of elastic fibers with Young's modulus E. when using the continuous approach, the fiber-reinforced composite material is replaced by a transversely isotropic material. Application of equations of the three-dimensional elasticity theory are used which leads to a lower estimate of the limiting strains. It is shown that the application of the three-dimensional linearized theory of stability to calculate unidirectional fiber-reinforced composite materials with the aluminum matrix and boron fibers is highly efficient; it is possible to predict the ultimate strength in compressive loading along the reinforcement direction

  12. Evaluation of Ground-Water and Boron Sources by Use of Boron Stable-Isotope Ratios, Tritium, and Selected Water-Chemistry Constituents near Beverly Shores, Northwestern Indiana, 2004

    Science.gov (United States)

    Buszka, Paul M.; Fitzpatrick, John A.; Watson, Lee R.; Kay, Robert T.

    2007-01-01

    from human-affected boron sources. Boron concentrations in potential ground-water sources of boron were largest (15,700 to 24,400 ?g/L) in samples of CCP-affected surficial aquifer water from four wells at a CCP landfill and smallest (27 to 63 ?g/L) in three wells in the surficial aquifer that were distant from human-affected boron sources. Boron concentrations in water from the basal sand aquifer ranged from 656 ?g/L to 1,800 ?g/L. Boron concentrations in water from three domestic-wastewater-affected surficial aquifer wells ranged from 84 to 387 ?g/L. Among the representative ground-water samples, boron concentrations from all four samples of CCP-affected surficial aquifer water and four of five samples of water from the basal sand aquifer had concentrations greater than the RAL. A comparison of boron concentrations in acid-preserved and unacidified samples indicated that boron concentrations reported for this investigation may be from about 11 to 16 percent less than would be reported in a standard analysis of an acidified sample. The stable isotope boron-11 was most enriched in comparison to boron-10 in ground water from a confined aquifer, the basal sand aquifer (d11B, 24.6 to 34.0 per mil, five samples); it was most depleted in CCP-affected water from the surficial aquifer (d11B, 0.1 to 6.6 per mil, four samples). Domestic-wastewater-affected water from the surficial aquifer (d11B, 8.7 to 11.7 per mil, four samples) was enriched in boron-11, in comparison to individual samples of a borax detergent additive and a detergent with perborate bleach; it was intermediate in composition between basal sand aquifer water and CCP-affected water from the surficial aquifer. The similarity between a ground-water sample from the surficial aquifer and a hypothetical mixture of unaffected surficial aquifer and basal sand aquifer waters indicates the potential for long-term upward discharge of ground water into the surficial aquifer from one or more confined aquifers. Est

  13. High Temperature Characteristic in Electrical Breakdown and Electrical Conduction of Epoxy/Boron-nitride Composite

    Science.gov (United States)

    Takenaka, Yutaka; Kurimoto, Muneaki; Murakami, Yoshinobu; Nagao, Masayuki

    The power module for the electrical vehicle needs electrical insulation material with high thermal conductivity. Recently, the epoxy insulating material filled with boron-nitride particles (epoxy/boron-nitride composite) is focused as an effective solution. However, the insulation performance of epoxy/boron-nitride composite was not investigated enough especially at the high temperature in which the power module was used, i.e. more than 100°C. In this paper, we investigated high temperature characteristics in electrical breakdown and conduction current of epoxy/boron-nitride composite. Breakdown test under the application of DC lamp voltage and impulse voltage clarified that the epoxy/boron-nitride composite had the constant breakdown strength even in the high temperature. Comparison of the epoxy/boron-nitride composite with previous material, which was epoxy/alumina composite, indicated that the breakdown voltage of the epoxy/boron-nitride composite in the high temperature was found to be higher than that of epoxy/alumina composite under the same thermal-transfer quantity among them. Furthermore, conduction current measurement of epoxy/boron-nitride composite in the high temperature suggested the possibility of the ionic conduction mechanism.

  14. Photon energy absorption parameters for composite mixtures with boron compounds

    International Nuclear Information System (INIS)

    Highlights: → An experimental investigation of photon energy absorption parameters for 12 composite mixture samples with boron compounds. → Calculations of total mass attenuation coefficients and effective atomic numbers for the energy up to 100 keV. → Radiation shielding properties varied with concentration of composite materials. → In general, the mixture with K2B4O7· 4H2O is more absorber than with H3BO3. - Abstract: Boron compounds that are used in the manufacturing of a variety of products are introduced to the environment in the form of waste. The radiation shielding measurements of mixtures that contain boron compounds is considered to be a topic of concern. The mass attenuation coefficients of (PbO and K2B4O7.4H2O) and (PbO and H3BO3) as functions of their changing contents have been measured in the X-ray energy range from 25.191 to 57.903 keV. These values are used to determine the effective atomic number of mixtures. The γ-rays emitted from an Am241 annular source have been sent to secondary sources whose characteristic X-rays have been used for transmission arrangement. The characteristic X-rays of the secondary sources have been counted by a Si(Li) detector with a resolution of 149 eV at 5.9 keV. Also, the total effective atomic number of each mixture was determined by using the mixture rule. The measured values were compared with theoretically calculated values.

  15. Isotope Separation Effect of Burnable Absorber for Long-cycle Boron-free Reactor Core

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Chidong; Choe, Jiwon; Lee, Deokjung Lee [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Shin, Ho Cheol [Korea Hydro and Nuclear Power Co., Daejeon (Korea, Republic of)

    2015-05-15

    To satisfy these requirements, BA rods in the boron-free reactor should be depleted in proportion to the cycle depletion, and burned out completely at EOC. However, there remain residues of the BA to the end, which reduces the cycle length of the reactors. In order to create more economic profits, these residues should be minimized so that the cycle length can get longer. The amount of burned BA and the corresponding assembly lifetime are analyzed to investigate the effectiveness of isotope separation for BA of a long-cycle boron-free reactor. It was noted that only Erbium and Hafnium can be burned relatively in a flat rate over the whole cycle, whereas Gd, Sm, Eu, Cd, {sup 157}Gd, {sup 149}Sm, {sup 151}Eu, and {sup 113}Cd are burned almost 100% even within the half of lifetime. In terms of assembly lifetime, Hafnium showed higher improvement than Erbium between the single isotope and its naturally occurring element.

  16. 2,4-Difluoro anisole. A promising complexing agent for boron isotopes separation by chemical exchange reaction and distillation

    International Nuclear Information System (INIS)

    Although methods of boron isotopes separation were intensively pursued about 60 years, the chemical exchange distillation is the only method that has been applied in industrial scale production of 10B. The present anisole BF3 system suffers from the drawbacks like high melting point, relatively low separation coefficient and instability under reaction conditions, which demand a continuous search for more effective and efficient donors for boron isotope separation. A series of fluoro-substituted anisole derivatives were screened in this paper, among which 2,4-difluoro anisole exhibited good properties compared with anisole. Studies on the boron trifluoride and 2,4-difluoro anisole adduct, its thermodynamic and physical properties related to large-scale isotopic separation is reported. The results showed that 2,4-difluoro anisole is better than anisole in separation coefficient, freezing point and stability under pyrolysis conditions, which suggest a further detailed investigations on boron trifluoride and 2,4-difluoro anisole adduct. (author)

  17. Isotopic composition of past precipitation

    International Nuclear Information System (INIS)

    The distribution of stable isotopes in precipitation provides critical quantitative information about the global water cycle. The first PAGES/IAEA ISOMAP workshop was held at the IAEA headquarters in Vienna, 24-26 August 1998, which gathered 32 participants. The presentation and discussions demonstrated that a high level of sophistication already exists in the development of transfer functions between measured parameters and precipitation, as a result of the extensive use of water isotope tracers in paleo-environmental investigations, but a major challenge facing both producers and users of paleo-isotope data is the effective management of data and meta-data, to permit ready retrieval of raw and inferred data for comparison and reinterpretation. This will be in important goal of future ISOMAP activities. The critical need for more paleo-data from low latitudes was clearly recognized

  18. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity.

    Science.gov (United States)

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets' interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation. PMID:26783258

  19. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity

    Science.gov (United States)

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets’ interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation.

  20. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity

    Science.gov (United States)

    Wang, Fangfang; Zeng, Xiaoliang; Yao, Yimin; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride nanosheets as fillers could effectively enhance the thermal conductivity of polymer, thanks to the bridging connections of silver nanoparticles among boron nitride nanosheets. The thermal conductivity of the composite is significantly increased from 1.63 W/m-K for the composite filled with the silver nanoparticle-deposited boron nitride nanosheets to 3.06 W/m-K at the boron nitride nanosheets loading of 25.1 vol %. In addition, the electrically insulating properties of the composite are well preserved. Fitting the measured thermal conductivity of epoxy composite with one physical model indicates that the composite with silver nanoparticle-deposited boron nitride nanosheets outperforms the one with boron nitride nanosheets, owning to the lower thermal contact resistance among boron nitride nanosheets’ interfaces. The finding sheds new light on enhancement of thermal conductivity of the polymeric composites which concurrently require the electrical insulation. PMID:26783258

  1. Preparation and characterization of boron nitride/carbon fiber composite with high specific surface area

    International Nuclear Information System (INIS)

    Boron nitride can be used as a good catalyst carrier because of its high thermal conductivity and chemical stability. However, a high specific surface area of boron nitride is still desirable. In this work, a carbon fiber composite coated with boron nitride villous nano-film was prepared, and was also characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The results indicated that the carbon fibers were covered by uniform villous boron nitride films whose thickness was about 150 - 200 nm. The specific surface area of the boron nitride/carbon fiber composite material was 96 m2 g-1, which was markedly improved compared with conventional boron nitride materials. (orig.)

  2. Stable isotope composition of Earth's large lakes

    Science.gov (United States)

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

    2011-12-01

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

  3. Boron carbide composite carbon material, method of manufacturing the same and plasma facing material

    International Nuclear Information System (INIS)

    A boron carbide composite material of the present invention is formed by compositing boron carbide, which is a material suitable as a plasma facing material especially for a thermonuclear reactor. Boron carbide is filled in open cells of a carbon fiber-carbon composite material containing carbon fibers and a carbon matrix. In addition, a boron carbide film is formed on the surface of the composite material. A CVD method and a plasma flaming method are generally known, but they involve problems of occurrence of cracks and peeling of coating film due to thermal stresses. Then, a boron compound is chemically reacted with the surface of a carbon material to convert the carbon on the surface to boron carbide. The composite material contains carbon fibers oriented in one direction, and a boron carbide coating film is formed on the plasma facing surface. With such a constitution, there can be obtained a useful plasma facing material which has excellent strength especially in the direction of the fibers and having heat resistance, chemical stability and ware resistance even after the boron carbide coating film is exhausted and the base material is exposed. (T.M.)

  4. Thermal conduction mechanisms in isotope-disordered boron nitride and carbon nanotubes

    Science.gov (United States)

    Savic, Ivana; Mingo, Natalio; Stewart, Derek

    2009-03-01

    We present first principles studies which determine dominant effects limiting the heat conduction in isotope-disordered boron nitride and carbon nanotubes [1]. Using an ab initio atomistic Green's function approach, we demonstrate that localization cannot be observed in the thermal conductivity measurements [1], and that diffusive scattering is the dominant mechanism which reduces the thermal conductivity [2]. We also give concrete predictions of the magnitude of the isotope effect on the thermal conductivities of carbon and boron nitride single-walled nanotubes [2]. We furthermore show that intershell scattering is not the main limiting mechanism for the heat flow through multi-walled boron nitride nanotubes [1], and that heat conduction restricted to a few shells leads to the low thermal conductivities experimentally measured [1]. We consequently successfully compare the results of our calculations [3] with the experimental measurements [1]. [1] C. W. Chang, A. M. Fennimore, A. Afanasiev, D. Okawa, T. Ikuno, H. Garcia, D. Li, A. Majumdar, A. Zettl, Phys. Rev. Lett. 2006, 97, 085901. [2] I. Savic, N. Mingo, D. A. Stewart, Phys. Rev. Lett. 2008, 101, 165502. [3] I. Savic, D. A. Stewart, N. Mingo, to be published.

  5. Separation of boron isotopes by ion exchange chromatography: studies with Duolite-162, a type-II resin

    International Nuclear Information System (INIS)

    The selection of resin plays an important role in the process of separation of boron isotopes by ion exchange chromatography. The determination of (i) ion exchange capacity of Duolite-162 resin for hydroxyl - chloride exchange, (ii) hydroxyl - borate exchange, (iii) isotopic exchange separation factor by batch method and (iv) effect of concentration of boric acid on isotopic exchange separation factor to test the suitability of the above resin for this process are discussed in this report. (author)

  6. Chemical and isotopic analysis of boron in uranium by mass spectrometry; Analyse chimique et isotopique du bore dans l'uranium par spectrometrie de masse

    Energy Technology Data Exchange (ETDEWEB)

    Chenouard, J.; Nief, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    A method is described for the determination by mass spectrometry of the concentration and the isotopic composition of small quantities of boron in uranium. The concentration range is between 10 and 100 ppm. The boron is extracted by distillation of methyl borate. The concentration is attained by isotopic dilution. Many precautions have to be taken to limit and correct contaminations. This method of analysis is applicable for at least 0.2 {mu}g of boron; the relative accuracy is about 2 per cent. (authors) [French] On decrit une methode de determination par spectrometrie de masse de la concentration et de la composition isotopique de faibles quantites de bore dans l'uranium. Le domaine de concentration est compris entre 10 et 100 ppm. L'extraction du bore s'effectue par distillation du borate de methyle. La concentration est atteinte par dilution isotopique. De nombreuses precautions doivent etre prises pour limiter et corriger les contaminations. L'analyse est possible a partir de 0,2 {mu}g de bore avec une precision relative de l'ordre de 2 pour cent. (auteurs)

  7. Calcium isotopic composition of mantle peridotites

    Science.gov (United States)

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

    2015-12-01

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

  8. Fundamental study of practical separation of boron isotopes by means of anion exchange resin, (1)

    International Nuclear Information System (INIS)

    Separation of boron isotopes was carried out using a weak base anion exchange column (in free base form). After boric acid solution was passed through the column, the boric acid band formed on the column was eluted with pure water. The authors discuss the effects on boron isotope separation caused by variations of the concentration of feed solution charged to the column, of the amount of boric acid charged and of the flow rate of feed and eluent solutions. Results were as follows: (1) As the concentration of boric acid charged to the column increased and the amount of boric acid charged became large, the amount of enriched 10B(D sup(γ)) increased. (2) The optimum flow rate was 10 -- 20 ml/cm2.hr. (3) The atomic fraction of 10B in the plateau region of the isotope enrichment curve was nearly 0.190, compared with 0.198 for the feed solution. (4) In cases where the boric acid concentration in the effluent never exceeded 0.3 mol/l, no significant tailling was observed at the end of the chromatographic band. (auth.)

  9. Rim region growth and its composition in reaction bonded boron carbide composites with core-rim structure

    International Nuclear Information System (INIS)

    Aluminum was detected in reaction-bonded boron carbide that had been prepared by pressureless infiltration of boron carbide preforms with molten silicon in a graphite furnace under vacuum. The presence of Al2O3 in the heated zone, even though not in contact with the boron carbide preform, stands behind the presence of aluminium in the rim region that interconnects the initial boron carbide particles. The composition of the rim corresponds to the Bx(C,Si,Al)y quaternary carbide phase. The reaction of alumina with graphite and the formation of a gaseous aluminum suboxide (Al2O) accounts for the transfer of aluminum in the melt and, subsequently in the rim regions. The presence of Al increases the solubility of boron in liquid silicon, but with increasing aluminum content the activity of boron decreases. These features dominate the structural evolution of the rim-core in the presence of aluminum in the melt.

  10. Rim region growth and its composition in reaction bonded boron carbide composites with core-rim structure

    Science.gov (United States)

    Hayun, S.; Weizmann, A.; Dilman, H.; Dariel, M. P.; Frage, N.

    2009-06-01

    Aluminum was detected in reaction-bonded boron carbide that had been prepared by pressureless infiltration of boron carbide preforms with molten silicon in a graphite furnace under vacuum. The presence of Al2O3 in the heated zone, even though not in contact with the boron carbide preform, stands behind the presence of aluminium in the rim region that interconnects the initial boron carbide particles. The composition of the rim corresponds to the Bx(C,Si,Al)y quaternary carbide phase. The reaction of alumina with graphite and the formation of a gaseous aluminum suboxide (Al2O) accounts for the transfer of aluminum in the melt and, subsequently in the rim regions. The presence of Al increases the solubility of boron in liquid silicon, but with increasing aluminum content the activity of boron decreases. These features dominate the structural evolution of the rim-core in the presence of aluminum in the melt.

  11. Isotope shifts in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

    Energy Technology Data Exchange (ETDEWEB)

    Nazé, C.; Verdebout, S. [Service de Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Brussels (Belgium); Rynkun, P.; Gaigalas, G. [Vilnius University, Institute of Theoretical Physics and Astronomy, LT-01108 Vilnius (Lithuania); Godefroid, M., E-mail: mrgodef@ulb.ac.be [Service de Chimie Quantique et Photophysique, CP160/09, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, B 1050 Brussels (Belgium); Jönsson, P. [Group for Materials Science and Applied Mathematics, Malmö University, 205-06 Malmö (Sweden)

    2014-09-15

    Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these electronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wavefunctions that account for valence, core–valence, and core–core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available.

  12. Isotope shifts in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

    International Nuclear Information System (INIS)

    Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these electronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wavefunctions that account for valence, core–valence, and core–core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available

  13. Radiation response of reaction-bonded and sintered SiC: Effects of boron isotopes

    Science.gov (United States)

    Carey, A. M.; Pineau, F. J.; Lee, C. W.; Corelli, J. C.

    The response of mechanical, thermal and microstructural properties of reaction-bonded SiC and sintered SiC were studied after reactor irradiation. The effects of 10B(n,α) 7Li reaction products were studied by doping the material from which samples were produced with enriched isotopes of 10B, 11B and natural boron. Silicon carbide doped with 10B exhibits a pronounced effect on the fracture strength. The thermal diffusivity decrease can account for the lowering of the resistance against thermal shock of irradiated material.

  14. Chemical and boron isotope microanalysis of tourmalines as a guide to fluid-rock interaction in the Habachtal emerald deposit, Tauern Window, Austria

    Science.gov (United States)

    Trumbull, R. B.; Krienitz, M.-S.; Grundmann, G.; Wiedenbeck, M.

    2009-04-01

    Tourmalines from the Habachtal emerald deposit in the Eastern Alps formed together with emerald in a ductile shear zone during blackwall metasomatism between pelitic country rocks and a serpentinite body. Electron microprobe and secondary ion mass spectrometric (SIMS) analyses provide a record of chemical and B-isotope variations in tourmalines which represent an idealized profile from metapelites into the blackwall sequence of biotite and chlorite schists. Tourmaline is intermediate schorl-dravite in the country rock and become increasingly dravitic in the blackwall zones, while F and Cr contents increase and Al drops. Metasomatic tourmaline from blackwall zones is typically zoned optically and chemically, with rim compositions rich in Mg, Ti, Ca and F compared with the cores. The total range in delta-11B values is -13.8 to -5.1 permil and the within-sample variations are typically 3 to 5 permil. Both of these ranges are beyond the reach of closed-system fractionation at the estimated 500-550C conditions of formation, and at least two boron components with contrasting isotopic composition are indicated. A key observation from tourmaline core analyses is a systematic shift in delta-11B from the country rock (-14 to -10 permil) to the inner blackwall zones (-9 to -5 permil). We suggest that two separate fluids were channeled and partially mixed in the Habachtal shear zone during blackwall alteration and tourmaline-emerald mineralization. A regional metamorphic fluid carried isotopically light boron as observed in the metapelite country rocks. The other fluid is derived from the serpentinite association and has isotopically heavier boron typical for MORB or altered oceanic crust.

  15. Insights into Ocean Acidification During the Middle Eocene Climatic Optimum from Boron Isotopes at Southern Ocean Site 738

    Science.gov (United States)

    Moebius, I.; Hoenisch, B.; Friedrich, O.

    2015-12-01

    The Middle Eocene Climatic Optimum (MECO) is a ~650-kyr interval of global warming, with a brief ~50 ky long peak warming interval, and an abrupt termination. Deep sea and surface ocean temperature evolution across this interval are fairly well constrained, but thus far we have little understanding of the mechanisms responsible for the gradual warming and rapid recovery. Carbonate mass accumulation rates suggest a shoaling of the carbonate compensation depth, and studies on alkenones indicate increasing atmospheric CO2 levels during the MECO. This suggests an increase in surface ocean CO2, and consequently ocean acidification. However, the severity and timing of the proposed ocean acidification with respect to the onset, peak warming and the termination are currently not well resolved. The boron isotopic composition (δ11B) recorded in planktic foraminifer shells offers an opportunity to infer oceanic pH across this interval. We are working on a boron isotope reconstruction from Southern Ocean IODP site 738 and South Atlantic IODP site 1263, covering 42.0 to 38.5 Ma. These sites are characterized by good carbonate preservation and well-defined age models have been established. Additionally, ecology, nutrient content and bottom-water oxygenation have been shown to change significantly across the event towards a more eutrophic, periodically oxygen-depleted environment supporting different biological communities. We selected the planktic foraminifera species Acarinina spinuloinflata for this study because it is symbiont-bearing, suggesting a near-surface habitat and little vertical migration in the water column, and because of its abundance in the samples. δ11B data will be translated to surface ocean pH and atmospheric pCO2 will be approximated to refine knowledge about the carbon cycle during this time. Parallel analysis of two core sites will help to evaluate the tenacity of the data.

  16. Ab initio prediction of equilibrium boron isotope fractionation between minerals and aqueous fluids at high P and T

    Science.gov (United States)

    Kowalski, Piotr M.; Wunder, Bernd; Jahn, Sandro

    2013-01-01

    Over the last decade experimental studies have shown a large B isotope fractionation between materials carrying boron incorporated in trigonally and tetrahedrally coordinated sites, but the mechanisms responsible for producing the observed isotopic signatures are poorly known. In order to understand the boron isotope fractionation processes and to obtain a better interpretation of the experimental data and isotopic signatures observed in natural samples, we use first principles calculations based on density functional theory in conjunction with ab initio molecular dynamics and a new pseudofrequency analysis method to investigate the B isotope fractionation between B-bearing minerals (such as tourmaline and micas) and aqueous fluids containing HBO and HBO4- species. We confirm the experimental finding that the isotope fractionation is mainly driven by the coordination of the fractionating boron atoms and have found in addition that the strength of the produced isotopic signature is strongly correlated with the Bsbnd O bond length. We also demonstrate the ability of our computational scheme to predict the isotopic signatures of fluids at extreme pressures by showing the consistency of computed pressure-dependent β factors with the measured pressure shifts of the Bsbnd O vibrational frequencies of HBO and HBO4- in aqueous fluid. The comparison of the predicted with measured fractionation factors between boromuscovite and neutral fluid confirms the existence of the admixture of tetrahedral boron species in neutral fluid at high P and T found experimentally, which also explains the inconsistency between the various measurements on the tourmaline-mica system reported in the literature. Our investigation shows that the calculated equilibrium isotope fractionation factors have an accuracy comparable to the experiments and give unique and valuable insight into the processes governing the isotope fractionation mechanisms on the atomic scale.

  17. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    Science.gov (United States)

    Ponomarev, V. I.; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.

    2015-09-01

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide В15- х С х , (1.5 ≤ x ≤ 3) and its magnesium derivative C4B25Mg1.42. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from В12.9С2.1 to В12.4С2.6.

  18. Composition and microhardness of CAE boron nitride films

    International Nuclear Information System (INIS)

    The paper deals with boron nitride produced by cathodic arc evaporation techniques.The films were applied on titanium and cemented carbide substrates. Their characterization was carried out using X-ray diffraction and Knoop microhardness tests. Demonstrated are the high properties of two-phase films, containing β (cubic) and γ (wurtzitic) modifications of boron nitride. (author). 7 refs., 1 fig., 3 tabs

  19. Carbon and Oxygen isotopic composition in paleoenvironmental determination

    International Nuclear Information System (INIS)

    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 O16 than the patterns from marine environments. The C12 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.)

  20. A novel paleo-bleaching proxy using boron isotopes and high-resolution laser ablation to reconstruct coral bleaching events

    Directory of Open Access Journals (Sweden)

    G. Dishon

    2015-06-01

    Full Text Available Coral reefs occupy only ~0.1% of the oceans habitat, but are the most biologically diverse marine ecosystem. In recent decades, coral reefs have experienced significant global declines due to a variety of causes, one of the major being widespread coral bleaching events. During bleaching the coral expels its symbiotic algae losing its main source of nutrition generally obtained through photosynthesis. While recent coral bleaching events have been extensively investigated, there is no scientific data on historical coral bleaching prior to 1979. In this study, we employ high-resolution femtosecond Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS to demonstrate a distinct biologically-induced decline of boron (B isotopic composition (δ11B as a result of coral bleaching. These findings and methodology offer a new use for a previously developed isotopic proxy to reconstruct paleo-coral bleaching events. Based on a literature review of published δ11B data and our recorded "vital effect" of coral bleaching on the δ11B signal, we also describe at least two possible coral bleaching events since the Last Glacial Maximum. The implementation of this bleaching proxy holds the potential of identifying occurrences of coral bleaching throughout the geological record. A deeper temporal view of coral bleaching will enable scientists to determine if it occurred in the past during times of environmental change and what outcome it may have had on coral population structure.

  1. Graphite–boron composite heater in a Kawai-type apparatus: the inhibitory effect of boron oxide and countermeasures

    Science.gov (United States)

    Xie, Longjian; Yoneda, Akira; Yoshino, Takashi; Fei, Hongzhan; Ito, Eiji

    2016-04-01

    We have investigated the performance of a graphite-boron composite (GBC) with 3 wt % boron as a precursor for a boron-doped diamond heater in a Kawai-type apparatus at 15 GPa. We first tested a machinable cylinder of GBC sintered at 1000°C in Ar/H2 gas (99:1 molar ratio). Boron oxide (B2O3) formed during sintering frequently hindered the GBC heater from stable operation at temperatures higher than 1400°C by producing melt throughout the heater together with oxide and/or silicates. We then rinsed the GBC heater in hydrochloric acid to remove B2O3. After rinsing, we succeeded in stably generating temperatures higher than 2000°C. We also improved a molding process of different-sized GBC tubes for convenient use and tested the molded GBC heater. It was free from the B2O3 problem. The electromotive force of the W/Re thermocouple was successfully monitored up to 2400°C.

  2. Measurement of the isotopic abundance of boron-10 by inductively coupled plasma-quadrupole mass spectrometry

    International Nuclear Information System (INIS)

    This article describes the method for measuring the isotopic abundance of 10B in nuclear grade boron carbide using inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS). The results of investigation revealed that both the integration time and the dwell time have a major influence on the reproducibility of ICP-QMS measurements. As a result of optimization of the measurement conditions, reproducibility below 0.2% relative standard deviation (RSD) (0.17% RSD maximum) was achieved. In addition, the measured value of the isotopic abundance of 10B for each sample well agreed with the values measured by the TIMS. Thus, the method described in the present investigation was very effective in the analysis of isotopic abundance of 10B in B4C or H3BO3. The results of this study suggest that ICP-QMS could be applied to the precise analysis of the isotopic abundance of 10B required in the field of nuclear applications. (author)

  3. An investigation on gamma attenuation behaviour of titanium diboride reinforced boron carbide–silicon carbide composites

    International Nuclear Information System (INIS)

    In this study, titanium diboride (TiB2) reinforced boron carbide–silicon carbide composites were investigated against Cs-137 and Co-60 gamma radioisotope sources. The composite materials include 70% boron carbide (B4C) and 30% silicon carbide (SiC) by volume. Titanium diboride was reinforced to boron carbide–silicon carbide composites as additive 2% and 4% by volume. Average particle sizes were 3.851 µm and 170 nm for titanium diboride which were reinforced to the boron carbide silicon carbide composites. In the experiments the gamma transmission technique was used to investigate the gamma attenuation properties of the composite materials. Linear and mass attenuation coefficients of the samples were determined. Theoretical mass attenuation coefficients were calculated from XCOM computer code. The experimental results and theoretical results were compared and evaluated with each other. It could be said that increasing the titanium diboride ratio causes higher linear attenuation values against Cs-137 and Co-60 gamma radioisotope sources. In addition decreasing the titanium diboride particle size also increases the linear and mass attenuation properties of the titanium diboride reinforced boron carbide–silicon carbide composites. - Highlights: • Linear and mass attenuation coefficients of B4C–SiC composites were investigated. • Reinforcing titanium diboride causes higher linear attenuation coefficients. • Decreasing titanium diboride particle size increases linear and mass attenuation coefficients. • Nano particle sized samples much closer to the theoretical results than micro sized ones

  4. Protosolar Irradiation in the Early Solar System: Clues from Lithium and Boron Isotopes

    CERN Document Server

    Liu, Ming-Chang; Alexander, Conel M O'D; Lee, Typhoon

    2011-01-01

    We report Li and B isotopic compositions of 10 Spinel-HIBonite spherules (SHIBs) separated from the Murchison meteorite, in order to understand their irradiation history in the early Solar System. The extremely low Be concentrations in SHIBs preclude detection of extinct 10Be, but instead allow for a search of the original Li and B isotopic ratios of the grains, as these isotopes are sensitive indicators for irradiation. We found that some of the SHIBs carried sub-chondritic 7Li/6Li and supra-chondritic 10B/11B ratios. Considering two possible irradiation scenarios that could have occurred in the early Solar System, irradiation of hibonite solids followed by addition of isotopically normal Li and B seems to be the most plausible explanation for the observed Li and B isotope ratios.

  5. Boron

    International Nuclear Information System (INIS)

    The trace element boron (B) is of interest in reclamation situations for several reasons. It plays an essential through largely unidentified role in the growth of higher plants. In argronomic situations B deficiencies are common, and deficiencies in reclamation situations have been suggested but not documented. Among micronutrients, B is unique because the range from deficient concentrations to toxic concentrations either in the soil solution or in plant tissue is narrower than for any other micronutrient. In reclamation situations excessive amounts of B can occur in the soil or in near-surface mining wastes and thus interfere with reclamation objectives, especially in arid and semiarid regions. Also, B is mobile and appears subject to both upward transport (and possible contamination of overlying material) and downward transport (and possible contamination of surface water and groundwater)

  6. An investigation on gamma attenuation behaviour of titanium diboride reinforced boron carbide-silicon carbide composites

    Science.gov (United States)

    Buyuk, Bulent; Beril Tugrul, A.

    2014-04-01

    In this study, titanium diboride (TiB2) reinforced boron carbide-silicon carbide composites were investigated against Cs-137 and Co-60 gamma radioisotope sources. The composite materials include 70% boron carbide (B4C) and 30% silicon carbide (SiC) by volume. Titanium diboride was reinforced to boron carbide-silicon carbide composites as additive 2% and 4% by volume. Average particle sizes were 3.851 µm and 170 nm for titanium diboride which were reinforced to the boron carbide silicon carbide composites. In the experiments the gamma transmission technique was used to investigate the gamma attenuation properties of the composite materials. Linear and mass attenuation coefficients of the samples were determined. Theoretical mass attenuation coefficients were calculated from XCOM computer code. The experimental results and theoretical results were compared and evaluated with each other. It could be said that increasing the titanium diboride ratio causes higher linear attenuation values against Cs-137 and Co-60 gamma radioisotope sources. In addition decreasing the titanium diboride particle size also increases the linear and mass attenuation properties of the titanium diboride reinforced boron carbide-silicon carbide composites.

  7. THE NITROGEN ISOTOPIC COMPOSITION OF METEORITIC HCN

    Energy Technology Data Exchange (ETDEWEB)

    Pizzarello, Sandra, E-mail: pizzar@asu.edu [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85018-1604 (United States)

    2014-12-01

    HCN is ubiquitous in extraterrestrial environments and is central to current theories on the origin of early solar system organic compounds such as amino acids. These compounds, observed in carbonaceous meteorites, were likely important in the origin and/or evolution of early life. As part of our attempts to understand the origin(s) of meteoritic CN{sup –}, we have analyzed the {sup 15}N/{sup 14}N isotopic composition of HCN gas released from water extracts of the Murchison meteorite and found its value to be near those of the terrestrial atmosphere. The findings, when evaluated viz-a-viz molecular abundances and isotopic data of meteoritic organic compounds, suggest that HCN formation could have occurred during the protracted water alteration processes known to have affected the mineralogy of many asteroidal bodies during their solar residence. This was an active synthetic stage, which likely involved simple gasses, organic molecules, their presolar precursors, as well as mineral catalysts and would have lead to the formation of molecules of differing isotopic composition, including some with solar values.

  8. Growth of crystals of several boron-carbon compositions by chemical vapor deposition

    Science.gov (United States)

    Kevill, D. N.; Rissmann, T. J.; Brewe, D.; Wood, C.

    1986-01-01

    Boron-carbon compounds have been deposited by the flow of carbon tetrachloride and boron trichloride, in the presence of a large excess of hydrogen, over a graphite surface maintained at 1000-1300 C. Deposits were formed on either an RF-heated disc or a tube or insert heated by a resistance furnace. Crystalline materials ranging in composition from B2C to B17C have been obtained.

  9. Preparation and properties of unidirectional boron nitride fibre reinforced boron nitride matrix composites via precursor infiltration and pyrolysis route

    International Nuclear Information System (INIS)

    Highlights: → BN fibres degrade little when exposed at elevated temperatures. → Precursor infiltration and pyrolysis route is useful to prepare BNf/BN composites. → Few reports have related to the preparation and properties of BNf/BN composites. → BNf/BN composites have desirable high-temperature mechanical properties. → BNf/BN composites have excellent dielectric properties at 2-18 GHz. - Abstract: The unidirectional boron nitride fibre reinforced boron nitride matrix (BNf/BN) composites were prepared via the precursor infiltration and pyrolysis (PIP) route, and the structure, composition, mechanical and dielectric properties were studied. The composites have a high content and fine crystallinity of BN. The density is 1.60 g cm-3 with a low open porosity of 4.66%. The composites display good mechanical properties with the average flexural strength, elastic modulus and fracture toughness being 53.8 MPa, 20.8 GPa and 6.88 MPa m1/2, respectively. Lots of long fibres pull-out from the fracture surface, suggesting a good fibre/matrix interface. As temperature increases, both of the flexural strength and elastic modulus exhibit a decreasing trend, with the lowest values being 36.2 MPa and 8.6 GPa at 1000 deg. C, respectively. The desirable residual ratios of the flexural strength and elastic modulus at 1000 deg. C are 67.3% and 41.3%, respectively. The composites have excellent dielectric properties, with the average dielectric constant and loss tangent being 3.07 and 0.0044 at 2-18 GHz, respectively.

  10. Oxygen isotope composition of trinitite postdetonation materials.

    Science.gov (United States)

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

    2013-12-17

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

  11. Ion exchange chromatographic separation and MS analysis of isotopes of boron

    International Nuclear Information System (INIS)

    Using electrochemical techniques of pH-metry and conductimetry, the choice of a suitable complexing reagent was made amongst ethylene glycol, propylene glycol, dextrose and mannitol for cost-effective separation of isotopes of boron by ion exchange chromatography. Quantitative relationships between pH and concentration; pKa and concentration of each of these complexing reagents were determined by least square polynomial curve fitting and an attempt was made to determine the formation constants of mannitol-borate complex. The results of experiments carried out for selection; regeneration of a resin; separation factor determinations using batch as well as column techniques and monitoring of band movements using these electrochemical techniques are discussed. (author)

  12. FiR 1 Reactor in Service for Boron Neutron Capture Therapy (BNCT) and Isotope Production

    International Nuclear Information System (INIS)

    The FiR 1 reactor, a 250 kW Triga reactor, has been in operation since 1962. The main purpose to run the reactor is now the Boron Neutron Capture Therapy (BNCT). Although BNCT dominates the current utilization of the reactor, it also has an important national role in providing local enterprises and research institutions in the fields of industrial measurements, pharmaceuticals, electronics, etc. with isotope produc- tion and activation analysis services. The whole reactor building has been renovated, creating a dedicated clinical BNCT facility at the reactor. Close to 30 patients have been treated since May 1999, when the licence for patient treatment was granted to the responsible BNCT treatment organization. The treatment organization has a close connection to the Helsinki University Central Hospital. (author)

  13. Neutron shielding properties of boron-containing ore and epoxy composites

    International Nuclear Information System (INIS)

    Using the boron-containing iron ore concentrate and boron-rich slag as studying object, the starting materials were got after the specific green ore containing boron dressing in China and blast furnace separation respectively. Monte-Carlo method was used to study the effect of the boron-containing iron ore concentrate and boron-rich slag and their composites with epoxy on the neutron shielding abilities. The reasons that affecting the shielding materials properties was discussed and the suitable proportioning of boron-containing ore to epoxy composites was confirmed; the 14.1 MeV fast neutron removal cross section and the total thermal neutron attenuation coefficient were obtained and compared with that of the common used concrete. The results show that the shielding property of 14.1 MeV fast neutron is mainly concerned with the low-Z elements in the shielding materials, the thermal neutron shielding ability is mainly concerned with boron concentrate in the composite, the attenuation of the accompany γ-ray photon is mainly concerned with the high atom number elements content in the ore and the density of the shielding material. The optimum Janume fractions of composites are in the range of 0.4-0.6 and the fast neutron shielding properties are similar to concrete while the thermal neutron shielding properties are higher than concrete. The composites are expected to be used as biological concrete shields crack injection and filling of the anomalous holes through the concrete shields around the radiation fields or directly to be prepared as shielding materials.(authors)

  14. The effect of aluminum on the microstructure and phase composition of boron carbide infiltrated with silicon

    International Nuclear Information System (INIS)

    Reaction-bonded boron carbide is prepared by pressureless infiltration of boron carbide preforms with molten silicon in a graphite furnace under vacuum. The presence of Al2O3 parts in the heated zone, even though not in contact with the boron carbide preform, causes aluminum to appear in the liquid silicon. The formation of aluminum sub-oxide (Al2O) stands behind the transport of aluminum into the composite. The presence of aluminum in the boron carbide-silicon system accelerates the transformation of the initial boron carbide particles into Bx(C,Si,Al)y and Al1.36B24C4, newly formed carbide phases. It also leads during cooling to the formation of some Si-Al solid solution particles. The effect of Al on the microstructural evolution is well accounted for by the calculated isothermal section of the quaternary Al-B-C-Si phase diagram, according to which the solubility of boron in liquid silicon increases with increasing aluminum content. This feature is a key factor in the evolution of the microstructure of the infiltrated composites.

  15. The effect of aluminum on the microstructure and phase composition of boron carbide infiltrated with silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hayun, S., E-mail: hayuns@bgu.ac.il [Department of Materials Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Dilman, H.; Dariel, M.P.; Frage, N. [Department of Materials Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel)

    2009-12-15

    Reaction-bonded boron carbide is prepared by pressureless infiltration of boron carbide preforms with molten silicon in a graphite furnace under vacuum. The presence of Al{sub 2}O{sub 3} parts in the heated zone, even though not in contact with the boron carbide preform, causes aluminum to appear in the liquid silicon. The formation of aluminum sub-oxide (Al{sub 2}O) stands behind the transport of aluminum into the composite. The presence of aluminum in the boron carbide-silicon system accelerates the transformation of the initial boron carbide particles into B{sub x}(C,Si,Al){sub y} and Al{sub 1.36}B{sub 24}C{sub 4}, newly formed carbide phases{sub .} It also leads during cooling to the formation of some Si-Al solid solution particles. The effect of Al on the microstructural evolution is well accounted for by the calculated isothermal section of the quaternary Al-B-C-Si phase diagram, according to which the solubility of boron in liquid silicon increases with increasing aluminum content. This feature is a key factor in the evolution of the microstructure of the infiltrated composites.

  16. Analytical chemistry methods for boron carbide absorber material. [Standard

    Energy Technology Data Exchange (ETDEWEB)

    DELVIN WL

    1977-07-01

    This standard provides analytical chemistry methods for the analysis of boron carbide powder and pellets for the following: total C and B, B isotopic composition, soluble C and B, fluoride, chloride, metallic impurities, gas content, water, nitrogen, and oxygen. (DLC)

  17. Isotopic composition of Riyadh rainfall, Saudi Arabia

    Science.gov (United States)

    Michelsen, Nils; Reshid, Mustefa; Siebert, Christian; Schulz, Stephan; Rausch, Randolf; Knöller, Kay; Weise, Stephan; Al-Saud, Mohammed; Schüth, Christoph

    2015-04-01

    Arid countries like Saudi Arabia often depend on fossil groundwater. Hence, thorough studies of the available resources are crucial. In the course of such investigations, analyses of δ18O and δD are frequently applied to constrain the provenance of the waters and to reconstruct the (paleo)climatic conditions during their recharge. Yet, to be able to evaluate the isotopic signature of the groundwater, one also has to know the isotopic composition of current precipitation. Although a few rain water analyses are available for Central Saudi Arabia in the literature - mostly in unpublished consultant reports - a Local Meteoric Water Line has never been established. To complement the available data, 28 rain events occurring in Riyadh between 2009 and 2013 were studied for their stable isotope composition. Samples were collected as integral samples, i.e., they represent the entire precipitation event. Moreover, one event was sampled several times, aiming at an evaluation of intra-storm variability. During selected storms, a grab sample was taken for 3H analysis. The event samples showed δ18O and δD values scattering between -6.5 and +9.5 and between -30 and +50 ‰ V-SMOW, respectively. In the course of the event that was sequentially sampled, a proceeding isotopic depletion was observed with respect to both isotopes. The relatively large ranges of δ-values for 18O and D of approximately 7 and 38 ‰ V-SMOW highlight the general need for integral sampling. The obtained grab samples are characterized by moderate 3H concentrations of a few Tritium Units. Further results will be presented and discussed in view of associated weather data (e.g. rain amount and temperature) and the probable moisture sources derived from back-trajectories, which were calculated using HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory Model; Draxler & Rolph, 2003). References Draxler, R.R. & Rolph, G.D. (2013): HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory

  18. Evaluation of mechanical properties of aluminium alloy–alumina–boron carbide metal matrix composites

    International Nuclear Information System (INIS)

    Highlights: • Fabrication of MMC with aluminium alloy–alumina–boron carbide is done. • Different proportions of reinforcements are added. • The effects of varying proportions are studied. • Investigation on mechanical properties above composites is performed. • Failure morphology analysis is done using SEM. - Abstract: This paper deals with the fabrication and mechanical investigation of aluminium alloy, alumina (Al2O3) and boron carbide metal matrix composites. Aluminium is the matrix metal having properties like light weight, high strength and ease of machinability. Alumina which has better wear resistance, high strength, hardness and boron carbide which has excellent hardness and fracture toughness are added as reinforcements. Here, the fabrication is done by stir casting which involves mixing the required quantities of additives into stirred molten aluminium. After solidification, the samples are prepared and tested to find the various mechanical properties like tensile, flexural, impact and hardness. The internal structure of the composite is observed using Scanning Electron Microscope (SEM)

  19. Lithium Isotopic Composition of Aleutian Arc Magmas

    Science.gov (United States)

    Rudnick, R. L.; Park, Y.; Liu, X.; Kay, S. M.; Kay, R. W.

    2012-12-01

    The lithium isotopic compositions of inputs to subduction zones can be highly variable. For example, altered oceanic crust is isotopically heavy (δ7Li = 4 to 22, Chan et al., 1996; Bouman et al., 2004) due to uptake of seawater Li (32). Sea floor sediments can have highly variable compositions, ranging from isotopically heavy pelagic sediments (6 to 14) to isotopically light terrigneous clays (-1.5 to 5), derived from highly weathered continental crust (Chan et al., 2006). Despite this variability in inputs, arc outputs (magmatic rocks) typically have mantle-like δ7Li (e.g., 2 to 6; Tomascak et al., 2002; Walker et al., 2009). To explore the behavior of lithium and its isotopes in arcs, we have analyzed [Li] and δ7Li in 48 lavas and plutons from the Aleutian island arc, which span the temporal (0 to 38 Ma), geographical (165-184oW) and compositional variations (SiO2 = 46-70 wt.%) seen in this arc. Previous studies have indicated a systematic geographic change in lava chemistry related to changing sediment composition along the arc (terrigneous in the east, pelagic in the west, e.g., Kay and Kay, 1994; Yogodinski et al., 2010), as well as temporal changes that may also reflect changes in sedimentary input (Kay and Kay, 1994), and we wished to determine if Li isotopes also reflect such changes. Lithium concentration [Li] shows a generally positive correlation with SiO2, consistent with the expected incompatible behavior of Li during magmatic differentiation. Intrusive rocks (all from the Adak region) show more scatter than lavas on this plot, suggesting the influence of cumulate processes. The δ7Li of the rocks span an immense range from -1 to +29, well outside the values considered typical for the MORB-source mantle (e.g., 2-6). However, the majority of the samples (28 out of 48) have δ7Li falling within the range of typical mantle values. There is a general tendency for the lavas (all but one are adakite (~11 Ma, Kay, 1978) has a δ7Li of 3.7. There is no

  20. Synthesis of calcium diborate CaO·B2O3·4H2O (Ca 114) containing definite boron isotope

    International Nuclear Information System (INIS)

    A new method for the synthesis of calcium diborate in aqueous solutions from calcium oxide, sodium hydroxide and boric acid containing a definite boron isotope (10B or 11B) has been elaborated. Since the mother liquid can be utilized for repeated synthesis, the yield of the diborate with respect to boron is higher than in other processes

  1. Enhanced thermal conductivity and isotope effect in single-layer hexagonal boron nitride

    Science.gov (United States)

    Broido, David; Lindsay, Lucas

    2012-02-01

    We have calculated the lattice thermal conductivity, k, of both naturally occurring and isotopically enriched single layers of hexagonal boron nitride (h-BN) as well as bulk h-BN using an exact numerical solution of the Boltzmann transport equation for phonons [1]. Good agreement is obtained with measured bulk h-BN data [2], and the stronger phonon-phonon scattering identified in these systems explains why their k values are significantly lower than those in graphene and graphite. A reduction in such scattering in the single layer arising mainly from a symmetry-based selection rule leads to a substantial increase in k, with calculated room temperature values of more than 600 W/m-K. Additional enhancement is obtained from isotopic enrichment, which exhibits a strong peak as a function of temperature, with magnitude growing rapidly with crystallite size. [1] L. Lindsay and D. A. Broido, Phys. Rev. B 84, 155421 (2011). [2] E. K. Sichel, R. E. Miller, M. S. Abrahams, and C. J. Buiocchi, Phys. Rev. B 13, 4607 (1976).

  2. Stable-isotope composition of the water of apple juice

    International Nuclear Information System (INIS)

    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

  3. A novel paleo-bleaching proxy using boron isotopes and high-resolution laser ablation to reconstruct coral bleaching events

    Science.gov (United States)

    Dishon, G.; Fisch, J.; Horn, I.; Kaczmarek, K.; Bijma, J.; Gruber, D. F.; Nir, O.; Popovich, Y.; Tchernov, D.

    2015-10-01

    Coral reefs occupy only ~ 0.1 percent of the ocean's habitat, but are the most biologically diverse marine ecosystem. In recent decades, coral reefs have experienced a significant global decline due to a variety of causes, one of the major causes being widespread coral bleaching events. During bleaching, the coral expels its symbiotic algae, thereby losing its main source of nutrition generally obtained through photosynthesis. While recent coral bleaching events have been extensively investigated, there is no scientific data on historical coral bleaching prior to 1979. In this study, we employ high-resolution femtosecond Laser Ablation Multiple Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS) to demonstrate a distinct biologically induced decline of boron (B) isotopic composition (δ11B) as a result of coral bleaching. These findings and methodology offer a new use for a previously developed isotopic proxy to reconstruct paleo-coral bleaching events. Based on a literature review of published δ11B data and our recorded vital effect of coral bleaching on the δ11B signal, we also describe at least two possible coral bleaching events since the Last Glacial Maximum. The implementation of this bleaching proxy holds the potential of identifying occurrences of coral bleaching throughout the geological record. A deeper temporal view of coral bleaching will enable scientists to determine if it occurred in the past during times of environmental change and what outcome it may have had on coral population structure. Understanding the frequency of bleaching events is also critical for determining the relationship between natural and anthropogenic causes of these events.

  4. Silver Nanoparticle-Deposited Boron Nitride Nanosheets as Fillers for Polymeric Composites with High Thermal Conductivity

    OpenAIRE

    Fangfang Wang; Xiaoliang Zeng; Yimin Yao; Rong Sun; Jianbin Xu; Ching-Ping Wong

    2016-01-01

    Polymer composites with high thermal conductivity have recently attracted much attention, along with the rapid development of the electronic devices toward higher speed and performance. However, a common method to enhance polymer thermal conductivity through an addition of high thermally conductive fillers usually cannot provide an expected value, especially for composites requiring electrical insulation. Here, we show that polymeric composites with silver nanoparticle-deposited boron nitride...

  5. Isotopic composition of precipitation and groundwater in Sicily, Italy

    International Nuclear Information System (INIS)

    Highlights: • Isotopic composition of precipitation and groundwater in Sicily (Italy). • Isotopic data processing for hydrogeological purpose. • GIS mapping of isotopic data. - Abstract: The isotopic composition of meteoric water in Sicily, Italy was investigated from May 2004 until June 2006. Samples were sampled monthly from a network of 50 rain gauges. During the same period 580 groundwater samples were collected from springs and wells to obtain insight into the isotopic composition of the water circulating in the main aquifers of the area. The mean weighted precipitation values were used to define the weighted local meteoric water line for five different sectors of Sicily. The use of Geographical Information System tools, coupled with isotopic vertical gradients, allowed designing an isotopic contour map of precipitation in Sicily. The defined meteoric compositions were highly consistent with most of the groundwater samples in each sector. However, in some areas fractionation processes occurring during and after rainfall slightly modify the isotopic composition of the groundwater. The obtained data set defines the present day isotopic composition of meteoric water in the central Mediterranean area and provides baseline values for future climatic and/or isotope-based hydrology studies

  6. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, V. I., E-mail: ksv17@ism.ac.ru; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

    2015-09-15

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide B{sub 15–x}C{sub x}, (1.5 ≤ x ≤ 3) and its magnesium derivative C{sub 4}B{sub 25}Mg{sub 1.42}. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from B{sub 12.9}C{sub 2.1} to B{sub 12.4}C{sub 2.6}.

  7. The Lithium Isotope Composition of Planktonic Foraminifera

    Science.gov (United States)

    Hathorne, E. C.; James, R. H.; Harris, N. B.

    2003-12-01

    The temporal record of the lithium isotopic composition of seawater has the potential to provide an important proxy of the relative rates of weathering and hydrothermal processes. One of the most powerful types of evidence for changes in ocean chemistry comes from analyses of foraminiferal calcium carbonate. Here, we explore the utility of foraminifera as recorders of the Li isotopic composition of seawater. The Li isotopic composition of foraminifera tests has been determined by multicollector inductively coupled plasma mass spectrometry (Nu Instruments) using a sample-standard bracketing technique. The external precision of this technique is +/- 0.3 ‰ (2σ ), based on fifteen analyses of seawater over a period of 9 months. Planktonic foraminifera ( ˜10 mg) have been picked from surface sediments of the equatorial Pacific and the North Atlantic. Samples from the equatorial Pacific are Holocene/Pleistocene in age; those from the North Atlantic are from the Holocene. The foraminifera were subject to; cleaning in methanol and water, oxidation (hydrogen peroxide and sodium hydroxide), and leaching in weak acid (0.001M nitric acid). Additional reductive and refractory-phase cleaning steps (respectively, hydrous hydrazine/ammonia and DTPA solutions) had no effect on δ 7Li or Li/Ca. The δ 7Li value of the foraminifera ranges from 27 to 31‰ ; slightly lighter than modern-day seawater (31.1 ‰ ). Different species have consistently different δ 7Li values; O. universa have δ 7Li values within error of seawater, while Gr. truncatulinoides record the lightest δ 7Li (27.1+/- 0.3‰ ). This indicates that there are species specific vital effects on foraminiferal δ 7Li. Samples of the same species from different latitudes in the North Atlantic have the same δ 7Li, suggesting that there is no temperature effect on foraminiferal δ 7Li. Furthermore, with the exception of G. sacculifer, there appears to be no variability in foraminiferal δ 7Li with test size

  8. Rim region growth and its composition in reaction bonded boron carbide composites with core-rim structure

    Energy Technology Data Exchange (ETDEWEB)

    Hayun, S; Weizmann, A; Dilman, H; Dariel, M P; Frage, N [Department of Materials Engineering, Ben-Gurion University of the Negev, P. O. Box 653, Beer-Sheva 84105 (Israel)], E-mail: hayuns@bgu.ac.il

    2009-06-01

    Aluminum was detected in reaction-bonded boron carbide that had been prepared by pressureless infiltration of boron carbide preforms with molten silicon in a graphite furnace under vacuum. The presence of Al{sub 2}O{sub 3} in the heated zone, even though not in contact with the boron carbide preform, stands behind the presence of aluminium in the rim region that interconnects the initial boron carbide particles. The composition of the rim corresponds to the B{sub x}(C,Si,Al){sub y} quaternary carbide phase. The reaction of alumina with graphite and the formation of a gaseous aluminum suboxide (Al{sub 2}O) accounts for the transfer of aluminum in the melt and, subsequently in the rim regions. The presence of Al increases the solubility of boron in liquid silicon, but with increasing aluminum content the activity of boron decreases. These features dominate the structural evolution of the rim-core in the presence of aluminum in the melt.

  9. On anomalous isotope composition of lithium in commercial reagents used as standards in isotope analysis

    International Nuclear Information System (INIS)

    Using the spectral method the isotope analysis of lithium is carried out to specify the value of anomalies of lithium isotope composition in salts. Accuracy of the results obtained has been checked according to standard mixtures, prepared of isotopically enriched lithium chlorides (lithium-6 chloride-90.5% 6Li and 9.5% 7Li; lithium-7 chloride-0.02% 6Li and 99.98% 7Li). The analysis has shown that commercial salts of lithium can have considerably shifted isotope composition, which must be taken into account when calibrating the instruments and applying salts as standards of isotope ratio

  10. Enhanced thermal-mechanical properties of polymer composites with hybrid boron nitride nanofillers

    Science.gov (United States)

    Yan, Haiyan; Tang, Yanxia; Su, Juling; Yang, Xiaoyan

    2014-02-01

    The present work focuses on the investigation of the thermal-mechanical properties of the epoxy composites with hybrid boron nitride nanotubes (BNNTs) and boron nitride nanosheets (BNNSs). The stable dispersions of BNNTs-BNNSs were achieved by a noncovalent functionalization with pyrene carboxylic acid. The resulting epoxy/BNNTs-BNNSs composites exhibited homogeneously dispersed BNNTs-BNNSs and a strong filler-matrix interface interaction. The composites showed a 95 % increase in thermal conductivity and a 57 % improvement in Young's modulus by addition of only 1 vol. % BNNTs-BNNSs. Meanwhile, the composites also retained a high electrical resistance of pure epoxy. Our study thus shows the potential for hybrid BNNTs-BNNSs to be successfully used as the nanofillers of polymer composites for applications in electrically insulating thermal interface materials.

  11. Morphology Composition Isotopes: Recent Results from Observations

    Science.gov (United States)

    Schulz, R.

    2008-07-01

    This article presents some recent imaging and spectroscopic observations that led to results which are significant for understanding the properties of comet nuclei. The coma morphology and/or composition were investigated for 12 comets belonging to different dynamical classes. The data analysis showed that the coma morphology of three non-periodic comets is not consistent with the general assumption that dynamically new comets still have a relatively uniform nucleus surface and therefore do not exhibit gas and/or dust jets in their coma. The determination of carbon and nitrogen isotopic ratios revealed the same values for all comets investigated at various heliocentric distances. However, the relative abundance of the rare nitrogen isotope 15N is about twice as high as in the Earth’s atmosphere. Observations of comets at splitting events and during outbursts led to indications for differences between material from the nucleus surface and the interior. The monitoring of the induced outburst of 9P/Temple revealed that under non-steady state conditions the fast disintegration of species is detectable.

  12. Electron screening effects in (p,alpha) reactions induced on boron isotopes studied via the Trojan Horse Method

    Czech Academy of Sciences Publication Activity Database

    Lamia, L.; Spitaleri, C.; Carlin, N.; Cherubini, S.; Munhoz, M. G.; Del Santo, M. G.; Gulino, M.; Kiss, G. G.; Kroha, Václav; Kubono, S.; La Cognata, M.; Li, C.; Mukhamedzhanov, A.; Pizzone, R. G.; Puglia, S. M. R.; Wen, Q. G.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Somorjai, E.; Souza, F. A .; de Toledo, A. S.; Tumino, A.; Wakabayashi, Y.; Yamaguchi, H.

    Vol. 436. Bristol: IOP Publishing, 2013, 012075. ISSN 1742-6588. [10th International Conference on Custering Aspects of Nuclear Structure and Dynamics (CLUSTER'12). Debrecen (HU), 24.09.2012-28.09.2012] R&D Projects: GA MŠk LM2011019 Institutional support: RVO:61389005 Keywords : Trojan horse methods * Bare nucleus * Boron isotopes * Electron screening Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  13. Combining boron isotopes and carbamazepine to trace sewage in salinized groundwater: A case study in Cap Bon, Tunisia

    International Nuclear Information System (INIS)

    Highlights: • Boron isotopes and carbamazepine contents were combined to assess groundwater contamination by effluents. • Carbamazepine contents ranged from 20 to 900 ng/L in groundwaters mixed with treated wastewaters. • The chemical and isotopic data showed a high spatial and temporal variability. • The system is highly vulnerable and permanently disturbed by the different temporal dynamics. • Wastewater treatments need to be greatly improved before recharge to prevent further degradation of groundwater quality. - Abstract: The Korba aquifer on the east coast of Cape Bon has been overexploited since the 1960s with a resultant reversal of the hydraulic gradient and a degradation of the quality due to seawater intrusion. In 2008 the authorities introduced integrated water resources planning based on a managed aquifer recharge with treated wastewater. Water quality monitoring was implemented in order to determine the different system components and trace the effectiveness of the artificial recharge. Groundwater samples taken from recharge control piezometers and surrounding farm wells were analyzed for their chemical contents, for their B isotopes, a proven tracer of groundwater salinization and domestic sewage, and their carbamazepine content, an anti-epileptic known to pass through wastewater treatment and so recognized as a pertinent tracer of wastewater contamination. The system equilibrium was permanently disturbed by the different temporal dynamics of continuous processes such as cation exchange, and by threshold processes linked to oxidation–reduction conditions. The B isotopic compositions significantly shifted back-and-forth due to mixing with end-members of various origin. Under the variable contribution of meteoric recharge, the Plio-Quaternary groundwater (δ11B of 35–40.6‰, a mean B concentration of 30 μmol/L, no carbamazepine, n = 7) was subject to seawater intrusion that induced a high δ11B level (δ11B of 41.5–48.0‰, a mean B

  14. Boron-doped MnO{sub 2}/carbon fiber composite electrode for supercapacitor

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Hong Zhong, E-mail: hzchi@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhu, Hongjie [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Gao, Linhui [Center of Materials Engineering, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

    2015-10-05

    Highlights: • Interstitial ion in MnO{sub 2} lattice. • Porous film composed by interlocking worm-like nanostructure. • Boron-doped birnessite-type MnO{sub 2}/carbon fiber composite electrode. • Enhanced capacitive properties through nonmetal element doping. - Abstract: The boron-doped MnO{sub 2}/carbon fiber composite electrode has been prepared via in situ redox reaction between potassium permanganate and carbon fibers in the presence of boric acid. The addition of boron as dopant results in the increase of growth-rate of MnO{sub 2} crystal and the formation of worm-like nanostructure. Based on the analysis of binding energy, element boron incorporates into the MnO{sub 2} lattice through interstitial mode. The doped electrode with porous framework is beneficial to pseudocapacitive reaction and surface charge storage, leading to higher specific capacitance and superior rate capability. After experienced 1000 cycles, the boron-doped MnO{sub 2} still retain a higher specific capacitance by about 80% of its initial value. The fall in capacitance is blamed to be the combination of the formation of soluble Mn{sup 2+} and the absence of active site on the outer surface.

  15. Boron-doped MnO2/carbon fiber composite electrode for supercapacitor

    International Nuclear Information System (INIS)

    Highlights: • Interstitial ion in MnO2 lattice. • Porous film composed by interlocking worm-like nanostructure. • Boron-doped birnessite-type MnO2/carbon fiber composite electrode. • Enhanced capacitive properties through nonmetal element doping. - Abstract: The boron-doped MnO2/carbon fiber composite electrode has been prepared via in situ redox reaction between potassium permanganate and carbon fibers in the presence of boric acid. The addition of boron as dopant results in the increase of growth-rate of MnO2 crystal and the formation of worm-like nanostructure. Based on the analysis of binding energy, element boron incorporates into the MnO2 lattice through interstitial mode. The doped electrode with porous framework is beneficial to pseudocapacitive reaction and surface charge storage, leading to higher specific capacitance and superior rate capability. After experienced 1000 cycles, the boron-doped MnO2 still retain a higher specific capacitance by about 80% of its initial value. The fall in capacitance is blamed to be the combination of the formation of soluble Mn2+ and the absence of active site on the outer surface

  16. Simultaneous determination of boron-10 and boron-11 under proton bombardment

    International Nuclear Information System (INIS)

    The isotopic analysis of boron gained importance with increased use of boron-10 in nuclear technology. Former techniques for determining the stable boron isotope either were limited to the determination of a single isotope or required tedious experimental prodecure. The use of proton induced reactions was therefore investigated as an alternative method for the simultaneous analysis of both stable isotopes of boron through a relatively simple experimental procedure. Aqueous solutions of natural boric acid (19,78 at. % 10B) and enriched boric acid (92,41 at. % 10B) were mixed and evaporated to dryness in order to obtain samples in which the isotopic concentration of boron was known. Thin targets were produced by evaporating boron oxide, converted by heat from the boric acid mixture, onto tantalum backing material. Standard samples with known contents of boron oxide were prepared by dry mixing standard reference boron-containing glass powers in a ball mill. Thick targets containing boron of different isotopic compositions were prepared in matrices of potassium bromide and of ion-exchange resins by mixing the matrix with aqueous solutions of boric acid and of sodium carbonate by fusion with boric oxide. The most intense prompt gamma-rays emitted from boron isotopes under irradiation with protons up to 4,5 MeV were the 428-KeV 10B α(1,0), 718-KeV 10B p(1,0) and the 2124-KeV 11B p(1,0) gamma-rays. Excitation functions for the production of each of these were measured using both thick and thin targets

  17. Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

    Science.gov (United States)

    Poindexter, A. M.

    1967-01-01

    Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.

  18. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

    OpenAIRE

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-01-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal...

  19. Boron cage compound materials and composites for shielding and absorbing neutrons

    Science.gov (United States)

    Bowen, III, Daniel E; Eastwood, Eric A

    2014-03-04

    Boron cage compound-containing materials for shielding and absorbing neutrons. The materials include BCC-containing composites and compounds. BCC-containing compounds comprise a host polymer and a BCC attached thereto. BCC-containing composites comprise a mixture of a polymer matrix and a BCC filler. The BCC-containing materials can be used to form numerous articles of manufacture for shielding and absorbing neutrons.

  20. FiR 1 reactor in service for boron neutron capture therapy (BNCT) and isotope production

    International Nuclear Information System (INIS)

    The FiR 1 reactor, a 250 kW Triga reactor, has been in operation since 1962. The main purpose for the existence of the reactor is now the Boron Neutron Capture Therapy (BNCT), but FiR 1 has also an important national role in providing local enterprises and research institutions in the fields of industrial measurements, pharmaceuticals, electronics etc. with isotope production and activation analysis services. In the 1990's a BNCT treatment facility was built at the FiR 1 reactor located at Technical Research Centre of Finland. A special new neutron moderator material FluentalTM (Al+AlF3+Li) developed at VTT ensures the superior quality of the neutron beam. Also the treatment environment is of world top quality after a major renovation of the whole reactor building in 1997. Recently the lithiated polyethylene neutron shielding of the beam aperture was modified to ease the positioning of the patient close to the beam aperture. Increasing the reactor power to 500 kW would allow positioning of the patient further away from the beam aperture. Possibilities to accomplish a safety analysis for this is currently under considerations. Over thirty patients have been treated at FiR 1 since May 1999, when the license for patient treatment was granted to the responsible BNCT treatment organization, Boneca Corporation. Currently three clinical trial protocols for tumours in the brain as well as in the head and neck region are recruiting patients. (author)

  1. Shockwave Processing of Composite Boron and Titanium Nitride Powders

    Science.gov (United States)

    Beason, Matthew T.; Gunduz, I. Emre; Mukasyan, Alexander S.; Son, Steven F.

    2015-06-01

    Shockwave processing of powders has been shown to initiate reactions between condensed phase reactants. It has been observed that these reactions can occur at very short timescales, resulting in chemical reactions occurring at a high pressure state. These reactions have the potential to produce metastable phases. Kinetic limitations prevent gaseous reactants from being used in this type of synthesis reaction. To overcome this limitation, a solid source of gaseous reactants must be used. An example of this type of reaction is the nitrogen exchange reaction (e.g. B + TiN, B + Si3N4 etc.). In these reactions nitrogen is ``carried'' by a material that can be then reduced by the second reactant. This work explores the possibility of using nitrogen exchange reactions to synthesize the cubic phase of boron nitride (c-BN) through shockwave processing of ball milled mixtures of boron and titanium nitride. The heating from the passage of the shock wave (pore collapse, plastic work, etc.) combined with thermochemical energy from the reaction may provide a means to synthesize c-BN. This material is based upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number(s) DE-NA0002377. National Defense Science & Engineering Graduate Fellowship (NDSEG), 32 CFR 168a.

  2. Boron reinforced composites. 1976-April 1980 (citations from the NTIS Data Base). Report for 1976-April 1980

    Energy Technology Data Exchange (ETDEWEB)

    Cavagnaro, D.M.

    1980-05-01

    The bibliography cites Federally-funded research on boron fibers and boron compounds used as reinforcing material in composites. Included are studies on fabrication, testing, uses, and structural and mechanical properties. (This updated bibliography contains 255 abstracts, 19 of which are new entries to the previous edition.)

  3. Reinforcement against crack propagation of PWR absorbers by development of boron-carbon-hafnium composites

    International Nuclear Information System (INIS)

    In order to improve the mechanical behaviour of materials used as neutron absorbers in nuclear reactors, we have developed CERCER or CERMET composites with boron and hafnium. Thus a new composite B4C/HfB2 has been especially studied. We have identified three kinds of degradation under irradiation (thermal gradient, swelling due to fission products and accidental corrosion) that induce imposed deformations cracking phenomena. Mechanical behaviour and crack propagation resistance have been studied by ball-on-three-balls and double torsion tests. A special device was developed to enable crack propagation and associated stress intensity factor measurements. Effects of structure and of a second phase are underline. First results show that these materials present crack initiation and propagation resistance much higher than pure boron carbide or hafnium diboride. We observe R-Curves effects, crack bridging or branching, crack arrests, and toughness increases that we can relate respectively to the composite structures. (author)

  4. Lightweight Ceramic Composition of Carbon Silicon Oxygen and Boron

    Science.gov (United States)

    Leiser, Daniel B. (Inventor); Hsu, Ming-Ta (Inventor); Chen, Timothy S. (Inventor)

    1997-01-01

    Lightweight, monolithic ceramics resistant to oxidation in air at high temperatures are made by impregnating a porous carbon preform with a sol which contains a mixture of tetraethoxysilane, dimethyldiethoxysilane and trimethyl borate. The sol is gelled and dried on the carbon preform to form a ceramic precursor. The precursor is pyrolyzed in an inert atmosphere to form the ceramic which is made of carbon, silicon, oxygen and boron. The carbon of the preform reacts with the dried gel during the pyrolysis to form a component of the resulting ceramic. The ceramic is of the same size, shape and form as the carbon precursor. Thus, using a porous, fibrous carbon precursor, such as a carbon felt, results in a porous, fibrous ceramic. Ceramics of the invention are useful as lightweight tiles for a reentry spacecraft.

  5. Influence of boron doped carbon nanotubes on electric and electromagnetic properties of phosphate composite materials

    International Nuclear Information System (INIS)

    The work presents a study of the possibility to develop the multifunctional composite materials based on the electromagnetically absorbing nonfired, mechanically strong and heat-resistant phosphate ceramics. The potentialities of using pure and boron doped multiwalled carbon nanotubes (MWCNTs and B-MWCNTs, respectively) as functional additives to the phosphate matrix were investigated. It was found that a length of MWCNT is the determining factor for the electrical conductivity and high-frequency conductivity of the composite. Growth of the intrinsic conductivity of boron-containing MWCNTs, compared to their undoped counterparts, has no significant influence on the possible resistance decrease of the composite on their basis in the static mode and also on its ability to electromagnetic shielding. This is due to a small length of B-MWCNTs and hence much greater concentrations required to achieve the percolation threshold than those studied (up to 1,5 wt. %). On the contrary, the use of long pure MWCNTs in small concentrations has a tremendous impact on the electromagnetic properties of the phosphate composite: on introduction of 1,5 wt. % of MWCNTs one can observe increase in the conductivity by 13 orders of magnitude, and the composite MWCNTs/phosphate 1 mm thick is opaque to microwave radiation. Taking into account the interest in using the boron-doped MWNT also as neutron-absorbing materials, it is essential to improve the synthesis methods of B-MWCNTs with the aim of increasing their length. (authors)

  6. Boron Isotopic Fractionation and Trace Element Incorporation in Various Species of Modern Corals in Sanya Bay, South China Sea

    Institute of Scientific and Technical Information of China (English)

    Haizhen Wei; Shaoyong Jiang; Yingkai Xiao; N Gary Hemming

    2014-01-01

    The boron isotope paleo-pH proxy has been extensively studied due to its potential for understanding past climate change, and further calibrations were considered for accurate applications of the proxy because of significant variability related to biocarbonate microstructure. In this work, we studied the boron isotopic fractionation between modern marine corals and their coexisting seawater collected along shallow area in Sanya Bay, South China Sea. The apparent partition coefficient of boron (KD) ranged from 0.83×10-3 to 1.69×10-3, which are in good agreement with previous studies. As the an-alyzed coral skeleton (~5 g) spanned the growth time period of 1-2 years, we discussed the boron iso-topic fractionation between pristine corals and modern seawater using the annual mean seawater pH of 8.12 in this sea area. Without taking the vital effect into account, (11B/10B)coral values of all living corals spread over the curves of (11B/10B)borate vs. (11B/10B)sw with theα4-3 values ranging from 0.974 to 0.982. After calibrating the biological effect on the calcifying fluid pH, the field-based calcification on calcify-ing fluid pH (i.e.,Δ(pHbiol-pHsw)) for coral species of Acropora, Pavona, Pocillopora, Faviidae, and others including Proites are 0.42, 0.33, 0.36, 0.19, respectively, and it is necessary to be validated by coral cul-turing experiment in the future. Correlations in B/Ca vs. Sr/Ca and B/Ca vs. pHbiol approve tempera-ture and calcifying fluid pH influence on skeletal B/Ca. Fundamental understanding of the thermody-namic basis of the boron isotopes in marine carbonates and seawater will strengthen the confidence in the use of paleo-pH proxy as a powerful tool to monitor atmospheric CO2 variations in the past.

  7. Use of type-II strong base anion exchange resins for ion exchange chromatographic separation of isotopes of boron

    International Nuclear Information System (INIS)

    The optimum conditions for the regeneration of strong base anion exchange resins of type-I and type-II were determined for cost - effective separation of isotopes of boron by ion exchange chromatography. The possibility of using unspent alkali content of the effluent was also exploited. Removal of carbonate impurity from rayon grade caustic lye (used as regenerant after dilution) and recycling of Ba(OH)2 was studied to avoid waste disposal problems. The determination of (i) ion exchange capacity of Duolite-162 resin for hydroxyl - chloride and hydroxyl - borate exchanges, (ii) isotopic exchange separation factor by batch method and (iii) effect of concentration of boric acid (in presence and absence of mannitol) on isotopic exchange separation factor to test the suitability of the type-II resin for this process are discussed. (author)

  8. Isotopic composition of precipitation in Ljubljana (Slovenia

    Directory of Open Access Journals (Sweden)

    Polona Vreča

    2008-12-01

    Full Text Available The stable isotopic composition of hydrogen and oxygen (δ2H and δ18O and tritium activity (3H are monitored in monthly precipitation at Ljubljana since 1981. Here we present complete set of numerical data and the statistical analysis for period 1981–2006. Seasonal variations of δ2H and δ18O are observed and are typical for continental stations of the Northern Hemisphere. The weighted mean δ2H and δ18O values are –59 ‰ and –8.6 ‰, respectively.The orthogonal Local Meteoric Water Line is δ2H = (8.06 ± 0.08δ18O + (9.84 ± 0.71, and the temperature coefficient of δ18O is 0.29 ‰/°C. Deuterium excess weighted mean value is 9.5 ‰ and indicates the prevailing influence of the Atlantic air masses. Tritium activity in monthly precipitation shows also seasonal variations which are superposed to the decreasing trend of mean annual activity.

  9. Stable isotopic composition of East African lake waters

    International Nuclear Information System (INIS)

    The investigation of stable isotopic composition of East African lake waters was conducted by scientists from the Department of Geology, University of Nairobi, as part of the International Decade for the East African Lakes (IDEAL) project and in close collaboration with the scientists from Large Lakes Observatory of the University of Minnesota and the Isotope Hydrology Laboratory of the IAEA in Vienna. The Research Contract was part of the IAEA Co-ordinated Research Programme on Isotope Techniques in Lake Dynamics Investigations, and was sponsored by the Agency. Water and grab sediment samples were obtained from East African Lakes during the month of January and February 1994 and July/August 1995. Water samples were analysed for oxygen and deuterium isotopic composition at the IAEA Laboratories in Vienna, Austria. In this final paper we report the results of the study of oxygen and deuterium isotopic composition from the East African lake waters. (author)

  10. Molybdenum isotopic composition of modern and Carboniferous carbonates

    OpenAIRE

    Voegelin, Andrea R.; Nägler, Thomas F.; Samankassou, Elias; Villa, Igor M.

    2009-01-01

    We investigate the redox-sensitive isotope system of molybdenum (Mo) in marine carbonates to evaluate their potential as archive of the Mo isotopic composition of coeval seawater. We present Mo isotope data (δ98/95Mo) of modern skeletal and non-skeletal carbonates as well as a variety of precipitates from the mid and late Carboniferous. The external reproducibility is determined by repeated analyses of two commercially available carbonate standards. The resulting uncertainty of the low concen...

  11. Boron isotope evidence for the involvement of non-marine evaporites in the origin of the Broken Hill ore deposits

    Science.gov (United States)

    Slack, J.F.; Palmer, M.R.; Stevens, B.P.J.

    1989-01-01

    IDENTIFYING the palaeogeographic setting and mode of origin of stratabound ore deposits can be difficult in high-grade metamorphic terranes, where the effects of metamorphism may obscure the nature of the protoliths. Here we report boron isotope data for tourmalines from the early Proterozoic Broken Hill block, in Australia, which hosts giant lead-zinc-silver sulphide deposits. With one exception the 11B/10B ratios are lower than those for all other tourmalines from massive sulphide deposits and tour-malinites elsewhere in the world. We propose that these low ratios reflect leaching of boron from non-marine evaporitic borates by convecting hydrothermal fluids associated with early Proterozoic continental rifting. A possible modern analogue is the Salton Sea geothermal field in California. ?? 1989 Nature Publishing Group.

  12. The Chlorine Isotopic Composition of Lunar urKREEP

    Science.gov (United States)

    Barnes, J. J.; Tartese, R.; Anand, M.; McCubbin, F. M.; Neal, C. R.; Franchi, I. A.

    2016-05-01

    We have measured the Cl isotopic composition of apatite in a range of lunar rocks using NanoSIMS. We find a correlation between Cl isotopes and bulk rock chemistry which strongly suggesting urKREEP was characterized by heavy Cl.

  13. Characters of chlorine isotopic composition in ocean water

    Digital Repository Service at National Institute of Oceanography (India)

    Xiao, Y.; Zhou, Y.; Liu, W.G.; Hong, A.; Wang, Q.; Wang, Y.; Wei, H.; Shirodkar, P.V.

    The chlorine isotopic composition of ocean water was determined using thermal ionization mass spectrometry based on the measurement of Cs sub(2) Cl sup(+) ion. The results show that the sup(37) Cl/ sup(35) Cl ratios are basically homogeneous...

  14. Ruthenium Isotopic Composition of Terrestrial Materials, Iron Meteorites and Chondrites

    Science.gov (United States)

    Becker, H.; Walker, R. J.

    2002-01-01

    Ru isotopic compositions of magmatic iron meteorites and chondrites overlap with terrestrial Ru at the 0.3 to 0.9 (epsilon) level. Additional information is contained in the original extended abstract.

  15. Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

    OpenAIRE

    Yongqiang Tan; Heng Luo; Haibin Zhang; Xiaosong Zhou; Shuming Peng

    2016-01-01

    Lightweight graphene nanoplatelet (GNP)/boron carbide (B4C) composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI) shielding effectiveness (SE) has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B4C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ∼ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high ...

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

    Science.gov (United States)

    Fujiya, Wataru; Hoppe, Peter; Ott, Ulrich

    2016-07-01

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

  17. FIR 1 reactor in service for boron neutron capture therapy (BNCT) and isotope production

    International Nuclear Information System (INIS)

    Full text: The FIR 1-reactor, a 250 kW Triga reactor, has been in operation since 1962. The main purpose for the existence of the reactor is now the Boron Neutron Capture Therapy (BNCT). The BNCT work dominates the current utilization of the reactor: three or four days per week are reserved for BNCT purposes and the rest for other purposes such as isotope production and neutron activation analysis. In the 1990's a BNCT treatment facility was build at the FiR1 reactor located at Technical Research Centre of Finland. A special new neutron moderator material FluentalTM (Al+AlF3+Li) developed at VTT ensures the superior quality of the neutron beam. Also the treatment environment is of world top quality. The ground floor of the reactor hall was provided with a new entrance, easily accessible by any patient vehicle, a radio therapy control room and rooms for patient preparation and laboratories. The top of the reactor tank was separated from the reactor hall in order to confine contamination in case of a leakage from irradiation samples or fuel elements. The ventilation of the building, emergency power supply system, heat exchangers and the secondary cooling circuit of the reactor including cooling towers were completely redesigned and rebuilt. The expenditure of designing and accomplishing the construction work described was about 4 million euros. The costs were partly financed with venture capital via Radtek Ltd., particularly established for this enterprise. Close to thirty patients have been treated at FiR 1 since May 1999, when the license for patient treatment was granted to the responsible BNCT treatment organization, Boneca Corporation. VTT as the reactor operator has a long term contract with the Boneca Corp. to provide the facility and irradiation services for the patient treatments. The BNCT facility has been licensed for clinical use and is being surveyed by several national public health authorities including the Finnish Nuclear and Radiation Safety

  18. Intra-shell boron isotope ratios in the symbiont-bearing benthic foraminiferan Amphistegina lobifera: Implications for δ 11B vital effects and paleo-pH reconstructions

    Science.gov (United States)

    Rollion-Bard, C.; Erez, J.

    2010-03-01

    The boron isotope composition of marine carbonates is considered to be a seawater pH proxy. Nevertheless, the use of δ 11B has some limitations such as the knowledge of the fractionation factor ( α4-3) between boric acid and the borate ion and the amplitude of "vital effects" on this proxy that are not well constrained. Using secondary ion mass spectrometry (SIMS) we have examined the internal variability of the boron isotope ratio in the shallow water, symbionts bearing foraminiferan Amphistegina lobifera. Specimens were cultured at constant temperature (24 ± 0.1 °C) in seawater with pH ranging between 7.90 and 8.45. Intra-shell boron isotopes showed large variability with an upper limit value of ≈30‰. Our results suggest that the fractionation factor α4-3 of 0.97352 ( Klochko et al., 2006) is in better agreement with our experiments and with direct pH measurements in seawater vacuoles associated with the biomineralization process in these foraminifera. Despite the large variability of the skeletal pH values in each cultured specimen, it is possible to link the lowest calculated pH values to the experimental culture pH values while the upper pH limit is slightly below 9. This variability can be interpreted as follows: foraminifera variably increase the pH at the biomineralization site to about 9. This increase above ambient seawater pH leads to a range in δ 11B (Δ 11B) for each seawater pH. This Δ 11B is linearly correlated with the culture seawater pH with a slope of -13.1 per pH unit, and is independent of the fractionation factor α4-3, or the δ 11B sw through time. It may also be independent of the p KB (the dissociation constant of boric acid) value. Therefore, Δ 11B in foraminifera can potentially reconstruct paleo-pH of seawater.

  19. Lead isotopic compositions of ash sourced from Australian bushfires

    International Nuclear Information System (INIS)

    This study identifies natural and industrial lead remobilized in ash deposits from three bushfires in relatively pristine areas of Australia in 2011 using lead isotopic compositions (208Pb/207Pb; 206Pb/207Pb). Lead concentrations in the ash ranged from 1 to 36 mg/kg, bracketing the range of lead (4–23 mg/kg) in surface soils (0–2 cm), subsurface (40–50 cm) soils and rocks. The lead isotopic compositions of ash and surface soil samples were compared to subsurface soils and local bedrock samples. The data show that many of the ash and surface soil lead isotopic compositions were a mixture of natural lead and legacy industrial lead depositions (such as leaded petrol combustion). However, some of the ash samples at each of the sites had lead isotopic compositions that did not fit a simple two end-member mixing model, indicating other, unidentified sources. - Highlights: • Lead isotopic compositions of ash deposits from wildfires in Australia were measured. • Not all ash lead isotopic compositions matched those of local soil and rock. • Ash lead was sourced from a mixture of natural and industrial sources. • The major industrial source was identified as depositions from historic leaded petrol. - This study shows that industrial lead is remobilized from large old trees in ash deposits following wildfires

  20. Structure and composition of plasma deposited boron-containing carbon films

    International Nuclear Information System (INIS)

    Deposition of boron-carbon films on silicon, nickel, graphite, Kh18N10T steel from gas discharge plasma, the film chemical composition and erosion resistance to ion-plasma effects are studied. Conclusion is made on possibility of such film application as well coating for discharge chambers of thermonuclear facilities. Method of deposition from plasma makes it possible to avoid application of the previously used high-toxic and dangerously explosive B2H6

  1. Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1994-01-01

    1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade aluminum oxide and aluminum oxide-boron carbide composite pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Boron by Titrimetry 7 to 13 Separation of Boron for Mass Spectrometry 14 to 19 Isotopic Composition by Mass Spectrometry 20 to 23 Separation of Halides by Pyrohydrolysis 24 to 27 Fluoride by Ion-Selective Electrode 28 to 30 Chloride, Bromide, and Iodide by Amperometric Microtitrimetry 31 to 33 Trace Elements by Emission Spectroscopy 34 to 46 1.3 The values stated in SI units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (F...

  2. Boron isotope ratio determination in carbonates /via/ LA-MC-ICP-MS using soda-lime glass standards as reference material

    OpenAIRE

    Fietzke, Jan; Heinemann, Agnes; Taubner, Isabelle; Böhm, Florian; Erez, Jonathan; Eisenhauer, Anton

    2010-01-01

    A new in situ method using LA-MC-ICP-MS (193 nm excimer laser) for the determination of stable boron isotope ratios (δ11B) in carbonates was developed. Data were acquired via a standard sample standard bracketing procedure typically providing a reproducibility of 0.5‰ (SD) for samples containing 35 ppm of boron. A single ablation interval consumed about 5 µg of sample corresponding to about 0.2 ng of boron. The major finding was the similar instrumental fractionation behaviour of carbonates, ...

  3. Separation of boron isotopes by ion exchange chromatography: studies on regeneration of strong base anion exchange resins

    International Nuclear Information System (INIS)

    The optimum conditions for the regeneration of strong base anion exchange resins of type-I and type-II were determined for cost-effective separation of isotopes of boron by ion exchange chromatography where the hydroxyl form of an anion exchange resin is equilibrated with boric acid solution containing mannitol as a complexing reagent. The possibility of using unspent alkali content of the effluent was also exploited. Removal of carbonate impurity from Rayon grade caustic lye (used as regenerant after dilution) and recycling of Ba(OH)2 was studied to avoid waste disposal problems. (author)

  4. Kinetics of formation of a platelet-reinforced ceramic composite prepared by the directed reaction of zirconium with boron carbide

    International Nuclear Information System (INIS)

    In this paper the kinetics of formation of a new class of ceramic composite material, zirconium diboride platelet-reinforced zirconium carbides, are discussed. These materials are prepared by the directed reaction of molten zirconium with boron carbide to form a ceramic material composed of zirconium diboride platelets approximately uniformly distributed in a zirconium carbide matrix containing a controlled amount of residual zirconium metal. Results from interrupted growth studies, differential thermal analysis, adiabatic reaction temperature calculations, and kinetic measurements have been used to study the kinetics of the process. The reaction is very fast and proceeds parabolically with time with a rate constant between 1.6 x 10-2 and 3.9 x 10-2 cm2/s. The proposed mechanism suggests that when molten zirconium contacts boron carbide, the molten zirconium exothermically reacts with the boron carbide to form a boron-rick liquid. Further reaction is sustained by the continuous dissolution of the boron carbide as the boron-rich liquid is drawn into the boron carbide. The product is a zirconium diboride/zirconium carbide/zirconium composite which homogenizes quickly at the reaction temperature to yield a uniform product microstructure throughout the composite. Two alternative rate-limiting steps are discussed and the implications of each are explored

  5. The Palladium Isotopic Composition in Iron Meteorites

    Science.gov (United States)

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

    2005-01-01

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

  6. Can boron and boron isotopes be used as a sedimentary marker for fire events? A case study from a historic urban fire event in W Finland

    International Nuclear Information System (INIS)

    The aim of this study was to seek the origin of a B peak found in two sediment profiles from a small lake close to a small-sized town in Finland. The peak was found by chance when an environmental multielement study was performed. Altogether 51 chemical elements were determined with ICP-MS, after aqua regia digestion. None of the other determined elements were enriched or depleted in the B rich layer, including elements derived from sea-salt inclusions (Na and Sr) and anthropogenic sources (Pb, Cu, Cd, Hg, etc.). Boron stable isotopes, dating of the sediment cores, and the B concentrations found in possible source materials suggest that the B rich layer is the result of leaching of wood ash produced in a fire that destroyed half of the nearby wooden town in the early 19th century. The results imply that the concentrations and isotopic signatures of B in lacustrine environments (sediments) can be used to detect historic fires

  7. Gamma and neutron attenuation behaviours of boron carbide–silicon carbide composites

    International Nuclear Information System (INIS)

    Highlights: • Gamma and neutron attenuation behaviours of B4C–SiC composites were investigated. • Increasing SiC ratio increases gamma attenuation behaviour of the B4C–SiC composites. • Increasing SiC ratio decrease attenuation behaviour of the B4C–SiC composites. • HVT values of the B4C–SiC composites were calculated for Cs-137, Co-60 and Pu–Be sources. • Experimental mass attenuation coefficient are compatible with theoretical (XCOM) values. - Abstract: In this study, the gamma and neutron attenuation behaviors of pure boron carbide and boron carbide–silicon carbide composites which include three different silicon carbide ratios (20%, 30%, and 40%) by volume were investigated against Cs-137, Co-60 gamma radioisotope sources and Pu–Be neutron source. Transmission technique was used in the experiments to investigate the gamma and neutron attenuation properties of the materials. Linear and mass attenuation coefficients of the samples were determined for 0.662 (Cs-137) and 1.25 MeV (Co-60) energetic gamma rays. In addition the total macroscopic cross-sections (∑T) were calculated for the materials against Pu–Be neutron source. Theoretical mass attenuation coefficients were calculated from XCOM computer code. The experimental and theoretical mass attenuation coefficients were compared and evaluated with each other. In addition half value thickness (HVT) calculations were carried out by using linear attenuation coefficients and total macroscopic cross-sections. The results showed that increasing silicon carbide ratio decreases HVTs against Cs-137 and Co-60 gamma radioisotope sources whereas increases HVTs against Pu–Be neutron source. The mass attenuation coefficients were compatible with the theoretical (XCOM) values. Increasing silicon carbide ratio in boron carbide–silicon carbide composites causes higher gamma attenuation and lower neutron attenuation values

  8. High variability in boron isotopes of deep-sea corals (Lophelia pertusa): implications for biomineralization processes and for paleo-pCO2 reconstruction

    International Nuclear Information System (INIS)

    Full text: The deep-sea coral Lophelia pertusa is a scleractinian coral (azooxanthellate) found on the continental margins of the major world oceans. Its aragonite skeleton can be precisely dated and measured for stable isotope composition (C-O) to reconstruct past oceanic conditions. O-C isotopic data obtained at a micrometer scale using either Secondary Ion Mass Spectrometry (SIMS) or micromilled samples and taking into account the skeleton microstructures, i.e. centres of calcification (COC) and surrounding fibres, exhibit large O-C isotopic variations. These variations have been interpreted in term of pH variations during and/or at the site of calcification. To document the boron isotopes behaviour in deep-sea coral we have performed several SIMS delta-11B profiles cross cutting the two main microstructures of the skeleton.With this technique the precision is about 0.5 %o. Within the entire data set δ11B ranges from 28.5 to 38.5 %o, which is twice the variation obtained from TIMS or MC-ICPMS on similar samples. The δ11B values of COC range from 27.1 to 33.6 with a mean value of 31.2 (n = 19). The δ11B values for the surrounding fibres are systematically heavier, ranging from 33.2 to 38.5 %oo with a mean value at 35.8 %o. Delta-11B values appear strongly correlated with the microstructure of the coral skeleton. This conclusion was also reached by Rollion-Bard et al. (2003), based on analyzes of zooxanthellate corals. From the δ11B values, we have calculated the pH value at the site of calcification. We used a value of delta-11B of seawater of 39.5 %o, a fractionation factor (3-4) of 0.974 and a pKA of 8.8. If a fractionation factor (3-4) of 0.981 is used in the calculation the resulting pH values are lower by about 0.2%.We calculate a mean pH value of 9.2 (±0.1) for the COC and 9.6 (±0.2) for the surrounding fibres. These calculated values are within the range measured with microelectrode (Vengosh et al. 1991) or by microsensor on calicoblastic layers (8

  9. The isotopic analysis of boron by charged particle irradiation; Analise isotopica de boro utilizando feixes de particulas carregadas

    Energy Technology Data Exchange (ETDEWEB)

    Vinagre Junior, Ubirajara M.; Costa, Vilmar L. da; Suita, Julio C.; Teixeira, Danilo L.; Bernedo, Alfredo V.B.; Cabral, Tania S. [Instituto de Engenharia Nuclear (IEN), Rio de Janeiro, RJ (Brazil)

    1997-12-01

    An analytical isotopic method for boron analysis is discribed, based in the spectrometry of protons at 130{sup 0} C from scattering and/or reactions like {sup 10} B(p,p){sup 10} B and {sup 11} B(p,p){sup 11} B which were simultaneously measured. The basic parameters involved in such measurements, are discussed including cinematic, angular distribution, preparation of targets and its substracs. Particle spectra of targets with natural isotopic concentration and enriched in {sup 10} B are presented. The ratio [{sup 11} B(p{sub o})/{sup 10} B(p{sub o})] at 130{sup 0} C for targets of {sup nat} B in respect of the incident proton beam energy between 14 and 24 MeV are shown. The results of our enriched {sup 10} B are compared with results obtained in mass spectrometry. (author). 14 refs., 6 figs., 1 tab.

  10. Variability (in time) of the isotopic composition of precipitation: consequences regarding the isotopic composition of hydrologic systems

    International Nuclear Information System (INIS)

    The stable isotopic signature in precipitation is primarily imposed by the synoptic history of the air masses, namely, by the vapour origin and the rainout history en route. Mixing patterns in the cloud and rain intensity affect the isotopic composition of rain to some extent. During the recharge to groundwaters, additional isotopic change may occur due to isotope fractionation which accompanies evaporative water loss from the surface or soil (mainly in arid zones), or selection of part of the rainfall by run off or transpiration. Changes in the meteorological pattern and climate express themselves 'isotopically' both due to the changing synoptic patterns and the secondary isotope fractionation and selection which accompany the rain forming and the groundwater recharge process. For the latter case, the rain intensities and the intervals between individual rain events are of major importance. (author). 23 refs, 6 figs

  11. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers

    Science.gov (United States)

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-11-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved.

  12. Solvent-free fabrication of thermally conductive insulating epoxy composites with boron nitride nanoplatelets as fillers.

    Science.gov (United States)

    Wang, Zifeng; Fu, Yuqiao; Meng, Wenjun; Zhi, Chunyi

    2014-01-01

    A solvent-free method for the fabrication of thermally conductive epoxy-boron nitride (BN) nanoplatelet composite material is developed in this study. By this method, polymer composites with nearly any filler fractions can be easily fabricated. The maximum thermal conductivity reaches 5.24 W/mK, which is 1,600% improvement in comparison with that of pristine epoxy material. In addition, the as-fabricated samples exhibit excellent overall performances with great mechanical property and thermal stability well preserved. PMID:25489292

  13. Stable isotope composition of food from different regions of Poland

    International Nuclear Information System (INIS)

    Full text: Stable isotope (hydrogen, oxygen, carbon and nitrogen) composition is important tool for food authenticity and control of origin. The isotopic fractionation of those elements in the environment follows complex patterns allowing to established the correlation between the food (fruits, vegetables etc.) and raw materials (water and CO2). The aim of the study is to explore the relationship between isotope composition of different sorts of food and its geographical origin. The purpose of the study is to compare the data from different regions of Poland. The samples are received directly from a producer. Hydrogen, oxygen, nitrogen and carbon composition is measured in many sorts of food. The collected data gives a possibility to find the relationship between time and place of origin and isotope ratio: 18O/16O, 13C/12C, 15N/14N and D/H. The composition of water presented in the food is tested. Hydrogen is measured by H/Device and oxygen isotope ratio by Gasbench II (both instruments connected with mass spectrometer). For the comparison the water samples from the region of plant growing are tested. In this study for measurements of carbon and nitrogen composition in food, we use our new instrument Elemental Analyser coupled with mass spectrometer. The correlation between stable isotope composition 18O/16O, 13C/12C, 15N/14N, D/H and geographical origin of food will be presented in the paper. In the future, the study will be continued and addition of parameters, as a sulfur isotope composition in food and in surrounding environment (as a pollutant), will be compared. (author)

  14. Stable isotope composition of food from different regions of Poland

    International Nuclear Information System (INIS)

    Full text: Stable isotope (hydrogen, oxygen, carbon and nitrogen) composition is an important tool for food authenticity and control of origin. The isotopic fractionation of those elements in the environment follows complex patterns, allowing to establish the correlation between food (fruits, vegetables etc.) and raw materials (water and CO2). The aim of the study is to explore the relationship between isotope composition of different sorts of food and its geographical origin. The purpose of the study is to compare the data from different regions of Poland. The samples are received directly from a producer. Hydrogen, oxygen, nitrogen and carbon composition is measured in many sorts of food. The collected data give a possibility to find the relationship between time and place of origin and isotope ratio: 18O/16O, 13C/12C, 15N/14N and D/H. The composition of water presented in food is tested. Hydrogen is measured by H/Device and oxygen isotope ratio, by Gasbench II (both instruments connected with mass spectrometer). For the comparison the water samples from the region of plant growing are tested. In this study, for measurements of carbon and nitrogen composition in food, we use our new instrument Elemental Analyser coupled with mass spectrometer. The correlation between stable isotope composition 18O/16O, 13C/12C, 15N/14N, D/H and geographical origin of food will be presented in the paper. In the future, the study will be continued and addition of parameters, as a sulfur isotope composition in food and in surrounding environment (as a pollutant), will be compared. (author)

  15. Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

    Science.gov (United States)

    Tan, Yongqiang; Luo, Heng; Zhang, Haibin; Zhou, Xiaosong; Peng, Shuming

    2016-03-01

    Lightweight graphene nanoplatelet (GNP)/boron carbide (B4C) composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI) shielding effectiveness (SE) has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B4C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ˜ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high dielectric loss as well as multiple reflections by aligned GNPs inside the composite. The GNP/B4C composite is demonstrated to be promising candidate of high-temperature microwave EMI shielding material.

  16. Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

    Directory of Open Access Journals (Sweden)

    Yongqiang Tan

    2016-03-01

    Full Text Available Lightweight graphene nanoplatelet (GNP/boron carbide (B4C composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI shielding effectiveness (SE has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B4C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ∼ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high dielectric loss as well as multiple reflections by aligned GNPs inside the composite. The GNP/B4C composite is demonstrated to be promising candidate of high-temperature microwave EMI shielding material.

  17. Cubic boron nitride based composites for cutting applications

    Directory of Open Access Journals (Sweden)

    P. Klimczyk

    2011-02-01

    Full Text Available Purpose: The aim of our work was to obtain durable fined-grained cBN-Si3N4 composite with high values of hardness and fracture toughness, which can be successfully used as a cutting tool. Little quantity of the Si3N4 nanopowder fills up the porous between cBN grains thus result in resistance to crack propagation by means so called “crack deflection” mechanism.Design/methodology/approach: Two variants of the cBN-Si3N4 composites („I” – with micropowder cBN and „II” – with mixture of micro- and nanopowdes cBN contained 3% of nanodispersed Si3N4 powder, have been sintered at High Pressure – High Temperature (HPHT conditions. Basic physical-mechanical properties, phase composition and microstructure of sintered materials have been investigated.Findings: The comparison of the mechanical properties of cBN-Si3N4 (I and cBN-Si3N4 (II composites showed that the addition of 10% cBN nanopowder to mixture caused small increase in hardness from 4750 up to 4855 HV10 and decrease in Young’s modulus from 842 to 812 GPa. Fracture toughness of both type of composites is on the same level above 10 MPa∙m1/2.Research limitations/implications: High hardness of cBN-Si3N4 composites present a technical challenge in shaping of them. Commercial application of presented materials, e.g. cutting tools production, needs to develop a high efficient cutting, lapping and grinding techniques.Practical implications: The material obtained could be successfully applied for different cutting applications due to its favourable combination of hardness and fracture toughness.Originality/value: Commercial superhard materials, so called “high content cBN composites”, have usually 10-20 vol% of binding phase, often in the form of Ti or/and Al compounds. In the presented work only 3% of Si3N4 phase was used as a sintering aid. The high content of cBN phase allows to keep Young’s modulus and hardness values close to the theoretical ones for pure PcBN.

  18. The high-strain-rate dynamic response of boron carbide-based composites: The effect of microstructure

    International Nuclear Information System (INIS)

    The dynamic high-strain-rate behavior of boron carbide-based composites with similar phase composition yet different microstructural features, namely, amount of residual silicon, average grain size and morphology of the SiC particles, was investigated as a function of the planar impact strength. The composites consisted of boron carbide preforms (compacted or partly sintered powder) with or without free carbon addition, infiltrated with molten silicon. The dynamic response of the composites depends strongly on the amount of residual silicon, on the average size of the boron carbide grains, and on the morphology of the SiC particles. The preliminary sintering of the preforms exerts no effect on the dynamic properties of the composites. The deformation and failure mechanisms under dynamic loading are discussed.

  19. The molybdenum isotope composition of the modern ocean

    International Nuclear Information System (INIS)

    Natural variations in the isotopic composition of molybdenum (Mo) are showing increasing potential as a tool in geochemistry. Although the ocean is an important reservoir of Mo, data on the isotopic composition of Mo in seawater are scarce. We have recently developed a new method for the precise determination of Mo isotope ratios on the basis of preconcentration using a chelating resin and measurement by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), which allows us to measure every stable Mo isotope (Nakagawa et al., 2008). In this study, 172 seawater samples obtained from 9 stations in the Pacific, Atlantic, and Southern Oceans were analyzed, giving global coverage and the first full depth-profiles. The average isotope composition in δA/95Mo (relative to a Johnson Matthey Mo standard solution) was as follows: δ92/95Mo=-2.54 ±0.16 per mille (2SD), δ94/95Mo=-0.73±0.19 per mille, δ96/95Mo=0.85±0.07 per mille, δ97/95Mo=1.68±0.08 per mille, δ98/95Mo=2.48±0.10 per mille, and δ100/95Mo=4.07±0.18 per mille. The δ values showed an excellent linear correlation with atomic mass of AMo (R2=0.999). Three-isotope plots for the Mo isotopes were fitted with straight lines whose slopes agreed with theoretical values for mass-dependent isotope fractionation. These results demonstrate that Mo isotopes are both uniformly distributed and follow a mass-dependent fractionation law in the modern oxic ocean. In addition, Mo isotopic analysis revealed that δ98/95Mo of the standard used in this study was 0.117±0.009 per mille lighter than the Mo standard that was used by Archer and Vance (2008). A common Mo standard is urgently required for the precise comparison of Mo isotopic compositions measured in different laboratories. On the other hand, our results strongly support the possibility of seawater as an international reference material for Mo isotopic composition. (author)

  20. High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

    Science.gov (United States)

    Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert George (Inventor)

    2015-01-01

    Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

  1. Certification of the uranium hexafluoride reference materials for isotopic composition

    OpenAIRE

    MIALLE SÉBASTIEN; Richter, Stephan; HENNESSY Carmel; TRUYENS Jan; Jakobsson, Ulf; Aregbe, Yetunde

    2014-01-01

    The IRMM-019 to IRMM-029 series of uranium hexafluoride materials is certified for the isotopic composition. After conversion into uranyl nitrate solution, certification and homogeneity measurements were performed by Thermal Ionization Mass Spectrometry. Analyses were performed by Modified Total Evaporation and for some materials the major isotope amount ratio n(235U)/n(238U) was measured using a n(233U)/n(236U) double spike. Measurements were confirmed by UF6 Gas Source Mass Spectrometry. Ma...

  2. Cadmium isotopic composition in the ocean

    International Nuclear Information System (INIS)

    Full text: Recent developments in mass spectrometric techniques are allowing the systematic study of metal isotope fractionation in the environment. Cd isotopes have, as yet, received little attention, notwithstanding the well-documented involvement of Cd in biological cycling and its wide range of isotopic masses, which make it a prime candidate for fractionation. We will present the first data in the ocean. A seawater profile from the North Pacific Ocean shows little yet probably significant variations. The later could result from water mass advection or biological processes or both. We will also present a seawater profile from the Mediterranean (Dyfamed site) and measurements in phytoplankton cultures. In addition we will present measurements carried out in a sewage treatment plant (where high bacterial degradation occurs). If confirmed, Cd isotopic fractionation could have wide-ranging biogeochemical and paleoceanographic applications. In particular, it could lead to the development of a paleoceanographic tracer for bottom water oxygen concentration, a parameter that would provide important new constraints on the marine carbon cycle and deep ocean circulation during glacial periods. (author)

  3. Plutonium isotopic composition by gamma-ray spectroscopy

    International Nuclear Information System (INIS)

    We discuss the general approach, computerized data analysis methods, and results of measurements to determine the isotopic composition of plutonium by gamma-ray spectroscopy. The simple techniques are designed to be applicable to samples of arbitrary size, geometry, chemical and isotopic composition that have attained 241Pu-237U equilibrium. The combination of the gamma spectroscopic measurement of isotopic composition coupled with calorimetric measurement of total sample power is shown to give a totally nondestructive determination of sample Pu mass with a precision of 0.6% for 1000-g samples of PuO2 with 12% 240Pu content. The precision of isotopic measurements depends upon many factors including sample size, sample geometry, and isotopic content. Typical ranges are found to be 238Pu, 239Pu, 0.1 to 0.5%; 240Pu, 2 to 5%; 241Pu, 0.3 to 0.7%; 242Pu (determined by isotopic correlation); and 241Am, 0.2 to 10%

  4. Enhancement of thermal conductive pathway of boron nitride coated polymethylsilsesquioxane composite.

    Science.gov (United States)

    Kim, Gyungbok; Ryu, Seung Han; Lee, Jun-Tae; Seong, Ki-Hun; Lee, Jae Eun; Yoon, Phil-Joong; Kim, Bum-Sung; Hussain, Manwar; Choa, Yong-Ho

    2013-11-01

    We report here in the fabrication of enhanced thermal conductive pathway nanocomposites of boron nitride (BN)-coated polymethylsilsesquioxane (PMSQ) composite beads using isopropyl alcohol (IPA) as a mixing medium. Exfoliated and size-reduced boron nitride particles were successfully coated on the PMSQ beads and explained by surface charge differences. A homogeneous dispersion and coating of BN on the PMSQ beads using IPA medium was confirmed by SEM. Each condition of the composite powder was carried into the stainless still mould and then hot pressed in an electrically heated hot press machine. Three-dimensional percolation networks and conductive pathways created by exfoliated BN were precisely formed in the nanocomposites. The thermal conductivity of nanocomposites was measured by multiplying specific gravity, specific heat, and thermal diffusivity, based upon the laser flash method. Densification of the composite resulted in better thermal properties. For an epoxy reinforced composite with 30 vol% BN and PMSQ, a thermal conductivity of nine times higher than that of pristine PMSQ was observed. PMID:24245317

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

    Science.gov (United States)

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

    2013-01-01

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

  6. Stable isotope composition of human fingernails from Slovakia

    International Nuclear Information System (INIS)

    Stable isotope composition of human fingernails has proven to be useful for documenting human dietary information and geographical patterns in archeological, forensic, anthropological and biological studies. Therefore, it is of interest to detect all factors influencing the stable isotopic composition in the certain regions in the world. Carbon and nitrogen isotope data of human fingernail keratin from 52 individuals from Slovakia were reported in this study. The online combustion and continuous flow isotope-ratio mass spectrometer Delta V Advantage was used for δ13C and δ15N analysis of fingernail keratin samples from 24 vegetarian and 28 omnivorous individuals. A group of people with frequent meat consumption showed enrichment in 13C and 15N isotopes in fingernails. A similar trend was observed with increasing seafood in an individual's diet. Moreover a significant difference was revealed between smokers and nonsmokers for both δ13C and δ15N values. These data were compared to previously published δ13C and δ15N fingernail values from across the globe. This study brings new information on the stable isotope signature of individuals from Slovakia and characterizes the Central European region for the first time. The stable isotope composition of fingernails is influenced by the frequency of meat and seafood consumption as well as smoking. - Highlights: • This study deals with stable isotope analyses of fingernails from Slovak volunteers. • δ13C and δ15N values of vegetarian and omnivore fingernails were compared. • Influence of sex, diet and smoking was studied

  7. Stable isotope composition of human fingernails from Slovakia

    Energy Technology Data Exchange (ETDEWEB)

    Grolmusová, Zuzana, E-mail: zuzana.grolmusova@geology.sk [Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina F2, 842 48 Bratislava (Slovakia); State Geological Institute of Dionýz Štúr, Laboratory of Isotope Geology, Mlynská dolina 1, 817 04 Bratislava (Slovakia); Rapčanová, Anna [Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina F2, 842 48 Bratislava (Slovakia); Michalko, Juraj; Čech, Peter [State Geological Institute of Dionýz Štúr, Laboratory of Isotope Geology, Mlynská dolina 1, 817 04 Bratislava (Slovakia); Veis, Pavel [Comenius University in Bratislava, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynská dolina F2, 842 48 Bratislava (Slovakia); State Geological Institute of Dionýz Štúr, Laboratory of Isotope Geology, Mlynská dolina 1, 817 04 Bratislava (Slovakia)

    2014-10-15

    Stable isotope composition of human fingernails has proven to be useful for documenting human dietary information and geographical patterns in archeological, forensic, anthropological and biological studies. Therefore, it is of interest to detect all factors influencing the stable isotopic composition in the certain regions in the world. Carbon and nitrogen isotope data of human fingernail keratin from 52 individuals from Slovakia were reported in this study. The online combustion and continuous flow isotope-ratio mass spectrometer Delta V Advantage was used for δ{sup 13}C and δ{sup 15}N analysis of fingernail keratin samples from 24 vegetarian and 28 omnivorous individuals. A group of people with frequent meat consumption showed enrichment in {sup 13}C and {sup 15}N isotopes in fingernails. A similar trend was observed with increasing seafood in an individual's diet. Moreover a significant difference was revealed between smokers and nonsmokers for both δ{sup 13}C and δ{sup 15}N values. These data were compared to previously published δ{sup 13}C and δ{sup 15}N fingernail values from across the globe. This study brings new information on the stable isotope signature of individuals from Slovakia and characterizes the Central European region for the first time. The stable isotope composition of fingernails is influenced by the frequency of meat and seafood consumption as well as smoking. - Highlights: • This study deals with stable isotope analyses of fingernails from Slovak volunteers. • δ{sup 13}C and δ{sup 15}N values of vegetarian and omnivore fingernails were compared. • Influence of sex, diet and smoking was studied.

  8. Surface functionalization of hexagonal boron nitride and its effect on the structure and performance of composites

    Science.gov (United States)

    Jin, Wenqin; Zhang, Wei; Gao, Yuwen; Liang, Guozheng; Gu, Aijuan; Yuan, Li

    2013-04-01

    A new organized hexagonal boron nitride (OhBN) with significantly increased amount of amine groups was synthesized, and characterized by Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric (TG) analysis, UV-vis Transmittance Spectra, Transmission Electron Microscope (TEM) and the potentiometric titration. The content of amine groups for OhBN is about 5 times of that for original hexagonal boron nitride (hBN). Based on the preparation of OhBN, new composites consisting of OhBN and bismaleimide (BD) resin were developed, which show greatly improved integrated performance (including dynamic mechanical, dielectric and thermal properties) compared with BD resin and the hBN/BD composites. In the case of the OhBN/BD composite with 15 wt% OhBN, its storage modulus, dielectric loss, thermal conductivity and coefficient of thermal expansion are about 1.2, 0.56, 1.11 and 0.92 times of the corresponding values of hBN/BD composite, respectively; moreover, the glass transition temperature of the former is 15 °C higher than that of the latter. These interesting results suggest that the integrated performance of the composites is closely related to the surface nature of the fillers because the change in the surface nature not only varies the chemical structure, free volume and crosslinking density of the composite, but also determines the interfacial nature between inorganic fillers and the resin matrix. This investigation demonstrates that the method proposed herein provides a new approach to prepare organized inorganic fillers as well as corresponding composites with controlled structure and expected performances for cutting-edge industries.

  9. Thermo-physical properties of boron carbide reinforced copper composites fabricated by electroless deposition process

    International Nuclear Information System (INIS)

    Highlights: ► B4C/Cu composites were prepared by spark plasma sintering (SPS). ► Electroless deposition of copper on the B4C particles surface was introduced. ► The salt-based colloid palladium was used in the electroless deposition. ► The uniform surface copper coating over B4C particles surface was formed. - Abstract: B4C/Cu composites with enhanced thermal–physical properties were prepared by spark plasma sintering (SPS) after the pretreatment of electroless deposition of copper on the boron carbide particles surface. The boron carbide particles underwent acid treatment, salt-based colloid palladium activation process, and electroless copper deposition on their surface respectively. Samples were analyzed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometer in terms of microstructure and chemical composition. The microstructure investigated by SEM shows that high quality copper deposits are obtained on the B4C particles surface accompanied by the good interfacial contact between the copper and the pretreated B4C powder in the sintered sample. It was found that the thermal conductivity decreased as B4C volume fraction increased in copper matrix, while the coefficient of thermal expansion increased

  10. Boron and chlorine isotopic signatures of seawater in the Central Indian Ridge

    Digital Repository Service at National Institute of Oceanography (India)

    Shirodkar, P.V.; Xiao, Y.K.; Hai, L.

    d11B values of seawater within the thermocline in the upper 300 m layer gave an average d11B value of 38.14‰ whereas below the thermocline the average d11B value was 39.3‰. The release of boron from remineralized organic matter and other unknown...

  11. Measurement of Plutonium Isotopic Composition - MGA

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Duc Ta [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-21

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

  12. Certification of uranium hexafluoride reference materials for isotopic composition

    International Nuclear Information System (INIS)

    The IRMM-019 to IRMM-029 series of uranium hexafluoride materials is certified for the isotopic composition. After conversion into uranyl nitrate solution, certification and homogeneity measurements were performed by thermal ionization mass spectrometry. Analyses were performed by Modified Total Evaporation and for some materials the major isotope amount ratio n(235U)/n(238U) was measured using a n(233U)/n(236U) double spike. Measurements were confirmed by UF6 gas source mass spectrometry. Major isotope amount ratios were certified with relative expanded uncertainties (k = 2) of 0.015-0.030 % and the minor isotope amount ratios n(234U)/n(238U) and n(236U)/n(238U) were certified with relative expanded uncertainties of 0.02-3 %. (author)

  13. Stable isotope composition and volume of Early Archaean oceans

    DEFF Research Database (Denmark)

    Pope, Emily Catherine; Rosing, Minik Thorleif; Bird, Dennis K.

    low-δ18O values of Precambrian sedimentary cherts and carbonates are not a consequence of isotope variability of seawater or extreme ocean temperatures [3,4], but rather are due to isotopic exchange with shallow hydrothermal fluids on the ocean floor or during diagenesis [5]. [1] Lécuyer et al. (1998......Oxygen and hydrogen isotope compositions of seawater are controlled by volatile fluxes between mantle, lithospheric (oceanic and continental crust) and atmospheric reservoirs. Throughout geologic time oxygen was likely conserved within these Earth system reservoirs, but hydrogen was not, as it can...... escape to space [1]. Hydrogen isotope ratios of serpentinites from the ~3.8Ga Isua Supracrustal Belt in West Greenland are between -53 and -99‰; the highest values are in antigorite ± lizardite serpentinites from a low-strain lithologic domain where hydrothermal reaction of Archaean seawater with oceanic...

  14. Pressure-dependent isotopic composition of iron alloys.

    Science.gov (United States)

    Shahar, A; Schauble, E A; Caracas, R; Gleason, A E; Reagan, M M; Xiao, Y; Shu, J; Mao, W

    2016-04-29

    Our current understanding of Earth's core formation is limited by the fact that this profound event is far removed from us physically and temporally. The composition of the iron metal in the core was a result of the conditions of its formation, which has important implications for our planet's geochemical evolution and physical history. We present experimental and theoretical evidence for the effect of pressure on iron isotopic composition, which we found to vary according to the alloy tested (FeO, FeH(x), or Fe3C versus pure Fe). These results suggest that hydrogen or carbon is not the major light-element component in the core. The pressure dependence of iron isotopic composition provides an independent constraint on Earth's core composition. PMID:27126042

  15. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    The objective of this study is to determine isotopic characteristics of precipitation, the climatic and geographical conditions affecting isotopic composition in order to obtain the input function of groundwater to evaluate the water resources.13 meteoric stations were selected in Syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the Syrian meteoric line (SMWL) was estimated with a slope of 6.62 and that of both Syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude of 18O was about 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14 % and -0.84% /100m respectively). The spatial distribution of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern Mediterranean climate type over this region.(author)

  16. Electron screening effects in (p,α) reactions induced on boron isotopes studied via the Trojan Horse Method

    Science.gov (United States)

    Lamia, L.; Spitaleri, C.; Carlin, N.; Cherubini, S.; Gameiro Munhoz, M.; Gimenez Del Santo, M.; Gulino, M.; Kiss, G. G.; Kroha, V.; Kubono, S.; La Cognata, M.; Li, C.; Mukhamedzhanov, A.; Pizzone, R. G.; Puglia, S. M. R.; Wen, Qungang; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Somorjai, E.; Souza, F. A.; Szanto de Toledo, A.; Tumino, A.; Wakabayashi, Y.; Yamaguchi, H.

    2013-04-01

    The Trojan Horse Method is a powerful indirect technique allowing one to measure the bare nucleus S(E)-factor and the electron screening potential for astrophysically relevant reactions without the needs of extrapolations. The case of the (p,α) reactions induced on the two boron isotopes 10,11B is here discussed in view of the recent Trojan Horse (TH) applications to the quasi-free 10,11B+2H reactions. The comparison between the TH and the low-energy direct data allowed us to determine the electron screening potential for the 11B(p,α) reaction, while preliminary results on the 10B(p,α) reaction have been extracted.

  17. OXYGEN ISOTOPIC COMPOSITION OF THE SUN AND MEAN OXYGEN ISOTOPIC COMPOSITION OF THE PROTOSOLAR SILICATE DUST: EVIDENCE FROM REFRACTORY INCLUSIONS

    International Nuclear Information System (INIS)

    Preliminary analysis of the oxygen isotopic composition of the solar wind recorded by the Genesis spacecraft suggests that the Sun is 16O-rich compared to most chondrules, fine-grained chondrite matrices, and bulk compositions of chondrites, achondrites, and terrestrial planets (Δ17O = -26.5 per mille ± 5.6 per mille and -33 per mille ± 8 per mille (2σ) versus Δ17O ∼ ±5 per mille ). The inferred 16O-rich composition of the Sun is similar or slightly lighter than the 16O-rich compositions of amoeboid olivine aggregates and typical calcium-aluminum-rich inclusions (CAIs) from primitive (unmetamorphosed) chondrites (Δ17O = -24 per mille ± 2 per mille ), which are believed to have condensed from and been melted in a gas of approximately solar composition (dust/gas ratio ∼ 0.01 by weight) within the first 0.1 Myr of the solar system formation. Based on solar system abundances, 26% of the solar system oxygen must be initially contained in dust and 74% in gas. Because solar oxygen is dominated by the gas component, these observations suggest that oxygen isotopic composition of the solar nebula gas was initially 16O-rich. Due to significant thermal processing of the protosolar molecular cloud silicate dust (primordial dust) in the solar nebula and its possible isotope exchange with the isotopically evolved solar nebula gas, the mean oxygen isotopic composition of the primordial dust is not known. In CO self-shielding models, it is assumed that primordial dust and solar nebula gas had initially identical, 16O-rich compositions, similar to that of the Sun (Δ17O ∼ -25 per mille or -35 per mille ), and solids subsequently evolved toward the terrestrial value (Δ17O = 0). However, there is no clear evidence that the oxygen isotopic compositions of the solar system solids evolved in the direction of increasing Δ17O with time and no 16O-rich primordial dust have yet been discovered. Here we argue that the assumption of the CO self-shielding models that primordial

  18. CALCIUM ISOTOPE COMPOSITION OF METEORITES, EARTH, AND MARS

    International Nuclear Information System (INIS)

    The relative abundances of calcium isotopes in the mass range 40-44 were measured in primitive and differentiated meteorites and igneous rocks from Earth and Mars in search of non-mass-dependent variations that could provide clues about early solar system processes. Most bulk samples of planetary materials have calcium isotopic compositions identical with Earth's within the current resolution of about 0.01% in 40Ca/44Ca. Possible exceptions include carbonaceous chondrites, some ordinary chondrites, and two samples of calcium-aluminum-rich inclusions, which have small excesses of 40Ca. The samples with 40Ca excesses are also known to have 50Ti and 135Ba excesses and 142Nd and 144Sm deficits. Collectively these data from refractory elements suggest that the planetary embryos represented by chondrites preserve isotopic heterogeneity that reflects different nucleosynthetic sources. No late admixture from a single nucleosynthetic source can explain all observations. The results are most compatible with variable proportions of material derived from Type II supernovae. The initial calcium isotope compositions of Earth and Mars are indistinguishable and similar to the 40Ca abundance found in some chondrites and all differentiated meteorites studied. It appears that isotopic heterogeneity in calcium was still present at the completion of disk formation but was homogenized during planetary accretion.

  19. Variations in isotopic composition of a reactor at its shutdown

    International Nuclear Information System (INIS)

    The effects of variation in reactor output shortly before shutdown on the evolution of isotopic composition following it were analyzed by the NICCA code for calculating the activity of fission nuclides normally accumulated in fuel rods. In the SPEEDI system, the isotopic composition of noble gas or iodine is employed to evaluated the release rate of each nuclide as source terms using a total amount of these nuclides or measured values with stack monitors etc.. The inventory of noble gas or iodine markedly depends on the operational history of a reactor shortly before its shutdown, since the half-lives of many nuclides among noble gas or iodine are less than a few days. When the shutdown should occur immediately after the continuation of rated output, therefore, the isotopic fraction of nuclides with longer half-lives was underestimated and that with shorter ones was overestimated in comparison with the results obtained considering the variation in reactor output shortly before the shutdown. From the standpoints of dose evaluation, it was found that the external exposure to total noble isotopes was estimated to be at most approximately 20 % higher 10 hour immediately after the shutdown, but the thyroidal exposure to total iodine isotopes was underestimated to be 30 % at maximum. (author)

  20. Carbon and hydrogen isotopic compositions of New Zealand geothermal gases

    International Nuclear Information System (INIS)

    Carbon and hydrogen isotopic compositions are reported for methane, hydrogen and carbon dioxide from four New Zealand geothermal areas; Ngawha, Wairakei, Broadlands and Tikitere. Carbon-13 contents are between -24.4 and -29.5 per mille (PDB) for methane, and between -3.2 and -9.1 per mille for carbon dioxide. Deuterium contents are between -142 and -197 per mille (SMOW) for methane and between -310 and -600 per mille for hydrogen. The different areas have different isotopic compositions with some general relationships to reservoir temperature. The isotopic exchange of hydrogen with water indicates acceptable reservoir temperatures of 180 to 260 deg C from most spring samples but often higher than measured temperatures in well samples. Indicated temperatures assuming 13C equilibria between CH4 and CO2 are 100 to 200 deg C higher than measured maxima. This difference may be due to partial isotopic equilibration or may reflect the origin of the methane. Present evidence cannot identify whether the methane is primordial, or from decomposing sediments or from reduction of magmatic CO2. The isotopic equilibria between CH4, CO2, H2 and H2O are reviewed and a new semiempirical temperature scale proposed for deuterium exchange between methane and water. (author)

  1. Effect of boron addition on microstructure and mechanical properties of TiC/Ti6Al4V composites

    International Nuclear Information System (INIS)

    Highlights: ► TiC/Ti6Al4V composites were fabricated by using the in situ melting–casting process. ► The microstructure and mechanical properties of the composites were investigated. ► It showed the addition of boron refined the TiC dendrite and influenced the mechanical properties. ► The reasons of refinement of TiC dendrite and change of wear property were explained. -- Abstract: TiC/Ti6Al4V composites with different boron additions were successfully fabricated, and the effects of the boron content on the microstructure, mechanical properties of composites were investigated. The results show that the dendritic TiC in the composites is remarkably refined when the boron content is less than 0.06 wt.%. The average primary axial length of TiC dendrite is decreased from 150 μm to 50 μm according to the increasing of the boron content from 0.01 wt.% to 0.06 wt.%. And TiC dendrite gradually changes from the coarse dendrite to the fine dendrite or granular, but the abrasive property is obviously reduced with the increase of boron content. On the other hand, when the boron content further increases from 0.1 wt.% to 0.6 wt.%, the dendritic TiC can not be refined obviously, the fiber-shape TiB begins to appear and the abrasive property of composites is improved. The compressive strength and hardness (HRC) of composites are obviously increased in the whole addition range. The refinement mechanism of boron is attributed to the combined effects of the increase in nucleation rate at the constitutionally supercooled zone in front of the solid–liquid interface and the reduction in growth rate of TiC. The improvement of its abrasive property is mainly attributed to the existence of large size TiC and fiber-shape TiB during the abrasion.

  2. Role of boron addition on the consolidation and properties of steel composites prepared by SPS

    Indian Academy of Sciences (India)

    Iwona Sulima

    2015-12-01

    Composites reinforced with 8 vol% TiB2 were subjected to the consolidation process by spark plasma sintering (SPS). The results show that the addition of boron (1 vol%) introduced to the steel matrix has a significant effect on the composite microstructure, as well as physical, mechanical and tribological properties. The full density of 97–99% was obtained in the composites sintered at a temperature of 1100°C. The steel–8% TiB2–1% B composite sintered at 1100°C for 30 min was characterized by the highest microhardness (465 HV0.3) and Young's modulus (229 GPa), combined with the best compressive strength (1150 MPa) and abrasive wear resistance ( = 0.25 and (disc) = 207.78 × 10−6 mm3 N−1m−1). The microstructure and chemical composition were examined by scanning electron microscopy and transmission electron microscopy. The examinations have revealed the presence of numerous fine complex borides in the microstructure of the steel–8% TiB2 and steel–8% TiB2–1% B composites.

  3. Chemical and isotopic composition of precipitations in Syria

    International Nuclear Information System (INIS)

    13 meteoric stations were selected in syria for cumulative monthly rainfall sampling during two hydrological cycles; 1991-1992 and 1992-1993. The chemical and isotopic compositions of monthly precipitation were studied. The winter and spring rainfall isotopic characteristics were determined, in addition to the syrian or local meteoric line (SMWL) was estimated with a slope of 6.63 and that of both syria and Jordan of 6.73. The effect of climatic factors as temperature and relative air humidity on oxygen-18, deuterium and d-excess were studied and it was found that the relationship between temperature and oxygen-18 and deuterium is a positive linear correlation; however, it is a negative correlation with d-excess. The mean seasonal variation amplitude was determined by 6%, and the amount effect on isotopic content of precipitation was studied. The geographic factors and its affect on isotopic contents of precipitation such as altitude were considered, furthermore, the isotopic gradient with altitude was determined for both oxygen-18 and deuterium (-0.14% and - 0.84%/100 m elevation respectively). The spatial variability of oxygen-18, deuterium, tritium and d-excess indicted the effect of mountain chains and gaps between mountains on the isotopic content of precipitation, the continental effect on tritium build-up by about 33% per 100 Km from the coast. The increase of d-excess values towards the south west proves the eastern mediterranean climate type over this region. (author)

  4. Friction and Wear Performance of Boron Doped, Undoped Microcrystalline and Fine Grained Composite Diamond Films

    Institute of Scientific and Technical Information of China (English)

    WANG Xinchang; WANG Liang; SHEN Bin; SUN Fanghong

    2015-01-01

    Chemical vapor deposition (CVD) diamond films have attracted more attentions due to their excellent mechanical properties. Whereas as-fabricated traditional diamond films in the previous studies don’t have enough adhesion or surface smoothness, which seriously impact their friction and wear performance, and thus limit their applications under extremely harsh conditions. A boron doped, undoped microcrystalline and fine grained composite diamond (BD-UM-FGCD) film is fabricated by a three-step method adopting hot filament CVD (HFCVD) method in the present study, presenting outstanding comprehensive performance, including the good adhesion between the substrate and the underlying boron doped diamond (BDD) layer, the extremely high hardness of the middle undoped microcrystalline diamond (UMCD) layer, as well as the low surface roughness and favorable polished convenience of the surface fine grained diamond (FGD) layer. The friction and wear behavior of this composite film sliding against low-carbon steel and silicon nitride balls are studied on a ball-on-plate rotational friction tester. Besides, its wear rate is further evaluated under a severer condition using an inner-hole polishing apparatus, with low-carbon steel wire as the counterpart. The test results show that the BD-UM-FGCD film performs very small friction coefficient and great friction behavior owing to its high surface smoothness, and meanwhile it also has excellent wear resistance because of the relatively high hardness of the surface FGD film and the extremely high hardness of the middle UMCD film. Moreover, under the industrial conditions for producing low-carbon steel wires, this composite film can sufficiently prolong the working lifetime of the drawing dies and improve their application effects. This research develops a novel composite diamond films owning great comprehensive properties, which have great potentials as protecting coatings on working surfaces of the wear-resistant and anti

  5. Effects of amphiphilic agent on thermal conductivity of boron nitride/poly(vinyl butyral) composites

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Hong Jun [Department of Materials Engineering, Kyonggi University, Suwon (Korea, Republic of); Cha, Sang-Ho [Department of Chemical Engineering, Kyonggi University, Suwon (Korea, Republic of); Lee, Woo Sung [Electronic Materials and Device Research Center, Korea Electronics Technology Institute, Seongnam (Korea, Republic of); Kim, Eung Soo, E-mail: eskim@kyonggi.ac.kr [Department of Materials Engineering, Kyonggi University, Suwon (Korea, Republic of)

    2014-09-10

    Highlights: • The platelet BN particles were oriented in poly(vinyl butyral) (PVB) matrix by tape-casting process. • The degree of BN orientation was estimated from XRD patterns of BN/PVB composites. • Surface treatment of BN with amphiphilic agent was confirmed by FT-IR and elemental analysis. • The BN/PVB composites with in-plane oriented 8-μm-sized BN particles showed a higher thermal conductivity than the other composites. - Abstract: Dependence of thermal conductivity of boron nitride (BN)/poly(vinyl butyral) (PVB) composites on the orientation and particle size of BN with an amphiphilic agent was investigated. The platelet BN particles were oriented in the polymer matrix by physical processes such as tape-casting process. A comparison of the thermal conductivity of the specimens with that of pristine BN showed that the BN/PVB composite treated with amphiphilic agents such as C{sub 14}H{sub 6}O{sub 8} and C{sub 27}H{sub 27}N{sub 3}O{sub 2} showed a higher thermal conductivity than the PVB composite with pristine BN. It was also found that the thermal conductivity of the C{sub 14}H{sub 6}O{sub 8}-treated BN/PVB composite was higher than that of the C{sub 27}H{sub 27}N{sub 3}O{sub 2}-treated composite due to the good dispersion and interfacial adhesion with C{sub 14}H{sub 6}O{sub 8}. Also, the thermal conductivity of the composite with an in-plane orientation of 8-μm-sized BN was higher than that of the composites with different particles sizes because of the improvement in the high degree of orientation.

  6. The abundance and isotopic composition of water in eucrites

    Science.gov (United States)

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

    2016-06-01

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

  7. The abundance and isotopic composition of water in eucrites

    Science.gov (United States)

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

    2016-05-01

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

  8. Oxygen isotope compositions of eclogites in Rongcheng,Eastern China

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Collected from the Rongcheng region, Shandong Province, the three types of eclogites suffering the UHP (i.e. ultra-high pressure) metamorphism have obviously different oxygen isotope compositions. The eclogites occurring in regional orthogneisses and ultramafic rocks have the oxygen isotope compositions of normal eclogites in the world, but the eclogites existing in marbles are extremelyenriched in 18O. By applying oxygen isotope geothermometry, for the all types of eclogites, the temperature estimates of quartz- garnet pair, in principle, indicate the formation temperatures of eclogites, so that the peak-metamorphic temperatures are estimated to be averagely little higher than 800℃, which are consistent with the estimates by using other geothermometers according to cation partitioning between coexisting phases. The ??18O values of eclogitic inclusions hosted in marbles from Yangguantun, Rongcheng region, are far higher than the values of eclogites (including eclogitic inclusions in marbles) from the Dabieshan and other places of the Sulu. The oxygen isotope compositions of various minerals indicate that the formation temperatures of eclogites from the Rongcheng region,in general, are higher than that from the Dabieshan and the southwestern part of the Sulu, but the dispersive temperatures estimated by different mineral pairsprobably reflect that the UHP eclogites from the Rongcheng region generally suffered overprinted metamorphisms during the exhumation.

  9. The Chlorine Isotopic Composition Of Lunar UrKREEP

    Science.gov (United States)

    Barnes, J. J.; Tartese, R.; Anand, M.; McCubbin, F. M.; Neal, C. R.; Franchi, I. A.

    2016-01-01

    Since the long standing paradigm of an anhydrous Moon was challenged there has been a renewed focus on investigating volatiles in a variety of lunar samples. Numerous studies have examined the abundances and isotopic compositions of volatiles in lunar apatite, Ca5(PO4)3(F,Cl,OH). In particular, apatite has been used as a tool for assessing the sources of H2O in the lunar interior. However, current models for the Moon's formation have yet to fully account for its thermal evolution in the presence of H2O and other volatiles. For ex-ample, in the context of the lunar magma ocean (LMO) model, it is anticipated that chlorine (and other volatiles) should have been concentrated in the late-stage LMO residual melts (i.e., the dregs enriched in incompatible elements such as K, REEs (Rare Earth Elements), and P, collectively called KREEP, and in its primitive form - urKREEP, given its incompatibility in mafic minerals like olivine and pyroxene, which were the dominant phases that crystallized early in the cumulate pile of the LMO. When compared to chondritic meteorites and terrestrial rocks, lunar samples have exotic chlorine isotope compositions, which are difficult to explain in light of the abundance and isotopic composition of other volatile species, especially H, and the current estimates for chlorine and H2O in the bulk silicate Moon (BSM). In order to better understand the processes involved in giving rise to the heavy chlorine isotope compositions of lunar samples, we have performed a comprehensive in situ high precision study of chlorine isotopes in lunar apatite from a suite of Apollo samples covering a range of geochemical characteristics and petrologic types.

  10. The Li isotope composition of modern biogenic carbonates

    Science.gov (United States)

    Dellinger, M.; West, A. J.; Adkins, J. F.; Paris, G.; Eagle, R.; Freitas, P. S.; Bagard, M. L.; Ries, J. B.; Corsetti, F. A.; Pogge von Strandmann, P.; Ullmann, C. V.

    2015-12-01

    The lithium stable isotope composition (δ7Li) of sedimentary carbonates has great potential to unravel weathering rates and intensity in the past, with implications for understanding the carbon cycle over geologic time. However, so far very little is known about the potential influence of fractionation of the stable Li isotope composition of biogenic carbonates. Here, we investigate the δ7Li of various organisms (particularly mollusks, echinoderms and brachiopods) abundant in the Phanerozoic record, in order to understand which geologic archives might provide the best targets for reconstructing past seawater composition. The range of measured samples includes (i) modern calcite and aragonite shells from variable natural environments, (ii) shells from organisms grown under controlled conditions (temperature, salinity, pCO2), and (iii) fossil shells from a range of species collected from Miocene deposits. When possible, both the inner and outer layers of bivalves were micro-sampled to assess the intra-shell heterogeneity. For calcitic shells, the measured δ7Li of bivalve species range from +32 to +41‰ and is systematically enriched in the heavy isotope relative to seawater (31 ‰) and to inorganic calcite, which is characterized by Δ7Licalcite-seawater = -2 to -5‰ [1]. The Li isotope composition of aragonitic bivalves, ranging from +16 to +22‰, is slightly fractionated to both high and low δ7Li relative to inorganic aragonite. The largest intra-shell Li isotope variability is observed for mixed calcite-aragonite shells (more than 20‰) whereas in single mineralogy shells, intra-shell δ7Li variability is generally less than 3‰. Overall, these results suggest a strong influence of vital effects on Li isotopes during bio-calcification of bivalve shells. On the contrary, measured brachiopods systematically exhibit fractionation that is very similar to inorganic calcite, with a mean δ7Li of 27.0±1.5‰, suggesting that brachiopods may provide good

  11. Probing the Isotopic Composition of Surface Waters Across Isotopic Extremes of Cryogenian Carbonates

    Science.gov (United States)

    Bosak, T.; Matys, E. D.; Bird, L. R.; Macdonald, F. A.; Freeman, K. H.

    2012-12-01

    Neoproterozoic carbonate strata record unusually large and positive carbon isotope values (δ13Ccarb from 4 to 10 per mil), and stratigraphically extensive large negative carbon isotope excursions (δ13Ccarb red algae, respectively, they can be used as tracers of organic matter production in surface waters. Fossil tests were extracted by acid maceration, cleaned and analyzed morphologically and microscopically. Their carbon isotopic composition was measured using a nano-scaled elemental analyzer inlet (nano-EA-IRMS), with ±1 per mil analytical precision. To date, we analyzed 12 samples of 100-150 organic tests, representing 3 different fossiliferous parts of the Tayshir anomaly (δ13Ccarb +5 per mil), respectively. More samples, including those of fossil algae and tests from the carbonate strata overlying the Tayshir anomaly, are currently being analyzed. Initial data reveal a rather constant isotopic composition of organic carbon in fossil tests (δ13Cfossil), with values of -23 ±1 per mil both within 13C-enriched and 13C-depleted carbonates. The isotopic difference between δ13Cfossil and 13C-enriched carbonates is 28 to 30 per mil, suggesting maximal isotopic fractionation by primary producers, and little environmental (or diagenetic) processing of primary photosynthetic carbon. The carbonates of the Tayshir anomaly preserve two organic materials: matrix or bulk carbon characterized by a δ13Corg that covaries with δ13Ccarb, and a small, but morphologically diagnostic component whose δ13Cfossil values do not covary with δ13Ccarb. The stratigraphic thickness (~ 50 m) and isotopic heterogeneity of the organic matter within the Tayshir anomaly (~ 50 m) suggest a prolonged and large contribution of organic carbon remineralization.

  12. Application of flame spraying coatings of neutron-absorbing boron-polymer composite powder for spent nuclear fuel container

    International Nuclear Information System (INIS)

    The traditional shielding method was mostly to use a thicker shielding of lead plates, and cast reinforced concrete, etc., mainly by reducing the neutron speed and preventing the passage of neutrons. However, the problem of making or machining the thick protective layers cannot meet the development needs of the security of the nuclear power industry. Currently, most widely used nuclear protective materials are polyethylene plastic plates adding boron carbide, because of polyethylene containing a relatively high content of hydrogen atoms that is an effective neutron moderator by virtue of its scattering power, and boron carbide that is also a good thermal neutron absorber by means of huge thermal neutron absorbing cross section. In this regard, in the present work, polymer flame spraying coatings of neutron-absorbing boron containing polymer composite powder is developed for application in the field of spent nuclear fuel. Changes in the microstructure of the coating layer are discussed with respect to the content of boron carbide and the thickness of the coating layer in view of the neutron absorbing efficiency. In this work, polymer flame spraying coatings of neutron-absorbing boron containing polymer composite powder was developed for application in the field of spent nuclear fuel. From the observation of coating layer, B4C particles were distributed uniformly in the polymer matrix and the LDPE-B4C composite coating layer was joined well with Al substrate without any detachment. The thermal neutron absorbing property is enhanced with an increase in the coating thickness. A flame spraying coating method of boron-containing polymer composite powder is very effective way for the application in a spent nuclear fuel facility

  13. Do foraminifera accurately record seawater neodymium isotope composition?

    Science.gov (United States)

    Scrivner, Adam; Skinner, Luke; Vance, Derek

    2010-05-01

    Palaeoclimate studies involving the reconstruction of past Atlantic meridional overturning circulation increasingly employ isotopes of neodymium (Nd), measured on a variety of sample media (Frank, 2002). In the open ocean, Nd isotopes are a conservative tracer of water mass mixing and are unaffected by biological and low-temperature fractionation processes (Piepgras and Wasserburg, 1987; Lacan and Jeandel, 2005). For decades, benthic foraminifera have been widely utilised in stable isotope and geochemical studies, but have only recently begun to be exploited as a widely distributed, high-resolution Nd isotope archive (Klevenz et al., 2008), potentially circumventing the difficulties associated with other methods used to recover past deep-water Nd isotopes (Klevenz et al., 2008; Rutberg et al., 2000; Tachikawa et al., 2004). Thus far, a single pilot study (Klevenz et al., 2008) has indicated that core-top sedimentary benthic foraminifera record a Nd isotope composition in agreement with the nearest available bottom seawater data, and has suggested that this archive is potentially useful on both millennial and million-year timescales. Here we present seawater and proximal core-top foraminifer Nd isotope data for samples recovered during the 2008 "RETRO" cruise of the Marion Dufresne. The foraminifer samples comprise a depth-transect spanning 3000m of the water column in the Angola Basin and permit a direct comparison between high-resolution water column and core-top foraminiferal Nd isotope data. We use these data to assess the reliability of both planktonic and benthic foraminifera as recorders of water column neodymium isotope composition. Frank, M., 2002. Radiogenic isotopes: Tracers of past ocean circulation and erosional input, Rev. Geophys., 40 (1), 1001, doi:10.1029/2000RG000094. Klevenz, V., Vance, D., Schmidt, D.N., and Mezger, K., 2008. Neodymium isotopes in benthic foraminifera: Core-top systematics and a down-core record from the Neogene south Atlantic

  14. Co-variation of Boron Concentrations and Isotope Ratios in Glasses From the Laki- Grimsvotn Fissure Eruption of 1783-1784

    Science.gov (United States)

    Brounce, M.; Feineman, M. D.; Gurenko, A.; Lafemina, P.

    2008-12-01

    The Laki-Grimsvotn fissure, located in the Eastern Volcanic Zone in southeast Iceland, erupted in 1783-1784 producing over 15 km3 of basaltic lava and associated aerosols. We have collected proximal tephra samples from the fissure, north and south of Laki (hyaloclastite mountain). Trace element concentrations and boron isotope analyses were performed on matrix glasses and plagioclase-hosted melt inclusions from various eruptive phases from this eruption using SIMS (Cameca IMS 3F and 1280) at the Woods Hole Oceanographic Institution. Preliminary data from SIMS boron isotope analyses shows variation in δ11B from -5 to -19‰ (2σ10‰fractionation observed in the Laki melt inclusions. Isotopically light boron may also be introduced into the system by shallow-level assimilation of preexisting altered hyaloclastite material prior to eruption, as has been suggested by Bindeman et al. (2008) on the basis of oxygen isotope data. R. Hervig et al. (2002), Am. Min. 87, 769-774 I. Bindeman et al. (2008), Geochim. Cosmochim. Acta, 72, 4397-4420

  15. Thermal diffusivity of hexagonal boron nitride composites based on cross-linked liquid crystalline polyimides.

    Science.gov (United States)

    Shoji, Yu; Higashihara, Tomoya; Tokita, Masatoshi; Morikawa, Junko; Watanabe, Junji; Ueda, Mitsuru

    2013-04-24

    Hexagonal boron nitride (h-BN) composites with the oriented cross-linked liquid crystalline (LC) polyimide have been developed as high thermally conductive materials. Well-dispersed h-BN composite films were obtained, as observed by scanning electron microscopy. The morphology of the composite films was further investigated in detail by the wide-angle X-ray diffraction. The obtained composite films based on the cross-linked LC polyimide showed that the polymer chains vertically aligned in the direction parallel to the films, while those based on the amorphous polyimide showed an isotropic nature. Moreover, the alignment of the cross-linked LC polyimides was maintained, even after increasing the volume fraction of h-BN. This alignment plays an important role in the effective phonon conduction between h-BN and the matrices. Indeed, the thermal diffusivity in the thickness direction of the composite films based on the LC polyimide measured by a temperature wave analysis method was increased to 0.679 mm(2) s(-1) at a 30 vol % h-BN loading, which was higher than that based on the amorphous polyimide. PMID:23506319

  16. The chromium isotope composition of reducing and oxic marine sediments

    Science.gov (United States)

    Gueguen, Bleuenn; Reinhard, Christopher T.; Algeo, Thomas J.; Peterson, Larry C.; Nielsen, Sune G.; Wang, Xiangli; Rowe, Harry; Planavsky, Noah J.

    2016-07-01

    The chromium (Cr) isotope composition of marine sediments has the potential to provide new insights into the evolution of Earth-surface redox conditions. There are significant but poorly constrained isotope fractionations associated with oxidative subaerial weathering and riverine transport, the major source of seawater Cr, and with partial Cr reduction during burial in marine sediments, the major sink for seawater Cr. A more comprehensive understanding of these processes is needed to establish global Cr isotope mass balance and to gauge the utility of Cr isotopes as a paleoredox proxy. For these purposes, we investigated the Cr isotope composition of reducing sediments from the upwelling zone of the Peru Margin and the deep Cariaco Basin. Chromium is present in marine sediments in both detrital and authigenic phases, and to estimate the isotopic composition of the authigenic fraction, we measured δ53Cr on a weakly acid-leached fraction in addition to the bulk sediment. In an effort to examine potential variability in the Cr isotope composition of the detrital fraction, we also measured δ53Cr on a variety of oxic marine sediments that contain minimal authigenic Cr. The average δ53Cr value of the oxic sediments examined here is -0.05 ± 0.10‰ (2σ, n = 25), which is within the range of δ53Cr values characteristic of the bulk silicate Earth. This implies that uncertainty in estimates of authigenic δ53Cr values based on bulk sediment analyses is mainly linked to estimation of the ratio of Cr in detrital versus authigenic phases, rather than to the Cr-isotopic composition of the detrital pool. Leaches of Cariaco Basin sediments have an average δ53Cr value of +0.38 ± 0.10‰ (2σ, n = 7), which shows no dependency on sample location within the basin and is close to that of Atlantic deepwater Cr (∼+0.5‰). This suggests that authigenic Cr in anoxic sediments may reliably reflect the first-order Cr isotope composition of deepwaters. For Peru Margin samples

  17. Modeling the carbon isotope composition of bivalve shells (Invited)

    Science.gov (United States)

    Romanek, C.

    2010-12-01

    The stable carbon isotope composition of bivalve shells is a valuable archive of paleobiological and paleoenvironmental information. Previous work has shown that the carbon isotope composition of the shell is related to the carbon isotope composition of dissolved inorganic carbon (DIC) in the ambient water in which a bivalve lives, as well as metabolic carbon derived from bivalve respiration. The contribution of metabolic carbon varies among organisms, but it is generally thought to be relatively low (e.g., 90%) in the shells from terrestrial organisms. Because metabolic carbon contains significantly more C-12 than DIC, negative excursions from the expected environmental (DIC) signal are interpreted to reflect an increased contribution of metabolic carbon in the shell. This observation contrasts sharply with modeled carbon isotope compositions for shell layers deposited from the inner extrapallial fluid (EPF). Previous studies have shown that growth lines within the inner shell layer of bivalves are produced during periods of anaerobiosis when acidic metabolic byproducts (e.g., succinic acid) are neutralized (or buffered) by shell dissolution. This requires the pH of EPF to decrease below ambient levels (~7.5) until a state of undersaturation is achieved that promotes shell dissolution. This condition may occur when aquatic bivalves are subjected to external stressors originating from ecological (predation) or environmental (exposure to atm; low dissolved oxygen; contaminant release) pressures; normal physiological processes will restore the pH of EPF when the pressure is removed. As a consequence of this process, a temporal window should also exist in EPF at relatively low pH where shell carbonate is deposited at a reduced saturation state and precipitation rate. For example, EPF chemistry should remain slightly supersaturated with respect to aragonite given a drop of one pH unit (6.5), but under closed conditions, equilibrium carbon isotope fractionation

  18. Effect of Glyphosate-boron Application on Seed Composition and Nitrogen Metabolism in Glyphosate-resistant Soybean

    Science.gov (United States)

    Information is limited on the effect of combined foliar application of glyphosate (Gly) and boron (B) on seed composition and nitrogen metabolism in glyphosate resistant soybean (Glycine max(L.)Merr.). Therefore, the objective of this two-year field study was to evaluate the effects of single foliar...

  19. The mechanical property and resistance ability to atomic oxygen corrosion of boron modified carbon/carbon composites

    International Nuclear Information System (INIS)

    Before being densified by chemical vapor deposition, carbon preform was modified by boron. The mechanical property and resistance to atomic oxygen corrosion of carbon/carbon composites were investigated. The results show that fiber surface modification induces the deposition of high texture pyrocarbon and a moderate interfacial transition layer between carbon fibers and matrix carbon. After being modified by boron, the flexural and compressive strength of carbon/carbon composite is significantly increased. The bending curve has been adjusted with obvious pseudo-ductility phenomenon. The resistance ability to atomic oxygen corrosion is improved significantly. The mass loss and corrosion degree of the modified composite are lower than that of pure carbon/carbon composite

  20. Investigations of isotopic composition of foodstuff - basic study and applications

    International Nuclear Information System (INIS)

    Study of food isotopic composition play actually an important role in food authenticity and origin control. In Institute of Nuclear Chemistry and technology the subject of study has been investigated for many years. In last time our work is concentrated on the implementation new methods for selected food and improves of our proficiency in laboratory work. The examples of our study results are presented. (author)

  1. Comparison of the chemical composition of boron-doped diamond surfaces upon different oxidation processes

    International Nuclear Information System (INIS)

    In spite of the high stability of polycrystalline diamond, oxidation of the hydrogenated surface is relatively easy to perform. This results in the introduction of ether (C-O-C), carbonyl (C=O) and hydroxyl (C-OH) groups on the surface. For further surface functionalization, it is important to quantify the presence of each group on the diamond surface when different oxidation processes are used. In this paper, we investigate the composition of oxidized boron-doped diamond surfaces using X-ray photoelectron spectroscopy (XPS) when electrochemical, photochemical or oxygen plasma methods were employed to introduce oxygen functionalities on as-deposited diamond interfaces. Cyclic voltammetry and C-V measurements were additionally performed to identify more clearly the formation of C-OH, C-O-C and/or C=O functions.

  2. Isotopic composition of precipitation during different atmospheric circulation patterns

    Science.gov (United States)

    Brenčič, Mihael; Kononova, Nina; Vreča, Polona

    2016-04-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. There are several approaches in which atmospheric circulation patterns are classified as elementary air circulation mechanisms - ECM; in our approach we have applied Dzerdzeevskii classification. Two types of models of relation between ECM and isotopic composition of precipitation are proposed; first is based on the linear combination of δ2H and δ18O values with precipitation amount weighted average (Brenčič et al., 2015) and the second new one is based on the multiple regression approach. Both approaches make possible also to estimate empirical distributions' dispersion parameters. Application of the models is illustrated on the precipitation records from Ljubljana and Portorož GNIP stations, Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Brenčič, M., Kononova, N.K., Vreča, P., 2015: Relation between isotopic composition of precipitation and atmospheric circulation patterns. Journal of Hydrology 529, 1422-1432: doi: 10.1016/j.jhydrol.2015.08.040

  3. Argon, oxygen, and boron isotopic evidence documenting 40ArE accumulation in phengite during water-rich high-pressure subduction metasomatism of continental crust

    Science.gov (United States)

    Menold, Carrie A.; Grove, Marty; Sievers, Natalie E.; Manning, Craig E.; Yin, An; Young, Edward D.; Ziegler, Karen

    2016-07-01

    The Luliang Shan area of the North Qaidam high pressure (HP) to ultrahigh pressure (UHP) metamorphic terrane in northwestern China features thick, garnet- and phengite-rich metasomatic selvages that formed around gneiss-hosted mafic eclogite blocks during HP conditions. Here we present new 40Ar/39Ar, δ18 O, and δ11 B results from a previously studied 30 m, 18 sample traverse that extends from the host gneiss into a representative eclogite block. Previous thermobarometry and new mica-quartz oxygen isotope thermometry from the traverse reveal that the phengite-rich selvage formed at temperatures similar to those recorded by the eclogites at peak pressure. Quartz and white mica δ18 O data from the selvage cannot be explained by simple mixing of gneiss and eclogite, and indicate a fluid/rock ratio >1 during regional-scale infiltration of high δ18 O (ca. 14‰) fluids. Heavy δ18 O overgrowths of metamorphic zircon over lighter δ18 O detrital grains indicate that the gneiss was similarly affected. Starkly contrasting boron content and δ11 B compositions for the host gneiss and the selvage also cannot be explained by local-scale devolatilization of the gneiss to form the selvage. Instead, the boron systematics are best attributed to two distinct phases of fluid infiltration: (1) low-boron selvage phengite with δ11 B from -10 to -30‰ grew under HP conditions; and (2) tourmaline and boron-rich muscovite with generally positive δ11 B crystallized in the host gneiss under subsequent lower pressure epidote-amphibolite facies conditions as the Luliang Shan gneiss terrane was exhumed past shallower portions of the subduction channel. Consistent with observations made worldwide, we were able to identify uptake of excess argon (40ArE) in phengite as a high pressure phenomenon. Phengite 40Ar/39Ar ages from massive eclogite exceed the ca. 490 Ma zircon U-Pb age of eclogite metamorphism by a factor of 1.5. However, phengite ages from the more permeable schistose selvage

  4. Global modelling of H2 mixing ratios and isotopic compositions with the TM5 model

    NARCIS (Netherlands)

    Pieterse, G.; Krol, M.C.; Batenburg, A.M.; Steele, L.P.; Krummel, P.B.; Langenfelds, R.L.; Röckmann, T.

    2011-01-01

    The isotopic composition of molecular hydrogen (H2) contains independent information for constraining the global H2 budget. To explore this, we have implemented hydrogen sources and sinks, including their stable isotopic composition and isotope fractionation constants, into the global chemistry tran

  5. Synthesis and Characterization of Nano Boron Nitride Reinforced Magnesium Composites Produced by the Microwave Sintering Method

    Directory of Open Access Journals (Sweden)

    Manoj Gupta

    2013-05-01

    Full Text Available In this study, magnesium composites with nano-size boron nitride (BN particulates of varying contents were synthesized using the powder metallurgy (PM technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture.

  6. Boron-doped cadmium oxide composite structures and their electrochemical measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lokhande, B.J., E-mail: bjlokhande@yahoo.com [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Ambare, R.C. [Lab of Smart Mtrls Supercapacitive and Energy Studies, School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra (India); Mane, R.S. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (India); Bharadwaj, S.R. [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2013-08-01

    Graphical abstract: Conducting nano-fibrous 3% boron doped cadmium oxide thin films were prepared by SILAR and its super capacitive properties were studied. - Highlights: • Samples are of nanofibrous nature. • All samples shows pseudocapacitive behavior. • 3% B doped CdO shows good specific capacitance. • 3% B doped CdO shows maximum 74.93% efficiency at 14 mA/cm{sup 2}. • 3% B doped CdO shows 0.8 Ω internal resistance. - Abstract: Boron-doped and undoped cadmium oxide composite nanostructures in thin film form were prepared onto stainless steel substrates by a successive ionic layer adsorption and reaction method using aqueous solutions of cadmium nitrate, boric acid and 1% H{sub 2}O{sub 2}. As-deposited films were annealed at 623 K for 1 h. The X-ray diffraction study shows crystalline behavior for both doped and undoped films with a porous topography and nano-wires type architecture, as observed in SEM image. Wettability test confirms the hydrophilic surface with 58° contact angle value. Estimated band gap energy is around 1.9 eV. Electrochemical behavior of the deposited films is attempted in 1 M KOH electrolyte using cyclic voltammetry (CV), electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Maximum values of the specific capacitance, specific energy and specific power obtained for 3% B doped CdO film at 2 mV/s scan rate are 20.05 F/g, 1.22 Wh/kg and 3.25 kW/kg, respectively.

  7. Clumped-isotope geochemistry of carbonates: A new tool for the reconstruction of temperature and oxygen isotope composition of seawater

    Energy Technology Data Exchange (ETDEWEB)

    Bernasconi, Stefano M., E-mail: Stefano.bernasconi@erdw.ethz.ch [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Schmid, Thomas W.; Grauel, Anna-Lena [Geological Institute, ETH Zuerich, Sonneggstrasse 5, 8092 Zuerich (Switzerland); Mutterlose, Joerg [Institut fuer Geologie, Mineralogie und Geophysik, Ruhr Universitaet Bochum, Universitaetsstr. 150, 44801 Bochum (Germany)

    2011-06-15

    Highlights: > Clumped-isotope thermometry of carbonates is discussed. > Clumped isotopes of Belemnites show higher sea surface temperatures than commonly assumed for the lower Cretaceous. > The potential of clumped-isotope measurement on foraminifera is discussed. - Abstract: Clumped-isotope geochemistry deals with State of ordering of rare isotopes in molecules, in particular with their tendency to form bonds with other rare isotopes rather than with the most abundant ones. Among its possible applications, carbonate clumped-isotope thermometry is the one that has gained most attention because of the wide potential of applications in many disciplines of the earth sciences. In particular, it allows reconstructing the temperature of formation of carbonate minerals without knowledge of the isotopic composition of the water from which they were formed. In addition, the O isotope composition of the waters from which they were formed can be calculated using the {delta}{sup 18}O of the same carbonate sample. This feature offers new approaches in paleoclimatology for reconstructing past global geochemical cycles. In this contribution two applications of this method are presented. First the potential of a new analytical method of measurement of clumped isotopes on small samples of foraminifera, for high-resolution SST and seawater {delta}{sup 18}O reconstructions from marine sediments is shown. Furthermore the potential of clumped isotope analysis of belemnites, for reconstructing seawater {delta}{sup 18}O and temperatures in the Cretaceous is shown.

  8. A new method for calibrating a boron isotope paleo-pH proxy using massive Porites corals

    Science.gov (United States)

    Kubota, Kaoru; Yokoyama, Yusuke; Ishikawa, Tsuyoshi; Suzuki, Atsushi

    2015-09-01

    The boron isotope ratio (δ11B) of marine biogenic carbonates can reconstruct pH and pCO2 of seawater, and potentially CO2 concentration in the atmosphere. To date, δ11B-pHSW calibration has been proposed via culturing experiments, where calcifying organisms are cultured under artificially acidified seawater. However, in scleractinian corals, reconstructed pH values using culture-based calibrations do not agree well with actual observations of seawater CO2 chemistry. Thus, another approach is needed to establish a more reliable calibration method. In this study, we established field-based calibrations for Chichijima and Tahiti, both located in subtropical gyres where surface seawater is close to CO2 equilibrium. We suggest a new approach to calibration of δ11B-pH in which the long-term δ11B variation of massive Porites corals is compared with the decreasing pH trend (i.e., ocean acidification) that has occurred since the Industrial Revolution. This calibration will offer a new avenue for studying seawater CO2 chemistry using coral δ11B in diverse settings, such as upwelling regions, coral reefs, and coastal areas.

  9. Measurement of plutonium isotopic composition by gamma-ray spectroscopy

    International Nuclear Information System (INIS)

    The technology of the analysis of plutonium isotopic ratio is independent of the measurement geometry and applicable to samples of physical and chemical composition. Three standard plutonium samples were measured in the HPGe system. The results showed that CRM 136 and CRM 137 containing 238Pu(0.223%) and 238Pu(0.268%) were 18.4% and 14.2% error and CRM 138 of 238Pu(0.01%) was 76% error. However the analysis represented less than 1.6% and 9% error in the three standard samples of highly involved 239Pu and 240Pu. Therefore, gamma-ray spectroscopy is very effective in the plutonium isotope analysis, having greater than 10% in content

  10. Fundamental study of practical separation of boron isotopes by means of anion exchange resin, (2)

    International Nuclear Information System (INIS)

    As we reported earlier, a boric acid band formed in a column of weak base anion exchange resin Diaion WA21 can be eluted with pure water, resulting in good isotope fractionation. In the present research, we carried out various experiments using this process in order to find the necessary conditions for producing a displacement chromatogram at the end of the boric acid band, where 10B is enriched. Suitable conditions were found to be as follows: the concentration of boric acid was 0.1 mol/l, the operating temperature was 400C and the flow rate was 20 ml/hr.cm2. Under these conditions, four experimental runs having different migration lengths (1, 2, 4, 8 m) were carried out by a new method which we named ''Isotopic Plateau Holding Displacement Chromatography''. In these experiments, the enriched part of band was always preceded by the isotopic plateau part, in which the atomic fraction of 10B was maintained at its original value. The results of these experiments carried out by this method showed that the concentration of 10B at the end of the chromatogram increased with the migration length, and in the case of 8 m migration, 10B was enriched from an original value of 19.84 to 33.26%. The separation factor S was found to be constant, 1.0097+-0.0002, irrespective of migration length. (auth.)

  11. Perchlorate in the Great Lakes: isotopic composition and origin.

    Science.gov (United States)

    Poghosyan, Armen; Sturchio, Neil C; Morrison, Candice G; Beloso, Abelardo D; Guan, Yunbin; Eiler, John M; Jackson, W Andrew; Hatzinger, Paul B

    2014-10-01

    Perchlorate is a persistent and mobile contaminant in the environment with both natural and anthropogenic sources. Stable isotope ratios of oxygen (δ(18)O, Δ(17)O) and chlorine (δ(37)Cl) along with the abundance of the radioactive isotope (36)Cl were used to trace perchlorate sources and behavior in the Laurentian Great Lakes. These lakes were selected for study as a likely repository of recent atmospheric perchlorate deposition. Perchlorate concentrations in the Great Lakes range from 0.05 to 0.13 μg per liter. δ(37)Cl values of perchlorate from the Great Lakes range from +3.0‰ (Lake Ontario) to +4.0‰ (Lake Superior), whereas δ(18)O values range from -4.1‰ (Lake Superior) to +4.0‰ (Lake Erie). Great Lakes perchlorate has mass-independent oxygen isotopic variations with positive Δ(17)O values (+1.6‰ to +2.7‰) divided into two distinct groups: Lake Superior (+2.7‰) and the other four lakes (∼+1.7‰). The stable isotopic results indicate that perchlorate in the Great Lakes is dominantly of natural origin, having isotopic composition resembling that measured for indigenous perchlorate from preindustrial groundwaters of the western USA. The (36)Cl/Cl ratio of perchlorate varies widely from 7.4 × 10(-12) (Lake Ontario) to 6.7 × 10(-11) (Lake Superior). These (36)ClO4(-) abundances are consistent with an atmospheric origin of perchlorate in the Great Lakes. The relatively high (36)ClO4(-) abundances in the larger lakes (Lakes Superior and Michigan) could be explained by the presence of (36)Cl-enriched perchlorate deposited during the period of elevated atmospheric (36)Cl activity following thermonuclear bomb tests in the Pacific Ocean. PMID:25171443

  12. Isotope Fractionation During N Mineralization and the N Isotope Composition of Terrestrial Ecosystem N Pools

    Science.gov (United States)

    Dijkstra, P.; Schwartz, E.; Hungate, B. A.; Hart, S. C.

    2008-12-01

    It has been an open question for several decades whether N mineralization is a fractionating process. This question is important for N cycling in terrestrial ecosystems because even a small fractionation during N mineralization could potentially have a large influence on the N isotope composition of other ecosystem N pools. Fractionation during N mineralization should result in a difference between the N isotope composition of the soil microorganisms, that of its substrates, and products. We analyzed the N isotope composition of the soil microbial biomass in a variety of ecosystems, and found that it was 15N enriched compared to that of other soil N pools, such as soil soluble, organic and inorganic N (Dijkstra et al. 2006a,b). We observed a negative correlation between the 15N enrichment of the microorganisms and the relative C and N availability for soil from ecosystems in Hawaii and Arizona, across a broad range of climates, grasslands and forests, and more than four million years of ecosystem development. This suggests that during N dissimilation (and associated transaminations) and N export, the lighter 14N N isotope is preferentially removed in a manner similar to that proposed for animals and ectomycorrhizae. This was further confirmed by the positive correlation between microbial 15N enrichment and net N mineralization rate (Dijkstra et al. 2008, Ecology Letters 11: 389-397) and by culture experiments with Escherichia coli (Collins et al. 2008). Since mineralization is the largest flux of N in ecosystems, fractionation during N mineralization has the potential to influence the N isotope composition of other N pools, such as inorganic N, plant N and soil organic matter N. We demonstrate that the N isotope compositions of these ecosystem N pools exhibit differences that are consistent with fractionation during N mineralization. Our results show that the N isotope composition can be used as a measure to trace N mineralization and decomposition in ecosystems

  13. Powder metallurgy routes toward aluminum boron nitride nanotube composites, their morphologies, structures and mechanical properties

    International Nuclear Information System (INIS)

    Aluminum/boron nitride nanotube (BNNT) composites with up to 5 wt% (i.e., 9.7 vol%) nanotube fractions were prepared via spark plasma sintering (SPS) and high-pressure torsion (HPT) methods. Various microscopy techniques, X-ray diffraction, and energy dispersive X-ray analysis confirmed the integration of the two phases into decently dense and compact composites. No other phases, like Al borides or nitrides, formed in the Al–BNNTs macrocomposites of the two series. The BNNTs were found to be preferentially located along Al grain boundaries in SPS samples (grain size was 10–20 μm) creating micro-discontinuities and pores which were found to be detrimental for the sample hardness, whereas in HPT samples, the tubes were rather evenly distributed within a fine-grained Al matrix (grain size of several hundred nm). Therefore, the hardness of HPT samples was drastically increased with increasing BNNTs content in Al pellets. The value for Al–BNNT 3.0 wt% sample was more than doubled (190 MPa) compared to a pure Al–HPT compact (90 MPa). And the room temperature ultimate tensile strength of Al–BNNTs HPT samples containing 3.0 wt% BNNT (∼300 MPa) became ∼1.5 times larger than that of a BNNT-free HPT–Al compact (∼200 MPa)

  14. Powder metallurgy routes toward aluminum boron nitride nanotube composites, their morphologies, structures and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Maho [Nanotube Unit, World Premier International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3050005 (Japan); Meng, Fanqiang [Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 3050044 (Japan); Firestein, Konstantin [Laboratory of Inorganic Nanomaterials, National University of Science and Technology “MISIS”, Leninsky pr. 4, Moscow 119049 (Russian Federation); Tsuchiya, Koichi [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3050005 (Japan); Research Center for Strategic Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 3050044 (Japan); Golberg, Dmitri, E-mail: GOLBERG.Dmitri@nims.go.jp [Nanotube Unit, World Premier International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3050005 (Japan)

    2014-05-01

    Aluminum/boron nitride nanotube (BNNT) composites with up to 5 wt% (i.e., 9.7 vol%) nanotube fractions were prepared via spark plasma sintering (SPS) and high-pressure torsion (HPT) methods. Various microscopy techniques, X-ray diffraction, and energy dispersive X-ray analysis confirmed the integration of the two phases into decently dense and compact composites. No other phases, like Al borides or nitrides, formed in the Al–BNNTs macrocomposites of the two series. The BNNTs were found to be preferentially located along Al grain boundaries in SPS samples (grain size was 10–20 μm) creating micro-discontinuities and pores which were found to be detrimental for the sample hardness, whereas in HPT samples, the tubes were rather evenly distributed within a fine-grained Al matrix (grain size of several hundred nm). Therefore, the hardness of HPT samples was drastically increased with increasing BNNTs content in Al pellets. The value for Al–BNNT 3.0 wt% sample was more than doubled (190 MPa) compared to a pure Al–HPT compact (90 MPa). And the room temperature ultimate tensile strength of Al–BNNTs HPT samples containing 3.0 wt% BNNT (∼300 MPa) became ∼1.5 times larger than that of a BNNT-free HPT–Al compact (∼200 MPa)

  15. Boron analyses in the reactor coolant system of French PWR by acid-base titration ([B]) and ICP-MS (10B atomic %): key to NPP safety

    International Nuclear Information System (INIS)

    Boron is widely used by Nuclear Power Plants and especially by EDF Pressurized Water Reactors to ensure the control of the neutron rate in the reactor coolant system and, by this way, the fission reaction. The Boron analysis is thus a major factor of safety which enables operators to guarantee the permanent control of the reactor. Two kinds of analyses carried out by EDF on the Boron species, recently upgraded regarding new method validation standards and developed to enhance the measurement quality by reducing uncertainties, will be discussed in this topic: Acid-Base titration of Boron and Boron isotopic composition by Inductively Coupled Plasma Mass Spectrometer - ICP MS. (authors)

  16. Stable isotope composition of atmospheric carbon monoxide. A modelling study

    International Nuclear Information System (INIS)

    This study aims at an improved understanding of the stable carbon and oxygen isotope composition of the carbon monoxide (CO) in the global atmosphere by means of numerical simulations. At first, a new kinetic chemistry tagging technique for the most complete parameterisation of isotope effects has been introduced into the Modular Earth Submodel System (MESSy) framework. Incorporated into the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model, an explicit treatment of the isotope effects on the global scale is now possible. The expanded model system has been applied to simulate the chemical system containing up to five isotopologues of all carbon- and oxygen-bearing species, which ultimately determine the δ13C, δ18O and Δ17O isotopic signatures of atmospheric CO. As model input, a new stable isotope-inclusive emission inventory for the relevant trace gases has been compiled. The uncertainties of the emission estimates and of the resulting simulated mixing and isotope ratios have been analysed. The simulated CO mixing and stable isotope ratios have been compared to in-situ measurements from ground-based observatories and from the civil-aircraft-mounted CARIBIC-1 measurement platform. The systematically underestimated 13CO/12CO ratios of earlier, simplified modelling studies can now be partly explained. The EMAC simulations do not support the inferences of those studies, which suggest for CO a reduced input of the highly depleted in 13C methane oxidation source. In particular, a high average yield of 0.94 CO per reacted methane (CH4) molecule is simulated in the troposphere, to a large extent due to the competition between the deposition and convective transport processes affecting the CH4 to CO reaction chain intermediates. None of the other factors, assumed or disregarded in previous studies, however hypothesised to have the potential in enriching tropospheric CO in 13C, were found significant when explicitly simulated. The inaccurate surface

  17. Isotopic composition of carbon monoxide in St. Louis, Missouri area

    International Nuclear Information System (INIS)

    The concentration and isotropic composition of carbon monoxide were determined for air samples taken in the vicinity of St. Louis, Missouri, to provide information as to the movement of the pollutant plume from the city. Urban air was detected as far as 48 miles downwind of St. Louis; however, movement of the pollutant plume was not detected. The effect of engine carbon monoxide produced along a highway in a rural area was found to be minimal three miles downwind of the highway. Diurnal studies demonstrated an inverse relationship between carbon monoxide concentration and oxygen and carbon isotopic ratios during the night. A parallel relation prevailed during the day

  18. The preparation and composition design of boron-rich lanthanum hexaboride target for sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Defang; Min, Guanghui; Wu, Yan; Yu, Huashun; Zhang, Lin, E-mail: zhanglin2007@sdu.edu.cn

    2015-07-25

    Highlights: • High-purity LaB{sub 6} powder was prepared due to significant reduction of residual B{sub 4}C and effective purification process. • The effects of raw materials ratio on the size, morphology, phase structure and crystalline size of LaB{sub 6} were studied. • The correlation of component between LaB{sub 6} films and boron-rich targets was established. • The variation of densities of LaB{sub 6} targets with sintering time and sintering temperature was investigated. - Abstract: Lanthanum Hexaboride (LaB{sub 6}) nano-film has been proved to be promising transparent thermal insulation material, while its properties are limited on purity and composition. High-purity LaB{sub 6} polycrystalline powder was prepared through boron carbide reduction method in this work. A series of techniques such as scanning electron microscopy, X-ray diffraction, laser particle analyzer and inductively coupled plasma emission spectrometer were employed to characterize LaB{sub 6} powder. As raising the content of La{sub 2}O{sub 3} in reactants, more uniform, finer (2.686 μm) and purer (99.5139 wt%) LaB{sub 6} powder is prepared, with only 0.4434 wt% residual B{sub 4}C. The density of targets increases with the rise of sintering temperature and the extension of sintering time, while crystallite size increases simultaneously with the extension of sintering time. The introduction of B powder in target is conductive to sintering process, increasing hardness and flexural strength of targets. X-ray photoelectron spectrometer was used to characterize the composition and microstructure of LaB{sub 6} nano-film which is tentatively considered to be composed of LaB{sub 6} nanocrystalline and amorphous microstructure of La and B atoms. The film LaB{sub 6.0627±0.02} was obtained when the ratio of B and La of sputtering target reached 12.5. The thickness and deposition rate decrease with the increase of B content in targets.

  19. Stable Isotopes of Dissolved Nitrate and Boron as Indicators of the Origin and Fate of Nitrate Contamination in Groundwater. Results from the Western Po Plain (Northern Italy)

    International Nuclear Information System (INIS)

    Stable isotopes of dissolved nitrates and boron represent a powerful tool, complementary to existing monitoring data, enabling the identification of nitrate sources, the assessment of their relative contribution to nitrate pollution and the quantification of nitrate transport and removal processes. This contribution aims to present groundwater isotope data obtained in an area of 15 000 km2 of the western Po plain. Nitrate isotope data show that synthetic fertilisers and anthropogenic organic matter are the main sources of contamination. δ11B allows the discrimination between manure derived and sewage derived contamination. Results indicate that even in agricultural areas, contamination from sewage exists. Samples from the suburban area of Milan, where sewage was considered the most likely source of contamination, show instead a δ11B typical for cattle manure. This study demonstrates that the attribution of the contamination to a source based solely on present-day land use may lead to inappropriate conclusions. (author)

  20. Isotopic composition and origin of the precipitation in Northern Chile

    Energy Technology Data Exchange (ETDEWEB)

    Aravena, R. [Department of Earth Sciences, University of Waterloo, Waterloo (Canada); Suzuki, O. [Exploracion y Desarrollo de Recursos Hidricos, Santiago (Chile); Pena, H. [Direccion General de Aguas, Ministerio de Obras Publicas, Santiago (Chile); Pollastri, A. [Comision Chilena de Energia Nuclear, Santiago (Chile); Fuenzalida, H. [Departamento de Geofisica, Universidad of Chile, Santiago (Chile); Grilli, A. [Empresa Metropolitana de Obras Sanitarias, Santiago (Chile)

    1999-06-01

    A 3 a data set of isotopes in precipitation from northern Chile show a very distinct pattern, with {delta}{sup 18}O values ranging between -18 and -15per thousand at high altitude stations, compared to {delta}{sup 18}O values between -10 and -6per thousand at the lower altitude areas. The {sup 18}O-depleted values observed in the high altitude area, the Altiplano, are related to processes that affect the air masses that originated over the Atlantic, cross the Amazon Basin (continental effect), ascend the Andes (altitude effect) and precipitated (convective effect) in the Altiplano. It is postulated that a second source of moisture, associated with air masses from the Pacific, may contribute to the {sup 18}O-enriched values observed in the lower altitude areas. Similar isotopic patterns are documented in springs and groundwater indicating that the data presented in this paper are an accurate representation of the long term behavior isotopic composition of rain in northern Chile. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  1. Reprocessing of the irradiated boron carbide enriched by boron-10 isotope and its reuse in the control rods of the fast breeder reactors

    International Nuclear Information System (INIS)

    The present paper discusses the development of technology for reprocessing of irradiated boron carbide, which provides complete removal of radionuclides from irradiated materials. This technology allows the repeated use of B10 enriched with B4C in fast reactors. (author). 4 figs, 1 tab

  2. Modelling the oceanic Nd isotopic composition on a global scale

    International Nuclear Information System (INIS)

    Since the end of the eighties, it is recognized that the Nd isotopic composition (expressed as εNd) varies from ca -13 in the North Atlantic to ca -5 in the Pacific. It has been clearly established that far from any source of lithogenic material, εNd is a conservative tracer of water mass mixing. Since the range of εNd values of the deep waters are imprinted in the metalliferous sediments, they are used by paleoceanographers to trace the past variations of the thermohaline circulation. However, many studies conducted in the present day ocean highlight that the Nd budgets based only on dust/riverine inputs were not able to reconcile the Nd content and εNd variations between the 3 oceanic basins (the 'Nd paradox'). The 'missing source' was often suspected to be the oceanic margins but was quantified only recently. This talk proposes modelling results of the Nd oceanic distribution (concentration and isotopic composition) on a global scale. For doing that, we first established an extensive compilation of the εNd signatures of the world continental margins (deduced from more than 50 references, figure below). Then, we applied the rate of exchange of Nd between the continental margins and the oceans, deduced from Lacan and Jeandel (in rev.). This allowed to simulate lithogenic Nd inputs into a large scale circulation model (ORCA/OPA). Simulated vertical profiles are compared to those measured in the different oceanic basins

  3. Recommendations for Determining Uranium Isotopic Composition by MGAU

    International Nuclear Information System (INIS)

    The study deals with testing the versions 4.0 and 4.2 of the Multi-Group Analysis for Uranium (MGAU) software. MGAU is used for determining uranium isotopic composition by gamma spectrometry. The aim of the study was to determine the optimal measurement conditions needed to get the MGAU results as accurate as possible. The optimal number of total counts and the optimal count rate were determined. The study also shows how the accuracy of MGAU depends on the 235U-enrichment for various total numbers of counts. The testing procedure is based on using simulated spectra generated from real spectra of certified reference materials and well characterized fuel pellets. The simulated spectra are generated by randomly sampling data from real ones by Cambio software. This approach allows producing a large number of spectra having different number of total counts to obtain statistically relevant data. More than 7000 spectra have been used in the study. The results of this work can help to appropriately set up a gamma-spectrometric measurement of the uranium isotopic composition. (author)

  4. The stable isotope composition of some East Coast natural gases

    International Nuclear Information System (INIS)

    The carbon and hydrogen isotopic ratios of methane from 17 natural gas seeps on the East Coast of the North Island, New Zealand, show a diversity of values. All isotopic ratios are consistent with overseas values for gases associated with oil. Chemical compositions and geological settings are used to make further interpretations, and to relate the gases to possible source rocks. Isotopic compositions suggest that mature source rocks have produced the gases from Otopotehetehe, Waitangi, Tukituki, Wairakau, Weber, Te Hoe and Langdale. The Rotokautuku gas appears to have been altered by secondary processes such as oxidation. Some of the cases are associated with oil seeps. Waimata gas may be from a less mature source than the above. All these gases have methane delta/sup 13/C values more positive than -45 per thousand implying, probable R/sub o/, values greater than 1% if the source matter is of marine origin. Kaikopu and Te Pohue gas seeps have more negative delta/sup 13/C values implying, they have been buried and/or heated to a lesser degree than the other gases. The warm springs at Te Puia also evolve a mature methane-rich gas with saline water. A warm spring in the greywacke ranges at Mangatainoka is suggestive of a reasonable degree of thermal maturity, but is nitrogen-rich and identical to other springs on the same fault. Morere warm springs and nearby seeps and mud volcanoes at Kopuawhara and Tiromoana suggest variable mixtures of thermogenic gas with a microbial gas although their /sup 3/He//sup 4/He values suggest a deeper gas contribution. (author). 26 refs.; 7 figs.; 2 tabs

  5. Continuous and cyclic thermal exposure induced degradation in boron reinforced 6061 aluminum composites

    Science.gov (United States)

    Olsen, G. C.; Tompkins, S. S.

    1977-01-01

    Boron reinforced 6061 aluminum (B/Al) composite was continuously exposed at 728 K for up to 240 hours and cyclically exposed between 293 K and 728 K for up to 6000 three-minute cycles. Room temperature tensile strengths were measured and the specimens were metallographically examined. The data suggest that, in addition to AlB2 formation, magnesium in the matrix diffused to the reaction layer and formed (Al,Mg)B2. This formation could weaken the matrix and embrittle the reaction layer. Continuous exposure degraded the strength of the B/Al specimens about 28% in 240 hours. However, the fracture mode, one indicative of high strength interfaces, did not change. The strength degradation was attributed to crack initiation in the brittle reaction layer causing stress concentrations in the fibers. Cyclic exposure degraded the strength of the B/Al about 34% in 6000 cycles. The fracture mode of the cyclic exposure specimens showed transition toward a mode characteristic of low interfacial strength. The lower interfacial strengths were attributed to stress fields induced by differential thermal expansion. Cyclic exposure degraded the strength of the B/Al specimens more than continuous exposure for similar cumulative exposure times.

  6. High Temperature Properties and Microstructure of Boron Nitride—Zirconia/Corundum/Mullite Composites

    Institute of Scientific and Technical Information of China (English)

    ZHAOHailei; ZHONGXiangchong; 等

    1997-01-01

    The high temperature properties and mi-crostructure of boron nitride matrix with addi-tion of 10wt%-30wt% zirconia/corundum/mullite hot-pressing sintered have been studied. The results reveal that addition of zirconia/corundum/mullite to BN-based material results in enhanement of bending strength and frac-ture toughness that may be due to the dispersion strengthening and toughness effects caused by the dispersion of oxide particles in the interwo-ven structure of BN.Furthermore,when oxide addition does not exceed 20wt%,the composite still retains excellent thermal shock resistance characteristic of BN material.The 9Al2O3·2B2O3 formed during the sintering process cre-ate a pull-out effect when the material tends to fracture,which may be beneficial for improve-ment of mechanial properties.The oxidation kinetics model has been worked out,together with formula for activation energy and rate,Thermal fatigue life formula has been derived,and the activation energy for subcritical crack growth and the stress intensity exponent have been calculated.

  7. The influence of Ryukyu subduction on magma genesis in the Northern Taiwan Volcanic Zone and Middle Okinawa Trough - Evidence from boron isotopes

    Science.gov (United States)

    Pi, Ju-Lien; You, Chen-Feng; Wang, Kuo-Lung

    2016-09-01

    Boron (B) is an excellent geochemical tracer for investigating crustal recycling processes at convergent margins, due to its high fluid mobility under high P-T conditions, distinct elemental abundances and isotopic compositions in the mantle wedge and subducting slabs. The Northern Taiwan Volcanic Zone (NTVZ), wherein the nature of magma genesis has long been a topic of debate, is located at the rear side of the Okinawa Trough (OT), an atypical back-arc rift in the Ryukyu subduction system. In this study, B and B isotopes (δ11B) were measured in 19 volcanic rocks collected from the NTVZ and the middle Okinawa Trough (MOT) to assess the influence of the Ryukyu subduction system on magma genesis. The B concentrations in the MOT and NTVZ volcanic rocks are 5.8 to 13.6 mg/L and 2.2 to 48.6 mg/L, respectively. The large B abundances variation in the NTVZ was caused mainly by variable degrees of partial melting. The Nb/B and δ11B in the MOT have small ranges of 0.5 to 0.6 and - 2.7‰ to 0.2‰, respectively, whereas they range widely from 0.4 to 2.5 and from - 8.6‰ to 2.4‰, respectively in the NTVZ. These Nb/B values suggest that the magma contains a smaller subduction component than that normally observed in arcs, although this component is still more substantial than in a typical back-arc setting. The δ11B results indicate insignificant influence of the subducting Philippine Sea Plate at 2.6 Ma, but it becomes more substantial later in the NTVZ. The mixing proportions of sediment derived fluids in onshore volcanoes in the NTVZ imply a rather heterogeneous mantle wedge near the plate boundary, most likely due to either a heterogeneous source of slab derived fluids or more complicated mantle flow. A substantial B flux from the subducting slab in the incipient back-arc rifting in the MOT and NTVZ may reflect characteristics of a cold, steep and fast subducting slab, which may be capable of carrying volatiles efficiently into greater depth in subduction zones. The

  8. Classifying wine according to geographical origin via quadrupole-based ICP-mass spectrometry measurements of boron isotope ratios

    International Nuclear Information System (INIS)

    The potential of quadrupole-based ICP-MS as a tool for B-isotopic analysis of wines and its usefulness in provenance determinations were assessed. A precision of 0.1-0.25% RSD (corresponding to a relative standard deviation of the mean of three replicate measurements of 0.06-0.12%) was sufficient to establish small differences in the B isotope ratios in wines from different geographical origins. Each sample measurement was bracketed by measurements of a standard and mass bias drift correction made by interpolation. Sample preparation was kept to a minimum to avoid possible fractionation. Dilution of the wine samples by a factor of 100 with 0.65% HNO3 was found to reduce matrix-induced mass discrimination substantially. Wines from three wine-producing regions, Stellenbosch, Robertson, and Swartland, in the Western Cape Province of South Africa, and wines from specific regions in France (Bergerac) and Italy (Valpolicella) were analyzed by ICP-QMS for their B-isotopic compositions. It was concluded that the 11B/10B ratios can be used to characterize wines from different geographical origins. Average 11B/10B ratios in red wines from South Africa (Stellenbosch), France (Bergerac), and Italy (Valpolicella) were found to differ by between 0.5 and 1.5%. (orig.)

  9. Perchlorate in The Great Lakes: Distribution, Isotopic Composition and Origin

    Science.gov (United States)

    Poghosyan, A.; Sturchio, N. C.; Jackson, W. A.; Guan, Y.; Eiler, J. M.; Hatzinger, P. B.

    2013-12-01

    Concentrations, stable chlorine and oxygen isotopic compositions, and 36Cl abundances of perchlorate were investigated in the five Laurentian Great Lakes. Samples were collected during monitoring cruises in 2007 and 2008 of the U.S. EPA's RV Lake Guardian and in 2010 at the water supply intake of Marquette, MI on the southern shore of Lake Superior. Concentrations of perchlorate were measured by IC/MS/MS at 24 locations, including one or two depth profiles in each lake. Mean concentrations (μg/L) are: Superior, 0.06 × 0.01; Michigan, 0.10 × 0.01; Huron, 0.11 × 0.01; Erie, 0.08 × 0.01, and Ontario, 0.09 × 0.01. Concentration vs. depth is nearly constant in each lake, indicating well-mixed conditions. Perchlorate was extracted from near-surface water by passing 15,000 to 80,000 L of water through 1-L cartridges containing Purolite A530E bifunctional anion-exchange resin. In the laboratory, perchlorate was eluted from the resin, purified, and precipitated as a >99% pure crystalline phase. Milligram amounts were recovered from each lake. Chlorine and oxygen isotopic analyses were performed at Caltech using the Cameca 7f-GEO SIMS instrument, following validation of the SIMS method with analyses of USGS-37 and USGS-38 isotopic reference materials. Results indicate a relatively narrow range in δ37Cl values (+2.9 to +3.9 ‰) and a wider range in δ18O values (-4.0 to +4.1 ‰), with a general geographic trend of increasing δ18O from west to east. Oxygen-17 was measured at UIC using dual-inlet IRMS of O2 produced by decomposition of KClO4. Great Lakes perchlorate has mass-independent oxygen isotopic variations with positive Δ17O values (+1.6 ‰ to +2.7 ‰) divided into two distinct groups: Lake Superior (+2.7 ‰) and the other four lakes (~ +1.7 ‰). The isotopic data indicate that perchlorate is dominantly of natural origin, having stable isotopic compositions resembling those of perchlorate from pre-industrial groundwaters in the western USA. The 36Cl

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-09

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

  11. Investigation of magnesium isotope fractionation during granite differentiation: Implication for Mg isotopic composition of the continental crust

    Science.gov (United States)

    Liu, Sheng-Ao; Teng, Fang-Zhen; He, Yongsheng; Ke, Shan; Li, Shuguang

    2010-09-01

    High-precision Mg isotopic analysis was performed on a suite of well-characterized I-type granitoids and associated hornblende and biotite minerals from the Dabie Orogen in central China, to address the behavior of Mg isotopes during granite differentiation. Although these granitoids formed through different degrees of partial melting and fractional crystallization, with large variations in elemental and mineral compositions, their δ26Mg values vary from -0.26 to -0.14 and are indistinguishable within our analytical precision (± 0.07‰; 2 SD). Coexisting hornblendes and biotites in these granitoids display similar Mg isotopic composition, with δ26Mg ranging from -0.31 to -0.14 in hornblendes and -0.23 to -0.12 in biotites. The inter-mineral fractionation factors (Δ 26Mg Hbl-Bt = δ26Mg Hbl - δ26Mg Bt) vary from -0.10 to -0.02, with an average = -0.06 ± 0.08 (2 SD). The limited inter-mineral fractionation agrees with the theoretic prediction that Mg cations in both hornblende and biotite are octahedrally coordinated with oxygen, which restricts the magnitude of equilibrium isotope fractionation. Overall, data from both bulk granitoids and associated mineral separates suggest that Mg isotope fractionation during I-type granite differentiation is limited. Collectively, granitoids studied here have Mg isotopic composition similar to that of terrestrial basalts and peridotites ( δ26Mg = -0.21 ± 0.07 vs. -0.25 ± 0.07; 2 SD), confirming that magmatic processes do not significantly fractionate Mg isotopes. The continental crust in the Dabie Orogen, as sampled by these I-type granitoids, has a mantle-like Mg isotopic composition. Given that significant Mg isotope fractionation occurs during chemical weathering processes, Mg isotopes may potentially be used for tracing granite genesis, in particular, if sedimentary materials are involved in granite sources.

  12. Global modelling of H2 mixing ratios and isotopic compositions with the TM5 model

    Directory of Open Access Journals (Sweden)

    R. L. Langenfelds

    2011-07-01

    Full Text Available The isotopic composition of molecular hydrogen (H2 contains independent information for constraining the global H2 budget. To explore this, we have implemented hydrogen sources and sinks, including their stable isotopic composition and isotope fractionation constants, into the global chemistry transport model TM5. For the first time, a global model now includes a simplified but explicit isotope reaction scheme for the photochemical production of H2. We present a comparison of modelled results for the H2 mixing ratio and isotope composition with available measurements on seasonal to inter annual time scales for the years 2001–2007. The base model results agree well with observations for H2 mixing ratios. For δD[H2], modelled values are slightly lower than measurements. A detailed sensitivity study is performed to identify the most important parameters for modelling the isotopic composition of H2. The results show that on the global scale, the discrepancy between model and measurements can be closed by adjusting the default values of the isotope effects in deposition, photochemistry and the stratosphere-troposphere exchange within the known range of uncertainty. However, the available isotope data do not provide sufficient information to uniquely constrain the global isotope budget. Therefore, additional studies focussing on the isotopic composition near the tropopause and on the isotope effects in the photochemistry and deposition are recommended.

  13. Probing nuclear molecular analogue states in carbon, boron and beryllium isotopes

    CERN Document Server

    Leask, P J

    2000-01-01

    enough for definitive statements to be made about the underlying cluster structure of this nucleus. However, some limited evidence for decays to the sup 1 sup 2 Be+alpha final state was obtained. In recent years the possibility of molecular-type binding on the nuclear scale has been raised and models based on this hypothesis have met with considerable success in describing the general energy-spin systematics of the beryllium isotopes. This thesis details the planning, implementation and analysis of two experiments to investigate such structures in the nuclei sup 1 sup 0 Be, sup 1 sup 0 B, sup 1 sup 0 C and sup 1 sup 6 C. The A=10 study was performed at the Australian National University and utilised a sup 1 sup 2 C beam incident on sup 1 sup 2 C and sup 7 Li targets. For the sup 1 sup 0 B decay channel useful data was extracted which provides evidence for two previously unobserved states in this nucleus which decay strongly into the sup 6 Li(3 sup + , 2.186 MeV)+alpha channel. It is possible that the type of ...

  14. Boron isotope separation by ion exchange chromatography using weakly basic anion exchange resin

    International Nuclear Information System (INIS)

    Influences of operating temperatures and concentrations of feed boric acid solutions were examined on the above titled process over the ranges of 25 - 70 0C and 0.1 - 1.6 mol/dm3 (M), respectively. The ideal displacement chromatography with a very sharp-cut boundary of the boric acid adsorption band was realized at higher temperatures and lower boric acid concentrations within the experimental conditions. The isotope separation coefficient epsilon was found to decrease with increases in either temperature or the boric acid concentration. The observed values of epsilon at 25 0C were 0.013, 0.012 and 0.011 corresponding to feed boric acid concentrations of 0.1 M, 0.4 M and 0.8 M, respectively. The epsilon's at 70 0C were 0.0097 (0.1 M), 0.0086 (0.4 M), 0.0083 (0.8 M) and 0.0073 (1.6 M). A temperature of 40 0C and 0.4 M of boric acid concentration was considered the optimum operating condition for the production of enriched 10B. (author)

  15. The Role of Boron Chloride and noble gas isotope ratios in Taupo Volcanic Zone geothermal systems

    International Nuclear Information System (INIS)

    The model of the geothermal system in which deep circulating groundwater con noble gases, at air saturated water concentrations, mixes with hot fluids of man origin at depth, is extended to include the effect of interaction of the ascending fluid with both solid and gaseous phases of basement (or other) rocks 'en route' the surface. It is demonstrated that this interaction is responsible for most of CO/sub 2/ in the Taupo Volcanic Zone (TVZ) geothermal systems. It is proposed th the modelling of this interaction might be accomplished by techniques similar to those used for the understanding of the oxygen isotope shift found in geothermal systems. The water rock interaction experiments of Ellis and Mahon (1964, 1967) provides some data on the kinetic rates for B and Cl dissolution from rocks like to be encountered in the geothermal system, but further information on the behaviour of B may be needed. If these problems can be overcome this modelling technique has promise for the estimation of the recharge of geothermal systems a hence the sustainability of these systems. (author). 17 refs., 4 figs

  16. Modeling the oxygen-isotopic composition of the North American Ice Sheet and its effect on the isotopic composition of the ocean during the last glacial cycle

    NARCIS (Netherlands)

    Sima, A.; Paul, A.; Schulz, M.; Oerlemans, J.

    2006-01-01

    We used a 2.5-dimensional thermomechanical icesheet model including the oxygen-isotope ratio 18O/16O as a passive tracer to simulate the isotopic composition (d18O) of the North American Ice Sheet (NAIS) during the last glacial cycle. This model allowed us to estimate the NAIS contribution to the ch

  17. Bayesian Nitrate Source Apportionment to Individual Groundwater Wells in the Central Valley by use of Nitrogen, Oxygen, and Boron Isotopic Tracers

    Science.gov (United States)

    Lockhart, K.; Harter, T.; Grote, M.; Young, M. B.; Eppich, G.; Deinhart, A.; Wimpenny, J.; Yin, Q. Z.

    2014-12-01

    Groundwater quality is a concern in alluvial aquifers underlying agricultural areas worldwide, an example of which is the San Joaquin Valley, California. Nitrate from land applied fertilizers or from animal waste can leach to groundwater and contaminate drinking water resources. Dairy manure and synthetic fertilizers are the major sources of nitrate in groundwater in the San Joaquin Valley, however, septic waste can be a major source in some areas. As in other such regions around the world, the rural population in the San Joaquin Valley relies almost exclusively on shallow domestic wells (≤150 m deep), of which many have been affected by nitrate. Consumption of water containing nitrate above the drinking water limit has been linked to major health effects including low blood oxygen in infants and certain cancers. Knowledge of the proportion of each of the three main nitrate sources (manure, synthetic fertilizer, and septic waste) contributing to individual well nitrate can aid future regulatory decisions. Nitrogen, oxygen, and boron isotopes can be used as tracers to differentiate between the three main nitrate sources. Mixing models quantify the proportional contributions of sources to a mixture by using the concentration of conservative tracers within each source as a source signature. Deterministic mixing models are common, but do not allow for variability in the tracer source concentration or overlap of tracer concentrations between sources. Bayesian statistics used in conjunction with mixing models can incorporate variability in the source signature. We developed a Bayesian mixing model on a pilot network of 32 private domestic wells in the San Joaquin Valley for which nitrate as well as nitrogen, oxygen, and boron isotopes were measured. Probability distributions for nitrogen, oxygen, and boron isotope source signatures for manure, fertilizer, and septic waste were compiled from the literature and from a previous groundwater monitoring project on several

  18. Trace element and oxygen isotope composition of Hawaiian hotspot zircon

    Science.gov (United States)

    Vazquez, J. A.; Bindeman, I. N.; Shamberger, P. J.; Hammer, J. E.

    2010-12-01

    The trace element and isotopic compositions of zircon are increasingly used to delimit the provenance of detrital minerals in sedimentary rocks, as well as the dynamics and timescales of magmagenesis and metamorphism. Numerous studies document the characteristics of zircon hosted by continental and MORB-related rocks, but the characteristics of zircon generated in magmas from oceanic hotspots are relatively unknown. We present the trace element and O-isotope compositions of Hawaiian zircon from gabbroic and dioritic xenoliths sampled by Holocene basalts at Hualalai volcano. The plutonic zircon yield U-Pb and 238U-230Th ages of ca. 250 ka and 40 ka and grew from intrusions of highly fractionated alkalic magma lodged at >10 km depths (Shamberger & Hammer, 2006; Vazquez et al., 2007). Individual Hualalai zircon are euhedral to anhedral with inclusions of feldspars, pyroxenes, and trachytic glass. Zoning apparent in cathodoluminescence images is generally indistinct, but a significant minority of crystals has rims with relatively high luminescence. Ion microprobe analyses of individual zircon crystals reveal trace element zoning that generally correlates with luminescence. Up to 20-fold variation in HREE concentrations, with overall positive correlation between Eu/Eu* and Ti and inverse correlation between Hf and Ti, characterize Hualalai zircon. These relations are similar to those reported for zircon from some felsic suites related by cooling-induced fractionation. Luminescent rims have relatively low REE, Hf, and Y, but have Ti concentrations like their corresponding interiors. Ti-in-zircon thermometry yields temperatures between 800-1000°C after adjustments for sub-unity TiO2 and SiO2 activities using silicate-oxide equilibria. These temperatures are generally consistent with temperatures derived from two-feldspar and glass-pyroxene pairs included by single zircon crystals. Despite compositional differences, zircon interiors and luminescent rims yield 238U-230Th

  19. Study on Processing Conditions of Aluminum Matrix Composites Reinforced with Boron Carbide Particles

    Institute of Scientific and Technical Information of China (English)

    Fu Xueying; Zhang Hong; Xi Huizhi; Yi Xiaosu

    2004-01-01

    Different pre-heating of boron carbide particles for reinforcement and different processing conditions were studied in this work. Being one of the most cost-effective industrial methods, conventional melt stir-casting route was utilized.Result showed that the boron carbide particles distributed well for a suitable pre-heating temperature and processed in air.No reaction product was found at the A1-B4C interfaces at the resolution limit of SEM used in that way.

  20. Morphology-Composition-Isotopes: Recent Results from Observations

    Science.gov (United States)

    Schulz, R.

    This article presents some recent imaging and spectroscopic observations that led to results which are significant for understanding the properties of comet nuclei. The coma morphology and/or composition were investigated for 12 comets belonging to different dynamical classes. The data analysis showed that the coma morphology of three non-periodic comets is not consistent with the general assumption that dynamically new comets still have a relatively uniform nucleus surface and therefore do not exhibit gas and/or dust jets in their coma. The determination of carbon and nitrogen isotopic ratios revealed the same values for all comets investigated at various heliocentric distances. However, the relative abundance of the rare nitrogen isotope 15N is about twice as high as in the Earth's atmosphere. Observations of comets at splitting events and during outbursts led to indications for differences between material from the nucleus surface and the interior. The monitoring of the induced outburst of 9P/Temple revealed that under non-steady state conditions the fast disintegration of species is detectable.

  1. Microphysical controls on the isotopic composition of wintertime orographic precipitation

    Science.gov (United States)

    Moore, M.; Blossey, P. N.; Muhlbauer, A.; Kuang, Z.

    2016-06-01

    The sensitivity of mixed-phase orographic clouds, precipitation, and their isotopic content to changes in dynamics, thermodynamics, and microphysics is explored in idealized two-dimensional flow over a mountain barrier. These simulations use the Weather Research and Forecasting (WRF) model with stable water isotopologues (HDO and H218O), which have been integrated into the Thompson microphysics scheme within WRF as part of the present project. In order to understand how the isotopic composition of precipitation (δ18Oprecip) is fixed, the mountain height, temperature, and the prescribed cloud droplet number concentration (CDNC) have been varied in a series of simulations. For the given range of values explored in this work, changes in mountain height and temperature induce stronger responses in domain-averaged δ18Oprecip than do changes in CDNC by a factor of approximately 10. The strongest response to changing CDNC leads to local variations of δ18Oprecip of about 3‰, though those occur in regions of weak precipitation (cloud liquid and vapor deposition onto snow, the leading sources of precipitation in these simulations. The changes in δ18Oprecip with mountain height, temperature, and CDNC are governed in part by the microphysical pathways through which precipitating hydrometeors are formed and grow.

  2. Relation between isotopic composition of precipitation and atmospheric circulation patterns

    Science.gov (United States)

    Brenčič, Mihael; Kononova, Nina K.; Vreča, Polona

    2015-10-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. Mathematical model based on the linear combination of δ2H and δ18O values and on precipitation amount weighted average related to elementary air circulation mechanisms - ECM is proposed. The model enables estimation of average δ2H and δ18O values and their standard deviation for the precipitation generated at distinctive atmospheric circulation patterns. Approach in which atmospheric circulation patterns were classified as ECM based on the Dzerdzeevskii classification was applied. Application of the model is illustrated on the long term precipitation record from Ljubljana GNIP station Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Further applications of the proposed model enable new insight into the understanding of isotopes spatial and temporal distribution in precipitation important also for better understanding of climate proxies.

  3. Lithium isotope fractionation in the Ganges-Brahmaputra floodplain and implications for groundwater impact on seawater isotopic composition

    Science.gov (United States)

    Bagard, Marie-Laure; West, A. Joshua; Newman, Karla; Basu, Asish R.

    2015-12-01

    Lithium isotopes are a promising proxy for reconstructing past weathering processes, but unraveling the seawater record requires a comprehensive understanding of the magnitude and isotopic composition of Li fluxes to the oceans, and of how these change over time. Little information is available on the role of floodplain sediments and groundwater systems in setting the Li isotope signature of the dissolved flux delivered from the continents to the oceans. Here we investigate the Li dissolved fluxes of river waters and groundwaters in the Ganges-Brahmaputra floodplain. The data suggest that a maximum of 3.1 ×108 and 1.5 ×108 moles Li/yr are carried to the Bay of Bengal by Ganges-Brahmaputra rivers and groundwaters, respectively. The riverine flux has a significantly heavier Li isotope composition (average δ7Li: 26‰) than the groundwater flux (average δ7Li: 16‰) and increases downstream across the floodplain. δ7Li in both river waters and shallow groundwater can be explained by Li scavenging by Quaternary floodplain sediments following a Rayleigh fractionation process, with preferential removal of 6Li. On the other hand, deep groundwaters (>40 m) contributing to submarine groundwater discharge to the Bay of Bengal are enriched in 6Li at depth, likely due to the dissolution of floodplain sediments releasing Li with a light isotope composition. Similarly low δ7Li has been reported in other large sedimentary aquifers. The deep groundwater values are close to the average isotope composition of the global Li inputs to the ocean (∼15‰), so groundwater submarine discharge has only a minor influence on the assessment of the modern Li isotope budget of the ocean. Our analysis further suggests that groundwater discharge of Li has probably played at most a small and secondary role in past changes in the isotope composition of the total continental flux of Li to the ocean.

  4. Producing Ti–6Al–4V/TiC composite with superior properties by adding boron and thermo-mechanical processing

    International Nuclear Information System (INIS)

    In order to study the effect of boron addition on the microstructure and tensile properties of titanium matrix composites, two Ti–6Al–4V/10 Vol% TiC ingots with and without boron were fabricated by VIM furnace and hot rolling. The microstructures of composites were examined using optical microscopy (OM). The X-ray diffraction (XRD) was used to identify the phases present in the composites. Addition of boron resulted in the formation of needle shaped TiB in the matrix that was followed by the refinement of grain size. Compared with Ti–6Al–4V/TiC composite, the composite containing boron content exhibited a significantly higher ductility and lower strength. It was caused by the effects of boron element on reducing TiC particle size and solubility of carbon in alpha matrix. According to the results obtained in this study, the hybrid effect of TiC and TiB plays an important role in the mechanical properties, especially ductility of titanium matrix composites (TMCs). Finally, we have produced TMCs strip with excellent ductility (9% elongation and 18% reduction area) and good strength (∼1240 MPa)

  5. Baseline shifts in coral skeletal oxygen isotopic composition: a signature of symbiont shuffling?

    Science.gov (United States)

    Carilli, J. E.; Charles, C. D.; Garren, M.; McField, M.; Norris, R. D.

    2013-06-01

    Decades-long records of the stable isotopic composition of coral skeletal cores were analyzed from four sites on the Mesoamerican Reef. Two of the sites exhibited baseline shifts in oxygen isotopic composition after known coral bleaching events. Changes in pH at the calcification site caused by a change in the associated symbiont community are invoked to explain the observed shift in the isotopic composition. To test the hypothesis that changes in symbiont clade could affect skeletal chemistry, additional coral samples were collected from Belize for paired Symbiodinium identification and skeletal stable isotopic analysis. We found some evidence that skeletal stable isotopic composition may be affected by symbiont clade and suggest this is an important topic for future investigation. If different Symbiodinium clades leave consistent signatures in skeletal geochemical composition, the signature will provide a method to quantify past symbiont shuffling events, important for understanding how corals are likely to respond to climate change.

  6. Geochemical and Isotopic Composition of Aerosols in Tucson

    Science.gov (United States)

    Riha, K. M.; Michalski, G. M.; Lohse, K. A.; Gallo, E. L.; Brooks, P. D.; Meixner, T.

    2010-12-01

    isotopic analyses have been conducted on these samples using the denitrifier method (Casciotti et al., 2002). Observed elevated δ18O values correspond to atmospheric oxidation processes and varying δ15N are possibly linked to different N sources. These isotopic values will be used as a proxy for deposition in a mass balance mixing model for nitrogen in arid streams. References: Casciotti, K. L., D. M. Sigman, M. G. Hastings, J. K. Böhlke and A. Hilkert, Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method, Anal. Chem., 74(19), 4905-4912, 2002. Michalski, G., Z. Scott, M. Kabiling and M. Thiemens, First Measurements and Modeling of Δ17O in Atmospheric Nitrate, Geophys. Res. Lett., 30(16), (1870), 2003.

  7. Investigation on the Effects of Titanium Diboride Particle Size on Radiation Shielding Properties of Titanium Diboride Reinforced Boron Carbide-Silicon Carbide Composites

    Directory of Open Access Journals (Sweden)

    A.O. Addemir

    2012-03-01

    Full Text Available Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion power plants. Titanium diboride reinforced boron carbide-silicon carbide composites which were produced from different titanium diboride particle sizes and ratios were studied for searching of the behaviour against the gamma ray. Cs-137 gamma radioisotope was used as gamma source in the experiments which has a single gamma-peak at 0.662 MeV. Gamma transmission technique was used for the measurements. The effects of titanium diboride particle size on radiation attenuation of titanium diboride reinforced boron carbide-silicon carbide composites were evaluated in related with gamma transmission and the results of the experiments were interpreted and compared with each other. Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion power plants. Titanium diboride reinforced boron carbide-silicon carbide composites which were produced from different titanium diboride particle sizes and ratios were studied for searching of the behaviour against the gamma ray. Cs-137 gamma radioisotope was used as gamma source in the experiments which has a single gamma-peak at 0.662 MeV. Gamma transmission technique was used for the measurements. The effects of titanium diboride particle size on radiation attenuation of titanium diboride reinforced boron carbide-silicon carbide composites were evaluated in related with gamma transmission and the results of the experiments were interpreted and compared with each other. Composite materials have wide application areas in industry. Boron Carbide is an important material for nuclear technology. Silicon carbide is a candidate material in the first wall and blankets of fusion

  8. New insights on Saturn's formation from its nitrogen isotopic composition

    CERN Document Server

    Mousis, Olivier; Fletcher, Leigh N; Mandt, Kathleen E; Ali-Dib, Mohamad; Gautier, Daniel; Atreya, Sushil

    2014-01-01

    The recent derivation of a lower limit for the $^{14}$N/$^{15}$N ratio in Saturn's ammonia, which is found to be consistent with the Jovian value, prompted us to revise models of Saturn's formation using as constraints the supersolar abundances of heavy elements measured in its atmosphere. Here we find that it is possible to account for both Saturn's chemical and isotopic compositions if one assumes the formation of its building blocks at $\\sim$45 K in the protosolar nebula, provided that the O abundance was $\\sim$2.6 times protosolar in its feeding zone. To do so, we used a statistical thermodynamic model to investigate the composition of the clathrate phase that formed during the cooling of the protosolar nebula and from which the building blocks of Saturn were agglomerated. We find that Saturn's O/H is at least $\\sim$34.9 times protosolar and that the corresponding mass of heavy elements ($\\sim$43.1 \\Mearth) is within the range predicted by semi-convective interior models.

  9. Analytical developments in the measurements of boron, nitrate, phosphate and sulphate isotopes and case examples of discrimination of nitrogen and sulphur sources in pollution studies

    International Nuclear Information System (INIS)

    Methods are documented for the analysis of B isotopes, O and N isotopes in nitrates. B isotopes can be measured by negative ion thermal ionisation mass spectrometry. Nitrate is recovered from groundwaters by ion exchange and the resulting silver nitrate combusted for stable isotope gas analysis. Oxygen isotope analysis of phosphates can be determined by generating and analysing CO2 gas from the combustion of silver phosphate produced from aqueous samples. Sulphate in ground and surface waters can be separated and concentrated by ion exchange and precipitated as barium sulphate. This is reacted with graphite to yield CO2 and CO, the latter being spark discharged to CO2 and the total CO2 measured for oxygen isotope analysis. Barium sulphide from this reaction is converted to silver sulphide which is reacted with cuprous oxide to give SO2 gas for sulphur isotope measurements. A case study of the semi-rural Manakau area in New Zealand was conducted to see if nitrate isotopes could be used to detect the source of nitrate contamination (groundwater nitrate -3-N). Nitrogen isotope (+4 to +12 per mille) coupled with oxygen isotope measurements (+5 to +9 per mille) demonstrated that the nitrogen is not sources from fertilisers but from some combination of septic tank and animal waste. For the case study of sulphate isotope use, sulphur and oxygen isotopic compositions of sulphate in river and lake water from seven major catchments of New Zealand were determined. The isotope analyses have allowed the distinction between natural (geological, geothermal and volcanic) and anthropogenic (fertiliser) sulphur sources. (author)

  10. Isotopic composition of atmospheric CO2 inferred from carbon in C4 plant cellulose

    International Nuclear Information System (INIS)

    The isotopic composition of atmospheric carbon dioxide provides an important constraint for models of the global carbon cycle. It is shown that carbon in C4 plants preserves an isotopic record of the CO2 used in photosynthesis. Data for the maize plant Zea mays yield results for the isotopic composition of atmospheric CO2 consistent with measurements of modern air and air trapped in polar ice. Data from C4 plants may thus be used to extend the isotopic record of atmospheric CO2 into the past, complementing data from other sources. (author)

  11. Light element isotopic compositions of cometary matter returned by the STARDUST mission

    Energy Technology Data Exchange (ETDEWEB)

    McKeegan, K D; Aleon, J; Bradley, J; Brownlee, D; Busemann, H; Butterworth, A; Chaussidon, M; Fallon, S; Floss, C; Gilmour, J; Gounelle, M; Graham, G; Guan, Y; Heck, P R; Hoppe, P; Hutcheon, I D; Huth, J; Ishii, H; Ito, M; Jacobsen, S B; Kearsley, A; Leshin, L A; Liu, M; Lyon, I; Marhas, K; Marty, B; Matrajt, G; Meibom, A; Messenger, S; Mostefaoui, S; Nakamura-Messenger, K; Nittler, L; Palma, R; Pepin, R O; Papanastassiou, D A; Robert, F; Schlutter, D; Snead, C J; Stadermann, F J; Stroud, R; Tsou, P; Westphal, A; Young, E D; Ziegler, K; Zimmermann, L; Zinner, E

    2006-10-10

    Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild2 particle fragments, however extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Non-terrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is {sup 16}O-enriched like refractory inclusions in meteorites, suggesting formation in the hot inner solar nebula and large-scale radial transport prior to comet accretion in the outer solar system.

  12. Nutritional assessment by isotope dilution analysis of body composition

    International Nuclear Information System (INIS)

    The three components of body mass, body cell mass (BCM), extracellular fluid (ECF), and fat + extracellular solids (ECS: bone, tendon, etc) can be quantified using established isotope dilution techniques. With these techniques, total body water (TBW) and ECF are measured using 3H2O and 82Bromine, respectively, as tracers. BCM is calculated from intracellular fluid (ICF) where ICF . TBW - ECF. Fat + ECS is estimated as: body weight - (BCM + ECF). TBW and ECF can be determined by either of two calculation methods, one requiring several timed plasma samples (extrapolation method) and one requiring a single plasma sample and a 4-h urine collection (urine-corrected method). The comparability of the two calculation methods was evaluated in 20 studies in 12 bone marrow transplant recipients. We found that for determination of TBW and ECF there was a very strong linear relationship (r2 greater than 0.98) between the calculation methods. Further comparisons (by t test, 2-sided) indicated that for the determination of ECF, the methods were not significantly (p greater than 0.90) different; however, TBW determined by the urine-corrected method was slightly (0.1 to 6%), but significantly (p less than 0.01) greater than that determined by the extrapolation method. Therefore, relative to the extrapolation method, the urine-corrected method ''over-estimates'' BCM and ''under-estimates'' fat + ECS since determination of these compartment sizes depends on measurement of TBW. We currently use serial isotope dilution studies to monitor the body composition changes of patients receiving therapeutic nutritional support

  13. Photons transport through ultra-high molecular weight polyethylene based composite containing tungsten and boron carbide fillers

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, S.M. [National Research Center “Kurchatov Institute”, Moscow 123182 (Russian Federation); Kuznetsov, S.A. [Russian State Technological University “MATI”, Moscow 121552 (Russian Federation); Volkov, A.E.; Terekhin, P.N.; Dmitriev, S.V. [National Research Center “Kurchatov Institute”, Moscow 123182 (Russian Federation); Tcherdyntsev, V.V.; Gorshenkov, M.V. [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Boykov, A.A., E-mail: kink03@gmail.com [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation)

    2014-02-15

    Highlights: • The developed method for predicting X-ray properties of the polymer. • Higher content of the fillers results in an increase of mechanical properties. • X-ray defensive properties of the samples were investigated experimentally. -- Abstract: Polymers are a base for creating of composite materials with high mechanical and chemical properties. Using the heavy metals as filler in these composites can give them X-ray protective properties. These materials have high deactivation rates and can be used to create Personal Protective Equipment (PPE) used in aggressive environments. It was proposed a model for calculation of X-ray protection properties of the polymer-based nanocomposite materials with ultra-high molecular weight polyethylene (UHMWPE) matrix, filled with tungsten and boron carbide particles. X-ray protective properties were calculated in a wide range of filler content using the developed model. Results of calculations allow selecting most effective compounds of X-ray protective UHMWPE based composites.

  14. Quantitative phase analysis of cubic boron nitride based composites by X-ray absorption near edge structure

    Energy Technology Data Exchange (ETDEWEB)

    Piskorska, Edyta [Institute of Physics Polish Academy of Science, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)], E-mail: pisko@ifpan.edu.pl; Lawniczak-Jablonska, Krystyna [Institute of Physics Polish Academy of Science, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)], E-mail: jablo@ifpan.edu.pl; Minikayev, Roman [Institute of Physics Polish Academy of Science, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)], E-mail: minik@ifpan.edu.pl; Wolska, Anna [Institute of Physics Polish Academy of Science, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)], E-mail: wolska@ifpan.edu.pl; Paszkowicz, Wojciech [Institute of Physics Polish Academy of Science, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)], E-mail: paszk@ifpan.edu.pl; Klimczyk, Piotr [Institute of Metal Cutting, Wroclawska 37A Str., 30-011 Cracow (Poland)], E-mail: Piotr.Klimczyk@ios.krakow.pl; Benko, Ewa [Institute of Metal Cutting, Wroclawska 37A Str., 30-011 Cracow (Poland)

    2007-05-15

    X-ray absorption near edge structure (XANES) spectra of Ti, Si, B and N K-edges were investigated to determine the phase composition of multicompounds cubic boron nitride (cBN) based composites formed by reaction of cBN with Ti{sub 3}SiC{sub 2} ceramics. Knowing that the shape of XANES spectra is a fingerprint of chemical bonding of the element in compound, a linear combination of XANES spectra of reference compounds (phases) was fitted to the spectra of the composites. This procedure permitted to determine the fraction of the componential phases in studied materials. X-ray Diffraction (XRD) analysis confirmed the presence of compounds detected by XANES analysis. The similarities and differences between XANES and XRD results are discussed. The combination of XANES and XRD techniques allowed to estimate the quantity of presented compounds within the limits of sensitivity of each method.

  15. Boron nitride nanotube reinforced polylactide-polycaprolactone copolymer composite: mechanical properties and cytocompatibility with osteoblasts and macrophages in vitro.

    Science.gov (United States)

    Lahiri, Debrupa; Rouzaud, Francois; Richard, Tanisha; Keshri, Anup K; Bakshi, Srinivasa R; Kos, Lidia; Agarwal, Arvind

    2010-09-01

    Biodegradable polylactide-polycaprolactone copolymer (PLC) has been reinforced with 0, 2 and 5wt.% boron nitride nanotubes (BNNTs) for orthopedic scaffold application. Elastic modulus of the PLC-5wt.% BNNT composite, evaluated through nanoindentation technique, shows a 1370% increase. The same amount of BNNT addition to PLC enhances the tensile strength by 109%, without any adverse effect on the ductility up to 240% elongation. Interactions of the osteoblasts and macrophages with bare BNNTs prove them to be non-cytotoxic. PLC-BNNT composites displayed increased osteoblast cell viability as compared to the PLC matrix. The addition of BNNTs also resulted in an increase in the expression levels of the Runx2 gene, the main regulator of osteoblast differentiation. These results indicate that BNNT is a potential reinforcement for composites for orthopedic applications. PMID:20226282

  16. Reassessing the stable isotope composition assigned to methane flux from natural wetlands in isotope-constrained budgets

    Science.gov (United States)

    Hornibrook, Edward; Maxfield, Peter; Gauci, Vincent; Stott, Andrew

    2013-04-01

    Stable isotope ratios in CH4 preserve information about its origin and history, and are commonly used to constrain global CH4 budgets. Wetlands are key contributors to the atmospheric burden of CH4 and typically are assigned a stable carbon isotope composition of ~-60 permil in isotope-weighted stable isotope models despite the considerable range of δ13C(CH4) values (~ -100 to -40 permil) known to occur in these diverse ecosystems. Kinetic isotope effects (KIEs) associated with the metabolism of CH4-producing microorganisms generate much of the natural variation but highly negative and positive δ13C(CH4) values generally result from secondary processes (e.g., diffusive transport or oxidation by soil methanotrophs). Despite these complexities, consistent patterns exist in the isotope composition of wetland CH4 that can be linked conclusively to trophic status and consequently, natural succession or human perturbations that impact nutrient levels. Another challenge for accurate representation of wetlands in carbon cycle models is parameterisation of sporadic CH4 emission events. Abrupt release of large volumes of CH4-rich bubbles in short periods of time can account for a significant proportion of the annual CH4 flux from a wetland but such events are difficult to detect using conventional methods. New infrared spectroscopy techniques capable of high temporal resolution measurements of CH4 concentration and stable isotope composition can readily quantify short-lived CH4 pulses. Moreover, the isotope data can be used conclusively to determine shifts in the mode of CH4 transport and provide the potential to link initiation of abrupt emission events to forcing by internal or external factors.

  17. A continuous flow isotope ratio mass spectrometry method for high precision determination of dissolved gas ratios and isotopic composition

    DEFF Research Database (Denmark)

    Charoenpong, C. N.; Bristow, L. A.; Altabet, M. A.

    2014-01-01

    Dissolved gas ratios and isotopic compositions provide essential information about the biological and physical mechanisms influencing N-2, O-2, and Ar in aquatic systems. Current methods available are either limited by overall cost, labor-intensive sample collection and analysis, or insufficient...... precision. Here, we present a new highly accurate and robust method for sample collection and subsequent simultaneous measurement of the dissolved gas ratios (N-2/Ar and O-2/Ar) and isotopic compositions (delta N-15(2) and delta O-18(2)) in seawater. The relatively simple sampling procedure using low cost...

  18. Modelling and interpreting the isotopic composition of water vapour in convective updrafts

    Directory of Open Access Journals (Sweden)

    M. Bolot

    2013-08-01

    Full Text Available The isotopic compositions of water vapour and its condensates have long been used as tracers of the global hydrological cycle, but may also be useful for understanding processes within individual convective clouds. We review here the representation of processes that alter water isotopic compositions during processing of air in convective updrafts and present a unified model for water vapour isotopic evolution within undiluted deep convective cores, with a special focus on the out-of-equilibrium conditions of mixed-phase zones where metastable liquid water and ice coexist. We use our model to show that a combination of water isotopologue measurements can constrain critical convective parameters, including degree of supersaturation, supercooled water content and glaciation temperature. Important isotopic processes in updrafts include kinetic effects that are a consequence of diffusive growth or decay of cloud particles within a supersaturated or subsaturated environment; isotopic re-equilibration between vapour and supercooled droplets, which buffers isotopic distillation; and differing mechanisms of glaciation (droplet freezing vs. the Wegener–Bergeron–Findeisen process. As all of these processes are related to updraft strength, particle size distribution and the retention of supercooled water, isotopic measurements can serve as a probe of in-cloud conditions of importance to convective processes. We study the sensitivity of the profile of water vapour isotopic composition to differing model assumptions and show how measurements of isotopic composition at cloud base and cloud top alone may be sufficient to retrieve key cloud parameters.

  19. Towards an understanding of deep boron: study of type IIb blue diamonds

    Science.gov (United States)

    Gaillou, E.; Rost, D.; Post, J. E.; Butler, J. E.

    2012-12-01

    diamonds, which was confirmed by mapping active boron using synchrotron FTIR. ToF-SIMS gives the spectrum of all the masses at once, so both 11B and 10B were detected. However, the counts on 10B were too low at the counting time we used (several hours) to provide significant δ11B measurements. We observed that there is not a strong correlation between the amount of boron and the color intensity in type IIb diamonds (Gaillou et al., 2012). However, the deep-blue colored diamonds are always associated with a "high" boron content, and therefore, future attempted measurements of boron isotopic ratios should be conducted on deep blue (and unfortunately, valuable) diamonds, using either a much longer counting time, or a different ion mass spectrometer (with different standards), that would consume more material. This study shows that the range of boron concentration, even if in the lower range of instrument detectability, should soon be able to provide boron isotopic measurements, and perhaps gives insights into the origin of boron in diamonds, e.g. from a subducted slab and/or from primitive mantle reservoir. Chaussidon M., Marty B. (1995) Primitive boron isotope composition of the mantle, Science, 269, 383-386. Gaillou E., Rost D., Post J.E., Butler J.E. (2012) Boron in natural type IIb blue diamonds: chemical and spectroscopic measurements. Am. Min., 1, 1-18.

  20. The stable isotope composition of vanadium, nickel, and molybdenum in crude oils

    International Nuclear Information System (INIS)

    Highlights: • First precise stable isotope measurements of V, Ni and Mo in crude oils. • First order constraints are placed on the magnitude of isotope variability. • Isotope compositions are unaffected by generation, expulsion, and migration. • V and Ni stable isotope compositions are likely source dependent. • V, Ni, and Mo isotope compositions are likely affected by paleoredox chemistry. - Abstract: Crude oils often have high concentrations of transition metals including vanadium (V), nickel (Ni), iron (Fe), and to a lesser extent molybdenum (Mo). Determining the conditions under which these metals enter into crude oil is of interest for the understanding of biogeochemical cycles and the pathways leading to oil formation. This study presents the first high precision measurements of V, Ni, and Mo stable isotopes determined for a set of globally distributed crude oils as a first examination of the magnitude of potential stable isotope fractionation. Vanadium stable isotope compositions are presented for crude oils formed from different source rocks spanning a range of geologic ages (Paleozoic–Tertiary) and are complemented by Ni and Mo stable isotope compositions on a subset of crude oils produced from lacustrine source rocks in the Campos Basin, Brazil. The crude oils span a wide range of V and Mo isotope compositions, and display more restricted Ni stable isotope signatures. Overall, the stable isotope composition of all three systems overlaps with previously determined values for igneous and inorganic sedimentary materials. Comparisons between vanadium concentration and stable isotope composition yield distinct clusters associated with crude oils predominantly derived from terrestrial/lacustrine or marine/carbonate source rocks. The Ni stable isotope signatures of studied crude oils are similar to that of carbonaceous shales. The Mo stable isotope signatures of the lacustrine sourced crude oils are similar to what is observed for rivers. This

  1. Standard specification for nuclear-grade aluminum oxide-boron carbide composite pellets

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This specification applies to pellets composed of mixtures of aluminum oxide and boron carbide that may be ultimately used in a reactor core, for example, in neutron absorber rods. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

  2. Chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    1981-01-01

    The standard covers analytical procedures to determine compliance of nuclear-grade boron carbide powder and pellets to specifications. The following methods are described in detail: total carbon by combustion and gravimetry; total boron by titrimetry; isotopic composition by mass spectrometry; chloride and fluoride separation by pyrohydrolysis; chloride by constant-current coulometry; fluoride by ion-selective electrode; water by constant-voltage coulometry; impurities by spectrochemical analysis; soluble boron by titrimetry; soluble carbon by a manometric measurement; metallic impurities by a direct reader spectrometric method. (JMT)

  3. Investigating the Source, Transport, and Isotope Composition of Water in the Atmospheric Boundary Layer

    Science.gov (United States)

    Griffis, T. J.; Schultz, N. M.; Lee, X.

    2011-12-01

    The isotope composition of water (liquid and vapor phases) can provide important insights regarding the source of water used by plants, the origins of atmospheric water vapor, and the sources of carbon dioxide. In recent years there have been significant advances in the ability to quantify the isotope composition of water and water vapor using optical isotope techniques. We have used and helped develop some of these techniques to determine the isotope composition of soil and plant waters, to measure the isoflux of water vapor between the land surface and atmosphere, and to examine the isotope composition of water vapor and deuterium excess in the atmospheric boundary layer. In this presentation we will discuss three related issues: 1) Identification and correction of spectral contamination in soil and plant water samples using optical techniques; 2) The benefits and practical limitations of quantifying the isotope composition of evapotranspiration using the eddy covariance approach; and 3) The scientific value and feasibility of tracking the long-term (seasonal and interannual) behavior of the isotope composition of water vapor and deuterium excess in the atmospheric boundary layer. A few short stories will be provided from experiments conducted in the lab, at the field scale, and from a very tall tower at the University of Minnesota from 2008 to 2011.

  4. Oxygen isotopic composition and U-Pb discordance in zircon

    Science.gov (United States)

    Booth, A.L.; Kolodny, Y.; Chamberlain, C.P.; McWilliams, M.; Schmitt, A.K.; Wooden, J.

    2005-01-01

    We have investigated U-Pb discordance and oxygen isotopic composition of zircon using high-spatial resolution ??18O measurement by ion microprobe. ??18O in both concordant and discordant zircon grains provides an indication of the relationship between fluid interaction and discordance. Our results suggest that three characteristics of zircon are interrelated: (1) U-Pb systematics and concomitant age discordance, (2) ??18O and the water-rock interactions implied therein, and (3) zircon texture, as revealed by cathodoluminescence and BSE imaging. A key observation is that U-Pb-disturbed zircons are often also variably depleted in 18O, but the relationship between discordance and ??18O is not systematic. ??18O values of discordant zircons are generally lighter but irregular in their distribution. Textural differences between zircon grains can be correlated with both U-Pb discordance and ??18O. Discordant grains exhibit either a recrystallized, fractured, or strongly zoned CL texture, and are characteristic of 18O depletion. We interpret this to be a result of metamictization, leading to destruction of the zircon lattice and an increased susceptibility to lead loss. Conversely, grains that are concordant have less-expressed zoning and a smoother CL texture and are enriched in 18O. From this it is apparent that various stages of water-rock interaction, as evidenced by systematic variations in ??18O, leave their imprint on both the texture and U-Pb systematics of zircon. Copyright ?? 2005 Elsevier Ltd.

  5. Performance of diffusive gradients in thin films for measurement of the isotopic composition of soluble Zn

    International Nuclear Information System (INIS)

    The application of diffusive gradients in thin films (DGT) samplers for measurements of the isotopic composition of soluble Zn by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) was tested under laboratory conditions. The effect of diffusion in hydrogels as a possible source of fractionation was investigated by measuring Zn isotope ratios for different fractions of Zn accumulated by DGT and comparing with the bulk isotope composition of the solution. An important finding of this study is that, provided quantitative elution is obtained, no fractionation of Zn isotopes due to the diffusion process is detectable within the reported precision of MC-ICPMS measurements. Consequently, DGT samplers are suitable for studies of the Zn isotopic composition in natural waters

  6. Hydrogen and oxygen in brine shrimp chitin reflect environmental water and dietary isotopic composition

    Science.gov (United States)

    Nielson, Kristine E.; Bowen, Gabriel J.

    2010-03-01

    Hydrogen and oxygen isotope ratios of the common structural biopolymer chitin are a potential recorder of ecological and environmental information, but our understanding of the mechanisms of incorporation of H and O from environmental substrates into chitin is limited. We report the results of a set of experiments in which the isotopic compositions of environmental water and diet were varied independently in order to assess the contribution of these variables to the H and O isotopic composition of Artemia franciscana chitin. Hydrogen isotope ratios of chitin were strongly linearly correlated with both food and water, with approximately 26% of the hydrogen signal reflecting food and approximately 38% reflecting water. Oxygen isotopes were also strongly correlated with the isotopic composition of water and food, but whereas 69% of oxygen in chitin exchanged with environmental water, only 10% was derived from food. We propose that these observations reflect the position-specific, partial exchange of H and O atoms with brine shrimp body water during the processes of digestion and chitin biosynthesis. Comparison of culture experiments with a set of natural samples collected from the Great Salt Lake, UT in 2006 shows that, with some exceptions, oxygen isotope compositions of chitin track those of water, whereas hydrogen isotopes vary inversely with those of lake water. The different behavior of the two isotopic systems can be explained in terms of a dietary shift from allochthonous particulate matter with relatively higher δ 2H values in the early spring to autochthonous particulate matter with significantly lower δ 2H values in the late summer to autumn. These results suggest oxygen in chitin may be a valuable proxy for the oxygen isotopic composition of environmental water, whereas hydrogen isotope values from the same molecule may reveal ecological and biogeochemical changes within lakes.

  7. Molecular Paleohydrology: Interpreting the Hydrogen- Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms

    NARCIS (Netherlands)

    Sachse, D.; Billault, I.; Bowen, G.J.; Chikaraishi, Y.; Dawson, T.E.; Feakins, S.J.; Freeman, Katherine; Magill, C.R.; McInerney, F.A.; van der Meer, M.T.J.; Polissar, P.; Robins, R.J.; Sachs, J.P.; Schmidt, H.L.; Sessions, A.L.; White, J.W.C.; West, J.B.; Kahmen, A.

    2012-01-01

    Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and te

  8. Isotopic composition of rainfall and runoff in a small arid basin with implications for deep percolation

    International Nuclear Information System (INIS)

    The aim of this work was to characterize the isotopic composition of potential recharge in an arid rocky watershed. Unique field observations were obtained from an arid watershed in the Negev Highlands, Israel, through utilization of the dynamic variations in the isotopic composition of rainfall and runoff. The hydrological system's inputs are rainfall and its isotopic composition. Rainfall and runoff were sampled in eight storms. High variability in the isotopic composition of rainfall was observed during any single rainstorm. The isotopic distribution in the runoff at the outlet of the basin appeared often not to be correlated to the isotopic patterns of the associated rain storm. A new mathematical model was developed to describe these physical processes. The model called A Double-Component Kinematic Wave Flow and Transport Approach, was designated to assess the dynamic isotopic distribution in arid rain storms and runoff. This model simulates the transport of rainfall into overland flow and runoff in an arid rocky watershed with uniformly distributed shallow depression storage. A numerical solution for the problem was developed, to estimate the depression storage parameters. The model also reflects the isotopic memory effect due to the depression storage between sequential rain showers. A good agreement between the observed and computed hydrograph and the change of the δ18O values in runoff in time confirms the validity of the model. (author) 138 figs., 125 refs

  9. Control factors of chemical and isotopic composition of groundwater in Varadero- Cardenas region, Matanzas, Cuba

    International Nuclear Information System (INIS)

    Multivariate analysis was performed to isotopic and chemical composition of groundwater from the karstic aquifer of Varadero- Cardenas in order to define those factor controlling or influencing its variations in time and space. The research was part of a project sponsored by International of Atomic Energy aimed to improve aquifer management applying isotopic techniques

  10. Thermally activated reactions of boron nitride nanotubes with C60 fullerene: a Raman study of boron nitride-carbon nanotube composites

    International Nuclear Information System (INIS)

    Full text: Boron nitride nanotubes (BNNT) are topological analogues to single wall carbon nanotubes (SWCNT). LiKEX the latter one expects that boron nitride nanotubes can be filled with fullerenes to maKEX BN-carbon peapods. This opens new possibilities of generating nanostructures with interesting physical properties. BNNTs were first heat treated in air to open the ends and to remove excess boron particles. We analysed and refined the filling process for SWCNTs and applied it to the BNNTs. For the carbon system critical conditions were determined for opening of tube ends. Filling with C60 fullerene via vapour phase was applied. Subsequently high temperature treatment was performed to transform the fullerenes in a carbon nanotube. We performed multi-frequency Raman spectroscopy to follow the process. Some spectral features of the reaction product in the low frequency range may be assigned to small diameter carbon nanotubes inside the boron nitride nanotubes. (author)

  11. Determination of plutonium traces isotopic composition by thermal ionization mass spectrometry

    International Nuclear Information System (INIS)

    Plutonium isotopic composition has been determined by thermal ionization mass spectrometry. An ion counting detector has been used. It allows to noticeably reduce the sample quantity to use. The accuracy of the obtained measures are very good

  12. Usage of burnt fuel isotopic compositions from engineering codes in Monte-Carlo code calculations

    Energy Technology Data Exchange (ETDEWEB)

    Aleshin, Sergey S.; Gorodkov, Sergey S.; Shcherenko, Anna I. [Nuclear Research Centre ' ' Kurchatov Institute' ' , Moscow (Russian Federation)

    2015-09-15

    A burn-up calculation of VVER's cores by Monte-Carlo code is complex process and requires large computational costs. This fact makes Monte-Carlo codes usage complicated for project and operating calculations. Previously prepared isotopic compositions are proposed to use for the Monte-Carlo code (MCU) calculations of different states of VVER's core with burnt fuel. Isotopic compositions are proposed to calculate by an approximation method. The approximation method is based on usage of a spectral functionality and reference isotopic compositions, that are calculated by engineering codes (TVS-M, PERMAK-A). The multiplication factors and power distributions of FA and VVER with infinite height are calculated in this work by the Monte-Carlo code MCU using earlier prepared isotopic compositions. The MCU calculation data were compared with the data which were obtained by engineering codes.

  13. Correlated modal mineralogy, aqueous alteration and oxygen isotope composition of CM Chondrites

    OpenAIRE

    Howard, K. T.; Benedix, G. K.; Bland, P. A.; Greenwood, R. C.; I. Franchi; Cressy, G.

    2010-01-01

    In this study we move beyond defining alteration sequences in CM chondrites towards understanding the relationship between modal mineralogy, the extent of aqueous alteration and O-isotope compositions.

  14. The IAEA programme on the acquisition of data for the fallout isotopic composition

    International Nuclear Information System (INIS)

    The IAEA, in collaboration with the World Meteorogical Organization, has been working since 1961 on a long-term project for acquistion, processing and publication of data for the isotopic composition (T,D, 180) of the fallout on a global scale. At present, IAEA has data, compiled from 347 hydrometeorogical stations in 79 countries. The analysis of isotope data, obtained from the global station network for more than 20 years, allows the following conclusions: (i)The global trends of forming the isotope composition of atmospheric fallout, which are one of the maior links of the hydrogeological cycle, are clarified; (ii)These regularities enabled the use of hydrogen and oxygen isotopes in scientific research and the practice; (iii)Extensive studies of the resourses of surface and ground water and of their genesis and dynamics have been carried out, using the fallout isotopic composition as an input function; (iv)The effectiveness of further efforts in isotope composition data acquisition is limited by the lack of analyses using models of the global atmospheric circulation; (v)Further regular observations of the variations in fallout isotope composition are needed for some large regions of Eurasia, Africa and the polar region

  15. Carbon and hydrogen isotopic composition and generation pathway of biogenic gas in China

    Institute of Scientific and Technical Information of China (English)

    SHEN Ping; WANG Xiaofeng; XU Yin; SHI Baoguang; XU Yongchang

    2009-01-01

    The carbon and hydrogen isotopic composition of biogenic gas is of great importance for the study of its generation pathway and reservoiring characteristics. In this paper, the formation pathways and reservoiring characteristics of biogenic gas reservoirs in China are described in terms of the carbon and hydrogen isotopic compositions of 31 gas samples from 10 biogenic gas reservoirs. The study shows that the hydrogen isotopic compositions of these biogenic gas reservoirs can be divided into three intervals:δDCH4>-200‰,-250‰<δDCH4<-200‰ and δDCH4<-250‰. The forerunners believed that the main generation pathway of biogenic gas under the condition of continental fresh water is acetic fermentation. Our research results showed that the generation pathway of biogenic gas under the condition of marine facies is typical CO2- reduction, the biogenic gas has heavy hydrogen isotopic composition: its δDCH4 values are higher than -200‰; that the biogenic gas under the condition of continental facies also was generated by the same way, but its hydrogen isotopic composition is lighter than that of biogenetic gas generated under typical marine facies condition: -250‰<δDCH4<-200‰, the δDCH4 values may be related to the salinity of the water medium in ancient lakes. From the relevant data of the Qaidam Basin, it can be seen that the hydrogen isotopic composition of biogenic methane has the same variation trend with increasing salinity of water medium. There are biogenic gas reservoirs formed in transitional regions under the condition of continental facies. These gas reservoirs resulted from both CO2- reduction and acetic fermentation, the formation of which may be related to the non-variant salinity of ancient water medium and the relatively high geothermal gradient, as is the case encountered in the Baoshan Basin. The biogenic gas generating in these regions has light hydrogen isotopic composition: δDCH4<-250‰, and relatively heavy carbon isotopic

  16. Ultrafast optical nonlinearity and photoacoustic studies on chitosan-boron nitride nanotube composite films

    Science.gov (United States)

    Kuthirummal, Narayanan; Philip, Reji; Mohan, Athira; Jenks, Cassidy; Levi-Polyachenko, Nicole

    2016-07-01

    Ultrafast optical nonlinearity in chitosan (CS) films doped with multi-walled boron nitride nanotubes (MWBN) has been investigated using 800 nm, 100 fs laser pulses, employing the open aperture Z-scan technique. Two-photon absorption coefficients (β) of CS-MWBN films have been measured at 800 nm by Z-scan. While chitosan with 0.01% MWBN doping gives a β value of 0.28×10-13 m/W, 1% doping results in a higher β value of 1.43×10-13 m/W, showing nonlinearity enhancement by a factor of 5. These nonlinearity coefficients are comparable to those reported for silver nanoclusters in glass matrix and Pt-PVA nanocomposites, indicating potential photonic applications for MWBN doped chitosan films. Characterization of the synthesized films using Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) reveals significant interactions between the NH and CO groups of chitosan with boron nitride.

  17. Oxygen isotopic composition of relict olivine grains in cosmic spherules: Links to chondrules from carbonaceous chondrites

    OpenAIRE

    N.G. Rudraswami, M. Shyam Prasad, K. Nagashima, R.H. Jones

    2015-01-01

    Most olivine relict grains in cosmic spherules selected for the present study are pristine and have not been disturbed during their atmospheric entry, thereby preserving their chemical, mineralogical and isotopic compositions. In order to understand the origin of the particles, oxygen isotope compositions of relict olivine grains in twelve cosmic spherules collected from deep sea sediments of the Indian Ocean were studied using secondary ion mass spectrometry. Most of the data lie close to th...

  18. Improvements to SFCOMPO - a database on isotopic composition of spent nuclear fuel

    International Nuclear Information System (INIS)

    Isotopic composition is one of the most relevant data to be used in the calculation of burnup of irradiated nuclear fuel. Since autumn 2002, the Organisation for Economic Co-operation and Development/Nuclear Energy Agency (OECD/NEA) has operated a database of isotopic composition - SFCOMPO, initially developed in Japan Atomic Energy Research Institute. This paper describes the latest version of SFCOMPO and the future development plan in OECD/NEA. (author)

  19. Molecular Paleohydrology: Interpreting the Hydrogen- Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms

    OpenAIRE

    D. Sachse; Billault, I.; G. J. Bowen; CHIKARAISHI, Y.; Dawson, T E; Feakins, S.J.; Freeman, Katherine; Magill, C.R.; McInerney, F.A.; Meer, M.T.J. van der; Polissar, P.; Robins, R.J.; Sachs, J.P.; Schmidt, H.L.; Sessions, A.L.

    2012-01-01

    Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and terrestrial organisms can be related to the composition of their growth (i.e., environmental) water. Subsequently, compound-specific deuterium/hydrogen (D/H) ratios of sedimentary biomarkers have bee...

  20. Isotopic and chemical composition of submarine geothermal gases from the Bay of Plenty, New Zealand

    International Nuclear Information System (INIS)

    Gas samples collected from the ocean floor near Whale Island, Bay of Plenty, New Zealand, are composed of carbon dioxide, methane, hydrogen, and air. The methane has an isotopic composition of delta13C(PDB) = -280/00 and deltaD(SMOW) = -1250/00. The isotopic and chemical composition show that the gases are of geothermal origin and similar to gas evolved from Whale Island hot springs

  1. The use of stable isotope compositions of selected elements in food origin control

    International Nuclear Information System (INIS)

    Stable isotope ratios have been used widely for authentication of foodstuffs especially for detection of added water and sugar in fruit juices and wines. Hydrogen and oxygen composition are particularly interesting probes for geographical origin and authenticity identification. Carbon and nitrogen composition of fruits contains the finger-print of their metabolism and growing condition. Exemplary data are presented which demonstrated the usefulness of the Isotope Ratio Mass Spectrometry (IRMS) methods for authenticating wines and fruits (juice and pulp). (author)

  2. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    Science.gov (United States)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    Carbonic anhydrases are a group of metalloenzymes that catalyse the hydration of aqueous carbon dioxide (CO2). The expression of carbonic anhydrase by bacteria, archaea and eukarya has been linked to a variety of important biological processes including pH regulation, substrate supply and biomineralisation. As oxygen isotopes are exchanged between CO2 and water during hydration, the presence of carbonic anhydrase in plants and soil organisms also influences the oxygen isotope budget of atmospheric CO2. Leaf and soil water pools have distinct oxygen isotope compositions, owing to differences in pool sizes and evaporation rates, which are imparted on CO2during hydration. These differences in the isotopic signature of CO2 interacting with leaves and soil can be used to partition the contribution of photosynthesis and soil respiration to net terrestrial CO2 exchange. However, this relies on our knowledge of soil carbonic anhydrase activity and currently, the prevalence and function of these enzymes in soils is poorly understood. Isotopic approaches used to estimate soil carbonic anhydrase activity typically involve the inversion of models describing the oxygen isotope composition of CO2 fluxes to solve for the apparent, potentially catalysed, rate of oxygen exchange during hydration. This requires information about the composition of CO2 in isotopic equilibrium with soil water obtained from destructive, depth-resolved soil water sampling. This can represent a significant challenge in data collection given the considerable potential for spatial and temporal variability in the isotopic composition of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by constraining carbonic anhydrase activity and the composition of soil water in isotopic equilibrium with CO2 by solving simultaneously the mass balance for two soil CO2 steady states differing only in the

  3. Alkynyl substituted carboranes as precursors to boron carbide thin films, fibers and composites

    International Nuclear Information System (INIS)

    In this paper the use of alkynyl substituted derivatives of o-carborane as precursors to boron containing ceramics is described. These compounds undergo a thermally or photochemically induced polymerization to afford cross linked polyakynyl-o-carborane derivatives. The increase in molecular weight should allow for increased Tg's and the retention of modelled polymer preforms. In this report, these modification reactions are described. In addition, the retention of molded polymer preforms were analyzed after UV exposure and inert atmosphere pyrolysis

  4. Carbon-13 kinetic isotope effects in the decarbonylation of lactic acid of natural isotopic composition in phosphoric acid medium

    International Nuclear Information System (INIS)

    The 13C kinetic isotope effect fractionation in the decarbonylation of lactic acid (LA) of natural isotopic composition by concentrated phosphoric acids (PA) and by 85% H3PO4 has been studied in the temperature interval of 60-150 deg C. The values of the 13C(1) isotope effects in the decarbonylation of lactic acid in 100% H3PO4, in pyrophosphoric acid and in more concentrated phosphoric acids are intermediate between the values calculated assuming that the C(1)-OH bond is broken in the rate-controlling step of dehydration and those calculated for rupture of the carbon-carbon bond in the transition state. In the temperature interval of 90-130 deg C the experimental 13C fractionation factors determined in concentrated PA approach quite closely the 13C fractionation corresponding to C(2)-C(1) bond scission. The 13C(1) kinetic isotope effects in the decarbonylation of LA in 85% orthophosphoric acid in the temperature range of 110-150 deg C coincide with the 13C isotope effects calculated assuming that the frequency corresponding to the C(1)-OH vibration is lost in the transition state of decarbonylation. A change of the mechanism of decarbonylation of LA in going from concentrated PA medium to 85% H3PO4 has been suggested. A possible secondary 18O and a primary18O kinetic isotope effect in decarbonylation of lactic acid in phosphoric acids media have been discussed, too. (author) 21 refs.; 3 tabs

  5. Dielectric and thermal properties of isotactic polypropylene/hexagonal boron nitride composites for high-frequency applications

    International Nuclear Information System (INIS)

    Highlights: • The degree of orientation of the hBN could be controlled by the fabrication process. • The dielectric constants of composites ranged between 2.25 and 3.39. • The dielectric loss of composites was on the order of 10−4 for all compositions. • The thermal conductivity were improved by controlling orientation of hBN. - Abstract: Dielectric composites aimed for high frequency applications were prepared by using anisotropic hexagonal boron nitride (hBN) particles as a fillers and isotactic polypropylene (iPP) as polymer matrix. Dielectric and thermal properties of the composites were studied, focusing on the filler orientation in the plate-shape specimens and filler concentration up to 40 vol%. The degree of orientation of the filler was controlled by the composite fabrication process. Hot-pressing gave relatively random orientation of the filler in the matrix, while injection molding induced a high orientation. Dielectric constant (εr) of the composites ranged between 2.25 and 3.39. The estimation of εr based on the Bruggeman mixing model agreed well with the measured value. Low dielectric losses (tan δ) at microwave frequencies, on the order of 10−4, were obtained for all the compositions. Through-thickness thermal conductivity (k) of the hot-pressed samples showed a drastic increase with increasing the filler concentration, reaching up to 2.1 W/m K at 40 vol% of hBN. The filler concentration dependence of k was less significant for the injection molded composites. In-plane thermal expansion was almost independent on the filler orientation, while the coefficient of thermal expansion for the thickness direction of the hot-pressed sample was reduced to approximately half of the injection molded counterpart. These differences in thermal conductivity and thermal expansion are thought to arise from the difference in hBN filler orientation

  6. Dielectric and thermal properties of isotactic polypropylene/hexagonal boron nitride composites for high-frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Susumu, E-mail: 143453501@ccalumni.meijo-u.ac.jp [Graduate School of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 4688502 (Japan); Imai, Yusuke [National Institute of Advanced Industrial Science and Technology (AIST), 2268-98 Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560 (Japan); Kan, Akinori [Graduate School of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 4688502 (Japan); Hotta, Yuji [National Institute of Advanced Industrial Science and Technology (AIST), 2268-98 Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560 (Japan); Ogawa, Hirotaka [Graduate School of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 4688502 (Japan)

    2014-12-05

    Highlights: • The degree of orientation of the hBN could be controlled by the fabrication process. • The dielectric constants of composites ranged between 2.25 and 3.39. • The dielectric loss of composites was on the order of 10{sup −4} for all compositions. • The thermal conductivity were improved by controlling orientation of hBN. - Abstract: Dielectric composites aimed for high frequency applications were prepared by using anisotropic hexagonal boron nitride (hBN) particles as a fillers and isotactic polypropylene (iPP) as polymer matrix. Dielectric and thermal properties of the composites were studied, focusing on the filler orientation in the plate-shape specimens and filler concentration up to 40 vol%. The degree of orientation of the filler was controlled by the composite fabrication process. Hot-pressing gave relatively random orientation of the filler in the matrix, while injection molding induced a high orientation. Dielectric constant (ε{sub r}) of the composites ranged between 2.25 and 3.39. The estimation of ε{sub r} based on the Bruggeman mixing model agreed well with the measured value. Low dielectric losses (tan δ) at microwave frequencies, on the order of 10{sup −4}, were obtained for all the compositions. Through-thickness thermal conductivity (k) of the hot-pressed samples showed a drastic increase with increasing the filler concentration, reaching up to 2.1 W/m K at 40 vol% of hBN. The filler concentration dependence of k was less significant for the injection molded composites. In-plane thermal expansion was almost independent on the filler orientation, while the coefficient of thermal expansion for the thickness direction of the hot-pressed sample was reduced to approximately half of the injection molded counterpart. These differences in thermal conductivity and thermal expansion are thought to arise from the difference in hBN filler orientation.

  7. Laser Ablation Molecular Isotopic Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Russo, Richard E., E-mail: rerusso@lbl.gov [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Applied Spectra, Inc., 46661 Fremont Boulevard, Fremont, CA 94538 (United States); Bol' shakov, Alexander A. [Applied Spectra, Inc., 46661 Fremont Boulevard, Fremont, CA 94538 (United States); Mao Xianglei [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); McKay, Christopher P. [NASA-Ames Research Center, Moffett Field, CA 94035 (United States); Perry, Dale L.; Sorkhabi, Osman [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

    2011-02-15

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

  8. Laser Ablation Molecular Isotopic Spectrometry

    Science.gov (United States)

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

    2011-02-01

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

  9. Role of friction stir processing parameters on microstructure and microhardness of boron carbide particulate reinforced copper surface composites

    Indian Academy of Sciences (India)

    R Sathiskumar; N Murugan; I Dinaharan; S J Vijay

    2013-12-01

    Friction stir processing (FSP) was applied to fabricate boron carbide (B4C) particulate reinforced copper surface composites. The effect of FSP parameters such as tool rotational speed, processing speed and groove width on microstructure and microhardness was investigated. A groove was contrived on the 6mm thick copper plates and packed with B4C particles. FSP was carried out using five various tool rotational speeds, processing speeds and groove widths. Optical and scanning electron microscopies were employed to study the microstructure of the fabricated surface composites. The results indicated that the selected FSP parameters significantly influenced the area of surface composite, distribution of B4C particles and microhardness of the surface composites. Higher tool rotational speed and lower processing speed produced an excellent distribution of B4C particles and higher area of surface composite due to higher frictional heat, increased stirring and material tranportation. The B4C particles were bonded well to the copper matrix and refined the grains of copper due to the pinning effect of B4C particles. B4C particles retained the original size and morphology because of its small size and minimum sharp corners in the morphology.

  10. Elemental and iron isotopic composition of aerosols collected in a parking structure

    International Nuclear Information System (INIS)

    The trace metal contents and iron isotope composition of size-resolved aerosols were determined in a parking structure in Tempe, AZ, USA. Particulate matter (PM) 2.5 μm were collected. Several air toxics (e.g., arsenic, cadmium, and antimony) were enriched above the crustal average, implicating automobiles as an important source. Extremely high levels of fine copper (up to 1000 ng m-3) were also observed in the parking garage, likely from brake wear. The iron isotope composition of the aerosols were found to be + 0.15 ± 0.03 per mille and + 0.18 ± 0.03 per mille for the PM 2.5 μm fractions, respectively. The similarity of isotope composition indicates a common source for each size fraction. To better understand the source of iron in the parking garage, the elemental composition in four brake pads (two semi-metallic and two ceramic), two tire tread samples, and two waste oil samples were determined. Striking differences in the metallic and ceramic brake pads were observed. The ceramic brake pads contained 10-20% copper by mass, while the metallic brake pads contained about 70% iron, with very little copper. Both waste oil samples contained significant amounts of calcium, phosphorous, and zinc, consistent with the composition of some engine oil additives. Differences in iron isotope composition were observed between the source materials; most notably between the tire tread (average = + 0.02 per mille ) and the ceramic brake linings (average = + 0.65 per mille ). Differences in isotopic composition were also observed between the metallic (average = + 0.18 per mille ) and ceramic brake pads, implying that iron isotope composition may be used to resolve these sources. The iron isotope composition of the metallic brake pads was found to be identical to the aerosols, implying that brake dust is the dominant source of iron in a parking garage.

  11. Effects of composition on the equilibrium between hydrogen isotopes and palladium

    International Nuclear Information System (INIS)

    The isotopic separation coefficient αHD and the equilibrium (or plateau) pressure peq of hydrogen and deuterium in equilibrium with palladium were measured at 298 K. The dependence of αHD and peq on the composition of the gas phase was determined from absorption and desorption batch experiments. A simple thermodynamic model allows one to predict αHD and peq on the basis of (1) the isotopic exchange equilibrium constants, (2) the plateau pressures of the pure isotopes, and (3) the composition. The reliability of the thermodynamic model for predicting the chromatographic separation of a binary mixture is discussed briefly. (author)

  12. Relationship between the oxygen isotopic composition of soil CO2 and water

    International Nuclear Information System (INIS)

    The stable oxygen isotope composition of soil CO2 at any soil depth is controlled by a combination of processes: (1) the isotopic composition of biologically produced CO2; (2) diffusional transport of CO2; and (3) equilibration between transported CO2 and soil water. Based on estimates of rates of CO2/H2O isotopic equilibration, and CO2 residence times for a variety of soils, it seems that at depths of more than 50 to 100 cm the δ18O values of CO2 will be in isotopic equilibrium with the water at that depth. Available data on the oxygen isotope composition of CO2 suggests that CO2, at certain soil depths, should be a good indicator of the isotopic composition of the soil water. Additionally, at steady state, the δ18O value of CO2 respired from soil appears to be in isotopic equilibrium with soil water, a finding that has implications for the role of the terrestrial biosphere on the δ18O value of atmospheric CO2. (author). 25 refs, 6 figs, 2 tabs

  13. Differences in Nanosecond Laser Ablation and Deposition of Tungsten, Boron, and WB2/B Composite due to Optical Properties

    Directory of Open Access Journals (Sweden)

    Tomasz Moscicki

    2016-01-01

    Full Text Available The first attempt to the deposition of WB3 films using nanosecond Nd:YAG laser demonstrated that deposited coatings are superhard. However, they have very high roughness. The deposited films consisted mainly of droplets. Therefore, in the present work, the explanation of this phenomenon is conducted. The interaction of Nd:YAG nanosecond laser pulse with tungsten, boron, and WB2/B target during ablation is investigated. The studies show the fundamental differences in ablation of those materials. The ablation of tungsten is thermal and occurs due to only evaporation. In the same conditions, during ablation of boron, the phase explosion and/or fragmentation due to recoil pressure is observed. The deposited films have a significant contribution of big debris with irregular shape. In the case of WB2/B composite, ablation is significantly different. The ablation seems to be the detonation in the liquid phase. The deposition mechanism is related mainly to the mechanical transport of the target material in the form of droplets, while the gaseous phase plays marginal role. The main origin of differences is optical properties of studied materials. A method estimating phase explosion occurrence based on material data such as critical temperature, thermal diffusivity, and optical properties is shown. Moreover, the effect of laser wavelength on the ablation process and the quality of the deposited films is discussed.

  14. Equivalence test for sample data of isotopic compositions in PWR spent fuel

    International Nuclear Information System (INIS)

    Statistical combination method for previous and JAERI data of isotopic compositions in PWR spent fuel has been investigated. Using the F and T statistical test method, tests for the normality, the homogeneous variance and equivalent mean at a 5 % significance level have been carried out for twenty two isotopes which consist of spent fuel over 30 GWd/tU in burnup. All isotopes except U-238 and Nd-148 seem to be satisfied with the normality. 16 isotopes including U-234 seem to be satisfied with the homogeneous variance. 9 isotopes including U-235 seem to have a equivalent mean. 6 isotopes of U-235, Pu-240, Pu-241, Cs-134, Nd-144 and Sm-148 are appeared to be satisfied simultaneously with 3 alternative test results

  15. Carbon and oxygen isotope compositions of the carbonate facies in the Vindhyan Supergroup, central India

    Indian Academy of Sciences (India)

    S Banerjee; S K Bhattacharya; S Sarkar

    2006-02-01

    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 subtle controls of facies variation,depositional setting and post-depositional diagenesis on stable isotope compositions are not yet clearly understood.The Vindhyan Super- group hosts four carbonate units,exhibiting a wide variability in depositional processes and paleogeography.A detailed facies-specific carbon and oxygen isotope study of the carbonate units was undertaken by us to investigate the effect of these processes and to identify the least altered isotope values.It is seen that both carbon and oxygen isotope compositions have been affected by early meteoric water diagenesis.The effect of diagenetic alteration is,however,more pronounced in case of oxygen isotopes than carbon isotopes.Stable isotope compositions remained insensitive to facies only when sediments accumulated in a shallow shelf setting without being exposed.Major alteration of original isotope ratios was observed in case of shallow marine carbonates,which became exposed to meteoric fluids during early diagenetic stage.Duration of exposure possibly determined the magnitude of alteration and shift from the original values.Moreover,dolomitization is found to be accompanied by appreciable alteration of isotope compositions in some of the carbonates.The present study suggests that variations in sediment depositional settings,in particular the possibility of subaerial exposure,need to be considered while extracting chronostratigraphic signi ficance from 13C data.

  16. Characterizing the origins of bottled water on the South Korean market using chemical and isotopic compositions

    International Nuclear Information System (INIS)

    We analyzed the major elements and stable isotopes of oxygen, hydrogen, and carbon (dissolved inorganic carbon: DIC) in various types of bottled water (domestic and foreign) commercially available in South Korea to classify the water types and to identify their origins. Only marine waters and some sparkling waters could be discriminated by their physicochemical compositions. Oxygen and hydrogen isotopes made marine waters more distinguishable from other water types. The determination of the carbon isotope composition of DIC was clearly useful for distinguishing between naturally and artificially sparkling waters. In addition, statistical analysis also appeared to aid in the discrimination of bottled water types. Our results indicate that a method that combines chemical and stable isotope composition analysis with statistical analysis is the most useful for discriminating water types and characterizing the origins of bottled water

  17. Variations in isotopic compositions of chlorine in evaporation-controlled salt lake brines of Qaidam Basin, China

    Digital Repository Service at National Institute of Oceanography (India)

    Xiao, Ying-kai; Liu, Wei-guo; Zhou, Y.M.; Wang, Yun-hui; Shirodkar, P.V.

    The variations in the isotopic compositions of chlorine in evaporation-controlled saline lake brines were determined by using an improved procedure for precise measurement of chlorine isotopes based on Cs sub(2) Cl sup(+) ion by thermal ionization...

  18. Modification of the isotopic composition of rainwater by processes which occur before groundwater recharge

    International Nuclear Information System (INIS)

    The isotopic composition of groundwaters differs from that of the average rain composition due to selection (seasonal or otherwise) from among different rainfalls during the replenishment of groundwaters, as well as to isotope fractionation which accompanies some of the steps in the recharge process. An assessment of the resulting concentration changes is required before one can use the characteristic variations of the isotopic composition of atmospheric waters as hydrological tracers to mark the origin of groundwaters. An over-all measure of the encountered effect is obtained by comparison of the isotopic composition of rain and groundwaters in regions in Israel of known hydrological pattern and recharge areas. Correlation of the effects with the environmental factors of the different areas gives preliminary clues concerning the causes of fractionation which operate in the natural process. Of these the formation of puddles after rain seems particularly effective. The following water-transport processes, all of which are steps in the rain-to-groundwater transition, are then evaluated regarding their potential contribution to the modification of the isotopic composition: interception by vegetation, open-water evaporation and exchange with ambient vapour from overland flow and surface run-off, evaporation of soil moisture, transpiration and water transport by unsaturated flow in the zone or aeration. The discussion is based partly on theoretical analysis and partly on case studies of isotope separations in open water-bodies and in lysimeter fields. (author)

  19. Chemical and Isotopic Compositions of the Euphrates River Water, Syria

    International Nuclear Information System (INIS)

    Stable isotope (18O and 2H) ratios, were measured together with tritium content and major ion concentrations on a monthly basis at 12 stations along the Syrian portion of the Euphrates River during the period January 2004-December 2006. Spatial variations of stable isotope ratios are moderated compared with other large rivers in the world. The concentrations of major ions and environmental isotopes systematically increased with distance downstream, with the sharpest enrichment at Al-Assad Lake. This systematic increase could be explained by: 1. direct evaporation from the river and its tributaries; and 2. drainage return flows of irrigation water via the groundwater system. The isotopic properties of the Euphrates water suggest negligible roles of precipitation and local runoff, compared with evaporation. (author)

  20. Perchlorate in The Great Lakes: Isotopic Composition and Origin

    OpenAIRE

    Poghosyan, Armen; Sturchio, Neil C.; Morrison, Candice G.; Beloso, Abelardo D., Jr.; Guan, Yunbin; Eiler, John M.; Jackson, W. Andrew; Hatzinger, Paul B.

    2014-01-01

    Perchlorate is a persistent and mobile contaminant in the environment with both natural and anthropogenic sources. Stable isotope ratios of oxygen (δ^(18)O, Δ^(17)O) and chlorine (δ^(37)Cl) along with the abundance of the radioactive isotope ^(36)Cl were used to trace perchlorate sources and behavior in the Laurentian Great Lakes. These lakes were selected for study as a likely repository of recent atmospheric perchlorate deposition. Perchlorate concentrations in the Great Lakes range from 0....

  1. Boron Nitride Nanosheets (BNNSs) Chemically Modified by "Grafting-From" Polymerization of Poly(caprolactone) for Thermally Conductive Polymer Composites.

    Science.gov (United States)

    Lee, Jinseong; Jung, Haejong; Yu, Seunggun; Man Cho, Suk; Tiwari, Vimal K; Babu Velusamy, Dhinesh; Park, Cheolmin

    2016-07-01

    To meet the growing demand for rapid heat dissipation in electronic devices to ensure their reliable performance with a high level of safety, many polymer composites with thermally conductive but electrically insulating 2D boron nitride nanosheets (BNNSs) are being developed. Here we present an efficient way to enhance the thermal conductivity (TC) of a polymer composite by means of "grafting-from" polymerization of a poly(caprolactone) (PCL) onto BNNSs. The BNNSs, which were exfoliated from bulk BN by means of ultra-sonication, were prepared by means of radical oxidation. These oxidized BNNSs (oxi-BNNSs) were employed as initiators for subsequent ring-opening polymerization of PCL, which successfully resulted in PCL chemically grafted onto BNNSs (PCL-g-BNNSs). The excellent dispersion of PCL-g-BNNSs in common solvents allowed us to readily fabricate a polymer composite that contained PCL-g-BNNSs embedded in a PCL matrix, and the composite showed TC values that were five and nine times greater in the out-of-plane and in-plane mode, respectively, than those of pristine PCL. PMID:27283727

  2. Boron nitride nanotubes reinforced aluminum composites prepared by spark plasma sintering: Microstructure, mechanical properties and deformation behavior

    International Nuclear Information System (INIS)

    Boron nitride nanotubes (BNNT) reinforced aluminum based composites are synthesized by spark plasma sintering (SPS). The concentration of BNNT is varied as 0, 2 and 5 vol% in the aluminum matrix. Micro-pillar compression testing revealed that Al–5 vol% BNNT has yield strength and compressive strength as 88 MPa and 216 MPa respectively, which is more than 50% improvement over unreinforced Al. BNNT play an active role in strengthening Al matrix through effective load bearing and transfer by crack bridging and sword in sheath mechanisms. Cold rolling of Al–5 vol% BNNT with 75% thickness reduction in a single pass exhibited high deformability without cracking or disintegration. The deformation is dominated by slip signifying ductile behavior in sintered Al with and without BNNT. BNNT survives the extreme temperature and pressure conditions during SPS processing and heavy deformation during cold rolling

  3. Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer

    Science.gov (United States)

    Piasecki, Alison; Sessions, Alex; Lawson, Michael; Ferreira, A. A.; Neto, E. V. Santos; Eiler, John M.

    2016-09-01

    Site-specific isotope ratio measurements potentially provide valuable information about the formation and degradation of complex molecules-information that is lost in conventional bulk isotopic measurements. Here we discuss the background and possible applications of such measurements, and present a technique for studying the site-specific carbon isotope composition of propane at natural abundance based on mass spectrometric analysis of the intact propane molecule and its fragment ions. We demonstrate the feasibility of this approach through measurements of mixtures of natural propane and propane synthesized with site-specific 13C enrichment, and we document the limits of precision of our technique. We show that mass balance calculations of the bulk δ13C of propane based on our site-specific measurements is generally consistent with independent constraints on bulk δ13C. We further demonstrate the accuracy of the technique, and illustrate one of its simpler applications by documenting the site-specific carbon isotope signature associated with gas phase diffusion of propane, confirming that our measurements conform to the predictions of the kinetic theory of gases. This method can be applied to propane samples of moderate size (tens of micromoles) isolated from natural gases. Thus, it provides a means of studying the site-specific stable isotope systematics of propane at natural isotope abundances on sample sizes that are readily recovered from many natural environments. This method may also serve as a model for future techniques that apply high-resolution mass spectrometry to study the site-specific isotopic distributions of larger organic molecules, with potential applications to biosynthesis, forensics and other geochemical subjects.

  4. Antimony isotopic composition in river waters affected by ancient mining activity.

    Science.gov (United States)

    Resongles, Eléonore; Freydier, Rémi; Casiot, Corinne; Viers, Jérôme; Chmeleff, Jérôme; Elbaz-Poulichet, Françoise

    2015-11-01

    In this study, antimony (Sb) isotopic composition was determined in natural water samples collected along two hydrosystems impacted by historical mining activities: the upper Orb River and the Gardon River watershed (SE, France). Antimony isotope ratio was measured by HG-MC-ICP-MS (Hydride Generation Multi-Collector Inductively Coupled Plasma Mass Spectrometer) after a preconcentration and purification step using a new thiol-cellulose powder (TCP) procedure. The external reproducibility obtained for δ(123)Sb measurements of our in-house Sb isotopic standard solution and a certified reference freshwater was 0.06‰ (2σ). Significant isotopic variations were evident in surface waters from the upper Orb River (-0.06‰≤δ(123)Sb≤+0.11‰) and from the Gardon River watershed (+0.27‰≤δ(123)Sb≤+0.83‰). In particular, streams that drained different former mining sites exploited for Sb or Pb-Zn exhibited contrasted Sb isotopic signature, that may be related to various biogeochemical processes occurring during Sb transfer from rocks, mine wastes and sediments to the water compartment. Nevertheless, Sb isotopic composition appeared to be stable along the Gardon River, which might be attributed to the conservative transport of Sb at distance from mine-impacted streams, due to the relative mobile behavior of Sb(V) in natural oxic waters. This study suggests that Sb isotopic composition could be a useful tool to track pollution sources and/or biogeochemical processes in hydrologic systems. PMID:26452900

  5. The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

    Science.gov (United States)

    Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

    2016-06-01

    The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate

  6. Isotope composition of iron delivered to the oceans by intertropical rivers: The Amazon River Basin case

    Science.gov (United States)

    Poitrasson, F.; Vieira, L. C.; Seyler, P.; dos Santos Pinheiro, G. M.; Mulholland, D. S.; Ferreira Lima, B. A.; Bonnet, M.; Martinez, J.; Prunier, J.

    2011-12-01

    Riverborne iron is a notable source for this biogeochemically key element to the oceans. Recent investigations have shown that its isotopic composition may vary significantly in oceanic waters. Hence, a proper understanding of the Fe cycle at the surface of the Earth requires a good characterization of the isotopic composition of its various reservoirs. However, as the database growths, it appears that the isotope composition of the riverborne Fe delivered to the oceans may be more varied than initially thought, in agreement with inferences from soil studies from different climatic contexts. It is therefore important to compare major rivers from different latitudes. We focused our attention on the Amazon River and its tributaries that represent ca. 20% of the freshwater delivered to the oceans by world rivers. Preliminary experiments suggest that water filtration may induce biases in stable Fe isotope composition. Therefore, we worked first on bulk waters, sampled during multidisciplinary field campaigns on the Amazon River and its tributaries, including the Solimoes, Negro, Madeira and Tapajos Rivers. Besides a complete sample physical-chemical characterization, Fe isotope determinations were conduced after water sample mineralization, iron purification and MC-ICP-MS analysis. Our first results reveal that most bulk water samples cluster close to the continental crust value (0.1% δ57FeIRMM-14) with an overall range of 0.2%. This is consistent with the restricted range found in lateritic soils elsewhere that represent 80% of the Amazon basin surface. Only black water rivers flowing over the podzols of the northern portion of the Amazon basin tend to show lighter isotopic compositions, down to -0.18%. However, sediment analyses suggest that this light Fe isotopic is lost through sedimentation on the river bed, thereby leading the waters to have Fe isotope compositions remaining close to that of the continental crust. This constant isotopic signature holds whatever

  7. Determination of plutonium’s isotopic composition in PWR spent nuclear fuel

    International Nuclear Information System (INIS)

    In this article the isotopic composition of the plutonium contained in spent nuclear fuel at discharge is analysed. The composition is analysed as a function of burn-up of a light water reactor using once-through cycle. The results are obtained using two different software products. Key words: pressurized water reactors, plutonium, spent nuclear fuel

  8. The effect of small scale variablity in isotopic composition of precipitation on hydrograph separation results

    Science.gov (United States)

    Fischer, Benjamin; van Meerveld, Ilja; Seibert, Jan

    2016-04-01

    Understanding runoff processes is important for predictions of streamflow quantity and quality. The two-component isotope hydrograph separation (IHS) method is a valuable tool to study how catchments transform rainfall into runoff. IHS allows the stormflow hydrograph to be separated into rainfall (event water) and water that was stored in the catchment before the event (pre-event water). To be able to perform an IHS, water samples of baseflow (pre-event water) and stormflow are collected at the stream outlet. Rainfall is usually collected at one location by hand as an event total or sampled sequentially during the event. It is usually assumed that the spatial variability in rainfall and the isotopic composition of rainfall are negligible for small (area of 0.15, 0.23, and 0.7 km2). The isotopic composition of rainfall and streamflow were sampled for 10 different rain events (P: 5 mm intervals, Q: 12 to 51 samples per events). This dataset was used to perform a two-component isotope hydrograph separation. The results show that for some events the spatial variability in total rainfall, mean and maximum rainfall intensity and stable isotope composition of rainfall was high. There was no relation between the stable isotope composition of rainfall and the rainfall sum, rainfall intensity or altitude. The spatial variability of the isotopic composition of rainfall was for 4 out of the 10 events as large as the temporal variability in the isotopic composition. Different rainfall weighing methods resulted in different minimum pre-event water fractions in streamflow. For small events with a small mean temporal range in stable isotope composition of rainfall, the different rainfall weighing methods had little effect on the calculated minimum pre-event water fractions. However with increasing temporal variability in stable isotope composition of rainfall, the range in the minimum pre-event water fractions increased and therefore the choice of the rainfall weighing method

  9. Coupled isotopes of plant wax and hemicellulose markers record information on relative humidity and isotopic composition of precipitation

    Science.gov (United States)

    Tuthorn, M.; Zech, R.; Ruppenthal, M.; Oelmann, Y.; Kahmen, A.; del Valle, H. F.; Eglinton, T.; Zech, M.

    2015-02-01

    The δ2H isotopic composition of leaf waxes is used increasingly for paleohydrological and -climate reconstructions. However, it is challenging to disentangle past changes in the isotopic composition of precipitation and changes in evapotranspirative enrichment of leaf water. We analyzed δ2H on n-alkanes and fatty acids in topsoils along a climate transect in Argentina, for which we had previously measured δ18O on plant-derived sugars. Our results indicate that leaf wax biomarker δ2H values (δ2Hlipids) primarily reflect δ2Hsource water (precipitation), but are modulated by evapotranspirative enrichment. A mechanistic model is able to produce the main trends in δ2Hlipids along the transect, but seems to slightly underestimate evapotranspirative enrichment in arid regions and overestimate it in grass-dominated ecosystems. Furthermore, the (i) coupling of the δ2Hlipid and δ18Osugar biomarker results and (ii) application of biosynthetic fractionation factors allows calculating the δ2H-δ18O isotopic composition of leaf water along the transect. This also yields the deuterium excess (d excess) of leaf water, which mainly reflects evapotranspirative enrichment, and can be used to model relative air humidity (RH). The high correlation of modeled (reconstructed based on biomarker results) and measured RH, as well as the good agreement between modeled and actual δ2H and δ18O of precipitation along the transect lends support to the coupled δ2Hlipid and δ18Osugar biomarker approach for future paleoclimate research.

  10. High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry

    International Nuclear Information System (INIS)

    Highlights: • Precise and accurate determination of seawater Pb isotope compositions. • Uncertainties (2sd) for 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb are better than ±3‰. • Analysis of a GEOTRACES depth profile from the South Atlantic Ocean. • Pb isotopic compositions reflect the different water masses that were sampled. • The 207Pb/206Pb and 206Pb/204Pb ratios display a correlation. - Abstract: A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2 L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a 207Pb–204Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28 ± 21 pg (1sd) and typical Pb recoveries of 40–60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12 ± 4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700–1500 ppm and 1000–2000 ppm were achieved for 207Pb/206Pb, 208Pb/206Pb and 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor 204Pb isotope. Both Pb concentration and isotope data, furthermore, show good

  11. The Isotopic Composition of Water Vapor in the Upper Troposphere/Lower Stratosphere Region : Modeling, Analysis and Sampling

    OpenAIRE

    Franz, P.

    2004-01-01

    The isotopic composition of water vapor in the upper troposphere/lower stratosphere:} Exact knowledge about the isotopic composition of water vapor in the tropopause region and the stratosphere provides important information for the understanding of atmospheric transport and photochemistry. The presented thesis describes with the help of models the processes governing the isotopic composition of atmospheric water vapor. The stable isotopologues - $HDO$, $H_2^{17}O$ and $H_2^{18}O$ - and the r...

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

    International Nuclear Information System (INIS)

    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 delta18O(PO43-) of fossil mammal bones

  13. Molybdenum isotopic composition of single silicon carbides from supernovae.

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-02-03

    Presolar silicon carbide grains form in a variety of types of stars, including asymptotic giant branch red giant stars and supernovae. The dominant mechanisms of heavy element nucleosynthesis, the s-process and r-process, are thought to occur in AGB stars and supernovae, respectively. We have previously reported that mainstream SiC grains have strong enrichments in the s-process isotopes of Sr, Zr and Mo. We report here the first measurements of Mo isotopes in X-type SiC grains, which have previously been identified as having formed from supernova ejecta.

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

    International Nuclear Information System (INIS)

    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)

  15. B, Sr, O and H Isotopic Compositions of Formation Waters from the Bachu Bulge in the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    CAI Chunfang; PENG Licai; MEI Bowen; XIAO Yingkai

    2006-01-01

    In order to elucidate the origin and migration of basinal brines in the Bachu Bulge, Tarim Basin, we have carried out analyses on chemical composition, and boron, hydrogen and oxygen isotopes of formation waters together with the XRD of clay minerals from the Paleozoic strata. The waters show Ca, B, Li and Sr enrichment and SO4 depletion in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater. The relationship between δD and δ18O shows that all the data of the waters decline towards the Global Meteoric Water Line with the intersection of them close to the present-day local meteoric water, suggesting that modern meteoric water has mixed with evaporated seawater. The 87Sr/86Sr ratios range from 0.7090 to 0.7011, significantly higher than those of the contemporary seawater. The δ11B values range from +19.7 to +32.3‰, showing a decrease with the depth and B concentrations. The results suggest that isotopically distinct B and Sr were derived from external sources. However, since the percentages of illite are shown to increase with depth among clay minerals in the study area, i.e., illite is due to precipitation rather than leaching during deeper burial, it is unlikely for illite to have contributed a significant amount of B to the waters. Thus, B with low δ11B values is interpreted to have been added mainly from thermal degradation of kerogen or the basalts in the Cambrian and Lower Ordovician.

  16. Transition of the Isotopic Composition of Leaf Water to the Isotopic Steady State in Soybean and Corn

    Science.gov (United States)

    Kim, K.; Lee, X.; Welp, L. R.

    2007-12-01

    The isotope composition of leaf water (δL) plays an important role in the isotopic water and carbon fluxes between terrestrial plants and the atmosphere. The objective of this study is to improve our understanding of environmental and biological controls on the transition of δL to steady state through laboratory experiments. Plants (soybean, Glycine max; corn, Zea mays) were grown hydroponically with water of a known isotopic content in a greenhouse. On the day of the experiment, they were first moved to ambient environment in full sunlight for at least 6 hr and then into a dark container inside the lab for up to 48 hr in which water vapor isotope ratios, temperature, and humidity were controlled. This arrangement created a step change in the forcing on the plant isotopic exchange. Leaves were sampled prior to the transfer to the dark container and 6 more times every 4 - 12 hr over the experiment. In the first set of experiments, humidity inside the container was saturated to mimic dew events in field conditions. In the second set, humidity was controlled at approximately 95%. Water from the leaf samples was extracted by a vacuum line and was analyzed for both δD and δ18O. The dataset will allow us to evaluate leaf water isotopic theories by exploring the transitions of δL in response to the step change. Specifically, we are interested in whether the stomatal opening is an effective pathway for gaseous exchange in total darkness and how the transitional behaviors of δL differ between the C3 and C4 photosynthesis pathways.

  17. Potassium Isotopic Compositions of NIST Potassium Standards and 40Ar/39Ar Mineral Standards

    Science.gov (United States)

    Morgan, Leah; Tappa, Mike; Ellam, Rob; Mark, Darren; Higgins, John; Simon, Justin I.

    2013-01-01

    Knowledge of the isotopic ratios of standards, spikes, and reference materials is fundamental to the accuracy of many geochronological methods. For example, the 238U/235U ratio relevant to U-Pb geochronology was recently re-determined [1] and shown to differ significantly from the previously accepted value employed during age determinations. These underlying values are fundamental to accurate age calculations in many isotopic systems, and uncertainty in these values can represent a significant (and often unrecognized) portion of the uncertainty budget for determined ages. The potassium isotopic composition of mineral standards, or neutron flux monitors, is a critical, but often overlooked component in the calculation of K-Ar and 40Ar/39Ar ages. It is currently assumed that all terrestrial materials have abundances indistinguishable from that of NIST SRM 985 [2]; this is apparently a reasonable assumption at the 0.25per mille level (1s) [3]. The 40Ar/39Ar method further relies on the assumption that standards and samples (including primary and secondary standards) have indistinguishable 40K/39K values. We will present data establishing the potassium isotopic compositions of NIST isotopic K SRM 985, elemental K SRM 999b, and 40Ar/39Ar biotite mineral standard GA1550 (sample MD-2). Stable isotopic compositions (41K/39K) were measured by the peak shoulder method with high resolution MC-ICP-MS (Thermo Scientific NEPTUNE Plus), using the accepted value of NIST isotopic SRM 985 [2] for fractionation [4] corrections [5]. 40K abundances were measured by TIMS (Thermo Scientific TRITON), using 41K/39K values from ICP-MS measurements (or, for SRM 985, values from [2]) for internal fractionation corrections. Collectively these data represent an important step towards a metrologically traceable calibration of 40K concentrations in primary 40Ar/39Ar mineral standards and improve uncertainties by ca. an order of magnitude in the potassium isotopic compositions of standards.

  18. Clumped isotope composition of cold-water corals: A role for vital effects?

    Science.gov (United States)

    Spooner, Peter T.; Guo, Weifu; Robinson, Laura F.; Thiagarajan, Nivedita; Hendry, Katharine R.; Rosenheim, Brad E.; Leng, Melanie J.

    2016-04-01

    The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes 'clumping' into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope 'vital effects' are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals' calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.

  19. Variation in the terrestrial isotopic composition and atomic weight of argon

    Science.gov (United States)

    Böhlke, John Karl

    2014-01-01

    The isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios (40Ar/36Ar, 38Ar/36Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic 40Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar. Within this interval, measurements of different isotope ratios (40Ar/36Ar or 38Ar/36Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

  20. Determining the oxygen isotope composition of evapotranspiration with eddy covariance

    Science.gov (United States)

    The oxygen isotope componsition of evapotranspiration (dF) represents an important tracer in the study of biosphere-atmosphere interactions, hydrology, paleoclimate, and carbon cycling. Here we demonstrate direct measurement of dF based on eddy covariance (EC) and tunable diode laser (EC-TDL) techni...

  1. Zirconium isotope constraints on the composition of Theia and current Moon-forming theories

    Science.gov (United States)

    Akram, W.; Schönbächler, M.

    2016-09-01

    The giant impact theory is the most widely recognized formation scenario of the Earth's Moon. Giant impact models based on dynamical simulations predict that the Moon acquired a significant amount of impactor (Theia) material, which is challenging to reconcile with geochemical data for O, Si, Cr, Ti and W isotopes in the Earth and Moon. Three new giant impact scenarios have been proposed to account for this discrepancy - hit-and-run impact, impact with a fast-spinning protoEarth and massive impactors - each one reducing the proportion of the impactor in the Moon compared to the original canonical giant impact model. The validity of each theory and their different dynamical varieties are evaluated here using an integrated approach that considers new high-precision Zr isotope measurements of lunar rocks, and quantitative geochemical modelling of the isotopic composition of the impactor Theia. All analysed lunar samples (whole-rock, ilmenite and pyroxene separates) display identical Zr isotope compositions to that of the Earth within the uncertainty of 13 ppm for 96Zr/90Zr (2σ weighted average). This 13 ppm upper limit is used to infer the most extreme isotopic composition that Theia could have possessed, relative to the Earth, for each of the proposed giant impact theories. The calculated Theian composition is compared with the Zr isotope compositions of different solar system materials in order to constrain the source region of the impactor. As a first order approximation, we show that all considered models (including the canonical) are plausible, alleviating the initial requirement for the new giant impact models. Albeit, the canonical and hit-and-run models are the most restrictive, suggesting that the impactor originated from a region close to the Earth. The fast-spinning protoEarth and massive impactor models are more relaxed and increase the allowed impactor distance from the Earth. Similar calculations carried out for O, Cr, Ti and Si isotope data support

  2. A large area multi-element telescope for measuring the cosmic ray isotope composition

    Science.gov (United States)

    Fisher, A. J.; Ormes, J. F.; Hagen, F. A.

    1974-01-01

    To measure the isotopic composition of cosmic rays up to Fe an instrument is needed with good isotopic resolution and a large exposure. The large geometry needed for a balloon-borne detector has been obtained with large mapped detectors and a trajectory determining spark chamber. The instrument achieves isotopic resolution only for stopping particles. For low charge particles where there is no Cerenkov response the detector works as a multiple dE/dx-Range-Energy detector. For higher charges where scintillator saturation becomes important it becomes a Cerenkov-range measurement.

  3. Isotopic composition of Ethiopian rainfall waters: Observation on its typical signature

    International Nuclear Information System (INIS)

    In the eastern Africa the major source of precipitation comes from Indian Ocean, and generally speaking, the isotopic composition is related to the regional circulation patterns; seasonal fluctuations correspond to the seasonal displacement of the Inter Tropical Convergence Zone (ITCZ). Ethiopia is located on the northern extreme of ITCZ. It is generally believed that, under the present conditions, the Ethiopian region is under the influence of North Indian Ocean in March and April and combined Atlantic and Indian Ocean monsoon in July-August depending of the position of the ITCZ. This generalization has been however subjected to debate but this complex situation probably explains the typical isotopic rainfall signature. As already observed by different authors, using the IAEA Addis Ababa time series, these rainfall regimes have distinct isotope signal. The March-April rainfall is characterized by enriched oxygen 18 and Deuterium compared to the July-August relatively depleted isotope values. In many part of the country rainfall in months of December, January and February is minimal and isotope signal usually tends to show influence of evaporation. Highly depleted values are also observed in some months of November since the start of the record. Another very important feature of the isotopic composition of the Ethiopian region is that irrespective of high altitude and lower mean annual temperature compared to other East African regions, the isotopic signature is enriched in Ethiopian rain waters. All non-evaporated rains and modern meteoric waters elsewhere in the country plot above the GMWL showing high deuterium excess

  4. Water transport in protoplanetary disks and the hydrogen isotopic composition of chondrites

    CERN Document Server

    Jacquet, Emmanuel

    2013-01-01

    The D/H ratios of carbonaceous chondrites, believed to reflect that of water in the inner early solar system, are intermediate between the protosolar value and that of most comets. The isotopic composition of cometary water has been accounted for by several models where the isotopic composition of water vapor evolved by isotopic exchange with hydrogen gas in the protoplanetary disk. However, the position and the wide variations of the distribution of D/H ratios in carbonaceous chondrites have yet to be explained. In this paper, we assume that the D/H composition of cometary ice was achieved in the disk building phase and model the further isotopic evolution of water in the inner disk in the classical T Tauri stage. Reaction kinetics compel isotopic exchange between water and hydrogen gas to stop at $\\sim$500 K, but equilibrated water can be transported to the snow line (and beyond) via turbulent diffusion and consequently mix with isotopically comet-like water. Under certain simplifying assumptions, we calcul...

  5. The anatectic effect on the zircon Hf isotope composition of migmatites and associated granites

    Science.gov (United States)

    Chen, Yi-Xiang; Gao, Peng; Zheng, Yong-Fei

    2015-12-01

    Zircon Hf isotope composition is widely used to trace the growth and evolution of continental crust. However, it is controversial whether the Hf isotope composition of magmatic zircons can faithfully reflect that of their sources, especially for S-type granites. In order to provide an insight into this issue, we have revisited the published Lu-Hf isotope data of zircons from well-studied migmatites and associated granites in the Sulu orogen and the Cathaysian terrane, respectively. The results show greatly elevated 176Hf/177Hf ratios (by more than 10ε units) for newly grown zircon domains compared to the relict zircon domains. This indicates considerable contributions from non-zircon Hf to anatectic melts during crustal anatexis and subsequent magmatism. Furthermore, this more radiogenic Hf isotope signature was not erased during magmatic processes such as crystal fractionation during melt ascent and emplacement. The budget of Hf isotopes in source rocks with respect to mineral Lu/Hf ratios suggests the involvement of Hf-bearing major minerals in anatectic reactions by dissolving Hf-bearing major minerals into the anatectic melts. The significant Hf isotope variations in some anatectic and magmatic zircon domains from the migmatites and granites suggest not only the source heterogeneity but also the variable non-zircon Hf contributions. As such, the Hf isotope compositions of anatectic and magmatic zircons are substantially dictated by the mass balance between the non-zircon Hf from anatectic reactions and the zircon-Hf from the dissolution of protolith zircons into the anatectic melts. They are primarily controlled by P-T conditions and mechanism of crustal anatexis, and the magmatic processes during melt evolution. The present study highlights the important contribution of non-zircon Hf to the anatectic and magmatic zircon domains. In this regard, the greatly elevated 176Hf/177Hf ratios for newly grown zircon domains in the migmatites and granites cannot reflect

  6. Isotopic and Elemental Composition of Roasted Coffee as a Guide to Authenticity and Origin.

    Science.gov (United States)

    Carter, James F; Yates, Hans S A; Tinggi, Ujang

    2015-06-24

    This study presents the stable isotopic and elemental compositions of single-origin, roasted coffees available to retail consumers. The δ(13)C, δ(15)N, and δ(18)O compositions were in agreement with those previously reported for green coffee beans. The δ(15)N composition was seen to be related to organic cultivation, reflected in both δ(2)H and δ(18)O compositions. The δ(13)C composition of extracted caffeine differed little from that of the bulk coffee. Stepwise discriminant analysis with jackknife tests, using isotopic and elemental data, provided up to 77% correct classification of regions of production. Samples from Africa and India were readily classified. The wide range in both isotopic and elemental compositions of samples from other regions, specifically Central/South America, resulted in poor discrimination between or within these regions. Simpler X-Y and geo-spatial plots of the isotopic data provided effective visual means to distinguish between coffees from different regions. PMID:26001050

  7. SIMSISH technique does not alter the apparent isotopic composition of bacterial cells.

    Directory of Open Access Journals (Sweden)

    Olivier Chapleur

    Full Text Available In order to identify the function of uncultured microorganisms in their environment, the SIMSISH method, combining in situ hybridization (ISH and nanoscale secondary ion mass spectrometry (nanoSIMS imaging, has been proposed to determine the quantitative uptake of specific labelled substrates by uncultured microbes at the single cell level. This technique requires the hybridization of rRNA targeted halogenated DNA probes on fixed and permeabilized microorganisms. Exogenous atoms are introduced into cells and endogenous atoms removed during the experimental procedures. Consequently differences between the original and the apparent isotopic composition of cells may occur. In the present study, the influence of the experimental procedures of SIMSISH on the isotopic composition of carbon in E. coli cells was evaluated with nanoSIMS and compared to elemental analyser-isotopic ratio mass spectrometer (EA-IRMS measurements. Our results show that fixation and hybridization have a very limited, reproducible and homogeneous influence on the isotopic composition of cells. Thereby, the SIMSISH procedure minimizes the contamination of the sample by exogenous atoms, thus providing a means to detect the phylogenetic identity and to measure precisely the carbon isotopic composition at the single cell level. This technique was successfully applied to a complex sample with double bromine - iodine labelling targeting a large group of bacteria and a specific archaea to evaluate their specific (13C uptake during labelled methanol anaerobic degradation.

  8. Isotopic composition of trace elements in presolar silicon carbide A+B grains

    Science.gov (United States)

    Savina, M.; Tripa, C.; Pellin, M.; Davis, A.; Clayton, R.; Lewis, R.; Amari, S.

    2003-04-01

    Presolar SiC are classified into several types based on C, N, and Si isotopic compositions. Most are mainstream, which are generally believed to derive from low-mass asymptotic giant branch (AGB) stars. Among the less common grains, A+B grains, which comprise ˜3-4% of presolar SiC, are perhaps the least well understood. Recent measurements of trace element concentration patterns in individual grains suggest that A+B grains can be divided into at least 4 groups, and thus have multiple astrophysical sites of origin^1. We report here our Resonant Ionization Mass Spectrometry (RIMS) measurements of Zr, Mo, Ba, and Fe isotopic compositions in individual mainstream and type A+B presolar SiC. While the mainstream grains show isotopic compositions compatible with condensation around low-mass AGB stars, most A+B grains have near-solar isotopic compositions, though some show Zr, Mo, and Fe isotope patterns that have not been observed in other types of presolar SiC grains. We discuss these results in terms of possible astrophysical sites for the production of these unusual grains. This work was supported in part by the Department of Energy, BES-Materials Sciences through Contract No. W-31-109-ENG-38. ^1 Amari S., Nittler L. R., Zinner E., Lodders K., and Lewis R. S. (2001) Astrophys. J. 559, 463-483.

  9. Intermediate-temperature environmental effects on boron nitride-coated silicon carbide-fiber-reinforced glass-ceramic composites

    International Nuclear Information System (INIS)

    The environmental effects on the mechanical properties of fiber-reinforced composites at intermediate temperatures were investigated by conducting flexural static-fatigue experiments in air at 600 and 950 C. The material that was studied was a silicon carbide/boron nitride (SiC/BN) dual-coated Nicalon-fiber-reinforced barium magnesium aluminosilicate glass-ceramic. Comparable time-dependent failure responses were found at 600 and 950 C when the maximum tensile stress applied in the bend bar was >60% of the room-temperature ultimate flexural strength of as-received materials. At both temperatures, the materials survived 500 h fatigue tests at lower stress levels. Among the samples that survived the 500 h fatigue tests, a 20% degradation in the room temperature flexural strength was measured in samples that were fatigued at 600 C. The growth rate of the Si-C-O fiber oxidation product at 600 C was not sufficient to seal the stress-induced cracks, so that the interior of the material was oxidized and resulted in a strength degradation and less fibrous fracture. In contrast, the interior of the material remained intact at 950 C because of crack sealing by rapid silicate formation, and strength/toughness of the composite was maintained. Also, at 600 C, BN oxidized via volatilization, because no borosilicate was formed

  10. Spurious and functional correlates of the isotopic composition of a generalist across a tropical rainforest landscape

    Directory of Open Access Journals (Sweden)

    Poirson Evan K

    2009-11-01

    Full Text Available Abstract Background The isotopic composition of generalist consumers may be expected to vary in space as a consequence of spatial heterogeneity in isotope ratios, the abundance of resources, and competition. We aim to account for the spatial variation in the carbon and nitrogen isotopic composition of a generalized predatory species across a 500 ha. tropical rain forest landscape. We test competing models to account for relative influence of resources and competitors to the carbon and nitrogen isotopic enrichment of gypsy ants (Aphaenogaster araneoides, taking into account site-specific differences in baseline isotope ratios. Results We found that 75% of the variance in the fraction of 15N in the tissue of A. araneoides was accounted by one environmental parameter, the concentration of soil phosphorus. After taking into account landscape-scale variation in baseline resources, the most parsimonious model indicated that colony growth and leaf litter biomass accounted for nearly all of the variance in the δ15N discrimination factor, whereas the δ13C discrimination factor was most parsimoniously associated with colony size and the rate of leaf litter decomposition. There was no indication that competitor density or diversity accounted for spatial differences in the isotopic composition of gypsy ants. Conclusion Across a 500 ha. landscape, soil phosphorus accounted for spatial variation in baseline nitrogen isotope ratios. The δ15N discrimination factor of a higher order consumer in this food web was structured by bottom-up influences - the quantity and decomposition rate of leaf litter. Stable isotope studies on the trophic biology of consumers may benefit from explicit spatial design to account for edaphic properties that alter the baseline at fine spatial grains.

  11. The isotopic composition of methane in the stratosphere: high-altitude balloon sample measurements

    Directory of Open Access Journals (Sweden)

    T. Röckmann

    2011-12-01

    Full Text Available The isotopic composition of stratospheric methane has been determined on a large suite of air samples from stratospheric balloon flights covering subtropical to polar latitudes and a time period of 16 yr. 154 samples were analyzed for δ13C and 119 samples for δD, increasing the previously published dataset for balloon borne samples by an order of magnitude, and more than doubling the total available stratospheric data (including aircraft samples published to date. The samples also cover a large range in mixing ratio from tropospheric values near 1800 ppb down to only 250 ppb, and the strong isotope fractionation processes accordingly increase the isotopic composition up to δ13C = −14‰ and δD = +190‰, the largest enrichments observed for atmospheric CH4 so far. When analyzing and comparing kinetic isotope effects (KIEs derived from single balloon profiles, it is necessary to take into account the residence time in the stratosphere in combination with the observed mixing ratio and isotope trends in the troposphere, and the range of isotope values covered by the individual profile. The isotopic composition of CH4 in the stratosphere is affected by both chemical and dynamical processes. This severely hampers interpretation of the data in terms of the relative fractions of the three important sink mechanisms (reaction with OH, O(1D and Cl. It is shown that a formal sink partitioning using the measured data severely underestimates the fraction removed by OH, which is likely due to the insensitivity of the measurements to the kinetic fractionation in the lower stratosphere. Full quantitative interpretation of the CH4 isotope data in terms of the three sink reactions requires a global model.

  12. Respiration and assimilation processes reflected in the carbon isotopic composition of atmospheric carbon dioxide

    International Nuclear Information System (INIS)

    The paper presents diurnal variations of concentration and carbon isotopic composition of atmospheric carbon dioxide caused by respiration and assimilation processes. Air samples were collected during early and late summer in 1998 in unpolluted area (village Guciow located near Roztocze National Park, SE Poland) in three different environments: uncultivated field on a hill, a meadow in the Wieprz river valley and a forest. The effect is very strong during intensive vegetation growth on a sunny day and clear night. The largest diurnal variations in atmospheric CO2 concentration and its carbon isotopic composition in June above the meadow were about 480 ppm and 10 pro mille, respectively. (author)

  13. Isotope Compositions Of Mekong River Flow Water In The South Of Vietnam

    International Nuclear Information System (INIS)

    As a part of the Research Contract No. VIE/12569, isotope composition of Mekong river flow water in the South of Vietnam has been monitored to provide information on water origin and residence times, surface-groundwater exchange in the monitoring area. According to the primary results obtained, a seasonal variation as well as the dependence on local precipitation and on the river water level of isotopic composition of two distributaries of Mekong river water have been observed. At the same time a slight change on season of tritium in rivers water and the difference between tritium content in local rainy water and river water has been recorded. (author)

  14. Isotopic composition of precipitation from Algiers and Assekrem

    International Nuclear Information System (INIS)

    Two stations of rainfall sampling and measurements of meteorological parameters were used in this study. The first one, located in Algiers, is under Mediterranean climatic influence. The second one, located in the Ahaggar massif, in the middle of Sahara desert, is subject to the extreme inflow of African western monsoon. In Algiers, the mean isotopic contents of precipitation [δ18O= -5 per mille; δ2H= -28 per mille vs VSMOW], define a meteoric water line of slope 7.1, in conformity with what is known in similar climatic situation. The deuterium excess is 11.4 per mille. In Assekrem, the isotopic results of period 2000/2004, indicate relatively enriched values δ18O=-0.2 per mille; δ2H= +8 per mille), compared to the normal. This is due to the preponderance of the summer rains (hot season) compared to the rains of the fresh season (autumn and winter). The oxygen/deuterium relationship presents a slope of 5.05, typical of evaporating line. The mean value of deuterium excess is 1.6 per mille. The strong isotopic signal in precipitation associated with Inter Tropical Convergence Zone (ITCZ) displacement represents an excellent methodology for a correct reconstruction of the current atmospheric circulation and climatic changes suffered by the region. (author)

  15. Sulfur isotopic composition of modern seafloor hydrothermal sediment and its geological significance

    Institute of Scientific and Technical Information of China (English)

    曾志刚; 李军; 蒋富清; 秦蕴珊; 翟世奎

    2002-01-01

    A total of 1 264 sulfur isotopic values for modem seafloor hydrothermel sediments from different hydrothermal fidds have been collected. On this basis, combining our sulfur isotpic data for surface hydrothermal sediments from the Jade hydrohtermal field in the Okinawa Trough and the TAG hydrothermal field in the Mid-Atlantic Ridge, respectively, and comparing the sulfur isotopic compositions and analyzing their sources of sulfur in seafloor hydrothermal sediments from different geologic-tectonic setting, the results show that: ( 1 ) sulfur isotopic values of sulfides and sulfates in modern seafloor hydrothermal sediments are concentrated in a narrow range, δ34S values of sulfides vary from l × 10-3 to 9 × 10- 3, with a mean of 4.5 × 10- 3 ( n = 1 042), δ34S values of sulfates vary from 19 × 10- 3 to 24× 10-3, with a mean of 21.3× 10-3 (n =217); (2) comparing the sulfur isotopic compositions of hydrothermal sediments from the sediment-hosted hydrothermal fields, the range of sulfur isotopic values for hydrothermal sediments from the sediment-free hydrothermal fields is narrow relatively; (3) the differences of sulfur isotopic compositions in sulfides from different hydrothermal fields show the differences in the sources of sulfur. The sulfur of hydrothermal sulfides in the sediment-free mid-ocean ridges is mainly from mid-ocean ridge basalt, and partially from the reduced seawater sulfate, and it is the result of partially reduced seawater sulfate mixed with basaltic sulfur. In the sediment-hosted nid-ocean ridges and the back-arc basins, the volcanics, the sediments and the organic matters also can offer their sulfur for forming hydrothermal sulfides; (4) the variations of sulfur isotopic compositions and the different sources of sulfur for hydrothermal sediments may be attributed to the various physical-chemical characteristics of hydrothermal fluids, the magmatic evolution and the different geologic-tectonic settings of seafloor hydrothermal systems.

  16. 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.

  17. H, C, and N isotopic compositions of Hayabusa category 3 organic samples

    Science.gov (United States)

    Ito, Motoo; Uesugi, Masayuki; Naraoka, Hiroshi; Yabuta, Hikaru; Kitajima, Fumio; Mita, Hajime; Takano, Yoshinori; Karouji, Yuzuru; Yada, Toru; Ishibashi, Yukihiro; Okada, Tatsuaki; Abe, Masanao

    2014-08-01

    Since isotopic ratios of H, C, and N are sensitive indicators for determining extraterrestrial organics, we have measured these isotopes of Hayabusa category 3 organic samples of RB-QD04-0047-02, RA-QD02-0120, and RB-QD04-0001 with ion imaging using a NanoSIMS ion microprobe. All samples have H, C, and N isotopic compositions that are terrestrial within errors (approximately ±50‰ for H, approximately ±9‰ for C, and approximately ±2‰ for N). None of these samples contain micrometer-sized hot spots with anomalous H, C, and N isotopic compositions, unlike previous isotope data for extraterrestrial organic materials, i.e., insoluble organic matters (IOMs) and nano-globules in chondrites, interplanetary dust particles (IDPs), and cometary dust particles. We, therefore, cannot conclude whether these Hayabusa category 3 samples are terrestrial contaminants or extraterrestrial materials because of the H, C, and N isotopic data. A coordinated study using microanalysis techniques including Fourier transform infrared spectrometry (FT-IR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), NanoSIMS ion microprobe, Raman spectroscopy, X-ray absorption near edge spectroscopy (XANES), and transmission electron microscopy/scanning transmission electron microscopy (TEM/STEM) is required to characterize Hayabusa category 3 samples in more detail for exploring their origin and nature.

  18. Plutonium isotopes in the atmosphere of Central Europe: Isotopic composition and time evolution vs. circulation factors.

    Science.gov (United States)

    Kierepko, Renata; Mietelski, Jerzy W; Ustrnul, Zbigniew; Anczkiewicz, Robert; Wershofen, Herbert; Holgye, Zoltan; Kapała, Jacek; Isajenko, Krzysztof

    2016-11-01

    This paper reports evidence of Pu isotopes in the lower part of the troposphere of Central Europe. The data were obtained based on atmospheric aerosol fraction samples collected from four places in three countries (participating in the informal European network known as the Ring of Five (Ro5)) forming a cell with a surface area of about 200,000km(2). We compared our original data sets from Krakow (Poland, 1990-2007) and Bialystok (Poland, 1991-2007) with the results from two other locations, Prague (Czech Republic; 1997-2004) and Braunschweig (Germany; 1990-2003) to find time evolution of the Pu isotopes. The levels of the activity concentration for (238)Pu and for ((239+240))Pu were estimated to be a few and some tens of nBqm(-3), respectively. However, we also noted some results were much higher (even about 70 times higher) than the average concentration of (238)Pu in the atmosphere. The achieved complex data sets were used to test a new approach to the problem of solving mixing isotopic traces from various sources (here up to three) in one sample. Results of our model, supported by mesoscale atmospheric circulation parameters, suggest that Pu from nuclear weapon accidents or tests and nuclear burnt-up fuel are present in the air. PMID:27450248

  19. Carbon isotope composition of latex does not reflect temporal variations of photosynthetic carbon isotope discrimination in rubber trees (Hevea brasiliensis).

    Science.gov (United States)

    Kanpanon, Nicha; Kasemsap, Poonpipope; Thaler, Philippe; Kositsup, Boonthida; Gay, Frédéric; Lacote, Régis; Epron, Daniel

    2015-11-01

    Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on average) with more variable δ(13)C values than those of untapped trees. δ(13)C-L was higher and more stable across seasons than δ(13)C-S and δ(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. δ(13)C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in δ(13)C-L and δ(13)C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between δ(13)C-L and δ(13)C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping. PMID:26358051

  20. Coupled isotopes of plant wax and hemicellulose markers record information on relative humidity and isotopic composition of precipitation

    Directory of Open Access Journals (Sweden)

    M. Tuthorn

    2015-02-01

    Full Text Available The δ2H isotopic composition of leaf waxes is used increasingly for paleohydrological and -climate reconstructions. However, it is challenging to disentangle past changes in the isotopic composition of precipitation and changes in evapotranspirative enrichment of leaf water. We analyzed δ2H on n-alkanes and fatty acids in topsoils along a climate transect in Argentina, for which we had previously measured δ18O on plant-derived sugars. Our results indicate that leaf wax biomarker δ2H values (δ2Hlipids primarily reflect δ2Hsource water (precipitation, but are modulated by evapotranspirative enrichment. A mechanistic model is able to produce the main trends in δ2Hlipids along the transect, but seems to slightly underestimate evapotranspirative enrichment in arid regions and overestimate it in grass-dominated ecosystems. Furthermore, the (i coupling of the δ2Hlipid and δ18Osugar biomarker results and (ii application of biosynthetic fractionation factors allows calculating the δ2H-δ18O isotopic composition of leaf water along the transect. This also yields the deuterium excess (d excess of leaf water, which mainly reflects evapotranspirative enrichment, and can be used to model relative air humidity (RH. The high correlation of modeled (reconstructed based on biomarker results and measured RH, as well as the good agreement between modeled and actual δ2H and δ18O of precipitation along the transect lends support to the coupled δ2Hlipid and δ18Osugar biomarker approach for future paleoclimate research.

  1. Factors controlling the stable isotopic composition of recent precipitation in Spain

    International Nuclear Information System (INIS)

    Composite monthly samples of precipitation were collected for the period 2000-2004 at 16 meteorological stations included in the 'Red Espanola de Vigilancia de Isotopos en la Precipitation' (REVIP), the Spanish Network for Isotopes in Precipitation, Oxygen-18 and deuterium results were used to review previous maps showing the spatial distribution of isotope contents over the Iberian Peninsula. Long-term mean weighted values of δ18O over the Iberian Peninsula range from ca. -4.0 per mille in stations from Andalusia to ca. -10.0 per mille in the stations located in the northern plateau. The δ2H-δ18O relationship of the long-term, weighted means is in good agreement with the GMWL, showing excess values only slightly above 10 per mille indicating the relevance of air masses of Atlantic origin, as the main source of water vapour over the Iberian Peninsula. The spatial distribution of δ18O and δ2H in precipitation over the Iberian Peninsula can be explained by a simple multiple regression model, based on two geographic factors: latitude and elevation. This polynomial model reproduces reasonably well the observed spatial distribution of the stable isotope composition of precipitation over Spain, facilitating the use of stable isotopes as a tool to trace the origin of surface and ground waters. Differences between measured and predicted δ18O values with both global and local scale models are explained by other regional and local factors that influence the isotopic composition of precipitation. (author)

  2. Factors controlling the stable isotopic composition of recent precipitation in Spain

    International Nuclear Information System (INIS)

    Composite monthly samples of precipitation were collected for the period 2000- 2004 at 16 meteorological stations included in the 'Red Espanola de Vigilancia de Isotopos en la Precipitacion' (REVIP), the Spanish Network for Isotopes in Precipitation. Oxygen-18 and deuterium results were used to review previous maps showing the spatial distribution of isotope contents over the Iberian Peninsula. Long-term mean weighted values of δ18O over the Iberian Peninsula range from ca. -4.0 per mille in stations from Andalusia to ca. -10.0 per mille in the stations located in the northern plateau. The δ2H-δ18O relationship of the long-term weighted means is in good agreement with the GMWL, showing d-excess values only slightly above 10 per mille, indicating the relevance of air masses of Atlantic origin, as the main source of water vapour over the Iberian Peninsula. The spatial distribution of δ18O and δ2H in precipitation over the Iberian Peninsula can be explained by a simple multiple regression model, based on two geographic factors: latitude and elevation. This polynomial model reproduces reasonably well the observed spatial distribution of the stable isotope composition of precipitation over Spain, facilitating the use of stable isotopes as a tool to trace the origin of surface and ground waters. Differences between measured and predicted δ18O values with both global and local scale models are explained by other regional and local factors that influence the isotopic composition of precipitation. (author)

  3. Source identification of Malaysian atmosphere polycyclic aromatic hydrocarbons nearby forest fires using molecular and isotopic compositions

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, Tomoaki; Takada, Hideshige [Tokyo Univ. of Agriculture and Technology (Japan). Faculty of Agriculture; Kumata, Hidetoshi [Tokyo Univ. of Pharmacy and Life Sciences (Japan); Zakaria, M.P. [Universiti Putra Malaysia, Selangor (Malaysia). Dept. of Environmental Sciences; Naraoka, Hiroshi; Ishiwatari, Ryoshi [Tokyo Metropolitan Univ., Hachioji (Japan). Graduate School of Science

    2002-07-01

    We report measurements of molecular and carbon isotopic compositions of Malaysian atmospheric polycyclic aromatic hydrocarbons (PAHs) in smoke haze from the 1997 Indonesian forest fire. Comparison of the carbon isotopic compositions ({sup {delta}}1{sup 3C}) of individual PAHs from the smoke haze, with those from other PAHs sources (soot collected from gasoline and diesel vehicle muffler, woodburning smoke), enables us to discriminate among the diverse sources of atmospheric PAHs. Soot PAHs extracted from gasoline and diesel vehicles show heavy isotopic signatures with a large inter-species {sup {delta}}1{sup 3C} variation from {sup -}12.9 per mille to {sup -}26.6 per mille, compared to soot PAHs extracted from woodburning smoke which are isotopically light, and have a small inter-species {sup {delta}}{sup 13}C variation from {sup -}26.8 per mille to -31.6 per mille. Values from -17.7 per mille to -27.9 per mille were obtained for the corresponding PAHs extracted from the smoke haze, indicating that they are derived mainly from automotive exhaust. Molecular and isotopic compositions of PAHs extracted from smoke haze were similar to those extracted from non-haze aerosol. Quantitative estimation shows that woodburning contribution to Malaysian atmospheric PAHs ranges from 25% to 35% with no relation to haze intensity, while automotive contribution ranges from 65% to 75%. These results suggest that the major contributor of PAHs in Malaysian air is automotive exhaust whether smoke haze is observed or not. (Author)

  4. Oxygen and carbon isotope composition from the UHP Shuanghe marbles, Dabie Mountains, China

    Institute of Scientific and Technical Information of China (English)

    王清晨; Douglas; Rumble

    1999-01-01

    Investigations on the oxygen and carbon isotope compositions from the ultrahigh-pressure (UHP)-metamorphosed Shuanghe marbles, that occur as a member of a UHP slab, show that the δ18O values range from +11.1‰ to+20.5‰ SMOW, and δ13C from+1.0‰ to+5.7‰ PDB, respectively. The variations in isotope compositions show a centimeter scale of homogeneity and a heterogeneity of regional scale larger than 1 meter. In contrast to the eclogite marbles from Norway, the Shuanghe marbles have inherited the carbon isotope compositions from their sedimentary precursor. The δ13C shows positive correlation to the content of dolomite. The depletion in 18O, compared with the protolithic carbonate strata, might result from three possible geological processes: 1) exchanging oxygen isotope with meteoric water before the UHP metamorphism, 2) decarbonation during the UHP metamorphism, and 3) exchanging oxygen isotope with country gneiss at local scale during retrograde metamorphism. It seems that the adveetion

  5. Isotopic composition and neutronics of the Okelobondo natural reactor

    Science.gov (United States)

    Palenik, Christopher Samuel

    The Oklo-Okelobondo and Bangombe uranium deposits, in Gabon, Africa host Earth's only known natural nuclear fission reactors. These 2 billion year old reactors represent a unique opportunity to study used nuclear fuel over geologic periods of time. The reactors in these deposits have been studied as a means by which to constrain the source term of fission product concentrations produced during reactor operation. The source term depends on the neutronic parameters, which include reactor operation duration, neutron flux and the neutron energy spectrum. Reactor operation has been modeled using a point-source computer simulation (Oak Ridge Isotope Generation and Depletion, ORIGEN, code) for a light water reactor. Model results have been constrained using secondary ionization mass spectroscopy (SIMS) isotopic measurements of the fission products Nd and Te, as well as U in uraninite from samples collected in the Okelobondo reactor zone. Based upon the constraints on the operating conditions, the pre-reactor concentrations of Nd (150 ppm +/- 75 ppm) and Te (operation were calculated as a function of burnup. These results provide a source term against which the present elemental and decay abundances at the fission reactor can be compared. Furthermore, they provide new insights into the extent to which a "fossil" nuclear reactor can be characterized on the basis of its isotopic signatures. In addition, results from the study of two other natural systems related to the radionuclide and fission product transport are included. A detailed mineralogical characterization of the uranyl mineralogy at the Bangombe uranium deposit in Gabon, Africa was completed to improve geochemical models of the solubility-limiting phase. A study of the competing effects of radiation damage and annealing in a U-bearing crystal of zircon shows that low temperature annealing in actinide-bearing phases is significant in the annealing of radiation damage.

  6. Oxygen and carbon isotopic compositions of gases respired by humans

    OpenAIRE

    Epstein, S.; Zeiri, L.

    1988-01-01

    Oxygen-isotope fractionation associated with respiration in human individuals at rest is linearly related to the fraction of the O2 utilized in the respiration process. The slope of this relationship is affected by a history of smoking, by vigorous exercise, and by the N2/O2 ratio of the inhaled gas. For patients who suffer anemia-related diseases, the slope of this relationship is directly proportional to their level of hemoglobin. These results introduce a new approach for studying the mech...

  7. Oxygen and carbon isotopic compositions of gases respired by humans

    International Nuclear Information System (INIS)

    Oxygen-isotope fractionation associated with respiration in human individuals at rest is linearly related to the fraction of the O2 utilized in the respiration process. The slope of this relationship is affected by a history of smoking, by vigorous exercise, and by the N2/O2 ratio of the inhaled gas. For patients who suffer anemia-related diseases, the slope of this relationship is directly proportional to their level of hemoglobin. These results introduce a new approach for studying the mechanisms of O2 consumption in human respiration and how they are affected by related diseases

  8. Measurement of the isotopic composition of germanium by k{sub 0}-INAA and INAA

    Energy Technology Data Exchange (ETDEWEB)

    Vermaercke, P., E-mail: pvermaer@sckcen.b [SCK-CEN, Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium); Hult, M. [EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg, B-2440 Geel (Belgium); Verheyen, L.; Farina Arbocco, F. [SCK-CEN, Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium)

    2010-10-11

    In experiments searching for neutrinoless double {beta}-decay high-purity Germanium detectors enriched in {sup 76}Ge will be used. Due to the nature of these experiments the isotopic composition of the enriched germanium is an important parameter. In order to determine the {sup 76}Ge/{sup 74}Ge isotopic ratio in this new material, but also in natural and depleted samples, the feasibility of using k{sub 0}- and relative standardisation neutron activation analysis for the determination of isotopic ratios was investigated. The paper will discuss the accuracy and the estimated uncertainty of both methods in general. It was found that both techniques are useful for the determination of isotopic ratios. The analysis also demonstrated that the k{sub 0}-data for Ge should be re-evaluated.

  9. The isotopic composition of precipitation on the Andes and Amazon of Bolivia

    International Nuclear Information System (INIS)

    In the years 1983-1985, the isotopic composition of precipitation was determined in monthly and annual samples collected from stations at different altitude along two transects from the Bolivian Altiplano to the Amazon basin. The data show variations with amount (in rainy season δ-values are more negative) and altitude. The isotopic gradient with altitude changes seasonally, being higher (in absolute value) in rainy months (January-February). The influence of the 1983 drought is clearly shown, with less negative δ-values and smaller isotopic gradients vs. altitude with respect to 1984. The drought was supposed to be connected with El Nino, very strong in 1982-1983, but this has not been confirmed in 1997-1998, when El Nino was even stronger. The isotopic contrast between the dry 1983 and the very humid 1984 can be identified in the ice core from the Sahama glacier. (author)

  10. Calculation of boron-isotope fractionation between B(OH)(3)(aq) and B(OH)(4)(-)(aq)

    Energy Technology Data Exchange (ETDEWEB)

    Rustad, James R.; Bylaska, Eric J.; Jackson, Virgil E.; Dixon, David A.

    2010-05-15

    Density functional and correlated molecular orbital calculations (MP2) are carried out on B(OH)3-nH2O clusters (n = 0, 6,32), and B(OH)-4.nH20 (n = 0, 8, 11, 32) to estimate the equilibrium distribution of 10B and 11B isotopes between boric acid and borate in aqueous solution. For the large 32-water clusters, multiple conformations are generated from ab initio molecular dynamics simulations to account for the effect of solvent fluctuations on the isotopic fractionation. We provide an extrapolated value of the equilibrium constant x34 for the isotope exchange reaction 10B(OH)3(aq) + 11B(OH)-4 (aq) = 11B(OH)3(aq) + 11B(OH)-4 (aq) of 1.026-1.028 near the MP2 complete basis set limit with 32 explicit waters of solvation. With some exchange-correlation functionals we find potentially important contributions from a tetrahedral neutral B(OH)3.H2O Lewis acid-base complex. The extrapolations presented here suggest that DFT calculations give a value for 103lnx34 about 15% higher than the MP2 calculations.

  11. Lattice dynamics of α boron and of boron carbide

    International Nuclear Information System (INIS)

    The atomic structure and the lattice dynamics of α boron and of B4C boron carbide have been studied by Density Functional Theory (D.F.T.) and Density Functional Perturbation Theory (D.F.P.T.). The bulk moduli of the unit-cell and of the icosahedron have been investigated, and the equation of state at zero temperature has been determined. In α boron, Raman diffusion and infrared absorption have been studied under pressure, and the theoretical and experimental Grueneisen coefficients have been compared. In boron carbide, inspection of the theoretical and experimental vibrational spectra has led to the determination of the atomic structure of B4C. Finally, the effects of isotopic disorder have been modeled by an exact method beyond the mean-field approximation, and the effects onto the Raman lines has been investigated. The method has been applied to isotopic alloys of diamond and germanium. (author)

  12. Variation of lithium isotope composition in the marine environment: A preliminary report

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Luiheung; Edmond, J.M. (Louisiana State Univ., Baton Rouge (USA))

    1988-06-01

    The Li isotopic compositions of ocean waters, lake water, hydrothermal solutions, altered and unaltered basalts have been determined using the technique of thermal ionization mass spectrometry of lithium tetraborate. Seawater appears to be homogeneous in Li isotopic composition. The mean {delta}{sup 6}Li value is {minus}32.3 {plus minus} 0.5{per thousand}, relative to an isotopic standard. Three lakes studied (Lake Tanganyika, Caspian Sea and Dead Sea) yield {delta}{sup 6}Li similar to the seawater isotopic composition. A fresh basalt glass from 21{degree}N, East Pacific Rise displays a {delta}{sup 6}Li value of {minus}4.7{per thousand}. A hydrothermal solution from a 21{degree}N vent field has {delta}{sup 6}Li of {minus}10{per thousand}, indicating incomplete extraction of Li from the igneous minerals or partial retention in secondary phases. The alteration margin of a basalt from the Mid-Atlantic Ridge has {delta}{sup 6}Li of {minus}8.4{per thousand}. The isotope data of submarine basalts suggest preferential removal of {sup 6}Li from seawater into alteration minerals during low temperature weathering. The {delta}{sup 6}Li values of two hydrothermal solutions from Guaymas Basin were found to be {minus}5{per thousand} and {minus}10{per thousand}. The results can be interpreted as the net effect of Li addition from basalt and sediments and incorporation in hydrothermal precipitates as the hydrothermal fluids interact with basin sediments. The observed enrichment of {sup 7}Li in seawater relative to submarine hydrothermal solutions, its principal Li input, is tentatively attributed to isotopic fractionation associated with low temperature alteration of sea floor basalt and incorporation in authigenic sediments. It appears that the Li isotope system may have characteristics that can resolve the mass balance of Li in the ocean.

  13. Lithium contents and isotopic compositions of ferromanganese deposits from the global ocean

    Science.gov (United States)

    Chan, L.-H.; Hein, J.R.

    2007-01-01

    To test the feasibility of using lithium isotopes in marine ferromanganese deposits as an indicator of paleoceanographic conditions and seawater composition, we analyzed samples from a variety of tectonic environments in the global ocean. Hydrogenetic, hydrothermal, mixed hydrogenetic–hydrothermal, and hydrogenetic–diagenetic samples were subjected to a two-step leaching and dissolution procedure to extract first the loosely bound Li and then the more tightly bound Li in the Mn oxide and Fe oxyhydroxide. Total leachable Li contents vary from 2 by coulombic force. Hence, the abundant Li in hydrothermal deposits is mainly associated with the dominant phase, MnO2. The surface of amorphous FeOOH holds a slightly positive charge and attracts little Li, as demonstrated by data for hydrothermal Fe oxyhydroxide. Loosely sorbed Li in both hydrogenetic crusts and hydrothermal deposits exhibit Li isotopic compositions that resemble that of modern seawater. We infer that the hydrothermally derived Li scavenged onto the surface of MnO2 freely exchanged with ambient seawater, thereby losing its original isotopic signature. Li in the tightly bound sites is always isotopically lighter than that in the loosely bound fraction, suggesting that the isotopic fractionation occurred during formation of chemical bonds in the oxide and oxyhydroxide structures. Sr isotopes also show evidence of re-equilibration with seawater after deposition. Because of their mobility, Li and Sr in the ferromanganese crusts do not faithfully record secular variations in the isotopic compositions of seawater. However, Li content can be a useful proxy for the hydrothermal history of ocean basins. Based on the Li concentrations of the globally distributed hydrogenetic and hydrothermal samples, we estimate a scavenging flux of Li that is insignificant compared to the hydrothermal flux and river input to the ocean.

  14. Electronic transport in boron carbides: temperature (4K-300K), frequency (0-1 GHz) and composition (B13C2-B4C) effects

    International Nuclear Information System (INIS)

    Boron carbide is a light ceramics of industrial interest. The equilibrium diagram reveals a large compositional range (B9C to B4C). The compositions close to the boundary B4C are obtained by pressing directly in graphite dies while the other compositions were obtained by using boron nitride lined graphite dies and boron additions to the commercial powders. The starting point of the present study was the idea to use the electrical transport properties as possible ways of characterising the industrial materials. We were thus led to measure at low temperatures dc and ac conductivity, dielectric constant and thermopower. The successful study of a measurement method for ac measurements between 10 KHz and 1 GHz and between 4 K and 300 K was one of the main experimental points of the present work. ac measurements have permitted a clear separation between bulk and grain boundary effects on the transport. The bulk results were analysed in terms of the usual conduction models in disordered solids (hopping, polarons...)

  15. Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

    Science.gov (United States)

    Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

    2016-09-01

    Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The "Multigroup γ-ray Analysis Method for Uranium" (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

  16. Comparisons of the predicted and measured isotopic composition for high burnup PWR spent fuels

    International Nuclear Information System (INIS)

    Comparisons between the calculated and measured isotopic composition for high burnup Korean PWR spent fuel samples were carried out. Spent fuel samples used in this study were obtained from commercial Korean PWRs, Ulchin unit 2 and Yonggwang unit 1. A radiochemical analysis of the spent fuel samples was performed to determine the isotopic compositions of U, Pu, and Nd. The depletion calculations which were carried out using the SAS2H control module in Version 5.1 of the SCALE code system were compared with the results of the radiochemical analyses. The results derived from the measured and calculated concentrations for each isotope of the corresponding samples were generally consistent with the earlier studies and the results were different within a few percent. The validity of the SAS2H control module in Version 5.1 of the SCALE code system could be confirmed in a high burnup spent fuel above 45 GWd/MTU

  17. Isotopic Composition of Xenon in Petroleum from the Shell Bullwinkle Field

    Indian Academy of Sciences (India)

    J Nuzzo*; M Hyman; M W Rowe; Mnraoz; R L Palma; J Westrich

    2000-03-01

    We have measured the abundance and isotopic composition of xenon in petroleum samples from the Shell Bullwinkle Field off the coast of Louisiana. We used an oxidation and purification procedure designed to insure complete extraction and clean up of xenon from the petroleum. The xenon isotopic composition was found to be similar to the atmospheric value for one petroleum sample. While the results of the second sample suggest possible enrichment of the heavier isotopes, the errors associated with these excesses preclude a definitive statement to that effect. No monoisotopic enrichment in 129Xe was detected in either sample, the presence of which might have allowed us to deduce the petroleum age. Our results represent only the second xenon measurement from petroleum, and the concentrations are within the range of values published in the earlier report.

  18. Isotopic composition of xenon in petroleum from the Shell Bullwinkle field

    International Nuclear Information System (INIS)

    We have measured the abundance and isotopic composition of xenon in petroleum samples from the Shell Bullwinkle field off the coast of Louisiana. We used an oxidation and purification procedure designed to insure complete extraction and clean up of xenon from the petroleum. The xenon isotopic composition was found to be similar to the atmospheric value for one petroleum sample. While the results of the second sample suggest possible enrichment of the heavier isotopes, the errors associated with these excesses preclude a definitive statement to that effect. No monoisotopic enrichment in 129Xe was detected in either sample, the presence of which might have allowed us to deduce the petroleum age. Our results represent only the second xenon measurement from petroleum, and the concentrations are within the range of values published in the earlier report. (author)

  19. Isotopic composition of xenon in petroleum from the shell bullwinkle field

    Science.gov (United States)

    Nuzzo, J.; Hyman, M.; Rowe, M. W.; Rao, M. N.; Palma, R. L.; Westrich, J.

    2000-03-01

    We have measured the abundance and isotopic composition of xenon in petroleum samples from the Shell Bullwinkle Field off the coast of Louisiana. We used an oxidation and purification procedure designed to insure complete extraction and clean up of xenon from the petroleum. The xenon isotopic composition was found to be similar to the atmospheric value for one petroleum sample. While the results of the second sample suggest possible enrichment of the heavier isotopes, the errors associated with these excesses preclude a definitive statement to that effect. No monoisotopic enrichment in129Xe was detected in either sample, the presence of which might have allowed us to deduce the petroleum age. Our results represent only the second xenon measurement from petroleum, and the concentrations are within the range of values published in the earlier report.

  20. Discrimination of the production sites of ancient pottery by using lead isotopic composition

    International Nuclear Information System (INIS)

    Discrimination of the production sites of ancient pottery by using lead isotopic composition is discussed in this paper. The authors have determined the lead isotopic compositions of ancient pottery from the Jiahu and Xishan sites, Henan Province. Most of Jiahu pottery show 206Pb/204Pb of 18.0 to 18.4 and 208Pb/204Pb of 38.4 to 38.8, while most of Xishan pottery show 20'6Pb/204Pb of 18.6 to 18.8 and 208Pb/204Pb of 38.7 to 39.1. Therefore, the lead isotopes are useful in discriminating the production sites of the ancient pottery in some cases

  1. Hydrochemistry and Isotopic Composition of the Sakumo Ramsar Site

    Directory of Open Access Journals (Sweden)

    C. Laar

    2011-03-01

    Full Text Available The objective of this study was geared towards determining the current pollution status of the Sakumo Ramsar site w ith the aim of identifying factors affecting the long-term “integrity” of the Ramsar site. Water quality deterioration, mainly salinization, has occurred in the Sakumo lagoon, Accra, Ghana. The cause of deterioration of water quality was studied using hydrochemical data and environmental isotopes of water; namely deuterium and oxygen-18 (measured as δ2H and δ180. Water samples were collected from the lagoon, feeder streams and some beverage and textile industries. The sequence of order of the heavy metals in the water observed in the Sakumo wetland was as follows: Fe > Mn > Cu >Hg. The δ2H and δ180 content prove successful when interpreted with corresponding hydrochemical data. The d-values of water samples from any source normally change due to history and processes to which the water molecules have been subjected in the environment. Results indicated both higher enrichment of heavier isotopes and higher chloride concentration in water sam ples from the lagoon than in water sam ples from other sources (industries and feeder stream s.

  2. [Isotopic composition of the delta-18O--delta-13C from the otoliths of reef fish from Taiaro (Tuamotu, French Polynesia): isotopic and biological implications].

    Science.gov (United States)

    Blamart, Dominique; Escoubeyrou, Karine; Juillet-Leclerc, Anne; Ouahdi, Rabia; Lecomte-Finiger, Raymonde

    2002-02-01

    Nuclei (larval stage) and outer parts (adult stage) of fish otoliths from the Taiaro closed lagoon (French Polynesia) and adjacent ocean have been analysed for the C-O isotopic compositions. delta 18O values of the nuclei of both populations indicate that isotopic equilibrium is reached. This implies that the lagoonal fish population has done its complete biological cycle in the lagoon and represents an adaptation in a closed system. delta 18O values of the outer parts show a slight isotopic disequilibrium (< 0.2@1000) interpreted in term of vital effect. All the delta 13C values exhibit a strong isotopic disequilibrium related to metabolic activity. PMID:11980181

  3. Stable isotope compositions (O-C) of reef fish otoliths from the Taiaro lagoon (Tuamotu, French Polynesia): isotopic and biologic implications

    International Nuclear Information System (INIS)

    Nuclei (larval stage) and outer parts (adult stage) of fish otoliths from the Taiaro closed lagoon (French Polynesia) and adjacent ocean have been analysed for the C-O isotopic compositions. δ18O values of the nuclei of both populations indicate that isotopic equilibrium is reached. This implies that the lagoonal fish population has done its complete biological cycle in the lagoon and represents an adaptation in a closed system. δ18O values of the outer parts show a slight isotopic disequilibrium (13C values exhibit a strong isotopic disequilibrium related to metabolic activity. (authors)

  4. Interpretation of groundwater origin in the Velenje coal mine on the basis of isotope composition

    Directory of Open Access Journals (Sweden)

    Janko Urbanc

    2002-12-01

    Full Text Available The aim of the investigation was to determine the isotopic properties of cave waters from the Velenje coal mine and define the recharge areas of individual aquifers. With regard to the oxygen isotope composition, groundwater in the Velenje coal mine can beclassified into three types. Typical d18O values of the first type are around -9 ‰ and are found in surface waters in the vicinity of the mine, therefore it is supposed that these waters are recharged locally. The second type is represented mainly by waters from thelower part of the pliocene aquifer. The average oxygen composition of these waters is about -11 ‰. This isotope composition is considerably different from the isotope composition of recent waters from the mine’s vicinity, which leads to the conclusion that these are older, fossile waters. These waters also have a very high degree of mineralization and consequently conductivity. Waters of the third type have average δ18O values around -10 ‰ and originate mainly from triassic dolomites. These waters could be a mixture of recentand old waters, but it is also possible that they flow into the coal mine from the higher areas of Paški Kozjak.

  5. The isotopic composition of soil organic carbon on a north - south transect in western Canada

    Czech Academy of Sciences Publication Activity Database

    Bird, M.; Šantrůčková, Hana; Lloyd, J.; Lawson, E.

    2002-01-01

    Roč. 53, - (2002), s. 393-403. ISSN 1351-0754 Institutional research plan: CEZ:AV0Z6066911 Keywords : isotopic composition * soil organic carbon * western Canada Subject RIV: EH - Ecology, Behaviour Impact factor: 1.452, year: 2002

  6. Diet control on carbon isotopic composition of land snail shell carbonate

    Institute of Scientific and Technical Information of China (English)

    LIU ZongXiu; GU ZhaoYan; WU NaiQin; XU Bing

    2007-01-01

    Carbon isotope compositions for both the carbonate shells and soft bodies (organic tissue) of living land snails collected mostly from the Loess Plateau, China have been measured. The result shows that δ13C values range from -13.1‰ to -4.3‰ for the aragonite shell samples and from -26.8‰ to -18.0‰ for the soft body samples. Although the shells are enriched in 13C relative to the bodies averagely by 14.2(±0.8)‰, the shell δ13Ca values are closely correlated to the body δ13Corg values, expressed as δ13Ca = 1.021 δ13Corg + 14.38 (R = 0.965; N = 31). This relationship indicates that δ13Ca is primarily a function of the isotopic composition of the snail diets since previous studies have proved that the snail body is the same as their food in carbon isotope composition. In other words, carbon isotope compo-sition of the carbonate shell can be used as a proxy to estimate the dietary 13C abundance of the land snails. The data also support that the 13C enrichment of the carbonate shells results mainly from the equilibrium fractionations between the metabolic CO2, HCO3- in the hemolymph and shell aragonite, and partially from kinetic fractionations when snail shells form during their activity.

  7. Isotopic composition of lead in oceanic basalt and its implication to mantle evolution

    International Nuclear Information System (INIS)

    New data are given in this report for (1) Pb isotopic compositions and U, Th, and Pb concentrations of basalts from the island of Hawaii: (2) redetermined Pb isotopic compositions of some abyssal tholeiites; and (3) U, Th, and Pb concentrations of altered and fresh abyssal basalts, and basalt genesis and mantle evolution are discussed. The Th/U ratios of abyssal and Japanese tholeiites are distinctly lower than those of tholeiites and alkali basalts from other areas. It is thought that these low values reflect a part of the mantle depleted in large ionic lithophile elements. Thus a mantle evolution model is presented, in which Th/U ratios of the depleted zone in the mantle have decreased to approximately 2, and U/Pb ratios have increased, showing an apparent approximately 1.5-b.y. isochron trend in the 207Pb/204Pb vs. 206Pb/204Pb plot. The Pb isotopic compositions of basalts from the island of Hawaii are distinct for each of the five volcanoes, and within each volcano, Pb's of tholeiites and alkali basalts are similar. An interaction between partially melted material (hot plume) of the asthenosphere and the lithosphere is suggested to explain the trend in the Pb isotopic compositions of Hawaiian basalts. (Auth.)

  8. A new and effective approach to boron removal by using novel boron-specific fungi isolated from boron mining wastewater.

    Science.gov (United States)

    Taştan, Burcu Ertit; Çakir, Dilara Nur; Dönmez, Gönül

    2016-01-01

    Boron-resistant fungi were isolated from the wastewater of a boron mine in Turkey. Boron removal efficiencies of Penicillium crustosum and Rhodotorula mucilaginosa were detected in different media compositions. Minimal Salt Medium (MSM) and two different waste media containing molasses (WM-1) or whey + molasses (WM-2) were tested to make this process cost effective when scaled up. Both isolates achieved high boron removal yields at the highest boron concentrations tested in MSM and WM-1. The maximum boron removal yield by P. crustosum was 45.68% at 33.95 mg l(-1) initial boron concentration in MSM, and was 38.97% at 42.76 mg l(-1) boron for R. mucilaginosa, which seemed to offer an economically feasible method of removing boron from the effluents. PMID:26877036

  9. Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

    Science.gov (United States)

    Zhang, Feifei; Zhu, Xiangkun; Yan, Bin; Kendall, Brian; Peng, Xi; Li, Jin; Algeo, Thomas J.; Romaniello, Stephen

    2015-11-01

    The nature of ocean redox chemistry between the Cryogenian Sturtian and Marinoan glaciations (ca. 663-654 Ma) is important for understanding the relationship between environmental conditions and the subsequent emergence and expansion of early animals. The Cryogenian-to-Ediacaran stratigraphic succession of the Nanhua Basin in South China provides a nearly complete sedimentary record of the Cryogenian, including a continuous record of interglacial sedimentation. Here, we present a high-resolution pyrite Fe isotope record for a ∼120-m-long drill-core (ZK105) through Sturtian glacial diamictites and the overlying interglacial sediments in the Nanhua Basin to explore changes in marine chemistry during the late Cryogenian. Our pyrite Fe isotope profile exhibits significant stratigraphic variation: Interval I, comprising middle to upper Tiesi'ao diamictites (correlative with the Sturtian glaciation), is characterized by light, modern seawater-like Fe isotope compositions; Interval II, comprising uppermost Tiesi'ao diamictites and the basal organic-rich Datangpo Formation, is characterized by an abrupt shift to heavier Fe isotope compositions; and Interval III, comprising organic-poor grey shales in the middle Datangpo Formation, is characterized by the return of lighter, seawater-like Fe isotope compositions. We infer that Interval I pyrite was deposited in a predominantly anoxic glacial Nanhua Basin through reaction of dissolved Fe2+ and H2S mediated by microbial sulfate reduction (MSR). The shift to heavier pyrite Fe isotope values in Interval II is interpreted as partial oxidation of ferrous iron to ferric iron and subsequent near-quantitative reduction and transformation of Fe-oxyhydroxides to pyrite through coupling with oxidation of organic matter in the local diagenetic environment. In Interval III, near-quantitative oxidation of ferrous iron to Fe-oxyhydroxides followed by near-quantitative reduction and conversion to pyrite in the local diagenetic environment

  10. Isotope variations of dissolved Zn in the Rio Grande watershed, USA: The role of adsorption on Zn isotope composition

    Science.gov (United States)

    Szynkiewicz, Anna; Borrok, David M.

    2016-01-01

    In order to better understand the factors influencing zinc (Zn) isotope composition in hydrological systems, we analyzed the δ66Zn of dissolved Zn in the streams and groundwater of the Upper and Middle Rio Grande watershed in Colorado and New Mexico, United States. The stream water samples have a wider variation of δ66Zn (-0.57 to + 0.41 ‰ relative to the JMC 3-0749-Lyon standard) than groundwater samples (-0.13 to + 0.12 ‰) and than samples from streams that are in close proximity to abandoned mining sites (+0.24 to + 0.40 ‰). Regional changes of bedrock geology, from primarily igneous rocks to primarily sedimentary rocks, have no resolvable effect on the δ66Zn of aqueous samples. Instead, an increase in water pH from 7.5 to 8.5 corresponds to a considerable decrease in the δ66Zn of dissolved Zn (R2 = - 0.37, p = 0.003, n = 22). Consequently, we link the observed Zn isotope variations to the process of adsorption of Zn onto suspended sediment and bedrock minerals (average Δ66Znadsorbed-dissolved = + 0.31 ‰). Our results are in good agreement with previous experimental and empirical studies suggesting that Zn adsorption leads to a residual dissolved pool enriched in light Zn isotopes. Given that anthropogenic Zn sources can also be responsible for lowering of δ66Zn, and may overlap with the pH/adsorption effect on δ66Zn, the latter needs to be carefully considered in future studies to differentiate between natural and anthropogenic factors influencing Zn isotopes in this and other aquatic systems.

  11. On the possibility of determining the radial profile of hydrogen isotope composition of JET plasmas, and of deducing radial transport of the isotope ions

    International Nuclear Information System (INIS)

    Measurements of internal hydrogen isotopic composition of plasmas in JET and elsewhere have been lacking. In this report we show that it is feasible to determine the profile of relative hydrogen isotope density, using a neutral particle analyzer. Using detailed modeling of the formation of atomic flux and its measurement, we have quantified sensitivity of the deduced plasma composition to uncertainty of plasma parameters that impact on the measurement. We have tested application of the proposed methodology by experimentally determining the perturbed deuteron density profile in a hydrogen plasma, when the deuteron density at the plasma edge was modulated using a short pulse of deuterium gas. We have also determined the deuteron density diffusivity. The determinations are very crude at present; however this exercise is intended to enable us to design better experiments to determine plasma isotopic composition and the radial isotope ion diffusivities. (author)

  12. Oxygen and nitrogen isotopic composition of nitrate in commercial fertilizers, nitric acid, and reagent salts.

    Science.gov (United States)

    Michalski, Greg; Kolanowski, Michelle; Riha, Krystin M

    2015-01-01

    Nitrate is a key component of synthetic fertilizers that can be beneficial to crop production in agro-ecosystems, but can also cause damage to natural ecosystems if it is exported in large amounts. Stable isotopes, both oxygen and nitrogen, have been used to trace the sources and fate of nitrate in various ecosystems. However, the oxygen isotope composition of synthetic and organic nitrates is poorly constrained. Here, we present a study on the N and O isotope composition of nitrate-based fertilizers. The δ(15)N values of synthetic and natural nitrates were 0 ± 2 ‰ similar to the air N2 from which they are derived. The δ(18)O values of synthetic nitrates were 23 ± 3 ‰, similar to air O2, and natural nitrate fertilizer δ(18)O values (55 ± 5 ‰) were similar to those observed in atmospheric nitrate. The Δ(17)O values of synthetic fertilizer nitrate were approximately zero following a mass-dependent isotope relationship, while natural nitrate fertilizers had Δ(17)O values of 18 ± 2 ‰ similar to nitrate produced photochemically in the atmosphere. These narrow ranges of values can be used to assess the amount of nitrate arising from fertilizers in mixed systems where more than one nitrate source exists (soil, rivers, and lakes) using simple isotope mixing models. PMID:26181213

  13. Determination of boron in steel by isotope-dilution inductively coupled plasma mass spectrometry after matrix separation

    International Nuclear Information System (INIS)

    The concentration of B in steels is important due to its influence on mechanical properties of steel such as hardenability, hot workability ,and creep resistance. An analytical method has been developed to determine B in steel samples by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). National Institute of Standard Reference Material (NIST SRM) 348a was analyzed to validate the analytical method. The steel sample was digested in a centrifuge bottle with addition of aqua regia and 10B spike isotope. Sample pH was then adjusted to higher than 10 to precipitate most matrix elements such as Fe, Cr and Ni. After centrifugation, the supernatant solution was passed through a cation exchange column to enhance the matrix separation efficiency. B recovery efficiency was about 37%, while matrix removal efficiency was higher than 99.9% for major matrix elements. The isotope dilution method was used for quantification and the determined B concentration was in good agreement with the certified value

  14. Influence of magnetite and boron carbide on radiation attenuation of cement-fiber/composite

    International Nuclear Information System (INIS)

    Trial was made to create composites from agriculture fibers, which have good mechanical, physical and radiation attenuation properties for different applications. Fast neutron and gamma ray spectra, as well as, slow neutron fluxes behind samples of cement-fiber (CF) (ρ=2.095 g cm-3) and cement-fiber-magnetite (CFM) (ρ=2.858 g cm-3)/composites have been investigated. Neutron and gamma spectra have been measured using a collimated reactor beam and neutron- gamma spectrometer with stilbene scintillator. A pulse shape discrimination technique based on zero cross over method was used to discriminate between neutron and gamma ray pulses. While, slow neutron fluxes have been measured using a collimated reactor beam and BF3 counter. Results were used to achieve removal cross sections (ΣR,meas.), total attenuation coefficients (μ) and macroscopic cross sections (Σ) of fast neutrons, gamma rays and slow neutrons respectively from the attenuation relations. Also, removal cross sections (ΣR,cal.) and total mass attenuation coefficients (μ/ρ) of fast neutrons and gamma rays have been calculated using the composites elemental composition and XCOM code respectively. Measured and calculated results were compared and a reasonable agreement was found

  15. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties. PMID:19687534

  16. Monitoring of chemical and isotopic composition of the Euphrates river in Syria

    International Nuclear Information System (INIS)

    The ratios of stable isotopes (18O and 2H), tritium content, together with the chemical composition of major ions of the Euphrates and Balikh (Euphrates tributary) Rivers, and the groundwaters of four wells drilled close to the Euphrates River course, were measured on a monthly basis. The Euphrates River water was monitored at twelve stations along its course in Syria during the period from January 2004 to December 2006, whereas those of the Balikh and groundwaters were only investigated during 2005. Although, the spatial variations of heavy stable isotope concentrations are moderated with respect to other large rivers in the world, the concentrations of these isotopes increase generally downstream the Euphrates River, with a sharp enrichment at Al-Assad Lake. This sharp increase could be explained by the effect of direct evaporation from the river and its tributaries; and the effect of drainage return flows of irrigation waters, isotopically more enriched. Enrichment of stable isotopes in the Euphrates River water was used as a direct indicator of evaporation. Based on an experimental evaporation result of a Euphrates water sample and the integral enrichment of heavy stable isotopes in the Euphrates River system, the amount of water losses by evaporation from Al-Assad Lake was estimated to be about 1.26 to 1.62 billion m''3, according to 18O and deuterium (2H), respectively. This amount represents about 12-16% of the renewable surface water resources in the country. (author)

  17. Stable bromine isotopic composition of methyl bromide released from plant matter

    Science.gov (United States)

    Horst, Axel; Holmstrand, Henry; Andersson, Per; Thornton, Brett F.; Wishkerman, Asher; Keppler, Frank; Gustafsson, Örjan

    2014-01-01

    Methyl bromide (CH3Br) emitted from plants constitutes a natural source of bromine to the atmosphere, and is a component in the currently unbalanced global CH3Br budget. In the stratosphere, CH3Br contributes to ozone loss processes. Studies of stable isotope composition may reduce uncertainties in the atmospheric CH3Br budget, but require well-constrained isotope fingerprints of the source end members. Here we report the first measurements of stable bromine isotopes (δ81Br) in CH3Br from abiotic plant emissions. Incubations of both KBr-fortified pectin, a ubiquitous cell-stabilizing macromolecule, and of a natural halophyte (Salicornia fruticosa), yielded an enrichment factor (ε) of -2.00 ± 0.23‰ (1σ, n = 8) for pectin and -1.82 ± 0.02‰ (1σ, n = 4) for Salicornia (the relative amount of the heavier 81Br was decreased in CH3Br compared to the substrate salt). For short incubations, and up to 10% consumption of the salt substrate, this isotope effect was similar for temperatures from 30 up to 300 °C. For longer incubations of up to 90 h at 180 °C the δ81Br values increased from -2‰ to 0‰ for pectin and to -1‰ for Salicornia. These δ81Br source signatures of CH3Br formation from plant matter combine with similar data for carbon isotopes to facilitate multidimensional isotope diagnostics of the CH3Br budget.

  18. Influence of carbon source on the stable carbon isotopic composition of the seagrass Thalassia testudinum

    International Nuclear Information System (INIS)

    The effects of isotopically distinct organic carbon sources in sediments and CO2 enrichment on the stable carbon isotope composition of Thalassia testudinum (turtle grass) seedlings were investigated. Seedling leaves became increasingly 13C depleted in all treatments with time. In the CO2 enriched treatment, δ13C values for seedlings declined from -9.1 to -57.1 per mille over the nine month culture period; the latter value is the lightest stable carbon isotope composition ever reported for a higher plant. In all non-CO2-enriched treatments, δ13C values declined from -9.1 per mille at T=0 to between -18.3 and -22.2 per mille after nine months. The lack of treatment effect in the non-CO2-enriched cultures was probably due to the release and exchange of isotopically light CO2 from the CO2 enriched treatment within the relatively closed environment of the culture room. This exchange was reflected in media dissolved inorganic carbon (DIC) δ13C values that indicated increasing 13C depletion relative to the initial compositions of the synthetic seawater salts. Depletion of 13C in leaf tissue of seedlings in the non-CO2-enriched treatments occurred faster than did media DIC 13C depletion, suggesting an increase in isotopic fractionation as seedlings grew. The reasons for this increasing fractionation are unclear, but they may reflect a decreasing contribution of isotopically heavy seed research and/or increasing availability of exogenous carbon. 18 refs, 1 fig., 2 tabs

  19. Data book of the isotopic composition of spent fuel in light water reactors

    International Nuclear Information System (INIS)

    In the framework of the activity of the working group on Evaluation of Nuclide Generation and Depletion in the Japanese Nuclear Data Committee, we summarized the assay data of the isotopic composition of LWR spent fuels in order to verify the accuracy of the burnup calculation codes. The report contains the data collected from the 13 light water reactors (LWRs) including the 9 LWRs (5 PWRs and 4 BWRs) in Europe and USA, the 4 LWRs (2 PWRs and 2 BWRs) in Japan. The collected data were sorted into the irradiation history of the fuel samples, the composition of the fuel assemblies, the sampling position and the isotopic composition of the fuel samples. (author)

  20. 87Sr/86Sr isotope composition of bottled British mineral waters for environmental and forensic purposes

    International Nuclear Information System (INIS)

    Mineral waters in Britain show a wide range of 87Sr/86Sr isotope compositions ranging between 87Sr/86Sr = 0.7059 from Carboniferous volcanic rock sources in Dunbartonshire, Scotland to 87Sr/86Sr = 0.7207 in the Dalradian aquifer of Aberdeenshire, Scotland. The 87Sr/86Sr composition of the waters shows a general correlation with the aquifer rocks, resulting in the waters from older rocks having a more radiogenic signature than those from younger rocks. This wide range of values means that the Sr isotope composition of mineral water has applications in a number of types of studies. In the modern commercial context, it provides a way of fingerprinting the various mineral waters and hence provides a method for recognising and reducing fraud. From an environmental perspective, it provides the first spatial distribution of bio-available 87Sr/86Sr in Britain that can be used in modern, historical and archaeological studies

  1. Mineralogy and Oxygen Isotope Compositions of Two C-Rich Hydrated Interplanetary Dust Particles

    Science.gov (United States)

    Snead, C. J.; McKeegan, K. D.; Messenger, S.; Nakamura-Messenger, K.

    2012-01-01

    Oxygen isotopic compositions of chondrites reflect mixing between a O-16-rich reservoir and a O-17,O-18-rich reservoir produced via mass-independent fractionation. The composition of the O-16-rich reservoir is reasonably well constrained, but material representing the O-17,O-18-rich end-member is rare. Self-shielding models predict that cometary water, presumed to represent this reservoir, should be enriched in O-17 and O-18 18O by > 200%. Hydrated interplanetary dust particles (IDPs) rich in carbonaceous matter may be derived from comets; such particles likely contain the products of reaction between O-16-poor water and anhydrous silicates that formed in the inner solar system. Here we present mineralogy and oxygen isotope compositions of two C-rich hydrated IDPs, L2083E47 and L2071E35.

  2. Stable carbon isotope composition of monoterpanes in essential oils and crude oils

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Twenty-five monoterpanes from six types of essential oils and hydrogenated turpentine oil have been identified and their stable carbon isotope composition determined.Monoterpanes in essential oils sourced from terrestrial higher plants display a δ13C value in the range of-34‰-26‰,and mostly between-29‰ and-27‰.The δ13C value of any single monoterpane is very consistent in different essential oils.Acyclic monoterpanes show closer isotope composition between-28.6‰ and-26.2‰,with an average value of-27.7‰.In contrast,the isotope composition of cyclic monoterpanes is more scattered with an average value of-28.6‰.Isotopic fractionation with 13C enrichment has been observed during both artificial and geological hydrogenation of monoterpenoids to monoterpanes,and this is more obvious for the acyclic monoterpenoids.In addition to higher plants,acyclic monoterpane 2,6-dimethylheptane in crude oil can also be originated from other organic inputs.

  3. Signature of terrestrial influence on nitrogen isotopic composition of suspended particulate

    Digital Repository Service at National Institute of Oceanography (India)

    Kumar, S.; Ramesh, R.; Sheshshayee, M.S.; Sardessai, S.; Patel, P.P.

    COMMUNICATIONS CURRENT SCIENCE, VOL. 8 8, NO. 5, 10 MARCH 2005 *For correspondence. (e - mail: sa n jeev@prl.ernet.in) Signature of terrestrial influence on n i trogen isotopic composition of su s pended particulate matter in the Bay of Bengal... ?C and stored for is o- topic analysis. Nitrogen isotope ratio and PON were measured in the laboratory using a Carlo Erba elemental analyser inte r faced via ConfloIII to a Finnigan Delta Plus mass spe c trometer. For precise anal y sis...

  4. On the iron isotope composition of Mars and volatile depletion in the terrestrial planets

    Science.gov (United States)

    Sossi, Paolo A.; Nebel, Oliver; Anand, Mahesh; Poitrasson, Franck

    2016-09-01

    Iron is the most abundant multivalent element in planetary reservoirs, meaning its isotope composition (expressed as δ57Fe) may record signatures of processes that occurred during the formation and subsequent differentiation of the terrestrial planets. Chondritic meteorites, putative constituents of the planets and remnants of undifferentiated inner solar system bodies, have δ57Fe ≈ 0 ‰; an isotopic signature shared with the Martian Shergottite-Nakhlite-Chassignite (SNC) suite of meteorites. The silicate Earth and Moon, as represented by basaltic rocks, are distinctly heavier, δ57Fe ≈ + 0.1 ‰. However, some authors have recently argued, on the basis of iron isotope measurements of abyssal peridotites, that the composition of the Earth's mantle is δ57Fe = + 0.04 ± 0.04 ‰, indistinguishable from the mean Martian value. To provide a more robust estimate for Mars, we present new high-precision iron isotope data on 17 SNC meteorites and 5 mineral separates. We find that the iron isotope compositions of Martian meteorites reflect igneous processes, with nakhlites and evolved shergottites displaying heavier δ57Fe (+ 0.05 ± 0.03 ‰), whereas MgO-rich rocks are lighter (δ57Fe ≈ - 0.01 ± 0.02 ‰). These systematics are controlled by the fractionation of olivine and pyroxene, attested to by the lighter isotope composition of pyroxene compared to whole rock nakhlites. Extrapolation of the δ57Fe SNC liquid line of descent to a putative Martian mantle yields a δ57Fe value lighter than its terrestrial counterpart, but indistinguishable from chondrites. Iron isotopes in planetary basalts of the inner solar system correlate positively with Fe/Mn and silicon isotopes. While Mars and IV-Vesta are undepleted in iron and accordingly have chondritic δ57Fe, the Earth experienced volatile depletion at low (1300 K) temperatures, likely at an early stage in the solar nebula, whereas additional post-nebular Fe loss is possible for the Moon and angrites.

  5. Features of isotopic composition of uranium in natural objects of the Chernobyl' NPP area

    International Nuclear Information System (INIS)

    It was shown that isotopic composition of U-natural objects of the zone (238U/235U, 235U/236U, 234U/238U) was shifted in reference to natural values and could be used for estimation of 'contamination' of environment by fuel. U content in 'contaminated' natural objects was not in excess of middle natural values. Correlation of the isotopic relationships 238U/236U and 235U/236U pointed to the fact that ejection of the fuel with high degree of burnup was lacking. 6 refs., 2 figs., 5 tabs

  6. Oxigen isotope compositions as indicators of epidote granite genesis in the Borborema Provinces, NE Brazil

    International Nuclear Information System (INIS)

    Neoproterozoic magmatic epidote-bearing granitoids intrude low-grade metapelites in the Cachoeirinha-Salgueiro terrane (CST), and gneisses and migmatites in the Serido terrane (ST), in the Borborema structural province, northeastern Brazil. Granitoids in both terranes contain biotite and hornblende, and are metaluminous, calc-alkalic, and oxidized I-type granites according to White's (1992) classification. However, in spite of these similarities, this work shows that mineral oxygen isotope data from plutons of the two terranes indicate different magma sources, and that magmatic epidote besides crystallizing at different pressure conditions, can have variable isotopic composition (au)

  7. Isotopic composition (δ18O) of the upper stalagmitic floor of Lazaret cave at Nice

    International Nuclear Information System (INIS)

    Radiochronological and mineralogical studies of the stalagmitic floor 'Ensemble E' of the Lazaret cave at Nice revealed that its formation has been continuous during the climatic period corresponding to 'stage 5'. In addition, biochemical analyses of this floor showed that the crystals behave as a closed system with respect to organic compounds (sterols). Oxygen isotopic compositions have registered variations which are qualitatively in agreement with those ascribed to stage 5. Therefore, these oxygen isotopic variations may be used as an independent geochemical chronometer. (authors). 15 refs

  8. Historical variations in the isotopic composition of atmospheric zinc deposition from a zinc smelter

    OpenAIRE

    Sonke, J. E.; Sivry, Y.; Viers, J.; Freydier, R.; Dejonghe, L; André, L.; Aggarwal, J. K.; Fontan, F.; Dupré, Bernard (collab.)

    2008-01-01

    In order to test the usefulness of stable zinc isotopes as an atmospheric source tracer, we analyzed the zinc isotopic composition of two sediment cores, taken at 1 km distance of the former zinc smelter in Lommel, Belgium. The peat bog lake sediments accumulate mainly atmospheric particles, have high organic matter contents (12-60 wt.%), are anoxic and highly contaminated with heavy metals (up to 4.7 wt.% Zn, and 1.1 wt.% Pb) with a sulfide mineralogical control on mobility. Down core variat...

  9. Certification of the uranium hexafluoride (UF6) isotopic composition: The IRMM-019 to IRMM-029 series

    OpenAIRE

    MIALLE SÉBASTIEN; Richter, Stephan; TRUYENS Jan; HENNESSY Carmel; Jakobsson, Ulf; Aregbe, Yetunde

    2014-01-01

    This report describes the re-determination and certification of the IRMM-019 to IRMM-029 series of uranium hexafluoride (UF6) reference materials certified for the uranium isotopic composition. The values were assigned following ISO Guide 34:2009. The IRMM-019 to IRMM-029 series was originally produced and certified in the 1980's-1990's. Since, the materials are stored in monel ampoules. Upon customer request, UF6 gas is distilled from a mother ampoule into a daughter ampoule, the isotopic...

  10. Assessment of body composition in Indian adults: comparison between dual-energy X-ray absorptiometry and isotope dilution technique.

    OpenAIRE

    Kulkarni, B.; Kuper, H; Taylor, A.; Wells, JC; Radhakrishna, KV; Kinra, S; BEN-SHLOMO, Y.; Smith, GD; Ebrahim, S; Kurpad, AV; Byrne, NM; Hills, AP

    2014-01-01

    Dual-energy X-ray absorptiometry (DXA) and isotope dilution technique have been used as reference methods to validate the estimates of body composition by simple field techniques; however, very few studies have compared these two methods. We compared the estimates of body composition by DXA and isotope dilution (18O) technique in apparently healthy Indian men and women (aged 19–70 years, n 152, 48 % men) with a wide range of BMI (14–40 kg/m2). Isotopic enrichment was assessed by isotope ratio...

  11. The influence of traffic and wood combustion on the stable isotopic composition of carbon monoxide

    Directory of Open Access Journals (Sweden)

    M. Saurer

    2008-11-01

    Full Text Available Carbon monoxide in the atmosphere is originating from various combustion and oxidation processes. Recently, the proportion of CO resulting from the combustion of wood for domestic heating may have increased due to political measures promoting this renewable energy source. Here, we used the stable isotope composition of CO (δ13C and δ18O for the characterization of different CO sources in Switzerland, along with other indicators for traffic and wood combustion (NOx-concentration, aerosol light absorption at different wavelengths. We assessed diurnal variations of the isotopic composition of CO at 3 sites during winter: a village site dominated by domestic heating, a site close to a motorway and a rural site. The isotope ratios of wood combustion emissions were studied at a test facility, indicating significantly lower δ18O of CO from wood combustion compared to traffic emissions. At the village and the motorway site, we observed very pronounced diurnal δ18O-variations of CO with an amplitude of up to 8‰. Solving the isotope mass balance equation for three distinct sources (wood combustion, traffic, clean background air resulted in diurnal patterns consistent with other indicators for wood burning and traffic. The average night-time contribution of wood-burning to total CO was 70% at the village site, 47% at the motorway site and 28% at the rural site based on the isotope mass balance. As this analysis showed a strong sensitivity towards the pure source isotope values, we additionally applied a combined CO/NOx-isotope model for verification. Here, we separated the CO emissions into different sources based on different CO/NOx emissions ratios for wood combustion and traffic, and inserted this information in the isotope mass balance equation. Accordingly, a highly significant agreement between measured and calculated δ18O-values of CO was found (r=0

  12. Constraints on Phanerozoic paleotemperature and seawater oxygen isotope evolution from the carbonate clumped isotope compositions of Late Paleozoic marine fossils (Invited)

    Science.gov (United States)

    Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Pérez-Huerta, A.; Shenton, B.; Yancey, T. E.

    2013-12-01

    A long-standing geoscience controversy has been the interpretation of the observed several per mil increase in the oxygen isotope compositions of marine calcites over the Phanerozoic Eon. Explanations for this trend have included decreasing seawater paleotemperatures, increasing seawater oxygen isotope values, and post-depositional calcite alteration. Carbonate clumped isotope paleothermometry is a useful geochemical tool to test these hypotheses because of its lack of dependence on the bulk isotopic composition of the water from which carbonate precipitated. This technique is increasingly applied to ancient marine invertebrate shells, which can be screened for diagenesis using chemical and microstructural approaches. After several years of clumped isotope analysis of these marine carbonates in a handful of laboratories, a long-term temperature and isotopic trend is emerging, with the results pointing to relatively invariant seawater δ18O and generally decreasing seawater temperatures through the Phanerozoic. Uncertainties remain, however, including the effects of reordering of primary clumped isotope compositions via solid-state diffusion of C and O through the mineral lattice at elevated burial temperatures over hundred million year timescales. To develop a quantitative understanding of such reordering, we present data from laboratory heating experiments of late Paleozoic brachiopod calcite. When combined with kinetic models of the reordering reaction, the results of these experiments suggest that burial temperatures less than ~120 °C allow for preservation of primary brachiopod clumped isotope compositions over geological timescales. Analyses of well-preserved Carboniferous and Permian brachiopods reinforce these results by showing that shells with apparent clumped isotope temperatures of ~150 °C are associated with deep sedimentary burial (>5 km), whereas those with putatively primary paleotemperatures in the 10-30 °C range experienced no more than ~1.5 km

  13. Use of new cross section data for uranium and boron isotopes obtained from recent ENDF/B-VI files

    International Nuclear Information System (INIS)

    Recently nuclear data for a few selected isotopes, as part of preliminary results of the IAEA WIMS Library Update Project derived from ENDF/B-VI, were made informally available. The data in WIMS library format was generated by them using the latest version of the NJOY code system by processing the ENDF/B-VI library. These data were incorporated in our WIMS69 data library. The eta values for U-235 are compared in Fig.1 in the energy range from 0.005 eV to 0.3 eV. The U-238 resonance integrals are now available up to 1100 deg. K compared to earlier tabulations of up to 900 deg. K. The new (WIMSKAL-88) B-10 cross sections in thermal energy range are seen to be higher by about 2% as compared to old WIMS data. 1 ref., 1 fig

  14. Preparation of Poly(p-phenylene sulfi de)/Carbon Composites with Enhanced Thermal Conductivity and Electrical Insulativity via Hybrids of Boron Nitride and Carbon Fillers

    Institute of Scientific and Technical Information of China (English)

    WU Jieli; WANG Jinwen; CHEN Feng

    2015-01-01

    The present work enhanced the thermal conductivity of poly(p-phenylene sulfi de)/expanded graphites and poly(p-phenylene sulfi de)/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which simultaneously succeeded in raising the electrical conductivity of the systems. A two-step mechanical processing method which includes rotating solid-state premixing and inner mixing was adopted to improve dispersion of the hybrids, contributing to the formation of an interspered thermal conductive network. Similar synergic effect in thermal conductivity enhancement was discovered in the hybrid systems regardless of the dimension difference between the two carbonfi llers. Such is postulated to be the one satisfying advantage generated by the afore-mentioned network; the other is the insulativity of the hybrid systems given by the effective blockage of hexagonal boron nitride as an insulating material in our network.

  15. Boron carbide nanolumps on carbon nanotubes

    Science.gov (United States)

    Lao, J. Y.; Li, W. Z.; Wen, J. G.; Ren, Z. F.

    2002-01-01

    Boron carbide nanolumps are formed on the surface of multiwall carbon nanotubes by a solid-state reaction between boron and carbon nanotubes. The reaction is localized so that the integrity of the structure of carbon nanotubes is maintained. Inner layers of multiwall carbon nanotubes are also bonded to boron carbide nanolumps. These multiwall carbon nanotubes with boron carbide nanolumps are expected to be the ideal reinforcing fillers for high-performance composites because of the favorable morphology.

  16. Modeling Environmental Controls on the Carbon Isotope Composition of Ecosystem Respired Carbon Dioxide

    Science.gov (United States)

    Cai, T.; Flanagan, L. B.

    2006-12-01

    Our main objective was to test whether the carbon isotope composition of ecosystem respired CO2 varied in response to environmental conditions in a manner consistent with well-known leaf-level studies of photosynthetic 13C discrimination. We developed an ecosystem-scale model that calculated leaf CO2 assimilation, stomatal conductance and chloroplast CO2 concentration separately for sunlit and shaded leaves within multiple canopy layers. The stomatal conductance model was linked to differences in water potential and resistances in the hydraulic pathway between the soil and the tree foliage. This part of the ecosystem model was validated by comparison to leaf-level gas exchange measurements and estimates of ecosystem-scale photosynthesis (GEP). The estimates of GEP were based on eddy covariance measurements of net ecosystem CO2 exchange (NEE) and the Fluxnet-Canada Research Network standard protocol for partitioning NEE into GEP and total ecosystem respiration (TER). The carbon isotope composition of carbohydrate formed during photosynthesis was calculated based on the Farquhar model of isotope effects. Total ecosystem respiration was modeled, based on measured temperature and soil moisture, as the sum of four components (1) above-ground plant, (2) root, (3) litter, and (4) mineral soil. We applied a variety of techniques to allocate the contribution of these different components so that modeled TER was consistent with TER calculated from NEE measurements. The carbon isotope composition of CO2 released during above-ground plant and root respiration was calculated based on an assimilated-weighted average of carbohydrate fixed during a variable number of days previous to the day of respiration. The isotope composition of CO2 released by litter and mineral soil respiration was based on measurements of the δ13C values of these components (we assumed no isotope fractionation during respiration) and held constant in all calculations. The model was compared to

  17. Abrupt pH Changes of sea Surface Waters in the sub-Equatorial Pacific Ocean at the end of the Younger Dryas (YD): MC-ICPMS Analysis of Boron Isotopes in Reef Corals

    Science.gov (United States)

    Douville, E.; Paterne, M.; Cabioch, G.; Isnard, H.; Chartier, F.; Bouman, C.; Juillet-Leclerc, A.; Caillon, N.

    2006-12-01

    The paleo-pH-δ^{11}B technique was applied to modern (1950) and ancient Porites sampled from Tahiti (Moorea) and Marquesas Islands in the (sub-Equatorial) Central Pacific Ocean in order to analyze possible past changes of Ocean acidification and past evolution of the Δ pCO2 (pCO2 Atm.- Ocean). The MC-ICP-MS δ^{11}B measurements have an internal reproducibility of 0.1 ‰ (n = 22, NBS 981, 2sigma) and an analytical error of 0.2 ‰ for the samples. Moreover, very rigorous cleaning techniques have been applied on corals resulting in a stunning relationship between B concentration and isotopic composition. By using a fractionation factor ( α4-3 ) of 0.9807 issued from this study, B isotopic composition of modern seawater, and instrumental T, S data, reconstruction of pH values from modern corals agree with in-situ pH measurements at a precision of 0.02 pH-unit. From 11,500 cal. yr to 3250 cal. yr, pH values changed significantly from 8.05 to 8.24, respectively, that is in agreement with previously published estimates from corals (Gaillardet and Allègre, 1995). Our data confirm and quantify a rapid rise of pH values in seawaters at the end of the YD, which strongly coincides with the rate of atmospheric pCO2 changes as observed in EPICA Dome C (Monnin et al., 2001, 2004) suggesting a close relationship between atmospheric and oceanic pCO2 changes. So, the atmospheric pCO2 - pH relationship observed here both in the Central and Western Pacific Ocean (ERDC-92, Palmer and Pearson, 2003) suggests that, not only the high atmospheric CO2 content modified the mean pH values (decreasing trend), but also the rate of atmospheric CO2 changes on shorter timescale. Gaillardet J. and C.J. Allègre, Boron isotopic compositions of corals: seawater or diagenesis record? Earth and Planetary Science Letters, 136, 665-676, 1995. Monnin E., E.J. Steig, U. Siegenthaler, K. Kawamura, J. Schwander, B. Stauffer, T. F. Stocker, D. L. Morse, J.-M. Barnola, B. Bellier, D. Raynaud and H

  18. Influence of magnetite, ilmenite and boron carbide on radiation attenuation of polyester composites

    International Nuclear Information System (INIS)

    This work is concerned with studying polyester/ magnetite CUP/Mag (ρ=2.75 g cm−3) and polyester/ ilmenite CUP/Ilm (ρ=2.7 g cm−3) composites for shielding of medical facilities, laboratory hot cells and for various purposes. Mechanical and physical properties such as compressive, flexural and impact strengths, as well as, a.c. electrical conductivity, specific heat, water absorption and porosity have been performed to evaluate the composite capabilities for radiation shielding. A collimated beam from fission 252Cf (100 µg) neutron source and neutron-gamma spectrometer with stilbene scintillator based on the zero cross over method and pulse shape discrimination (P.S.D.) technique have been used to measure neutron and gamma ray spectra. Fluxes of thermal neutrons have been measured using the BF3 detector and thermal neutron detection system. The attenuation parameters, namely macroscopic effective removal cross-section ΣR, total attenuation coefficient µ and macroscopic cross-section Σ of fast neutrons, gamma rays and thermal neutrons respectively have been evaluated. Theoretical calculations using MCNP–4C2 code was used to calculate ΣR,μ and Σ. Also, MERCSF-N program was used to calculate macroscopic effective removal cross-section ΣR. Measured and calculated results were compared and reasonable agreement was found. - Highlights: • Loaded polyester composites were investigated for radiation shielding. • Some mechanical and physical properties were examined. • Experimental and theoretical attenuation parameters were studied. • Experimental and theoretical (MCNP-4C2) results were in good agreement

  19. Associated chemical and carbon isotopic composition variations in diamonds from Finsch and Premier kimberlite, South Africa

    International Nuclear Information System (INIS)

    The carbon isotopic composition of 66 inclusion-containing diamonds from the Premier kimberlite, South Africa, 93 inclusion-containing diamonds and four diamonds of two diamond-bearing peridotite xenoliths from the Finsch kimberlite, South Africa was measured. The data suggest a relationship between the carbon isotopic composition of the diamonds and the chemical composition of the associated silicates. For both kimberlites similar trends are noted for diamonds containing peridotite-suite inclusions (P-type) and for diamonds containing eclogite-suite inclusions (E-type): Higher delta13C P-type diamonds tend to have inclusions lower in SiO2, Al2O3, Cr2O3, MgO, Mg/(Mg + Fe) and higher in FeO and CaO. Higher delta13C E-type diamonds tend to have inclusions lower in SiO2, Al2O3, MgO, Mg/(Mg + Fe), Na2O, K2O, TiO2 and higher in CaO, Ca/(Ca + Mg). Consideration of a number of different models that have been proposed for the genesis of kimberlites, their zenoliths and diamonds shows that they are all consistent with the conclusion that in the mantle, regions exist that are characterized by different mean carbon isotopic compositions. (author)

  20. Origin and release date assessment of environmental plutonium by isotopic composition

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Zsolt [Hungarian Academy of Sciences, Radiation Safety Department, Institute of Isotopes, Budapest (Hungary)

    2007-10-15

    The origin and release date of environmental plutonium have been assessed by the measurement of plutonium and americium isotopic composition. The applicability and sensitivity of different plutonium isotope ratios, {sup 240}Pu/{sup 239}Pu and {sup 241}Pu/{sup 239}Pu measured by inductively coupled plasma sector field mass spectrometry and {sup 238}Pu/{sup 239}Pu analysed by alpha spectrometry, have been evaluated for origin determination in several types of environmental samples. With use of mixing models the contribution of different sources (e.g. global fallout or Chernobyl) can be calculated. By the measurement of the {sup 241}Am/{sup 241}Pu isotope ratio, the release date (i.e. formation of {sup 241}Pu by irradiation) can be estimated in environmental samples, which is an important parameter to distinguish recent plutonium release from previous (e.g. Chernobyl) emissions. (orig.)

  1. Origin and release date assessment of environmental plutonium by isotopic composition

    International Nuclear Information System (INIS)

    The origin and release date of environmental plutonium have been assessed by the measurement of plutonium and americium isotopic composition. The applicability and sensitivity of different plutonium isotope ratios, 240Pu/239Pu and 241Pu/239Pu measured by inductively coupled plasma sector field mass spectrometry and 238Pu/239Pu analysed by alpha spectrometry, have been evaluated for origin determination in several types of environmental samples. With use of mixing models the contribution of different sources (e.g. global fallout or Chernobyl) can be calculated. By the measurement of the 241Am/241Pu isotope ratio, the release date (i.e. formation of 241Pu by irradiation) can be estimated in environmental samples, which is an important parameter to distinguish recent plutonium release from previous (e.g. Chernobyl) emissions. (orig.)

  2. Modelling the regional climate and isotopic composition of Svalbard precipitation using REMOiso

    DEFF Research Database (Denmark)

    Divine..[], D.V.; Sjolte, Jesper; Isaksson, E.;

    2011-01-01

    Simulations of a regional (approx. 50 km resolution) circulation model REMOiso with embedded stable water isotope module covering the period 1958-2001 are compared with the two instrumental climate and four isotope series (d18O) from western Svalbard. We examine the data from ice cores drilled on...... Svalbard ice caps in 1997 (Lomonosovfonna, 1250 m asl) and 2005 (Holtedahlfonna, 1150 m asl) and the GNIP series from Ny-angstrom lesund and Isfjord Radio. The surface air temperature (SAT) and precipitation data from Longyearbyen and Ny-angstrom lesund are used to assess the skill of the model in...... reproducing the local climate. The model successfully captures the climate variations on the daily to multidecadal times scales although it tends to systematically underestimate the winter SAT. Analysis suggests that REMOiso performs better at simulating isotope compositions of precipitation in the winter...

  3. Stable isotope and chemical compositions of European and Australasian ciders as a guide to authenticity.

    Science.gov (United States)

    Carter, James F; Yates, Hans S A; Tinggi, Ujang

    2015-01-28

    This paper presents a data set derived from the analysis of bottled and canned ciders that may be used for comparison with suspected counterfeit or substitute products. Isotopic analysis of the solid residues from ciders (predominantly sugar) provided a means to determine the addition of C4 plant sugars. The added sugars were found to comprise cane sugar, high-fructose corn syrup, glucose, or combinations. The majority of ciders from Australia and New Zealand were found to contain significant amounts of added sugar, which provided a limited means to distinguish these ciders from European ciders. The hydrogen and oxygen isotopic compositions of the whole ciders (predominantly water) were shown to be controlled by two factors, the water available to the parent plant and evaporation. Analysis of data derived from both isotopic and chemical analysis of ciders provided a means to discriminate between regions and countries of manufacture. PMID:25536876

  4. Abrupt sea surface pH change at the end of the Younger Dryas in the central sub-equatorial Pacific inferred from boron isotope abundance in corals (Porites

    Directory of Open Access Journals (Sweden)

    A. Juillet-Leclerc

    2010-08-01

    Full Text Available The "δ11B-pH" technique was applied to modern and ancient corals Porites from the sub-equatorial Pacific areas (Tahiti and Marquesas spanning a time interval from 0 to 20.720 calendar years to determine the amplitude of pH changes between the Last Glacial Period and the Holocene. Boron isotopes were measured by Multi-Collector – Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS with an external reproducibility of 0.25‰, allowing a precision of about ±0.03 pH-units for pH values between 8 and 8.3. The boron concentration [B] and isotopic composition of modern samples indicate that the temperature strongly controls the partition coefficient KD for different aragonite species. Modern coral δ11B values and the reconstructed sea surface pH values for different Pacific areas match the measured pH expressed on the seawater scale and confirm the calculation parameters that were previously determined by laboratory calibration exercises. Most ancient sea surface pH reconstructions near Marquesas are higher than modern values. These values range between 8.19 and 8.27 for the Holocene and reached 8.30 at the end of the last glacial period (20.7 kyr BP. At the end of the Younger Dryas (11.50±0.1 kyr BP, the central sub-equatorial Pacific experienced a dramatic drop of up to 0.2 pH-units from the average pH of 8.2 before and after this short event. Using the marine carbonate algorithms, we recalculated the aqueous pCO2 to be 440±25 ppmV at around 11.5 kyr BP for corals at Marquesas and ~500 ppmV near Tahiti where it was assumed that pCO2 in the atmosphere was 250 ppmV. Throughout the Holocene, the difference in pCO2 between the ocean and the atmosphere at Marquesas (ΔpCO2 indicates that the surface waters behave as a moderate CO2 sink or source (−53 to 20 ppmV during El Niño-like conditions. By contrast, during the last glacial/interglacial transition, this area was a marked source of CO2 (21 to 92 ppmV for the atmosphere, highlighting

  5. Chemical analyses and calculation of isotopic compositions of high-burnup UO2 fuels and MOX fuels

    International Nuclear Information System (INIS)

    Chemical analysis activities of isotopic compositions of high-burnup UO2 fuels and MOX fuels in CRIEPI and calculation evaluation are reviewed briefly. C/E values of ORIGEN2, in which original libraries and JENDL-3.2 libraries are used, and other codes with chemical analysis data are reviewed and evaluated. Isotopic compositions of main U and Pu in fuels can be evaluated within 10% relative errors by suitable libraries and codes. Void ratio is effective parameter for C/E values in BWR fuels. JENDL-3.2 library shows remarkable improvement compared with original libraries in isotopic composition evaluations of FP nuclides. (author)

  6. Intraskeletal isotopic compositions (δ(13) C, δ(15) N) of bone collagen: nonpathological and pathological variation.

    Science.gov (United States)

    Olsen, Karyn C; White, Christine D; Longstaffe, Fred J; von Heyking, Kristin; McGlynn, George; Grupe, Gisela; Rühli, Frank J

    2014-04-01

    Paleodiet research traditionally interprets differences in collagen isotopic compositions (δ(13) C, δ(15) N) as indicators of dietary distinction even though physiological processes likely play some role in creating variation. This research investigates the degree to which bone collagen δ(13) C and δ(15) N values normally vary within the skeleton and examines the influence of several diseases common to ancient populations on these isotopic compositions. The samples derive from two medieval German cemeteries and one Swiss reference collection and include examples of metabolic disease (rickets/osteomalacia), degenerative joint disease (osteoarthritis), trauma (fracture), infection (osteomyelitis), and inflammation (periostitis). A separate subset of visibly nonpathological skeletal elements from the German collections established normal intraindividual variation. For each disease type, tests compared bone lesion samples to those near and distant to the lesions sites. Results show that normal (nonpathological) skeletons exhibit limited intraskeletal variation in carbon- and nitrogen-isotope ratios, suggesting that sampling of distinct elements is appropriate for paleodiet studies. In contrast, individuals with osteomyelitis, healed fractures, and osteoarthritis exhibit significant intraskeletal differences in isotope values, depending on whether one is comparing lesions to near or to distant sites. Skeletons with periostitis result in significant intraskeletal differences in nitrogen isotope values only, while those with rickets/osteomalacia do not exhibit significant intraskeletal differences. Based on these results, we suggest that paleodiet researchers avoid sampling collagen at or close to lesion sites because the isotope values may be reflecting both altered metabolic processes and differences in diet relative to others in the population. PMID:24374993

  7. New views on the isotopic composition of atmospheric oxygen

    Science.gov (United States)

    Luz, B.

    2001-05-01

    Air oxygen is enriched in O-18 with respect to ocean water by about 23 permil. This enrichment is named "Dole effect" after its discoverer. Air oxygen originates from marine and terrestrial photosynthesis that produces oxygen gas without fractionation with respect to the substrate water. The O-18 enrichment results primarily from preferential removal of O-16 during respiratory uptake. However, the discrimination against O-18 in ordinary dark respiration is only 18 permil, and cannot account for the entire magnitude of the Dole effect. Part of the discrepancy may be explained by enrichment of the substrate water in terrestrial evapo-transpiration. But the existing evidence on the magnitude of this enrichment shows that this mechanism alone cannot explain the discrepancy. In an attempt to better understand the Dole effect we have studied the overall fractionation in soil and aquatic oxygen uptake. Due to slow gas diffusion in soils and roots the discrimination is smaller than in respiration. This result thus increases the discrepancy. On the other hand, our new estimates show that discrimination in aquatic oxygen uptake is considerably greater than previously assumed. Oxygen uptake in the surface waters of oceans and lakes takes place by ordinary dark respiration as well as by cyanide resistant respiration in both dark and light conditions, and by photorespiration and Mehler reaction that occur only during illumination. Thus in order to study the overall discrimination in aquatic systems it is necessary to evaluate its effects in both light and dark conditions and to separate the effect of photosynthetic production of oxygen. Such separation is possible if gross rates of oxygen production and consumption are known. We have estimated these rates from in situ incubation experiments and from the natural distribution of O-16, O-17, O-18 and the ratio of dissolved oxygen/argon. We have used isotopic and elemental budgets to derive the overall respiratory fractionation in

  8. Stable isotope study of a new chondrichthyan fauna (Kimmeridgian, Porrentruy, Swiss Jura): an unusual freshwater-influenced isotopic composition for the hybodont shark Asteracanthus

    Science.gov (United States)

    Leuzinger, L.; Kocsis, L.; Billon-Bruyat, J.-P.; Spezzaferri, S.; Vennemann, T.

    2015-12-01

    Chondrichthyan teeth (sharks, rays, and chimaeras) are mineralized in isotopic equilibrium with the surrounding water, and parameters such as water temperature and salinity can be inferred from the oxygen isotopic composition (δ18Op) of their bioapatite. We analysed a new chondrichthyan assemblage, as well as teeth from bony fish (Pycnodontiformes). All specimens are from Kimmeridgian coastal marine deposits of the Swiss Jura (vicinity of Porrentruy, Ajoie district, NW Switzerland). While the overall faunal composition and the isotopic composition of bony fish are generally consistent with marine conditions, unusually low δ18Op values were measured for the hybodont shark Asteracanthus. These values are also lower compared to previously published data from older European Jurassic localities. Additional analyses on material from Solothurn (Kimmeridgian, NW Switzerland) also have comparable, low-18O isotopic compositions for Asteracanthus. The data are hence interpreted to represent a so far unique, freshwater-influenced isotopic composition for this shark that is classically considered a marine genus. While reproduction in freshwater or brackish realms is established for other hybodonts, a similar behaviour for Asteracanthus is proposed here. Regular excursions into lower salinity waters can be linked to the age of the deposits and correspond to an ecological adaptation, most likely driven by the Kimmeridgian transgression and by the competition of the hybodont shark Asteracanthus with the rapidly diversifying neoselachians (modern sharks).

  9. Recent planktic foraminifers in the Fram Strait (Arctic Ocean): carbon and oxygen stable isotope composition

    Science.gov (United States)

    Pados, T.; Spielhagen, R. F.; Bauch, D.; Meyer, H.; Segl, M.

    2012-12-01

    In paleoceanographic reconstructions the carbon isotopic compositions (δ13C) of fossil foraminifers refer to, e.g., paleoproductivity and stratification, while oxygen isotopic (δ18O) records provide information about variations in sea surface temperatures and salinities in the past. However, for a correct interpretation of the fossil data it is important to improve our understanding of the correlation between recent oceanic variability and the composition of shells of living calcareous microorganisms. For this, the upper water column and sediment surface in the Fram Strait (Arctic Ocean, 78°50'N, 5°W-8°E) were sampled for planktic foraminifer species Neogloboquadrina pachyderma (sin.) and Turborotalita quinqueloba with a large-diameter multinet and a multicorer, respectively. The δ13C and δ18O values of the shells are compared to the stable isotope composition of the ambient water and to equilibrium calcite values to define the preferred calcification depths of the foraminifers and to determine the factors controlling the isotopic signature of these calcareous microorganisms. The study area was chosen because of its high oceanographic variability: in the eastern Fram Strait the northward flowing West Spitsbergen Current (WSC) carries Atlantic Water, with a thin mixed layer on top, while in the west the upper 200 m consists of cold, low-saline Arctic outflow waters of the East Greenland Current (EGC) and warmer, saline waters of Atlantic origin underneath. Despite this variable oceanographic regime along the studied transect, the stable carbon isotope ratios of the shells do not show major differences according to their horizontal but to their vertical distribution: the δ13C values of N. pachyderma (sin.) from plankton tow samples vary roughly between -1 and -0.1‰ depending on the water depth, while the δ18O values of the tests differ more between the stations.

  10. Reconstructing Cambro-Ordovician Seawater Composition using Clumped Isotope Paleothermometry on Calcitic and Phosphatic Brachiopods

    Science.gov (United States)

    Bergmann, K.; Robles, M.; Finnegan, S.; Hughes, N. C.; Eiler, J. M.; Fischer, W. W.

    2012-12-01

    A secular increase in δ18O values of marine fossils through early Phanerozoic time raises questions about the evolution of climate and the water cycle. This pattern suggests two end-member hypotheses 1) surface temperatures during early Paleozoic time were very warm, in excess of 40°C (tropical MAT), or 2) the isotopic composition of seawater increased by up to 7-8‰. It has been difficult to evaluate these hypotheses because the δ18O composition of fossils depends on both temperature and the δ18O of water. Furthermore, primary isotopic signatures can be overprinted by diagenetic processes that modify geological materials. This too could explain the decrease in δ18O values of marine fossils with age. Carbonate clumped isotope thermometry can constrain this problem by providing an independent measure of crystallization temperature and, when paired with classical δ18O paleothermometry, can determine the isotopic composition of the fluid the mineral last equilibrated with. Combined with traditional tools, this method has the potential to untangle primary isotopic signatures from diagenetic signals. We measured the isotopic ordering of CO3 groups (Δ47) substituted into the phosphate lattice of phosphatic brachiopods in Cambrian strata. Phosphatic fossils are generally less soluble than carbonates in surface and diagenetic environments, and so are hypothesized to provide a more robust record of primary growth conditions. They also provide an archive prior to the rise of thick shelled calcitic fossils during the Ordovician Radiation. Additionally, measurements of the δ18O of the CO3 groups can be compared with the δ18O of PO4 groups to test whether their mutual fractionation is consistent with primary growth and the apparent temperature recorded by carbonate clumped isotope measurements. We are constructing a phosphatic brachiopod calibration for carbonate clumped isotope thermometry, and Δ47 values of CO2 extracted from modern phosphatic brachiopods suggest

  11. Boron and strontium isotope ratios and major/trace elements concentrations in tea leaves at four major tea growing gardens in Taiwan.

    Science.gov (United States)

    Chang, Cheng-Ta; You, Chen-Feng; Aggarwal, Suresh Kumar; Chung, Chuan-Hsiung; Chao, Hung-Chun; Liu, Hou-Chun

    2016-06-01

    Isotopic compositions of B and Sr in rocks and sediments can be used as tracers for plant provincial sources. This study aims to test whether tea leaf origin can be discriminated using (10)B/(11)B and Sr isotopic composition data, along with concentrations of major/trace elements, in tea specimens collected from major plantation gardens in Taiwan. The tea leaves were digested by microwave and analyzed by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The data showed significant variations in (87)Sr/(86)Sr ratios (from 0.70482 to 0.71462), which reflect changes in soil, groundwater or irrigation conditions. The most radiogenic tea leaves were found at the Taitung garden and the least radiogenic ones were from the Hualien garden. The δ (11)B was found to change appreciably (δ (11)B = 0.38-23.73 ‰) which could be due to fertilizers. The maximum δ (11)B was also observed in tea samples from the Hualien garden. Principal component analysis combining (87)Sr/(86)Sr, δ (11)B and major/trace elements results successfully discriminated different sources of major tea gardens in Taiwan, except the Hualien gardens, and this may be due to rather complicated local geological settings. PMID:26254888

  12. Determination of isotopic shift for some compounds having stable isotopic composition using FTIR technique

    International Nuclear Information System (INIS)

    A new route has been devised, leading to the production of VOX3 molecules where X = F, Br and I by an on-line process using vanadium oxytrichloride, VOCl3 as a starting compound passed over the following heated salts NaF, KBr and KI at 375, 700, and 550 Centigrades, respectively. The products have been characterized by the IR spectra of their vapors. The low resolution gas phase on-line Fourier transform infrared spectra reported for the first time show strong bands, with PQR type structure, centered at 1058, 1035, 1030 and 1025 cm-1 assigned to the ν1(a1), the O = V stretching fundamental mode of VOF3, COCl3, VOBr3 and VOI3 respectively. A new route has been devised, leading to the production of phosphorus thiotrihalides SPX3 where X = F, Br and I by an on-line process using phosphorus thio trichloride, SPCl3 as starting compound passed over the following heated salts NaF, KBr and KI at 530, 800, and 440 Centigrades, respectively. The products have been characterized by their IR spectra, showing bands with PQR type structure, centered at 985, 762, 744 and 715 cm-1. These bands are assigned to ν1(a1), the S = P stretching fundamental modes of SPF3, SPCl3, SPBr3 and SPI3, respectively. Isotopic shifts of the following groups P81-Br, P97-Br, P81-Br, P79-Br, P37-Cl, P35-Cl3, FP34S, FP32S, 34S=P, 32S = PF3, 34S = PF3 were determined. (author)

  13. SFCOMPO: A database for isotopic composition of nuclear spent fuel; current status and future development

    International Nuclear Information System (INIS)

    The isotopic composition of the nuclear fuel, after the irradiation in a power reactor, is one of the most important characteristics of spent nuclear fuel (SNF). It is the basis for the evaluation of several properties of SNF, including decay heat, radiation dose, and the multiplication factor of any configuration containing the spent fuel. Since the determination of this isotopic composition is usually carried out using calculation tools, the validation of these tools is an important aspect to be taken into consideration. Several experiments involving Post Irradiation Examination (PIE) of SNF have been conducted in different countries to obtain experimental data for the isotopic composition of SNF. These experimental data can be used for the validation of the calculation tools. Based on this background, the Japan Atomic Energy Research Institute (JAERI) developed SFCOMPO, a database system for the compilation of the isotopic composition of SNF. The database was available for consultation on the Internet. After this initial phase, and given the suitable framework of the NEA for the collection of additional data from member countries, it was agreed that the NEA would maintain and further develop SFCOMPO. This involves both the compilation and the dissemination of the data. Since autumn 2002, this database has been operated on the NEA web server (http://www.nea.fr/html/ science/wpncs/sfcompo/). Table 1 summarizes the content of the SFCOMPO database. Measured isotopic composition data from 14 reactors (7 PWRs and 7 BWRs), operated in 4 countries, are contained in the database. The composition of 246 samples is described, including 30 samples from UO2- Gd2O3 fuel. The database gives the composition of U, Pu, Am, Cm and several fission products (Nd, Cs, Sr). These data were collected from the open literature. In view of the importance of these data, the NEA plans to further develop the SFCOMPO database. The aim is to give more details on the operating conditions under

  14. Sulfide isotopic compositions in shergottites and ALH84001, and possible implications for life on Mars

    International Nuclear Information System (INIS)

    The shergottite and ALH84001 meteorites hold keys for understanding geologic and possibly biologic processes on Mars. Recently, it has been proposed that carbonates in ALH84001, and the Fe-sulfides they contain, are products of extraterrestrial biogenic activity. Here we report ion microprobe analyses of sulfides in shergottites and ALH84001. The sulfur isotope ratios of igneous pyrrhotites in shergottites (mean δ34SCDT: Shergotty = -0.4 per-thousand, Zagami = +2.7 per-thousand, EETA79001A = 1.9 per-thousand, EETA79001B = -1.7 per-thousand, LEW88516 = -1.9 per-thousand, QUE94201 = +0.8 per-thousand) are similar to those of terrestrial ocean-floor basalts, suggesting that the sulfur isotopic composition of the Martian mantle may be similar to that of the mantle of the Earth. The sulfur isotopic systematics of ALH84001 sulfides are distinct from the shergottites. Measured sulfur isotope ratios of eight pyrite grains (δ34SCDT = +2.0 to +7.3 per-thousand) in crushed zones confirm previously reported analyses of isotopically heavy sulfides and are indistinguishable from an Fe-sulfide zone within a carbonate globule (δ34SCDT = +6.0 per-thousand). Analyses of synthesized, fine-grained mixtures of sulfide, carbonate, and magnetite indicate than the measured sulfur isotope ratio is independent of the presence of carbonate and magnetite in the sputtered volume, confirming the accuracy of the analysis of the fine-grained sulfide in the carbonate globule. Terrestrial biogenic sulfate reduction typically results in light isotopic enrichments. The similarity of δ34S values of the sulfides in ALH84001 imply that the Fe-sulfide zones within ALH84001 carbonates are probably not the result of bacterial reduction of sulfate. 38 refs., 3 figs., 1 tab

  15. Natural Ca Isotope Composition of Urine as a Rapid Measure of Bone Mineral Balance

    Science.gov (United States)

    Skulan, J.; Gordon, G. W.; Morgan, J.; Romaniello, S. J.; Smith, S. M.; Anbar, A. D.

    2011-12-01

    Naturally occurring stable Ca isotope variations in urine are emerging as a powerful tool to detect changes in bone mineral balance. Bone formation depletes soft tissue of light Ca isotopes while bone resorption releases isotopically light Ca into soft tissue. Previously published work found that variations in Ca isotope composition could be detected at 4 weeks of bed rest in a 90-day bed rest study (data collected at 4, 8 and 12 weeks). A new 30-day bed rest study involved 12 patients on a controlled diet, monitored for 7 days prior to bed rest and 7 days post bed rest. Samples of urine, blood and food were collected throughout the study. Four times daily blood samples and per void urine samples were collected to monitor diurnal or high frequency variations. An improved chemical purification protocol, followed by measurement using multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) allowed accurate and precise determinations of mass-dependent Ca isotope variations in these biological samples to better than ±0.2% (δ44/42Ca) on alkaline phosphatase, a bone formation biomarker, is unchanged over this period. Ca isotopes can in principle be used to quantify net changes in bone mass. Using a mass-balance model, our results indicate an average loss of 0.62 ± 0.16 % in bone mass over the course of this 30-day study. This is consistent with the rate of bone loss in longer-term studies as seen by X-ray measurements. This Ca isotope technique should accelerate the pace of discovery of new treatments for bone disease and provide novel insights into the dynamics of bone metabolism.

  16. Anthropogenic Pb input into Bohai Bay, China: Evidence from stable Pb isotopic compositions in sediments

    Science.gov (United States)

    Ning-jing, Hu; Peng, Huang; Hui, Zhang; Ai-mei, Zhu; Ji-hua, Liu; Jun, Zhang; Lian-hua, He

    2015-10-01

    To investigate the source of Pb within Bohai Bay, Pb concentrations and Pb isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of surface sediments in this area were determined. The Pb concentration in this bay varied widely from 6.9 to 39.2 μg/g (average: 21.8±7.8 μg/g), and the Pb isotopic compositions ranged from 0.8338 to 0.8864 (average: 2.0997±0.0180) for 208Pb/206Pb and from 2.0797 to 2.1531 (average: 0.8477±0.0135) for 207Pb/206Pb, presenting in three distinct clusters. The Pb isotopic ratios of sediments from the northeastern (NE zone) and northwestern (NW zone) coastal areas were significantly influenced by anthropogenic sources such as coal combustion and automobile emission. In sediments from the central and southern Bohai Bay (C-S zone); however, Pb mainly originated from the Yellow River catchment, as a result of lithogenic sediment (from rock weathering) accumulation. The Pb isotopic ratios further indicate that, apart from riverine inputs, the neighboring large-scale ports and aerosols significantly contributed to the anthropogenic Pb contained in these sediments. Pb contamination in the Haihe and Luanhe river mouths as well as in the regions near ports is also suggested from anthropogenic enrichment factors. As cities and ports continue to develop around Bohai Bay, a long-term extensive sewage monitoring program is highly recommended.

  17. Pb Isotope Compositions of Shibaqinghao Gold Deposit in Central Inner Mongolia, China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hongying; LIANG Yibo

    2002-01-01

    There are two types of gold ore in Shibaqinghao gold deposit, a mylonite ore and a quartz - vein ore. Pb isotope compositions for mylonite ore are characterized by lower Pb isotope ratios ranging from 16.63 to 17.45 (206Pb/204Pb), 15.31 to15.48 (207Pb/204pb), 36.52 to 38.85 (208Pb/204Pb). They are scattered very close to a model curve of the mantle evolution. These ratios suggest that gold in the mylonite ore might be derived from the country rocks, which originated directly in the upper mantle. Pb isotope compositions for quartz - vein ore are characterized by higher Pb isotope ratios ranging from 18.23 to 19.74 (206Pb/204Pb), 15.69 to 15.89 (207Pb/204Pb), 38.64 to 40. 13 (208Pb/204Pb). They are scattered very close to a model curve of the upper crustal evolution. These facts indicate that the gold in the quartz - vein ore might be related to some granitic magma generated in the crust.

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

    International Nuclear Information System (INIS)

    In order to research on stable hydrogen, oxygen, sulfur isotopes composition in different tissues of cattle, as well as the breed, δ 2H and δ 34S values of different defatted muscle, cattle tail hair, blood, liver, also δ 2h and δ 18O 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 2H and δ 34S values between different defatted muscle, blood, liver, cattle hair were significantly different, at the same time the δ 34S and δ 2H values between each tissue were not significantly correlated; the δ 2H values were strongly correlated with the δ 18O 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)

  19. Hydrogen isotope composition of leaf wax n-alkanes in Arabidopsis lines with different transpiration rates

    Science.gov (United States)

    Pedentchouk, N.; Lawson, T.; Eley, Y.; McAusland, L.

    2012-04-01

    Stable isotopic compositions of oxygen and hydrogen are used widely to investigate modern and ancient water cycles. The D/H composition of organic compounds derived from terrestrial plants has recently attracted significant attention as a proxy for palaeohydrology. However, the role of various plant physiological and biochemical factors in controlling the D/H signature of leaf wax lipids in extant plants remains unclear. The focus of this study is to investigate the effect of plant transpiration on the D/H composition of n-alkanes in terrestrial plants. This experiment includes 4 varieties of Arabidopsis thaliana that differ with respect to stomatal density and stomatal geometry. All 4 varieties were grown indoors under identical temperature, relative humidity, light and watering regimes and then sampled for leaf wax and leaf water stable isotopic measurements. During growth, stomatal conductance to carbon dioxide and water vapour were also determined. We found that the plants varied significantly in terms of their transpiration rates. Transpiration rates were significantly higher in Arabidopsis ost1 and ost1-1 varieties (2.4 and 3.2 mmol m-2 s-1, respectively) than in Arabidopsis RbohD and Col-0 (1.5 and 1.4). However, hydrogen isotope measurements of n-alkanes extracted from leaf waxes revealed a very different pattern. Varieties ost1, ost1-1, and RbohD have very similar deltaD values of n-C29 alkane (-125, -128, and -127 per mil), whereas the deltaD value of Col-0 is more negative (-137 per mil). The initial results of this work suggest that plant transpiration is decoupled from the D/H composition of n-alkanes. In other words, physical processes that affect water vapour movement between the plant and its environment apparently cannot account for the stable hydrogen isotope composition of organic compounds that comprise leaf waxes. Additional, perhaps biochemical, processes that affect hydrogen isotope fractionation during photosynthesis might need to be invoked

  20. Spatial and Temporal Characterization of the Stable Isotopic Composition of the Great Lakes

    Science.gov (United States)

    St. Amour, N. A.; Longstaffe, F. J.; MacDonald, R. A.; Crowe, A. S.

    2012-12-01

    The Great Lakes of North America are a valuable resource for the region's growing population, which depends on them for drinking water, hydroelectric power, shipping, recreation and other services. Even small shifts in the water balance of this large-scale chain-of-lakes system causes significant stress for the economy, environment and society. The Great Lakes also have a substantial impact on the region's climate through lake-effect precipitation and enhanced humidity, which is superimposed on the large-scale processes involving three main air masses (i.e., Pacific, Arctic, Tropical), which generate a characteristic temperature, humidity and atmospheric/precipitation isotopic gradient across the region. The potential consequences of climate change for the Great Lakes are a serious concern, given the lake level fluctuations known to have occurred throughout the Holocene. To understand this hydrological system better, we have collected a total of 2719 surface water samples, and some at depth of 2 m from bottom, intermittently during spring, summer and fall seasons from 2004 to 2011 across the Great Lakes, including connecting channels. The distribution of water isotopes along the Great Lakes chain produces a mixing line, defined as δ2H = 8.0(±0.2)δ18O + 3.1(±1.6) ‰. Several hydrological processes affect the variability of the lake-water isotope signatures in each of the Great Lakes, which are modified under their own characteristic climatic setting before exiting downstream. These processes include the amount and isotopic composition of precipitation, surface runoff and river inputs, groundwater seepage, surface water evaporative enrichment, and the proportion and isotopic composition of upstream water contributions. The Great Lakes mixing line provides a baseline against which spatial and temporal variability in lake water isotopic composition can be evaluated. Isotopic shifts parallel to the mixing line denote connectedness or degree of mixing along the

  1. Isotope composition of precipitation along the Adriatic coasts of Croatia and Slovenia

    International Nuclear Information System (INIS)

    Monitoring of isotope composition of precipitation includes measurements of radioactive isotope tritium (3H) and stable isotopes (2H, 18O) in monthly precipitation samples. Isotope composition of precipitation at Zagreb (Croatia) and Ljubljana (Slovenia) have been performed for more than 20 years within the Global Network for Isotopes in Precipitation (GNIP) organized jointly by the International Atomic Energy Agency (IAEA) and the World Meteorological Organization (WMO). Within the IAEA Co-ordinated Research Program 'Isotopic composition of precipitation in the Mediterranean Basin in relation to air circulation patterns and climate' the network has been extended since September 2000 to several stations along the Adriatic coast: Malinska on Krk Island, Zadar, Komiza on Vis Island, Dubrovnik, and Zavizan on Mt. Velebit (alt 1594 m) in Croatia, as well as Portoroz-Airport and Kozina in Slovenia. The sampling sites are situated in areas characterized with three different types of climate: (i) in the northern part continental climate prevails, (ii) in the mountainous middle part, mostly karst area, colder continental climate dominates, and (iii) the area along the Adriatic coast is controlled by the Mediterranean climate. In this work we present tritium activity and stable isotope content in monthly precipitation samples at the mentioned stations, together with the corresponding meteorological data: precipitation amount and mean monthly temperature. The results of tritium activity in monthly precipitation are presented. The results cover the period from September 2000 to September 2001 for marine stations and from January 2000 to December 2001 for continental stations Zagreb and Ljubljana (GNIP stations). Seasonal variations are typical for the continental stations of the Northern Hemisphere. The minimal activities in winter approach in the last years the natural, pre-bomb tritium level. Seasonal variations at maritime stations of mid- and south-Adriatic stations are

  2. Stable chromium isotopic composition of meteorites and metal-silicate experiments: Implications for fractionation during core formation

    Science.gov (United States)

    Bonnand, P.; Williams, H. M.; Parkinson, I. J.; Wood, B. J.; Halliday, A. N.

    2016-02-01

    We present new mass independent and mass dependent Cr isotope compositions for meteorites measured by double spike thermal ionisation mass spectrometry. Small differences in both mass independent 53Cr and 54Cr relative to the Bulk Silicate Earth are reported and are very similar to previously published values. Carbonaceous chondrites are characterised by an excess in 54Cr compared to ordinary and enstatite chondrites which make mass independent Cr isotopes a useful tool for distinguishing between meteoritic groups. Mass dependent stable Cr isotope compositions for the same samples are also reported. Carbonaceous and ordinary chondrites are identical within uncertainty with average δ53 Cr values of - 0.118 ± 0.040 ‰ and - 0.143 ± 0.074 ‰ respectively. The heaviest isotope compositions are recorded by an enstatite chondrite and a CO carbonaceous chondrite, both of which have relatively reduced chemical compositions implying some stable Cr isotope fractionation related to redox processes in the circumstellar disk. The average δ53 Cr values for chondrites are within error of the estimate for the Bulk Silicate Earth (BSE) also determined by double spiking. The lack of isotopic difference between chondritic material and the BSE provides evidence that Cr isotopes were not fractionated during core formation on Earth. A series of high-pressure experiments was also carried out to investigate stable Cr isotope fractionation between metal and silicate and no demonstrable fractionation was observed, consistent with our meteorites data. Mass dependent Cr isotope data for achondrites suggest that Cr isotopes are fractionated during magmatic differentiation and therefore further work is required to constrain the Cr isotopic compositions of the mantles of Vesta and Mars.

  3. Situation of sewage input reflected by nitrogen isotopic composition in a sediment core of Hongfeng Lake

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nitrogen in Hongfeng South Lake water mainly comes from sewage with high N concentrations from Pingba Chemical Fertilizer Plant (PCFP). Studies on the sediment core HF010427 sampled in the lake showed that the upward increase of nitrogen isotopic composition of sedimentary organic nitrogen (δ15Norg) accorded with the trend of industrial total production (TP) of PCFC. On the contrary, diagenesis will theoretically cause an upward decrease of δ15Norg. Because no treatment of sewage water was carried out, TP corresponds with sewage emission, indicating that sedimentary δ15Norg can reflect well the total trend of sewage input. The very similar profile shape between nitrogen isotopic composition of sedimentary absorbed ammonium (δ15NH4+absorbed) and TP of PCFP suggests that δ15NH4+absorbed can be used to reconstruct more detailed situation of sewage input. The study has a reference to history investigation of sewage input.

  4. Accurate measurement of neodymium isotopic composition using Neptune MC-ICP-MS

    Institute of Scientific and Technical Information of China (English)

    Yueheng YANG; Hongfu ZHANG; Liewen XIE; Fuyuan WU

    2008-01-01

    This paper reports the measurement of the Neodymium isotopic composition by Neptune Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) over the last two years. Although there is concomitant Cerium in the chemical separation process, this has no significant influence on the Neodymium analysis. As for the sample containing small amounts of Samarium (Sm/Nd<0.04), direct calibration for isobaric interference and mass discrimina-tion by the exponential law can be obtained by assuming that Samarium mass discrimination is the same as that of Neodymium. Geological samples after traditional chemi-cal separation were measured by Neptune MC-ICP-MS and Thermal Ionization Mass Spectrometry (TIMS) respectively. The results show that Neptune MC-ICP-MS can measure Neodymium isotopic composition as precisely the TIMS does and is even more effective and less time-consuming than the TIMS Method.

  5. Anthropogenic lead distribution in soils under arable land and permanent grassland estimated by Pb isotopic compositions

    International Nuclear Information System (INIS)

    The role of land use on fate of metals in soils is poorly understood. In this work, we studied the incorporation of lead in two neighboring soils with comparable pedogenesis but under long-term different agricultural management. Distributions of anthropogenic Pb were assessed from concentrations and isotopic compositions determined on bulk horizon samples, systematical 5-10 cm increment samples, and on 24-h EDTA extracts. Minor amounts of anthropogenic lead were detected until 1-m depth under permanent grassland, linked to high earthworm activity. In arable land, exogenous Pb predominantly accumulated at depths <60 cm. Although the proximity between the two sites ensured comparable exposition regarding atmospheric Pb deposition, the isotopic compositions clearly showed the influence of an unidentified component for the cultivated soil. This work highlights the need for exhaustive information on historical human activities in such anthropized agrosystems when fate of metal pollution is considered. - Incorporation and distribution of airborne Pb in soils are related to agricultural management

  6. High-resolution food webs based on nitrogen isotopic composition of amino acids

    OpenAIRE

    Chikaraishi, Yoshito; Steffan, Shawn A.; Ogawa, Nanako O.; Ishikawa, Naoto F.; SASAKI, Yoko; TSUCHIYA, Masashi; Ohkouchi, Naohiko

    2014-01-01

    Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position esti...

  7. Mechanisms controlling the carbon stable isotope composition of phytoplankton in karst reservoirs

    OpenAIRE

    Baoli Wang; Cong-Qiang Liu; Xi Peng; Fushun Wang

    2013-01-01

    In order to systematically understand the mechanisms controlling the carbon stable isotope composition of phytoplankton (δ13CPHY)in freshwater ecosystems, seasonal changes in δ13CPHY and related environmental factors were determined in karst reservoirs from the Wujiang river basin, China. Substantial and systematic differences within seasons and reservoirs were observed for δ13CPHY, which ranged from -39.2‰ to -15.1‰. An increase in water temperature triggered fast growth of phytoplankton whi...

  8. Mineralogy and Oxygen Isotope Compositions of an Unusual Hibonite-Perovskite Refractory Inclusion from Allende

    Science.gov (United States)

    Keller, L. P.; Snead, C.; Rahman, Z.; McKeegan, K. D.

    2012-01-01

    Hibonite-rich Ca- and Al-rich inclusions (CAIs) are among the earliest formed solids that condensed in the early nebula. We discovered an unusual refractory inclusion from the Allende CV3 chondrite (SHAL) containing an approx 500 micron long single crystal of hibonite and co-existing coarse-grained perovskite. The mineralogy and petrography of SHAL show strong similarities to some FUN inclusions, especially HAL. Here we report on the mineralogy, petrography, mineral chemistry and oxygen isotopic compositions in SHAL.

  9. Isotopic composition of carbon and nitrogen in ureilitic fragments of the Almahata Sitta meteorite

    OpenAIRE

    Downes, Hilary; Abernethy, F.A.J.; Smith, C.L.; Ross, A. J.; Verchovsky, A. B.; Grady, M. M.; Jenniskens, P.; Shaddad, M.H.

    2015-01-01

    This study characterizes carbon and nitrogen abundances and isotopic compositions in ureilitic fragments of Almahata Sitta. Ureilites are carbon-rich (containing up to 7 wt% C) and were formed early in solar system history, thus the origin of carbon in ureilites has significance for the origin of solar system carbon. These samples were collected soon after they fell, so they are among the freshest ureilite samples available and were analyzed using stepped combustion mass spectrometry. They co...

  10. Investigating the source, transport, and isotope composition of water vapor in the planetary boundary layer

    Science.gov (United States)

    Griffis, Timothy J.; Wood, Jeffrey D.; Baker, John M.; Lee, Xuhui; Xiao, Ke; Chen, Zichong; Welp, Lisa R.; Schultz, Natalie M.; Gorski, Galen; Chen, Ming; Nieber, John

    2016-04-01

    Increasing atmospheric humidity and convective precipitation over land provide evidence of intensification of the hydrologic cycle - an expected response to surface warming. The extent to which terrestrial ecosystems modulate these hydrologic factors is important to understand feedbacks in the climate system. We measured the oxygen and hydrogen isotope composition of water vapor at a very tall tower (185 m) in the upper Midwest, United States, to diagnose the sources, transport, and fractionation of water vapor in the planetary boundary layer (PBL) over a 3-year period (2010 to 2012). These measurements represent the first set of annual water vapor isotope observations for this region. Several simple isotope models and cross-wavelet analyses were used to assess the importance of the Rayleigh distillation process, evaporation, and PBL entrainment processes on the isotope composition of water vapor. The vapor isotope composition at this tall tower site showed a large seasonal amplitude (mean monthly δ18Ov ranged from -40.2 to -15.9 ‰ and δ2Hv ranged from -278.7 to -113.0 ‰) and followed the familiar Rayleigh distillation relation with water vapor mixing ratio when considering the entire hourly data set. However, this relation was strongly modulated by evaporation and PBL entrainment processes at timescales ranging from hours to several days. The wavelet coherence spectra indicate that the oxygen isotope ratio and the deuterium excess (dv) of water vapor are sensitive to synoptic and PBL processes. According to the phase of the coherence analyses, we show that evaporation often leads changes in dv, confirming that it is a potential tracer of regional evaporation. Isotope mixing models indicate that on average about 31 % of the growing season PBL water vapor is derived from regional evaporation. However, isoforcing calculations and mixing model analyses for high PBL water vapor mixing ratio events ( > 25 mmol mol-1) indicate that regional evaporation can account

  11. Isotopic Composition of Natural Nitrate in Groundwater in Los Alamos, New Mexico, USA

    Science.gov (United States)

    Chrystal, A. E.; Heikoop, J. M.; Longmire, P.; Dale, M.; Larson, T. E.; Perkins, G.; Fabyrka-Martin, J.; Simmons, A. M.; Fessenden-Rahn, J.

    2009-12-01

    Los Alamos National Laboratory (LANL) has established background concentrations for various dissolved constituents in local groundwater from perched-intermediate and regional aquifers in the vicinity of Los Alamos in north-central New Mexico. Typical background concentrations of nitrate (NO3-) are on the order of 0.31 mg/L as N (0.02 mM/L). In addition to natural sources, anthropogenic sources of NO3- in local groundwaters include industrial and treated sewage discharges released from LANL facilities, and treated sewage effluent discharges from Los Alamos County. We are using stable isotopes of nitrogen and oxygen in NO3- to distinguish among these sources, define groundwater flow paths, and evaluate groundwater mixing. Following the approach of McMahon and Böhlke (2006), we have explored the δ18O[NO3-] of water samples taken from background wells and springs in the Los Alamos area. NO3- from a spring and a well located in the Valles caldera, upgradient and upwind (relative to prevailing winds) of Los Alamos has δ15N and δ18O values of approximately 4.8 ‰ and -2.6 ‰, respectively. Tritium and unadjusted radiocarbon analyses indicate that these caldera waters predate LANL operations commencing in 1943. NO3- from groundwater locations in Los Alamos that exhibit background conditions has isotopic values similar to those of the caldera groundwater. Because local groundwater is relatively oxidizing, denitrification is not expected to be a factor in altering isotopic compositions of NO3-. Results indicate that there is little direct atmospheric contribution to dissolved NO3-, and that most NO3- is derived from bacterial nitrification in which one oxygen atom comes from atmospheric oxygen and two oxygen atoms come from soil porewater. Oxygen isotope values plot slightly below the expected isotopic trend for a 1:2 mix of these two sources, indicating either slight fractionation of oxygen isotopes during nitrification, or potential mixing with geological sources of

  12. U and Th Concentration and Isotopic Composition of Hydrothermal Fluids at the Lost City Hydrothermal Field

    Science.gov (United States)

    Ludwig, K. A.; Shen, C.; Cheng, H.; Edwards, R.; Kelley, D. S.; Butterfield, D. A.

    2006-12-01

    Uranium and Th concentration and isotopic composition of hydrothermal fluids at the Lost City Hydrothermal Field (LCHF) were determined using multi-collector inductively coupled plasma mass spectrometry (MC-ICP- MS). The LCHF is an off-axis, serpentinite-hosted hydrothermal system located at 30°N near the Mid- Atlantic Ridge. Carbonate chimneys reaching 60 m in height vent alkaline (pH~10), calcium-rich fluids at 40- 91°C and the towers are home to dense microbial communities. Vent fluid and seawater U and Th concentration and isotopic composition data provide critical information for constraining U-Th chimney ages. The increased sensitivity (1-2%) of MC-ICP-MS combined with an Aridus nebulization system allows the precise measurement of small quantities of sample (~150 ml) with low concentrations (Thorium concentrations of fluids are close to deep seawater values. U and Th isotopic compositions are reported at the permil level. These data may provide new insights into the role of serpentinite-hosted hydrothermal systems in the budgets of U and Th in the ocean. Techniques presented in this study may be applied to other hydrothermal and seep environments.

  13. Extermination Of Uranium Isotopes Composition Using A Micro Computer With An IEEE-488 Interface For Mass Spectrometer Analysis

    International Nuclear Information System (INIS)

    A mass spectrometry method can be used to make qualitative or quantitative analysis. For qualitative analysis, identification of unknown materials by a Mass Spectrometer requires definite assignment of mass number to peak on chart. In quantitative analysis, a mass spectrometer is used to determine isotope composition material in the sample. Analysis system of a Mass Spectrometer possession of PPNY-BATAN based on comparison ion current intensity which enter the collector, and have been used to analyse isotope composition. Calculation of isotope composition have been manually done. To increase the performance and to avoid manual data processing, a micro computer and IEEE-488 interface have been installed, also software packaged has been made. So that the determination of the isotope composition of material in the sample will be faster and more efficient. Tile accuracy of analysis using this program on sample standard U3O8 NBS 010 is between 93,87% - 99,98%

  14. s-process Ba isotopic compositions in presolar SiC from the Murchison meteorite

    Science.gov (United States)

    Prombo, C. A.; Podosek, F. A.; Amari, S.; Lewis, R. S.

    1993-01-01

    We have measured, by thermal ionization mass spectrometry, the isotopic composition of Ba in interstellar SiC-enriched samples (the KJ series) prepared from the Murchison meteorite. Ba in these samples is strongly enriched in components plausibly understood as s-process nucleosynthetic products. Inferred s-process compositions are different from the average s-process contribution to solar system materials in the sense of indicating lower effective neutron exposure. There are variations in s-process compositions which correlate with grain size, indicating lower neutron exposure for the larger grains. The inferred s-process compositions differ significantly from previous theoretical predictions, indicating the need for revision of relevant neutron capture cross sections and providing a target for more detailed modeling of s-process nucleosynthesis in specific stellar environments.

  15. Studies on stable isotopic composition of daily rainfall from Kozhikode, Kerala, India.

    Science.gov (United States)

    Unnikrishnan Warrier, C; Praveen Babu, M; Sudheesh, M; Deshpande, Rajendrakumar D

    2016-06-01

    The stable isotopic compositions of all major daily rain fall samples (n = 113) collected from Kozhikode station in Kerala, India, for the year 2010 representing the pre-monsoon, southwest and northeast monsoon seasons are examined. The isotopic variations δ(18)O, δ(2)H and d-excess in daily rainfall ranged from δ(18)O: -4.4 to 2 ‰, δ(2)H: -25.3 to 13.8 ‰, and d-excess: -2.4 to 15.3 ‰; δ(18)O: -9.7 to -0.6 ‰, δ(2)H: -61.7 to 5.3 ‰, and d-excess 5.8 to 17.4 ‰; δ(18)O -11.3 to -1.4 ‰, δ(2)H: -75.3 to 0.9 ‰, and d-excess: 8.8 to 21.3 ‰ during the pre-, southwest and northeast monsoon periods, respectively. Thus, daily rainfall events during two monsoon periods had a distinct range of isotopic variations. The daily rain events within the two monsoon seasons also exhibited periodic variations. The isotopic composition of rain events during pre-monsoon and a few low-intensity events during the southwest monsoon period had imprints of secondary evaporation. This study analysing the stable isotopic characteristics of individual rain events in southern India, which is influenced by dual monsoon rainfall, will aid in a better understanding of its mechanism. PMID:26617222

  16. Probing the homogeneity of the isotopic composition and molar mass of the ‘Avogadro’-crystal

    Science.gov (United States)

    Pramann, Axel; Lee, Kyoung-Seok; Noordmann, Janine; Rienitz, Olaf

    2015-12-01

    Improved measurements on silicon crystal samples highly enriched in the 28Si isotope (known as ‘Si28’ or AVO28 crystal material) have been carried out at PTB to investigate local isotopic variations in the original crystal. This material was used for the determination of the Avogadro constant NA and therefore plays an important role in the upcoming redefinition of the SI units kilogram and mole, using fundamental constants. Subsamples of the original crystal have been extensively studied over the past few years at the National Research Council (NRC, Canada), the National Metrology Institute of Japan (NMIJ, Japan), the National Institute of Standards and Technology (NIST, USA), the National Institute of Metrology (NIM, People’s Republic of China), and multiple times at PTB. In this study, four to five discrete, but adjacent samples were taken from three distinct axial positions of the crystal to obtain a more systematic and comprehensive understanding of the distribution of the isotopic composition and molar mass throughout the crystal. Moreover, improved state-of-the-art techniques in the experimental measurements as well as the evaluation approach and the determination of the calibration factors were utilized. The average molar mass of the measured samples is M  =  27.976 970 12(12) g mol-1 with a relative combined uncertainty uc,rel(M)  =  4.4 ×10-9. This value is in astounding agreement with the values of single samples measured and published by NIST, NMIJ, and PTB. With respect to the associated uncertainties, no significant variations in the molar mass and the isotopic composition as a function of the sample position in the boule were observed and thus could not be traced back to an inherent property of the crystal. This means that the crystal is not only ‘homogeneous’ with respect to molar mass but also has predominantly homogeneous distribution of the three stable Si isotopes.

  17. Chemistry and oxygen isotopic composition of cluster chondrite clasts and their components in LL3 chondrites

    Science.gov (United States)

    Metzler, Knut; Pack, Andreas

    2016-02-01

    Cluster chondrites are characterized by close-fit textures of deformed and indented chondrules, taken as evidence for hot chondrule accretion (Metzler). We investigated seven cluster chondrite clasts from six brecciated LL3 chondrites and measured their bulk oxygen isotopic and chemical composition, including REE, Zr, and Hf. The same parameters were measured in situ on 93 chondrules and 4 interchondrule matrix areas. The CI-normalized REE patterns of the clasts are flat, showing LL-chondritic concentrations. The mean chemical compositions of chondrules in clasts and other LL chondrites are indistinguishable and we conclude that cluster chondrite chondrules are representative of the normal LL chondrule population. Type II chondrules are depleted in MgO, Al2O3 and refractory lithophiles (REE, Zr, Hf) by factors between 0.65 and 0.79 compared to type I chondrules. The chondrule REE patterns are basically flat with slight LREE fractionations. Many chondrules exhibit negative Eu anomalies while matrix shows a complementary pattern. Chondrules scatter along a correlation line with a slope of 0.63 in the oxygen 3-isotope diagram, interpreted as the result of O-isotope exchange between chondrule melts and 18O-rich nebular components. In one clast, a distinct anticorrelation between chondrule size and δ18O is found, which may indicate a more intense oxygen isotope exchange by smaller chondrules. In some clasts the δ18O values of type I chondrules are correlated with concentrations of SiO2 and MnO and anticorrelated with MgO, possibly due to the admixture of a SiO2- and MnO-rich component to chondrule melts during oxygen isotope exchange. Two chondrules with negative anomalies in Sm, Eu, and Yb were found and may relate their precursors to refractory material known from group III CAIs. Furthermore, three chondrules with strong LREE > HREE and Zr/Hf fractionations were detected, whose formation history remains to be explained.

  18. Sulfur isotopic composition and source identification of atmospheric environment in central Zhejiang,China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Sulfur dioxide and sulfate aerosols in the atmosphere are significant factors leading to acidification of the atmospheric environment and worsening the pollution of acid deposition. Because of the "fingerprint" characteristics of the stable sulfur isotopic composition, sulfur isotope has been widely adopted in environmental researches concerning sulfur cycle and source identification. In this study, the atmospheric environment of Jinhua City, central Zhejiang Province, was continuously monitored, and the sulfur isotopic composition of SO2 and sulfate aerosols in the atmosphere was analyzed. The results indicate that the variation of δ34S values for SO2 ranges from 1.0‰ to 7.5‰, and annual average is 4.7‰±2.3‰, whereas that of sulfate aerosols ranges from 6.4‰ to 9.8‰,and annual average is 8.1‰±1.0‰. The δ 34S values for SO2 have significant seasonal variations, which are 7.0‰ in winter and 3.3‰ in summer. These variations cannot be attributed to a single factor, and we suggest a temperature-dependent isotope equilibrium fractionation and elevated biogenic sulfur emissions of isotopically light S in summer may be the main controlling mechanisms. Furthermore, we also discuss the δ 34S model of atmospheric SO2 oxidation to form sulfate, and suggest that heterogeneous oxidation dominates in the oxidation reactions of atmospheric SO2 in the central Zhejiang Province. We further suggest that the relative humidity in the atmosphere plays an important role in the oxidation mechanism of atmospheric SO2.

  19. Isotopic Composition of the Neolithic Alpine Iceman's Tooth Enamel and Clues to his Origin

    Science.gov (United States)

    Muller, W.; Muller, W.; Halliday, A. N.

    2001-12-01

    Five small enamel fragments from three teeth of the upper right jaw from the mummy of the Neolithic Alpine Iceman have been investigated for their isotopic composition in order to shed light on his geographic origins. Soils from approximately contemporaneous sites were sampled for comparison. Tooth enamel forms ontogenetically very early and is not re-mineralized during later lifetime (unlike with bone material). Therefore, unique insights into the Iceman's childhood can be acquired. Enamel also is the densest tissue of a human body and is thus less susceptible to post-mortem alteration. Both radiogenic (Sr, Pb, Nd) and stable isotopes (O, C) are investigated. Radiogenic isotopes allow reconstruction of the local geological background, because humans incorporate Sr, Pb and Nd from their local environment by eating local food. Stable isotopes provide information about altitude and/or position relative to the main Alpine watershed. High spatial-resolution laser-ablation ICPMS profiles reveal that most elements are distributed in a manner that is essentially similar to modern human teeth except of that La, Ce, Nd (LREE) show up to a 100-fold enrichment towards the outer enamel surface. These uptake-profiles may reflect interaction with melt water, consistent with data for the composition of samples of the Iceman's skin. Biogenic apatites (enamel, bone) have very low in-vivo LREE concentrations, but take up LREEs post-mortem from the burial environment. Ice core samples from the finding site show concentrations up to 400 ppt Ce. Such high uptake of the LREEs precludes the derivation of an in-vivo Nd isotopic signal, but both other radiogenic tracers, Sr and Pb, show pristine (in-vivo) concentrations of 87 ppm and 0.1 ppm, respectively. Strontium isotopic compositions were determined on fragments from the canine, the first and second premolar (1 - 9 mg) and two hip bone samples, utilizing three sequential leaching steps for each sample to detect possible alteration

  20. Discrimination of the Cigarettes Geographical Origin by DRC-ICP-MS Measurements of Pb Isotope Compositions

    Science.gov (United States)

    Guo, W.; Hu, S.; Jin, L.

    2014-12-01

    Trace Pb are taken up with the same isotopic ratios as is present in the source soil, and the isotopic composition of Pb could used to reflect these sources and provide powerful indicators of the geographic origin of agriculture products derived from vegetative matter. We developed a simple and high throughput method, which based on DRC-ICP-MS for determination of Pb isotope ratios for discriminating the geographic origin of cigarettes. After acid digestion procedure, the cigarette digested solutions were directly analyzed by ICP-QMS with a DRC pressurized by the non-reactive gas Ne. In the DRC, Ne molecules collision with Pb ions and improves Pb isotope ratios precision 3-fold, which may be due to the collisional dampling smoothes out the ion beam fluctuations. Under the optimum DRC rejection parameter Q (RPq = 0.45), the main matrix components (K, Na, Ca, Mg, Al, Fe etc.) originating from cigarettes were filtered out. Mass discrimination of 208Pb/206Pb ratio in Ne DRC mode increased 0.3% compared to the standard mode, the mass bias due to the in-cell Ne gas collision can be accurately corrected by NIST 981 Pb isotope standard. This method was verified by a tobacco reference material CTV-OTL-2. Results of 208Pb/206Pb and 207Pb/206Pb were 2.0848 ± 0.0028 (2δ) and 0.8452 ± 0.0011 (2δ) for CTA-VTL-2, which were agreed with the literature values (208Pb/206Pb = 2.0884 ± 0.0090 and 207Pb/206Pb = 0.8442 ± 0.0032). The precision of Pb isotope ratios (208Pb/206Pb and 207Pb/206Pb) for the cigarette samples are ranged from 0.01 to 0.08% (N = 5). It has sufficient precision to discriminate 91 different brand cigarettes originated from four different geographic regions (Shown in Fig).

  1. An updated estimation of the stable carbon and oxygen isotopic compositions of automobile CO emissions

    Science.gov (United States)

    Tsunogai, Urumu; Hachisu, Yosuke; Komatsu, Daisuke D.; Nakagawa, Fumiko; Gamo, Toshitaka; Akiyama, Ken-ichi

    We estimate up-to-date values of the average isotopic compositions of CO emitted from automobiles. In the estimation, we determined the isotopic compositions of CO in tail pipe exhaust for four gasoline automobiles and two diesel automobiles under varying conditions of both idling and running. While the dependence on the automobile manufacturer is little, each automobile equipped with functional catalytic converter exhibits a large temporal δ13C and δ18O variation. They tend to show 13C and 18O enrichment in accordance with the reduction of CO in exhaust, suggesting that the functional catalytic converter in engines enhances the δ13C and δ18O values of CO from tail pipes through a kinetic isotope effect during CO destruction. Assuming that automobiles run a modeled driving cycle, we estimated the average δ13C and δ18O of CO to be -23.8±0.8‰ PDB and +25.3±1.0‰ SMOW, respectively, for recent gasoline automobiles, and -19.5±0.7‰ PDB and +15.1±1.0‰ SMOW, respectively, for recent diesel automobiles. While the δ13C and δ18O values of recent gasoline automobiles coincide well with the isotopic compositions of source CO in present trunk road atmosphere estimated in this study, those are +4-+6‰ ( δ13C) and +1-+3‰ ( δ18O) higher than those reported previously and also those emitted from old, non-catalyst automobiles determined in this study. Recent improvements in functional catalytic converters have enhanced and will enhance the δ13C and δ18O values of CO from automobiles.

  2. The stable isotope compositions of mercury in atmospheric particles (PM10) from Paris (France) and vicinity

    Science.gov (United States)

    Widory, D.; Petelet-Giraud, E.; Johnson, T.; Quétel, C.; Snell, J.; van Bocxstaele, M.; Bullen, T. D.

    2010-12-01

    Solid mercury (Hg) in atmospheric particles in the environment can be derived from a variety of primary sources and cycled through numerous secondary processes, complicating identification of its origin. Using the PM10 fraction of aerosols from Paris and vicinity, we investigated the possibility that Hg stable isotope compositions could help identify the origins of atmospheric Hg and processes affecting the atmospheric Hg budget. Characterization of Hg isotope compositions of emissions from the different potential sources (e.g. waste incinerators, coal-fired power plants, metal refining plants, road traffic, heating sources and volcanic gases) shows that those containing Hg are clearly discriminated by specific Hg isotope signatures. PM10 were sampled in three different locations: A) downtown Paris, characterized by diffuse pollution, B) nearby suburb of the city, close to suspected Hg emitters, and C) in distant suburb of the city, having only a few industrial activities in the area. Results indicate that Hg in most of the PM10 samples is explained by binary mixings. The mixing end-members include at least two distinct sources at low Hg concentrations in the aerosols, compatible with industrial activity. At high Hg concentration in the aerosols, the isotopes may likewise indicate two distinct sources with δ202Hg compositions of -4.1 and -11.4 ‰. This range is significantly less than that measured on the potential sources of Hg pollution, and may indicate secondary processes, such as gas to solid phase transfers. The occurrence of post-emission processes is reinforced by the strong correlations existing between these low δ202Hg and MIF Δ201Hg values.

  3. The use of oxygen isotopic composition to study water dynamics in Amazon floodplain lakes

    International Nuclear Information System (INIS)

    The lakes formed in the Amazon floodplain play a key role in sustaining the highest populational density in the Amazon Basin because of its high primary productivity. The water volume in these lakes vary greatly during the year and possible water sources are the feeding river during high water state of the hydrographs and local inputs from its drainage basin. As these sources are chemically distinct, to understand the nutrient dynamics in these lakes, it is very important to know the relative water contribution of different water sources. In this paper we use 18O as a conservative to know the water sources for the lakes and our hypothesis is that: 1) In the high water stage lake water is derived predominantly from its feeding river. Therefore their δ18O should be similar. 2) In the low water stage lake water is a mixture of watershed and last flood event waters. In this case, lake δ18O should be indicative of the relative contribution of each source. To test this hypothesis we assume a two end member mixing a model. If the 18O isotopic composition of these two sources are known the relative contribution of each source may be calculated by isotopic dilution equation. The first step in this work was to know the 18O isotopic composition of the lakes and feeding rivers and its spatial and temporal variability. Clearly the δ18O signal in the lakes of Amazon varzea is controlled by the 18O content of the feeding river. But there is a consistent pattern in the 18O enrichment of the lakes versus the feeding rivers, which is most pronounced on low water period. Our initial hypothesis requires that this water be of local drainage basin origin. Although it was not possible to measure the isotopic composition of local drainage water, indirect measurement suggest that this could be the case. (author). 17 refs, 4 figs, 2 tabs

  4. The stable vanadium isotope composition of the mantle and mafic lavas

    Science.gov (United States)

    Prytulak, J.; Nielsen, S. G.; Ionov, D. A.; Halliday, A. N.; Harvey, J.; Kelley, K. A.; Niu, Y. L.; Peate, D. W.; Shimizu, K.; Sims, K. W. W.

    2013-03-01

    Vanadium exists in multiple valence states under terrestrial conditions (2+, 3+, 4+, 5+) and its isotopic composition in magmas potentially reflects the oxidation state of their mantle source. We present the first stable vanadium isotope measurements of 64 samples of well-characterized mantle-derived mafic and ultramafic rocks from diverse localities. The δ51V ranges from -0.27‰ to -1.29‰, reported relative to an Alfa Aesar (AA) vanadium solution standard defined as 0‰. This dataset is used to assess the effects of alteration, examine co-variation with other geochemical characteristics and define a value for the bulk silicate Earth (BSE). Variably serpentinised peridotites show no resolvable alteration-induced δ51V fractionation. Likewise, altered mafic oceanic crustal rocks have identical δ51V to fresh hand-picked MORB glass. Intense seafloor weathering can result in slightly (˜0.2-0.3‰) heavier isotope compositions, possibly related to late-stage addition of vanadium. The robustness of δ51V to common alteration processes bodes well for its potential application to ancient mafic material. The average δ51V of mafic lavas, including MORB, Icelandic tholeiites and lavas from the Shatsky Rise large igneous province is -0.88±0.27‰ 2sd. Peridotites show a large range in primary δ51V (-0.62‰ to -1.17‰), which co-varies positively with vanadium concentrations and indices of fertility such as Al2O3. Although these data suggest preferential extraction of heavier isotopes during partial melting, the isotope composition of basalts (δ51V=-0.88±0.27‰ 2sd) and MORB glass in particular (δ51V=-0.95±0.13‰ 2sd) is lighter than fertile peridotites and thus difficult to reconcile with a melt extraction scenario. Determination of fractionation factors between melt and mineral phases such as pyroxenes and garnet are necessary to fully understand the correlation. We arrive at an estimate of δ51VBSE=-0.7±0.2‰ (2sd) for the bulk silicate Earth by averaging

  5. Uranium isotope composition of a laterite profile during extreme weathering of basalt in Guangdong, South China

    Science.gov (United States)

    Huang, J.; Zhou, Z.; Gong, Y.; Lundstrom, C.; Huang, F.

    2015-12-01

    Rock weathering and soil formation in the critical zone are important for material cycle from the solid Earth to superficial system. Laterite is a major type of soil in South China forming at hot-humid climate, which has strong effect on the global uranium cycle. Uranium is closely related to the environmental redox condition because U is stable at U(Ⅳ) in anoxic condition and U(Ⅵ) as soluble uranyl ion (UO22+) under oxic circumstance. In order to understand the behavior of U isotopes during crust weathering, here we report uranium isotopic compositions of soil and base rock samples from a laterite profile originated from extreme weathering of basalt in Guangdong, South China. The uranium isotopic data were measured on a Nu Plasma MC-ICP-MS at the University of Illinois at Urbana-Champaign using the double spike method. The δ238U of BCR-1 is -0.29±0.03‰ (relative to the international standard CRM-112A), corresponding to a 238U/235U ratio of 137.911±0.004. Our result of BCR-1 agrees with previous analyses (e.g., -0.28‰ in Weyer et al. 2008) [1]. U contents of the laterite profile decrease from 1.9 ppm to 0.9 ppm with depth, and peak at 160 - 170 cm (2.3 ppm), much higher than the U content of base rocks (~0.5 ppm). In contrary, U/Th of laterites is lower than that of base rock (0.27) except the peak at the depth of 160-170 cm (0.38), indicating significant U loss during weathering. Notably, U isotope compositions of soils show a small variation from -0.38 to -0.28‰, consistent with the base rock within analytical error (0.05‰ to 0.08‰, 2sd). Such small variation can be explained by a "rind effect" (Wang et al., 2015) [2], by which U(Ⅳ) can be completely oxidized to U(VI) layer by layer during basalt weathering by dissolved oxygen. Therefore, our study indicates that U loss during basalt weathering at the hot-humid climate does not change U isotope composition of superficial water system. [1] Weyer S. et al. (2008) Natural fractionation of 238U/235

  6. First data on helium isotope composition obtained with the use of single-cascade static mass-spectrometer MI-1201

    Energy Technology Data Exchange (ETDEWEB)

    Kalinskij, I.L.; Tolstikhin, I.N.; Sharkov, I.V.; Pushkarev, Yu.D. (AN SSSR, Apatity. Geologicheskij Inst. Kol' skogo Filiala)

    1984-01-01

    Determination of isotope ratio and helium content in samples of the most ancient rocks of basic composition and in rocks of carbonatite complex of a relatively young alkali massif, and also in samples of the most ancient lithium-containing minerals( Kola Peninsula) has been carried out. For isotope analysis of helium the MI-1201 single-cascade static mass-spectrometer is used. The /sup 3/He//sup 4/He ratio in gabbro-anorthosite is shown to reach high values( up to 1.26x10/sup -6/). Isotope analysis of helium in the Khibiny alkal massif rock samples has shown these rocks, characterized by higher contents of radioactive elements to preserve a /sup 3/He excess. The content and isotope composition of helium in larga spodumene crystal samples show the excess of helium light isotope to be related to high contents of radioactive elements in enclosing rocks.

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

    International Nuclear Information System (INIS)

    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 (PO43-). 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 (δ18Op) may be used as a tracer for phosphate sources and cycling in aquatic ecosystems. Recently, several studies have been conducted utilizing δ18Op as a tracer for phosphate sources and cycling in various aquatic environments. Specifically, work to date indicates that δ18Op 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 δ18Op 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 δ18Op of phosphate in rivers and streams. (author)

  8. C, Sr and Sr isotopic composition on probable vendian- tommotian carbonate sequences in Nw Argentina

    International Nuclear Information System (INIS)

    C-isotope stratigraphy is one of the most powerfool tools in Precambrian chronostratigraphy, especially when sediments lack recognizable animal fossils. The δ13C secular variation curves for marine carbonates in the Neoproterozoic-Cambrian interval show strong positive-negative excursions, several of them interpreted as the stratigraphic position of ancient ice ages (Hoffman et al. 1998). The Sr isotope composition of the seawater for this age interval is characterized by a continuous increase of 87Sr/86Sr that is interrupted, several times, by sharp rises, which represent important changes in the Earth history (Montanez et al. 2000). Only limited data on the behavior of C and Sr isotopes in carbonates are available in South America. We examine here carbonate sequences from the Argentine Precordillera, San Juan province, and from other carbonate sequences in NW Argentina that could be, potentially, proxies for the Precambrian-Cambrian transition. We have studied their δ13C and 87Sr/86Sr chemostratigraphy and compare it to global C and Sr isotope secular variation curves for this time span. This study aims to improve the relatively coarse stratigraphic resolution provided only by the study of the fossil record in some of the carbonate successions under consideration (au)

  9. Factors controlling the temporal variability of ecosystem respiration and its carbon isotope composition

    Science.gov (United States)

    Fassbinder, J.; Griffis, T. J.; Baker, J. M.; Erickson, M.; Billmark, K.; Smith, J.

    2009-12-01

    Ecosystem respiration (FR ) is the major pathway for carbon loss from terrestrial ecosystems. Stable carbon isotope analyses have been used to improve our understanding of the processes controlling ecosystem respiration. In particular, 13CO2 has been used to partition the autotrophic (Fa) and heterotrophic (Fh) contributions to FR. Further, there has been some concern in the literature regarding the temporal variability of the isotopic composition of ecosystem respiration (δR) and its potential influence on ecosystem flux partitioning based on isotope methods. In this study, we used an automated chamber and tunable diode laser system to measure soil respiration (FRs) and its isotopic composition (δRs) in an agricultural ecosystem under a C3/C4 crop rotation. Further, we used the same chamber-TDL system in a climate controlled greenhouse facility with C3/C4 treatments to examine the main factors causing variability in δRs and δR. The chamber data revealed strong diurnal patterns in the isotopic composition of Fh in the agricultural soil plots before crop emergence and in the greenhouse experiments involving bare soils. The diurnal pattern consisted of a sharp enrichment of up to 6‰ from 0700 to 1200 hr followed by a gradual depletion throughout the afternoon and evening. The diurnal signals of FR and soil temperature closely resembled the diurnal signal of δh, but consistently lagged δh by 3 to 4 hours. During peak corn growth, diurnal variation in δRs was strongly influenced by the isotopic composition of root respiration (δas), which enriched nighttime δRs by as much as 7‰ and daytime δRs by as much as 3‰. Chamber and flux-gradient data also indicated considerable seasonal variation in δR during corn growing seasons, ranging from -25‰ at the time of planting to -11‰ during peak growth. Less variation in δR was observed during soybean seasons, with values ranging from -26 to -21‰. Major shifts in δR during corn seasons were consistently

  10. Ore lead isotopical composition of lower Proterozoic volcanogenic sulfide ores at Garpenberg, south central Sweden

    International Nuclear Information System (INIS)

    The isotopic composition of ore lead in galena from the volcanogenic sulfide ores at Garpenberg district is presented. Compared with the average growth curve of Stacey and Kramers, the ore lead at Garpenberg is slightly enriched in radiogenic lead. The influence of metamorphism on the ore lead composition of galena samples is negligible. The observed trend in the standard diagrams may be explained in terms of a mixing line, where the ore lead was derived from two different crustal sources originally enriched in radiogenic lead (e.g. volcanic and sedimentary rocks). Alternatively, it could represent sulfide ores of slightly different ages derived from a common rock source. The composition of the ore lead in the Garpenberg district displays the typical signature of the volcanogenic sulfide ores in Bergslagen, which at a regional scale is relatively homogeneous and is interpreted as derived form an isotopically well mixed orogen-upper crust reservoir. The results are consistent with a common origin for all the sulfide ore types present in the Garpenberg and Garpenberg Norra deposits. However, at a local scale, minor variations in the ore lead composition can be detected within a particular district or single deposit. These differences may be interpreted as due to the influence of the local lithology on the ore lead or differences in mineralization age. (L.E.)

  11. Ore lead isotopical composition of lower Proterozoic volcanogenic sulfide ores at Garpenberg, south central Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Gebeyehu, M.; Vivallo, W. (Stockholm Univ. (Sweden). Dept. of Geology and Geochemistry)

    1991-01-01

    The isotopic composition of ore lead in galena from the volcanogenic sulfide ores at Garpenberg district is presented. Compared with the average growth curve of Stacey and Kramers, the ore lead at Garpenberg is slightly enriched in radiogenic lead. The influence of metamorphism on the ore lead composition of galena samples is negligible. The observed trend in the standard diagrams may be explained in terms of a mixing line, where the ore lead was derived from two different crustal sources originally enriched in radiogenic lead (e.g. volcanic and sedimentary rocks). Alternatively, it could represent sulfide ores of slightly different ages derived from a common rock source. The composition of the ore lead in the Garpenberg district displays the typical signature of the volcanogenic sulfide ores in Bergslagen, which at a regional scale is relatively homogeneous and is interpreted as derived form an isotopically well mixed orogen-upper crust reservoir. The results are consistent with a common origin for all the sulfide ore types present in the Garpenberg and Garpenberg Norra deposits. However, at a local scale, minor variations in the ore lead composition can be detected within a particular district or single deposit. These differences may be interpreted as due to the influence of the local lithology on the ore lead or differences in mineralization age. (L.E.).

  12. Stable isotopic composition of bivalve shell organic matrix: Mytilus edulis collected along the Scheldt estuary

    Science.gov (United States)

    Mas, R.; Claeys, P.; Keppens, E.; Dehairs, F.

    2009-04-01

    Bivalve shells are biostructures composed of a mineral and an organic phase. For paleoclimatology applications, the mineral part (carbonates) is most widely studied. In contrast, understanding of the composition and the proxy-function of the organic matrix is much less developed. The quantity of organic matrix in shells is relatively small compared to the mineral phase (a few wt %) and the biochemical composition is quite complex, consisting mainly of sugars and proteins. Lipids, which represent a small fraction of the organic matrix, are rather poorly known. We studied the potential of stable isotope composition (C, N, H) of bulk organic matrix and specific lipid compounds of Mytilis edulis shells, as environmental and climatic proxies, with special focus on the effects due to changing salinity. Mytilus specimens were collected along the salinity gradient of the Scheldt estuary (The Netherlands) and we analysed the isotopic composition of the organic matrix and associated specific lipid compounds and related these to averaged physico-chemical characteristics of the water, in particular salinity. We discuss these relationships in the light of their usefulness as proxies for reconstructing past environmental conditions.

  13. Utilizing geochemical, hydrologic, and boron isotopic data to assess the success of a salinity and selenium remediation project, Upper Colorado River Basin, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Naftz, David L. [U.S. Geological Survey, 2329 West Orton Circle, Salt Lake City, Utah, 84119 (United States)], E-mail: dlnaftz@usgs.gov; Bullen, Thomas D. [U.S. Geological Survey, MS 420, 345 Middlefield Rd., Menlo Park, California, 94025 (United States); Stolp, Bert J.; Wilkowske, Christopher D. [U.S. Geological Survey, 2329 West Orton Circle, Salt Lake City, Utah, 84119 (United States)

    2008-03-15

    Stream discharge and geochemical data were collected at two sites along lower Ashley Creek, Utah, from 1999 to 2003, to assess the success of a site specific salinity and Se remediation project. The remediation project involved the replacement of a leaking sewage lagoon system that was interacting with Mancos Shale and increasing the dissolved salinity and Se load in Ashley Creek. Regression modeling successfully simulated the mean daily dissolved salinity and Se loads (R{sup 2} values ranging from 0.82 to 0.97) at both the upstream (AC1) and downstream (AC2/AC2A) sites during the study period. Prior to lagoon closure, net gain in dissolved-salinity load exceeded 2177 metric tons/month and decreased after remediation to less than 590 metric tons/month. The net gain in dissolved Se load during the same pre-closure period exceeded 120 kg/month and decreased to less than 18 kg/month. Sen's slope estimator verified the statistical significance of the modeled reduction in monthly salinity and Se loads. Measured gain in dissolved constituent loads during seepage tests conducted during September and November 2003 ranged from 0.334 to 0.362 kg/day for dissolved Se and 16.9 to 26.1 metric tons/day for dissolved salinity. Stream discharge and changes in the isotopic values of delta boron-11 ({delta}{sup 11}B) were used in a mixing model to differentiate between constituent loadings contributed by residual sewage effluent and naturally occurring ground-water seepage entering Ashley Creek. The majority of the modeled {delta}{sup 11}B values of ground-water seepage were positive, indicative of minimal seepage contributions from sewage effluent. The stream reach between sites S3 and AC2A contained a modeled ground-water seepage {delta}{sup 11}B value of - 2.4 per mille , indicative of ground-water seepage composed of remnant water still draining from the abandoned sewage lagoons.

  14. Elemental and isotopic compositions of noble gases in the mantle: Pete's path

    Science.gov (United States)

    Moreira, Manuel; Péron, Sandrine; Colin, Aurélia

    2016-04-01

    Noble gases are tracers of the origin of the volatiles on Earth and other terrestrial planets. The determination of their isotopic compositions in oceanic basalts allows discriminating between different possible scenarios for the origin of volatiles (chondritic, solar, cometary). However, oceanic basalts show a ubiquitous component having atmospheric noble gas compositions, which reflects a shallow air contamination. This component masks the mantle composition and only step crushing is able to (partially) remove it. Nevertheless, the exact mantle composition is always unconstrained due to the uncertainty on its complete removal. Developed by Pete Burnard (Burnard et al., 1997; Burnard, 1999), single vesicle analysis using laser ablation is a challenging technique to determine the mantle composition, free of atmospheric contamination. We have used this technique to measure He, Ne, Ar isotopes and CO2 in single vesicles from both MORB and OIB (Galapagos, Iceland). Vesicles are located using microtomography and the noble gases are measured using the Noblesse mass spectrometer from IPGP using an Excimer laser to open the vesicles. Both Galapagos and Iceland samples show that the 20Ne/22Ne ratio is limited to ~12.8 in the primitive mantle, suggesting that the origin of the light noble gases can be attributed to irradiated material instead of a simple dissolution of solar gases into a magma ocean (Moreira and Charnoz, 2016). Such a scenario of incorporation of light noble gases by irradiation also explains the terrestrial argon isotopic composition. However, the Kr and Xe contribution of implanted solar wind is small and these two noble gases were carried on Earth by chondrites and/or cometary material. Burnard, P., D. Graham and G. Turner (1997). "Vesicle-specific noble gas analyses of « popping rock »: implications for primordial noble gases in the Earth." Science 276: 568-571. Burnard, P. (1999). "The bubble-by-bubble volatile evolution of two mid-ocean ridge

  15. Measuring and utilizing the hydrogen isotopic composition of deep-sea corals

    Science.gov (United States)

    Davin, Samuel; Hillaire-Marcel, Claude; Edinger, Evan; Gelinas, Yves

    2016-04-01

    Despite the widespread use of hydrogen isotopic analysis of bioarchives in paleoenvironmental reconstructions, no previously-published work has yet attempted to measure or utilize the hydrogen isotopic composition (δD) of deep-sea corals. Geographically ubiquitous and with lifespans on the scale of hundreds of years, δD measurements of deep-sea corals have the potential to elucidate physical paleoceanographic parameters at well-resolved spatial and temporal resolutions. We present a method for the determination of annually-resolved δD from deep-sea corals measured from gorgonin, a complex proteinaceous material making up the horny skeleton of gorgonian corals. We address the issue of exchangeable hydrogen in gorgonin by controlling the isotopic composition of exchangeable hydrogen using a heated batch dual-equilibration technique. Coupled with δ15N measurements, we attempt to identify the relationships between trophic feeding levels, physical oceanographic parameters, and the δD of gorgonin from corals collected from chemically distinct ocean basins. Preliminary results from 43 samples indicate reproducible measurements on coral species Primnoa pacifica, Primnoa resedaeformis, and Keratoisis grayii with bulk δD values ranging from -40‰ to -110‰ and bulk δ15N values ranging from +13‰ to +17‰. Final results will include a full suite of non-exchangeable δD values and δ15N of corals from the Labrador Sea and from the Gulf of Alaska.

  16. Lead contamination and transfer in urban environmental compartments analyzed by lead levels and isotopic compositions

    International Nuclear Information System (INIS)

    Lead levels and isotopic compositions in atmospheric particles (TSP and PM2.5), street dust and surface soil collected from Nanjing, a mega city in China, were analyzed to investigate the contamination and the transfer of lead in urban environmental compartments. The lead contents in TSP and PM2.5 are significantly higher than them in the surface soil and street dust (p 206Pb/207Pb vs.208Pb/206Pb and 206Pb/207Pb vs. 1/Pb imply that the street dust and atmospheric particles (TSP and PM2.5) have very similar lead sources. Coal emissions and smelting activities may be the important lead sources for street dust and atmospheric particles (TSP and PM2.5), while the deposition of airborne lead is an important lead source for urban surface soil. - Highlights: • Lead levels and isotope ratios in atmospheric particles, street dust and surface soil. • Significant enrichment of lead in atmospheric particles was observed. • Street dust and atmospheric particles have similar lead sources. • Endmembers of soil lead differ from street dust and atmospheric particles. • Airborne lead poses the main risks to unban environmental quality. - Transfer of airborne particle bound lead into street dust and surface soil in unban environmental based on lead levels and isotopic compositions

  17. Metamorphic zircon from Xindian eclogite, Dabie Terrain: U-Pb age and oxygen isotope composition

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Detailed CL image, U-Pb age and oxygen isotope composition in situ analyses for two metamorphic zircons from ultra-high pressure Xindian eclogite, Southern Dabie Terrain were carried out. There are two kinds of zircon in eclogite. The major subpopulation is podgy and isometric, and interpreted as protolith magmatic zircon with partial recrystallization. Its formation age is 811±22 Ma.The less abundant one is euhedral prismatic with core-rim structure and the rim being metamorphic overgrowth and formed at 221 -217 Ma. Zircon CL image strength is mainly controlled by U and Th contents. The magmatic zircon has its Th/U ratio around 1.3 and decreasing with recrystallization,whereas metamorphic zircon has Th/U ratio of lower than 0.1. Magmatic and metamorphic zircon domains all show very low oxygen isotopic compositions with average δ8O values of 1.8‰ and 2.8‰,respectively. The low δ18O values in protolith zircon indicated meteoric water involvement in their magma source region. It may correlate with snowball earth event during Neoproterozoic. It also indicates that protolith zircon could survive its oxygen isotope signature during Dabie eclogite facies UHP metamorphism.

  18. Continental paleothermometry and seasonality using the isotopic composition of aragonitic otoliths of freshwater fishes

    Science.gov (United States)

    Patterson, William P.; Smith, Gerald R.; Lohmann, Kyger C.

    To investigate the applicability of oxygen isotope themometry using fish aragonite, the δ18O values of paired otolith and water samples were analyzed from six large modem temperate lakes. Otoliths are accretionaiy aragonitic structures which are precipitated within the sacculus of fish ears. Deep-water obligate benthic species from the hypolimnion of the Laurentian Great Lakes of North America and Lake Baikal, Siberia, provided cold-water end member values for aragonite δ18O. Warm-water values were obtained from naturally grown warm-water stenothermic species and from fish grown in aquaria under controlled conditions. These two groups, which represent growth over a temperature range of 3.2-30.3°C. were employed to determine the oxygen isotope temperature fractionation relationship for aragonite-water: 103lnα = 18.56 (±0.319)·(103)T-1 K -33.49 (±0.307). Empirical calibration of a fish aragonite thennometry equation allows its direct application to studies of paleoclimate. For example, high-resolution sampling of shallow-water eurythermic species coupled with a knowledge of the isotopic composition of meteoric waters can be used to determine seasonal temperature variation. This approach was tested using a modem shallow-water eurythermic species from Sandusky Bay, Lake Erie. Temperatures calculated from carbonate composition agree with meteorological records from the Sandusky Bay weather station for the same time period.

  19. The growth environments of sloan diamonds: inferences based on their carbon isotope composition

    International Nuclear Information System (INIS)

    Carbon isotope compositions have been determined from the Sloan diatremes of the Colorado-Wyoming State Line kimberlite district (North America). The diamonds were previously broken for a study of their mineral inclusions. Based on mineral inclusion composition, the Sloan diamonds are divided into the broad peridotitic and eclogitic categories found for diamonds worldwide. Group I is comprised entirely of peridotitic diamonds whereas most of the diamonds in Group II and Group III are of eclogitic affinity. Differences in diamond morphology and mass are found between the three groups. Significant variation in δ13C was documented within single diamonds. Carbon isotope modelling of the Sloan diamond data suggests that the ranges in δ13C found for Group I and Group II diamonds at Sloan could have been produced from relatively homogeneous carbon reservoirs undergoing Rayleigh fractionation. The Group III diamonds were probably not produced from a single, isotopically homogeneous carbon reservoir. It is possible that the wide range of δ13C values for Group III diamonds was formed from an initially inhomogeneous (primordial or recycled) carbon source. Alternatively, the Group III diamonds may have crystallized from a less inhomogeneous, 13C-depleted fraction remaining after crystallization of Group I and Group II diamonds. The latter posibility suggests that the full range of δ13C values found for Sloan diamonds could have been produced in stages from an initially homogeneous carbon source. 2 figs., 3 refs

  20. Soybean seed phenol, lignin, and isoflavones and sugars composition are altered by Foliar Boron application in soybean under water stress

    Science.gov (United States)

    Previous research showed that foliar boron (B) fertilizer at flowering or seed-fill growth stages altered seed protein, oil, and fatty acids. The objective of this research was to investigate the effects of foliar B fertilizer on seed phenolics (phenol, lignin, and isoflavones) and sugars concentrat...