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Sample records for selenium hydride trapping

  1. Electrochemical selenium hydride generation with in situ trapping in graphite tube atomizers

    NASA Astrophysics Data System (ADS)

    Šíma, Jan; Rychlovský, Petr

    2003-05-01

    A manifold coupling continuous electrolytic hydride generation of volatile hydrides with atomization in graphite tube atomizers after in situ collection was used for Se(IV) determination. Laboratory-made thin-layer flow-through cells with lead wire (cell I) and granular lead (cell II) as the cathode material were used as the electrolytic generators of volatile selenium hydride. The automatic sampling equipment of the graphite atomizer, with an untreated fused silica capillary, was used both for the introduction of volatile hydride into the atomizer and for pretreatment of the graphite furnace surface with a palladium modifier. The influence of the experimental parameters on the analytical signal was studied and optimum conditions for selenium determination were found. The optimum experimental parameters for hydride generation were: catholyte (1 mol l -1 HCl)/anolyte (2 mol l -1 H 2SO 4) flow rate of 2.0 ml min -1; applied generation current of 1.2 A (cell I) and 0.8 A (cell II); and carrier gas flow rate of 40 (cell I) and 70 ml min -1 (cell II). The hydride generated was collected in the graphite tube (pre-treated with 5 μg of Pd reduced at 800 °C) at a temperature of 400 °C for 30 s. The overall efficiency of H 2Se electrochemical generation, transport and collection was 71±7% for cell I and 80±5% for cell II. The results for electrochemical generation of H 2Se (cell II) (absolute limit of detection 50 pg, 3σ criterion) were compared with the original generation of H 2Se using NaBH 4 as a reduction agent (absolute limit of detection 30 pg) and with conventional liquid sampling. The repeatability at the 1.0 ng ml -1 level was better than 2.4% (relative standard deviation) for electrochemical hydride generation and better than 2.8% for chemical hydride generation.

  2. Trapping of hydride forming elements within miniature electrothermal devices. Part 2. Investigation of collection of arsenic and selenium hydrides on a surface and in a cavity of a graphite rod

    NASA Astrophysics Data System (ADS)

    Dočekal, Bohumil

    2004-04-01

    The interaction of arsenic and selenium hydrides with bare and modified graphite was investigated by atomic absorption spectrometry and by radiotracer technique using 75Se radionuclide in a laboratory made brass cylindrical chamber equipped with a vertical quartz tube torch for supporting miniature hydrogen diffusion flame atomizer. Strong interaction was observed at elevated temperatures above 800 °C. In contrast to the very often-reported data for conventional graphite tube atomizers, this high temperature interaction was also accompanied by a pronounced trapping of analytes at elevated temperatures close to 1100-1200 °C when modified graphite was used. Comparing modifiers tested (Ir, Pt and Rh), iridium appeared the only useful permanent modifier. Among various graphite-rod traps designed, the most efficient trapping of analytes was achieved in a graphite cavity. The net selenium trapping efficiencies of approximately 53% and 70% were found by radiotracer technique for the iridium-treated graphite surface and the iridium-treated graphite cavity, respectively. In contrast to the molybdenum surface, bare graphite did not exhibit any significant trapping effect. Trapping isotherms obtained at different temperatures displayed non-linear course in the range up to the upper limit of the analytical relevance of 100 ng of an analyte, indicating a limited trapping capacity of the modified graphite surface and the same trapping mechanism at low and elevated temperatures applied (300-1300 °C). Radiography experiments with 75Se radiotracer showed that a major part of selenium was collected within the small cavity of the graphite rod and that selenium was also deposited after the trapping and vaporization steps in the trap chamber and on the quartz tube wall of the burner. Complementary experiments performed with the conventional transversally heated graphite tube and with bare and thermally shielded injection capillaries for hydride introduction, showed that the

  3. Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides

    NASA Astrophysics Data System (ADS)

    Zhang, Shoutao; Wang, Yanchao; Zhang, Jurong; Liu, Hanyu; Zhong, Xin; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2015-10-01

    Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and opens up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicated by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40-110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification.

  4. Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides

    PubMed Central

    Zhang, Shoutao; Wang, Yanchao; Zhang, Jurong; Liu, Hanyu; Zhong, Xin; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2015-01-01

    Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and opens up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicated by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40–110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification. PMID:26490223

  5. Phase Diagram and High-Temperature Superconductivity of Compressed Selenium Hydrides.

    PubMed

    Zhang, Shoutao; Wang, Yanchao; Zhang, Jurong; Liu, Hanyu; Zhong, Xin; Song, Hai-Feng; Yang, Guochun; Zhang, Lijun; Ma, Yanming

    2015-01-01

    Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and opens up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicated by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40-110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification. PMID:26490223

  6. Determination of arsenic and selenium in environmental and agricultural samples by hydride generation atomic absorption spectrometry

    SciTech Connect

    Hershey, J.W.; Oostdyk, T.S.; Keliher, P.N.

    1988-11-01

    Agricultural and environmental samples are digested with acid, and arsenic and selenium are determined using hydride generation atomic absorption spectrometry. Interelement interferences are eliminated by high acid concentrations or cation-exchange resins. Agreement with standard reference material is excellent. The technique is also applied to actual samples.

  7. Automated determinations of selenium in thermal power plant wastewater by sequential hydride generation and chemiluminescence detection.

    PubMed

    Ezoe, Kentaro; Ohyama, Seiichi; Hashem, Md Abul; Ohira, Shin-Ichi; Toda, Kei

    2016-02-01

    After the Fukushima disaster, power generation from nuclear power plants in Japan was completely stopped and old coal-based power plants were re-commissioned to compensate for the decrease in power generation capacity. Although coal is a relatively inexpensive fuel for power generation, it contains high levels (mgkg(-1)) of selenium, which could contaminate the wastewater from thermal power plants. In this work, an automated selenium monitoring system was developed based on sequential hydride generation and chemiluminescence detection. This method could be applied to control of wastewater contamination. In this method, selenium is vaporized as H2Se, which reacts with ozone to produce chemiluminescence. However, interference from arsenic is of concern because the ozone-induced chemiluminescence intensity of H2Se is much lower than that of AsH3. This problem was successfully addressed by vaporizing arsenic and selenium individually in a sequential procedure using a syringe pump equipped with an eight-port selection valve and hot and cold reactors. Oxidative decomposition of organoselenium compounds and pre-reduction of the selenium were performed in the hot reactor, and vapor generation of arsenic and selenium were performed separately in the cold reactor. Sample transfers between the reactors were carried out by a pneumatic air operation by switching with three-way solenoid valves. The detection limit for selenium was 0.008 mg L(-1) and calibration curve was linear up to 1.0 mg L(-1), which provided suitable performance for controlling selenium in wastewater to around the allowable limit (0.1 mg L(-1)). This system consumes few chemicals and is stable for more than a month without any maintenance. Wastewater samples from thermal power plants were collected, and data obtained by the proposed method were compared with those from batchwise water treatment followed by hydride generation-atomic fluorescence spectrometry.

  8. Automated determinations of selenium in thermal power plant wastewater by sequential hydride generation and chemiluminescence detection.

    PubMed

    Ezoe, Kentaro; Ohyama, Seiichi; Hashem, Md Abul; Ohira, Shin-Ichi; Toda, Kei

    2016-02-01

    After the Fukushima disaster, power generation from nuclear power plants in Japan was completely stopped and old coal-based power plants were re-commissioned to compensate for the decrease in power generation capacity. Although coal is a relatively inexpensive fuel for power generation, it contains high levels (mgkg(-1)) of selenium, which could contaminate the wastewater from thermal power plants. In this work, an automated selenium monitoring system was developed based on sequential hydride generation and chemiluminescence detection. This method could be applied to control of wastewater contamination. In this method, selenium is vaporized as H2Se, which reacts with ozone to produce chemiluminescence. However, interference from arsenic is of concern because the ozone-induced chemiluminescence intensity of H2Se is much lower than that of AsH3. This problem was successfully addressed by vaporizing arsenic and selenium individually in a sequential procedure using a syringe pump equipped with an eight-port selection valve and hot and cold reactors. Oxidative decomposition of organoselenium compounds and pre-reduction of the selenium were performed in the hot reactor, and vapor generation of arsenic and selenium were performed separately in the cold reactor. Sample transfers between the reactors were carried out by a pneumatic air operation by switching with three-way solenoid valves. The detection limit for selenium was 0.008 mg L(-1) and calibration curve was linear up to 1.0 mg L(-1), which provided suitable performance for controlling selenium in wastewater to around the allowable limit (0.1 mg L(-1)). This system consumes few chemicals and is stable for more than a month without any maintenance. Wastewater samples from thermal power plants were collected, and data obtained by the proposed method were compared with those from batchwise water treatment followed by hydride generation-atomic fluorescence spectrometry. PMID:26653491

  9. Determination of selenium in meat products by hydride generation atomic absorption spectrophotometry.

    PubMed

    Tinggi, U

    1999-01-01

    Wet digestion using a mixture of nitric, sulfuric, and perchloric acids and an aluminum block digester effectively and rapidly decomposed meat samples for selenium determination by hydride generation atomic absorption spectrophotometry. Digestion did not require constant attention by an operator. Selenium recoveries (range, 94-105%) from National Institute of Standards and Technology standard reference materials and spiked samples were used to validate method accuracy. Coefficients of variation (CVs) of repeatability of in-house reference materials used for precision study were 6.4 and 5.6%, respectively, for seafood mix and mutton liver. Selenium levels in meat products from Brisbane markets varied widely: 0.042-0.142, 0.081-0.42, and 0.050-0.198 microgram/g (wet weight) respectively, for beef, chicken, and pork. Overall, selenium levels in manufactured meat ranged from 0.041 to 0.189 microgram/g. The levels of selenium found in this study were generally lower than those reported in Finland but comparable with those reported in some parts of the United States.

  10. Dielectric barrier discharge plasma atomizer for hydride generation atomic absorption spectrometry-Performance evaluation for selenium

    NASA Astrophysics Data System (ADS)

    Duben, Ondřej; Boušek, Jaroslav; Dědina, Jiří; Kratzer, Jan

    2015-09-01

    Atomization of selenium hydride in a quartz dielectric barrier discharge (DBD) atomizer was optimized and its performance was compared to that of the externally heated quartz multiatomizer. Argon was found as the best DBD discharge gas employing a flow rate of 75 ml min- 1 Ar while the DBD power was optimized at 14 W. The detection limits reached 0.24 ng ml- 1 Se in the DBD and 0.15 ng ml- 1 Se in the multiatomizer. The tolerance of DBD to interferences is even better than with the multiatomizer.

  11. Speciation of arsenic(III)/arsenic(V) and selenium(IV)/ selenium(VI) using coupled ion chromatography - hydride generation atomic absorption spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Simple analytical methods have been developed to speciate inorganic arsenic and selenium in the ppb range using coupled ion chromatography-hydride generation atomic absorption spectrometry. Because of the differences in toxicity and adsorption behavior, determinations of the redox states arsenite A...

  12. In situ trapping of As, Sb and Se hydrides on nanometer-sized ceria-coated iron oxide-silica and slurry suspension introduction to ICP-OES.

    PubMed

    Dados, A; Kartsiouli, E; Chatzimitakos, Th; Papastephanou, C; Stalikas, C D

    2014-12-01

    A procedure is developed for the analysis of sub-μg L(-1) levels of arsenic, antimony and selenium after preconcentration of their hydrides. The study highlights the capability of an aqueous suspension of a nanometer-sized magnetic ceria, in the presence of iodide, to function as a sorbent for the in situ trapping and preconcentration of the hydrides of certain metalloids. After extraction, the material is magnetically separated from the trapping solution and analyzed. A slurry suspension sampling approach with inductively coupled plasma-optical emission spectrometry (ICP-OES) is employed for measurements, as the quantitative elution of the adsorbed metalloids is not feasible. The whole analytical procedure consists of five steps: (i) pre-reduction of As, Sb and Se, (ii) generation of the hydrides AsH3, SbH3 and SeH2, (iii) in situ collection in the trapping suspension of magnetic ceria, (iv) isolation of the particles by applying a magnetic field, and (v) measurement of As, Sb and Se concentrations using ICP-OES. Under the established experimental conditions, the efficiency of trapping accounted for 94 ± 2%, 89 ± 2% and 98 ± 3% for As, Sb and Se, respectively, signifying the effective implementation of the overall procedure. The applicability of the procedure has been demonstrated by analyzing tap and lake water and a reference material (soft drinking water). The obtained analytical figures of merit were satisfactory for the analysis of the above metalloids in natural waters by ICP-OES.

  13. An automated microtechnique for selenium determination in human body fluids by flow injection hydride atomic absorption spectrometry (FI-HAAS).

    PubMed

    Negretti de Brätter, V E; Brätter, P; Tomiak, A

    1990-03-01

    The automation of a flow injection system for the hydride generation of selenium and its subsequent determination by atomic absorption spectrometry (FI-HAAS) is described. Pre-treatment of the sample and the details of the automated equipment are reviewed. For the FI-HAAS selenium analysis a volume of 350 microL of acid-digested sample solution is injected. The on-line generated hydride is delivery by the gas-liquid separator and is transported together with an Ar stream to the heated quartz cell for the atomic absorption determination. The absolute detection limit is 35 pg Se; the relative detection limit 0.10 micrograms/L Se. The absolute determination limit in real biological samples is 110 pg Se; the relative detection limit 0.31 micrograms/L Se. The accuracy of the method was evaluated via analysis of certified standard reference materials. Quality control was made by comparing FI-HAAS and instrumental neutron activation analysis (INAA), as an independent analytical method. Two acid-digestion procedures (in open vessels at atmospheric pressure and bomb-digestion in pressure vessels) were experimentally tested. To determine the effectiveness of the selenium reduction and the completeness of the selenium hydride formation a parallel selenium determination was carried out by means of ICP-AES and FI-HAAS analysis. FI-HAAS was applied for blood serum analysis of children undergoing long-term total parenteral nutrition, as well as of persons with high dietary selenium intake, and for human milk analysis. PMID:2135957

  14. SPECIATION OF SELENIUM AND ARSENIC COMPOUNDS BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW AND ON-LINE REDUCTION OF SELENIUM(VI) TO SELENIUM(IV) WITH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRIC DETECTION

    EPA Science Inventory

    Capillary electrophoresis (CE) with hydride generation inductively coupled plasma mass spectrometry was used to determine four arsenicals and two selenium species. Selenate (SeVI) was reduced on-line to selenite (SeIV') by mixing the CE effluent with concentrated HCl. A microporo...

  15. Determination of arsenic and selenium by hydride generation and headspace solid phase microextraction coupled with optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Tyburska, Anna; Jankowski, Krzysztof; Rodzik, Agnieszka

    2011-07-01

    A hydride generation headspace solid phase microextraction technique has been developed in combination with optical emission spectrometry for determination of total arsenic and selenium. Hydrides were generated in a 10 mL volume septum-sealed vial and subsequently collected onto a polydimethylsiloxane/Carboxen solid phase microextraction fiber from the headspace of sample solution. After completion of the sorption, the fiber was transferred into a thermal desorption unit and the analytes were vaporized and directly introduced into argon inductively coupled plasma or helium microwave induced plasma radiation source. Experimental conditions of hydride formation reaction as well as sorption and desorption of analytes have been optimized showing the significant effect of the type of the solid phase microextraction fiber coating, the sorption time and hydrochloric acid concentration of the sample solution on analytical characteristics of the method developed. The limits of detection of arsenic and selenium were 0.1 and 0.8 ng mL - 1 , respectively. The limit of detection of selenium could be improved further using biosorption with baker's yeast Saccharomyces cerevisiae for analyte preconcentration. The technique was applied for the determination of total As and Se in real samples.

  16. Flow injection determination of selenium by successive retention of Se(IV) and tetrahydroborate(III) on an anion-exchange resin and hydride generation electrothermal atomization atomic absorption spectrometry with in-atomizer trapping. Part 1. Method development and investigation of interferences

    NASA Astrophysics Data System (ADS)

    Carrero, Pablo E.; Tyson, Julian F.

    1998-12-01

    A sample solution was passed at 20 ml min -1 through a column (150×4 mm 2) of Amberlite IRA-410Stron anion-exchange resin for 60 s. After washing, a solution of 0.1% sodium borohydride was passed through the column for 60 s at 5.1 ml min -1. Following a second wash, a solution of 8 mol l -1 hydrochloric acid was passed at 5.1 ml min -1 for 45 s. The hydrogen selenide was stripped from the eluent solution by the addition of an argon flow at 150 ml min -1 and the bulk phases were separated by a glass gas-liquid separator containing glass beads. The gas stream was dried by passing through a Nafion® dryer and fed, via a quartz capillary tube, into the dosing hole of a transversely heated graphite cuvette containing an integrated L'vov platform which had been pretreated with 120 μg of iridium as trapping agent. The furnace was held at a temperature of 250°C during this trapping stage and then stepped to 2000°C for atomization. The calibration was performed with aqueous standards solution of selenium (selenite, SeO 32-) with quantification by peak area. A number of experimental parameters, including reagent flow rates and composition., nature of the gas-liquid separator, nature of the anion-exchange resin, column dimensions, argon flow rate and sample pH, were optimized. The effects of a number of possible interferents, both anionic and cationic were studies for a solution of 500 ng 1 -1 of selenium. The most severe depressions were caused by iron (III) and mercury (II) for which concentrations of 20 and 10 mg 1 -1 caused a 5% depression on the selenium signal. For the other cations (cadmium, cobalt, copper, lead,. magnesium, and nickel) concentrations of 50-70 mg 1 -1 could be tolerated. Arsenate interfered at a concentration of 3 mg -1, whereas concentrations of chloride, bromide, iodide, perchlorate, and sulfate of 500-900 mg l -1 could be tolerated. A linear response was obtained between the detection limit of 4 ng 1 -1, with a characteristic mass of 130 pg. The

  17. Atomic-absorption spectrochemical analysis for ultratrace elements in geological materials by hydride-forming techniques: Selenium.

    PubMed

    Sighinolfi, G P; Gorgoni, C

    1981-03-01

    A method based on hydride generation for the AAS determination of selenium at nanogram levels in geological materials is described. The sample is decomposed by aqua regia attack in a sealed Teflon bomb. After treatment with hydrochloric acid, selenium is converted into hydrogen selenide by reaction with sodium borohydride and determined by AAS. Matrix interference effects have been investigated, but though they are rarely significant, the standard-additions method is recommended. The absolute sensitivity of the method is about 2.0 ng of Se (in 10 ml of solution). Detection limits of about 5-10 ng in a 1.0-g sample have been achieved with the use of "Suprapure" reagents. The selenium content of some USGS, CRPG and ANRT reference samples is reported. PMID:18962885

  18. Atomic-absorption spectrochemical analysis for ultratrace elements in geological materials by hydride-forming techniques: Selenium.

    PubMed

    Sighinolfi, G P; Gorgoni, C

    1981-03-01

    A method based on hydride generation for the AAS determination of selenium at nanogram levels in geological materials is described. The sample is decomposed by aqua regia attack in a sealed Teflon bomb. After treatment with hydrochloric acid, selenium is converted into hydrogen selenide by reaction with sodium borohydride and determined by AAS. Matrix interference effects have been investigated, but though they are rarely significant, the standard-additions method is recommended. The absolute sensitivity of the method is about 2.0 ng of Se (in 10 ml of solution). Detection limits of about 5-10 ng in a 1.0-g sample have been achieved with the use of "Suprapure" reagents. The selenium content of some USGS, CRPG and ANRT reference samples is reported.

  19. Determination of trace selenium in high purity tellurium by hydride generation atomic fluorescence spectrometry after solid phase extraction of a diaminobenzidine-selenium chelate

    NASA Astrophysics Data System (ADS)

    Tong, Wang; Ying, Zeng; Jinyong, Xu

    2016-09-01

    Macroporous adsorption resin was used as the sorbent for solid phase extraction and determination of the trace Se content in high purity tellurium prior to hydride generation atomic fluorescence spectrometry analysis. Selenium was converted into an organic Se chelate using 3,3‧-diaminobenzidine and was separated from the tellurium matrix by solid phase extraction. The resin was packed as a column for solid phase extraction. Under optimum conditions, trace Se can be quantitatively extracted and the tellurium matrix can be removed. The Se in the eluate was determined by hydride generation atomic fluorescence spectrometry. The limit of detection (3σ) of this method was 0.22 ng g- 1 and the relative standard deviation (RSD, n = 5) ranged from 2.0 to 2.5% for the three investigated tellurium samples. The proposed method was successfully applied for the determination of the trace Se content in high purity tellurium samples.

  20. Determination and interference studies of bismuth by tungsten trap hydride generation atomic absorption spectrometry.

    PubMed

    Kula, Ibrahim; Arslan, Yasin; Bakirdere, Sezgin; Titretir, Serap; Kendüzler, Erdal; Ataman, O Yavuz

    2009-11-15

    The determination of bismuth requires sufficiently sensitive procedures for detection at the microg L(-1) level or lower. W-coil was used for on-line trapping of volatile bismuth species using HGAAS (hydride generation atomic absorption spectrometry); atom trapping using a W-coil consists of three steps. Initially BiH(3) gas is formed by hydride generation procedure. The analyte species in vapor form are transported through the W-coil trap held at 289 degrees C where trapping takes place. Following the preconcentration step, the W-coil is heated to 1348 degrees C; analyte species are released and transported to flame-heated quartz atom cell where the atomic signal is formed. In our study, interferences have been investigated in detail during Bi determination by hydride generation, both with and without trap in the same HGAAS system. Interferent/analyte (mass/mass) ratio was kept at 1, 10 and 100. Experiments were designed for carrier solutions having 1.0M HNO(3). Interferents such as Fe, Mn, Zn, Ni, Cu, As, Se, Cd, Pb, Au, Na, Mg, Ca, chloride, sulfate and phosphate were examined. The calibration plot for an 8.0 mL sampling volume was linear between 0.10 microg L(-1) and 10.0 microg L(-1) of Bi. The detection limit (3s/m) was 25 ng L(-1). The enhancement factor for the characteristic concentration (C(o)) was found to be 21 when compared with the regular system without trap, by using peak height values. The validation of the procedure was performed by the analysis of the certified water reference material and the result was found to be in good agreement with the certified values at the 95% confidence level.

  1. Development of a MSFIA system for sequential determination of antimony, arsenic and selenium using hydride generation atomic fluorescence spectrometry.

    PubMed

    de Santana, Fernanda A; Portugal, Lindomar A; Serra, Antonio M; Ferrer, Laura; Cerdà, Víctor; Ferreira, Sergio L C

    2016-08-15

    This paper proposed a multisyringe flow injection analysis (MSFIA) system for antimony, arsenic and selenium determination in peanut samples by hydride generation atomic fluorescence spectrometry (HG-AFS). The optimization step of the hydride generation was performed using a two-level full factorial design involving the parameters: hydrochloric acid, sodium tetrahydroborate and potassium iodide concentrations. So, using the chemical conditions optimized, this method allows the determination of these elements employing the external calibration technique using aqueous standards with limits of detection and quantification of 0.04 and 0.14µgL(-1) for antimony, 0.04 and 0.14µgL(-1) for arsenic and 0.14 and 0.37µgL(-1) for selenium, respectively. Additionally, the effect of vanadium, chromium, cobalt, nickel, zinc, copper, iron and molybdenum on the generation of chemical vapour was also studied. The precision expressed as relative standard deviation varied from 1.2 to 3.6% for antimony, 1.8-3.9% for arsenic and 1.8-2% for selenium. The accuracy for arsenic and selenium was confirmed using the certified peach leaves reference material SRM 1547 produced by National Institute of Standard and Technology. The proposed method showed 45 injection throughput (h(-1)) using 1.6mL sample volume for each element, 0.8mL NaBH4 0.5% (w/v) containing NaOH 0.05% (w/v), 0.8mL HCl 5M and 0.4mL KI 14% (w/v) containing L-ascorbic acid 2.5% (w/v). The method was applied to the determination of antimony, arsenic and selenium in peanut samples, which were firstly lyophilized and afterward digested using microwave assisted radiation. Six samples were analyzed and the contents of the elements found were: 28.7-41.3µgkg(-1) for arsenic, 86.4-480.1µgkg(-1) for selenium and 32.6-52.4µgkg(-1) for antimony. Addition/recovery tests were also performed to confirm the method accuracy for the three elements.

  2. Development of a MSFIA system for sequential determination of antimony, arsenic and selenium using hydride generation atomic fluorescence spectrometry.

    PubMed

    de Santana, Fernanda A; Portugal, Lindomar A; Serra, Antonio M; Ferrer, Laura; Cerdà, Víctor; Ferreira, Sergio L C

    2016-08-15

    This paper proposed a multisyringe flow injection analysis (MSFIA) system for antimony, arsenic and selenium determination in peanut samples by hydride generation atomic fluorescence spectrometry (HG-AFS). The optimization step of the hydride generation was performed using a two-level full factorial design involving the parameters: hydrochloric acid, sodium tetrahydroborate and potassium iodide concentrations. So, using the chemical conditions optimized, this method allows the determination of these elements employing the external calibration technique using aqueous standards with limits of detection and quantification of 0.04 and 0.14µgL(-1) for antimony, 0.04 and 0.14µgL(-1) for arsenic and 0.14 and 0.37µgL(-1) for selenium, respectively. Additionally, the effect of vanadium, chromium, cobalt, nickel, zinc, copper, iron and molybdenum on the generation of chemical vapour was also studied. The precision expressed as relative standard deviation varied from 1.2 to 3.6% for antimony, 1.8-3.9% for arsenic and 1.8-2% for selenium. The accuracy for arsenic and selenium was confirmed using the certified peach leaves reference material SRM 1547 produced by National Institute of Standard and Technology. The proposed method showed 45 injection throughput (h(-1)) using 1.6mL sample volume for each element, 0.8mL NaBH4 0.5% (w/v) containing NaOH 0.05% (w/v), 0.8mL HCl 5M and 0.4mL KI 14% (w/v) containing L-ascorbic acid 2.5% (w/v). The method was applied to the determination of antimony, arsenic and selenium in peanut samples, which were firstly lyophilized and afterward digested using microwave assisted radiation. Six samples were analyzed and the contents of the elements found were: 28.7-41.3µgkg(-1) for arsenic, 86.4-480.1µgkg(-1) for selenium and 32.6-52.4µgkg(-1) for antimony. Addition/recovery tests were also performed to confirm the method accuracy for the three elements. PMID:27260431

  3. On-line pre-reduction of Se(VI) by thiourea for selenium speciation by hydride generation

    NASA Astrophysics Data System (ADS)

    Qiu, Jianhua; Wang, Qiuquan; Ma, Yuning; Yang, Limin; Huang, Benli

    2006-07-01

    In this study, thiourea (TU) was novelly developed as a reduction reagent for on-line pre-reduction of selenium(VI) before conventional hydride generation (HG) by KBH 4/NaOH-HCl. After TU on-line pre-reduction, the HG efficiency of Se(VI) has been greatly improved and because even higher than that of the same amount of Se(IV) obtained in the conventional HG system. The possible pre-reduction mechanism is discussed. The detection limit (DL) of selenate reaches 10 pg mL - 1 when using on-line TU pre-reduction followed by HG atomic fluorescence detection. When TU pre-reduction followed by HG is used as an interface between ion-pair high performance liquid chromatography and atomic fluorescence spectrometry, selenocystine, selenomethionine, selenite and selenate can be measured simultaneously and quantitatively. The DLs of these are 0.06, 0.08, 0.05 and 0.04 ng mL - 1 , respectively, and the relative standard deviations of 9 duplicate runs for all the 4 species are less than 5%. Furthermore, it was successfully applied to Se speciation analysis of cultured garlic samples, and validated by determination of total selenium and selenium species in certified reference material NIST 1946.

  4. Determination of tellurium by hydride generation with in situ trapping flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Matusiewicz, Henryk; Krawczyk, Magdalena

    2007-03-01

    The analytical performance of coupled hydride generation — integrated atom trap (HG-IAT) atomizer flame atomic absorption spectrometry (FAAS) system was evaluated for determination of Te in reference material (GBW 07302 Stream Sediment), coal fly ash and garlic. Tellurium, using formation of H 2Te vapors, is atomized in air-acetylene flame-heated IAT. A new design HG-IAT-FAAS hyphenated technique that would exceed the operational capabilities of existing arrangements (a water-cooled single silica tube, double-slotted quartz tube or an "integrated trap") was investigated. An improvement in detection limit was achieved compared with using either of the above atom trapping techniques separately. The concentration detection limit, defined as 3 times the blank standard deviation (3 σ), was 0.9 ng mL - 1 for Te. For a 2 min in situ pre-concentration time (sample volume of 2 mL), sensitivity enhancement compared to flame AAS, was 222 fold, using the hydride generation — atom trapping technique. The sensitivity can be further improved by increasing the collection time. The precision, expressed as RSD, was 7.0% ( n = 6) for Te. The designs studied include slotted tube, single silica tube and integrated atom trap-cooled atom traps. The accuracy of the method was verified using a certified reference material (GBW 07302 Stream Sediment) by aqueous standard calibration curves. The measured Te contents of the reference material was in agreement with the information value. The method was successfully applied to the determination of tellurium in coal fly ash and garlic.

  5. Hydride vapor phase GaN films with reduced density of residual electrons and deep traps

    SciTech Connect

    Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Yugova, T. G.; Cox, H.; Helava, H.; Makarov, Yu.; Usikov, A. S.

    2014-05-14

    Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ∼10{sup 17} cm{sup −3} to (2–5) × 10{sup 14} cm{sup −3}. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ∼5 × 10{sup 13} cm{sup −3} versus 2.9 × 10{sup 16} cm{sup −3} in the standard samples, with a similar decrease in the electron traps concentration.

  6. Simple decomposition procedure for determination of selenium in whole blood, serum and urine by hydride generation atomic absorption spectroscopy.

    PubMed

    Tiran, B; Tiran, A; Rossipal, E; Lorenz, O

    1993-12-01

    A digestion procedure for selenium determination by hydride generation atomic absorption spectroscopy (AAS) in whole blood, serum and urine is described, it employs sulfuric acid, hydrogen peroxide and vanadium (V) sulfuric acid reagent solution. The method is rapid, uses no explosive reagents and can be performed at a constant temperature of 100 degrees C. Therefore, it is easily applicable in a routine clinical laboratory for a large amount of samples. The coefficient of intra-assay variation was 4.3-5.6%, the coefficient for inter-assay variation was 5-5.9% in the medium and high concentration range, and 5.8-8.6% in the low range. In analyzing several commercial reference materials our results showed good agreement with the target values. Analytical recovery by addition of sodium selenite and seleno-DL-methionine to samples ranged between 97 and 104%. The correlation between the described digestion procedure and the nitric, sulfuric and perchloric acid digestion procedure recommended by the International Union of Pure and Applied Chemistry showed good agreement for whole blood, serum and for urine. We determined selenium in serum (n = 58) and whole blood (n = 50) in a collective of healthy children from 1 to 5 years living in Styria, Austria. The low values in serum (35 +/- 11 micrograms/L) and whole blood (42 +/- 6 micrograms/L) at one year of life increased significantly to 48 +/- 13 mu/L (p = 0.033) and 55 +/- 6 micrograms/L (p = 0.004) at three years of life in serum and whole blood, respectively. The selenium concentration showed no further increase up to five years of age.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. SYSTEM OPTIMIZATION FOR THE AUTOMATIC SIMULTANEOUS DETERMINATION OF ARSENIC, SELENIUM, AND ANTIMONY, USING HYDRIDE GENERATION INTRODUCTION TO AN INDUCTIVELY COUPLED PLASMA.

    USGS Publications Warehouse

    Pyen, Grace S.; Browner, Richard F.; Long, Stephen

    1986-01-01

    A fixed-size simplex has been used to determine the optimum conditions for the simultaneous determination of arsenic, selenium, and antimony by hydride generation and inductively coupled plasma emission spectrometry. The variables selected for the simplex were carrier gas flow rate, rf power, viewing height, and reagent conditions. The detection limit for selenium was comparable to the preoptimized case, but there were twofold and fourfold improvements in the detection limits for arsenic and antimony, respectively. Precision of the technique was assessed with the use of artificially prepared water samples.

  8. Hydride Generation for Headspace Solid-Phase Extraction with CdTe Quantum Dots Immobilized on Paper for Sensitive Visual Detection of Selenium.

    PubMed

    Huang, Ke; Xu, Kailai; Zhu, Wei; Yang, Lu; Hou, Xiandeng; Zheng, Chengbin

    2016-01-01

    A low-cost, simple, and highly selective analytical method was developed for sensitive visual detection of selenium in human urine both outdoors and at home, by coupling hydride generation with headspace solid-phase extraction using quantum dots (QDs) immobilized on paper. The visible fluorescence from the CdTe QDs immobilized on paper was quenched by H2Se from hydride generation reaction and headspace solid-phase extraction. The potential mechanism was investigated by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) as well as Density Functional Theory (DFT). Potential interferences from coexisting ions, particularly Ag(+), Cu(2+), and Zn(2+), were eliminated. The selectivity was significantly increased because the selenium hydride was effectively separated from sample matrices by hydride generation. Moreover, due to the high sampling efficiency of hydride generation and headspace solid phase extraction, the sensitivity and the limit of detection (LOD) were significantly improved compared to conventional methods. A LOD of 0.1 μg L(-1) and a relative standard deviation (RSD, n = 7) of 2.4% at a concentration of 20 μg L(-1) were obtained when using a commercial spectrofluorometer as the detector. Furthermore, a visual assay based on the proposed method was developed for the detection of Se, 5 μg L(-1) of selenium in urine can be discriminated from the blank solution with the naked eye. The proposed method was validated by analysis of certified reference materials and human urine samples with satisfactory results. PMID:26631425

  9. Simultaneous quantitative analysis of arsenic, bismuth, selenium, and tellurium in soil samples using multi-channel hydride-generation atomic fluorescence spectrometry.

    PubMed

    Wang, Fang; Zhang, Gai

    2011-03-01

    The basic principles and the application of hydride-generation multi-channel atomic fluorescence spectrometry (HG-MC-AFS) in soil analysis are described. It is generally understood that only one or two elements can be simultaneously detected by commonly used one- or two-channel HG-AFS. In this work, a new sample-sensitive and effective method for the analysis of arsenic, bismuth, tellurium, and selenium in soil samples by simultaneous detection using HG-MC-AFS was developed. The method detection limits for arsenic, bismuth, tellurium, and selenium are 0.19 μg/g, 0.10 μg/g, 0.11 μg/g, and 0.08 μg/g, respectively. This method was successfully applied to the simultaneous determination of arsenic, bismuth, tellurium, and selenium in soil samples.

  10. Determination of selenium in nutritional supplements and shampoos by flow injection-hydride generation-atomic fluorescence spectrometry.

    PubMed

    Gámiz-Gracia, L; Luque de Castro, M D

    1999-11-15

    A method for the determination of Se in pharmaceutical samples (nutritional supplements and shampoos) is proposed. The method involves two steps: (1) digestion of the samples and reduction of all forms of Se to Se(IV), which is complete in only 10 min by the use of a focused microwave digestor; and (2) continuous derivatisation (hydride formation) and spectrometry detection by atomic fluorescence. The method can be applied over a wide range of concentrations (0.3-1300 ng ml(-1) of Se) with good repeatability (RSD values lower than 4.6%). The method has been applied successfully to a reference material, and two different types of pharmaceuticals (namely, five different nutritional supplements-with Se present as sodium selenite and Se-methionine-and two shampoos, with selenium sulphide), in agreements with the certified and nominal values, respectively. Yields ranged between 86.5 and 104.8%, and good precision (RSD values lower than 4.2%) were obtained in all instances.

  11. Determination of total selenium in pharmaceutical and herbal supplements by hydride generation and graphite furnace atomic absorption spectrometry.

    PubMed

    Kazi, Tasneem G; Kolachi, Nida F; Afridi, Hassan I; Brahman, Kapil Dev; Shah, Faheem

    2014-01-01

    The total selenium (Se) was determined in herbal and pharmaceutical supplements used for liver diseases. The total Se contents were determined in different pharmaceutical and herbal supplements by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after microwave-assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material and the standard addition method. The recoveries of total Se were 99.4 and 99.0% for HGAAS and GFAAS, respectively. The precision of the techniques expressed as RSD were 2.34 and 4.54% for HGAAS and GFAAS measurements, respectively. The LOD values for HGAAS and GFAAS were 0.025 and 0.052 pglg, respectively. The concentrations of Se in pharmaceutical and herbal supplements were found in the range of 19.2-53.8 and 25.0-42.5 pg/g, respectively, corresponding to 35-76% and 45-76% of the total recommended dose of Se for adults.

  12. Determination of total selenium in pharmaceutical and herbal supplements by hydride generation and graphite furnace atomic absorption spectrometry.

    PubMed

    Kazi, Tasneem G; Kolachi, Nida F; Afridi, Hassan I; Brahman, Kapil Dev; Shah, Faheem

    2014-01-01

    The total selenium (Se) was determined in herbal and pharmaceutical supplements used for liver diseases. The total Se contents were determined in different pharmaceutical and herbal supplements by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after microwave-assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material and the standard addition method. The recoveries of total Se were 99.4 and 99.0% for HGAAS and GFAAS, respectively. The precision of the techniques expressed as RSD were 2.34 and 4.54% for HGAAS and GFAAS measurements, respectively. The LOD values for HGAAS and GFAAS were 0.025 and 0.052 pglg, respectively. The concentrations of Se in pharmaceutical and herbal supplements were found in the range of 19.2-53.8 and 25.0-42.5 pg/g, respectively, corresponding to 35-76% and 45-76% of the total recommended dose of Se for adults. PMID:25632445

  13. Selenium

    MedlinePlus

    ... of the colon and rectum, prostate, lung, bladder, skin, esophagus, and stomach. But whether selenium supplements reduce ... can cause the following: Garlic breath Nausea Diarrhea Skin rashes Irritability Metallic taste in the mouth Brittle ...

  14. High-Precision Selenium Isotope Analysis by Hydride Generation MC-ICP-MS: Environmental Applications

    NASA Astrophysics Data System (ADS)

    Schmidberger, S.; Simonetti, A.; Gariépy, C.

    2003-04-01

    The global cycle and the natural isotopic variation of Se in the lithosphere, biosphere, hydrosphere and atmosphere are currently little constrained. The study of Se isotope systematics by negative thermal ionization mass spectrometry (NTIMS) has documented large Se isotope variations up to 15 ppm in various natural samples (δ80Se/76Se; Johnson et al., 1999), indicating its important potential as a tracer in geological and biological processes. Recently, Se isotope measurements on sulfide deposits from hydrothermal systems were obtained using a Micromass IsoProbe multicollector inductively coupled plasma mass spectrometer coupled to a hydride generator (Rouxel et al. 2002). This technique allows for high-precision Se isotope analysis on small sample sizes (<= 100 ng), and thus is a prerequisite for precise Se isotope measurements in low abundance samples such as precipitations, freshwaters and atmospheric aerosols (1 ppb or less). We have developed a 74-82Se double spike technique, which corrects for instrumental mass fractionation during both isotopic analysis and chemical processing. During double spike calibration, mass discrimination was monitored using a Germanium Specpuretextregistered standard (25 ppb). The isotopic composition of the Ge standard was accurately determined using a 10 ppb solution of the isotopic Gallium standard SRM 994. Repeated measurements (n=8) of the Ge standard yielded an external reproducibility of 0.13 ppm and a 74Ge/72Ge ratio of 1.32987. Instrumental mass bias evaluated with the Ge standard was essentially invariant over a three-month period. Our results yield an external reproducibility of 0.4 ppm (80Se/76Se) for a 100 ppb solution of the Se standard SRM 3149 (˜100 ng of total Se consumed). This ongoing study focuses on determining the Se isotopic compositions of precipitations and aerosol samples from remote and urban areas in northeastern North America. The preliminary results for precipitation samples (˜100 to 300 ml of rain

  15. On-line electrochemically controlled in-tube solid phase microextraction of inorganic selenium followed by hydride generation atomic absorption spectrometry.

    PubMed

    Asiabi, Hamid; Yamini, Yadollah; Seidi, Shahram; Shamsayei, Maryam; Safari, Meysam; Rezaei, Fatemeh

    2016-05-30

    In this work, for the first time, a rapid, simple and sensitive microextraction procedure is demonstrated for the matrix separation, preconcentration and determination of inorganic selenium species in water samples using an electrochemically controlled in-tube solid phase microextraction (EC-in-tube SPME) followed by hydride generation atomic absorption spectrometry (HG-AAS). In this approach, in which EC-in-tube SPME and HG-AAS system were combined, the total analysis time, was decreased and the accuracy, repeatability and sensitivity were increased. In addition, to increases extraction efficiency, a novel nanostructured composite coating consisting of polypyrrole (PPy) doped with ethyleneglycol dimethacrylate (EGDMA) was prepared on the inner surface of a stainless-steel tube by a facile electrodeposition method. To evaluate the offered setup and the new PPy-EGDMA coating, it was used to extract inorganic selenium species in water samples. Extraction of inorganic selenium species was carried out by applying a positive potential through the inner surface of coated in-tube under flow conditions. Under the optimized conditions, selenium was detected in amounts as small as 4.0 parts per trillion. The method showed good linearity in the range of 0.012-200 ng mL(-1), with coefficients of determination better than 0.9996. The intra- and inter-assay precisions (RSD%, n = 5) were in the range of 2.0-2.5% and 2.7-3.2%, respectively. The validated method was successfully applied for the analysis of inorganic selenium species in some water samples and satisfactory results were obtained.

  16. On-line electrochemically controlled in-tube solid phase microextraction of inorganic selenium followed by hydride generation atomic absorption spectrometry.

    PubMed

    Asiabi, Hamid; Yamini, Yadollah; Seidi, Shahram; Shamsayei, Maryam; Safari, Meysam; Rezaei, Fatemeh

    2016-05-30

    In this work, for the first time, a rapid, simple and sensitive microextraction procedure is demonstrated for the matrix separation, preconcentration and determination of inorganic selenium species in water samples using an electrochemically controlled in-tube solid phase microextraction (EC-in-tube SPME) followed by hydride generation atomic absorption spectrometry (HG-AAS). In this approach, in which EC-in-tube SPME and HG-AAS system were combined, the total analysis time, was decreased and the accuracy, repeatability and sensitivity were increased. In addition, to increases extraction efficiency, a novel nanostructured composite coating consisting of polypyrrole (PPy) doped with ethyleneglycol dimethacrylate (EGDMA) was prepared on the inner surface of a stainless-steel tube by a facile electrodeposition method. To evaluate the offered setup and the new PPy-EGDMA coating, it was used to extract inorganic selenium species in water samples. Extraction of inorganic selenium species was carried out by applying a positive potential through the inner surface of coated in-tube under flow conditions. Under the optimized conditions, selenium was detected in amounts as small as 4.0 parts per trillion. The method showed good linearity in the range of 0.012-200 ng mL(-1), with coefficients of determination better than 0.9996. The intra- and inter-assay precisions (RSD%, n = 5) were in the range of 2.0-2.5% and 2.7-3.2%, respectively. The validated method was successfully applied for the analysis of inorganic selenium species in some water samples and satisfactory results were obtained. PMID:27154830

  17. Photochemical alkylation of inorganic selenium in the presence of low molecular weight organic acids.

    PubMed

    Guo, Xuming; Sturgeon, Ralph E; Mester, Zoltán; Gardner, Graeme J

    2003-12-15

    Using a flow-through photochemical reactor and a low pressure mercury lamp as a UV source, alkyl selenium species are formed from inorganic selenium(IV) in the presence of low molecular weight organic acids (LMW acids). The volatile alkyl Se species were cryogenically trapped and identified by GC-MS and GC-ICP-MS. In the presence of formic, acetic, propionic and malonic acids, inorganic selenium(IV) is converted by UV irradiation to volatile selenium hydride and carbonyl, dimethylselenide and diethylselenide, respectively. Se(IV) was successfully removed from contaminated agricultural drainage waters (California, U.S.A.) using a batch photoreactor system Se. Photochemical alkylation may thus offer a promising means of converting toxic selenium salts, present in contaminated water, to less toxic dimethylselenide. The LMW acids and photochemical alkylation process may also be key to understanding the source of atmospheric selenium and are likely involved in its mobility in the natural anaerobic environment.

  18. [Determination of Total Selenium and Arsenic in Coal by Wet Digestion Hydride Generation Atomic Fluorescence Spectrometry (HG-AFS)].

    PubMed

    Ni, Run-xiang; Luo, Kun-li

    2015-05-01

    In the present work we presented a new method for determination of total Se and As in coal by electric hot plate-mixed acids-hydride generation atomic fluorescence spectrometry (HG-AFS), the wet digestion method. The detailed operation procedures of the new method are as follows: About 0. 05~0. 10 g of powdered (200 mesh) coal sample was placed in a glass beaker, 10 mL of nitric acid (HNO3) and 2 mL of perchloric acid (HClO4) were added to the beaker in sequence, then the beaker was covered with a watching glass and placed in a fume cupboard standing overnight. The beaker was placed on an electric hot plate (180 °C) for sample decomposition the next day. The beaker was moved away from the electric hot plate when white smoke arose in the beaker, the sample color turned white or grey and the solution turned clear. Three milliliter of hydrochloric acid (HCl) solution (6 mol . L-1) was added to the beaker after the temperature of the beaker returned to room temperature. The beaker was heated on the electric hot plate again, and then moved away when white smoke started arising again. One milliliter of HCI was added in the beaker after the temperature of the beaker returned to room temperature. After that, the digested sample was transferred to a 25 mL test tube which was filled with ultrapure water to the tube's full volume. This solution was used for Se determination directly. Three milliliter of the Se test solution prepared above was transferred to a 15 mL glass test tube, 1 mL of thiourea/ascorbic acid solution (2. 5 g . mL-1) and 1 mL of the concentrated HCl was added to the 15 mL test tube. The test tube was then filled with ultrapure water to its full volume. The solution was used for As determination after shaking well and 40 min standing. Finally, Se and As concentrations in these prepared solutions were measured by using the AFS-9780 instrument (Beijing Haiguang Instrument Co. , LTD, Beijing, China). Two Chinese Coal Certified Reference Materials (GBW11115

  19. A method to quantitatively trap volatilized organoselenides for stable selenium isotope analysis.

    PubMed

    Schilling, Kathrin; Wilcke, Wolfgang

    2011-01-01

    If volatile organoselenides are to be analyzed for their stable Se isotope composition to elucidate sources and formation processes, organoselenides need to be trapped quantitatively to avoid artificial Se isotope fractionation. We developed an efficient trap of organoselenides to be used in microcosms designed to determine the Se isotope fractionation by microbial transformation of inorganic Se to volatile organoselenides. The recoveries of volatilized dimethyldiselenide (DMDSe) from aqueous standard solutions by activated charcoal and alkaline peroxide solution with subsequent freeze-drying and purification via a cation exchange resin were tested. Microcosm experiments with the Se-methylating fungus in a growth medium were conducted, and tightness of the microcosm was assessed by comparing mass balances of total Se of the fungus, medium, and trapped organoselenides with the supplied Se mass. At the end of the experiment, we calculated δSe values of the whole microcosm and compared them with the δSe value of supplied Se(IV) and Se(VI). Our results demonstrated that activated charcoal cannot be used for quantitative trapping of organoselenides because generally <64% of the outgassed DMDSe were recovered. The mean recovery of Se volatilized from an aqueous DMDSe standard trapped in alkaline peroxide, in contrast, was 96 ± 11% (SD) after 2 h ( = 4). The mass balances of total Se in microcosm experiments with alkaline peroxide traps run for 11 to 15 d were 96 ± 15 and 102 ± 2.4% for Se(IV) and Se(VI) ( = 3), respectively. The mass-weighted mean δSe values for the Se(IV) and Se(VI) batch experiments were -0.31 ± 0.05‰ ( = 3) and -0.76 ± 0.07‰ ( = 3), compared with -0.20 ± 0.10‰ and -0.69 ± 0.10‰ in the supplied Se oxyanions, respectively. We conclude that the alkaline peroxide trap can reliably be used to determine the Se isotope composition of organoselenides. PMID:21546688

  20. Hydriding process

    DOEpatents

    Raymond, J.W.; Taketani, H.

    1973-12-01

    BS>A method is described for hydriding a body of a Group IV-B metal, preferably zirconium, to produce a crack-free metal-hydride bedy of high hydrogen content by cooling the body at the beta to beta + delta boundary, without further addition of hydrogen, to precipitate a fine-grained delta-phase metal hydride in the beta + delta phase region and then resuming the hydriding, preferably preceded by a reheating step. (Official Gazette)

  1. Percutaneous absorption of selenium sulfide

    SciTech Connect

    Farley, J.; Skelly, E.M.; Weber, C.B.

    1986-01-01

    The purpose of this study was to determine selenium levels in the urine of Tinea patients before and after overnight application of a 2.5% selenium sulfide lotion. Selenium was measured by atomic absorption spectroscopy (AAS). Hydride generation and carbon rod atomization were studied. It was concluded from this study that selenium is absorbed through intact skin. Selenium is then excreted, at least partially, in urine, for at least a week following treatment. The data show that absorption and excretion of selenium vary on an individual basis. Selenium levels in urine following a single application of selenium sulfide lotion do not indicate that toxic amounts of selenium are being absorbed. Repeated treatments with SeS/sub 2/ result in selenium concentrations in urine which are significantly higher than normal. Significant matrix effects are observed in the carbon rod atomization of urine samples for selenium determinations, even in the presence of a matrix modifier such as nickel. The method of standard additions is required to obtain accurate results in the direct determination of selenium in urine by carbon rod AAS.

  2. Selenium content of breast milk.

    PubMed

    Mandić, Z; Mandić, M L; Grgić, J; Hasenay, D; Grgić, Z

    1995-09-01

    Selenium levels in human milk in the winter period ranged from 5.3 micrograms/l to 23.8 micrograms/l, the mean value being 11.0 micrograms/l. The nursing women were divided into several groups according to the results of a questionnaire, i.e. according to their social status (refugees or otherwise), number of deliveries, post partum days, the weight they had gained during pregnancy, their age and smoking habits. The mean levels of selenium for each group are presented. Selenium was determined by hydride generation atomic absorption spectrometry.

  3. Interstellar Hydrides

    NASA Astrophysics Data System (ADS)

    Gerin, Maryvonne; Neufeld, David A.; Goicoechea, Javier R.

    2016-09-01

    Interstellar hydrides—that is, molecules containing a single heavy element atom with one or more hydrogen atoms—were among the first molecules detected outside the solar system. They lie at the root of interstellar chemistry, being among the first species to form in initially atomic gas, along with molecular hydrogen and its associated ions. Because the chemical pathways leading to the formation of interstellar hydrides are relatively simple, the analysis of the observed abundances is relatively straightforward and provides key information about the environments where hydrides are found. Recent years have seen rapid progress in our understanding of interstellar hydrides, thanks largely to FIR and submillimeter observations performed with the Herschel Space Observatory. In this review, we discuss observations of interstellar hydrides, along with the advanced modeling approaches that have been used to interpret them and the unique information that has thereby been obtained.

  4. Immuno-spin trapping detection of antioxidant/pro-oxidant properties of zinc or selenium on DNA and protein radical formation via hydrogen peroxide.

    PubMed

    Deletioglu, Vedia; Tuncay, Erkan; Toy, Aysegul; Atalay, Mustafa; Turan, Belma

    2015-11-01

    Trace elements can participate in the catalysis of group-transfer reactions and can serve as their structural components. However, most of them including zinc and selenium have multifunctional roles in biological environments such as antioxidant and/or pro-oxidant effects, as concentration-dependent manner. Although it has been demonstrated the antioxidant actions of either selenium or zinc compounds, there are several documents pointing out their pro-oxidant/oxidant roles in biological systems. Here we have used ELISA-based immuno-spin trapping, a method for detection of free radical formation, to detect whether or not a zinc compound, Zn3(PO4)2, or a selenium compound, Na2SeO3, has antioxidant and/or pro-oxidant effect on 5,5-Dimethyl-1-Pyrroline-N-Oxide (DMPO)-DNA nitrone adducts induced with Cu(II)-H2O2-oxidizing system in in vitro preparations. Second, we examined whether this technique is capable to demonstrate the different DMPO-protein nitrone adduct productions in isolated protein crude of hearts from normal rats (CON) or rats with metabolic syndrome (MetS). Our data demonstrated that either Zn(2+) (100 µM) or SeO3(-2) (50 nM) has very strong antioxidant action against 200 µM H2O2-induced DMPO-DNA nitrone adduct production, whereas their higher concentrations have apparent pro-oxidant actions. We also used verification by Western blotting analysis whether immuno-spin trapping can be used to assess H2O2-induced DMPO-protein nitrone adducts in heart protein crudes. Our Western blot data further confirmed the ELISA-data from proteins and demonstrated how Zn(2+) or SeO3(-2) are dual-functioning ions such as antioxidant at lower concentrations while pro-oxidant at higher concentrations. Particularly, our present data with SeO3(-2) in DMPO-protein nitrone adducts, being in line with our previous observation on its dual-actions in ischemia/reperfusion-induced damaged heart, have shown that this ion has higher pro-oxidant actions over 50 nM in Met

  5. Hydride compositions

    DOEpatents

    Lee, Myung W.

    1995-01-01

    A composition for use in storing hydrogen, and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the hydrogen equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to hydrogen and then heating at a temperature below the softening temperature of any of the. constituents so that their chemical and structural integrity is preserved. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P.sub.H.sbsb.2 and determining H/M from the isothermic function of the composition.

  6. Hydride compositions

    DOEpatents

    Lee, Myung, W.

    1994-01-01

    Disclosed are a composition for use in storing hydrogen and a method for making the composition. The composition comprises a mixture of two or more hydrides, each hydride having a different series of hydrogen sorption isotherms that contribute to the overall isotherms of the mixture. The hydrides are chosen so that the isotherms of the mixture have regions wherein the H equilibrium pressure increases with increasing hydrogen, preferably linearly. The isotherms of the mixture can be adjusted by selecting hydrides with different isotherms and by varying the amounts of the individual hydrides, or both. Preferably, the mixture is made up of hydrides that have isotherms with substantially flat plateaus and in nearly equimolar amounts. The composition is activated by degassing, exposing to H, and then heating below the softening temperature of any of the constituents. When the composition is used to store hydrogen, its hydrogen content can be found simply by measuring P{sub H}{sub 2} and determining H/M from the isothermic function of the composition.

  7. Entrapped elemental selenium nanoparticles affect physicochemical properties of selenium fed activated sludge.

    PubMed

    Jain, Rohan; Seder-Colomina, Marina; Jordan, Norbert; Dessi, Paolo; Cosmidis, Julie; van Hullebusch, Eric D; Weiss, Stephan; Farges, François; Lens, Piet N L

    2015-09-15

    Selenite containing wastewaters can be treated in activated sludge systems, where the total selenium is removed from the wastewater by the formation of elemental selenium nanoparticles, which are trapped in the biomass. No studies have been carried out so far on the characterization of selenium fed activated sludge flocs, which is important for the development of this novel selenium removal process. This study showed that more than 94% of the trapped selenium in activated sludge flocs is in the form of elemental selenium, both as amorphous/monoclinic selenium nanospheres and trigonal selenium nanorods. The entrapment of the elemental selenium nanoparticles in the selenium fed activated sludge flocs leads to faster settling rates, higher hydrophilicity and poorer dewaterability compared to the control activated sludge (i.e., not fed with selenite). The selenium fed activated sludge showed a less negative surface charge density as compared to the control activated sludge. The presence of trapped elemental selenium nanoparticles further affected the spatial distribution of Al and Mg in the activated sludge flocs. This study demonstrated that the formation and subsequent trapping of elemental selenium nanoparticles in the activated sludge flocs affects their physicochemical properties.

  8. Hydride compressor

    DOEpatents

    Powell, James R.; Salzano, Francis J.

    1978-01-01

    Method of producing high energy pressurized gas working fluid power from a low energy, low temperature heat source, wherein the compression energy is gained by using the low energy heat source to desorb hydrogen gas from a metal hydride bed and the desorbed hydrogen for producing power is recycled to the bed, where it is re-adsorbed, with the recycling being powered by the low energy heat source. In one embodiment, the adsorption-desorption cycle provides a chemical compressor that is powered by the low energy heat source, and the compressor is connected to a regenerative gas turbine having a high energy, high temperature heat source with the recycling being powered by the low energy heat source.

  9. Electrochemical and chemical routes to hydride loss from an iridium dihydride.

    PubMed

    Walden, A G; Kumar, A; Lease, N; Goldman, A S; Miller, A J M

    2016-06-14

    With a view towards replacing sacrificial hydrogen acceptors in alkane dehydrogenation catalysis, electrochemical methods for oxidative activation of a pincer-ligated iridium hydride intermediate were explored. A 1H(+)/2e(-) oxidation process was observed in THF solvent, with net hydride loss leading to a reactive cationic intermediate that can be trapped by chloride. Analogous reactivity was observed with the concerted hydride transfer reagent Ph3C(+), connecting chemical and electrochemical hydride loss pathways. PMID:26979786

  10. Selenium Sulfide

    MedlinePlus

    Selenium sulfide comes in a lotion and is usually applied as a shampoo. As a shampoo, selenium sulfide usually is used twice a week for the first ... it is irritating. Rinse off all of the lotion.Do not use this medication on children younger ...

  11. Facile preparation of an immobilized surfactant-free palladium nanocatalyst for metal hydride trapping: a novel sensing platform for TXRF analysis

    NASA Astrophysics Data System (ADS)

    Romero, V.; Costas-Mora, I.; Lavilla, I.; Bendicho, C.

    2015-01-01

    In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol group of the alkoxysilane that is adsorbed on the surface of NPs without the dissociation of the S-H bond. Different parameters affecting the synthesis of Pd NPs and their immobilization onto quartz substrates were evaluated. A comprehensive characterization of the synthesized Pd NPs was carried out by transmission electron microscopy (TEM), whereas total reflection X-ray fluorescence (TXRF) spectrometry was applied in order to evaluate their catalytic activity for solid-gas reactions. Immobilized Pd NPs were applied as nanocatalysts for the dissociative chemisorption of arsine at room temperature, yielding the formation of As-Pd bonds. Quartz substrates coated with nanosized Pd could be used as novel sensing platforms for total reflection X-ray fluorescence analysis. Arsenic can be detected in situ in natural water with a limit of detection of 0.08 μg L-1.In this work, a simple route for the synthesis of surfactant-free immobilized palladium nanoparticles (Pd NPs) and their use as effective nanocatalysts for metal hydride decomposition is described. A mixture of ethanol : water was used as the reducing agent. Ethanol was added in a large excess to reduce the ionic Pd and stabilize the obtained Pd NPs. Ethanol is adsorbed on the surface of Pd allowing steric stabilization. Freshly prepared Pd NPs were immobilized onto quartz substrates modified with 3-mercaptopropyltrimethoxysilane. Pd interacts with the thiol

  12. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  13. SPECIATION OF SELENIUM AND ARSENIC COMPOUNDS BY CAPILLARY...

    EPA Science Inventory

    Capillary electrophoresis (CE) with hydride generation inductively coupled plasma mass spectrometry was used to determine four arsenicals and two selenium species. Selenate (SeVI) was reduced on-line to selenite (SeIV) by mixing the CE effluent with concentrated HCl. A microporou...

  14. Determination of selenium speciation in biogenic particles and sediments

    SciTech Connect

    Cutter, G.A.

    1985-12-01

    Selenium can exist in a variety of chemical forms in the suspended particles and bottom sediments of natural waters. A procedure for sediments and planktonic material has been developed that uses a multistep nitric/perchloric acids digestion to solubilize total selenium and a weak sodium hydroxide treatment to release selenite and selenate. The solubilized selenium species are determined by a selective hydride generation/atomic absorption technique. Accuracy was verified by using a combination of standard reference materials, radiotracers, and existing sediment leach methods. For field and reference samples the average precision (relative standard deviation) for total selenium determinations is 8.8% (n = 8 samples) and 19.3% for selenite + selenate determinations (n = 6 samples). The detection limit for total particulate selenium is 10 ng/g using a sample size of 0.2 g. The method has been used on a variety of plankton, planktonic detritus, and sediment samples. 22 references, 1 figure, 3 tables.

  15. Hysteresis in Metal Hydrides.

    ERIC Educational Resources Information Center

    Flanagan, Ted B., And Others

    1987-01-01

    This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)

  16. Selenium sulfide

    Integrated Risk Information System (IRIS)

    Selenium sulfide ; CASRN 7446 - 34 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  17. Chemistry of intermetallic hydrides

    SciTech Connect

    Reilly, J.J.

    1991-01-01

    Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

  18. Nutritional aspects of selenium

    SciTech Connect

    Choe, M.

    1987-01-01

    The overall objective of this project was to investigate the effect of protein and/or dietary fiber supplementation on selenium absorption and metabolism. These relationships might be of importance in determining either minimum selenium nutritional requirements or levels of intake at which this mineral becomes toxic. Three studies compose the project. The first study involved the controlled feeding of fifteen young adults mice. Subjects were fed a laboratory-controlled diet with and without supplements of selenium or selenium plus guar gum. Selenium supplementation resulted in increased selenium excretion in urine and feces. Supplementation of guar gum, as a dietary fiber, tended to increase fecal selenium excretion and to decrease selenium balance and glutathione peroxidase (GSH-Px) activity regardless of dietary selenium levels. In study II, seventy two weanling mice were fed varied levels of dietary selenium and protein. Numerically, urinary selenium excretion increased and fecal selenium excretion and selenium balance decreased with increased dietary protein level within the same level of dietary selenium; however, selenium absorption rate tended to decrease with increased dietary protein level. Whole blood and brain tissue glutathione peroxidase activities were higher in animals fed moderate protein level than those fed the other two protein levels. In study III, a survey was conducted to investigate the correlation between dietary fiber or protein intake and urinary selenium excretion. There was a negative correlation between dietary fiber and urinary selenium excretion levels while dietary protein and urinary selenium excretion were positively correlated.

  19. Regenerative Hydride Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A.

    1992-01-01

    Hydride heat pump features regenerative heating and single circulation loop. Counterflow heat exchangers accommodate different temperatures of FeTi and LaNi4.7Al0.3 subloops. Heating scheme increases efficiency.

  20. The selenium content of edible mushrooms in Finland.

    PubMed

    Piepponen, S; Liukkonen-Lilja, H; Kuusi, T

    1983-01-01

    In this investigation the selenium contents of 142 mushroom samples were determined. The majority of the samples were wild Finnish mushroom species generally used for human consumption. The selenium contents of some cultivated mushrooms were also determined. In all, the material analyzed consisted of 38 different mushroom species. Selenium concentrations were assayed after modified wet and dry ashing, by atomic-absorption spectrometry using the hydride technique and the standard-addition procedure. The reliability of the method was tested with certified standard reference materials. The results of analysis obtained indicate that selenium contents vary considerably between different mushroom species. Of the species investigated, by far the highest selenium contents were found in Boletus edulis (mean 17 mg/kg dry weight). Other mushrooms having considerable selenium contents included Macrolepiota (5.0 mg/kg), wild Agaricus spp. (2.7 mg/kg), Gasteromycetes (1.9 mg/kg), Lactarius torminosus (1.9 mg/kg) and Marasmius oreades (1.6 mg/kg). The contents in these mushrooms are sufficient to provide an amount of selenium that is nutritionally significant in relation to the total daily intake of selenium of the Finnish population. Other edible mushrooms generally used in Finnland, e.g. species belonging to Cantharellaceae, Russula, Boletaceae (other than B. edulis) and Lactarius (other than L. torminosus) contained only small amounts of selenium. The importance of these mushrooms as a source of selenium is therefore marginal. The selenium content of Lactarius torminosus decreased by an average of 32% during the blanching necessary before consumption of these mushrooms.

  1. Precipitation of hydrides in high purity niobium after different treatments

    SciTech Connect

    Barkov, F.; Romanenko, A.; Trenikhina, Y.; Grassellino, A.

    2013-01-01

    Precipitation of lossy non-superconducting niobium hydrides represents a known problem for high purity niobium in superconducting applications. Using cryogenic optical and laser confocal scanning microscopy we have directly observed surface precipitation and evolution of niobium hydrides in samples after different treatments used for superconducting RF cavities for particle acceleration. Precipitation is shown to occur throughout the sample volume, and the growth of hydrides is well described by the fast diffusion-controlled process in which almost all hydrogen is precipitated at $T=140$~K within $\\sim30$~min. 120$^{\\circ}$C baking and mechanical deformation are found to affect hydride precipitation through their influence on the number of nucleation and trapping centers.

  2. Comprehensive speciation of low-molecular weight selenium metabolites in mustard seeds using HPLC-electrospray linear trap/Orbitrap tandem mass spectrometry.

    PubMed

    Ouerdane, Laurent; Aureli, Federica; Flis, Paulina; Bierla, Katarzyna; Preud'homme, Hugues; Cubadda, Francesco; Szpunar, Joanna

    2013-09-01

    An analytical methodology based on high-resolution high mass accuracy electrospray ionization (ESI) tandem MS assisted by Se-specific detection using inductively coupled plasma mass spectrometry (ICP MS) was developed for speciation of selenium (Se) in seeds of black mustard (Brassica nigra) grown on Se-rich soil. Size-exclusion LC-ICP MS allowed the determination of the Se distribution according to the molecular mass and the control of the species stability during extraction. The optimization of hydrophilic interaction of LC and cation-exchange HPLC resulted in analytical conditions making it possible to detect and characterize over 30 Se species using ESI MS, including a number of minor (<0.5%) metabolites. Selenoglucosinolates were found to be the most important class of species accounting for at least 15% of the total Se present and over 50% of all the metabolites. They were found particularly unstable during aqueous extraction leading to the loss of Se by volatilization as methylselenonitriles and methylselenoisothiocyanates identified using gas chromatography (GC) with the parallel ICP MS and atmospheric pressure chemical ionization (APCI) MS/MS detection. However, selenoglucosinolates could be efficiently recovered by extraction with 70% methanol. Other classes of identified species included selenoamino acids, selenosugars, selenosinapine and selenourea derivatives. The three types of reactions leading to the formation of selenometabolites were: the Se-S substitution in the metabolic pathway, oxidative reactions of -SeH groups with endogenous biomolecules, and chemical reactions, e.g., esterification, of Se-containing molecules and other biomolecules through functional groups not involving Se. PMID:23925428

  3. Volatile Selenium Flux in the Great Salt Lake

    NASA Astrophysics Data System (ADS)

    Diaz, X.; Johnson, W. P.

    2006-12-01

    Volatilization of selenium has been proven to be the major source of selenium vapor from oceans and estuaries and it may be the major mechanism of permanent selenium removal from the Great Salt Lake (other than brine shrimp harvest). However, the volatilization flux of selenium from the Great Salt Lake has not been previously measured due to challenges of analysis in this hyper-saline environment. This work presents results from recent field studies examining the spatial distribution of volatile selenium (geographical and with depth) in the South Arm (main body) of the Great Salt Lake. The analyses involved collection of volatile selenium in a cryo-focusing trap system via sparging with helium. The cryo-trapped volatile selenium was digested with nitric acid and analyzed by ICP-MS. The results show concentrations of volatile selenium that are much greater than values reported for marine estuaries and oceans. Volatile selenium flux to the atmosphere was determined using mass transport equations corrected to simulate the highly saline environment of the South Arm of the Great Salt Lake.

  4. Lightweight hydride storage materials

    SciTech Connect

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.

    1995-09-01

    The need for lightweight hydrides in vehicular applications has prompted considerable research into the use of magnesium and its alloys. Although this earlier work has provided some improved performance in operating temperature and pressure, substantial improvements are needed before these materials will significantly enhance the performance of an engineered system on a vehicle. We are extending the work of previous investigators on Mg alloys to reduce the operating temperature and hydride heat of formation in light weight materials. Two important results will be discussed in this paper: (1) a promising new alloy hydride was found which has better pressure-temperature characteristics than any previous Mg alloy and, (2) a new fabrication process for existing Mg alloys was developed and demonstrated. The new alloy hydride is composed of magnesium, aluminum and nickel. It has an equilibrium hydrogen overpressure of 1.3 atm. at 200{degrees}C and a storage capacity between 3 and 4 wt.% hydrogen. A hydrogen release rate of approximately 5 x 10{sup -4} moles-H{sub 2}/gm-min was measured at 200{degrees}C. The hydride heat of formation was found to be 13.5 - 14 kcal/mole-H{sub 2}, somewhat lower than Mg{sub 2}Ni. The new fabrication method takes advantage of the high vapor transport of magnesium. It was found that Mg{sub 2}Ni produced by our low temperature process was better than conventional materials because it was single phase (no Mg phase) and could be fabricated with very small particle sizes. Hydride measurements on this material showed faster kinetic response than conventional material. The technique could potentially be applied to in-situ hydride bed fabrication with improved packing density, release kinetics, thermal properties and mechanical stability.

  5. Selenium species in selenium fortified dietary supplements.

    PubMed

    Niedzielski, Przemyslaw; Rudnicka, Monika; Wachelka, Marcin; Kozak, Lidia; Rzany, Magda; Wozniak, Magdalena; Kaskow, Zaneta

    2016-01-01

    This article presents a study of dietary supplements available on the Polish market. The supplements comprised a large group of products with selenium content declared by the producer. The study involved determination of dissolution time under different conditions and solubility as well as content and speciation of selenium. The total content was determined as well as organic selenium and the inorganic forms Se(IV) and Se(VI). The organic selenium content was calculated as the difference between total Se and inorganic Se. The values obtained were compared with producers' declarations. The work is the first such study of selenium supplements available on the market of an EU Member State.

  6. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  7. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  8. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K.; Bystroff, Roman I.; Miller, Dale E.

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  9. Selenium: Poison and Preventive.

    ERIC Educational Resources Information Center

    Marmion Howe, Sister

    1978-01-01

    Selenium is an essential nutrient to the human body, but it can reach toxic levels causing a disease called selenosis. This article discusses selenium, its geographical distribution, toxicity, nutritional role, and carcinogenicity. (MA)

  10. Selenium in diet

    MedlinePlus

    ... cardiovascular disease Protect the body from the poisonous effects of heavy metals and other harmful substances Taking a selenium supplement in addition to food sources of selenium is not currently recommended for these conditions.

  11. Selenium: Element of Contrasts

    ERIC Educational Resources Information Center

    Goldsmith, Robert H.; And Others

    1978-01-01

    Reports on recent findings concerning the impact of selenium on human and animal health. In its various oxidation states, different concentrations of selenium may be helpful or detrimental to human health. (CP)

  12. Hydrogen Outgassing from Lithium Hydride

    SciTech Connect

    Dinh, L N; Schildbach, M A; Smith, R A; Balazs1, B; McLean II, W

    2006-04-20

    Lithium hydride is a nuclear material with a great affinity for moisture. As a result of exposure to water vapor during machining, transportation, storage and assembly, a corrosion layer (oxide and/or hydroxide) always forms on the surface of lithium hydride resulting in the release of hydrogen gas. Thermodynamically, lithium hydride, lithium oxide and lithium hydroxide are all stable. However, lithium hydroxides formed near the lithium hydride substrate (interface hydroxide) and near the sample/vacuum interface (surface hydroxide) are much less thermally stable than their bulk counterpart. In a dry environment, the interface/surface hydroxides slowly degenerate over many years/decades at room temperature into lithium oxide, releasing water vapor and ultimately hydrogen gas through reaction of the water vapor with the lithium hydride substrate. This outgassing can potentially cause metal hydriding and/or compatibility issues elsewhere in the device. In this chapter, the morphology and the chemistry of the corrosion layer grown on lithium hydride (and in some cases, its isotopic cousin, lithium deuteride) as a result of exposure to moisture are investigated. The hydrogen outgassing processes associated with the formation and subsequent degeneration of this corrosion layer are described. Experimental techniques to measure the hydrogen outgassing kinetics from lithium hydride and methods employing the measured kinetics to predict hydrogen outgassing as a function of time and temperature are presented. Finally, practical procedures to mitigate the problem of hydrogen outgassing from lithium hydride are discussed.

  13. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, Moshe; Gruen, Dieter M.; Mendelsohn, Marshall H.; Sheft, Irving

    1981-01-01

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  14. Method for preparing porous metal hydride compacts

    DOEpatents

    Ron, M.; Gruen, D.M.; Mendelsohn, M.H.; Sheft, I.

    1980-01-21

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  15. 17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF HYDRIDING SYSTEM IN BUILDING 881. THE HYDRIDING SYSTEM WAS PART OF THE FAST ENRICHED URANIUM RECOVERY PROCESS. (11/11/59) - Rocky Flats Plant, General Manufacturing, Support, Records-Central Computing, Southern portion of Plant, Golden, Jefferson County, CO

  16. Iron Hydride Detection and Intramolecular Hydride Transfer in a Synthetic Model of Mono-Iron Hydrogenase with a CNS Chelate.

    PubMed

    Durgaprasad, Gummadi; Xie, Zhu-Lin; Rose, Michael J

    2016-01-19

    We report the identification and reactivity of an iron hydride species in a synthetic model complex of monoiron hydrogenase. The hydride complex is derived from a phosphine-free CNS chelate that includes a Fe-C(NH)(═O) bond (carbamoyl) as a mimic of the active site iron acyl. The reaction of [((O═)C(HN)N(py)S(Me))Fe(CO)2(Br)] (1) with NaHBEt3 generates the iron hydride intermediate [((O═)C(HN)N(py)S(Me))Fe(H)(CO)2] (2; δFe-H = -5.08 ppm). Above -40 °C, the hydride species extrudes CH3S(-) via intramolecular hydride transfer, which is stoichiometrically trapped in the structurally characterized dimer μ2-(CH3S)2-[((O═)C(HN)N(Ph))Fe(CO)2]2 (3). Alternately, when activated by base ((t)BuOK), 1 undergoes desulfurization to form a cyclometalated species, [((O═)C(NH)NC(Ph))Fe(CO)2] (5); derivatization of 5 with PPh3 affords the structurally characterized species [((O═)C(NH)NC)Fe(CO)(PPh3)2] (6), indicating complex 6 as the common intermediate along each pathway of desulfurization.

  17. Dimensionally stable metallic hydride composition

    DOEpatents

    Heung, Leung K.

    1994-01-01

    A stable, metallic hydride composition and a process for making such a composition. The composition comprises a uniformly blended mixture of a metal hydride, kieselguhr, and a ballast metal, all in the form of particles. The composition is made by subjecting a metal hydride to one or more hydrogen absorption/desorption cycles to disintegrate the hydride particles to less than approximately 100 microns in size. The particles are partly oxidized, then blended with the ballast metal and the kieselguhr to form a uniform mixture. The mixture is compressed into pellets and calcined. Preferably, the mixture includes approximately 10 vol. % or more kieselguhr and approximately 50 vol. % or more ballast. Metal hydrides that can be used in the composition include Zr, Ti, V, Nb, Pd, as well as binary, tertiary, and more complex alloys of La, Al, Cu, Ti, Co, Ni, Fe, Zr, Mg, Ca, Mn, and mixtures and other combinations thereof. Ballast metals include Al, Cu and Ni.

  18. Determination of selenium in nuts by cathodic stripping potentiometry (CSP).

    PubMed

    Dugo, Giacomo; La Pera, Lara; Lo Turco, Vincenzo; Mavrogeni, Ekaterini; Alfa, Maria

    2003-06-18

    The aim of this work was to determine the selenium content in nut samples by cathodic stripping potentiometry. Dry-powdered nuts were digested by HNO(3) and dissolved with concentrated hydrochloric acid. To avoid the interference of natural oxygen, the potentiometric determination of selenium was carried out in an electrolyte solution consisting of 2 M CaCl(2) and 4 M HCl. The analysis was executed applying an electrolysis potential of -150 mV for 60 s and a constant current of -30 microA. Under these conditions, detection limits lower than 1.0 ng g(-)(1) were obtained for selenium analysis in nuts. The relative standard deviation of these measurements (expressed as rsd %) ranged from 0.44 to 0.88% while recoveries ranged from 90.2 to 95.3%. The results obtained with the proposed method were compared with those obtained via hydride vapor generation atomic absorption spectroscopy, a common method for determining selenium. The results of the two methods agreed within 5% for almond, hazelnut, and pistachio samples. The mean concentrations of selenium determined in Sicilian samples of almond, hazelnut, and pistachio were 531 +/- 1, 865 +/- 1, and 893 +/- 4 microg/kg, respectively.

  19. Development of metal hydride composites

    SciTech Connect

    Congdon, J.W.

    1992-12-01

    Most of current hydride technology at Savannah River Site is based on beds of metal hydride powders; the expansion upon hydridation and the cycling results in continued breakdown into finer particles. Goal is to develop a composite which will contain the fines in a dimensionally stable matrix, for use in processes which require a stable gas flow through a hydride bed. Metal hydride composites would benefit the advanced Thermal Cycling Absorption process (hydrogen isotope separation), and the Replacement Tritium Facility (storage, pumping, compression, purification of hydrogen isotopes). These composites were fabricated by cold compaction of a mixture of metal hydride granules and coarse copper powder; the porosity in the granules was introduced by means of ammonium carbonate. The composite pellets were cycled 138 times in hydrogen with the loss of LANA0.75 (LaNi{sub 4.25}Al{sub 0.75}) limited to the surface. Vacuum sintering can provide additional strength at the edges. Without a coating, the metal hydride particles exposed at the pellet surface can be removed by cycling several times in hydrogen.

  20. Changes in the chemical form of selenium observed during the manufacture of a selenium-enriched sourdough bread for use in a human nutrition study.

    PubMed

    Bryszewska, M A; Ambroziak, W; Diowksz, A; Baxter, M J; Langford, N J; Lewis, D J

    2005-02-01

    High-performance liquid chromatography interfaced with inductively coupled plasma mass spectrometry, and hydride generation-inductively coupled plasma mass spectrometry were used, respectively, to investigate changes in both the chemical form and the concentration of selenium during its bio-incorporation and bio-accumulation into rye seedlings. A 60-fold increase in the total level of selenium in the seedlings ('control' biomass = 0.99 mg kg(-1), 'enriched' biomass = 55.27 mg kg(-1)) was accompanied by a change from selenite to several organo-selenium forms, with more than 40% being present as selenomethionine. The seedling biomass was dried, ground and used as an ingredient in the production of a fermented sourdough bread (popular in Poland and many Eastern European countries). The selenium in the resulting bread was also characterized in terms of its speciation, as well as its total selenium content ('control' bread = 0.06 mg kg(-1), 'enriched' bread = 3.56 mg kg(-1)). The breads were then fed to 24 volunteers as part of a human intervention study designed to establish the efficacy of this mode of selenium supplementation. The human study data subsequently showed the bread was a good source of dietary selenium.

  1. A study of serum zinc, selenium and copper levels in carcinoma of esophagus patients.

    PubMed

    Goyal, M M; Kalwar, A K; Vyas, R K; Bhati, A

    2006-03-01

    The association of serum trace elements like selenium, zinc and copper has been found in different types of cancer. This study was conducted to see the serum level of these three trace elements in cancer esophagus patients. Biopsy confirmed cancer esophagus, 24 patients (12 males, 12 females, mean age 54.5±11.65 year with 23 healthy subjects (16 males, 7 females, mean age 44 ±13.82 years) were included in this study. Both control and study group patients were of same socio-economic status and dietary habits. Serum zinc and copper level were estimated using standard absorption spectrometer technique and serum selenium by Hydride generation method.We observed significant low serum levels of zinc and selenium while high level of serum copper in carcinoma esophagus patients, as compared with normal healthy controls. This shows an association of serum selenium zinc and copper with cancer esophagus.

  2. Swedish views on selenium.

    PubMed

    Bruce, A

    1986-01-01

    For a long time selenium was known only for its toxic characteristics. During the last few decades selenium deficiency has been recognized as an important agricultural problem in Sweden. On average, grains and pastures only contain one tenth of the amount of selenium considered necessary to avoid symptoms of deficiency. However, the incidence of muscle degeneration among the animals has been low, probably due to imported animal feed. Since 1980 selenium has been added to animal feed, but only minor changes in the selenium content of Swedish food stuffs have been recorded. Some studies have shown that the average Swedish dietary intake of selenium is 10-70 micrograms/day. The lowest levels were found in vegan diets, based on locally-grown products. Swedish studies have found depressed glutathione peroxidase (GSH-Px) levels in patients with various skin disorders, including acne; myotonic dystrophy and rheumatic arthritis. Clinical trials with selenium supplementation have given positive results in some of these disorders as well as in some patients with disabling muscular and joint pains. Today there is a large sale of selenium tablets sometimes with additional vitamin E. The marketing of these tablets, however, is often based on unsubstantiated claims. PMID:3717875

  3. Erbium hydride decomposition kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2006-11-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report are analyzed quantitatively using Redhead's method to yield kinetic parameters (E{sub A} {approx} 54.2 kcal/mol), which are then utilized to predict hydrogen outgassing in vacuum for a variety of thermal treatments. Interestingly, it was found that the activation energy for desorption can vary by more than 7 kcal/mol (0.30 eV) for seemingly similar samples. In addition, small amounts of less-stable hydrogen were observed for all erbium dihydride films. A detailed explanation of several approaches for analyzing thermal desorption spectra to obtain kinetic information is included as an appendix.

  4. Complex Hydrides for Hydrogen Storage

    SciTech Connect

    Slattery, Darlene; Hampton, Michael

    2003-03-10

    This report describes research into the use of complex hydrides for hydrogen storage. The synthesis of a number of alanates, (AIH4) compounds, was investigated. Both wet chemical and mechano-chemical methods were studied.

  5. Hydride development for hydrogen storage

    SciTech Connect

    Thomas, G.J.; Guthrie, S.E.; Bauer, W.; Yang, N.Y.C.; Sandrock, G.

    1996-10-01

    The purpose of this project is to develop and demonstrate improved hydride materials for hydrogen storage. The work currently is organized into four tasks: hydride development, bed fabrication, materials support for engineering systems, and IEA Annex 12 activities. At the present time, hydride development is focused on Mg alloys. These materials generally have higher weight densities for storing hydrogen than rare earth or transition metal alloys, but suffer from high operating temperatures, slow kinetic behavior and material stability. The authors approach is to study bulk alloy additions which increase equilibrium overpressure, in combination with stable surface alloy modification and particle size control to improve kinetic properties. This work attempts to build on the considerable previous research in this area, but examines specific alloy systems in greater detail, with attention to known phase properties and structures. The authors have found that specific phases can be produced which have significantly improved hydride properties compared to previous studies.

  6. Low density metal hydride foams

    DOEpatents

    Maienschein, Jon L.; Barry, Patrick E.

    1991-01-01

    Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam.

  7. Mineral Commodity Profiles: Selenium

    USGS Publications Warehouse

    Butterman, W.C.; Brown, R.D.

    2004-01-01

    Overview -- Selenium, which is one of the chalcogen elements in group 16 (or 6A) of the periodic table, is a semiconductor that is chemically similar to sulfur for which it substitutes in many minerals and synthetic compounds. It is a byproduct of copper refining and, to a much lesser extent, lead refining. It is used in many applications, the major ones being a decolorizer for glass, a metallurgical additive to free-machining varieties of ferrous and nonferrous alloys, a constituent in cadmium sulfoselenide pigments, a photoreceptor in xerographic copiers, and a semiconductor in electrical rectifiers and photocells. Refined selenium amounting to more than 1,800 metric tons (t) was produced by 14 countries in 2000. Japan, Canada, the United States, and Belgium, which were the four largest producers, accounted for nearly 85 percent of world production. An estimated 250 t of the world total is secondary selenium, which is recovered from scrapped xerographic copier drums and selenium rectifiers; the selenium in nearly all other uses is dissipated (not recoverable as waste or scrap). The present selenium reserve bases for the United States and the world (including the United States), which are associated with copper deposits, are expected to be able to satisfy demand for selenium for several decades without difficulty.

  8. Physics of hydride fueled PWR

    NASA Astrophysics Data System (ADS)

    Ganda, Francesco

    The first part of the work presents the neutronic results of a detailed and comprehensive study of the feasibility of using hydride fuel in pressurized water reactors (PWR). The primary hydride fuel examined is U-ZrH1.6 having 45w/o uranium: two acceptable design approaches were identified: (1) use of erbium as a burnable poison; (2) replacement of a fraction of the ZrH1.6 by thorium hydride along with addition of some IFBA. The replacement of 25 v/o of ZrH 1.6 by ThH2 along with use of IFBA was identified as the preferred design approach as it gives a slight cycle length gain whereas use of erbium burnable poison results in a cycle length penalty. The feasibility of a single recycling plutonium in PWR in the form of U-PuH2-ZrH1.6 has also been assessed. This fuel was found superior to MOX in terms of the TRU fractional transmutation---53% for U-PuH2-ZrH1.6 versus 29% for MOX---and proliferation resistance. A thorough investigation of physics characteristics of hydride fuels has been performed to understand the reasons of the trends in the reactivity coefficients. The second part of this work assessed the feasibility of multi-recycling plutonium in PWR using hydride fuel. It was found that the fertile-free hydride fuel PuH2-ZrH1.6, enables multi-recycling of Pu in PWR an unlimited number of times. This unique feature of hydride fuels is due to the incorporation of a significant fraction of the hydrogen moderator in the fuel, thereby mitigating the effect of spectrum hardening due to coolant voiding accidents. An equivalent oxide fuel PuO2-ZrO2 was investigated as well and found to enable up to 10 recycles. The feasibility of recycling Pu and all the TRU using hydride fuels were investigated as well. It was found that hydride fuels allow recycling of Pu+Np at least 6 times. If it was desired to recycle all the TRU in PWR using hydrides, the number of possible recycles is limited to 3; the limit is imposed by positive large void reactivity feedback.

  9. Bulk Hydrides and Delayed Hydride Cracking in Zirconium Alloys

    NASA Astrophysics Data System (ADS)

    Tulk, Eric F.

    Zirconium alloys are susceptible to engineering problems associated with the uptake of hydrogen throughout their design lifetime in nuclear reactors. Understanding of hydrogen embrittlement associated with the precipitation of brittle hydride phases and a sub-critical crack growth mechanism known as Delayed Hydride Cracking (DHC) is required to provide the engineering justifications for safe reactor operation. The nature of bulk zirconium hydrides at low concentrations (< 100 wt. ppm) is subject to several contradictory descriptions in the literature associated with the stability and metastability of gamma-phase zirconium hydride. Due to the differing volume expansions (12-17%) and crystallography between gamma and delta hydride phases, it is suggested that the matrix yield strength may have an effect on the phase stability. The present work indicated that although yield strength can shift the phase stability, other factors such as microstructure and phase distribution can be as or more important. This suggests that small material differences are the reason for the literature discrepancies. DHC is characterised by the repeated precipitation, growth, fracture of brittle hydride phases and subsequent crack arrest in the ductile metal. DHC growth is associated primarily the ability of hydrogen to diffuse under a stress induced chemical potential towards a stress raiser. Knowledge of the factors controlling DHC are paramount in being able to appropriately describe DHC for engineering purposes. Most studies characterise DHC upon cooling to the test temperature. DHC upon heating has not been extensively studied and the mechanism by which it occurs is somewhat controversial in the literature. This work shows that previous thermo-mechanical processing of hydrided zirconium can have a significant effect on the dissolution behaviour of the bulk hydride upon heating. DHC tests with gamma-quenched, furnace cooled-delta and reoriented bulk hydrides upon heating and DHC upon

  10. Selenium contents of human milk and infant formulas in Spain.

    PubMed

    Torres, M A; Verdoy, J; Alegría, A; Barberá, R; Farré, R; Lagarda, M J

    1999-04-01

    The selenium content of Spanish human milk samples and different milk-based and soy-based infant formulas has been estimated by using a flow injection hydride atomic absorption spectrometric method after microwave digestion of the organic matter. Mean values of 11.4 +/- 3.7 and 10.7 +/- 4.6 ng/ml for colostrum and transitional milk, 8.4 +/- 3.4 and 5.3 +/- 1.9 ng/ml for mature milk at 1 month and up to 2 months respectively, was obtained. These values are close to those reported by others authors in Europe, and lower than the ones from the US, Japan and Korea. Selenium contents of the analyzed infants' formulas ranged from 2.7 to 9.6 ng/ml and from 1.8 to 7.5 ng/ml for soy and milk-based infant formulas, respectively. The variability in selenium contents is large, although mean values are close to the ones given in other European countries. Selenium contents are not usually given on the product. The selenium intakes were estimated assuming that infants fed only human milk. The intakes ranged from 2.0 to 8.4 micrograms/day and from 3.4 to 12.9 micrograms/day for colostrum and transitional milk, respectively, and from 2.6 to 10.3 micrograms/day for mature milk at 1 month, and from 1.2 to 8.3 micrograms/day for milk up to 2 months. The analyzed infant formulas provide significantly less selenium than the 10 micrograms/day corresponding to the recommended daily allowance for infants from 0 to 6 months.

  11. Method and apparatus for regenerating cold traps within liquid-metal systems

    DOEpatents

    McKee, Jr., John M.

    1976-01-01

    Oxide and hydride impurities of a liquid metal such as sodium are removed from a cold trap by heating to a temperature at which the metal hydroxide is stable in a molten state. The partial pressure of hydrogen within the system is measured to determine if excess hydride or oxide is present. Excess hydride is removed by venting hydrogen gas while excess oxide can be converted to molten hydroxide through the addition of hydrogen. The resulting, molten hydroxide is drained from the trap which is then returned to service at cold trap temperatures within the liquid-metal system.

  12. Photochemistry of Transition Metal Hydrides.

    PubMed

    Perutz, Robin N; Procacci, Barbara

    2016-08-10

    Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

  13. Method of producing a chemical hydride

    DOEpatents

    Klingler, Kerry M.; Zollinger, William T.; Wilding, Bruce M.; Bingham, Dennis N.; Wendt, Kraig M.

    2007-11-13

    A method of producing a chemical hydride is described and which includes selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of a hydrocarbon; and reacting the composition with the source of the hydrocarbon to generate a chemical hydride.

  14. Hydrogen, lithium, and lithium hydride production

    DOEpatents

    Brown, Sam W; Spencer, Larry S; Phillips, Michael R; Powell, G. Louis; Campbell, Peggy J

    2014-03-25

    A method of producing high purity lithium metal is provided, where gaseous-phase lithium metal is extracted from lithium hydride and condensed to form solid high purity lithium metal. The high purity lithium metal may be hydrided to provide high purity lithium hydride.

  15. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, Leslie D.

    1982-01-01

    A pressure controlled vanadium hydride gas generator to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  16. Selenium interactions and toxicity: a review. Selenium interactions and toxicity.

    PubMed

    Zwolak, Iwona; Zaporowska, Halina

    2012-02-01

    Selenium is an essential trace element for mammals. Through selenoproteins, this mineral participates in various biological processes such as antioxidant defence, thyroid hormone production, and immune responses. Some reports indicate that a human organism deficient in selenium may be prone to certain diseases. Adverse health effects following selenium overexposure, although very rare, have been found in animals and people. Contrary to selenium, arsenic and cadmium are regarded as toxic elements. Both are environmental and industrial pollutants, and exposure to excessive amounts of arsenic or cadmium can pose a threat to many people's health, especially those living in polluted regions. Two other elements, vanadium and chromium(III) in trace amounts are believed to play essential physiological functions in mammals. This review summarizes recent studies on selenium interactions with arsenic and cadmium and selenium interactions with vanadium and chromium in mammals. Human studies have demonstrated that selenium may reduce arsenic accumulation in the organism and protect against arsenic-related skin lesions. Selenium was found to antagonise the prooxidant and genotoxic effects of arsenic in rodents and cell cultures. Also, studies on selenium effects against oxidative stress induced by cadmium in various animal tissues produced promising results. Reports suggest that selenium protection against toxicity of arsenic and cadmium is mediated via sequestration of these elements into biologically inert conjugates. Selenium-dependent antioxidant enzymes probably play a secondary role in arsenic and cadmium detoxification. So far, few studies have evaluated selenium effects on chromium(III) and vanadium actions in mammals. Still, they show that selenium may interact with these minerals. Taken together, the recent findings regarding selenium interaction with other elements extend our understanding of selenium biological functions and highlight selenium as a potential

  17. Methods of Selenium Supplementation: Bioavailability and Determination of Selenium Compounds.

    PubMed

    Bodnar, Malgorzata; Szczyglowska, Marzena; Konieczka, Piotr; Namiesnik, Jacek

    2016-01-01

    Selenium, a "dual-surface" element, maintains a very thin line between a level of necessity and harmfulness. Because of this, a deficiency or excess of this element in an organism is dangerous and causes health-related problems, both physically and mentally. The main source of selenium is a balanced diet, with a proper selection of meat and plant products. Meanwhile, the proper assimilation of selenium into these products depends on their bioavailability, bioaccessibility, and/or bioactivity of a given selenium compound. From the time when it was discovered that selenium and its compounds have a significant influence on metabolic processes and in many countries throughout the world, a low quantity of selenium was found in different parts of the environment, pressure was put upon an effective and fast method of supplementing the environment with the help of selenium. This work describes supplementation methods applied with the use of selenium, as well as new ideas for increasing the level of this element in various organisms. Based on the fact that selenium appears in the environment at trace levels, the determination of total amount of selenium or selenium speciation in a given sample demands the selection of appropriate measurement methods. These methods are most often comprised of a sample preparation technique and/or a separation technique as well as a detection system. The work presents information on the subject of analytical methods used for determining selenium and its compounds as well as examples in literature of their application.

  18. Selenium: finding the delicate balance

    SciTech Connect

    McBride, J.

    1987-01-01

    A deficiency of selenium can lead to the degeneration of heart muscle in children. Yet, an excess of selenium can produce a garlicky breath, and extreme levels can cause a loss of nails and hair. People get adequate selenium in their diets in North America, but there are areas around the world where the people exist on foods containing little or no selenium. A person is said to be in balance when the daily intake of selenium equals the amount excreted. However, the need for the mineral varies depending on the population, as well as the sex, studied. For example, Chinese men living in a selenium-deficient area need only 10 micrograms a day to maintain their body stores of selenium, whereas US men need 80 micrograms. In addition, there is a difference in how the body treats different forms and sources of selenium. The body absorbs the mineral better from plant sources than from animal sources, in many instances.

  19. Characterization of hydrides and delayed hydride cracking in zirconium alloys

    NASA Astrophysics Data System (ADS)

    Fang, Qiang

    This thesis tries to fill some of the missing gaps in the study of zirconium hydrides with state-of-art experiments, cutting edge tomographical technique, and a novel numerical algorithm. A new hydriding procedure is proposed. The new anode material and solution combination overcomes many drawbacks of the AECLRTM hydriding method and leads to superior hydriding result compared to the AECL RTM hydriding procedure. The DHC crack growth velocity of as-received Excel alloy and Zr-2.5Nb alloy together with several different heat treated Excel alloy samples are measured. While it already known that the DHC crack growth velocity increases with the increase of base metal strength, the finding that the transverse plane is the weaker plane for fatigue crack growth despite having higher resistance to DHC crack growth was unexpected. The morphologies of hydrides in a coarse grained Zircally-2 sample have been studied using synchrotron x-rays at ESRF with a new technique called Diffraction Contrast Tomography that uses simultaneous collection of tomographic data and diffraction data to determine the crystallographic orientation of crystallites (grains) in 3D. It has been previously limited to light metals such as Al or Mg (due to the use of low energy x-rays). Here we show the first DCT measurements using high energy x-rays (60 keV), allowing measurements in zirconium. A new algorithm of a computationally effcient way to characterize distributions of hydrides - in particular their orientation and/or connectivity - has been proposed. It is a modification of the standard Hough transform, which is an extension of the Hough transform widely used in the line detection of EBSD patterns. Finally, a basic model of hydrogen migration is built using ABAQUS RTM, which is a mature finite element package with tested modeling modules of a variety of physical laws. The coupling of hydrogen diffusion, lattice expansion, matrix deformation and phase transformation is investigated under

  20. Properties of nanoscale metal hydrides.

    PubMed

    Fichtner, Maximilian

    2009-05-20

    Nanoscale hydride particles may exhibit chemical stabilities which differ from those of a macroscopic system. The stabilities are mainly influenced by a surface energy term which contains size-dependent values of the surface tension, the molar volume and an additional term which takes into account a potential reduction of the excess surface energy. Thus, the equilibrium of a nanoparticular hydride system may be shifted to the hydrogenated or to the dehydrogenated side, depending on the size and on the prefix of the surface energy term of the hydrogenated and dehydrogenated material. Additional complexity appears when solid-state reactions of complex hydrides are considered and phase segregation has to be taken into account. In such a case the reversibility of complex hydrides may be reduced if the nanoparticles are free standing on a surface. However, it may be enhanced if the system is enclosed by a nanoscale void which prevents the reaction partners on the dehydrogenated side from diffusing away from each other. Moreover, the generally enhanced diffusivity in nanocrystalline systems may lower the kinetic barriers for the material's transformation and, thus, facilitate hydrogen absorption and desorption. PMID:19420657

  1. Selenium for preventing cancer

    PubMed Central

    Vinceti, Marco; Dennert, Gabriele; Crespi, Catherine M; Zwahlen, Marcel; Brinkman, Maree; Zeegers, Maurice PA; Horneber, Markus; D'Amico, Roberto; Del Giovane, Cinzia

    2015-01-01

    Background This review is an update of the first Cochrane publication on selenium for preventing cancer (Dennert 2011). Selenium is a metalloid with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers. Objectives Two research questions were addressed in this review: What is the evidence for: an aetiological relation between selenium exposure and cancer risk in humans? andthe efficacy of selenium supplementation for cancer prevention in humans? Search methods We conducted electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), MEDLINE (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), CancerLit (February 2004) and CCMed (February 2011). As MEDLINE now includes the journals indexed in CancerLit, no further searches were conducted in this database after 2004. Selection criteria We included prospective observational studies (cohort studies including sub-cohort controlled studies and nested case-control studies) and randomised controlled trials (RCTs) with healthy adult participants (18 years of age and older). Data collection and analysis For observational studies, we conducted random effects meta-analyses when five or more studies were retrieved for a specific outcome. For RCTs, we performed random effects meta-analyses when two or more studies were available. The risk of bias in observational studies was assessed using forms adapted from the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies; the criteria specified in the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias in RCTs. Main results We included 55 prospective observational studies (including more than 1,100,000 participants) and eight RCTs (with a total of 44,743 participants). For the observational studies, we found lower cancer incidence (summary odds ratio (OR) 0

  2. Selenium heterostructure solar cells

    NASA Astrophysics Data System (ADS)

    Shaw, R. F.; Ghosh, A. K.

    1980-08-01

    Selenium solar cells with an exposed area efficiency of about 3.72% and an engineering efficiency of 3.04% are reported. Elemental selenium is fused and crystallized on a semipolished iron substrate previously coated with tellurium. CdSe and CdO layers are then formed in one process by reactively sputtering cadmium metal in air at 1.3 Pa for 18 min at an RF power density of 0.5 W/sq cm. A typical photovoltaic cell produced by this technique has an open-circuit voltage of 0.74, a short-circuit current of 8 mA/sq cm, and a fill factor of 0.49 with a sunlight irradiance of 95 mW/sq cm. It is estimated that engineering efficiencies of better than 10% can be achieved with these selenium devices.

  3. Microstructure of surface cerium hydride growth sites

    SciTech Connect

    Brierley, Martin; Knowles, John; Montgomery, Neil; Preuss, Michael

    2014-05-15

    Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

  4. Selenium and Compounds

    Integrated Risk Information System (IRIS)

    Selenium and Compounds ; CASRN 7782 - 49 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  5. Selenium Treatment Technologies

    EPA Science Inventory

    Selenium (Se) is a metalloid that is a dietary requirement in small quantities, but toxic at higher quantities. It also is known to bioaccumulate. In oxic environments, it exists as selenate (+6) and selenite (+4), both of which are soluble. Selenite will sorb more strongly to...

  6. Biomarkers of selenium status

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The essential trace element selenium (Se) has multiple biological activities, which depend on the level of Se intake. Relatively low Se intakes determine the expression of selenoenzymes in which it serves as an essential constituent. Higher intakes have been shown to have anti-tumorigenic potentia...

  7. Rechargeable metal hydrides for spacecraft application

    NASA Technical Reports Server (NTRS)

    Perry, J. L.

    1988-01-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  8. Metal hydride composition and method of making

    DOEpatents

    Congdon, James W.

    1995-01-01

    A dimensionally stable hydride composition and a method for making such a composition. The composition is made by forming particles of a metal hydride into porous granules, mixing the granules with a matrix material, forming the mixture into pellets, and sintering the pellets in the absence of oxygen. The ratio of matrix material to hydride is preferably between approximately 2:1 and 4:1 by volume. The porous structure of the granules accommodates the expansion that occurs when the metal hydride particles absorb hydrogen. The porous matrix allows the flow of hydrogen therethrough to contact the hydride particles, yet supports the granules and contains the hydride fines that result from repeated absorption/desorption cycles.

  9. Reproduction in mallards fed selenium

    USGS Publications Warehouse

    Heinz, G.H.; Hoffman, D.J.; Krynitsky, A.J.; Weller, D.M.G.

    1987-01-01

    Mallards (Anas platyrhynchos) were fed diets containing 1, 5, 10, 25 or 100 ppm selenium as sodium selenite, a diet containing 10 ppm selenium as seleno-DL-methionine or a control diet. There were no effects of 1, 5 or 10 ppm selenium as sodium selenite on either weight or survival of adults or on reproductive success, and there did not appear to be a dose-response relationship at these lower levels. The 100 ppm selenium diet killed 11 of 12 adults; one adult male fed 25 ppm selenium died. Selenium at 25 and 100 ppm caused weight loss in adults. Females fed 25 ppm selenium took longer to begin laying eggs and intervals between eggs were longer than in females in other treatment groups. Hatching success appeared to be reduced in birds fed 10 ppm selenium at selenomethionine, but the reduction was not statistically significant. The survival of ducklings and the mean number of 21-d-old ducklings produced per female were reduced in the 25 ppm selenium as sodium selenite group and the 10 ppm selenium as selenomethionine group. Egg weights were not affected by any selenium treatment, but 25 ppm selenium lowered the Ratcliffe Index. Duckling weights at hatching and at 21 d of age were reduced 28 and 36%, respectively, in birds fed 25 ppm selenium, as compared with controls. Body weights measured on day 21 were lower for ducklings fed 10 ppm selenium as selenomethionine than in some other groups. Selenium in concentrations of 10 and 25 ppm as sodium selenite caused mainly embryotoxic effects, whereas 10 ppm as selenomethionine was more teratogenic, causing hydrocephaly, bill defects, eye defects (microphthalmia and anophthalmia) and foot and toe defects, including ectrodactyly. Selenomethionine was much more readily taken up by mallards and passed into their eggs than was sodium selenite, and a greater proportion of the selenium in the eggs ended up in the white when selenomethionine was fed. Adult males accumulated more selenium than did females, probably because of the

  10. Complex hydrides for hydrogen storage

    DOEpatents

    Zidan, Ragaiy

    2006-08-22

    A hydrogen storage material and process of forming the material is provided in which complex hydrides are combined under conditions of elevated temperatures and/or elevated temperature and pressure with a titanium metal such as titanium butoxide. The resulting fused product exhibits hydrogen desorption kinetics having a first hydrogen release point which occurs at normal atmospheres and at a temperature between 50.degree. C. and 90.degree. C.

  11. Ten degree Kelvin hydride refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1987-01-01

    A compact hydride absorption refrigeration system with few moving parts for 10 Kelvin operation is disclosed and comprises liquid hydrogen producing means in combination with means for solidifying and subliming the liquid hydrogen produced. The liquid hydrogen is sublimed at about 10 Kelvin. By using a symmetrical all hydrogen redundant loop system, a 10 Kelvin refrigeration system can be operated for many years with only a fraction of the power required for prior art systems.

  12. Acute selenium toxicosis in sheep

    SciTech Connect

    Blodgett, D.J.

    1983-01-01

    The toxicity, toxicokinetics, and progressive pathological changes produced by sodium selenite in sheep following parenteral administration were evaluated. In the intramuscular study, the LD/sub 50/ for sodium selenite was 0.7 mg selenium/kg body weight. In the continuous intravenous infusion study, a gradient of tissue selenium/kg body weight with a standard error of 0.035 over a 192 hour observation period. The most evident clinical signs were dyspnea and depression . At necropsy, the most consistent lesions were edematous lungs and pale mottled hearts. Highest tissue selenium concentrations in declining order were found in the liver, kidney, and heart. Four sheep injected intravenously with 0.7 mg selenium/kg body weight survived the 192 hour post-injection observation period. Semilogarithmic plots of blood selenium concentration versus time were triphasic. The ..cap alpha.. and ..gamma.. rate constants of sheep administered a single dose of selenium intravenously were significantly greater than those obtained when sheep were injected intramuscularly with 0.7 mg selenium concentrations was attained with 4, 8, and 12 hour infusions at steady state concentrations of 2500, 3000, and 3500 ppb selenium in the blood. The heart was the target organ of acute selenium toxicosis. A dose-response relationship was observed in the heart with degeneration evident in all hearts and necrosis present in the 2 hearts with the highest concentrations of selenium.

  13. Hydrogen /Hydride/-air secondary battery

    NASA Technical Reports Server (NTRS)

    Sarradin, J.; Bronoel, G.; Percheron-Guegan, A.; Achard, J. C.

    1979-01-01

    The use of metal hydrides as negative electrodes in a hydrogen-air secondary battery seems promising. However, in an unpressurized cell, more stable hydrides that LaNi5H6 must be selected. Partial substitutions of nickel by aluminium or manganese increase the stability of hydrides. Combined with an air reversible electrode, a specific energy close to 100 Wh/kg can be expected.

  14. Inhibited solid propellant composition containing beryllium hydride

    NASA Technical Reports Server (NTRS)

    Thompson, W. W. (Inventor)

    1978-01-01

    An object of this invention is to provide a composition of beryllium hydride and carboxy-terminated polybutadiene which is stable. Another object of this invention is to provide a method for inhibiting the reactivity of beryllium hydride toward carboxy-terminated polybutadiene. It was found that a small amount of lecithin inhibits the reaction of beryllium hydride with the acid groups in carboxy terminated polybutadiene.

  15. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, L.D.

    1980-03-13

    A pressure controlled vanadium hydride gas generator was designed to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  16. Multi-stage hydride-hydrogen compressor

    NASA Astrophysics Data System (ADS)

    Golben, P. M.

    A 4-stage metal hydride/hydrogen compressor that uses low temperature hot water (75 C) as its energy source has been built and tested. The compressor utilizes a new hydride heat exchanger technique that has achieved fast cycling time (with 20 C cooling water) on the order of 1 min. This refinement substantially decreases the size, weight and cost of the unit when compared to previous hydride compressors or even conventional mechanical diaphragm compressors.

  17. Thermodynamic Hydricity of Transition Metal Hydrides.

    PubMed

    Wiedner, Eric S; Chambers, Matthew B; Pitman, Catherine L; Bullock, R Morris; Miller, Alexander J M; Appel, Aaron M

    2016-08-10

    Transition metal hydrides play a critical role in stoichiometric and catalytic transformations. Knowledge of free energies for cleaving metal hydride bonds enables the prediction of chemical reactivity, such as for the bond-forming and bond-breaking events that occur in a catalytic reaction. Thermodynamic hydricity is the free energy required to cleave an M-H bond to generate a hydride ion (H(-)). Three primary methods have been developed for hydricity determination: the hydride transfer method establishes hydride transfer equilibrium with a hydride donor/acceptor pair of known hydricity, the H2 heterolysis method involves measuring the equilibrium of heterolytic cleavage of H2 in the presence of a base, and the potential-pKa method considers stepwise transfer of a proton and two electrons to give a net hydride transfer. Using these methods, over 100 thermodynamic hydricity values for transition metal hydrides have been determined in acetonitrile or water. In acetonitrile, the hydricity of metal hydrides spans a range of more than 50 kcal/mol. Methods for using hydricity values to predict chemical reactivity are also discussed, including organic transformations, the reduction of CO2, and the production and oxidation of hydrogen. PMID:27483171

  18. Fundamental experiments on hydride reorientation in zircaloy

    NASA Astrophysics Data System (ADS)

    Colas, Kimberly B.

    In the current study, an in-situ X-ray diffraction technique using synchrotron radiation was used to follow directly the kinetics of hydride dissolution and precipitation during thermomechanical cycles. This technique was combined with conventional microscopy (optical, SEM and TEM) to gain an overall understanding of the process of hydride reorientation. Thus this part of the study emphasized the time-dependent nature of the process, studying large volume of hydrides in the material. In addition, a micro-diffraction technique was also used to study the spatial distribution of hydrides near stress concentrations. This part of the study emphasized the spatial variation of hydride characteristics such as strain and morphology. Hydrided samples in the shape of tensile dog-bones were used in the time-dependent part of the study. Compact tension specimens were used during the spatial dependence part of the study. The hydride elastic strains from peak shift and size and strain broadening were studied as a function of time for precipitating hydrides. The hydrides precipitate in a very compressed state of stress, as measured by the shift in lattice spacing. As precipitation proceeds the average shift decreases, indicating average stress is reduced, likely due to plastic deformation and morphology changes. When nucleation ends the hydrides follow the zirconium matrix thermal contraction. When stress is applied below the threshold stress for reorientation, hydrides first nucleate in a very compressed state similar to that of unstressed hydrides. After reducing the average strain similarly to unstressed hydrides, the average hydride strain reaches a constant value during cool-down to room temperature. This could be due to a greater ease of deforming the matrix due to the applied far-field strain which would compensate for the strains due to thermal contraction. Finally when hydrides reorient, the average hydride strains become tensile during the first precipitation regime and

  19. Selenium biomineralization for biotechnological applications.

    PubMed

    Nancharaiah, Yarlagadda V; Lens, Piet N L

    2015-06-01

    Selenium (Se) is not only a strategic element in high-tech electronics and an essential trace element in living organisms, but also a potential toxin with low threshold concentrations. Environmental biotechnological applications using bacterial biomineralization have the potential not only to remove selenium from contaminated waters, but also to sequester it in a reusable form. Selenium biomineralization has been observed in phylogenetically diverse microorganisms isolated from pristine and contaminated environments, yet it is one of the most poorly understood biogeochemical processes. Microbial respiration of selenium is unique because the microbial cells are presented with both soluble (SeO(4)(2-) and SeO(3)(2-)) and insoluble (Se(0)) forms of selenium as terminal electron acceptor. Here, we highlight selenium biomineralization and the potential biotechnological uses for it in bioremediation and wastewater treatment. PMID:25908504

  20. Selenium biomineralization for biotechnological applications.

    PubMed

    Nancharaiah, Yarlagadda V; Lens, Piet N L

    2015-06-01

    Selenium (Se) is not only a strategic element in high-tech electronics and an essential trace element in living organisms, but also a potential toxin with low threshold concentrations. Environmental biotechnological applications using bacterial biomineralization have the potential not only to remove selenium from contaminated waters, but also to sequester it in a reusable form. Selenium biomineralization has been observed in phylogenetically diverse microorganisms isolated from pristine and contaminated environments, yet it is one of the most poorly understood biogeochemical processes. Microbial respiration of selenium is unique because the microbial cells are presented with both soluble (SeO(4)(2-) and SeO(3)(2-)) and insoluble (Se(0)) forms of selenium as terminal electron acceptor. Here, we highlight selenium biomineralization and the potential biotechnological uses for it in bioremediation and wastewater treatment.

  1. Selenium for preventing cancer

    PubMed Central

    Vinceti, Marco; Dennert, Gabriele; Crespi, Catherine M; Zwahlen, Marcel; Brinkman, Maree; Zeegers, Maurice PA; Horneber, Markus; D'Amico, Roberto; Del Giovane, Cinzia

    2015-01-01

    Background This review is an update of the first Cochrane publication on selenium for preventing cancer (Dennert 2011). Selenium is a metalloid with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers. Objectives Two research questions were addressed in this review: What is the evidence for: an aetiological relation between selenium exposure and cancer risk in humans? andthe efficacy of selenium supplementation for cancer prevention in humans? Search methods We conducted electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), MEDLINE (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), CancerLit (February 2004) and CCMed (February 2011). As MEDLINE now includes the journals indexed in CancerLit, no further searches were conducted in this database after 2004. Selection criteria We included prospective observational studies (cohort studies including sub-cohort controlled studies and nested case-control studies) and randomised controlled trials (RCTs) with healthy adult participants (18 years of age and older). Data collection and analysis For observational studies, we conducted random effects meta-analyses when five or more studies were retrieved for a specific outcome. For RCTs, we performed random effects meta-analyses when two or more studies were available. The risk of bias in observational studies was assessed using forms adapted from the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies; the criteria specified in the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias in RCTs. Main results We included 55 prospective observational studies (including more than 1,100,000 participants) and eight RCTs (with a total of 44,743 participants). For the observational studies, we found lower cancer incidence (summary odds ratio (OR) 0

  2. Selenium incorporation using recombinant techniques

    SciTech Connect

    Walden, Helen

    2010-04-01

    An overview of techniques for recombinant incorporation of selenium and subsequent purification and crystallization of the resulting labelled protein. Using selenomethionine to phase macromolecular structures is common practice in structure determination, along with the use of selenocysteine. Selenium is consequently the most commonly used heavy atom for MAD. In addition to the well established recombinant techniques for the incorporation of selenium in prokaryal expression systems, there have been recent advances in selenium labelling in eukaryal expression, which will be discussed. Tips and things to consider for the purification and crystallization of seleno-labelled proteins are also included.

  3. Changes in Phase Composition of NaAlH{sub 4}+FeCl{sub 2} Complex Hydride Exposed to Air

    SciTech Connect

    Roupcova, P.; Schneeweiss, O.

    2010-07-13

    Phase composition in AlNaH{sub 4} doped with FeCl{sub 2} was studied by Moessbauer spectroscopy and X-ray diffraction and stabilities in Ar and air were compared. The results show that the hydride disappeared during the exposition to air. The major sodium alanate hydride traps gaseous impurities and transforms to Na{sub 2}CO{sub 3} and Al(OH){sub 3}.

  4. Selenium speciation in flue desulfurization residues.

    PubMed

    Zhong, Liping; Cao, Yan; Li, Wenying; Xie, Kechang; Pan, Wei-Ping

    2011-01-01

    Flue gas from coal combustion contains significant amounts of volatile selenium (Se). The capture of Se in the flue gas desulfurization (FGD) scrubber unit has resulted in a generation of metal-laden residues. It is important to determine Se speciation to understand the environmental impact of its disposal. A simple method has been developed for selective inorganic Se(IV), Se(VI) and organic Se determination in the liquid-phase FGD residues by hydride generation atomic fluorescence spectrometry (AFS). It has been determined that Se(IV), Se(VI) and organic Se can be accurately determined with detection limits (DL) of 0.05, 0.06 and 0.06 microg/L, respectively. The accuracy of the proposed method was evaluated by analyzing the certified reference material, NIST CRM 1632c, and also by analyzing spiked tap-water samples. Analysis indicates that the concentration of Se is high in FGD liquid residues and primarily exists in a reduced state as selenite (Se(IV)). The toxicity of Se(IV) is the strongest of all Se species. Flue gas desulfurization residues pose a serious environmental risk.

  5. Erbium hydride thermal desorption : controlling kinetics.

    SciTech Connect

    Ferrizz, Robert Matthew

    2007-08-01

    Thermal desorption spectroscopy (TDS) is used to study the decomposition kinetics of erbium hydride thin films. The TDS results presented in this report show that hydride film processing parameters directly impact thermal stability. Issues to be addressed include desorption kinetics for dihydrides and trihydrides, and the effect of film growth parameters, loading parameters, and substrate selection on desorption kinetics.

  6. Effective selenium volatilization under aerobic conditions and recovery from the aqueous phase by Pseudomonas stutzeri NT-I.

    PubMed

    Kagami, Tsubasa; Narita, Takanobu; Kuroda, Masashi; Notaguchi, Emi; Yamashita, Mitsuo; Sei, Kazunari; Soda, Satoshi; Ike, Michihiko

    2013-03-01

    Selenium is an important rare metal and its recovery from waste and wastewater is necessary for its sustainable utilization. Microbial selenium volatilization is suitable for selenium recovery from industrial wastewater because volatile selenium can be recovered in recyclable forms free from other chemicals. We found that Pseudomonas stutzeri NT-I can aerobically transform selenate, selenite, and biogenic elemental selenium into dimethyldiselenide as well as dimethylselenide; these were temporarily accumulated in the aqueous phase and then transferred into the gaseous phase. The rate of selenium volatilization using strain NT-I ranged 6.5-7.6 μmol/L/h in flask experiments and was much higher than the rates reported previously for other microbes. The selenium volatilization rate accelerated to 14 μmol/L/h in a jar fermenter. Furthermore, 82% of the selenium volatilized using strain NT-I was recovered with few impurities within 48 h in a simple gas trap with nitric acid, demonstrating that strain NT-I is a promising biocatalyst for selenium recovery through biovolatilization from the aqueous phase.

  7. Zirconium hydride containing explosive composition

    DOEpatents

    Walker, Franklin E.; Wasley, Richard J.

    1981-01-01

    An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a donor additive comprising a non-explosive compound or mixture of non-explosive compounds which when subjected to an energy fluence of 1000 calories/cm.sup.2 or less is capable of releasing free radicals each having a molecular weight between 1 and 120. Exemplary donor additives are dibasic acids, polyamines and metal hydrides.

  8. Direct synthesis of catalyzed hydride compounds

    DOEpatents

    Gross, Karl J.; Majzoub, Eric

    2004-09-21

    A method is disclosed for directly preparing alkali metal aluminum hydrides such as NaAlH.sub.4 and Na.sub.3 AlH.sub.6 from either the alkali metal or its hydride, and aluminum. The hydride thus prepared is doped with a small portion of a transition metal catalyst compound, such as TiCl.sub.3, TiF.sub.3, or a mixture of these materials, in order to render them reversibly hydridable. The process provides for mechanically mixing the dry reagents under an inert atmosphere followed by charging the mixed materials with high pressure hydrogen while heating the mixture to about 125.degree. C. The method is relatively simple and inexpensive and provides reversible hydride compounds which are free of the usual contamination introduced by prior art wet chemical methods.

  9. Automated method for the determination of total arsenic and selenium in natural and drinking water by HG-AAS.

    PubMed

    Pistón, Mariela; Silva, Javier; Pérez-Zambra, Ramiro; Dol, Isabel; Knochen, Moisés

    2012-04-01

    A multicommutated flow system was designed and evaluated for the determination of total arsenic and selenium by Hydride Generation Atomic Absorption Spectrometry (HG-AAS). It was applied to the determination of arsenic and selenium in samples of natural and drinking water. Detection limits were 0.46 and 0.08 μg l(-1) for arsenic and selenium, respectively; sampling frequency was 120 samples h(-1) for arsenic and 160 samples h(-1) for selenium. Linear ranges found were 1.54-10 μg l(-1) (R = 0.999) for arsenic and 0.27-27 μg l(-1) (R = 0.999) for selenium. Accuracy was evaluated by spiking various water samples and using a reference material. Recoveries were in the range 95-116%. Analytical precision (s ( r ) (%), n = 10) was 6% for both elements. Compared with the Standard Methods, APHA, 3114B manual method, the system consumes at least 10 times less sample per determination, and the quantities of acid and reducing agent used are significantly lower with a reduction in the generation of pollutants and waste. As an additional advantage, the system is very fast, efficient and environmentally friendly for monitoring total arsenic and selenium levels in waters.

  10. Toenail selenium as an indicator of selenium intake among middle-aged men in an area with low soil selenium.

    PubMed

    Ovaskainen, M L; Virtamo, J; Alfthan, G; Haukka, J; Pietinen, P; Taylor, P R; Huttunen, J K

    1993-05-01

    Toenail selenium concentration has been proposed as a long-term (6-12 mo) indicator of human selenium status. This study investigated the association between toenail selenium concentration and selenium intake and other dietary factors among 166 urban men aged 55-69 y. The dietary information was collected by food records covering a 6-mo period. Toenail clippings were collected by mail 9-10 mo after food recording. The mean selenium intake from food was 42.5 micrograms/d and the dietary intake was equal to that of users and nonusers of selenium supplements. The mean toenail selenium concentration was 0.47 mg/kg. The mean selenium intake from supplements was 29.7 micrograms/d among supplement users. In the analysis of covariance the best predictors of toenail selenium concentration were selenium intake from supplements and food, and among supplement users dietary beta-carotene also.

  11. Hydrogen-storing hydride complexes

    DOEpatents

    Srinivasan, Sesha S.; Niemann, Michael U.; Goswami, D. Yogi; Stefanakos, Elias K.

    2012-04-10

    A ternary hydrogen storage system having a constant stoichiometric molar ratio of LiNH.sub.2:MgH.sub.2:LiBH.sub.4 of 2:1:1. It was found that the incorporation of MgH.sub.2 particles of approximately 10 nm to 20 nm exhibit a lower initial hydrogen release temperature of 150.degree. C. Furthermore, it is observed that the particle size of LiBNH quaternary hydride has a significant effect on the hydrogen sorption concentration with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160.degree. C. and the other around 300.degree. C., with the main hydrogen release temperature reduced from 310.degree. C. to 270.degree. C., while hydrogen is first reversibly released at temperatures as low as 150.degree. C. with a total hydrogen capacity of 6 wt. % to 8 wt. %. Detailed thermal, capacity, structural and microstructural properties have been demonstrated and correlated with the activation energies of these materials.

  12. A Search for the Optimum Selenium Source to Obtain Mushroom-Derived Chemopreventive Preparations.

    PubMed

    Savic, Milena; Klimaszewska, Marzenna; Bamburowicz-Klimkowska, Magdalena; Suchocki, Piotr; Niksic, Miomir; Szutowski, Miroslaw; Wroczynski, Piotr; Turlo, Jadwiga

    2016-01-01

    The objective of this research was to test whether selenium-yeast (Se-yeast) is a better source of selenium than sodium selenite for accumulation in mycelia and immunoactive cell wall polysaccharides. Culture media were enriched in selenium to a concentration of 20 µg/mL. Selenium was added to the medium either in the form of sodium selenite or in form of Se-yeast (Sel-Plex; Alltech Inc., Lexington, KY). The total selenium concentrations in the mycelium biomass and in the isolated crude polysaccharides were determined using atomic absorption spectroscopy. We found that selenium accumulated more efficiently in cultures enriched with Se-yeast. A higher concentration of selenium was also found in the crude polysaccharide fractions isolated from the mycelium grown in Se-yeast-enriched media. With the use of the needle trap gas chromatography-mass spectrometry method, we found that there are significant differences in the composition of the volatile aroma and flavor compounds secreted by the mycelia cultivated in different media. PMID:27481294

  13. Activated aluminum hydride hydrogen storage compositions and uses thereof

    DOEpatents

    Sandrock, Gary; Reilly, James; Graetz, Jason; Wegrzyn, James E.

    2010-11-23

    In one aspect, the invention relates to activated aluminum hydride hydrogen storage compositions containing aluminum hydride in the presence of, or absence of, hydrogen desorption stimulants. The invention particularly relates to such compositions having one or more hydrogen desorption stimulants selected from metal hydrides and metal aluminum hydrides. In another aspect, the invention relates to methods for generating hydrogen from such hydrogen storage compositions.

  14. Cyclopentadiene-mediated hydride transfer from rhodium complexes.

    PubMed

    Pitman, C L; Finster, O N L; Miller, A J M

    2016-07-12

    Attempts to generate a proposed rhodium hydride catalytic intermediate instead resulted in isolation of (Cp*H)Rh(bpy)Cl (1), a pentamethylcyclopentadiene complex, formed by C-H bond-forming reductive elimination from the fleeting rhodium hydride. The hydride transfer ability of diene 1 was explored through thermochemistry and hydride transfer reactions, including the reduction of NAD(+). PMID:26949917

  15. Liquid suspensions of reversible metal hydrides

    DOEpatents

    Reilly, J.J.; Grohse, E.W.; Winsche, W.E.

    1983-12-08

    The reversibility of the process M + x/2 H/sub 2/ ..-->.. MH/sub x/, where M is a metal hydride former that forms a hydride MH/sub x/ in the presence of H/sub 2/, generally used to store and recall H/sub 2/, is found to proceed under a liquid, thereby to reduce contamination, provide better temperature control and provide in situ mobility of the reactants. Thus, a slurry of particles of a metal hydride former with an inert solvent is subjected to temperature and pressure controlled atmosphere containing H/sub 2/, to store hydrogen (at high pressures) and to release (at low pressures) previously stored hydrogen. The direction of the flow of the H/sub 2/ through the liquid is dependent upon the H/sub 2/ pressure in the gas phase at a given temperature. When the former is above the equilibrium absorption pressure of the respective hydride the reaction proceeds to the right, i.e., the metal hydride is formed and hydrogen is stored in the solid particle. When the H/sub 2/ pressure in the gas phase is below the equilibrium dissociation pressure of the respective hydride the reaction proceeds to the left, the metal hydride is decomposed and hydrogen is released into the gas phase.

  16. Arsenic and Selenium

    NASA Astrophysics Data System (ADS)

    Plant, J. A.; Kinniburgh, D. G.; Smedley, P. L.; Fordyce, F. M.; Klinck, B. A.

    2003-12-01

    Arsenic (As) and selenium (Se) have become increasingly important in environmental geochemistry because of their significance to human health. Their concentrations vary markedly in the environment, partly in relation to geology and partly as a result of human activity. Some of the contamination evident today probably dates back to the first settled civilizations which used metals.Arsenic is in group 15 of the periodic table (Table 1) and is usually described as a metalloid. It has only one stable isotope, 75As. It can exist in the -III, -I, 0, III, and V oxidation states (Table 2).

  17. Hydride heat pump with heat regenerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative hydride heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system. A series of at least four canisters containing a lower temperature performing hydride and a series of at least four canisters containing a higher temperature performing hydride is provided. Each canister contains a heat conductive passageway through which a heat transfer fluid is circulated so that sensible heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  18. Toxicology of selenium: a review.

    PubMed

    Wilber, C G

    1980-09-01

    The concentration of selenium in soil, water, or minerals is site specific. World or regional averages are of little practical value. In one report from the front range area of Colorado, average selenium concentrations in bodies of standing water were from 0.3 to 15.8 micrograms Se per liter of water. In some aquatic organisms there is a strong correlation between the Se content of the water ant that of the body tissues; in others no such correlation obtains. Some organisms bioaccumulate Se by factors as high as 1300 to 3800. In most fish the amount of Se in the flesh seems to depend on the amount in the food taken in; there are exceptions, however. Aquatic organisms from seleniferous regions bioconcentrate selenium so as to reach total body levels of 60 micrograms Se per gram or up to 100 micrograms Se per gram of liver. There seems to be no evidence for "biomagnification" of selenium by aquatic organisms. Selenium exerts a strong protective action against the poisoning effects of many heavy metals (lead, cadmium, arsenic, and mercury, for example) and of some organic toxicants (paraquat, for example) in birds, mammals, and man. Data on man are sketchy. Selenium is released into the environment from the burning of coal. No identifiable hazard to man or to plants and animals useful to man can, at this time, be attributed to this source. Selenium is poisonous to man and animal in large amounts. It is a necessary micronutrient for many animals in small amounts; it may also be a needed micronutrient for man, but the data are sparse. The usual American diet contains adequate selenium for human health. Occupational selenium poisoning is mostly accidental and rare.

  19. Formation and superconductivity of hydrides under pressure

    NASA Astrophysics Data System (ADS)

    Kim, Duck Young; Scheicher, Ralph H.; Pickard, Chris J.; Needs, Richard J.; Ahuja, Rajeev

    2011-03-01

    Hydrogen is the lightest and smallest element in the periodic table. Despite its simplest electronic structure, enormous complexity can arise when hydrogen participates in the formation of solids. Pressure as a controllable parameter can provide an excellent platform to investigate novel physics of hydrides because it can induce structural transformation and even changes in stoichiometry accompanied with phenomena such as metallization and superconductivity. In this presentation, we will briefly overview contemporary high-pressure research on hydrides and show our most recent results on predicting crystal structures of metal hydrides under pressure using ab initio random structure searching. Our findings allow for a better understanding of pressure-induced metallization/superconductivity in hydrides which can help to shed light on recent observations of pressure-induced metallization and superconductivity in hydrogen-rich materials. Wenner-Gren Foundations and VR in Sweden, The Royal Society in UK.

  20. Sealed aerospace metal-hydride batteries

    NASA Technical Reports Server (NTRS)

    Coates, Dwaine

    1992-01-01

    Nickel metal hydride and silver metal hydride batteries are being developed for aerospace applications. There is a growing market for smaller, lower cost satellites which require higher energy density power sources than aerospace nickel-cadmium at a lower cost than space nickel-hydrogen. These include small LEO satellites, tactical military satellites and satellite constellation programs such as Iridium and Brilliant Pebbles. Small satellites typically do not have the spacecraft volume or the budget required for nickel-hydrogen batteries. NiCd's do not have adequate energy density as well as other problems such as overcharge capability and memory effort. Metal hydride batteries provide the ideal solution for these applications. Metal hydride batteries offer a number of advantages over other aerospace battery systems.

  1. Method of forming metal hydride films

    NASA Technical Reports Server (NTRS)

    Steinberg, R.; Alger, D. L.; Cooper, D. W. (Inventor)

    1977-01-01

    The substrate to be coated (which may be of metal, glass or the like) is cleaned, both chemically and by off-sputtering in a vacuum chamber. In an ultra-high vacuum system, vapor deposition by a sublimator or vaporizer coats a cooled shroud disposed around the substrate with a thin film of hydride forming metal which getters any contaminant gas molecules. A shutter is then opened to allow hydride forming metal to be deposited as a film or coating on the substrate. After the hydride forming metal coating is formed, deuterium or other hydrogen isotopes are bled into the vacuum system and diffused into the metal film or coating to form a hydride of metal film. Higher substrate temperatures and pressures may be used if various parameters are appropriately adjusted.

  2. Determination of selenium in serum by FI-HG-AAS and calculation of dietary intake.

    PubMed

    Li, F; Rossipal, E; Micetic-Turk, D

    2000-03-01

    A method was developed for the determination of selenium concentration in serum by flow injection-hydride generation-atomic absorption spectrometry (FI-HG-AAS) following microwave digestion of serum samples and reduction of selenate to selenite. The detection limit of the method was 0.3 microg Se/L and the characteristic concentration, corresponding to the 0.0044 absorbance signal, was 0.12 microg Se/L. The results from the analysis of two Seronorm standard reference materials showed good agreement with the certified values. The method was then used to analyze selenium in sera of Austrian and Slovenian people for the calculation of dietary intakes. The selenium concentrations in sera of mothers at delivery, their neonates, and the male and female adults were 71+/-14, 42+/-6, 75+/-21, and 65+/-16 microg/L for the Austrians and 62+/-15, 34+/-7, 70+/-12, and 66+/-15 microg/L for the Slovenians. The dietary intakes of selenium of the mothers and the male and the female adults were calculated as 52, 37, and 46 microg/d for the Austrians and 45, 38, and 32 microg/d for the Slovenians.

  3. A classical but new kinetic equation for hydride transfer reactions.

    PubMed

    Zhu, Xiao-Qing; Deng, Fei-Huang; Yang, Jin-Dong; Li, Xiu-Tao; Chen, Qiang; Lei, Nan-Ping; Meng, Fan-Kun; Zhao, Xiao-Peng; Han, Su-Hui; Hao, Er-Jun; Mu, Yuan-Yuan

    2013-09-28

    A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions.

  4. Metastable Metal Hydrides for Hydrogen Storage

    DOE PAGES

    Graetz, Jason

    2012-01-01

    The possibility of using hydrogen as a reliable energy carrier for both stationary and mobile applications has gained renewed interest in recent years due to improvements in high temperature fuel cells and a reduction in hydrogen production costs. However, a number of challenges remain and new media are needed that are capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides offer some hope of overcoming these challenges; however, many of the high capacity “reversible” hydrides exhibit a large endothermic decomposition enthalpy making it difficult to release the hydrogen at low temperatures. Onmore » the other hand, the metastable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favorable under ambient conditions. The rapid, low temperature hydrogen evolution rates that can be achieved with these materials offer much promise for mobile PEM fuel cell applications. However, a critical challenge exists to develop new methods to regenerate these hydrides directly from the reactants and hydrogen gas. This spotlight paper presents an overview of some of the metastable metal hydrides for hydrogen storage and a few new approaches being investigated to address the key challenges associated with these materials.« less

  5. Isotopic Fractionation of Selenium Oxyanions in Wetlands

    NASA Astrophysics Data System (ADS)

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

    2004-05-01

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

  6. Selenium semiconductor core optical fibers

    SciTech Connect

    Tang, G. W.; Qian, Q. Peng, K. L.; Wen, X.; Zhou, G. X.; Sun, M.; Chen, X. D.; Yang, Z. M.

    2015-02-15

    Phosphate glass-clad optical fibers containing selenium (Se) semiconductor core were fabricated using a molten core method. The cores were found to be amorphous as evidenced by X-ray diffraction and corroborated by Micro-Raman spectrum. Elemental analysis across the core/clad interface suggests that there is some diffusion of about 3 wt % oxygen in the core region. Phosphate glass-clad crystalline selenium core optical fibers were obtained by a postdrawing annealing process. A two-cm-long crystalline selenium semiconductor core optical fibers, electrically contacted to external circuitry through the fiber end facets, exhibit a three times change in conductivity between dark and illuminated states. Such crystalline selenium semiconductor core optical fibers have promising utility in optical switch and photoconductivity of optical fiber array.

  7. COLD TRAPS

    DOEpatents

    Thompson, W.I.

    1958-09-30

    A cold trap is presented for removing a condensable component from a gas mixture by cooling. It consists of a shell, the exterior surface of which is chilled by a refrigerant, and conductive fins welded inside the shell to condense the gas, and distribute the condensate evenly throughout the length of the trap, so that the trap may function until it becomes completely filled with the condensed solid. The contents may then be removed as either a gas or as a liquid by heating the trap. This device has particuinr use as a means for removing uranium hexafluoride from the gaseous diffusion separation process during equipment breakdown and repair periods.

  8. Optical trapping

    PubMed Central

    Neuman, Keir C.; Block, Steven M.

    2006-01-01

    Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on—and the measurement of nanometer-level displacements of—optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications. PMID:16878180

  9. Selenium status in fibromyalgia.

    PubMed

    Reinhard, P; Schweinsberg, F; Wernet, D; Kötter, I

    1998-08-01

    Fibromyalgia (FM) is a chronic musculoskeletal pain syndrome of unknown etiology. The serum concentration of selenium (Se) was measured in 68 consecutive patients (nine male, mean age: 47 years; 59 female, mean age 49 years) with FM. The age- and sex-matched control group included 97 female healthy blood donors (mean age 46 years). The method is based on high-performance liquid chromatography (HPLC) involving detection of the fluorescent diaminonaphthalene (DAN) derivate of selenite. There was a statistical significant difference (P < 0.05) in serum Se between control (median 77 microg/l; range: 50-118 microg/l) and patients (median 71 microg/l; range: 39-154 microg/l) groups in the region of Tübingen, Germany.

  10. Selenium bioaccessibility and speciation in biofortified Pleurotus mushrooms grown on selenium-rich agricultural residues.

    PubMed

    Bhatia, Poonam; Aureli, Federica; D'Amato, Marilena; Prakash, Ranjana; Cameotra, Swaranjit Singh; Nagaraja, Tejo Prakash; Cubadda, Francesco

    2013-09-01

    Cultivation of saprophytic fungi on selenium-rich substrates can be an effective means to produce selenium-fortified food. Pleurotus florida, an edible species of oyster mushrooms, was grown on wheat straw from the seleniferous belt of Punjab (India) and its potential to mobilize and accumulate selenium from the growth substrate was studied. Selenium concentration in biofortified mushrooms was 800 times higher compared with control samples grown on wheat straw from non selenium-rich areas (141 vs 0.17 μg Se g(-1) dry weight). Seventy-five percent of the selenium was extracted after in vitro simulated gastrointestinal digestion and investigation of the selenium molecular fractions by size exclusion HPLC-ICP-MS revealed that proteins and any other high molecular weight selenium-containing molecule were hydrolyzed to peptides and low molecular weight selenocompounds. Analysis of the gastrointestinal hydrolysates by anion exchange HPLC-ICP-MS showed that the bioaccessible selenium was mainly present as selenomethionine, a good bioavailable source of selenium, which accounted for 73% of the sum of the detected species. This study demonstrates the feasibility of producing selenium-biofortified edible mushrooms using selenium-rich agricultural by-products as growth substrates. The proposed approach can be used to evaluate whether selenium-contaminated plant waste materials harvested from high-selenium areas may be used to produce selenium-biofortified edible mushrooms based on the concentration, bioaccessibility and speciation of selenium in the mushrooms. PMID:23578637

  11. Thin-film metal hydrides.

    PubMed

    Remhof, Arndt; Borgschulte, Andreas

    2008-12-01

    The goal of the medieval alchemist, the chemical transformation of common metals into nobel metals, will forever be a dream. However, key characteristics of metals, such as their electronic band structure and, consequently, their electric, magnetic and optical properties, can be tailored by controlled hydrogen doping. Due to their morphology and well-defined geometry with flat, coplanar surfaces/interfaces, novel phenomena may be observed in thin films. Prominent examples are the eye-catching hydrogen switchable mirror effect, the visualization of solid-state diffusion and the formation of complex surface morphologies. Thin films do not suffer as much from embrittlement and/or decrepitation as bulk materials, allowing the study of cyclic absorption and desorption. Therefore, thin-metal hydride films are used as model systems to study metal-insulator transitions, for high throughput combinatorial research or they may be used as indicator layers to study hydrogen diffusion. They can be found in technological applications as hydrogen sensors, in electrochromic and thermochromic devices. In this review, we discuss the effect of hydrogen loading of thin niobium and yttrium films as archetypical examples of a transition metal and a rare earth metal, respectively. Our focus thereby lies on the hydrogen induced changes of the electronic structure and the morphology of the thin films, their optical properties, the visualization and the control of hydrogen diffusion and on the study of surface phenomena and catalysis.

  12. The nutritional selenium status of healthy Greeks.

    PubMed

    Bratakos, M S; Kanaki, H C; Vasiliou-Waite, A; Ioannou, P V

    1990-02-01

    The nutritional selenium status of apparently healthy Greeks has been assessed by measuring fluorimetrically the selenium content of whole blood, morning urine, hair and finger nails. The means and standard deviations were 165 +/- 33, 25 +/- 7 ng Se ml-1, 416 +/- 86, and 536 +/- 91 ng Se g-1, respectively. No significant difference was found between the selenium content of whole blood, hair and finger nails, but, for morning urine, there was a significant difference between males and females. The young and the elderly have less selenium in these biological materials than other Greeks. Whole blood selenium correlates significantly with morning urine, hair, and finger nail selenium, as does hair and nail selenium of male, female and male + female Greeks. The results are compared with those in the literature and possible explanations for the observations are presented. It is concluded that the selenium status of Greeks is satisfactory.

  13. Production of selenium-72 and arsenic-72

    DOEpatents

    Phillips, Dennis R.

    1993-01-01

    Methods for producing selenium-72, separating it from its daughter isotope arsenic-72, and generating multiple portions of a solution containing arsenic-72 from a reusable parent substance comprised of selenium-72.

  14. Production of selenium-72 and arsenic-72

    DOEpatents

    Phillips, D.R.

    1993-04-20

    Methods are described for producing selenium-72, separating it from its daughter isotope arsenic-72, and generating multiple portions of a solution containing arsenic-72 from a reusable parent substance comprised of selenium-72.

  15. 21 CFR 573.920 - Selenium.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... section, or as selenium yeast, as provided in paragraph (h) of this section. (c) It is added to feed as... months.” (h) Selenium yeast is a dried, non-viable yeast (Saccharomyces cerevisiae) cultivated in a fed-batch fermentation which provides incremental amounts of cane molasses and selenium salts in a...

  16. 21 CFR 573.920 - Selenium.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... section, or as selenium yeast, as provided in paragraph (h) of this section. (c) It is added to feed as... months.” (h) Selenium yeast is a dried, non-viable yeast (Saccharomyces cerevisiae) cultivated in a fed-batch fermentation which provides incremental amounts of cane molasses and selenium salts in a...

  17. 21 CFR 573.920 - Selenium.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... section, or as selenium yeast, as provided in paragraph (h) of this section. (c) It is added to feed as... months.” (h) Selenium yeast is a dried, non-viable yeast (Saccharomyces cerevisiae) cultivated in a fed-batch fermentation which provides incremental amounts of cane molasses and selenium salts in a...

  18. 21 CFR 573.920 - Selenium.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... section, or as selenium yeast, as provided in paragraph (h) of this section. (c) It is added to feed as... months.” (h) Selenium yeast is a dried, non-viable yeast (Saccharomyces cerevisiae) cultivated in a fed-batch fermentation which provides incremental amounts of cane molasses and selenium salts in a...

  19. 21 CFR 573.920 - Selenium.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... section, or as selenium yeast, as provided in paragraph (h) of this section. (c) It is added to feed as... months.” (h) Selenium yeast is a dried, non-viable yeast (Saccharomyces cerevisiae) cultivated in a fed-batch fermentation which provides incremental amounts of cane molasses and selenium salts in a...

  20. Can hydridic-to-protonic hydrogen bonds catalyze hydride transfers in biological systems?

    PubMed

    Marincean, Simona; Jackson, James E

    2010-12-30

    Catalysis of hydride transfer by hydridic-to-protonic hydrogen (HHH) bonding in α-hydroxy carbonyl isomerization reactions was examined computationally in the lithium salts of 7-substituted endo-3-hydroxybicyclo[2.2.1]hept-5-en-2-ones. The barrier for intramolecular hydride transfer in the parent system was calculated to be 17.2 kcal/mol. Traditional proton donors, such as OH and NH(3)(+), stabilized the metal cation-bridged transition state by 1.4 and 3.3 kcal/mol, respectively. Moreover, among the conformers of the OH systems, the one in which the proton donor is able to interact with the migrating hydride (H(m)) has an activation barrier lower by 1.3 and 1.7 kcal/mol than the other possible OH conformers. By contrast, the presence of an electronegative group such as F, which disfavors the migration electronically by opposing development of hydridic charge, destabilizes the hydride migration by 1.5 kcal/mol relative to the epimeric exo system. In both ground and transition states the H(m)···H distance decreased with increasing acidity of the proton donor, reaching a minimum of 1.58 Å at the transition state for NH(3)(+). Both Mulliken and NPA charges show enhancement of negative character of the migrating hydride in the cases in which HHH bonding is possible. PMID:21141894

  1. Selenium Uptake and Volatilization by Marine Algae

    NASA Astrophysics Data System (ADS)

    Luxem, Katja E.; Vriens, Bas; Wagner, Bettina; Behra, Renata; Winkel, Lenny H. E.

    2015-04-01

    Selenium (Se) is an essential trace nutrient for humans. An estimated one half to one billion people worldwide suffer from Se deficiency, which is due to low concentrations and bioavailability of Se in soils where crops are grown. It has been hypothesized that more than half of the atmospheric Se deposition to soils is derived from the marine system, where microorganisms methylate and volatilize Se. Based on model results from the late 1980s, the atmospheric flux of these biogenic volatile Se compounds is around 9 Gt/year, with two thirds coming from the marine biosphere. Algae, fungi, and bacteria are known to methylate Se. Although algal Se uptake, metabolism, and methylation influence the speciation and bioavailability of Se in the oceans, these processes have not been quantified under environmentally relevant conditions and are likely to differ among organisms. Therefore, we are investigating the uptake and methylation of the two main inorganic Se species (selenate and selenite) by three globally relevant microalgae: Phaeocystis globosa, the coccolithophorid Emiliania huxleyi, and the diatom Thalassiosira oceanica. Selenium uptake and methylation were quantified in a batch experiment, where parallel gas-tight microcosms in a climate chamber were coupled to a gas-trapping system. For E. huxleyi, selenite uptake was strongly dependent on aqueous phosphate concentrations, which agrees with prior evidence that selenite uptake by phosphate transporters is a significant Se source for marine algae. Selenate uptake was much lower than selenite uptake. The most important volatile Se compounds produced were dimethyl selenide, dimethyl diselenide, and dimethyl selenyl sulfide. Production rates of volatile Se species were larger with increasing intracellular Se concentration and in the decline phase of the alga. Similar experiments are being carried out with P. globosa and T. oceanica. Our results indicate that marine algae are important for the global cycling of Se

  2. Selenium and inflammatory bowel disease.

    PubMed

    Kudva, Avinash K; Shay, Ashley E; Prabhu, K Sandeep

    2015-07-15

    Dietary intake of the micronutrient selenium is essential for normal immune functions. Selenium is cotranslationally incorporated as the 21st amino acid, selenocysteine, into selenoproteins that function to modulate pathways involved in inflammation. Epidemiological studies have suggested an inverse association between selenium levels and inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis that can potentially progress to colon cancer. However, the underlying mechanisms are not well understood. Here we summarize the current literature on the pathophysiology of IBD, which is multifactorial in origin with unknown etiology. We have focused on a few selenoproteins that mediate gastrointestinal inflammation and activate the host immune response, wherein macrophages play a pivotal role. Changes in cellular oxidative state coupled with altered expression of selenoproteins in macrophages drive the switch from a proinflammatory phenotype to an anti-inflammatory phenotype to efficiently resolve inflammation in the gut and restore epithelial barrier integrity. Such a phenotypic plasticity is accompanied by changes in cytokines, chemokines, and bioactive metabolites, including eicosanoids that not only mitigate inflammation but also partake in restoring gut homeostasis through diverse pathways involving differential regulation of transcription factors such as nuclear factor-κB and peroxisome proliferator-activated receptor-γ. The role of the intestinal microbiome in modulating inflammation and aiding in selenium-dependent resolution of gut injury is highlighted to provide novel insights into the beneficial effects of selenium in IBD.

  3. 49 CFR 173.311 - Metal hydride storage systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Metal hydride storage systems. 173.311 Section 173... systems. The following packing instruction is applicable to transportable UN Metal hydride storage systems... maximum developed pressure not exceeding 25 MPa. Metal hydride storage systems must be...

  4. Generation of selenium-enriched rice with enhanced grain yield, selenium content and bioavailability through fertilisation with selenite.

    PubMed

    Wang, Yu-Dong; Wang, Xu; Wong, Yum-Shing

    2013-12-01

    To fulfill the natural human needs of selenium, selenium biofortification has been carried out in rice (Oryza sativa) in recent years. Despite some improvements have been made, the increase of selenium content in rice was still limited and a large amount of fertilisers are often required, which may cause environmental pullution. In this study, we further improved the selenium biofortification of rice by using less selenium fertilisers (10.5 g selenium/hectare) whereas, largely increasing selenium content in rice grains (up to 51 times vs. control). Furthermore, selenium speciation analysis, in vitro gastrointestinal digestion and antioxidant assays were performed to evaluate the selenium bioaccessibility and bioavailability in selenium-enriched rice grains. The major selenium species found were readily absorbable selenomethionine. Meanwhile, the selenium-enriched rice grains have significantly higher antioxidant bioactivities. In conclusion, this selenium-enriched rice has enormous potential for selenium supplementation in humans. PMID:23870972

  5. Predictors of selenium concentration in human toenails.

    PubMed

    Hunter, D J; Morris, J S; Chute, C G; Kushner, E; Colditz, G A; Stampfer, M J; Speizer, F E; Willett, W C

    1990-07-01

    To assess the validity of the selenium concentration in human toenails as a measure of selenium intake and to determine other correlates of toenail selenium level, the authors examined the predictors of toenail selenium within two subgroups of a large cohort study of US women. Mean toenail selenium was higher among 38 consumers of selenium supplements (0.904 micrograms/g, standard deviation (SD) 0.217) than among 96 nonusers (0.748 micrograms/g, SD 0.149; p less than 0.001), and a dose-response relation was observed among supplement users (Spearman's r = 0.32; p = 0.05). In a second subgroup of 677 women, selenium supplement use was also associated with higher mean toenail selenium (0.906 micrograms/g, SD 0.214, among 18 users and 0.801 micrograms/g, SD 0.148, among 659 nonusers; p = 0.02), and the dose-response relation was also significant (Spearman's r = 0.50; p = 0.03). The geographic variation in toenail selenium levels was consistent with the geographic distribution of selenium in forage crops. Toenail selenium declined with age and was significantly reduced among cigarette smokers (mean = 0.746, SD 0.124, among 146 current smokers and mean = 0.817, SD 0.159, among 311 never smokers; p less than 0.001) but was not materially affected by alcohol consumption. A dietary selenium score calculated from a food frequency questionnaire failed to predict toenail selenium level, demonstrating the suspected inability of diet questionnaires to measure individual selenium intake because of the highly variable selenium composition of different samples of the same food.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Antihydrogen Trapped

    NASA Astrophysics Data System (ADS)

    Bowe[1], Paul

    2011-05-01

    In 2010 the ALPHA collaboration succeeded in trapping antihydrogen atoms for the first time. Stored antihydrogen promises to be a unique tool for making high precision measurements of the structure of this first anti-atom. Achieving this milestone presented several substantial experimental challenges and this talk will describe how they were overcome. The unique design features of the ALPHA apparatus will be explained. These allow a high intensity positron source and an antiproton imaging detector similar to the one used in the ATHENA experiment to be combined with an innovative magnet design of the anti-atom trap. This seeks to minimise the perturbations to trapped charged particles which may cause particle loss and heating. The diagnostic techniques used to measure the diameter, number, density, and temperatures of both plasmas will be presented as will the methods developed to actively compress and cool of both plasma species to sizes and temperatures,, where trapping attempts with a reasonable chance of success can be tried. The results of the successful trapping experiments will be outlined as well as some subsequent experiments to improve the trapping rate and storage time.

  7. Atomistic potentials for palladium-silver hydrides

    NASA Astrophysics Data System (ADS)

    Hale, L. M.; Wong, B. M.; Zimmerman, J. A.; Zhou, X. W.

    2013-06-01

    New embedded-atom method potentials for the ternary palladium-silver-hydrogen system are developed by extending a previously developed palladium-hydrogen potential. The ternary potentials accurately capture the heat of mixing and structural properties associated with solid solution alloys of palladium-silver. Stable hydrides are produced with properties that smoothly transition across the compositions. Additions of silver to palladium are predicted to alter the properties of the hydrides by decreasing the miscibility gap and increasing the likelihood of hydrogen atoms occupying tetrahedral interstitial sites over octahedral interstitial sites.

  8. Selenium uptake by edible oyster mushrooms (Pleurotus sp.) from selenium-hyperaccumulated wheat straw.

    PubMed

    Bhatia, Poonam; Prakash, Ranjana; Prakash, N Tejo

    2013-01-01

    In an effort to produce selenium (Se)-fortifying edible mushrooms, five species of oyster mushroom (Pleurotus sp.), were cultivated on Se-rich wheat straw collected from a seleniferous belt of Punjab, India. Total selenium was analyzed in the selenium hyperaccumulated wheat straw and the fruiting bodies. Significantly high levels (p<0.0001) of Se uptake were observed in fruiting bodies of all mushrooms grown on Se-rich wheat straw. To the best of our knowledge, accumulation and quantification of selenium in mushrooms has hitherto not been reported with substrates naturally enriched with selenium. The results demonstrate the potential of selenium-rich agricultural residues as substrates for production of Se-enriched mushrooms and the ability of different species of oyster mushrooms to absorb and fortify selenium. The study envisages potential use of selenium-rich agricultural residues towards cultivation of Se-enriched mushrooms for application in selenium supplementation or neutraceutical preparations. PMID:23535542

  9. Selenium metabolite levels in human urine after dosing selenium in different chemical forms

    SciTech Connect

    Hasunuma, Ryoichi; Tsuda, Morizo; Ogawa, Tadao; Kawanishi, Yasuhiro

    1993-11-01

    It has been well known that selenium in marine fish such as tuna and swordfish protects the toxicity of methylmercury in vivo. The protective potency might depend on the chemical forms of selenium in the meat of marine fish sebastes and sperm whale. Little has been revealed, however, on the chemical forms of selenium in the meat of these animals or the selenium metabolites in urine, because the amount of the element is very scarce. Urine is the major excretory route for selenium. The chemical forms of urinary selenium may reflect the metabolism of the element. We have developed methodology for analysis of selenium-containing components in human urine. Using this method, we have observed the time courses of excretory levels of urinary selenium components after a single dose of selenium as selenious acid, selenomethionine, trimethylselenonium ion or tuna meat. 14 refs., 6 figs., 1 tab.

  10. Selenium in pregnancy: is selenium an active defective ion against environmental chemical stress?

    PubMed

    Kantola, M; Purkunen, R; Kröger, P; Tooming, A; Juravskaja, J; Pasanen, M; Seppänen, K; Saarikoski, S; Vartiainen, T

    2004-09-01

    Transportation of selenium from mother to fetus and its possible effects on mother's zinc, copper, cadmium, and mercury levels were studied together during the first trimester and at term in 216 mothers. Mothers came from three geographical places with different selenium intakes. The role of selenium as a biomarker for the vital function was estimated by studying the associations between tissue or blood selenium content and placental cytochrome P450 enzyme activities and the newborn's birth weight. Regardless of the selenium intake of the mothers, higher concentrations were found in the cord blood than in mother's blood reflecting active transportation of selenium to the fetus. Active smoking was associated with higher placental selenium concentrations like it is associated with higher placental zinc concentrations. When the cadmium concentrations were high in placenta, as in smokers, the transfer of selenium from blood to placenta was increased, decreasing the selenium levels in blood. On the other hand, the high selenium concentrations in blood were connected to lower cadmium concentrations in placenta also in nonsmokers. Selenium had correlations with copper and zinc. ECOD activity in placental tissue, mercury in mothers' hair, mothers' age, and selenium concentrations in cord blood and placental selenium all seem to have connections with xenobiotic-metabolizing enzymes linked effects among mothers. These data suggest that selenium has an active role in the mother's defense systems against the toxicity of environmental pollutants and the constituents of cigarette smoke.

  11. Selenium speciation in ground water

    SciTech Connect

    Atalay, A.

    1990-07-10

    Selenium toxicity diseases in animals may occur when the intake exceeds 4 mg/kg and selenium deficiency symptoms may occur when dietary intake is less than 0.04 mg/kg. Since the selenium dietary requirement is very close to toxic concentration, it is important to understand the distribution of selenium in the environment. Selenium occurs in four oxidation states (-II, 0, +IV, and +VI) as selenide, elemental selenium, selenite and selenate. Selenate is reported as more soluble and less adsorbed than selenite. Selenate is more easily leached from soils and is the most available form for plants. Increased mobility of Se into the environment via anthropogenic activities, and the potential oxidation-reduction behavior of the element have made it imperative to study the aquatic chemistry of Se. For this purpose, Se species are divided into two different categories: dissolved Se (in material that passes through filters with 0.45 u openings) and particulate Se (in material of particle size > 0.45 mm) typically suspended sediment and other suspended solids. Element and colloidal phase, not truly dissolved, but passing through the filter is deemed to consist of selenium (-2,0). In dissolved state selenium may exist in three of its four oxidation states; Se(-II), Se(+IV), and Se(+VI). Particulate Se may exist in the same oxidation states as dissolved Se and can be found in different phases of the particulate matter. In sediments, Se may be within the organic material, iron and manganese oxides, carbonates or other mineral phases. The actual chemical forms of Se may be adsorbed to or coprecipitated with these phases (primarily selenite, SeO{sub 3}{sup 2{minus}}) and selenate, SeO{sub 4}{sup 2{minus}}. Selenide, Se(-II), can be covalently bound in the organic portion of a sediment. In addition, Se may be found in anoxic sediments as insoluble metal selenide precipitates, an insoluble elemental Se or as ferroselite (FeSe{sub 2}) and Se containing pyrite.

  12. Selenium Content in Seafood in Japan

    PubMed Central

    Yamashita, Yumiko; Yamashita, Michiaki; Iida, Haruka

    2013-01-01

    Selenium is an essential micronutrient for humans, and seafood is one of the major selenium sources, as well as red meat, grains, eggs, chicken, liver and garlic. A substantial proportion of the total amount of selenium is present as selenium containing imidazole compound, selenoneine, in the muscles of ocean fish. In order to characterize the selenium content in seafood, the total selenium levels were measured in the edible portions of commercially important fish and shellfish species. Among the tested edible portions, alfonsino muscle had the highest selenium levels (concentration of 1.27 mg/kg tissue). High levels of selenium (1.20–1.07 mg/kg) were also found in the salted ovary products of mullet and Pacific herring. In other fish muscles, the selenium levels ranged between 0.12 and 0.77 mg/kg tissue. The selenium levels were closely correlated with the mercury levels in the white and red muscles in alfonsino. The selenium content in spleen, blood, hepatopancreas, heart, red muscle, white muscle, brain, ovary and testis ranged between 1.10 and 24.8 mg/kg tissue in alfonsino. PMID:23434904

  13. 1. VIEW OF A PORTION OF THE HYDRIDE PROCESSING LABORATORY. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. VIEW OF A PORTION OF THE HYDRIDE PROCESSING LABORATORY. OPERATIONS IN THE GLOVE BOX IN THE BACKGROUND OF THE PHOTOGRAPH INCLUDED HYDRIDING OF PLUTONIUM AND HYDRIDE SEPARATION. IN THE FOREGROUND, THE VACUUM MONITOR CONTROL PANEL MEASURED TEMPERATURES WITHIN THE GLOVEBOX. THE CENTER CONTROL PANEL REGULATED THE FURNACE INSIDE THE GLOVE BOX USED IN THE HYDRIDING PROCESSES. THIS EQUIPMENT WAS ESSENTIAL TO THE HYDRIDING PROCESS, AS WELL AS OTHER GLOVE BOX OPERATIONS. - Rocky Flats Plant, Plutonium Laboratory, North-central section of industrial area at 79 Drive, Golden, Jefferson County, CO

  14. Selenium requirement of shrimp Penaeus chinensis

    NASA Astrophysics Data System (ADS)

    Tian, Yuchuan; Liu, Fayi

    1993-09-01

    Penaeus chinensis were reared in fibreglass tanks for the study of their selenium requirements. The shrimp were fed semipurified diets containing graded levels of selenium, and weight gains, activities of glutatione peroxidase (GSH-Px) and selenium contents in muscle and hepatopancreas were determined. Weight gain and GSH-Px activity were the highest when the shrimp were fed diet containing 20 mg/kg selenium. Good linear correlation was found between GSH-Px activities and selenium contents in the diets, and the number of healthy shrimp. The experiment showed that 20 mg/kg selenium in the diet is optimal for the shrimp and that GSH-Px activity can be an important biochemical index of the selenium nutrition status of the animal.

  15. Hydridable material for the negative electrode in a nickel-metal hydride storage battery

    DOEpatents

    Knosp, Bernard; Bouet, Jacques; Jordy, Christian; Mimoun, Michel; Gicquel, Daniel

    1997-01-01

    A monophase hydridable material for the negative electrode of a nickel-metal hydride storage battery with a "Lave's phase" structure of hexagonal C14 type (MgZn.sub.2) has the general formula: Zr.sub.1-x Ti.sub.x Ni.sub.a Mn.sub.b Al.sub.c Co.sub.d V.sub.e where ##EQU1##

  16. Radioprotection by metals: Selenium

    NASA Astrophysics Data System (ADS)

    Weiss, J. F.; Srinivasan, V.; Kumar, K. S.; Landauer, M. R.

    The need exists for compounds that will protect individuals from high-dose acute radiation exposure in space and for agents that might be less protective but less toxic and longer acting. Metals and metal derivatives provide a small degree of radioprotection (dose reduction factor <= 1.2 for animal survival after whole-body irradiation). Emphasis is placed here on the radioprotective potential of selenium (Se). Both the inorganic salt, sodium selenite, and the organic Se compound, selenomethionine, enhance the survival of irradiated mice (60Co, 0.2 Gy/min) when injected IP either before (-24 hr and -1 hr) or shortly after (+15 min) radiation exposure. When administered at equitoxic doses (one-fourth LD10; selenomethionine = 4.0 mg/kg Se, sodium selenite = 0.8 mg/kg Se), both drugs enhanced the 30-day survival of mice irradiated at 9 Gy. Survival after 10-Gy exposure was significantly increased only after selenomethionine treatment. An advantage of selenomethionine is lower lethal and behavioral toxicity (locomotor activity depression) compared to sodium selenite, when they are administered at equivalent doses of Se. Sodium selenite administered in combination with WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, enhances the radioprotective effect and reduces the lethal toxicity, but not the behavioral toxicity, of WR-2721. Other studies on radioprotection and protection against chemical carcinogens by different forms of Se are reviewed. As additional animal data and results from human chemoprevention trials become available, consideration also can be given to prolonged administration of Se compounds for protection against long-term radiation effects in space.

  17. Nutrigenetics, Nutrigenomics, and Selenium

    PubMed Central

    Ferguson, Lynnette R.; Karunasinghe, Nishi

    2011-01-01

    Selenium (Se) is an important micronutrient that, as a component of selenoproteins, influences oxidative and inflammatory processes. Its’ levels vary considerably, with different ethnic and geographic population groups showing varied conditions, ranging from frank Se deficiencies to toxic effects. An optimum Se level is essential for the maintenance of homeostasis, and this optimum may vary according to life stage, general state of health, and genotype. Nutrigenetic studies of different Se levels, in the presence of genetic variants in selenoproteins, suggest that an effective dietary Se intake for one individual may be very different from that for others. However, we are just starting to learn the significance of various genes in selenoprotein pathways, functional variants in these, and how to combine such data from genes into pathways, alongside dietary intake or serum levels of Se. Advances in systems biology, genetics, and genomics technologies, including genetic/genomic, epigenetic/epigenomic, transcriptomic, proteomic, and metabolomic information, start to make it feasible to assess a comprehensive spectrum of the biological activity of Se. Such nutrigenomic approaches may prove very sensitive biomarkers of optimal Se status at the individual or population level. The premature cessation of a major human Se intervention trial has led to considerable controversy as to the value of Se supplementation at the population level. New websites provide convenient links to current information on methodologies available for nutrigenetics and nutrigenomics. These new technologies will increasingly become an essential tool in optimizing the level of Se and other micronutrients for optimal health, in individuals and in population groups. However, definitive proof of such effects will require very large collaborative studies, international agreement on study design, and innovative approaches to data analysis. PMID:22303312

  18. Shedding Light on Selenium Biomineralization: Proteins Associated with Bionanominerals ▿

    PubMed Central

    Lenz, Markus; Kolvenbach, Boris; Gygax, Benjamin; Moes, Suzette; Corvini, Philippe F. X.

    2011-01-01

    Selenium-reducing microorganisms produce elemental selenium nanoparticles with particular physicochemical properties due to an associated organic fraction. This study identified high-affinity proteins associated with such bionanominerals and with nonbiogenic elemental selenium. Proteins with an anticipated functional role in selenium reduction, such as a metalloid reductase, were found to be associated with nanoparticles formed by one selenium respirer, Sulfurospirillum barnesii. PMID:21602371

  19. Volatilization of selenium from astragalus plants irrigated with selenium-laden water. Open file report

    SciTech Connect

    MacDonald, D.J.; Lujan, M.J.; Ary, T.S.

    1989-01-01

    Living plants of Astragalus bisulcatus and Atriplex canescens were irrigated with solutions containing selenium to investigate the plants' ability to selectively remove selenium from selenium-contaminated water. The plants were grown from seed in an indoor environment and harvested for analysis at the end of a typical 7-month growing season. Of the total selenium applied to soil in which the plants were grown, only about 1% was incorporated in plant tissues of Astragalus, but approximately 18% of applied selenium was dissipated into the air from the living plants. Atriplex plants did not absorb or dissipate detectable amounts of selenium.

  20. Metal hydride fuel storage and method thereof

    SciTech Connect

    Morse, Jeffrey D.; Jankowski, Alan F.; Yu, Conrad

    2006-10-17

    Disclosed herein is a metal hydride fuel storage cartridge having integrated resistive heaters that can be used in conjunction with fuel cells such as MEMS-based fuel cells. The cartridge is fabricated using micromachining methods and thin/thick film materials synthesis techniques.

  1. Metal hydride fuel storage and method thereof

    DOEpatents

    Morse, Jeffrey D [Martinez, CA; Jankowski, Alan F [Livermore, CA; Yu, Conrad [Antioch, CA

    2009-05-05

    Disclosed herein is a metal hydride fuel storage cartridge having integrated resistive heaters that can be used in conjunction with fuel cells such as MEMS-based fuel cells. The cartridge is fabricated using micromachining methods and thin/thick film materials synthesis techniques.

  2. Trapped Antihydrogen

    NASA Astrophysics Data System (ADS)

    Robicheaux, Francis

    2012-03-01

    Atoms made of a particle and an antiparticle are unstable, usually surviving less than a microsecond. Antihydrogen, the bound state of an antiproton and a positron, is made entirely of antiparticles and is believed to be stable. It is this longevity that holds the promise of precision studies of matter-antimatter symmetry. Low energy (Kelvin scale) antihydrogen has been produced at CERN since 2002. I will describe the experiment which has recently succeeded in trapping antihydrogen in a cryogenic Penning trap for times up to approximately 15 minutes.

  3. Metabolic interrelationships between arsenic and selenium.

    PubMed

    Levander, O A

    1977-08-01

    In 1938, Moxon discovered that arsenic protected against selenium toxicity. Since that time it has been shown that this protective effect of arsenic against selenium poisoning can be demonstrated in many different animal species under a wide variety of conditions. Antagonistic effects between arsenic and selenium have also been noted in teratologic experiments. Early metabolic studies showed that arsenic inhibited the expiration of volatile selenium compounds by rats injected with acutely toxic doses of both elements. This was puzzling since pulmonary excretion had long been regarded as a means by which animals could rid themselves of excess selenium. However, later work demonstrated that arsenic increased the biliary excretion of selenium. Not only did arsenic stimulate the excretion of selenium in the bile, but selenium also stimulated the excretion of arsenic in the bile. This increased biliary excretion of selenium caused by arsenic provides a reasonable rationale for the ability of arsenic to counteract the toxicity of selenium, although the chemical mechanism by which arsenic does this is not certain. The most satisfactory explanation is that these two elements react in the liver to form a detoxication conjugate which is then excreted into the bile. This is consistent with the fact that both arsenic and selenium each increase the biliary excretion of the other. Several other metabolic interactions between arsenic and selenium have been demonstrated in vitro, but their physiological significance is not clear. Although arsenic decreased selenium toxicity under most conditions, there is a pronounced synergistic toxicity between arsenic and two methylated selenium metabolites, trimethylselenonium ion or dimethyl selenide. The ecological consequences of these synergisms are largely unexplored, although it is likely that selenium methylation occurs in the environment. All attempts to promote or prevent selenium deficiency diseases in animals by feeding arsenic have

  4. Evaluation of flushing of a high-selenium backwater channel in the Colorado River

    USGS Publications Warehouse

    Hamilton, S.J.; Holley, K.M.; Buhl, K.J.; Bullard, F.A.; Weston, L.K.; McDonald, S.F.

    2004-01-01

    Concern has been raised that selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The objective of the study was to determine if operation of a water control structure (opened in December 1996) that allowed the Colorado River to flow through a channel area at Walter Walker State Wildlife Area (WWSWA) would reduce selenium and other inorganic elements in water, sediment, aquatic invertebrates, and forage fish. Endangered Colorado pikeminnow were collected and muscle plug samples taken for selenium analysis. Selenium concentrations in filtered water were 21.0 ??g/L in 1995, 23.5 ??g/L in 1996, 2.1 ??g/L in 1997, and 2.1 ??g/L in 1998. Selenium concentrations in sediment cores and sediment traps were 8.5 ??/g in 1995, 8.2 ??g/g in 1996, 4.8 ??g/g in 1997, and 1.1 ??g/g in 1998. Selenium concentrations in aquatic invertebrates were 27.4 ??g/g in 1996, 15.5 ??g/g in 1997, and 4.9 ??g/g in 1998. Selenium concentrations in forage fish were 27.2 ??g/g in 1996, 20.2 ??g/g in 1997, and 8.6 ??g/g in 1998. Selenium concentrations in muscle plugs of Colorado pikeminnow were 9.8 ??g/g in 1995, 9.5 ??g/g in 1996, 9.0 ??g/g in 1997, and 10.3 ??g/g in 1998. Although selenium concentrations in water, sediment, aquatic invertebrates, and forage fish decreased substantially after operation of the water control structure, a corresponding change in Colorado pikeminnow did not seem to occur. Selenium concentrations in muscle plugs decreased with increasing fish total length and weight, did not change between repeat sampling in the same year or recapture in subsequent years, and seemed to be most closely associated with the mean monthly river flow for the March-July period. ?? 2004 Wiley Periodicals, Inc.

  5. Internal correction of spectral interferences and mass bias for selenium metabolism studies using enriched stable isotopes in combination with multiple linear regression.

    PubMed

    Lunøe, Kristoffer; Martínez-Sierra, Justo Giner; Gammelgaard, Bente; Alonso, J Ignacio García

    2012-03-01

    The analytical methodology for the in vivo study of selenium metabolism using two enriched selenium isotopes has been modified, allowing for the internal correction of spectral interferences and mass bias both for total selenium and speciation analysis. The method is based on the combination of an already described dual-isotope procedure with a new data treatment strategy based on multiple linear regression. A metabolic enriched isotope ((77)Se) is given orally to the test subject and a second isotope ((74)Se) is employed for quantification. In our approach, all possible polyatomic interferences occurring in the measurement of the isotope composition of selenium by collision cell quadrupole ICP-MS are taken into account and their relative contribution calculated by multiple linear regression after minimisation of the residuals. As a result, all spectral interferences and mass bias are corrected internally allowing the fast and independent quantification of natural abundance selenium ((nat)Se) and enriched (77)Se. In this sense, the calculation of the tracer/tracee ratio in each sample is straightforward. The method has been applied to study the time-related tissue incorporation of (77)Se in male Wistar rats while maintaining the (nat)Se steady-state conditions. Additionally, metabolically relevant information such as selenoprotein synthesis and selenium elimination in urine could be studied using the proposed methodology. In this case, serum proteins were separated by affinity chromatography while reverse phase was employed for urine metabolites. In both cases, (74)Se was used as a post-column isotope dilution spike. The application of multiple linear regression to the whole chromatogram allowed us to calculate the contribution of bromine hydride, selenium hydride, argon polyatomics and mass bias on the observed selenium isotope patterns. By minimising the square sum of residuals for the whole chromatogram, internal correction of spectral interferences and mass

  6. Selenium and mining in the Powder River Basin, Wyoming: Phase III - a preliminary survey of selenium concentrations in deer mice (Peromyscus maniculatus) livers

    SciTech Connect

    Raisbeck, M.L.; Vance, G.F.; Steward, D.G.

    1995-09-01

    Samples of liver tissue from deer mice trapped on not-yet-mined areas and reclaimed areas at five surface coal mines in the Powder River Basin of northeastern Wyoming were analyzed for selenium. The overall mean concentration of selenium in wet weight liver tissue was 1.685 ppm. The mean value from not-yet-mined areas was 1.437 ppm; the mean value from reclaimed areas was 1.910 ppm (significant at p<0.1016). When one not-yet-mined outlier was removed, significance rose to p<0.0004. Mine-to-mine comparison of samples stratified by type (that is, by not-yet-mined or reclaimed), showed average tissue concentrations from the reclaimed area of Mine 1 were also higher (p<0.0143) then not-yet-mined area samples at Mine 1. No statistically significant differences were found between mines for samples from not-yet-mined areas, and no statistically significant differences were found between Mines 2, 3, 4, and 5 for samples from reclaimed areas. Multiple analysis of variance using the factors: site (mine) and type (not-yet-mined or reclaimed) was not significantly significant (p<0.2115). Simple linear regression showed that selenium concentrations in dry tissue could easily be predicted from wet tissue selenium (r2=0.9775), demonstrating that percent water in the samples was relatively constant. Animal body weight in general was not a predictor for either wet or dry tissue selenium concentrations, but was related to body weight at the higher tissue concentrations of selenium encountered in samples from the reclaimed area at Mine 1. Mouse body weights at Mine 1 were higher on the reclaimed area than mouse body weights from the not-yet-mined area.

  7. High temperature superconductivity in sulfur and selenium hydrides at high pressure

    NASA Astrophysics Data System (ADS)

    Flores-Livas, José A.; Sanna, Antonio; Gross, E. K. U.

    2016-03-01

    Due to its low atomic mass, hydrogen is the most promising element to search for high-temperature phononic superconductors. However, metallic phases of hydrogen are only expected at extreme pressures (400 GPa or higher). The measurement of the record superconducting critical temperature of 203 K in a hydrogen-sulfur compound at 160 GPa of pressure [A.P. Drozdov, M.I. Eremets, I.A. Troyan, arXiv:1412.0460; [cond-mat.supr-con] (2014); A.P. Drozdov, M.I. Eremets, I.A. Troyan, V. Ksenofontov, S.I. Shylin, Nature 525, 73 (2015)], shows that metallization of hydrogen can be reached at significantly lower pressure by inserting it in the matrix of other elements. In this work we investigate the phase diagram and the superconducting properties of the H-S systems by means of minima hopping method for structure prediction and density functional theory for superconductors. We also show that Se-H has a similar phase diagram as its sulfur counterpart as well as high superconducting critical temperature. We predict H3Se to exceed 120 K superconductivity at 100 GPa. We show that both H3Se and H3S, due to the critical temperature and peculiar electronic structure, present rather unusual superconducting properties. Supplementary material in the form of one pdf file available from the Journal web page at: http://dx.doi.org/10.1140/epjb/e2016-70020-0

  8. Selenopeptides and elemental selenium in Thunbergia alata after exposure to selenite: quantification method for elemental selenium.

    PubMed

    Aborode, Fatai Adigun; Raab, Andrea; Foster, Simon; Lombi, Enzo; Maher, William; Krupp, Eva M; Feldmann, Joerg

    2015-07-01

    Three month old Thunbergia alata were exposed for 13 days to 10 μM selenite to determine the biotransformation of selenite in their roots. Selenium in formic acid extracts (80 ± 3%) was present as selenopeptides with Se-S bonds and selenium-PC complexes (selenocysteinyl-2-3-dihydroxypropionyl-glutathione, seleno-phytochelatin2, seleno-di-glutathione). An analytical method using HPLC-ICPMS to detect and quantify elemental selenium in roots of T. alata plants using sodium sulfite to quantitatively transform elemental selenium to selenosulfate was also developed. Elemental selenium was determined as 18 ± 4% of the total selenium in the roots which was equivalent to the selenium not extracted using formic acid extraction. The results are in an agreement with the XAS measurements of the exposed roots which showed no occurrence of selenite or selenate but a mixture of selenocysteine and elemental selenium. PMID:25747595

  9. Chemical Form of Selenium in Naturally Selenium-Rich Lentils (Lens Culinaris L.) From Saskatchewan

    SciTech Connect

    Thavarajah, D.; Vandenberg, A.; George, G.N.; Pickering, I.J.

    2009-06-04

    Lentils (Lens culinaris L.) are a source of many essential dietary components and trace elements for human health. In this study we show that lentils grown in the Canadian prairies are additionally enriched in selenium, an essential micronutrient needed for general well-being, including a healthy immune system and protection against cancer. Selenium K near-edge X-ray absorption spectroscopy (XAS) has been used to examine the selenium biochemistry of two lentil cultivars grown in various locations in Saskatchewan, Canada. We observe significant variations in total selenium concentration with geographic location and cultivar; however, almost all the selenium (86--95%) in these field-grown lentils is present as organic selenium modeled as selenomethionine with a small component (5--14%) as selenate. As the toxicities of certain forms of arsenic and selenium are antagonistic, selenium-rich lentils may have a pivotal role to play in alleviating the chronic arsenic poisoning in Bangladesh.

  10. Selenopeptides and elemental selenium in Thunbergia alata after exposure to selenite: quantification method for elemental selenium.

    PubMed

    Aborode, Fatai Adigun; Raab, Andrea; Foster, Simon; Lombi, Enzo; Maher, William; Krupp, Eva M; Feldmann, Joerg

    2015-07-01

    Three month old Thunbergia alata were exposed for 13 days to 10 μM selenite to determine the biotransformation of selenite in their roots. Selenium in formic acid extracts (80 ± 3%) was present as selenopeptides with Se-S bonds and selenium-PC complexes (selenocysteinyl-2-3-dihydroxypropionyl-glutathione, seleno-phytochelatin2, seleno-di-glutathione). An analytical method using HPLC-ICPMS to detect and quantify elemental selenium in roots of T. alata plants using sodium sulfite to quantitatively transform elemental selenium to selenosulfate was also developed. Elemental selenium was determined as 18 ± 4% of the total selenium in the roots which was equivalent to the selenium not extracted using formic acid extraction. The results are in an agreement with the XAS measurements of the exposed roots which showed no occurrence of selenite or selenate but a mixture of selenocysteine and elemental selenium.

  11. Daily dietary selenium intake and hair selenium content in a high selenium area of Enshi, China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium is essential to humans and is widely distributed within the human body. Its content in blood, urine, hair and nails are important indicators to evaluate Se level in the human body. In China (Shadi, Enschi city), human selenosis of residents is reported to occur in high numbers. In this stud...

  12. High performance amorphous selenium lateral photodetector

    NASA Astrophysics Data System (ADS)

    Abbaszadeh, Shiva; Allec, Nicholas; Karim, Karim S.

    2012-03-01

    Lateral amorphous selenium (a-Se) detectors based on the metal-semiconductor-metal (MSM) device structure have been studied for indirect detector medical imaging applications. These detectors have raised interest due to their simple structure, ease of fabrication, high-speed, low dark current, low capacitance per unit area and better light utilization. The lateral device structure has a benefit that the electrode spacing may be easily controlled to reduce the required bias for a given desired electric field. In indirect conversion x-ray imaging, the scintillator is coupled to the top of the a-Se MSM photodetector, which itself is integrated on top of the thin-film-transistor (TFT) array. The carriers generated at the top surface of the a-Se layer experience a field that is parallel to the surface, and does not initially sweep them away from the surface. Therefore these carriers may recombine or get trapped in surface states and change the field at the surface, which may degrade the performance of the photodetector. In addition, due to the finite width of the electrodes, the fill factor of the device is less than unity. In this study we examine the effect of lateral drift of carriers and the fill factor on the photodetector performance. The impact of field magnitude on the performance is also investigated.

  13. Selenium nanoparticles inhibit Staphylococcus aureus growth.

    PubMed

    Tran, Phong A; Webster, Thomas J

    2011-01-01

    Staphylococcus aureus is a key bacterium commonly found in numerous infections. S. aureus infections are difficult to treat due to their biofilm formation and documented antibiotic resistance. While selenium has been used for a wide range of applications including anticancer applications, the effects of selenium nanoparticles on microorganisms remain largely unknown to date. The objective of this in vitro study was thus to examine the growth of S. aureus in the presence of selenium nanoparticles. Results of this study provided the first evidence of strongly inhibited growth of S. aureus in the presence of selenium nanoparticles after 3, 4, and 5 hours at 7.8, 15.5, and 31 μg/mL. The percentage of live bacteria also decreased in the presence of selenium nanoparticles. Therefore, this study suggests that selenium nanoparticles may be used to effectively prevent and treat S. aureus infections and thus should be further studied for such applications.

  14. Acute toxicity of selenium compounds commonly found in selenium-accumulator plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium (Se) accumulating plants, such as Astragalus spp. and Aster spp., can accumulate up to 8,000 to 13,000 ppm selenium and can cause acute toxicity when consumed by livestock or wildlife. Recent research has shown that much of the selenium in some Se-accumulating plants is stored as selenate ...

  15. Recovering selenium from copper refinery slimes

    NASA Astrophysics Data System (ADS)

    Hyvärinen, Olli; Lindroos, Leo; Yllö, Erkki

    1989-07-01

    The selenium contained within copper refinery slimes may be recovered advantageously by roasting at about 600°C. While roasting in air is inefficient, roasting in a sulfating atmosphere enables practically complete selenium recovery. Based on laboratory tests, a new selenium recovery process was adopted at Outokumpu Copper Refinery. In this process, sulfation is achieved by feeding sulfur dioxide and oxygen into the roasting furnace.

  16. GPX1 Pro198Leu polymorphism and GSTM1 deletion do not affect selenium and mercury status in mildly exposed Amazonian women in an urban population.

    PubMed

    Rocha, Ariana V; Rita Cardoso, Bárbara; Zavarize, Bruna; Almondes, Kaluce; Bordon, Isabella; Hare, Dominic J; Teixeira Favaro, Déborah Inês; Franciscato Cozzolino, Silvia Maria

    2016-11-15

    Mercury is potent toxicant element, but its toxicity can be reduced by forming a complex with selenium for safe excretion. Considering the impact of mercury exposure in the Amazon region and the possible interaction between these two elements, we aimed to assess the effects of Pro198Leu polymorphism to GPX1 and GSTM1 deletion, on mercury levels in a population from Porto Velho, an urban locality in the Brazilian Amazon region. Two hundred women from the capital city of Rondônia state were recruited for this study with 149 deemed suitable to participate. We assessed dietary intake using 24-hour recall. Selenium levels in plasma and erythrocytes were measured using hydride generation quartz tube atomic absorption spectroscopy and total hair mercury using cold vapor atomic absorption spectrometry. Oxidative stress parameters (GPx activity, oxygen radical absorbency capacity [ORAC] and malondialdehyde [MDA]) were also analyzed. All participants were genotyped for Pro198Leu polymorphism and GSTM1 deletion. We observed that this population presented high prevalence of selenium deficiency, and also low levels of mercury, likely due to food habits that did not include selenium-rich food sources or significant consumption of fish (mercury biomagnifiers) regularly. Univariate statistical analysis showed that Pro198Leu and GSTM1 genotypes did not affect selenium and mercury levels in this population. Pro198Leu polymorphism and GSTM1 deletion had no effect on mercury levels in mildly exposed people, suggesting these genetic variants impact mercury levels only in highly exposed populations. PMID:27450956

  17. Removal of selenium from contaminated waters

    SciTech Connect

    Gleason, K.J.; Yu, Jianhan; Wright, J.D.

    1995-12-01

    Selenium, an essential nutrient in minute quantities, is known to be toxic and is a suspected carcinogen at higher concentrations. The toxicity and teratogenicity of selenium to waterfowl present difficulties in disposing of selenium contaminated waters. Included in the U.S. EPA`s list of priority pollutants, selenium is presently the primary water treatment challenge for many West Coast petroleum refineries. Depending on the type of crude oil processed, selenium can be found in refinery process waters at levels up to 5 mg/L with flowrates approaching 1000 gallons per minute. Agricultural drainage waters emanating from irrigated farm lands in the seleniferous areas of the western United States are another major source of selenium contaminated waters. Because of the high mobility of some selenium compounds, they are easily leached from these soils by irrigation water. Within central California alone, there is a current need for the treatment of about 2 million gallons per day of selenium contaminated agricultural drainage water in concentrations approaching 0.5 mg/L. This paper will present an improved process for the removal of selenium from contaminated waters.

  18. Selenium. Nutritional, toxicologic, and clinical aspects

    SciTech Connect

    Fan, A.M.; Kizer, K.W. )

    1990-08-01

    Despite the recent findings of environmental contamination, selenium toxicosis in humans is exceedingly rare in the United States, with the few known cases resulting from industrial accidents and an episode involving the ingestion of superpotent selenium supplements. Chronic selenosis is essentially unheard of in this country because of the typical diversity of the American diet. Nonetheless, because of the growing public interest in selenium as a dietary supplement and the occurrence of environmental selenium contamination, medical practitioners should be familiar with the nutritional, toxicologic, and clinical aspects of this trace element. 53 references.

  19. Selenium supplementation for the preterm Indian neonate.

    PubMed

    Gathwala, Geeta; Aggarwal, Rahul

    2016-01-01

    Deficient antioxidant defenses in preterm infants have been implicated in diseases such as bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, periventricular leukomalacia, and intraventricular hemorrhage. The antioxidant properties of selenium make it important in the nutrition of very low-birth weight (VLBW) infants. Selenium is a component of glutathione peroxidase (GPX), an enzyme that prevents the production of free radicals. Preterm infants have low selenium stores and require supplementation by parenteral and enteral routes. This communiquι reviews the beneficial role that selenium supplementation might play in improving neonatal outcomes. PMID:27350709

  20. Selenium. Nutritional, toxicologic, and clinical aspects.

    PubMed Central

    Fan, A. M.; Kizer, K. W.

    1990-01-01

    Despite the recent findings of environmental contamination, selenium toxicosis in humans is exceedingly rare in the United States, with the few known cases resulting from industrial accidents and an episode involving the ingestion of superpotent selenium supplements. Chronic selenosis is essentially unheard of in this country because of the typical diversity of the American diet. Nonetheless, because of the growing public interest in selenium as a dietary supplement and the occurrence of environmental selenium contamination, medical practitioners should be familiar with the nutritional, toxicologic, and clinical aspects of this trace element. PMID:2219873

  1. Revised reference values for selenium intake.

    PubMed

    Kipp, A P; Strohm, D; Brigelius-Flohé, R; Schomburg, L; Bechthold, A; Leschik-Bonnet, E; Heseker, H

    2015-10-01

    The German, Austrian and Swiss nutrition societies are the joint editors of the 'reference values for nutrient intake'. They have revised the reference values for the intake of selenium and published them in February 2015. The saturation of selenoprotein P (SePP) in plasma is used as a criterion for the derivation of reference values for selenium intake in adults. For persons from selenium-deficient regions (China) SePP saturation was achieved with a daily intake of 49μg of selenium. When using the reference body weights the D-A-CH reference values are based upon, the resulting estimated value for selenium intake is 70μg/day for men and 60μg/day for women. The estimated value for selenium intake for children and adolescents is extrapolated using the estimated value for adults in relation to body weight. For infants aged 0 to under 4 months the estimated value of 10μg/day was derived from the basis of selenium intake via breast milk. For infants aged 4 to under 12 months this estimated value was used and taking into account the differences regarding body weight an estimated value of 15μg/day was derived. For lactating women compared to non-lactating women a higher reference value of 75μg/day is indicated due to the release of selenium with breast milk. The additional selenium requirement for pregnant women is negligible, so that no increased reference value is indicated.

  2. Selenium bioavailability with reference to human nutrition

    SciTech Connect

    Young, V.R.; Nahapetian, A.; Janghorbani, M.

    1982-05-01

    Various aspects of selenium metabolism and nutrition in relation to the question of selenium bioavailability in foods and the diet of man are reviewed. Few published studies exist on selenium metabolism in human subjects, particularly those representative of healthy individuals in the United States. Animal studies reveal that various factors, including the source and chemical form of selenium in foods and feeds, influence selenium bioavailability. However, the quantitative significance of animal assay data for human nutrition is not known. The limited number of published studies in man suggest that the metabolic fate and physiological function of dietary selenite may differ from that of selenomethionine or of food selenium. However, much additional research will be required to establish an adequate picture of the significance of dietary selenium bioavailability in human nutrition and health. Based on initial human experiments carried out at the Massachusetts Institute of Technology, use of stable isotopes of selenium offers promising opportunities for closing the gap of knowledge that now exists concerning the role and significance of factors that determine how the selenium present in foods is used to meet the physiological requirements of the consumer.

  3. METHOD OF FABRICATING A URANIUM-ZIRCONIUM HYDRIDE REACTOR CORE

    DOEpatents

    Weeks, I.F.; Goeddel, W.V.

    1960-03-22

    A method is described of evenly dispersing uranlum metal in a zirconium hydride moderator to produce a fuel element for nuclear reactors. According to the invention enriched uranium hydride and zirconium hydride powders of 200 mesh particle size are thoroughly admixed to form a mixture containing 0.1 to 3% by weight of U/sup 235/ hydride. The mixed powders are placed in a die and pressed at 100 tons per square inch at room temperature. The resultant compacts are heated in a vacuum to 300 deg C, whereby the uranium hydride deoomposes into uranium metal and hydrogen gas. The escaping hydrogen gas forms a porous matrix of zirconium hydride, with uramum metal evenly dispersed therethrough. The advantage of the invention is that the porosity and uranium distribution of the final fuel element can be more closely determined and controlled than was possible using prior methods of producing such fuel ele- ments.

  4. Ambient-temperature trap/release of arsenic by dielectric barrier discharge and its application to ultratrace arsenic determination in surface water followed by atomic fluorescence spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A novel dielectric barrier discharge reactor (DBDR) was utilized to trap/release arsenic coupled to hydride generation atomic fluorescence spectrometry (HGAFS). On the DBD principle, the precise and accurate control of trap/release procedures was fulfilled at ambient temperature, and an analytical m...

  5. Dissipative hydride precipitates in superconducting niobium cavities

    SciTech Connect

    Romanenko, A.; Cooley, L.D.; Ciovati, G.; Wu, G.; /Argonne

    2011-10-01

    We report the first direct observation of the microstructural features exhibiting RF losses at high surface magnetic fields of above 100 mT in field emission free superconducting niobium cavities. The lossy areas were identified by advanced thermometry. Surface investigations using different techniques were carried out on cutout samples from lossy areas and showed the presence of dendritic niobium hydrides. This finding has possible implications to the mechanisms of RF losses in superconducting niobium at all field levels.

  6. Flow in a metal hydride chromatographic column

    SciTech Connect

    Nichols, G.S.

    1990-01-01

    The flow of hydrogen isotopes in a metal hydride chromatographic column is calculated by a one-dimensional finite difference method. The Ergun equation is used to define the gas flow; and equilibrium pressure isotherms are used to define the column holdup. Solid phase loadings are shown to move as a wave front on absorption, but remain more uniform on desorption. 3 refs., 4 figs.

  7. Nickel metal hydride LEO cycle testing

    NASA Technical Reports Server (NTRS)

    Lowery, Eric

    1995-01-01

    The George C. Marshall Space Flight Center is working to characterize aerospace AB5 Nickel Metal Hydride (NiMH) cells. The cells are being evaluated in terms of storage, low earth orbit (LEO) cycling, and response to parametric testing (high rate charge and discharge, charge retention, pulse current ability, etc.). Cells manufactured by Eagle Picher are the subjects of the evaluation. There is speculation that NiMH cells may become direct replacements for current Nickel Cadmium cells in the near future.

  8. How to use the world's scarce selenium resources efficiently to increase the selenium concentration in food

    PubMed Central

    Haug, Anna; Graham, Robin D.; Christophersen, Olav A.; Lyons, Graham H.

    2007-01-01

    The world's rare selenium resources need to be managed carefully. Selenium is extracted as a by-product of copper mining and there are no deposits that can be mined for selenium alone. Selenium has unique properties as a semi-conductor, making it of special value to industry, but it is also an essential nutrient for humans and animals and may promote plant growth and quality. Selenium deficiency is regarded as a major health problem for 0.5 to 1 billion people worldwide, while an even larger number may consume less selenium than required for optimal protection against cancer, cardiovascular diseases and severe infectious diseases including HIV disease. Efficient recycling of selenium is difficult. Selenium is added in some commercial fertilizers, but only a small proportion is taken up by plants and much of the remainder is lost for future utilization. Large biofortification programmes with selenium added to commercial fertilizers may therefore be a fortification method that is too wasteful to be applied to large areas of our planet. Direct addition of selenium compounds to food (process fortification) can be undertaken by the food industry. If selenomethionine is added directly to food, however, oxidation due to heat processing needs to be avoided. New ways to biofortify food products are needed, and it is generally observed that there is less wastage if selenium is added late in the production chain rather than early. On these bases we have proposed adding selenium-enriched, sprouted cereal grain during food processing as an efficient way to introduce this nutrient into deficient diets. Selenium is a non-renewable resource. There is now an enormous wastage of selenium associated with large-scale mining and industrial processing. We recommend that this must be changed and that much of the selenium that is extracted should be stockpiled for use as a nutrient by future generations. PMID:18833333

  9. Producing selenium-enriched eggs and meat to improve the selenium status of the general population.

    PubMed

    Fisinin, Vladimir I; Papazyan, Tigran T; Surai, Peter F

    2009-01-01

    The role of selenium (Se) in human health and diseases has been discussed in detail in several recent reviews, with the main conclusion being that selenium deficiency is recognised as a global problem which urgently needs resolution. Since selenium content in plant-based food depends on its availability from soil, the level of this element in food and feeds varies among regions. In general, eggs and meat are considered to be good sources of selenium in human diet. When considering ways to improve human selenium intake, there are several potential options. These include direct supplementation, soil fertilisation and supplementation of food staples such as flour, and production of functional foods. Analysing recent publications related to functional food production, it is evident that selenium-enriched eggs can be used as an important delivery system of this trace mineral for humans. In particular, developments and commercialisation of organic forms of selenium have initiated a new era in the availability of selenium-enriched products. It has been shown that egg selenium content can easily be manipulated to give increased levels, especially when organic selenium is included in hens' diet at levels that provide 0.3-0.5 mg/kg selenium in the feed. As a result, technology for the production of eggs delivering approximately 50% (30-35 microg) of the human selenium RDA have been developed and successfully tested. Currently companies all over the world market selenium-enriched eggs including the UK, Ireland, Mexico, Columbia, Malaysia, Thailand, Australia, Turkey, Russia and the Ukraine. Prices for enriched eggs vary from country to country, typically being similar to free-range eggs. Selenium-enriched chicken, pork and beef can also be produced when using organic selenium in the diet of poultry and farm animals. The scientific, technological and other advantages and limitations of producing designer/modified eggs as functional foods are discussed in this review.

  10. HYDRIDE-RELATED DEGRADATION OF SNF CLADDING UNDER REPOSITORY CONDITIONS

    SciTech Connect

    K. McCoy

    2000-12-12

    The purpose and scope of this analysis/model report is to analyze the degradation of commercial spent nuclear fuel (CSNF) cladding under repository conditions by the hydride-related metallurgical processes, such as delayed hydride cracking (DHC), hydride reorientation and hydrogen embrittlement, thereby providing a better understanding of the degradation process and clarifying which aspects of the process are known and which need further evaluation and investigation. The intended use is as an input to a more general analysis of cladding degradation.

  11. Density Functional Screening of Metal Hydride Reactions

    NASA Astrophysics Data System (ADS)

    Johnson, Karl; Alapati, Sudhakar; Dai, Bing; Kim, Ki-Chul; Sholl, David

    2008-03-01

    The on-board storage of hydrogen is one of the most vexing problems associated with the development of viable fuel cell vehicles. Hydrides of period 2 or 3 metals can store hydrogen at high gravimetric and volumetric densities. However, existing hydrides either have unacceptable thermodynamics or kinetics. New materials for hydrogen storage are therefore needed. We demonstrate how first principles density functional theory (DFT) can be used to screen potential candidate materials for hydrogen storage. We have used DFT calculations in conjunction with a free energy analysis to screen over a million reactions involving 212 known compounds. This approach has identified several interesting reaction schemes that have not yet been explored experimentally. We have computed the phonon density of states and used this information to predict the van't Hoff plots for some of the most promising candidate reactions identified though our modeling. We have also examined the thermodynamics of thin films and nanoparticles for selected metal hydrides by accounting for the surface energies of the films or nanoparticles.

  12. METAL HYDRIDE HYDROGEN COMPRESSORS: A REVIEW

    SciTech Connect

    Bowman Jr, Robert C; Yartys, Dr. Volodymyr A.; Lototskyy, Dr. Michael V; Pollet, Dr. B.G.

    2014-01-01

    Metal hydride (MH) thermal sorption compression is an efficient and reliable method allowing a conversion of energy from heat into a compressed hydrogen gas. The most important component of such a thermal engine the metal hydride material itself should possess several material features in order to achieve an efficient performance in the hydrogen compression. Apart from the hydrogen storage characteristics important for every solid H storage material (e.g. gravimetric and volumetric efficiency of H storage, hydrogen sorption kinetics and effective thermal conductivity), the thermodynamics of the metal-hydrogen systems is of primary importance resulting in a temperature dependence of the absorption/desorption pressures). Several specific features should be optimized to govern the performance of the MH-compressors including synchronisation of the pressure plateaus for multi-stage compressors, reduction of slope of the isotherms and hysteresis, increase of cycling stability and life time, together with challenges in system design associated with volume expansion of the metal matrix during the hydrogenation. The present review summarises numerous papers and patent literature dealing with MH hydrogen compression technology. The review considers (a) fundamental aspects of materials development with a focus on structure and phase equilibria in the metal-hydrogen systems suitable for the hydrogen compression; and (b) applied aspects, including their consideration from the applied thermodynamic viewpoint, system design features and performances of the metal hydride compressors and major applications.

  13. Selenium content in sulfide ores from the Chalkidiki peninsula, Greece.

    PubMed

    Nicolaidou, A E

    1998-01-01

    Selenium (Se) was assessed in galena, sphalerite, and pyrite samples. These are components of mixed sulfide ores from the Olympias and Madem Lakkos-Mavres Petres deposits and the Skouries porphyry-copper deposit. We used atomic absorption spectroscopy (AAS) with a hydride generator system. The highest concentration of Se (516 ppm) was found in the fine-grained galena at the -135 level of the Olympias deposits. In the Madem Lakkos-Mavres Petres deposit, the highest concentration of Se (33 ppm) was found in the pyrites of the level 30. The concentration of Se in the arsenopyrites and chalcopyrites is lower than the detection limit of the analytical method (< 100 ppb). The concentrated chalcopyrite from the porphyry copper deposit at Skouries exhibits a significant Se content (average 200 ppm) in contrast to the chalcopyrite from the Olympias and the Madem Lakkos-Mavres Petres. Variations in the Se content of the sulfide minerals studied could be caused by redox-pH and/or temperature conditions, as well as by the difference in crystal structure. The Se found in the areas studied may positively affect the environment. Sulfide minerals are oxidized by microorganisms, infiltrate in the soil-water in the form of selenate or selenite ion, and directly or indirectly influence the human organism. PMID:9726790

  14. Selenium content in sulfide ores from the Chalkidiki peninsula, Greece.

    PubMed

    Nicolaidou, A E

    1998-01-01

    Selenium (Se) was assessed in galena, sphalerite, and pyrite samples. These are components of mixed sulfide ores from the Olympias and Madem Lakkos-Mavres Petres deposits and the Skouries porphyry-copper deposit. We used atomic absorption spectroscopy (AAS) with a hydride generator system. The highest concentration of Se (516 ppm) was found in the fine-grained galena at the -135 level of the Olympias deposits. In the Madem Lakkos-Mavres Petres deposit, the highest concentration of Se (33 ppm) was found in the pyrites of the level 30. The concentration of Se in the arsenopyrites and chalcopyrites is lower than the detection limit of the analytical method (< 100 ppb). The concentrated chalcopyrite from the porphyry copper deposit at Skouries exhibits a significant Se content (average 200 ppm) in contrast to the chalcopyrite from the Olympias and the Madem Lakkos-Mavres Petres. Variations in the Se content of the sulfide minerals studied could be caused by redox-pH and/or temperature conditions, as well as by the difference in crystal structure. The Se found in the areas studied may positively affect the environment. Sulfide minerals are oxidized by microorganisms, infiltrate in the soil-water in the form of selenate or selenite ion, and directly or indirectly influence the human organism.

  15. Materials compatibility of hydride storage materials with austenitic stainless steels

    SciTech Connect

    Clark, E.A.

    1992-09-21

    This task evaluated the materials compatibility of LaNi{sub 5-x}Al{sub x} (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

  16. Materials compatibility of hydride storage materials with austenitic stainless steels

    SciTech Connect

    Clark, E.A.

    1992-09-21

    This task evaluated the materials compatibility of LaNi[sub 5-x]Al[sub x] (x= 0.3, 0.75) hydrides and palladium coated kieselguhr with austenitic stainless steel in hydrogen and tritium process environments. Based on observations of retired prototype hydride storage beds and materials exposure testing samples designed for this study, no materials compatibility problem was indicated. Scanning electron microscopy observations of features on stainless steel surfaces after exposure to hydrides are also commonly found on as-received materials before hydriding. These features are caused by either normal heat treating and acid cleaning of stainless steel or reflect the final machining operation.

  17. Fe induced hydride formation in ZrPd2

    SciTech Connect

    Gupta, Michele; Gupta, Raju; Singh, David J

    2008-01-01

    We show via first-principles calculations that the electronic structure of ZrPd{sub 2}, which does not form a hydride, can be modified by partial substitution of Fe for Pd, leading to a material that forms a hydride. We also show that PdZr{sub 2}, which forms a very stable hydride, can also be modified by Fe addition to lower the enthalpy of hydride formation. These results are explained in terms of electronic structure, specifically electronegativity, charge transfer, and s-d bonding, and clearly have implications in the search of new materials for hydrogen storage.

  18. Storing hydrogen in the form of light alloy hydrides

    NASA Technical Reports Server (NTRS)

    Freund, E.; Gillerm, C.

    1981-01-01

    Different hydrides are investigated to find a system with a sufficiently high storage density (at least 3%). The formation of hydrides with light alloys is examined. Reaction kinetics for hydride formation were defined and applied to the systems Mg-Al-H, Mg-Al-Cu-H, Ti-Al-H, Ti-Al-Cu-H, and Ti-Al-Ni-H. Results indicate that the addition of Al destabilizes MgH2 and TiH2 hydrides while having only a limited effect on the storage density.

  19. METHOD AND APPARATUS FOR MAKING URANIUM-HYDRIDE COMPACTS

    DOEpatents

    Wellborn, W.; Armstrong, J.R.

    1959-03-10

    A method and apparatus are presented for making compacts of pyrophoric hydrides in a continuous operation out of contact with air. It is particularly useful for the preparation of a canned compact of uranium hydride possessing high density and purity. The metallic uranium is enclosed in a container, positioned in a die body evacuated and nvert the uranium to the hydride is admitted and the container sealed. Heat is applied to bring about the formation of the hydride, following which compression is used to form the compact sealed in a container ready for use.

  20. Trapped antihydrogen.

    PubMed

    Andresen, G B; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jonsell, S; Jørgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; el Nasr, S Seif; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

    2010-12-01

    Antimatter was first predicted in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 10(14) for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 10(7) antiprotons and 7 × 10(8) positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen. PMID:21085118

  1. Trapped antihydrogen.

    PubMed

    Andresen, G B; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Deller, A; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jonsell, S; Jørgensen, L V; Kurchaninov, L; Madsen, N; Menary, S; Nolan, P; Olchanski, K; Olin, A; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; el Nasr, S Seif; Silveira, D M; So, C; Storey, J W; Thompson, R I; van der Werf, D P; Wurtele, J S; Yamazaki, Y

    2010-12-01

    Antimatter was first predicted in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature's fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 10(14) for the frequency of the 1s-to-2s transition), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 10(7) antiprotons and 7 × 10(8) positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.

  2. VACUUM TRAP

    DOEpatents

    Gordon, H.S.

    1959-09-15

    An improved adsorption vacuum trap for use in vacuum systems was designed. The distinguishing feature is the placement of a plurality of torsionally deformed metallic fins within a vacuum jacket extending from the walls to the central axis so that substantially all gas molecules pass through the jacket will impinge upon the fin surfaces. T fins are heated by direct metallic conduction, thereby ol taining a uniform temperature at the adeorbing surfaces so that essentially all of the condensible impurities from the evacuating gas are removed from the vacuum system.

  3. COLD TRAP

    DOEpatents

    Milleron, N.

    1963-03-12

    An improved linear-flow cold trap is designed for highvacuum applications such as mitigating back migration of diffusion pump oil moiecules. A central pot of liquid nitrogen is nested within and supported by a surrounding, vertical, helical coil of metai sheet, all enveloped by a larger, upright, cylindrical, vacuum vessel. The vertical interstices between successive turns of the coil afford lineal, axial, high-vacuum passages between open mouths at top and bottom of said vessel, while the coil, being cold by virtue of thermal contact of its innermost turn with the nitrogen pot, affords expansive proximate condensation surfaces. (AEC)

  4. Changing selenium nutritional status of Chinese residents

    Technology Transfer Automated Retrieval System (TEKTRAN)

    China has been designated as one of 40 countries deficient in selenium (Se) according to the World Health Organization. Selenium concentrations in hair are commonly used to evaluate the Se level of the human body. Moreover, hair Se concentrations are significantly correlated with Se concentrations ...

  5. Nutritional selenium supplements: product types, quality, and safety.

    PubMed

    Schrauzer, G N

    2001-02-01

    Selenium supplements contain selenium in different chemical forms. In the majority of supplements, the selenium is present as selenomethionine. However, in multivitamin preparations, infant formulas, protein mixes, weight-loss products and animal feed, sodium selenite and sodium selenate are predominantly used. In some products, selenium is present in protein- or amino acid chelated forms; in still others, the form of selenium is not disclosed. Current evidence favors selenomethionine over the other forms of selenium. Extradietary supplementation of selenium at the dosage of 200 micrograms per day is generally considered safe and adequate for an adult of average weight subsisting on the typical American diet.

  6. Distribution of selenium in zebrafish larvae after exposure to organic and inorganic selenium forms.

    PubMed

    Dolgova, N V; Hackett, M J; MacDonald, T C; Nehzati, S; James, A K; Krone, P H; George, G N; Pickering, I J

    2016-03-01

    Selenium is an essential micronutrient for many organisms, and in vertebrates has a variety of roles associated with protection from reactive oxygen species. Over the past two decades there have been conflicting reports upon human health benefits and detriments arising from consumption of selenium dietary supplements. Thus, early studies report a decrease in the incidence of certain types of cancer, whereas subsequent studies did not observe any anti-cancer effect, and adverse effects such as increased risks for type 2 diabetes have been reported. A possible contributing factor may be that different chemical forms of selenium were used in different studies. Using larval stage zebrafish (Danio rerio) as a model organism, we report a comparison of the toxicities and tissue selenium distributions of four different chemical forms of selenium. We find that the organic forms of selenium tested (Se-methyl-l-selenocysteine and l-selenomethionine) show considerably more toxicity than inorganic forms (selenite and selenate), and that this appears to be correlated with the level of bioaccumulation. Despite differences in concentrations, the tissue specific pattern of selenium accumulation was similar for the chemical forms tested; selenium was found to be highly concentrated in pigment (melanin) containing tissues especially for the organic selenium treatments, with lower concentrations in eye lens, yolk sac and heart. These results suggest that pigmented tissues might serve as a storage reservoir for selenium. PMID:26781816

  7. Tumorigenesis, metabolism, speciation, bioavailability, and tissue deposition of selenium in selenium-enriched ramps (Allium tricoccum).

    PubMed

    Whanger, P D; Ip, C; Polan, C E; Uden, P C; Welbaum, G

    2000-11-01

    Ramps (Allium tricoccum) were grown either in a mixture of vermiculite and peat moss or hydroponically with various concentrations of selenium as sodium selenate. The concentrations used were from 30 to 300 mg of selenium/kg of vermiculite-peat moss or from 10 to 120 mg/L in the hydroponic solutions. Levels as high as 784 mg of selenium/kg were obtained in the ramp bulbs when grown with high levels of selenium in the vermiculite-peat moss, and up to 600 mg of selenium/kg was obtained hydroponically. The predominant form of selenium in the ramp bulbs at all concentrations of selenium was Se-methylselenocysteine, with lower amounts of selenate, Se-cystathionine, and glutamyl-Se-methylselenocysteine. There was a approximately 43% reduction in chemically induced mammary tumors when rats were fed a diet with Se-enriched ramps. Dietary Se-enriched ramps for rats did not result in excessive tissue selenium accumulation or undesirable side effects. Bioavailability studies with rats indicated that selenium in ramps was 15-28% more available for regeneration of glutathione peroxidase activity than inorganic selenium as selenite. Therefore, Se-enriched ramps appear to have potential for the reduction of cancer in humans. PMID:11087545

  8. Method of making crack-free zirconium hydride

    DOEpatents

    Sullivan, Richard W.

    1980-01-01

    Crack-free hydrides of zirconium and zirconium-uranium alloys are produced by alloying the zirconium or zirconium-uranium alloy with beryllium, or nickel, or beryllium and scandium, or nickel and scandium, or beryllium and nickel, or beryllium, nickel and scandium and thereafter hydriding.

  9. Metal Hydrides for High-Temperature Power Generation

    DOE PAGES

    Ronnebro, Ewa; Whyatt, Greg A.; Powell, Michael R.; Westman, Matthew P.; Zheng, Feng; Fang, Zhigang Zak

    2015-08-10

    Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES) applications. By using TES with solar technologies, heat can be stored from sun energy to be used later which enables continuous power generation. We are developing a TES technology based on a dual-bed metal hydride system, which has a high-temperature (HT) metal hydride operating reversibly at 600-800°C to generate heat as well as a low-temperature (LT) hydride near room temperature that is used for hydrogen storage during sun hours until there is a need to produce electricity, such as during night time, a cloudy day, ormore » during peak hours. We proceeded from selecting a high-energy density, low-cost HT-hydride based on performance characterization on gram size samples, to scale-up to kilogram quantities and design, fabrication and testing of a 1.5kWh, 200kWh/m3 bench-scale TES prototype based on a HT-bed of titanium hydride and a hydrogen gas storage instead of a LT-hydride. COMSOL Multiphysics was used to make performance predictions for cylindrical hydride beds with varying diameters and thermal conductivities. Based on experimental and modeling results, a bench-scale prototype was designed and fabricated and we successfully showed feasibility to meet or exceed all performance targets.« less

  10. Hydrogen storage in the form of metal hydrides

    NASA Technical Reports Server (NTRS)

    Zwanziger, M. G.; Santana, C. C.; Santos, S. C.

    1984-01-01

    Reversible reactions between hydrogen and such materials as iron/titanium and magnesium/ nickel alloy may provide a means for storing hydrogen fuel. A demonstration model of an iron/titanium hydride storage bed is described. Hydrogen from the hydride storage bed powers a converted gasoline electric generator.

  11. High energy density battery based on complex hydrides

    DOEpatents

    Zidan, Ragaiy

    2016-04-26

    A battery and process of operating a battery system is provided using high hydrogen capacity complex hydrides in an organic non-aqueous solvent that allows the transport of hydride ions such as AlH.sub.4.sup.- and metal ions during respective discharging and charging steps.

  12. Metal Hydrides for High-Temperature Power Generation

    SciTech Connect

    Ronnebro, Ewa; Whyatt, Greg A.; Powell, Michael R.; Westman, Matthew P.; Zheng, Feng; Fang, Zhigang Zak

    2015-08-10

    Metal hydrides can be utilized for hydrogen storage and for thermal energy storage (TES) applications. By using TES with solar technologies, heat can be stored from sun energy to be used later which enables continuous power generation. We are developing a TES technology based on a dual-bed metal hydride system, which has a high-temperature (HT) metal hydride operating reversibly at 600-800°C to generate heat as well as a low-temperature (LT) hydride near room temperature that is used for hydrogen storage during sun hours until there is a need to produce electricity, such as during night time, a cloudy day, or during peak hours. We proceeded from selecting a high-energy density, low-cost HT-hydride based on performance characterization on gram size samples, to scale-up to kilogram quantities and design, fabrication and testing of a 1.5kWh, 200kWh/m3 bench-scale TES prototype based on a HT-bed of titanium hydride and a hydrogen gas storage instead of a LT-hydride. COMSOL Multiphysics was used to make performance predictions for cylindrical hydride beds with varying diameters and thermal conductivities. Based on experimental and modeling results, a bench-scale prototype was designed and fabricated and we successfully showed feasibility to meet or exceed all performance targets.

  13. Selenium and its redox speciation in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores.

    PubMed

    De, Gregori Ida; Lobos, Maria G; Pinochet, Hugo

    2002-01-01

    The determination of the total concentration of selenium does not provide sufficient information about its toxicity and its bioavailability. The determination of its chemical forms is the basis for understanding the biogeochemical cycle in terrestrial and aquatic ecosystems and for detecting the species which might be toxic to biota. In this work we describe an analytical procedure to carry out the redox speciation of selenium present at ultratrace levels in rainwater from sites of Valparaiso region in Chile, impacted by mining activities of copper ores. A simple preconcentration step of the rainwater sample on a rotavapor system, in vacuum at low temperature permits the concentration of the different redox selenium species until levels quantifiable by sensitive techniques such as differential pulse cathodic stripping voltammetry or by spectrometric techniques, based on the hydride generation and detection by atomic absorption or atomic fluorescence spectrometry. These techniques coupled to redox chemical reactions allow the redox speciation of selenium. The results show that the open evaporation system can be used to concentrate water samples when the aim of the analysis is the determination of the total selenium concentration. On the contrary, to carry out its redox speciation only the preconcentration performed on rotavapor system, in vacuum can be used. When synthetic solutions containing different redox species of selenium, at ultratrace levels, were slowly evaporated on open system, Se(II) and Se(IV) were oxidized. The optimized procedure was then applied to the selenium determination and its redox speciation in rainwater samples collected in sites impacted by mining activities of copper ores. It was found that the amounts of total selenium in rainwater, as copper, from Puchuncavi valley decrease exponentially with the distance from the source, indicating that these elements in this region arise from the industrial complex Las Ventanas. In the redox

  14. Blood selenium levels and contribution of food groups to selenium intake in adolescent girls in Iceland

    PubMed Central

    Gudmundsdottir, Edda Y.; Gunnarsdottir, Ingibjorg; Thorlacius, Arngrimur; Reykdal, Olafur; Gunnlaugsdottir, Helga; Thorsdottir, Inga; Steingrimsdottir, Laufey

    2012-01-01

    Background/objectives Significant changes have been reported in dietary habits and food availability in Iceland that would be expected to compromise selenium intake and status, especially among young people. These include substantial decreases in the consumption of fish and milk, as well as the selenium content of imported wheat. The aim of this study was to assess selenium in the diet and whole blood of adolescent girls, as well as define the most important foods contributing to intake and blood concentrations of selenium. Design The subjects were 96 randomly selected girls, aged 16–20, who answered a validated food frequency questionnaire (FFQ) for dietary assessment. Selenium intake from each food group was calculated in µg/day. Blood samples were collected for measurement of whole blood selenium. Results Mean dietary selenium was 51±25 µg/day. Milk/dairy products, including cheese, contributed 36±14% of total dietary selenium; fish 18±12%; and bread/cereal products 13±6%. Mean whole blood selenium was 117±12 µg/l (range 90–208); nearly 90% of subjects were above the optimal level of 100 µg/l. Fish and bread/cereal products were the only foods significantly correlated with selenium in blood (r=0.32; P=0.002 and r=0.22; P=0.04, respectively) while no correlation was found with milk and dairy products in spite of their greater contribution to total selenium intake. Conclusion In this population of Icelandic adolescent girls, selenium intake and status seem acceptable. Judging from associations between intake and blood levels, fish and cereals may be the most important contributors to blood selenium. PMID:22952457

  15. AC electrokinetic manipulation of selenium nanoparticles for potential nanosensor applications

    SciTech Connect

    Mahmoodi, Seyed Reza; Bayati, Marzieh; Hosseinirad, Somayeh; Foroumadi, Alireza; Gilani, Kambiz; Rezayat, Seyed Mahdi

    2013-03-15

    Highlights: ► Se nanoparticles were synthesized using a reverse-microemulsion process. ► AC osmotic fluid flow repulses the particles from electrode edges. ► Dielectrophoretic force attracts the particles to electrode edges. ► Dielectrophoresis electrode showed non-ohmic behavior. ► The device can potentially be used as a nanosensor. - Abstract: We report the AC electrokinetic behavior of selenium (Se) nanoparticles for electrical characterization and possible application as micro/nano devices. selenium Se nanoparticles were successfully synthesized using a reverse-microemulsion process and investigated structurally using X-ray diffraction and transmission electron microscope. Interdigitated castellated ITO and non-castellated platinum electrodes were employed for manipulation of suspended materials in the fluid. Using ITO electrodes at low frequency limits resulted in deposition of Se particles on electrode surface. When Se particles exposed to platinum electrodes in the 10 Hz–1 kHz range and V {sub p−p}> 8, AC osmotic fluid flow repulses the particles from electrode edges. However, in 10 kHz–10 MHz range and V {sub p−p}> 5, dielectrophoretic force attracts the particles to electrode edges. As the Se particle concentration increased, the trapped Se particles were aligned along the electric field line and bridged the electrode gap. The device was characterized and can potentially be useful in making micro/nano electronic devices.

  16. Modular hydride beds for mobile applications

    SciTech Connect

    Malinowski, M.E.; Stewart, K.D.

    1997-08-01

    Design, construction, initial testing and simple thermal modeling of modular, metal hydride beds have been completed. Originally designed for supplying hydrogen to a fuel cell on a mobile vehicle, the complete bed design consists of 8 modules and is intended for use on the Palm Desert Vehicle (PDV) under development at the Schatz Energy Center, Humbolt State University. Each module contains approximately 2 kg of a commercially available, low temperature, hydride-forming metal alloy. Waste heat from the fuel cell in the form of heated water is used to desorb hydrogen from the alloy for supplying feed hydrogen to the fuel cell. In order to help determine the performance of such a modular bed system, six modules were constructed and tested. The design and construction of the modules is described in detail. Initial testing of the modules both individually and as a group showed that each module can store {approximately} 30 g of hydrogen (at 165 PSIA fill pressure, 17 C), could be filled with hydrogen in 6 minutes at a nominal, 75 standard liters/min (slm) fueling rate, and could supply hydrogen during desorption at rates of 25 slm, the maximum anticipated hydrogen fuel cell input requirement. Tests made of 5 modules as a group indicated that the behavior of the group run in parallel both in fueling and gas delivery could be directly predicted from the corresponding, single module characteristics by using an appropriate scaling factor. Simple thermal modeling of a module as an array of cylindrical, hydride-filled tubes was performed. The predictions of the model are in good agreement with experimental data.

  17. Selenium in Cattle: A Review.

    PubMed

    Mehdi, Youcef; Dufrasne, Isabelle

    2016-01-01

    This review article examines the role of selenium (Se) and the effects of Se supplementation especially in the bovine species. Selenium is an important trace element in cattle. Some of its roles include the participation in the antioxidant defense the cattle farms. The nutritional requirements of Se in cattle are estimated at 100 μg/kg DM (dry matter) for beef cattle and at 300 μg/kg DM for dairy cows. The rations high in fermentable carbohydrates, nitrates, sulfates, calcium or hydrogen cyanide negatively influence the organism's use of the selenium contained in the diet. The Se supplementation may reduce the incidence of metritis and ovarian cysts during the postpartum period. The increase in fertility when adding Se is attributed to the reduction of the embryonic death during the first month of gestation. A use of organic Se in feed would provide a better transfer of Se in calves relative to mineral Se supplementation. The addition of Se yeasts in the foodstuffs of cows significantly increases the Se content and the percentage of polyunsaturated fatty acids (PUFA) in milk compared to the addition of sodium selenite. The enzyme 5-iodothyronine deiodinase is a seleno-dependent selenoprotein. It is one of the last proteins to be affected in the event of Se deficiency. This delay in response could explain the fact that several studies did not show the effect of Se supplementation on growth and weight gain of calves. Enrichment of Se in the diet did not significantly affect the slaughter weight and carcass yield of bulls. The impact and results of Se supplementation in cattle depend on physiological stage, Se status of animals, type and content of Se and types of Se administration. Further studies in Se supplementation should investigate the speciation of Se in food and yeasts, as well as understanding their metabolism and absorption. This constitute a path to exploit in order to explain certain different effects of Se. PMID:27120589

  18. Highly Concentrated Palladium Hydrides/Deuterides; Theory

    SciTech Connect

    Papaconstantopoulos, Dimitrios

    2013-11-26

    Accomplishments are reported in these areas: tight-binding molecular dynamics study of palladium; First-principles calculations and tight-binding molecular dynamics simulations of the palladium-hydrogen system; tight-binding studies of bulk properties and hydrogen vacancies in KBH{sub 4}; tight-binding study of boron structures; development of angular dependent potentials for Pd-H; and density functional and tight-binding calculations for the light-hydrides NaAlH4 and NaBH4

  19. Metal hydride fuel storage and method thereof

    DOEpatents

    Morse, Jeffrey D.; Jankowski, Alan F.; Yu, Conrad

    2010-08-10

    An apparatus having a first substrate having (1) a cavity, (2) one or more resistive heaters, and (3) one or more coatings forming a diffusion barrier to hydrogen; a second substrate having (1) an outlet valve comprising a pressure relief structure and (2) one or more coatings forming a diffusion barrier to hydrogen, wherein said second substrate is coupled to said first substrate forming a sealed volume in said cavity; a metal hydride material contained within said cavity; and a gas distribution system formed by coupling a microfluidic interconnect to said pressure relief structure. Additional apparatuses and methods are also disclosed.

  20. Development of nickel-metal hydride cell

    NASA Technical Reports Server (NTRS)

    Kuwajima, Saburo; Kamimori, Nolimits; Nakatani, Kensuke; Yano, Yoshiaki

    1993-01-01

    National Space Development Agency of Japan (NASDA) has conducted the research and development (R&D) of battery cells for space use. A new R&D program about a Nickel-Metal Hydride (Ni-MH) cell for space use from this year, based on good results in evaluations of commercial Ni-MH cells in Tsukuba Space Center (TKSC), was started. The results of those commercial Ni-MH cell's evaluations and recent status about the development of Ni-MH cells for space use are described.

  1. Metal hydrides for concentrating solar thermal power energy storage

    NASA Astrophysics Data System (ADS)

    Sheppard, D. A.; Paskevicius, M.; Humphries, T. D.; Felderhoff, M.; Capurso, G.; Bellosta von Colbe, J.; Dornheim, M.; Klassen, T.; Ward, P. A.; Teprovich, J. A.; Corgnale, C.; Zidan, R.; Grant, D. M.; Buckley, C. E.

    2016-04-01

    The development of alternative methods for thermal energy storage is important for improving the efficiency and decreasing the cost of concentrating solar thermal power. We focus on the underlying technology that allows metal hydrides to function as thermal energy storage (TES) systems and highlight the current state-of-the-art materials that can operate at temperatures as low as room temperature and as high as 1100 °C. The potential of metal hydrides for thermal storage is explored, while current knowledge gaps about hydride properties, such as hydride thermodynamics, intrinsic kinetics and cyclic stability, are identified. The engineering challenges associated with utilising metal hydrides for high-temperature TES are also addressed.

  2. Porous metal hydride composite and preparation and uses thereof

    DOEpatents

    Steyert, W.A.; Olsen, C.E.

    1980-03-12

    A composite formed from large pieces of aggregate formed from (1) metal hydride (or hydride-former) powder and (2) either metal powder or plastic powder or both is prepared. The composite has large macroscopic interconnected pores (much larger than the sizes of the powders which are used) and will have a very fast heat transfer rate and low windage loss. It will be useful, for example, in heat engines, hydrogen storage devices, and refrigerator components which depend for their utility upon both a fast rate of hydriding and dehydriding. Additionally, a method of preparing the composite and a method of increasing the rates of hydriding and dehydriding of metal hydrides are also given.

  3. Porous metal hydride composite and preparation and uses thereof

    DOEpatents

    Steyert, William A.; Olsen, Clayton E.

    1982-01-01

    A composite formed from large pieces of aggregate formed from (1) metal hydride (or hydride-former) powder and (2) either metal powder or plastic powder or both is prepared. The composite has large macroscopic interconnected pores (much larger than the sizes of the powders which are used) and will have a very fast heat transfer rate and low windage loss. It will be useful, for example, in heat engines, hydrogen storage devices, and refrigerator components which depend for their utility upon both a fast rate of hydriding and dehydriding. Additionally, a method of preparing the composite and a method of increasing the rates of hydriding and dehydriding of metal hydrides are also given.

  4. Recent advances in metal hydrides for clean energy applications

    SciTech Connect

    Ronnebro, Ewa; Majzoub, Eric H.

    2013-06-01

    Metal hydrides are a fascinating class of materials that can be utilized for a surprising variety of clean energy applications, including smart solar collectors, smart windows, sensors, thermal energy storage, and batteries, in addition to their traditional application for hydrogen storage. Over the past decade, research on metal hydrides for hydrogen storage increased due to global governmental incentives and an increased focus on hydrogen storage research for polymer electrolyte membrane fuel cell operation. Tremendous progress has been made in so-called complex metal hydrides for hydrogen storage applications with the discovery of many new hydrides containing covalently bound complex anions. Many of these materials have applications beyond hydrogen storage and are being investigated for lithium-ion battery separator and anode materials. In this issue of MRS Bulletin , we present the state of the art of key evolving metal-hydride-based clean energy technologies with an outlook toward future needs.

  5. A metallomics approach discovers selenium-containing proteins in selenium-enriched soybean.

    PubMed

    Chan, Qilin; Caruso, Joseph A

    2012-05-01

    Our previous study found that high-molecular-weight selenium (Se) species make up 82% of the total Se in the bean of Se-enriched soybean plants (Chan et al. 2010, Metallomics, 2(2): p. 147-153). The Se species have been commonly seen in other plants in addition to soybean, but their identities remain unresolved. The present study employs a multi-technique metallomics approach to characterize the proteins containing Se in the beans of Se-enriched soybean plants. Two main categories of proteins, maturation proteins and protease inhibitors, were found in Se-containing high-performance liquid chromatography (HPLC) fractions. The proteins were screened by two-dimensional HPLC-inductively coupled plasma mass spectrometry, size-exclusion chromatography, and anion-exchange chromatography, and the Se-containing fractions were then identified by peptide mapping using HPLC-Chip-electrospray ion trap mass spectrometry. Based on the belief that Se goes into proteins through non-specific incorporation, a new method was designed and applied for the Se-containing peptide identification. The Se-containing peptide KSDQSSSYDDDEYSKPCCDLCMCTRS, part of the sequence of protein Bowman-Birk proteinase isoinhibitor (Glycine max), was found in one of the Se-containing fractions. The nutritional value of the Se-containing proteins in Se-enriched soybeans will be an interesting topic for the future studies.

  6. Results of NDE Technique Evaluation of Clad Hydrides

    SciTech Connect

    Dennis C. Kunerth

    2014-09-01

    This report fulfills the M4 milestone, M4FT-14IN0805023, Results of NDE Technique Evaluation of Clad Hydrides, under Work Package Number FT-14IN080502. During service, zirconium alloy fuel cladding will degrade via corrosion/oxidation. Hydrogen, a byproduct of the oxidation process, will be absorbed into the cladding and eventually form hydrides due to low hydrogen solubility limits. The hydride phase is detrimental to the mechanical properties of the cladding and therefore it is important to be able to detect and characterize the presence of this constituent within the cladding. Presently, hydrides are evaluated using destructive examination. If nondestructive evaluation techniques can be used to detect and characterize the hydrides, the potential exists to significantly increase test sample coverage while reducing evaluation time and cost. To demonstrate the viability this approach, an initial evaluation of eddy current and ultrasonic techniques were performed to demonstrate the basic ability to these techniques to detect hydrides or their effects on the microstructure. Conventional continuous wave eddy current techniques were applied to zirconium based cladding test samples thermally processed with hydrogen gas to promote the absorption of hydrogen and subsequent formation of hydrides. The results of the evaluation demonstrate that eddy current inspection approaches have the potential to detect both the physical damage induced by hydrides, e.g. blisters and cracking, as well as the combined effects of absorbed hydrogen and hydride precipitates on the electrical properties of the zirconium alloy. Similarly, measurements of ultrasonic wave velocities indicate changes in the elastic properties resulting from the combined effects of absorbed hydrogen and hydride precipitates as well as changes in geometry in regions of severe degradation. However, for both approaches, the signal responses intended to make the desired measurement incorporate a number of contributing

  7. Nanoindentation measurements of the mechanical properties of zirconium matrix and hydrides in unirradiated pre-hydrided nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Rico, A.; Martin-Rengel, M. A.; Ruiz-Hervias, J.; Rodriguez, J.; Gomez-Sanchez, F. J.

    2014-09-01

    It is well known that the mechanical properties of the nuclear fuel cladding may be affected by the presence of hydrides. The average mechanical properties of hydrided cladding have been extensively investigated from a macroscopic point of view. In addition, the mechanical and fracture properties of bulk hydride samples fabricated from zirconium plates have also been reported. In this paper, Young's modulus, hardness and yield stress are measured for each phase, namely zirconium hydrides and matrix, of pre-hydrided nuclear fuel cladding. To this end, nanoindentation tests were performed on ZIRLO samples in as-received state, on a hydride blister and in samples with 150 and 1200 ppm of hydrogen homogeneously distributed along the hoop direction of the cladding. The results show that the measured mechanical properties of the zirconium hydrides and ZIRLO matrix (Young's modulus, hardness and yield stress) are rather similar. From the experimental data, the hydride volume fraction in the cladding samples with 150 and 1200 ppm was estimated and the average mechanical properties were calculated by means of the rule of mixtures. These values were compared with those obtained from ring compression tests. Good agreement between the results obtained by both methods was found.

  8. Selenium uptake by sulfur-accumulating bacteria

    NASA Astrophysics Data System (ADS)

    Nelson, Douglas C.; Casey, William H.; Sison, Jennette D.; Mack, E. Erin; Ahmad, Azeem; Pollack, Jeffrey S.

    1996-09-01

    Selenium is a trace metal in many rock-forming minerals but is a major environmental contaminant worldwide. Uptake of selenium by S-accumulating bacteria was examined in both pure cultures of Chromatium vinosum and in co-culture with Desulfovibrio desulfuricans. We used dual cultures including these bacteria to concentrate selenium into intracellular globules. The bacterium D. desulfuricans reduces sulfate [SO 42- (aq)] to sulfide [H 2S(aq)] and also reduces selenate [SeO 42- (aq)] to selenide [H 2Se (aq)]. Once reduced, sulfide is enzymatically oxidized and formed into intracellular globules by C. vinosum. We found that the selenium also forms an intercellular solid but the reaction is thermodynamically driven and proceeds by reducing S° (s) with H 2Se(aq). Relative to the initial molar ratio of selenate and sulfate in the medium, selenium is concentrated 4.5 to 32-fold in the globules. Because solid selenium is so much more stable than sulfur at growth conditions, other S-depositing bacteria, such as Beggiatoa and Chlorobium, should also concentrate selenium via this reaction, providing a strategy for eliminating contamination or for concentrating low natural levels into a usable form.

  9. Decreased selenium levels in acute myocardial infarction

    SciTech Connect

    Kok, F.J.; Hofman, A.; Witteman, J.C.M.; de Bruijn, A.M.; Kruyssen, D.H.C.M.; de Bruin, M.; Valkenburg, H.A. )

    1989-02-24

    To study the association between selenium status and the risk of myocardial infarction, the authors compared plasma, erythrocyte, and toenail selenium levels and the activity of erythrocyte glutathione peroxidase among 84 patients with acute myocardial infarction and 84 population controls. Mean concentrations of all selenium measurements were lower in cases than controls. The differences were statistically significant, except for the plasma selenium level. A positive trend in the risk of acute myocardial infarction from high to low toenail selenium levels was observed, which persisted after adjustment for other risk factors for myocardial infarction. In contrast, erythrocyte glutathione peroxidase activity was significantly higher in cases than controls. Because toenail selenium level reflects blood levels up to one year before sampling, these findings suggest that a low selenium status was present before the infarction and, thus, may be of etiologic relevance. The higher glutathione peroxidase activity in the cases may be interpreted as a defense against increased oxidant stress either preceding or following the acute event.

  10. Distribution and mode of occurrence of selenium in US coals

    USGS Publications Warehouse

    Coleman, L.; Bragg, L.J.; Finkelman, R.B.

    1993-01-01

    Selenium excess and deficiency have been established as the cause of various health problems in man and animals. Combustion of fossil fuels, especially coal, may be a major source of the anthropogenic introduction of selenium in the environment. Coal is enriched in selenium relative to selenium's concentration in most other rocks and relative to selenium in the Earth's crust. Data from almost 9,000 coal samples have been used to determine the concentration and distribution of selenium in US coals. The geometric mean concentration of selenium in US coal is 1.7 ppm. The highest mean selenium value (geometric mean 4.7 ppm) is in the Texas Region. Atlantic Coast (Virginia and North Carolina) and Alaska coals have the lowest geometric means (0.2 and 0.42 ppm, respectively). All western coal regions have mean selenium concentrations of less than 2.0 ppm. In contrast, all coal basins east of the Rocky Mountains (except for several small basins in Rhode Island, Virginia, and North Carolina) have mean selenium values of 1.9 or greater. Generally, variations in selenium concentration do not correlate with variations in ash yield, pyritic sulphur, or organic sulphur concentrations. This may be the result of multiple sources of selenium; however, in some non-marine basins with restricted sources of selenium, selenium has positive correlations with other coal quality parameters. Selenium occurs in several forms in coal but appears to be chiefly associated with the organic fraction, probably substituting for organic sulphur. Other important forms of selenium in coal are selenium-bearing pyrite, selenium-bearing galena, and lead selenide (clausthalite). Water-soluble and ion-exchangeable selenium also have been reported. ?? 1993 Copyright Science and Technology Letters.

  11. Selenium and Methionine Sulfoxide Reduction.

    PubMed

    Gladyshev, Vadim N

    2014-10-01

    Selenium is an essential trace element because it is present in proteins in the form of selenocysteine residue. Functionally characterized selenoproteins are oxidoreductases. Selenoprotein methionine-R-sulfoxide reductase B1 (MsrB1) is a repair enzyme that reduces ROS-oxidized methionine residues in proteins. Here, we explored a possibility that reversible methionine oxidation is also a mechanism that regulates protein function. We found that MsrB1, together with Mical proteins, regulated mammalian actin assembly via stereospecific methionine oxidation and reduction in a reversible, site-specific manner. Two methionine residues in actin were specifically converted to methionine-R-sulfoxide by Mical1 and Mical2 and reduced back to methionine by MsrB1, supporting actin disassembly and assembly, respectively. Macrophages utilized this redox control during cellular activation by stimulating MsrB1 expression and activity. Thus, we identified the regulatory role of MsrB1 as a Mical antagonist in orchestrating actin dynamics and macrophage function. More generally, our study showed that proteins can be regulated by reversible site-specific methionine-R-sulfoxidation and that selenium is involved in this regulation by being a catalytic component of MsrB1. PMID:26461418

  12. Selenium content of game meat

    SciTech Connect

    Medeiros, L.C.; Belden, R.P. Univ. of Wyoming, Laramie )

    1991-03-11

    Selenium (Se) content of elk, deer, bison and beef were measured and compared. Samples were obtained from animals grazed on soil known to contain high, but variable amounts of Se. Beef were feedlot grazed and elk, deer, and bison were from captive or semi-captive herds. Selenium content was determined by graphite furnace after high pressure wet microwave digestion of samples. Deer and bison contained more Se than elk or beef. On a dry weight basis, deer contained more Se than bison. Game species contained more Se than beef. Within samples from male elk and deer and elk and bison of both genders, there were interactions between specie and muscle effects. Muscle and gender did not significantly influence Se content. The animals from which these samples were taken were supplemented with feeds grown on high Se containing soils, which was reflected in all values. Se values were twofold higher than those previously reported for meat. Those consuming large quantities of game from areas with high Se soil may need to monitor Se intake to avoid consuming excessive quantities.

  13. Determination of methylmercury by electrothermal atomic absorption spectrometry using headspace single-drop microextraction with in situ hydride generation

    NASA Astrophysics Data System (ADS)

    Gil, Sandra; Fragueiro, Sandra; Lavilla, Isela; Bendicho, Carlos

    2005-01-01

    A new method is proposed for preconcentration and matrix separation of methylmercury prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Generation of methylmercury hydride (MeHgH) from a 5-ml solution is carried out in a closed vial and trapped onto an aqueous single drop (3-μl volume) containing Pd(II) or Pt(IV) (50 and 10 mg/l, respectively). The hydrogen evolved in the headspace (HS) after decomposition of sodium tetrahydroborate (III) injected for hydride generation caused the formation of finely dispersed Pd(0) or Pt(0) in the drop, which in turn, were responsible for the sequestration of MeHgH. A preconcentration factor of ca. 40 is achieved with both noble metals used as trapping agents. The limit of detection of methylmercury was 5 and 4 ng/ml (as Hg) with Pd(II) or Pt(IV) as trapping agents, and the precision expressed as relative standard deviation was about 7%. The preconcentration system was fully characterised through optimisation of the following variables: Pd(II) or Pt(IV) concentration in the drop, extraction time, pH of the medium, temperatures of both sample solution and drop, concentration of salt in the sample solution, sodium tetrahydroborate (III) concentration in the drop and stirring rate. The method has been successfully validated against two fish certified reference materials (CRM 464 tuna fish and CRM DORM-2 dogfish muscle) following selective extraction of methylmercury in 2 mol/l HCl medium.

  14. Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX3 Compounds

    SciTech Connect

    Mock, Michael T.; Potter, Robert G.; O'Hagan, Molly J.; Camaioni, Donald M.; Dougherty, William G.; Kassel, W. S.; DuBois, Daniel L.

    2011-12-05

    Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H{sub 2} gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe){sub 2}, dmpe = 1,2-bis(dimethylphosphinoethane) was capable of reducing a variety of BX{sub 3} compounds having hydride affinity (HA) greater than or equal to HA of BEt{sub 3}. This study examines the reactivity of less expensive cobalt and nickel hydride complexes, (HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +}), to form B-H bonds. The hydride donor abilities ({Delta}G{sub H{sup -}}{sup o}) of HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +} were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX{sub 3} compounds. The collective data guided our selection of BX{sub 3} compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe){sub 2} was observed to transfer H{sup -} to BX{sub 3} compounds with X = H, OC{sub 6}F{sub 5} and SPh. The reaction with B(SPh){sub 3} is accompanied by formation of (BH{sub 3}){sub 2}-dmpe and (BH{sub 2}SPh){sub 2}-dmpe products that follow from reduction of multiple BSPh bonds and loss of a dmpe ligand from Co. Reactions between HCo(dmpe){sub 2} and B(SPh){sub 3} in the presence of triethylamine result in formation of Et{sub 3}N-BH{sub 2}SPh and Et{sub 3}N-BH{sub 3} with no loss of dmpe ligand. Reactions of the cationic complex [HNi(dmpe){sub 2}]{sup +} with B(SPh){sub 3} under analogous conditions give Et{sub 3}N-BH{sub 2}SPh as the final product along with the nickel-thiolate complex [Ni(dmpe){sub 2}(SPh)]{sup +}. The synthesis and characterization of HCo(dedpe){sub 2} (dedpe = diethyldiphenyl(phosphino)ethane) from H{sub 2} and a base is also discussed; including the formation of an uncommon trans

  15. Selenium accumulation and loss in mallard eggs

    SciTech Connect

    Heinz, G.H. )

    1993-04-01

    Five female mallards (Anas platyhynchos) that had just started egg laying were first fed a diet containing 15 ppm selenium in the form of selenomethionine for 20 d and then an untreated diet for 20 d. Selenium levels in eggs peaked (to about 13-20 ppm) in about two weeks on the treated diet and leveled off at a low level (< 5 ppm) after about 10 d back on the untreated diet. Selenium levels in egg whites responded faster than levels in yolks to the females' consumption of treated and untreated diets.

  16. Selenium isotope geochemistry: A new approach to characterizing the environmental chemistry of selenium. Final report

    SciTech Connect

    Volpe, A.M.; Esser, B.K.

    1997-02-05

    High levels of selenium in the environment will be a prominent water quality issue in the western United States for many years. Selenium accumulation is linked to increased rates of death and deformity in migratory birds, blind staggers in livestock, and selenosis in humans. In California, agricultural drain waters and oil refinery effluent contribute to high selenium content in the San Joaquin Valley and the San Francisco Bay. The importance of these industries to California`s economy precludes simple abatement, while the complexity of selenium cycling precludes simple remediation. The purpose of this project is to measure variations in the isotopic composition of selenium in water and soil samples caused by natural processes and to show, for the first time, the value of isotopic measurements in characterizing selenium pollution. The research seeks to identify sources of selenium pollution, determine processes in the selenium cycle, and support selenium remediation studies. The project required the successful integration of three components: (1) appropriate sampling a field setting showing Se enrichment and possibly isotopic fractionation, (2) analytical chemical methods for isolating and purifying the various species of Se in waters and sediment, and (3) mass spectroscopic instrumentation for high precision isotope abundance measurements.

  17. Selenium content in wheat and estimation of the selenium daily intake in different regions of Algeria.

    PubMed

    Beladel, B; Nedjimi, B; Mansouri, A; Tahtat, D; Belamri, M; Tchanchane, A; Khelfaoui, F; Benamar, M E A

    2013-01-01

    In this work, we have measured the selenium content in wheat produced locally in eight different regions of Algeria from east to west, and we have established the annual consumption of selenium for five socio-professional categories. Instrumental neutron activation analysis is used. The selenium levels in wheat samples varied from 21 (Tiaret) to 153 μg/kg (Khroub), with a mean value about 52 μg/kg. The mean of selenium daily consumption from ingestion of wheat per person in the eight regions varied from 32 to 52 μg/day which is close to the minimal FAO recommendation.

  18. Red selenium nanoparticles and gray selenium nanorods as antibacterial coatings for PEEK medical devices.

    PubMed

    Wang, Qi; Mejía Jaramillo, Alejandra; Pavon, Juan J; Webster, Thomas J

    2016-10-01

    Bacterial infections are commonly found on various poly(ether ether ketone) (PEEK) medical devices (such as orthopedic instruments, spinal fusion devices, and segments in dialysis equipment), and thus, there is a significant need for introducing antibacterial properties to such materials. The objective of this in vitro study was to introduce antibacterial properties to PEEK medical devices by coating them with nanosized selenium. In this study, red selenium (an elemental form of selenium) nanoparticles were coated on PEEK medical devices through a quick precipitation method. Furthermore, with heat treatment at 100°C for 6 days, red selenium nanoparticles were transferred into gray selenium nanorods on the PEEK surfaces. Bacteria test results showed that both red and gray selenium-coated PEEK medical devices significantly inhibited the growth of Pseudomonas aeruginosa compared with uncoated PEEK after either 1, 2, or 3 days. Red selenium nanoparticle-coated PEEK showed less bacteria growth on its surface than gray selenium nanorod-coated PEEK after 3 days. This study demonstrated that red, and to a lesser extent gray, nanosized selenium could be used as potential antibacterial coatings to prevent bacteria function on PEEK medical devices. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1352-1358, 2016. PMID:26138597

  19. Fracture Resistance of a Zirconium Alloy with Reoriented Hydrides

    NASA Astrophysics Data System (ADS)

    Chan, Kwai S.; He, Xihua; Pan, Yi-Ming

    2015-01-01

    Zirconium alloy cladding materials typically contain circumferential hydrides that may be reoriented to align along the radial direction when the cladding tubes are heated above and then cooled below the solvus temperature. The objectives of this study were to investigate the critical stress levels required to cause hydride reorientation (HRT) and to characterize the fracture resistance of Zircaloy-2 after hydride reorientation. HRT heat-treatment was performed on hydrogen-charged Zircaloy-2 specimens at 593 K (320 °C) or 623 K (350 °C) for 1 to 2 hours, followed by cooling to 473 K (200 °C). Fracture testing was conducted on hydride-reoriented three-point bend specimens at 473 K (200 °C) using an in situ loading stage inside a scanning electron microscope. Direct observations indicated that the reoriented hydrides, which ranged from ≈1 to 22 μm in lengths, were more prone to fracture at larger sizes (>10 μm) compared to smaller sizes (<0.5 μm). The reoriented hydrides reduced fracture resistance through a void nucleation, growth, and coalescence process at the crack tip. The resulting crack-resistance curves for Zircaloy-2 with reoriented hydrides decrease from 38 to 21 MPa(m)1/2 with increasing hydrogen contents from 51 to 1265 wt ppm hydrogen.

  20. Tolerance of the preruminant calf for selenium in milk replacer

    SciTech Connect

    Jenkins, K.J.; Hidiroglou, M.

    1986-07-01

    Calves were fed skim milk powder-based milk replacer containing either .2, 1, 3, 5, or 10 ppm selenium (added as sodium selenate) in the dry matter from 3 to 45 d of age to estimate the lowest amount of dietary selenium that would reduce calf performance and feed utilization. Only at the highest selenium (10 ppm) did calves show reduced average daily gain and feed efficiency and lower blood packed cell volume. Apparent digestibility of dry matter, nitrogen, and lipid, and plasma creatine phosphokinase activity were not affected by any of the selenium intakes. In general, selenium in blood, bile, duodenal mucosa, liver, kidney, and muscle reflected selenium intakes with liver and kidney reaching the highest selenium concentrations. Postmortem examinations of calves revealed no gross abnormalities for any of the selenium treatments. The preruminant calf is very tolerant of high inorganic selenium concentrations in skim milk powder-based milk replacer.

  1. Selenium in human milk and dietary selenium intake by Greeks.

    PubMed

    Bratakos, M S; Ioannou, P V

    1991-06-01

    Fluorimetric determination of selenium in colostrum, transitional and mature human milk gave the following concentrations (mean and standard deviation): 41 +/- 16, 23 +/- 6 and 17 +/- 3 ng Se ml-1, respectively. The ranges for each kind of milk, especially for mature milk, were narrow. For all cases studied, the Se concentration in milk decreased with lactation time, reaching a plateau, at 17 ng Se ml-1, after 20 days. It is estimated that breast-fed-only babies in Greece receive approximately 5-11 micrograms Se day-1 up to 6 months of age. From consumed food data it was estimated that adult Greeks receive 100 +/- 6 micrograms Se day-1, in close agreement with our previously determined value of 110 micrograms Se day-1 estimated from food disappearance data.

  2. Arsenic-Selenium And Mercury-Selenium Bonds in Biology

    SciTech Connect

    Gailer, Jurgen; /Calgary U.

    2007-07-10

    When rabbits are simultaneous injected with arsenite and selenite or mercuric chloride and selenite, compounds with As-Se and Hg-Se bonds are formed in the bloodstream. The combined application of liquid chromatography-inductively coupled plasma atomic emission spectrometry (ICP-AES) and X-ray absorption spectroscopy (XAS) has revealed the molecular structure of these toxicologically important compounds and provided insight into their mechanism of formation. The glutathione-driven formation of these compounds in the bloodstream fundamentally links the metabolism of the environmental pollutants mercuric mercury and arsenite with that of the essential ultratrace element selenium, which establishes a feasible mechanism by which the chronic low-level exposure of various human populations to these toxic metals and metalloid compounds is linked to human diseases, including cancer and neurodegenerative diseases.

  3. Molecular rare-earth-metal hydrides in non-cyclopentadienyl environments.

    PubMed

    Fegler, Waldemar; Venugopal, Ajay; Kramer, Mathias; Okuda, Jun

    2015-02-01

    Molecular hydrides of the rare-earth metals play an important role as homogeneous catalysts and as counterparts of solid-state interstitial hydrides. Structurally well-characterized non-metallocene-type hydride complexes allow the study of elementary reactions that occur at rare-earth-metal centers and of catalytic reactions involving bonds between rare-earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available.

  4. Selenium: environmental significance, pollution, and biological treatment technologies.

    PubMed

    Tan, Lea Chua; Nancharaiah, Yarlagadda V; van Hullebusch, Eric D; Lens, Piet N L

    2016-01-01

    Selenium is an essential trace element needed for all living organisms. Despite its essentiality, selenium is a potential toxic element to natural ecosystems due to its bioaccumulation potential. Though selenium is found naturally in the earth's crust, especially in carbonate rocks and volcanic and sedimentary soils, about 40% of the selenium emissions to atmospheric and aquatic environments are caused by various industrial activities such as mining-related operations. In recent years, advances in water quality and pollution monitoring have shown that selenium is a contaminant of potential environmental concern. This has practical implications on industry to achieve the stringent selenium regulatory discharge limit of 5μgSeL(-1) for selenium containing wastewaters set by the United States Environmental Protection Agency. Over the last few decades, various technologies have been developed for the treatment of selenium-containing wastewaters. Biological selenium reduction has emerged as the leading technology for removing selenium from wastewaters since it offers a cheaper alternative compared to physico-chemical treatments and is suitable for treating dilute and variable selenium-laden wastewaters. Moreover, biological treatment has the advantage of forming elemental selenium nanospheres which exhibit unique optical and spectral properties for various industrial applications, i.e. medical, electrical, and manufacturing processes. However, despite the advances in biotechnology employing selenium reduction, there are still several challenges, particularly in achieving stringent discharge limits, the long-term stability of biogenic selenium and predicting the fate of bioreduced selenium in the environment. This review highlights the significance of selenium in the environment, health, and industry and biotechnological advances made in the treatment of selenium contaminated wastewaters. The challenges and future perspectives are overviewed considering recent

  5. Selenium: environmental significance, pollution, and biological treatment technologies.

    PubMed

    Tan, Lea Chua; Nancharaiah, Yarlagadda V; van Hullebusch, Eric D; Lens, Piet N L

    2016-01-01

    Selenium is an essential trace element needed for all living organisms. Despite its essentiality, selenium is a potential toxic element to natural ecosystems due to its bioaccumulation potential. Though selenium is found naturally in the earth's crust, especially in carbonate rocks and volcanic and sedimentary soils, about 40% of the selenium emissions to atmospheric and aquatic environments are caused by various industrial activities such as mining-related operations. In recent years, advances in water quality and pollution monitoring have shown that selenium is a contaminant of potential environmental concern. This has practical implications on industry to achieve the stringent selenium regulatory discharge limit of 5μgSeL(-1) for selenium containing wastewaters set by the United States Environmental Protection Agency. Over the last few decades, various technologies have been developed for the treatment of selenium-containing wastewaters. Biological selenium reduction has emerged as the leading technology for removing selenium from wastewaters since it offers a cheaper alternative compared to physico-chemical treatments and is suitable for treating dilute and variable selenium-laden wastewaters. Moreover, biological treatment has the advantage of forming elemental selenium nanospheres which exhibit unique optical and spectral properties for various industrial applications, i.e. medical, electrical, and manufacturing processes. However, despite the advances in biotechnology employing selenium reduction, there are still several challenges, particularly in achieving stringent discharge limits, the long-term stability of biogenic selenium and predicting the fate of bioreduced selenium in the environment. This review highlights the significance of selenium in the environment, health, and industry and biotechnological advances made in the treatment of selenium contaminated wastewaters. The challenges and future perspectives are overviewed considering recent

  6. Technical and economic aspects of hydrogen storage in metal hydrides

    NASA Technical Reports Server (NTRS)

    Schmitt, R.

    1981-01-01

    The recovery of hydrogen from such metal hydrides as LiH, MgH2, TiH2, CaH2 and FeTiH compounds is studied, with the aim of evaluating the viability of the technique for the storage of hydrogen fuel. The pressure-temperature dependence of the reactions, enthalpies of formation, the kinetics of the hydrogen absorption and desorption, and the mechanical and chemical stability of the metal hydrides are taken into account in the evaluation. Economic aspects are considered. Development of portable metal hydride hydrogen storage reservoirs is also mentioned.

  7. Structural Characterization of Metal Hydrides for Energy Applications

    NASA Astrophysics Data System (ADS)

    George, Lyci

    Hydrogen can be an unlimited source of clean energy for future because of its very high energy density compared to the conventional fuels like gasoline. An efficient and safer way of storing hydrogen is in metals and alloys as hydrides. Light metal hydrides, alanates and borohydrides have very good hydrogen storage capacity, but high operation temperatures hinder their application. Improvement of thermodynamic properties of these hydrides is important for their commercial use as a source of energy. Application of pressure on materials can have influence on their properties favoring hydrogen storage. Hydrogen desorption in many complex hydrides occurs above the transition temperature. Therefore, it is important to study the physical properties of the hydride compounds at ambient and high pressure and/or high temperature conditions, which can assist in the design of suitable storage materials with desired thermodynamic properties. The high pressure-temperature phase diagram, thermal expansion and compressibility have only been evaluated for a limited number of hydrides so far. This situation serves as a main motivation for studying such properties of a number of technologically important hydrides. Focus of this dissertation was on X-ray diffraction and Raman spectroscopy studies of Mg2FeH6, Ca(BH4) 2, Mg(BH4)2, NaBH4, NaAlH4, LiAlH4, LiNH2BH3 and mixture of MgH 2 with AlH3 or Si, at different conditions of pressure and temperature, to obtain their bulk modulus and thermal expansion coefficient. These data are potential source of information regarding inter-atomic forces and also serve as a basis for developing theoretical models. Some high pressure phases were identified for the complex hydrides in this study which may have better hydrogen storage properties than the ambient phase. The results showed that the highly compressible B-H or Al-H bonds and the associated bond disordering under pressure is responsible for phase transitions observed in brorohydrides or

  8. Finite difference program for calculating hydride bed wall temperature profiles

    SciTech Connect

    Klein, J.E.

    1992-10-29

    A QuickBASIC finite difference program was written for calculating one dimensional temperature profiles in up to two media with flat, cylindrical, or spherical geometries. The development of the program was motivated by the need to calculate maximum temperature differences across the walls of the Tritium metal hydrides beds for thermal fatigue analysis. The purpose of this report is to document the equations and the computer program used to calculate transient wall temperatures in stainless steel hydride vessels. The development of the computer code was motivated by the need to calculate maximum temperature differences across the walls of the hydrides beds in the Tritium Facility for thermal fatigue analysis.

  9. Selenium sulfide: adjunctive therapy for tinea capitis.

    PubMed

    Allen, H B; Honig, P J; Leyden, J J; McGinley, K J

    1982-01-01

    Selenium sulfide lotion used as a shampoo has been shown to be an effective adjunctive agent to griseofulvin in the treatment of tinea capitis. Of 16 children with Trichophyton tonsurans infections 15 had negative fungal cultures at two weeks following a regimen of daily oral griseofulvin and selenium sulfide shampooing twice weekly. All patients treated with griseofulvin alone or in combination with either a bland shampoo or topical clotrimazole had positive cultures not only at the two-week interval but also as long as eight weeks later. In vitro analysis shows selenium sulfide to be sporicidal, correlating well with the in vivo observations. It is postulated that selenium sulfide usage may lessen the chances for spreading of infectious spores to other individuals.

  10. Biofortification and phytoremediation of selenium in China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biofortification is an agricultural process that increases the uptake and accumulation of specific nutrients, e.g. selenium (Se), in agricultural food products through plant breeding, genetic engineering, and manipulation of agronomic practices. The development and uses of biofortified agricultural ...

  11. Vacuum hydride epitaxy of silicon: kinetics of monosilane pyrolysis on the growth surface

    SciTech Connect

    Orlov, L. K.; Ivin, S. V.

    2011-04-15

    Analytical expressions relating the rate of silicon atom incorporation into a growing crystal to the typical frequency of silane molecule pyrolysis on the silicon surface in the growth temperature range are derived. Based on currently available experimental data, the range of typical decomposition frequencies of hydride molecule radicals adsorbed at the silicon wafer surface in the temperature range of 450-700 Degree-Sign C is determined for the most widely used physicochemical models. It is shown that the most probable molecular decomposition model can be chosen based on the experimental study of the temperature dependence of the decomposition rate of adsorbed hydride molecules. A change in the silane molecule pyrolysis rate or the hydrogen desorption rate from the surface in principle makes it possible to increase the Si layer growth rate without additional substrate heating under conditions of low-temperature epitaxy (450-550 Degree-Sign C), but no larger than by a factor of 2-3 in the former case and up to 100 times in the latter case. The analysis performed shows that physicochemical pyrolysis models in which hydrogen is trapped by the surface, mostly at the stage of decomposition of silane radicals adsorbed by the surface, are more realistic.

  12. METHOD FOR PRODUCING ISOTOPIC METHANES FROM LITHIUM CARBONATE AND LITHIUM HYDRIDE

    DOEpatents

    Frazer, J.W.

    1959-10-27

    A process is descrlbed for the production of methane and for the production of methane containing isotopes of hydrogen and/or carbon. Finely divided lithium hydrlde and litldum carbonate reactants are mixed in intimate contact and subsequently compacted under pressures of from 5000 to 60,000 psl. The compacted lithium hydride and lithium carbenate reactunts are dispised in a gas collecting apparatus. Subsequently, the compact is heated to a temperature in the range 350 to 400 deg C whereupon a solid-solid reaction takes place and gaseous methane is evolved. The evolved methane is contaminated with gaseous hydrogen and a very small amount of CO/sub 2/; however, the desired methane product is separated from sald impurities by well known chemical processes, e.g., condensation in a cold trap. The product methane contalns isotopes of carbon and hydrogen, the Isotopic composition being determined by the carbon isotopes originally present In the lithium carbonate and the hydrogen isotopes originally present in the lithium hydride.

  13. Production of selenium-72 and arsenic-72

    DOEpatents

    Phillips, Dennis R.

    1994-01-01

    Methods and apparatus for producing selenium-72, separating it from its daughter isotope arsenic-72, and generating multiple portions of a solution containing arsenic-72 from a reusable parent substance comprised of selenium-72. The invention provides apparatus which can be located at a site where arsenic-72 is used, for purposes such as PET imaging, to produce arsenic-72 as needed, since the half-life of arsenic-72 is very short.

  14. Production of selenium-72 and arsenic-72

    DOEpatents

    Phillips, D.R.

    1994-12-06

    Methods and apparatus are described for producing selenium-72, separating it from its daughter isotope arsenic-72, and generating multiple portions of a solution containing arsenic-72 from a reusable parent substance comprised of selenium-72. The invention provides apparatus which can be located at a site where arsenic-72 is used, for purposes such as PET imaging, to produce arsenic-72 as needed, since the half-life of arsenic-72 is very short. 2 figures.

  15. Production of selenium-72 and arsenic-72

    DOEpatents

    Phillips, Dennis R.

    1995-01-01

    Methods and apparatus for producing selenium-72, separating it from its daughter isotope arsenic-72, and generating multiple portions of a solution containing arsenic-72 from a reusable parent substance comprised of selenium-72. The invention provides apparatus which can be located at a site where arsenic-72 is used, for purposes such as PET imaging, to produce arsenic-72 as needed, since the half-life of arsenic-72 is very short.

  16. Selenium deficiency mitigates hypothyroxinemia in iodine-deficient subjects.

    PubMed

    Vanderpas, J B; Contempré, B; Duale, N L; Deckx, H; Bebe, N; Longombé, A O; Thilly, C H; Diplock, A T; Dumont, J E

    1993-02-01

    Studies were performed to assess the role of combined selenium and iodine deficiency in the etiology of endemic myxedematous cretinism in a population in Zaire. One effect of selenium deficiency may be to lower glutathione peroxidase activity in the thyroid gland, thus allowing hydrogen peroxide produced during thyroid hormone synthesis to be cytotoxic. In selenium-and-iodine-deficient humans, selenium supplementation may aggravate hypothyroidism by stimulating thyroxin metabolism by the selenoenzyme type I iodothyronine 5'-deiodinase. Selenium supplementation is thus not indicated without iodine or thyroid hormone supplementation in cases of combined selenium and iodine deficiencies.

  17. Selenium deficiency mitigates hypothyroxinemia in iodine-deficient subjects.

    PubMed

    Vanderpas, J B; Contempré, B; Duale, N L; Deckx, H; Bebe, N; Longombé, A O; Thilly, C H; Diplock, A T; Dumont, J E

    1993-02-01

    Studies were performed to assess the role of combined selenium and iodine deficiency in the etiology of endemic myxedematous cretinism in a population in Zaire. One effect of selenium deficiency may be to lower glutathione peroxidase activity in the thyroid gland, thus allowing hydrogen peroxide produced during thyroid hormone synthesis to be cytotoxic. In selenium-and-iodine-deficient humans, selenium supplementation may aggravate hypothyroidism by stimulating thyroxin metabolism by the selenoenzyme type I iodothyronine 5'-deiodinase. Selenium supplementation is thus not indicated without iodine or thyroid hormone supplementation in cases of combined selenium and iodine deficiencies. PMID:8427203

  18. Thioacetamide-induced cirrhosis in selenium-adequate mice displays rapid and persistent abnormity of hepatic selenoenzymes which are mute to selenium supplementation

    SciTech Connect

    Zhang Jinsong Wang Huali; Yu Hanqing

    2007-10-01

    Selenium reduction in cirrhosis is frequently reported. The known beneficial effect of selenium supplementation on cirrhosis is probably obtained from nutritionally selenium-deficient subjects. Whether selenium supplementation truly improves cirrhosis in general needs additional experimental investigation. Thioacetamide was used to induce cirrhosis in selenium-adequate and -deficient mice. Selenoenzyme activity and selenium content were measured and the influence of selenium supplementation was evaluated. In Se-adequate mice, thioacetamide-mediated rapid onset of hepatic oxidative stress resulted in an increase in thioredoxin reductase activity and a decrease in both glutathione peroxidase activity and selenium content. The inverse activity of selenoenzymes (i.e. TrxR activity goes up and GPx activity goes down) was persistent and mute to selenium supplementation during the progress of cirrhosis; accordingly, cirrhosis was not improved by selenium supplementation in any period. On the other hand, selenium supplementation to selenium-deficient mice always more efficiently increased hepatic glutathione peroxidase activity and selenium content compared with those treated with thioacetamide, indicating that thioacetamide impairs the liver bioavailability of selenium. Although thioacetamide profoundly affects hepatic selenium status in selenium-adequate mice, selenium supplementation does not modify the changes. Selenium supplementation to cirrhotic subjects with a background of nutritional selenium deficiency can improve selenium status but cannot restore hepatic glutathione peroxidase and selenium to normal levels.

  19. Biological activity of selenium: Revisited.

    PubMed

    Wrobel, Jagoda K; Power, Ronan; Toborek, Michal

    2016-02-01

    Selenium (Se) is an essential micronutrient that exerts multiple and complex effects on human health. Se is essential for human well-being largely due to its potent antioxidant, anti-inflammatory, and antiviral properties. The physiological functions of Se are carried out by selenoproteins, in which Se is specifically incorporated as the amino acid, selenocysteine. Importantly, both beneficial and toxic effects of Se have been reported suggesting that the mode of action of Se is strictly chemical form and concentration dependent. Additionally, there is a relatively narrow window between Se deficiency and toxicity and growing evidence suggests that Se health effects depend greatly on the baseline level of this micronutrient. Thus, Se supplementation is not an easy task and requires an individualized approach. It is essential that we continue to explore and better characterize Se containing compounds and mechanisms of action, which could be crucial for disease prevention and treatment. PMID:26714931

  20. [Selenium and cardiovascular disease: selected issues].

    PubMed

    Zagrodzki, Paweł; Laszczyk, Paulina

    2006-01-01

    The paper presents current knowledge of the role of selenium in the development of cardiovascular system disease (CSD). Already known mechanisms of selenium action in the cardiovascular system are described, whilst underlining the fact that they do not explain all relevant observations and need to be clarified by more studies. Clinical, epidemiological, and experimental studies devoted to the relationship between the progression of CSD and selenium status indices are then reviewed. It could be expected that any explanation of the pathophysiological mechanisms of the influence of tobacco smoking (as one of the classical risk factors for CSD) on selenium status might help to bring about a better understanding of the progression of cardiovascular disorders. Based on studies conducted on animal models, the role of selenium in the antioxidant defense of cardiac muscle is described. Particular attention is paid to a dilated cardiomyopathy known as Keshan disease, for which it has been shown that selenium deficiency is an environmental factor predisposing to the onset of this disease. Similar symptoms of cardiomyopathy are also observed in patients on total parenteral nutrition and patients with AIDS.

  1. Selenium in Gluten-free Products.

    PubMed

    Rybicka, Iga; Krawczyk, Magdalena; Stanisz, Ewa; Gliszczyńska-Świgło, Anna

    2015-06-01

    The nutritional value of gluten-free products is the subject of interest for food technologists and nutritionists, as the only effective treatment for celiac disease is a lifelong gluten-free diet. As selenium deficiencies in celiac disease are observed, the aim of the study was to determine the selenium content in 27 grain gluten-free products available on the European Union (EU) market. Moreover, selenium content in products based on popular gluten-free cereals like corn, rice, and buckwheat and in relatively new or less popular products based on oat, amaranth, teff, and quinoa was compared. Selenium content in the tested products ranged from 0.9 to 24.5 μg/100 g. The average content of selenium in products based on popular gluten-free cereals was 2.8 μg/100 g and in products based on oat, amaranth, teff, and quinoa was 10.8 μg/100 g. It indicates that products based on less popular grains, especially on oat, should be more frequently chosen as a source of selenium by people on gluten-free diet than traditionally consumed gluten-free grains. PMID:25690718

  2. Anticipated soil selenium concentrations at Kesterson Reservoir

    SciTech Connect

    Benson, S.M.; Tokunaga, T.K.; Zawislanski, P.

    1992-10-01

    Temporal trends from soil monitoring data collected at Kesterson Reservoir have been reviewed to shed light on anticipated concentrations of total and water-extractable selenium in surface and subsurface soils. Based on these data, a mass balance model for selenium has been developed and employed to evaluate the rate of leaching, remobilization and volatilization that has occurred since the Reservoir was dried out in 1987. Results from a series of calibration runs were then extrapolated 25 years in the future to forecast the evolution and redistribution of selenium within the soil profile. Projected water-extractable selenium concentrations within the 0.15 to 1 m depth interval were then used to drive a food-chain based risk-assessment model described in a separate report (CH2M Hill, 1992). Inventories of water-extractable selenium in the root zone increased in 4 of the 5 scenarios investigated. However, predicted values for the average concentration of water-extractable selenium in the root zone fall within the range of values observed at Kesterson today. Consequences of these projected increases on wildlife residing in and around Kesterson are addressed in CH2M Hill (1992).

  3. Process for production of a metal hydride

    SciTech Connect

    Allen, Nathan Tait; Butterick, III, Robert; Chin, Arthur Achhing; Millar, Dean Michael; Molzahn, David Craig

    2014-08-12

    A process for production of a metal hydride compound MH.sub.x, wherein x is one or two and M is an alkali metal, Be or Mg. The process comprises combining a compound of formula (R.sup.1O).sub.xM with aluminum, hydrogen and at least one metal selected from among titanium, zirconium, hafnium, niobium, vanadium, tantalum and iron to produce a compound of formula MH.sub.x. R.sup.1 is phenyl or phenyl substituted by at least one alkyl or alkoxy group. A mole ratio of aluminum to (R.sup.1O).sub.xM is from 0.1:1 to 1:1. The catalyst is present at a level of at least 200 ppm based on weight of aluminum.

  4. Novel Hydride Transfer Catalysis for Carbohydrate Conversions

    SciTech Connect

    Holladay, John E.; Brown, Heather M.; Appel, Aaron M.; Zhang, Z. Conrad

    2008-04-03

    5-Hydroxymethylfurfural (HMF), an important versatile sugar derivative has been synthesized from glucose using catalytic amounts of CrCl2 in 1-ethyl-3-methylimidizolium chloride. Glycerol and glyceraldehyde were tested as sugar model compounds. Glycerol is unreactive and does not interfere with glucose conversion. Glyceraldehyde is reactive and does interfere with glucose conversion in competitive experiments. MnCl2 or FeCl2 catalyze dehydration of glyceraldehyde dimer to form compound I, a cyclic hemiacetal with an exocyclic double bond. Upon aqueous work-up I forms pyruvaldehyde. CrCl2 or VCl3 further catalyze a hydride transfer of I to form lactide. Upon aqueous work-up lactide is converted to lactic acid.

  5. Ni/metal hydride secondary element

    DOEpatents

    Bauerlein, Peter

    2005-04-19

    A Ni/metal hydride secondary element having a positive nickel hydroxide electrode, a negative electrode having a hydrogen storage alloy, and an alkaline electrolyte, the positive electrode, provided with a three-dimensional metallic conductive structure, also contains an aluminum compound which is soluble in the electrolyte, in addition to nickel hydroxide and cobalt oxide. The aluminum compound is aluminum hydroxide and/or aluminum oxide, and the mass of the aluminum compound which is present in the positive bulk material mixture is 0.1 to 2% by weight relative to the mass of the nickel hydroxide which is present. In combination with aluminum hydroxide or aluminum oxide, the positive electrode further contains lanthanoid oxidic compounds Y.sub.2 O.sub.3, La.sub.2 O.sub.3 and Ca(OH).sub.2, as well as mixtures of these compounds.

  6. Zirconium Hydride Space Power Reactor design.

    NASA Technical Reports Server (NTRS)

    Asquith, J. G.; Mason, D. G.; Stamp, S.

    1972-01-01

    The Zirconium Hydride Space Power Reactor being designed and fabricated at Atomics International is intended for a wide range of potential applications. Throughout the program a series of reactor designs have been evaluated to establish the unique requirements imposed by coupling with various power conversion systems and for specific applications. Current design and development emphasis is upon a 100 kilowatt thermal reactor for application in a 5 kwe thermoelectric space power generating system, which is scheduled to be fabricated and ground tested in the mid 70s. The reactor design considerations reviewed in this paper will be discussed in the context of this 100 kwt reactor and a 300 kwt reactor previously designed for larger power demand applications.

  7. Hydrogen storage in sodium aluminum hydride.

    SciTech Connect

    Ozolins, Vidvuds; Herberg, J.L. (Lawrence Livermore National Laboratories, Livermore, CA); McCarty, Kevin F.; Maxwell, Robert S. (Lawrence Livermore National Laboratories, Livermore, CA); Stumpf, Roland Rudolph; Majzoub, Eric H.

    2005-11-01

    Sodium aluminum hydride, NaAlH{sub 4}, has been studied for use as a hydrogen storage material. The effect of Ti, as a few mol. % dopant in the system to increase kinetics of hydrogen sorption, is studied with respect to changes in lattice structure of the crystal. No Ti substitution is found in the crystal lattice. Electronic structure calculations indicate that the NaAlH{sub 4} and Na{sub 3}AlH{sub 6} structures are complex-ionic hydrides with Na{sup +} cations and AlH{sub 4}{sup -} and AlH{sub 6}{sup 3-} anions, respectively. Compound formation studies indicate the primary Ti-compound formed when doping the material at 33 at. % is TiAl{sub 3} , and likely Ti-Al compounds at lower doping rates. A general study of sorption kinetics of NaAlH{sub 4}, when doped with a variety of Ti-halide compounds, indicates a uniform response with the kinetics similar for all dopants. NMR multiple quantum studies of solution-doped samples indicate solvent interaction with the doped alanate. Raman spectroscopy was used to study the lattice dynamics of NaAlH{sub 4}, and illustrated the molecular ionic nature of the lattice as a separation of vibrational modes between the AlH{sub 4}{sup -} anion-modes and lattice-modes. In-situ Raman measurements indicate a stable AlH{sub 4}{sup -} anion that is stable at the melting temperature of NaAlH{sub 4}, indicating that Ti-dopants must affect the Al-H bond strength.

  8. Natural selenium-rich feeds manage selenium deficiency in Oregon sheep

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A natural selenium-rich feed product (SePR) was developed by the USDA, ARS, U.S. Sheep Experiment Station for the purposes of enhancing the long-term selenium status of grazing livestock. In cooperation with Intermountain Farmers Association (Salt Lake City, UT), a bulk amount of SePR was manufactur...

  9. Thin film solar cells by selenization sulfurization using diethyl selenium as a selenium precursor

    SciTech Connect

    Dhere, Neelkanth G.; Kadam, Ankur A.

    2009-12-15

    A method of forming a CIGSS absorber layer includes the steps of providing a metal precursor, and selenizing the metal precursor using diethyl selenium to form a selenized metal precursor layer (CIGSS absorber layer). A high efficiency solar cell includes a CIGSS absorber layer formed by a process including selenizing a metal precursor using diethyl selenium to form the CIGSS absorber layer.

  10. Updates on clinical studies of selenium supplementation in radiotherapy

    PubMed Central

    2014-01-01

    To establish guidelines for the selenium supplementation in radiotherapy we assessed the benefits and risks of selenium supplementation in radiotherapy. Clinical studies on the use of selenium in radiotherapy were searched in the PubMed electronic database in January 2013. Sixteen clinical studies were identified among the 167 articles selected in the initial search. Ten articles were observational studies, and the other 6 articles reported studies on the effects of selenium supplementation in patients with cancer who underwent radiotherapy. The studies were conducted worldwide including European, American and Asian countries between 1987 and 2012. Plasma, serum or whole blood selenium levels were common parameters used to assess the effects of radiotherapy and the selenium supplementation status. Selenium supplementation improved the general conditions of the patients, improved their quality of life and reduced the side effects of radiotherapy. At the dose of selenium used in these studies (200–500 μg/day), selenium supplementation did not reduce the effectiveness of radiotherapy, and no toxicities were reported. Selenium supplementation may offer specific benefits for several types of cancer patients who undergo radiotherapy. Because high-dose selenium and long-term supplementation may be unsafe due to selenium toxicity, more evidence-based information and additional research are needed to ensure the therapeutic benefits of selenium supplementation. PMID:24885670

  11. Self-Consistent-Field Calculation on Lithium Hydride for Undergraduates.

    ERIC Educational Resources Information Center

    Rioux, Frank; Harriss, Donald K.

    1980-01-01

    Describes a self-consistent-field-linear combination of atomic orbitals-molecular orbital calculation on the valence electrons of lithium hydride using the method of Roothaan. This description is intended for undergraduate physics students.

  12. Life test results of hydride compressors for cryogenic refrigerators

    NASA Technical Reports Server (NTRS)

    Jones, J. A.; Golben, P. M.

    1984-01-01

    A development status assessment is made, from the viewpoint of system durability, for the hydride compressors used in such cryogenic refrigerators as that of the JPL, which has operated at 29 K for 500 hours and at lower temperatures for over 1000. Attention is given to a novel hydride compressor unit which has operated through 35,000 cycles and exhibits negligible degradation of check valves, hydride particle size, and expansion valves. The power requirement for liquid hydrogen cooling can be halved through the use of recuperative hot water heating methods, making this system comparable in power use to liquid hydrogen refrigeration systems operating on electricity. Due to the lack of moving parts in hydride refrigerator designs, potential service lifetimes of many years, and perhaps decades, are being projected.

  13. Nonaqueous actinide hydride dissolution and production of actinide $beta$- diketonates

    DOEpatents

    Crisler, L.R.

    1975-11-11

    Actinide beta-diketonate complex molecular compounds are produced by reacting a beta-diketone compound with a hydride of the actinide material in a mixture of carbon tetrachloride and methanol. (auth)

  14. Process for massively hydriding zirconium--uranium fuel elements

    DOEpatents

    Katz, N.H.

    1973-12-01

    A method is described of hydriding uranium-zirconium alloy by heating the alloy in a vacuum, introducing hydrogen and maintaining an elevated temperature until occurrence of the beta--delta phase transformation and isobarically cooling the composition. (Official Gazette)

  15. Randomised clinical trial of parenteral selenium supplementation in preterm infants.

    PubMed Central

    Daniels, L.; Gibson, R.; Simmer, K.

    1996-01-01

    AIM: To determine whether selenium supplementation of parenteral nutrition with 3 micrograms/kg/day of selenious acid is safe and effective in improving the selenium status of preterm infants. METHODS: Thirty eight preterm infants with mean (SEM) birthweight of 1171 (38) g and gestational age 29 (0.3) weeks were randomly allocated to a non-supplemented (PN-selenium, n = 19) or supplemented (PN+selenium, n = 19) group. The study began at 2.8 (0.2) (range 1-5) days of age. Term breastfed (n = 23) and formula fed (n = 8) infants were used as a reference group. RESULTS: Initially there was no difference between the preterm groups in plasma or erythrocyte selenium or glutathione peroxidase activity. Plasma selenium declined by a mean (SEM) of -13.3 (3.2) micrograms/l from 28 (4) to 16 (3) micrograms/l over the first three weeks in the PN-selenium group, but there was no fall in the supplemented infants and no net change in either group over six weeks. Over six weeks, there was a net decline in erythrocyte selenium of -106 (27) ng/g haemoglobin in the PN-selenium group, but no change in the PN+selenium group, such that at week 6 erythrocyte selenium was lower in the PN-selenium group (401 (17) ng/g haemoglobin) than the PN+selenium group (493 (25) ng/g haemoglobin). Urinary selenium was substantially higher in the PN+selenium group at each week. Initially term and preterm plasma selenium concentrations were similar, but they increased in term breastfed infants (+17 (2) micrograms/l), with both groups of preterm infants having lower plasma selenium concentrations at week 6 compared with term breastfed infants (PN-selenium 22 (3) micrograms/l; PN+selenium 23 (4) micrograms/l and term breastfed 49 (2) micrograms/l). CONCLUSIONS: Selenium supplementation of PN at 3 g/kg/day prevented depletion in newborns, but was inadequate to achieve selenium concentrations equivalent to those of breastfed term infants. Whether higher doses are more effective remains to be determined

  16. Quantification of Methylated Selenium, Sulfur, and Arsenic in the Environment

    PubMed Central

    Vriens, Bas; Ammann, Adrian A.; Hagendorfer, Harald; Lenz, Markus; Berg, Michael; Winkel, Lenny H. E.

    2014-01-01

    Biomethylation and volatilization of trace elements may contribute to their redistribution in the environment. However, quantification of volatile, methylated species in the environment is complicated by a lack of straightforward and field-deployable air sampling methods that preserve element speciation. This paper presents a robust and versatile gas trapping method for the simultaneous preconcentration of volatile selenium (Se), sulfur (S), and arsenic (As) species. Using HPLC-HR-ICP-MS and ESI-MS/MS analyses, we demonstrate that volatile Se and S species efficiently transform into specific non-volatile compounds during trapping, which enables the deduction of the original gaseous speciation. With minor adaptations, the presented HPLC-HR-ICP-MS method also allows for the quantification of 13 non-volatile methylated species and oxyanions of Se, S, and As in natural waters. Application of these methods in a peatland indicated that, at the selected sites, fluxes varied between 190–210 ng Se·m−2·d−1, 90–270 ng As·m−2·d−1, and 4–14 µg S·m−2·d−1, and contained at least 70% methylated Se and S species. In the surface water, methylated species were particularly abundant for As (>50% of total As). Our results indicate that methylation plays a significant role in the biogeochemical cycles of these elements. PMID:25047128

  17. Solid-state gadolinium{endash}magnesium hydride optical switch

    SciTech Connect

    Armitage, R.; Rubin, M.; Richardson, T.; OBrien, N.; Chen, Y.

    1999-09-01

    The optical switching properties of gadolinium{endash}magnesium hydride have been demonstrated in a solid-state electrochromic device. With positive polarization of the hydride electrode, the visible reflectance approaches 35{percent} with virtually zero transmission, while with negative polarization, the visible transmission exceeds 25{percent} at 650 nm. The switching is reversible, with intermediate optical properties between the transparent and reflecting states. {copyright} {ital 1999 American Institute of Physics.}

  18. Development of the Low-Pressure Hydride/Dehydride Process

    SciTech Connect

    Rueben L. Gutierrez

    2001-04-01

    The low-pressure hydride/dehydride process was developed from the need to recover thin-film coatings of plutonium metal from the inner walls of an isotope separation chamber located at Los Alamos and to improve the safety operation of a hydride recovery process using hydrogen at a pressure of 0.7 atm at Rocky Flats. This process is now the heart of the Advanced Recovery and Integrated Extraction System (ARIES) project.

  19. Ab-Initio Study of the Group 2 Hydride Anions

    NASA Astrophysics Data System (ADS)

    Harris, Joe P.; Wright, Timothy G.; Manship, Daniel R.

    2013-06-01

    The beryllium hydride (BeH)- dimer has recently been shown to be surprisingly strongly bound, with an electronic structure which is highly dependent on internuclear separation. At the equilibrium distance, the negative charge is to be found on the beryllium atom, despite the higher electronegativity of the hydrogen. The current study expands this investigation to the other Group 2 hydrides, and attempts to explain these effects. M. Verdicchio, G. L. Bendazzoli, S. Evangelisti, T. Leininger J. Phys. Chem. A, 117, 192, (2013)

  20. Method of selective reduction of polyhalosilanes with alkyltin hydrides

    DOEpatents

    Sharp, Kenneth G.; D'Errico, John J.

    1989-01-01

    The invention relates to the selective and stepwise reduction of polyhalosilanes by reacting at room temperature or below with alkyltin hydrides without the use of free radical intermediates. Alkyltin hydrides selectively and stepwise reduce the Si--Br, Si--Cl, or Si--I bonds while leaving intact any Si--F bonds. When two or more different halogens are present on the polyhalosilane, the halogen with the highest atomic weight is preferentially reduced.

  1. Method of selective reduction of halodisilanes with alkyltin hydrides

    DOEpatents

    D'Errico, John J.; Sharp, Kenneth G.

    1989-01-01

    The invention relates to the selective and sequential reduction of halodisilanes by reacting these compounds at room temperature or below with trialkyltin hydrides or dialkyltin dihydrides without the use of free radical intermediates. The alkyltin hydrides selectively and sequentially reduce the Si-Cl, Si-Br or Si-I bonds while leaving intact the Si-Si and Si-F bonds present.

  2. Optimization of Hydride Rim Formation in Unirradiated Zr 4 Cladding

    SciTech Connect

    Shimskey, Rick W.; Hanson, Brady D.; MacFarlan, Paul J.

    2013-09-30

    The purpose of this work is to build on the results reported in the M2 milestone M2FT 13PN0805051, document number FCRD-USED-2013-000151 (Hanson, 2013). In that work, it was demonstrated that unirradiated samples of zircaloy-4 cladding could be pre-hydrided at temperatures below 400°C in pure hydrogen gas and that the growth of hydrides on the surface could be controlled by changing the surface condition of the samples and form a desired hydride rim on the outside diameter of the cladding. The work performed at Pacific Northwest National Laboratory since the issuing of the M2 milestone has focused its efforts to optimize the formation of a hydride rim on available zircaloy-4 cladding samples by controlling temperature variation and gas flow control during pre-hydriding treatments. Surface conditioning of the outside surface was also examined as a variable. The results of test indicate that much of the variability in the hydride thickness is due to temperature variation occurring in the furnaces as well as how hydrogen gas flows across the sample surface. Efforts to examine other alloys, gas concentrations, and different surface conditioning plan to be pursed in the next FY as more cladding samples become available

  3. AIR PASSIVATION OF METAL HYDRIDE BEDS FOR WASTE DISPOSAL

    SciTech Connect

    Klein, J; R. H. Hsu, R

    2007-07-02

    Metal hydride beds offer compact, safe storage of tritium. After metal hydride beds have reached the end of their useful life, the beds will replaced with new beds and the old beds prepared for disposal. One acceptance criteria for hydride bed waste disposal is that the material inside the bed not be pyrophoric. To determine the pyrophoric nature of spent metal hydride beds, controlled air ingress tests were performed. A simple gas handling manifold fitted with pressure transducers and a calibrated volume were used to introduce controlled quantities of air into a metal hydride bed and the bed temperature rise monitored for reactivity with the air. A desorbed, 4.4 kg titanium prototype hydride storage vessel (HSV) produced a 4.4 C internal temperature rise upon the first air exposure cycle and a 0.1 C temperature rise upon a second air exposure. A total of 346 scc air was consumed by the bed (0.08 scc per gram Ti). A desorbed, 9.66 kg LaNi{sub 4.25}Al{sub 0.75} prototype storage bed experienced larger temperature rises over successive cycles of air ingress and evacuation. The cycles were performed over a period of days with the bed effectively passivated after the 12th cycle. Nine to ten STP-L of air reacted with the bed producing both oxidized metal and water.

  4. Novel fuel cell stack with coupled metal hydride containers

    NASA Astrophysics Data System (ADS)

    Liu, Zhixiang; Li, Yan; Bu, Qingyuan; Guzy, Christopher J.; Li, Qi; Chen, Weirong; Wang, Cheng

    2016-10-01

    Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system. To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

  5. Electrochemical behavior of chemically synthesized selenium thin film.

    PubMed

    Patil, A M; Kumbhar, V S; Chodankar, N R; Lokhande, A C; Lokhande, C D

    2016-05-01

    The facile and low cost simple chemical bath deposition (CBD) method is employed to synthesize red colored selenium thin films. These selenium films are characterized for structural, morphological, topographical and wettability studies. The X-ray diffraction (XRD) pattern showed the crystalline nature of selenium thin film with hexagonal crystal structure. The scanning electron microscopy (SEM) study displays selenium nanoparticles ranging from 20 to 475 nm. A specific surface area of 30.5 m(2) g(-1) is observed for selenium nanoparticles. The selenium nanoparticles hold mesopores in the range of 1.39 nm, taking benefits of the good physicochemical stability and excellent porosity. Subsequently, the electrochemical properties of selenium thin films are deliberated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques. The selenium thin film shows specific capacitance (Cs) of 21.98 F g(-1) with 91% electrochemical stability. PMID:26896773

  6. Geochemistry of selenium in a coastal salt marsh

    SciTech Connect

    Velinsky, D.J.; Cutter, G.A. )

    1991-01-01

    The cycling of sedimentary selenium was examined over a one-year period in the Great Marsh, Delaware (USA). While total selenium and elemental selenium decrease with depth in the sediments at similar rates, Se(IV + VI) exhibits pronounced seasonality related to the redox conditions of the marsh. Porewater selenium reflects the diagenetic cycling of Se(IV + VI) in the sediments and suggests that a partial remobilization of sedimentary selenium occurs when the upper sediments become oxidizing. Diagenetic and mass-balance models indicate that the major sources of selenium to the marsh are creek waters and atmospheric deposition, while total selenium may be removed from the sediments via the flux of volatile selenium compounds.

  7. Re-exposure of mallards to selenium after chronic exposure

    SciTech Connect

    Heinz, G.H. . Patuxent Wildlife Research Center)

    1993-09-01

    Adult male mallards (Anas platyrhynchos) were fed a control diet or a diet containing 15 ppm selenium as seleno-D,L-methionine for 21 weeks. After this initial exposure, the mallards were fed untreated food for 12 weeks, then were re-exposed to selenium at 100 ppm for five weeks. During re-exposure to 100 ppm selenium, the birds that had previously been exposed to 15 ppm selenium and those that had not previously been exposed did not differ in percentage of mortality, weight loss in survivors, selenium concentrations in the livers of survivors, or selenium concentrations in the livers of birds that died. When the data from the birds that had previously been exposed to 15 ppm selenium were combined in the livers of birds that had died on the 100-ppm selenium treatment did not differ from the concentrations in the livers of birds that had survived.

  8. EURRECA-Estimating selenium requirements for deriving dietary reference values.

    PubMed

    Hurst, Rachel; Collings, Rachel; Harvey, Linda J; King, Maria; Hooper, Lee; Bouwman, Jildau; Gurinovic, Mirjana; Fairweather-Tait, Susan J

    2013-01-01

    Current reference values for selenium, an essential micronutrient, are based on the intake of selenium that is required to achieve maximal glutathione peroxidase activity in plasma or erythrocytes. In order to assess the evidence of relevance to setting dietary reference values for selenium, the EURRECA Network of Excellence focused on systematic searches, review, and evaluation of (i) selenium status biomarkers and evidence for relationships between intake and status biomarkers, (ii) selenium and health (including the effect of intake and/or status biomarkers on cancer risk, immune function, HIV, cognition, and fertility), (iii) bioavailability of selenium from the diet, and (iv) impact of genotype/single nucleotide polymorphisms on status or health outcomes associated with selenium. The main research outputs for selenium and future research priorities are discussed further in this review. PMID:23952089

  9. Selenised compressed salt blocks for selenium deficient sheep.

    PubMed

    Money, D F; Meads, W J; Morrison, L

    1986-06-01

    Salt blocks containing 30 or 120 ppm selenium were tested as the sole supplement for sheep farmed in a selenium-deficient area of New Zealand (Te Anau). Both concentrations were unsatisfactory in preventing selenium deficiency. In five trials using 120 ppm Se salt, the highest percentages of sheep found to be deficient were 31% (lambs) and 32% (ewes). If sheep which were classed as marginally deficient were included these percentages became 63% (lambs) and 56% (ewes). Some instances of selenium-responsive unthriftiness in lambs were encountered, and in one trial there was the possibility of selenium-responsive infertility having contributed to the low lambing performance of the ewes. There was no evidence of white muscle disease. Selenium levels in the liver and kidney were well below the permitted maximum. Because selenised salt failed to eliminate selenium deficiency, its use as a sole supplement for sheep grazing selenium deficient pasture is not recommended. PMID:16031288

  10. Terminal Hydride in [FeFe]-Hydrogenase Model Has Lower Potential for H2 Production Than the Isomeric Bridging Hydride

    PubMed Central

    Barton, Bryan E.; Rauchfuss, Thomas B.

    2008-01-01

    Protonation of the symmetrical tetraphosphine complexes Fe2(S2CnH2n)(CO)2(dppv)2 afforded the corresponding terminal hydrides, establishing that even symmetrical diiron(I) dithiolates undergo protonation at terminal sites. The terminal hydride [HFe2(S2C3H6)(CO)2(dppv)2]+ was found to catalyze proton reduction at potentials 200 mV milder than the isomeric bridging hydride, thereby establishing a thermodynamic advantage for catalysis operating via terminal hydride. The azadithiolate protonates to afford, [Fe2[(SCH2)2NH2](CO)2(dppv)2]+, [HFe2[(SCH2)2NH](CO)2−(dppv)2]+, and [HFe2[(SCH2)2NH2](CO)2(dppv)2]2+, depending on conditions. PMID:18333613

  11. Avoidance of selenium-treated food by mallards

    USGS Publications Warehouse

    Heinz, G.H.; Sanderson, C.J.

    1990-01-01

    Adult, male mallards (Anas platyrhynchos) were given a choice between a control diet and a diet containing 5, 10 or 20 ppm selenium as selenomethionine dissolved in water and mixed into the diet. At 10 and 20 ppm, selenium-treated diets were avoided. Avoidance appeared to be caused by a conditioned response, probably to illness caused by the selenium and not to an aversion to the taste of the selenium.

  12. Trapping polar molecules in an ac trap

    SciTech Connect

    Bethlem, Hendrick L.; Veldhoven, Jacqueline van; Schnell, Melanie; Meijer, Gerard

    2006-12-15

    Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.

  13. A quantitative phase field model for hydride precipitation in zirconium alloys: Part II. Modeling of temperature dependent hydride precipitation

    NASA Astrophysics Data System (ADS)

    Xiao, Zhihua; Hao, Mingjun; Guo, Xianghua; Tang, Guoyi; Shi, San-Qiang

    2015-04-01

    A quantitative free energy functional developed in Part I (Shi and Xiao, 2014 [1]) was applied to model temperature dependent δ-hydride precipitation in zirconium in real time and real length scale. At first, the effect of external tensile load on reorientation of δ-hydrides was calibrated against experimental observations, which provides a modification factor for the strain energy in free energy formulation. Then, two types of temperature-related problems were investigated. In the first type, the effect of temperature transient was studied by cooling the Zr-H system at different cooling rates from high temperature while an external tensile stress was maintained. At the end of temperature transients, the average hydride size as a function of cooling rate was compared to experimental data. In the second type, the effect of temperature gradients was studied in a one or two dimensional temperature field. Different boundary conditions were applied. The results show that the hydride precipitation concentrated in low temperature regions and that it eventually led to the formation of hydride blisters in zirconium. A brief discussion on how to implement the hysteresis of hydrogen solid solubility on hydride precipitation and dissolution in the developed phase field scheme is also presented.

  14. Selenium deficiency and the effects of supplementation on preterm infants

    PubMed Central

    Freitas, Renata Germano B. O. N.; Nogueira, Roberto José N.; Antonio, Maria Ângela R. G. M.; Barros-Filho, Antonio de Azevedo; Hessel, Gabriel

    2014-01-01

    Objective: This study aimed to review the literature about blood concentrations of selenium associated with gestational age, feeding, supplementation and related clinical features in preterm infants. Data sources: Systematic review in the following databases: MEDLINE, PubMed, Google academics, SciELO. org, ScienceDirect (Elsevier) and CINAHL-Plus with Full Text (EBSCO). Articles published up to January 2013 with the keywords "selenium deficiency", "selenium supplementation", "neonates", "infants", "newborn" and "preterm infants" were selected. Data synthesis: The studies reported that low blood selenium levels are associated with increased risk of respiratory diseases. Preterm infants, especially with low birth weight, presented lower selenium levels. Selenium deficiency has also been associated with the use of oral infant formula, enteral and parenteral nutrition (with or without selenium addition). The optimal dose and length of selenium supplementation is not well-established, since they are based only on age group and selenium ingestion by breastfed children. Furthermore, the clinical status of the infant affected by conditions that may increase oxidative stress, and consequently, selenium requirements is not taken into account. Conclusions: Prematurity and low birth weight can contribute to low blood selenium in premature infants. Selenium supplementation seems to minimize or prevent clinical complications caused by prematurity. PMID:24676200

  15. 21 CFR 524.2101 - Selenium disulfide suspension.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Selenium disulfide suspension. 524.2101 Section... § 524.2101 Selenium disulfide suspension. (a) Specifications. The product contains 0.9-percent weight in weight (w/w) selenium disulfide (1-percent weight in volume (w/v)). (b) Sponsors. See Nos. 000061,...

  16. 21 CFR 524.2101 - Selenium disulfide suspension.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Selenium disulfide suspension. 524.2101 Section... § 524.2101 Selenium disulfide suspension. (a) Specifications. The product contains 0.9-percent weight in weight (w/w) selenium disulfide (1-percent weight in volume (w/v)). (b) Sponsors. See Nos. 000061,...

  17. 21 CFR 524.2101 - Selenium disulfide suspension.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Selenium disulfide suspension. 524.2101 Section... § 524.2101 Selenium disulfide suspension. (a) Specifications. The product contains 0.9-percent weight in weight (w/w) selenium disulfide (1-percent weight in volume (w/v)). (b) Sponsors. See Nos. 000061,...

  18. 21 CFR 524.2101 - Selenium disulfide suspension.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Selenium disulfide suspension. 524.2101 Section... § 524.2101 Selenium disulfide suspension. (a) Specifications. The product contains 0.9-percent weight in weight (w/w) selenium disulfide (1-percent weight in volume (w/v)). (b) Sponsors. See Nos. 000061,...

  19. 21 CFR 520.2100 - Selenium, vitamin E capsules.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Selenium, vitamin E capsules. 520.2100 Section 520...) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.2100 Selenium, vitamin... to 1 milligram of selenium) and 56.2 milligrams of vitamin E (68 I.U.) (as d-alpha tocopheryl...

  20. 21 CFR 520.2100 - Selenium, vitamin E capsules.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Selenium, vitamin E capsules. 520.2100 Section 520...) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.2100 Selenium, vitamin... to 1 milligram of selenium) and 56.2 milligrams of vitamin E (68 I.U.) (as d-alpha tocopheryl...

  1. 21 CFR 520.2100 - Selenium, vitamin E capsules.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Selenium, vitamin E capsules. 520.2100 Section 520...) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.2100 Selenium, vitamin... to 1 milligram of selenium) and 56.2 milligrams of vitamin E (68 I.U.) (as d-alpha tocopheryl...

  2. 21 CFR 520.2100 - Selenium, vitamin E capsules.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Selenium, vitamin E capsules. 520.2100 Section 520...) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.2100 Selenium, vitamin... to 1 milligram of selenium) and 56.2 milligrams of vitamin E (68 I.U.) (as d-alpha tocopheryl...

  3. 21 CFR 520.2100 - Selenium, vitamin E capsules.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Selenium, vitamin E capsules. 520.2100 Section 520...) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.2100 Selenium, vitamin... to 1 milligram of selenium) and 56.2 milligrams of vitamin E (68 I.U.) (as d-alpha tocopheryl...

  4. Selenium: an element for life.

    PubMed

    Duntas, Leonidas H; Benvenga, Salvatore

    2015-04-01

    This review aims to illustrate the importance of selenium (Se) for maintenance of overall health, especially for the thyroid, immunity, and homeostasis. Furthermore, it outlines the role of Se in reproduction and in virology and discusses the effects of Se supplementation in critical illness. The multifaceted aspects of this essential nutrient have attracted worldwide clinical and research interest in the last few decades. Se exerts its activity in the form of the aminoacid selenocysteine incorporated in selenoproteins. The impact of Se administration should be considered in relation to its apparent U shaped effects, i.e., exhibiting major advantages in Se-deficient individuals but specific health risks in those with Se excess. Addition of selenium to the administration of levothyroxine may be useful in patients with low Se intake and with mild-form or early-stage Hashimoto's thyroiditis (HT). Serum Se concentration (possibly also at tissue level) decreases in inflammatory conditions and may vary with the severity and duration of the inflammatory process. In such cases, the effect of Se supplementation seems to be useful and rational. Meanwhile, Se's ability to improve the activity of T cells and the cytotoxicity of natural killer cells could render it effective in viral disease. However, the evidence, and this should be stressed, is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves' Orbitopathy. The role of Se in type 2 diabetes mellitus (T2DM) is ambiguous, driven by both Se intake and serum levels. The evidence that insulin and glycaemia influence the transport and activity of Se, via regulatory activity on selenoproteins, and that high serum Se may have a diabetogenic effect suggests a 'Janus-effect' of Se in T2DM. Though the evidence is not as yet clear-cut, the organic form (selenomethionine), due to its pharmacokinetics, is likely to

  5. [Pharmaconutrition with parenteral selenium in sepsis].

    PubMed

    Langlois, P L; de Oliveira Figliolino, L F; Hardy, G; Manzanares, W

    2014-04-01

    Critical illness is characterized by oxidative stress which leads to multiple organ failure, and sepsis-related organ dysfunction remains the most common cause of death in the intensive care unit. Over the last 2 decades, different antioxidant therapies have been developed to improve outcomes in septic patients. According to recent evidence, selenium therapy should be considered the cornerstone of the antioxidant strategies. Selenium given as selenious acid or sodium selenite should be considered as a drug or pharmaconutrient with prooxidant and cytotoxic effects when a loading dose in intravenous bolus form is administered, particularly in the early stage of severe sepsis/septic shock. To date, several phase ii trials have demonstrated that selenium therapy may be able to decrease mortality, improve organ dysfunction and reduce infections in critically ill septic patients. The effect of selenium therapy in sepsis syndrome must be confirmed by large, well designed phase iii clinical trials. The purpose of this review is to discuss current evidence on selenium pharmaconutrition in sepsis syndrome.

  6. [Pharmaconutrition with parenteral selenium in sepsis].

    PubMed

    Langlois, P L; de Oliveira Figliolino, L F; Hardy, G; Manzanares, W

    2014-04-01

    Critical illness is characterized by oxidative stress which leads to multiple organ failure, and sepsis-related organ dysfunction remains the most common cause of death in the intensive care unit. Over the last 2 decades, different antioxidant therapies have been developed to improve outcomes in septic patients. According to recent evidence, selenium therapy should be considered the cornerstone of the antioxidant strategies. Selenium given as selenious acid or sodium selenite should be considered as a drug or pharmaconutrient with prooxidant and cytotoxic effects when a loading dose in intravenous bolus form is administered, particularly in the early stage of severe sepsis/septic shock. To date, several phase ii trials have demonstrated that selenium therapy may be able to decrease mortality, improve organ dysfunction and reduce infections in critically ill septic patients. The effect of selenium therapy in sepsis syndrome must be confirmed by large, well designed phase iii clinical trials. The purpose of this review is to discuss current evidence on selenium pharmaconutrition in sepsis syndrome. PMID:24021703

  7. Selenium in Camel – A Review

    PubMed Central

    Faye, Bernard; Seboussi, Rabiha

    2009-01-01

    Requirements for trace minerals in camels, particularly selenium, are not well-known. Selenium supplementation using a pharmaceutical form or commercial mineral mixture is common practice in camels to address the cardiomyopathy often attributed to selenium deficiency. This supplementation is often empirical and based on estimated needs for cattle. Nowadays the use of selenium in animal foodstuffs is commonplace and further investigation of its metabolism (ingestion, dynamic of storage-destocking, excretion) in camels is warranted. The present review aimed to synthesize all the experimental research (comparative selenium status in cow and camel, response to different levels of supplementation at different physiological stages, excretion maternal transfer, experimental toxicosis) and field observations (deficiency, supplementation practices) undertaken in camels. The results underline the particularity of the unique metabolic profile of the camel and lead to practical recommendations for supplementation in camels, highlighting its relative sensitivity to excess Se intake at lower levels than in cattle. The maximal tolerable dose is 8 mg and the recommended doses range from 2 to 4 mg. PMID:22253966

  8. Chemical Hydride Slurry for Hydrogen Production and Storage

    SciTech Connect

    McClaine, Andrew W

    2008-09-30

    The purpose of this project was to investigate and evaluate the attractiveness of using a magnesium chemical hydride slurry as a hydrogen storage, delivery, and production medium for automobiles. To fully evaluate the potential for magnesium hydride slurry to act as a carrier of hydrogen, potential slurry compositions, potential hydrogen release techniques, and the processes (and their costs) that will be used to recycle the byproducts back to a high hydrogen content slurry were evaluated. A 75% MgH2 slurry was demonstrated, which was just short of the 76% goal. This slurry is pumpable and storable for months at a time at room temperature and pressure conditions and it has the consistency of paint. Two techniques were demonstrated for reacting the slurry with water to release hydrogen. The first technique was a continuous mixing process that was tested for several hours at a time and demonstrated operation without external heat addition. Further work will be required to reduce this design to a reliable, robust system. The second technique was a semi-continuous process. It was demonstrated on a 2 kWh scale. This system operated continuously and reliably for hours at a time, including starts and stops. This process could be readily reduced to practice for commercial applications. The processes and costs associated with recycling the byproducts of the water/slurry reaction were also evaluated. This included recovering and recycling the oils of the slurry, reforming the magnesium hydroxide and magnesium oxide byproduct to magnesium metal, hydriding the magnesium metal with hydrogen to form magnesium hydride, and preparing the slurry. We found that the SOM process, under development by Boston University, offers the lowest cost alternative for producing and recycling the slurry. Using the H2A framework, a total cost of production, delivery, and distribution of $4.50/kg of hydrogen delivered or $4.50/gge was determined. Experiments performed at Boston

  9. Loss of selenium-binding protein 1 decreases sensitivity to clastogens and intracellular selenium content in HeLa cells

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium-binding protein 1 (SBP1) is not a selenoprotein but structurally binds selenium. Loss of SBP1 during carcinogenesis usually predicts poor prognosis. Because genome instability is a hallmark of cancer, we hypothesized that loss of SBP1 modulates cellular selenium content and the response of ...

  10. Influence of uranium hydride oxidation on uranium metal behaviour

    SciTech Connect

    Patel, N.; Hambley, D.; Clarke, S.A.; Simpson, K.

    2013-07-01

    This work addresses concerns that the rapid, exothermic oxidation of active uranium hydride in air could stimulate an exothermic reaction (burning) involving any adjacent uranium metal, so as to increase the potential hazard arising from a hydride reaction. The effect of the thermal reaction of active uranium hydride, especially in contact with uranium metal, does not increase in proportion with hydride mass, particularly when considering large quantities of hydride. Whether uranium metal continues to burn in the long term is a function of the uranium metal and its surroundings. The source of the initial heat input to the uranium, if sufficient to cause ignition, is not important. Sustained burning of uranium requires the rate of heat generation to be sufficient to offset the total rate of heat loss so as to maintain an elevated temperature. For dense uranium, this is very difficult to achieve in naturally occurring circumstances. Areas of the uranium surface can lose heat but not generate heat. Heat can be lost by conduction, through contact with other materials, and by convection and radiation, e.g. from areas where the uranium surface is covered with a layer of oxidised material, such as burned-out hydride or from fuel cladding. These rates of heat loss are highly significant in relation to the rate of heat generation by sustained oxidation of uranium in air. Finite volume modelling has been used to examine the behaviour of a magnesium-clad uranium metal fuel element within a bottle surrounded by other un-bottled fuel elements. In the event that the bottle is breached, suddenly, in air, it can be concluded that the bulk uranium metal oxidation reaction will not reach a self-sustaining level and the mass of uranium oxidised will likely to be small in relation to mass of uranium hydride oxidised. (authors)

  11. Fatigue crack growth in lithium hydride

    SciTech Connect

    Healy, T.E.

    1993-09-01

    Subcritical fatigue crack growth, from cyclic tensile loading, was demonstrated in warm pressed Polycrystalline lithium hydride. Experiments were performed with cyclic tension-tension crack opening (mode I) loads applied to a pre-cracked compact type specimen in an argon environment at a temperature of 21C (70F). The fatigue crack growth was found to occur between 7.56 {times} 10{sup {minus}ll} M/cycle (2.98 {times} l0{sup {minus}9} in/cycle) and 2.35 {times} l0{sup {minus}8} m/cycle (9.24{times}10{sup {minus}7} in/cycle) for a range of stress intensity factors between 1.04 MPa{center_dot}{radical}m (0.95 ksi{center_dot}{radical}in) and 1.49 MPa{center_dot}{radical}m (1.36 ksi{center_dot}{radical}in). The rate of fatigue crack growth from cyclic tensile loading was found to be in excess of crack growth from sustained loading at an equivalent stress intensity factor. Furthermore, a fatigue threshold was not evident from the acquired data.

  12. Transition-Metal Hydride Radical Cations.

    PubMed

    Hu, Yue; Shaw, Anthony P; Estes, Deven P; Norton, Jack R

    2016-08-10

    Transition-metal hydride radical cations (TMHRCs) are involved in a variety of chemical and biochemical reactions, making a more thorough understanding of their properties essential for explaining observed reactivity and for the eventual development of new applications. Generally, these species may be treated as the ones formed by one-electron oxidation of diamagnetic analogues that are neutral or cationic. Despite the importance of TMHRCs, the generally sensitive nature of these complexes has hindered their development. However, over the last four decades, many more TMHRCs have been synthesized, characterized, isolated, or hypothesized as reaction intermediates. This comprehensive review focuses on experimental studies of TMHRCs reported through the year 2014, with an emphasis on isolated and observed species. The methods used for the generation or synthesis of TMHRCs are surveyed, followed by a discussion about the stability of these complexes. The fundamental properties of TMHRCs, especially those pertaining to the M-H bond, are described, followed by a detailed treatment of decomposition pathways. Finally, reactions involving TMHRCs as intermediates are described. PMID:26828562

  13. Transition-Metal Hydride Radical Cations.

    PubMed

    Hu, Yue; Shaw, Anthony P; Estes, Deven P; Norton, Jack R

    2016-08-10

    Transition-metal hydride radical cations (TMHRCs) are involved in a variety of chemical and biochemical reactions, making a more thorough understanding of their properties essential for explaining observed reactivity and for the eventual development of new applications. Generally, these species may be treated as the ones formed by one-electron oxidation of diamagnetic analogues that are neutral or cationic. Despite the importance of TMHRCs, the generally sensitive nature of these complexes has hindered their development. However, over the last four decades, many more TMHRCs have been synthesized, characterized, isolated, or hypothesized as reaction intermediates. This comprehensive review focuses on experimental studies of TMHRCs reported through the year 2014, with an emphasis on isolated and observed species. The methods used for the generation or synthesis of TMHRCs are surveyed, followed by a discussion about the stability of these complexes. The fundamental properties of TMHRCs, especially those pertaining to the M-H bond, are described, followed by a detailed treatment of decomposition pathways. Finally, reactions involving TMHRCs as intermediates are described.

  14. Hydrides in Space: Past, Present, and Future

    NASA Astrophysics Data System (ADS)

    Lis, D. C.; Goldsmith, P. F.; Bergin, E. A.; Falgarone, E.; Gerin, M.; Roueff, E.

    2009-12-01

    One of the central questions of modern astrophysics concerns the life cycle of molecules in the Universe—from the diffuse interstellar medium to planetary systems—and the chemical pathways leading from simple atoms and diatomic molecules to complex organic species. In the past two decades, the Caltech Submillimeter Observatory (CSO) has contributed a number of key discoveries on these topics. Light hydrides are of particular interest for astrochemistry, as the basic building blocks of the chemical networks in both diffuse and dense clouds. Ongoing and planned submillimeter wide-field continuum surveys will yield hundreds of potential galactic targets suitable for detailed spectroscopic follow-ups. Recent advances in detector and digital spectrometer technologies promise to truly revolutionize further the field of high-resolution submillimeter spectroscopy and its application to the study of the life cycle of molecules. This will greatly improve our understanding of astrochemistry, astrobiology, the origin of life on Earth, and allow assessing the possibilities of life in other planetary systems.

  15. Selenium and Iodine in Autoimmune Thyroiditis.

    PubMed

    Guastamacchia, Edoardo; Giagulli, Vito Angelo; Licchelli, Brunella; Triggiani, Vincenzo

    2015-01-01

    Selenium and iodine are essential for thyroid hormone synthesis and function. Selenium, in form of selenocysteine, is found either in the catalytic center of enzymes involved in the protection of the thyroid gland from free radicals originating during thyroid hormone synthesis, and in three different iodothyronine deiodinases catalyzing the activation and the inactivation of thyroid hormones. Iodine is an essential constituent of thyroid hormones and its deficiency causes different disorders that include goiter, hypothyroidism, reduced fertility and alteration in growth, physical and neurological development. These two micronutrients could be involved in the pathogenesis of autoimmune thyroid diseases, a spectrum of pathological conditions including Hashimoto's thryoiditis, post-partum thyroiditis, the so-called painless thyroiditis, Graves' disease and Graves' ophtalmopathy. Aim of this paper is to review the role played by selenium and iodine in autoimmune thyroiditis.

  16. Synthesis and stabilization of selenium nanoparticles on cellulose nanocrystal

    SciTech Connect

    Shin, Yongsoon; Blackwood, Jade M.; Bae, In-Tae; Arey, Bruce W.; Exarhos, Gregory J.

    2007-08-01

    Selenium nanoparticles of 10-20 nm in diameter have been prepared using cellulose nanocrystal (CNXL) as a reducing and structure-directing agent under hydrothermal conditions. Na2SeO3 was reduced to form elemental selenium nanoparticles under hydrothermal conditions. During the hydrothermal process (120-160 oC), CNXL rods were mainly maintained and selenium nanoparticles were interfacially bound to CNXL surface. The reaction temperature affects the sizes of interfacially bound selenium nanoparticles. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and transmission electron microscope (TEM) were employed to characterize interfacially bound selenium nanoparticles on CNXL surface.

  17. Investigation of electrical noise in selenium-immersed thermistor bolometers

    NASA Technical Reports Server (NTRS)

    Tarpley, J. L.; Sarmiento, P. D.

    1980-01-01

    The selenium immersed, thermistor bolometer, IR detector failed due to spurious and escalating electrical noise outburst as a function of time at elevated temperatures during routine ground based testing in a space simulated environment. Spectrographic analysis of failed bolometers revealed selenium pure zones in the insulating selenium arsenic (Se-As) glass film which surrounds the active sintered Mn, Ni, Co oxide flake. The selenium pure film was identified as a potentially serious failure mechanism. Significant changes were instituted in the manufacturing techniques along with more stringent process controls which eliminated the selenium pure film and successfully produced 22study bolometers.

  18. Selenium speciation in ground water. Quarterly report

    SciTech Connect

    Atalay, A.

    1990-07-10

    Selenium toxicity diseases in animals may occur when the intake exceeds 4 mg/kg and selenium deficiency symptoms may occur when dietary intake is less than 0.04 mg/kg. Since the selenium dietary requirement is very close to toxic concentration, it is important to understand the distribution of selenium in the environment. Selenium occurs in four oxidation states (-II, 0, +IV, and +VI) as selenide, elemental selenium, selenite and selenate. Selenate is reported as more soluble and less adsorbed than selenite. Selenate is more easily leached from soils and is the most available form for plants. Increased mobility of Se into the environment via anthropogenic activities, and the potential oxidation-reduction behavior of the element have made it imperative to study the aquatic chemistry of Se. For this purpose, Se species are divided into two different categories: dissolved Se (in material that passes through filters with 0.45 u openings) and particulate Se (in material of particle size > 0.45 mm) typically suspended sediment and other suspended solids. Element and colloidal phase, not truly dissolved, but passing through the filter is deemed to consist of selenium (-2,0). In dissolved state selenium may exist in three of its four oxidation states; Se(-II), Se(+IV), and Se(+VI). Particulate Se may exist in the same oxidation states as dissolved Se and can be found in different phases of the particulate matter. In sediments, Se may be within the organic material, iron and manganese oxides, carbonates or other mineral phases. The actual chemical forms of Se may be adsorbed to or coprecipitated with these phases (primarily selenite, SeO{sub 3}{sup 2{minus}}) and selenate, SeO{sub 4}{sup 2{minus}}. Selenide, Se(-II), can be covalently bound in the organic portion of a sediment. In addition, Se may be found in anoxic sediments as insoluble metal selenide precipitates, an insoluble elemental Se or as ferroselite (FeSe{sub 2}) and Se containing pyrite.

  19. Hydrogen storage as a hydride. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Zollars, G. F.

    1980-01-01

    These citations from the international literature concern the storage of hydrogen in various metal hydrides. Binary and intermetallic hydrides are considered. Specific alloys discussed are iron titanium, lanthanium nickel, magnesium copper and magnesium nickel among others.

  20. Micro-scale fracture experiments on zirconium hydrides and phase boundaries

    NASA Astrophysics Data System (ADS)

    Chan, H.; Roberts, S. G.; Gong, J.

    2016-07-01

    Fracture properties of micro-scale zirconium hydrides and phase boundaries were studied using microcantilever testing methods. FIB-machined microcantilevers were milled on cross-sectional surfaces of hydrided samples, with the most highly-stressed regions within the δ-hydride film, within the α-Zr or along the Zr-hydride interface. Cantilevers were notched using the FIB and then tested in bending using a nanoindenter. Load-displacement results show that three types of cantilevers have distinct deformation properties. Zr cantilevers deformed plastically. Hydride cantilevers fractured after a small amount of plastic flow; the fracture toughness of the δ-hydride was found to be 3.3 ± 0.4 MPam1/2 and SEM examination showed transgranular cleavage on the fracture surfaces. Cantilevers notched at the Zr-hydride interface developed interfacial voids during loading, at loads considerably lower than that which initiate brittle fracture of hydrides.

  1. Ab Initio Thermochemistry and Elastic Properties of Alkaline Earth Hydrides

    NASA Astrophysics Data System (ADS)

    Hector, Louis, Jr.; Herbst, Jan; Wolf, Walter; Saxe, Paul

    2006-03-01

    In addition to comprising a scientifically interesting class of materials, the binary alkaline earth hydrides are important components of hydrogen sorption/desorption reactions. Of critical importance for predicting the thermodynamic stability of hydrides is the enthalpy of hydride formation, δH, which links the temperature and pressure of hydrogen sorption via the van't Hoff relation. We compare LDA and GGA predictions of the heats of formation and elastic properties of alkaline earth metals and their binary hydrides BeH2, MgH2, CaH2, SrH2, and BaH2 using a plane wave density functional method. Phonon calculations using the direct method enabled prediction of the zero point energies of each material and the 0K and 298K heats of formation. We also computed the 0K and 298K cohesive energies for the alkaline earth metals. Born effective charge tensors were computed via the Berry phase method and enabled prediction of the phonon dispersion curves with LO/TO zone center splittings. It was found that the LO/TO splittings have no effect on the computed zero point energies and heats of formation. The elastic constants were computed with a least squares fitting method using a set of sequentially-applied strains to improve the accuracy of each calculation. Comparison of results from the least squares methodology with prior results using the Hartree-Fock method suggest that the former is substantially more accurate for predicting hydride elastic properties.

  2. Multidimensional simulations of hydrides during fuel rod lifecycle

    NASA Astrophysics Data System (ADS)

    Stafford, D. S.

    2015-11-01

    In light water reactor fuel rods, waterside corrosion of zirconium-alloy cladding introduces hydrogen into the cladding, where it is slightly soluble. When the solubility limit is reached, the hydrogen precipitates into crystals of zirconium hydride which decrease the ductility of the cladding and may lead to cladding failure during dry storage or transportation events. The distribution of the hydride phase and the orientation of the crystals depend on the history of the spatial temperature and stress profiles in the cladding. In this work, we have expanded the existing hydride modeling capability in the BISON fuel performance code with the goal of predicting both global and local effects on the radial, azimuthal and axial distribution of the hydride phase. We compare results from 1D simulations to published experimental data. We demonstrate the new capability by simulating in 2D a fuel rod throughout a lifecycle that includes irradiation, short-term storage in the spent fuel pool, drying, and interim storage in a dry cask. Using the 2D simulations, we present qualitative predictions of the effects of the inter-pellet gap and the drying conditions on the growth of a hydride rim.

  3. Sodium-based hydrides for thermal energy applications

    NASA Astrophysics Data System (ADS)

    Sheppard, D. A.; Humphries, T. D.; Buckley, C. E.

    2016-04-01

    Concentrating solar-thermal power (CSP) with thermal energy storage (TES) represents an attractive alternative to conventional fossil fuels for base-load power generation. Sodium alanate (NaAlH4) is a well-known sodium-based complex metal hydride but, more recently, high-temperature sodium-based complex metal hydrides have been considered for TES. This review considers the current state of the art for NaH, NaMgH3- x F x , Na-based transition metal hydrides, NaBH4 and Na3AlH6 for TES and heat pumping applications. These metal hydrides have a number of advantages over other classes of heat storage materials such as high thermal energy storage capacity, low volume, relatively low cost and a wide range of operating temperatures (100 °C to more than 650 °C). Potential safety issues associated with the use of high-temperature sodium-based hydrides are also addressed.

  4. The effect of stress state on zirconium hydride reorientation

    NASA Astrophysics Data System (ADS)

    Cinbiz, Mahmut Nedim

    Prior to storage in a dry-cask facility, spent nuclear fuel must undergo a vacuum drying cycle during which the spent fuel rods are heated up to elevated temperatures of ≤ 400°C to remove moisture the canisters within the cask. As temperature increases during heating, some of the hydride particles within the cladding dissolve while the internal gas pressure in fuel rods increases generating multi-axial hoop and axial stresses in the closed-end thin-walled cladding tubes. As cool-down starts, the hydrogen in solid solution precipitates as hydride platelets, and if the multiaxial stresses are sufficiently large, the precipitating hydrides reorient from their initial circumferential orientation to radial orientation. Radial hydrides can severely embrittle the spent nuclear fuel cladding at low temperature in response to hoop stress loading. Because the cladding can experience a range of stress states during the thermo-mechanical treatment induced during vacuum drying, this study has investigated the effect of stress state on the process of hydride reorientation during controlled thermo-mechanical treatments utilizing the combination of in situ X-ray diffraction and novel mechanical testing analyzed by the combination of metallography and finite element analysis. The study used cold worked and stress relieved Zircaloy-4 sheet containing approx. 180 wt. ppm hydrogen as its material basis. The failure behavior of this material containing radial hydrides was also studied over a range of temperatures. Finally, samples from reactor-irradiated cladding tubes were examined by X-ray diffraction using synchrotron radiation. To reveal the stress state effect on hydride reorientation, the critical threshold stress to reorient hydrides was determined by designing novel mechanical test samples which produce a range of stress states from uniaxial to "near-equibiaxial" tension when a load is applied. The threshold stress was determined after thermo-mechanical treatments by

  5. [The role of selenium in endocrine system diseases].

    PubMed

    Balázs, Csaba; Rácz, Károly

    2013-10-13

    Oxygen derived free radicals, generated by a number of cellular reactions, include superoxide anion, hydrogen peroxide and hydroxyl radicals. They exert their cytotoxic effects mainly via peroxidation of the cell membrane resulting in the loss of membrane integrity. The essential trace element, selenium exerts complex effects on the endocrine systems, partly due to its antioxidant capacity. Well-characterized selenoproteins include iodothyronine deiodinases, glutathione peroxidases and thioredoxin reductases involved in thyroid hormone metabolism and protection from oxidative damage. The value of selenium supplementation in autoimmune thyroid disorders has been investigated and most studies confirmed the beneficial effect of selenium supplementation in Hashimoto's and Graves's diseases. Recently, selenium proved to be effective in mild inflammatory orbitopathy. There are a number of reports about the effect of selenium in diabetes mellitus, but the data are controversial as both insulin-like and diabetes-inducing effects of selenium have been described. Selenium was successfully used in both female and male infertility of autoimmune origin.

  6. Sorption vacuum trap

    NASA Technical Reports Server (NTRS)

    Barrington, A. E.; Caruso, A. J.

    1970-01-01

    Modified sorption trap for use in high vacuum systems contains provisions for online regeneration of sorbent material. Trap is so constructed that it has a number of encapsulated resistance heaters and a valving and pumping device for removing gases from heated sorbing material. Excessive downtime is eliminated with this trap.

  7. Influences of fiber, methionine and form of selenium on selenium hindgut targeting and tissue accumulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased selenium (Se) status has beneficial outcomes, including decreased colorectal cancer risk, yet obesity may interfere with Se metabolism. Commensal bacteria can influence colon carcinogenesis and Se influences the microbiome, including production of volatile fatty acids by these microbes. We...

  8. Determination of selenium via the fluorescence quenching effect of selenium on hemoglobin-catalyzed peroxidative reaction.

    PubMed

    Chen, Ya-Hong; Zhang, Ya-Nan; Tian, Feng-Shou

    2015-05-01

    A new method for the determination of selenium based on its fluorescence quenching on the hemoglobin-catalyzed reaction of H2 O2 and l-tyrosine has been established. The effect of pH, foreign ions and the optimization of variables on the determination of selenium was examined. The calibration curve was found to be linear between the fluorescence quenching (F0 /F) and the concentration of selenium within the range of 0.16-4.00 µg/mL. The detection limit was 1.96 ng/mL and the relative standard deviation was 3.14%. This method can be used for the determination of selenium in Se-enriched garlic bulbs with satisfactory results.

  9. Electrocoagulation of colloidal biogenic selenium.

    PubMed

    Staicu, Lucian C; van Hullebusch, Eric D; Lens, Piet N L; Pilon-Smits, Elizabeth A H; Oturan, Mehmet A

    2015-02-01

    Colloidal elemental selenium (Se(0)) adversely affects membrane separation processes and aquatic ecosystems. As a solution to this problem, we investigated for the first time the removal potential of Se(0) by electrocoagulation process. Colloidal Se(0) was produced by a strain of Pseudomonas fluorescens and showed limited gravitational settling. Therefore, iron (Fe) and aluminum (Al) sacrificial electrodes were used in a batch reactor under galvanostatic conditions. The best Se(0) turbidity removal (97 %) was achieved using iron electrodes at 200 mA. Aluminum electrodes removed 96 % of colloidal Se(0) only at a higher current intensity (300 mA). At the best Se(0) removal efficiency, electrocoagulation using Fe electrode removed 93 % of the Se concentration, whereas with Al electrodes the Se removal efficiency reached only 54 %. Due to the less compact nature of the Al flocs, the Se-Al sediment was three times more voluminous than the Se-Fe sediment. The toxicity characteristic leaching procedure (TCLP) test showed that the Fe-Se sediment released Se below the regulatory level (1 mg L(-1)), whereas the Se concentration leached from the Al-Se sediment exceeded the limit by about 20 times. This might be related to the mineralogical nature of the sediments. Electron scanning micrographs showed Fe-Se sediments with a reticular structure, whereas the Al-Se sediments lacked an organized structure. Overall, the results obtained showed that the use of Fe electrodes as soluble anode in electrocoagulation constitutes a better option than Al electrodes for the electrochemical sedimentation of colloidal Se(0).

  10. Factors affecting the selenium intake of people in Transbaikalian Russia.

    PubMed

    Aro, A; Kumpulainen, J; Alfthan, G; Voshchenko, A V; Ivanov, V N

    1994-03-01

    The selenium concentration in foods grown and consumed and in plasma, red blood cells, and toenails of people living in the district of Chita in the transbaikalian part of Russia were studied in August 1991. Preliminary results from the area have suggested low selenium intakes and the possible occurrence of cardiomyopathy (Keshan disease) in the population. A low selenium concentration in foods grown locally was found: mean selenium concentration in wheat grains was 1, 5, and 28 micrograms/kg, respectively, in three villages studied, that of oats was between 3-6 micrograms/kg, and of cow's milk 10-27 micrograms/kg dry matter. The selenium concentration of bread was considerably higher, between 87-337 micrograms/kg dry wt, presumably because wheat imported from the US had been used for baking. Occasional samples of pork, beef, and mutton contained between 32-218 micrograms selenium/kg dry wt. Low selenium concentrations were observed in samples of soil and river water. The mean plasma selenium concentration of 52 persons was 1.02 mumol/L, including 33 children and 19 adult subjects. The selenium concentrations in red blood cells and toenails were 1.95 mumol/L and 0.61 mg/kg, respectively. No symptoms of heart disease caused by selenium deficiency were observed. It is concluded that the selenium status of people was fairly good thanks to the contribution to dietary intake of imported wheat with a high selenium content. As the selenium concentration was very low in foods grown in the area, the selenium intake of the population will be reduced to a very low level if only locally produced foods are consumed.

  11. A study of advanced magnesium-based hydride and development of a metal hydride thermal battery system

    NASA Astrophysics Data System (ADS)

    Zhou, Chengshang

    Metal hydrides are a group of important materials known as energy carriers for renewable energy and thermal energy storage. A concept of thermal battery based on advanced metal hydrides is studied for heating and cooling of cabins in electric vehicles. The system utilizes a pair of thermodynamically matched metal hydrides as energy storage media. The hot hydride that is identified and developed is catalyzed MgH2 due to its high energy density and enhanced kinetics. TiV0.62Mn1.5, TiMn2, and LaNi5 alloys are selected as the matching cold hydride. A systematic experimental survey is carried out in this study to compare a wide range of additives including transitions metals, transition metal oxides, hydrides, intermetallic compounds, and carbon materials, with respect to their effects on dehydrogenation properties of MgH2. The results show that additives such as Ti and V-based metals, hydride, and certain intermetallic compounds have strong catalytic effects. Solid solution alloys of magnesium are exploited as a way to destabilize magnesium hydride thermodynamically. Various elements are alloyed with magnesium to form solid solutions, including indium and aluminum. Thermodynamic properties of the reactions between the magnesium solid solution alloys and hydrogen are investigated, showing that all the solid solution alloys that are investigated in this work have higher equilibrium hydrogen pressures than that of pure magnesium. Cyclic stability of catalyzed MgH2 is characterized and analyzed using a PCT Sievert-type apparatus. Three systems, including MgH2-TiH 2, MgH2-TiMn2, and MgH2-VTiCr, are examined. The hydrogenating and dehydrogenating kinetics at 300°C are stable after 100 cycles. However, the low temperature (25°C to 150°C) hydrogenation kinetics suffer a severe degradation during hydrogen cycling. Further experiments confirm that the low temperature kinetic degradation can be mainly related the extended hydrogenation-dehydrogenation reactions. Proof

  12. The effect of consumption of selenium enriched rye/wheat sourdough bread on the body's selenium status.

    PubMed

    Bryszewska, Malgorzata A; Ambroziak, Wojciech; Langford, Nicola J; Baxter, Malcolm J; Colyer, Alison; Lewis, D John

    2007-09-01

    The potential of selenium-enriched rye/wheat sourdough bread as a route for supplementing dietary selenium intakes is reported. In addition to their normal diets, 24 female volunteers (24 to 25 years old) were fed either selenium-enriched bread or non-enriched bread each day (68.02 and 0.84 microg selenium day(-1) respectively) for 4 weeks. The chemical form of the selenium in the bread had been characterised using HPLC-ICP-MS, which showed that 42% of the extractable selenium was present as selenomethionine. Plasma selenium levels and plasma platelet glutathione peroxidase (GPx1) activity were measured in the volunteers' blood over a 6-week period. A statistically significant difference (p = 0.001) was observed in the mean percentage change data, calculated from the plasma selenium level measurements for the enriched and control group, over the duration of the study. A comparable difference was not observed for the platelet GPx1 activity (p = 0.756), over the same period. Two weeks after cessation of the feeding stage, i.e., at t = 6 weeks, the mean percentage change value for the selenium plasma levels in the enriched group was still significantly elevated, suggesting that the absorbed selenium had been incorporated into the body's selenium reserves, and was then being slowly released back into the volunteers' blood.

  13. High-resolution imaging of selenium in kidneys: a localized selenium pool associated with glutathione peroxidase 3

    SciTech Connect

    Malinouski, M.; Kehr, S.; Finney, L.; Vogt, S.; Carlson, B.A.; Seravalli, J.; Jin, R.; Handy, D.E.; Park, T.J.; Loscalzo, J.; Hatfield, D.L.; Gladyshev, V.N.

    2012-04-17

    Recent advances in quantitative methods and sensitive imaging techniques of trace elements provide opportunities to uncover and explain their biological roles. In particular, the distribution of selenium in tissues and cells under both physiological and pathological conditions remains unknown. In this work, we applied high-resolution synchrotron X-ray fluorescence microscopy (XFM) to map selenium distribution in mouse liver and kidney. Liver showed a uniform selenium distribution that was dependent on selenocysteine tRNA{sup [Ser]Sec} and dietary selenium. In contrast, kidney selenium had both uniformly distributed and highly localized components, the latter visualized as thin circular structures surrounding proximal tubules. Other parts of the kidney, such as glomeruli and distal tubules, only manifested the uniformly distributed selenium pattern that co-localized with sulfur. We found that proximal tubule selenium localized to the basement membrane. It was preserved in Selenoprotein P knockout mice, but was completely eliminated in glutathione peroxidase 3 (GPx3) knockout mice, indicating that this selenium represented GPx3. We further imaged kidneys of another model organism, the naked mole rat, which showed a diminished uniformly distributed selenium pool, but preserved the circular proximal tubule signal. We applied XFM to image selenium in mammalian tissues and identified a highly localized pool of this trace element at the basement membrane of kidneys that was associated with GPx3. XFM allowed us to define and explain the tissue topography of selenium in mammalian kidneys at submicron resolution.

  14. High-Spin Cobalt Hydrides for Catalysis

    SciTech Connect

    Holland, Patrick L.

    2013-08-29

    Organometallic chemists have traditionally used catalysts with strong-field ligands that give low-spin complexes. However, complexes with a weak ligand field have weaker bonds and lower barriers to geometric changes, suggesting that they may lead to more rapid catalytic reactions. Developing our understanding of high-spin complexes requires the use of a broader range of spectroscopic techniques, but has the promise of changing the mechanism and/or selectivity of known catalytic reactions. These changes may enable the more efficient utilization of chemical resources. A special advantage of cobalt and iron catalysts is that the metals are more abundant and cheaper than those currently used for major industrial processes that convert unsaturated organic molecules and biofeedstocks into useful chemicals. This project specifically evaluated the potential of high-spin cobalt complexes for small-molecule reactions for bond rearrangement and cleavage reactions relevant to hydrocarbon transformations. We have learned that many of these reactions proceed through crossing to different spin states: for example, high-spin complexes can flip one electron spin to access a lower-energy reaction pathway for beta-hydride elimination. This reaction enables new, selective olefin isomerization catalysis. The high-spin cobalt complexes also cleave the C-O bond of CO2 and the C-F bonds of fluoroarenes. In each case, the detailed mechanism of the reaction has been determined. Importantly, we have discovered that the cobalt catalysts described here give distinctive selectivities that are better than known catalysts. These selectivities come from a synergy between supporting ligand design and electronic control of the spin-state crossing in the reactions.

  15. Investigation of metal hydride materials as hydrogen reservoirs for metal-hydrogen batteries

    NASA Technical Reports Server (NTRS)

    ONISCHAK

    1976-01-01

    The performance and suitability of various metal hydride materials were examined for use as possible hydrogen storage reservoirs for secondary metal-hydrogen batteries. Lanthanum pentanickel hydride appears as a probable candidate in terms of stable hydrogen supply under feasible thermal conditions. A kinetic model describing the decomposition rate data of the hydride has been developed.

  16. The coordination chemistry of organo-hydride donors: new prospects for efficient multi-electron reduction.

    PubMed

    McSkimming, Alex; Colbran, Stephen B

    2013-06-21

    In biological reduction processes the dihydronicotinamides NAD(P)H often transfer hydride to an unsaturated substrate bound within an enzyme active site. In many cases, metal ions in the active site bind, polarize and thereby activate the substrate to direct attack by hydride from NAD(P)H cofactor. This review looks more widely at the metal coordination chemistry of organic donors of hydride ion--organo-hydrides--such as dihydronicotinamides, other dihydropyridines including Hantzsch's ester and dihydroacridine derivatives, those derived from five-membered heterocycles including the benzimidazolines and benzoxazolines, and all-aliphatic hydride donors such as hexadiene and hexadienyl anion derivatives. The hydride donor properties--hydricities--of organo-hydrides and how these are affected by metal ions are discussed. The coordination chemistry of organo-hydrides is critically surveyed and the use of metal-organo-hydride systems in electrochemically-, photochemically- and chemically-driven reductions of unsaturated organic and inorganic (e.g. carbon dioxide) substrates is highlighted. The sustainable electrocatalytic, photochemical or chemical regeneration of organo-hydrides such as NAD(P)H, including for driving enzyme-catalysed reactions, is summarised and opportunities for development are indicated. Finally, new prospects are identified for metal-organo-hydride systems as catalysts for organic transformations involving 'hydride-borrowing' and for sustainable multi-electron reductions of unsaturated organic and inorganic substrates directly driven by electricity or light or by renewable reductants such as formate/formic acid. PMID:23507957

  17. Hydrogen storage in fullerenes and in an organic hydride

    SciTech Connect

    Wang, J.C.; Murphy, R.W.; Chen, F.C.; Loutfy, R.O.; Veksler, E.; Li, W.

    1998-05-29

    While the authors have demonstrated the importance and usefulness of thermal management to the hydrogen storage in fullerenes, their recent effort has concentrated on materials improvement and physical model development. In this paper, they report the results of this effort as follows: (1) Liquid phase hydrogenation of fullerenes indicated that more than 6 wt% capacity can be obtained at 180 C, 350--400 psi; (2) Dehydrogenation of fullerenes hydrides below 225 C was demonstrated using an Ir-based P-C-P pincer complex catalyst; (3) Cyclic hydrogenation and dehydrogenation tests of an organic hydride at 7 wt% capacity were conducted at 180--260 C; and (4) Physical models developed for fullerenes were determined to be applicable to this organic hydride (with much smaller activation energies).

  18. Metal hydride hydrogen compression: Recent advances and future prospects

    DOE PAGES

    Bowman, Jr., Robert C.; Yartys, Volodymyr A.; Lototskyy, Mykhaylo V.; Linkov, Vladimir; Grant, David; Stuart, Alastair; Eriksen, Jon; Denys, Roman

    2016-03-17

    Metal hydride (MH) thermal sorption compression is one of the more important applications of the metal hydrides. The present paper reviews recent advances in the field based on the analysis of the fundamental principles of this technology. The performances when boosting hydrogen pressure, along with two- and three-step compression units are analyzed. The paper includes also a theoretical modeling of a two-stage compressor aimed at both describing the performance of the experimentally studied systems, but, also, on their optimization and design of more advanced MH compressors. Business developments in the field are reviewed for the Norwegian company HYSTORSYS AS andmore » the South African Institute for Advanced Materials Chemistry. Finally, future prospects are outlined presenting the role of the metal hydride compression in the overall development of the hydrogen driven energy systems. Lastly, the work is based on the analysis of the development of the technology in Europe, USA and South Africa.« less

  19. CO2 hydrogenation on a metal hydride surface.

    PubMed

    Kato, Shunsuke; Borgschulte, Andreas; Ferri, Davide; Bielmann, Michael; Crivello, Jean-Claude; Wiedenmann, Daniel; Parlinska-Wojtan, Magdalena; Rossbach, Peggy; Lu, Ye; Remhof, Arndt; Züttel, Andreas

    2012-04-28

    The catalytic hydrogenation of CO(2) at the surface of a metal hydride and the corresponding surface segregation were investigated. The surface processes on Mg(2)NiH(4) were analyzed by in situ X-ray photoelectron spectroscopy (XPS) combined with thermal desorption spectroscopy (TDS) and mass spectrometry (MS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). CO(2) hydrogenation on the hydride surface during hydrogen desorption was analyzed by catalytic activity measurement with a flow reactor, a gas chromatograph (GC) and MS. We conclude that for the CO(2) methanation reaction, the dissociation of H(2) molecules at the surface is not the rate controlling step but the dissociative adsorption of CO(2) molecules on the hydride surface. PMID:22433948

  20. A new heat storage system using metal hydrides

    NASA Astrophysics Data System (ADS)

    Ono, S.; Kawamura, M.; Ishido, Y.; Akiba, E.; Higano, S.

    The development of a prototype chemical heat storage system, designed for the accumulation of fairly high temperature (300 - 400 C) waste heat, and called the Hydriding Heat Storage system is presented. Mg2Ni hydride is used as the high temperature heat storing medium, and LaNi5H6 is used as a reservoir for the hydrogen released from the heat storing medium. The system has been in development since 1976, and a 2000 kcal heat capacity prototype system is to be completed by 1982. Basic investigations, i.e., reaction kinetics of absorption and desorption, and heat transfer characteristics of the hydride and/or the metal powder packed bed, are described.

  1. The Relationship between Selenium and T3 in Selenium Supplemented and Nonsupplemented Ewes and Their Lambs

    PubMed Central

    Hefnawy, Abd Elghany; Youssef, Seham; Aguilera, P. Villalobos; Rodríguez, C. Valverde; Pérez, J. L. Tórtora

    2014-01-01

    Twenty pregnant ewes were selected and classified into two groups. The first group received subcutaneous selenium supplementation (0.1 mg of sodium selenite/kg BW) at the 8th and 5th weeks before birth and 1st week after birth while the other was control group without selenium injection. Maternal plasma and serum samples were collected weekly from the 8th week before birth until the 8th week after birth and milk samples were taken from ewes weekly, while plasma and serum samples were collected at 48 hours, 1st, 2nd, 3rd, 5th, and 8th weeks after birth from the newborn lambs. Results demonstrated significant positive relationship between maternal plasma selenium and serum T3 in supplemented and control ewes (r = 0.69 to 0.72, P < 0.05). There was significant (P < 0.001) increase in T3 in supplemented ewes and their lambs until the 8th week after birth. There was positive relationship between milk, selenium concentration, and serum T3 in the newborn lambs of the supplemented group (r = 0.84, P < 0.01), while the relationship was negative in the control one (r = −0.89, P < 0.01). Muscular and thyroid pathological changes were independent of selenium supplementation. Selenium supplementation was important for maintaining T3 in ewes and newborn lambs until the 8th week after birth. PMID:24660087

  2. Selenoprotein gene expression during selenium-repletion of selenium-deficient rats.

    PubMed

    Bermano, G; Nicol, F; Dyer, J A; Sunde, R A; Beckett, G J; Arthur, J R; Hesketh, J E

    1996-03-01

    Selenium repletion of selenium-deficient rats with 20 micrograms selenium / kg body weight as Na2SeO3 was used as a model to investigate the mechanisms that control the distribution of the trace element to specific selenoproteins in liver and thyroid. Cytosolic glutathione peroxidase (cGSHPx), phospholipid hydroperoxide glutathione peroxidase (PHGSHPx), and iodothyronine 5'-deiodinase (IDI) activities were all transiently increased in liver 16 to 32 h after ip injection with selenium. However, only cGSHPx and PHGSHPx activities increased in the thyroid where IDI activity was already increased by selenium deficiency. These responses were owing to synthesis of the seleoproteins on newly synthesised and/or existing mRNAs. The selenoprotein mRNAs in the thyroid gland were increased two- and threefold after the transitory increases in selenoprotein activity. In contrast, there were parallel changes in selenoprotein mRNAs and enzyme activities in the liver, with no prolonged rises in mRNA levels. The organ differences suggest that increased thryotrophin (TSH) concentrations, which are known to induce thyrodial IDI and mRNA, may control the mRNAs for all the thyroidal selenoproteins investigated and be a major mechanism for the preservation of thyroidal selenoproteins when selenium supplies are limited. PMID:8727669

  3. Blood selenium and glutathione peroxidase levels and dietary selenium of free-living and institutionalized elderly subjects.

    PubMed

    Lane, H W; Warren, D C; Taylor, B J; Stool, E

    1983-05-01

    The purpose of this study was to evaluate the selenium status of healthy free-living and institutionalized elderly people. For the 36 free-living elderly dietary selenium intake averaged 94 +/- 44 micrograms Se/day and a positive correlation coefficient was found between dietary selenium and dietary calories (r = 0.46; P less than 0.05), dietary protein (r = 0.60; P less than 0.01), and dietary fat (r = 0.43; P less than 0.05). Diet histories from the institutionalized subjects revealed a strong correlation coefficient between selenium and carbohydrate (r = 0.51; P less than 0.005) and selenium and calories (r = 0.44; P less than 0.05). Mean erythrocyte and plasma selenium levels for the free-living subjects were 0.20 +/- 0.06 micrograms/ml and 0.10 +/- 0.03 micrograms/ml, respectively, while mean erythrocyte glutathione peroxidase (GSH-Px) activity was 27.5 +/- 5.0 units/g protein. For the free-living subjects positive correlation was found between dietary selenium and erythrocyte selenium levels (r = 0.38; P less than 0.05) but no correlation existed between dietary selenium and plasma selenium (r = 0.13; P greater than 0.05) and RBC GSH-Px (r = -0.15; P greater than 0.05). The dietary selenium levels and blood selenium and GSH-Px levels were above the levels found in populations proposed to be at risk for selenium deficiency. Thus, these elderly appear to have adequate selenium status.

  4. Mercury and selenium content of Taiwanese seafood.

    PubMed

    Fang, G C; Nam, D H; Basu, N

    2011-01-01

    Fish consumption is avid in Taiwan (and other Asian nations), but little is known about the mercury and selenium content in local seafood. This paper reports on total mercury, methylmercury and selenium levels from 14 commonly consumed seafood items obtained from Taichung, Taiwan. Mean total mercury concentrations varied nearly 100-fold across species. Fifty per cent of the marlins sampled and 35% of the sharks exceeded the 0.3 µg g(-1) US Environmental Protection Agency (USEPA) guideline. Methylmercury comprised a majority of the total mercury in all species. In all species studied there was a molar excess of selenium over mercury. The rank order of mean selenium-mercury molar ratios was red tilapia (166.8) > abura (87.9) > river prawn (82.4) > whiteleg shrimp (64.2) > butterfish (44.6) > milkfish (37.0) > tuna (15.6) > grouper (13.9) > ayu (13.4) > coral hind (13.0) > weever (11.8) > saury (9.0) > shark (7.8) > marlin (4.2). PMID:24786009

  5. Selenium, glutathione peroxidase and other selenoproteins

    SciTech Connect

    Wilhelmsen, E.C.

    1983-01-01

    Selenium, as essential trace element, has long been associated with protein. The essentiality of selenium is partially understood as glutathione peroxidase contains an essential selenocysteine. Glutathione peroxidase has been purified from many tissues including rat liver. An estimated molecular weight of 105,000 was obtained for glutathione peroxidase by comparison to standards. A subunit size of 26,000 was obtained by SDS-gel electrophoresis. Glutathione peroxidase is not the only selenoprotein in the rat. In seven rat tissues examined, there were many different subunit sizes and change groups representing between 9 and 23 selenoproteins. Selenocysteine in glutathione peroxidase accounts for ca. 36% of the selenium in the rat. The mode of synthesis of glutathione peroxidase and the other selenoproteins is not understood. Glutathione peroxidase is strongly and reversibly inhibited by mercaptocarboxylic acids and other mercaptans, including some used as slow-acting drugs for the symtomatic treatment of rheumatoid arthritis. The mechanism and chemistry of this inhibition is discussed. This inhibition may provide a link between selenium and arthritis.

  6. Selenium in Oklahoma ground water and soil

    SciTech Connect

    Atalay, A.; Vir Maggon, D.

    1991-03-30

    Selenium with a consumption of 2 liters per day (5). The objectives of this study are: (1) to determine the concentrations of Se in Oklahoma ground water and soil samples. (2) to map the geographical distribution of Se species in Oklahoma. (3) to relate groundwater depth, pH and geology with concentration of Se.

  7. Chapter 6: Selenium Toxicity to Aquatic Organisms

    EPA Science Inventory

    This chapter addresses the characteristics and nature of organic selenium (Se) toxicity to aquatic organisms, based on the most current state of scientific knowledge. As such, the information contained in this chapter relates to the 'toxicity assessment' phase of aquatic ecologi...

  8. Status of selenium in cancer prevention

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An abundance of data indicate that selenium (Se) can be antitumorigenic. Those data, mostly from controlled studies using animal tumor models and some from clinical studies in free-living people, indicate that treatment with Se in the absence of nutritional Se-deficiency, can reduce cancer risk. T...

  9. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H. E-mail: kiran@mcneese.edu; Li, Xiang; Kiran, Boggavarapu E-mail: kiran@mcneese.edu; Kandalam, Anil K.

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup −}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  10. Ab-initio study of transition metal hydrides

    SciTech Connect

    Sharma, Ramesh; Shukla, Seema Dwivedi, Shalini Sharma, Yamini

    2014-04-24

    We have performed ab initio self consistent calculations based on Full potential linearized augmented plane wave (FP-LAPW) method to investigate the optical and thermal properties of yttrium hydrides. From the band structure and density of states, the optical absorption spectra and specific heats have been calculated. The band structure of Yttrium metal changes dramatically due to hybridization of Y sp orbitals with H s orbitals and there is a net charge transfer from metal to hydrogen site. The electrical resistivity and specific heats of yttrium hydrides are lowered but the thermal conductivity is slightly enhanced due to increase in scattering from hydrogen sites.

  11. METHOD OF PREPARING SINTERED ZIRCONIUM METAL FROM ITS HYDRIDES

    DOEpatents

    Angier, R.P.

    1958-02-11

    The invention relates to the preparation of metal shapes from zirconium hydride by powder metallurgical techniques. The zirconium hydride powder which is to be used for this purpose can be prepared by rendering massive pieces of crystal bar zirconium friable by heat treatment in purified hydrogen. This any then be ground into powder and powder can be handled in the air without danger of it igniting. It may then be compacted in the normal manner by being piaced in a die. The compact is sintered under vacuum conditions preferably at a temperature ranging from 1200 to 1300 deg C and for periods of one to three hours.

  12. Hydride Reduction by a Sodium Hydride–Iodide Composite

    PubMed Central

    Too, Pei Chui; Chan, Guo Hao; Tnay, Ya Lin

    2016-01-01

    Abstract Sodium hydride (NaH) is widely used as a Brønsted base in chemical synthesis and reacts with various Brønsted acids, whereas it rarely behaves as a reducing reagent through delivery of the hydride to polar π electrophiles. This study presents a series of reduction reactions of nitriles, amides, and imines as enabled by NaH in the presence of LiI or NaI. This remarkably simple protocol endows NaH with unprecedented and unique hydride‐donor chemical reactivity. PMID:26878823

  13. Copper(I)-Catalyzed Allylic Substitutions with a Hydride Nucleophile.

    PubMed

    Nguyen, T N Thanh; Thiel, Niklas O; Pape, Felix; Teichert, Johannes F

    2016-05-20

    An easily accessible copper(I)/N-heterocyclic carbene (NHC) complex enables a regioselective hydride transfer to allylic bromides, an allylic reduction. The resulting aryl- and alkyl-substituted branched α-olefins, which are valuable building blocks for synthesis, are obtained in good yields and regioselectivity. A commercially available silane, (TMSO)2Si(Me)H, is employed as hydride source. This protocol offers a unified alternative to the established metal-catalyzed allylic substitutions with carbon nucleophiles, as no adaption of the catalyst to the nature of the nucleophile is required. PMID:27151495

  14. Method for preparing hydride configurations and reactive metal surfaces

    DOEpatents

    Silver, G.L.

    1984-05-18

    A method for preparing reactive metal surfaces, particularly uranium surfaces is disclosed, whereby the metal is immediately reactive to hydrogen gas at room temperature and low pressure. The metal surfaces are first pretreated by exposure to an acid which forms an adherent hydride-bearing composition on the metal surface. Subsequent heating of the pretreated metal at a temperature sufficient to decompose the hydride coating in vacuum or inert gas renders the metal surface instantaneously reactive to hydrogen gas at room temperature and low pressure.

  15. Phase I. Lanthanum-based Start Materials for Hydride Batteries

    SciTech Connect

    Gschneidner, K. A.; Schmidt, F. A.; Frerichs, A. E.; Ament, K. A.

    2013-08-20

    The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La1-xRx)(Ni1-yMy)(Siz), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.

  16. Selenium Supplementation and Prostate Cancer Mortality

    PubMed Central

    Van Blarigan, Erin L.; DuPre, Natalie; Stampfer, Meir J.; L. Giovannucci, Edward; Chan, June M.

    2015-01-01

    Background: Few studies have evaluated the relation between selenium supplementation after diagnosis and prostate cancer outcomes. Methods: We prospectively followed 4459 men initially diagnosed with nonmetastatic prostate cancer in the Health Professionals Follow-Up Study from 1988 through 2010 and examined whether selenium supplement use (from selenium-specific supplements and multivitamins) after diagnosis was associated with risk of biochemical recurrence, prostate cancer mortality, and, secondarily, cardiovascular disease mortality and overall mortality, using Cox proportional hazards models. All P values were from two-sided tests. Results: We documented 965 deaths, 226 (23.4%) because of prostate cancer and 267 (27.7%) because of cardiovascular disease, during a median follow-up of 8.9 years. In the biochemical recurrence analysis, we documented 762 recurrences during a median follow-up of 7.8 years. Crude rates per 1000 person-years for prostate cancer death were 5.6 among selenium nonusers and 10.5 among men who consumed 140 or more μg/day. Crude rates per 1000 person-years were 28.2 vs 23.5 for all-cause mortality and 28.4 vs 29.3 for biochemical recurrence, for nonuse vs highest-dose categories, respectively. In multivariable analyses, men who consumed 1 to 24 μg/day, 25 to 139 μg/day, and 140 or more μg/day of supplemental selenium had a 1.18 (95% confidence interval [CI] = 0.73 to 1.91), 1.33 (95% CI = 0.77 to 2.30), and 2.60-fold (95% CI = 1.44 to 4.70) greater risk of prostate cancer mortality compared with nonusers, respectively, P trend = .001. There was no statistically significant association between selenium supplement use and biochemical recurrence, cardiovascular disease mortality, or overall mortality. Conclusion: Selenium supplementation of 140 or more μg/day after diagnosis of nonmetastatic prostate cancer may increase risk of prostate cancer mortality. Caution is warranted regarding usage of such supplements among men with prostate

  17. Exploring "aerogen-hydride" interactions between ZOF2 (Z = Kr, Xe) and metal hydrides: An ab initio study

    NASA Astrophysics Data System (ADS)

    Esrafili, Mehdi D.; Mohammadian-Sabet, Fariba

    2016-06-01

    In this work, a new σ-hole interaction formed between ZOF2 (Z = Kr and Xe) as the Lewis acid and a series of metal-hydrides HMX (M = Be, Mg, Zn and X = H, F, CN, CH3) is reported. The nature of this interaction, called "aerogen-hydride" interaction, is unveiled by molecular electrostatic potential, non-covalent interaction, quantum theory of atoms in molecules and natural bond orbital analyses. Our results indicate that the aerogen-hydride interactions are quite strong and can be comparable in strength to other σ-hole bonds. An important charge-transfer interaction is also associated with the formation of OF2Z⋯HMX complexes.

  18. An examination of the selenium nutrition of sheep in Victoria.

    PubMed

    Caple, I W; Andrewartha, K A; Edwards, S J; Halpin, C G

    1980-04-01

    The selenium nutrition of sheep throughout Victoria was assessed by a survey of the blood glutathione peroxidase activity in 708 flocks. It was shown that the blood glutathione peroxidase activity in sheep had a seasonal variation with lowest levels in the spring. The enzyme activity was correlated with the blood selenium concentration. Areas where blood selenium was less than 0.03 micrograms/ml in spring were defined. Sheep with low selenium nutrition were grazing pastures in the high rainfall areas on acid soils, particularly those derived from granite. Selenium concentrations in pasture samples examined were greater than 0.02 mg/kg, and it was found that superphosphate application had no significant effect on the selenium content of pasture. However, management practices such as high stocking rates and rates of application of superphosphate to pasture were associated with low blood glutathione peroxidase activities in sheep. It was concluded that the selenium nutrition of most of the sheep flocks in Victoria is adequate, and that the deficient areas are localised. There seems little requirement for supplementation of adult sheep. As the delayed type of white muscle disease in spring lambs appears to be the main selenium-responsive disorder, direct supplementation of lambs in the low selenium areas would be the most effective method of ensuring adequate selenium nutrition.

  19. Effect of selenium-deficient diet in experimental glomerular disease.

    PubMed

    Baliga, R; Baliga, M; Shah, S V

    1992-07-01

    We examined the effect of a selenium-deficient diet on two experimental models of glomerular disease, the puromycin aminonucleoside (PAN)-induced nephrotic syndrome, a model of minimal change disease, and passive Heymann nephritis, a complement-dependent and neutrophil-independent model that resembles membranous nephropathy. The specific activity of selenium-dependent glutathione peroxidase was markedly reduced in the liver, the kidney cortex, and in glomeruli in weanling male Sprague-Dawley rats placed on a selenium-deficient diet for 6 wk compared with rats fed a selenium-replete diet, with no significant differences in the specific activities of superoxide dismutase or catalase. PAN-injected selenium-deficient rats had a marked and significantly greater proteinuria throughout the course of the experiment compared with PAN-injected selenium-replete rats with no significant histological differences. In the passive Heymann nephritis model induced by injecting anti-Fx1A immunoglobulin G, rats fed a selenium-deficient diet had significantly higher urinary protein (day 5: 91 +/- 16 mg/24 h, n = 10) compared with rats fed a selenium-replete diet (52 +/- 5 mg/24 h, n = 11) with no differences in the amount of antibody deposited in the kidney. The most likely explanation for the effect of a selenium-deficient diet is that selenium deficiency resulted in a marked reduction of glutathione peroxidase, thus indicating an important role of glutathione peroxidase in these models of glomerular injury.

  20. Skeletal muscle disorders associated with selenium deficiency in humans.

    PubMed

    Chariot, Patrick; Bignani, Olivier

    2003-06-01

    Skeletal muscle disorders manifested by muscle pain, fatigue, proximal weakness, and serum creatine kinase (CK) elevation have been reported in patients with selenium deficiency. The object of this report was to review the conditions in which selenium deficiency is associated with human skeletal muscle disorders and to evaluate the importance of mitochondrial alterations in these disorders. A systematic literature review using the Medline database and Cochrane Library provided 38 relevant articles. The main conditions associated with selenium deficiency fell into three categories: (1) insufficient selenium intake in low soil-selenium areas; (2) parenteral or enteral nutrition, or malabsorption; and (3) chronic conditions associated with oxidative stress, such as chronic alcohol abuse and human immunodeficiency virus (HIV) infection. In low soil-selenium areas, reversibility of muscle symptoms was similar after selenium supplementation and placebo administration, suggesting a role for other factors in the development of disease. In parenteral or enteral nutrition, or malabsorption, muscle symptoms improved after selenium supplementation in 18 of 19 patients (median delay: 4 weeks). The reason that only a minority of selenium-deficient patients present with skeletal muscle disorders is unclear and is possibly related to cofactors, such as viral infections and drugs. Prospective studies of selenium-deficient myopathies would be useful in critically ill patients, alcohol abusers, and HIV-infected patients. PMID:12766976

  1. Selenium toxicosis in three California sea lions (Zalophus californianus).

    PubMed

    Edwards, W C; Whitenack, D L; Alexander, J W; Solangi, M A

    1989-12-01

    Selenium poisoning occurs worldwide in nearly all domestic animals. Acute selenium poisoning is associated with feeding high levels or injecting excessive amounts of selenium and is usually fatal. The acute poisoning may cause gastrointestinal disturbance, muscle weakness, depression of the central nervous system, prostration and death (1-2). Chronic selenium poisoning in cattle, sheep and horses may result from the consumption of seleniferous plants over an extended period of time. Chronic selenium results in ataxia, incoordination, partial blindness, paralysis, loss of hair or wool, abnormal hoof growth and possibly abnormal changes in behavior (1). There is little information regarding the clinical signs and pathology of selenium toxicosis in marine mammals. Likewise, there is little information regarding normal tissue levels or toxicologically significant levels of selenium in these species. The results of these investigations in sea lions, based on clinical signs, pathologic findings and tissue levels of selenium, suggest subacute or chronic selenium poisoning was most likely from dietary fish high in selenium. PMID:2617840

  2. Recovery of stream communities from experimental selenium exposure

    SciTech Connect

    Swift, M.C.; Kuklinskal, B.; Ferkull, K.; Allen, K.N.; Hermanutz, R.O.; Roush, T.H.; Hedtke, S.F.

    1994-12-31

    The effects of selenium on stream communities and their recovery from those effects were studied at MERS from 1987--1991. Selenium was dosed into two replicate streams each at concentrations of 30, 10, 2.5 and 0 (control) {mu}g L{sup {minus}1} for 18, 30, and 12 months, respectively. Recovery was monitored for three (30) or two (1 0, 2.5) years following cessation of selenium dosing. Selenium rapidly accumulated in the sediment, plants, macroinvertebrates and fish during dosing. Selenium concentrations in sediment, macroinvertebrates, and plants were as high as 2X--4X, 2X--4X, and 1X--1OX the dosed concentration in the 30, 10, and 2.5 treatments, respectively. Selenium decreased relatively rapidly following cessation of dosing. By two years after dosing ceased, selenium concentrations in plants and macroinvertebrates were little different from the controls; selenium in sediment from the 30 and 10 streams was still higher than in the control streams two years after dosing ceased. The macroinvertebrate community changed little during the dosing and recovery period. Commonly used indices of community structure showed no effect of selenium dosing. The isopod Asellus and oligochaetes in the family Tubificidae decreased rapidly following the onset of selenium dosing; their recovery following cessation of dosing was slow.

  3. Studies on the origin and transformation of selenium and its chemical species along the process of petroleum refining

    NASA Astrophysics Data System (ADS)

    Stivanin de Almeida, Cibele M.; Ribeiro, Anderson S.; Saint'Pierre, Tatiana D.; Miekeley, Norbert

    2009-06-01

    Inductively coupled plasma optical emission spectrometry and mass spectrometry (ICPMS), the latter hyphenated to flow injection hydride generation, electrothermal vaporization or ion chromatography, have been applied to the chemical characterization of crude oil, aqueous process stream samples and wastewaters from a petroleum refinery, in order to get information on the behavior of selenium and its chemical species along effluent generation and treatment. Multielemental characterization of these effluents by ICPMS revealed a complex composition of most of them, with high salinity and potential spectral and non-spectral interferents present. For this reason, a critical re-assessment of the analytical techniques for the determination of total selenium and its species was performed. Methane was employed as gas in dynamic reaction cell ICPMS and cell parameters were optimized for a simulated brine matrix and for diluted aqueous solutions to match the expected process and treated wastewaters samples. The signal-to-background ratios for 78Se and 80Se were used as criteria in optimization, the first isotope resulting in better detection limits for the simulated brine matrix ( 78Se: 0.07 μg L - 1 , 80Se: 0.31 μg L - 1 ). A large variability in the concentration of selenium (from < 10 μg kg - 1 up to 960 μg kg - 1 ) was observed in 16 of the most frequently processed crude oil samples in the refinery here investigated, which may explain the pronounced concentrations changes of this element measured in aqueous process stream and wastewater samples. Highest concentrations of total selenium were analyzed in samples from the hydrotreater (up to about 1800 μg L - 1 ). The predominance of selenocyanate (SeCN -) was observed in most of the wastewaters so far investigated, but also other species were detected with retention times different from Se(IV), Se(VI) and SeCN -. Colloidal selenium (Se 0) was the only Se-species observed in samples from the atmospheric distillation

  4. Impaired reproduction of mallards fed an organic form of selenium

    USGS Publications Warehouse

    Heinz, G.H.; Hoffman, D.J.; Gold, L.G.

    1989-01-01

    We fed mallards (Anas platyrhynchos) diets supplemented with 0-, 1-, 2-, 4-, 8-, or 16-ppm selenium in the form of selenomethionine. We fed another group of mallards a diet containing 16-ppm selenium as selenocystine. Females fed the control diet produced a mean of 8.1 ducklings that survived to 6 days of age, which was significantly greater than the 4.6 young produced by females fed 8-ppm selenium as selenomethionine and the zero surviving young of females fed 16-ppm selenium as selenomethionine. Selenocystine did not impair reproduction. Diets containing 8- and 16-ppm selenium as selenomethionine caused malformations in 6.8 and 67.9%, respectively, of unhatched eggs compared with 0.6% for controls. The most common malformations were of eyes, bill, legs, and feet. Selenium did not affect the onset or frequency of egg laying, egg size, shell thickness, fertility of eggs, or sex ratio of ducklings. Reduced survival and growth occurred in ducklings hatched from groups whose parents had received 8- or 16-ppm selenium as selenomethionine, even though all ducklings were fed a control diet. Concentrations of selenium in eggs and liver of adults could be predicted from dietary concentrations. We conclude that the dietary threshold of selenium as selenomethionine necessary to impair reproduction is between 4 and 8 ppm. It is difficult to identify 1 level of selenium in eggs that will be diagnostic of reproductive impairment in the field because different chemical forms of selenium appear to have different toxicities in eggs. However, when eggs from a wild population contain .gtoreq. 1-ppm selenium on a wet-weight basis, reproductive impairment may be possible and should be evaluated in that population. At 5-ppm selenium in eggs, reproductive impairment is much more likely to occur.

  5. Determination of antimony in ores and related materials by continuous hydride-generation atomic-absorption spectrometry after separation by xanthate extraction.

    PubMed

    Donaldson, E M

    1990-10-01

    A continuous hydride-generation atomic-absorption spectrometric method for determining approximately 0.02 mug/g or more of antimony in ores, concentrates, rocks, soils and sediments is described. The method involves the reduction of antimony(V) to antimony(III) by heating with hypophosphorous acid in a 4.5M hydrochloric acid-tartaric acid medium and its separation by filtration, if necessary, from any elemental arsenic, selenium and tellurium produced during the reduction step. Antimony is subsequently separated from iron, lead, zinc, tin and various other elements by a single cyclohexane extraction of its xanthate complex from approximately 4.5M hydrochloric acid/0.2M sulphuric acid in the presence of ascorbic acid as a reluctant for iron(III). After the extract is washed, if necessary, with 10% hydrochloric acid-2% thiourea solution to remove co-extracted copper, followed by 4.5M hydrochloric acid to remove residual iron and other elements, antimony(III) in the extract is oxidized to antimony(V) with bromine solution in carbon tetrachloride and stripped into dilute sulphuric acid containing tartaric acid. Following the removal of bromine by evaporation of the solution, antimony(V) is reduced to antimony(III) with potassium iodide in approximately 3M hydrochloric acid and finally determined by hydride-generation atomic-absorption spectrometry at 217.8 nm with sodium borohydride as reluctant. Interference from platinum and palladium, which are partly co-extracted as xanthates under the proposed conditions, is eliminated by complexing them with thiosemicarbazide during the iodide reduction step. Interference from gold is avoided by using a 3M hydrochloric acid medium for the hydride-generation step. Under these conditions gold forms a stable iodide complex.

  6. Room temperature oxidative intercalation with chalcogen hydrides: Two-step method for the formation of alkali-metal chalcogenide arrays within layered perovskites

    SciTech Connect

    Ranmohotti, K.G. Sanjaya; Montasserasadi, M. Dariush; Choi, Jonglak; Yao, Yuan; Mohanty, Debasish; Josepha, Elisha A.; Adireddy, Shiva; Caruntu, Gabriel; Wiley, John B.

    2012-06-15

    Highlights: ► Topochemical reactions involving intercalation allow construction of metal chalcogenide arrays within perovskite hosts. ► Gaseous chalcogen hydrides serve as effect reactants for intercalation of sulfur and selenium. ► New compounds prepared by a two-step intercalation strategy are presented. -- Abstract: A two-step topochemical reaction strategy utilizing oxidative intercalation with gaseous chalcogen hydrides is presented. Initially, the Dion-Jacobson-type layered perovskite, RbLaNb{sub 2}O{sub 7}, is intercalated reductively with rubidium metal to make the Ruddlesden-Popper-type layered perovskite, Rb{sub 2}LaNb{sub 2}O{sub 7}. This compound is then reacted at room-temperature with in situ generated H{sub 2}S gas to create Rb-S layers within the perovskite host. Rietveld refinement of X-ray powder diffraction data (tetragonal, a = 3.8998(2) Å, c = 15.256(1) Å; space group P4/mmm) shows the compound to be isostructural with (Rb{sub 2}Cl)LaNb{sub 2}O{sub 7} where the sulfide resides on a cubic interlayer site surrounded by rubidium ions. The mass increase seen on sulfur intercalation and the refined S site occupation factor (∼0.8) of the product indicate a higher sulfur content than expected for S{sup 2−} alone. This combined with the Raman studies, which show evidence for an H-S stretch, indicate that a significant fraction of the intercalated sulfide exists as hydrogen sulfide ion. Intercalation reactions with H{sub 2}Se{sub (g)} were also carried out and appear to produce an isostructural selenide compound. The utilization of such gaseous hydride reagents could significantly expand multistep topochemistry to a larger number of intercalants.

  7. Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy

    PubMed Central

    Zhou, Shengqiang; Liu, Fang; Prucnal, S.; Gao, Kun; Khalid, M.; Baehtz, C.; Posselt, M.; Skorupa, W.; Helm, M.

    2015-01-01

    Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

  8. Are pikas exposed to and affected by selenium deficiency?

    PubMed

    Palmer, K M; Stanton, N L; Ben-David, M; Mionczynski, J; Williams, S E

    2007-07-01

    Regional extirpations of pikas (Ochatona princeps) within the last few decades have been attributed to global warming. Other recent global alterations such as increased nitrogen (N) deposition and associated selenium (Se) deficiency may further stress pika populations. In 2003 and 2004, we live-trapped pikas from three populations in Wyoming and measured Se values in their hair. We also sampled hair and liver from museum specimens collected throughout the Northern Rocky Mountains in 1987 and 1988. Our results suggest that liver and hair values were related, and that pika hair reflected the Se concentrations of the geologic parent materials. We determined that animals residing in several remote areas in the Rocky Mountain region could be Se deficient and that increase in N deposition correlated with an increase rather than a decrease in Se values in pika hair. In addition, we found no relation between Se contents in hair and body condition index, suggesting that low Se levels may not have negative effects on individual pikas. Whether Se levels influence reproductive success of pikas is unknown and should be the focus of future studies. PMID:17699085

  9. Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy.

    PubMed

    Zhou, Shengqiang; Liu, Fang; Prucnal, S; Gao, Kun; Khalid, M; Baehtz, C; Posselt, M; Skorupa, W; Helm, M

    2015-01-01

    Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

  10. Trap style influences wild pig behavior and trapping success

    USGS Publications Warehouse

    Williams, B.L.; Holtfreter, R.W.; Ditchkoff, S.S.; Grand, J.B.

    2011-01-01

    Despite the efforts of many natural resource professionals, wild pig (Sus scrofa) populations are expanding in many areas of the world. Although many creative techniques for controlling pig populations are being explored, trapping has been and still is themost commonly usedmethod of population control formany public and private land managers. We conducted an observational study to examine the efficiency of 2 frequently used trap styles: a small, portable box-style trap and a larger, semi-permanent, corral-style trap.We used game cameras to examine patterns of trap entry by wild pigs around each style of trap, and we conducted a trapping session to compare trapping success between trap styles. Adult female and juvenile wild pigs entered both styles of trap more readily than did adult males, and adult males seemed particularly averse to entering box traps. Less than 10% of adult male visits to box traps resulted in entries, easily the least percentage of any class at any style of trap. Adult females entered corral traps approximately 2.2 times more often per visit than box traps and re-entered corral traps >2 times more frequently. Juveniles entered and reentered both box and corral traps at similar rates. Overall (all-class) entry-per-visit rates at corral traps (0.71) were nearly double that of box traps (0.37). Subsequent trapping data supported these preliminary entry data; the capture rate for corral traps was >4 times that of box traps. Our data suggest that corral traps are temporally and economically superior to box traps with respect to efficiency; that is, corral traps effectively trap more pigs per trap night at a lower cost per pig than do box traps. ?? 2011 The Wildlife Society.

  11. Uranium Hydride Nucleation Kinetics: Effects of Oxide Thickness and Vacuum Outgassing

    SciTech Connect

    David F. Teter; Robert J. Hanrahan; Christopher J. Wetteland

    2001-03-01

    Many factors such as impurities in the oxide and metal, microstructure, gas impurities, and oxide thickness may influence the rate and location of the nucleation of hydride on uranium. This work has concentrated on isolating one of these variables, the oxide thickness, and measuring the effect of the oxide thickness on uranium hydride nucleation. Uranium samples, all from the same lot, were prepared with different oxide thicknesses. The oxide thickness was measured using Rutherford Backscattering Spectroscopy. Oxidized uranium samples were then exposed to ultra-high purity hydrogen gas under constant volume conditions. Decreases in pressure indicated hydrogen uptake by the sample. The time for hydride nucleation--as well as the maximum hydriding rate--was then calculated from the measured decreases in pressure. The time to nucleate a hydride was found to increase whereas the maximum hydriding rate was found to decrease with increasing oxide thickness. The density of hydride pits also decreased with increasing oxide thickness. The observed results support the argument that the nucleation of hydride is controlled somewhat by diffusion of hydrogen through the oxide layer. Vacuum outgassing of samples, thereby removing the oxide impurities and keeping the oxide thickness constant, dramatically decreased the nucleation time and increased the maximum hydriding rate. Again, this is consistent with hydrogen diffusion through the oxide controlling the nucleation of hydride. Impurities in the oxide layer can decrease the diffusivity of hydrogen and therefore delay the nucleation of uranium hydride.

  12. Ecological and evolutionary traps

    USGS Publications Warehouse

    Schlaepfer, Martin A.; Runge, M.C.; Sherman, P.W.

    2002-01-01

    Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become 'trapped' by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid 'trapping' them.

  13. Microfabricated ion trap array

    DOEpatents

    Blain, Matthew G.; Fleming, James G.

    2006-12-26

    A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

  14. Fabrication of lotus-type porous copper through thermal decomposition of titanium hydride

    NASA Astrophysics Data System (ADS)

    Ide, T.; Nakajima, H.

    2009-05-01

    Lotus-type porous copper was fabricated by unidirectional solidification through thermal decomposition of titanium hydride. Effects of additive method and additive amount of titanium hydride on pore formation were investigated. The porosity of lotus copper depends on additive method and additive amount of titanium hydride. The pore formation effectively occurs in the method that titanium hydride decomposes in molten copper. For all the additive methods of titanium hydride, the porosity increases and pore diameter does not change with increasing additive amount of titanium hydride. While, for adding large amount of titanium hydride, the porosity became constant. This is because hydrogen solubility in liquid phase does not change owing to bubbling of hydrogen gas.

  15. Neutral atom traps.

    SciTech Connect

    Pack, Michael Vern

    2008-12-01

    This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

  16. Process of forming a sol-gel/metal hydride composite

    DOEpatents

    Congdon, James W.

    2009-03-17

    An external gelation process is described which produces granules of metal hydride particles contained within a sol-gel matrix. The resulting granules are dimensionally stable and are useful for applications such as hydrogen separation and hydrogen purification. An additional coating technique for strengthening the granules is also provided.

  17. Catalytic arene hydrogenation using early transition metal hydride compounds

    SciTech Connect

    Rothwell, I.P.

    1993-03-15

    Progress was achieved in four areas: development of surface supported Group 5 metal organometallic compounds for catalytic arene hydrogenation, isolation and reactivity of possible intermediates in catalytic arene hydrogenation, synthesis and characterization of new d[sup 0]-metal hydride compounds, and stoichiometric reactivity of d[sup 0] metal hydrido, aryloxide compounds. (DLC)

  18. Structure Properties of Ternary Hydrides Ni3AlHx

    NASA Astrophysics Data System (ADS)

    Pan, Yi-wei; Zhang, Wen-qing; Chen, Nan-xian

    1996-09-01

    The structure properties of the ternary hydrides Ni3AlHx are studied by use of the interatomic pair potentials obtained from the first principles electronic structure calculation and Chen-Mobius 3-dimensional lattice inversion method. The heat of formation and volume expansion of the hydrogenized systems are investigated.

  19. Ecology and Biotechnology of Selenium-Respiring Bacteria

    PubMed Central

    2015-01-01

    SUMMARY In nature, selenium is actively cycled between oxic and anoxic habitats, and this cycle plays an important role in carbon and nitrogen mineralization through bacterial anaerobic respiration. Selenium-respiring bacteria (SeRB) are found in geographically diverse, pristine or contaminated environments and play a pivotal role in the selenium cycle. Unlike its structural analogues oxygen and sulfur, the chalcogen selenium and its microbial cycling have received much less attention by the scientific community. This review focuses on microorganisms that use selenate and selenite as terminal electron acceptors, in parallel to the well-studied sulfate-reducing bacteria. It overviews the significant advancements made in recent years on the role of SeRB in the biological selenium cycle and their ecological role, phylogenetic characterization, and metabolism, as well as selenium biomineralization mechanisms and environmental biotechnological applications. PMID:25631289

  20. Selenium Recycling in the United States in 2004

    USGS Publications Warehouse

    George, Micheal W.; Wagner, Lorie A.

    2009-01-01

    The vast majority of selenium consumption in the United States is in dissipative uses, such as alloys, animal feeds, fertilizers, glass decolorizer, and pigments. The nondissipative use as a photoreceptor for xerographic copiers is declining. As a result of a lack of a substantial supply of selenium-containing scrap, there are no longer selenium recycling facilities in the United States. Selenium-containing materials collected for recycling, primarily selenium-containing photocopier drums, are exported for processing in other countries. Of the estimated 350 metric tons (t) of selenium products that went to the U.S. market in 2004, an estimated 300 t went to dissipative uses. An estimated 4 t was recovered from old scrap and exported for recycling.

  1. Ecology and biotechnology of selenium-respiring bacteria.

    PubMed

    Nancharaiah, Y V; Lens, P N L

    2015-03-01

    In nature, selenium is actively cycled between oxic and anoxic habitats, and this cycle plays an important role in carbon and nitrogen mineralization through bacterial anaerobic respiration. Selenium-respiring bacteria (SeRB) are found in geographically diverse, pristine or contaminated environments and play a pivotal role in the selenium cycle. Unlike its structural analogues oxygen and sulfur, the chalcogen selenium and its microbial cycling have received much less attention by the scientific community. This review focuses on microorganisms that use selenate and selenite as terminal electron acceptors, in parallel to the well-studied sulfate-reducing bacteria. It overviews the significant advancements made in recent years on the role of SeRB in the biological selenium cycle and their ecological role, phylogenetic characterization, and metabolism, as well as selenium biomineralization mechanisms and environmental biotechnological applications. PMID:25631289

  2. Speciation of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry after cloud point extraction.

    PubMed

    Sun, Mei; Liu, Guijian; Wu, Qianghua

    2013-11-01

    A new method was developed for the determination of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry detection after cloud point extraction. Effective separation of organic and inorganic selenium in selenium-enriched rice was achieved by sequentially extracting with water and cyclohexane. Under the optimised conditions, the limit of detection (LOD) was 0.08 μg L(-1), the relative standard deviation (RSD) was 2.1% (c=10.0 μg L(-1), n=11), and the enrichment factor for selenium was 82. Recoveries of inorganic selenium in the selenium-enriched rice samples were between 90.3% and 106.0%. The proposed method was successfully applied for the determination of organic and inorganic selenium as well as total selenium in selenium-enriched rice.

  3. Selenium accumulation and selenium-salt co-tolerance in five grass species. [Festuca arundinaceae; Agropyron deserorum; Buchloe dactyloides; Agrostis stolonifera; Cynodon dactylon

    SciTech Connect

    Wu, L.; Huang, Z.; Burau, R.G.

    1987-04-01

    Five grass species including Tall fescue (Festuca arundinaceae Schred), Crested wheatgrass (Agropyron deserorum Fisch), Buffalo grass (Buchlor dactyloides (Nutt.) Engelm.), Seaside bentgrass (Agrostis stolonifera L.) and Bermuda grass (Cynodon dactylon (L.) Pers., Syn.) were examined for selenium and salt tolerance and selenium accumulation under solution culture conditions. Distinct differences in both selenium and salt tolerance were detected among the five species, but no direct association between selenium and salt resistance was found. Tall fescue displayed considerable tolerance under 1 ppm selenium and 100 mM salt treatment. Combined selenium and salt treatment revealed that selenium uptake was increased by the incorporation of salt in the culture solution. However, salt uptake was not significantly affected by the presence of selenium in the culture solution. At moderate toxic levels of selenium, the species with greater tolerance accumulated less selenium than did the less tolerant species.

  4. Final Report: Baseline Selenium Monitoring of Agricultural Drains Operated by the Imperial Irrigation District in the Salton Sea Basin, California

    USGS Publications Warehouse

    Saiki, Michael K.; Martin, Barbara A.; May, Thomas W.

    2010-01-01

    This report summarizes comprehensive findings from a 4-year-long field investigation to document baseline environmental conditions in 29 agricultural drains and ponds operated by the Imperial Irrigation District along the southern border of the Salton Sea. Routine water-quality collections and fish community assessments were conducted on as many as 16 sampling dates at roughly quarterly intervals from July 2005 to April 2009. The water-quality measurements included total suspended solids and total (particulate plus dissolved) selenium. With one exception, fish were surveyed with baited minnow traps at quarterly intervals during the same time period. However, in July 2007, fish surveys were not conducted because we lacked permission from the California Department of Fish and Game for incidental take of desert pupfish (Cyprinodon macularius), an endangered species. During April and October 2006-08, water samples also were collected from seven intensively monitored drains (which were selected from the 29 total drains) for measurement of particulate and dissolved selenium, including inorganic and organic fractions. In addition, sediment, aquatic food chain matrices [particulate organic detritus, filamentous algae, net plankton, and midge (chironomid) larvae], and two fish species (western mosquitofish, Gambusia affinis; and sailfin molly, Poecilia latipinna) were sampled from the seven drains for measurement of total selenium concentrations. The mosquitofish and mollies were intended to serve as surrogates for pupfish, which we were not permitted to sacrifice for selenium determinations. Water quality (temperature, dissolved oxygen, pH, specific conductance, and turbidity) values were typical of surface waters in a hot, arid climate. A few drains exhibited brackish, near-anoxic conditions, especially during summer and fall when water temperatures occasionally exceeded 30 degrees Celsius. Total selenium concentrations in water were directly correlated with salinity and

  5. Electrochemical cell utilizing selenium as an electrode-reactant

    SciTech Connect

    Virkar, A.V.; Miller, G.R.; Rasmussen, J.R.

    1990-01-23

    This patent describes an electrochemical cell. It comprises: an anolyte containing substantially a molten alkali metal; a solid beta-alumina electrolyte possessing mobile alkali metal ions of the same alkali metal as is present in the anolyte; and a catholyte comprising a mixture of molten selenium and molten sulfur in a molar ration of about 3:1 to about 30:1 selenium to sulfur, wherein at least a portion of the selenium and sulfur is present in elemental form.

  6. Selenium Poisoning of Wildlife and Western Agriculture: Cause and Effect

    SciTech Connect

    Korte, N.E.

    2000-02-01

    This project examined the hypothesis that selenium contamination is not the principal cause of the decline of endemic fish species in the Upper Colorado Basin. Activities employed to test this hypothesis included a reconnaissance of locations altered by recent road construction, a re-interpretation of available literature regarding selenium toxicity, and the interpretation of unpublished data obtained from the Upper Colorado Basin Fish Recovery Program. The project demonstrates that most of the evidence implicating selenium is circumstantial.

  7. 21 CFR 522.2100 - Selenium and vitamin E.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Selenium and vitamin E. 522.2100 Section 522.2100... Selenium and vitamin E. (a)(1) Specifications. Each milliliter of emulsion contains 5.48 milligrams (mg) sodium selenite (equivalent to 2.5 mg selenium) and 50 mg of vitamin E (68 I.U.) (as d-alpha...

  8. Effect of selenium supplementation in hypothyroid subjects of an iodine and selenium deficient area: the possible danger of indiscriminate supplementation of iodine-deficient subjects with selenium.

    PubMed

    Contempre, B; Dumont, J E; Ngo, B; Thilly, C H; Diplock, A T; Vanderpas, J

    1991-07-01

    Selenium and seleno dependent glutathione peroxidase (GPX) deficiency has been described in endemias of myxedematous cretinism. In northern Zaire, a selenium supplementation trial has been conducted. Beside correcting the GPX activity, two months of selenium supplementation was shown to modify the serum thyroid hormones parameters in clinically euthyroid subjects and to induce a dramatic fall of the already impaired thyroid function in clinically hypothyroid subjects. These results further support a role of selenium in thyroid hormone metabolism. In an iodine deficient area, this selenium deficiency could lead to opposite clinical consequences: protect the general population and the fetus against iodine deficiency and brain damage; and in turn, favour the degenerative process of the thyroid gland leading to myxoedematous cretinism. PMID:2045471

  9. Modeling of photocurrent and lag signals in amorphous selenium x-ray detectors

    SciTech Connect

    Siddiquee, Sinchita; Kabir, M. Z.

    2015-07-15

    A mathematical model for transient photocurrent and lag signal in x-ray imaging detectors has been developed by considering charge carrier trapping and detrapping in the energy distributed defect states under exponentially distributed carrier generation across the photoconductor. The model for the transient and steady-state carrier distributions and hence the photocurrent has been developed by solving the carrier continuity equation for both holes and electrons. The residual (commonly known as lag signal) current is modeled by solving the trapping rate equations considering the thermal release and trap filling effects. The model is applied to amorphous selenium (a-Se) detectors for both chest radiography and mammography. The authors analyze the dependence of the residual current on various factors, such as x-ray exposure, applied electric field, and temperature. The electron trapping and detrapping mostly determines the residual current in a-Se detectors. The lag signal is more prominent in chest radiographic detector than in mammographic detectors. The model calculations are compared with the published experimental data and show a very good agreement.

  10. [Selenium toxicity in domestic animals].

    PubMed

    Mihajlović, M

    1992-01-01

    The earliest written report of selenium poisoning is thought to be the description by Marco Polo of a necrotic hoof disease of horses that occurred in China in 13. century. However recognition of Se as toxic principle come in the early 1930s. Severity of Se poisoning depends on chemical forms of the element, species of animals and routes of administration. The soluble Se salts (Na2SeO3 and Na2SeO4) appear to be among the more toxic compounds; the Se inherent in grains and selenoamino acids (selenomethionine and selenocystine) appear to have relative moderate toxicity; the poorly soluble forms (e.g., elemental Se, Na2Se, SeS2 and diphenyl selenide) are among the least toxic of the Se compounds. In general, toxicity of Se compounds are substantially less when they are administered orally than when they are given parenterally. Rosenfeld and Beath described three clinical types of Se intoxication: acute selenosis, subacute selenosis (i.e., blind staggers type), and chronic selenosis (i.e., alkali disease type). Acute poisoning occurs when high Se content plants are consumed in large quantities within short period. Accidental acute poisoning occurs as consequence of errors in formulation of a Se supplemented diet. The most characteristic sign of acute selenosis is garlic breath due to the pulmonary excretion of volatile Se metabolites. Other signs include lethargy, excessive salivation, vomiting, dyspnea, muscle tremors and respiratory distress. Pathological findings are: congestion of the liver and kidney, fatty degeneration and focal necrosis of the liver, endocarditis and myocarditis. Subacute selenosis ("blind staggers") occurs as a consequence of exposure to large doses of Se over a longer period of time and manifests with neurological signs (e.g., blindness, ataxia, disorientation) and respiratory distress. This form of selenosis is most frequently observed in grazing animals that have consumed Se-accumulated plants. Chronic selenosis ("alkali disease") comes

  11. Immunomodulatory effect of selenosemicarbazides and selenium inorganic compounds, distribution in organs after selenium supplementation.

    PubMed

    Musik, I; Koziol-Montewka, M; Toś-Luty, S; Pasternak, K; Latuszyńska, J; Tokarska, M; Kielczykowska, M

    1999-12-01

    Antioxidant properties of selenium producing a protective barrier against free radicals play an important role in numerous metabolic and immunologic processes associated with oxidation-reduction reactions which take place during intracellular digestion of phagocyted bacteria. The aim of our study was to examine the properties of an organic compound of selenium, 4-(o-tolilo)-selenosemicarbazide of p-chlorobenzoic acid in terms of its retention in organs, effect on erythropoesis and phagocytic abilities of neutrophiles as well as antioxidant properties in neutrophiles tested with NBT test. This compound as well as inorganic sodium selenate was given to Swiss mice at the dose of 10(-3) g Se/kg for the period of 10 days. The concentrations of selenium in livers of mice treated with sodium selenate and selenosemicarbazide were found to be higher than in controls (18.7 micrograms lg-1 and 23.2 micrograms lg-1 vs. 12 micrograms lg-1, respectively). Analysis of blood cells count has shown a significant decrease in neutrophile levels in both groups treated with selenium. The influence of selenium compounds on phagocytosis and especially NBT test has been determined (3.8% of positive cells in the controls vs. 2.2% and 0.9% in the groups treated with sodium selenate and selenosemicarbazide, respectively). Our preliminary investigations suggest that selenosemicarbazides are biologically active compounds and can modify neutrophile functions.

  12. 5-year review of Metal Hydride Center of Excellence.

    SciTech Connect

    Keller, Jay O.; Klebanoff, Leonard E.

    2010-05-01

    The purpose of the DOE Metal Hydride Center of Excellence (MHCoE) is to develop hydrogen storage materials with engineering properties that allow the use of these materials in a way that satisfies the DOE/FreedomCAR Program system requirements for automotive hydrogen storage. The Center is a multidisciplinary and collaborative effort with technical interactions divided into two broad areas: (1) mechanisms and modeling (which provide a theoretically driven basis for pursuing new materials) and (2) materials development (in which new materials are synthesized and characterized). Driving all of this work are the hydrogen storage system specifications outlined by the FreedomCAR Program for 2010 and 2015. The organization of the MHCoE during the past year is show in Figure 1. During the past year, the technical work was divided into four project areas. The purpose of the project areas is to organize the MHCoE technical work along appropriate and flexible technical lines. The four areas summarized are: (1) Project A - Destabilized Hydrides, The objective of this project is to controllably modify the thermodynamics of hydrogen sorption reactions in light metal hydrides using hydride destabilization strategies; (2) Project B - Complex Anionic Materials, The objective is to predict and synthesize highly promising new anionic hydride materials; (3) Project C - Amides/Imides Storage Materials, The objective of Project C is to assess the viability of amides and imides (inorganic materials containing NH{sub 2} and NH moieties, respectively) for onboard hydrogen storage; and (4) Project D - Alane, AlH{sub 3}, The objective of Project D is to understand the sorption and regeneration properties of AlH{sub 3} for hydrogen storage.

  13. Inert blanketing of a hydride bed using typical grade protium

    SciTech Connect

    Klein, J.E.

    2015-03-15

    This paper describes the impact of 500 ppm (0.05%) impurities in protium on the absorption rate of a 9.66 kg LaNi{sub 4.25}Al{sub 0.75} (LANA0.75) metal hydride bed. The presence of 500 ppm or less inerts (i.e. non-hydrogen isotopes) can significantly impact hydrogen bed absorption rates. The impact on reducing absorption rates is significantly greater than predicted assuming uniform temperature, pressure, and compositions throughout the bed. Possible explanations are discussed. One possibility considered was the feed gas contained impurity levels higher than 500 ppm. It was shown that a level of 5000 ppm of inerts would have been necessary to fit the experimental result so this possibility wa dismissed. Another possibility is that the impurities in the protium supply reacted with the hydride material and partially poisoned the hydride. If the hydride were poisoned with CO or another impurity, the removal of the over-pressure gas in the bed would not be expected to allow the hydride loading of the bed to continue as the experimental results showed, so this possibility was also dismissed. The last possibility questions the validity of the calculations. It is assumed in all the calculations that the gas phase composition, temperature, and pressure are uniform throughout the bed. These assumptions are less valid for large beds where there can be large temperature, pressure, and composition gradients throughout the bed. Eventually the impact of 0.05% inerts in protium on bed absorption rate is shown and explained in terms of an increase in inert partial pressure as the bed was loaded.

  14. Review of selenium toxicity in the aquatic food chain.

    PubMed

    Hamilton, Steven J

    2004-06-29

    In many environmental contaminant situations selenium has become the primary element of concern because of its bioaccumulative nature in food webs. Initial concerns about selenium were related to fish kills at Belews Lake, NC, Martin Lake, TX, and Kesterson Reservoir, CA, and to bird deformities at Kesterson Reservoir. Additional concerns were identified under the National Irrigation Water Quality Program at Salton Sea, CA, Kendrick, WY, Stewart Lake, UT, and Grand Valley and Uncompahgre Valley, CO. Recent studies have raised concerns about selenium impacts on aquatic resources in Southeastern Idaho and British Columbia. The growing discomfort among the scientific community with a waterborne criterion has lead the US Environment Protection Agency to consider a tissue-based criterion for selenium. Some aquatic ecosystems have been slow to recover from selenium contamination episodes. In recent years, non-governmental researchers have been proposing relatively high selenium thresholds in diet and tissue relative to those proposed by governmental researchers. This difference in opinions is due in part to the selection of datasets and caveats in selecting scientific literature. In spite of the growing selenium literature, there are needs for additional research on neglected organisms. This review also discusses the interaction of selenium with other elements, inconsistent effects of selenium on survival and growth of fish, and differences in depuration rates and sensitivity among species. PMID:15142762

  15. Hazard assessment of selenium to endangered razorback suckers (Xyrauchen texanus)

    USGS Publications Warehouse

    Hamilton, S.J.; Holley, K.M.; Buhl, K.J.

    2002-01-01

    A hazard assessment was conducted based on information derived from two reproduction studies conducted with endangered razorback suckers (Xyrauchen texanus) at three sites near Grand Junction, CO, USA. Selenium contamination of the upper and lower Colorado River basin has been documented in water, sediment, and biota in studies by US Department of the Interior agencies and academia. Concern has been raised that this selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The reproduction studies with razorback suckers revealed that adults readily accumulated selenium in various tissues including eggs, and that 4.6 ??g/g of selenium in food organisms caused increased mortality of larvae. The selenium hazard assessment protocol resulted in a moderate hazard at the Horsethief site and high hazards at the Adobe Creek and North Pond sites. The selenium hazard assessment was considered conservative because an on-site toxicity test with razorback sucker larvae using 4.6 ??g/g selenium in zooplankton caused nearly complete mortality, in spite of the moderate hazard at Horsethief. Using the margin of uncertainty ratio also suggested a high hazard for effects on razorback suckers from selenium exposure. Both assessment approaches suggested that selenium in the upper Colorado River basin adversely affects the reproductive success of razorback suckers. ?? 2002 Elsevier Science B.V. All rights reserved.

  16. Selenium sulfide in tinea versicolor: blood and urine levels.

    PubMed

    Sánchez, J L; Torres, V M

    1984-08-01

    The safety of topical selenium sulfide lotion in man has been demonstrated previously. Twenty male patients with a diagnosis of tinea versicolor were randomly assigned to two parallel groups who applied selenium sulfide lotion or the vehicle to the entire skin surface, excluding mucous membranes, for 10 minutes once daily for 7 consecutive days. Blood and urine selenium levels were determined before and after treatment and showed no significant differences between the active drug and vehicle groups on any study day. It would appear that no significant absorption of selenium took place as a result of this treatment regimen.

  17. Effects of selenium on mallard duck reproduction and immune function

    SciTech Connect

    Whiteley, P.L.; Yuill, T.M.; Fairbrother, A.

    1989-11-01

    Selenium from irrigation drain water and coal-fired power stations is a significant environmental contaminant in some regions of the USA. The objectives were to examine whether selenium-exposed waterfowl had altered immune function, disease resistance, or reproduction. Pairs of adult mallards were exposed for 95-99 days on streams with sodium selenite-treated water at 10 and 30 ppb, or on untreated streams. Selenium biomagnified through the food chain to the ducks. Disease resistance was decreased in ducklings hatched on the streams and challenged with duck hepatitis virus 1 (DHV1) when 15-days old. Liver selenium concentrations for these ducklings on the 10 and 30 ppb streams was 3.6 and 7.6 ppm dry weight, respectively. Mortality of ducklings purchased when 7-days old, exposed to selenium for 14 days, and challenged when 22-days old was not affected. However, their selenium exposure was lower (liver selenium 4.1 ppm dry weight for the 30 ppb stream). Five parameters of immune function were measured in adult ducks. Phagocytosis of killed Pasteurella multocida by blood heterophils and monocytes, and blood monocyte concentrations were higher in adult males following 84 days exposure to 30 ppb selenium. Their liver selenium concentrations were 11.1 ppm dry weight after 95-99 days exposure.

  18. Preventing metal-mediated oxidative DNA damage with selenium compounds.

    PubMed

    Battin, Erin E; Zimmerman, Matthew T; Ramoutar, Ria R; Quarles, Carolyn E; Brumaghim, Julia L

    2011-05-01

    Copper and iron are two widely studied transition metals associated with hydroxyl radical (˙OH) generation, oxidative damage, and disease development. Because antioxidants ameliorate metal-mediated DNA damage, DNA gel electrophoresis assays were used to quantify the ability of ten selenium-containing compounds to inhibit metal-mediated DNA damage by hydroxyl radical. In the Cu(I)/H(2)O(2) system, selenocystine, selenomethionine, and methyl-selenocysteine inhibit DNA damage with IC(50) values ranging from 3.34 to 25.1 μM. Four selenium compounds also prevent DNA damage from Fe(II) and H(2)O(2). Additional gel electrophoresis experiments indicate that Cu(I) or Fe(II) coordination is responsible for the selenium antioxidant activity. Mass spectrometry studies show that a 1 : 1 stoichiometry is the most common for iron and copper complexes of the tested compounds, even if no antioxidant activity is observed, suggesting that metal coordination is necessary but not sufficient for selenium antioxidant activity. A majority of the selenium compounds are electroactive, regardless of antioxidant activity, and the glutathione peroxidase activities of the selenium compounds show no correlation to DNA damage inhibition. Thus, metal binding is a primary mechanism of selenium antioxidant activity, and both the chemical functionality of the selenium compound and the metal ion generating damaging hydroxyl radical significantly affect selenium antioxidant behavior. PMID:21286651

  19. Selenium nanomaterials: applications in electronics, catalysis and sensors.

    PubMed

    Chaudhary, Savita; Mehta, S K

    2014-02-01

    This review provides insights into the synthesis, functionalization, and applications of selenium nanoparticles in electronics, optics, catalysis and sensors. The variation of physicochemical properties such as particle size, surface area, and shape of the selenium nanoparticles and the effect of experimental conditions has also been discussed. An overview has also been provided on the fundamental electrical and optical properties of selenium nanomaterials as well as their utilization in different research fields. The work presents an insight on selenium nanoparticles with interesting properties and their future applications.

  20. Conceptual Model for Selenium Cycling in the Great Salt Lake

    NASA Astrophysics Data System (ADS)

    Johnson, W. P.; Conover, M. R.; Wurtsbaugh, W. A.; Adams, J.

    2006-12-01

    The conceptual model for Selenium cycling in the Great Salt Lake was developed to guide investigations in support of determining an open water selenium standard for the Great Salt Lake. The motivation to determine this particular selenium standard derives from public concern for a plan to allow disposal of reverse osmosis (RO) concentrate in the GSL, which would contain elevated concentrations of major and trace elements, including selenium. The development of an open water standard for selenium requires a working knowledge of the biological significance of existing selenium concentrations in the Great Salt Lake, as well as a working understanding of the likely changes of these concentrations over time given existing and proposed loads to the system. This working knowledge" is being represented in a conceptual model that accounts for selenium in various stocks" in the system (e.g. water, sediment, biota) and the flow" of selenium between stocks (e.g., precipitation and settling, volatilization, bioconcentration). It illustrates the critical pathway of selenium in the Great Salt Lake from water, to microorganisms, to brine shrimp and brine flies, to birds, and to their eggs. It also addresses the complexity of the GSL system: a) Spatially diverse, being comprised by four distinct bays and two layers, with major differences in salinity among their waters. b) Temporally dynamic, due to seasonal and inter-annual variations in runoff. The conceptual model is presently descriptive, but will serve as the basis for a semi-quantitative model that will be fed by data accumulated during subsequent investigations.

  1. Selenium status in soils of northern districts of India.

    PubMed

    Yadav, Sanjiv K; Singh, Ishwar; Singh, Devender; Han, Sang-Do

    2005-04-01

    The HG-AAS technique was used to estimate the soil selenium status of the agricultural lands of northern parts of India. The drier lands where lesser rains were received or where less irrigation water was available in Rajasthan and southern parts of the Haryana states had above normal soil selenium levels. These soils were also found to be alkaline. Punjab, Himachal Pradesh and northern parts of the Haryana states had normal levels of selenium in their soils, except with slightly lower selenium levels in a few areas that were affected by floods along the river Yamuna. The results were also confirmed using the ICP-OES technique. PMID:15763155

  2. Selenium status in food grains of northern districts of India.

    PubMed

    Yadav, Sanjiv K; Singh, Ishwar; Sharma, Anita; Singh, Devender

    2008-09-01

    The selenium status in the food grains of the agricultural lands of northern parts of India was estimated by using the HG-AAS technique. The areas where lesser rains were received or less irrigation water was available in northern Indian states viz. Rajasthan and southern parts of the Haryana had higher selenium levels in food grains. Punjab, Himachal Pradesh and northern parts of the Haryana states had normal levels of selenium in their food grains, except for slightly lower selenium levels in a few areas that were affected by floods along the river Yamuna. PMID:17574725

  3. Hazard assessment of selenium to endangered razorback suckers (Xyrauchen texanus).

    PubMed

    Hamilton, Steven J; Holley, Kathleen M; Buhl, Kevin J

    2002-05-27

    A hazard assessment was conducted based on information derived from two reproduction studies conducted with endangered razorback suckers (Xyrauchen texanus) at three sites near Grand Junction, CO, USA. Selenium contamination of the upper and lower Colorado River basin has been documented in water, sediment, and biota in studies by US Department of the Interior agencies and academia. Concern has been raised that this selenium contamination may be adversely affecting endangered fish in the upper Colorado River basin. The reproduction studies with razorback suckers revealed that adults readily accumulated selenium in various tissues including eggs, and that 4.6 microg/g of selenium in food organisms caused increased mortality of larvae. The selenium hazard assessment protocol resulted in a moderate hazard at the Horsethief site and high hazards at the Adobe Creek and North Pond sites. The selenium hazard assessment was considered conservative because an on-site toxicity test with razorback sucker larvae using 4.6 microg/g selenium in zooplankton caused nearly complete mortality, in spite of the moderate hazard at Horsethief. Using the margin of uncertainty ratio also suggested a high hazard for effects on razorback suckers from selenium exposure. Both assessment approaches suggested that selenium in the upper Colorado River basin adversely affects the reproductive success of razorback suckers. PMID:12150431

  4. Total selenium concentration in various waters of Turkey.

    PubMed

    Yanardağ, R; Orak, H

    2001-02-01

    The total selenium levels of 335 water samples of Turkey were determined by a spectrofluorometric method. The samples were digested in nitric-perchloric acid mixture, potential interferences were masked with disodium EDTA-HONH2.HCl and selenium was complexed with freshly prepared 2,3-diaminonaphthalene solution and estimated spectrofluorometrically after extraction in cyclohexane. The selenium content of various waters (rain, tap, mineral, sea, lake, river, bottled drinking waters and collected drinking waters from 42 cities in Turkey) were determined. The selenium levels were compared with the literature data from different countries.

  5. The leaching characteristics of selenium from coal fly ashes

    SciTech Connect

    Wang, T.; Wang, J.; Burken, J.G.; Ban, H.; Ladwig, K.

    2007-11-15

    The leaching characteristics of selenium from several bituminous and subbituminous coal fly ashes under different pH conditions were investigated using batch methods. Results indicated that pH had a significant effect on selenium leaching from bituminous coal ash. The minimum selenium leaching occurred in the pH range between 3 and 4, while the maximum selenium leaching occurred at pH 12. The release of selenium from subbituminous coal ashes was very low for the entire experimental pH range, possibly due to the high content of calcium which can form hydration or precipitation products as a sink for selenium. The adsorption results for different selenium species indicated that Se(VI) was hardly adsorbable on either bituminous coal ashes or subbitumminous coal ashes at any pH. However, Se(I) was highly adsorbed by bituminous coal ashes under acidic pH conditions and was mostly removed by subbitumminous coal ashes across the entire pH range. This result suggests that the majority of selenium released from the tested fly ashes was Se(IV). A speciation-based model was developed to simulate the adsorption of Se(IV) on bituminous coal fly ash, and the pH-independent adsorption constants of HSeO{sup 3-} and SeO{sub 3}{sup 2-} were determined. The modeling approach is useful for understanding and predicting the release process of selenium from fly ash.

  6. Selenium and Human Health: Witnessing a Copernican Revolution?

    PubMed

    Jablonska, Ewa; Vinceti, Marco

    2015-01-01

    In humans, selenium was hypothesized to lower the risk of several chronic diseases, mainly due to the antioxidant activity of selenium-containing proteins. Recent epidemiologic and laboratory studies, however, are changing our perception of the biological effects of this nutritionally essential trace element. We reviewed the most recent epidemiologic and biochemical literature on selenium, synthesizing the findings from these studies into a unifying view. Randomized trials have shown that selenium did not protect against cancer and other chronic diseases, but even increased the risk of specific neoplasms such as advanced prostate cancer and skin cancer, in addition to type 2 diabetes. Biochemical studies indicate that selenium may exert a broad pattern of toxic effects at unexpectedly low concentrations. Furthermore, its upregulation of antioxidant proteins (selenium-dependent and selenium-independent) may be a manifestation of self-induced oxidative stress. In conclusion, toxic effects of selenium species occur at lower concentrations than previously believed. Those effects may include a large range of proteomic changes and adverse health effects in humans. Since the effects of environmental exposure to this element on human health still remain partially unknown, but are potentially serious, the toxicity of selenium exposure should be further investigated and considered as a public health priority. PMID:26074278

  7. Re-exposure of mallards to selenium after chronic exposure

    USGS Publications Warehouse

    Heinz, G.H.

    1993-01-01

    Adult male mallards (Anas platyrhynchos) were fed a control diet or a diet containing 15 ppm selenium as seleno-D,L-methionine for 21 weeks. After this initial exposure, the mallards were fed untreated food for 12 weeks, then were re-exposed to selenium at 100 ppm for five weeks. During re-exposure to 100 ppm selenium, the birds that had previously been exposed to 15 ppm selenium and those that had not previously been exposed did not differ in percentage of mortality (14.7 and 14.3%), weight loss in survivors (39.3 and 41.20%), selenium concentrations in the livers of survivors (35 and 53 ppm, wet weight), or selenium concentrations in the livers of birds that died (35 and 40 ppm, respectively). When the data from the birds that had previously been exposed to 15 ppm selenium were combined with the data from the birds that had not previously been exposed, selenium concentrations in the livers of birds that had died on the 100-ppm selenium treatment (38 ppm) did not differ from the concentrations in the livers of birds that had survived (43 ppm).

  8. Processes affecting the distribution and speciation of selenium in seawater

    SciTech Connect

    Cutter, G.A.

    1982-01-01

    The analyses of dissolved selenium species in the Pacific Ocean and anoxic waters of the Saanich Inlet, selenium in fluxing particles, and the regeneration of selenium from biogenic matter has been undertaken in order to evaluate the processes affecting selenium in the ocean. Analyses of oceanic surface waters show selenite to be severely depleted, and the degree of selenate depletion, a function of the oceanic regime (i.e. most depleted in oligotrophic regions). Both species are enriched in deeper waters with an approximately 60:40 ratio of Se +6 to +4. A major species in surface waters and the upper thermocline is organic selenide. A secondary maximum of organic selenide is seen in the suboxic oxygen minimum of the eastern tropical Pacific, while selenite shows a negative anomaly. The regeneration of selenium from biogenic matter shows a multistep behavior, with organic selenide being released rapidly and primarily, selenite and selenate being produced by the slow oxidation of this fraction. Selenium in the ocean is affected by several processes. First organisms preferentially take-up selenite over selenate. This incorporation of selenium into biological material involves reduction to selenide. As selenium is regenerated from biogenic matter, first organic selenide is released, which in turn oxidizes to selenite, which then oxidizes very slowly to selenate. Finally, selenium does appear to undergo redox reactions in anoxic systems, but the products of the reactions remain unidentified.

  9. Selenium status in food grains of northern districts of India.

    PubMed

    Yadav, Sanjiv K; Singh, Ishwar; Sharma, Anita; Singh, Devender

    2008-09-01

    The selenium status in the food grains of the agricultural lands of northern parts of India was estimated by using the HG-AAS technique. The areas where lesser rains were received or less irrigation water was available in northern Indian states viz. Rajasthan and southern parts of the Haryana had higher selenium levels in food grains. Punjab, Himachal Pradesh and northern parts of the Haryana states had normal levels of selenium in their food grains, except for slightly lower selenium levels in a few areas that were affected by floods along the river Yamuna.

  10. Selenium status in soils of northern districts of India.

    PubMed

    Yadav, Sanjiv K; Singh, Ishwar; Singh, Devender; Han, Sang-Do

    2005-04-01

    The HG-AAS technique was used to estimate the soil selenium status of the agricultural lands of northern parts of India. The drier lands where lesser rains were received or where less irrigation water was available in Rajasthan and southern parts of the Haryana states had above normal soil selenium levels. These soils were also found to be alkaline. Punjab, Himachal Pradesh and northern parts of the Haryana states had normal levels of selenium in their soils, except with slightly lower selenium levels in a few areas that were affected by floods along the river Yamuna. The results were also confirmed using the ICP-OES technique.

  11. New plasma source of hydrides for epitaxial growth. Final subcontract report, 15 April 1991--3 September 1993

    SciTech Connect

    Stanbery, B.J.

    1994-05-01

    This report describes a novel plasma-activated selenium source that was developed during the course of this subcontract and which is significantly different than any other heretofore reported in the scientific literature. It involves microwave excited, magnetically confined plasma sources that are intended to operate under electron cyclotron resonance (ECR) conditions at 2.455 GHz. This source is designed to excite and dissociate the molecular vapor evaporating or subliming from a heated solid or liquid reservoir. It can combine an effusion cell vapor flux with a stream of hydrogen or helium gas, enabling the in-situ generation of hydrides for use in low-pressure growth techniques where long mean free paths are desirable. Experiments were conducted to demonstrate a stable discharge within the source, and measures were identified to improve its operational characteristics. Application of this novel source is anticipated to enable a low-temperature, safe process for the growth of high-quality epitaxial compound semiconductor films. This reduction of epitaxial growth temperatures may enable the fabrication of novel photovoltaic devices that have heretofore been impossible due to the deleterious effects of interdiffusion at heterointerfaces resulting from the high temperatures required to grow adequate quality material using conventional processes.

  12. Liquid metal cold trap

    DOEpatents

    Hundal, Rolv

    1976-01-01

    A cold trap assembly for removing impurities from a liquid metal being provided with a hole between the incoming impure liquid metal and purified outgoing liquid metal which acts as a continuous bleed means and thus prevents the accumulation of cover gases within the cold trap assembly.

  13. Clearance of absorbed selenium by the liver

    SciTech Connect

    Kato, Tatsuko; Read, R.; Rozga, J.; Burk, R.F. )

    1991-03-11

    The liver plays a central role in the metabolism of selenium. It secretes plasma selenoproteins, contains a major fraction of the glutathione peroxidase in the body, and synthesizes excretory metabolites. The role of the liver in processing newly absorbed selenium was studied. Male chow-fed rats were fasted overnight and given 24 ng of selenium as {sup 75}SeO{sub 3}{sup 2{minus}} by stomach tube. Animals were exsanguinated at 15, 30, 45, 60, 90, 120, and 180 min after dosing. Comparison of {sup 75}Se uptake by liver, kidney, heart, muscle, testis, brain, and spleen indicated an earlier uptake by liver than by any other tissue. At 15 min, {sup 75}Se in the portal vein blood was 2.6 times that in the hepatic vein blood. Gel filtration analysis suggested a loose association of {sup 75}Se with protein in plasma at 15 min, but immunoprecipitation indicated it was largely in the form of selenoprotein P after 30 min. End-to-side portacaval shunts (PCS) were constructed in rats and sham-operated animals were used as controls. When {sup 75}SeO{sub 3}{sup 2{minus}} was given to animals with PCS, uptake of {sup 75}Se by liver did not precede uptake by other tissues. Also no gradient was detected across the lungs or kidney. {sup 75}Se content of the kidney was higher in PCS rats than in sham-operated rats. This is consistent with removal of the first-pass effect of the liver facilitating uptake of {sup 75}Se by systemic tissues. These results suggest that the preferential uptake of absorbed selenium by the liver is due both to its position in the portal circulation and to an intrinsic high uptake capacity.

  14. Genetic polymorphisms that affect selenium status and response to selenium supplementation in United Kingdom pregnant women1

    PubMed Central

    Mao, Jinyuan; Vanderlelie, Jessica J; Perkins, Anthony V; Redman, Christopher WG; Ahmadi, Kourosh R; Rayman, Margaret P

    2016-01-01

    Background: Low selenium status in pregnancy has been associated with a number of adverse conditions. In nonpregnant populations, the selenium status or response to supplementation has been associated with polymorphisms in dimethylglycine dehydrogenase (DMGDH), selenoprotein P (SEPP1) and the glutathione peroxidases [cytosolic glutathione peroxidase (GPx1) and phospholipid glutathione peroxidase (GPx4)]. Objective: We hypothesized that, in pregnant women, these candidate polymorphisms would be associated with selenium status in early pregnancy, its longitudinal change, and the interindividual response to selenium supplementation at 60 μg/d. Design: With the use of stored samples and data from the United Kingdom Selenium in Pregnancy Intervention (SPRINT) study in 227 pregnant women, we carried out genetic-association studies, testing for associations between selenium status, its longitudinal change, and response to supplementation and common genetic variation in DMGDH (rs921943), SEPP1 (rs3877899 and rs7579), GPx1 (rs1050450) and GPx4 (rs713041). Selenium status was represented by the concentration of whole-blood selenium at 12 and 35 wk of gestation, the concentration of toenail selenium at 16 wk of gestation, and plasma glutathione peroxidase (GPx3) activity at 12 and 35 wk of gestation. Results: Our results showed that DMGDH rs921943 was significantly associated with the whole-blood selenium concentration at 12 wk of gestation (P = 0.032), which explained ≤2.0% of the variance. This association was replicated with the use of toenail selenium (P = 0.043). In unsupplemented women, SEPP1 rs3877899 was significantly associated with the percentage change in whole-blood selenium from 12 to 35 wk of gestation (P = 0.005), which explained 8% of the variance. In supplemented women, SEPP1 rs3877899 was significantly associated with the percentage change in GPx3 activity from 12 to 35 wk of gestation (P = 0.01), which explained 5.3% of the variance. Selenium status was

  15. Optical Trapping of Nanoparticles

    PubMed Central

    Bergeron, Jarrah; Zehtabi-Oskuie, Ana; Ghaffari, Saeedeh; Pang, Yuanjie; Gordon, Reuven

    2013-01-01

    Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3. A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure. The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm

  16. Distribution and geological sources of selenium in environmental materials in Taoyuan County, Hunan Province, China.

    PubMed

    Ni, Runxiang; Luo, Kunli; Tian, Xinglei; Yan, Songgui; Zhong, Jitai; Liu, Maoqiu

    2016-06-01

    The selenium (Se) distribution and geological sources in Taoyuan County, China, were determined by using hydride generation atomic fluorescence spectrometry on rock, soil, and food crop samples collected from various geological regions within the county. The results show Se contents of 0.02-223.85, 0.18-7.05, and 0.006-5.374 mg/kg in the rock, soil, and food crops in Taoyuan County, respectively. The region showing the highest Se content is western Taoyuan County amid the Lower Cambrian and Ediacaran black rock series outcrop, which has banding distributed west to east. A relatively high-Se environment is found in the central and southern areas of Taoyuan County, where Quaternary Limnetic sedimentary facies and Neoproterozoic metamorphic volcanic rocks outcrop, respectively. A relatively low-Se environment includes the central and northern areas of Taoyuan County, where Middle and Upper Cambrian and Ordovician carbonate rocks and Cretaceous sandstones and conglomerates outcrop. These results indicate that Se distribution in Taoyuan County varies markedly and is controlled by the Se content of the bedrock. The Se-enriched Lower Cambrian and Ediacaran black rock series is the primary source of the seleniferous environment observed in Taoyuan County. Potential seleniferous environments are likely to be found near outcrops of the Lower Cambrian and Ediacaran black rock series in southern China.

  17. Distribution and geological sources of selenium in environmental materials in Taoyuan County, Hunan Province, China.

    PubMed

    Ni, Runxiang; Luo, Kunli; Tian, Xinglei; Yan, Songgui; Zhong, Jitai; Liu, Maoqiu

    2016-06-01

    The selenium (Se) distribution and geological sources in Taoyuan County, China, were determined by using hydride generation atomic fluorescence spectrometry on rock, soil, and food crop samples collected from various geological regions within the county. The results show Se contents of 0.02-223.85, 0.18-7.05, and 0.006-5.374 mg/kg in the rock, soil, and food crops in Taoyuan County, respectively. The region showing the highest Se content is western Taoyuan County amid the Lower Cambrian and Ediacaran black rock series outcrop, which has banding distributed west to east. A relatively high-Se environment is found in the central and southern areas of Taoyuan County, where Quaternary Limnetic sedimentary facies and Neoproterozoic metamorphic volcanic rocks outcrop, respectively. A relatively low-Se environment includes the central and northern areas of Taoyuan County, where Middle and Upper Cambrian and Ordovician carbonate rocks and Cretaceous sandstones and conglomerates outcrop. These results indicate that Se distribution in Taoyuan County varies markedly and is controlled by the Se content of the bedrock. The Se-enriched Lower Cambrian and Ediacaran black rock series is the primary source of the seleniferous environment observed in Taoyuan County. Potential seleniferous environments are likely to be found near outcrops of the Lower Cambrian and Ediacaran black rock series in southern China. PMID:26563208

  18. Nonlinear integrable ion traps

    SciTech Connect

    Nagaitsev, S.; Danilov, V.; /SNS Project, Oak Ridge

    2011-10-01

    Quadrupole ion traps can be transformed into nonlinear traps with integrable motion by adding special electrostatic potentials. This can be done with both stationary potentials (electrostatic plus a uniform magnetic field) and with time-dependent electric potentials. These potentials are chosen such that the single particle Hamilton-Jacobi equations of motion are separable in some coordinate systems. The electrostatic potentials have several free adjustable parameters allowing for a quadrupole trap to be transformed into, for example, a double-well or a toroidal-well system. The particle motion remains regular, non-chaotic, integrable in quadratures, and stable for a wide range of parameters. We present two examples of how to realize such a system in case of a time-independent (the Penning trap) as well as a time-dependent (the Paul trap) configuration.

  19. Trapping radioactive ions

    NASA Astrophysics Data System (ADS)

    Kluge, H.-J.; Blaum, K.

    2004-12-01

    Trapping devices for atomic and nuclear physics experiments with radioactive ions are becoming more and more important at accelerator facilities. While about ten years ago only one online Penning trap experiment existed, namely ISOLTRAP at ISOLDE/CERN, meanwhile almost every radioactive beam facility has installed or plans an ion trap setup. This article gives an overview on ion traps in the operation, construction or planing phase which will be used for fundamental studies with short-lived radioactive nuclides such as mass spectrometry, laser spectroscopy and nuclear decay spectroscopy. In addition, this article summarizes the use of gas cells and radiofrequency quadrupole (Paul) traps at different facilities as a versatile tool for ion beam manipulation like retardation, cooling, bunching, and cleaning.

  20. Optically programmable excitonic traps

    PubMed Central

    Alloing, Mathieu; Lemaître, Aristide; Galopin, Elisabeth; Dubin, François

    2013-01-01

    With atomic systems, optically programmed trapping potentials have led to remarkable progress in quantum optics and quantum information science. Programmable trapping potentials could have a similar impact on studies of semiconductor quasi-particles, particularly excitons. However, engineering such potentials inside a semiconductor heterostructure remains an outstanding challenge and optical techniques have not yet achieved a high degree of control. Here, we synthesize optically programmable trapping potentials for indirect excitons of bilayer heterostructures. Our approach relies on the injection and spatial patterning of charges trapped in a field-effect device. We thereby imprint in-situ and on-demand electrostatic traps into which we optically inject cold and dense ensembles of excitons. This technique creates new opportunities to improve state-of-the-art technologies for the study of collective quantum behavior of excitons and also for the functionalisation of emerging exciton-based opto-electronic circuits. PMID:23546532

  1. Biofortification and phytoremediation of selenium in China.

    PubMed

    Wu, Zhilin; Bañuelos, Gary S; Lin, Zhi-Qing; Liu, Ying; Yuan, Linxi; Yin, Xuebin; Li, Miao

    2015-01-01

    Selenium (Se) is an essential trace element for humans and animals but at high concentrations, Se becomes toxic to organisms due to Se replacing sulfur in proteins. Selenium biofortification is an agricultural process that increases the accumulation of Se in crops, through plant breeding, genetic engineering, or use of Se fertilizers. Selenium phytoremediation is a green biotechnology to clean up Se-contaminated environments, primarily through phytoextraction and phytovolatilization. By integrating Se phytoremediation and biofortification technologies, Se-enriched plant materials harvested from Se phytoremediation can be used as Se-enriched green manures or other supplementary sources of Se for producing Se-biofortified agricultural products. Earlier studies primarily aimed at enhancing efficacy of phytoremediation and biofortification of Se based on natural variation in progenitor or identification of unique plant species. In this review, we discuss promising approaches to improve biofortification and phytoremediation of Se using knowledge acquired from model crops. We also explored the feasibility of applying biotechnologies such as inoculation of microbial strains for improving the efficiency of biofortification and phytoremediation of Se. The key research and practical challenges that remain in improving biofortification and phytoremediation of Se have been highlighted, and the future development and uses of Se-biofortified agricultural products in China has also been discussed. PMID:25852703

  2. Biofortification and phytoremediation of selenium in China

    PubMed Central

    Wu, Zhilin; Bañuelos, Gary S.; Lin, Zhi-Qing; Liu, Ying; Yuan, Linxi; Yin, Xuebin; Li, Miao

    2015-01-01

    Selenium (Se) is an essential trace element for humans and animals but at high concentrations, Se becomes toxic to organisms due to Se replacing sulfur in proteins. Selenium biofortification is an agricultural process that increases the accumulation of Se in crops, through plant breeding, genetic engineering, or use of Se fertilizers. Selenium phytoremediation is a green biotechnology to clean up Se-contaminated environments, primarily through phytoextraction and phytovolatilization. By integrating Se phytoremediation and biofortification technologies, Se-enriched plant materials harvested from Se phytoremediation can be used as Se-enriched green manures or other supplementary sources of Se for producing Se-biofortified agricultural products. Earlier studies primarily aimed at enhancing efficacy of phytoremediation and biofortification of Se based on natural variation in progenitor or identification of unique plant species. In this review, we discuss promising approaches to improve biofortification and phytoremediation of Se using knowledge acquired from model crops. We also explored the feasibility of applying biotechnologies such as inoculation of microbial strains for improving the efficiency of biofortification and phytoremediation of Se. The key research and practical challenges that remain in improving biofortification and phytoremediation of Se have been highlighted, and the future development and uses of Se-biofortified agricultural products in China has also been discussed. PMID:25852703

  3. Selenium Derivatization of Nucleic Acids for Crystallography

    SciTech Connect

    Jiang,J.; Sheng, J.; Carrasco, N.; Huang, Z.

    2007-01-01

    The high-resolution structure of the DNA (5'-GTGTACA-C-3') with the selenium derivatization at the 2'-position of T2 was determined via MAD and SAD phasing. The selenium-derivatized structure (1.28 {angstrom} resolution) with the 2'-Se modification in the minor groove is isomorphorous to the native structure (2.0 {angstrom}). To directly compare with the conventional bromine derivatization, we incorporated bromine into the 5-postion of T4, determined the bromine-derivatized DNA structure at 1.5 {angstrom} resolution, and found that the local backbone torsion angles and solvent hydration patterns were altered in the structure with the Br incorporation in the major groove. Furthermore, while the native and Br-derivatized DNAs needed over a week to form reasonable-size crystals, we observed that the Se-derivatized DNAs grew crystals overnight with high-diffraction quality, suggesting that the Se derivatization facilitated the crystal formation. In addition, the Se-derivatized DNA sequences crystallized under a broader range of buffer conditions, and generally had a faster crystal growth rate. Our experimental results indicate that the selenium derivatization of DNAs may facilitate the determination of nucleic acid X-ray crystal structures in phasing and high-quality crystal growth. In addition, our results suggest that the Se derivatization can be an alternative to the conventional Br derivatization.

  4. Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.

    SciTech Connect

    Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

    2012-02-01

    In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested

  5. Selenoprotein P Is the Major Selenium Transport Protein in Mouse Milk

    PubMed Central

    Hill, Kristina E.; Motley, Amy K.; Winfrey, Virginia P.; Burk, Raymond F.

    2014-01-01

    Selenium is transferred from the mouse dam to its neonate via milk. Milk contains selenium in selenoprotein form as selenoprotein P (Sepp1) and glutathione peroxidase-3 (Gpx3) as well as in non-specific protein form as selenomethionine. Selenium is also present in milk in uncharacterized small-molecule form. We eliminated selenomethionine from the mice in these experiments by feeding a diet that contained sodium selenite as the source of selenium. Selenium-replete dams with deletion of Sepp1 or Gpx3 were studied to assess the effects of these genes on selenium transfer to the neonate. Sepp1 knockout caused a drop in milk selenium to 27% of the value in wild-type milk and a drop in selenium acquisition by the neonates to 35%. In addition to decreasing milk selenium by eliminating Sepp1, deletion of Sepp1 causes a decline in whole-body selenium, which likely also contributes to the decreased transfer of selenium to the neonate. Deletion of Gpx3 did not decrease milk selenium content or neonate selenium acquisition by measurable amounts. Thus, when the dam is fed selenium-adequate diet (0.25 mg selenium/kg diet), milk Sepp1 transfers a large amount of selenium to neonates but the transfer of selenium by Gpx3 is below detection by our methods. PMID:25068390

  6. Hydriding performances and modeling of a small-scale ZrCo bed

    SciTech Connect

    Koo, D.; Lee, J.; Park, J.; Paek, S.; Chung, H.; Chang, M.H.; Yun, S.H.; Cho, S.; Jung, K.J.

    2015-03-15

    In order to evaluate the performance of the hydriding of a ZrCo bed, a small-scale getter bed of ZrCo was designed and fabricated. The results show that the hydriding time at room temperature was somewhat shorter than that at higher temperatures of ZrCo and that the performance of hydriding at low temperatures of ZrCo was better than that at high temperatures of ZrCo. The experimental results of the hydrogen pressure of hydriding (ZrCoH{sub 2.8}) at different temperatures were in agreement with the computed values using a numerical modeling equation but with a small difference during the first 10 minutes of the hydriding of ZrCo. The model is based on the Kozeny-Carman equation. The effect of a helium blanket on hydriding was measured and analyzed. The hydriding with no helium blanket in the primary vessel of ZrCo is much faster than that with a helium blanket. The hydriding at a helium concentration of 8% is slower than that at 0%. As the helium concentration increases, the hydriding of ZrCo decreases. The experimental results of the hydriding with 0 %, 4%, and 8% of helium concentration are in agreement with the calculated values but with minimal differences during the first 10 minutes.

  7. Hydride structures in Ti-aluminides subjected to high temperature and hydrogen pressure charging conditions

    NASA Technical Reports Server (NTRS)

    Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

    1991-01-01

    The distribution and chemistry of hydrides produced in single and dual phase alloys with a composition near TiAl have been investigated by using a combination of TEM and X-ray diffraction techniques. The alloys were exposed at 650 C to 13.8 MPa of gaseous H2 for 100 h. In the single-phase gamma alloy, large hydrides preferentially nucleated on the grain boundaries and matrix dislocations and a population of small hydrides was distributed throughout the matrix. X-ray and electron diffraction patterns from these hydrides indicated that they have an fcc structure with a lattice parameter of 0.45 nm. EDAX analysis of the hydrides showed that they were enriched in Ti. The hydrides were mostly removed by vacuum annealing at 800 C for 24 h. On dissolution of the hydrides, the chemistry of hydride-free regions of the grain boundary returned to the matrix composition, suggesting that Ti segregation accompanied the hydride formation rather than Ti enrichment causing the formation of the hydride.

  8. Efficient catalysis by MgCl2 in hydrogen generation via hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis.

    PubMed

    Zhao, Zelun; Zhu, Yunfeng; Li, Liquan

    2012-06-01

    Magnesium chloride efficiently catalyzed the hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis. Hydrogen yield of 1635 mL g(-1) was obtained (MgH(2)), i.e. with 96% conversion in 30 min at 303 K.

  9. Stibine and bismuthine trapping in quartz tube atomizers for atomic absorption spectrometry — Method optimization and analytical applications

    NASA Astrophysics Data System (ADS)

    Kratzer, Jan; Dědina, Jiří

    2008-08-01

    The compact trap-and-atomizer device was employed to trap stibine and bismuthine, and subsequently to volatilize collected analyte and atomize it for atomic absorption spectrometric detection. The device is actually the multiple microflame quartz tube atomizer (multiatomizer) with inlet arm modified to serve as the trap and to accommodate the oxygen delivery capillary employed for burning out hydrogen during the trapping step. The optimization of Sb and Bi collection in the device is presented based on a study of the influence of relevant experimental parameters on preconcentration efficiency of both analytes. The parameters studied were: (1) trap temperature during trapping and (2) hydrogen flow rate and (3) trap temperature during volatilization and (4) the stability of the trapped analyte species. Under optimized conditions, the preconcentration efficiency was 100% for both analytes. The trap-and-atomizer device can be replaced by the simple conventional externally heated quartz tube atomizer without any trap as demonstrated on the ultratrace antimony determination in groundwater reference material and mineral water samples. The interference of other hydride forming elements on Bi in-situ collection in the conventional externally heated quartz tube atomizer was investigated.

  10. Formation of noble-gas hydrides and decay of solvated protons revisited: diffusion-controlled reactions and hydrogen atom losses in solid noble gases.

    PubMed

    Tanskanen, Hanna; Khriachtchev, Leonid; Lignell, Antti; Räsänen, Markku; Johansson, Susanna; Khyzhniy, Ivan; Savchenko, Elena

    2008-02-01

    UV photolysis and annealing of C2H2/Xe, C2H2/Xe/Kr, and HBr/Xe matrices lead to complicated photochemical processes and reactions. The dominating products in these experiments are noble-gas hydrides with general formula HNgY (Ng = noble-gas atom, Y = electronegative fragment). We concentrate on distinguishing the local and global mobility and losses of H atoms, barriers of the reactions, and the decay of solvated protons. Different deposition temperatures change the amount of lattice imperfections and thus the amount of traps for H atoms. The averaged distance between reacting species influencing the reaction kinetics is controlled by varying the precursor concentration. A number of solid-state processes connected to the formation of noble-gas hydrides and decay of solvated protons are discussed using a simple kinetic model. The most efficient formation of noble-gas hydrides is connected with global (long-range) mobility of H atoms leading to the H + Xe + Y reaction. The highest concentration of noble-gas hydrides was obtained in matrices of highest optical quality, which probably have the lowest concentration of defects and H-atom losses. In matrices with high amount of geometrical imperfections, the product formation is inefficient and dominated by a local (short-range) process. The decay of solvated protons is rather local than a global process, which is different from the formation of noble-gas molecules. However, the present data do not allow distinguishing local proton and electron mobilities. Our previous results indicate that these are electrons which move to positively-charged centers and neutralize them. It is believed that the image obtained here for solid xenon is applicable to solid krypton whereas the case of argon deserves special attention.

  11. A global perspective of selenium deficiency and toxicity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium is an essential nutrient that has a relatively narrow margin between ingested amounts that cause deficiency and toxicosis. Both selenium deficiency and toxicosis occur in several regions in many countries throughout the world and result in substantial losses to the livestock industry. Sel...

  12. Selenium impacts on razorback sucker, Colorado: Colorado River: III. Larvae

    USGS Publications Warehouse

    Hamilton, S.J.; Holley, K.M.; Buhl, K.J.; Bullard, F.A.

    2005-01-01

    Razorback sucker (Xyrauchen texanus) larvae from adults exposed to selenium at three sites near Grand Junction, Colorado, for 9 months were used in a 30-day waterborne and dietary selenium study. Selenium concentrations in water averaged <1.6 ??g/L from 24-Road, 0.9 ??g/L from Horsethief, 5.5 ??g/L from Adobe Creek, and 10.7 ??g/L from the North Pond. Selenium in dietary items averaged 2.7 ??g/g in brine shrimp, 5.6 ??g/g in zooplankton from Horsethief east wetland, 20 ??g/g in zooplankton from Adobe Creek, and 39 ??g/g in zooplankton from North Pond. The lowest survival occurred in larvae fed zooplankton rather than brine shrimp. Survival of larvae at Adobe Creek and North Pond was lower in site water than in reference water. Survival of brood stock larvae was higher than Horsethief larvae even though they received the same water and dietary treatments. Arsenic concentrations in brine shrimp may have resulted in an antagonistic interaction with selenium and reduced adverse effects in larvae. Deformities in larvae from North Pond were similar to those reported for selenium-induced teratogenic deformities in other fish species. Selenium concentrations of ???4.6 ??g/g in food resulted in rapid mortality of larvae from Horsethief, Adobe Creek, and North Pond, and suggested that selenium toxicity in the Colorado River could limit recovery of this endangered fish.

  13. Selenium impacts on razorback sucker, Colorado: Colorado River III. Larvae.

    PubMed

    Hamilton, Steven J; Holley, Kathy M; Buhl, Kevin J; Bullard, Fern A

    2005-06-01

    Razorback sucker (Xyrauchen texanus) larvae from adults exposed to selenium at three sites near Grand Junction, Colorado, for 9 months were used in a 30-day waterborne and dietary selenium study. Selenium concentrations in water averaged <1.6 microg/L from 24-Road, 0.9 microg/L from Horsethief, 5.5 microg/L from Adobe Creek, and 10.7 microg/L from the North Pond. Selenium in dietary items averaged 2.7 microg/g in brine shrimp, 5.6 microg/g in zooplankton from Horsethief east wetland, 20 microg/g in zooplankton from Adobe Creek, and 39 microg/g in zooplankton from North Pond. The lowest survival occurred in larvae fed zooplankton rather than brine shrimp. Survival of larvae at Adobe Creek and North Pond was lower in site water than in reference water. Survival of brood stock larvae was higher than Horsethief larvae even though they received the same water and dietary treatments. Arsenic concentrations in brine shrimp may have resulted in an antagonistic interaction with selenium and reduced adverse effects in larvae. Deformities in larvae from North Pond were similar to those reported for selenium-induced teratogenic deformities in other fish species. Selenium concentrations of 4.6 microg/g in food resulted in rapid mortality of larvae from Horsethief, Adobe Creek, and North Pond, and suggested that selenium toxicity in the Colorado River could limit recovery of this endangered fish.

  14. Selenium impacts on razorback sucker, Colorado: Colorado River III. Larvae.

    PubMed

    Hamilton, Steven J; Holley, Kathy M; Buhl, Kevin J; Bullard, Fern A

    2005-06-01

    Razorback sucker (Xyrauchen texanus) larvae from adults exposed to selenium at three sites near Grand Junction, Colorado, for 9 months were used in a 30-day waterborne and dietary selenium study. Selenium concentrations in water averaged <1.6 microg/L from 24-Road, 0.9 microg/L from Horsethief, 5.5 microg/L from Adobe Creek, and 10.7 microg/L from the North Pond. Selenium in dietary items averaged 2.7 microg/g in brine shrimp, 5.6 microg/g in zooplankton from Horsethief east wetland, 20 microg/g in zooplankton from Adobe Creek, and 39 microg/g in zooplankton from North Pond. The lowest survival occurred in larvae fed zooplankton rather than brine shrimp. Survival of larvae at Adobe Creek and North Pond was lower in site water than in reference water. Survival of brood stock larvae was higher than Horsethief larvae even though they received the same water and dietary treatments. Arsenic concentrations in brine shrimp may have resulted in an antagonistic interaction with selenium and reduced adverse effects in larvae. Deformities in larvae from North Pond were similar to those reported for selenium-induced teratogenic deformities in other fish species. Selenium concentrations of 4.6 microg/g in food resulted in rapid mortality of larvae from Horsethief, Adobe Creek, and North Pond, and suggested that selenium toxicity in the Colorado River could limit recovery of this endangered fish. PMID:15883090

  15. Lentils (Lens culinaris L.) as a source of dietary selenium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The chapter discusses the nutritional value of lentils, with a focus on factors affecting lentils as a source of dietary selenium. It addresses the chemical nature of lentil-selenium, pointing out that more than 90% is present in organic compounds which are generally well absorbed by humans. The se...

  16. Iodine and selenium deficiency associated with cretinism in northern Zaire.

    PubMed

    Vanderpas, J B; Contempré, B; Duale, N L; Goossens, W; Bebe, N; Thorpe, R; Ntambue, K; Dumont, J; Thilly, C H; Diplock, A T

    1990-12-01

    Selenium status was determined in an endemic-goiter area and in a control area of Zaire. Compared with the reference values of a noniodine-deficient area, serum selenium in subjects living in the core of the northern Zaire endemic-goiter belt (Karawa villages) was seven times lower in 52 school-children and similarly low in 23 cretins; erythrocyte glutathione peroxidase (RBC-GPX) was five times lower in schoolchildren and still two times lower in cretins (P = 0.004). In a less severely iodine-deficient city of the same endemia (Businga), selenium status was moderately altered. RBC-GPX activity was linearly associated with serum selenium concentration up to a value of 1140 nmol/L and leveled off at approximately 15 U/g Hb at greater selenium concentration. At Karawa villages, selenium supplementation normalized both the serum selenium and the RBC-GPX. This combined iodine and selenium deficiency could be associated with the elevated frequency of endemic myxedematous cretinism in Central Africa.

  17. Iodine and selenium deficiency associated with cretinism in northern Zaire.

    PubMed

    Vanderpas, J B; Contempré, B; Duale, N L; Goossens, W; Bebe, N; Thorpe, R; Ntambue, K; Dumont, J; Thilly, C H; Diplock, A T

    1990-12-01

    Selenium status was determined in an endemic-goiter area and in a control area of Zaire. Compared with the reference values of a noniodine-deficient area, serum selenium in subjects living in the core of the northern Zaire endemic-goiter belt (Karawa villages) was seven times lower in 52 school-children and similarly low in 23 cretins; erythrocyte glutathione peroxidase (RBC-GPX) was five times lower in schoolchildren and still two times lower in cretins (P = 0.004). In a less severely iodine-deficient city of the same endemia (Businga), selenium status was moderately altered. RBC-GPX activity was linearly associated with serum selenium concentration up to a value of 1140 nmol/L and leveled off at approximately 15 U/g Hb at greater selenium concentration. At Karawa villages, selenium supplementation normalized both the serum selenium and the RBC-GPX. This combined iodine and selenium deficiency could be associated with the elevated frequency of endemic myxedematous cretinism in Central Africa. PMID:2239787

  18. 21 CFR 522.2100 - Selenium, vitamin E injection.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Selenium, vitamin E injection. 522.2100 Section... § 522.2100 Selenium, vitamin E injection. (a)(1) Specifications. The drug is an emulsion containing in... of vitamin E (68 I.U.) (as d-alpha tocopheryl acetate). (2) Sponsor. See No. 000061 in §...

  19. 21 CFR 522.2100 - Selenium, vitamin E injection.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Selenium, vitamin E injection. 522.2100 Section... § 522.2100 Selenium, vitamin E injection. (a)(1) Specifications. The drug is an emulsion containing in... of vitamin E (68 I.U.) (as d-alpha tocopheryl acetate). (2) Sponsor. See No. 000061 in §...

  20. CANOLA CROP TAKES UP SELENIUM PROVIDES BIOFUEL AND FEED SUPPLEMENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many of the Brassica plant taxi that are candidates for phytoremediation of selenium also produce products that be used for refining into biodiesel, as well as selenium enriched animal feeds. These include canola (Brassica napus) that is planted in the Westside soils of central California (Oxalis si...

  1. Microbial Transformations of Selenium Species of Relevance to Bioremediation.

    PubMed

    Eswayah, Abdurrahman S; Smith, Thomas J; Gardiner, Philip H E

    2016-08-15

    Selenium species, particularly the oxyanions selenite (SeO3 (2-)) and selenate (SeO4 (2-)), are significant pollutants in the environment that leach from rocks and are released by anthropogenic activities. Selenium is also an essential micronutrient for organisms across the tree of life, including microorganisms and human beings, particularly because of its presence in the 21st genetically encoded amino acid, selenocysteine. Environmental microorganisms are known to be capable of a range of transformations of selenium species, including reduction, methylation, oxidation, and demethylation. Assimilatory reduction of selenium species is necessary for the synthesis of selenoproteins. Dissimilatory reduction of selenate is known to support the anaerobic respiration of a number of microorganisms, and the dissimilatory reduction of soluble selenate and selenite to nanoparticulate elemental selenium greatly reduces the toxicity and bioavailability of selenium and has a major role in bioremediation and potentially in the production of selenium nanospheres for technological applications. Also, microbial methylation after reduction of Se oxyanions is another potentially effective detoxification process if limitations with low reaction rates and capture of the volatile methylated selenium species can be overcome. This review discusses microbial transformations of different forms of Se in an environmental context, with special emphasis on bioremediation of Se pollution. PMID:27260359

  2. Algal-bacterial treatment facility removes selenium from drainage water

    SciTech Connect

    Quinn, Nigel W.T.; Lundquist, Tryg J.; Green, F. Bailey; Zarate, Max A.; Oswald, William J.; Leighton, Terrance

    2000-01-25

    A demonstration algal-bacterial selenium removal (ABSR) facility has been treating agricultural drainage water in the Panoche Drainage District on the west side of the San Joaquin Valley since 1997. The project goals are to demonstrate the effectiveness of the ABSR technology for selenium removal, to investigate potential wildlife exposure to selenium at full-scale facilities, and to develop an operational plant configuration that will minimize the life-cycle cost for each pound of selenium removed. The facility consists of a series of ponds designed to promote native microorganisms that remove nitrate and selenium. Previous treatment research efforts sought to reduce selenium concentrations to less than 5 mu g/L, but the ABSR Facility demonstration focuses on providing affordable reduction of the selenium load that is discharged to the San Joaquin River. During 1997 and 1998, the best-performing ABSR plant configuration reduced nitrate by more than 95 percent and reduced total soluble selenium mass by 80 percent. Ongoing investigations focus on optimizing operational parameters and determining operational costs and scale-up engineering requirements. The preliminary total cost estimate for a 10-acre-foot per day ABSR facility is less than $200 per acre-foot of treated drainage water.

  3. Stratigraphic traps 2

    SciTech Connect

    Not Available

    1991-01-01

    This volume contains studies of fields with traps that are mainly stratigraphic in nature. Structure plays a role in the traps of several fields, but overall, it is clear that the main trapping features with the group of fields in this volume are stratigraphic. The first six fields in this volume, Alabama Ferry, Rospo Mare, Walker Creek, Bindley, Lexington, and Newburg/South Westhope, have carbonate reservoirs. The latter two of these, Lexington and Newburg/South Westhope, also have sandstone reservoirs. The remaining fields, East Texas, East Clinton, Stockholm Southwest, Sorrento, Port Acres, and Lagoa Parda, have only sandstone reservoirs.

  4. The nature of the TRAP-Anti-TRAP complex.

    PubMed

    Watanabe, Masahiro; Heddle, Jonathan G; Kikuchi, Kenichi; Unzai, Satoru; Akashi, Satoko; Park, Sam-Yong; Tame, Jeremy R H

    2009-02-17

    Tryptophan biosynthesis is subject to exquisite control in species of Bacillus and has become one of the best-studied model systems in gene regulation. The protein TRAP (trp RNA-binding attenuation protein) predominantly forms a ring-shaped 11-mer, which binds cognate RNA in the presence of tryptophan to suppress expression of the trp operon. TRAP is itself regulated by the protein Anti-TRAP, which binds to TRAP and prevents RNA binding. To date, the nature of this interaction has proved elusive. Here, we describe mass spectrometry and analytical centrifugation studies of the complex, and 2 crystal structures of the TRAP-Anti-TRAP complex. These crystal structures, both refined to 3.2-A resolution, show that Anti-TRAP binds to TRAP as a trimer, sterically blocking RNA binding. Mass spectrometry shows that 11-mer TRAP may bind up to 5 AT trimers, and an artificial 12-mer TRAP may bind 6. Both forms of TRAP make the same interactions with Anti-TRAP. Crystallization of wild-type TRAP with Anti-TRAP selectively pulls the 12-mer TRAP form out of solution, so the crystal structure of wild-type TRAP-Anti-TRAP complex reflects a minor species from a mixed population. PMID:19164760

  5. Tribochemical Decomposition of Light Ionic Hydrides at Room Temperature.

    PubMed

    Nevshupa, Roman; Ares, Jose Ramón; Fernández, Jose Francisco; Del Campo, Adolfo; Roman, Elisa

    2015-07-16

    Tribochemical decomposition of magnesium hydride (MgH2) induced by deformation at room temperature was studied on a micrometric scale, in situ and in real time. During deformation, a near-full depletion of hydrogen in the micrometric affected zone is observed through an instantaneous (t < 1 s) and huge release of hydrogen (3-50 nmol/s). H release is related to a nonthermal decomposition process. After deformation, the remaining hydride is thermally decomposed at room temperature, exhibiting a much slower rate than during deformation. Confocal-microRaman spectroscopy of the mechanically affected zone was used to characterize the decomposition products. Decomposition was enhanced through the formation of the distorted structure of MgH2 with reduced crystal size by mechanical deformation.

  6. ALUMINUM HYDRIDE: A REVERSIBLE STORAGE MATERIAL FOR HYDROGEN STORAGE

    SciTech Connect

    Zidan, R; Christopher Fewox, C; Brenda Garcia-Diaz, B; Joshua Gray, J

    2009-01-09

    One of the challenges of implementing the hydrogen economy is finding a suitable solid H{sub 2} storage material. Aluminium (alane, AlH{sub 3}) hydride has been examined as a potential hydrogen storage material because of its high weight capacity, low discharge temperature, and volumetric density. Recycling the dehydride material has however precluded AlH{sub 3} from being implemented due to the large pressures required (>10{sup 5} bar H{sub 2} at 25 C) and the thermodynamic expense of chemical synthesis. A reversible cycle to form alane electrochemically using NaAlH{sub 4} in THF been successfully demonstrated. Alane is isolated as the triethylamine (TEA) adduct and converted to unsolvated alane by heating under vacuum. To complete the cycle, the starting alanate can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride (NaH) This novel reversible cycle opens the door for alane to fuel the hydrogen economy.

  7. Composition and function in AB{sub 5} hydride electrodes

    SciTech Connect

    Adzic, G.D.; Johnson, J.R.; Mukerjee, S.; McBreen, J.; Reilly, J.J.

    1996-12-31

    Multicomponent AB, hydrides are attractive replacements for the cadmium electrode in nickel - cadmium batteries. This paper is concerned with the differential effects of Ni substitution by cobalt, Mn and Al upon electrode corrosion and capacity, using alloys having the generic composition of Al(NiCoMnAl){sub 5} and similar to those used for the preparation of commercial battery electrodes. The corrosion of metal hydride electrodes is determined by two factors, surface passivation due to the presence of surface oxides or hydroxides and crystal lattice expansion - contraction the charge - discharge process. Thus, in addition to determining the effects of Ni substitution we will also address the question of whether an observed change is due to a change lattice expansion or to a change in surface passivation, e.g. the formation a corrosion resistant oxide layer.

  8. Detecting low concentrations of plutonium hydride with magnetization measurements

    SciTech Connect

    Kim, Jae Wook; Mun, E. D.; Baiardo, J. P.; Zapf, V. S.; Mielke, C. H.; Smith, A. I.; Richmond, S.; Mitchell, J.; Schwartz, D.

    2015-02-07

    We report the formation of plutonium hydride in 2 at. % Ga-stabilized δ-Pu, with 1 at. % H charging. We show that magnetization measurements are a sensitive, quantitative measure of ferromagnetic plutonium hydride against the nonmagnetic background of plutonium. It was previously shown that at low hydrogen concentrations, hydrogen forms super-abundant vacancy complexes with plutonium, resulting in a bulk lattice contraction. Here, we use magnetization, X-ray, and neutron diffraction measurements to show that in addition to forming vacancy complexes, at least 30% of the H atoms bond with Pu to precipitate PuH{sub x} on the surface of the sample with x ∼ 1.9. We observe magnetic hysteresis loops below 40 K with magnetic remanence, consistent with ferromagnetic PuH{sub 1.9}.

  9. A low tritium hydride bed inventory estimation technique

    SciTech Connect

    Klein, J.E.; Shanahan, K.L.; Baker, R.A.; Foster, P.J.

    2015-03-15

    Low tritium hydride beds were developed and deployed into tritium service in Savannah River Site. Process beds to be used for low concentration tritium gas were not fitted with instrumentation to perform the steady-state, flowing gas calorimetric inventory measurement method. Low tritium beds contain less than the detection limit of the IBA (In-Bed Accountability) technique used for tritium inventory. This paper describes two techniques for estimating tritium content and uncertainty for low tritium content beds to be used in the facility's physical inventory (PI). PI are performed periodically to assess the quantity of nuclear material used in a facility. The first approach (Mid-point approximation method - MPA) assumes the bed is half-full and uses a gas composition measurement to estimate the tritium inventory and uncertainty. The second approach utilizes the bed's hydride material pressure-composition-temperature (PCT) properties and a gas composition measurement to reduce the uncertainty in the calculated bed inventory.

  10. Structural isotope effects in metal hydrides and deuterides.

    PubMed

    Ting, Valeska P; Henry, Paul F; Kohlmann, Holger; Wilson, Chick C; Weller, Mark T

    2010-03-01

    Historically the extraction of high-quality crystallographic information from inorganic samples having high hydrogen contents, such as metal hydrides, has involved preparing deuterated samples prior to study using neutron powder diffraction. We demonstrate, through direct comparison of the crystal structure refinements of the binary hydrides SrH(2) and BaH(2) with their deuteride analogues at 2 K and as a function of temperature, that precise and accurate structural information can be obtained from rapid data collections from samples containing in excess of 60 at.% hydrogen using modern high-flux, medium resolution, continuous wavelength neutron powder diffraction instruments. Furthermore, observed isotope-effects in the extracted lattice parameters and atomic positions illustrate the importance of investigating compounds in their natural hydrogenous form whenever possible.

  11. The free-energy barrier to hydride transfer across a dipalladium complex.

    PubMed

    Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique. PMID:25652724

  12. FEASIBILITY OF RECYCLING PLUTONIUM AND MINOR ACTINIDES IN LIGHT WATER REACTORS USING HYDRIDE FUEL

    SciTech Connect

    Greenspan, Ehud; Todreas, Neil; Taiwo, Temitope

    2009-03-10

    The objective of this DOE NERI program sponsored project was to assess the feasibility of improving the plutonium (Pu) and minor actinide (MA) recycling capabilities of pressurized water reactors (PWRs) by using hydride instead of oxide fuels. There are four general parts to this assessment: 1) Identifying promising hydride fuel assembly designs for recycling Pu and MAs in PWRs 2) Performing a comprehensive systems analysis that compares the fuel cycle characteristics of Pu and MA recycling in PWRs using the promising hydride fuel assembly designs identified in Part 1 versus using oxide fuel assembly designs 3) Conducting a safety analysis to assess the likelihood of licensing hydride fuel assembly designs 4) Assessing the compatibility of hydride fuel with cladding materials and water under typical PWR operating conditions Hydride fuel was found to offer promising transmutation characteristics and is recommended for further examination as a possible preferred option for recycling plutonium in PWRs.

  13. The free-energy barrier to hydride transfer across a dipalladium complex.

    PubMed

    Vanston, C R; Kearley, G J; Edwards, A J; Darwish, T A; de Souza, N R; Ramirez-Cuesta, A J; Gardiner, M G

    2015-01-01

    We use density-functional theory molecular dynamics (DFT-MD) simulations to determine the hydride transfer coordinate between palladium centres of the crystallographically observed terminal hydride locations, Pd-Pd-H, originally postulated for the solution dynamics of the complex bis-NHC dipalladium hydride [{(MesIm)2CH2}2Pd2H][PF6], and then calculate the free-energy along this coordinate. We estimate the transfer barrier-height to be about 20 kcal mol(-1) with a hydride transfer rate in the order of seconds at room temperature. We validate our DFT-MD modelling using inelastic neutron scattering which reveals anharmonicity of the hydride environment that is so pronounced that there is complete failure of the harmonic model for the hydride ligand. The simulations are extended to high temperature to bring the H-transfer to a rate that is accessible to the simulation technique.

  14. Higher selenium status is associated with adverse blood lipid profile in British adults

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent findings have raised concern about possible associations of high selenium exposure with diabetes and hyperlipidemia in the US, a population with high selenium status. In the UK, a population with lower selenium status, there is little data on the association of selenium status with cardio-met...

  15. Effect of thermo-mechanical cycling on zirconium hydride reorientation studied in situ with synchrotron X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Colas, Kimberly B.; Motta, Arthur T.; Daymond, Mark R.; Almer, Jonathan D.

    2013-09-01

    The circumferential hydrides normally present in nuclear reactor fuel cladding after reactor exposure may dissolve during drying for dry storage and re-precipitate when cooled under load into a more radial orientation, which could embrittle the fuel cladding. It is necessary to study the rates and conditions under which hydride reorientation may happen in order to assess fuel integrity in dry storage. The objective of this work is to study the effect of applied stress and thermal cycling on the hydride morphology in cold-worked stress-relieved Zircaloy-4 by combining conventional metallography and in situ X-ray diffraction techniques. Metallography is used to study the evolution of hydride morphology after several thermo-mechanical cycles. In situ X-ray diffraction performed at the Advanced Photon Source synchrotron provides real-time information on the process of hydride dissolution and precipitation under stress during several thermal cycles. The detailed study of diffracted intensity, peak position and full-width at half-maximum provides information on precipitation kinetics, elastic strains and other characteristics of the hydride precipitation process. The results show that thermo-mechanical cycling significantly increases the radial hydride fraction as well as the hydride length and connectivity. The radial hydrides are observed to precipitate at a lower temperature than circumferential hydrides. Variations in the magnitude and range of hydride strains due to reorientation and cycling have also been observed. These results are discussed in light of existing models and experiments on hydride reorientation. The study of hydride elastic strains during precipitation shows marked differences between circumferential and radial hydrides, which can be used to investigate the reorientation process. Cycling under stress above the threshold stress for reorientation drastically increases both the reoriented hydride fraction and the hydride size. The reoriented hydride

  16. Gas chromatographic separation of hydrogen isotopes using metal hydrides

    SciTech Connect

    Aldridge, F.T.

    1984-05-09

    A study was made of the properties of metal hydrides which may be suitable for use in chromatographic separation of hydrogen isotopes. Sixty-five alloys were measured, with the best having a hydrogen-deuterium separation factor of 1.35 at 60/sup 0/C. Chromatographic columns using these alloys produced deuterium enrichments of up to 3.6 in a single pass, using natural abundance hydrogen as starting material. 25 references, 16 figures, 4 tables.

  17. Ground-state energy and relativistic corrections for positronium hydride

    SciTech Connect

    Bubin, Sergiy; Varga, Kalman

    2011-07-15

    Variational calculations of the ground state of positronium hydride (HPs) are reported, including various expectation values, electron-positron annihilation rates, and leading relativistic corrections to the total and dissociation energies. The calculations have been performed using a basis set of 4000 thoroughly optimized explicitly correlated Gaussian basis functions. The relative accuracy of the variational energy upper bound is estimated to be of the order of 2x10{sup -10}, which is a significant improvement over previous nonrelativistic results.

  18. METHOD OF MAKING DELTA ZIRCONIUM HYDRIDE MONOLITHIC MODERATOR PIECES

    DOEpatents

    Vetrano, J.B.

    1962-01-23

    A method is given for preparing large, sound bodies of delta zirconium hydride. The method includes the steps of heating a zirconium body to a temperature of not less than l000 deg C, providing a hydrogen atmosphere for the zirconium body at a pressure not greater than one atmosphere, reducing the temperature slowly to 800 deg C at such a rate that cracks do not form while maintaining the hydrogen pressure substantially constant, and cooling in an atmosphere of hydrogen. (AEC)

  19. Risks and benefits in agricultural uses of selenium.

    PubMed

    Oldfield, J E

    1992-10-01

    Selenium deficiency in soils, and subsequently in crops that are grown on them, has been charted in various parts of the world. Use of carefully regulated amounts of supplemental selenium in such areas has been effective in improving productive performance of domestic food-producing animals, and some 30 years' experience has now been gained with various supplementation practices. Coincidentaliy, there have been instances reported of situations where selenium toxicity has resulted from a combination of naturally-high environmental levels, enhanced by agricultural, environmental and industrial practices, and questions have been raised as to whether continued animal supplementation may contribute to selenium toxicity. This paper examines some of the various factors involved and concludes that presently-established animal supplementation uses of selenium are small compared with other sources of the element and that they do not constitute a hazard to animals, including humans, or the environment.

  20. Ionic liquid-induced synthesis of selenium nanoparticles

    SciTech Connect

    Langi, Bhushan; Shah, Chetan; Singh, Krishankant; Chaskar, Atul; Kumar, Manmohan; Bajaj, Parma N.

    2010-06-15

    A simple wet chemical method has been used to synthesize selenium nanoparticles by the reaction of ionic liquid with sodium selenosulphate, a selenium precursor, in the presence of polyvinyl alcohol stabilizer, in aqueous medium. The method is capable of producing spherical selenium nanoparticles in the size range of 76-150 nm under ambient conditions. This is a first report on the production of nano-selenium assisted by an ionic liquid. The synthesized nanoparticles can be separated easily from the aqueous sol by a high-speed centrifuge machine, and can be re-dispersed in an aqueous medium. The synthesized selenium nanoparticles have been characterized by X-ray diffraction, energy dispersive X-ray analysis, differential scanning calorimetry and transmission electron microscopy techniques.

  1. Selenium fertilization on lentil (Lens culinaris Medikus) grain yield, seed selenium concentration, and antioxidant activity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Selenium (Se) is an essential element for mammals but has not been considered as an essential element for higher plants. Lentil (Lens culinaris Medik.) is a cool season food legume rich in protein and a range of micronutrients including minerals (iron and zinc), folates, and carotenoids. The objecti...

  2. Daily selenium intake in a moderate selenium deficiency area of Suzhou China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Daily dietary selenium (Se) intake in Suzhou China was investigated to determine whether residents were susceptible to Se deficiency. Food samples were purchased from local supermarkets, including vegetables, fruits, meats and seafood. Hair samples were collected from 285 people ranging from 20 to ...

  3. SPECIATION OF ARSENIC COMPOUNDS IN DRINKING WATER BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW DETECTED THROUGH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS...

    EPA Science Inventory

    Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride s...

  4. SPECIATION OF ARSENIC COMPOUNDS IN DRINKING WATER BY CAPILLARY ELECTROPHORESIS WITH HYDRODYNAMICALLY MODIFIED ELECTROOSMOTIC FLOW DETECTED THROUGH HYDRIDE GENERATION INDUCTIVELY COUPLED PLASMA MASS..

    EPA Science Inventory

    Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride ...

  5. High temperature metal hydrides as heat storage materials for solar and related applications.

    PubMed

    Felderhoff, Michael; Bogdanović, Borislav

    2009-01-01

    For the continuous production of electricity with solar heat power plants the storage of heat at a temperature level around 400 degrees C is essential. High temperature metal hydrides offer high heat storage capacities around this temperature. Based on Mg-compounds, these hydrides are in principle low-cost materials with excellent cycling stability. Relevant properties of these hydrides and their possible applications as heat storage materials are described.

  6. High Temperature Metal Hydrides as Heat Storage Materials for Solar and Related Applications

    PubMed Central

    Felderhoff, Michael; Bogdanović, Borislav

    2009-01-01

    For the continuous production of electricity with solar heat power plants the storage of heat at a temperature level around 400 °C is essential. High temperature metal hydrides offer high heat storage capacities around this temperature. Based on Mg-compounds, these hydrides are in principle low-cost materials with excellent cycling stability. Relevant properties of these hydrides and their possible applications as heat storage materials are described. PMID:19333448

  7. Orbital-like motion of hydride ligands around low-coordinate metal centers.

    PubMed

    Ortuño, Manuel A; Vidossich, Pietro; Conejero, Salvador; Lledós, Agustí

    2014-12-15

    Hydrogen atoms in the coordination sphere of a transition metal are highly mobile ligands. Here, a new type of dynamic process involving hydrides has been characterized by computational means. This dynamic event consists of an orbital-like motion of hydride ligands around low-coordinate metal centers containing N-heterocyclic carbenes. The hydride movement around the carbene-metal-carbene axis is the lowest energy mode connecting energy equivalent isomers. This understanding provides crucial information for the interpretation of NMR spectra.

  8. Performance study of a hydrogen powered metal hydride actuator

    NASA Astrophysics Data System (ADS)

    Mainul Hossain Bhuiya, Md; Kim, Kwang J.

    2016-04-01

    A thermally driven hydrogen powered actuator integrating metal hydride hydrogen storage reactor, which is compact, noiseless, and able to generate smooth actuation, is presented in this article. To test the plausibility of a thermally driven actuator, a conventional piston type actuator was integrated with LaNi5 based hydrogen storage system. Copper encapsulation followed by compaction of particles into pellets, were adopted to improve overall thermal conductivity of the reactor. The operation of the actuator was thoroughly investigated for an array of operating temperature ranges. Temperature swing of the hydride reactor triggering smooth and noiseless actuation over several operating temperature ranges were monitored for quantification of actuator efficiency. Overall, the actuator generated smooth and consistent strokes during repeated cycles of operation. The efficiency of the actuator was found to be as high as 13.36% for operating a temperature range of 20 °C-50 °C. Stress-strain characteristics, actuation hysteresis etc were studied experimentally. Comparison of stress-strain characteristics of the proposed actuator with traditional actuators, artificial muscles and so on was made. The study suggests that design modification and use of high pressure hydride may enhance the performance and broaden the application horizon of the proposed actuator in future.

  9. Air passivation of metal hydride beds for waste disposal

    SciTech Connect

    Klein, J. E.; Hsu, R. H.

    2008-07-15

    One waste acceptance criteria for hydride bed waste disposal is that the bed be non-pyrophoric. Batch-wise air ingress tests were performed which determined the amount of air consumed by a metal hydride bed. A desorbed, 4.4 kg titanium prototype hydride storage vessel (HSV) produced a 4.4 deg.C internal temperature rise upon the first air exposure cycle and a 0.1 deg.C temperature rise upon a second air exposure. A total of 346 sec air was consumed by the bed (0.08 sec per gram Ti). A desorbed, 9.66 kg LaNi{sub 4.25}Al{sub 0.75} prototype storage bed experienced larger temperature rises over successive cycles of air ingress and evacuation. The cycles were performed over a period of days with the bed effectively passivated after the 12. cycle. Nine to ten STP-L of air reacted with the bed producing both oxidized metal and water. (authors)

  10. Hydrides and dimers of C(58) fullerenes: structures and stabilities.

    PubMed

    Bihlmeier, Angela; Klopper, Wim

    2009-02-21

    A density functional theory (DFT) study of fullerene hydrides C(58)H(2x) (2x = 2,4,...,34) is presented. We consider two relevant isomers, the most stable classical isomer C(58)-C(3v) and the energetically close non-classical isomer C(58)-C(s), which contains a heptagonal ring. Iterative pairwise addition of hydrogen atoms to only the energetically favoured products of the previous iteration yields a set of low energy structures for each composition. From these, low energy pathways are extracted. Analysis of the C-H binding energies along the reaction pathways is performed to identify particularly stable hydride compositions. These are 2x = 6,18,28,34 for C(58)-C(s) and 2x = 10,26,30 for C(58)-C(3v). We therefore suggest that these hydrides are preferably formed in hydrogenation experiments and that it should be possible to distinguish between the two C(58) isomers. We further investigate the dimer formation based on low energy C(58)H(2) addition patterns. All dimers show binding energies of more than 1 eV whereby dispersion interactions play a significant role. Both C(58) isomers can also undergo further aggregation. This leads us to the conclusion that in the absence of other reactant molecules C(58) will form intercage bonds and cannot be isolated in molecular form, which is in accordance with experimental results.

  11. Initial report on molecular modeling of metal hydrides

    SciTech Connect

    Mansour, K.A.; Wolf, R.J.

    1990-12-01

    Metal hydrides are for hydrogen/tritium storage and handling. Examples of such metals and metal alloys include palladium (Pd) and lanthanum-nickel-aluminum (LaNiAl). These materials have the unique properties of being hydrogen/tritium sponges''. (1) Metal hydrides absorb enormous quantities of hydrogen/tritium, where the hydrogen density is much larger than in liquid hydrogen. There is a unique problem that develops in tritium storage, mainly due to its radioactive decay into helium. Helium is inert (i.e., non-reactive due to its closed shell electronic structure) and tends to remain in the hydride once it forms there. A clear understanding of such a phenomenon (and how to minimize it and possibly get rid of it) is the foundation of our current work. Our main focus is to fundamentally understand hydrogen/tritium behavior and interactions in these metals, so that we can design better and more efficient tritium handling materials and facilities. As a by-product of this work, we will able to apply our state-of-the-art techniques to study other problems involving hydrogen/tritium and helium in SRS materials. Examples include hydrogen and helium interactions in lithium-aluminum reactor targets, tritium reservoirs, and stainless steel reactor tanks. 2 tabs., 4 figs., 10 refs.

  12. Investigation of long term stability in metal hydrides

    NASA Technical Reports Server (NTRS)

    Marmaro, Roger W.; Lynch, Franklin E.; Chandra, Dhanesh; Lambert, Steve; Sharma, Archana

    1991-01-01

    It is apparent from the literature and the results of this study that cyclic degradation of AB(5) type metal hydrides varies widely according to the details of how the specimens are cycled. The Rapid Cycle Apparatus (RCA) used produced less degradation in 5000 to 10000 cycles than earlier work with a Slow Cycle Apparatus (SCA) produced in 1500 cycles. Evidence is presented that the 453 K (356 F) Thermal Aging (TA) time spent in the saturated condition causes hydride degradation. But increasing the cooling (saturation) period in the RCA did not greatly increase the rate of degradation. It appears that TA type degradation is secondary at low temperatures to another degradation mechanism. If rapid cycles are less damaging than slow cycles when the saturation time is equal, the rate of hydriding/dehydriding may be an important factor. The peak temperatures in the RCA were about 30 C lower than the SCA. The difference in peak cycle temperatures (125 C in the SCA, 95 C in RCA) cannot explain the differences in degradation. TA type degradation is similar to cyclic degradation in that nickel peaks and line broadening are observed in X ray diffraction patterns after either form of degradation.

  13. Pressure-driven formation and stabilization of superconductive chromium hydrides

    PubMed Central

    Yu, Shuyin; Jia, Xiaojing; Frapper, Gilles; Li, Duan; Oganov, Artem R.; Zeng, Qingfeng; Zhang, Litong

    2015-01-01

    Chromium hydride is a prototype stoichiometric transition metal hydride. The phase diagram of Cr-H system at high pressures remains largely unexplored due to the challenges in dealing with the high activation barriers and complications in handing hydrogen under pressure. We have performed an extensive structural study on Cr-H system at pressure range 0 ∼ 300 GPa using an unbiased structure prediction method based on evolutionary algorithm. Upon compression, a number of hydrides are predicted to become stable in the excess hydrogen environment and these have compositions of Cr2Hn (n = 2–4, 6, 8, 16). Cr2H3, CrH2 and Cr2H5 structures are versions of the perfect anti-NiAs-type CrH with ordered tetrahedral interstitial sites filled by H atoms. CrH3 and CrH4 exhibit host-guest structural characteristics. In CrH8, H2 units are also identified. Our study unravels that CrH is a superconductor at atmospheric pressure with an estimated transition temperature (T c) of 10.6 K, and superconductivity in CrH3 is enhanced by the metallic hydrogen sublattice with T c of 37.1 K at 81 GPa, very similar to the extensively studied MgB2. PMID:26626579

  14. Superconductivity of novel tin hydrides (SnnHm) under pressure

    NASA Astrophysics Data System (ADS)

    Mahdi Davari Esfahani, M.; Wang, Zhenhai; Oganov, Artem R.; Dong, Huafeng; Zhu, Qiang; Wang, Shengnan; Rakitin, Maksim S.; Zhou, Xiang-Feng

    2016-03-01

    With the motivation of discovering high-temperature superconductors, evolutionary algorithm USPEX is employed to search for all stable compounds in the Sn-H system. In addition to the traditional SnH4, new hydrides SnH8, SnH12 and SnH14 are found to be thermodynamically stable at high pressure. Dynamical stability and superconductivity of tin hydrides are systematically investigated. Im2-SnH8, C2/m-SnH12 and C2/m-SnH14 exhibit higher superconducting transition temperatures of 81, 93 and 97 K compared to the traditional compound SnH4 with Tc of 52 K at 200 GPa. An interesting bent H3-group in Im2-SnH8 and novel linear H in C2/m-SnH12 are observed. All the new tin hydrides remain metallic over their predicted range of stability. The intermediate-frequency wagging and bending vibrations have more contribution to electron-phonon coupling parameter than high-frequency stretching vibrations of H2 and H3.

  15. Superconductivity of novel tin hydrides (SnnHm) under pressure

    PubMed Central

    Mahdi Davari Esfahani, M.; Wang, Zhenhai; Oganov, Artem R.; Dong, Huafeng; Zhu, Qiang; Wang, Shengnan; Rakitin, Maksim S.; Zhou, Xiang-Feng

    2016-01-01

    With the motivation of discovering high-temperature superconductors, evolutionary algorithm USPEX is employed to search for all stable compounds in the Sn-H system. In addition to the traditional SnH4, new hydrides SnH8, SnH12 and SnH14 are found to be thermodynamically stable at high pressure. Dynamical stability and superconductivity of tin hydrides are systematically investigated. Im2-SnH8, C2/m-SnH12 and C2/m-SnH14 exhibit higher superconducting transition temperatures of 81, 93 and 97 K compared to the traditional compound SnH4 with Tc of 52 K at 200 GPa. An interesting bent H3–group in Im2-SnH8 and novel linear H in C2/m-SnH12 are observed. All the new tin hydrides remain metallic over their predicted range of stability. The intermediate-frequency wagging and bending vibrations have more contribution to electron-phonon coupling parameter than high-frequency stretching vibrations of H2 and H3. PMID:26964636

  16. Superconductivity of novel tin hydrides (SnnHm) under pressure

    NASA Astrophysics Data System (ADS)

    Mahdi Davari Esfahani, M.; Wang, Zhenhai; Oganov, Artem R.; Dong, Huafeng; Zhu, Qiang; Wang, Shengnan; Rakitin, Maksim S.; Zhou, Xiang-Feng

    2016-03-01

    With the motivation of discovering high-temperature superconductors, evolutionary algorithm USPEX is employed to search for all stable compounds in the Sn-H system. In addition to the traditional SnH4, new hydrides SnH8, SnH12 and SnH14 are found to be thermodynamically stable at high pressure. Dynamical stability and superconductivity of tin hydrides are systematically investigated. Im2-SnH8, C2/m-SnH12 and C2/m-SnH14 exhibit higher superconducting transition temperatures of 81, 93 and 97 K compared to the traditional compound SnH4 with Tc of 52 K at 200 GPa. An interesting bent H3–group in Im2-SnH8 and novel linear H in C2/m-SnH12 are observed. All the new tin hydrides remain metallic over their predicted range of stability. The intermediate-frequency wagging and bending vibrations have more contribution to electron-phonon coupling parameter than high-frequency stretching vibrations of H2 and H3.

  17. Steam trap monitor

    DOEpatents

    Ryan, M.J.

    1987-05-04

    A steam trap monitor positioned downstream of a steam trap in a closed steam system includes a first sensor (a hot finger) for measuring the energy of condensate and a second sensor (a cold finger) for measuring the total energy of condensate and steam in the line. The hot finger includes one or more thermocouples for detecting condensate level and energy, while the cold finger contains a liquid with a lower boiling temperature than that of water. Vapor pressure from the liquid is used to do work such as displacing a piston or bellow in providing an indication of total energy (steam + condensate) of the system. Processing means coupled to and responsive to outputs from the hot and cold fingers subtracts the former from the latter to provide an indication of the presence of steam downstream from the trap indicating that the steam trap is malfunctioning. 2 figs.

  18. Trapping and Probing Antihydrogen

    SciTech Connect

    Wurtele, Jonathan

    2013-03-27

    Precision spectroscopy of antihydrogen is a promising path to sensitive tests of CPT symmetry. The most direct route to achieve this goal is to create and probe antihydrogen in a magnetic minimum trap. Antihydrogen has been synthesized and trapped for 1000s at CERN by the ALPHA Collaboration. Some of the challenges associated with achieving these milestones will be discussed, including mixing cryogenic positron and antiproton plasmas to synthesize antihydrogen with kinetic energy less than the trap potential of .5K. Recent experiments in which hyperfine transitions were resonantly induced with microwaves will be presented. The opportunity for gravitational measurements in traps based on detailed studies of antihydrogen dynamics will be described. The talk will conclude with a discussion future antihydrogen research that will use a new experimental apparatus, ALPHA-I.

  19. Versatile electrostatic trap

    SciTech Connect

    Veldhoven, Jacqueline van; Bethlem, Hendrick L.; Schnell, Melanie; Meijer, Gerard

    2006-06-15

    A four electrode electrostatic trap geometry is demonstrated that can be used to combine a dipole, quadrupole, and hexapole field. A cold packet of {sup 15}ND{sub 3} molecules is confined in both a purely quadrupolar and hexapolar trapping field and additionally, a dipole field is added to a hexapole field to create either a double-well or a donut-shaped trapping field. The profile of the {sup 15}ND{sub 3} packet in each of these four trapping potentials is measured, and the dependence of the well-separation and barrier height of the double-well and donut potential on the hexapole and dipole term are discussed.

  20. Total Selenium and Selenium Species in Irrigation Drain Inflows to the Salton Sea, California, April and July 2008

    USGS Publications Warehouse

    May, Thomas W.; Walther, Michael J.; Saiki, Michael K.; Brumbaugh, William G.

    2009-01-01

    This report presents the results for two sampling periods (April 2008 and July 2008) during a 4-year monitoring program to characterize selenium concentrations in selected irrigation drains flowing into the Salton Sea, California. Total selenium, selenium species (dissolved selenite, selenate, organoselenium), and total suspended solids were determined in water samples and total selenium was determined in water column particulates and in sediment, detritus, and biota that included algae, plankton, midge larvae (family, Chironomidae), and two fish species - western mosquitofish (Gambusia affinis) and sailfin molly (Poecilia latipinna). In addition, sediments were analyzed for percent total organic carbon and particle size. Mean total selenium concentrations in water for both sampling periods ranged from 1.93 to 44.2 micrograms per liter, predominately as selenate, which is typical of waters where selenium is leached out of selenium-containing marine shales and associated soils under alkaline and oxidizing conditions. Total selenium concentrations (micrograms per gram dry weight) ranged as follows: algae, 0.75 to 3.39; plankton, 0.88 to 4.03; midges, 2.52 to 44.3; fish, 3.37 to 18.9; detritus, 1.11 to 13.6; sediment, 0.11 to 8.93.