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Sample records for iron sulfur molybdenum

  1. Microstructure And Erosion-Corrosion Behaviour Of As-Cast High Chromium White Irons Containing Molybdenum In Aqueous Sulfuric-Acid Slurry

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    Imurai S.

    2015-06-01

    Full Text Available Microstructure and erosion-corrosion behaviour of as-cast high chromium white irons containing molybdenum in aqueous sulfuric-acid slurry was studied. The experimental irons contained 28 wt.%Cr with a Cr:C ratio of about 10 and up to 10 wt.%Mo. The irons with up to 6 wt.%Mo are hypoeutectic, whereas the iron with 10 wt.%Mo becomes eutectic/peritectic. Mo addition promotes formation of M23C6 and M6C, instead of typical M7C3. Erosion-corrosion testing was performed in aqueous sulfuric-acid slurry containing alumina particles. The hypoeutectic Fe-28Cr-2.7C-1Mo with mainly M7C3 and the eutectic/peritectic Fe-28Cr-2.6C-10Mo showed reduced wear rates of about 30% and 7% of that of the reference iron without Mo addition, respectively. The reduction of the carbide-matrix hardness difference, the increase of corrosion resistance of the matrices, and the increase of macro-hardness are determining factors for the improvement of erosion-corrosion resistance of the irons.

  2. Characterization of the NifS-like domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration.

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    Heidenreich, Torsten; Wollers, Silke; Mendel, Ralf R; Bittner, Florian

    2005-02-11

    The molybdenum cofactor sulfurase ABA3 from Arabidopsis thaliana specifically regulates the activity of the molybdenum enzymes aldehyde oxidase and xanthine dehydrogenase by converting their molybdenum cofactor from the desulfo-form into the sulfo-form. ABA3 is a two-domain protein with an NH2-terminal domain sharing significant similarities to NifS proteins that catalyze the decomposition of l-cysteine to l-alanine and elemental sulfur for iron-sulfur cluster synthesis. Although different in its physiological function, the mechanism of ABA3 for sulfur mobilization was found to be similar to NifS proteins. The protein binds a pyridoxal phosphate cofactor and a substrate-derived persulfide intermediate, and site-directed mutagenesis of strictly conserved binding sites for the cofactor and the persulfide demonstrated that they are essential for molybdenum cofactor sulfurase activity. In vitro, the NifS-like domain of ABA3 activates aldehyde oxidase and xanthine dehydrogenase in the absence of the C-terminal domain, but in vivo, the C-terminal domain is required for proper activation of both target enzymes. In addition to its cysteine desulfurase activity, ABA3-NifS also exhibits selenocysteine lyase activity. Although l-selenocysteine is unlikely to be a natural substrate for ABA3, it is decomposed more efficiently than l-cysteine. Besides mitochondrial AtNFS1 and plastidial AtNFS2, which are both proposed to be involved in iron-sulfur cluster formation, ABA3 is proposed to be a third and cytosolic NifS-like cysteine desulfurase in A. thaliana. However, the sulfur transferase activity of ABA3 is used for post-translational activation of molybdenum enzymes rather than for iron-sulfur cluster assembly.

  3. Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

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    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

  4. Iron binary and ternary coatings with molybdenum and tungsten

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    Yar-Mukhamedova, Gulmira, E-mail: gulmira-alma-ata@mail.ru [Institute Experimental and Theoretical Physics Al-Farabi Kazakh National University, 050038, Al-Farabi av., 71, Almaty (Kazakhstan); Ved, Maryna; Sakhnenko, Nikolay; Karakurkchi, Anna; Yermolenko, Iryna [National Technical University “Kharkov Polytechnic Institute”, Kharkov (Ukraine)

    2016-10-15

    Highlights: • High quality coatings of double Fe-Mo and ternary Fe-Mo-W electrolytic alloys can be produced both in a dc and a pulsed mode. • Application of unipolar pulsed current allows receiving an increased content of the alloying components and their more uniform distribution over the surface. • It is established that Fe-Mo and Fe-Mo-W coatings have an amorphous structure and exhibit improved corrosion resistance and microhardness as compared with the steel substrate due to the inclusion molybdenum and tungsten. - Abstract: Electrodeposition of Fe-Mo-W and Fe-Mo layers from a citrate solution containing iron(III) on steel and iron substrates is compared. The utilization of iron(III) compounds significantly improved the electrolyte stability eliminating side anodic redox reactions. The influence of concentration ratios and electrodeposition mode on quality, chemical composition, and functional properties of the alloys is determined. It has been found that alloys deposited in pulse mode have more uniform surface morphology and chemical composition and contain less impurities. Improvement in physical and mechanical properties as well as corrosion resistance of Fe-Mo and Fe-Mo-W deposits when compared with main alloy forming metals is driven by alloying components chemical passivity as well as by alloys amorphous structure. Indicated deposits can be considered promising materials in surface hardening technologies and repair of worn out items.

  5. The ineluctable requirement for the trans-iron elements molybdenum and/or tungsten in the origin of life

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    Schoepp-Cothenet, Barbara; van Lis, Robert; Philippot, Pascal; Magalon, Axel; Russell, Michael J.; Nitschke, Wolfgang

    2012-02-01

    An evolutionary tree of key enzymes from the Complex-Iron-Sulfur-Molybdoenzyme (CISM) superfamily distinguishes ``ancient'' members, i.e. enzymes present already in the last universal common ancestor (LUCA) of prokaryotes, from more recently evolved subfamilies. The majority of the presented subfamilies and, as a consequence, the Molybdo-enzyme superfamily as a whole, appear to have existed in LUCA. The results are discussed with respect to the nature of bioenergetic substrates available to early life and to problems arising from the low solubility of molybdenum under conditions of the primordial Earth.

  6. Leaching kinetics of molybdenum from Ni-Mo ore in sulfuric acid solution with sodium peroxodisulfate as oxidant

    Institute of Scientific and Technical Information of China (English)

    刘志雄; 尹周澜; 陈义光; 熊利芝

    2015-01-01

    The leaching kinetics of molybdenum from Ni-Mo ore in sulfuric acid solution with sodium peroxodisulfate was studied. The effects including leaching temperature, reaction time, particle size, stirring speed, and concentrations of sulfuric acid and sodium peroxodisulfate were investigated. The leaching process of molybdenum from Ni-Mo ore is controlled by the chemical reaction through the solid layer across the unreacted shrinking core. The apparent activation energy of the leaching of molybdenum is calculated to be 41.0 kJ/mol and the leaching kinetics equation of molybdenum from Ni-Mo ore is expressed as 1−(1−a)1/3=3405.7exp[−41030.0/(RT)]t.

  7. Cytochromes and iron sulfur proteins in sulfur metabolism of phototrophic bacteria

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    Fischer, U.

    1985-01-01

    Dissimilatory sulfur metabolism in phototrophic sulfur bacteria provides the bacteria with electrons for photosynthetic electron transport chain and, with energy. Assimilatory sulfate reduction is necessary for the biosynthesis of sulfur-containing cell components. Sulfide, thiosulfate, and elemental sulfur are the sulfur compounds most commonly used by phototrophic bacteria as electron donors for anoxygenic photosynthesis. Cytochromes or other electron transfer proteins, like high-potential-iron-sulfur protein (HIPIP) function as electron acceptors or donors for most enzymatic steps during the oxidation pathways of sulfide or thiosulfate. Yet, heme- or siroheme-containing proteins themselves undergo enzymatic activities in sulfur metabolism. Sirohemes comprise a porphyrin-like prosthetic group of sulfate reductase. eenzymatic reactions involve electron transfer. Electron donors or acceptors are necessary for each reaction. Cytochromes and iron sulfur problems, are able to transfer electrons.

  8. COMBINED RETENTION OF MOLYBDENUM AND SULFUR IN SIMULATED HIGH LEVEL WASTE GLASS

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    Fox, K.

    2009-10-16

    This study was undertaken to investigate the effect of elevated sulfate and molybdenum concentrations in nuclear waste glasses. A matrix of 24 glasses was developed and the glasses were tested for acceptability based on visual observations, canister centerline-cooled heat treatments, and chemical composition analysis. Results from the chemical analysis of the rinse water from each sample were used to confirm the presence of SO{sup 2-}{sub 4} and MoO{sub 3} on the surface of glasses as well as other components which might form water soluble compounds with the excess sulfur and molybdenum. A simple, linear model was developed to show acceptable concentrations of SO{sub 4}{sup 2-} and MoO{sub 3} in an example waste glass composition. This model was constructed for scoping studies only and is not ready for implementation in support of actual waste vitrification. Several other factors must be considered in determining the limits of sulfate and molybdenum concentrations in the waste vitrification process, including but not limited to, impacts on refractory and melter component corrosion, effects on the melter off-gas system, and impacts on the chemical durability and crystallization of the glass product.

  9. Reduction of molybdenum oxide from steelmaking slags by pure liquid iron

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    Gao Y.M.

    2012-01-01

    Full Text Available The effects of reaction temperature, slag basicity and FeO concentration on the reduction of molybdenum oxide from steelmaking slags by pure liquid iron were investigated experimently. The reduction kinetics of molybdenum oxide by liquid iron was analysed. The reaction models were developed based on the condition that diffusion of [Mo] in liquid iron and CaMoO4 in slag is the control steps, respectively. These reaction models were tested using data from a series of experiments. The results indicate that under the present experimental conditions, the temperature and the FeO content, other than slag basicity, have some effects on the reduction of molybdenum oxide from steelmaking slags by pure liquid iron. Both the molybdenum oxide reduction rate and final reduction ratio increase with an increase of temperature and a decrease of FeO content. The diffusion of CaMoO4 in slag which dominated overall reduction process is the only one ratecontrolling step with its apparent activation energy 294 kJ/mol. The reduction of molybdenum oxide used directly as alloy additive can be further enhanced by strong stirring in the converter practice.

  10. Iron-Catalyzed Synthesis of Sulfur-Containing Heterocycles.

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    Bosset, Cyril; Lefebvre, Gauthier; Angibaud, Patrick; Stansfield, Ian; Meerpoel, Lieven; Berthelot, Didier; Guérinot, Amandine; Cossy, Janine

    2016-10-13

    An iron-catalyzed synthesis of sulfur- and sulfone-containing heterocycles is reported. The method is based on the cyclization of readily available substrates and proceeded with high efficiency and diastereoselectivity. A variety of sulfur-containing heterocycles bearing moieties suitable for subsequent functionalization are prepared. Illustrative examples of such postcyclization modifications are also presented.

  11. Bacterial iron-sulfur cluster sensors in mammalian pathogens

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    Miller, Halie K.; Auerbuch, Victoria

    2015-01-01

    Iron-sulfur clusters act as important cofactors for a number of transcriptional regulators in bacteria, including many mammalian pathogens. The sensitivity of iron-sulfur clusters to iron availability, oxygen tension, and reactive oxygen and nitrogen species enables bacteria to use such regulators to adapt their gene expression profiles rapidly in response to changing environmental conditions. In this review, we discuss how the [4Fe-4S] or [2Fe-2S] cluster-containing regulators FNR, Wbl, aconitase, IscR, NsrR, SoxR, and AirSR contribute to bacterial pathogenesis through control of both metabolism and classical virulence factors. In addition, we briefly review mammalian iron homeostasis as well as oxidative/nitrosative stress to provide context for understanding the function of bacterial iron-sulfur cluster sensors in different niches within the host. PMID:25738802

  12. An efficient hydrogenation catalyst in sulfuric acid for the conversion of nitrobenzene to p-aminophenol: N-doped carbon with encapsulated molybdenum carbide.

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    Wang, Tao; Dong, Zhen; Cai, Weimeng; Wang, Yongzheng; Fu, Teng; Zhao, Bin; Peng, Luming; Ding, Weiping; Chen, Yi

    2016-08-23

    The transfer of catalytic function from molybdenum carbide to N-doped carbon has been tested by encapsulating molybdenum carbide with N-doped carbon using a one-pot preparation process. The outer layer of N-doped carbon, inert itself, exhibits high activity and excellent selectivity with molybdenum carbide as the catalyst for the hydrogenation of nitrobenzene to p-aminophenol in sulfuric acid.

  13. Mitochondrial Iron-Sulfur Cluster Activity and Cytosolic Iron Regulate Iron Traffic in Saccharomyces cerevisiae*

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    Wofford, Joshua D.; Lindahl, Paul A.

    2015-01-01

    An ordinary differential equation-based mathematical model was developed to describe trafficking and regulation of iron in growing fermenting budding yeast. Accordingly, environmental iron enters the cytosol and moves into mitochondria and vacuoles. Dilution caused by increasing cell volume is included. Four sites are regulated, including those in which iron is imported into the cytosol, mitochondria, and vacuoles, and the site at which vacuolar FeII is oxidized to FeIII. The objective of this study was to determine whether cytosolic iron (Fecyt) and/or a putative sulfur-based product of iron-sulfur cluster (ISC) activity was/were being sensed in regulation. The model assumes that the matrix of healthy mitochondria is anaerobic, and that in ISC mutants, O2 diffuses into the matrix where it reacts with nonheme high spin FeII ions, oxidizing them to nanoparticles and generating reactive oxygen species. This reactivity causes a further decline in ISC/heme biosynthesis, which ultimately gives rise to the diseased state. The ordinary differential equations that define this model were numerically integrated, and concentrations of each component were plotted versus the concentration of iron in the growth medium and versus the rate of ISC/heme biosynthesis. Model parameters were optimized by fitting simulations to literature data. The model variant that assumed that both Fecyt and ISC biosynthesis activity were sensed in regulation mimicked observed behavior best. Such “dual sensing” probably arises in real cells because regulation involves assembly of an ISC on a cytosolic protein using Fecyt and a sulfur species generated in mitochondria during ISC biosynthesis and exported into the cytosol. PMID:26306041

  14. Iron-molybdenum cofactor from nitrogenase. Modified extraction methods as probes for composition.

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    Yang, S S; Pan, W H; Friesen, G D; Burgess, B K; Corbin, J L; Stiefel, E I; Newton, W E

    1982-07-25

    Five modifications of the preparative procedure for isolating iron-molybdenum cofactor (FeMoco) from the molybdenum-iron (MoFe) protein of Azotobacter vinelandii nitrogenase have been developed. This variety of isolation methods has established that no single component of the original isolation protocol, i.e. Tris, Cl-, citrate, HPO4(2-), N,N-dimethylformamide, and N-methylformamide, is essential for the effective isolation and/or structural stability of FeMoco, although any of them may act as ligands to FeMoco when present. The acid-bse status (effective pH) of the extracting solvent is a key adjustable parameter in the isolation procedure. The new procedures produced FeMoco with yields, metal analysis, charge, EPR spectrum, and specific activity (after reconstituting crude extracts from A. vinelandii UW45 mutant cells) essentially identical with FeMoco isolated by the original procedure. After purification, FeMoco apparently contains molybdenum, iron, and sulfide in a 1:7:4 ratio with N-methylformamide as a ligand but no amino acid residues, common sugars, coenzyme A, or lipoic acid. Reaction with o-phenanthroline allows quantitation of both adventitious and FeMoco-associated iron. Correlations of total activity after UW45 reconstitution with molybdenum, total iron, and o-phenanthroline-resistant iron contents show that only the last gives a consistent relationship of 35 +/- 5 nmol of C2H4/min/ng atom of Fe. Both o-phenanthroline and EDTA interact with FeMoco to abolish its EPR signal in reactions reversible by additions of Fe2+ or Zn2+, respectively. These and related reactions point against the presence of an endogenous organic component in FeMoco and toward the presence of exogenous ligands and imply a relatively labile coordination sphere whose nature may be determinable by a systematic investigation.

  15. Shared Sulfur Mobilization Routes for tRNA Thiolation and Molybdenum Cofactor Biosynthesis in Prokaryotes and Eukaryotes

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    Silke Leimkühler

    2017-01-01

    Full Text Available Modifications of transfer RNA (tRNA have been shown to play critical roles in the biogenesis, metabolism, structural stability and function of RNA molecules, and the specific modifications of nucleobases with sulfur atoms in tRNA are present in pro- and eukaryotes. Here, especially the thiomodifications xm5s2U at the wobble position 34 in tRNAs for Lys, Gln and Glu, were suggested to have an important role during the translation process by ensuring accurate deciphering of the genetic code and by stabilization of the tRNA structure. The trafficking and delivery of sulfur nucleosides is a complex process carried out by sulfur relay systems involving numerous proteins, which not only deliver sulfur to the specific tRNAs but also to other sulfur-containing molecules including iron–sulfur clusters, thiamin, biotin, lipoic acid and molybdopterin (MPT. Among the biosynthesis of these sulfur-containing molecules, the biosynthesis of the molybdenum cofactor (Moco and the synthesis of thio-modified tRNAs in particular show a surprising link by sharing protein components for sulfur mobilization in pro- and eukaryotes.

  16. Iron binary and ternary coatings with molybdenum and tungsten

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    Yar-Mukhamedova, Gulmira; Ved, Maryna; Sakhnenko, Nikolay; Karakurkchi, Anna; Yermolenko, Iryna

    2016-10-01

    Electrodeposition of Fe-Mo-W and Fe-Mo layers from a citrate solution containing iron(III) on steel and iron substrates is compared. The utilization of iron(III) compounds significantly improved the electrolyte stability eliminating side anodic redox reactions. The influence of concentration ratios and electrodeposition mode on quality, chemical composition, and functional properties of the alloys is determined. It has been found that alloys deposited in pulse mode have more uniform surface morphology and chemical composition and contain less impurities. Improvement in physical and mechanical properties as well as corrosion resistance of Fe-Mo and Fe-Mo-W deposits when compared with main alloy forming metals is driven by alloying components chemical passivity as well as by alloys amorphous structure. Indicated deposits can be considered promising materials in surface hardening technologies and repair of worn out items.

  17. Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum--Importance of surface oxides.

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    Mörsdorf, Alexander; Odnevall Wallinder, Inger; Hedberg, Yolanda

    2015-08-01

    The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys.

  18. Sulfur and molybdenum fractionation in marine and riverine alluvium paddy soils

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    Hamed Zakikhani

    2016-10-01

    Full Text Available Intermittently submergence and drainage status of paddy fields can cause alterations in morphological and chemical characteristics of soils. We conducted a sequential fractionation study to provide an insight into solubility of Sulfur (S and Molybdenum (Mo in flooded alluvial paddy soils. The samples (0–15 and 15–30 cm were taken from marine and riverine alluvial soils in Kedah and Kelantan areas, respectively, and were sequentially extracted with NaHCO3, NaOH, HCl, and HClO4–HNO3. Total S in upper and lower layers of Kedah and Kelantan ranged between 273 and 1121 mg kg−1, and 177 to 1509 mg kg−1, respectively. In upper layers and subsoil of Kedah, average total Mo were 0.34 and 0.27 mg kg−1, respectively. Average total Mo in Kelantan were 0.25 mg kg−1 (surface layer and 0.28 mg kg−1 (subsoil. Cation exchange capacity (CEC was positively correlated with plant available amounts of Mo in upper layers of Kedah area. Also, total and medium-term plant-available S was correlated with total carbon (C at lower layers of Kelantan soil series. But in surface layers of Kelantan soil series, CEC was strongly correlated with total and medium-term plant-available S. Our results indicates that the influence of flooding conditions on soil S and Mo contents in paddy fields may cause long-term changes in S and Mo chemical reactivities.

  19. Sulfur-Tolerant Molybdenum Carbide Catalysts Enabling Low-Temperature Stabilization of Fast Pyrolysis Bio-Oil

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    Li, Zhenglong; Choi, Jae Soon; Wang, Huamin; Lepore, Andrew W.; Connatser, Raynella M.; Lewis, Sam; Meyer, Harry; Santosa, Daniel M.; Zacher, Alan H.

    2017-08-18

    Low-temperature hydrogenation of carbonyl fractions can greatly improve the thermal stability of fast pyrolysis bio-oil which is crucial to achieve long-term operation of high-temperature upgrading reactors. The current state of the art, precious metals such as ruthenium, although highly effective in carbonyl hydrogenation, rapidly loses performance due to sulfur sensitivity. The present work showed that molybdenum carbides were active and sulfur-tolerant in low-temperature conversion carbonyl compounds. Furthermore, due to surface bifunctionality (presence of both metallic and acid sites), carbides catalyzed both C-O bond hydrogenation and C-C coupling reactions retaining most of carbon atoms in liquid products as more stable and higher molecular weight oligomeric compounds while consuming less hydrogen than ruthenium. The carbides proved to be resistant to other deactivation mechanisms including hydrothermal aging, oxidation, coking and leaching. These properties enabled carbides to achieve and maintain good catalytic performance in both aqueous-phase furfural conversion and real bio-oil stabilization with sulfur present. This finding strongly suggests that molybdenum carbides can provide a catalyst solution necessary for the development of commercially viable bio-oil stabilization technology.

  20. A chemical approach toward low temperature alloying of immiscible iron and molybdenum metals

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    Nazir, Rabia [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Applied Chemistry Research Centre, Pakistan Council of Scientific and Industrial Research Laboratories Complex, Lahore 54600 (Pakistan); Ahmed, Sohail [Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Mazhar, Muhammad, E-mail: mazhar42pk@yahoo.com [Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Akhtar, Muhammad Javed; Siddique, Muhammad [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Khan, Nawazish Ali [Material Science Laboratory, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shah, Muhammad Raza [HEJ Research Institute of Chemistry, University of Karachi, Karachi 75270 (Pakistan); Nadeem, Muhammad [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

    2013-11-15

    Graphical abstract: - Highlights: • Low temperature pyrolysis of [Fe(bipy){sub 3}]Cl{sub 2} and [Mo(bipy)Cl{sub 4}] homogeneous powder. • Easy low temperature alloying of immiscible metals like Fe and Mo. • Uniform sized Fe–Mo nanoalloy with particle size of 48–68 nm. • Characterization by EDXRF, AFM, XRPD, magnetometery, {sup 57}Fe Mössbauer and impedance. • Alloy behaves as almost superparamagnetic obeying simple –R(CPE)– circuit. - Abstract: The present research is based on a low temperature operated feasible method for the synthesis of immiscible iron and molybdenum metals’ nanoalloy for technological applications. The nanoalloy has been synthesized by pyrolysis of homogeneous powder precipitated, from a common solvent, of the two complexes, trisbipyridineiron(II)chloride, [Fe(bipy){sub 3}]Cl{sub 2}, and bipyridinemolybedenum(IV) chloride, [Mo(bipy)Cl{sub 4}], followed by heating at 500 °C in an inert atmosphere of flowing argon gas. The resulting nanoalloy has been characterized by using EDXRF, AFM, XRD, magnetometery, {sup 57}Fe Mössbauer and impedance spectroscopies. These results showed that under provided experimental conditions iron and molybdenum metals, with known miscibility barrier, alloy together to give (1:1) single phase material having particle size in the range of 48–66 nm. The magnetism of iron is considerably reduced after alloy formation and shows its trend toward superparamagnetism. The designed chemical synthetic procedure is equally feasible for the fabrication of other immiscible metals.

  1. Synthesis and degradation of nucleic acid components by formamide and iron sulfur minerals.

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    Saladino, Raffaele; Neri, Veronica; Crestini, Claudia; Costanzo, Giovanna; Graciotti, Michele; Di Mauro, Ernesto

    2008-11-19

    We describe the one-pot synthesis of a large panel of nucleic bases and related compounds from formamide in the presence of iron sulfur and iron-copper sulfur minerals as catalysts. The major products observed are purine, 1H-pyrimidinone, isocytosine, adenine, 2-aminopurine, carbodiimide, urea, and oxalic acid. Isocytosine and 2-aminopurine may recognize natural nucleobases by Watson-Crick and reverse Watson-Crick interactions, thus suggesting novel scenarios for the origin of primordial nucleic acids. Since the major problem in the origin of informational polymers is the instability of their precursors, we also investigate the effects of iron sulfur and iron-copper sulfur minerals on the stability of ribooligonucleotides in formamide and in water. All of the iron sulfur and iron-copper sulfur minerals stimulated degradation of RNA. The relevance of these findings with respect to the origin of informational polymers is discussed.

  2. The Friction-Reducing, Antiwear and Antioxidation Properties of an Organo-Molybdenum Lube Additive without Sulfur and Phosphorus

    Institute of Scientific and Technical Information of China (English)

    Junbing Yao; Gaston Aguilar; Glenn A. Mazzamaro

    2007-01-01

    The engine oil specifications of ILSAC GF-4 (implemented 2004) and GF-5 (expected 2010) have in common three important OEM needs: (1) improved fuel economy and its retention, (2) emissions system compatibility (related to phosphorus and sulfur content), and (3) improved oil robustness for extended oil life capability (e.g., reduced high temperature deposits and engine sludge, improved oxidative stability, and better valve train wear protection). For emission systems compatibility, there is a trend towards lower phosphorus and sulfur content in engine oils while maintaining high anti-oxidation and anti-wear performances. In this paper, the friction-reducing, antiwear and antioxidant properties of a sulfur-free and phosphorus-free molybdate ester compound as lubricant additive are discussed. The investigation showed that the molybdate ester enables good friction-reducing ability of the lubricant, and maintains low friction coefficients even after period of severe oil oxidation, which indicates the potential for excellent fuel economy retention in passenger car vehicles. For other organo-molybdenum additives, the investigation showed their friction-reducing ability decreased greatly after oxidation of the oil, although the performance appeared to be very good with the fresh oil before aging. In addition, the molybdate ester demonstrated a synergistic effect in anti-wear protection with zinc dialkyl dithiophosphate (ZDDP), a well-known commonly used additive in engine oils; this suggests that excellent wear protection is possible for an engine oil with reduced sulfur and phosphorus content. Moreover, the molybdate ester is also a strong synergist with arylamine antioxidants, which can retard its depletion in oxidized oil, extend its oxidative induction time, and reduce its high temperature deposit-forming tendency. Thus, this type of sulfur-free and phosphorus-free organo-molybdenum lubricant additive truly provides multifunctional performances, reducing friction, wear

  3. Friction and wear of iron in sulfuric acid

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    Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

    1983-01-01

    Elemental iron sliding on aluminum oxide in aerated sulfuric acid concentrations ranging from very dilute (0.000007 N; i.e., 4 ppm) to very concentrated (96 percent acid) was studied. Load and reciprocating sliding speeds were kept constant. With the most dilute acid of 0.7 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent, the high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid, and decreased somewhat at 50 percent in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It is apparent that the normal passivating film was being worn away and a galvanic cell established which rapidly attached to the wear area.

  4. Interaction of sulfuric acid corrosion and mechanical wear of iron

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    Rengstorff, G. W. P.; Miyoshi, K.; Buckley, D. H.

    1986-01-01

    Friction and wear experiment were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

  5. 1H NMR of High-Potential Iron-Sulfur Protein from the Purple Non-Sulfur Bacterium Rhodoferax fermentans

    DEFF Research Database (Denmark)

    Ciurli, Stefano; Cremonini, Mauro Andrea; Kofod, Pauli

    1996-01-01

    Oxidized and reduced forms of high-potential iron-sulfur protein (HiPIP) from the purple non-sulfur photosynthetic bacterium Rhodoferux fermentans have been characterized using 1H-NMR spectroscopy. Pairwise and sequence-specific assignments of hyperfine-shifted 1H-NMR signals to protons of cysteine...

  6. Formation and Oxidation of Hydrogen Molybdenum Bronze on platinum electrode in sulfuric acid solution

    Institute of Scientific and Technical Information of China (English)

    Jin LU; Jun Hua DU; Wei Shan Li; Jia Mo FU

    2004-01-01

    Hydrogen molybdenum bronze (HxMoO3) can be electrodeposited on platinum and oxidized in two steps to the hydrogen molybdenum bronze with less amount of hydrogen HyMoO3 (y

  7. Exploiting Bacterial Operons To Illuminate Human Iron-Sulfur Proteins.

    Science.gov (United States)

    Andreini, Claudia; Banci, Lucia; Rosato, Antonio

    2016-04-01

    Organisms from all kingdoms of life use iron-sulfur proteins (FeS-Ps) in a multitude of functional processes. We applied a bioinformatics approach to investigate the human portfolio of FeS-Ps. Sixty-one percent of human FeS-Ps bind Fe4S4 clusters, whereas 39% bind Fe2S2 clusters. However, this relative ratio varies significantly depending on the specific cellular compartment. We compared the portfolio of human FeS-Ps to 12 other eukaryotes and to about 700 prokaryotes. The comparative analysis of the organization of the prokaryotic homologues of human FeS-Ps within operons allowed us to reconstruct the human functional networks involving the conserved FeS-Ps common to prokaryotes and eukaryotes. These functional networks have been maintained during evolution and thus presumably represent fundamental cellular processes. The respiratory chain and the ISC machinery for FeS-P biogenesis are the two conserved processes that involve the majority of human FeS-Ps. Purine metabolism is another process including several FeS-Ps, in which BOLA proteins possibly have a regulatory role. The analysis of the co-occurrence of human FeS-Ps with other proteins highlighted numerous links between the iron-sulfur cluster machinery and the response mechanisms to cell damage, from repair to apoptosis. This relationship probably relates to the production of reactive oxygen species within the biogenesis and degradation of FeS-Ps.

  8. High-Sulfur-Vacancy Amorphous Molybdenum Sulfide as a High Current Electrocatalyst in Hydrogen Evolution

    KAUST Repository

    Lu, Ang-Yu

    2016-08-31

    The remote hydrogen plasma is able to create abundant S-vacancies on amorphous molybdenum sulfide (a-MoSx) as active sites for hydrogen evolution. The results demonstrate that the plasma-treated a-MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof-of-concept of industrial application.

  9. Studies on the iron - sulfur clusters of hydrogenase, sulfite reductase, nitrogenase and the prismane protein

    NARCIS (Netherlands)

    Pierik, A.J.

    1993-01-01

    Iron-sulfur clusters are present in a large number of proteins. Sofar structures of four types of protein-bound iron-sulfur clusters have been determined by X-ray diffraction: rubredoxin-like, [2Fe-2S], [3Fe-4S] and [4Fe-4S] centers. The presence of any of these clusters in a protein can be

  10. Relationship between Paratuberculosis and the microelements Copper, Zinc, Iron, Selenium and Molybdenum in Beef Cattle

    Directory of Open Access Journals (Sweden)

    F. Paolicchi

    2013-01-01

    Full Text Available To study the deficiency of minerals and its relationship with Paratuberculosis, blood, serum, and fecal samples were obtained from 75 adult bovines without clinical symptoms of the disease and from two bovines with clinical symptoms of the disease, from two beef herds with a previous history of Paratuberculosis in the Province of Buenos Aires, Argentina. Serum samples were processed by ELISA and feces were cultured in Herrolds medium. Copper, zinc and iron in serum were quantified by spectrophotometry and selenium was measured by the activity of glutathione peroxidase. We also determined copper, zinc, iron and molybdenum concentrations in pastures and the concentration of sulfate in water. Mycobacterium avium subsp paratuberculosis (Map was isolated from 17.3% of fecal samples of asymptomatic animals and from the fecal samples from the two animals with clinical symptoms. All the Map-positive animals were also ELISA-positive or suspect, and among them, 84.6% presented low or marginal values of selenium and 69.2% presented low or marginal values of copper. The two animals with clinical symptoms, and isolation of Map from feces and organs were selenium-deficient and had the lowest activity of glutathione peroxidase of all the animals from both herds. All the animals negative to Map in feces and negative to ELISA had normal values of Se, while 13.8% of animals with positive ELISA or suspect and culture negative presented low levels of Se. Half of the animals that were negative both for ELISA and culture in feces were deficient in copper but none of them presented low values of selenium. The content of molybdenum and iron in pasture was high, 2.5 ppm and 1.13 ppm in one herd and 2.5 ppm and 2.02 ppm in the other, respectively, whereas the copper:molybdenum ratio was 1.5 and 5.2, respectively. These results do not confirm an interaction between imbalances of the micronutrients and clinical Paratuberculosis, but show evidence of the relationship

  11. Moessbauer studies of frataxin role in iron-sulfur cluster assembly and dysfunction-related disease

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Serres, Ricardo [Universite Joseph Fourier (France); Clemancey, Martin [CNRS, UMR5249 (France); Oddou, Jean-Louis [Universite Joseph Fourier (France); Pastore, Annalisa [Medical Research Council National Institute for Medical Research (United Kingdom); Lesuisse, Emmanuel [Laboratoire Mitochondries, Metaux et Stress oxydant, Institut Jacques Monod, CNRS-Universite Paris (France); Latour, Jean-Marc, E-mail: jean-marc.latour@cea.fr [CEA, iRTSV, LCBM (France)

    2012-03-15

    Friedreich ataxia is a disease that is associated with defects in the gene coding for a small protein frataxin. Several different roles have been proposed for the protein, including iron chaperoning and iron storage. Moessbauer spectroscopy was used to probe these hypotheses. Iron accumulation in mutant mitochondria unable to assemble iron sulfur clusters proved to be insensitive to overexpression of frataxin, ruling out its potential involvement as an iron storage protein similar to ferritin. Rather, it was found that frataxin negatively regulates iron sulfur cluster assembly.

  12. Cytosolic iron-sulfur cluster assembly (CIA) system: factors, mechanism, and relevance to cellular iron regulation.

    Science.gov (United States)

    Sharma, Anil K; Pallesen, Leif J; Spang, Robert J; Walden, William E

    2010-08-27

    FeS cluster biogenesis is an essential process in virtually all forms of life. Complex protein machineries that are conserved from bacteria through higher eukaryotes facilitate assembly of the FeS cofactor in proteins. In the last several years, significant strides have been made in our understanding of FeS cluster assembly and the functional overlap of this process with cellular iron homeostasis. This minireview summarizes the present understanding of the cytosolic iron-sulfur cluster assembly (CIA) system in eukaryotes, with a focus on information gained from studies in budding yeast and mammalian systems.

  13. Large scale isolation and characterization of the molybdenum-iron cluster from nitrogenase.

    Science.gov (United States)

    Ma, L; Gavini, N; Liu, H I; Hedman, B; Hodgson, K O; Burgess, B K

    1994-07-08

    Here we report the large scale isolation and characterization of a species, designated MoFe cluster, that exhibits an S = 3/2 EPR signal, and the comparison of this entity to isolated FeMo cofactor in N-methylformamide and to the active site of the enzyme nitrogenase. MoFe cluster is isolated from purified nitrogenase by extraction into acidic methyl ethyl ketone and it is stable in that solvent in the absence of thiols. As initially isolated, MoFe cluster solutions exhibit an S = 1/2 EPR signal that arises from an oxidized species that can be reduced by dithionite or thiols to an EPR silent state and then to a state that exhibits an S = 3/2 EPR signal. The S = 3/2 signal is as sharp as the signal exhibited by the protein and much sharper than the signal exhibited by isolated FeMo cofactor. Circular dichroism experiments indicate that unlike the last two species, MoFe cluster does not contain the endogenous ligand R-homocitrate and thus, the sharpness of the S = 3/2 signal is an intrinsic property of the metal center and does not depend upon specific interactions with this organic ligand or with the protein. Metal analyses indicate that the metal core responsible for the S = 3/2 signal contains 6 Fe atoms per molybdenum. X-ray absorption spectroscopy experiments show that although the molybdenum atom in MoFe cluster retains its pseudo-octahedral geometry, its first coordination shell has one less iron atom than that of FeMo cofactor and there has been a significant change in the long range order of the cluster.

  14. Manganese oxide shuttling in pre-GOE oceans - evidence from molybdenum and iron isotopes

    Science.gov (United States)

    Kurzweil, Florian; Wille, Martin; Gantert, Niklas; Beukes, Nicolas J.; Schoenberg, Ronny

    2016-10-01

    The local occurrence of oxygen-rich shallow marine water environments has been suggested to significantly predate atmospheric oxygenation, which occurred during the Great Oxidation Event (GOE) ca. 2.4 billion years ago. However, the potential influence of such 'oxygen oases' on the mobility, distribution and isotopic composition of redox sensitive elements remains poorly understood. Here, we provide new molybdenum and iron isotopic data from shallow marine carbonate and silicate iron formations of the Koegas Subgroup, South Africa, that confirm local ocean redox stratification prior to the GOE. Mn concentrations correlate negatively with both δ98 Mo and δ56 Fe values, which highlights the substantial role of particulate manganese for the cycling of Mo and Fe in the Paleoproterozoic oceans. Based on these trends we propose that pore water molybdate was recharged (1) by the diffusional transport of seawater molybdate with high δ98 Mo and (2) by the re-liberation of adsorbed molybdate with low δ98 Mo during Mn oxide dissolution within the sediment. The relative contribution of isotopically light Mo is highest close to a Mn chemocline, where the flux of Mn oxides is largest, causing the negative correlation of Mn concentrations and δ98 Mo values in the Koegas sediments. The negative correlation between δ56 Fe values and Mn concentrations is likely related to Fe isotope fractionation during Fe(II) oxidation by Mn oxides, resulting in lower δ56 Fe values in the uppermost water column close to a Mn chemocline. We argue that the preservation of these signals within Paleoproterozoic sediments implies the existence of vertically extended chemoclines with a smoother gradient, probably as a result of low atmospheric oxygen concentrations. Furthermore, we suggest that abiotic oxidation of Fe(II) by a Mn oxide particle shuttle might have promoted the deposition of the Koegas iron formations.

  15. Effect of molybdenum, vanadium, boron on mechanical properties of high chromium white cast iron in as-cast condition

    Science.gov (United States)

    Nurjaman, F.; Sumardi, S.; Shofi, A.; Aryati, M.; Suharno, B.

    2016-02-01

    In this experiment, the effect of the addition carbide forming elements on high chromium white cast iron, such as molybdenum, vanadium and boron on its mechanical properties and microstructure was investigated. The high chromium white cast iron was produced by casting process and formed in 50 mm size of grinding balls with several compositions. Characterization of these grinding balls was conducted by using some testing methods, such as: chemical and microstructure analysis, hardness, and impact test. From the results, the addition of molybdenum, vanadium, and boron on high chromium white cast iron provided a significant improvement on its hardness, but reduced its toughness. Molybdenum induced fully austenitic matrix and Mo2C formation among eutectic M7C3 carbide. Vanadium was dissolved in the matrix and carbide. While boron was played a role to form fine eutectic carbide. Grinding balls with 1.89 C-13.1 Cr-1.32 Mo-1.36 V-0.00051 B in as-cast condition had the highest hardness, which was caused by finer structure of eutectic carbide, needle like structure (upper bainite) matrix, and martensite on its carbide boundary.

  16. Hydrophilic Nitrogen and Sulfur Co-doped Molybdenum Carbide Nanosheets for Electrochemical Hydrogen Evolution.

    Science.gov (United States)

    Ang, Huixiang; Tan, Hui Teng; Luo, Zhi Min; Zhang, Yu; Guo, Yuan Yuan; Guo, Guilue; Zhang, Hua; Yan, Qingyu

    2015-12-16

    Nitrogen and sulfur dual-doped Mo2 C nanosheets provide low operating potential (-86 mV for driving 10 mA cm(-2) of current density). Co-doping of N and S heteroatoms can improve the wetting property of the Mo2C electrocatalyst in aqueous solution and induce synergistic effects via σ-donation and π-back donation with hydronium cation.

  17. Geochemistry, geochronology, mineralogy, and geology suggest sources of and controls on mineral systems in the southern Toquima Range, Nye County, Nevada; with geochemistry maps of gold, silver, mercury, arsenic, antimony, zinc, copper, lead, molybdenum, bismuth, iron, titanium, vanadium, cobalt, beryllium, boron, fluorine, and sulfur; and with a section on lead associations, mineralogy and paragenesis, and isotopes

    Science.gov (United States)

    Shawe, Daniel R.; Hoffman, James D.; Doe, Bruce R.; Foord, Eugene E.; Stein, Holly J.; Ayuso, Robert A.

    2003-01-01

    distribution patterns that suggest specific sources and lithologic influences on deposition, as well as multiple episodes of mineralization. Principal episodes of mineralization are Late Cretaceous (molybdenum and tungsten in and near granite; silver at Belmont and Silver Point mines), early Oligocene [tourmaline and base- and precious-metals around the granodiorite of Dry Canyon stock as well as at Manhattan(?)], late Oligocene (gold at Round Mountain and Jefferson), and Miocene (gold at Manhattan). Most likely principal sources of molybdenum, tungsten, silver, and bismuth are Cretaceous granites; of antimony, arsenic, and mercury are intermediate-composition early Oligocene intrusives; and of gold are early and late Oligocene and early Miocene magmas of the volcanic cycle. Lead may have been derived principally from Cretaceous granitic magma and Paleozoic sedimentary rocks. Several areas prospective for undiscovered mineral deposits are suggested by spatial patterns of element distributions related to geologic features. The Manhattan district in the vicinity of the White Caps mine may be underlain by a copper-molybdenum porphyry system related to a buried stock; peripheral high-grade gold veins and skarn deposits may be present below deposits previously mined. The Jefferson district also may be underlain by a copper-molybdenum porphyry system related to a buried stock, it too with peripheral high-grade gold deposits. The Bald Mountain Canyon belt of small gold veins has potential for deeper deposits in buried porous ash-flow tuff similar to the huge Round Mountain low-grade gold-silver deposit. Several other areas have potential for a variety of mineral deposits. Altogether the geochemical, geochronologic, mineralogic, and geologic evidence suggests recurring mineralizing episodes of varied character, from Late Cretaceous to late Tertiary time, related to a long-lived hot spot deep in the crust or in the upper mantle. Granite plutons of Late Cretaceous age were minerali

  18. Insights into the iron and sulfur energetic metabolism of Acidithiobacillus ferrooxidans by microarray transcriptome profiling

    Energy Technology Data Exchange (ETDEWEB)

    R. Quatrini; C. Appia-Ayme; Y. Denis; J. Ratouchniak; F. Veloso; J. Valdes; C. Lefimil; S. Silver; F. Roberto; O. Orellana; F. Denizot; E. Jedlicki; D. Holmes; V. Bonnefoy

    2006-09-01

    Acidithiobacillus ferrooxidans is a well known acidophilic, chemolithoautotrophic, Gram negative, bacterium involved in bioleaching and acid mine drainage. In aerobic conditions, it gains energy mainly from the oxidation of ferrous iron and/or reduced sulfur compounds present in ores. After initial oxidation of the substrate, electrons from ferrous iron or sulfur enter respiratory chains and are transported through several redox proteins to oxygen. However, the oxidation of ferrous iron and reduced sulfur compounds has also to provide electrons for the reduction of NAD(P) that is subsequently required for many metabolic processes including CO2 fixation. To help to unravel the enzymatic pathways and the electron transfer chains involved in these processes, a genome-wide microarray transcript profiling analysis was carried out. Oligonucleotides corresponding to approximately 3000 genes of the A. ferrooxidans type strain ATCC23270 were spotted onto glass-slides and hybridized with cDNA retrotranscribed from RNA extracted from ferrous iron and sulfur grown cells. The genes which are preferentially transcribed in ferrous iron conditions and those preferentially transcribed in sulfur conditions were analyzed. The expression of a substantial number of these genes has been validated by real-time PCR, Northern blot hybridization and/or immunodetection analysis. Our results support and extend certain models of iron and sulfur oxidation and highlight previous observations regarding the possible presence of alternate electron pathways. Our findings also suggest ways in which iron and sulfur oxidation may be co-ordinately regulated. An accompanying paper (Appia-Ayme et al.) describes results pertaining to other metabolic functions.

  19. Diastereomer-dependent substrate reduction properties of a dinitrogenase containing 1-fluorohomocitrate in the iron-molybdenum cofactor.

    OpenAIRE

    Madden, M S; Kindon, N D; Ludden, P W; Shah, V K

    1990-01-01

    In vitro synthesis of the iron-molybdenum cofactor (FeMo-co) of dinitrogenase using homocitrate and its analogs allows the formation of modified forms of FeMo-co that show altered substrate specificities (N2, acetylene, cyanide, or proton reduction) of nitrogenase [reduced ferredoxin:dinitrogen oxidoreductase (ATP-hydrolyzing), EC 1.18.6.1]. The (1R,2S)-threo- and (1S,2S)-erythro-fluorinated diastereomers of homocitrate have been incorporated in vitro into dinitrogenase in place of homocitrat...

  20. Chemisorption and catalytic reactivity of cobalt and sulfur monolayers on ordered molybdenum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Knight, C.C.

    1992-03-01

    Complex Co/Mo sulfide catalysts are modelled by the chemisorption of layers on Mo single crystal surfaces. Growth and structure of overlayers on flat, stepped and kinked surfaces were investigated. Growth of Co overlayers on clean and S covered Mo surfaces was studied using AES and CO chemisorption; results reveal that Co grows as a flat monolayer on clean Mo surfaces. Co multilayers then form 3-D islands. When Co is deposited on S covered surfaces, the S overlayer migrates to the top; this topmost overlayer reduces CO adsorption capacity. While growth mode of Co overlayers are similar on flat and stepped surfaces, the number and type of ordered Co and S structures on flat and stepped surfaces are different. In the case of Co, an ordered (3 {times} 1) structure is formed on Mo(910) and (28,4,1) surfaces; this structure does not develop on clean (100) surface. Only one of two possible (3 {times} 1) Co domains are formed on Mo(910) and Mo(28,4,1) surfaces. These domains have one side of (3 {times} 1) unit cell parallel to the step edges, suggesting that Co adsorbs at the step edges. The (3 {times} 1) structure does not form on Mo(911) surface, indicating that step orientation can restrict formation of ordered overlayers. For chemisorbed S, only a subset of ordered overlayers on flat (100) surface nucleate on (910) and (911) and (28,4,1) surfaces. Ordered S overlayers also form domains that maximize the number of sulfur-step atom bonds. The adsorption and ordering of S overlayers on stepped and kinked Mo surfaces lead to doubling of step height and terrace width. Thiophene hydrodesulfurization (HDS) reactions were performed over Mo crystal surfaces modified by chemisorption of S, Co, C, and S + Co. The stepped and kinked Mo surfaces have reactivities greater than low Miller index (100) surface. Chemisorption of adsorbates decreased the thiophene HDS reactivity. Deposition of Co on Mo single crystal surfaces did not lead to increased HDS activity.

  1. Synthesis of the iron-molybdenum cofactor of nitrogenase is inhibited by a low-molecular-weight metabolite of Klebsiella pneumoniae.

    Science.gov (United States)

    Downs, D M; Ludden, P W; Shah, V K

    1990-10-01

    The in vitro synthesis of the iron-molybdenum cofactor nitrogenase was inhibited by a low-molecular-weight factor. This inhibitory factor was present in the membrane extracts of wild-type and nif mutant strains of Klebsiella pneumoniae that were grown under conditions that either repressed or derepressed nitrogenase expression. In vitro, the inhibition was specific for the NifB protein. Addition of this factor to K. pneumoniae cells at various times during nif derepression decreased nitrogenase activity, presumably through inhibition of iron-molybdenum cofactor synthesis. The inhibitor was purified by solvent extraction and chromatography on DEAE-cellulose, silica gel, and aluminum oxide columns.

  2. MetalPredator: a web server to predict iron-sulfur cluster binding proteomes.

    Science.gov (United States)

    Valasatava, Yana; Rosato, Antonio; Banci, Lucia; Andreini, Claudia

    2016-09-15

    The prediction of the iron-sulfur proteome is highly desirable for biomedical and biological research but a freely available tool to predict iron-sulfur proteins has not been developed yet. We developed a web server to predict iron-sulfur proteins from protein sequence(s). This tool, called MetalPredator, is able to process complete proteomes rapidly with high recall and precision. The web server is freely available at: http://metalweb.cerm.unifi.it/tools/metalpredator/ andreini@cerm.unifi.it Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  3. Sulfur reactions and cryptic cross-linkages to oxygen, iron, and carbon cyclin

    Science.gov (United States)

    Druschel, G.; Kafantaris, F. C. A.; Fike, D. A.; Schmitt-Kopplin, P.; Dvorski, S.; Oduro, H.

    2014-12-01

    Sulfur speciation in any setting is controlled by a complex series of redox reactions, polymerization, and complexation reactions that are affected by both biotic and abiotic processes. Additionally there are several crossroads of reactions with oxygen, carbon, and iron in which polysulfide molecules serve as a key reaction component that affects not only sulfur speciation, but the speciation, solubility, and bioavailability of these elements as well. Utilizing a combination of analytical approaches including electrochemistry, spectroscopy, mass spectrometry, and chromatography, we have started to unravel the interconnections between sulfur and other key elements, and how microorganisms may be either direct or indirect contributors to these chemical and mineralogical signatures. In microbial mats, we have observed microbial production of significant hydrogen peroxide under UV-stressed conditions. This peroxide interaction with hydrogen sulfide changes the kinetics and the pathways of abiotic sulfur reactions, potentially affecting the overall bioavailability and isotopic fractionations for specific reactions via a change in the linkage between oxygen and sulfur cycling. In systems containing significant iron, we have observed the production of an electroactive form of ferrous iron and sulfide (FeS(aq)) that is of a size that can be described between a dissolved molecular cluster and a small nanoparticle. This FeS(aq) can be a significant fraction of the dissolved iron or sulfide in a system, and is a key part of both the solubility of iron and sulfur and the pathways potentially important for pyritization reactions. In systems where we investigate the links between sulfur and carbon, laboratory and field experiments indicate a wide range of large and more reduced organic compounds are highly reactive towards polysulfide. Utilizing Fourier-transform ion cyclotron resonance mass spectrometry in conjunction with electrochemistry and chromatography, we are seeing a

  4. Evidence for nifU and nifS participation in the biosynthesis of the iron-molybdenum cofactor of nitrogenase.

    Science.gov (United States)

    Zhao, Dehua; Curatti, Leonardo; Rubio, Luis M

    2007-12-21

    The nifU and nifS genes encode the components of a cellular machinery dedicated to the assembly of [2Fe-2S] and [4Fe-4S] clusters required for growth under nitrogen-fixing conditions. The NifU and NifS proteins are involved in the production of active forms of the nitrogenase component proteins, NifH and NifDK. Although NifH contains a [4Fe-4S] cluster, the NifDK component carries two complex metalloclusters, the iron-molybdenum cofactor (FeMo-co) and the [8Fe-7S] P-cluster. FeMo-co, located at the active site of NifDK, is composed of 7 iron, 9 sulfur, 1 molybdenum, 1 homocitrate, and 1 unidentified light atom. To investigate whether NifUS are required for FeMo-co biosynthesis and to understand at what level(s) they might participate in this process, we analyzed the effect of nifU and nifS mutations on the formation of active NifB protein and on the accumulation of NifB-co, an isolatable intermediate of the FeMo-co biosynthetic pathway synthesized by the product of the nifB gene. The nifU and nifS genes were required to accumulate NifB-co in a nifN mutant background. This result clearly demonstrates the participation of NifUS in NifB-co synthesis and suggests a specific role of NifUS as the major provider of [Fe-S] clusters that serve as metabolic substrates for the biosynthesis of FeMo-co. Surprisingly, although nifB expression was attenuated in nifUS mutants, the assembly of the [Fe-S] clusters of NifB was compensated by other non-nif machinery for the assembly of [Fe-S] clusters, indicating that NifUS are not essential to synthesize active NifB.

  5. Extraction of transplutionium and rare-earth elements, molybdenum and iron with zirconium salt of dibutyl phosphoric acid

    Science.gov (United States)

    Zilberman, B. Ya.; Fedorov, Yu. S.; Shmidt, O. V.; Goletsky, N. D.; Sukhareva, S. Yu.; Puzikov, E. A.; Suglobov, D. N.; Mashirov, L. G.; Choppin, G. R.

    2003-01-01

    Zirconium salt of dibutyl phosphoric acid (ZS-HDBP) dissolved in dilute tributyl phosphate (TBP) is proposed as a solvent for separation of transplutonium and rare-earth elements (TPE, RE), including yttrium, from high-level waste in the presence of molybdenum and iron. The optimum HDBP:Zr ratio is 9 for RE and TPE extraction and is 12.5 for Mo. IR spectra indicate formation of Zr(DBP)4(HDBP)4 complex as a base of solvation. HNO3 depresses RE and TPE extraction, while Mo extraction is characterised by a minimum at 2.5 mol/L HNO3. Presence of TBP in the solvent, independently of the used diluent, leads to reduction of the distribution coefficients, but ZS-HDBP extraction capacity for the above elements is increased, as well as solubility of their solvates. Two types of complexes M(DBP)3 and MNO3(DBP)2 are formed at RE and TPE extraction by ZS-HDBP in dilute TBP. Molybdenum extraction is based both on cation exchange and on Mo solvation with HDBP as a neutral ligand. Iron extraction is formally similar to that of Mo, being influenced by the latter if both metals are present in the solution.

  6. Up-gradation of MoO{sub 3} and separation of copper, iron, zinc from roasted molybdenum ore by a leaching process

    Energy Technology Data Exchange (ETDEWEB)

    Jin-Young, Lee; Jyothi Rajesh, Kumar; Ho-Seok, Jeon; Joon-Soo, Kim, E-mail: rajeshkumarphd@rediffmail.com, E-mail: rkumarphd@kigam.re.kr [Extractive Metallurgy Department, Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM) (Korea, Republic of)

    2013-04-15

    The present research paper deals with the oxidation process of molybdenum ore. The main target of the present study is the up-gradation of MoO{sub 3} from roasted molybdenum ore by a leaching process without waste generation. The most important application of hydrometallurgical processing is the leaching process of the ore and it is the primary process to make pure metal from ore. The present investigations optimize the following experimental parameters to improve the concentration of MoO{sub 3} as well as the separation of copper, iron and zinc in roasted molybdenum ore: effect of acid concentration, temperature, pulp density and leaching time were studied systematically. The temperature study was carried out at 550-595 Degree-Sign C for the oxidation process. The XRD result shows that oxidation process of molybdenum ore and SEM pictures were taken for particles before and after the oxidation process at 585 Degree-Sign C for 360 min. (author)

  7. Biogeochemistry of sulfur and iron in Thioploca-colonized surface sediments in the upwelling area off central Chile

    DEFF Research Database (Denmark)

    Zopfi, Jakob; Michael E., Böttcher; Jørgensen, Bo Barker

    2008-01-01

    The biogeochemistry of sedimentary sulfur was investigated on the continental shelf off central Chile at water depths between 24 and 88 m under partial influence of an oxygen minimum zone. Dissolved and solid iron and sulfur species, including the sulfur intermediates sulfite, thiosulfate...

  8. Geochemistry of iron,sulfur and related heavy metals in metal-polluted Taihu Lake sediments

    Institute of Scientific and Technical Information of China (English)

    YIN Hong-Bin; FAN Cheng-Xin; DING Shi-Ming; ZHANG Lu; ZHONG Ji-Cheng

    2008-01-01

    To understand the geochemical characteristics of iron and sulfur and the extent of iron-sulfide minerals influencing heavy metal behaviour in metal-polluted sediments of Talhu Lake,two sites,in Meiliang Bay (ML) and Wuli Lake (WL),were selected to study the fractionation of iron,sulfur and related heavy metals.There were relatively high concentrations of Fe2+ and low concentrations of total S2- in porewaters,indicating that conditions in these sediments favored iron reduction.The concentrations of acid volatile sulfides in sediments were 1.9-9.6μmol g-1 at ML and 1.0-11.7 μmol g-1 at WL,both in the range of values detected in unpolluted lakes.Pyrite-S was 10.2-49.4 μmol g-1 at ML and 10.333.0 μmol g-1 at WL,accounting for more than 69% of the reduced inorganic sulfur at both sites.The low degree of sulphidization (<14%) and pyritization (<10%) indicate that sulfate may be the limiting factor for pyrite formation.The extractability of Mn,Cu,Pb,Zn,Ni,and Cr in sediments all suggest that sulfides are not the major binding phase for these metals during early diagenesis.Sulfur may play a modest role in the geochemistry of iron and traced metals in the sediments.

  9. Extending the models for iron and sulfur oxidation in the extreme Acidophile Acidithiobacillus ferrooxidans

    Directory of Open Access Journals (Sweden)

    Holmes David S

    2009-08-01

    Full Text Available Abstract Background Acidithiobacillus ferrooxidans gains energy from the oxidation of ferrous iron and various reduced inorganic sulfur compounds at very acidic pH. Although an initial model for the electron pathways involved in iron oxidation has been developed, much less is known about the sulfur oxidation in this microorganism. In addition, what has been reported for both iron and sulfur oxidation has been derived from different A. ferrooxidans strains, some of which have not been phylogenetically characterized and some have been shown to be mixed cultures. It is necessary to provide models of iron and sulfur oxidation pathways within one strain of A. ferrooxidans in order to comprehend the full metabolic potential of the pangenome of the genus. Results Bioinformatic-based metabolic reconstruction supported by microarray transcript profiling and quantitative RT-PCR analysis predicts the involvement of a number of novel genes involved in iron and sulfur oxidation in A. ferrooxidans ATCC23270. These include for iron oxidation: cup (copper oxidase-like, ctaABT (heme biogenesis and insertion, nuoI and nuoK (NADH complex subunits, sdrA1 (a NADH complex accessory protein and atpB and atpE (ATP synthetase F0 subunits. The following new genes are predicted to be involved in reduced inorganic sulfur compounds oxidation: a gene cluster (rhd, tusA, dsrE, hdrC, hdrB, hdrA, orf2, hdrC, hdrB encoding three sulfurtransferases and a heterodisulfide reductase complex, sat potentially encoding an ATP sulfurylase and sdrA2 (an accessory NADH complex subunit. Two different regulatory components are predicted to be involved in the regulation of alternate electron transfer pathways: 1 a gene cluster (ctaRUS that contains a predicted iron responsive regulator of the Rrf2 family that is hypothesized to regulate cytochrome aa3 oxidase biogenesis and 2 a two component sensor-regulator of the RegB-RegA family that may respond to the redox state of the quinone pool

  10. Extending the models for iron and sulfur oxidation in the extreme Acidophile Acidithiobacillus ferrooxidans

    Science.gov (United States)

    2009-01-01

    Background Acidithiobacillus ferrooxidans gains energy from the oxidation of ferrous iron and various reduced inorganic sulfur compounds at very acidic pH. Although an initial model for the electron pathways involved in iron oxidation has been developed, much less is known about the sulfur oxidation in this microorganism. In addition, what has been reported for both iron and sulfur oxidation has been derived from different A. ferrooxidans strains, some of which have not been phylogenetically characterized and some have been shown to be mixed cultures. It is necessary to provide models of iron and sulfur oxidation pathways within one strain of A. ferrooxidans in order to comprehend the full metabolic potential of the pangenome of the genus. Results Bioinformatic-based metabolic reconstruction supported by microarray transcript profiling and quantitative RT-PCR analysis predicts the involvement of a number of novel genes involved in iron and sulfur oxidation in A. ferrooxidans ATCC23270. These include for iron oxidation: cup (copper oxidase-like), ctaABT (heme biogenesis and insertion), nuoI and nuoK (NADH complex subunits), sdrA1 (a NADH complex accessory protein) and atpB and atpE (ATP synthetase F0 subunits). The following new genes are predicted to be involved in reduced inorganic sulfur compounds oxidation: a gene cluster (rhd, tusA, dsrE, hdrC, hdrB, hdrA, orf2, hdrC, hdrB) encoding three sulfurtransferases and a heterodisulfide reductase complex, sat potentially encoding an ATP sulfurylase and sdrA2 (an accessory NADH complex subunit). Two different regulatory components are predicted to be involved in the regulation of alternate electron transfer pathways: 1) a gene cluster (ctaRUS) that contains a predicted iron responsive regulator of the Rrf2 family that is hypothesized to regulate cytochrome aa3 oxidase biogenesis and 2) a two component sensor-regulator of the RegB-RegA family that may respond to the redox state of the quinone pool. Conclusion

  11. Anodic Dissolution of Spheroidal Graphite Cast Iron with Different Pearlite Areas in Sulfuric Acid Solutions

    Directory of Open Access Journals (Sweden)

    Yoshikazu Miyata

    2013-01-01

    Full Text Available The rate equation of anodic dissolution reaction of spheroidal graphite cast iron in sulfuric acid solutions at 298 K has been studied. The cast irons have different areas of pearlite. The anodic Tafel slope of 0.043 V decade−1 and the reaction order with respect to the hydroxyl ion activity of 1 are obtained by the linear potential sweep technique. The anodic current density does not depend on the area of pearlite. There is no difference in the anodic dissolution reaction mechanisms between pure iron and spheroidal graphite cast iron. The anodic current density of the cast iron is higher than that of the pure iron.

  12. Effects of sulfur in flooded paddy soils: Implications for iron chemistry and arsenic mobilization

    Science.gov (United States)

    Avancha, S.; Boye, K.

    2013-12-01

    In the Mekong delta in Cambodia, naturally occurring arsenic (amplified by erosion in the Himalaya Mountains) in paddy soils is mobilized during the seasonal flooding. As a consequence, rice grown on the flooded soils may take up arsenic and expose people eating the rice to this carcinogenic substance. Iron and sulfur both interact strongly with arsenic in paddy soils: iron oxides are strong adsorbents for arsenic in oxic conditions, and sulfur (in the form of sulfide) is a strong adsorbent under anoxic conditions. In the process of reductive dissolution of iron oxides, arsenic, which had been adsorbed to the iron oxides, is released. Therefore, higher levels of reduced iron (ferrous iron) will likely correlate with higher levels of mobilized arsenic. However, the mobilized arsenic may then co-precipitate with or adsorb to iron sulfides, which form under sulfate-reducing conditions and with the aid of certain microbes already present in the soil. In a batch experiment, we investigated how these processes correlate and which has the greatest influence on arsenic mobilization and potential plant availability. The experiment was designed to measure the effects of various sources of sulfur (dried rice straw, charred rice straw, and gypsum) on the iron and arsenic release in an arsenic-contaminated paddy soil from Cambodia under flooded conditions. The two types of rice straw were designed to introduce the same amount of organic sulfur (7.7 μg/g of soil), but different levels of available carbon, since carbon stimulates microbial activity in the soil. In comparison, two different levels of gypsum (calcium sulfate) were used, 7.7 and 34.65 μg/g of soil, to test the effect of directly available inorganic sulfate without carbon addition. The soil was flooded with a buffer solution at pH 7.07 in airtight serum vials and kept as a slurry on a shaker at 25 °C. We measured pH, alkalinity, ferrous iron, ferric iron, sulfide, sulfate, total iron, sulfur, and arsenic in the

  13. Effect of Iron Oxides (Ordinary and Nano and Municipal Solid Waste Compost (MSWC Coated Sulfur on Wheat (Triticum aestivum L. Plant Iron Concentration and Growth

    Directory of Open Access Journals (Sweden)

    S Mazaherinia

    2011-02-01

    Full Text Available Abstract A greenhouse study was conducted to compare the effects of ordinary iron oxide (0.02-0.06 mm and nano iron oxide (25-250 nm and five levels of both iron oxides (0, 0.05, 0.1, 0.5, and 1.0 %w/w and two levels of sulfurous granular compost (MSW (0 and 2% w/w on plant height, spike length, grain weight per spike, total plant dry matter weight and thousands grain weight of wheat. The experimental factors were combined in factorial arrangement in a completely randomized design with 3 replications. Results showed that nano iron oxide was superior over ordinary iron oxide in all parameters studied. Fe concentration, spike length, plant height, grain weight per spike, total plant dry weight and thousands grain weight showed increasing trend per increase in both of iron oxides levels. Also, all parameters studied in sulfurous granular compost (MSW treatment were superior over granular compost without sulfurous (MSW. This increase in all parameters were significantly higher when urban solid waste compost coated with sulfur coupled with nano iron oxide compared to urban sulfurous granular compost (MSW along with ordinary iron oxide. Keywords: Sulfurous granular compost (MSW, Nano and ordinary iron oxides, Wheat

  14. Sulfur and iron speciation in surface sediments along the northwestern margin of the Black Sea

    NARCIS (Netherlands)

    Wijsman, J.W.M.; Middelburg, J.J.; Herman, P.M.J.; Bottcher, M.E.; Heip, C.H.R.

    2001-01-01

    The speciation of sedimentary sulfur (pyrite, acid volatile sulfides (AVS), S-0 H2S, and sulfate) was analyzed in surface sediments recovered at different water depths from the northwestern margin of the Black Sea. Additionally, dissolved and dithionite-extractable iron were quantified, and the sulf

  15. Superclusters : a search for novel structures and functions of biological iron-sulfur clusters

    NARCIS (Netherlands)

    Arendsen, A.F.

    1996-01-01


    Iron sulfur (Fe-S) proteins are found in a variety of organisms. They usually function in electron transport, but they may also be involved in other functions like gene regulation and Lewis acid catalysis. The structure and spectroscopic properties of Fe-S clusters holding one, two,

  16. Manganese, Iron, and sulfur cycling in Louisiana continental shelf sediments

    Science.gov (United States)

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cyclin...

  17. Manganese, Iron, and sulfur cycling in Louisiana continental shelf sediments

    Science.gov (United States)

    Sulfate reduction is considered the primary pathway for organic carbon remineralization on the northern Gulf of Mexico Louisiana continental shelf (LCS) where bottom waters are seasonally hypoxic, yet limited information is available on the importance of iron and manganese cyclin...

  18. Superclusters. A search for novel structures and functions of biological iron-sulfur clusters.

    OpenAIRE

    Arendsen, A.F.

    1996-01-01

    Iron sulfur (Fe-S) proteins are found in a variety of organisms. They usually function in electron transport, but they may also be involved in other functions like gene regulation and Lewis acid catalysis. The structure and spectroscopic properties of Fe-S clusters holding one, two, three, or four iron atoms is known to a great extent. These 'common' clusters share some basic properties. Firstly, they contain not more than four iron atoms. Secondly, despite the fact that they may contain more...

  19. Characterization and study of reduction and sulfurization processing in phase transition from molybdenum oxide (MoO{sub 2}) to molybdenum disulfide (MoS{sub 2}) chalcogenide semiconductor nanoparticles prepared by one-stage chemical reduction method

    Energy Technology Data Exchange (ETDEWEB)

    Shomalian, K.; Bagheri-Mohagheghi, M.M.; Ardyanian, M. [Damghan University, School of Physics, Damghan (Iran, Islamic Republic of)

    2017-01-15

    In this research, molybdenum disulfide (MoS{sub 2}) nanoparticles were prepared by chemical reduction method using MoO{sub 3} and thiourea as a precursor. The physical properties of the synthesized MoO{sub 2}-MoS{sub 2} nanoparticles annealed at different temperatures of 200, 300, 750 C have been investigated, before and after exposure to sulfur vapor. The nanostructure of nanoparticles has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) analyses and UV-Vis spectrophotometer. The X-ray diffraction analysis showed the formation of MoS{sub 2} single phase at annealing temperature of 750 C in the presence of sulfur vapor. The Raman spectrum of the nanoparticles revealed that the formation of MoS{sub 2} at 750 C after annealing in sulfur vapor. The values of band gap were obtained in the range of 3.64-3.17 eV and 3.47-1.95 eV for MoS{sub 2} nanoparticles before and after exposure to sulfur vapor, respectively. According to SEM images, the grain size decreases with increasing annealing temperature up to 750 C. Also, nanoplate-nanoparticles of MoS{sub 2} are formed at annealing temperature of 200-750 C. The TEM images of MoS{sub 2} nanoparticles at T{sub a} = 750 C confirm that the nanoparticles have a homogeneous distribution with a hexagonal structure. The FTIR spectra of the MoS{sub 2} nanoparticles showed the peaks at about 467 cm {sup -1} belong to the characteristic bands of Mo-S. (orig.)

  20. Characterization and study of reduction and sulfurization processing in phase transition from molybdenum oxide (MoO2) to molybdenum disulfide (MoS2) chalcogenide semiconductor nanoparticles prepared by one-stage chemical reduction method

    Science.gov (United States)

    Shomalian, K.; Bagheri-Mohagheghi, M.-M.; Ardyanian, M.

    2017-01-01

    In this research, molybdenum disulfide (MoS2) nanoparticles were prepared by chemical reduction method using MoO3 and thiourea as a precursor. The physical properties of the synthesized MoO2-MoS2 nanoparticles annealed at different temperatures of 200, 300, 750 °C have been investigated, before and after exposure to sulfur vapor. The nanostructure of nanoparticles has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) analyses and UV-Vis spectrophotometer. The X-ray diffraction analysis showed the formation of MoS2 single phase at annealing temperature of 750 °C in the presence of sulfur vapor. The Raman spectrum of the nanoparticles revealed that the formation of MoS2 at 750 °C after annealing in sulfur vapor. The values of band gap were obtained in the range of 3.64-3.17 eV and 3.47-1.95 eV for MoS2 nanoparticles before and after exposure to sulfur vapor, respectively. According to SEM images, the grain size decreases with increasing annealing temperature up to 750 °C. Also, nanoplate-nanoparticles of MoS2 are formed at annealing temperature of 200-750 °C. The TEM images of MoS2 nanoparticles at T a = 750 °C confirm that the nanoparticles have a homogeneous distribution with a hexagonal structure. The FTIR spectra of the MoS2 nanoparticles showed the peaks at about 467 cm-1 belong to the characteristic bands of Mo-S.

  1. Leaching of molybdenum and arsenic from uranium ore and mill tailings

    Science.gov (United States)

    Landa, E.R.

    1984-01-01

    A sequential, selective extraction procedure was used to assess the effects of sulfuric acid milling on the geochemical associations of molybdenum and arsenic in a uranium ore blend, and the tailings derived therefrom. The milling process removed about 21% of the molybdenum and 53% of the arsenic initially present in the ore. While about one-half of the molybdenum in the ore was water soluble, only about 14% existed in this form in the tailings. The major portion of the extractable molybdenum in the tailings appears to be associated with hydrous oxides of iron, and with alkaline earth sulfate precipitates. In contrast with the pattern seen for molybdenum, the partitioning of arsenic into the various extractable fractions differs little between the ore and the tailings. ?? 1984.

  2. Determination of aluminium in molybdenum and tungsten metals, iron, steel and ferrous and non-ferrous alloys with pyrocatechol violet.

    Science.gov (United States)

    Donaldson, E M

    1971-09-01

    A method for determining 0.001-0.10% of aluminium in molybdenum and tungsten metals is described. After sample dissolution, aluminium is separated from the matrix materials by chloroform extraction of its acetylacetone complex, at pH 6.5, from an ammonium acetate-hydrogen peroxide medium, then back-extracted into 12M hydrochloric add. Following separation of most co-extracted elements, except for beryllium and small amounts of chroinium(III) and copper(II), by a combined ammonium pyrrolidincdithiocarbamate-cupfen-on-chlorofonn extraction, aluminium is determined spectrophotometrically with Pyrocatechol Violet at 578 nm. Chromium interferes during colour development but beryllium, in amounts equivalent to the aluminium concentration, does not cause significant error in the results. Interference from copper(II) is eliminated by reduction with ascorbic acid. The proposed method is also applicable to iron, steel, ferrovanadium, and copper-base alloys after preliminary removal of the matrix elements by a mercury cathode separation.

  3. Sulfur Versus Iron Oxidation in an Iron-Thiolate Model Complex

    Energy Technology Data Exchange (ETDEWEB)

    A McDonald; M Bukowski; E Farquhar; T Jackson; K Koehntop; M Seo; R De Hont; A Stubna; J Halfen; E Munck

    2011-12-31

    In the absence of base, the reaction of [Fe{sup II}(TMCS)]PF{sub 6} (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at -20 C did not yield the oxoiron(IV) complex (2, [Fe{sup IV}(O)(TMCS)]PF{sub 6}), as previously observed in the presence of strong base (KO{sup t}Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Moessbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe{sup II}(TMCS) + 2O]{sup +}, while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 {angstrom}, Fe-S = 3.26 {angstrom}). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Moessbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe{double_bond}O = 1.64 {angstrom}) and resonance Raman ({nu}{sub Fe{double_bond}O} = 831 cm{sup -1}) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety ({nu}{sub s}(SO{sub 2}) {approx} 1000 cm{sup -1}, {nu}{sub as}(SO{sub 2}) {approx} 1150 cm{sup -1}). Investigations into the reactivity of 1 and 2 toward H{sup +} and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.

  4. [Silica, aluminum, iron, sulfur, and barium in a urinary calculus].

    Science.gov (United States)

    Rodríguez-Miñón Cifuentes, J L; Salvador, E; Bellanato, J; Medina, J A

    1994-05-01

    Presentation of the analytical results by Sweep Microscopy of a small papillary calculus spontaneously eliminated after a nephritic colic. The main component is monohydrate calcium oxalate. When the stone core was analyzed with EDAX, silica, aluminium, iron, sulphur and barium were detected. The origin of these elements is discussed and the presence of barium emphasized as exceptional.

  5. Molten iron oxysulfide as a superior sulfur sorbent. Final report, [September 1989--1993

    Energy Technology Data Exchange (ETDEWEB)

    Hepworth, M.T.

    1993-03-31

    The studies had as original objective the analysis of conditions for using liquid iron oxysulfide as a desulfuring agent during coal gasification. Ancillary was a comparison of iron oxysulfide with lime as sorbents under conditions where lime reacts with S-bearing gases to form Ca sulfate or sulfide. Primary thrust is to determine the thermodynamic requirements for desulfurization by iron additions (e.g., taconite concentrate) during combustion in gasifiers operating at high equivalence ratios. Thermodynamic analysis of lime-oxygen-sulfur system shows why lime is injected into burners under oxidizing conditions; reducing conditions forms CaS, requiring its removal, otherwise oxidation and release of S would occur. Iron as the oxysulfide liquid has a range of stability and can be used as a desulfurizing agent, if the burner/gasifier operates in a sufficiently reducing regime (high equivalence ratio); this operating range is given and is calculable for a coal composition, temperature, stoichiometry. High moisture or hydrogen contents of the coal yield a poorer degree of desulfurization. Kinetic tests on individual iron oxide particles on substrates or Pt cups with a TGA apparatus fail to predict reaction rates within a burner. Preliminary tests on the Dynamic Containment Burner with acetylene give some promise that this system can produce the proper conditions of coal gasification for use of added iron as a sulfur sorbent.

  6. Chloroplast iron-sulfur cluster protein maturation requires the essential cysteine desulfurase CpNifS

    OpenAIRE

    Van Hoewyk, Douglas; Abdel-Ghany, Salah E.; Cohu, Christopher M.; Herbert, Stephen K.; Kugrens, Paul; Pilon, Marinus; Elizabeth A H Pilon-Smits

    2007-01-01

    NifS-like proteins provide the sulfur (S) for the formation of iron-sulfur (Fe-S) clusters, an ancient and essential type of cofactor found in all three domains of life. Plants are known to contain two distinct NifS-like proteins, localized in the mitochondria (MtNifS) and the chloroplast (CpNifS). In the chloroplast, five different Fe-S cluster types are required in various proteins. These plastid Fe-S proteins are involved in a variety of biochemical pathways including photosynthetic electr...

  7. Superoxide generated from the glutathione-mediated reduction of selenite damages the iron-sulfur cluster of chloroplastic ferredoxin.

    Science.gov (United States)

    Fisher, Brian; Yarmolinsky, Dmitry; Abdel-Ghany, Salah; Pilon, Marinus; Pilon-Smits, Elizabeth A; Sagi, Moshe; Van Hoewyk, Doug

    2016-09-01

    Selenium assimilation in plants is facilitated by several enzymes that participate in the transport and assimilation of sulfate. Manipulation of genes that function in sulfur metabolism dramatically affects selenium toxicity and accumulation. However, it has been proposed that selenite is not reduced by sulfite reductase. Instead, selenite can be non-enzymatically reduced by glutathione, generating selenodiglutathione and superoxide. The damaging effects of superoxide on iron-sulfur clusters in cytosolic and mitochondrial proteins are well known. However, it is unknown if superoxide damages chloroplastic iron-sulfur proteins. The goals of this study were twofold: to determine whether decreased activity of sulfite reductase impacts selenium tolerance in Arabidopsis, and to determine if superoxide generated from the glutathione-mediated reduction of selenite damages the iron-sulfur cluster of ferredoxin. Our data demonstrate that knockdown of sulfite reductase in Arabidopsis does not affect selenite tolerance or selenium accumulation. Additionally, we provide in vitro evidence that the non-enzymatic reduction of selenite damages the iron-sulfur cluster of ferredoxin, a plastidial protein that is an essential component of the photosynthetic light reactions. Damage to ferredoxin's iron-sulfur cluster was associated with formation of apo-ferredoxin and impaired activity. We conclude that if superoxide damages iron-sulfur clusters of ferredoxin in planta, then it might contribute to photosynthetic impairment often associated with abiotic stress, including toxic levels of selenium.

  8. Microbial transformations of nitrogen, sulfur, and iron dictate vegetation composition in wetlands: A review

    OpenAIRE

    Leon P.M. Lamers; van Diggelen, Josepha M. H.; Op Den Camp, Huub J M; Visser, Eric J. W.; Lucassen, Esther C. H. E. T.; Vile, Melanie A.; Jetten, Mike S. M.; Smolders, Alfons J. P.; Roelofs, Jan G. M.

    2012-01-01

    The majority of studies on rhizospheric interactions between microbial communities and vegetation focus on pathogens, mycorrhizal symbiosis, and/or carbon transformations. Although the biogeochemical transformations of nitrogen (N), sulfur (S) and iron (Fe) have profound effects on plants, these effects have received far less attention. Firstly, all three elements are plant nutrients, and microbial activity significantly changes their mobility and availability. Secondly, microbial oxidation w...

  9. The lure of a LYR: The logistics of iron sulfur cluster delivery.

    Science.gov (United States)

    Lane, D J R; Merlot, A M; Richardson, D R

    2014-03-04

    How are nascent iron-sulfur (Fe-S) clusters directed to specific recipient proteins? In this issue of Cell Metabolism, Maio et al. (2014) show that the mitochondrial Fe-S cochaperone protein HSC20 guides nascent Fe-S clusters based on a highly conserved motif, LYR, that exists in target proteins in different molecular contexts. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. 2010 IRON-SULFUR ENZYMES GORDON RESEARCH CONFERENCE, JUNE 6-11, 2010

    Energy Technology Data Exchange (ETDEWEB)

    Nancy Ryan Gray

    2010-06-11

    Iron-sulfur (FeS) centers are essential for biology and inspirational in chemistry. These protein cofactors are broadly defined as active sites in which Fe is coordinated by S-donor ligands, often in combination with extra non-protein components, for example, additional metal atoms such as Mo and Ni, and soft ligands such as CN{sup -} and CO. Iron-sulfur centers are inherently air sensitive: they are found in essentially all organisms and it is possible that they were integral components of the earliest forms of life, well before oxygen (O{sub 2}) appeared. Proteins containing FeS cofactors perform a variety of biological functions ranging across electron transfer, acid-base catalysis, and sensing where they are agents for cell regulation through transcription (DNA) or translation (RNA). They are redox catalysts for radical-based reactions and the activation of H{sub 2}, N{sub 2} and CO{sub 2}, processes that offer scientific and economic challenges for industry. Iron-sulfur centers provide the focus for fundamental investigations of chemical bonding, spectroscopy and paramagnetism, and their functions have numerous implications for health and medicine and applications for technology, including renewable energy. The 2010 Iron-Sulfur Enzymes GRC will bring together researchers from different disciplines for in-depth discussions and presentations of the latest developments. There will be sessions on structural and functional analogues of FeS centers, advances in physical methods, roles of FeS centers in energy and technology, catalysis (including radical-based rearrangements and the activation of nitrogen, hydrogen and carbon), long-range electron transfer, FeS centers in health and disease, cellular regulation, cofactor assembly, their relevance in industry, and experiments and hypotheses relating to the origins of life.

  11. Occurrence and activity of iron- and sulfur-oxidizing microorganisms in alkaline coal strip mine spoils.

    Science.gov (United States)

    Olson, G J; McFeters, G A; Temple, K L

    1981-03-01

    Spoils samples collected from a coal strip mine in southeastern Montana were examined for populations and activities of iron- and sulfur-oxidizing bacteria. Spoils examined were of three types: (a) acidic pyrite-rich waste coal, (b) oxidation halo material, and (c) alkaline material, which was the most widespread type. Bacterial numbers, sulfur oxidation, and(14)CO2 uptake activity declined to low levels in the summer when spoils were dry. Even in wetter spring months pyritic spoils contained relatively low numbers of acidophilic iron- and sulfur-oxidizing bacteria, probably indicative of water stress since the same spoils incubated with excess water or dilute mineral salts showed considerably greater bacterial numbers and activity. Certain wells in coal and spoils aquifers contained substantial populations of iron-oxidizing acidophilic bacteria. However, these wells were always of alkaline or neutral pH, indicating that bacterial pyrite oxidation occurred where groundwaters contacted either replaced spoils or coal that contained pyrite or other metal sulfides. Bacterial activity may contribute to trace metal and sulfate leaching in the area.

  12. Thermodynamic Calculation among Cerium, Oxygen, and Sulfur in Liquid Iron

    Science.gov (United States)

    Pan, Fei; Zhang, Jian; Chen, Hao-Long; Su, Yen-Hsun; Su, Yen-Hao; Hwang, Weng-Sing

    2016-10-01

    Thermodynamic calculation has been applied to predict the inclusion formation in molten SS400 steel. When the Cerium addition in liquid iron is 70 ppm and the initial Oxygen and Sulphur are both 110 ppm, the formation of oxides containing Cerium would experience the transformation from Ce2O3 to CeO2 and also the formation of sulfides containing Cerium would experience the transformation from CeS to Ce2S3 and then to Ce3S4. Below 2000 K the most thermodynamic stable matter is CeO2 and the less thermodynamic stable inclusion is CeS. Only when the amount of [O] is extremely low and the amount of [S] and [Ce] is relatively high, Ce2S3 has the possibility to form.

  13. Synthesis of the iron-molybdenum cofactor of nitrogenase is inhibited by a low-molecular-weight metabolite of Klebsiella pneumoniae.

    OpenAIRE

    Downs, D M; Ludden, P W; Shah, V. K.

    1990-01-01

    The in vitro synthesis of the iron-molybdenum cofactor nitrogenase was inhibited by a low-molecular-weight factor. This inhibitory factor was present in the membrane extracts of wild-type and nif mutant strains of Klebsiella pneumoniae that were grown under conditions that either repressed or derepressed nitrogenase expression. In vitro, the inhibition was specific for the NifB protein. Addition of this factor to K. pneumoniae cells at various times during nif derepression decreased nitrogena...

  14. Synthesis by reactive grinding of molybdenum iron bimetallic nitride; Sintesis por molienda reactiva del nitruro bimetalico Mo-Fe: Mo{sub 3}Fe{sub 3}N

    Energy Technology Data Exchange (ETDEWEB)

    Roldan, M. A.; Ortega, A.; Palencia, I.; Real, C.

    2008-07-01

    The transition metal nitride ternary show similar properties to the binary nitride and some times this behaviour are improved. In the present work, the molybdenum-iron nitride has been prepared by reactive grinding form the two metals under nitrogen atmosphere at a pressure of 11 bar. The characterization of the compounds is presented and it is also shown a study of the stability of the nitride under several atmospheres. (Author) 42 refs.

  15. Sulfur and iron cycling in deep-subsurface, coal bed-containing sediments off Shimokita (Japan)

    Science.gov (United States)

    Riedinger, N.; Smirnoff, M. N.; Gilhooly, W.; Phillips, S. C.; Lyons, T. W.; 337 Scientific Party, I.

    2013-12-01

    The main goal of IODP Expedition 337 was the identification and characterization of the deep coal bed biosphere and hydrocarbon system off the Shimokita Peninsula (Japan) in the northwestern Pacific using the D/V Chikyu. To accomplish this scientific objective, it was also necessary to investigate the inorganic biogeochemistry in order to identify possible electron acceptors and bio-essential nutrients. These biogeochemical parameters greatly influence both, the composition and abundance of microbial communities as well as the organic carbon cycle. In turn, the microbially mediated carbon cycle influences the diagenetic reactions in the subsurface, thus, altering geochemical and physical characteristics of the material. Here we present results from metal and sulfur geochemical analyses from the deep-subsurface sediments (about 1250 to 2466 mbsf) at Site C0020 off Shimokita. The measured concentrations of acid volatile sulfur (AVS) as well as chromium reducible sulfur (CRS) reflect the alteration of iron oxides to iron sulfides and indicate that the main sulfur-bearing phase in the investigated sediments is pyrite. Concentrations of intermediate sulfur species are minor and occur mainly in the coal-bearing interval. Our data show that the uppermost sediments contain higher amounts of pyrite (up to 1.2 wt.%) with an average of 0.5 wt.% compared to the deeper deposits (below about 1800 mbsf), which show an average of 0.16 wt.%. In contrast, iron oxide concentrations are highest in the deeper sediment sections (up to 0.4%), where pyrite concentrations are low. The alteration of iron oxides to sulfides in theses lower section was probably governed by the amount of available sulfide in the pore water. The occurrence of (bio-)reactive iron phases in these deeply buried sediments has implications for the deep biosphere as those minerals have the potential to serve as electron acceptors during burial, including reactions involving deep sourced electron donors, such as

  16. Interfacial analysis of tribological systems containing molybdenum disulfide and iron using XPS and CEMS

    Science.gov (United States)

    Zabinski, J. S.; George, T.; Tatarchuk, B. J.

    1989-01-01

    In the present evaluation of results from studies of the interfacial chemistry and morphology of a buried lubricant-substrate interface, specimens of increasing complexity that culminated with the effects of excess sulfur and defects were characterized by XPS and SEM, as well as conversion-electron Moessbauer spectroscopy (CEMS). In order to simulate sputtered systems, single crystals of MoS2 were damaged with Ar(+) bombardment and coated with Fe. Fe is found to react differently with MoS2 depending on surface treatments, surface defects, annealing treatments, and the presence of excess sulfur. The annealing temperature determines which compounds are formed, as well as the crystal habit and plane at the Fe-MoS2 interface.

  17. Copper Stress Affects Iron Homeostasis by Destabilizing Iron-Sulfur Cluster Formation in Bacillus subtilis

    NARCIS (Netherlands)

    Chillappagari, Shashi; Seubert, Andreas; Trip, Hein; Kuipers, Oscar P.; Marahiel, Mohamed A.; Miethke, Marcus

    2010-01-01

    Copper and iron are essential elements for cellular growth. Although bacteria have to overcome limitations of these metals by affine and selective uptake, excessive amounts of both metals are toxic for the cells. Here we investigated the influences of copper stress on iron homeostasis in Bacillus

  18. NIF-type iron-sulfur cluster assembly system is duplicated and distributed in the mitochondria and cytosol of Mastigamoeba balamuthi

    OpenAIRE

    2013-01-01

    In most eukaryotes, the mitochondrion is the main organelle for the formation of iron-sulfur (FeS) clusters. This function is mediated through the iron-sulfur cluster assembly machinery, which was inherited from the α-proteobacterial ancestor of mitochondria. In Archamoebae, including pathogenic Entamoeba histolytica and free-living Mastigamoeba balamuthi, the complex iron-sulfur cluster machinery has been replaced by an ε-proteobacterial nitrogen fixation (NIF) system consisting of two compo...

  19. Investigation on the Effect of Sulfur and Titanium on the Microstructure of Lamellar Graphite Iron

    DEFF Research Database (Denmark)

    Moumeni, Elham; Stefanescu, Doru Michael; Tiedje, Niels Skat

    2013-01-01

    The goal of this work was to identify the inclusions in lamellar graphite cast iron in an effort to explain the nucleation of the phases of interest. Four samples of approximately the same carbon equivalent but different levels of sulfur and titanium were studied. The Ti/S ratios were from 0.......15 to 29.2 and the Mn/S ratios from 4.2 to 48.3. Light and electron microscopy were used to examine the unetched, color-etched, and deep-etched samples. It was confirmed that in irons with high sulfur content (0.12 wt pct) nucleation of type-A and type-D graphite occurs on Mn sulfides that have a core...... of complex Al, Ca, Mg oxide. An increased titanium level of 0.35 pct produced superfine interdendritic graphite (~10 μm) at low (0.012 wt pct) as well as at high-S contents. Ti also caused increased segregation in the microstructure of the analyzed irons and larger eutectic grains (cells). TiC did not appear...

  20. Nucleosynthetic molybdenum isotope anomalies in iron meteorites - new evidence for thermal processing of solar nebula material

    Science.gov (United States)

    Poole, Graeme M.; Rehkämper, Mark; Coles, Barry J.; Goldberg, Tatiana; Smith, Caroline L.

    2017-09-01

    We have investigated nucleosynthetic Mo isotope anomalies in 38 different bulk iron meteorites from 11 groups, to produce by far the largest and most precise dataset available to date for such samples. All magmatic iron groups were found to display deficits in s-process Mo isotopes, with essentially constant anomalies within but significant variations between groups. Only meteorites of the non-magmatic IAB/IIICD complex revealed terrestrial Mo isotopic compositions. The improved analytical precision achieved in this study enables two isotopically distinct suites of iron meteorites to be identified. Of these, the r=p suite encompasses the IC, IIAB, IIE, IIIAB, IIIE and IVA groups and exhibits relatively modest but 'pure' s-process deficits, relative to Earth. The second r>p suite includes groups IIC, IIIF and IVB. These iron meteorites show larger s-process deficits than the r=p suite, coupled with an excess of r-process relative to p-process components. Comparison of the results with data for other elements (e.g., Cr, Ni, Ru, Ti, Zr) suggests that the Mo isotope variability is most likely produced by thermal processing and selective destruction of unstable presolar phases. An updated model is proposed, which relates the iron meteorite suites to different extents of thermal processing in the solar nebula, as governed by heliocentric distance. In detail, the r=p suite of iron meteorite parent bodies is inferred to have formed closer to the Sun, where the extent of thermal processing was similar to that experienced by terrestrial material, so that the meteorites exhibit only small s-process deficits relative to Earth. In contrast, the r>p suite formed at greater heliocentric distance, where more subtle thermal processing removed a smaller proportion of r- and p-process host phases, thereby generating larger s-process deficits relative to the terrestrial composition. In addition, the thermal conditions enabled selective destruction of p- versus r-isotope carrier phases

  1. The Synthetic Effects of Iron with Sulfur and Fluorine on Photoabsorption and Photocatalytic Performance in Codoped

    Directory of Open Access Journals (Sweden)

    Xiaohua Li

    2012-01-01

    Full Text Available The structural and electronic properties of iron-fluorine (Fe-F and iron-sulfur (Fe-S codoped anatase TiO2 are investigated by first-principles based on density functional theory. Our results show that the formation energy of codoped system is lower than that of single-element doping, which indicates the synergic effect of codoping on the stability of the structure. Codopants introduced impurity gap states resulting in the electron transition energy reduction and thus the visible light absorption observed in the samples. It is concluded that Fe-S should be a better codoping pair because Fe-S codoping introduces extended impurity states resulting in stronger visible light absorption than that of Fe-F codoped compounds. This work gives understanding to the recent experiment and provides the evidence of choosing the more effective co-dopants in TiO2.

  2. Adsorption of 2-naphthalenesulfonic acid/sulfuric acid/sulfurous acid from aqueous solution by iron-impregnated weakly basic resin:Equilibrium and model

    Institute of Scientific and Technical Information of China (English)

    Changhai Li; Dongmei Jia

    2016-01-01

    Commercial grade weakly basic resin D301 was impregnated with iron through a simple method using ferric chloride. Experiments for single, bisolute and trinary competitive adsorption were carried out to investigate the adsorption behavior of 2-naphthalenesulfonic acid (NSA), sulfuric acid and sulfurous acid from their solution at 298K onto the novel hybrid iron impregnated D301(Fe-D301). Adsorption affinity of NSA on Fe-D301 was found to be much higher than that of sulfuric acid, while adsorption affinity of sulfuric acid was slightly higher than that of sulfurous acid. The data of single-solute adsorption were fitted to the Langmuir model and the Freundlich adsorption model. The non-ideal competitive adsorbed model coupled with the single-solute adsorp-tion models were used to predict the bisolute and trinary-solute competitive adsorption equilibria. The NICM coupled with the Langmuir model yields the favorable representation of the bisolute and trinary-solute compet-itive adsorption behavior.

  3. Biogenesis of iron-sulfur clusters in mammalian cells: new insights and relevance to human disease

    Directory of Open Access Journals (Sweden)

    Tracey A. Rouault

    2012-03-01

    Full Text Available Iron-sulfur (Fe-S clusters are ubiquitous cofactors composed of iron and inorganic sulfur. They are required for the function of proteins involved in a wide range of activities, including electron transport in respiratory chain complexes, regulatory sensing, photosynthesis and DNA repair. The proteins involved in the biogenesis of Fe-S clusters are evolutionarily conserved from bacteria to humans, and many insights into the process of Fe-S cluster biogenesis have come from studies of model organisms, including bacteria, fungi and plants. It is now clear that several rare and seemingly dissimilar human diseases are attributable to defects in the basic process of Fe-S cluster biogenesis. Although these diseases –which include Friedreich’s ataxia (FRDA, ISCU myopathy, a rare form of sideroblastic anemia, an encephalomyopathy caused by dysfunction of respiratory chain complex I and multiple mitochondrial dysfunctions syndrome – affect different tissues, a feature common to many of them is that mitochondrial iron overload develops as a secondary consequence of a defect in Fe-S cluster biogenesis. This Commentary outlines the basic steps of Fe-S cluster biogenesis as they have been defined in model organisms. In addition, it draws attention to refinements of the process that might be specific to the subcellular compartmentalization of Fe-S cluster biogenesis proteins in some eukaryotes, including mammals. Finally, it outlines several important unresolved questions in the field that, once addressed, should offer important clues into how mitochondrial iron homeostasis is regulated, and how dysfunction in Fe-S cluster biogenesis can contribute to disease.

  4. Effect of CO2 on the Conversion of Isobutane over Iron, Cerium and Molybdenum Mixed Oxides

    Directory of Open Access Journals (Sweden)

    Daifallah Al-Dhayan

    2016-10-01

    Full Text Available A series of cerium and iron mixed oxide catalysts were prepared by thermal decomposition of Fe1.5PMo12O40 and Ce1.5PMo12O40 heteropolyanions mixture. The prepared catalysts have been characterized and tested for the conversion of isobutane in the presence of CO2. Characterization by XRD showed that besides Fe2O3 and CeO2, α-MoO3 was the main phase formed after thermal treatment. The effect of the support, the reaction temperature, and the presence of H2O in the reactant mixture was investigated. It has been found that the support enhanced both the conversion and isobutene selectivity. As for the reaction temperature and addition of water, it has been found that increasing the temperature increased both the conversion and isobutene selectivity, whereas the presence of water increased the isobutene selectivity but decreased the conversion.

  5. Gene cloning, purification, and characterization of two cyanobacterial NifS homologs driving iron-sulfur cluster formation.

    Science.gov (United States)

    Kato, S; Mihara, H; Kurihara, T; Yoshimura, T; Esaki, N

    2000-11-01

    Iron-sulfur proteins are essential in the photosynthetic system and many other biological processes. We have isolated and characterized enzymes driving the formation of iron-sulfur clusters from Synechocystis sp. PCC6803. Two genes (slr0387 and sll0704), showing similarity to nifS of Azotobacter vinelandii, were cloned, and their gene products (SsCsdl and SsCsd2) were purified. They catalyzed the desulfuration of L-cysteine. Reconstitution of a [2Fe-2S] cluster of cyanobacterial ferredoxin proceeded much faster in the presence of L-cysteine and either of these enzymes than when using sodium sulfide. These results suggest that SsCsdl and SsCsd2 facilitate the iron-sulfur cluster assembly by producing inorganic sulfur from L-cysteine. Synechocystis sp. PCC6803 has no gene coding for a protein with similarity to the N-terminal domain of NifU of A. vinelandii, which is believed to cooperate with NifS to assemble iron-sulfur clusters. Thus, the cluster formation in the cyanobacterium probably proceeds through a mechanism that is different from that in A. vinelandii.

  6. A Quantitative Evaluation of the Iron-Sulfur World and Its Relevance to Life's Origins

    Science.gov (United States)

    Ross, David S.

    2008-04-01

    The significance of Wächtershäuser's iron-sulfur world to the origin of life and the limits to its notional autocatalytic cycles are examined in kinetic simulations of the chain polymerization sequence The simulations were run for the formation of all oligomers up to the 20-mer over a 1 Gy interval from the end of the period of heavy bombardment, during which period life emerged. Upper-limit rate constant estimates developed from the studies of Huber and Wächtershäuser were employed. The simulations showed that oligomer production consistent with life's start within that interval emerges only with an autocatalyst exhibiting a catalytic proficiency comparable to that of contemporary enzymes. The simulations, moreover, ignored likely thermodynamic and statistical burdens which, if included, would have led to the need for catalytic capacities well in excess of those in present-day enzymes. Prebiotic oligomers with such levels of activity are clearly not likely, and it is apparent that the iron-sulfur scheme could not have played a role in life's beginnings.

  7. A quantitative evaluation of the iron-sulfur world and its relevance to life's origins

    Science.gov (United States)

    Ross, D.S.

    2008-01-01

    The significance of Wa??chtersha??user's iron-sulfur world to the origin of life and the limits to its notional autocatalytic cycles are examined in kinetic simulations of the chain polymerization sequence primitive materials ??? amino acids ??? oligomers The simulations were run for the formation of all oligomers up to the 20-mer over a 1 Gy interval from the end of the period of heavy bombardment, during which period life emerged. Upper-limit rate constant estimates developed from the studies of Huber and Wa??chtersha?? user were employed. The simulations showed that oligomer production consistent with life's start within that interval emerges only with an autocatalyst exhibiting a catalytic proficiency comparable to that of contemporary enzymes. The simulations, moreover, ignored likely thermodynamic and statistical burdens which, if included, would have led to the need for catalytic capacities well in excess of those in present-day enzymes. Prebiotic oligomers with such levels of activity are clearly not likely, and it is apparent that the iron-sulfur scheme could not have played a role in life's beginnings. ?? 2008 Mary Ann Liebert, Inc.

  8. Corrosion and high temperature resistant coatings for molybdenum, made out of iron and nickel alloys and applied by explosive welding

    Energy Technology Data Exchange (ETDEWEB)

    Pruemmer, R.; Henne, R.

    1980-04-01

    The impact parameters of the explosive welding of molybdenum with Inconel 601 were determined. The combination Mo and Inconel 601 was considered as nonweldable. It can be applied in solar radiation concentrating devices, allowing a higher operating temperature and higher energy conversion efficiency. The usual velocities of the explosive welding process (collision velocities of 2200 m/sec) lead at best to samples affected by cracks, due to the insufficient workability of molybdenum. At higher velocities cracks no longer occur, molybdenum being a strain rate sensitive material. Layer composite materials can be manufactured in flat as well as in tube form. (ESA)

  9. Structural Basis for Iron-Mediated Sulfur Transfer in Archael and Yeast Thiazole Synthases.

    Science.gov (United States)

    Zhang, Xuan; Eser, Bekir E; Chanani, Prem K; Begley, Tadhg P; Ealick, Steven E

    2016-03-29

    Thiamin diphosphate is an essential cofactor in all forms of life and plays a key role in amino acid and carbohydrate metabolism. Its biosynthesis involves separate syntheses of the pyrimidine and thiazole moieties, which are then coupled to form thiamin monophosphate. A final phosphorylation produces the active form of the cofactor. In most bacteria, six gene products are required for biosynthesis of the thiamin thiazole. In yeast and fungi only one gene product, Thi4, is required for thiazole biosynthesis. Methanococcus jannaschii expresses a putative Thi4 ortholog that was previously reported to be a ribulose 1,5-bisphosphate synthase [Finn, M. W. and Tabita, F. R. (2004) J. Bacteriol., 186, 6360-6366]. Our structural studies show that the Thi4 orthologs from M. jannaschii and Methanococcus igneus are structurally similar to Thi4 from Saccharomyces cerevisiae. In addition, all active site residues are conserved except for a key cysteine residue, which in S. cerevisiae is the source of the thiazole sulfur atom. Our recent biochemical studies showed that the archael Thi4 orthologs use nicotinamide adenine dinucleotide, glycine, and free sulfide to form the thiamin thiazole in an iron-dependent reaction [Eser, B., Zhang, X., Chanani, P. K., Begley, T. P., and Ealick, S. E. (2016) J. Am. Chem. Soc. , DOI: 10.1021/jacs.6b00445]. Here we report X-ray crystal structures of Thi4 from M. jannaschii complexed with ADP-ribulose, the C205S variant of Thi4 from S. cerevisiae with a bound glycine imine intermediate, and Thi4 from M. igneus with bound glycine imine intermediate and iron. These studies reveal the structural basis for the iron-dependent mechanism of sulfur transfer in archael and yeast thiazole synthases.

  10. The effects of sulfur amendments on the geochemistry of sulfur, phosphorus and iron in the mangrove plant (Kandelia obovata (S. L.)) rhizosphere.

    Science.gov (United States)

    Jian, Li; Junyi, Yu; Jingchun, Liu; Chongling, Yan; Haoliang, Lu; Spencer, Kate L

    2017-01-30

    P (phosphorus) and Fe (iron) are limiting elements and S (sulfur) is an important element of the biogeochemical cycle in the mangrove environment. To assess the effects of sulfur on the geochemical cycling of Fe and P at the sediment-plant interface, the speciation distributions of Fe, P and S in sediments were examined. The data showed that higher proportions of amorphous Fe, Fe-bound phosphate, chromium reducible sulfur and elemental sulfur were found in the rhizosphere, while more crystalline Fe, exchangeable phosphate and acid-volatile sulfide were determined in the non-rhizosphere. Sulfate application induced an increase in the Ex-P concentration, high P accumulation and high iron plaque deposition in the roots. In conclusion, sulfate applications had a significant influence on the geochemical cycling of Fe and P in the sediments. It significantly curtailed the Fe and P limit to plant growth and enhanced plant resistance to the rugged surroundings in mangrove. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Oxidative stress enhances the expression of sulfur assimilation genes: preliminary insights on the Enterococcus faecalis iron-sulfur cluster machinery regulation

    Science.gov (United States)

    Riboldi, Gustavo Pelicioli; Bierhals, Christine Garcia; de Mattos, Eduardo Preusser; Frazzon, Ana Paula Guedes; d‘Azevedo, Pedro Alves; Frazzon, Jeverson

    2014-01-01

    The Firmicutes bacteria participate extensively in virulence and pathological processes. Enterococcus faecalis is a commensal microorganism; however, it is also a pathogenic bacterium mainly associated with nosocomial infections in immunocompromised patients. Iron-sulfur [Fe-S] clusters are inorganic prosthetic groups involved in diverse biological processes, whose in vivo formation requires several specific protein machineries. Escherichia coli is one of the most frequently studied microorganisms regarding [Fe-S] cluster biogenesis and encodes the iron-sulfur cluster and sulfur assimilation systems. In Firmicutes species, a unique operon composed of the sufCDSUB genes is responsible for [Fe-S] cluster biogenesis. The aim of this study was to investigate the potential of the E. faecalis sufCDSUB system in the [Fe-S] cluster assembly using oxidative stress and iron depletion as adverse growth conditions. Quantitative real-time polymerase chain reaction demonstrated, for the first time, that Gram-positive bacteria possess an OxyR component responsive to oxidative stress conditions, as fully described for E. coli models. Likewise, strong expression of the sufCDSUB genes was observed in low concentrations of hydrogen peroxide, indicating that the lowest concentration of oxygen free radicals inside cells, known to be highly damaging to [Fe-S] clusters, is sufficient to trigger the transcriptional machinery for prompt replacement of [Fe-S] clusters. PMID:24936909

  12. Modelling phosphorus (P), sulfur (S) and iron (Fe) interactions for dynamic simulations of anaerobic digestion processes

    DEFF Research Database (Denmark)

    Flores Alsina, Xavier; Solon, Kimberly; Kazadi Mbamba, Christian

    2016-01-01

    This paper proposes a series of extensions to functionally upgrade the IWA Anaerobic Digestion Model No. 1 (ADM1) to allow for plant-wide phosphorus (P) simulation. The close interplay between the P, sulfur (S) and iron (Fe) cycles requires a substantial (and unavoidable) increase in model......) inhibition effect and stripping to the gas phase (GH2S). The third extension (A3) accounts for chemical iron (III) (SFe 3+) reduction to iron (II) (SFe 2+) using hydrogen (SH2) and sulfides (SIS) as electron donors. A set of pre/post interfaces between the Activated Sludge Model No. 2d (ASM2d) and ADM1...... to form (or not) precipitation products. Implementations A1 and A2,1/A2,2 lead to a reduction in the predicted methane/biogas production (and potential energy recovery) compared to reference ADM1 predictions (A0). This reduction is attributed to two factors: (1) loss of electron equivalents due to sulfate...

  13. Molten iron oxysulfide as a superior sulfur sorbent. Technical progress report, September 1, 1991--November 30, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Hepworth, M.T.

    1991-12-31

    Slagging combustors with injected lime or limestone are being considered as replacements for conventional coal burners. They have advantages in that they can be staged to reduce NO{sub x} and So{sub x} emissions. Iron oxide, as an alternative to lime or limestone may be effective not only as a desulfurizing agent, but under the right conditions of oxygen potential and after combination with sulfur, the reaction products of coal gases with iron oxide can act as a flux to produce a fluid phase. The thermodynamic conditions for optimum removal of sulfur from the first stage of a coal combustor are being determined by experiment and by use of existing data. Analysis of the phase equilibria indicates that optimum conditions for deployment of the reducing stage of a multi-stage burner operating with iron injection are close to the boundary of the liquid iron oxysulfide phase with iron-saturation. Two prior investigations differ with respect to the location of this phase boundary at temperatures over 1400{degree}C, with reference 1, showing the phase boundary nearer the iron-rich corner than reference 2 which gives the boundary further into the liquid region. Effort has been directed during this quarter to showing that this phase boundary is sufficiently close to the iron-rich liquid region, at higher temperatures, in order to allow for smooth operation of a multistage burner without the problem of iron deposition.

  14. Evidence for free oxygen in the Neoarchean ocean based on coupled iron-molybdenum isotope fractionation

    Science.gov (United States)

    Czaja, Andrew D.; Johnson, Clark M.; Roden, Eric E.; Beard, Brian L.; Voegelin, Andrea R.; Nägler, Thomas F.; Beukes, Nicolas J.; Wille, Martin

    2012-06-01

    Most geochemical proxies and models of atmospheric evolution suggest that the amount of free O2 in Earth’s atmosphere stayed below 10-5 present atmospheric level (PAL) until the Great Oxidation Event (GOE) that occurred between ∼2.2 and 2.4 Ga, at which time free O2 in the atmosphere increased to approximately 10-1 to 10-2 PAL. Although photosynthetically produced “O2 oases” have been proposed for the photic zone of the oceans prior to the GOE, it has been difficult to constrain absolute O2 concentrations and fluxes in such paleoenvironments. Here we constrain free O2 levels in the photic zone of a Late Archean marine basin by the combined use of Fe and Mo isotope systematics of Ca-Mg carbonates and shales from the 2.68 to 2.50 Ga Campbellrand-Malmani carbonate platform of the Kaapvaal Craton in South Africa. Correlated Fe and Mo isotope compositions require a key role for Fe oxide precipitation via oxidation of aqueous Fe(II) by photosynthetically-derived O2, followed by sorption of aqueous Mo to the newly formed Fe oxides. A dispersion/reaction model illustrates the effects of Fe oxide production and Mo sorption to Fe oxides, and suggests that a few to a few tens of μM free O2 was available in the photic zone of the Late Archean marine basin, consistent with some previous estimates. The coupling of Fe and Mo isotope systematics provides a unique view into the processes that occurred in the ancient shallow ocean after production of free O2 began, but prior to oxygenation of the deep ocean, or significant accumulation of free O2 in the atmosphere. These results require oxygenic photosynthesis to have evolved by at least 2.7 Ga and suggest that the Neoarchean ocean may have had a different oxygenation history than that of the atmosphere. The data also suggest that the extensive iron formation deposition that occurred during this time was unlikely to have been produced by anoxygenic photosynthetic Fe(II) oxidation. Finally, these data indicate that the ocean

  15. Unravelling atmospheric photolysis and ocean redox chemistry from Paleoarchean pyrite : a multiple sulfur and iron stable isotope study

    NARCIS (Netherlands)

    Galić, A.

    2015-01-01

    This thesis brought together four individual studies on the geochemistry of three recently obtained drill cores from the Barberton Greenstone Belt, South Africa. These data were used to provide a synthesis of the iron and sulfur cycles in the Paleoarchean, with a particular focus on the nature and o

  16. Effects of RE, V, Ti and B composite modification on the microstructure and properties of high chromium cast iron containing 3 % molybdenum

    Institute of Scientific and Technical Information of China (English)

    GUO Erjun; WANG Lihua; WANG Liping; HUANG Yongchang

    2009-01-01

    The effects of RE, V, Ti and B on the microstructure and properties of high chromium cast iron containing 3% molybdenum under as-cast and heat treatment conditions were investigated with the method of comparing experiments. The results show that with the increase of RE content, the primary austenite of high chromium east iron is obviously refined. The morphology of carbide is changed from netlike and lath to small multiangular isolated blocks or massive blocks, the isolated degree of carbide is improved obviously, and the size is significantly re-fined. The addition of V and B into high chromium cast iron can refine the microstructure, reduce coarse columnar crystals and make the carbide smaller and uniform. Through composite modification with RE, V, Ti and B, the hardness, wear resistance and impact toughness of high chromium cast iron are increased conspicuously. After heat treatment, the hardness of high chromium iron is increased significantly, but the toughness and wear resistance do not show great improvement.

  17. [Reference values of iron, iodine, zinc, selenium, copper, molybdenum, vitamin C, vitamin E, vitamin K, carotenoids and polyphenols for the Venezuelan population].

    Science.gov (United States)

    García-Casal, Maria Nieves; Landaeta, Maritza; Adrianza de Baptista, Gertrudis; Murillo, Carolain; Rincón, Mariela; Bou Rached, Lizet; Bilbao, Arantza; Anderson, Hazel; García, Doris; Franquiz, Julia; Puche, Rafael; Garcia, Omar; Quintero, Yurimay; Peña-Rosas, Juan Pablo

    2013-12-01

    The review on iron, iodine, zinc, selenium, copper, molybdenum, vitamin C, vitamin E, vitamin K, carotenoids and polyphenols recommendations for Venezuela comprise the definitions adopted worldwide known as Dietary Reference Intakes (DRIs) that include Recommended Dietary Allowance (RDA), Estimated Average Requirement (EAR), Adequate Intake (AI) and Tolerable Upper Intake Levels (UL). The RDA for iron: 11 mg/day for infants Vitamin C: 40-50 mg/day for infants, 15-45 mg/ day for children, 75 mg/day for male adolescents, 65 mg/day for female adolescents, 90 mg/day for adult males, 75 mg/day for adult females, 80-85 mg/day during pregnancy and 115-120 mg/day during lactation. Recommendations for copper, selenium, molybdenum, vitamins E, K, carotenoids and polyphenols are also presented. These recommendations will help to design adequate and efficient policies that could help to avoid or to treat the consequences derived from the deficiency or the excess of these nutrients.

  18. The chloroplast Rieske iron-sulfur protein. At the crossroad of electron transport and signal transduction.

    Science.gov (United States)

    de Vitry, Catherine; Ouyang, Yexin; Finazzi, Giovanni; Wollman, Francis-André; Kallas, Toivo

    2004-10-22

    We have addressed the functional and structural roles of three domains of the chloroplast Rieske iron-sulfur protein; that is, the flexible hinge that connects the transmembrane helix to the soluble cluster-bearing domain, the N-terminal stromal protruding domain, and the transmembrane helix. To this aim mutants were generated in the green alga Chlamydomonas reinhardtii. Their capacities to assemble the cytochrome b6f complex, perform plastoquinol oxidation, and signal redox-induced activation of the light-harvesting complex II kinase during state transition were tested in vivo. Deletion of one residue and extensions of up to five residues in the flexible hinge had no significant effect on complex accumulation or electron transfer efficiency. Deletion of three residues (Delta3G) dramatically decreased reaction rates by a factor of approximately 10. These data indicate that the chloroplast iron-sulfur protein-linking domain is much more flexible than that of its counterpart in mitochondria. Despite greatly slowed catalysis in the Delta3G mutant, there was no apparent delay in light-harvesting complex II kinase activation or state transitions. This indicates that conformational changes occurring in the Rieske protein did not represent a limiting step for kinase activation within the time scale tested. No phenotype could be associated with mutations in the N-terminal stromal-exposed domain. In contrast, the N17V mutation in the Rieske protein transmembrane helix resulted in a large decrease in the cytochrome f synthesis rate. This reveals that the Rieske protein transmembrane helix plays an active role in assembly-mediated control of cytochrome f synthesis. We propose a structural model to interpret this phenomenon based on the C. reinhardtii cytochrome b6f structure.

  19. 2008 GRC Iron Sulfur Enzymes-Conference to be held June 8-13, 2008

    Energy Technology Data Exchange (ETDEWEB)

    Stephen Cramer, Nancy Ryan Gray

    2009-01-01

    Iron-sulfur proteins are among the most common and ancient enzymes and electron-transfer agents in nature. They play key roles in photosynthesis, respiration, and the metabolism of small molecules such as H2, CO, and N2. The Iron Sulfur Enzyme Gordon Research Conference evolved from an earlier GRC on Nitrogen Fixation that began in 1994. The scope of the current meeting has broadened to include all enzymes or metalloproteins in which Fe-S bonds play a key role. This year's meeting will focus on the biosynthesis of Fe-S clusters, as well as the structure and mechanism of key Fe-S enzymes such as hydrogenase, nitrogenase and its homologues, radical SAM enzymes, and aconitase-related enzymes. Recent progress on the role of Fe-S enzymes in health, disease, DNA/RNA-processing, and alternative bio-energy systems will also be highlighted. This conference will assemble a broad, diverse, and international group of biologists and chemists who are investigating fundamental issues related to Fe-S enzymes, on atomic, molecular, organism, and environmental scales. The topics to be addressed will include: Biosynthesis & Genomics of Fe-S Enzymes; Fundamental Fe-S Chemistry; Hydrogen and Fe-S Enzymes; Nitrogenase & Homologous Fe-S Enzymes; Fe-S Enzymes in Health & Disease; Radical SAM and Aconitase-Related Fe-S Enzymes; Fe-S Enzymes and Synthetic Analogues in BioEnergy; and Fe-S Enzymes in Geochemistry and the Origin of Life.

  20. The iron-sulfur cluster assembly machineries in plants: current knowledge and open questions

    Directory of Open Access Journals (Sweden)

    Jérémy eCouturier

    2013-07-01

    Full Text Available Many metabolic pathways and cellular processes occurring in most sub-cellular compartments depend on the functioning of iron-sulfur (Fe-S proteins, whose cofactors are assembled through dedicated protein machineries. Recent advances have been made in the knowledge of the functions of individual components through a combination of genetic, biochemical and structural approaches, primarily in prokaryotes and non-plant eukaryotes. Whereas most of the components of these machineries are conserved between kingdoms, their complexity is likely increased in plants owing to the presence of additional assembly proteins and to the existence of expanded families for several assembly proteins. This review focuses on the new actors discovered in the past few years, such as glutaredoxin, BOLA and NEET proteins as well as MIP18, MMS19, TAH18, DRE2 for the cytosolic machinery, which are integrated into a model for the plant Fe-S cluster biogenesis systems. It also discusses a few issues currently subjected to an intense debate such as the role of the mitochondrial frataxin and of glutaredoxins, the functional separation between scaffold, carrier and iron-delivery proteins and the crosstalk existing between different organelles.

  1. Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nikel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) seamless pipe and tube

  2. Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045 and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) plate, sheet and strip

  3. Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    Standard specification for Nickel-Chromium-Iron alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten alloy (UNS N06674) rod, bar, and wire

  4. miR-210 Targets Iron-Sulfur Cluster Scaffold Homologue in Human Trophoblast Cell Lines

    Science.gov (United States)

    Lee, Deug-Chan; Romero, Roberto; Kim, Jung-Sun; Tarca, Adi L.; Montenegro, Daniel; Pineles, Beth L.; Kim, Ernest; Lee, JoonHo; Kim, Sun Young; Draghici, Sorin; Mittal, Pooja; Kusanovic, Juan Pedro; Chaiworapongsa, Tinnakorn; Hassan, Sonia S.; Kim, Chong Jai

    2011-01-01

    This study was performed to assess the biological significance of miR-210 in preeclampsia and small-for-gestational-age (SGA) pregnancies. Placental miR-210 expression was evaluated by quantitative RT-PCR (RT-qPCR) in the following groups: i) appropriate-for-gestational-age pregnancies (n = 72), ii) preeclampsia (n = 52), iii) SGA (n = 66), and iv)preeclampsia with SGA (n = 31). The effects of hypoxia (1% O2) on miR-210 and iron-sulfur cluster scaffold homologue (ISCU) expressions and miR-210 binding to ISCU 3′ UTR were examined in Swan 71 and BeWo cell lines. Perls' reaction (n = 229) and electron microscopy (n = 3) were conducted to verify siderosis of trophoblasts. miR-210 expression was increased in preeclampsia and SGA cases and was decreased with birth weight and gestational age. In both cell lines, miR-210 was induced by hypoxia, whereas ISCU expression was decreased. The luciferase assay confirmed miR-210 binding to ISCU mRNA 3′ UTR. RNA interference knockdown of ISCU expression in Swan 71, but not in BeWo, cells resulted in autophagosomal and siderosomal iron accumulation and a fourfold decrease of Matrigel invasion (P = 0.004). Placental ISCU expression was decreased in preeclampsia (P = 0.002) and SGA (P = 0.002) cases. Furthermore, hemosiderin-laden trophoblasts were more frequent in the placental bed of preterm preeclampsia and/or SGA births than in control cases (48.7% versus 17.9%; P = 0.004). Siderosis of interstitial trophoblasts is a novel pathological feature of preeclampsia and SGA. The findings herein suggest that ISCU down-regulation by miR-210 perturbing trophoblast iron metabolism is associated with defective placentation. PMID:21801864

  5. Effect of sulfur addition and heat treatment on electrical conductivity of barium vanadate glasses containing iron

    Energy Technology Data Exchange (ETDEWEB)

    Hassaan, M.Y., E-mail: myhassaan@yahoo.com [Al-Azhar University, Faculty of Science, Physics Department, 11884 Cairo (Egypt); Ebrahim, F.M.; Mostafa, A.G. [Al-Azhar University, Faculty of Science, Physics Department, 11884 Cairo (Egypt); El-Desoky, M.M., E-mail: mmdesoky@gmail.com [Suez Canal University, Faculty of Science, Physics Department, Suez (Egypt)

    2011-09-15

    Highlights: {yields} Selected glasses of V{sub 2}O{sub 5}-BaO-5Fe{sub 2}O{sub 3} system have been transformed into nanomaterials by annealing at temperature close to crystallization temperature (T{sub c}) for 1 h. {yields} Glass ceramic nanocrystals are important because of their physical properties which are not obtainable in other classes of materials. {yields} Crystal and grain sizes are the most significant structural parameters in electronic nanocrystalline glassy phases. {yields} These phases have very high electrical conductivity, hence glass-ceramic nanocrystals are expected to be used, for example, as a gas sensor. - Abstract: Six glass samples with a composition of 75V{sub 2}O{sub 5} + 10BaO + 15Fe{sub 2}O{sub 3} mol%, with 0, 10, 15, 20, and 25 wt% of sulfur were prepared by using a quenching method. The samples were measured by XRD, DSC, TEM, Moessbauer spectrometry and D.C. conductivity. The prepared samples were heat treated at temperature close to their crystallization temperatures for 1 h, and then the previous measurements were repeated. The results showed that the treatment process caused the formation of V{sub 2}O{sub 5} and FeVO{sub 4} nanocrystals with size of 17-25 nm dispersed in the glass matrix. The addition of sulfur reduced only the vanadium ions to V{sup 4+}, while it was found that iron ions were Fe{sup 3+} only. D.C. conduction enhanced due to the small polaron or electron hopping from V{sup 4+} to V{sup 5+} ions. The heat treated samples exhibit much higher conductivity and much lower activation energy than the as-prepared glasses. The heat treated samples showed decreased thermal stability with the addition of sulfur. This considerable enhancement of electrical conductivity after nanocrystallization referred to the formation of extensive and dense network of electronic conduction paths which are situated between V{sub 2}O{sub 5} nanocrystals and their surfaces.

  6. Coupled Iron and Sulfur Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State

    Science.gov (United States)

    Rouxel, O. J.; Bekker, A.

    2009-05-01

    The rise of atmospheric oxygen level by ca. 2.3 Ga have led to dramatic shifts in the iron and sulfur oceanic cycles. Past studies of non-mass dependent and mass dependent sulfur isotope record in sedimentary sulfides over geological time have placed important constraints on biogeochemical cycle of sulfur and evolution of Precambrian ocean chemistry. Recently, we applied a similar time-record approach to explore potential changes in Fe isotope composition of pyrite in black shales. Although the underlying mechanisms for Fe isotope fractionation in organic-rich sediments are debated, we identified direct link between the rise of atmospheric oxygen and changes in the Fe ocean cycle suggesting that Fe isotopes are useful proxies to the past ocean redox state. Since biogeochemical cycles of Fe and S are closely coupled in marine systems, Fe-limitation and S-limitation for pyrite formation in black shales should leave imprint on the isotopic record of both elements. Coupled Fe and S isotope systematics of Devonian pyrite display a range of 50‰ in δ34S values whereas δ56Fe values vary between - 1.0 and +0.1‰ consistent with Fe isotope variations in modern marine sediments. Similarly, pyrite in the 1.88 Ga Gunflint Formation has δ34S values ranging from - 32‰ to +10‰ and displays a range of δ56Fe values between 0 to - 0.4‰. In contrast, Archean black shales (e.g. Manjeri Fm., Belingwe Belt and Jeerinah Fm., Hamersley Basin) display a smaller range of δ34S values between together with ubiquitous non-mass dependent S-isotope fractionation but a larger range of δ56Fe values from - 3.5 to +0.2‰. A transitional period between ca. 2.3 and ca. 1.8 Ga is marked by a larger spread of δ34S values from - 34 to +28‰, disappearance of MIF and a larger range of δ56Fe values from - 1.7 to +1.1‰. These results confirm that after the rise of atmospheric oxygen by ca. 2.3 Ga, Paleoproterozoic ocean became stratified and gradually affected by an increase of seawater

  7. Ferrous iron oxidation by sulfur-oxidizing Acidithiobacillus ferrooxidans and analysis of the process at the levels of transcription and protein synthesis.

    Science.gov (United States)

    Kucera, Jiri; Bouchal, Pavel; Lochman, Jan; Potesil, David; Janiczek, Oldrich; Zdrahal, Zbynek; Mandl, Martin

    2013-04-01

    In contrast to iron-oxidizing Acidithiobacillus ferrooxidans, A. ferrooxidans from a stationary phase elemental sulfur-oxidizing culture exhibited a lag phase in pyrite oxidation, which is similar to its behaviour during ferrous iron oxidation. The ability of elemental sulfur-oxidizing A. ferrooxidans to immediately oxidize ferrous iron or pyrite without a lag phase was only observed in bacteria obtained from growing cultures with elemental sulfur. However, these cultures that shifted to ferrous iron oxidation showed a low rate of ferrous iron oxidation while no growth was observed. Two-dimensional gel electrophoresis was used for a quantitative proteomic analysis of the adaptation process when bacteria were switched from elemental sulfur to ferrous iron. A comparison of total cell lysates revealed 39 proteins whose increase or decrease in abundance was related to this phenotypic switching. However, only a few proteins were closely related to iron and sulfur metabolism. Reverse-transcription quantitative PCR was used to further characterize the bacterial adaptation process. The expression profiles of selected genes primarily involved in the ferrous iron oxidation indicated that phenotypic switching is a complex process that includes the activation of genes encoding a membrane protein, maturation proteins, electron transport proteins and their regulators.

  8. Table of interplanar spacings for crystal-structure determinations by X-ray diffraction with molybdenum, copper, cobalt, iron, and chromium radiations

    Science.gov (United States)

    Kittel, J Howard

    1945-01-01

    For a simple diffraction pattern, the time required to calculate interplanar distances from measurements of the pattern is not excessive. If more than a few lines are present, however, or if several patterns are to be studied, it is very advantageous to have available a table giving interplanar spacings directly in terms of the linear measurements made on the film of the lines appearing on the diffraction pattern. The preparation of the table given here was undertaken when the expansion of research activities involving X-ray diffraction techniques indicated that such a table would greatly decrease the time required to analyze diffraction patterns. The table was prepared for use with K alpha(sub 1) radiation from the following target materials: molybdenum, copper, cobalt, iron, and chromium.

  9. Determination of tin, vanadium, iron, and molybdenum in various matrices by atomic absorption spectrometry using a simultaneous liquid-liquid extraction procedure.

    Science.gov (United States)

    Sánchez-Viñas, M; Bagur, G M; Gázquez, D; Camino, M; Romero, R

    1999-01-01

    An atomic-absorption spectrometric method is described for the determination of tin, vanadium, iron, and molybdenum in two certified reference materials, food samples, and petroleum crude. After treatment with acids, these elements are separated from matrix elements by simultaneous solvent extraction of 5,5'-methylenedisalicylohydroxamic acid complexes from HCl/NaClO4 solution into an isobutyl methyl ketone/tributyl phosphate solution. The detection limits range from 0.018 to 0.19 microg/mL (n = 3), and the relative standard deviations do not exceed 2.0% at levels of 0.5, 0.6, 2.0, and 7.0 microg/mL of Fe, Mo, V, and Sn, respectively. The method is selective and suffers only from interference by Zr(IV), Ti(IV), Th(IV), W(VI), PO4(3-), and F-.

  10. Comparative study of reactions between µ-nitrido- or µ-oxo-bridged iron tetrasulfophthalocyanines and sulfur-containing reductants

    Directory of Open Access Journals (Sweden)

    Dereven’kov Ilia A.

    2013-01-01

    Full Text Available A comparative study of reactivity of μ-nitrido- and μ-oxo-dimers of iron tetrasulfophthalocyanine has been performed in aqueous solutions of various acidity. The substantially higher stability of nitrido-bridged structure under both strongly acidic and strongly alkaline environments was demonstrated. Reactions of the complexes with sulfur-containing reductants (sodium dithionite, thiourea dioxide, sodium hydroxymethanesulfinate, L-cysteine has been studied. Differences in reduction processes were explained.

  11. Biochemical analysis of essential components involved in mitochondrial and cytosolic iron-sulfur protein biogenesis in Saccharomyces cerevisiae

    OpenAIRE

    Urzica, Eugen

    2007-01-01

    Iron-sulfur (Fe/S) clusters are inorganic cofactors of many proteins found in nearly all prokaryotic and eukaryotic organisms. Fe/S proteins play important roles in different cellular processes, such as electron transport, enzyme catalysis or gene regulation. Eukaryotes contain Fe/S proteins in mitochondria, chloroplasts, cytosol and nucleus. In S. cerevisiae 3 different machineries cooperate to synthesise Fe/S proteins. ...

  12. The chloroplast NifS-like protein of Arabidopsis thaliana is required for iron-sulfur cluster formation in ferredoxin.

    Science.gov (United States)

    Ye, Hong; Garifullina, Gulnara F; Abdel-Ghany, Salah E; Zhang, Lihong; Pilon-Smits, Elizabeth A H; Pilon, Marinus

    2005-02-01

    Plastids are known to be able to synthesize their own iron-sulfur clusters, but the biochemical machinery responsible for this process is not known. In this study it is investigated whether CpNifS, the chloroplastic NifS-like cysteine desulfurase of Arabidopsis thaliana (L.) Heynh. is responsible for the release of sulfur from cysteine for the biogenesis of iron-sulfur (Fe-S) clusters in chloroplasts. Using an in vitro reconstitution assay it was found that purified CpNifS was sufficient for Fe-S cluster formation in ferredoxin in the presence of cysteine and a ferrous iron salt. Antibody-depletion experiments using stromal extract showed that CpNifS is also essential for the Fe-S cluster formation activity of chloroplast stroma. The activity of CpNifS in the stroma was 50- to 80-fold higher than that of purified CpNifS on a per-protein basis, indicating that other stromal factors cooperate in Fe-S cluster formation. When stromal extract was separated on a gel-filtration column, most of the CpNifS eluted as a dimer of 86 kDa, but a minor fraction of the stromal CpNifS eluted at a molecular weight of approx. 600 kDa, suggesting the presence of a multi-protein complex. The possible nature of the interacting proteins is discussed.

  13. Mitochondrial Bol1 and Bol3 function as assembly factors for specific iron-sulfur proteins

    Science.gov (United States)

    Uzarska, Marta A; Nasta, Veronica; Weiler, Benjamin D; Spantgar, Farah; Ciofi-Baffoni, Simone; Saviello, Maria Rosaria; Gonnelli, Leonardo; Mühlenhoff, Ulrich; Banci, Lucia; Lill, Roland

    2016-01-01

    Assembly of mitochondrial iron-sulfur (Fe/S) proteins is a key process of cells, and defects cause many rare diseases. In the first phase of this pathway, ten Fe/S cluster (ISC) assembly components synthesize and insert [2Fe-2S] clusters. The second phase is dedicated to the assembly of [4Fe-4S] proteins, yet this part is poorly understood. Here, we characterize the BOLA family proteins Bol1 and Bol3 as specific mitochondrial ISC assembly factors that facilitate [4Fe-4S] cluster insertion into a subset of mitochondrial proteins such as lipoate synthase and succinate dehydrogenase. Bol1-Bol3 perform largely overlapping functions, yet cannot replace the ISC protein Nfu1 that also participates in this phase of Fe/S protein biogenesis. Bol1 and Bol3 form dimeric complexes with both monothiol glutaredoxin Grx5 and Nfu1. Complex formation differentially influences the stability of the Grx5-Bol-shared Fe/S clusters. Our findings provide the biochemical basis for explaining the pathological phenotypes of patients with mutations in BOLA3. DOI: http://dx.doi.org/10.7554/eLife.16673.001 PMID:27532772

  14. The multitude of iron-sulfur clusters in respiratory complex I.

    Science.gov (United States)

    Gnandt, Emmanuel; Dörner, Katerina; Strampraad, Marc F J; de Vries, Simon; Friedrich, Thorsten

    2016-08-01

    Respiratory complex I couples the electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. Complex I contains one non-covalently bound flavin mononucleotide and, depending on the species, up to ten iron-sulfur (Fe/S) clusters as cofactors. The reason for the presence of the multitude of Fe/S clusters in complex I remained enigmatic for a long time. The question was partly answered by investigations on the evolution of the complex revealing the stepwise construction of the electron transfer domain from several modules. Extension of the ancestral to the modern electron input domain was associated with the acquisition of several Fe/S-proteins. The X-ray structure of the complex showed that the NADH oxidation-site is connected with the quinone-reduction site by a chain of seven Fe/S-clusters. Fast enzyme kinetics revealed that this chain of Fe/S-clusters is used to regulate electron-tunneling rates within the complex. A possible function of the off-pathway cluster N1a is discussed. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.

  15. Mitochondrial iron-sulfur cluster biogenesis from molecular understanding to clinical disease.

    Science.gov (United States)

    Alfadhel, Majid; Nashabat, Marwan; Abu Ali, Qais; Hundallah, Khalid

    2017-01-01

    Iron_sulfur clusters (ISCs) are known to play a major role in various protein functions. Located in the mitochondria, cytosol, endoplasmic reticulum and nucleus, they contribute to various core cellular functions. Until recently, only a few human diseases related to mitochondrial ISC biogenesis defects have been described. Such diseases include Friedreich ataxia, combined oxidative phosphorylation deficiency 19, infantile complex II/III deficiency defect, hereditary myopathy with lactic acidosis and mitochondrial muscle myopathy, lipoic acid biosynthesis defects, multiple mitochondrial dysfunctions syndromes and non ketotic hyperglycinemia due to glutaredoxin 5 gene defect. Disorders of mitochondrial import, export and translation, including sideroblastic anemia with ataxia, EVEN-PLUS syndrome and mitochondrial complex I deficiency due to nucleotide-binding protein-like protein gene defect, have also been implicated in ISC biogenesis defects. With advances in next generation sequencing technologies, more disorders related to ISC biogenesis defects are expected to be elucidated. In this article, we aim to shed the light on mitochondrial ISC biogenesis, related proteins and their function, pathophysiology, clinical phenotypes of related disorders, diagnostic approach, and future implications.

  16. Role of IscX in Iron-Sulfur Cluster Biogenesis in Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Hae; Bothe, Jameson R.; Frederick, Ronnie O.; Holder, Johneisa C.; Markley, John L. [UW

    2014-08-20

    The Escherichia coli isc operon encodes key proteins involved in the biosynthesis of iron–sulfur (Fe–S) clusters. Whereas extensive studies of most ISC proteins have revealed their functional properties, the role of IscX (also dubbed YfhJ), a small acidic protein encoded by the last gene in the operon, has remained in question. Previous studies showed that IscX binds iron ions and interacts with the cysteine desulfurase (IscS) and the scaffold protein for cluster assembly (IscU), and it has been proposed that IscX functions either as an iron supplier or a regulator of Fe–S cluster biogenesis. We have used a combination of NMR spectroscopy, small-angle X-ray scattering (SAXS), chemical cross-linking, and enzymatic assays to enlarge our understanding of the interactions of IscX with iron ions, IscU, and IscS. We used chemical shift perturbation to identify the binding interfaces of IscX and IscU in their complex. NMR studies showed that Fe2+ from added ferrous ammonium sulfate binds IscX much more avidly than does Fe3+ from added ferric ammonium citrate and that Fe2+ strengthens the interaction between IscX and IscU. We found that the addition of IscX to the IscU–IscS binary complex led to the formation of a ternary complex with reduced cysteine desulfurase activity, and we determined a low-resolution model for that complex from a combination of NMR and SAXS data. We postulate that the inhibition of cysteine desulfurase activity by IscX serves to reduce unproductive conversion of cysteine to alanine. By incorporating these new findings with results from prior studies, we propose a detailed mechanism for Fe–S cluster assembly in which IscX serves both as a donor of Fe2+ and as a regulator of cysteine desulfurase activity.

  17. Modelling phosphorus (P), sulfur (S) and iron (Fe) interactions for dynamic simulations of anaerobic digestion processes.

    Science.gov (United States)

    Flores-Alsina, Xavier; Solon, Kimberly; Kazadi Mbamba, Christian; Tait, Stephan; Gernaey, Krist V; Jeppsson, Ulf; Batstone, Damien J

    2016-05-15

    This paper proposes a series of extensions to functionally upgrade the IWA Anaerobic Digestion Model No. 1 (ADM1) to allow for plant-wide phosphorus (P) simulation. The close interplay between the P, sulfur (S) and iron (Fe) cycles requires a substantial (and unavoidable) increase in model complexity due to the involved three-phase physico-chemical and biological transformations. The ADM1 version, implemented in the plant-wide context provided by the Benchmark Simulation Model No. 2 (BSM2), is used as the basic platform (A0). Three different model extensions (A1, A2, A3) are implemented, simulated and evaluated. The first extension (A1) considers P transformations by accounting for the kinetic decay of polyphosphates (XPP) and potential uptake of volatile fatty acids (VFA) to produce polyhydroxyalkanoates (XPHA) by phosphorus accumulating organisms (XPAO). Two variant extensions (A2,1/A2,2) describe biological production of sulfides (SIS) by means of sulfate reducing bacteria (XSRB) utilising hydrogen only (autolithotrophically) or hydrogen plus organic acids (heterorganotrophically) as electron sources, respectively. These two approaches also consider a potential hydrogen sulfide ( [Formula: see text] inhibition effect and stripping to the gas phase ( [Formula: see text] ). The third extension (A3) accounts for chemical iron (III) ( [Formula: see text] ) reduction to iron (II) ( [Formula: see text] ) using hydrogen ( [Formula: see text] ) and sulfides (SIS) as electron donors. A set of pre/post interfaces between the Activated Sludge Model No. 2d (ASM2d) and ADM1 are furthermore proposed in order to allow for plant-wide (model-based) analysis and study of the interactions between the water and sludge lines. Simulation (A1 - A3) results show that the ratio between soluble/particulate P compounds strongly depends on the pH and cationic load, which determines the capacity to form (or not) precipitation products. Implementations A1 and A2,1/A2,2 lead to a reduction in

  18. Molten iron oxysulfide as a superior sulfur sorbent. Technical progress report, December 1, 1991--February 29, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Hepworth, M.T.

    1992-02-28

    Slagging combustors with injected lime or limestone are being considered as replacements for conventional coal burners. They have advantages in that they can be staged to reduce NO{sub x} and SO{sub x} emissions. Iron oxide, as an alternative to lime or limestone may be effective not only as a desulfurizing agent, but under the right conditions of oxygen potential and after combination with sulfur, the reaction products of coal gases with iron oxide can act as a flux to produce a fluid phase. The thermodynamic conditions for optimum removal of sulfur from the first stage of a coal combustor are being determined by experiment and by use of existing data. Analysis of the phase equilibria indicates that optimum conditions for deployment of the reducing stage of a multi-stage, burner operating with iron injection are close to the boundary of the liquid iron oxysulfide phase with iron-saturation. Two prior investigations differ with respect to the location of this phase boundary at temperatures over 1400{degree}C: with reference 1, showing the phase boundary nearer the iron-rich corner than reference 2 which gives the boundary further into the liquid region. In this quarter experimental studies were conducted on equilibrium compositions which are the most effective in achieving desulfurization. These conditions were studied by thermogravimetric analysis (TGA). They serve to check the data reported by the two above-reference investigations for their experimental conditions of 1200{degree}C, and also to check extend the data given in the literature to a temperature of 1300{degree}C. The model used for this interpolation was reported upon in the prior quarterly report (9/1/91-11/30/92 Appendix A).

  19. Siliconizing of iron and molybdenum by electrochemical reduction of silicon in molten SiO{sub 2}–Li{sub 2}O–MgO

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Hideaki, E-mail: hideakis@iis.u-tokyo.ac.jp; Maeda, Masafumi

    2015-08-25

    Highlights: • Silicon in molten silicate was reduced electrochemically on metal electrodes. • Potentials of Fe and Mo electrodes were controlled in SiO{sub 2}–Li{sub 2}O–MgO at 1273 K. • Formation of a Si-containing layer was observed on Fe, depending on the potential. • MoSi{sub 2} layer was formed on the surface of the Mo electrode. - Abstract: Electrochemical reduction of silicon on metal electrodes in molten silicate was studied. An iron sheet was immersed in SiO{sub 2}–Li{sub 2}O–MgO at 1273 K, and the electrode potential was controlled for 1 h. Formation on the iron of a Si-containing layer about 10–30 μm thick was observed after the electrolysis, depending on the potential. When a molybdenum electrode was used, α-MoSi{sub 2} layer about 5 μm thick was formed on the surface. The results suggest the applicability of molten oxide electrolysis as a synthesis method of Si-containing alloy layers.

  20. Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H2O2, O3 and iron catalysis

    Directory of Open Access Journals (Sweden)

    J. N. Crowley

    2012-01-01

    Full Text Available The oxidation of SO2 to sulfate is a key reaction in determining the role of sulfate in the environment through its effect on aerosol size distribution and composition. Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sulfate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in major transformation pathways. This paper presents laboratory measurements of the fractionation factors for the major atmospheric oxidation reactions for SO2: Gas-phase oxidation by OH radicals, and aqueous oxidation by H2O2, O3 and a radical chain reaction initiated by iron. The measured fractionation factor for 34S/32S during the gas-phase reaction is αOH = (1.0089±0.0007−((4±5×10−5 T(°C. The measured fractionation factor for 34S/32S during aqueous oxidation by H2O2 or O3 is αaq = (1.0167±0.0019−((8.7±3.5 ×10−5T(°C. The observed fractionation during oxidation by H2O2 and O3 appeared to be controlled primarily by protonation and acid-base equilibria of S(IV in solution, which is the reason that there is no significant difference between the fractionation produced by the two oxidants within the experimental error. The isotopic fractionation factor from a radical chain reaction in solution catalysed by iron is αFe = (0.9894±0.0043 at 19 °C for 34S/32S. Fractionation was mass-dependent with regards to 33S/32S for all the reactions investigated. The radical chain reaction mechanism was the only measured reaction that had a faster rate for the light isotopes. The results presented in this study will be particularly useful to determine the importance of the transition metal-catalysed oxidation pathway compared to other oxidation pathways, but other main oxidation pathways can not be distinguished based on stable sulfur isotope measurements alone.

  1. Abundant iron and sulfur oxidizers in the stratified sediment of a eutrophic freshwater reservoir with annual cyanobacterial blooms

    Science.gov (United States)

    Jin, Long; Lee, Chang Soo; Ahn, Chi-Yong; Lee, Hyung-Gwan; Lee, Sanghyup; Shin, Hyeon Ho; Lim, Dhongil; Oh, Hee-Mock

    2017-03-01

    The microbial community in eutrophic freshwater sediment was investigated from a 67-cm-deep sediment core collected from the Daechung Reservoir in South Korea, where cyanobacterial blooms have occurred annually for the past 30 years. The majority of core sediments were characterized by dark-grayish, fine-grained mud with abundant gas-escaped and thinly laminated layers. Intervals of summer and winter seasons were represented by periodic peaks of geochemical profiles of parameters such as grain size and relative carbon mass ratios to various nutrients such as nitrogen, sulfur, and phosphorus. In bacteria, Proteobacteria (66.6%) was the most prevalent phylum, followed by Chloroflexi (8.9%), Bacteroidetes (5.1%), and Spirochaetes (2.6%). Archaea were also abundant, representing approximately half of the total prokaryotes in the sediments. Notably, three Bacteria (Sulfuricurvum, Sideroxydans, and Gallionella) and one Archaea (Thermoplasmata) accounted for 43.4% and 38.4% of the total bacteria and archaea, respectively, implying that iron and sulfur oxidizing microorganisms dominate in this eutrophic freshwater sediment. These results indicate that 1) eutrophic freshwater lakes in monsoon climates undergo a stratified sedimentary process with seasonal and annual variations in geochemical and microbial profiles, and 2) the microbial oxidative metabolism of iron and sulfur is notably active in sediments from a eutrophic lake.

  2. Mutation of the iron-sulfur cluster assembly gene IBA57 causes fatal infantile leukodystrophy.

    Science.gov (United States)

    Debray, François-Guillaume; Stümpfig, Claudia; Vanlander, Arnaud V; Dideberg, Vinciane; Josse, Claire; Caberg, Jean-Hubert; Boemer, François; Bours, Vincent; Stevens, René; Seneca, Sara; Smet, Joél; Lill, Roland; van Coster, Rudy

    2015-11-01

    Leukodystrophies are a heterogeneous group of severe genetic neurodegenerative disorders. A multiple mitochondrial dysfunctions syndrome was found in an infant presenting with a progressive leukoencephalopathy. Homozygosity mapping, whole exome sequencing, and functional studies were used to define the underlying molecular defect. Respiratory chain studies in skeletal muscle isolated from the proband revealed a combined deficiency of complexes I and II. In addition, western blotting indicated lack of protein lipoylation. The combination of these findings was suggestive for a defect in the iron-sulfur (Fe/S) protein assembly pathway. SNP array identified loss of heterozygosity in large chromosomal regions, covering the NFU1 and BOLA3, and the IBA57 and ABCB10 candidate genes, in 2p15-p11.2 and 1q31.1-q42.13, respectively. A homozygous c.436C > T (p.Arg146Trp) variant was detected in IBA57 using whole exome sequencing. Complementation studies in a HeLa cell line depleted for IBA57 showed that the mutant protein with the semi-conservative amino acid exchange was unable to restore the biochemical phenotype indicating a loss-of-function mutation of IBA57. In conclusion, defects in the Fe/S protein assembly gene IBA57 can cause autosomal recessive neurodegeneration associated with progressive leukodystrophy and fatal outcome at young age. In the affected patient, the biochemical phenotype was characterized by a defect in the respiratory chain complexes I and II and a decrease in mitochondrial protein lipoylation, both resulting from impaired assembly of Fe/S clusters.

  3. Microbial transformations of nitrogen, sulfur and iron dictate vegetation composition in wetlands: a review

    Directory of Open Access Journals (Sweden)

    Leon P.M. Lamers

    2012-04-01

    Full Text Available The majority of studies on rhizospheric interactions between microbial communities and vegetation focus on pathogens, mycorrhizal symbiosis, and/or carbon transformations. Although the biogeochemical transformations of nitrogen (N, sulfur (S and iron (Fe have profound effects on plants, these effects have received far less attention. Firstly, all three elements are plant nutrients, and microbial activity significantly changes their mobility and availability. Secondly, microbial oxidation with oxygen supplied by radial oxygen loss (ROL from roots in wetlands causes acidification, while reduction using alternative electron acceptors leads to generation of alkalinity, affecting pH in the rhizosphere and hence plant composition. Thirdly, reduced species of all three elements may become phytotoxic. In addition, Fe cycling is tightly linked to that of S and phosphorus (P. As water level fluctuations are very common in wetlands, rapid changes in the availability of oxygen and alternative terminal electron acceptors will result in strong changes in the prevalent microbial redox reactions, with significant effects on plant growth. Depending on geological and hydrological settings, these interacting microbial transformations change the conditions and resource availability for plants, which are strong drivers of vegetation development and composition by changing relative competitive strengths. Conversely, microbial composition is strongly driven by vegetation composition. Therefore, the combination of micro- and macroecological knowledge is essential to understand the biogeochemical and biological key factors driving heterogeneity and total (i.e., micro-macro community composition at different spatial and temporal scales. As N and S inputs have drastically increased due to anthropogenic forcing and Fe inputs have decreased at a global scale, this combined approach has become even more urgent.

  4. Lunar sulfur

    Science.gov (United States)

    Kuck, David L.

    Ideas introduced by Vaniman, Pettit and Heiken in their 1988 Uses of Lunar Sulfur are expanded. Particular attention is given to uses of SO2 as a mineral-dressing fluid. Also introduced is the concept of using sulfide-based concrete as an alternative to the sulfur-based concretes proposed by Leonard and Johnson. Sulfur is abundant in high-Ti mare basalts, which range from 0.16 to 0.27 pct. by weight. Terrestrial basalts with 0.15 pct. S are rare. For oxygen recovery, sulfur must be driven off with other volatiles from ilmenite concentrates, before reduction. Troilite (FeS) may be oxidized to magnetite (Fe3O4) and SO2 gas, by burning concentrates in oxygen within a magnetic field, to further oxidize ilmenite before regrinding the magnetic reconcentration. SO2 is liquid at -20 C, the mean temperature underground on the Moon, at a minimum of 0.6 atm pressure. By using liquid SO2 as a mineral dressing fluid, all the techniques of terrestrial mineral separation become available for lunar ores and concentrates. Combination of sulfur and iron in an exothermic reaction, to form iron sulfides, may be used to cement grains of other minerals into an anhydrous iron-sulfide concrete. A sulfur-iron-aggregate mixture may be heated to the ignition temperature of iron with sulfur to make a concrete shape. The best iron, sulfur, and aggregate ratios need to be experimentally established. The iron and sulfur will be by-products of oxygen production from lunar minerals.

  5. Selective catalytic reduction of sulfur dioxide by carbon monoxide over iron oxide supported on activated carbon

    OpenAIRE

    2014-01-01

    The selective reduction of sulfur dioxide with carbon monoxide to elemental sulfur was studied over AC-supported transition-metal oxide catalysts. According to the study, Fe2O3/AC was the most active catalyst among the 4 AC-supported catalysts tested. By using Fe2O3/AC, the best catalyst, when the feed conditions were properly optimized (CO/SO2 molar ratio = 2:1; sulfidation temperature, 400 °C; Fe content, 20 wt%; GHSV = 7000 mL g-1 h-1), 95.43% sulfur dioxide conversion and 86.59% sulfur yi...

  6. An Innovative Approach to Separate Iron Oxide Concentrate from High-sulfur and Low-grade Pyrite Cinders

    Institute of Scientific and Technical Information of China (English)

    Yong LI; Fu-chun ZHOU; Zhao-xin ZHOU; Zhi-han TIAN; Chao YANG; Xi-ke TIAN

    2016-01-01

    High-sulfur and low-grade pyrite cinders are the waste products of sulfuric acid manufacturing plants. Many valuable components,such as iron oxide,are contained in pyrite cinders and difficult to be separated and puri-fied j ust via the high temperature roasting process.Considering this,an innovative method including water-washing, aqua regia leaching,hydrothermal alkali activation and acid-washing was developed.And the effects of different pa-rameters on recovery efficiency of iron oxide were systematically investigated.The optimum parameters were pro-posed as follows:water rinse-leaching at room temperature for 5-20 min,and melting at 160 ℃ for 2.0 h with NaOH (concentration of 30 mass%),followed by leaching with aqua regia solution (3.0 vol.%)for 1.0 h.After the treatment,the content of iron oxides increased from 54.3 to 96.0 mass% with the recovery rate exceeding 85%. Meanwhile,calcium sulphate was recovered as the high value-added products by alkali extraction liquid.Further-more,the phase transformation and microstructure of the samples in the process were studied by physicochemical methods to reveal the separation mechanisms of different components in the pyrite cinders.

  7. Metal mobilization by iron- and sulfur-oxidizing bacteria in a multiple extreme mine tailings in the Atacama Desert, Chile.

    Science.gov (United States)

    Korehi, H; Blöthe, M; Sitnikova, M A; Dold, B; Schippers, A

    2013-03-05

    The marine shore sulfidic mine tailings dump at the Chañaral Bay in the Atacama Desert, northern Chile, is characterized by extreme acidity, high salinity, and high heavy metals concentrations. Due to pyrite oxidation, metals (especially copper) are mobilized under acidic conditions and transported toward the tailings surface and precipitate as secondary minerals (Dold, Environ. Sci. Technol. 2006, 40, 752-758.). Depth profiles of total cell counts in this almost organic-carbon free multiple extreme environment showed variable numbers with up to 10(8) cells g(-1) dry weight for 50 samples at four sites. Real-time PCR quantification and bacterial 16S rRNA gene diversity analysis via clone libraries revealed a dominance of Bacteria over Archaea and the frequent occurrence of the acidophilic iron(II)- and sulfur-oxidizing and iron(III)-reducing genera Acidithiobacillus, Alicyclobacillus, and Sulfobacillus. Acidophilic chemolithoautotrophic iron(II)-oxidizing bacteria were also frequently found via most-probable-number (MPN) cultivation. Halotolerant iron(II)-oxidizers in enrichment cultures were active at NaCl concentrations up to 1 M. Maximal microcalorimetrically determined pyrite oxidation rates coincided with maxima of the pyrite content, total cell counts, and MPN of iron(II)-oxidizers. These findings indicate that microbial pyrite oxidation and metal mobilization preferentially occur in distinct tailings layers at high salinity. Microorganisms for biomining with seawater salt concentrations obviously exist in nature.

  8. The role of mitochondria and the CIA machinery in the maturation of cytosolic and nuclear iron-sulfur proteins.

    Science.gov (United States)

    Lill, Roland; Dutkiewicz, Rafal; Freibert, Sven A; Heidenreich, Torsten; Mascarenhas, Judita; Netz, Daili J; Paul, Viktoria D; Pierik, Antonio J; Richter, Nadine; Stümpfig, Martin; Srinivasan, Vasundara; Stehling, Oliver; Mühlenhoff, Ulrich

    2015-01-01

    Mitochondria have been derived from alpha-bacterial endosymbionts during the evolution of eukaryotes. Numerous bacterial functions have been maintained inside the organelles including fatty acid degradation, citric acid cycle, oxidative phosphorylation, and the synthesis of heme or lipoic acid cofactors. Additionally, mitochondria have inherited the bacterial iron-sulfur cluster assembly (ISC) machinery. Many of the ISC components are essential for cell viability because they generate a still unknown, sulfur-containing compound for the assembly of cytosolic and nuclear Fe/S proteins that perform important functions in, e.g., protein translation, DNA synthesis and repair, and chromosome segregation. The sulfur-containing compound is exported by the mitochondrial ABC transporter Atm1 (human ABCB7) and utilized by components of the cytosolic iron-sulfur protein assembly (CIA) machinery. An appealing minimal model for the striking compartmentation of eukaryotic Fe/S protein biogenesis is provided by organisms that contain mitosomes instead of mitochondria. Mitosomes have been derived from mitochondria by reductive evolution, during which they have lost virtually all classical mitochondrial tasks. Nevertheless, mitosomes harbor all core ISC components which presumably have been maintained for assisting the maturation of cytosolic-nuclear Fe/S proteins. The current review is centered around the Atm1 export process. We present an overview on the mitochondrial requirements for the export reaction, summarize recent insights into the 3D structure and potential mechanism of Atm1, and explain how the CIA machinery uses the mitochondrial export product for the assembly of cytosolic and nuclear Fe/S proteins.

  9. MicroRNA-210 Controls Mitochondrial Metabolism during Hypoxia by Repressing the Iron-Sulfur Cluster Assembly Proteins ISCU1/2

    Science.gov (United States)

    Chan, Stephen Y.; Zhang, Ying-Yi; Hemann, Craig; Mahoney, Christopher E.; Zweier, Jay L.; Loscalzo, Joseph

    2009-01-01

    Summary Repression of mitochondrial respiration represents an evolutionarily ancient cellular adaptation to hypoxia and profoundly influences cell survival and function; however, the underlying molecular mechanisms are incompletely understood. Primarily utilizing pulmonary arterial endothelial cells as a representative hypoxic cell type, we identify the iron-sulfur cluster assembly proteins (ISCU1/2) as direct targets for repression by the hypoxia-induced microRNA-210 (miR-210). ISCU1/2 facilitate the assembly of iron-sulfur clusters, prosthetic groups that are critical for electron transport and mitochondrial oxidation-reduction reactions. Under in vivo conditions of up-regulating miR-210 and repressing ISCU1/2, the integrity of iron-sulfur clusters is disrupted. In turn, by repressing ISCU1/2 during hypoxia, miR-210 decreases the activity of prototypical iron-sulfur proteins controlling mitochondrial metabolism, including Complex I and aconitase. Consequently, miR-210 represses mitochondrial respiration and associated downstream functions. These results identify important mechanistic connections among microRNA, iron-sulfur cluster biology, hypoxia, and mitochondrial function, with broad implications for cellular metabolism and adaptation to cellular stress. PMID:19808020

  10. Sulfur and iron accumulation in three marine-archaeological shipwrecks in the Baltic Sea: The Ghost, the Crown and the Sword

    Science.gov (United States)

    Fors, Yvonne; Grudd, Håkan; Rindby, Anders; Jalilehvand, Farideh; Sandström, Magnus; Cato, Ingemar; Bornmalm, Lennart

    2014-02-01

    Sulfur and iron concentrations in wood from three 17th century shipwrecks in the Baltic Sea, the Ghost wreck, the Crown and the Sword, were obtained by X-ray fluorescence (XRF) scanning. In near anaerobic environments symbiotic microorganisms degrade waterlogged wood, reduce sulfate and promote accumulation of low-valent sulfur compounds, as previously found for the famous wrecks of the Vasa and Mary Rose. Sulfur K-edge X-ray absorption near-edge structure (XANES) analyses of Ghost wreck wood show that organic thiols and disulfides dominate, together with elemental sulfur probably generated by sulfur-oxidizing Beggiatoa bacteria. Iron sulfides were not detected, consistent with the relatively low iron concentration in the wood. In a museum climate with high atmospheric humidity oxidation processes, especially of iron sulfides formed in the presence of corroding iron, may induce post-conservation wood degradation. Subject to more general confirmation by further analyses no severe conservation concerns are expected for the Ghost wreck wood.

  11. The involvement of molybdenum in life.

    Science.gov (United States)

    Williams, R J P; Fraústo da Silva, J J R

    2002-03-29

    Quite extraordinarily molybdenum is an essential element in life for the uptake of nitrogen from both nitrogen gas and nitrate, yet it is a relatively rare heavy trace element. It also functions in a few extremely important oxygen-atom transfer reactions at low redox potential. This review poses the question "Why does life depend upon molybdenum?" The answer has to be based upon the availability of the element and on chemical superiority in carrying out the essential tasks. We illustrate here the peculiarities of molybdenum chemistry and how they have become part of certain enzymes. The uptake and incorporation of molybdenum are dependent on its availability, selective pumps, and carriers (chaperones), but 4.5 x 10(9) years ago molybdenum was not available when both tungsten and vanadium or even iron were possibly used in its place. While these possibilities are explored, they leave many unanswered questions concerning the selection today of molybdenum. (c)2002 Elsevier Science (USA).

  12. Anaerobic oxidation of methane alters sediment records of sulfur, iron and phosphorus in the Black Sea

    Science.gov (United States)

    Egger, Matthias; Kraal, Peter; Jilbert, Tom; Sulu-Gambari, Fatimah; Sapart, Célia J.; Röckmann, Thomas; Slomp, Caroline P.

    2016-09-01

    The surface sediments in the Black Sea are underlain by extensive deposits of iron (Fe)-oxide-rich lake sediments that were deposited prior to the inflow of marine Mediterranean Sea waters ca. 9000 years ago. The subsequent downward diffusion of marine sulfate into the methane-bearing lake sediments has led to a multitude of diagenetic reactions in the sulfate-methane transition zone (SMTZ), including anaerobic oxidation of methane (AOM) with sulfate. While the sedimentary cycles of sulfur (S), methane and Fe in the SMTZ have been extensively studied, relatively little is known about the diagenetic alterations of the sediment record occurring below the SMTZ.Here we combine detailed geochemical analyses of the sediment and porewater with multicomponent diagenetic modeling to study the diagenetic alterations below the SMTZ at two sites in the western Black Sea. We focus on the dynamics of Fe, S and phosphorus (P), and demonstrate that diagenesis has strongly overprinted the sedimentary burial records of these elements. In line with previous studies in the Black Sea, we show that sulfate-mediated AOM substantially enhances the downward diffusive flux of sulfide into the deep limnic deposits. During this downward sulfidization, Fe oxides, Fe carbonates and Fe phosphates (e.g., vivianite) are converted to sulfide phases, leading to an enrichment in solid-phase S and the release of phosphate to the porewater. Below the sulfidization front, high concentrations of dissolved ferrous Fe (Fe2+) lead to sequestration of downward-diffusing phosphate as authigenic vivianite, resulting in a transient accumulation of total P directly below the sulfidization front.Our model results further demonstrate that downward-migrating sulfide becomes partly re-oxidized to sulfate due to reactions with oxidized Fe minerals, fueling a cryptic S cycle and thus stimulating slow rates of sulfate-driven AOM ( ˜ 1-100 pmol cm-3 d-1) in the sulfate-depleted limnic deposits. However, this process is

  13. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

    Science.gov (United States)

    Avery, Katherine R.

    Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

  14. Microbial mediators of the sulfur, nitrogen, and iron cycles in freshwater ecosystems

    NARCIS (Netherlands)

    Haaijer, S.C.M.

    2007-01-01

    Human activities and concominant sulfur and nitrogen pollution endanger freshwater ecosystem quality. Improved knowledge on wetland biogeochemistry is a necessity to protect these valuable and fragile ecosystems. Effects of increased nitrate concentrations (stimulation of sulfide mineral oxidation,

  15. A split and rearranged nuclear gene encoding the iron-sulfur subunit of mitochondrial succinate dehydrogenase in Euglenozoa

    Directory of Open Access Journals (Sweden)

    Gray Michael W

    2009-02-01

    Full Text Available Abstract Background Analyses based on phylogenetic and ultrastructural data have suggested that euglenids (such as Euglena gracilis, trypanosomatids and diplonemids are members of a monophyletic lineage termed Euglenozoa. However, many uncertainties are associated with phylogenetic reconstructions for ancient and rapidly evolving groups; thus, rare genomic characters become increasingly important in reinforcing inferred phylogenetic relationships. Findings We discovered that the iron-sulfur subunit (SdhB of mitochondrial succinate dehydrogenase is encoded by a split and rearranged nuclear gene in Euglena gracilis and trypanosomatids, an example of a rare genomic character. The two subgenic modules are transcribed independently and the resulting mRNAs appear to be independently translated, with the two protein products imported into mitochondria, based on the presence of predicted mitochondrial targeting peptides. Although the inferred protein sequences are in general very divergent from those of other organisms, all of the required iron-sulfur cluster-coordinating residues are present. Moreover, the discontinuity in the euglenozoan SdhB sequence occurs between the two domains of a typical, covalently continuous SdhB, consistent with the inference that the euglenozoan 'half' proteins are functional. Conclusion The discovery of this unique molecular marker provides evidence for the monophyly of Euglenozoa that is independent of evolutionary models. Our results pose questions about the origin and timing of this novel gene arrangement and the structure and function of euglenozoan SdhB.

  16. The presence of the iron-sulfur motif is important for the conformational stability of the antiviral protein, Viperin.

    Directory of Open Access Journals (Sweden)

    Shubhasis Haldar

    Full Text Available Viperin, an antiviral protein, has been shown to contain a CX(3CX(2C motif, which is conserved in the radical S-adenosyl-methionine (SAM enzyme family. A triple mutant which replaces these three cysteines with alanines has been shown to have severe deficiency in antiviral activity. Since the crystal structure of Viperin is not available, we have used a combination of computational methods including multi-template homology modeling and molecular dynamics simulation to develop a low-resolution predicted structure. The results show that Viperin is an α-β protein containing iron-sulfur cluster at the center pocket. The calculations suggest that the removal of iron-sulfur cluster would lead to collapse of the protein tertiary structure. To verify these predictions, we have prepared, expressed and purified four mutant proteins. In three mutants individual cysteine residues were replaced by alanine residues while in the fourth all the cysteines were replaced by alanines. Conformational analyses using circular dichroism and steady state fluorescence spectroscopy indicate that the mutant proteins are partially unfolded, conformationally unstable and aggregation prone. The lack of conformational stability of the mutant proteins may have direct relevance to the absence of their antiviral activity.

  17. A novel acidophilic, thermophilic iron and sulfur-oxidizing archaeon isolated from a hot spring of tengchong, yunnan, China

    Directory of Open Access Journals (Sweden)

    Jiannan Ding

    2011-06-01

    Full Text Available A novel thermoacidophilic iron and sulfur-oxidizing archaeon, strain YN25, was isolated from an in situ enriched acid hot spring sample collected in Yunnan, China. Cells were irregular cocci, about 0.9-1.02 µm×1.0-1.31 µm in the medium containing elemental sulfur and 1.5-2.22 µm×1.8-2.54 µm in ferrous sulfate medium. The ranges of growth and pH were 50-85 (optimum 65 and pH 1.0-6.0 (optimum 1.5-2.5. The acidophile was able to grow heterotrophically on several organic substrates, including various monosaccharides, alcohols and amino acids, though the growth on single substrate required yeast extract as growth factor. Growth occurred under aerobic conditions or via anaerobic respiration using elemental sulfur as terminal electron acceptor. Results of morphology, physiology, fatty acid analysis and analysis based on 16S rRNA gene sequence indicated that the strain YN25 should be grouped in the species Acidianus manzaensis. Bioleaching experiments indicated that this strain had excellent leaching capacity, with a copper yielding ratio up to 79.16% in 24 d. The type strain YN25 was deposited in China Center for Type Culture Collection (=CCTCCZNDX0050.

  18. Sulfur and iron accumulation in three marine-archaeological shipwrecks in the Baltic Sea: The Ghost, the Crown and the Sword

    OpenAIRE

    Fors, Yvonne; Grudd, Håkan; Rindby, Anders; Jalilehvand, Farideh; Sandström, Magnus; Cato, Ingemar; Bornmalm, Lennart

    2014-01-01

    Sulfur and iron concentrations in wood from three 17th century shipwrecks in the Baltic Sea, the Ghost wreck, the Crown and the Sword, were obtained by X-ray fluorescence (XRF) scanning. In near anaerobic environments symbiotic microorganisms degrade waterlogged wood, reduce sulfate and promote accumulation of low-valent sulfur compounds, as previously found for the famous wrecks of the Vasa and Mary Rose. Sulfur K-edge X-ray absorption near-edge structure (XANES) analyses of Ghost wreck wood...

  19. Inactivation of iron-sulfur cluster biogenesis regulator SufR in Synechocystis sp. PCC 6803 induces unique iron-dependent protein-level responses.

    Science.gov (United States)

    Vuorijoki, Linda; Tiwari, Arjun; Kallio, Pauli; Aro, Eva-Mari

    2017-05-01

    Iron-sulfur (Fe-S) clusters are protein-bound cofactors associated with cellular electron transport and redox sensing, with multiple specific functions in oxygen-evolving photosynthetic cyanobacteria. The aim here was to elucidate protein-level effects of the transcriptional repressor SufR involved in the regulation of Fe-S cluster biogenesis in the cyanobacterium Synechocystis sp. PCC 6803. The approach was to quantitate 94 pre-selected target proteins associated with various metabolic functions using SRM in Synechocystis. The evaluation was conducted in response to sufR deletion under different iron conditions, and complemented with EPR analysis on the functionality of the photosystems I and II as well as with RT-qPCR to verify the effects of SufR also on transcript level. The results on both protein and transcript levels show that SufR acts not only as a repressor of the suf operon when iron is available but also has other direct and indirect functions in the cell, including maintenance of the expression of pyruvate:ferredoxin oxidoreductase NifJ and other Fe-S cluster proteins under iron sufficient conditions. Furthermore, the results imply that in the absence of iron the suf operon is repressed by some additional regulatory mechanism independent of SufR. The study demonstrates that Fe-S cluster metabolism in Synechocystis is stringently regulated, and has complex interactions with multiple primary functions in the cell, including photosynthesis and central carbon metabolism. The study provides new insight into the regulation of Fe-S cluster biogenesis via suf operon, and the associated wide-ranging protein-level changes in photosynthetic cyanobacteria. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  20. Simultaneous expression and maturation of the iron-sulfur protein ferredoxin in a cell-free system.

    Science.gov (United States)

    Boyer, Marcus E; Wang, Chia-Wei; Swartz, James R

    2006-05-05

    The model iron-sulfur (Fe-S) protein ferredoxin (Fd) from Synechocystis sp. PCC 6803 has been simultaneously produced and matured in a cell-free production system. After 6 h of incubation at 37 degrees C, Fd accumulated to >450 microg/mL. Essentially all was soluble, and 85% was active. Production and maturation of the protein in the cell-free system were found to be dependent in a coupled manner on the concentration of the supplemented iron and sulfur sources, ferrous ammonium sulfate and cysteine, respectively. The recombinant expression of ISC helper proteins during cell extract preparation did not increase cell-free Fd accumulation or activity, although the efficiency of iron and cysteine utilization increased. Fd maturation was independent of protein production rate, and proceeded at a constant rate throughout the period of active translation. In addition, incubation of denatured apo Fd with cell-free reaction components resulted in recovery of Fd activity, supporting the interpretation that maturation mechanisms did not act co-translationally. Incubation at 28 degrees C increased total and active protein accumulation, but decreased the ratio of active to total Fd produced. In summary, the high product yields and folding efficiency make the cell-free system described here an attractive platform for the study of Fe-S protein production and maturation. The system enables both small-volume, high throughput investigations as well as larger scale production. To our knowledge, this is the first demonstration of directed, high-yield production and maturation of an Fe-S protein in a cell-free system.

  1. An integrative computational model for large-scale identification of metalloproteins in microbial genomes: a focus on iron-sulfur cluster proteins.

    Science.gov (United States)

    Estellon, Johan; Ollagnier de Choudens, Sandrine; Smadja, Myriam; Fontecave, Marc; Vandenbrouck, Yves

    2014-10-01

    Metalloproteins represent a ubiquitous group of molecules which are crucial to the survival of all living organisms. While several metal-binding motifs have been defined, it remains challenging to confidently identify metalloproteins from primary protein sequences using computational approaches alone. Here, we describe a comprehensive strategy based on a machine learning approach to design and assess a penalized generalized linear model. We used this strategy to detect members of the iron-sulfur cluster protein family. A new category of descriptors, whose profile is based on profile hidden Markov models, encoding structural information was combined with public descriptors into a linear model. The model was trained and tested on distinct datasets composed of well-characterized iron-sulfur protein sequences, and the resulting model provided higher sensitivity compared to a motif-based approach, while maintaining a good level of specificity. Analysis of this linear model allows us to detect and quantify the contribution of each descriptor, providing us with a better understanding of this complex protein family along with valuable indications for further experimental characterization. Two newly-identified proteins, YhcC and YdiJ, were functionally validated as genuine iron-sulfur proteins, confirming the prediction. The computational model was then applied to over 550 prokaryotic genomes to screen for iron-sulfur proteomes; the results are publicly available at: . This study represents a proof-of-concept for the application of a penalized linear model to identify metalloprotein superfamilies on a large-scale. The application employed here, screening for iron-sulfur proteomes, provides new candidates for further biochemical and structural analysis as well as new resources for an extensive exploration of iron-sulfuromes in the microbial world.

  2. Chalcopyrite dissolution: Scanning photoelectron microscopy examination of the evolution of sulfur species with and without added iron or pyrite

    Science.gov (United States)

    Li, Yubiao; Qian, Gujie; Brown, Paul L.; Gerson, Andrea R.

    2017-09-01

    Dissolution and oxidation of sulfide minerals play key roles in both acid and metalliferous rock drainage and supergene enrichment. Surface speciation heterogeneity, critical to understanding mechanisms of mineral sulfide dissolution, has to date largely not been considered. To this end synchrotron scanning photoelectron microscopy (SPEM) was employed to examine freshly fractured and partially dissolved chalcopyrite (CuFeS2) surfaces (pH 1.0 HClO4 solution, redox potential 650 mV relative to a standard hydrogen electrode, 75 °C). S2- (bulk), S22- and Sn2- were found to be present on all samples at varying concentrations. Oxidation was observed to take place heterogeneously at the sub-micron scale. As compared to chalcopyrite partially dissolved for 5 days, extended dissolution to 10 days did not show appreciably enhanced oxidation of surface species; however surface roughness increased markedly due to the growth/overlap of oxidised sulfur species. On addition of 4 mM iron both S0 and SO42- were observed but not SO32-, indicating that the greater Fe3+ activity/concentration promotes heterogeneous sulfur oxidation. On contact of pyrite (FeS2) with chalcopyrite, significantly greater chalcopyrite surface oxidation was observed than for the other systems examined, with S0, SO32- and SO42- being identified heterogeneously across the surface. It is proposed that chalcopyrite oxidative dissolution is enhanced by increasing its cathodic area, e.g. contacting with pyrite, while increased Fe3+ activity/concentration also contributes to increased dissolution rates. The high degree of surface heterogeneity of these surface products indicates that these surfaces are not passivated by their formation. These results suggest that chalcopyrite dissolution will be accelerated when in contact with pyrite at solution redox potential intermediate between the rest potentials of chalcopyrite and pyrite (560 mV and 660 mV, respectively) and/or iron rich acidic waters with resulting

  3. Bacterial disproportionation of elemental sulfur coupled to chemical reduction of iron or manganese

    DEFF Research Database (Denmark)

    Thamdrup, Bo; Finster, Kai; Hansen, Jens Würgler

    1993-01-01

    the formed sulfide and the added FeOOH led to the observed precipitation of iron sulfides. Sulfate and iron sulfides were also produced when FeOOH was replaced by FeCO(3). Further enrichment with manganese oxide, MnO(2), instead of FeOOH yielded stable cultures which formed sulfate during concomitant...... significantly in the presence of sulfide-scavenging agents such as iron and manganese compounds. The population density of bacteria capable of S disproportionation in the presence of FeOOH or MnO(2) was high, > 10 cm in coastal sediments. The metabolism offers an explanation for recent observations of anaerobic...

  4. Targeting of a human iron-sulfur cluster assembly enzyme, nifs, to different subcellular compartments is regulated through alternative AUG utilization.

    Science.gov (United States)

    Land, T; Rouault, T A

    1998-12-01

    Iron-sulfur clusters are prosthetic groups that are required for the function of numerous enzymes in the cell, including enzymes important in respiration, photosynthesis, and nitrogen fixation. Here we report cloning of the human homolog of NifS, a cysteine desulfurase that is proposed to supply the inorganic sulfur in iron-sulfur clusters. In human cells, different forms of NifS that localize either to mitochondria or to the cytosol and nucleus are synthesized from a single transcript through initiation at alternative inframe AUGs, and initiation site selection varies according to the pH of the medium or cytosol. Thus, a novel form of translational regulation permits rapid redistribution of NifS proteins into different compartments of the cell in response to changes in metabolic status.

  5. Rapid, high-purity chemical separation of molybdenum from iron meteorites for isotopic analysis by using thermal ionization mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Qi-Lu; Masuda, Akimasa (Tokyo Univ. (Japan). Dept. of Chemistry)

    1992-05-01

    A chemical procedure has been developed, which combines both solvent extraction and anion exchange, so that microgram amounts of Mo can be cleanly, rapidly and efficiently separated from gram amounts of iron meteorites. Particular attention was directed to the complete separation of Mo from Zr and Ru. The isotopic abundance ratios of Mo can subsequently be determined with high accuracy by using thermal ionization mass spectrometry. The experiments indicate that the behaviour of Mo during solvent extraction and anion exchange is considerably different from that reported previously. In particular, it was found that there is a very narrow range of HCl concentrations within which it is possible to separate Mo from Fe by solvent extraction. The reproducibility and recovery of the method were examined by using inductively coupled plasma atomic emission spectrometry. (Author).

  6. Research on Recovery of Sulfur From Hydroxyl Iron Oxide Desulfurizer%脱硫剂羟基氧化铁中硫磺的回收研究

    Institute of Scientific and Technical Information of China (English)

    吕诗淇; 赖君玲; 罗根祥

    2015-01-01

    以四氯乙烯为溶剂,采用溶剂法从脱硫剂羟基氧化铁中回收硫磺。考察了浸取温度、浸取时间、液-固比和溶剂重复使用等因素对硫磺回收率的影响,并对羟基氧化铁和产物硫磺进行了 XRD 表征。结果表明:在羟基氧化铁20 g、浸取温度为80℃、浸取时间60 min、液-固比8:1的条件下,硫磺的回收率为97.5%;XRD表征结果证实了该产物为硫磺。%Sulfur was recovered from hydroxyl iron oxide desulfurizer containing 25.0% sulfur by solvent method in tetrachloroethylene solvent. The influence of reaction temperature,reaction time,liquid-solid ratio and reusing times of organic solution on sulfur recovery was investigated. The hydroxyl iron oxide desulfurizer and the product were characterized by X-ray diffraction (XRD) technology. The results show that, when the liquid-solid ratio of tetrachloroethylene to desulfurizer hydroxyl iron oxide containing 25.0% sulfur is 8:1, leaching temperature is 80 ℃, leaching time is 60 min, hydroxyl iron oxide is 20 g, the recovery of sulfur can be over 97.5%. The XRD characterization result has proved that recovered product is sulfur.

  7. An Ipomoea batatas iron-sulfur cluster scaffold protein gene, IbNFU1, is involved in salt tolerance.

    Directory of Open Access Journals (Sweden)

    Degao Liu

    Full Text Available Iron-sulfur cluster biosynthesis involving the nitrogen fixation (Nif proteins has been proposed as a general mechanism acting in various organisms. NifU-like protein may play an important role in protecting plants against abiotic and biotic stresses. An iron-sulfur cluster scaffold protein gene, IbNFU1, was isolated from a salt-tolerant sweetpotato (Ipomoea batatas (L. Lam. line LM79 in our previous study, but its role in sweetpotato stress tolerance was not investigated. In the present study, the IbNFU1 gene was introduced into a salt-sensitive sweetpotato cv. Lizixiang to characterize its function in salt tolerance. The IbNFU1-overexpressing sweetpotato plants exhibited significantly higher salt tolerance compared with the wild-type. Proline and reduced ascorbate content were significantly increased, whereas malonaldehyde (MDA content was significantly decreased in the transgenic plants. The activities of superoxide dismutase (SOD and photosynthesis were significantly enhanced in the transgenic plants. H2O2 was also found to be significantly less accumulated in the transgenic plants than in the wild-type. Overexpression of IbNFU1 up-regulated pyrroline-5-carboxylate synthase (P5CS and pyrroline-5-carboxylate reductase (P5CR genes under salt stress. The systemic up-regulation of reactive oxygen species (ROS scavenging genes was found in the transgenic plants under salt stress. These findings suggest that IbNFU1gene is involved in sweetpotato salt tolerance and enhances salt tolerance of the transgenic sweetpotato plants by regulating osmotic balance, protecting membrane integrity and photosynthesis and activating ROS scavenging system.

  8. Iron dissolution of dust source materials during simulated acidic processing: the effect of sulfuric, acetic, and oxalic acids.

    Science.gov (United States)

    Chen, Haihan; Grassian, Vicki H

    2013-09-17

    Atmospheric organic acids potentially display different capacities in iron (Fe) mobilization from atmospheric dust compared with inorganic acids, but few measurements have been made on this comparison. We report here a laboratory investigation of Fe mobilization of coal fly ash, a representative Fe-containing anthropogenic aerosol, and Arizona test dust, a reference source material for mineral dust, in pH 2 sulfuric acid, acetic acid, and oxalic acid, respectively. The effects of pH and solar radiation on Fe dissolution have also been explored. The relative capacities of these three acids in Fe dissolution are in the order of oxalic acid > sulfuric acid > acetic acid. Oxalate forms mononuclear bidentate ligand with surface Fe and promotes Fe dissolution to the greatest extent. Photolysis of Fe-oxalate complexes further enhances Fe dissolution with the concomitant degradation of oxalate. These results suggest that ligand-promoted dissolution of Fe may play a more significant role in mobilizing Fe from atmospheric dust compared with proton-assisted processing. The role of atmospheric organic acids should be taken into account in global-biogeochemical modeling to better access dissolved atmospheric Fe deposition flux at the ocean surface.

  9. Treatment of air pollution control residues with iron rich waste sulfuric acid: does it work for antimony (Sb)?

    Science.gov (United States)

    Okkenhaug, Gudny; Breedveld, Gijs D; Kirkeng, Terje; Lægreid, Marit; Mæhlum, Trond; Mulder, Jan

    2013-03-15

    Antimony (Sb) in air pollution control (APC) residues from municipal solid waste incineration has gained increased focus due to strict Sb leaching limits set by the EU landfill directive. Here we study the chemical speciation and solubility of Sb at the APC treatment facility NOAH Langøya (Norway), where iron (Fe)-rich sulfuric acid (∼3.6M, 2.3% Fe(II)), a waste product from the industrial extraction of ilmenite, is used for neutralization. Antimony in water extracts of untreated APC residues occurred exclusively as pentavalent antimonate, even at low pH and Eh values. The Sb solubility increased substantially at pHSb in porewater, occurring exclusively as Sb(V). Concentrations of Sb decreased from 87-918μgL(-1) (day 3) to 18-69μgL(-1) (day 600). We hypothesize that an initial sorption of Sb to Fe(II)-Fe(III) hydroxides (green rust) and eventually precipitation of Ca- and Fe-antimonates (tripuhyite; FeSbO4) occurred. We conclude that Fe-rich, sulfuric acid waste is efficient to immobilize Sb in APC residues from waste incineration.

  10. Quantification of abiotic reaction rates in mine tailings: evaluation of treatment methods for eliminating iron- and sulfur-oxidizing bacteria.

    Science.gov (United States)

    Herbert, Roger B; Malmström, Maria; Ebenå, Gustav; Salmon, Ursula; Ferrow, Embaie; Fuchs, Matthias

    2005-02-01

    Effective treatment techniques for eliminating iron-oxidizing (IOB) and sulfur-oxidizing bacteria (SOB) are required for the comparison of abiotic and microbial sulfide oxidation rates and mechanisms in mine tailings. This study evaluates the effect of autoclaving, repeated heating, ethanol treatment, antibiotic treatment, gamma-radiation, and washing with deionized water on tailings characteristics and concentrations of IOB and SOB. Most probable number enumeration indicates that IOB and SOB were present at very low concentrations or below detection limits following treatment with all methods except rinsing and antibiotics treatment, where higher concentrations of IOB and SOB were present. The physical, chemical, and mineralogical characterization of the tailings indicated no changes in bulk mineralogy or bulk chemical composition as a result of treatment. However, an increase in oxidized sulfur species at the tailings surface, as determined by X-ray photoelectron spectroscopy, was observed for the heating, autoclaving, and antibiotics treatments. Batch weathering experiments, used to evaluate the effect of treatment on element release rates, indicated that the final element release rates (after >30 d) were similar between treated and untreated control samples. On the basis of the results of this study, experiments over relatively long periods (>30 d) are to be recommended forthe establishment of microbial and abiotic weathering rates in mill tailings samples. For the determination of abiotic reaction rates, treatment by gamma-radiation is suggested to be the most appropriate method for sulfide-rich tailings.

  11. Isolation, Characterization, and Functional Role of the High-Potential Iron-Sulfur Protein (HiPIP) from Rhodoferax fermentans

    DEFF Research Database (Denmark)

    Hochkoeppler, A.; Kofod, P.; Ferro, G.;

    1995-01-01

    A new high-potential iron-sulfur protein (HiPIP) has been isolated and purified to homogeneity from the soluble fraction obtained from light-grown cells of the facultative photoheterotrophic bacterium Rhodoferax fermentans. The new protein was identified as a HiPIP by virtue of its molecular...... properties such as the molecular mass (Mr = 8.7 kDa), the Fe/protein ratio (3.8 ± 0.2), the reduction potential (Em,7 = +351 mV), the electronic spectrum of the reduced and the oxidized protein, and the EPR spectrum of the oxidized protein. These molecular properties lie in the range observed for HiPIPs from...... other sources and, in particular, the iron content is consistent with the presence of one [Fe4S4] cubane cluster per molecule. The isoelectric pH values of the two redox forms are consistent with a basic protein. Kinetic studies of HiPIP oxidation, performed by monitoring the absorbance changes induced...

  12. Heterotrophic Bioleaching of Sulfur, Iron, and Silicon Impurities from Coal by Fusarium oxysporum FE and Exophiala spinifera FM with Growing and Resting Cells.

    Science.gov (United States)

    Etemadzadeh, Shekoofeh Sadat; Emtiazi, Giti; Etemadifar, Zahra

    2016-06-01

    Coal is the most abundant fossil fuel containing sulfur and other elements which promote environmental pollution after burning. Also the silicon impurities make the transportation of coal expensive. In this research, two isolated fungi from oil contaminated soil with accessory number KF554100 (Fusarium oxysporum FE) and KC925672 (Exophiala spinifera FM) were used for heterotrophic biological leaching of coal. The leaching were detected by FTIR, CHNS, XRF analyzer and compared with iron and sulfate released in the supernatant. The results showed that E. spinifera FM produced more acidic metabolites in growing cells, promoting the iron and sulfate ions removal while resting cells of F. oxysporum FE enhanced the removal of aromatic sulfur. XRF analysis showed that the resting cells of E. spinifera FM proceeded maximum leaching for iron and silicon (48.8, 43.2 %, respectively). CHNS analysis demonstrated that 34.21 % of sulfur leaching was due to the activities of resting cells of F. oxysporum FE. Also F. oxysporum FE removed organic sulfur more than E. spinifera FM in both growing and resting cells. FTIR data showed that both fungi had the ability to remove pyrite and quartz from coal. These data indicated that inoculations of these fungi to the coal are cheap and impurity removals were faster than autotrophic bacteria. Also due to the removal of dibenzothiophene, pyrite, and quartz, we speculated that they are excellent candidates for bioleaching of coal, oil, and gas.

  13. Laser Double Ablation Reactions of Chromium(Iron) and Sulfur Clusters

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Introduction The sulfides of transitional metals chromium[1-3] and iron[4] are of great importance in material and biology sciences due to their characteristic structures and properties. So the study on the properties of Cr-S and Fe-S clusters will give many contributions to the understanding of physical and chemical behavior of those compounds.

  14. Anaerobic oxidation of methane alters sediment records of sulfur, iron and phosphorus in the Black Sea

    NARCIS (Netherlands)

    Egger, M.J.; Kraal, P.; Jilbert, T.S.; Sulu-Gambari, F.A.; Sapart, C.J.; Roeckmann, T.; Slomp, C.P.

    2016-01-01

    The surface sediments in the Black Sea are underlain by extensive deposits of iron (Fe)-oxide-rich lake sediments that were deposited prior to the inflow of marine Mediterranean Sea waters ca. 9000 years ago. The subsequent downward diffusion of marine sulfate into the methane-bearing lake sediments

  15. Sulfur K-edge Spectroscopic Investigation of Second Coordination Sphere Effects in Oxomolybdenum-Thiolates: Relationship to Molybdenum-Cysteine Covalency and Electron Transfer in Sulfite Oxidase

    Energy Technology Data Exchange (ETDEWEB)

    Peariso,K.; Helton, M.; Duesler, E.; Shadle, S.; Kirk, M.

    2007-01-01

    Second-coordination sphere effects such as hydrogen bonding and steric constraints that provide for specific geometric configurations play a critical role in tuning the electronic structure of metalloenzyme active sites and thus have a significant effect on their catalytic efficiency. Crystallographic characterization of vertebrate and plant sulfite oxidase (SO) suggests that an average O{sub oxo}-Mo-S{sub Cys}-C dihedral angle of {approx}77{sup o} exists at the active site of these enzymes. This angle is slightly more acute ({approx}72{sup o}) in the bacterial sulfite dehydrogenase (SDH) from Starkeya novella. Here we report the synthesis, crystallographic, and electronic structural characterization of Tp*MoO(mba) (where Tp* = (3,5-dimethyltrispyrazol-1-yl)borate; mba = 2-mercaptobenzyl alcohol), the first oxomolybdenum monothiolate to possess an O{sub ax}-Mo-S{sub thiolate}-C dihedral angle of {approx}90{sup o}. Sulfur X-ray absorption spectroscopy clearly shows that O{sub ax}-Mo-S{sub thiolate}-C dihedral angles near 90{sup o} effectively eliminate covalency contributions to the Mo(xy) redox orbital from the thiolate sulfur. Sulfur K-pre-edge X-ray absorption spectroscopy intensity ratios for the spin-allowed S(1s) {yields} S{sup v}(p) + Mo(xy) and S(1s) {yields} S{sup v}(p) + Mo(xz,yz) transitions have been calibrated by a direct comparison of theory with experiment to yield thiolate S{sup v}(p) orbital contributions, c{sup 2}{sub i}, to the Mo(xy) redox orbital and the Mo(xz,yz) orbital set. Furthermore, these intensity ratios are related to a second coordination sphere structural parameter, the O{sub oxo}-Mo-S{sub thiolate}-C dihedral angle. The relationship between Mo-S{sub thiolate} and Mo-S{sub dithiolene} covalency in oxomolydenum systems is discussed, particularly with respect to electron-transfer regeneration in SO.

  16. Solution NMR Structure of the Iron-Sulfur Cluster Assembly Protein U (IscU) with Zinc Bound at the Active Site

    Energy Technology Data Exchange (ETDEWEB)

    Ramelot, Theresa A.; Cort, John R.; Goldsmith-Fischman, Sharon; Kornhaber, Greg J.; Xiao, Rong; Shastry, Ritu; Acton, Thomas; Honig, Barry; Montelione, Gaetano; Kennedy, Michael A.

    2004-11-19

    IscU is a highly conserved protein that serves as the scaffold for IscS-mediated assembly of iron-sulfur ([Fe-S]) clusters. We report the NMR solution structure of monomeric Haemophilus influenzae IscU with zinc bound at the [Fe-S] cluster assembly site. The compact core of the globular structure has an {alpha}-{beta} sandwich architecture with a three-stranded antiparallel {beta}-sheet and four {alpha}-helices. A nascent helix is located N-terminal to the core structure. The zinc is ligated by three cysteines and one histidine that are located in and near conformationally dynamic loops at one end of the IscU structure. Removal of the zinc metal by chelation results in widespread loss of structure in the apo form. The zinc-bound IscU may be a good model for iron-loaded IscU and may demonstrate structural features found in the iron-sulfur cluster bound form. Structural and functional similarities, genomic context in operons containing other homologous genes, and distributions of conserved surface residues support the hypothesis that IscU protein domains are homologous (i.e. derived from a common ancestor) with the SufE/YgdK family of iron sulfur cluster assembly proteins.

  17. MicroRNA-210 regulates mitochondrial free radical response to hypoxia and krebs cycle in cancer cells by targeting iron sulfur cluster protein ISCU.

    Science.gov (United States)

    Favaro, Elena; Ramachandran, Anassuya; McCormick, Robert; Gee, Harriet; Blancher, Christine; Crosby, Meredith; Devlin, Cecilia; Blick, Christopher; Buffa, Francesca; Li, Ji-Liang; Vojnovic, Borivoj; Pires das Neves, Ricardo; Glazer, Peter; Iborra, Francisco; Ivan, Mircea; Ragoussis, Jiannis; Harris, Adrian L

    2010-04-26

    Hypoxia in cancers results in the upregulation of hypoxia inducible factor 1 (HIF-1) and a microRNA, hsa-miR-210 (miR-210) which is associated with a poor prognosis. In human cancer cell lines and tumours, we found that miR-210 targets the mitochondrial iron sulfur scaffold protein ISCU, required for assembly of iron-sulfur clusters, cofactors for key enzymes involved in the Krebs cycle, electron transport, and iron metabolism. Down regulation of ISCU was the major cause of induction of reactive oxygen species (ROS) in hypoxia. ISCU suppression reduced mitochondrial complex 1 activity and aconitase activity, caused a shift to glycolysis in normoxia and enhanced cell survival. Cancers with low ISCU had a worse prognosis. Induction of these major hallmarks of cancer show that a single microRNA, miR-210, mediates a new mechanism of adaptation to hypoxia, by regulating mitochondrial function via iron-sulfur cluster metabolism and free radical generation.

  18. MicroRNA-210 regulates mitochondrial free radical response to hypoxia and krebs cycle in cancer cells by targeting iron sulfur cluster protein ISCU.

    Directory of Open Access Journals (Sweden)

    Elena Favaro

    Full Text Available BACKGROUND: Hypoxia in cancers results in the upregulation of hypoxia inducible factor 1 (HIF-1 and a microRNA, hsa-miR-210 (miR-210 which is associated with a poor prognosis. METHODS AND FINDINGS: In human cancer cell lines and tumours, we found that miR-210 targets the mitochondrial iron sulfur scaffold protein ISCU, required for assembly of iron-sulfur clusters, cofactors for key enzymes involved in the Krebs cycle, electron transport, and iron metabolism. Down regulation of ISCU was the major cause of induction of reactive oxygen species (ROS in hypoxia. ISCU suppression reduced mitochondrial complex 1 activity and aconitase activity, caused a shift to glycolysis in normoxia and enhanced cell survival. Cancers with low ISCU had a worse prognosis. CONCLUSIONS: Induction of these major hallmarks of cancer show that a single microRNA, miR-210, mediates a new mechanism of adaptation to hypoxia, by regulating mitochondrial function via iron-sulfur cluster metabolism and free radical generation.

  19. Molybdenum: Industrial applications

    Energy Technology Data Exchange (ETDEWEB)

    Bulla, W.; Fairhurst, W.; King, P.

    1982-12-01

    Molybdenum availability and molybdenum consumption are reviewed. About 9% of the total amount of molybdenum consumed is used in the production of nonferrous metals. The authors list applications for which molybdenum materials, owing to their physical and high-temperature characteristics, are particularly well suited.

  20. Application of indigenous sulfur-oxidizing bacteria from municipal wastewater to selectively bioleach phosphorus from high-phosphorus iron ore: effect of particle size.

    Science.gov (United States)

    Shen, Shaobo; Rao, Ruirui; Wang, Jincao

    2013-01-01

    The effects of ore particle size on selectively bioleaching phosphorus (P) from high-phosphorus iron ore were studied. The average contents of P and Fe in the iron ore were 1.06 and 47.90% (w/w), respectively. The particle sizes of the ores used ranged from 58 to 3350 microm. It was found that the indigenous sulfur-oxidizing bacteria from municipal wastewater could grow well in the slurries of solid high-phosphorus iron ore and municipal wastewater. The minimum bioleaching pH reached for the current work was 0.33. The P content in bioleached iron ore reduced slightly with decreasing particle size, while the removal percentage of Fe decreased appreciably with decreasing particle size. The optimal particle size fraction was 58-75 microm, because the P content in bioleached iron ore reached a minimum of 0.16% (w/w), the removal percentage of P attained a maximum of 86.7%, while the removal percentage of Fe dropped to a minimum of 1.3% and the Fe content in bioleached iron ore was a maximum of 56.4% (w/w) in this case. The iron ores thus obtained were suitable to be used in the iron-making process. The removal percentage of ore solid decreased with decreasing particle size at particle size range of 106-3350 microm. The possible reasons resulting in above phenomena were explored in the current work. It was inferred that the particle sizes of the iron ore used in this work have no significant effect on the viability of the sulfur-oxidizing bacteria.

  1. Iron-sulfur cluster biosynthesis: functional characterization of the N- and C-terminal domains of human NFU.

    Science.gov (United States)

    Liu, Yushi; Qi, Wenbin; Cowan, J A

    2009-02-10

    Human NFU (also known as HIRIP5) has been implicated in cellular iron-sulfur cluster biosynthesis. Bacterial and yeast forms are smaller than the human protein and are homologous to the C-terminal domain of the latter. This C-terminal domain contains a pair of redox active cysteines and demonstrates thioredoxin-like activity by mediating persulfide bond cleavage of sulfur-loaded NifS (an IscS-type protein), the sulfide donor for [2Fe-2S] cluster assembly on ISU-type scaffold proteins. Herein, the affinity of full-length human NFU and the individual N- and C-terminal domains for sulfide donor and cluster scaffold proteins is assessed. The influence of the N-terminal domain on C-terminal NFU binding to NifS and persulfide reductase activity is also examined. Only the C-terminal domain is required for persulfide reductase activity, while complex formation of NifS with full-length NFU is similar to that of the C-terminal domain alone (K(D) approximately 9.7 +/- 0.7 and 10.1 +/- 0.6 microM, respectively). There is negligible affinity between the isolated C- and N-terminal domains, while the N-terminal domain has negligible affinity for either sulfide donor or cluster scaffold proteins. The temperature dependence of the binding enthalpy for formation of the complex between NifS and the C-terminal domain of NFU yields a change in molar heat capacity (DeltaC(p) approximately 138 cal mol(-1) K(-1)) that suggests bonding at the protein-protein interface is dominated by electrostatic interactions. This is consistent with electrostatic potential maps for bacterial homologues of the N- and C-terminal domains of human NFU, which most likely reflect the structural characteristics expected for full-length human NFU.

  2. Structural and functional characterization of an iron-sulfur cluster assembly scaffold protein-SufA from Plasmodium vivax.

    Science.gov (United States)

    Pala, Zarna Rajeshkumar; Saxena, Vishal; Saggu, Gagandeep Singh; Yadav, Sushil Kumar; Pareek, R P; Kochar, Sanjay Kumar; Kochar, Dhanpat Kumar; Garg, Shilpi

    2016-07-01

    Iron-sulfur (Fe-S) clusters are utilized as prosthetic groups in all living organisms for diverse range of cellular processes including electron transport in respiration and photosynthesis, sensing of ambient conditions, regulation of gene expression and catalysis. In Plasmodium, two Fe-S cluster biogenesis pathways are reported, of which the Suf pathway in the apicoplast has been shown essential for the erythrocytic stages of the parasite. While the initial components of this pathway detailing the sulfur mobilization have been elucidated, the components required for the assembly and transfer of Fe-S clusters are not reported from the parasite. In Escherichia coli, SufB acts as a scaffold protein and SufA traffics the assembled Fe-S cluster from SufB to target apo-proteins. However, in Plasmodium, the homologs of these proteins are yet to be characterized for their function. Here, we report a putative SufA protein from Plasmodium vivax with signature motifs of A-type scaffold proteins, which is evolutionarily conserved. The presence of the [Fe4S4](3+) cluster under reduced conditions was confirmed by UV-visible and EPR spectroscopy and the interaction of these clusters with the conserved cysteine residues of chains A and B of PvSufA, validates its existence as a dimer, similar to that in E. coli. The H-bond interactions at the PvSufA-SufB interface demonstrate SufA as a scaffold protein in conjunction with SufB for the pre-assembly of Fe-S clusters and their transfer to the target proteins. Co-localization of the protein to the apicoplast further provides an experimental evidence of a functional scaffold protein SufA for the biogenesis of Fe-S clusters in apicoplast of Plasmodium.

  3. Synthesis of carbon nanotubes by CVD method using iron and molybdenum-based catalysts supported on ceramic matrices;Sintese de nanotubos de carbono por CVD utilizando catalisadores a base de ferro e molibdenio suportados em matrizes ceramicas

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, Ana Paula de Carvalho

    2010-07-01

    Molybdenum is known for its synergistic effect in the synthesis of carbon nanotubes (CNs) by chemical vapor deposition (CVD method). When added to typical catalysts like iron, nickel, and cobalt, even in small quantities, it is increases the yield of these nanostructures. The presence of Mo also has an influence on the type and number of CN walls formed. Although this effect is widely documented in the literature, there is not yet a consensus about the mechanism of action of molybdenum in catalytic systems. The objective of the present work is to study the influence of molybdenum on the catalytic activity of iron nanoparticle-based catalysts supported on magnesium oxide (Fe/MgO system) in the synthesis of carbon nanotubes by the CVD method. The Mo concentration was systematically varied from null to molar ratio values four times greater than the quantity of Fe, and the obtained material (catalysts and carbon nanotubes) were broadly characterized by different techniques. In order to also study the influence of the preparation method on the final composition of the catalytic system phases, the catalytic systems (Fe/MgO e FeMo{sub x}/MgO) were synthesized by two different methods: co-precipitation and impregnation. The greatest CN yields were observed for the catalysts prepared by coprecipitation. The difference was attributed to better dispersion of the Fe and Mo phases in the catalyst ceramic matrix. In the precipitation stage, it was observed the formation of layered double hydroxides whose concentration increased with the Mo content up to the ratio of Mo/Fe equal to 0.2. This phase is related to a better distribution of Fe and Mo in this concentration range. Another important characteristic observed is that the ceramic matrix is not inert. It can react both with Fe and Mo and form the iron solid solution in the magnesium oxide and the phases magnesium-ferrite (MgFe{sub 2}0{sub 4}) and magnesium molybdate (MgMo0{sub 4}). The MgFe{sub 2}0{sub 4} phase is observed in

  4. Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

    Science.gov (United States)

    Brown, C.J.; Schoonen, M.A.A.; Candela, J.L.

    2000-01-01

    Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO4/2- in the aerobic zone, and to the reduction of SO4/2- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55 x 10-4 to 48.6 x 10-4 mmol 1-1 yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO4/2- (1.31 x 10-4 to 15 x 10-4 mmol 1-1 yr-1). The overall increase in SO4/2- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO4/2- loss through microbial reduction is exceeded by SO4/2- gain through diffusion from sediments and through the oxidation of FeS2. Geochemichal and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO4/2- -rich zones have localized SO4/2- -reducing zones in which the formation of iron disulfides been depleted by microbial reduction and resulted in decreases dissolved iron concentrations. These localized zones of SO4/2- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling. (C) 2000 Elsevier Science B.V.Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron

  5. SRM dataset of the proteome of inactivated iron-sulfur cluster biogenesis regulator SufR in Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Vuorijoki, Linda; Kallio, Pauli; Aro, Eva-Mari

    2017-04-01

    This article contains SRM proteomics data related to the research article entitled"Inactivation of iron-sulfur cluster biogenesis regulator SufR in Synechocystis sp. PCC 6803 induces unique iron-dependent protein-level responses" (L. Vuorijoki, A. Tiwari, P. Kallio, E.M. Aro, 2017) [1]. The data described here provide comprehensive information on the applied SRM assays, together with the results of quantifying 94 Synechocystis sp. PCC 6803 proteins. The data has been deposited in Panorama public (https://panoramaweb.org/labkey/SufR) and in PASSEL under the PASS00765 identifier (http://www.peptideatlas.org/PASS/PASS00765).

  6. {gamma} alumina- and HY zeolite-supported molybdenum catalysts: characterisation of the oxidic and sulfided phases; Catalyseurs a base de molybdene supporte sur alumine {gamma} et zeolithe HY: caracterisation des phases oxydes et sulfures

    Energy Technology Data Exchange (ETDEWEB)

    Plazenet, G.

    2001-10-01

    Oxidic precursors of hydro-treatment catalysts (Co)Mo/alumina or zeolite were characterised by Raman spectroscopy, NMR and EXAFS at the Mo and Co K-edges. The formation of an Anderson-type alumino-molybdate compound upon impregnation of the support with an ammonium hepta-molybdate solution was confirmed for alumina, and also observed for the HY zeolitic support, with consumption of the amorphous alumina of the zeolite. In absence of the latter, ammonium hepta-molybdate precipitates. The species are conserved upon drying; upon calcination, the alumino-molybdate evolves into a surface aluminium molybdate type phase, whereas the hepta-molybdate transforms into MoO{sub 3}. The species formed upon impregnation are located in the inter-granular porosity whereas MoO{sub 3} vapor-condensation leads to formation of dimers located inside the zeolitic structure. The study of the cobalt-promoted precursors showed that the evolution of the molybdenum is the same in the case of co-impregnation preparation. Impregnation with cobalt-molybdate prevents the formation of the alumino-molybdate anion and thus enables the preservation of the Mo-Co interaction but, whatever the precursor, the leveling effect of the calcination-re-hydration steps was demonstrated. An EXAFS study at different sulfur coverages of the MoS{sub 2} platelets in the alumina-supported sulfided catalysts showed the limitations of EXAFS for size determination of MoS{sub 2} crystallites, a parameter that can be reached by AWAXS, which also conveys information about sheet-stacking. The EXAFS study of sulfided (Co)Mo/HY systems revealed incomplete sulfidation of the samples and the very high dispersion of the active phase. The absence of an observable Mo-Co interaction whatever the preparation of the promoted catalysts is consistent with the absence of promoting effect in toluene hydrogenation. (author)

  7. The presence of multiple cellular defects associated with a novel G50E iron-sulfur cluster scaffold protein (ISCU) mutation leads to development of mitochondrial myopathy.

    Science.gov (United States)

    Saha, Prasenjit Prasad; Kumar, S K Praveen; Srivastava, Shubhi; Sinha, Devanjan; Pareek, Gautam; D'Silva, Patrick

    2014-04-11

    Iron-sulfur (Fe-S) clusters are versatile cofactors involved in regulating multiple physiological activities, including energy generation through cellular respiration. Initially, the Fe-S clusters are assembled on a conserved scaffold protein, iron-sulfur cluster scaffold protein (ISCU), in coordination with iron and sulfur donor proteins in human mitochondria. Loss of ISCU function leads to myopathy, characterized by muscle wasting and cardiac hypertrophy. In addition to the homozygous ISCU mutation (g.7044G→C), compound heterozygous patients with severe myopathy have been identified to carry the c.149G→A missense mutation converting the glycine 50 residue to glutamate. However, the physiological defects and molecular mechanism associated with G50E mutation have not been elucidated. In this report, we uncover mechanistic insights concerning how the G50E ISCU mutation in humans leads to the development of severe ISCU myopathy, using a human cell line and yeast as the model systems. The biochemical results highlight that the G50E mutation results in compromised interaction with the sulfur donor NFS1 and the J-protein HSCB, thus impairing the rate of Fe-S cluster synthesis. As a result, electron transport chain complexes show significant reduction in their redox properties, leading to loss of cellular respiration. Furthermore, the G50E mutant mitochondria display enhancement in iron level and reactive oxygen species, thereby causing oxidative stress leading to impairment in the mitochondrial functions. Thus, our findings provide compelling evidence that the respiration defect due to impaired biogenesis of Fe-S clusters in myopathy patients leads to manifestation of complex clinical symptoms.

  8. Effective sulfur and energy recovery from hydrogen sulfide through incorporating an air-cathode fuel cell into chelated-iron process.

    Science.gov (United States)

    Sun, Min; Song, Wei; Zhai, Lin-Feng; Cui, Yu-Zhi

    2013-12-15

    The chelated-iron process is among the most promising techniques for the hydrogen sulfide (H2S) removal due to its double advantage of waste minimization and resource recovery. However, this technology has encountered the problem of chelate degradation which made it difficult to ensure reliable and economical operation. This work aims to develop a novel fuel-cell-assisted chelated-iron process which employs an air-cathode fuel cell for the catalyst regeneration. By using such a process, sulfur and electricity were effectively recovered from H2S and the problem of chelate degradation was well controlled. Experiment on a synthetic sulfide solution showed the fuel-cell-assisted chelated-iron process could maintain high sulfur recovery efficiencies generally above 90.0%. The EDTA was preferable to NTA as the chelating agent for electricity generation, given the Coulombic efficiencies (CEs) of 17.8 ± 0.5% to 75.1 ± 0.5% for the EDTA-chelated process versus 9.6 ± 0.8% to 51.1 ± 2.7% for the NTA-chelated process in the pH range of 4.0-10.0. The Fe (III)/S(2-) ratio exhibited notable influence on the electricity generation, with the CEs improved by more than 25% as the Fe (III)/S(2-) molar ratio increased from 2.5:1 to 3.5:1. Application of this novel process in treating a H2S-containing biogas stream achieved 99% of H2S removal efficiency, 78% of sulfur recovery efficiency, and 78.6% of energy recovery efficiency, suggesting the fuel-cell-assisted chelated-iron process was effective to remove the H2S from gas streams with favorable sulfur and energy recovery efficiencies.

  9. Manganese, Iron, and Sulfur Cycling in a Coastal Marine Sediment, Aarhus Bay, Denmark

    DEFF Research Database (Denmark)

    THAMDRUP, B.; FOSSING, H.; JØRGENSEN, BB

    1994-01-01

    -scale measurements showed that it extended to the upper 0-2.5 mm during summer, when the zones of Mn and Fe reduction were compressed towards the surface. Most of the H2S produced precipitated as iron sulfides and S0 by reaction with Fe. Both Fe(III) and a nonsulfur-bound authigenic Fe(II) pool reacted efficiently...... with H2S. The authigenic Fe(II) pool was present at one hundredfold higher concentration than dissolved Fe2+. Only 15% of the precipitated sulfide was buried permanently. Most of the reoxidation of reduced S occurred within 1 cm of the sediment-water interface and was supported by upward bioturbation......The seasonal variation in oxidized and reduced pools of Mn, Fe, and S, as well as the rates of SO4(2-) reduction, were studied in a fine-grained sediment. Below the 1-5 mm thick oxic zone, a zone of net Mn reduction extended to 1-2 cm depth, while iron reduction was found to 4-6 cm depth. Although...

  10. Deficiency of the iron-sulfur clusters of mitochondrial reduced nicotinamide-adenine dinucleotide-ubiquinone oxidoreductase (complex I) in an infant with congenital lactic acidosis.

    Science.gov (United States)

    Moreadith, R W; Batshaw, M L; Ohnishi, T; Kerr, D; Knox, B; Jackson, D; Hruban, R; Olson, J; Reynafarje, B; Lehninger, A L

    1984-09-01

    We report the case of an infant with hypoglycemia, progressive lactic acidosis, an increased serum lactate/pyruvate ratio, and elevated plasma alanine, who had a moderate to profound decrease in the ability of mitochondria from four organs to oxidize pyruvate, malate plus glutamate, citrate, and other NAD+-linked respiratory substrates. The capacity to oxidize the flavin adenine dinucleotide-linked substrate, succinate, was normal. The most pronounced deficiency was in skeletal muscle, the least in kidney mitochondria. Enzymatic assays on isolated mitochondria ruled out defects in complexes II, III, and IV of the respiratory chain. Further studies showed that the defect was localized in the inner membrane mitochondrial NADH-ubiquinone oxidoreductase (complex I). When ferricyanide was used as an artificial electron acceptor, complex I activity was normal, indicating that electrons from NADH could reduce the flavin mononucleotide cofactor. However, electron paramagnetic resonance spectroscopy performed on liver submitochondrial particles showed an almost total loss of the iron-sulfur clusters characteristic of complex I, whereas normal signals were noted for other mitochondrial iron-sulfur clusters. This infant is presented as the first reported case of congenital lactic acidosis caused by a deficiency of the iron-sulfur clusters of complex I of the mitochondrial electron transport chain.

  11. Sulfur metabolism in phototrophic sulfur bacteria

    DEFF Research Database (Denmark)

    Frigaard, Niels-Ulrik; Dahl, Christiane

    2008-01-01

    Phototrophic sulfur bacteria are characterized by oxidizing various inorganic sulfur compounds for use as electron donors in carbon dioxide fixation during anoxygenic photosynthetic growth. These bacteria are divided into the purple sulfur bacteria (PSB) and the green sulfur bacteria (GSB......). They utilize various combinations of sulfide, elemental sulfur, and thiosulfate and sometimes also ferrous iron and hydrogen as electron donors. This review focuses on the dissimilatory and assimilatory metabolism of inorganic sulfur compounds in these bacteria and also briefly discusses these metabolisms...... in other types of anoxygenic phototrophic bacteria. The biochemistry and genetics of sulfur compound oxidation in PSB and GSB are described in detail. A variety of enzymes catalyzing sulfur oxidation reactions have been isolated from GSB and PSB (especially Allochromatium vinosum, a representative...

  12. Differential expression of two bc1 complexes in the strict acidophilic chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans suggests a model for their respective roles in iron or sulfur oxidation.

    Science.gov (United States)

    Bruscella, Patrice; Appia-Ayme, Corinne; Levicán, Gloria; Ratouchniak, Jeanine; Jedlicki, Eugenia; Holmes, David S; Bonnefoy, Violaine

    2007-01-01

    Three strains of the strict acidophilic chemolithoautotrophic Acidithiobacillus ferrooxidans, including the type strain ATCC 23270, contain a petIIABC gene cluster that encodes the three proteins, cytochrome c1, cytochrome b and a Rieske protein, that constitute a bc1 electron-transfer complex. RT-PCR and Northern blotting show that the petIIABC cluster is co-transcribed with cycA, encoding a cytochrome c belonging to the c4 family, sdrA, encoding a putative short-chain dehydrogenase, and hip, encoding a high potential iron-sulfur protein, suggesting that the six genes constitute an operon, termed the petII operon. Previous results indicated that A. ferrooxidans contains a second pet operon, termed the petI operon, which contains a gene cluster that is similarly organized except that it lacks hip. Real-time PCR and Northern blot experiments demonstrate that petI is transcribed mainly in cells grown in medium containing iron, whereas petII is transcribed in cells grown in media containing sulfur or iron. Primer extension experiments revealed possible transcription initiation sites for the petI and petII operons. A model is presented in which petI is proposed to encode the bc1 complex, functioning in the uphill flow of electrons from iron to NAD(P), whereas petII is suggested to be involved in electron transfer from sulfur (or formate) to oxygen (or ferric iron). A. ferrooxidans is the only organism, to date, to exhibit two functional bc1 complexes.

  13. Human CIA2A (FAM96A) and CIA2B (FAM96B) integrate maturation of different subsets of cytosolic-nuclear iron-sulfur proteins and iron homeostasis

    OpenAIRE

    Stehling, Oliver; Mascarenhas, Judita; Ajay A Vashisht; Sheftel, Alex D.; Niggemeyer, Brigitte; Rösser, Ralf; Pierik, Antonio J.; Wohlschlegel, James A.; Lill, Roland

    2013-01-01

    Numerous cytosolic and nuclear proteins involved in metabolism, DNA maintenance, protein translation, or iron homeostasis depend on iron-sulfur (Fe/S) cofactors, yet their assembly is poorly defined. Here, we identify and characterize human CIA2A (FAM96A), CIA2B (FAM96B), and CIA1 (CIAO1) as components of the cytosolic Fe/S protein assembly (CIA) machinery. CIA1 associates with either CIA2A or CIA2B and the CIA targeting factor MMS19. The CIA2B-CIA1-MMS19 complex binds to and facilitates asse...

  14. Growth-promoting effect on iron-sulfur proteins on axenic cultures of Entamoeba dispar

    Directory of Open Access Journals (Sweden)

    Khalifa S.A.M.

    2006-03-01

    Full Text Available A growth-promoting factor (GPF that promotes the growth of Entamoeba dispar under axenic culture conditions was found in fractions of mitochondria (Mt, hydrogenosomes (Hg and chloroplasts (Cp obtained from cells of six different protozoan, mammalian and plant species. We were able to extract the GPF from the Cp-rich leaf cells of a plant (spiderwort: Commelina communis L. in an acetone-soluble fraction as a complex of chlorophyll with low molecular weight proteins (molecular weight [MW] approximately 4,600. We also found that on treatment with 0.6 % complexes of 2-mercapthoethanol (2ME, complexes of chlorophyll-a with iron-sulphur (Fe-S proteins (e.g., ferredoxins [Fd] from spinach and Clostridium pasteurianum and noncomplex rubredoxin (Rd from C. pasteurianum have a growth-promoting effect on E. dispar. These findings suggest that E. dispar may lack a sufficient quantity of some essential components of Fe-S proteins, such as Fe-S center.

  15. FeS/S/FeS(2) redox system and its oxidoreductase-like chemistry in the iron-sulfur world.

    Science.gov (United States)

    Wang, Wei; Yang, Bin; Qu, Youpeng; Liu, Xiaoyang; Su, Wenhui

    2011-06-01

    The iron-sulfur world (ISW) theory is an intriguing prediction regarding the origin of life on early Earth. It hypothesizes that life arose as a geochemical process from inorganic starting materials on the surface of sulfide minerals in the vicinity of deep-sea hot springs. During the last two decades, many experimental studies have been carried out on this topic, and some interesting results have been achieved. Among them, however, the processes of carbon/nitrogen fixation and biomolecular assembly on the mineral surface have received an inordinate amount of attention. To the present, an abiotic model for the oxidation-reduction of intermediates participating in metabolic pathways has been ignored. We examined the oxidation-reduction effect of a prebiotic FeS/S/FeS(2) redox system on the interconversion between several pairs of α-hydroxy acids and α-keto acids (i.e., lactate/pyruvate, malate/oxaloacetate, and glycolate/glyoxylate). We found that, in the absence of FeS, elemental sulfur (S) oxidized α-hydroxy acids to form corresponding keto acids only at a temperature higher than its melting point (113°C); in the presence of FeS, such reactions occurred more efficiently through a coupled reaction mechanism, even at a temperature below the phase transition point of S. On the other hand, FeS was shown to have the capacity to reversibly reduce the keto acids. Such an oxidoreductase-like chemistry of the FeS/S/FeS(2) redox system suggests that it can determine the redox homeostasis of metabolic intermediates in the early evolutionary phase of life. The results provide a possible pathway for the development of primordial redox biochemistry in the iron-sulfur world. Key Words: Iron-sulfur world-FeS/S/FeS(2) redox system-Oxidoreductase-like chemistry. Astrobiology 11, 471-476.

  16. [Isolation, identification and oxidizing characterization of an iron-sulfur oxidizing bacterium LY01 from acid mine drainage].

    Science.gov (United States)

    Liu, Yu-jiao; Yang, Xin-ping; Wang, Shi-mei; Liang, Yin

    2013-05-01

    An acidophilic iron-sulfur oxidizing bacterium LY01 was isolated from acid mine drainage of coal in Guizhou Province, China. Strain LY01 was identified as Acidithiobacillusferrooxidans by morphological and physiological characteristics, and phylogenetic analysis of its 16S rRNA gene sequence. Strain LY01 was able to grow using ferrous ion (Fe2+), elemental sulfur (S0) and pyrite as sole energy source, respectively, but significant differences in oxidation efficiency and bacterial growth were observed when different energy source was used. When strain LY01 was cultured in 9K medium with 44.2 g x L(-1) FeSO4.7H2O as the substrate, the oxidation efficiency of Fe2+ was 100% in 30 h and the cell number of strain LY01 reached to 4.2 x 10(7) cell x mL(-1). When LY01 was cultured in 9K medium with 10 g x L(-1) S0 as the substrate, 6.7% S0 oxidation efficiency, 2001 mg x L(-1) SO4(2-) concentration and 8.9 x 10(7) cell x mL(-1) cell number were observed in 21 d respectively. When LY01 was cultured with 30 g x L(-1) pyrite as the substrate, the oxidation efficiency of pyrite, SO4(2-) concentration and cell number reached 10%, 4443 mg x L(-1) and 3.4 x 10(8) cell x mL(-1) respectively in 20 d. The effects of different heavy metals (Ni2+, Pb2+) on oxidation activity of strain LY01 cultured with pyrite were investigated. Results showed that the oxidation activity of strain LY01 was inhibited to a certain extent with the addition of Ni2+ at 10-100 mg x L(-1) to the medium, but the addition of 10-100 mg x L(-1) Pb2+ had no effect on LY01 activity.

  17. A Glutaredoxin·BolA Complex Serves as an Iron-Sulfur Cluster Chaperone for the Cytosolic Cluster Assembly Machinery.

    Science.gov (United States)

    Frey, Avery G; Palenchar, Daniel J; Wildemann, Justin D; Philpott, Caroline C

    2016-10-21

    Cells contain hundreds of proteins that require iron cofactors for activity. Iron cofactors are synthesized in the cell, but the pathways involved in distributing heme, iron-sulfur clusters, and ferrous/ferric ions to apoproteins remain incompletely defined. In particular, cytosolic monothiol glutaredoxins and BolA-like proteins have been identified as [2Fe-2S]-coordinating complexes in vitro and iron-regulatory proteins in fungi, but it is not clear how these proteins function in mammalian systems or how this complex might affect Fe-S proteins or the cytosolic Fe-S assembly machinery. To explore these questions, we use quantitative immunoprecipitation and live cell proximity-dependent biotinylation to monitor interactions between Glrx3, BolA2, and components of the cytosolic iron-sulfur cluster assembly system. We characterize cytosolic Glrx3·BolA2 as a [2Fe-2S] chaperone complex in human cells. Unlike complexes formed by fungal orthologs, human Glrx3-BolA2 interaction required the coordination of Fe-S clusters, whereas Glrx3 homodimer formation did not. Cellular Glrx3·BolA2 complexes increased 6-8-fold in response to increasing iron, forming a rapidly expandable pool of Fe-S clusters. Fe-S coordination by Glrx3·BolA2 did not depend on Ciapin1 or Ciao1, proteins that bind Glrx3 and are involved in cytosolic Fe-S cluster assembly and distribution. Instead, Glrx3 and BolA2 bound and facilitated Fe-S incorporation into Ciapin1, a [2Fe-2S] protein functioning early in the cytosolic Fe-S assembly pathway. Thus, Glrx3·BolA is a [2Fe-2S] chaperone complex capable of transferring [2Fe-2S] clusters to apoproteins in human cells. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Site-directed mutagenesis reveals new and essential elements for iron-coordination of the sulfur oxygenasereductase from the acidothermophilic Acidianus teng-chongensis

    Institute of Scientific and Technical Information of China (English)

    CHEN ZhiWei; JIANG ChengYing; LIU ShuangJiang

    2009-01-01

    Previous study on refolding of sulfur oxygenase reductase (SOR) inclusion bodies from recombinant Escherichia coli showed that iron was critical to the activity of the SOR from Acidianus ambivalens. In this study, enzymatic assays showed that 2,2'-Dipyridyl, Tiron and 8-hydroxyquinoline, which are spe-cific for chelating ferrous or ferric ions, strongly inhibited the activity of SOR from A. tengchongensis, suggesting that iron atom is essential for SOR activity. Alignment of several functionally identified SORs and SOR-like sequences from genome database revealed a conserved, putative iron binding motif, H86-X3-H90-Xn-E114-Xn-E129 (numbering according to the Acidianus tengchongensis SOR sequence). Three mutants of SOR were generated by site-directed mutagenesis of H86, H90 and E129 into phenyla-lanine or alanine residue in this study. Circular dichroism spectrum determination indicated that there was no change of the secondary structures of mutant SORs, H86F, H90F and E129A, but all mutants were completely inactive. Through determination of iron contents we found that SOR mutants of H86F, H90F and E129A completely or partially lost iron, while mutants of C31S, C101S, and C104S (generated in a pre-vious study) did not. This result indicated that H86, H90 and E129 but not C31, C101, and C104 were involved in binding to iron atom. Based on this and previous studies, it is proposed that the conserved motifs, C31-Xn-C101-X2-C104 and H86-X3-H90-X23-E114-X14-(E/D)129, are respectively for sulfur and molecular oxygen binding and activation. These two conserved motifs are essential elements for the SOR activity.

  19. Malfunctioning of the Iron–Sulfur Cluster Assembly Machinery in Saccharomyces cerevisiae Produces Oxidative Stress via an Iron-Dependent Mechanism, Causing Dysfunction in Respiratory Complexes

    Science.gov (United States)

    Gomez, Mauricio; Pérez-Gallardo, Rocío V.; Sánchez, Luis A.; Díaz-Pérez, Alma L.; Cortés-Rojo, Christian; Meza Carmen, Victor; Saavedra-Molina, Alfredo; Lara-Romero, Javier; Jiménez-Sandoval, Sergio; Rodríguez, Francisco; Rodríguez-Zavala, José S.; Campos-García, Jesús

    2014-01-01

    Biogenesis and recycling of iron–sulfur (Fe–S) clusters play important roles in the iron homeostasis mechanisms involved in mitochondrial function. In Saccharomyces cerevisiae, the Fe–S clusters are assembled into apoproteins by the iron–sulfur cluster machinery (ISC). The aim of the present study was to determine the effects of ISC gene deletion and consequent iron release under oxidative stress conditions on mitochondrial functionality in S. cerevisiae. Reactive oxygen species (ROS) generation, caused by H2O2, menadione, or ethanol, was associated with a loss of iron homeostasis and exacerbated by ISC system dysfunction. ISC mutants showed increased free Fe2+ content, exacerbated by ROS-inducers, causing an increase in ROS, which was decreased by the addition of an iron chelator. Our study suggests that the increment in free Fe2+ associated with ROS generation may have originated from mitochondria, probably Fe–S cluster proteins, under both normal and oxidative stress conditions, suggesting that Fe–S cluster anabolism is affected. Raman spectroscopy analysis and immunoblotting indicated that in mitochondria from SSQ1 and ISA1 mutants, the content of [Fe–S] centers was decreased, as was formation of Rieske protein-dependent supercomplex III2IV2, but this was not observed in the iron-deficient ATX1 and MRS4 mutants. In addition, the activity of complexes II and IV from the electron transport chain (ETC) was impaired or totally abolished in SSQ1 and ISA1 mutants. These results confirm that the ISC system plays important roles in iron homeostasis, ROS stress, and in assembly of supercomplexes III2IV2 and III2IV1, thus affecting the functionality of the respiratory chain. PMID:25356756

  20. High Pressure Melting of Iron with Nonmetals Sulfur, Carbon, Oxygen, and Hydrogen: Implications for Planetary Cores

    Science.gov (United States)

    Buono, Antonio Salvatore

    The earth's core consists of a solid metallic center surrounded by a liquid metallic outer layer. Understanding the compositions of the inner and outer cores allows us to better understand the dynamics of the earth's core, as well as the dynamics of the cores of other terrestrial planets and moons. The density and size of the earth's core indicate that it is approximately 90% metallic, predominantly iron, with about 10% light elements. Iron meteorites, believed to be the remnants of planetary cores, provide further constraints on the composition of the earth's core, indicating a composition of 86% iron, 4% nickel, and 10% light elements. Any potential candidate for the major light element core component must meet two criteria: first, it must have high cosmic abundances and second, it must be compatible with Fe. Given these two constraints there are five plausible elements that could be the major light element in the core: H, O, C, S, and Si. Of these five possible candidates this thesis focuses on S and C as well exploring the effect of minor amounts of O and H on the eutectic temperature in a Fe-FeS core. We look at two specific aspects of the Fe-FeS system: first, the shape of the liquidus as a function of pressure, second, a possible cause for the reported variations in the eutectic temperature, which draws on the effect of H and O. Finally we look at the effect of S and C on partitioning behavior of Ni, Pt, Re,Co, Os and W between cohenite and metallic liquid. We are interested in constraining the shape of the Fe-FeS liquidus because as a planet with a S-enriched core cools, the thermal and compositional evolution of its core is constrained by this liquidus. In Chapter 1 I present an equation that allows for calculation of the temperature along the liquidus as a function of pressure and composition for Fe-rich compositions and pressures from 1 bar to 10 GPa. One particularly interesting feature of the Fe --rich side of the Fe-FeS eutectic is the sigmoidal shape

  1. Linking sedimentary sulfur and iron biogeochemistry to growth patterns of a cold-water coral mound in the Porcupine Basin, S.W. Ireland (IODP Expedition 307).

    Science.gov (United States)

    Wehrmann, L M; Titschack, J; Böttcher, M E; Ferdelman, T G

    2015-09-01

    Challenger Mound, a 150-m-high cold-water coral mound on the eastern flank of the Porcupine Seabight off SW Ireland, was drilled during Expedition 307 of the Integrated Ocean Drilling Program (IODP). Retrieved cores offer unique insight into an archive of Quaternary paleo-environmental change, long-term coral mound development, and the diagenetic alteration of these carbonate fabrics over time. To characterize biogeochemical carbon-iron-sulfur transformations in the mound sediments, the contents of dithionite- and HCl-extractable iron phases, iron monosulfide and pyrite, and acid-extractable calcium, magnesium, manganese, and strontium were determined. Additionally, the stable isotopic compositions of pore-water sulfate and solid-phase reduced sulfur compounds were analyzed. Sulfate penetrated through the mound sequence and into the underlying Miocene sediments, where a sulfate-methane transition zone was identified. Small sulfate concentration decreases (<7 mM) within the top 40 m of the mound suggested slow net rates of present-day organoclastic sulfate reduction. Increasing δ(34)S-sulfate values due to microbial sulfate reduction mirrored the decrease in sulfate concentrations. This process was accompanied by oxygen isotope exchange with water that was indicated by increasing δ(18)O-sulfate values, reaching equilibrium with pore-water at depth. Below 50 mbsf, sediment intervals with strong (34)S-enriched imprints on chromium-reducible sulfur (pyrite S), high degree-of-pyritization values, and semi-lithified diagenetic carbonate-rich layers characterized by poor coral preservation, were observed. These layers provided evidence for the occurrence of enhanced microbial sulfate-reducing activity in the mound in the past during periods of rapid mound aggradation and subsequent intervals of non-deposition or erosion when geochemical fronts remained stationary. During these periods, especially during the Early Pleistocene, elevated sulfate reduction rates facilitated

  2. A role for tetrahydrofolates in the metabolism of iron-sulfur clusters in all domains of life.

    Science.gov (United States)

    Waller, Jeffrey C; Alvarez, Sophie; Naponelli, Valeria; Lara-Nuñez, Aurora; Blaby, Ian K; Da Silva, Vanessa; Ziemak, Michael J; Vickers, Tim J; Beverley, Stephen M; Edison, Arthur S; Rocca, James R; Gregory, Jesse F; de Crécy-Lagard, Valérie; Hanson, Andrew D

    2010-06-08

    Iron-sulfur (Fe/S) cluster enzymes are crucial to life. Their assembly requires a suite of proteins, some of which are specific for particular subsets of Fe/S enzymes. One such protein is yeast Iba57p, which aconitase and certain radical S-adenosylmethionine enzymes require for activity. Iba57p homologs occur in all domains of life; they belong to the COG0354 protein family and are structurally similar to various folate-dependent enzymes. We therefore investigated the possible relationship between folates and Fe/S cluster enzymes using the Escherichia coli Iba57p homolog, YgfZ. NMR analysis confirmed that purified YgfZ showed stereoselective folate binding. Inactivating ygfZ reduced the activities of the Fe/S tRNA modification enzyme MiaB and certain other Fe/S enzymes, although not aconitase. When successive steps in folate biosynthesis were ablated, folE (lacking pterins and folates) and folP (lacking folates) mutants mimicked the ygfZ mutant in having low MiaB activities, whereas folE thyA mutants supplemented with 5-formyltetrahydrofolate (lacking pterins and depleted in dihydrofolate) and gcvP glyA mutants (lacking one-carbon tetrahydrofolates) had intermediate MiaB activities. These data indicate that YgfZ requires a folate, most probably tetrahydrofolate. Importantly, the ygfZ mutant was hypersensitive to oxidative stress and grew poorly on minimal media. COG0354 genes of bacterial, archaeal, fungal, protistan, animal, or plant origin complemented one or both of these growth phenotypes as well as the MiaB activity phenotype. Comparative genomic analysis indicated widespread functional associations between COG0354 proteins and Fe/S cluster metabolism. Thus COG0354 proteins have an ancient, conserved, folate-dependent function in the activity of certain Fe/S cluster enzymes.

  3. Analysis of NFU-1 Metallocofactor Binding Site Substitutions: Impacts on Iron-Sulfur Cluster Coordination and Protein Structure and Function.

    Science.gov (United States)

    Wesley, Nathaniel A; Wachnowsky, Christine; Fidai, Insiya; Cowan, J A

    2017-09-14

    Iron-sulfur (Fe/S) clusters are ancient prosthetic groups found in numerous metalloproteins and are conserved across all kingdoms of life due to their diverse, yet essential functional roles. Genetic mutations to a specific subset of mitochondrial Fe/S cluster delivery proteins are broadly categorized as disease related under multiple mitochondrial dysfunction syndrome (MMDS), with symptoms indicative of a general failure of the metabolic system. Multiple mitochondrial dysfunction syndrome 1 (MMDS1) arises as a result of the missense mutation in NFU1, an Fe/S cluster scaffold protein, which substitutes a glycine near the Fe/S cluster binding pocket to a cysteine (p.Gly208Cys). This substitution has been shown to promote protein dimerization such that cluster delivery to NFU1 is blocked, preventing downstream cluster trafficking. However, the possibility of this additional cysteine, located adjacent to the cluster binding site, serving as an Fe/S cluster ligand has not yet been explored. To fully understand the consequences of this Gly208Cys replacement, complementary substitutions at the Fe/S cluster binding pocket for native and Gly208Cys NFU1 were made, along with six other variants. Herein we report the results of an investigation on the effect of these substitutions on both cluster coordination and NFU1 structure and function. The data suggest that the G208C substitution does not contribute to cluster binding. Rather, replacement of the glycine at position 208 changes the oligomerization state as a result of global structural alterations that result in the downstream effects manifest as MMDS1, but does not perturb the coordination chemistry of the Fe-S cluster. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  4. Iron-Sulfur Cluster Biogenesis Chaperones: Evidence for Emergence of Mutational Robustness of a Highly Specific Protein-Protein Interaction.

    Science.gov (United States)

    Delewski, Wojciech; Paterkiewicz, Bogumiła; Manicki, Mateusz; Schilke, Brenda; Tomiczek, Bartłomiej; Ciesielski, Szymon J; Nierzwicki, Lukasz; Czub, Jacek; Dutkiewicz, Rafal; Craig, Elizabeth A; Marszalek, Jaroslaw

    2016-03-01

    Biogenesis of iron-sulfur clusters (FeS) is a highly conserved process involving Hsp70 and J-protein chaperones. However, Hsp70 specialization differs among species. In most eukaryotes, including Schizosaccharomyces pombe, FeS biogenesis involves interaction between the J-protein Jac1 and the multifunctional Hsp70 Ssc1. But, in Saccharomyces cerevisiae and closely related species, Jac1 interacts with the specialized Hsp70 Ssq1, which emerged through duplication of SSC1. As little is known about how gene duplicates affect the robustness of their protein interaction partners, we analyzed the functional and evolutionary consequences of Ssq1 specialization on the ubiquitous J-protein cochaperone Jac1, by comparing S. cerevisiae and S. pombe. Although deletion of JAC1 is lethal in both species, alanine substitutions within the conserved His-Pro-Asp (HPD) motif, which is critical for Jac1:Hsp70 interaction, have species-specific effects. They are lethal in S. pombe, but not in S. cerevisiae. These in vivo differences correlated with in vitro biochemical measurements. Charged residues present in the J-domain of S. cerevisiae Jac1, but absent in S. pombe Jac1, are important for tolerance of S. cerevisiae Jac1 to HPD alterations. Moreover, Jac1 orthologs from species that encode Ssq1 have a higher sequence divergence. The simplest interpretation of our results is that Ssq1's coevolution with Jac1 resulted in expansion of their binding interface, thus increasing the efficiency of their interaction. Such an expansion could in turn compensate for negative effects of HPD substitutions. Thus, our results support the idea that the robustness of Jac1 emerged as consequence of its highly efficient and specific interaction with Ssq1. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. Iron, Sulfur, Arsenic and Water: Geochemical Implications of Facultative Anoxygenic Photosynthesis in Cyanobacteria and the Slow Rise of Oxygen

    Science.gov (United States)

    Wolfe-Simon, F.; Johnston, D. T.; Girguis, P. R.; Pearson, A.; Knoll, A. H.

    2008-12-01

    Over geologic time, the global rise in atmospheric oxygen (O2) is attributed to the evolution and wide spread proliferation of oxygenic photosynthesis in cyanobacteria. However, cyanobacteria maintain a metabolic flexibility that may not always result in O2 release. Specifically, cyanobacteria can use a variety of alternative electron donors, rather than water, that are also readily oxidized. These may include sulfur, iron, and arsenic. Cyanobacteria are thus not uniquely constrained towards O2 production. Changes in the bioavailability of these key elements may have had dramatic consequences for and resulted in the slow accumulation of O2 in the atmosphere. In particular, by using facultative anoxygenic photosynthesis the cells maintain advantageous anaerobic conditions for N2-fixation. Although other types of bacteria are capable of N2-fixation, cyanobacteria singularly possess the dynamic capability of generating and surviving O2. These two processes "pull" the cells in opposite directions, metabolically speaking, around an aerobic-anaerobic continuum. Such a strategy also confers a distinct competitive advantage for cyanobacteria over photosynthetic eukaryotes, as they can endure widespread euxinia and maintain their cellular N quota. In an anoxic and/or sulfidic ocean, cyanobacteria would be expected to dominate over eukaryotic algae. Here we present Bayesian constructed phylogenetic distribution of specific genes and the metabolic role of key enzymes that form the basis of this hypothesis. We further suggest that the consequences of this proposed ecosystem structure altered the redox balance of the fluid Earth (atmosphere and oceans) and can help explain the observed long-term geochemical stasis and slow rates of eukaryotic diversification. We suggest that the underlying control for global oxygenation was a synergistic interplay between the evolution and elastic physiology of cyanobacteria as they impacted the redox state of early Earth.

  6. High sulfur isotope fractionation associated with anaerobic oxidation of methane in a low sulfate, iron rich environment

    Directory of Open Access Journals (Sweden)

    Hannah Sophia Weber

    2016-06-01

    Full Text Available Sulfur isotope signatures provide key information for the study of microbial activity in modern systems and the evolution of the Earth surface redox system. Microbial sulfate reducers shift sulfur isotope distributions by discriminating against heavier isotopes. This discrimination is strain-specific and often suppressed at sulfate concentrations in the lower micromolar range that are typical to freshwater systems and inferred for ancient oceans. Anaerobic oxidation of methane (AOM is a sulfate-reducing microbial process with a strong impact on global sulfur cycling in modern habitats and potentially in the geological past, but its impact on sulfur isotope signatures is poorly understood, especially in low sulfate environments. We investigated sulfur cycling and 34S fractionation in a low-sulfate freshwater sediment with biogeochemical conditions analogous to Early Earth environments. The zone of highest AOM activity was associated in situ with a zone of strong 34S depletions in the pool of reduced sulfur species, indicating a coupling of sulfate reduction and AOM at sulfate concentrations < 50 µmol L-1. In slurry incubations of AOM-active sediment, the addition of methane stimulated sulfate reduction and induced a bulk sulfur isotope effect of ~29 ‰. Our results imply that sulfur isotope signatures may be strongly impacted by AOM even at sulfate concentrations two orders of magnitude lower than at present oceanic levels. Therefore, we suggest that sulfur isotope fractionation during AOM must be considered when interpreting 34S signatures in modern and ancient environment.

  7. Iron and Sulfur Geochemistry in Class H Wellbore Cements Exposed to CO2 and H2S

    Science.gov (United States)

    Lopano, C. L.; Webb, S. M.; Kutchko, B. G.; Strazisar, B. R.; Hawthorne, S. B.; Miller, D. J.; Guthrie, G.; Hakala, A.

    2013-12-01

    The effects of CO2 & co-constituents (such as H2S) sequestration on cement seal integrity are not well understood in the context of wellbore integrity for CO2 storage. This study evaluates the redox effects that co-contaminants such as H2S present to the CO2-cement reaction system via synchrotron X-ray XANES mapping specific to the iron and sulfur edge energies. Portland Class H cement was exposed to various proportions of H2S:CO2 in 1% NaCl saturated brine (1%, 21 mol%, and 40% H2S) under supercritical conditions (50°C and 15MPa). The reaction of cement with H2S-CO2 results in the formation of pyrite associated with the Fe-rich cement clinker phase, brownmillerite (also termed ferrite). Ferrite has not reacted in previous exposures to CO2 alone, which was confirmed by synchrotron spectroscopic analysis of cement exposed to supercritical CO2 alone. Thus it is hypothesized that the reaction is a result of redox conditions introduced by H2S. The synchrotron X-ray microprobe fluorescence (μXRF) imaging and spectroscopy capabilities at beamlines 2-3 and 14-3 at SSRL were used to collect multiple energy (ME) maps for both Fe and S in order to evaluate reaction fronts in the cement matrix and to monitor the chemical changes in the cement associated with exposure to CO2 (and H2S) at sequestration conditions. The use of this micro-spectroscopy technique allows for in-situ identification of any reaction intermediates (including amorphous materials) for the Fe and S phases in the cement. The coupled μXANES and μXRF data were used to generate iron and S speciation maps of the cement cores. Synchrotron microprobe capabilities at 2-3 were used to collected ME maps of Fe, and show differences in Fe oxidation between the rims (Fe2+) and cores (Fe3+) of the cement thin section. Analysis of Fe XANES indicates that there are potentially 4+ distinct coordination environments for the Fe in the cement cores studied: pyrite, ferrihydrite, brownmillerite (Fe3+, and/or Fe2+) and

  8. Iron

    Science.gov (United States)

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  9. Iron

    Science.gov (United States)

    ... of iron stored in the body become low, iron deficiency anemia sets in. Red blood cells become smaller and ... from the lungs throughout the body. Symptoms of iron deficiency anemia include tiredness and lack of energy, GI upset, ...

  10. Molybdenum, molybdenum oxides, and their electrochemistry.

    Science.gov (United States)

    Saji, Viswanathan S; Lee, Chi-Woo

    2012-07-01

    The electrochemical behaviors of molybdenum and its oxides, both in bulk and thin film dimensions, are critical because of their widespread applications in steels, electrocatalysts, electrochromic materials, batteries, sensors, and solar cells. An important area of current interest is electrodeposited CIGS-based solar cells where a molybdenum/glass electrode forms the back contact. Surprisingly, the basic electrochemistry of molybdenum and its oxides has not been reviewed with due attention. In this Review, we assess the scattered information. The potential and pH dependent active, passive, and transpassive behaviors of molybdenum in aqueous media are explained. The major surface oxide species observed, reversible redox transitions of the surface oxides, pseudocapacitance and catalytic reduction are discussed along with carefully conducted experimental results on a typical molybdenum glass back contact employed in CIGS-based solar cells. The applications of molybdenum oxides and the electrodeposition of molybdenum are briefly reviewed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery: THE SUB-COMPLEX FORMED BY THE IRON DONOR, Yfh1 PROTEIN, AND THE SCAFFOLD, Isu1 PROTEIN.

    Science.gov (United States)

    Ranatunga, Wasantha; Gakh, Oleksandr; Galeano, Belinda K; Smith, Douglas Y; Söderberg, Christopher A G; Al-Karadaghi, Salam; Thompson, James R; Isaya, Grazia

    2016-05-06

    The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24 Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly.

  12. A novel DNA modification by sulfur: DndA is a NifS-like cysteine desulfurase capable of assembling DndC as an iron-sulfur cluster protein in Streptomyces lividans.

    Science.gov (United States)

    You, Delin; Wang, Lianrong; Yao, Fen; Zhou, Xiufen; Deng, Zixin

    2007-05-22

    A novel DNA modification system by sulfur (S) in Streptomyces lividans 66 was reported to be encoded by a cluster of five genes designated dndA-E [Zhou, X., He, X., Liang, J., Li, A., Xu, T., Kieser, T., Helmann, J. D., and Deng, Z. (2005) Mol. Microbiol. 57, 1428-1438]. The dndA gene was cloned and the protein product expressed in Escherichia coli, purified to homogeneity, and characterized as a homodimeric protein of ca. 91 kDa. Purified DndA has a yellow color and UV-visible spectra characteristic of a pyridoxal phosphate-containing enzyme and was proven to be a cysteine desulfurase able to catalyze removal of elemental S atoms from l-cysteine to produce l-alanine with substrate specificity similar to that of E. coli IscS. DndC was also purified to homogeneity and found to contain a 4Fe-4S cluster by spectral analysis and have obvious ATP pyrophosphatase activity. DndA could catalyze iron-sulfur cluster assembly by activation of apo-Fe DndC protein prepared by removal of its iron-sulfur cluster using alpha,alpha'-dipyridyl. A mutated DndA, with serine substituted for cysteine at position 327, which was confirmed to have lost its corresponding cysteine desulfurase activity, also lost its ability to reactivate the apo-Fe DndC. The likely involvement of an interaction between DndA and DndC in the biochemical pathway for the unusual site-specific DNA modification in S. lividans 66 is discussed.

  13. NIF-type iron-sulfur cluster assembly system is duplicated and distributed in the mitochondria and cytosol of Mastigamoeba balamuthi.

    Science.gov (United States)

    Nývltová, Eva; Šuták, Robert; Harant, Karel; Šedinová, Miroslava; Hrdy, Ivan; Paces, Jan; Vlček, Čestmír; Tachezy, Jan

    2013-04-30

    In most eukaryotes, the mitochondrion is the main organelle for the formation of iron-sulfur (FeS) clusters. This function is mediated through the iron-sulfur cluster assembly machinery, which was inherited from the α-proteobacterial ancestor of mitochondria. In Archamoebae, including pathogenic Entamoeba histolytica and free-living Mastigamoeba balamuthi, the complex iron-sulfur cluster machinery has been replaced by an ε-proteobacterial nitrogen fixation (NIF) system consisting of two components: NifS (cysteine desulfurase) and NifU (scaffold protein). However, the cellular localization of the NIF system and the involvement of mitochondria in archamoebal FeS assembly are controversial. Here, we show that the genes for both NIF components are duplicated within the M. balamuthi genome. One paralog of each protein contains an amino-terminal extension that targets proteins to mitochondria (NifS-M and NifU-M), and the second paralog lacks a targeting signal, thereby reflecting the cytosolic form of the NIF machinery (NifS-C and NifU-C). The dual localization of the NIF system corresponds to the presence of FeS proteins in both cellular compartments, including detectable hydrogenase activity in Mastigamoeba cytosol and mitochondria. In contrast, E. histolytica possesses only single genes encoding NifS and NifU, respectively, and there is no evidence for the presence of the NIF machinery in its reduced mitochondria. Thus, M. balamuthi is unique among eukaryotes in that its FeS cluster formation is mediated through two most likely independent NIF machineries present in two cellular compartments.

  14. Photoelectron Spectroscopy and Density Functional Theory Studies of Iron Sulfur (FeS)m(-) (m = 2-8) Cluster Anions: Coexisting Multiple Spin States.

    Science.gov (United States)

    Yin, Shi; Bernstein, Elliot R

    2017-10-05

    Iron sulfur cluster anions (FeS)m(-) (m = 2-8) are studied by photoelectron spectroscopy (PES) at 3.492 eV (355 nm) and 4.661 eV (266 nm) photon energies, and by density functional theory (DFT) calculations. The most probable structures and ground state spin multiplicities for (FeS)m(-) (m = 2-8) clusters are tentatively assigned through a comparison of their theoretical and experiment first vertical detachment energy (VDE) values. Many spin states lie within 0.5 eV of the ground spin state for the larger (FeS)m(-) (m ≥ 4) clusters. Theoretical VDEs of these low lying spin states are in good agreement with the experimental VDE values. Therefore, multiple spin states of each of these iron sulfur cluster anions probably coexist under the current experimental conditions. Such available multiple spin states must be considered when evaluating the properties and behavior of these iron sulfur clusters in real chemical and biological systems. The experimental first VDEs of (FeS)m(-) (m = 1-8) clusters are observed to change with the cluster size (number m). The first VDE trends noted can be related to the different properties of the highest singly occupied molecular orbitals (NBO, HSOMOs) of each cluster anion. The changing nature of the NBO/HSOMO of these (FeS)m(-) (m = 1-8) clusters from a p orbital on S, to a d orbital on Fe, and to an Fe-Fe bonding orbital is probably responsible for the observed increasing trend for their first VDEs with respect to m.

  15. High sulfur isotope fractionation associated with anaerobic oxidation of methane in a low sulfate, iron rich environment

    Science.gov (United States)

    Weber, Hannah; Thamdrup, Bo; Habicht, Kirsten

    2016-06-01

    Sulfur isotope signatures provide key information for the study of microbial activity in modern systems and the evolution of the Earth surface redox system. Microbial sulfate reducers shift sulfur isotope distributions by discriminating against heavier isotopes. This discrimination is strain-specific and often suppressed at sulfate concentrations in the lower micromolar range that are typical to freshwater systems and inferred for ancient oceans. Anaerobic oxidation of methane (AOM) is a sulfate-reducing microbial process with a strong impact on global sulfur cycling in modern habitats and potentially in the geological past, but its impact on sulfur isotope signatures is poorly understood, especially in low sulfate environments. We investigated sulfur cycling and 34S fractionation in a low-sulfate freshwater sediment with biogeochemical conditions analogous to Early Earth environments. The zone of highest AOM activity was associated in situ with a zone of strong 34S depletions in the pool of reduced sulfur species, indicating a coupling of sulfate reduction and AOM at sulfate concentrations oceanic levels. Therefore, we suggest that sulfur isotope fractionation during AOM must be considered when interpreting 34S signatures in modern and ancient environment.

  16. The Global Redox Responding RegB/RegA Signal Transduction System Regulates the Genes Involved in Ferrous Iron and Inorganic Sulfur Compound Oxidation of the Acidophilic Acidithiobacillus ferrooxidans

    Directory of Open Access Journals (Sweden)

    Danielle Moinier

    2017-07-01

    Full Text Available The chemical attack of ore by ferric iron and/or sulfuric acid releases valuable metals. The products of these reactions are recycled by iron and sulfur oxidizing microorganisms. These acidophilic chemolithotrophic prokaryotes, among which Acidithiobacillus ferrooxidans, grow at the expense of the energy released from the oxidation of ferrous iron and/or inorganic sulfur compounds (ISCs. In At. ferrooxidans, it has been shown that the expression of the genes encoding the proteins involved in these respiratory pathways is dependent on the electron donor and that the genes involved in iron oxidation are expressed before those responsible for ISCs oxidation when both iron and sulfur are present. Since the redox potential increases during iron oxidation but remains stable during sulfur oxidation, we have put forward the hypothesis that the global redox responding two components system RegB/RegA is involved in this regulation. To understand the mechanism of this system and its role in the regulation of the aerobic respiratory pathways in At. ferrooxidans, the binding of different forms of RegA (DNA binding domain, wild-type, unphosphorylated and phosphorylated-like forms of RegA on the regulatory region of different genes/operons involved in ferrous iron and ISC oxidation has been analyzed. We have shown that the four RegA forms are able to bind specifically the upstream region of these genes. Interestingly, the phosphorylation of RegA did not change its affinity for its cognate DNA. The transcriptional start site of these genes/operons has been determined. In most cases, the RegA binding site(s was (were located upstream from the −35 (or −24 box suggesting that RegA does not interfere with the RNA polymerase binding. Based on the results presented in this report, the role of the RegB/RegA system in the regulation of the ferrous iron and ISC oxidation pathways in At. ferrooxidans is discussed.

  17. The Global Redox Responding RegB/RegA Signal Transduction System Regulates the Genes Involved in Ferrous Iron and Inorganic Sulfur Compound Oxidation of the Acidophilic Acidithiobacillus ferrooxidans.

    Science.gov (United States)

    Moinier, Danielle; Byrne, Deborah; Amouric, Agnès; Bonnefoy, Violaine

    2017-01-01

    The chemical attack of ore by ferric iron and/or sulfuric acid releases valuable metals. The products of these reactions are recycled by iron and sulfur oxidizing microorganisms. These acidophilic chemolithotrophic prokaryotes, among which Acidithiobacillus ferrooxidans, grow at the expense of the energy released from the oxidation of ferrous iron and/or inorganic sulfur compounds (ISCs). In At. ferrooxidans, it has been shown that the expression of the genes encoding the proteins involved in these respiratory pathways is dependent on the electron donor and that the genes involved in iron oxidation are expressed before those responsible for ISCs oxidation when both iron and sulfur are present. Since the redox potential increases during iron oxidation but remains stable during sulfur oxidation, we have put forward the hypothesis that the global redox responding two components system RegB/RegA is involved in this regulation. To understand the mechanism of this system and its role in the regulation of the aerobic respiratory pathways in At. ferrooxidans, the binding of different forms of RegA (DNA binding domain, wild-type, unphosphorylated and phosphorylated-like forms of RegA) on the regulatory region of different genes/operons involved in ferrous iron and ISC oxidation has been analyzed. We have shown that the four RegA forms are able to bind specifically the upstream region of these genes. Interestingly, the phosphorylation of RegA did not change its affinity for its cognate DNA. The transcriptional start site of these genes/operons has been determined. In most cases, the RegA binding site(s) was (were) located upstream from the -35 (or -24) box suggesting that RegA does not interfere with the RNA polymerase binding. Based on the results presented in this report, the role of the RegB/RegA system in the regulation of the ferrous iron and ISC oxidation pathways in At. ferrooxidans is discussed.

  18. Role of evaporitic sulfates in iron skarn mineralization: a fluid inclusion and sulfur isotope study from the Xishimen deposit, Handan-Xingtai district, North China Craton

    Science.gov (United States)

    Wen, Guang; Bi, Shi-Jian; Li, Jian-Wei

    2017-04-01

    The Xishimen iron skarn deposit in the Handan-Xingtai district, North China Craton, contains 256 Mt @ 43 % Fe (up to 65 %). The mineralization is dominated by massive magnetite ore along the contact zone between the early Cretaceous Xishimen diorite stock and middle Ordovician dolomite and dolomitic limestones with numerous intercalations of evaporitic beds. Minor lenticular magnetite-dominated bodies also occur in the carbonate rocks proximal to the diorite stock. Hydrothermal alteration is characterized by extensive albitization within the diorite stock and extreme development of magnesian skarn along the contact zone consisting of diopside, forsterite, serpentine, tremolite, phlogopite, and talc. Magmatic quartz and amphibole from the diorite and hydrothermal diopside from the skarns contain abundant primary or pseudosecondary fluid inclusions, most of which have multiple daughter minerals dominated by halite, sylvite, and opaque phases. Scanning electron microscopy (SEM) and laser Raman spectrometry confirm that pyrrhotite is the predominant opaque phase in most fluid inclusions, in both the magmatic and skarn minerals. These fluid inclusions have total homogenization temperatures of 416-620 °C and calculated salinities of 42.4-74.5 wt% NaCl equiv. The fluid inclusion data thus document a high-temperature, high-salinity, ferrous iron-rich, reducing fluid exsolved from a cooling magma likely represented by the Xishimen diorite stock. Pyrite from the iron ore has δ34S values ranging from 14.0 to 18.6 ‰, which are significantly higher than typical magmatic values (δ34S = 0 ± 5 ‰). The sulfur isotope data thus indicate an external source for the sulfur, most likely from the evaporitic beds in the Ordovician carbonate sequences that have δ34S values of 24 to 29 ‰. We suggest that sulfates from the evaporitic beds have played a critically important role by oxidizing ferrous iron in the magmatic-hydrothermal fluid, leading to precipitation of massive

  19. Role of evaporitic sulfates in iron skarn mineralization: a fluid inclusion and sulfur isotope study from the Xishimen deposit, Handan-Xingtai district, North China Craton

    Science.gov (United States)

    Wen, Guang; Bi, Shi-Jian; Li, Jian-Wei

    2016-08-01

    The Xishimen iron skarn deposit in the Handan-Xingtai district, North China Craton, contains 256 Mt @ 43 % Fe (up to 65 %). The mineralization is dominated by massive magnetite ore along the contact zone between the early Cretaceous Xishimen diorite stock and middle Ordovician dolomite and dolomitic limestones with numerous intercalations of evaporitic beds. Minor lenticular magnetite-dominated bodies also occur in the carbonate rocks proximal to the diorite stock. Hydrothermal alteration is characterized by extensive albitization within the diorite stock and extreme development of magnesian skarn along the contact zone consisting of diopside, forsterite, serpentine, tremolite, phlogopite, and talc. Magmatic quartz and amphibole from the diorite and hydrothermal diopside from the skarns contain abundant primary or pseudosecondary fluid inclusions, most of which have multiple daughter minerals dominated by halite, sylvite, and opaque phases. Scanning electron microscopy (SEM) and laser Raman spectrometry confirm that pyrrhotite is the predominant opaque phase in most fluid inclusions, in both the magmatic and skarn minerals. These fluid inclusions have total homogenization temperatures of 416-620 °C and calculated salinities of 42.4-74.5 wt% NaCl equiv. The fluid inclusion data thus document a high-temperature, high-salinity, ferrous iron-rich, reducing fluid exsolved from a cooling magma likely represented by the Xishimen diorite stock. Pyrite from the iron ore has δ34S values ranging from 14.0 to 18.6 ‰, which are significantly higher than typical magmatic values (δ34S = 0 ± 5 ‰). The sulfur isotope data thus indicate an external source for the sulfur, most likely from the evaporitic beds in the Ordovician carbonate sequences that have δ34S values of 24 to 29 ‰. We suggest that sulfates from the evaporitic beds have played a critically important role by oxidizing ferrous iron in the magmatic-hydrothermal fluid, leading to precipitation of massive

  20. Study of the sulfur mechanism on the formation of coke deposition on iron surfaces; Etude des mecanismes d'action du soufre sur le cokage catalytique du fer

    Energy Technology Data Exchange (ETDEWEB)

    Bonnet, F.

    2001-12-01

    The formation of coke deposition which occurs in a range of temperature 500 deg C-650 deg C is a major problem in many chemical and petrochemical processes where hydrocarbons or other strongly carburizing atmospheres are involved. To reduce the rate of coke deposition, sulfur can be added in the gas phase. The topic of this work is to study the sulfur mechanism on the formation of coke deposition on iron surfaces. Firstly, we study the mechanism of graphitic filament formation on reduced and oxidised iron surfaces. A new mechanism of catalytic particle formation is proposed when the surface is initially oxidised. This mechanism is based on thermodynamic, kinetic and structural considerations. The results show that oxide/carbide transitions are involved in the transformation of the oxide layer in catalytic particles. Although the different iron oxides are precursors for the formation of catalytic particles, wustite (FeO) has a better reactivity than magnetite (Fe{sub 3}O{sub 4}) and hematite (Fe{sub 2}O{sub 3}). Sulfur acts on different steps of the coke formation, preventing phase transformations (carburation, graphitization) which occur during the formation of catalytic particles. Sulfur activity required to prevent these transformations changes with the temperature, the chemical state of iron (reduced or oxidised) and the carbon activity in the gas phase. Sulfur/ethylene co-adsorption studies were performed on mono-crystal of iron (110). The results show that sulfur can prevent adsorption and decomposition of this hydrocarbon on metallic surface (Fe) and on magnetite (Fe{sub 3}O{sub 4}). Then, sulfur prevents the reaction leading to the carburation and graphitization of the surface. (author)

  1. Coupled sulfur, iron and molybdenum isotope data from black shales of the Teplá-Barrandian unit argue against deep ocean oxygenation during the Ediacaran

    Science.gov (United States)

    Kurzweil, Florian; Drost, Kerstin; Pašava, Jan; Wille, Martin; Taubald, Heinrich; Schoeckle, Daniel; Schoenberg, Ronny

    2015-12-01

    The Earth's atmosphere and hydrosphere changed from an Archean anoxic to a modern oxygenated world in two major steps, the Paleoproterozoic Great Oxidation Event (2.4-2.3 billion years ago) and the Neoproterozoic Oxidation Event (0.8-0.5 billion years ago). Both events had a strong influence on the availability of redox sensitive and bio-essential metals within the ocean and are, thus, strongly linked to fundamental biological innovations and diversification. Biological diversification during the Precambrian-Cambrian transition between 555 and 540 million years ago may have been driven by ocean-atmosphere oxygenation. The exact timing and the extent of (deep) ocean oxygenation within this time period remains unresolved though. Here we present major and trace element compositions as well as Mo, S and Fe isotopic data of organic-rich black shales from the Teplá-Barrandian unit, Czech Republic. New in situ zircon U-Pb ages provide a maximum depositional age of 559.8 ± 3.8 million years. Black shales with strong metal enrichment show low δ56Fe values due to the dominance of authigenic pyrite-Fe with δ56Fe values around -0.6‰ over detrital Fe with δ56Fe values around 0.1‰. Samples with lower authigenic metal enrichment show relatively low Mo/TOC ratios and increasing δ34S values, which is interpreted to reflect basinal restriction and longer seawater renewal times. In analogy to the modern Black Sea, the accompanied depletion of basinal Moaq due to near quantitative Mo removal might have led to the preservation of the seawater δ98Mo in the respective black shales. Our best estimate for this seawater Mo isotopic composition Proterozoic black shales. The lack of higher δ98Mo values in black shales (and seawater) argues against contemporaneous Mn oxide formation in well oxygenated deep sea settings, which would preferentially adsorb isotopically light Mo leaving behind an isotopically heavy ocean. By contrast, the deep ocean might have remained ferruginous with the hydrothermal Fe still outbalancing surficial oxygen production. Our results therefore contribute to a growing data set, which suggests limited deep water oxygenation during major biological innovations in the late Ediacaran period.

  2. Sites for phosphates and iron-sulfur thiolates in the first membranes: 3 to 6 residue anion-binding motifs (nests).

    Science.gov (United States)

    Milner-White, E James; Russell, Michael J

    2005-02-01

    Nests are common three to six amino acid residue motifs in proteins where successive main chain NH groups bind anionic atoms or groups. On average 8% of residues in proteins belong to nests. Nests form a key part of a number of phosphate binding sites, notably the P-loop, which is the commonest of the binding sites for the phosphates of ATP and GTP. They also occur regularly in sites that bind [Fe2S2](RS)4 [Fe3S4](RS)3and [Fe4S4](RS)4 iron-sulfur centers, which are also anionic groups. Both phosphates and iron-sulfur complexes would have occurred in the precipitates within hydrothermal vents of moderate temperature as key components of the earliest metabolism and it is likely existing organisms emerging in this milieu would have benefited from evolving molecules binding such anions. The nest conformation is favored by high proportions of glycine residues and there is evidence for glycine being the commonest amino acid during the stage of evolution when proteins were evolving so it is likely nests would have been common features in peptides occupying the membranes at the dawn of life.

  3. Iron

    DEFF Research Database (Denmark)

    Hansen, Jakob Bondo; Moen, I W; Mandrup-Poulsen, T

    2014-01-01

    The interest in the role of ferrous iron in diabetes pathophysiology has been revived by recent evidence of iron as an important determinant of pancreatic islet inflammation and as a biomarker of diabetes risk and mortality. The iron metabolism in the β-cell is complex. Excess free iron is toxic......, but at the same time, iron is required for normal β-cell function and thereby glucose homeostasis. In the pathogenesis of diabetes, iron generates reactive oxygen species (ROS) by participating in the Fenton chemistry, which can induce oxidative damage and apoptosis. The aim of this review is to present...... and discuss recent evidence, suggesting that iron is a key pathogenic factor in both type 1 and type 2 diabetes with a focus on inflammatory pathways. Pro-inflammatory cytokine-induced β-cell death is not fully understood, but may include iron-induced ROS formation resulting in dedifferentiation by activation...

  4. Bioleaching of metal from municipal waste incineration fly ash using a mixed culture of sulfur-oxidizing and iron-oxidizing bacteria.

    Science.gov (United States)

    Ishigaki, Tomonori; Nakanishi, Akane; Tateda, Masafumi; Ike, Michihiko; Fujita, Masanori

    2005-08-01

    We investigated the behavior and characteristics of metal leaching from municipal solid waste incineration (MSWI) fly ash among pure cultures of a sulfur-oxidizing bacterium (SOB) and an iron-oxidizing bacterium (IOB) and a mixed culture. The IOB has a high metal-leaching ability, though its tolerability against the ash addition is low. The SOB might better tolerate an increase in ash addition than the IOB, though metal leaching ability of the SOB is limited. Mixed culture could compensate for these deficiencies, and high metal leachability was exhibited in the 1% ash culture, i.e., 67% and 78% of leachabilities for Cu and Zn, respectively, and 100% for Cr and Cd. Furthermore, comparably high leachabilities such as 42% and 78% for Cu and Zn were observed even in the 3% ash cultures. Characterization of metal leaching by the mixed culture revealed that the acidic and oxidizing condition had remained stable thorough the experimental period. Ferric iron remained in the mixed culture, and the metal leaching was enhanced by redox mechanisms coupling with the leaching by sulfate. An increase of ferrous iron enhanced the Cr, Cu, and As leaching. The optimum concentration of sulfur existed for As and Cr (5 gl(-1)) and Cu (2 gl(-1)). The presence of the degradable and non-degradable organic compound that must be existed in the natural environment or waste landfills made no significant change in the leachability of metals other than Zn. These results suggested that bioleaching using a mixed culture of SOB and IOB is a promising technology for recovering the valuable metals from MSWI fly ash.

  5. Sulfur Earth

    Science.gov (United States)

    de Jong, B. H.

    2007-12-01

    Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to

  6. Alkylation of Sulfur Ligand in Cysteinate-Iron Chelates by a 1,2,4,5-Tetraoxane

    Institute of Scientific and Technical Information of China (English)

    刘鹤华; 伍贻康; 沈鑫

    2003-01-01

    Reaction of a 1,2, 4, 5-tetraoxane with cysteinate-iron in the presence of excess methyl cysteinate led to formation of sulfuralkylated methyl cysteinate in 33 % yield, illustrating a possible mechanism for tetraoxanes' antimalarial action.

  7. Impairment of respiratory chain under nutrient deficiencies in plants: does it play a role in the regulation of iron and sulfur responsive genes?

    Directory of Open Access Journals (Sweden)

    GIANPIERO eVIGANI

    2016-01-01

    Full Text Available Plant production and plant product quality strongly depends on the availability of mineral nutrients. Among them, sulfur (S and iron (Fe play a central role, as they are needed for many proteins of the respiratory chain. Plant mitochondria play essential bioenergetic and biosynthetic functions as well as they have an important role in signalling processes into the cell. Here, by comparing several transcriptomic data sets from plants impaired in their respiratory function with the genes regulated under Fe or S deficiencies obtained from other data sets, nutrient-responsive genes potentially regulated by hypothetical mitochondrial retrograde signalling pathway are evidenced. It leads us to hypothesize that plant mitochondria could be therefore required for regulating the expression of key genes involved both in Fe and S metabolisms.

  8. X-ray absorption near the edge structure and x-ray photoelectron spectroscopy studies on pyrite prepared by thermally sulfurizing iron films

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Liu Ying-Shu; Wang Bao-Yi; Wei Long; Kui Re-Xi; Qian Hai-Jie

    2009-01-01

    This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by x-ray absorption near edge structure spectra and x-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.

  9. Impairment of Respiratory Chain under Nutrient Deficiency in Plants: Does it Play a Role in the Regulation of Iron and Sulfur Responsive Genes?

    Science.gov (United States)

    Vigani, Gianpiero; Briat, Jean-François

    2016-01-01

    Plant production and plant product quality strongly depend on the availability of mineral nutrients. Among them, sulfur (S) and iron (Fe) play a central role, as they are needed for many proteins of the respiratory chain. Plant mitochondria play essential bioenergetic and biosynthetic functions as well as they have an important role in signaling processes into the cell. Here, by comparing several transcriptomic data sets from plants impaired in their respiratory function with the genes regulated under Fe or S deficiencies obtained from other data sets, nutrient-responsive genes potentially regulated by hypothetical mitochondrial retrograde signaling pathway are evidenced. It leads us to hypothesize that plant mitochondria could be, therefore, required for regulating the expression of key genes involved both in Fe and S metabolisms. PMID:26779219

  10. Cancer-Related NEET Proteins Transfer 2Fe-2S Clusters to Anamorsin, a Protein Required for Cytosolic Iron-Sulfur Cluster Biogenesis

    Science.gov (United States)

    Lipper, Colin H.; Paddock, Mark L.; Onuchic, José N.; Mittler, Ron; Nechushtai, Rachel; Jennings, Patricia A.

    2015-01-01

    Iron-sulfur cluster biogenesis is executed by distinct protein assembly systems. Mammals have two systems, the mitochondrial Fe-S cluster assembly system (ISC) and the cytosolic assembly system (CIA), that are connected by an unknown mechanism. The human members of the NEET family of 2Fe-2S proteins, nutrient-deprivation autophagy factor-1 (NAF-1) and mitoNEET (mNT), are located at the interface between the mitochondria and the cytosol. These proteins have been implicated in cancer cell proliferation, and they can transfer their 2Fe-2S clusters to a standard apo-acceptor protein. Here we report the first physiological 2Fe-2S cluster acceptor for both NEET proteins as human Anamorsin (also known as cytokine induced apoptosis inhibitor-1; CIAPIN-1). Anamorsin is an electron transfer protein containing two iron-sulfur cluster-binding sites that is required for cytosolic Fe-S cluster assembly. We show, using UV-Vis spectroscopy, that both NAF-1 and mNT can transfer their 2Fe-2S clusters to apo-Anamorsin with second order rate constants similar to those of other known human 2Fe-2S transfer proteins. A direct protein-protein interaction of the NEET proteins with apo-Anamorsin was detected using biolayer interferometry. Furthermore, electrospray mass spectrometry of holo-Anamorsin prepared by cluster transfer shows that it receives both of its 2Fe-2S clusters from the NEETs. We propose that mNT and NAF-1 can provide parallel routes connecting the mitochondrial ISC system and the CIA. 2Fe-2S clusters assembled in the mitochondria are received by NEET proteins and when needed transferred to Anamorsin, activating the CIA. PMID:26448442

  11. Synthesis and characterization of homochiral polymeric S-malato molybdate(VI): toward the potentially stereospecific formation and absolute configuration of iron-molybdenum cofactor in nitrogenase.

    Science.gov (United States)

    Zhou, Zhao-Hui; Yan, Wen-Bin; Wan, Hui-Lin; Tsai, Khi-Rui

    2002-06-07

    Reaction of sodium or potassium molybdate and excess malic acid in a wide range of pH values (pH 4.0-7.0) resulted in the isolation of two cis-dioxo-bis(malato)-Mo(VI) complexes, viz. Na(3)[MoO(2)H(S-mal)(2)] and K(3)[MoO(2)H(S-mal)(2)].H(2)O (H(3)mal=malic acid). The sodium complex is also characterized by an X-ray structure analysis, showing that the mononuclear Mo units are linked together via very strong symmetric CO(2)...H... O(2)C-hydrogen bond [2.432(5) A], forming a polymeric chain. The molybdenum atoms are quasi-octahedrally coordinated by two cis-oxo groups and two bidentate malate ligands via its alkoxy and alpha-carboxyl groups, while the beta-carboxylic and carboxylate groups remain uncomplexed, as the coordination of vicinal carboxylate and alkoxide of homocitrate in FeMo cofactor of nitrogenase. The absolute configuration of the metal center in this S-malato complex is assigned as Lambda and the homochirality within the chain is established as a homochiral form ...Lambda(S)-Lambda(S)-Lambda(S)-Lambda(S)... . It is proposed that the chiral configuration of the metal center in wild-type FeMo-co biosynthesis might be induced by the early coordination of the chiral R-homocitric acid, while a mixture of raceme might be obtained in the biosynthesis of NifV(-) FeMo-cofactor. The absolute configuration of wild-type FeMo-cofactor is assigned as Delta(R).

  12. Enhancing sensitivity and selectivity in a label-free colorimetric sensor for detection of iron(II) ions with luminescent molybdenum disulfide nanosheet-based peroxidase mimetics.

    Science.gov (United States)

    Wang, Yong; Hu, Jie; Zhuang, Qianfen; Ni, Yongnian

    2016-06-15

    In the present study, we demonstrated that the luminescent molybdenum disulfide (MoS2) nanosheets, which were prepared hydrothermally by using sodium molybdate and thiourea as precursors, possessed peroxidase-like activity, and could catalyze the oxidation of peroxidase substrate o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2) to produce a yellow color reaction. Further addition of Fe(2+) into the nanosheets led to peroxidase mimetics with greatly enhanced catalytic activity. The observation was exploited to develop a label-free colorimetric nanozyme sensor for detection of Fe(2+). The fabricated MoS2/OPD/H2O2 sensor showed a wide linear range of 0.01-0.8 µM with a detection limit of 7 nM. Moreover, it was found that the MoS2/OPD/H2O2 sensor displayed enhanced sensitivity and selectivity toward Fe(2+) compared with the OPD/H2O2 sensor, suggesting that the MoS2 nanosheets could improve the performance of the Fe(2+) sensor. An advanced chemometrics algorithm, multivariate curve resolution by alternating least squares (MCR-ALS), was further applied to interpret the origin of enhancing sensitivity and selectivity in the Fe(2+) sensor with the MoS2 nanosheets. The time-dependent UV-vis spectral data of the studied systems were collected, and submitted to the MCR-ALS. The results showed that the increased sensitivity and selectivity of the MoS2/OPD/H2O2 sensor for Fe(2+) detection likely arose from its large reaction rate constant. Finally, the proposed MoS2/OPD/H2O2 sensor was successfully applied for detection of Fe(2+) in water samples.

  13. Comparison of bioleaching of heavy metals from municipal sludge using indigenous sulfur and iron-oxidizing microorganisms: continuous stirred tank reactor studies.

    Science.gov (United States)

    Pathak, Ashish; Kothari, Richa; Dastidar, M G; Sreekrishnan, T R; Kim, Dong J

    2014-01-01

    A comparative study was undertaken using indigenous sulfur-oxidizing microorganisms and iron-oxidizing microorganisms in separate 12 litre continuous stirred tank reactors (CSTRs) for solubilization of heavy metals from anaerobically digested sewage sludge. The CSTRs were operated at hydraulic retention times (HRTs) ranging from 4 to 10 days using sewage sludge feed having near neutral pH. The pH, oxidation-reduction potential (ORP) and solubilization efficiency of metals were found to be highly dependent on HRT and an increase in HRT led to higher solubilization of metals in both the CSTRs. In both the CSTRs, the CSTR operated with sulfur-oxidizing microorganisms at an HRT of 8 days was found to be optimum in solubilizing 58% Cu, 52% Ni, 72% Zn and 43% Cu from the sludge. The nutrient value, nitrogen and phosphorus of bioleached sludge was also conserved (<20% loss) at 8 days HRT. The metals fractionation study conducted using BCR sequential extraction procedure suggested that most of the metals remaining in the bioleached sludge were in the more stable fractions (F3 and F4) and, therefore, can be safely apply as a fertilizer on land.

  14. The N-Terminus of Iron-Sulfur Cluster Assembly Factor ISD11 Is Crucial for Subcellular Targeting and Interaction with l-Cysteine Desulfurase NFS1.

    Science.gov (United States)

    Friemel, Martin; Marelja, Zvonimir; Li, Kuanyu; Leimkühler, Silke

    2017-03-28

    Assembly of iron-sulfur (FeS) clusters is an important process in living cells. The initial sulfur mobilization step for FeS cluster biosynthesis is catalyzed by l-cysteine desulfurase NFS1, a reaction that is localized in mitochondria in humans. In humans, the function of NFS1 depends on the ISD11 protein, which is required to stabilize its structure. The NFS1/ISD11 complex further interacts with scaffold protein ISCU and regulator protein frataxin, thereby forming a quaternary complex for FeS cluster formation. It has been suggested that the role of ISD11 is not restricted to its role in stabilizing the structure of NFS1, because studies of single-amino acid variants of ISD11 additionally demonstrated its importance for the correct assembly of the quaternary complex. In this study, we are focusing on the N-terminal region of ISD11 to determine the role of N-terminal amino acids in the formation of the complex with NFS1 and to reveal the mitochondrial targeting sequence for subcellular localization. Our in vitro studies with the purified proteins and in vivo studies in a cellular system show that the first 10 N-terminal amino acids of ISD11 are indispensable for the activity of NFS1 and especially the conserved "LYR" motif is essential for the role of ISD11 in forming a stable and active complex with NFS1.

  15. Sulfur and Iron Speciation in Gas-rich Impact-melt Glasses from Basaltic Shergottites Determined by Microxanes

    Science.gov (United States)

    Sutton, S. R.; Rao, M. N.; Nyquist, L. E.

    2008-01-01

    Sulfur is abundantly present as sulfate near Martian surface based on chemical and mineralogical investigations on soils and rocks in Viking, Pathfinder and MER missions. Jarosite is identified by Mossbauer studies on rocks at Meridian and Gusev, whereas MgSO4 is deduced from MgO - SO3 correlations in Pathfinder MER and Viking soils. Other sulfate minerals such as gypsum and alunogen/ S-rich aluminosilicates and halides are detected only in martian meteorites such as shergottites and nakhlites using SEM/FE-SEM and EMPA techniques. Because sulfur has the capacity to occur in multiple valence states, determination of sulfur speciation (sulfide/ sulfate) in secondary mineral assemblages in soils and rocks near Mars surface may help us understand whether the fluid-rock interactions occurred under oxidizing or reducing conditions. To understand the implications of these observations for the formation of the Gas-rich Impact-melt (GRIM) glasses, we determined the oxidation state of Fe in the GRIM glasses using Fe K micro-XANES techniques.

  16. Organometallic Chemistry of Molybdenum.

    Science.gov (United States)

    Lucas, C. Robert; Walsh, Kelly A.

    1987-01-01

    Suggests ways to avoid some of the problems students have learning the principles of organometallic chemistry. Provides a description of an experiment used in a third-year college chemistry laboratory on molybdenum. (TW)

  17. Storage and Bioavailability of Molybdenum in Soils Increased by Organic Matter Complexation

    Energy Technology Data Exchange (ETDEWEB)

    Wichard, T.; Mishra, B; Myneni, S; Bellenger, J; Kraepiel, A

    2009-01-01

    The micronutrient molybdenum is a necessary component of the nitrogen-fixing enzyme nitrogenase1, 2. Molybdenum is very rare in soils, and is usually present in a highly soluble form, making it susceptible to leaching3, 4. However, it is generally thought that molybdenum attaches to mineral surfaces in acidic soils; this would prevent its escape into the groundwater, but would also impede uptake by microbes3. Here we use X-ray spectroscopy to examine the chemical speciation of molybdenum in soil samples from forests in Arizona and New Jersey. We show that in the leaf litter layer, most of the molybdenum forms strong complexes with plant-derived tannins and tannin-like compounds; molybdenum binds to these organic ligands across a wide pH range. In deeper soils, molybdenum binds to both iron oxides and natural organic matter. We suggest that the molybdenum bound to organic matter can be captured by small complexing agents that are released by nitrogen-fixing bacteria; the molybdenum can then be incorporated into nitrogenase. We conclude that the binding of molybdenum to natural organic matter helps prevent leaching of molybdenum, and is thus a critical step in securing new nitrogen in terrestrial ecosystems.

  18. Reactive oxygen species production induced by ethanol in Saccharomyces cerevisiae increases because of a dysfunctional mitochondrial iron-sulfur cluster assembly system.

    Science.gov (United States)

    Pérez-Gallardo, Rocio V; Briones, Luis S; Díaz-Pérez, Alma L; Gutiérrez, Sergio; Rodríguez-Zavala, José S; Campos-García, Jesús

    2013-12-01

    Ethanol accumulation during fermentation contributes to the toxic effects in Saccharomyces cerevisiae, impairing its viability and fermentative capabilities. The iron-sulfur (Fe-S) cluster biogenesis is encoded by the ISC genes. Reactive oxygen species (ROS) generation is associated with iron release from Fe-S-containing enzymes. We evaluated ethanol toxicity, ROS generation, antioxidant response and mitochondrial integrity in S. cerevisiae ISC mutants. These mutants showed an impaired tolerance to ethanol. ROS generation increased substantially when ethanol accumulated at toxic concentrations under the fermentation process. At the cellular and mitochondrial levels, ROS were increased in yeast treated with ethanol and increased to a higher level in the ssq1∆, isa1∆, iba57∆ and grx5∆ mutants - hydrogen peroxide and superoxide were the main molecules detected. Additionally, ethanol treatment decreased GSH/GSSG ratio and increased catalase activity in the ISC mutants. Examination of cytochrome c integrity indicated that mitochondrial apoptosis was triggered following ethanol treatment. The findings indicate that the mechanism of ethanol toxicity occurs via ROS generation dependent on ISC assembly system functionality. In addition, mutations in the ISC genes in S. cerevisiae contribute to the increase in ROS concentration at the mitochondrial and cellular level, leading to depletion of the antioxidant responses and finally to mitochondrial apoptosis. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  19. Pristine but metal-rich Río Sucio (Dirty River) is dominated by Gallionella and other iron-sulfur oxidizing microbes.

    Science.gov (United States)

    Arce-Rodríguez, Alejandro; Puente-Sánchez, Fernando; Avendaño, Roberto; Libby, Eduardo; Rojas, Leonardo; Cambronero, Juan Carlos; Pieper, Dietmar H; Timmis, Kenneth N; Chavarría, Max

    2017-03-01

    Whether the extreme conditions of acidity and heavy metal pollution of streams and rivers originating in pyritic formations are caused primarily by mining activities or by natural activities of metal-oxidizing microbes living within the geological formations is a subject of considerable controversy. Most microbiological studies of such waters have so far focused on acid mine drainage sites, which are heavily human-impacted environments, so it has been problematic to eliminate the human factor in the question of the origin of the key metal compounds. We have studied the physico-chemistry and microbiology of the Río Sucio in the Braulio Carrillo National Park of Costa Rica, 22 km from its volcanic rock origin. Neither the remote origin, nor the length of the river to the sampling site, have experienced human activity and are thus pristine. The river water had a characteristic brownish-yellow color due to high iron-dominated minerals, was slightly acidic, and rich in chemolithoautotrophic iron- and sulfur-oxidizing bacteria, dominated by Gallionella spp. Río Sucio is thus a natural acid-rock drainage system whose metal-containing components are derived primarily from microbial activities.

  20. RECYCLING TECHNOLOGY INTO INDUSTRIAL TURNOVER OF BISMUTH AND MOLYBDENUM FROM DEAD CATALYST

    Directory of Open Access Journals (Sweden)

    O. S. Komarov

    2013-01-01

    Full Text Available The technology of separate extraction of bismuth and molybdenum from spent catalyst was presented and information on the effectiveness of its use in a composition of comprehensive modifier in the iron-carbon alloy was given.

  1. A new method for extraction of iron-molybdenum cofactor (FeMoco) from nitrogenase adsorbed to DEAE-cellulose. 2. Solubilization of FeMoco in a wide range of organic solvents.

    Science.gov (United States)

    Wink, D A; McLean, P A; Hickman, A B; Orme-Johnson, W H

    1989-11-28

    While the iron-molybdenum cofactor (FeMoco) of nitrogenase, a constituent of the active site for nitrogen reduction, can be extracted into N-methylformamide (NMF) and pyrrollidinone, the inability to solubilize it in any other organic solvents has hampered further understanding of its structure and chemical properties. A method to solubilize FeMoco, prepared in N,N-dimethylformamide (DMF) with Bu4N+ as counterion [McLean, P. A., Wink, D. A., Chapman, S. K., Hickman, A. B., McKillop, D. M., & Orme-Johnson, W. H. (1989) Biochemistry (preceding paper in this issue)], in acetonitrile, acetone, methylene chloride, tetrahydrofuran, and benzene is reported. FeMoco evaporated to dryness in vacuo dissolves readily in good yield (55-100%) and with no significant loss in specific activity. In addition, FeMoco can be extracted directly into these solvents from MoFe protein bound to a DEAE-Sepharose column if the protein is pretreated with DMF. Methods have also been developed to extract fully active FeMoco into acetone and acetonitrile in the absence of any amide solvents (NMF or DMF). Extraction of FeMoco into acetone (30% yield) involves only pretreatment of column-bound protein with methanol, while extraction into acetonitrile (22% yield) requires pretreatment with methanol followed by THF. We conclude that the presence of a suitable soluble cation confers solubility to the cofactor in many common organic solvents and that the solubility of FeMoco in a given solvent may be independent of the ability of that solvent to extract the cofactor from column-bound protein.

  2. Mercury: its iron and sulfur enrichment has roots in mechanical concentration of dense particles in the inner part of rotating primordial gas-dust cloud

    Science.gov (United States)

    Kochemasov, G. G.

    2013-09-01

    After MESSENGER explorations one could crystallize an idea of nature of this innermost planet of the Solar system. It has on the whole dull low albedo surface with small variations in compositions of Mg-rich Fe-poor large tectonic units. Only widespread small hollows and their groups with darker and brighter haloes brighten this dull landscape. The relief variations are small (maximum 10 km, but normally within 3-5 km), much less than on other rocky planets. The large iron core making the planet's density high leaves a modest place for mantle. Atmosphere is practically absent notwithstanding strong degassing, and this is due to strong cleaning by the solar wind. All mentioned peculiarities could be explained by the Mercury's position in the innermost zone. This was done even before the first orbital explorations just on a basis of the wave planetology connecting planets' properties with their orbital characteristics [ 1, 2]. Surprising many planetologists the high sulfur presence in Mercury, not justified by its position in the hot inner zone was, however, practically predicted by a new model of primordial matter differentiation in a rotating gas-dust cloud [ 3, 4]. This cloud consisting of gas and mixture of solids with various densities under rotation produces concentration of heavy particles in the inner zone. This process is well known for prospectors making heavy concentrations (schlich) with use of a spiral separator. There separation of heavies is made by descending and rotating in a spiral water-sand mixture. This model for differentiation of a planetary system was presented at LPSC [3, 4]. At that time nobody could imagine volatile sulfur in the inner hot zone. In [1] is written "It is suggested that primary accretion minerals in some meteorites and probably also in the larger bodies of the Solar system are united by nearness of their densities rather than by temperatures of their condensation out of the protoplanet gas (for example, common association of

  3. Molybdenum oxide nanowires: synthesis & properties

    Directory of Open Access Journals (Sweden)

    Liqiang Mai

    2011-07-01

    Full Text Available Molybdenum oxide nanowires have been found to show promise in a diverse range of applications, ranging from electronics to energy storage and micromechanics. This review focuses on recent research on molybdenum oxide nanowires: from synthesis and device assembly to fundamental properties. The synthesis of molybdenum oxide nanowires will be reviewed, followed by a discussion of recent progress on molybdenum oxide nanowire based devices and an examination of their properties. Finally, we conclude by considering future developments.

  4. Transition from Sign-Reversed to Sign-Preserved Cooper-Pairing Symmetry in Sulfur-Doped Iron Selenide Superconductors.

    Science.gov (United States)

    Wang, Qisi; Park, J T; Feng, Yu; Shen, Yao; Hao, Yiqing; Pan, Bingying; Lynn, J W; Ivanov, A; Chi, Songxue; Matsuda, M; Cao, Huibo; Birgeneau, R J; Efremov, D V; Zhao, Jun

    2016-05-13

    An essential step toward elucidating the mechanism of superconductivity is to determine the sign or phase of the superconducting order parameter, as it is closely related to the pairing interaction. In conventional superconductors, the electron-phonon interaction induces attraction between electrons near the Fermi energy and results in a sign-preserved s-wave pairing. For high-temperature superconductors, including cuprates and iron-based superconductors, prevalent weak coupling theories suggest that the electron pairing is mediated by spin fluctuations which lead to repulsive interactions, and therefore that a sign-reversed pairing with an s_{±} or d-wave symmetry is favored. Here, by using magnetic neutron scattering, a phase sensitive probe of the superconducting gap, we report the observation of a transition from the sign-reversed to sign-preserved Cooper-pairing symmetry with insignificant changes in T_{c} in the S-doped iron selenide superconductors K_{x}Fe_{2-y}(Se_{1-z}S_{z})_{2}. We show that a rather sharp magnetic resonant mode well below the superconducting gap (2Δ) in the undoped sample (z=0) is replaced by a broad hump structure above 2Δ under 50% S doping. These results cannot be readily explained by simple spin fluctuation-exchange pairing theories and, therefore, multiple pairing channels are required to describe superconductivity in this system. Our findings may also yield a simple explanation for the sometimes contradictory data on the sign of the superconducting order parameter in iron-based materials.

  5. Characterization of the Fe site in iron-sulfur cluster-free hydrogenase (Hmd) and of a model compound via nuclear resonance vibrational spectroscopy (NRVS).

    Science.gov (United States)

    Guo, Yisong; Wang, Hongxin; Xiao, Yuming; Vogt, Sonja; Thauer, Rudolf K; Shima, Seigo; Volkers, Phillip I; Rauchfuss, Thomas B; Pelmenschikov, Vladimir; Case, David A; Alp, Ercan E; Sturhahn, Wolfgang; Yoda, Yoshitaka; Cramer, Stephen P

    2008-05-19

    We have used (57)Fe nuclear resonance vibrational spectroscopy (NRVS) to study the iron site in the iron-sulfur cluster-free hydrogenase Hmd from the methanogenic archaeon Methanothermobacter marburgensis. The spectra have been interpreted by comparison with a cis-(CO)2-ligated Fe model compound, Fe(S2C2H4)(CO)2(PMe3)2, as well as by normal mode simulations of plausible active site structures. For this model complex, normal mode analyses both from an optimized Urey-Bradley force field and from complementary density functional theory (DFT) calculations produced consistent results. For Hmd, previous IR spectroscopic studies found strong CO stretching modes at 1944 and 2011 cm(-1), interpreted as evidence for cis-Fe(CO)2 ligation. The NRVS data provide further insight into the dynamics of the Fe site, revealing Fe-CO stretch and Fe-CO bend modes at 494, 562, 590, and 648 cm(-1), consistent with the proposed cis-Fe(CO)2 ligation. The NRVS also reveals a band assigned to Fe-S stretching motion at approximately 311 cm(-1) and another reproducible feature at approximately 380 cm(-1). The (57)Fe partial vibrational densities of states (PVDOS) for Hmd can be reasonably well simulated by a normal mode analysis based on a Urey-Bradley force field for a five-coordinate cis-(CO)2-ligated Fe site with additional cysteine, water, and pyridone cofactor ligands. A "truncated" model without a water ligand can also be used to match the NRVS data. A final interpretation of the Hmd NRVS data, including DFT analysis, awaits a three-dimensional structure for the active site.

  6. Crucial role of conserved cysteine residues in the assembly of two iron-sulfur clusters on the CIA protein Nar1.

    Science.gov (United States)

    Urzica, Eugen; Pierik, Antonio J; Mühlenhoff, Ulrich; Lill, Roland

    2009-06-09

    Iron-sulfur (Fe/S) protein maturation in the eukaryotic cytosol and nucleus requires conserved components of the essential CIA machinery. The CIA protein Nar1 performs a specific function in transferring an Fe/S cluster that is assembled de novo on the Cfd1-Nbp35 scaffold to apoproteins. Here, we used systematic site-directed mutagenesis and a combination of in vitro and in vivo studies to show that Nar1 holds two Fe/S clusters at conserved N- and C-terminal cysteine motifs. A wealth of biochemical studies suggests that the assembly of these Fe/S clusters on Nar1 cannot be studied in Escherichia coli, as the recombinant protein does not contain the native Fe/S clusters. We therefore followed Fe/S cluster incorporation directly in yeast by a (55)Fe radiolabeling method in vivo, and we measured the functional consequences of Nar1 mutations in the assembly of cytosolic Fe/S proteins. We find that both Fe/S clusters are essential for Nar1 function and cell viability. Molecular modeling using a structurally but not functionally related bacterial iron-only hydrogenase as a template provided compelling structural explanations for our mutational data. The C-terminal Fe/S cluster is stably buried within Nar1, whereas the N-terminal one is exposed at the protein surface and hence may be more easily lost. Insertion of an Fe/S cluster into the C-terminal location depends on the N-terminal motif, suggesting the participation of the latter motif in the assembly process of the C-terminal cluster. The vicinity of the two Fe/S centers suggests a close functional cooperation during cytosolic Fe/S protein maturation.

  7. Orientations of Iron-Sulfur Clusters FA and FB in the Homodimeric Type-I Photosynthetic Reaction Center of Heliobacterium modesticaldum.

    Science.gov (United States)

    Kondo, Toru; Matsuoka, Masahiro; Azai, Chihiro; Itoh, Shigeru; Oh-Oka, Hirozo

    2016-05-12

    Orientations of the FA and FB iron-sulfur (FeS) clusters in a structure-unknown type-I homodimeric heriobacterial reaction center (hRC) were studied in oriented membranes of the thermophilic anaerobic photosynthetic bacterium Heliobacterium modesticaldum by electron paramagnetic resonance (EPR), and compared with those in heterodimeric photosystem I (PS I). The Rieske-type FeS center in the cytochrome b/c complex showed a well-oriented EPR signal. Illumination at 14 K induced an FB(-) signal with g-axes of gz = 2.066, gy = 1.937, and gx = 1.890, tilted at angles of 60°, 60°, and 45°, respectively, with respect to the membrane normal. Chemical reduction with dithionite produced an additional signal of FA(-), which magnetically interacted with FB(-), with gz = 2.046, gy = 1.942, and gx = 1.911 at 30°, 60°, and 90°, respectively. The angles and redox properties of FA(-) and FB(-) in hRC resemble those of FB(-) and FA(-), respectively, in PS I. Therefore, FA and FB in hRC, named after their g-value similarities, seem to be located like FB and FA, not like FA and FB, respectively, in PS I. The reducing side of hRC could resemble those in PS I, if the names of FA and FB are interchanged with each other.

  8. Concentrations and Fractionation of Carbon, Iron, Sulfur, Nitrogen and Phosphorus in Mangrove Sediments Along an Intertidal Gradient (Semi-Arid Climate, New Caledonia

    Directory of Open Access Journals (Sweden)

    Jonathan Deborde

    2015-02-01

    Full Text Available In mangrove ecosystems, strong reciprocal interactions exist between plant and substrate. Under semi-arid climate, Rhizophora spp. are usually predominant, colonizing the seashore, and Avicennia marina develops at the edge of salt-flats, which is the highest zone in the intertidal range. Along this zonation, distribution and speciation of C, Fe, S, N, and P in sediments and pore-waters were investigated. From the land-side to the sea-side of the mangrove, sediments were characterized by I/ increase in: (i water content; (ii TOC; (iii mangrove-derived OM; II/ and decrease in: (i salinity; (ii redox; (iii pH; (iv solid Fe and solid P. Beneath Avicennia and Rhizophora, TS accumulated at depth, probably as a result of reduction of iron oxides and sulfate. The loss of total Fe observed towards the sea-side may be related to sulfur oxidation and to more intense tidal flushing of dissolved components. Except the organic forms, dissolved N and P concentrations were very low beneath Avicennia and Rhizophora stands, probably as a result of their uptake by the root systems. However, in the unvegetated salt-flat, NH4+ can accumulate in organic rich and anoxic layers. This study shows: (i the evolution of mangrove sediment biogeochemistry along the intertidal zone as a result of the different duration of tidal inundation and organic enrichment; and (ii the strong links between the distribution and speciation of the different elements.

  9. Cells lacking Rieske iron-sulfur protein have a reactive oxygen species-associated decrease in respiratory complexes I and IV.

    Science.gov (United States)

    Diaz, Francisca; Enríquez, José Antonio; Moraes, Carlos T

    2012-01-01

    Mitochondrial respiratory complexes of the electron transport chain (CI, CIII, and CIV) can be assembled into larger structures forming supercomplexes. We analyzed the assembly/stability of respiratory complexes in mouse lung fibroblasts lacking the Rieske iron-sulfur protein (RISP knockout [KO]cells), one of the catalytic subunits of CIII. In the absence of RISP, most of the remaining CIII subunits were able to assemble into a large precomplex that lacked enzymatic activity. CI, CIV, and supercomplexes were decreased in the RISP-deficient cells. Reintroduction of RISP into KO cells restored CIII activity and increased the levels of active CI, CIV, and supercomplexes. We found that hypoxia (1% O(2)) resulted in increased levels of CI, CIV, and supercomplex assembly in RISP KO cells. In addition, treatment of control cells with different oxidative phosphorylation (OXPHOS) inhibitors showed that compounds known to generate reactive oxygen species (ROS) (e.g., antimycin A and oligomycin) had a negative impact on CI and supercomplex levels. Accordingly, a superoxide dismutase (SOD) mimetic compound and SOD2 overexpression provided a partial increase in supercomplex levels in the RISP KO cells. Our data suggest that the stability of CI, CIV, and supercomplexes is regulated by ROS in the context of defective oxidative phosphorylation.

  10. Multiple turnover transfer of [2Fe2S] clusters by the iron-sulfur cluster assembly scaffold proteins IscU and IscA.

    Science.gov (United States)

    Bonomi, Francesco; Iametti, Stefania; Ta, Dennis; Vickery, Larry E

    2005-08-19

    IscU/Isu and IscA/Isa (and related NifU and SufA proteins) have been proposed to serve as molecular scaffolds for preassembly of [FeS] clusters to be used in the biogenesis of iron-sulfur proteins. In vitro studies demonstrating transfer of preformed scaffold-[FeS] complexes to apoprotein acceptors have provided experimental support for this hypothesis, but investigations to date have yielded only single-cluster transfer events. We describe an in vitro assay system that allows for real-time monitoring of [FeS] cluster formation using circular dichroism spectroscopy and use this to investigate de novo [FeS] cluster formation and transfer from Escherichia coli IscU and IscA to apo-ferredoxin. Both IscU and IscA were found to be capable of multiple cycles of [2Fe2S] cluster formation and transfer suggesting that these scaffold proteins are capable of acting "catalytically." Kinetic studies further showed that cluster transfer exhibits Michaelis-Menten behavior indicative of complex formation of holo-IscU and holo-IscA with apoferredoxin and consistent with a direct [FeS] cluster transfer mechanism. Analysis of the dependence of the rate of cluster transfer, however, revealed enhanced efficiency at low ratios of scaffold to acceptor protein suggesting participation of a transient, labile scaffold-[FeS] species in the transfer process.

  11. Isolation and phylogenetic characterization of iron-sulfur-oxidizing heterotrophic bacteria indigenous to nickel laterite ores of Sulawesi, Indonesia: Implications for biohydrometallurgy

    Science.gov (United States)

    Chaerun, Siti Khodijah; Hung, Sutina; Mubarok, Mohammad Zaki; Sanwani, Edy

    2015-09-01

    The main objective of this study was to isolate and phylogenetically identify the indigenous iron-sulfur-oxidizing heterotrophic bacteria capable of bioleaching nickel from laterite mineral ores. The bacteria were isolated from a nickel laterite mine area in South Sulawesi Province, Indonesia. Seven bacterial strains were successfully isolated from laterite mineral ores (strains SKC/S-1 to SKC/S-7) and they were capable of bioleaching of nickel from saprolite and limonite ores. Using EzTaxon-e database, the 16S rRNA gene sequences of the seven bacterial strains were subjected to phylogenetic analysis, resulting in a complete hierarchical classification system, and they were identified as Pseudomonas taiwanensis BCRC 17751 (98.59% similarity), Bacillus subtilis subsp. inaquosorum BGSC 3A28 (99.14% and 99.32% similarities), Paenibacillus pasadenensis SAFN-007 (98.95% and 99.33% similarities), Bacillus methylotrophicus CBMB 205 (99.37% similarity), and Bacillus altitudinis 41KF2b (99.37% similarity). It is noteworthy that members of the phylum Firmicutes (in particular the genus Bacillus) predominated in this study, therefore making them to have the high potential to be candidates for the bioleaching of nickel from laterite mineral ores. To our knowledge, this is the first report on the predominance of the phylum Firmicutes in the Sulawesi laterite mineral ores.

  12. Geochemical and mineralogical characterization of sulfur and iron in coal waste rock, Elk Valley, British Columbia, Canada.

    Science.gov (United States)

    Essilfie-Dughan, Joseph; Hendry, M Jim; Dynes, James J; Hu, Yongfeng; Biswas, Ashis; Lee Barbour, S; Day, S

    2017-02-12

    Exposure of coal waste rock to atmospheric oxygen can result in the oxidation of sulfide minerals and the release of sulfate (SO4(2-)) and associated trace elements (e.g., Se, As, Cd, and Zn) to groundwaters and surface waters. Similarly, reduced iron minerals such as siderite, ankerite, and the sulfide, pyrite, present in the waste rock can also undergo oxidation, resulting in the formation of iron oxyhydroxides that can adsorb trace elements released from the oxidation of the sulfide minerals. Characterization and quantification of the distribution of sulfide and iron minerals, their oxidation products, as well as leaching rates are critical to assessing present-day and future impacts of SO4(2-) and associated trace elements on receiving waters. Synchrotron-based X-ray absorption near edge spectroscopic analysis of coal waste rock samples from the Elk Valley, British Columbia showed Fe present as pyrite (mean 6.0%), siderite (mean 44.3%), goethite (mean 35.4%), and lepidocrocite (mean 14.3%) with S present as sulfide (mean 26.9%), organic S (mean 58.7%), and SO4(2-) (mean 14.4%). Squeezed porewater samples from dump solids yielded mean concentrations of 0.28mg/L Fe and 1246mg/L SO4(2-). Geochemical modeling showed the porewaters in the dumps to be supersaturated with respect to Fe oxyhydroxides and undersaturated with respect to gypsum, consistent with solids analyses. Coupling Fe and S mineralogical data with long-term water quality and quantity measurements from the base of one dump suggest about 10% of the sulfides (which represent 2% of total S) in the dump were oxidized over the past 30years. The S from these oxidized sulfides was released to the receiving surface water as SO4(2-) and the majority of the Fe precipitated as secondary Fe oxyhydroxides (only 3.0×10(-5)% of the Fe was released to the receiving waters over the past 30years). Although the data suggest that the leaching of SO4(2-) from the waste rock dump could continue for about 300years

  13. Flotation technology of refractory low-grade molybdenum ore

    Institute of Scientific and Technical Information of China (English)

    Du Shuhua; Luo Zhenfu

    2013-01-01

    Because of the low grade,high oxidation rate and the accumulation of little associated metal sulfide ore in the molybdenum concentrate during flotation,the Qingyang molybdenum ore is difficult to beneflciate.The experimental studies of grinding fineness,the amount of roughing modifier,depressant and collector were completed.In the cleaning process,the contrast experiments of one regrinding.the regrinding and scrubbing,two-stage regrinding was carried.The result shows that the grade of molybdenum ore concentrate is 45.31%,the recovery is 65.98% and the rich ore ratio reaches 20.59% by the regrinding and scrubbing seven cleaning,the regrinding of concentrations from middling of molybdenum-sulfur separation.The regularly-concentrated material from the apparatus was as the middling products.Hence,ideal beneficiation index can be obtained with a rational mineral processing,which offers new beneficiating technology for the refractory low-grade molybdenum ore in China.

  14. Arsenic Removal from Water Using Various Adsorbents: Magnetic Ion Exchange Resins, Hydrous Ion Oxide Particles, Granular Ferric Hydroxide, Activated Alumina, Sulfur Modified Iron, and Iron Oxide-Coated Microsand

    KAUST Repository

    Sinha, Shahnawaz

    2011-09-30

    The equilibrium and kinetic adsorption of arsenic on six different adsorbents were investigated with one synthetic and four natural types (two surface and two ground) of water. The adsorbents tested included magnetic ion exchange resins (MIEX), hydrous ion oxide particles (HIOPs), granular ferric hydroxide (GFH), activated alumina (AA), sulfur modified iron (SMI), and iron oxide-coated mic - rosand (IOC-M), which have different physicochemical properties (shape, charge, surface area, size, and metal content). The results showed that adsorption equilibriums were achieved within a contact period of 20 min. The optimal doses of adsorbents determined for a given equilibrium concentration of C eq = 10 μg/L were 500 mg/L for AA and GFH, 520–1,300 mg/L for MIEX, 1,200 mg/L for HIOPs, 2,500 mg/L for SMI, and 7,500 mg/L for IOC-M at a contact time of 60 min. At these optimal doses, the rate constants of the adsorbents were 3.9, 2.6, 2.5, 1.9, 1.8, and 1.6 1/hr for HIOPs, AA, GFH, MIEX, SMI, and IOC-M, respectively. The presence of silicate significantly reduced the arsenic removal efficiency of HIOPs, AA, and GFH, presumably due to the decrease in chemical binding affinity of arsenic in the presence of silicate. Additional experiments with natural types of water showed that, with the exception of IOC-M, the adsorbents had lower adsorption capacities in ground water than with surface and deionized water, in which the adsorption capacities decreased by approximately 60–95 % .

  15. The role and properties of the iron-sulfur cluster in Escherichia coli dihydroxy-acid dehydratase.

    Science.gov (United States)

    Flint, D H; Emptage, M H; Finnegan, M G; Fu, W; Johnson, M K

    1993-07-15

    Dihydroxy-acid dehydratase has been purified from Escherichia coli and characterized as a homodimer with a subunit molecular weight of 66,000. The combination of UV visible absorption, EPR, magnetic circular dichroism, and resonance Raman spectroscopies indicates that the native enzyme contains a [4Fe-4S]2+,+ cluster, in contrast to spinach dihydroxy-acid dehydratase which contains a [2Fe-2S]2+,+ cluster (Flint, D. H., and Emptage, M. H. (1988) J. Biol. Chem. 263, 3558-3564). In frozen solution, the reduced [4Fe-4S]+ cluster has a S = 3/2 ground state with minor contributions from forms with S = 1/2 and possibly S = 5/2 ground states. Resonance Raman studies of the [4Fe-4S]2+ cluster in E. coli dihydroxy-acid dehydratase indicate non-cysteinyl coordination of a specific iron, which suggests that it is likely to be directly involved in catalysis as is the case with aconitase (Emptage, M. H., Kent, T. A., Kennedy, M. C., Beinert, H., and Münck, E. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 4674-4678). Dihydroxy-acid dehydratase from E. coli is inactivated by O2 in vitro and in vivo as a result of oxidative degradation of the [4Fe-4S]cluster. Compared to aconitase, the oxidized cluster of E. coli dihydroxy-acid dehydratase appears to be less stable as either a cubic or linear [3Fe-4S] cluster or a [2Fe-2S] cluster. Oxidative degradation appears to lead to a complete breakdown of the Fe-S cluster, and the resulting protein cannot be reactivated with Fe2+ and thiol reducing agents.

  16. Inorganic Polymer Nanocomposite Cathode for Long Cycle Life Lithium - Sulfur Batteries Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. (PSI) proposes to develop a hybrid composite structure of molybdenum disulfide (MoS2) with a class of polysulfide for lithium-sulfur...

  17. Photochemical degradation of natural organic sulfur compounds (CHOS) from iron-rich mine pit lake pore waters--an initial understanding from evaluation of single-elemental formulae using ultra-high-resolution mass spectrometry.

    Science.gov (United States)

    Herzsprung, Peter; Hertkorn, Norbert; Friese, Kurt; Schmitt-Kopplin, Philippe

    2010-10-15

    In order to better understand the chemical diversity of dissolved organic matter (DOM) in iron-rich mine waters, a variety of sediment pore waters was analysed by means of ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). A considerable number of the DOM elemental formulae were found to contain sulfur. In a rather simplified experiment, DOM was exposed to sunlight in the presence of dissolved ferric iron, which is common in the oxygenated acidified epilimnetic waters of mine pit lakes. The photochemical alteration of the CHOS (carbon-, hydrogen-, oxygen- and sulfur-containing) compounds was then categorised by following the changes in signal intensity of mass peaks. Nearly 20,000 elemental compositions were identified and sorted into the following categories: totally degraded, partially degraded, not significantly degraded, minor new photoproducts, and newly formed photoproducts. A large proportion of the CHOS compounds were found to be entirely degraded; the degradation ratios exceeded those of the CHO compounds. The pools of totally degraded compounds and those of newly formed products were contrasted with respect to photochemically relevant mass differences. These results indicate that photochemical loss of sulfur-containing low molecular weight compounds can be considered likely. One feasible explanation is the photodegradation of sulfonic acids within the CHOS pool eventually leading to the release of sulfate. Copyright © 2010 John Wiley & Sons, Ltd.

  18. Cloning, expression and protective immunity evaluation of the full-length cDNA encoding succinate dehydrogenase iron-sulfur protein of Schistosoma japonicum

    Institute of Scientific and Technical Information of China (English)

    YU JunLong; WANG ShiPing; LI WenKai; DAI Gan; XU ShaoRui; HE Zhuo; PENG XianChu; ZHOU SongHua; LIU XueQin

    2007-01-01

    1071-bp fragment was obtained from the Schistosoma japonicum (Chinese strain) adult cDNA library after the 3' and 5' ends of the incomplete expression sequence tag (EST) of succinate dehydrogenase iron-sulfur protein of Schistosoma japonicum (SjSDISP) were amplified by the anchored PCR with 2pairs of primers designed according to the EST of SjSDISP and the sequence of multiclone sites of the library vector. Sequence analysis indicated that the fragment was a full-length cDNA with a complete open reading frame (ORF), encoding 278 amino acid residues. The fragment was cloned into prokaryotic expression vector pQE30, and subsequently sequenced and expressed in Escherichia coll.SDS-PAGE and Western-blot analyses showed that the recombinant protein was about 32 kD and could be recognized by the polyclonal antisera from rabbits immunized with Schistosoma japonicum adult worm antigen. Compared with the FCA controls, mice vaccinated with rSjSDISP (test) or rSjGST (positive control) all revealed high levels of specific antibody and significant reduction in worm burden, liver eggs per gram (LEPG), fecal eggs per gram (FEPG) and intrauterine eggs. These results suggest that SjSDISP may be a novel and partially protective vaccine candidate against schistosomiasis. In contrast to the worm burden reduction rate, the higher degree of egg reduction rate in the test group also suggested that SjSDISP vaccine may primarily play a role in anti-embryonation or anti-fecundity immunity.

  19. Cloning, expression and protective immunity evalua- tion of the full-length cDNA encoding succinate dehydrogenase iron-sulfur protein of Schistosoma japonicum

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    1071-bp fragment was obtained from the Schistosoma japonicum (Chinese strain) adult cDNA library after the 3′ and 5′ ends of the incomplete expression sequence tag (EST) of succinate dehydrogenase iron-sulfur protein of Schistosoma japonicum (SjSDISP) were amplified by the anchored PCR with 2 pairs of primers designed according to the EST of SjSDISP and the sequence of multiclone sites of the library vector. Sequence analysis indicated that the fragment was a full-length cDNA with a complete open reading frame (ORF), encoding 278 amino acid residues. The fragment was cloned into prokary- otic expression vector pQE30, and subsequently sequenced and expressed in Escherichia coli. SDS-PAGE and Western-blot analyses showed that the recombinant protein was about 32 kD and could be recognized by the polyclonal antisera from rabbits immunized with Schistosoma japonicum adult worm antigen. Compared with the FCA controls, mice vaccinated with rSjSDISP (test) or rSjGST (posi- tive control) all revealed high levels of specific antibody and significant reduction in worm burden, liver eggs per gram (LEPG), fecal eggs per gram (FEPG) and intrauterine eggs. These results suggest that SjSDISP may be a novel and partially protective vaccine candidate against schistosomiasis. In contrast to the worm burden reduction rate, the higher degree of egg reduction rate in the test group also sug- gested that SjSDISP vaccine may primarily play a role in anti-embryonation or anti-fecundity immunity.

  20. Characteristics and adaptability of iron- and sulfur-oxidizing microorganisms used for the recovery of metals from minerals and their concentrates

    Directory of Open Access Journals (Sweden)

    Rawlings Douglas E

    2005-05-01

    Full Text Available Abstract Microorganisms are used in large-scale heap or tank aeration processes for the commercial extraction of a variety of metals from their ores or concentrates. These include copper, cobalt, gold and, in the past, uranium. The metal solubilization processes are considered to be largely chemical with the microorganisms providing the chemicals and the space (exopolysaccharide layer where the mineral dissolution reactions occur. Temperatures at which these processes are carried out can vary from ambient to 80°C and the types of organisms present depends to a large extent on the process temperature used. Irrespective of the operation temperature, biomining microbes have several characteristics in common. One shared characteristic is their ability to produce the ferric iron and sulfuric acid required to degrade the mineral and facilitate metal recovery. Other characteristics are their ability to grow autotrophically, their acid-tolerance and their inherent metal resistance or ability to acquire metal resistance. Although the microorganisms that drive the process have the above properties in common, biomining microbes usually occur in consortia in which cross-feeding may occur such that a combination of microbes including some with heterotrophic tendencies may contribute to the efficiency of the process. The remarkable adaptability of these organisms is assisted by several of the processes being continuous-flow systems that enable the continual selection of microorganisms that are more efficient at mineral degradation. Adaptability is also assisted by the processes being open and non-sterile thereby permitting new organisms to enter. This openness allows for the possibility of new genes that improve cell fitness to be selected from the horizontal gene pool. Characteristics that biomining microorganisms have in common and examples of their remarkable adaptability are described.

  1. Sulfur and iron diagenesis in temperate unsteady sediments of the East China Sea inner shelf and a comparison with tropical mobile mud belts (MMBs)

    Science.gov (United States)

    Zhu, Mao-Xu; Chen, Ke-Ke; Yang, Gui-Peng; Fan, De-Jiang; Li, Tie

    2016-11-01

    Redox cycling of iron (Fe) and sulfur (S) exerts profound influences on fates of numerous elements in coastal marine sediments. In this study, S and Fe cycling and its geochemical expressions in the East China Sea (ECS) inner shelf, a representative of temperate mobile mud belts (MMBs), were characterized and compared with tropical counterparts (the Amazon shelf and the Gulf of Papua). Fe and S speciation consistently points to the dominance of authigenic nonsulfidized Fe(II) phases (i.e., poorly crystalline clays (PCCs) and carbonates) and the prevalence of Fe redox cycling in the suboxic or weakly sulfidic regimes of the ECS-MMBs. High contents of authigenic magnetite may be a common diagenetic expression in all MMBs. Compared to the tropical MMBs, three main differences of diagenetic expressions in the ECS-MMBs are (i) light 34Spyrite in the ECS-MMB versus characteristically heavy 34Spyrite in the Amazon shelf MMBs; (ii) lower total reactive Fe (FeTR), total diagenetic Fe(II), and ratio of FeTR to total Fe in the ECS-MMBs; and (iii) Fe(II) carbonates and PCCs are equally important sinks for nonsulfidized Fe(II) in the ECS-MMBs, whereas PCCs are the predominant sink in the tropical counterparts. These differences are ascribable to factors including low degradability of organic matter, small diffusion scales, less intense chemical weathering in the drainage basin, and/or weaker reverse weathering in the ECS-MMBs. Despite the differences above, Fe and S diagenetic expressions that characterize the prevalence of Fe redox cycling in the unsteady suboxic regimes are shared by the ECS-MMBs and tropical MMBs.

  2. Microbial processes of the carbon and sulfur cycles in an ice-covered, iron-rich meromictic lake Svetloe (Arkhangelsk region, Russia).

    Science.gov (United States)

    Savvichev, Alexander S; Kokryatskaya, Natalia M; Zabelina, Svetlana A; Rusanov, Igor I; Zakharova, Elena E; Veslopolova, Elena F; Lunina, Olga N; Patutina, Ekaterina O; Bumazhkin, Boris K; Gruzdev, Denis S; Sigalevich, Pavel A; Pimenov, Nikolay V; Kuznetsov, Boris B; Gorlenko, Vladimir M

    2017-02-01

    Biogeochemical, isotope geochemical and microbiological investigation of Lake Svetloe (White Sea basin), a meromictic freshwater was carried out in April 2014, when ice thickness was ∼0.5 m, and the ice-covered water column contained oxygen to 23 m depth. Below, the anoxic water column contained ferrous iron (up to 240 μμM), manganese (60 μM), sulfide (up to 2 μM) and dissolved methane (960 μM). The highest abundance of microbial cells revealed by epifluorescence microscopy was found in the chemocline (redox zone) at 23-24.5 m. Oxygenic photosynthesis exhibited two peaks: the major one (0.43 μmol C L(-1)  day(-1) ) below the ice and the minor one in the chemocline zone, where cyanobacteria related to Synechococcus rubescens were detected. The maximum of anoxygenic photosynthesis (0.69 μmol C L(-1)  day(-1) ) at the oxic/anoxic interface, for which green sulfur bacteria Chlorobium phaeoclathratiforme were probably responsible, exceeded the value for oxygenic photosynthesis. Bacterial sulfate reduction peaked (1.5 μmol S L(-1)  day(-1) ) below the chemocline zone. The rates of methane oxidation were as high as 1.8 μmol CH4  L(-1)  day(-1) at the oxi/anoxic interface and much lower in the oxic zone. Small phycoerythrin-containing Synechococcus-related cyanobacteria were probably involved in accumulation of metal oxides in the redox zone. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  3. Mapping cellular Fe-S cluster uptake and exchange reactions - divergent pathways for iron-sulfur cluster delivery to human ferredoxins.

    Science.gov (United States)

    Fidai, Insiya; Wachnowsky, Christine; Cowan, J A

    2016-12-07

    Ferredoxins are protein mediators of biological electron-transfer reactions and typically contain either [2Fe-2S] or [4Fe-4S] clusters. Two ferredoxin homologues have been identified in the human genome, Fdx1 and Fdx2, that share 43% identity and 69% similarity in protein sequence and both bind [2Fe-2S] clusters. Despite the high similarity, the two ferredoxins play very specific roles in distinct physiological pathways and cannot replace each other in function. Both eukaryotic and prokaryotic ferredoxins and homologues have been reported to receive their Fe-S cluster from scaffold/delivery proteins such as IscU, Isa, glutaredoxins, and Nfu. However, the preferred and physiologically relevant pathway for receiving the [2Fe-2S] cluster by ferredoxins is subject to speculation and is not clearly identified. In this work, we report on in vitro UV-visible (UV-vis) circular dichroism studies of [2Fe-2S] cluster transfer to the ferredoxins from a variety of partners. The results reveal rapid and quantitative transfer to both ferredoxins from several donor proteins (IscU, Isa1, Grx2, and Grx3). Transfer from Isa1 to Fdx2 was also observed to be faster than that of IscU to Fdx2, suggesting that Fdx2 could receive its cluster from Isa1 instead of IscU. Several other transfer combinations were also investigated and the results suggest a complex, but kinetically detailed map for cellular cluster trafficking. This is the first step toward building a network map for all of the possible iron-sulfur cluster transfer pathways in the mitochondria and cytosol, providing insights on the most likely cellular pathways and possible redundancies in these pathways.

  4. Mutated forms of the [2Fe-2S] ferredoxin from Clostridium pasteurianum with noncysteinyl ligands to the iron-sulfur cluster.

    Science.gov (United States)

    Meyer, J; Fujinaga, J; Gaillard, J; Lutz, M

    1994-11-22

    The [2Fe-2S] ferredoxin from Clostridium pasteurianum is unique among ferredoxins, both by its sequence and by the distribution of its cysteine residues (in positions 11, 14, 24, 56, 60). Thus, no homologous sequences are available to infer, by comparison, the identity of the ligands of the iron-sulfur cluster. Therefore, in order to obtain information on the latter point, a combination of site-directed mutagenesis and UV-vis, EPR, and resonance Raman spectroscopy has been implemented. All of the cysteine residues have individually been replaced by serine and two of them by alanine. Cysteine 14 could be replaced by either serine or alanine without any modification of the spectroscopic properties of the protein and was therefore dismissed as a ligand of the [2Fe-2S] cluster. The C56S, and C60S-mutated proteins were both found to display UV-vis, EPR, and resonance Raman spectra consistent with serine-coordinated [2Fe-2S] clusters. The C11S-mutated protein was considerably less stable than the wild type ferredoxin. This observation, together with the hypsochromic shifts of UV-visible absorption features upon cysteine 11-->serine mutation, suggested cysteine 11 to be a ligand of the [2Fe-2S] cluster. Cysteine 24 could be replaced by either serine or alanine without decreasing the stability of the protein and without dramatically changing its spectroscopic properties. Thus, either cysteine 24 is not a ligand of the [2Fe-2S] cluster or it is replaced by another ligand in the C24A mutated protein. A [2Fe-2S] cluster was also assembled in the C14A/C24A doubly mutated protein, i.e., in a polypeptide chain containing only three cysteine residues.2+ off

  5. Dry sliding friction and wear characteristics of Fe-C-Cu alloy containing molybdenum di sulphide

    Energy Technology Data Exchange (ETDEWEB)

    Dhanasekaran, S. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India); Gnanamoorthy, R. [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India)]. E-mail: gmoorthy@iitm.ac.in

    2007-07-01

    Sintered steels find increasing application as bearings and gears due to economical and technical reasons. Materials used for making these machine elements need to have high strength, good wear resistance and low coefficient of friction. An attempt is made to develop molybdenum di sulphide added iron-copper-carbon sintered steels using simple single stage compaction and sintering elemental powders. Friction and wear characteristics of the developed materials were evaluated using cylindrical specimens in a pin-on-disc sliding apparatus. Addition of molybdenum di sulphide increases the compressibility and increases the part density. Strength and hardness of the molybdenum di sulphide added compositions are better than the base composition. Addition of the 3% molybdenum di sulphide is found to be beneficial in improving friction and wear characteristics. Higher amount of brittle phases in the 5% molybdenum di sulphide added sample contributes to the reduction in the wear resistance.

  6. Determination of the Silicon, Vanadium, Iron, Aluminum, Nickel, Molybdenum and Chromium in Titanium Alloy by ICP-AES%ICP-AES测定钛合金中硅钒铁铝镍钼铬

    Institute of Scientific and Technical Information of China (English)

    成勇

    2012-01-01

    This paper has built an analysis method of inductively coupled plasma atomic emission spectrometry (ICP-AES) for direct and simultaneous determination of alloying elements or trace impurities of silicon, vanadium, iron, aluminum, nickel, molybdenum and chromium in the titanium alloy. The titanium alloy samples were digested completely by hydrofluoric acid and nitric acid mixed reagents and the heating conditions of the digestion reaction were controlled at room temperature or 70 ℃ water bath to avoid the volatilization loss of the element and ensure that the hydrolysis reaction of high-concentration titanium in the low acidity medium did not occur. The effect of titanium matrix and coexisting elements on the determination of the spectral interference was tested. The internal standard correction method using the yttrium as internal standard element was employed, and elemental analysis of spectral lines, internal calibration spectrum, the synchronous background correction positions and ICP spectrometer working conditions were selected preferably to effectively eliminate the physical interference resulting from titanium substrate and improve the detection precision and detection limit level. The test results of the practical application show that the detection limit is 10~27 μg/L, the background equivalent density is 5~38 μg/L, the correlation coefficient r≥0.9992, the recovery rate is 95.0%~105.0% and the RSD≤2.27%.%建立了电感耦合等离子体原子发射光谱法(ICP-AES)直接同时测定钛合金中合金元素或微量杂质硅钒铁铝镍钼铬的分析方法.采用氢氟酸和硝酸混合试剂并且在室温或70℃水浴控制加热条件下消解样品,从而避免了待测元素的挥发损失以及确保了高浓度钛基体在低酸度介质中也不会发生水解反应.试验了钛基体和共存元素对测定的光谱干扰影响,采取以钇作为内标元素的内标校正法,并且优选了待测元素分析谱线、内标校正谱

  7. The conserved protein Dre2 uses essential [2Fe-2S] and [4Fe-4S] clusters for its function in cytosolic iron-sulfur protein assembly.

    Science.gov (United States)

    Netz, Daili J A; Genau, Heide M; Weiler, Benjamin D; Bill, Eckhard; Pierik, Antonio J; Lill, Roland

    2016-07-15

    The cytosolic iron-sulfur (Fe-S) protein assembly (CIA) machinery comprises 11 essential components and matures Fe-S proteins involved in translation and genome maintenance. Maturation is initiated by the electron transfer chain NADPH-diflavin reductase Tah18-Fe-S protein Dre2 that facilitates the de novo assembly of a [4Fe-4S] cluster on the scaffold complex Cfd1-Nbp35. Tah18-Dre2 also play a critical role in the assembly of the diferric tyrosyl radical cofactor of ribonucleotide reductase. Dre2 contains eight conserved cysteine residues as potential co-ordinating ligands for Fe-S clusters but their functional importance and the type of bound clusters is unclear. In the present study, we use a combination of mutagenesis, cell biological and biochemical as well as UV-visible, EPR and Mössbauer spectroscopic approaches to show that the yeast Dre2 cysteine residues Cys(252), Cys(263), Cys(266) and Cys(268) (motif I) bind a [2Fe-2S] cluster, whereas cysteine residues Cys(311), Cys(314), Cys(322) and Cys(325) (motif II) co-ordinate a [4Fe-4S] cluster. All of these residues with the exception of Cys(252) are essential for cell viability, cytosolic Fe-S protein activity and in vivo (55)Fe-S cluster incorporation. The N-terminal methyltransferase-like domain of Dre2 is important for proper Fe-S cluster assembly at motifs I and II, which occurs in an interdependent fashion. Our findings further resolve why recombinant Dre2 from Arabidopsis, Trypanosoma or humans has previously been isolated with a single [2Fe-2S] instead of native [2Fe-2S] plus [4Fe-4S] clusters. In the presence of oxygen, the motif I-bound [2Fe-2S] cluster is labile and the motif II-bound [4Fe-4S] cluster is readily converted into a [2Fe-2S] cluster.

  8. Mineral resource of the month: molybdenum

    Science.gov (United States)

    Polyak, Désire E.

    2011-01-01

    The article offers information about the mineral molybdenum. Sources includes byproduct or coproduct copper-molybdenum deposits in the Western Cordillera of North and South America. Among the uses of molybdenum are stainless steel applications, as an alloy material for manufacturing vessels and as lubricants, pigments or chemicals. Also noted is the role played by molybdenum in renewable energy technology.

  9. Suitability of the hydrocarbon-hydroxylating molybdenum-enzyme ethylbenzene dehydrogenase for industrial chiral alcohol production.

    Science.gov (United States)

    Tataruch, M; Heider, J; Bryjak, J; Nowak, P; Knack, D; Czerniak, A; Liesiene, J; Szaleniec, M

    2014-12-20

    The molybdenum/iron-sulfur/heme protein ethylbenzene dehydrogenase (EbDH) was successfully applied to catalyze enantiospecific hydroxylation of alkylaromatic and alkylheterocyclic compounds. The optimization of the synthetic procedure involves use of the enzyme in a crude purification state that saves significant preparation effort and is more stable than purified EbDH without exhibiting unwanted side reactions. Moreover, immobilization of the enzyme on a crystalline cellulose support and changes in reaction conditions were introduced in order to increase the amounts of product formed (anaerobic atmosphere, electrochemical electron acceptor recycling or utilization of ferricyanide as alternative electron acceptor in high concentrations). We report here on an extension of effective enzyme activity from 4h to more than 10 days and final product yields of up to 0.4-0.5g/l, which represent a decent starting point for further optimization. Therefore, we expect that the hydrocarbon-hydroxylation capabilities of EbDH may be developed into a new process of industrial production of chiral alcohols. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Speciation of the elements and compositions on the surfaces of dust storm particles: The evidence for the coupling of iron with sulfur in aerosol during the long-range transport

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xingying; ZHUANG Guoshun; CHEN Jianmin; XUE Huaxin

    2005-01-01

    The speciation of the elements on the surface of the particles collected during dust storm and non-dust storm in Beijing and Inner Mongolia was studied by XPS. The major species of iron on the surface were oxides, sulfate, silicate, FeOOH and minor part sorbed on SiO2/Al2O3. Sulfate is the dominant species of sulfur on the surface. SiO2 and Al2O3 are the main components of Si and Al on the surface respectively. One of the most important findings was that the Fe(II) (FeS and FeSO4) produced could account for up to 44.3% and 45.6% of the total Fe on the surface in the aerosol sample collected at that night and next day of the "peak" time of the dust storm occurring on March 20, 2002, while Fe2(SO4)3, one of the Fe(III) species on the surface decreased from 67.1% to 49.5% and 48.0% respectively. Both S and Fe enriched on the surface of aerosol particles. Fe(II) accounted for 1.3%-5.3% of total Fe in bulk aerosol samples during dust storm. These results provided strong evidence to support the hypothesis of the coupling between iron and sulfur in aerosols during the long-range transport, which would have important impact on the global biogeochemical cycle.

  11. Analysis of iron- and sulfur-oxidizing bacteria in a treatment plant of acid rock drainage from a Japanese pyrite mine by use of ribulose-1, 5-bisphosphate carboxylase/oxygenase large-subunit gene.

    Science.gov (United States)

    Kamimura, Kazuo; Okabayashi, Ai; Kikumoto, Mei; Manchur, Mohammed Abul; Wakai, Satoshi; Kanao, Tadayoshi

    2010-03-01

    Iron- and sulfur-oxidizing bacteria in a treatment plant of acid rock drainage (ARD) from a pyrite mine in Yanahara, Okayama prefecture, Japan, were analyzed using the gene (cbbL) encoding the large subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (RubisCO). Analyses of partial sequences of cbbL genes from Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidithiobacillus caldus strains revealed the diversity in their cbbL gene sequences. In contrast to the presence of two copies of form I cbbL genes (cbbL1 and cbbL2) in A. ferrooxidans genome, A. thiooxidans and A. caldus had a single copy of form I cbbL gene in their genomes. A phylogenetic analysis based on deduced amino acid sequences from cbbL genes detected in the ARD treatment plant and their close relatives revealed that 89% of the total clones were affiliated with A. ferrooxidans. Clones loosely affiliated with the cbbL from A. thiooxidans NB1-3 or Thiobacillus denitrificans was also detected in the treatment plant. cbbL gene sequences of iron- or sulfur-oxidizing bacteria isolated from the ARD and the ARD treatment plant were not detected in the cbbL libraries from the treatment plant, suggesting the low frequencies of isolates in the samples. Copyright 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  12. Identification of a novel candidate gene in the iron-sulfur pathway implicated in ataxia-susceptibility: human gene encoding HscB, a J-type co-chaperone.

    Science.gov (United States)

    Sun, Guifeng; Gargus, J Jay; Ta, Dennis T; Vickery, Larry E

    2003-01-01

    Iron-sulfur proteins participate in a wide range of biochemical processes, including many that are central to mitochondrial electron transfer and energy metabolism. Mutations in two such proteins, frataxin and ABCB7, cause Friedreich ataxia and X-linked sideroblastic anemia with ataxia, respectively, rendering other participants in this pathway functional candidates for hereditary ataxia syndromes. Recently frataxin was shown to have an identical phylogenetic distribution with two genes and was most likely specifically involved in the same sub-process in iron-sulfur cluster assembly as one gene, designated hscB, in bacteria. To set the stage for an analysis of the potential role of this candidate gene in human disease, we defined the human HscB cDNA, its genomic locus, and its pattern of expression in normal human tissues. The isolated human HscB cDNA spans 785 bp and encodes a conserved 235-amino-acid protein, including a putative mitochondrial import leader. The HscB gene is found at chromosome 22q11-12 and is composed of six exons and five introns. Northern blot analyses of RNA from adult and fetal tissues defined a pattern of expression in mitochondria-rich tissues similar to that of frataxin, an expression pattern compatible with its implied role in mitochondrial energetics and related disease phenotypes.

  13. Molybdenum Tube Characterization report

    Energy Technology Data Exchange (ETDEWEB)

    Beaux II, Miles Frank [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Usov, Igor Olegovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-02-07

    Chemical vapor deposition (CVD) techniques have been utilized to produce free-standing molybdenum tubes with the end goal of nuclear fuel clad applications. In order to produce tubes with properties desirable for this application, deposition rates were lowered requiring long deposition durations on the order of 50 hours. Standard CVD methods as well as fluidized-bed CVD (FBCVD) methods were applied towards these objectives. Characterization of the tubes produced in this manner revealed material suitable for fuel clad applications, but lacking necessary uniformity across the length of the tubes. The production of freestanding Mo tubes that possess the desired properties across their entire length represents an engineering challenge that can be overcome in a next iteration of the deposition system.

  14. Simultaneous determination of arsenic, cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, molybdenum, nickel, selenium, and zinc in fertilizers by microwave acid digestion and inductively coupled plasma-optical emission spectrometry detection: single-laboratory validation of a modification and extension of AOAC 2006.03.

    Science.gov (United States)

    Webb, Sharon; Bartos, James; Boles, Rhonda; Hasty, Elaine; Thuotte, Ethel; Thiex, Nancy J

    2014-01-01

    A single-laboratory validation study was conducted for the simultaneous determination of arsenic, cadmium, calcium, cobalt, copper, chromium, iron, lead, magnesium, manganese, molybdenum, nickel, selenium, and zinc in all major types of commercial fertilizer products by microwave digestion and inductively coupled plasma-optical emission spectroscopy analysis. This validation study proposes an extension and modification of AOAC 2006.03. The extension is the inclusion of calcium, copper, iron, magnesium, manganese, and zinc, and the modification is incorporation of hydrochloric acid in the digestion system. This dual acid digestion utilizes both hydrochloric and nitric acids in a 3 to 9 mL volume ratio/100 mL. In addition to 15 of the 30 original validation materials used in the 2006.03 collaborative study, National Institute of Standards and Technology Standard Reference Material 695 and Magruder 2009-06 were incorporated as accuracy materials. The main benefits of this proposed method are a significant increase in laboratory efficiency when compared to the use of both AOAC Methods 965.09 and 2006.03 to achieve the same objective and an enhanced recovery of several metals.

  15. Molybdenum Evidence for Inherited Planetary Scale Isotope Heterogeneity of the Protosolar Nebula

    CERN Document Server

    Dauphas, N; Reisberg, L

    2001-01-01

    Isotope anomalies provide important information about early solar system evolution. Here we report molybdenum isotope abundances determined in samples of various meteorite classes. There is no fractionation of molybdenum isotopes in our sample set within 0.1 permil and no contribution from the extinct radionuclide 97Tc at mass 97 (97Tc/92Mo<3E-6). Instead, we observe clear anomalies in bulk iron meteorites, mesosiderites, pallasites, and chondrites characterized by a coupled excess in p- and r- or a mirror deficit in s-process nuclides (Mo-HL). This large scale isotope heterogeneity of the solar system observed for molybdenum must have been inherited from the interstellar environment where the sun was born, illustrating the concept of ``cosmic chemical memory''. The presence of molybdenum anomalies is used to discuss the filiation between planetesimals.

  16. 基于反硝化脱氮的硫铁复合填料除磷机制%Phosphorus Removal Mechanism of Sulfur/Sponge Iron Composite Fillers Based on Denitrification

    Institute of Scientific and Technical Information of China (English)

    范军辉; 郝瑞霞; 李萌; 朱晓霞; 万京京

    2016-01-01

    In order to improve the phosphorus removal effect in the denitrification and phosphorus synchronous removal process by sulfur/ sponge iron composite fillers, the phosphorus removal effect by different fillers with the coupling microorganisms was studied to analyze the denitrifying phosphorus removal mechanism of the microbial coupling sulfur/ sponge iron composite fillers. The research result showed that the phosphorus removal ratio of sponge iron/ sulfur composite fillers was over 95% , which was increased by 30% as compared to only sponge iron filler. In addition, the effluent TP concentration was reduced to less than 0. 1 mg•L - 1 . The analysis of X-ray diffraction(XRD)and total iron concentration indicated that the main phosphorus removal system products which were produced in the corrosion and phosphorus removal process of sponge iron were FeOOH, FeS and Fe4 (PO4 ) 3 (OH) 3 deposits and dissolved iron ions; FeS and FeOOH which were the hydrolysis products of Fe2 + and Fe3 + converted PO3 -4 to Fe4 (PO4 ) 3 (OH) 3 by adsorption and deposition so that phosphorus removal could be achieved. After the reactor of microbial coupling sulfur/ sponge iron carbon composite fillers became stable, the removal efficiency of TN and TP could reach 90% and more than 83% , respectively; Corrosion of sponge iron and phosphorus removal process could also be promoted by biological iron and H + that was produced in the sulfur autotrophic denitrification process, the system could realize the combination of “heterotrophic synergy autotrophic” composite denitrification and chemical phosphorus removal, and efficient denitrifying denitrification synchronous phosphorus removal process could be achieved in the urban sewage treatment plant.%为提高硫铁复合填料反硝化脱氮同步除磷效果,对比研究了不同填料和耦合微生物后的除磷效果,分析了微生物耦合硫铁复合填料反硝化脱氮同步实现除磷的机制.结果表

  17. 极谱法测定钼矿石中的总钼氧化钼硫化钼%Determination of Total Molybdenum, Molybdic Oxide and Molybdenum Sulfide in Molybdenum Ore by Polarography

    Institute of Scientific and Technical Information of China (English)

    薛静

    2012-01-01

    Molybdenite is the major mineral in molybdenum ore. The phase analysis of molybdenum ore is required to determine sulfide minerals and oxide minerals. The phase analyses of molybdenum ores such as molybdenite, molybdite, powellite and molybdate galena were taken by photometry and Inductively Coupled Plasma-Atomic Emission Spectrometry ( ICP-AES). In this paper, the molybdenum ore sample was dissolved with aqua regia-sulfuric acid. The total molybdenum was extracted by alkali solution and the majority of the other elements were separated by precipitation. Molybdic oxides were leached by sodium carbonate and ammonium hydroxide solution. Molybdenum sulfides were obtained to dissolve residue. The contents of total molybdenum, molybdic oxide and molybdenum sulfide were determined by rapid polarography in a sulfuric acid-potassium chlorate-diphenyl glycollic acid system. The linear range of the method was 0. 04 -0. 4 mg/L, and the detection limit was 0. 028 mg/L. Three molybdenum ore samples were carried on phase analysis and the results were consistent with those obtained by photometry. The sum contents of molybdic oxide and molybdenum sulfide conformed to the total molybdenum content. RSDs (n=8) were 1.69% -3.56% for total molybdenum, molybdic oxide and molybdenum sulfide. This method was fast and suitable for practical batch samples.%钼的物相分析要求测定硫化矿物相和氧化矿物相,常用比色法和电感耦合等离子体发射光谱法等对辉钼矿、钼华矿、钼钨钙矿、钼酸铅矿等钼矿石进行物相分析,但分离物相的品种较多,方法繁琐耗时.本文用王水-硫酸消解钼矿石样品,碱溶液复溶浸提得到钼总量,使其他大多数元素形成沉淀而分离,用碳酸钠-氢氧化铵混合溶液浸取钼的氧化矿物,将残渣进一步溶解得到硫化矿物含量,在硫酸-氯酸钾-二苯羟乙酸体系中用极谱法简单快速测定钼总量、氧化钼和硫化钼含量.方法的线性范围为0.04~0

  18. Iron and sulfur isotope constraints on redox conditions associated with the 3.2 Ga barite deposits of the Mapepe Formation (Barberton Greenstone Belt, South Africa)

    Science.gov (United States)

    Busigny, Vincent; Marin-Carbonne, Johanna; Muller, Elodie; Cartigny, Pierre; Rollion-Bard, Claire; Assayag, Nelly; Philippot, Pascal

    2017-08-01

    The occurrence of Early Archean barite deposits is intriguing since this type of sediment requires high availability of dissolved sulfate (SO42-), the oxidized form of sulfur, although most authors argued that the Archean eon was dominated by reducing conditions, with low oceanic sulfate concentration (gases produced by large subaerial volcanic events, and possibly SO42- produced by magmatic SO2 disproportionation in hydrothermal systems.

  19. Genomic Insights into the Sulfur Metabolism of Phototrophic Green Sulfur Bacteria

    DEFF Research Database (Denmark)

    Frigaard, Niels-Ulrik; Bryant, Donald A.

    2008-01-01

    Green sulfur bacteria (GSB) utilize various combinations of sulfide, elemental sulfur, thiosulfate, ferrous iron, and hydrogen for anaerobic photoautotrophic growth. Genome sequence data is currently available for 12 strains of GSB. We present here a genome-based survey of the distribution...

  20. Molybdenum sulfide/carbide catalysts

    Science.gov (United States)

    Alonso, Gabriel; Chianelli, Russell R.; Fuentes, Sergio; Torres, Brenda

    2007-05-29

    The present invention provides methods of synthesizing molybdenum disulfide (MoS.sub.2) and carbon-containing molybdenum disulfide (MoS.sub.2-xC.sub.x) catalysts that exhibit improved catalytic activity for hydrotreating reactions involving hydrodesulfurization, hydrodenitrogenation, and hydrogenation. The present invention also concerns the resulting catalysts. Furthermore, the invention concerns the promotion of these catalysts with Co, Ni, Fe, and/or Ru sulfides to create catalysts with greater activity, for hydrotreating reactions, than conventional catalysts such as cobalt molybdate on alumina support.

  1. X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials

    Energy Technology Data Exchange (ETDEWEB)

    DeWitt, J.G.

    1992-12-01

    The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 {Angstrom}. The Fe-Fe distance was determined to be 3.4 {Angstrom}. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

  2. X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials

    Energy Technology Data Exchange (ETDEWEB)

    DeWitt, J.G.

    1992-12-01

    The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 [Angstrom]. The Fe-Fe distance was determined to be 3.4 [Angstrom]. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

  3. Effect of Sulfur on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-S System in Equilibrium with Metallic Iron

    Science.gov (United States)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2011-10-01

    The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-S system have been determined experimentally in equilibrium with metallic iron. A pseudoternary section of the form ZnO-"FeO"-(Al2O3+CaO+SiO2) for CaO/SiO2 = 0.71 (weight), (CaO+SiO2)/Al2O3 = 5.0 (weight), and fixed 2.0 wt pct S concentration has been constructed. It was found that the addition of 2.0 wt pct S to the liquid extends the spinel primary phase field significantly and decreases the size of the wustite primary phase field. The liquidus temperature in the wustite primary phase field is decreased by approximately 80 K and the liquidus temperature in the spinel primary phase field is decreased by approximately 10 K with addition of 2.0 wt pct S in the composition range investigated. It was also found that iron-zinc sulfides are present in some samples in the spinel primary phase field, which are matte appearing at low zinc concentrations and sphalerite (Zn,Fe)S at higher zinc concentrations. The presence of sulfur in the slag has a minor effect on the partitioning of ZnO between the wustite and liquid phases but no effect on the partitioning of ZnO between the spinel and liquid phases.

  4. Separation of molybdenum from interfering elements by extraction as phosphomolybdenum blue.

    Science.gov (United States)

    Yatirajam, V; Ram, J

    1973-09-01

    A simple method is described for the separation of molybdenum from titanium, zirconium, chromium, manganese, iron, cobalt, nickel, uranium and aluminium in a wide variety of samples in molybdenum concentration of 0.6-5 my/ml in 0.4-0.5N sulphuric acid. The phosphomolybdenum blue is 99.5% extracted with methyl isobutyl ketone in a single extraction. The residual molybdenum and hydrazine in the aqueous phase are oxidized with a few drops of liquid bromine and the molybdenum is quantitatively extracted with the same solvent from 1N sulphuric acid as its reddish brown thiosulphato complex. The molybdenum is stripped by ammonia-hydrogen peroxide solution. The back-extract is heated to boiling and filtered to remove the insoluble hydroxides of traces of accompanying elements. The thiosulphate in the filtrate is destroyed by boiling for 4-5 min with excess of hydrogen peroxide in slightly ammoniacal medium. The molybdenum is determined finally by cerimetry or other standard methods.

  5. Gel Fabrication of Molybdenum “Beads”

    Energy Technology Data Exchange (ETDEWEB)

    Lowden, Richard Andrew [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Armstrong, Beth L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Cooley, Kevin M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

    2016-11-01

    Spherical molybdenum particles or “beads” of various diameters are of interest as feedstock materials for the additive manufacture of targets and assemblies used in the production of 99Mo medical isotopes using accelerator technology. Small metallic beads or ball bearings are typically fabricated from wire; however, small molybdenum spheres cannot readily be produced in this manner. Sol-gel processes are often employed to produce small dense microspheres of metal oxides across a broad diameter range that in the case of molybdenum could be reduced and sintered to produce metallic spheres. These Sol-gel type processes were examined for forming molybdenum oxide beads; however, the molybdenum trioxide was chemically incompatible with commonly used gelation materials. As an alternative, an aqueous alginate process being assessed for the fabrication of oxide spheres for catalyst applications was employed to form molybdenum trioxide beads that were successfully reduced and sintered to produce small molybdenum spheres.

  6. Systematic variation of the sodium/sulfur promoter content on carbon-supported iron catalysts for the Fischer-Tropsch to olefins reaction

    NARCIS (Netherlands)

    Oschatz, M.; Krans, N.A.; Xie, J.; de Jong, K.P.

    2016-01-01

    The Fischer–Tropsch to olefins (FTO) process is a method for the direct conversion of synthesis gas to lower C2–C4 olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction. The catalytic activity can be improved and undesired formation of alkanes can be suppres

  7. Systematic variation of the sodium/sulfur promoter content on carbon-supported iron catalysts for the Fischer-Tropsch to olefins reaction

    NARCIS (Netherlands)

    Oschatz, M.; Krans, N.A.|info:eu-repo/dai/nl/41128942X; Xie, J.; de Jong, K.P.|info:eu-repo/dai/nl/06885580X

    2016-01-01

    The Fischer–Tropsch to olefins (FTO) process is a method for the direct conversion of synthesis gas to lower C2–C4 olefins. Carbon-supported iron carbide nanoparticles are attractive catalysts for this reaction. The catalytic activity can be improved and undesired formation of alkanes can be

  8. HYDROGEN VACANCY INTERACTION IN MOLYBDENUM

    NARCIS (Netherlands)

    Abd El Keriem, M.S.; van der Werf, D.P.; Pleiter, F

    1993-01-01

    Vacancy-hydrogen interaction in molybdenum was investigated by means of the perturbed angular correlation technique, using the isotope In-111 as a probe. The complex InV2 turned out to trap up to two hydrogen atoms: trapping of a single hydrogen atom gives rise to a decrease of the quadrupole

  9. Molybdenum Dithiocarbamates:A New Approach to "Old" Technology

    Institute of Scientific and Technical Information of China (English)

    Kevin J. Chase; William T. Wallack; Gaston A. Aguilar

    2012-01-01

    A new method for the preparation of dinuclear molybdenum dithiocarbamates(MoDDCs) is reported.This new method allows for the control of the amount of sulfurization of the Mo2SxO4-x core(x = 1 to 4) in the dinuclear MoDDCs.This control assists in the tailoring of specific tribological properties of the MoDDCs in both greases and lubricating oils.

  10. Origin of sulfur and crustal recycling of copper in polymetallic (Cu-Au-Co-Bi-U ± Ag) iron-oxide-dominated systems of the Great Bear Magmatic Zone, NWT, Canada

    Science.gov (United States)

    Acosta-Góngora, P.; Gleeson, S. A.; Samson, I. M.; Corriveau, L.; Ootes, L.; Jackson, S. E.; Taylor, B. E.; Girard, I.

    2017-06-01

    The Great Bear Magmatic Zone, in northwest Canada, contains numerous polymetallic mineral occurrences, prospects, and deposits of the iron oxide copper-gold deposit (IOCG) family. The mineralization is hosted by the Treasure Lake Group and igneous rocks of the Great Bear arc and was deposited concomitantly with the arc magmatism (ca. 1.88 to 1.87 Ga). In situ δ 34S (n = 48) and δ 65Cu (n = 79) analyses were carried out on ore-related sulfides from a number of these systems. The δ 34S values mainly vary between 0 and +5‰, consistent with derivation of sulfur from the mantle. Lower δ 34S values (-7.7 to +1.4‰) from the Sue-Dianne breccia may indicate SO2 disproportionation of a magmatic hydrothermal fluid. The δ 65Cu values vary between -1.2 and -0.3‰, and are lower than the igneous δ 65Cu range of values (0.0 ± 0.27‰). The S and Cu isotopic data are decoupled, which suggests that Cu (and possibly some S) was dissolved and remobilized from supracrustal rocks during early stages of alteration (e.g., sodic alteration) and then precipitated by lower temperature, more oxidizing fluids (e.g., Ca-Fe-K alteration). A limited fluid inclusion dataset and δ 13C and δ 18O values are also presented. The δ 18Ofluid values are consistent with a magmatic origin or a host-rock equilibrated meteoric water source, whereas the δ 13Cfluid values support a marine carbonate source. Combined, the S and Cu isotopic data indicate that while the emplacement of the Great Bear magmatic bodies may have driven fluid convection and may be the source of fluids and sulfur, metals such as Cu could have been recycled from crustal sources.

  11. Examination of sulfur-functionalized, copper-doped iron nanoparticles for vapor-phase mercury capture in entrained-flow and fixed-bed systems

    Energy Technology Data Exchange (ETDEWEB)

    D.E. Meyer; S.K. Sikdar; N.D. Hutson; D. Bhattacharyya [University of Kentucky, Lexington, KY (United States). Department of Chemical and Materials Engineering

    2007-09-15

    The use of copper-doped Fe nanoaggregates silanized with organic sulfur as bis-(triethoxy silyl propyl)-tetra sulfide has been investigated for the capture of elemental mercury (Hg{sup 0}) from the vapor phase for potential power plant applications. Silanization procedures resulted in 70% deposition of the targeted sulfur level, with particles containing approximately 4 wt % S. The addition of copper was found to increase the fixed-bed (total) capacity of this type of sorbent from 170 {+-} {mu}20 g Hg{center_dot}g sorbent{sup -1} with no copper doping to 2730 {+-} 80 {mu}g Hg{center_dot}g sorbent{sup -1} at 1.2 wt % Cu. When no S is deposited, the capacity of Fe/Cu nanoaggregates was only 180 g Hg{center_dot}g sorbent{sup -1}. These findings suggest that a combined Cu-S mechanism is responsible for Hg capture. Moving-bed (injection) testing of the Fe-based sorbents in a simulated flue gas stream showed that the 1.2 wt % Cu sample was able to achieve significant removal of the Hg. At a modest sorbent injection rate of 3.6 x 10{sup -3} g{center_dot}L{sup -1}{center_dot}h{sup -1}, this material showed a steady-state removal capacity of 107.5 {mu}g Hg{center_dot}g sorbent{sup -1} for an inlet concentration of 17.8 {mu}g{center_dot}m{sup -3}. On the basis of only 4% usage of the total capacity during single-pass injection, it might be beneficial to develop methods to separate and recycle these materials to reduce power plant operation costs for Hg emissions control. 17 refs., 5 figs., 10 tabs.

  12. [Molybdenum as an air pollutant].

    Science.gov (United States)

    Lindner, R; Junker, E; Hoheiser, H

    1990-07-01

    Investigations into the reasons for the retarded growth and discolouration of a small area of a field of rape situated on the outskirts of Vienna revealed higher than normal levels of molybdenum in the soil (up to 430 micrograms/l) and in the water (up to 9.7 mg/l). The source of the pollution was traced to a neighbouring industrial plant that was emitting the metal via the chimney stack. A review of the literature on the toxic effects of molybdenum in general and as an air pollutant in particular is provided. This shows that, in contrast to animals, this effect is relatively small in humans and plants. Nevertheless, the occupation-related inhalation of the metal has been shown to be associated with pneumoconiosis and gout-like symptoms.

  13. Overexpression of the yeast frataxin homolog (Yfh1): contrasting effects on iron-sulfur cluster assembly, heme synthesis and resistance to oxidative stress.

    Science.gov (United States)

    Seguin, Alexandra; Bayot, Aurélien; Dancis, Andrew; Rogowska-Wrzesinska, Adelina; Auchère, Françoise; Camadro, Jean-Michel; Bulteau, Anne-Laure; Lesuisse, Emmanuel

    2009-04-01

    Friedreich's ataxia is generally associated with defects in [Fe-S] cluster assembly/stability and heme synthesis and strong susceptibility to oxidative stress. We used the yeast (Saccharomyces cerevisiae) model of Friedreich's ataxia to study the physiological consequences of modulating the expression of the frataxin gene (YFH1). We show that the number of frataxin molecules per wild-type cell varies from less than 200 to 1500 according to the iron concentration in the medium. Cells overexpressing YFH1 on a plasmid (2muYFH1; about 3500 molecules Yfh1/cell) took up more iron than wild-type cells and displayed defective [Fe-S] cluster assembly/stability in vivo. By contrast, endogenous mitochondrial iron was more available to ferrochelatase in 2muYFH1 cells than in wild-type cells, resulting in higher levels of heme synthesis in vitro. Frataxin overproduction resulted in a shift from frataxin trimers to frataxin oligomers of higher molecular mass in the mitochondrial matrix. Much fewer carbonylated proteins were present in 2muYFH1 cells, and these cells were more resistant to oxidizing agents than wild-type cells, which probably resulted from the lower production of hydrogen peroxide by the mitochondria of 2muYFH1 cells compared to wild-type cells. To our knowledge, this work is the first description where major frataxin-related phenotypes ([Fe-S] cluster assembly and heme synthesis) can be split in vivo, suggesting that frataxin has independent roles in both processes, and that the optimal conditions for these independent roles are different.

  14. Zirconia-molybdenum disilicide composites

    Science.gov (United States)

    Petrovic, John J.; Honnell, Richard E.

    1991-01-01

    Compositions of matter comprised of molybdenum disilicide and zirconium oxide in one of three forms: pure, partially stabilized, or fully stabilized and methods of making the compositions. The stabilized zirconia is crystallographically stabilized by mixing it with yttrium oxide, calcium oxide, cerium oxide, or magnesium oxide and it may be partially stabilized or fully stabilized depending on the amount of stabilizing agent in the mixture.

  15. Effects of carbon and molybdenum on the microstructures of high chromium white cast irons; Efeito do carbono e do molibdenio na microestrutura dos ferros fundidos brancos de alto cromo

    Energy Technology Data Exchange (ETDEWEB)

    Sinatora, Amilton; Ambrosio Filho, Francisco; Goldenstein, Helio; Fuoco, Ricardo; Albertin, Eduardo; Mei, Paulo Roberto

    1992-12-31

    The effects of 3 levels of carbon and 1.5% Mo addition on the solidification structures of a 15% chromium white cast iron were studied. The volume fraction of primary austenite and of eutectic carbides, as well as the number of carbide particles per unit length and the mean secondary dendrite arm spacing were measured. By means of thermal analysis, thermal arrest corresponding to the formation of the primary austenite and of the eutectic were determined. The increase in the carbon content and the addition of Mo led to lowering of the thermal arrests and to coarsening of the particles. (author) 15 refs., 6 figs., 5 tabs.

  16. IOP1 protein is an external component of the human cytosolic iron-sulfur cluster assembly (CIA) machinery and functions in the MMS19 protein-dependent CIA pathway.

    Science.gov (United States)

    Seki, Mineaki; Takeda, Yukiko; Iwai, Kazuhiro; Tanaka, Kiyoji

    2013-06-07

    The emerging link between iron metabolism and genome integrity is increasingly clear. Recent studies have revealed that MMS19 and cytosolic iron-sulfur cluster assembly (CIA) factors form a complex and have central roles in CIA pathway. However, the composition of the CIA complex, particularly the involvement of the Fe-S protein IOP1, is still unclear. The roles of each component are also largely unknown. Here, we show that MMS19, MIP18, and CIAO1 form a tight "core" complex and that IOP1 is an "external" component of this complex. Although IOP1 and the core complex form a complex both in vivo and in vitro, IOP1 behaves differently in vivo. A deficiency in any core component leads to down-regulation of all of the components. In contrast, IOP1 knockdown does not affect the level of any core component. In MMS19-overproducing cells, other core components are also up-regulated, but the protein level of IOP1 remains unchanged. IOP1 behaves like a target protein in the CIA reaction, like other Fe-S helicases, and the core complex may participate in the maturation process of IOP1. Alternatively, the core complex may catch and hold IOP1 when it becomes mature to prevent its degradation. In any case, IOP1 functions in the MMS19-dependent CIA pathway. We also reveal that MMS19 interacts with target proteins. MIP18 has a role to bridge MMS19 and CIAO1. CIAO1 also binds IOP1. Based on our in vivo and in vitro data, new models of the CIA machinery are proposed.

  17. The Low-temperature Ion Sulfurizing Technology and its Applications

    Science.gov (United States)

    Ma, G. Z.; Xu, B. S.; Wang, H. D.; Li, G. L.; Zhang, S.

    A solid lubrication film mainly consists of FeS, which has excellent tribology properties, can be formed on the sulfurized iron or steel surface. The sulfurizing technology has aroused intense attention from the day it appeared. However, the widespread industrial application of sulfurizing technology was promoted by the low-temperature ion sulfurizing (LTIS) process. This paper summarized the phylogeny and sorts of sulfurizing technology firstly; then, the process flow of LTIS technology, the forming mechanism, microstructure and tribological properties of ion sulfurized layer were introduced detailedly; and then, the technological, economic and environmental merits of LTIS technology were generalized; finally, the industrial applications of LTIS technology in various typical rolling, sliding and heavy duty parts were reviewed briefly. LTIS technology, with the advantages of high sulfurizing speed, good performance of sulfurized layer and without sideeffect, has played an important role in the tribology modification of ferrous parts, and the LTIS process will become more green, simple and efficient in the future.

  18. Reduction of unusual iron-sulfur clusters in the H2-sensing regulatory Ni-Fe hydrogenase from Ralstonia eutropha H16.

    Science.gov (United States)

    Buhrke, Thorsten; Löscher, Simone; Lenz, Oliver; Schlodder, Eberhard; Zebger, Ingo; Andersen, Lars K; Hildebrandt, Peter; Meyer-Klaucke, Wolfram; Dau, Holger; Friedrich, Bärbel; Haumann, Michael

    2005-05-20

    The regulatory Ni-Fe hydrogenase (RH) from Ralstonia eutropha functions as a hydrogen sensor. The RH consists of the large subunit HoxC housing the Ni-Fe active site and the small subunit HoxB containing Fe-S clusters. The heterolytic cleavage of H(2) at the Ni-Fe active site leads to the EPR-detectable Ni-C state of the protein. For the first time, the simultaneous but EPR-invisible reduction of Fe-S clusters during Ni-C state formation was demonstrated by changes in the UV-visible absorption spectrum as well as by shifts of the iron K-edge from x-ray absorption spectroscopy in the wild-type double dimeric RH(WT) [HoxBC](2) and in a monodimeric derivative designated RH(stop) lacking the C-terminal 55 amino acids of HoxB. According to the analysis of iron EXAFS spectra, the Fe-S clusters of HoxB pronouncedly differ from the three Fe-S clusters in the small subunits of crystallized standard Ni-Fe hydrogenases. Each HoxBC unit of RH(WT) seems to harbor two [2Fe-2S] clusters in addition to a 4Fe species, which may be a [4Fe-3S-3O] cluster. The additional 4Fe-cluster was absent in RH(stop). Reduction of Fe-S clusters in the hydrogen sensor RH may be a first step in the signal transduction chain, which involves complex formation between [HoxBC](2) and tetrameric HoxJ protein, leading to the expression of the energy converting Ni-Fe hydrogenases in R. eutropha.

  19. Biologically produced sulfur

    NARCIS (Netherlands)

    Kleinjan, W.E.; Keizer, de A.; Janssen, A.J.H.

    2003-01-01

    Sulfur compound oxidizing bacteria produce sulfur as an intermediate in the oxidation of hydrogen sulfide to sulfate. Sulfur produced by these microorganisms can be stored in sulfur globules, located either inside or outside the cell. Excreted sulfur globules are colloidal particles which are stabil

  20. Controlled expression of nif and isc iron-sulfur protein maturation components reveals target specificity and limited functional replacement between the two systems.

    Science.gov (United States)

    Dos Santos, Patricia C; Johnson, Deborah C; Ragle, Brook E; Unciuleac, Mihaela-Carmen; Dean, Dennis R

    2007-04-01

    The nitrogen-fixing organism Azotobacter vinelandii contains at least two systems that catalyze formation of [Fe-S] clusters. One of these systems is encoded by nif genes, whose products supply [Fe-S] clusters required for maturation of nitrogenase. The other system is encoded by isc genes, whose products are required for maturation of [Fe-S] proteins that participate in general metabolic processes. The two systems are similar in that they include an enzyme for the mobilization of sulfur (NifS or IscS) and an assembly scaffold (NifU or IscU) upon which [Fe-S] clusters are formed. Normal cellular levels of the Nif system, which supplies [Fe-S] clusters for the maturation of nitrogenase, cannot also supply [Fe-S] clusters for the maturation of other cellular [Fe-S] proteins. Conversely, when produced at the normal physiological levels, the Isc system cannot supply [Fe-S] clusters for the maturation of nitrogenase. In the present work we found that such target specificity for IscU can be overcome by elevated production of NifU. We also found that NifU, when expressed at normal levels, is able to partially replace the function of IscU if cells are cultured under low-oxygen-availability conditions. In contrast to the situation with IscU, we could not establish conditions in which the function of IscS could be replaced by NifS. We also found that elevated expression of the Isc components, as a result of deletion of the regulatory iscR gene, improved the capacity for nitrogen-fixing growth of strains deficient in either NifU or NifS.

  1. Friedreich's Ataxia Variants I154F and W155R Diminish Frataxin-Based Activation of the Iron-Sulfur Cluster Assembly Complex

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Chi-Lin; Bridwell-Rabb, Jennifer; Barondeau, David P

    2011-11-07

    Friedreich's ataxia (FRDA) is a progressive neurodegenerative disease that has been linked to defects in the protein frataxin (Fxn). Most FRDA patients have a GAA expansion in the first intron of their Fxn gene that decreases protein expression. Some FRDA patients have a GAA expansion on one allele and a missense mutation on the other allele. Few functional details are known for the ~15 different missense mutations identified in FRDA patients. Here in vitro evidence is presented that indicates the FRDA I154F and W155R variants bind more weakly to the complex of Nfs1, Isd11, and Isu2 and thereby are defective in forming the four-component SDUF complex that constitutes the core of the Fe-S cluster assembly machine. The binding affinities follow the trend Fxn ~ I154F > W155F > W155A ~ W155R. The Fxn variants also have diminished ability to function as part of the SDUF complex to stimulate the cysteine desulfurase reaction and facilitate Fe-S cluster assembly. Four crystal structures, including the first for a FRDA variant, reveal specific rearrangements associated with the loss of function and lead to a model for Fxn-based activation of the Fe-S cluster assembly complex. Importantly, the weaker binding and lower activity for FRDA variants correlate with the severity of disease progression. Together, these results suggest that Fxn facilitates sulfur transfer from Nfs1 to Isu2 and that these in vitro assays are sensitive and appropriate for deciphering functional defects and mechanistic details for human Fe-S cluster biosynthesis.

  2. Extraction of Molybdenum from Molybdenite Concentrates with Hydrometallurgical Processing

    Science.gov (United States)

    Jiang, Kaixi; Wang, Yufang; Zou, Xiaoping; Zhang, Lei; Liu, Sanping

    2012-11-01

    Molybdenite concentrates are usually treated by roasting, but low-concentration SO2 pollution is an associated problem. A hydrometallurgical process with pressure oxidation leaching (POX) and solvent extraction (SX) was developed in recent years. During POX, the oxidation of molybdenum (Mo) is above 98%. More than 95% of the rhenium (Re) and 15% to 20% of the Mo are leached into solution. The sulfur in the concentrate is converted to H2SO4, which results in high acidity of the solution. SX was used to recover the Re and Mo from the solution. The extraction of Re and Mo were above 98%. The loaded organic reagent is stripped with ammonia. More than 98% of the Mo can be stripped from the organic phase. Compared with the roasting process, the total recovery of Mo increased from 93% to 97% and that of Re from 60% to 90% when POX and SX are utilized.

  3. The production of sulfur targets for gamma-ray spectroscopy

    CERN Document Server

    Greene, J P

    2002-01-01

    The production of thin sulfur targets for nuclear physics, either in elemental or in compound form, is problematic, due to low melting points, high vapor pressures and high dissociation rates. Many sulfur compounds have been tried in the past without great success. In this paper, we report the use of spray coating molybdenum disulfide onto a thin carbon backing. The targets were of thickness 750 mu g/cm sup 2 (approx 300 mu g/cm sup 2 of sulfur) on 15 mu g/cm sup 2 carbon backings, and withstood 4 pnA (approx 10 mW/cm sup 2) of deposited beam power for several days without apparent loss of sulfur content.

  4. 新型炼钢钼产品的开发%Development of new molybdenum product for steelmaking

    Institute of Scientific and Technical Information of China (English)

    王磊; 郭培民; 罗林根; 赵沛; 庞建明

    2015-01-01

    分析了传统炼钢钼产品(钼铁、氧化钼)的生产工艺及其在应用过程中存在的问题,介绍了新一代钼冶金产品的生产工艺,并对新型炼钢产品的性质进行了研究.结果表明,钼铁和氧化钼的生产过程能耗高、污染较大,在炼钢过程中总收得率较低;而新型炼钢钼产品生产工艺简单,几乎无环境污染,冶炼过程中回收率高.所得到的新型炼钢钼产品呈疏松多孔状,堆积密度约为3.2~3.3 g/cm3,真密度为6.0~8.5 g/cm3,孔隙率为45%~60%,钼质量分数较高,杂质质量分数很低,在使用过程中收得率高,对现有的炼钢合金化流程影响小,因此可作为一种优质的炼钢钼产品.%The problems in the production process of molybdenum products (molybdenum iron and molybdenum oxide) used in steelmaking were analyzed,and a new process of molybdenum metallurgy was introduced and the properties of molybdenum products were studied. The results show that the production process of molybdenum iron and molybdenum oxide was high energy consumption,serious pollution and the yield in the steelmaking process was low. While the new production process of molybdenum products was a simple process with almost no pollution and high recovery. The ob-tained new molybdenum product was porous state,with a bulk density of approximately 3.2-3.3 g/cm3,a true density of 6.0-8.5 g/cm3 and a porosity of 45%-60%. The molybdenum content of the new product was higher and impurities content was lower. When the new product was used in the steelmaking process,it can be used as an excellent molybdenum prod-uct because it has little impact on the steelmaking process and the yield was higher.

  5. Geochemical evidence for cryptic sulfur cycling in salt marsh sediments

    DEFF Research Database (Denmark)

    Mills, Jennifer V.; Antler, Gilad; Turchyn, Alexandra V.

    2016-01-01

    investigate sulfur cycling in salt marsh sediments from Norfolk, England where we observe high ferrous iron concentrations with no depletion of sulfate or change in the sulfur isotope ratio of that sulfate, but a 5‰ increase in the oxygen isotope ratio in sulfate, indicating that sulfate has been through...

  6. Ocean iron cycle

    Science.gov (United States)

    Boyd, Philip W.

    Interest in the biogeochemical cycle of iron has grown rapidly over the last two decades, due to the potential role of this element in modulating global climate in the geological past and ocean productivity in the present day. This trace metal has a disproportionately large effect (1 × 105 C:Fe) on photosynthetic carbon fixation by phytoplankton. In around one third of the open ocean, so-called high-nitrate low-chlorophyll (HNLC) regions, the resident phytoplankton have low growth rates despite an abundance of plant nutrients. This is due to the low supply of iron. Iron is present in the ocean in three phases, dissolved, colloidal, and particulate (biogenic and lithogenic). However, iron chemistry is complex with interactions between chemistry and biology such as the production of iron-binding siderophores by oceanic bacteria. This results in the interplay of inorganic chemistry, photochemistry, and organic complexation. Sources of new iron include dust deposition, upwelling of iron-rich deep waters, and the resuspension and lateral transport of sediments. Sinks for iron are mainly biological as evidenced by the vertical nutrient-like profile for dissolved iron in the ocean. Iron is rapidly recycled by the upper ocean biota within a so-called "ferrous wheel." The fe ratio [(new iron)/(new + regenerated iron)] provides an index of the relative supply of iron to the biota by new versus recycled iron. Over the last 15 years, interest in the potential role of iron in shaping climate in the geological past resulted in some of the most ambitious experiments in oceanography: large-scale (i.e., 50-1000 km2) iron enrichment of HNLC waters. They have provided valuable insights into how iron supply influences the biogeochemical cycles of elements such as carbon, sulfur, silicon, nitrogen, and phosphate.

  7. Pseudomonas aeruginosa IscR-Regulated Ferredoxin NADP(+ Reductase Gene (fprB Functions in Iron-Sulfur Cluster Biogenesis and Multiple Stress Response.

    Directory of Open Access Journals (Sweden)

    Adisak Romsang

    Full Text Available P. aeruginosa (PAO1 has two putative genes encoding ferredoxin NADP(+ reductases, denoted fprA and fprB. Here, the regulation of fprB expression and the protein's physiological roles in [4Fe-4S] cluster biogenesis and stress protection are characterized. The fprB mutant has defects in [4Fe-4S] cluster biogenesis, as shown by reduced activities of [4Fe-4S] cluster-containing enzymes. Inactivation of the gene resulted in increased sensitivity to oxidative, thiol, osmotic and metal stresses compared with the PAO1 wild type. The increased sensitivity could be partially or completely suppressed by high expression of genes from the isc operon, which are involved in [Fe-S] cluster biogenesis, indicating that stress sensitivity in the fprB mutant is partially caused by a reduction in levels of [4Fe-4S] clusters. The pattern and regulation of fprB expression are in agreement with the gene physiological roles; fprB expression was highly induced by redox cycling drugs and diamide and was moderately induced by peroxides, an iron chelator and salt stress. The stress-induced expression of fprB was abolished by a deletion of the iscR gene. An IscR DNA-binding site close to fprB promoter elements was identified and confirmed by specific binding of purified IscR. Analysis of the regulation of fprB expression supports the role of IscR in directly regulating fprB transcription as a transcription activator. The combination of IscR-regulated expression of fprB and the fprB roles in response to multiple stressors emphasizes the importance of [Fe-S] cluster homeostasis in both gene regulation and stress protection.

  8. Price Hike in Molybdenum Industrial Chain Picked Up Speed

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    Affected by industry-wide joint production restriction,prices of molybdenum concentrate,molybdenum oxide and ferromolybdenum surged across the board.Following the average rising margin up to 1%to 2%on May 23,on May 24,prices of molybdenum concentrate and molybdenum oxide again were adjusted upward by 50 yuan per tonne,rising by 5%,which

  9. Axial Ligation and Redox Changes at the Cobalt Ion in Cobalamin Bound to Corrinoid Iron-Sulfur Protein (CoFeSP or in Solution Characterized by XAS and DFT.

    Directory of Open Access Journals (Sweden)

    Peer Schrapers

    Full Text Available A cobalamin (Cbl cofactor in corrinoid iron-sulfur protein (CoFeSP is the primary methyl group donor and acceptor in biological carbon oxide conversion along the reductive acetyl-CoA pathway. Changes of the axial coordination of the cobalt ion within the corrin macrocycle upon redox transitions in aqua-, methyl-, and cyano-Cbl bound to CoFeSP or in solution were studied using X-ray absorption spectroscopy (XAS at the Co K-edge in combination with density functional theory (DFT calculations, supported by metal content and cobalt redox level quantification with further spectroscopic methods. Calculation of the highly variable pre-edge X-ray absorption features due to core-to-valence (ctv electronic transitions, XANES shape analysis, and cobalt-ligand bond lengths determination from EXAFS has yielded models for the molecular and electronic structures of the cobalt sites. This suggested the absence of a ligand at cobalt in CoFeSP in α-position where the dimethylbenzimidazole (dmb base of the cofactor is bound in Cbl in solution. As main species, (dmbCoIII(OH2, (dmbCoII(OH2, and (dmbCoIII(CH3 sites for solution Cbl and CoIII(OH2, CoII(OH2, and CoIII(CH3 sites in CoFeSP-Cbl were identified. Our data support binding of a serine residue from the reductive-activator protein (RACo of CoFeSP to the cobalt ion in the CoFeSP-RACo protein complex that stabilizes Co(II. The absence of an α-ligand at cobalt not only tunes the redox potential of the cobalamin cofactor into the physiological range, but is also important for CoFeSP reactivation.

  10. Determination of Tungsten and Molybdenum in Geochemical Exploration Samples by Polarography%催化波极谱法测定化探样品中钨量及钼量

    Institute of Scientific and Technical Information of China (English)

    许卓; 于健; 马建学

    2012-01-01

    试样经碱熔分解,水提取,铁、锰、铺、镍元素量氢氧化物沉淀与钨、钼分离。在0.34moL/L硫酸-2g/L苯羟乙酸-24g/L氯酸钠-0.08g/L辛兜宁体系中,钨和锢均能产生灵敏的极谱催化波,峰电位约为-0.70V和-0.07V(对饱和日‘汞电极)。方法检出限为WO.29蚓g、Mo0.26μg/g,精密度(RSD,n=12)为W1.21%-10.1%、Mo2.7%~12.4%,准确度(RE,n=12)为W-3.7%-2.33%、Mo-4.79%~3.17%。适用于化探样品中钨钿厄索的连续测定。%The sample was melted with potassium hydroxide and extracted with water. Tungsten and molybdenum were separated from iron, manganese, cobalt and nickel with their hydroxides. In 0.34 moL/L sulfuric acid-2 g/L hydroxyphenylacetic acid-24 g/L sodium chlorate -0.08 g/L cinchonine system, tungsten and molybdenum were produced sensitive polarographic catalytic waves with peak potentials (with a saturated calomel electrode) at -0.70 V and-0.07 V, respectively. The detection limit of tungsten and molybdenum were 0.29/ag/g and 0.26μg/g, respectively. The RSD (n=12) of method were 1.21%-10.1% for W, 2.7 %~12.4 % for Mo. The RE (n=12) of method were -3.7 %-2.33 % for W,-4.79 %-3.17% for Mo. The method has been applied to the continuous determination of tungsten and molybdenum in geochemical exploration samples.

  11. MOLYBDENUM

    African Journals Online (AJOL)

    electron donor), have been found to have 3:4 square pyramidal structures with the cyclopentadienyl .... The relative ratios of the cis to trans ring proton resonances gives the proportion of cis to .... relationship is not obvious by our analysis.

  12. SMELTING METHOD OF MIXED MOLYBDENUM CONCENTRATES%试论混合钼精矿的冶炼方法

    Institute of Scientific and Technical Information of China (English)

    伍耀明

    2016-01-01

    对铜钼混选矿,采用纯氧焙烧-真空升华的冶炼工艺,试剂投入低,产品档次高. 对低钼铜钼混选矿和所有铅钼混选矿以及镍钼矿原矿,采用硫酸加硝酸常压强化催化氧化浸出,可以简化选矿工序,实现铅钼彻底分离,避免铅对钼产品的连环污染. 钼和铅外金属元素从浸出液回收,铅和贵金属从浸出渣回收,金属收率高. 还介绍了卧式常压强化浸出槽的特点和功能.%For copper-molybdenum mixed ores , smelting technology of pure oxidation roasting-vacuum submilation was adopted with low reagent adding and high quality products .However , for copper-molybdenum mixed ores with less molybdenum , all lead-molybdenum ores and nikecl-molybdenum raw ores ,the technology of sulfuric acid and nitric acid ordinary pressure strengthening and catalytic oxidation leaching was adopted with simplified benefication procedure and complete lead-molybdenum separation .Other elements except molybdenum and lead were recovered from leaching agent ,lead and precious metals were recovered from leaching slags ,metal yield coefficient was high.The characteristic and function of horizontal leaching tank were introduced .

  13. Process for Functionalizing Biomass using Molybdenum Catalysts

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention concerns a process for converting biomass into useful organic building blocks for the chemical industry. The process involves the use of molybdenum catalysts of the formula Aa+a(MovXxR1yR2zR3e)a*3-, which may be readily prepared from industrial molybdenum compounds.......The present invention concerns a process for converting biomass into useful organic building blocks for the chemical industry. The process involves the use of molybdenum catalysts of the formula Aa+a(MovXxR1yR2zR3e)a*3-, which may be readily prepared from industrial molybdenum compounds....

  14. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, Low-Carbon Nickel-Chromium-Molybdenum-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Tungsten, and Low-Carbon Nickel-Molybdenum-Chromium Alloy Plate, Sheet, and Strip

  15. Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Low-Carbon Nickel-Chromium-Molybdenum, Low-Carbon Nickel-Molybdenum-Chromium, Low-Carbon Nickel-Molybdenum-Chromium-Tantalum, Low-Carbon Nickel-Chromium-Molybdenum-Copper, and Low-Carbon Nickel-Chromium-Molybdenum-Tungsten Alloy Rod

  16. Development of Direct Alloying by Molybdenum Oxides%氧化钼直接合金化炼钢的发展

    Institute of Scientific and Technical Information of China (English)

    李正邦; 朱航宇; 杨海森

    2013-01-01

    Theoretical basis of direct alloying by use of molybdenum oxides and the better period for adding molybdenum oxides to EAF (electric arc furnace) was introduced, and resent research results of stabilizing molybdenum trioxide to inhibit its sublimation and difference of direct alloying by molybdenum oxides was both compared at home and abroad. The suggested conclusion is that the use of calcium oxide, calcium carbonate, magnesium oxide or iron oxide mixed with molybdenum trioxide adding to EAF can inhibit volatilization of molybdenum trioxide significantly, molybdenum yield can be improved accordingly.%介绍了氧化钼直接合金化炼钢的理论依据和电炉炼钢过程中的最佳加入时期,总结了抑制氧化钼挥发的研究成果并对比分析了国内外氧化钼炼钢工艺流程的差别.由此得出,采用氧化钙、碳酸钙、氧化镁或氧化铁和三氧化钼混加的方式能显著抑制三氧化钼的挥发,提高钼的收得率.

  17. The Densification of Molybdenum and Molybdenum Alloy Powders Using Hot Isostatic Pressing.

    Science.gov (United States)

    1985-08-01

    TECHNICAL REPORT ARLCB-TR-85025 00 THE DENSIFICATION OF MOLYBDENUM (n AND MOLYBDENUM ALLOY POWDERS USING HOT ISOSTATIC PRESSING J. BARRANCO I. AHMAD S...ISOSTATIC PRESSING Final 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(o) . CONTRACT OR GRANT NUMBER(e) J. Barranco , I. Ahmad, S. Isserow, and R. Warenchak

  18. Solubility of Sulfur Dioxide in Sulfuric Acid

    Science.gov (United States)

    Chang, K. K.; Compton, L. E.; Lawson, D. D.

    1982-01-01

    The solubility of sulfur dioxide in 50% (wt./wt.) sulfuric acid was evaluated by regular solution theory, and the results verified by experimental measurements in the temperature range of 25 C to 70 C at pressures of 60 to 200 PSIA. The percent (wt./wt.) of sulfur dioxide in 50% (wt./wt.) sulfuric acid is given by the equation %SO2 = 2.2350 + 0.0903P - 0.00026P 10 to the 2nd power with P in PSIA.

  19. Fast and large-area growth of uniform MoS2 monolayers on molybdenum foils

    Science.gov (United States)

    Tai, Guoan; Zeng, Tian; Yu, Jin; Zhou, Jianxin; You, Yuncheng; Wang, Xufeng; Wu, Hongrong; Sun, Xu; Hu, Tingsong; Guo, Wanlin

    2016-01-01

    A controllable synthesis of two-dimensional crystal monolayers in a large area is a prerequisite for potential applications, but the growth of transition metal dichalcogenide monolayers in a large area with spatial homogeneity remains a great challenge. Here we report a novel and efficient method to fabricate large-scale MoS2 monolayers by direct sulfurization of pre-annealed molybdenum foil surfaces with large grain boundaries of more than 50 μm in size at elevated temperatures. Continuous MoS2 monolayers can be formed uniformly by sulfurizing the Mo foils in sulfur vapor at 600 °C within 1 min. At a lower temperature even down to 500 °C, uniform MoS2 monolayers can still be obtained but in a much longer sulfurizing duration. It is demonstrated that the formed monolayers can be nondestructively transferred onto arbitrary substrates by removing the Mo foil using diluted ferric chloride solution and can be successfully fabricated into photodetectors. The results show a novel avenue to efficiently fabricate two-dimensional crystals in a large area in a highly controllable way and should have great potential for the development of large-scale applications of two-dimensional crystals in electrophotonic systems.A controllable synthesis of two-dimensional crystal monolayers in a large area is a prerequisite for potential applications, but the growth of transition metal dichalcogenide monolayers in a large area with spatial homogeneity remains a great challenge. Here we report a novel and efficient method to fabricate large-scale MoS2 monolayers by direct sulfurization of pre-annealed molybdenum foil surfaces with large grain boundaries of more than 50 μm in size at elevated temperatures. Continuous MoS2 monolayers can be formed uniformly by sulfurizing the Mo foils in sulfur vapor at 600 °C within 1 min. At a lower temperature even down to 500 °C, uniform MoS2 monolayers can still be obtained but in a much longer sulfurizing duration. It is demonstrated that the

  20. Physics of iron

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, O.

    1993-10-01

    This volume comprises papers presented at the AIRAPT Conference, June 28 to July 1993. The iron sessions at the meeting were identified as the Second Ironworkers Convention. The renewal of interest stems from advances in technologies in both diamond-anvil cell (DAC) and shock wave studies as well as from controversies arising from a lack of consensus among both experimentalists and theoreticians. These advances have produced new data on iron in the pressure-temperature regime of interest for phase diagrams and for temperatures of the core/mantle and inner-core/outer-core boundaries. Particularly interesting is the iron phase diagram inferred from DAC studies. A new phase, {beta}, with a {gamma}-{beta}-{epsilon} triple point at about 30 GPa and 1190 K, and possible sixth phase, {omega}, with an {epsilon}-{Theta}-melt triple point at about 190 GPa and 4000 K are deemed possible. The importance of the equation of state of iron in consideration of Earth`s heat budget and the origin of its magnetic field invoke the interest of theoreticians who argue on the basis of molecular dynamics and other first principles methods. While the major thrust of both meetings was on the physics of pure iron, there was notable contributions on iron alloys. Hydrogen-iron alloys, iron-sulfur liquids, and the comparability to rhenium in phase diagram studies are discussed. The knowledge of the physical properties of iron were increased by several contributions.

  1. Molybdenum Metallopharmaceuticals Candidate Compounds - The "Renaissance" of Molybdenum Metallodrugs?

    Science.gov (United States)

    Jurowska, Anna; Jurowski, Kamil; Szklarzewicz, Janusz; Buszewski, Boguslaw; Kalenik, Tatiana; Piekoszewski, Wojciech

    2016-01-01

    Metal-based drugs, also called "metallopharmaceuticals" or "metallodrugs", are examples of sophisticated compounds that have been used in inorganic medicinal chemistry as therapeutic agents for a long time. Few of them have shown substantially promising results and many of them have been used in different phases of clinical trials. The Mo-based metallodrugs were successfully applied in the past for treating conditions such as anemia or Wilson's disease. Moreover, Mo complexes are supposed to exert their effect by intercalation/ cleavage of DNA/RNA, arrest of the cell cycle, and alteration of cell membrane functions. However, in the current literature, there are no reliable and in-depth reviews about the hypothetical therapeutic applications of all of the known molybdenum complexes as metallopharmaceuticals/ metallodrugs. The main emphasis was on the in-depth review of the potential applications of Mo-based complexes in medicinal chemistry as metallopharmaceuticals in treating diseases such as cancer and tumors, Wilson's disease, diabetes mellitus, Huntington's disease, atherosclerosis, and anemia. It must be emphasized that today the development of innovative and new Mo-based metalo-pharmaceuticals is not rapid, and hence the aim of this paper was also to inspire colleagues working in the field of Mo compounds who are trying to find "signpost" for research. The authors hope that this article will increase interest and initiate the Renaissance of Mo-compounds among medicinal inorganic chemists. This paper is the first review article in the literature that refers to and emphasizes many different and complex aspects of possible applications and capabilities of Mo-based metallodrugs.

  2. 高碳镍钼矿催化氧化镍钼分离工艺条件%Catalytic Oxidation Separation of Nickel and Molybdenum in the High Carbon Nickel Molybdenum

    Institute of Scientific and Technical Information of China (English)

    旷林雄; 颜文斌; 周晓江

    2011-01-01

    研究了高碳镍钼矿催化氧化分离的工艺方法,并对工艺条件进行了探讨.通过单因素实验确定了高碳镍钼矿镍、钼分离的最佳条件:当硫酸浓度为15%,软锰矿的过量系数为20%,液固比3∶1,反应时间6 h,反应温度95℃,催化剂C与镍的质量比为4.4时,镍的浸出率可达到95.84%,钼的浸出率仅3.74%,钼主要以钼酸的形式富集于渣中,实现了镍、钼的初步分离。%The craft method of catalytic oxidation separation of high carbon nickel molybdenum was studied,and the craft condition was discussed.The best separation condition of nickel and molybdenum in the high-carbon Nickel molybdenum was identified by the single factor test:the sulfuric acid concentration was 15%,excess coefficient of pyrolusite was 20%,liquid-solid ratio was 1∶3,response time was 6 h,and reaction temperature was 95 ℃;when the mass ratio of catalyzer C and nickel is 4.4,the leaching rate could reach 95.84%,the leaching rate of molybdenum was only 3.74%,and the molybdenum mainly gathered in the residue in the form of molybdic acid.In such conditions,the preliminary separation of nickel and molybdenum was realized.

  3. Preparation of selective molybdenum concentrate from collective coppermolybdenum concentrate

    Directory of Open Access Journals (Sweden)

    N. Tusupbaev

    2016-06-01

    Full Text Available The paper considers possibilities of selective separation of the concentrate of copper and molybdenum from a collective copper-molybdenum concentrate of Aktogay deposit using regrinding and conventional flotation reagents. In the case of conventional flotoreagents, the content of molybdenum in a molybdenum concentrate was 8.0% at extraction effectiveness 83.12%. At 27.96% extraction degree of copper, it’s content in the concentrate equaled to 21.3%. After regrinding, molybdenum content in the concentrate was 24.0% at the extraction effectiveness 59.63%, and copper content in the concentrate was 21.9% at the recovery of 61.23%. Thus, the regrinding of a collective copper-molybdenum concentrate resulted in an increase in the content of molybdenum in molybdenum concentrate by 16%, and the copper concentration increased by 0.6%.

  4. Zunyi Molybdenum & Nickel Mining Enterprises Are Still in Suspension Status

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    According to the 2015 mid-year report of Tiancheng Holding,because Guizhou Province is still enforcing policy regulation&environmental; protection policy for molybdenum&nickel; mining industry,currently all molybdenum and nickel mining

  5. A Review of Oil-soluble Organo-molybdenum as Friction Modifier Additive%油溶性有机钼作为摩擦改进剂的研究进展∗

    Institute of Scientific and Technical Information of China (English)

    肖德志; 陈国需; 程鹏; 林彬

    2016-01-01

    With the increasing demand of energy conserving and emission reducing,organo-molybdenum com-pounds have been widely used as friction modifier additives because of the excellent tribological performance.In this paper,the development histories of oil-soluble organo-molybdenum additives are reviewed.The mechanisms of organo-molybdenum additives with sulfur and phosphorus are introduced.The research status of sulfur-free and phosphorus-free organo-molybdenum additives are concluded.Furthermore,the recent research hotspots of organo-molybdenum are analyzed.Finally,the prospect of organic molybdenum additives is pointed out.%随着节能减排要求的不断提高,有机钼添加剂因优异的摩擦学性能在润滑剂中得到广泛应用。回顾了油溶性有机钼添加剂的发展历史,综述了硫磷型有机钼添加剂改善摩擦学性能的作用机理,总结了非活性有机钼添加剂的研究现状,分析了目前有机钼添加剂的最新研究热点,最后展望了有机钼添加剂的研究前景。

  6. Reduction property of rare earth oxide doped molybdenum oxide

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Rare earth oxide doped molybdenum powders were prepared by the reduction of rare earth nitrites doped MoO3. The effect of rare earth oxide on the reduction behavior of molybdenum oxide had been studied by means of Temperature Programmed Reduction (TPR), thermal analysis, X-ray diffraction. Doping rare earth oxide in the powder could lower the reduction temperature of molybdenum oxide and decrease the particle size of molybdenum. The mechanism for the effects had been discussed in this paper.

  7. Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2014-01-01

    Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625), Nickel-Chromium-Molybdenum-Silicon Alloy (UNS N06219), and Nickel-Chromium-Molybdenum-Tungsten Alloy (UNS N06650) Rod and Bar

  8. Bacterial leaching of metal sulfides proceeds by two indirect mechanisms via thiosulfate or via polysulfides and sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Schippers, A.; Sand, W. [Univ. Hamburg (Germany). Inst. fuer Allgemeine Botanik

    1999-01-01

    Bacterial leaching, the biooxidation of metal sulfides to soluble metal sulfates and sulfuric acid, is effected by specialized bacteria. The acid-insoluble metal sulfides FeS{sub 2}, MoS{sub 2}, and WS{sub 2} are chemically attacked by iron(III) hexahydrate ions, generating thiosulfate, which is oxidized to sulfuric acid. Other metal sulfides are attacked by iron(III) ions and by protons, resulting in the formation of elemental sulfur via intermediary polysulfides. Sulfur is biooxidized to sulfuric acid. This explains leaching of metal sulfides by Thiobacillus thiooxidans.

  9. Sulfuric acid on Europa and the radiolytic sulfur cycle

    Science.gov (United States)

    Carlson, R. W.; Johnson, R. E.; Anderson, M. S.

    1999-01-01

    A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

  10. Volatile Sulfur Compounds from Livestock Production

    DEFF Research Database (Denmark)

    Kasper, Pernille

    2017-01-01

    Volatile sulfur compounds, i.e. hydrogen sulfide, methanethiol and dimethyl sulfide have been identified as key odorants in livestock production due to their high concentration levels and low odor threshold values. At the same time their removal with abatement technologies based on mass transfer...... and, thus, odor removal in these systems. In this context, two processes based on the absorptive oxidation of sulfur compounds in trickling filters containing metal catalysts were examined. One process with iron chelated by ethylenediaminetetraacetic acid (EDTA) was shown to remove hydrogen sulfide...... that the original sample composition was significantly impaired due to adsorption and diffusion at the walls of the measuring equipment. Generally, sulfur compounds were best preserved in both olfactometers and sample bags, while carboxylic acids, 4-methylphenol and trimethylamine were found to undergo substantial...

  11. A Cooperative Interface for Highly Efficient Lithium-Sulfur Batteries.

    Science.gov (United States)

    Peng, Hong-Jie; Zhang, Ze-Wen; Huang, Jia-Qi; Zhang, Ge; Xie, Jin; Xu, Wen-Tao; Shi, Jia-Le; Chen, Xiang; Cheng, Xin-Bing; Zhang, Qiang

    2016-11-01

    A cooperative interface constructed by "lithiophilic" nitrogen-doped graphene frameworks and "sulfiphilic" nickel-iron layered double hydroxides (LDH@NG) is proposed to synergistically afford bifunctional Li and S binding to polysulfides, suppression of polysulfide shuttles, and electrocatalytic activity toward formation of lithium sulfides for high-performance lithium-sulfur batteries. LDH@NG enables high rate capability, long lifespan, and efficient stabilization of both sulfur and lithium electrodes.

  12. Effect of La203 nanoparticles on properties of molybdenum powder

    Institute of Scientific and Technical Information of China (English)

    王金淑; 周美玲; 左铁镛; 聂祚仁; 张久兴; 刘娟

    2001-01-01

    The properties of La2O3-doped molybdenum powder were studied. The La2O3 nanoparticles on the surface of molybdenum powder which is produced by the reduction of La(NO3)3-doped MoO2 in hydrogen decrease the intensity of feature energy loss peak of molybdenum substrate; but increase that of peak of Mo 3d. The surface of molybdenum powder exposed to the atmosphere can be reduced because the surface is mainly covered with La2O3 nanoparticles. As a result, the capability of anti-oxidation of molybdenum is improved.

  13. X-ray crystal structure of arsenite-inhibited xanthine oxidase: μ-sulfido,μ-oxo double bridge between molybdenum and arsenic in the active site.

    Science.gov (United States)

    Cao, Hongnan; Hall, James; Hille, Russ

    2011-08-17

    Xanthine oxidoreductase is a molybdenum-containing enzyme that catalyzes the hydroxylation reaction of sp(2)-hybridized carbon centers of a variety of substrates, including purines, aldehydes, and other heterocyclic compounds. The complex of arsenite-inhibited xanthine oxidase has been characterized previously by UV-vis, electron paramagnetic resonance, and X-ray absorption spectroscopy (XAS), and the catalytically essential sulfido ligand of the square-pyrimidal molybdenum center has been suggested to be involved in arsenite binding through either a μ-sulfido,μ-oxo double bridge or a single μ-sulfido bridge. However, this is contrary to the crystallographically observed single μ-oxo bridge between molybdenum and arsenic in the desulfo form of aldehyde oxidoreductase from Desulfovibrio gigas (an enzyme closely related to xanthine oxidase), whose molybdenum center has an oxo ligand replacing the catalytically essential sulfur, as seen in the functional form of xanthine oxidase. Here we use X-ray crystallography to characterize the molybdenum center of arsenite-inhibited xanthine oxidase and solve the structures of the oxidized and reduced inhibition complexes at 1.82 and 2.11 Å resolution, respectively. We observe μ-sulfido,μ-oxo double bridges between molybdenum and arsenic in the active sites of both complexes. Arsenic is four-coordinate with a distorted trigonal-pyramidal geometry in the oxidized complex and three-coordinate with a distorted trigonal-planar geometry in the reduced complex. The doubly bridged binding mode is in agreement with previous XAS data indicating that the catalytically essential sulfur is also essential for the high affinity of reduced xanthine oxidoreductase for arsenite.

  14. Biological nitrogen fixation by alternative nitrogenases in boreal cyanolichens: importance of molybdenum availability and implications for current biological nitrogen fixation estimates.

    Science.gov (United States)

    Darnajoux, Romain; Zhang, Xinning; McRose, Darcy L; Miadlikowska, Jolanta; Lutzoni, François; Kraepiel, Anne M L; Bellenger, Jean-Philippe

    2017-01-01

    Cryptogamic species and their associated cyanobacteria have attracted the attention of biogeochemists because of their critical roles in the nitrogen cycle through symbiotic and asymbiotic biological fixation of nitrogen (BNF). BNF is mediated by the nitrogenase enzyme, which, in its most common form, requires molybdenum at its active site. Molybdenum has been reported as a limiting nutrient for BNF in many ecosystems, including tropical and temperate forests. Recent studies have suggested that alternative nitrogenases, which use vanadium or iron in place of molybdenum at their active site, might play a more prominent role in natural ecosystems than previously recognized. Here, we studied the occurrence of vanadium, the role of molybdenum availability on vanadium acquisition and the contribution of alternative nitrogenases to BNF in the ubiquitous cyanolichen Peltigera aphthosa s.l. We confirmed the use of the alternative vanadium-based nitrogenase in the Nostoc cyanobiont of these lichens and its substantial contribution to BNF in this organism. We also showed that the acquisition of vanadium is strongly regulated by the abundance of molybdenum. These findings show that alternative nitrogenase can no longer be neglected in natural ecosystems, particularly in molybdenum-limited habitats.

  15. The Corrosion and Preservation of Iron Antiques.

    Science.gov (United States)

    Walker, Robert

    1982-01-01

    Discusses general corrosion reactions (iron to rust), including corrosion of iron, sulfur dioxide, chlorides, immersed corrosion, and underground corrosion. Also discusses corrosion inhibition, including corrosion inhibitors (anodic, cathodic, mixed, organic); safe/dangerous inhibitors; and corrosion/inhibition in concrete/marble, showcases/boxes,…

  16. Enhanced photochromism in nanostructured molybdenum trioxide films

    Science.gov (United States)

    Beydaghyan, Gisia; Doiron, Serge; Haché, Alain; Ashrit, P. V.

    2009-08-01

    We present evidence of enhancement of photochromism in nanostructured thin films of molybdenum oxide fabricated by glancing angle deposition. The strong correlation of coloration response with the internal surface area of the films provides evidence of the importance of nanostructuring on the photochromic effect and the vital role played by the availability of water in the photochromic mechanism.

  17. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  18. Geochemical evidence for cryptic sulfur cycling in salt marsh sediments

    DEFF Research Database (Denmark)

    Mills, Jennifer V.; Antler, Gilad; Turchyn, Alexandra V.

    2016-01-01

    to represent the salt marsh sediments suggests that the uptake rate of sulfate during this cryptic sulfur cycling is similar to the uptake rate of sulfate during the fastest microbial sulfate reduction that has been measured in the natural environment. The difference is that during cryptic sulfur cycling, all...... investigate sulfur cycling in salt marsh sediments from Norfolk, England where we observe high ferrous iron concentrations with no depletion of sulfate or change in the sulfur isotope ratio of that sulfate, but a 5‰ increase in the oxygen isotope ratio in sulfate, indicating that sulfate has been through...... a reductive cycle replacing its oxygen atoms. This cryptic sulfur cycle was replicated in laboratory incubations using 18O-enriched water, demonstrating that the field results do not solely result from mixing processes in the natural environment. Numerical modeling of the laboratory incubations scaled...

  19. Carbon, chromium and molybdenum contents; Teores de carbono, cromo e molibdenio

    Energy Technology Data Exchange (ETDEWEB)

    Sinatora, A; Goldenstein, H.; Mei, P.R.; Albertin, E.; Fuoco, R.; Mariotto, C.L

    1992-12-31

    This work describes solidification experiments on white cast iron, with 15 and 20% of chromium, 2.3, 3.0 and 3.6 % of carbon and 0.0, 1.5 and 2.5 % of molybdenum in test de samples with 30 mm diameter. Measurements were performed on the austenite and eutectic formation arrests, the number of the eutectic carbide particles relative to the total and the eutectic volumes, and the volume fraction of the primary austenite 9 figs., 3 tabs.

  20. Determination of traces of Mo in soils and geological materials by solvent extraction of the molybdenum-thiocyanate complex and atomic absorption.

    Science.gov (United States)

    Kim, C H; Owens, C M; Smythe, L E

    1974-06-01

    Comprehensive studies of the extraction of the molybdenum-thiocyanate complex with methyl isobutyl ketone have resulted in an improved method for the determination of traces of molybdenum in soils and geological materials by atomic-absorption spectroscopy. The method is applicable in the range 1-500 ppm Mo, with 1-g samples, giving relative standard deviations not exceeding about 8% at a level of 1 ppm. The limit of detection is 0.1 ppm. There are few interferences, and large quantities of iron are without effect.

  1. As-Cast Acicular Ductile Aluminum Cast Iron

    Institute of Scientific and Technical Information of China (English)

    S M Mostafavi Kashani; S M A Boutorabi

    2009-01-01

    The effects of nickel (2.2%)and molybdenum (0.6%)additions on the kinetics, microstructure, and me-chanical properties of ductile aluminum cast iron were studied under the as-cast and tempered conditions. Test bars machined from cast to size samples were used for mechanical and metallurgical studies. The results showed that adding nickel and molybdenum to the base iron produced an upper bainitic structure, resulting in an increase in strength and hardness. The same trend was shown when the test bars were tempered at 300 ℃ in the range of 300℃ to 400 ℃. The elongation increased with increasing the temperature from 300 ℃ to 400 ℃. The carbon content of the retained austenite also increased with increasing the temperature. The results also showed that the kinetics, mi-crostructure, and mechanical properties of this iron were similar to those of Ni-Mo alloyed silicon ductile iron.

  2. Technology of Iron Carbide Synthesis

    Institute of Scientific and Technical Information of China (English)

    M.Bahgat

    2006-01-01

    Iron carbides are very promising metallurgical products and can be used for steelmaking process, where it plays as an alternative raw material with significant economic advantages. Also it has many other applications,e.g. catalysts, magnets, sensors. The present review investigates the different properties and uses of the iron carbides. The commercial production and the different varieties for the iron carbides synthesis (gaseous carburization, mechanochemical synthesis, laser pyrolysis, plasma pyrolysis, chemical vapor deposition and ion implantation) were reviewed. Also the effect of different factors on the carburization process like gas composition, raw material, temperature, reaction time, catalyst presence and sulfur addition was indicated.

  3. ADVANCED SULFUR CONTROL CONCEPTS

    Energy Technology Data Exchange (ETDEWEB)

    Apostolos A. Nikolopoulos; Santosh K. Gangwal; William J. McMichael; Jeffrey W. Portzer

    2003-01-01

    Conventional sulfur removal in integrated gasification combined cycle (IGCC) power plants involves numerous steps: COS (carbonyl sulfide) hydrolysis, amine scrubbing/regeneration, Claus process, and tail-gas treatment. Advanced sulfur removal in IGCC systems involves typically the use of zinc oxide-based sorbents. The sulfides sorbent is regenerated using dilute air to produce a dilute SO{sub 2} (sulfur dioxide) tail gas. Under previous contracts the highly effective first generation Direct Sulfur Recovery Process (DSRP) for catalytic reduction of this SO{sub 2} tail gas to elemental sulfur was developed. This process is currently undergoing field-testing. In this project, advanced concepts were evaluated to reduce the number of unit operations in sulfur removal and recovery. Substantial effort was directed towards developing sorbents that could be directly regenerated to elemental sulfur in an Advanced Hot Gas Process (AHGP). Development of this process has been described in detail in Appendices A-F. RTI began the development of the Single-step Sulfur Recovery Process (SSRP) to eliminate the use of sorbents and multiple reactors in sulfur removal and recovery. This process showed promising preliminary results and thus further process development of AHGP was abandoned in favor of SSRP. The SSRP is a direct Claus process that consists of injecting SO{sub 2} directly into the quenched coal gas from a coal gasifier, and reacting the H{sub 2}S-SO{sub 2} mixture over a selective catalyst to both remove and recover sulfur in a single step. The process is conducted at gasifier pressure and 125 to 160 C. The proposed commercial embodiment of the SSRP involves a liquid phase of molten sulfur with dispersed catalyst in a slurry bubble-column reactor (SBCR).

  4. Sulfur recovery further improved

    Energy Technology Data Exchange (ETDEWEB)

    Borsboom, J.; Grinsven, M. van; Warners, A. van [Jacobs Nederland B.V., (Netherlands); Nisselrooy, P. van [Gastec N.V., (Netherlands)

    2002-04-01

    The original 100-year-old Claus process for producing sulfur from hydrogen sulfide in acid gas is described together with improvements which have been made over the years. The most recent modification, EUROCLAUS, achieves sulfur recoveries of 99-99.9 per cent. Five commercial units are being designed.

  5. 用N235从富铁高酸度硫酸浸出液中萃取除铁%Removal of Fe3+ from iron rich and high acidity sulfuric acid leaching liquid by extraction of N235

    Institute of Scientific and Technical Information of China (English)

    张魁芳; 刘志强; 曹洪杨; 邱显扬

    2015-01-01

    The extraction of Fe 3+ by N235 was studied based on the technology gap on the removal of Fe3+ from iron rich and high acidity sulfuric acid leaching liquid by extraction. The effects of H2O2 dosage, feed initial pH, extractant concentration, extractant composition and extraction time on the extraction, and the effects of H2SO4 concentration and tripping time on the stripping were investigated. The cross current extraction process was designed and the isotherms of stripping were plotted, and the conditions of extractant transformation were researched. The results show that, when 30% (mass fraction) H2O2 dosage is 3.85 times of theoretical one, Fe2+ can be oxidized into Fe3+ totally, and with 30% (volume fraction) N235 and10% (volume fraction) TBP in sulphonated kerosene as extractant, the extraction rate of Fe3+ from the solution with initial pH of 0.11reaches 96.67% in four-stage cross current extraction with O/A ratio of 1:1 (volume ratio of oil phase to aqueous phase) at 25℃ for 2 min, and the loss rate of Cu2+, Co2+, Ni2+ are 3.04%, 1.39%, 3.84%, respectively. The Fe3+ in loaded organic can be stripped into Fe2(SO4)3 with purity of 98.87% using 0.3 mol/L H2SO4 solution and the stripping rate reaches 99.12% in two-stage counter current stripping with O/A ratio of 1:1 (volume ratio of oil phase to aqueous phase) at 25℃ for 6 min. After stripping, the acid in loaded organic phase can be neutralized using Na2CO3. The organic phase returns to extraction circularly.%对N235萃取除铁进行研究,考察H 2 O 2用量、料液初始pH、萃取剂浓度、萃取剂组成、萃取时间对萃取的影响以及H2SO4浓度、反萃时间对反萃的影响,设计错流萃取过程并绘制反萃平衡等温线,对萃取剂转型条件进行研究。结果表明:H 2 O 2用量为理论量3.85倍时可将Fe2+完全氧化成Fe3+,并采用有机相组成30%(体积分数)N235+10%(体积分数)TBP+磺化煤油作为萃取剂,料液初始pH为0.11,其最佳萃

  6. Molybdenum-catalyzed deoxydehydration of vicinal diols

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Lupp, Daniel; Oh, Byung Chang

    2014-01-01

    The commercially available (NH4)6Mo7O24 and other molybdenum compounds are shown to be viable substitutes for the typically employed rhenium compounds in the catalytic deoxydehydration of aliphatic diols into the corresponding alkenes. The transformation, which represents a model system for the v......The commercially available (NH4)6Mo7O24 and other molybdenum compounds are shown to be viable substitutes for the typically employed rhenium compounds in the catalytic deoxydehydration of aliphatic diols into the corresponding alkenes. The transformation, which represents a model system...... for the various hydroxyl groups found in biomass-derived carbohydrates, can be conducted in an inert solvent (dodecane), under solvent-free conditions, and in a solvent capable of dissolving biomass-derived polyols (1,5-pentanediol). The reaction is driven by the simultaneous oxidative deformylation of the diol...

  7. Nanostructured sulfur cathodes

    KAUST Repository

    Yang, Yuan

    2013-01-01

    Rechargeable Li/S batteries have attracted significant attention lately due to their high specific energy and low cost. They are promising candidates for applications, including portable electronics, electric vehicles and grid-level energy storage. However, poor cycle life and low power capability are major technical obstacles. Various nanostructured sulfur cathodes have been developed to address these issues, as they provide greater resistance to pulverization, faster reaction kinetics and better trapping of soluble polysulfides. In this review, recent developments on nanostructured sulfur cathodes and mechanisms behind their operation are presented and discussed. Moreover, progress on novel characterization of sulfur cathodes is also summarized, as it has deepened the understanding of sulfur cathodes and will guide further rational design of sulfur electrodes. © 2013 The Royal Society of Chemistry.

  8. Synthesis and Characterization of Ethylenediammonium Molybdenum Thiocomplex [-H3NCH2CH2NH3] [Mo3Si3

    Institute of Scientific and Technical Information of China (English)

    WANG, Yimg; CHEN, Jie-Sheng; YUAN, Hong-Ming; SHI, 7han; YU, Shao-Fang; CHEN, Wei

    2001-01-01

    An organo-sfaced molybdenum thiocomples[H3NCH2CH2NH3] [Mo3S13]had been synthesized under hydrothermal condition and the structure of the compound was determined bysingle-crystal X-ray diffraction.The title compound crystalμ3-sulfur atom,with each Mo atom being also coordinated toome terminal disulfur ligand and two bridging disulfur ligands.The negativi charges on the inorganic cluster are balanced bythe ciprotonated ethylenediamine cations [H3NCH2CH2-NH3]2+located in the space between the clusters. N~-

  9. Deformation localization and cyclic strength in polycrystalline molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Sidorov, O.T.; Rakshin, A.F.; Fenyuk, M.I.

    1983-06-01

    Conditions of deformation localization and its interrelation with cyclic strength in polycrystalline molybdenum were investigated. A fatigue failure of polycrystalline molybdenum after rolling and in an embrittled state reached by recrystallization annealing under cyclic bending at room temperature takes place under nonuniform distribution of microplastic strain resulting in a temperature rise in separate sections of more than 314 K. More intensive structural changes take place in molybdenum after rolling than in recrystallized state.

  10. Gigantic Copper-Molybdenum Mining Project Contract Signed in Guangdong

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>With the reserves of nearly 1,000,000 tons of copper and approximately 250,000 tons of molybdenum and a total investment of RMB 5 billion, Guangdong Fengkai Yuanzhushan copper-molybdenum mining project contract was inked on October 13, 2011. It is reported that this is China’s second largest open-cast copper molybdenum mine next only to Dexing Copper Mine.

  11. Selection of molybdenum sheet for deep drawing applications

    Energy Technology Data Exchange (ETDEWEB)

    Salt, P.J. (Marconi Elliott Avionic Systems Ltd., Borehamwood (UK))

    1982-06-01

    Finished tubes are considered to be an extreme example of the art of deep drawing thin molybdenum sheet. This paper describes an investigation into the manufacture of unalloyed molybdenum tube from sheet material 0.5 mm thick. Metallographic examination of different starting materials revealed the most suitable molybdenum sheet materials for this application and so avoid the conditions that bring about undesirable structures or properties.

  12. Scientific Opinion on Dietary Reference Values for molybdenum

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA

    2013-08-01

    Full Text Available Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA derived Dietary Reference Values (DRVs for molybdenum. Molybdenum is efficiently and rapidly absorbed at a wide range of intakes, and the body is able to maintain homeostasis through the regulation of excretion via the urine. Molybdenum deficiency in otherwise healthy humans has not been observed and there are no biomarkers of molybdenum status. Various metabolic balance studies have been performed to establish molybdenum requirements. However, only one balance study, which was performed with a constant diet and under controlled conditions in adult men, was considered to be of sufficient duration. In this small study, balance was reported to be near zero when molybdenum intakes were 22 µg/day. Biochemical changes or symptoms suggestive of molybdenum deficiency were not observed, and it is possible that humans may be able to achieve molybdenum balance at even lower intakes. Data on molybdenum intakes and health outcomes were unavailable for the setting of DRVs for molybdenum. As the evidence required to derive an Average Requirement and a Population Reference Intake was considered insufficient, an Adequate Intake (AI is proposed. Observed molybdenum intakes from mixed diets in Europe were taken into consideration in setting this value. An AI of 65 µg/day is proposed for adults; a figure that is based on molybdenum intakes at the lower end of the wide range of observed intakes. It is suggested that the adult AI also applies to pregnant and lactating women. An AI is also proposed for infants from seven months and for children based on extrapolation from the adult AI using isometric scaling and the reference body weights of the respective age groups.

  13. Biomass as biosorbent for molybdenum ions

    Energy Technology Data Exchange (ETDEWEB)

    Yamaura, Mitiko; Santos, Jacinete L. dos; Damasceno, Marcos O.; Egute, Nayara dos S.; Moraes, Adeniane A.N.; Santos, Bruno Z., E-mail: myamaura@ipen.br, E-mail: jlsantos@ipen.br, E-mail: molidam@ipen.br, E-mail: nayara.egute@usp.br, E-mail: adenianemrs@ig.com.br, E-mail: bzsantos@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    Biosorbents have been focused as renewable materials of low cost, and have been used for metal removal from the wastewater by adsorption phenomenon. Biosorbents are prepared of biomass, whose reactive sites in its chemical structure have affinity to bind to metal ions. In this work, performance of corn husk, sugarcane bagasse, coir, banana peel, fish scale, chitin and chitosan as biosorbents of molybdenum (VI) ions in aqueous medium was evaluated. The adsorption experiments were investigated in a batch system varying the pH solution from 0.5 to 12 and the contact time between the phases from 2 min to 70 min. {sup 99}Mo radioisotope was used as radioactive tracer for analysis of molybdenum ions by gamma spectroscopy using a HPGe detector. Results revealed that acidity of the solution favored the adsorption of Mo (VI) ions on the all biosorbents. Adsorption values higher than 85% were found on sugarcane bagasse, coir, corn husk, chitin and chitosan at pH 2.0. Only the chitosan was dissolved at pH 0.5 and a gel was formed. The models of pseudo-second order and external film diffusion described the kinetics of adsorption of Mo ions on the coir. This work showed that the studied biomass has high potential to be used as biosorbent of molybdenum ions from acidic wastewater, and the kinetics of Mo adsorption on the coir suggested high-affinity adsorption governed by chemisorption. (author)

  14. A solvent extraction study of molybdenum chloride and molybdenum thiocyanate complexes

    Science.gov (United States)

    Greenland, L.P.; Lillie, E.G.

    1974-01-01

    The effect of reducing agents on molybdenum(VI) solutions in hydrochloric acid was studied by a solvent extraction technique to elucidate the composition of the colored molybdenum thiocyanate complex. Neither copper(I) chloride nor ascorbic acid have any effect on the extraction of MoO2Cl2; it is inferred that tin(II) chloride reduces Mo(VI) stepwise to a polynuclear Mo(V)??Mo(VI) complex and then to Mo(V). The colored thiocyanate complex produced by copper(I) and by ascorbic acid differs only slightly in extraction characteristics from the uncolored Mo(VI) complex. It is suggested that the color may be produced by an isomerization reaction of MoO2(SCN)2, and thus that the colored species may be a hexavalent rather than pentavalent molybdenum complex. ?? 1974.

  15. Removal of phosphorus from iron ores by chemical leaching

    Institute of Scientific and Technical Information of China (English)

    JIN Yong-shi; JIANG Tao; YANG Yong-bin; LI Qian; LI Guang-hui; GUO Yu-feng

    2006-01-01

    Alkali-leaching and acid-leaching were proposed for the dephosphorization of Changde iron ore, which contains an average of 1.12% for phosphorus content. Sodium hydroxide, sulfuriced, hydrochloric and nitric acids were used for the preparation of leach solutions. The results show that phosphorus occurring as apatite phase could be removed by alkali-leaching, but those occurring in the iron phase could not. Sulfuric acid is the most effective among the three kinds of acid. 91.61% phosphorus removal was attained with 1% sulfuric acid after leaching for 20 min at room temperature. Iron loss during acid-leaching can be negligible, which was less than 0.25%.The pH value of solution after leaching with 1% sulfuric acid was about 0.86, which means acid would not be exhausted during the process and it could be recycled, and the recycle of sulfuric acid solution would make the dephosphorization process more economical.

  16. Sulfuric Acid on Europa

    Science.gov (United States)

    1999-01-01

    Frozen sulfuric acid on Jupiter's moon Europa is depicted in this image produced from data gathered by NASA's Galileo spacecraft. The brightest areas, where the yellow is most intense, represent regions of high frozen sulfuric acid concentration. Sulfuric acid is found in battery acid and in Earth's acid rain. This image is based on data gathered by Galileo's near infrared mapping spectrometer.Europa's leading hemisphere is toward the bottom right, and there are enhanced concentrations of sulfuric acid in the trailing side of Europa (the upper left side of the image). This is the face of Europa that is struck by sulfur ions coming from Jupiter's innermost moon, Io. The long, narrow features that crisscross Europa also show sulfuric acid that may be from sulfurous material extruded in cracks. Galileo, launched in 1989, has been orbiting Jupiter and its moons since December 1995. JPL manages the Galileo mission for NASA's Office of Space Science, Washington DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

  17. Iron Test

    Science.gov (United States)

    ... as: Serum Iron; Serum Fe Formal name: Iron, serum Related tests: Ferritin ; TIBC, UIBC and Transferrin ; Hemoglobin ; Hematocrit ; Complete Blood Count ; Reticulocyte Count ; Zinc Protoporphyrin ; Iron Tests ; Soluble Transferrin Receptor ... I should know? How is it used? Serum iron, total iron-binding capacity (TIBC) , and/or ...

  18. Sulfur isotopes in coal constrain the evolution of the Phanerozoic sulfur cycle.

    Science.gov (United States)

    Canfield, Donald E

    2013-05-21

    Sulfate is the second most abundant anion (behind chloride) in modern seawater, and its cycling is intimately coupled to the cycling of organic matter and oxygen at the Earth's surface. For example, the reduction of sulfide by microbes oxidizes vast amounts of organic carbon and the subsequent reaction of sulfide with iron produces pyrite whose burial in sediments is an important oxygen source to the atmosphere. The concentrations of seawater sulfate and the operation of sulfur cycle have experienced dynamic changes through Earth's history, and our understanding of this history is based mainly on interpretations of the isotope record of seawater sulfates and sedimentary pyrites. The isotope record, however, does not give a complete picture of the ancient sulfur cycle. This is because, in standard isotope mass balance models, there are more variables than constraints. Typically, in interpretations of the isotope record and in the absence of better information, one assumes that the isotopic composition of the input sulfate to the oceans has remained constant through time. It is argued here that this assumption has a constraint over the last 390 Ma from the isotopic composition of sulfur in coal. Indeed, these compositions do not deviate substantially from the modern surface-water input to the oceans. When applied to mass balance models, these results support previous interpretations of sulfur cycle operation and counter recent suggestions that sulfate has been a minor player in sulfur cycling through the Phanerozoic Eon.

  19. Cytoplasmic sulfur trafficking in sulfur-oxidizing prokaryotes.

    Science.gov (United States)

    Dahl, Christiane

    2015-04-01

    Persulfide groups are chemically versatile and participate in a wide array of biochemical pathways. Although it is well documented that persulfurated proteins supply a number of important and elaborate biosynthetic pathways with sulfane sulfur, it is far less acknowledged that the enzymatic generation of persulfidic sulfur, the successive transfer of sulfur as a persulfide between multiple proteins, and the oxidation of sulfane sulfur in protein-bound form are also essential steps during dissimilatory sulfur oxidation in bacteria and archaea. Here, the currently available information on sulfur trafficking in sulfur oxidizing prokaryotes is reviewed, and the idea is discussed that sulfur is always presented to cytoplasmic oxidizing enzymes in a protein-bound form, thus preventing the occurrence of free sulfide inside of the prokaryotic cell. Thus, sulfur trafficking emerges as a central element in sulfur-oxidizing pathways, and TusA homologous proteins appear to be central and common elements in these processes.

  20. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    Science.gov (United States)

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  1. Intermediary sulfur compounds in pyrite oxidation: implications for bioleaching and biodepyritization of coal

    Energy Technology Data Exchange (ETDEWEB)

    Schippers, A.; Rohwerder, T.; Sand, W. [Hamburg Univ. (Germany). Inst. fuer Allgemeine Botanik und Botanischer Garten

    1999-07-01

    Accumulation of elemental sulfur during pyrite oxidation lowers the efficiency of coal desulfurization and bioleaching. In the case of pyrite bioleaching by Leptospirillum ferrooxidans, an iron(II)-ion-oxidizing organism without sulfur-oxidizing capacity, from the pyritic sulfur moiety about 10% elemental sulfur, 2% pentathionate, and 1% tetrathionate accumulated by a recently described cyclic pyrite oxidation mechanism. In the case of pure cultures of Thiobacillus ferrooxidans and mixed cultures of L. ferrooxidans and T. thiooxidans, pyrite was nearly completely oxidized to sulfate because of the capacity of these cultures to oxidize both iron(II) ions and sulfur compounds. Pyrite oxidation in acidic solutions, mediated chemically by iron(III) ion, resulted in an accumulation of similar amounts of sulfur compounds as obtained with L. ferrooxidans. Changes of pH to values below 2 or in the iron ion concentration are not decisive for diverting the flux of sulfur compounds. The literature on pyrite bioleaching is in agreement with the findings indicating that the chemistry of direct and indirect pyrite leaching is identical. (orig.)

  2. Rational design of multifunctional devices based on molybdenum disulfide and graphene hybrid nanostructures

    Science.gov (United States)

    Lim, Yi Rang; Lee, Young Bum; Kim, Seong Ku; Kim, Seong Jun; Kim, Yooseok; Jeon, Cheolho; Song, Wooseok; Myung, Sung; Lee, Sun Sook; An, Ki-Seok; Lim, Jongsun

    2017-01-01

    We rationally designed a new type of hybrid materials, molybdenum disulfide (MoS2) synthesized by Mo pre-deposition followed by subsequent sulfurization process directly on thermal chemical vapor deposition (TCVD)-grown graphene, for applications in a multifunctional device. The synthesis of stoichiometric and uniform multilayer MoS2 and high-crystalline monolayer graphene was evaluated by X-ray photoelectron spectroscopy and Raman spectroscopy. To examine the electrical transport and photoelectrical properties of MoS2-graphene hybrid films, field effect transistors (FETs) and visible-light photodetectors based on MoS2-graphene were both fabricated. As a result, the extracted mobility for MoS2-graphene hybrid FETs was two times higher than that of MoS2 FETs. In addition, the MoS2-graphene photodetectors revealed a significant photocurrent with abrupt switching behavior under periodic illumination.

  3. Purification of molybdenum-99, obtained from uranium-235 fission, employing the resin Chelex-100

    CERN Document Server

    Lavinas, T

    1998-01-01

    The present work has the purpose of studying the purification of sup 9 sup 9 Mo employing the chelating resin Chelex-100 (Bio-Rad), due to the high distribution coefficient (10 sup 4) of the molybdenum when compared to the impurities. This fact is based on the complexation of Mo with thiocyanate ions producing a stable complex which is retained by the nitrilodiacetate groups present in the Chelex-100. Prior to the purification of sup 9 sup 9 Mo , the formation and stability of the Mo-SCN complex in different conditions were studied. The spectrophotometric studies showed the optimum conditions to obtain a stable complex: KI + Na sub 2 SO sub 3 solution was the more effective reducing agent; when in 6M sulfuric medium the complexation was faster and 6M potassium thiocyanate (complexing agent) guaranteed that all reduced molybdenum was complexed. Both the retention of Mo-SCN complex by the Chelex-100 and the elution of sup 9 sup 9 Mo, showed satisfactory, (99.6 +- 0,5)% and (96.8 +-2)% respectively, which confir...

  4. Catalytic activity of oil soluble molybdenum compounds for heavy oil hydrotreatment

    Energy Technology Data Exchange (ETDEWEB)

    Kushiyama, Satoshi; Aizawa, Reiji; Kobayashi, Satoru; Koinuma, Yutaka; Uemasu, Isamu; Shimizu, Yoshikazu (National Research Institute for Pollution and Resources, Tsukuba (Japan))

    1989-04-20

    Catalytic activity of oil-soluble molybdenum compounds in the hydrotreatment of heavy oil, with high content of the catalyst-poison compounds such as vanadium compounds and asphaltene, was studied. Reactions were performed using Venezuela Morichal crude and catalysts: molybdenum-dithiophoshpates, -dithiocarbamates and -naphthenates; and cobalt-cotylates, -dioctylphosphates. Catalyst systems containing Mo, Co, P and S (or mixtures of compounds containing each element) were found to show high activity for sulfur and vanadium removal. It was revealed that the addition of P compounds is essential for vanadium removal and the effect of Co compounds on the activity enhancement is shown in the only case of coexistence of P and S. No Mo, Co, P were found in the oil products. Recycle use of the Mo-Co-P-S catalyst resulted in a gradual decline of activity. However, the activity seems to be constant after three to four recycle uses, its activity was still higher than the initial activity of conventional Co-Mo-Al{sub 2}O{sub 3} catalyst. 13 refs., 5 tabs.

  5. Extraction and determination of molybdenum with tributyl phosphate Application to analysis of copper-molybdenum ores.

    Science.gov (United States)

    Caiozzi, M; Zunino, H; Sepúlveda, L

    1969-12-01

    A differential spectrophotometric method is described for the determination of molybdenum by means of solvent extraction with tributylphosphate of the peroxymolybdate complex formed with H(2)O(2) in 3.5N H(2)SO(4). The extraction parameters are studied, and the behaviour of some other ions is reported. The method is used for ore analysis.

  6. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    Science.gov (United States)

    Lowden, Richard A.

    1994-01-01

    A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

  7. REDUCTION AND CONSOLIDATION OF SUPERIOR QUALITY MOLYBDENUM ALLOYS

    Science.gov (United States)

    diameter bomb. Techniques were developed for the electron beam melting of hydrogen-reduced molybdenum powder. Although this material contains low... beam melting of the thermitically-reduced molybdenum presented difficulties; primarily because of the melting configuration. The use of a remote...interstitial elements, it exhibited severe grain boundary brittleness. Physical properties of these single crystals are being determined. The electron

  8. Molybdenum limitation of asymbiotic nitrogen fixation in tropical forest soils

    Science.gov (United States)

    Barron, Alexander R.; Wurzburger, Nina; Bellenger, Jean Phillipe; Wright, S. Joseph; Kraepiel, Anne M. L.; Hedin, Lars O.

    2009-01-01

    Nitrogen fixation, the biological conversion of di-nitrogen to plant-available ammonium, is the primary natural input of nitrogen to ecosystems, and influences plant growth and carbon exchange at local to global scales. The role of this process in tropical forests is of particular concern, as these ecosystems harbour abundant nitrogen-fixing organisms and represent one third of terrestrial primary production. Here we show that the micronutrient molybdenum, a cofactor in the nitrogen-fixing enzyme nitrogenase, limits nitrogen fixation by free-living heterotrophic bacteria in soils of lowland Panamanian forests. We measured the fixation response to long-term nutrient manipulations in intact forests, and to short-term manipulations in soil microcosms. Nitrogen fixation increased sharply in treatments of molybdenum alone, in micronutrient treatments that included molybdenum by design and in treatments with commercial phosphorus fertilizer, in which molybdenum was a `hidden' contaminant. Fixation did not respond to additions of phosphorus that were not contaminated by molybdenum. Our findings show that molybdenum alone can limit asymbiotic nitrogen fixation in tropical forests and raise new questions about the role of molybdenum and phosphorus in the tropical nitrogen cycle. We suggest that molybdenum limitation may be common in highly weathered acidic soils, and may constrain the ability of some forests to acquire new nitrogen in response to CO2 fertilization.

  9. Structural state of native molybdenum in the lunar regolith

    Science.gov (United States)

    Mokhov, A. V.; Gornostaeva, T. A.; Kartashov, P. M.; Bogatikov, O. A.; Sakharov, O. A.; Trubkin, N. V.

    2016-11-01

    The structural state was determined for zero-valence molybdenum in the lunar regolith. The body- and face-centered molybdenum forms (BCC and FCC, respectively) were identified. Disruption of the structure down to complete amorphization was noted. This might be caused by the long-term influence of the solar wind.

  10. Kinetics of Molybdenum Reduction to Molybdenum Blue by Bacillus sp. Strain A.rzi

    Directory of Open Access Journals (Sweden)

    A. R. Othman

    2013-01-01

    Full Text Available Molybdenum is very toxic to agricultural animals. Mo-reducing bacterium can be used to immobilize soluble molybdenum to insoluble forms, reducing its toxicity in the process. In this work the isolation of a novel molybdate-reducing Gram positive bacterium tentatively identified as Bacillus sp. strain A.rzi from a metal-contaminated soil is reported. The cellular reduction of molybdate to molybdenum blue occurred optimally at 4 mM phosphate, using 1% (w/v glucose, 50 mM molybdate, between 28 and 30°C and at pH 7.3. The spectrum of the Mo-blue product showed a maximum peak at 865 nm and a shoulder at 700 nm. Inhibitors of bacterial electron transport system (ETS such as rotenone, sodium azide, antimycin A, and potassium cyanide could not inhibit the molybdenum-reducing activity. At 0.1 mM, mercury, copper, cadmium, arsenic, lead, chromium, cobalt, and zinc showed strong inhibition on molybdate reduction by crude enzyme. The best model that fitted the experimental data well was Luong followed by Haldane and Monod. The calculated value for Luong’s constants pmax, Ks, Sm, and n was 5.88 μmole Mo-blue hr−1, 70.36 mM, 108.22 mM, and 0.74, respectively. The characteristics of this bacterium make it an ideal tool for bioremediation of molybdenum pollution.

  11. Selective laser sintering mechanism of polymer-coated molybdenum powder

    Institute of Scientific and Technical Information of China (English)

    BAI Pei-kang; WANG Wen-feng

    2007-01-01

    A type of polymer-coated molybdenum powder used in selective laser sintering technology was prepared by coating polymer on molybdenum particles and frozen grinding techniques, with the maximum particle diameter of 71 μm. The laser sintering experiments of polymer-coated molybdenum powder were conducted by using the self-developed selective laser sintering machine (HLRP-350I). The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated molybdenum powder. Based on the study, the laser sintering mechanisms of polymer-coated molybdenum powder were presented. It is found that the mechanism is viscous flow when the laser sintering temperature is between 100 ℃ and 160 ℃, which can be described by a two-sphere model; and the mechanism is melting /solidification when the temperature is above 160 ℃.

  12. Hot rolling of thick uranium molybdenum alloys

    Science.gov (United States)

    DeMint, Amy L.; Gooch, Jack G.

    2015-11-17

    Disclosed herein are processes for hot rolling billets of uranium that have been alloyed with about ten weight percent molybdenum to produce cold-rollable sheets that are about one hundred mils thick. In certain embodiments, the billets have a thickness of about 7/8 inch or greater. Disclosed processes typically involve a rolling schedule that includes a light rolling pass and at least one medium rolling pass. Processes may also include reheating the rolling stock and using one or more heavy rolling passes, and may include an annealing step.

  13. Behaviour of helium after implantation in molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Viaud, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France)], E-mail: viaud@dircad.cea.fr; Maillard, S.; Carlot, G.; Valot, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France); Gilabert, E. [Chimie Nucleaire Analytique and Bio-environnementale (CNAB), Gradignan (France); Sauvage, T. [CEMHTI-CNRS, Orleans (France); Peaucelle, C.; Moncoffre, N. [Institut de Physique Nucleaire de Lyon (IPNL), Lyon (France)

    2009-03-31

    This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.

  14. Molybdenum oxide nanocubes: Synthesis and characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Muthamizh, S.; Suresh, R.; Giribabu, K.; Manigandan, R.; Kumar, S. Praveen; Munusamy, S.; Narayanan, V., E-mail: vnnara@yahoo.co.in [Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai -600025 (India); Stephen, A. [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai-600025 (India)

    2015-06-24

    Molybdenum oxide nanoparticles were prepared by Solid state synthesis. The MoO{sub 3} nanoparticles were synthesized by using commercially available ammonium heptamolybdate. The XRD pattern reveals that the synthesized MoO{sub 3} has orthorhombic structure. In addition, lattice parameter values were also calculated using XRD data. The Raman analysis confirm the presence of Mo-O in MoO{sub 3} nanoparticles. DRS-UV analysis shows that MoO{sub 3} has a band gap of 2.89 eV. FE-SEM analysis confirms the material morphology in cubes with nano scale.

  15. Electrochemical ammonia production on molybdenum nitride nanoclusters

    DEFF Research Database (Denmark)

    Howalt, Jakob Geelmuyden; Vegge, Tejs

    2013-01-01

    Theoretical investigations of electrochemical production of ammonia at ambient temperature and pressure on nitrogen covered molybdenum nanoparticles are presented. Density functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free...... energy profile for electrochemical protonation of N2 and N adatoms on cuboctahedral Mo13 nanoparticles. Pathways for electrochemical ammonia production via direct protonation of N adatoms and N2 admolecules with an onset potential as low as -0.5 V and generally lower than -0.8 V on both a nitrogen...

  16. Molybdenum protective coatings adhesion to steel substrate

    Science.gov (United States)

    Blesman, A. I.; Postnikov, D. V.; Polonyankin, D. A.; Teplouhov, A. A.; Tyukin, A. V.; Tkachenko, E. A.

    2017-06-01

    Protection of the critical parts, components and assemblies from corrosion is an urgent engineering problem and many other industries. Protective coatings’ forming on surface of metal products is a promising way of corrosionprevention. The adhesion force is one of the main characteristics of coatings’ durability. The paper presents theoretical and experimental adhesion force assessment for coatings formed by molybdenum magnetron sputtering ontoa steel substrate. Validity and reliability of results obtained by simulation and sclerometry method allow applying the developed model for adhesion force evaluation in binary «steel-coating» systems.

  17. Molybdenum oxide nanocubes: Synthesis and characterizations

    Science.gov (United States)

    Muthamizh, S.; Suresh, R.; Giribabu, K.; Manigandan, R.; Kumar, S. Praveen; Munusamy, S.; Stephen, A.; Narayanan, V.

    2015-06-01

    Molybdenum oxide nanoparticles were prepared by Solid state synthesis. The MoO3 nanoparticles were synthesized by using commercially available ammonium heptamolybdate. The XRD pattern reveals that the synthesized MoO3 has orthorhombic structure. In addition, lattice parameter values were also calculated using XRD data. The Raman analysis confirm the presence of Mo-O in MoO3 nanoparticles. DRS-UV analysis shows that MoO3 has a band gap of 2.89 eV. FE-SEM analysis confirms the material morphology in cubes with nano scale.

  18. The rate characteristics of lithium iron sulfide

    Science.gov (United States)

    Kendrick, E.; Barker, J.; Bao, J.; Świątek, A.

    The electrochemical rate properties of Li 2FeS 2 synthesized via a low cost solid state method have been investigated. Apparent diffusion coefficients calculated from EVS and GITT measurements show rate limitations upon charge with distinct differences between the iron redox and sulfur redox regions. These differences between the iron and sulfur redox reactions are not mimicked upon discharge. The apparent diffusion coefficients are greater upon discharge than charge and this is reflected in the rate capabilities as measured by galvanostatic discharge and charge measurements.

  19. 纳雍钼镍矿的熔池熔炼%Bath Smelting of Nayong Molybdenum Nickel Ore

    Institute of Scientific and Technical Information of China (English)

    周方栋; 伍耀明

    2012-01-01

    In this paper, analysis and concrete terms of the nature and composition of a detailed theoretical of nickel-molybdenum mineral of Nayong, to clarify the various elements in the mineral bath smelting process behavior. Analysis to achieve separation of molybdenum pyrometallurgical nickel smelting favorable conditions and mature furnace. That as long as the measures taken to collecting reliable smelting slag and enhanced leaching method, to obtain a high yield of Mo-Ni, high-quality products and to provide arsenic-free sulfuric acid and sulfur dioxide gas is possible.%文章对纳雍钼镍矿的矿物性质和成分进行了详细的理论分析和具体计算,阐明了矿物中各元素在熔池熔炼过程中的行为。分析了实现火法冶炼分离钼镍的有利条件和成熟的冶炼炉型。指出只要采取可靠的收尘措施和强化浸出熔炼渣的方法,获得钼镍的高收率、高品质的产品以及提供无砷的二氧化硫烟气制硫酸是可能的。

  20. A cascade of iron-containing proteins governs the genetic iron starvation response to promote iron uptake and inhibit iron storage in fission yeast.

    Directory of Open Access Journals (Sweden)

    Javier Encinar del Dedo

    2015-03-01

    Full Text Available Iron is an essential cofactor, but it is also toxic at high levels. In Schizosaccharomyces pombe, the sensor glutaredoxin Grx4 guides the activity of the repressors Php4 and Fep1 to mediate a complex transcriptional response to iron deprivation: activation of Php4 and inactivation of Fep1 leads to inhibition of iron usage/storage, and to promotion of iron import, respectively. However, the molecular events ruling the activity of this double-branched pathway remained elusive. We show here that Grx4 incorporates a glutathione-containing iron-sulfur cluster, alone or forming a heterodimer with the BolA-like protein Fra2. Our genetic study demonstrates that Grx4-Fra2, but not Fep1 nor Php4, participates not only in iron starvation signaling but also in iron-related aerobic metabolism. Iron-containing Grx4 binds and inactivates the Php4 repressor; upon iron deprivation, the cluster in Grx4 is probably disassembled, the proteins dissociate, and Php4 accumulates at the nucleus and represses iron consumption genes. Fep1 is also an iron-containing protein, and the tightly bound iron is required for transcriptional repression. Our data suggest that the cluster-containing Grx4-Fra2 heterodimer constitutively binds to Fep1, and upon iron deprivation the disassembly of the iron cluster between Grx4 and Fra2 promotes reverse metal transfer from Fep1 to Grx4-Fra2, and de-repression of iron-import genes. Our genetic and biochemical study demonstrates that the glutaredoxin Grx4 independently governs the Php4 and Fep1 repressors through metal transfer. Whereas iron loss from Grx4 seems to be sufficient to release Php4 and allow its nuclear accumulation, total or partial disassembly of the Grx4-Fra2 cluster actively participates in iron-containing Fep1 activation by sequestering its iron and decreasing its interaction with promoters.

  1. Climax-Type Porphyry Molybdenum Deposits

    Science.gov (United States)

    Ludington, Steve; Plumlee, Geoffrey S.

    2009-01-01

    Climax-type porphyry molybdenum deposits, as defined here, are extremely rare; thirteen deposits are known, all in western North America and ranging in age from Late Cretaceous to mainly Tertiary. They are consistently found in a postsubduction, extensional tectonic setting and are invariably associated with A-type granites that formed after peak activity of a magmatic cycle. The deposits consist of ore shells of quartz-molybdenite stockwork veins that lie above and surrounding the apices of cupola-like, highly evolved, calc-alkaline granite and subvolcanic rhyolite-porphyry bodies. These plutons are invariably enriched in fluorine (commonly >1 percent), rubidium (commonly >500 parts per million), and niobium-tantalum (Nb commonly >50 parts per million). The deposits are relatively high grade (typically 0.1-0.3 percent Mo) and may be very large (typically 100-1,000 million tons). Molybdenum, as MoS2, is the primary commodity in all known deposits. The effect on surface-water quality owing to natural influx of water or sediment from a Climax-type mineralized area can extend many kilometers downstream from the mineralized area. Waste piles composed of quartz-silica-pyrite altered rocks will likely produce acidic drainage waters. The potential exists for concentrations of fluorine or rare metals in surface water and groundwater to exceed recommended limits for human consumption near both mined and unmined Climax-type deposits.

  2. Bioleaching of marmatite in high concentration of iron

    Institute of Scientific and Technical Information of China (English)

    邱冠周; 吴伯增; 覃文庆; 蓝卓越

    2002-01-01

    Bioleaching of marmatite with a culture of Thiobacillus ferrooxidans and Thiobacillus thiooxidans in high concentration of iron was studied, the results show that the zinc leaching rate of the mixed culture is faster than that of the sole Thiobacillus ferrooxidans, the increasing iron concentration in leaching solution enhances the zinc leaching rate. The SEM analysis indicates that the chemical leaching residues is covered with porous solid layer of elemental sulfur, while elemental sulfur is not found in the bacterial leaching residues. The primary role of bacteria in bioleaching of sphalerite is to oxidize the chemical leaching products of ferrous ion and elemental sulfur, thus the indirect mechanism prevails in the bioleaching of marmatite.

  3. Aircraft exhaust sulfur emissions

    Energy Technology Data Exchange (ETDEWEB)

    Brown, R.C.; Anderson, M.R.; Miake-Lye, R.C.; Kolb, C.E. [Aerodyne Research, Inc., Billerica, MA (United States). Center for Chemical and Environmental Physics; Sorokin, A.A.; Buriko, Y.I. [Scientific Research Center `Ecolen`, Moscow (Russian Federation)

    1997-12-31

    The extent to which fuel sulfur is converted to SO{sub 3} during combustion and the subsequent turbine flow in supersonic and subsonic aircraft engines is estimated numerically. The analysis is based on: a flamelet model with non-equilibrium sulfur chemistry for the combustor, and a one-dimensional, two-stream model with finite rate chemical kinetics for the turbine. The results indicate that between 2% and 10% of the fuel sulfur is emitted as SO{sub 3}. It is also shown that, for a high fuel sulfur mass loading, conversion in the turbine is limited by the level of atomic oxygen at the combustor exit, leading to higher SO{sub 2} oxidation efficiency at lower fuel sulfur loadings. While SO{sub 2} and SO{sub 3} are the primary oxidation products, the model results further indicate H{sub 2}SO{sub 4} levels on the order of 0.1 ppm for supersonic expansions through a divergent nozzle. This source of fully oxidized S(6) (SO{sub 3} + H{sub 2}SO{sub 4}) exceeds previously calculated S(6) levels due to oxidation of SO{sub 2} by OH in the exhaust plume outside the engine nozzle. (author) 26 refs.

  4. Corrosion-resistant sulfur concretes

    Science.gov (United States)

    McBee, W. C.; Sullivan, T. A.; Jong, B. W.

    1983-04-01

    Sulfur concretes have been developed by the Bureau of Mines as construction materials with physical and mechanical properties that suit them for use in acid and salt corrosive environments where conventional concretes fail. Mixture design methods were established for preparing sulfur concretes using different types of aggregates and recently developed mixed-modified sulfur cements. Bench-scale testing of the sulfur concretes has shown their potential value. Corrosion resistance, strength, and durability of sulfur concrete are superior to those of conventional materials. Field in situ evaluation tests of the sulfur concretes as replacement for conventional concrete materials are in progress in corrosive areas of 24 commercial chemical, fertilizer, and metallurgical plants.

  5. Iron deprivation results in a rapid but not sustained increase of the expression of genes involved in iron metabolism and sulfate uptake in tomato (Solanum lycopersicum L.) seedlings.

    Science.gov (United States)

    Paolacci, Anna Rita; Celletti, Silvia; Catarcione, Giulio; Hawkesford, Malcolm J; Astolfi, Stefania; Ciaffi, Mario

    2014-01-01

    Characterization of the relationship between sulfur and iron in both Strategy I and Strategy II plants, has proven that low sulfur availability often limits plant capability to cope with iron shortage. Here it was investigated whether the adaptation to iron deficiency in tomato (Solanum lycopersicum L.) plants was associated with an increased root sulfate uptake and translocation capacity, and modified dynamics of total sulfur and thiols accumulation between roots and shoots. Most of the tomato sulfate transporter genes belonging to Groups 1, 2, and 4 were significantly upregulated in iron-deficient roots, as it commonly occurs under S-deficient conditions. The upregulation of the two high affinity sulfate transporter genes, SlST1.1 and SlST1.2, by iron deprivation clearly suggests an increased root capability to take up sulfate. Furthermore, the upregulation of the two low affinity sulfate transporter genes SlST2.1 and SlST4.1 in iron-deficient roots, accompanied by a substantial accumulation of total sulfur and thiols in shoots of iron-starved plants, likely supports an increased root-to-shoot translocation of sulfate. Results suggest that tomato plants exposed to iron-deficiency are able to change sulfur metabolic balance mimicking sulfur starvation responses to meet the increased demand for methionine and its derivatives, allowing them to cope with this stress.

  6. Iron deprivation results in a rapid but not sustained increase of the expression of genes involved in iron metabolism and sulfate uptake in tomato (Solanum lycopersicum L.) seedlings

    Institute of Scientific and Technical Information of China (English)

    Anna Rita Paolacci; Silvia Celletti; Giulio Catarcione; Malcolm J. Hawkesford; Stefania Astolfi; Mario Ciaffi

    2014-01-01

    Characterization of the relationship between sulfur and iron in both Strategy I and Strategy II plants, has proven that low sulfur availability often limits plant capability to cope with iron shortage. Here it was investigated whether the adaptation to iron deficiency in tomato (Solanum lycopersicum L.) plants was associated with an increased root sulfate uptake and translocation capacity, and modified dynamics of total sulfur and thiols accumulation between roots and shoots. Most of the tomato sulfate transporter genes belonging to Groups 1, 2, and 4 were significantly upregulated in iron-deficient roots, as it commonly occurs under S-deficient conditions. The upregulation of the two high affinity sulfate transporter genes, SlST1.1 and SlST1.2, by iron deprivation clearly suggests an increased root capability to take up sulfate. Furthermore, the upregulation of the two low affinity sulfate transporter genes SlST2.1 and SlST4.1 in iron-deficient roots, accompanied by a substantial accumulation of total sulfur and thiols in shoots of iron-starved plants, likely supports an increased root-to-shoot translocation of sulfate. Results suggest that tomato plants exposed to iron-deficiency are able to change sulfur metabolic balance mimicking sulfur starvation responses to meet the increased demand for methionine and its derivatives, al owing them to cope with this stress.

  7. Genetic/metabolic effect of iron metabolism and rare anemias

    Directory of Open Access Journals (Sweden)

    Clara Camaschella

    2013-03-01

    Full Text Available Advances in iron metabolism have allowed a novel classification of iron disorders and to identify previously unknown diseases. These disorders include genetic iron overload (hemochromatosis and inherited iron-related anemias, in some cases accompanied by iron overload. Rare inherited anemias may affect the hepcidin pathway, iron absorption, transport, utilization and recycling. Among the genetic iron-related anemias the most common form is likely the iron-refractory iron-deficiency anemia (IRIDA, due to mutations of the hepcidin inhibitor TMPRSS6 encoding the serine protease matriptase-2. IRIDA is characterized by hepcidin up-regulation, decrease iron absorption and macrophage recycling and by microcytic- hypochromic anemia, unresponsive to oral iron. High serum hepcidin levels may suggest the diagnosis, which requires demonstrating the causal TMPRSS6 mutations by gene sequencing. Other rare microcytic hypochromic anemias associated with defects of iron transport-uptake are the rare hypotransferrinemia, and DMT1 and STEAP3 mutations. The degree of anemia is variable and accompanied by secondary iron overload even in the absence of blood transfusions. This is due to the iron-deficient or expanded erythropoiesis that inhibits hepcidin transcription, increases iron absorption, through the erythroid regulator, as in untransfused beta-thalassemia. Sideroblastic anemias are due to decreased mitochondrial iron utilization for heme or sulfur cluster synthesis. Their diagnosis requires demonstrating ringed sideroblasts by Perl’s staining of the bone marrow smears. The commonest X-linked form is due to deltaamino- levulinic-synthase-2-acid (ALAS2 mutations. The recessive, more severe form, affects SLC25A38, which encodes a potential mitochondrial importer of glycine, an amino acid essential for ALA synthesis and thus results in heme deficiency. Two disorders affect iron/sulfur cluster biogenesis: deficiency of the ATP-binding cassette B7 (ABCB7 causes X

  8. HYBRID SULFUR RECOVERY PROCESS FOR NATURAL GAS UPGRADING

    Energy Technology Data Exchange (ETDEWEB)

    Girish Srinivas; Steven C. Gebhard; David W. DeBerry

    2001-05-01

    This first quarter report of 2001 describes progress on a project funded by the U.S. Department of Energy (DOE) to test a hybrid sulfur recovery process for natural gas upgrading. The process concept represents a low cost option for direct treatment of natural gas streams to remove H{sub 2}S in quantities equivalent to 0.2-25 metric tons (LT) of sulfur per day. This process is projected to have lower capital and operating costs than the competing technologies, amine/aqueous iron liquid redox and amine/Claus/tail gas treating, and have a smaller plant footprint, making it well suited to both on-shore and offshore applications. CrystaSulf{trademark} (service mark of Gas Research Institute) is a new nonaqueous sulfur recovery process that removes hydrogen sulfide (H{sub 2}S) from gas streams and converts it into elemental sulfur. CrystaSulf features high sulfur recovery similar to aqueous-iron liquid redox sulfur recovery processes, but differs from the aqueous processes in that CrystaSulf controls the location where elemental sulfur particles are formed. In the hybrid process, approximately 1/3 of the total H{sub 2}S in the natural gas is first oxidized to SO{sub 2} at low temperatures over a heterogeneous catalyst. Low temperature oxidation is done so that the H{sub 2}S can be oxidized in the presence of methane and other hydrocarbons without oxidation of the hydrocarbons. The project involves the development of a catalyst using laboratory/bench-scale catalyst testing, and then demonstration of the catalyst at CrystaTech's pilot plant in west Texas. During this reporting periods new catalyst formulations were tested. The experiments showed that the newest catalyst has slightly better performance, but catalyst TDA No.2 is still superior overall for use with the hybrid CrystaSulf process due to lower costs. Plans for catalyst pelletization and continued testing are described.

  9. Iron deficiency.

    Science.gov (United States)

    Scrimshaw, N S

    1991-10-01

    The world's leading nutritional problem is iron deficiency. 66% of children and women aged 15-44 years in developing countries have it. Further, 10-20% of women of childbearing age in developed countries are anemic. Iron deficiency is identified with often irreversible impairment of a child's learning ability. It is also associated with low capacity for adults to work which reduces productivity. In addition, it impairs the immune system which reduces the body's ability to fight infection. Iron deficiency also lowers the metabolic rate and the body temperature when exposed to cold. Hemoglobin contains nearly 73% of the body's iron. This iron is always being recycled as more red blood cells are made. The rest of the needed iron does important tasks for the body, such as binds to molecules that are reservoirs of oxygen for muscle cells. This iron comes from our diet, especially meat. Even though some plants, such as spinach, are high in iron, the body can only absorb 1.4-7% of the iron in plants whereas it can absorb 20% of the iron in red meat. In many developing countries, the common vegetarian diets contribute to high rates of iron deficiency. Parasitic diseases and abnormal uterine bleeding also promote iron deficiency. Iron therapy in anemic children can often, but not always, improve behavior and cognitive performance. Iron deficiency during pregnancy often contributes to maternal and perinatal mortality. Yet treatment, if given to a child in time, can lead to normal growth and hinder infections. However, excess iron can be damaging. Too much supplemental iron in a malnourished child promotes fatal infections since the excess iron is available for the pathogens use. Many countries do not have an effective system for diagnosing, treating, and preventing iron deficiency. Therefore a concerted international effort is needed to eliminate iron deficiency in the world.

  10. Iron monosulfide accumulation and pyrite formation in eutrophic estuarine sediments

    NARCIS (Netherlands)

    Kraal, P.; Burton, E.D.; Bush, R.T.

    2013-01-01

    This study investigates iron (Fe) and sulfur (S) cycling in sediments from the eutrophic Peel–Harvey Estuary in Western Australia, which is subject to localized accumulation of strongly reducing, organic- and sulfide-rich sediments. Sedimentary iron was mostly present in highly reactive form (on

  11. PURIFICATION OF URANIUM FROM URANIUM/MOLYBDENUM ALLOY

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, R; Ann Visser, A; James Laurinat, J

    2007-10-15

    The Savannah River Site will recycle a nuclear fuel comprised of 90% uranium-10% molybdenum by weight. The process flowsheet calls for dissolution of the material in nitric acid to a uranium concentration of 15-20 g/L without the formation of precipitates. The dissolution will be followed by separation of uranium from molybdenum using solvent extraction with 7.5% tributylphosphate in n-paraffin. Testing with the fuel validated dissolution and solubility data reported in the literature. Batch distribution coefficient measurements were performed for the extraction, strip and wash stages with particular focus on the distribution of molybdenum.

  12. Mass-dependent sulfur isotope fractionation during reoxidative sulfur cycling

    DEFF Research Database (Denmark)

    Pellerin, André; Bui, Thi Hao; Rough, Mikaella

    2015-01-01

    of Mangrove Lake appears to include sulfide oxidation to elemental sulfur followed by the disproportionation of the elemental sulfur to sulfate and sulfide. This model also indicates that the reoxidative sulfur cycle of Mangrove Lake turns over from 50 to 80% of the sulfide produced by microbial sulfate...... that the two processes cannot be discriminated from each other....

  13. Single-step thermal carburization synthesis of supported molybdenum carbides from molybdenum-containing methyl-silica

    Institute of Scientific and Technical Information of China (English)

    Juan Zou; Minglin Xiang; Bo Hou; Dong Wu; Yuhan Sun

    2011-01-01

    A novel synthesis route to obtain highly dispersed molybdenum carbides in porous silica is described. The synthesis was carried out by a single-step heat treatment of molybdenum-containing and methyl-modified silica (Mo-M-SiO2) in argon atmosphere at 973 K. Mo-M-SiO2 precursor was facilely obtained via a one-pot synthesis route, using (NH4)6Mo7O24·4H2O (AHM) as molybdenum sources and polymethylhydrosiloxane (PMHS) as silica sources at the initial synthetic step. The optimal C/Mo molar ratio in reaction system for complete carburization of molybdenum species was 7. The carburization process of molybdenum species followed a nontopotactic route involving a MoO2 intermediate phase, which was evidenced by XRD, N2 adsorption-desorption and in situ XPS. Formation mechanism of Mo-M-SiO2 precursor was also proposed by observation of the reaction between AHM and PMHS with TEM. Furthermore, by adding TEOS into silica sources and adjusting TEOS/PMHS mass ratio, crystal phase of molybdenum carbides transferred fromβ-Mo2C to α-MoC1-x, and SiO2 structure changed from microporous to micro/mesoporous. Catalytic performances of samples were tested using CO hydrogenation as a probe reaction. The supported molybdenum carbides exhibited high selectivity for higher alcohol synthesis compared with bulkβ-Mo2C and α-MoC1-x.

  14. Lunar Sulfur Capture System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Lunar Sulfur Capture System (LSCS) is an innovative method to recover sulfur compounds from lunar soil using sorbents derived primarily from in-situ resources....

  15. Lunar Sulfur Capture System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Lunar Sulfur Capture System (LSCS) is an innovative method to capture greater than 90 percent of sulfur gases evolved during thermal treatment of lunar soils....

  16. Selective Sulfidation of Lead Smelter Slag with Sulfur

    Science.gov (United States)

    Han, Junwei; Liu, Wei; Wang, Dawei; Jiao, Fen; Qin, Wenqing

    2016-02-01

    The selective sulfidation of lead smelter slag with sulfur was studied. The effects of temperature, sulfur dosage, carbon, and Na salts additions were investigated based on thermodynamic calculation. The results indicated that more than 96 pct of zinc in the slag could be converted into sulfides. Increasing temperature, sulfur dosage, or Na salts dosage was conducive to the sulfidation of the zinc oxides in the slag. High temperature and excess Na salts would result in the more consumption of carbon and sulfur. Carbon addition not only promoted the selective sulfidation but reduced the sulfur dosage and eliminated the generation of SO2. Iron oxides had a buffering role on the sulfur efficient utilization. The transformation of sphalerite to wurtzite was feasible under reducing condition at high temperature, especially above 1273 K (1000 °C). The growth of ZnS particles largely depended upon the roasting temperature. They were significantly increased when the temperature was above 1273 K (1000 °C), which was attributed to the formation of a liquid phase.

  17. Sulfur isotopes in coal constrain the evolution of the Phanerozoic sulfur cycle

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene

    2013-01-01

    Sulfate is the second most abundant anion (behind chloride) in modern seawater, and its cycling is intimately coupled to the cycling of organic matter and oxygen at the Earth’s surface. For example, the reduction of sulfide by microbes oxidizes vast amounts of organic carbon and the subsequent...... reaction of sulfide with iron produces pyrite whose burial in sediments is an important oxygen source to the atmosphere. The concentrations of seawater sulfate and the operation of sulfur cycle have experienced dynamic changes through Earth’s history, and our understanding of this history is based mainly...... on interpretations of the isotope record of seawater sulfates and sedimentary pyrites. The isotope record, however, does not give a complete picture of the ancient sulfur cycle. This is because, in standard isotope mass balance models, there are more variables than constraints. Typically, in interpretations...

  18. Zeolites Remove Sulfur From Fuels

    Science.gov (United States)

    Voecks, Gerald E.; Sharma, Pramod K.

    1991-01-01

    Zeolites remove substantial amounts of sulfur compounds from diesel fuel under relatively mild conditions - atmospheric pressure below 300 degrees C. Extracts up to 60 percent of sulfur content of high-sulfur fuel. Applicable to petroleum refineries, natural-gas processors, electric powerplants, and chemical-processing plants. Method simpler and uses considerably lower pressure than current industrial method, hydro-desulfurization. Yields cleaner emissions from combustion of petroleum fuels, and protects catalysts from poisoning by sulfur.

  19. Thermal ripples in model molybdenum disulfide monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Microplastic relaxations of single and polycrystalline molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Pichl, W.; Weiss, B. [Wien Univ. (Austria). Inst. fuer Materialphysik; Chen, D.L.

    1998-05-01

    The microplasticity of high-purity molybdenum single crystals and of Mo polycrystals of technical purity has been investigated by relaxation step tests in uniaxial compression. A new model for the evaluation of relaxation tests in the microplastic range of b.c.c metals is presented which takes into account the decrease of the mobile dislocation density due to exhaustion of non-screw dislocations. The model allows an independent determination of the activation volume and of the microstructure parameters controlling dislocation exhaustion. The results indicate that in the high-purity single crystals the deformation rate is controlled by interactions of non-screw dislocations with the grown-in network. In the polycrystals additional interactions with impurity atoms seem to occur. In the single crystals the activity and subsequent exhaustion of two different glide systems was observed, followed by a gradual onset of screw dislocation motion. (orig.) 26 refs.

  1. Radio Frequencv Induction Plasma Spraying of Molybdenum

    Institute of Scientific and Technical Information of China (English)

    Jiang Xianliang(蒋显亮); Maher Boulos

    2003-01-01

    Radio frequency (RF) induction plasma was used to make free-standing depositionof molybdenum (Mo). The phenomena of particle melting, flattening, and stacking were inves-tigated. The effect of process parameters such as plasma power, chamber pressure, and spraydistance on the phenomena mentioned above was studied. Scanning electron microscopy (SEM)was used to analyze the plasma-processed powder, splats formed, and deposits obtained. Exper-imental results show that less Mo particles are spheroidized when compared to the number ofspheroidized tungsten (W) particles at the same powder feed rate under the same plasma spraycondition. Molten Mo particles can be sufficiently flattened on substrate. The influence of theprocess parameters on the flattening behavior is not significant. Mo deposit is not as dense as Wdeposit, due to the splash and low impact of molten Mo particles. Oxidation of the Mo powderwith a large particle size is not evident under the low pressure plasma spray.

  2. Structure of amorphous sulfur

    CSIR Research Space (South Africa)

    Eichinger, BE

    2001-06-01

    Full Text Available The lambda-transition of elemental sulfur occurring at about 159°C has long been associated with the conversion of cyclic S8 rings (c-S8) to amorphous polymer (a-S) via a ring opening polymerization. It is demonstrated, with the use of both density...

  3. Accidents with sulfuric acid

    Directory of Open Access Journals (Sweden)

    Rajković Miloš B.

    2006-01-01

    Full Text Available Sulfuric acid is an important industrial and strategic raw material, the production of which is developing on all continents, in many factories in the world and with an annual production of over 160 million tons. On the other hand, the production, transport and usage are very dangerous and demand measures of precaution because the consequences could be catastrophic, and not only at the local level where the accident would happen. Accidents that have been publicly recorded during the last eighteen years (from 1988 till the beginning of 2006 are analyzed in this paper. It is very alarming data that, according to all the recorded accidents, over 1.6 million tons of sulfuric acid were exuded. Although water transport is the safest (only 16.38% of the total amount of accidents in that way 98.88% of the total amount of sulfuric acid was exuded into the environment. Human factor was the common factor in all the accidents, whether there was enough control of the production process, of reservoirs or transportation tanks or the transport was done by inadequate (old tanks, or the accidents arose from human factor (inadequate speed, lock of caution etc. The fact is that huge energy, sacrifice and courage were involved in the recovery from accidents where rescue teams and fire brigades showed great courage to prevent real environmental catastrophes and very often they lost their lives during the events. So, the phrase that sulfuric acid is a real "environmental bomb" has become clearer.

  4. Parkinson's Disease: The Mitochondria-Iron Link.

    Science.gov (United States)

    Muñoz, Yorka; Carrasco, Carlos M; Campos, Joaquín D; Aguirre, Pabla; Núñez, Marco T

    2016-01-01

    Mitochondrial dysfunction, iron accumulation, and oxidative damage are conditions often found in damaged brain areas of Parkinson's disease. We propose that a causal link exists between these three events. Mitochondrial dysfunction results not only in increased reactive oxygen species production but also in decreased iron-sulfur cluster synthesis and unorthodox activation of Iron Regulatory Protein 1 (IRP1), a key regulator of cell iron homeostasis. In turn, IRP1 activation results in iron accumulation and hydroxyl radical-mediated damage. These three occurrences-mitochondrial dysfunction, iron accumulation, and oxidative damage-generate a positive feedback loop of increased iron accumulation and oxidative stress. Here, we review the evidence that points to a link between mitochondrial dysfunction and iron accumulation as early events in the development of sporadic and genetic cases of Parkinson's disease. Finally, an attempt is done to contextualize the possible relationship between mitochondria dysfunction and iron dyshomeostasis. Based on published evidence, we propose that iron chelation-by decreasing iron-associated oxidative damage and by inducing cell survival and cell-rescue pathways-is a viable therapy for retarding this cycle.

  5. Innovative Molybdenum Alloy for Extreme Operating Conditions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Molybdenum has been identified as a promising material for many high temperature NASA applications due to its high melting temperature, resistance to liquid metals,...

  6. Electroanalytical determination of tungsten and molybdenum in proteins.

    Science.gov (United States)

    Hagedoorn, P L; van't Slot, P; van Leeuwen, H P; Hagen, W R

    2001-10-01

    Recent crystal structure determinations accelerated the progress in the biochemistry of tungsten-containing enzymes. In order to characterize these enzymes, a sensitive determination of this metal in protein-containing samples is necessary. An electroanalytical tungsten determination has successfully been adapted to determine the tungsten and molybdenum content in enzymes. The tungsten and molybdenum content can be measured simultaneously from 1 to 10 microg of purified protein with little or no sample handling. More crude protein samples require precipitation of interfering surface active material with 10% perchloric acid. This method affords the isolation of novel molybdenum- and tungsten-containing proteins via molybdenum and tungsten monitoring of column fractions, without using radioactive isotopes. A screening of soluble proteins from Pyrococcus furiosus for tungsten, using anion-exchange column chromatography to separate the proteins, has been performed. The three known tungsten-containing enzymes from P. furiosus were recovered with this screening.

  7. Isotopically Modified Molybdenum: Production for Application in Nuclear Energy

    Science.gov (United States)

    Smirnov, A. Yu.; Bonarev, A. K.; Sulaberidze, G. A.; Borisevich, V. D.; Kulikov, G. G.; Shmelev, A. N.

    The possibility to use the isotopically modified molybdenum as a constructive material for the fuel rods of light water and fast reactors is discussed. The calculations demonstrate that the isotopically modified molybdenum with an average neutron absorption cross-section comparable to that of zirconium can be obtained with the reasonable for practice cost by a cascade of gas centrifuges, specially designed for separation of non-uranium isotopes.

  8. Molybdenum evidence for expansive sulfidic water masses in ~ 750 Ma oceans

    DEFF Research Database (Denmark)

    Dahl, Tais Wittchen; Canfield, Donald Eugene; Rosing, Minik Thorleif

    2011-01-01

    composition of ancient seawater. Further, we investigate the ~ 750 Ma Walcott Member of the Chuar Group, Grand Canyon, which accumulated in a rift basin with open connection to the ocean. Iron speciation data from upper Walcott shales indicate that local bottom waters were anoxic and sulfidic, consistent......The Ediacaran appearance of large animals, including motile bilaterians, is commonly hypothesized to reflect a physiologically enabling increase in atmospheric and oceanic oxygen abundances (pO2). To date, direct evidence for low oxygen in pre-Ediacaran oceans has focused on chemical signatures...... in the rock record that reflect conditions in local basins, but this approach is both biased to constrain only shallower basins and statistically limited when we seek to follow the evolution of mean ocean chemical state through time. Because the abundance and isotopic composition of molybdenum (Mo) in organic...

  9. Native iron

    DEFF Research Database (Denmark)

    Brooks, Charles Kent

    2015-01-01

    , a situation unique in the Solar System. In such a world, iron metal is unstable and, as we all know, oxidizes to the ferric iron compounds we call 'rust'. If we require iron metal it must be produced at high temperatures by reacting iron ore, usually a mixture of ferrous (Fe2+) and ferric (Fe3+) oxides (Fe2O3......, hematite, or FeO.Fe2O3, magnetite), with carbon in the form of coke. This is carried out in a blast furnace. Although the Earth's core consists of metallic iron, which may also be present in parts of the mantle, this is inaccessible to us, so we must make our own. In West Greenland, however, some almost...... unique examples of iron metal, otherwise called 'native iron' or 'telluric iron', occur naturally....

  10. Sedimentary pyrite δ34S differs from porewater sulfide in Santa Barbara Basin: Proposed role of organic sulfur

    Science.gov (United States)

    Raven, Morgan Reed; Sessions, Alex L.; Fischer, Woodward W.; Adkins, Jess F.

    2016-08-01

    Santa Barbara Basin sediments host a complex network of abiotic and metabolic chemical reactions that knit together the carbon, sulfur, and iron cycles. From a 2.1-m sediment core collected in the center of the basin, we present high-resolution profiles of the concentrations and isotopic compositions of all the major species in this system: sulfate, sulfide (∑H2S), elemental sulfur (S0), pyrite, extractable organic sulfur (OS), proto-kerogen S, total organic and dissolved inorganic carbon, and total and reducible iron. Below 10 cm depth, the core is characterized by low apparent sulfate reduction rates (biogeochemical cycles and redox structure in sedimentary paleoenvironments.

  11. Risk of overestimation of urinary cadmium concentrations: interference from molybdenum

    Directory of Open Access Journals (Sweden)

    Cañas A.I.

    2013-04-01

    Full Text Available We show here that the selection of analytical method is critical when measuring low levels of cadmium in human urine. Cadmium is today usually analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS, which has a higher sensitivity than Atomic Absorption Spectroscopy (AAS. ICP-MS cadmium measurements show interference from tin (114Sn and molybdenum oxides, which can result in an overestimation of cadmium levels. The 114Sn interference is stable and can be mathematically corrected. Molybdenum concentrations in urine are variable and different from individual to individual. We have estimated the degree of error which molybdenum interference introduces in the measurement of cadmium in urine by conventional ICP-MS. 268 urine samples from mothers and their children were measured. Removal of the molybdenum oxide interference (DRC-ICP-MS method reduced urinary cadmium concentrations significantly (47.8%. The urinary molybdenum concentration in children was higher than in their mothers, resulting in greater overestimation. Our results clearly show that the DRC method is essential for reliable measurements of urinary cadmium concentrations, particularly in children. Furthermore, care should be taken when comparing Human Biomonitoring data for cadmium in urine and attention should be paid to which analytical method has been used (e.g. AAS and ICP-Ms, and especially if the measurements have been corrected for molybdenum interference.

  12. Solvent extraction, ion chromatography, and mass spectrometry of molybdenum isotopes.

    Science.gov (United States)

    Dauphas, N; Reisberg, L; Marty, B

    2001-06-01

    A procedure was developed that allows precise determination of molybdenum isotope abundances in natural samples. Purification of molybdenum was first achieved by solvent extraction using di(2-ethylhexyl) phosphate. Further separation of molybdenum from isobar nuclides was obtained by ion chromatography using AG1-X8 strongly basic anion exchanger. Finally, molybdenum isotopic composition was measured using a multiple collector inductively coupled plasma hexapole mass spectrometer. The abundances of molybdenum isotopes 92, 94, 95, 96, 97, 98, and 100 are 14.8428(510), 9.2498(157), 15.9303(133), 16.6787(37), 9.5534(83), 24.1346(394), and 9.6104(312) respectively, resulting in an atomic mass of 95.9304(45). After internal normalization for mass fractionation, no variation of the molybdenum isotopic composition is observed among terrestrial samples within a relative precision on the order of 0.00001-0.0001. This demonstrates the reliability of the method, which can be applied to searching for possible isotopic anomalies and mass fractionation.

  13. The behavior of sulfur in industrial pyrometallurgical slags

    Science.gov (United States)

    Nagamori, Meguru

    1994-08-01

    Dissolution of sulfur in industrial slags, even at such a low level as 1 mass% S or so, increases the solubility of certain valuable metals by an order of magnitude. The phenomenon is accounted for in terms of Flood-Førland-Grjotheim's model for dianionic salt solutions, whereas its rigorous analysis requires the digaseous Gibbs-Duhem integration. In the research described here, the distribution of sulfur among gas, slag, and metallic iron phases in the bath smelting of iron ore was computer-simulated based on a two-sites model coupled with sulfide capacity data. The solubilities of Ag, Cu, Co, and Ni in industrial slags are reviewed by applying the sulfidic-oxidic dissolution model to copper-matte smelting, nickel-slag cleaning (Falconbridge, Canada), and the imperial smelting process for zinc and lead (Hachinohe, Japan).

  14. ENGINEERING EVALUATION OF HOT-GAS DESULFURIZATION WITH SULFUR RECOVERY

    Energy Technology Data Exchange (ETDEWEB)

    G.W. ROBERTS; J.W. PORTZER; S.C. KOZUP; S.K. GANGWAL

    1998-05-31

    Engineering evaluations and economic comparisons of two hot-gas desulfurization (HGD) processes with elemental sulfur recovery, being developed by Research Triangle Institute, are presented. In the first process, known as the Direct Sulfur Recovery Process (DSRP), the SO{sub 2} tail gas from air regeneration of zinc-based HGD sorbent is catalytically reduced to elemental sulfur with high selectivity using a small slipstream of coal gas. DSRP is a highly efficient first-generation process, promising sulfur recoveries as high as 99% in a single reaction stage. In the second process, known as the Advanced Hot Gas Process (AHGP), the zinc-based HGD sorbent is modified with iron so that the iron portion of the sorbent can be regenerated using SO{sub 2} . This is followed by air regeneration to fully regenerate the sorbent and provide the required SO{sub 2} for iron regeneration. This second-generation process uses less coal gas than DSRP. Commercial embodiments of both processes were developed. Process simulations with mass and energy balances were conducted using ASPEN Plus. Results show that AHGP is a more complex process to operate and may require more labor cost than the DSRP. Also capital costs for the AHGP are higher than those for the DSRP. However, annual operating costs for the AHGP appear to be considerably less than those for the DSRP with a potential break-even point between the two processes after just 2 years of operation for an integrated gasification combined cycle (IGCC) power plant using 3 to 5 wt% sulfur coal. Thus, despite its complexity, the potential savings with the AHGP encourage further development and scaleup of this advanced process.

  15. 粉煤灰硫酸浸出液中钛和铁的萃取分离%Extraction and Separation of Titanium and Iron with Sulfuric Acid Leaching of Fly Ash

    Institute of Scientific and Technical Information of China (English)

    薛茹君

    2011-01-01

    By adjusting the pH of the H2SO4 leaching liquor of fly ash, Ti4 + and Fe + were extract-separated with trioctylphosphineoxide (TOPO)-kerosene and di ( 2-ethylhexyl) phosphoric acid (P204)-kerosene, respectively. Effects of the extractants, the concentration of the cations, pH of the aqueous solution, extracting temperature, and extracting time on the extracting efficiency were investigated. Effect of the recycle conditions of the loaded extractants on the recovery yield and the purity of recovered products were discussed as well. The phase of the precursor and its calcined products were characterized by X-ray diffraction(XRD). The purity of the TiO2 and Fe2O3 were determined by X-ray fluorescence (XRF). The analysis results show that the extracting-titanium efficiency and the extracting-iron efficiency were as high as 97%. The extraction yields of ferric oxide and titanium dioxide are 96% and greater than 92% , respectively. The purities of TiO2 and Fe2O3 are 98% and 97% , respectively, which can be used as a white pigment or iron oxide red pigment in the production of paints, respectively.%将粉煤灰的硫酸浸出液,用氨水调节pH值后,用三正辛基氧膦-煤油、磷酸二异辛酯-煤油萃取分离溶液中的Ti和Fe.考察了萃取剂、水相阳离子浓度、pH值及萃取温度和时间等实验条件对萃取率的影响;讨论了萃取剂再生条件对提取率及分离产物纯度的影响.用XRD表征了反萃取煅烧产物的物相组成,用X射线荧光分析测定了煅烧产物TiO和FeO的纯度.分析结果表明,钛的萃取率达到97%,提取率>92%;铁的萃取率达到97%,提取率达到96%;TiO和FeO的纯度分别为98%和97%,均可以用作涂料的颜料.

  16. Effect of Microstructure on Exhaust Manifold Cracks Produced From SiMo Ductile Iron

    Institute of Scientific and Technical Information of China (English)

    Havva Kazdal Zeytin; Ceylan Kubilay; H(u)seyin Aydin; Ali Aslan Ebrinc; Bilal Aydemir

    2009-01-01

    Ductile cast irons are used as high temperature materials in internal combustion engines,because they are microstructurally stable at high operating temperatures.SiMo granular graphite cast irons contain Fe2 MoC and M6C carbide precipitates due to their higher concentration of both silicon and molybdenum.The microstructure of these cast irons consists of carbides dispersed within the ferrite matrix.The microstructural change and the crack formation mechanism in manifolds produced from SiMo ductile iron are studied.Chemical analysis,optical and scanning electron microscope studies have been completed and evaluated.

  17. The impact of ocean deoxygenation on iron release from continental margin sediments

    OpenAIRE

    Scholz, Florian; McManus, James; Mix, Alan C; Hensen, Christian; Schneider, Ralph

    2014-01-01

    In the oceans’ high-nitrate–low-chlorophyll regions, such as the Peru/Humboldt Current system and the adjacent eastern equatorial Pacific1, primary productivity is limited by the micronutrient iron. Within the Peruvian upwelling area, bioavailable iron is released from the reducing continental margin sediments2. The magnitude of this seafloor source could change with fluctuations in the extension or intensity of the oxygen minimum zones3, 4. Here we show that measurements of molybdenum, urani...

  18. Iron Homeostasis and Nutritional Iron Deficiency123

    OpenAIRE

    2011-01-01

    Nonheme food ferritin (FTN) iron minerals, nonheme iron complexes, and heme iron contribute to the balance between food iron absorption and body iron homeostasis. Iron absorption depends on membrane transporter proteins DMT1, PCP/HCP1, ferroportin (FPN), TRF2, and matriptase 2. Mutations in DMT1 and matriptase-2 cause iron deficiency; mutations in FPN, HFE, and TRF2 cause iron excess. Intracellular iron homeostasis depends on coordinated regulation of iron trafficking and storage proteins enc...

  19. Effects of Feed Composition and Feed Impurities in the Catalytic Conversion of Syngas to Higher Alcohols over Alkali-Promoted Cobalt–Molybdenum Sulfide

    DEFF Research Database (Denmark)

    Christensen, Jakob Munkholt; Jensen, Peter Arendt; Jensen, Anker Degn

    2011-01-01

    Alkali-promoted cobalt–molybdenum sulfide is a potential catalyst for the conversion of syngas into higher alcohols. This work is an investigation of how the feed composition influences the behavior of the sulfide catalyst. In a sulfur-free syngas the production of higher alcohols is observed...... to be optimal with an equimolar mixture of CO and H2 in the feed, while the methanol production benefits from an increasing hydrogen content in the feed. The influence of NH3 and H2O in the syngas feed has also been investigated. Ammonia (741 ppmv) in the feed is observed to cause a general and largely...

  20. Chemiluminescence Determination of Molybdenum by on-Line Reduction with a Flow Injection System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The chemiluminescence (CL) reaction between lucigenin (Lu) and molybdenum (Ⅲ) produced by a Jones reductor was investigated using a flow injection system. On the basis of this, a novel method for the determination of trace amount of molybdenum has been established. The emission intensity was linear with molybdenum concentration in the range of 0.1-1000 ng/mL; the detection limit was 0.02 ng/mL molybdenum; the relative standard deviation was less than 2% for the determination of 0.1 ng/mL molybdenum (n=11). The method has been applied successfully to the analysis of trace molybdenum in water and steel samples.

  1. Electron accelerator-based production of molybdenum-99: Bremsstrahlung and photoneutron generation from molybdenum vs. tungsten

    Science.gov (United States)

    Tsechanski, A.; Bielajew, A. F.; Archambault, J. P.; Mainegra-Hing, E.

    2016-01-01

    A new "one-stage" approach for production of 99Mo and other radioisotopes by means of an electron linear accelerator is described. It is based on using a molybdenum target both as a bremsstrahlung converter and as a radioisotope producing target for the production of 99Mo via the photoneutron reaction 100Mo(γ,n)99Mo. Bremsstrahlung characteristics, such as bremsstrahlung efficiency, angular distribution, and energy deposition for molybdenum targets were obtained by means of the EGSnrc Monte Carlo simulation code system. As a result of our simulations, it is concluded that a 60 MeV electron beam incident on a thick Mo target will have greater bremsstrahlung efficiency than the same thickness (in units of r0) W target, for target thickness z > 1.84r0, where r0 is the electron range. A 50 MeV electron beam incident on a Mo target will result in greater bremsstrahlung efficiency than the same thickness W target (in units of r0) for target thickness case: z ⩾ 2.0r0. It is shown for the one-stage approach with thicknesses of (1.84-2.0)r0, that the 99Mo-production bremsstrahlung efficiency of a molybdenum target is greater by ∼100% at 30 MeV and by ∼70% at 60 MeV compared to the values for tungsten of the same thickness (in units of the appropriate r0) in the traditional two-stage approach (W converter and separate 99Mo producing target). This advantage of the one-stage approach arises from the fact that the bremsstrahlung produced is attenuated only once from attenuation in the molybdenum converter/target. In the traditional, two-stage approach, the bremsstrahlung generated in the W-converter/target is attenuated both in the converter in the 99Mo-producing molybdenum target. The photoneutron production yield of molybdenum and tantalum (as a substitute for tungsten) target was calculated by means of the MCNP5 transport code. On the basis of these data, the specific activity for the one-stage approach of three enriched 100Mo-targets of a 2 cm diameter and

  2. Electron accelerator-based production of molybdenum-99: Bremsstrahlung and photoneutron generation from molybdenum vs. tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Tsechanski, A. [Ben-Gurion University of the Negev, Department of Nuclear Engineering, P.O. Box 653, Beer-Sheva 84105 (Israel); Bielajew, A.F. [Department of Nuclear Engineering and Radiological Sciences, The University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Archambault, J.P.; Mainegra-Hing, E. [National Research Council of Canada, Ionizing Radiation Standards Laboratory, Ottawa, ON K1A 0R6 (Canada)

    2016-01-01

    A new “one-stage” approach for production of {sup 99}Mo and other radioisotopes by means of an electron linear accelerator is described. It is based on using a molybdenum target both as a bremsstrahlung converter and as a radioisotope producing target for the production of {sup 99}Mo via the photoneutron reaction {sup 100}Mo(γ,n){sup 99}Mo. Bremsstrahlung characteristics, such as bremsstrahlung efficiency, angular distribution, and energy deposition for molybdenum targets were obtained by means of the EGSnrc Monte Carlo simulation code system. As a result of our simulations, it is concluded that a 60 MeV electron beam incident on a thick Mo target will have greater bremsstrahlung efficiency than the same thickness (in units of r{sub 0}) W target, for target thickness z > 1.84r{sub 0}, where r{sub 0} is the electron range. A 50 MeV electron beam incident on a Mo target will result in greater bremsstrahlung efficiency than the same thickness W target (in units of r{sub 0}) for target thickness case: z ⩾ 2.0r{sub 0}. It is shown for the one-stage approach with thicknesses of (1.84–2.0)r{sub 0}, that the {sup 99}Mo-production bremsstrahlung efficiency of a molybdenum target is greater by ∼100% at 30 MeV and by ∼70% at 60 MeV compared to the values for tungsten of the same thickness (in units of the appropriate r{sub 0}) in the traditional two-stage approach (W converter and separate {sup 99}Mo producing target). This advantage of the one-stage approach arises from the fact that the bremsstrahlung produced is attenuated only once from attenuation in the molybdenum converter/target. In the traditional, two-stage approach, the bremsstrahlung generated in the W-converter/target is attenuated both in the converter in the {sup 99}Mo-producing molybdenum target. The photoneutron production yield of molybdenum and tantalum (as a substitute for tungsten) target was calculated by means of the MCNP5 transport code. On the basis of these data, the specific activity

  3. Molybdenum oxide and molybdenum oxide-nitride back contacts for CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Drayton, Jennifer A., E-mail: drjadrayton@yahoo.com; Geisthardt, Russell M., E-mail: Russell.Geisthardt@gmail.com; Sites, James R., E-mail: james.sites@colostate.edu [Department of Physics, Colorado State University, Fort Collins, Colorado 80523 (United States); Williams, Desiree D., E-mail: daisyw@rams.colostate.edu; Cramer, Corson L., E-mail: clcramer@rams.colostate.edu; Williams, John D., E-mail: john.d.williams@colostate.edu [Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States)

    2015-07-15

    Molybdenum oxide (MoO{sub x}) and molybdenum oxynitride (MoON) thin film back contacts were formed by a unique ion-beam sputtering and ion-beam-assisted deposition process onto CdTe solar cells and compared to back contacts made using carbon–nickel (C/Ni) paint. Glancing-incidence x-ray diffraction and x-ray photoelectron spectroscopy measurements show that partially crystalline MoO{sub x} films are created with a mixture of Mo, MoO{sub 2}, and MoO{sub 3} components. Lower crystallinity content is observed in the MoON films, with an additional component of molybdenum nitride present. Three different film thicknesses of MoO{sub x} and MoON were investigated that were capped in situ in Ni. Small area devices were delineated and characterized using current–voltage (J-V), capacitance–frequency, capacitance–voltage, electroluminescence, and light beam-induced current techniques. In addition, J-V data measured as a function of temperature (JVT) were used to estimate back barrier heights for each thickness of MoO{sub x} and MoON and for the C/Ni paint. Characterization prior to stressing indicated the devices were similar in performance. Characterization after stress testing indicated little change to cells with 120 and 180-nm thick MoO{sub x} and MoON films. However, moderate-to-large cell degradation was observed for 60-nm thick MoO{sub x} and MoON films and for C/Ni painted back contacts.

  4. Accidents with sulfuric acid

    OpenAIRE

    Rajković Miloš B.

    2006-01-01

    Sulfuric acid is an important industrial and strategic raw material, the production of which is developing on all continents, in many factories in the world and with an annual production of over 160 million tons. On the other hand, the production, transport and usage are very dangerous and demand measures of precaution because the consequences could be catastrophic, and not only at the local level where the accident would happen. Accidents that have been publicly recorded during the last eigh...

  5. Equation of State of Fe3S and Limits on the Sulfur Content of Earth's Core

    Science.gov (United States)

    Campbell, A.; Mattillion, A.; Bausch, H.; Tecklenburg, S.; Fischer, R. A.; Chidester, B.; Prakapenka, V.

    2016-12-01

    Sulfur is a common component of protoplanetary cores, as represented by iron meteorites, and it is likely to be a significant alloying component with iron in Earth's core as well, along with silicon, oxygen, and perhaps other light elements. Cosmochemical limits on the sulfur content of Earth's core, based on the relative volatilities of sulfur and other elements, are weakened by the observation that this approach fails to accurately predict the sulfur content in iron meteorite parent bodies. To better understand the geophysical consequences of sulfur addition to Earth's core, we report equation of state measurements of Fe3S to pressures and temperatures exceeding 140 GPa and 2000 K, using synchrotron X-ray diffraction in a laser heated diamond anvil cell. New room temperature measurements are also reported, improved by the use of a neon pressure medium. With this P-V-T equation of state for Fe3S, along with an assumed 2% density change upon melting and a 4000 K core-mantle boundary temperature, the PREM density in the outer core can be matched with 14 wt% sulfur, which should be considered an upper bound because of the likely additional presence of other light elements.

  6. Molybdenum isotope signatures from the Yangtze block continental margin and its indication to organic burial rate

    Science.gov (United States)

    Zhou, L.; Zhou, H. B.; Huang, J. H.

    2007-12-01

    The paper presents the molybdenum isotope data, along with the trace element content, to investigate the geochemical behavior of authigenic Mo during long-term burial in sediments in continental margin settings of the Yangtze block, as well as their indication to the burial of original organic carbon. The burial rate of original organic carbon were estimated on the basis of the amount of sedimentary sulfur (TS content), whilst the carbon loss by aerobic degradation was estimated according to calculated Mn contents. On these points, the original organic carbon flux was calculated, exhibiting a large range of variation (2.54-15.82 mmol/m2/day). The strong correlation between sedimentary Mo isotope values and organic carbon burial rates previously proposed on the basis of the investigations on modern ocean sediments was also used here to estimate the organic carbon burial rate. The data gained through this model showed that organic carbon burial rates have large variations, ranging from 0.43- 2.87mmol/m2/day. Although the two sets of data gained through different geochemical records in the Yangtze block show a deviation of one order of magnitude, they do display a strong correlation. It is thus tempting to speculate that the Mo isotope signature of sediments may serve as a tracer for the accumulation rate of original organic carbon in the continental margin sediments. Keywords: Molybdenum isotopes; organic carbon burial rate; ancient continental margin setting ACKNOWLEDGMENTS We thank Professor Xie Shucheng for his constructive review comments. This research is co-supported by the Program for Changjiang Scholars and Innovative Research Team in University (grants IRT0441), the SinoPec project (grant no. G0800-06-ZS-319) and the National Nature Science Foundation of China (grants 40673020).

  7. 含钼铜精矿氧化焙烧-浸出分离钼研究%Study on sepatation of molybdenum ftom molybdenum-containing coppet concenttate by oxidizing toasting-leaching

    Institute of Scientific and Technical Information of China (English)

    肖军辉; 施哲; 陈金花

    2016-01-01

    Absttact:An oxidizing roasting-leaching flowsheet was proposed to further separate molybdenum because of complex minerals composition and tightness paragenetic relationship of molybdenum and copper in the molybdenum-containing copper concentrate in western Panzhihua of Sichuan province.Samples were put into the roasting furnace to conduct oxidizing roasting,and sulphide ore was oxidized into CuO,MoO3 , Fe2 O3 ,etc.Then,NaOH and H2 O were added to react with MoO3 ,and Na2 MoO4 was produced,and leaching residue was taken as the copper concentrate.Study results indicate that copper and molybdenum occur in the form of oxide in the roasting ores.The sulfur content is 0.53%in the roasting ores,and sulfur volatilizes in the form of SO2 .The leaching ratio of molybdenum is 94.24%and the copper mass fraction in the copper concentrate(leaching residue)is 24.27% when the roasting temperature is 650 ℃,roasting time is 120 min,NaOH dosage is 30%,leaching temperature is 60℃,leaching time is 120 min,and leaching liquid-solid ratio is 2∶1 .The effect of molybdenum separation is obvious.%四川攀西地区的含钼铜精矿中,由于钼、铜矿物组成复杂,共生关系紧密,提出了氧化焙烧-浸出工艺进一步分离钼。将试样置入焙烧炉中进行氧化焙烧,使硫化物转化为CuO、MoO3、Fe2 O3等氧化物后;添加NaOH、H2 O 与 MoO3反应生成可溶性Na2 MoO4,浸出渣作为铜精矿产品。研究结果表明:铜、钼等以氧化物形式赋存于焙烧矿中,氧化焙烧矿中的硫含量较低为0.53%,硫以SO2气相形式挥发;在焙烧温度650℃、焙烧时间120 min、氢氧化钠用量为30%、浸出温度60℃、浸出时间120 min、浸出液固比2∶1的综合条件下,钼的浸出率为94.24%,铜精矿(浸出渣)中铜的质量分数为24.27%,钼分离效果明显。

  8. Iron-induced changes in the proteome of Trichomonas vaginalis hydrogenosomes.

    Directory of Open Access Journals (Sweden)

    Neritza Campo Beltrán

    Full Text Available Iron plays a crucial role in metabolism as a key component of catalytic and redox cofactors, such as heme or iron-sulfur clusters in enzymes and electron-transporting or regulatory proteins. Limitation of iron availability by the host is also one of the mechanisms involved in immunity. Pathogens must regulate their protein expression according to the iron concentration in their environment and optimize their metabolic pathways in cases of limitation through the availability of respective cofactors. Trichomonas vaginalis, a sexually transmitted pathogen of humans, requires high iron levels for optimal growth. It is an anaerobe that possesses hydrogenosomes, mitochondrion-related organelles that harbor pathways of energy metabolism and iron-sulfur cluster assembly. We analyzed the proteomes of hydrogenosomes obtained from cells cultivated under iron-rich and iron-deficient conditions employing two-dimensional peptide separation combining IEF and nano-HPLC with quantitative MALDI-MS/MS. We identified 179 proteins, of which 58 were differentially expressed. Iron deficiency led to the upregulation of proteins involved in iron-sulfur cluster assembly and the downregulation of enzymes involved in carbohydrate metabolism. Interestingly, iron affected the expression of only some of multiple protein paralogues, whereas the expression of others was iron independent. This finding indicates a stringent regulation of differentially expressed multiple gene copies in response to changes in the availability of exogenous iron.

  9. Structure, activity and kinetics of supported molybdenum oxide and mixed molybdenum-vanadium oxide catalysts prepared by flame spray pyrolysis for propane OHD

    DEFF Research Database (Denmark)

    Høj, Martin; Kessler, Thomas; Beato, Pablo

    2013-01-01

    reflectance UV-vis spectroscopy and evaluated as catalysts for the oxidative dehydrogenation (ODH) of propane. The results show that samples with high specific surface areas between 122 and 182 m2/g were obtained, resulting in apparent MoOx and VOx surface densities from 0.7 to 7.7 nm -2 and 1.5 to 1.9 nm-2......, respectively. Raman spectroscopy, UV-vis spectroscopy and XRD confirmed the high dispersion of molybdenum and vanadia species on γ-Al2O3 as the main crystalline phase. Only at the highest loading of 15 wt% Mo, with theoretically more than monolayer coverage, some crystalline molybdenum oxide was observed....... For the mixed molybdenum-vanadium oxide catalysts the surface species were separate molybdenum oxide and vanadium oxide monomers at low loadings of molybdenum, but with increasing molybdenum loading interactions between surface molybdenum and vanadium oxide species were observed with Raman spectroscopy...

  10. Amorphous molybdenum silicon superconducting thin films

    Directory of Open Access Journals (Sweden)

    D. Bosworth

    2015-08-01

    Full Text Available Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using WxSi1−x, though other amorphous superconductors such as molybdenum silicide (MoxSi1−x offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc reaches a maximum of 7.6 K at a composition of Mo83Si17. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, R- and C-plane sapphire, x-plane lithium niobate and quartz, there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.

  11. Vertically aligned biaxially textured molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, Rahul [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Riley, Michael [Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Lee, Sabrina [US Army Armament Research, Development and Engineering Center, Benet Labs, Watervliet, New York 12189 (United States); Lu, Toh-Ming [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2011-09-15

    Vertically aligned, biaxially textured molybdenum nanorods were deposited using dc magnetron sputtering with glancing flux incidence (alpha = 85 degrees with respect to the substrate normal) and a two-step substrate-rotation mode. These nanorods were identified with a body-centered cubic crystal structure. The formation of a vertically aligned biaxial texture with a [110] out-of-plane orientation was combined with a [-110] in-plane orientation. The kinetics of the growth process was found to be highly sensitive to an optimum rest time of 35 seconds for the two-step substrate rotation mode. At all other rest times, the nanorods possessed two separate biaxial textures each tilted toward one flux direction. While the in-plane texture for the vertical nanorods maintains maximum flux capture area, inclined Mo nanorods deposited at alpha = 85 degrees without substrate rotation display a [-1-1-4] in-plane texture that does not comply with the maximum flux capture area argument. Finally, an in situ capping film was deposited with normal flux incidence over the biaxially textured vertical nanorods resulting in a thin film over the porous nanorods. This capping film possessed the same biaxial texture as the nanorods and could serve as an effective substrate for the epitaxial growth of other functional materials.

  12. Groundwater Molybdenum from Emerging Industries in Taiwan.

    Science.gov (United States)

    Tsai, Kuo-Sheng; Chang, Yu-Min; Kao, Jimmy C M; Lin, Kae-Long

    2016-01-01

    This study determined the influence of emerging industries development on molybdenum (Mo) groundwater contamination. A total of 537 groundwater samples were collected for Mo determination, including 295 samples from potentially contaminated areas of 3 industrial parks in Taiwan and 242 samples from non-potentially contaminated areas during 2008-2014. Most of the high Mo samples are located downstream from a thin film transistor-liquid crystal display (TFT-LCD) panel factory. Mean groundwater Mo concentrations from potentially contaminated areas (0.0058 mg/L) were significantly higher (p groundwater and surface water contamination. Nine samples of groundwater exceed the World Health Organization's suggested drinking water guideline of 0.07 mg/L. A non-carcinogenic risk assessment for Mo in adults and children using the Mo concentration of 0.07 mg/L yielded risks of 0.546 and 0.215, respectively. These results indicate the importance of the development of a national drinking water quality standard for Mo in Taiwan to ensure safe groundwater for use. According to the human health risk calculation, the groundwater Mo standard is suggested as 0.07 mg/L. Reduction the discharge of Mo-contaminated wastewater from factories in the industrial parks is also the important task in the future.

  13. Electro-oxidation process for molybdenum concentrates

    Institute of Scientific and Technical Information of China (English)

    FU Jian-gang; ZHONG Hong; BU Xiang-ming; WANG Fu-li

    2005-01-01

    Sodium hypochlorite was used to treat the standard molybdenum concentrates; the oxidization conditions for sodium hypochlorite were investigated, and the electro-oxidation process was performed. The results indicate that in the suitable conditions, such as temperature around 25 ℃, NaCl concentration 4.0 mol/L, mass ratio of ore slurry liquid to solid (mL/mS) 20, electric charge per gram Mo 0.522 C, pH value of original slurry 8, anodic current density 700 A·m-2 (cell potential 2.7-2.9 V), the Mo leaching rate and the current efficiency reach 98% and 36%, respectively. In order to overcome some shortages of the electro-oxidation process, such as low current efficiency, low Mo concentration in the leaching solution, ultrasonic was adopted to intensify the leaching process. The results show that the Mo leaching rate exceeds 98%, current efficiency increases from 36% to 50% and the Mo concentration in the leaching solution reaches about 60 g/L at low mL/mS of 8 and low electric charge of 0.373 C.

  14. Structural phase transitions in monolayer molybdenum dichalcogenides

    Science.gov (United States)

    Choe, Duk-Hyun; Sung, Ha June; Chang, Kee Joo

    2015-03-01

    The recent discovery of two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs) has provided opportunities to develop ultimate thin channel devices. In contrast to graphene, the existence of moderate band gap and strong spin-orbit coupling gives rise to exotic electronic properties which vary with layer thickness, lattice structure, and symmetry. TMDs commonly appear in two structures with distinct symmetries, trigonal prismatic 2H and octahedral 1T phases which are semiconducting and metallic, respectively. In this work, we investigate the structural and electronic properties of monolayer molybdenum dichalcogenides (MoX2, where X = S, Se, Te) through first-principles density functional calculations. We find a tendency that the semiconducting 2H phase is more stable than the metallic 1T phase. We show that a spontaneous symmetry breaking of 1T phase leads to various distorted octahedral (1T') phases, thus inducing a metal-to-semiconductor transition. We discuss the effects of carrier doping on the structural stability and the modification of the electronic structure. This work was supported by the National Research Foundation of Korea (NRF) under Grant No. NRF-2005-0093845 and Samsung Science and Technology Foundation under Grant No. SSTFBA1401-08.

  15. Catalyst for the reduction of sulfur dioxide to elemental sulfur

    Science.gov (United States)

    Jin, Y.; Yu, Q.; Chang, S.G.

    1996-02-27

    The inventive catalysts allow for the reduction of sulfur dioxide to elemental sulfur in smokestack scrubber environments. The catalysts have a very high sulfur yield of over 90% and space velocity of 10,000 h{sup {minus}1}. They also have the capacity to convert waste gases generated during the initial conversion into elemental sulfur. The catalysts have inexpensive components, and are inexpensive to produce. The net impact of the invention is to make this technology practically available to industrial applications. 21 figs.

  16. Electroanalytical methods in characterization of sulfur species in aqueous environment

    Directory of Open Access Journals (Sweden)

    Irena Ciglenečki

    2014-12-01

    Full Text Available Electroanalytical (voltammetric, polarographic, chronoamperometric methods on an Hg electrode were applied for studying of different sulfur compounds in model and natural water systems (anoxic lakes, waste water, rain precipitation, sea-aerosols. In all investigated samples typical HgS reduction voltammetric peak, characteristic for many different reduced sulfur species (RSS: sulfide, elemental sulfur, polysulfide, labile metal sulfide and organosulfur species was recorded at about -0.6 V vs. Ag/AgCl reference electrode. In addition, in anoxic waters which are enriched with sulfide and iron species, voltammetric peaks characteristic for the presence of free Fe(II and FeS nanoparticles (NPs were recorded at -1.4 V and around -0.45 V, respectively. Depending on the used electroanalytical method and experimental conditions (varying deposition potential, varying time of oxidative and/or reductive accumulation, sample pretreatment i.e. acidification followed by purging it is possible to distinguish between different sulfur species. This work clearly shows a large potential of the electrochemistry as a powerful analytical technique for screening water quality regarding presence of different reduced sulfur species and their speciation between dissolved and colloidal/nanoparticle phases.

  17. A study of the Apollo aqueous redox process for converting hydrogen sulfide in biogas to elemental sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Ellenor, D.T.

    2004-07-01

    An experimental study was conducted to develop a commercial biogas scrubber for municipal and agricultural use. The specific objectives were to provide design and scaling parameters that would improve the performance while minimizing the capital and operating costs of the biogas scrubber; provide a useful reaction model of the aqueous phase iron chelate catalyzed oxide of hydrogen sulfide to elemental sulfur; develop hypotheses and determine what data are of relevance in comprehending the interfacial phenomena of colloidal sulfur in aqueous solutions that could result in unwanted sulfur deposition and poor sulfur quality; obtain interfacial chemistry data that could improve the understanding of how sulfur particles behave during flocculation and deposition on surfaces, and the factors that lead to poor surface quality; and, determine whether crystal size and characteristics of deposited and flocculated sulfur could be changed by surfactants to enhance sulfur purity and reduce process operability. Interfacial chemistry experiments were performed to determine the factors that influence the operating problems and poor quality associated with the sulfur product. Results suggest that a low foaming nonionic surfactant can improve the quality and processability of the elemental sulfur product. It was concluded that the addition of surfactant to the redox solution reduces the mean hydrogen removal efficiency of the process. The addition of surfactants also decreases the mean particle size of the precipitated sulfur product, but increases the purity of the precipitated product. This study contributed to the successful installation by Apollo Environmental Systems of a commercial biogas scrubber that is very resistant to sulfur plugging.

  18. The potential roles of lime and molybdenum on the growth, nitrogen ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-04-26

    Apr 26, 2010 ... Experiments with soybean have shown that molybdenum fertilization in .... Evidence in the literature shows that lime, organic and different ...... Foliar application of molybdenum in common beans. I. Nitrogenase and reductase ...

  19. Ultra-rapid processing of refractory carbides; 20 s synthesis of molybdenum carbide, Mo2C.

    Science.gov (United States)

    Vallance, Simon R; Kingman, Sam; Gregory, Duncan H

    2007-02-21

    The microwave synthesis of molybdenum carbide, Mo(2)C, from carbon and either molybdenum metal or the trioxide has been achieved on unprecedented timescales; Ex- and in-situ characterisation reveals key information as to how the reaction proceeds.

  20. Largest domestic tungsten and molybdenum deep processing project finding its home in Luan-chuan

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>Recently, a tungsten and molybdenum deep processing project was formally executed with a joint investment of 300 million yuan from Luanchuan Molybdenum Mining & Smelting Co., Ltd, Beijing Tian-Long Tungsten & Mo-

  1. Influence of various surface pretreatments on adherence of sputtered molybdenum disulfide to silver, gold, copper, and bronze

    Science.gov (United States)

    Spalvins, T.

    1973-01-01

    Solid film lubricants of radio frequency sputtered molybdenum disulfide (MoS2) were applied to silver, gold, copper, and bronze surfaces that had various pretreatments (mechanical polishing, sputter etching, oxidation, and sulfurization). Optical and electron transmission micrographs and electron diffraction patterns were used to interpret the film formation characteristics and to evaluate the sputtering conditions in regard to the film and substrate compatibility. Sputtered MoS2 films flaked and peeled on silver, copper, and bronze surfaces except when the surfaces had been specially oxidized. The flaking and peeling was a result of sulfide compound formation and the corresponding grain growth of the sulfide film. Sputtered MoS2 films showed no peeling and flaking on gold surfaces regardless of surface pretreatment.

  2. Iron load

    Directory of Open Access Journals (Sweden)

    Filippo Cassarà

    2013-03-01

    Full Text Available Recent research addressed the main role of hepcidin in the regulation of iron metabolism. However, while this mechanism could be relevant in causing iron load in Thalassemia Intermedia and Sickle-Cell Anemia, its role in Thalassemia Major (TM is marginal. This is mainly due to the high impact of transfusional requirement into the severe increase of body iron. Moreover, the damage of iron load may be worsened by infections, as HCV hepatitis, or liver and endocrinological damage. One of the most relevant associations was found between splenectomy and increase of risk for mortality due,probably, to more severe iron load. These issues suggest as morbidity and mortality of this group of patients they do not depend only by our ability in controlling heart damage but even in preventing or treating particular infections and complications. This finding is supported by the impairment of survival curves in patients with complications different from heart damage. However, because, during recent years different direct and indirect methods to detect iron overload in patients affected by secondary hemochromatosis have been implemented, our ability to maintain under control iron load is significantly improved. Anyway, the future in iron load management remains to be able to have an iron load map of our body for targeting chelation and other medical treatment according to the single organ damage.

  3. HYBRID SULFUR RECOVERY PROCESS FOR NATURAL GAS UPGRADING

    Energy Technology Data Exchange (ETDEWEB)

    Girish Srinivas; Steven C. Gebhard; David W. DeBerry

    2002-07-01

    This second quarter report of 2002 describes progress on a project funded by the U.S. Department of Energy (DOE) to test a hybrid sulfur recovery process for natural gas upgrading. The process concept represents a low cost option for direct treatment of natural gas streams to remove H{sub 2}S in quantities equivalent to 0.2-25 metric tons (LT) of sulfur per day. This process is projected to have lower capital and operating costs than the competing technologies, amine/aqueous iron liquid redox and amine/Claus/tail gas treating, and have a smaller plant footprint, making it well suited to both on-shore and offshore applications. CrystaSulf (service mark of CrystaTech, Inc.) is a new nonaqueous sulfur recovery process that removes hydrogen sulfide (H{sub 2}S) from gas streams and converts it into elemental sulfur. CrystaSulf features high sulfur recovery similar to aqueous-iron liquid redox sulfur recovery processes, but differs from the aqueous processes in that CrystaSulf controls the location where elemental sulfur particles are formed. In the hybrid process, approximately 1/3 of the total H{sub 2}S in the natural gas is first oxidized to SO{sub 2} at low temperatures over a heterogeneous catalyst. Low temperature oxidation is done so that the H{sub 2}S can be oxidized in the presence of methane and other hydrocarbons without oxidation of the hydrocarbons. The project involves the development of a catalyst using laboratory/bench-scale catalyst testing, and then demonstration of the catalyst at CrystaTech's pilot plant in west Texas. Previous reports described development of a catalyst with the required selectivity and efficiency for producing sulfur dioxide from H{sub 2}S. In the laboratory, the catalyst was shown to be robust and stable in the presence of several intentionally added contaminants, including condensate from the pilot plant site. This report describes testing using the laboratory apparatus but operated at the pilot plant using the actual pilot

  4. Mitochondrial iron metabolism and sideroblastic anemia.

    Science.gov (United States)

    Sheftel, Alex D; Richardson, Des R; Prchal, Josef; Ponka, Prem

    2009-01-01

    Sideroblastic anemias are a heterogeneous group of disorders, characterized by mitochondrial iron overload in developing red blood cells. The unifying characteristic of all sideroblastic anemias is the ring sideroblast, which is a pathological erythroid precursor containing excessive deposits of non-heme iron in mitochondria with perinuclear distribution creating a ring appearance. Sideroblastic anemias may be hereditary or acquired. Hereditary sideroblastic anemias are caused by defects in genes present on the X chromosome (mutations in the ALAS2, ABCB7, or GRLX5 gene), genes on autosomal chromosomes, or mitochondrial genes. Acquired sideroblastic anemias are either primary (refractory anemia with ring sideroblasts, RARS, representing one subtype of the myelodysplastic syndrome) or secondary due to some drugs, toxins, copper deficiency, or chronic neoplastic disease. The pathogenesis of mitochondrial iron loading in developing erythroblasts is diverse. Ring sideroblasts can develop as a result of a heme synthesis defect in erythroblasts (ALAS2 mutations), a defect in iron-sulfur cluster assembly, iron-sulfur protein precursor release from mitochondria (ABCB7 mutations), or by a defect in intracellular iron metabolism in erythroid cells (e.g. RARS).

  5. Supported molybdenum carbide for higher alcohol synthesis from syngas

    DEFF Research Database (Denmark)

    Wu, Qiongxiao; Christensen, Jakob Munkholt; Chiarello, Gian Luca

    2013-01-01

    Molybdenum carbide supported on active carbon, carbon nanotubes, and titanium dioxide, and promoted by K2CO3, has been prepared and tested for methanol and higher alcohol synthesis from syngas. At optimal conditions, the activity and selectivity to alcohols (methanol and higher alcohols) over...... supported molybdenum carbide are significantly higher compared to the bulk carbide. The CO conversion reaches a maximum, when about 20wt% Mo2C is loaded on active carbon. The selectivity to higher alcohols increases with increasing Mo2C loading on active carbon and reaches a maximum over bulk molybdenum...... carbide, while the selectivity to methanol follows the opposite trend. The effect of Mo2C loading on the alcohol selectivity at a fixed K/Mo molar ratio of 0.14 could be related to the amount of K2CO3 actually on the active Mo2C phase and the size, structure and composition of the supported carbide...

  6. Molybdenum sputtering film characterization for high gradient accelerating structures

    Institute of Scientific and Technical Information of China (English)

    S.Bini; B.Spataro; A.Marcelli; S.Sarti; V.A.Dolgashev; S.Tantawi; A.D.Yeremian

    2013-01-01

    Technological advancements are strongly required to fulfill the demands of new accelerator devices with the highest accelerating gradients and operation reliability for the future colliders.To this purpose an extensive R&D regarding molybdenum coatings on copper is in progress.In this contribution we describe chemical composition,deposition quality and resistivity properties of different molybdenum coatings obtained via sputtering.The deposited films are thick metallic disorder layers with different resistivity values above and below the molibdenum dioxide reference value.Chemical and electrical properties of these sputtered coatings have been characterized by Rutherford backscattering,XANES and photoemission spectroscopy.We will also consider multiple cells standing wave section coated by a molybdenum layer designed to improve the performance of X-Band accelerating systems.

  7. Molybdenum chloride catalysts for Z-selective olefin metathesis reactions

    Science.gov (United States)

    Koh, Ming Joo; Nguyen, Thach T.; Lam, Jonathan K.; Torker, Sebastian; Hyvl, Jakub; Schrock, Richard R.; Hoveyda, Amir H.

    2017-01-01

    The development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. The incorporation of appropriate ligands within complexes based on molybdenum, tungsten and ruthenium has led to reactivity and selectivity levels that were previously inaccessible. Here we show that molybdenum monoaryloxide chloride complexes furnish higher-energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis reactions with the commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloroethene and 1,2-dibromoethene can be effected with substantially improved efficiency and Z selectivity. The use of such molybdenum monoaryloxide chloride complexes enables the synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds. The origins of the activity and selectivity levels observed, which contradict previously proposed principles, are elucidated with the aid of density functional theory calculations.

  8. Molybdenum removal from copper ore concentrate by sodium hypochlorite leaching

    Institute of Scientific and Technical Information of China (English)

    Liu Youcai; Zhong Hong; Cao Zhanfang

    2011-01-01

    The removal of molybdenum from a copper ore concentrate by sodium hypochlorite leaching was investigated. The results show that leaching time, liquid to solid ratio, leaching ternperature, agitation speed, and sodium hypochlorite and sodium hydroxide concentrations all have a significant effect on the removal of molybdenum. The optimum process operating parameters were found to be: time, 4 h: sodium hydroxide concentration, 10%; sodium hypochlorite concentration, 8%; liquid to solid ratio, 10:1; temperature, 50℃; and,agitation speed, 500 r/min. Under these conditions the extraction of molybdenum is greater than 99.9% and the extraction of copper is less than 0.01%. A shrinking particle model could be used to describe the leaching process. The apparent activation energy of the dissolution reaction was found to be approximately 8.8 kJ/mol.

  9. Adsorption behavior of molybdenum onto D314 ion exchange resin

    Institute of Scientific and Technical Information of China (English)

    王明玉; 蒋长俊; 王学文

    2014-01-01

    The adsorption behavior of molybdenum onto D314 was studied with the static adsorption method. The adsorption process was analyzed from thermodynamic and kinetic aspects. The experimental results show that the equilibrium adsorption data conform satisfactorily to the Langmuir equation. In the adsorption process of D314 for molybdenum, the enthalpy changeΔH is positive when temperature is in the range of 298−338 K, which indicates that the adsorption is an endothermic process, and the elevated temperature benefits to the adsorption. Kinetic analysis shows that the adsorption rate is controlled by intraparticle diffusion and chemical diffusion at the same time. The adsorption mechanism of molybdenum onto D314 was discussed based on IR spectra.

  10. Molybdenum sputtering film characterization for high gradient accelerating structures

    CERN Document Server

    Bini, S; Marcelli, A; Sarti, S; Dolgashev, V A; Tantawi, S; Yeremian, A D; Higashi, Y; Grimaldi, M G; Romano, L; Ruffino, F; Parodi, R; Cibin, G; Marrelli, C; Migliorati, M; Caliendo, C

    2012-01-01

    Technological advancements are strongly required to fulfill the demands of new accelerator devices with the highest accelerating gradients and operation reliability for the future colliders. To this purpose an extensive R&D regarding molybdenum coatings on copper is in progress. In this contribution we describe chemical composition, deposition quality and resistivity properties of different molybdenum coatings obtained via sputtering. The deposited films are thick metallic disorder layers with different resistivity values above and below the molibdenum dioxide reference value. Chemical and electrical properties of these sputtered coatings have been characterized by Rutherford backscattering, XANES and photoemission spectroscopy. We will also present a three cells standing wave section coated by a molybdenum layer $\\sim$ 500 nm thick designed to improve the performance of X-Band accelerating systems.

  11. The behaviour of molybdenum dialkyldithiocarbamate friction modifier additives

    CERN Document Server

    Graham, J C H

    2001-01-01

    In recent years there has been growing concern to produce energy-efficient lubricated components and modem engine oil specifications require lubricants to demonstrate fuel efficiency in standardised engine tests. One important method of producing low friction and thus fuel-efficient lubricants is to use oil-soluble, molybdenum-containing, friction modifier additives. In optimal conditions these additives are able to produce very low friction coefficients, in the range 0.045 to 0.075 in boundary lubrication conditions. Very little is known about the chemical and physical mechanisms by which oil soluble molybdenum additives form low friction films in tribological contacts. Information about their activity could lead to optimal use of these additives in lubricants and, therefore, more efficient engine running. The work outlined in this thesis investigated the behaviour of oil-soluble molybdenum additives and showed that these additives were able to effectively reduce friction in the absence of other additives su...

  12. Lithium sulfur batteries and electrolytes and sulfur cathodes thereof

    Energy Technology Data Exchange (ETDEWEB)

    Visco, Steven J.; Goncharenko, Nikolay; Nimon, Vitaliy; Petrov, Alexei; Nimon, Yevgeniy S.; De Jonghe, Lutgard C.; Katz, Bruce D.; Loginova, Valentina

    2017-05-23

    Lithium sulfur battery cells that use water as an electrolyte solvent provide significant cost reductions. Electrolytes for the battery cells may include water solvent for maintaining electroactive sulfur species in solution during cell discharge and a sufficient amount of a cycle life-enhancing compound that facilitates charging at the cathode. The combination of these two components enhances one or more of the following cell attributes: energy density, power density and cycle life. For instance, in applications where cost per Watt-Hour (Wh) is paramount, such as grid storage and traction applications, the use of an aqueous electrolyte in combination with inexpensive sulfur as the cathode active material can be a key enabler for the utility and automotive industries, for example, providing a cost effective and compact solution for load leveling, electric vehicles and renewable energy storage. Sulfur cathodes, and methods of fabricating lithium sulfur cells, in particular for loading lithium sulfide into the cathode structures, provide further advantages.

  13. Iron refractory iron deficiency anemia

    OpenAIRE

    De Falco, Luigia; Sanchez, Mayka; Silvestri, Laura; Kannengiesser, Caroline; Muckenthaler, Martina U; Iolascon, Achille; Gouya, Laurent; Camaschella, Clara; Beaumont, Carole

    2013-01-01

    Iron refractory iron deficiency anemia is a hereditary recessive anemia due to a defect in the TMPRSS6 gene encoding Matriptase-2. This protein is a transmembrane serine protease that plays an essential role in down-regulating hepcidin, the key regulator of iron homeostasis. Hallmarks of this disease are microcytic hypochromic anemia, low transferrin saturation and normal/high serum hepcidin values. The anemia appears in the post-natal period, although in some cases it is only diagnosed in ad...

  14. Sulfur in Cometary Dust

    Science.gov (United States)

    Fomenkova, M. N.

    1997-01-01

    The computer-intensive project consisted of the analysis and synthesis of existing data on composition of comet Halley dust particles. The main objective was to obtain a complete inventory of sulfur containing compounds in the comet Halley dust by building upon the existing classification of organic and inorganic compounds and applying a variety of statistical techniques for cluster and cross-correlational analyses. A student hired for this project wrote and tested the software to perform cluster analysis. The following tasks were carried out: (1) selecting the data from existing database for the proposed project; (2) finding access to a standard library of statistical routines for cluster analysis; (3) reformatting the data as necessary for input into the library routines; (4) performing cluster analysis and constructing hierarchical cluster trees using three methods to define the proximity of clusters; (5) presenting the output results in different formats to facilitate the interpretation of the obtained cluster trees; (6) selecting groups of data points common for all three trees as stable clusters. We have also considered the chemistry of sulfur in inorganic compounds.

  15. The Sulfide Capacity of Iron Oxide-Rich Slags

    Science.gov (United States)

    Motlagh, M.

    1988-03-01

    The relationship between the sulfide capacity of slags rich in iron oxide and the sulfur partition ratio between the metal and slag is strongly related to the slag's iron oxide concentration. For slags containing little or no lime, this relationship is linear for a constant concentration of iron oxide in the slag. The effect of silica on changes in the sulfide capacity of slags rich in iron oxide is similar to that of basic steel-making slags, particularly at low activity of silica in slag.

  16. Nitrogen incorporation in sputter deposited molybdenum nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Stöber, Laura, E-mail: laura.stoeber@tuwien.ac.at; Patocka, Florian, E-mail: florian.patocka@tuwien.ac.at; Schneider, Michael, E-mail: michael.schneider@tuwien.ac.at; Schmid, Ulrich, E-mail: ulrich.e366.schmid@tuwien.ac.at [Institute of Sensor and Actuator Systems, TU Wien, Gußhausstraße 27-29, A-1040 Vienna (Austria); Konrath, Jens Peter, E-mail: jenspeter.konrath@infineon.com; Haberl, Verena, E-mail: verena.haberl@infineon.com [Infineon Technologies Austria AG, Siemensstraße 2, 9500 Villach (Austria)

    2016-03-15

    In this paper, the authors report on the high temperature performance of sputter deposited molybdenum (Mo) and molybdenum nitride (Mo{sub 2}N) thin films. Various argon and nitrogen gas compositions are applied for thin film synthetization, and the amount of nitrogen incorporation is determined by Auger measurements. Furthermore, effusion measurements identifying the binding conditions of the nitrogen in the thin film are performed up to 1000 °C. These results are in excellent agreement with film stress and scanning electron microscope analyses, both indicating stable film properties up to annealing temperatures of 500 °C.

  17. Sulfur plant start-up

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, Hank; Grigson, Susan [Ortloff Engineers Ltd. (United States)

    2002-02-01

    The authors discuss an Ortloff sulfur plant design concept using the Claus reaction that differs from accepted 'industry practice': cold reactor bed start-up. The process is designed to eliminate catalyst sulfation, heat damage and furnace overheating in sulfur recovery units. (UK)

  18. Preparation and characterization of molybdenum disilicide coating on molybdenum substrate by air plasma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yi [Key Laboratory of Ministry of Education for Non-ferrous Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals, Central South University, Changsha 410083 (China); School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Dezhi, E-mail: dzwang68@163.com [Key Laboratory of Ministry of Education for Non-ferrous Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals, Central South University, Changsha 410083 (China); School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yan, Jianhui [Advanced Materials Synthesis and Application Technology Laboratory, Hunan University of Science and Technology, Xiangtan 411201 (China); Sun, Aokui [Key Laboratory of Ministry of Education for Non-ferrous Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals, Central South University, Changsha 410083 (China); School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

    2013-11-01

    MoSi{sub 2} oxidation protective coatings on molybdenum substrate were prepared by air plasma spraying technique (APS). Microstructure, phase composition, porosity, microhardness and bonding strength of the coatings were investigated and determined. Oxidation behavior of the coating at high temperature was also examined. Results show that composition of the coatings is constituted with MoSi{sub 2} and Mo{sub 5}Si{sub 3}, the surface morphology is described as flattened lamellar features, insufficiently flattened protuberance with some degree of surface roughness, a certain quantity of spherical particles, microcracks and pores. Testing results reveal that microhardness and bonding strength of the coatings increase, and porosity decreases with increasing power or decreasing Ar gas flow rate. Moreover, with decreasing the porosity, the microhardness of the coatings increases. The bonding strength of the coatings also increases with increasing spray distance. The MoSi{sub 2} coated Mo substrate exhibited a good oxidation resistance at 1200 °C.

  19. Cast irons

    CERN Document Server

    1996-01-01

    Cast iron offers the design engineer a low-cost, high-strength material that can be easily melted and poured into a wide variety of useful, and sometimes complex, shapes. This latest handbook from ASM covers the entire spectrum of one of the most widely used and versatile of all engineered materials. The reader will find the basic, but vital, information on metallurgy, solidification characteristics, and properties. Extensive reviews are presented on the low-alloy gray, ductile, compacted graphite, and malleable irons. New and expanded material has been added covering high-alloy white irons used for abrasion resistance and high-alloy graphitic irons for heat and corrosion resistance. Also discussed are melting furnaces and foundry practices such as melting, inoculation, alloying, pouring, gating and rising, and molding. Heat treating practices including stress relieving, annealing, normalizing, hardening and tempering, autempering (of ductile irons), and surface-hardening treatments are covered, too. ASM Spec...

  20. Assessing Potential Acidification of Marine Archaeological Wood Based on Concentration of Sulfur Species

    Energy Technology Data Exchange (ETDEWEB)

    2011-06-22

    The presence of sulfur in marine archaeological wood presents a challenge to conservation. Upon exposure to oxygen, sulfur compounds in waterlogged wooden artifacts are being oxidized, producing sulfuric acid. This speeds the degradation of the wood, potentially damaging specimens beyond repair. Sulfur K-edge x-ray absorption spectroscopy was used to identify the species of sulfur present in samples from the timbers of the Mary Rose, a preserved 16th century warship known to undergo degradation through acidification. The results presented here show that sulfur content varied significantly on a local scale. Only certain species of sulfur have the potential to produce sulfuric acid by contact with oxygen and seawater in situ, such as iron sulfides and elemental sulfur. Organic sulfurs, such as the amino acids cysteine and methionine, may produce acid but are integral parts of the wood's structure and may not be released from the organic matrix. The sulfur species contained in the sample reflect the exposure to oxygen while submerged, and this exposure can differ greatly over time and position. A better understanding of the species pathway to acidifications required, along with its location, in order to suggest a more customized and effective preservation strategy. Waterlogged archaeological wood, frequently in the form of shipwrecks, is being excavated for historical purposes in many countries around the world. Even after extensive efforts towards preservation, scientists are discovering that accumulation of sulfate salts results in acidic conditions on the surfaces of the artifacts. Sulfuric acid degrades structural fibers in the wood by acid hydrolysis of cellulose, accelerating the decomposition of the ship timbers. Determining the sulfur content of waterlogged wood is now of great importance in maritime archaeology. Artifact preservation is often more time consuming and expensive than the original excavation; but it is key to the availability of objects for

  1. Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

    Science.gov (United States)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

  2. Commercial Alloys for Sulfuric Acid Vaporization in Thermochemical Hydrogen Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Thomas M. Lillo; Karen M. Delezene-Briggs

    2005-10-01

    Most thermochemical cycles being considered for producing hydrogen include a processing stream in which dilute sulfuric acid is concentrated, vaporized and then decomposed over a catalyst. The sulfuric acid vaporizer is exposed to highly aggressive conditions. Liquid sulfuric acid will be present at a concentration of >96 wt% (>90 mol %) H2SO4 and temperatures exceeding 400oC [Brown, et. al, 2003]. The system will also be pressurized, 0.7-3.5 MPa, to keep the sulfuric acid in the liquid state at this temperature and acid concentration. These conditions far exceed those found in the commercial sulfuric acid generation, regeneration and handling industries. Exotic materials, e.g. ceramics, precious metals, clad materials, etc., have been proposed for this application [Wong, et. al., 2005]. However, development time, costs, reliability, safety concerns and/or certification issues plague such solutions and should be considered as relatively long-term, optimum solutions. A more cost-effective (and relatively near-term) solution would be to use commercially-available metallic alloys to demonstrate the cycle and study process variables. However, the corrosion behavior of commercial alloys in sulfuric acid is rarely characterized above the natural boiling point of concentrated sulfuric acid (~250oC at 1 atm). Therefore a screening study was undertaken to evaluate the suitability of various commercial alloys for concentration and vaporization of high-temperature sulfuric acid. Initially alloys were subjected to static corrosion tests in concentrated sulfuric acid (~95-97% H2SO4) at temperatures and exposure times up to 200oC and 480 hours, respectively. Alloys with a corrosion rate of less than 5 mm/year were then subjected to static corrosion tests at a pressure of 1.4 MPa and temperatures up to 375oC. Exposure times were shorter due to safety concerns and ranged from as short as 5 hours up to 144 hours. The materials evaluated included nickel-, iron- and cobalt

  3. Corrosion Evaluation of RERTR Uranium Molybdenum Fuel

    Energy Technology Data Exchange (ETDEWEB)

    A K Wertsching

    2012-09-01

    As part of the National Nuclear Security Agency (NNSA) mandate to replace the use of highly enriched uranium (HEU) fuel for low enriched uranium (LEU) fuel, research into the development of LEU fuel for research reactors has been active since the late 1970’s. Originally referred to as the Reduced Enrichment for Research and Test Reactor (RERTR) program the new effort named Global Threat Reduction Initiative (GTRI) is nearing the goal of replacing the standard aluminum clad dispersion highly enriched uranium aluminide fuel with a new LEU fuel. The five domestic high performance research reactors undergoing this conversion are High Flux Isotope reactor (HFIR), Advanced Test Reactor (ATR), National Institute of Standards and Technology (NIST) Reactor, Missouri University Research Reactor (MURR) and the Massachusetts Institute of Technology Reactor II (MITR-II). The design of these reactors requires a higher neutron flux than other international research reactors, which to this point has posed unique challenges in the design and development of the new mandated LEU fuel. The new design utilizes a monolithic fuel configuration in order to obtain sufficient 235U within the LEU stoichoimetry to maintain the fission reaction within the domestic test reactors. The change from uranium aluminide dispersion fuel type to uranium molybdenum (UMo) monolithic configuration requires examination of possible corrosion issues associated with the new fuel meat. A focused analysis of the UMo fuel under potential corrosion conditions, within the ATR and under aqueous storage indicates a slow and predictable corrosion rate. Additional corrosion testing is recommended for the highest burn-up fuels to confirm observed corrosion rate trends. This corrosion analysis will focus only on the UMo fuel and will address corrosion of ancillary components such as cladding only in terms of how it affects the fuel. The calculations and corrosion scenarios are weighted with a conservative bias to

  4. Test methodology for elemental sulfur resistant advanced materials for oil and gas field equipment

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, G. [Verein Deutscher Eisenhuettenleute, Duesseldorf (Germany); Bruckhoff, W. [BEB Erdgas und Erdoel GmbH, Hannover (Germany); Koehler, M. [Krupp-VDM AG, Werdohl (Germany); Schlerkmann, H. [Mannesmann Forschungsinstitut, Duisburg (Germany); Schmitt, G. [Iserlohn Polytechnic (Germany). Lab. for Corrosion Protection

    1995-10-01

    The great variety of methodologies for testing the performance of advanced materials for resistance to elemental sulfur in oil and gas industry prompted the Technical Committee for Corrosion of the German Iron and Steel Institute (VDEh) to define recommended test procedures. These procedures have already found wide acceptance in the German materials and oil and gas industry.

  5. Effects of aerobic-anaerobic transient conditions on sulfur and metal cycles in sewer biofilms

    NARCIS (Netherlands)

    Nielsen, A.; Lens, P.N.L.; Vollertsen, J.; Hvitved-Jacobsen, Th.

    2005-01-01

    Interactions between sulfur and metals were studied in aerobic and anaerobic biofilms grown on domestic waste water at 15°C. The dominant metals in the waste water were iron, zinc and copper, which were present in average concentrations of 0.5mg/l, 0.6mg/l and 0.1m/l, respectively. Copper and zinc

  6. Reductive Dechlorination of Trichloroethene by Zero-valent Iron Nanoparticles: Reactivity Enhancement through Sulfidation Treatment.

    Science.gov (United States)

    Han, Yanlai; Yan, Weile

    2016-12-06

    Zero-valent iron nanoparticles (nZVI) synthesized in the presence of reduced sulfur compounds have been shown to degrade trichloroethene (TCE) at significantly higher rates. However, the applicability of sulfidation as a general means to enhance nZVI reactivity under different particle preparation conditions and the underlying cause for this enhancement effect are not well understood. In this study, the effects of sulfidation reagent, time point of sulfidation, and sulfur loading on the resultant particles were assessed through TCE degradation experiments. Up to 60-fold increase in TCE reaction rates was observed upon sulfidation treatment, with products being fully dechlorinated hydrocarbons. While the reactivity of these sulfur-treated nZVI (S-nZVI) was relatively unaffected by the sulfidation reagent (viz., sodium sulfide, dithionite, or thiosulfate) or the sequence of sulfidation relative to iron reduction, TCE reaction rates were found to depend strongly on sulfur to iron ratio. At a low sulfur loading, TCE degradation was accelerated with increasing sulfur dose. The rate constant reached a limiting value, however, as the sulfur to iron mole ratio was greater than 0.025. Different from previous propositions that iron sulfidation leads to more efficient TCE or tetrachloroethene (PCE) degradation by enabling depassivation of iron surface, affording catalytic pathways, or facilitating electron transfer, we show that the role of sulfur in nZVI lies essentially in its ability to poison hydrogen recombination, which drives surface reactions to favor reduction by atomic hydrogen. This implies that the reactivity of S-nZVI is contaminant-specific and is selective against the background reaction of water reduction. As the effect of sulfur manifests through surface processes, sulfidation represents a broadly applicable surface modification approach to modulate or increase the reactivity of nZVI for treating TCE and other related contaminants.

  7. Top-Down Integration of Molybdenum Disulfide Transistors with Wafer-Scale Uniformity and Layer Controllability.

    Science.gov (United States)

    Shi, Mao-Lin; Chen, Lin; Zhang, Tian-Bao; Xu, Jing; Zhu, Hao; Sun, Qing-Qing; Zhang, David Wei

    2017-09-01

    The lack of stable and efficient techniques to synthesize high-quality large-area thin films is one of the major bottlenecks for the real-world application of the 2D transition metal dichalcogenides. In this work, the growth of molybdenum disulfide (MoS2 ) on sapphire substrates by sulfurizing the MoO3 film deposited by atomic layer deposition (ALD) is reported. The advantages of the ALD method can be well inherited, and the synthesized MoS2 films exhibit excellent layer controllability, wafer-scale uniformity, and homogeneity. MoS2 films with desired thickness can be obtained by varying MoO3 ALD cycles. The atomic force microscope and Raman measurements demonstrate that the ALD-based MoS2 has good uniformity. Clear Raman shift as a function of the film thickness is observed. Field-effect transistor devices are fabricated through a transfer-free and top-down process. High On/Off current ratio (≈10(4) ) and medium-level electron mobilities (≈0.76 cm(2) V(-1) s(-1) for monolayer, and 5.9 cm(2) V(-1) s(-1) for four-layer) are obtained. The work opens up an attractive approach to realize the application of wafer-scale 2D materials in integrated circuits and systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Molybdenum isotope composition from Yangtze block continental margin and its indication to organic burial rate

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lian; HUANG Junhua; Corey Archer; Chris Hawkesworth

    2007-01-01

    The paper presents the molybdenum isotope data,along with the trace element content,to investigate the geochemical behavior of authigenic Mo during long-term burial in sediments in continental margin settings of the Yangtze block,as well as their indication to the burial of original organic carbon.The burial rate of original organic carbon was estimated on the basis of the amount of sedimentary sulfur (TS content),whilst the carbon loss by aerobic degradation was estimated according to calculated Mn contents.On these points,the original organic carbon flux was calculated,exhibiting a large range of variation (0.17-0.67mmol/m2/day).The strong correlation between sedimentary Mo isotope values and organic carbon burial rates previously proposed on the basis of the investigations on modern ocean sediments,was also used here to estimate the organic carbon burial rate.The data gained through this model showed that organic carbon burial rates have large variations,ranging from 0.43-2.87 mmol/m2/day.Although the two sets of data gained through different geochemical records in the Yangtze block show a deviation of one order of magnitude,they do display a strong correlation.It is thus tempting to speculate that the Mo isotope signature of sediments may serve as a tracer for the accumulation rate of original organic carbon in the continental margin sediments.

  9. The influence of molybdenum disulfide nanoplatelets on the dispersion of nano silica in natural rubber composites

    Science.gov (United States)

    Weng, Peijin; Wei, Qiuyan; Tang, Zhenghai; Lin, Tengfei; Guo, Baochun

    2015-12-01

    The dispersion of nanofiller in polymer composites is critical in governing the ultimate performances. Present study aimed to improve the dispersion of silica in elastomeric materials based on natural rubber (NR) composites using the nanoplatelets of molybdenum disulfide (MoS2), a graphene-like layered inorganic. NR latex was co-coagulated with MoS2 suspension to form NR/MoS2 compounds (1∼5 phr). Then silica (30 phr) was incorporated into NR/MoS2 compounds, followed by curing with sulfur, to obtained NR/MoS2/silica composites. The dispersion state of silica in the composites was examined by TEM and the effects of MoS2 on the performance of the composites were investigated. It was found that a small amount of MoS2 nanoplatelets significantly improved the silica dispersion. Consequently, the static and dynamic mechanical properties of the crosslinked natural rubber materials were greatly enhanced. The improved dispersion of silica is associated with charge transfer interaction, giving rise to electrostatic repulsion among silica.

  10. REDOX CHEMISTRY OF MOLYBDENUM IN NATURAL WATERS AND ITS INVOLVEMENT IN BIOLOGICAL EVOLUTION

    Directory of Open Access Journals (Sweden)

    Deli eWang

    2012-12-01

    Full Text Available The transition element molybdenum (Mo possesses diverse valances (+II to +VI, and is involved in forming cofactors in more than 60 enzymes in biology. Redox switching of the element in these enzymes catalyzes a series of metabolic reactions in both prokaryotes and eukaryotes, and the element therefore plays a fundamental role in the global carbon, nitrogen, and sulfur cycling. In the present oxygenated waters, oxidized Mo(VI predominates thermodynamically, whilst reduced Mo species are mainly confined within specific niches including cytoplasm. Only recently has the reduced Mo(V been separated from Mo(VI in sulfidic mats and even in some reducing waters. Given the presence of reduced Mo(V in contemporary anaerobic habitats, it seems that reduced Mo species were present in the ancient reducing ocean (probably under both ferrigenous and sulfidic conditions, prompting the involvement of Mo in enzymes including nitrogenase and nitrate reductase. During the global transition to oxic conditions, reduced Mo species were constrained to specific anaerobic habitats, and efficient uptake systems of oxidized Mo(VI became a selective advantage both for prokaryotic and eukaryotic cells. Some prokaryotes are still able to directly utilize reduced Mo if any exists in ambient environments. In total, this mini-review describes the redox chemistry and biogeochemistry of Mo over the Earth’s history.

  11. HYBRID SULFUR RECOVERY PROCESS FOR NATURAL GAS UPGRADING

    Energy Technology Data Exchange (ETDEWEB)

    Girish Srinivas; Steven C. Gebhard; David W. DeBerry

    2002-04-01

    This first quarter report of 2002 describes progress on a project funded by the U.S. Department of Energy (DOE) to test a hybrid sulfur recovery process for natural gas upgrading. The process concept represents a low cost option for direct treatment of natural gas streams to remove H{sub 2}S in quantities equivalent to 0.2-25 metric tons (LT) of sulfur per day. This process is projected to have lower capital and operating costs than the competing technologies, amine/aqueous iron liquid redox and amine/Claus/tail gas treating, and have a smaller plant footprint, making it well suited to both on-shore and offshore applications. CrystaSulf{sup SM} (service mark of CrystaTech, Inc.) is a new nonaqueous sulfur recovery process that removes hydrogen sulfide (H{sub 2}S) from gas streams and converts it into elemental sulfur. CrystaSulf features high sulfur recovery similar to aqueous-iron liquid redox sulfur recovery processes, but differs from the aqueous processes in that CrystaSulf controls the location where elemental sulfur particles are formed. In the hybrid process, approximately 1/3 of the total H{sub 2}S in the natural gas is first oxidized to SO{sub 2} at low temperatures over a heterogeneous catalyst. Low temperature oxidation is done so that the H{sub 2}S can be oxidized in the presence of methane and other hydrocarbons without oxidation of the hydrocarbons. The project involves the development of a catalyst using laboratory/bench-scale catalyst testing, and then demonstration of the catalyst at CrystaTech's pilot plant in west Texas. In a previous reporting period tests were done to determine the effect of hydrocarbons such as n-hexane on catalyst performance with and without H{sub 2}S present. The experiments showed that hexane oxidation is suppressed when H{sub 2}S is present. Hexane represents the most reactive of the C1 to C6 series of alkanes. Since hexane exhibits low reactivity under H{sub 2}S oxidation conditions, and more importantly, does not

  12. Directional uv photoemission from (100) and (110) molybdenum surfaces

    DEFF Research Database (Denmark)

    Cinti, R. C.; Khoury, E. Al; Chakraverty, B. K.;

    1976-01-01

    A study of the (100) and (110) molybdenum surfaces by directional photoemission spectroscopy is presented. Energy distribution spectra formed by photoelectrons emitted normal to the surfaces have been measured for photon energies between 10.2 and 21.2 eV. The results are discussed in terms of cal...

  13. Molybdenum incorporation in tungsten aldehyde oxidoreductase enzymes from Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M; Bevers, L.E.; Pinkse, M.W.H.; Krijger, G.C.; Wolterbeek, H.T.; Verhaert, P.D.E.M.; Hagen, W.R.; Hagedoorn, P.L.

    2010-01-01

    The hyperthermophilic archaeon Pyrococcus furiosus expresses five aldehyde oxidoreductase (AOR) enzymes, all containing a tungsto-bispterin cofactor. The growth of this organism is fully dependent on the presence of tungsten in the growth medium. Previous studies have suggested that molybdenum is no

  14. Femtosecond laser surface structuring of molybdenum thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: Kotsedi@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Mthunzi, P. [Council for Scientific and Industrial Research (CSIR), Biophotonics Lab: National Laser Centre Pretoria, 0001 (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Itala (Italy); Sechoghela, P.; Mongwaketsi, N. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa); Ramponi, R. [Institute for Photonics and Nanotechnologies (IFN)–CNR, Piazza Leanardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province (South Africa)

    2015-10-30

    Highlights: • Color change of the molybdenum thin film from shinny to violet–yellowish color after laser irradiation at various laser powers. • Formation of the molybdenum dioxide coating after laser exposure, as confirmed by the X-ray diffraction spectrometry. • Selective solar absorbing nature of the laser exposed films. • Study of the binding energies is presented in this contribution using the XPS spectrometry. - Abstract: This contribution reports on the femtosecond surface structuring of molybdenum thin coatings deposited by electron beam evaporation onto Corning glass substrates. The 1-D type periodic grating lines created by such an ablation showed that the widths of the shallow grooves followed a logarithmic dependence with the laser energy incident on the molybdenum film. The electronic valence “x” of the created oxide surface layer MoO{sub x} was found to be incident laser power dependent via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction investigations. Such a photo-induced MoO{sub x}–Mo nanocomposite exhibited effective selective solar absorption in the UV–vis–IR spectral range.

  15. GEMAS: Molybdenum Spatial Distribution Patterns in European Soil

    Science.gov (United States)

    Cicchella, Domenico; Zuzolo, Daniela; Demetriades, Alecos; De Vivo, Benedetto; Eklund, Mikael; Ladenberger, Anna; Negrel, Philippe; O'Connor, Patrick

    2017-04-01

    Molybdenum is an essential trace element for both plants and animals as well as for human being. It is one such trace element for which potential health concerns have been raised but for which few data exist and little investigation or interpretation of distributions in soils has been made. The main goal of this study was to fill this gap. Molybdenum (Mo) concentrations are reported for the governed by geology (parent material and mineralisation), as well as weathering, soil formation and climate since the last glaciations period. The dominant feature is represented by low Mo concentrations over the coarse-grained sandy deposits of the last glaciations in central northern Europe while the most extensive anomalies occur in Scandinavian soils. The highest Mo concentration value occurs to the North of Oslo close to one of the largest porphyry Mo deposit of the World. Some interesting anomalous patterns occur also in Italy in correspondence with alkaline volcanics, in Spain and Greece associated with sulfides mineralizations and in Slovenia and Croatia where are probably related to the long weathering history of karstic residual soils. Anomalous concentrations in some areas of Ireland represent a clear example of how an excess of molybdenum has produced potentially toxic pastures. In fact, these give rise to problems particularly in young cattle when excess molybdenum in the herbage acts as an antagonist, which militates against efficient copper absorption by the animal.

  16. Molybdenum incorporation in tungsten aldehyde oxidoreductase enzymes from Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M; Bevers, L.E.; Pinkse, M.W.H.; Krijger, G.C.; Wolterbeek, H.T.; Verhaert, P.D.E.M.; Hagen, W.R.; Hagedoorn, P.L.

    2010-01-01

    The hyperthermophilic archaeon Pyrococcus furiosus expresses five aldehyde oxidoreductase (AOR) enzymes, all containing a tungsto-bispterin cofactor. The growth of this organism is fully dependent on the presence of tungsten in the growth medium. Previous studies have suggested that molybdenum is no

  17. Flexible Molybdenum Electrodes towards Designing Affinity Based Protein Biosensors.

    Science.gov (United States)

    Kamakoti, Vikramshankar; Panneer Selvam, Anjan; Radha Shanmugam, Nandhinee; Muthukumar, Sriram; Prasad, Shalini

    2016-07-18

    Molybdenum electrode based flexible biosensor on porous polyamide substrates has been fabricated and tested for its functionality as a protein affinity based biosensor. The biosensor performance was evaluated using a key cardiac biomarker; cardiac Troponin-I (cTnI). Molybdenum is a transition metal and demonstrates electrochemical behavior upon interaction with an electrolyte. We have leveraged this property of molybdenum for designing an affinity based biosensor using electrochemical impedance spectroscopy. We have evaluated the feasibility of detection of cTnI in phosphate-buffered saline (PBS) and human serum (HS) by measuring impedance changes over a frequency window from 100 mHz to 1 MHz. Increasing changes to the measured impedance was correlated to the increased dose of cTnI molecules binding to the cTnI antibody functionalized molybdenum surface. We achieved cTnI detection limit of 10 pg/mL in PBS and 1 ng/mL in HS medium. The use of flexible substrates for designing the biosensor demonstrates promise for integration with a large-scale batch manufacturing process.

  18. Research on the effect of phosphorus and molybdenum applications ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-05-02

    May 2, 2008 ... applications on the yield and yield parameters in lentil ... and from 6 g/kg seed molybdenum with 1231 kg ha-1 in the first year, the values were 80 kg ha-1 P with ... easier for the plant to benefit from the other nutritional.

  19. Preparation of isotopic molybdenum foils utilizing small quantities of material

    Science.gov (United States)

    Lipski, A. R.; Lee, L. L.; Liang, J. F.; Mahon, J. C.

    1993-09-01

    A simple method utilizing a small amount of isotopic material for production of molybdenum foils is discussed. An e-gun is used in the procedure. The Mo powder undergoes reduction-sintering and melting-solidifying steps leading to the creation of a metallic droplet suitable for further cold rolling or vacuum deposition.

  20. Synthesis and characterization of molybdenum incorporated mesoporous aluminophosphate

    Science.gov (United States)

    Ho, Li-Ngee; Ikegawa, Tasuku; Nishiguchi, Hiroyasu; Nagaoka, Katsutoshi; Takita, Yusaku

    2006-07-01

    A synthesis of molybdenum incorporated mesoporous aluminophosphate with long-chain n-alkylamine as template material had been prepared under non-aqueous condition. These materials were extensively characterized by using X-ray diffraction (XRD), nitrogen sorption isotherms, nuclear magnetic resonance of 27Al and 31P (NMR), inductive coupled plasma (ICP), electron spin resonance (ESR), Fourier transform infrared (FTIR) and thermogravimetric-differential thermal analysis (TG-DTA). Morphology of the materials had been observed by using transmission electron microscope (TEM) that revealed the mesoporous materials possessed wormhole-like structures. Alkaline solvent extraction using n-butylamine/ethanol had been efficiently removed the n-alkylamine from the mesoporous samples which yielded BET surface areas around 550-730 m 2/g. BJH analysis showed a narrow pore size distribution which increased with increasing of the carbon chain length of alkylamine (template). Valence state and coordination of the molybdenum in the obtained samples were investigated by using ESR and FTIR where it was found that Mo 4+ and Mo 6+ molybdenum species existed in the molybdenum incorporated mesoporous aluminophosphate in tetrahedral coordination.

  1. Sulfur cycling of intertidal Wadden Sea sediments (Konigshafen, Island of Sylt, Germany): sulfate reduction and sulfur gas emission

    Science.gov (United States)

    Kristensen, E.; Bodenbender, J.; Jensen, M. H.; Rennenberg, H.; Jensen, K. M.

    2000-05-01

    Sulfate reduction rates (SRR t) and reduced inorganic sulfur pools (RIS) in Wadden Sea sediment as well as sulfur gas emissions directly to the atmosphere were measured at intervals of 2 to 12 months from 1991 to 1994. Three stations were chosen in the intertidal embayment, Königshafen, representing the range of sediments found in the Wadden Sea: Organic-poor coarse sand, organic-poor and Arenicola marina inhabited medium sand, and organic-rich muddy sand. Maximum SRR t were 2 to 5 times higher in muddy sand than in the sandy sediments. The depth-integrated SRR t varied 12 to 13-fold on a seasonal basis at the three stations. Although temperature controls biochemical processes, the overall control is more complex due to the simultaneous influence of other seasonal factors such as availability of organic matter and oxidation level of surface sediment. The sedimentary RIS pools were low due to iron limitation and contained only 30% acid volatile sulfur (AVS). Muddy sand had up to an order of magnitude more RIS than the two sandy sediments. The turnover of RIS was rapid (turnover time from ˜1 to 32 h), fastest during summer and at the sandy stations. The emission of S-gases was dominated by H 2S during summer (45-67% of the total), and was highest in muddy and lowest in coarse sand. H 2S was less important in early spring (3-49% of the total). Other sulfur gases, such as COS, DMS and CS 2, each accounted for less than 20% of the total sulfur emissions with no specific temporal and spatial pattern. Due to the low content of metals in the sediment, the reduced sulfur pools are cycled rapidly with chemical and biological reoxidation at oxic-anoxic boundaries as a major sink. Thus, the emissions of H 2S account for less than 1‰ of the sulfide produced.

  2. Fossilization of melanosomes via sulfurization.

    Science.gov (United States)

    McNamara, Maria E; van Dongen, Bart E; Lockyer, Nick P; Bull, Ian D; Orr, Patrick J

    2016-05-01

    Fossil melanin granules (melanosomes) are an important resource for inferring the evolutionary history of colour and its functions in animals. The taphonomy of melanin and melanosomes, however, is incompletely understood. In particular, the chemical processes responsible for melanosome preservation have not been investigated. As a result, the origins of sulfur-bearing compounds in fossil melanosomes are difficult to resolve. This has implications for interpretations of original colour in fossils based on potential sulfur-rich phaeomelanosomes. Here we use pyrolysis gas chromatography mass spectrometry (Py-GCMS), fourier transform infrared spectroscopy (FTIR) and time of flight secondary ion mass spectrometry (ToF-SIMS) to assess the mode of preservation of fossil microstructures, confirmed as melanosomes based on the presence of melanin, preserved in frogs from the Late Miocene Libros biota (NE Spain). Our results reveal a high abundance of organosulfur compounds and non-sulfurized fatty acid methyl esters in both the fossil tissues and host sediment; chemical signatures in the fossil tissues are inconsistent with preservation of phaeomelanin. Our results reflect preservation via the diagenetic incorporation of sulfur, i.e. sulfurization (natural vulcanization), and other polymerization processes. Organosulfur compounds and/or elevated concentrations of sulfur have been reported from melanosomes preserved in various invertebrate and vertebrate fossils and depositional settings, suggesting that preservation through sulfurization is likely to be widespread. Future studies of sulfur-rich fossil melanosomes require that the geochemistry of the host sediment is tested for evidence of sulfurization in order to constrain interpretations of potential phaeomelanosomes and thus of original integumentary colour in fossils.

  3. Sulfur cycling and metabolism of phototrophic and filamentous sulfur bacteria

    Science.gov (United States)

    Guerrero, R.; Brune, D.; Poplawski, R.; Schmidt, T. M.

    1985-01-01

    Phototrophic sulfur bacteria taken from different habitate (Alum Rock State Park, Palo Alto salt marsh, and Big Soda Lake) were grown on selective media, characterized by morphological and pigment analysis, and compared with bacteria maintained in pure culture. A study was made of the anaerobic reduction of intracellular sulfur globules by a phototrophic sulfur bacterium (Chromatium vinosum) and a filamentous aerobic sulfur bacterium (Beggiatoa alba). Buoyant densities of different bacteria were measured in Percoll gradients. This method was also used to separate different chlorobia in mixed cultures and to assess the relative homogeneity of cultures taken directly or enriched from natural samples (including the purple bacterial layer found at a depth of 20 meters at Big Soda Lake.) Interactions between sulfide oxidizing bacteria were studied.

  4. 杂质元素对钼丝力学性能和显微组织的影响%EFFECT OF IMPURITY ELEMENTS ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF MOLYBDENUM WIRE

    Institute of Scientific and Technical Information of China (English)

    张菊平; 付小俊

    2015-01-01

    Molybdenum wire(φ0.18 mm) was produced by the same pressing,sintering,rotary swaging and drawing process from molybdenum powder with different impurity elements ( Fe、Ni、C、O ) .And microscopic structure and mechanical properties of the molybdenum wire were compared.Results have shown that with the reduction of impu-rity elements, graln boundaries will be significantly purified and narrowed, then to help improve molybdenum metal plasticity and formability;When the oxygen content is reduced from 2100 mg/kg to 580 mg/kg, molybdenum wire rotary forging yield would be increased by 57 .2%.When the content of iron and nickel was reduced , the elongation of the finished molybdenum wire would be increased by 0.51%at room temperature.%在相同的制备工艺(压制、烧结、旋锻、拉拔)下,采用碳、氧、铁、镍元素含量不同的钼粉分别制备出两种φ0.18 mm的钼丝,对其成形过程和成品的显微组织和力学性能进行分析对比。结果表明,杂质元素含量降低,将显著净化晶界和窄化晶界,进而有助于提高钼金属的塑性和成形性;当氧含量由2100 mg/kg降低到580 mg/kg时,钼丝的旋锻成品率提高57.2%;当铁、镍含量降低时,成品钼丝的室温延伸率提高0.51%。

  5. Redox Transformations of Iron at Extremely Low pH: Fundamental and Applied Aspects

    Science.gov (United States)

    Johnson, D. Barrie; Kanao, Tadayoshi; Hedrich, Sabrina

    2012-01-01

    Many different species of acidophilic prokaryotes, widely distributed within the domains Bacteria and Archaea, can catalyze the dissimilatory oxidation of ferrous iron or reduction of ferric iron, or can do both. Microbially mediated cycling of iron in extremely acidic environments (pH iron and far greater solubility of ferric iron under such conditions. Cycling of iron has been demonstrated in vitro using both pure and mixed cultures of acidophiles, and there is considerable evidence that active cycling of iron occurs in acid mine drainage streams, pit lakes, and iron-rich acidic rivers, such as the Rio Tinto. Measurements of specific rates of iron oxidation and reduction by acidophilic microorganisms show that different species vary in their capacities for iron oxido-reduction, and that this is influenced by the electron donor provided and growth conditions used. These measurements, and comparison with corresponding data for oxidation of reduced sulfur compounds, also help explain why ferrous iron is usually used preferentially as an electron donor by acidophiles that can oxidize both iron and sulfur, even though the energy yield from oxidizing iron is much smaller than that available from sulfur oxidation. Iron-oxidizing acidophiles have been used in biomining (a technology that harness their abilities to accelerate the oxidative dissolution of sulfidic minerals and thereby facilitate the extraction of precious and base metals) for several decades. More recently they have also been used to simultaneously remediate iron-contaminated surface and ground waters and produce a useful mineral by-product (schwertmannite). Bioprocessing of oxidized mineral ores using acidophiles that catalyze the reductive dissolution of ferric iron minerals such as goethite has also recently been demonstrated, and new biomining technologies based on this approach are being developed. PMID:22438853

  6. Redox transformations of iron at extremely low pH: fundamental and applied aspects

    Directory of Open Access Journals (Sweden)

    D. Barrie eJohnson

    2012-03-01

    Full Text Available Many different species of acidophilic prokaryotes, widely distributed within the domains Bacteria and Archaea, can catalyze the dissimilatory oxidation of ferrous iron or reduction of ferric iron, or can do both. Microbially-mediated cycling of iron in extremely acidic environments (pH <3 is strongly influenced by the enhanced chemical stability of ferrous iron and far greater solubility of ferric iron under such conditions. Cycling of iron has been demonstrated in vitro using both pure and mixed cultures of acidophiles, and there is considerable evidence that active cycling of iron occurs in acid mine drainage streams, pit lakes and iron-rich acidic rivers, such as the Rio Tinto. Measurements of specific rates of iron oxidation and reduction by acidophilic microorganisms show that different species vary in their capacities for iron oxido-reduction, and that this is influenced by the electron donor provided and growth conditions used. These measurements, and comparison with corresponding data for oxidation of reduced sulfur compounds, also help explain why ferrous iron is usually used preferentially as an electron donor by acidophiles that can oxidize both iron and sulfur, even though the energy yield from oxidizing iron is much smaller than that available from sulfur oxidation. Iron-oxidizing acidophiles have been used in biomining (a technology that harness their abilities to accelerate the oxidative dissolution of sulfidic minerals and thereby facilitate the extraction of precious and base metals for several decades. More recently they have also been used to simultaneously remediate iron-contaminated surface and ground-waters and produce a useful mineral by-product (schwertmannite. Bioprocessing of oxidized mineral ores using acidophiles that bring about the reductive dissolution of ferric iron minerals such as goethite has also recently been demonstrated, and new biomining technologies based on this approach are being developed.

  7. Mössbauer study of the inorganic sulfur removal from coals

    Science.gov (United States)

    Reyes Caballero, F.; Martínez Ovalle, S. A.

    2014-01-01

    Mössbauer Spectroscopy (MS) was applied to study the occurrence and behavior of the iron-sulfur-containing minerals in coal and coal fractions obtained by different separation methods: hydrocyclonic, flotation and chemical removal process. Samples of one high sulfur coal from Guachinte mine (Valle, Colombia) and three low sulfur coals from the El Salitre zone (Paipa-Boyacá, Colombia) were analyzed. MS evidenced only the presence of pyrite in Esmeralda and Las Casitas coals, while it identified pyrite and siderite on Cerezo coal. MS and SEM- EDX confirm the inorganic sulfur removal on Guachinte coal submitted to hydrocyclonic removal process. MS of the precipitated coal fraction from Las Casitas mine obtained by flotation in water showed the presence of ferrous sulfate because of coal-weathering process. Treatment with hot diluted HNO3 equal to 27 acid on raw coal sample from Las Casitas mine showed that almost all of the pyrite in raw coal was removed.

  8. Method of preparing graphene-sulfur nanocomposites for rechargeable lithium-sulfur battery electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jun; Lemmon, John P; Yang, Zhenguo; Cao, Yuliang; Li, Xiaolin

    2015-04-07

    A method of preparing a graphene-sulfur nanocomposite for a cathode in a rechargeable lithium-sulfur battery comprising thermally expanding graphite oxide to yield graphene layers, mixing the graphene layers with a first solution comprising sulfur and carbon disulfide, evaporating the carbon disulfide to yield a solid nanocomposite, and grinding the solid nanocomposite to yield the graphene-sulfur nanocomposite. Rechargeable-lithium-sulfur batteries having a cathode that includes a graphene-sulfur nanocomposite can exhibit improved characteristics. The graphene-sulfur nanocomposite can be characterized by graphene sheets with particles of sulfur adsorbed to the graphene sheets. The sulfur particles have an average diameter of less than 50 nm.

  9. Photomixotrophic growth of Rhodobacter capsulatus SB1003 on ferrous iron

    OpenAIRE

    Kopf, Sebastian H.; Newman, Dianne K.

    2011-01-01

    This study investigates the role iron oxidation plays in the purple non-sulfur bacterium Rhodobacter capsulatus SB1003. This organism is unable to grow photoautotrophically on unchelated ferrous iron [Fe(II)] despite its ability to oxidize chelated Fe(II). This apparent paradox was partly resolved by the discovery that SB1003 can grow photoheterotrophically on the photochemical breakdown products of certain ferric iron–ligand complexes, yet whether it could concomitantly benefit from the oxid...

  10. Novel synthetic route to molybdenum hydrido-thiocarbamoyl and hydrosulfido-carbyne complexes by reactions of trans-Mo(N{sub 2}){sub 2}(R{sub 2}PC{sub 2}H{sub 4}PR{sub 2}){sub 2} with N,N-dimethylthioformamide

    Energy Technology Data Exchange (ETDEWEB)

    Luo, X.L.; Kubas, G.J.; Burns, C.J.; Butcher, R.J. [Los Alamos National Lab., NM (United States)

    1995-07-01

    The reactions of bis(dinitrogen)molybdenum complexes trans-Mo(N{sub 2}){sub 2}(R{sub 2}PC{sub 2}H{sub 4}PR{sub 2}){sub 2} (R = Ph, Et) with N,N-dimethylthioformamide (HC(S)NMe{sub 2}) in refluxing benzene under argon give the molybdenum hydrido-thiocarbamoyl complexes MoH({eta}{sup 2}-C(S)NMe{sub 2})(R{sub 2}PC{sub 2}H{sub 4}PR{sub 2}){sub 2} (R = Ph (1a), Et (1b)). On heating at 125{degree}C in toluene solutions, compounds 1a and 1b rearrange to form the molybdenum hydrosulfido-aminocarbyne complexes trans-Mo(SH)-(=CNMe{sub 2})(R{sub 2}PC{sub 2}H{sub 4}PR{sub 2}){sub 2} (R = Ph (2a), Et (2b)). A mechanism is proposed for this thermal rearrangement which involves migration of the hydride ligand from molybdenum to the sulfur atom of the thiocarbamoyl ligand to give the 16-electron Fischer carbene intermediate Mo-(=C(SH)NMe{sub 2})(R{sub 2}PC{sub 2}H{sub 4}PR{sub 2}){sub 2}, followed by migration of the hydrosulfido group from the carbene carbon to molybdenum. The molecular structures of compounds 1a and 2a have been determined by single-crystal X-ray diffraction studies. 30 refs., 4 figs., 4 tabs.

  11. Lowering Global Temperature by Enhancing the Natural Sulfur Cycle

    Science.gov (United States)

    Wingenter, O. W.; Elliot, S. M.; Blake, D. R.

    2007-12-01

    We describe a well leveraged approach to partially regulate climate using limited iron enhancement to stimulate the natural sulfur cycle resulting in increased cloud reflectivity that could cool large regions of our planet. Our plan differs greatly in size and intended outcome from full scale ocean iron fertilization of the Southern Ocean (SO) as proposed previously to help mitigate rising CO2 in the atmosphere. Some regions of the Earth's oceans are high in nutrients but low in primary productivity. The largest such region is the SO followed by the equatorial Pacific. Several mesoscale (100 km2) experiments have shown that the limiting nutrient to productivity is iron. Yet, the effectiveness of iron fertilization for sequestering significant amounts of atmospheric CO2 is still in question. However, marine microorganisms not only consume inorganic carbon but also produce and consume many climate relevant organic gases. The greatest climate effect of iron fertilization may be in enhancing dimethyl sulfide (DMS) production, leading to changes in the optical properties of the atmosphere and cooling of the region. It appears that that full scale fertilization of the SO is not a viable solution because it would lead to over cooling of the region. Furthermore, our initial proposal differs from other solar shading plans as primary productivity may actually increase somewhat despite the slight loss in sunlight.

  12. METABOLISM OF IRON STORES

    OpenAIRE

    Saito, Hiroshi

    2014-01-01

    ABSTRACT Remarkable progress was recently achieved in the studies on molecular regulators of iron metabolism. Among the main regulators, storage iron, iron absorption, erythropoiesis and hepcidin interact in keeping iron homeostasis. Diseases with gene-mutations resulting in iron overload, iron deficiency, and local iron deposition have been introduced in relation to the regulators of storage iron metabolism. On the other hand, the research on storage iron metabolism has not advanced since th...

  13. Graphene-sulfur nanocomposites for rechargeable lithium-sulfur battery electrodes

    Science.gov (United States)

    Liu, Jun; Lemmon, John P; Yang, Zhenguo; Cao, Yuiliang; Li, Xiaolin

    2014-06-17

    Rechargeable lithium-sulfur batteries having a cathode that includes a graphene-sulfur nanocomposite can exhibit improved characteristics. The graphene-sulfur nanocomposite can be characterized by graphene sheets with particles of sulfur adsorbed to the graphene sheets. The sulfur particles have an average diameter less than 50 nm..

  14. Pseudomonas aeruginosa PA1006, which plays a role in molybdenum homeostasis, is required for nitrate utilization, biofilm formation, and virulence.

    Science.gov (United States)

    Filiatrault, Melanie J; Tombline, Gregory; Wagner, Victoria E; Van Alst, Nadine; Rumbaugh, Kendra; Sokol, Pam; Schwingel, Johanna; Iglewski, Barbara H

    2013-01-01

    Pseudomonas aeruginosa (Pae) is a clinically important opportunistic pathogen. Herein, we demonstrate that the PA1006 protein is critical for all nitrate reductase activities, growth as a biofilm in a continuous flow system, as well as virulence in mouse burn and rat lung model systems. Microarray analysis revealed that ΔPA1006 cells displayed extensive alterations in gene expression including nitrate-responsive, quorum sensing (including PQS production), and iron-regulated genes, as well as molybdenum cofactor and Fe-S cluster biosynthesis factors, members of the TCA cycle, and Type VI Secretion System components. Phenotype Microarray™ profiles of ΔPA1006 aerobic cultures using Biolog plates also revealed a reduced ability to utilize a number of TCA cycle intermediates as well as a failure to utilize xanthine as a sole source of nitrogen. As a whole, these data indicate that the loss of PA1006 confers extensive changes in Pae metabolism. Based upon homology of PA1006 to the E. coli YhhP protein and data from the accompanying study, loss of PA1006 persulfuration and/or molybdenum homeostasis are likely the cause of extensive metabolic alterations that impact biofilm development and virulence in the ΔPA1006 mutant.

  15. Pseudomonas aeruginosa PA1006, which plays a role in molybdenum homeostasis, is required for nitrate utilization, biofilm formation, and virulence.

    Directory of Open Access Journals (Sweden)

    Melanie J Filiatrault

    Full Text Available Pseudomonas aeruginosa (Pae is a clinically important opportunistic pathogen. Herein, we demonstrate that the PA1006 protein is critical for all nitrate reductase activities, growth as a biofilm in a continuous flow system, as well as virulence in mouse burn and rat lung model systems. Microarray analysis revealed that ΔPA1006 cells displayed extensive alterations in gene expression including nitrate-responsive, quorum sensing (including PQS production, and iron-regulated genes, as well as molybdenum cofactor and Fe-S cluster biosynthesis factors, members of the TCA cycle, and Type VI Secretion System components. Phenotype Microarray™ profiles of ΔPA1006 aerobic cultures using Biolog plates also revealed a reduced ability to utilize a number of TCA cycle intermediates as well as a failure to utilize xanthine as a sole source of nitrogen. As a whole, these data indicate that the loss of PA1006 confers extensive changes in Pae metabolism. Based upon homology of PA1006 to the E. coli YhhP protein and data from the accompanying study, loss of PA1006 persulfuration and/or molybdenum homeostasis are likely the cause of extensive metabolic alterations that impact biofilm development and virulence in the ΔPA1006 mutant.

  16. Molecular studies on iron-sulfur proteins in Desulfovibrio.

    NARCIS (Netherlands)

    Stokkermans, J.P.W.G.

    1993-01-01

    Desulfovibrio vulgaris (Hildenborough) . The organism described in this thesis, is an anaerobic gram-negative sulfate reducing bacterium (SRB). Its natural environments are the anaerobic sediments in lower levels of lakes and pools. This habitat is rich in sulfate that is used as te

  17. Iron Dextran Injection

    Science.gov (United States)

    ... allergic to iron dextran injection; any other iron injections such as ferric carboxymaltose (Injectafer), ferumoxytol (Feraheme), iron sucrose (Venofer), or sodium ferric gluconate (Ferrlecit);any other ...

  18. Proteomic analysis of iron acquisition, metabolic and regulatory responses of Yersinia pestis to iron starvation

    Directory of Open Access Journals (Sweden)

    Fleischmann Robert D

    2010-01-01

    Full Text Available Abstract Background The Gram-negative bacterium Yersinia pestis is the causative agent of the bubonic plague. Efficient iron acquisition systems are critical to the ability of Y. pestis to infect, spread and grow in mammalian hosts, because iron is sequestered and is considered part of the innate host immune defence against invading pathogens. We used a proteomic approach to determine expression changes of iron uptake systems and intracellular consequences of iron deficiency in the Y. pestis strain KIM6+ at two physiologically relevant temperatures (26°C and 37°C. Results Differential protein display was performed for three Y. pestis subcellular fractions. Five characterized Y. pestis iron/siderophore acquisition systems (Ybt, Yfe, Yfu, Yiu and Hmu and a putative iron/chelate outer membrane receptor (Y0850 were increased in abundance in iron-starved cells. The iron-sulfur (Fe-S cluster assembly system Suf, adapted to oxidative stress and iron starvation in E. coli, was also more abundant, suggesting functional activity of Suf in Y. pestis under iron-limiting conditions. Metabolic and reactive oxygen-deactivating enzymes dependent on Fe-S clusters or other iron cofactors were decreased in abundance in iron-depleted cells. This data was consistent with lower activities of aconitase and catalase in iron-starved vs. iron-rich cells. In contrast, pyruvate oxidase B which metabolizes pyruvate via electron transfer to ubiquinone-8 for direct utilization in the respiratory chain was strongly increased in abundance and activity in iron-depleted cells. Conclusions Many protein abundance differences were indicative of the important regulatory role of the ferric uptake regulator Fur. Iron deficiency seems to result in a coordinated shift from iron-utilizing to iron-independent biochemical pathways in the cytoplasm of Y. pestis. With growth temperature as an additional variable in proteomic comparisons of the Y. pestis fractions (26°C and 37°C, there was

  19. Dazhou Becomes China's Sulfur Base

    Institute of Scientific and Technical Information of China (English)

    Zhang He

    2008-01-01

    @@ Located at the juncture of Sichuan, Hubei, Shaanxi provinces and Chongqing municipality, Dazhou,which is a city in the eastem part of Southwest China's Sichuan Province and has convenient transport facilities, boasts natural gas reserves of 3.8 trillion cubic meters, of which 660 billion cubic meters have been found. It will make full use of its natural gas reserves to build Asia's largest sulfur producing base by 2010 when its annual sulfur output is expected to surpass 4 million tons.

  20. In-situ molybdenum nano-attached particle synthesis from spent Mo scrap.

    Science.gov (United States)

    Han, Chulwoong; Kim, Byungmoon; Choi, Hanshin

    2014-10-01

    Radio frequency thermal plasma is a versatile process for engineering powder preparation owing to its high energy density and reactivity. Molybdenum powders were prepared from molybdenum sheet scrap by RF thermal plasma in association with powder comminution process. Molybdenum scrap which was used in high temperature environment was friable enough to be broken into micropowders by hammer milling. Spherical molybdenum micro-powder was obtained from the hammer milled powders were treated via thermal plasma. On the other hand, vaporization and condensation pathway for nanoparticle synthesis is largely dependent on both thermo-physical properties and thermal plasma properties. In this regard, molybdenum trioxide was chosen for the feedstock of nanoparticle synthesis. Additional reactivity of argon-hydrogen thermal plasma, oxide feedstock was fully reduced to bcc molybdenum. Considering different reaction pathway of each feedstock, molybdenum nanoparticle attached molybdenum spherical micro-powder could be effectively synthesized by feeding a blended feedstock of molybdenum micro-powder and molybdenum trioxide micro-powder into argon-hydrogen thermal plasma.

  1. Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury

    Science.gov (United States)

    Namur, Olivier; Charlier, Bernard; Holtz, Francois; Cartier, Camille; McCammon, Catherine

    2016-08-01

    Chemical data from the MESSENGER spacecraft revealed that surface rocks on Mercury are unusually enriched in sulfur compared to samples from other terrestrial planets. In order to understand the speciation and distribution of sulfur on Mercury, we performed high temperature (1200-1750 °C), low- to high-pressure (1 bar to 4 GPa) experiments on compositions representative of Mercurian lavas and on the silicate composition of an enstatite chondrite. We equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions (IW-1.5 to IW-9.4; IW = iron-wüstite oxygen fugacity buffer). Under these oxygen fugacity conditions, sulfur dissolves in the silicate melt as S2- and forms complexes with Fe2+, Mg2+ and Ca2+. The sulfur concentration in silicate melts at sulfide saturation (SCSS) increases with increasing reducing conditions (from 10 wt.% S at IW-8) and with increasing temperature. Metallic melts have a low sulfur content which decreases from 3 wt.% at IW-2 to 0 wt.% at IW-9. We developed an empirical parameterization to predict SCSS in Mercurian magmas as a function of oxygen fugacity (fO2), temperature, pressure and silicate melt composition. SCSS being not strictly a redox reaction, our expression is fully valid for magmatic systems containing a metal phase. Using physical constraints of the Mercurian mantle and magmas as well as our experimental results, we suggest that basalts on Mercury were free of sulfide globules when they erupted. The high sulfur contents revealed by MESSENGER result from the high sulfur solubility in silicate melt at reducing conditions. We make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and/or that the mantle contains a minor metal phase and combine our parameterization of SCSS with chemical data from MESSENGER to constrain the oxygen fugacity of Mercury's interior to IW- 5.4 ± 0.4. We also calculate that the mantle of Mercury

  2. Sulphur-binding in recent environments. II. Speciation of sulphur and iron and implications for the occurrence of organo-sulphur compounds

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Hartgers, W.A.; Lopez, J.F.; Reiss, C.; Maxwell, J.R.; Grimalt, J.O.

    1997-01-01

    Speciation of iron and sulfur species was determined for two recent sediments (La Trinitat and Lake Cisó) which were deposited in environments with a high biological productivity and sulfate-reducing activity. In sediments from calcite ponds of La Trinitat an excess of reactive iron species (iron mo

  3. Paleoredox Reconstructions on the Century Time Scale; Place of Molybdenum in the Toolbox

    Science.gov (United States)

    Helz, G. R.

    2004-05-01

    The need to set realistic goals for restoration of coastal environments calls for knowledge of conditions prior to anthropogenic impacts. Environmental monitoring data mostly span less than 3 decades, whereas human impacts have accrued for several centuries. Therefore, the pristine state of coastal environments usually is not determinable from archived data. Where restoration of eutrophic or hypoxic-anoxic ecosystems is contemplated, paleoredox indicators in dated sediments can be used to fill the knowledge gap. The requirement that sediments be datable limits application of this approach to deep, anaerobic sediments that are minimally turbated physically or biologically. Examples of indicators that have been found useful in Chesapeake Bay are trace elements (Mo, U), isotopes (15-N), organic biomarkers (fatty acids, sterols), bulk components (TOC, TON, biogenic silica, degree of pyritization) and microfossils (ostracods, diatoms, foraminifera). Most of these, especially those depending on viability of indicator organisms, respond to multiple environmental forcing factors. They therefore do not provide information solely about paleoredox conditions. Molybdenum concentrations in sediments appear to be an exception. Although Mo is biologically an essential trace element, its concentration in coastal and estuarine waters is large relative to needs of organisms, so biological mechanisms affect its distribution in a minor and often undetectable way. Even though Mo is enriched in coal vs. continental crust and is an important component of stainless steels, anthropogenic sources of Mo rarely control Mo concentrations in coastal sediments. Seawater is a strong and uniform source of Mo, dampening temporal variations in other sources to estuarine and coastal waters. Molybdenum is deposited in sediments primarily in Mn oxydyroxides, in Fe mono- and disulfides and in organic materials. The first of these is unstable and redissolves in the anoxic sediments that are most suitable

  4. Session 4: The Mo/Al{sub 2}O{sub 3}-H{sub 2}O{sub 2} a catalytic system for the obtention of ultra low sulfur diesel by oxidative desulfurization process

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Gutierrez, J.L.; Jimenez Cruz, F.; Atocha Hernandez Cortazar, F. de; Cano Dominguez, J.L.; Ramirez Verduzco, L.F.; Murrieta Guevara, F.R. [Programa de Tratamiento de Crudo Maya. Instituto Mexicano del Petroleo Eje Central Lazaro Cardenas 152, D. F. (Mexico)

    2004-07-01

    At present the production of transportation fuels free of polluting compounds is a matter of consequence worldwide. Particularly, sulfur compounds are undesirable in gasoline and diesel because they contribute to air pollution and acid rain. In this work, we present the results obtained in the development of some supported catalysts containing molybdenum and its evaluation in the desulfurization of several model sulfur systems and diesel by the oxidation-extraction process using hydrogen peroxide with the aim of produce ultra low sulfur diesel. The molybdenum catalysts were prepared by the equilibrium adsorption method. The oxidizing reagent was hydrogen peroxide (30 wt % solution in water) and the fuel was a Mexican diesel with 0.0320 wt % sulfur. The sulfur concentration in the samples was measured by a total sulfur analyzer equipped with a X-ray fluorescence detector, the accuracy is {+-} 5 %. The oxidation-extraction process of diesel was carried out in a batch reactor in presence of hydrogen peroxide, a solvent and the catalyst. The oxidation proceeds under mild conditions: temperature less than 373 K and atmospheric pressure. Oxidized sulfur compounds were separated from the diesel by extraction with the same solvent used in the oxidation process. The effect of the reaction variables, e. g.: time, temperature, hydrogen peroxide concentration, solvent and its concentration, molybdenum precursor, support, the stability of the catalytic activity, structure of the model sulfur compounds, were examined. The results show that the catalyst activity depends on the isoelectric point of the support. It was observed that the oxidation was carried out with good yield only in the presence of a polar solvent. A linear dependence was found between the electric density of the sulfur atom for the organosulfur compounds and its oxidation facility with the oxidation system in matter. This is in good agreement with the work reported by Otsuki. In the oxidation of diesel, it was

  5. Optimizing stratospheric sulfur geoengineering by seasonally changing sulfur injections

    Science.gov (United States)

    Laakso, Anton; Partanen, Antti-Ilari; Kokkola, Harri; Lehtinen, Kari; Korhonen, Hannele

    2015-04-01

    Solar radiation management (SRM) by stratospheric sulfur injection has been shown to have potential in counteracting global warming if reducing of greenhouse gases has not been achieved fast enough and if climate warming will continue. Injecting large amounts of sulfate particles to the stratosphere would increase the reflectivity of the atmosphere and less sunlight would reach the surface. However, the effectivity (per injected sulphur mass unit) of this kind of geoengineering would decrease when amount of injected sulfur is increased. When sulfur concentration increases, stratospheric particles would grow to larger sizes which have larger gravitational settling velocity and which do not reflect radiation as efficiently as smaller particles. In many previous studies, sulfur has been assumed to be injected along the equator where yearly mean solar intensity is the highest and from where sulfur is spread equally to both hemispheres. However, the solar intensity will change locally during the year and sulfate has been assumed to be injected and spread to the hemisphere also during winter time, when the solar intensity is low. Thus sulfate injection could be expected to be more effective, if sulfur injection area is changed seasonally. Here we study effects of the different SRM injection scenarios by using two versions of the MPI climate models. First, aerosol spatial and temporal distributions as well as the resulting radiative properties from the SRM are defined by using the global aerosol-climate model ECHAM6.1-HAM2.2-SALSA. After that, the global and regional climate effects from different injection scenarios are predicted by using the Max Planck Institute's Earth System Model (MPI-ESM). We carried out simulations, where 8 Tg of sulfur is injected as SO2 to the stratosphere at height of 20-22 km in an area ranging over a 20 degree wide latitude band. Results show that changing the sulfur injection area seasonally would lead to similar global mean shortwave

  6. Molybdenum isotope fractionation in the mantle

    Science.gov (United States)

    Liang, Yu-Hsuan; Halliday, Alex N.; Siebert, Chris; Fitton, J. Godfrey; Burton, Kevin W.; Wang, Kuo-Lung; Harvey, Jason

    2017-02-01

    We report double-spike molybdenum (Mo) isotope data for forty-two mafic and fifteen ultramafic rocks from diverse locations and compare these with results for five chondrites. The δ98/95Mo values (normalized to NIST SRM 3134) range from -0.59 ± 0.04 to +0.10 ± 0.08‰. The compositions of one carbonaceous (CI) and four ordinary chondrites are relatively uniform (-0.14 ± 0.01‰, 95% ci (confidence interval)) in excellent agreement with previous data. These values are just resolvable from the mean of 10 mid-ocean ridge basalts (MORBs) (0.00 ± 0.02‰, 95% ci). The compositions of 13 mantle-derived ultramafic xenoliths from Kilbourne Hole, Tariat and Vitim are more diverse (-0.39 to -0.07‰) with a mean of -0.22 ± 0.06‰ (95% ci). On this basis, the isotopic composition of the bulk silicate Earth (BSE or Primitive Mantle) is within error identical to chondrites. The mean Mo concentration of the ultramafic xenoliths (0.19 ± 0.07 ppm, 95% ci) is similar in magnitude to that of MORB (0.48 ± 0.13 ppm, 95% ci), providing evidence, either for a more compatible behaviour than previously thought or for selective Mo enrichment of the subcontinental lithospheric mantle. Intraplate and ocean island basalts (OIBs) display significant isotopic variability within a single locality from MORB-like to strongly negative (-0.59 ± 0.04‰). The most extreme values measured are for nephelinites from the Cameroon Line and Trinidade, which also have anomalously high Ce/Pb and low Mo/Ce relative to normal oceanic basalts. δ98/95Mo correlates negatively with Ce/Pb and U/Pb, and positively with Mo/Ce, explicable if a phase such as an oxide or a sulphide liquid selectively retains isotopically heavy Mo in the mantle and fractionates its isotopic composition in low degree partial melts. If residual phases retain Mo during partial melting, it is possible that the [Mo] for the BSE may be misrepresented by values estimated from basalts. This would be consistent with the high Mo

  7. Iron Sucrose Injection

    Science.gov (United States)

    Iron sucrose injection is used treat iron-deficiency anemia (a lower than normal number of red blood cells due ... and may cause the kidneys to stop working). Iron sucrose injection is in a class of medications called iron ...

  8. Iron-Deficiency Anemia

    Medline Plus

    Full Text Available ... enough iron, your body starts using the iron it has stored. Soon, the stored iron gets used ... fewer red blood cells. The red blood cells it does make have less hemoglobin than normal. Iron- ...

  9. Sulfur-impregnated disordered carbon nanotubes cathode for lithium-sulfur batteries.

    Science.gov (United States)

    Guo, Juchen; Xu, Yunhua; Wang, Chunsheng

    2011-10-12

    The commercialization of lithium-sulfur batteries is hindered by low cycle stability and low efficiency, which are induced by sulfur active material loss and polysulfide shuttle reaction through dissolution into electrolyte. In this study, sulfur-impregnated disordered carbon nanotubes are synthesized as cathode material for the lithium-sulfur battery. The obtained sulfur-carbon tube cathodes demonstrate superior cyclability and Coulombic efficiency. More importantly, the electrochemical characterization indicates a new stabilization mechanism of sulfur in carbon induced by heat treatment.

  10. In situ hydrogenation of molybdenum oxide nanowires for enhanced supercapacitors

    KAUST Repository

    Shakir, Imran

    2014-01-01

    In situ hydrogenation of orthorhombic molybdenum trioxide (α-MoO 3) nanowires has been achieved on a large scale by introducing alcohol during the hydrothermal synthesis for electrochemical energy storage supercapacitor devices. The hydrogenated molybdenum trioxide (H xMoO3) nanowires yield a specific capacitance of 168 F g-1 at 0.5 A g-1 and maintain 108 F g-1 at 10 A g-1, which is 36-fold higher than the capacitance obtained from pristine MoO3 nanowires at the same conditions. The electrochemical devices made with HxMoO3 nanowires exhibit excellent cycling stability by retaining 97% of their capacitance after 3000 cycles due to an enhanced electronic conductivity and increased density of hydroxyl groups on the surface of the MoO3 nanowires. This journal is © The Royal Society of Chemistry.

  11. Induction plasma spheroidization of tungsten and molybdenum powders

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.

  12. Cranial ultrasound and chronological changes in molybdenum cofactor deficiency

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, Mercedes; Dias, Anna P.; Perez-Duenas, Belen; Campistol, Jaume; Garcia-Cazorla, Angels [Hospital Sant Joan de Deu, Department of Pediatric Neurology, Paseo de Sant Joan de Deu, Barcelona (Spain); Lizarraga, Isabel [Hospital Sant Joan de Deu, Department of Neonatology, Barcelona (Spain); Reiss, Jochen [University of Goettingen, Institute for Human Genetics, Goettingen (Germany); Vilaseca, Maria A.; Artuch, Rafael [Hospital Sant Joan de Deu, Clinical Biochemistry Department, Barcelona (Spain)

    2007-10-15

    Molybdenum cofactor is essential for the function of three human enzymes: sulphite oxidase, xanthine dehydrogenase, and aldehyde oxidase. Molybdenum cofactor deficiency is a rare autosomal recessively inherited disease. Disturbed development and damage to the brain may occur as a result of accumulation of toxic levels of sulphite. The CT and MRI findings include severe early brain abnormalities and have been widely reported, but the cranial US imaging findings have seldom been reported. We report a chronological series of cranial US images obtained from an affected infant that show the rapid development of cerebral atrophy, calcifications and white matter cysts. Our report supports the utility of cranial US, a noninvasive bed-side technique, in the detection and follow-up of these rapidly changing lesions. (orig.)

  13. The Structure and Stability of Molybdenum Ditelluride Thin Films

    Directory of Open Access Journals (Sweden)

    Zhouling Wang

    2014-01-01

    Full Text Available Molybdenum-tellurium alloy thin films were fabricated by electron beam evaporation and the films were annealed in different conditions in N2 ambient. The hexagonal molybdenum ditelluride thin films with well crystallization annealed at 470°C or higher were obtained by solid state reactions. Thermal stability measurements indicate the formation of MoTe2 took place at about 350°C, and a subtle weight-loss was in the range between 30°C and 500°C. The evolution of the chemistry for Mo-Te thin films was performed to investigate the growth of the MoTe2 thin films free of any secondary phase. And the effect of other postdeposition treatments on the film characteristics was also investigated.

  14. Production of Molybdenum-99 using Neutron Capture Methods

    Energy Technology Data Exchange (ETDEWEB)

    Toth, James J; Greenwood, Lawrence R; Soderquist, Chuck Z; Wittman, Richard S; Pierson, Bruce D; Burns, Kimberly A; Lavender, Curt A; Painter, Chad L; Love, Edward F; Wall, Donald E

    2011-01-01

    Pacific Northwest National Laboratory (PNNL), operated by Battelle, has identified a reference process for the production of molybdenum-99 (99Mo) for use in a chromatographic generator to separate the daughter product, technetium-99m (99mTc). The reference process uses the neutron capture reaction of natural or enriched molybdenum oxide via the reaction 98Mo(n,γ)99Mo. The irradiated molybdenum is dissolved in an alkaline solution, whereby the molybdenum, dissolved as the molybdate anion, is loaded on a proprietary ion exchange material in the chromatographic generator. The approach of this investigation is to provide a systematic collection of technologies to make the neutron capture method for Mo-99 production economically viable. This approach would result in the development of a technetium Tc99m generator and a new type of target. The target is comprised of molybdenum, either natural or enriched, and is tailored to the design of currently operating U.S. research reactors. The systematic collection of technologies requires evaluation of new metallurgical methods to produce the target, evaluation of target geometries tailored to research reactors, and chemical methods to dissolve the irradiated target materials for use in a chromatographic generator. A Technical specification for testing the target and neutron capture method in a research reactor is also required. This report includes identification of research and demonstration activities needed to enable deployment of neutron capture production method, including irradiations of prototypic targets, chemical processing of irradiated targets, and loading and extraction tests of Mo99 and Tc99m on the sorbent material in a prototypic generator design. The prototypical generator design is based on the proprietary method and systems for isotope product generation. The proprietary methods and systems described in this report are clearly delineated with footnotes. Ultimately, the Tc-99m generator solution provided by

  15. Spectrophotometric determination of molybdenum by extraction of its thiosulphate complex.

    Science.gov (United States)

    Yatirajam, V; Ram, J

    1974-12-01

    A simple and rapid spectrophotometric determination of molybdenum is described. The molybdenum thiosulphate complex is extracted into isoamyl alcohol from 1.0-1.5M hydrochloric acid containing 36-40 mg of Na(2)S(2)O(3).5H(2)O per ml. The absorbance at lambda(max) = 475 nm obeys Beer's law over the range 0-32 microg of Mo per ml of solvent phase. Up to 5 mg/ml of Ti(IV), V(V), Cr(VI), Fe(III), Co(II), Ni(II), U(VI), W(VI), Sb(III), 1 mg/ml of Cu(II), Sn(II), Bi(V) and 10 microg/ml of Pt(IV) and Pd(II) do not interfere. Large amounts of complexing agents interfere. The method has been applied to analysis of synthetic and industrial samples.

  16. Layer number controllability of transition-metal dichalcogenides and the establishment of hetero-structures by using sulfurization of thin transition metal films

    Science.gov (United States)

    Chen, Kuan-Chao; Chu, Tung-Wei; Wu, Chong-Rong; Lee, Si-Chen; Lin, Shih-Yen

    2017-02-01

    Large-area and uniform MoS2 films are fabricated by using sulfurization of pre-deposited molybdenum (Mo) films. One- and three-layer MoS2 films are obtained by sulfurizing 0.5 and 1.0 nm Mo films, respectively. The results have demonstrated the good layer number controllability of this growth technique down to single-layer MoS2. By sequential sulfurization of 0.5 nm W, 0.5 nm Mo and 0.5 nm W under the same condition, three layers of the WS2/MoS2/WS2 hetero-structure are established, which has demonstrated the potential of this growth technique for the establishment of 2D crystal hetero-structures.

  17. Iron deficiency

    DEFF Research Database (Denmark)

    Schou, Morten; Bosselmann, Helle; Gaborit, Freja

    2015-01-01

    BACKGROUND: Both iron deficiency (ID) and cardiovascular biomarkers are associated with a poor outcome in heart failure (HF). The relationship between different cardiovascular biomarkers and ID is unknown, and the true prevalence of ID in an outpatient HF clinic is probably overlooked. OBJECTIVES.......043). CONCLUSION: ID is frequent in an outpatient HF clinic. ID is not associated with cardiovascular biomarkers after adjustment for traditional confounders. Inflammation, but not neurohormonal activation is associated with ID in systolic HF. Further studies are needed to understand iron metabolism in elderly HF...

  18. Concentrations of boron, molybdenum, and selenium in chinook salmon

    Science.gov (United States)

    Hamilton, Steven J.; Wiedmeyer, Raymond H.

    1990-01-01

    The concentrations of boron, molybdenum, and selenium in young chinook salmon Oncorhynchus tshawytscha were determined in three partial life cycle chronic toxicity studies. In each study, fish were exposed to a mixture of boron, molybdenum, selenate, and selenite in the proportions found in subsurface agricultural drainage water in the basin of the San Joaquin Valley, California. Tests were conducted in well water and in site-specific fresh and brackish waters. No boron or molybdenum was detected in fish exposed to concentrations as high as 6,046 μg boron/L and 193 μg molybdenum/L for 90 d in well water or fresh water; however, whole-body concentrations of selenium increased with increasing exposure concentrations in well water and fresh water, but not in brackish water. Concentrations of selenium in chinook salmon were strongly correlated with reduced survival and growth of fish in well water and with reduced survival in a 15-d seawater challenge test of fish from fresh water. Concentrations of selenium in fish seemed to reach a steady state after 60 d of exposure in well water or fresh water. Fish in brackish water had only background concentrations of selenium after 60 d of exposure, and no effects on survival and growth in brackish water or on survival in a 10-d seawater challenge test were exhibited. This lack of effect in brackish water was attributed to initiation of the study with advanced fry, which were apparently better able to metabolize the trace element mixture than were the younger fish used in studies with well water and fresh water. In all three experimental waters, concentration factors (whole-body concentration/waterborne concentration) for selenium decreased with increasing exposure concentrations, suggesting decreased uptake or increased excretion, or both, of selenium at the higher concentrations.

  19. Bulk molybdenum field emitters by inductively coupled plasma etching.

    Science.gov (United States)

    Zhu, Ningli; Cole, Matthew T; Milne, William I; Chen, Jing

    2016-12-07

    In this work we report on the fabrication of inductively coupled plasma (ICP) etched, diode-type, bulk molybdenum field emitter arrays. Emitter etching conditions as a function of etch mask geometry and process conditions were systematically investigated. For optimized uniformity, aspect ratios of >10 were achieved, with 25.5 nm-radius tips realised for masks consisting of aperture arrays some 4.45 μm in diameter and whose field electron emission performance has been herein assessed.

  20. Molybdenum work function determined by electron emission microscopy.

    Science.gov (United States)

    Jacobson, D. L.; Campbell, A. E.

    1971-01-01

    A polycrystalline molybdenum sample was recrystallized and thermally stabilized. Quantitative measurements of the emission from each individual grain were obtained with an electron emission microscope. The effective work function for each grain was then calculated. The crystallographic orientation of each grain was determined by Laue back-reflection techniques. A polar plot of effective work function vs crystallographic orientation for the sample was constructed to provide a correlation between effective work function and crystallographic orientation.