Science.gov

Sample records for molybdenum disulphide particles

  1. Exploring atomic defects in molybdenum disulphide monolayers

    PubMed Central

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    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 × 1013 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. PMID:25695374

  2. Exploring atomic defects in molybdenum disulphide monolayers.

    PubMed

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    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. PMID:25695374

  3. Dichroic spin–valley photocurrent in monolayer molybdenum disulphide

    PubMed Central

    Eginligil, Mustafa; Cao, Bingchen; Wang, Zilong; Shen, Xiaonan; Cong, Chunxiao; Shang, Jingzhi; Soci, Cesare; Yu, Ting

    2015-01-01

    The aim of valleytronics is to exploit confinement of charge carriers in local valleys of the energy bands of semiconductors as an additional degree of freedom in optoelectronic devices. Thanks to strong direct excitonic transitions in spin-coupled K valleys, monolayer molybdenum disulphide is a rapidly emerging valleytronic material, with high valley polarization in photoluminescence. Here we elucidate the excitonic physics of this material by light helicity-dependent photocurrent studies of phototransistors. We demonstrate that large photocurrent dichroism (up to 60%) can also be achieved in high-quality molybdenum disulphide monolayers grown by chemical vapour deposition, due to the circular photogalvanic effect on resonant excitations. This opens up new opportunities for valleytonic applications in which selective control of spin–valley-coupled photocurrents can be used to implement polarization-sensitive light-detection schemes or integrated spintronic devices, as well as biochemical sensors operating at visible frequencies. PMID:26134143

  4. Modified chemical route for deposition of molybdenum disulphide thin films

    SciTech Connect

    Vyas, Akshay N. Sartale, S. D.

    2014-04-24

    Molybdenum disulphide (MoS{sub 2}) thin films were deposited on quartz substrates using a modified chemical route. Sodium molybdate and sodium sulphide were used as precursors for molybdenum and sulphur respectively. The route involves formation of tetrathiomolybdate ions (MoS{sub 4}{sup 2−}) and further reduction by sodium borohydride to form MoS{sub 2}. The deposition was performed at room temperature. The deposited films were annealed in argon atmosphere at 1073 K for 1 hour to improve its crystallinity. The deposited films were characterized using scanning electron microscopy (SEM) for morphology, UV-Vis absorption spectroscopy for optical studies and X-ray diffraction (XRD) for structure determination.

  5. Superconductivity in the alkali metal intercalates of molybdenum disulphide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.

    1972-01-01

    The complete series of alkali metals, lithium through cesium, have been intercalated into molybdenum disulphide, using both the liquid ammonia and vapor techniques. All the intercalates with the exception of lithium yielded full superconducting transitions with onset temperatures of 6 K for AxMoS2(Ax=K,Rb,Cs) and 4 K for BxMoS2(Bx=Li,Na). The superconducting transition for lithium was incomplete down to 1.5 K. Stoichiometries and unit cell parameters have been determined for the intercalation compounds. Both rhombohedral and hexagonal polymorphs of MoS2 have been intercalated and found to exhibit the same superconductivity behavior. The nature of the extraneous superconducting transition of some intercalated samples on exposure to air was elucidated.

  6. Optoelectronic crystal of artificial atoms in strain-textured molybdenum disulphide

    NASA Astrophysics Data System (ADS)

    Li, Hong; Contryman, Alex W.; Qian, Xiaofeng; Ardakani, Sina Moeini; Gong, Yongji; Wang, Xingli; Weisse, Jeffery M.; Lee, Chi Hwan; Zhao, Jiheng; Ajayan, Pulickel M.; Li, Ju; Manoharan, Hari C.; Zheng, Xiaolin

    2015-06-01

    The isolation of the two-dimensional semiconductor molybdenum disulphide introduced a new optically active material possessing a band gap that can be facilely tuned via elastic strain. As an atomically thin membrane with exceptional strength, monolayer molybdenum disulphide subjected to biaxial strain can embed wide band gap variations overlapping the visible light spectrum, with calculations showing the modified electronic potential emanating from point-induced tensile strain perturbations mimics the Coulomb potential in a mesoscopic atom. Here we realize and confirm this `artificial atom' concept via capillary-pressure-induced nanoindentation of monolayer molybdenum disulphide from a tailored nanopattern, and demonstrate that a synthetic superlattice of these building blocks forms an optoelectronic crystal capable of broadband light absorption and efficient funnelling of photogenerated excitons to points of maximum strain at the artificial-atom nuclei. Such two-dimensional semiconductors with spatially textured band gaps represent a new class of materials, which may find applications in next-generation optoelectronics or photovoltaics.

  7. Controlled charge trapping by molybdenum disulphide and graphene in ultrathin heterostructured memory devices.

    PubMed

    Choi, Min Sup; Lee, Gwan-Hyoung; Yu, Young-Jun; Lee, Dae-Yeong; Lee, Seung Hwan; Kim, Philip; Hone, James; Yoo, Won Jong

    2013-01-01

    Atomically thin two-dimensional materials have emerged as promising candidates for flexible and transparent electronic applications. Here we show non-volatile memory devices, based on field-effect transistors with large hysteresis, consisting entirely of stacked two-dimensional materials. Graphene and molybdenum disulphide were employed as both channel and charge-trapping layers, whereas hexagonal boron nitride was used as a tunnel barrier. In these ultrathin heterostructured memory devices, the atomically thin molybdenum disulphide or graphene-trapping layer stores charge tunnelled through hexagonal boron nitride, serving as a floating gate to control the charge transport in the graphene or molybdenum disulphide channel. By varying the thicknesses of two-dimensional materials and modifying the stacking order, the hysteresis and conductance polarity of the field-effect transistor can be controlled. These devices show high mobility, high on/off current ratio, large memory window and stable retention, providing a promising route towards flexible and transparent memory devices utilizing atomically thin two-dimensional materials. PMID:23535645

  8. Optoelectronic crystal of artificial atoms in strain-textured molybdenum disulphide.

    PubMed

    Li, Hong; Contryman, Alex W; Qian, Xiaofeng; Ardakani, Sina Moeini; Gong, Yongji; Wang, Xingli; Weisse, Jeffery M; Lee, Chi Hwan; Zhao, Jiheng; Ajayan, Pulickel M; Li, Ju; Manoharan, Hari C; Zheng, Xiaolin

    2015-01-01

    The isolation of the two-dimensional semiconductor molybdenum disulphide introduced a new optically active material possessing a band gap that can be facilely tuned via elastic strain. As an atomically thin membrane with exceptional strength, monolayer molybdenum disulphide subjected to biaxial strain can embed wide band gap variations overlapping the visible light spectrum, with calculations showing the modified electronic potential emanating from point-induced tensile strain perturbations mimics the Coulomb potential in a mesoscopic atom. Here we realize and confirm this 'artificial atom' concept via capillary-pressure-induced nanoindentation of monolayer molybdenum disulphide from a tailored nanopattern, and demonstrate that a synthetic superlattice of these building blocks forms an optoelectronic crystal capable of broadband light absorption and efficient funnelling of photogenerated excitons to points of maximum strain at the artificial-atom nuclei. Such two-dimensional semiconductors with spatially textured band gaps represent a new class of materials, which may find applications in next-generation optoelectronics or photovoltaics. PMID:26088550

  9. Optoelectronic crystal of artificial atoms in strain-textured molybdenum disulphide

    PubMed Central

    Li, Hong; Contryman, Alex W.; Qian, Xiaofeng; Ardakani, Sina Moeini; Gong, Yongji; Wang, Xingli; Weisse, Jeffery M.; Lee, Chi Hwan; Zhao, Jiheng; Ajayan, Pulickel M.; Li, Ju; Manoharan, Hari C.; Zheng, Xiaolin

    2015-01-01

    The isolation of the two-dimensional semiconductor molybdenum disulphide introduced a new optically active material possessing a band gap that can be facilely tuned via elastic strain. As an atomically thin membrane with exceptional strength, monolayer molybdenum disulphide subjected to biaxial strain can embed wide band gap variations overlapping the visible light spectrum, with calculations showing the modified electronic potential emanating from point-induced tensile strain perturbations mimics the Coulomb potential in a mesoscopic atom. Here we realize and confirm this ‘artificial atom' concept via capillary-pressure-induced nanoindentation of monolayer molybdenum disulphide from a tailored nanopattern, and demonstrate that a synthetic superlattice of these building blocks forms an optoelectronic crystal capable of broadband light absorption and efficient funnelling of photogenerated excitons to points of maximum strain at the artificial-atom nuclei. Such two-dimensional semiconductors with spatially textured band gaps represent a new class of materials, which may find applications in next-generation optoelectronics or photovoltaics. PMID:26088550

  10. Low-temperature growth of layered molybdenum disulphide with controlled clusters.

    PubMed

    Mun, Jihun; Kim, Yeongseok; Kang, Il-Suk; Lim, Sung Kyu; Lee, Sang Jun; Kim, Jeong Won; Park, Hyun Min; Kim, Taesung; Kang, Sang-Woo

    2016-01-01

    Layered molybdenum disulphide was grown at a low-temperature of 350 °C using chemical vapour deposition by elaborately controlling the cluster size. The molybdenum disulphide grown under various sulphur-reaction-gas to molybdenum-precursor partial-pressure ratios were examined. Using spectroscopy and microscopy, the effect of the cluster size on the layered growth was investigated in terms of the morphology, grain size, and impurity incorporation. Triangular single-crystal domains were grown at an optimized sulphur-reaction-gas to molybdenum-precursor partial-pressure ratio. Furthermore, it is proved that the nucleation sites on the silicon-dioxide substrate were related with the grain size. A polycrystalline monolayer with the 100-nm grain size was grown on a nucleation site confined substrate by high-vacuum annealing. In addition, a field-effect transistor was fabricated with a MoS2 monolayer and exhibited a mobility and on/off ratio of 0.15 cm(2) V(-1) s(-1) and 10(5), respectively. PMID:26902316

  11. Low-temperature growth of layered molybdenum disulphide with controlled clusters

    PubMed Central

    Mun, Jihun; Kim, Yeongseok; Kang, Il-Suk; Lim, Sung Kyu; Lee, Sang Jun; Kim, Jeong Won; Park, Hyun Min; Kim, Taesung; Kang, Sang-Woo

    2016-01-01

    Layered molybdenum disulphide was grown at a low-temperature of 350 °C using chemical vapour deposition by elaborately controlling the cluster size. The molybdenum disulphide grown under various sulphur-reaction-gas to molybdenum-precursor partial-pressure ratios were examined. Using spectroscopy and microscopy, the effect of the cluster size on the layered growth was investigated in terms of the morphology, grain size, and impurity incorporation. Triangular single-crystal domains were grown at an optimized sulphur-reaction-gas to molybdenum-precursor partial-pressure ratio. Furthermore, it is proved that the nucleation sites on the silicon-dioxide substrate were related with the grain size. A polycrystalline monolayer with the 100-nm grain size was grown on a nucleation site confined substrate by high-vacuum annealing. In addition, a field-effect transistor was fabricated with a MoS2 monolayer and exhibited a mobility and on/off ratio of 0.15 cm2 V−1 s−1 and 105, respectively. PMID:26902316

  12. Low-temperature growth of layered molybdenum disulphide with controlled clusters

    NASA Astrophysics Data System (ADS)

    Mun, Jihun; Kim, Yeongseok; Kang, Il-Suk; Lim, Sung Kyu; Lee, Sang Jun; Kim, Jeong Won; Park, Hyun Min; Kim, Taesung; Kang, Sang-Woo

    2016-02-01

    Layered molybdenum disulphide was grown at a low-temperature of 350 °C using chemical vapour deposition by elaborately controlling the cluster size. The molybdenum disulphide grown under various sulphur-reaction-gas to molybdenum-precursor partial-pressure ratios were examined. Using spectroscopy and microscopy, the effect of the cluster size on the layered growth was investigated in terms of the morphology, grain size, and impurity incorporation. Triangular single-crystal domains were grown at an optimized sulphur-reaction-gas to molybdenum-precursor partial-pressure ratio. Furthermore, it is proved that the nucleation sites on the silicon-dioxide substrate were related with the grain size. A polycrystalline monolayer with the 100-nm grain size was grown on a nucleation site confined substrate by high-vacuum annealing. In addition, a field-effect transistor was fabricated with a MoS2 monolayer and exhibited a mobility and on/off ratio of 0.15 cm2 V-1 s-1 and 105, respectively.

  13. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    NASA Astrophysics Data System (ADS)

    Zhao, Junhua; Jiang, Jin-Wu; Rabczuk, Timon

    2013-12-01

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS2) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS2. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  14. Characterization of viscoelastic properties of molybdenum disulphide filled polyamide by indentation

    NASA Astrophysics Data System (ADS)

    Stan, Felicia; Fetecau, Catalin

    2013-05-01

    In this paper, the creep behavior of molybdenum disulphide (MoS2) filled polyamide 66 composite was investigated through sharp indentation at room temperature. Two types of indentation creep test, the 3-step indentation test, and the 5-step indentation test were considered in order to explore whether the measured creep response is mainly viscoelastic or includes a significant contribution from the plastic deformation developed during the loading phase. The experimental indentation creep data were analyzed within an analytical framework based on the hereditary integral operator for the ramp creep and a viscoelastic-plastic (VEP) model in order to determine the indentation creep compliance function including the short- and long-time modulus. The equivalent shear modulus calculated from the creep compliance function was compared to the indentation plane strain modulus derived from the initial slope of the unloading curve in order to investigate the validity of the Oliver and Pharr method.

  15. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    SciTech Connect

    Zhao, Junhua; Jiang, Jin-Wu; Rabczuk, Timon

    2013-12-02

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS{sub 2}) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS{sub 2}. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  16. Computational study of electronic and thermal properties of single-layer molybdenum disulphide folded nanostructure

    NASA Astrophysics Data System (ADS)

    Peng, Jie; Chung, Peter

    Single-layer Molybdenum disulphide (SLMoS2), a two-dimensional transition-metal dichalcogenide with a large band gap and high mobility, is considered to be a next generation material for transistors and optoelectronic devices. We present recent results on the electronic and thermal behavior of SLMoS2 folded nanostructures. Through an approach that uses both molecular dynamics (MD) and density functional theory (DFT), we estimate the stable equilibrium structure of folded sheets as well as the related phonon and electronic band structures. The MD simulations are based on a Stillinger-Weber potential and the DFT simulations employ projector augmented wave (PAW) pseudopotentials using generalized gradient approximation (GGA) and local density approximation (LDA). The structure is examined as a function of folding orientation, layer number and system size. Mechanisms of the phonon transport and electronic band gap properties in such a mechanically distorted atomic-layer nanostructure will be discussed.

  17. A coarse-grained simulation for the folding of molybdenum disulphide

    NASA Astrophysics Data System (ADS)

    Wang, Cui-Xia; Zhang, Chao; Jiang, Jin-Wu; Rabczuk, Timon

    2016-01-01

    We investigate the folding of molybdenum disulphide (MoS2) using coarse-grained (CG) simulations, in which all the parameters are determined analytically from the Stillinger-Weber atomic potential. Owing to its simplicity, the CG model can be used to derive analytic predictions for the relaxed configuration of the folded MoS2 and the resonant frequency for the breathing-like oscillation. We disclose two interesting phenomena for the breathing-like oscillation in the folded MoS2. First, the breathing-like oscillation is self-actuated, since this oscillation can be actuated by intrinsic thermal vibrations without any external actuation force. Second, the resonant frequency of the breathing-like oscillation is insensitive to the adsorption effect. These two features enable practical applications of the folded MoS2 based nanoresonators, where stable resonant oscillations are desirable.

  18. Seeded growth of highly crystalline molybdenum disulphide monolayers at controlled locations.

    PubMed

    Han, Gang Hee; Kybert, Nicholas J; Naylor, Carl H; Lee, Bum Su; Ping, Jinglei; Park, Joo Hee; Kang, Jisoo; Lee, Si Young; Lee, Young Hee; Agarwal, Ritesh; Johnson, A T Charlie

    2015-01-01

    Monolayer transition metal dichalcogenides are materials with an atomic structure complementary to graphene but diverse properties, including direct energy bandgaps, which makes them intriguing candidates for optoelectronic devices. Various approaches have been demonstrated for the growth of molybdenum disulphide (MoS2) on insulating substrates, but to date, growth of isolated crystalline flakes has been demonstrated at random locations only. Here we use patterned seeds of molybdenum source material to grow flakes of MoS2 at predetermined locations with micrometre-scale resolution. MoS2 flakes are predominantly monolayers with high material quality, as confirmed by atomic force microscopy, transmission electron microscopy and Raman and photoluminescence spectroscopy. As the monolayer flakes are isolated at predetermined locations, transistor fabrication requires only a single lithographic step. Device measurements exhibit carrier mobility and on/off ratio that exceed 10 cm(2) V(-1) s(-1) and 10(6), respectively. The technique provides a path for in-depth physical analysis of monolayer MoS2 and fabrication of MoS2-based integrated circuits. PMID:25630052

  19. Band Alignment at Molybdenum Disulphide/Boron Nitride/Aluminum Oxide Interfaces

    NASA Astrophysics Data System (ADS)

    DiStefano, Jennifer; Lin, Yu-Chuan; Robinson, Joshua; Glavin, Nicholas R.; Voevodin, Andrey A.; Brockman, Justin; Kuhn, Markus; French, Benjamin; King, Sean W.

    2016-02-01

    To facilitate the design of future heterostructure devices employing two-dimensional (2D) materials such as molybdenum disulphide (MoS2) and hexagonal/sp2 boron nitride (BN), x-ray photoelectron spectroscopy (XPS) has been utilized to determine the valence band offset (VBO) present at interfaces formed between these materials. For MoS2 grown on a pulsed laser-deposited amorphous BN (a-BN) layer with sp2 bonding, the VBO was determined to be 1.4 ± 0.2 eV. Similarly, the VBO between the a-BN layer and the aluminum oxide (Al2O3) substrate was determined to be 1.1 ± 0.2 eV. Using the bandgaps established in the literature for MoS2, h-BN, and Al2O3, the conduction band offsets (CBOs) at the MoS2/a-BN and a-BN/Al2O3 interfaces were additionally calculated to be 3.3 ± 0.2 and 1.7 ± 0.2 eV, respectively. The resulting large VBOs and CBOs indicate BN and Al2O3 are attractive gate dielectrics and substrates for future 2D MoS2 devices.

  20. The energy-band alignment at molybdenum disulphide and high-k dielectrics interfaces

    SciTech Connect

    Tao, Junguang; Chai, J. W.; Zhang, Z.; Pan, J. S.; Wang, S. J.

    2014-06-09

    Energy-band alignments for molybdenum disulphide (MoS{sub 2}) films on high-k dielectric oxides have been studied using photoemission spectroscopy. The valence band offset (VBO) at monolayer MoS{sub 2}/Al{sub 2}O{sub 3} (ZrO{sub 2}) interface was measured to be 3.31 eV (2.76 eV), while the conduction-band offset (CBO) was 3.56 eV (1.22 eV). For bulk MoS{sub 2}/Al{sub 2}O{sub 3} interface, both VBO and CBO increase by ∼0.3 eV, due to the upwards shift of Mo 4d{sub z{sup 2}} band. The symmetric change of VBO and CBO implies Fermi level pinning by interfacial states. Our finding ensures the practical application of both p-type and n-type MoS{sub 2} based complementary metal-oxide semiconductor and other transistor devices using Al{sub 2}O{sub 3} and ZrO{sub 2} as gate materials.

  1. Characterization of large area molybdenum disulphide by low energy electron microscopy

    NASA Astrophysics Data System (ADS)

    Man, K. L.; Yamaguchi, H.; Najmaei, S.; Lei, S.; Ajayan, P. M.; Lou, J.; Gupta, G.; Mohite, A. D.; Dani, K. M.

    2014-03-01

    Molybdenum disulphide (MoS2) is a new 2D direct-bandgap semiconductor material which has recently attracted substantial interest due to its potential applications in electronics, optics and energy storage. One of the challenges that needed to be overcome is in the large scale synthesis of high quality single crystal MoS2. Recently, it is shown that chemical vapor deposition (CVD) is a promising way of in the production of single layer MoS2. Here we report our study using low energy electron microscopy (LEEM) of large area MoS2 synthesized by CVD technique. The MoS2 samples are grown on Si/SiO2 substrates and then transferred onto n-doped Si substrates. In the LEEM images, we observe large triangular shaped MoS2 flakes along with irregular shaped flakes. Using low energy electron diffraction (LEED) and dark field imaging technique, we identify the triangularly shaped flakes as MoS2 single crystal while the irregular ones contain multiple domains orientations. These studies provide insight into the growth of large area single domain MoS2 crystals using CVD technique and the transfer process onto different substrates for potential device applications.

  2. Molybdenum disulphide and graphene quantum dots as electrode modifiers for laccase biosensor.

    PubMed

    Vasilescu, Ioana; Eremia, Sandra A V; Kusko, Mihaela; Radoi, Antonio; Vasile, Eugeniu; Radu, Gabriel-Lucian

    2016-01-15

    A nanocomposite formed from molybdenum disulphide (MoS2) and graphene quantum dots (GQDs) was proposed as a novel and suitable support for enzyme immobilisation displaying interesting electrochemical properties. The conductivity of the carbon based screen-printed electrodes was highly improved after modification with MoS2 nanoflakes and GQDs, the nanocomposite also providing compatible matrix for laccase immobilisation. The influence of different modification steps on the final electroanalytical performances of the modified electrode were evaluated by UV-vis absorption and fluorescence spectroscopy, scanning electron microscopy, transmission electron microscopy, X ray diffraction, electrochemical impedance spectroscopy and cyclic voltammetry. The developed laccase biosensor has responded efficiently to caffeic acid over a concentration range of 0.38-100µM, had a detection limit of 0.32µM and a sensitivity of 17.92nAµM(-1). The proposed analytical tool was successfully applied for the determination of total polyphenolic content from red wine samples. PMID:26319166

  3. Tension-induced phase transition of single-layer molybdenum disulphide (MoS2) at low temperatures.

    PubMed

    Zhao, Junhua; Kou, Liangzhi; Jiang, Jin-Wu; Rabczuk, Timon

    2014-07-25

    We show that the hexagonal structure of single-layer molybdenum disulphide (MoS2), under uniaxial tension along a zigzag direction for large deformations, can transfer to a new quadrilateral structure by molecular dynamics (MD) simulations when the temperature is below 40 K. The new phase remains stable after unloading, even at room temperature. The Young's modulus of the new phase along the zigzag direction is about 2.5 times higher than that of normal MoS2. Checking against density functional theory calculations shows that the new phase is preserved and displays excellent electrical conductivity. Our results provide physical insights into the origins of the new phase transition of MoS2 at low temperatures. PMID:24980057

  4. Impact of high energy ball milling on the nanostructure of magnetite–graphite and magnetite–graphite–molybdenum disulphide blends

    SciTech Connect

    Österle, W.; Orts-Gil, G.; Gross, T.; Deutsch, C.; Hinrichs, R.; Vasconcellos, M.A.Z.; Zoz, H.; Yigit, D.; Sun, X.

    2013-12-15

    Different, partly complementary and partly redundant characterization methods were applied to study the transition of magnetite, graphite and MoS{sub 2} powders to mechanically alloyed nanostructures. The applied methods were: Transmission electron microscopy (TEM), Mössbauer spectroscopy (MS), Raman spectroscopy (RS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The main objective was to prepare a model material providing the essential features of a typical tribofilm forming during automotive braking, and to assess the impact of different constituents on sliding behaviour and friction level. Irrespective of the initial grain size, the raw materials were transferred to a nanocrystalline structure and mixed on a nanoscopic scale during high energy ball milling. Whereas magnetite remained almost unchanged, graphite and molybdenum disulphide were transformed to a nanocrystalline and highly disordered structure. The observed increase of the coefficient of friction was attributed to a loss of lubricity of the latter ingredient due to this transformation and subsequent oxidation. - Highlights: • Characterization of microstructural changes induced by high energy ball milling • Assessment of the potential of different characterization methods • Impact of mechanical alloying on tribological performance revealed by tests • Preparation of an artificial third body resembling the one formed during braking.

  5. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures

    PubMed Central

    Pierucci, Debora; Henck, Hugo; Naylor, Carl H.; Sediri, Haikel; Lhuillier, Emmanuel; Balan, Adrian; Rault, Julien E.; Dappe, Yannick J.; Bertran, François; Fèvre, Patrick Le; Johnson, A. T. Charlie; Ouerghi, Abdelkarim

    2016-01-01

    Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design. PMID:27246929

  6. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures.

    PubMed

    Pierucci, Debora; Henck, Hugo; Naylor, Carl H; Sediri, Haikel; Lhuillier, Emmanuel; Balan, Adrian; Rault, Julien E; Dappe, Yannick J; Bertran, François; Fèvre, Patrick Le; Johnson, A T Charlie; Ouerghi, Abdelkarim

    2016-01-01

    Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design. PMID:27246929

  7. Large area molybdenum disulphide- epitaxial graphene vertical Van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Pierucci, Debora; Henck, Hugo; Naylor, Carl H.; Sediri, Haikel; Lhuillier, Emmanuel; Balan, Adrian; Rault, Julien E.; Dappe, Yannick J.; Bertran, François; Fèvre, Patrick Le; Johnson, A. T. Charlie; Ouerghi, Abdelkarim

    2016-06-01

    Two-dimensional layered transition metal dichalcogenides (TMDCs) show great potential for optoelectronic devices due to their electronic and optical properties. A metal-semiconductor interface, as epitaxial graphene - molybdenum disulfide (MoS2), is of great interest from the standpoint of fundamental science, as it constitutes an outstanding platform to investigate the interlayer interaction in van der Waals heterostructures. Here, we study large area MoS2-graphene-heterostructures formed by direct transfer of chemical-vapor deposited MoS2 layer onto epitaxial graphene/SiC. We show that via a direct transfer, which minimizes interface contamination, we can obtain high quality and homogeneous van der Waals heterostructures. Angle-resolved photoemission spectroscopy (ARPES) measurements combined with Density Functional Theory (DFT) calculations show that the transition from indirect to direct bandgap in monolayer MoS2 is maintained in these heterostructures due to the weak van der Waals interaction with epitaxial graphene. A downshift of the Raman 2D band of the graphene, an up shift of the A1g peak of MoS2 and a significant photoluminescence quenching are observed for both monolayer and bilayer MoS2 as a result of charge transfer from MoS2 to epitaxial graphene under illumination. Our work provides a possible route to modify the thin film TDMCs photoluminescence properties via substrate engineering for future device design.

  8. Unusual isotope effect on thermal transport of single layer molybdenum disulphide

    SciTech Connect

    Wu, Xufei; Yang, Nuo; Luo, Tengfei

    2015-11-09

    Thermal transport in single layer molybdenum disulfide (MoS{sub 2}) is critical to advancing its applications. In this paper, we use molecular dynamics simulations with first-principles force constants to study the isotope effect on the thermal transport of single layer MoS{sub 2}. Through phonon modal analysis, we found that isotopes can strongly scatter phonons with intermediate frequencies, and the scattering behavior can be radically different from that predicted by conventional scattering model based on perturbation theory, where Tamura's formula is combined with Matthiessen's rule to include isotope effects. Such a discrepancy becomes smaller for low isotope concentrations. Natural isotopes can lead to a 30% reduction in thermal conductivity for large size samples. However, for small samples where boundary scattering becomes significant, the isotope effect can be greatly suppressed. It was also found that the Mo isotopes, which contribute more to the phonon eigenvectors in the intermediate frequency range, have stronger impact on thermal conductivity than S isotopes.

  9. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction.

    PubMed

    Rowley-Neale, Samuel J; Fearn, Jamie M; Brownson, Dale A C; Smith, Graham C; Ji, Xiaobo; Banks, Craig E

    2016-08-21

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm(-2) modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR. PMID:27448174

  10. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Rowley-Neale, Samuel J.; Fearn, Jamie M.; Brownson, Dale A. C.; Smith, Graham C.; Ji, Xiaobo; Banks, Craig E.

    2016-08-01

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm-2 modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR.Two-dimensional molybdenum disulphide nanosheets

  11. Two-dimensional molybdenum disulphide nanosheet-covered metal nanoparticle array as a floating gate in multi-functional flash memories.

    PubMed

    Han, Su-Ting; Zhou, Ye; Chen, Bo; Zhou, Li; Yan, Yan; Zhang, Hua; Roy, V A L

    2015-11-01

    Semiconducting two-dimensional materials appear to be excellent candidates for non-volatile memory applications. However, the limited controllability of charge trapping behaviors and the lack of multi-bit storage studies in two-dimensional based memory devices require further improvement for realistic applications. Here, we report a flash memory consisting of metal NPs-molybdenum disulphide (MoS2) as a floating gate by introducing a metal nanoparticle (NP) (Ag, Au, Pt) monolayer underneath the MoS2 nanosheets. Controlled charge trapping and long data retention have been achieved in a metal (Ag, Au, Pt) NPs-MoS2 floating gate flash memory. This controlled charge trapping is hypothesized to be attributed to band bending and a built-in electric field ξbi between the interface of the metal NPs and MoS2. The metal NPs-MoS2 floating gate flash memories were further proven to be multi-bit memory storage devices possessing a 3-bit storage capability and a good retention capability up to 10(4) s. We anticipate that these findings would provide scientific insight for the development of novel memory devices utilizing an atomically thin two-dimensional lattice structure. PMID:26445097

  12. Modeling of Oxidation of Molybdenum Particles during Plasma Spray Deposition

    SciTech Connect

    Fincke, James Russell; Wan, Y. P.; Jiang, X. Y.; Sampath, S.; Prasad, V.; Herman, H.

    2001-06-01

    An oxidation model for molybdenum particles during the plasma spray deposition process is presented. Based on a well-verified model for plasma chemistry and the heating and phase change of particles in a plasma plume, this model accounts for the oxidant diffusion around the surface of particles or splats, oxidation on the surface, as well as oxygen diffusion in molten molybdenum. Calculations are performed for a single molybdenum particle sprayed under Metco-9MB spraying conditions. The oxidation features of particles during the flight are compared with those during the deposition. The result shows the dominance of oxidation of a molybdenum particle during the flight, as well as during deposition when the substrate temperature is high (above 400 °C).

  13. Carbonization behavior of pitches containing fine molybdenum particles

    SciTech Connect

    Ishihara, Atsushi; Wang, Xiangsheng; Kabe, Toshiaki . Dept. of Chemical Engineering); Shono, Hiroaki . Mineral Fiber Research Lab.)

    1993-08-01

    In the carbonization of coal tar pitch and naphthalene pitch containing fine molybdenum particles, it was found by using a tritium tracer method that the fine molybdenum particles added into pitch in advance can selectively catalyze the dehydrogenation and polycondensation of saturated hydrocarbons below 700 C, and thereby the carbonization yield of coal tar pitch containing partially saturated structures or aliphatic side chains in its component molecules increased. Further, it could be inferred that the fine molybdenum particles mainly accelerate the release of the hydrogen which is difficult to isotopically exchange with water in the preparation of tritiated pitch in the presence of Pt/Al[sub 2]O[sub 3].

  14. Two-dimensional molybdenum disulphide nanosheet-covered metal nanoparticle array as a floating gate in multi-functional flash memories

    NASA Astrophysics Data System (ADS)

    Han, Su-Ting; Zhou, Ye; Chen, Bo; Zhou, Li; Yan, Yan; Zhang, Hua; Roy, V. A. L.

    2015-10-01

    Semiconducting two-dimensional materials appear to be excellent candidates for non-volatile memory applications. However, the limited controllability of charge trapping behaviors and the lack of multi-bit storage studies in two-dimensional based memory devices require further improvement for realistic applications. Here, we report a flash memory consisting of metal NPs-molybdenum disulphide (MoS2) as a floating gate by introducing a metal nanoparticle (NP) (Ag, Au, Pt) monolayer underneath the MoS2 nanosheets. Controlled charge trapping and long data retention have been achieved in a metal (Ag, Au, Pt) NPs-MoS2 floating gate flash memory. This controlled charge trapping is hypothesized to be attributed to band bending and a built-in electric field ξbi between the interface of the metal NPs and MoS2. The metal NPs-MoS2 floating gate flash memories were further proven to be multi-bit memory storage devices possessing a 3-bit storage capability and a good retention capability up to 104 s. We anticipate that these findings would provide scientific insight for the development of novel memory devices utilizing an atomically thin two-dimensional lattice structure.Semiconducting two-dimensional materials appear to be excellent candidates for non-volatile memory applications. However, the limited controllability of charge trapping behaviors and the lack of multi-bit storage studies in two-dimensional based memory devices require further improvement for realistic applications. Here, we report a flash memory consisting of metal NPs-molybdenum disulphide (MoS2) as a floating gate by introducing a metal nanoparticle (NP) (Ag, Au, Pt) monolayer underneath the MoS2 nanosheets. Controlled charge trapping and long data retention have been achieved in a metal (Ag, Au, Pt) NPs-MoS2 floating gate flash memory. This controlled charge trapping is hypothesized to be attributed to band bending and a built-in electric field ξbi between the interface of the metal NPs and MoS2. The metal

  15. Microemulsion-mediated synthesis of nanosize molybdenum sulfide particles

    SciTech Connect

    Boakye, E.; Radovic, L.R.; Osseo-Asare, K. . Dept. of Materials Science and Engineering)

    1994-03-01

    A microemulsion-based method for the synthesis of molybdenum sulfide nanoparticles is reported. Molybdenum sulfide particles in the size range 10--80 nm have been precipitated in water-in-oil microemulsions (water-containing inverse micelles) formulated with polyoxyethylene(5)nonylphenyl ether (NP-5). The particles were synthesized in the NP-5/cyclohexane/water microemulsion system by acidifying ammonium tetrathiomolybdate solubilized in the water cores of the inverse micelles. Particle characterization was accomplished by chemical analysis, transmission electron microscopy, and ultraviolet/visible spectroscopy. The small size and the cage-like nature of the microemulsion water cores limit particle growth and aggregation. The particle size was found to be a function of the water-to-surfactant molar ratio and the average number of ammonium tetrathiomolybdate ions solubilized per water core. These trends are rationalized in terms of classical nucleation theory and aggregative growth concepts.

  16. Molybdenum

    Integrated Risk Information System (IRIS)

    Molybdenum ; CASRN 7439 - 98 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

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

    PubMed

    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. PMID:26032492

  18. Investigation of the α-particle induced nuclear reactions on natural molybdenum

    NASA Astrophysics Data System (ADS)

    Ditrói, F.; Hermanne, A.; Tárkányi, F.; Takács, S.; Ignatyuk, A. V.

    2012-08-01

    Cross-sections of alpha particle induced nuclear reactions on natural molybdenum have been studied in the frame of a systematic investigation of charged particle induced nuclear reactions on metals for different applications. The excitation functions of 93mTc, 93gTc(m+), 94mTc, 94gTc, 95mTc, 95gTc, 96gTc(m+), 99mTc, 93mMo, 99Mo(cum), 90Nb(m+), 94Ru, 95Ru,97Ru, 103Ru and 88Zr were measured up to 40 MeV alpha energy by using a stacked foil technique and activation method. The main goals of this work were to get experimental data for accelerator technology, for monitoring of alpha beam, for thin layer activation technique and for testing nuclear reaction theories. The experimental data were compared with critically analyzed published data and with the results of model calculations, obtained by using the ALICE-IPPE, EMPIRE and TALYS codes (TENDL-2011).

  19. Kinetics and specificity of homogeneous protein disulphide-isomerase in protein disulphide isomerization and in thiol-protein-disulphide oxidoreduction.

    PubMed

    Lambert, N; Freedman, R B

    1983-07-01

    The protein disulphide-bond isomerization activity of highly active homogeneous protein disulphide-isomerase (measured by re-activation of 'scrambled' ribonuclease) is enhanced by EDTA and by phosphate buffers. As shown for previous less-active preparations, the enzyme has a narrow pH optimum around pH 7.8 and requires the presence of either a dithiol or a thiol. The dithiol dithiothreitol is effective at concentrations 100-fold lower than the monothiols reduced glutathione and cysteamine. The enzyme follows Michaelis-Menten kinetics with respect to these substrates; Km values are 4,620 and 380 microM respectively. The enzyme shows apparent inhibition by high concentrations of thiol or dithiol compounds (greater than 10 X Km), but the effect is mainly on the extent of reaction, not the initial rate. This is interpreted as indicating the formation of significant amounts of reduced ribonuclease in these more reducing conditions. The purified enzyme will also catalyse net reduction of insulin disulphide bonds by reduced glutathione (i.e. it has thiol:protein-disulphide oxidoreductase or glutathione:insulin transhydrogenase activity), but this requires considerably higher concentrations of enzyme and reduced glutathione than does the disulphide-isomerization activity. The Km for reduced glutathione in this reaction is an order of magnitude greater than that for the disulphide-isomerization activity, and the turnover number is considerably lower than that of other enzymes that can catalyse thiol-disulphide oxidoreduction. Conventional two-substrate steady-state analysis of the thiol:protein-disulphide oxidoreductase activity indicates that it follows a ternary-complex mechanism. The protein disulphide-isomerase and thiol:protein-disulphide oxidoreductase activities co-purify quantitatively through the final stages of purification, implying that a single protein species is responsible for both activities. It is concluded that previous preparations, from various sources

  20. Radiolysis of solutions containing organo-disulphides

    NASA Astrophysics Data System (ADS)

    Elliot, Allen John; Simsons, Anita Sandra; Sopchyshyn, Frederick Charles

    When oxidized dithiothreitol (DTT- ox), oxidized gluthathione (GSSG), or dithiodiproprionic acid is radiolysed in N 2O-saturated sodium formate solutions, a chain reduction of the disulphide to the corresponding thiol occurs. The chain propagating step is the abstraction of the hydrogen atom in the formate ion by the thiyl radical. For the dithiothreitol thiyl radical, the rate constant for the abstraction is ≥ 3.6 × 10 4 mol -1 dm 3 s -1. The more sterically hindered penicillamine disulphide does not undergo this chain reaction. While the (CH 3) 2ĊOH radical does not reduce DTT- ox, it reduces GSSG to glutathione. At pH 9, the acetone radical anion, (CH 3) 2ĊO -, reduces both DTT- ox and GSSG.

  1. Low temperature photoresponse of monolayer tungsten disulphide

    SciTech Connect

    Cao, Bingchen; Shen, Xiaonan; Shang, Jingzhi; Cong, Chunxiao; Yang, Weihuang; Eginligil, Mustafa E-mail: meginligil@ntu.edu.sg; Yu, Ting E-mail: meginligil@ntu.edu.sg

    2014-11-01

    High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD) method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup), while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  2. The disulphide bridges of a mouse immunoglobulin G1 protein

    PubMed Central

    Svasti, J.; Milstein, C.

    1972-01-01

    [35S]Cystine-labelled immunoglobulin MOPC21 (IgG1) was prepared from myeloma cells in tissue culture. Carrier myeloma protein was added and the protein was digested with pepsin. The digest was fractionated on Sephadex G-50 into two fractions, further digested with trypsin and again fractionated on Sephadex. Disulphide-bridge peptides were purified by electrophoresis and chromatography and identified by radioautography. A peptide of 96 residues was isolated, which contains both the heavy–light interchain disulphide bridge and all the inter-heavy-chain disulphide bridges. Other peptides were isolated, accounting for all the intrachain disulphide bridges (which could be placed by homology with proteins of other species), except for the variable section of the light chain. Sequences describing this missing disulphide bridge were obtained from totally reduced and alkylated light chains. Peptides related to the interchain disulphide-bridge peptide were isolated from partially reduced and alkylated myeloma protein and from totally reduced heavy chain. The interchain disulphide-bridge peptide was placed at the C-terminal position of the F(ab′)2 fragment, prepared by digestion of the protein with pepsin at pH4.0. Sequences from the heavy-chain intrachain disulphide bridges of MOPC 21 immunoglobulin are compared with homologous sequences from mouse myeloma proteins of other subclasses and proteins of other species. PMID:5073237

  3. Several N-Glycans on the HIV Envelope Glycoprotein gp120 Preferentially Locate Near Disulphide Bridges and Are Required for Efficient Infectivity and Virus Transmission

    PubMed Central

    Mathys, Leen; Balzarini, Jan

    2015-01-01

    The HIV envelope glycoprotein gp120 contains nine disulphide bridges and is highly glycosylated, carrying on average 24 N-linked glycans. Using a probability calculation, we here demonstrate that there is a co-localization of disulphide bridges and N-linked glycans in HIV-1 gp120, with a predominance of N-linked glycans in close proximity to disulphide bridges, at the C-terminal side of the involved cysteines. Also, N-glycans are frequently found immediately adjacent to disulphide bridges in gp120 at the N-terminal side of the involved cysteines. In contrast, N-glycans at positions close to, but not immediately neighboring disulphide bridges seem to be disfavored at the N-terminal side of the involved cysteines. Such a pronounced co-localization of disulphide bridges and N-glycans was also found for the N-glycans on glycoprotein E1 of the hepatitis C virus (HCV) but not for other heavily glycosylated proteins such as E2 from HCV and the surface GP from Ebola virus. The potential functional role of the presence of N-glycans near disulphide bridges in HIV-1 gp120 was studied using site-directed mutagenesis, either by deleting conserved N-glycans or by inserting new N-glycosylation sites near disulphide bridges. The generated HIV-1NL4.3 mutants were subjected to an array of assays, determining the envelope glycoprotein levels in mutant viral particles, their infectivity and the capture and transmission efficiencies of mutant virus particles by DC-SIGN. Three N-glycans located nearby disulphide bridges were found to be crucial for the preservation of several of these functions of gp120. In addition, introduction of new N-glycans upstream of several disulphide bridges, at locations where there was a significant absence of N-glycans in a broad variety of virus strains, was found to result in a complete loss of viral infectivity. It was shown that the N-glycan environment around well-defined disulphide bridges of gp120 is highly critical to allow efficient viral infection

  4. Significance of the disulphide bonds of human growth hormone.

    PubMed

    Junnila, Riia K; Kopchick, John J

    2013-01-01

    Growth hormone (GH) structure is stabilised by two disulphide bonds, C53-C165 and C182-C189 in human GH. Researchers have investigatedthe role of these structural features since the late 1960s. Early studies implied that the disulphide bonds would not be importantfor biological activity of GH. However, more advanced techniques, as well as clues from patients carrying mutations in their GH1 gene,have demonstrated that the integrity of the disulphide bond between cysteines C53 and C165 is required for biological activity of GH.In contrast, disruption of the C-terminal disulphide bond (C182-C189) has only modest effects on the biological potency of GH, despitedecreased binding affinity to GH receptor and reduced stability as shown by a comprehensive in vitro study.To confirm these results, we generated transgenic mice that express a human GH analogue, C189A, and observed normal growth-promotingand lipolytic activities. In this article, we present new data and review old results concerning the disulphide bonds of GH. We also discussrelevant mutations found in patients with growth disorders. PMID:24002958

  5. Disulphide bond assignment in human tissue inhibitor of metalloproteinases (TIMP).

    PubMed Central

    Williamson, R A; Marston, F A; Angal, S; Koklitis, P; Panico, M; Morris, H R; Carne, A F; Smith, B J; Harris, T J; Freedman, R B

    1990-01-01

    Disulphide bonds in human recombinant tissue inhibitor of metalloproteinases (TIMP) were assigned by resolving proteolytic digests of TIMP on reverse-phase h.p.l.c. and sequencing those peaks judged to contain disulphide bonds by virtue of a change in retention time on reduction. This procedure allowed the direct assignment of Cys-145-Cys-166 and the isolation of two other peptides containing two disulphide bonds each. Further peptide cleavage in conjunction with fast-atom-bombardment m.s. analysis permitted the assignments Cys-1-Cys-70, Cys-3-Cys-99, Cys-13-Cys-124 and Cys-127-Cys-174 from these peptides. The sixth bond Cys-132-Cys-137 was assigned by inference, as the native protein has no detectable free thiol groups. Images Fig. 1. PMID:2163605

  6. Weldable ductile molybdenum alloy development

    SciTech Connect

    Cockeram, B. V.; Ohriner, Evan Keith; Byun, Thak Sang; Schneibel, Joachim H; Miller, Michael K; Snead, Lance Lewis

    2008-01-01

    Molybdenum and its alloys are attractive structural materials for high-temperature applications. However, various practical issues have limited its use. One concern relates to the loss of ductility occurring in the heat-affected weld zone caused by segregation of oxygen to grain boundaries. In this study, a series of arc melted molybdenum alloys have been produced containing controlled additions of B, C, Zr, and Al. These alloys were characterized with respect to their tensile properties, smooth bend properties, and impact energy for both the base metal and welds. These alloys were compared with a very high purity low carbon arc cast molybdenum reference. For discussion purposes the alloys produced are separated into two categories: Mo Al B alloys, and Mo Zr B alloys. The properties of Mo Zr B alloy welds containing higher carbon levels exhibited slight improvement over unalloyed molybdenum, though the base-metal properties for all Mo Zr B alloys were somewhat inconsistent with properties better, or worse, than unalloyed molybdenum. A Mo Al B alloy exhibited the best DBTT values for welds, and the base metal properties were comparable to or slightly better than unalloyed molybdenum. The Mo Al B alloy contained a low volume fraction of second-phase particles, with segregation of boron and carbon to grain boundaries believed to displace oxygen resulting in improved weld properties. The volume fractions of second-phase particles are higher for the Mo Zr B alloys, and these alloys were prone to brittle fracture. It is also noted that these Mo Zr B alloys exhibited segregation of zirconium, boron and carbon to the grain boundaries.

  7. Hybrid graphene-molybdenum disulphide based ring resonator for label-free sensing

    NASA Astrophysics Data System (ADS)

    Zangeneh-Nejad, Farzad; Safian, Reza

    2016-07-01

    In this paper, a novel graphene-MoS2 hybrid structure based surface plasmon resonance sensor is presented for label-free analysis. The structure consists of a silicon nitride (Si3N4) dielectric layer vertically coupled to a thin layer of metallic strip made of silver (Ag) on top. A hybrid graphene-MoS2 layer is added on top of the metallic strip to enhance the sensitivity and the quality factor of the sensor. The cladding layer is assumed to be porous alumina (p-Al2O3) increasing the interaction of the surface plasmon mode and the target molecules. Finite difference time domain analysis (FDTD) has been used to design and to analyze the performance of the sensor. It is shown that by addition of hybrid graphene-MoS2 layer to the structure of a surface plasmon resonance based sensor, the refractive index sensitivity and the intrinsic quality factor of the sensor are enhanced simultaneously. It is also shown that addition of the hybrid graphene-MoS2 layer leads to higher values of figure of merit (FOM) for the sensor, and consequently better performance of the sensor. Moreover, the effect of increasing the number of graphene and MoS2 layers is investigated. The proposed sensor is very compact and can be used for lab-on-a-chip sensing applications.

  8. High density decoration of noble metal nanoparticles on polydopamine-functionalized molybdenum disulphide.

    PubMed

    Hussain, Muhammad Asif; Yang, MinHo; Lee, Tae Jae; Kim, Jung Won; Choi, Bong Gill

    2015-08-01

    Here, we report a highly stable colloidal suspension of nanoparticles (i.e., Pt and Au)-deposited MoS2 sheets, in which polydopamine (PD) serves as surface functional groups. The adoption of polydopamine coating onto the MoS2 surface enables homogeneous deposition of nanoparticles in an aqueous solution. As-synthesized nanohybrids are thoroughly characterized by transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD) measurement. These intensive investigations reveal that noble metal nanocrystals are uniformly distributed on the surface of ultrathin MoS2 sheets (∼4 layers). Moreover, as-prepared Au/PD/MoS2 nanohybrids can be applied as a heterogeneous catalyst for reduction of 4-nitrophenol to 4-aminophenol, and they exhibit an excellent catalytic activity. PMID:25898116

  9. First-principles study of electronic structures and phase transitions of lithiated molybdenum disulphide

    NASA Astrophysics Data System (ADS)

    Li, Jun; Chen, Xiaobo

    2012-02-01

    By first-principles calculations, electronic structures of MoS2, intercalation-induced 2H to 1T phase transition and reversibility are investigated. It is revealed that change of interlayer stacking from 2H to 3R imposes negligible influence on the band structure and stability of MoS2. In contrast, the change of intralayer stacking from 2H to 1T changes the character of p-d repulsion, resulting in a semiconductor-to-metal transition. We demonstrate that the Kohn-Sham band energy, rather than the coulomb repulsion energy, plays dominant roles in both the phase stabilization and transition during Li intercalation. It is found that the evolution of 1T phase is crucially determined by chemical hardness, which underlies the cycle irreversibility. Due to the charge-density-wave (CDW) phase, Li extraction is impeded by the enhancement of Li-host binding. It is indicated that the cycle reversibility can be improved by electron-donor doping in MoS2, because the resultant pre-reduction of Mo and S eliminates the electron transfer from Li to host.

  10. Study on preparation and properties of molybdenum alloys reinforced by nano-sized ZrO2 particles

    NASA Astrophysics Data System (ADS)

    Cui, Chaopeng; Gao, Yimin; Wei, Shizhong; Zhang, Guoshang; Zhou, Yucheng; Zhu, Xiangwei; Guo, Songliang

    2016-03-01

    The nano-sized ZrO2-reinforced Mo alloy was prepared by a hydrothermal method and a subsequent powder metallurgy process. During the hydrothermal process, the nano-sized ZrO2 particles were added into the Mo powder via the hydrothermal synthesis. The grain size of Mo powder decreases obviously with the addition of ZrO2 particles, and the fine-grain sintered structure is obtained correspondingly due to hereditation. In addition to a few of nano-sized ZrO2 particles in grain boundaries or sub-boundaries, most are dispersed in grains. The tensile strength and yield strength have been increased by 32.33 and 53.76 %.

  11. Selective reduction of a disulphide bridge in hen ovotransferrin.

    PubMed Central

    Williams, J; Moreton, K; Goodearl, A D

    1985-01-01

    Brief treatment of iron-saturated hen ovotransferrin with dithiothreitol selectively cleaves the disulphide bridge between residues 478 and 671, which is in the C-terminal domain of the protein. The reduced alkylated protein is less stable than the native protein, and its iron-binding properties are different. A fluorescent derivative was prepared by coupling N-iodoacetyl-N'-(5-sulpho-1-naphthyl)ethylenediamine to the thiol groups. Images Fig. 3. PMID:4026802

  12. Isolation and characterization of lost copper and molybdenum particles in the flotation tailings of Kennecott copper porphyry ores

    NASA Astrophysics Data System (ADS)

    Tserendavga, Tsend-Ayush

    The importance of flotation separation has long been, and continues to be, an important technology for the mining industry, especially to metallurgical engineers. However, the flotation process is quite complex and expensive, in addition to being influenced by many variables. Understanding the variables affecting flotation efficiency and how valuable minerals are lost to the tailings gives metallurgists an advantage in their attempts to increase efficiency by designing operations to target the areas of greatest potential value. A successful, accurate evaluation of lost minerals in the tailings and appropriate solutions to improve flotation efficiency can save millions of dollars in the effective utilization of our mineral resources. In this dissertation research, an attempt has been made to understand the reasons for the loss of valuable mineral particles in the tailings from Kennecott Utah Copper ores. Possibilities include liberation, particle aggregation (slime coating) and surface chemistry issues associated with the flotation separation. This research generally consisted of three main aspects. The first part involved laboratory flotation experiments and factors, which affect the flotation efficiency. Results of flotation testing are reported that several factors such as mineral exposure/liberation and slime coating and surface oxidation strongly affect the flotation efficiency. The second part of this dissertation research was to develop a rapid scan dual energy (DE) methodology using 2D radiography to identify, isolate, and prepare lost sulfide mineral particles with the advantages of simple sample preparation, short analysis time, statistically reliable accuracy and confident identification. The third part of this dissertation research was concerned with detailed characterization of lost particles including such factors as liberation, slime coating, and surface chemistry characteristics using advanced analytical techniques and instruments. Based on the

  13. Microstructure and Wear Resistance of Plasma-Sprayed Molybdenum Coating Reinforced by MoSi2 Particles

    NASA Astrophysics Data System (ADS)

    Yan, Jianhui; He, Zheyu; Wang, Yi; Qiu, Jingwen; Wang, Yueming

    2016-08-01

    Mo coatings with or without incorporated MoSi2 were fabricated by atmospheric plasma spraying, and their microstructure, microhardness, bond strength, and wear resistance were compared. Two kinds of spray powder, i.e., pure Mo and a blend of Mo and MoSi2, were sprayed onto low-carbon steel. Microstructural analysis of the MoSi2-Mo coating showed MoSi2 homogeneously distributed in a Mo matrix. Addition of MoSi2 particles increased the microhardness of the as-sprayed Mo coating. The adhesion strength of the Mo coating was better than that of the MoSi2-Mo coating. Wear test results showed that the wear rate and friction coefficient of the two coatings increased with increasing load, and the friction coefficient of the MoSi2-Mo coating was lower than that of the Mo coating. The MoSi2-Mo composite coating exhibited better wear resistance than the Mo coating. The wear failure mechanisms of the two coatings were local plastic deformation, delamination, oxidation, and adhesion wear.

  14. Transfer of molybdenum disulfide to various metals

    NASA Technical Reports Server (NTRS)

    Barton, G. C.; Pepper, S. V.

    1977-01-01

    Sliding friction experiments were conducted with molybdenum disulfide single crystals in contact with sputter cleaned surfaces of copper, nickel, gold, and 304 stainless steel. Transfer of the molybdenum disulfide to the metals was monitored with Auger electron spectroscopy. Results of the investigation indicate molybdenum disulfide transfers to all clean metal surfaces after a single pass over the metal surface with film thickness observed to increase with repeated passes over the same surfaces. Large particle transfer occurs when the orientation of the crystallites is other than basal. This is frequently accompanied by abrasion of the metal. Adhesion of molybdenum disulfide films occurred readily to copper and nickel, less readily to 304 stainless steel, and even less effectively to the gold, which indicates a chemical effect.

  15. Mixture of a molybdenum carboxylate and a molybdenum dithiophosphate or a molybdenum dithiocarbamate for use in a hydrovisbreaking process

    SciTech Connect

    Howell, J.A.; Kukes, S.G.

    1987-11-10

    A molybdenum is described containing mixture selected from the group consisting of a mixture comprising a molybdenum dithiophosphate and a molybdenum carboxylate and a mixture comprising a molybdenum dithiocarbamate and a molybdenum carboxylate.

  16. Molybdenum disilicide composites

    DOEpatents

    Rodriguez, Robert P.; Petrovic, John J.

    2001-01-01

    Molybdenum disilicide/.beta.'-Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z, wherein z=a number from greater than 0 to about 5, composites are made by use of in situ reactions among .alpha.-silicon nitride, molybdenum disilicide, and aluminum. Molybdenum disilicide within a molybdenum disilicide/.beta.'-Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z eutectoid matrix is the resulting microstructure when the invention method is employed.

  17. Molybdenum nutriture in humans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Molybdenum is a trace element that functions as a cofactor for at least four enzymes: sulfite oxidase, xanthine oxidase, aldehyde oxidase, and mitochondrial amidoxime reducing component. In each case, molybdenum is bound to a complex, multi-ring organic component called molybdopterin, forming the e...

  18. Molybdenum disilicide matrix composite

    DOEpatents

    Petrovic, John J.; Carter, David H.; Gac, Frank D.

    1991-01-01

    A composition consisting of an intermetallic compound, molybdenum disilicide, which is reinforced with VS silicon carbide whiskers dispersed throughout it and a method of making the reinforced composition. Use of the reinforcing material increases fracture toughness at low temperatures and strength at high temperatures, as compared to pure molybdenum disilicide.

  19. Molybdenum disilicide matrix composite

    DOEpatents

    Petrovic, John J.; Carter, David H.; Gac, Frank D.

    1990-01-01

    A composition consisting of an intermetallic compound, molybdenum disilicide, which is reinforced with VS silicon carbide whiskers dispersed throughout it and a method of making the reinforced composition. Use of the reinforcing material increases fracture toughness at low temperatures and strength at high temperatures, as compared to pure molybdenum disilicide.

  20. The role of disulphide bonds in human intestinal mucin

    PubMed Central

    Forstner, Janet F.; Jabbal, Inderjit; Qureshi, Rauf; Kells, David I. C.; Forstner, Gordon G.

    1979-01-01

    Goblet-cell mucin (mucin 1) was isolated and purified from human small-intestinal scrapings. After application of mucin 1 to DEAE-Bio-Gel (A) columns, most of the glycoprotein (76–94% of hexoses) was eluted in the first peak (designated mucin 2). Minor amounts of acidic glycoproteins were eluted with 0.2m- and 0.4m-NaCl in later peaks. Analyses of mucin 1 and mucin 2 revealed mucin 2 to be a monodisperse highly glycosylated glycoprotein containing 6.3% by wt. of protein, N-acetylgalactosamine, N-acetylglucosamine, galactose and fucose. Mucin 1 was similar in composition, but was polydisperse and contained more protein (12.3% by wt.) as well as N-acetylneuraminic acid. Analytical CsCl-gradient ultracentrifugation showed both mucin 1 and mucin 2 to have a major component with an average buoyant density of 1.47000g/ml. Mucin 1 also contained a slightly less-dense minor glycoprotein component. After exhaustive reduction and alkylation mucin 1 retained its major component, but partly dissociated into two lighter glycoprotein components. Mucin 2, in contrast, did not change its density distribution after reduction. Band ultracentrifugation in 2H2O-containing iso-osmotic buffers showed that mucin 1 contained a major fast-sedimenting component (so=37±2S), and a minor amount of a slower-sedimenting component. After reduction there was an increased quantity of the latter component, for which an so value of 14.5S was calculated. In contrast, mucin 2 was unaltered by reduction (so=33±2S). These findings indicate that the major component of goblet-cell mucin (mucin 2) does not dissociate after S–S-bond reduction, and thus does not apparently rely for its polymeric structure on the association of subunits through covalent disulphide bonds. However, the effects of reduction on mucin 1 suggest that in the native mucin intramolecular disulphide bonds in the minor glycoproteins may stabilize their structure, permitting secondary non-covalent interactions to develop with the

  1. Organometallic Chemistry of Molybdenum.

    ERIC Educational Resources Information Center

    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)

  2. Polyneuropathy induced by carbon disulphide in viscose rayon workers.

    PubMed Central

    Chu, C C; Huang, C C; Chen, R S; Shih, T S

    1995-01-01

    OBJECTIVES--To understand the prevalence of polyneuropathy and correlations among the clinical manifestations, electrophysiological findings, and degree of exposure to carbon disulphide (CS2) in workers who were exposed to variable concentrations of CS2 in a viscose rayon factory. METHODS--All the 163 workers received a detailed physical and neurological evaluation. Fixed point air samples were analysed for CS2. Nerve conduction velocity was studied in 26 workers with symptoms similar to neuropathy. RESULTS--Nine workers (53%) with overt polyneuropathy from the fibre cutting department and 19 workers (13%) with oligosymptoms similar to polyneuropathy from various jobs were noted. The fixed point air concentrations of CS2 were 150-300 ppm in the cutting areas and 15 to 100 ppm in the spinning areas. The estimated eight hour time weighted averages in the fibre cutting areas were 40-67 ppm. The occurrence of polyneuropathy was generally correlated with the degree of exposure to CS2. Nerve conduction velocities (NCVs) were significantly different in the overt polyneuropathy and subclinical polyneuropathy groups from the normal controls. The sensitive indicators for CS2 polyneuropathy were distal latency, motor NCV, and amplitude of sensory nerve action potentials in sensory NCVs. CONCLUSION--The outbreak of polyneuropathy was attributed to higher concentrations of CS2 in fibre cutting areas. Even in other jobs with relatively lower concentrations of CS2, the hazard of subclinical polyneuropathy cannot be overlooked. PMID:7627318

  3. Disposition and metabolism of dipropyl disulphide in vivo in rat.

    PubMed

    Germain, E; Semon, E; Siess, M-H; Teyssier, C

    2008-01-01

    The metabolism of dipropyl disulphide (DPDS), a sulphur compound from onion, was investigated in vivo in the rat. A single dose (200 mg kg(-1)) was administered by gastric intubation and the time courses of DPDS and its metabolites were followed over 48 h by gas chromatography coupled with mass spectrometry in the stomach, intestine, liver, and blood. DPDS was detected in the stomach where it was transformed into propyl mercaptan, whereas the liver contained only traces of DPDS and none at all in the other examined organs. The metabolites methylpropyl sulphide, methylpropyl sulphoxide (MPSO), and methylpropyl sulphone (MPSO2) were sequentially formed in the liver. The route of elimination from the liver seemed to be mainly via the blood. The bile also participated in the excretory process, but only for MPSO2. The pharmacokinetic parameters were determined for all of the above compounds. Whereas the bioavailability of DPDS was very low (0.008 h mM), the areas under the curve were higher for the S-oxidized metabolites MPSO and MPSO2, i.e. 9.64 and 24.15 h mM, respectively. The half-lives for DPDS and its metabolites varied between 2.0 and 8.25 h, except for MPSO2, which had a half-life of 29.6 h. MPSO2 was the most abundant and persistent of these metabolites. PMID:18098065

  4. Preparation of thick molybdenum targets

    NASA Technical Reports Server (NTRS)

    Singh, J. J.

    1974-01-01

    Thick natural molybdenum deposits on nickel plated copper substrates were prepared by thermal decomposition of molybdenum hexacarbonyl vapors on a heated surface in an inert gas atmosphere. The molybdenum metal atoms are firmly bonded to the substrate atoms, thus providing an excellent thermal contact across the junction. Molybdenum targets thus prepared should be useful for internal bombardment in a cyclotron where thermal energy inputs can exceed 10 kW.

  5. Method of producing molybdenum-99

    DOEpatents

    Pitcher, Eric John

    2013-05-28

    Method of producing molybdenum-99, comprising accelerating ions by means of an accelerator; directing the ions onto a metal target so as to generate neutrons having an energy of greater than 10 MeV; directing the neutrons through a converter material comprising techentium-99 to produce a mixture comprising molybdenum-99; and, chemically extracting the molybdenum-99 from the mixture.

  6. 2D nanosheet molybdenum disulphide (MoS2) modified electrodes explored towards the hydrogen evolution reaction.

    PubMed

    Rowley-Neale, Samuel J; Brownson, Dale A C; Smith, Graham C; Sawtell, David A G; Kelly, Peter J; Banks, Craig E

    2015-11-21

    We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER. PMID:26478468

  7. 2D nanosheet molybdenum disulphide (MoS2) modified electrodes explored towards the hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Rowley-Neale, Samuel J.; Brownson, Dale A. C.; Smith, Graham C.; Sawtell, David A. G.; Kelly, Peter J.; Banks, Craig E.

    2015-10-01

    We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER.We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05164a|ART

  8. Aberrant disulphide bonding contributes to the ER retention of alpha1-antitrypsin deficiency variants.

    PubMed

    Ronzoni, Riccardo; Berardelli, Romina; Medicina, Daniela; Sitia, Roberto; Gooptu, Bibek; Fra, Anna Maria

    2016-02-15

    Mutations in alpha1-antitrypsin (AAT) can cause the protein to polymerise and be retained in the endoplasmic reticulum (ER) of hepatocytes. The ensuing systemic AAT deficiency leads to pulmonary emphysema, while intracellular polymers are toxic and cause chronic liver disease. The severity of this process varies considerably between individuals, suggesting the involvement of mechanistic co-factors and potential for therapeutically beneficial interventions. We show in Hepa1.6 cells that the mildly polymerogenic I (Arg39Cys) AAT mutant forms aberrant inter- and intra-molecular disulphide bonds involving the acquired Cys39 and the only cysteine residue in the wild-type (M) sequence (Cys232). Substitution of Cys39 to serine partially restores secretion, showing that disulphide bonding contributes to the intracellular retention of I AAT. Covalent homodimers mediated by inter-Cys232 bonding alone are also observed in cells expressing the common Z and other polymerising AAT variants where conformational behaviour is abnormal, but not in those expressing M AAT. Prevention of such disulphide linkage through the introduction of the Cys232Ser mutation or by treatment of cells with reducing agents increases Z AAT secretion. Our results reveal that disulphide interactions enhance intracellular accumulation of AAT mutants and implicate the oxidative ER state as a pathogenic co-factor. Redox modulation, e.g. by anti-oxidant strategies, may therefore be beneficial in AAT deficiency-associated liver disease. PMID:26647313

  9. Molybdenum cofactor deficiency.

    PubMed

    Atwal, Paldeep S; Scaglia, Fernando

    2016-01-01

    Molybdenum cofactor deficiency (MoCD) is a severe autosomal recessive inborn error of metabolism first described in 1978. It is characterized by a neonatal presentation of intractable seizures, feeding difficulties, severe developmental delay, microcephaly with brain atrophy and coarse facial features. MoCD results in deficiency of the molybdenum cofactor dependent enzymes sulfite oxidase, xanthine dehydrogenase, aldehyde oxidase and mitochondrial amidoxime reducing component. The resultant accumulation of sulfite, taurine, S-sulfocysteine and thiosulfate contributes to the severe neurological impairment. Recently, initial evidence has demonstrated early treatment with cyclic PMP can turn MoCD type A from a previously neonatal lethal condition with only palliative options, to near normal neurological outcomes in affected patients. We review MoCD and focus on describing the currently published evidence of this exciting new therapeutic option for MoCD type A caused by pathogenic variants in MOCD1. PMID:26653176

  10. An ERp57-mediated disulphide exchange promotes the interaction between Burkholderia cenocepacia and epithelial respiratory cells

    PubMed Central

    Pacello, Francesca; D’Orazio, Melania; Battistoni, Andrea

    2016-01-01

    Previous studies have demonstrated that extracellular glutathione reduces the ability of the Cystic Fibrosis pathogen Burkholderia cenocepacia to infect primary or immortalized epithelial respiratory cells. We report here that the adhesion and invasion ability of B. cenocepacia is limited also by thiol-oxidizing and disulphide-reducing agents and by protein disulfide isomerase (PDI) inhibitors. PDI inhibitors also reduce the proinflammatory response elicited by cells in response to Burkholderia. These findings indicate that a membrane-associated PDI catalyzes thiol/disulphide exchange reactions which favor bacterial infection. The combined use of selective PDI inhibitors, RNA silencing and specific antibodies identified ERp57 as a major PDI involved in the interaction between B. cenocepacia and epithelial cells. This study contributes to the elucidation of the Burkholderia pathogenic mechanisms by showing that this microorganism exploits a membrane-associated host protein to infect epithelial cells and identifies ERp57 as a putative pharmacological target for the treatment of Burkholderia lung infections. PMID:26879174

  11. A structural homologue of colipase in black mamba venom revealed by NMR floating disulphide bridge analysis.

    PubMed

    Boisbouvier, J; Albrand, J P; Blackledge, M; Jaquinod, M; Schweitz, H; Lazdunski, M; Marion, D

    1998-01-01

    The solution structure of mamba intestinal toxin 1 (MIT1), isolated from Dendroaspis polylepis polylepis venom, has been determined. This molecule is a cysteine-rich polypeptide exhibiting no recognised family membership. Resistance to MIT1 to classical specific endoproteases produced contradictory NMR and biochemical information concerning disulphide-bridge topology. We have used distance restraints allowing ambiguous partners between S atoms in combination with NMR-derived structural information, to correctly determine the disulphide-bridge topology. The resultant solution structure of MIT1, determined to a resolution of 0.5 A, reveals an unexpectedly similar global fold with respect to colipase, a protein involved in fatty acid digestion. Colipase exhibits an analogous resistance to endoprotease activity, indicating for the first time the possible topological origins of this biochemical property. The biochemical and structural homology permitted us to propose a mechanically related digestive function for MIT1 and provides novel information concerning snake venom protein evolution. PMID:9761684

  12. Novel roles for protein disulphide isomerase in disease states: a double edged sword?

    PubMed Central

    Parakh, Sonam; Atkin, Julie D.

    2015-01-01

    Protein disulphide isomerase (PDI) is a multifunctional redox chaperone of the endoplasmic reticulum (ER). Since it was first discovered 40 years ago the functions ascribed to PDI have evolved significantly and recent studies have recognized its distinct functions, with adverse as well as protective effects in disease. Furthermore, post translational modifications of PDI abrogate its normal functional roles in specific disease states. This review focusses on recent studies that have identified novel functions for PDI relevant to specific diseases. PMID:26052512

  13. Mineral resource of the month: molybdenum

    USGS Publications Warehouse

    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.

  14. Parameters affecting in vitro oxidation/folding of maurotoxin, a four-disulphide-bridged scorpion toxin.

    PubMed Central

    di Luccio, E; Azulay, D O; Regaya, I; Fajloun, Z; Sandoz, G; Mansuelle, P; Kharrat, R; Fathallah, M; Carrega, L; Estève, E; Rochat, H; De Waard, M; Sabatier, J M

    2001-01-01

    Maurotoxin (MTX) is a 34-mer scorpion toxin cross-linked by four disulphide bridges that acts on various K(+) channel subtypes. MTX adopts a disulphide bridge organization of the type C1-C5, C2-C6, C3-C4 and C7-C8, and folds according to the common alpha/beta scaffold reported for other known scorpion toxins. Here we have investigated the process and kinetics of the in vitro oxidation/folding of reduced synthetic L-MTX (L-sMTX, where L-MTX contains only L-amino acid residues). During the oxidation/folding of reduced L-sMTX, the oxidation intermediates were blocked by iodoacetamide alkylation of free cysteine residues, and analysed by MS. The L-sMTX intermediates appeared sequentially over time from the least (intermediates with one disulphide bridge) to the most oxidized species (native-like, four-disulphide-bridged L-sMTX). The mathematical formulation of the diffusion-collision model being inadequate to accurately describe the kinetics of oxidation/folding of L-sMTX, we have formulated a derived mathematical description that better fits the experimental data. Using this mathematical description, we have compared for the first time the oxidation/folding of L-sMTX with that of D-sMTX, its stereoisomer that contains only D-amino acid residues. Several experimental parameters, likely to affect the oxidation/folding process, were studied further; these included temperature, pH, ionic strength, redox potential and concentration of reduced toxin. We also assessed the effects of some cellular enzymes, peptidylprolyl cis-trans isomerase (PPIase) and protein disulphide isomerase (PDI), on the folding pathways of reduced L-sMTX and D-sMTX. All the parameters tested affect the oxidative folding of sMTX, and the kinetics of this process were indistinguishable for L-sMTX and D-sMTX, except when stereospecific enzymes were used. The most efficient conditions were found to be: 50 mM Tris/HCl/1.4 mM EDTA, pH 7.5, supplemented by 0.5 mM PPIase and 50 units/ml PDI for 0.1 m

  15. Oxygen Plasma Interactions with Molybdenum: Formation of Volatile Molybdenum Oxides

    NASA Astrophysics Data System (ADS)

    Saburi, Tei; Murata, Hirotoshi; Suzuki, Tatsuya; Fujii, Yasuhiko; Kiuchi, Kiyoshi

    The oxidation of molybdenum by oxygen plasma was studied. The oxygen plasma was discharged by helicon wave at the frequency of 18.1 MHz and at the power of 200W. The weight change of molybdenum in oxygen plasma was measured at 400 °C and at oxygen pressure of 5 Pa. The specimen was found to be oxidized and to lose it's weight drastically with the oxygen plasma, while the weight change of the specimen in the oxidation without plasma was not observed under the same conditions. The energetic species of oxygen atoms generated by rf plasma is regarded to accelerate the oxidation of molybdenum and the oxidation leads to the formation of volatile molybdenum trioxide at the surface.

  16. Molybdenum enzymes in higher organisms

    PubMed Central

    Hille, Russ; Nishino, Takeshi; Bittner, Florian

    2010-01-01

    Recent progress in our understanding of the structural and catalytic properties of molybdenum-containing enzymes in eukaryotes is reviewed, along with aspects of the biosynthesis of the cofactor and its insertion into apoprotein. PMID:21516203

  17. Oxide strengthened molybdenum-rhenium alloy

    SciTech Connect

    Bianco, Robert; Buckman, Jr., R. William

    2000-01-01

    Provided is a method of making an ODS molybdenum-rhenium alloy which includes the steps of: (a) forming a slurry containing molybdenum oxide and a metal salt dispersed in an aqueous medium, the metal salt being selected from nitrates or acetates of lanthanum, cerium or thorium; (b) heating the slurry in the presence of hydrogen to form a molybdenum powder comprising molybdenum and an oxide of the metal salt; (c) mixing rhenium powder with the molybdenum powder to form a molybdenum-rhenium powder; (d) pressing the molybdenum-rhenium powder to form a molybdenum-rhenium compact; (e) sintering the molybdenum-rhenium compact in hydrogen or under a vacuum to form a molybdenum-rhenium ingot; and (f) compacting the molybdenum-rhenium ingot to reduce the cross-sectional area of the molybdenum-rhenium ingot and form a molybdenum-rhenium alloy containing said metal oxide. The present invention also provides an ODS molybdenum-rhenium alloy made by the method. A preferred Mo--Re-ODS alloy contains 7-14 weight % rhenium and 2-4 volume % lanthanum oxide.

  18. Oxide strengthened molybdenum-rhenium alloy

    SciTech Connect

    Bianco, Robert; Buckman, William R. Jr.

    1998-12-01

    Provided is a method of making an ODS molybdenum-rhenium alloy which includes the steps of: (1) forming a slurry containing molybdenum oxide and a metal salt dispersed in an aqueous medium, the metal salt being selected from nitrates or acetates of lanthanum, cerium or thorium; (2) heating the slurry in the presence of hydrogen to form a molybdenum powder comprising molybdenum and an oxide of the metal salt; (3) mixing rhenium powder with the molybdenum powder to form a molybdenum-rhenium powder; (4) pressing the molybdenum-rhenium powder to form a molybdenum-rhenium compact; (5) sintering the molybdenum-rhenium compact in hydrogen or under a vacuum to form a molybdenum-rhenium ingot; and (6) compacting the molybdenum-rhenium ingot to reduce the cross-sectional area of the molybdenum-rhenium ingot and form a molybdenum-rhenium alloy containing said metal oxide. The present invention also provides an ODS molybdenum-rhenium alloy made by the method.

  19. Trichinella spiralis: genome database searches for the presence and immunolocalization of protein disulphide isomerase family members.

    PubMed

    Freitas, C P; Clemente, I; Mendes, T; Novo, C

    2016-01-01

    The formation of nurse cells in host muscle cells during Trichinella spiralis infection is a key step in the infective mechanism. Collagen trimerization is set up via disulphide bond formation, catalysed by protein disulphide isomerase (PDI). In T. spiralis, some PDI family members have been identified but no localization is described and no antibodies specific for T. spiralis PDIs are available. In this work, computational approaches were used to search for non-described PDIs in the T. spiralis genome database and to check the cross-reactivity of commercial anti-human antibodies with T. spiralis orthologues. In addition to a previously described PDI (PDIA2), endoplasmic reticulum protein (ERp57/PDIA3), ERp72/PDIA4, and the molecular chaperones calreticulin (CRT), calnexin (CNX) and immunoglobulin-binding protein/glucose-regulated protein (BIP/GRP78), we identified orthologues of the human thioredoxin-related-transmembrane proteins (TMX1, TMX2 and TMX3) in the genome protein database, as well as ERp44 (PDIA10) and endoplasmic reticulum disulphide reductase (ERdj5/PDIA19). Immunocytochemical staining of paraffin sections of muscle infected by T. spiralis enabled us to localize some orthologues of the human PDIs (PDIA3 and TMX1) and the chaperone GRP78. A theoretical three-dimensional model for T. spiralis PDIA3 was constructed. The localization and characteristics of the predicted linear B-cell epitopes and amino acid sequence of the immunogens used for commercial production of anti-human PDIA3 antibodies validated the use of these antibodies for the immunolocalization of T. spiralis PDIA3 orthologues. These results suggest that further study of the role of the PDIs and chaperones during nurse cell formation is desirable. PMID:25475092

  20. Disulphide bonds in wheat gluten: cystine peptides derived from gluten proteins following peptic and thermolytic digestion.

    PubMed

    Keck, B; Köhler, P; Wieser, H

    1995-06-01

    Gluten from the wheat variety Rektor was extracted with 70% aqueous ethanol. The insoluble portion (whole glutenin) was partially hydrolysed with trypsin at pH 6.5 and separated on a Sephadex G25 column. The high molecular weight fraction 1 was further hydrolysed with pepsin at pH 2.0. To remove low molecular weight proteins, a portion of whole glutenin was extracted with dilute acetic acid. The residue (enriched glutenin), which contained mostly LMW and HMW subunits of glutenin, was hydrolysed with thermolysin at pH 6.5. The peptic and tryptic hydrolysates were separated on a Sephadex G25 column and the peptide fractions with the highest cystine content were separated further by reversed-phase high-performance liquid chromatography (RP-HPLC). Cystine peptides were detected by differential chromatography (RP-HPLC prior to and after reduction of disulphide bonds) and then isolated by preparative RP-HPLC. After reduction, cysteine peptides were alkylated and analysed for their amino acid sequence. Altogether, 19 cystine peptides were characterized and assigned to known sequences of gluten proteins; 16 peptides confirmed the positions of disulphide bonds present in LMW subunits and gamma-gliadins, as described previously. For the first time, a cystine peptide has been isolated, representing an intermolecular disulphide bond between the y-type of HMW and LMW subunits. Furthermore, a cystine peptide was assigned to gamma-gliadins; thus, all cysteine residues of gamma-gliadins are documented by at least one cystine peptide. One peptide analysed came from the alpha-amylase inhibitor CM 16. Altogether the results indicate that the intramolecular linkages of gluten proteins are not formed at random, but are strongly directed.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7668061

  1. Genetics Home Reference: molybdenum cofactor deficiency

    MedlinePlus

    ... molybdenum, is essential to the function of several enzymes. These enzymes help break down (metabolize) different substances in the ... molybdenum cofactor biosynthesis. Without the cofactor, the metabolic enzymes that rely on it cannot function. The resulting ...

  2. Nitrogen reduction: Molybdenum does it again

    NASA Astrophysics Data System (ADS)

    Schrock, Richard R.

    2011-02-01

    Nature reduces dinitrogen under mild conditions using nitrogenases, the most active of which contains molybdenum and iron. The only abiological dinitrogen reduction catalyst that avoids the harsh conditions of the Haber-Bosch process contains just molybdenum.

  3. Silicon nitride reinforced with molybdenum disilicide

    SciTech Connect

    Petrovic, J.J.; Honnell, R.E.

    1990-12-31

    Compositions of matter comprised of silicon nitride and molybdenum disilicide and methods of making the compositions, where the molybdenum disilicide is present in amounts ranging from about 5 to about 50 vol%.

  4. Silicon nitride reinforced with molybdenum disilicide

    DOEpatents

    Petrovic, John J.; Honnell, Richard E.

    1991-01-01

    Compositions of matter comprised of silicon nitride and molybdenum disilicide and methods of making the compositions, where the molybdenum disilicide is present in amounts ranging from about 5 to about 50 vol. %.

  5. High-performance MoS{sub 2} transistors with low-resistance molybdenum contacts

    SciTech Connect

    Kang, Jiahao; Liu, Wei; Banerjee, Kaustav

    2014-03-03

    In this Letter, molybdenum (Mo) is introduced and evaluated as an alternative contact metal to atomically-thin molybdenum disulphide (MoS{sub 2}), and high-performance field-effect transistors are experimentally demonstrated. In order to understand the physical nature of the interface and highlight the role of the various factors contributing to the Mo-MoS{sub 2} contacts, density functional theory (DFT) simulations are employed, which reveal that Mo can form high quality contact interface with monolayer MoS{sub 2} with zero tunnel barrier and zero Schottky barrier under source/drain contact, as well as an ultra-low Schottky barrier (0.1 eV) at source/drain-channel junction due to strong Fermi level pinning. In agreement with the DFT simulations, high mobility, high ON-current, and low contact resistance are experimentally demonstrated on both monolayer and multilayer MoS{sub 2} transistors using Mo contacts. The results obtained not only reveal the advantages of using Mo as a contact metal for MoS{sub 2} but also highlight the fact that the properties of contacts with 2-dimensional materials cannot be intuitively predicted by solely considering work function values and Schottky theory.

  6. Sulfolobus solfataricus protein disulphide oxidoreductase: insight into the roles of its redox sites.

    PubMed

    Limauro, Danila; Saviano, Michele; Galdi, Ilaria; Rossi, Mosè; Bartolucci, Simonetta; Pedone, Emilia

    2009-01-01

    Sulfolobus solfataricus protein disulphide oxidoreductase (SsPDO) contains three disulphide bridges linking residues C(41)XXC(44), C(155)XXC(158), C(173)XXXXC(178). To get information on the role played by these cross-links in determining the structural and functional properties of the protein, we performed site-directed mutagenesis on Cys residues and investigated the changes in folding, stability and functional features of the mutants and analysed the results with computational analysis. The reductase activity of SsPDO and its mutants was evaluated by insulin and thioredoxin reductase assays also coupled with peroxiredoxin Bcp1 of S. solfataricus. The three-dimensional model of SsPDO was constructed and correlated with circular dichroism data and functional results. Biochemical analysis indicated a key function for the redox site constituted by Cys155 and Cys158. To discriminate between the role of the two cysteine residues, each cysteine was mutagenized and the behaviour of the single mutants was investigated elucidating the basis of the electron-shuffling mechanism for SsPDO. Finally, cysteine pK values were calculated and the accessible surface for the cysteine side chains in the reduced form was measured, showing higher reactivity and solvent exposure for Cys155. PMID:18988690

  7. Determination of small amounts of molybdenum in tungsten and molybdenum ores

    USGS Publications Warehouse

    Grimaldi, F.S.; Wells, R.C.

    1943-01-01

    A rapid method has been developed for the determination of small amounts of molybdenum in tungsten and molybdenum ores. After removing iron and other major constituents the molybdenum thiocyanate color is developed in water-acetone solutions, using ammonium citrate to eliminate the interference of tungsten. Comparison is made by titrating a blank with a standard molybdenum solution. Aliquots are adjusted to deal with amounts of molybdenum ranging from 0.01 to 1.30 mg.

  8. Molybdenum sulfide/carbide catalysts

    DOEpatents

    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.

  9. Sintering, Microstructure, and Electrical Conductivity of Zirconia-Molybdenum Cermet

    NASA Astrophysics Data System (ADS)

    Guo, Yanling; Tang, Lei; Zhang, Jieyu

    2015-08-01

    Monolithic zirconia-molybdenum ( m-ZrO2/Mo) cermets of different compositions (5-40 vol.% Mo) and different initial Mo particles sizes (0.08-13 μm) were prepared by traditional powder metallurgy process. The influences of metal content and initial particle sizes on the densification behavior, microstructure, and electrical conductivity of the cermets were studied. A percolation threshold value was obtained about 17.1 vol.% molybdenum fraction, above which a sharp increase in the electrical conductivity was observed. The temperature dependence of the electrical conductivity of cermets was studied. The cermet containing 5 vol.% Mo showed the ionic nature of the conductivity, while the metallic nature was observed in the samples of Mo fraction up to 16 vol.%. The activation of conductivity for ionic type of conductivity and the temperature coefficient of resistivity as well as the effect of porosity on electronic type conductivity are discussed.

  10. SURFACE TREATMENT OF MOLYBDENUM METAL

    DOEpatents

    Coffer, C.O.

    1961-12-01

    A process of descaling molybdenum articles comprises first immersing them in an aqueous sodium hydroxide-potassium permanganate solution of between 60 and 85 deg C, rinsing, and then immersing them in an aqueous solution containing a mixture of sulfuric, hydrochloric, and chromic acids.

  11. Enhanced molybdenum uptake in rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Molybdenum (Mo) is a cofactor for nitrate reductase. When nitrate reductase activity is limited by Mo deficiency, crop yields are also potentially limited. Plant deficiencies in Mo often occur in acidic soil due to mineral fixation. The long-term goal is to identify genes that can be used to develop...

  12. Molybdenum recycling in the United States in 1998

    USGS Publications Warehouse

    Blossom, John W.

    2002-01-01

    This report describes the flow of molybdenum in the United States in 1998 with emphasis on the extent to which molybdenum was recycled. Molybdenum was mostly recycled from products of molybdenum-bearing steels and superalloys, with some molybdenum products recovered specifically for their high molybdenum content. In 1998, 8,000 metric tons (t) of molybdenum was estimated to have been recycled, and the recycling rate was calculated to be 33 percent, with recycling efficiency at about 30 percent.

  13. Reptilian transferrins: evolution of disulphide bridges and conservation of iron-binding center.

    PubMed

    Ciuraszkiewicz, Justyna; Biczycki, Marian; Maluta, Aleksandra; Martin, Samuel; Watorek, Wiesław; Olczak, Mariusz

    2007-07-01

    Transferrins, found in invertebrates and vertebrates, form a physiologically important family of proteins playing a major role in iron acquisition and transport, defense against microbial pathogens, growth and differentiation. These proteins are bilobal in structure and each lobe is composed of two domains divided by a cleft harboring an iron atom. Vertebrate transferrins comprise of serotransferrins, lactoferrins and ovotransferrins. In mammals serotransferrins transport iron in physiological fluids and deliver it to cells, while lactoferrins scavenge iron, limiting its availability to invading microbes. In oviparous vertebrates there is only one transferrin gene, expressed either in the liver to be delivered to physiological fluids as serotransferrin, or in the oviduct with a final localization in egg white as ovotransferrin. Being products of one gene sero- and ovotransferrin are identical at the amino-acid sequence level but with different, cell specific glycosylation patterns. Our knowledge of the mechanisms of transferrin iron binding and release is based on sequence and structural data obtained for human serotransferrin and hen and duck ovotransferrins. No sequence information about other ovotransferrins was available until our recent publication of turkey, ostrich, and red-eared turtle (TtrF) ovotransferrin mRNA sequences [Ciuraszkiewicz, J., Olczak, M., Watorek, W., 2006. Isolation, cloning and sequencing of transferrins from red-eared turtle, African ostrich and turkey. Comp. Biochem. Physiol. 143 B, 301-310]. In the present paper, ten new reptilian mRNA transferrin sequences obtained from the Nile crocodile (NtrF), bearded dragon (BtrF), Cuban brown anole (AtrF), veiled and Mediterranean chameleons (VtrF and KtrF), sand lizard (StrF), leopard gecko (LtrF), Burmese python (PtrF), African house snake (HtrF), and grass snake (GtrF) are presented and analyzed. Nile crocodile and red-eared turtle transferrins have a disulphide bridge pattern identical to

  14. Amorphous molybdenum sulfides as hydrogen evolution catalysts.

    PubMed

    Morales-Guio, Carlos G; Hu, Xile

    2014-08-19

    Providing energy for a population projected to reach 9 billion people within the middle of this century is one of the most pressing societal issues. Burning fossil fuels at a rate and scale that satisfy our near-term demand will irreversibly damage the living environment. Among the various sources of alternative and CO2-emission-free energies, the sun is the only source that is capable of providing enough energy for the whole world. Sunlight energy, however, is intermittent and requires an efficient storage mechanism. Sunlight-driven water splitting to make hydrogen is widely considered as one of the most attractive methods for solar energy storage. Water splitting needs a hydrogen evolution catalyst to accelerate the rate of hydrogen production and to lower the energy loss in this process. Precious metals such as Pt are superior catalysts, but they are too expensive and scarce for large-scale applications. In this Account, we summarize our recent research on the preparation, characterization, and application of amorphous molybdenum sulfide catalysts for the hydrogen evolution reaction. The catalysts can be synthesized by electrochemical deposition under ambient conditions from readily available and inexpensive precursors. The catalytic activity is among the highest for nonprecious catalysts. For example, at a loading of 0.2 mg/cm(2), the optimal catalyst delivers a current density of 10 mA/cm(2) at an overpotential of 160 mV. The growth mechanism of the electrochemically deposited film catalysts was revealed by an electrochemical quartz microcrystal balance study. While different electrochemical deposition methods produce films with different initial compositions, the active catalysts are the same and are identified as a "MoS(2+x)" species. The activity of the film catalysts can be further promoted by divalent Fe, Co, and Ni ions, and the origins of the promotional effects have been probed. Highly active amorphous molybdenum sulfide particles can also be prepared

  15. Effects of Diaceto-Dipropyl-Disulphide on Plasma Sialic Acid and Renal Tissue Thiol Levels in Alloxan Diabetic Rats

    PubMed Central

    Vickram; Thirumalarao, Kashinath Rattihalli; Raiker, Veena Gajana; Puttaswamy, Sandhya Hanumanthappa

    2016-01-01

    Introduction Plasma sialic acid levels are elevated in Diabetes Mellitus (DM) patients with proteinuria. Renal damage is mainly caused by free radicals that are excessively generated in DM. Thiols play an important role in the cellular antioxidative defence mechanisms mainly through thiol-disulphide exchange reaction. Diallyl disulphide, a garlic oil principle component, is known for its anti-diabetic properties. Its structural analogue, Diaceto-Dipropyl Disulphide (DADPDS), is a less toxic and more palatable disulphide and possesses similar anti-diabetic actions. Aim This study was undertaken to assess the usefulness of DADPDS in prevention of de-sialation of Glomerular Basement Membrane (GBM) in alloxan diabetic rats and to assess effect of DADPDS on renal tissue thiol levels. Materials and Methods Rats were divided into Normal, Diabetic and DADPDS treated diabetic groups. Diabetes was induced by intraperitoneal injection (IP) of alloxan. DADPDS was fed by gastric intubation. Plasma Sialic acid was determined by Ehrlich’s method and renal tissue thiol levels by Nitroprusside reaction method. Results This study showed a significant decrease (p<0.001) in plasma sialic acid, plasma glucose and renal tissue TBARS levels along with significant increase (p<0.001) in renal tissue thiol levels in DADPDS treated alloxan diabetic rats when compared to diabetic control rats. Conclusion Hence it may be concluded that DADPDS helps in preventing de-sialation of GBM in alloxan diabetic rats and improves renal tissue antioxidant defence mechanisms, may be through thiol-disulphide exchange reaction and thereby exhibits a possible clinical use in prevention of renal complications like diabetic nephropathy. PMID:27504279

  16. Tungsten disulphide based all fiber Q-switching cylindrical-vector beam generation

    SciTech Connect

    Lin, J.; Yan, K.; Zhou, Y.; Xu, L. X. Gu, C.; Zhan, Q. W.

    2015-11-09

    We proposed and demonstrated an all fiber passively Q-switching laser to generate cylindrical-vector beam, a two dimensional material, tungsten disulphide (WS{sub 2}), was adopted as a saturable absorber inside the laser cavity, while a few-mode fiber Bragg grating was used as a transverse mode-selective output coupler. The repetition rate of the Q-switching output pulses can be varied from 80 kHz to 120 kHz with a shortest duration of 958 ns. Attributed to the high damage threshold and polarization insensitivity of the WS{sub 2} based saturable absorber, the radially polarized beam and azimuthally polarized beam can be easily generated in the Q-switching fiber laser.

  17. Mode-locked ytterbium-doped fiber laser based on tungsten disulphide

    NASA Astrophysics Data System (ADS)

    Guoyu, Heyang; Song, Yanrong; Li, Kexuan; Dou, Zhiyuan; Tian, Jinrong; Zhang, Xinping

    2015-12-01

    We demonstrated an all-normal-dispersion Yb-doped mode-locked fiber laser based on tungsten disulphide (WS2). The saturable absorbers (SA) were made by mixing WS2 solution with polyvinyl alcohol (PVA), and then evaporated on a substrate. The modulation depth of the WS2 film was 2.06% and the saturable optical intensity was 71.6 MW cm-2. When the WS2 film was inserted into the fiber laser, the mode-locked pulses with pulse width of 2.5 ns and repetition rate of 2.84 MHz were obtained. As the pump power increased to 350 mW, the maximum output power was measured to be 8.02 mW. To the best of our knowledge, this is the first time to realize mode-locked pulses based on WS2-SA at 1 μm waveband.

  18. Violaxanthin de-epoxidase disulphides and their role in activity and thermal stability.

    PubMed

    Hallin, Erik Ingmar; Guo, Kuo; Åkerlund, Hans-Erik

    2015-05-01

    Violaxanthin de-epoxidase (VDE) catalyses the conversion of violaxanthin to zeaxanthin at the lumen side of the thylakoids during exposure to intense light. VDE consists of a cysteine-rich N-terminal domain, a lipocalin-like domain and a negatively charged C-terminal domain. That the cysteines are important for the activity of VDE is well known, but in what way is less understood. In this study, wild-type spinach VDE was expressed in E. coli as inclusion bodies, refolded and purified to give a highly active and homogenous preparation. The metal content (Fe, Cu, Ni, Mn, Co and Zn) was lower than 1 mol% excluding a metal-binding function of the cysteines. To investigate which of the 13 cysteines that could be important for the function of VDE, we constructed mutants where the cysteines were replaced by serines, one by one. For 12 out of 13 mutants the activity dropped by more than 99.9%. A quantification of free cysteines showed that only the most N-terminal of these cysteines was in reduced form in the native VDE. A disulphide pattern in VDE of C9-C27, C14-C21, C33-C50, C37-C46, C65-C72 and C118-C284 was obtained after digestion of VDE with thermolysin followed by mass spectroscopy analysis of reduced versus non-reduced samples. The residual activity found for the mutants showed a variation that was consistent with the results obtained from mass spectroscopy. Reduction of the disulphides resulted in loss of a rigid structure and a decrease in thermal stability of 15 °C. PMID:25764016

  19. Formation of molybdenum boride cermet coating by the detonation spray process

    NASA Astrophysics Data System (ADS)

    Yang, Gao; Zu-Kun, Hei; Xiaolei, Xu; Gang, Xin

    2001-09-01

    The effects of the powder particle size and the acetylene/oxygen gas flow ratio during the detonation spray process on the amount of molybdenum phase, porosity, and hardness of the coatings using MoB powder were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results show that the presence of metallic molybdenum in the coating results from decomposition of MoB powder during thermal spray. The compositions of the coatings are metallic Mo, MoB, and Mo2B, which are different from the phases of the original powder. The amount of molybdenum phase increases monotonously with the oxygen/acetylene ratio, but the increasing rate for the fine powder is faster than that for the coarse powder. The porosity and hardness of the coating are related to the amount of molybdenum phase. The phase constitution of the coating is discussed.

  20. Molybdenum cofactor and human disease.

    PubMed

    Schwarz, Guenter

    2016-04-01

    Four molybdenum-dependent enzymes are known in humans, each harboring a pterin-based molybdenum cofactor (Moco) in the active site. They catalyze redox reactions using water as oxygen acceptor or donator. Moco is synthesized by a conserved biosynthetic pathway. Moco deficiency results in a severe inborn error of metabolism causing often early childhood death. Disease-causing symptoms mainly go back to the lack of sulfite oxidase (SO) activity, an enzyme in cysteine catabolism. Besides their name-giving functions, Mo-enzymes have been recognized to catalyze novel reactions, including the reduction of nitrite to nitric oxide. In this review we cover the biosynthesis of Moco, key features of Moco-enzymes and focus on their deficiency. Underlying disease mechanisms as well as treatment options will be discussed. PMID:27055119

  1. Mechanical properties of electron-beam-melted molybdenum and dilute molybdenum-rhenium alloys

    NASA Technical Reports Server (NTRS)

    Klopp, W. D.; Witzke, W. R.

    1972-01-01

    A study of molybdenum and three dilute molybdenum-rhenium alloys was undertaken to determine the effects of rhenium on the low temperature ductility and other mechanical properties of molybdenum. Alloys containing 3.9, 5.9, and 7.7 atomic percent rhenium exhibited lower ductile-brittle transition temperatures than did the unalloyed molybdenum. The maximum improvement in the annealed condition was observed for molybdenum - 7.7 rhenium, which had a ductile-brittle transition temperature approximately 200 C (360 F) lower than that for unalloyed molybdenum. Rhenium additions also increased the low and high temperature tensile strengths and the high temperature creep strength of molybdenum. The mechanical behavior of dilute molybdenum-rhenium alloys is similar to that observed for dilute tungsten-rhenium alloys.

  2. Molybdenum disilicide alloy matrix composite

    DOEpatents

    Petrovic, John J.; Honnell, Richard E.; Gibbs, W. Scott

    1991-01-01

    Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

  3. Molybdenum disilicide alloy matrix composite

    DOEpatents

    Petrovic, J.J.; Honnell, R.E.; Gibbs, W.S.

    1991-12-03

    Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions are disclosed. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms. 3 figures.

  4. Molybdenum disilicide alloy matrix composite

    DOEpatents

    Petrovic, John J.; Honnell, Richard E.; Gibbs, W. Scott

    1990-01-01

    Compositions of matter consisting of matrix matrials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

  5. Zirconia-molybdenum disilicide composites

    DOEpatents

    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.

  6. Annealed CVD molybdenum thin film surface

    DOEpatents

    Carver, Gary E.; Seraphin, Bernhard O.

    1984-01-01

    Molybdenum thin films deposited by pyrolytic decomposition of Mo(CO).sub.6 attain, after anneal in a reducing atmosphere at temperatures greater than 700.degree. C., infrared reflectance values greater than reflectance of supersmooth bulk molybdenum. Black molybdenum films deposited under oxidizing conditions and annealed, when covered with an anti-reflecting coating, approach the ideal solar collector characteristic of visible light absorber and infrared energy reflector.

  7. Mineral resource of the month: molybdenum

    USGS Publications Warehouse

    Magyar, Michael J.

    2004-01-01

    Molybdenum is a metallic element that is most frequently used in alloy and stainless steels, which together represent the single largest market for molybdenum. Molybdenum has also proven invaluable in carbon steel, cast iron and superalloys. Its alloying versatility is unmatched because its addition enhances material performance under high-stress conditions in expanded temperature ranges and in highly corrosive environments. The metal is also used in catalysts, other chemicals, lubricants and many other applications.

  8. Mechanical Properties of Iron Alumininides Intermetallic Alloy with Molybdenum Addition

    SciTech Connect

    Zuhailawati, H.; Fauzi, M. N. A.

    2010-03-11

    In this work, FeAl-based alloys with and without molybdenum addition were fabricated by sintering of mechanically alloyed powders in order to investigate the effect of molybdenum on iron aluminide mechanical properties. Bulk samples were prepared by mechanical alloying for 4 hours, pressing at 360 MPa and sintering at 1000 deg. C for 2 hours. The specimens were tested in compression at room temperature using Instron machine. The phase identification and microstructure of the consolidated material was examined by x-ray diffraction and scanning electron microscope correspondingly. Results show that 2.5 wt%Mo addition significantly increased the ultimate stress and ultimate strain in compressive mode due to solid solution hardening. However, the addition of Mo more than 2.5 wt% was accompanied by a reduction in both properties caused by the presence of Mo-rich precipitate particles.

  9. ER stress and unfolded protein response in amyotrophic lateral sclerosis-a controversial role of protein disulphide isomerase.

    PubMed

    Jaronen, Merja; Goldsteins, Gundars; Koistinaho, Jari

    2014-01-01

    Accumulation of proteins in aberrant conformation occurs in many neurodegenerative diseases. Furthermore, dysfunctions in protein handling in endoplasmic reticulum (ER) and the following ER stress have been implicated in a vast number of diseases, such as amyotrophic lateral sclerosis (ALS). During excessive ER stress unfolded protein response (UPR) is activated to return ER to its normal physiological balance. The exact mechanisms of protein misfolding, accumulation and the following ER stress, which could lead to neurodegeneration, and the question whether UPR is a beneficial compensatory mechanism slowing down the neurodegenerative processes, are of interest. Protein disulphide isomerase (PDI) is a disulphide bond-modulating ER chaperone, which can also facilitate the ER-associated degradation (ERAD) of misfolded proteins. In this review we discuss the recent findings of ER stress, UPR and especially the role of PDI in ALS. PMID:25520620

  10. Molybdenum-base cermet fuel development

    NASA Astrophysics Data System (ADS)

    Pilger, James P.; Gurwell, William E.; Moss, Ronald W.; White, George D.; Seifert, David A.

    Development of a multimegawatt (MMW) space nuclear power system requires identification and resolution of several technical feasibility issues before selecting one or more promising system concepts. Demonstration of reactor fuel fabrication technology is required for cermet-fueled reactor concepts. The MMW reactor fuel development activity at Pacific Northwest Laboratory (PNL) is focused on producing a molybdenum-matrix uranium-nitride (UN) fueled cermte. This cermet is to have a high matrix density (greater than or equal to 95 percent) for high strength and high thermal conductance coupled with a high particle (UN) porosity (approximately 25 percent) for retention of released fission gas at high burnup. Fabrication process development involves the use of porous TiN microspheres as surrogate fuel material until porous Un microspheres become available. Process development was conducted in the areas of microsphere synthesis, particle sealing/coating, and high-energy-rate forming (HERF) and the vacuum hot press consolidation techniques. This paper summarizes the status of these activities.

  11. Chromatin condensation, cysteine-rich protamine, and establishment of disulphide interprotamine bonds during spermiogenesis of Eledone cirrhosa (Cephalopoda).

    PubMed

    Gimenez-Bonafé, Pepita; Ribes, Enric; Sautière, Pierre; Gonzalez, Angel; Kasinsky, Harold; Kouach, Mustafa; Sautière, Pierre-Eric; Ausió, Juan; Chiva, Manel

    2002-06-01

    During spermiogenesis in Eledone cirrhosa a single protamine substitutes for histones in nuclei of developing spermatids. This protein displays a peculiar primary structure. It contains 22.6 mol% cysteine residues (19 cysteines in 84 residues). This makes it the most cysteine-rich protamine known. The proportion of basic residues is relatively low (arginine 36.9 mol%, lysine 19.0 mol%). The protamine of E. cirrhosa condenses spermiogenic chromatin in a pattern which comprises fibres with a progressively larger diameter and lamellae that finally undergo definitive coalescence. We have also performed a study that estimates the number of interprotamine disulphide bonds formed during the process of spermiogenic chromatin condensation by means of sequential disappearance of MMNA (monomaleimido-nanogold) labelling. During the first step of spermiogenesis, protamines are found spread over very slightly condensed chromatin with their cysteines in a reactive state (protamine-cys-SH). From this stage the interprotamine disulphide bonds are established in a progressive way. First they are formed inside the chromatin fibres. Subsequently, they participate in the mechanism of fibre coalescence and finally, in the last step of spermiogenesis, the remaining free reactive -SH groups of cysteine form disulphide bonds, thus promoting a definitive stabilization of the nucleoprotein complex in the ripe sperm nucleus. PMID:12113475

  12. Molybdenum Enzymes, Cofactors, and Model Systems.

    ERIC Educational Resources Information Center

    Burgmayer, S. J. N; Stiefel, E. I.

    1985-01-01

    Discusses: (l) molybdoenzymes (examining their distribution and metabolic role, composition and redox strategy, cofactors, substrate reactions, and mechanistic possibilities); (2) structural information on molybdenum (Mo) centers; (3) modeling studies (Mo-co models, nitrogenase models, and the MO-S duo); and (4) the copper-molybdenum antagonism.…

  13. Formation of alumina-nickel-molybdenum catalysts

    SciTech Connect

    Erofeev, V.I.; Basov, V.G.; Vagin, A.I.; Kalechits, I.V.

    1982-06-01

    On the basis of the results obtained in physical and chemical studies of alumina-nickel-molybdenum oxide catalysts as well as binary system and the individual oxides, the conclusions show that the commercial catalyst consists mainly of nickel and aluminium molybdates, aluminium molybdates, molybdenum oxide, and the alumina support. 4 figures.

  14. Dynamic Modeling of Molybdenum Metabolism in Humans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Molybdenum is an essential nutrient in the human diet and is a cofactor for several enzymes. While intakes can vary widely with geographical region, both deficiency and toxicity in humans are rare. To determine if humans have adaptive mechanisms for maintaining molybdenum status under varying inta...

  15. Molybdenum sealing glass-ceramic composition

    DOEpatents

    Eagan, Robert J.

    1976-01-01

    The invention relates to a glass-ceramic composition having low hydrogen and helium permeability properties, along with high fracture strength, a thermal coefficient of expansion similar to that of molybdenum, and adaptable for hermetically sealing to molybdenum at temperatures of between about 900.degree. and about 950.degree.C. to form a hermatically sealed insulator body.

  16. Characterization of low dimensional molybdenum sulfide nanostructures

    SciTech Connect

    Camacho-Bragado, G. Alejandra; Elechiguerra, Jose Luis; Yacaman, Miguel Jose

    2008-03-15

    It is presented a detailed structural characterization of a nanostructured form of molybdenum disulfide. The material consists of a layer of highly textured molybdenum sulfide growing off a molybdenum dioxide core. The structure and chemical composition of the synthesized nanostructured sulfide was compared to two well-known forms of molybdenum disulfide, i.e. a commercial molybdenite sample and a poorly crystalline sulfide. X-ray diffraction, high-resolution electron microscopy and electron diffraction showed that the material reported here presents crystalline nanodomains with a crystal structure corresponding to the 2H polytype of molybdenum disulfide. X-ray photoelectron spectroscopy was used to demonstrate the differences between our sulfide and other materials such as amorphous MoS{sub 3}, oxysulfides and poorly crystalline MoS{sub 2}, corroborating the molybdenite-2H stacking in this form of sulfide. The material under study showed a high proportion of crystalline planes different from the basal plane.

  17. The protein disulphide-isomerase family: unravelling a string of folds.

    PubMed Central

    Ferrari, D M; Söling, H D

    1999-01-01

    The mammalian protein disulphide-isomerase (PDI) family encompasses several highly divergent proteins that are involved in the processing and maturation of secretory proteins in the endoplasmic reticulum. These proteins are characterized by the presence of one or more domains of roughly 95-110 amino acids related to the cytoplasmic protein thioredoxin. All but the PDI-D subfamily are composed entirely of repeats of such domains, with at least one domain containing and one domain lacking a redox-active -Cys-Xaa-Xaa-Cys- tetrapeptide. In addition to their known roles as redox catalysts and isomerases, the last few years have revealed additional functions of the PDI proteins, including peptide binding, cell adhesion and perhaps chaperone activities. Attention is now turning to the non-redox-active domains of the PDIs, which may play an important role in all of the known activities of these proteins. Thus the presence of both redox-active and -inactive domains within these proteins portends a complexity of functions differentially accommodated by the various family members. PMID:10085220

  18. Protein disulphide isomerase as a target for nanoparticle-mediated sensitisation of cancer cells to radiation

    NASA Astrophysics Data System (ADS)

    Taggart, L. E.; McMahon, S. J.; Butterworth, K. T.; Currell, F. J.; Schettino, G.; Prise, K. M.

    2016-05-01

    Radiation resistance and toxicity in normal tissues are limiting factors in the efficacy of radiotherapy. Gold nanoparticles (GNPs) have been shown to be effective at enhancing radiation-induced cell death, and were initially proposed to physically enhance the radiation dose deposited. However, biological responses of GNP radiosensitization based on physical assumptions alone are not predictive of radiosensitisation and therefore there is a fundamental research need to determine biological mechanisms of response to GNPs alone and in combination with ionising radiation. This study aimed to identify novel mechanisms of cancer cell radiosensitisation through the use of GNPs, focusing on their ability to induce cellular oxidative stress and disrupt mitochondrial function. Using N-acetyl-cysteine, we found mitochondrial oxidation to be a key event prior to radiation for the radiosensitisation of cancer cells and suggests the overall cellular effects of GNP radiosensitisation are a result of their interaction with protein disulphide isomerase (PDI). This investigation identifies PDI and mitochondrial oxidation as novel targets for radiosensitisation.

  19. Headspace solid-phase microextraction analysis of volatile sulphides and disulphides in wine aroma.

    PubMed

    Mestres, M; Busto, O; Guasch, J

    1998-05-29

    Sulphur compounds (S-compounds) are important constituents of wine off-flavours. Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography coupled to flame photometric detection (GC-FPD) was used to develop a suitable method to analyse volatile sulphides and disulphides. This is a very simple and fast technique which gives good reproducibility at microgram/l levels (relative standard deviations < 10%). The analytes were extracted from the headspace of the samples by using either polydimethylsiloxane or polyacrylate coated fused-silica fibers in an SPME unit. Then, the fiber was inserted into the injector of a gas chromatograph and the extracted S-compounds were thermally desorbed. The influence of different parameters, such as ionic strength, stirring, headspace volume, ethanol concentration, time and temperature of extraction, was studied. The extraction of the fibers varies considerably for the different sulphur compounds studied. The most volatile compounds were the least extracted by the coating fibers tested. The standard additions technique, applied to real samples, gave the recoveries > 94%. The detection limits range between 3 micrograms/l and 50 ng/l. The overall process was successfully applied to identify and quantify S-compounds in white and red wines. PMID:9652119

  20. An effective approach to synthesize monolayer tungsten disulphide crystals using tungsten halide precursor

    NASA Astrophysics Data System (ADS)

    Thangaraja, Amutha; Shinde, Sachin M.; Kalita, Golap; Tanemura, Masaki

    2016-02-01

    The synthesis of large-area monolayer tungsten disulphide (WS2) single crystal is critical for realistic application in electronic and optical devices. Here, we demonstrate an effective approach to synthesize monolayer WS2 crystals using tungsten hexachloride (WCl6) as a solid precursor in atmospheric chemical vapor deposition process. In this technique, 0.05M solution of WCl6 in ethanol was drop-casted on SiO2/Si substrate to create an even distribution of the precursor, which was reduced and sulfurized at 750 °C in Ar atmosphere. We observed growth of triangular, star-shaped, as well as dendritic WS2 crystals on the substrate. The crystal geometry evolves with the shape and size of the nuclei as observed from the dendritic structures. These results show that controlling the initial nucleation and growth process, large WS2 single crystalline monolayer can be grown using the WCl6 precursor. Our finding shows an easier and effective approach to grow WS2 monolayer using tungsten halide solution-casting, rather than evaporating the precursor for gas phase reaction.

  1. Redox signalling directly regulates TDP-43 via cysteine oxidation and disulphide cross-linking.

    PubMed

    Cohen, Todd J; Hwang, Andrew W; Unger, Travis; Trojanowski, John Q; Lee, Virginia M Y

    2012-03-01

    TDP-43 is the major disease protein in ubiquitin-positive inclusions of amyotrophic lateral sclerosis and frontotemporal lobar degeneration (FTLD) characterized by TDP-43 pathology (FTLD-TDP). Accumulation of insoluble TDP-43 aggregates could impair normal TDP-43 functions and initiate disease progression. Thus, it is critical to define the signalling mechanisms regulating TDP-43 since this could open up new avenues for therapeutic interventions. Here, we have identified a redox-mediated signalling mechanism directly regulating TDP-43. Using in vitro and cell-based studies, we demonstrate that oxidative stress promotes TDP-43 cross-linking via cysteine oxidation and disulphide bond formation leading to decreased TDP-43 solubility. Biochemical analysis identified several cysteine residues located within and adjacent to the second RNA-recognition motif that contribute to both intra- and inter-molecular interactions, supporting TDP-43 as a target of redox signalling. Moreover, increased levels of cross-linked TDP-43 species are found in FTLD-TDP brains, indicating that aberrant TDP-43 cross-linking is a prominent pathological feature of this disease. Thus, TDP-43 is dynamically regulated by a redox regulatory switch that links oxidative stress to the modulation of TDP-43 and its downstream targets. PMID:22193716

  2. Redox signalling directly regulates TDP-43 via cysteine oxidation and disulphide cross-linking

    PubMed Central

    Cohen, Todd J; Hwang, Andrew W; Unger, Travis; Trojanowski, John Q; Lee, Virginia M Y

    2012-01-01

    TDP-43 is the major disease protein in ubiquitin-positive inclusions of amyotrophic lateral sclerosis and frontotemporal lobar degeneration (FTLD) characterized by TDP-43 pathology (FTLD-TDP). Accumulation of insoluble TDP-43 aggregates could impair normal TDP-43 functions and initiate disease progression. Thus, it is critical to define the signalling mechanisms regulating TDP-43 since this could open up new avenues for therapeutic interventions. Here, we have identified a redox-mediated signalling mechanism directly regulating TDP-43. Using in vitro and cell-based studies, we demonstrate that oxidative stress promotes TDP-43 cross-linking via cysteine oxidation and disulphide bond formation leading to decreased TDP-43 solubility. Biochemical analysis identified several cysteine residues located within and adjacent to the second RNA-recognition motif that contribute to both intra- and inter-molecular interactions, supporting TDP-43 as a target of redox signalling. Moreover, increased levels of cross-linked TDP-43 species are found in FTLD-TDP brains, indicating that aberrant TDP-43 cross-linking is a prominent pathological feature of this disease. Thus, TDP-43 is dynamically regulated by a redox regulatory switch that links oxidative stress to the modulation of TDP-43 and its downstream targets. PMID:22193716

  3. Disulphide cross linked pullulan based cationic polymer for improved gene delivery and efflux pump inhibition.

    PubMed

    S, Priya S; R, Rekha M

    2016-10-01

    Multidrug resistance is a hurdle to successful cancer chemotherapy. Over expression of P-glycoprotein (P-gp) is a prime contributing factor for drug resistance. In this study, a disulphide cross-linked pullulan-based cationic polymer (PPSS) was synthesized to act simultaneously as gene delivery vehicle and efflux pump inhibitor. The PPSS nanoplexes were of size <200nm with the zeta potential of +15 to +20mV. The cytotoxicity studies using C6 and L929 cells showed that PPSS polymers are non-toxic even at high polymer concentrations. The PPSS/pDNA nanoplex showed superior uptake in confocal microscopy with 97% uptake by flow cytometry. The efficacy of efflux pump inhibition by the PPSS nanoplex was established by the enhanced intracellular retention of DOX. The enhanced cell death by p53/PPSS/DOX nanoplexes was attributed to the synergistic effect of P-gp inhibition and p53 transfection efficiency. Therefore, this multifunctional polymeric system may have significant promise for therapeutic application against cancer drug resistance. PMID:27459414

  4. Protein disulphide isomerase as a target for nanoparticle-mediated sensitisation of cancer cells to radiation.

    PubMed

    Taggart, L E; McMahon, S J; Butterworth, K T; Currell, F J; Schettino, G; Prise, K M

    2016-05-27

    Radiation resistance and toxicity in normal tissues are limiting factors in the efficacy of radiotherapy. Gold nanoparticles (GNPs) have been shown to be effective at enhancing radiation-induced cell death, and were initially proposed to physically enhance the radiation dose deposited. However, biological responses of GNP radiosensitization based on physical assumptions alone are not predictive of radiosensitisation and therefore there is a fundamental research need to determine biological mechanisms of response to GNPs alone and in combination with ionising radiation. This study aimed to identify novel mechanisms of cancer cell radiosensitisation through the use of GNPs, focusing on their ability to induce cellular oxidative stress and disrupt mitochondrial function. Using N-acetyl-cysteine, we found mitochondrial oxidation to be a key event prior to radiation for the radiosensitisation of cancer cells and suggests the overall cellular effects of GNP radiosensitisation are a result of their interaction with protein disulphide isomerase (PDI). This investigation identifies PDI and mitochondrial oxidation as novel targets for radiosensitisation. PMID:27080849

  5. Supported molybdenum carbide catalysts: Structure-function relationships for hydrodenitrogenation

    SciTech Connect

    Dolce, G.M.; Thompson, L.T.

    1997-12-31

    There continues to be a need for new catalysts that can efficiently upgrade petroleum crudes. Heavy oils and coal-derived liquids contain higher levels of nitrogen, sulfur, and oxygen than conventional light crudes, and therefore require more rigorous refining. Currently available commercial catalysts are not as active and efficient at hydrotreating these heavy oils compared to light crudes. Early transition metal carbides and nitrides have been shown to be active for the hydrotreatment of model compounds and petroleum crudes. In this paper the authors describe their investigations of the structural and compositional properties of {gamma}-Al{sub 2}O{sub 3}-supported molybdenum carbides and efforts to correlate these properties with their pyridine and quinoline hydrodenitrogenation (HDN) activities. The HDN activities of the materials scaled linearly with the loading and oxygen chemisorptive uptake. Oxygen chemisorption results also suggested that the molybdenum carbide particles were highly dispersed and perhaps raft-like. Using temperature programmed desorption and infrared spectroscopy of carbon monoxide, they were able to identify two types of sites on the carbides; sites on top of the particle and sites at the perimeter. They have tentatively concluded that the most active sites for HDN were on top of the supported carbide particles.

  6. Cluster-like molybdenum phosphide anchored on reduced graphene oxide for efficient hydrogen evolution over a broad pH range.

    PubMed

    Yan, Haijing; Jiao, Yanqing; Wu, Aiping; Tian, Chungui; Zhang, Xiaomeng; Wang, Lei; Ren, Zhiyu; Fu, Honggang

    2016-07-21

    Cluster-like molybdenum phosphide particles were anchored on reduced graphene oxide (MoP/rGO) with high uniformity by using phosphomolybdic acid as a molybdenum precursor based on a robust assembly-immobilization method. Benefiting from the small size, and even distribution of the MoP particles, the MoP/rGO hybrid exhibits superior electrocatalytic activity towards the hydrogen evolution reaction both in acidic and alkaline media. PMID:27380736

  7. Haematopoietic, Antioxidant and Membrane Stabilizing Property of Diallyl Disulphide in Irradiated Mice

    PubMed Central

    Tenkanidiyoor, Yogish Somayaji; Vasudeva, Vidya; Rao, Shama; Gowda, Damodara; Rao, Chandrika; Sanjeev, Ganesh

    2016-01-01

    Introduction Diallyl disulphide is an organo-sulphur compound which is present in garlic and responsible for the characteristic odor of garlic. It is known for its anticancer and invitro membrane stabilizing properties. Aim The main aim was to evaluate the haematopoietic, antioxidant and membrane stabilizing property of diallyl disulfide in irradiated mice. Materials and Methods Mice were grouped into 6 groups as control, drug control, radiation control and drug pre-treatment groups (i.e. drug administration + radiation group) The mice were fed orally for 15 consecutive days and on the 15th day, one hour after drug administration, the mice were irradiated with 6Gy electron beam radiation. The changes in blood cell count, total antioxidant levels, malondialdehyde and reduced glutathione levels were determined. The immunomodulatory response of DADS to the radiological effects was determined by the estimation of IL-6 levels. Results A significant improvement in pre-drug treatment group when compared to control groups in the haemoglobin, red blood cell count, white blood cell count, haematocrit and platelet counts was observed. There is an increased level of interleukin-6 in the drug treated groups compared to the radiation control. An increase in the malondialdehyde levels and decrease in the glutathione levels in the irradiated group indicate increased lipid peroxidation and oxidative stress, whereas, there is a significant reduction in the malondialdehyde levels and increased glutathione levels in the drug pre-treatment groups showing membrane stabilization. Conclusion Thus DADS proves to be an effective haematopoietic and antioxidative agent to counter radiation induced haematopoietic suppression and oxidative stress. PMID:27042448

  8. Chest pain in rubber chemical workers exposed to carbon disulphide and methaemoglobin formers.

    PubMed Central

    Oliver, L C; Weber, R P

    1984-01-01

    A cross sectional prevalence study of chest pain in 94 rubber chemical workers exposed to carbon disulphide (CS2) and methaemoglobin forming aromatic amines was carried out. The purpose of the study was to determine whether the prevalence of chest pain or coronary heart disease (CHD), or both, in exposed individuals exceeded that of a group of non-exposed individuals from the same plant. Cardiovascular, smoking, and occupational histories were obtained. Blood pressure, height, weight, serum cholesterol, and fasting blood glucose were measured. Resting electrocardiograms (ECGs) were obtained on all study participants, as were exercise stress tests on selected exposed individuals. Matching eliminated important known risk factors for coronary artery disease. Both chest pain and angina were significantly related to exposure, controlling for age and cigarette smoking. This association was not dependent on duration of exposure as defined by 10 or more years of employment in the department of interest. CHD as defined by angina, a history of myocardial infarction, or a coronary ECG or a combination of these occurred more frequently among exposed workers. The number of abnormal ECGs in the exposed group was twice that in the control group, but the difference was not statistically significant. Age rather than exposure appeared to be the important variable associated with raised blood pressure. Neither biological measures of exposure nor ECGs showed an acute effect of workplace exposures on the myocardium. Possible additive or multiplicative effects of individual chemical agents could not be evaluated. Appropriate modification of medical surveillance of rubber chemical workers with exposure to CS2 and aromatic amines is warranted. PMID:6611171

  9. Photophysics, photochemistry and energetics of UV light induced disulphide bridge disruption in apo-α-lactalbumin.

    PubMed

    Correia, Manuel; Neves-Petersen, Maria Teresa; Parracino, Antonietta; di Gennaro, Ane Kold; Petersen, Steffen B

    2012-01-01

    Continuous 295 nm excitation of whey protein bovine apo-α-lactalbumin (apo-bLA) results in an increase of tryptophan fluorescence emission intensity, in a progressive red-shift of tryptophan fluorescence emission, and breakage of disulphide bridges (SS), yielding free thiol groups. The increase in fluorescence emission intensity upon continuous UV-excitation is correlated with the increase in concentration of free thiol groups in apo-bLA. UV-excitation and consequent SS breakage induce conformational changes on apo-bLA molecules, which after prolonged illumination display molten globule spectral features. The rate of tryptophan fluorescence emission intensity increase at 340 nm with excitation time increases with temperature in the interval 9.3-29.9°C. The temperature-dependent 340 nm emission kinetic traces were fitted by a 1st order reaction model. Native apo-bLA molecules with intact SS bonds and low tryptophan emission intensity are gradually converted upon excitation into apo-bLA molecules with disrupted SS, molten-globule-like conformation, high tryptophan emission intensity and red-shifted tryptophan emission. Experimental Ahrrenius activation energy was 21.8 ± 2.3 kJ x mol(-1). Data suggests that tryptophan photoionization from the S(1) state is the likely pathway leading to photolysis of SS in apo-bLA. Photoionization mechanism(s) of tryptophan in proteins and in solution and the activation energy of tryptophan photoionization from S(1) leading to SS disruption in proteins are discussed. The observations present in this paper raise concern regarding UV-light pasteurization of milk products. Though UV-light pasteurization is a faster and cheaper method than traditional thermal denaturation, it may also lead to loss of structure and functionality of milk proteins. PMID:21997288

  10. Separation of molybdenum and technetium

    NASA Astrophysics Data System (ADS)

    Andersson, J. D.; Gagnon, K.; Wilson, J. S.; Romaniuk, J.; Abrams, D. N.; McQuarrie, S. A.

    2012-12-01

    After the production of 99mTc via the 100Mo(p,2n)99mTc reaction, there is a requirement for separating 99mTc from bulk 100Mo. Although a number of separation methods have been demonstrated, the possibility of using a cartridge-based system is particularly attractive for routine use in a good manufacturing practice (GMP) regulatory environment. This study confirmed that hydrophobic interaction chromatography (HIC) solid phase extraction (SPE) with PEG as stationary phase is an efficient and easily automated method for separating molybdate and pertechnetate, and that PEG degradation in the conditions used does not affect the performance of the resin. In addition, reversed phase SPE using Waters Oasis® HLB shows promise for successful separation of molybdenum and technetium and work continues to extend this technology to readily available commercial SPE cartridges.

  11. Upper critical field of copper molybdenum sulfide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Woollam, J. A.

    1978-01-01

    The upper critical field of sintered and sputtered copper molybdenum sulfide Cu(x)Mo6S8 was measured and found to exceed the Werthamer, Helfand, and Hohenberg (1966) value for a type II superconductor characterized by dirty limit, weak isotropic electron phonon coupling, and no paramagnetic limiting. It is suggested that the enhancement results from anisotropy or clean limit or both. Other ternary molybdenum sulfides appear to show similar anomalies.

  12. A four-disulphide-bridged toxin, with high affinity towards voltage-gated K+ channels, isolated from Heterometrus spinnifer (Scorpionidae) venom.

    PubMed Central

    Lebrun, B; Romi-Lebrun, R; Martin-Eauclaire, M F; Yasuda, A; Ishiguro, M; Oyama, Y; Pongs, O; Nakajima, T

    1997-01-01

    A new toxin, named HsTX1, has been identified in the venom of Heterometrus spinnifer (Scorpionidae), on the basis of its ability to block the rat Kv1.3 channels expressed in Xenopus oocytes. HsTX1 has been purified and characterized as a 34-residue peptide reticulated by four disulphide bridges. HsTX1 shares 53% and 59% sequence identity with Pandinus imperator toxin1 (Pi1) and maurotoxin, two recently isolated four-disulphide-bridged toxins, whereas it is only 32-47% identical with the other scorpion K+ channel toxins, reticulated by three disulphide bridges. The amidated and carboxylated forms of HsTX1 were synthesized chemically, and identity between the natural and the synthetic amidated peptides was proved by mass spectrometry, co-elution on C18 HPLC and blocking activity on the rat Kv1.3 channels. The disulphide bridge pattern was studied by (1) limited reduction-alkylation at acidic pH and (2) enzymic cleavage on an immobilized trypsin cartridge, both followed by mass and sequence analyses. Three of the disulphide bonds are connected as in the three-disulphide-bridged scorpion toxins, and the two extra half-cystine residues of HsTX1 are cross-linked, as in Pi1. These results, together with those of CD analysis, suggest that HsTX1 probably adopts the same general folding as all scorpion K+ channel toxins. HsTX1 is a potent inhibitor of the rat Kv1.3 channels (IC50 approx. 12 pM). HsTX1 does not compete with 125I-apamin for binding to its receptor site on rat brain synaptosomal membranes, but competes efficiently with 125I-kaliotoxin for binding to the voltage-gated K+ channels on the same preparation (IC50 approx. 1 pM). PMID:9359871

  13. Effects of copper sulfate supplement on growth, tissue concentration, and ruminal solubilities of molybdenum and copper in sheep fed low and high molybdenum diets

    SciTech Connect

    Ivan, M.; Veira, D.M.

    1985-01-01

    Each of four groups of six wethers were fed one of a low molybdenum, high molybdenum, high molybdenum plus copper sulfate, or high molybdenum plus copper sulfate corn silage-based diet for ad libitum intake for 221 days. Average daily gains and ratios of feed/gain were depressed for the high molybdenum diet as compared with the low molybdenum diet suggesting molybdenum toxicity in sheep fed the high molybdenum diet. This was alleviated partly by the copper sulfate supplement. The supplement also decreased solubility of both copper and molybdenum in the rumen but had no effect on copper concentration in blood plasma. Concentration of molybdenum was higher in both liver and kidney in sheep fed high-molybdenum diets as compared with low-molybdenum diets. Copper concentration was higher in kidneys of sheep fed high-molybdenum diets, but no difference was significant in liver copper between sheep fed diets high or low in molybdenum.

  14. Potentiation of the reductase activity of protein disulphide isomerase (PDI) by 19-nortestosterone, bacitracin, fluoxetine, and ammonium sulphate.

    PubMed

    Hassan, Maya Haj; Alvarez, Eva; Cahoreau, Claire; Klett, Danièle; Lecompte, François; Combarnous, Yves

    2011-10-01

    Protein disulphide isomerase (PDI) in the endoplasmic reticulum catalyzes the rearrangement of disulphide bridges during folding of secreted proteins. It binds various molecules that inhibit its activity. But here, we looked for molecules that would potentiate its activity. PDI reductase activity was measured in vitro using di-eosin-oxidized glutathione as substrate. Its classical inhibitor bacitracin was found to exert a biphasic effect: stimulatory at low concentrations (∼10(-6) M) and inhibitory only at higher concentrations (∼10(-4)-10(-3) M). The weak oestrogenic molecule bisphenol A was found to exert a weak inhibitory effect on PDI reductase activity relative to the strong oestrogens, ethynylestradiol, and diethylstilbestrol. Like 19-nortestosterone, fluoxetine was found to exert a potentiating effect on PDI reductase activity and their potentiating effects could be reversed by increasing concentrations of oestrogens. In conclusion, this paper provides the first identification of potentiators of PDI activity that are potential pharmaceuticals against pathologies affecting protein folding such as Alzheimer's disease. PMID:21250820

  15. Tungsten-molybdenum fractionation in estuarine environments

    NASA Astrophysics Data System (ADS)

    Mohajerin, T. Jade; Helz, George R.; Johannesson, Karen H.

    2016-03-01

    Dissolved tungsten (W) and molybdenum (Mo) concentrations were measured in surface waters and sediment pore waters of Terrebonne Bay, a shallow estuary in the Mississippi River delta, to investigate the biogeochemical processes that fractionate these Group 6 elements relative to one another during transit from weathering to sedimentary environments. Although many of the chemical properties of W and Mo are similar, the two elements behave autonomously, and the fractionation mechanisms are only partly understood. In sulfidic pore waters, dissolved Mo is depleted relative to river water-seawater mixtures, whereas dissolved W is >10-fold enriched. Reductive dissolution of poorly crystalline phases like ferrihydrite, which is a preferential host of W relative to Mo in grain coatings on river-borne particles, can explain the dissolved W enrichment. Dissolved W becomes increasingly enriched as H2S(aq) rises above about 60 μM due to transformation of WO42- to thiotungstates as well as to additional reductive dissolution of phases that host W. In contrast, as rising sulfide transforms MoO42- to thiomolybdates in pore waters, dissolved Mo is suppressed, probably owing to equilibration with an Fe-Mo-S phase. This putative phase appears to control the aqueous ion product, Q = [Fe2+][MoS42-]0.6 [H2S0]0.4/[H+]0.8, at a value of 10-7.78. Concentrations of dissolved W and Mo in pore waters bear no relation to concentrations in surface waters of the same salinity. In surface waters, dissolved Mo is nearly conserved in the estuarine mixing zone. Dissolved W appears also to be conserved except for several cases where W may have been enhanced by exchange with underlying, W-rich pore waters. With increasing salinity, the molar Mo/W ratio rises from about 10 to about 1000 in surface waters whereas it is mostly <10 in underlying pore waters and in highly sulfidic pore waters is mostly near 1. Differences in two chemical properties may account for this fractionation of Mo with respect to

  16. Evaluation of Oxide Dispersion Strengthened (ODS) molybdenum alloys

    SciTech Connect

    Bianco, R.; Buckman, R.W. Jr.

    1995-12-31

    A series of fourteen (14) novel high-strength molybdenum alloy compositions containing a dispersion of very fine (< 1 {mu}m diameter) oxide particles were consolidated using two proprietary powder metallurgy techniques. The developmental compositions were evaluated to determine the microstructural stability and mechanical properties from cryogenic (-148{degrees}F) to elevated temperatures (4000{degrees}F) for material in the as-swaged (>98% cold work) condition and for as-swaged material in the heat treated condition. Extremely fine oxide particle sizes (<1000 {Angstrom}) were observed by Transmission Electron Microscopy (TEM) for a number of the experimental compositions in the as-swaged condition. A one hour recrystallization temperature as high as 3990{degrees}F was measured and a ductile-to-brittle transition temperature as low as {approximately}58{degrees}F for material in the recrystallized condition was determined. The preliminary results support the alloy design concept feasibility.

  17. Molybdenum reduction to molybdenum blue in Serratia sp. Strain DRY5 is catalyzed by a novel molybdenum-reducing enzyme.

    PubMed

    Shukor, M Y; Halmi, M I E; Rahman, M F A; Shamaan, N A; Syed, M A

    2014-01-01

    The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C). A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a V max for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent K m for NADH was 0.79 mM. At 5 mM NADH, the apparent V max and apparent K m values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (k cat/K m ) of the Mo-reducing enzyme was 5.47 M(-1) s(-1). The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction. PMID:24724104

  18. Molybdenum Reduction to Molybdenum Blue in Serratia sp. Strain DRY5 Is Catalyzed by a Novel Molybdenum-Reducing Enzyme

    PubMed Central

    Shukor, M. Y.; Halmi, M. I. E.; Rahman, M. F. A.; Shamaan, N. A.; Syed, M. A.

    2014-01-01

    The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C). A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a Vmax for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent Km for NADH was 0.79 mM. At 5 mM NADH, the apparent Vmax and apparent Km values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (kcat/Km) of the Mo-reducing enzyme was 5.47 M−1 s−1. The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction. PMID:24724104

  19. Zinc deficiency in molybdenum poisoned cattle

    SciTech Connect

    Parada, R.

    1981-02-01

    Clinical signs ascribable to zinc deficiency were noted in a group of Friesian cows industrially poisoned with molybdenum. Zinc, copper, and molybdenum were determined in blood serum and black hair, and in the contaminated alfalfa pasture the group grazed on. Hematological parameters, and serum calcium and alkaline phosphatase activity, were also determined. Pooled samples of alfalfa from 2 uncontaminated pastures, and of blood, serum and black hair of clinically normal Friesian cattle grazing on these were used as controls. A mixed contamination of the polluted pasture with molybdenum and copper was found, both metals being inversely correlated with he distance to the polluting chimney. Zinc concentrations were normal and not significantly correlated with the distance to the chimney very high molybdenum was found in serum and hair of the poisoned animals; copper was normal in serum and hair. Low calcium and Alkaline phosphatase activity were found in serum, both variables being significantly correlated with serum zinc. Reduced red blood cell number, packed cell volumes and hemoglobin concentrations were also found, but no significant correlation of these parameters with any of the trace metals in serum or hair was found. Signs ascribed to zinc deficiency were consistent with the reduction of zinc in serum and hair and decreased alkaline phosphatase activity in serum. A zinc deficiency conditioned by a simultaneous increased intake of molybdenum and copper is proposed.

  20. Western Molybdenum Company mine, Chewelah District, Stevens County, Washington

    USGS Publications Warehouse

    Cooper, John R.

    1954-01-01

    The Western Molybdenum Co. mine was opened many years ago to obtain copper. The only production was several carloads of crude copper ore shipped during World War I. An unsuccessful attempt to produce molybdenum was made in 1939-1941.

  1. Molybdenum scavenging by iron monosulfide.

    PubMed

    Helz, George R; Vorlicek, Trent P; Kahn, Mani D

    2004-08-15

    Molybdenum profiles in dated sediment cores provide useful historical information about anoxia in anthropogenically impacted natural waters but would be of greater service if Mo fixation mechanisms were better understood. Here, we explore Mo scavenging by precipitated FeS in a model system consisting of an FeIII-bearing kaolinite (KGa-1B) dispersed in NaHS solutions. Test solutions contain 18 microM thiomolybdates (mainly MoOS3(2-)). Optically measuring dissolved polysulfides monitors the rate of FeS production from FeIII minerals. Even though the exposed clay surface area is large (450 m2/L), the clay itself sorbs little Mo at pH 8.6. As FeS forms, Mo is taken up in initial Mo/Fe mole ratios of 0.04-0.06, irrespective of HS- concentration (4-40 mM range). After about a day, Mo expulsion from the solids begins, accompanied by net polysulfide consumption. These changes reflect recrystallization of amorphous FeS to more ordered products such as greigite. FeS captures some MoO4(2-) but captures thiomolybdates more effectively. Kaolinite accelerates conversion of MoOS3(2-) to MoS4(2-), as predicted previously, and thiomolybdates facilitate reduction of FeIII minerals in the clay compared to Mo-free solutions. FeS is a potentially effective, transient scavenging agent for Mo in sulfidic environments, although FeS2 and organic matter appear to be the ultimate sedimentary hosts. PMID:15382851

  2. Effect of molybdenum treatment on molybdenum concentration and nitrate reduction in maize seedlings.

    PubMed

    Kovács, Béla; Puskás-Preszner, Anita; Huzsvai, László; Lévai, László; Bódi, Éva

    2015-11-01

    Since 1940 molybdenum has been known as an essential trace element in plant nutrition and physiology. It has a central role in nitrogen metabolism, and its deficiency leads to nitrate accumulation in plants. In this study, we cultivated maize seedlings (Zea mays L. cv. Norma SC) in nutrient solution and soil (rhizoboxes) to investigate the effect of molybdenum treatment on the absorption of molybdenum, sulfur and iron. These elements have been previously shown to play important roles in nitrate reduction, because they are necessary for the function of the nitrate reductase enzyme. We also investigated the relationship between molybdenum treatments and different nitrogen forms in maize. Molybdenum treatments were 0, 0.96, 9.6 and 96 μg kg(-1) in the nutrition solution experiments, and 0, 30, 90, 270 mg kg(-1) in the rhizobox experiments. On the basis of our results, the increased Mo level produced higher plant available Mo concentration in nutrient solution and in soil, which resulted increased concentration of Mo in shoots and roots of maize seedlings. In addition it was observed that maize seedlings accumulated more molybdenum in their roots than in their shoots at all treatments. In contrast, molybdenum treatments did not affect significantly either iron or sulfur concentrations in the plant, even if these elements (Mo, S and Fe) play alike important roles in nitrogen metabolism. Furthermore, the physiological molybdenum level (1× Mo = 0.01 μM) reduced NO3-N and enhanced the NH4-N concentrations in seedlings, suggesting that nitrate reduction was more intense under a well-balanced molybdenum supply. PMID:26226599

  3. Molybdenum Valence in Basaltic Silicate Melts

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Pando, K.

    2010-01-01

    The moderately siderophile element molybdenum has been used as an indicator in planetary differentiation processes, and is particularly relevant to core formation [for example, 1-6]. However, models that apply experimental data to an equilibrium differentiation scenario infer the oxidation state of molybdenum from solubility data or from multivariable coefficients from metal-silicate partitioning data [1,3,7]. Partitioning behavior of molybdenum, a multivalent element with a transition near the J02 of interest for core formation (IW-2) will be sensitive to changes in JO2 of the system and silicate melt structure. In a silicate melt, Mo can occur in either 4+ or 6+ valence state, and Mo6+ can be either octahedrally or tetrahedrally coordinated. Here we present first XANES measurements of Mo valence in basaltic run products at a range of P, T, and JO2 and further quantify the valence transition of Mo.

  4. UV-Light Exposure of Insulin: Pharmaceutical Implications upon Covalent Insulin Dityrosine Dimerization and Disulphide Bond Photolysis

    PubMed Central

    Correia, Manuel; Neves-Petersen, Maria Teresa; Jeppesen, Per Bendix; Gregersen, Søren; Petersen, Steffen B.

    2012-01-01

    In this work we report the effects of continuous UV-light (276 nm, ∼2.20 W.m−2) excitation of human insulin on its absorption and fluorescence properties, structure and functionality. Continuous UV-excitation of the peptide hormone in solution leads to the progressive formation of tyrosine photo-product dityrosine, formed upon tyrosine radical cross-linkage. Absorbance, fluorescence emission and excitation data confirm dityrosine formation, leading to covalent insulin dimerization. Furthermore, UV-excitation of insulin induces disulphide bridge breakage. Near- and far-UV-CD spectroscopy shows that UV-excitation of insulin induces secondary and tertiary structure losses. In native insulin, the A and B chains are held together by two disulphide bridges. Disruption of either of these bonds is likely to affect insulin’s structure. The UV-light induced structural changes impair its antibody binding capability and in vitro hormonal function. After 1.5 and 3.5 h of 276 nm excitation there is a 33.7% and 62.1% decrease in concentration of insulin recognized by guinea pig anti-insulin antibodies, respectively. Glucose uptake by human skeletal muscle cells decreases 61.7% when the cells are incubated with pre UV-illuminated insulin during 1.5 h. The observations presented in this work highlight the importance of protecting insulin and other drugs from UV-light exposure, which is of outmost relevance to the pharmaceutical industry. Several drug formulations containing insulin in hexameric, dimeric and monomeric forms can be exposed to natural and artificial UV-light during their production, packaging, storage or administration phases. We can estimate that direct long-term exposure of insulin to sunlight and common light sources for indoors lighting and UV-sterilization in industries can be sufficient to induce irreversible changes to human insulin structure. Routine fluorescence and absorption measurements in laboratory experiments may also induce changes in protein

  5. Nanostructured Molybdenum Oxides for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Lee, Se-Hee; Deshpande, Rohit; Parilla, Phil; Jones, Kim; To, Bobby; Mahan, Harv; Dillon, Anne

    2007-03-01

    Lithium-ion batteries are the current power sources of choice for portable electronics. Although such batteries are commercially successful, they are not keeping pace with the rapid advances in computing technologies. Also, further improvement of performance and simultaneous reduction in cost as well as material toxicity remain the subject of intensive research. Here we report the synthesis and electrochemical performance of a novel molybdenum oxide nanoparticle anode that dramatically improves current Li-ion battery technologies. Crystalline MoOx nanoparticles have been grown by an economical hot-wire chemical-vapor-deposition (HWCVD) technique and a recently developed electrophoresis technique is employed for the fabrication of porous nanoparticle anodes. Our material exhibits a high reversible capacity of ˜600 mAh/g in the range 0.005-3.0 V with excellent cycling characteristics as well as high-rate capability. Both cycling stability and rate capability issues are addressed by employing these porous molybdenum oxide films that consist of nanoscale active particles. These materials will impact the next generations of rechargeable lithium batteries, not only for applications in consumer electronics, but also for clean energy storage and use in hybrid electric vehicles.

  6. Effect of surface chemistry on the morphology, resistance, and colloidal behavior of small silver particles

    NASA Astrophysics Data System (ADS)

    Schwab, Scott D.; McCreery, Richard L.; Cummings, Kevin D.

    1985-07-01

    Raman spectrometry, transmission electron microscopy, and elemental analysis were used to characterize small silver particles prepared by evaporation of silver from a molybdenum or tungsten boat into a reduced-pressure atmosphere of argon and oxygen. Particles prepared with both molybdenum and oxygen present were 50-400-Å-diam spheres, but much larger aspherical particles resulted if either molybdenum or oxygen was absent. The spherical particles were coated with approximately one monolayer of polymeric molybdenum oxide formed during fabrication from volatile MoO3. The polymolybdate-coated particles form a stable suspension in water and have high electrical resistance, while those prepared in the absence of molybdenum have low resistance and do not suspend in water. No evidence of silver oxide formation was obtained, even for particles prepared by silver evaporation in oxygen in the absence of molybdenum, We conclude that the polymolybdate coating prevents the formation of very large (>1000 Å) particles during fabrication. Furthermore, the coating becomes negatively charged in polar solvents, leading to formation of a stable colloidal suspension. Thus the molybdenum boat is essential for the fabrication of small spherical particles, and has a large effect on the properties of the final material. While silver oxide formation cannot be rigorously ruled out, it is clear that molybdenum, not silver, oxides determine the morphology and resistance of the particles.

  7. Pre-treatment for molybdenum or molybdenum-rich alloy articles to be plated

    DOEpatents

    Wright, Ralph R.

    1980-01-01

    This invention is a method for etching a molybdenum or molybdenum-rich alloy surface to promote the formation of an adherent bond with a subsequently deposited metallic plating. In a typical application, the method is used as a pre-treatment for surfaces to be electrolessly plated with nickel. The pre-treatment comprises exposing the crystal boundaries of the surface by (a) anodizing the surface in acidic solution to form a continuous film of gray molybdenum oxide thereon and (b) removing the film.

  8. Controlling pore assembly of staphylococcal gamma-haemolysin by low temperature and by disulphide bond formation in double-cysteine LukF mutants.

    PubMed

    Nguyen, Vananh T; Higuchi, Hideo; Kamio, Yoshiyuki

    2002-09-01

    Staphylococcal LukF and Hlg2 are water-soluble monomers of gamma-haemolysin that assemble into oligomeric pores on the erythrocyte membranes. Here, we have created double-cysteine LukF mutants, in which single disulphide bonds connect either the prestem domain and the cap domain (V12C-T136C, Cap-Stem), or two beta-strands within the prestem domain (T117C-T136C, Stem-Stem) to control pore assembly of gamma-haemolysin at intermediate stages. The disulphide-trapped mutants were inactive in erythrocyte lysis, but gained full haemolytic activity if the disulphide bonds were reduced. The disulphide bonds blocked neither the membrane binding ability nor the intermediate prepore oligomerization, but efficiently inhibited the transition from prepores to pores. The prepores of Cap-Stem were dissociated into monomers in 1% SDS. In contrast, the prepores of Stem-Stem were stable in SDS and had ring-shaped structures similar to those of wild-type LukF, as observed by transmission electron microscopy. The transition of both mutants from prepores to pores could even be achieved by reducing disulphide bonds at low temperature (2 degrees C), whereas prepore oligomerization was effectively inhibited by low temperature. Finally, real-time transition of Stem-Stem from prepores to pores on ghost cells, visualized using a Ca2+-sensitive fluorescent indicator (Rhod2), was shown by the sequential appearance of fluorescence spots, indicating pore-opening events. Taken together, these data indicate that the prepores are legitimate intermediates during gamma-haemolysin pore assembly, and that conformational changes around residues 117 and 136 of the prestem domain are essential for pore formation, but not for membrane binding or prepore oligomerization. We propose a mechanism for gamma-haemolysin pore assembly based on the demonstrated intermediates. PMID:12354220

  9. Synthesis of finely divided molybdenum sulfide nanoparticles in propylene carbonate solution

    SciTech Connect

    Afanasiev, Pavel

    2014-05-01

    Molybdenum sulfide nanoparticles have been prepared from the reflux solution reaction involving ammonium heptamolybdate and elemental sulfur in propylene carbonate. Addition to the reaction mixture of starch as a natural capping agent leads to lesser agglomeration and smaller size of the particles. Nanoparticles of MoS{sub x} (x≈4) of 10–30 nm size are highly divided and form stable colloidal suspensions in organic solvents. Mo K edge EXAFS of the amorphous materials shows rapid exchange of oxygen to sulfur in the molybdenum coordination sphere during the solution reaction. Thermal treatment of the amorphous sulfides MoS{sub x} under nitrogen or hydrogen flow at 400 °C allows obtaining mesoporous MoS{sub 2} materials with very high pore volume and specific surface area, up to 0.45 cm{sup 3}/g and 190 m{sup 2}/g, respectively. The new materials show good potential for the application as unsupported hydrotreating catalysts. - Graphical abstract: Solution reaction in propylene carbonate allows preparing weakly agglomerated molybdenum sulfide with particle size 20 nm and advantageous catalytic properties. - Highlights: • Solution reaction in propylene carbonate yields MoS{sub x} particles near 20 nm size. • Addition of starch as capping agent reduces particles size and hinder agglomeration. • EXAFS at Mo K edge shows rapid oxygen to sulfur exchange in the solution. • Thermal treatment leads to MoS{sub 2} with very high porosity and surface area.

  10. Comparison of radiation shielding ratios of nano-sized bismuth trioxide and molybdenum

    NASA Astrophysics Data System (ADS)

    Cho, J. H.; Kim, M. S.; Rhim, J. D.

    2015-07-01

    In this study, radiation shielding fibers using non-hazardous nano-sized bismuth trioxide and molybdenum instead of lead were developed and evaluated. Among the elements with high densities and atomic numbers, non-hazardous elements such as bismuth trioxide and molybdenum were chosen as a shielding element. Then, bismuth trioxide (Bi2O3) with average particle size 1-500 µm was ball milled for 10 min to produce a powdered form of nanoparticles with average particle size of 10-100 nm. Bismuth trioxide nanoparticles were dispersed to make a colloidal suspension, followed by spreading and hardening onto one or two sides of fabric, to create the radiation shielding fabric. The thicknesses of the shielding sheets using nano-sized bismuth and molybdenum were 0.4 and 0.7 mm. According to the lead equivalent test of X-ray shielding products suggested by KS, the equivalent dose was measured, followed by calculation of the shielding rate. The shielding rate of bismuth with 0.4 mm thickness and at 50 kVp was 90.5%, which is comparable to lead of 0.082 mm thickness. The shielding rate of molybdenum was 51.89%%, which is comparable to lead of 0.034 mm. At a thickness of 0.7 mm, the shielding rate of bismuth was 98.73%, equivalent to 0.101 mm Pb, whereas the shielding rate of molybdenum was 74.68%, equivalent to 0.045 mm Pb. In conclusion, the radiation shielding fibers using nano-sized bismuth developed in this study are capable of reducing radiation exposure by X-ray and its low-dose scatter ray.

  11. The effect of chemical modifications induced in insulin on the reactivity of the interchain disulphide bonds towards sodium sulphite

    PubMed Central

    Massaglia, A.; Pennisi, F.; Rosa, U.; Ronca-Testoni, S.; Rossi, C. A.

    1968-01-01

    The reactivity of the three disulphide bridges of insulin towards sodium sulphite was studied by amperometric titration of the liberated thiol groups. In the native, acetylated or succinylated molecule two bridges react at pH7, but in the methylated or phenylcarbamoylated molecule only one bridge reacts. All three bridges react in all derivatives in 8m-urea or at pH9. Loss in biological activity parallels the loss in reactivity of one of the bridges during methylation. It is suggested that change in reactivity of the S·S bonds reflects the occurrence of a conformational modification of the protein. The possibility is discussed that the unusually high reactivity of the S·S bonds in native insulin depends strictly on the integrity of the native molecule, suggesting that S·S bonds are in some way involved in the hormone's mode of action. PMID:5665887

  12. The effect of chemical modifications induced in insulin on the reactivity of the interchain disulphide bonds towards sodium sulphite.

    PubMed

    Massaglia, A; Pennisi, F; Rosa, U; Ronca-Testoni, S; Rossi, C A

    1968-06-01

    The reactivity of the three disulphide bridges of insulin towards sodium sulphite was studied by amperometric titration of the liberated thiol groups. In the native, acetylated or succinylated molecule two bridges react at pH7, but in the methylated or phenylcarbamoylated molecule only one bridge reacts. All three bridges react in all derivatives in 8m-urea or at pH9. Loss in biological activity parallels the loss in reactivity of one of the bridges during methylation. It is suggested that change in reactivity of the S.S bonds reflects the occurrence of a conformational modification of the protein. The possibility is discussed that the unusually high reactivity of the S.S bonds in native insulin depends strictly on the integrity of the native molecule, suggesting that S.S bonds are in some way involved in the hormone's mode of action. PMID:5665887

  13. Cyst(e)ine residues of bovine white-matter proteolipid proteins. Role of disulphides in proteolipid conformation.

    PubMed Central

    Oteiza, P I; Adamo, A M; Aloise, P A; Paladini, A C; Paladini, A A; Soto, E F

    1987-01-01

    Cyst(e)ine residues of bovine white-matter proteolipid proteins were characterized in a highly purified preparation. From a total of 10.6 cyst(e)ine residues/molecule of protein, as determined by performic acid oxidation, 2.5-3 thiol groups were freely accessible to iodoacetamide, iodoacetic acid and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), when the proteins were solubilized in chloroform/methanol (C/M) (2:1, v/v). The presence of lipids had no effect on thiol-group exposure. One thiol group available to DTNB in C/M could not be detected when proteolipids were solubilized in the more polar solvent n-butanol. In a C/M solution of purified proteolipid proteins, SDS did not increase the number of reactive thiol groups, but the cleavage of one disulphide bridge made it possible to alkylate six more groups. C.d. and fluorescence studies showed that rupture of this disulphide bond changed the protein conformation, which was reflected in partial loss of helical structure and in a greater exposure to the solvent of at least one tryptophan residue. Cyst(e)ine residues were also characterized in the different components [PLP (principal proteolipid protein), DM20 and LMW (low-Mr proteins)] of the proteolipid preparation. Although the numbers of cyst(e)ine residues in PLP and DM20 were similar, in LMW fewer residues were alkylated under four different experimental conditions. The differences, however, are not simply related to differences in Mr. PMID:3663175

  14. Evaluation of molybdenum and its alloys. [Reactor core heat pipes

    SciTech Connect

    Lundberg, L.B.

    1981-01-01

    The choice of pure molybdenum as the prime candidate material for space reactor core heat pipes is critically examined. Pure molybdenum's high ductile-brittle transition temperature appears to be its major disadvantage. The candidate materials examined in detail for this application include low carbon arc-cast molybdenum, TZM-molybdenum alloy, and molybdenum-rhenium alloys. Published engineering properties are collected and compared, and it appears that Mo-Re alloys with 10 to 15% rhenium offer the best combination. Hardware is presently being made from electron beam melted Mo-13Re to test this conclusion.

  15. Molybdenum silicide based materials and their properties

    SciTech Connect

    Yao, Z.; Stiglich, J.; Sudarshan, T.S.

    1999-06-01

    Molybdenum disilicide (MoSi{sub 2}) is a promising candidate material for high temperature structural applications. It is a high melting point (2030 C) material with excellent oxidation resistance and a moderate density (6.24 g/cm{sup 3}). However, low toughness at low temperatures and high creep rates at elevated temperatures have hindered its commercialization in structural applications. Much effort has been invested in MoSi{sub 2} composites as alternatives to pure molybdenum disilicide for oxidizing and aggressive environments. Molybdenum disilicide-based heating elements have been used extensively in high-temperature furnaces. The low electrical resistance of silicides in combination with high thermal stability, electron-migration resistance, and excellent diffusion-barrier characteristics is important for microelectronic applications. Projected applications of MoSi{sub 2}-based materials include turbine airfoils, combustion chamber components in oxidizing environments, missile nozzles, molten metal lances, industrial gas burners, diesel engine glow plugs, and materials for glass processing. On this paper, synthesis, fabrication, and properties of the monolithic and composite molybdenum silicides are reviewed.

  16. Method for welding chromium molybdenum steels

    DOEpatents

    Sikka, Vinod K.

    1986-01-01

    Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

  17. Molybdenum oxide electrodes for thermoelectric generators

    DOEpatents

    Schmatz, Duane J.

    1989-01-01

    The invention is directed to a composite article suitable for use in thermoelectric generators. The article comprises a thin film comprising molybdenum oxide as an electrode deposited by physical deposition techniques onto solid electrolyte. The invention is also directed to the method of making same.

  18. Piezoelectric resonator assembly with thin molybdenum mounting clips

    DOEpatents

    Peters, R. Donald

    1981-01-01

    A resonator mounting assembly wherein the resonator blank is mounted agai an essentially planar surface presented by a plurality of peripherally disposed mounting clips and bonded to this surface to provide substantially all the mechanical support for the blank in a direction normal to the major faces of the resonator blank, while being flexible in the directions parallel to said major faces so as to minimize radial stresses on the resonator blank, particularly during thermal cycling of the resonator assembly. The clips are fabricated of a low thermal expansion material, such as molybdenum, which also has considerable yield strength after exposure to processing temperatures; the bonding of the clips to the edges of the resonator blank can be achieved by a polyimide containing electrically conductive particles.

  19. Post-Irradiation Fracture Toughness of Unalloyed Molybdenum, ODS molybdenum, and TZM molybdenum following irradiation at 244C to 507C

    SciTech Connect

    Cockeram, Brian V; Byun, Thak Sang; Leonard, Keith J; Snead, Lance Lewis

    2013-01-01

    Commercially available unalloyed molybdenum (Low Carbon Arc Cast (LCAC)), Oxide Dispersion Strengthened (ODS) molybdenum, and TZM molybdenum were neutron irradiated at temperatures of nominally 244 C, 407 C, and 509 C to neutron fluences between 1.0 to 4.6x1025 n/m2 (E>0.1 MeV). Post-irradiation fracture toughness testing was performed. All alloys exhibited a Ductile to Brittle Transition Temperature that was defined to occur at 30 4 MPa-m1/2. The highest post-irradiated fracture toughness values (26-107 MPa-m1/2) and lowest DBTT (100-150 C) was observed for ODS molybdenum in the L-T orientation. The finer grain size for ODS molybdenum results in fine laminates that improve the ductile laminate toughening. The results for ODS molybdenum are anisotropic with lower post-irradiated toughness values (20-30 MPa-m1/2) and higher DBTT (450-600 C) in the T-L orientation. The results for T-L ODS molybdenum are consistent or slightly better than those for LCAC molybdenum (21-71 MPa-m1/2 and 450-800 C DBTT). The fracture toughness values measured for LCAC and T-L ODS molybdenum at temperatures below the DBTT were determined to be 8-18 MPa-m1/2. Lower non-irradiated fracture toughness values were measured for TZM molybdenum that are attributed to the large carbide precipitates serving as preferential fracture initiation sites. The role of microstructure and grain size on post-irradiated fracture toughness was evaluated by comparing the results for LCAC molybdenum and ODS molybdenum.

  20. Densification of molybdenum and molybdenum alloy powders using hot isostatic pressing. Final technical report

    SciTech Connect

    Barranco, J.; Ahmad, I.; Isserow, S.; Warenchak, R.

    1985-08-01

    This study was conducted to determine a superior erosion-resistant gun-barrel liner material with improved properties at higher temperatures. Four categories of powders were examined: 1. TZM spherical containing 0.5 titanium, 0.08 zirconium, and 0.02 carbon (wt. % nominally), balance molybdenum (Mo), produced by REP (Rotating Electrode Process), PREP (Plasma Rotating Electrode Process), and PMRS (Plasma Melted and Rapidly Solidified); 2. Mo reduced 2 and 5 microns; 3. Mo-0.1% cobalt, co-reduced; 4. Mo-5 wt. % alumina (A12O3), dispersion strengthened. Hot Isostatic Pressing (HIP) densification occurred at 15-30 Ksi, 1300-1600 C, for 1.5 to 3.0 hours. The TZM REP/PREP powders (220/74 microns) were not fully densified even at 1600 C, 30 Ksi, 3 hours. Point-particle contact prevented complete void elimination. TZM PMRS powder (24.7 microns) achieved 99% of theoretical density while maintaining a small grain size (10.4 ASTM eq.) Bend deflection and fracture energies were approximately three times those for PREP powder at a bend rupture strength of about 120 Ksi. Mo reduced and Mo-0.1% Co powders showed less (or the same) ductility with increasing HIP temperatures. Fractures were intergranular with decreased bend rupture and compression strength. The Mo-5A1/sub 2/O/sub 3/ powder maintained a fine grain size (13 ASTM eq.), but with fracture energies usually less than 0.6 in.-lbs. Included are results from bending and compression testing with metallographic and fracture mode interpretation.

  1. Stability of molybdenum nanoparticles in Sn-3.8Ag-0.7Cu solder during multiple reflow and their influence on interfacial intermetallic compounds

    SciTech Connect

    Haseeb, A.S.M.A. Arafat, M.M. Johan, Mohd Rafie

    2012-02-15

    This work investigates the effects of molybdenum nanoparticles on the growth of interfacial intermetallic compound between Sn-3.8Ag-0.7Cu solder and copper substrate during multiple reflow. Molybdenum nanoparticles were mixed with Sn-3.8Ag-0.7Cu solder paste by manual mixing. Solder samples were reflowed on a copper substrate in a 250 Degree-Sign C reflow oven up to six times. The molybdenum content of the bulk solder was determined by inductive coupled plasma-optical emission spectrometry. It is found that upon the addition of molybdenum nanoparticles to Sn-3.8Ag-0.7Cu solder, the interfacial intermetallic compound thickness and scallop diameter decreases under all reflow conditions. Molybdenum nanoparticles do not appear to dissolve or react with the solder. They tend to adsorb preferentially at the interface between solder and the intermetallic compound scallops. It is suggested that molybdenum nanoparticles impart their influence on the interfacial intermetallic compound as discrete particles. The intact, discrete nanoparticles, by absorbing preferentially at the interface, hinder the diffusion flux of the substrate and thereby suppress the intermetallic compound growth. - Highlights: Black-Right-Pointing-Pointer Mo nanoparticles do not dissolve or react with the SAC solder during reflow. Black-Right-Pointing-Pointer Addition of Mo nanoparticles results smaller IMC thickness and scallop diameter. Black-Right-Pointing-Pointer Mo nanoparticles influence the interfacial IMC through discrete particle effect.

  2. Shock compaction of molybdenum powder

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.; Kostka, D.; Vreeland, T., Jr.; Schwarz, R. B.; Kasiraj, P.

    1983-01-01

    Shock recovery experiments which were carried out in the 9 to 12 GPa range on 1.4 distension Mo and appear adequate to compact to full density ( 45 (SIGMA)m) powders were examined. The stress levels, however, are below those calculated to be from 100 to approx. 22 GPa which a frictional heating model predicts are required to consolidate approx. 10 to 50 (SIGMA)m particles. The model predicts that powders that have a distension of m=1.6 shock pressures of 14 to 72 GPa are required to consolidate Mo powders in the 50 to 10 (SIGMA)m range.

  3. Kinetics of Molybdenum Reduction to Molybdenum Blue by Bacillus sp. Strain A.rzi

    PubMed Central

    Othman, A. R.; Bakar, N. A.; Halmi, M. I. E.; Johari, W. L. W.; Ahmad, S. A.; Jirangon, H.; Syed, M. A.; Shukor, M. Y.

    2013-01-01

    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. PMID:24369531

  4. Biosynthesis of the iron-molybdenum cofactor and the molybdenum cofactor in Klebsiella pneumoniae: effect of sulfur source.

    PubMed Central

    Ugalde, R A; Imperial, J; Shah, V K; Brill, W J

    1985-01-01

    NifQ- and Mol- mutants of Klebsiella pneumoniae show an elevated molybdenum requirement for nitrogen fixation. Substitution of cystine for sulfate as the sulfur source in the medium reduced the molybdenum requirement of these mutants to levels required by the wild type. Cystine also increased the intracellular molybdenum accumulation of NifQ- and Mol- mutants. Cystine did not affect the molybdenum requirement or accumulation in wild-type K. pneumoniae. Sulfate transport and metabolism in K. pneumoniae were repressed by cystine. However, the effect of cystine on the molybdenum requirement could not be explained by an interaction between sulfate and molybdate at the transport level. Cystine increased the molybdenum requirement of Mol- mutants for nitrate reductase activity by at least 100-fold. Cystine had the same effect on the molybdenum requirement for nitrate reductase activity in Escherichia coli ChlD- mutants. This shows that cystine does not have a generalized effect on molybdenum metabolism. Millimolar concentrations of molybdate inhibited nitrogenase and nitrate reductase derepression with sulfate as the sulfur source, but not with cystine. The inhibition was the result of a specific antagonism of sulfate metabolism by molybdate. The effects of nifQ and mol mutations on nitrogenase could be suppressed either by the addition of cystine or by high concentrations of molybdate. This suggests that a sulfur donor and molybdenum interact at an early step in the biosynthesis of the iron-molybdenum cofactor. This interaction might occur nonenzymatically when the levels of the reactants are high. PMID:3905765

  5. Reactively evaporated films of copper molybdenum sulfide

    NASA Technical Reports Server (NTRS)

    Chi, K. C.; Dillon, R. O.; Bunshah, R. F.; Alterovitz, S.; Woollam, J. A.

    1978-01-01

    Films of superconducting Chevrel-phase copper molybdenum sulfide CuxMo6S8 were deposited on sapphire substrates by reactive evaporation using H2S as the reacting gas. Two superconducting temperatures (10.0 K and 5.0 K) of the films were found, corresponding to two different phases with different copper concentrations. All films were superconducting above 4.2 K and contained Chevrel-phase compound as well as free molybdenum. The critical current was measured as a function of applied field. One sample was found to deviate from the scaling law found for co-evaporated or sputtered samples, which possibly indicates a different pinning mechanism or inhomogeneity of the sample.

  6. Critical currents in sputtered copper molybdenum sulphide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Woollam, J. A.; Kammerdiner, L.; Luo, H.-L.

    1977-01-01

    Critical currents in a sputtered Chevrel-phase copper molybdenum sulfide have been measured at 4.2 K as a function of applied magnetic field. Self-field critical-current values up to 10 to the 9th A/sq m were found, decreasing to 10 to the 8th A/sq m at 3 T. Graphs of pinning forces versus field were found to be independent of field direction, and the pinning mechanism is sample independent. Critical-current densities for sputtered lead molybdenum sulphide are estimated to be about 10 to the 8th A/sq m at 26 T based on a scaling law for pinning.

  7. Alkali metal intercalates of molybdenum disulfide.

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.

    1973-01-01

    Study of some of the physicochemical properties of compounds obtained by subjecting natural molybdenite and single crystals of molybdenum disulfide grown by chemical vapor transport to intercalation with the alkali group of metals (Li, Na, K, Rb, and Cs) by means of the liquid ammonia technique. Reported data and results include: (1) the intercalation of the entire alkali metal group, (2) stoichiometries and X-ray data on all of the compounds, and (3) superconductivity data for all the intercalation compounds.

  8. The alkaline earth intercalates of molybdenum disulfide

    NASA Technical Reports Server (NTRS)

    Somoano, R. B.; Hadek, V.; Rembaum, A.; Samson, S.; Woollam, J. A.

    1975-01-01

    Molybdenum disulfide has been intercalated with calcium and strontium by means of the liquid ammonia technique. Chemical, X-ray, and superconductivity data are presented. The X-ray data reveal a lowering of crystal symmetry and increase of complexity of the structure upon intercalation with the alkaline earth metals. The Ca and Sr intercalates start to superconduct at 4 and 5.6 K, respectively, and show considerable anisotropy regarding the critical magnetic field.

  9. The conserved His8 of the Moloney murine leukemia virus Env SU subunit directs the activity of the SU-TM disulphide bond isomerase

    SciTech Connect

    Li Kejun; Zhang, Shujing; Kronqvist, Malin; Ekstroem, Maria; Wallin, Michael; Garoff, Henrik . E-mail: henrik.garoff@cbt.ki.se

    2007-04-25

    Murine leukemia virus (MLV) fusion is controlled by isomerization of the disulphide bond between the receptor-binding surface (SU) and fusion-active transmembrane subunits of the Env-complex. The bond is in SU linked to a CXXC motif. This carries a free thiol that upon receptor binding can be activated (ionized) to attack the disulphide and rearrange it into a disulphide isomer within the motif. To find out whether His8 in the conserved SPHQ sequence of Env directs thiol activation, we analyzed its ionization in MLV vectors with wtEnv and Env with His8 deleted or substituted for Tyr or Arg, which partially or completely arrests fusion. The ionization was monitored by following the pH effect on isomerization in vitro by Ca{sup 2+} depletion or in vivo by receptor binding. We found that wtEnv isomerized optimally at slightly basic pH whereas the partially active mutant required higher and the inactive mutants still higher pH. This suggests that His8 directs the ionization of the CXXC thiol.

  10. New slow-releasing molybdenum fertilizer.

    PubMed

    Bandyopadhyay, Siladitya; Bhattacharya, Ishita; Ghosh, Kunal; Varadachari, Chandrika

    2008-02-27

    This paper describes a new water-insoluble molybdenum compound that has been developed as a slow-release fertilizer. The compound is an inorganic polymer formed by inclusion of molybdenum within a long-chain polyphosphate structure. It was designed by a process of "reverse engineering" of the molecule. Synthesis involved reaction of phosphoric acid with magnesium oxide, molybdenum trioxide, and sodium carbonate at 275 degrees C. Kinetics of reaction revealed complex multistage processes. X-ray diffraction patterns showed a crystalline nature with short-range as well as long-range ordering. The magnesium sodium polymolybdophosphate had ideal slow-release characteristics; it had low water solubility and high citrate solubility and was powdery, free flowing, and nonhygroscopic. Field testing showed an 80% increase in yield of green gram at a low dose of 0.04 kg/ha Mo. Nodulation increased by over 161%, and N content of gram increased by 20%. The slow-release fertilizer would provide an effective, low-cost, and environmentaly friendly alternative to Mo fertilization. PMID:18247562

  11. Dynamic Abnormal Grain Growth in Molybdenum

    NASA Astrophysics Data System (ADS)

    Worthington, Daniel L.; Pedrazas, Nicholas A.; Noell, Philip J.; Taleff, Eric M.

    2013-11-01

    A new abnormal grain growth phenomenon that occurs only during continuous plastic straining, termed dynamic abnormal grain growth (DAGG), was observed in molybdenum (Mo) at elevated temperature. DAGG was produced in two commercial-purity molybdenum sheets and in a commercial-purity molybdenum wire. Single crystals, centimeters in length, were created in these materials through the DAGG process. DAGG was observed only at temperatures of 1713 K (1440 °C) and above and occurred across the range of strain rates investigated, ~10-5 to 10-4 s-1. DAGG initiates only after a critical plastic strain, which decreases with increasing temperature but is insensitive to strain rate. Following initiation of an abnormal grain, the rate of boundary migration during DAGG is on the order of 10 mm/min. This rapid growth provides a convenient means of producing large single crystals in the solid state. When significant normal grain growth occurs prior to DAGG, island grains result. DAGG was observed in sheet materials with two very different primary recrystallization textures. DAGG grains in Mo favor boundary growth along the tensile axis in a <110> direction, preferentially producing single crystals with orientations from an approximately <110> fiber family of orientations. A mechanism of boundary unpinning is proposed to explain the dependence of boundary migration on plastic straining during DAGG.

  12. A solvent extraction study of molybdenum chloride and molybdenum thiocyanate complexes

    USGS Publications Warehouse

    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.

  13. Reactive melt infiltration of silicon-molybdenum alloys into microporous carbon preforms

    NASA Technical Reports Server (NTRS)

    Singh, M.; Behrendt, D. R.

    1995-01-01

    Investigations on the reactive melt infiltration of silicon-1.7 and 3.2 at.% molybdenum alloys into microporous carbon preforms have been carried out by modeling, differential thermal analysis (DTA), and melt infiltration experiments. These results indicate that the pore volume fraction of the carbon preform is a very important parameter in determining the final composition of the reaction-formed silicon carbide and the secondary phases. Various undesirable melt infiltration results, e.g. choking-off, specimen cracking, silicon veins, and lake formation, and their correlation with inadequate preform properties are presented. The liquid silicon-carbon reaction exotherm temperatures are influenced by the pore and carbon particle size of the preform and the compositions of infiltrants. Room temperature flexural strength and fracture toughness of materials made by the silicon-3.2 at.% molybdenum alloy infiltration of medium pore size preforms are also discussed.

  14. Selective cleavage of pepsin by molybdenum metallopeptidase

    SciTech Connect

    Yenjai, Sudarat; Malaikaew, Pinpinat; Liwporncharoenvong, Teerayuth; Buranaprapuk, Apinya

    2012-03-02

    Graphical abstract: Molybdenum metallopeptidase: the Mo(VI) cluster with six molybdenum cations has the ability to cleave protein under mild conditions (37 Degree-Sign C, pH 7) without reducing agents. The reaction required only low concentration of ammonium heptamolybdatetetrahydrate ((NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}{center_dot}4H{sub 2}O) (0.125 mM). The reaction undergoes possibly via a hydrolytic mechanism. This is the first demonstration of protein cleavage by a molybdenum cluster. Highlights: Black-Right-Pointing-Pointer This is the first demonstration of protein cleavage by a Mo(VI) cluster with six molybdenum cations. Black-Right-Pointing-Pointer The cleavage reaction undergoes at mild conditions. Black-Right-Pointing-Pointer No need of reducing agents. Black-Right-Pointing-Pointer Only low concentration of Mo(VI) cluster and short time of incubation are needed. -- Abstract: In this study, the cleavage of protein by molybdenum cluster is reported for the first time. The protein target used is porcine pepsin. The data presented in this study show that pepsin is cleaved to at least three fragments with molecular weights of {approx}23, {approx}19 and {approx}16 kDa when the mixture of the protein and ammonium heptamolybdate tetrahydrate ((NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}{center_dot}4H{sub 2}O) was incubated at 37 Degree-Sign C for 24 h. No self cleavage of pepsin occurs at 37 Degree-Sign C, 24 h indicating that the reaction is mediated by the metal ions. N-terminal sequencing of the peptide fragments indicated three cleavage sites of pepsin between Leu 112-Tyr 113, Leu 166-Leu 167 and Leu 178-Asn 179. The cleavage reaction occurs after incubation of the mixture of pepsin and (NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}{center_dot}4H{sub 2}O) only for 2 h. However, the specificity of the cleavage decreases when incubation time is longer than 48 h. The mechanism for cleavage of pepsin is expected to be hydrolytic chemistry of the amide bonds in the protein

  15. mRNA and Protein levels of rat pancreas specific protein disulphide isomerase are downregulated during Hyperglycemia.

    PubMed

    Gupta, Rajani; Bhar, Kaushik; Sen, Nandini; Bhowmick, Debajit; Mukhopadhyay, Satinath; Panda, Koustubh; Siddhanta, Anirban

    2016-02-01

    Diabetes (Type I and Type II) which affects nearly every organ in the body is a multi-factorial non-communicable disorder. Hyperglycemia is the most characteristic feature of this disease. Loss of beta cells is common in both types of diabetes whose detailed cellular and molecular mechanisms are yet to be elucidated. As this disease is complex, identification of specific biomarkers for its early detection, management and devising new therapies is challenging. Based on the fact that functionally defective proteins provide the biochemical basis for many diseases, in this study, we tried to identify differentially expressed proteins during hyperglycemia. For that, hyperglycemia was induced in overnight fasted rats by intra-peritoneal injection of streptozotocin (STZ). The pancreas was isolated from control and treated rats for subsequent analyses. The 2D-gel electrophoresis followed by MALDI-TOF-MS-MS analyses revealed several up- and down-regulated proteins in hyperglycemic rat pancreas including the downregulation of a pancreas specific isoform of protein disulphide isomerase a2 (Pdia2).This observation was validated by western blot. Quantitative PCR experiments showed that the level of Pdia2 mRNA is also proportionally reduced in hyperglycemic pancreas. PMID:26934777

  16. Complexes of tetraethylthiuram disulphide with group 12 metals: single-source precursor in metal sulphide nanoparticles' synthesis

    NASA Astrophysics Data System (ADS)

    Shukla, Satyendra N.; Gaur, Pratiksha; Rai, Nidhi

    2015-06-01

    Six new complexes of Zn(II), Cd(II) and Hg(II) with sulphur containing ligand, tetraethylthiuram disulphide in 2:2 and 1:4 ratio have been synthesized. The resulting complexes have been characterized on the basis of molar conductance measurement, elemental analyses, FT-IR, 1H-NMR, and FAB/ESI-mass studies. The complexes were used as a single-source precursor for the synthesis of ZnS/CdS/HgS nanoparticles by their thermal decomposition in the presence of different surfactants. The precursor:surfactant ratio and temperature play an important role in determining the size of the nanoparticles. The size and morphology of nanoparticles have been ascertained by ultra violet-visible spectroscopy, X-ray diffraction measurements and transmission electron microscopy. Schiff bases, complexes and nanoparticles were tested for antibacterial activity and minimum inhibitory concentration values against Escherichia coli. The complexes were found more potent than the corresponding Schiff bases and nanoparticles.

  17. Complexes of tetraethylthiuram disulphide with group 12 metals: single-source precursor in metal sulphide nanoparticles' synthesis

    NASA Astrophysics Data System (ADS)

    Shukla, Satyendra N.; Gaur, Pratiksha; Rai, Nidhi

    2014-09-01

    Six new complexes of Zn(II), Cd(II) and Hg(II) with sulphur containing ligand, tetraethylthiuram disulphide in 2:2 and 1:4 ratio have been synthesized. The resulting complexes have been characterized on the basis of molar conductance measurement, elemental analyses, FT-IR, 1H-NMR, and FAB/ESI-mass studies. The complexes were used as a single-source precursor for the synthesis of ZnS/CdS/HgS nanoparticles by their thermal decomposition in the presence of different surfactants. The precursor:surfactant ratio and temperature play an important role in determining the size of the nanoparticles. The size and morphology of nanoparticles have been ascertained by ultra violet-visible spectroscopy, X-ray diffraction measurements and transmission electron microscopy. Schiff bases, complexes and nanoparticles were tested for antibacterial activity and minimum inhibitory concentration values against Escherichia coli. The complexes were found more potent than the corresponding Schiff bases and nanoparticles.

  18. Passively Q-switched dual-wavelength Yb:LSO laser based on tungsten disulphide saturable absorber

    NASA Astrophysics Data System (ADS)

    Jing-Hui, Liu; Jin-Rong, Tian; He-Yang, Guoyu; Run-Qin, Xu; Ke-Xuan, Li; Yan-Rong, Song; Xin-Ping, Zhang; Liang-Bi, Su; Jun, Xu

    2016-03-01

    We demonstrate a passively Q-switched Yb:LSO laser based on tungsten disulphide (WS2) saturable absorber operating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 μs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets. Project supported by the National Scientific Research Project of China (Grant No. 61177047), Beijing Municipal Natural Science Foundation, China (Grant No. 1102005), and the Basic Research Foundation of Beijing University of Technology, China (Grant No. X3006111201501).

  19. Large-Scale Phosphoproteome of Human Whole Saliva Using Disulphide-Thiol-Interchange Covalent Chromatography and Mass Spectrometry

    PubMed Central

    Salih, Erdjan; Siqueira, Walter L.; Helmerhorst, Eva J.; Oppenheim, Frank G.

    2010-01-01

    Thus far only a handful of phosphoproteins with important biological functions have been identified and characterized in oral fluids and these include some of the abundant protein constituents of saliva. Whole saliva (WS) samples were trypsin digested followed by chemical derivatization using dithiothreitol (DTT) of the phospho-serine/threonine containing peptides. The DTT-phosphopeptides were enriched by covalent disulphide-thiol-interchange chromatography and analysis by nano-flow LC-ESI-MS/MS. The specificity of DTT chemical derivatization was evaluated separately under different base-catalyzed conditions with NaOH and Ba(OH)2, blocking cysteine residues by iodoacetamide and enzymatic O-deglycosylation prior to DTT reaction. Further analysis of WS samples which were subjected to either of these conditions provided supporting evidence for phosphoprotein identifications. The combined chemical strategies and mass spectrometric analyses identified 65 phosphoproteins in WS of which 28 were based on two or more peptide identification criteria with high confidence, and 37 were based on a single phosphopeptide identification. Most of the identified proteins, ~80%, were hitherto unknown phosphoprotein components. This study represents the first large-scale documentation of phosphoproteins of WS. The origins and identity of WS phosphoproteome suggest significant implications for both basic science and the development of novel biomarkers/diagnostic tools for both systemic and oral disease states. PMID:20659418

  20. Minimisation of artefact formation of dimethyl disulphide during sampling and analysis of methanethiol in air using solid sorbent materials.

    PubMed

    Andersen, Kristin Barkve; Hansen, Michael Jørgen; Feilberg, Anders

    2012-07-01

    Methanethiol (MT) is a potent odorant that can be difficult to measure due to its high volatility and reactivity; it easily reacts to form dimethyl disulphide (DMDS) during sampling and/or analysis. This paper focuses on finding an optimal method for sampling and measuring MT with minimum artefact formation using sorbent materials and a thermal desorption-gas chromatography-mass spectrometry method (TD-GC-MS). Experiments were conducted to identify suitable sorbent materials and tubes for analysis. Breakthrough, desorption rate, the effects of storage and desorption temperatures were investigated and different drying methods were established with respect to quantitative sampling and formation of DMDS. Proton-transfer-reaction mass spectrometry (PTR-MS) was used in the development of the method and was an especially useful tool for determination of breakthrough. The results show that glass tubes packed with silica gel for pre-concentration of MT before analysis with TD-GC-MS give the best results. In addition, a combination of Tenax TA and carbonised molecular sieve or Tenax TA cooled to ≤0°C gives acceptable results. 80°C was found to be the optimal desorption temperature. For all the sampling methods tested, storage conditions were observed to be very critical for transformation of MT. Room temperature storage should be limited to few minutes and, in general, tubes should be kept at 0°C or lower during storage. PMID:22658137

  1. Stability and activity of Dictyoglomus thermophilum GH11 xylanase and its disulphide mutant at high pressure and temperature.

    PubMed

    Li, He; Voutilainen, Sanni; Ojamo, Heikki; Turunen, Ossi

    2015-03-01

    The functional properties of extremophilic Dictyoglomus thermophilum xylanase (XYNB) and the N-terminal disulphide-bridge mutant (XYNB-DS) were studied at high pressure and temperature. The enzymes were quite stable even at the pressure of 500MPa at 80°C. The half-life of inactivation in these conditions was over 30h. The inactivation at 80°C in atmospheric pressure was only 3-times slower. The increase of pressure up to 500MPa at 80°C decreased only slightly the enzyme's stability, whereas in 500MPa the increase of temperature from 22 to 80°C decreased significantly more the enzyme's stability. While the high temperature (80-100°C) decreased the enzyme reaction with short xylooligosaccharides (xylotetraose and xylotriose), the high pressure (100-300MPa) had an opposite effect. The temperature of 100°C strongly increased the Km but did not affect the kcat to the same extent, thus indicating that the interaction of the substrate with the active site suffers before the catalytic reaction begins to decrease as the temperature rises. Circular dichroism spectroscopy showed the high structural stability of XYNB and XYNB-DS at 93°C. PMID:25659634

  2. Wear resistance and friction reduction in acrylo nitrile butadiene rubber through hybrid combination of graphite flakes and nano tungsten disulphide

    NASA Astrophysics Data System (ADS)

    Agrawal, Neha; Pandey, Akanksha; Parihar, A. S.; Mishra, A. K.; Gandhi, M. N.; Bhattacharyya, A. R.; Mukhopadhyay, K.; Prasad, N. E.

    2016-05-01

    Friction and wear have considerable role in the life span of two interacting parts. Incorporation of nanofillers in polymers/elastomers matrix causes commendable changes in its tribologicalproperties. The main purpose of this work is to reduce the coefficient of friction and wear rate of Acrylo Nitrile Butadiene rubber (NBR). To achieve such objective traditionally well knownlubricants graphite(G), tungsten disulphide (WS2) and there hybrid combination was incorporated in NBR matrix. Effect of applied load (force) and concentration of fillers on tribological properties of NBR had been studied. The filler incorporation enhanced the hardnessby 8%, showed resistance to hydraulic oil and aging effect also got improved significantly. A particular optimized concentration of NBR with hybrid combination of 2% WS2 and 4% Graphite showed minimum coefficient of friction as well as wear rate. A hypothesis could be attributed that similar lamellar structure of WS2 and Graphite along with formation of a stable nanoscale disulfide tribofilmcould result in lowering of friction. These substantially improved properties of nanoreinforced rubber materials would definitely pave promising path for plethora of potential technological applications.

  3. Predicting Boron, Molybdenum, Selenium, and Arsenic Adsorption in Soil Systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A chemical surface complexation model was applied to boron, molybdenum, selenium, and arsenic adsorption on up to 49 soils selected for variation in soil properties. The surface complexation model was able to fit boron, molybdenum, selenite, and arsenate adsorption on the soils. General regression...

  4. Influence of Soil Solution Salinity on Molybdenum Adsorption by Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Molybdenum (Mo) adsorption on five arid-zone soils from California was investigated as a function of equilibrium solution Mo concentration (0-30 mg L-1), solution pH (4-8), and electrical conductivity (EC = 0.3 or 8 dS m-1). Molybdenum adsorption decreased with increasing pH. An adsorption maximum...

  5. Tetrathionate reductase of Salmonella thyphimurium: a molybdenum containing enzyme

    SciTech Connect

    Hinojosa-Leon, M.; Dubourdieu, M.; Sanchez-Crispin, J.A.; Chippaux, M.

    1986-04-29

    Use of radioactive molybdenum demonstrates that the tetrathionate reductase of Salmonella typhimurium is a molydenum containing enzyme. It is proposed that this enzyme shares with other molybdo-proteins, such as nitrate reductase, a common molybdenum containing cofactor the defect of which leads to the loss of the tetrathionate reductase and nitrate reductase activities.

  6. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    SciTech Connect

    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. Normal state properties of the ternary molybdenum sulfides

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Alterovitz, S. A.

    1978-01-01

    By making a large number of normal state and superconducting properties measurements, all on the same ternary molybdenum sulfide samples, we obtain values for Fermi surface and superconducting parameters. From these we conclude that sputtered ternary molybdenum sulfides are not completely in the dirty superconductor limit, and that they are d-band metals with a high electron carrier density.

  8. Molybdenum In Cathodes Of Sodium/Metal Chloride Cells

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

    1992-01-01

    Cyclic voltammetric curves of molybdenum wire in NaAlCl4 melt indicate molybdenum chloride useful as cathode material in rechargeable sodium/metal chloride electrochemical cells. Batteries used in electric vehicles, for electric-power load leveling, and other applications involving high energy and power densities.

  9. Hot rolling of thick uranium molybdenum alloys

    DOEpatents

    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.

  10. Molybdenum oxide nanocubes: Synthesis and characterizations

    SciTech Connect

    Muthamizh, S.; Suresh, R.; Giribabu, K.; Manigandan, R.; Kumar, S. Praveen; Munusamy, S.; Narayanan, V.; Stephen, A.

    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.

  11. D-penicillamine prevents ram sperm agglutination by reducing the disulphide bonds of a copper-binding sperm protein.

    PubMed

    Leahy, T; Rickard, J P; Aitken, R J; de Graaf, S P

    2016-05-01

    Head-to-head agglutination of ram spermatozoa is induced by dilution in the Tyrode's capacitation medium with albumin, lactate and pyruvate (TALP) and ameliorated by the addition of the thiol d-penicillamine (PEN). To better understand the association and disassociation of ram spermatozoa, we investigated the mechanism of action of PEN in perturbing sperm agglutination. PEN acts as a chelator of heavy metals, an antioxidant and a reducing agent. Chelation is not the main mechanism of action, as the broad-spectrum chelator ethylenediaminetetraacetic acid and the copper-specific chelator bathocuproinedisulfonic acid were inferior anti-agglutination agents compared with PEN. Oxidative stress is also an unlikely mechanism of sperm association, as PEN was significantly more effective in ameliorating agglutination than the antioxidants superoxide dismutase, ascorbic acid, α-tocopherol and catalase. Only the reducing agents cysteine and dl-dithiothreitol displayed similar levels of non-agglutinated spermatozoa at 0 h compared with PEN but were less effective after 3 h of incubation (37 °C). The addition of 10 µM Cu(2+) to 250 µM PEN + TALP caused a rapid reversion of the motile sperm population from a non-agglutinated state to an agglutinated state. Other heavy metals (cobalt, iron, manganese and zinc) did not provoke such a strong response. Together, these results indicate that PEN prevents sperm association by the reduction of disulphide bonds on a sperm membrane protein that binds copper. ADAM proteins are possible candidates, as targeted inhibition of the metalloproteinase domain significantly increased the percentage of motile, non-agglutinated spermatozoa (52.0% ± 7.8) compared with TALP alone (10.6% ± 6.1).Reproduction (2016) 151 1-10. PMID:26860122

  12. Androctonin, a hydrophilic disulphide-bridged non-haemolytic anti-microbial peptide: a plausible mode of action.

    PubMed Central

    Hetru, C; Letellier, L; Oren, Z; Hoffmann, J A; Shai, Y

    2000-01-01

    Androctonin is a 25-residue non-haemolytic anti-microbial peptide isolated from the scorpion Androctonus australis and contains two disulphide bridges. Androctonin is different from known native anti-microbial peptides, being a relatively hydrophilic and non-amphipathic molecule. This raises the possibility that the target of androctonin might not be the bacterial membrane, shown to be a target for most amphipathic lytic peptides. To shed light on its mode of action on bacteria and its non-haemolytic activity, we synthesized androctonin, its fluorescent derivatives and its all-D-amino acid enantiomer. The enantiomer preserved high activity, suggesting a lipid-peptide interaction between androctonin and bacterial membranes. In Gram-positive and (at higher concentrations) Gram-negative bacteria, androctonin induced an immediate perturbation of the permeability properties of the cytoplasmic membrane of the bacterial energetic state, concomitant with perturbation of the morphology of the cell envelope as revealed by electron microscopy. Androctonin binds only to negatively charged lipid vesicles and induces the leakage of markers at high concentrations and with a slow kinetics, in contrast with amphipathic alpha-helical anti-microbial peptides that bind and permeate negatively charged vesicles, and to a smaller extent also zwitterionic ones. This might explain the selective lytic activity of androctonin towards bacteria but not red blood cells. Polarized attenuated total reflection-Fourier transform infrared spectroscopy revealed that androctonin adopts a beta-sheet structure in membranes and did not affect the lipid acyl chain order, which supports a detergent-like effect. The small size of androctonin, its hydrophilic character and its physicochemical properties are favourable features for its potential application as a replacement for commercially available antibiotics to which bacteria have developed resistance. PMID:10642525

  13. Biosynthesis of the iron-molybdenum cofactor and the molybdenum cofactor in Klebsiella pneumoniae: effect of sulfur source

    SciTech Connect

    Ugalde, R.A.; Imperial, J.; Shah, V.K.; Brill, W.J.

    1985-12-01

    NifQ/sup -/ and Mol/sup -/ mutants of Klebsiella pneumoniae show an elevated molybdenum requirement for nitrogen fixation. Substitution of cystine for sulfate as the sulfur source in the medium reduced the molybdenum requirement of these mutants to levels required by the wild type. Cystine also increased the intracellular molybdenum accumulation of NifQ/sup -/ and Mol/sup -/ mutants. Cystine did not affect the molybdenum requirement or accumulation in wild-type K. pneumoniae. Sulfate transport and metabolism in K. pneumoniae were repressed by cystine. However, the effect of cystine on the molybdenum requirement could not be explained by an interaction between sulfate and molybdate at the transport level. The data show that cystine does not have a generalized effect on molybdenum metabolism. Millimolar concentrations of molybdate inhibited nitrogenase and nitrate reductase derepression with sulfate as the sulfur source, but not with cystine. The inhibition was the result of a specific antagonism of sulfate metabolism by molybdate. This study suggests that a sulfur donor and molybdenum interact at an early step in the biosynthesis of the iron-molybdenum cofactor. This interaction might occur nonenzymatically when the levels of the reactants are high.

  14. Boron modified molybdenum silicide and products

    DOEpatents

    Meyer, M.K.; Akinc, M.

    1999-02-02

    A boron-modified molybdenum silicide material is disclosed having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo{sub 5}Si{sub 3} phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi{sub 2} heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo{sub 5}Si{sub 3} for structural integrity. 7 figs.

  15. Boron modified molybdenum silicide and products

    DOEpatents

    Meyer, Mitchell K.; Akinc, Mufit

    1999-02-02

    A boron-modified molybdenum silicide material having the composition comprising about 80 to about 90 weight % Mo, about 10 to about 20 weight % Si, and about 0.1 to about 2 weight % B and a multiphase microstructure including Mo.sub.5 Si.sub.3 phase as at least one microstructural component effective to impart good high temperature creep resistance. The boron-modified molybdenum silicide material is fabricated into such products as electrical components, such as resistors and interconnects, that exhibit oxidation resistance to withstand high temperatures in service in air as a result of electrical power dissipation, electrical resistance heating elements that can withstand high temperatures in service in air and other oxygen-bearing atmospheres and can span greater distances than MoSi.sub.2 heating elements due to improved creep resistance, and high temperature structural members and other fabricated components that can withstand high temperatures in service in air or other oxygen-bearing atmospheres while retaining creep resistance associated with Mo.sub.5 Si.sub.3 for structural integrity.

  16. Climax-Type Porphyry Molybdenum Deposits

    USGS Publications Warehouse

    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.

  17. CSTX-9, a toxic peptide from the spider Cupiennius salei: amino acid sequence, disulphide bridge pattern and comparison with other spider toxins containing the cystine knot structure.

    PubMed

    Schalle, J; Kämpfer, U; Schürch, S; Kuhn-Nentwig, L; Haeberli, S; Nentwig, W

    2001-09-01

    CSTX-9 (68 residues, 7530.9 Da) is one of the most abundant toxic polypeptides in the venom of the wandering spider Cupiennius salei. The amino acid sequence was determined by Edman degradation using reduced and alkylated CSTX-9 and peptides generated by cleavages with endoproteinase Asp-N and trypsin, respectively. Sequence comparison with CSTX-1, the most abundant and the most toxic polypeptide in the crude spider venom, revealed a high degree of similarity (53% identity). By means of limited proteolysis with immobilised trypsin and RP-HPLC, the cystine-containing peptides of CSTX-9 were isolated and the disulphide bridges were assigned by amino acid analysis, Edman degradation and nanospray tandem mass spectrometry. The four disulphide bonds present in CSTX-9 are arranged in the following pattern: 1-4, 2-5, 3-8 and 6-7 (Cys6-Cys21, Cys13-Cys30, Cys20-Cys48, Cys32-Cys46). Sequence comparison of CSTX-1 with CSTX-9 clearly indicates the same disulphide bridge pattern, which is also found in other spider polypeptide toxins, e.g. agatoxins (omega-AGA-IVA, omega-AGA-IVB, mu-AGA-I and mu-AGA-VI) from Agelenopsis aperta, SNX-325 from Segestria florentina and curtatoxins (CT-I, CT-II and CT-III) from Hololena curta. CSTX-1/CSTX-9 belong to the family of ion channel toxins containing the inhibitor cystine knot structural motif. CSTX-9, lacking the lysine-rich C-terminal tail of CSTX-1, exhibits a ninefold lower toxicity to Drosophila melanogaster than CSTX-1. This is in accordance with previous observations of CSTX-2a and CSTX-2b, two truncated forms of CSTX-1 which, like CSTX-9, also lack the C-terminal lysine-rich tail. PMID:11693532

  18. Chill block melt spinning of nickel-molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Hemker, Kevin J.; Glasgow, Thomas K.

    1987-01-01

    Samples of Ni-Mo alloys ranging in composition from pure nickel to Ni-40 at. pct molybdenum were cast by the chill block melt-spinning rapid solidification technique and examined by optical metallography, X-ray diffraction, and microhardness testing. Casting difficulties were encountered with lean alloys, but richer alloys spread more readily on the casting wheel. Alloy microstructures for 5 to 37.5 at. pct molybdenum ribbons were primarily cellular/dendritic; microstructure feature size decreased with increasing molybdenum content. Extended solubility of molybdenum in gamma-nickel, with fcc lattice parameter increasing with composition to the 1.05 power, was observed up to 37/5 at. pct molybdenum. Substoichiometric Ni-Mo (delta) nucleated on the wheel side of the ribbons of compositions 35, 37.5, and 40 at. pct molybdenum. The amount of partitionless delta-phase thus formed increased with increasing molybdenum content and quench rate. This substoichiometric delta transformed readily to a fine structure gamma-delta mixture.

  19. Spreading of liquid Silver and Silver-Molybdenum alloys on molybdenum substrates

    SciTech Connect

    Rauch, Nicole; Saiz, Eduardo; Tomsia, Antoni P.

    2002-08-01

    The spreading of liquid Ag and Ag-Mo alloys on molybdenum substrates has been studied using a drop-transfer setup. Even though initial spreading velocities as fast as {approx}1 m/s have been recorded in some experiments, a large variation in the spreading dynamics has been observed, and there is no unique relationship between the contact angle and the spreading velocity. This can be attributed to the formation of ridges at the triple junction, the movement of which controls spreading. The fastest spreading rates are consistent with results reported for low temperature liquids; these can be described using a molecular-kinetic model. Spreading kinetics and final contact angles were similar for pure silver and silver-molybdenum liquids.

  20. Atomic layer deposition of molybdenum oxide using bis(tert-butylimido)bis(dimethylamido) molybdenum

    SciTech Connect

    Bertuch, Adam Sundaram, Ganesh

    2014-01-15

    Molybdenum trioxide films have been deposited using thermal atomic layer deposition techniques with bis(tert-butylimido)bis(dimethylamido)molybdenum. Films were deposited at temperatures from 100 to 300 °C using ozone as the oxidant for the process. The Mo precursor was evaluated for thermal stability and volatility using thermogravimetric analysis and static vapor pressure measurements. Film properties were evaluated with ellipsometry, x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and secondary electron microscopy. The growth rate per cycle was determined to extend from 0.3 to 2.4 Å/cycle with <4% nonuniformity (1-sigma) with-in-wafer across a 150 mm wafer for the investigated temperature range.

  1. The extended family of hexagonal molybdenum oxide

    SciTech Connect

    Hartl, Monika; Daemen, Luke; Lunk, J H; Hartl, H; Frisk, A T; Shendervich, I; Mauder, D; Feist, M; Eckelt, R

    2009-01-01

    Over the last 40 years, a large number of isostructural compounds in the system MoO{sub 3}-NH{sub 3}-H{sub 2}O have been published. The reported molecular formulae of 'hexagonal molybdenum oxide' (HEMO) varied from MoO{sub 3}, MoO{sub 3} {center_dot} 0.33NH{sub 3}, MoO{sub 3} {center_dot} nH{sub 2}O (0.09 {le} n {le} 0.69) to MoO{sub 3} {center_dot} mNH{sub 3} {center_dot} nH{sub 2}O (0.09 {le} m {le} 0.20; 0.18 {le} n {le} 0.60). Samples, prepared by the acidification route, were investigated using thermal analysis coupled on-line to a mass spectrometer for evolved gas analysis; X-ray powder diffraction; Fourier Transform Infrared, Raman and Magic-Angle-Spinning {sup 1}H-NMR spectroscopy; Incoherent Inelastic Neutron Scattering. The X-ray study of a selected monocrystal confirmed the presence of the well-known framework of edge-sharing MoO{sub 6} octahedra: Space group P6{sub 3}/m, a = 10.527(1), c =3.7245(7) {angstrom}, {gamma} = 120{sup o}. The structure of the synthesized samples can best be described by the structural formula (NH{sub 4})[Mo{sub x}{open_square}{sub 1/2+p/2}(O{sub 3x + 1/2-p/2})(OH){sub p}] {center_dot} yH{sub 2}O (x 5.9-7.1; p {approx} 0.1; y = 1.2-2.6), which is consistent with the existence of one vacancy for 12-15 molybdenum sites. The 'chimie douce' reaction of MoO{sub 3} {center_dot} 0.155NH{sub 3} {center_dot} 0.440H{sub 2}O with a 1:1 mixture of NO/NO{sub 2} at 100 C resulted in the synthesis of MoO{sub 3} {center_dot} 0.539H{sub 2}O. Tailored nano-sized molybdenum powders can be produced using HEMO as precursor.

  2. Mechanical properties of oxide dispersion strengthened (ODS) molybdenum alloys

    SciTech Connect

    Bianco, R.; Buckman, R.W. Jr.

    1998-03-01

    Oxide dispersion strengthened molybdenum, Mo-ODS, developed by a proprietary powder metallurgy process, exhibits a creep rupture life at 0.65T{sub m} (1,600 C) of three to five orders of magnitude greater than unalloyed molybdenum, while maintaining ductile fracture behavior at temperatures significantly below room temperature. In comparison, the creep rupture life of the Mo-50Re solid solution strengthened alloy at 1,600 C is only an order of magnitude greater than unalloyed molybdenum. The results of microstructural characterization and thermal stability and mechanical property testing are discussed.

  3. Pterin chemistry and its relationship to the molybdenum cofactor

    PubMed Central

    Basu, Partha; Burgmayer, Sharon J.N.

    2011-01-01

    The molybdenum cofactor is composed of a molybdenum coordinated by one or two rather complicated ligands known as either molybdopterin or pyranopterin. Pterin is one of a large family of bicyclic N-heterocycles called pteridines. Such molecules are widely found in Nature, having various forms to perform a variety of biological functions. This article describes the basic nomenclature of pterin, their biological roles, structure, chemical synthesis and redox reactivity. In addition, the biosynthesis of pterins and current models of the molybdenum cofactor are discussed. PMID:21607119

  4. PURIFICATION OF URANIUM FROM URANIUM/MOLYBDENUM ALLOY

    SciTech Connect

    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.

  5. Superconducting properties of evaporated copper molybdenum sulfide films

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Chi, K. C.; Dillon, R. O.; Bunshah, R. F.; Alterovitz, S. A.

    1978-01-01

    Films of copper molybdenum sulfide were produced by coevaporation. Those that were superconducting contained only the ternary compound and free molybdenum. The range of copper content in the ternary compound was as large as that in polycrystalline material, that is, it includes either phase alone, or a mixture of the two phases of this material. This is in contrast with sputtered materials where copper concentration has been limited to a narrower range. The upper critical field and the critical current were measured as functions of external magnetic field, and found to be similar to those of sputtered copper molybdenum sulfide, when the comparison was made for samples having the same amount of copper.

  6. Pressure-induced metallization of molybdenum disulfide.

    PubMed

    Chi, Zhen-Hua; Zhao, Xiao-Miao; Zhang, Haidong; Goncharov, Alexander F; Lobanov, Sergey S; Kagayama, Tomoko; Sakata, Masafumi; Chen, Xiao-Jia

    2014-07-18

    X-ray diffraction, Raman spectroscopy, and electrical conductivity measurements of molybdenum disulfide MoS(2) are performed at pressures up to 81 GPa in diamond anvil cells. Above 20 GPa, we find discontinuous changes in Raman spectra and x-ray diffraction patterns which provide evidence for isostructural phase transition from 2H(c) to 2H(a) modification through layer sliding previously predicted theoretically. This first-order transition, which is completed around 40 GPa, is characterized by a collapse in the c-lattice parameter and volume and also by changes in interlayer bonding. After the phase transition completion, MoS(2) becomes metallic. The reversibility of the phase transition is identified from all these techniques. PMID:25083660

  7. Molybdenum Abundances in Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Peterson, R. C.

    2012-08-01

    Peterson (2011) has analyzed HST spectra near 2000Å of five metal-poor turnoff stars with mild enhancements of heavy r-process elements. Two stars, HD 94028 and HD 160617, are unique in showing an extreme overabundance of the light trans-ironic element molybdenum (Z = 42), but less extreme enhancements of Zr (Z = 40) and Ru (Z = 44). Of several nucleosynthesis scenarios that can produce nuclei in this mass range in the oldest stars, a high-entropy wind (HEW) acting in a core-collapse supernova seems uniquely capable of a high overproduction confined to a narrow mass range. That this unusual elemental distribution is achieved only under very limited physical conditions suggests that very few individual nucleosynthesis events were responsible for the synthesis of the light trans-ironic elements in these stars, even though both are only moderately metal-poor.

  8. Ultrafast response of monolayer molybdenum disulfide photodetectors

    PubMed Central

    Wang, Haining; Zhang, Changjian; Chan, Weimin; Tiwari, Sandip; Rana, Farhan

    2015-01-01

    The strong light emission and absorption exhibited by single atomic layer transitional metal dichalcogenides in the visible to near-infrared wavelength range make them attractive for optoelectronic applications. In this work, using two-pulse photovoltage correlation technique, we show that monolayer molybdenum disulfide photodetector can have intrinsic response times as short as 3 ps implying photodetection bandwidths as wide as 300 GHz. The fast photodetector response is a result of the short electron–hole and exciton lifetimes in this material. Recombination of photoexcited carriers in most two-dimensional metal dichalcogenides is dominated by nonradiative processes, most notable among which is Auger scattering. The fast response time, and the ease of fabrication of these devices, make them interesting for low-cost ultrafast optical communication links. PMID:26572726

  9. Advances in rechargeable lithium molybdenum disulfide batteries

    NASA Technical Reports Server (NTRS)

    Brandt, K.; Stiles, J. A. R.

    1985-01-01

    The lithium molybdenum disulfide system as demonstrated in a C size cell, offers performance characteristics for applications where light weight and low volume are important. A gravimetric energy density of 90 watt hours per kilogram can be achieved in a C size cell package. The combination of charge retention capabilities, high energy density and a state of charge indicator in a rechargeable cell provides power package for a wide range of devices. The system overcomes the memory effect in Nicads where the full capacity of the battery cannot be utilized unless it was utilized on previous cycles. The development of cells with an advanced electrolyte formulation led to an improved rate capability especially at low temperatures and to a significantly improved life cycle.

  10. Environmental behavior of two molybdenum porphyry systems

    USGS Publications Warehouse

    Tuttle, M.L.W.; Wanty, R.B.; Berger, B.R.

    2004-01-01

    Our study focuses on the geology, hydrology, and geochemistry of a variety of molybdenum (Mo) porphyry systems. The systems are either high fluorine, granite, Climax-type, systems (e.g. Mount Emmons/ Redwell Mo deposit, Colorado and Questa Mo deposit, New Mexico) or low fluorine granodiorite systems (e.g. Buckingham Stockwork Mo deposit, Battle Mountain, Nevada and Cannivan Gulch Mo deposit, Montana). The water quality of streams, natural springs, mine discharge, and ground water from drill holes were assessed in the region of these deposits. The ultimate goal of our study is to understand the environmental behavior of these Mo porphyry systems in the context of geologic setting, hydrologic regime, and climate.

  11. Fate and Transport of Molybdenum Disulfide Nanomaterials in Sand Columns

    PubMed Central

    Lanphere, Jacob D.; Luth, Corey J.; Guiney, Linda M.; Mansukhani, Nikhita D.; Hersam, Mark C.; Walker, Sharon L.

    2015-01-01

    Abstract Research and development of two-dimensional transition metal dichalcogenides (TMDC) (e.g., molybdenum disulfide [MoS2]) in electronic, optical, and catalytic applications has been growing rapidly. However, there is little known regarding the behavior of these particles once released into aquatic environments. Therefore, an in-depth study regarding the fate and transport of two popular types of MoS2 nanomaterials, lithiated (MoS2-Li) and Pluronic PF-87 dispersed (MoS2-PL), was conducted in saturated porous media (quartz sand) to identify which form would be least mobile in aquatic environments. The electrokinetic properties and hydrodynamic diameters of MoS2 as a function of ionic strength and pH were determined using a zeta potential analyzer and dynamic light scattering techniques. Results suggest that the stability is significantly decreased beginning at 10 and 31.6 mM KCl, for MoS2-PL and MoS2-Li, respectively. Transport study results from breakthrough curves, column dissections, and release experiments suggest that MoS2-PL exhibits a greater affinity to be irreversibly bound to quartz surfaces as compared with the MoS2-Li at a similar ionic strength. Derjaguin–Landau–Verwey–Overbeek theory was used to help explain the unique interactions between the MoS2-PL and MoS2-Li surfaces between particles and with the quartz collectors. Overall, the results suggest that the fate and transport of MoS2 is dependent on the type of MoS2 that enters the environment, where MoS2-PL will be least mobile and more likely be deposited in porous media from pluronic–quartz interactions, whereas MoS2-Li will travel greater distances and have a greater tendency to be remobilized in sand columns. PMID:25741176

  12. Mass spectrometry analysis of the oxidation states of the pro-oncogenic protein anterior gradient-2 reveals covalent dimerization via an intermolecular disulphide bond.

    PubMed

    Clarke, David J; Murray, Euan; Faktor, Jakub; Mohtar, Aiman; Vojtesek, Borek; MacKay, C Logan; Smith, Pat Langridge; Hupp, Ted R

    2016-05-01

    Anterior Gradient-2 (AGR2) is a component of a pro-oncogenic signalling pathway that can promote p53 inhibition, metastatic cell migration, limb regeneration, and cancer drug-resistance. AGR2 is in the protein-disulphide isomerase superfamily containing a single cysteine (Cys-81) that forms covalent adducts with its client proteins. We have found that mutation of Cysteine-81 attenuates its biochemical activity in its sequence-specific peptide docking function, reduces binding to Reptin, and reduces its stability in cells. As such, we evaluated how chemical oxidation of its cysteine affects its biochemical properties. Recombinant AGR2 spontaneously forms covalent dimers in the absence of reductant whilst DTT promotes dimer to monomer conversion. Mutation of Cysteine-81 to alanine prevents peroxide catalysed dimerization of AGR2 in vitro, suggesting a reactive cysteine is central to covalent dimer formation. Both biochemical assays and ESI mass spectrometry were used to demonstrate that low levels of a chemical oxidant promote an intermolecular disulphide bond through formation of a labile sulfenic acid intermediate. However, higher levels of oxidant promote sulfinic or sulfonic acid formation thus preventing covalent dimerization of AGR2. These data together identify the single cysteine of AGR2 as an oxidant responsive moiety that regulates its propensity for oxidation and its monomeric-dimeric state. This has implications for redox regulation of the pro-oncogenic functions of AGR2 protein in cancer cells. PMID:26876500

  13. Enhanced dispersion and the reactivity of atomically thin Rh layers supported by molybdenum oxide films

    NASA Astrophysics Data System (ADS)

    Szenti, Imre; Bugyi, László; Kónya, Zoltán

    2015-11-01

    The behavior of rhodium layers deposited on oxidized, 0.15-20.0 ML thick Mo films formed on a nearly stoichiometric TiO2(110) single crystal was characterized by AES, TPD and work function (WF) measurements. The oxidation of 0.15-2.7 ML thick Mo deposits was performed via the redox reaction with the titania support at 1000 K. Molybdenum oxide supports of MoO3 and MoO2 surface composition were formed by the oxidation of 20 ML thick Mo multilayers by O2 at 650 K and 1000 K, respectively. Rh grows in a layer-by-layer fashion on a mixed titanium-molybdenum oxide produced in the reaction between titania and 0.15 ML Mo, corresponding to a considerably enhanced dispersion of rhodium as compared with that on the clean TiO2(110). The surface reactivity of Rh layers supported by molybdenum oxides as a function of pre-annealing temperature was followed by carbon monoxide adsorption-desorption cycles. The CO uptake of a 0.4 ML thick Rh film formed on the MoO3 support was strongly suppressed at 300 K, indicating the encapsulation of rhodium with MoOX species of low surface free energy. The CO adsorption capability of rhodium particles supported by both MoO3 and MoO2 layers was eliminated due to pre-annealing at 600 K, related to the extended decoration of metal particles by MoOX moiety. The encapsulation of the rhodium films proceeded above 600 K on both supports, and annealing to 1000 K resulted in nearly equal WF values, indicating the formation of MoOX overlayers of similar surface composition close to MoO2. AES depth profiles revealed that the 0.4 ML thick Rh deposits covered by MoOX at 1000 K preserved their island structure.

  14. A terminal molybdenum arsenide complex synthesized from yellow arsenic.

    PubMed

    Curley, John J; Piro, Nicholas A; Cummins, Christopher C

    2009-10-19

    A terminal molybdenum arsenide complex is synthesized in one step from the reactive As(4) molecule. The properties of this complex with its arsenic atom ligand are discussed in relation to the analogous nitride and phosphide complexes. PMID:19764796

  15. Improved molybdenum disulfide-silver motor brushes have extended life

    NASA Technical Reports Server (NTRS)

    Horton, J. C.; King, H. M.

    1964-01-01

    Motor brushes of proper quantities of molybdenum disulfide and copper or silver are manufactured by sintering techniques. Graphite molds are used. These brushes operate satisfactorily for long periods in normal atmosphere or in a high-vacuum environment.

  16. High Molybdenum availability for evolution in a Mesoproterozoic lacustrine environment

    NASA Astrophysics Data System (ADS)

    Parnell, John; Spinks, Samuel; Andrews, Steven; Thayalan, Wanethon; Bowden, Stephen

    2015-05-01

    Trace metal data for Proterozoic marine euxinic sediments imply that the expansion of nitrogen-fixing cyanobacteria and diversification of eukaryotes were delayed while the availability of bioessential metals such as molybdenum in the ocean was limited. However, there is increasing recognition that the Mesoproterozoic evolution of nitrogen fixation and eukaryotic life may have been promoted in marginal marine and terrestrial environments, including lakes, rather than in the deep ocean. Molybdenum availability is critical to life in lakes, just as it is in the oceans. It is, therefore, important to assess molybdenum availability to the lacustrine environment in the Mesoproterozoic. Here we show that the flux of molybdenum to a Mesoproterozoic lake was 1 to 2 orders of magnitude greater than typical fluxes in the modern and ancient marine environment. Thus, there was no barrier to availability to prevent evolution in the terrestrial environment, in contrast to the nutrient-limited Mesoproterozoic oceans.

  17. Molybdenum-UO2 cermet irradiation at 1145 K.

    NASA Technical Reports Server (NTRS)

    Mcdonald, G.

    1971-01-01

    Two molybdenum-uranium dioxide cermet fuel pins with molybdenum clad were fission-heated in a forced-convection helium coolant for sufficient time to achieve 5.3% burnup. The cermet core contained 20 wt % of 93.2% enriched uranium dioxide. The results were as follows: there was no visible change in the appearance of the molybdenum clad during irradiation; the maximum increase in diameter of the fuel pins was 0.8%; there was no migration of uranium dioxide along grain boundaries and no evident interaction between molybdenum and uranium dioxide; and, finally, approximately 12% of the fission gas formed was released from the cermet core into the gas plenum.

  18. Synthesis of Dinitrogen and Dihydrogen Complexes of Molybdenum.

    ERIC Educational Resources Information Center

    Archer, Leonard J.; And Others

    1981-01-01

    Presents background information, safety notes, and laboratory procedures for synthesizing dinitrogen and dihydrogen complexes of molybdenum. The one-step method described is suitable for advanced inorganic chemistry classes. (SK)

  19. Electroplating and stripping copper on molybdenum and niobium

    NASA Technical Reports Server (NTRS)

    Power, J. L.

    1978-01-01

    Molybdenum and niobium are often electroplated and subsequently stripped of copper. Since general standard plating techniques produce poor quality coatings, general procedures have been optimized and specified to give good results.

  20. High Molybdenum availability for evolution in a Mesoproterozoic lacustrine environment.

    PubMed

    Parnell, John; Spinks, Samuel; Andrews, Steven; Thayalan, Wanethon; Bowden, Stephen

    2015-01-01

    Trace metal data for Proterozoic marine euxinic sediments imply that the expansion of nitrogen-fixing cyanobacteria and diversification of eukaryotes were delayed while the availability of bioessential metals such as molybdenum in the ocean was limited. However, there is increasing recognition that the Mesoproterozoic evolution of nitrogen fixation and eukaryotic life may have been promoted in marginal marine and terrestrial environments, including lakes, rather than in the deep ocean. Molybdenum availability is critical to life in lakes, just as it is in the oceans. It is, therefore, important to assess molybdenum availability to the lacustrine environment in the Mesoproterozoic. Here we show that the flux of molybdenum to a Mesoproterozoic lake was 1 to 2 orders of magnitude greater than typical fluxes in the modern and ancient marine environment. Thus, there was no barrier to availability to prevent evolution in the terrestrial environment, in contrast to the nutrient-limited Mesoproterozoic oceans. PMID:25988499

  1. Molybdenum-A Key Component of Metal Alloys

    USGS Publications Warehouse

    Kropschot, S.J.

    2010-01-01

    Molybdenum, whose chemical symbol is Mo, was first recognized as an element in 1778. Until that time, the mineral molybdenite-the most important source of molybdenum-was believed to be a lead mineral because of its metallic gray color, greasy feel, and softness. In the late 19th century, French metallurgists discovered that molybdenum, when alloyed (mixed) with steel in small quantities, creates a substance that is remarkably tougher than steel alone and is highly resistant to heat. The alloy was found to be ideal for making tools and armor plate. Today, the most common use of molybdenum is as an alloying agent in stainless steel, alloy steels, and superalloys to enhance hardness, strength, and resistance to corrosion.

  2. Oxidation characteristics of molybdenum-zirconium oxide cermets

    NASA Technical Reports Server (NTRS)

    Heitzinger, B.

    1984-01-01

    The oxidation of molybdenum is affected by the factors of temperature, the oxygen pressure in the oxidizing atmosphere, and the time of exposure. Studies of the oxidation characteristics of Mo show that the oxidation rate increases strongly when the temperature exceeds 600 C. Investigations of the behavior of cermets with various percentages of zirconium oxide are discussed, taking into account oxidation conditions at temperatures under and above the melting point of molybdenum trioxide.

  3. A study of the mechanisms of hydrogen embrittlement in molybdenum

    NASA Technical Reports Server (NTRS)

    Taheri, M.

    1978-01-01

    The mechanical properties of polycrystalline molybdenum samples in both the 'as annealed' and hydrogenized conditions were studied. The results indicate that hydrogen does not alter the yield stress of samples significantly although it reduces both the ultimate tensile strength and the ductility considerably. Fractographic study of samples shows a tendency to intercrystalline cracking of the hydrogenised molybdenum at low temperatures. In the light of the results, a mechanism involving grain boundary weakening is suggested.

  4. Isotopically Modified Molybdenum: Production for Application in Nuclear Energy

    NASA Astrophysics Data System (ADS)

    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.

  5. Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

    DOEpatents

    Lowden, R.A.

    1994-04-05

    A process for chemical vapor deposition of crystalline silicon nitride is described 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. 5 figures.

  6. Carminic acid as a reagent for the spectrofluorimetric determination of molybdenum and tungsten-II Determination of molybdenum in mild steel.

    PubMed

    Kirkbright, G F; West, T S; Woodward, C

    1966-12-01

    A method is described for the spectrofluorimetric determination of molybdenum in mild steel down to 0.01 %. After dissolution of the sample, molybdenum is separated from the bulk of iron by extraction of molybdenum(V) thiocyanate with isoamyl acetate. It is then determined with carminic acid as described in Part I. PMID:18960052

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

    SciTech Connect

    Nazir, Rabia; Ahmed, Sohail; Mazhar, Muhammad; Akhtar, Muhammad Javed; Siddique, Muhammad; Khan, Nawazish Ali; Shah, Muhammad Raza; Nadeem, Muhammad

    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.

  8. Electron accelerator-based production of molybdenum-99: Bremsstrahlung and photoneutron generation from molybdenum vs. tungsten

    NASA Astrophysics Data System (ADS)

    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

  9. Molybdenum oxide and molybdenum oxide-nitride back contacts for CdTe solar cells

    SciTech Connect

    Drayton, Jennifer A. Geisthardt, Russell M. Sites, James R.; Williams, Desiree D. Cramer, Corson L. Williams, John D.

    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.

  10. Dilithiation of Bis(benzene)molybdenum and subsequent isolation of a molybdenum-containing paracyclophane.

    PubMed

    Braunschweig, Holger; Buggisch, Nele; Englert, Ulli; Homberger, Melanie; Kupfer, Thomas; Leusser, Dirk; Lutz, Matthias; Radacki, Krzysztof

    2007-04-18

    The homoleptic sandwich complex bis(benzene)molybdenum, [Mo(eta6-C6H6)2], was successfully dilithiated by employing an excess of BuLi in the presence of N,N,N',N'-tetramethylethylenediamine (up to 6 equiv each) at slightly elevated temperatures furnishing the highly reactive, ring metalated species [Mo(eta6-C6H5Li)2].tmeda in high yields. Alternatively, this compound was synthesized upon prolonged sonication with 5 equiv of tBuLi/tmeda without heating. An X-ray crystal structure determination revealed a symmetrical, dimeric composition in the solid state, i.e., a formula of [Mo(eta6-C6H5Li)2]2.(thf)6, where the six-membered rings are connected by two pairs of bridging lithium atoms. The synthesis of an elusive ansa-bridged complex failed in the case of a [1]bora and a [1]sila bridge due to the thermal lability of the resulting compounds. Instead, reverse addition of the dilithio precursor to an excess of the appropriate element dihalide facilitated the isolation of several unstrained, 1,1'-disubstituted derivatives, namely, [Mo{eta6-C6H5(BN(SiMe3)2X)}2] (X = Cl, Br) and [Mo{eta6-C6H5(SiiPr2Cl)}2], respectively. However, the incorporation of a less congesting [2]sila bridge was accomplished. In addition to the formation of [Mo{(eta6-C6H5)2Si2Me4}], a molybdenum-containing paracylophane complex was isolated and characterized by means of crystal structure analysis. The ancillary formation of 1 equiv of bis(benzene)molybdenum strongly suggests that this species is generated by deprotonation of the ansa-bridged complex by the dilithiated precursor and subsequent reaction with a second equivalent of the disilane. PMID:17375929

  11. A comprehensive study on atomic layer deposition of molybdenum sulfide for electrochemical hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Kwon, Do Hyun; Jin, Zhenyu; Shin, Seokhee; Lee, Wook-Seong; Min, Yo-Sep

    2016-03-01

    Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically-active surface area. In addition, the ALD-MoSx/CFP catalysts exhibit excellent catalytic stability due to the strong adhesion of MoSx on the CFP and the mixed phase.Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically

  12. Scalable Production of Molybdenum Disulfide Based Biosensors.

    PubMed

    Naylor, Carl H; Kybert, Nicholas J; Schneier, Camilla; Xi, Jin; Romero, Gabriela; Saven, Jeffery G; Liu, Renyu; Johnson, A T Charlie

    2016-06-28

    We demonstrate arrays of opioid biosensors based on chemical vapor deposition grown molybdenum disulfide (MoS2) field effect transistors (FETs) coupled to a computationally redesigned, water-soluble variant of the μ-opioid receptor (MOR). By transferring dense films of monolayer MoS2 crystals onto prefabricated electrode arrays, we obtain high-quality FETs with clean surfaces that allow for reproducible protein attachment. The fabrication yield of MoS2 FETs and biosensors exceeds 95%, with an average mobility of 2.0 cm(2) V(-1) s(-1) (36 cm(2) V(-1) s(-1)) at room temperature under ambient (in vacuo). An atomic length nickel-mediated linker chemistry enables target binding events that occur very close to the MoS2 surface to maximize sensitivity. The biosensor response calibration curve for a synthetic opioid peptide known to bind to the wild-type MOR indicates binding affinity that matches values determined using traditional techniques and a limit of detection ∼3 nM (1.5 ng/mL). The combination of scalable array fabrication and rapid, precise binding readout enabled by the MoS2 transistor offers the prospect of a solid-state drug testing platform for rapid readout of the interactions between novel drugs and their intended protein targets. PMID:27227361

  13. Intrinsic structural defects in monolayer molybdenum disulfide

    SciTech Connect

    Zhou, Wu; Idrobo Tapia, Juan C

    2013-01-01

    Monolayer molybdenum disulfide (MoS2) is a two-dimensional direct band gap semiconductor with distinctive mechanical, electronic, optical and chemical properties that can be utilized for novel nanoelectronics and optoelectronics devices. The performance of these electronic devices strongly depends on the quality and defect morphology of the MoS2 layers. Yet, little is known about the atomic structure of defects present in monolayer MoS2 and their influences on the material properties. Here we provide a systematic study of various intrinsic structural defects, including point defects, grain boundaries, and edges, in chemical vapor phase grown monolayer MoS2 via direct atomic resolution imaging, and explore their energy landscape and electronic properties using first-principles calculations. We discover that one-dimensional metallic wires can be created via two different types of 60 grain boundaries consisting of distinct 4-fold ring chains. A new type of edge reconstruction, representing a transition state during growth, was also identified, providing insights into the material growth mechanism. The atomic scale study of structural defects presented here brings new opportunities to tailor the properties of MoS2 via controlled synthesis and defect engineering.

  14. Vertically aligned biaxially textured molybdenum thin films

    SciTech Connect

    Krishnan, Rahul; Riley, Michael; Lee, Sabrina; Lu, Toh-Ming

    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.

  15. Amorphous molybdenum silicon superconducting thin films

    SciTech Connect

    Bosworth, D. Sahonta, S.-L.; Barber, Z. H.; Hadfield, R. H.

    2015-08-15

    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 W{sub x}Si{sub 1−x}, though other amorphous superconductors such as molybdenum silicide (Mo{sub x}Si{sub 1−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 Mo{sub 83}Si{sub 17}. 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.

  16. Structural phase transitions in monolayer molybdenum dichalcogenides

    NASA Astrophysics Data System (ADS)

    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.

  17. Molybdenum disilicide composites produced by plasma spraying

    SciTech Connect

    Castro, R.G.; Hollis, K.J.; Kung, H.H.; Bartlett, A.H.

    1998-05-25

    The intermetallic compound, molybdenum disilicide (MoSi{sub 2}) is being considered for high temperature structural applications because of its high melting point and superior oxidation resistance at elevated temperatures. The lack of high temperature strength, creep resistance and low temperature ductility has hindered its progress for structural applications. Plasma spraying of coatings and structural components of MoSi{sub 2}-based composites offers an exciting processing alternative to conventional powder processing methods due to superior flexibility and the ability to tailor properties. Laminate, discontinuous and in situ reinforced composites have been produced with secondary reinforcements of Ta, Al{sub 2}O{sub 3}, SiC, Si{sub 3}N{sub 4} and Mo{sub 5}Si{sub 3}. Laminate composites, in particular, have been shown to improve the damage tolerance of MoSi{sub 2} during high temperature melting operations. A review of research which as been performed at Los Alamos National Laboratory on plasma spraying of MoSi{sub 2}-based composites to improve low temperature fracture toughness, thermal shock resistance, high temperature strength and creep resistance will be discussed.

  18. The biological and toxicological importance of molybdenum in the environment and in the nutrition of plants, animals and man. Part 1: Molybdenum in plants.

    PubMed

    Anke, M; Seifert, M

    2007-09-01

    In 1930, Bortels showed that molybdenum is necessary for nitrogen fixation in Acetobacter, and in 1939 Arnon and Stout reported that molybdenum is essential for life in higher plants. Nitrogenase is the nitrogen-fixing enzyme complex, while nitrate reductase requires molybdenum for its activity. Molybdenum occurs in the earth crust with an abundance of 1.0-1.4 mg/kg. The molybdenum content of the vegetation is determined by the amount of this element in the soil and its pH-value. The weathering soils of granite, porphyry, gneiss and Rotliegendes produce a molybdenum-rich vegetation. Significantly poorer in Mo is the vegetation on loess, diluvial sands, alluvial riverside soils and especially on Keuper and Muschelkalk weathering soils, which produce legumes and, e.g. cauliflower with molybdenum deficiency symptoms. The molybdenum content of the flora decreases with increasing age. Legumes store the highest molybdenum levels in the bulbs of their roots; on average, they accumulate more molybdenum than herbs and grasses do. The danger of molybdenum toxicity in plants is small. PMID:17899788

  19. Electrothermal atomic absorption spectrometry determination of molybdenum in whole blood

    NASA Astrophysics Data System (ADS)

    Burguera, J. L.; Rondón, C.; Burguera, M.; Roa, M. E.; Petit de Peña, Y.

    2002-03-01

    A method for the determination of molybdenum in whole blood by atomic absorption spectrometry with electrothermal atomization was developed and evaluated. Erbium (25 μg) was chosen from several potential chemical modifiers (Sm, Lu, Ho, Eu and Pd+Mg) as the most appropriate for the sensitive and reliable determination of molybdenum in such sample. The process used was direct dilution of the sample in a ratio 1:2 with a 0.1% (v/v) Triton X-100 solution. The injection of 20 μl of a solution of 15% (w/v) hydrogen peroxide and running the temperature program after 5 firings greatly reduced the effect of build-up of carbonaceous residues within the atomizer. The limit of detection and working ranges, respectively, were 0.6 and 2.0-100.0 μg l -1, and the characteristic mass was 7.2 pg. The relative standard deviation varied from 0.8 to 1.5% for within and between batch determinations, respectively. The determination of molybdenum in Seronorm™ Trace Elements in Whole Blood with known added amounts of the analyte was performed to asses the accuracy. The optimized procedure has been applied to the determination of molybdenum in whole blood specimens of 20 subjects taken before and 10-12 h after receiving an over-supply of 1 mg of molybdenum. The molybdenum concentrations (±S.D.) were 10.9±0.4 μg Mo l -1 (range 9.9-11.6 μg Mo l -1) and 15.4±0.4 μg Mo l -1 (range 13.1-16.9 μg Mo l -1) for the individuals before and after the administration of molybdenum.

  20. Activity and selectivity of molybdenum catalysts in coal liquefaction reactions

    SciTech Connect

    Curtis, C.W.; Pellegrino, J.L. )

    1988-01-01

    The purpose of this work is to evaluate how effectively three different molybdenum catalysts promote reactions involving heteroatom removal and cleavage of alkyl bridge hydrodeoxygenation (HDO), hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrocracking (HYC). Both model and coal liquefaction reactions were performed to test the activity and selectivity of three different molybdenum catalysts. The three catalysts used were molybdenum naphthenate, molybdenum supported on gamma alumina (Mo/Al{sub 2}O{sub 3}) and precipitated, poorly crystalline molybdenum disulfide (MoS{sub 2}). The model compounds, chosen to mimic coal structure, on which the effectiveness of the catalysts for the model reactions was tested were: 1-methylnaphthalene, representing aromatic hydrocarbons, for hydrogenation; 1-naphthol, representing oxygen containing compounds, for deoxygenation; benzothiophene, representing sulfur containing compounds, for desulfurization; indole, representing nitrogen containing compounds, for denitrogenation; and bibenzyl, representing alkyl bridging structures, for hydrocracking. Catalytic reactions of combinations of reactants were performed to simulate a complex coal matrix. Thermal and catalytic coal liquefaction reactions were performed using Illinois No. 6 coal with anthracene as a solvent. The efficacy of the catalysts was determined by comparing the product and compound class fractions obtained from the liquefaction reactions.

  1. Activity and selectivity of molybdenum catalysts in coal liquefaction reactions

    SciTech Connect

    Curtis, C.W.; Pellegrino, J.L. )

    1988-06-01

    During coal liquefaction, coal fragments forming a liquid product with reduced heteroatom content. Coal can be considered to be a large network of polynuclear aromatic species connected by heteroatoms and alkyl bridging structures. Predominant heteroatoms contained in coal are sulfur, oxygen, and nitrogen. Predominant alkyl bridges are methylene and ethylene structures. The purpose of this work is to evaluate how effectively three different molybdenum catalysts promote reactions involving heteroatom removal and cleavage of alkyl bridge structures. The reactions studied include: hydrogenation (HYD), hydrodeoxygenation (HDO), hydrosulfurization (HDS), hydrodenitrogenation (HDN) and hydrocracking (HYC). Both model and coal liquefaction reactions were performed to test the activity and selectivity of three different molybdenum catalysts. The three catalysts used were molybdenum napththenate, molybdenum supported on gamma alumina (Mo/Al/sub 2/O/sub 3/) and precipitated, poorly crystalline molybdenum disulfide (MoS/sub 2/). The model compounds, chosen to mimic coal structure, on which the effectiveness of the catalysts for the model reactions was tested were: 1-methylnaphthalene, representing aromatic hydrocarbons, for hydrogenation; 1-naphthol, representing oxygen containing compounds, for deoxygenation; benzothiophene, representing sulfur containing compounds, for desulfurization; indole, representing nitrogen containing compounds, for denitrogenation; and bibenzyl, representing alkyl bridging structures, for hydrocracking. Catalytic reactions of combinations of reactants were performed to simulate a complex coal matrix. Thermal and catalytic coal liquefaction reactions were performed using Illinois No. 6 coal with anthracene as a solvent. The efficacy of the catalysts was determined by comparing the product and compound class fractions obtained from the liquefaction reactions.

  2. Yield strength of molybdenum at high pressures.

    PubMed

    Jing, Qiumin; Bi, Yan; Wu, Qiang; Jing, Fuqian; Wang, Zhigang; Xu, Jian; Jiang, Sheng

    2007-07-01

    In the diamond anvil cell technology, the pressure gradient approach is one of the three major methods in determining the yield strength for various materials at high pressures. In the present work, by in situ measuring the thickness of the sample foil, we have improved the traditional technique in this method. Based on this modification, the yield strength of molybdenum at pressures has been measured. Our main experimental conclusions are as follows: (1) The measured yield strength data for three samples with different initial thickness (100, 250, and 500 microm) are in good agreement above a peak pressure of 10 GPa. (2) The measured yield strength can be fitted into a linear formula Y=0.48(+/-0.19)+0.14(+/-0.01)P (Y and P denote the yield strength and local pressure, respectively, both of them are in gigapascals) in the local pressure range of 8-21 GPa. This result is in good agreement with both Y=0.46+0.13P determined in the pressure range of 5-24 GPa measured by the radial x-ray diffraction technique and the previous shock wave data below 10 GPa. (3) The zero-pressure yield strength of Mo is 0.5 GPa when we extrapolate our experimental data into the ambient pressure. It is close to the tensile strength of 0.7 GPa determined by Bridgman [Phys. Rev. 48, 825 (1934)] previously. The modified method described in this article therefore provides the confidence in determination of the yield strength at high pressures. PMID:17672772

  3. Butene oxidation by molybdenum crystallographic shear compounds

    SciTech Connect

    McCormick, R.L.

    1984-06-01

    The reduced molybdenum oxides Mo/sub 4/O/sub 11/-orh, Mo/sub 4/O/sub 11/-mon, Mo/sub 8/O/sub 23/, and Mo/sub 18/O/sub 52/ were synthesized. These compounds, as well as MoO/sub 3/, were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, Raman and FT-IR spectroscopies, and BET surface area measurements. The oxides were then studied in a pulsed reactor at 500/sup 0/C in the selective oxidation of butene and butadiene. The data suggested a process in which the surface site must become more oxidized in parallel with the oxidation of the adsorbed hydrocarbon. Evidence supporting this idea included the high selectivity to maleic anhydride observed over a completely oxidized surface and differences in the reactivity of butene and butadiende. In particular, oxygen insertion into butadiene to form furan occurred in the absence of gas phase O/sub 2/ over the reduced phases, while oxygen insertion into butene required the presence of molecular oxygen. Maleic anhydride formation required the presence of molecular oxygen except in the case of butadiene oxidation over MoO/sub 3/. The long range ordering of defects, known as crystallographic shear, was not shown to have any influence on the initial interaction of reactant and solid. However, the unusual coordination geometries and surface structures that are thought to be caused by the presence of shear planes may be related to the differences in catalytic selectivity observed for these oxides.

  4. METHOD FOR FORMING A COATING OF MOLYBDENUM CARBIDE ON A CARBON BODY

    DOEpatents

    Simnad, M.T.

    1962-04-01

    A method is described for coating a carbon bodywith molybdenum carbide in such a manner that the carbon body is rendered less permeable to the flow of gases and has increased resistance to corrosion and erosion. The method includes coating a carbon body with molybdenum trioxide by contacting it at a temperature below the condensation temperature with molybdenum trioxide vapors and thereafter carburizing the molybdenum trioxide in situ in an inert atmosphere on the carhon body. (AEC)

  5. X-ray Diffraction Study of Molybdenum to 900 GPa

    NASA Astrophysics Data System (ADS)

    Wang, J.; Coppari, F.; Smith, R.; Eggert, J.; Boehly, T.; Collins, G. W.; Duffy, T. S.

    2013-12-01

    Molybdenum (Mo) is a transition metal that is important as a high-pressure standard. Its equation of state, structure, and melting behavior have been explored extensively in both experimental and theoretical studies. Melting data up to the Mbar pressure region from static compression experiments in the diamond anvil cell [Errandonea et al. 2004] are inconsistent with shock wave sound velocity measurements [Hixson et al., 1989]. There are also conflicting reports as to whether body-centered cubic (BCC) Mo transforms to a face-centered cubic (FCC), hexagonal close packed (HCP) or double hexagonal close packed (DHCP) structure at either high pressure or high pressure and temperature conditions [Belonoshko et al. 2008, Mikhaylushkin et al., 2008 and Cazorla et al., 2008]. Recently, a phase transition from BCC to the DHCP phase at 660 GPa and 0 K was predicted using the particle swam optimization (PSO) method (Wang et al, 2013). Here we report an x-ray diffraction study of dynamically compressed molybdenum. Experiments were conducted using the Omega laser at the Laboratory for Laser Energetics at the University of Rochester. Mo targets were either ramp or shock compressed using a laser drive. In ramp loading, the sample is compressed sufficiently slowly that a shock wave does not form. This results in lower temperatures, keeping the sample in the solid state to higher pressures. X-ray diffraction measurements were performed using quasi-monochromatic x-rays from a highly ionized He-α Cu source and image plate detectors. Upon ramp compression, we found no evidence of phase transition in solid Mo up to 900 GPa. The observed peaks can be assigned to the (110) and (200) or (220) reflections of BCC Mo up to the highest pressure, indicating that Mo does not melt under ramp loading to maximum pressure reached. Under shock loading, we did not observe any evidence for the solid-solid phase transformation around 210 GPa as reported in previous work (Hixson et al, 1989). The BCC

  6. HVOF and plasma sprayed molybdenum coatings -- microstructure and properties

    SciTech Connect

    Zimmermann, S.; Kreye, H.

    1995-12-31

    High velocity oxy-fuel (HVOF) and plasma spray experiments were carried out to investigate the oxidation mechanism of molybdenum in the spray process and to determine how the various process parameters affect the microstructure and properties of the coatings. HVOF coatings exhibit their highest hardness and wear resistance at an oxygen content of 6 to 8% by weight. Such an oxygen level can be achieved with Mo and Mo-MoO{sub 2} composite powders as well. In the plasma spray process oxidation of molybdenum is less pronounced and Mo-MoO{sub 2} composite powders containing 6 to 8% oxygen have to be used to obtain similar properties as compared to HVOF-coatings. When Mo-Mo{sub 2}C composite powders are used oxidation of molybdenum becomes greatly reduced and highly wear resistant coatings are obtained at a low hardness level in both spray processes.

  7. Molecular Epoxidation Reactions Catalyzed by Rhenium, Molybdenum, and Iron Complexes.

    PubMed

    Kück, Jens W; Reich, Robert M; Kühn, Fritz E

    2016-02-01

    Epoxidations are of high relevance in many organic syntheses, both in industry and academia. In this personal account, the development of rhenium, molybdenum, and iron complexes in molecular epoxidation catalysis is presented. Methyltrioxorhenium (MTO) is the benchmark catalyst for these reactions, with a thoroughly investigated mechanism and reactivity profile. More recently, highly active molecular molybdenum and iron catalysts have emerged, challenging the extraordinary role of MTO in epoxidation catalysis with high turnover frequencies (TOFs). This development is highlighted in its use of cheaper, more readily available metals, and the challenges of using base metals in catalysis are discussed. These results show the promise that relatively cheap and abundant metals, such as molybdenum and iron, hold for the future of epoxidation catalysis. PMID:26776087

  8. Recent Developments in Homogeneous Dinitrogen Reduction by Molybdenum and Iron

    PubMed Central

    MacLeod, K. Cory; Holland, Patrick L.

    2013-01-01

    The reduction of gaseous nitrogen (N2) is a challenge for industrial, biological and synthetic chemists, who want to understand the formation of ammonia (NH3) for agriculture and also want to form N-C and N-Si bonds for fine chemical synthesis. The iron-molybdenum active site of nitrogenase has inspired chemists to explore the ability of iron and molybdenum complexes to bring about transformations related to N2 reduction. This area of research has gained significant momentum, and the last two years have witnessed a number of significant advances in synthetic Fe-N2 and Mo-N2 chemistry. In addition, the identities of all atoms in the iron-molybdenum cofactor of nitrogenase have finally been elucidated, and the discovery of a carbide has generated new questions and targets for coordination chemists. This Perspective summarizes the recent work on iron and molydenum complexes, and highlights the opportunities for continued research. PMID:23787744

  9. A comprehensive study on atomic layer deposition of molybdenum sulfide for electrochemical hydrogen evolution.

    PubMed

    Kwon, Do Hyun; Jin, Zhenyu; Shin, Seokhee; Lee, Wook-Seong; Min, Yo-Sep

    2016-03-24

    Atomic layer deposition (ALD) has emerged as an efficient method to design and prepare catalysts with atomic precision. Here, we report a comprehensive study on ALD of molybdenum sulfide (MoSx) for an electrocatalytic hydrogen evolution reaction. By using molybdenum hexacarbonyl and dimethyldisulfide as the precursors of Mo and S, respectively, the MoSx catalysts are grown at 100 °C on porous carbon fiber papers (CFPs). The ALD process results in the growth of particle-like MoSx on the CFP due to the lack of adsorption sites, and its crystallographic structure is a mixture of amorphous and nano-crystalline phases. In order to unveil the intrinsic activity of the ALD-MoSx, the exchange current densities, Tafel slopes, and turnover frequencies of the catalysts grown under various ALD conditions have been investigated by considering the fractional surface coverage of MoSx on the CFP and catalytically-active surface area. In addition, the ALD-MoSx/CFP catalysts exhibit excellent catalytic stability due to the strong adhesion of MoSx on the CFP and the mixed phase. PMID:26973254

  10. 40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable...

  11. 40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable...

  12. 40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of Environment... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable...

  13. 40 CFR 421.220 - Applicability: Description of the secondary molybdenum and vanadium subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... secondary molybdenum and vanadium subcategory. 421.220 Section 421.220 Protection of Environment... POINT SOURCE CATEGORY Secondary Molybdenum and Vanadium Subcategory § 421.220 Applicability: Description of the secondary molybdenum and vanadium subcategory. The provisions of this subpart are...

  14. 40 CFR 421.220 - Applicability: Description of the secondary molybdenum and vanadium subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... secondary molybdenum and vanadium subcategory. 421.220 Section 421.220 Protection of Environment... POINT SOURCE CATEGORY Secondary Molybdenum and Vanadium Subcategory § 421.220 Applicability: Description of the secondary molybdenum and vanadium subcategory. The provisions of this subpart are...

  15. 40 CFR 421.220 - Applicability: Description of the secondary molybdenum and vanadium subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... secondary molybdenum and vanadium subcategory. 421.220 Section 421.220 Protection of Environment... POINT SOURCE CATEGORY Secondary Molybdenum and Vanadium Subcategory § 421.220 Applicability: Description of the secondary molybdenum and vanadium subcategory. The provisions of this subpart are...

  16. 40 CFR 421.220 - Applicability: Description of the secondary molybdenum and vanadium subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... secondary molybdenum and vanadium subcategory. 421.220 Section 421.220 Protection of Environment... POINT SOURCE CATEGORY Secondary Molybdenum and Vanadium Subcategory § 421.220 Applicability: Description of the secondary molybdenum and vanadium subcategory. The provisions of this subpart are...

  17. 40 CFR 421.220 - Applicability: Description of the secondary molybdenum and vanadium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... secondary molybdenum and vanadium subcategory. 421.220 Section 421.220 Protection of Environment... POINT SOURCE CATEGORY Secondary Molybdenum and Vanadium Subcategory § 421.220 Applicability: Description of the secondary molybdenum and vanadium subcategory. The provisions of this subpart are...

  18. 40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of...

  19. 40 CFR 421.210 - Applicability: Description of the primary molybdenum and rhenium subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... POINT SOURCE CATEGORY Primary Molybdenum and Rhenium Subcategory § 421.210 Applicability: Description of the primary molybdenum and rhenium subcategory. The provisions of this subpart are applicable to... primary molybdenum and rhenium subcategory. 421.210 Section 421.210 Protection of...

  20. HEU and LEU comparison in the production of Molybdenum-99

    SciTech Connect

    Cestau, Daniel; Novello, Ariel; Cristini, Pablo; Bronca, Marcelo; Centurion, Roberto; Bavaro, Ricardo; Cestau, Julian; Carranza, Eduardo

    2008-07-15

    Fission Molybdenum-99 from LEU targets is being produced in Argentina, at the Ezeiza Atomic Centre, since 2002. Before 2002, Argentina produced for more than 15 years fission molybdenum-99 from HEU targets. Both production procedures involve the irradiation of the targets composed by an Uranium-Aluminium compound 'meat' cladded with aluminum and a chemical processing of the targets. A statistic relative efficiency analysis of the production results, a brief description of the LEU method and quality control data of both procedures will be presented. (author)

  1. Selective emission multilayer coatings for a molybdenum thermophotovoltaic radiator

    DOEpatents

    Cockeram, Brian Vern

    2004-01-27

    Multilayer coating designs have been developed to provide selective emission for a molybdenum thermophotovoltaic (TPV) radiator surface. These coatings increase the surface emissivity of a molybdenum TPV radiator substrate in the wavelength range that matches the bandgap of the TPV cells to increase the power density of the TPV system. Radiator emission at wavelengths greater than the bandgap energy of the TPV cells is greatly reduced through the use of these coatings, which significantly increases the efficiency of the TPV system. The use of this coating greatly improves the performance of a TPV system, and the coating can be tailored to match the bandgap of any practical TPV system.

  2. Breaking America’s Dependence on Foreign…Molybdenum

    PubMed Central

    Einstein, Andrew J.

    2009-01-01

    Brief Unstructured Abstract Approximately 9 million nuclear cardiology studies performed each year in the United States employ technetium-99m, which is produced from the decay of molybdenum-99. The fragility of the worldwide technetium-99m supply chain has been underscored by current shortages caused by an unplanned shutdown of Europe’s largest reactor. The majority of the United States’ supply derives from a reactor in Canada nearing the end of its lifespan, whose planned replacements have been recently cancelled. In this article, the clinical importance of technetium-99m and our tenuous dependence on foreign supply of Molybdenum is addressed. PMID:19356583

  3. Magnetoresistance measurements of superconducting molybdenum nitride thin films

    NASA Astrophysics Data System (ADS)

    Baskaran, R.; Arasu, A. V. Thanikai; Amaladass, E. P.

    2016-05-01

    Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc2(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

  4. A review of chromium, molybdenum, and tungsten alloys

    NASA Technical Reports Server (NTRS)

    Klopp, W. D.

    1975-01-01

    The mechanical properties of chromium, molybdenum, and tungsten alloys are reviewed with particular emphasis on high-temperature strength and low-temperature ductility. Precipitate strengthening is highly effective at 0.4 to 0.8 times the melting temperature in these metals, with HfC being most effective in tungsten and molybdenum, and Ta(B,C) most effective in chromium. Low-temperature ductility can be improved by alloying to promote rhenium ductilizing or solution softening. The low-temperature mechanical properties of these alloys appear related to electronic interactions rather than to the usual metallurgical considerations.

  5. Influence of the conserved disulphide bond, exposed to the putative binding pocket, on the structure and function of the immunoglobulin-like molecular chaperone Caf1M of Yersinia pestis.

    PubMed Central

    Zav'yalov, V P; Chernovskaya, T V; Chapman, D A; Karlyshev, A V; MacIntyre, S; Zavialov, A V; Vasiliev, A M; Denesyuk, A I; Zav'yalova, G A; Dudich, I V; Korpela, T; Abramov, V M

    1997-01-01

    The Yersinia pestis protein Caf1M is a typical representative of a subfamily of periplasmic molecular chaperones with characteristic structural and functional features, one of which is the location of two conserved cysteine residues close to the putative binding pocket. We show that these residues form a disulphide bond, the reduction and alkylation of which significantly increases the dissociation constant of the Caf1M-Caf1 (where Caf 1 is a polypeptide subunit of the capsule) complex [from a Kd of (4.77+/-0.50)x10(-9) M for the intact protein to one of (3.68+/-0.68)x10(-8) M for the modified protein]. The importance of the disulphide bond for the formation of functional Caf1M in vivo was demonstrated using an Escherichia coli dsbA mutant carrying the Y. pestis f1 operon. In accordance with the CD and fluorescence measurements, the disulphide bond is not important for maintenance of the overall structure of the Caf1M molecule, but would appear to affect the fine structural properties of the subunit binding site. A three-dimensional model of the Caf1M-Caf1 complex was designed based on the published crystal structure of PapD (a chaperone required for Pap pili assembly) complexed with a peptide corresponding to the C-terminus of the papG subunit. In the model the disulphide bond is in close proximity to the invariant Caf1M Arg-23 and Lys-142 residues that are assumed to anchor the C-terminal group of the subunit. The importance of this characteristic disulphide bond for the orchestration of the binding site and subunit binding, as well as for the folding of the protein in vivo, is likely to be a common feature of this subfamily of Caf1M-like chaperones. A possible model for the role of the disulphide bond in Caf1 assembly is discussed. PMID:9182720

  6. Corrosion Evaluation of RERTR Uranium Molybdenum Fuel

    SciTech Connect

    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

  7. Cleavage and formation of molecular dinitrogen in a single system assisted by molybdenum complexes bearing ferrocenyldiphosphine.

    PubMed

    Miyazaki, Takamasa; Tanaka, Hiromasa; Tanabe, Yoshiaki; Yuki, Masahiro; Nakajima, Kazunari; Yoshizawa, Kazunari; Nishibayashi, Yoshiaki

    2014-10-20

    The N≡N bond of molecular dinitrogen bridging two molybdenum atoms in the pentamethylcyclopentadienyl molybdenum complexes that bear ferrocenyldiphosphine as an auxiliary ligand is homolytically cleaved under visible light irradiation at room temperature to afford two molar molybdenum nitride complexes. Conversely, the bridging molecular dinitrogen is reformed by the oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and formation of molecular dinitrogen induced by a pair of two different external stimuli using a single system assisted by molybdenum complexes bearing ferrocenyldiphosphine under ambient conditions. PMID:25214300

  8. Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

    NASA Technical Reports Server (NTRS)

    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.

  9. Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

    DOE PAGESBeta

    Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; Glatzel, Uwe

    2015-01-31

    Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is moremore » than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.« less

  10. Quantitative experimental determination of the solid solution hardening potential of rhenium, tungsten and molybdenum in single-crystal nickel-based superalloys

    SciTech Connect

    Fleischmann, Ernst; Miller, Michael K.; Affeldt, Ernst; Glatzel, Uwe

    2015-01-31

    Here, the solid-solution hardening potential of the refractory elements rhenium, tungsten and molybdenum in the matrix of single-crystal nickel-based superalloys was experimentally quantified. Single-phase alloys with the composition of the nickel solid-solution matrix of superalloys were cast as single crystals, and tested in creep at 980 °C and 30–75 MPa. The use of single-phase single-crystalline material ensures very clean data because no grain boundary or particle strengthening effects interfere with the solid-solution hardening. This makes it possible to quantify the amount of rhenium, tungsten and molybdenum necessary to reduce the creep rate by a factor of 10. Rhenium is more than two times more effective for matrix strengthening than either tungsten or molybdenum. The existence of rhenium clusters as a possible reason for the strong strengthening effect is excluded as a result of atom probe tomography measurements. If the partitioning coefficient of rhenium, tungsten and molybdenum between the γ matrix and the γ' precipitates is taken into account, the effectiveness of the alloying elements in two-phase superalloys can be calculated and the rhenium effect can be explained.

  11. Flexible Molybdenum Electrodes towards Designing Affinity Based Protein Biosensors.

    PubMed

    Kamakoti, Vikramshankar; Panneer Selvam, Anjan; Radha Shanmugam, Nandhinee; Muthukumar, Sriram; Prasad, Shalini

    2016-01-01

    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. PMID:27438863

  12. Application of the solid lubricant molybdenum disulfide by sputtering

    NASA Technical Reports Server (NTRS)

    Przybyszewski, J.; Spalvins, T.

    1968-01-01

    Molybdenum disulfide lubricant film is deposited on two substrates, niobium and nickel-chromium alloys, by means of physical direct-current sputtering. The sputtering system uses a three-electrode /triode/ geometry - a thermionic cathode, an anode, and the target, all enclosed in a vacuum chamber.

  13. Molybdenum-platinum-oxide electrodes for thermoelectric generators

    DOEpatents

    Schmatz, Duane J.

    1990-01-01

    The invention is directed to a composite article suitable for use in thermoelectric generators. The article comprises a solid electrolyte carrying a thin film comprising molybdenum-platinum-oxide as an electrode deposited by physical deposition techniques. The invention is also directed to the method of making same.

  14. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    SciTech Connect

    Petrovic, J.J.

    1992-12-31

    This patent pertains to compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia. Fabrication, fracture toughness, and bend strength are covered.

  15. Process for producing molybdenum foil and collapsible tubing

    NASA Technical Reports Server (NTRS)

    Bretts, G. R.; Gavert, R. B.; Groschke, G. F.

    1971-01-01

    Manufacturing process produces molybdenum foil 0.002 cm thick and 305 m long, and forms foil into high-strength, thin-walled tubing which can be flattened for storage on a spool. Desirable metal properties include high thermal conductivity stiffness, yield and tensile stress, and low thermal expansion coeffecient.

  16. Dissolution kinetics of a sintered molybdenum coating applied on ceramics

    SciTech Connect

    Kuz`ko, V.S.

    1994-11-01

    Using weighing and corrosion diagrams, the etching parameters are determined for a sintered M-21 molybdenum coating applied to VK 94-1 vacuum-tight ceramics. Dissolution of M-21 in an alkaline solution of potassium hexacyanoferrate(III) can be treated as a corrosion process proceeding with kinetic control.

  17. Molybdenum Hazards to Fish, Wildlife, and Invertebrates: A Synoptic Review

    USGS Publications Warehouse

    Eisler, R.

    1989-01-01

    Ecological and toxicological aspects of molybdenum (Mo) in the environment are briefly reviewed, with emphasis on fish and wildlife. Subtopics include sources and uses, chemical properties, mode of action, background concentrations in biological and nonbiological samples, and lethal and sublethal effects on terrestrial plants and invertebrates, aquatic organisms, birds, and mammals. Current recommendations for Mo and the protection of sensitive living resources are presented.

  18. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOEpatents

    Petrovic, J.J.

    1995-01-17

    Compositions are disclosed consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  19. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOEpatents

    Petrovic, John J.

    1995-01-01

    Compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  20. HUMAN HEALTH EFFECTS OF MOLYBDENUM IN DRINKING WATER

    EPA Science Inventory

    Molybdenum plays an important biological role as a micronutrient for plants and animals. At high levels it can be toxic to animals. While concentrations in surface waters are generally less than 5 micrograms Mo/L, concentrations as high as 500 micrograms Mo/L have been reported i...

  1. Discovery of rubidium, strontium, molybdenum, and rhodium isotopes

    SciTech Connect

    Parker, A.M.; Thoennessen, M.

    2012-07-15

    Currently, 31 rubidium, 35 strontium, 35 molybdenum, and 38 rhodium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  2. Storage and bioavailability of molybdenum in soils increased by organic matter complexation

    NASA Astrophysics Data System (ADS)

    Wichard, Thomas; Mishra, Bhoopesh; Myneni, Satish C. B.; Bellenger, Jean-Philippe; Kraepiel, Anne M. L.

    2009-09-01

    The micronutrient molybdenum is a necessary component of the nitrogen-fixing enzyme nitrogenase. Molybdenum is very rare in soils, and is usually present in a highly soluble form, making it susceptible to leaching. 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 microbes. 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.

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

    SciTech Connect

    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.

  4. Synthesis and characterization of zinc-molybdenum oxide photocatalysts using an electrochemical-thermal process

    NASA Astrophysics Data System (ADS)

    Goveas, J. J.; Gonsalves, R. A.; Rao, P.; Pinto, R.

    2016-05-01

    Dyes act as major pollutants in water and can be degraded by photocatalysis. This paper establishes the role of electrochemically generated nanostructures of Zinc-Molybdenum oxides (ZMO) as photocatalysts by degrading EBT (Eriochrome Black- T) taken as a model pollutant under UV light. A facile, rapid and low cost process to synthesize these nanostructures (ZMO) is presented. Various factors that affect the synthesis and photocatalytic activity of these nanostructures are discussed. The role of calcination temperature and pulverization on the photocatalytic action has also been established. Particles have been synthesized in pure form as well as using surfactants such as cetrimide (cetyl trimethyl ammonium bromide), polyethylene glycol (PEG) and SDS (sodium dodecyl sulphate) to enhance their photocatalytic action. This paper also discusses the characterization of these nanoparticles by powder XRD, SEM, FT-IR and UV-Visible spectroscopy. Decolourisation was achieved to completion under optimum experimental conditions at room temperature ascertaining the application of these nanostructures as effective photocatalysts.

  5. Fretting wear in titanium, Monel-400, and cobalt 25-percent-molybdenum using scanning electron microscopy

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1972-01-01

    Damage scar volume measurements taken from like metal fretting pairs combined with scanning electron microscopy observations showed that three sequentially operating mechanisms result in the fretting of titanium, Monel-400, and cobalt - 25-percent molybdenum. Initially, adhesion and plastic deformation of the surface played an important role. This was followed after a few hundred cycles by a fatigue mechanism which produced spall-like pits in the damage scar. Finally, a combination of oxidation and abrasion by debris particles became most significant. Damage scar measurements made on several elemental metals after 600,000 fretting cycles suggested that the ratio of oxide hardness to metal hardness was a measure of the susceptibility of a metal to progressive damage by fretting.

  6. Electrodeposition of low contraction chromium/molybdenum alloys using pulse-reverse plating. Final report

    SciTech Connect

    Miller, M.D.; Langston, S.

    1994-12-01

    The use of modulated pulse periodic reverse (pulse-reverse) current to electrodeposit a low contraction (LC) chromium/molybdenum alloy has been evaluated. When using one full pulse-reverse plating cycle, the percent molybdenum in the deposit increased almost 400 percent (from 1 to 4 percent) as the current in the reverse cycle was increased from 0 to 10 amps. However, when the pulse reverse current was carried to six full plating cycles, the percent molybdenum in the deposit was not dependent upon the current and remained constant at about 1 percent. This is about the same percent molybdenum that could be expected in direct current-plated LC chromium/molybdenum alloy and about half the percent molybdenum that could be expected in an on/off pulse-plated LC chromium/molybdenum alloy.

  7. Molybdenum Isotopes in Some Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Qi, L.; Masuda, A.

    1992-07-01

    Measurement of all seven stable Mo isotopes in iron meteorites has been continued for study of possible direct evidences for processes of nucleosynthesis in the pre-solar stage and information on extinct radioactive nuclides. Mo in iron meteorite was extracted by using recently developed chemical separation method [1], then loaded on 5 pass zone refined Re ribbon. Molybdenum isotope analysis was performed [2] in a VG SECTOR 54-30 thermal ionization mass spectrometer using a Faraday collector in peak jumping mode. The measured ratios of Mo were normalized provisionally to ^94Mo/^98Mo = 0.3802. Particular caution was drawn on the isobaric interferences of Zr, Ru, etc., which were negligible as a result. A small but distinct anomaly of Mo isotopes was found in Acuna iron meteorite. The normalized data show a growth trend from ^92Mo to ^97Mo, and this increment decreased suddenly at ^98Mo, then slightly increased at ^100Mo. The isotope variations might be explained as a result of excess s-process component (^95Mo to ^98Mo) contained in the sample. Gibeon suggested that isotopic anomalies at ^92Mo, ^95Mo, and ^97Mo are about -3-epsilon, -1.2-epsilon, and -0.5-epsilon respectively. It is difficult to give a perfect explanation to the observed data at present. However, it is interesting to note that ^92Mo (N=50) has a closed shell and only ^95Mo and ^97Mo are even-odd nuclides in all seven stable Mo isotopes and the 30-keV Maxwellian-averaged neutron capture cross sections for ^95Mo and ^97Mo are about 3 times bigger than others [3]. The depletions at ^95Mo and ^97Mo might be attributed to the higher cross section for their destruction by (n, gamma) reaction. The apparent opposite aberrations are found for Odessa iron. We reported anomalies of Mo isotopes in a specimen of Sikhote-Alin iron meteorite [4,5]. Further investigations have shown that the isotopic compositions of Mo in this iron are heterogeneous and that the "general anomaly" of Mo isotopes is related with the

  8. Uranium-Molybdenum Dissolution Flowsheet Studies

    SciTech Connect

    Pierce, R. A.

    2007-03-01

    The Super Kukla (SK) Prompt Burst Reactor operated at the Nevada Test Site from 1964 to 1978. The SK material is a uranium-molybdenum (U-Mo) alloy material of 90% U/10% Mo by weight at approximately 20% 235U enrichment. H-Canyon Engineering (HCE) requested that the Savannah River National Lab (SRNL) define a flowsheet for safely and efficiently dissolving the SK material. The objective is to dissolve the material in nitric acid (HNO3) in the H-Canyon dissolvers to a U concentration of 15-20 g/L (3-4 g/L 235U) without the formation of precipitates or the generation of a flammable gas mixture. Testing with SK material validated the applicability of dissolution and solubility data reported in the literature for various U and U-Mo metals. Based on the data, the SK material can be dissolved in boiling 3.0-6.0 M HNO3 to a U concentration of 15-20 g/L and a corresponding Mo concentration of 1.7-2.2 g/L. The optimum flowsheet will use 4.0-5.0 M HNO3 for the starting acid. Any nickel (Ni) cladding associated with the material will dissolve readily. After dissolution is complete, traditional solvent extraction flowsheets can be used to recover and purify the U. Dissolution rates for the SK material are consistent with those reported in the literature and are adequate for H-Canyon processing. When the SK material dissolved at 70-100 o C in 1-6 M HNO3, the reaction bubbled vigorously and released nitrogen oxide (NO) and nitrogen dioxide (NO2) gas. Gas generation tests in 1 M and 2 M HNO3 at 100 o C generated less than 0.1 volume percent hydrogen (H2) gas. It is known that higher HNO3 concentrations are less favorable for H2 production. All tests at 70-100 o C produced sufficient gas to mix the solutions without external agitation. At room temperature in 5 M HNO3, the U-Mo dissolved slowly and the U-laden solution sank to the bottom of the dissolution vessel because of its greater density. The effect of the density difference insures that the SK material cannot dissolve and

  9. Reflectance, Optical Properties, and Stability of Molybdenum/Strontium and Molybdenum/Yttrium Multilayer Mirrors

    SciTech Connect

    Kjornrattanawanich, B

    2002-09-01

    The motivation of this work is to develop high reflectance normal-incidence multilayer mirrors in the 8-12 nm wavelength region for applications in astronomy and extreme ultraviolet lithography. To achieve this goal, Mo/Sr and Mo/Y multilayers were studied. These multilayers were deposited with a UHV magnetron sputtering system and their reflectances were measured with synchrotron radiation. High normal-incidence reflectances of 23% at 8.8 nm, 40.8% at 9.4 nm, and 48.3% at 10.5 nm were achieved. However, the reflectance of Mo/Sr multilayers decreased rapidly after exposure to air. Attempts to use thin layers of carbon to passivate the surface of Mo/Sr multilayers were unsuccessful. Experimental results on the refractive index {tilde n} = 1-{delta} + i{beta} of yttrium and molybdenum in the 50-1300 eV energy region are reported in this work. This is the first time ever that values on the refractive index of yttrium are measured in this energy range. The absorption part {beta} was determined through transmittance measurements. The dispersive part {delta} was calculated by means of the Kramers-Kronig formalism. The newly determined values of the refractive index of molybdenum are in excellent agreement with the published data. Those of yttrium are more accurate and contain fine structures around the yttrium M-absorption edges where Mo/Y multilayers operate. These improved sets of optical data lead to better design and modeling of the optical properties of Mo/Y multilayers. The reflectance quality of Mo/Y multilayers is dependent on their optical and structural properties. To correlate these properties with the multilayer reflectance, x-ray diffraction, Rutherford backscattering spectrometry, and transmission electron microscopy were used to analyze samples. Normal-incidence reflectances of 32.6% at 9.27 nm, 38.4% at 9.48 nm, and 29.6% at 9.46 nm were obtained from three representative Mo/Y multilayers which had about 0%, 25%, and 39% atomic oxygen assimilated in their

  10. The trappin gene family: proteins defined by an N-terminal transglutaminase substrate domain and a C-terminal four-disulphide core.

    PubMed Central

    Schalkwijk, J; Wiedow, O; Hirose, S

    1999-01-01

    Recently, several new genes have been discovered in various species which are homologous to the well-characterized human epithelial proteinase inhibitor elafin/SKALP (skin-derived anti-leukoproteinase). Because of the high degree of conservation and the similarities in genomic organization, we propose that these genes belong to a novel gene family. At the protein level, the family members are defined by: (1) an N-terminal domain consisting of a variable number of repeats with the consensus sequence Gly-Gln-Asp-Pro-Val-Lys that can act as an anchoring motif by transglutaminase cross-linking, and (2) a C-terminal four-disulphide core or whey acidic protein (WAP) domain, which harbours a functional motif involved in binding of proteinases and possibly other proteins. We have proposed the name trappin gene family as a unifying nomenclature for this group of proteins (trappin is an acronym for TRansglutaminase substrate and wAP domain containing ProteIN, and refers to its functional property of 'getting trapped' in tissues by covalent cross-linking). Analysis of the trappin family members shows extensive diversification in bovidae and suidae, whereas the number of primate trappins is probably limited. Recent biochemical and cell biological data on the human trappin family member elafin/SKALP suggest that this molecule is induced in epidermis by cellular stress. We hypothesize that trappins play an important role in the regulation of inflammation and in protection against tissue damage in stratified epithelia. PMID:10359639

  11. The failure to express a protein disulphide isomerase-like protein results in a floury endosperm and an endoplasmic reticulum stress response in rice

    PubMed Central

    Han, Xiaohua; Wang, Yihua; Liu, Xi; Jiang, Ling; Ren, Yulong; Liu, Feng; Peng, Cheng; Li, Jingjing; Jin, Ximing; Wu, Fuqing; Wang, Jiulin; Guo, Xiuping; Zhang, Xin; Cheng, Zhijun; Wan, Jianmin

    2012-01-01

    The rice somaclonal mutant T3612 produces small grains with a floury endosperm, caused by the loose packing of starch granules. The positional cloning of the mutation revealed a deletion in a gene encoding a protein disulphide isomerase-like enzyme (PDIL1-1). In the wild type, PDIL1-1 was expressed throughout the plant, but most intensely in the developing grain. In T3612, its expression was abolished, resulting in a decrease in the activity of plastidial phosphorylase and pullulanase, and an increase in that of soluble starch synthase I and ADP-glucose pyrophosphorylase. The amylopectin in the T3612 endosperm showed an increase in chains with a degree of polymerization 8–13 compared with the wild type. The expression in the mutant's endosperm of certain endoplasmic reticulum stress-responsive genes was noticeably elevated. PDIL1-1 appears to play an important role in starch synthesis. Its absence is associated with endoplasmic reticulum stress in the endosperm, which is likely to underlie the formation of the floury endosperm in the T3612 mutant. PMID:21984651

  12. Large Scale Solid Phase Synthesis of Peptide Drugs: Use of Commercial Anion Exchange Resin as Quenching Agent for Removal of Iodine during Disulphide Bond Formation

    PubMed Central

    Reddy, K. M. Bhaskara; Kumari, Y. Bharathi; Mallikharjunasarma, Dokka; Bulliraju, Kamana; Sreelatha, Vanjivaka; Ananda, Kuppanna

    2012-01-01

    The S-acetamidomethyl (Acm) or trityl (Trt) protecting groups are widely used in the chemical synthesis of peptides that contain one or more disulfide bonds. Treatment of peptides containing S-Acm protecting group with iodine results in simultaneous removal of the sulfhydryl protecting group and disulfide formation. However, the excess iodine needs to be quenched or adsorbed as quickly as possible after completion of the disulfide bond formation in order to minimize side reactions that are often associated with the iodination step. We report here a simple method for simultaneous quenching and removal of iodine and isolation of disulphide bridge peptides. The use of excess inexpensive anion exchange resin to the oxidized peptide from the aqueous acetic acid/methanol solution affords quantitative removal of iodine and other color impurities. This improves the resin life time of expensive chromatography media that is used in preparative HPLC column during the purification of peptide using preparative HPLC. Further, it is very useful for the conversion of TFA salt to acetate in situ. It was successfully applied commercially, to the large scale synthesis of various peptides including Desmopressin, Oxytocin, and Octreotide. This new approach offers significant advantages such as more simple utility, minimal side reactions, large scale synthesis of peptide drugs, and greater cost effectiveness. PMID:23118772

  13. The thioredoxin reductase--Thioredoxin redox system cleaves the interchain disulphide bond of botulinum neurotoxins on the cytosolic surface of synaptic vesicles.

    PubMed

    Pirazzini, Marco; Tehran, Domenico Azarnia; Zanetti, Giulia; Lista, Florigio; Binz, Thomas; Shone, Clifford C; Rossetto, Ornella; Montecucco, Cesare

    2015-12-01

    Botulinum neurotoxins (BoNTs) are Janus toxins, as they are at the same time the most deadly substances known and one of the safest drugs used in human therapy. They specifically block neurotransmission at peripheral nerves through the proteolysis of SNARE proteins, i.e. the essential proteins which are the core of the neuroexocytosis machinery. Even if BoNTs are traditionally known as seven main serotypes, their actual number is much higher as each serotype exists in many different subtypes, with individual biological properties and little antigenic relations. Since BoNTs can be used as biological weapons, and the only currently available therapy is based on immunological approaches, the existence of so many different subtypes is a major safety problem. Nevertheless, all BoNT isoforms are structurally similar and intoxicate peripheral nerve endings via a conserved mechanism. They consist of two chains linked by a unique disulphide bond which must be reduced to enable their toxicity. We found that thioredoxin 1 and its reductase compose the cell redox system responsible for this reduction, and its inhibition via specific chemicals significantly reduces BoNTs activity, in vitro as well as in vivo. Such molecules can be considered as lead compounds for the development of pan-inhibitors. PMID:26130523

  14. Synthesis, cellular uptake and HIV-1 Tat-dependent trans-activation inhibition activity of oligonucleotide analogues disulphide-conjugated to cell-penetrating peptides

    PubMed Central

    Turner, John J.; Arzumanov, Andrey A.; Gait, Michael J.

    2005-01-01

    Oligonucleotides composed of 2′-O-methyl and locked nucleic acid residues complementary to HIV-1 trans-activation responsive element TAR block Tat-dependent trans-activation in a HeLa cell assay when delivered by cationic lipids. We describe an improved procedure for synthesis and purification under highly denaturing conditions of 5′-disulphide-linked conjugates of 3′-fluorescein labelled oligonucleotides with a range of cell-penetrating peptides and investigate their abilities to enter HeLa cells and block trans-activation. Free uptake of 12mer OMe/LNA oligonucleotide conjugates to Tat (48–58), Penetratin and R9F2 was observed in cytosolic compartments of HeLa cells. Uptake of the Tat conjugate was enhanced by N-terminal addition of four Lys or Arg residues or a second Tat peptide. None of the conjugates entered the nucleus or inhibited trans-activation when freely delivered, but inhibition was obtained in the presence of cationic lipids. Nuclear exclusion was seen for free delivery of Tat (48–58), Penetratin and R9 conjugates of 16mer phosphorothioate OMe oligonucleotide. Uptake into human fibroblast cytosolic compartments was seen for Tat, Penetratin, R9F2 and Transportan conjugates. Large enhancements of HeLa cell uptake into cytosolic compartments were seen when free Tat peptide was added to Tat conjugate of 12mer OMe/LNA oligonucleotide or Penetratin peptide to Penetratin conjugate of the same oligonucleotide. PMID:15640444

  15. Preparation of molybdenum carbides with multiple morphologies using surfactants as carbon sources

    SciTech Connect

    Wang, Hongfen; Wang, Zhiqi; Chen, Shougang

    2012-10-15

    Molybdenum carbides with surfactants as carbon sources were prepared using the carbothermal reduction of the appropriate precursors (molybdenum oxides deposited on surfactant micelles) at 1023 K under hydrogen gas. The carburized products were characterized using scanning electron microscopy (SEM), X-ray diffraction and BET surface area measurements. From the SEM images, hollow microspherical and rod-like molybdenum carbides were observed. X-ray diffraction patterns showed that the annealing time of carburization had a large effect on the conversion of molybdenum oxides to molybdenum carbides. And BET surface area measurements indicated that the difference of carbon sources brought a big difference in specific surface areas of molybdenum carbides. - Graphical abstract: Molybdenum carbides having hollow microspherical and hollow rod-like morphologies that are different from the conventional monodipersed platelet-like morphologies. Highlights: Black-Right-Pointing-Pointer Molybdenum carbides were prepared using surfactants as carbon sources. Black-Right-Pointing-Pointer The kinds of surfactants affected the morphologies of molybdenum carbides. Black-Right-Pointing-Pointer The time of heat preservation at 1023 K affected the carburization process. Black-Right-Pointing-Pointer Molybdenum carbides with hollow structures had larger specific surface areas.

  16. Measurement of low levels of molybdenum in the environment by using aquatic insects

    SciTech Connect

    Colburn, T.

    1982-10-01

    Starting at high altitudes and extending down the valley, near and below a molybdenum mine, aquatic insects and water samples were collected for atomic absorption spectrophotometric analysis of molybdenum. Eight stations were sampled in the East River - Upper Gunnison Rive drainage, Gunnison County, Colorado. Five water samples were collected at each station by using resin column extraction of ions. No molybdenum was found above the detectable level of 1 ..mu..g/L in any of the water samples, even after concentrating the ions in the water 40 times. The geographical profile of insect-molybdenum in this area starts very low at Gothic, increases at all stations around the molybdenum lode, peaks at SR-2, and then decreases as the riverine system flows farther away from the main ore body. The plotting of the insect molybdenum concentrations on a continuum graph correlated with a known lode of molybdenum. Molybdenum-insect data sets should be collected above, near, and below other suspected molybdenum lodes to prove the feasibility of using aquatic insects to prospect for molybdenum. (JMT)

  17. Contrast and dose with molybdenum, molybdenum-rhodium, and rhodium-rhodium target-filter combinations in mammography

    SciTech Connect

    Gingold, E.L.; Wu, Xizeng; Barnes, G.T.

    1997-03-01

    Molybdenum target-molybdenum filter (Mo-Mo) source assemblies are commonly used for screen-film mammography and produce spectra rich in bremsstrahlung between 15 and 20 keV, and molybdenum characteristic x-rays (K{sub {alpha}} = 17.5 keV and K{sub {beta}} = 19.6 keV) that are, optimal for imaging a large segment of patients. With the normal variability of breast size and tissue composition that occurs in the population, Mo-Mo spectra are not always optimal, however. Particularly for thick, fibroglandular breast tissue, higher energy spectra are required, and are achieved to a limited degree by operating Mo-Mo tubes at higher tube potentials. At these higher tube potentials (28-31 kVp), the spectrum exiting the breast has a large contribution from bremsstrahlung of more than 23 keV. Most of the lower energy photons, including the molybdenum characteristic x-rays, are absorbed and result in a higher average tissue dose than is necessary. Incident spectra with x-ray energies in the 20-23 keV range are preferable. Such spectra have been realized with higher atomic number materials, such as rhodium (Rh), used for the anode or k-edge filter. The higher K-absorption edge of rhodium allows transmission of bremsstrahlung in the 20-23.2 keV range, and at a given kilovoltage the Rh-Rh combination results in a more penetrating beam than either Mo-Mo or Mo-Rh (molybdenum x-ray tube anode with rhodium K-edge filter) because of the difference in energy between the rhodium and molybdenum characteristic x-rays. The greater penetrating power of these spectra results in decreased entrance skin exposure and average glandular dose to the breast than with the conventional Mo-Mo spectra. However, associated with this can be a reduction in subject contrast in the mammogram. The objective of this study was to compare the contrast and dose produced with the three source assemblies as a function of x-ray tube potential, breast thickness, and breast parenchymal composition.

  18. Thermoelectric transport properties of molybdenum from abinitio simulations

    NASA Astrophysics Data System (ADS)

    French, Martin; Mattsson, Thomas R.

    2014-10-01

    We employ abinitio simulations based on density functional theory (DFT) to calculate the electronic transport coefficients (electrical conductivity, thermal conductivity, and thermopower) of molybdenum over a broad range of thermodynamic states. By comparing to available experimental data, we show that DFT is able to describe the desired transport properties of this refractory metal with high accuracy. Most noteworthy, both the positive sign and the quantitative values of the thermopower of solid molybdenum are reproduced very well. We calculate the electrical and thermal conductivity in the solid and the fluid phase between 1000 and 20 000 K and a wide span in density and develop empirical fit formulas for direct use in practical applications, such as magneto-hydrodynamics simulations. The influence of thermal expansion in conductivity measurements at constant pressure is also discussed in some detail.

  19. Layered Vanadium and Molybdenum Oxides: Batteries and Electrochromics

    SciTech Connect

    Chernova, N. A.; Roppolo, M.; Dillon, A. C.; Whittingham, M. S.

    2009-01-01

    The layered oxides of vanadium and molybdenum have been studied for close to 40 years as possible cathode materials for lithium batteries or electrochromic systems. The highly distorted metal octahedra naturally lead to the formation of a wide range of layer structures, which can intercalate lithium levels exceeding 300 Ah/kg. They have found continuing success in medical devices, such as pacemakers, but many challenges remain in their application in long-lived rechargeable devices. Their high-energy storage capability remains an encouragement to researchers to resolve the stability concerns of vanadium dissolution and the tendency of lithium and vanadium to mix changing the crystal structure on cycling the lithium in and out. Nanomorphologies have enabled higher reactivities to be obtained for both vanadium and molybdenum oxides, and with the latter show promise for electrochromic displays.

  20. High pressure polyhydrides of molybdenum: A first-principles study

    NASA Astrophysics Data System (ADS)

    Feng, Xiaolei; Zhang, Jurong; Liu, Hanyu; Iitaka, Toshiaki; Yin, Ketao; Wang, Hui

    2016-07-01

    We present results from first-principles calculations on molybdenum polyhydrides under pressure. In addition to the experimental ε-phase of MoH, we find several novel structures of MoH2 and MoH3 at pressures below 100 GPa. A hexagonal structure of MoH2 becomes stable with respect to decomposition into MoH and H2 above 9 GPa, and transforms into an orthorhombic structure at 24 GPa, which remains stable up to 100 GPa. MoH3 is unstable relative to decomposition into MoH and H2 over the whole pressure range studied. Electronic structure calculations reveal that molybdenum polyhydrides are metallic under pressure.

  1. Evolution of interlayer coupling in twisted molybdenum disulfide bilayers

    NASA Astrophysics Data System (ADS)

    Liu, Kaihui; Zhang, Liming; Cao, Ting; Jin, Chenhao; Qiu, Diana; Zhou, Qin; Zettl, Alex; Yang, Peidong; Louie, Steve G.; Wang, Feng

    2014-09-01

    Van der Waals coupling is emerging as a powerful method to engineer physical properties of atomically thin two-dimensional materials. In coupled graphene-graphene and graphene-boron nitride layers, interesting physical phenomena ranging from Fermi velocity renormalization to Hofstadter’s butterfly pattern have been demonstrated. Atomically thin transition metal dichalcogenides, another family of two-dimensional-layered semiconductors, can show distinct coupling phenomena. Here we demonstrate the evolution of interlayer coupling with twist angles in as-grown molybdenum disulfide bilayers. We find that the indirect bandgap size varies appreciably with the stacking configuration: it shows the largest redshift for AA- and AB-stacked bilayers, and a significantly smaller but constant redshift for all other twist angles. Our observations, together with ab initio calculations, reveal that this evolution of interlayer coupling originates from the repulsive steric effects that leads to different interlayer separations between the two molybdenum disulfide layers in different stacking configurations.

  2. Molybdenum-UO2 cerment irradiation at 1145 K

    NASA Technical Reports Server (NTRS)

    Mcdonald, G.

    1971-01-01

    Two molybdenum-UO2 cermet fuel pins were fission heated in a helium-cooled loop at a temperature of 1145 K and to a total burnup of 5.3 % of the U-235. After irradiation the fuel pins were measured to check dimensional stability, punctured at the plenums to determine fission gas release, and examined metallographically to determine the effect of irradiation. Burnup was determined in several sections of the fuel pin. The results of the postirradiation examination indicated: (1) There was no visible change in the fuel pins on irradiation under the above conditions. (2) The maximum swelling of the fuel pins was less than 1%. (3) There was no migration of UO2 and no visible interaction between the molybdenum and the UO2. (4) Approximately 12% of the fission gas formed was released from the cermet cone into the gas plenum.

  3. Structural Framework for Metal Incorporation during Molybdenum Cofactor Biosynthesis.

    PubMed

    Kasaragod, Vikram Babu; Schindelin, Hermann

    2016-05-01

    The molybdenum cofactor (Moco) is essential for the catalytic activity of all molybdenum-containing enzymes with the exception of nitrogenase. Moco biosynthesis follows an evolutionarily highly conserved pathway and genetic deficiencies in the corresponding human enzymes result in Moco deficiency, which manifests itself in severe neurological symptoms and death in childhood. In humans the final steps of Moco biosynthesis are catalyzed by gephyrin, specifically the penultimate adenylation of molybdopterin (MPT) by its N-terminal G domain (GephG) and the final metal incorporation by its C-terminal E domain (GephE). To better understand the poorly defined molecular framework of this final step, we determined high-resolution crystal structures of GephE in the apo state and in complex with ADP, AMP, and molybdate. Our data provide novel insights into the catalytic steps leading to final Moco maturation, namely deadenylation as well as molybdate binding and insertion. PMID:27112598

  4. Molybdenum work function determined by electron emission microscopy.

    NASA Technical Reports Server (NTRS)

    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.

  5. Retention of Sputtered Molybdenum on Ion Engine Discharge Chamber Surfaces

    NASA Technical Reports Server (NTRS)

    Sovey, James S.; Dever, Joyce A.; Power, John L.

    2001-01-01

    Grit-blasted anode surfaces are commonly used in ion engines to ensure adherence of sputtered coatings. Next generation ion engines will require higher power levels, longer operating times, and thus there will likely be thicker sputtered coatings on their anode surfaces than observed to date on 2.3 kW-class xenon ion engines. The thickness of coatings on the anode of a 10 kW, 40-centimeter diameter thruster, for example, may be 22 micrometers or more after extended operation. Grit-blasted wire mesh, titanium, and aluminum coupons were coated with molybdenum at accelerated rates to establish coating stability after the deposition process and after thermal cycling tests. These accelerated deposition rates are roughly three orders of magnitude more rapid than the rates at which the screen grid is sputtered in a 2.3 kW-class, 30-centimeter diameter ion engine. Using both RF and DC sputtering processes, the molybdenum coating thicknesses ranged from 8 to 130 micrometers, and deposition rates from 1.8 micrometers per hour to 5.1 micrometers per hour. In all cases, the molybdenum coatings were stable after the deposition process, and there was no evidence of spalling of the coatings after 20 cycles from about -60 to +320 C. The stable, 130 micrometer molybdenum coating on wire mesh is 26 times thicker than the thickest coating found on the anode of a 2.3 kW, xenon ion engine that was tested for 8200 hr. Additionally, this coating on wire mesh coupon is estimated to be a factor of greater than 4 thicker than one would expect to obtain on the anode of the next generation ion engine which may have xenon throughputs as high as 550 kg.

  6. CdTe solar cells on thin molybdenum substrates

    NASA Astrophysics Data System (ADS)

    Matulionis, Ilvydas

    2000-10-01

    We report on the development of Mo/(ZnTe:N)/CdTe/CdS/ITO (inverted structure) solar cells grown by radio frequency sputtering. The 0.1 mm thick molybdenum substrate is lightweight and flexible which is advantageous for both terrestrial and space applications. Conversion efficiencies close to 8 percent have been achieved for 5 square millimeter area devices. The photovoltaic activity has also been observed on similar cells deposited on Mo coated kapton and stainless steel substrates.

  7. The nuclear response of molybdenum to supernova neutrinos

    SciTech Connect

    Ydrefors, E.; Suhonen, J.

    2011-12-16

    Neutrino-nucleus interactions play a prominent role in many astrophysical applications. Knowledge about nuclear responses to neutrinos is therefore of paramount importance. We present cross sections for neutral-current neutrino-nucleus scattering off the stable (A = 92,94,95,96,97,98,100) molybdenum isotopes. The nuclear responses for these nuclei are additionally computed by folding the computed cross sections with a Fermi-Dirac distribution.

  8. Performance and Safety Characteristics of Lithium-molybdenum Disulfide Cells

    NASA Technical Reports Server (NTRS)

    Stiles, J. A.

    1984-01-01

    The lithium-molybdenum disulfide system offers attractive characteristics including high rate capability, successful operation up to 75 C, a very low self-discharge rate, a good cycle life and safety characteristics which compare favorably to those of other lithium cells. Moreover, the materials and manufacturing costs for the system is effectively controlled, so the cells should ultimately be competitive with currently marketed rechargeable cells.

  9. Molybdenum as a contact material in zinc tin oxide thin film transistors

    SciTech Connect

    Hu, W.; Peterson, R. L.

    2014-05-12

    Amorphous oxide semiconductors are of increasing interest for a variety of thin film electronics applications. Here, the contact properties of different source/drain electrode materials to solution-processed amorphous zinc tin oxide (ZTO) thin-film transistors are studied using the transmission line method. The width-normalized contact resistance between ZTO and sputtered molybdenum is measured to be 8.7 Ω-cm, which is 10, 20, and 600 times smaller than that of gold/titanium, indium tin oxide, and evaporated molybdenum electrodes, respectively. The superior contact formed using sputtered molybdenum is due to a favorable work function lineup, an insulator-free interface, bombardment of ZTO during molybdenum sputtering, and trap-assisted tunneling. The transfer length of the sputtered molybdenum/ZTO contact is 0.34 μm, opening the door to future radio-frequency sub-micron molybdenum/ZTO thin film transistors.

  10. Molybdate Reduction to Molybdenum Blue by an Antarctic Bacterium

    PubMed Central

    Ahmad, S. A.; Shukor, M. Y.; Shamaan, N. A.; Mac Cormack, W. P.; Syed, M. A.

    2013-01-01

    A molybdenum-reducing bacterium from Antarctica has been isolated. The bacterium converts sodium molybdate or Mo6+ to molybdenum blue (Mo-blue). Electron donors such as glucose, sucrose, fructose, and lactose supported molybdate reduction. Ammonium sulphate was the best nitrogen source for molybdate reduction. Optimal conditions for molybdate reduction were between 30 and 50 mM molybdate, between 15 and 20°C, and initial pH between 6.5 and 7.5. The Mo-blue produced had a unique absorption spectrum with a peak maximum at 865 nm and a shoulder at 710 nm. Respiratory inhibitors such as antimycin A, sodium azide, potassium cyanide, and rotenone failed to inhibit the reducing activity. The Mo-reducing enzyme was partially purified using ion exchange and gel filtration chromatography. The partially purified enzyme showed optimal pH and temperature for activity at 6.0 and 20°C, respectively. Metal ions such as cadmium, chromium, copper, silver, lead, and mercury caused more than 95% inhibition of the molybdenum-reducing activity at 0.1 mM. The isolate was tentatively identified as Pseudomonas sp. strain DRY1 based on partial 16s rDNA molecular phylogenetic assessment and the Biolog microbial identification system. The characteristics of this strain would make it very useful in bioremediation works in the polar and temperate countries. PMID:24381945

  11. Molybdate reduction to molybdenum blue by an Antarctic bacterium.

    PubMed

    Ahmad, S A; Shukor, M Y; Shamaan, N A; Mac Cormack, W P; Syed, M A

    2013-01-01

    A molybdenum-reducing bacterium from Antarctica has been isolated. The bacterium converts sodium molybdate or Mo⁶⁺ to molybdenum blue (Mo-blue). Electron donors such as glucose, sucrose, fructose, and lactose supported molybdate reduction. Ammonium sulphate was the best nitrogen source for molybdate reduction. Optimal conditions for molybdate reduction were between 30 and 50 mM molybdate, between 15 and 20°C, and initial pH between 6.5 and 7.5. The Mo-blue produced had a unique absorption spectrum with a peak maximum at 865 nm and a shoulder at 710 nm. Respiratory inhibitors such as antimycin A, sodium azide, potassium cyanide, and rotenone failed to inhibit the reducing activity. The Mo-reducing enzyme was partially purified using ion exchange and gel filtration chromatography. The partially purified enzyme showed optimal pH and temperature for activity at 6.0 and 20°C, respectively. Metal ions such as cadmium, chromium, copper, silver, lead, and mercury caused more than 95% inhibition of the molybdenum-reducing activity at 0.1 mM. The isolate was tentatively identified as Pseudomonas sp. strain DRY1 based on partial 16s rDNA molecular phylogenetic assessment and the Biolog microbial identification system. The characteristics of this strain would make it very useful in bioremediation works in the polar and temperate countries. PMID:24381945

  12. On the Origin of the Lightest Molybdenum Isotopes

    SciTech Connect

    Fisker, J L; Hoffman, R D; Pruet, J

    2007-10-24

    We discuss implications of recent precision measurements for the {sup 93}Rh proton separation energy for the production of the lightest molybdenum isotopes in proton-rich type II supernova ejecta. It has recently been shown that a novel neutrino-induced process makes these ejecta a promising site for the production of the light molybdenum isotopes and other 'p-nuclei' with atomic mass near 100. The origin of these isotopes has long been uncertain. A distinguishing feature of nucleosynthesis in neutrino-irradiated outflows is that the relative production of {sup 92}Mo and {sup 94}Mo is set by a competition governed by the proton separation energy of {sup 93}Rh. We use detailed nuclear network calculations and the recent experimental results for this proton separation energy to place constraints on the outflow characteristics that produce the lightest molybdenum isotopes in their solar proportions. It is found that for the conditions calculated in recent two-dimensional supernova simulations, and also for a large range of outflow characteristics around these conditions, the solar ratio of {sup 92}Mo to {sup 94}Mo cannot be achieved. This suggests that either proton-rich winds from type II supernova do not exclusively produce both isotopes, or that these winds are qualitatively different than calculated in today's supernova models.

  13. Pulsed electrodeposition and characterization of molybdenum diselenide thin film

    SciTech Connect

    Delphine, S. Mary; Jayachandran, M.; Sanjeeviraja, C. . E-mail: sanjeeviraja@rediffmail.com

    2005-01-04

    Molybdenum dichalcogenides are semiconductors with layered type structure, which can act as efficient electrodes in the realization of photoelectrochemical solar cells. The main advantage of this molybdenum diselenide (MoSe{sub 2}) semiconductor is the prevention of electrolyte corrosion because of the phototransitions involving non-bonding d-d orbital of the Mo atoms. Polycrystalline molybdenum diselenide thin films are prepared by pulsed electrodeposition on conducting glass and titanium substrates in galvanostatic mode from an ammoniacal solution of H{sub 2}MoO{sub 4} and SeO{sub 2}. The growth kinetics of the film was studied and the deposition parameters such as electrolyte bath concentration, bath temperature, time of deposition, deposition current, pH of the electrolyte and duty cycle of the current are optimized. X-ray diffraction analysis of the as deposited and annealed films showed the presence of highly textured MoSe{sub 2} films with polycrystalline nature. EDAX spectrum of the surface composition confirms the nearly stoichiometric MoSe{sub 2} nature of the film. Surface morphology studies by scanning electron microscope (SEM) shows that the films are pinhole free and of device quality nature. The optical absorption spectra show an indirect band gap value of 1.16 eV. Conductivity measurements were carried out at different temperatures and electrical constants such as activation energy, trapped energy state and barrier height were calculated.

  14. A study of high-velocity combustion wire molybdenum coatings

    NASA Astrophysics Data System (ADS)

    Modi, S. C.; Calla, Eklavya

    2001-09-01

    In this paper, coatings manufactured using the high-velocity combustion wire (HVCW) spray process have been studied. Molybdenum coatings were prepared in this study, and wavelength dispersive x-ray analysis (WDX) investigations were carried out to ascertain the oxygen content of the coating and its distribution. The x-ray diffraction (XRD) analysis of the coating was also carried out to determine the phases present in the coating. Based on the above data, the authors explain the HVCW-sprayed molybdenum coating microstructure properties. These coatings were also sprayed using a modified aircap design. The parameters varied for the molybdenum coatings by HVCW and were (1) the distance of the substrate from the spray gun and (2) the wire feed rate of the gun. The wear test and coefficient of friction measurements were also carried out for the coatings. Air plasma spraying of Mo-25% NiCrBSi coatings was carried out, and these coatings were further checked for wear friction properties.

  15. Characterization of molybdenum interfacial crud in a uranium mill that employs tertiary-amine solvent extraction

    SciTech Connect

    Moyer, B.; McDowell, W.J.

    1983-01-01

    In the present work, samples of a molybdenum-caused green gummy interfacial crud from an operating western US uranium mill have been physically and chemically examined. Formaton of cruds of this description has been a long-standing problem in the use of tertiary amine solvent extraction for the recovery of uranium from low-grade ores (Amex Process). The crud is essentially an organic-continuous dispersion containing about 10 wt % aqueous droplets and about 37 wt % greenish-yellow crystalline solids suspended in kerosene-amine process solvent. The greenish-yellow crystals were found to be a previously unknown double salt of tertiary amine molybdophosphate with three tertiary amine chlorides having the empirical formula (R/sub 3/NH)/sub 3/(PMo/sub 12/O/sub 40/).3(R/sub 3/NH)Cl. To confirm the identification of the compound, a pure trioctylamine (TOA) analog was synthesized. In laboratory extraction experiments, it was demonstrated that organic-soluble amine molydophosphate forms slowly upon contact of TOA solvent with dilute sulfuric acid solutions containing low concentrations of molybdate and phosphate. If the organic solutions of amine molybdophosphate were then contacted with aqueous NaCl solutions, a greenish-yellow precipitate of (TOAH)/sub 3/(PMo/sub 12/O/sub 40/).3(TOAH)Cl formed at the interface. The proposed mechanism for the formation of the crud under process conditions involves build up of molybdenum in the solvent, followed by reaction with extracted phosphate to give dissolved amine molybdophosphate. The amine molybdophosphate then co-crystallizes with amine chloride, formed during the stripping cycle, to give the insoluble double salt, which precipitates as a layer of small particles at the interface. The proposed solution to the problem is the use of branched-chain, instead of straight-chain, tertiary amine extractants under the expectation that branching would increase the solubility of the double salt. 2 figures, 5 tables.

  16. Electrochromic properties of molybdenum trioxide thin films prepared by chemical vapor deposition

    SciTech Connect

    Maruyama, Toshiro; Kanagawa, Tetsuya

    1995-05-01

    Electrochromic molybdenum trioxide thin films were prepared by chemical vapor deposition. The source material was molybdenum carbonyl. Amorphous molybdenum trioxide thin films were produced at a substrate temperature 300 C. Reduction and oxidation of the films in a 0.3M LiClO{sub 4} propylene carbonate solution caused desirable changes in optical absorption. Coulometry indicated that the coloration efficiency was 25.8 cm{sup 2}/C.

  17. Feasibility of preparing patterned molybdenum coatings on bismuth telluride thermoelectric modules.

    SciTech Connect

    Sarobol, Pylin; Hall, Aaron Christopher; Miller, Stephen Samuel; Knight, Marlene E.; LePage, William S.; Sobczak, Catherine Elizabeth.; Wesolowski, Daniel Edward

    2013-09-01

    Molybdenum electrical interconnects for thermoelectric modules were produced by air plasma spraying a 30%CE%BCm size molybdenum powder through a laser-cut Kapton tape mask. Initial feasibility demonstrations showed that the molybdenum coating exhibited excellent feature and spacing retention (~170%CE%BCm), adhered to bismuth-telluride, and exhibited electrical conductivity appropriate for use as a thermoelectric module interconnect. A design of experiments approach was used to optimize air plasma spray process conditions to produce a molybdenum coating with low electrical resistivity. Finally, a molybdenum coating was successfully produced on a fullscale thermoelectric module. After the addition of a final titanium/gold layer deposited on top of the molybdenum coating, the full scale module exhibited an electrical resistivity of 128%CE%A9, approaching the theoretical resistivity value for the 6mm module leg of 112%CE%A9. Importantly, air plasma sprayed molybdenum did not show significant chemical reaction with bismuth-telluride substrate at the coating/substrate interface. The molybdenum coating microstructure consisted of lamellar splats containing columnar grains. Air plasma sprayed molybdenum embedded deeply (several microns) into the bismuth-telluride substrate, leading to good adhesion between the coating and the substrate. Clusters of round pores (and cracks radiating from the pores) were found immediately beneath the molybdenum coating. These pores are believed to result from tellurium vaporization during the spray process where the molten molybdenum droplets (2623%C2%B0C) transferred their heat of solidification to the substrate at the moment of impact. Substrate cooling during the molybdenum deposition process was recommended to mitigate tellurium vaporization in future studies.

  18. Criticality experiments and analysis of molybdenum reflected cylindrical uranyl fluoride water solution reactors

    NASA Technical Reports Server (NTRS)

    Fieno, D.; Fox, T.; Mueller, R.

    1972-01-01

    Clean criticality data were obtained from molybdenum-reflected cylindrical uranyl-fluoride-water solution reactors. Using ENDF/B molybdenum cross sections, a nine energy group two-dimensional transport calculation of a reflected reactor configuration predicted criticality to within 7 cents of the experimental value. For these reactors, it was necessary to compute the reflector resonance integral by a detailed transport calculation at the core-reflector interface volume in the energy region of the two dominant resonances of natural molybdenum.

  19. Coupled cluster investigation on the thermochemistry of dimethyl sulphide, dimethyl disulphide and their dissociation products: the problem of the enthalpy of formation of atomic sulphur

    NASA Astrophysics Data System (ADS)

    Denis, Pablo A.

    2014-04-01

    By means of coupled cluster theory and correlation consistent basis sets we investigated the thermochemistry of dimethyl sulphide (DMS), dimethyl disulphide (DMDS) and four closely related sulphur-containing molecules: CH3SS, CH3S, CH3SH and CH3CH2SH. For the four closed-shell molecules studied, their enthalpies of formation (EOFs) were derived using bomb calorimetry. We found that the deviation of the EOF with respect to experiment was 0.96, 0.65, 1.24 and 1.29 kcal/mol, for CH3SH, CH3CH2SH, DMS and DMDS, respectively, when ΔHf,0 = 65.6 kcal/mol was utilised (JANAF value). However, if the recently proposed ΔHf,0 = 66.2 kcal/mol was used to estimate EOF, the errors dropped to 0.36, 0.05, 0.64 and 0.09 kcal/mol, respectively. In contrast, for the CH3SS radical, a better agreement with experiment was obtained if the 65.6 kcal/mol value was used. To compare with experiment avoiding the problem of the ΔHf,0 (S), we determined the CH3-S and CH3-SS bond dissociation energies (BDEs) in CH3S and CH3SS. At the coupled cluster with singles doubles and perturbative triples correction level of theory, these values are 48.0 and 71.4 kcal/mol, respectively. The latter BDEs are 1.5 and 1.2 kcal/mol larger than the experimental values. The agreement can be considered to be acceptable if we take into consideration that these two radicals present important challenges when determining their EOFs. It is our hope that this work stimulates new studies which help elucidate the problem of the EOF of atomic sulphur.

  20. [Validity of urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) as biomarker of exposure to very low concentrations of carbon disulphide: preliminary results].

    PubMed

    Lovreglio, P; Bergonzi, R; Meliddo, G; Pesola, G; Mascia, L; Basso, A; Imbriani, M; Apostoli, P; Soleo, L

    2008-01-01

    The possibility to use urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) as biomarker of occupational exposure to very low doses of carbon disulphide (CS2) was evaluated preliminarily in 10 workers employed in a chemical plant where rubber vulcanization accelerators are produced, and in 10 workers, residents in the same geographical area and not occupationally exposed to CS2 and dithiocarbamates (DTC). Exposure to airborne CS2 was assessed, only for exposed workers, by both personal and area samplers. For the determination of TTCA, a spot urine sample was collected for each worker, exposed and non exposed, at the end of work-shift. A questionnaire probing lifestyle and dietary habits and non occupational exposure to CS2 and DTC was administered to all workers involved in the study. Environmental exposure to CS2 in 2007 ranged between 0.21 mg/m3 and 0.73 mg/m3 for personal sampling, and between 0.23 mg/m3 and 0.41 mg/m3 for area sampling. Urinary TTCA levels resulted very low and did not show any significant difference between exposed (Median: 10.8 microg/g creat; Range: 6.1-26.4 microg/g creat) and non exposed workers (Median: 9.3 microg/g creat; Range: 3.0-33.0 microg/g creat), while higher, but not significant concentrations of TTCA were observed in smokers than in non smokers (p = 0.09). No correlation was found between urinary TTCA levels and environmental exposure to CS2, age, body mass index, smoking and dietary habits. In conclusion, the low sensibility and specificity in the assessment of occupational exposure to low doses of CS2 in workers compared to general population subjects, makes urinary TTCA a biomarker with a low usefulness in biological monitoring. ACGIH, besides, should also introduce "B" (background) notation, at present not considered for the BEI indicated for urinary TTCA. PMID:18700678

  1. Feasibility study of accelerator based production of molybdenum-99/technetium-99m

    NASA Astrophysics Data System (ADS)

    Tchelidze, Lali

    Stability of supply in the medical radioisotope market is now of overriding importance. One of the most commonly used radioisotopes is 99mTc, which is produced from 99Mo decay. 99Mo has been produced in nuclear reactors before, however these reactors are aging and have been not reliable lately and there is a great need to find an alternative for the production. In the current project, photo-neutron production of 99Mo/ 99mTc was investigated. An electron linear accelerator at the Idaho Accelerator Center was used to study the feasibility of 99mTc production using bremsstrahlung photon beams from the accelerator. The kinematic recoil process that occurs with every photo nuclear reaction was exploited. With the emission of a neutron in a photo nuclear reaction, the parent nucleus recoils in order to conserve momentum. This recoil can be used to separate 99Mo from 100Mo, at which point one has a very pure and very high specific activity source of 99Mo. We verified the photo-neutron production rates for 99Mo. Also, the kinematic recoil process was modeled and separation efficiencies were measured experimentally. We concluded that it is feasible to produce high 99Mo activities, however nano-particles of molybdenum have to be used and a clean nano-particle separation method has to be achieved.

  2. CONTROL OF AIR POLLUTION EMISSIONS FROM MOLYBDENUM ROASTING. VOLUME 2. ALTERNATIVES FOR CONTROL OF WEAK SULFUR DIOXIDE EMISSIONS

    EPA Science Inventory

    This report covers the second phase of a three phase effort evaluating (1) characterization of particulate control of a molybdenum sulfide roasters, (2) assessment of sulfur dioxide abatement alternatives for nonferrous smelting and, in particular, for molybdenum roasting, and (3...

  3. Relief Creation on Molybdenum Plates in Discharges Initiated by Gyrotron Radiation in Metal-Dielectric Powder Mixtures

    NASA Astrophysics Data System (ADS)

    Skvortsova, N. N.; Stepakhin, V. D.; Malakhov, D. V.; Sorokin, A. A.; Batanov, G. M.; Borzosekov, V. D.; Glyavin, M. Yu.; Kolik, L. V.; Konchekov, E. M.; Letunov, A. A.; Petrov, A. E.; Ryabikina, I. G.; Sarksyan, K. A.; Sokolov, A. S.; Smirnov, V. A.; Kharchev, N. K.

    2016-02-01

    We show the possibility of creating a metal microcrystalline relief (micro- and nanosized) on molybdenum plates in a plasma gas-phase discharge initiated by gyrotron radiation in molybdenum-dielectric powder mixtures.

  4. Electron-diffraction study of the interaction of carbon with the products of reduction of molybdenum from the trioxide

    SciTech Connect

    Solonin, Yu. M.

    1986-03-01

    This paper studies the mechanisms of the structural transformations at the remaining possible stages of the process of reduction of molybdenum trioxide by hydrogen in the presence of simultaneous interaction of the reaction products with carbon. The authors find that the intermediate molybdenum suboxide (NaC1 structural type) in this case restructures directly into hexagonal molybdenum carbide. The hexagonal Mo/sub 2/C apparently forms on the (110) planes of molybdenum.

  5. Measurement of Actinides in Molybdenum-99 Solution Analytical Procedure

    SciTech Connect

    Soderquist, Chuck Z.; Weaver, Jamie L.

    2015-11-01

    This document is a companion report to a previous report, PNNL 24519, Measurement of Actinides in Molybdenum-99 Solution, A Brief Review of the Literature, August 2015. In this companion report, we report a fast, accurate, newly developed analytical method for measurement of trace alpha-emitting actinide elements in commercial high-activity molybdenum-99 solution. Molybdenum-99 is widely used to produce 99mTc for medical imaging. Because it is used as a radiopharmaceutical, its purity must be proven to be extremely high, particularly for the alpha emitting actinides. The sample of 99Mo solution is measured into a vessel (such as a polyethylene centrifuge tube) and acidified with dilute nitric acid. A gadolinium carrier is added (50 µg). Tracers and spikes are added as necessary. Then the solution is made strongly basic with ammonium hydroxide, which causes the gadolinium carrier to precipitate as hydrous Gd(OH)3. The precipitate of Gd(OH)3 carries all of the actinide elements. The suspension of gadolinium hydroxide is then passed through a membrane filter to make a counting mount suitable for direct alpha spectrometry. The high-activity 99Mo and 99mTc pass through the membrane filter and are separated from the alpha emitters. The gadolinium hydroxide, carrying any trace actinide elements that might be present in the sample, forms a thin, uniform cake on the surface of the membrane filter. The filter cake is first washed with dilute ammonium hydroxide to push the last traces of molybdate through, then with water. The filter is then mounted on a stainless steel counting disk. Finally, the alpha emitting actinide elements are measured by alpha spectrometry.

  6. Ultrafast Optical Microscopy of Single Monolayer Molybdenum Disulfide Flakes

    PubMed Central

    Seo, Minah; Yamaguchi, Hisato; Mohite, Aditya D.; Boubanga-Tombet, Stephane; Blancon, Jean-Christophe; Najmaei, Sina; Ajayan, Pulickel M.; Lou, Jun; Taylor, Antoinette J.; Prasankumar, Rohit P.

    2016-01-01

    We have performed ultrafast optical microscopy on single flakes of atomically thin CVD-grown molybdenum disulfide, using non-degenerate femtosecond pump-probe spectroscopy to excite and probe carriers above and below the indirect and direct band gaps. These measurements reveal the influence of layer thickness on carrier dynamics when probing near the band gap. Furthermore, fluence-dependent measurements indicate that carrier relaxation is primarily influenced by surface-related defect and trap states after above-bandgap photoexcitation. The ability to probe femtosecond carrier dynamics in individual flakes can thus give much insight into light-matter interactions in these two-dimensional nanosystems. PMID:26876194

  7. Sintering behavior of biporous molybdenum-copper pseudoalloys

    SciTech Connect

    Chernyshev, L.I.; Kostornov, A.G.; Pavlenko, N.P.; Rostunova, O.N.

    1986-02-01

    This paper describes solid- and liquid-phase sintering experiments performed on a biporous molybdenum-copper material, the purpose of which was to investigate the processes taking place at the microporosity level. It is shown that the sintering is accompanied by an increase in pore size at the macroporosity level, which is a manifestation of the law of zonal separation. At the microporosity level, the sintering of a biporous material determines the structural characteristics of the material at the macroporosity level. Some characteristics of the solidand liquid-phase sintering behavior of the material investigated have been established.

  8. Physicochemical investigation of NiAl with small molybdenum additions

    NASA Technical Reports Server (NTRS)

    Troshkina, V. A.; Kucherenko, L. A.; Fadeeva, V. I.; Aristova, N. M.

    1982-01-01

    Specimens of four cast NiAl alloys, three of them containing 0.5, 1.0 and 1.5 at. % Mo., were homogenized for 10, 10, and 140 hr at 1373, 1523 and 1273 K, respectively, then kept at 1073, 1173 and 1323 K for 60, 120 and 3 hr, respectively, and quenched in icy water. The precipitation of a metastable Ni3Mo phase was observed at temperatures between 1073 and 1523 K. Molybdenum substituted for nickel was found to inhibit the lattice disordering in NiAl at 1073 and 1523 K.

  9. Processing-Structure Correlation in DC Sputtered Molybdenum Thin Films

    NASA Astrophysics Data System (ADS)

    Khan, Majid; Islam, Mohammad; Akram, Aftab; Manzoor, Umair

    2013-12-01

    Molybdenum thin films were sputter deposited under different conditions of DC power and chamber pressure. The structure and topography of the films were investigated using AFM, SEM and XRD techniques. Van der Pauw method and tape test were employed to determine electrical resistivity and interfacial strength to the substrate, respectively. All the films are of sub-micron thickness with maximum growth rate of 78 nm/min and crystallite size in the range of 4 to 21 nm. The films produced at high power and low pressure exhibit compressive residual strains, low electrical resistivity and poor adhesion to the glass substrate, whereas the converse is true for films produced at high pressure.

  10. Ultrafast Optical Microscopy of Single Monolayer Molybdenum Disulfide Flakes

    DOE PAGESBeta

    Seo, Minah; Yamaguchi, Hisato; Mohite, Aditya D.; Boubanga-Tombet, Stephane; Blancon, Jean-Christophe; Najmaei, Sina; Ajayan, Pulickel M.; Lou, Jun; Taylor, Antoinette J.; Prasankumar, Rohit P.

    2016-02-15

    We performed ultrafast optical microscopy on single flakes of atomically thin CVD-grown molybdenum disulfide, using non-degenerate femtosecond pump-probe spectroscopy to excite and probe carriers above and below the indirect and direct band gaps. These measurements reveal the influence of layer thickness on carrier dynamics when probing near the band gap. Furthermore, fluence-dependent measurements indicate that carrier relaxation is primarily influenced by surface-related defect and trap states after above-bandgap photoexcitation. Furthermore, the ability to probe femtosecond carrier dynamics in individual flakes can thus give much insight into light-matter interactions in these two-dimensional nanosystems.

  11. Geology of the Starr molybdenum mine, Okanogan County, Washington

    USGS Publications Warehouse

    Creasey, S.C.

    1954-01-01

    The Starr molybdenum mine, Okanogan County, Wash., is about 5 airline miles west of Tonasket in the north-central part of the State. The mineralized zone has been explored to a depth of 250 feet by means of three adit levels, one sublevel, and a raise which connects two of the adits and the sublevel. In all, there are about 2,700 feet of underground workings. The mine has neither machinery nor a developed water supply adequate for any work other than a small exploratory program.

  12. A 65 Ah rechargeable lithium molybdenum disulfide battery

    NASA Technical Reports Server (NTRS)

    Brandt, K.

    1986-01-01

    A rechargeable lithium molybdenum disulfide battery which has a number of superior performance characteristics which includes a high energy density, a high power density, and a long charge retention time was developed. The first cell sizes developed included a C size cell and an AA size cell. Over the last two years, a project to demonstrate the feasibility of the scale up to this technology to a BC size cell with 65 Ah capacity was undertaken. The objective was to develop, build, and test a .6 kWh storage battery consisting of 6 BC cells in series.

  13. Ultrafast Optical Microscopy of Single Monolayer Molybdenum Disulfide Flakes.

    PubMed

    Seo, Minah; Yamaguchi, Hisato; Mohite, Aditya D; Boubanga-Tombet, Stephane; Blancon, Jean-Christophe; Najmaei, Sina; Ajayan, Pulickel M; Lou, Jun; Taylor, Antoinette J; Prasankumar, Rohit P

    2016-01-01

    We have performed ultrafast optical microscopy on single flakes of atomically thin CVD-grown molybdenum disulfide, using non-degenerate femtosecond pump-probe spectroscopy to excite and probe carriers above and below the indirect and direct band gaps. These measurements reveal the influence of layer thickness on carrier dynamics when probing near the band gap. Furthermore, fluence-dependent measurements indicate that carrier relaxation is primarily influenced by surface-related defect and trap states after above-bandgap photoexcitation. The ability to probe femtosecond carrier dynamics in individual flakes can thus give much insight into light-matter interactions in these two-dimensional nanosystems. PMID:26876194

  14. The Change in the hardness of LCAC. TZM, and ODS molybdenum in the post-irradiated and annealed conditions

    SciTech Connect

    Cockeram, Brian V; Smith, Richard W; Byun, Thak Sang; Snead, Lance Lewis

    2009-01-01

    Hardness measurements were performed on wrought Low Carbon Arc Cast (LCAC), TZM, and Oxide Dispersion Strengthened (ODS) molybdenum in the post-irradiated and post-irradiated + annealed condition to determine the recovery kinetics. Irradiations performed in the High Flux Isotope Reactor (HFIR) at nominally 300 C and 600 C to neutron fluence levels that range from 10.5 to 246 x 10{sup 24} n/m{sup 2} (E > 0.1 MeV) resulted in relatively large increases in hardness (77-109%), while small increases in hardness (<18%) were observed for irradiations at 870-1100 C. The hardness recovery for ODS and LCAC irradiated at 300 C and 600 C were shown to be complete at 980 C and {approx} 1100-1250 C, respectively. Isothermal annealing at 700 C was used to determine the activation energy for recovery of LCAC and ODS (3.70-4.88 eV {+-} 0.28-0.77 eV), which is comparable to values reported in the literature for molybdenum vacancy self-diffusion. This suggests that recovery of LCAC and ODS is controlled by the solid-state diffusion of vacancies in the bulk, and that the finer grain size and particle size ODS does not affect this mechanism. TZM exhibited slower recovery kinetics, which can be explained by the solute atoms (titanium and zirconium) inhibiting vacancy diffusion.

  15. Experimental investigation of the behaviour of tungsten and molybdenum alloys at high strain-rate and temperature

    NASA Astrophysics Data System (ADS)

    Scapin, Martina; Fichera, Claudio; Carra, Federico; Peroni, Lorenzo

    2015-09-01

    The introduction in recent years of new, extremely energetic particle accelerators such as the Large Hadron Collider (LHC) gives impulse to the development and testing of refractory metals and alloys based on molybdenum and tungsten to be used as structural materials. In this perspective, in this work the experimental results of a tests campaign on Inermet® IT180 and pure Molybdenum (sintered by two different producers) are presented. The investigation of the mechanical behaviour was performed in tension varying the strain-rates, the temperatures and both of them. Overall six orders of magnitude in strain-rate (between 10-3 and 103 s-1) were covered, starting from quasi-static up to high dynamic loading conditions. The high strain-rate tests were performed using a direct Hopkinson Bar setup. Both in quasi-static and high strain-rate conditions, the heating of the specimens was obtained with an induction coil system, controlled in feedback loop, based on measurements from thermocouples directly welded on the specimen. The temperature range varied between 25 and 1000°C. The experimental data were, finally, used to extract the parameters of the Zerilli-Armstrong model used to reproduce the mechanical behaviour of the investigated materials.

  16. Mechanism of molybdenum removal from the sea and its concentration in black shales: EXAFS evidence

    USGS Publications Warehouse

    Helz, G.R.; Miller, C.V.; Charnock, J.M.; Mosselmans, J.F.W.; Pattrick, R.A.D.; Garner, C.D.; Vaughan, D.J.

    1996-01-01

    Molybdenum K-edge EXAFS (extended X-ray absorption fine structure) spectra yield new structural information about the chemical environment of Mo in high-Mo black shales and sediments. Two spectral types are found. The less common one, associated with Mo ores developed in shale in China, is that of a MoS2 phase, possibly X-ray amorphous jordisite. The other, associated with Cretaceous deep sea sediments and with other black shales, is characterized by short Mo-O distances (1.69-1.71 A??), by Mo-S distances of 2.30-2.38 A??, and in some cases by second shell Mo and Fe interactions, which suggests that some Mo resides in transition metal-rich phases. EXAFS spectra of synthetic amorphous materials, prepared by scavenging Mo from HS solutions with Fe(II), FeOOH, and humic acid, suggest that the second spectral type arises from Mo present chiefly in two forms. One is a compact, Mo-Fe-S "cubane" type compound with Mo-S distances of ???2.36 A?? and Mo-Fe distances of ???2.66 A??, while the other is probably an organic form containing some Mo-O double bonds (???1.69 A??). Laboratory products, that were prepared by scavenging dissolved Mo from sulfidic solutions with humic acid, yield spectra quite similar to the second spectral type observed in shales and sediments, including unexpected indications of Mo-Fe interactions. Molybdenum L-edge spectra indicate that the mean oxidation state in the sediments and shales lies between IV and VI. This work demonstrates the merit of EXAFS for obtaining structural information on natural materials containing X-ray amorphous components which defeat conventional mineralogical characterization. The implications of these findings regarding Mo scavenging from sulfidic natural waters are considered. We introduce the concept of a geochemical switch, in which HS- transforms the marine behavior of Mo from that of a conservative element to that of a particle reactive element. The action point of the HS- switch is calculated to be, aHS- = 10

  17. Evaluation of Molybdenum as a Surrogate for Iridium in the GPHS Weld Development

    SciTech Connect

    Stine, Andrew Martin; Pierce, Stanley W.; Moniz, Paul F.

    2015-10-17

    The welding equipment used for welding iridium containers (clads) at Los Alamos National Laboratory is twenty five years old and is undergoing an upgrade. With the upgrade, there is a requirement for requalification of the welding process, and the opportunity for process improvement. Testing of the new system and requalification will require several welds on iridium test parts and clads, and any efforts to improve the process will add to the need for iridium parts. The extreme high cost of iridium imposes a severe limitation on the extent of test welding that can be done. The 2 inch diameter, 0.027 inch thick, iridium blank disc that the clad cup is formed from, is useful for initial weld trials, but it costs $5000. The development clad sets needed for final tests and requalification cost $15,000 per set. A solution to iridium cost issue would be to do the majority of the weld development on a less expensive surrogate metal with similar weld characteristics. One such metal is molybdenum. Since its melting index (melting temperature x thermal conductivity) is closest to iridium, welds on molybdenum should be similar in size for a given weld power level. Molybdenum is inexpensive; a single 2 inch molybdenum disc costs only $9. In order to evaluate molybdenum as a surrogate for iridium, GTA welds were first developed to provide full penetration on 0.030 inch thick molybdenum discs at speeds of 20, 25, and 30 inches per minute (ipm). These weld parameters were then repeated on the standard 0.027 inch thick iridium blanks. The top surface and bottom surface (root) width and grain structure of the molybdenum and iridium welds were compared, and similarities were evident between the two metals. Due to material and thickness differences, the iridium welds were approximately 35% wider than the molybdenum welds. A reduction in iridium weld current of 35% produce welds slightly smaller than the molybdenum welds yet showed that current could be scaled according to molybdenum

  18. 40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... copper, lead, zinc, gold, silver, and molybdenum ores subcategory. 440.100 Section 440.100 Protection of... MINING AND DRESSING POINT SOURCE CATEGORY Copper, Lead, Zinc, Gold, Silver, and Molybdenum Ores Subcategory § 440.100 Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum...

  19. 40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... copper, lead, zinc, gold, silver, and molybdenum ores subcategory. 440.100 Section 440.100 Protection of... MINING AND DRESSING POINT SOURCE CATEGORY Copper, Lead, Zinc, Gold, Silver, and Molybdenum Ores Subcategory § 440.100 Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum...

  20. 40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... copper, lead, zinc, gold, silver, and molybdenum ores subcategory. 440.100 Section 440.100 Protection of... MINING AND DRESSING POINT SOURCE CATEGORY Copper, Lead, Zinc, Gold, Silver, and Molybdenum Ores Subcategory § 440.100 Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum...

  1. 40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... copper, lead, zinc, gold, silver, and molybdenum ores subcategory. 440.100 Section 440.100 Protection of... DRESSING POINT SOURCE CATEGORY Copper, Lead, Zinc, Gold, Silver, and Molybdenum Ores Subcategory § 440.100 Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory. (a)...

  2. 40 CFR 440.100 - Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... copper, lead, zinc, gold, silver, and molybdenum ores subcategory. 440.100 Section 440.100 Protection of... DRESSING POINT SOURCE CATEGORY Copper, Lead, Zinc, Gold, Silver, and Molybdenum Ores Subcategory § 440.100 Applicability; description of the copper, lead, zinc, gold, silver, and molybdenum ores subcategory. (a)...

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

    USGS Publications Warehouse

    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.

  4. Molybdenum and copper levels in white-tailed deer near uranium mines in Texas

    USGS Publications Warehouse

    King, K.A.; LeLeux, J.; Mulhern, B.M.

    1984-01-01

    Molybdenum toxicity, molybdenosis, in ruminant animals has been identified in at least 15 states and in Canada, England, Australia, and New Zealand. In most western states, molybdenosis has been associated with strip-mine spoil deposits. Molybdenum toxicity has been diagnosed in cattle pastured near uranium strip-mine spoils in several Texas counties. Recent reports from hunters and the authors' observations indicated that white-tailed deer (Odocoileus virginianus ) that fed near uranium-mine spoil deposits may also have been exposed to high levels of molybdenum. The objectives of this study were to determine if white-tailed deer from a South Texas uranium mining district were accumulating harmful levels of molybdenum and to compare molybdenum and copper levels with antler development in deer from the mined area vs. an unmined control area.

  5. Studies by electron-paramagnetic-resonance spectroscopy of the environment of the metal in the molybdenum cofactor of molybdenum-containing enzymes.

    PubMed Central

    Hawkes, T R; Bray, R C

    1984-01-01

    The molybdenum cofactor prepared by denaturing xanthine oxidase by heat treatment or other methods was partially purified by anaerobic gel filtration in the presence of sodium dithionite, with little loss of activity. A range of products with different elution volumes was obtained. This behaviour is apparently related to association of the molybdenum cofactor with various residual peptides. E.p.r. signals from molybdenum (V) in the active cofactor, present either in crude preparations or in purified fractions, may be generated in dimethyl sulphoxide solution by controlled oxidation carried out on the molybdenum cofactor alone or in the presence of added thiols. The g-values of the spectra suggest that in the oxidized cofactor molybdenum has one terminal oxygen ligand and four ligands from thiolate groups. It is proposed that two of these are from the organic part of the cofactor and two from cysteine residues in the protein or in residual peptides. A signal generated in high yield with little loss of cofactor activity in the presence of thiophenol has g parallel = 2.0258 and g = 1.9793. It is suggested that in this species two cysteine residues have been replaced by two thiophenol molecules. The possible usefulness of the thiophenol complex in further purification of the molybdenum cofactor is discussed. PMID:6091619

  6. Metam sodium intoxication: the specific role of degradation products--methyl isothiocyanate and carbon disulphide--as a function of exposure.

    PubMed

    Bretaudeau Deguigne, Marie; Lagarce, Laurence; Boels, David; Harry, Patrick

    2011-06-01

    Introduction. The objective was to evaluate the toxicity of poisoning by metam sodium, a dithiocarbamate fumigant, the breakdown products of which are methyl isothiocyanate (MITC), carbon disulphide (CS2), and dihydrogen sulphide (H2S). Methods. This is a retrospective, observational case series of metam sodium exposure cases reported to the Angers Poison and Toxicovigilance Centre from 1992 through 2009. Results. A total of 106 cases of metam sodium exposure were recorded and 102 cases were included in this study. All cases of exposure were unintentional. Occupational poisoning occurred in eight cases. The most common route of exposure was inhalation (n = 96). In 79 cases, the patients were people living near fields where metam sodium had recently been applied. Most of the reported symptoms involved irritation of the eyes (n = 76), throat and nose (n = 65), attributable to MITC. Cough and dyspnoea occurred in four cases but no persistent, irritant-induced asthma or persistent exacerbation of asthma was observed. Sixteen patients at two different sites of pollution were exposed to emanations from the drainage system in their homes following the illicit discharge of metam sodium into the sewers. Most presented with nausea and headaches, but only four experienced eye or throat irritation. A breakdown product other than MITC was involved: air analysis at one site revealed the presence of CS2 (337 mg/m(3)) and no H2S. Two of these patients, who had consumed some alcohol, experienced dysgeusia but no disulfiram-like reaction. The only lethal case recorded was a truck driver who was found dead of acute lung injury after falling into a tank that had previously contained metam sodium. Two patients who ingested a dilute solution, presented with mild epigastric pain. Four skin exposures caused erythema (n = 2), moderate burns (n = 1), and urticaria (n = 1). According to the poisoning severity score, their symptoms were minor in 99% of cases. Conclusion. Acute metam sodium

  7. Synthesizing aluminum particles towards controlling electrostatic discharge ignition sensitivity

    SciTech Connect

    Eric S. Collins; Jeffery P. Gesner; Michelle L. Pantoya; Michael A. Daniels

    2014-02-01

    Aluminum particles were synthesized with shell thicknesses ranging from 2.7 to 8.3 nm and a constant diameter of 95 nm. These fuel particles were combined with molybdenum trioxide particles and the electrostatic discharge (ESD) sensitivity of the mixture was measured. Results show ignition delay increased as the alumina shell thickness increased. These results correlated with electrical resistivity measurements of the mixture which increased with alumina concentration. A model was developed using COMSOL for ignition of a single Al particle. The ignition delay in the model was consistent with the experimental results suggesting that the primary ESD ignition mechanism is joule heating.

  8. Role of molybdenum in dinitrogen fixation by Clostridium pasteurianum.

    PubMed Central

    Cardenas, J; Mortenson, L E

    1975-01-01

    The role of Mo in the activity and synthesis of the nitrogenase components of Clostridium pasteurianum has been studied by observing the competition of Mo with its structural analogue W. Clostridial cells when fixing N2 appeared strictly dependent upon the available Mo, showing maximal N2-fixing activity at molybdate concentrations in the media of 10 muM. Cells grown in media with 3 times 10(-6) muM Mo, although showing good growth, had only 15% as much N2-fixing activity. In the presence of W the synthesis of both nitrogenase components, molybdoferredoxin and azoferredoxin, was affected. Attempts to produce nitrogenase in W-grown cells by addition of high molybdenum to the media in the presence of inhibitors of protein synthesis showed that Mo incorporation into a possible inactive preformed apoenzyme did not occur. Unlike other molybdoenzyme-containing cells, in which W either is incorporated in place of Mo to yield inactive protein or initiates the production of apoprotein, C. pasteurianum forms neither a tungsten substituted molybdoferredoxin nor an apoprotein. It is concluded that in C. pasteurianum molybdenum is an essential requirement for both the biosynthesis and activity of its nitrogenase. PMID:1158853

  9. Sulphur shuttling across a chaperone during molybdenum cofactor maturation

    NASA Astrophysics Data System (ADS)

    Arnoux, Pascal; Ruppelt, Christian; Oudouhou, Flore; Lavergne, Jérôme; Siponen, Marina I.; Toci, René; Mendel, Ralf R.; Bittner, Florian; Pignol, David; Magalon, Axel; Walburger, Anne

    2015-02-01

    Formate dehydrogenases (FDHs) are of interest as they are natural catalysts that sequester atmospheric CO2, generating reduced carbon compounds with possible uses as fuel. FDHs activity in Escherichia coli strictly requires the sulphurtransferase EcFdhD, which likely transfers sulphur from IscS to the molybdenum cofactor (Mo-bisPGD) of FDHs. Here we show that EcFdhD binds Mo-bisPGD in vivo and has submicromolar affinity for GDP—used as a surrogate of the molybdenum cofactor’s nucleotide moieties. The crystal structure of EcFdhD in complex with GDP shows two symmetrical binding sites located on the same face of the dimer. These binding sites are connected via a tunnel-like cavity to the opposite face of the dimer where two dynamic loops, each harbouring two functionally important cysteine residues, are present. On the basis of structure-guided mutagenesis, we propose a model for the sulphuration mechanism of Mo-bisPGD where the sulphur atom shuttles across the chaperone dimer.

  10. Magnetic ordering in lanthanide-molybdenum oxide nanostructure arrays

    NASA Astrophysics Data System (ADS)

    Hagmann, Joseph; Le, Son; Schneemeyer, Lynn; Olsen, Patti; Besara, Tiglet; Siegrist, Theo; Seiler, David; Richter, Curt

    Reduced ternary molybdenum oxides, or bronzes, offer an attractive materials platform to study a wide variety of remarkable physical phenomena in a system with highly varied structural chemistry. Interesting electronic behaviors, such as superconductivity, charge density waves, and magnetism, in these materials arise from the strong hybridization of the 4d states of high-valent Mo with O p orbitals. We investigate a series of molybdenum bronze materials with Lanthanide-Mo16O44 composition that can be described as a three-dimensional array of metallic Mo8O32 nanostructures computationally predicted to contain a single charge with spin 1/2 separated by insulating MoO4 tetrahedra. This study reveals novel magnetic ordering in Lanthanide-Mo16O44 systems arising, not from the inclusion of magnetic elements, but rather from an exchange interaction between cubic Mo8O32 units. Here, we report the magnetometry and transport behaviors of a series of Lanthanide-Mo16O44 materials, emphasizing an observed low-temperature phase transition signifying the onset of antiferromagnetic ordering between the arrayed nanostructures, and relate these behaviors to their experimentally-characterized structures to reveal the intriguing physics of these correlated electronic systems.

  11. Authigenic Molybdenum Isotopes Record Lake Baikal in the Past

    NASA Astrophysics Data System (ADS)

    Yu, E.; Liu, H.; Lee, D.

    2013-12-01

    Authigenic molybdenum isotope signatures in marine sediments reflect the mechanisms of deposits under both oxic and reducing conditions. The studies are mainly focusing on marine environment, and the application on lake record is rare. A three-meters long gravity core (GC-99; 52°05'23'N, 105°50'24'E; water depth 201m) from Lake Baikal is studied for Mo isotopes and concentration. The result is using to examine the sources of material or/and the changes in conditions of Lake Baikal with climate changes. To approach on extracting Mo isotope signal directly related to lake water, a sequential leaching technique to extract the Mo isotopes coating on the Fe-Mn oxides and a robust chromatography technique to purify molybdenum isotopes is modified and used for all lake sediment samples. Then, Mo isotope composition is measured by applying double spike method with Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). According to the Mo concentration and its isotope composition δ98/95Mo relative to NIST-SRM-3134, the results imply Lake Baikal stayed oxic condition over the last 24 ka. Moreover, the sediment core GC-99 from Lake Baikal imply two stages fluctuations of the lake environment separated at core depth of 100cm (around 12ka); and the shifting of δ98/95Mo isotope composition shows that the lake during interglacial period was more oxic than the last glacial period due to absence of ice cover.

  12. Synthesis and characterization of several molybdenum chloride cluster compounds

    SciTech Connect

    Beers, W.W.

    1983-06-01

    Investigation into the direct synthesis of Mo/sub 4/Cl/sub 8/(P(C/sub 2/H/sub 5/)/sub 3/)/sub 4/ from Mo/sub 2/(OAc)/sub 4/ led to a synthetic procedure that produces yields greater than 80%. The single-crystal structure disclosed a planar rectangular cluster of molybdenum atoms. Metal-metal bond distances suggest that the long edges of the rectangular cluster should be considered to be single bonds and the short metal-metal bonds to be triple bonds. This view is reinforced by an extended Hueckel calculation. Attempts to add a metal atom to Mo/sub 4/Cl/sub 8/(PR/sub 3/)/sub 4/ to form Mo/sub 5/Cl/sub 10/(PR/sub 3/)/sub 3/ led instead to a compound with the composition Mo/sub 8/Cl/sub 16/(PR/sub 3/)/sub 4/. Solution and reflectance uv-visible spectra and x-ray photoelectron spectra suggest that tetranuclear molybdenum units are present. The facile reaction between Mo/sub 8/Cl/sub 16/(PR/sub 3/)/sub 4/ and PR/sub 3/ imply that the linkage between tetrameric units is weak.

  13. Physical properties about metal matrix FGM of molybdenum and copper

    SciTech Connect

    Nakano, Kouichi; Nishida, Shinichi

    1995-11-01

    Metal matrix composites (MMC) have been made trials to produce by a lot of fabrication processes such as the powder metallurgical method, the plasma spraying, the diffusion bonding, the physical vapor deposition method, the hot isostatic pressing (HIP) etc. In the most cases of these processes, dissimilar materials are combined or bonded directly. The various physical properties are discontinuous at the bonded interface of the dissimilar materials. In order to overcome the problem, functionally gradient materials (FGM) have been considered recently, and have attracted the authors. Its compositions are prepared so that physical properties continuously vary across the bond interface of the dissimilar metals. In this study, a FGM is produced by a new process based on HIP. Copper and molybdenum, which are distinct in the thermo-physical property to each other, are the constitutents for the FGM. This composition have been confirmed by absorbed electron and characteristics X-ray images of each mixed layer for FGM to be uniform or continuous. The following items have been investigated and compared with the linear law of mixture rule: Vickers hardness, thermal expansion, and thermal conductivity at a one-dimensional non-steady state. Those physical properties have been identified to depend on the mixing ratios of copper and molybdenum. Pretty good agreements have been obtained between the experimental data and the calculated values according to the linear law of mixture rule.

  14. Full Densification of Molybdenum Powders Using Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Mouawad, B.; Soueidan, M.; Fabrègue, D.; Buttay, C.; Bley, V.; Allard, B.; Morel, H.

    2012-09-01

    Pure molybdenum powder was sintered using spark plasma sintering (SPS) under various temperatures and holding times, under a pressure of 77 MPa and a heating rate at 700 K/min (700 °C/min). After sintering, a carbide layer was observed at the surface. The carbide layer thickness, the relative density of the sample as well as the microhardness, and the grain size of Mo were measured. The carbide thickness depends on time and temperature, and it was found that the carbide layer grows in a parabolic manner, with the activation energy of carbon diffusion in Mo being equal to 34 Kcal/mol. The densification of Mo is controlled mainly by the sintering temperature and the holding time. The molybdenum powder was successfully consolidated by SPS in short times. A relative density of 100 pct is achieved at a sintering temperature of 2123.15 K (1850 °C) and a holding time of 30 minutes. It was shown that the hardness decreases slightly with temperature and time. It should be related to the increase in grain size with the sintering temperature and time.

  15. Full Densification of Molybdenum Powders Using Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Mouawad, B.; Soueidan, M.; Fabrègue, D.; Buttay, C.; Bley, V.; Allard, B.; Morel, H.

    2012-05-01

    Pure molybdenum powder was sintered using spark plasma sintering (SPS) under various temperatures and holding times, under a pressure of 77 MPa and a heating rate at 700 K/min (700 °C/min). After sintering, a carbide layer was observed at the surface. The carbide layer thickness, the relative density of the sample as well as the microhardness, and the grain size of Mo were measured. The carbide thickness depends on time and temperature, and it was found that the carbide layer grows in a parabolic manner, with the activation energy of carbon diffusion in Mo being equal to 34 Kcal/mol. The densification of Mo is controlled mainly by the sintering temperature and the holding time. The molybdenum powder was successfully consolidated by SPS in short times. A relative density of 100 pct is achieved at a sintering temperature of 2123.15 K (1850 °C) and a holding time of 30 minutes. It was shown that the hardness decreases slightly with temperature and time. It should be related to the increase in grain size with the sintering temperature and time.

  16. High temperature oxidation of molybdenum in water vapor environments

    NASA Astrophysics Data System (ADS)

    Nelson, A. T.; Sooby, E. S.; Kim, Y.-J.; Cheng, B.; Maloy, S. A.

    2014-05-01

    Molybdenum has recently gained attention as a candidate cladding material for use in light water reactors. Its excellent high temperature mechanical properties and stability under irradiation suggest that it could offer benefits to performance under a wide range of reactor conditions, but little is known about its oxidation behavior in water vapor containing atmospheres. The current study was undertaken to elucidate the oxidation behavior of molybdenum in water vapor environments to 1200 °C in order to provide an initial assessment of its feasibility as a light water reactor cladding. Initial observations indicate that at temperatures below 1000 °C, the kinetics of mass loss in water vapor would not be detrimental to cladding integrity during an off-normal event. Above 1000 °C, degradation is more rapid but remains slower than observed for optimized zirconium cladding alloys. The effect of hydrogen-water vapor and oxygen-water vapor mixtures on material loss was also explored at elevated temperatures. Parts-per-million levels of either hydrogen or oxygen will minimally impact performance, but hydrogen contents in excess of 1000 ppm were observed to limit volatilization at 1000 °C.

  17. Molybdenum-silicon multilayer mirrors for the extreme ultraviolet

    NASA Technical Reports Server (NTRS)

    Barbee, T. W., Jr.; Mrowka, S.; Hetrick, M. C.

    1985-01-01

    Multilayer structures of molybdenum and silicon have been synthesized by sputter deposition onto flat silicon single-crystal silicon substrates and spherically ground (0.5and 22.0-m radii) fused silica substrates; and the reflectivities for 170.4-A (72.8-eV), 160.1-A (77.4-eV), and 228-A (54.4-eV) light measured at near normal incidence. Observed peak values ranged from 26.2 to 78 percent, the highest reflectivities occurring closest to normal incidence. Energy resolutions were about 10 in all cases. Model calculations were performed using optical constants and experimentally determined multilayer structural parameters. In all cases the measured reflectivities were equal to or larger (by up to a factor of 2) than the calculated values, a result attributed to uncertainty in the optical constants used in the calculations. Experimental and calculated angular-peak positions and energy resolutions were in good agreement. The high reflectivities of these molybdenum-silicon structures will make possible application of traditional optics approaches in the EUV and support new developments including free-electron lasers.

  18. Dependence of fracture toughness of molybdenum laser welds on processing parameters and in-situ oxygen gettering

    SciTech Connect

    Pope, L.E.; Jellison, J.L.

    1980-01-01

    Fracture toughness properties have been determined for laser welds in different grades of molybdenum. The fracture toughness of welds in sintered molybdenum was consistently less than the fracture toughness of welds in vacuum arc remelted molybdenum. These differences cannot be attributed to oxygen content, since the oxygen level was nominally the same for all grades of molybdenum examined in this program. Alloy additions of titanium by means of physically deposited coatings significantly improved the fracture toughness of welds in sintered molybdenum, whereas titanium additions to welds in vacuum arc remelted molybdenum decreased the fracture toughness slightly. Pulsed laser welds exhibited fine columnar structures and, in the case of sintered molybdenum, superior fracture toughness when compared with continuous wave laser welds. 6 figures, 3 tables.

  19. Evidence of High Electrocatalytic Activity of Molybdenum Carbide Supported Platinum Nanorafts

    SciTech Connect

    Elbaz, Lior; Phillips, Jonathan; Artyushkova, Kateryna; More, Karren Leslie; Brosha, Eric

    2015-01-01

    A remarkable new supported metal catalyst structure on Mo2C substrates, ‘rafts’ of platinum consisting of less than 6 atoms, was synthesized and found to be catalytically active electrocatalyst for oxygen reduction. A novel catalytic synthesis method: Reduction-Expansion-Synthesis of Catalysts (RES-C), from rapid heating of dry mixture of solid precursors of molybdenum, platinum and urea in an inert gas environment, led to the creation of unique platinum Nanorafts on Mo2C. The Pt Nanorafts offer a complete utilization of the Pt atoms for electrocatalysis with no “hidden” atoms. This structure is strongly affected by its interaction with the substrate as was observed by XPS. In this work, we show for the first time, evidence of electrocatalytic activity with such small clusters of non-crystalline Pt atoms as catalysts for oxygen reduction. Electrochemical half-cell characterization shows that this structure permit more efficient utilization of platinum, with mass activity conservatively measured to be 50% that of platinum particles generated using traditional approaches. These novel material may dramatically enhance stability relative to the commercial Pt/carbon catalysts.

  20. Reconstructing the rise of recent coastal anoxia; molybdenum in Chesapeake Bay sediments^1

    NASA Astrophysics Data System (ADS)

    Adelson, J. M.; Helz, G. R.; Miller, C. V.

    2001-01-01

    Sporadic, direct observations over a 50 yr period inadequately characterize the history of seasonal hypoxia and anoxia in Chesapeake Bay, a large estuary threatened by eutrophication. Here, we undertake a reconstruction of 20th century oxygen depletion in this estuary using Mo concentrations in 210Pb-dated sediments; Cu concentrations are used to control for anthropogenic influences. Cores from the central channel display mild Mo enrichments above crustal backgrounds (up to 5 μg/g) and strong Cu enrichments (up to 35 μg/g). Temporally, Cu enrichment (mostly anthropogenic) began earlier and stabilized in the last two thirds of the 20th century. In contrast, Mo enrichment has grown during the last two thirds of the century. Molybdenum enrichment is mostly hydrogenic, except in a section of the channel that receives additional Mo from erosion of Early Miocene shore deposits. Two geochemical mechanisms promote Mo enrichment: manganese refluxing concentrates dissolved MoO 42- at the sediment-water interface and sulfide substitution into MoO 42- produces thiomolybdates, which can be fixed by particles. The Mo enrichment mechanisms operate primarily during periods when bottom waters are anoxic and thiomolybdate formation can occur near the sediment-water interface. This implies a temporal coupling between water-column anoxia and Mo fixation even though fixation occurs only within sediments. The Mo enrichment profiles suggest that Chesapeake Bay has experienced growing O 2 depletion since the first half of the 20th century, but especially after 1960.

  1. Effects of molybdenum and silver on iodine transport in primary circuit on severe nuclear accidents

    SciTech Connect

    Kalilainen, J.; Rantanen, P.; Karkela, T.; Lipponen, M.; Auvinen, A.; Jokiniemi, J.

    2012-07-01

    This experimental study was a continuation of the study conducted at VTT to investigate the effects of reactions on primary circuit surfaces to transport of gaseous and aerosol phase iodine during the hypothetical severe nuclear accident. Cesium iodide was used as a precursor in every experiment. In the experiments it was observed that the hydrogen in the atmosphere decreased the fraction of released gaseous iodine. As the temperature was lowered, less iodine was released, but the fraction of gaseous iodine from the overall released iodine was increased. As molybdenum trioxide was introduced to the precursor, the fraction of gaseous iodine from the overall released iodine was increased significantly. Also, Mo decreased the transport of Cs and caused significant depositions to the reaction furnace. Addition of silver to the CsI precursor at 650 deg. C decreased the release of iodine as well as the fraction of gaseous iodine. At 400 deg. C, Ag + CsI as well as Ag + MoO{sub 3} + CsI precursor significantly increased the release of gaseous iodine, where almost no aerosol particles were released. With B{sub 2}O{sub 3} + CsI precursor it was observed that in the atmosphere without H{sub 2}O, the released iodine was mostly in gaseous form. (authors)

  2. Improved Irradiation Performance of Uranium-Molybdenum/Aluminum Dispersion Fuel by Silicon Addition in Aluminum

    SciTech Connect

    Yeon Soo Kim; G. L. Hofman; A. B. Robinson; D. M. Wachs

    2013-10-01

    Uranium-molybdenum fuel particle dispersion in aluminum is a form of fuel under development for conversion of high-power research and test reactors from highly enriched to low-enriched uranium in the U.S. Global Threat Reduction Initiative program (also known as the Reduced Enrichment for Research and Test Reactors program). Extensive irradiation tests have been conducted to find a solution for problems caused by interaction layer growth and pore formation between U-Mo and Al. Adding a small amount of Si (up to [approximately]5 wt%) in the Al matrix was one of the proposed remedies. The effect of silicon addition in the Al matrix was examined using irradiation test results by comparing side-by-side samples with different Si additions. Interaction layer growth was progressively reduced with increasing Si addition to the matrix Al, up to 4.8 wt%. The Si addition also appeared to delay pore formation and growth between the U-Mo and Al.

  3. Evidence of High Electrocatalytic Activity of Molybdenum Carbide Supported Platinum Nanorafts

    DOE PAGESBeta

    Elbaz, Lior; Phillips, Jonathan; Artyushkova, Kateryna; More, Karren Leslie; Brosha, Eric

    2015-01-01

    A remarkable new supported metal catalyst structure on Mo2C substrates, ‘rafts’ of platinum consisting of less than 6 atoms, was synthesized and found to be catalytically active electrocatalyst for oxygen reduction. A novel catalytic synthesis method: Reduction-Expansion-Synthesis of Catalysts (RES-C), from rapid heating of dry mixture of solid precursors of molybdenum, platinum and urea in an inert gas environment, led to the creation of unique platinum Nanorafts on Mo2C. The Pt Nanorafts offer a complete utilization of the Pt atoms for electrocatalysis with no “hidden” atoms. This structure is strongly affected by its interaction with the substrate as was observedmore » by XPS. In this work, we show for the first time, evidence of electrocatalytic activity with such small clusters of non-crystalline Pt atoms as catalysts for oxygen reduction. Electrochemical half-cell characterization shows that this structure permit more efficient utilization of platinum, with mass activity conservatively measured to be 50% that of platinum particles generated using traditional approaches. These novel material may dramatically enhance stability relative to the commercial Pt/carbon catalysts.« less

  4. Influence of oxygen concentration on mechanical properties of molybdenum powder during sintering.

    PubMed

    Lee, Back-Kyu; Oh, Jung-Min; Shon, In-Jin; Kim, Hyung-Seok; Lim, Jae-Won

    2014-12-01

    In this study, the influence of oxygen concentration on the mechanical properties of sintered bodies produced from commercial and low-oxygen molybdenum powder via pulsed-current-activated sintering was determined. The hardness of the sintered bodies increased with the sintering temperature up to 1,500 degrees C and then decreased with further temperature increase. The hardness of the sintered low-oxygen-molybdenum body was slightly higher than the rest of the sintered bodies. This was because the relative density of the sintered low-oxygen-molybdenum body increased more than that of others as the sintering temperature increased. Furthermore, the grain size of the sintered commercial-molybdenum body was larger than that of the sintered low-oxygen-molybdenum body. This was attributed to the positive effect of molybdenum oxide on grain growth during sintering. Thus, it was established that low-oxygen molybdenum powder can suppress grain growth during sintering, resulting in improved mechanical properties of the sintered bodies. PMID:25971004

  5. Contamination by slow diffusers in ion implantation processes: The examples of molybdenum and tungsten

    NASA Astrophysics Data System (ADS)

    Polignano, M. L.; Mica, I.; Barbarossa, F.; Galbiati, A.; Grasso, S.; Soncini, V.

    2015-08-01

    A procedure to measure molybdenum and tungsten contamination in implantation processes by DLTS (Deep Level Transient Spectroscopy) is defined and calibrated for the evaluation of molybdenum and tungsten contaminant dose. The obtained calibrations are used to study molybdenum contamination in BF2 implantations and tungsten contamination by sputtering from a previously contaminated wafer holder. In molybdenum-implanted samples, the molybdenum level located 0.3 eV above valence band is revealed only. In tungsten-implanted samples, two levels are revealed. One of these levels is the tungsten-related hole trap located 0.4 eV above valence band. The other level does not correspond to any tungsten-related level, however it is related to the presence of tungsten and to the sample preparation process. The SPV (Surface Photovoltage) measurement sensitivity to tungsten contamination was also tested, and it was found much lower than the DLTS sensitivity, due to the low tungsten diffusivity. This procedure was used to evaluate contamination in implantation processes. In BF2 implantations, in addition to molybdenum, tungsten contamination is found. Molybdenum and tungsten contamination is found in boron implantation too. The tungsten contamination induced by implantation in a previously contaminated implanter was quantified, and the efficiency of arsenic implantation as a decontamination process was tested. Finally, it was shown that TXRF (Total reflection X-ray Fluorescence) is much less sensitive than DLTS for monitoring tungsten contamination.

  6. Selective Autooxidation of Ethanol over Titania-Supported Molybdenum Oxide Catalysts: Structure and Reactivity

    PubMed Central

    Caro, Carlos; Thirunavukkarasu, K; Anilkumar, M; Shiju, N R; Rothenberg, Gadi

    2012-01-01

    We study the selective catalytic oxidation of ethanol with air as a sustainable alternative route to acetaldehyde. The reaction is catalysed by molybdenum oxide supported on titania, in a flow reactor under ambient pressure. High selectivity to acetaldehyde (70%–89%, depending on the Mo loading) is obtained at 150 °C. Subsequently, we investigate the structure/performance relationship for various molybdenum oxide species using a combination of techniques including diffuse reflectance UV-visible, infrared, X-ray photoelectron spectroscopies, X-ray diffraction and temperature programmed reduction. As their surface density increases, the monomeric molybdenum oxide species undergo two-dimensional and three-dimensional oligomerisation. This results in polymolybdates and molybdenum oxide crystallites. Importantly, the ethanol oxidation rate depends not only on the overall molybdenum loading and dispersion, but also on the type of molybdenum oxide species prevalent at each surface density and on the domain size. As the molybdenum oxide oligomerisation increases, electron delocalisation becomes easier. This lowers the absorption edge energy and increases the reaction rate. PMID:23396482

  7. Characterization of chlD gene required for molybdenum utilization in Escherichia coli

    SciTech Connect

    Scott, D.J.; Amy, N.K.

    1986-05-01

    ChlD mutants in E. coli have altered biochemical utilization of molybdenum from wild type cells. These mutants have reduced nitrate reductase and molybdenum cofactor activities when grown in low concentrations of molybdenum. When molybdenum is supplemented to 100..mu..M the mutants have wild type levels of both activities. In this study they have isolated a single copy episome containing the chlD gene using interrupted mating techniques as well as a multiple copy plasmid pBR322 with an insert containing the chlD gene using cloning techniques. The introduction of these additional chlD genes into a chlD mutant healed the phenotype when grown in low molybdenum concentrations. This indicates the chlD locus encodes for a transacting gene product. The restoration of phenotype was identical for both the single copy as well as multiple copy merodiploids. The pBR322 with the insert containing the chlD gene is currently being further characterized by restriction mapping. Previous studies have shown that the expression of the chlD gene as measured by ..beta..-galactosidase activity in chlD lac operon fusion mutants was high in cells grown in low molybdenum concentrations and low in cells grown in high molybdenum concentrations. This expression was unaltered when the episome containing the chlD gene was introduced into the chlD lac operon fusion mutant. This indicates that the product of the chlD gene is not required for regulation by molybdenum. The effect of multiple copies of the chlD gene on the expression of the chlD lac operon fusion is presently being studied. The eventual goal of these studies is to determine the function of the chlD gene in the activation of molybdenum.

  8. Reduced ternary molybdenum and tungsten sulfides and hydroprocessing catalysis therewith

    DOEpatents

    Hilsenbeck, S.J.; McCarley, R.E.; Schrader, G.L.; Xie, X.B.

    1999-02-16

    New amorphous molybdenum/tungsten sulfides with the general formula M{sup n+}{sub 2x/n}(L{sub 6}S{sub 8})S{sub x}, where L is molybdenum or tungsten and M is a ternary metal, has been developed. Characterization of these amorphous materials by chemical and spectroscopic methods (IR, Raman, PES) shows that the (M{sub 6}S{sub 8}){sup 0} cluster units are present. Vacuum thermolysis of the amorphous Na{sub 2x}(Mo{sub 6}S{sub 8})S{sub x}{hor_ellipsis}yMeOH first produces poorly crystalline NaMo{sub 6}S{sub 8} by disproportionation at 800 C and well-crystallized NaMo{sub 6}S{sub 8} at {>=} 900 C. Ion-exchange of the sodium material in methanol with soluble M{sup 2+} and M{sup 3+} salts (M=Sn, Co, Ni, Pb, La, Ho) produces the M{sup n+}{sub 2x/n}(Mo{sub 6}S{sub 8})S{sub x}{hor_ellipsis}yMeOH compounds. Additionally, the new reduced ternary molybdenum sulfides with the general formula M{sup n+}{sub 2x/n}Mo{sub 6}S{sub 8+x}(MeOH){sub y}[MMOS] (M=Sn, Co, Ni) is an effective hydrodesulfurization (HDS) catalyst both as-prepared and after a variety of pretreatment conditions. Under specified pretreatment conditions with flowing hydrogen gas, the SnMoS type catalyst can be stabilized, and while still amorphous, can be considered as ``Chevrel phase-like`` in that both contain Mo{sub 6}S{sub 8} cluster units. Furthermore, the small cation NiMoS and CoMoS type pretreated catalyst is shown to be very active HDS catalysts with rates that exceeded the model unpromoted and cobalt-promoted MoS{sub 2} catalysts. 9 figs.

  9. Reduced ternary molybdenum and tungsten sulfides and hydroprocessing catalysis therewith

    DOEpatents

    Hilsenbeck, Shane J.; McCarley, Robert E.; Schrader, Glenn L.; Xie, Xiaobing

    1999-02-16

    New amorphous molybdenum/tungsten sulfides with the general formula M.sup.n+.sub.2x/n (L.sub.6 S.sub.8)S.sub.x, where L is molybdenum or tungsten and M is a ternary metal, has been developed. Characterization of these amorphous materials by chemical and spectroscopic methods (IR, Raman, PES) shows that the (M.sub.6 S.sub.8).sup.0 cluster units are present. Vacuum thermolysis of the amorphous Na.sub.2x (Mo.sub.6 S.sub.8)S.sub.x .multidot.yMeOH first produces poorly crystalline NaMo.sub.6 S.sub.8 by disproportionation at 800.degree. C. and well-crystallized NaMo.sub.6 S.sub.8 at .gtoreq. 900.degree. C. Ion-exchange of the sodium material in methanol with soluble M.sup.2+ and M.sup.3+ salts (M=Sn, Co, Ni, Pb, La, Ho) produces the M.sup.n+.sub.2x/n (Mo.sub.6 S.sub.8)S.sub.x .multidot.yMeOH compounds. Additionally, the new reduced ternary molybdenum sulfides with the general formula M.sup.n+.sub.2x/n Mo.sub.6 S.sub.8+x (MeOH).sub.y ›MMOS! (M=Sn, Co, Ni) is an effective hydrodesulfurization (HDS) catalyst both as-prepared and after a variety of pretreatment conditions. Under specified pretreatment conditions with flowing hydrogen gas, the SnMoS type catalyst can be stabilized, and while still amorphous, can be considered as "Chevrel phase-like" in that both contain Mo.sub.6 S.sub.8 cluster units. Furthermore, the small cation NiMoS and CoMoS type pretreated catalyst showed to be very active HDS catalysts with rates that exceeded the model unpromoted and cobalt-promoted MoS.sub.2 catalysts.

  10. On the genesis of molybdenum carbide phases during reduction-carburization reactions

    SciTech Connect

    Guil-Lopez, R.; Nieto, E.

    2012-06-15

    Molybdenum carbide has been prepared according to the carbothermal reduction method. Carbon black substrate was used as C-source whereas a H{sub 2}-flow was the reducing agent. Two different H{sub 2} consumption steps were identified during the carburization treatment. The low temperature step is related to the reduction of Mo{sup 6+}-to-Mo{sup 4+}, the higher temperature process accounts for the deep reduction of Mo{sup 4+}-to-metal Mo{sup 0} and its subsequent reaction with C to form the Mo-carbide. The influences of the maximum carburization temperature, carburization time, gas hourly space velocity regarding Mo-loading, heating rate and temperature of Ar pre-treatment were analyzed. All these conditions are interrelated to each other. Thus, the carburization process ends at 700 Degree-Sign C when Mo-loading is 10 wt%, however Mo-loading higher than 10 wt% requires higher temperatures. Carburization temperatures up to 800 Degree-Sign C are needed to fulfill Mo-carbide formation with samples containing 50 wt% Mo. Nevertheless, Ar pre-treatment at 550 Degree-Sign C and slow heating rates favor the carburization, thus requiring lower carburization temperatures to reach the same carburization level. - Graphical Abstract: H{sub 2}-consumption profile (TPR) during the molybdenum carburization process, XRD patterns of the reduced Mo-samples after carburization and TEM-micrographs with two different enlargement of the samples with 5, 20 and 50 wt% Mo. Highlights: Black-Right-Pointing-Pointer Control of carburization variables: tailor the reduced/carbide Mo-phases (single/mixture). Black-Right-Pointing-Pointer Mo carburization in two stages: (1) Mo{sup 6+}-Mo{sup 4+}; (2) Mo{sup 4+}-Mo{sup 0} and, at once, MoC. Black-Right-Pointing-Pointer The carburization process is faster than Mo{sup 4+} reduction. Black-Right-Pointing-Pointer XPS probed: reduced Mo particles show core-shell structure. Black-Right-Pointing-Pointer Core: reduced Mo (Mo{sub 2}C, MoO{sub 2} and/or Mo

  11. Molybdenum Cycling in Upwelling Sediments: An Example from Namibian Margin Sediments

    NASA Astrophysics Data System (ADS)

    Arnold, G. L.; Goldhammer, T.; Formolo, M.; Brunner, B.; Ferdelman, T.

    2008-12-01

    The paleo-redox application of molybdenum (Mo) isotopes is strongly tied to our knowledge of the modern marine Mo cycle. Elemental mass balance indicates that ~47% of the Mo supplied to the oceans is removed to deep sea sediments, leaving the remaining Mo to "near-shore" reducing sediments (1). The Black Sea is likely the best studied reducing environment with regards to Mo isotopes, yet accounts for only a small fraction of the Mo mass balance. The accumulation of Mo in continental margin sediments has been recently re-assessed and may account for a larger fraction of the marine Mo reservoir than previously thought (2). In the presence of sulfide, the molybdate anion is transformed, by the replacement of oxygen with sulfur, to particle reactive oxy-thiomolybdates (3). This is often cited as the mechanism by which Mo removal proceeds in the Black Sea where sulfide concentrations in the water are high. In contrast, in continental margin settings, the removal mechanism is poorly understood, and the extent to which sulfur cycling plays a role remains un-quantified. To better understand removal/cycling processes in a continental margin setting, where sulfide may only be present in the pore waters and not in the water column, Mo was studied in an array of marine settings off the Namibian coast. Surface sediments were collected across a transect from near-shore/high productivity to deep water/low productivity sediments. These sediments were incubated in bag experiments to study the relationship between sulfur and Mo cycling. Molybdenum concentrations in the Namibian sediments range from detrital values at the lowest productivity site to 25 ppm in surface sediments with high productivity. Preliminary results allude to a correlation between sulfate reduction rates and Mo accumulation in these sediments. Detailed studies of Mo, Mo isotopes, other trace metals, and sulfur investigations from both sediment cores and bag experiments will be presented. (1)Bertine and Turekian

  12. Role of electron concentration in softening and hardening of ternary molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1975-01-01

    Effects of various combinations of hafnium, tantalum, rhenium, osmium, iridium, and platinum in ternary molybdenum alloys on alloy softening and hardening were determined. Hardness tests were conducted at four test temperatures over the temperature range 77 to 411 K. Results showed that hardness data for ternary molybdenum alloys could be correlated with anticipated results from binary data based upon expressions involving the number of s and d electrons contributed by the solute elements. The correlation indicated that electron concentration plays a dominant role in controlling the hardness of ternary molybdenum alloys.

  13. Comparison of effects on crustaceans: carbon nanoparticles and molybdenum compounds nanowires

    NASA Astrophysics Data System (ADS)

    Baumerte, A.; Sakale, G.; Zavickis, J.; Putna, I.; Balode, M.; Mrzel, A.; Knite, M.

    2013-04-01

    Carbon nanomaterials (CNM) and molybdenum compound nanostructures are materials with various applications yet little is known regarding the toxicity of these nanoparticles in pristine form in aquatic environment. Daphnia magna standard acute toxicity test (EN ISO 6341:1996; freshwater) and Artemia salina standard acute toxicity test (ArtoxKit standard method; 15 ppt saltwater) were applied to assess the toxicity of non-modified CNM and molybdenum compound nanowires in water. It has been observed that CNM are more toxic in freshwater suspensions and somewhat more toxic than the tested molybdenum compound nanowires.

  14. Enhanced electrochromism in cerium doped molybdenum oxide thin films

    SciTech Connect

    Dhanasankar, M.; Purushothaman, K.K.; Muralidharan, G.

    2010-12-15

    Cerium (5-15% by weight) doped molybdenum oxide thin films have been prepared on FTO coated glass substrate at 250 {sup o}C using sol-gel dip coating method. The structural and morphological changes were observed with the help of XRD, SEM and EDS analysis. The amorphous structure of the Ce doped samples, favours easy intercalation and deintercalation processes. Mo oxide films with 10 wt.% of Ce exhibit maximum anodic diffusion coefficient of 24.99 x 10{sup -11} cm{sup 2}/s and the change in optical transmittance of ({Delta}T at 550 nm) of 79.28% between coloured and bleached state with the optical density of ({Delta}OD) 1.15.

  15. Selective and efficient electrochemical biosensing of ultrathin molybdenum disulfide sheets

    NASA Astrophysics Data System (ADS)

    Narayanan, Tharangattu N.; Vusa, Chiranjeevi S. R.; Alwarappan, Subbiah

    2014-08-01

    Atomically thin molybdenum disulfide (MoS2) sheets were synthesized and isolated via solvent-assisted chemical exfoliation. The charge-dependent electrochemical activities of these MoS2 sheets were studied using positively charged hexamine ruthenium (III) chloride and negatively charged ferricyanide/ferrocyanide redox probes. Ultrathin MoS2 sheet-based electrodes were employed for the electrochemical detection of an important neurotransmitter, namely dopamine (DA), in the presence of ascorbic acid (AA). MoS2 electrodes were identified as being capable of distinguishing the coexistence of the DA and the AA with an excellent stability. Moreover, the enzymatic detection of the glucose was studied by immobilizing glucose oxidase on the MoS2. This study opens enzymatic and non-enzymatic electrochemical biosensing applications of atomic MoS2 sheets, which will supplement their established electronic applications.

  16. Wet chemical thinning of molybdenum disulfide down to its monolayer

    SciTech Connect

    Amara, Kiran Kumar; Chu, Leiqiang; Kumar, Rajeev; Toh, Minglin; Eda, Goki

    2014-09-01

    We report on the preparation of mono- and bi-layer molybdenum disulfide (MoS{sub 2}) from a bulk crystal by facile wet chemical etching. We show that concentrated nitric acid (HNO{sub 3}) effectively etches thin MoS{sub 2} crystals from their edges via formation of MoO{sub 3}. Interestingly, etching of thin crystals on a substrate leaves behind unreacted mono- and bilayer sheets. The flakes obtained by chemical etching exhibit electronic quality comparable to that of mechanically exfoliated counterparts. Our findings indicate that the self-limiting chemical etching is a promising top-down route to preparing atomically thin crystals from bulk layer compounds.

  17. Temperature effect on optical spectra of monolayer molybdenum disulfide

    NASA Astrophysics Data System (ADS)

    Soklaski, Ryan; Liang, Yufeng; Yang, Li

    2014-05-01

    Recently, measured optical absorption and photoluminescence spectra reveal substantial frequency shifts of both exciton and trion peaks as monolayer molybdenum disulfide, MoS2, is cooled from 363 K to 4 K. First-principles simulations using the GW-Bethe-Salpeter equation approach satisfactorily reproduce these frequency shifts by incorporating the thermal expansion effect. Studying these temperature effects in monolayer MoS2 is crucial for rectifying the results of available experiments with the previous predictions of zero-temperature-limit simulations. Moreover, our estimated thermal expansion coefficient of monolayer MoS2 is less than that of bulk counterpart by tracking the frequency shifts of the exciton peaks in optical spectra. This may serve as a convenient way to estimate thermal expansion coefficients of general two-dimensional chalcogenides.

  18. Molybdenum-tin as a solar cell metallization system

    NASA Astrophysics Data System (ADS)

    Boyd, D. W.; Radics, C.

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  19. Molybdenum-tin as a solar cell metallization system

    NASA Technical Reports Server (NTRS)

    Boyd, D. W.; Radics, C.

    1981-01-01

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  20. High Performance Molybdenum Disulfide Amorphous Silicon Heterojunction Photodetector

    PubMed Central

    Esmaeili-Rad, Mohammad R.; Salahuddin, Sayeef

    2013-01-01

    One important use of layered semiconductors such as molybdenum disulfide (MoS2) could be in making novel heterojunction devices leading to functionalities unachievable using conventional semiconductors. Here we demonstrate a metal-semiconductor-metal heterojunction photodetector, made of MoS2 and amorphous silicon (a-Si), with rise and fall times of about 0.3 ms. The transient response does not show persistent (residual) photoconductivity, unlike conventional a-Si devices where it may last 3–5 ms, thus making this heterojunction roughly 10X faster. A photoresponsivity of 210 mA/W is measured at green light, the wavelength used in commercial imaging systems, which is 2−4X larger than that of a-Si and best reported MoS2 devices. The device could find applications in large area electronics, such as biomedical imaging, where a fast response is critical. PMID:23907598

  1. Powder Metallurgy Fabrication of Molybdenum Accelerator Target Disks

    SciTech Connect

    Lowden, Richard Andrew; Kiggans Jr., James O.; Nunn, Stephen D.; Parten, Randy J.

    2015-12-01

    Powder metallurgy approaches for the fabrication of accelerator target disks are being examined to support the development of Mo-99 production by NorthStar Medical Technologies, LLC. An advantage of powder metallurgy is that very little material is wasted and at present, dense, quality parts are routinely produced from molybdenum powder. The proposed targets, however, are thin wafers, 29 mm in diameter with a thickness of 0.5 mm, with very stringent dimensional tolerances. Although tooling can be machined to very high tolerance levels, the operations of powder feed, pressing and sintering involve complicated mechanisms, each of which affects green density and shrinkage, and therefore the dimensions and shape of the final product. Combinations of powder morphology, lubricants and pressing technique have been explored to produce target disks with minimal variations in thickness and little or no distortion. In addition, sintering conditions that produce densities for optimum target dissolvability are being determined.

  2. Towards slide enhancement with the titanium-molybdenum wire?

    PubMed

    Thiry, Pol; Barthélémi, Stéphane

    2010-12-01

    This study aims to improve the tribological properties of titanium-molybdenum wire. Following an analysis of the wire/bracket/ligation friction parameters and an overview of the technological research into means of reducing such friction,we set up several types of surface treatment in the laboratory by physical deposition in the vapor phase and using cold plasma technology. The specimens obtained underwent two types of tribological tests and were then subjected to traction and bending tests in order to determine the variations in their mechanical properties induced by the different types of treatment. For purposes of comparison, all the tests were conducted on untreated wire, TMA® Low-friction® wire and stainless steel wire and with two types of elastomeric ties. We were able to demonstrate some remarkable slide performances obtained using cold plasma nitriding while preserving the mechanical properties. A significant difference was observed relative to the other surface treatments. PMID:21094102

  3. The Myszkow porphyry copper-molybdenum deposit, Poland

    USGS Publications Warehouse

    Chaffee, M.A.; Eppinger, R.G.; Lason, K.; Slosarz, J.; Podemski, M.

    1994-01-01

    The porphyry copper-molybdenum deposit at Myszkow, south-central Poland, lies in the Cracow-Silesian orogenic belt, in the vicinity of a Paleozoic boundary between two tectonic plates. The deposit is hosted in a complex that includes early Paleozoic metasedimentary rocks intruded in the late Paleozoic by a predominantly granodioritic pluton. This deposit exhibits many features that are typical of porphyry copper deposits associated with calc-alkaline intrusive rocks, including ore- and alteration-mineral suites, zoning of ore and alteration minerals, fluid-inclusion chemistry, tectonic setting, and structural style of veining. Unusual features of the Myszkow deposit include high concentrations of tungsten and the late Paleozoic (Variscan) age. -Authors

  4. The history of development of molybdenum alloys for structural applications

    SciTech Connect

    Wadsworth, J.; Wittenauer, J.P.

    1993-02-01

    Molybdenum was first isolated as an element in 1893 and found initial commercial application as a filament support for incandescent lamps in 1910. The advent of arc melting practice in the 1940s led to an increase in availability of Mo sheet, bar, and plate products. Alloy development programs were heavily supported starting in the 1950s and several key alloys emerged over the next twenty years that remain in use to the present time such as Mo-TZM, unalloyed Mo, and Mo-Re. In recent years, improved understanding of the role of oxygen and carbide distributions at grain boundaries have led to increased reliability and use of Mo in aerospace products. Current developmental programs in areas of propulsion and energy conversion will ensure the prominent position of Mo as a high-temperature structural material. This paper highlights some of these key developments in the evolution of Mo alloys.

  5. Predicting the stability of surface phases of molybdenum selenides

    SciTech Connect

    Roma, Guido; Ghorbani, Elaheh; Mirhosseini, Hossein; Kühne, Thomas D.; Kiss, Janos; Felser, Claudia

    2014-02-10

    The selenization of molybdenum might become an important step in the production of nanostructures based on the layered compound MoSe{sub 2}. It is already technologically relevant for the production of thin film chalcopyrite solar cells. However, the control of the process is still very poor, due to the lack of basic knowledge of the surface thermodynamics of the system. Here, we present a theoretical study on the stability of surface adlayers of Se on the Mo(110) surface, predicting surface patterns and their stability range in terms of temperature and selenium partial pressure. Our results, based on density functional theory, show that the attainable Se coverages range from 1/4 to 3/4 of a monolayer for systems in equilibrium with a gas formed of Se molecules. We provide simulated scanning tunneling microscopy images to help the experimental characterization of adsorbed surface patterns.

  6. Magnetic properties of sputtered Permalloy/molybdenum multilayers

    SciTech Connect

    Romera, M.; Ciudad, D.; Maicas, M.; Aroca, C.

    2011-10-15

    In this work, we report the magnetic properties of sputtered Permalloy (Py: Ni{sub 80}Fe{sub 20})/molybdenum (Mo) multilayer thin films. We show that it is possible to maintain a low coercivity and a high permeability in thick sputtered Py films when reducing the out-of-plane component of the anisotropy by inserting thin film spacers of a non-magnetic material like Mo. For these kind of multilayers, we have found coercivities which are close to those for single layer films with no out-of-plane anisotropy. The coercivity is also dependent on the number of layers exhibiting a minimum value when each single Py layer has a thickness close to the transition thickness between Neel and Bloch domain walls.

  7. Friction Properties of Molybdenum Alloyed Steel at Elevated Temperatures

    SciTech Connect

    Li Jianliang; Xiong Dangsheng; Wu Hongyan

    2011-01-17

    The high-temperature properties of steel surface can be improved by molybdenum surface alloying. Molybdenzing was carried out on carbon steel in the multi-function double glow plasma surface alloying furnace. The friction and wear tests were conducted on a high temperature ball-on-disk tribometer under the temperature of 25 deg. C{approx}600 deg. C. The contents of alloy element varied with alloyed layer were detected by SEM attached with EDS. The molybdenized layer is composed of the deposited layer and diffused layer. The micro-hardness of alloyed layer decreases from HV650 on the top layer to HV240. The friction coefficient of molybdenized layer decreases from 0.5{approx}0.6 to 0.2{approx}0.3 and wear rate decreases by 20% at elevated temperature after molybdenizing.

  8. Temperature effect on optical spectra of monolayer molybdenum disulfide

    SciTech Connect

    Soklaski, Ryan; Liang, Yufeng; Yang, Li

    2014-05-12

    Recently, measured optical absorption and photoluminescence spectra reveal substantial frequency shifts of both exciton and trion peaks as monolayer molybdenum disulfide, MoS{sub 2}, is cooled from 363 K to 4 K. First-principles simulations using the GW-Bethe-Salpeter equation approach satisfactorily reproduce these frequency shifts by incorporating the thermal expansion effect. Studying these temperature effects in monolayer MoS{sub 2} is crucial for rectifying the results of available experiments with the previous predictions of zero-temperature-limit simulations. Moreover, our estimated thermal expansion coefficient of monolayer MoS{sub 2} is less than that of bulk counterpart by tracking the frequency shifts of the exciton peaks in optical spectra. This may serve as a convenient way to estimate thermal expansion coefficients of general two-dimensional chalcogenides.

  9. Spreading of Viscous Liquids at High Temperature: Silicate Glasseson Molybdenum

    SciTech Connect

    Lopez-Esteban, Sonia; Saiz, Eduardo; Moya, Jose S.; Tomsia,Antoni P.

    2004-12-15

    The spreading of Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. By controlling the oxygen activity in the furnace, spreading can take place under reactive or non-reactive conditions. As the nucleation of the reaction product under reactive conditions is slow in comparison to the spreading kinetics, in both cases the glass front moves on the metal surface with similar spreading velocities. Spreading can be described using a molecular dynamics model where the main contribution to the wetting activation energy comes from the viscous interactions in the liquid. Enhanced interfacial diffusions in low-oxygen activities (reactive cases) form triple-line ridges that can pin the wetting front and cause a stick-slip motion.

  10. Study of molybdenum electrodes for hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Padilha, Janine Carvalho; Martini, Emilse Maria Agostini; Brum, Cauã; de Souza, Michèle Oberson; de Souza, Roberto Fernando

    The molybdenum electrode, Mo, has been investigated for hydrogen production via water electrolysis in 10 vol.% aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF 4) using electrochemical impedance spectroscopy (EIS). The EIS measurements show that the Mo system has much higher interfacial capacitance, and correspondently the electrical double layer formed on this electrode is thicker than those formed on nickel or platinum. The positive displacement of potential of zero charge (PZC) values indicates the specific adsorption of the imidazolium cation on the Mo surface. This study provides an elegant explanation for the better performance of Mo electrodes in the hydrogen evolution reaction (HER): the BMI cation acts as an intermediate for the proton transfer from water to the electrode surface, thereby decreasing the overpotential of HER. This model explains the synergism between Mo and the BMI cation in the HER process.

  11. Plasma-flash radiography utilizing a molybdenum target in dentistry

    SciTech Connect

    Yamamoto, Mariko; Takabe, Akihito; Sakamaki, Kimio

    1995-12-31

    The construction and the radiographic characteristics of a plasma flash x-ray generator having a molybdenum-target (anode tip) triode are described. This generator was primarily designed in order to perform soft radiography in dental medicine and employed the following essential components: a high-voltage power supply, a low-impedance coaxial transmission line with a gap switch, a coaxial oil condenser of 0.2 {micro}F, a turbo-molecular pump, a Krytron pulser as a trigger device, and a flash x-ray tube. The high-voltage main condenser of 0.2 {micro}F was charged from 40 to 60 kV by the power supply, and the electric charges in the condenser were discharged to the tube after closing the gap switch. Because this tube employed a long target, the plasma x-ray source which consists of molybdenum ions and electrons was easily produced by the target evaporating. The maximum tube voltage was nearly equivalent to the initial charging voltage of the main condenser, and the maximum current had a value of about 25 kA with a charging voltage of 60 kV. The average width of flash x rays was less than 1 {micro}s, and the time-integrated x-ray intensity with a charging voltage of 60 kV was approximately 20 {micro}C/kg at 1.0 m per pulse. The characteristic K-series intensity substantially increased according to increases in the charging voltage. High-speed dental radiography was performed by using a laser timing switch and a trigger-delay device.

  12. Soil organic matter regulates molybdenum storage and mobility in forests

    USGS Publications Warehouse

    Marks, Jade A; Perakis, Steven; King, Elizabeth K; Pett-Ridge, Julie

    2015-01-01

    The trace element molybdenum (Mo) is essential to a suite of nitrogen (N) cycling processes in ecosystems, but there is limited information on its distribution within soils and relationship to plant and bedrock pools. We examined soil, bedrock, and plant Mo variation across 24 forests spanning wide soil pH gradients on both basaltic and sedimentary lithologies in the Oregon Coast Range. We found that the oxidizable organic fraction of surface mineral soil accounted for an average of 33 %of bulk soil Mo across all sites, followed by 1.4 % associated with reducible Fe, Al, and Mn-oxides, and 1.4 % in exchangeable ion form. Exchangeable Mo was greatest at low pH, and its positive correlation with soil carbon (C) suggests organic matter as the source of readily exchangeable Mo. Molybdenum accumulation integrated over soil profiles to 1 m depth (τMoNb) increased with soil C, indicating that soil organic matter regulates long-term Mo retention and loss from soil. Foliar Mo concentrations displayed no relationship with bulk soil Mo, and were not correlated with organic horizon Mo or soil extractable Mo, suggesting active plant regulation of Mo uptake and/or poor fidelity of extractable pools to bioavailability. We estimate from precipitation sampling that atmospheric deposition supplies, on average, over 10 times more Mo annually than does litterfall to soil. In contrast, bedrock lithology had negligible effects on foliar and soil Mo concentrations and on Mo distribution among soil fractions. We conclude that atmospheric inputs may be a significant source of Mo to forest ecosystems, and that strong Mo retention by soil organic matter limits ecosystem Mo loss via dissolution and leaching pathways.

  13. Plasma-flash radiography utilizing a molybdenum target in dentistry

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mariko; Takabe, Akihito; Sakamaki, Kimio; Sato, Eiichi; Takahashi, Kei; Sagae, Michiaki; Oizumi, Teiji; Hayasi, Yasuomi; Sasaki, Katsuaki; Tamakawa, Yoshiharu; Yanagisawa, Toru

    1995-09-01

    The construction and the radiographic characteristics of a plasma flash x-ray generator having a molybdenum-target (anode tip) triode are described. This generator was primarily designed in order to perform soft radiography in dental medicine and employed the following essential components: a high-voltage power supply, a low-impedance coaxial transmission line with a gap switch, a coaxial oil condenser of 0.2 (mu) F, a turbo-molecular pump, a Krytron pulser as a trigger device, and a flash x-ray tube. The high-voltage main condenser of 0.2 (mu) F was charged from 40 to 60 kV by the power supply, and the electric charges in the condenser were discharged to the tube after closing the gap switch. Because this tube employed a long target, the plasma x-ray source which consists of molybdenum ions and electrons was easily produced by the target evaporating. The maximum tube voltage was nearly equivalent to the initial charge voltage of the main condenser, and the maximum current had a value of about 25 kA with a charging voltage of 60 kV. The average width of flash x rays was less than 1 microsecond(s) , and the time-integrated x-ray intensity with a charging voltage of 60 kV was approximately 20 (mu) C/kg at 1.0 m per pulse. The characteristic K-series intensity substantially increased according to increases in the charged voltage. High-speed dental radiography was performed using a laser timing switch and a trigger-delay device.

  14. Contamination of water and soil by the Erdenet copper-molybdenum mine in Mongolia

    NASA Astrophysics Data System (ADS)

    Battogtokh, B.; Lee, J.; Woo, N. C.; Nyamjav, A.

    2013-12-01

    As one of the largest copper-molybdenum (Cu-Mo) mines in the world, the Erdenet Mine in Mongolia has been active since 1978, and is expected to continue operations for at least another 30 years. In this study, the potential impacts of mining activities on the soil and water environments have been evaluated. Water samples showed high concentrations of sulfate, calcium, magnesium, Mo, and arsenic, and high pH values in the order of high to low as follows: tailing water > Khangal River > groundwater. Statistical analysis and the δ2H and δ18O values of water samples indicate that the tailing water directly affects the stream water and indirectly affects groundwater through recharge processes. Soil and stream sediments are highly contaminated with Cu and Mo, which are major elements of ore minerals. Based on the contamination factor (CF), the pollution load index (PLI), and the degree of contamination (Cd), soil appears to be less contaminated than stream sediments. The soil particle size is similar to that of tailing materials, but stream sediments have much coarser particles, implying that the materials have different origins. Contamination levels in stream sediments display a tendency to decrease with distance from the mine, but no such changes are found in soil. Consequently, soil contamination by metals is attributable to wind-blown dusts from the tailing materials, and stream sediment contamination is caused by discharges from uncontained subgrade ore stock materials. Considering the evident impact on the soil and water environment, and the human health risk from the Erdenet Mine, measures to mitigate its environmental impact should be taken immediately including source control, the establishment of a systematic and continuous monitoring system, and a comprehensive risk assessment. Sampling locations around the Erdenet Mine

  15. Molybdenum and tungsten nanostructures and methods for making and using same

    DOEpatents

    Kotaro, Sasaki; Chen, Wei-Fu; Muckerman, James T; Adzic, Radoslav R

    2015-01-06

    The present invention provides molybdenum and tungsten nanostructures, for example, nanosheets and nanoparticles, and methods of making and using same, including using such nanostructures as catlysts for hydrogen evolution reactions.

  16. Mapping the formation areas of giant molybdenum blue clusters: a spectroscopic study

    SciTech Connect

    Botar, Bogdan; Ellern, Arkady; Kogerler, Paul

    2012-05-18

    The self-assembly of soluble molybdenum blue species from simple molybdate solutions has primarily been associated with giant mixed-valent wheel-shaped cluster anions, derived from the {MoV/VI154/176} archetypes, and a {MoV/VI368} lemon-shaped cluster. The combined use of Raman spectroscopy and kinetic precipitation as self-assembly monitoring techniques and single-crystal X-ray diffraction is key to mapping the realm of molybdenum blue species by establishing spherical {MoV/VI102}-type Keplerates as an important giant molybdenum blue-type species. We additionally rationalize the empirical effect of reducing agent concentration on the formation of all three relevant skeletal types: wheel, lemon and spheres. Whereas both wheels and the lemon-shaped {MoV/VI368} cluster are obtained from weakly reduced molybdenum blue solutions, considerably higher reduced solutions lead to {MoV/VI102}-type Keplerates.

  17. Alkene to carbyne: tandem Lewis acid activation and dehydrogenation of a molybdenum ethylene complex.

    PubMed

    Stennett, Tom E; Haddow, Mairi F; Wass, Duncan F

    2013-10-18

    Carbyne formation: Treatment of a molybdenum ethylene complex with B(C6 F5 )3 induces ditopic activation of an ethylene ligand and acceptor-assisted ethane elimination to generate a novel type of zwitterionic carbyne complex. PMID:24038792

  18. High-strength, creep-resistant molybdenum alloy and process for producing the same

    DOEpatents

    Bianco, Robert; Buckman, Jr., R. William; Geller, Clint B.

    1999-01-01

    A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2-4% by volume (.about.1-4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T.sub.m of molybdenum.

  19. Influence of organic amendments on the mobilization of molybdenum in soils

    SciTech Connect

    Calderone, S.J.; Frankenberger, W.T. Jr. )

    1990-08-01

    Recent attention has been focused on toxic levels of selenium (Se), arsenic, chromium, mercury, boron and molybdenum (Mo) accumulating in saline agricultural evaporation pond waters. Although this is an effective disposal practice for agricultural drainage water, the ponds attract wildlife and waterfowl which may create adverse environmental risks. There is a major concern with the Mo content in these saline waters and its effect on the upper food chain. Molybdenum can be fixed in soil or liberated into soil solution and become available for biotic uptake. Molybdenum is a metallic element that can exist in different valences and oxidation states. Oxidation and alkaline conditions favor Mo mobility. The objective of this study was to determine the effect of various organic materials on the solubilization and mobilization of molybdenum in soil.

  20. High-strength, creep-resistant molybdenum alloy and process for producing the same

    SciTech Connect

    Bianco, Robert; Buckman, Jr. William R.; Geller, Clint B.

    1997-12-01

    A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2--4% by volume ({approximately}1--4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T{sub m} of molybdenum.

  1. Reactions of a Dinitrogen Complex of Molybdenum: Formation of a Carbon-Nitrogen Bond.

    ERIC Educational Resources Information Center

    Busby, David C.; And Others

    1981-01-01

    Reports a procedure for the formation of alkyldiazenido complexes of molybdenum in the absence of dioxygen, suitable for inclusion in an advanced inorganic chemistry laboratory. Includes background information and experimental procedures for two complexes. (SK)

  2. Mapping the formation areas of giant molybdenum blue clusters: a spectroscopic study.

    PubMed

    Botar, Bogdan; Ellern, Arkady; Kögerler, Paul

    2012-08-01

    The self-assembly of soluble molybdenum blue species from simple molybdate solutions has primarily been associated with giant mixed-valent wheel-shaped cluster anions, derived from the {Mo(V/VI)(154/176)} archetypes, and a {Mo(V/VI)(368)} lemon-shaped cluster. The combined use of Raman spectroscopy and kinetic precipitation as self-assembly monitoring techniques and single-crystal X-ray diffraction is key to mapping the realm of molybdenum blue species by establishing spherical {Mo(V/VI)(102)}-type Keplerates as an important giant molybdenum blue-type species. We additionally rationalize the empirical effect of reducing agent concentration on the formation of all three relevant skeletal types: wheel, lemon and spheres. Whereas both wheels and the lemon-shaped {Mo(V/VI)(368)} cluster are obtained from weakly reduced molybdenum blue solutions, considerably higher reduced solutions lead to {Mo(V/VI)(102)}-type Keplerates. PMID:22717474

  3. Structural and morphological properties of mesoporous carbon coated molybdenum oxide films

    NASA Astrophysics Data System (ADS)

    Dayal, Saurabh; Kumar, C. Sasi

    2016-05-01

    In the present study, we report the structural and morphological properties of mesoporous carbon coated molybdenum oxide films. The deposition of films was carried out in a two-step process, the first step involves deposition of molybdenum and carbon bilayer thin films using DC magnetron sputtering. In the second step the sample was ex-situ annealed in a muffle furnace at different temperatures (400°C to 600°C) and air cooled in the ambient atmosphere. The formation of the meso-porous carbon clusters on molybdenum oxide during the cooling step was investigated using FESEM and AFM techniques. The structural details were explored using XRD. The meso-porous carbon were found growing over molybdenum oxide layer as a result of segregation phenomena.

  4. High-strength, creep-resistant molybdenum alloy and process for producing the same

    DOEpatents

    Bianco, R.; Buckman, R.W. Jr.; Geller, C.B.

    1999-02-09

    A wet-doping process for producing an oxide-dispersion strengthened (ODS), creep-resistant molybdenum alloy is disclosed. The alloy is made by adding nitrate or acetate salts of lanthanum, cerium, thorium, or yttrium to molybdenum oxide to produce a slurry, heating the slurry in a hydrogen atmosphere to produce a powder, mixing and cold isostatically pressing the powder, sintering in a hydrogen atmosphere, and thermomechanically processing (swaging, extruding, cold drawing) the product. The ODS molybdenum alloy produced by the process contains 2--4% by volume (ca. 1--4% by weight) of an oxide of lanthanum, cerium, thorium, or yttrium. The alloy has high strength and improved creep-resistance at temperatures greater than 0.55T{sub m} of molybdenum. 10 figs.

  5. In vitro synthesis of the iron-molybdenum cofactor of nitrogenase from iron, sulfur, molybdenum, and homocitrate using purified proteins.

    PubMed

    Curatti, Leonardo; Hernandez, Jose A; Igarashi, Robert Y; Soboh, Basem; Zhao, Dehua; Rubio, Luis M

    2007-11-01

    Biological nitrogen fixation, the conversion of atmospheric N2 to NH3, is an essential process in the global biogeochemical cycle of nitrogen that supports life on Earth. Most of the biological nitrogen fixation is catalyzed by the molybdenum nitrogenase, which contains at its active site one of the most complex metal cofactors known to date, the iron-molybdenum cofactor (FeMo-co). FeMo-co is composed of 7Fe, 9S, Mo, R-homocitrate, and one unidentified light atom. Here we demonstrate the complete in vitro synthesis of FeMo-co from Fe(2+), S(2-), MoO4(2-), and R-homocitrate using only purified Nif proteins. This synthesis provides direct biochemical support to the current model of FeMo-co biosynthesis. A minimal in vitro system, containing NifB, NifEN, and NifH proteins, together with Fe(2+), S(2-), MoO4(2-), R-homocitrate, S-adenosyl methionine, and Mg-ATP, is sufficient for the synthesis of FeMo-co and the activation of apo-dinitrogenase under anaerobic-reducing conditions. This in vitro system also provides a biochemical approach to further study the function of accessory proteins involved in nitrogenase maturation (as shown here for NifX and NafY). The significance of these findings in the understanding of the complete FeMo-co biosynthetic pathway and in the study of other complex Fe-S cluster biosyntheses is discussed. PMID:17978192

  6. The Application of Gravity and CSAMT Survey on Baishan Molybdenum Deposit, Hami, Xinjiang,China

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Lu, H.; Zhang, K.

    2014-12-01

    Baishan molybdenum deposit is located in the eastern Tianshan Carboniferous rift at Hami, Xinjiang, China, where exposed upper Carboniferous Gandun formation. Molybdenum ore appeared at thermal contact metamorphism hornfelsed banded quartz stockwork in the concealed porphyritic granite top, Potassium and metal sulfide mineralization existed in the top of concealed rockbody.The Baishan molybdenum ore bodies were delineated 2700 meters long and 40 meters thickness, with molybdenum @ 0.59%. The main orebody shows in stratoid, small orebody appears in lenticular and vein.In order to predict potential resources, we proposes a combined method of CSAMT and GS technology,and has applied it to the survey of concealed molybdenum deposit in the Baishan.This combind method can explore to larger depths, discriminate anomalies well and has higher resolution to deep objects, thus it is an efficient tool for surveys.By drilling, we found there exsit a hidden granite body in 1400 meters deep of Hami Baishan molybdenum mine, it confirmed that Baishan molybdenum mine is a porphyry molybdenum ore. Cataclastic hornfelsed zone in the coping granite are the product of heat contact metamorphism, the ore materials are mainly derived from deep magma hydrothermal solution. The CSAMT and Gravity Survey were able to reflect the space and intrusive boundary in rough of buried granite body clearly, deep hidden granite showed high-resistivity and high-gravity anomaly and the low-resistivity anomaly distributied around them, drilling verified that 200-2500Ω low-resistivity anomaly range at top of high-resistivity corresponded to the molybdenum ore horizon. Line 15 of southern section shows two low resistance anomaly zone, and the surface of them is corresponding to the granite and intrusive contact parts,inferring it was caused by the fault structure.In granite gravity anomaly is obviously high and the width is about 560m,Δg residual value is 400 × 10-8m/s2. According to the control of

  7. Material and Energy Flows Associated with Select Metals in GREET 2. Molybdenum, Platinum, Zinc, Nickel, Silicon

    SciTech Connect

    Benavides, Pahola T.; Dai, Qiang; Sullivan, John L.; Kelly, Jarod C.; Dunn, Jennifer B.

    2015-09-01

    In this work, we analyzed the material and energy consumption from mining to production of molybdenum, platinum, zinc, and nickel. We also analyzed the production of solar- and semiconductor-grade silicon. We described new additions to and expansions of the data in GREET 2. In some cases, we used operating permits and sustainability reports to estimate the material and energy flows for molybdenum, platinum, and nickel, while for zinc and silicon we relied on information provided in the literature.

  8. Substoichiometric two-dimensional molybdenum oxide flakes: a plasmonic gas sensing platform

    NASA Astrophysics Data System (ADS)

    Alsaif, Manal M. Y. A.; Field, Matthew R.; Murdoch, Billy J.; Daeneke, Torben; Latham, Kay; Chrimes, Adam F.; Zoolfakar, Ahmad Sabirin; Russo, Salvy P.; Ou, Jian Zhen; Kalantar-Zadeh, Kourosh

    2014-10-01

    Two-dimensional (2D) molybdenum oxides at their various stoichiometries are promising candidates for generating plasmon resonances in visible light range. Herein, we demonstrate plasmonic 2D molybdenum oxide flakes for gas sensing applications, in which hydrogen (H2) is selected as a model gas. The 2D molybdenum oxide flakes are obtained using a grinding-assisted liquid exfoliation method and exposed to simulated sunlight to acquire its substoichiometric quasi-metallic form. After the exposure to H2 gas molecules, the quasi-metallic molybdenum oxide flakes are partially transformed into semiconducting states, thus gradually losing their plasmonic properties. The novel 2D plasmonic sensing platform is tested using different concentrations of H2 gas at various operating temperatures to comprehensively assess its sensing performance. The presented 2D plasmonic system offers great opportunities for future sensing and optical applications.Two-dimensional (2D) molybdenum oxides at their various stoichiometries are promising candidates for generating plasmon resonances in visible light range. Herein, we demonstrate plasmonic 2D molybdenum oxide flakes for gas sensing applications, in which hydrogen (H2) is selected as a model gas. The 2D molybdenum oxide flakes are obtained using a grinding-assisted liquid exfoliation method and exposed to simulated sunlight to acquire its substoichiometric quasi-metallic form. After the exposure to H2 gas molecules, the quasi-metallic molybdenum oxide flakes are partially transformed into semiconducting states, thus gradually losing their plasmonic properties. The novel 2D plasmonic sensing platform is tested using different concentrations of H2 gas at various operating temperatures to comprehensively assess its sensing performance. The presented 2D plasmonic system offers great opportunities for future sensing and optical applications. Electronic supplementary information (ESI) available: Details on optical gas measurement setup and

  9. Molybdenum-copper and tungsten-copper alloys and method of making

    DOEpatents

    Schmidt, Frederick A.; Verhoeven, John D.; Gibson, Edwin D.

    1989-05-23

    Molybdenum-copper and tungsten-copper alloys are prepared by a consumable electrode method in which the electrode consists of a copper matrix with embedded strips of refractory molybdenum or tungsten. The electrode is progressively melted at its lower end with a superatmospheric inert gas pressure maintained around the liquifying electrode. The inert gas pressure is sufficiently above the vapor pressure of copper at the liquidus temperature of the alloy being formed to suppress boiling of liquid copper.

  10. Molybdenum-copper and tungsten-copper alloys and method of making

    DOEpatents

    Schmidt, F.A.; Verhoeven, J.D.; Gibson, E.D.

    1989-05-23

    Molybdenum-copper and tungsten-copper alloys are prepared by a consumable electrode method in which the electrode consists of a copper matrix with embedded strips of refractory molybdenum or tungsten. The electrode is progressively melted at its lower end with a superatmospheric inert gas pressure maintained around the liquefying electrode. The inert gas pressure is sufficiently above the vapor pressure of copper at the liquidus temperature of the alloy being formed to suppress boiling of liquid copper. 6 figs.

  11. Rapid chemical test for the identification of chromium-molybdenum steel

    NASA Technical Reports Server (NTRS)

    Redmond, John C

    1932-01-01

    This note describes a simple, rapid, qualitative test which can be applied to solutions of drilling or chips for the identification of chromium-molybdenum steel. The test is based on the orange-red compound which is formed when thiocyanate and inequivalent molybdenum react. This test is much more reliable than the potassium ethylxanthate test which has been recommended for a like purpose. A list of the apparatus and reagents which are required, and a description of the procedure follows.

  12. Electrochemical way of molybdenum extraction from the Bimetallic systems of Mo-W

    NASA Astrophysics Data System (ADS)

    Kudreeva, L. K.; Nauryzbaev, M. K.; Kurbatov, A. P.; Kamysbaev, D. H.; Adilbekova, A. O.; Mukataeva, Z. S.

    2015-12-01

    Electrochemical dissolution of molybdenum and tungsten was investigated in water- dimethylsulfoxide (DMSO) media at different concentrations of lithium chloride and magnesium perchlorate. The terms of efficient extraction of molybdenum from bimetallic systems of Mo-W have been determined. The polarization curves of the electrooxidation of molybdenum in the solution of 0.25 M LiCl in the DMSO at the different rates of rotations and the scan rate equal to 50 mV/s were obtained. In the presence of the addition of water at the potential of 0.1-0.75 V the small area of polarizability occurs, then with increasing potentials above 1.5 V there is a sharp increase of the oxidation current. Comparison of the current values of anodic dissolution of molybdenum and tungsten showed that the rate of anodic dissolution of molybdenum significantly exceeds the rate of anodic dissolution of tungsten. In the case of molybdenum, the dissolution process is limited by diffusion, in the case of tungsten - by the passive film formation on the electrode surface.

  13. Environmental exposure to metals and male reproductive hormones: Circulating testosterone is inversely associated with blood molybdenum

    PubMed Central

    Meeker, John D.; Rossano, Mary G.; Protas, Bridget; Padmanabhan, Vasantha; Diamond, Michael P.; Puscheck, Elizabeth; Daly, Douglas; Paneth, Nigel; Wirth, Julia J.

    2010-01-01

    Study Objective To explore associations between exposure to metals and male reproductive hormone levels. Design Cross-sectional epidemiology study with adjustment for potential confounders. Setting Metal concentrations and reproductive hormone levels were measured in blood samples collected from 219 men. Patients: Men recruited through two Michigan, USA infertility clinics. Interventions None Main Outcome Measures Serum FSH, LH, inhibin B, testosterone, and SHBG. Results Cadmium, copper and lead were all significantly or suggestively positively associated with testosterone when modeled individually (p-values = 0.1, 0.03, and 0.07, respectively), findings that are consistent with limited previous human and animal studies. Conversely, molybdenum was associated with reduced testosterone (p-value for trend = 0.001). A significant inverse trend between molybdenum and testosterone remained when additionally considering other metals in the model, where a positive association between testosterone and zinc was also found. Finally, in exploratory analysis there was evidence for an interaction between molybdenum and zinc, where high molybdenum was associated with a 37% reduction in testosterone (relative to the population median level) among men with low zinc. Conclusions While reductions in testosterone and reproductive toxicity following molybdenum exposure have been previously demonstrated in animal studies, more research is needed to determine whether molybdenum poses a risk to human reproductive health. PMID:18990371

  14. Calculated mammographic spectra confirmed with attenuation curves for molybdenum, rhodium, and tungsten targets.

    PubMed

    Blough, M M; Waggener, R G; Payne, W H; Terry, J A

    1998-09-01

    A model for calculating mammographic spectra independent of measured data and fitting parameters is presented. This model is based on first principles. Spectra were calculated using various target and filter combinations such as molybdenum/molybdenum, molybdenum/rhodium, rhodium/rhodium, and tungsten/aluminum. Once the spectra were calculated, attenuation curves were calculated and compared to measured attenuation curves. The attenuation curves were calculated and measured using aluminum alloy 1100 or high purity aluminum filtration. Percent differences were computed between the measured and calculated attenuation curves resulting in an average of 5.21% difference for tungsten/aluminum, 2.26% for molybdenum/molybdenum, 3.35% for rhodium/rhodium, and 3.18% for molybdenum/rhodium. Calculated spectra were also compared to measured spectra from the Food and Drug Administration [Fewell and Shuping, Handbook of Mammographic X-ray Spectra (U.S. Government Printing Office, Washington, D.C., 1979)] and a comparison will also be presented. PMID:9775364

  15. DsbA2 (27 kDa Com1-like protein) of Legionella pneumophila catalyses extracytoplasmic disulphide-bond formation in proteins including the Dot/Icm type IV secretion system.

    PubMed

    Jameson-Lee, Max; Garduño, Rafael A; Hoffman, Paul S

    2011-05-01

    In Gram-negative bacteria, thiol oxidoreductases catalyse the formation of disulphide bonds (DSB) in extracytoplasmic proteins. In this study, we sought to identify DSB-forming proteins required for assembly of macromolecular structures in Legionella pneumophila. Here we describe two DSB-forming proteins, one annotated as dsbA1 and the other annotated as a 27 kDa outer membrane protein similar to Com1 of Coxiella burnetii, which we designate as dsbA2. Both proteins are predicted to be periplasmic, and while dsbA1 mutants were readily isolated and without phenotype, dsbA2 mutants were not obtained. To advance studies of DsbA2, a cis-proline residue at position 198 was replaced with threonine that enables formation of stable disulphide-bond complexes with substrate proteins. Expression of DsbA2 P198T mutant protein from an inducible promoter produced dominant-negative effects on DsbA2 function that resulted in loss of infectivity for amoeba and HeLa cells and loss of Dot/Icm T4SS-mediated contact haemolysis of erythrocytes. Analysis of captured DsbA2 P198T-substrate complexes from L. pneumophila by mass spectrometry identified periplasmic and outer membrane proteins that included components of the Dot/Icm T4SS. More broadly, our studies establish a DSB oxidoreductase function for the Com1 lineage of DsbA2-like proteins which appear to be conserved among those bacteria also expressing T4SS. PMID:21375592

  16. Nanoparticles of Molybdenum Chlorophyllin Photosensitizer and Magnetic Citrate-Coated Cobalt Ferrite Complex Available to Hyperthermia and Photodynamic Therapy Clinical Trials

    NASA Astrophysics Data System (ADS)

    Primo, Fernando L.; Cordo, Paloma L. A. G.; Neto, Alberto F.; Morais, Paulo C.; Tedesco, Antonio C.

    2010-12-01

    This study report on the synthesis and characterization of molybdenum chlorophyllin (Mo-Chl) compounds associated in a complex with magnetic nanoparticles (citrate-coated cobalt ferrite), the latter prepared as a biocompatible magnetic fluid (MF). The complex material was developed for application as a synergic drug for cancer treatment using Photodynamic Therapy (PDT) and Hyperthermia (HPT). Chlorophyllin was obtained from alkaline extraction of Ilex paraguariensis following molybdenum insertion from hydrolysis with molybdate sodium. Fluorescence quantum yield (Φf) of Mo-Chl/dimethyl-sulphoxide (DMSO) was lower than 0.1, with a lifetime of 5.0 ns, as obtained from time-correlated single-photon counting technique. The oxygen quantum yield of Mo-Chl was carried out using laser flash-photolysis studies in homogeneous medium saturated with O2(g) (ΦΔ = 0.50). Cellular viability was also evaluated via the classical MTT assay using gingival fibroblasts cells as a biological model. Studies performed with the complex Mo-Chl (5.0 μmol.L-1)/MF at different magnetic nanoparticle concentrations (ranging from 1012 to 1015 particle.mL-1) revealed a cellular viability of approximately 95% for the ideal magnetic material concentration of 1×10 particle.mL-1. The present study shows that natural photosensitizers molecules Mo-Chl used in association with magnetic nanoparticles represent a promising generation of drug developed to work synergistically in the treatment of neoplastic tissues using PDT and HPT.

  17. Synthesis, characterization, and reactivity of sulfided hexanuclear molybdenum cluster compounds

    SciTech Connect

    Spink, D.

    1990-09-21

    Hexanuclear molybdenum clusters with mixed chloride and sulfide bridging ligands were prepared by reacting {alpha}-MoCl{sub 2} with sodium hydrosulfide in the presence of sodium butoxide. The resulting species, Mo{sub 6}Cl{sub (8-x)}S{sub x}{center dot}npy(x {congruent} 3.6, n {congruent} 4, py = pyridine), was pyrophoric and insoluble. The mixed sulfide chloride cluster species Mo{sub 6}S{sub 4}Cl{sub 4}{center dot}6OPEt{sub 3} and Mo{sub 6}S{sub {approximately}5}Cl{sub {approximately}3}{center dot}6PEt{sub 3} and Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3} were isolated and characterized. Phosphorus-31 nuclear magnetic resonance, electron paramagnetic resonance, and UV/visible spectra were obtained for each fraction. The completely sulfided cluster, Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3}, was prepared similarly and used in various experiments as a possible precursor to Chevrel phase materials of the type Mo{sub 6}S{sub 8}or M{sub n}Mo{sub 6}S{sub 8}. With the goal of removing all of the triethylphosphine ligands, Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3} was reacted with the transition metal carbonyls molybdenum hexacarbonyl and dicobalt octacarbonyl. Reaction on the molecular sulfide cluster with copper(I) chloride in toluene gave a completely insoluble product. The reaction of Mo{sub 6}S{sub 8}{center dot}6PEt{sub 3} with propylene sulfide gave a product whose infrared spectra showed only very weak peaks associated with coordinated triethylphosphine. The elemental analysis of this product fit the formula Mo{sub 6}S{sub 8}{center dot}5SPEt{sub 3}. Reactivity of the outer ligands of the Mo{sub 6}S{sub 8}{center dot}npy and Mo{sub 6}S{sub 8}{center dot}(6{minus}x)PrNH{sub x} clusters were investigated. Crystalline Mo{sub 6}S{sub 8}{center dot}6THT was recovered from the reaction of the n-propylamine derivative with THT. A crystal structure determination was done. 87 refs., 12 fig., 15 tabs.

  18. The bioconcentration and bioaccumulation factors for molybdenum in the aquatic environment from natural environmental concentrations up to the toxicity boundary.

    PubMed

    Regoli, Lidia; Van Tilborg, Wim; Heijerick, Dagobert; Stubblefield, William; Carey, Sandra

    2012-10-01

    In a regulatory context, bioaccumulation or bioconcentration factors are used for considering secondary poisoning potential and assessing risks to human health via the food chain. In this paper, literature data on the bioaccumulation of molybdenum in the aquatic organisms are reviewed and assessed for relevance and reliability. The data available in the literature were generated at exposure concentrations below those recommended in the REACH registration dossiers for molybdenum compounds i.e. PNEC(freshwater) 12.7 mg Mo/L. To address possible environmental concerns at regulatorily-relevant molybdenum concentrations, both a field study and a laboratory study were conducted. In the field study, whole body and organ-specific molybdenum levels were evaluated in fish (eel, stickleback, perch, carp bream, roach) held in the discharge water collector tanks of a molybdenum processing plant, containing a mean measured molybdenum level of 1.03 mg Mo/L. In the laboratory study, rainbow trout were exposed to two different nominal molybdenum levels (1.0 and 12.7 mg Mo/L), for 60 days followed by a 60-day depuration period. Whole body concentrations in rainbow trout during the exposure period were between <0.20 and 0.53 mg Mo/L. Muscle tissue molybdenum concentrations in fish taken from both experiments remained below 0.2mg/kg dry wt. These studies show an inverse relationship between exposure concentration and bioconcentration or bioaccumulation factor for molybdenum. In aquatic organisms, and in fish in particular, internal molybdenum concentrations are maintained in the presence of variation in external molybdenum concentrations. These observations must be considered when evaluating potential risks associated with the bioconcentration and/or bioaccumulation of molybdenum in the aquatic environment. PMID:22846769

  19. A Method for the Calculation of Lattice Energies of Complex Crystals with Application to the Oxides of Molybdenum

    NASA Technical Reports Server (NTRS)

    Chaney, William S.

    1961-01-01

    A theoretical study has been made of molybdenum dioxide and molybdenum trioxide in order to extend the knowledge of factors Involved in the oxidation of molybdenum. New methods were developed for calculating the lattice energies based on electrostatic valence theory, and the coulombic, polarization, Van der Waals, and repulsion energie's were calculated. The crystal structure was examined and structure details were correlated with lattice energy.

  20. As-cast uranium-molybdenum based metallic fuel candidates and the effects of carbon addition

    NASA Astrophysics Data System (ADS)

    Blackwood, Van Stephen

    The objective of this research was to develop and recommend a metallic nuclear fuel candidate that lowered the onset temperature of gamma phase formation comparable or better than the uranium-10 wt. pct. molybdenum alloy, offered a solidus temperature as high or higher than uranium-10 wt. pct. zirconium (1250°C), and stabilized the fuel phase against interaction with iron and steel at least as much as uranium-10 wt. pct. zirconium stabilized the fuel phase. Two new as-cast alloy compositions were characterized to assess thermal equilibrium boundaries of the gamma phase field and the effect of carbon addition up to 0.22 wt. pct. The first system investigated was uranium- x wt. pct. M where x ranged between 5-20 wt. pct. M was held at a constant ratio of 50 wt. pct. molybdenum, 43 wt. pct. titanium, and 7 wt. pct. zirconium. The second system investigated was the uranium-molybdenum-tungsten system in the range 90 wt. pct. uranium - 10 wt. pct. molybdenum - 0 wt. pct. tungsten to 80 wt. pct. uranium - 10 wt. pct. molybdenum - 10 wt. pct. tungsten. The results showed that the solidus temperature increased with increased addition of M up to 12.5 wt. pct. for the uranium-M system. Alloy additions of titanium and zirconium were removed from uranium-molybdenum solid solution by carbide formation and segregation. The uranium-molybdenum-tungsten system solidus temperature increased to 1218°C at 2.5 wt. pct. with no significant change in temperature up to 5 wt. pct. tungsten suggesting the solubility limit of tungsten had been reached. Carbides were observed with surrounding areas enriched in both molybdenum and tungsten. The peak solidus temperatures for the alloy systems were roughly the same at 1226°C for the uranium-M system and 1218°C for the uranium-molybdenum-tungsten system. The uranium-molybdenum-tungsten system required less alloy addition to achieve similar solidus temperatures as the uranium-M system.

  1. The History of the Discovery of the Molybdenum Cofactor and Novel Aspects of its Biosynthesis in Bacteria.

    PubMed

    Leimkühler, Silke; Wuebbens, Margot M; Rajagopalan, K V

    2011-05-01

    Biosynthesis of the molybdenum cofactor in bacteria is described with a detailed analysis of each individual reaction leading to the formation of stable intermediates during the synthesis of molybdopterin from GTP. As a starting point, the discovery of molybdopterin and the elucidation of its structure through the study of stable degradation products are described. Subsequent to molybdopterin synthesis, the molybdenum atom is added to the molybdopterin dithiolene group to form the molybdenum cofactor. This cofactor is either inserted directly into specific molybdoenzymes or is further modified by the addition of nucleotides to the molybdopterin phosphate group or the replacement of ligands at the molybdenum center. PMID:21528011

  2. Fabrication, strength and oxidation of molybdenum-silicon-boron alloys from reaction synthesis

    NASA Astrophysics Data System (ADS)

    Middlemas, Michael Robert

    Mo-Si-B alloys are a leading candidate for the next generation of jet turbine engine blades and have the potential to raise the operating temperatures by 300-400°C, which would dramatically increase power and efficiency. The alloys of interest are a three-phase mixture of the molybdenum solid solution (Moss) and two intermetallic phases, Mo3Si (A15) and Mo5SiB2 (T2). A novel powder metallurgical method was developed which uses the reaction of molybdenum, silicon nitride (Si3N4) and boron nitride (BN) powders to synthesize a fine dispersion of the intermetallic phases in a Moss matrix. The covalent nitrides are stable in oxidizing environments up to 1000ºC, allowing for fine particle processing without the formation of silicon and boron oxides. The process developed uses standard powder processing techniques to create Mo-Si-B alloys in a less complex and expensive manner than previously demonstrated. The formation of the intermetallic phases was examined by thermo-gravimetric analysis and x-ray diffraction. The start of the reactions to form the T2 and A15 phases were observed at 1140°C and 1193°C and the reactions have been demonstrated to be complete in as little as two hours at 1300°C. This powder metallurgy approach yields a fine dispersion of intermetallics in the Moss matrix, with average grain sizes of 2-4mum. Densities up to 95% of theoretical were attained from pressureless sintering at 1600°C and full theoretical density was achieved by hot-isostatic pressing (HIP). Low temperature sintering and HIPing was attempted to limit grain growth and to reduce the equilibrium silicon concentration in the Moss matrix. Sintering and HIPing at 1300°C reduced the grain sizes of all three phases by over a factor of two. Powder metallurgy provides an opportunity for microstructure control through changes in raw materials and processing parameters. Microstructure examination by electron back-scatter diffraction (EBSD) imaging was used to precisely define the

  3. Recovery of cobalt, molybdenum, nickel and vanadium from an aqueous ammonia and ammonium salt solution by coextracting molybdenum and vanadium and sequential extraction of nickel and cobalt

    SciTech Connect

    Hubred, G.L.; Van Leirsburg, D.A.

    1984-02-28

    A method is claimed for recovering metal values from an aqueous stream. The metal values are preferably obtained from leaching spent hydroprocessing catalysts, and include nickel, cobalt, vanadium and molybdenum. The metal values are extracted, isolated and purified by liquid, liquid extraction techniques.

  4. Optoelectrical Molybdenum Disulfide (MoS2)--Ferroelectric Memories.

    PubMed

    Lipatov, Alexey; Sharma, Pankaj; Gruverman, Alexei; Sinitskii, Alexander

    2015-08-25

    In this study, we fabricated and tested electronic and memory properties of field-effect transistors (FETs) based on monolayer or few-layer molybdenum disulfide (MoS2) on a lead zirconium titanate (Pb(Zr,Ti)O3, PZT) substrate that was used as a gate dielectric. MoS2-PZT FETs exhibit a large hysteresis of electronic transport with high ON/OFF ratios. We demonstrate that the interplay of polarization and interfacial phenomena strongly affects the electronic behavior and memory characteristics of MoS2-PZT FETs. We further demonstrate that MoS2-PZT memories have a number of advantages and unique features compared to their graphene-based counterparts as well as commercial ferroelectric random-access memories (FeRAMs), such as nondestructive data readout, low operation voltage, wide memory window and the possibility to write and erase them both electrically and optically. This dual optoelectrical operation of these memories can simplify the device architecture and offer additional practical functionalities, such as an instant optical erase of large data arrays that is unavailable for many conventional memories. PMID:26222209

  5. Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films

    SciTech Connect

    Deki, Shigehito; Beleke, Alexis Bienvenu; Kotani, Yuki; Mizuhata, Minoru

    2009-09-15

    Hexagonal molybdenum trioxide thin films with good crystallinity and high purity have been fabricated by the liquid phase deposition (LPD) technique using molybdic acid (H{sub 2}MoO{sub 4}) dissolved in 2.82% hydrofluoric acid (HF) and H{sub 3}BO{sub 3} as precursors. The crystal was found to belong to a hexagonal hydrate system MoO{sub 3}.nH{sub 2}O (napprox0.56). The unit cell lattice parameters are a=10.651 A, c=3.725 A and V=365.997 A{sup 3}. Scanning electron microscope (SEM) images of the as-deposited samples showed well-shaped hexagonal rods nuclei that grew and where the amount increased with increase in reaction time. X-ray photon electron spectroscopy (XPS) spectra showed a Gaussian shape of the doublet of Mo 3d core level, indicating the presence of Mo{sup 6+} oxidation state in the deposited films. The deposited films exhibited an electrochromic behavior by lithium intercalation and deintercalation, which resulted in coloration and bleaching of the film. Upon dehydration at about 450 deg. C, the hexagonal MoO{sub 3}.nH{sub 2}O was transformed into the thermodynamically stable orthorhombic phase. - Abstract: SEM photograph of typical h-MoO{sub 3}.nH{sub 2}O thin film nuclei obtained after 36 h at 40 deg. C by the LPD method. Display Omitted

  6. Template synthesis and characterization of molybdenum disulfide nanotubules

    SciTech Connect

    Yu, Dongbo; Feng, Yi; Zhu, Yanfang; Zhang, Xuebin; Li, Bin; Liu, Huiqiang

    2011-09-15

    Graphical abstract: The image is a SEM image of branched MoS{sub 2} nanotubes, which are prepared in AAO templates. It is obvious to observe the branch of MoS{sub 2} nanotubes (labeled by arrows), and it reflects the microcosmic morphologies of pores in templates. Highlights: {yields} Large quantities of hollow MoS2 tubules. {yields} Explanation for the formation of branched shape. {yields} Explanation for the morphology of bamboo-like structure. -- Abstract: Molybdenum disulfide nanotubules were prepared by thermal decomposition of ammonium thiomolybdate ((NH{sub 4}){sub 2}MoS{sub 4}) precursors on anodized aluminum oxide template. Large quantities of hollow MoS{sub 2} nanotubules with the bamboo-like structure were obtained. The morphology and structures of MoS{sub 2} tubules were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, electron diffraction and optical absorption spectroscopy. MoS{sub 2} nanotubules completely reflected the three-dimensional structure of nanopores in template. The properties of Mo-S chemical bonds in lattice structure and the wetting state between porous surface and precursor have a great effect on the formation of sections in nanotubules, the ridges in the nanopores also play a very special role of this formation.

  7. Processing and properties of molybdenum silicide intermetallics containing boron

    SciTech Connect

    Schneibel, J.H.; Liu, C.T.; Heatherly, L.; Wright, J.L.; Carmichael, C.A.

    1997-08-01

    Molybdenum-silicon-boron intermetallics with the composition Mo-10.5 Si-1.1 B, wt% (Mo-26.7 Si-7.3 B, at. %) were fabricated by several processing techniques. Powder processing (PM) resulted in macrocrack-free material containing no or only few microcracks. The PM materials contained quasi-equilibrium pores and large concentrations of oxygen. Average room temperature flexure strengths of 270 MPa were obtained. At 1,200 C in air, flexure strengths as high as 600 MPa were observed. These high values are attributed to crack healing and incipient plasticity. Ingot metallurgy (IM) materials contained much less oxygen than their PM counterparts. Depending on the cooling rate during solidification, they developed either mostly macrocracks or mostly microcracks. Due to the high flaw densities, the room temperature flexure strengths were only of the order of 100 MPa. However, the flexure strengths at 1,200 C were up to 3 times higher than those at room temperature. Again, this is attributed to crack healing and incipient plasticity. The IM materials will require secondary processing to develop their full potential. A preliminary examination of secondary processing routes included isothermal forging and hot extrusion.

  8. Molybdenum Sequestration in Brassica Species. A Role for Anthocyanins?1

    PubMed Central

    Hale, Kerry L.; McGrath, Steve P.; Lombi, Enzo; Stack, Stephen M.; Terry, Norman; Pickering, Ingrid J.; George, Graham N.; Pilon-Smits, Elizabeth A.H.

    2001-01-01

    To elucidate plant mechanisms involved in molybdenum (Mo) sequestration and tolerance, Brassica spp. seedlings were supplied with molybdate, and the effects on plant physiology, morphology, and biochemistry were analyzed. When supplied with (colorless) molybdate Indian mustard (Brassica juncea) seedlings accumulated water-soluble blue crystals in their peripheral cell layers. Energy dispersive x-ray analysis showed that Mo accumulated predominantly in the vacuoles of the epidermal cells. Therefore, the blue crystals are likely to be a Mo compound. The x-ray absorption spectrum of the plant-accumulated Mo was different than that for molybdate, indicating complexation with a plant molecule. Because the blue compound was water soluble and showed a pH-dependent color change, possible involvement of anthocyanins was investigated. An anthocyanin-less mutant of Brassica rapa (“fast plants”) was compared with varieties containing normal or high anthocyanin levels. The anthocyanin-less mutant did not show accumulation of a blue compound when supplied with molybdate. In the anthocyanin-containing varieties, the blue compound colocalized with anthocyanins in the peripheral cell layers. Mo accumulation by the three B. rapa varieties was positively correlated with anthocyanin content. Addition of molybdate to purified B. rapa anthocyanin resulted in an in vitro color change from pink to blue. Therefore, Mo appears to be sequestered in vacuoles of the peripheral cell layers of Brassica spp. as a blue compound, probably a Mo-anthocyanin complex. PMID:11500539

  9. Melting of aluminum, molybdenum and the light actinides

    SciTech Connect

    Ross, M; Yang, L H; Boehler, R

    2004-06-25

    A semi-empirical model was used to explain why the measured melting curves of molybdenum, and the other bcc transition metals, have an unusually low slope (dT/dP{approx}0). The total binding energy of Mo is written as the sum of the repulsive energy of the ions and sp-electrons (modeled by an inverse 6th power potential) and the d-band cohesive energy described by the well known Friedel equation. Using literature values for the Mo band width energy, the number of d-electrons and their volume dependence, we find that a small broadening of the liquid d-band width ({approx}1%) leads to an increase in the stability of the liquid relative to the solid. This is sufficient to depress the melting temperature and lower the melting slope to a value in agreement with the diamond-anvil cell measurements. Omission of the d-band physics results in an Al-like melting curve with a much steeper melt slope. The model, when applied to the f-electrons of the light actinides (Th-Am), gives agreement with the observed fall and rise in the melting temperature with increasing atomic number.

  10. Estimating natural background groundwater chemistry, Questa molybdenum mine, New Mexico

    USGS Publications Warehouse

    Verplanck, Phillip L.; Nordstrom, D Kirk; Plumlee, Geoffrey S.; Walker, Bruce M.

    2010-01-01

    This 2 1/2 day field trip will present an overview of a U.S. Geological Survey (USGS) project whose objective was to estimate pre-mining groundwater chemistry at the Questa molybdenum mine, New Mexico. Because of intense debate among stakeholders regarding pre-mining groundwater chemistry standards, the New Mexico Environment Department and Chevron Mining Inc. (formerly Molycorp) agreed that the USGS should determine pre-mining groundwater quality at the site. In 2001, the USGS began a 5-year, multidisciplinary investigation to estimate pre-mining groundwater chemistry utilizing a detailed assessment of a proximal natural analog site and applied an interdisciplinary approach to infer pre-mining conditions. The trip will include a surface tour of the Questa mine and key locations in the erosion scar areas and along the Red River. The trip will provide participants with a detailed understanding of geochemical processes that influence pre-mining environmental baselines in mineralized areas and estimation techniques for determining pre-mining baseline conditions.

  11. One-Dimensional Electrical Contact to Molybdenum Disulfide

    NASA Astrophysics Data System (ADS)

    Yang, Zheng; Ra, Changho; Ahmed, Faisal; Lee, Daeyeong; Choi, Minsup; Liu, Xiaochi; Qu, Deshun; Yoo, Won Jong; Nano Device Processing Lab Team

    Molybdenum disulfide (MoS2) is one of the promising two-dimensional materials for future application in nano electronics, which has high carrier mobility, very good stability under atmosphere, proper band gap, etc. However, its application to electronic switching devices is hindered by Fermi level pinning at metal-MoS2 interfaces. Here, we experimentally demonstrate one-dimensional electrical contact to MoS2 formed via controllable plasma etching. We fabricated Al/MoS2 FET (n-type), Mo/MoS2 FET (n-type), and Pd/MoS2 FET (ambipolar). For Mo/MoS2 FET (n-type), on/off current ratio is around 108 and mobility is around 104 cm2/(Vs). By contrast, for Pd/MoS2 FET (ambipolar), on/off current ratio is around 108, hole mobility is ranged from 350 to 650 cm2/(Vs), and the mean free path of holes at 9K is around 23 nm. All the measured mobilities are evaluated by using two-terminal field-effect configuration. We can also achieve complementary logic gates with intrinsic MoS2/metal one-dimensional electrical contact.

  12. Copper and molybdenum in silicate melt-aqueous fluid systems

    SciTech Connect

    Candela, P.A.

    1982-01-01

    The partitioning of copper (Cu) and molybdenum (Mo) between silicate melts and aqueous fluids has been determined. The vapor/melt partition coefficient for Cu, D(Cu) was found to be D(Cu) = 9.2 m/sub Cl//sup v/ at NNO. The partition coefficient for Mo, D(Mo), is equal to 2.5 at NNO and QFM, and is independent of the F and Cl concentration. Equations have been derived for the efficiency of the removal of the metals from magmas into aqueous fluids. Copper is concentrated so efficiently into a moderately to highly saline aqueous phase that liquid-vapor extraction seems to be a reasonable process to account for the concentration of Cu in porphyry Cu deposits. However, geological evidence suggests that Cu behaves as a compatible element during magmatic processes(BPC > 1). Therefore, the efficiency of Cu removal from magmas into aqueous fluids is strongly dependent upon the amount of the melt crystallized before water saturation, and efficient extraction of Cu results when aqueous fluids are evolved early in the crystallization of the intrusion. The value of D(Mo) is small relative to D(Cu) at moderate to high chloride concentrations, and the extraction of Mo from melts into aqueous fluids therefore tends to be less efficient. However, vapor-liquid partitioning can extract the requisite quantities of Mo from granitic melts of batholithic size.

  13. Differential reduction of CO₂ by molybdenum and vanadium nitrogenases.

    PubMed

    Rebelein, Johannes G; Hu, Yilin; Ribbe, Markus W

    2014-10-20

    The molybdenum and vanadium nitrogenases are two homologous enzymes with distinct structural and catalytic features. Previously, it was demonstrated that the V nitrogenase was nearly 700 times more active than its Mo counterpart in reducing CO to hydrocarbons. Herein, a similar discrepancy between the two nitrogenases in the reduction of CO2 is reported, with the V nitrogenase being capable of reducing CO2 to CO, CD4, C2D4, and C2D6, and its Mo counterpart only capable of reducing CO2 to CO. Furthermore, it is shown that the V nitrogenase may direct the formation of CD4 in part via CO2-derived CO, but that it does not catalyze the formation of C2D4 and C2D6 along this route. The exciting observation of a V nitrogenase-catalyzed C-C coupling with CO2 as the origin of the building blocks adds another interesting reaction to the catalytic repertoire of this unique enzyme system. The differential activities of the V and Mo nitrogenases in CO2 reduction provide an important framework for systematic investigations of this reaction in the future. PMID:25205285

  14. Sequential biological process for molybdenum extraction from hydrodesulphurization spent catalyst.

    PubMed

    Vyas, Shruti; Ting, Yen-Peng

    2016-10-01

    Spent catalyst bioleaching with Acidithiobacillus ferrooxidans has been widely studied and low Mo leaching has often been reported. This work describes an enhanced extraction of Mo via a two stage sequential process for the bioleaching of hydrodesulphurization spent catalyst containing Molybdenum, Nickel and, Aluminium. In the first stage, two-step bioleaching was performed using Acidithiobacillus ferrooxidans, and achieved 89.4% Ni, 20.9% Mo and 12.7% Al extraction in 15 days. To increase Mo extraction, the bioleached catalyst was subjected to a second stage bioleaching using Escherichia coli, during which 99% of the remaining Mo was extracted in 25 days. This sequential bioleaching strategy selectively extracted Ni in the first stage and Mo in the second stage, and is a more environmentally friendly alternative to sequential chemical leaching with alkaline reagents for improved Mo extraction. Kinetic modelling to establish the rate determining step in both stages of bioleaching showed that in the first stage, Mo extraction was chemical reaction controlled whereas in the subsequent stage, product layer diffusion model provided the best fit. PMID:27351900

  15. Molybdenum sequestration in Brassica species. A role for anthocyanins?

    PubMed

    Hale, K L; McGrath, S P; Lombi, E; Stack, S M; Terry, N; Pickering, I J; George, G N; Pilon-Smits, E A

    2001-08-01

    To elucidate plant mechanisms involved in molybdenum (Mo) sequestration and tolerance, Brassica spp. seedlings were supplied with molybdate, and the effects on plant physiology, morphology, and biochemistry were analyzed. When supplied with (colorless) molybdate Indian mustard (Brassica juncea) seedlings accumulated water-soluble blue crystals in their peripheral cell layers. Energy dispersive x-ray analysis showed that Mo accumulated predominantly in the vacuoles of the epidermal cells. Therefore, the blue crystals are likely to be a Mo compound. The x-ray absorption spectrum of the plant-accumulated Mo was different than that for molybdate, indicating complexation with a plant molecule. Because the blue compound was water soluble and showed a pH-dependent color change, possible involvement of anthocyanins was investigated. An anthocyanin-less mutant of Brassica rapa ("fast plants") was compared with varieties containing normal or high anthocyanin levels. The anthocyanin-less mutant did not show accumulation of a blue compound when supplied with molybdate. In the anthocyanin-containing varieties, the blue compound colocalized with anthocyanins in the peripheral cell layers. Mo accumulation by the three B. rapa varieties was positively correlated with anthocyanin content. Addition of molybdate to purified B. rapa anthocyanin resulted in an in vitro color change from pink to blue. Therefore, Mo appears to be sequestered in vacuoles of the peripheral cell layers of Brassica spp. as a blue compound, probably a Mo-anthocyanin complex. PMID:11500539

  16. EUV nanosecond laser ablation of silicon carbide, tungsten and molybdenum

    NASA Astrophysics Data System (ADS)

    Frolov, Oleksandr; Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Choukourov, Andrei; Kasuya, Koichi

    2015-09-01

    In this paper we present results of study interaction of nanosecond EUV laser pulses at wavelength of 46.9 nm with silicon carbide (SiC), tungsten (W) and molybdenum (Mo). As a source of laser radiation was used discharge-plasma driver CAPEX (CAPillary EXperiment) based on high current capillary discharge in argon. The laser beam is focused with a spherical Si/Sc multilayer-coated mirror on samples. Experimental study has been performed with 1, 5, 10, 20 and 50 laser pulses ablation of SiC, W and Mo at various fluence values. Firstly, sample surface modification in the nanosecond time scale have been registered by optical microscope. And the secondly, laser beam footprints on the samples have been analyzed by atomic-force microscope (AFM). This work supported by the Czech Science Foundation under Contract GA14-29772S and by the Grant Agency of the Ministry of Education, Youth and Sports of the Czech Republic under Contract LG13029.

  17. Ductility Enhancement of Molybdenum Phase by Nano-sizedd Oxide Dispersions

    SciTech Connect

    Bruce Kang

    2008-07-31

    The present research is focused on ductility enhancement of molybdenum (Mo) alloys by adding nano-sized oxide particles to the alloy system. The research approach includes: (1) determination of microscopic mechanisms responsible for the macroscopic ductility enhancement effects through atomistic modeling of the metal-ceramic interface; (2) subsequent computer simulation-aided optimization of composition and nanoparticle size of the dispersion for improved performance; (3) synthesis and characterization of nanoparticle dispersion following the guidance from atomistic computational modeling analyses (e.g., by processing a small sample of Mo alloy for evaluation); and (4) experimental testing of the mechanical properties to determine optimal ductility enhancement.Through atomistic modeling and electronic structure analysis using full-potential linearized muffin-tin orbital (FP-LMTO) techniques, research to date has been performed on a number of selected chromium (Cr) systems containing nitrogen (N) and/or magnesium oxide (MgO) impurities. The emphasis has been on determining the properties of the valence electrons and the characteristics of the chemical bonds they formed. It was found that the brittle/ductile behavior of this transitional metal system is controlled by the relative population of valence charges: bonds formed by s valence electrons yield metallic, ductile behavior, whereas bonds formed by d valence electrons lead to covalent, brittle behavior. The presence of valence bands from impurities also affects the metal bonding, thereby explaining the detrimental and beneficial effects induced by the inclusion of N impurities and MgO dispersions. These understandings are useful for optimizing ductility enhancement effects on the dispersion materials.

  18. Sulfite Oxidase Catalyzes Single-Electron Transfer at Molybdenum Domain to Reduce Nitrite to Nitric Oxide

    PubMed Central

    Wang, Jun; Krizowski, Sabina; Fischer-Schrader, Katrin; Niks, Dimitri; Tejero, Jesús; Sparacino-Watkins, Courtney; Wang, Ling; Ragireddy, Venkata; Frizzell, Sheila; Kelley, Eric E.; Zhang, Yingze; Basu, Partha; Hille, Russ

    2015-01-01

    Abstract Aims: Recent studies suggest that the molybdenum enzymes xanthine oxidase, aldehyde oxidase, and mARC exhibit nitrite reductase activity at low oxygen pressures. However, inhibition studies of xanthine oxidase in humans have failed to block nitrite-dependent changes in blood flow, leading to continued exploration for other candidate nitrite reductases. Another physiologically important molybdenum enzyme—sulfite oxidase (SO)—has not been extensively studied. Results: Using gas-phase nitric oxide (NO) detection and physiological concentrations of nitrite, SO functions as nitrite reductase in the presence of a one-electron donor, exhibiting redox coupling of substrate oxidation and nitrite reduction to form NO. With sulfite, the physiological substrate, SO only facilitates one turnover of nitrite reduction. Studies with recombinant heme and molybdenum domains of SO indicate that nitrite reduction occurs at the molybdenum center via coupled oxidation of Mo(IV) to Mo(V). Reaction rates of nitrite to NO decreased in the presence of a functional heme domain, mediated by steric and redox effects of this domain. Using knockdown of all molybdopterin enzymes and SO in fibroblasts isolated from patients with genetic deficiencies of molybdenum cofactor and SO, respectively, SO was found to significantly contribute to hypoxic nitrite signaling as demonstrated by activation of the canonical NO-sGC-cGMP pathway. Innovation: Nitrite binds to and is reduced at the molybdenum site of mammalian SO, which may be allosterically regulated by heme and molybdenum domain interactions, and contributes to the mammalian nitrate-nitrite-NO signaling pathway in human fibroblasts. Conclusion: SO is a putative mammalian nitrite reductase, catalyzing nitrite reduction at the Mo(IV) center. Antioxid. Redox Signal. 23, 283–294. PMID:25314640

  19. Microstructures and Hardness/Wear Performance of High-Carbon Stellite Alloys Containing Molybdenum

    NASA Astrophysics Data System (ADS)

    Liu, Rong; Yao, J. H.; Zhang, Q. L.; Yao, M. X.; Collier, Rachel

    2015-12-01

    Conventional high-carbon Stellite alloys contain a certain amount of tungsten which mainly serves to provide strengthening to the solid solution matrix. These alloys are designed for combating severe wear. High-carbon molybdenum-containing Stellite alloys are newly developed 700 series of Stellite family, with molybdenum replacing tungsten, which are particularly employed in severe wear condition with corrosion also involved. Three high-carbon Stellite alloys, designated as Stellite 706, Stellite 712, and Stellite 720, with different carbon and molybdenum contents, are studied experimentally in this research, focusing on microstructure and phases, hardness, and wear resistance, using SEM/EDX/XRD techniques, a Rockwell hardness tester, and a pin-on-disk tribometer. It is found that both carbon and molybdenum contents influence the microstructures of these alloys significantly. The former determines the volume fraction of carbides in the alloys, and the latter governs the amount of molybdenum-rich carbides precipitated in the alloys. The hardness and wear resistance of these alloys are increased with the carbide volume fraction. However, with the same or similar carbon content, high-carbon CoCrMo Stellite alloys exhibit worse wear resistance than high-carbon CoCrW Stellite alloys.

  20. Molybdenum, Tungsten, and Aluminium Substitution for Enhancement of the Thermoelectric Performance of Higher Manganese Silicides

    NASA Astrophysics Data System (ADS)

    Nhi Truong, D. Y.; Berthebaud, David; Gascoin, Franck; Kleinke, Holger

    2015-10-01

    An easy and efficient process involving ball milling under soft conditions and spark plasma sintering was used to synthesize higher manganese silicide (HMS)-based compounds, for example MnSi1.75Ge0.02, with different molybdenum, tungsten, and aluminium substitution. The x-ray diffraction patterns of the samples after sintering showed the main phase to be HMS with the presence of some side products. Molybdenum substitution enlarges the unit cells more than tungsten substitution, owing to its greater solubility in the HMS structure, whereas substitution with aluminium did not substantially alter the cell parameters. The electrical resistivity of HMS-based compounds was reduced by <10% by this substitution, because of increased carrier concentrations. Changes of the Seebeck coefficient were insignificant after molybdenum and aluminium substitution whereas tungsten substitution slightly reduced the thermopower of the base material by approximately 8% over the whole temperature range; this was ascribed to reduced carrier mobility as a result of enhanced scattering. Substitution with any combination of two of these elements resulted in no crucial modification of the electrical properties of the base material. Large decreases of lattice thermal conductivity were observed, because of enhanced phonon scattering, with the highest reduction up to 25% for molybdenum substitution; this resulted in a 20% decrease of total thermal conductivity, which contributed to improvement of the figure of merit ZT of the HMS-based materials. The maximum ZT value was approximately 0.40 for the material with 2 at.% molybdenum substitution at the Mn sites.

  1. Reduction of molybdate to molybdenum blue by Enterobacter sp. strain Dr.Y13.

    PubMed

    Shukor, M Y; Rahman, M F; Shamaan, N A; Syed, M A

    2009-09-01

    Extensive use of metals in various industrial applications has caused substantial environmental pollution. Molybdenum-reducing bacteria isolated from soils can be used to remove molybdenum from contaminated environments. In this work we have isolated a local bacterium with the capability to reduce soluble molybdate to the insoluble molybdenum blue. We studied several factors that would optimize molybdate reduction. Electron donor sources such as glucose, sucrose, lactose, maltose and fructose (in decreasing efficiency) supported molybdate reduction after 24 h of incubation with optimum glucose concentration for molybdate reduction at 1.5% (w/v). The optimum pH, phosphate and molybdate concentrations, and temperature for molybdate reduction were pH 6.5, 5.0, 25 to 50 mM and 37 degrees C, respectively. The Mo-blue produced by cellular reduction exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium, cadmium, copper, silver and mercury caused approximately 73, 71, 81, 77 and 78% inhibition of the molybdenum-reducing activity, respectively. All of the respiratory inhibitors tested namely rotenone, azide, cyanide and antimycin A did not show any inhibition to the molybdenum-reducing activity suggesting components of the electron transport system are not responsible for the reducing activity. The isolate was tentatively identified as Enterobacter sp. strain Dr.Y13 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. PMID:19455513

  2. Synthesis and characterisation of thiosemicarbazonato molybdenum(VI) complexes and their in vitro antitumor activity.

    PubMed

    Vrdoljak, Visnja; Dilović, Ivica; Rubcić, Mirta; Kraljević Pavelić, Sandra; Kralj, Marijeta; Matković-Calogović, Dubravka; Piantanida, Ivo; Novak, Predrag; Rozman, Andrea; Cindrić, Marina

    2010-01-01

    New dioxomolybdenum(VI) complexes were obtained by the reaction of [MoO2(acac)2] with thiosemicarbazone ligands derived from 3-thiosemicarbazide and 4-(diethylamino)salicylaldehyde (H2L1), 2-hydroxy-3-methoxybenzaldehyde (H2L2) or 2-hydroxy-1-naphthaldehyde (H2L3). In all complexes thiosemicarbazonato ligands are coordinated to molybdenum as tridentate ONS-donors. Octahedral coordination of each molybdenum atom is completed by methanol molecule (in 1a-3a) or by oxygen atom of Mo=O unit from the neighbouring molecule (in 1-3). All complexes were characterized by means of chemical analyses, IR spectroscopy, TG and NMR measurements. The molecular structures of the ligand H2L2 and complex [MoO2L2(CH3OH)].CH3OH (2a) have been determined by single crystal X-ray crystallography. The characterisation of thiosemicarbazonato molybdenum(VI) complexes (1-4) as well as of the 4-phenylthisemicarbazonato molybdenum(VI) complexes (5-8) in aqueous medium revealed that upon dissolving complexes in water, most likely to some extent dissociation took place, although experimental data didn't allow exact quantification of dissociation. The antiproliferative effects of studied molybdenum(VI) complexes (1-8) on the human cell lines were identical to the activity of their corresponding ligands. PMID:19815314

  3. The role of oxygen in porous molybdenum electrodes for the alkali metal thermoelectric converter

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Nagasubramanian, G.; Khanna, S. K.; Bankston, C. P.; Thakoor, A. P.; Cole, T.

    1986-01-01

    A model for chemical reactions in porous molybdenum electrodes is presented which is based on thermochemical and kinetic data, known sodium-molybdenum-oxygen chemistry, X-ray diffraction analysis of molybdenum and molybdenum oxide electrodes, and the electrochemical behavior of the cell. Enhanced sodium transport through the electrode in its optimum performance state is found to be due to the high sodium ion conductivity of molten Na2MoO4 in the pores, and the electrical conduction to the molybdenum matrix by Na2Mo3O6. The decline of electrode performance is shown to be due to a combination of loss mechanisms for the Na-Mo-O compounds including reduction at short circuit, disproportionation of Na2Mo3O6 at open circuit, and the evaporation of Na2MoO4 at elevated temperature. It is suggested that operation of the cell at moderate voltage of about 0.5 V corresponding to maximum power may be a more stable condition for the porous electrode than open-circuit stand or short-circuit, where degradation reactions are heightened.

  4. Hydrometallation of model compounds of a cobalt-molybdenum catalyst

    SciTech Connect

    West, M.; Smith, M.C.; Petersen, E.E.

    1983-05-01

    One solution to corrosion and environmental problems is to remove sulfur from the fuel or feedstock before burning or processing by catalytic hydrosulfurization (HDS). Besides sulfur, heavy petroleum fractions and coal liquids contain high levels of trace metal compounds compared to traditional HDS feedstocks. In resids, these metals are mainly vanadium and nickel and in coal-liquids they are mostly titanium and iron. Under typical HDS conditions the organometallic compounds in these liquids also decompose and yield metal-free organics and metal sulfides. This hydrometallation (HDM) reaction is a double-edged sword. Since the sulfides are insoluble in the oil, the reaction effectively demetallizes the feedstock. This is desirable because, like sulfur, these metals pose environmental corrosion, and catalyst poisoning problems. The undesirable aspect of the reaction is that these insoluble metal sulfides collect in and around the HDS catalyst pellets, plugging pores and covering active surface sites thereby reducing both the HDS and the HDM catalytic activity. The deactivating effect of metal deposition on HDS and HDM is the focus of this study. Since the metal sulfides produced by HDM remain at the site of their reaction, the amount of metal at any point in the catalyst is a record of the reaction rate at that point. By carefully measuring the metal concentrations inside a series of cobalt-molybdenum-alumina catalyst pellets exposed for different lengths of time, demetallation rate profiles are measured within the pellets. There is no similar way to measure local HDS rates. Measurements of the global HDS rates, a knowledge of HDS kinetics, and measurements of the local HDM rates permit us to model the effect of metal deposits on catalyst activity. We have chosen to work with two model classes of compounds, metal naphthenates and metalloporphyrins.

  5. Molybdenum Storage in Cyanobacteria: "Mopping" Up Excess Mo

    NASA Astrophysics Data System (ADS)

    Glass, J. B.; Wolfe-Simon, F.; Anbar, A. D.

    2008-12-01

    The heavy metal molybdenum (Mo) plays an essential role in the nitrogen (N) cycle. In order to acquire N from the environment, microorganisms utilize Mo-containing enzymes such as nitrogenase (for N2 fixation) and nitrate reductase (for NO3- assimilation). N2-fixing cyanobacteria likely played an important role in both marine and terrestrial N cycling throughout Earth history. Low Mo levels in Precambrian oceans may have necessitated evolution of cyanobacterial Mo-storage ("Mop") proteins. If so, mop genes were likely lost in marine cyanobacteria after the rise of Mo (to approximately 100 nanomolar (nM) 600 Ma (Scott et al., 2008)). The distribution of mop genes in N2-fixing cyanobacteria supports this hypothesis; freshwater species contain this gene whereas marine species lack it. To assess the importance of Mo-storage in modern environments we are integrating laboratory and field investigations. In the lab, we grew N2-fixing freshwater cyanobacteria possessing the mop gene at high Mo levels (1500 nM) to assess whether excess Mo is accumulated Extremely high intracellular accumulation of Mo, much higher than could be accounted for by nitrogenase requirements alone, was observed. Investigation of mop gene expression and protein localization in Mo-replete and deplete conditions is underway. In the field, we are isolating indigenous cyanobacteria and cloning mop genes from Castle Lake, California. This field locale is of particular interest because previous studies show that periphyton consortia in this lake assimilate large quantities of N, even though Mo concentrations are <5 nM. This adaptation to low Mo may be aided by intracellular Mo storage.

  6. Synthesis and structure of dihydridodichlorotetrakis(dimethyl-phenylphosphine)molybdenum

    SciTech Connect

    Lenenko, V.S.; Yanovskii, A.I.; Struchkov, Yu.T.; Shur, V.B.; Vol'pin, M.E.

    1987-03-01

    The reduction of (THF)/sub 3/MoCl/sub 3/ by magnesium in THF in the presence of Me/sub 2/PhP followed by treatment with MeOH gives the hydride complex of molybdenum (Me/sub 2/PhP)/sub 4/-MoH/sub 2/Cl/sub 2/ (I), which has been characterized by IR and NMR spectroscopy and investigated by x-ray diffraction analysis (-120/sup 0/C, lambdaMo, 3656 reflections, R = 0.077). The crystals of I are triclinic, and at -120/sup 0/C a = 8.902, b = 9.820, c = 22.73 A ..cap alpha.. = 86.13, ..beta.. = 89.28, ..gamma.. = 67.62/sup 0/, Z = 2, and the space group is P anti 1. The hydride H atoms could not be located objectively; however, their positions were established approximately on the basis of the arrangement of the remaining ligands. The coordination polyhedron of the Mo atom may be described as a distorted triangular dodecahedron. The lengths of the Mo-P bonds differ appreciably: the longer Mo-P bonds, which are equal to 2.544 and 2.531 A, form a 157.8/sup 0/ angle with one another, the angle between the two shorter Mo-P bonds, which measure 2.459 and 2.445 A, is equal to 119.6/sup 0/, and the remaining PMoP angles lie in the range from 90.6 to 100.0/sup 0/. The Mo-P and Mo-Cl bonds (2.542 and 2.532 A) in complex I are close to the corresponding distances in the tungsten analog, which was previously investigated.

  7. Ergonomic study of an operator's work of a molybdenum plant.

    PubMed

    Oñate, Esteban; Meyer, Felipe

    2012-01-01

    This study was part of an ergonomic program which is being carried out through an agreement between the University of Concepción and a Chilean private mining company. The purpose of this case study was to identify working conditions in which the physical and mental workload could be over the capabilities of the operator. He was responsible for loading trucks with sacks of molybdenum and for downloading reagents and handles them. The methods employed in this study included electronic records, interviews, surveys, review of the company standards, a time study and physical and mental workload analysis. Results showed that 84% of the time the operator was carrying out principal and secondary activities and no break periods were detected. It was found that the pace of work and the shift system generated unfavorable conditions by imbalance in the workload on the different days of the week. In the light of the results recommendations were made for a number of ergonomic changes. Most of them were accepted by the company. The most important achievement was a change in the shift system. The overload of the operator was due to the fact that he was in a shift working 5 days and resting on weekends. The imbalance was mainly because the work of the week end was accumulated for Monday. As a result of the study, the company contracted a second worker for this job and adopted a 7x7 shift system, meaning that they work seven days and rest seven days. An evaluation carried out two month after adopting the new shift revealed that changes were well accepted by the worker. PMID:22317731

  8. (Pentamethylcyclopentadienyl)molybdenum(IV) chloride. Synthesis, structure, and properties

    SciTech Connect

    Abugideiri, F.; Desai, J.U.; Gordon, J.C.

    1994-08-17

    Three different syntheses of trichloro(pentamethylcyclopentadienyl)molybdenum(IV) are described, I.E. (1) thermal decarbonylation of Cp{sup *}MoCl{sub 3}(CO){sub 2}, (2) reduction of Cp{sup *}MoCl{sub 4}, and (3) chlorination of [Cp{sup *}MoCl{sub 2}]{sub 2}. A fourth route (conproportionation of [Cp{sup *}MoCl{sub 2}]{sub 2} and Cp{sup *}MoCl{sub 4}) has been investigated by {sup 1}H-NMR. The product has a dinuclear, dichloro-bridged structure with a four-legged piano stool geometry around each metal atom; the two piano stools have a mutual anti arrangement and the two metals are 3.888(1) {Angstrom} from each other, indicating the absence of a direct metal-metal bonding interaction. Crystal data: monoclinic, space group P2{sub 1}/n, a = 8.424(1) {Angstrom}, b = 13.323(4) {Angstrom}, c = 11.266(2) {Angstrom}, {beta} = 93.87(1){degrees}, V = 1261.6(8) {Angstrom}{sup 3}, Z = 2, R = 0.038, R{sub w} = 0.057 for 127 parameters and 1350 observed reflections with F{sub o}{sup 2} > 3{sigma}(F{sub o}{sup 2}). The temperature dependent magnetic moment of the material could be fit to the sum of two Bleany-Bowers equations. [Cp{sup *}MoCl{sub 3}]{sub 2} reacts readily with CO, Cl{sup {minus}}, and PMe{sub 3} to afford Cp{sup *}MoCl{sub 3}(CO){sub 2}, [Cp{sup *}MoCl{sub 4}]{sup {minus}}, and Cp{sup *}MoCl{sub 3}(PMe{sub 3}), respectively, while the reaction with 1,2-bis(diphenylphosphino)ethane (dppe) affords the reduction product Cp{sup *}MoCl{sub 2}(dppe).

  9. Isotopic fingerprints of anthropogenic molybdenum in lake sediments.

    PubMed

    Chappaz, Anthony; Lyons, Timothy W; Gordon, Gwyneth W; Anbar, Ariel D

    2012-10-16

    We measured the molybdenum isotope compositions (δ(98)Mo) of well-dated sediment cores from two lakes in eastern Canada in an effort to distinguish between natural and anthropogenic contributions to these freshwater aquatic systems. Previously, Chappaz et al. (1) ascribed pronounced 20th-century Mo concentration enrichments in these lakes to anthropogenic inputs. δ(98)Mo values in the deeper sediments (reflecting predominantly natural Mo sources) differ dramatically between the two lakes: -0.32 ± 0.17‰ for oxic Lake Tantare and +0.64 ± 0.09‰ for anoxic Lake Vose. Sediment layers previously identified as enriched in anthropogenic Mo, however, reveal significant δ(98)Mo shifts of ± 0.3‰, resulting in isotopically heavier values of +0.05 ± 0.18‰ in Lake Tantare and lighter values of +0.31 ± 0.03‰ in Lake Vose. We argue that anthropogenic Mo modifies the isotopic composition of the recent sediments, and we determine δ(98)Mo(anthropogenic) values of 0.1 ± 0.1‰ (Lake Vose) and 0.2 ± 0.2‰ (Lake Tantare). These calculated inputs are consistent with the δ(98)Mo of molybdenite (MoS(2)) likely delivered to the lakes via smelting of porphyry copper deposits (Lake Vose) or through combustion of coal and oil also containing Mo (Lake Tantare). Our results confirm the utility of Mo isotopes as a promising fingerprint of human impacts and perhaps the specific sources of contamination. Importantly, the magnitudes of the anthropogenic inputs are large enough, relative to the natural Mo cycles in each lake, to have an impact on the microbiological communities. PMID:22970917

  10. Aqueous corrosion behavior of uranium-molybdenum alloys

    NASA Astrophysics Data System (ADS)

    Gardner, Levi D.

    Nuclear fuel characterization requires understanding of the various conditions to which materials are exposed in-reactor. One of these important conditions is corrosion, particularly that of fuel constituents. Therefore, corrosion behavior is of special interest and an essential part of nuclear materials characterization efforts. In support of the Office of Material Management and Minimization's Reactor Conversion Program, monolithic uranium-10 wt% molybdenum alloy (U-Mo) is being investigated as a low enriched uranium alternative to highly enriched uranium dispersion fuel currently used in domestic high performance research reactors. The aqueous corrosion behavior of U-Mo is being examined at Pacific Northwest National Laboratory (PNNL) as part of U-Mo fuel fabrication capability activity. No prior study adequately represents this behavior given the current state of alloy composition and thermomechanical processing methods, and research reactor water chemistry. Two main measurement techniques were employed to evaluate U-Mo corrosion behavior. Low-temperature corrosion rate values were determined by means of U-Mo immersion testing and subsequent mass-loss measurements. The electrochemical behavior of each processing condition was also qualitatively examined using the techniques of corrosion potential and anodic potentiodynamic polarization. Scanning electron microscopy (SEM) and optical metallography (OM) imagery and hardness measurements provided supplemental corrosion analysis in an effort to relate material corrosion behavior to processing. The processing effects investigated as part of this were those of homogenization heat treatment (employed to mitigate the effects of coring in castings) and sub-eutectoid heat treatment, meant to represent additional steps in fabrication (such as hot isostatic pressing) performed at similar temperatures. Immersion mass loss measurements and electrochemical results both showed very little appreciable difference between

  11. Phase identification in reactive sintering of molybdenum disilicide composites

    SciTech Connect

    Alba, J. Jr.

    1996-10-01

    Molybdenum disilicide has been predominantly used for furnace heating elements, but recently there has been interest in its use for high temperature structural applications. The reason for this increased interest stems from its desirable characteristics which are a high melting point, relatively low density, good oxidation resistance, relatively good thermal conductivity and electronically conductive. The melting point of MoSi{sub 2} is approximately 2030{degrees}C as compared to a melting point of 1340{degrees}C for the Ni-based superalloys. This could potentially give MoSi{sub 2} a big advantage over the Ni-based superalloys in turbine applications because the operating temperature can be increased resulting in an increase in turbine efficiency and reduced emissions. The relatively low density (6.25g/cm{sup 3}) compared to the Ni-based superalloys (8.9 g/cm{sup 3}) is an important advantage in turbine applications because of the need for low weight. Good oxidation resistance stems from the ability of MoSi{sub 2} to form a protective SiO{sub 2} surface layer when exposed to oxygen. Another advantageous feature of MoSi{sub 2} is its thermal conductivity which is superior to Ni-based superalloys at low temperatures and comparable to the Ni-based superalloys at high temperatures. This allows heat to be dissipated at a rate better than ceramics and comparable to metals. MoSi{sub 2} is electrically conductive allowing it to be electro discharge machined. This is desirable since conventional ceramics are not generally conductive and cannot be electro discharge machined.

  12. New pathways to tungsten and molybdenum oxides, nitrides and azides

    SciTech Connect

    Close, M.R.

    1992-10-07

    [WNCl{sub 3}]{sub 4} was prepared and characterized structurally by X-ray diffraction. [WNCl{sub 3}]{sub 4} crystallizes in space group P{bar 1} as planar 8-membered W-N rings interconnected through chloride bridges. The inter-tetramer linkage is weak and broken easily to accommodate basic ligands in the site trans to the W-N triple bond. Reactivity of WNCl{sub 3}, with nitriding agents, such as ammonia, trimethylsilylazide and lithium nitride, has been investigated, which resulted in preparation of new tungsten azido and nitrido compounds. Second, the reactivity of the metal dimers MO{sub 2}(O{sub 2}CCH{sub 3}){sub 4} and MO{sub 2}Cl{sub 4}py{sub 4} with trimethylsilylazide has been explored, and the reactions in pyridine were found to yield a material corresponding to the formulation, MoN(N{sub 3})py. Thermolytic decomposition of this azide at 280{degree}C was performed under argon, dynamic vacuum or ammonia. Thermal decomposition in ammonia produces a molybdenum nitride relatively free of carbon with a Mo:N ratio of 1:1.8. WNCl{sub 3} was converted into a hexagonal ammonium tungsten bronze, (NH{sub 4}){sub 0.28}WO{sub 3-y}(NH){sub y}. This synthesis increased the probability of isoelectronic imido substitution for oxide in the bronze framework. Rietveld refinements of neutron powder data indicated strongly that nitrogen, in the form of imide, does not substitute for oxygen. A model for ammonium cation motion in the hexagonal channels of the bronze was developed. Electrical resistivity measurements on a pressed pellet of this hexagonal bronze show a temperature dependence like that of a low-band gap semiconductor, in contrast to conventionally prepared metallic hexagonal bronze phases.

  13. Reactions of l-ergothioneine and some other aminothiones with 2,2′- and 4,4′-dipyridyl disulphides and of l-ergothioneine with iodoacetamide. 2-Mercaptoimidazoles, 2- and 4-thiopyridones, thiourea and thioacetamide as highly reactive neutral sulphur nucleophiles

    PubMed Central

    Carlsson, Jan; Kierstan, Marek P. J.; Brocklehurst, Keith

    1974-01-01

    1. The reactions of 2,2′- and 4,4′-dipyridyl disulphide (2-Py–S–S–2-Py and 4-Py–S–S–4-Py) with l-ergothioneine (2-mercapto-l-histidine betaine), 2-mercaptoimidazole, 1-methyl-2-mercaptoimidazole, thiourea, thioacetamide, 2-thiopyridone (Py–2-SH) and 4-thiopyridone (Py–4-SH) were investigated spectrophotometrically in the pH range approx. 1–9. 2. These reactions involve two sequential reversible thiol–disulphide interchanges. 3. The reaction of l-ergothioneine with 2-Py–S–S–2-Py and/or with the l-ergothioneine–Py–2-SH mixed disulphide, both of which provide Py–2-SH, is characterized by at least three reactive protonic states. This provides definitive evidence that neutral l-ergothioneine is a reactive nucleophile, particularly towards the highly electrophilic protonated disulphides. 4. A similar situation appears to obtain in the reactions of l-ergothioneine and Py–2-SH with 4-Py–S–S–4-Py and in the reactions of the other 2-mercaptoimidazoles, thiourea and Py–4-SH with 2-Py–S–S–2-Py. The nucleophilic reactivity of Py–4-SH suggests that general base catalysis provided by the disulphide in a cyclic or quasi-cyclic transition state is not necessary to generate nucleophilic reactivity in the other amino-thiones whose geometry could permit such catalysis. 5. The existence of a positive deuterium isotope effect in the l-ergothioneine–2-Py–S–S–2-Py system at pH6–7 provides no evidence for general base catalysis but is in accord with a mechanism involving specific acid catalysis and post-transition-state proton transfer. 6. The pH-dependences of the overall equilibrium positions of the various thiol–disulphide interchanges are described. 7. Reaction of thioacetamide with a stoicheiometric quantity of 2-Py–S–S–2-Py at pH1 provides 2 molecules of Py–2-SH per molecule of thioacetamide and elemental sulphur; these findings can be accounted for by thiol–disulphide interchange to provide a thioacetamide

  14. Intrinsic and extrinsic modification of niobium aluminides and molybdenum disilicide composites

    NASA Astrophysics Data System (ADS)

    Ye, Fan

    Molybdenum Disilicide (MoSisb2) is considered as a potential structural high temperature material due to the attractive combinations of lower density (6.33 g/cc, 75% of that of conventional superalloys); excellent oxidation resistance due to the formation of a protective oxide film above 900sp° C; good elevated temperature strength retention at temperatures up to about 1200sp° C; high thermal conductivity; low coefficient of thermal expansion and thermodynamic compatibility with most of the commonly used reinforcements such as SiC, Mo, W and Nb. However, MoSisb2 is brittle at room temperatures. There is, therefore, a need for approaches designed to toughen MoSisb2 at lower temperatures. Ductile phase toughening of MoSisb2 with Nb fibers and Nb laminae was examined in this study. The toughening levels in the MoSisb2/Nb composites were quantified using micromechanics-based crack-tip shielding models. Fatigue and fracture mechanisms were also be elucidated for the fiber- and laminate-reinforced composites. Transformation toughening was also studied on MoSisb2 reinforced with 2 mol.% TZ-2Y. Toughening level due to transformation was also quantified using micromechanical models. Synergistic toughening was studied in model MoSisb2 composites reinforced with 2 mole % yttria partially stabilized zirconia particle, and Nb layers. Synergistic toughening was shown to occur in these composites due to additional transformations that were induced as a result of higher interfacial stresses. However, the overall level of transformation toughening was limited. Nevertheless, a synergistically toughened MoSisb2 composite with a toughness of {˜}20.5+1.0\\ MPasurd m was produced by hybrid reinforcement with Nb layers and 2 mole % yttria-stabilized zirconia particles. Following the study of ductile Nb reinforced MoSisb2 composites, an effort was made to examine the fatigue and fracture behavior of a new class of damage tolerant niobium aluminide intermetallics. Effects of alloying

  15. Differential expression of proteins in response to molybdenum deficiency in winter wheat leaves under low-temperature stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Molybdenum (Mo) is an essential micronutrient for plants. To obtain a better understanding of the molecular mechanisms of cold resistance enhanced by molybdenum application in winter wheat, we applied a proteomic approach to investigate the differential expression of proteins in response to molybden...

  16. Hydrophilic molybdenum oxide nanomaterials with controlled morphology and strong plasmonic absorption for photothermal ablation of cancer cells.

    PubMed

    Song, Guosheng; Shen, Jia; Jiang, Feiran; Hu, Ronggui; Li, Wenyao; An, Lei; Zou, Rujia; Chen, Zhigang; Qin, Zongyi; Hu, Junqing

    2014-03-26

    The molybdenum oxide nanosheets have shown strong localized surface plasmon resonance (LSPR) absorption in the near-infrared (NIR) region. However, the long alky chains of ligands made them hydrophobic and less biocompatible. To meet the requirements of molybdenum based nanomaterials for use as a future photothermal therapy, a simple hydrothermal route has been developed for hydrophilic molybdenum oxide nanospheres and nanoribbons using a molybdenum precursor and poly(ethylene glycol) (PEG). First, molybdenum oxide nanomaterials prepared in the presence of PEG exhibit strong localized surface plasmon resonance (LSPR) absorption in near-infrared (NIR) region, compared with that of no PEG. Second, elevation of synthetic temperature leads to a gradual transformation of molybdenum oxide nanospheres into nanoribbons, entailing the evolution of an intense LSPR absorption in the NIR region. Third, as-prepared molybdenum oxide nanomaterials coated with PEG possess a hydrophilic property and thus can be directly used for biological applications without additional post treatments. Moreover, molybdenum oxide nanoribbons as a model of photothermal materials can efficiently convert the 980 nm wavelength laser energy into heat energy, and this localized hyperthermia produces the effective thermal ablation of cancer cells, meaning a potential photothermal material. PMID:24564332

  17. Strain hardening and structural changes in molybdenum in tension with the application of ultrasonic vibrations

    SciTech Connect

    Ivashchenko, V.V.; Kozlov, A.V.; Moiseev, V.F.; Mordyuk, N.S.; Pechkovskii, E.P.

    1985-11-01

    This paper investigates the influence of the amplitude of the applied ultrasonic vibrations on the rules of strain hardening and their interrelationship with the structural changes in molybdenum in tension. The investigated molybdenum was rolled at 950 degrees C into 1 mm thick sheet and annealed at 950 degrees C for 1 hours. In the tension of molybdenum with the application of ultrasonic vibrations, the general rules of strain hardening are observed, but under the influence of the ultrasonic vibration, the stage of parabolic hardening with a tangle type dislocation structure is significantly broadened within the studied range of amplitudes. A later transition to the stage of formatin of the dislocation cell structure is noted.

  18. The Extreme Overabundance of Molybdenum in Two Metal-poor Stars

    NASA Astrophysics Data System (ADS)

    Peterson, Ruth C.

    2011-11-01

    We report determinations of the molybdenum abundances in five mildly to extremely metal-poor turnoff stars using five Mo II lines near 2000 Å. In two of the stars, the abundance of molybdenum is found to be extremely enhanced, as high or higher than the neighboring even-Z elements ruthenium and zirconium. Of the several nucleosynthesis scenarios envisioned for the production of nuclei in this mass range in the oldest stars, a high-entropy wind acting in a core-collapse supernova seems uniquely capable of the twin aspects of a high molybdenum overproduction confined to a narrow mass range. Whatever the details of the nucleosynthesis mechanism, however, this unusual excess suggests that very few individual nucleosynthesis events were responsible for the synthesis of the light trans-Fe heavy elements in these cases, an unexpected result given that both are only moderately metal-poor.

  19. Recent developments in the homogeneous reduction of dinitrogen by molybdenum and iron

    NASA Astrophysics Data System (ADS)

    MacLeod, K. Cory; Holland, Patrick L.

    2013-07-01

    The reduction of gaseous nitrogen is a challenge for industrial, biological and synthetic chemists. Major goals include understanding the formation of ammonia for agriculture, and forming N-C and N-Si bonds for the synthesis of fine chemicals. The iron-molybdenum active site of the enzyme nitrogenase has inspired chemists to explore iron and molybdenum complexes in transformations related to N2 reduction. This area of research has gained significant momentum, and the past two years have witnessed a number of significant advances in synthetic Fe-N2 and Mo-N2 chemistry. Furthermore, the identities of all atoms in the iron-molybdenum cofactor of nitrogenase have finally been elucidated, and the discovery of a carbide has generated new questions and targets for coordination chemists. This Perspective summarizes the recent work on iron and molydenum complexes, and highlights the opportunities for continued research.

  20. Molybdenum disulfide (MoS2) nanoflakes as inherently electroactive labels for DNA hybridization detection.

    PubMed

    Loo, Adeline Huiling; Bonanni, Alessandra; Ambrosi, Adriano; Pumera, Martin

    2014-10-21

    The detection of specific DNA sequences plays a critical role in the areas of medical diagnostics, environmental monitoring, drug discovery and food safety. This has therefore become a strong driving force behind the ever-increasing demand for simple, cost-effective, highly sensitive and selective DNA biosensors. In this study, we report for the first time, a novel approach for the utilization of molybdenum disulfide nanoflakes, a member of the transition metal dichalcogenides family, in the detection of DNA hybridization. Herein, molybdenum disulfide nanoflakes serve as inherently electroactive labels, with the inherent oxidation peak exploited as the analytical signal. The principle of detection is based on the differential affinity of molybdenum disulfide nanoflakes towards single-stranded DNA and double-stranded DNA. The employment of transition metal dichalcogenide nanomaterials for sensing and biosensing purposes represents an upcoming research area which holds great promise. Hence, our findings are anticipated to have significant contributions towards the fabrication of future DNA biosensors. PMID:25177907

  1. Structure and photochromic properties of molybdenum-containing silica gels obtained by molecular-lamination method

    SciTech Connect

    Belotserkovskaya, N.G.; Dobychin, D.P.; Pak, V.N.

    1992-05-10

    The structure and physicochemical properties of molybdenum-containing silica gels obtained by molecular lamination have been studied quite extensively. Up to the present, however, no studies have been made of the influence of the pore structure of the original silica gel on the structure and properties of molybdenum-containing silica gels (MSG). The problem is quite important, since molybdenum silicas obtained by molecular lamination may find applications in catalysis and as sensors of UV radiation. In either case, the structure of the support is not a factor to be ignored. Here, the authors are reporting on an investigation of the structure of MSG materials with different pore structures and their susceptibility to reduction of the Mo(VI) oxide groupings when exposed to UV radiation. 16 refs., 2 figs., 2 tabs.

  2. Ion pairs of a molybdenum thiocyanate complex with dyes of the xanthene series

    SciTech Connect

    Ganago, L.I.; Ivanova, I.F.

    1988-03-10

    It has been ascertained that thiocyanate complexes of molybdenum react with dyes of the xanthene series, Rhodamine 6G and Rhodamine B, to form ion pairs. The Mo:SCN:Rhod. component ratios are respectively 1:5:2 and 1:6:3. The ion pairs are stable in an acid medium: 4.5-5.5 M H/sub 2/SO/sub 4/ (MTC-Rhod. 6G) and 3 M H/sub 2/SO (MTC-Rhod. B), and their molecular extinction coefficients are 2.22 x 10/sup 5/ and 3.8 x 10/sub 5/ respectively; MTC in a molybdenum thiocyanate complex. A procedure has been worked out for determining molybdenum in films, making use of the reaction of forming an MTC-Rhod. B ion pair.

  3. THE EXTREME OVERABUNDANCE OF MOLYBDENUM IN TWO METAL-POOR STARS

    SciTech Connect

    Peterson, Ruth C.

    2011-11-20

    We report determinations of the molybdenum abundances in five mildly to extremely metal-poor turnoff stars using five Mo II lines near 2000 A. In two of the stars, the abundance of molybdenum is found to be extremely enhanced, as high or higher than the neighboring even-Z elements ruthenium and zirconium. Of the several nucleosynthesis scenarios envisioned for the production of nuclei in this mass range in the oldest stars, a high-entropy wind acting in a core-collapse supernova seems uniquely capable of the twin aspects of a high molybdenum overproduction confined to a narrow mass range. Whatever the details of the nucleosynthesis mechanism, however, this unusual excess suggests that very few individual nucleosynthesis events were responsible for the synthesis of the light trans-Fe heavy elements in these cases, an unexpected result given that both are only moderately metal-poor.

  4. Influence of nickel and molybdenum on the phase stability and mechanical properties of maraging steels

    SciTech Connect

    Ahmed, M.; Nasim, I.; Husain, S.W. )

    1994-04-01

    The effect of nickel and molybdenum concentrations on the phase transformation and mechanical properties of conventional 10Ni(350) maraging steel has been investigated. Both of these elements act as strong austenite stabilizers. When the concentration of molybdenum or nickel is greater than 7.5 or 24 wt%, respectively, the austenite phase remains stable up to room temperature. In both molybdenum- and nickel-alloyed steels, the austenite phase could be transformed to martensite by either dipping the material in liquid nitrogen or subjecting it to cold working. When 7.5 wt% Mo and 24 wt% Ni were added in combination, however, the austenite phase obtained at room temperature did not transform to martensite when liquid-nitrogen quenched or even when cold rolled to greater than 95% reduction. The aging response of these materials has also been investigated using optical, scanning electron, and scanning transmission electron microscopy.

  5. Selective intercalation of o-phenylene diamine into molybdenum oxide layers

    SciTech Connect

    Shao Ke Cao Huiqun; Qiu Qi

    2009-03-05

    o-Phenylene diamine molecules were intercalated into molybdenum oxide layers by an in situ co-precipitation method. The structure and composition of the intercalated material were studied by X-ray diffraction (XRD), infrared spectroscopy (IR) and elemental analysis. XRD data evidenced a layered structure with a spacing of 18 A, which corresponds to an organic-inorganic hybrid-layered structure. IR and UV-vis spectra indicated the polymerization of o-phenylene between the molybdenum oxide layers. It was also observed that compared with aniline molecules, o-phenylene diamine molecules can be selectively intercalated into molybdenum oxide layers. We provide evidence that affinity for o-phenylene diamine to form intermolecular polymers is the reason for its selective intercalation. The polymer chain structure of o-phenylene diamine makes it a preferential guest species compared with aniline. We believe that this opens a new way to create organic-inorganic hybrid structures.

  6. The role of FeS clusters for molybdenum cofactor biosynthesis and molybdoenzymes in bacteria

    PubMed Central

    Yokoyama, Kenichi; Leimkühler, Silke

    2016-01-01

    Molybdenum is the only second row transition metal essential for biological systems, which is biologically available as molybdate ion. In eukarya, bacteria and archaea, molybdenum is bound to either to a tricyclic pyranopterin, thereby forming the molybdenum cofactor (Moco), or in some bacteria to the FeS cluster based iron-molybdenum cofactor (FeMoco), which forms the active site of nitrogenase. To date more than 50 Moco-containing enzymes have been purified and biochemically or structurally characterized. The physiological role of molybdenum in these enzymes is fundamental to organisms, since the reactions include the catalysis of key steps in carbon, nitrogen and sulfur metabolism. The catalyzed reactions are in most cases oxo-transfer reactions or the hydroxylation of carbon centers. The biosynthesis of Moco has been intensively studied, in addition to its insertion into molybdoenzymes. In particular, a link between the biosynthesis and maturation of molybdoenzymes and the biosynthesis and distribution of FeS clusters has been identified in the last years: 1) The synthesis of the first intermediate in Moco biosynthesis requires an FeS-cluster containing protein, 2) The sulfurtransferase for the dithiolene group in Moco is common also for the synthesis of FeS clusters, thiamin and thiolated tRNAs, 3) the modification of the active site with a sulfur atom additionally involves a sulfurtransferase, 4) most molybdoenzymes in bacteria require FeS clusters as additional redox active cofactors. In this review we will focus on the biosynthesis of the molybdenum cofactor in bacteria, its modification and insertion into molybdoenzymes, with an emphasis to its link to FeS cluster biosynthesis and sulfur transfer. PMID:25268953

  7. Survey of Portions of the Chromium-Cobalt-Nickel-Molybdenum Quaternary System at 1,200 Degrees C

    NASA Technical Reports Server (NTRS)

    Rideout, Sheldon Paul; Beck, Paul A

    1953-01-01

    A survey was made of portions of the chromium-cobalt-nickel-molybdenum quaternary system at 1,200 degrees c by means of microscopic and x-ray diffraction studies. Since the face-centered cubic (alpha) solid solutions form the matrix of almost all practically useful high-temperature alloys, the solid solubility limits of the quaternary alpha phase were determined up to 20 percent molybdenum. The component cobalt-nickel-molybdenum, chromium-cobalt-molybdenum, and chromium-nickel-molybdenum ternary systems were also studied. The survey of these systems was confined to the determination of the boundaries of the face-centered cubic (alpha) solid solutions and of the phases coexisting with alpha at 1,200 degrees c.

  8. Mouse model for molybdenum cofactor deficiency type B recapitulates the phenotype observed in molybdenum cofactor deficient patients.

    PubMed

    Jakubiczka-Smorag, Joanna; Santamaria-Araujo, Jose Angel; Metz, Imke; Kumar, Avadh; Hakroush, Samy; Brueck, Wolfgang; Schwarz, Guenter; Burfeind, Peter; Reiss, Jochen; Smorag, Lukasz

    2016-07-01

    Molybdenum cofactor (MoCo) deficiency is a rare, autosomal-recessive disorder, mainly caused by mutations in MOCS1 (MoCo deficiency type A) or MOCS2 (MoCo deficiency type B) genes; the absence of active MoCo results in a deficiency in all MoCo-dependent enzymes. Patients with MoCo deficiency present with neonatal seizures, feeding difficulties, severe developmental delay, brain atrophy and early childhood death. Although substitution therapy with cyclic pyranopterin monophosphate (cPMP) has been successfully used in both Mocs1 knockout mice and in patients with MoCo deficiency type A, there is currently no Mocs2 knockout mouse and no curative therapy for patients with MoCo deficiency type B. Therefore, we generated and characterized a Mocs2-null mouse model of MoCo deficiency type B. Expression analyses of Mocs2 revealed a ubiquitous expression pattern; however, at the cellular level, specific cells show prominent Mocs2 expression, e.g., neuronal cells in cortex, hippocampus and brainstem. Phenotypic analyses demonstrated that Mocs2 knockout mice failed to thrive and died within 11 days after birth. None of the tested MoCo-dependent enzymes were active in Mocs2-deficient mice, leading to elevated concentrations of purines, such as hypoxanthine and xanthine, and non-detectable levels of uric acid in the serum and urine. Moreover, elevated concentrations of S-sulfocysteine were measured in the serum and urine. Increased levels of xanthine resulted in bladder and kidney stone formation, whereas increased concentrations of toxic sulfite triggered neuronal apoptosis. In conclusion, Mocs2-deficient mice recapitulate the severe phenotype observed in humans and can now serve as a model for preclinical therapeutic approaches for MoCo deficiency type B. PMID:27138983

  9. Neutron irradiation embrittlement of molybdenum rhenium alloys and their improvement by heat treatment

    NASA Astrophysics Data System (ADS)

    Hasegawa, Akira; Ueda, Kazukiyo; Satou, Manabu; Abe, Katsunori

    1998-10-01

    Irradiation-induced embrittlement is one of the major problems with molybdenum alloys, which have been considered as one of the candidates for divertor structural materials. The effects of rhenium content, heat-treatment and irradiation condition on mechanical properties and microstructural development of molybdenum rhenium alloys were studied after neutron exposure by FFTF/MOTA up to high fluence (˜1 × 10 27 n/m 2, En>0.1 MeV). Appreciable plastic deformation was observed in a bending test on stress-relieved Mo-5 wt% Re irradiated at high temperatures. Fine, dense precipitates were observed in Mo-41 wt% Re, resulting in large hardening and embrittlement.

  10. Separation of Molybdenum-Uranium by a Process Combining Ion Exchange Resin and Membranes

    NASA Astrophysics Data System (ADS)

    Lounis, A.; Setti, L.; Djennane, A.; Melikchi, R.

    The purpose of this study is to determine whether the electrodeionization with ion-exchange resin is suitable for removing uranium from a solution containing molybdenum. A hybrid process combining ion exchange (resins and membranes) using electric current. For this electroextraction process, the cation exchange resin is introduced into an electrodialysis cell and compressed between two cations exchange membranes. We have investigated a continuous electroextraction process. As important result we note that: The factor of selectivity,r, for molybdenum versus uranium is superior to 3; the concentration in radio active element (U3O8) is lower than 1.5 mg L-1 and small cell voltage is observed.

  11. Monocrystalline molybdenum silicide based quantum dot superlattices grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Savelli, Guillaume; Silveira Stein, Sergio; Bernard-Granger, Guillaume; Faucherand, Pascal; Montès, Laurent

    2016-09-01

    This paper presents the growth of doped monocrystalline molybdenum-silicide-based quantum dot superlattices (QDSL). This is the first time that such nanostructured materials integrating molybdenum silicide nanodots have been grown. QDSL are grown by reduced pressure chemical vapor deposition (RPCVD). We present here their crystallographic structures and chemical properties, as well as the influence of the nanostructuration on their thermal and electrical properties. Particularly, it will be shown some specific characteristics for these QDSL, such as a localization of nanodots between the layers, unlike other silicide based QDSL, an accumulation of doping atoms near the nanodots, and a strong decrease of the thermal conductivity obtained thanks to the nanostructuration.

  12. 22.5% efficient silicon heterojunction solar cell with molybdenum oxide hole collector

    SciTech Connect

    Geissbühler, Jonas Werner, Jérémie; Martin de Nicolas, Silvia; Hessler-Wyser, Aïcha; Tomasi, Andrea; Niesen, Bjoern; De Wolf, Stefaan; Barraud, Loris; Despeisse, Matthieu; Nicolay, Sylvain; Ballif, Christophe

    2015-08-24

    Substituting the doped amorphous silicon films at the front of silicon heterojunction solar cells with wide-bandgap transition metal oxides can mitigate parasitic light absorption losses. This was recently proven by replacing p-type amorphous silicon with molybdenum oxide films. In this article, we evidence that annealing above 130 °C—often needed for the curing of printed metal contacts—detrimentally impacts hole collection of such devices. We circumvent this issue by using electrodeposited copper front metallization and demonstrate a silicon heterojunction solar cell with molybdenum oxide hole collector, featuring a fill factor value higher than 80% and certified energy conversion efficiency of 22.5%.

  13. Investigation of welding and brazing of molybdenum and TZM alloy tubes

    NASA Technical Reports Server (NTRS)

    Lundblad, Wayne E.

    1991-01-01

    This effort involved investigating the welding and brazing techniques of molybdenum tubes to be used as cartridges in the crystal growth cartridge. Information is given in the form of charts and photomicrographs. It was found that the recrystallization temperature of molybdenum can be increased by alloying it with 0.5 percent titanium and 0.1 percent zirconium. Recrystallization temperatures for this alloy, known as TZM, become significant around 2500 F. A series of microhardness tests were run on samples of virgin and heat soaked TZM. The test results are given in tabular form. It was concluded that powder metallurgy TZM may be an acceptable cartridge material.

  14. Individual and combined toxicity of manganese and molybdenum to mussel, Mytilus edulis, larvae

    SciTech Connect

    Morgan, J.D.; Mitchell, D.G.; Chapman, P.M.

    1986-08-01

    During toxicity testing of mine tailings from the proposed Quartz Hill molybdenum mine, which will be situated near Ketchikan, Alaska, the metals molybdenum (Mo) and manganese (Mn) showed evidence of leaching from the tailings. In order to determine whether these metals could be responsible for toxicities observed previously, Mytilus edulis mussel larvae bioassays (ASTM 1984) were conducted with these metals, both individually and in combination. The results of the bioassays showed that these metals could account for only a very small proportion of the tailings toxicity.

  15. Improved porous mixture of molybdenum nitride and tantalum oxide as a charge storage material

    SciTech Connect

    Deng, C.Z.; Pynenburg, R.A.J.; Tsai, K.C.

    1998-04-01

    High surface area {gamma}-molybdenum nitride has shown promise as a charge storage material. The addition of amorphous tantalum oxide to the molybdenum nitride system not only improves the film cohesion tremendously, but also widens the voltage stability window from 0.8 to 1.1 V. This occurs without adversely effecting the capacitance. Ultracapacitors, also called supercapacitors or electrochemical capacitors, are high power storage devices which have found application in products as diverse as cardiac pacemakers, cellular phones, electric vehicles, and air bags.

  16. 22.5% efficient silicon heterojunction solar cell with molybdenum oxide hole collector

    NASA Astrophysics Data System (ADS)

    Geissbühler, Jonas; Werner, Jérémie; Martin de Nicolas, Silvia; Barraud, Loris; Hessler-Wyser, Aïcha; Despeisse, Matthieu; Nicolay, Sylvain; Tomasi, Andrea; Niesen, Bjoern; De Wolf, Stefaan; Ballif, Christophe

    2015-08-01

    Substituting the doped amorphous silicon films at the front of silicon heterojunction solar cells with wide-bandgap transition metal oxides can mitigate parasitic light absorption losses. This was recently proven by replacing p-type amorphous silicon with molybdenum oxide films. In this article, we evidence that annealing above 130 °C—often needed for the curing of printed metal contacts—detrimentally impacts hole collection of such devices. We circumvent this issue by using electrodeposited copper front metallization and demonstrate a silicon heterojunction solar cell with molybdenum oxide hole collector, featuring a fill factor value higher than 80% and certified energy conversion efficiency of 22.5%.

  17. Thermocouples of molybdenum and iridium alloys for more stable vacuum-high temperature performance

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1978-01-01

    Thermocouples providing stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor are described. Each metal of the sensor is selected from a group of metals comprising molybdenum and iridium and alloys containing only those two metals. The molybdenum, iridium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibility and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys result in improved emf, temperature properties and thermocouple hot junction performance.

  18. Particle separation

    DOEpatents

    Moosmuller, Hans; Chakrabarty, Rajan K.; Arnott, W. Patrick

    2011-04-26

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  19. Particle separation

    NASA Technical Reports Server (NTRS)

    Moosmuller, Hans (Inventor); Chakrabarty, Rajan K. (Inventor); Arnott, W. Patrick (Inventor)

    2011-01-01

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  20. Complex Molybdenum Isotope Behavior During Weathering and Erosional Transport

    NASA Astrophysics Data System (ADS)

    Siebert, C.; Pett-Ridge, J. C.; Burton, K.; Halliday, A. N.

    2009-12-01

    The oceans play a major role in regulating global climate because they both react and drive changes in other geochemical reservoirs. Non-traditional stable isotope systems have become important proxies for changes in ocean chemistry making the quantification of these changes possible. Molybdenum isotopes have great potential as tracers of changes in the oxygenation of the oceans over geological time scales. Although significant progress has been made and the amount of data on the biogeochemical behaviour of Mo in the marine environment has been increasing rapidly over the last few years, some important aspects of Mo geochemistry remain poorly understood. These include diagenetic processes at continental margins and continental weathering. Mo isotope behaviour in these settings has a potentially large impact on the interpretation of the geological record. A recent study of Archer and Vance (2008) has shown that dissolved Mo in many of Earths major rivers has a heavy isotope composition relative to most magmatic rocks. A potential cause for this isotope composition in modern rivers is isotope fractionation during weathering and erosion processes. We investigated Mo isotope behaviour in weathering profiles from Hawaii and Puerto Rico. Results clearly show significant Mo isotope fractionation during chemical weathering. Mo retained in saprolithe samples from Hawaii has light isotope compositions of up to -0.5 permill. The extent of fractionation is dependent on redox-conditions in the investigated profiles. The particular setting of these profiles keeps other factors that might influence the Mo isotope composition to a minimum. The results also indicate the possible use of Mo isotope signals as paleoredox-proxy of weathering processes. However, a weathering profile with intermittent changes in redox, pH and porewater saturation show more variable Mo isotope signals with partly positive isotope values. Sequential extractions of saphrolite samples show a clear

  1. Alpha Particle

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Term that is sometimes used to describe a helium nucleus, a positively charged particle that consists of two protons and two neutrons, bound together. Alpha particles, which were discovered by Ernest Rutherford (1871-1937) in 1898, are emitted by atomic nuclei that are undergoing alpha radioactivity. During this process, an unstable heavy nucleus spontaneously emits an alpha particle and transmut...

  2. Particle generator

    DOEpatents

    Hess, Wayne P.; Joly, Alan G.; Gerrity, Daniel P.; Beck, Kenneth M.; Sushko, Peter V.; Shlyuger, Alexander L.

    2005-06-28

    Energy tunable solid state sources of neutral particles are described. In a disclosed embodiment, a halogen particle source includes a solid halide sample, a photon source positioned to deliver photons to a surface of the halide, and a collimating means positioned to accept a spatially defined plume of hyperthermal halogen particles emitted from the sample surface.

  3. An efficient molybdenum disulfide/cobalt diselenide hybrid catalyst for electrochemical hydrogen generation

    PubMed Central

    Gao, Min-Rui; Liang, Jin-Xia; Zheng, Ya-Rong; Xu, Yun-Fei; Jiang, Jun; Gao, Qiang; Li, Jun; Yu, Shu-Hong

    2015-01-01

    The electroreduction of water for sustainable hydrogen production is a critical component of several developing clean-energy technologies, such as water splitting and fuel cells. However, finding a cheap and efficient alternative catalyst to replace currently used platinum-based catalysts is still a prerequisite for the commercialization of these technologies. Here we report a robust and highly active catalyst for hydrogen evolution reaction that is constructed by in situ growth of molybdenum disulfide on the surface of cobalt diselenide. In acidic media, the molybdenum disulfide/cobalt diselenide catalyst exhibits fast hydrogen evolution kinetics with onset potential of −11 mV and Tafel slope of 36 mV per decade, which is the best among the non-noble metal hydrogen evolution catalysts and even approaches to the commercial platinum/carbon catalyst. The high hydrogen evolution activity of molybdenum disulfide/cobalt diselenide hybrid is likely due to the electrocatalytic synergistic effects between hydrogen evolution-active molybdenum disulfide and cobalt diselenide materials and the much increased catalytic sites. PMID:25585911

  4. An efficient molybdenum disulfide/cobalt diselenide hybrid catalyst for electrochemical hydrogen generation.

    PubMed

    Gao, Min-Rui; Liang, Jin-Xia; Zheng, Ya-Rong; Xu, Yun-Fei; Jiang, Jun; Gao, Qiang; Li, Jun; Yu, Shu-Hong

    2015-01-01

    The electroreduction of water for sustainable hydrogen production is a critical component of several developing clean-energy technologies, such as water splitting and fuel cells. However, finding a cheap and efficient alternative catalyst to replace currently used platinum-based catalysts is still a prerequisite for the commercialization of these technologies. Here we report a robust and highly active catalyst for hydrogen evolution reaction that is constructed by in situ growth of molybdenum disulfide on the surface of cobalt diselenide. In acidic media, the molybdenum disulfide/cobalt diselenide catalyst exhibits fast hydrogen evolution kinetics with onset potential of -11 mV and Tafel slope of 36 mV per decade, which is the best among the non-noble metal hydrogen evolution catalysts and even approaches to the commercial platinum/carbon catalyst. The high hydrogen evolution activity of molybdenum disulfide/cobalt diselenide hybrid is likely due to the electrocatalytic synergistic effects between hydrogen evolution-active molybdenum disulfide and cobalt diselenide materials and the much increased catalytic sites. PMID:25585911

  5. A structure-based catalytic mechanism for the xanthine oxidase family of molybdenum enzymes.

    PubMed Central

    Huber, R; Hof, P; Duarte, R O; Moura, J J; Moura, I; Liu, M Y; LeGall, J; Hille, R; Archer, M; Romão, M J

    1996-01-01

    The crystal structure of the xanthine oxidase-related molybdenum-iron protein aldehyde oxido-reductase from the sulfate reducing anaerobic Gram-negative bacterium Desulfovibrio gigas (Mop) was analyzed in its desulfo-, sulfo-, oxidized, reduced, and alcohol-bound forms at 1.8-A resolution. In the sulfo-form the molybdenum molybdopterin cytosine dinucleotide cofactor has a dithiolene-bound fac-[Mo, = O, = S, ---(OH2)] substructure. Bound inhibitory isopropanol in the inner compartment of the substrate binding tunnel is a model for the Michaelis complex of the reaction with aldehydes (H-C = O,-R). The reaction is proposed to proceed by transfer of the molybdenum-bound water molecule as OH- after proton transfer to Glu-869 to the carbonyl carbon of the substrate in concert with hydride transfer to the sulfido group to generate [MoIV, = O, -SH, ---(O-C = O, -R)). Dissociation of the carboxylic acid product may be facilitated by transient binding of Glu-869 to the molybdenum. The metal-bound water is replenished from a chain of internal water molecules. A second alcohol binding site in the spacious outer compartment may cause the strong substrate inhibition observed. This compartment is the putative binding site of large inhibitors of xanthine oxidase. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:8799115

  6. Electrotransport of Molybdenum Through an Electrodialysis Membrane. Concentration and Potentiel Profiles in Aqueous Interfacial Layers

    NASA Astrophysics Data System (ADS)

    Lounis, Azzedine; Benmhidi, Kamel

    In the first part we have observed the electrotransport of molybdenum in carbonate media (OH-,CO=3) through a commercial electrodialysis anion exchange membrane. The values of the molybdenum, hydrogen oxide and carbonate fluxes obtained in this study show that molybdenum is present as molybdate ion MoO=4 in carbonate solution and that the molybdyl tricarbonate ion existence hypothesis MoO2(CO3)4-3 an't no longer be maintained. In order to confirm this result we have studied the electrotransport of molybdenum and carbonate ions with different CO=3/MoO=4 ratio. The used theory is based on the fact that, the concentration ratio in the membrane equals the one of the same species within the solution. These hypothesis have to be justified given that this equality is actually usual for unstirred layers extremity. Therefore, in the second part the concentration and the potential profiles in aqueous interfacial layers were determined by a numerical resolution of the Nernst-Planck electrodiffusion equation coupled with the Poisson equation. The obtained concentration profiles from numerical resolution differ from 3 to 6% from the ones acquired by analytical resolution method assuming the constant electrical field hypothesis for OH-, CO=3 ions, respectively. However the potential profiles display that constant electrical field hypothesis is strictly valid.

  7. Magnetic composites based on metallic nickel and molybdenum carbide: a potential material for pollutants removal.

    PubMed

    Mambrini, Raquel V; Fonseca, Thales L; Dias, Anderson; Oliveira, Luiz C A; Araujo, Maria Helena; Moura, Flávia C C

    2012-11-30

    New magnetic composites based on metallic nickel and molybdenum carbide, Ni/Mo(2)C, have been produced via catalytic chemical vapor deposition from ethanol. Scanning electron microscopy, thermal analysis, Raman spectroscopy and X-ray diffraction studies suggest that the CVD process occurs in a single step. This process involves the reduction of NiMo oxides at different temperatures (700, 800 and 900°C) with catalytic deposition of carbon from ethanol producing molybdenum carbide on Ni surface. In the absence of molybdenum the formation of Ni/C was observed. The magnetic molybdenum carbide was successfully used as pollutants removal by adsorption of sulfur and nitrogen compounds from liquid fuels and model dyes such as methylene blue and indigo carmine. The dibenzothiofene adsorption process over Ni/Mo(2)C reached approximately 20 mg g(-1), notably higher than other materials described in the literature and also removed almost all methylene blue dye. The great advantage of these carbide composites is that they may be easily recovered magnetically and reused. PMID:23036701

  8. Coordination polymer structure and revisited hydrogen evolution catalytic mechanism for amorphous molybdenum sulfide

    NASA Astrophysics Data System (ADS)

    Tran, Phong D.; Tran, Thu V.; Orio, Maylis; Torelli, Stephane; Truong, Quang Duc; Nayuki, Keiichiro; Sasaki, Yoshikazu; Chiam, Sing Yang; Yi, Ren; Honma, Itaru; Barber, James; Artero, Vincent

    2016-06-01

    Molybdenum sulfides are very attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) from water. The atomic structure and identity of the catalytically active sites have been well established for crystalline molybdenum disulfide (c-MoS2) but not for amorphous molybdenum sulfide (a-MoSx), which exhibits significantly higher HER activity compared to its crystalline counterpart. Here we show that HER-active a-MoSx, prepared either as nanoparticles or as films, is a molecular-based coordination polymer consisting of discrete [Mo3S13]2- building blocks. Of the three terminal disulfide (S22-) ligands within these clusters, two are shared to form the polymer chain. The third one remains free and generates molybdenum hydride moieties as the active site under H2 evolution conditions. Such a molecular structure therefore provides a basis for revisiting the mechanism of a-MoSx catalytic activity, as well as explaining some of its special properties such as reductive activation and corrosion. Our findings open up new avenues for the rational optimization of this HER electrocatalyst as an alternative to platinum.

  9. Chemical nature and reaction mechanisms of the molybdenum cofactor of xanthine oxidoreductase.

    PubMed

    Okamoto, Ken; Kusano, Teruo; Nishino, Takeshi

    2013-01-01

    Xanthine oxidoreductase (XOR), a complex flavoprotein, catalyzes the metabolic reactions leading from hypoxanthine to xanthine and from xanthine to urate, and both reactions take place at the molybdenum cofactor. The enzyme is a target of drugs for therapy of gout or hyperuricemia. We review the chemical nature and reaction mechanisms of the molybdenum cofactor of XOR, focusing on molybdenum-dependent reactions of actual or potential medical importance, including nitric oxide (NO) synthesis. It is now generally accepted that XOR transfers the water-exchangeable -OH ligand of the molybdenum atom to the substrate. The hydroxyl group at OH-Mo(IV) can be replaced by urate, oxipurinol and FYX-051 derivatives and the structures of these complexes have been determined by xray crystallography under anaerobic conditions. Although formation of NO from nitrite or formation of xanthine from urate by XOR ischemically feasible, it is not yet clear whether these reactions have any physiological significance since the reactions are catalyzed at a slow rate even under anaerobic conditions. PMID:23116398

  10. Austenite Grain Growth and Precipitate Evolution in a Carburizing Steel with Combined Niobium and Molybdenum Additions

    NASA Astrophysics Data System (ADS)

    Enloe, Charles M.; Findley, Kip O.; Speer, John G.

    2015-11-01

    Austenite grain growth and microalloy precipitate size and composition evolution during thermal processing were investigated in a carburizing steel containing various additions of niobium and molybdenum. Molybdenum delayed the onset of abnormal austenite grain growth and reduced the coarsening of niobium-rich precipitates during isothermal soaking at 1323 K, 1373 K, and 1423 K (1050 °C, 1100 °C, and 1150 °C). Possible mechanisms for the retardation of niobium-rich precipitate coarsening in austenite due to molybdenum are considered. The amount of Nb in solution and in precipitates at 1373 K (1100 °C) did not vary over the holding times evaluated. In contrast, the amount of molybdenum in (Nb,Mo)C precipitates decreased with time, due to rejection of Mo into austenite and/or dissolution of fine Mo-rich precipitates. In hot-rolled alloys, soaking in the austenite regime resulted in coarsening of the niobium-rich precipitates at a rate that exceeded that predicted by the Lifshitz-Slyozov-Wagner relation for volume-diffusion-controlled coarsening. This behavior is attributed to an initial bimodal precipitate size distribution in hot-rolled alloys that results in accelerated coarsening rates during soaking. Modification of the initial precipitate size distribution by thermal processing significantly lowered precipitate coarsening rates during soaking and delayed the associated onset of abnormal austenite grain growth.

  11. Synthesis of MCM-41 frameworks incorporating oxygen-sulphur derivates of molybdenum and tungsten

    SciTech Connect

    Gonzalez-Cortes, Sergio L. . E-mail: sergio.gonzalezcortes@chem.ox.ac.uk; Xiao Tiancun; Al-Megren, Hamid A.; Ruiz-Gonzalez, Luisa; Rees, Nick; Hannus, Istvan; Mehn, Dora; Li Jiang; Green, Malcolm L.H. . E-mail: malcolm.green@chem.ox.ac.uk

    2005-07-12

    The first examples of mesostructured materials containing Mo- and W-oxo-sulphur species incorporated into a poorly ordered MCM-41 framework have been prepared under hydrothermal condition and alkaline medium. The incorporation of oxygen-sulphur derivates of molybdenum and tungsten not only increases significantly the pore diameter, but also improves the thermal stability of the MCM-41-related mesoporous material.

  12. Behavior of dissolved molybdenum during localized corrosion of austenitic stainless steel

    SciTech Connect

    Isaacs, H.S.; Huang, S.M.

    1995-12-01

    An in situ study of the chemistry of molybdenum during localized of corrosion of stainless steel in chloride solutions has been carried using energy dispersive x-ray techniques. An artificial pit was used to maintained a one dimensional diffusion geometry by dissolving back the cross section of strip of Type 316 stainless steel foil mounted in an epoxy resin. A high intensity 8 {mu}m diameter polychromatic x-ray beam at Beamline x26A was scanned across the steel, a salt layer on the steel, and the concentrated dissolution products within the artificial pit. The resulting x-ray fluorescence was analyzed to determine changes in concentration of the constituent alloying elements. It has been found that the salt layer on the steel was formed mainly by iron chloride and all other alloying elements were present at relatively lower concentrations than n the steel. Virtually no chromium remained in the salt layer. Also, little molybdenum was present negating proposed corrosion inhibition by a definitive molybdenum forming salt layer. Within the concentrated artificial pit solution it was found that alloying elements dissolved and migrated down a concentration gradient, but closer to the mouth of deep ({approximately}2 mm) pits, precipitation of molybdenum occurred to a minor extent that did not affect the localized corrosion processes.

  13. Microsegregation in high-molybdenum austenitic stainless steel laser beam and gas tungsten arc welds

    SciTech Connect

    Kujanpaeae, V.P.; David, S.A.

    1986-01-01

    An austenitic stainless steel with 6% molybdenum (thickness 6 mm) was welded using laser beam (LB) and gas tungsten arc (GTA) processes at various welding speeds. Depending on the welding speed the primary dendrite spacing ranged from 12 to 17 ..mu..m and from 2 to 7 ..mu..m for the GTA and LB welds, respectively. Extensive segregation of molybdenum was observed in the GTA welds. The segregation ratio for molybdenum, C/sub ID//C/sub D/, was found to be 1.9 in the GTA weld, and 1.2 in the LB weld. Distribution of iron, chromium and nickel was found nearly uniform in both welds. A recovered microstructure was observed after a post-weld annealing heat treatment. Annealing had a profound effect on the molybdenum segregation ratio in the laser weld. The critical pitting temperature (CPT) determined by a standard test was 55/sup 0/C for welds made using both processes, whereas it was 75/sup 0/C for the base metal. Upon homogenization the CPT of the laser beam weld increased to the base metal value, while that of the gas tungsten arc weld remained at 60/sup 0/C.

  14. Molybdenum determination in iron matrices by ICP-AES after separation and preconcentration using polyurethane foam.

    PubMed

    Ferreira, S L; dos Santos, H C; de Jesus, D S

    2001-01-01

    A procedure is proposed for the separation and determination of molybdenum in iron matrices by a batch process. It is based on the solid-phase extraction of the molybdenum(V) ion as thiocyanate complex on polyurethane (PU) foam. The extraction parameters were optimized. Using 0.20 mol L-1 hydrochloric acid, a thiocyanate concentration of 0.10 mol L-1, 100 mg of polyurethane foam and shaking time of 10 min, molybdenum (5-400 micrograms) can be separated and preconcentrated from large amounts of iron (10 mg). Desorption was carried out instantaneously by conc. nitric acid or acetone. Distribution coefficients, sorption capacity of the PU foam and coefficients of variation were also evaluated. The effect of some ions on the separation procedure was assessed. Iron(III) should be reduced to iron(II). The proposed procedure was used to determine molybdenum in standard iron matrices such as steel and pure iron. The achieved results did not show significant differences with certified values. PMID:11225364

  15. Electrosprayed molybdenum trioxide aqueous solution and its application in organic photovoltaic cells.

    PubMed

    Suzuki, Katsumi; Fukuda, Takeshi; Liao, Yingjie

    2014-01-01

    A molybdenum trioxide thin film with smooth surface and uniform thickness was successfully achieved by an electrospray deposition method using an aqueous solution with a drastically low concentration of 0.05 wt%. Previous papers demonstrated that an additive solvent technique is useful for depositing the thin film by the electrospray deposition, and the high vapor pressure and a low surface tension of an additive solvent were found to be important factors. As a result, the smooth molybdenum trioxide thin film was obtained when the acetonitrile was used as the additive solvent. Furthermore, the vapor pressure of acetone is much higher than that of aqueous solution, and this indicates that the acetone is easily evaporated after spraying from the glass capillary. By optimizing a concentration of acetone in the molybdenum aqueous solution, a minimum root mean square roughness of the MoO3 thin film became 3.7 nm. In addition, an organic photovoltaic cell was also demonstrated using the molybdenum trioxide as a hole transport layer. Highest photoconversion efficiency was 1.72%, a value comparable to that using conventional thermal evaporation process even though the aqueous solution was used for the solution process. The photovonversion efficiency was not an optimized value, and the higher value can be achieved by optimizing the coating condition of the active layer. PMID:25148047

  16. Compaction of Ceramic Microspheres, Spherical Molybdenum Powder and Other Materials to 3 GPa

    SciTech Connect

    Carlson, S R; Bonner, B P; Ryerson, F J; Hart, M M

    2006-01-27

    Pressure-volume relationships were measured at room temperature for eight granular materials and one specimen of epoxy foam. The granular materials included hollow ceramic microspheres, spherical molybdenum powder, Ottawa sand, aluminum, copper, titanium and silicon carbide powders and glassy carbon spheres. Measurements were made to 0.9 GPa in a liquid medium press for all of the granular materials and to 3 GPa in a solid medium press for the ceramic microspheres and molybdenum powder. A single specimen of epoxy foam was compressed to 30 MPa in the liquid medium press. Bulk moduli were calculated as a function of pressure for the ceramic microspheres, the molybdenum powder and three other granular materials. The energy expended in compacting the granular materials was determined by numerically integrating pressure-volume curves. More energy was expended per unit volume in compacting the molybdenum powder to 1 GPa than for the other materials, but compaction of the ceramic microspheres required more energy per gram due to their very low initial density. The merge pressure, the pressure at which all porosity is removed, was estimated for each material by plotting porosity against pressure on a semi-log plot. The pressure-volume curves were then extrapolated to the predicted merge pressures and numerically integrated to estimate the energy required to reach full density for each material. The results suggest that the glassy carbon spheres and the ceramic microspheres would require more energy than the other materials to attain full density.

  17. Coordination polymer structure and revisited hydrogen evolution catalytic mechanism for amorphous molybdenum sulfide.

    PubMed

    Tran, Phong D; Tran, Thu V; Orio, Maylis; Torelli, Stephane; Truong, Quang Duc; Nayuki, Keiichiro; Sasaki, Yoshikazu; Chiam, Sing Yang; Yi, Ren; Honma, Itaru; Barber, James; Artero, Vincent

    2016-06-01

    Molybdenum sulfides are very attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) from water. The atomic structure and identity of the catalytically active sites have been well established for crystalline molybdenum disulfide (c-MoS2) but not for amorphous molybdenum sulfide (a-MoSx), which exhibits significantly higher HER activity compared to its crystalline counterpart. Here we show that HER-active a-MoSx, prepared either as nanoparticles or as films, is a molecular-based coordination polymer consisting of discrete [Mo3S13](2-) building blocks. Of the three terminal disulfide (S2(2-)) ligands within these clusters, two are shared to form the polymer chain. The third one remains free and generates molybdenum hydride moieties as the active site under H2 evolution conditions. Such a molecular structure therefore provides a basis for revisiting the mechanism of a-MoSx catalytic activity, as well as explaining some of its special properties such as reductive activation and corrosion. Our findings open up new avenues for the rational optimization of this HER electrocatalyst as an alternative to platinum. PMID:26974410

  18. Chemical Nature and Reaction Mechanisms of the Molybdenum Cofactor of Xanthine Oxidoreductase

    PubMed Central

    Okamoto, Ken; Kusano, Teruo; Nishino, Takeshi

    2013-01-01

    Xanthine oxidoreductase (XOR), a complex flavoprotein, catalyzes the metabolic reactions leading from hypoxanthine to xanthine and from xanthine to urate, and both reactions take place at the molybdenum cofactor. The enzyme is a target of drugs for therapy of gout or hyperuricemia. We review the chemical nature and reaction mechanisms of the molybdenum cofactor of XOR, focusing on molybdenum-dependent reactions of actual or potential medical importance, including nitric oxide (NO) synthesis. It is now generally accepted that XOR transfers the water-exchangeable -OH ligand of the molybdenum atom to the substrate. The hydroxyl group at OH-Mo(IV) can be replaced by urate, oxipurinol and FYX-051 derivatives and the structures of these complexes have been determined by x-ray crystallography under anaerobic conditions. Although formation of NO from nitrite or formation of xanthine from urate by XOR is chemically feasible, it is not yet clear whether these reactions have any physiological significance since the reactions are catalyzed at a slow rate even under anaerobic conditions. PMID:23116398

  19. Field Validation of Molybdenum Accumulation as an Indicator of Hypoxic Water Conditions

    EPA Science Inventory

    Laboratory experiments have shown that the accumulation rate of authigenic molybdenum (Mo) in marine sediments may serve as a quantitative surrogate for direct measurement of hypoxic conditions in overlying waters: Mo accumulation in the top 1 cm of sediment is linearly related t...

  20. MoS{sub 2} nanotube exfoliation as new synthesis pathway to molybdenum blue

    SciTech Connect

    Visic, B.; Gunde, M. Klanjsek; Kovac, J.; Iskra, I.; Jelenc, J.; Remskar, M.

    2013-02-15

    Graphical abstract: . Display Omitted Highlights: ► New synthesis approach to obtaining molybdenum blue via exfoliated MoS{sub 2} nanotubes. ► Material is prone to self assembly and is stable in high vacuum. ► Molecules are as small as 2 nm and their clusters are up to tens of nanometers. ► Change in absorption and oxidation states from the precursor MoS{sub 2}. -- Abstract: Molybdenum blue-type materials are usually obtained by partially reducing Mo{sup VI+} in acidic solutions, while in the presented method it is formed in ethanol solution of exfoliated MoS{sub 2} nanotubes, where the MoS{sub 2} flakes are the preferential location for their growth. Material was investigated by means of scanning electron and atomic force microscopy, showing the structure and self assembly, while also confirming that it is stable in high vacuum with molecules as small as 1.6 nm and the agglomerates of few tens of nanometres. The ultraviolet–visible and photoelectron spectrometry show the change in absorption properties and oxidation states from MoS{sub 2} structure to molybdenum blue, while the presence of sulphur suggests that this is a new type of molybdenum blue material.